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AE 142
Engr. Vasma A. Hassan
Mindanao State University
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It is the art of planning or devising new
or improved machines to accomplish
specific purposes.
It consists of a combination of several
different mechanical elements properlydesigned and arranged to work
together, as a whole.
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Agriculture is the primary industry of thePhilippines.
Agricultural development can be speed upthrough mechanization.
Increase in crop production and reduction inpostharvest losses can be achieved by the use ofappropriate agricultural machines.
At present, there is a limited supply of locallyavailable designs of agricultural machines is thePhilippines.
Experienced have shown that designingagricultural machines suitable for farmers is quite
a difficult job because one should come up with amachine that is low cost but effective and efficient.
In order for the designer to meet this challenge,he or she needs to have enough skills and abilityto do the job.
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The designers need to have a full understanding of the
variable of the field conditions and other factors which
influence machinery performance including the
environmental and human-related factors. Note that
the machine should be operationally reliable and
economically acceptable to farmers.
The designers need to apply engineering principles so
that functional requirements of a certain machine aremet. This includes the laws of mechanics, strength of
materials, fluid flows, heat transfer, etc.
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The designers should have the knowledge
of the analytical design process which isessential in the design of machine
components, main frames, mounting
arrangement, balancing, etc.The designers must integrate analytical
design and results of experimental
investigation to develop machines that aresimple to fabricate, affordable, light in
weights, easy to maintain, and require
readily available and low cost materials.
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Unless the designer tries to meet the
needs of actual users, no amount of
design work will be utilized.
The success of a good design is
indicated by the extent by which the
machine is adopted by farmers.
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It includes the process of organizing the
methodology needed to proceed from concept
to final product, determining which
technological resources to use, the economicsof production and operation, and the human
and social factors that will be needed.
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To attempt to predict the stress or
deformation in the part in order that
it may safely carry the loads whichwill be imposed upon it, and that it
may last for the expected life of the
machine.
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Mathematical calculations be looked
upon as absolute and final. They are all
subject to the accuracy of the various
assumptions which must necessarily be
made in engineering work.
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To produce a machine which is
not only sufficiently rugged to
function properly for areasonable life, but is at the same
time cheap enough to be
economically feasible.
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Loading
Type of kinematic elements to be
usedCorrect utilization of the properties
of engineering materials
Economic consideration
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Cost of design
Manufacture
Sale
Installation
Cost of Servicing
Safety
Aesthetics
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A. Based on the Design Information andConsideration Needed in Coming Upwith the Product
Rational Designcarried out using mathematicalformula and other engineering principles.
Empirical Designbased upon empiricalformula derived from existing practices and past
experiences. Industrial Designinvolves consideration like
aesthetics, ergonomics, and production aspect.
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B. Based on the Process that is Taking Placein Coming Up with the Product
Original Designdoes not exist before and it isonly done by few dedicated designer who havepersonal qualities of a sufficiently high order. Thisalso requires a lots of research, experimental
activities, and creative brain. Adaptive Designthis is more concerned of the
adoption of existing designs. This does notdemand special knowledge or skills. Problemscan be solved with ordinary training.
Development Design -This begins with anexisting design but the final result may quietlydiffer from the initial product.
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Imaginative powerHighly developed intellectual powerGood memory
Ability to work thoroughly andconscientiously
Inventive talent and good judgmentAbility to concentrateSense of responsibility and self-
confidence Integrity
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Ability to work with people
Ability to do simulation, experiments,
and measurements
Environment conscious
Aesthetics and conscious on the
ergonomics of machine
Ability to make technical reportsAbility to optimize design
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Used to include uncertainties in thedesign.
The degree of use of the FS depends onthe technical competence and design
experience of the designer. Large FS are usually uneconomical.
Sufficient FS is required if failures andloss in time, and inconveniences are to be
minimized The use of excessive FS can be minimized
if the latest tools and techniques indesigning are to be used.
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Excessive strength and oversized
machine are usually wasteful in
engineering design.
Machine to be design if possible should
have 99.9% reliability.
Continuous replacement of defective
machine components may keep thedesign more reliable and economical.
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Technical reports approved and
recommended for practice by engineers.
The use of standard is voluntary and no
liability is assumed by the sponsoring
organization for their misuse.
The use of standard can minimize the
potential liability of the organization in
designing a product. It is a mechanism for interchanging
machinery parts thus resulting to a lower
product cost to consumers.
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The durability, service, and cost agriculturalmachines depends largely on the kind and quality
of materials used in manufacturing the machine.
Machine fabricated from substandard materials are
usually easy to wear off and have short life span. Heavy materials usually affects power requirement
and performance.
Engineers should have a knowledge of the physical
characteristics, selective and effective utilization ofmaterials and their processing techniques to avoid
waste and spoilage.
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Metals
Ferrous
Iron and steel, Cast Iron, Carbon
Steel, Alloy Steel, etc
Non-Ferrous
Aluminum, copper, magnesium, etc
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Non-MetalsInorganic materials
glass, ceramics, plastic, etc
Organic Materials
wood, rubber, leather, canvass,
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Metallic ore is mined beneath the earth
surface. Iron is produced from iron ore while
copper is produced from copper ore.
Aluminum is produced from an ore calledbauxite. A blast furnace is used to produce
metal by passing a hot gases to the furnace
that is mixed with iron ore, limestone, and
coke at about 3000 C. Melted metal isseparated into a ladle for cooling to form pig
iron. Pigs are then melted and poured into
mold to make iron, steel, and cast iron.
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Hard
Easy to shape
High melting temperature
Low specific heat
Good electrical conductivityGood thermal conductivities
Ability to be deformed without fracture
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Pure Metalare single element that are notcombined with any other chemical element.
They are too soft, low and strength, or low insome other desired property to be used inany commercial applications.
Alloysare mixture of two or more metal toproduce new metal. Example are stainlesssteel, bronze, etc.
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It is a pure ferrite.
Pig ironit is produced from ore of hematite
or magnetite in the blast furnace by melting
with limestone and coke.
Cast Iron with carbon content of 1.7 to
6/7%. They are low cost, good casting
property, high compressive strength, highwearing resistance, brittle and lower tensile
strength.
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It is a molten steel that is cast into an ingot andthen rolled, forged, hammered, pressed, or
machine into desired shape
Structural steel, steel bars and cylinder, and
steel plate are commonly used as machineelements and frame
Soft Centered Steeldurable to shock because
the mild steel in the center layer is deformable
and is higher wear resistance than hard steel at
the outer side. They are usually used for
moldboard and share of a plow.
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Low Carbon Steelwith carbon contentnot exceeding 0.25%.
Medium Carbon Steelcontains 0.25 to0.50% carbon. They are usually used inmaking structural and machinery steel.
High Carbon Steelcarbon content isabove 0.50%. They are usually used inthe manufacture of spring and tool steel.
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Mild Steel (MS)
contains carbon of 0.15 to0.25%. They are malleable and easy to cut
and weld.
Cold Rolled Steel (CRS)are medium carbon
steel which are used for parts andcomponents of machine requiring greater
strength and hardness such as shafting and
connecting rods.
Stainless Steel (SS)1% Ni, 11-14% Cr, 0.6%
Mn, 0.6% Si. They have high resistance to
corrosion and oxidation. They are used for
valves, nozzles, and dairy machines.
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Includes all the metals such as
copper, aluminum, magnesium,
and zinc in which iron is not
present in large amount
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Have an outstanding characteristics of good
strength, light weight, high thermal and electrical
conductivities, and good corrosion resistance.
Y alloy (4%Cu, 2% Snalloy)it is strong as a castingand is used for cylinder head and piston.
Silmin(14% Sialloy)casting metal used for
cylinder head and crankcase.
Duralumin (4% Cu, 0.5-1.5% Mg, 0.4 Mnalloy)quenched at high temperature and then aged to
gradually increase strength and hardness.
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It has high electric conductivity and thermal
conductivity, soft, high resistance tocorrosion.
Commonly use for electric wire, fuel pipe,gasket, radiator, and electric motor
Brass (10-40% zinc alloy)used for radiator,pipe, screen, and instrument parts.
Bronze (5-20% tin alloy)used for bushing,spring, pipe, fittings, sprayer and pump.
Kelmet Alloy (20-40% lead alloy) used forbearing of diesel engine.
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Sheets, Strips, and Plates Sheet-a piece of metal which has been rolled into a
sheet of 3/16 in. or less in thickness. Commonly
available sizes are 3 wide x 6 long and 4 wide and
8 long. The thickness is expressed in terms ofgauge number which is equivalent to number of
sheets in 1 in. thick pile pf metal sheet.
Stripsa long sheet of metal that is less than 12 in.
wide Platea metal with thickness over 3/16 in.
Commonly available size is 4 wide x 8 long.
Thickness are given in terms of mm or in inch.
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Metal Barsmade of different shapes and are
usually available in standard length of 20 ft or 6meters. They are purchased in terms of quantity,shape, size, and kind of metal used.
Structural Shapescommonly used in theconstruction of agricultural machines. They arespecified in terms of quantity wanted, the kind ofmaterial and shape, size, and length of eachpiece.
Tubular Productsincludes all hollow metalshapes such as pipes and tubes. They areavailable in round, square, and rectangular inshape. Specifications are given in terms of shape,schedule number, size, and length.
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Physical Propertiescharacteristics of metalswhen not acted upon by outside forces. This
includes color, density, weight, and electrical and
heat conductivity.
Mechanical Propertiescharacteristics exhibitedby metal when outside forces are applied to them.
The understanding of these property would result
in a better processing of metal into product.
Chemical Propertiescharacteristics of the
chemical composition of metal and their chemical
reaction to other metals. Example, resistance to
corrosion.
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Tensile Strengthit is the greatest stress seen by
the materials resistance to being pulled apart. Itis sometimes called as the ultimate strength.
Yield Strengthusually designated at a 0.2%
permanent elongation. Ductilityindicate how much a material is
deformed as it is stretched. The greater thedeformation the more ductile is the material.
Hardnessit is the materials resistance topenetration and permanent deformation.
Brittlenessis the tendency of a material to breakunder impact.
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Compressive strengthis a materials resistance
to being compressed.
Malleabilityis the capability of a material to beshaped and formed.
Toughnessis the ability of a material to
withstand bending and twisting. It is the
desirable property for loader frame andcrankshaft.
Grain Sizeis the microscopic measurement of
metal that shows differences in sizes that relate
directly to strength.
Machinabilitythe ease with which metals are
machined or cut by a machine tool.
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Fusibilityis the property to which metal when it is
at the liquid state easily join with other metals. Metal
with high fusibility are usually high in weldability.
Strengthis the resistance to deformation.
Tensile strengthresistance from being pulled
apart.
Compressive strengthresistance of being
squeezed together.
Shear strengthresistance to cutting or slicing
forces.
Torsional strengthresistance to twisting forces.
Elasticitythe ability of metal to return to its original
size and shape after the external force causing a
change in shape has been removed.
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Wood
Plastics
RubberCeramics
Fibers
Glass
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Heart Wood- the hard solid wood in thecenter of the trunk
Sap Wood- the layer of wood beneath the
bark of a tree and carries moisture.
Bark- the outer part of the wood
The wood is turned into lumber in a lumber
mill, after the bark has been removed,mechanical saws cut the wood into thin
planks or thicker beams, depending on what
the lumber is to be used for.
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Material obtained from rubber tree. It iscapable to withstand extreme
deformability with more or less complete
recovery upon removal of deforming
force.
Engineering applications:
shock, noise, and vibration control,
Sealing, Corrosion protection,Friction production, Electrical and
thermal insulation, Waterproofing,
Confining other materials, Load bearing
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Latex are collected by tapping rubbertree.
Adding of Acid- helps the latex to
coagulate or clot in a vat.Rollers form the coagulated latex into
sheets called crepe.
Rubber is dried in hot air or over smoke.
Rubber is dyed to desired color.
Rubber is shaped and finished into the
final product
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Large group of materials consisting of
combination of carbon and oxygen,
hydrogen, nitrogen, and other organic
and organic elements.
Non-metallic material that can be
molded into shape. They are light inweight, resistance to deterioration by
moisture, low elastic and thermal
conductivity, and good color range.
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Acrylic thermoplasticsEpoxy
Flouroplastics
NylonPhenolic Resin
Phenylene oxide
Polystyrene
Polyurethene
Polyvinyl chloride
Silicone
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Materials ranging from glass to
furnace brick
This includes ceramic oxides, glass-
ceramics, carbides and nitrides
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The oldest engineering material that
includes jute, flax, and hemp.
Usually used for engineered products
such as rope, cordage, nets, water hose,and containers.
Plant and animal fibers are used for felt,
paper, brushes, and heavy structuralcloth.
This includes metal fibers, glass fibers,
and aramid fibers
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A non-crystalline or amorphous solid
Most glass are made from silica, lime, and
sodium carbonate
Types includes soda-lime glass,
Borosilicate glass, lead-alkali glass,aluminosilicate glass, silica glass, and
fused silica.