The Nature of Glass
Glass is a totally brittle substance. It will bend a very small amount, but has no capacity like most metals to deform. It will bend to a point and then break. It is this bending stress that is the focus for calculating the thickness.
Glass also has a wide variability in strength. Testing samples of uniform manufacture has proved this (see specifications for glass, - Tensile Strength 19.3 to 28.4MPa).
Glass is weak in tension, is elastic up to its breaking point, and has no ductility. It is not capable of being permanently deformed, and does not give any pre-warning of impending failure by showing a permanent set after an excessive load has been removed.
An important characteristic is its ability to carry an impulse load approximately twice its rated load (i.e. banging the aquarium with your hand quite hard). This is inevitably what saves many aquariums when they are accidentally knocked.
The variability of the strength of glass due to limitations of the manufacturing process means a suitable safety factor must be used when calculating glass thickness. The factor commonly used is 3.8. While not a perfect guarantee, it will remove all risk bar that of damaged or very poor quality glass. The main damage that will cause failures is scratches and chips. Also a point load on the glass surface will cause it to fail. For this reason a soft packer like polystyrene is used under aquariums to stop the point loading of dirt and grit.
Also when manufacturing an aquarium, the joining compound (commonly silicone) must have a minimum thickness (0.5-1mm) to allow for irregularities along the glass edge. When glass is cut it is not flat along its edge unless it has been specially ground.
It is possible to use a lower safety factor if the glass is of excellent quality and has no internal stress. It is at the designers risk however to lower the safety factor
Toughened glass is considerably stronger than standard glass. It cannot however be cut. If toughened glass is to be used it must first be cut to size, have its edges finished and then be send away for toughening. The thermal resistance properties of glass are also improved by toughening. Standard 6mm glass will rupture if plunged into water at 21’C if the temperature of the glass is more than 55’C hotter or colder. Toughened glass will rupture at approximately 250’C difference. Toughened glass also has a tensile strength greater than 5 times that of standard glass. Standard glass has a very important advantage when used on aquariums. It tends to fail in a non-spectacular manner, - typically a vertical or diagonal crack. Toughened glass however will fail completely, much like the old style car windscreen (100% shattering).
Glass has a much lower coefficient of linear expansion that most metals. This is important if a metal frame is to be used as part of the structure of the aquarium. If so, the aquarium should be built and stored at a temperature similar to that which it will run at. The length of the aquarium will decide how much elasticity will need to be accommodated by the sealing compound used. Silicone Rubber is the most common sealing compound today. The thickness of the sealing layer needs to be changed as the seal length increases. A general rule of thumb is to allow 2-3mm per meter of joint length. This allows the silicone to take up the stretching forces between the glass and steel.
Glass Physical Characteristics:
Density:
Coefficient of linear expansion:
Softening Point:
Modulus of Elasticity:
Poisson’s ratio:
Compressive Strength:
Tensile Strength:
Tensile Strength (toughened glass):
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approx 2.5 at 21’C
86 x 10-7m/’C
730’C
69GPa (69 x 109 Pa)
Float Glass .22 to .23
25mm
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Lokve, Gorski Kotar Hrvatska
« Odgovori #15 u: Studeni 29, 2005, 23:06:00 poslijepodne »
kvadrat 10mm float stakla je 288 + škegro, a isto kaljeno 390 + škegro.... za cijenu kaljene 10ke mogu dobiti 12mm obično staklo (naravno + škegro  )
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Vraćam se odmah - Godot
« Odgovori #16 u: Studeni 30, 2005, 11:49:00 prijepodne »
A koje su prednosti kaljenog stakla u izradi akvarija? Ne trebaju ojacanja? Ako to pise na gore na engleskom, nemojte zamjeriti, ne ide mi engelski... 
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Kvatric tj. kilometar sjevernije / Zagreb
All the Dude ever wanted was his rug back... it really tied the room together...
« Odgovori #17 u: Studeni 30, 2005, 12:04:00 poslijepodne »
kakav ti je avatar, rekli bi ljudi da nisi ni sa hrvatskim doma
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Vraćam se odmah - Godot
« Odgovori #18 u: Studeni 30, 2005, 12:08:00 poslijepodne »
pa Juwel Visioni su napravljeni od kaljenog stakla ... kaj vam se to ne sviđa ???
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« Odgovori #19 u: Studeni 30, 2005, 12:29:00 poslijepodne »
Meni ne. Jel trebaju ojacanja ako ide kaljeno? Jel ide tanje staklo ako je kaljeno? A sto se hrvatskog tice... a ucim...
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Kvatric tj. kilometar sjevernije / Zagreb
All the Dude ever wanted was his rug back... it really tied the room together...
« Odgovori #20 u: Studeni 30, 2005, 17:51:00 poslijepodne »
Onda nek ti frend objasni kako to da su akvariji na veterinarskom
fakultetu, piranha bar-u, bircu na remetincu itd... rađeni od kaljenog
stakla??
Taj kvrc mora bit malo jaèi da bi se sve raspuklo... kaljno je sasvim pogodno za akvarije, no i skuplje je.
@stina Mislim da je to tako radi osiguranja od mogucnosti tuzbe a ne kvalitete. Mislim da kaljeno nema nikakve prednosti, to sto je cvrsce nema puno koristi ako mislis tu cvrscocu isprovati, odnosno ako mislis tuc akvarij ovecim cekicem onda ti je svejedno. Ako zahebes nesto s podlogom za akvarij ili postoljem ili slicno, nekako mi je draza opcija da akvarij procuri radi puknuca nego da dobijem 1001 komadic stakla i sav sadrzaj akvarija po sobi. Ako oces sigurnost uzmi ljepljeno staklo(auta koriste triplex za vjetrobran) i rijesio si problem, ali mislim da je to skupa opcija i neznam sto je s lomom svjetlosti odnosno kvalitetom boja (sigurno je losija ali je pitanje koliko) Edited by: Toce
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« Odgovori #21 u: Studeni 30, 2005, 19:30:00 poslijepodne »
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Lipik Croatia
« Odgovori #22 u: Studeni 30, 2005, 23:41:00 poslijepodne »
možda je tema već bila, al mi je promakla.... pa se ispričavam .... no sad mi je ta tema malo vruća i zato je tu thnx svima na informacijama sad ostaje pitanje... imam novce u đepu i treba otić kupit.....ŠTA????? (samo sad nemojte off-topic, a znam da je pitanje ko stvoreno ta to )
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Vraćam se odmah - Godot
« Odgovori #23 u: Studeni 30, 2005, 23:49:00 poslijepodne »
Za mali akvarij kaljeno je totalno nepotrebno, iako je puno bistrije na oko, pa se isplati recimo samo prednju šajbu od kaljenog napravit!
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« Odgovori #24 u: Studeni 30, 2005, 23:53:00 poslijepodne »
dobra ideja
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Vraćam se odmah - Godot
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Tema: kaljeno ili obično staklo za DIY akvarij (Posjeta: 11119 vremena)