View Factor Orientation (or View factor or shape factor) plays an important role in radiation heat transfer. View factor is defined as, "fraction of radiation leaving surface 'i' and strike 'j' ". Summation Rule (View Factor) If there is are similar surfaces 'i' and 'j' , then: Blackbody Radiation Exchange Radiation Exchange between Opaque, Diffuse, Gray surfaces in an Enclosure 1. Opaque 2. Surfaces 3. Two surface enclosure Radiation Shield It is used to protect surfaces from radiation act like a reflective surface. References: Material from Class Lectures + Book named Fundamentals of Heat and Mass Transfer by Theodore L. Bergman + My knowledge. Photoshoped pics are developed. Some pics and GIF from Google. Videos from YouTube ( Engineering Sights ).
Several processing operations are done for the manufacturing gears, which are as:
Performing of Blank (with or without) ↠ important part of gears.
Annealing of Blank (Forged or Cast steel)
Machining of Gear Blank
Producing Teeth or Machining of Teeth
Finishing of Teeth (by shearing, grinding) ↠ if required
Full or Surface Hardening of Machined Gear ↠ case hardening
Inspection and Testing of Finished Gears
Manufacturing process involves following categories:
Forming ↠ shaping of plastic deformation in which volume remains constant (approx.) before and after the process. E.g.: Direct casting, rolling, powder metallurgy, injection molding, drawing, extrusion, stamping, forging, etc.
Machining ↠ shaping of parts by removing material (involves roughing, finishing operation). E.g.: Cutting, Shaping, Planning, Slotting, Broaching, Milling, Grinding, Hobbing, etc.
Forming Methods for Gear Manufacturing
Following are the methods for forming gears:
Sand Casting ↠ cast tooth are produced by melting and pouring into the mold cavity.
Die Casting ↠ casted tooth are produced by injecting material into mold cavity using high pressure.
Rolling ↠ deformation process in which thickness is reduced by compression forces exerted by two opposing rolls.
Powder Metallurgy ↠ pressing of metal powder in dies final shape.
Injection Molding ↠ producing teeth by injecting molten material into a mold.
Cold Drawing ↠ forming teeth from steel rods by drawing (pulling) them through hardened dies.
Extrusion ↠ shaping of teeth by pushing rod through a die having gear shape.
Stamping ↠ a cutting process in which sheet metal is placed between portions of die which removes the gear from the sheet.
Forging ↠ material shaping process by the application of localized compressive forces with power hammers, presses.
Machining Methods for Gear Manufacturing
Gears are manufactured in several routes:
Blanks are performed through machining, finishing and then teeth are produced.
Full Gears with teeth are made by different processes and then finished by further machining and grinding.
Accurate gears in finished form are directly produced by Near-Net-Shape process like rolling, plastic molding, powder metallurgy.
Machining methods for gear manufacturing are:
Forming (or Form-Cutting or Copying or Profiling Method) ↠ teeth profiles is obtained as the replica of the form of cutting tool (milling, shear cutting, teeth cutting).
Generation ↠ complicated tooth profile is provided by much simpler form cutting tool (edges) through rolling type, tool-work motion (Hobbing, gear shaping).
Projection: The term Projection is defined as: Presentation of an image or an object on a surface. The principles used to graphically represent 3-D objects and structures on 2-D media and it based on two variables: Line of Sight. Plane of Projection. Line of Sight & Plane of Projection: Line of sight is divided into 2 types: Parallel Projection Converging Projection & A plane of projection is an imaginary flat plane upon which the image created by the lines of sight is projected. Orthographic Projection: When the projectors are parallel to each other and perpendicular to the plane of projection. The lines pf sight of the observer create a view on the screen. The screen is referred to as the Plane of Projection (POP). The lines of sight are called Projection lines or projectors. Rules of Orthographic Projection: Edges that are parallel to a plane of projection appear as lines. Edges that are incl...
Gear Forming by Machining Formation of gear through machining consists of following methods: Form Milling by Disc Cutter Form Milling by End Mill Cutter Shaper, Planner and Slotter Broaching 1. Form Milling by Disc Cutter It is defined as, " Tooth is cut one by one by plunging the rotating cutter into the blank " . Each gear needs a separate cutter. 8 - 10 standard cutters are available for producing 12 - 120 teeth gears. Used for big spur gears of large pitch. 2. Form Milling by End Mill Cutter It includes the cutting of tooth at a time and then indexed for the next tooth space for cutting. For a small volume production of low precision gears. Set of 10 cutters ↠ 12 - 120 teeth gears . Used for teeth of large gears/module. To reduce cost, same cutter is often used for multiple sized gears resulting in profile errors . Characteristics: Use of Hardened stainless steels (HSS) form milling cutters. Use of Ordinary milling machines. Low production rate (need of indexing...
Reynolds Number: Reynolds Number is the ratio of Inertial forces to the Viscous forces. By knowing this number, one can describe the flow whether the flow is laminar, turbulent or transitional flow. There are three possibilities of the range of Reynolds Number: If Reynolds number < 2100 or 2300 ⟺ Laminar Flow If Reynolds number > 4000 ⟺ Turbulent Flow If 2300 < Reynolds number < 4000 ⟺ Transitional Flow In case of different shapes other than circle, the formula for Reynolds Number remain the same however diameter involves in the formula become Hydraulic Diameter which is given by: For pipe: Critical Reynolds Number ⟾ The Reynolds number at which the flow becomes turbulent Re cr For different shapes, the hydraulic diameters are given by: Completely Filled Flow In Closed Channel: If pipe is is considered to filled completely with closed channel, then following are the conditions which...
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