Assignment 4- Crash Worthiness Analysis using Hypermesh and Radioss
Assignment 4- Crash Worthiness Analysis using Hypermesh and Radioss
Objective - To analyse different types of material properties and compare their results with the same boundary conditions.
Compare 7 cases as discussed in last 3 slides, in a tabulated format on the basis of:
1. Total number of cycles, Energy error, mass error and simulation time.
2. Notice the animation of all 5 and describe the animations in brief on the
basis of whether the elements are being deleted or cracked.
3. Plot energies and notice any difference.
4. Based on all the results, which case would represent the on-field
scenario.
5. Prepare a ppt/Docx and list down case by case result and your conclusion
as to why the failure happened.
Presentation
https://drive.google.com/open?id=1KCxJvLxBKxgN1kNt5Yr8e14Vfr0Z5nf2
Folder Content
https://drive.google.com/open?id=13ooQ2X5H9AHiezq2aU5qqXRri9AuHUhHk
Case 1 - M2_PLAS_JOHNS_ZERIL
In this case, the material is considered to be elastoplastic with input parameters given to the question of that Fail_Johnson card is added which helps with capturing the stresses under compression. The input parameters such as eps_p_max, sigma_maxo, a, b, n are already filled in. Here, my role is to input the improved shell element properties as we discussed previous assignment for the 2D shell elements. The recommended inputs for a non-linear analysis were added as follows,
Image 1 Material Image 2 Shell Properties
Now, as per this inputs, I can Solve this into Radioss,
First I open M2_PLAS_JOHNS_ZERIL_0000.rad file into Notepad and check the material Properties.
Open file in Notepad 'M2_PLAS_JOHNS_ZERIL_0001.out'
Maximum energy error in this base simulation case is 0.2%
Energy error is acceptable up to 15%
Therefore positive signal for further simulation
Maximum mass error is 0.000
1.Displacement
In geometry, displacement is a vector whose length is the shortest distance from the initial to the final position of a point P undergoing motion. It quantifies both the distance and direction of the net or total motion along a straight line from the initial position to the final position of the point trajectory. A displacement may be identified with the translation that maps the initial position to the final position.
A displacement may be also described as a relative position resulting from the motion, that is, as the final position xf of a point relatively to its initial position xi. The corresponding displacement vector can be defined as the difference between the final and initial positions:
- `{\displaystyle {s}={x_{\textrm {f}}-x_{\textrm {i}}}=\Delta {x}}`
Maximum Displacement at node no. 3598 is 2.75E+01 and
Minimum Displacement at node no. 3697 is 0.000E+00
2. Von Mises yield Criterion
The von Mises yield criterion (also known as the maximum distortion energy criterion[1]) suggests that yielding of a ductile material begins when the second deviatoric stress invariant {\displaystyle J_{2}}
reaches a critical value.[2] It is part of plasticity theory that applies best to ductile materials, such as some metals. Prior to yield, the material response can be assumed to be of a nonlinear elastic, viscoelastic, or linear elastic behaviour.
The Von mises stress plot shows a peak value is 2.876E+02 at node 3575 and Minimum Value is 0.000E+00
3.Velocity
Velocity is defined as a vector measurement of the rate and direction of motion. Put simply, velocity is the speed at which something moves in a particular direction, such as the speed of a car traveling north on a major freeway, or the speed a rocket travels as it launches into space. The scalar (absolute value) magnitude of the velocity vector is the speed of the motion. In calculus terms, velocity is the first derivative of position with respect to time. You can calculate velocity by using a simple formula that uses rate, distance, and time.
Maximum Velocity is 2.803E+01 at node 3598 and Minimum is 000E+00 at node 3635
4. % Thickness Reduction Calculated
Maximum %Thickness Reduction is 7.392E+00 and the minimum is -1.169e+01 at node 3896
5. Plastic Strain along the thickness
Maximum Plastic Strain is 1.502E-01 at node 3863 and Minimum is 0.000E+00
5. If acceptable, Plot rigid wall forces, internal energy, hourglass energy, contact energy, the total energy of the simulations.
Graph 1 - Internal Energy, Kinetic Energy, Contact Energy, Hourglass Energy and Total Energy
Graph 2 Total Resultant Force Vs Normal Force
Case 2- Law 2 with fail-Johnson and crack visualization
In this case, a few parameters are added to the defined case 1to visualize checking or braking down of elements with the help of 'Ixfem' option in Fail-Johnson failure model card. The necessary changes were made in the parameters as follows,
Folder Name: CASE 2
File Name - FAILURE_JOHNSON_0000_0000.rad using Notepad
Open file in Notepad 'FAILURE_JOHNSON_0000_0001.out'
Maximum energy error in this base simulation case is 4%
Energy error is acceptable up to 15%
Therefore positive signal for further simulation
Maximum mass error is 0.000
1. Displacement
Maximum Displacement at node no. 3984 is 1.327E+01 and
Minimum Displacement at node no. 3697 is 0.000E+00
2. Von Mises yield Criterion
The Von mises stress plot shows a peak value is 2.947E+02 at node 4380 and Minimum Value is 0.000E+00 at node 3697
3.Velocity
Maximum Velocity is 2.311E+01 at node 3598 and Minimum is 000E+00 at node 3635
4. % Thickness Reduction Calculated
Maximum %Thickness Reduction is 9.908E+00 at node 56316 and minimum is -1.325E+01 at node 3949
5. Plastic Strain along the thickness
Maximum Plastic Strain is 1.489E-01 at node 3863 and Minimum is 0.000E+00
Graph 1 - Internal Energy, Kinetic Energy, Contact Energy, Hourglass Energy and Total Energy
Graph 2 Total Resultant Force Vs Normal Force
Case 3 - Law Johnson card without Fail
In this case, the material model is same in case elastoplastic but the failure model card s removed to look for any difference in results. Hence, the Plas-Johnson card has deleted and the simulation was done, As we know the law material model is not capable of simulation compression under forces with realistic results. Plas-Johnson card is recommended addition.
Open file in Notepad 'Law2_espmax_nofail_0001.out'
Maximum energy error in this base simulation case is 0.8%
Energy error is acceptable up to 15%
Therefore positive signal for further simulation
Maximum mass error is 0.000
1.Displacement
Maximum Displacement at node no. 3844 is 1.858E+01 and
Minimum Displacement at node no. 3697 is 0.000E+00
2.Von Mises Stress
The Von mises stress plot shows a peak value is 2.705E+02 at node 3812 and Minimum Value is 0.000E+00
3. Velocity
Maximum Velocity is 2.793E+01 at node 3868 and Minimum is 000E+00 at node 3635
4. % Thickness Reduction Calculated
5.Plastic Strain along the thickness
Graph 1 - Internal Energy, Kinetic Energy, Contact Energy, Hourglass Energy and Total Energy
Graph 2 Total Resultant Force Vs Normal Force
Case 4 Law 2 with infinite eps_p_max value
In this case 4, the eps_p_max which defines the maximum permitted plastic strain is changed to '0' which input value of 10^3 as default. This makes the material to behave like deal Elastoplastic such that strain is computed but not failure due to plastic deformation beyond the limit is experienced.
Import file - 'Law2_0000.rad'
Open file in Notepad 'Law2_0001.out'
Maximum energy error in this base simulation case is 1.1%
Energy error is acceptable up to 15%
Therefore positive signal for further simulation
Maximum mass error is 0.000
1.Displacement
Maximum Displacement at node no. 3999 is 5.629E+00 and
Minimum Displacement at node no. 3697 is 0.000E+00
2.Von Mises Stress
The Von mises stress plot shows a peak value is 2.5316E+02 at node 3574 and Minimum Value is 0.000E+00
3. Velocity
Maximum Velocity is 3.031E+01 at node 3688 and Minimum is 000E+00 at node 3635
4. % Thickness Reduction Calculated
Maximum %Thickness Reduction is 5.429E+00 and the minimum is -1.169e+01 at node 3896
5.Plastic Strain along the thickness
Graph 1 - Internal Energy, Kinetic Energy, Contact Energy, Hourglass Energy and Total Energy
Graph 2 Total Resultant Force Vs Normal Force
Case 5: Law 1 Elastic Material
Here, the material is elastic as an ideal elastic which linearly follows hooks law up to the elastic limit and when the goes a plastic stage throughout any stress no matters the magnitude. The basic E, nu, Rho Parameters are input and the analysis is done. Here no plasticity is expected from the component material.
import file 'Law1_0000.rad'
Open file in Notepad 'Law1_0001.out'
Maximum energy error in this base simulation case is 0.3%
Energy error is acceptable up to 15%
Therefore positive signal for further simulation
Maximum mass error is 0.000
1. Displacement
Maximum Displacement at node no. 3688 is 4.999E+00 and
Minimum Displacement at node no. 3697 is 0.000E+00
2.Von Mises Stress
The Von mises stress plot shows a peak value is 1.086E+02 at node 3688 and Minimum Value is 0.000E+00
3. Velocity
Maximum Velocity is 9.881E+01 at node 3902 and Minimum is 000E+00 at node 3635
4.% Thickness Reduction Calculated
Maximum %Thickness Reduction is 4..584E+00 and the minimum is -1.169e+01 at node 3896
5.Plastic Strain along the thickness
Graph 1 - Internal Energy, Kinetic Energy, Contact Energy, Hourglass Energy and Total Energy
Graph 2 Total Resultant Force Vs Normal Force
Case 6: Law 27 Plas_Brit Material
In this case, the material is Plas_brit which is an elastic-Plastic Material with additional parameters to define in nature of material such as eps_t1, t2, eps_f1, f2 eps_m1, m2, and dmax1, 2 which are a tensile failure in strain. Maximum tensile failure , tensile strain at element detection and maximum tensile damage to limit in two directions. To start with Law 27 is nothing but Law 2 with additional parameters hence, much detail analysis can be done.
Import File-'Law27_0000.rad'
Open file In Notepad'Law27_0001.out'
Maximum energy error in this base simulation case is 1.1%
Energy error is acceptable up to 15%
Therefore positive signal for further simulation
Maximum mass error is 0.000
1.Displacement
Maximum Displacement at node no. 3990 is 6.013E+00E+00 and
Minimum Displacement at node no. 3697 is 0.000E+00
2.Von Mises Stress
The Von mises stress plot shows a peak value is 2.76E+02 at node 3820 and Minimum Value is 0.000E+00
3.Velocity
Maximum Velocity is 6.906E+01 at node 3990 and Minimum is 000E+00 at node 3635
4.% Thickness Reduction Calculated
Maximum %Thickness Reduction is 6.669E+00 and the minimum is -1.169e+01 at node 3896
5.Plastic Strain along the thickness
Maximum Plastic Strain is 1.689E-01 at node 3697 and Minimum is 0.000E+00
Graph 1 - Internal Energy, Kinetic Energy, Contact Energy, Hourglass Energy and Total Energy
Graph 2 Total Resultant Force Vs Normal Force
Case 7: Law 36 Plas_Tab Material
In this material model, the input parameters previously discussed eps_p_max, eps_m and eps_f in a single direction are defined. The important feature of the model is a user can input a stress v/s strain Plot as a curve and callit in the card from which the strain rate parameter is capturing. also, scaling factor, hardening coefficients etc can also be added to give further details for better analysis. The necessary inputs ere gathered from video lecture 6 and 7 were to added mode.
Import File'Law36_0000.rad'
Open File in Notepad 'Law36_0001.out'
Maximum energy error in this base simulation case is 4.2%
Energy error is acceptable up to 15%
Therefore positive signal for further simulation
Maximum mass error is 0.000
1.Displacement
Maximum Displacement at node no. 36880 is 5.000E+00E+00 and
Minimum Displacement at node no. 3697 is 0.000E+00
2.Von Mises Stress
The Von mises stress plot shows a peak value is 3.03E+02 at node 3688 and Minimum Value is 0.000E+00
3.velocity
Maximum Velocity is 1.404E+01 at node 3594 and Minimum is 000E+00 at node 3635
4. % Thickness Reduction Calculated
Maximum %Thickness Reduction is 4.589E+00 and the minimum is -9.229e+01 at node 3626
5. Plastic Strain along with the thickness
Maximum Plastic Strain is 5.94E-01 at node 3688 and Minimum is 0.000E+00
Graph 1 - Internal Energy, Kinetic Energy, Contact Energy, Hourglass Energy and Total Energy
Graph 2 Total Resultant Force Vs Normal Force
Conclusion:
As stated, in summary for the current problem where the material in question is Aluminium alloy case 1, case 6 and with proper inputs case 7 will give out realistic results. Law 27-Plas_brit material model is the best option with given inputs with more detailed results than Law 2-Elastoplastic with Fail_Johnson card. At last Plas_tab material model being sensitive to its inputs(Stress v/s strain curve), Plastic strain parameters could be another option but need accurate data preferably from physical testing.