How to find stiffness using load versus defelection curve?

AI Thread Summary
Stiffness can be determined from a load versus deflection curve by calculating the slope of the curve, though nonlinearity may complicate this. The initial slope can provide a basic stiffness value, but for more accurate results, an average stiffness over a specific deflection range is often recommended. This average stiffness is represented by the slope of a chord connecting two points on the curve, rather than a single point. The choice of stiffness definition may depend on the intended application and the nature of the load-deflection relationship. Understanding these nuances is essential for accurate stiffness evaluation.
perfectz
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I know that stiffness is load per unit deflection. I have the load versus deflection curve for a steel plate. Is it possible for me to find the stiffness of the plate?
Thank you.
 
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You could translate it into a stress strain curve and the slope in the elastic zone is the E-modulus. If you have the geometry.
 
perfectz said:
I know that stiffness is load per unit deflection. I have the load versus deflection curve for a steel plate. Is it possible for me to find the stiffness of the plate?

By definition the stiffness would be the slope of the line at any given point. However, due to nonlinearities, your line is probably not linear. You could simply take the initial slope of line.
 
yes of course
 
THank you...
 
The stiffness value you want depends somewhat on your purpose for finding the stiffness, particularly if the load-deflection relation is nonlinear.

For many purposes, it is useful to define an average stiffness that represents the average slope over some working deflection range, whatever is appropriate to the situation appropriate to your problem. This would be the slope of a chord to the load-deflection curve, rather than the slope at a point. Obviously it will not be exactly correct at more than one point (the mean value point), but it will be somewhat close over the whole range.
 
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