Home / Examples / Stress Analysis [Galileo] / Example 51: Deformation of Viscoelastic Bar

Example 51: Deformation of Viscoelastic Bar


General

 

Analysis Space

Item

Settings

Analysis Space

3D

Model Unit

mm

 

Analysis Conditions

The bar is subjected to the temperature change below and over the glass transition temperature.

Select [Thermal Load].

 

Item

Settings

Solver

Stress Analysis [Galileo]

Analysis Type

Static Analysis

Options

Select Thermal Load
 

The Step/Thermal Load tab is set as follows.

Tab

Setting Item

Settings

Step/Thermal Load

Step Setting

Multi-step Thermal Load Analysis

Time Setting

Set up

Reference temperature

25 [deg]

Step/Reached Temperature Setting

Step

Time [s]

Substeps

Reached Temperature [deg]

1

60

5

25

2

3540

5

25

3

3600

5

25

4

3660

5

120

5

3720

5

120

6

7200

5

120

7

7260

5

120

 

Options for the Multi-Step Analysis

Save the results of substeps : Select

 

The reference temperature (non-stress temperature) is 25 [deg]

Time setting is required in the viscoelasticity analysis. Select [Multiple steps] for the step setting and [Set up] for the time setting,
and set the time, substeps, and reached temperature for the step/reached temperature setting.

 

Each step below consists of 5 substeps.

 

Step 1 : 60 [s] : The load is increased gradually for 1 min.

Step 2 : 3540 [s] : The load is sustained for almost 1 hour.

Step 3 : 3600 [s] : The load is decreased gradually for 1 min.

Step 4 : 3660 [s] : The temperature is increased to 120 [deg] in 1 min.

Step 5 : 3720 [s] : The load is increased gradually for 1 min.

Step 6 : 7200 [s] : The load is sustained for almost 1 hour.

Step 7 : 7260 [s] : The load is decreased gradually for 1 min.

 

Save results of substeps is selected by default to output all the results at substeps.

Model

The model is a box solid body with a thickness of 0.4 mm. The material is polystyrene.

 

Body Attributes and Materials

Body Number/Type

Body Attribute Name

Material Name

0/Solid

Plate

PS

 

The material properties for PS are set up as follows:

Material Name

Tab

Properties

PS

Elasticity

Material Type: Elastic/Isotropic

Temperature Dependency: None

Material Property:

Young's Modulus: 1.39x109 [Pa]

Poisson's Ratio: 0.35

Viscoelasticity

Defined by: Prony Series [Coefficient Input]

Relaxation Component: Shear Only

Relaxation Table:

 

Temperature Dependency and Shift Function: WLF

Reference Temperature: 113 [deg]

C1: 8.86

C2: 101.6

 

Coefficient of Linear Thermal Expansion

0X10-6-6 [1/deg]

Boundary Conditions

Boundary Condition Name/Topology

Tab

Boundary Condition Type

Settings

Fix_all/Face

Mechanical

Displacement

Select all X/Y/Z components.

UX=0, UY=0, UZ=0

Pz/Edge

Mechanical

Distributed Edge Load

Select [Set the total load].

X=0, Y=0, Z=-1.0x10-2

 

Select [Time Dependency] and set [Weight function] as follows.

This setting means the following.

60 [s] : The load is increased gradually for 1 min.

3540 [s] : The load is sustained for almost 1 hour.

3600 [s] : The load is decreased gradually for 1 min.

3720 [s] : The load is increased gradually for 1 min.

7200 [s] : The load is sustained for almost 1 hour.

7260 [s] : The load is decreased gradually for 1 min.

Results

Below are the diagrams of displacements at time 3540 s (about one hour after retaining the bending at 25℃) and

at time 7200 s (about one hour after retaining the bending at 120℃).

The magnitude of displacement is shown.

 

Displacement at 3540 [s] (Temperature: 25 [deg])

 

Displacement at 7200 [s] (Temperature:120 [deg])

 

The deformation is larger at 120 [deg], even though the mechanical load is the same as that of 25 [deg].

The graph below shows the displacement of the plate tip.

 

 

The displacement is constant at 25 [deg].

If unloaded, it returns to the original state.

The displacement increases at 120 [deg] even though the load is constant.

If unloaded, it doesn't return to the original state.