I showed my dad your post and he read it with great interest. He's not a member of this forum but asked me to post the following response on his behalf:
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"Unfortunately for you I am a Structural Engineer, and you apparently are not such a good Mechanical Engineer as you think!
Why do you need to be so rude to Kastenbrust? He/She is basically correct.
Denting is as you say post-elastic deformation (i.e.plastic). Impact involves high strain-rate behaviour of materials. For aluminium (and other ductile materials) the creation of a dent is limited by the applied flexural tensile stress. It is limited in two ways: by the yield (tensile) stress and the ultimate (tensile) stress. Both of which are characteristics of the particular grade of aluminium from which the case is made.
If there is enough kinetic energy in the impacting object the 3mm thick aluminium will bend locally and if the yield tensile stress is exceeded a permanent dent will be produced. If there is not enough energy there will be a local "elastic" deformation under load but the 3 mm thick aluminium will regain its shape before impact.
If there is enough energy to cause applied flexural tensile stress in exceedence of the yield tensile stress then the "dent" will progress into a "dent plus tear" i.e. a hole ( a term which even a Mechanical Engineer of your capability can understand).
In fact the mechanics and physics are quite complex and the process is not even as simple as I have described it. The applied shear stress and also the limiting characteristic shear strength of the 3mm thick material is involved. And the actual resultant applied stresses (what you should have remembered or perhaps never were educated to understand) are the Von Mises stresses.
Whatever - the bottom line is that Kastenbrust is correct. The most important material parameter for the 3 mm case material is the Tensile Strength i.e. the tensile yield and the ultimate tensile strength.
Please think about being less arrogant in future?"
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my unibody has some minor dents/chips
not specifcially sure how they happened, just through general wear and tear and i would say i baby my mbp quite alot lol
theyre so small that unless you know theyre there you wont notice them really or unless u run your finger along where the chips are which is where u can really feel them - that bothers me the most, the fact u can feel them.
this one is on the top half above the magnetic latch thing
and this one is on the top half above the disc slot
Indeed, I have forgotten lots of erroneous details from Engineering because I only did it as an undergraduate. But I have remembered enough to identify when someone doesn't know what they are talking about and are clearly just copying and pasting empty words from Wikipedia. After I received my bachelor's, I worked for a year but am now in medical school pursuing a more worthwhile cause (have fun waxing philosophical about strengths of materials
I'm being arrogant? Does your dad know how to read? Or did he not even bother to read kastenbrust's posts prior to mine?
Indeed, I have forgotten lots of erroneous details from Engineering because I only did it as an undergraduate. But I have remembered enough to identify when someone doesn't know what they are talking about and are clearly just copying and pasting empty words from Wikipedia. After I received my bachelor's, I worked for a year but am now in medical school pursuing a more worthwhile cause (have fun waxing philosophical about strengths of materials
Adopting the typical Apple fanboy posture, would you like to substantiate that with some proof?
Apple's obsession with silence is well known and they tailor their cooling to offer this. But if you look at the innards, there's no overt effort made to use the shell specifically as a heat dissipating structure: you couldn't because we'd be back to the days of the HibachiBook Pros. It just happens to be one of it's attributes. The heavy lifting of the cooling is still done by the usual arrangements, and if you do attempt to use the power of the machine the shell doesn't contribute in a spectacular way to cooling when compared to the likes of say the Dell XPS M1330. The silenced cooling is actually achieved in a bigger way by Apple in terms of having less of it (the cooling that is), and making reasonably sure that in terms of most consumer use it won't fry the machine. As I said, light use. If you try and use the power they have on paper, the compromises in the cooling becomes rapidly apparent - due to either straight-up overheating or a hugely increased noise signature (as the nominally silent fans ramp up) - or in some Macs both - in comparison to something else which is designed to put more airflow through the system more consistently. Case in point: Certain Pros in uncooled areas of my office becomes noticeably noisier than the directly comparable Dell Precisions (The Dells are noisier at idle) when doing computationally intensive work.
Weight - as I've said before, the new unibody structure is actually not that great when you consider the ratios of weight and strength relative to other manufacturing methods.
Lighter use makes for happier Macs. Not so silly actually.
The choice of aluminium and how they use it could be said to be a tossup between tactile impression, visual impact, manufacturing cost and other factors which have nothing to do with what you mentioned. Most of it is in fact more to do with skilled marketing to the layman - like most of Apple's products - and Apple's expression of design flair than any sound engineering decisions. And that feeding / effect of marketing to the layman who nevertheless has an ego is never more apparent than it is on these forums.
Let's face it, the unibodies are sexy machines... but they aren't necessarily any better cooled, any better built, nor any stronger than other machines on the market, and in fact come with quite a number of downsides if you aren't the raving Apple fanboy who strokes his Mac before he turns in, or if your use of a computer is so inconsequential in terms of it's scope so as to not notice some of these compromises. Fortunately for Apple, I'd wager that they have a far greater percentage-by-usage number of such users.
