Search Results for Deviations from ideality

This article is intended to help engineers understand why the fatigue behavior of weldments can be such a confusing and seemingly contradictory topic and hopefully to clarify this complex subject. It first reexamines the factors influencing the fatigue behavior of an individual weldment using extensive experimental data and a computer model that simulates the fatigue resistance of weldments. Next, the process of fatigue in weldments is discussed in general terms, and the service conditions that favor long crack growth and the conditions that favor crack nucleation are contrasted. The article then presents experimental data that show the effect of weldment geometry on fatigue resistance. Several useful geometry classification systems are compared. Finally, a computer model is employed to investigate the behavior of two hypothetical weldments: a discontinuity-containing ("Nominal") weldment and a discontinuity-free ("Ideal") weldment.

This appendix explains how to calculate atomic packing factors, lattice parameters, and coordination numbers for cubic crystal structures, including simple, body-centered, and face-centered cubic systems. It also addresses hexagonal close-packed systems.

This chapter discusses the history of hardness testing and defines the term hardness. It describes the interrelationship between material structure and hardness and the relationships between hardness and other mechanical material properties. In addition, information on the hardness unit and traceability of the hardness measurement are provided.

Users of steel castings establish performance requirements for specific characteristics of the castings based on the planned use. They express tolerance for variation in those characteristics to the producer of the castings. One issue which should never be taken for granted in considering capability and tolerances is the ability to measure with accuracy and precision (repeatability and reproducibility). This chapter discusses the methods for measuring accuracy and precision. It describes the variation of process characteristics, capability indices in general use, and factors related to process performance and tolerance specification.

Transistors are the most important active structure of any semiconductor component. Performance characteristics of such devices within the specifications are key to ensuring proper functionality and long-term reliability of the product. In this article, a summary of the semiconductor technology from design to manufacturing and the characterization methods are discussed. The focus is on two prominent MOS structures: planar MOS device and FinFET device. The article covers the device parameters and device properties that determine the design criteria and the device tuning procedures. The discussion includes the effects of drain induced barrier lowering, velocity saturation, hot carrier degradation, and short channel on these devices.

Bonding in solids may be classified as either primary or secondary bonding. Methods of primary bonding include the metallic, ionic, and covalent bonds. This chapter discusses and provides a comparison of the properties of these bonds. This is followed by a discussion on crystalline structure, providing information on space lattices and crystal systems, hexagonal close-packed systems, and face-centered and body-centered cubic systems. The chapter then covers slip systems and closes with a brief section on allotropic transformations that occur at a constant temperature during either heating or cooling.

This chapter discusses the characteristics, advantages, and disadvantages of nondestructive hardness testing methods for metals, including electromagnetic impulse testing, photothermal testing, scratch hardness testing, and ultrasonic contact impedance testing. It also discusses the use of ultrasound to determine the depth of hardening in a metal or alloy. The chapter reviews methods used to check and calibrate hardness testing machines and indenters and the use of hardness reference blocks for verification and calibration of test machines. It also addresses conversion of hardness values determined by one method to equivalent values for a different method.

Instrumented indentation hardness testing significantly expands on the capabilities of traditional hardness testing. It employs high-resolution instrumentation to continuously control and monitor the loads and displacements of an indenter as it is driven into and withdrawn from a material. The scope of application comprises displacements even smaller than 200 nm (nano range) and forces even up to 30 kN . Mechanical properties are derived from the indentation load-displacement data obtained in simple tests. The chapter presents the elements of contact mechanics that are important for the application of the instrumented indentation test. The test method according to the international standard (ISO 14577) is discussed, and this information is supplemented by information about the testing technique and some example applications. The chapter concludes with a discussion on the extensions of the standard that are expected in the future (estimation of the measurement uncertainty and procedures for the determination of true stress-strain curves).

This chapter deals with the technology of stainless steel as it pertains to its proper use in architecture, art, and construction. It begins with an overview of the corrosion resistance of stainless steel, providing guidelines for balancing corrosion resistance, processing characteristics, and economy. This is followed by sections describing the influence of surface finish on corrosion resistance of stainless steel and reviewing some of the factors pertinent to balancing service environment, design requirements, and maintenance considerations. The chapter then discusses the various factors pertinent to important considerations in buildings, namely surface finish aesthetics, flatness, maintenance, repair, fabrication, and service considerations. It ends with a section providing information on concrete reinforcing bar.

Tensile tests are performed for several reasons related to materials development, comparison, selection, and quality control. The properties derived from tensile tests are used in selecting materials for engineering applications. Tensile properties often are used to predict or estimate the behavior of a material under forms of loading other than uniaxial tension. This chapter provides a brief overview of tensile specimens and test machines, stress-strain curves, true stress and strain, and test methodology and data analysis.

In the case of gearboxes, vibration is the primary mode of failure even at the mid-range of operating speeds. Avoiding such failures requires an understanding of gearbox design, vibration theory, and material properties. This chapter details sources and types of gearbox vibrations; characteristics of gearbox vibrations; fundamentals of periodic vibrations; and vibration theory. It provides housing design for single-stage offset parallel gearboxes, high-speed gearboxes, and epicyclic gearboxes. The chapter then provides an analysis and selection of design factors for vibration reduction. It presents five types of gear tooth geometry errors. The chapter also focuses on gear quality inspection and on bearing-induced vibrations.

Hardness tests provide valuable information about the quality of materials and how they are likely to perform in different types of service. This chapter covers some of the most widely used hardness testing methods, including Vickers, Rockwell, and Brinell tests, Shore scleroscope and Equotip hardness tests, and microindentation tests. It describes the equipment and procedures used, discusses the factors that influence accuracy, and provides hardness conversion equations for different types of materials. It also explains how hardness testing sheds light on anisotropy, machinability, wear, fracture toughness, and tensile strength as well as temperature effects, residual stress, and quality control.

This chapter provides an overview of a computational method, called CALPHAD, used for the study of phase equilibria in multicomponent systems. It describes the thermodynamic models and calculation techniques employed in the software and explains how it applies to complex alloys used in industry. It also provides examples showing how CALPHAD has been used to determine the formability of metallic glass, calculate the dilation of stainless steel during phase transformation, and predict the beta transus and approach curves of commercial titanium alloys.

Time-domain based characterization methods, mainly time-domain reflectometry (TDR) and time-domain transmissometry (TDT), have been used to locate faults in twisted cables, telegraph lines, and connectors in the electrical and telecommunication industry. This article provides a brief review of conventional TDR and its application limitations to advanced packages in semiconductor industry. The article introduces electro optical terahertz pulse reflectometry (EOTPR) and discusses how its improvements of using high frequency impulse signal addressed application challenges and quickly made it a well-adopted tool in the industry. The third part of this article introduces a new method which combines impulse signal and the TDT concept, and discusses a combo TDR and TDT method. Cases studies and application notes are shared and discussed for each technique. Application benefits and limitations of these techniques (TDR, EOTPR, and combo TDR/TDT) are summarized and compared.

This appendix provides a detailed overview of the crystal structure of metals. It describes primary bonding mechanisms, space lattices and crystal systems, unit cell parameters, slip systems, and crystallographic planes and directions as well as plastic deformation mechanisms, crystalline imperfections, and the formation of surface or planar defects. It also discusses the use of X-ray diffraction for determining crystal structure.

The inspection of castings normally involves checking for shape and dimensions, coupled with aided and unaided visual inspection for external discontinuities and surface quality. This chapter discusses methods for determining surface quality, internal discontinuities, and dimensional inspection. Casting defects including porosity, oxide films, inclusions, hot tears, metal penetration, and surface defects are reviewed. Liquid penetrant inspection, magnetic particle inspection, eddy current inspection, radiographic inspection, ultrasonic inspection, and leak testing for castings are discussed. The chapter provides information on the procedures involved in the inspection of castings that are limited to visual and dimensional inspections, weight testing, and hardness testing. It also discusses the use of computer equipment in foundry inspection operations.

This chapter discusses some of the methods and measurements used to construct phase diagrams. It explains how cooling curves were widely used to determine phase boundaries, and how equilibrated alloys examined under controlled heating and cooling provide information for constructing isothermal and vertical sections as well as liquid projections. It also explains how diffusion couples provide a window into local equilibria and identifies typical phase diagram construction errors along with problems stemming from phase-boundary curvatures and congruent transformations.

The testing of plastics includes a wide variety of chemical, thermal, and mechanical tests. This chapter reviews the tensile testing of plastics, which has been standardized in ASTM D 638, "Standard Test Method for Tensile Properties of Plastics," and other comparable standards. It describes the fundamental factors that affect data from tensile tests, examines the stipulations in standardized tensile testing, and discusses the utilization of data from tensile tests.