Checking Deformation from Thermal Loading


Can I check if two parts will come apart if a thermal load is applied?

Well, it depends upon how they are put together in the first place. Two parts can either be snap fit/press fit together, or injection molded together. Let’s see how to work with both these cases:

SNAP FIT SCENARIO:  If the two components are snap-fit, then they already experience a pre-load that needs to be captured. In such an event, the analysis becomes a two-step process, and has to be solved as a non-linear analysis using the SOLIDWORKS Simulation Premium version (COSMOSWorks Advanced Professional).

STEP 1:  Setup the snap-fit problem and simulate the two parts being fit together. This can be done by putting a load/prescribed displacement to move the components together, while capturing the no-penetration contact as they move into place. Make sure that the time interval is defined correctly to make this the first event in the loading curve. The end result at this stage would be the stresses after the snap-fit process (pre-load for step 2).

STEP2: Re-start the analysis (under the properties of the study) for the next time interval while using the temperature load at this instant. This will show the stresses and deformations caused because of the temperature load. However, this would have captured the effect of the snap fit and carried the analysis forward from there.NOTE: This can also be setup in one stage if you stagger the time-intervals for the two loading conditions accordingly.

INJECTION MOLDED FIT:  This becomes a little trickier because the interface between the two connected components is as good as glued. The possibility of separation becomes a function of the strength of the bond at the contact interface. Usually, one of the two components is plastic, and the molten surface of the plastic stick to the adjoining component. Capturing this property becomes more tedious, and the alternative is to search for an in-direct approach to setup the case.

The problem can be set up as linear or non-linear based upon the material properties of the two components. If the components are linear materials, the linear module is sufficient. The problem is setup exactly as any other linear analysis, except for the contact condition and the solver type. Make sure you set the contact to Bonded, Incompatible, and the solver to Direct Sparse.

If the materials are non-linear, the material properties need to be appropriately modified as Von-Mises plastic or Hyper-Elastic in order to capture their subsequent effects.

In either case, the results of interest would be the stress plot. If the stresses at the contact interface exceed the yield strength of the material, the possibility of separation escalates. Thus, capturing the stresses at the interface is an indirect indication of failure at the contact areas.