Friday, March 27, 2009

CAE Tool Effectivity and Opportunities

CAE design tool development has made continual and sometimes amazing progress in the last 3 to 4 decades. 3D, interconnectivity and multiphysics are readily available. However, as an end user, manager of users and even developer of such tools I see several keys challenges or perhaps opportunities in the field:

- Expense: in many cases the expense of the tool(s) keeps a large engineering segment from using them. Some of the systems can be priced upwards of $50k and higher with correspondingly high hardware and maintenance costs. Certainly options exist for access to the tools such as consultants and in some cases pay as you go use but these options are many times cumbersome.

- Hardware capability lag: Even with 64bit processing, dual core, hugh RAM.....some CAE models take too much time to develop, execute and results process to really be effective in the design process. They at best may offer a final analytical validation but are ineffective for routine iterations for optimizing a complex design. I see some movement towards internet hosted systems and/or clustered systems that may help crack this problem coupled with the continual computer and memory improvements. Other options include supercomputer time sharing but that can be expensive.

- Casual users: Even though many software developers tout the user friendliness of their wares in most cases a casual user is always relearning how to use the tool. This reduces their effectivity. The larger and well funded organizations can perhaps afford the "full time expert" but it's not as common as in years past.

- Software sophification exceeding many users experience: In many instances the tool has too much capability for the users. Doing a 3D CFD simulation without understanding the assumptions behind the algorithms can lead to garbage in garbage out without anyone necessarily being the wiser until perhaps late in the process.

- Keeping with the prior generation process box. The example I repeatedly cite are the teams that spend hours and hours developing 3D CAD models and then revert back to creating 2D drawings for communicating to other team members like suppliers. I see no technical reason why this is necessary. The 3D model with perhaps referenced specs should contain all necessary information.

- Forgetting Occam's Razor or probably better known as the KISS principle. Many models end up being way too complex for the need. The software has so many features and capabilites that the user is too easily pulled into trying to model virtually everything and many times ends up with a very cumbersome model. This is more of a management issue. It needs to be continually reinforced that modeling should be taken in progressively more complext levels and never beyond the need of the design. If it doesn't work for the simple hand calculation it likely won't work for the 100,000 node FE model that might take days or even weeks to develop.

- Accuracy understanding. Many users lose sight of the bigger picture with respect to precision. An FE stress analysis will never be any more accurate than the certainity of the loads, boundary conditions and/or material properties.

- Virtually all the analytical CAE tools available today performing analyses on an existing concept. This certainly is a value added capability but the next leap forward will be evolving them to direct design tools. In other words, the tool will provide direct design content with assist from the analytical tools semi and or fully automatically. This will likely bring expert systems and intelligent design to bear in the process. Today's process is to layout a concept generally in a CAD system. The design is then ported to the various analytical simulations for stress, dynamics, CFD, thermal and so on. Each simulation provides feedback to the team for decisions on needed changes. The next generation tools will take the set of design needs and criteria and the tools will provide the design or at minimum various options.

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Thursday, March 26, 2009

vibration/shock isolators provide double benefit

Vibration and shock isolators have been used forever in countless applications. A recent application I have been associated with highlights a double benefit that can be gained by their use. A diesel engine propulsion system on a railroad locomotive has isolators that are used to mount the engine to the locomotive frame. The engine is very dynamic and has relatively high vibration levels from the normal sources like driveshaft unbalance, piston firing and so. The isolators reduce the amount of this vibration that gets transmitted to the frame. The benefits are lower noise, reduced dynamic loads on the frame and adjacent equipment, increased crew comfort, etc.

The second benefit is for the engine itself. Locomotives experience high shock loads from coupling into rail cars and other locomotives in building up the consists and from pulling and braking. The coupler shock loads are somewhat attenuated by the coupler draft gear which is typically a laminated rubber bumper, however, some shock load still occurs at the frame and makes its way to the engine mounts. For this case the shock load is isolated from the engine by the isolators.

A generally inexpensive device serving two important functions: reducing engine loads passing into the frame and reducing the frame transmitted shock loads passing back to the engine.