All About Mechanical Engineering

Mathematical functions:- Following the continuous assumption, the mathematical description of the state of a moving fluid can be characterized by functions of the coordinates x, y, z and of the time t. These functions of (x, y, z, t) are related to the quantities defined for the fluid at a given point (x, y, z) in space and at a given time t, which refers to fixed points in space and not to fixed particles of the fluid. For example, we can consider the mean local velocity v(x, y, z, t) of fluid particles or fluid points, called the fluid velocity, and two thermodynamic quantities that characterize the fluid state, the pressure p(x, y, z, t) and the mass density (x, y, z, t), the mass per unit volume of fluid. Following the discussion of §2, two remarks can be done at this stage:  i). The fluid is assumed to be a continuum. This implies that all space-time derivatives of all dependent variables exist in some reasonable sense. In other words, local properties such as density pressur...

 BASIC PRINCIPLES OF FLUID:-    The application of the principles of fluid dynamics to the flow of air in underground openings. Airflow is induced from the atmosphere, through the intake opening, underground airways, return opening, and back to the atmosphere again by differential pressure between intake and return openings of the mine. This pressure differential is usually very small, in the order of 2 to 3% in most cases, when compared to the absolute pressure of the system. Therefore, volume and density changes are neglected without serious loss of accuracy or validity. Airflow in mines is also generally treated as steady-state, turbulent, and incompressible. However, in situations where the pressure, temperatures, and humidity changes are large and air conditioning processes are involved, calculations must incorporate the compressibility effect of air. Definition of A Fluid:- A fluid may be defined broadly as a substance that deforms continuously when subjected to she...

  Kinematic chains:- • Kinematic chain: links joined together for motion • Mechanism: grounded kinematic chain • Machine: mechanism designed to do work Link classification:-  Ground : any link or links that are fixed, nonmoving with respect to the reference frame  Crank: pivoted to ground, makes complete revolutions  Rocker: pivoted to ground, has oscillatory motion  Coupler: link has complex motion, not attached to the ground. Elements: 0: Ground (Casing, Frame) 1: Rocker 2: Coupler 3: Crank The “Ground” Link:-  When studying mechanisms it is very helpful to establish a fixed reference frame by assigning one of the links as “ground”.  The motion of all other links are described with respect to the ground link.  For example, a fourbar mechanism often looks like a 3-bar mechanism, where the first “bar” is simply the ground link. Determining Degrees of Freedom Two unconnected links: 6 DOF (each link has 3 DOF) When connected by a full joint: 4 DOF (each full joint eliminate...

 Linkage design:  Linkages are the basic building blocks of all mechanisms  All common forms of mechanisms (cams, gears, belts, chains) are in fact variations on a common theme of linkages. • Linkages are made up of links and joints. • Links: rigid member having nodes • Node: attachment points 1. Binary link: 2 nodes 2. Ternary link: 3 nodes 3. Quaternary link: 4 nodes Joint: a connection between two or more links (at their nodes) which allows motion; (Joints also called kinematic pairs). Joint Classification Joints can be classified in several ways: 1) By the type of contact between the elements, line, point, or surface. 2) By the number of degrees of freedom allowed at the joint. 3) By the type of physical closure of the joint: either force or form closed. 4) By the number of links joined (order of the joint). A joint with more than one freedom may also be a higher pair • Type of contact: line, point, surface • Number of DOF: full joint=1DOF, half joint=2DOF • Form closed (clo...

  Degrees of Freedom (DOF) or Mobility • DOF: Number of independent parameters(measurements) needed to uniquely define the position of a system in space at any instant of time. • A mechanical system’s mobility (M) can be classified according to the number of degrees of freedom (DOF). • DOF is defined with respect to a selected frame of reference (ground).  Rigid body in a plane has 3 DOF: x,y,z  Rigid body in 3D-space has 6 DOF, 3 translations & 3 rotations  three lengths (x, y, z), plus three angles(θ, φ, ρ).  The pencil in these examples represents a rigid body or link. Types of Motion • Pure rotation: the body possesses one point (center of rotation) that has no motion with respect to the “stationary” frame of reference. All other points move in circular arcs. • Pure translation: all points on the body describe parallel (curvilinear or rectilinear) paths. • Complex motion: a simultaneous combination of rotation and translation.

 Definitions:- The subject Theory of Machines may be defined as that branch of Engineering-science, which deals with the study of relative motion between the various parts of a machine, and forces which act on them. The knowledge of this subject is very essential for an engineer in designing the various parts of a machine. Kinematics : The study of motion without regard to forces More particularly, kinematics is the study of position, displacement, rotation, speed, velocity, and acceleration. Kinetics : The study of forces on systems in motion A mechanism: is a device that transforms motion to some desirable pattern and typically develops very low forces and transmits little power. A machine: typically contains mechanisms that are designed to provide significant forces and transmit significant power. Application of Kinematics Any machine or device that moves contains one or more kinematic elements such As linkages, … gears…. belts and chains. Bicycle is a simple example of a kine...

NOZZLES                                                                                                                                                         A nozzle (from the nose, meaning 'small spout') is a tube of varying cross-sectional area (usually axisymmetric) aiming at increasing the speed of an outflow and controlling its direction and shape. Nozzle flow always generates forces associated to the change in flow momentum, as we can feel by handholding a hose and opening the tap....