1. → Calculation aborts due to lack of memory. What should I do?
If the size of the system of equations exceeds 32 GB the complexity of the model should be reduced.
Windows 95/98: Check the Settings/Control Panel/System/Performance/Virtual Memory dialog window.
a.) If Windows manages the virtual memory it means that the operation system changes the paging file size according to the actual memory requirements. However it is limited by the amount of free disk space. If it is less than the memory required an error message appears. Free the necessary disk space and try again.
b.) If you specified your own virtual memory settings check if the maximum is less than the memory required. If so set an appropriate value (It is usually recommended to set twice the physical RAM).
Windows NT4: Each drive can have its own page file. Check Settings/Control Panel/System/Performance/Virtual Memory/Change dialog. Set Paging File Size for Selected Drive according to Clause b above.
Windows 2000: Each drive can have its own page file. Check Settings/Control Panel/System/Advanced/Performance Options/Virtual Memory/Change dialog. Set Paging File Size for Selected Drive according to Clause b above.
2. → What is the difference between the nonlinear and second order analysis?
AxisVM is able to perform geometrically linear/nonlinear analysis (1st /2nd or 3rd order analysis) on models with finite elements having linear/nonlinear force-displacement characteristics. The order of analysis is an entirely independent question from the elements’ force-displacement behavior. Any source of nonlinearity will lead to a nonlinear analysis performed in an incremental/iterative process.
2nd order Analysis:
It takes into account the fact that the displacements of the structure slightly change the load effects (usually create extra moments). 2nd order analysis assumes that the rotation of elements is small (cos alpha = 1, sin alpha = alpha).
3rd order Analysis:
It is the same as 2nd order analysis but does not assume that the displacements are small. It can follow extreme displacements.
3. → How should I know, that the solution of equilibrium equations (the calculated displacements) is not affected by the
AxisVM evaluates the condition of the system of equilibrium equations each time you run an analysis. A special technique is used to estimate the error in the results (displacements) due to the round-offs that is present in computer based calculation. The expected error magnitude is displayed in the Info window as E (Eq). If the expected error is less than 10-6, usually the result is considered accurate in "engineering" terms.
4. → How can I study the post-buckling behavior of a structure using non-linear static analysis?
To pass the peak of a load-displacement characteristics (of a degree of freedom of your model) you need to use the displacement control technique when applying a geometric non-linear analysis.