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Computational Method for Bulging in Insulating Glass Units

Svensson, Daniel LU (2015) In TVSM VSM820 20151
Department of Construction Sciences
Structural Mechanics
Abstract
An insulating glass unit (IGU) normally consists of two or three glass panes which are separated by a spacer. The spacer creates a cavity between the glass panes which is filled with a gas to increase the insulating capacity of the IGU. To keep the gas in the cavity and to stop vapor from getting in, the cavity has to be hermetically sealed. This makes the IGU sensitive to pressure change and volume change which may occur if the unit is subjected to temperature changes, changes in ambient pressure or lateral loads such as wind loads. Any of these load cases will inflict a change in the gas pressure that changes the cavity volume. When the gas pressure changes the glass panes will bulge and stresses will occur.

To study this problem a... (More)
An insulating glass unit (IGU) normally consists of two or three glass panes which are separated by a spacer. The spacer creates a cavity between the glass panes which is filled with a gas to increase the insulating capacity of the IGU. To keep the gas in the cavity and to stop vapor from getting in, the cavity has to be hermetically sealed. This makes the IGU sensitive to pressure change and volume change which may occur if the unit is subjected to temperature changes, changes in ambient pressure or lateral loads such as wind loads. Any of these load cases will inflict a change in the gas pressure that changes the cavity volume. When the gas pressure changes the glass panes will bulge and stresses will occur.

To study this problem a computational method was created with the finite element method. In the method, was a three dimensional model created to calculate the displacement and the stress in the glass that occurs when the unit is subjected to various loads. The computational method handles different dimensions of the IGU but is restricted to rectangular shapes. The method uses the ideal gas law to find the solution by iterations.

FE-models were also created in Abaqus to evaluate the developed method for different dimensions and load cases. The Abaqus model used hydrostatic fluid elements to represent the gas in the cavity. The difference between the Abaqus model and the computational method was small and a difference of 8% was the largest when comparing displacements.

The computational method was also compared with the results from the master thesis made by Martin Andersson and Simon Nilsson, who made experimental tests and FE-analyzes of insulating glass units subjected to temperature change. The developed method had a difference of 2-5 mm in comparison with the experimental results, which was similar to the difference between the experimental results and their FE-analysis. (Less)
Popular Abstract (Swedish)
Isolerglas består normalt av två eller tre separerade glasrutor. Mellan dessa skapas en kavitet som består av en fyllnadsgas för att öka den isolerande förmågan hos enheten. Kaviteten måste vara försluten för att
gasen inte ska sippra ut och för att förhindra att fukt ska trängas in i kaviteten. Detta gör att ett isolerglas är känsligt för tryck- och volymändring som kan uppstå om den blir utsatt för temperaturändring, ändring i omgivande tryck eller om en yttre last, så som vindlast, belastar isolerglasenheten. Om isolerglaset blir utsatt för något av dessa laster kommer en tryckändring ske i gasen samt att kavitetens volym kommer att ändras. En volymändring ger upphov till att glaset i isolerglasenheten får en deformation.
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author
Svensson, Daniel LU
supervisor
organization
course
VSM820 20151
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
IGU, insulating glass units, FEM, finite element method
publication/series
TVSM
report number
TVSM-5206
ISSN
0281-6679
language
English
id
7988404
alternative location
http://www.byggmek.lth.se/english/publications/tvsm-5000-masters-dissertations/
date added to LUP
2015-09-29 10:02:50
date last changed
2015-09-29 10:02:50
@misc{7988404,
  abstract     = {An insulating glass unit (IGU) normally consists of two or three glass panes which are separated by a spacer. The spacer creates a cavity between the glass panes which is filled with a gas to increase the insulating capacity of the IGU. To keep the gas in the cavity and to stop vapor from getting in, the cavity has to be hermetically sealed. This makes the IGU sensitive to pressure change and volume change which may occur if the unit is subjected to temperature changes, changes in ambient pressure or lateral loads such as wind loads. Any of these load cases will inflict a change in the gas pressure that changes the cavity volume. When the gas pressure changes the glass panes will bulge and stresses will occur.

To study this problem a computational method was created with the finite element method. In the method, was a three dimensional model created to calculate the displacement and the stress in the glass that occurs when the unit is subjected to various loads. The computational method handles different dimensions of the IGU but is restricted to rectangular shapes. The method uses the ideal gas law to find the solution by iterations.

FE-models were also created in Abaqus to evaluate the developed method for different dimensions and load cases. The Abaqus model used hydrostatic fluid elements to represent the gas in the cavity. The difference between the Abaqus model and the computational method was small and a difference of 8% was the largest when comparing displacements.

The computational method was also compared with the results from the master thesis made by Martin Andersson and Simon Nilsson, who made experimental tests and FE-analyzes of insulating glass units subjected to temperature change. The developed method had a difference of 2-5 mm in comparison with the experimental results, which was similar to the difference between the experimental results and their FE-analysis.},
  author       = {Svensson, Daniel},
  issn         = {0281-6679},
  keyword      = {IGU,insulating glass units,FEM,finite element method},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVSM},
  title        = {Computational Method for Bulging in Insulating Glass Units},
  year         = {2015},
}