ME 1104: Calculus and Analytical Geometry

ME 3507: Theory of MachinesIntroductionDr. Faraz JunejoAssessments 2 Quizzes: 10 Marks (5 Marks each) You will be notified 1 Week in advance 1 Course Work 2 parts: 5 Marks (Submission after mid and final exams) Mid Term Exam (9th Week 7th October): 20 MarksLab (Lab Manual, Quiz, Mid Term & Final/Viva) : 25 MarksFinal Exam (17th Week 2nd December) : 40 MarksClass ConductAbsences from classLate in classAssignment submissionAbsence from Mid Term or Final ExamCheatingAnything you want to ask, ASK NOW !!Text & Reference Books

Basic Concepts: MachineA machine is an assemblage of rigid bodies thattransmits and/or transforms forces, motion andenergy in a predetermined manner, to do work.OR It is a combination of resistant bodies (the deformation, if any, due to application of forces is negligible)which are shaped and interconnected in such a way so as to transform and transmit the available energy to do some particular kind of work.Machine

Example: MachineA screw jack is a machine which enables the muscular energy of a man to be employed in raising a vehicle, as in figure shown below by turning the lead screw.

Example: Dumping TruckHere input motion is linear, provided by a hydraulic actuator.Whereas, output motion is the rotary motion of the dumper

Theory of Machines (TOM)It is the branch of engineering science that deals with the study of: Relative motion between the various parts of the machine, and Forces which act on them.Why do we study Theory of Machines?The knowledge of this subject is essential for an engineer in designing the various parts of the machine.Subdivision of TOMTOM Constitutes of many sub-areas, such as:StaticsKinematicsKineticsDynamics Review: What is Mechanics?Mechanics is the physical science that deals with the behavior of bodies under the influence of forces, i.e.

Study of what happens to a thing (the technical name is BODY) when FORCES are applied to it.Review: Mechanics of Rigid Bodies Mechanics can be divided into 3 categories: 1.) mechanics of rigid bodies, 2.) mechanics of deformable bodies, and 3.) mechanics of fluids.This course deals solely with the mechanics of rigid bodies.A rigid body is a body which does not deform under the influence of forces.Review: Mechanics of Rigid Bodies In all real applications, there is always deformation, however, many structures, such as bridges and machines exhibit very small deformations under normal loading conditions, and rigid body mechanics can be used with sufficient accuracy in those cases.Structures v/s MachinesMachines: An arrangement of parts and/or mechanisms for doing work and there are constrained relative motions between its parts.Structure: The same definition of machine, but its purpose is not to do work and there is no relative motion between its parts.

Statics The mechanics of rigid bodies is sub-divided into two areas, statics and dynamics.Statics is the study of bodies in equilibrium.This means there are no unbalanced forces on the body, thus the body is either at rest or moving at a uniform velocity (i.e. it has no acceleration, implying body is moving with constant speed along a straight path).

Dynamics Dynamics is the study of bodies which are not in equilibrium, thus there is acceleration.Dynamics is further subdivided into: kinematics and kinetics.

KinematicsKinematics is the study of the motion of a body, without regard for how the motion is produced.During this course, Kinematic principles are often applied to the analysis of machine members to determine positions, velocities, or accelerations at various parts of the machines' operation.

KineticsKinetics is the study of the forces which cause motion, or the forces which result from motion.

Summary: MechanicsDeals with the action of forces on bodies at rest and in motion. Statics: The part of mechanics, which deals with the action of forces on bodies at rest. Dynamics: The part of mechanics, which deals with the action of forces on bodies in motion. Summary: StaticsIt is the branch of TOM which deals with the forces and their effects while the machine parts are at rest. The mass of the part is assumed to be negligible.Summary: Kinematics & KineticsKinematics is that branch of TOM which deals with the relative motion between the various machine parts without regard to forces causing the motion i.e. it does not tell us effect of the forces.Kinetics is the study of the forces which cause motion, or the forces which result from motion.Important Note !!KINEMATICS: The study of motion without regard to forces.KINETICS The study of forces on systems in motion.These two concepts are really not physically separable. We arbitrarily separate them for instructional reasons in engineering education. It is also valid in engineering design practice to: First consider the desired kinematic motions and their consequences, and then Subsequently investigate the kinetic forces associated with those motions. Important Note !!For example; it is quite logical to consider them in the order listed since, from Newton's second law, F = ma, one typically needs to know the accelerations (a) in order to compute the dynamic forces (F) due to the motion of the system's mass (m). There are also many situations in which the applied forces are known and the resultant accelerations are to be found.Fundamental quantitiesThe following concepts and definitions are basic, and they should be understood at the outset.LengthTimeMassForce

Basic Concepts: Length Length is the quantity used to describe the position of a point in space relative to another point. This distance is described in terms of a standard unit of length. The universally accepted standard unit for length is the meter. Basic Concepts: Time Time is conceived as succession of events (i.e. interval between two events) and is a basic quantity in dynamics.Principles of Statics are time independent, i.e. Time is not directly involved in the analysis of statics problems.The generally accepted standard unit for time is the second. Basic Concepts: Mass Mass is a property of matter, as it can be considered to be the amount of matter contained in a body. The mass of a body determines both the action of gravity on the body, andthe resistance to changes in motion. This resistance to changes in motion is referred to as inertia, which is a result of the mass of a body.Basic Concepts: Force Force is the action of one body on another. For example, push or pull exerted by one body on another. A force tends to move a body in the direction of its action. The action of a force is characterized by its magnitude, by the direction of its action, and by its point of application.Mechanisms and MachinesA mechanism is a device which transforms motion to some desirable pattern and typically develops very low forces and transmits little power.

A machine typically contains mechanisms which are designed to provide significant forces and transmit significant power.

Mechanisms and Machines (contd.)Examples of mechanisms include pencil sharpener, a camera shutter, an analog clock, an adjustable desk lamp.Some examples of machines which possess motions similar to the mechanisms listed above are a food blender, a bank vault door, an automobile transmission and a robot.Mechanisms and Machines (contd.)There is no clear-cut dividing line between mechanisms and machines. They differ in degree rather than in kind. If the forces or energy levels within the device are significant, it is considered a machine; if not, it is considered a mechanism.

Thesimilaritybetweenmachinesand mechanismsis that:they are both combinations of rigid bodiesthe relative motion among the rigid bodies are definite.

Mechanisms and Machines (contd.)What is a Mechanism?A mechanism is the part of a machine which contains two or more pieces arranged so that the motion of one compels the motion of the others.

Generally used to:Change the direction of movement; Ex: pulley on the flagpoleChange the type of movement; Ex: lead screw in screw jackChange the speed of movementChange the amount of torque or force available to do work; Ex: Crowbar

MechanismsGateway To TechnologyUnit 2 Lesson 2.2 Mechanical SystemsMechanisms: ExampleLead Screw

JackVice

Changes rotary movement into linear movementSignificantly increases forceA person can put a little force into turning the handle to move a heavy car.MechanismsGateway To TechnologyUnit 2 Lesson 2.2 Mechanical SystemsMechanisms and simple Machines: Incline Plane

The Egyptians used simple machines to build the pyramids. One method was to build a very long incline out of dirt that rose upward to the top of the pyramid very gently. The blocks of stone were placed on large logs (another type of simple machine - the wheel and axle) and pushed slowly up the long, gentle inclined plane to the top of the pyramid.

Mechanisms Mechanisms, if lightly loaded and run at slow speeds, can sometimes be treated strictly as kinematic devices; that is, they can be analyzed kinematically without regard to forces.Machines Machines (and mechanisms running at higher speeds), on the other hand, must first be treated as mechanisms, a kinematic analysis of their velocities and accelerations must be done, and Then they must be subsequently analyzed as dynamic systems in which their static and dynamic forces due to those accelerations are analyzed using the principles of kinetics.Course Overview Initially, we will focus on Kinematics of Mechanisms, in which we will study:Kinematics Fundamentals, Different types of Mechanisms, Position, Velocity and Acceleration analysis and Cam Design. Then we will shift our attention to Dynamics of machinery, in which we will study: Dynamics Fundamentals, Dynamic force analysis and Balancing.Reminder !!Get Text Book andGeometrical Set!Thank You