1. Kırılma Mekaniğine Giriş
Problems
Problem 1:20 inc. in width and inc. İn thickness of a plate is fixed at one end and pulled from the other end with a force of lbs. The fracture toughness of this plate made of steel is KIC = 50 ksi(in) ½ . When the plate contains the center crack, calculate the critical crack length before fracture occurs.
Answer 1 : a=0.60 inc (15.2mm) , 2a=1.20 inc (30.4 mm)
Dokuz Eylül University, Mechanical Engineering Department Prof. Dr. M. Evren TOYGAR

2. Kırılma Mekaniğine Giriş
Problem 2: The width of the plate made of low carb is 4 in. And the tensile stress applied to this plate is 32 ksi. Calculate the value of the minimum fracture toughness to be tolerated for the plate with a 2 mm crack with edge notch.
Answer 2 : 19.4 MPa(m)1/2
Problem 3: Plates with dimensions of mm from two different A and B steels are subjected to a pull load of P = N. If the minimum crack size is 2.5 mm with non-destructive control and the minimum weight in design is taken into consideration, which steel should be selected?
A steel : yield strength = 91 N/mm2 , fracture toughness = 364 N/mm 3/2
B steel : yield strngth = N/mm2 , fracture toughness = 174 N/mm 3/2
Answer 3: A steel must be choosen.
Dokuz Eylül University, Mechanical Engineering Department Prof. Dr. M. Evren TOYGAR

3. a) calculate the fracture toughness parameter,
Problem 4: The width and thickness of a plate containing center crack are w = 6 inc. and B = 0.2 inc, respectively. The maximum applied load is Pmax = 41 kips and the yield stress value is ys = 50 ksi. For this system that contains a center crack as 2a = 2 in;
a) calculate the fracture toughness parameter,
b) calculate the size of the plastics zone that occurs during the fracture.
Answer 4: a) 64.9 ksi(in)1/2. b) The length of the plastic zone is equal to the length outside the crack.
Dokuz Eylül University, Mechanical Engineering Department Prof. Dr. M. Evren TOYGAR

4. Answer 5: a) ac = 0.13m, b) fr = 150.65 MPa
Problem 5: On a plate containing an edge crack, β = R curves representing the resistance of the material to fracture progression for plane stress is
Here, the fracture toughness is 50 MN/m3/2 elastic modulus is 2*105 MN/m is the amount of steady cracks going forward. Initial crack length is ai = 10 cm Therefore, a) calculate stable crack growth, b) calculate fracture stress. ai is the initial crack length, ac is the final crack length
Answer 5: a) ac = 0.13m, b) fr = MPa
Dokuz Eylül University, Mechanical Engineering Department Prof. Dr. M. Evren TOYGAR

5. a) calculate the critical length of the center crack in the plate,
Problem: MPa stress is applied to a plate. The fracture toughness of the material is given as 80 MPam . According to this,
a) calculate the critical length of the center crack in the plate,
b) calculate the energy release rate.
Note : E = 207 GPa’ dır.
Problem 7: Bir A tensile sample is 10 mm wide and the half of a crack length is a = 0.3 mm long. When the applied tensile stress reaches 450 MPa on this sample, the crack propagates suddenly. The elastic modulus is given as 200 GPa
a) when there is a center crack,
b) when there is a edge crack,
Calculate the fracture toughness.
Dokuz Eylül University, Mechanical Engineering Department Prof. Dr. M. Evren TOYGAR