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Mechanical Engineering

Mechanical Engineering is a branch of engineering that encompasses the generation and application of heat and mechanical power and the design, production, and use of machines and tools. Mechanical engineering involves application of the principles of dynamics, control, thermodynamics and heat transfer, fluid mechanics, strength of materials, materials science, electronics, and mathematics.

10,989 Questions

Why do most hydraulic systems use oil instead of water?

The short answer: Cost effectiveness.

The long answer: Employing water as a hydraulic fluid is entirely possible for many applications, but produces several additional challenges which will dramatically and likely prohibitively raise the price of the apparatus. For most applications, the higher costs will represent an unmarketable product.

The issues include:

Viscosity: Water has a much lower viscosity and higher specific gravity than hydraulic oil. This results in at least 3 other issues. First, the piston and cylinder materials (usually steel) will erode much quicker due to the resulting higher velocity and more turbulent flow. Second, the use of special valves will be required to prevent the mechanical shock caused by abrupt fluid flow stoppage inherent to water. Third, the lower viscosity also means it will be more difficult to prevent leaks, requiring more stringently machined parts with much finer tolerances.

Bacteria: A closed water system can provide a breeding ground for all kinds of microorganisms. This can result in clogged lines, filters and a potentially unsafe/unhealthy condition in the event of a leak.

Corrosion: Oxygen in the water as well as sulfurous by-products from bacteria can potentially corrode component materials.

Temperature Range: Water freezes at 32 degrees Fahrenheit. If freezing occurs, and due to the non-compressible nature of ice, it will almost certainly damage or destroy hydraulic parts. Anti-freeze agents will need to be utilized at the cost of the inherent environmental and toxicity concerns of such substances.

Lubricity: Water's comparatively low lubricity will lead to increased contact friction and resulting wear of components.

All of these issues can be addressed and overcome, with the disadvantage of dramatically higher cost vs. hydraulic oil.

What is centrifugal tension?

As with any other rotational system in a belt drive during rotation, the belt is subjected to centrifugal force. Due to the centrifugal force the belt is thrown outward from the grooves of the pulley and causes additional tensioning of the belt. The effect of centrifugal tension is that it reduces the pretension of the belt and hence increases belt slip.

How are buildings built to withstand volcanoes?

There are no building standards for structures that include designs for withstanding volcanic action. If a building could somehow survive the blast and the intense heat as well as seal out the toxic gas, it would have to withstand being buried in molten lava.

Is high carbon steel stronger than tempered steel?

Tempered steel is not a classification of steel. It is a term used to indicate that the steel has undergone proper heat treatment in which case..yes, the steel that has been properly hardened and tempered would be stronger. This answer assumes that the high carbon steel is in its annealed state and has not received heat treatment and tempering of its own.

Who wrote this quote Give you a lever and a place to stand and you can move the world?

According to Pappus of Alexandria, Archimedes' work on levers caused him to remark:

'δῶς μοι πᾶ στῶ καὶ τὰν γᾶν κινάσω'

which translates from Greek as:

'Give me a place to stand on and I will move the world.'

Therefore, the answer is Archimedes of Syracuse.

What is the chemical composition of EN 353?

Please see BS 970 for detailed description.

The chemical composition is:

- C: max. 0,2 %

- Mn: 0,5-1,o

- Si: max. 0,35

- S: 0,04

- P: 0,04

- Cr: 0,75-1,25

- Ni: 1,0-1,5

- Mo: 0,08-0,15

Who and when invented the ball point pens?

The earliest historical record of a reservoir pen dates back to the 10th century. In 953, Ma'ād al-Mu'izz, the caliph of Egypt, demanded a pen which would not stain his hands or clothes, and was provided with a pen which held ink in a reservoir and delivered it to the nib via gravity and capillary action. Al-Mu'izz commissioned the construction of the pen instructing: : "'We wish to construct a pen which can be used for writing without having recourse to an ink-holder and whose ink will be contained inside it. A person can fill it with ink and write whatever he likes. The writer can put it in his sleeve or anywhere he wishes and it will not stain nor will any drop of ink leak out of it. The ink will flow only when there is an intention to write. We are unaware of anyone previously ever constructing (a pen such as this) and an indication of 'penetrating wisdom' to whoever contemplates it and realises its exact significance and purpose'. I exclaimed, 'Is this possible?' He replied, 'It is possible if God so wills'. [1] The earliest historical record of a reservoir pen dates back to the 10th century. In 953, Ma'ād al-Mu'izz, the caliph of Egypt, demanded a pen which would not stain his hands or clothes, and was provided with a pen which held ink in a reservoir and delivered it to the nib via gravity and capillary action. Al-Mu'izz commissioned the construction of the pen instructing: : "'We wish to construct a pen which can be used for writing without having recourse to an ink-holder and whose ink will be contained inside it. A person can fill it with ink and write whatever he likes. The writer can put it in his sleeve or anywhere he wishes and it will not stain nor will any drop of ink leak out of it. The ink will flow only when there is an intention to write. We are unaware of anyone previously ever constructing (a pen such as this) and an indication of 'penetrating wisdom' to whoever contemplates it and realises its exact significance and purpose'. I exclaimed, 'Is this possible?' He replied, 'It is possible if God so wills'. [1] The earliest historical record of a reservoir pen dates back to the 10th century. In 953, Ma'ād al-Mu'izz, the caliph of Egypt, demanded a pen which would not stain his hands or clothes, and was provided with a pen which held ink in a reservoir and delivered it to the nib via gravity and capillary action. Al-Mu'izz commissioned the construction of the pen instructing: : "'We wish to construct a pen which can be used for writing without having recourse to an ink-holder and whose ink will be contained inside it. A person can fill it with ink and write whatever he likes. The writer can put it in his sleeve or anywhere he wishes and it will not stain nor will any drop of ink leak out of it. The ink will flow only when there is an intention to write. We are unaware of anyone previously ever constructing (a pen such as this) and an indication of 'penetrating wisdom' to whoever contemplates it and realises its exact significance and purpose'. I exclaimed, 'Is this possible?' He replied, 'It is possible if God so wills'. [1]

How much does 1 inch thick 96 x 120 inches steel weigh?

in carbon steel it will weigh 3,267.2 lbs.

For weight of we have to know:-

1. volume (in cubic centimeter)

2. density

so now

1 inch = 2.54 cm

96 inch = 96*2.54=243.84

120 inch = 120*2.54=304.8

so

volume=(2.54*243.84*304.8)=188779 cubic cm

density = 7.8g/cm3 (varies based on alloying element from 7.8 to 8.05)

now mass= density*volume

m= 7.8*176980.29=1472476.022 gram= 1472.5 kg=3246.25 lbs (depends on density)

Examples of materials?

Black Friday, the lifestyle of current celebrities.

What is En-8 material?

EN8 also know as 080M40. An unalloyed medium carbon steel. EN8 is a medium strength steel, good tensile strength. Suitable for shafts, stressed pins, studs, keys etc. AISI 1040.

Available as normalised or rolled. EN8 is supplied as round drawn/turned, round hot rolled, hexagon, square, flats and plate.

Is mechanical engineering easy?

Bull hocky easy! If you want to plan a job and make a bit more you have to know how to add. The test is: You have to start wiring a home from the main panel plans and add six inches at an outlet box. You measure to the next box and so on to the last box in that circuit then go back to the panel and start on the next line of outlets. How much wire do you need?

Which is the difference between a level valve and level control valve?

The purpose of both the valves is same - that to maintain a certain level(in a vessel or tank...) Simple Level valve could be referred to an ON - OFF valve where as control valve could be referred to an analog type of valve. On - OFF valve is for a crude control of level, while control valve is used where a fine level control is needed.

What is the difference between nc machining and cnc machining?

Re: Difference between CNC & NC machinesIn a Numerical Control machine, the program is fed to the machine through magnetic tapes or other such media. The original NC machines were essentially basic machine tools which were modified to have motors for movement along the axes.

In a Computer Numerical Controlled machine, the machines are interfaced with computers. This makes them more versatile in the sense that, suppose a change in dimension of a part is required. In a NC machine, you would have had to change the program in the tape and then feed it to the machine again. But in a CNC machine, you just change a variable in the computer and your modification is done!!

What is the difference between national pipe thread and male iron pipe?

Yes there are differences.
See these two links for comparison.


NPT http:/en.wikipedia.org/wiki/National_pipe_thread

BSPT (PT)
http:/en.wikipedia.org/wiki/British_standard_pipe_thread

What is the difference between mechanical engineer and manufacturing engineer?

Manufacturing is a specific branch of mechanical engineering that deals with manufacturing processes.

Fire point of diesel?

As low as 126 degrees Fahrenheit, diesel fuel could potentially catch on fire. This is known as the temperature of ignition.

What is the density of Carbon steel SA 516 Gr. 70?

The density of mild steel is 7,861.093 kg/m³ (490.751 lb/ft³ , 0.2839 lb/in³)

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

Compare with 0.28333 lb/in³

Pressure Vessel Handbook 13 Ed.

by Eugene F. Megyesy

pg 388

ISBN-10: 091445823X

ISBN-13: 9780914458234

How did airplanes improve?

Airplanes over the past 90 or so years have changed a lot. We have gone from small, propeler driven, fragile, all fabric and wood, 100mph top speed aircraft only able to reach 200 feet in the air at most, to all metal jet aircraft that can double the speed of sound at up to 60,000 feet up.

How many BTU per Hour equals 1 Ton of Air Conditioning?

Air conditioners are rated in three ways, by B.T.U.'s, tons of refrigeration, or by horsepower. One ton of refrigeration removes the amount of heat needed to melt one ton of ice in 24 hours. One ton of refrigeration can remove 12,000 B.T.U.'s of heat in one hour. The B.T.U. is the amount of heat needed to raise 1 lb. of pure water 1 deg F.

What is an automata toy?

Dude you need to be quite dumb to ask that question! An automata is simply a hand-cranked machine usally made out of wood. Keep that in mind or else....

Why do machines fail?

Machines fail due to various reasons; they may have been used for the wrong

purposes or they may have been used for loads that exceed their design capacity,

they can also fail after numerous usage due to fatigue or wear, manual operation

of machines can also result in failure due to mishandling by operators. Engines and

motors fail due to lubrication and electrical problems most of the times.