PROJECTS
Symmetry Engineering and Forensic Consulting undertakes a wide-range of different projects and investigations. These projects can be (a) as simple as independent critiques of the design process early during development, (b) providing engineering expertise to overcome already identified design deficits or (c) more extensive, on-site technical accident investigation involving multiple systems.
Fracture-Safe Satellite Pressure Vessel
Design calculations were performed for a metallic liner of a composite-overwrapped-pressure-vessel. NASA requires all pressurized launch hardware to exhibit leak-before-break (LBB) performance. Given a stress analysis for the variable amplitude pressurization schedule, advanced fracture mechanics software was used to demonstrate LBB behavior. The pressure vessel subsequently flew without issue.
Damage-Tolerant Bracket
During product development testing, a bracket exhibited fatigue failure at a known stress concentration. Stress analysis calculations were performed along with fatigue lifing that predicted laboratory cyclic performance. The manfacturer implemented the recommended fatigue design process and selected a more fatigue resistant material that mitigated premature failure of the component.
Inadvertent Wire Rope Cracking
A stainless steel wire rope was blackened prior to service by using a corrosion process to deposit a thick oxide film. The processing was inadvertently causing cracking of the strands of the wire rope. Although the observed cracks were orthogonal to the primary principal stress in the wire, they still posed a risk for degrading the strength and fracture behavior of the wire rope. This cracking was documented and the root-cause identified which allowed modifying the wire rope processing to eliminate the problem.
Helicopter Crash
The energy absorption characteristics of passenger restraints were implicated in a fatal helicopter crash. The key question was what was the speed of impact. Using high speed photographs of the accident, an analysis was performed that indicated the vehicle was traveling in excess of crashworthiness design constraints.
Complex, Multi-Disciplinary Failure Analysis
Complex failures require extensive scene documentation and application of engineering fundamentals to understand the sequence of failure. Rigid body motion of components is a critical clue regarding how large structures fail and sequentially fragment and come apart. This type of analysis often provides the critical evidence for what portion of the structure needs to be focused on to understand the root-cause of failure.
These complex failures typically requires teams of experts, from different disciplines, to fully identify the components and rationalize the full failure process. More often than not, failure initates with a chain of often unrelated events; breaking one link in the chain will result in the failure not occurring. Identifying the links in the chain, essentially the mitigating factors that lead to failure, is a critical step in the process to understand why the failure occurred.
These large-scale failure investigations often lead to process modification so as to insure that the failure does not occur again in the future.