Manufacturing Technology: Properties of Materials

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Questions and Answers

What is the primary property described by resilience in materials?

The ability to withstand shear stress

The ability to absorb energy during elastic deformation and recover it upon unloading (correct)

The ability to withstand permanent deformation

The ability to conduct electricity

What is the modulus of resilience associated with?

Elastic deformation (correct)

Mechanical fatigue

Thermal expansion

Plastic deformation

Using Hooke's law, if a piece of copper with an original length of 305 mm is subjected to a tensile stress of 276 MPa, what principle do we apply to determine its elongation?

Compressive modulus

Secant modulus

Modulus of toughness

Elastic modulus (correct)

Ductility can be quantified in which of the following ways?

As percent elongation and percent reduction in area Signup and view all the answers

What does fracture toughness measure in a material?

Resistance to fracture when a crack is present Signup and view all the answers

When considering nonlinear elastic behavior, which moduli are determined?

Secant and tangent moduli Signup and view all the answers

Which shape is the indenter used in the Vickers hardness test?

Square pyramid Signup and view all the answers

What is the primary measurement taken in the Brinell hardness test?

Diagonal length of the indented square Signup and view all the answers

Which materials are typically used for the ball in the Brinell hardness test?

Hardened steel or tungsten carbide Signup and view all the answers

How is the Vickers hardness number determined after measuring the indentation?

Through a conversion calculation from measurements Signup and view all the answers

Which property is measured by a tensile test?

Ductility Signup and view all the answers

What is the primary purpose of measuring hardness in materials?

To measure resistance to deformation Signup and view all the answers

What is an indication of a material's resilience?

The ability to return to its original shape after deformation Signup and view all the answers

Which property describes the maximum stress that a material can withstand while being stretched or pulled?

Tensile strength Signup and view all the answers

In a tensile test, what does the term 'stiffness' refer to?

The resistance to elastic deformation Signup and view all the answers

What is the term for the ability of a material to absorb energy and plastically deform without fracturing?

Toughness Signup and view all the answers

What does the limit of elasticity signify in materials?

The stress beyond which a material will deform permanently Signup and view all the answers

Which property is primarily assessed when evaluating a material's ability to conduct electricity?

Electrical conductivity Signup and view all the answers

What is the thermal protection system for the Space Shuttle Orbiter primarily made of?

Silica tiles Signup and view all the answers

Which polymer has the highest thermal resistance based on the given properties?

Teflon Signup and view all the answers

What is the approximate porosity of the silica tiles used in the Space Shuttle Orbiter?

90% Signup and view all the answers

At what temperature do the silica tiles operate effectively?

400-1260ºC Signup and view all the answers

Which material is not mentioned as part of the thermal protection system for the Space Shuttle?

Polystyrene Signup and view all the answers

What process is used to bond the silica fibers in the thermal protection tiles?

Heat treatment Signup and view all the answers

What is the purpose of using high porosity materials like silica tiles in thermal protection?

To reduce heat transfer Signup and view all the answers

Which thermal protection material can operate at the highest temperature?

Reinforced carbon-carbon Signup and view all the answers

What is the primary use of measuring the diameter of an indentation in materials?

To indicate the hardness of the material Signup and view all the answers

What does Ohm's Law express the relationship between?

Voltage, current, and resistance Signup and view all the answers

What does resistivity ($ ho$) describe?

A material property independent of sample size Signup and view all the answers

Which metal has the highest conductivity based on the provided information?

Silver Signup and view all the answers

Which equation correctly relates linear thermal expansion?

$l_{final} = l_{initial} + eta l_{initial} (T_{final} - T_{initial})$ Signup and view all the answers

What unit is used to express conductivity ($ au$)?

Siemens per meter (S/m) Signup and view all the answers

Which material has the lowest conductivity according to the comparison provided?

Soda-lime glass Signup and view all the answers

What does the notation $k$ refer to in thermal conductivity?

Thermal conductivity Signup and view all the answers

Study Notes

Lecture 2: Physical and Mechanical Properties of Materials

Topic: Physical and mechanical properties of materials.
Course: Manufacturing Technology (EIM1101)
Instructor: Dr. Mohamed Taha Eldaly
Reference Book: Materials Science and Engineering, Nine Edition, by William D. Callister, Jr. and David G. Rethwisch.
Course Outline: Weeks 1-16 cover topics including: introduction to manufacturing, physical and mechanical properties of materials, classification of metals and alloys, polymers and composites, metal casting, metal forming (rolling, extrusion, drawing), machining operations; tool life and materials; joining operations; shaping of plastics; and exams.

Physical and Mechanical Properties of Materials

Tensile Test: A test to determine a material's response to stretching forces.
Stiffness: A material's resistance to deformation under stress.
Limit of Elasticity: The point on a stress-strain curve beyond which the material will deform permanently.
Ductility and Tensile Strength: Measures the material's ability to be stretched before fracturing and its ability to withstand a tensile load.
Hardness: A measure of a material's resistance to indentation or scratching.
Toughness: A measure of a material's ability to absorb energy before fracturing.
Resilience: A measure of a material's ability to absorb energy during elastic deformation and have it recovered upon unloading.
Electrical Conductivity: A measure of how easily a material allows electric current to flow through it.
Thermal Conductivity: A measure of how easily a material transmits heat.

Tensile Testing Apparatus

Load Cell: Measures the applied load.
Extensometer: Measures the elongation of the specimen.
Moving Crosshead: Elongates the specimen.

Hooke's Law and Stress-Strain Diagrams

Hooke's Law: Relates engineering stress and engineering strain for elastic deformation.
Stress-Strain Diagrams: Illustrate the relationship between stress and strain during loading and unloading cycles, showing both elastic and plastic behaviors, tangent and secant moduli.

Solved Example (Copper Elongation)

Original Length (l₀): 305 mm
Stress (σ): 276 MPa
Young's Modulus (E): 110 x 10³ MPa
Resultant Elongation (Δl): 0.77 mm

Mechanical Properties (further details)

Ductility (percent elongation): Measures the material's ability to deform plastically before fracture, calculated as (l_f − l_i) / l_i * 100%.
Ductility (percent reduction in area): (A_i - A_f) / A_i *100%, where A_i is initial area and A_f is final area.
Brittle vs. Ductile: Classification of materials based on their behavior under stress.

Hardness Testing

Brinell Hardness Test: Uses a hardened steel or tungsten carbide ball to indent the material.
Vickers Hardness Test: Uses a square-based pyramid-shaped indenter.
Rockwell Hardness Test: Measures the depth of indentation using a diamond or steel cone indenter.

Electrical Properties

Ohm's Law: V = IR (Voltage = Current × Resistance).
Resistivity (ρ): A material's intrinsic resistance to current flow, independent of size or shape.
Conductivity (σ): Reciprocal of resistivity.

Thermal Properties

Heat Capacity (C): The amount of heat required to raise the temperature of one mole of a substance by one degree.
Specific Heat (cp): Heat capacity per unit mass.
Modulus of Resilience: Energy absorbed during elastic deformation.
Thermal Expansion: Materials change size with temperature changes.
Linear coefficient of thermal expansion: Measures the change in length per unit length per degree change in temperature.

Thermal Conductivity (k):

Thermal Conductivity(k): Measures the amount of heat transmitted through a material.

Material Applications (Space Shuttle Orbiter)

Silica Tiles: Large-scale application in the Space Shuttle Orbiter thermal protection system, due to their high temperature resistance.

Additional Information

Units: Ensure you understand the units used for each property (e.g., MPa for stress, J/mol-K for heat capacity).
Material Classifications: Metals, Polymers, Ceramics, Semiconductors.

Recommended Internet Resources (for further study)

The provided URLs are for checking for further study material on these properties.

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Description

This quiz covers physical and mechanical properties of materials as outlined in Manufacturing Technology course EIM1101. Topics include tensile tests, stiffness, and the limit of elasticity. Test your understanding of these fundamental concepts from the reference book by Callister and Rethwisch.