Experimental and finite element analysis of residual stresses in cold tube drawing with a fixed mandrel for AISI 1010 steel

In this thesis, analysis of tube drawings with a fixed mandrel and residual stress measurements inside the tube wall are made. Dies and mandrels were designed and manufactured to produce AISI 1010 steel tubes at the reduction of areas of R=16% and 23%. Tube drawing was efficiently performed under lubricated conditions by a bench chain-driven cold drawing machine. Some of the most common defects that occur through the cold tube drawing process are non uniform, undesired deformations of the material. Determining residual stress inside the tube wall is quite important in order to decide the final quality of the product. In this study, various measurement methods are utilized to measure residual stresses. Besides a new innovative technique with using removing layer method (RLM) is developed to measure residual stress within the tubular shape. The RLM using milling process is performed on the inner and outer surfaces of the tubes while measuring the developed strains at the outer and the inner surfaces, respectively. The slitting method (SM) is proposed to determine the residual stress in one direction while X-Ray diffraction (XRD) are used to identify residual stresses at five orientations below the inner and the outer surfaces of the tube. A finite element model (FEM) with an axisymmetry is developed to evaluate drawing force vs. displacement and residual stress according to the distance from the outer to the inner surfaces. The FEM is also improved to determine optimum drawing parameters that may lead to minimized drawing stress. The results of the experimental approach are shown to be in good agreement and the RLM is the most appropriate method to measure residual stresses inside the tube wall. The results showed that residual stresses present inside the tube wall are completely different for R=16% and 23%