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What is drop weight tear test?
The Drop Weight Tear Test (DWTT) is a test used to determine the fracture properties of steel at certain temperatures, and also to determine the temperature at which a steel transitions from ductile to brittle fractures. The test is performed by dropping a weighted hammer on to a full-thickness standard sized (usually 12" by 3") and notched sample, causing the sample to fracture ("tear") completely through the middle. The fractured surface is then observed and measured to determine what percentage of the "torn" area is ductile fracture. Ductile fractures are desired because they mitigate how fast and far fractures travel through the steel. The temperature at which this test is performed is important because steel becomes more likely to experience brittle fracture (which is not desired) at lower temperatures. The advantage of this test is that it can be used on full-thickness specimens, providing a more accurate demonstration of how the steel would fracture in a real application. This test is required by API standards for certain sizes and grades of steel line pipe for oil, gas, and petroleum products, to demonstrate that the pipe can experience ductile fracture at reasonably low temperatures. Sources: Seeing and running DWTT's first hand ASTM E436 API 5L API 5L3 "Don't drop the drop-weight tear test" by Dr. Andrew Cosham et al.
Why you need bearings?
Bearings help machines work smoothly and keep gears and machines that need bushings (with bearings in them) from wearing out too quickly. Bearings significantly reduce friction in working machines (with the help of a bit of oil and grease), thus reducing wear and tear--and reducing maintenance costs and times of repair.
Why Use Rubber Tracks For Your Machinery?
Rubber tracks can help your heavy machinery perform better on the roads. Using them can help reduce wear and tear on your undercarriage parts. There are other benefits to using them as well. The main benefit is the ability to use your vehicle in all terrains and weather. When you’re dealing with construction or farming equipment, your vehicle is subject to different road and off-road conditions. Rubber tracks help your vehicle move as smoothly as a car on the open road, without damage to your machinery. Using your vehicle on all types of terrain has the potential for producing unsettling and startling noises. Using these types of tracks can reduce and often eliminate the noise altogether, making for a more quite and enjoyable ride. Unlike normal wheels, rubber tracks have a better grip on all terrains to help move the machinery along smoothly. They are designed to reduce vibrations and allow the machine to move more effortlessly due to the weight on the machinery getting refocused away from the tires. Rubber tracks help increase productivity and performance. Even the heaviest of machinery can move like the lightest of commercial vehicle with the use of these tracks because the weight is redistributed and distributed evenly. You can find a great deal more information on rubber tracks online. There are a wide range of sizes to choose from as well as a great selection of different brand names right at your fingertips. Most tracks can be delivered to your doorstep in as little as one day and can be delivered internationally. The latest products from a wide range of manufacturers can be found just by doing a simple search. Most sites have some form of contact information on the front page to make them easily accessible should you have questions or concerns about their products and services. It’s a good idea to contact someone in customer service should you have maintenance and repair issues as well.
Aviation Mechanics Are Highly Trusted?
Keeping modern aircraft running smoothly takes a lot more than good intentions. In order to become an aviation mechanic who can be trusted with the increasingly complex parts and practices required by the Federal Aviation Administration (FAA), you must ensure you're appropriately trained. There are around 170 FAA certified schools where workers can learn to perform their jobs. This work includes all aspects of aircraft preventive maintenance, including pre-flight checks, parts, repairs and precision inspection of components for wear and tear. Mechanics find work ensuring that many types of aircraft, from civilian commercial airliners to military jets and transports are ready to fly on demand. Because of the nature of their work, mechanics often have to work overtime and are exposed to hazardous conditions. While their jobs are somewhat stressful affairs, they can minimize their danger by meeting the FAA regulations dictating they attend a minimum of 1,900 class hours. The overall training process generally requires a 1-2 year commitment to hands on training with pertinent tools and equipment. Additionally, extended training is available in about 33% of the FAA recognized programs, which award 2 or 4-year degrees in avionics related fields. Aviation mechanics job aspirants must be able to communicate fluently in English, with an emphasis on understanding technical language, but they also need to have a good command of mathematics, physics, chemistry and mechanical drawing. This knowledge, along with familiarity in other related subjects like electronics and computer science, comes in handy when it's time to attempt the written, oral, and practical tests required to earn certification. Civilian sector aviation mechanics and service techs can expect high salaries of about $24.71 once they gain some experience. Starting mechanics may earn less than $15.95, but by attending extended training sessions, one can increase their chances of getting higher salaries. For military technicians, the training path and career outlook is markedly different, with individuals in these areas finding that salaries reflect their pay grades, rank and other armed services-related pay factors.
Working of camless engine with electromechanical valve actuator?
INTRODUCTIONThe cam has been an integral part of the IC engine from its invention. The cam controls the "breathing channels" of the IC engines, that is, the valves through which the fuel air mixture (in SI engines) or air (in CI engines) is supplied and exhaust driven out. Besieged by demands for better fuel economy, more power, and less pollution, motor engineers around the world are pursuing a radical "camless" design that promises to deliver the internal - combustion engine's biggest efficiency improvement in years.Cams, lifters, pushrods... all these things have up until now been associated with the internal combustion engine. But the end is near or these lovely shiny metal objects that comprise the valve train hardware in your pride and joy. Camless engine technology is soon to be a reality for mass-produced vehicles. In the camless valvetrain, the valve motion is controlled directly by a valve actuator - there's no camshaft or connecting mechanisms. Various studies have shown that a camless valve train can eliminate many otherwise necessary engine design trade-offs. Automotive engines equipped with camless valve trains of the electro-hydraulic and electro-mechanical type have been studied for over twenty years, but production vehicles with such engines are still not available. The issues that have had to be addressed in the actuator design include:• Reliable valve performance cost• packaging• power consumption• noise and vibrationNoise has been identified as the main problem with the electromechanical actuator technology, arising from high contact velocities of the actuator's moving parts. For this noise to be reduced, a so-called soft-landing of the valves has to be achieved.The valvetrain in a typical internal combustion engine comprises several moving components. Some are rotating and some are moving in a linear manner. Included are poppet valves that are operated by rocker arms or tappets, with valve springs used to return the valves to their seats. In such a system the parasitic power losses are major - power is wasted in accelerating and decelerating the components of the valvetrain. Friction of the camshaft, springs, cam belts, etc also robs us of precious power and worsens fuel economy, not to mention contributing to wear and tear. The power draw on the crankshaft to operate the conventional valve train is 5 to 10 percent of total power outputAnother factor working against the conventional valve train is that of the cam profile. Usually, it is fixed to deliver only one specific cam timing. The cam lobes have to be shaped such that when the valve travels up and down at the engines maximum speed it should still be able to slow down and gently contact the valve seat. The valves crashing down on their valve seats results in an engine that is real noisy and has a short life expectancy.Having different cam profiles will result in different engine characteristics. While high-rpm power and low rpm-torque can be each optimized, a compromise is required to obtain the best of both in the same engine. With Variable Valve Timing (VVT) technologies the compromise is getting better and better - reasonable low down torque and high-speed power are being produced by many sub 2-litre engines.But the problem remains that the cam grind is still a fixed quantity - or two fixed quantities in the case of Honda V-TEC engines. That's why the Electromechanical Valve Train is considered the next evolution of VVT. With the potential to dial in any conceivable valve timing at any point of the combustion cycle for each individual cylinder, valves can be opened with more lift and/or duration, as the computer deems necessary.Conventional valve train mechanismPushrod engines have been installed in cars since the dawn of the horseless carriage. A pushrod is exactly what its name implies. It is a rod that goes from the camshaft to the top of the cylinder head which push open the valves for the passage of fuel air mixture and exhaust gases. Each cylinder of a pushrod engine has one arm (rocker arm) that operates the valves to bring the fuel air mixture and another arm to control the valve that lets exhaust gas escape after the engine fires. There are several valve train arrangements for a pushrod.CrankshaftCrankshaft is the engine component from which the power is taken. It receives the power from the connecting rods in the designated sequence for onward transmission to the clutch and subsequently to the wheels. The crankshaft assembly includes the crankshaft and bearings, the flywheel, vibration damper, sprocket or gear to drive camshaft and oil seals at the front and rear.CamshaftThe camshaft provides a means of actuating the opening and controlling the period before closing, both for the inlet as well as the exhaust valves, it also provides a drive for the ignition distributor and the mechanical fuel pump.The camshaft consists of a number of cams at suitable angular positions for operating the valves at approximate timings relative to the piston movement and in the sequence according to the selected firing order. There are two lobes on the camshaft for each cylinder of the engine; one to operate the intake valve and the other to operate the exhaust valve.PROBLEMS RELATED TO CONVENTIONAL VALVE TRAINThe poppet valves that are operated by rocker arms or tappets, with valve springs used to return the valves to their seats. In such a system the parasitic power losses are major - power is wasted in accelerating and decelerating the components of the valve train. Friction of the camshaft, springs, cam belts, etc also robs us of precious power and worsens fuel economy, not to mention contributing to wear and tear. The power draw on the crankshaft to operate the conventional valve train is 5 to 10 percent of total power output.Another factor working against the conventional valve train is that of the cam profile. Usually , it is fixed to deliver only one specific cam timing. The cam lobes have to be shaped such that when the valve travels up and down at the engines maximum speed it should still be able to slow down and gently contact the valve seat.The single lobed cam is designed to operate the valves at only specific periods of the Otto cycle, thus preventing the engine from achieving maximum torque at higher rpms. The opening and closing of the valves is constrained by the geometry of the cam profile.ELECTROMECHANICAL CAMLESS VALVE ACTUATORIn recent years camless engine has caught much attention in the automotive industry. Camless valve train offers programmable valve motion control capability. An EMV system consists of two opposing electromagnets, an armature, two springs and an engine valve. The armature moves between the two magnets. When neither magnet is energized, the armature is held at the mid-point of the two magnets by the two springs located on either side of the armature. This system is used to control the motion of the engine valve. The engine valve is then in turn used to control the flow of air into and out of a combustion engine cylinder. The camless engine, where lift and valve timing can be adjusted freely from valve to valve and from cycle to cycle. It also allows multiple lift events per cycle and, indeed, no events per cycle-switching off the cylinder entirely.Computer controlled- opening and closing of valves make it possible to optimize the various phases of engine running. During idling phases, specific intake valve opening strategies make it possible to admit just the necessary quantity of air without having recourse to throttling the intake with a butterfly valve, something that generates consumption of fuel not used by the engine. Timing of valve opening or the latitude to only open a single intake valve make it possible to stabilize the engine on idling points which consume little fuel while ensuring a good level of drive ability or the driver.During urban driving and on the open road, both adequate opening and timing of the valves make it possible to admit a quantity of air limited to the requirement so the engine mixed with a massofburned gases purposely retained in the engine. This strategy ensures reduction of fuel consumption, polluting exhaust emissions, in particular, nitrogen oxides, produced by the engine. In terms of performance, the modularity of the system makes it possible to maximize the massof fresh air trapped in the cylinder at all engine speeds, ensuring both good torque and high power.Apart from these advantages, deactivation of the cylinder also delivers additional savings in terms offuel consumption and exhaust emissions when the engine is only using a small amount of its power as, or example, in urban use. In this mode, only halfof the cylinders are used to provide energy to the wheels, significantly limiting losses due to poor engine efficiency. The camless system is there or system which, on an air aspirated supercharged engine provides the customer with a significant improvement in engine features. In addition, it is a system that has a strong potential or evolution and its functions will be consumption required in order to implement combustion through auto-ignition, such as the HCCI system, which is under consideration as the next stage in the battle to reduce fuel consumption.Electromechanical Valve Train is considered the next evolution of VVT. With the potential to dial in any conceivable valve timing point of the combustion cycle for each individual cylinder, valves can be opened with more lift and/or duration, as the computer deems necessary. Just imagine that you have your latest 2-litre 16-valve EMVT powered engine on the dyno after installing an exhaust. Simply changing a couple of numbers on the computer will have a set of completely revised valve timing maps to suit your exhaust - or cold air intake for that mater. There will be no need for expensive cam changes that may not even give the results you are after. Electronically altering valve events will have a far more major impact on engine performance than any current electronically-controlled item.CONTROL DESIGNWhen the valve-closing event starts, the lower solenoid coil is deactivated, and the valve moves up towards its seating position by the mechanical spring force. An electro mechanical valve actuator works according to the spring-mass pendulum principle, which means that the system follows its own natural oscillation frequency, and external electromagnetic force is only needed for overcoming the friction loss. The electromagnetic actuator is only effective in a relatively short range closing to the seating position, and so it is not efficient in the sense of energy consumption to apply closed-loop control when the valve is still far away from theseating position. The system goes unstable as the engine valve moves to the region within one-third of the total lift.This type of system uses an armature attached to the valve stem. The outside casing contains a magnetic coil of some sort that can be used to either attract or repel the armature, hence opening or closing the valve.Most early systems employed solenoid and magnetic attraction/repulsion actuating principals using an iron or ferromagnetic armature. These types of armatures limited the performance of the actuator because they resulted in a variable air gap. As the air gap becomes larger (ie when the distance between the moving and stationary magnets or electromagnets increases), there is a reduction in the force. To maintain high forces on the armature as the size of the air gap increases, a higher current is employed in the coils of such devices. This increased current leads to higher energy losses in the system, not to mention non-linear behaviour that makes it difficult to obtain adequate performance. The result of this is that most such designs have high seating velocities (ie the valves slam open and shut hard!) and the system cannot vary the amount of valve lift.The electromechanical valve actuators of the latest poppet valve design eliminate the iron or ferromagnetic armature. Instead it is replaced with a current-carrying armature coil. A magnetic field is generated by a magnetic field generator and is directed across the fixed air gap. An armature having a current-carrying armature coil is exposed to the magnetic field in the air gap. When a current is passed through the armature coil and that current is perpendicular to the magnetic field, a force is exerted on the armature.When a current runs through the armature coil in either direction and perpendicular to the magnetic field, an electromagnetic vector force, known as a Lorentz force, is exerted on the armature coil. The force generated on the armature coil drives the armature coil linearly in the air gap in a direction parallel with the valve stem. Depending on the direction of the current supplied to the armature coil, the valve will be driven toward an open or closed position. These latest electromechanical valve actuators develop higher and better-controlled forces than those designs mentioned previously. These forces are constant along the distance of travel of the armature because the size of the air gap does not change.The key component of the Siemens-developed infinitely variable electromechanical valve train is an armature-position sensor. This sensor ensures the exact position of the armature is known to the ECU at all times and allows the magnetic coil current to be adjusted to obtain the desired valve motion.The ability of the electromechanical valve actuator to generate force in either direction and to vary the amount of force applied to the armature in either direction is an important advantage of this design. For instance, varying the value of the current through the armature coil and/or changing the intensity of the magnetic field can control the speed of opening and closing of the valve. This method can also be used to slow the valve closure member to reduce the seating velocity, thereby lessening wear as well as reducing the resulting noise.A special software algorithm is used to control the actuator coil currents such that the valves are decelerated to a speed near zero as they land - in conjunction with a switching time of barely three milliseconds. For the valves this means minimal wear and minimum noise generation. The 16-valve four cylinder engine that is currently undergoing tests in Germany, by Siemens, is equipped with 16 valve actuators and the corresponding armature-position sensors. A ECU is used and two cable rails connect the actuators to it. A 42-volt starter-generator provides the power.WORKINGCamless engines generally employ one of two types of camless actuators: electro-hydraulic or electro-mechanical valve actuators. The actuators receive input from the ECU via a dedicated CAN bus to open and close the poppet valves at a prescribed crankshaft angle timing, transition time and lift, matching the valve timing request sent by the ECU. Feedback is then sent by the actuators through the CAN bus to verify the actual occurrence of the operation.Electromechanical actuators are generally made with two solenoids and two springs. As can be seen in Figure 1 the ECM receives input from the crankshaft position sensor to close the valve, which activates Solenoid 1 by taking current from the battery. The current is passed through a pulse width modulator which tunes the amplitude of the current to control the speed of valve seating. The magnetic field created by Solenoid 1 attracts the armature in the upper position. Spring 1 is compressed and thus closes the valve. Solenoid 2 pulls the armature down to open the valve as shown in Figure 2.
What happens to a machine when it has too much friction?
The excess friction will cause the moving parts to heat up - even to becoming red hot! A cooling system: water, fans and radiator, or lubricating oil, is used to reduce the friction and so lessen the wear and tear on the moving parts.
What word goes before duct?
tear heating air conditioning
What cause is it when your intestine tear open?
What casues an intestine to tear?
What lubricants can cause a condom to tear or break?
Silicone-based lubricants and vaseline can cause a condom to tear or break.
Examples of friction as a foe?
wear and tear the machine parts
Does tear love Luke?
Who's tear? Do you mean: Thaila? Annabeth? Cause the answer is no for both
What might cause a tendon to totally tear?
Any thing will tear due to excessive force.
Does acid reflex cause the intestine to tear?
NO
Is a central heating system covered on your house insurance?
Not for normal "wear and tear" that resulted in repair or replacement.
What cause skin in the butt crack to tear?
Scissors
Is it allergies when your eyes tear?
Allergies can cause eye tearing but there is also other conditions that cause eye tearing. Allergy eyes usually have itching and tearing, not sole tearing. Infections, blocked tear ducts, and eye irritation are causes of tearing. Consult your doctor if you continue having issues.
Why balancing is require in steam engines?
If you think of a steam engine as a machine either any machine is balanced or it will tear itself apart in normally use
