Mechanical Shock Techniques
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Mechanical Shock Techniques Course
Introduction:
Course Objectives:
The course commences with a review of basic dynamic theory and then covers natural frequencies and modes before the discussion system response to shock. The Shock Response Spectrum (SRS) is discussed as it relates to shock measurement and testing, as well as design. The relative merits of various types of shakers and shock test machines are briefly considered before covering various shock test methods, including pyrotechnic shock testing. The course then covers shock measurements, also calibration. Shock-resistant design is discussed, including the selection and use of isolators.
Who Should Attend?
Most engineers need specialized education in order to properly measure, quantize and analyze this generally unfamiliar environment, and to reproduce it in environmental test laboratories. This course is for packaging designers, test laboratory managers, engineers and aides. It also helps quality and reliability specialists and acquisition personnel in government and military activities and their contractors.
Instrumentation specialists who will measure transportation, service and laboratory shock need this course. Metrologists learn about shock calibration of accelerometers and systems. Project personnel, structure and packaging engineers learn about developmental shock testing. Product assurance and acquisition specialists learn to evaluate shock test facilities and methods and to interpret shock test specifications.
Course Outlines:
Introduction — what is Shock?
- Review of Dynamics and Theory of Materials
- Basic concepts
- Weight
- Mass
- Density
- Specific gravity
- Definitions of terms
- Friction, wear
- Work, power, energy
- Engineering materials
- Stress and Strain
- Elasticity
- Shear
- Stiffness
- Mass
- Spring-Mass Model
- Degrees of Freedom
Vibration Theory
- Degrees of Freedom
- Natural frequency (resonance)
- Displacement, Velocity and Acceleration
- Transmissibility
- Damping
- Critical Frequencies
- Random Vibration
- Gaussian Random Signal
- Spectral Density
System Response to Shock
- Natural Frequencies
- SDoF Transient Response
- The Transient Response Problem
- Free, Forced Response
A Closer Look at Shock
- Terminology
- Input Pulse and Response of a Sprung Mass
- Typical Complex Shock Pulses
- Haversine Pulse
- Classical Shock Pulse Shapes
- Examples
- Critical Frequency Response
- Response to Shock Pulse
Shock Response Spectrum (SRS)
- Shock Measurement
- Definitions
- SRS Mechanical analogy
- How SRS is developed during shock testing
- Maximize values
- Maximum Response Spectra for Various Shock Pulse Shapes
- Damping and SRS
- Damped Spectra
- Designing with SRS
- SRS in shock test specifications
- Shock spectrum analyzers
Shock Testing: Shock Test Machines
- Drop test machines
- Impact machines
- MIPS tables
- Electrodynamic, Electrohydraulic and Piezoelectric shakers
- Shaker Optimized Cosine (SHOC)
- Pyro shock simulation
- Problem Areas
- Pendulum and Free-fall machines
Shock Measurements
- Sensors for Force, Displacement, Velocity, Acceleration
- Seismic transducers
- Dynamic calibration of motion sensors
- Sensor attachment
- Cabling
- Accelerometer loading effects
Designing for Shock
- Shock Resistant Design
- Isolation Methods
- Isolators which approach the ideal
- Shock isolation vs. Vibration Isolation
- Isolator selection