Formation Mechanism Of Residual Stress Research Articles

The formation mechanism and the influence factor of residual stress in machining

Residual stresses generated in cutting process have important influences on workpiece performance. The paper presents a method of theoretical analysis in order to explicate the formation mechanism of residual stresses in cutting. An important conclusion is drawn that the accumulated plastic strain is the main factor which determines the nature and the magnitude of surface residual stresses in the workpiece. On the basis of the analytical model for residual stress, a series of simulations for residual stress prediction during cutting AISI 1045 steel are implemented in order to obtain the influences of cutting speed, depth of cut and tool edge radius on surface residual stress in the workpiece. And these influences are explained from the perspective of formation mechanism of residual stress in cutting. The conclusions have good applicability and can be used to guide the parameters selection in actual production.

Understanding the Formation Mechanism of Residual Stress during Precision Glass Moulding

Precision glass moulding is a technique that enables the production of optical lenses of complex geometries in a single step. However, it has been reported that the product quality highly depends on the properties of a raw material, the design of a die, and the selection of a processing program. This paper aims to reveal the formation mechanism of the residual stresses by optical lens moulding. To this end, a modulus-based constitutive model was developed to integrate with the deformation and stress analyses by the finite element method. The investigation showed that the residual stresses are caused by the variability and heterogeneity of thermal expansion in a lens, but that they can be reduced effectively by decreasing the rate of cooling within the stage from the molding temperature to the glass transition temperature.

Numerical Simulation of Temperature Field and Stress Field of Direct Laser Metal Deposition Shaping Process of Titanium Alloys

In order to control the thermal stress of forming process,based on "element birth and death" technology of finite element method,a numerical simulation of three-dimensional temperature field and stress field during multi-track and multi-layer laser metal deposition shaping(LMDS) process is developed with ANSYS parametric design language(APDL).The dynamic variances of temperature field and stress field of forming process are calculated with the energy compensation of interaction between molten pool-powder and laser-powder.The temperature field,temperature gradient,thermal stress field and distribution of residual stress are obtained.The results indicate that although the nodes on different layers are activated at different time,their temperature variations are similar.The temperature gradients of samples are larger near the molten pool area and mainly along z-direction.The transient thermal stress has concentrated in large temperature gradient area,which is in accordance with thermal stress forming theory.Through analyzing the residual stress of the as-formed samples in different directions,distribution rule of residual stress is achieved from temperature gradient perspective.And formation mechanism of residual stress is verified with an indirect way.Finally,it's verified that the analysis results are consistent with actual situation by the experiments with same process parameters.

Research on the Influence Parameter of Thermal Fatigue of the Composites Material SiCp/A356 Used on Brake Disc

Thermal fatigue tests are carried out to the notch specimens made of particle-reinforced composites entitled SiCp/A356 between 20°C and 300°C. The thermal elastic-plastic finite element method is used to simulate the stress and strain response at the notch root of the thermal fatigue test specimen, and thus the formation mechanism of residual stress is revealed. Then according to the finite element simulation of the stress-strain, the thermal fatigue strain life curves of SiCp/A356 material are given considering the residual stress. This can give the basis for the thermal fatigue properties study of the particle reinforced composite SiCp/A356 used in high-speed train brake disc.