Effect of Localized Wear Damage on Strength of Climbing Carabiners

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Misiaszek, David C. Dunand This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7942642/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Climbing carabiners are critical safety tools in mountaineering, yet their failure due to wear and fatigue over time remains a fatal cause of climbing-related accidents. Manufacturer ratings are based on uniaxial tensile tests of new carabiners to failure, yet carabiners may develop wear grooves/notches over time that cause overloading failure during a lead-climbing fall. Current safety standards do not account for this wear, leaving climbers to subjectively determine the threshold for carabiner retirement. This study investigates the relationship between wear-induced groove depth and carabiner strength using Finite Element Modeling (FEM) to simulate stress-strain behavior of 7075-T6 aluminum carabiners under forces equivalent to realistic lead-climbing falls. Detailed carabiner models with varying groove depths identify the critical area reduction beyond which structural integrity is compromised. We find that for grooves deeper than 3 mm (corresponding to a 32% area reduction for a standard carabiner), carabiners experience a critical reduction in load-bearing capability as stress concentrations locally exceed the tensile yield strength of 7075-T6 aluminum, posing a safety risk under typical lead-climbing fall forces. Materials Engineering Mechanical Engineering Finite Element Modeling Climbing Safety Wear Damage Carabiner Strength Plastic Deformation Stress Concentration Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction Climbing carabiners are one of the most important tools to ensure the safety of climbers who critically depend on the durability of their equipment. A carabiner is a metal loop (usually made from high-strength aluminum alloy) with a spring-loaded steel gate that is used to secure harnesses, ropes, or other climbing gear. Despite manufacturer ratings for maximum vertical force and modern production methods, carabiners are known to fail when in use, which can result in potentially catastrophic accidents that cause injuries or even death. Several studies have examined the causes of rock-climbing accidents. Falls account for 75% of cases in traditional climbing [ 1 ], and equipment failure, including carabiner failure, contributes significantly to climbing injuries and fatalities. Approximately 10% of all mountain-climbing accidents are gear-related, and of these, almost all involve some type of carabiner failure [ 12 ]. An important factor that compromises the structural integrity of aluminum carabiners is the development of wear-induced grooves on their surface after prolonged use. These grooves develop when the repeated back-and-forth movement of a climbing rope wears away the alloy, forming a notch. This wear-induced material loss occurs most as the rope slides under tension, usually during belaying or rappelling. Although dangerous, this wear damage is not accounted for in manufacturer ratings, leaving it to the climber’s judgment to decide when a carabiner is no longer safe to use. In September 2011, a climber in Kentucky’s Red River Gorge took a lead fall between the first and second bolt, loading a fixed aluminum quickdraw with a significant groove wear, severing his rope and causing a ground fall [ 1 ]. The standard industry practice for testing and rating the strength of carabiners involves single pull-to-failure tests. These tests return the maximum tensile strength of the carabiner. However, in the field, carabiners do not fail in a single pull. They usually fracture after multiple loads, indicating low-cycle fatigue failure, and they can be loaded up to 20 kN [ 6 ]. To simulate the weight of a climber taking a lead fall on a dynamic rope attached to the carabiner, this research used a range of forces from 4 to 8 kN. A force below 4 kN is insufficient to affect the carabiner and a force over 8 kN would cause significant physical harm to the climber before the carabiner poses durability issues [ 2 ]. Here, we develop detailed carabiner models with different groove depths and use Finite Element Modeling (FEM) to replicate the geometrical and material characteristics of aluminum climbing carabiners subjected to forces representative of the impact of a climber's fall. We determine the groove depth for which the carabiners' structural integrity is reduced to the point of large-scale deformation (and thus functional failure) by computing the force-displacement curves of carabiners with various groove depths. This study establishes a relationship between groove depth and carabiner load-bearing capacity, and it provides climbers and manufacturers with actionable data to enhance safety standards and reduce climbing-related accidents. 2. Methods To analyze the impact of groove depth on the structural integrity of climbing carabiners, a Finite Element Modeling (FEM) approach was adopted to evaluate how grooved carabiners deform under a single tensile loading scenario representative of fall forces in lead climbing. A comprehensive overview of the FEM method is provided in [ 7 ], which describes it as a numerical technique for approximating solutions to complex engineering problems by discretizing a structure into smaller elements. The work also outlines the method’s historical development, mathematical foundations, and broad applicability to structural mechanics and related fields. 2.1. CAD Modeling The base geometry of the carabiner model was first created and refined in Autodesk Fusion 360. A reference model was imported, with several modifications made to ensure dimensional accuracy and compatibility with Abaqus 2023 simulations. The final model (Fig. 1 d) measured 100.0 mm in height, 58.8 mm in width, and had a cross-sectional width of 11.1 mm, closely matching the dimensions of commercially available carabiners. Grooves were modeled as semicircular notches with a radius of curvature of 5 mm, mimicking real-world wear from climbing ropes (Fig. 1 c). These grooves were located at the basket area, a region subjected to high wear and rope contact during belaying and rappelling. Groove depths were varied incrementally from 0 mm (ungrooved control) to 7 mm, simulating realistic progression of wear. The cross-sectional area, which is taken perpendicular to the notch as shown in Fig. 1 b, is reduced by up to 76% in the deepest 7 mm groove. The groove depth was measured as the perpendicular distance from the inner curve along the major axis of the carabiner to the deepest point of the groove. All models were exported as STEP files and imported into Abaqus CAE for meshing and simulation. To simulate fall forces experienced during lead climbing, experimental equivalence was used to apply a monotonically increasing vertical load to the inner surface of the basket region, where the rope typically contacts the carabiner. Specifically, a surface with an area of 40 mm 2 was defined at the deepest portion of each simulated wear groove to represent the contact area of a rope. A reference point was created 70 mm above the centroid of this surface to mimic the offset height from which force would be applied in a real world climbing scenario. A tie constraint was used to couple the defined surface to the reference point, and a vertical displacement of 4 mm was applied to that point. This setup induced strain in the groove region and across the carabiner in a manner consistent with how a rope under tension would load the carabiner during a fall, providing a realistic approximation of rope-carabiner interaction under dynamic conditions. The modeled 4 mm displacement is consistent with the displacement observed during real world tests to failure. The band of material at the runner end (highlighted blue in Fig. 1 e) was fully constrained in all translational and rotational degrees of freedom to simulate anchoring to a fixed point. 2.2. Material Properties All simulations assumed the frame of the carabiner was made of 7075-T6 aluminum alloy, a material commonly used in climbing gear due to its excellent strength-to-weight ratio. The elastic properties used in the simulation were a Young’s modulus of 71.7 GPa and a Poisson’s ratio of 0.33 [ 16 ]. Plastic deformation of the aluminum alloy was modeled using a true stress-strain curve extracted from [ 9 ], as shown in Fig. 2 , specifying the flow stress as a function of strain to capture the non-linear, plastic behavior of the alloy. This curve, which was fully incorporated into the simulation, extended beyond the yield stress (σ y,0.2 = 503 MPa) encompassing ~ 80 data points to ensure accuracy in post-yield response modeling. The wire gate was modeled using material properties for cold-drawn stainless steel 304, representative of commercial carabiners. The cold-drawing process significantly increases the strength and hardness of the wire, giving it the necessary spring-like qualities to function as a gate. The steel was assigned a Young’s modulus of 200 GPa and a Poisson’s ratio of 0.29 [ 17 ]. To capture its post-yield behavior, a true stress-strain curve specific to stainless steel 304 was also implemented using data extracted from literature [ 15 ], showing a yield stress of 676 MPa and moderate strain hardening in the plastic range. Yield stress values were determined using the 0.2% offset method for both stress-strain curves. 2.3. Meshing and Simulation Setup Due to the complex, curved geometry of the carabiner and its grooved regions, a tetrahedral mesh was used, as shown in Fig. 1 . The global seed size was set to 0.13 mm, with mesh refinement performed iteratively to ensure convergence of the simulation and accurate capture of stress concentrations, especially around the groove. Forces ranging from 4 to 8 kN were applied, mimicking the range of loads typically seen in lead climbing falls, based on field data from prior studies [ 6 ]. These forces were chosen to evaluate both typical and worst-case loading conditions, well below the catastrophic failure threshold of new, ungrooved carabiners, which are rated at 20 kN by the International Climbing and Mountaineering Federation [ 18 ]. 2.4. Simulation Type and Critical Load Criteria Each simulation was conducted as a “dynamic explicit analysis” in Abaqus to capture time-dependent force-displacement and stress distribution responses. The von Mises stress was used as the primary metric to assess onset of plasticity, a precursor to failure (which is not modeled here). Here, we define functional failure as the point at which an entire cross-section of the grooved region of the carabiner reached the tensile yield strength of 7075-T6 aluminum alloy (503 MPa). We refer to this point using the term “critical load” in the following. This criterion represents the transition from elastic to plastic behavior across the full cross-sectional area at the groove, indicating large-scale plastic deformation in the carabiner. To quantify performance loss, the ultimate load-bearing capacity was defined as the maximum force sustained by the ungrooved carabiner before this threshold was reached - measured at ~ 22 kN (Fig. 4 ). This value served as the baseline for calculating strength reduction across grooved models. An example of failure onset, where the von Mises stress throughout a cross-section of the groove reaches or exceeds 503 MPa, is shown in Fig. 3 . No contact modeling was used for the gate or rope interaction, as the focus was on evaluating stress and deformation due to applied loading. Modeling material contact friction or sliding is left for future work, as is the effect of fatigue cracks. 3. Results Finite Element simulations across groove depths from 0 to 7 mm reveal a progressive decrease in load-bearing capacity with increasing wear, as expected. The primary metrics analyzed are (i) maximum force sustained before large-scale plastic deformation, (ii) total displacement, and (iii) von Mises stress distribution, particularly in the groove and spine regions (the spine, shown in Fig. 1 d, is opposite the gate and typically bears most of the load). 3.1. Force vs. Displacement Behavior As shown in Fig. 4 , the mechanical response of each carabiner varies systematically with groove depth. For the ungrooved carabiner, plastic deformation begins at ~ 8.5 kN and the load increases steadily to 22 kN, the critical load where the cross section reaches the yield strength of 7075-T6 aluminum. All simulations are terminated at a displacement of 4 mm, which is beyond the “critical load” for every carabiner. For the 3 mm groove (corresponding to 32% cross-sectional area reduction), large-scale plastic deformation begins at a load of ~ 5.5 kN, and the carabiner reaches its “critical load” at ~ 6.1 kN, well below the force typically experienced in worst-case lead climbing falls (10 kN). For the deepest 7 mm groove depth, yielding begins at ~ 1.6 kN, and the “critical load” is at ~ 5.1 kN. Grooved carabiners not only reach this threshold at lower loads but also exhibit reduced energy absorption, which is defined as the area under the force–displacement curve up to the point of critical load. These results emphasize the importance of both groove depth and displacement-based criteria when evaluating carabiner degradation. Under an identical load of 8 kN, which corresponds to the maximum load experienced in a fall, Fig. 5 shows the von Mises average stress values for carabiners with varying groove depths. A groove of 3 mm exceeds the yield strength of 7075-T6 aluminum (503 MPa) under an 8 kN force after accounting for standard error. This makes 3 mm a useful estimated threshold for the onset of plastic deformation under lead fall loads, and a measurable criterion for establishing a safety retirement guideline. Strain hardening is also analyzed by comparing the force at the onset of plastic deformation (shown with white dots on Fig. 4 ) with the force when the carabiner experiences “critical load.” This difference reflects the material’s ability to carry additional load after yielding, which prevents sudden failure. In the ungrooved carabiner, the force increases from 8.5 kN at yield (0.15 mm) to a peak of 22 kN at 1.5 mm, indicating substantial strain hardening. In contrast, the carabiner with a deep 7 mm groove shows a smaller increase from 1.6 kN at yield (0.13 mm) to 5.1 kN (when it fails at 0.43 mm), demonstrating significantly reduced strain hardening. This smaller load increment in the plastic range suggests that heavily worn carabiners are more susceptible to catastrophic failure, as they have a reduced capacity to strengthen as they deform plastically. These trends are illustrated in Fig. 4 , where the approximate onset of yielding is marked on each force–displacement curve with a white dot. The decreasing slope beyond yield with groove depth reflects the progressive loss of energy absorption. Stress concentrations are consistently located at the basket region - where the groove is created - and extends to the spine-gate interface. For groove depths of 3 mm and above, the simulations indicate that the average stress values over each carabiner’s cross section surpasses the yield stress of 7075-T6 aluminum alloy, suggesting the onset of plastic deformation in the carabiner. At groove depths of 5–7 mm, the simulations show a rise in localized stress in the groove region, while the force–displacement response plateaued, indicating that the carabiner has reached its maximum load-bearing capacity with minimal additional resistance to deformation. These results reinforce the conclusion that groove depth is an important element of carabiner strength, but significant visible wear is required to pose serious risks under typical lead climbing forces. 4. Discussion Through Finite Element Analysis, we observe that carabiners with grooves as shallow as 3 mm exhibit a significant reduction in load-bearing capacity under fall forces typical of lead climbing. While these grooves cause localized von Mises stress to exceed the yield strength of 7075-T6 aluminum (503 MPa), yielding is not used as a failure criterion. Instead, we evaluate a “critical load” where the entire cross-section of the grooved region of the carabiner reaches/exceeds the tensile yield strength of 7075-T6 aluminum alloy. Under this framework, grooved carabiners - particularly those with grooves at or beyond 3 mm - demonstrate a loss of up to 70.4% of their original load-bearing capacity, measured relative to the critical load of the ungrooved carabiner (22 kN). This critical load drops below 6 kN in models with deeper grooves, a level that presents a clear safety risk even if the part has not yet fractured. According to the UIAA, new, unworn carabiners must withstand a force of at least 20 kN [ 18 ]. However, our study shows that worn carabiners with grooves ≥ 3 mm can exhibit extensive plastic deformation and reach a plateau in load-bearing capacity at or below 8 kN - a dramatic 64% strength reduction. Thus, groove wear is an unaccounted but critical factor in carabiner degradation, and retirement guidelines should reflect groove-based failure thresholds. Future work should address several limitations existing in the present numerical study which were conducted under simplified conditions; in particular, corrosion, asymmetric loading, and rope-induced heating (and associated oxidation and softening) are ignored - all of which can significantly influence material behavior and accelerate critical load. Additionally, groove wear is modeled as a single, uniform circular groove (as illustrated in Fig. 1 d), whereas in practice, wear patterns can be irregular, asymmetrical, or combined with other damage types such as pitting or gate deformation which create additional stress concentrations. Furthermore, dynamic interactions with climbing ropes are not included in the model. In actual climbing scenarios, the movement and friction of the rope can introduce localized stresses and fatigue damage (cracks) which are not captured in static simulations, potentially leading to premature failure. Additionally, carabiners with solid gates are more prone to gate flutter, a momentary opening of the gate, which can lead to exceptionally low carabiner strength when combined with carabiner grooves. There is a need for modeling cyclic loading, multi-groove wear, crack formation, or incorporating non-destructive evaluation techniques (e.g., dye penetrant inspection or digital surface scanning) to validate groove depth and cracks in field-used carabiners. Additionally, experimental tensile testing of worn carabiners could offer comparison with, and validation of, FEM predictions and further strengthen the case for updated safety guidelines. 5. Conclusions This study used finite element modeling to evaluate how rope-induced wear grooves affect the strength and deformation behavior of aluminum carabiners under static loads. We find that groove depth significantly reduces structural integrity, and even moderate wear, such as a 3 mm groove corresponding to a 32% area reduction, causes large-scale plastic deformation that extends beyond the immediate groove region. Grooved carabiners deform earlier and develop higher stress concentrations, which reduces their ability to absorb energy during falls. As groove depth increases, the load-bearing capacity drops to as little as 20–30% of the ungrooved maximum value (~22 kN), falling well below the 8 kN threshold typically encountered in lead climbing falls. Carabiners with groove depths of 3 mm or greater plateau at or below 8 kN, representing a 64% strength reduction relative to the 20 kN required by UIAA standards. Taken together, these results demonstrate that quantifying groove depth provides a more objective and field-relevant retirement criterion than current subjective or yield-based assessments. Declarations CRediT authorship contribution statement: Atmaj Shelar : Writing – review & editing, Writing – original draft, Visualization, Validation, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. John P. Misiaszek : Writing – review & editing, Validation, Methodology, Formal analysis, Conceptualization. David C. Dunand : Writing – review & editing, Supervision, Methodology, Conceptualization. Declaration of Competing Interests: The authors declare that they have no conflict of interest. Acknowledgments: This work made use of Northwestern University’s MRSEC (Materials Research Science and Engineering Center) program (NSF DMR-2308691), Materials Characterization Laboratory (MatCI) and the Central Laboratory for Materials Mechanical Properties (CLaMMP), which received support from the MRSEC program (NSF DMR-2308691). The authors thank Ryan Jenks and the HowNOT2 team for their assistance in providing carabiners machined to simulate wear, shown in Fig. 1c. The authors acknowledge financial support from the National Science Foundation through grant DMR- 2317002 and the GEM National Consortium, sponsored through Idaho National Lab (for JPM). AS was supported by IMSA through the Student Inquiry and Research program. References D. G. Addiss and S. P. Baker, “Mountaineering and rock-climbing injuries in US national parks,” Annals of Emergency Medicine , vol. 18, no. 9, pp. 975–979, Sept. 1989, doi: 10.1016/s0196-0644(89)80463-9. M. R. M. Aliha, A. Bahmani, and S. 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Available: https://www.asminternational.org/technical-books/-/journal_content/56/10192/05387G/PUBLICATION. [Accessed: Sep. 28, 2025]. International Climbing and Mountaineering Federation, "UIAA 121 Connectors (Karabiners)," UIAA Safety Standard, May 2022. [Online]. Available: https://www.theuiaa.org/documents/safety-standards/121_UIAAConnectors_V4_2018.pdf [Accessed: Sep. 28, 2025]. Additional Declarations The authors declare no competing interests. Supplementary Files SupplementaryMaterialEffectofLocalizedWearDamageonStrengthofClimbingCarabiners.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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18:15:35","extension":"png","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":44607,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7942642/v1/82b90fe8020c07483cd5c952.png"},{"id":94584246,"identity":"66cb5e42-6254-43ad-af41-3be6881ffb66","added_by":"auto","created_at":"2025-10-28 18:15:04","extension":"xml","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":54198,"visible":true,"origin":"","legend":"","description":"","filename":"rs79426420structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7942642/v1/73b1dbab24f9692fd942aa41.xml"},{"id":94584208,"identity":"662fa3fe-faf0-4793-9395-09b4e4978848","added_by":"auto","created_at":"2025-10-28 18:15:01","extension":"html","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":60792,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7942642/v1/aafed407fe8e0cadbc2f39a5.html"},{"id":94584541,"identity":"9c823fe6-b687-4095-8db7-36f78852cd7b","added_by":"auto","created_at":"2025-10-28 18:15:18","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1030503,"visible":true,"origin":"","legend":"\u003cp\u003eStress and geometry comparisons of carabiners with and without wear-induced groove. (a) Von Mises stress distribution in ungrooved carabiner under a 6 kN load. (b) Von Mises stress in carabiner with the deepest 7 mm groove under a 6 kN load. (c) Photograph of aluminum carabiner, machined to simulate wear. Cells in the background are 5 mm by 5mm. (d) Meshed FEM model labeled to show features of the carabiner with a red area representing the basket region where the groove develops. (e) The region highlighted in blue indicates where the nodes at the surface of the model were constrained.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7942642/v1/b87656482b081dd006f1c22b.jpeg"},{"id":94584101,"identity":"4459a648-c6c9-476a-9285-6ce16f835eda","added_by":"auto","created_at":"2025-10-28 18:14:48","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":163792,"visible":true,"origin":"","legend":"\u003cp\u003eThe stress-strain curves for 7075-T6 aluminum [9] and 304 stainless steel [15], used as input for the model. The yield stress is shown as a point on each curve.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7942642/v1/05c270742cb7565ebfaf19f0.png"},{"id":94584545,"identity":"132e5c3d-2963-4128-a8da-20025a6b99d0","added_by":"auto","created_at":"2025-10-28 18:15:19","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":531960,"visible":true,"origin":"","legend":"\u003cp\u003eVon Mises stress distribution for a carabiner with a 3 mm groove (cross-sectional area reduction of 32%) under a ~6 kN applied load and a displacement of ~1.44 mm. Grey region displays where the von Mises stress exceeds the 503 MPa yield strength of 7075-T6 aluminum (a) full carabiner model showing overall stress distribution. (b) magnified view of the groove region (black line shows where the cross-section is taken) (c) Cross-section view of stress distribution halfway across the width of the carabiner (along black line in (b)), showing plastic region (grey) spanning the cross-section.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7942642/v1/21c3213450080020860799e0.png"},{"id":94584234,"identity":"202b28d4-0923-42d4-b9b6-d417c96050a2","added_by":"auto","created_at":"2025-10-28 18:15:03","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":482236,"visible":true,"origin":"","legend":"\u003cp\u003eThe force vs displacement curves for all carabiner groove depths (0-7 mm). The white dots indicate the approximate onset of yielding for each carabiner and the black dots are the critical load, where the totality of the cross section reaches the yield strength of 7075-T6 aluminum. The black horizontal line at 8 kN represents the maximum force experienced in a lead climbing fall. The inset graph illustrates how the carabiner critical load decreases as groove depth increases.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7942642/v1/f85db89e2784634ce2e7df6e.png"},{"id":94584794,"identity":"69d5ef21-fa8d-4a75-83f4-498694b6f6a6","added_by":"auto","created_at":"2025-10-28 18:15:38","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":172792,"visible":true,"origin":"","legend":"\u003cp\u003eVon Mises stress values for carabiners with varying groove depths under identical load of 8 kN, taken as an average across the minimum groove cross-section. Error bars are representative of one standard deviation around the average value. Numbers above points represent notch depth in mm. The dotted red line is the yield strength of 7075-T6 aluminum.\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7942642/v1/0ad229ed5bdd7daa6f7db06c.jpeg"},{"id":94595540,"identity":"ad1c3717-ee91-4b4e-8f94-66ae3f92bc10","added_by":"auto","created_at":"2025-10-28 18:34:25","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2714738,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7942642/v1/9c092161-86ac-4e23-9838-be2c8babe28b.pdf"},{"id":94584077,"identity":"a3efb8f9-26cd-4f33-987e-b37fdd67331c","added_by":"auto","created_at":"2025-10-28 18:14:47","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":287758,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterialEffectofLocalizedWearDamageonStrengthofClimbingCarabiners.docx","url":"https://assets-eu.researchsquare.com/files/rs-7942642/v1/90220a1fb4566e8a2087bd02.docx"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eEffect of Localized Wear Damage on Strength of Climbing Carabiners \u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eClimbing carabiners are one of the most important tools to ensure the safety of climbers who critically depend on the durability of their equipment. A carabiner is a metal loop (usually made from high-strength aluminum alloy) with a spring-loaded steel gate that is used to secure harnesses, ropes, or other climbing gear. Despite manufacturer ratings for maximum vertical force and modern production methods, carabiners are known to fail when in use, which can result in potentially catastrophic accidents that cause injuries or even death. Several studies have examined the causes of rock-climbing accidents. Falls account for 75% of cases in traditional climbing [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], and equipment failure, including carabiner failure, contributes significantly to climbing injuries and fatalities. Approximately 10% of all mountain-climbing accidents are gear-related, and of these, almost all involve some type of carabiner failure [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAn important factor that compromises the structural integrity of aluminum carabiners is the development of wear-induced grooves on their surface after prolonged use. These grooves develop when the repeated back-and-forth movement of a climbing rope wears away the alloy, forming a notch. This wear-induced material loss occurs most as the rope slides under tension, usually during belaying or rappelling. Although dangerous, this wear damage is not accounted for in manufacturer ratings, leaving it to the climber\u0026rsquo;s judgment to decide when a carabiner is no longer safe to use. In September 2011, a climber in Kentucky\u0026rsquo;s Red River Gorge took a lead fall between the first and second bolt, loading a fixed aluminum quickdraw with a significant groove wear, severing his rope and causing a ground fall [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe standard industry practice for testing and rating the strength of carabiners involves single pull-to-failure tests. These tests return the maximum tensile strength of the carabiner. However, in the field, carabiners do not fail in a single pull. They usually fracture after multiple loads, indicating low-cycle fatigue failure, and they can be loaded up to 20 kN [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. To simulate the weight of a climber taking a lead fall on a dynamic rope attached to the carabiner, this research used a range of forces from 4 to 8 kN. A force below 4 kN is insufficient to affect the carabiner and a force over 8 kN would cause significant physical harm to the climber before the carabiner poses durability issues [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eHere, we develop detailed carabiner models with different groove depths and use Finite Element Modeling (FEM) to replicate the geometrical and material characteristics of aluminum climbing carabiners subjected to forces representative of the impact of a climber's fall. We determine the groove depth for which the carabiners' structural integrity is reduced to the point of large-scale deformation (and thus functional failure) by computing the force-displacement curves of carabiners with various groove depths. This study establishes a relationship between groove depth and carabiner load-bearing capacity, and it provides climbers and manufacturers with actionable data to enhance safety standards and reduce climbing-related accidents.\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cp\u003eTo analyze the impact of groove depth on the structural integrity of climbing carabiners, a Finite Element Modeling (FEM) approach was adopted to evaluate how grooved carabiners deform under a single tensile loading scenario representative of fall forces in lead climbing. A comprehensive overview of the FEM method is provided in [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], which describes it as a numerical technique for approximating solutions to complex engineering problems by discretizing a structure into smaller elements. The work also outlines the method\u0026rsquo;s historical development, mathematical foundations, and broad applicability to structural mechanics and related fields.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. CAD Modeling\u003c/h2\u003e\u003cp\u003eThe base geometry of the carabiner model was first created and refined in Autodesk Fusion 360. A reference model was imported, with several modifications made to ensure dimensional accuracy and compatibility with Abaqus 2023 simulations. The final model (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed) measured 100.0 mm in height, 58.8 mm in width, and had a cross-sectional width of 11.1 mm, closely matching the dimensions of commercially available carabiners.\u003c/p\u003e\u003cp\u003eGrooves were modeled as semicircular notches with a radius of curvature of 5 mm, mimicking real-world wear from climbing ropes (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). These grooves were located at the basket area, a region subjected to high wear and rope contact during belaying and rappelling. Groove depths were varied incrementally from 0 mm (ungrooved control) to 7 mm, simulating realistic progression of wear. The cross-sectional area, which is taken perpendicular to the notch as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb, is reduced by up to 76% in the deepest 7 mm groove. The groove depth was measured as the perpendicular distance from the inner curve along the major axis of the carabiner to the deepest point of the groove. All models were exported as STEP files and imported into Abaqus CAE for meshing and simulation.\u003c/p\u003e\u003cp\u003eTo simulate fall forces experienced during lead climbing, experimental equivalence was used to apply a monotonically increasing vertical load to the inner surface of the basket region, where the rope typically contacts the carabiner. Specifically, a surface with an area of 40 mm\u003csup\u003e2\u003c/sup\u003e was defined at the deepest portion of each simulated wear groove to represent the contact area of a rope. A reference point was created 70 mm above the centroid of this surface to mimic the offset height from which force would be applied in a real world climbing scenario. A tie constraint was used to couple the defined surface to the reference point, and a vertical displacement of 4 mm was applied to that point. This setup induced strain in the groove region and across the carabiner in a manner consistent with how a rope under tension would load the carabiner during a fall, providing a realistic approximation of rope-carabiner interaction under dynamic conditions. The modeled 4 mm displacement is consistent with the displacement observed during real world tests to failure. The band of material at the runner end (highlighted blue in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee) was fully constrained in all translational and rotational degrees of freedom to simulate anchoring to a fixed point.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Material Properties\u003c/h2\u003e\u003cp\u003eAll simulations assumed the frame of the carabiner was made of 7075-T6 aluminum alloy, a material commonly used in climbing gear due to its excellent strength-to-weight ratio. The elastic properties used in the simulation were a Young\u0026rsquo;s modulus of 71.7 GPa and a Poisson\u0026rsquo;s ratio of 0.33 [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e\u003cp\u003ePlastic deformation of the aluminum alloy was modeled using a true stress-strain curve extracted from [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, specifying the flow stress as a function of strain to capture the non-linear, plastic behavior of the alloy. This curve, which was fully incorporated into the simulation, extended beyond the yield stress (σ\u003csub\u003ey,0.2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;503 MPa) encompassing\u0026thinsp;~\u0026thinsp;80 data points to ensure accuracy in post-yield response modeling.\u003c/p\u003e\u003cp\u003eThe wire gate was modeled using material properties for cold-drawn stainless steel 304, representative of commercial carabiners. The cold-drawing process significantly increases the strength and hardness of the wire, giving it the necessary spring-like qualities to function as a gate. The steel was assigned a Young\u0026rsquo;s modulus of 200 GPa and a Poisson\u0026rsquo;s ratio of 0.29 [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. To capture its post-yield behavior, a true stress-strain curve specific to stainless steel 304 was also implemented using data extracted from literature [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], showing a yield stress of 676 MPa and moderate strain hardening in the plastic range. Yield stress values were determined using the 0.2% offset method for both stress-strain curves.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Meshing and Simulation Setup\u003c/h2\u003e\u003cp\u003eDue to the complex, curved geometry of the carabiner and its grooved regions, a tetrahedral mesh was used, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The global seed size was set to 0.13 mm, with mesh refinement performed iteratively to ensure convergence of the simulation and accurate capture of stress concentrations, especially around the groove.\u003c/p\u003e\u003cp\u003eForces ranging from 4 to 8 kN were applied, mimicking the range of loads typically seen in lead climbing falls, based on field data from prior studies [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. These forces were chosen to evaluate both typical and worst-case loading conditions, well below the catastrophic failure threshold of new, ungrooved carabiners, which are rated at 20 kN by the International Climbing and Mountaineering Federation [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Simulation Type and Critical Load Criteria\u003c/h2\u003e\u003cp\u003eEach simulation was conducted as a \u0026ldquo;dynamic explicit analysis\u0026rdquo; in Abaqus to capture time-dependent force-displacement and stress distribution responses. The von Mises stress was used as the primary metric to assess onset of plasticity, a precursor to failure (which is not modeled here). Here, we define functional failure as the point at which an entire cross-section of the grooved region of the carabiner reached the tensile yield strength of 7075-T6 aluminum alloy (503 MPa). We refer to this point using the term \u0026ldquo;critical load\u0026rdquo; in the following. This criterion represents the transition from elastic to plastic behavior across the full cross-sectional area at the groove, indicating large-scale plastic deformation in the carabiner.\u003c/p\u003e\u003cp\u003eTo quantify performance loss, the ultimate load-bearing capacity was defined as the maximum force sustained by the ungrooved carabiner before this threshold was reached - measured at ~\u0026thinsp;22 kN (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). This value served as the baseline for calculating strength reduction across grooved models. An example of failure onset, where the von Mises stress throughout a cross-section of the groove reaches or exceeds 503 MPa, is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eNo contact modeling was used for the gate or rope interaction, as the focus was on evaluating stress and deformation due to applied loading. Modeling material contact friction or sliding is left for future work, as is the effect of fatigue cracks.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eFinite Element simulations across groove depths from 0 to 7 mm reveal a progressive decrease in load-bearing capacity with increasing wear, as expected. The primary metrics analyzed are (i) maximum force sustained before large-scale plastic deformation, (ii) total displacement, and (iii) von Mises stress distribution, particularly in the groove and spine regions (the spine, shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed, is opposite the gate and typically bears most of the load).\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Force vs. Displacement Behavior\u003c/h2\u003e\u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the mechanical response of each carabiner varies systematically with groove depth. For the ungrooved carabiner, plastic deformation begins at ~\u0026thinsp;8.5 kN and the load increases steadily to 22 kN, the critical load where the cross section reaches the yield strength of 7075-T6 aluminum. All simulations are terminated at a displacement of 4 mm, which is beyond the \u0026ldquo;critical load\u0026rdquo; for every carabiner. For the 3 mm groove (corresponding to 32% cross-sectional area reduction), large-scale plastic deformation begins at a load of ~\u0026thinsp;5.5 kN, and the carabiner reaches its \u0026ldquo;critical load\u0026rdquo; at ~\u0026thinsp;6.1 kN, well below the force typically experienced in worst-case lead climbing falls (10 kN). For the deepest 7 mm groove depth, yielding begins at ~\u0026thinsp;1.6 kN, and the \u0026ldquo;critical load\u0026rdquo; is at ~\u0026thinsp;5.1 kN.\u003c/p\u003e\u003cp\u003eGrooved carabiners not only reach this threshold at lower loads but also exhibit reduced energy absorption, which is defined as the area under the force\u0026ndash;displacement curve up to the point of critical load. These results emphasize the importance of both groove depth and displacement-based criteria when evaluating carabiner degradation.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eUnder an identical load of 8 kN, which corresponds to the maximum load experienced in a fall, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the von Mises average stress values for carabiners with varying groove depths. A groove of 3 mm exceeds the yield strength of 7075-T6 aluminum (503 MPa) under an 8 kN force after accounting for standard error. This makes 3 mm a useful estimated threshold for the onset of plastic deformation under lead fall loads, and a measurable criterion for establishing a safety retirement guideline.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eStrain hardening is also analyzed by comparing the force at the onset of plastic deformation (shown with white dots on Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) with the force when the carabiner experiences \u0026ldquo;critical load.\u0026rdquo; This difference reflects the material\u0026rsquo;s ability to carry additional load after yielding, which prevents sudden failure. In the ungrooved carabiner, the force increases from 8.5 kN at yield (0.15 mm) to a peak of 22 kN at 1.5 mm, indicating substantial strain hardening. In contrast, the carabiner with a deep 7 mm groove shows a smaller increase from 1.6 kN at yield (0.13 mm) to 5.1 kN (when it fails at 0.43 mm), demonstrating significantly reduced strain hardening. This smaller load increment in the plastic range suggests that heavily worn carabiners are more susceptible to catastrophic failure, as they have a reduced capacity to strengthen as they deform plastically. These trends are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, where the approximate onset of yielding is marked on each force\u0026ndash;displacement curve with a white dot. The decreasing slope beyond yield with groove depth reflects the progressive loss of energy absorption.\u003c/p\u003e\u003cp\u003eStress concentrations are consistently located at the basket region - where the groove is created - and extends to the spine-gate interface. For groove depths of 3 mm and above, the simulations indicate that the average stress values over each carabiner\u0026rsquo;s cross section surpasses the yield stress of 7075-T6 aluminum alloy, suggesting the onset of plastic deformation in the carabiner. At groove depths of 5\u0026ndash;7 mm, the simulations show a rise in localized stress in the groove region, while the force\u0026ndash;displacement response plateaued, indicating that the carabiner has reached its maximum load-bearing capacity with minimal additional resistance to deformation. These results reinforce the conclusion that groove depth is an important element of carabiner strength, but significant visible wear is required to pose serious risks under typical lead climbing forces.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThrough Finite Element Analysis, we observe that carabiners with grooves as shallow as 3 mm exhibit a significant reduction in load-bearing capacity under fall forces typical of lead climbing. While these grooves cause localized von Mises stress to exceed the yield strength of 7075-T6 aluminum (503 MPa), yielding is not used as a failure criterion. Instead, we evaluate a \u0026ldquo;critical load\u0026rdquo; where the entire cross-section of the grooved region of the carabiner reaches/exceeds the tensile yield strength of 7075-T6 aluminum alloy. Under this framework, grooved carabiners - particularly those with grooves at or beyond 3 mm - demonstrate a loss of up to 70.4% of their original load-bearing capacity, measured relative to the critical load of the ungrooved carabiner (22 kN).\u003c/p\u003e\u003cp\u003eThis critical load drops below 6 kN in models with deeper grooves, a level that presents a clear safety risk even if the part has not yet fractured. According to the UIAA, new, unworn carabiners must withstand a force of at least 20 kN [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. However, our study shows that worn carabiners with grooves\u0026thinsp;\u0026ge;\u0026thinsp;3 mm can exhibit extensive plastic deformation and reach a plateau in load-bearing capacity at or below 8 kN - a dramatic 64% strength reduction. Thus, groove wear is an unaccounted but critical factor in carabiner degradation, and retirement guidelines should reflect groove-based failure thresholds.\u003c/p\u003e\u003cp\u003eFuture work should address several limitations existing in the present numerical study which were conducted under simplified conditions; in particular, corrosion, asymmetric loading, and rope-induced heating (and associated oxidation and softening) are ignored - all of which can significantly influence material behavior and accelerate critical load. Additionally, groove wear is modeled as a single, uniform circular groove (as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed), whereas in practice, wear patterns can be irregular, asymmetrical, or combined with other damage types such as pitting or gate deformation which create additional stress concentrations. Furthermore, dynamic interactions with climbing ropes are not included in the model. In actual climbing scenarios, the movement and friction of the rope can introduce localized stresses and fatigue damage (cracks) which are not captured in static simulations, potentially leading to premature failure. Additionally, carabiners with solid gates are more prone to gate flutter, a momentary opening of the gate, which can lead to exceptionally low carabiner strength when combined with carabiner grooves.\u003c/p\u003e\u003cp\u003eThere is a need for modeling cyclic loading, multi-groove wear, crack formation, or incorporating non-destructive evaluation techniques (e.g., dye penetrant inspection or digital surface scanning) to validate groove depth and cracks in field-used carabiners. Additionally, experimental tensile testing of worn carabiners could offer comparison with, and validation of, FEM predictions and further strengthen the case for updated safety guidelines.\u003c/p\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eThis study used finite element modeling to evaluate how rope-induced wear grooves affect the strength and deformation behavior of aluminum carabiners under static loads. We find that groove depth significantly reduces structural integrity, and even moderate wear, such as a 3 mm groove corresponding to a 32% area reduction, causes large-scale plastic deformation that extends beyond the immediate groove region. Grooved carabiners deform earlier and develop higher stress concentrations, which reduces their ability to absorb energy during falls. As groove depth increases, the load-bearing capacity drops to as little as 20\u0026ndash;30% of the ungrooved maximum value (~22 kN), falling well below the 8 kN threshold typically encountered in lead climbing falls. Carabiners with groove depths of 3 mm or greater plateau at or below 8 kN, representing a 64% strength reduction relative to the 20 kN required by UIAA standards. Taken together, these results demonstrate that quantifying groove depth provides a more objective and field-relevant retirement criterion than current subjective or yield-based assessments.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAtmaj Shelar\u003c/strong\u003e: Writing \u0026ndash; review \u0026amp; editing, Writing \u0026ndash; original draft, Visualization, Validation, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. \u003cstrong\u003eJohn P. Misiaszek\u003c/strong\u003e: Writing \u0026ndash; review \u0026amp; editing, Validation, Methodology, Formal analysis, Conceptualization. \u003cstrong\u003eDavid C. Dunand\u003c/strong\u003e: Writing \u0026ndash; review \u0026amp; editing, Supervision, Methodology, Conceptualization.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of Competing Interests:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work made use of Northwestern University\u0026rsquo;s MRSEC (Materials Research Science and Engineering Center) program (NSF DMR-2308691), Materials Characterization Laboratory (MatCI) and the Central Laboratory for Materials Mechanical Properties (CLaMMP), which received support from the MRSEC program (NSF DMR-2308691). The authors thank Ryan Jenks and the HowNOT2 team for their assistance in providing carabiners machined to simulate wear, shown in Fig. 1c. The authors acknowledge financial support from the National Science Foundation through grant DMR- 2317002 and the GEM National Consortium, sponsored through Idaho National Lab (for JPM). AS was supported by IMSA through the Student Inquiry and Research program.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eD. G. Addiss and S. P. Baker, \u0026ldquo;Mountaineering and rock-climbing injuries in US national parks,\u0026rdquo; \u003cem\u003eAnnals of Emergency Medicine\u003c/em\u003e, vol. 18, no. 9, pp. 975\u0026ndash;979, Sept. 1989, doi: 10.1016/s0196-0644(89)80463-9.\u003c/li\u003e\n\u003cli\u003eM. R. M. Aliha, A. Bahmani, and S. Akhondi, \u0026ldquo;Fracture and fatigue analysis for a cracked carabiner using 3D finite element simulations,\u0026rdquo; \u003cem\u003eStrength of Materials\u003c/em\u003e, vol. 47, no. 6, pp. 890\u0026ndash;902, Nov. 2015, doi: 10.1007/s11223-015-9726-z.\u003c/li\u003e\n\u003cli\u003eK. B. Blair, D. R. Custer, J. M. Graham, and M. H. Okal, \u0026ldquo;Analysis of fatigue failure in D-shaped karabiners,\u0026rdquo; \u003cem\u003eSports Engineering\u003c/em\u003e, vol. 8, no. 2, pp. 107\u0026ndash;113, Dec. 2005, doi: 10.1007/BF02844009.\u003c/li\u003e\n\u003cli\u003eP. Buzzacott, I. Sch\u0026ouml;ffl, J. Chimiak, and V. Sch\u0026ouml;ffl, \u0026ldquo;Rock climbing injuries treated in US emergency departments, 2008\u0026ndash;2016,\u0026rdquo; \u003cem\u003eWilderness \u0026amp; Environmental Medicine\u003c/em\u003e, vol. 30, no. 2, pp. 121\u0026ndash;128, June 2019, doi: 10.1016/j.wem.2018.11.009.\u003c/li\u003e\n\u003cli\u003eT. Fett, \u0026ldquo;Stress intensity factors and T-stress for internally cracked circular disks under various boundary conditions,\u0026rdquo; \u003cem\u003eEngineering Fracture Mechanics\u003c/em\u003e, vol. 68, no. 9, pp. 1119\u0026ndash;1136, June 2001, doi: 10.1016/S0013-7944(01)00025-X.\u003c/li\u003e\n\u003cli\u003eJ. Graham, K. Blair, D. Custer, and M. H. Okal, \u003cem\u003eCarabiner Testing \u0026ndash; Final Report\u003c/em\u003e. Cambridge, MA, USA: Massachusetts Institute of Technology, May 16, 2001.\u003c/li\u003e\n\u003cli\u003eV. Jagota, A. P. S. Sethi, and K. Kumar, \u0026ldquo;Finite element method: An overview,\u0026rdquo; \u003cem\u003eWalailak Journal of Science and Technology (WJST)\u003c/em\u003e, vol. 10, no. 1, pp. 1\u0026ndash;8, Jan. 2013.\u003c/li\u003e\n\u003cli\u003eW.-S. Lee, T.-H. Chen, and C.-F. Lin, \u0026ldquo;Dynamic mechanical response of biomedical 316L stainless steel as function of strain rate and temperature,\u0026rdquo; \u003cem\u003eResearchGate\u003c/em\u003e, doi: 10.1155/2011/173782.\u003c/li\u003e\n\u003cli\u003eM. R. Maraki, A. Hosseinzadeh, and D. Ghahremani Moghadam, \u0026ldquo;Investigation of the notch angle effect on Charpy fracture energy in 7075-T651 aluminum alloy,\u0026rdquo; \u003cem\u003eJournal of Stress Analysis\u003c/em\u003e, vol. 5, no. 2, Mar. 2021, doi: 10.22084/jrstan.2021.23165.1165.\u003c/li\u003e\n\u003cli\u003eM. Pavier, \u0026ldquo;Experimental and theoretical simulations of climbing falls,\u0026rdquo; \u003cem\u003eSports Engineering\u003c/em\u003e, vol. 1, no. 2, pp. 79\u0026ndash;91, Feb. 1999, doi: 10.1046/j.1460-2687.1999.00010.x.\u003c/li\u003e\n\u003cli\u003eK. J. R. Rasmussen, \u0026ldquo;Full-range stress\u0026ndash;strain curves for stainless steel alloys,\u0026rdquo; \u003cem\u003eJournal of Constructional Steel Research\u003c/em\u003e, vol. 59, no. 1, pp. 47\u0026ndash;61, Jan. 2003, doi: 10.1016/S0143-974X(02)00018-4.\u003c/li\u003e\n\u003cli\u003eS. Rauch, B. Wallner, M. Str\u0026ouml;hle, T. Dal Cappello, and M. Brodmann Maeder, \u0026ldquo;Climbing accidents\u0026mdash;prospective data analysis from the International Alpine Trauma Registry and systematic review of the literature,\u0026rdquo; \u003cem\u003eInternational Journal of Environmental Research and Public Health\u003c/em\u003e, vol. 17, no. 1, p. 203, Dec. 2019, doi: 10.3390/ijerph17010203.\u003c/li\u003e\n\u003cli\u003eC. X. Ren, Q. Wang, Z. J. Zhang, H. J. Yang, and Z. F. Zhang, \u0026ldquo;Enhanced tensile and bending yield strengths of 304 stainless steel and H62 brass by surface spinning strengthening,\u0026rdquo; Materials Science and Engineering: A, vol. 754, pp. 593\u0026ndash;601, Apr. 2019, doi: 10.1016/j.msea.2019.03.113.\u003c/li\u003e\n\u003cli\u003eK. Tanaka, Y. Teranishi, and S. Ujihashi, \u0026ldquo;Experimental and finite element analyses of a golf ball colliding with a simplified club during a two-dimensional swing,\u0026rdquo; \u003cem\u003eProcedia Engineering\u003c/em\u003e, vol. 2, no. 2, pp. 3249\u0026ndash;3254, June 2010, doi: 10.1016/j.proeng.2010.04.140.\u003c/li\u003e\n\u003cli\u003eR. R. Gomatam and E. Sancaktar, \u0026ldquo;A comprehensive fatigue life predictive model for electronically conductive adhesive joints under constant-cycle loading,\u0026rdquo; Journal of Adhesion Science and Technology, vol. 20, no. 1, pp. 87\u0026ndash;104, Jan. 2006, doi: 10.1163/156856106775212413.\u003c/li\u003e\n\u003cli\u003eThe Aluminum Association, \u0026ldquo;International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys,\u0026rdquo; Teal Sheet, Revised August 2018. [Online]. Available: https://www.aluminum.org/sites/default/files/2021-11/TealSheet.pdf. [Accessed: Sep. 28, 2025].\u003c/li\u003e\n\u003cli\u003eJ. R. Davis, Ed., Metals Handbook Desk Edition, 2nd ed. Materials Park, OH, USA: ASM International, 1998. [Online]. Available: https://www.asminternational.org/technical-books/-/journal_content/56/10192/05387G/PUBLICATION. [Accessed: Sep. 28, 2025]. \u003c/li\u003e\n\u003cli\u003eInternational Climbing and Mountaineering Federation, \u0026quot;UIAA 121 Connectors (Karabiners),\u0026quot; UIAA Safety Standard, May 2022. [Online]. Available: https://www.theuiaa.org/documents/safety-standards/121_UIAAConnectors_V4_2018.pdf [Accessed: Sep. 28, 2025].\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Northwestern University","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Finite Element Modeling, Climbing Safety, Wear Damage, Carabiner Strength, Plastic Deformation, Stress Concentration","lastPublishedDoi":"10.21203/rs.3.rs-7942642/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7942642/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eClimbing carabiners are critical safety tools in mountaineering, yet their failure due to wear and fatigue over time remains a fatal cause of climbing-related accidents. Manufacturer ratings are based on uniaxial tensile tests of new carabiners to failure, yet carabiners may develop wear grooves/notches over time that cause overloading failure during a lead-climbing fall. Current safety standards do not account for this wear, leaving climbers to subjectively determine the threshold for carabiner retirement. This study investigates the relationship between wear-induced groove depth and carabiner strength using Finite Element Modeling (FEM) to simulate stress-strain behavior of 7075-T6 aluminum carabiners under forces equivalent to realistic lead-climbing falls. Detailed carabiner models with varying groove depths identify the critical area reduction beyond which structural integrity is compromised. We find that for grooves deeper than 3 mm (corresponding to a 32% area reduction for a standard carabiner), carabiners experience a critical reduction in load-bearing capability as stress concentrations locally exceed the tensile yield strength of 7075-T6 aluminum, posing a safety risk under typical lead-climbing fall forces.\u003c/p\u003e","manuscriptTitle":"Effect of Localized Wear Damage on Strength of Climbing Carabiners","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-28 16:31:13","doi":"10.21203/rs.3.rs-7942642/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"47b203ea-3ecf-48cb-abf4-5e86973e42b5","owner":[],"postedDate":"October 28th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":56844966,"name":"Materials Engineering"},{"id":56844967,"name":"Mechanical Engineering"}],"tags":[],"updatedAt":"2025-10-28T16:31:13+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-28 16:31:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7942642","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7942642","identity":"rs-7942642","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}