Mechanical Engineering Seminar Topics 2014
PLASMA ARC CUTTING
The Plasma Arc Cutting system employs the use of an electric arc and a pressurized volume of ionized air forced through a small orifice (TIP) fitted between the electrode in the plasma torch and the work piece to be cut. This constricted, high speed and high temperature plasma arc stream cuts through metal in a concentrated localized area and the molten metal is blown away by the high velocity arc and air steam. The Plasma Arc Cutting process is capable of cutting and gouging most Ferrous (steel) and Non-Ferrous (Aluminum, Copper etc) metals producing a clean narrow cut width (determined by the tip orifice size) and smoother surfaces. The process is more portable, cuts faster and cleaner than the gas cutting (oxy/fuel) process, requiring no pre-heat, and with the added advantage of being able to cut Stainless Steel and Non-Ferrous metals (oxy/fuel cannot) cleanly and effectively, using less cumbersome equipment. The process can be used with either a hand held torch or on automated systems. The Plasma Power source has drooping current characteristics, using higher voltages than standard welding machines and the torches are well insulated to protect the operator against the high voltages present. The majority of Plasma Arc Cutters today have high frequency arc starting features meaning that non base metal contact is used as opposed to machines without high frequency that require scratch start to initiate the arc. Hand cutting torches using stand-off guides (determines tip distance from work piece) enables the operator to rest the torch on the work piece and by using a template or straight edge is able to cut straight or profile edges cleanly and accurately. The torch can also be used for gouging by changing the tip to a gouging tip that enables the operator to angle the torch to + - 30 degrees as opposed to the 90 degree used when cutting.
FRACTURE MECHANICS
A fracture is the local separation of the body into two or more pieces under the action of stress. The word fracture is often applied to bones of living creatures, or to crystals or crystalline materials, such as gemstones or metal. With the improving skill of metal working, applications of metal in structures increased progressively. Then it was experienced that structure built of these materials did not always behave satisfactorily and unexpected failures occurred. The vastly increased use of metals in the 19th century caused number of accidents and casualties to reach unknown levels. Some of these accidents were due to poor design, but it was gradually discovered that material deficiencies in the form of pre-existing flows could initiate Cracks and Fractures.The failure often occurred under conditions of low stress(several ships failed suddenly while in the harbor) which made them seemingly inexplicable. As a result extensive investigation were initiated in many countries and especially in USA. This occurrence of low stress fracture in high strength material induced the development of Fracture Mechanics. This paper deals with fracture mechanics clearly distinguishing between crack and fracture, types of fracture etc. Here we take into study, an incidence of fracture that occurred in the rear wheel of Karizma bike and analysing the effect of dynamic fracture in that incidence and influence of fatigue on it. Discussion of preventive measures to be taken to avoid the fracture is also discussed.
KINETIC ENERGY RECOVERY SYSTEM
KERS means Kinetic Energy Recovery System and it refers to the mechanisms that recover the energy that would normally be lost when reducing speed. The energy is stored in a mechanical form and re transmitted to the wheel in order to help the acceleration. Electric vehicles and hybrid have a similar system called Regenerative Brake which restores the energy in the batteries.The device recovers the kinetic energy that is present in the waste heat created by the car’s braking process. It stores that energy and converts it into power that can be called upon to boost acceleration.There are principally two types of system - battery (electrical) and flywheel (mechanical). Electrical systems use a motor-generator incorporated in the car’s transmission which converts mechanical energy into electrical energy and vice versa. Once the energy has been harnessed, it is stored in a battery and released when required.Mechanical systems capture braking energy and use it to turn a small flywheel which can spin at up to 80,000 rpm. When extra power is required, the flywheel is connected to the car’s rear wheels. In contrast to an electrical KERS, the mechanical energy doesn't change state and is therefore more efficient. There is one other option available - hydraulic KERS, where braking energy is used to accumulate hydraulic pressure which is then sent to the wheels when required.
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