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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Advance High Strength Steel (AHSS)
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Advance High Strength Steel
Conventional low carbon mild steel has simpler ferritic structure (α-iron) and good ductility.
Common type of HSS is High Strength Low Alloy (HSLA) ⇥ has yield strength 550 - 690 N/sq.mm.
Manganese ⇥ supporter (stabilizer) of ferrite.
Conventional HSS:
Is single-phase ferritic steel with a potential for some pearlite in C-Mn steel.
Lower strain hardening capacity.
Advance HSS:
primarily steel with a microstructure containing a phase other than ferrite, pearlite, cementite.
Crumple Zone ⇥ Made with those materials which absorb maximum amount of energy.
Safety Cage ⇥ Multiple areas (like cabins, structural elements).
Areas of Safety cage are described ahead:
Cabins (Blue Areas) ⇥ Should have high strength with a good balance of strength, formability, energy absorption and durability.
Structural Elements (Red Areas) ⇥ Safety critical parts.
Conclusion is:
Dual phase (DP) & Transformation induced plasticity (TRIP) steels are excellent in crash zone (high energy absorption capacity), so it is used to make Crumple Zone.
For structural elements ⇥ Extremely high strength steels such as Martensite and Boron-based Press Hardened (PHS) steels are used.
Advance HSS Family
Dual Phase (DP)
Complex Phase (CP)
Ferritic Bainitic (FB)
Martensite
Transformation Induced Plasticity (TRIP)
Hot Formed (HF)
Twinning Induced Plasticity (TWIP)
Dual Phase (DP) Steel
It consist of a ferritic matrix containing a hard martensite second phase in the form of island.
Microstructure is produced by giving steel a Sub-Critical Anneal at 800℃ and is quenched to room temperature.
Sub-Critical Anneal ⇥ Heating a material (steel) lower than the equilibrium line between austenite and α-phase and then cool it.
Ferrite is unaffected by heat treatment but Austenite grains transformed to martensite during quenching and is tempered at low temperature to increase ductility.
Tempering ⇥ heat treatment process that is performed in steels containing martensite just to relief some stresses.
DP Steel exhibits high work hardening rate, ultimate tensile strength, Tensile & Yield strength ratio.
Transformation Induced Plasticity (TRIP) Steel
It consist of Austenite embedded in a primary matrix of ferrite.
To get retained austenite ⇥ use Step Quenching (from Transformation Time VS Transformation Temperature Graph)
TRIP steel has lower initial work hardening rate than DP.
It uses higher quantities of carbon than DP to obtain sufficient carbon content for stabilizing the retained austenite phase to below ambient temperature.
Si & Al ⇥ used to avoid carbide precipitation in the bainite region.
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...
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...
Lubrication: It is defined as the admittance of oil between two surfaces having relative motion. Why do we need Lubrication? The functions of lubrication are described ahead: Reduce friction between moving parts. Reduce wear and tear of parts. Shock absorbing. To cool the surfaces in contact. Properties of Lubricants: Following are the properties of Lubricants: Viscosity ➸ Internal resistance to flow of liquid. It is the ability of oil to resists internal deformation due to load and mechanical stresses. Viscosity Index ➸ It represents the change in viscosity of oil with temperature. The greater the viscosity index, the smaller the change in viscosity with temperature. Flash Point Temperature ➸ The lowest temperature at which vapor of lubricating oil will ignite when given an ignition source. Fire Point Temperature ➸ It is the minimum temperature at which vapor of fluid will keep burning after the i...
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