Search Results for geometric irregularities

This chapter begins by presenting a generic eutectic phase diagram and identifying critical points, lines, and features. It then describes the composition and properties of aluminum-silicon and lead-tin eutectic systems, the characteristics of eutectic morphologies, the solidification and scale of eutectic structures, and the competitive growth of dendrites and eutectic colonies or cells. It also examines the different types of precipitation structures that form during slow cooling cycles.

The coordinate measuring machine (CMM) is used for three-dimensional inspection of both in-process and finished parts. This chapter provides a detailed account of the operating principles, measurement techniques, capabilities, and applications of CMMs. The types of CMMs are described. Vertical CMMs include cantilever-type, bridge-type, and gantry CMMs; horizontal CMMs, such as the horizontal-arm type, are also covered. The CMM application for geometric measurement, contour measurement, and specialized surface measurement are discussed.

Weldments made by the various welding processes may contain discontinuities that are characteristic of that process. This chapter discusses the different welding processes as well as the discontinuities typical of each process. It provides a detailed discussion on the methods of nondestructive inspection of weldments including visual inspection, liquid penetrant inspection, magnetic particle inspection, radiographic inspection, ultrasonic inspection, leak testing, and eddy current and electric current perturbation inspection. The chapter also describes the properties of brazing filler metals and the types of flaws exhibited by brazed joints.

This chapter describes how notches affect the load-carrying capacity and fatigue life of materials under cyclic loads. It explains that stresses and strains can be three to four times higher in the vicinity of a notch, greatly accelerating fatigue damage. It discusses the use of stress concentration factors and how they are determined for the general case and for specific geometries, materials, and surface conditions. The chapter covers both elastic and plastic fatigue behaviors as well as a wide range of methods. It also explains how small nuances in loading can introduce tensile or compressive stress in the hysteresis loops causing variations in fatigue life as large as 50:1 depending on where the transition in fatigue behavior occurs.

Microstructural analysis of the composite matrix is necessary to understand the performance of the part and its long-term durability. This chapter focuses on the microstructural analysis of engineering thermoplastic-matrix composites and the influence of cooling rate and nucleation on the formation of spherulites in high-temperature thermoplastic-matrix carbon-fiber-reinforced composites. It also describes the microstructural analysis of a bio-based thermosetting-matrix natural fiber composite system.

This chapter provides a concise, design-oriented summary of more than 30 sheet forming processes within the categories of bending and flanging, stretch forming, deep drawing, blank preparation, and incremental and hybrid forming. Each summary includes a description and diagram of the process and a bullet-point list identifying relevant equipment, materials, variations, and applications. The chapter also discusses critical process variables, interactions, and components and the classification of sheet metal parts based on geometry.

The wear caused by contact stress fatigue is the result of a wide variety of mechanical forces and environments. This chapter discusses the characteristics of four types of contact stress fatigue on mating metal surfaces: surface, subsurface, subcase, and cavitation. Features and corrective actions for these contact stress fatigue are discussed. The chapter also lists some possible ways to reduce the cavitation fatigue problem.

This chapter introduces the key powder fabrication attributes to assist in the identification of the right powders for an application. First, it describes the characteristics of engineering powders such as particle size distribution, powder shape and packing density, surface area, powder flow and rheology, and chemical analysis. The chapter then describes the general categories of powder fabrication methods, namely mechanical comminution, electrochemical precipitation, thermochemical reaction, and phase change and atomization. It provides information on the two largest contributors to powder price, namely raw material cost and conversion cost. The applicability of various processes to specific material systems is mentioned throughout this chapter.

Welded joints in any component or structure require a thorough inspection. The role of nondestructive evaluation (NDE) in the inspection of welds is very important, and the technology has become highly developed as a result. This article describes the applications, methods, evaluation procedures, performance, and limitations of NDE. It provides information on the training and certification of NDE operators, evaluation of test results, and guidance to method selection. Typical examples of various NDE methods for welds are also described.

Fatigue failures occur due to the application of fluctuating stresses that are much lower than the stress required to cause failure during a single application of stress. This chapter describes three basic factors that cause fatigue: a maximum tensile stress of sufficiently high value, a large enough variation or fluctuation in the applied stress, and a sufficiently large number of cycles of the applied stress. The discussion covers high-cycle fatigue, low-cycle fatigue, and fatigue crack propagation. The chapter then discusses the stages where fatigue crack nucleation and growth occurs. It describes the most effective methods of improving fatigue life. The chapter also explains the effect of geometrical stress concentrations on fatigue. In addition, it explores the environmental effects of corrosion fatigue, low-temperature fatigue, high-temperature fatigue, and thermal fatigue. Finally, the chapter discusses a number of design philosophies or methodologies to deal with design against fatigue failures.

This chapter is a compilation of terms and definitions related to surface engineering for corrosion and wear resistance.

This chapter discusses radiography methods using x-rays, gamma rays, and neutrons. It begins with a discussion on the applications and principles of radiography followed by sections providing information on the sources of radiation, classifications, and characteristics of x-ray tubes. Three primary attenuation processes of electromagnetic radiation, namely photoelectric effect, Compton scattering, and pair production, are covered. The chapter then discusses the principles of shadow formation, the process involved in the conversion of radiation into a form suitable for observation, and the characteristics of x-ray film. It provides information on various exposure factors in film radiography. The chapter provides a description of the characteristics that differentiate neutron radiography from x-ray or gamma ray radiography. The application of neutron radiography is described in terms of its advantages for improved contrast on low atomic number materials, discrimination between isotopes, or inspection of radioactive specimens.

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 serves as a study and guide on the main phase constituents of cast aluminum-silicon alloys, alpha-Al solid solution and Si crystals. The first section focuses on the structure of Al-Si castings in the as-cast state, covering the morphology of the alpha-Al solid solution grains and the process by which they form. It describes how cooling rates, temperature gradients, and local concentrations influence the topology of the crystallization front, and how they play a role in determining the morphology and dispersion degree of the grains observed in cross sections of cast parts. It also describes the mechanism behind dendritic grain crystallization and how factors such as surface tension, capillary length, and lattice symmetry affect dendritic arm size and spacing. The section that follows examines the morphology of the silicon crystals that form in aluminum-silicon castings and its effect on properties and processing characteristics. It discusses the faceted nature of primary Si crystals and the modification techniques used to optimize their shape. It also describes the morphology of the (alpha-Al + Si) eutectic, which can be lamellar or rodlike in shape, and explains how it can be modified through temperature control or alloy additions to improve properties such as tensile strength and plasticity and reduce shrinkage.

Discontinuities are interruptions in the desirable physical structure of a weld. This article describes the types of weld discontinuities that are characteristic of the principal welding processes. Discontinuities covered are metallurgical discontinuities, discontinuities associated with specialized welding processes, and base metal discontinuities. In addition, information on the common inspection methods used to detect these discontinuities is provided.

Stainless steel powders are usually made by water or gas atomization. This chapter describes both processes and the properties and characteristics of the powders they produce. It also discusses secondary processes, including drying, screening, annealing, and lubricating, and the effects of iron contamination on corrosion resistance.

The Nuclear Waste Management Organization (NWMO) investigates approaches for managing Canada's used nuclear fuel. As part of a larger program investigating concepts of copper coatings, NWMO has begun exploring copper cold spray in collaboration with the National Research Council. Within the coating program, a large variety of copper coating sizes have been investigated, from small corrosion coupons to full-scale used-fuel containers/canisters (UFCs). This chapter demonstrates the successful application of copper coating technology to full-scale geometric representative Mark II UFC mock-up configurations through activities involving powder selection, general coating development, UFC coating optimization, and prototyping.

This chapter presents a fracture-mechanics-based approach to damage tolerance, accounting for mechanical, metallurgical, and environmental factors that drive crack development and growth. It begins with a review of stress-intensity factors corresponding to a wide range of crack geometries, specimen configurations, and loading conditions. The discussion covers two- and three-dimensional cracks as well as the use of correction factors and problem-simplification techniques for dealing with nonstandard configurations. The chapter goes on to describe how fatigue loading affects crack growth rates in each of the three stages of progression. Using images, diagrams, and data plots, it reveals how cracks advance in step with successive stress cycles and explains how fatigue crack growth rates can be determined by examining striations on fracture specimens and correlating their widths with stress profiles. It also describes how material-related factors, load history, corrosion, and temperature affect crack growth rates, and discusses the steps involved in life assessment.

This chapter reviews the types of friction that are of concern in tribological systems along with their associated causes and effects. It discusses some of the early discoveries that led to the development of friction laws and the understanding that friction is a system effect that can be analyzed based on energy dissipation. It describes the stick-slip behavior observed in wiper blades, the concept of asperities, and the significance of the shape, lay, roughness, and waviness of surfaces in sliding contact. It explains how friction forces are measured and how they are influenced by speed, load, and operating environment. It also covers rolling contact and fluid friction and the effect of lubrication.