| name | environmental-testing |
| description | Environmental testing — MIL-STD-810H (vibration, shock, thermal, humidity), DO-160, HALT/HASS, salt spray (ASTM B117), thermal cycling, HALT procedures, failure analysis. |
| metadata | {"priority":6,"promptSignals":{"phrases":["environmental test","MIL-STD-810","HALT","thermal cycling","salt spray","vibration test","DO-160","HASS","qualification"],"minScore":4}} |
Environmental Testing — Complete Skill
MIL-STD-810H Overview
US military standard for equipment environmental testing
Method number + procedure letter designates test type
Must tailor to actual service environment (measured or estimated field data)
Key methods:
| Method | Environmental Condition |
|---|
| 500.6 | Low pressure (altitude) |
| 501.7 | High temperature |
| 502.7 | Low temperature |
| 503.7 | Temperature shock |
| 504.3 | Contamination by fluids |
| 505.7 | Solar radiation |
| 506.6 | Rain |
| 507.6 | Humidity |
| 509.7 | Salt fog |
| 510.7 | Sand and dust |
| 514.8 | Vibration |
| 516.8 | Shock |
| 519.8 | Gunfire vibration |
| 520.4 | Temperature/altitude |
| 521.4 | Icing/freezing rain |
Vibration Testing (MIL-STD-810H Method 514)
Tailoring Process
- Identify life cycle environments (transportation, operational)
- Measure or estimate PSD (Power Spectral Density) in field
- Apply composite profiles (mix ground vehicle, aircraft, shipping)
- Duration: derived from mission life × fatigue equivalence factor
Common profiles:
Fixed-wing aircraft (Procedure I): 0.04 g²/Hz at 15-1000 Hz, 1 hr/axis
Helicopter (Procedure II): higher 4-10 Hz spike (blade passage)
Ground vehicles (Procedure III): high at 5-20 Hz (road roughness), ASTM D4169 for shipping
3-axis testing: test X, Y, Z sequentially or simultaneously (MESA)
Duration per axis: full life equivalent, or compressed per fatigue damage model
Sine Sweep (Resonance Dwell)
Sweep rate: 2 oct/min (standard) or slower
Resonance search: identify f_n during sweep (amplitude spike)
Resonance dwell: operate at f_n for 10-30 minutes (endurance at resonance)
Shock Testing (MIL-STD-810H Method 516)
Shock Pulse Shapes
Half-sine: 11ms × 15g peak (handling/transportation drop)
Sawtooth: high peak, fast rise (pyrotechnic, explosive shock)
Trapezoidal: sustained shock (vehicle crash)
Test machines:
Drop tower: free fall onto cushion; half-sine shape; up to 100g peak
Pneumatic shaker: programmable waveforms; precision SRS control
Explosively driven: for pyrotechnic shock (re-entry, stage separation)
Shock Response Spectrum (SRS) control:
Specify SRS shape → drive signal synthesized to produce SRS
Verify SRS achieved within ±3 dB tolerance
Q = 10 (5% damping) standard for SRS
Thermal Testing
Temperature Extremes (Methods 501/502)
Storage: -55°C to +85°C typical military; -20 to +70°C commercial
Operational: -40°C to +70°C (military), -20 to +55°C (commercial)
Dwell time: 1-4 hours at temperature extreme (allow thermal soak)
Monitor: measure functional performance at temperature extremes
Temperature Shock (Method 503 — HALT variant)
Rapid temperature change: 10-20°C/min (standard), up to 60°C/min (HALT)
Transfer time between hot and cold chambers: < 3 minutes (standard), < 30 sec (HALT)
Standard: -55°C to +125°C, 5+ cycles
Purpose: CTE mismatch → differential expansion → solder joint cracking, delamination, seal failure
Thermal Cycling (IEC 60068-2-14)
Slower: 1-5 cycles/hour; many more cycles (100-1000)
Represents seasonal/diurnal temperature variation
Failure modes: fatigue from thermal strain cycling (Coffin-Manson), connector intermittency
Arrhenius acceleration model:
AF = exp[Ea/k × (1/T_use - 1/T_test)] [acceleration factor, T in Kelvin]
Ea = activation energy: 0.6-0.9 eV (solder), 0.3-0.5 eV (electromigration)
k = Boltzmann constant = 8.617×10⁻⁵ eV/K
Example: T_use = 40°C, T_test = 85°C, Ea = 0.7 eV: AF = 44×
Humidity Testing
Damp Heat (IEC 60068-2-78 / Method 507)
40°C / 93% RH, 10+ days (corrosion, insulation resistance, delamination)
Or: 65°C / 90% RH, Peck model for humidity acceleration
Cyclic Humidity (MIL-STD-810H Method 507)
Cycling temperature with high humidity (condensation on surfaces)
Tests: seal integrity, breathing vents, gaskets
Salt Fog / Salt Spray (ASTM B117 / Method 509)
5% NaCl salt fog at 35°C
Duration: 48-1000 hr (96hr basic, 240hr for severe marine)
Evaluation: % coverage with corrosion, coating failure area
Not correlated to real-world time (highly accelerated, mechanism differs)
Alternatives with better real-world correlation:
ASTM G85: modified salt spray (SO₂, acetic acid, cyclic)
ISO 11997: cyclic corrosion (wet + dry + salt)
HALT (Highly Accelerated Life Testing)
Purpose
Find design weaknesses quickly using stresses beyond spec
NOT a standards-compliance test — a design improvement tool
Apply: thermal cycling (rapid), vibration, combined simultaneously
Typical HALT progression:
Cold step stress: -40°C to limit of destruction → find cold limit
Hot step stress: +50°C to +130°C step stress → find hot limit
Combined thermal + vibration: identify synergistic failures
Vibration step stress: 0 to 50+ Grms — find vibration limit
Goal: operational limit >> design spec → margin demonstrated
Fundamental limit of technology (FLT): stress level where physics fails (not design)
Operational limit (OL): stress at which device fails
Spec limit (SL): design specification limit
Margin = OL/SL > 2× → robust design
HASS (Highly Accelerated Stress Screening)
Production 100% screening to catch manufacturing defects
Run at < HALT limits (damage-free stresses) but higher than field stresses
Profile: thermal cycling + random vibration (combined), shorter duration than HALT
DO-160 (Aerospace)
RTCA DO-160G: environmental conditions for airborne equipment
Sections: temperature, altitude, temperature variation, humidity, shock, vibration, explosion, waterproofness, fluids susceptibility, sand and dust, fungus, salt fog, magnetic effect, power input, voltage spike, audio susceptibility, induced signal susceptibility, radio frequency susceptibility, emission, lightning, electrostatic discharge, fire/flammability
Section 8 (vibration): Category S (aircraft specific), U (helicopter), test levels per aircraft type
Section 7 (shock): half-sine and saw tooth, 6 g to 20 g typical
Failure Analysis
After environmental test failures:
- Functional failure → identify symptoms
- Physical inspection: VT, stereo microscope, SEM
- Failure site: cross-section, EDS/EDX elemental analysis
- Root cause: moisture ingress, CTE mismatch crack, corrosion, fatigue fracture
- Design change: address root cause (material, coating, geometry, process)
Output
Provide: applicable standard + method number, test conditions (T_min/T_max, cycle rate, duration), vibration PSD profile [g²/Hz], shock SRS [g vs. Hz], number of cycles, acceptance criteria, failure mode risk.
