Intro Every product is subject to real-world conditions that ultimately cause failure in one way or another. SolidWorks Simulation is a tool to computationally quantify the performance of our assemblies and components inside SolidWorks. Using the extended capabilities of SolidWorks Simulation Professional, a company's development team can model more real-world challenges and scenarios.
Typically designs are sensitive to cost, safety, durability, and quality. Making use of today's software leads toward higher product quality, lower costs, longer durability, and far less physical testing. This will propel company innovation.
How does software, such as Simulation, add value to a company? In other words: As engineers and designers, what is our value? Our value is our production of technical work. If we have tools with which we can create, publish, and validate our technical work more quickly, with fewer errors, higher quality, and greater consistency, how will this affect our top and bottom lines? These topics are exactly what we refer to when we say "SolidWorks helps you Design Better Products." We are ultimately going to increase the effectiveness and efficiency of your workflow by adding key capabilities such as SolidWorks Simulation Professional.
The example product is a medium-duty paint sprayer. This is a product I am sure you have seen in the home improvement store.
Thermal Study
The motor creates heat in addition to periodic structural excitation. This heat is ultimately transferred into the materials, the air, and quite possibly into the operator's hand or into the paint. The Thermal study type visualizes this heat flow through the structure. Investigation with a thermal situation allows a designer to quantify exactly the temperature of the materials. It also allows us to evaluate how much stress and deformation arise due to the heat. From a durability standpoint, we can gauge the temperature around the motor and look for ways to dissipate more heat, allowing us to increase the life and efficiency of the motor. At a more basic level, we can assure ourselves that the off-the-shelf motor is not being exposed to conditions above those which its operating specifications allow.
The motor draws 450 W, of which we will assume ten percent, or 22.5 W, is dissipated as heat. Simulation allows us to apply that as a heat source to the motor component and view the resulting temperatures and heat fluxes in the materials.
Initially, the temperature plot has shown us that there is little issue of the casing or the handle becoming too hot, as those pieces remained roughly at ambient (90° F or slightly above). Internally, however, we might have structural issues if the plastic expands too much as it heats up. Taking the temperature from the thermal study, let's simulate how much thermal stress will result in the plastic:
Depending on our material selection 1,500 psi stress could be quite high indeed. In this model, the material is generic ABS plastic with a tensile strength of about 4,000 psi. We have used up 3/8 of the material's strength with just the thermal expansion. We have not yet included the reaction force from the motor. Does this indicate need for design change to increase product durability and quality?
We could then move into a conjugate heat transfer analysis with Flow Simulation. This Simulation would increase accuracy and fidelity by including the surrounding air in the calculations of heat transfer. Notice the venting on the side. Is it effective? Most likely. Is it as effective and as cost-effective as it should be? How can a thermal mitigation design be validated? The major advantage of the Flow tool is the ability to calculate air flow in the product, whether active or passive. Flow is absolutely necessary when dealing with any type of active cooling system or when visualization of the surrounding fluid temperatures is otherwise required.
Getting a little more complicated, solving fluid flow in addition to heat transfer provides a much more accurate thermal picture since we are taking into account the air filling the interior and surrounding the exterior of the model. We are including the natural convection in our solution physics and not assuming a constant, uniform convective heat transfer to ambient. In the Flow results the exterior shell of the sprayer sees much more heat than we previously anticipated. This is because we no longer neglect the heat transfer from motor to air to housing, nor the hot air build-up in and around the paint sprayer. We can compare the results of this flow simulation to our product specifications and see if these temperatures are too high. Further, we can take the temperature field from the Flow solution and add that to our structural simulations directly. The results plot here shows 200 °F surface temperatures on the product - seems a little beyond what is safe in my mind. Remember, this is the steady state temperature. I can also solve temperature versus time and we can use that information to further define operation limitations of the device.
What I found from my simulation is that it takes 13 minutes of constant heat power to reach 100 degrees on the surface, and over one hour to reach 200 °F. A further study could show temperature based on an input from a typical usage vs. time profile.
All of the results gleaned is information that is extremely difficult, costly, and time-consuming to get from physical testing, particularly with this level of elucidation.
Look for our other Study examples elsewhere in our Blog on Design Optimization, Fatigue and Frequency Simulation.