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Design validation is a very important aspect of Manufacturing Industry. Once we have a conceptual design on paper; unless we do field tests there is little chance we can assure the product will meet design needs. Developing a prototype could be expensive and then performing field tests could take a lot of time. This only delays time to market. One therefore needs to make sure our conceptual designs work. If it’s a simple part or an assembly having a few parts one can use standard formulas or come up with formulas to suit design scenarios. To generate a formula could be very tedious in complex assemblies, besides its very easy to miss a parameter. For example, the model below shows a suspension system hinged at one end, has vertical and lateral loads on the other. There is a spring damping the loads. Besides, all parts are held together using pins. Coming up with formulas to validate this design would be a tedious task.
Alternate Design Scenarios
If you actually do field tests on your design prototypes; testing alternate designs is a very time consuming process. Analyzing alternate designs is a simple process in COSMOS. For example if one was to analyze a cylinder experiencing a uniform pressure on all the surfaces and the design goal is to have a factor of safety of 1 or more to ensure the parts sustains the load. The figure shows red arrows indicating pressure (1200 psi) and the green arrows prevent body from moving in circumferential and axial direction. The Factor of safety plot (FOS) indicates a minimum factor of safety of 0.93 under the current loading scenario.
Design Revision
From the above plots it is clear we need to make changes to meet our design goals. There are numerous ways to bump up FOS. Two obvious methods are ::
(a) use a stiffer material (b) add material to strengthen model
Using a stiffer material will add to cost substantially. Let us try the second option. We will add ribs to end caps. This should strengthen the whole model.
This test of adding ribs and running analysis took around 20 minutes. Hence making subtle changes to your conceptual model and checking them using software could save us substantial time. This is obviously a simple design, but for complex assemblies this probably is the only alternative to building physical prototypes and mounting strain gages to validate design.
My Parts Never Fail
Well if my parts never fail under the current loading conditions why do I need to analyze? If the parts do not fail, could it be that we have over designed components. The part dimensions are more than what is needed for the current loading scenario. Reducing material at appropriate areas would reduce weight; hence reduce costs to the end user. Optimizing designs for loading scenarios is an iterative process with generating different prototypes and running field tests. This again has been significantly simplified in COSMOS.
For example, this assembly is fixed at the four legs and has a vertical load (5000 lbs). We need to make changes to this model such that it meets the design needs and the dimensions are optimized too. Running an optimization test with options to change the dimensions within a certain range should help me reduce the weight of component and yet meet design goals.
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The dimensions being changed are 4”, 15” plate and 4” gap between the legs. The idea is to reduce the current mass from 163.65 lbs and yet be able to sustain 5000 lbs load. The software goes through an iterative process running multiple scenarios (changing dimensions) till it converges onto a solution. Even for simple designs making multiple prototypes and testing them in the field is a time consuming and very expensive process. Optimizing using hand calculations is a very cumbersome task. The concept is to solve for minimum mass using loads as limiting values and variables as dimensions. COSMOS thus helps us focus on the design rather than the design tool by removing the complexity.
In about 20 minutes I was able to reduce weight by ~30 lbs. Boy I wish we had COSMOS to spare us from sweating out at the gym.
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