Surface Pro 3 bends by itself due to heat

[Perttu Lehtinen]

Discussion on Microsoft's forum:

http://answers.microsoft.com/en-us/...gbending/55cdc620-5117-47eb-8066-72e0a912cf93

There are multiple reports from different users, including me.

 

[ptrkhh]

Luckily I got the one with the least heat, the i3 model

 

[RémiM]

It bends due to heat --> sorry to be a little rude, but please do not post irrational comments.

Do you really believe it ?

A little bit of material science + mechanics and a little bit of good sense will certainly be very helpful.

The yield stress of a basic aluminum-magnesium alloy, heat treated let's say T5 or T7, is around 200MPa.

200 MPa is roughly equivalent to 2000kg per square centimeter.

Do you really believe that the heat, that by the way would probably help to restore the material if there was any initial residual stress in it, could create a stress superior to 2000kg/cm2 and bend the chassis like magic ???

 

[megatronium]

Not my i7 256. Maybe I'm lucky. I render with Premiere on this all the time too.

 

[jnjroach]

If these are bent, it was a manufacturing defect and not caused by heat. The melting point for Magnesium is 650 C or 1202 F, if they are heating to a temperature that significantly softens the metal we have bigger issues.... as that well over the <90 C Thermal Envelope the SP3 maintains.

 

[Maximus3D]

This device is most likely manufactured from an alloy of magnesium and aluminium which is stronger than pure aluminium, however both of them still deforms to some degree.

My own device has a slight curvature in the upper part of the screen, it's a bit annoying as the keyboard does not lay flat on the display but returning it to get a new one feels like a lot of work for a device which works just fine otherwise.

I can imagine the metal chassis is so thin that exposure to a higher temperature during a longer time will cause it to deform and 'bend out of shape'.

/ Magnus

 

[ptrkhh]

If these are bent, it was a manufacturing defect and not caused by heat. The melting point for Magnesium is 650 C or 1202 F, if they are heating to a temperature that significantly softens the metal we have bigger issues.... as that well over the <90 C Thermal Envelope the SP3 maintains.

Agree, I dont think its caused by heat, especially after the i7 user above confirmed. It might be the combination of many factors, like how the kickstand holds the device on either side, but not in the center.
Could u guys with bent SP3s confirm if you often use your device with the kickstand or not?

 

[RémiM]

If these are bent, it was a manufacturing defect and not caused by heat. The melting point for Magnesium is 650 C or 1202 F, if they are heating to a temperature that significantly softens the metal we have bigger issues.... as that well over the <90 C Thermal Envelope the SP3 maintains.

In this precise case, the melting point has nothing to do with the utopic bending.

It would be the stress generated by the dillatation of the constrained chassis. And this stress would never exceed the yield strength of the alloy. It's impossible.

Metallurgically, the critical temperature is 0.5*melting point of the alloy which, as you correctly mentioned, is way to high to be reached.

 

[Maximus3D]

The problem with metal, especially aluminium is that it's not only the high temperature which melts it, it's will also weaken when exposed to a much lower temperature for a longer period of time.

Aluminium actually starts to weaken and deform at temperatures at around 100 degrees Celcius, then it exponentially increases as the temperature increases.

/ Magnus

 

[RémiM]

This device is most likely manufactured from an alloy of magnesium and aluminium which is stronger than pure aluminium, however both of them still deforms to some degree.

My own device has a slight curvature in the upper part of the screen, it's a bit annoying as the keyboard does not lay flat on the display but returning it to get a new one feels like a lot of work for a device which works just fine otherwise.

I can imagine the metal chassis is so thin that exposure to a higher temperature during a longer time will cause it to deform and 'bend out of shape'.

/ Magnus

Generally pure metals are not used because of their poor mechanical properties.

The "impurities" (alloy elements) create precipitates inside the aluminum matrix and make the gliding of the dislocations much more complicated. It improves a lot the mechanical properties (mainly the yield strength) of the alloy under static load.

The effect of the temperature is the dillatation of the material. This dillatation, in the case of metals is isotropic and homogeneous.

Since the chassis is not constrained and can freely expand, the temperature will have no effect on the integrity of the SP3.

The only effect it can have is to ruin the glue of the front glass panel, and damage the LCD.

 

[jnjroach]

Obviously my subtle attempt at a wee bit of sarcasm didn't come across.... my point is this isn't an heat issue, the bend if there is a manufacturing defect and will be exchanged by Microsoft. It is neither wide spread nor indicative of the device....

 

[RémiM]

The problem with metal, especially aluminium is that it's not only the high temperature which melts it, it's will also weaken when exposed to a much lower temperature for a longer period of time.

Aluminium actually starts to weaken and deform at temperatures at around 100 degrees Celcius, then it exponentially increases as the temperature increases.

/ Magnus

Sorry sir, I totally disagree. It depends on the initial microstructure.

If the precipitates inside the matrix are coherent and very small (Guinier-Preston zones) the aging of the material will harden the aluminum.

If the precipitates are initially coarsened, then it will weaken a the microstructure.

Since we don't know the heat treatment applied on the chassis of the SP3, we cannot state or predict anything.

No matter what, the temperature has to be high enough to activate the diffusion of the solute elements inside the matrix.

It is likely that under 180°C nothing happens in aluminum alloys (copper or magnesium as second constituant).

And 180°C will never be reached here.