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 ).
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Techniques to Examine Crystal Defects
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Microscopic Techniques
It is defined as, "techniques used to examine structural elements and defects in crystalline materials".
Microstructure ↠ combination of crystal structure + grain size + defects in crystal structure + phase + impurities.
Microscopy ↠ used for the investigation of microstructural features (instruments).
Applications of microscopy and micro-structure are:
Ensure association between the properties, structures and defects.
To predict property of material (after relationship created).
To design alloys with new property combination.
Check material has been properly heat treated.
To study various mode of mechanical fracture.
Types of Microscopy
1. Optical Microscopy
It is defined as, "microscopy in which visible light and system of lenses to magnify images of small samples". Upper limit magnification is 2000x.
It consists of two major systems, which are
Magnification System ↠ have lenses to magnify.
Illuminating System ↠ have light and camera for capturing images.
Metallographic investigation (optical microscopy of metals) consist of following steps:
Sectioning ↠ cutting of material to observe a structure of large crystal structure.
Grinding ↠ to remove buds over the surfaces.
Polishing ↠ to further smoothen the surface.
Etching ↠ workpiece is dipped in Nitric Acid to highlight boundaries.
2. Electron Microscopy
It is defined as, "microscopy in which image of investigated structure is formed using beams of electrons".
Magnification power is smaller than that of optical microscopy.
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...
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