Additionally, vectors of

principal strain [[epsilon].

For each step, observed peak strain value in three directions were tabulated and

principal strain was calculated using a data analysis software [10,11].

This model was transformed into an all-strain based space by involving the stress ratio and the ratio of in-plane

principal strain increments.

For X80 pipeline steel with the occurrence of ductile failure, the maximum

principal strain criterion is used for damage initiation of the crack, and the exponential response is used for damage evolution.

When the tensile or compressive

principal strain in the FE model exceeded the tensile or compressive tissue yield strain, the postyield tissue elastic modulus was set to 5% of the initial elastic modulus [37, 38].

Under constant amplitude alternating load, the maximum

principal strain and the cycle change over time.

Next, rectangular rosette pattern strain gauges are attached to the neural arch to calculate the direction and magnitude of

principal strain under various loads and motions.

Pituba (2006) suggested a criterion to locate the transversal isotropy plane based on the signs of the

principal strain rates.

The maximum

principal strain rate results showed the corner areas of the spring seat experienced higher strain rates than the rest of the casting during solidification (Fig.

The contour colors indicate the maximum

principal strain in the specimens calculated based on the dimensions of the printed grid by using the image analysis technique described above.

There was no force measurement in the dynamic tests therefore the final comparison graphs were represented by the line plots where time was on the x-axis and

principal strain on the yaxis.

2) Based on the maximal

principal strain theory, when the maximal

principal strain of a specimen equals the strain corresponding to the yield stress in a simple tensile test, yield failure happens to this specimen.