COTS 510 – Shock and Vibration Isolation of COTS Equipment

Overview for management and participants

  • Purpose of environmental testing, particularly vibration and shock
  • Types of vibration tests: resonance search/dwell, fatigue, specification
  • Approximate scheduling so managers can audit special topics

Quiz for evaluation of attendee prior knowledge

Classical sinusoidal vibration never observed in service; useful concept

Terminology

Structural resonant behavior

Passive isolation

  • Elastomers
  • Pneumatic
  • Metallic

Active isolation

The following topics are suggested

  • Sinusoidal vibration measurements: units, sensors, readouts, errors
  • Calibration of sensors and systems; traceability to NIST
  • Most machinery vibration is complex; introduction to spectrum analysis

Sinusoidal vibration testing

  • Electrohydraulic and electrodynamic shakers; theory, tradeoffs, limits
  • Power amplifier theory, operation, limitations, distortion effects
  • Controls for sinusoidal vibration testing
  • Sinusoidal vibration test practice
    • Interpretation of standards; e.g. MIL-STD-810
    • Controversial test methodology: tracking filters, switching and averaging among sensors
  • Vibration and shock test fixtures; fixtures for stress screening
    • Recommended designs, materials, fabrication methods
    • Experimental evaluation before use
  • Practical limits: transverse motion; specimen size and weight

Introduction to random vibration

  • Sources of random vibration in service and transportation
  • No possible equivalence to sinusoidal vibration
  • Terminology and definitions
  • Spectral density measurement and analysis – the frequency domain
  • Probability density – the time domain

Random vibration test practice

  • Interpreting and implementing standards, e.g. MIL-STD-810
  • Equalization before testing; methods and limits
  • Controls

Combined environment (CERT) testing; reliability tests, e.g. MIL-STD-781

Environmental stress screening (ESS) of electronics hardware production

  • Single vs. multi-axis vibration
  • Pneumatic repetitive-shock machines

Acoustical environment (intense noise) testing

Instrumentation for measuring shock in service and during tests

  • Sensors, readouts, errors
  • Calibration
  • Shock spectrum analysis; shock response spectrum

Shock testing standards and methods

  • Shock testing machines; limitations
  • Use of shaker

Witnessing of tests

Course summary; optional final examination; award of certificates

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