Vibration Analysis For Electronic Equipment

Vibration Analysis For Electronic Equipment
اسم المؤلف
Dave S. Steinberg
1 أكتوبر 2018

Vibration Analysis For Electronic Equipment
Dave S. Steinberg
Steinberg & Associates and University of California, Los Angeles
Preface xvii
List of Symbols xix
1. Introduction
Vibration Sources
Vibration Representation
Degrees of Freedom
Vibration Modes
Vibration Nodes
Coupled Modes
Electronic Equipment for Airplanes and Missiles
Electronic Equipment for Ships and Submarines
Electronic Equipment for Automobiles, Trucks, and Trains
Electronics for Oil Drilling Equipment
Electronics for Computers, Communication, and
2. Vibrations of Simple Electronic Systems
2.1 Single Spring-Mass System Without Damping
Sample Problem-Natural Frequency of a Cantilever
Sample Problem-Natural Frequency of a Torsion System
Springs in Series and Parallel
Sample Problem-Resonant Frequency of a Spring System
Relation of Frequency and Acceleration to Displacement
Sample Problem-Natural Frequency and Stress in a Beam
Forced Vibrations with Viscous Damping
Transmissibility as a Function of Frequency
Sample Problem-Relating the Resonant Frequency to
the Dynamic Displacement
2.2 Single-Degree-of-Freedom Torsional Systems
2.7 Multiple Spring-Mass Systems Without Damping
Sample Problem-Resonant Frequency of a System
3 Component Lead Wire and Solder Joint Vibration Fatigue Life
Vibration Problems with Components Mounted High
Above the PCB
Sample Problem-Vibration Fatigue Life in the Wires of
a TO-5 Transistor
Vibration Fatigue Life in Solder Joints of a TO-5
Recommendations to Fix the Wire Vibration Problem
Dynamic Forces Developed in Transformer Wires During
Sample Problem-Dynamic Forces and Fatigue Life in
Transformer Lead Wires
Relative Displacements Between PCB and Component
Produce Lead Wire Strain
Sample Problem-Effects of PCB Displacement on Hybrid
4. Beam Structures for Electronic Subassemblies
4.1 Natural Frequency of a Uniform Beam
Sample Problem-Natural Frequencies of Beams
4.2 Nonuniform Cross Sections
Sample Problem-Natural Frequency of a Box with
Nonuniform Sections
4.3 Composite Beams
5. Component Lead Wires as Bents, Frames, and Arcs
Electronic Components Mounted on Circuit Boards
Bent with a Lateral Load-Hinged Ends
Strain Energy-Bent with Hinged Ends
Strain Energy-Bent with Fixed Ends
Strain Energy-Circular Arc with Hinged Ends
Strain Energy-Circular Arc with Fixed Ends
Strain Energy-Circular Arcs for Lead Wire Strain
Sample Problem-Adding an Offset in a Wire to Increase
the Fatigue Life
6 Printed Circuit Boards and Flat Plates
Various Types of Printed Circuit Boards
Changes in Circuit Board Edge Conditions
Estimating the Transmissibility of a Printed Circuit Board
Natural Frequency Using a Trigonometric Series
Natural Frequency Using a Polynomial Series
Sample Problem-Resonant Frequency of a PCB
Natural Frequency Equations Derived Using the Rayleigh
Dynamic Stresses in the Circuit Board
Sample Problem-Vibration Stresses in a PCB
Ribs on Printed Circuit Boards
Ribs Fastened to Circuit Boards with Screws
Printed Circuit Boards With Ribs in Two Directions
Proper Use of Ribs to Stiffen Plates and Circuit Boards
Quick Way to Estimate the Required Rib Spacing for
Circuit Boards
Natural Frequencies for Different PCB Shapes with
Different Supports
Sample Problem-Natural Frequency of a Triangular PCB
with Three Point Supports
7. Octave Rule, Snubbing, and Damping to Increase the PCB
Fatigue Life
Dynamic Coupling Between the PCBs and Their Support
Effects of Loose Edge Guides on Plug-in Type PCBs
Description of Dynamic Computer Study for the Octave
The Forward Octave Rule Always Works
The Reverse Octave Rule Must Have Lightweight PCBs
Sample Problem-Vibration Problems with Relays
Mounted on PCBs
Proposed Corrective Action for Relays
Using Snubbers to Reduce PCB Displacements and
Sample Problem-Adding Snubbers to Improve PCB
Controlling the PCB Transmissibility with Damping
Properties of Material Damping
Constrained Layer Damping with Viscoelastic Materials
Why Stiffening Ribs on PCBs are Often Better than
Problems with PCB Viscoelastic Dampers
8. Preventing Sinusoidal Vibration Failures in Electronic
Estimating the Vibration Fatigue Life
Sample Problem-Qualification Test for an Electronic
Electronic Component Lead Wire Strain Relief
Designing PCBs for Sinusoidal Vibration Environments
Sample Problem-Determining Desired PCB Resonant
How Location and Orientation of Component on PCB
Affect Life
How Wedge Clamps Affect the PCB Resonant Frequency
Sample Problem-Resonant Frequency of PCB with Side
Wedge Clamps
Effects of Loose PCB Side Edge Guides
Sample Problem-Resonant Frequency of PCB with Loose
Edge Guides
Sine Sweep Through a Resonance
Sample Problem-Fatigue Cycles Accumulated During a
Sine Sweep
9. Designing Electronics for Random Vibration
Basic Failure Modes in Random Vibration
Characteristics of Random Vibration
Differences Between Sinusoidal and Random Vibrations
Random Vibration Input Curves
Sample Problem-Determining the Input RMS
Acceleration Level
Random Vibration Units
Shaped Random Vibration Input Curves
Sample Problem-Input RMS Accelerations for Sloped
PSD Curves
Relation Between Decibels and Slope
Integration Method for Obtaining the Area Under a PSD
Finding Points on the PSD Curve
Sample Problem-Finding PSD Values
Using Basic Logarithms to Find Points on the PSD Curve
Probability Distribution Functions
Gaussian or Normal Distribution Curve
Correlating Random Vibration Failures Using the
Three-Band Technique
Rayleigh Distribution Function
Response of a Single-Degree-of-Freedom System to
Random Vibration
Sample Problem-Estimating the Random Vibration
Fatigue Life
How PCBs Respond to Random Vibration
Designing PCBs for Random Vibration Environments
Sample Problem-Finding the Desired PCB Resonant
Effects of Relative Motion on Component Fatigue Life
Sample Problem-Component Fatigue Life
It’s the Input PSD that Counts, Not the Input RMS
Connector Wear and Surface Fretting Corrosion
Sample Problem-Determining Approximate Connector
Fatigue Life
Multiple-Degree-of-Freedom Systems
Octave Rule for Random Vibration
Sample Problem-Response of Chassis and PCB to
Random Vibration
Sample Problem-Dynamic Analysis of an Electronic
Determining the Number of Positive Zero Crossings
Sample Problem-Determining the Number of Positive
Zero Crossings
10 Acoustic Noise Effects on Electronics
Sample Problem-Determining the Sound Pressure Level
Microphonic Effects in Electronic Equipment
Methods for Generating Acoustic Noise Tests
One-Third Octave Bandwidth
Determining the Sound Pressure Spectral Density
Sound Pressure Response to Acoustic Noise Excitation
Sample Problem-Fatigue Life of a Sheet-Metal Panel
Exposed to Acoustic Noise
Determining the Sound Acceleration Spectral Density
Sample Problem-Alternate Method of Acoustic Noise
11. Designing Electronics for Shock Environments
Specifying the Shock Environment
Pulse Shock
Half-Sine Shock Pulse for Zero Rebound and Full
Sample Problem-Half-Sine Shock-Pulse Drop Test
Response of Electronic Structures to Shock Pulses
Response of a Simple System to Various Shock Pulses
How PCBs Respond to Shock Pulses
Determining the Desired PCB Resonant Frequency for
Sample Problem-Response of a PCB to a Half-Sine
Shock Pulse
Response of PCB to Other Shock Pulses
Sample Problem-Shock Response of a Transformer
Mounting Bracket
Equivalent Shock Pulse
Sample Problem-Shipping Crate for an Electronic Box
Low Values of the Frequency Ratio R
Sample Problem-Shock Amplification for Low
Frequency Ratio R
Shock Isolators
Sample Problem-Heat Developed in an Isolator
Information Required for Shock Isolators
Sample Problem-Selecting a Set of Shock Isolators
Ringing Effects in Systems with Light Damping
How Two-Degree-of-Freedom Systems Respond to Shock
The Octave Rule for Shock
Velocity Shock
Sample Problem-Designing a Cabinet for Velocity
Nonlinear Velocity Shock
Sample Problem-Cushioning Material for a Sensitive
Electronic Box
Shock Response Spectrum
How Chassis and PCBs Respond to Shock
Sample Problem-Shock Response Spectrum Analysis
for Chassis and PCB
How Pyrotechnic Shock Can Affect Electronic
Sample Problem-Resonant Frequency of a Hybrid Die
Bond Wire
12. Design and Analysis of Electronic Boxes
Different Types of Mounts
Preliminary Dynamic Analysis
Bolted Covers
Coupled Modes
Dynamic Loads in a Chassis
Bending Stresses in the Chassis
Buckling Stress Ratio for Bending
Torsional Stresses in the Chassis
Buckling Stress Ratio for Shear
Margin of Safety for Buckling
Center-of-Gravity Mount
Simpler Method for Obtaining Dynamic Forces and
Stresses on a Chassis
13. Effects of Manufacturing Methods on the Reliability of
Typical Tolerances in Electronic Components and
Lead Wires
Sample Problem-Effects of PCB Tolerances on
Frequency and Fatigue Life
Problems Associated with Tolerances on PCB Thickness
Effects of Poor Bonding Methods on Structural Stiffness
Soldering Small Axial Leaded Components on ThroughHole PCBs
Areas Where Poor Manufacturing Methods Have Been
Known to Cause Problems
Avionic Integrity Program and Automotive Integrity
Program (AVIP)
The Basic Philosophy for Performing an AVIP Analysis
Different Perspectives of Reliability
14. Vibration Fixtures and Vibration Testing
14.1 Vibration Simulation Equipment
14.2 Mounting the Vibration Machine
14.3 Vibration Test Fixtures
14.4 Basic Fixture Design Considerations
14.6 Bolt Preload Torque
Effective Spring Rates for Bolts
Sample Problem-Determining Desired Bolt Torque
Rocking Modes and Overturning Moments
Oil-Film Slider Tables
Vibration Fixture Counterweights
A Summary for Good Fixture Design
Suspension Systems
Mechanical Fuses
Distinguishing Bending Modes from Rocking Modes
Push-Bar Couplings
Slider Plate Longitudinal Resonance
Acceleration Force Capability of Shaker
Positioning the Servo-Control Accelerometer
More Accurate Method for Estimating the
Transmissibility Q in Structures
Sample Problem-Transmissibility Expected for a Plug-in
Vibration Testing Case Histories
14.19 Cross-Coupling Effects in Vibration Test Fixtures
14.20 Progressive Vibration Shear Failures in Bolted Structures
14.21 Vibration Push-Bar Couplers with Bolts Loaded in Shear
14.22 Bolting PCB Centers Together to Improve Their
Vibration Fatigue Life
14.23 Vibration Failures Caused by Careless Manufacturing
14.24 Alleged Vibration Failure that was Really Caused by
Dropping a Large Chassis
14.25 Methods for Increasing the Vibration and Shock
Capability on Existing Systems
15. Environmental Stress Screening for Electronic Equipment
Environmental Stress Screening Philosophy
Screening Environments
Things an Acceptable Screen Are Expected to Do
Things an Acceptable Screen Are Not Expected to Do
To Screen or Not to Screen, That is the Problem
Preparations Prior to the Start of a Screening Program
Combined Thermal Cycling, Random Vibration, and
Electrical Operation
Separate Thermal Cycling, Random Vibration, and
Electrical Operation
15.10 Importance of the Screening Environment Sequence 389
15.11 How Damage Can Be Developed in a Thermal Cycling
Screen 390
15.12 Estimating the Amount of Fatigue Life Used Up in a
Random Vibration Screen 392
Sample Problem-Fatigue Life Used Up in Vibration
and Thermal Cycling Screen 395
Bibliography 401
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