Journal of Failure Analysis and Prevention

, Volume 16, Issue 1, pp 173–178 | Cite as

Failure Analysis of a Striking Bar

  • P. A. Manohar
Technical Article---Peer-Reviewed


This paper describes the failure investigation of a tubular shaft that is part of a hammer drill assembly. The failure investigation was particularly challenging as the fracture surfaces were completely damaged during service subsequent to the failure process. However, careful examination of the component and its assembly revealed many clues that pointed to the root causes of failure. The basic failure mode was identified as torsional fatigue failure in combination with high bending stresses. The failure was determined to be originated on the inside diameter of the tubular shaft. The root causes were determined to be operational overload in the presence of rough machining marks on the bore surface and higher than necessary operating torque required to overcome the dry adhesive friction in the system. The preventative measures recommended were manyfold including improving surface finish on the bore diameter, reducing dry sliding friction, decreasing the overall level of dynamic loads by appropriate design changes, and adding a surface strengthening heat treatment.


Torsional fatigue Bending stresses Stress concentration Hammer drill 



The author wishes to thank the management of Modern Industries Inc., Erie for permission to publish the photographs. The work was carried out at Modern’s Pittsburgh Labs while the author worked there.


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Copyright information

© ASM International 2016

Authors and Affiliations

  1. 1.Research and Outreach Center (ROC), School of Engineering, Mathematics and Science (SEMS)Robert Morris UniversityMoon TownshipUSA

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