virtual prototyping pays off1 May, 2003 By: Don LaCourse
When Surfaces Meet Solids, January 2003
Applying Finite-Element Analysis, March 2003
Validate Designs with Todays CAE Options, July 2002
Virtual prototyping (also called systems performance modeling) refers to the design, simulation, and testing of new ideas, concepts, products, schemes, or processes in a synthetic but interactive computer environment. Systems performance modeling will enjoy vigorous growth of 14% annually over the next five years, topping $1.4 billion in 2007, according to a forecast (figure 1) by market research firm Daratech.
Robert R. Ryan, president and CEO of Mechanical Dynamics (recently acquired by MSC.Software), says we may be reaching levels of diminishing return in applying CAD/CAM/CAE technologies to part design. The big opportunity to increase quality and reduce time and cost has now shifted to the system level.
But what about the three Fs of product design?
- Form. Make it look and feel good.
- Fit. Make it easy to assemble within acceptable variances in the manufacturing process.
- Function. Make it perform as specified under normal conditions.
Aren't the traditional CAD/CAM/CAE disciplines getting the job done?
Figure 1. Pressures on manufacturers to drive cost out of product development and shorten time-to-market by reducing physical prototype counts, while at the same time improving product quality to rein in warranty expenses, are driving growth in the virtual prototyping segment of the digital prototyping (CAE) market. (Courtesy of Daratech.)
More significant returns on investment, Ryan says, today can come through the effective use of simulation-based design processes and virtual prototyping applied to system-level design (figure 2). Manufacturers need a means to quickly assess form and fit of entire assemblies of 3D models that define a digital product mockup. They need to assess the operating function of the entire assembled product (functional virtual prototyping), not just component parts.
Virtual prototyping may entail different analysis solutions, depending on the application. The Procter & Gamble Company, for example, uses the ABAQUS FEA application, along with customized programs and
Figure 2. Traditional component-focused CAD/CAM/CAE compared with system-focused virtual prototyping. (Courtesy of MSC Software.)
Researchers with Siemens in Munich developed a digital model using Centric Innovation's Functional Prototyping solution. Siemens' engineers use Functional Prototyping to create a complete cross-functional product definition and system-level simulation environment to digitally validate total product functionality during the crucial concept phase. The benefit: planners significantly reduce time-to-market for new subway systems (figure 3).
Figure 3. A Siemens subway railcar displayed in the Centric Innovation environment, which enables cross-functional railcar definition and system-level simulation to digitally validate total functionality during the crucial concept phase.
The implementation of durability analysis at John Deere Welland Works, Welland, Ontario, was a key factor in shortening development time for its rotary cutter systems. On the last two product generations, it cut the cycle from 4-5 years to 1-2 years.
According to Terry Ewanochko, product engineer for John Deere Welland Works, the company used the ADAMS/Durability product to integrate key virtual prototyping techniques such as FEA (finite element analysis), multibody simulation, and fatigue life prediction. Designers generated the initial ADAMS model of the cutter and test fixture in Pro/ENGINEER using MECHANISM/Pro, an embedded product from Mechanical Dynamics. The virtual prototyping procedure mimics a rotating drum test used in physical durability testing. The virtual tests produce stress time-histories that the durability analysis software then uses to predict fatigue life. These predictions have proven very accurate when compared to physical testing.
PROS AND CONS
Like any technology, virtual prototyping has its strengths and weaknesses. As Robert Ryan notes, virtual prototyping can cut costs and increase product quality and manufacturing efficiency. However, these benefits occur only if the process of virtual prototyping works efficiently. Design and analysis are by tradition separate disciplines performed by different professionals. Virtual prototyping must bring these disciplines together (figure 4).
Figure 4. Each phase (build, test, validate, refine, and automate) in the functional virtual prototyping process can directly affect time, quality, and efficiency of product development. (Courtesy of MSC Software.)
Design geometry must be fed to visualization and analysis applications, and they in turn must provide feedback so that the design can be tweaked.
The key to the iteration process is speed. Designers must make critical what-if decisions quickly. Some vendors provide a suite of integrated applications. Others are entering strategic development agreements, such as the recent Dassault Systemes and ESI Group announcement. However, people and departments by tradition are not integrated.
Also, virtual prototyping models are always simplified representations of the real world in terms of geometry and conditions because an increase in accuracy directly increases time and cost. As such, the results will only be approximate until CPU speeds advance to the point where the software can analyze exact replicas. On the other hand, a quick and approximate analysis can often bring to light design flaws that might otherwise be overlooked.
Virtual prototypes are productive because they can test many variations of a design, including geometry, materials, and conditions, thus providing valuable feedback to the design team. The new role of physical prototypes is to validate the final design of the virtual prototype.
Efficiency also comes into play when you can apply a single validation to a family of parts or when a history of validations leads to a knowledge base of understanding and trust in the virtual prototyping process. Virtual prototyping is also more cost effective for products that require millions of dollars to bring to market and where the risk of failures are high, such as automotive, aerospace, industrial equipment, and weapons systems design.
Virtual prototyping can encompass a myriad of disciplines, depending on the manufacturer, the products, and the software vendors involved. They use many different front-end CAD systems for geometry definition and a host of applications to handle model analysis. Companies realize the maximum benefits of virtual prototyping when:
- Various disciplines are tightly integrated.
- Designers can move seamlessly among modeling, meshing, finite-element analysis, process-oriented performance analysis, and design optimization.
- They share design and data models and the results of one analysis are fed directly as inputs to another and then back again.
- Relatively quick what-if decision making occurs within the same user interface.
A big "thank you" to the software developers and manufacturers cited for sharing their insights and first-hand experiences with virtual prototyping.
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