Winning Technologies: Procision Structural Analysis Software

To speed up product development, Procision Analysis Inc. integrates design and analysis.

It has long been the dream of engineering-software providers -- both on the analysis side and design side -- that these two stages of product development be more closely integrated. That's also the vision of Victor Apanovitch, president, Procision Analysis Inc., Mississauga, Ont. By integrating design and analysis, his company's software is intended to be a strategic competitive tool for manufacturers. Early, upfront analysis of designs in progress offers the possibility of shortening the process and speeding new products to market. By flagging problems early in the product-development process, changes can be made while the design data still resides on the computers of engineers, not after proposed designs reach the shop floor. At that point not only do changes cost money, but also the manufacturer loses the most valuable part of a product's profit life -- the introductory phase when competitors have not yet entered that product's market. Traditionally when new products are designed, an engineer uses computer-aided design (CAD) software to create the geometry of the physical part or assembly of parts. The engineer then hands off the geometry to a specialist in analysis who uses software to evaluate and analyze the mechanical functions of that component. With traditional analysis techniques, parts are divided into small elements with easily defined stress and deflection characteristics. Then finite-element modeling (FEM) software automatically creates the mesh of elements that mimic part geometry, defines loading and boundary conditions, selects materials, and prepares a model for analysis. Analysis vendors have tried to provide finite-element analysis (FEA) tools that are functional, intuitive, and easy to use. But despite the efforts to create an integrated CAD/analysis product-development process, FEA remains today in the realm of specialists. One problem is the fact that FEA is a complex endeavor. There is a significant learning curve associated with traditional FEA programs, and engineers as a whole have been reluctant to incorporate FEA into product development processes. Though FEA software providers for years have promised users a seamless CAD-FEA interface, no such software currently exists. While the CAD models are easily imported into FEA programs, the model must first be idealized, defeatured (features assigned to parts by the CAD software are removed), or simplified to make it suitable for analysis. In traditional practice CAD models often contain minute part details that are essential for CAD but meaningless to the analysis program and troublesome if not removed. If small details remain on the part, the FEA program creates meshes on these tiny features, producing extremely large FEA models that would take hours or days to solve. With traditional FEA analysis, it is, therefore, necessary to separate CAD geometry from analysis-specific geometry. Technology developed by Apanovitch changes that and improves how CAD relates to analysis. His Precise Solids Method (PSM) overcomes traditional limitations of FEA, which require meshing as a prerequisite to solving the analysis. PSM works directly on the solid CAD geometry, regardless of complexity and without idealization, simplification, clean-up, or defeaturing. PSM is based on mathematical methods Apanovitch developed in 1981 while a professor at Minsk University in Belarus, then part of the Soviet Union. Prior to his work at the university he was a structural analyst at Minsk Tractor. During that time he applied various analysis techniques, including FEA, to the stresses and vibrations of tractor mechanisms. "I understood very well how far the analysis tools were from the needs of design engineers," says Apanovitch. PSM is now commercially marketed as Procision software by Procision Analysis, where Apanovitch leads the development team. First commercially released in 1995, the software runs directly inside Pro/Engineer CAD software from Parametric Technology Corp., Waltham, Mass. Engineers using Pro/Engineer to design products can launch the Procision program from within their CAD system and analyze their Pro/Engineer models for structural and thermal problems. By being completely integrated with CAD, Procision allows for a more concurrent design process and delivers the time and cost savings of integrated analysis. In addition, by using a familiar CAD interface, design engineers can learn to use Procision after a few hours of training, not the weeks or months required for similar FEA software, reports the company. Another benefit of the technology is that complex surfaces, blends, fillets, and other details of a part that are often difficult to mesh can be left in place. In addition, unlike traditional analysis tools, Procision can efficiently analyze parts with both thin-walled and solid sections. Because there is no mesh, users don't have to grapple with meshing problems such as degenerated elements, the inability to mesh complicated details, and difficulties with "dirty" or flawed geometry. Here's how it works: Instead of a mesh, models are broken down into compact subparts, not elements. Subparts differ from elements because they can have any topology and are not constrained to simple shapes such as triangles and bricks. The software provides feedback so the user knows where to apply more divisions when necessary. The geometry must be broken down into subparts to facilitate the description of field variables (displacements) in each chunk. Splitting the model reduces the complexity of its formulations. Simple geometry requires no splitting. Apanovitch says the software's theorems are general enough for all types of analyses. Currently the software can perform linear-static-structural, steady-state-thermal, natural-frequency-modal, dynamic-time-response, dynamic-frequency-response, and dynamic-random-response analyses. The software also can display rigid-body motion at the beginning of a solution, a function missing from most standard FEA programs. After the Procision program finds a solution, it can calculate and display results for any point, either on the surface or inside a solid model. Stress and displacement graphs provide results for any part edge or curve between two points, and precise shaded models of deformed shapes show both vibration mode shapes and static deflections. Procision, says Apanovitch, "has eliminated the major limitations of conventional FEA by means of mathematics, not by software and hardware power." What about payback? According to the company, an investment in Procision usually is recovered during the first project in which it is implemented.

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