This chapter discusses the critical soldering faults that lead to quality degradation and potential failure of a soldered connection. It then describes the types of nondestructive evaluations used to inspect soldered and brazed joints, including dimensional and visual inspection, ultrasonic testing, radiographic examination, dye penetrant inspection, and leak testing, including overpressure tests. The chapter also provides an overview of destructive physical analysis.

Most of the counterfeit parts detected in the electronics industry are either novel or surplus parts or salvaged scrap parts. This article begins by discussing the type of parts used to create counterfeits. It discusses the three most commonly used methods used by counterfeiters to create counterfeits. These include relabeling, refurbishing, and repackaging. The article presents a systematic inspection methodology that can be applied for detecting signs of possible part modifications. The methodology consists of external visual inspection, marking permanency tests, and X-ray inspection followed by material evaluation and characterization. These processes are typically followed by evaluation of the packages to identify defects, degradations, and failure mechanisms that are caused by the processes (e.g., cleaning, solder dipping of leads, reballing) used in creating counterfeit parts.

This chapter provides an overview of the various inspection methods used with metals and alloys, namely visual inspection, coordinate measuring machines, machine vision, hardness testing, tensile testing, chemical analysis, metallography, and nondestructive testing. The nondestructive testing methods discussed are liquid penetrant inspection, magnetic particle inspection, eddy current inspection, radiographic inspection, and ultrasonic testing.

Visual inspection is the most important method of inspection of materials. This chapter describes the procedures involved in visual inspection such as identification markings, identification of defects caused by heating problems, scaling of materials, cracking characterization, and measurement of material dimensions. It discusses the mechanisms, advantages, limitations, components, and applications of various visual inspection tools, namely magnifying devices, lighting for visual inspection, measuring devices, miscellaneous measuring equipment, record-keeping devices, and macroetching.

This chapter focuses on the inspection of steel bars for the detection and evaluation of flaws. The principles involved also apply, for the most part, to the inspection of steel wire. The nondestructive inspection methods discussed include magnetic particle inspection, liquid penetrant inspection, ultrasonic inspection, and electromagnetic inspection. Eddy current and magnetic permeability are also covered.

In forgings of both ferrous and nonferrous metals, the flaws that most often occur are caused by conditions that exist in the ingot, by subsequent hot working of the ingot or the billet, and by hot or cold working during forging. The inspection methods most commonly used to detect these flaws include visual, magnetic particle, liquid penetrant, ultrasonic, eddy current, and radiographic inspection. This chapter provides a detailed discussion on the characteristics, process steps, applications, advantages, and limitations of these methods. It also describes the flaws caused by the forging operation and the principal factors that influence the selection of a nondestructive inspection method for forgings.

This chapter discusses the use of nondestructive inspection methods, including visual, ultrasonic, radiographic, and thermographic techniques, and the types of flaws and damages they can reveal in composite parts and assemblies. It describes the basic principles behind each method along with best practices and procedures.

This chapter documents the key findings of an investigation into the failure of an aircraft’s main wheel bearing housing. Using annotated images and a detailed SEM fractograph, it shows what investigators observed that led them to conclude that the flange on one of the hubs broke off due to a combination of fatigue, bending stresses, and wear. It also includes a recommendation to assess the structural integrity of the bearing housing after every 100 h of service using nondestructive techniques.

This chapter discusses the key findings of an investigation into the failure of an aircraft engine fuel pump. It explains how investigators came to the conclusion that metal slivers from a heavily worn spring may have interrupted the flow of lubricant to one of the slipper pads, causing adhesive wear and the welding of slipper pad material onto the surface of a mating cam plate. Excessive friction between the slipper pads and cam plate, in turn, created a torsional overload that caused the camshaft to break. The chapter presents SEM images showing the wear pattern on one of the springs along with photographs of the damaged slipper pads and cam plate. It also includes an image of a copper flake found in one of the pistons and discusses the results of qualitative x-ray chemical analysis.

An adaptor and a bolt were overloaded during a flight causing them to fracture. This chapter recounts the circumstances that led to the failure and the investigation that followed. It includes images of the fracture surfaces which show that both components failed quickly due to overload conditions. It also recommends the use of twin suspension hooks to make attachment points more stable under difficult flight conditions.

This chapter explains how investigators determined that a stabilizer link rod fractured due to overload, possibly by a combination of tension and bending forces that occurred during an accident. It includes images comparing the fractured rod with its undamaged counterpart recovered from the starboard side of the aircraft. A close-up view of the threads near the fracture surface provides evidence of bending, while the presence of dimples in an SEM fractograph supports the theory that the link rod failed as a result of overload.

A tie rod on a 70-ton aircraft towing tractor failed during a test run, fracturing near a welded bracket that connects to a hydraulic jack. This chapter discusses the failure and the investigation that followed. It presents a close-up view of the fracture surface showing what appears to be a brittle fracture that initiated from a zone of poor-quality weld. It also provides photographic evidence of a weld crack in the heat-affected zone and includes a drawing of a modified weld design that passed subsequent testing.

This chapter discusses the investigation of a helicopter tail rotor blade that fractured during a test flight. It includes images of the damaged blade along with close-ups of both sides of the blade tip showing that the tip tore off at the rivets. Based on their observations, investigators concluded that the rotor blade encountered a foreign object in flight causing the tip to shear off.

An aircraft tire burst while inflating, causing one of the flanges on the wheel hub to fracture. This chapter provides a summary of the investigation along with key findings. It includes images of the damaged hub and describes how various parts failed as the pressure in the tire increased. It explains that the hub material was of good quality under uniform load and that it fractured quickly by cleavage due to the force exerted by the overinflated tire.

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.

A pair of bearings mounted side by side in an aircraft engine failed in service. Photographs show that the inner rings were either broken or deformed, the balls were worn and flattened, and the cages severely damaged. The bearing races were damaged as well, but only on one side indicating a directional thrust. In addition to their examination, investigators also conducted metallographic studies and hardness tests, which indicated that the balls and inner rings reached temperatures above 825 °C (1520 °F). Based on their findings, investigators concluded that the bearings failed due to overheating, possibly as a result of misalignment compounded by insufficient lubrication and high speeds.

Metal particles were frequently detected in the oil of an aircraft engine, triggering an investigation that led to a torque sensor and its mounting components. The sensor assembly was removed and examined in greater detail. As the chapter explains, investigators discovered that one of the bearings had been subjected to excessive friction, evidenced by brinelling, metal flow, heat tinting, deformation, and wear. They also observed extensive grooving on a retaining plate and several washers matching the diameter of the outer bearing races. Based on their findings, investigators concluded that excessive clearance allowed the outer bearing races to rotate, thus removing material from adjacent contact surfaces and accelerating the buildup of metal particles in the engine oil. The chapter recommends several design changes to remedy the problem.

After several failed attempts to lower their starboard wheels for landing, pilots engaged the help of gravity through g-force maneuvers and managed to coax the wheels into place. An inspection following the incident revealed a broken universal joint in one of the linkages that opens and closes the doors to the undercarriage compartment. The failed component was removed from the aircraft and examined using optical and electron microscopes. Under low magnification, the fracture surface appeared jagged except for one corner that was relatively smooth. SEM fractography revealed the presence of fatigue striations in the smooth region and dimpling elsewhere. Based on their findings, investigators concluded that fatigue loading initiated a crack in the universal joint that progressed with time and that the final fracture occurred due to bending tensile overload.

A helicopter lost the outboard rib on a tail rotor blade in flight and was forced to land because of the resulting vibrations. The investigation that followed is described in this chapter along with key findings. As shown in a sketch, the rib is held in place by a set of six rivets. All of the rivets on the failed blade were missing and sections of skin were torn from most of the rivet holes. One such rivet hole was examined in a SEM, revealing corrosion on one of the tear surfaces and dimples (characteristic of ductile overload failure) on the other. In addition, the inner surface of the skin nearest the rib was found to be coated with soot, the paint on the leading edge of the top skin was abraded, and the skin in that area had thinned. Based on their findings, investigators concluded that the outboard rib separated because of stress-corrosion cracking around the rivets, and erosion may have contributed.