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.

Fracture is the separation of a solid body into two or more pieces under the action of stress. Fracture can be classified into two broad categories: ductile fracture and brittle fracture. Beginning with a comparison of these two categories, this chapter discusses the nature and causes of these failure modes. Some body-centered cubic and hexagonal close-packed metals, and steels in particular, exhibit a ductile-to-brittle transition when loaded under impact and the chapter describes the use of notched bar impact testing to determine the temperature at which a normally ductile failure transitions to a brittle failure. The discussion then covers the Griffith theory of brittle fracture and the formulation of fracture mechanics. Procedures for determination of the plane-strain fracture toughness are subsequently covered. Finally, the chapter describes the effects of microstructural variables on fracture toughness of steels, aluminum alloys, and titanium alloys.

Metals are used in many engineering applications because of their mechanical properties, particularly strength and ductility. This chapter explains how mechanical properties are measured and how to interpret the results. It describes the most widely used tests, including tensile tests; Rockwell, Brinell, Vickers, and Knoop hardness tests; and Charpy V-notch impact tests. The chapter also provides information on loading conditions that can lead to fatigue failure, and in some cases, counteract or prevent it.

This article briefly introduces some commonly used methods of mechanical testing of plastics for determining mechanical properties, also describing the test methods and providing comparative data for the mechanical property tests. In addition, creep testing and dynamic mechanical analyses of viscoelastic plastics are briefly described. The discussion covers the most commonly used tests for impact performance, various types of hardness test for plastics, the fatigue strength of viscoelastic materials, and the tension testing of elastomers and fibers.

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.