Compliant Mechanism Adaptive Suppression of the Force Fluctuation in Motor-Driven Scratch Testers

Scratch testing is an effective technique for evaluating surface mechanical properties of materials. However, for motor-driven scratch testers, the micron-scale axial transmission clearance of ball screws and the millisecond response time of the motor greatly affect the compensation of the normal force, leading to a large fluctuation of the normal force. Accordingly, this study proposed a compliant mechanism adaptive suppression method to adapt to the change in geometric characteristics and mechanical properties of a sample surface, thereby reducing the fluctuation of the normal force. The structural characteristics of the compliant mechanism were discussed, followed by theoretical and simulation analysis to demonstrate the effectiveness of the method. Comparative experiments were performed on materials with heterogeneous mechanical properties and rough surfaces by scratch testers with and without the compliant mechanism. The results confirmed that the proposed method could well suppress the fluctuation of the normal force in motor-driven scratch testers under various experimental conditions.