XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX''"> Loading and Units
MSC Fatigue has been designed to appear to use units in the same way that FE modeling does (i.e., independent of any specific units system). However, the models for fatigue life estimation are not independent of the units system and so MSC Fatigue actually uses the S.I. system internally to carry out its computations. In order to appear independent of units, the relationship between S.I. units and the chosen units system has to be defined for different kinds of loading. This definition is held in two ASCII tables which are located in the MSC Fatigue central system directory in the ptime directory.
The tables have the following file names:
ltypes.ind loading types definition
utypes.ind units definition
Loading Types
The loading types table will have a form similar to
Table 4‑4.
Table 4‑4 Load Number | Object Load Group | Description Load Name |
1 | 1 | Point Load |
2 | 2 | Pressure |
3 | 3 | Temperature |
4 | 4 | Acceleration |
6 | 6 | Displacement |
7 | 7 | Angular Speed |
8 | 8 | Speed |
9 | 9 | Uncalibrated |
10 | 10 | Scalar |
11 | 11 | Moment |
The basic form of the loading types table is defined within the file ltypes.ind. Each new type of loading is given a unique index number, a group number which is the same as the index number and a title. The title will appear at various places in MSC Fatigue wherever loading types are being manipulated (e.g., when defining a new loading time history in PTIME).
The list of loading types may be extended by adding a new line to the bottom of the ltypes.ind file. The user should NOT insert a loading type in the middle of the existing list and renumber the loading types since this will seriously interfere with any existing MSC Fatigue jobs and make the loading types incompatible with previous jobs. The maximum load number cannot exceed 99.
As well as defining a new loading type in the
ltypes.ind file, the user must also define the units system for this loading type. This is explained in
Units Types, 259.
Units Types
The units types table will have a form similar to
Table 4‑5. The base units types for any loading type is the S.I. units system as defined below:
Note: Kilograms | for mass |
Meters | for length |
Seconds | for time |
Kelvin | for temperature |
All other units may be derived from these (i.e., stress base units are N/m or Pascals). Once a new loading type has been added, the user must also define the relationship between the units for this loading type. Failure to do so will produce an error message in the MSC Fatigue software. The units relationship is held in the utypes.ind file. To add new lines to the utypes.ind file, the user must first understand the format of the file. There are five columns of information required.
Table 4‑5 Units Number | Load Group Number | Conversion Factor | Conversion Offset | Units Name |
0 | 1 | 1 | 0 | Newtons |
1 | 1 | 1000 | 0 | kNewtons |
2 | 1 | 4.448 | 0 | lbs force |
3 | 1 | 9964 | 0 | Tons force |
4 | 1 | 9807 | 0 | Tonnes force |
10 | 2 | 1 | 0 | Pascals |
11 | 2 | 1E6 | 0 | MPa |
12 | 2 | 6894.65 | 0 | PSI |
13 | 2 | 6894650 | 0 | KSI |
14 | 2 | 1.3788E7 | 0 | TSI |
15 | 2 | 9806.81 | 0 | kgf/m2 |
20 | 3 | 1 | 0 | Degrees Kelvin |
21 | 3 | 1 | 273 | Degrees Celsius |
22 | 3 | 0.55556 | 255 | Degrees Fahrenheit |
30 | 4 | 1 | 0 | m/s2 |
31 | 4 | 9.80655 | 0 | g |
32 | 4 | 0.0254 | 0 | feet/s2 |
40 | 6 | 1 | 0 | m |
41 | 6 | 0.001 | 0 | mm |
42 | 6 | 0.0254 | 0 | inches |
43 | 6 | 0.0254E-3 | 0 | milliinches |
44 | 6 | 0.0254E-3 | 0 | microinches |
50 | 7 | 1 | 0 | rps |
51 | 7 | 0.0166667 | 0 | rpm |
52 | 7 | 2.7778E-4 | 0 | rph |
53 | 7 | 0.159155 | 0 | rad/s |
54 | 7 | 2.6526E-3 | 0 | rad/min |
60 | 8 | 1 | 0 | m/s |
61 | 8 | 0.001 | 0 | mm/s |
62 | 8 | 0.27778 | 0 | kph |
63 | 8 | 0.0254 | 0 | ips |
64 | 8 | 0.4470 | 0 | mph |
70 | 9 | 1 | 0 | none |
80 | 10 | 1 | 0 | none |
81 | 10 | 1 | 0 | % |
82 | 10 | 1 | 0 | levels |
90 | 11 | 1 | 0 | Nm |
91 | 11 | 0.73759 | 0 | Ft lbs |
92 | 11 | 0.001 | 0 | Nmm |
Units Number: This is a unique number and will usually be the next number which leaves room for later expansion if it becomes necessary. The maximum number allowable is 999.
Load Group Number: This number MUST correspond to the loading group number allocated in the ltypes.ind file (see above).
Conversion Factor: This is the multiplier which converts the new units into S.I. units (see note on units).
Conversion Offset: This is the offset number which converts the new units into S.I.units (e.g., 273 to convert temperature from Kelvin to degrees Celsius).
Units Name: This is the text which will appear whenever a units option is presented.