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http://dx.doi.org/10.5762/KAIS.2020.21.5.648

Case Study on the Firing Pin Fatigue Destruction of the Korean Rifle by Repeated Impact  

Lee, Ho-Jun (Defense Agency for Technology and Quality)
Choi, Si-Young (Defense Agency for Technology and Quality)
Shin, Tae-Sung (Defense Agency for Technology and Quality)
Seo, Hyun-Su (Defense Agency for Technology and Quality)
Publication Information
Journal of the Korea Academia-Industrial cooperation Society / v.21, no.5, 2020 , pp. 648-655 More about this Journal
Abstract
The firing pin of modern automatic rifles detonates the primer of loaded ammunition via a hammer. During this process, the firing pin receives an impact load and repetitive force throughout the life of the rifle. An endurance test of a rifle showed that the firing pin breaks prematurely at 96.26% of life. Accordingly, a case study was conducted through cause analysis and a reconstruction test. Optical microscopy and scanning electron microscopy of the broken surface of the firing pin showed that a crack began in the circumferential direction of the surface, resulting in a fatigue crack to the core after repeated impact. Crack growth and fatigue destruction occurred at the end due to the repetitive impact and was estimated using a notch. For verification, a sample that produced a 0.03mm circumferential notch was broken at 64.25% of life in the reconstruction test. A test of breakage according to the notch types showed that a 0.3mm and a 0.5mm one-side notch were broken at 66.53% and 50.76%, respectively, and a 0.03mm six-point notch was broken at 85.65%. The endurance life of a sample firing pin with a rough surface and tool mark was examined, but an approximately 381 ㎛ internal crack formed. Through this study, failure for each notch type was considered. These results show that quality control of the notch and surface roughness is essential for ensuring the reliability of a component subjected to repeated impact.
Keywords
Small Arms; Fatigue; Firing Pin; Repeated Impact; Notch;
Citations & Related Records
Times Cited By KSCI : 2  (Citation Analysis)
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