Abstract
Key words :
Pipe Bending Procedure, Plastic Deformation, Residual Stress (RS), Circular Deformation Rate (CDR), Neutron Scattering Method, X-ray Diffract-meter (X.R.D), Spacing Distance, Defocusing Error, Eulerian Cradle, Psi Tilt, Omega Offset Method
Abstract:
Steel and aluminum pipes are widely used in automotive parts. These pipes are usually manufactured through bending-process. During bending-process, the pipe wall undergoes elastoplastic deformation. The outside pipe thickness becomes thinned and the inside one becomes thickened, the cross-section of the bent pipe becomes oval, and bending angle suffers some springback caused by elastic deformation after unloading. After bending-process, residual stress remains in the pipe inside and causes early failure due to the reduction of fatigue strength. This type of failure of pipe may cause severe problem when vehicle operates. And actually result into many accidents in field. However, little researches have been studied about residual stress and circular deformation ratio of bend pipe. Therefore, computer simulations and X-ray diffraction tests were conducted in this paper to evaluate the variation of residual stress and circular deformation ratio considering different parameters such as bending radius, diameter and thickness of pipe. The influence of Young’s modulus of pipe material is also examined.