Happy Independence Day from all of us here at Team UV!
As you celebrate the 239th anniversary of our the day the United States of America officially declared its independence with your friends and family today, please don’t forget the men and women who fight to protect this great country on a daily basis and remember that neither Independence Day nor the United States of America would exist had it not been for the sacrifice of the 200,000 patriots who fought for our independence and freedoms during the American Revolutionary War, more than 25,000 of whom paid the ultimate sacrifice.
So please enjoy this time with your friends and family, barbecuing, watching fireworks, just hanging out, or whatever other special plans you may have in store for today, but please also spend some time today thinking about the debt of gratitude that we owe to the brave men and women of our armed forces who have continuously fought for freedoms over the last 240 years.
Thank you for your service to all our troops, past, present, and future.
Ferrofluid sculpture. Photo Credit: P.Davis, et al. (FYFD)
Today, Brian will be filling in for Ketton due to last minute scheduling issues, we apologize for the post delay.
Ferrofluids are quite complex fluids that display interesting behavior in the presence of magnetic fields. These ferromagneticfluids are created through the colloidal suspension of ferromagnetic particles of the nano-scale. What does this all mean? In simpler terms, you essentially take tiny (nano-scale, or on the scale of a nanometer/a billionth of a meter; think the size of the base width of a single strand of DNA) magnetic particles and disperse them homogenously (or evenly) throughout a carrier fluid in a way so that the particles are fully wetted (meaning that the particles surfaces are fully coated by the liquid, without other particles in contact with them).
Once the ferrofluid has been created, the next step is as simple as subjecting the fluid to a magnetic field, at which point the ferrofluid becomes magnetized. As the ferrofluid begins to be affected by the magnetic field, it wants to follow this field and comply with its geometry; basically, the fluid wants to become shaped like the field it is being subjected to, but there is a problem: the fluid has surface tension. Because the fluid has cohesive bonding between liquid molecules, the molecules are very strongly attracted to each other on the molecular scale. This should make sense to you, as when you run your hand through water (for example), you are able to readily cause bulk disturbances (you can split up the water on the large scale), but try as you might, you will not be able to split the water apart on a molecular scale (the smallest you can get water to by hand is tiny visible droplets, which are still collections of a ridiculously large amount of water molecules (on the order of sextillions, or thousands of thousands of thousands of thousands of thousands of thousands of thousands!).
Surface tension. Photo Credit: Wikipedia.org
Because of the aforementioned strong attraction between the liquid molecules, fully immersed liquid molecules are pulled on by other molecules in all directions, as shown above in the picture. However, the molecules on the surface are only pulled on by molecules around and below (but not above) them, leading to a breach in the equilibrium and causing the water to be pulled in the direction of the rest of the water (hence the curved water surface exhibited in the above diagram). So, armed with this knowledge of how surface tension works, we can revisit the ferrofluids and figure out what is going on.
Ferrofluid and magnet, separated by glass. CLICK TO EXPAND TO SEE THE SPIKES BETTER! Photo Credit: Wikipedia.org
The magnetic field wants to push the ferrofluid outwards, but the ferrofluid itself wants to pull itself back inwards towards the liquid base due to the surface tension, all while gravity is also resisting the spike formation (this kind of interaction is explained through the normal field instability). At some point all of these forces equate and the fluid is said to be in equilibrium. The result of this? Really cool looking spikes in the ferrofluid as shown above. This gets even cooler when sculptures are created (as in the top picture) by using shaped bases and manipulating the shape of the magnetic field. It should be noted that art is most definitely not the only application for these fluids; in fact, ferrofluids also find application as: liquid seals around the shafts of spinning hard disks/drives, as a convective heat transfer fluid for wicking away heat in small scale and low gravity application, as an imaging agent in some medical imaging techniques (especially magnetic resonance imaging, MRI), as friction reducing agents, as mass dampers to cancel out vibrations, and even as miniature thrusters for small (nanoscale) sattelites!
So there you have it, another awesome engineering phenomenon! Please tune in Sunday for Ketton’s last Open Mind post and remember to continue following us at EngineeringAFuture.com when Engineering A Future (EAF) launches on Monday, July 13th! Enjoy the video below, created by altering the magnetic field in a ferrofluid sculpture!
Before we go any further into the purpose of the “breather hole”, we will first check out how a window in a pressurized passenger cabin is set up. As shown in the Boeing 737 maintenance manual (the most widely produced jet airliner in aviation history), the window structure consists of three layers of acrylic – a tough, transparent and flexible resin – although only two of them have an actual structural function.
These structural layers are the intermediate and outer ones – while the inner layer (called “scratch pane”) only serves as a buffer between the passengers and the structure of the window itself. These layers prevent the cabin from reaching the external pressures that, depending on altitude, are too low for the vital functions of the human body.
Basically, the primary structural window guarantees the cabin remains at a constant pressure equivalent to an altitude of 7,000 feet, which is still quite acceptable for the body. However, in most cases, only the last acrylic layer is responsible for ensuring such conditions; the intermediate layer is just there for extra safety. Having said that, let us get back to the mysterious little hole.
As can be noted in the diagram shown above, the breather hole is located in the middle layer of the window. This little puncture acts as a bleed valve ensuring that the pressure between the last two layers and the cabin always remains the same. This is necessary as a way of preserving the middle layer (the extra safety one) so it is only exposed to severe pressure differences in cases of emergency – that is, if the last layer the window is fractured in some way.
The breather hole also serves to prevent freezing and fogging between the outer layers of the window. Of course, that doesn’t always work since it is not rare to find photographs showing some frost on the windows.
Let’s face it, your house was probably built over half a century ago. It has the appeal of an old high school sweatshirt: comfortable but covered in bleach stains. The future is now! Time to design some new homes that will last longer, are more affordable and sexier than your parent’s house. Engineering can add a lot of interesting choices to your home. Here are a few of mine.
Tuned Mass Damper living room center piece: Your friends come over to watch the big game. You’ve got it all set up: comfortable couches, plenty of beer, nachos, wings, and a projection tv that covers the entire two-story bare wall. Unsurprisingly, you are almost immediately asked about the gigantic hanging sphere of death above your head. Tuned mass dampers are used to theoretically reduce vibrations from your structure to zero. So essentially in the event of an earthquake, the forcing frequency (earthquake), the frequency of the additional mass and spring, and the natural frequency of your home will become equal to each other. When this happens, the mass and spring will move and the building will not shake, providing the best uninterrupted viewing party experience!
Composite homes: Say you build your dream home out of new lightweight composites. Composites are strong, formable, and can be designed to fit most structural purpose that you can think of. Now say you love your home but don’t like the neighborhood because your neighbor’s cat always relieves himself on your porch. Easy fix. Simply un-anchor your lightwieght home put it on a bed and take it with you. Currently homes made in the US are pretty much made of wood, dry wall, nails, and concrete. Although they are tried and true, they do add a lot of unnecessary weight to your home making it virtual impossible to transport and dangerous in the event of an earthquake. Today new composites can make your home stronger, corrosion resistant, and even more architecturally interesting because composites are currently able to be 3D printed. Of course, there are other things to think about (i.e. insulation, fireproofing, water damage, etc.).
A 3-D printed composite. Photo Credit: gizmag.com
Using the power of the Sun: If you live here in So Cal, you’re probably experiencing high 90s temperatures right about now. Luckily the state of California has initiatives to generate your electricity for your home using solar panels which can be a huge help to your budget and environment. But why stop there? Cut some holes in your roof put some opaque glass and make sun roofs where you can absorb as much light as you want, illuminating your home for free. Design a control system that uses a light sensitive sensor to activate and rotate your blinds automatically to save on using electricity to light your home. Harnessing the power of the sun can even go as far as your car and fashion choices. Your vehicle can also become solar powered, Hanergy is working on it as we speak! And one last thing, I’m just going to throw this out there. Solar powered pants.
Solar powered pants. Photo Credit: news.discovery.com
Thanks for reading, hope this helped you make some interesting choices for your home and fashion choices of the future.
Have you ever heard of Ultrasonic Melt Treatment? Me neither but I did some research and found some pretty interesting things. Ultrasonic Melt Treatment (UST) is essentially the addition of high frequency acoustic waves to a liquid melt of a metal (typically aluminum) to induce acoustic cavitation. Please note that acoustic cavitation is essential. The acoustic waves introduced into the melt have to be at a high enough amplitude and frequency to alternate pressure above the cavitation threshold to create cavities in the melt. Essentially what is happening is the rapid formation and collapse of bubbles in the melt which can have some beneficial effects before, after, and during solidification. The acoustic cavitation is said to activate the melt which means that it will accelerate diffusion, wetting, dissolution, and dispersion which will directly affect degassing, solidification, and refining of metallic alloys. Now if you’re into metallurgy this all sounds incredibly interesting, but if you’re not I will try to explain what each of these mean.
Degassing is one of the primary uses of UST in which the concentration of a certain gas will be lowered in the melt. In light aluminum alloys, acoustic cavitation will cause the growth of fine bubbles in the melt on the surface of non-wettable oxides. As a result, cavitation will cause direct diffusion of hydrogen into the bubbles from the melt. Acoustic flow will assist in floating these bubbles to the surface and out of the melt. The benefits of degassing are that lower porosities can be achieved and thus higher densities in the final material. It has also been found that lowering the concentration of hydrogen in aluminum alloys will raise the ultimate tensile strength and ductility of the material. It is noteworthy that one study concluded that UST is the best amongst other commercial degassing techniques in terms of effectiveness in degassing and in time of treatment.
Degassing of oil using UST is similar to the UST process in liquid metal melts. Photo Credit: hielscher.com
Melts are usually cleaned of inclusions before final treatment. Aluminum melts usually use mesh filters but in order to filter out very fine particulates, multiple layers of successive filters need to be used. This is often not allowed because of the restriction of capillary action of the liquid melt through the filters, however with the use of UST during filtration, a sonocapillary effect is produced. This sonocapillary effect is caused by the cavitation field that is formed which allows for the melt to freely pass through the multiple layers and disperse unwanted oxides.
Ceramic filters. Photo Credit: induceramic.com
One of the most important benefits of UST is that it produces non-dendritic structures during solidification. A dendrite is a branched tree-like structure that grows during solidification of liquid metals (fun fact: dendritic solidification is actually what is behind the unique shape of snowflakes!). As mentioned earlier, acoustic cavitation allows for the wetting of non-metallic impurities in the melt and these become sites for nucleation (aka the start of solidification). Because these nucleation sites are ahead of the solidification front, there is no growth of dendritic structures.
As non-dendritic solidification occurs, the grain becomes only a fraction of the matrix structure so there is refinement in grain size. It is important to note that grain size is only a function of cooling rate in these conditions, therefore this method of refinement is applicable to all metallic materials. One of the major benefits of materials with non-dendritic structures in Al-Si-Mg systems is that they are able to deform very easily at a semi-solid temperature ranges. Essentially what this does is allows the grains to rotate and slide relative to each other without the interference of the dendritic braches. This can dramatically improve mold filling by lowering the viscosity. The apparent viscosity of non-dendritic melts at the semi-solid temperature range is lower than that of the regular melts and is comparable to that of olive oil, at least for aluminum.
Comparison of dendritic and non-dendritic strutures. Photo Credit: scielo.org.za
Overall there are many benefits to Ultrasonic Melt Treatment in aluminum alloys such as degassing, refinement of grain size, and filtration. Although UST has only been extensively studied in non-ferrous alloys, recent research has been done on its effects in low-carbon steels and even epoxy based nanocomposites. In all cases it is the acoustic cavitation, duration of the treatment, and force of frequency that dictate the effectiveness of UST. Hopefully this taught you a little bit about UST. For more info, please refer to the paper by Eskin, G.I. “Broad prospects for commercial application of the ultrasonic (cavitation) melt treatment of light alloys”.
Over the last few years 3D printing has gone from a obscure manufacturing process into a mainstream solution for everyday problems. The reason for this transition is mainly due to the types of materials that are able to be extruded out of a hot-end of a 3D printer. PLS was first used because of low melting point but with advances in hotend technology, materials such as ABS, nylon, polycarbonate, PEEK and more can be used in additive manufacturing. The more materials you have to work with, the more applications your product can have and that’s exactly the beauty of 3D printing. It is amazing for prototyping and making unique parts that you cannot find anywhere else.
The average 3D printer’s extruders have a temperature range of about 180-325°C, however, this limits the types of materials that can be used. A small Israeli company called Micron3DP has been experimenting with glass as a medium for 3D printers and (as of today) has announced that it has had a successful test using molten glass! Now if you know a little about materials, you know that glass and ceramics have extremely high melting points which means using them as a medium for a 3D printer requires an extremely hot extruder. And that’s exactly what they did.
Micron3DP’s tests were done using “soft” glass at a melting point of 850 °C and borosilicate glass at a melting point of 1640 °C using an innovative way of 3D printing in an extremely hot extruder. The process is analogous to that of printing with molten thermoplastics on a Cartesian based machine, one layer is laid down and cooled rapidly before the next layer is set down.
3D printed glass shapes. Photo Credit: 3DPrintingIndustry.com
If you have ever 3D printed anything, you know how empowering it feels when you are able to create exactly what you want and use it immediately. Soon you can add glass to your arsenal and you will be an unstoppable creative force. Glass has very unique optical, corrosion resistant, and temperature resistant properties and this new technology and process will hopefully harness the power of glass for use in the medical industry, aerospace industry, and even the art industry. Now this breakthrough is so recent that as of June 22, 2015 (yesterday) the company is still seeking investors to help them further the technology. If you want to get started on the 3D printing game, here’s how you can make your own 3D printer for cheap:
Summer is here and with it brings barbecuing season. While the average charcoal BBQ may seem like a pretty simple appliance there is some solid engineering behind its design.
First let’s look at the charcoal briquettes. An engineer took chunks of wood and organic matter and heated it up in the absence of oxygen to produce an energy dense fuel that is fairly clean burning. This process is called pyrolysis and it removes all the moisture and fumes so that the avid BBQ enthusiast will be able to cook their food without coating it in a black smoke of tiny particles.
The BBQ itself is designed to control the combustion process. By opening and closing vents the user is able to regulate the flow of oxygen to the fuel. This directly affects the combustion rate, the rate at which energy is released in the form of heat.
And, as with any cooking process, heat transfer is an important consideration. When the coals are glowing hot they are emitting a lot of their heat as radiation. Radiation requires a direct line of sight and this is what causes one side of your food to get a nice sear on it before you flip it. When the lid to the BBQ is closed the air inside heats up and this allow for some natural convection, heat transfer from the hot air moved by its change in buoyancy (hot air rises). There is also some conduction, from relatively still hot air and the heated metal components that compose the grill (not to mention conduction through the food itself). Each one of these modes of heat transfer provide a different aspect to the grilling process. Radiation causes the sear, conduction is responsible for the grill marks and convection is responsible for the even heating and temperature of the food.
A deeper understanding of any process can lead to better results and engineering gives perspective into many of these processes. As far as grilling goes most of it can be picked up from experiences, but isn’t it more fun to know why these things happen! Happy Father’s Day to all the dads out there, no matter who does the grilling!
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