Learning Forum

[sombodyfromtheworld]

[danielshaw]

yes, for 2 load cases. You can use Constant Amplitude, non-proportional loading. You need to define a Solution Combination with the 2 load cases and insert the Fatigue Tool under the Solution Combination.nNote: Constant Amplitude, non-proportional loading in the Fatigue Tool is only valid for 2 load cases. If you have more than 2 load cases, then you must use Ansys nCode DesignLife.n

[sombodyfromtheworld]

Thanks DanielnDo you mean only two load cases are two environments? If I create first environment with these loads: Internal Pressure (a)psi, External Pressure (b)psi and Compression Force (c)lbfnAnd the second environment with these loads: Internal Pressure (a+n)psi, External Pressure (b+m)psi and Compression Force (c+k)lbfnCan I simulate how many fluctuating cycles the pipe can handle between these two loading environments using Solution Combination? nFluctuating cycles means this: Valley (Env1) - PEAK (Env2) - Valley (Env1) - PEAK (Env2) - Valley (Env1) and so onnn

[danielshaw]

The FT calculates the fatigue damage caused by cycling between 2 result sets. It does not matter that the 2 result sets are within one WB system (say time step 1 and time step 2) or that they are in 2 separate systems (different Environments). It just matters that you specify 2 unique result sets in the Solution Combination and place the FT under that solution combination.nIt also does not matter, if the stresses in the result sets are caused by one load or multiple loads. The FT just considers the total stress state from each result set. The FT calculates the difference in component stress (delta SX, delta SY, etc.) between the 2 stress states, and then uses those delta component stresses to calculate the fatigue damage (and life) caused by alternating between those stress states.