Machine Design

FEA inside CAD simplifies complex analysis

Ever wished you could just push a button in your solid modeler to quickly analyze how designs will operate at service conditions?

David R. Dearth

Adaptive Analysis, which uses h-adaptive technology to increase the number of elements in regions of high stress, reduces the time and experience users require to come up with the right mesh for even complex models such as a piston and connecting rod assembly.

CosmosWorks 2007 lets users capture FEA results in SolidWorks Animator to make AVI animations. These show the colorful analysis of the six-jaw chuck as it rotates, explodes, and collapses. The chart at the bottom of the window shows the position of each component in the assembly with respect to timescale used for animation.

The software generates standard plots for each type of analysis and puts them in folders in a feature-manager tree (on the left). The new release lets users specify the default folders and plots. For example, novice users can generate only plots for von Mises stress and factors of safety, while expert users may need more detailed information such as principle stresses.

A hose clip is a small thin metal strip that is bent to assume the circular shape of the hose. When a user pushes one end of the clip, force direction changes as the clip shape changes from straight line to a circle. The right side of the image shows a hose clip modeled with the follower-load option. Initial force direction was horizontal from left to right and as the shape changes, force direction is vertical upwards. The left side shows the hose clip modeled without the follower-load option.

CosmosWorks 2007, one FEA program that works inside Solid-Works 2007, comes close to this capability. CosmosWorks has a sizable amount of built-in intelligence, letting both novice and expert user perform sophisticated analysis without worrying about the complexities often associated with traditional FEA software. For example, in a recent application, CosmosWorks made short work of a complex analysis for nonlinear contact between deformable parts. This analysis is often required for parts such as rubber seals. The software's built-in intelligence made setting up the analysis model a breeze. And the results compared favorably to those from a high-end, full-featured FEA program costing thousands more.

I especially like the convenient way in which Version 2007 displays the solution results. In previous releases, the software generated standard plots for each type of analysis and put them in folders in a feature-manager tree. The new release lets users specify the default folders and plots. This frees users from manually modifying plots and folders one by one. For example, novice users can choose to generate only automatic plot results for von Mises stresses and factors of safety, while expert users can generate detailed, advanced plots such as principal stresses.

The Adaptive Analysis feature for meshing models is also improved. This uses h-adaptive technology to increase the number of mesh elements in regions of higher stress. In each iteration, the software refines the mesh in critical areas to produce correct results. The technology minimizes manual mesh refinements and helps users feel more confident about the accuracy of analysis results.

Another notable feature is the Spring Connector. It originally simulated springs that exerted tension and compression, and now simulates tension only and compression-only springs. This lets engineers indicate, for example, that a certain spring exerts no force during compression. The program also lets users define springs between cylindrical faces or between two points or vertices. And the Spot Weld Connector now supports mixed meshes, so users can connect shells to solids.

An expanded nonlinear analysis feature lets users update load direction with deflection (follower loads) for pressure and torque loads. The follower load option is helpful, for example, in modeling a pressure vessel such as a pipe. When subjected to high pressure, the vessel undergoes a drastic change of shape. The pressure load always acts normal to the walls of the pressure vessel. Linear analysis of this scenario assumes that the shape of the vessel does not change, which is incorrect. A realistic analysis requires analyzing-geometric nonlinearity with nonconservative (or follower) loading.

Users will find the online tutorials well written. They open in a separate window and teach some of the basics of analysis. The tutorials also include sample analyses in problems that represent real-life scenarios.

CosmosWorks 2007 comes from SolidWorks Corp., 300 Baker Ave., Concord, MA 01742, (800) 693-9000,

David R. Dearth is president of Applied Analysis &Technology, Huntington Beach, Calif., and can be contacted at [email protected]

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