The essence of re-election is summarized as a loose-layered-separation process. The layer of loose ore (called the bed) placed in the sorting device is loosened by the buoyancy, power or other mechanical forces of the fluid, in order to stratify the different density (or particle size) particles. Re-election is to achieve stratification by density. Therefore, the loose action of the fluid must obey the requirement of stratification of the particles. This is the difference between re-election and other two-phase flow engineering. The looseness of the fluid is different and the stratification results are also affected. The rhyme problem of re-election theory is simply to explore the relationship between looseness and stratification. The stratified ore is discharged separately under mechanical action. That is, sorting is achieved. Therefore, looseness is a condition, stratification is the purpose, and separation is the result. The various re-selection processes described above are implemented. The means of this process. Their work is governed by such basic principles; (1) the theory of sedimentation of particles and particle groups, (2) the theory of stratification of particle groups by density, and (3) the separation theory of particle groups in slant flow. There is also a sorting in the swirling flow, although the medium moves differently. However, the basic law of action is the same except for the difference between gravity and centrifugal force. According to the theory of density stratification, the earliest research is based on the jigging process. A lot of jigging stratification theory has been proposed, and later some special theory of vertical stratification: middle stratification. The bevel flow beneficiation is the first to treat coarser ore in a thick water layer. The sorting is based on the difference in velocity of the particles along the trough. After the 1940s, the bevel flow beneficiation developed towards the film-mining process, mainly for sorting fine-grained and fine-grained grade ore. The flow state has a laminar flow and a turbulent flow. It has been consistently believed that the turbulent pulsation velocity is the basic force of the loose bed, which is difficult to explain under laminar flow conditions. 1954 R. A. The inter-layer shear repulsion mechanics proposed by Bagn0ld complements this interesting gap. However, as with stratification theory, it is still difficult to make reliable calculations based on existing theory. Although re-election theory has not yet reached perfection today, like many process disciplines, it has provided basic guidance for production and can serve as the basis for mathematical statistics and similarity and simulation studies.
Sheet metal forming processes are those in which force is applied to a piece of sheet metal to modify its geometry rather than remove any material. The applied force stresses the metal beyond its yield strength, causing the material to plastically deform, but not to fail. By doing so, the sheet can be bent or stretched into a variety of complex shapes. Sheet metal forming processes include the following:
l Bending
l Roll forming
l Deep Drawing
l Stretch forming
Bending
Bending is a metal forming process in which a force is applied to a piece of sheet metal, causing it to bend at an angle and form the desired shape. A bending operation causes deformation along one axis, but a sequence of several different operations can be performed to create a complex part. Bent parts can be quite small, such as a bracket, such as a large enclosure or chassis.
V bending and Wipe bending
Roll forming
Roll forming, is a metal forming process in which sheet metal is progressively shaped through a series of bending operations. The process is performed on a roll forming line. Each station has a roller, referred to as a roller die, positioned on both sides of the sheet. The shape and size of the roller die may be unique to that station, or several identical roller dies may be used in different positions. The roller dies may be above and below the sheet, along the sides, at an angle, etc. the roller dies are lubricated to reduce friction between the die and the sheet, thus reducing the tool wear. Also, lubricant can allow for a higher production rate, which will also depend on the material thickness, number of roll stations, and radius of each bend. The roll forming line can also include other Sheet Metal Fabrication operations before or after the roll forming, such as punching or shearing.
Deep drawing
Deep drawing is a metal forming process in which sheet metal is stretched into the desired part shape. A tool pushes downward on the sheet metal, forcing it into a die cavity in the shape of the desired part. The tensile forces applied to the sheet cause it to plastically deform into a cup-shaped part. Deep drawn parts are characterized by a depth equal to more than half of the diameter of the part. These parts can have a variety of cross sections with straight, tapered, or even curved walls, but cylindrical or rectangular parts are most common. Deep drawing is most effective with ductile metals, such as aluminum, brass, copper, and mild steel. Examples of parts formed with deep drawing include automotive bodies and fuel tanks, cans, cups, kitchen sinks, and pots and pans
Stretch Forming
Stretch forming is a metal forming process in which a piece of sheet metal is stretched and bent simultaneously over a die in order to form large contoured parts. Stretch forming is performed on a stretch press, in which a piece of sheet metal is securely gripped along its edges by gripping jaws. The gripping jaws are each attached to a carriage that is pulled by pneumatic or hydraulic force to stretch the sheet. The tooling used in this process is a stretch form block, called a form die, which is a solid contoured piece against which the sheet metal will be pressed. The most common stretch presses are oriented vertically, in which the form die rests on a press table that can be raised into the sheet by a hydraulic ram. As the form die is driven into the sheet, which is gripped tightly at its edges, the tensile forces increase and the sheet plastically deforms into a new shape. Horizontal stretch presses mount the form die sideways on a stationary press table, while the gripping jaws pull the sheet horizontally around the form die
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