UNDER WATER WELDING:





The Welding is an unavoidable process of modern engineering – civil, electrical,
mechanical, automobiles, marine aeronautical – in all branches. It is used in
fabrications and erections in infrastructures and installations. It joins metals
or thermoplastics.
The Hyperbaric welding OR UNDER WATER WELDING is the process of welding at elevated pressures, normally in underwater. It is of 2 types DRY & WET Welding. The Hyperbaric welding can either take place wet in the water itself OR dry inside. Here a specially constructed positive pressure enclosure is used and hence it is called dry welding. Similarly Hyperbaric welding term used in dry environment & underwater welding term used as in wet environment. The hyperbaric welding is used to repair damaged ships, under water pipe line & etc.
INTRODUCTION:-



The fact that electric arc could operate was known for over a 100 years. The first ever underwater welding was carried out by British Admiralty – Dockyard for sealing leaking ship rivets below the water line.
Underwater welding is an important tool for underwater fabrication works. In 1946, special waterproof electrodes were developed in Holland by ‘Van der Willingen’. In recent years the number of offshore structures including oil drilling rigs, pipelines, platforms are being installed significantly. Some of these structures will experience failures of its elements during normal usage and during unpredicted occurrences like storms, collisions. Any repair method will require the use of underwater welding.
UNDERWATER WELDING PRINCIPLES:-





Underwater welding can be performed under wet or dry conditions. Dry underwater welding refers to underwater welding which is performed under hyperbaric conditions (an underwater habitat is displacing the water with a gas at the prevailing pressure), and wet underwater welding refers to welding which is performed in fresh- or salt-water without a protecting habitat.
Wet underwater welding will here after be referred to as ―wet welding‖, and wet/dry underwater welding will simply be referred to as ―underwater welding‖. The most commonly used wet welding technique is shielded metal arc welding (SMAW), also known as manual metal arc (MMA) welding or informally as stick welding. The main differences for the welding equipment (wet welding equipment versus ―workshop‖ welding equipment) are shown in Figure 1. Note that wet underwater welding is performed by using a (usually motor generated) power source generating DC current only (for wet welding AC is not used on account of electrical safety and difficulty in maintaining a welding arc underwater), the inclusion of a single or dual pole knife switch (circuit breaker), which protects a welding diver from electrocution, and the use of double insulated cables. Both the power source and knife switch (capable of breaking the full wet welding current) are secured above water (grounded) and controlled (on the diver welders command) by an operator. The cross section of the welding cable is adjusted to the length of the cable and should be highly wear resistant (marine growth) and sufficiently flexible; special welding electrode holders are used with extra insulation against the ingress of water.


CLASSIFICATION OF UNDERWATER WELDING:-
The Underwater welding can be classified as:-
1) Wet Welding:- In wet welding the welding is performed underwater, directly exposed to the wet environment.
2) Dry Welding :- In dry welding, a dry chamber is created near the area to be welded and the welder does the job by staying inside the chamber



COMPONENTS OF WATER WELDING:-
Electrode Holder:-

This new generation compression type welding stinger is engineered with features that let you know it’s from Broco. Lightweight, durable and designed to hold the electrode at the optimum angle to reduce diver fatigue. The new BR-21... Setting the wet welding standard.


Water Resistant Electrodes:- 




The fundamental process of welding underwater does not differ from welding on land. An electrode carrying a direct current creates an arc of electricity. That arc is then applied to melt the target metal. The difference is that the electrodes used underwater are waterproof. Extra insulation around the connections ensure that the current will be able to generate the arc and not degrade the copper wiring. Doing this underwater presents a new set of risks. Both the risk of electrocution and the technical difficulty of maintaining the electrical arc underwater, is the reason why direct currents are used instead of alternating currents.
Line Diagram :




The power source should be a direct current machine rated at 300 or 400 amperes. Motor generator welding machines are most often used for underwater welding in the wet. The welding machine frame must be grounded to the ship. The welding circuit must include a positive type of switch, usually a knife switch operated on the surface and commanded by the welder-diver. The knife switch in the electrode circuit must be capable of breaking the full welding current and is used for safety reasons. The welding power should be connected to the electrode holder only during welding. Direct current with electrode negative (straight polarity) is used. Special welding electrode holders with extra insulation against the water are used. The underwater welding electrode holder utilizes a twist type head for gripping the electrode. It accommodates two sizes of electrodes. The electrode types used conform to AWS E6013 classification. The electrodes must be waterproofed. All connections must be thoroughly insulated so that the water cannot come in contact with the metal parts. If the insulation does leak, seawater will come in contact with the metal conductor and part of the current will leak away and will not be available at the arc. In addition, there will be rapid deterioration of the copper cable at the point of the leak.

Metal particles in solids aren't as fixed as they seem, new memristor study shows

 In work that unmasks some of the magic behind memristors and "resistive random access memory," or RRAM -- cutting-edge computer components that combine logic and memory functions -- researchers have shown that the metal particles in memristors don't stay put as previously thought.

The findings have broad implications for the semiconductor industry and beyond. They show, for the first time, exactly how some memristors remember.

"Most people have thought you can't move metal particles in a solid material," said Wei Lu, associate professor of electrical and computer engineering at the University of Michigan. "In a liquid and gas, it's mobile and people understand that, but in a solid we don't expect this behavior. This is the first time it has been shown."

The results could lead to a new approach to chip design -- one that involves using fine-tuned electrical signals to lay out integrated circuits after they're fabricated. And it could also advance memristor technology, which promises smaller, faster, cheaper chips and computers inspired by biological brains in that they could perform many tasks at the same time.

Lu, who led the project, and colleagues at U-M and the Electronic Research Centre Jülich in Germany used transmission electron microscopes to watch and record what happens to the atoms in the metal layer of their memristor when they exposed it to an electric field. The metal layer was encased in the dielectric material silicon dioxide, which is commonly used in the semiconductor industry to help route electricity.

They observed the metal atoms becoming charged ions, clustering with up to thousands of others into metal nanoparticles, and then migrating and forming a bridge between the electrodes at the opposite ends of the dielectric material.

They demonstrated this process with several metals, including silver and platinum. And depending on the materials involved and the electric current, the bridge formed in different ways.

The bridge, also called a conducting filament, stays put after the electrical power is turned off in the device. So when researchers turn the power back on, the bridge is there as a smooth pathway for current to travel along. Further, the electric field can be used to change the shape and size of the filament, or break the filament altogether, which in turn regulates the resistance of the device, or how easy current can flow through it.

Computers built with memristors would encode information in these different resistance values, which is in turn based on a different arrangement of conducting filaments.

Memristor researchers like Lu and his colleagues had theorized that the metal atoms in memristors moved, but previous results had yielded different shaped filaments and so they thought they hadn't nailed down the underlying process.

"We succeeded in resolving the puzzle of apparently contradicting observations and in offering a predictive model accounting for materials and conditions," said Ilia Valov, principle investigator at the Electronic Materials Research Centre Jülich. "Also the fact that we observed particle movement driven by electrochemical forces within dielectric matrix is in itself a sensation."

Lu is a co-founder of Crossbar Inc., a Santa Clara, Calif.-based startup working to commercialize RRAM. Crossbar has just completed a $25 million Series C funding round.

The study is titled "Electrochemical dynamics of nanoscale metallic inclusions in dielectrics." It is newly published online in Nature Communications. The work was funded by the Air Force Office of Scientific Research, the U.S. Department of Energy and the National Science Foundation and the German Research Foundation priority program SFB 917.

Story Source:

The above story is based on materials provided by University of Michigan.

Researchers made world's best thermometer from light.

Published in the journal Physical Review Letters , the researchers from the University's Institute for Photonics and Advanced Sensing (IPAS) report they have been able to measure temperature with a precision of 30 billionths of a degree.

"We believe this is the best measurement ever made of temperature − at room temperature," says project leader Professor Andre Luiten, Chair of Experimental Physics in IPAS and the School of Chemistry and Physics, pointing out that it is possible to make more sensitive measurements of temperature in cryogenic environments (at very low temperatures) near absolute zero.
"We've been able to measure temperature differences to 30 billionths of a degree in one second," says Professor Luiten. "To emphasise how precise this is, when we examine the temperature of an object we find that it is always fluctuating. We all knew that if you looked closely enough you find that all the atoms in any material are always jiggling about, but we actually see this unceasing fluctuation with our thermometer, showing that the microscopic world is always in motion."
The paper -- Nano-Kelvin Thermometry and Temperature Control: Beyond the Thermal Noise Limit -- describes a new and very sensitive, but unorthodox, thermometer that uses light to measure temperature. PhD candidate Wenle Weng carried out the work.

The thermometer injects two colours of light (red and green) into a highly polished crystalline disk. The two colours travel at slightly different speeds in the crystal, depending on the temperature of the crystal.

"When we heat up the crystal we find that the red light slows down by a tiny amount with respect to the green light," Professor Luiten says.

"By forcing the light to circulate thousands of times around the edge of this disk in the same way that sound concentrates and reinforces itself in a curve in a phenomena known as a "whispering gallery" -- as seen in St Paul's Cathedral in London or the Whispering Wall at Barossa Reservoir -- then we can measure this minuscule difference in speed with great precision."

Professor Luiten says the researchers have developed a new technique which could be redesigned for ultra-sensitive measurements of other things such as pressure, humidity, force or searching for a particular chemical.

"Being able to measure many different aspects of our environment with such a high degree of precision, using instruments small enough to carry around, has the capacity to revolutionise technologies used for a variety of industrial and medical applications where detection of trace amounts has great importance," Professor Luiten says.

The research is supported by the Australian Research Council and the South Australian Government's Premier's Science and Research Fund.

IMAGE: A computer generated image of the Light Thermometer. A slight difference in the speed of the green and red light can tell us the temperature.

SOURCE: Science Daily

Staircaseclimber trolley

The project aims to bring forward a means to transport heavy objects over stairs. The need of such a system is obvious from the day-to-day requirements of our society. Devices such as hand trucks are used to relieve the stress of lifting while on flat ground; however, these devices usually fail when it becomes necessary to negotiate a short flight of stairs. In the light of this, the project attempts to design a stair climbing hand cart which can carry heavy objects up the stairs with less effort compared to carrying them manually. It also endeavours to study the commercial viability and importance of such a product. Several designs were conceived that would allow a non-industrial hand truck to travel over stairs, curbs, or uneven terrain while putting minimal strain on the user. 

In our project, the trolley is equipped with Tri-Star wheels, which, as the name implies, is designed to go up and down stairs. It also eases the movement of trolley in irregular surfaces like holes, bumps, etc.

For more details contact me :)

Mechanical engineering:

Mechanical engineering is a discipline of engineering that applies the principles of engineering, physics and

materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the production and usage of heat and mechanical power for the design, production, and operation of machines and tools. It is one of the oldest and broadest engineering disciplines.

The engineering field requires an understanding of core concepts including mechanics, kinematics, thermodynamics, materials science, structural analysis, and electricity. Mechanical engineers use these core principles along with tools like computer-aided engineering, and product lifecycle management to design and analyze manufacturing plants, industrial equipment and machinery, heating and cooling systems, transport systems, aircraft, watercraft, robotics, medical devices, weapons, and others.

Mechanical engineering emerged as a field during the industrial revolution in Europe in the 18th century; however, its development can be traced back several thousand years around the world. Mechanical engineering science emerged in the 19th century as a result of developments in the field of physics. The field has continually evolved to incorporate advancements in technology, and mechanical engineers today are pursuing developments in such fields as composites, mechatronics, and nanotechnology. Mechanical engineering overlaps with aerospace engineering, metallurgical engineering, civil engineering, electrical engineering, petroleum engineering, manufacturing engineering, chemical engineering, and other engineering disciplines to varying amounts. Mechanical engineers may also work in the field of Biomedical engineering, specifically with biomechanics, transport phenomena, biomechatronics, bionanotechnology and modeling of biological systems, like soft tissue mechanics. 

http://en.wikipedia.org/wiki/Mechanical_engineering

                                                                                                                        

Portable Engine

A portable Engine

 A precursor to modern engineering vehicles