Difference between actual and visual rupture point?

@ammar-aziz-7MLZYl • Oct 27, 2024

Oct 27, 2024

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hi friends, we are studying mechanics of materials. during the study of stress - strain diagram i encounter 1 point which still confuses me. please explain me that what is actual rupture point and what is visual rupture point on stress - strain diagram of material under testing.

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CE Designer

@ce-designer-BWq0yl • Sep 26, 2012

Do you mean true vs. engineering stress points?
Ammar Aziz

@ammar-aziz-7MLZYl • Sep 27, 2012

yes certainly! i am talking about true and engineering stress point. but what is the relation between actual and visual rupture point with true and engineering stress points.
CE Designer

@ce-designer-BWq0yl • Sep 27, 2012

I am not certain, I have honestly never come across the terms actual and visual rupture point.
Ammar Aziz

@ammar-aziz-7MLZYl • Sep 27, 2012

here is the picture attached so although from figure the actual and visual rupture point or true and engineering stress point are in same vertical line then what does it shoes?
CE Designer

@ce-designer-BWq0yl • Sep 28, 2012

OK Point 3 on the red graph is called the Engineering Stress (Visual) point.
When the graph peaks at the Ultimate Tensile strength necking begins soon after. When necking sets in the cross-sectional area of the specimen is shrinking. The load bearing capacity is therefore reducing. This means that the force required to further strain the specimen is smaller.

Engineering Stress is calculated using the applied load divided by the original cross sectional area of the specimen (not the cross-sectional area of the necking region). So the Force required to strain is decreasing and the area is remaining the same (Stress = Force/Area) This is why the graph dips.

However the Actual Stress should be calculated using the instantaneous cross-sectional area , not the original. Since the area is decreasing the actual/true stress will be higher as shown at point 3 on the blue graph.

I Hope this helps you.
Ammar Aziz

@ammar-aziz-7MLZYl • Sep 28, 2012

thank you very much. now i got the clear concept.