Combined Experimental and Computational Failure and Fatigue Analysis of a Socket Drive Adapter

Hand tooling represents a sizable cost in many industries, which is often exacerbated by premature tool failures. Prevention of these failures is a cost-saving strategy that can be applied to industrial as well as personal projects. The present study employs an integrated theoretical, experimental, and computational approach to investigate the failure of a socket drive adapter of unknown material after being subjected to unknown torsional loading. The failure surface was first compared against a torsion-tested chromium-vanadium adapter using scanning electron microscopy, and it was determined that a torsional overstress caused ductile shearing around the periphery of the adapter, until the smaller cross-sectional area allowed a smaller, non-torsional load to induce a final tensile failure. Results obtained from optical emission spectroscopy and Rockwell hardness test indicated that the failed adapter was likely made from AISI 1025 or a similar grade mild steel, which had been extensively cold worked and/or heat treated during the production process to improve its strength. Finite element analysis was then used to confirm the validity of theoretical calculations for maximum stress at the failure location. The approximate failure load was finally estimated via a strength-hardness correlation, with a conservative estimate for allowable torque of as little as 10.6 N m. The method presented in this paper shows that the load applied on hand tools in everyday use can be too high and can cause failure. The quality of the hand tools plays a key role in determining the amount of load that the hand tools can withstand.