Overshoot (older)
If the system is underdamped, the response of the transducer or measuring system overshoots the step-input magnitude and the corresponding oscillation occurs with a first-order decay. This type of response leads to additional response specifications which may be used by transducer manufacturers. These specifications include overshoot OS, peak time Tp, settling time T5, rise time Tn and delay time Td. If the viscous damping is at the critical value, the measuring system responds up to the step-input magnitude only after a very long period of time. If the damping is more than critical, the response of the measuring system never reaches a magnitude equivalent to the step input. Measuring-system components following a second-order behavior are normally designed and/or selected such that the damping is less than critical. With underdamping the second-order system responds with some time delay and a characteristic phase shift.
(Standard Handbook of Machine Design (3rd Edition), Edited by: Shigley, Joseph E.; Mischke, Charles R.; Brown, Thomas H. Jr., p3-18)
If the system is underdamped, the response of the transducer or measuring system overshoots the step-input magnitude and the corresponding oscillation occurs with a first-order decay. This type of response leads to additional response specifications which may be used by transducer manufacturers. These specifications include overshoot OS, peak time Tp, settling time T5, rise time Tn and delay time Td. If the viscous damping is at the critical value, the measuring system responds up to the step-input magnitude only after a very long period of time. If the damping is more than critical, the response of the measuring system never reaches a magnitude equivalent to the step input. Measuring-system components following a second-order behavior are normally designed and/or selected such that the damping is less than critical. With underdamping the second-order system responds with some time delay and a characteristic phase shift.
(Standard Handbook of Machine Design (3rd Edition), Edited by: Shigley, Joseph E.; Mischke, Charles R.; Brown, Thomas H. Jr., p3-18)
Overshoot (Newer) (control)
the standard second order type 1 system is characterised by having zero
steady state error to a step input. Only underdamped systems (-1<ksi<1) have an oscillatory step response.
for the stable under damped case (0<ksi<1), its dynamic response when subjected to a step input is characterised by an error signal that oscillates with diminishing amplitude about the final, zero level. Succesive maxima and minima relative to this final level have a constant ratio and the largest error, apart from the initial value of 1, is the first minimum. This corresponds to the maximum overshoot. The overshoot is uniquely defined by the damping factor, being independent of the natural frequency. The defining equation is repeated here for convenience
for the stable under damped case (0<ksi<1), its dynamic response when subjected to a step input is characterised by an error signal that oscillates with diminishing amplitude about the final, zero level. Succesive maxima and minima relative to this final level have a constant ratio and the largest error, apart from the initial value of 1, is the first minimum. This corresponds to the maximum overshoot. The overshoot is uniquely defined by the damping factor, being independent of the natural frequency. The defining equation is repeated here for convenience
%overshoot = 100.€^x
where x = -ksi*pi/squareroot(1-ksi^2) (T. Dougherty, System& Control, pg.596)
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Laser Glazing (14 Nisan 2011 00:22) (older)
Laser glazing involves some surface melting. As the beam from a multikilowatt CO2 laser is scanned over a surface, a thin melt layer is produced under proper conditions of irradiance and traverse speed. The interior of the workpiece remains cold. After the beam moves on, resolidification occurs very rapidly. The surface layer is quickly quenched. As a result of this process, one may produce surface microstructures with unusual and possibly useful characteristics. The grain size near the surface is very small, because of the high quench rate. The surface structure can appear glassy; hence, the name laser glazing. This technique is applicable both to metals and ceramics. It appears to be controllable and reproducible. Laser glazing can produce surfaces that are amorphous or that have a glassy, noncrystalline structure. Such surfaces can have increased resistance to corrosion. One example of laser glazing is surface melting of cast iron with rapid resolidification. This produces a thin surface layer of very hard material called white cast iron, which can provide excellent wear resistance. Another example that has been demonstrated is the glazing of aluminum bronze, which leads to surface structures with enhanced corrosion resistance.
(Industrial Applications of Lasers, John F. Ready; Page: 380)
Laser Glazing (Newer) (Manufacturing Process)
Laser glazing is a process in which is a focused laser beam is used to melt a very small portion of a component. As the beam moves away from the melted region, the underlying mass of the component causes the liquid pool to rapidly solidify. A major advantage of laser glazing is that the refined structure is only created in areas where high load carrying capacity required(J.J.C. Hoo, Bearing Steels: Into the 21st century, pg.471)
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Laser glazing is a process in which is a focused laser beam is used to melt a very small portion of a component. As the beam moves away from the melted region, the underlying mass of the component causes the liquid pool to rapidly solidify. A major advantage of laser glazing is that the refined structure is only created in areas where high load carrying capacity required(J.J.C. Hoo, Bearing Steels: Into the 21st century, pg.471)
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Over-damping (older)
The effect of forces on an oscillating system is that the oscillations will evetually stop and the energy of the system will be dissipated mainly as thermal energy to the environment and the system itself. Oscillations taking place in the presence of resistance forces are called damped oscillations. The behaviour of the system depends on the degree of damping. We may distinguish three distinct cases: under-damping, critical damping and over-damping. In over-damping case degree of damping is so great that the system returns to equilibrium without oscillations (as in the case of critical damping) but much slower than in the case of critical damping.
(Tsokos K. A., Physics for the IB Diploma, p.208)
Over Damping (Control) (Newer) (beter)
An over-damping state the amplitude drops significantly at frequencies well below w(n), For an optimum damping (a critical damping state), the amplitude-frequency relationship has a maximum bandwith. Note that in the conditions of critical damping and over-damping, the damping ratio ksi is used instead of the Q factor as tere is no resonant peak in the curves. (Min Hang Bao, Micro Mechanical Transducers ,pg.8)
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An over-damping state the amplitude drops significantly at frequencies well below w(n), For an optimum damping (a critical damping state), the amplitude-frequency relationship has a maximum bandwith. Note that in the conditions of critical damping and over-damping, the damping ratio ksi is used instead of the Q factor as tere is no resonant peak in the curves. (Min Hang Bao, Micro Mechanical Transducers ,pg.8)
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Mask welding (older)
A laser beam diverged out in the shape of a line is translated across the parts to be joined through a mask or shield.The laser beam heat is joint wherever a weld seam is not masked (shadowed).Mask welding can result in very high resolutions between welded and non-welded areas.Today it is possible to produce a weld width of less than 100 μm.
(Plastics pocket power welding, Hanser,p.66) 00.26
A laser beam diverged out in the shape of a line is translated across the parts to be joined through a mask or shield.The laser beam heat is joint wherever a weld seam is not masked (shadowed).Mask welding can result in very high resolutions between welded and non-welded areas.Today it is possible to produce a weld width of less than 100 μm.
(Plastics pocket power welding, Hanser,p.66) 00.26
Mask Welding (Newer) (Weld)
A laser beam diverged out in the shape of a line is translated across the parts to be joined through a mask or shield. The laser beam heats the joint wherever a weld seam isn't masked (shadowed). Mask welding can result in very high resolutions between welded and non-wlded areas. Today, ıt's possible to produce a weld width of less than 100x103^-6 m (D. Grewell, A. Benatar, C. Bonten, Welding, pg.66)
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A laser beam diverged out in the shape of a line is translated across the parts to be joined through a mask or shield. The laser beam heats the joint wherever a weld seam isn't masked (shadowed). Mask welding can result in very high resolutions between welded and non-wlded areas. Today, ıt's possible to produce a weld width of less than 100x103^-6 m (D. Grewell, A. Benatar, C. Bonten, Welding, pg.66)
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Hot Spinning (older) (better)
The hot spinning process is schematically shown in fig. the process is carried out on thick steel sheets to form a dish or other circ
ular cross-sectional shapes which are symmetrical about the axis of rotation. In hot spinning,
metal blank is heated to forging temperature and then it is held on lathe with the help of metallic form or chuck attached to the lathe spindle. The adapter at the tail stock end helps in the holding the hot blank against the chuck. Blunt hand spinning tools when fed forward(or pushed with pressure), bend and give shape to the revolving hot blank. Thin sheets are formed to various shapes by ‘cold spinning’ process discussed later.
(Kaushish,J.P., Manufacturing Processes, Eastern Economy Edition, pg. 411)
Hot Spinning (Newer) (Manufacturing Process)
Hot spinning is the process used for making cup shaped articles which are axisymmetrical with heated to the forging temperature. The process of hot spinning consists of rotating the blank, fixed against the form block and then applying a gradually moving force on the blank so that, the blank takes the shape of the form block. The set-up essentially consists of a machine similar to a centre lathe. In the head stock of the spinning machine, a hard wood form block which has the shape of the desired part, is fixed. The blank is held against the form block by means of the freely rotating wooden block from the tail stock. After proper clamping, the blank is rotated to its operating speed. The spinning speed depends on the blank material, thickness and complexity of the desired cup. Then the hard wood or roller type metallic tool is pressed and moved gradually on the blank so that it conforms to the shape of the form block. The manipulation of spinning tools is a highly skilled art. The tool is to be moved back and forth on the blank so that no thinning takes place anywhere on the blank.
Spinning is comparable to drawing for making cylindrical shaped parts. Because of the simple tools used in spinning, it's economical for smaller lots. But the time required for making a cup is more in spinning and also more skill is required in the process. Thus, it isn't suitable for large-scale production. Complicated shapes and re-entrant shapes aren't feasible by drawing, but can be made by spinning using the sectional and collapsible form blocks. Large parts are much more easily made in spinning than by drawing. When sheet thickness is more, for example, in making the dished ends of pressure vessels, cold spinning isn't sufficent. Then the blank is heated to the forging temperature and so the process is called hot spinning. Also in hot spinning the tools are mechanically manipulated because of higher magnitudes of forces required. (Rao, Manufacturing Technology, pg.317 )
Spinning is comparable to drawing for making cylindrical shaped parts. Because of the simple tools used in spinning, it's economical for smaller lots. But the time required for making a cup is more in spinning and also more skill is required in the process. Thus, it isn't suitable for large-scale production. Complicated shapes and re-entrant shapes aren't feasible by drawing, but can be made by spinning using the sectional and collapsible form blocks. Large parts are much more easily made in spinning than by drawing. When sheet thickness is more, for example, in making the dished ends of pressure vessels, cold spinning isn't sufficent. Then the blank is heated to the forging temperature and so the process is called hot spinning. Also in hot spinning the tools are mechanically manipulated because of higher magnitudes of forces required. (Rao, Manufacturing Technology, pg.317 )
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