RESULTS CALCULATE SAFETY Loadcase_name [Step_number]

    

This command calculates factors of safety from nodal values. A new combination loadcase is generated in which the factors of safety are stored as an attribute named `FACTOR'. The name of the new loadcase is specified in the command.

Temperature dependent values for Fatigue Strength (FS) and Ultimate Tensile Strength (UTS) may be input to FEMVIEW via the material properties data set, see Appendix B of the User Manual Appendices. This data set allows pairs of values for temperature versus Fatigue Strength and temperature versus Ultimate Tensile Strength to be given. Alternatively, the user may input constant values for FS and UTS during a prompt sequence.

The prompt sequence first requires the user to give some reference text to be associated with the factor of safety loadcase; then to give the names of the loadcases containing the values of nodal temperature and thermal stress and thermal plus mechanical stress which are to be used in the calculation; and finally to give the name of the attribute in these latter two loadcases containing the actual stress data. Note that this attribute must occur with identical attribute and component names in both the thermal stress and thermal plus mechanical stress loadcases. If no temperature dependant data has been given in the material properties data set, or if no temperature loadcase is specified, then the user will be prompted for constant values of FS and UTS.

The minimum safety factor is then calculated and stored for each node in the current subset of the model. The calculation will consist of the following steps :

• The relevant FS and UTS values will be taken as specified in the prompt sequence or interpolated from the tables input for the material properties at this node and from the temperature given in the temperature loadcase.
• The thermal and mechanical stress components will be used to calculate the mean stress and the alternating stress, and their respective principal stresses P-Mean and P-Alt will be calculated.
• The principal stresses will then be paired according to their directions.
• For each pair of principal stresses the Factor of Safety (FOS) is calculated as defined in the Appendix H of the User Manual Appendices.
• The minimum Factor of Safety is stored along with the direction cosines of the pair of stresses that caused it.

Examples:

1.

RESULTS CALCULATE SAFETY CASE3

The following is an example prompt sequence:

 20 Character Ref => FATIGUE - F.O.S.
 TEMPERATURE LOADCASE => CASE1
 THERMAL LOADCASE => CASE2
 ATTRIBUTE => NODAL STRESS
 THERMAL+MECHANICAL LOADCASE => CASE1