What's the difference between toughness and strength?


by bullet
Tags: difference, strength, toughness
bullet
bullet is offline
#1
Mar14-05, 11:57 AM
P: 5
whoever could give a detailed explanation?
Phys.Org News Partner Engineering news on Phys.org
Lifting the brakes on fuel efficiency
PsiKick's batteryless sensors poised for coming 'Internet of things'
Researcher launches successful tech start-up to help the blind
Astronuc
Astronuc is offline
#2
Mar15-05, 12:14 AM
Admin
Astronuc's Avatar
P: 21,634
Strength refers to resistance to deformation, and also to a large elastic range. In the Elastic region of the stress-strain relationship, the relationship is described by a linear function, such that [itex]\sigma[/itex] = E [itex]\epsilon[/itex], where [itex]\sigma[/itex] is the stress, E is the Elastic modulus, and [itex]\epsilon[/itex] is the strain.

At a point called the yield point, the relationship between stress and strain depart from linear, and the material yields meaning that permanent or inelastic and plastic deformation occur.

Beyond the yield point or yield strength, less stress is required for a given amount of strain (deformation). This proceeds up to the ultimate tensile strength, which is where uniform elongation is measured. At this point, a tensile specimen begins to 'neck', i.e. the change in cross-section becomes non-uniform. Also, beyond the ultimate tensile strength, the strain increases without additional stress. If the load is not immediately removed, the material will strain to failure.

Toughness is the resistance to failure or crack propagation. It is somewhat related to strength. Very strong materials will have low toughness, i.e. low tolerance for flaws or defects, i.e. incipient cracks.

Toughness relates to the amount of energy absorbed in order to propagate a crack. Materials with high toughness require greater energy (by virtue of force or stress) to maintain crack propagation. Toughness is described in terms of a stress intensity factor (K) or J-integral, or the strain energy release rate of nonlinear elastic materials, (J).

See - http://www.efunda.com/formulae/solid.../fm_epfm_J.cfm - for more on J-integral.
bullet
bullet is offline
#3
Mar15-05, 04:05 AM
P: 5
Thank you Astronuc. Much helpful.

rdt2
rdt2 is offline
#4
Mar16-05, 09:08 AM
rdt2's Avatar
P: 124

What's the difference between toughness and strength?


Quote Quote by bullet
whoever could give a detailed explanation?
Picture the stress-strain curve for an elastic-plastic metal. Strength is how high the curve reaches on the stress axis. Toughness is the area under the curve (and so related to energy).

A good structural alloy is both strong and tough.


Register to reply

Related Discussions
difference between phase difference and path difference General Physics 5
High Strength Steel with Corrosion Resistance and High Toughness Materials & Chemical Engineering 7
how toughness different from strengh Materials & Chemical Engineering 3
Fracture Toughness Mechanical Engineering 5
What's the difference between toughness and strength? General Engineering 4