2010 Issue

33 O PTIMIZATION ANSWERS QUESTIONS LIKE, “WHERE do I place the material to most effectively carry loads through my product?” or, “How do I change component features to reduce stresses and meet design requirements?” Concept Design Optimization results in greater Product Knowledge early in the design cycle when you have the most Design Freedom. Bet- ter concepts result in fewer changes during the Detailed Design and Testing phases when mak- ing changes is both painful and expensive. Size/ ShapeOptimization greatly reduces the trial and error process associatedwith design fine-tuning. The overall result is Better Products in Less Time. Following are some examples to show how optimization works. We begin with the design of a Pressure Tank where our goal is to minimize tank displacement. We think that if a few ribs are good, then more ribs must be better. But in this case, as the deflection results show, more is not always better. So enter stage right, Optimization. The optimi- zation problem is set up by defining three sym- metry planes, applying the load cases the tank will experience in operation, and setting a goal to minimize the tank deflection. The solution Better Products in Less Time with Optimization RONALD B. THUE So what is optimization and how does it apply to the products you design and analyze? In short optimization is a set of mathematical methods for developing better conceptual designs and for minimizing trial and error in the product fine-tuning process. provided by optimization is counter-intuitive and results in a tank that is both manufacturable and demonstrates minimum tank deflection. For an engine mount the optimization process begins by defining the available Design Space, the space where material can exist. This defini- tion includes identifying bolt-down locations and the critical loads the engine-mount will experience. Next we use Topology Optimiza- tion to whittle away the design space and place material to most effectively carry the loads. This approach produces a Preliminary Design. Finally we fine-tune the design with Size and Shape Optimization to ensure that all design require- ments such as stress, displacement, buckling, and fatigue are met. A comparison of the traditional engine mount vs. the optimized engine mount demonstrates the value optimization brings to the design process. The optimized design is simpler, lighter, has the same stiffness and strength, and is more fatigue tolerant. Our third example is a door hinge from a Eurocopter aircraft. Using an optimization process similar to that used for the engine mount, we obtained the following results. Not only was the mass reduced by 18 percent, but the design time was decreased from 3 months to 3 weeks. Our final example is the AIRBUS A380 Leading Edge Wing Rib package. Traditionally wing ribs have employed a horizontal/vertical stiffener and shear web design. The problem with the tradi- tional design method is that loads come into wing ribs normal to the wing surface. Therefore continued on page 34