Quote:
Originally Posted by Rick TYler
I've confessed in these pages before that I am not an ME, so treat this as a question rather than an argument, please.
Is the "strength" of the beam the same as "bending resistance?" I read in Dave Gerr's book on boat design that the stiffness (which I would think is the same as bending resistance) of a beam, all else being equal, goes up with the fourth power of thickness, not the third power. Of course, the failure strength might go up as the third power -- about this I know nothing.
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Good question... strength and bending resistance are not the same. Strength is basically the material's ability to resist being pulled apart (breaking due to stress). Stiffness is the part's resistance to deflection. Stiffness is contributed to by both the material choice (Young's modulus, E) and the shape of the part (Moment of Inertia, I). In many cases devices fail due to being insufficient stiffness rather than not being strong enough... think of a long, small diameter PVC arm.
I'm not familiar with Gerr's book, so I can't speak to the context. <speculation> Since you reference 'thickness' he may be experiencing both an increase in height and width of the section, but I can't be certain.</speculation>
Not sure if I am clarifying or confusing things... pics to follow.