This work introduces two innovative rolling pair concepts to minimize slippage and reduce mass in cam-roller systems of large-scale hydraulic drivetrains: The variable contact length and the Shifting Contact Geometry concepts. Both aim to improve traction in the low contact force phase in cyclically loaded rolling contacts. The shifting contact geometry concept was validated using three custom rolling contacts: a line contact, a double elliptical contact, and a combination of both (i.e., shifting contact geometry). The tests were conducted under synchronized cyclic loading to mimic the conditions in a hydraulic drivetrain. Furthermore, a model from previous work was implemented to make predictions and compare them against the experimental results. During preliminary tests, the double elliptical contact displayed superior tractive behavior than the line contact under the same load thanks to higher contact pressures. Under synchronized cyclic loading, the line contact displayed high sensitivity to applied resisting torques at low contact forces, leading to high slide-to-roll ratios and traction force peaks. In contrast, the rolling pair with shifting contact geometry exhibited minimum slippage even under high resisting torques, resulting in substantially lower (and in most cases negligible) slide-to-roll ratio and traction force peaks. The simulations also captured this behavior, proving the validity of the model for predicting and comparing the rolling-sliding dynamics of these two different rolling pairs. This study demonstrates that rolling pairs with shifting contact geometry can not only improve the tribological performance of cam-roller contacts in large-scale hydraulic drivetrains but also yield a more favorable dynamic behavior.

中文翻译：

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具有移动接触几何形状的滚动副：设计、开发和验证

这项工作引入了两个创新的滚动副概念，以最大限度地减少大型液压传动系统的凸轮滚子系统中的滑动并减少质量：可变接触长度和移动接触几何概念。两者的目的都是提高循环负载滚动接触中低接触力阶段的牵引力。使用三种定制滚动接触来验证移动接触几何概念：线接触、双椭圆接触以及两者的组合（即移动接触几何形状）。这些测试是在同步循环加载下进行的，以模拟液压传动系统的条件。此外，还实现了以前工作的模型来进行预测并将其与实验结果进行比较。在初步测试中，由于接触压力更高，在相同负载下，双椭圆接触表现出比线接触更优异的牵引性能。在同步循环加载下，线接触在低接触力下对施加的抵抗扭矩表现出高敏感性，从而导致高滑动滚动比和牵引力峰值。相比之下，具有移动接触几何形状的滚动副即使在高阻力矩下也表现出最小的滑动，从而导致显着较低（并且在大多数情况下可忽略不计）的滑动滚动比和牵引力峰值。模拟也捕捉到了这种行为，证明了该模型用于预测和比较这两个不同滚动副的滚动滑动动力学的有效性。这项研究表明，具有移动接触几何形状的滚动副不仅可以改善大型液压传动系统中凸轮-滚子接触的摩擦学性能，而且还可以产生更有利的动态行为。