| The ultimate failure of engineering materials and their products often comes from micro-deformation damage and defects.Therefore,the research on micro-nano mechanical properties of materials has become a hot topic at present.As a test method to accurately characterize the friction and wear properties,machinability,adhesion properties and surface damage mechanism of materials,scratch test has been widely concerned.In particular,in situ scratch test can observe the contact state between indenter and material at the same time of scratching,which is widely used to study the damage evolution and removal characteristics of materials at micro and nano scale.However,at present,the development of scratch tester,especially the micro-nano scratch tester and in situ scratch tester manufacturing technology,is mainly held by foreign companies.Since China has not mastered the core technology of high-end in situ scratch tester,it is difficult to carry out relevant research,which seriously restricts the development and application of scratch test technology.Therefore,the development of high precision in situ scratch tester with independent intellectual property rights is of strategic significance for breaking through foreign technology blockade,improving the level of independent instrument development and promoting the development of material testing technology.Based on the shortcomings of in situ scratch test in China,the design,manufacture,assembly,control,calibration,debugging and performance evaluation of the in situ scratch tester are carried out in this paper,and the in situ/out of position scratch test is carried out for typical materials.Specific research contents are as follows:(1)The structural design,prototype fabrication and integrated control of the whole machine and key components of the in situ scratch tester were carried out.Firstly,the functional analysis and disassembly of the in situ scratch tester were carried out,and it was divided into functional modules such as base,piezoelectric precision indentation assembly,piezoelectric precision scratch assembly,and two axis force sensor.To ensure the compactness of the in situ scratch tester,the reasonable layout of each functional module was determined,the piezoelectric precision indentation assembly and the piezoelectric precision scratching assembly were designed to achieve precision positioning,the two axis force sensor capable of measuring both lateral and normal forces was designed and optimized,and the calibration and decoupling tests were conducted on the two axis force sensor.Further,the parts of the in situ scratch tester were machined and the in situ scratch tester was assembled.After the structural design and optimization of the in situ scratch tester,the control logic was analyzed and the control software of the in situ scratch tester was written.(2)Performance tests of the in situ scratch tester were carried out.The noise level of the two axis force sensor was measured under working conditions.The displacement resolution of the piezoelectric precision indentation assembly was measured in step mode and scan mode for upward and downward pressure respectively using a capacitive displacement sensor,and the motion resolution and speed range of the piezoelectric precision scratching assembly were measured by a laser displacement sensor.Finally,the reliability and stability of the in situ scratch tester were verified by conducting scratch tests in different modes and loads on typical materials.(3)Based on the designed in situ scratch tester,scratch tests were carried out for typical materials.The frictional characteristics and removal mechanisms of three typical metallic materials,namely 1050 aluminum alloy,Ti6Al4 V and Zr-based metallic glass,during the scratching process were investigated.Linear load scratch tests were carried out for two typical hard and brittle materials,silicon and fused silica,to analyze the crack emergence and transformation mechanism during their ductile transformation.Finally,the in situ scratch tester was integrated into the scanning electron microscope(SEM)to conduct in situ scratch tests on 1050 aluminum alloy and Ti6Al4 V,and the correspondence between SEM images and force parameters was established to investigate the material flow and removal characteristics during the scratch process. |
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