By Damon Tordini
If you’re familiar with the world of simulation (and the suite of SolidWorks Simulation tools specifically), you might be aware that in most cases, the real-world scenarios we try to reproduce are often limited to analyzing one particular aspect of the real physical conditions that occur. For example, in a typical stress analysis, we’re only concerned with the deformation of a material and the corresponding stresses and strains. In a thermal study, we’re only looking at temperatures resulting from various heat sources and sinks. In most of these cases, the physical aspects that we’re simulating are the only important factors that could potentially cause a product to fail, so focusing only on them is usually a valid approach. This is also possible when we can approximate certain physical conditions by making the appropriate assumptions (for example, manually defining a pressure load to represent some airflow).
Several of the SolidWorks analysis tools have the ability to export their results to another type of simulation. For example, temperatures from a thermal study (in SolidWorks Simulation Professional) or from SolidWorks Flow Simulation can be exported to a stress analysis (along with fluid pressures in the latter case). From SolidWorks Plastics, the in-mold residual stresses and plastic material properties can also be exported to a stress analysis in order to predict the warped shape of the part after it cools.
However, there is a realm of analysis where a product might fail based on multiple physical conditions that affect one another, making such assumptions invalid. For example, some small-scale circuit breakers use a bimetal strip to break the circuit when the current causes it to get too hot. The heat from the current causes the bimetal strip to bend due to thermal expansion; however, as soon as the strip bends enough to break the circuit, the heat conduction would cease, thereby stopping the heat buildup. So, the only way to accurately simulate the true deformed shape of the strip would be to model all these physical conditions at the same time. Such an approach requires software that has multiphysics analysis capabilities.
Some of the existing simulation products in SolidWorks already have certain multiphysics capabilities. In SolidWorks Flow Simulation, it’s possible to enable heat transfer calculations between the fluids and your solid model, which is often useful for designing cooling solutions for electronics or heat exchangers. Similarly, in SolidWorks Plastics, the heat transfer in the mold and molten plastic can be calculated to see how that affects the filling process and eventual cooling of the material.
There are, of course, limitations to every software. If you need to do advanced multiphysics simulations like fluid-structure interactions or thermal with electromagnetics, Hawk Ridge Systems’ latest simulation offering, SIMULIA Abaqus, rises to the challenge. Abaqus/CAE, the complete standalone simulation environment, has a range of capabilities for simulating simultaneous physical processes both internally (with Abaqus Multiphysics and Extended Multiphysics) and by linking with other codes (via Multiphysics Coupling)
For example, in the area of fluid-structure interactions, there are multiple technologies available that have various strengths. Abaqus/CFD is the built-in computational fluid dynamics engine for Abaqus, and this can do fluid simulations similar to SolidWorks Flow Simulation with the added benefit of a two-way interaction where the solid components can move or deform, and affect the fluid flow accordingly. If some of the more detailed aspects of fluid flow like turbulence or flow through porous materials are important for your analysis, this is the best approach. Abaqus can even use the Multiphysics Coupling technology to link with completely separate CFD programs if necessary.
Coupled Euler-Lagrangian or CEL is another technology that is excellent for tracking the free surfaces of a fluid, such as water sloshing around in a washing machine or a tire driving over a puddle. It can also handle compressible fluids (which is great for simulating inflating materials, like airbags or balloons). Smooth Particle Hydrodynamics or SPH is a different technology that can do many of the same types of problems as CEL in addition to ballistic impacts, nozzle sprays, or other large displacements of a fluid, as long as heat transfer aspects aren’t needed. This approach has the added benefit of not needed a mesh, which can greatly improve the solution time in certain cases.
When it comes to multiphysics, figuring out what assumptions you can and cannot make about your real-world scenario is the key. Whether you’d like to use a faster, simpler approach with SolidWorks’ analysis tools, or go to the next level of realism with Abaqus’s variety of powerful multiphysics techniques, Hawk Ridge Systems can provide a solution that makes sense.