03.46 · Fatigue residual properties

A residual-property curve describes an assumed evolution of stiffness or strength over cycling, not simply the number of cycles to failure. This exercise makes the independent calibration of those retention laws visible and separates their outputs from a conventional life estimate.

Illustrative calibration only. Start with a 16-ply cross-ply reference laminate; this is a separate, reference-state study.

Open this exercise in Workbench

Prepare the baseline

Inspect the reference properties, life basis and fitted loss parameters for stiffness and strength. Check that the loading condition and temperature belong to the same calibration. Run the baseline and vary one supported parameter without changing the remaining cycle basis, then compare the full curves rather than one isolated point.

Worked procedure

1. Follow the study’s laminate link and inspect the stack and resolved properties that it will use. Then read the model scope and identify the additional specimen, loading or calibration inputs belonging to this separate study. Record which values are supplied independently rather than assuming that every required quantity is inherited from the laminate.

2. Run the supplied study as a baseline and inspect the complete response curves, including their axes, units and parameter settings. Retain the numerical values or a clearly labelled capture before changing an input. Use the interpretation guidance below and the linked formulation to identify what each curve represents and which conclusions remain outside its scope.

3. Choose one editable parameter that belongs to this model and record its original and revised values. Keep the other inputs fixed, rerun the study, and compare the same output quantities over the same range. Explain the observed change using the linked formulation, including a discussion of whether the comparison stays within the model’s calibration and assumptions.

Review checkpoints

Do not interpret example calibration values as material allowables.

Record the assumptions and distinguish analytical verification from experimental validation.

Model limits

Prescribed power-law retention fitted to constant-amplitude tests at a fixed stress ratio, amplitude and temperature. Stiffness and strength have independent coefficients. S–N life alone cannot calibrate either. Does not modify the saved laminate.

Interpret the comparison

State which part of the change follows directly from the prescribed retention law. Do not infer its coefficients from an S–N life alone or extrapolate beyond the supported range. The separate study’s curves do not automatically overwrite a saved laminate or update optimization properties.

How information passes between models

Micro → Laminates: Predicted ply stiffness, strength, density and expansion properties.

Materials → Micro: Constituent stiffness, strength, density and thermal / moisture properties.

Mechanical → Simulation: SIMULATION selects this case and its analysis model; the case owns its applicable cycle and input references.

Laminates → Mechanical: Ply angles and thicknesses, stiffness, mass and ply properties.

Models → Micro: Applied model assignment: Halpin–Tsai. Model parameters and formulation are used by Micro.

Models → Mechanical: Applied model assignment: Calibrated residual-property fatigue. Model parameters and formulation are used by Mechanical.

Further reading and evidence

• Advanced analytical models: equations, calibration and limits
• Edit laminate materials, angles and thicknesses
• Run and review a model
• Connected inputs and result freshness

Review the recorded validation scope. Retain the original inputs and solver notices with the results. Representative teaching data are not design allowables.