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Desktop Engineering Blog

Virtual Loads Modelling

Posted by Andy Woodward on 17-Feb-2017 08:30:00

There are three key inputs to any finite element analysis process; the geometry representation as a mesh, the materials data and the loads.  The validity of your decisions made from an analysis depends on capturing all of these accurately. 

virtual loads modelling fig1

Accurate loading can be difficult to obtain.  Some years ago we were involved in a project where the loads were provided by an OEM through a chain of suppliers.  The stress results on the assembly indicated a catastrophic failure and no amount of tinkering with geometry and materials could go any way towards mitigating it. 

So we decided to examine the validity of the loading.  Tracing the loads back through the supply chain showed that they were based on an early hand calculation to which each successive supplier had added a factor of safety increase to cover for the fact they were not sure about the basis of the loads.  This resulted in a load being applied that was 5-6 times what could be realistically seen by the structure.  An integrated Virtual Product Development (VPD) approach could have avoided the wasted time and potential over-engineering that resulted.

Early in a project you will not have realistic loads to work with.  Fag-packet hand calculations and test measurements from a similar system are often what is used.  As the designs are refined the fidelity of these loads can be improved, but often isn’t because it involves a lot of effort. 

Using MSC Adams as the backbone of a VPD process can address this.

virtual loads modelling fig2 MSC Adams

Starting with simple stick and mass models in Adams and modelling system dynamics allows you to quickly play with design concepts for your dynamic system and produce first approximation loads.  As the system gets refined and broken down into sub-systems the loads get better defined and give the designers the input they need to size and produce initial designs for the components.  The beauty of Adams is that the process doesn’t end there.

Adams has a module, called ‘Flex’, that allows you to easily incorporate the finite element models of your components back into the system dynamics model.  This uses reduced Degree of Freedom (DOF) representations that can be generated by most good FEA tools.  The benefit of this is that you can validate that the real stiffness of the components as designed does not adversely affect the performance of the system as well as improve the accuracy of your loading to insure against over or under designing your components.  

Working in a large supply chain might make it difficult as a supplier to simulate the whole operation of a system or subsystem, but Adams Controls provides a means to share sub-systems in a way that communicates mechanical behaviour without revealing IP to other suppliers.

The MSC One licensing system provides flexible access to the Adams systems simulation software as well as the Nastran and Marc stress analysis tools meaning SME companies can now have access to a software portfolio used by major OEM’s for their VPD processes without the overhead of owning multiple software products.  MSC One for small teams is surprisingly affordable too with the Start Edition packaging.

Call us or email for information on how you can get started with this technology.

 

MSC One pricing and information UK

MSC One can offer the most cost-effective route to owning Nastran and other MSC Software products.  Need more Information on MSC One?

 

Topics: Finite Element Analysis (FEA), Hexagon MSC Software