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Join Date: May 2007
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Fracture Toughness Test ASTM D5045

11/07/2012 9:28 AM

Hello dear colleagues,

I have to perform a test for a brittle polymer and I am using the standard ASTM D5045*.

In the section 7. there is a geometrical requirement which is at the same time a validation of the reliability of the obtained results. It involves the calculation of the following quantity:

2.5*(Kq/σy) -------- it gives an idea of the size of the plastic zone

Kq is the fracture toughness calculated. σy is the yield stress. My doubt is that in my case my material does not show yielding. Should I just take the tensile strength instead?

*Standard test methods for plane-strain fracture toughness and strain energy release rate of plastic materials.

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Guru

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#1

Re: Fracture Toughness Test ASTM D5045

11/07/2012 10:09 AM
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Active Contributor

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#2
In reply to #1

Re: Fracture Toughness Test ASTM D5045

11/07/2012 4:09 PM

Thank you very much lyn. However what I need is the fracture toughness and not the impact toughness (izod or charpy). Fracture toughness is given by the stress intensity factor or the energy release rate.

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Guru

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#3
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Re: Fracture Toughness Test ASTM D5045

11/07/2012 5:04 PM

Sorry. I was never required to document fracture toughness.

What does the material supplier say?

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Guru
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#4

Re: Fracture Toughness Test ASTM D5045

11/08/2012 9:56 AM

Every material will yield (however slightly to strain). The real questions is whether or not the experimental apparatus at hand is physically capable of measuring the deformation. Understood that brittle materials will not exhibit much yield prior to the fracture point.

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gustavoququ (1); James Stewart (1); lyn (2)

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