Why is Material Toughness the Ability to Absorb Energy Before Fracture?

[Dario56]

Toughness is defined as ability of material to absorb energy when deforming before fracture. Materials with high ductility and strength will have high toughness.

What is meant by ability of material to absorb energy? What is connection between strength, ductility and ability to absorb energy so that materials with high strength and ductility can absorb a lot of energy before fracture?

 

[sysprog]

These questions seem to me to be too general. The answers I suppose probably should be material-specfic. Iron is regarded as tough, but it rusts, so we carbonize it, alloy it with other materials, and thereby turn it to steel and so make it tougher. Gold doesn't rust, and it's very malleable and ductile, but you wouldn't want to rely upon it for structure -- neither for cutlery nor skyscrapers -- chromium is the hardest element, and it can be shiny, but (unoxidized) silver is the shiniest element.

 

[Dario56]

These questions seem to me to be too general. The answers are material-specfic. Iron is regarded as tough, but it rusts, so we carbonize it, alloy it with other materials, and thereby turn it to steel and so make it tougher. Gold doesn't rust, and it's very malleable and ductile, but you wouldn't want to rely upon it for structure -- neither for cutlery nor skyscrapers -- chromium is the hardest element, and it can be shiny, but (unoxidized) silver is the shiniest element.

Question is general. However, answer doesn't need to be material specific. How can we connect material's ability to absorb energy with its ductility and strength?

 

[sysprog]

If we're avoiding being material-specific, can we instead be purpose-specific? -- I think that your question,

How can we connect material's ability to absorb energy with its ductility and strength?

is not well formulated enough to be well answerable.

 

[russ_watters]

See the charpy impact test:
https://en.m.wikipedia.org/wiki/Charpy_impact_test

The test measures the energy absorbed by the fracturing sample. Consider the definition of work: W = F * D. If you want to increase work done at fracture(by the sample on the hammer) you can either increase the force (tensile strength) or the distance (ductility/how far it stretches before breaking).

 

[Dario56]

See that chirpy impact test:
https://en.m.wikipedia.org/wiki/Charpy_impact_test

The test measures the energy absorbed by the fracturing sample. Consider the definition of work: W = F * D. If you want to increase work done at fracture(by the sample on the hammer) you can either increase the force (tensile strength) or the distance (ductility/how far it stretches before breaking).

Yes, I think got it. It is important to know that to deform material, work needs to be done which material absorbs. For example in uniaxial tensile test, work is done by outer tension force of the machine acting on the material sample. If material is strong, it requires a lot of force to break it which increases work done or energy absorbed. If material is ductile, it requires a lot of deformation to break it which increases displacement of the sample from starting point.