Fracture Toughness Testing 1

[will123123]

I am looking to undertake some fracture toughness testing of aluminium metal matrix composites (SiC particulate reinforcement). There are a number of test standards, ie. ASTM E399, ASTM E1820, BS 7448 etc.
Have anyone undertaken these tests and are able to advise on the pro and con of each test method and on the different specimen designs.

Thanks for your assistance.

 

[CoryPad]

ASTM E1820 is more comprehensive testing than E399. E1820 provides data for the entire R-curve, while E399 provides the single value of K_Ic. What is your goal?

 

[will123123]

The intention is to compare the toughness between three different, but similar materials. I am reading through E1820 and E399 and I have to say I am getting lost!!

 

[will123123]

Further to my last reply. E399, contains recommended sizes to ensure plane-strain in the specimen, E1820, does not as it no longer covers plane-strain. If my requirement is just to compare the toughness of different materials (SiC particulate reinforced aluminium, with diffrent reinformace loading, which chagnes stiffness and strength), is it necessary to used plain-strain (and the large specimens specified, as a result of the ratio of yield strength over modulus)?

As only a comparsion is required, would simple charpy testing be a viable alternative?

 

[EdStainless]

It depends on how brittle they will be.
If they will have very low impact toughness then maybe you could use unnotched bars, of go to a bending test like they do with ceramics (4 point bending).
You don't want to prep CVN bars and have them only absorb 5 lb-ft on impact.

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P.E. Metallurgy, Plymouth Tube

 

[will123123]

If we approach this from a different direction. The structures personnel in my company wishes to obtain some 'toughness' values for range of material. They will not be used for design purposes, but to provide some information on the relative 'robustness' or 'tolerance' of components made from different material to unexpected overloads and or damage.

If you had a clean sheet to start, what would be the recommended test to carry out, which would require reasonable amounts of material (some of the material I have will likely require 100mm3 samples to obtain plane-strain fracture toughness).

 

[EdStainless]

One easy place to start is by pulling both smooth and notched tensile bars. It will give you and indication of notch sensitivity and damage tolerance.


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P.E. Metallurgy, Plymouth Tube

 

[CoryPad]

If you want qualitative toughness, then a Charpy impact test (ASTM E23) is another test to consider. If you want quantitative toughness, then ASTM E1820.

 

[DeleteriousPhases]

The place I worked at previously would conduct CTOD (crack tip opening displacement) tests to examine crack progression in materials.