MachinesMachines

UNIT 1UNIT 1THE PHYSICAL WORLD OF A THE PHYSICAL WORLD OF A

MACHINEMACHINE

Machines are a combination of different components placed together Machines are a combination of different components placed together in such a way that they perform useful work. Fluid power is the in such a way that they perform useful work. Fluid power is the engineering science that pertains to the flow of pressurized fluids.engineering science that pertains to the flow of pressurized fluids.

ForceForce

Force is simply a “push” or a “pull.” It is linear in Force is simply a “push” or a “pull.” It is linear in nature meaning “straight line” and can represent nature meaning “straight line” and can represent the energy of a body.the energy of a body.

MeasuringMeasuring ForceForce

PoundPound

NewtonNewton

In our customary system of measurement, force is In our customary system of measurement, force is measured in pounds. In the metric system, force is measured in pounds. In the metric system, force is measured in a unit called the Newton.measured in a unit called the Newton.

ResistanceResistance

Any force that can stop or retard a body’s motion is Any force that can stop or retard a body’s motion is resistance. There is a lot of resistance in fluid power resistance. There is a lot of resistance in fluid power systems.systems.

InertiaInertia

Newton’s First Law: Newton’s First Law: InertiaInertia

The tendency of a body in motion to stay in motion or a body The tendency of a body in motion to stay in motion or a body at rest to stay at rest until acted on by a body of equal or at rest to stay at rest until acted on by a body of equal or greater mass. greater mass.

Energy FormsEnergy Forms

The illustration shows us energy forms found in The illustration shows us energy forms found in every day life. We will concern ourselves with the every day life. We will concern ourselves with the energy form that relates to motion control.energy form that relates to motion control.

Law of ConservationLaw of Conservation

Energy cannot be created or destroyed but it will Energy cannot be created or destroyed but it will change form.change form.

Heat from light bulbsHeat from light bulbs

Heat from frictionHeat from friction..

Energy StatesEnergy States

The state of energy refers to whether it is in The state of energy refers to whether it is in motion(kinetic) or stored(potential). In fluid motion(kinetic) or stored(potential). In fluid power systems, the energy is in the form of power systems, the energy is in the form of pressurized fluids which must be in pressurized fluids which must be in movement to accomplish any useful work.movement to accomplish any useful work.

WorkWorkWork is defined as Work is defined as

moving an object over a moving an object over a distance.distance.

Since work is moving a Since work is moving a object over a distance, its object over a distance, its

unit of measure is the unit of measure is the “foot- pound.”“foot- pound.”

Work=Distance moved X Force Work=Distance moved X Force exertedexerted

PowerPower

Power is defined as the rate at which Power is defined as the rate at which energy is being produced or energy is being produced or

consumed.consumed.

Power can be thought of as Work Power can be thought of as Work divided by Time.divided by Time.

The mathematical expression the describes The mathematical expression the describes power is:power is:

Power = Power = Distance moved X Force exertedDistance moved X Force exerted

TimeTime

Horsepower can be thought of as a Horsepower can be thought of as a reference point to equate a numerical reference point to equate a numerical value.value.

Horsepower = Horsepower = PowerPower

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PressurePressure

Pressure, as it will be discussed in this class, can be thought Pressure, as it will be discussed in this class, can be thought of as the “pushing” effort produced by a fluid when a force of as the “pushing” effort produced by a fluid when a force is applied to it.is applied to it.

Pressure = Force, in pounds/ Area, usually in Pressure = Force, in pounds/ Area, usually in square inchessquare inches

A way to consider Force over A way to consider Force over Area is given in the following Area is given in the following example:example:

When a weighted object rests on a surface, its weight is When a weighted object rests on a surface, its weight is divided over the surface to generate a pressure.divided over the surface to generate a pressure.

Working EnergyWorking EnergyIn a fluid power system, working In a fluid power system, working

energy is in the form of pressurized, energy is in the form of pressurized, moving fluid.moving fluid.

In a fluid power system, working In a fluid power system, working energy changes form to perform work.energy changes form to perform work.

The source of energy in most machines is not at The source of energy in most machines is not at the point of operation so it must be transmitted the point of operation so it must be transmitted by various means.by various means.

Transmission of EnergyTransmission of Energy

Methods of transmitting EnergyMethods of transmitting Energy

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Hydraulic and Pneumatic Hydraulic and Pneumatic Transmission of EnergyTransmission of Energy

In Hydraulics, energy is In Hydraulics, energy is transmitted through transmitted through pressurized moving liquid.pressurized moving liquid.

In Pneumatics, energy is In Pneumatics, energy is transmitted through transmitted through pressurized moving gas.pressurized moving gas.

In both systems, the In both systems, the movement of the fluid is movement of the fluid is referred to as “flow.”referred to as “flow.”

GPM = Gallons Per MinuteGPM = Gallons Per Minute

CFM = Cubic Feet Of Air Per MinuteCFM = Cubic Feet Of Air Per Minute

InefficiencyInefficiency

In fluid power systems, the energy of moving In fluid power systems, the energy of moving pressurized fluids changes form as the fluid meets pressurized fluids changes form as the fluid meets resistance. The transformation is usually in the resistance. The transformation is usually in the form of heat.form of heat.