Research On Prediction Method Of Residual Stress Fields For Mechanical Parts From Surface Residual Stress Measurements

The existence of residual stresses may cause many undesired phenomena in workpieces,such as load deformation,dimensional instability,and fatigue crack propagation,which is one of the major causes of accidental damage accidents during the use of machinery.All kinds of manufacturing processes and remanufacturing processes will cause different magnitudes of residual stresses in mechanical parts.At present,the concept of component design and manufacturing based on residual stress is gradually being taken seriously by enterprises.Accurately characterizing the residual stress field has an important application value for improving the stability and reliability of the parts and their recycling,as well as improving the accuracy and stability of machines.Residual stress fields cannot be easily and accurately measured or simulated.This paper aims at exploring a predicting method for surface and internal residual stress fields from local residual stresses obtained without knowing the details of the mechanical manufacturing process.The prediction method of residual stress fields of mechanical parts based on that surface stress measurements is studied by selecting the researched objects from small surfaces to large surfaces,and then from surfaces to interior.The main research work of the thesis is:Firstly,according to the elastic-plastic stress boundary conditions and the equilibrium theory,residual stress fields in small surfaces are analyzed.Considering that residual stresses of surface discrete points can be easily obtained and combined with regression analysis,a method of predicting small surface residual stress fields using stresses of limit test points and boundaries is proposed.The method was validated by being applied on two samples.Secondly,to avoid the blindness of selecting test points on the large-scale surface,a prediction method of surface residual stress fields based on Bivariate Fourier series using partial stress measurements is proposed.The method is proposed by introducing the bivariate Fourier series as the Airy stress function and deducing Bivariate Fourier-based governing equations of surface residual stress fields.The key solution technologies of the proposed model are described.The effectiveness of the method is well verified by a numerical example and an experimental example.Thirdly,a prediction method of internal residual stresses from surface stress measurements is proposed.The principle and key technologies of the method are described.The method was applied to a numerical beam sample and an experimental case.The results show that residual stress fields can be predicted with good accuracy,using perfect surface measurements via this method.Meanwhile,the parameters influencing the results are studied in numerous experiments utilizing synthetic imperfect measurements.Finally,a system integrating the above three prediction technologies for predicting residual stress fields in mechanical parts is developed and applied with indexable coated blades.This introduces a new idea for obtaining the initial stress fields for coated inserts.The proposed prediction method of residual stress fields in this paper breaks through the technical difficulties that the residual stress fields are difficult to predict.The residual stress field can be solved only by using partial surface residual stress according to the proposed models.A key feature of the proposed method is that it is applicable to complex mechanical parts,where the residual stress generation can hardly be known in detail.Using this method to obtain the initial residual stress field will help to explore the release rules of large residual stress,the structural optimization design and manufacturing process of parts,the evaluation and use of parts quality,and the influence of overall performance.It has great significance in eliminating or reducing the adverse effects of residual stress on components,accelerating the development of manufacturing and remanufacturing technologies in China,and realizing green remanufacturing of mechanical parts.