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 ).
Principal Strain and stresses can occur in the same directions.
Material Properties Relation (Young, bulk Rigidity Modulus) ⇼ Hooke's Law
General State of Strain ⇼ ЄX, ЄY, ЄZ and ૪X, ૪Y, ૪Z.
Stress (normal or shear)/Strain (normal or shear) ⇼ vary with element orientation.
Transformation equations for Plane strain derived from:
Interpretation of Experimental measurements
Represent in graphical form for plane strain (Mohr's Circle).
Geometry and independent of material properties.
Mohr's Circle
It is defined as., "A graphical method for determining normal and shear Shear stresses without using the stress transformation equations".
While considering the circle CCW ⇼ Shear strain positive upward & Normal strain positive towards right.
The construction of Mohr's circle (with normal and shear stresses are known) is quite easy which include following steps:
Draw a set of coordinate axes with ЄX (+ve right) and ૪Y/2(+ve upward).
Locate the center C of the circle at points ЄX1 = Єavg and ૪X1Y1= 0.
Locate point A which represents strain on X-face corresponds to (ЄX,૪Y/2).
Draw a line from point A to point C.
Using point C as center, draw Mohr's circle through point A.
Some key observations are:
Plane Strain ⇼ Stress condition in linear elastic fracture mechanics in which there is zero strain in the direction normal to the axis of applied tensile stress and direction of crack growth.
Principal Strain ⇼ maximum and minimum normal strain possible for a specific point on a structural element. Shear strain = 0 at the orientation where principal strain occurs. Important for predicting failure.
References:
Material from Class Lectures + Book named Engineering Mechanics of Materials by R.C. Hibbeler (6/9th Edition) + 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 temperature at which the tape is standardized. L = the measure length in m. For Foot Unit : C t = 6.45×10^-6 (T m – 68 )L For Metric Unit : C t = 1.16
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 inclined to a plan
ENGINEERING SURVEY Surveying is the science, art and technology of determine the relative positions of points above, on or beneath the Earth's surface so as to construct a map, plan or description. TYPES OF SURVEY : There are many types of survey but we discuss some of them. 1. Plane & Geodatic Survey : Ordinary field and topographical surveying in which the Curvature of Earth's surface is disregarded is called Plane Survey. It is performed when the area is smaller than 250sq.km. A survey of a large land area in which corrections are made for the Curvature of Earth's surface is called Geodatic survey. Why Geodatic Survey is important? Earth's surface is not flat, it is sphere. So all the calculations which were made by considering the Earth's surface flat are incorrect. So a new type of survey came into play which made calculations on the basis of geodatic condition of Earth's surface. 2. Topographic Survey : Topographic surv
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