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LS-DYNA Reader Variable Description

Can you give me a quick tutorial of the LS_DYNA variables? 

LS-DYNA variable description 

EnSight Element types are discussed in Chapter 11 of the EnSight User Manual. 

EnSight can read in LS-Dyna D3PLOT files which are described in the 
LSTC(http://www.lstc.com) publication, "LS-DYNA Database Binary Output 
Files", revised January 2002. 

Element Variable Description 

The first portion of the variable description tells what kind of 
element it is located on. 
el8 - Hexahedron 3-node 
el2 - Bar 2-node 
el4 - Quadrangle 4-node shell 
elt - Quadrangle 8-node thick shell 

The next portion (for shells only) tells where the variable is located 
on the element. 
in - inner shell surface 
out - outer shell surface 
mid - mid shell surface 
pt## - selected integration points from 01 to number of points 

The next portion describes the type of variable. 
s - stress 
e - strain 
force - force 
shear - shear 
moment - moment 

The next portion describes the location and direction 
xx 
yy 
zz 
etc.. 

Element variable listing 

Hexahedron 8-node element variables 
Hexahedron 8-node element variables are always output in reference to 
the global coordinate system. 

Hexahedron 8-node Stress variables 
el8_s-xx - True stress xx in global system 
el8_s-yy - True stress yy in global system 
el8_s-zz - True stress zz in global system 
el8_s-xy - etc. 
el8_s-yz 
el8_s-yz 
el8_s-zx 
el8_pstrn - Effective plastic strain or material dependent variable 
el8_var## - extra variables where ## is 01 to number of extra variables 

Hexahedron 8-node strain variables 
el8_e-xx - Strain xx 
el8_e-yy - Strain yy 
el8_e-zz - etc. 
el8_e-xy 
el8_e-yz 
el8_e-zx 

Bar 2-node Elements 

Bar 2-node elements are always output in the local coordinate system 
and the variables below are annotated as such. 

el2_force_axial 
el2_shear_s - S shear resultant 
el2_shear_t - T shear resultant 
el2_moment_s - S bemding moment 
el2_moment_t - T bending moment 
torsion - Torsional resultant 

Bar 2-node extra variables 
el2_shear_rs## - shear extra variable ## where ## is from 1 to num vars 
el2_shear_tr## 
el2_stress_axial## 
el2_strain_plastic## 
el2_strain_axial## 

Quadrangle 4-node elements 
Quadrangle 4-node elements variables are normally in global coordinate systems. 
Quadrangle 4-node orthotropic and anisotropic element variables 
can be output in a local system if a flag, 
CMPFLG, is set. See ls-dyna 960 keyword users manual page 9.18. flag CMPFLG. 
It is up to the user to know if this flag is set and interpret 
the variables appropriately. 

Quadrangle 4-node midsurface values 
el4_mid_s-xx - midsurface x-stress 
el4_mid_s-yy - midsurface y-stress 
el4_mid_s-zz - midsurface z-stress 
el4_mid_s-xy - midsurface xy-stress 
el4_mid_s-yz - midsurface yz-stress 
el4_mid_s-zx - midsurface zx-stress 
el4_mid_pstrn - midsurface effective plastic strain 
el4_mid_var## - midsurface additional value 01 to number of extra values 

Quadrangle 4-node inner surface values 
el4_in_s-xx - inner surface x-stress 
el4_in_s-yy - etc. 
el4_in_s-zz 
el4_in_s-xy 
el4_in_s-yz 
el4_in_s-zx 
el4_in_pstrn 
el4_in_var## 

Quadrangle 4-node outer surface values 
el4_out_s-xx - outer surface x-stress 
el4_out_s-yy - etc. 
el4_out_s-zz 
el4_out_s-xy 
el4_out_s-yz 
el4_out_s-zx 
el4_out_pstrn 
el4_out_var## 

Quadrangle 4-node values at pt 01 to number of other points 
el4_pt##_s-xx - pt ## x-stress 
el4_pt##_s-yy - etc. 
el4_pt##_s-zz 
el4_pt##_s-xy 
el4_pt##_s-yz 
el4_pt##_s-zx 
el4_pt##_pstrn 
el4_pt##_var## 

Quadrangle 4-node other values 
el4_mxx - bending moment about x 
el4_myy - bending moment about y 
el4_mxy - bending moment xy 
el4_qxx - shear resultant x 
el4_qyy - shear resultant y 
el4_nxx - normal resultant x 
el4_nyy - normal resultant y 
el4_nxy - normal resultant xy 
el4_thick - thickness 
el4_dv01 - element dependent variable 
el4_dv02 - element dependent variable 

Quadrangle 4-node inner surface strain values 
el4_in_e-xx - inner surface x-strain 
el4_in_e-yy - etc. 
el4_in_e-zz 
el4_in_e-xy 
el4_in_e-yz 
el4_in_e-zx 

Quadrangle 4-node outer surface strain values 
el4_out_e-xx - outer surface x-strain 
el4_out_e-yy - etc. 
el4_out_e-zz 
el4_out_e-xy 
el4_out_e-yz 
el4_out_e-zx 

Quadrangle 4-node internal energy value 
el4_IE 

Quadrangle 8-node Thick Shell 
(Represented in EnSight as a Hexahedron 8-node) 

Thick Shell elements variables are normally in global coordinate systems. 
Thick Shell orthotropic and anisotropic element variables 
can be output in a local system if a flag, 
CMPFLG, is set. See ls-dyna 960 keyword users manual page 9.18. flag CMPFLG. 
It is up to the user to know if this flag is set and interpret 
the variables appropriately. 

elt_mid_s-xx 
elt_mid_s-yy 
elt_mid_s-zz 
elt_mid_s-xy 
elt_mid_s-yz 
elt_mid_s-zx 
elt_mid_pstrn 
elt_mid_var## where ## =1 to number extra variables 

Thick Shell inner surface values 
elt_in_s-xx 
elt_in_s-yy 
elt_in_s-zz 
elt_in_s-xy 
elt_in_s-yz 
elt_in_s-zx 
elt_in_pstrn 
elt_in_var## 1 to number of variables 

Thick Shell outer surface values 
elt_out_s-xx 
elt_out_s-yy 
elt_out_s-zz 
elt_out_s-xy 
elt_out_s-yz 
elt_out_s-zx 
elt_out_pstrn 
elt_out_var## 1 to number of variables 

Thick Shell values at pt 01 to number of other points 
elt_pt##_s-xx 
elt_pt##_s-yy 
elt_pt##_s-zz 
elt_pt##_s-xy 
elt_pt##_s-yz 
elt_pt##_s-zx 
elt_pt##_pstrn 
elt_pt##_var&& with ## = 1 to number of pts ## and && = 1 to num variables 

Thick Shell inner surface strain values 
elt_in_e-xx 
elt_in_e-yy 
elt_in_e-zz 
elt_in_e-xy 
elt_in_e-yz 
elt_in_e-zx 

Thick Shell outer surface strain values 
elt_out_e-xx 
elt_out_e-yy 
elt_out_e-zz 
elt_out_e-xy 
elt_out_e-yz 
elt_out_e-zx 

Other Variables 

The LS-DYNA database stores some variables such as velocity and acceleration 
vectors as nodal variables. However, the LS-DYNA D3PLOT binary file does not store a displacement vector. Rather, it stores all the grid positions for every timestep. Thus, you can animate the displacement in a flipbook because every timestep has a new set of coordinates. EnSight creates a displacement variable which is the current coordinates minus the original coordinates at the first timestep. This variable is called 

d_displacement 

Turning on displacement using the d_displacment vector and setting the scale factor to -1 will effectively turn off displacements. 

CALCULATED VARIABLES 

Some have asked us how to create a pressure variable for parts that are liquid. Since the part is a liquid, the pressure is simply any one of the normal stresses (s-xx, s-yy, or s-zz) which should all be equal, and no calculation is required. 

You can calculate the Principal Stresses in the EnSight calculator as simply the EigenValues of the stress tensor, using EnSight's TensorEigenvalue calculator function. 

You can then use the Principal Stresses to calculate the VonMises Stress in the calculator, or you can directly use EnSight's calculator function TensorVonmises.

Mid-surface strains will NOT be shown directly in the reader and can easily be calculated as the average of the in/out surface results.

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