Over a period of 2 or 3 years, 40 to 50 premature failures of drawn high-tensile, pearlitic high-carbon (0.8 wt% C) steel wires used as cables for towing targets behind aircraft occurred. Six service failures were examined in detail. Four types of failure characteristics were noted. A close examination of wire that had been flown several times without failure was also made, and dynamic tests were conducted to investigate the fracture characteristics of wire subjected to dynamic loading. It was concluded that dynamic shock loading transmitted by the target during unsteady flight conditions was the major cause of failure. Recommendations emphasized the need for a suitable shock absorber to be fitted at the constant-tensioning device of the winch system.

A Marine Corps helicopter crash was investigated. Efforts were directed to the failure of one of the main rotor blades that had apparently separated in the air. The apparent failure of a blade integrity monitor (BIM) system was also considered. The rotor blade comprised a long, hollow 6061-T651 aluminum alloy extrusion and 26 fiberglass “pockets” that provided the trailing-edge airfoil shape. Visual examination of the fracture surface of the aluminum extrusion indicated fatigue crack growth followed by ductile overload separation. Examination of the fatigue fracture region revealed several pits that appeared to have acted as fracture origin sites. Time to failure was determined using fracture mechanics. It was concluded that failure was caused by a fatigue crack that grew to critical length without detection. The crack originated at pits that resulted from the use of an improperly designed heating element used to cure fiberglass repairs.

This article discusses the failure analysis of several steel transmission pipeline failures, describes the causes and characteristics of specific pipeline failure modes, and introduces pipeline failure prevention and integrity management practices and methodologies. In addition, it covers the use of transmission pipeline in North America, discusses the procedures in pipeline failure analysis investigation, and provides a brief background on the most commonly observed pipeline flaws and degradation mechanisms. A case study related to hydrogen cracking and a hard spot is also presented.

This introductory article describes the various aspects of chemical structure that are important to an understanding of polymer properties and thus their eventual effect on the end-use performance of engineering plastics. The polymers covered include hydrocarbon polymers, carbon-chain polymers, heterochain polymers, and polymers containing aromatic rings. The article also includes some general information on the classification and naming of polymers and plastics. The most important properties of polymers, namely, thermal, mechanical, chemical, electrical, and optical properties, and the most significant influences of structure on those properties are then discussed. A variety of engineering thermoplastics, including some that are regarded as high-performance thermoplastics, are covered in this article. In addition, a few examples of commodity thermoplastics and biodegradable thermoplastics are presented for comparison. Finally, the properties and applications of six common thermosets are briefly considered.