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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
Coefficient of thermal expansion of water at 300C?
This can be found from the steam tables. www.x-eng.com gives steam tables. At different temperatures and pressures wolume of water can be found. To find the coefficient of expansion of water, find the volume at 5degree lower and 5 degree higher at same pressure. Take the mean and divide with the volume of water at desired temperature. Cross check the calculation for which you have the answer.
I have used the way and works well. The coefficient of expansion of water changes rapidly with temperature at constant pressure.
What is the difference between engineering stress and true stress?
The difference between true stress & engineering stress is summarised as follows:
Engineering stress assumes that the area a force is acting upon remains constant, true stress takes into account the variation in the cross sectional area as a result of the stress induced deformation (strain) of a material.
For example a steel bar in tension once its yield point or stress is reached will start to "neck". Necking is the localized concentration of strain in a small region of the material, causing a reduction in cross sectional area at this point.
To calculate the engineering stress in the above case, the applied load is divided by the original cross sectional area, however the true stress would be equal to the load divided by the new deformed cross sectional area. Therefore true stress is likely to be significantly higher than engineering stress. Note that while the material is deforming elastically before the yield point is reached there will be some difference between true and engineering stress (as the material is changing shape) but it will be much smaller than the difference after the yield point is reached.
A rock core in a uni-axial compression test will typically expand radially under loading. Therefore in this case, the engineering stress (based on the original diameter) will be larger than the true stress within the material.
How do you calculate pipe area for pipe insulation jobs?
THE DIAMETER OF THE OUTSIDE OF THE PIPE TIMES PI TIMES THE LENGTH OF THE PIPE or D x Pi x L = A
ANSI stands for "American National Standars Institute"
Examples of a first class lever?
seesaws
crowbars
sissors
oar attached to a boat
hammer removing a nail
fishing rod
pliers
teter totters
you can fin them lots of place's you just have to look =)
differential expansion is refer to differential distance between rotor blade and fix blade.rotor expand to
ward generator and casing expand toward control valve.when temperature increase ,expansion in casing and rotor.so rotor mass is less than casing which rotor expand more than casing.
Is there another name for a ball check valve?
No
Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave. There are various types of check valves used in a wide variety of application. And a ball check valve is one of types of check valves, it a check valve in which the closing member, the movable part to block the flow, is a spherical ball.
Then a ball valve is a valve with a spherical disc, the part of the valve which controls the flow through it. The sphere has a hole, or port, through the middle so that when the port is in line with both ends of the valve, flow will occur.
As you see, they are not the same.
What is a cold agglutinins test?
There is a bedside version of the test in which the doctor collects four or five drops of blood in a small tube, cools the tube in ice water for 30-60 seconds, and looks for clumping of red blood cells.
What is the weight of corrugated sheet metal?
we can weight one sheet and calculate the unit weight we can weight one sheet and calculate the unit weight
How do you identify workpiece reference points and systems of tolerance?
Reference points: Think about how the part will be made, and how it will be inspected. Usually something will make sense. Try to keep common references between drawing views, and if possible try to base everything from points, planes, or edges that appear in multiple views.
Tolerances: Consider how the part will be made- what minimum tolerances can be held on the intended equipment and processes? What is the maximum tolerance on the individual parts that will allow the assembly to fit together and function properly? The right answers lie between those extremes.
Properties of Bright Drawn Mild Steel?
Bright mild steel is an alloy. It is usually used to make hammer heads and shears, and it has a smooth, but tough surface.
What is the definition of modulus of elasticity?
applications of modulas of elasticity
As the term implies, "Modulus of Elasticity" basically relates to the elasticity or "flexibility" of a material. The value of modulus of elasticity are very much significant relating to deflection of certain materials used in the construction industry. Take for example the general E value of mild carbon steel is about 200 GPa compared to about 70 GPa for aluminum. This simply translate that aluminum is 3 times flexible than steel.
What is the material equivalent to AISI 8630?
The following specifications cover AISI 4130
- AMS 6348
- AMS 6350
- AMS 6351
- AMS 6360
- AMS 6361
- AMS 6362
- AMS 6370
- AMS 6371
- AMS 6373
- AMS 6374
- AMS 6528
- AMS 7496
- ASTM A29
- ASTM A322
- ASTM A331
- ASTM A506
- ASTM A507
- ASTM A513
- ASTM A519
- ASTM A646 (Forging - Open Die)
- ASTM A752
- ASTM A829 (Plate)
- MIL S-18729
- MIL S-6758
- SAE J1397
- SAE J404
- SAE J412
- UNS G41300
What qualifications do mechanical engineers need?
Most businesses hiring mechanical engineers want applicants with at least a BS in mechanical engineering and an EIT (Engineer in Training) certificate or preferably a PE (Professional Engineer) certificate.
Is a short or long screwdriver better to open a can of paint?
It's all about torque.
Basically, the further away from the pivot you apply the force, the less force you need to apply.
Since the screwdriver means you can apply a force further away from the pivot (where you put the head of the screwdriver underneath the lid of the paint can), it means you can apply less force.
Where do you find a table base for a glass top?
YOU HAVE A FEW OPTIONS....IF YOU KNOW WHAT BASE BELONGS UNDER GLASS TOP, CALL THE MANUFACTURER AND SEE IF YOU CAN BUY ONE. YOU CAN CALL A TABLE MAKER AND HAVE ONE CUSTOM MADE. TAKE THE MEASUREMENTS OF GLASS TOP AND GO SCOUTING GARAGE SALES FOR TABLES AND LAY GLASS ON TOP, LOOKS REALLY COOL TO PUT YOUR FAVORITE PICTURES UNDER GLASS. YOU CAN MAKE ONE YOURSELF IF YOUR CREATIVE....
What are the type of pumps used for ballast and bilge?
Manual ballast water/bilge pumps are often diaphragm pumps with flapper valves. Large pumps are often positive displacement, centrifugal or moving cavity pumps depending on the amount of crud expected in the ballast.
What is the definition of Electromechanical Control Relays?
an electrmagnet relay uses an electromagnet to pull a piece of iron or steel towards it such that it causes to contacts (pieces of metal such as gold) together and complete a circuit. They can range in size from as small as your fingernail (to switch low power signals such as the inputs to an audio amplifier) to as large as stuffed sofa (to switch the output of a power plant). An electromagnet is a coil of wire wound on a iron core. When a current is run through the coil, it becomes a magnet.
How do you caluclate weight of H beam?
A simple way is to use the specification of the beam, most beams will have a specification saying how much it ways per meter or per foot.
Calculation.
weight = Area*Length*density
*Note that when calculating the weight of a beam for structures a safety factor which will be defined in you country design code
Why is iron used for railway lines?
Iron is rarely used anymore in railway lines. Steel is used mostly now because it is very flexible and is less vulnerable to cracking and chipping.
What are the disadvantages of Electro pneumatic?
ADVANTAGES OF PNEUMATICS.
1. Simplicity of Design And Control
The control machines are easy to design. i.e they can be manufactured using standard cylinders & other components. Controlling mechanism simply contains two ON-OFF states, so its easy to implement and understand.
Also these components have versatile usage, they can be used in many situations. Pneumatics are easy to install and have useful mechanical movements. For an instance Straight-line movements can be obtained without further adjustments, such as levers, cams...etc
2.Reliability
pneumatic control mechanism is well known for its long lasting operation life time. In fact they need very little maintenance but operates continuously with high reliability.
Air /gas used as the working fluid is less likely to damage the equipments since gas are good in absorption of shock, and excessive forces, but hydraulics react directly transferring the stress to mechanical parts.
3.Safe to use
Pneumatic controls have high safety profile due to many reasons. Air used in these are fire proof, and less vulnerable to explosions and electric hazards. These are adoptable in extreme weather conditions, and we can rely on their continuous operation. This is because compressed air can stay in good condition in high temperature fluctuations, unlike hydraulic s ystems that tend freeze or boil in these situations.
Even a leak occur there is less chance of getting fire. Also there is no toxicity in air used, so we can expect no harm to living beans. Since pneumatics are sound in safety, very less precautions need to be taken.
4.Storage
Compressed Gas can be stored easily, and once compressed, above a certain threshold level they can be operate with out further need of compressing. This feature allows the use of machines when electrical power is lost.
5. Clean
Since working fluid is purified air, there is no messy waste produce at the end of the day. A little leak will not make the surrounding shady. Also, since ir is used no risk of toxic hazards t o machines or humans. Industries like pharmaceutical, food..etc tend prefer pneumatics for their cleanness.
6. Easily transported
Air is easily obtainable from atmosphere and can be used with little purification. Air can be pumped to long distances in pipelines, so can control pneumatic equipments for long distances. This makes central controlling possible. These also requires no return line, so easy to manage and cost effective.
7. Light in weight
Air is very light compared with other fluids, which are very heavy. They don't need high power to transfer.
8.Cost Effective
This is a very economical controlling mechanism. The Pneumatics require low maintenance cost, since wear of equipments are very less. These operates at low pressure , so equipments can be produced for low cost using cheap materials. In contrast hydraulic controlling systems require high pressure, so need tough materials, which comes in high prices.
9 high speed working medium
Compressed air controllers are able to achieve high work speeds, the flow rate may go up to 20 m/s, while hydraulics is restricted around 5m/s.
10.safe operation in Overloads
The shock absorbent properties of air make overloading safe. Under excessive forces air can compress easily avoiding damage to equipments.
11 Variable pressure
Pneumatic systems can work in various pressures, this also alow the speed control.
DISADVANTAGES OF PNEUMATICS.
1. Air is largely compressible, which may be good for some reasons, but the major draw back is the inefficiency in accurate positioning and speed controlling. These often need to be tuned to work correct and sound. Since Compressible,not possible to achieve uniform and constant piston speeds.
2.Unable to work with heavy loads (commonly used working pressure of 7 bar, the require output force is economical only up to about 20 KN to 30 KN ) Unlike hydraulics or electrical system these cant be used for heavily loaded operation.
3. Air used needs to be purified, air containing moisture may lead to corrosion of the equipments.
How to Calculate fluid capacity of pipe?
The internal capacity of a pipe is pi x internal radius x internal radius x length of pipe where pi = 3.142 This is the volume of a cylinder; pipe capacity is usually amount of flow per unit of time under given conditions of internal roughness, and viscosity of the flowing fluid with a given pressure loss per length unit. Q = DELTA PRESSURE * PI*( DIAMETER TO FOURTH POWER)/ (128 * VISCOSITY* LENGTH) VISCOSITY OFWATER IS ABOUT 2X1O TO -5 POWER LB SECOND/FT SQUARED NOTE PRESSURE MUST BE BELOW AMOUNT THAT RUPTURES THE PIPE.
