SOLIDWORKS Simulation Professional enables us to replicate the infamous lab drop test. The idea is simple. Will your product survive if dropped on the ground? We can define the orientation that the device strikes the ground as well as the impact velocity, or initial height. Below are the steps to complete a successful drop test analysis in SOLIDWORKS Simulation.
Linear-elastic or elastoplastic material can be defined for the drop test. For most simulation studies in SOLIDWORKS Simulation Professional, we use linear elastic materials. In a drop test, if you have the material data, it is desirable to define an elastoplastic material. When defining the material, the Model Type is “Plasticity – von Mises”. This enables the software to account for energy lost in the dynamic simulation. This is in contrast to a linear elastic material that would bounce at the same magnitude repeatedly.
A height or impact velocity can be chosen for the drop test. Gravity is also defined. The choice of parameters here is dependent on your test conditions. Maybe the situation you are trying to replicate is a cell phone falling off a three foot table, or a computer hard drive hitting the ground at 10 m/s. In either case, rotation of the device is not considered until after impact. Why is this the case? The product is falling through a vacuum, so there are not any effects from the air, such as wind resistance.
Decide how long the simulation will be run and what options will be saved. The maximum stresses will occur immediately following the impact. Therefore the time that we will record in the simulation will be on the order of ~50 microseconds. We can also select what time we want to start recording after impact. Usually, this value will be set to zero, but this parameter can be helpful to narrow down the window if you know the behavior you are interested in occurs later on in the simulation.
Create an appropriate mesh that will obtain accurate results for the simulation. If you are predicting a large displacement or high-stress concentration, apply mesh control as well as a curvature-based mesh to accurately take small features into account.
As easy as it sounds.
Properly analyze the results of the study. Animate the stress and displacement plots to get an idea of the behavior after impact. You have the option of selecting which frame you are viewing in the plot. If the deformation does not make sense, check back into your model setup for any errors. To track data at specific points, add sensors to the model and track them with a time history graph.
Refinements to the study, such as an elastoplastic material model or contact can be applied to make the simulation more realistic. Be mindful of the “ground” conditions that have been set. The default is a rigid wall. This is a perfectly stiff surface. The opposite end of the spectrum would be an elastic surface like that of a trampoline. The elasticity of the “ground” can also be set to have orientation-specific material properties. After you have assessed the correct condition, the next step is to create accurate contact conditions if an assembly is being simulated. For example, if there are two plastic parts with a snap-fit, change the global contact from bonded to no penetration. Then add local contacts to the surfaces of the snap-fit. Now our model will be more consistent with the actual test conditions.
GoEngineer delivers software, technology and expertise that enable companies to unlock design innovation and deliver better products faster. With more than 30 years experience and thousands of customers in high tech, medical, machine design, energy and other industries, GoEngineer provides best-in-class design solutions from SOLIDWORKS, Stratasys, Altair, CAMWorks, Creaform and Product Lifecycle Management (PLM).
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