A characteristic feature of bending is the inhomogeneous (nonuniform) nature of the deformation. Therefore, in a bent specimen, the strain and stress at a given point are dependent on the location of the point with respect to the neutral axis of the cross-sectional area of the specimen. This article discusses the stress-strain relationships, strain curvature, and stress-moment equations for elastic, noncylindrical, elastic-plastic, and pure plastic bending conditions. It also reviews the distribution of residual stress and springback.

This article discusses the deformation and viscoelastic characteristics of plastics as polymeric materials, focusing on the test methods used for the evaluation of their mechanical properties, methods available for analytically predicting the deformation response of polymers, and the effect of viscoelasticity on the test methods used. Two common ways of evaluating viscoelasticity of plastics are by means of creep experiments and dynamic mechanical experiments. Graphic or tabular analysis of test data, time-temperature superposition, and empirical correlation methods are commonly employed for analytical prediction of deformation characteristics of polymers.

This article describes concepts and tools that can be used by the failure analyst to understand and address deformation, cracking, or fracture after a stress-related failure has occurred. Issues related to the determination and use of stress are detailed. Stress is defined, and a procedure to deal with stress by determining maximum values through stress transformation is described. The article provides the stress analysis equations of typical component geometries and discusses some of the implications of the stress analysis relative to failure in components. It focuses on linear elastic fracture mechanics analysis, with some mention of elastic-plastic fracture mechanics analysis. The article describes the probabilistic aspects of fatigue and fracture. Information on crack-growth simulation of the material is also provided.

This article describes the viscoelastic behavior of plastics in their solid state only, from the standpoint of the material deforming without fracturing. The consequences of viscoelasticity on the mechanical properties of plastics are described, especially in terms of time-dependencies, as well as the dependence of the viscoelastic character of a plastic on chemical, physical, and compositional variables. By examining the viscoelastic behavior of plastics, the information obtained are then applied in situations in which it may be important to anticipate the long-term properties of a material. This includes assessing the extent of stress decay in materials that are pre-stressed, the noise and vibration transmission characteristics of a material, the amount of heat build-up in a material subjected to cyclic deformation, and the extent a material can recover from any prior deformation. Several qualitative graphs are presented, which highlights the possible differences in the viscoelastic behavior that can exist among plastics.

This article describes a method to predict mechanical properties of cast iron materials and illustrates how to use the predictions in computer-aided tools for the analysis of castings subjected to load. It outlines some ways to predict the hardness and elastic modulus of cast iron without going into dislocation theory. The article discusses modeling of hardness in cast iron based on a regular solution equation in which the properties of each phase depend on chemical composition and coarseness. It describes the evaluation of material parameters from the tensile stress-strain curve. The article concludes with an illustration of a finite-element method (FEM) model containing heterogeneous mechanical properties using local material definitions.

The fracture-mechanics technology has significantly improved the ability to design safe and reliable structures and identify and quantify the primary parameters that affect structural integrity of materials. This article provides a discussion on fracture toughness of notched materials by explaining the ductile-to-brittle fracture transition and by correlating KId, KIc, and Charpy V-notch impact energy absorptions. It highlights the effects of constraint, temperature, and loading rate on the fracture transition. The article discusses the applications of fracture mechanism in limiting of operating stresses. It describes the mechanisms, testing methods, and effecting parameters of two main categories of fracture mechanics: linear-elastic fracture mechanics and elastic-plastic fracture mechanics. The article concludes with a discussion on the three major progressive stages of fatigue: crack initiation, crack growth, and fracture on the final cycle.

Fracture toughness is an empirical material property that is determined by one or more of a number of standard fracture toughness test methods. This article describes the fracture toughness test methods in a chronological outline, beginning with the methods that use the linear-elastic parameter. After this, the methods that use the nonlinear parameters are discussed. The article reviews some of the work in progress to update the standard test methods, namely, common fracture toughness test method and transition fracture toughness test method. Finally, an overview of fracture toughness testing for ceramic and polymer materials is provided.

Nonlinear ultrasonic nondestructive examination (NDE) techniques are based on nonlinear interaction of ultrasonic waves with the material to be characterized and defects to be detected. This article introduces the basic principles of nonlinear material-wave interaction, the origin of intrinsic nonlinearity in intact solids, and the main mechanisms of excess nonlinearity in damaged metals. It describes the measurement methods for nonlinear ultrasonic materials characterization and flaw-detection. The article schematically illustrates the instrumentation used for measurements of longitudinal wave and Rayleigh surface acoustic waves. It concludes with information on the applications of nonlinear ultrasonics.

There are many different types of polymeric materials, ranging from glassy to semicrystalline polymers and even blends. Their mechanical properties range from pure elastic with very high strains to fracture (elastomers) to almost pure linear elastic (Hookian behavior) with low strains to fracture (glassy polymers). This article provides an overview of historical development of fracture behavior in polymers. It discusses the processes involved in three fracture test methods for polymers, namely linear elastic fracture mechanics, elastic-plastic fracture mechanics, and post-yield fracture mechanics.

This article reviews the fundamental relationships between microstructure and mechanical properties for major classes of nonmetallic engineering materials: metals, ceramics and glasses, intermetallic compounds, polymers, and composites. It details the structures of inorganic crystalline solids, inorganic noncrystalline solids, and polymers. The article describes the various strengthening mechanisms of crystalline solids, namely, work hardening, solid-solution hardening, particle/precipitation hardening, and grain size hardening. Deformation and strengthening of composite materials, polymers, and glasses are reviewed. The article concludes with information on the two important aspects of the mechanical behavior of any class of engineering material: fatigue response and fracture resistance.

In the case of steels, heat treatment plays a fundamental role because no other process step can manipulate the microstructure in order to fulfill such a wide variety of possible in-service conditions. This article addresses heat treatment with regard to hardening and subsequent tempering of steel components in order to optimize tribological properties. It focuses on the heat treatment of tempering and bearing steels and on volume changes that take place due to phase transformations. Plastic deformations that occur due to shrinking and phase transformation are also discussed. The article also describes the generation of thermal, transformation, and hardening residual stresses.

Torsion tests can be carried out on most materials, using standard specimens, to determine mechanical properties such as modulus of elasticity in shear, yield shear strength, ultimate shear strength, modulus of rupture in shear, and ductility. This article discusses the torsional deformation of prismatic bars of circular cross-section and torsional response of prismatic bars of noncircular cross-section. It analyzes the elastic deformation, plastic deformation, and the effect of strain rate on plastic deformation. The article describes the theory of anisotropy in plastic torsion and the various components of a torsion testing machine. These include drive system, test section, torque and rotational displacement transducers, and rigid frame.

This article discusses the J-integral-based single and multiple specimen techniques of the ASTM E 1737 test method for determining plane strain fracture toughness of polymeric materials. It describes the fracture toughness testing of thin sheets and films. The article concludes with information on the alternative methods for determining the fracture toughness of polymer materials.

This article is a compilation of terms related to mechanical testing and evaluation of metals, plastics, ceramics, and composites.

This article focuses on mechanical behavior of materials under conditions of uniaxial tension and compression. The emphasis is on mechanical behavior during the engineering tension test, which is used to provide basic design information on the strength of materials and as an acceptance test for the specification of materials. The article presents mathematical expressions for a flow curve of many metals in the region of uniform plastic deformation. It explains that the rate at which strain is applied to the tension specimen has an important influence on the stress-strain curve. The point of necking at maximum load can be obtained from the true stress-true strain curve by finding the point on the curve having a subtangent of unity. The article concludes with an overview of the ductility measurements performed by notch tensile and compression tests.

Bending is a common metalworking operation to create localized deformation in sheets (or blanks), plates, sections, tubes, and wires. This article emphasizes on the bending of sheet metal along with some coverage on flanging. It informs that variations in the bending stresses cause springback after bending, and discusses the variables and their effects on springback, as well as the methods to overcome or counteract them. These methods include overbending, bottoming or setting, and stretch bending. The article provides information on elastic bending, non-cylindrical bending, elastic-plastic bending, and pure plastic bending. Sheet metal bendability is a critical factor in many forming operations. The article illustrates the derivation of two relevant bend-ductility equations.

Power metallurgy (PM) is a process of shaping metal powders into near-net or net shape parts combined with densification or consolidation processes for the development of final material and design properties. This article introduces the general considerations, models, and applications in the modeling of PM processes. It describes the PM process in terms of powder compaction and sintering. The article schematically illustrates powder injection molding for the production of plastic parts and describes PM process models such as discrete-element model (DEM), linear continuum model, and nonlinear continuum model. It concludes with information on the application of press and sinter modeling to practical problems in PM.