الفهرس 
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Abstract
Bolt, a crucial part of the Pulemyot Kalashnikova Modernizirovannyi (PKM) machine gun, has recently failed too frequently while being fired. Due to the high temperature, propellant gas pressure, and thermal accumulation, the bolt body is exposed to severe circumstances for ablating, corroding, and erosion. The original bolt dimensions were measured using laser scanning with 0.005 mm accuracy, and a CAD model of the bolt was created based on those measurements. Photographic records, chemical analysis, Macro graphic examination (Visual examination), Metallographic examination (microstructure examination), Scanning electron microscopy, SEM, Energy dispersive x-ray, EDX, and hardness measurements of the brand-new bolt before firing and failed bolt after firing material at different points, all the above have been practically implemented. At that time, to determine the loads due to firing, the internal ballistic parameters of the 7.62*54mm PKM were calculated. The stress distributions and fatigue behaviour of the failed bolt are both determined using the Finite Element Modelling (FEM) in the environment of ANSYS Workbench 18. 2. This study suggests that fatigue played a role in bolt failure. Furthermore, SEM examinations reveal that the fractured surface contains dimples and micro dimples. The bolt’s fatigue life was decreased by these dimples. The main objective of this work is to create an accurate and verified finite element transient model of the bolt body, analyse the failure of the bolt body by calculating the thermomechanical cyclic fatigue life, fatigue damage, and fatigue safety factor. Also, determine the main cause of failure and verify that the failure locations are exactly as shown in the photographic record. select an appropriate suitable alternative material for the one that was used to manufacture the failed bolt body and prove how is it suitable by analysing the failure of the bolt body made from the new material using the created ANSYS WORKBENCH model and comparing the results with those for the original bolt material.
Keywords:
Machine gun, SEM, internal ballistic, fatigue life, fatigue failure, material selection.