Zencrack input files

The main Zencrack input file uses a keyword type structure similar in concept to the majority of finite element programs. The input file may consist of comment lines, keyword lines and data lines. The majority of options have default values and only a minimal amount of "essential" data is needed. For example, for analysis of an initial crack:

*FILES,UNCRACKED=example.inp
*OPTIONS,INTERFACE=ABAQUS,TYPE=INITIAL
*CRACK FRONT, INITIAL=SIZE
s01_q103x4.sup
 1 5 2 1.0 1.0
*MATERIAL
 210000 0.3
*END

In this example, a single crack-block, s01_q103x4.sup, replaces element number 1 in the uncracked mesh. The crack is oriented using corner nodes 5 and 2 on that element. The initial crack size is 1.0 along the crack-block edges where the crack front meets the crack-block boundary. The material data is provided to allow conversions between stress intensity factors and energy release rate.

Extending this for a crack growth analysis:

*FILES,UNCRACKED=example.inp
*OPTIONS,INTERFACE=ABAQUS,TYPE=FATIGUE
*CRACK FRONT, INITIAL=SIZE
s01_q103x4.sup
 1 5 2 1.0 1.0
*MATERIAL
 210000 0.3
*LOAD SYSTEM,TYPE=CONSTANT AMPLITUDE
 0.1  1.0
*CRACK GROWTH DATA,TYPE=PARIS
 7.75E-13 3.2
*END

To extend the data for a basic crack growth analysis, a constant amplitude load system is defined with stress ratio 0.1. Crack growth data is provided via Paris law constants.

A variety of keyword options are available to give the user full control of the analysis. Some of these are mandatory but most are optional. In the majority of cases the optional keywords can be omitted allowing the defaults to be used for those options.

User subroutines

In addition to the standard options built into Zencrack a number of user subroutines are available to give extended control to the user. These allow, for example, the use of proprietary crack growth models and data. Available subroutines include:

• Crack growth data for fatigue analysis.
• Crack growth data for time dependent analysis.
• Threshold data for fatigue analysis.
• Threshold data for time dependent analysis.

Additional input files

Depending upon the analysis type there are a number of additional input files that may be required. These are all ASCII files whose format is provided in the user manual:

• Tabular crack growth data file.
• Cyclic spectrum file defining counted load cycles.
• Load time history file for time dependent crack growth.
• Temperature time history file for time dependent crack growth.