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 ).
Get link
Facebook
X
Pinterest
Email
Other Apps
Crystal Structures
Get link
Facebook
X
Pinterest
Email
Other Apps
-
Crystalline Solids and it's Structures
Crystalline Solids are defined as, "atoms arranged in periodic manner over long atomic distances in 3D patterns".
It deals with the unit cell (smallest part of structure).
If no 3D pattern ⇔ non-crystalline or amorphous solids.
Single Crystal ⇔ all unit cells interlock in the same way in the same orientation.
Polycrystalline Material ⇔ collection of small crystals (or grains) having random crystallographic orientation.
There are two types of unit cells, namely
Hard-Sphere unit cell
Reduced-Sphere unit cell
Types of Crystal Structures
Following are the types of crystal structures:
1. Face-Centered Cubic (FCC) Crystal Structure
It is defined as, "Unit cell of cubic geometry in which atoms are located at each of corners and centers of all cubic faces".
Each corner atom is shared among 8 unit cells.
Face-centered atom shared with 2 unit cells.
2. Body-Centered Cubic (BCC) Crystal Structure
It is defined as, "Cubic unit cell with atoms located at all eight corners and single atom at cubic center".
Center and corner atoms touch one another along cube diagonals.
Coordination number of BCC is 8.
3. Hexagonal Close-Packed (HCP) Crystal Structure
It is defined as, "Unit cell having cubic structure and have top and bottom faces consist of 6 atoms that forms regular hexagon and surround a single atom in the center".
Three additional atoms ⇔ provided to a plane between top and bottom face.
Coordination number is 12.
Atomic Packing factor is 0.74.
Stacking Sequence
It is defined as, "conversion of 2D layers to 3D structures to minimize empty spaces".
Important Terms
Point Coordinates ↔ are lattice parameters. It can be used to define which plane is more denser.
Crystallographic Directions ↔ Line between two points.
Crystallographic Planes ↔ Set of equally spaced planes that may be supposed to pass through the center of atoms in a crystal.
Linear Atomic Density ↔ It is the ratio between number of atoms and unit length of direction vector.
Theoretical Density ↔ Crystal structure of metallic solid permits computation of its theoretical density through the relationship.
References:
Material from Class Lectures + Book named Materials Science and Engineering: An Introduction by Callister and Rethwick + my knowledge.
TAPING CORRECTIONS There are two types of corrections depending upon the type of errors in tape due to the different conditions. 1. Systematic Errors : Slope Erroneous tape length Temperature Tension Sag 2. Random Errors : Slope Alignment Marking & Plumbing Temperature Tension & Sag 1. Temperature Correction It is necessary to apply this correction, since the length of a tape is increased as its temperature is raised, and consequently, the measured distance is too small. It is given by the formula, C t = 𝛼 (T m – T o )L Where, C t = the correction for temperature, in m. 𝛼 = the coefficient of thermal expansion. T m = the mean temperature during measurement. T o = the tempe...
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...
Diffusion It is defined as, " The transportation of one atom from one state into other state " . Used for hardening of surfaces like die parts, gear, bolt, machine element. Hardening can be done using Temperature-Heat treatment ( diffusion couple ). There are two types of diffusion: Inter-diffusion ↔ in which atoms tend to migrate from region of high concentration to low concentration . Self-diffusion ↔ in which atoms migrate within a solid. Diffusion Mechanism There can be two conditions of moving atoms Empty spaces between adjacent sites. Atoms have sufficient energy to break bond with neighbors atoms which cause lattice distortion during displacement. If we rise temperature, small fractions of atoms is capable of diffusive motion (which cause lattice distortion). Types of Diffusion 1. Vacancy Diffusion It is defined as, " interchange of an atom from a normal lattice position to the adjacent vacant lattice site " . Extent of vacancy diffusion is a function...
Comments
Post a Comment
HI, we wI'll contact you later