June 18, 2006
June 18, 2006
June 21, 2006
11.363.1 - 11.363.9
Cost Effective Mechanical Design in Relation to Material and Structural Rigidity and Design Alternatives Abstract The integration of cost effective design techniques into Engineering and Engineering Technology programs is necessary in order to provide graduating Engineers the necessary skills to become more immediate contributors to the goals and profits of their chosen companies. Example teaching and analysis techniques are discussed which will allow faculty to introduce and reinforce cost effective design into Mechanical Engineering courses. These techniques can be applied to other courses as well. Introduction In over 30 years of work with engineers, designers and architects it has been observed that many have difficulty determining the proper combination of material and shape to meet design and cost criteria. There are a number of recognized methods available to evaluate the structural rigidity or integrity of design components. However many design professionals lack the ability to incorporate cost effectiveness into their design. How do you get the most rigidity for the least cost and in many cases at the lowest weight? That is, to say, “the most bang for your buck”. Graduating Engineering and Engineering Technology students do not have a good grasp of this concept and it is suggested that faculty have the responsibility to introduce and nurture cost effective design. It is the purpose of this paper to demonstrate one method of introducing this concept to Mechanical Engineering students in typical Strength of Materials courses. Rigidity will be defined considering both the material and the shape of the cross section. Different combinations of material and shape will be evaluated. A simple decision matrix will be shown as one method of comparison and the entire concept will be pulled together. This concept should be incorporated into a variety of other Engineering and Engineering Technology courses in order to demonstrate and reinforce its application. Definitions The rigidity (or stiffness) of a material is simply a measure of the amount of deflection, δ, that occurs when a simple cantilevered beam is exposed to some applied load as shown in Figure 1.
P y L
δ x Figure 1 A simple cantilevered beam showing an applied load at the end of the beam and depicting the amount of deflection.
The amount of deflection, δ, is a function of both a material property and the cross sectional shape of the beam. The material property is the Modulus of Elasticity, E, of the material being used and can be determined by a simple tension test or found in published literature. Normally
Drigel, G. (2006, June), Cost Effective Mechanical Design In Relation To Material And Structural Rigidity And Design Alternatives Paper presented at 2006 Annual Conference & Exposition, Chicago, Illinois. https://peer.asee.org/126
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