They are exceedingly nice, pleasant, trustworthy, mostly honest, well-intentioned, and utterly decent. But their brains are largely empty, devoid of any substantial knowledge that might be the fruits of an education in an inheritance and a gift of a previous generation. They are the culmination of western civilization, a civilization that has forgotten nearly everything about itself, and as a result, has achieved near-perfect indifference to its own culture. Students at these institutions have done what has been demanded of them:
Principle of operation[ edit ] Two discrete metal workpieces butted together, along with the tool with a probe The progress of the tool through the joint, also showing the weld zone and the region affected by the tool shoulder A rotating cylindrical tool with a profiled probe is fed into a butt joint between two clamped workpieces, until the shoulder, which has a larger diameter than the pin, touches the surface of the workpieces.
The probe is slightly shorter than the weld depth required, with the tool shoulder riding atop the work surface. This heat, along with that generated by the mechanical mixing process and the adiabatic heat within the material, cause the stirred materials to soften without melting.
As the tool is moved forward, a special profile on the probe forces plasticised material from the leading face to the rear, where the high forces assist in a forged consolidation of the weld. This process of the tool traversing along the weld line in a plasticised tubular shaft of metal results in severe solid-state deformation involving dynamic recrystallization of the base material.
The micro-structure can be broken up into the following zones: The stir zone also known as the dynamically recrystallised zone is a region of heavily deformed material that roughly corresponds to the location of the pin during welding.
The grains within the stir zone are roughly equiaxed and often an order of magnitude smaller than the grains in the parent material. The flow arm zone is on the upper surface of the weld and consists of material that is dragged by the shoulder from the retreating side of the weld, around the rear of the tool, and deposited on the advancing side.
In this region the strain and temperature are lower and the effect of welding on the micro-structure is correspondingly smaller. Unlike the stir zone, the micro-structure is recognizably that of the parent material, albeit significantly deformed and rotated.
Although the term TMAZ technically refers to the entire deformed region, it is often used to describe any region not already covered by the terms stir zone and flow arm.
As indicated by the name, this region is subjected to a thermal cycle but is not deformed during welding. The temperatures are lower than those in the TMAZ but may still have a significant effect if the micro-structure is thermally unstable.
In fact, in age-hardened aluminum alloys this region commonly exhibits the poorest mechanical properties. Issues such as porositysolute redistribution, solidification cracking and liquation cracking do not arise during FSW.
In general, FSW has been found to produce a low concentration of defects and is very tolerant to variations in parameters and materials. Nevertheless, FSW is associated with a number of unique defects if it isn't done properly.
Insufficient weld temperatures, due to low rotational speeds or high traverse speeds, for example, mean that the weld material is unable to accommodate the extensive deformation during welding.
This may result in long, tunnel-like defects running along the weld, which may occur on the surface or subsurface. Low temperatures may also limit the forging action of the tool and so reduce the continuity of the bond between the material from each side of the weld.
The light contact between the material has given rise to the name "kissing bond". This defect is particularly worrying, since it is very difficult to detect using nondestructive methods such as X-ray or ultrasonic testing.
If the pin is not long enough or the tool rises out of the plate, then the interface at the bottom of the weld may not be disrupted and forged by the tool, resulting in a lack-of-penetration defect. This is essentially a notch in the material, which can be a potential source of fatigue cracks.
A number of potential advantages of FSW over conventional fusion-welding processes have been identified: Improved safety due to the absence of toxic fumes or the spatter of molten material. Can operate in all positions horizontal, vertical, etc.Thanks Tawcan for the great post.
I love reading more of your story. Your post about having to learn English in the fly was a classic. The people around you have a huge impact on your life.
There may not be anyone who knows more about emoticons than Tyler Schnoebelen, a man who literally wrote his Stanford doctorate thesis on the subject.
He found, for instance, that older people. Friction stir welding (FSW) is a solid-state joining process that uses a non-consumable tool to join two facing workpieces without melting the workpiece material.
Heat is generated by friction between the rotating tool and the workpiece material, which leads to a softened region near the FSW tool. Chevrolet Silverado mk3 (Third Generation) – – fuse box diagram.
Year of production: , Engine Compartment Fuse Block. The engine compartment fuse block is in the engine compartment, on the driver side of the vehicle. Thesis and Research Topics in Computer Science. With each passing day, new and innovative developments are coming out in this era of mechanization.
If there’s a problem with the Millenials, it’s the fault of the older Boomer generation in control of school curricula.
My parents’ generation was the Great Depression and WWII and they did an okay job of transmitting the best of Western civilization to us, but we squandered it when it came our turn to pass it on the younger generations.