Creating a .fat File - CAESAR II - Help

CAESAR II Users Guide

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CAESAR II
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CAESAR II Version
12

The .fat file is an ASCII text file containing the data points necessary to describe the fatigue curve for the material, for both butt-welded and fillet-welded fittings. A sample.fat file is shown below.

* ASME SECTION VIII DIVISION 2 FATIGUE CURVE

* FIGURE 5-110.1

* DESIGN FATIGUE CURVES FOR CARBON, LOW ALLOY, SERIES 4XX,

* HIGH ALLOY AND HIGH TENSILE STEELS FOR TEMPERATURES NOT

* EXCEEDING 700 F

* FOR UTS £ 80 KSI

*

0.5000000 - STRESS MULTIPLIER (PSI); ALSO CONVERTS AMPLITUDE TO FULL RANGE

*

10 580000.0
100 205000.0

1000 83000.0

10000 38000.0

100000 20000.0

500000 13500.0

1000000 12500.0

0 0.0

*

You can create this text file by using any text editor. Lines beginning with an * are treated as comment lines. It is good practice to use comment lines so that the data can be tied to a specific material curve.

The first data line in the file the stress multiplier. This value is used to adjust the data values from "zero to peak" to "peak to peak" or to convert the stress levels to psi. The entered values are divided by this number. For example, if the stress values in the file represent the stress amplitude, in psi, rather than a range, this "stress multiplier" should be 0.5. Following the stress multiplier is the Fatigue Curve Data table. This table consists of eight lines, of two columns. The first column is the Cycle column, and the second is the Stress column. For each value in the cycle column, a corresponding stress value from the material fatigue curve is listed in the stress column.

Fatigue curves intended for use with IGE/TD/12 are built slightly different. The first data line contains three values: the stress multiplier, a modulus of elasticity correction, and a modulus of elasticity multiplier (the correction factor is divided by this to convert to psi). After the files are read in, the modulus of elasticity correction is inserted into the appropriate field on the Fatigue Curve dialog. IGE/TD/12 fatigue files also include five sequential fatigue curves, Fatigue Class D, E, F, G, and W, rather than one. You can use optional comment lines to separate the tables. The comments help with the readability of the data file. You can best determine the format of the IGE/TD/12 fatigue files by reviewing the contents of the TD12ST.fat file.

In all tables, the number of cycles increases as you work down the table. If you do not have enough data to use all eight lines, fill the unused lines with zeros.

For information on editing ASCII text, see ASCII Text File Rules.