mechanical engineering

General Characteristics for Selection of Measuring Instruments Various specific terms describe the characteristics and quality of measuring instruments, defined as follows: Accuracy:  The degree of agreement of the measured dimension with its true magnitude. Amplification:  The ratio of measuring instrument output to the input dimension; it is also called magnification. Calibration:  The adjustment or setting of a measuring instrument to give readings that are accurate within a reference standard. Drift:  An instrument’s capability to maintain its calibration over time; also called stability. Linearity:  The accuracy of the readings of a tool over its full working range. Magnification:  The ratio of measuring instrument output to the input dimension; also called amplification. Precision:  Degree to which a measuring instrument gives repeated measurement of the same standard. Repeat accuracy:  The same as accuracy, but rep...

Water Jet Machining (WJM) In  Water Jet Machining (WJM)  process, water jets alone (without abrasives) can be used for cutting. Thin jets of high pressure and high velocity have been used to cut materials such wood, coal, textiles, rocks, concrete, asbestos. The mechanism of material removal rate is by erosion. When high-pressure water jet emerges from a nozzle, it attains a large kinetic energy. High-velocity jet strikes the workpiece, its kinetic energy is converted into pressure energy including high stresses in the work material. When the induced stress exceeds the ultimate shear stress of the material, rupture takes place. Schematic illustration of water jet machining Characteristics: The pressures normally used in WJM are 1500 to 4000 MPa. The nozzle is made of sintered diamond and exit nozzle is about 0.05 to 0.35 mm in diameter. No moving parts in the system, so less operating and maintenance costs and safe process. No thermal damage to work and ...

Centrifugal Compressor A  centrifugal compressor  is one of its class machines in producing a pressure rise and is known as turbo-compressors. In centrifugal compressors, energy is transferred by dynamic means from a rotating member (or impeller) to the continuously flowing working fluid. The main feature of the centrifugal compressor is that the angular momentum of the fluid flowing through the impeller is increased partly by virtue of the impeller’s outlet diameter being significantly larger than its inlet diameter. Essential parts of a centrifugal compressor: The inlet casing with the converging nozzle, whose function is to accelerate the fluid to impeller inlet. The outlet of the inlet casing is known as the eye. The impeller in which the energy transfer takes place, resulting in a rise of fluid  kinetic energy  and static pressure. The diffuse, whose function is to transform the high kinetic energy of the fluid at the impeller outlet into s...

Magneto Ignition System Magneto ignition system  is a special type of ignition system with its own electric generator to provide the required necessary energy for the vehicle (automobile) system. It is mounted on the engine and replaces all components of the coil ignition system except the spark plug. A magneto, when rotated by the engine, is capable of producing a very high voltage and doesn’t need a battery as source of external energy. A schematic diagram of a high tension magneto ignition system is shown in the figure 1 under. The high tension magneto ignition system incorporates the windings to generate the primary voltage as well as to set up the voltage and thus does not require to operate the spark plug. Figure 1: Schematic Diagram of Magneto Ignition System Magneto ignition system can be either rotating armature type or rotating magneto type. In the first type, the armature consisting of the primary and secondary windings all rotate between the poles ...

Lathe Machine: Parts, Operations A  lathe machine  is a mechanical device in which the workpiece is rotated against a suitable  cutting tool  for producing cylindrical forms in the metal, wood or any other machinable material. Figure 1: Lathe machine Various types of lathe machine tools: Copy Lathe Automatic Lathe Turret lathe machine Engine lathe Bench lathe Chucking lathe Speed lathe Automatic screw machine or a bar machine Numerically controlled lathe Lathe Machine parts: Figure 2: Lathe machine parts labeled Different parts of Lathe: Headstock : Headstock supports the central spindle in the bearings and aligns it correctly. It also houses necessary transmission mechanism for different speeds. It supports the main spindle in the bearings and aligns it properly. It has a mechanism for getting different speeds. Accessories mounted to headstock spindle are 3/4 jaw chuck, lathe center, and lathe dog, collect chuck, face plat...

Reversible and Irreversible Processes Figure 1: Graph of Reversible and Irreversible processes. Image source:  Theoretical Physics, University of Manchester A thermodynamic process which does not fulfill conditions of a reversible process is termed irreversible processes. Irreversibilities are the reasons causing the process to be irreversible. The irreversibilities can be termed as internal irreversibility and external irreversibility. Internal irreversibility is there because of internal factors whereas external irreversibility is caused by external factors at the system-surrounding interface. Generic types of irreversibilities are due to: Friction:  Friction is invariably present in real systems. It causes irreversibility in the process as work done does not show an equivalent rise in the kinetic or potential  energy of the system. The fraction of energy wasted due to frictional effects leads to deviation from reversible states. Electrical re...

Laser Beam Machining (LBM) Laser technology is being used for a variety of industrial applications, including heat treatment, welding, measurement, as well as scribing, cutting, and drilling (described here). The term laser stands for light amplification by stimulated emission of radiation.A laser is an optical transducer that converts electrical energy into a highly coherent light beam. A laser light beam has several properties that distinguish it from other forms of light. It is monochromatic (theoretically, the light has a single wavelength) and highly collimated (the light rays in the beam are almost perfectly parallel). These properties allow the light generated by a laser to be focused, using conventional optical lenses, onto a tiny spot with resulting high power densities. Depending on the amount of energy contained in the light beam, and its degree of concentration at the spot, the various laser processes identified in the preceding can be accomplished. Figur...