Assignment 2

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

The Speed of Sound:

Sound travels at different speeds depending on what it is traveling through. Of the three mediums (gas, liquid, and solid) sound waves travel the slowest through gases, faster through liquids, and fastest through solids. Temperature also affects the speed of sound.

From the FIRST_RUN_0000 rad file

We find the following values:

Young’s Modulus = 210000.0

Density = 0.0078

The unit system followed in these file is g,mm,ms

From this we can calculate the remaining units

Force N = Kgm/s²

= (1000g x 1000mm)/(1000ms)²

= g.mm.(ms)^-2

Density = Kg/m³

= 1000g/(1000mm)³

= 10^-6g/mm³

Calculated units:

Young’s Modulus = 210000.0 g.mm.(ms)^-2

Density = 0.0078 g/mm³ (SI unit 7800 kg/m³ x 10^-6 )

Speed of sound in air =

√E/ρ

√(210000/0.0078)

= 5188.7 g/ms

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

In the context of explicit analysis, time step is the time required for a shock wave to propagate across the smallest distance of the element. A run is a single model simulation and it starts at time zero and continues till the user defined endpoint is reached. The basic time unit in the run is the time step.

The time step is directly dependent on the length of the element and inversely proportional to the speed of sound of material. The speed of sound of the material is dependent on both material modulus and density of the material. So, if the material is stiffer (higher modulus of elasticity), the speed of sound increases resulting in a lower solution time step.

L is the length of the steel rail

c is the speed of sound in air.

From the above result, we find

L = 1000 mm

c = 5188.7 mm/ms

∆t=L/c

∆t=1000/5188.7

= 0.192 ms

Thus, the time takes for a shock wave to travel from one end of the rail to the other is 0.192 ms.

3.Time for sound to travel length of rail = 0.192 ms

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

Open the hypermesh file

Import the engine file,

Go to View - Solver Browser -Run - Engine Run

Change the time step to Tstop to 0.192

5. Set the frequency animation output to a time that will give 20 animation steps

Since we need 20 animation steps, we need to divide the time 20

The total time is 0.192ms

T_freq = 0.192/20

T_freq = 0.0096ms

Change the T_freq to 0.0096

Go to Engine keywords - Anim - Anim/DT - Eng Anim/DT

Set T_freq to 0.0096

6. Change /print -10

7. 2D Meshing

Check the element quality for the three components, 2D meshed and repair where needed

Repair if required Imax = 7, Imin = 3.5 Aspect , Skew 60, Jacobian 0.5 Warpage 15, Tria Angles 20 to 120, quad angles 40 to 140

Open the model

There are four components, we can start with bottom base part

Seperate the base part into proper rectangles, so that the element size will be uniform

Take only the bottom part , hide the remaining parts by using mask opton or press F5

Mesh the component

Go to 2D page , select automesh set element size to 10,set the type as quad, set surface as rectangle

From the 2d mesh, generated on the surface ,apply the mesh along the depth,

Go to 3d page, solid map - line drag - select the elements , lines to drag, set the element size to 10,

Unmask the arm curve

Create a node at the centre of the curve,

Go to Geom-nodes- arc, center

Select the curve and a node is created at the center.

In order to mesh the arc curve

Go to 3d - spin, select the elements , center node ,drag lines, & keep the element size to 10.

Also click on equiv/faces to genrate faces

In order to mesh the arm straight , mesh the front face of the arm straight with the same number of elements

GO to 3d solid map,select the source elements, destination elements,and same 3 nodes for the both the faces for the direction,N1,N2,N3

Generate faces for the above mesh

In oder to mesh the boss,from the arm straight , project nodes on the edges of the boss

Go to 2d ,use drag, select the nodes & edges, create the elements

Similarly project nodes on sides & create the elements

Go to 3d, solid map select the source & destination surface,elements, & along geom-mixed,select the nodes, give the elements size

Top half suface of the boss is meshed

Go to 3dsolid mesh - line drag ,select the elements, & drag lines & element size as 10

Also click on equiv/faces

Use reflect to mesh the remaining half of the mesh

Open the next component, creat solid from these surfaces,

Go to geom-solids-bounding surfaces,click on create

To check , view by 3d topology

Mesh the outer surface , 2d- Automesh,size 5, types as trias

The outer surface is meshed

In order to mesh inner portion, go to 3d-tetrameshsh

Check the quality of the elements, tet collapse,jacobian,& aspect ratio

237 elements failed,in order to fix that, click on save failed,

Go to mask-elements-retrieve-mask-reverse

Go to F5 - find attached-select the elements & remesh it

Again check the quality

Repeat the above steps, such as mask,find attached & remesh

The component is now meshed completely with zero elements failed.

The same procedure is repeated for hub 3d tria is generated

Check for element quality

Mask failed elements & find attached elements

Remesh those elements

Finally check for quality