This chapter describes an investigation that was conducted to determine why quill shafts were failing prematurely in gear boxes on aircraft engines. The investigation focused on the splines in a splined bore. Visual examination showed that the splines were heavily worn and covered with red powder on one end. Investigators also observed blueing, an effect of overheating. Based on these observations and the results of SEM imaging, it was concluded that the splines in the spline bore were wearing out for lack of lubrication.

The quill shaft in an aircraft engine was found in two pieces following a flameout. One piece was short, straight, and otherwise undamaged; the other piece was bent in several places as was the sleeve that covered it. The facture surface, as viewed under optical and scanning electron microscopes, was flat and shiny with deformation marks and dimples, typical of torsional overload, and signs of severe rubbing on the periphery. Based on their observations, investigators concluded that the quill shaft failed by torsional overload, the source of which could not be determined.

An aircraft fuel pump failed just after takeoff, resulting in engine flameout. Investigators discovered that one of the seven pistons broke into several pieces, causing the quill shaft to fracture. An examination of the fracture surfaces revealed severe rubbing on the quill shaft and beach marks on the piston along with a nick on the opposite side of the barrel. In addition, the metal around the corresponding hole in the rotor had plastically deformed and the slipper pad was gone. Based on the investigation, the failure most likely occurred due to a problem with the spring guides or a jammed slipper pad. The chapter provides several recommendations to avoid such failures in the future.

This chapter identifies the primary causes of service failures and discusses the types of defects from which they stem. It presents more than a dozen examples of failures attributed to such causes as design defects, material defects, and manufacturing or processing defects as well as assembly errors, abnormal operating conditions, and inadequate maintenance. It also describes the precise usage of terms such as defect, flaw, imperfection, and discontinuity.

This chapter discusses the use of coating methods and materials and their impact on corrosion and wear behaviors. It provides detailed engineering information on a wide range of processes, including organic, ceramic, and hot dip coating, metal plating and cladding, and the use of weld overlays, thermal spraying, and various deposition technologies.

This chapter covers the practical aspects of machining, particularly for turning, milling, drilling, and grinding operations. It begins with a discussion on machinability and its impact on quality and cost. It then describes the dimensional and surface finish tolerances that can be achieved through conventional machining methods, the mechanics of chip formation, the factors that affect tool wear, the selection and use of cutting fluids, and the determination of machining parameters based on force and power requirements. It also includes information on nontraditional machining processes such as electrical discharge, abrasive jet, and hydrodynamic machining, laser and electron beam machining, ultrasonic impact grinding, and electrical discharge wire cutting.