iMac 5K Screen cracked by itself?

steelzeh

macrumors newbie
Original poster
Jun 3, 2014
9
0
I was using my pc last night and it was all fine, so today i come home from work, and notice my iMac's screen is cracked.

How the hell can it be cracked by itself? There was nobody home the whole day, no items were laying around the screen that could have cracked it.

It also doesnt look like anything has hit the screen, more like it got hot expanded and ruptured, even tho it has been turned off since 10 pm last night.

Here are the images (BIG ONES)
Right side of the screen around middle.


 

steelzeh

macrumors newbie
Original poster
Jun 3, 2014
9
0
It just sounds weird, as nobody was home (so they say) and it got cracked.
No signs of cracks yesterday.
 

purpletalon55

macrumors member
Apr 1, 2017
54
5
looks as if it cracked because maybe the screen was being pulled or held to tightly and it stress cracked.
 

cynics

macrumors G4
Jan 8, 2012
11,313
1,696
Something happened to the spot at one point in time. And Wednesday was the day the nick/imperfection in the glass decided to splinter. It was small enough that you likely just didn't see it.

Was there and drastic temp changes in that room on Wednesday (AC/Heat running for the first time in a long time)?
 

Maxx Power

macrumors 6502a
Apr 29, 2003
862
331
That's not necessarily impact. Glass cracking due to thermal stress can look like that too (in my research), with initiation at the edges and creeps inwards. The process is spontaneous, so there would not seem (to the naked eye) any immediate causal factor.

See https://www.pilkington.com/en-gb/uk/architects/glass-information/functions-of-glass/mechanicalfunctionsofglass/glass-and-thermal-stress

I quote: "Thermal Stress is created when one area of a glass pane gets hotter than an adjacent area. If the stress is too great then the glass will crack. The stress level at which the glass will break is governed by several factors. Toughened glass is very resilient and not prone to failing due to thermal stress. Laminated glass and annealed glass behave in a similar way. Thicker glasses are less tolerant. Glass containing wire is more vulnerable. The edge quality of the glass can play a part. Glass with damaged edges will take less stress than clean cut glass. A good clean cut edge is the best finish along with fully polished edges. Ground edges and arrissed edges may not be as good. A ground or arrissed edge is a series of small defects around the glass. The effect brings all the defects to an average level and may at best be only more predictable than a glass with more random damage."

So it is possible that your glass initially had some small, tiny defect at the site of the crack (which COULD be primary due to fabrication, or secondary due to usage), which eventually gave and fractured inwards following repeated heat-cooling cycles.