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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
What is the difference between a screw and a bolt?
a cap screw has a top bigger than the threaded portion [a cap]. the cap screw does not sit flush with the material being screwed into. a machine screw has a tapered top that fits into a countersunk hole and when screwed in is flush with the surface being screwed into;
What is the difference between ac arc and dc arc welding?
Both are shielded metal welders but differ in the electricity they use. Ac welders can weld heavier metal while dc welders are better for thinner metals. Ac welders can weld magnetized metals. Dc welders can not. The arc in an ac welder is harder to control because of the pulsating current. Dc welders are more expensive. Some welding machines offer both options.
Why injection molding is capable of producing parts with complex shapes and fine detail?
it can produce highly detailed parts very rapidly that require little or no finishing
A turbine extracts some of the energy from a moving fluid or gas and turns it into rotational motion. In a power plant, the rotational motion drives a generator, and the generator produces electricity.
If the turbine is in a hydroelectric plant, the moving fluid is river water pulled towards lower elevations by gravity. If the turbine is in a coal-fired plant, the fluid is high-pressure steam escaping from a boiler heated by the coal. Generating electricity by wind also uses turbines (they look a lot different, though!) to change the motion of the air into the rotation needed to drive the generator.
What is the value of Youngs Modulus of Elasticity of brass?
Brass is an alloy and as such can very greatly in its properties depending on its content, so there is no single shear modulus for brass. The only way to be certain is to either test it your self or go by data provided by the manufacturer.
If, on the other hand, you are only working theoretically 40GPa is a good estimate for brass in general. Source: http://www.engineeringtoolbox.com/modulus-rigidity-d_946.html
Which heat treatment process is suitable to increase the ductility in steel?
how to increse the Tensil more than 1100 for Crmo4
Are a skyscraper's walls made of concrete?
No. The (exterior) walls are usually steel and glass (perhaps incorporating some aluminum), all of the weight of which is borne by the floors. The weight of the floors is borne by the vertical support columns, which are steel or reinforced concrete. They're tucked inside. The massive weight of the building is transferred into the support columns, and that compressive force is transferred in turn down into bedrock. Most of the tallest buildings have their load bearing columns "inside" away from the outer walls. That allows the outer wall of the building to be more fully developed for "the view" from higher elevations. It also protects the columns from damage due to the possible impact of an aircraft. That was part of the design consideration for the Empire State Building. And a good thing, too. The 102-story structure was struck by a B-25 flying in a thick fog on the morning of July 28th, 1945. That was Sunday. Much of the building was open for business the following day. In the case of the World Trade Center, the exterior of the buildings were steel load bearing walls. It was an extraordinary engineering concept! And the buildings were superb! But, in retrospect, it may have been an engineering error - a fatal idea.
How much do Mechanical Engineers get paid an Hour?
It depends on your experience, region, industry and organization.
Why Is the modulus of elasticity in tension and compression for mild steel the same?
Most metals have the same elastic modulus in tension and compression as the molecules which make up the metal expand and contract under load by the same amount. This might not be true for composite beams of different materials like concrete, where you may be compressing small particles of stone but pulling on the cement only that holds them together.
How many gallons per minute will flow through a 2 inch pipe at 60 psi?
What fittings are installed and type of valves and height as friction losses have a lot to do with the calculations. Also the piping material and lenght have to be taken into consideration.
What is the difference between A36 steel and ASTM572?
A36 is commonly used for the purpose of storage tank, containers and other structural products where the strength and reliability required is not so High.
ASTM572 has many grades and is generally used in the manufacturing of the pressure vessels. Depending upon the fluid properties and the strength requirements, appropriate grade is selected.
The area is called the combustion chamber.
How do you calculate the mechanical advantage of block and tackle?
Let's look at a simple system. A block with three wheels is attached to the ceiling and a block with three wheels is attached to a load to be lifted off the floor. As well as the block attached to the ceiling, we have a hook there also near to the block and we start by knotting one end of our rope onto that hook.
We now run the free end of the rope through the bottom block, back up through the top block, back down to the bottom block and so on, finishing up with the free end of the rope coming out of the third wheel at the top and hanging down.
Now for the physics. Physics says that a well oiled pulley wheel cannot alter the load in a rope passing over it. Therefore, we have to accept that the load in any part of the rope is the same. Now we count how many lengths of rope are going to be lifting the load. I see six. Three wheels in the bottom block and two lengths of rope to each wheel. As these six ropes are all pulling upwards when we pull down on the free end, and the load in each rope is the same, the load in the rope is one sixth of the weight to be lifted. This is the pull required on the free end just to hold the load off the floor. A sightly greater pull will overcome any friction in the pulleys and start the load moving upwards.
The mechanical advantage of the system we have here is 6.
An interesting variation is when we have four wheels in the bottom block and pass what was the free end hanging down through the fourth wheel. We now have the free end to be pulled upwards and it will be contributing to the lifting forces on the weight. There are now eight lengths of rope lifting the weight and the pull required will be just a tad more than one eighth (1/8) of the weight to be lifted.
How do you construct a rubber band powered plane?
A rubber band is attached to any fixed surface of the car and then the other end is attached to the rear axle of the car. You wind the car up by turning the back tires but be sure and keep the tires from free spinning until you are ready for the car to go. When you let it go, the rubber band that has been stretched will unwind from the axle and force the cars tires to turn thus pushing the car forward.
What is the equivalent IS steel of ASTM A36 steel?
Its IS226 for structural steel & IS2062 for fusion weldable structural steel.
What is the difference between gas power cycles and vapour power cycles?
The vapor-compression cycle is used in most household refrigerators as well as in many large commercial and industrial refrigeration systems. Figure 1 provides a schematic diagram of the components of a typical vapor-compression refrigeration system.Figure 1: Vapor compression refrigeration
The thermodynamics of the cycle can be analyzed on a diagram[11][12] as shown in Figure 2. In this cycle, a circulating refrigerant such as Freon enters the compressor as a vapor. From point 1 to point 2, the vapor is compressed at constant entropy and exits the compressor as a vapor at a higher temperature, but still below the vapor pressure at that temperature. From point 2 to point 3 and on to point 4, the vapor travels through the condenser which cools the vapor until it starts condensing, and then condenses the vapor into a liquid by removing additional heat at constant pressure and temperature. Between points 4 and 5, the liquid refrigerant goes through the expansion valve (also called a throttle valve) where its pressure abruptly decreases, causing flash evaporation and auto-refrigeration of, typically, less than half of the liquid.Figure 2: Temperature-Entropy diagram
That results in a mixture of liquid and vapor at a lower temperature and pressure as shown at point 5. The cold liquid-vapor mixture then travels through the evaporator coil or tubes and is completely vaporized by cooling the warm air (from the space being refrigerated) being blown by a fan across the evaporator coil or tubes. The resulting refrigerant vapor returns to the compressor inlet at point 1 to complete the thermodynamic cycle.
The above discussion is based on the ideal vapor-compression refrigeration cycle, and does not take into account real-world effects like frictional pressure drop in the system, slight thermodynamic irreversibility during the compression of the refrigerant vapor, or non-ideal gas behavior (if any).
More information about the design and performance of vapor-compression refrigeration systems is available in the classic Perry's Chemical Engineers' Handbook.[13]
Vapor absorption cycleMain article: Absorption refrigeratorIn the early years of the twentieth century, the vapor absorption cycle using water-ammonia systems was popular and widely used. After the development of the vapor compression cycle, the vapor absorption cycle lost much of its importance because of its low coefficient of performance (about one fifth of that of the vapor compression cycle). Today, the vapor absorption cycle is used mainly where fuel for heating is available but electricity is not, such as in recreational vehicles that carry LP gas. It is also used in industrial environments where plentiful waste heat overcomes its inefficiency.
The absorption cycle is similar to the compression cycle, except for the method of raising the pressure of the refrigerant vapor. In the absorption system, the compressor is replaced by an absorber which dissolves the refrigerant in a suitable liquid, a liquid pump which raises the pressure and a generator which, on heat addition, drives off the refrigerant vapor from the high-pressure liquid. Some work is needed by the liquid pump but, for a given quantity of refrigerant, it is much smaller than needed by the compressor in the vapor compression cycle. In an absorption refrigerator, a suitable combination of refrigerant and absorbent is used. The most common combinations are ammonia (refrigerant) and water (absorbent), and water (refrigerant) and lithium bromide[absorbent].
What is the working principle of a monoblock pump?
It consist of
1.a cylinder with a piston
2.piston rod,connecting rod
3.crank and crank shaft
4.delivery pipe
5.suction pipe
6.delivery valve
7.suction pipe with a foot and filter
During suction stroke the piston moves to the left, causing the inlet valve to open.
Water is admitted into the cylinder through the inlet valve.
During the discharge stroke the piston moves to the right closes the suction valve and opens the out let valve.
Through the outlet valve the volume of liquid moved out of the cylinder.
How did the airplane improve daily life?
Today we can see the various shapes and designs of the original aircraft being retooled into their future use in space to replace the aging space transportation system (space shuttle) and new civilian endeavors such as spaceship one. Overall, the gaps of distance and time are being shortened everyday by more advanced and sophisticated aircraft. The aircraft of yesteryear have helped us see new avenues, new frontiers, and push the limits of design to develop a new aviation history.
What is the value of Poisson's ratio of wood?
Poisson's ratio is the negative ratio of how compression affects distortion. When an object is compressed in one direction it expands in two directions perpendicular to the direction of compression. The ratio is equal to d(transverse strain)/d(axial strain).
A fixed single pulley that is used to lift a block does what?
The choices are:
A. Doubles the force required to lift the block
B. Decreases the force required to lift the block
C. Makes the block easier to lift by changing the direction of the force needed to lift it.
D. Decreases the force required and changes the direction of the force required
What is the relationship between enthalpy and temperature?
Enthalpy is the amount of energy in a system and when this changes (when a reaction happens), the energy is either released (exothermic) or absorbed (endothermic) and this energy is usually released or absorbed as heat. Therefore when the enthalpy decreases, heat is released from the system making it exothermic. In contrast, when the enthalpy increases, heat is absorbed making it endothermic.
How do you calculate weight for ms beam?
There are several ways. The easiest is to find a chart, like in the related link, which gives a weight per unit length of a specific cross section beam. With a weight per unit length, multiply this by the length in question, and you have the weight. In the related chart, your length would have the units of meters. The other way is to calculate the cross sectional area of the beam. Then multiply the cross sectional area by the length in question, which will give you the beam volume. Then multiply the volume by the density of the material, which will give you the weight.
What is the economic advantages of absorption chiller compared with electric chiller?
· Cost effective and more economical than electrical chillers. Use heat for compression while vapour compression chillers use mechanical compressor for compression purposes which consume a lot of electrical energy.
· Since the compression is caused by heat and does not include any moving mechanical parts, it is less noisy and vibration free.
· For a facility that demands high system reliability, the lower electricity demands of the absorption chiller will reduce emergency generator load requirements.
· Good for the environment as it eliminates the requirement of using CFC and HCFC refrigerants used in electrical chillers which have high global warming potential and instead use natural refrigerants such as water.
