Talk:A-level Applied Science/Choosing and Using Materials/Properties

Hi there, in your first two paragraphs you define "stiffness" and "stress".

I am not sure what the curriculum for A Level states, but in engineering, stiffness is generally defined as force per unit deflection (as in the Wikipedia entry on stiffness). Stress is defined in two terms: "Engineering stress" is force per unit area - without taking into account the change in cross-sectional area as the material deforms. "True stress" is force per unit area taking into account the change in area.

Please let me know your thoughts,

MHCABI


 * Hi there! Thanks for chipping in. I'm not sure how the stiffness definition came about. 'Area' seems to have snuck in where 'defelection' should have been. The difference between true and engineering stress is much more subtle but worth mentioning. How about...


 * "The formula for stiffness is the force divided by the change in length.


 * "Stress is a measure of the force per unit area within a body. (This is the definition of "Engineering stress" which does not take into account the change in cross-sectional area as the material deforms. "True stress" is force per unit area taking into account the change in area.)"


 * ?  Ewen 05:44, 9 July 2007 (UTC)

Yes that seems reasonable, like I said though I don't know how much detail you want to go into for A Level. I will leave it up to you. Always happy to help with any engineering/maths/science related issues (if I can!).

MHCABI (forgot to log on on that last post whoops!)