Experimental investigation of energy and punch wear in piercing of advanced high-strength steel sheet

The short service life of tools used to pierce advanced high-strength steel sheet (AHSS) is one of the primary concerns of the automotive industry. A high tool wear rate is expected due to high strength of the sheet to be pierced. This work investigated the effects of tool clearances on the quality of pierced holes, the piercing force, the piercing energy, and tool wear in piercing operations of AHSS and carbon steel sheet. The piercing energy was observed to be the major factor affecting tool wear. The energy was high when using a small tool clearance on AHSS. The tool with large clearance piercing AHSS exhibited a similar degree of wear as that piercing the low carbon sheet. A double shear zone on the cutting edge of AHSS was responsible for the high piercing energy, especially the energy required to push the slug through the die hole and that required for the return stroke, and the high wear rate of the piercing tool with small clearance.