Crack Propagation by Cohesive Zone

7/17/2019 Crack Propagation by Cohesive Zone

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Homework 3Crack propagation by cohesive

surface

Student: T. Arriessa Sukhairi (ID 108013235855)



RUHR Universität Bochum

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Crack propagation by cohesive surface

Problem Description

The problem is about two plate connected, in which there is a cohesive surface in between thistwo plat. The structure is composed of steel box-sections with elastic value (E = 210 GPa, ν =

0.3), plastic value can be seen from the figure 2.The dimension of the plate is (h = 0.5mm, b =

2mm). There is a crack with dimension a = 0.1mm:

Figure 1: Model

Figure 2: Plastic Properties Figure 3: Cohesive Properties.

The Cohesive Properties are:

1. Knn, Kss, Ktt = 210 000MPa

2. tini

a. Normal only = 550 MPa b. Shear-1 /Shear-2 only = 0 Mpa

3. δf = 0.001 mm

The displacement (u) is calculate by:

ISND = 5

u = 0.1 + 0.05 (mm)= 0.15




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Student: T. Arriessa Sukhairi

(ID 108013235855)

Figure 4. Global Mesh

Figure 5. Mesh at the Crack Tip




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1. By using the plastic material, given in the stress-strain curve and the cohesivebehaviour. The von Mises stress before the crack propagates is shown in figure6 and the von Mises at the end of the calculation shown in figure 7.

Figure 6. Von Misses on the Crack tip before crack propagate

Figure 7. Von Misses at the end.

Figure 6 show the contours of von Mises before crack propagate, afterthe crack has grown to a length a = 0.1 mm under the action of

displacement 0.15 MPa. As may can be seen a well-defined plastic wakehas formed behind the crack tip.

The Crack propagate through the cohesive zone.

The specimen does not completely break because of the constraint inthe end of the edge. As the result of this constrain, it makes the structureat that position is so tough because of the pressure that come from theupper and the lower position. However if we move the constraint to thelower or upper position, the crack will propagate until the end and breakthis structure.




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2. Figure 8 shown all reaction forces in y-direction on the edge Z and plot againsttime.

Figure 8. RF vs Time

From 0 to the highest point is at the elastic region of the material beforecrack is propagate.

The highest point here is at the crack tip, before the crack going topropagate in the cohesive zone at this phase it is in the plastic region..

After 1 s there is only steady state crack growing

Crack Propagation by Cohesive Zone

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