Accelerated Mechanical Testing

James McLinn

Many modern mechanical systems are made up of mechanical components and assemblies combined with electrical components used for monitor and control. Examples range from bomb disposal robots to computers, game consoles, cable converter boxes and most home appliances. Reliability focus since the 1970s has tended to be on the electronic components of such systems and not on the mechanical design or mechanical component functions. As market forces desire more reliable systems, the mechanical reliability portions of a system must improve. Methods for describing and treating mechanical reliability have focused on components and simple functions, and thus were incomplete in the past. Better ways to document and accelerate mechanical functions and failure modes are required to achieve long term reliability of systems. One reliability handbook has been issued by the US military. It mainly documented some common component failure modes and provided limited guidance for addressing mechanical stress. Physics of Failure (PoF) could be a valuable tool to extend knowledge of failure modes beyond book models. Real world mechanical systems connect stress and life through failure mechanisms and ultimately failure modes. Vibration has been well documented, but other stresses such as thermal cycles or corrosion are still hard to incorporate. Component failures often arise from design defects, corrosion, humidity, loss of lubrication, the presence of multiple stresses or off state (non-use) conditions. These are seldom present in any reliability or POF models. Some detailed examples can help improve many situations. This paper will demonstrate how mechanical failure modes may be identified and accelerated through test in order to determine longevity and impact to systems.