Utility software

Two pre-processing utility programs (relating to fatigue crack growth analysis) are provided with Zencrack:

• tanh
• rainflow

Tanh

The tanh utility allows use of crack growth data which is in the standard tanh equation form by generating tabular format data from the tanh equation. The tabular data is generated as a function of stress ratio. Interpolation between the tabular curves will not be identical to direct use of the tanh equation, but if enough curves are generated the differences will be negligible.

The input to this utility is a set of coefficients for the tanh equation and control values to specify the output curve creation. The output is a set of tabular growth curves in a format ready for use on the Zencrack option *CRACK GROWTH DATA, TYPE=TABULAR.

The alternative to the use of this pre-processing utility is that a user subroutine is written to directly use the tanh equation data.

Rainflow

The rainflow utility has been developed to perform cycle counting of uncounted load spectra using the "rainflow" algorithm. The generated spectrum files are in a format that can be used by Zencrack directly on the option *LOAD SYSTEM, TYPE=SPECTRUM. The program includes a capability for inclusion of time dependent information in the spectrum data for compatibility with the combined fatigue and time dependent growth capability in Zencrack.

The input to the program is an uncounted spectrum file. This consists of one data point per record (i.e. load level) for time independent spectra and two data points per record for time dependent spectra (i.e. load level, time).

The program can handle load spectra with a large number of data points. Random uncounted spectrum with 8 million data points have been analysed for testing purposes. The upper limit on the number of data points is determined by available memory.