Difference between force-elongation and stress - strain diagram?

[teng125]

what is the difference between force-elongation and stress - strain diagram??

pls show some example such as diagrams for future reference

thanx

 

[Astronuc]

Well, stress is derived from force. Stress is the force divided by cross-sectional area.

By elongation, does one mean displacement? Strain is derived from elongation or displacement, and is the ratio of the change in elongation (displacement) to the intial elongation (displacement).

I believe that the term "force-elongation" is more commonly known as "load-displacement", and load and displacement are 'directly measured', and from these the corresponding stress and strain are calculated. Nowadays, tensile test machines have digital instrumentation and software to automatically calculate stress and strain from measured load and displacement.

 

[teng125]

may i have some diagrams for the two cases above??

thanx

 

[Astronuc]

http://www-ec.njit.edu/civil/som/define.html - find the entry for Stress - Strain Diagram. This page is useful for definitions.

Also see this discussion - http://www.ae.msstate.edu/vlsm/materials/stress_strain_diagrams/stress_strain_diagrams.htm

http://www.ni.com/pdf/academic/us/me105_lab3_2003.pdf (save target as) - useful discussion of engineering vs true stress-strain.

http://www.tpub.com/content/doe/h1017v1/css/h1017v1_69.htm

http://physics.uwstout.edu/Statstr/statics/Stress/strs32.htm

http://web.mit.edu/course/3/3.11/www/pset03/Definitions.pdf - (save target as)

Here is an image of a load-displacement curve, however the person placed stress and strain titles next to it and describes the image as a stress-strain curve. The title of the abscissa is "Deflection (in)", which indicates elongation or displacement.
http://invsee.asu.edu/srinivas/stress-strain/phase.html

This might be useful - http://scholar.lib.vt.edu/theses/available/etd-6197-6556/unrestricted/ch3.PDF (use save target as)

I am unable to find an example of a load-displacement curve and the derived stress-strain curve.

 

[teng125]

thanx...