Many SOLIDWORKS users have discovered SimulationXpress to be a very easy-to-use, first-pass analysis tool to test their products and quickly generate reports to document results. While SimulationXpress can certainly help us understand the effects of forces and pressures on individual parts, there are many cases where a more advanced SOLIDWORKS Simulation package will allow us to gain better insight into the design. This can often help us make important design decisions that improve quality, increase performance, and reduce costs.
Let’s take a look at an example using a rally car steering bracket assembly. The worst-case test load for this bracket is 1800 lbf, which we will test using SOLIDWORKS SimulationXpress. This tool is available in every seat of SOLIDWORKS. In order to run the study in SimulationXpress, the model must consist of a single body. To accomplish this, the assembly components have been combined and a single material is assigned to the new part. The casting is fixed in place and the force is applied to the steering rod-end ball. We can see that the maximum displacement is 0.0226 inches, the maximum stress is 25,930 psi and the Factor of Safety is 1.54.
This can be very valuable information, but we must consider the assumptions that went into the model. Since we combined the assembly components, the steering bracket now behaves as a single body. Bolted connections are ignored and all of the components act like they are fused together. When restraining the model, we can only use completely fixed geometry (all 6 DOF constrained). We are also limited to applying only forces or pressures, and we cannot account for more complex loading scenarios. Lastly, we cannot apply any local mesh settings to control the element sizes in specific regions.
Now let’s analyze the same model using a Linear Static study found in SOLIDWORKS Premium and the SOLIDWORKS Simulation packages. With this tool, we can actually analyze the full assembly. Each component can have its own assigned material properties, and we can analyze the contact and friction forces and that develop between the parts. We can also use connectors such as pins, bolts, and springs to more accurately describe how the components interact. This simulation yields a larger displacement of 0.031 inches because the pinned and bolted connections allow for slightly more deflection between parts. The maximum stress is 47,131 psi, which is much higher than the previous study. This is due to local stress concentrations in the areas where the pin is being pressed against the bracket. These stress hot spots were not visible in the SimulationXpress study because all of the components were virtually “welded” together and the contact stresses between the pin and the bracket were not allowed to develop. We can see from this example that modeling the entire assembly as a single body was not a very good assumption.
The design insights gained from SOLIDWORKS Simulation are not limited to stress and displacement results. Using the SOLIDWORKS Simulation Professional package, we can use Design Optimization to minimize the mass of our steering bracket while still maintaining the required Factor of Safety. We can also test for possible fatigue failure and estimate the product life. This steering bracket must be able to last an entire racing season consisting of 10 to 20 rallies, which means it must withstand approximately 1 million loading cycles without failure. The Fatigue Study results indicate that the estimated life for the assembly is approximately 1.3 million cycles, which passes the requirement.
Lastly, we can run a Frequency Study to check the natural frequency of the steering bracket. If it falls within the 1 – 400 Hz range (corresponding to the road noise), then vibrations could travel up through the steering column and make it difficult or uncomfortable for the driver to operate. As we can see from the plot, the first natural frequency is over 934 Hz and well outside the critical range.
This simple example with the steering bracket illustrates how the full SOLIDWORKS Simulation package provides a more complete tool for validating product performance. It can prevent over-design and reduce the costs associated with prototypes and repetitive physical testing. Not only does it enable innovation and new product development, but it can also help you to optimize your existing designs for better quality and performance.
If you are interested in taking your product development process to the next level with SOLIDWORKS Simulation, please contact us or call 866-378-6829 to speak with a product specialist about any questions you may have.
Editor's Note: This post was originally published in April 2015 and has been updated for accuracy and comprehensiveness.
Written by Tim Spielman
Tim Spielman is an Application Engineer at Alignex, Inc. When Tim isn't teaching a variety of Simulation courses or developing tailored software solutions for customers, he spends his free time working on his truck or flying airplanes.