An embedded-strain-gauge technique of stress analysis in rod drawing

Abstract The work presented in this paper describes the development of an experimental method of establishing the three-dimensional stress in a rod-drawing die during the deformation process and from this determining the variation of die pressure along its length. The investigations were carried out by pulling a lead rod through a suitably modeled epoxy die into which strain-gauges had been embedded at points along its length in order to obtain a number of the strain values in the axial, radial and hoop direction. The stress at various critical points of the die was established from the strain readings using three-dimensional stress-analysis techniques and the known drawing force on the lead rod. Lames equations for thick cylinders, in association with the stress values already found, were then applied towards establishing the stress acting normal to the die/rod interface by regarding the sections bounding the length of the strain gauges as thick cylinders themselves. The lead rod was drawn successfully through the epoxy die and reasonable results were achieved. Further work is to be carried out, including the re-design of the die.