CURVE YIELD STRAIN USING STM METHOD

Computes yield strain and yield stress from a stress-strain curve using the STM (Secant-Tangent-Mean) method, as defined in Dr. Maximilian Benz’s PhD dissertation. The yield point is identified where the arithmetic mean of the secant and tangent modulus ratios exceeds a user-defined threshold.

When to use

Classification: process.

Tagged: benz, material_characterization, secant_modulus, stm, stress_strain, tangent_modulus, yield_strain, yield_stress.

Inputs

Label ID Type Default Required Description
Curve In curve_in vector   Input stress-strain curve (X = strain, Y = stress) to be analysed; must cover the elastic-to-plastic transition region.
Threshold th scalar 1.2   Threshold value for the arithmetic mean of the secant-to-tangent modulus ratio; the first point where this ratio exceeds the threshold is taken as the yield point (dimensionless; default 1.2).
Smooth Derivatives smooth scalar yes   Whether to apply smoothing to the derivative (tangent modulus) before computing the STM ratio; set to ‘yes’ (default) to reduce noise sensitivity, ‘no’ to use raw derivatives.
Offset curve so the initial point is at origin of 0,0 offset scalar no   Whether to shift the curve so that its initial point coincides with the origin (0, 0) before processing; set to ‘yes’ if the raw data has a non-zero start offset, ‘no’ (default) to use the curve as-is.
Average Over average_over scalar 0.0   Window half-width (in strain units) over which the modulus is averaged around the detected threshold point; leave at 0.0 (default) to use a single-point detection without windowed averaging.

Outputs

Label ID Type Description
Yield Stats yield_stats keyvalue Key-value map containing the computed yield results, including yield strain, yield stress, and associated STM modulus values at the detected yield point.

Disciplines

  • data.curve.transform
  • engineering.material.characterization

Runnable example

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