This article, prepared under the auspices of the ASM Thermal Spray Society Committees on Accepted Practices, describes a procedure for evaluating residual stresses in thermal spray coatings, which is an extension of the well-known layer removal method to include the Young’s modulus and Poisson’s ratio properties of the thermal spray coating material and the substrate. It presents questions and answers that were selected to introduce residual stresses in thermal spray coatings. The article describes equipment and the laboratory procedure for the modified layer removal method and provides the description of the residual stress specimen. It also describes the procedures for applying or installing bonded resistance strain gages, the dimensions of the test specimen, the procedure for removing layers, and the method for interpreting the data to evaluate residual stresses. The spreadsheet program, “ MLRM for Residual Stresses ,” is available as a supplement to this document.

This chapter provides an overview of the blanking process and the forces and stresses involved. It discusses the factors that affect part quality and tool life, including punch and die geometry, stagger, clearance, and wear as well as punch velocities, misalignment, and snap-thru forces. It also discusses ultra-high-speed blanking, fine blanking, and shearing, and the use finite-element simulations to predict part edge quality.

This chapter begins with a review of the mechanics of bending and the primary elements of a bending system. It examines stress-strain distributions defined by elementary bending theory and explains how to predict stress, strain, bending moment, and springback under various bending conditions. It describes the basic principles of air bending, stretch bending, and U- and V-die bending as well as rotary, roll, and wipe die bending, also known as straight flanging. It also discusses the steps involved in contour (stretch or shrink) flanging, hole flanging, and hemming and describes the design and operation of press brakes and other bending machines.

This chapter discusses the use of modeling and simulation technology in the development of sheet metal forming processes. It describes the five major steps involved in finite-element analysis and the various ways functions of interest can be approximated at each point or node in a finite-element mesh. It explains how to obtain input data, what to expect in terms of output data, and how to predict specific types of defects. In addition, it presents several case studies demonstrating the use of finite elements in blanking and piercing, deep drawing of round and rectangular cups, progressive die sequencing, blank holder force optimization, sheet hydroforming, hot stamping, and springback and bending of advanced high-strength steels. It also discusses the factors that affect the accuracy of finite element simulations such as springback, thickness variations, and nonisothermal effects.

This chapter presents two case studies; one demonstrating the use of finite-element analysis (FEA) in the design of a progressive die forming operation, the other explaining how software simulations helped engineers reduce thinning and eliminate cracking and deformation observed in clutch hubs formed using a three-step transfer die process. It also discusses the role of FEA and commercial software in the design of progressive dies.

This chapter describes the effect of temperature and strain rate on the mechanical properties and forming characteristics of aluminum and magnesium sheet materials. It discusses the key differences between isothermal and nonisothermal warm forming processes, the factors that affect heat transfer, die heating techniques, and press systems. It also discusses the effect of forming temperature, punch velocity, blank size, and other parameters on deep drawing processes, making use of both experimental and simulated data.

This chapter discusses the forming characteristics of dual-phase (DP) and transformation-induced plasticity (TRIP) steels. It begins with a review of the mechanical behavior of advanced high-strength steels (AHSS) and how they respond to stress-strain conditions associated with deformation processes such as stretching, bending, flanging, deep drawing, and blanking. It then describes the complex tribology of AHSS forming operations, the role of lubrication, the effect of tool steels and coatings, and the force and energy requirements of various forming presses. It also discusses the cause of springback and explains how to predict and compensating for its effects.

Hot stamping is a forming process for ultrahigh-strength steels (UHSS) that maximizes formability while minimizing springback. This chapter covers several aspects of hot stamping, including the methods used, the effect of process variables, and the role of finite-element analysis in process development and die design. It also discusses heating methods, cooling mechanisms, and the role of coatings in preventing oxidation.

This chapter describes a sheet metal forming method, called hydroforming, that uses pressurized liquid and a shaped punch or die. It discusses the advantages and disadvantages of the two approaches, the effect of process variations, and tooling modifications intended to reduce sheet bulging. It identifies the factors that influence part quality and explains how finite-element analysis can be used to optimize hydroforming operations. It also discusses the economics of sheet hydroforming and presents several application examples.

Tube hydroforming is a material-forming process that uses pressurized fluid to plastically deform tubular materials into desired shapes. It is widely used in the automotive industry for making exhaust manifolds, catalytic converters, shock absorber housings, and other parts. This chapter discusses the basic methods of tube hydroforming and the underlying process mechanics. It explains how to determine if a material is a viable candidate and whether it can withstand preforming or bending operations. It describes critical process parameters, such as interface pressure, surface expansion and contraction, and sliding velocity, and how they influence friction, lubrication, and wear. The chapter also provides information on forming presses and tooling, tube hydropiercing, and the use of finite elements to determine optimal processing conditions and loading paths.

Roll forming is a process in which flat strip or sheet material is progressively bent as it passes through a series of contoured rollers. This chapter describes the basic configuration and operating principles of a roll forming line and the cross-sectional profiles that can be achieved. It explains how to determine strip width and bending sequences and identifies the cause of common roll-forming defects. It also discusses the selection of roll materials and explains how software helps simplify the design of roll forming lines.

Any forming process that converts stored energy to plastic deformation in less than a few milliseconds is considered a high-velocity or impulse forming process. This chapter discusses the operating principles, equipment, and applications of the most common high-rate forming processes, including high-velocity hydroforming, high-velocity mechanical forming, and electromagnetic or energy-based forming.

Sheet metal spinning is a forming technique that produces axially symmetric hollow bodies with nearly any contour. It is often used in combination with flow forming and shear spinning to manufacture a wide range of complex parts. This chapter describes the operating principles, stress states, and failure modes of each process along with typical applications and tooling requirements.

This chapter describes incremental sheet forming processes, including single-point, two-point, and kinematic (two tool) techniques. It provides information on the tooling and equipment used, work flow and forming parameters, process mechanics and forming limits. It also discusses multistage forming strategies, process modeling and simulation, and advanced hybrid forming processes.

This chapter describes joining by forming processes including riveting, clinching, crimping, and dieless joining techniques. It also discusses the fatigue behavior of clinched joints and the results of fatigue tests that compare clinched and spot welded joints.

This chapter discusses the types of sensors used in sheet forming operations and the information they provide. It explains how force sensors protect equipment from overloads due to tool wear, friction, and misfeeds, how displacement and proximity sensors help to prevent die crashes, how acoustic emission, ultrasonic, and eddy current sensors detect tool breakage and part defects such as cracks, and how roller ball and optical sensors measure material flow. It also discusses the role of draw-in, wrinkle, oil-monitoring, and vision sensors and explains how material properties can be derived in real time from various sensor outputs.

This chapter discusses the types of failures that can occur in sheet metal forming tools and explains how to mitigate their effects. It describes the factors that influence galling and wear and the benefits of special treatments and coatings. It provides information on through hardening, case (surface) hardening, and nitriding as well as hard chrome plating, vapor deposition, and thermal diffusion coating. It explains how to measure wear resistance using various tests and provides guidelines for selecting tool materials, treatments, and coatings.

Temperature is a critical process parameter in the heat treatment and forging of steel and must be accurately measured to properly control it. This appendix discusses the operating principles of thermocouples and infrared pyrometers, describing the various types as well as advantages and applications.

The temperature and atmosphere conditions must be precisely controlled in order to achieve the desired metallurgical results during heat treating operations. In order to ensure the repeatability of operation, a heat treating system must have the necessary sensors, timers, and variable (temperature, atmosphere, etc.) controllers to hold the process within prescribed or specified limits. This chapter discusses temperature and atmosphere sensors used in a heat treating system. The temperature sensors covered are contact and noncontact types. The atmosphere sensors covered are oxygen probe, dew point, and infrared. The chapter concludes with an overview of the development of integrated control systems.