Fracture toughness measurement testing

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This is a ppt which will give u a better understanding of fracture toughness of a material in short time. It also has great exposure to testing method that we do in our laboratory class in undergraduate courses. So good luck with slide.

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Fracture toughness measurement testing

  1. 1. FRACTURE TOUGHNESS & its MEASUREMENT JAVED ALAM 10MT10015
  2. 2. What is fracture toughness?It is a property which describes the ability of amaterial with a crack to resist fracture.The linear-elastic fracture toughness of a material isdetermined by Stress intensity factor(K) at which athin crack in the material begins to grow, denotedby KICPlastic-elastic fracture toughness is denoted byJIC
  3. 3. Fracture toughness is a quantitative way ofexpressing a material’s resistance to brittlefracture when a crack is present.*If a material has much fracture toughness it will probably undergo ductile fracture.*Brittle fracture is very characteristic ofmaterials with less fracture toughness.
  4. 4. Stress intensity factor (K):It is used to predict the stress state nearthe tip of a crack caused by a remote loador residual stresses.It depends on nominal stress, and crackgeometry: K = f(σ, a); It also depends on thelocation of crack, magnitude anddistribution of stresses
  5. 5. Fracture Toughness Tests A test sample is fatigue loaded to extend the machined notch by a prescribed amount. A clip gage extensometer is placed at the mouth of crack to monitor displacement. If a lower toughness level is achieved with a thicker sample, then the value obtained initially is not valid.
  6. 6. Type of Specimens for Fracture Toughness Tests
  7. 7. Clip Gage Extensometer
  8. 8. Experimental setupThe sample was Perspex
  9. 9. Group-2 Max. load= 85.11 N Extension at break=6.98mm
  10. 10. Flexural Tests with Pre-cracked SpecimensFor three point bending: (D = S/2) = KIC = Y.(3PS/2W2t).√ aY = 1.93-3.07(a/w)+13.66(a/w)2-23.98(a/w)3+25.22(a/w)4
  11. 11. Calculation of KICWidth=10.88 mm, t=5.7mm , a(crack length)=4.46mm , S=44mm(a/w)=0.41Y=2.027Now P= Pmax=85.11 NSubstituting the value of P: KIC = 1.143 MPa · m1/2
  12. 12. Group-1 a= 4.7166 a/w = 0.414 Y=2.039 KIC = 1.086 MPa · m1/2
  13. 13. Group-3 Crack length=5.066mm KIC =1.231 MPa · m1/2Group -4 Crack length=6.05mm
  14. 14. Thank you

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