The primary goal of quality control in electron beam (EB) welding is to consistently produce defect-free and structurally sound welds. This article discusses the common procedures for controlling the EB welding process, the control of the essential machine parameters, and the introduction of closed-loop controls and diagnostic feedback systems in the EB welding systems. It reviews the beam diagnostic tools that interrogate the beam to produce a reconstruction of the power density distribution and provide additional information on the size and shape of the EB. Knowledge of these beam parameters can be used to improve process understanding and control. The article also describes the application areas of beam diagnostics: machine characterization, weld parameter transfer, and weld quality control.

This article provides an overview of the methods used to control aspects of the arc welding process and research associated with the development of closed-loop feedback control of the process. Successful implementation of a closed-loop feedback control system requires sensing, modeling, and control. The article describes the commonly applied sensing techniques for arc welding control: arc sensing and nonimaging and imaging optics. It reviews the physics-based, empirically-derived, and neural network models for arc welding control. The article also discusses the research and development activities that attempt to extend the commercial, welding process controllers, namely, adaptive control, intelligent control, multivariable control, and distributed, hierarchical control.

The basic elements of control design are safety, process control, process verification, machine control, productivity, repeatability, and ease of setup. Effective systems of quality control/quality assurance are essential for heat treating practices. This article provides information on process control modes, as well as on process signatures of some items that require control, monitoring, verifying, and logging methods. It provides information on programmable logic controllers that have become efficient in machine control and monitoring. The article describes possible noise issues, National Electric Code clearance requirements, monitoring requirements, and machine accuracy that need to be considered when designing induction equipment.

Induction heating system control is straightforward after the design and application of the coil and power supply required for the job. This article provides an overview of the basic components of an induction heating system, including a machine controller (computer or programmable logic controller), interface wiring, an operator interface, and safety controls. It also provides information on programming devices and temperature controllers, such as manual, auto, and auto-manual temperature controllers.

This article discusses the evolution of computer numerical control and direct numerical control for machine tools. It describes the fundamentals and advantages of numerical control (NC) systems. The article reviews the manual or computer assisted off-line programming methods for programming the tools with the aid of the automatically programmed tool language. It also explains point-to-point and continuous-path or contouring of NC systems and the adaptive systems used for NC.

This article provides an overview of the adoption of additively manufactured materials in dentistry. It discusses the practical workflows of a three-dimensional printing technology, vat photopolymerization. Three subgroups of the vat photopolymerization process are laser beam or classic stereolithography apparatus (SLA), direct light processing, and liquid-crystal-display-masked SLA. The article covers two subgroups of 3D printing resins-based appliances, namely intraoral and extraoral appliances. Information on various types of dental appliances and the fabrication of in-office appliances is provided. The article also reviews fourth-dimension printing and discusses the applications of the personalized care model in medicine and dentistry.

This article provides a description of various systems for computer-aided materials selection that deals primarily with promising prototypes that have emerged for various applications. These include expert systems, quantitative selection systems, qualitative and experiential selection systems, and object-oriented systems.

Induction heating has many different applications, such as melting, heating stock for forging, and heat treating. This article begins with a discussion on the types of power supplies, namely, solid-state power supplies and oscillator tubes. It provides information on system elements, including cooling systems, power supplies, heat stations, work handling fixtures, induction or work coils, and quench systems. The article discusses the influence of system elements on induction heat treating system design. It also deals with the general theory, types, and applications of induction coils.

This article discusses the principles and limitations of micromagnetic techniques, namely, magnetic Barkhausen noise (MBN) and magnetoacoustic emission (MAE). It also discusses various factors limiting the establishment of acceptance criteria for test components as they pertain to the successful application of MBN measurement and signal interpretation. The article provides an overview of basic magnetic phenomena and dynamics in ferromagnetic materials that underlie the origin of MBN emissions. It describes the changes in the domain structure of the ferromagnetic material under an applied external field. The relationship between uniaxial stress and angular-dependent strain is also discussed. The influence of stress on domain walls, and therefore, the generation of Barkhausen noise are described. The article also describes the directional and angular MBN measurements and provides information on detection, angular dependence, and advanced analysis methods of MBN emissions.

Heat treating furnaces require different control systems and integration for achieving optimum technical results and enabling safe operation. This article focuses on atmosphere furnaces, with some coverage on controls for vacuum furnaces. Heat treating operations require reliable monitoring and control of motion and position of various mechanical components with the help of mechanical limit switches, proximity sensors, and distance- and position-measuring devices. Using inputs from both flow meters and sensors, such as thermocouples and oxygen sensors, flow measurement control systems must be able to adjust the flow of gases for process optimization. The operator interface of a furnace-control system displays critical information such as the furnace temperature, atmosphere status, alarms, electronic chart recorders, recipe, and maintenance. A supervisory control and data-acquisition (SCADA) system is used to monitor, collect, and store data from multiple pieces of equipment.

Ultrasonic inspection is a nondestructive technique that is useful in both quality control and research applications for flaw detection in fiber-reinforced composite materials. This article describes ultrasonic nondestructive analysis by outlining its three basic types of scans. It reviews the important quality control techniques used during the manufacture of composite components by analyzing tooling control, material control, pattern orientation control, and in-process control.

This article discusses various control processes carried out in powder feeding, thermal spraying, and gas flow of the thermal spray process to standardize the coating quality. Quality of the entire powder feeding process can be achieved by controlling the processing of feeding equipment as well as the characteristics of the powder being fed. Gas flow control can be achieved by using rotameters, critical orifices, and thermal mass flowmeters, whose ability to provide useful information is defined by their resolution, accuracy, linearity, and repeatability. The commercial thermal spray controls discussed here include the open-loop input-based, open-loop output-based, closed-loop input-based, and closed-loop output-based or adaptive controls. The article discusses the common causes and practical solutions for arc starting problems. It also outlines certain important developments in measuring individual and collective particle velocities, temperature, and trajectories as well as other plume characteristics for the plasma spray process.

The article provides an overview of the various types of testing machines: gear-driven or screw-driven machines and servohydraulic machines. It examines force application systems, force measurement, and strain measurement. The article discusses important instrument considerations and describes gripping techniques of test specimens. It analyzes test diagnostics and reviews the use of computers for gathering and reducing data. Emphasis is placed on universal testing machines with separate discussions of equipment factors for tensile testing and compressing testing. The influence of the machine stiffness on the test results is also described, along with a general assessment of test accuracy, precision, and repeatability of modern equipment.

Three-dimensional plotting of biomaterials (also known as bioprinting) has been a major milestone for scientists and engineers working in nanobiotechnology, nanoscience, and nanomedicine. It is typically classified into two major categories, depending on the plotting principle, as contact and noncontact techniques. This article focuses on the working principles of contact and noncontact printing methods along with their advantages, disadvantages, applications, and challenges. Contact printing methods include micro-plotter, pen printing, screen printing, nanoimprint printing, flexography printing, and gravure printing. Noncontact printing methods include extrusion printing, droplet printing, laser-based polymerization, and laser-based cell transfer. The wide variety of printable biomaterials, such as DNA, peptides, proteins, lipids, and cells, also are discussed.

This article describes the methodology for performing a failure modes and effects analysis (FMEA). It explains the methodology with the help of a hot water heater and provides a discussion on the role of FMEA in the design process. The article presents the analysis procedures and shows how proper planning, along with functional, interface, and detailed fault analyses, makes FMEA a process that facilitates the design throughout the product development cycle. It also discusses the use of fault equivalence to reduce the amount of labor required by the analysis. The article shows how fault trees are used to unify the analysis of failure modes caused by design errors, manufacturing and maintenance processes, materials, and so on, and to assess the probability of failure mode occurrence. It concludes with information on some of the approaches to automating the FMEA.

Corrosion monitoring is important in the operation of modern industrial plants and in the use and maintenance of expensive assets such as bridges and aircrafts, because the damage caused by corrosion and the rate of the deterioration can be huge and the risks devastating. This article discusses the system considerations and installation techniques of different types of direct and indirect techniques in electrochemically based on-line corrosion monitoring process. It describes the importance of probe location and on-line corrosion monitoring techniques with examples.

Computed tomography (CT) is an imaging technique that generates a three-dimensional (3-D) volumetric image of a test piece. This article illustrates the basic principles of CT and provides information on the types, applications, and capabilities of CT systems. A comparison of performance characteristics for film radiography, real-time radiography, and X-ray computed tomography is presented in a table. A functional block diagram of a typical computed tomography system is provided. The article discusses CT scanning geometry that is used to acquire the necessary transmission data. It also provides information on digital radiography, image processing and analysis, dual-energy imaging, and partial angle imaging, of a CT system.

The atmosphere within a furnace chamber is a basic factor in achieving the desired chemical reactions with metals during heat treating. This article presents the fundamentals of heat treating atmospheres, and describes two groups of atmosphere control, namely, furnace atmosphere control and supply atmosphere control. The two basic types of atmospheric supply systems are generated atmospheres and nitrogen-base atmospheres. The article provides a brief overview of the gas reactions associated with oxidation and carbon control to ensure either carburization, or to prevent decarburization. It demonstrates how the carbon potential control is achieved by controlling water vapor concentration, carbon dioxide concentration, or oxygen partial pressure. The article also describes the various devices and analyzers used to monitor sampled gas from furnace atmospheres, namely, chromatographs, oxygen probes, Orsat analyzers, infrared analyzers, dewpoint analyzers, and hot-wire analyzers. Finally, it discusses the advantages, disadvantages, and limitations of these analyzers.

Additive manufacturing (AM), or three-dimensional (3D) printing, is a class of manufacturing processes that create the desired geometries of an object, or an assembly of objects, layer by layer or volumetrically. AM has been used extensively for manufacturing medical devices, due to its versatility to satisfy the specific needs of an intended medical field for the product/device. This article provides a comprehensive review of AM in medical devices by the medical specialty panels of the Food and Drug Administration (FDA) Code of Federal Regulations, Parts 862 to 892, including anesthesiology, ear and nose, general hospital, ophthalmic, plastic surgery, radiology, cardiovascular, orthopedic, dental, neurology, gynecology, obstetrics, physical medicine, urology, toxicology, and pathology. It is classified under these panels, and critical reviews and future outlooks are provided. The application of AM to fabricate medical devices in each panel is reviewed; lastly, a comparison is provided to reveal relevant gaps in each medical field.

This article covers in-line process monitoring of the metal additive manufacturing (AM) methods of laser and electron beam (e-beam) powder-bed fusion (PBF) and directed-energy deposition (DED). It focuses on methods that monitor the component directly throughout the build process. This article is organized by the type of AM process and by the physics of the monitoring method. The discussion covers two types of monitoring possible with the PBF process: monitoring the area of the powder bed and component and monitoring the melt pool created by the laser or e-beam. Methods for layer monitoring include optical and thermal methods that monitor light reflected or emitted in the visible and infrared wavelengths, respectively. Monitoring methods for laser directed-energy deposition (DED) discussed are those that measure the size and shape of the melt pool, the temperature of the melt pool, and the plasma generated by the laser as it interacts with the molten metal.