Non linear static analysis with Opts. (Plastic stress problem)

zeynepbkurt

Hello all,

 

It is known that plastic stress or strain occurs when the material is above the yield point by applied force. According to results, the stress value was lower than the yield point of the materials used in  the model but plastic stress was observed. What could be the reason?

 

Thank you. 

Adriano Koga_20259

Can you share more details on your setup and some pictures? How are you plotting stresses? Are you using averaged results?

zeynepbkurt

Adriano Koga_20259 said:

Can you share more details on your setup and some pictures? How are you plotting stresses? Are you using averaged results?

Hello,

Two subcases are defined in the model: Load and unload. You can see  material curves, load step definitions and result pictures below. 

 

 

Thanks for your help. 

Adriano Koga_20259

zeynep begüm kurt said:

Hello,

Two subcases are defined in the model: Load and unload. You can see  material curves, load step definitions and result pictures below. 

 

 

Thanks for your help. 

considering that you are running loading and then unloading subcases, probably, during loading, your model has reached yield stress for some points, and then plastic strain started to show up.

Then after you unloaded the structure, stress values have decreased below yield.

 

Are you sure the picture that you sent here for LC1 was at the 100% of load/increment?

Can you share some pics of the plastic strain area too?

zeynepbkurt

Adriano Koga_20259 said:

considering that you are running loading and then unloading subcases, probably, during loading, your model has reached yield stress for some points, and then plastic strain started to show up.

Then after you unloaded the structure, stress values have decreased below yield.

 

Are you sure the picture that you sent here for LC1 was at the 100% of load/increment?

Can you share some pics of the plastic strain area too?

"Are you sure the picture that you sent here for LC1 was at the 100% of load / increment?" How can I control this situation?

Subcase 2- strain value:

Adriano Koga_20259

zeynep begüm kurt said:

"Are you sure the picture that you sent here for LC1 was at the 100% of load / increment?" How can I control this situation?

Subcase 2- strain value:

Hi,

 

you are plotting 'Element Strains', which means Total Strain (Elastic + plastic).

There is a result type for Plastic Strain, in case you had any.

 

For steel, the elastic curve goes until something close to 0.02. So you are indeed very far from the yield zone.

 

For NL Analysis, you can check the increment when plotting yur results.

In case you have requested NLOUT, you will see the increment values in your plot. (upper left and upper right).