5. general+yielding.pdf

Question 1

What is the J-Integral?

Answer 1

where:

C is the contour around the crack

ds = increment along contour C

Tbar = stress vector acting on contour

ubar = displacement vector

W = strain energy density = integral of rate of yield stress with respect to d(rate of yield strain)

Question 2

What is the simplified J-integral

Question 3

What does the J represent in the J-Integral?

Answer 3

J is the energy made available at the crack tip per unit extension of the crack.

Question 4

What is the equation for J for a plate with a deep notch in bending?

Answer 4

Answer 5

where:

dc = displacement of sample containing crack

P = load/unit thickness

d = remaining ligament (unbroken)

Question 6

How do you determine J_IC in a single specimen?

Answer 6

(a) A single specimen is loaded and unloaded multiple times with different crck opening displacments, info is recorded.

(b) A J value is calculated for these displacements (J=2Area/Bb)

(c) The J values are then plotted, forming the tearing line.

(d) The blunting line is also calculated and plotted (J=2σ_flow(delta a))

(d) Intersection of tearing line and blunting line is the J_IC

Question 7

Illustrate Blunting Effects

Answer 7