There are numerous approximate methods, both analytical and numerical, for analyzing forging processes. None are perfect because of the assumptions made to simplify the mathematical approach, but all have merit. This chapter discusses the slab, upperbound, and finite element methods, covering basic principles, implementation, and advantages and disadvantages in various applications.

This article reviews the fundamental and specific factors that control the properties of steel weldments in both the weld metal and heat-affected zone (HAZ). The influence of welding processes, welding consumables, and welding parameters on the weldment properties is emphasized. The service properties of weldments in corrosive environments are considered and subjected to cyclic loading. The article summarizes the effects of major alloying elements in carbon and low-alloy steels on HAZ microstructure and toughness. It discusses the processes involved in controlling toughness in the HAZ and the selection of the proper filler metal. The article provides a comparison between single-pass and multipass welding and describes the effect of welding procedures on weldment properties and the effects of residual stresses on the service behavior of welded structures. It also describes the fatigue strength and fracture toughness of welded structures. The article reviews various types of corrosion of weldments.

This chapter discusses the use of finite-element modeling in forging design. It describes key modeling parameters and inputs, mesh generation and computation time, and process modeling outputs such as metal flow, strain rate, loading profiles, and microstructure. It also includes a variety of application examples.

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 discusses the selection, use, and integration of methods to control process variables in induction heating, including control of workpiece and processing temperature and materials handling systems. The discussion of temperature control includes a review of proportional controllers and heat-regulating devices. Integration of control functions is illustrated with examples related to heating of steel slabs, surface hardening of steel parts, vacuum induction melting for casting operations, and process optimization for electric-demand control. Distributed control within larger manufacturing systems is discussed. The chapter also covers nondestructive techniques for process control and methods for process simulation.

Duplex stainless steels are two-phase alloys based on the iron-chromium-nickel system. Duplex stainless steels offer corrosion resistance and cost advantages over the common austenitic stainless steels. Although there are some problems with welding duplex alloys, considerable progress has been made in defining the correct parameters and chemistry modifications for achieving sound welds. This chapter provides a basic understanding of the development, grade designations, microstructure, properties, and general welding considerations of duplex stainless steel. It also discusses the influence of ferrite-austenite balance on corrosion resistance and the influence of different welding conditions on various material properties of alloy 2205 (UNS S31803).

The overall chemical composition of metals and alloys is most commonly determined by x-ray fluorescence (XRF) and optical emission spectroscopy (OES). High-temperature combustion and inert gas fusion methods are typically used to analyze dissolved gases (oxygen, nitrogen, and hydrogen) and, in some cases, carbon and sulfur in metals. This chapter discusses the operating principles of XRF, OES, combustion and inert gas fusion analysis, surface analysis, and scanning auger microprobe analysis. The details of equipment set-up used for chemical composition analysis as well as the capabilities of related techniques of these methods are also covered.

Ion nitriding equipment can be categorized into two groups: cold-wall continuous direct current (dc) equipment and hot-wall pulsed dc equipment. This chapter focuses on these two categories along with other important considerations for ion (plasma) nitriding equipment and processing. Other important considerations discussed include the hollow cathode effect, sputter cleaning, furnace loading, pressure/voltage relationships, workpiece masking, and furnace configuration options. The chapter describes five methods of cooling parts from the process temperature to an acceptable exposure temperature after plasma nitriding. The chapter also presents some of the advantages of the pulsed plasma process.

Induction heating, in most applications, is used to selectively heat only a portion of the workpiece that requires treatment. This chapter covers the basic principles, features, and metallurgical aspects of induction heating. The discussion includes the conditions required for induction heating and quenching, the use of magnetic flux concentrators to improve the efficiency of surface heating, and the quenching systems used for induction hardening. The discussion also provides information on time-temperature dependence in induction heating, workpiece distortion in induction surface hardening, residual stresses after induction surface hardening and finish grinding, and input and output control of steel for induction surface hardening of gears.

This chapter discusses the equipment and processes used to convert titanium billet and bar into useful shapes or more refined product forms. These secondary working operations include open-die, closed-die, hot-die and isothermal forging as well as ring rolling and extruding. The chapter describes each method in detail and how it affects the microstructure and mechanical properties of various titanium alloys. It also discusses the propensity of titanium to react with oxygen and hydrogen when heated and explains how to mitigate the effects.

This chapter discusses the basic principles of induction heating and related engineering considerations. It describes the design and operation of induction coils, the magnitude and distribution of magnetic fields, and the forces that generate eddy currents in metals. It explains how induced electrical current causes metal to heat in proportion to their electrical resistance and how it affects temperature dependent properties such as resistivity and specific heat and, in turn, heating rates and efficiencies. It also discusses the effect of hysteresis and explains why eddy currents tend to be confined to the outer surface of the workpiece, a phenomenon known as the skin effect. The chapter includes several data plots showing how the depth of heating varies with frequency and how heating time, power density, and thermal conduction rate correspond with hardening depth.

During fusion welding, the thermal cycles produced by the moving heat source causes physical state changes, metallurgical phase transformations, and transient thermal stresses and metal movement. This chapter begins by discussing weld metal solidification behavior and the solid-state transformations of the main classes of metals and alloys during fusion welding. The main classes include work- or strain-hardened metals and alloys, precipitation-hardened alloys, transformation-hardened steels and cast irons, stainless steels, and solid-solution and dispersion-hardened alloys. The following section provides information on the residual stresses and distortion that remain after welding. The focus then shifts to distortion control of weldments. Inclusions and cracking are discussed in detail. The chapter also discusses the causes for reduced fatigue strength of a component by a weld: stress concentration due to weld shape and joint geometry; stress concentration due to weld imperfections; and residual welding stresses. Inspection and characterization of welds are described in the final section of this chapter.

This chapter surveys both basic quality and basic reliability concepts as an introduction to the failure analysis professional. It begins with a section describing the distinction between quality and reliability and moves on to provide an overview of the concept of experiment design along with an example. The chapter then discusses the purposes of reliability engineering and introduces four basic statistical distribution functions useful in reliability engineering, namely normal, lognormal, exponential, and Weibull. It also provides information on three fundamental acceleration models used by reliability engineers: Arrhenius, Eyring, and power law models. The chapter concludes with information on failure rates and mechanisms and the two techniques for uncovering reliability issues, namely burn-in and outlier screening.

This chapter discusses various factors that affect corrosion of stainless steel weldments. It begins by providing an overview of the metallurgical factors associated with welding. This is followed by a discussion on preferential attack associated with weld metal precipitates in austenitic stainless steels as well as several forms of corrosion associated with welding. The effects of gas-tungsten arc weld shielding gas composition and heat-tint oxides on corrosion resistance are then covered. Microbiological corrosion of butt welds in water tanks is also illustrated. In addition, the chapter provides information on corrosion of ferritic and duplex stainless steel weldments.

Induction hardened steels are often tempered to increase their ductility and relieve quenching stresses. During tempering, martensitic microstructures supersaturated with carbon decompose into a more stable, ductile form. This chapter discusses the transformations associated with the tempering process and their effect on ductility as well as other properties. It describes the structural and compositional changes that occur during the four stages of tempering, the relative influence of time and temperature, and how tempering affects the hardness of various grades of steel. The chapter discusses the practice of both furnace and induction tempering, describing where and how they are used, their tempering characteristics, strengths and limitations, and operating parameters. It also discusses the use of residual heat tempering, a self-tempering process.

Many defects generate excessive heat during operation; this is due to the power dissipation associated with the excess current flow at the defect site. There are several thermal detection techniques for failure analysis and this article focuses on infrared thermography with lock-in detection, which detects an object's temperature from its infrared emission based on blackbody radiation physics. The basic principles and the interpretation of the results are reviewed. Some typical results and a series of examples illustrating the application of this technique are also shown. Brief sections are devoted to the discussion on liquid-crystal imaging and fluorescent microthermal imaging technique for thermal detection.

This chapter provides a discussion of nitriding furnace equipment and control systems. The discussion covers the essential design criteria of the furnace, types of nitriding furnaces, insulation for the reduction of furnace heat losses, and factors influencing furnace configuration and design. It also covers the processes involved in the construction and maintenance of retorts, methods for sealing a retort to prevent ammonia leaks, and safety precautions to be taken while using ammonia. Further, the chapter provides information on the factors for choosing a heating medium and discusses the processes involved in controlling temperature, gas dissociation, oxygen probes, and nitriding sensors.

Photon emission (PE) is one of the major optical techniques for contactless isolation of functional faults in integrated circuits (ICs) in full electrical operation. This article describes the fundamental mechanisms of PE in silicon based ICs. It presents the opportunities of contactless characterization for the most important electronic device, the MOS - Field Effect Transistor, the heart of ICs and their basic digital element, the CMOS inverter. The article discusses the specification and selection of detectors for proper PE applications. The main topics are image resolution, sensitivity, and spectral range of the detectors. The article also discusses the value and application of spectral information in the PE signal. It describes state of the art IC technologies. Finally, the article discusses the applications of PE in ICs and also I/O devices, integrated bipolar transistors in BiCMOS technologies, and parasitic bipolar effects like latch up.

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.

This chapter provides an introduction to metal forming processes and where they fit among the five general areas of manufacturing. It also discusses the basic differences between bulk deformation and sheet-metal forming processes and how they relate to hybrid forming processes such as drawing, bending, and coining.