Description of a micro-mechanical testing system

In recent years, technological advances have significantly enhanced the capability to produce milli- and micro-sized components which may be incorporated into the design of small, less costly, reproducible and more reliable nuclear weapons components. Two promising micro-scale processing technologies are Silicon surface micromachining (SMM), a process derived from microelectronics fabrication, and LIGA, a process involving electrodeposition of metals into a polymeric mask containing very fine, sharp features. Complicated SMM structures with micron sized features such as microengines, gears and pop-up mirrors have already been successfully developed. As part of an overall broad effort to develop mechanical test capability of millisized and microsized structures, a mechanical test system has been designed and assembled with the primary goal of characterizing the mechanical properties of LIGA synthesized structures and materials. The current system utilizes many off-the-shelf items including an MTS 3,000 pound 1.0 inch travel hydraulic actuator and an Interface 100 pound load cell. Load, stroke and displacement control is provided by an MTS TestStar system and two 0.100 inch LVDT displacement gages situated in a parallel arrangement at the specimen. Load resolution is on the order of 50 {micro} oz. and displacement resolution less than 45 {micro} inch. The system can test dynamically up to 100 hz at 0.005 inch actuator displacement and loads of 100 lb., statically at up to 250 lb. (limited by the load cell). The scope and flexibility of the microscale test system extends far beyond simply testing LIGA synthesized parts. A detailed description of the machine and a diverse set of results are presented in this report