DIfference between ESE and strain energy

Element strain energy (ESE) is the amount of strain energy stored in a finite element.If a set ID is given, element strain energy and strain energy density are output only for elements listed in that set.

The energy stored in a body due to deformation is called the strain energy.

Element strain energy (ESE) is the amount of strain energy stored in a finite element.If a set ID is given, element strain energy and strain energy density are output only for elements listed in that set.

The energy stored in a body due to deformation is called the strain energy.

Hi, George

      Thanks for your answering. But I still have some questions. I used Opstruct as solver and checked energy output cards.  When I checked the result in hyperview, I found the element specific energy is about 10e13. But in the .out file, I found I-enengy is about 10e7. I don't know why.

      shouldn't the I-energy be greater than element specific energy? I am confused about this. Does the sum of ESE equal to I-Energy?

     Eager for your answering!

I have made an example to show that the sum of ESE is different from the result I-Energy in .out file. 

Eager for your answering! Thanks!

Unable to find an attachment - read this blog

Regarding Strain Energy & Strain Energy (Density) here is some more info.

The units of energy are force*distance, so when a load is applied and the material deforms, we are putting energy into the material. This energy introduced into the material due to the loading is referred to as “strain energy.” We prefer to normalize strain energy by unit volume, and when we do so, this is referred to as strain energy density. The area under a stress-strain curve is the energy per unit volume (stress*strain has units of force per area such as N/mm2 , which is the same as energy per unit volume N-mm/mm3 . We will be assuming linear elastic material only. Most metals and alloys are linear elastic prior to the onset of plastic deformation, so this is a valid assumption.

Though Element Strain Energy is a good measure to watch in Modal analysis, as it gives an idea on the area of concern & to go for the mesh refinement there as ESE in modal analysis is somewhat similar to what Stress in Static analysis.

But if we go for Static/Structural analysis then Strain Energy Density could give you an idea on what elements/area of your model are contributing more in taking the load (absorbing). This same factor is used in optimization as well, where the load-paths are identified where the model have high strain energy density. So basically you get idea where you should strengthen your part. High stresses & High strain energy could be on common areas in some cases but not always guaranteed.

So better to go for Stress results when your main concern is Stress (which is there in most of the cases). But when your main concern is Stiffness of the structure i.e you want to limit the deflection/displacement happening in your structure then you may want to stiffen your part wherever it is showing high strain energy density.

Just to add, Strain Energy Density dependent function is also the main criteria on which Hyperplastic materials are based, as the behavior of Hyperelastic materials can’t be described with a single modulus like we describe for a general elastic-plastic material.

Refer below link for ESE.

http://www.altairhyperworks.com/hwhelp/Altair/hw14.0/help/hwsolvers/hwsolvers.htm?ese.htm

Regarding Strain Energy & Strain Energy (Density) here is some more info.

 

 

 

 

 

The units of energy are force*distance, so when a load is applied and the material deforms, we are putting energy into the material. This energy introduced into the material due to the loading is referred to as “strain energy.” We prefer to normalize strain energy by unit volume, and when we do so, this is referred to as strain energy density. The area under a stress-strain curve is the energy per unit volume (stress*strain has units of force per area such as N/mm2 , which is the same as energy per unit volume N-mm/mm3 . We will be assuming linear elastic material only. Most metals and alloys are linear elastic prior to the onset of plastic deformation, so this is a valid assumption.

 

 

 

 

 

Though Element Strain Energy is a good measure to watch in Modal analysis, as it gives an idea on the area of concern & to go for the mesh refinement there as ESE in modal analysis is somewhat similar to what Stress in Static analysis.

 

 

But if we go for Static/Structural analysis then Strain Energy Density could give you an idea on what elements/area of your model are contributing more in taking the load (absorbing). This same factor is used in optimization as well, where the load-paths are identified where the model have high strain energy density. So basically you get idea where you should strengthen your part. High stresses & High strain energy could be on common areas in some cases but not always guaranteed.

 

 

So better to go for Stress results when your main concern is Stress (which is there in most of the cases). But when your main concern is Stiffness of the structure i.e you want to limit the deflection/displacement happening in your structure then you may want to stiffen your part wherever it is showing high strain energy density.

 

 

 

 

 

Just to add, Strain Energy Density dependent function is also the main criteria on which Hyperplastic materials are based, as the behavior of Hyperelastic materials can’t be described with a single modulus like we describe for a general elastic-plastic material.

 

 

 

Refer below link for ESE.

 

http://www.altairhyperworks.com/hwhelp/Altair/hw14.0/help/hwsolvers/hwsolvers.htm?ese.htm

 

 

 

Thanks for your answering. You can check the example I have uploaded. I sumed up the ESE, but the results is different from the .out file I-energy. In my opinion, the sum of ESE is equal to I-energy. Am I wrong?

Eager for your answering! Thanks!

why you are compairing ESE with internal energy?

why you are compairing ESE with internal energy?

To monitor the energy changed during simulation time.

I want to know the total energy with time increase.  Because in the .out file I could not plot the results. But with sum of ESE I could plot the sum of ESE vs time.

Hi, Rahul

      Or in other words, I want to know the total energy in the whole body when I applied a load with time. What should I set the global output cards?

hi, Rahul

     Could you answer my question? Thanks!

The simplest way could be to print the result to a .pch file

ESE (punch) = all

Copy the result values to excel file to sum up.

Else, use query option on HV and export the ESE values directly to an excel file to sum up.

The simplest way could be to print the result to a .pch file

 

 

ESE (punch) = all

 

 

Copy the result values to excel file to sum up.

 

 

Else, use query option on HV and export the ESE values directly to an excel file to sum up.

 

 

Thanks for your answering. I want to know what the sum up of ESE mean. Does that mean total energy?

it will be Total strain energy.

it will be Total strain energy.

Is The total strain energy  different from I-energy in .out file?

hi, Rahul

     Eager for your answering! The key point is the difference between total strain energy and I-energy. Could you answer my question? Thanks!

Internal Energy is the energy in a SYSTEM arising from the relative positions and interactions of its parts. Whereas, the external work done by the forces is stored in the ELEMENTS as strain energy.

Usually for crash analysis where loading condition is initial velocity energy balance is important.

Internal Energy is the energy in a SYSTEM arising from the relative positions and interactions of its parts. Whereas, the external work done by the forces is stored in the ELEMENTS as strain energy.

You mean if I want to check the strain energy,I should sum up ESE?

You mean if I want to check the strain energy,I should sum up ESE?

Anybody answer my question? Thanks!

If you want to check the strain energy of the all elements you can keep the output option to ALL and ESE output for all elements can be fetched.

If you want to check the strain energy of the all elements you can keep the output option to ALL and ESE output for all elements can be fetched.

hi, George

     I still don't understand why the ESE and I-Energy in my example are not same. Could you explain why?

I think in my example the sum of ESE is equal to I-energy.

Unable to find an attachment - read this blog

Check the .out file for Compliance, which simply equals to 1/2 total strain energy in theory