This article discusses the material and engineering issues associated with plastic components subjected to impact. The first part covers the effects of loading rate, temperature, and state of stress on both deformation and mode of failure. It discusses standard impact tests, along with their associated results. A brief discussion on the linear elastic fracture mechanics method is presented, along with an example of its effectiveness as a predictive tool for impact performance. Various issues with a bearing on impact performance, such as processing, chemical attack, and aging, are also described. The second part describes the engineering calculations used to predict the performance of thin plastic beams, plates, and shells. The issue of assuming small displacements for the calculation of plastic structure performance is discussed and its limitations described. An example of the consequence of the very low modulus of elasticity associated with plastics and some plastic design solutions are offered.

Fracture mechanics is the science of predicting the load-carrying capabilities of cracked structures based on a mathematical description of the stress field surrounding the crack. The fundamental ideas stem from the work of Griffith, who demonstrated that the strain energy released upon crack extension is the driving force for fracture in a cracked material under load. This chapter provides a summary of Griffith’s work and the subsequent development of linear elastic and elastic-plastic fracture mechanics. It includes detailed illustrations and examples, familiarizing readers with the steps involved in determining strain energy release rates, stress intensity factors, J-integrals, R-curves, and crack tip opening displacement parameters. It also covers fracture toughness testing methods and the effect of measurement variables.

This chapter focuses on some of the facts of mechanical properties of metals that must be understood to successfully undertake the task of failure analysis. The discussion begins by describing the causes and effects of elastic and plastic deformation followed by a section describing the effects of temperature variations on mechanical properties, both in tension and in compression. The nonlinear behavior of gray cast iron caused by the graphite flakes is then described. Finally, the effect of stress concentrations on high-strength metals is considered.

The relationship of stress and strength gradients must be considered simultaneously in analysis of a particular type of fracture. This chapter discusses the principal elastic stress distribution in members of various shapes under different types of pure loads. A basic understanding of both the stress and strength gradients of metal parts with and without stress concentrations and under different types of loading is provided. The chapter also describes the effect of service conditions on applied stresses.

A brittle fracture occurs at stresses below the material's yield strength (i.e., in the elastic range of the stress-strain diagram). This chapter focuses on brittle fracture in metals and, more specifically, ferrous alloys. It lists the factors that must all be present simultaneously in order to cause brittle fracture in a normally ductile steel. The chapter then discusses the macroscale characteristics and microstructural aspects of brittle fracture. A summary of the types of embrittlement experienced by ferrous alloys is presented. The chapter concludes with a brief section providing information on mixed fracture morphology.

Fracture mechanics is a well-developed quantitative approach to the study of failures. This chapter discusses fracture toughness and fracture mechanics, linear-elastic fracture mechanics, and modes of loading. The discussion also covers plane strain and stress and crack growth kinetics. The chapter presents a case history that illustrates the use of fracture mechanics in failure analysis. An appendix provides a more detailed discussion of fracture mechanics concepts.

This chapter addresses the challenge of selecting an appropriate stress-corrosion cracking (SCC) test to evaluate the serviceability of a material for a given application. It begins by establishing a generic model in which SCC is depicted in two stages, initiation and propagation, that further subdivide into several zones plus a transition region. It then discusses SCC test standards before describing basic test objectives and selection criteria. The chapter explains how to achieve the required loading conditions for different tests and how to prepare test specimens to determine elastic strain, plastic strain, and residual stress responses. It also describes the difference between smooth and precracked specimens and how they are used, provides information on slow-strain-rate testing and how to assess the results, and discusses various test environments and procedures, including tests for weldments. The chapter concludes with a section on how to interpret time to failure, threshold stress, percent survival, stress intensity, and propagation rate data, and assess the precision of the associated tests.

This chapter introduces the concepts of mechanical properties and the various underlying metallurgical mechanisms that can be used to alter the strength of materials. The mechanical properties discussed include elasticity, plasticity, creep deformation, fatigue, toughness, and hardness. The strengthening mechanisms covered are solid-solution strengthening, cold working, and dispersion strengthening. The effect of grain size on the yield strength of a material is also discussed.

This article describes the general aspects of and practical problems of failure analysis of creep, stress relaxation, and yielding for homogeneous polymers. The effect of temperature and strain rate on the relationship between yield point and elastic modulus and the aging effect that polymers often undergo at room temperature are also discussed.

This article briefly describes the historical development of fracture resistance testing of polymers and reviews several test methods developed for determining the fracture toughness of polymeric materials. The discussion covers J-integral testing, the methods for determining linear elastic fracture toughness, testing of thin sheets and films, normalization methods, and hysteresis methods.

This appendix provides readers with worked solutions to 25 problems involving calculations associated with tensile testing and the determination of mechanical properties and variables. The problems deal with engineering factors and considerations such as stress and strain, loading force, sample lengthening, and machine stiffness, and with mechanical properties and parameters such as elastic modulus, Young’s modulus, strength coefficient, strain-hardening exponent, and modulus of resilience. They also cover a wide range of materials including various grades of aluminum and steel as well as iron, titanium, brass, and copper alloys.

Beryllium, despite its relatively simple atomic structure, possesses a wide range of useful engineering properties. It has the highest strength-to-weight ratio and modulus of elasticity among structural metals and is an important alloy addition in copper, nickel, and aluminum alloys. It also has excellent thermal properties, low atomic mass, a small x-ray absorption cross section, and a large neutron scattering cross section. This brief introductory chapter provides an overview of the unique qualities of beryllium along with typical applications and uses.

This chapter provides a thorough review of the crystal structure of beryllium and its elastic, thermal, and nuclear properties. It also includes information on electrical and optical properties and an extensive amount of data in the form of tables and plots.

This chapter provides an overview of the physical metallurgy of beryllium, discussing phases and phase transformations, physical and mechanical properties, heat treatment, and alloying. It explains how the atomic structure of beryllium, particularly its sp hybrid state, contributes to the anisotropy of elastic constants and slip properties, resulting in a specific stiffness, or modulus-to-density ratio, six times higher than that of any other structural material.

This appendix contains tables listing the physical and mechanical properties of stainless steel engineering alloys. The physical properties covered are density, modulus of elasticity, coefficient of thermal expansion, thermal conductivity, specific heat, and electrical resistivity. The mechanical properties listed include yield strength, tensile strength, elongation and hardness.

The mechanical behavior of a material, in the most practical sense, is how it deforms or breaks under load; in other words, how it responds when stressed. This chapter provides a brief review of the properties associated with mechanical behavior, including stress, strain, elasticity, plastic deformation, ductility, hardness, creep, fatigue, and fracture. It also describes the primary components of a Charpy impact tester and the role they serve.

This article discusses the role of alloying in the production and use of titanium. It explains how alloying elements affect transformation temperatures, tensile and creep strength, elasticity, hardness, and corrosion behaviors. It provides composition and property data for commercial grades of titanium, addresses processing issues, and identifies operating environments where certain titanium alloys are susceptible to stress-corrosion cracking.

This chapter is a detailed account of various attributes related to mixing and testing of powder-binder feedstocks. Mixing parameters and their effects on feedstock properties is discussed. The attributes reviewed include mixture homogeneity, wetting, powder-binder ratio, feedstock density, elastic modulus, rheological behavior, particle size, formulation control, feedstock mixing, and feedstock properties. The chapter also provides information on the processes involved in feedstock preparation and testing.

This chapter discusses the stress-strain response of materials, how it is measured, and how it used to set performance expectations. It begins by describing the common tensile test and how it sheds light on the elastic design of structures as well as plasticity and fracture behaviors. It explains how engineering and true stress-strain curves differ, how one is used for design and the other for analyzing metal forming operations. It discusses the effect of holes, fillets, and radii on the distribution of stresses and the use of notch tensile testing to detect metallurgical embrittlement. The chapter also covers compression, shear, and torsion testing, the prediction of yielding, residual stress, and hardness.

This chapter reviews the fundamentals of stress, strain, and deformation and demonstrates some of the tools and techniques used to analyze how materials and structures respond to tension, compression, bending, and shear. It begins with an overview of the behavior of perfectly elastic and plastic materials and viscous substances. It then describes the stress-strain response of two- and three-dimensional solids, explaining how to determine principle stresses and strains using Mohr’s circle and how to derive equivalent stress and strain using the von Mises relationship. It then goes on to analyze the stress state of load-bearing members, pressurized tubes, and pin-loaded lugs, accounting for the effect of geometric discontinuities, such as cutouts, fillets, and holes, as well as cracks. It also explains how finite element methods are used to solve problems involving complex geometric and loading conditions.