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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
How does a pulse arc welder work?
For MIG (wire welder), the welder switches between a high energy arc and a low energy arc thousands of times a second, that gives it that distinct buzzing sound. This gives you control over the heat input on the metal that your welding, and you will have a lot of control over the arc characteristics, like arc width and length. Some machines will give you control right down to the amperage for each side of the pulse, and frequency of the pulse. A pulse welder takes some practice to set, but once set properly, you will have little to now spatter to clean up, and less distortion on parts. That's it in a nut shell anyway.
NOTE: This is done in DC, some machines that are designed for welding aluminum can pulse in AC, most MIG welders that use pulse are only CV or both CC/CV power sources and ARE NOT capable of welding in AC.
SIDE NOTE: Welding Aluminum is possible with a DC Pulse welder, given that the proper gas, wire, and weld gun is used.
CC: Constant Current
CV: Constant Voltage
AC: Alternating Current
DC: Direct Current
What alloy is a penny covered in?
Current pennies (since 1982) are copper-plated zinc, so the answer is it's covered in copper. The penny is 2.5% copper, and 97.5% zinc. See the related links for a history of penny composition over the years.
What does it mean by hardness in tensile?
For metals, hardness is a measure of the deformation of a surface of the metal when subjected to a normal compressive force with a ball or other shape. Its units are arbitrary.
Tensile strength is a measure of the maximum tensile load per unit of cross sectional area a material can withstand without breaking. Units are force/area.
What is the working principle of pressure transmitter?
I think your are asking about the working principle of a pneumatic transmitter. (not transmeter) A pneumatic transmitter measures liquds or air temperatures over a given range-usually a 200 degree temperature range. The range, selected for its purpose could be -40 to +160 or 0 to 200 -as in the case of Honeywell or even 100 deg. ranges, as in the case of say-Johnson Controls. (0-100) Aside from temperature range, the other important criteria is the output of the transmitter. In the case of commercial controls, the correlation of 200 degree temperatures (which is 201 values, not 200) occurs over a pressure span/output of 3 to 15 pounds.(13 values) For example, in the case of a 200 degree transmitter of say 0 to 200 degrees, the zero temperature value output equates to a 3 psi signal. At 200 degrees, the top of the range, the transmitter would output a 15 psi signal. In other words every degree change up from zero degrees would account for a pressure increase (rounded)of .064 psi. (13 pounds divided by 201 degrees)=.0646766) Pneumatic transmitters are typically direct acting and are one-pipe constant bleed devices. Their working principle involves movement of a flapper a given distance in direct response to the sensed temperature acting upon it. As the temperature rises, the bleed port positions itself toward a closed position which allows less air to escape to atmosphere. Less air to atmosphere dictates more air building up in the air line. This value is then transmitted/measured by the controller-which is pneumatically attached to the transmitter.
Is iron wire stronger than steel wire?
Steel - Pure iron is a relatively soft maleable metal - the addition of small amounts of carbon and other elements during the steel making process add strength and hardness. High strength steels have more carbon than low strength steels, but more carbon also adds brittleness after a point. Silicon, Tungsten and Molybdenum are common alloying elements added to iron to make higher strength steels.
How do you calculate cooling energy?
That's a big question. Do you mean how much cooling is required, or how much energy is required to cool something?
Required cooling involves calculating the heat leaks into the cooled space. This could involve solar loading, the heat leak through a wall or a window. Maybe it's the structural supports that hold up a detector at cryogenic temperatures. Typically you know something about how the amount of the heat leak varies with the temperature at its two sides. House insulation and windows have an R value that tells you how much heat leaks through as a function of the internal and external temperatures.
Once you know the load, you can calculate the amount of energy required to provide that much cooling. An air conditioner sold in the United States will have an "Energy Efficiency Rating" that tells how many BTUs/hr of cooling are produced per watt of electrical power input. So if you need 5000 BTU of cooling and your A.C. has an EER of 10, you will need 5000/10 = 500 W of electrical power to run it.
In a country that uses a sensible unit system the cooling requirement and the electrical power are both measured in Watts, so an A.C. will simply have a coefficient of performance (COP) which is the Watts of cooling per Watt of electrical power. COPs for typical air conditioners is about 3, so in the above example you would have calculated that you needed 1450 W of cooling, and with a COP of 3 you would need 480 W.
No, steel is not an element. It is actually considered an alloy, and the elements iron and carbon are the basic ingredients for making steel. Certainly other elements can be added for different reasons, like chromium for the production of stainless steel. But it is iron and carbon that make steel.
Flow diagram of chilled water system?
You are probably referring to Absorption refrigeration. Try Google.
What is the difference between ultimate tensile stress and ultimate shear stress?
Tensile Strength for a Bolt is determined by applying a Force along it long axis. Shear Strength for a Bolt is determined by applying a Force across its diameter, as it would be loaded in a lug joint. Tensile strength is strength in tension when pulling force is applied. And shear strength is strength against cutting force which is known as shear force.
What is the efficiency of the pulley system?
If the pulley is frictionless the angle does not matter, the tension in the rope will be the same on both sides of the pulley.
If there is friction in the pulley however then you want to reduce the friction as much as possible. You do that by creating as large an angle between the two ropes as possible.
What does friction allow us to do?
In general, friction acts to prevent objects in contact with each other from moving with respect to each other. Friction keeps your furniture where you place it. The friction between your feet [or shoes] and the ground enables you to walk. When you apply the brakes in a car, friction causes the wheels to stop rotating . Friction holds a screw or nail into a board and a nut onto a bolt. Friction between your fingers and an object allows you to pick it up. Friction is proportional to surface roughness. A measurement of the force needed to overcome friction can be used as an indicator of a surface's roughness/smoothness.
When friction is used to reduce relative motion (or to get objects moving), a portion of energy needed to do so is dissipated in the form of heat. This is why a car's brakes get hot and why a nail pulled out of a board can feel warm. Usually, this heat is just a waste byproduct, but it can be useful. The friction of rubbing your hands together will warm them, and the heat of driving a nail into a board can be used to temporarily melt the adhesive on 'cement coated' nails.
What is the primary advantage of mechanical vibration in concrete construction?
Close packing and compression of aggregates for maximum rigidity and strength after curing.
cheaper than closed loop
open loop
turn the switch you assume the light is on
closed loop
turn the switch observe the current observe the light level...
can predict how much below optimal the performance is and predict when total failure will occur
A. A 2-in schedule 40 sheets pipe is used as a leg for a machine. The Load carried by the leg is 2350lb. a. Compute the bearing stress on the floor if the pipe is left open at its end b. Compute the bearing stress on the floor if a flat plate is welded to the bottom of the pipe having a diameter of the pipe
What makes Truss bridge stable?
Truss bridges are made up of triangles which are quite stable since all loads are carried mostly in tension/compression and not bending. Long members may not be stablebecause of buckling in compression, butt most truss designs will account for that.
What is high performance steel?
for constructions . because it have a high resistance for static load
What materials are used to make a pulley?
A pulley system is made up of a pulley and a rope. A pulley is, in essence, a wheel with a groove going all the way around it so that a rope or a cable can fit in it securely.
One could also run an indented track around a wheel.
When you have a cold shower does the bathroom mirror fog up?
No. The steam from a hot shower fogs the mirror.
