Simulation and Experiment of Dynamic Properties of Joint Surfaces Based on Fractal Theory

Haitao Liu,Yazhou Sun,Zongshan Liu

doi:10.1155/2015/382626

Abstract

Dynamic properties of joint surfaces are researched, micro behavior is also analyzed and a mathematical model based on fractal theory is built, and the relationships between normal dynamic characteristics of joints and surface pressure, surface roughness, and real contact area were simulated. The contact pressure in joint, equivalent stiffness, and damping in joint were nonstrict proportional relationship, higher surface quality of the contact joint surface, can increase normal stiffness and reduce normal damping in joint. Experiments are arranged according to the theoretical model in order to analyze the share of every major factor that affects dynamic properties of joint surfaces. Two common materials HT200 and 2Cr13 under different processing methods, surface roughness, and surface areas are used, and law curves were built between the dynamic behavior of fixed joints and preload, processing method of contact surface, surface roughness; the correctness of the theory simulation results was confirmed. A spring-damping element joints finite model was built based on the pressure distribution contours. Based on the experimental data, we simulated the model of HT200 specimen by ANSYS, at the same time, compared our model, traditional model, and experimental result, and proved that the spring-damping distribution model based on pressure has a better simulative precision.

Highlights

The joint surfaces are common in mechanical structures, and nonlinear characteristics of joint surfaces are the main factor which affects the dynamic behavior of whole machine
It indicates that the dynamic properties of joint faces increase while surface roughness decreases
It can be proved by FEM simulations that when normal stiffness of combined elements in the FEM model is around the real stiffness of joint surfaces, the stress distribution will not be affected too much by stiffness variation of combined elements

Summary

Introduction

The joint surfaces are common in mechanical structures, and nonlinear characteristics of joint surfaces are the main factor which affects the dynamic behavior of whole machine. On the basis of static properties, scholars have researched the stiffness and damp properties of joint surfaces according to theoretical model and experiment results and studied dynamic properties and parameter recognition methods of joint surfaces These works are of great importance to building a precise dynamic model. Many scholars carried out further research on dynamic properties of joint surfaces along with the factors that influence these dynamics Both Oden and Martins [5], Schofield et al [6, 7] and Sherif [8, 9] carried out experiments between under different pressure joint surfaces of real machine tools, results indicated that normal load and deload curves of joint surfaces under high pressure different from that of low pressure. The author compared the advantages and disadvantaged of these methods in practical applications and proposed the idea of using different method when facing different loading conditions

Theoretical Modeling of Joint Surfaces

Experimental Analyses

Improving Simulation Precision

Conclusions