Assignment 2

Objetive: To answer the questions that were asked in the challenge.

Questions:

1) Check the material properties of the rail component and calculate the speed of sound in steel rail.

Ans.

* The material properties of the rail component as seen from the "engine input file" that is -

" FIRSTRUN_0000.rad " = are as shown below:


## Material Law No 2. JOHNSON-COOK / ZERILLI-ARMSTRONG ELASTOPLASTIC
##--------------------------------------------------------------------------------------------------
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#- 2. MATERIALS:
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
# E Nu
# a b n EPS_max SIG_max0
# c EPS_DOT_0 ICC Fsmooth F_cut
# m T_melt rhoC_p T_r
/MAT/PLAS_JOHNS/1
Steel
# RHO_I
0.0078 0.0
210000.0 0.29
180.0 450.0 0.5 0.0 350.0
0.0 0.0 0 0 0.0
0.0 0.0 0.0 0.0
##--------------------------------------------------------------------------------------------------

* The Speed of sound in steel is given by

= under root of (Elasticity of the material / density of the material)

= `root` (E/`rho`)

= `root` (210,000/0.0078)

= 5,188.745216627708 second

2) The length of the rail is 1000 mm. Calculate the time it takes for a shock wave to travel from one end of the rail to the other.

Ans.

Time = distance / speed

Time = 1000/5,188.745216627708

Time = 0.1927248223318863‬ second

3) Time for sound to travel length of rail = ____?

Ans. 0.1927248223318863 second

4) Edit the engine file so that the stress wave can be monitored , moving from one end of the rail to the other during impact – this will require termination time equal to the time it takes for the sound to travel the length of the rail (set on / RUN card).

new value = 0.19272482233188

5) Set the frequency of the animation output to a time that will give 20 animation steps (/ANIM/DT)

Animation frequency = total runtime / animation steps

Animation frequency = 0.19272482233188 / 20

Animation frequency = 0.009636241116594‬

6) Change /print – 10

new value = -10

*Answer to the questions 4,5 and 6, can be seen in the screen shot of the edited engine file, is shown below:

7) 3D meshing tetra mesh and hex mesh:

Quality criteria :

model 1 ) target tetra element length sizes: 5 mm
minimum length size : 3.5mm
maximum lentgth size : 7mm
Tet collapse: 0.15

model 2 ) target hexa element length sizes: 10 mm

Procedure:
1) The provided first model contains two different
components, which is needed to segrigate. To seperate the components, i used
mask option to highlight the inner component and then made a new compnent id
for the same and then moved the component into the respective id. The options
that i used are:

(tools > mask > surfaces > (select by attached) > click "mask" > return )

(tools > organise > collectors > select surfaces > make a new component id
and select it > click move)

here are the pictures shown below for the procedure done:

*later i changed the component name to housing part 1 and 2

2) I checked for any topological errors and distorted geometry portions.
There were some portions of the geometry near the corners where the
geometry was either distorted or misaligned or improper. I used the
(Geometry > autocleanup option) and at some places i did it mannualy
with the (Geometry > edge edit option). Checked again for the errors
if any.

3) defeaturing small fillets and edges. Some of the edges and fillets were too short and closely present which could lead to minimum length errors, after meshing. I checked the distance between any two closely situated cutlines and featurelines and used the defeature option on it.

go to geometry > defeture > surface/edge fillets > select edges > click delete

featured- defeatured -

3)check for solids

-checked for presence of solids inside the surfaces of components, some had just surfaces and some had only surfaces and some had surfaces and solids.

- components which had just surfaces, solids can be formesd with the help of option:

(Geometry > solid > bounding surfaces > select surfaces > click create )

4) Change the quality criteria for meshing parameters with the given values by going to the
following menu :
-for 2d mesh and then converting it to 3d, go to

(2D > Automesh > QI optimize > edit criteria (put values) > select surface > mesh )
select surfaces and press mesh.

-For tetra mesh (direct 3d mesh)

(3D > tetra mesh > (go to tetramesh peramater if required to change) > select option components or elements (select elements if you want to make 3d mesh from 2d mesh (2d should be present already) > click mesh )

the meshed components are shown below:

5) Tried to solve maximum of the quality criteria errors, such as min length,
maximum length, skew, etc.
did some mesh flow correction with the options shown below.

(press F10 for check elem option and check for errors such as minimum length and max length and tet colapse)

6) Similarly, i used different options, for the creation of hexa mesh, such as the options marked in the picture below.

the screen shots of the on going model changes can be seen below:

*through element offset in 3D menu:

*through spin command in 3D menu:

*through solid map command in 3D menu:

*at the end, i used equvelence command (press F3), to join all the miss aligned nodes as seen in the picture below:

Result: All the models after 3d meshing are shown below

a)

tetramesh for model - housing

b) hexamesh for model 2

Conclusion : In this challenge i learned the folloing points:

*significance and functioning of starter input (0.rad) and engine input (1.rad) files.
*editing starter input and engine files.
*suppress and unsuppress the lines for preparing geometry for meshing.
*joining elements which were meshed seperately before.
*improoving mesh flow.
*meshing with tetrahedron and hexahedron elements.