Category Archives: Uncategorized

An Engineer’s Take on Bendgate

GettingBent

Bendgate, so much controversy. What started as a few complaints with pictures about the new iPhone 6+ bending while in people’s pockets has turned into a certified internet frenzy. There are videos of people bending the iPhone 6+ with their hands. Countless blogs and news pieces have been written on the subject. Consumer reports did their own test to see if there was any truth to this complaint. Even Apple quickly weighed in to assure consumers that the iPhone 6 bending is not a serious issue. Yes, I know you are asking yourself what more can be written on the subject, and maybe more importantly how much more can I read about this before my brain cells get bent? Well, I am a licensed structural engineer with an advanced degree in the field. I often design and specify materials and members to resist given forces including bending. I’ve read a lot posts and listened to a number of podcasts that address bendgate. There seem to be lingering technical questions and misunderstandings regarding materials and forces (in particular “bending”). I do not intend to resolve all issues but I hope to answer a few technical questions.

Jim I’m an engineer not a lawyer

As a disclaimer I own many Apple products and could be considered an Apple fan. In my free time I develop a number of iOS apps, including a tool for structural engineers that coincidentally aids in performing bending calculations. I do not own an iPhone 6 or 6 Plus, so my assumptions regarding the dimensions and specifications of the device are based on information found online and not from first hand testing.

Bending, broken or deformed?

When stressed, an object changes shape. This deformation can be classified as elastic or inelastic (plastic). After the stress is removed if the object returns to its original shape then the deformation was elastic. If it does not return to its original shape it has deformed plastically. In both cases it is not “broken” i.e. the material is still together. All materials are different in how much stress they can tolerate before they begin to deform permanently (plastic). For some materials it takes very little stress to cause plastic deformation (think rubber band), and for others it takes little stress to cause plastic deformation (think play dough).

Aluminum, plastic or how I learned to stop worrying and love titanium

A lot has been said about how the iPhone is aluminum and aluminum is “soft” and easier to “bend” than plastic. I don’t want to get into the details of Young’s Modulus, Yield Strength and Ultimate Strength here, but in the tradition of Jim Dalrymple let me respond with one word,  wrong. I’m assuming the aluminum used in the iPhone is comparable to the 6061 alloy. If you replaced all the iPhone 6’s aluminum parts with plastic parts, not only would it be easier to bend, it would reach plastic deformation with less stress and it would take less stress to break it. Precisely because aluminum is stronger, the engineer’s that designed the iPhone were able to reduce the amount / thickness of material used. I’d be surprised if any “Plastic” phone as thin as the iPhone only used plastic materials to resist bending.

It’s the shape stupid

On to the crux of the issue, the shape. First I must apologize now if I’ve been too technical in this post. I have done my best to keep it simple but out of necessity in describing the issues at play and stoking my ego, I’m about to drop some “letter” math on you. Not only does the material (steel, plastic, aluminum, etc…) of an object affect its ability to resist bending, the cross section shape of the object does as well. We can say as the phone gets thinner its ability to resist bending without deformation is reduced, but by how much? A cross section of a member has a property called “moment of inertia”, or “MI” as I will call it. The MI of a shape describes the shapes ability to resist rotation (bending). The greater the MI is the more force is required to change the members rotation rate. We can calculate the MI of any cross section shape and compare the results to other cross sections to get an idea of bending resistance. For a simple rectangle the MI can be calculated with:

MI = B*H^3 / 12

Where, B = width H = height (thickness)

We can see that as we decrease the width of a rectangle its ability to resist bending only decreases linearly, but if we decrease the height (thickness) of the rectangle because H is cubed the ability to resist bending is decreased more dramatically. To illustrate a point I’ve compiled a table of various smart phones cross sectional properties. If we assume full thickness of the phone is used but only 5% of the width of the phone is used to resist bending you can get an idea what making your phone thinner will do to its ability to resist bending.

Phone Thickness (in) Width (in) MI (in^4) Relative
iPhone 6 0.27 2.64 0.000217 1.00
iPhone 5s 0.3 2.31 0.00026 1.20
iPhone 6 Plus 0.28 3.06 0.00028 1.29
Samsung Galaxy Note 4 0.33 3.09 0.000463 2.14
Samsung Galaxy Note 3 0.33 3.12 0.000467 2.16
iPhone 4s 0.37 2.31 0.000488 2.25
HTC One (M8) 0.37 2.78 0.000587 2.71
LG G3 0.35 2.94 0.000525 2.43
Moto X (2014) 0.39 2.85 0.000704 3.25
Nokia lumia 0.41 2.81 0.000807 3.73

So we can see thinner phones = inherently less ability to resist bending. As a phone design becomes thinner the engineers will have to come up with additional ways to provide stiffness. That brings me to some pictures and comments I read on imgur here. While I agree with much that was written in that post I have one major disagreement with this picture: metal insert The metal insert they talk about is not there to reinforce the phone’s frame. It is there to provide a rigid surface for the volume buttons to push against. To pass bending moment from the frame and into the metal insert you would need 2 sets of screws each side of the metal insert. As it is now the author (alleras4), of the piece is correct that the insert does not reinforce the reduced section of the phone frame at the volume cutouts, but it was never intended to.

How much load is a butt load of load?

So how much bending force should a phone be expected to resist? How much force is generated in hipster jeans under a giant tush? I don’t know the answers to these questions. I do know that as a phone gets longer in length there is the potential to generate more bending moment with the same amount of applied force. The equation used to find the max bending moment (BM) in a simple beam with a single load applied to its center span is:

BM = P * L / 4

Where, P = single point of force L = span between supports

So as the span gets longer (length of phone) the same amount of force will increase the bending moment linearly. This explains why it appears the iPhone 6 Plus is easier to bend even though it is slightly thicker than the iPhone 6.

TL;DR but at least it got its own browser tab for a day

To wrap it up, thinner phones = easier to bend. Based on the required force shown in the original video that kicked off bendgate, and based on Consumer Reports tests,I think it’s safe to say its unlikely you will bend your phone with typical use. I would guess most phones that get bent do so during a dynamic event. Even though I am a structural engineer and not a mechanical engineer I know enough about dynamics to know it doesn’t take much to generate dynamic forces much greater than typical static forces. I was at one point a sad owner of a bent iPhone 5. I have neither tight jeans nor a big rear but all it took was an unfortunate drop from pretty high up to bend it slightly at the volume cut outs (it was in a case). These phones are with us all the time and it’s easy to drop something on them, drop them, toss them, whack them into things and maybe even sit on them quickly from height onto a hard surface. As far as portable electronic devices go, I think these phones are insanely robust. It’s an engineering marvel they could be made so thin, and remain as durable as they are. If you’ve made it this far in the post I unfortunately do not have the authority to give you college engineering class credits, but rest assured the next time Young’s Modulus comes up at a dinner party you won’t get bent.

On the way to 8!

Thought I would post a quick update. I am hard at work updating my apps for iOS 8.

I have had the beta version of iOS 8 on my phone for over a month and it looks promising. It opens a lot of doors previously closed to developers. I can’t wait to see what other developers do with the new tools. I am also excited to show you the updates I’ve been working on.

I hope to have updates ready the day Apple releases iOS 8 publicly, but I may not finish all of the apps. As a hobby developer, time is constrained. However, I personally use all my apps pretty much daily, so I am highly motivated to keep them up to date.

I am also working on a new little app called On This Day. It will use the new iCloud stored photos to show pictures you took a year ago in a nice widget in the today view of the notification center.

Regardless, I need more time in the day! :)

My Music is now in the app store!

AppIcon76x76@2x

Well it was just approved and is in the app store.

My Music

A perfect to do list for your music. Keep track of new artists you’ve just discovered. Watch their hot new music videos. Explore their discography. Listen for free to samples of their tracks. Read up on their story. Conveniently link to their iTunes music store page.

Beautifully designed. Extremely helpful. Amazingly simple.

If you are like me you listen to a lot of streaming music and radio. When I hear a great new sound or discover an artist I can never remember them after the song is over. With My Music not only will I remember them later, but I will be able to explore more of their tracks and videos.

-The colors and themes for each artist is dynamically created to match the colors of the album art work.
-Search and save any artist in the iTunes library.
-Tap and hold artist to organize the layout of saved artists.
-Swipe to the left to delete.
-Read Wikipedia entries in app of your saved artists.
-Watch music videos in app via YouTube.
-Dive deep into the discography of saved artists, to find new tracks and albums.
-Listen to a sample of any track provided by iTunes.
-All artists, albums and tracks have a convenient link to the iTunes Store.

If you love discovering new music, you will love this app!

Enjoy…

link to App Store

Now I’m working on updating all the apps to iOS 8 so they will be ready come the fall release of iOS 8.

01 My Music 4in02 My Music 4in03 My Music 4in04 My Music 4in05 My Music 4in

Got Music?

 

My Music 1         My Music 2

I am almost done with my next app!

It is a todo list for music. You can keep track of artists / bands you like.

I listen to a lot of iTunes Radio and Pandora while I work. I hear new artists all the time and I usually jot them down on a paper to check out later. I always lose the paper and forget all about that cool new artist. :(

Never again! Now I keep track of them with my new app. With the app I can read more about the artist, check out their discography, and even search for you tube videos. Ultimately I can even link to the iTunes store and buy their music.

I am still trying to come up with a name for the app. So far I have thought of:

My Music     –     Music List     –     Music Mark     –     Music Time     –     Player

But I can’t decide. In the comments below tell me what you think it should be called (your own idea or one of mine) and I just might use your idea. The first 20 people will get a free promo code for the app when it is released :)

Hello world!

Hi.  My name is Nick Fanger.  I am a structural engineer by training and by trade.  I currently work in the entertainment rigging industry here in sunny southern California.

I am also a iOS developer.  I started by writing in-house apps for the company I work for.  What started as a hobby has since progressed into a full blown obsession.  I am now branching out and commercially releasing apps I originally built for myself.

This is what Thru Bolt is about: building useful intuitive iOS apps.  Enjoy!