Creep, Stress Relaxation & Fatigue Design of Plastics

The long-term mechanical behavior no intro course teaches: creep rupture, polymer S-N curves, stress relaxation in snap-arms and bolted joints, thermal aging — the mathematics of how plastic parts fail slowly.

Private cohorts & on-site
Format: 2-day (8:30 a.m.–4:30 p.m.)
Level: Advanced
Location: Scheduled on demand · on-site at your facility or a regional venue
Date(s): Not yet scheduled for open enrollment. Get notified when it is, or book it privately for your team.
Includes: Certificate of Completion · printed slide binder · take-home reference text

Get notified when this course is scheduled

One email when dates are set. Or skip the wait: run it as a private cohort, on-site at your plant.

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Faculty

Faculty details for this seminar will be announced with the full schedule.

Fees

Early: $1,895 (payment 4+ weeks ahead)
Standard: $2,095 (check/ACH) · $2,165 (card)

Group discount: $200 off per attendee for 3+ from the same organization.

Also Available

  • Corporate on-site delivery at your facility
  • Private cohort sessions
  • Digital curriculum licensing

Seminar Overview

A plastic part that passes every short-term test can still fail in the field at 11,000 hours — and the reason is always the same family: creep under sustained load, relaxation in a preloaded joint, fatigue under vibration, or thermal aging that embrittles the compound. This seminar teaches the long-term mechanical behavior of plastics from isochronous stress-strain curves and creep-rupture envelopes to polymer fatigue (S-N) behavior and the design methods that keep snap-arms, bolted bosses, and press-fits alive for the life of the vehicle.

The day is quantitative: you read real isochronous curves from resin-producer data (the DuPont/Covestro/BASF guide corpus already in the ETS knowledge base), compute apparent-modulus reductions at design life, size a boss for 10-year preload retention, and set snap-arm strain limits against fatigue knockdowns at weld lines. Interlaminate: temperature and moisture enter every calculation as first-class variables, not footnotes.

You leave with worked design limits — strain limits, stress limits, preload-retention margins — you can apply Monday morning, plus the ability to interrogate a supplier's long-term data instead of trusting the single 1-hour yield value on the datasheet.

Ideal Learner

  • Design engineers sizing snap-fits, bosses, and press-fits for long service life
  • Structural/CAE engineers validating long-term performance
  • Materials engineers specifying long-term property data
  • Failure analysts diagnosing delayed field failures

Learning Objectives

  • Read isochronous and isochronous-failure curves and compute apparent modulus at design life
  • Design bolted joints and press-fits for preload retention under relaxation
  • Set snap-arm strain limits against fatigue with weld-line knockdown
  • Apply thermal-aging derating to long-term load ratings
  • Interrogate supplier creep data: what to ask for, what to distrust

Consulting Sessions

Seminar attendees can sign up for individual consulting sessions with the instructor. Sessions are free for registered attendees, first-come first-served — sign up when registering by calling 248-539-0473 or during the seminar.

Seminar Outline

  • Modulus is a curve, not a number: time-temperature superposition
  • Isochronous and isometric reading practice
  • Linear vs. nonlinear viscoelasticity: where the safety zone ends
  • Creep-rupture envelopes and extrapolation discipline
  • Apparent-modulus method with worked examples
  • Long-term loading: cantilever arms, shelves, gasketed housings
  • Moisture and temperature as first-class variables
  • Relaxation physics in snap-arms and screws
  • Bolted boss design for 10-year preload retention
  • Gasket and seal preload with relaxation stacking
  • Worked example: a boss that survived 12 years — and one that didn't
  • Polymer S-N curves: frequency, mean stress, temperature effects
  • Weld-line fatigue knockdown in design terms
  • Snap-arm design limits from fatigue data
  • Ratcheting and thermal cycling: combined duty
  • Thermal aging and embrittlement derating
  • Chemical exposure accelerating creep (ESC linkage)
  • Combined-duty design cases from ETS case history
  • Design-limit checklist you keep

More in Track C — Design, Molding & Tooling

Full Course Catalog