| In recent years,the technology of membranes and surface tratement s played a important role in many different surface functions.And these types of material had been widely used in modern industry.For their thickness are usually at the micr on or nanometer level,the traditional testing methods are difficult to obtain their mechnical performance.The research on the mechanical properties of materials at the microscale has promoted the development of nano-indentation technology.Nano-indentation technology has the adavantages of high resolution、low damage to materials and low cost,and is especially suitable for testing the mechanical properties of membranes and coating materials.With more and more nano-indentation techniques are been used researchers have found that the hardness of materials increases with the reduction of the head size or indentation depth in nano-nardness testing,a phenomenon known as indentation scale effect(ISE).It is generally believed that the ISE of materials is the result of combined action of various factors such as material characteristics,surface morphology,contact effect and material oxidation etc.In this paper,the gaussian random rough surface with different roughness were simulated with numerical method through MATLAB.The elastic-viscoplastic material model describing the mechanical properties of polymer materials was established by using the Two-layer viscoplasticity model.The law of influences about the surface roughness on the nardness of the material w ere obtained.Based on the finite element simulation experiment,the simulation results of flat surface and rough surface were compared.With the increase of surface roughness,the ability of absorbing energy and resisting deformation in the process of s urface compression is enhanced,and the calculation of contact area between the head and surface by empirical formula is deviated greatly due to the uneven surface. |
