Assignment 5
HyperCrash Introduction
Preprocessing for RADIOSS Crash Analysis
HyperCrash is a pre-process for RADIOSS which is tailored to meet the needs of automotive crash users. HyperCrash enables the users to build the highest quality model, with significant decrease in modeling time, and with highest level of homogeneity. Also, HyperCrash has an Automotive Safety module which consists of the following tools: Dummy Positioner, SeatBelt Generator, Airbag Folder and Seat Deformer. HyperCrash has various quality checks, including it most powerful intersection/penetration checking and fixing routine, which enables the users to setup a model that is perfectly consistent with the RADIOSS solver. HyperCrash has built-in automated routines that allow the users to significantly reduce the modeling time. Also, it allows the users in a specific group to build a homogeneous model by allowing these users to access the same databases like materials, properties, spotweld connections, dummies, barriers, same checks and etc.
Objective :
To analyze and compare different cases with various contact types and different parameters as well as notch positions and compare the results for the same boundary conditions.
Given model is Crash_tube_0000.rad
The model is a crash tube with hollow square configuration meshed with all Quad QEPH 24 shell elements. Two halves of the tube are joined with a
weld contact (Type 2). The face of tube has several notches placed symmetrically.
Given task
- Run the crash tube model as it is.
- Change the Inacti=6 and run.
- Create the type 11 contact and run.
- Remove both notches and remove boundary condition on rigid body node then run.
- Create a new notch in the middle ,select the whole section and run.
- Create a new notch with nodes only from opposing 2 faces and run. we are going compare these result use hypermesh, hyperview, hypergraph and hypercrash
CASE 1: The Crash tube model is run as it is. Default parameters for the contacts. Type 7 contact defined as to prevent penetration(due to crushing).
To start Hypercrash ,first opren hypermesh - Application - Hypercrash.
Before moving to Hypercrash check the unit system and user profile. Unit system should in KN mm ms kg and click new and run it.
After Hypercrash open , import - Crash_tube_0000.rad - move to model - browser - double click contact interface and select Type 7 edit and check the parameter .
After completion of these step export to radioss file .Move to hypermesh import the saved file and run the stimulation in radioss we will two set of file .
After stimulation completes we have look into open Crash_tube_0000.rad in note pad, to check material properties .
After stimulation completes we have look into open Crash_tube_0001.rad in note pad and check energy errror and mass error using default value , energy error and mass error had been highlighted using sketch.
Energy error in the basic stimulation case is -38%
Energy error is accepted upto 15%
Mass error =0.000
time =29.71
Next move to hyperview For run the stimulation select h3d file - open,
Click contour - Resultant type as displacement - Apply
Maximum displacement at node 765 is 2.800E+00
Minimum displacement at node 765 is 0.000E+00
Instead of von mises select - plastic strain along the thickness - apply.
Maximum displacement at node 1929 is 1.401E+00
Minimum displacement at node 135 is 0.000E+00
Instead of displacement select - von mises - apply.(it will shows different stress of each and every element)
Maximum vonmises peak is 6.968E-01 in node 1920
Minimum value is 0.000E+00 in node as 765
When initial velocity applied on the steel material tube with Plas_john material card undergoes elasto-plastic deformation. The Max von mises stress is recorded was 6.968E-01 in node 1920 . Like the plastic strain, Von mises stress are maximum on the corner edges of the tube as the faces undergo bending and crushing.
Next move to hyper graph 2D ,For run the graph select To1 file - open
plot the graph for Global variable as Internal energy and kinetic energy,hoursglass energy, total energy,contact energy
As we plot a graph for Global variable as Internal energy and kinetic energy,hoursglass energy, total energy,contact energy, where Internal energy of system is the mirror value for Kinatic energy. The contact energy which represent the contact force from 0 to 100 ms.As there isn’t room for further absorption of energy the whole crushed tube acts as a block undergoing compression.where total energy is the sum all the energy is ploted.
Plot the rigid wall - 4 rigid wall - total resultant force and FNZ-Z Normal force
The peaks in rigid wall force are seen after valley as the crumbling of tube divides the tube in two parts momentarily ,which consumes some energy and hence less force is generated on wall. The continuation of force as velocity pushes the upper part into lower causing it to become single unit again.
This process repeats itself till the whole tube is crushed into a small dense box.
After peaking , no further transmission of force is seen as the thick crushed tube below the rigid body node resists further compression. A significantly higher force is required to flatten the crushed tube.
Case 2 : Change the Inacti=6 and run.
After Hypercrash open , import - Crash_tube_0000.rad - move to model - browser - double click contact interface and select Type 11 edit Inacti=6 and check the remaining parameter .
After stimulation completes we have look into open Crash_tube_0000.rad in note pad, to check material properties .
After stimulation completes we have look into open Crash_tube_0000.rad in note pad and check energy errror and mass error using default value , energy error and mass error had been highlighted using sketch.
Energy error in the basic stimulation case is -3.8%
Energy error is accepted upto 15%
Mass error =0.000
time =29.71
Next move to hyperview For run the stimulation select h3d file - open,
Click contour - Resultant type as displacement - Apply
Maximum displacement at node 765 is 2.793E+00
Minimum displacement at node 765 is 0.000E+00
Instead of displacement select - von mises - apply.(it will shows different stress of each and every element)
Maximum vonmises peak is 6.968E-01 in node 1920
Minimum value is 0.000E+00 in node as 765
Next move to hyper graph 2D ,For run the graph select To1 file - open
plot the graph for Global variable as Internal energy and kinetic energy,hoursglass energy, total energy,contact energy
Plot the rigid wall - 4 rigid wall - total resultant force
The Inacti =6 setup is only influential when there are any initial penetrations. As in our case the contact is type-7 (self contact), there no any
changes in any output .
Case 3 : Create the type 11 contact and run.
In type 11 edge crossing, it can added the capture the physics correctly, it has edge to edge contact , its defines as Identifying master and slaves lines.
The recommended parameters are defined for the already present type-7 contact.Type-11 edge to edge contact with similar parameters is defined for better coverage. The gap minimum is kept lower in type-11 than that in type-7 to compensate for bigger the element size. like Fric, min gap,
After stimulation completes we have look into open Crash_tube_0001.rad in note pad and check energy errror and mass error using default value , energy error and mass error had been highlighted using sketch.
Energy error in the basic stimulation case is -4.8%
Energy error is accepted upto 15%
Mass error =0.000
Next move to hyperview For run the stimulation select h3d file - open,
Click contour - Resultant type as displacement - Apply
Maximum displacement at node 765 is 2.706E+00
Minimum displacement at node 765 is 0.000E+00
Instead of displacement select - von mises - apply.(it will shows different stress of each and every element)
Maximum vonmises peak is 6.455E+02 in node 871
Minimum value is 0.000E+00 in node as 765
The max. Von Mises stress out come was lesser than compare to case 1. The significant difference is seen in the contact force analysis. The peak value is 6.455E+02 compared to 6.968E-01 .
Next move to hyper graph 2D ,For run the graph select To1 file - open
plot the graph for Global variable as Internal energy and kinetic energy,hoursglass energy, total energy,contact energy
Plot the rigid wall - 4 rigid wall - total resultant force anf FNZ-ZNormal force
The nature of the Rigid wall plot is same as Case-1 till 20ms afterwards no dips and peaks are seen as in case-1 and the plot climbs steadily till a peak of 1.5MN a good 100 KN more than case 1. The added parameters and additional contact type-11 gets better details of the analysis. The internal energy plot gets a bit steeper for the same time window.
Case: 4- Removing notches and boundary conditions on node.
The notches are removed with the help of ‘align node’ option in hypermesh. The boundary conditions(DOFs) applied on the rigid node at the upper end are removed .
After stimulation completes we have look into open Crash_tube_0000.rad in note pad and check energy errror and mass error using default value , energy error and mass error had been highlighted using sketch.
Energy error in the basic stimulation case is -3.9%
Energy error is accepted upto 15%
Mass error =0.000
Next move to hyperview For run the stimulation select h3d file - open,
Click contour - Resultant type as displacement - Apply
Maximum displacement at node 765 is 2.788E+00
Minimum displacement at node 765 is 0.000E+00
Instead of displacement select - von mises - apply.(it will shows different stress of each and every element)
Maximum vonmises peak is 6.395E-01 in node 1282
Minimum value is 0.000E+00 in node as 765
Next move to hyper graph 2D ,For run the graph select To1 file - open
plot the graph for Global variable as Internal energy and kinetic energy,hoursglass energy, total energy,contact energy
Plot the rigid wall - 4 rigid wall - total resultant force
As we had plot due to the absence of notches the crushing of tube is random and hence uncontrolled. This gives sharp edges as output here. The usualb climb around 20ms is a bit delayed in this case
and after that a significantly lower peak value of 13MN is achieved. A rough estimate being non-concentrated stresses due to absence of notches means random loading and hence random straining and may cause failure in case of surface defects.
A boundary condition removed, notched tube result for the same is a good comparison material to assess the effects of notches.
Case 5: Adding a notch on one of the faces at the middle.
Using the ‘move node’ option or translate a square set of nodes was pushed inwards on one of the faces approximately in the middle of the lower part of tube. All the other analysis parameters and inputs were kept the same.
After stimulation completes we have look into open Crash_tube_0001.rad in note pad and check energy errror and mass error using default value , energy error and mass error had been highlighted using sketch.
Energy error in the basic stimulation case is -2.7%
Energy error is accepted upto 15%
Mass error =0.000
Next move to hyperview For run the stimulation select h3d file - open,
Click contour - Resultant type as displacement - Apply
Maximum displacement at node 765 is 2.799E+00
Minimum displacement at node 765 is 0.000E+00
Instead of displacement select - von mises - apply.(it will shows different stress of each and every element)
Maximum vonmises peak is 5.743E-01 in node 1925
Minimum value is 0.000E+00 in node as 765
Next move to hyper graph 2D ,For run the graph select To1 file - open
plot the graph for Global variable as Internal energy and kinetic energy,hoursglass energy, total energy,contact energy
Where compare to previous cases here the presence of notch for the first compression is recorded immediately and is shown by the high slope in I.E. and mirror is k.E as been plotted
The magnitudes in both the plots for single notch and zero notch tubes .
Plot the rigid wall - 4 rigid wall - total resultant force
In these we added a notches where as previously we had removed the notched placed in tube. The notch is the first part of the tube that undergoes bending such kinf of bent metal are formed on either side of the notchs.
The Notch placement at end tube, the tube is divides in two parts such that the lower part gets crushed first as it is transmitting the load into Rigid wall. This bent metal is out of the line because force applied at top and doesn’t undergo compression initially as the tube continues to crush. When the tube is compressed into a block, these series of bend get in contact with each other and undergo compression as they now come into line of action, till the tube is completely crushed to a plate.
Case 6: Another notch is added to the opposite face with same setup.
Similar to the previous case another notch is added to the opposite face of the tube using ‘move node’ option. The notches are randomly placed around the middle
of the lower half of the tube.
After stimulation completes we have look into open Crash_tube_0000.rad in note pad and check energy errror and mass error using default value , energy error and mass error had been highlighted using sketch.
Energy error in the basic stimulation case is -4.3%
Energy error is accepted upto 15%
Mass error =0.000
Next move to hyperview For run the stimulation select h3d file - open,
Click contour - Resultant type as displacement - Apply
Maximum displacement at node 765 is 2.555E+02
Minimum displacement at node 765 is 0.000E+00
Instead of displacement select - von mises - apply.(it will shows different stress of each and every element)
Maximum vonmises peak is 6.129E-01 in node 1985
Minimum value is 0.000E+00 in node as 765
The contact forces are significantly lower than a single notched tube as even though the placement could be better, two notches result in a more uniform compression
and bending of the tube. Other outputs are similar to single notched tube.
Next move to hyper graph 2D ,For run the graph select To1 file - open
plot the graph for Global variable as Internal energy and kinetic energy,hoursglass energy, total energy,contact energy
There is close to no difference between the single and two notches tube energy plots, similarimmediate compression around the notch is recorded.
Plot the rigid wall - 3 rigid wall - total resultant force
In previous it consist of one notchs placement on the tube here notchs are placed on both the side, such kind of bent metal are formed on either side of the notchs. In this case the notch is nearbottom and so instead of 2 only a single bulge is formed and the bottom end collapses.
simiarly best is formed in the top of tube also.
Conclusion:
The results given in first 2steps has nothed tube and boundary conditions which gives an least contact force output, where Internal energy of system is the mirror value for K.E.
In previous slide where zero notched tube with an boundary condition ,which gives least outputs for an contact energy ,however the comparsion and stresses are non uniform.
The plastic strain across these cases are within the limits .
A notched tubes gives an higher contact forces ,but an smoother transmission of load had been seen. These symmentrial notch tubecan undergoes predictable compression a head with similar size it had bulged to prevent any formation of loads.
When the input parameter has zero notched on crash tube with type 7 andtype 11 contact ,which gives an perfect results.