Vizzini Simone

Description of the problem

Simone Vizzini

The task of the exercise is to study the:

• temperature distribution

• the structural deformation of the dashboard

surface when part of it is subjected to direct sun

light.

Description of the problem

Material

used:

Simone Vizzini

Polypropylene

E [Gpa] ν ρ [kg/m3]Thermal

Expansioncoefficient [1/C°]

ThermalConductivity

[W/mC°]

HeatTransfer

coefficient [W/m2C°]

1.8 0.45 946 150 e-6 0.16 25.4

Dashboard property:

– thickness t= 2.5 mm

Steel

210 0.3 7800 1 e-5 73 40

Description of the problem

Loading condition.It is suggested to reach the target following some

intermediate steps:

• to obtain the temperature on the dashboard due to

convection with the inner temperature of the cockpit,

• to apply a heat flux of 400 W/m2 to part of the

dashboard in order to simulate the sun light (heat flows

in the dashboard material by conduction),

• to define a coupled thermo-structural analysis and to

analyse the stress/strain distribution on the dashboard.

Simone Vizzini

Creation of the model

Simone Vizzini

Import the geometry

Creation of the model

Simone Vizzini

Move some surface from dashboard to air tunnel

– [tool-organize]

Creation of the model

Simone Vizzini

Create the Material and insert the specific

properties

– [card image:MAT1 and MAT4 for thermal properties]

Creation of the model

Simone Vizzini

Create the “Properties” and assign to the

components

• [card image:PSHELL, choose the material and define

the thickness]

Creation of the model

Simone Vizzini

Create the mesh and merging the common

nodes

– [2D-automesh, tool-edges]

Creation of the model

Simone Vizzini

Create the constraint point

– create the master nodes [geom-nodes]

– connect to the dashboard [1D-rigids]

Creation of the model

Simone Vizzini

Create the convection heat exchange surface

– [analysis-interfaces]

Creation of the model

Simone Vizzini

Create the internal heat source, creating a constraint node with the specific initial T and assign to to the dashboard

– [geom-node, analysis-constraint, card edit-insert the inner T ]

Creation of the model

Simone Vizzini

Constraint all the air-tunnel nodes and assign

the initial T

– [analysis-constraints, card edit-insert the T ]

Creation of the model

Simone Vizzini

Create the load-step and Simulate

Creation of the model

Simone Vizzini

Create the conduction heat exchange surface,create the flux, update the loadstep adding the flux to the laod and Simulate

– [analysis-interfaces]

– [analysis-flux]

Creation of the model

Simone Vizzini

Create the constraints for the master nodes.

– [analysis-constraints]

Create a generic load-step for the thermal stress

Simulate

Results

Temperature due to convection with

dashboard made of polypropylene

Simone Vizzini

Results

Temperature due to convection with

dashboard made of steel

Simone Vizzini

Results

Temperature due to convection and sun light

with dashboard made of polypropylene

Simone Vizzini

Results

Temperature due to convection and sun light

with dashboard made of steel

Simone Vizzini

Results

Strain distribution due to convection and

sunlight with dashboard made of polypropylene

Simone Vizzini

Results

Strain distribution due to convection and

sunlight with dashboard made of steel

Simone Vizzini

Results

Stress distribution due to convection and

sunlight with dashboard made of

polypropylene

Simone Vizzini

Results

Stress distribution due to convection and

sunlight with dashboard made of steel

Simone Vizzini

Results discussion

Temperature due to convection:

– in both cases, polypropylene and steel, we can see

that the temperature of the dashboard achieved

without the sunlight is 30 C , i.e. the internal

temperature, except for some points in the

polypropylene simulation that achieve a slightly

higher temperature due to maybe a simulation

errors. The difference in the two cases is the

temperature field near the air-tunnel. Because of

the steel has an higher thermal conductivity we can

see an bigger aerea with a temperature ranging

from 10 C (air-tunnel T ) and 30 C (internal T ),

while with poly this boundary area is very limited.

Simone Vizzini

Results discussion

Temperature due to convection and sun-light:

– again, like in the previous simulation, we ca see

that the steel is better in distribute the heat in the

all surface. the temperature distribution is more

uniform and we have a maximum value of 39 C

– in the poly dashboard the sun light tends to

increase, up to 49 C , the temperature of the upper

part.

Simone Vizzini

Results discussion

Stress/Strain due to convection and sun-light:

– from the simulation we can see that with steel we

have lower displacement and higher stress near

the constraint points because of the E modulus is

much higher than the poly one.

Simone Vizzini

But just think to a 2.5mm steel dashboard

without the flexibility in shape of the

polypropylene?? It’s a crazy thing.