Prediction of chevron crack initiation in inclusion copper shaped-wire drawing

In the copper superfine wire drawing, the internal cracks such as chevron cracks and breakage of the wire were fatal to the success of quantitative drawing operations. This paper shows how four of the main process parameters, the position, size and shape of an inclusion and drawing pass numbers, influence the plastic deformation, hydrostatic stress, maximum principal tensile stress and chevron cracks initiation by FEM simulation. The influence of the central and non-central cylindrical inclusion in the single-pass copper shaped-wire drawing was investigated. Influence of a central elliptical inclusion in the single-pass copper shaped-wire drawing was also investigated and compared. The effect of the lateral and longitudinal sizes of a central cylindrical inclusion in the multi-pass copper shaped-wire drawing was carried out. The plastic deformation, plastic strain, hydrostatic stress and maximum principal tensile stress of the copper shaped-wire containing an inclusion were obtained for the drawing condition, position, size and shape of the inclusion mentioned above. A ductile fracture criterion was chosen from literature, a large number of ductile fracture initiation criteria, to predict the chevron crack initiation of the drawn copper shaped-wire for this investigation. The problem of chevron cracks initiation for the investigated material was solved. This investigation gives very good results.