Welding Residual Stress And Its Effect On Structural Vibration Characteristics

The measurement of welding residual stress is mainly measured by destructive methods and non-destructive methods.However,as for the residual stress measurement of in-service objects,after finishing the destructive method measurement,the in-service objects cannot meet the requirements of the structure and non-destructive methods have the difficulty of carrying the equipment.Furthermore,the study of the effect of pre-stress on the vibration characteristics of the structure did not consider the actual welding residual stress.In view of the above problems,this article proposes instrumented indentation method to measure the welding residual stress and studies the distribution of residual stress under different welding parameters.Based on this,the influence of the residual stress on the vibration characteristics of the structure was explored,which could be of constructive significance for the safety evaluation of welded structures.The main contents of this article are as follows:Firstly,a standard device based on the principle of four-point bending was proposed.The stress measurement of standard parts was performed by the instrumented indentation method.The results showed that the measured results of the instrumented indentation method is accurate.The instrumented indentation method is compared with the measurement results of the hole-drilling method and the cutting-edge method.The stress distribution trends of these methods are similar,and the difference between the measurement results is not great.At the same time,the measurement results of the residual stress are also providing experimental verification for the finite element method later.Then this article establishes a finite element model to simulate the welding process and explores the influence of welding speed,welding form and welding sequence on welding residual stress: 1)Selecting a slower welding speed during the welding process can ensure the strength of the structure,but it is necessary to pay attention to the problem of stress concentration at the beginning and end of the weld;2)Double-sided welding can increase the residual tensile and compressive stress value than single-sided welding,and different welding forms can affect the distribution of residual stress;3)Different welding sequences will change the residual stress distribution and value.Welding the longest weld seams and then welding the shortest welding seam will reduce the strength of the plate,so it is necessary to determine the proper welding sequence in the welding process to minimize the impact of welding on the structural strength.Finally,based on this,a modal analysis model with welding residual prestress calculation is established.The results of experimental modal analysis are compared with the results of calculated modal analysis.The mode shapes are the same and the average natural frequency difference of the first 4 orders is 2.2%,and the maximum natural frequency difference is 3.8%,so the modal analysis model has high reliability.The effects of welding residual stress on structures with different thicknesses and different residual stress fields on structural vibration characteristics are explored.Welding residual stress has little effect on the vibration characteristics of structures with higher thicknesses and the residual stress field dominated by tensile stress affects the structural vibration characteristics with the biggest influence.