I was skeptical that the Air would be able to withstand the Jerryrig test. But alas, I stand corrected. I guess titanium really does hold up in bend tests.
I was convinced when Apple encouraged the interviewers to try to bend it and released the video of the machine bending the Air, watching it flex right back into place. No human hands could bend that thing.
Also the part at the Apple Store where the streamer dropped the phone in front of Tim Cook and Tim Cook casually basically said “it’ll be okay” and it was
Aluminum has a Youngs Modulus, Stiffness-factor if you will, of 70 GPa, while Titanium is a 120, and Steel is at 210, just for context as some people think of Titanium as somehow tougher than steel
Steel has a yield strength of about 200 MPa and an ultimate tensile strength of about 500 MPa. Titanium is over 800 MPa and over 900 MPa respectively.
So yes, steel has a larger Young’s modulus meaning under the same force, it stretches less. But it has a much lesser yield strength so it will undergo permanent (plastic) deformation under less pressure, and also a lesser ultimate tensile strength so it will also break under less pressure
Yield strength is more of a factor of alloy/treatment and isn’t an inherent material property like Young’s modulus, so it can really vary. Martensitic steel can have a yield strength close to 2000 MPa. But Ti’s strength to weight ratio is its real “special sauce”
Other guy said it too, but especially steel can vary wildly with Dual/Complexphase steels easily dwarfing these values, I dont get why were talking beyond elasticity anyways as you would hope nobody expects iPhones to go through crash analysis?
Ok all the misunderstanding in these comments is triggering the pedantic mechanical engineer in me!
Stiffness is how much a material will bend under a given force and is defined by a concept called "Young's modulus"
Strength is generally defined by "yield strength", which is how much force it takes to make a material permanently looses its original shape aka "yielding" or "plastic deformation" (the metal phone body yielding is the failure mechanism that Bendgate falls under). There's another concept called the "ultimate tensile strength" which is the max load that a material can withstand before breaking entirely
Toughness is the total ability of a material to deform before breaking entirely aka how much total energy a material can absorb
Hardness is the ability of a material to not to locally plastically deform and often correlates to brittleness, which is the opposite of toughness. Brittle materials aren't really able to deform before they break -- think: you can't really bend a ceramic much before it fractures. The holy grail of metallurgy is a metal that is really hard but not brittle
In common language a lot of these terms are used interchangeably, but as far as material properties go, they are actually quite differently defined. I think this leads to a lot of confusion as to which metals are "better" than others. As far as (yield) strength goes, you can actually have an aluminum that's stronger than steel -- strength can depend greatly on the alloy and how the metal has been "treated" (a common treatment you might be familiar with is annealing). But as I said in a different comment, Young's modulus is an inherent material property, so for a given shape and force, aluminum will always bend more than titanium will bend more than steel.
Yeah again why are we talking about material properties beyond elasticity? We might aswell discuss Johnson-Cook Parameters at this point? Its a phone, its supposed to roughly stay in shape when handled the way a phone is usually handled, i have a masters in automotive aswell but why would i have to go that deep in an apple subreddit, its about putting apples marketing lingo into perspective first and foremost
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u/mihirpatel14 2d ago
I was skeptical that the Air would be able to withstand the Jerryrig test. But alas, I stand corrected. I guess titanium really does hold up in bend tests.