Dr. HABEEB HATTAB HABEEB Office: BN-Block, Level-3, Room-088 Email: [email protected]...

Dr. HABEEB HATTAB HABEEBDr. HABEEB HATTAB HABEEB

Office: BN-Block, Level-3, Office: BN-Block, Level-3, Room-088Room-088

Email: Email: [email protected]. No.: 7292Ext. No.: 7292

Lecturer: Dr. HABEEB ALANI

mailto:[email protected]

http://www.dewittindustries.com/cgibin/ibrowse/images/of_12/animations/mechanical/gear/gear

Manufacturing ProcessesManufacturing Processes

University TENAGA National

College Of EngineeringMechanical Department

Academic Year - 2009

University TENAGA National

College Of EngineeringMechanical Department

Academic Year - 2009

Lecture NoteLecture Note


http://www.dewittindustries.com/cgibin/ibrowse/images/of_12/animations/mechanical/gear/gear

Nature and Properties of Materials



- Classification of Materials Used in Manufacturing - Classification of Materials Used in Manufacturing

- Engineering Properties of Material- Engineering Properties of Material

- Composites and New Materials- Composites and New Materials




MaterialsMaterials

Metallic Metallic Non-Metallic Non-Metallic

Ferrous Ferrous

Non-Ferrous Non-Ferrous

OrganicOrganic

Inorganic Inorganic

- CLASSIFICATION OF MATERIALS


FerrousFerrous

AluminumAluminum

Titanium Titanium

Non-FerrousNon-Ferrous

MATERIALS

Gray Cast IronGray Cast Iron

Malleable Iron Malleable Iron

Steel Steel Zinc Zinc

METALLIC METALLIC


OrganicOrganic

GlassGlass

CeramicCeramic

InorganicInorganic

MATERIALS

LeatherLeather

Wood Wood

Rubber Rubber Fused silica Fused silica

NON-METALLIC NON-METALLIC


MATERIALS

Ferrous and Non-Ferrous alloys Ferrous and Non-Ferrous alloys

Non-ferrous materials are very important because they are alloyed with ferrous materials special properties can be obtained.

Example: Good cutting properties can be added to tool steel by alloying it with molybdenum or vanadium.

Non-ferrous materials are very important because they are alloyed with ferrous materials special properties can be obtained.

Example: Good cutting properties can be added to tool steel by alloying it with molybdenum or vanadium.


MATERIALS

Non-metallic materials are classified as inorganic if they do not contain organic cells or carbon compounds. See Table 2.1&2.2 (Metals and Non-Metals)

Non-metallic materials are classified as inorganic if they do not contain organic cells or carbon compounds. See Table 2.1&2.2 (Metals and Non-Metals)

All materials have their importance in manufacturing. In automobile industry we can find all types of materials in a car (fig.next slide):- Ferrous → Steel (Body), Non-Ferrous → Aluminum, organic → Rubber, Inorganic→ Glass.

All materials have their importance in manufacturing. In automobile industry we can find all types of materials in a car (fig.next slide):- Ferrous → Steel (Body), Non-Ferrous → Aluminum, organic → Rubber, Inorganic→ Glass.




MATERIALS

Glass

-Petroleum-Wood-Ceramic-Animal product-Nickel

Steel Plastic Lead

RubberCompositeAluminum


According to service characteristic and cost a designer (Material Engineer or R&D Engineer) can suggest a compromise of choice between metallic and non-metallic, and between organic and inorganic.

Example: To reduce weight and improve some specific properties, manufacturers are used to designing ADVANCED COMPOSITES MATERIALS (Fiber Reinforced Plastics) These material are composed at least two material:1. Fiber (fiber class, carbon, Graphite)2. Binder or matrix (Thermoplastic, Polymer)


Engineering propertiesEngineering properties

Tensile strength Tensile strength

- ENGINEERING PROPERTIES OF MATERIALS

ShearShear

Compressive Compressive

Torsion strengthTorsion strength

Ductility Ductility

CreepCreep

Notch sensitivity Notch sensitivity


Engineering properties

Tensile strength Tensile strength

Strength - The amount of ultimate and yield strength in psi a material can withstand.Strength - The ability of a materials to resist deformation when external forces are applied.

Strength - The amount of ultimate and yield strength in psi a material can withstand.Strength - The ability of a materials to resist deformation when external forces are applied.



Specimen Test: A specimen is tested by pulling its two ends. Then the tensile strength is determined by finding:-

1. Stress = Force per unit area. = N/m2 (Pa) or lb/in2 (psi)

Specimen Test: A specimen is tested by pulling its two ends. Then the tensile strength is determined by finding:-

1. Stress = Force per unit area. = N/m2 (Pa) or lb/in2 (psi)



2.Strain = units of in/in Strain (ε) =Change in length over the original length. ε =3. Modulus of Elasticity = Stress / Strain = σ/ε A measure of Elasticity Determines the slope of the stress / strain curve where it is a straight line.

2.Strain = units of in/in Strain (ε) =Change in length over the original length. ε =3. Modulus of Elasticity = Stress / Strain = σ/ε A measure of Elasticity Determines the slope of the stress / strain curve where it is a straight line.

L1 - L

L


• Normalize Applied-Force to Supporting Area

• TENSILE Stress,

Area, A

Ft

Ft

FtAo

original area before loading

– Engineering Stress Units → N/m2 (Pa) or lb/in2 (psi)

Stress, Stress,


¾ inch½ inch

8 ½ inches

L - Failure ZoneGripping Zone Gripping Zone

Tensile specimen




Point a: Point a:

-Represents the Elastic Limit. After this point with more force a Permanente deformation takes place. (The curve is no longer straight line)

-Represents the Elastic Limit. After this point with more force a Permanente deformation takes place. (The curve is no longer straight line)

Point b: Point b:

-At this point the material Yield Strength is determined. -At this point the material Yield Strength is determined.


Point c: Point c:

-At this point the material Ultimate Strength is determined. -At this point the material Ultimate Strength is determined.

Point d: Point d:

-A fracture will occur after Maximum Deformation. -A fracture will occur after Maximum Deformation.


• Tensile – applied loads “pull” the sample

Forces and Responses


• Simple tension: cable

o

FA

• Simple shear: drive shaft

o

FsA

Ski lift

Ao = cross sectional Area (when unloaded)

FF

M

M Ao

2R

FsAc

Common States Of Stress


Common States Of Stress Cont..

• Simple COMPRESSION:

Ao

Balanced Rock

o

FA

Bridge


Shear strength Shear strength

-There is no universal standard used for evaluating shear or torsion characteristic

-There is no universal standard used for evaluating shear or torsion characteristic

-Shear can be determined from hand- books. -Shear can be determined from hand- books.

- Usually Shear Strength = 50% of tensile strength

- Usually Shear Strength = 50% of tensile strength



- Torsional Strength = 75% of tensile strength

- Torsional Strength = 75% of tensile strength

- Shear Stress G୪ - Shear Stress G୪

୪ – Displacement angle (Shear angle or shear strain) ୪ – Displacement angle (Shear angle or shear strain)

o

FsA



G – Shear modules or the modulus

of rigidity.

G – Shear modules or the modulus

of rigidity.

G = (3 / 8) E or G = E / 2 (1 + ୪ ) G = (3 / 8) E or G = E / 2 (1 + ୪ )


Page-23


Compressive Strength Compressive Strength

It is easily determined for brittle materials (Cast iron) that will fractures when a sufficient load is applied.Compressive strength for cast iron= (3 to 4) tensile strength. Because of this properties of some ,material which fracture easily we should use a factor of safety FS,


Compressive Strength Compressive Strength

FS = σ actual / σ allowable

Recommended values of FS = 1 to 3

High values of FS are used for unreliable material or when severe load is applied

Low values of FS are used for reliable materials (steel).


Ductility Ductility

This property enable the material to be bent, drawn, stretched, formed or permanently distorted without rupture (aluminum, structural steel). Ductility for cast iron is minimum (a brittle material)

Tensile test is used to evaluate ductility:

Percentage of elongation= [(Lf-L)/L]x100 Lecturer: Dr. HABEEB ALANI

Ductility Ductility

L- Original length , Lf- New length after fracture


Ductility Ductility

ductility: Ability of a material to deform under tension without rupture. Two ductility parameters may be obtain from the tensile test:

1- Relative elongation - ratio between the increase of the specimen length before its rupture and its original length:


Ductility Ductility

ε = (Lm– L0) / L0 Where Lm– maximum specimen length.

2-Relative reduction of area – ratio between the decrease of the specimen cross-section area before its rupture and its original cross-section area: ψ= (S0– Smin) / S0 Where Smin– minimum specimen cross-section area.


Creep And Notch sensitivityCreep And Notch sensitivity

Creep: Is a permanent deformation resulting from the loading of members over a long period of time.

High Temperature creep lead to: Failure of loaded units such as (High-

pressure steam piping)


Creep And Notch sensitivity

Elongating caused by creep will occure below the yeild strength of the material.

Heat treatment, grain size, and chemical composition appreciably

affect Creep strength


Creep And Notch sensitivity

Notch sensitivity On the other hand is a measure of the ease with which a crack progresses through a material from an existing notch, crack, or sharp corner.


Next Lecture:Foundry


THANK YOU


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