Identification of Lap Joint Dynamics Using Interfacial Nanocomposite Force Sensor

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Machine tools are complex structures consisting of several parts connected through different types of joints. Mechanical joints affect dynamics of the machine tools significantly, and any virtual model of the structure should include joint properties. It is desirable to use an interfacial sensor inside the joint to directly identify joint dynamic properties without changing the joint’s design and dynamics. In this study, a polymeric nanocomposite sensor with high sensitivity and a wide frequency bandwidth is implemented inside a bolted lap joint to identify the joint dynamic properties. The sensor implementation does not require any modifications to the joint design which makes the proposed approach suitable for many applications. An identification procedure is developed to find the micro-slip regime and the stick-slip boundaries in the joint interface using the acquired data of the nanocomposite sensor. Lab scale experiments are then conducted on a structure that consists of two beams attached to each other using a bolted lap joint. The proposed method is then used to identify the joint dynamics and the results are then compared with an existing approach named hysteresis loop technique. The experimental results show that the proposed method can predict the joint properties effectively with maximum deviations of 17% compared to the hysteresis loop results. Furthermore, effects of the contact normal load and the excitation load on the joint properties are investigated.