Failure and Design

Jaime BaberOctober 12, 2000BME 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

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

Similar Terms

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 AnalysisUsersTasks

Risk AssessmentFour levels of severity