Simulation software (CAE) tests a design on a computer, to find out whether the part will bend, break, overheat or shake under load. CAE stands for computer-aided engineering. It saves the cost of building real samples and breaking them.
The software starts from the CAD model. It divides the model into a very large number of tiny pieces, which together are called a mesh. For each piece, it calculates the forces and the temperature, using the laws of physics. This method is called finite element analysis. Then it shows the result as colours on the part. Red marks where the stress or heat is highest. A finer mesh gives a more accurate answer, but the calculation takes longer.
There are several kinds of test. A structural test finds out how much a part bends or whether it breaks. A thermal test finds out how hot it gets. A flow test finds out how air or water moves around or through it. Flow tests usually use a related method called computational fluid dynamics (CFD). A vibration test finds out whether it shakes too much when a motor runs near it.
Say a company in Chennai makes steel brackets that hold the outdoor unit of an air conditioner on a wall. The unit weighs 40 kg. An engineer loads the bracket's CAD model into the simulation and adds the 40 kg load. The software shows that the bracket bends by 6 mm at its corner, and that the stress is highest at the bend. She makes the steel 4 mm thick instead of 3 mm and runs the test again. The bend is now 2.5 mm. She has fixed the weak point without making one real bracket.
The results are saved in PLM software, next to the version that was tested. The same idea is used in many other areas. Signal and thermal simulation tests circuit boards. Autonomous vehicle simulation tests self-driving software on a virtual road. Model-based design tests the control software of a machine, using models of it built in tools such as MATLAB and Simulink.
Simulation does not replace real testing. Its answers are only as good as the loads and the materials that the engineer enters. If the engineer enters the wrong load, the software still gives a confident-looking answer, and the part may fail in real life. So important parts are still tested in real life, but with far fewer samples.