Aircraft wing stress example

There are a couple of things about this relationship. First of all it is only an approximation. We ll get back to that in a while. Second, we have only considered simple elongation so far. There is a modulus associated with shear and also a bulk modulus. The most important point, however, is that the modulus determined this way, dividing stress by strain, is a material property and independent of the shape of an object. It is what we mean when we talk about the stiffness of a material. Stiffness is crucial in many engineering applications. If a strain of just 1.6% were allowed in an aircraft s wing spar booms, for example, it would look something like Figure 13-8. 

Intimate knowledge of the application. It is clear that the first step in determining durability is to spedfy which performance criteria are vital to the products function. For example, in an aircraft application such as a structural wing part, performance requirements may be such as retaining dimensional stability and yield stress for 12,000 supersonic hours xmder cyclic loads and temperatures up to 175 C. 

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