July 2014 Herb Schueneman President & CEO Presenter Eric Lau Senior Test Engineer Presenter Greg Schwinghammer Director of Engineering Moderator
1. Brief History of Mechanical Shock Testing 2. Purpose of Shock Testing (Simulations and Determining Fragility) 3. Shock Response Spectrum (SRS) Overview 4. Shock Test Parameters (waveform parameters, test levels, tested orientations, fixturing ) 5. Industry Standards 6. Case Studies 7. Conclusion 2014, Westpak, Inc. 2
History of Shock Testing 1. Definition of Mechanical Shock The acceleration (or deceleration) resulting from a sudden non-repetitive (transient) impact of two surfaces (masses). Mechanical shock normally refers to a laboratory programmed event where the acceleration vs time signature is generated by equipment designed for that purpose. (The term impact usually refers to an uncontrolled event.) Normally measured with an accelerometer who s electrical output is proportional to the mechanical input. 2014, Westpak, Inc. 3
History of Shock Testing 2. Brief History Normally the birth of shock testing as we know it today is credited to the US military in an attempt to improve equipment reliability 11 millisecond pulse durations originated from early designs using sand as shock programmers From then, newer machines were designed using various programmer materials including felt & rubber 2014, Westpak, Inc. 4
Purpose of Shock Testing Simulate Actual In-Use Environments (everyday occurrences to worst case scenarios) Determine the Fragility of a Product (determining critical acceleration/critical velocity change or equivalent drop height before product is damaged) 2014, Westpak, Inc. 5
Purpose of Shock Testing 1. Critical for a successful product! 2. Your product has value only after reaching the end user damage-free and achieving its expected life cycle. 2014, Westpak, Inc. 6
Shock Response Spectrum (SRS) 1. Definition of SRS 2. Shows the peak acceleration response (y-axis) of an infinite number of SDOFs, each with different natural frequencies (x-axis) 3. Example 4. What we can determine from this plot SRS, SDOF SPRING-MASS MAXIMUM RESPONSE 2 UNDAMPED SYSTEM SQUARE WAVE Ar A i 1 HALF SINE TRAPEZOIDAL PULSE 1/6 1/2 f r / f i 2014, Westpak, Inc. 7
Shock Test Parameters PULSE PARAMETERS 1. Waveform parameters include: Peak Acceleration, Duration, and Velocity Change (V c ) 100 G s Peak Acceleration (G s or m/s 2 ) 10 G s 10 G s Duration (ms) Measured at 10% of peak amplitude 2014, Westpak, Inc. 8
Shock Test Parameters WAVEFORM PULSE Classical Shock Pulses Half-sine Square (Trapezoidal) Sawtooth (Terminal Peak) Theoretical Pulse Shape Actual Pulse Shape Programmer Type Elastomer (i.e. Urethane) Nitrogen Gas or Lead Cylinders Lead Cones 2014, Westpak, Inc. 9
Shock Test Waveform COMMON USAGES Waveform Pulse Pulse Length Common Use NOTES Half-sine Short Critical Velocity Change (bare product) 2-3 msec pulse recommended per ASTM D3332 Method A (Critical Velocity). The input pulse should have a duration of 1/6 or less than the natural period of the critical component In general: Tp 167 / fc where: Tp = maximum shock test machine pulse duration in ms, and fc = component natural frequency in Hz 2014, Westpak, Inc. 10
Shock Test Waveform COMMON USAGES Waveform Pulse Pulse Length Common Use NOTES ASTM D3332 Method B Excites all residual resonances (SRS) Square (trapezoidal) Long Critical Acceleration (distribution/pack aged events) Specified/ Defined Specified/ Defined Simulate actual characterized event Based on company specification or recommended in industry standard 2014, Westpak, Inc. 11
Number of Impacts Shock Test Parameters ADDITIONAL FACTORS Based on probability that the product would see the shock event throughout its expected lifecycle. If unknown throughout product lifecycle, refer to industry standards. Impact Orientations Generally all 6 orthogonal sides(±x, ±y, ±z). Unless certain orientations have absolutely no probability of being impacted at the chosen test level or only certain orientations of product are fragile. Fixturing Any form of securement. For odd shaped test samples, the samples can be affixed to a rigid fixture for ease of re-orienting, a fixture can be designed to house the unit. 2014, Westpak, Inc. 12
Questions? 2014, Westpak, Inc. 13
Industry Standards ASTM D3332 1. Determination of the shock fragility of products 2. Method A Critical Velocity Change ( V c ) 3. Method B Critical Acceleration (A c ) 4. Recommends a total of 12 new samples (6 per test method, 1 for each orthogonal orientation) 2014, Westpak, Inc. 14
Industry Standards MIL-STD-810G 1. AAF released Spec 41065 in 1945 2. First revision of MIL-STD-810 was created in 1962 3. Provides methods, procedures, and parameter levels to tailor to product/environment. 4. Section 516.7 SHOCK 2014, Westpak, Inc. 15
Industry Standards IEC 60068-2-27 International Electrotechnical Commission (IEC) Collaborates with International Organization for Standardization (ISO) For components, equipment, electro-technical products 2014, Westpak, Inc. 16
Industry Standards IEC 60068-2-27 2014, Westpak, Inc. 17
Industry Standards and Westpak Capabilities Half-sine Pulse Typical Uses: ASTM D3332 Method A Critical Velocity Change Simulating Product Drops Elastomer Programmers Elastomer Programmers on Shock Tester Machine Capabilities: 38 x 45 table surface 600G s Velocity change 50 to 250 in/sec 2msec shortest duration 1,000 lb max load 2014, Westpak, Inc. 18
Industry Standards and Westpak Capabilities Trapezoidal Typical Uses: ASTM D3332 Method B Critical Acceleration Simulating Packaged/Distribution Impacts Machine Capabilities: 38 x 45 table surface 5G s to 120 G s up to 288 inches/second ~30 msec 9 msec 2,500 lb max load 2014, Westpak, Inc. 19
Industry Standards and Westpak Capabilities Half-sine Pulse Typical Uses: ASTM D3332 Method B Critical Acceleration Simulating Packaged/Distribution Impacts Machine Capabilities: 9 x 9 table surface Up to 5,000 G s 0.5 msec short duration 2,500 lb max load 2014, Westpak, Inc. 20
Industry Standards and Westpak Capabilities Horizontal Impact (Half-sine and trapezoidal) Herb Eric Typical Uses: ASTM D3332 Method A Critical Velocity, Method B Critical Acceleration Simulating impacts such as truck/forklift bumps, rail switching Machine Capabilities: Table surface 72 x 88 with 73 high sail Up to 300 inch/sec velocity change Rated up to 13 mph 2014, Westpak, Inc. 21
Case Study #1 Product: Laptop Purpose of test: Determine Fragility of Product and Design Package for Distribution Step: 1. First find resonant frequencies of critical components (determine pulse duration for test) 2. Determine critical velocity (ASTM D3332, Method A, Critical Velocity Change) 3. Using Half-sine pulse, increment velocity change using determined pulse duration until failure occurs 4. Perform critical acceleration testing (ASTM D3332, Method B) 2014, Westpak, Inc. 22
Case Study #2 Product: Cell Phone Goal: To determine product characteristics Steps: 1. The expected drop heights are known (i.e. off table, waist level; ~36 ) 2. Velocity change = (1 + e) x 2 x g x h e = coefficient of restitution from 0 to 1 g = gravitational constant of 386.1 in/sec 2, h = equivalent drop height Velocity change = (1 + 0.5) x 2 x 386 x 36 = 175 inches/second 3. Specification should be written based on expected velocity changes during the products lifecycle 2014, Westpak, Inc. 23
Case Study #3 Product: Black Box, unknown Goal: Required EUT must be able to sustain/exceed 50 G s in its in-use environment Steps: 1. Use step acceleration per ASTM D3332 Method B (trapezoidal pulse to excite all residual responses at maximum) 2. Increase acceleration level until failure is observed 3. Determine critical in-use environment characteristics; results can also be used for packaging design 2014, Westpak, Inc. 24
Any Questions 2014, Westpak, Inc. 25
Next Webinar Package Integrity Testing Westpak will discuss package integrity testing. Review of commonly used test specs How/when they should be applied How does Integrity Testing differ from package performance testing? Case studies 2014, Westpak, Inc. 26
About WESTPAK, INC. Two Locations: San Jose Laboratory San Diego Laboratory 83 Great Oaks Boulevard 10326 Roselle Street San Jose, CA 95119 San Diego, CA 92121 408-224-1300 858-623-8100 www.westpak.com projects@westpak.com 2014, Westpak, Inc. 27
THANK YOU! Please feel free to Contact Us with any questions or assistance with your product reliability testing needs. Herb Schueneman herb@westpak.com projects@westpak.com Eric Lau eric@westpak.com 2014, Westpak, Inc. 28