Failure and Design Jaime Baber October 12, 2000 BME 272: Dr. Paul H. King

Introduction Failure: Degradation of performance of a device outside of a specified value Non Performance or inability to perform for a certain time within space conditions Causes of Failure: Systemic and Random Diabetes Test Kit

Similar Terms Defect : An imperfection (which may/may not lead to failure) Deficiency: Lack of conformance to specifications Malfunction: Unsatisfactory performance Fault: Cause of failure Could be something in environment Something that happens to device: not internal

Failure is a fact of life...

Failure is a fact of life... Define operational issues/normal operation Failure rate Anticipate the worst Failure Mode Analysis Design around it: FAIL SAFE

Hardware Failure Early: First 1,000 hours Random: Mid-life Wearout: Late Artificial Hip

Software Failure Specification errors Design Error Typo Ommission Lack of Verification

Human Error….

Human Error Most important Documentation: Not up-to-date or missing Engineers must review and test Track Failures

Reliability Describes how dependable a device is over time Performs for a stated environment/time w/o failure Plan/Design/Manufacture reliability into product vs Quality

Mechanical Reliability Due to deterioration of design strength or assembly

Electronic Reliability Three distinct time periods

Software Reliability

Overall Device Reliability

Reliabilty Assurance Design Fault Tolerance Improve Manufacturing Quality Assurance Teams/ Inspect Service Manuals Test Monitor

Design….

designsafe... Task Based Safety Analysis Hazard Analysis Users Tasks Risk Assessment Four levels of severity