Study On The Contact Characteristics Of Anisotropic Rough Surfaces Considering The Interaction Of Asperities

In the field of practical engineering,the mutual contact between mechanical parts widely exists,which is very important for the study of mechanical properties of two contact objects.On the macro level,it is considered that the surface of the object is smooth and flat.However,through the observation of microscope,the real surface of the object is composed of many peaks and valleys of bulges and depressions,that is,rough surface.The contact between two rough surfaces is actually the contact between these asperities covering the surface of the object.The prediction of the contact characteristics of rough surfaces plays an important role in the structural design,such as the contact stiffness of joints,MEMS,wear of contact elements,etc.Based on the fractal contact theory,this paper studies the contact performance of rough surfaces.Firstly,the Weierstrass Mandelbrot function is used to characterize the two-dimensional and three-dimensional rough surfaces,and the influence of fractal parameters and function variables on the surface morphology is analyzed.Then,a two-dimensional rough surface contact model considering the interaction of asperities is established.Finally,the contact model of three-dimensional anisotropic rough surface considering the interaction of asperities is proposed,and the loading contact experiment is designed.The experimental results are compared with the theoretical calculation results of three-dimensional contact model to verify the correctness of the model.In order to simplify the calculation model,the contact between two rough surfaces is idealized as the contact between a rigid plate and an equivalent rough surface.In the two-dimensional model,the relationship between the contact area and the contact load of a single asperity in the state of full plastic,elastic-plastic and elastic deformation is derived;the base deformation of a single asperity in each deformation state is analyzed,and the total local deformation of the base on the rough surface is derived by using the area distribution function of the asperities;on the basis of the MB model,the calculation formula of the local deformation of the base is combined Finally,a two-dimensional rough surface contact model considering the interaction of asperities is obtained.In this model,the influence of the interaction of the asperities on the actual total contact load and contact area is studied,and the influence of the fractal parameters on the area load relationship is analyzed.The results show that under the constant contact load,the total area of dimensionless contact with asperities interaction is smaller than that without asperities interaction;the contact area is inversely proportional to the fractal roughness parameter G;with the increase of fractal dimension D,the actual contact area increases from D=1.1 to D=1.5,then from D=1.5 to D=1.9.When the model does not consider the interaction between elastic-plastic deformation,the dimensionless contact area load relationship of the model is equal to that of MB modelIn the three-dimensional contact model,the influence of the interaction and anisotropic distribution of the asperities on the contact characteristics is considered.The modified two variable Weierstrass Mandelbrot function is used to characterize the three-dimensional anisotropic rough surface.When the parameter M=1,the rough surface is isotropic,when the parameter M?1,the rough surface is anisotropic.The relationship between the contact area and the contact load of a single asperity in each deformation stage is derived;the deformation formula of a single asperity base is obtained,and the local total deformation of the rough surface base is derived by considering the interaction between asperities;based on YK model,a three-dimensional anisotropic rough surface contact model considering the interaction of asperities is established.The effects of the interaction and anisotropy of the asperities on the contact area and the contact load are studied.The results show that the contact mechanical behavior of rough surface under medium and high loads is greatly affected by the interaction of asperities,and the influence of anisotropy on rough surface is very obvious in the whole contact process.The correctness of the model is verified by designing the contact experiment of rough surface.