Material Science Fundamentals

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Questions and Answers

Which classification of metals includes materials where the principal element is iron?

  • Industrial
  • Natural
  • Ferrous (correct)
  • Non-ferrous

Concrete is classified under which type of material production?

  • Naturally Occurring Materials
  • Materials Produced at Construction Site (correct)
  • Industrially Produced Materials
  • Non-metallic Materials

What property of materials relates to their ability to resist external dynamic forces?

  • Acoustic Permeability
  • Mechanical Properties (correct)
  • Chemical Properties
  • Thermal property

Which of the following is a non-ferrous metal?

<p>Copper (D)</p>
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Which physical property relates to a material's ability to absorb sound?

<p>Acoustic/Sound Permeability (A)</p>
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What is NOT a classification criterion for construction materials based on their properties?

<p>Environmental Impact (B)</p>
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Which of the following materials is an example of a naturally occurring material?

<p>Timber (A)</p>
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Which property of materials is concerned with their durability against chemical reactions?

<p>Corrosion Resistance (A)</p>
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What internal phenomenon occurs alongside the development of internal resisting forces when a solid body is under load?

<p>The body is deformed to a varying degree. (B)</p>
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Which mechanical test specifically measures the ability of a material to withstand compressive stress?

<p>Compression Test (A)</p>
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Which type of stress is primarily assessed during a shear test?

<p>Shearing stress on cross-sectional area parallel to the load. (D)</p>
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What sets dynamic tests apart from static tests in material examination?

<p>Dynamic tests are made with suddenly applied loads. (A)</p>
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What is the primary distinction of destructive tests compared to non-destructive tests?

<p>Destructive tests render the specimen useless after testing. (D)</p>
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In the context of bending tests, what characterizes the resulting stresses within the specimen?

<p>Tensile stress on one side and compressive stress on the opposite side. (A)</p>
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Which mechanical characteristic can be evaluated through fatigue tests?

<p>Material performance under fluctuating stresses. (C)</p>
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During which type of test are the specimens subjected to prolonged loading over an extended time?

<p>Long time Tests (D)</p>
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What does the tensile stress $ au_t$ denote in the context of a standard tension test?

<p>The force per unit area at the specimen's cross-section (C)</p>
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Which property corresponds to the greatest stress a material can withstand without permanent deformation?

<p>Elastic Limit (C)</p>
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In the stress-strain diagram, which point indicates the yield point for ductile materials?

<p>Point B (B)</p>
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What does the modulus of elasticity represent in a material's stress-strain behavior?

<p>The slope of the stress-strain curve in the elastic region (B)</p>
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What is the formula for calculating strain ε in a standard tension test?

<p>$\varepsilon = \frac{L - L_o}{L_o}$ (D)</p>
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Non-destructive tests are primarily used for which purpose?

<p>To test the strength of existing structures without causing damage (C)</p>
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During a standard tension test, what is measured alongside the applied load?

<p>Change in length of the specimen (D)</p>
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For ductile materials, what characterizes the behavior at the yield point?

<p>Strain increases significantly without an increase in stress (B)</p>
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What does the initial-tangent modulus represent in a non-linear stress-strain curve?

<p>The slope at the origin of the stress-strain curve. (A)</p>
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How is the secant modulus defined?

<p>As the slope of the line that joins the origin to a selected point on the curve. (C)</p>
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Which modulus is defined as the slope of the tangent to the stress-strain curve at a specific point?

<p>Tangent modulus (D)</p>
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What property indicates that a material has higher stiffness?

<p>A larger modulus of elasticity. (D)</p>
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What characteristic defines Poisson's Ratio?

<p>The ratio of transverse strain to longitudinal strain. (B)</p>
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What does ultimate strength refer to in material science?

<p>The maximum strength a material can resist before failure. (B)</p>
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How does the stiffness of steel alloys compare to aluminum alloys based on their moduli of elasticity?

<p>Steel alloys are three times as stiff as aluminum alloys. (A)</p>
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What is a defining feature of materials in the plastic range?

<p>They show permanent deformation after the load is completely removed. (A)</p>
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Flashcards

What is a material?

A substance or thing used to make other things, like cement, brick, or aluminum.

What is Material Engineering?

The branch of engineering that studies the properties and uses of materials employed in construction, ensuring their suitability for various applications.

What are Ferrous Metals?

A category of materials primarily composed of iron, including steel, wrought iron, and cast iron.

What are Non-ferrous Metals?

A category of metals where the primary element is not iron, examples include copper, aluminum, lead, and zinc.

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What are Non-metallic Materials?

Materials that are not metals, including concrete, timber, stone, and lime.

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What are Mechanical Properties?

A material's resistance to breaking or deforming under the influence of external forces.

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What is Tensile Strength?

The ability of a material to resist being pulled apart by tension forces.

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What is Compressive Strength?

The ability of a material to withstand compression forces, pushing inwards.

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Internal resisting force

A force that resists deformation within a material when an external force is applied.

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Deformation

Change in shape or size of a material due to applied force.

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Stress

Internal force per unit area within a material resisting deformation.

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Strain

The change in dimension per unit of original dimension under stress.

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Tension Test

A mechanical test where a material is subjected to a gradually increasing tensile force.

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Compression Test

A mechanical test where a material is subjected to a gradually increasing compressive force.

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Bending Test

A mechanical test where a material is subjected to forces that cause bending moments, resulting in compressive and tensile stresses on opposite sides of the neutral axis.

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Torsion Test

A mechanical test conducted to determine the torsional strength of a material, typically involving cylindrical specimens.

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Ultimate Strength Test

A test that determines the maximum load a material can withstand before breaking.

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Yield Strength Test

A test that determines the maximum load a material can withstand before permanently deforming.

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Elasticity

The ability of a material to return to its original shape after being deformed.

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Modulus of Elasticity

The ratio of stress to strain in the elastic range of a material.

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Non-Destructive Testing

A type of test used to assess the strength of existing structures without damaging them.

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Compressive Strength Test

A test that determines the maximum load a material can withstand before it starts to crack.

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Initial-Tangent Modulus (E1)

The slope of the stress-strain curve at the origin, representing the material's stiffness at the beginning of loading.

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Secant Modulus (E2)

The slope of the line connecting the origin to a chosen point on the stress-strain curve, indicating the average stiffness up to that point.

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Tangent Modulus (E3)

The slope of the tangent line to the stress-strain curve at a chosen point, showing the local stiffness at that exact point.

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Stiffness

A material's ability to resist deformation when subjected to an external force.

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Poisson's Ratio (µ)

The ratio of transverse strain (change in width or thickness) to longitudinal strain (change in length) within the material's proportional limit.

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Ultimate Strength

The maximum stress a material can withstand before permanent deformation or failure occurs.

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Plastic Deformation

A type of permanent deformation that occurs after a material has been loaded beyond its elastic limit.

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Yield Strength

The stress at which a material begins to deform permanently (i.e., it doesn't return to its original shape after the load is removed).

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Study Notes

Course Information

  • Course Title: Construction Materials
  • Course Code: CENG 2092
  • University: Addis Ababa Science and Technology University
  • Date: November 2024

Chapter One: Nature & Properties of Materials

  • Contents:
    • Classification of Materials
    • General Properties of Materials
    • Nature and Properties of Materials Under Load

1.1 Classification of Construction Materials

  • Material: A substance from which something else can be made.
  • Examples: Cement, brick, aluminum, soil, water
  • Material Engineering: Understanding and reviewing properties and uses of materials in engineering
  • Classification Basis:
    • Metallic Property
    • Physical Nature
    • Mode of Production

Classification Based on Metallic Property

  • Metallic Materials:
    • Ferrous: Metal with iron as the main element.
      • Examples: Steel, wrought iron, cast iron
    • Non-ferrous: Metal without iron as the main element.
      • Examples: Copper, aluminum, lead, zinc
  • Non-metallic Materials:
    • Examples: Concrete, timber, stone, lime

Classification Based on Physical Nature

  • Solids
  • Liquids
  • Gases

Classification Based on Mode of Production

  • Naturally Occurring:
    • Examples: Stone, timber
  • Industrially Produced:
    • Example: Cement, glass
  • Materials Produced at Construction Site:
    • Examples: Concrete, mortar

1.2 General Properties of Materials

  • Physical Properties:
    • Density & specific gravity
    • Thermal property
    • Acoustic/sound permeability
    • Fire resistance
    • Porosity
  • Chemical Properties:
    • Corrosion Resistance
    • Combustibility
    • Toxicity
    • Decay Resistance
  • Mechanical Properties:
    • Resistance to external static forces (compressive, tensile, bending, shear, torsional strength)
    • Resistance to external dynamic forces (impact and vibratory loads)

1.3 Nature and Performance of Materials under Load

  • Load Application: Applying force on a solid body under equilibrium.
  • Results: Development of internal resisting forces, deformation of the body.
  • Stress and Strain: Internal forces and deformation in solid bodies under load.
  • Types of stresses (Depending on Arrangement and Direction):
    • Tensile stress
    • Compressive stress
    • Shearing stress
    • Bending stress
    • Torsional stress
    • Combinations

Testing of Materials for Mechanical Properties

  • Mechanical Tests: Classified based on external forces:
    • Tension Test: Specimen subjected to axial tensile force.
      • Tensile stress on cross-section perpendicular to force.
    • Compression Test: Specimen subjected to axial compressive force.
      • Compressive stress on specimen.
    • Shear Test: Shearing stress on cross-section parallel to force.
    • Bending Test: Specimen subjected to forces causing bending moments.
    • Torsion Test: Determine torsional strength; specimens usually cylindrical.

Tests Based on Load Application Rate & Duration

  • Static Tests: Gradually increasing load.
  • Dynamic Tests: Suddenly applied loads.
  • Wear Tests: Resistance to abrasion and impact.
  • Long-Time Tests: Loads applied for a long period.
  • Fatigue Tests: Fluctuating stresses repeated many times.

Tests Based on Effect on the Specimen

  • Destructive Tests: Specimen damaged or destroyed.
    • Examples: Ultimate strength of steel, Compressive strength of concrete
  • Non-destructive Tests: Specimen not damaged.
    • Example: Hammer test

2.4 Stress-Strain Properties in Simple Tension Test

  • Tension Test: Specimen subjected to gradual increasing axial tensile force.
  • Change in Length: Measured at various load increments.
  • Stress Calculation: Stress = load/cross-sectional area.
  • Strain Calculation: Strain = change in length/original length
  • Stress-Strain Diagram: Plotted to show relationship between stress and strain.

Properties in the Elastic Range

  • Proportional Limit: Maximum stress with no deflection from Hook's law.
  • Elastic Limit: Maximum stress without permanent deformation.
  • Yield Point: Stress where significant increase in strain occurs with no increase in stress

Modulus of Elasticity

  • Young's Modulus: Slope of the initial linear portion of the stress-strain diagram; measure of material stiffness.
  • Methods for Finding Modulus of Elasticity:
    • Ductile materials with linear stress-strain.
    • Non-linear stress-strain curves; initial tangents, secant, and tangents along curves.

Stiffness

  • Ability of material to resist deformation
  • Higher modulus of elasticity = stiffer material.
  • Steel alloys are stiffer than aluminum alloys.

Poisson's Ratio

  • Ratio of transverse strain to longitudinal strain (within proportional limit).
  • Measures material stiffness in direction perpendicular to load.

Properties in the Plastic Range

  • Ultimate Strength: Maximum strength before failure.
    • Determined by stress-strain relationship

Ductility

  • Ability to deform plastically
  • Measured by percentage elongation or reduction in area.

Toughness

  • Ability of material to absorb energy plastically.
  • Materials with high toughness absorb high strain energy in the plastic range.

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