The formation of microcracks in composite materials may arise from static-, dynamic-, impact-, or fatigue-loading situations and also by temperature changes or thermal cycles. This chapter discusses the processes involved in the various methods for the microcrack analysis of composite materials, namely bright-field analysis, polarized-light analysis, contrast dyes analysis, and dark-field analysis. The analysis of microcracked composites using epi-fluorescence is also covered. In addition, the chapter describes the procedures for the determination and recording of microcracks in composite materials.

This chapter is a study of the microstructure of case-hardened steels. It explains what can be learned by examining grain size, microcracking, nonmetallic inclusions, and the effects of microsegregation. It identifies information-rich features, describing their ideal characteristics, the likely cause of variations observed, and their effect on mechanical properties and behaviors. The discussions throughout the chapter are aided by the use of images, diagrams, data plots, and tables.

This chapter examines the cooling of steels from the austenite region. It describes the processes of determining the severity of quench. The chapter examines the methods to estimate the quench required if the size and shape of the part are known and the required cooling rate is known. The cooling rate correlation is used to calculate the hardness distribution across the diameter of cylinders. The calculations are used to illustrate the sensitivity of the hardness distribution to the severity of quench and the hardenability. The chapter discusses the methods of determining cooling rates in quenched steel components. It describes the formation of residual stresses in materials in which no phase change occurs on cooling. The chapter also examines the effect on the residual stresses of the phase changes in austenite. It provides information on two types of quench cracks in quenched steels, namely, microcracking and gross cracking during quenching.