Measurement And Simulation Of Residual Stress Distribution Of High Strength Steel Plate

Entering the twenty-first Century,the world’s steel industry into a new stage,"high strength,thinning" as the representative of the high strength steel products are gradually being paid attention to.The problem of plate shape has become the most prominent problem in the application of high strength steel,and the shape of the plate is essentially a large residual stress in the steel plate and the distribution is not uniform.In this paper,a new method named Specific Volume Difference Method was applied to measure the three-dimensional residual stress of different kind of materials,according to the limitations of traditional present method,which confirms the validity of the new method.The method is based on the measurement of the relative volume change of the material after plastic processing,and the result of the residual stress can be obtained.Residual stress of the material will cause the volume change,which can be accurately measured by the volume.This research has certain guiding significance for the development of new technology of reducing the residual stress and improving the stability of the plate.Firstly in this paper,the three-dimensional residual stress inside materials were measured and analyzed,in which the cold heading,cold rolling and hot rolling process were used as examples.The results show that the residual stress was generated inside the material,and its volume was changed after plastic deformation,which were consistent with the Hooke’s law of elastic mechanics.It can be concluded that the method can measure and analyze the residual stress state after plastic deformation of the material accurately.Strain in different directions can be obtained by the thermal expansion test,which measures the size change that is the strain of material due to the release of residual stress in the heating process,as well as the volume strain obtained by the volume difference method.The results above prove the feasibility and scientificalness of the volume difference method to measure the three-dimensional residual stress.The results of the traditional facial residual stress measuring method,the blind hole method,confirm that the volume difference method was effective and feasible,whose measuring results were accurate and reliable.On the basis of above results,the distribution of residual stresses of plate thickness for the hot rolled composite plate and the plate width for the high strength steel plate width was studied separately.Results show that the three-dimensional residual stress distribution in the thickness direction of the hot rolled composite plate is not uniform,the residual compressive stress reached the maximum value in the slab at the center,and decreased along the thickness direction gradually in a continuous symmetric way.For high strength steel plate,the residual stress in the plate width direction is gradually reduced from the edge to the center.Finally,the influence of the cutting on the residual stress release is discussed,and the conclusion is that the influence of cutting on the release of residual stress decreases with the increase of the size of the sheet.When the sample size is about 10mm,the residual stress is reduced to zero,and the residual stress reaches a stable value when the sample size is above 120×120mm,that is,the effect of cutting on the residual stress is reduced to zero.The influence law can be expressed by Gauss function,and a mathematical model is given to describe the effect of cutting on the release of residual stress.On the other hand,it was a goal to predict the residual stress of the high strength steel,the temperature field of small size high strength steel plate after rolling and cooling process by using ANSYS finite element simulation software for modeling and calculation was obtain,as well as the cloud chart for distribution and Temp-Time curve of transient temperature field of the high strength steel cooling in the water spray quenching way of different time.And the experimental measurement curve of the heart was compared with the simulation curve,the simulation results are basically consistent with the experimental results,the maximum error is less than 10%.Through the ANSYS thermal mechanical coupling algorithm,simulation of the residual stress for high strength steel plate was conducted,and the distribution of the residual stress in the cooling process were studied.According to the similarity principle,the temperature field and residual stress field of large size high strength steel plate after rolling are simulated and analyzed.The simulation results show that the residual stress field was similar to the distribution rule,the value of residual stress is large,the rolling direction and the plate width to both ends of the residual stress are gradually reduced.Along the width and rolling direction,the distribution law of residual stress was the same basically,the residual stress value of the heart was larger,and the residual stress value at both ends was smaller.