The specimen is first ground on the '220' grade paper. Assuming that a stationary table is being used, this is achieved by rubbing it back and forth on the paper, in a direction which is roughly at right angles to the scratches left by the filling operation. In this way, it can easily be seen when the original deep scratches left by the file have been completely removed. If the specimen were ground so that the new scratches ran in the same diraction as the old ones, it would be virtually impossible to see when the latter had been erased. With the primary grinding marks removed, the specimen is now washed free of '220' grit. Grinding is then continued on the '320' paper, again turning the specimen through 90 degree and grinding until the previous scratch marks have been erased. The process is repeated with the '440' and '600' papers.
(Materials for Engineers and technicians Materials for Engineers and Technicians, Yazar: Raymond Aurelius Higgins, Page 121-122)
(Materials for Engineers and technicians Materials for Engineers and Technicians, Yazar: Raymond Aurelius Higgins, Page 121-122)
Burr
At the top of the cut surface isa region called the rollover. This corresponds to the depression made by the punch in the work prior to cutting. It is where initial plastic deformation occured in the work. Just below the rollover is a relatively smooth region called the burnish. This results from penetration of the punch into the work before fracture began. Beneath the burnish is the fractured zone, a relatively rough surface of the cut edge where continued downward movement of the punch caused fracture of the metal. Finally, at the at the bottom of the edge is a burr, a sharp corner on the edge caused by elongation of the meatl during final seperation of the two pieces.
(Fundamentals of modern manufacturing: Materials,Processes, and Systems, Yazar: Mikell Groover, Page 445)
The Firing Process (seramics)
After the shaping but before firing, the ceramic piece is said to be green (the same term as in powder metallurgy), meaning not fully processed or treated. The green piece lacks hardness and strength: it must be fired to fix the part shape and achieve hardness and strength in the finished ware. Firing is the heat treatment process that sinters the ceramic material; it is performed in a furnace called a kiln. In sintering, bonds are developed between the ceramic grains, and this is accompanied by densification and reduction of porosity. Therefore, shrinkage occurs in the polycrystalline materialin addition to the shrinkage that has already occured in drying. Sintering in ceramics is basically the same mechanism as in powder metallurgy. In the firing of traditional ceramics, certain chemical reactions between the components in the mixture may also take place, and a glassy phase alsoforms among the crystals that acts as a binder. Both of these phenomena depend on the chemical composition of the ceramic composition of the ceramic material and the firing temperatures used.
(Fundamentals of modern manufacturing: Materials,Processes, and Systems, Yazar: Mikell Groover, Page 375-376)
Resonance
The natural frequency (and its overtones) are of great interest to the designer as they define the frequencies at which the system will resonate. The single-DOF lumped parameter systems are the simplest possible to describe a dynamic system, yet they contain all the basic dynamic elements. Masses and springs are energy storage elements. A mass stores kinetic energy, and a spring stores potential energy. The damper is a dissipative element. It uses energy and converts it to heat. Thus all the losses in the model occur through the damper.
These are "pure" idealized elements which posses only their own special characteristics. That is, the spring hasno damping and the damper no springiness, etc. Any system that contains more than one energy storage device, such as a mass and a spring, will posses at least one natural frequency. If we excite the system at its natural frequency, we will set up the condition called resonance in which the energy stored in the system`s elements will oscillate from one element to the other at that frequency. The result can be violent oscillations in the displacements of the movable elements in the system as the energy moves from potential to kinetic form and vice versa.
(Cam Design and Manufacturing Handbook, Yazar: Robert L. Norton, Page 224)
(Fundamentals of modern manufacturing: Materials,Processes, and Systems, Yazar: Mikell Groover, Page 445)
The Firing Process (seramics)
After the shaping but before firing, the ceramic piece is said to be green (the same term as in powder metallurgy), meaning not fully processed or treated. The green piece lacks hardness and strength: it must be fired to fix the part shape and achieve hardness and strength in the finished ware. Firing is the heat treatment process that sinters the ceramic material; it is performed in a furnace called a kiln. In sintering, bonds are developed between the ceramic grains, and this is accompanied by densification and reduction of porosity. Therefore, shrinkage occurs in the polycrystalline materialin addition to the shrinkage that has already occured in drying. Sintering in ceramics is basically the same mechanism as in powder metallurgy. In the firing of traditional ceramics, certain chemical reactions between the components in the mixture may also take place, and a glassy phase alsoforms among the crystals that acts as a binder. Both of these phenomena depend on the chemical composition of the ceramic composition of the ceramic material and the firing temperatures used.
(Fundamentals of modern manufacturing: Materials,Processes, and Systems, Yazar: Mikell Groover, Page 375-376)
Resonance
The natural frequency (and its overtones) are of great interest to the designer as they define the frequencies at which the system will resonate. The single-DOF lumped parameter systems are the simplest possible to describe a dynamic system, yet they contain all the basic dynamic elements. Masses and springs are energy storage elements. A mass stores kinetic energy, and a spring stores potential energy. The damper is a dissipative element. It uses energy and converts it to heat. Thus all the losses in the model occur through the damper.
These are "pure" idealized elements which posses only their own special characteristics. That is, the spring hasno damping and the damper no springiness, etc. Any system that contains more than one energy storage device, such as a mass and a spring, will posses at least one natural frequency. If we excite the system at its natural frequency, we will set up the condition called resonance in which the energy stored in the system`s elements will oscillate from one element to the other at that frequency. The result can be violent oscillations in the displacements of the movable elements in the system as the energy moves from potential to kinetic form and vice versa.
(Cam Design and Manufacturing Handbook, Yazar: Robert L. Norton, Page 224)
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