Taking advantage of the magnetic field inside transmission electron microscope (TEM), a unique Lorentz-force-actuated method for quantitative friction tests was developed via a commercial electromechanical holder. With this approach, a submicron-sized silver asperity sliding on a tungsten flat punch was actuated by Lorentz force due to electrical current through the punch, with the normal force imposed by the built-in transducer of the holder. The friction force was determined by tracking the elastic deflection of the fabricated cantilever from in situ video. Through correlating the friction behavior with the microstructural evolution near the silver-tungsten interface, we revealed that even when the relative motion commenced with the plastic deformation of the silver asperity, the interface can still sustain the further increasing static friction force. Exactly following the arrival of the maximum static friction force, the sliding occurred at the interface, indicating the transition from static to dynamic friction. This work enriches our understanding of the underlying physics of the dynamic friction process for metallic friction behavior.

利用透射电子显微镜（TEM）内部的磁场，通过商用机电支架开发了一种独特的洛伦兹力驱动的定量摩擦测试方法。通过这种方法，由于通过冲头的电流而产生的洛伦兹力驱动了在钨制扁平冲头上滑动的亚微米级银粗糙物，而法向力则由支架的内置传感器施加。摩擦力通过从跟踪所制造的悬臂的弹性挠曲来确定原位视频。通过将摩擦行为与银-钨界面附近的微观结构演变相关联，我们发现，即使相对运动开始于银粗糙的塑性变形，界面仍可以承受进一步增加的静摩擦力。恰好在最大静摩擦力到来之后，在界面处发生滑动，表明从静摩擦到动摩擦的过渡。这项工作丰富了我们对金属摩擦行为的动态摩擦过程的基础物理学的理解。