Mechanical Engineering Department, Universidad Carlos III de Madrid, Leganés, 28911 Madrid, Spain.
Sensors (Basel). 2020 Mar 25;20(7):1814. doi: 10.3390/s20071814.
In this study, a finite element model of a bicycle crank arm are compared to experimental results. The structural integrity of the crank arm was analyzed in a universal dynamic test bench. The instrumentation used has allowed us to know the fatigue behavior of the component tested. For this, the prototype was instrumented with three rectangular strain gauge rosettes bonded in areas where failure was expected. With the measurements made by strain gauges and the forces registers from the load cell used, it has been possible to determine the state of the stresses for different loads and boundary conditions, which has subsequently been compared with a finite element model. The simulations show a good agreement with the experimental results, when the potential sources of uncertainties are considered in the validation process. This analysis allowed us to improve the original design, reducing its weight by 15%. The study allows us to identify the manufacturing process that requires the best metrological control to avoid premature crank failure. Finally, the numerical fatigue analysis carried out allows us to conclude that the new crank arm can satisfy the structural performance demanded by the international bicycle standard. Additionally, it can be suggested to the standard to include the verification that no permanent deformations have occurred in the crank arm during the fatigue test. It has been observed that, in some cases this bicycle component fulfils the minimum safety requirements, but presents areas with plastic strains, which if not taken into account can increase the risk of injury for the cyclist due to unexpected failure of the component.
在这项研究中，对自行车曲柄臂的有限元模型进行了比较，以实验结果。曲柄臂的结构完整性在通用动态测试台上进行了分析。所使用的仪器使我们能够了解测试部件的疲劳行为。为此，将原型用三个矩形应变计花键粘在预期失效的区域。通过应变计的测量和使用的负载单元记录的力，可以确定在不同载荷和边界条件下的应力状态，随后将其与有限元模型进行比较。考虑到验证过程中的潜在不确定源，模拟结果与实验结果吻合良好。该分析使我们能够改进原始设计，将其重量减轻 15%。该研究使我们能够确定需要最佳计量控制的制造工艺，以避免曲柄臂过早失效。最后，进行的数值疲劳分析使我们得出结论，新的曲柄臂可以满足国际自行车标准所要求的结构性能。此外，可以建议标准包括验证在疲劳试验期间曲柄臂没有发生永久变形。已经观察到，在某些情况下，这种自行车部件符合最低安全要求，但存在塑性应变区域，如果不加以考虑，可能会由于部件的意外失效而增加骑车者受伤的风险。
