When dealing with mechanical loading, the nature of the loading itself is important. Evaluation of the relative strength of a component or engineering system is determined by several factors. Some of these factors are: magnitude of the load, speed of application of the load, location and direction of the load, whether there is repetition of the load and the number of repetitions. These load characteristics lead to different types of failures including fatigue and overload failures. Fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material. The failure of a component in a single event is known as mechanical overload. These terms and many others are used in forensic engineering when analyzing product failure. Failure may occur because either the product is weaker than expected or the applied load is greater than expected.
WHA has performed multiple tests involving mechanical loading for numerous industries, including: automotive, aviation, railroad, marine, manufacturing, pressurized systems, and many others. The challenge for the investigator is to determine which failures have been caused by the incident, and/or which may have caused the incident.