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I had posted this in the General Engineering forum but perhaps it is a better question for mechanical engineering forum:

1) Consider a centre crack specimen subjected to a wedge load a shown in the figure:

https://www.physicsforums.com/attachments/centre_crack_wedge_load-jpg.112584/ [Broken]

In such a case the stress intensity factor

2) Now, consider a centre crack specimen subjected to a far field stress as shown below

https://www.physicsforums.com/attachments/centre_crack_far_field_stress-jpg.112585/ [Broken]

Here the stress intensity factor

Now, my question is,

Case 2 is intuitively appealing / understandable since with increase in crack length we move towards the fracture toughness of the material thus stress intensity factor increases with increasing crack length

I'm not able to intuitively understand case 1. With increase in crack length the stress intensity factor is decreasing and in fact with increasing crack length we are moving away from fracture toughness of the material?

Can anyone help, please?

1) Consider a centre crack specimen subjected to a wedge load a shown in the figure:

https://www.physicsforums.com/attachments/centre_crack_wedge_load-jpg.112584/ [Broken]

In such a case the stress intensity factor

**DECREASES with the INCREASE in crack length**2) Now, consider a centre crack specimen subjected to a far field stress as shown below

https://www.physicsforums.com/attachments/centre_crack_far_field_stress-jpg.112585/ [Broken]

Here the stress intensity factor

**INCREASES with increase in crack length**Now, my question is,

Case 2 is intuitively appealing / understandable since with increase in crack length we move towards the fracture toughness of the material thus stress intensity factor increases with increasing crack length

I'm not able to intuitively understand case 1. With increase in crack length the stress intensity factor is decreasing and in fact with increasing crack length we are moving away from fracture toughness of the material?

Can anyone help, please?

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