Workability study for adiabatic shear band phenomenon in the steel cold heading process

The motivation behind this study is the lack of specialized analysis regarding internal failure caused by the adiabatic shear hand (ASB) phenomenon in the cold-headed products. Its aim was to present an integrated workability study to improve and assist cold-heading (CH) multistage design procedures to replace the current design rules of thumb, as they are neither effective nor adequate in fulfilling the needs of the new developments in the rapidly expanding CH industry.A detailed experimental and FE study for the ASB stages in the CH process was introduced to uncover the affect of different parameters controlling the failure mechanisms within the ASBs in the CH process. This study investigated the effect of the thermal, geometric and the material flow softening and hardening mechanisms affecting ASB evolution. Moreover, a detailed metallurgical and FE study of the internal ductile and Transformed Adiabatic Shear Band (TASB) failures caused by the ASB phenomenon in DWCT was conducted.Three ductile failure criteria were introduced to predict the initiation and location of the internal ductile failure in the ASBs. One TASB failure criteria was introduced to predict the phase transformation to undesirable brittle martensite. These failure criteria were employed to establish integrated workability methodologies to indicate the objective workability limits.Applying these workability methodologies on multistage CH FE models showed that these methodologies are an efficient tool to predict the damage levels and failure initiation locations within the cold-headed bolts. Moreover, these methodologies were successful in optimizing the die designs in order to reduce damage levels.To achieve these goals, a comprehensive testing methodology and FE modeling, implemented within ABAQUS/Explicit, were established. This methodology includes an instrumented Drop Weight Compression Test (DWCT) tower equipped with a guided pocket die-set configuration capable of developing internal failure at different stages of ASBs and integrated metallographic inspection techniques. A validated FE model of the DWCT and guided pocket die-set configuration was a valuable tool in establishing the failure criteria and indicating the workability limits.