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Bulging of Insulating Glass Units - Numerical and Experimental Analysis

Martin, Andersson and Simon, Nilsson (2014) In TVSM-5000 VSM820 20141
Structural Mechanics
Department of Construction Sciences
Abstract
Insulating glass unit (IGU) is separated double or triple glass panes with closed cavities in between, usually filled with argon to reduce the heat transfer. When a construction like this is exposed to temperature variations the volume of the gas will change and pressure changes will occur. The glass panes will bulge which will give displacements and stresses in the glass panes. For large dimensions of the insulating glass along with large temperature variations give a high bulge of the glass panes but the stresses are relatively small. For small dimensions the bulging of the glass panes are smaller but the stresses can be so high that the glass must be toughened. The change of atmospheric pressure can also increase the bulging of the... (More)
Insulating glass unit (IGU) is separated double or triple glass panes with closed cavities in between, usually filled with argon to reduce the heat transfer. When a construction like this is exposed to temperature variations the volume of the gas will change and pressure changes will occur. The glass panes will bulge which will give displacements and stresses in the glass panes. For large dimensions of the insulating glass along with large temperature variations give a high bulge of the glass panes but the stresses are relatively small. For small dimensions the bulging of the glass panes are smaller but the stresses can be so high that the glass must be toughened. The change of atmospheric pressure can also increase the bulging of the glass panes.

There is a demand for integrated blind in insulating glass. An integrated blind will not be in the way and it would ease the cleaning but during a cold day the integrated blind may be clamped between the glass panes due to the bulging. During an extremely cold day or a warm and sunny day the stresses in the glass panes can instead be so high that the glass may crack. There are many parameters affecting the bulging of the insulating glass e.g. the geometry, glass type and the magnitude of the load. These parameters were investigated in this thesis using modelling analyses and experimental analyses.

The temperature variation through the IGU was formulated with a 1D-FE model in the middle of the IGU. The average temperatures in the cavities were calculated and used in a finite element model made in Abaqus/CAE where the IGU was modeled. The difference from the initial temperatures and the temperatures in the cavities when the IGU was installed gave the pressure change calculated with the ideal gas law. The difference between the initial pressure in the cavities and the atmospheric pressure were used as an external load. The finite element model was used to determine the stresses and the displacements of the glass panes. The 1D-FE model and the finite element model were verified with experimental analyses in a climate chamber (Hotbox).

The temperature in the middle glass was approximately 1-2°C higher than the calculated temperature with the 1D-FE model, which is due to the heat transfer change as an effect of the bulging. When the IG units was exposed to cold temperature a remaining bulging occurred in glass panes of 1-4 mm on each side of the IG units. The total bulging of the finite element model was approximately 1 mm to high than the experimental tests neglecting the remaining bulging.

A parameter study was made changing parameters such as the geometry of the IGU, glass type and magnitude of the load. The choice of gas did not have a major effect on the bulging of the glass panes but it did have a big influence on the insulating capacity. The thickness of the glass panes was found out to have a big effect on the bulging. When the thickness of one glass pane was increased the bulging of that glass pane decreased but the bulging of the other two glass panes increased.

A regression model was carried out to fit a function to the modelled data which makes it possible to change the affecting parameters as the user wants. (Less)
Please use this url to cite or link to this publication:
author
Martin, Andersson and Simon, Nilsson
supervisor
organization
course
VSM820 20141
year
type
H3 - Professional qualifications (4 Years - )
subject
publication/series
TVSM-5000
report number
TVSM-5200
ISSN
0281-6679
language
English
id
8893854
alternative location
http://www.byggmek.lth.se/english/publications/tvsm-5000-masters-dissertations/tvsm-5200-5151/
date added to LUP
2016-10-21 15:20:54
date last changed
2016-10-21 15:20:54
@misc{8893854,
  abstract     = {Insulating glass unit (IGU) is separated double or triple glass panes with closed cavities in between, usually filled with argon to reduce the heat transfer. When a construction like this is exposed to temperature variations the volume of the gas will change and pressure changes will occur. The glass panes will bulge which will give displacements and stresses in the glass panes. For large dimensions of the insulating glass along with large temperature variations give a high bulge of the glass panes but the stresses are relatively small. For small dimensions the bulging of the glass panes are smaller but the stresses can be so high that the glass must be toughened. The change of atmospheric pressure can also increase the bulging of the glass panes.

There is a demand for integrated blind in insulating glass. An integrated blind will not be in the way and it would ease the cleaning but during a cold day the integrated blind may be clamped between the glass panes due to the bulging. During an extremely cold day or a warm and sunny day the stresses in the glass panes can instead be so high that the glass may crack. There are many parameters affecting the bulging of the insulating glass e.g. the geometry, glass type and the magnitude of the load. These parameters were investigated in this thesis using modelling analyses and experimental analyses.

The temperature variation through the IGU was formulated with a 1D-FE model in the middle of the IGU. The average temperatures in the cavities were calculated and used in a finite element model made in Abaqus/CAE where the IGU was modeled. The difference from the initial temperatures and the temperatures in the cavities when the IGU was installed gave the pressure change calculated with the ideal gas law. The difference between the initial pressure in the cavities and the atmospheric pressure were used as an external load. The finite element model was used to determine the stresses and the displacements of the glass panes. The 1D-FE model and the finite element model were verified with experimental analyses in a climate chamber (Hotbox).

The temperature in the middle glass was approximately 1-2°C higher than the calculated temperature with the 1D-FE model, which is due to the heat transfer change as an effect of the bulging. When the IG units was exposed to cold temperature a remaining bulging occurred in glass panes of 1-4 mm on each side of the IG units. The total bulging of the finite element model was approximately 1 mm to high than the experimental tests neglecting the remaining bulging.

A parameter study was made changing parameters such as the geometry of the IGU, glass type and magnitude of the load. The choice of gas did not have a major effect on the bulging of the glass panes but it did have a big influence on the insulating capacity. The thickness of the glass panes was found out to have a big effect on the bulging. When the thickness of one glass pane was increased the bulging of that glass pane decreased but the bulging of the other two glass panes increased.

A regression model was carried out to fit a function to the modelled data which makes it possible to change the affecting parameters as the user wants.},
  author       = {Martin, Andersson and Simon, Nilsson},
  issn         = {0281-6679},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVSM-5000},
  title        = {Bulging of Insulating Glass Units - Numerical and Experimental Analysis},
  year         = {2014},
}