Chapter 15: Fundamentals of Metalworking

Fundamentals of Metalworking explores the mechanics of deformation through various analytical frameworks, ranging from the elementary slab method which assumes homogeneous deformation and friction effects, to more complex upper-bound solutions that utilize hodographs and velocity fields to estimate energy consumption, as well as the slip-line field theory for plane-strain conditions. The text details the application of the Finite Element Method (FEM) and matrix methods for simulating rigid-plastic material behavior and predicting local stress distributions in modern manufacturing. Significant attention is devoted to determining flow stress through experimental procedures like the plane-strain compression test and the hot torsion test, while addressing the limitations of the standard tension test due to necking and the compression test due to barreling caused by friction. The summary explains the critical influence of temperature, contrasting cold-working, which results in strain hardening and anisotropic textures, with hot-working, where metallurgical mechanisms such as dynamic recovery and dynamic recrystallization restore ductility and reduce forces. Tribological factors are thoroughly analyzed, including the friction hill concept, the distinction between Coulomb sliding and sticking friction, and the use of the ring-compression test to evaluate interface friction factors and lubrication efficiency. Furthermore, the chapter discusses the impact of deformation-zone geometry, defined by the delta parameter, on redundant work and hydrostatic pressure, which plays a vital role in preventing defects like center bursts or chevron cracks. Finally, it covers workability criteria such as the Cockcroft and Latham model, the generation of residual stresses due to inhomogeneous deformation, and the integration of computer-aided design and manufacturing (CAD/CAM) to optimize process variables and tooling.