3.3 Environmental & Life Tests
Flex, vibration, temperature/humidity exposures for confidence in use.
Environmental and life testing proves a harness can survive its real-world stresses—flexing, vibration, temperature swings, humidity, chemicals, UV, and ingress—without losing electrical or mechanical integrity. Tests are run on representative builds mounted with actual clamp spacing, and monitored for glitches, resistance drift, and visible damage. Profiles are tailored to the product’s environment, from gentle office bends to million-cycle drag-chain runs or salt fog for marine gear. Electrical checks before and after each exposure confirm insulation health and contact performance, while detailed logs tie results to the harness’s serial record. Done this way, the tests become a predictable proof of durability, not a gamble.
3.3.1 What this proves (and when to run it)
- Design/qualification: “Will this harness survive its world?” Run at NPI or when materials change (wire, boots, backshells, overmold).
- Process monitoring: “Are builds consistent?” Run smaller samples per quarter or per vendor shift (sleeve, resin, contacts).
- Failure analysis: reproduce the customer’s environment to see the break and fix the mechanism.
Always bookend exposures with electrical checks: Continuity → Resistance (Kelvin on power) → IR → Hipot (3.1), plus visuals.
3.3.2 Test planning (four decisions first)
- Specimens: exact PN–Rev–Variant; route them on a board to final install clamp spacing and bend radii.
- Instrumentation: continuity glitch monitor (≥1 kHz), Kelvin taps on power/grounds, thermocouples on suspect joints.
- Success criteria: define limits up front (drops, ΔR, ΔT, IR/Hipot, cosmetic).
- Sequence (typical): Baseline → Flex/Torsion → Vibration → Temp/Humidity cycles → Chemical/Ingress (if relevant) → Final electrical.
Keep one unit as a control (no exposure) to compare drifts.
3.3.3 Flex & bend cycling (where most field issues start)
Setups
- Mandrel bend: wrap over a radius = design minimum (static: ≥6× OD; dynamic: ≥10× OD unless high-flex cable).
- Rolling flex / drag-chain: for motion-class cables.
- Torsion: clamp ends; twist ±90–180° about axis.
Starter profiles (tune to product)
Monitor & limits
- Continuity glitches >1 ms = fail; ≤3 blips <1 ms allowed (log).
- ΔR end-to-end ≤ 10–20% vs baseline (Kelvin on power).
- No jacket cracks, sleeve retreat, or shield breakouts.
3.3.4 Vibration (find loose pins, fretting, bad clamps)
Replicate the installed clamp scheme on the shaker; first clamp before first bend.
Screening sweep (find resonances)
- Sine 5→200 Hz, 0.5 g, 2 oct/min, 3 axes; dwell 1 min at peaks if needed.
Random vibration starter (industrial)
- 10–500 Hz, overall 3–5 grms, 3 axes, 30–60 min/axis (tune to product/vehicle spec if provided).
Pass indicators
- 0 continuity opens >1 ms during any axis.
- No bent/broken contacts or backshell loosening.
- Post-test IR ≥ limit and Hipot PASS (21.1).
3.3.5 Temperature cycling & thermal shock
Temperature cycling (air-to-air)
- Range: −40 → +85 °C (or your product limits), ramp ≤ 5 °C/min, dwell 30 min at extremes, 50–100 cycles.
- Monitor continuity at extremes if possible.
Thermal shock (two-chamber)
- −40 ↔ +85/105 °C, transfer ≤ 30 s, dwell 10–15 min, 50–100 cycles.
Pass
- No cracks in boots/overmolds, label legible, ΔR ≤ 10–20%, IR/Hipot PASS.
- Shield bonds intact (< 0.1 Ω end-to-end or to chassis point).
3.3.6 Humidity & moisture
Insulation resistance loves to fall when wet. Prove your materials.
Damp heat steady state (starter)
- 40 °C / 95% RH, 96 h; unpowered, then 1 h dry at room conditions → run IR/Hipot.
Damp heat severe (materials-permitting)
- 85 °C / 85% RH, 168–500 h (verify jacket/adhesive ratings first).
- Acceptance: IR ≥ 10–100 MΩ (per product), boots/labels still adhered, no green corrosion.
3.3.7 Chemicals, UV, salt fog (if the environment demands it)
Chemical splash/soak
- Fluids: oil/coolant/IPA/brake fluid/cleaners from your use-case.
- Method: 24–72 h soak or periodic splash at room temp; then flex 2k cycles on mandrel.
- Pass: no swelling >10%, no softening/cracks, labels legible, IR/Hipot PASS.
UV/outdoor
- UV exposure (lamp/arc) ≥ 100 h; then bend test. Pass = no embrittlement/cracking; print still readable.
Salt fog
- 5% NaCl, 35 °C, 48–96 h; focus on backshells/lugs. Pass = no red rust on stainless, minor cosmetic only on plated, continuity unchanged.
3.3.8 Ingress (IP) & washdowns
- IP54 spray: multi-angle spray 5–10 min; IR/Hipot afterward.
- IP67 dunk: 1 m / 30 min with mated seals; look for bubbles; post IR/Hipot.
- Washdown: if applicable, run spray with detergent and relabel legibility check.
3.3.9 Mate/unmate life & latch strength
Cycle per expected service.
Mating cycles
- 50–100 cycles for general purpose; ≥500 if field-serviceable.
- Track contact resistance (per pin) every 25 cycles; drift ≤ 50 mΩ from baseline.
Latch/CPA pull
- Pull at rated direction; latch must hold ≥ spec without damage; visual OK after test.
3.3.10 What to record (tie to SN, not a notebook)
- Profile IDs (flex/vibe/temp), dates, operator, fixture IDs.
- Baseline and post-exposure: Continuity/shorts, Kelvin R, IR/Hipot, shield bond Ω, photos.
- Real-time: glitch timestamps, ΔT at connectors, resonance notes.
- Disposition (PASS/REWORK/FAIL) with mechanism if failed (e.g., “shield wire break at bend after 12k cycles”).
Store with the harness SN (20.5) so RMAs find it in seconds.
3.3.11 Starter acceptance table (tune to your spec)
3.3.12 Common traps → smallest reliable fix
3.3.13 Pocket checklists
Setup
- Specimens PN–Rev–Variant; board-mounted with real clamp spacing
- TC and Kelvin leads on suspect points; glitch logger armed
- Success limits posted; control unit set aside
Run
- Flex/drag-chain to target cycles; log glitches/ΔR
- Vib: sine sweep then random 3 axes; no opens >1 ms
- Temp/humidity per profile; stabilize before electrical retest
- Chemical/UV/salt/IP as required
Closeout
- Post-test Continuity, Kelvin R, IR, Hipot recorded
- Visuals & photos (boots, labels, overmold, shields)
- Failures tagged with mechanism; samples archived