Easier design analysis

The latest software package from SRAC is a user-friendly tool for testing designs at the conceptual stage, pre-empting the need for costly changes later on in the production process, reports Charles Clarke.

For many years, finite element analysis was shrouded in mystery – the realm of the ‘rocket scientist’, rather than the average design engineer.

But during the past decade, there have been many attempts to provide the design engineering community with simple tools for finite element analysis – the process of creating a mathematical simulation of a part or assembly for stress and load testing. Today, powerful PCs and more user friendly graphics software and operating systems are opening up the arcane world of the stress engineer to the average design engineer.

This new openness has given rise to the concept of design analysis, as an addition to more rigorous and traditional finite element analysis. Today’s design analysis software packages are quick, affordable and easy to use by non-specialist engineers.

A number of companies, most publicly Rolls-Royce and Ford, have conducted studies to evaluate the expense of design changes at various points in the design process. The overwhelming conclusion has been that the expense increases by several orders of magnitude as a design moves through its various development stages; it is far cheaper to make changes at the conceptual stage than during the production phase. The need to minimise the number of engineering changes requires engineers to get it right early on – which is where design analysis software can help.

Supporters of design analysis are at pains to point out that it is an additional segment of computer aided engineering, and has been developed to assist more rigorous analysis, rather than to replace more expensive, specialist or sophisticated applications.

Low-cost design analysis systems are intended to complement more rigorous analysis, and can be used for mundane parts that are rarely analysed, or to provide a more cost-effective conceptual analysis prior to more rigorous studies.

Structural Research and Analysis Corporation, developer of the Cosmos design analysis system, embraced the mid-range CAD market with open arms in 1995, leading to early versions of CosmosWorks with SolidWorks. In 2001, SRAC was acquired by Dassault Systemes (owner of SolidWorks), which lead to the development of CosmosXpress – the bundled linear static analysis module in SolidWorks 2003.

The trend in recent years has been for design engineers to carry out increasingly diversified roles- they have become CAD operators, machinists, or word processing operators. They have also had to take responsibility for more parts of their design than they used to. Low-end analysis tools have become popular in providing these more diversified, non-specialist design engineers with a sophisticated, stand-alone analysis capability.

This new interest in design analysis is reflected in strong demand for analysis awareness seminars run by Cosmos consultancy Integrated Analysis Solutions. It seems the design community can’t get enough: Cosmos’s seminars, built around CosmosXpress, are full to bursting and everyone who has signed up for them actually turns up – a rare phenomenon.

The analysis awareness seminar is concerned with getting useful results quickly and easily while keeping tabs on accuracy and relevance. According to Integrated Analysis Solutions, for design analysis to work effectively the software must allow analysis to become an integral part of the design process. This can only be achieved if it is both easy to use and fast.

While design analysis software will never cover the range of problems that a full-blown finite element analysis program offers, a program such as Cosmos- Works allows engineers and designers to investigate the basic performance parameters of CAD modelled designs at an early stage. Advanced and safety critical analyses, meanwhile, will always remain the work of dedicated analysts.

The earlier conceptual analysis is carried out the better. If the design is at an early stage, then the analysis will be quick, because the component will not have been modelled in any great detail. At this stage designs can be optimised easily – many design changes can be investigated in a short time and the design can be modified easily, as there are fewer constraints during this phase.

The development synergy Cosmos enjoys under the Dassault Systemes umbrella has allowed CosmosWorks 2003 to use the SolidWorks Property Manager function instead of dialogue boxes for analysis inputs. This allows graphics to be fully displayed instead of being overlaid by dialogue boxes and gives CosmosWorks the same ‘heads up’ interface as SolidWorks.

The function makes it easier for novice or casual users to learn or return to the program. Since the graphics are no longer hidden by dialogue boxes, the geometry selection process is much easier.

Also, it is not necessary to pre-select faces, edges, vertices or co-ordinatesystems when applying restraints or loads. The selection lists can be modified without exiting the input box.

This flexibility in modifying the selected entities works in a similar way to SolidWorks. It also saves time when applying loads and restraints. The direction of loads and restraints and prescribed displacements can also be previewed before they are applied.

CosmosWorks 2003 can generate SolidWorks eDrawings of analysis results. These results can be viewed in 3D, rotated and zoomed in and out of using the SolidWorks eDrawings viewer. This means that dynamic 3D analysis results can be easily shared with, and marked up by, team members who do not have CosmosWorks. It also provides a more compact file format for sharing analysis results over the internet.

One of the most important enhancements to CosmosWorks 2003 is the ability to define analysis inputs such as materials, restraints, loads, mesh size or contact resistance, and to define geometric dimensions as parameters or parametric equations.

Parameters are defined at the model level and can be used across various design studies.

Also, during the design process, analysis inputs can be defined as parameters without giving them exact numerical values. These values can be modified in the parameter table, propagating changes to multiple inputs across different design studies.

CosmosWorks 2003 also supports a design table study to automate the analysis process. It works in a similar way to design tables in SolidWorks. Multiple sets with different parameter values can be assigned and analysed in a batch process. Once the analysis is complete, results between different sets can be compared. This helps to study the effect of variations in geometry, material or load parameters on analysis results. This automated batch processing saves time while comparing different designs.

CosmosWorks 2003 automatically converges analysis solutions using h-adaptive technology. This convergence is achieved through an iterative process. In each iteration, the mesh in critical areas is refined automatically. H-Adaptive convergence minimises the need for manual mesh refinements and helps operators to feel more confident about the accuracy of their analysis results.

The recent trend among engineering firms has been to cut (or eliminate outright) analytical departments. But on the plus side, integration between computer aided design and engineering has improved substantially. What has been lacking – until now – has been the packaging of computer aided engineering tools in a form that design engineers can take immediate advantage of, without feeling like they need to become rocket scientists.

However, as design analysis becomes ever more popular, Cosmos- Works and similarly integrated products have the potential to change the way we think about computer-assisted engineering and its application to design engineering. While it doesn’t do everything that full-blown analysis codes do, what it does do, it does well.

Packages such as CosmosWorks can inspire confidence among users and their clients, and are set to make an important contribution to the wider understanding of analysis.

Dr. Charles Clarke is an independent IT, CAD/CAM consultant and writer.