Engineers

Underwater welding

2008-05-11T12:06:00.000-07:00

Underwater welding refers to a number of distinct welding processes that are performed underwater.
The two main categories of underwater welding techniques are wet underwater welding and dry underwater welding, both are classified as hyperbaric welding.
In wet underwater welding, a variation of shielded metal arc welding is commonly used, employing a waterproof electrode. Other processes that are used include flux-cored arc welding and friction welding. In each of these cases, the welding power supply is connected to the welding equipment through cables and hoses. The process is generally limited to low carbon equivalent steels, especially at greater depths, because of hydrogen-caused cracking.
In dry underwater welding the weld is performed at the prevailing pressure in a chamber filled with a gas mixture sealed around the structure being welded. For this process, gas tungsten arc welding is often used, and the resulting welds are of high integrity.
The applications of underwater welding are diverse—it is often used to repair ships, offshore oil platforms, and pipelines. Steel is the most common material welded. For deepwater welds and other applications where high strength is necessary, dry underwater welding is most commonly used. Research into using dry underwater welding at depths of up to 1000 m are ongoing. In general, assuring the integrity of underwater welds can be difficult (but is possible using various non-destructive testing applications), especially for wet underwater welds, because defects are difficult to detect if the defects are beneath the surface of the weld.
For the structures being welded by wet underwater welding, inspection following welding may be more difficult than for welds deposited in air. Assuring the integrity of such underwater welds may be more difficult, and there is a risk that defects may remain undetected.
The risks of underwater welding include the risk of electric shock to the welder. To prevent this, the welding equipment must be adaptable to a marine environment, properly insulated and the welding current must be controlled. Underwater welders must also consider the safety issues that normal divers face; most notably, the risk of decompression sickness due to the increased pressure of inhaled breathing gases. Another risk, generally limited to wet underwater welding, is the buildup of hydrogen and oxygen pockets, because these are potentially explosive.

from this link download good file about
AN ANALYSIS OF MICROSTRUCTURE AND CORROSION
RESISTANCE IN UNDERWATER FRICTION
STIR WELDED 304L STAINLESS STEEL : http://mihd.net/8eh3nwo

and this file about
Development of Compressive Residual
Stresses in Underwater PTA Welds

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Welding pipeline handbook

2008-05-09T02:00:00.000-07:00

book about welding of pipeline

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Catalogue of super precision bearing

2008-05-06T10:22:00.000-07:00

World ofBarden Precision Ball Bearings
Barden/FAG is the pre-eminent leader in super precision ball bearing manufacturing in the world today. Barden super precision bearings excel in applications where bearings of lesser quality have failed. If superior accuracy, reliability of operation, long-life, high running speeds and low noise and vibration are requirements in your application, Barden/FAG precision bearings are the bearings of choice.

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Good vedio for CNC

2008-04-28T02:32:00.000-07:00

The abbreviation CNC stands for computer numerical control, and refers specifically to a computer "controller" that reads G-code instructions and drives a machine tool, a powered mechanical device typically used to fabricate components by the selective removal of material. CNC does numerically directed interpolation of a cutting tool in the work envelope of a machine. The operating parameters of the CNC can be altered via a software load program.

CNC was preceded by NC (Numerically Controlled) machines, which were hard wired and their operating parameters could not be changed. NC was developed in the late 1940s and early 1950s by John T. Parsons in collaboration with the MIT Servomechanisms Laboratory. The first CNC systems used NC style hardware, and the computer was used for the tool compensation calculations and sometimes for editing.
Punched tape continued to be used as a medium for transferring G-codes into the controller for many decades after 1950, until it was eventually superseded by RS232 cables, floppy disks, and now is commonly tied directly into plant networks. The files containing the G-codes to be interpreted by the controller are usually saved under the .NC extension. Most shops have their own saving format that matches their ISO certification requirements.
The introduction of CNC machines radically changed the manufacturing industry. Curves are as easy to cut as straight lines, complex 3-D structures are relatively easy to produce, and the number of machining steps that required human action have been dramatically reduced.
With the increased automation of manufacturing processes with CNC machining, considerable improvements in consistency and quality have been achieved with no strain on the operator. CNC automation reduced the frequency of errors and provided CNC operators with time to perform additional tasks. CNC automation also allows for more flexibility in the way parts are held in the manufacturing process and the time required to change the machine to produce different components.

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Very good book for welding

2008-04-27T11:35:00.000-07:00

Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material (the weld puddle) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld. This is in contrast with soldering and brazing, which involve melting a lower-melting-point material between the workpieces to form a bond between them, without melting the workpieces.

Arc welding
Many different energy sources can be used for welding, including a gas flame, an electric arc, a laser, an electron beam, friction, and ultrasound. While often an industrial process, welding can be done in many different environments, including open air, underwater and in space. Regardless of location, however, welding remains dangerous, and precautions must be taken to avoid burns, electric shock, poisonous fumes, and overexposure to ultraviolet light.
Until the end of the 19th century, the only welding process was forge welding, which blacksmiths had used for centuries to join metals by heating and pounding them. Arc welding and oxyfuel welding were among the first processes to develop late in the century, and resistance welding followed soon after. Welding technology advanced quickly during the early 20th century as World War I and World War II drove the demand for reliable and inexpensive joining methods. Following the wars, several modern welding techniques were developed, including manual methods like shielded metal arc welding, now one of the most popular welding methods, as well as semi-automatic and automatic processes such as gas metal arc welding, submerged arc welding, flux-cored arc welding and electroslag welding. Developments continued with the invention of laser beam welding and electron beam welding in the latter half of the century. Today, the science continues to advance. Robot welding is becoming more commonplace in industrial settings, and researchers continue to develop new welding methods and gain greater understanding of weld quality and properties.

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Heat exchanger

2008-04-26T12:15:00.000-07:00

A heat exchanger is a device built for efficient heat transfer from one medium to another, whether the media are separated by a solid wall so that they never mix, or the media are in direct contact.[1] They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, and natural gas processing. One common example of a heat exchanger is the radiator in a car, in which a hot engine-cooling fluid, like antifreeze, transfers heat to air flowing through the radiator

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Ergonomics

2008-04-25T15:15:00.000-07:00

Ergonomics is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance. [1] The field is also called human engineering, and human factors engineering.
Ergonomic research is primarily performed by ergonomists, who study human capabilities in relationship to their work demands. Information derived from ergonomists contributes to the design and evaluation of tasks, jobs, products, environments and systems in order to make them compatible with the needs, abilities and limitations of people (IEA, 2000). In the UK the professional body for ergonomists is the Ergonomics Society.

Physical ergonomics: is concerned with human anatomical, anthropometric, physiological and biomechanical characteristics as they relate to physical activity. (Relevant topics include working postures, materials handling, repetitive movements, work related musculoskeletal disorders, workplace layout, safety and health.)
Cognitive ergonomics: is concerned with mental processes, such as perception, memory, reasoning, and motor response, as they affect interactions among humans and other elements of a system. (Relevant topics include mental workload, decision-making, skilled performance, human-computer interaction, human reliability, work stress and training as these may relate to human-system design.)
Organizational ergonomics: is concerned with the optimization of sociotechnical systems, including their organizational structures, policies, and processes.(Relevant topics include communication, crew resource management, work design, design of working times, teamwork, participatory design, community ergonomics, cooperative work, new work paradigms, virtual organizations, telework, and quality management.)

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Sheet Metal forming

2008-04-25T15:00:00.000-07:00

Sheet metal is simply metal formed into thin and flat pieces. It is one of the fundamental forms used in metalworking, and can be cut and bent into a variety of different shapes. Countless everyday objects are constructed of the material. Thicknesses can vary significantly, although extremely thin pieces of sheet metal would be considered to be foil or leaf, and pieces thicker than 1/4 inch or a centimeter can be considered plate.
Sheet metal is generally produced in sheets less than 6 mm. Sheet metals are available as flat pieces or as strip in coils. It is characterized by its thickness or gauge of the metal. The gauge of sheet metal ranges from 30 gauge to about 8 gauge. The higher the gauge, the thinner the metal is. There are many different metals that can be made into sheet metal. Aluminum, brass, copper, cold rolled steel, mild steel, tin, nickel and titanium are just a few examples of metal that can be made into sheet metal. Sheet metal has applications in car bodies, airplane wings, medical tables, roofs for building and many other things.

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Simulation of the superplastic forming of an aircraft part

2008-04-25T14:46:00.000-07:00

Superplastic forming

Superplastic forming (SPF) is a metal forming process that takes advantage of the high extendibility of certain materials in order to form components whose shapes might be otherwise very difficult to obtain.

In a SPF process, a thin plate is hot formed in a die by means of gas pressure. The evolution of pressures must be closely controlled during the process since the alloys of interest only exhibits superplastic behaviour for certain temperature dependent range of strain rates.

Applications

The process is increasingly being applied in the aerospace industry as a way of manufacturing very complex geometries at a fraction of the cost of conventional machining, but some practical problems are still of concern, the main ones being:
predicting the final thickness distribution of the formed parts
determining the optimum pressure cycles
specifying the overall forming times

Instead of carrying out an extensive experimental program of tests, the superplastic forming process can be optimised with the application of numerical simulation techniques, resulting in a reduction of the time and costs needed to design a specific forming process. Due to the highly non-linear aspects inherent with the superplastic forming processes, expertise in advanced numerical analysis is unavoidably required

The Project

In the development of the fabrication process for the slats of the Dornier 728 aircraft, a numerical simulation of the superplastic forming of the pockets of the slat was carried out by IDOM for Construcciones Aeronauticas, S.A. (CASA).

The main concern was whether the thickness distribution over the formed pockets would lie within acceptable limits. There was also a lot of interest in knowing the optimum pressure cycle and the overall forming time. The first geometry analysed turned out to be inappropriate according to CASA´s design requirements for the pocket and the forming process of a second alternative had to be simulated.

The whole interactive process was over in two weeks time, with the subsequent reduction of time, costs and uncertainties regarding deadlines.

Internal combustion engine

2008-04-25T13:35:00.000-07:00

The internal combustion engine is an engine in which the combustion of fuel and an oxidizer (typically air) occurs in a confined space called a combustion chamber. This exothermic reaction creates gases at high temperature and pressure, which are permitted to expand. The defining feature of an internal combustion engine is that useful work is performed by the expanding hot gases acting directly to cause movement of solid parts of the engine, by acting on pistons, rotors, or even by pressing on and moving the entire engine itself.
This contrasts with external combustion engines, such as steam engines and Stirling engines, which use an external combustion chamber to heat a separate working fluid, which then in turn does work, for example by moving a piston or a turbine.
The term Internal Combustion Engine (ICE) is almost always used to refer specifically to reciprocating piston engines, Wankel engines and similar designs in which combustion is intermittent. However, continuous combustion engines, such as jet engines, most rockets and many gas turbines are also internal combustion engines.

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Introduction of Non Destructive Testing

2008-04-25T06:29:00.000-07:00

Nondestructive testing (NDT), also called nondestructive examination (NDE) and nondestructive inspection (NDI), is testing that does not destroy the test object. NDE is vital for constructing and maintaining all types of components and structures. To detect different defects such as cracking and corrosion, there are different methods of testing available, such as X-ray (where cracks show up on the film) and ultrasound (where cracks show up as an echo blip on the screen). This article is aimed mainly at industrial NDT, but many of the methods described here can be used to test the human body. In fact methods from the medical field have often been adapted for industrial use, as was the case with Phased array ultrasonics and Computed radiography.
While destructive testing usually provides a more reliable assessment of the state of the test object, destruction of the test object usually makes this type of test more costly to the test object's owner than nondestructive testing. Destructive testing is also inappropriate in many circumstances, such as forensic investigation. That there is a tradeoff between the cost of the test and its reliability favors a strategy in which most test objects are inspected nondestructively; destructive testing is performed on a sampling of test objects that is drawn randomly for the purpose of characterizing the testing reliability of the nondestructive test.

The need for NDT

It is very difficult to weld or mold a solid object that has the risk of breaking in service, so testing at manufacture and during use is often essential. During the process of casting a metal object, for example, the metal may shrink as it cools, and crack or introduce voids inside the structure. Even the best welders (and welding machines) do not make 100% perfect welds. Some typical weld defects that need to be found and repaired are lack of fusion of the weld to the metal and porous bubbles inside the weld, both of which could cause a structure to break or a pipeline to rupture.
During their service lives, many industrial components need regular nondestructive tests to detect damage that may be difficult or expensive to find by everyday methods. For example:
aircraft skins need regular checking to detect cracks;
underground pipelines are subject to corrosion and stress corrosion cracking;
pipes in industrial plants may be subject to erosion and corrosion from the products they carry;
concrete structures may be weakened if the inner reinforcing steel is corroded;
pressure vessels may develop cracks in welds;
the wire ropes in suspension bridges are subject to weather, vibration, and high loads, so testing for broken wires and other damage is important.
Over the past centuries, swordsmiths, blacksmiths, and bell-makers would listen to the ring of the objects they were creating to get an indication of the soundness of the material. The wheel-tapper would test the wheels of locomotives for the presence of cracks, often caused by fatigue — a function that is now carried out by instrumentation and referred to as the acoustic impact technique.

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Animation show the hydraulic circuts componants

2008-04-24T12:41:00.000-07:00

Hydraulics is a topic of science and engineering dealing with the mechanical properties of liquids. Hydraulics is part of the more general discipline of fluid power. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. Hydraulic topics range through most science and engineering disciplines, and cover concepts such as pipe flow, dam design, fluid control circuitry, pumps, turbines, hydropower, computational fluid dynamics, flow measurement, river channel behavior and erosion. However if used incorrectly, hydraulic instruments can result in weird occurrences because of the nature of high pressure fluids.
The word "hydraulics" originates from the Greek word ὑδραυλικός (hydraulikos) which in turn originates from ὕδραυλος (hydraulos) meaning water organ which in turn comes from ὕδωρ (hydor, Greek for water) and αὐλός (aulos, meaning pipe).

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Good vedio about gear box

2008-04-24T11:05:00.000-07:00

In mechanics, a transmission (also called a "standard" or "manual" transmission) or gearbox, is the system of gears and/or the hydraulic system (called variously "hydrodynamic", "fluid" or "automatic" transmission) that transmits mechanical power from a prime mover—such as an engine or electric motor—to some form of useful output device, normally rotary in form, and generally at a reduced rate of angular speed but at a higher motive torque.

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thesite: http://www.motive.it/eng/boxmovie.htm

Centrifugal pump (good ppt files

2008-04-24T10:25:00.000-07:00

A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the velocity of a fluid. Centrifugal pumps are commonly used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber, from where it exits into the downstream piping system

.A centrifugal pump works by the conversion of the rotational kinetic energy, typically from an electric motor or turbine, to an increased static fluid pressure. This action is described by Bernoulli's principle. The rotation of the pump impeller imparts kinetic energy to the fluid as it is drawn in from the impeller eye (centre) and is forced outward through the impeller vanes to the periphery. As the fluid exits the impeller, the fluid kinetic energy (velocity) is then converted to (static) pressure due to the change in area the fluid experiences in the volute section. Typically the volute shape of the pump casing (increasing in volume), or the diffuser vanes (which serve to slow the fluid, converting to kinetic energy in to flow work) are responsible for the energy conversion. The energy conversion results in an increased pressure on the downstream side of the pump, causing flow

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vedio about mechanical vibration

2008-04-23T08:21:00.000-07:00

Vibration is a term that describes oscillation in a mechanical system. It is defined by
the frequency (or frequencies) and amplitude. Either the motion of a physical object
or structure or, alternatively, an oscillating force applied to a mechanical system is
vibration in a generic sense. Conceptually, the time-history of vibration may be considered
to be sinusoidal or simple harmonic in form. The frequency is defined in
terms of cycles per unit time, and the magnitude in terms of amplitude (the maximum
value of a sinusoidal quantity). The vibration encountered in practice often
does not have this regular pattern. It may be a combination of several sinusoidal
quantities, each having a different frequency and amplitude. If each frequency component
is an integral multiple of the lowest frequency, the vibration repeats itself
after a determined interval of time and is called periodic. If there is no integral relation
among the frequency components, there is no periodicity and the vibration is
defined as complex.
Vibration may be described as deterministic or random. If it is deterministic, it
follows an established pattern so that the value of the vibration at any designated
future time is completely predictable from the past history. If the vibration is random,
its future value is unpredictable except on the basis of probability. Random
vibration is defined in statistical terms wherein the probability of occurrence of designated
magnitudes and frequencies can be indicated.The analysis of random vibration
involves certain physical concepts that are different from those applied to the
analysis of deterministic vibration.
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Animation show obviously power plant opreation and system

2008-04-20T11:14:00.000-07:00

Introduction to power plant

Thermal power plants (including those that use fissile elements or burn coal, petroleum, or natural gas), and heat engines in general, do not convert all of their available energy into electricity. In most heat engines, a bit more than half is wasted as excess heat (see: Second law of thermodynamics). By capturing the excess heat, CHP uses heat that would be wasted in a conventional power plant, potentially reaching an efficiency of up to 89%, compared with 55%[3] for the best conventional plants. This means that less fuel needs to be consumed to produce the same amount of useful energy. Also, less pollution is produced for a given economic benefit.
this animation show that basic cycle,combind cycle, power plant system and operation
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program show parts all parts of car

2008-04-20T10:33:00.000-07:00

automotive parts

concern parts that are not specifically or only found on automobiles but also on other vehicles. Multi-part technologies are addressed in the parent Automotive technologies. Non-essential, optional parts are the domain of Automotive accessories, while retailers and suppliers of essential and non-essential parts are found in:Auto parts suppliers and Automotive part retailers,

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BEARING

2008-04-20T08:43:00.000-07:00

Bearing (mechanical):

A bearing is a device to permit constrained relative motion between two parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can handle.

Bearing friction

Low friction bearings are often important for efficiency, to reduce wear and to facilitate high speeds. Essentially, a bearing can reduce friction by virtue of its shape, by its material, or by introducing and containing a fluid between surfaces.
By shape, gains advantage usually by using spheres or rollers.
By material, exploits the nature of the bearing material used. (An example would be using plastics that have low surface friction.)
By fluid, exploits the low viscosity of a layer of fluid, such as a lubricant or as a pressurised medium to keep the two solid parts from touching.
By fields, exploits electromagnetic fields, such as magnetic fields, to keep solid parts from touching.
Combinations of these can even be employed with the same bearing. An example of this is where the cage is made of plastic, and it separates the rollers/balls, which reduce friction by their shape and finish

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gear design

2008-04-20T08:07:00.000-07:00

Gears are machine elements used to transmit rotary motion between two shafts, normally with a constant ratio. The pinion is the smallest gear and the larger gear is called the gear wheel.. A rack is a rectangular prism with gear teeth machined along one side- it is in effect a gear wheel with an infinite pitch circle diameter. In practice the action of gears in transmitting motion is a cam action each pair of mating teeth acting as cams. Gear design has evolved to such a level that throughout the motion of each contacting pair of teeth the velocity ratio of the gears is maintained fixed and the velocity ratio is still fixed as each subsequent pair of teeth come into contact. When the teeth action is such that the driving tooth moving at constant angular velocity produces a proportional constant velocity of the driven tooth the action is termed a conjugate action. The teeth shape universally selected for the gear teeth is the involute profile.Consider one end of a piece of string is fastened to the OD of one cylinder and the other end of the string is fastened to the OD of another cylinder parallel to the first and both cylinders are rotated in the opposite directions to tension the string(see figure below). The point on the string midway between the cylinder P is marked. As the left hand cylinder rotates CCW the point moves towards this cylinder as it wraps on . The point moves away from the right hand cylinder as the string unwraps. The point traces the involute form of the gear teeth.

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Machine Design Databook

2008-04-20T05:11:00.000-07:00

Machine Design Databook

By K. LingaiahPublisher: McGraw-Hill Professional

Number Of Pages: 1344
Publication Date: 2002-11-13
Sales Rank: 281857
ISBN / ASIN: 0071367071
EAN: 0639785327752

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Download Free Engineering Books !

2008-04-20T05:01:00.000-07:00

The Best Free Online Mechanical And Production Engineering Library

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Good book for solidwork user

2008-04-20T04:48:00.000-07:00

SolidWorks is a 3D mechanical CAD (computer-aided design) program that runs on Microsoft Windows and was developed by SolidWorks CorporationSolidworks is used primarily by mechanical engineers and designers. Its user base ranges from individuals to large companies, and covers a wide cross-section of manufacturing market segments, with its only significant weaknesses among large aerospace and automotive companies (which have historically been users of CATIA and Unigraphics CAD software.). Commercial sales are made through an indirect channel, which includes dealers and partners throughout the world. Directly competitive products to SolidWorks include Autodesk Inventor, Solid Edge, and Pro/ENGINEER

WebSite : http://www.solidworks.com

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