Metal Forming Processes

This chapter first presents an overview of stress and strain by defining engineering stress, engineering strain, true stress, and true strain, including the relevant mathematical relationships and the curves in the stress–strain plot. A distinction is made between the elastic deformation and the plastic deformation with the aid of a stress–strain curve; here the three moduli (the Young’s modulus E, the plastic modulus H, and the tangent modulus K) are introduced. The six deformation models (linear elastic, linear elastic/plastic, elastic/perfectly plastic, rigid/perfectly plastic, rigid/linear strain hardening, and the power law deformation model) are discussed and illustrated with the aid of sketches. Plastic deformation mechanism is explained with reference to dislocation motion and the deformation by slip. Finally, deformation of single crystal is discussed and analyzed. This chapter contains 11 worked numerical examples, 9 diagrams, 2 tables, 21 formulae/equations, and 11 MCQs with answers provided at the end of the book.

This chapter first classifies metal forming into cold working (CW), warm working, and hot working (HW) and then discusses them with reference to their advantages and limitations to enable a manufacturing engineer to select the best type of metal forming. Cold working is explained both qualitatively and quantitatively by considering the increase in dislocation density as well as the changes in the microstructure and mechanical properties. The three stages of annealing (recovery, recrystallization, and grain growth) are described with the aid of formulae (including Avrami’s equation). Finally, hot working is discussed with reference to hot rolling to obtain refined recrystallized microstructure. This chapter contains 6 diagrams, 11 worked numerical examples, 7 MCQs, and 5 problems with their answers given at the end of the book.

Rolled metallic products find wide applications in building construction, the automotive industry, the aerospace industry, the defense sector, and the like. This chapter first introduces metal rolling, including the role of friction in the rolling operation; here, various rolled products of different geometries produced by flat rolling and shape rolling are also illustrated. Rolling mill practices are discussed with reference to 2-high single-pass mill, 2-high reversing mill, 3-high rolling mill, 4-high rolling mill, cluster rolling mill, and tandem rolling mill; here, the advantage of small-sized rolls in power saving is scientifically justified. Engineering analysis of flat rolling is presented with reference to forward slip, reduction, rolling force, rolling torque, rolling power, feasibility of rolling, and the number of passes. Shape rolling is also analyzed, including roll pass design for bar mills. This chapter contains 21 worked numerical examples, 9 diagrams, 23 formulae, 8 problems, and 10 MCQs with their answers provided at the end of the book.

This chapter first presents a brief history and industrial importance of metal forging (including the author’s real-life contribution to the industry) and then highlights the advantages and limitations of forging process. Different types of forging operations (e.g., open-die forging, closed-die forging, flash-less forging) are classified and described with the aid of sketches. Hammer forging and press forging are also differentiated and explained. Engineering analysis of open-die forging is presented taking into consideration the forging shape factor and forging force for upset forging/cold-heading. The role of friction in sticky and sliding regions in open-die forging is also analyzed by presenting appropriate mathematical models. This chapter contains 10 diagrams, 16 worked numerical examples, 10 formulae, 8 problems, and 9 MCQs with their answers provided at the end of the book.

This chapter develops in readers the skill of extruding metals to manufacture good quality parts both with round and complex cross-sections. Firstly, the advantages and applications of extrusion are reviewed, followed by presenting a classification chart of extrusion processes. Cold and hot extrusions are compared, including their advantages. Direct extrusion and indirect extrusion operations are explained with the aid of labeled diagrams, including tube manufacture. Hydrostatic extrusion, lateral extrusion, and impact extrusion operations are also described. Finally, the engineering analysis of extrusion is presented with the aid of a diagram and mathematical models. This chapter contains 21 worked numerical examples, 9 diagrams, 12 formulae, 9 problems, and 10 MCQ with their answers given at the end of the book.

This chapter first defines rod/wire drawing operation, taking into consideration the diameter ranges for bar, rod, and wire. The advantages and developments in the wire drawing process have been reviewed, including the recently developed die-less wire drawing practice. Rod/wire drawing has been analyzed by developing mathematical models for the reduction ratio, the draft, the true strain, the av. flow stress, the ideal draw stress, the actual draw stress, the draw force, and power (both in SI and ft-lb-min units). Continuous wire drawing has been discussed with reference to lubrication and the formula for determining the number of dies and capstan drums required for a wire drawing operation has been derived. This chapter contains 8 diagrams, 24 worked numerical examples, 12 formulae or equations, 8 problems, and 8 MCQs with their answers given at the end of the book.

This chapter first introduces sheet metal forming processes, including their industrial importance. The principal strain increments in uniaxial loading are analyzed using calculus tools; they are also discussed with reference to isotropy and anisotropy. The plane stress deformation is analyzed, and the terms stress ratio (α) and strain ratio (β) have been defined. Theories of failure/yielding are introduced with reference to the Tresca yield condition and the von Mises yield theory. The deviatoric stresses have been diagrammatically illustrated, and workable mathematical models have been derived. The Levy-Mises flow rule has been applied using integral calculus to establish the mathematical relationship between α and β. The formulae for determining the effective stress \( \left(\overline{\sigma}\right), \) the effective strain \( \left(\overline{\varepsilon}\right), \) and the work of plastic deformation are presented. Finally, the mechanics of a stretch-forming operation is given. This chapter includes 26 worked numerical examples, 10 diagrams, 45 formulae/equations, 15 numerical problems, and 6 MCQs with their answers given at the end of this book.

Shearing and blanking are primary operations in sheet metal forming. This chapter first distinguishes between open shearing, blanking, and piercing. Then, open shearing is discussed with reference to its advantages and limitations. The working principles of hydraulic shearing machines are also explained. Blanking and piercing operations are compared and discussed with several sketches/illustrations, including the underlying geometric design parameters. Engineering analyzes of shearing, blanking, and piercing operations are presented with the aid of mathematical models. Progressive and compound dies for blanking and piercing operations are discussed, including recent advances in their technologies. This chapter contains 17 diagrams/figures, 36 worked numerical examples, 9 formulae/equations, 12 problems, and 5 MCQs with their answers given at the end of the book.

This chapter develops the skill of performing correct sheet-metal bending operations for manufacturing good-quality components for applications in automobile body panels, aircraft structures, storage tanks, pressure vessels, race car bumpers, steel furniture, fridges, electronic casings, brackets, and the like. The principal types of bending methods (V-bending, air bending, bottoming, edge bending, roll bending, etc.) have been discussed and analyzed, including the recent advances in bending technology. Important terminologies in bending (e.g., neutral axis, bend radius, bend angle, bending angle, bent angle, springback, and bend allowance) have been defined with the aid of sketches. An in-depth explanation and analysis of the springback effect has been presented. This chapter contains 19 diagrams/photos, 15 worked numerical examples, 9 formulae/equations, 7 problems, and 7 MCQs with their answers given at the end of the book.

This chapter develops the skills of readers to perform deep drawing operation for manufacturing defect-free components for a wide variety of applications, including automotive, aeronautical, and food industries. Deep drawing is explained with reference to its applications and advantages. The equipment and operational steps in deep drawing are illustrated with the aid of a picture and sketches. The deep drawing process has been analyzed, taking into considerations the clearance (c), blank diameter (D_b), punch diameter (D_p), die corner radius (R_d), punch corner radius (R_p), drawing force (F) and the blank holder force (BHF) (F_h); accordingly the relevant mathematical models are presented for computing the drawing force and BHF, and for checking the severity and feasibility of a deep-drawing operation for quality. The role of friction and compression played in the flange of the blank during the deep drawing process is also discussed. Finally, recent advances in deep drawing technology for eliminating wrinkling and tearing defects are briefly explained. This chapter contains 10 diagrams, a picture, 7 worked numerical examples, 7 problems, and 9 MCQs with their answers given at the end of the book.

This industrially oriented chapter develops, in readers, the skill of manufacturing machine components by using a sequence of metal forming operations with their complete engineering analyses. There are two metal forming projects in this chapter; project 1 involves bolt manufacturing, whereas project 2 deals with the manufacture of cups. Project 1 presents the description, the available material and equipment, the objectives/requirements, and, key solutions, including the determination of process parameters in extrusion, wire drawing, and upset forging. Project 2 describes the description, the available material and equipment, the objectives/requirements, and, key solutions, including calculations for rolling (including the calculation for rolling cost), shearing, blanking, and deep drawing. A process flow chart has also been developed for project 2 that presents the sequence of all operations involved in the cup manufacture with the changes in dimensions of the work after each step/operation. Finally, projects are given for practice.

This chapter presents a metal-forming project using a business-oriented approach. The manufacture of L-beams is analyzed by three methods: (a) Method 1 (rolling, shearing, and bending), (b) Method 2 (extrusion and shearing) using a direct extrusion machine, and (c) Method 2 (extrusion and shearing) using an indirect extrusion machine. The process flow charts for the manufacturing methods are presented; the flow charts show the dimensions of the work after each step (operation). The complete analyses for all the three manufacturing methods are conducted, including the calculations for rolling force, rolling power, rolling times, rolling cost, shearing force, shearing cost, bending force, bending cost, extrusion force, extrusion power, and extrusion cost. The most economical metal-forming method has been recommended based on the economics of manufacturing. This chapter contains 5 diagrams and 2 tables.