Talk:Stiffness

Suggestion about definition
It is recommended that more general expression of stiffness should be described as that the stiffness of an object at a certain moment and under some certain conditions is equal to partial load over partial deformation if any nonlinearity is taken account for (Gere and Timoshenko, 1997).

Gere, J. M. and Timoshenko, S. P. 1997. Mechanics of materials. 4th ed. Boston: PWS Publishing.

--- Kingchara (talk) 15:53, 10 September 2008 (UTC)

Further, in the Youngs modulus article there is this sentence: Do not confuse rigidity and stiffness: the beam stiffness (for example) depends on its Young's modulus but also on the ratio of its section to its length. The rigidity characterises the materials (it is an intensive property) while the stiffness regards products and constructions (it is an extensive property): a massive mechanical plastic part can be much stiffer than a steel spring;"Testem (talk) 08:12, 27 April 2015 (UTC)

From rigidity
I recently cleaned up the rigidity article. It had a short blurb describing rigidity in solid mechanics and then referenced this article. Below is the blurb and now it links to this article. I wasn't sure if any of this could be incorporated.

In solid mechanics, "rigidity" refers to the degree of deforming ability of a solid material. Modulus of elasticity with moment of inertia (E·I) is the numeric value of rigidity. According to this expression, one can see only two criteria affect deformation, which are geometry and the material of an object. Rigidity is also known as the material property of shear modulus which is a measure of force per unit area needed to change the shape of a material.

Wizard191 (talk) 14:05, 9 May 2009 (UTC)

There should be a link to the article of second moment of area. http://en.wikipedia.org/wiki/Area_moment_of_inertia And elastic modulus. http://en.wikipedia.org/wiki/Young's_modulus Euler Bernoulli beam theory http://en.wikipedia.org/wiki/Beam_theory — Preceding unsigned comment added by 2001:708:30:1220:B499:630A:7A67:ABF1 (talk) 10:32, 17 November 2012 (UTC)

Stiffness equation
Isn't stiffness the derivative of the force with respect to the direction of the displacement? I find the F/displacement equation confusing. — Preceding unsigned comment added by 90.165.115.237 (talk) 10:03, 11 January 2012 (UTC)

Inconsistancy
The article as currently written seems to give conflicting definitions for stiffness:


 * 1) Stiffness or flexibility is the pliability or rigidity of an object — the extent to which it resists bending.


 * 1) For an elastic body with a single Degree of Freedom (for example, stretching or compression of a rod), the stiffness is defined as k = F/δ where F is the force applied on the body, and δ is the displacement produced by the force along the same degree of freedom (for instance, the change in length of a stretched spring).

So, is it bending or change in length? -AndrewDressel (talk) 21:01, 28 March 2012 (UTC)


 * Per a reliable reference, it is simply deformation. I've added the reference and adjusted the text accordingly. -AndrewDressel (talk) 14:26, 4 April 2012 (UTC)

torsional stiffness
I removed a factor of 4 from the stiffness equation. i suspect the original author was applying a torque Mx to the MID POINT OF THE length axis X OF A BEAM ENCASTRE at both ends. Unless that is explicitly stated then it is not obvious, and is not the usual form of the shaft stiffness equation. sorry about the caps. Also this article perpetuated the myth that the torsional constant is the second moment of area. It is but only for a few shapes. Greglocock (talk) 08:35, 3 January 2015 (UTC)

Definition is over-specific
I think the term stiffness is the quotient of action over effect.

In the special case of mechano-elasticity, we consider the action as the force and the effect as deformation.

In the special case of numerical compution-expense, we consider the action as the computation effort and the effect as computation progress.

In the special case of ... 2A02:908:1650:6DA0:45AC:2589:C9EF:60BB (talk) 15:26, 31 December 2023 (UTC)


 * Or even more elegant: The quantity stiffness describes the reluctance of an achievement to develop under an effort purposed at yielding it. 2A02:908:1650:6DA0:45AC:2589:C9EF:60BB (talk) 15:28, 31 December 2023 (UTC)