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.

1. FRACTURE TOUGHNESS
&
its MEASUREMENT
JAVED ALAM
10MT10015

2. What is fracture toughness?
It is a property which describes the ability of a
material with a crack to resist fracture.
The linear-elastic fracture toughness of a material is
determined by Stress intensity factor(K) at which a
thin crack in the material begins to grow, denoted
by KIC
Plastic-elastic fracture toughness is denoted by
JIC

3. Fracture toughness is a quantitative way of
expressing a material’s resistance to brittle
fracture when a crack is present.
*If a material has much fracture toughness it
will probably undergo ductile fracture.
*Brittle fracture is very characteristic of
materials with less fracture toughness.

4. Stress intensity factor (K):
It is used to predict the stress state near
the tip of a crack caused by a remote load
or residual stresses.
It depends on nominal stress, and crack
geometry: K = f(σ, a); It also depends on the
location of crack, magnitude and
distribution of stresses

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. Type of Specimens for Fracture Toughness Tests

7. Clip Gage Extensometer

8. Experimental setup
The sample was Perspex

10. Group-2
Max. load= 85.11 N
Extension at
break=6.98mm

11. Flexural Tests with Pre-cracked Specimens
For three point bending:
(D = S/2) = KIC = Y.(3PS/2W2t).√ a
Y = 1.93-3.07(a/w)+13.66(a/w)2-23.98(a/w)3+25.22(a/w)4

12. Calculation of KIC
Width=10.88 mm, t=5.7mm , a(crack length)=4.46mm , S=44
mm
(a/w)=0.41
Y=2.027
Now P= Pmax=85.11 N
Substituting the value of P:
KIC = 1.143 MPa · m1/2

13. Group-1
a= 4.7166
a/w = 0.414
Y=2.039
KIC = 1.086 MPa · m1/2

14. Group-3 Crack length=5.066mm
KIC =1.231 MPa · m1/2
Group -4
Crack length=6.05mm

15. Thank you