How to set up sensor_define_element_set without SETOPT parameter?

Alberto Perticone

Hi everyone,

I'm struggling with sensor_define_element_set configuration in Ls-Dyna 12.0. Looking at the manual (see below), I found out an useful example I need to reproduce:

My issue is that SENSOR_DEFINE_ELEMENT_SET actually requires a one more parameter (missing in this example), SETOPT, which seems to be mandatory when "set" flag is on. SETOPT makes the set output as a unique value, so that I cannot specify a "minus" ELEMID, otherwise LsDyna outputs an error saying the -ID set is missing and it cannot find such a set. (This is correct since you ask for an output for each single element with a -ID set, while the SETOPT outputs a single value derived from the whole set).

Having saying that, what about this issue? How can I unflag the SETOPT option? Is that a bug? Am I doing something wrong? I want to reproduce the exact same example above, but in that case the SETOPT seems to be deactivated, which I cannot unflag even though the exact same LsDyna version (r 12.0)...

Thank you for any help!

Michael Herve_21439

Hello Alberto,

as the sensor is based on a set on elements, the SETOPT option looks mandatory for me regarding the options available in HyperMesh:

Indeed, it will tells LS Dyna how the sensor should measure the value based on the selection of entities.

 

Let's say that you select 100 elements, and you measure the VonMises stress, with a target value of 400MPa.

What is the condition for activating your sensor? do you activate it:

- when the first element reaches 400 MPa

- when the last elements reach 400 MPa

- when the average value over the elements reaches 400 MPa

 

So the SETOPT seems mandatory. Ypou can double check with LS Dyna if you want to be sure of SETOPT usage.

 

Best Regards,

Michael

Alberto Perticone

Michael Herve_21439 said:

Hello Alberto,

as the sensor is based on a set on elements, the SETOPT option looks mandatory for me regarding the options available in HyperMesh:

Indeed, it will tells LS Dyna how the sensor should measure the value based on the selection of entities.

 

Let's say that you select 100 elements, and you measure the VonMises stress, with a target value of 400MPa.

What is the condition for activating your sensor? do you activate it:

- when the first element reaches 400 MPa

- when the last elements reach 400 MPa

- when the average value over the elements reaches 400 MPa

 

So the SETOPT seems mandatory. Ypou can double check with LS Dyna if you want to be sure of SETOPT usage.

 

Best Regards,

Michael

First of all thank you for answering!

This doesn't seem to be correct, imo, as the "negative" ELEMID actually tells when the sensor_switch should be triggered. If sensor_define_element_set calculated the strain for every element in the set (without specifying SETOPT), then the sensor_switch could check which element overcome the threshold (if "-ELEMID") or wait until all of them are over the threshold (if "ELEMID").

Don't you agree with me? SETOPT outputs a single value for the whole set, so it's impossible to ask for the switch of the sensor just if at least one of 100 elements has a strain magnitude>threshold. Besides, even if I went for a SETOPT=MAX, I wouldn't calculate the resultant, as the max for xx, yy, zz in each sensor could occur for different elements...