Contact Performance Of Deformed Interfaces And The Electrical Measurement Method

The electromagnetic solid interface,as a key part of the internal force transmission,heat transfer,and conductivity of electromagnetic devices,has a significant impact on the development level of extreme electromagnetic equipment in fields such as nuclear energy,electromagnetic propulsion,and aerospace due to its contact characteristics.Establishing the contact mechanics theory of electromagnetic solid interface is the basis for improving the performance of extreme electromagnetic equipment,and also the key to improving the important "puzzle" of electromagnetic solid mechanics.The existing contact theory usually solves two-dimensional plane force,electrical(thermal)contact problems based on the assumption of "rough contour rigid plane",or statistically analyzes the characteristics of the entire contact interface based on the assumption of positive contact between asperities.It cannot consider the friction of the contact interface and is difficult to expand and apply to the deformation interface contact problem of complex structures under extreme environmental conditions(extreme temperature,strong current).Therefore,studying the influence mechanism of interface deformation on contact behavior and establishing interface performance measurement methods is the key to solving this problem.In this paper,four contact forms of asperities are proposed,and a rough interface contact mechanics model is established based on the volume contact theory,revealing the influence mechanism of tensile and bending deformation on the interface contact behavior.The oblique contact form proposed by this model provides a mechanism for the generation and variation of friction force from the perspective of asperity balance,which cannot be considered by traditional contact models.Tension and bending have a significant impact on the real contact area,which increases with the tensile deformation.Under bending load,there exists a maximum value of the real contact area and a minimum value of contact resistance.On this basis,the proposed contact model is extended and applied to the pancake shaped superconducting coil structure,and an electrical measurement method for interface stress and contact resistance is proposed.In this paper,the calculation formulas of the inter turn stress of the pancake coil and the internal stress of the strip in the elastic range are first given,and then the distribution characteristics of the coil resistance are given by using the equivalent circuit method.Furthermore,the proposed contact mechanics model is extended to effectively correlate the inter turn pressure and contact resistance.At the same time,a pancake coil preparation and contact resistance measurement platform was independently built,and experiments were conducted to measure the contact resistance of coils made of different materials under the influence of winding force.The proposed electrical measurement method is in good agreement with the experimental results,indicating its universality and providing a new method for measuring the interface performance of complex engineering structures.To sum up,four contact forms of asperities are proposed in this paper,so as to establish the contact mechanics model of deformation interface,and reveal the influence mechanism of interface deformation on contact behavior;Based on this,an electrical measurement method for the interface performance of superconducting coils was developed,and the distribution characteristics of coil inter turn stress and contact resistance were obtained through the measurement of overall contact resistance,providing reference for the evaluation and detection of contact interface performance in superconducting structures.