Static characteristics and cohesive zone model of joint surfaces in machine tools

To satisfy the functional, process and design requirements, each type of machine tool is assembled by various parts or components at certain order instead of a complete and continuous structure, and hence a variety of joint surfaces exist between different parts or components. As the joint surfaces are discrete surfaces, their stiffness and damping affect considerably the static and dynamic performance of the machine tool. In the present paper, model experiments were firstly carried out to characterize the relationship between contact pressure and deformation of nominally plain joint surfaces. The contact behavior of the joint was then simulated using the method of finite elements by simplifying the measured morphology of the joint surfaces as semi-circular or sinusoidal. It was demonstrated that the numerical simulations agreed better with the experimental measurements if the joint surface morphology was taken as semi-circular. Finally, by assuming that the interaction between a pair of joint surfaces is equivalent to cohesion effects, the classical cohesive zone model (CZM) was adopted to analyze the mechanical behavior of the joint. It was established that the model predictions agree well with the experimental results.