Influence Of Microcosmic Morphology Parameters On Contact Characteristics And System Stability

In order to meet the specific functions,machining accuracy,service life and transportation requirements,machinery is often not a continuous whole,but by a large number of parts assembled into the assembly.Parts and parts contact to form interface.Complex machinery is often assembled from hundreds of parts,which form a large number of joint surfaces.The large number of joint surface accumulated will have a great impact on the overall dynamic characteristics and functional realization of the machinery.With the improvement of the quality and precision of the mechanical products,the requirement of dynamic performance is higher and higher.Therefore,considering the influence of the binding surface is particularly important in the design of machinery.Based on the three-dimensional fractal theory,the contact stiffness and contact thermal conductivity model of joint surface are established in this paper.In the case of considering joint surface,the influence of the micro topography parameters on the contact characteristics and the stability of the system are studied by using the modal coupling system as the research object.The work is as follows:(1)By consulting the relevant literature,the significance of the research on joint surfaces dynamics is discussed.From three directions of the contact model:Hertz contact model,statistical contact model,fractal theory contact model,the development path and the present research situation both at home and abroad are summarized.Finally,the research direction and contents of this paper are put forward.(2)Based on three-dimensional fractal theory,the normal and tangential contact stiffness models are established.And the effect of microcosmic topography parameters on contact characteristics is analyzed by simulation software.This is to prepare for the analysis of the influence of microcosmic topography parameters on the dynamic characteristics of the whole mechanical system.(3)The contact thermal conductivity model is established by using the contact load of the asperities and the joint surfaces.The effects of single microcosmic topography parameter and multiple microscopic topography parameters on the thermal conductivity of the joint surface are studied.In two cases of contact thermal conductivity considered and not,the thermal analysis of motorized spindle is carried out,which indicates the importance of considering joint surfaces in the analysis of the dynamic characteristics of mechanical systems.(4)The modal coupling system is used as the research object.Considering the effect of joint surfaces,the stability analysis model of the system with micro topography parameters is established.According to the complex modal theory,the dynamic equation of the stability of the system considering joint surfaces is established by applying the three-dimensional fractal dynamic characteristic model of joint surfaces.Thus a bridge between the microscopic topography parameters and the macroscopic system stability analysis is established.(5)From the microscopic point of view,the influence of microcosmic topography parameters on the system stability is analyzed.Firstly,the influence of single microcosmic topography parameter on the stability of macroscopic system is studied.And the range of values for a single parameter that stabilizes the system is obtained.Then the influence of several morphological parameters on the stability of the system is analyzed.And the value region of the plurality of parameters that stabilizes the system is obtained.(6)Taking components as the research object,the correctness and feasibility of the work are verified by the finite element analysis and the modal experiment.The stiffness of joint surfaces of components is obtained using the established contact characteristic model.And the"solid-gap-solid" contact model is used to equivalently bond joint surfaces.Firstly,the natural frequencies of components are obtained by finite element simulation analysis.Then the natural frequencies of the components are obtained by modal test.And the two kinds of results are compared.