EXERCISE TO TOPIC 5: CRACK TIP SIMULATIONSSubmitted by:

Mohit Gupta

IIT Delhi, India.

Build up the model shown above using a linear elastic plane stress model. Due to symmetry, only of the model is necessary to include in the model. Make a focused mesh at the crack tip by using a partition around the crack tip with a swept mesh and a focused mesh with collapsed nodes at the crack-tip. Make a linear simulation in order to be able to extract the stress intensity factor.Soln 1.

Fig 1. Stress Intensity factor K1 at 10 points.

Fig 2. Avg. Stress Intensity factor: K1avg= 2.9134e07.

Soln 2.

Fig: Showing the path in front of crack tip.

Fig 3. Log-Log plot of S22 in front of crack tip.

Figure 3 shows the variation of stress field S22 in front of crack tip. The KI dominated field is till .0025 m (2.5 mm) from the crack tip, as can be seen by drawing a tangent across the curve.

Soln 3.

Fig 4: Comparison of FEM and Analytical for S22.Soln 4. It would be very near the crack tip, so we can take small value of r. Assuming and taking the stress value from plot gives stress S22 = 340 MPa.

Soln 5.

Fig 6. Shows S22 for Load = 10,20,30,40,60,80 MPa consecutively from brown to red with the elastic curve shown in dots.

The figure 6 shows the plots for different loading conditions for a plastic model. The load is varied from 10 MPa to 80 MPa. The curve in brown (lowest) is for 10 MPa and one in red is 80 MPa. The dotted one shown is for Elastic model.