Investigation of Plane-Strain Fracture Toughness and Failure Analysis of AISI-4140 Alloy Steel †

AISI-4140 alloy steel is a widely used a material in various fields of engineering like automotive, aerospace, oil and gas industries, construction, and structural engineering. Its application in diverse industries is mainly due to its excellent combination of strength, toughness, and wear resistance properties. Understanding the fracture toughness of AISI-4140 alloy steel is essential for ensuring the structural integrity and reliability of engineering components made from this material. The current study focuses on the experimental evaluation of fracture toughness due to its critical role in determining the material’s resistance to fracture and crack propagation. In this research, the plane-strain fracture toughness of AISI-4140 alloy steel material is investigated. Five compact tension specimens (CT) with three different thicknesses 12.5 mm, 20 mm, and 25 mm, are prepared as per ASTM standard E 399-90. The initial pre-crack in these specimens is introduced using fatigue loading. The fracture toughness test is conducted as per established procedures, and the specimens are subjected to controlled loading until a fracture occurs. Scanning electron microscopy analysis of the fractured surfaces allowed for a detailed examination of the fracture features, including crack propagation paths and microstructural characteristics. The average fracture toughness value for the AISI-4140 alloy steel is determined as 44.8 MPa (Formula presented.).