mechanics of material

nature.com
The quest to crystallize time
Bizarre forms of matter called time crystals were supposed to be physically impossible. Now they’re not.

Christopher Monroe spends his life poking at atoms with light. He arranges them into rings and chains and then massages them with lasers to explore their properties and make basic quantum computers. Last year, he decided to try something seemingly impossible: to create a time crystal.

The name sounds like a prop from Doctor Who, but it has roots in actual physics. Time crystals are hypothetical structures that pulse without requiring any energy — like a ticking clock that never needs winding. The pattern repeats in time in much the same way that the atoms of a crystal repeat in space. The idea was so challenging that when Nobel prizewinning physicist Frank Wilczek proposed the provocative concept1 in 2012, other researchers quickly proved there was no way to create time crystals.

But there was a loophole — and researchers in a separate branch of physics found a way to exploit the gap. Monroe, a physicist at the University of Maryland in College Park, and his team used chains of atoms they had constructed for other purposes to make a version of a time crystal2 (see ‘How to create a time crystal’). “I would say it sort of fell in our laps,” says Monroe.

And a group led by researchers at Harvard University in Cambridge, Massachusetts, independently fashioned time crystals out of 'dirty’ diamonds3. Both versions, which are published this week in Nature, are considered time crystals, but not how Wilczek originally imagined. “It’s less weird than the first idea, but it’s still fricking weird,” says Norman Yao, a physicist at the University of California, Berkeley, and an author on both papers.

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Heat Treating Steel Weapon Teeth

Here’s the stages of a set of S7 tool steel teeth for Cavalier as I took them through a heat treatment. They were cut and countersunk raw at a Brinell hardness of 197, brought up to 1250°F in an Olympic Kiln and held for a half hour, and then brought up to 1545°F, held for a half hour, and the kiln faulted out before it could ramp up to the recommended 1750°F for hardening S7. No matter, after the steel air cooled with a fan to 150°F, they were thrown in the oven for an hour at 300°F, which tempered them nicely. The hardness is floating around 480 Brinell/50 Rockwell, which definitely lower than the 555 Brinell/55 Rockwell hardness I was aiming for, but is such a vast improvement over raw S7 that I’m still considering my first attempt at heat treating steel a success!

A New Shock Absorber Design

This new compression design could be the thing that keeps you out of the auto body shop next time you accidentally back into an unseen post. The prototype above is a 3-D printed, 3.5-inch nylon structure that can repeatedly absorb the energy of a 100 mph fastball in 0.03 seconds.

Mechanical engineers at the University of Texas at Austin weren’t content with the shock absorbers commonly used in automobiles, football helmets, aerospace applications and military gear. Even the newer honeycomb-patterned materials, which can compress only once during the force of a collision, weren’t good enough. 

So they rethought what happens when an object gets crushed and came up with a structure they call a negative-stiffness honeycomb, which can absorb energy from an impact and then return to its original shape. Read more and see an infographic below.

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medium.com
Women in Science You Should Be Following On Social Media
Your Guide To #WomeninSTEM on Social
By Sci Chic

Hey check out who made the list ;) 

This list does a great job of covering a bunch of different fields within STEM so even if you are not interested in space there will be something for you!

Lance Family Tragedy AU

I doubt this will happen in the canon series, but say the Galra invade Earth and enslave the population into becoming soldiers as their own soldiers are dwindling. Prince Lotor oversees the housing and experimenting on Lance’s family personally in a twisted endeavor to coax him to his side. With Lance’s older sister, Tina, he has Haggar and the druids brainwash her by magnifying her despair over having to be the parent to her siblings and failing to keep Lance safe. She’s turned into the Galra’s best sniper/sharpshooter who acts according to the belief she must eliminate anything and anyone that would do Lance harm, including her own family. She executes their mother and father and sets her sights on Craig next, Lance’s older brother. His legs had been replaced with the same biotic mechanical material used to craft Shiro’s arm. When she arrives at his cell, he’s thrilled and relieved to see her, but the reunion turns to heartbreak and horror when she admits to killing their parents and is going to kill him for being a bully to Lance. She claims Prince Lotor awakened and freed her. With his new enhanced strength, Craig is able to fend her off and escape and eventually meets up with Lance and the Voltron crew. With only each other and their self-loathing to comfort them, they promise each other they’ll go to any length to get their sister back and rescue their younger siblings who have been taken to orphanages where children taken there are told their families abandoned them and now they must train to be soldiers for the Galra empire.

Craig, like Lance, was jealous of the attention Tina and the younger siblings would get, so he resorted to extreme measures to get noticed: performing dangerous stunts and often getting hurt really badly. He’d chastise Lance for being too much of a wuss to participate. Overtime, this harmful behavior developed into masochism. He would try to find any opportunity to get hurt without getting killed so he could live receiving the only affection he’d ever known. 

Anyhoo, I drabbed up a little script to go along with this AU of mine: Craig and Lance taking their training in the training deck too far and Lance coming to understand how Craig feels

CAPS I DO NOT IN ANY WAY SHAPE OR FORM CONDONE MASOCHISM AND SELF-HARM OF ANY KIND! IT’S FOR STORY/CHARACTER DEVELOPMENT PURPOSES AND IF ANY OF YOU ARE IN A DARK PLACE SEEK HELP FROM YOUR LOVED ONES OR SUICIDE HOT-LINES ON THE DOUBLE!!

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More Than You Ever Wanted to Know About Mechanical Engineering: Latent Heat

Let’s look in detail at the process of boiling a pure substance.

We’ll start out with a compressed liquid. We’ll say it’s water at 25 deg C. Moreover, let’s say it’s contained in a cylinder with a piston so that the pressure inside the cylinder is always at atmospheric pressure.

If we start heating up the cylinder, the water inside will expand slightly. The pressure will remain constant as the piston moves with the water’s expansion. Once we get to 100 deg C, the water exists as a saturated liquid - any additional heat will cause it to vaporize.

If we keep adding heat to it, things get interesting. The water will start to boil. It’s volume will increase drastically, but its temperature will remain the same. All the energy you’re putting into it is going into the phase change. The amount of energy it takes to go from a liquid to a vapor is called the latent heat of vaporization. (Similarly, the amount of heat it takes for a solid to melt into a liquid is the latent heat of fusion.)  So while the water in your cylinder is in the process of boiling, it exists as a mixture of saturated liquid and saturated vapor. Its temperature will remain at a constant 100 deg C throughout the process. Although its apparent volume will increase, its specific volume - the volume per unit mass - will also remain constant.

Once all the water has been vaporized, if you continue adding heat to the cylinder, the water will start to rise in temperature again and its specific volume will start to increase. In this state, it exists as a superheated vapor.

The entire process we just described looks like this.

Note that this show temperature vs. specific volume for only one pressure - if we varied the pressure as well, things would look quite different. The interdependence of temperature, volume, and pressure will be important in our analysis of thermodynamic processes.

I bet Kai in the first stages of his crush on Cinder wrote “Linh Kaito” in some important paper bc he kept daydreaming about the cute mechanic who was totally wifey material

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04.17.2017 : 🌱

Update on my Academic Life

It has begun. I feel the flames of “Hell Week” approaching. Its heat dances on my flesh. Today, i took exam 3 for Mechanics of Materials class. I’m certain that i didn’t get an A+, but maybe a B+. ( fingers crossed ) Tomorrow, exam 3 for Dynamics. it’s gonna be tough, no doubt about that.

Quiz in Physics this Thursday.

Next week: Differential Equations Final.
Then, I have three more finals the following week.

Update on my Non-Academic Life

I’ve only this year grown a small interest in anime. My interest in it is still small, but i’ve recently started watching one called “Golden Time”

Anime-like music is growing on me fast, though! A music artist called “Meltycanon” is my favorite right now! idk, just the aesthetics of some of the animes are very appealing to me.

youtube

(via https://www.youtube.com/watch?v=fyuv3WXPQsM)

Ok, so this is a bit outside the standard Tumblr fare. 

As someone who works wth machinery on a daily basis, I love this channel. He generally does power tool reviews taking them apart and seeing how they tick.

He is very knowledgeable about mechanical and electrical engineering, materials and processes. Throw in the vocabulary of someone who has spent many years working in industry along with a good dose of humor and it’s a winner. 

So enjoy a power tool teardown of a different sort. His  awkwardness is delicious.  “A cork stuffer that will rattle your fillings from downstairs” 😂

Never Forget & Never Stop Fighting

27 years ago today, 14 women were mercilessly executed at l’École Polytechnique de Montréal. Why? Because they were women.

Fourteen incredibly intelligent women with bright futures of now unknown potential were murdered by one man. One man crusading against the “Feminist Agenda.”

  • Geneviève Bergeron, a civil engineering student
  • Hélène Colgan, a mechanical engineering student
  • Nathalie Croteau, also a mechanical engineering student
  • Barbara Daigneault, another mechanical engineering student
  • Anne-Marie Edward, a chemical engineering student
  • Maud Haviernick, a materials engineering student
  • Maryse Laganière, a budget clerk in l’École Polytechnique finance department
  • Maryse Leclair, another materials engineering student
  • Anne-Marie Lemay, another mechanical engineering student
  • Sonia Pelletier, also a mechanical engineering student
  • Michèle Richard, a materials engineering student
  • Annie St-Arneault, a mechanical engineering student
  • Annie Turcotte, also a materials engineering student
  • Barbara Klucznik-Widajewicz, a nursing student

These are the names we need to remember, the names that we must celebrate, honour, and mourn. The misogynist that was so insecure, he was threatened by women studying engineering –– and women in general –– does not even deserve his name to be written in a footnote. 

These fourteen women are the ones who need to be remembered. They were rounded up, terrorized, and shot dead –– because they were women –– because they were smart, curious, and brave enough to enter a male-dominated field of study.

These women are the reason a pit grows in my stomach, the reason fear strangles my heart, whenever I see a man passionately argue #NotAllMen when faced with the innumerable accounts of #YesAllWomen. Because all it takes is one man with one gun to kill fourteen women when he feels like his rights, his place in society is threatened. 

One insecure man. Fourteen defenseless women.

This is why we need feminism, why we need to challenge the status quo to be better, to want better. We need men who can’t fathom why a woman shouldn’t be a physicist or an engineer. We need men who think it’s perfectly normal to cry or show emotion around their friends. We need boys who don’t understand how throwing or hitting like a girl is an insult. We need boys who are just as happy to dress up as Elsa for Halloween as they are Batman. We need toys that don’t separate the genders, that don’t tell the boys that they can be the next Einstein while telling girls that being cute is as far as they get to go in life. We need men to stop being threatened by a woman’s independence, strength, and success.

Feminism is not about the success of women at the expense of men, it’s about the success of women alongside men. It’s about respect and dignity. There is no reason (other than insecurity) for men to feel threatened by feminism, no reason (other than guilt) to try to discredit the negative experiences of women. Feminism should be about basic human decency, not about attacking (or defending) the patriarchy.

These fourteen women found out that you don’t even need to be an activist to be vilified as a feminist, you just need to be a woman. You don’t need to march in the streets for women’s rights, you just need to study engineering. You don’t need to take action, you just need to exist, and that’s enough to get you killed.

“When a circular shaft is subjected to torsion, every cross section remains plane and undistorted.”
“The property we are discussing is characteristic of circular shafts, whether solid or hollow; it is not enjoyed by members of non-circular cross section.” 
- Mechanics of Materials 6th Edition

Bows are not primitive weapons

They were the most technologically superior weapons of their day. The best that could be devised with the level of tools and expertise available. Bows were cutting edge tech in any time frame they were used.

Just think about it. Multiple people from multiple cultures figured out that storing potential energy by compression could be turned into potential energy. people figuring out that applying fletching imparted spin on the projectile which increased accuracy dramatically. Composite materials ranging from two different types of wood cut from different parts of the same log allowing for both strength and compression. The same being done with sinew, horn and wood layered together to make up for the deficiencies of a single material. Adjusting bow limb angles to dramatically increase the mechanical advantage. Its physics and material sciences working in harmony.

All these elements blending together to create a specialist weapon requiring years of practice to master and being suited to both hunting and warfare. There’s nothing primitive about a bow.