It’s been a while.
Hi everyone, how are you?
materialsscienceandengineering:
Materials Testing: Tensile Tests
Extremely useful for determining various mechanical properties, the tensile test (or tension test, as it is also called) is one of the most common methods of materials testing.
A tensile test is carried out by taking a sample of a material and subjecting it to increasing tension, stretching the sample until failure. This simple test results in the graph shown above (or something similar, depending on the material) called a stress-strain diagram. The elongation of the sample is determined with relation to the force required to produce such stretching and, knowing the cross-sectional area of the sample, the resulting stress and strain can be calculated and graphed.
This simple diagram gives a surprising number of mechanical properties, including the Modulus of Elasticity (or Young’s Modulus), yield strength, ultimate strength (also called ultimate tensile strength or tensile strength), and ductility (depending on the elongation before failure). Though less common, the stress-strain diagram can also be used to calculate the modulus of toughness and of resilience.
Along with the many properties that can be determined, another reason that tensile tests are so popular is that they can be used for almost any material. Depending on said material, the specimen is usually shaped similar to those in the bottom right image in what is called a ‘dog bone’ sample. The top left and bottom left images show brittle and ductile failure, respectively.
Image sources: top left, top right, bottom left, bottom middle, bottom right
New Job
Hey so I am back after a short hiatus from staring a new job a few months ago and getting some home projects done. Expect to see more posts showing up on your dashboard here soon.
Also don’t forget there is a submit page to share interesting projects.
Hackaday Useful Tools Links
So I am an avid reader of Hackaday for a long time now and they have been putting out a lot of great introductions to tools and processes to get makers up to speed on the resources that are available. This is just a splattering of links that I have found lately that you guys might be interested in.
- DC Motors
- Lessons in Small Scale Manufacturing
- Grinding Gears: Figuring out gear ratios
- Tools of the trade: Injection Molding
- Are todays engineers worse?
- How to nail a technical presentation
- Tools of the trade: Vacuum Forming
- The Art and Science of Bending Sheetmetal
- A how-to of designing, fab, and assembly with structural framing systems (t slot)
- Machine learning foundations
- A machine shop in a box
- How to: Cold resin casting
- Join the GUI generation: Qtcreator
Do you guys have any other great resources that you’d like to share and/or are you enjoying this type of content?
Canadian engineering team Aerovelo just broke their own world record in the Eta, a recumbent bicycle fitted with a windowless, egg-like shell. Most of the incredibly efficient machine is built of carbon fiber. The engine is muscle, sweat and sinew – engineer Todd Reichert.
I’ve covered Aerovelo’s efforts before: in 2012, they were racing to build a human powered helicopter. They succeeded in 2013.
Here’s a video I made about their competitors, a team of graduate students and undergrads from the University of Maryland.
Why CVT’s (continuously variable transmissions) are awesome. It covers the basics of torque, HP, rpm, and speed.
She never dreamed having her picture taken to recruit engineers would turn out to be a controversy.
When Isis Wenger agreed to be part of a recruiting campaign for engineers, she never imagined she’d face the controversy that arose.
What exactly was it about this image that had people clamoring to dissect her involvement? Did she say something messed up about engineering? Did she do something offensive in her pose?
All of the hubbub is over what she looks like. Because she’s a woman.
NASA Captures Details of a Rocket Test With Its New Camera
NASA unveiled a new camera during its recent space launch test, which is able to show the detail in a rocket plume. And it looks pretty spectacular.
Normally cameras can’t properly capture something like a rocket plume. You can fiddle with the exposure settings, but reducing them darkens the rest of the image. Most cameras also only record one exposure at a time.
However, the new High Dynamic Range Stereo X (HiDyRS-X) project overcomes this by being able to record multiple slow motion exposures at once and combining them into a more high-quality video. It uses a similar technique to what night photographers use when they splice multiple images together in post to get an impressive image.
The Othermill is something else - Hackaday
Hackaday has done a terrific write up of the engineering behind the Othermill cnc machine. In the article, which is way too long to post, they compare it to another generic desktop CNC kit, but at the same time they point out all the key areas that the designers had to take into account in order to build the machine. One detail is the hdpe frame vs aluminum extrusion that results in greater machinabililty (yep, it is a word), lighter weight, and cheaper cost of goods. It’s a great demonstration of how engineering doesn’t happen in a vacuum. There are many factors that have to be taken into account like materials, vibrations, loose material, wiring, fasteners, cost of goods, and ease of use.
While Hackaday is mainly an electronics and software blog, they occasionally branch out into the mechanical area. Definitely check it out.
Note: Just like Hackaday, we have not received any form of compensation for posting this from Othermill, I just think its a well designed machine.
Scientist Colin Furze Builds His Own Thermite Canon.
Thermite is a metal powder that burns at around 2500 degrees C. Whether or not Colin made this canon to teach others about chemistry (or just to blow stuff up), it’s still really cool regardless.
materialsscienceandengineering:
New record in materials research: One terapascals in a laboratory
An international team of researchers headed by Prof. Dr. Natalia Dubrovinskaia and Prof. Dr. Leonid Dubrovinsky of the University of Bayreuth has succeeded in creating a pressure of 1 trillion pascals in a laboratory. A study published in Science Advances is opening up new research prospects in physics, solid state chemistry, materials science, geophysics, and astrophysics.
The extreme pressures and temperatures that can be achieved and controlled with great precision in a laboratory are ideal objects of investigation in physics, chemistry, and materials science. They allow the structures and properties of materials to be explained, new materials to be synthesized for industrial applications, new material states to be discovered, and a deeper understanding of materials to be achieved, thereby yielding insights into the structure and dynamics of Earth and other planets. For this reason, scientists around the world have a strong research interest in continuing to increase the amount of pressure generated in laboratories for purposes of material analysis.
Why Tactile Intelligence Is the Future of Robotic Grasping
This is a guest post. The views expressed here are solely those of the author and do not represent positions of IEEE Spectrum or the IEEE.
The simple task of picking something up is not as easy as it seems. Not for a robot, at least. Roboticists aim to develop a robot that can pick up anything—but today most robots perform “blind grasping,” where they’re dedicated to picking up an object from the same location every time. If anything changes, such as the shape, texture, or location of the object, the robot won’t know how to respond, and the grasp attempt will most likely fail.
Robots are still a long way off from being able to grasp any object perfectly on their first attempt. Why do grasping tasks pose such a difficult problem? Well, when people try to grasp something they use a combination of senses, the primary ones being visual and tactile. But so far, most attempts at solving the grasping problem have focused on using vision alone.
Ruchi Sanghvi (b. 1982) is an Indian engineer, and the first female engineer employed by Facebook. She was one of the primary developers for the Facebook News Feed, and was behind many initiatives and new products released by the social network over time.
She left Facebook in 2011 in order to found her own company, called Cove, which was later sold to Dropbox. She also founded FWD.us, a lobbying group in Silicone Valley concerned with promoting immigration reform and education.
