environmental-testing

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

1. Identify life cycle environments (transportation, operational)
2. Measure or estimate PSD (Power Spectral Density) in field
3. Apply composite profiles (mix ground vehicle, aircraft, shipping)
4. 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:

1. Functional failure → identify symptoms
2. Physical inspection: VT, stereo microscope, SEM
3. Failure site: cross-section, EDS/EDX elemental analysis
4. Root cause: moisture ingress, CTE mismatch crack, corrosion, fatigue fracture
5. 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.