News

Why do our phones shatter?

We’ve all accidentally dropped our phones and watched them shatter in apparent slow motion while we vainly grasp at the air or, worse, kick out a foot, only to propel the (now smashed) phone across the room.

But why do our smartphones shatter, when your old Nokia 3210 would bounce around happily on concrete with barely a scratch?

I had a drawer full of these, the iPhone 5 was an awkward shape.

Part of the reason is that there is now a big screen that can shatter – the screen in a 3210 was only about 20% of the size of the phone, modern smartphones are nearly all screen.

Another reason is that modern phones are slabs of glass and aluminium, made to feel heavy so they feel expensive compared to the cheap/flimsy/plastic versions that creak when you hold them to your ear. So is it all that extra weight that’s causing the issue? Well yes, that is a part of it. The Nokia 8210 is only about 1/3 of the weight of a plus phone, which means only 1/3 of the kinetic energy that must be dissipated when it hits the floor. Surprisingly though, the difference isn’t normally that stark – this modern droppable from Huawei weighs the same as a 3210!

So what gives?

Exactly.

Part of the expensive feeling of a heavy phone isn’t actually the weight, it’s the stiffness: the phone doesn’t flex, so it feels more substantial. It also feels more substantial to the ground and does not flex elastically (i.e. bounce back) as readily when struck or dropped, compared to a thin plastic shell. If the structure cannot flex, the energy is then dissipated locally, typically as cracks in your screen or dents in the aluminium chassis.

The challenge of efficiently absorbing and distributing impact energy is studied across a huge range of fields, subjects such as:

  • car crashes (cars have crumple zones, and air bags, which are crumple zones for your face)
  • tennis racquet and ball design
  • ships and berthing structures
  • pile driving hammers
  • karate masters, and
  • phone case makers (probably, though that might just be fashion)

Below is a short clip from a study of different designs of bumper for our subsea mooring connector. You can see how the different structures absorb energy very differently, one flexes like bamboo in the wind, the other results in a dented dome. So, which is better?

Lighter and more flexible is often a desirable outcome for the simple reasons of less material, less cost. However, structural integrity and interfaces with adjacent objects can often be the deciding factor. In the above case, where the bumper is just a bumper, the overriding design factor is the interfacing geometry during and after impact. We can tolerate a dent in the dome and it is covered by a flexible urethane coating, so this is acceptable. The first case shown has large lateral deflections, these will impact the working parts of the connector so must be avoided.

I’m off to buy a phone case.


Got a comment or correction? Here’s the post on linkedin.

InterMoor picks Rocksteady QD

InterMoor, the world leader in mooring services, has obtained the exclusive rights to our quick disconnect variant of Rocksteady – Rocksteady QD – for traditional offshore mooring. The connector will be used as part of their game-changing mooring technology called Inter-M Release, which allows operators to safely drop moorings away from the rig and saves days in prelay moves and weather avoidance.

The QD connector retains all the functionality of a subsea mooring connector as well, so can be used with InterMoor’s SEPLA and other pre-installed anchor technologies.

Read more on InterMoor’s press release on their website. If you would like to know more about using the Inter-M Release system, you can drop us a line, we’re more than happy to put you in contact with the right people.

Rocksteady size calculator

Our engineers are power users of Sharepoint’s PowerApps functionality, so we have put it to good use – creating a size calculator to enable our sales team and partners to rapidly respond to requests for quotation.

Rocksteady holds design approval certificates from both DNV and ABS for our scaling method all the way up to 3,000t; and each bespoke size is subject to FEA performance verification, proof and break load testing.

Contact us to find out more!

Finite element analysis

FEA has always been one of our core analysis tools, though it has become more important as our products are developed with advanced strain based design techniques.

Why do we do this? It is driven by the our markets, for example: mooring applications define manufacturing test loads above yield (see video below!), and HPHT (20,000psi) codes refer to ASME Div III design methods. Strain based design also confers reliability and efficiency advantages: localised regions of stress above yield can be assessed and checked against strain data from testing.

Our engineers operate ANSYS FEA software, routinely modelling subsea and riser equipment with 2D & 3D linear (elastic) analysis and non-linear (plastic) analysis. Some of the services we offer include:

  • Simplified axi-symmetric stress analysis for concept level designs
  • Detailed 3D stress analysis for complex components and structures
  • Analysis of parts and assemblies with complex contacts
  • Modal and frequency response analyses
  • Stress linearisation and assessment against API, ISO, DNV and NORSOK codes

Below you can see a video of a stud-link chain analysis that we completed with our sister company InterMoor. We developed a detailed wear model of the chain interfaces to predict wear rates with bending loads applied, following deformation of the chain to the proof loaded condition.

 

Making a riser

Here is a sequence of clips that detail the manufacturing process of a drilling riser, including flange forging, machining and welding.

Unfortunately we don’t have a video of the seam welded pipe manufacture, so please let us know if you have one and we’ll include the link.

 

Nimway technology readiness

In early 2014, SRP completed a successful proof of concept test of a full-size 15,000psi Nimway™ connector as the first step to the qualification for completion and workover riser applications.

Nimway™ is made-up using bolt tensioning technology, so the test was designed to prove the repeatability of make/break, as well as to validate the finite element analysis completed on the connector.

Strain was measured at key locations as over 1000t of tensile load was applied to the sleeve with hydraulic bolt tensioners and the connector was made up and then hydrotested to 22,500psi.

Repeatability of make/break was proven over 8 cycles, with average strain values varying by less than 2% and within just 2.4% of the values predicted in computer analysis. This predictability and accuracy of Nimway™ demonstrates the advantage of the directly tensioned make-up method over torqued connectors, which can suffer 25% preload variability due to friction and galling.

The connector successfully passed two 15 minute hydrostatic tests at 22,500psi, showing no signs of face separation or leakage from the metal seal.

The tests gave SRP and Acteon the confidence to invest in a full qualification programme of 5” and 7” 10,000psi Nimway™ connectors to service the well intervention market.