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Questions and Answers
A material with a high Young's modulus is considered flexible.
A material with a high Young's modulus is considered flexible.
False
The volume of a material can be measured easily and accurately on a sensitive balance.
The volume of a material can be measured easily and accurately on a sensitive balance.
False
Specific stiffness is defined as Young's modulus divided by density.
Specific stiffness is defined as Young's modulus divided by density.
True
Density is generally measured in kg/m3.
Density is generally measured in kg/m3.
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Gold has a low density, making it easy to carry.
Gold has a low density, making it easy to carry.
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Stiffness is irrelevant in the design of bridges and bicycles.
Stiffness is irrelevant in the design of bridges and bicycles.
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The maximum service temperature for metals is usually around half of the melting temperature.
The maximum service temperature for metals is usually around half of the melting temperature.
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Tensile testing is used to measure the resistance of materials to permanent deformation.
Tensile testing is used to measure the resistance of materials to permanent deformation.
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Lead is used for weights and has a relatively high density compared to some common materials.
Lead is used for weights and has a relatively high density compared to some common materials.
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The Archimedes method for measuring volume involves submerging the object in water.
The Archimedes method for measuring volume involves submerging the object in water.
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In transport applications, materials with low specific stiffness are preferred for light-weight structures.
In transport applications, materials with low specific stiffness are preferred for light-weight structures.
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Creep refers to the temporary stretching of a material under prolonged loading.
Creep refers to the temporary stretching of a material under prolonged loading.
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The density of materials with a uniform internal structure is likely to show significant variation between different samples.
The density of materials with a uniform internal structure is likely to show significant variation between different samples.
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The compression test uses a stocky specimen to prevent flexural deformation.
The compression test uses a stocky specimen to prevent flexural deformation.
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It is safe to assume that any operating temperature below the maximum service temperature is suitable for design down to zero degrees Celsius.
It is safe to assume that any operating temperature below the maximum service temperature is suitable for design down to zero degrees Celsius.
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Wood has a crystalline structure similar to that of metals.
Wood has a crystalline structure similar to that of metals.
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Relative density is calculated by dividing the density of a material by the density of water.
Relative density is calculated by dividing the density of a material by the density of water.
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Specific stiffness is calculated by dividing Young's modulus by density.
Specific stiffness is calculated by dividing Young's modulus by density.
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Stiffness affects how a material deflects under a given load.
Stiffness affects how a material deflects under a given load.
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The range of maximum service temperature indicates the specific temperatures that a material must always be used at.
The range of maximum service temperature indicates the specific temperatures that a material must always be used at.
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A strong material is one that can withstand many loads without breaking.
A strong material is one that can withstand many loads without breaking.
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High density is always undesirable in product design.
High density is always undesirable in product design.
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Lightweight design is critical primarily for sports products and not for transport applications.
Lightweight design is critical primarily for sports products and not for transport applications.
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Specific strength is defined as strength divided by density.
Specific strength is defined as strength divided by density.
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Elongation to failure measures the ductility of a material.
Elongation to failure measures the ductility of a material.
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Ceramics typically exhibit high elongation due to their ductile properties.
Ceramics typically exhibit high elongation due to their ductile properties.
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Rubber has low elongation because it does not deform significantly before failure.
Rubber has low elongation because it does not deform significantly before failure.
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Elongation is measured in units of strain, often expressed as a percentage.
Elongation is measured in units of strain, often expressed as a percentage.
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High elongation to failure is beneficial for components like crash barriers.
High elongation to failure is beneficial for components like crash barriers.
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The density of a material is affected significantly by changes in temperature.
The density of a material is affected significantly by changes in temperature.
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A ductile material will typically show low elongation values.
A ductile material will typically show low elongation values.
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Tensile testing is used to determine the elongation of materials.
Tensile testing is used to determine the elongation of materials.
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Young's modulus is defined as the ratio of elastic stress to elastic strain.
Young's modulus is defined as the ratio of elastic stress to elastic strain.
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Specific stiffness is used to compare materials and its units are essential.
Specific stiffness is used to compare materials and its units are essential.
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Brittle materials, like ceramics, fail in tension primarily by yielding.
Brittle materials, like ceramics, fail in tension primarily by yielding.
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In selection charts, 'strength' for metals refers to failure by tension and is measured by yield strength.
In selection charts, 'strength' for metals refers to failure by tension and is measured by yield strength.
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The specific strength of a material is defined as the ratio of tensile strength to density.
The specific strength of a material is defined as the ratio of tensile strength to density.
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Materials with high specific strength are ideal for applications needing high strength at reduced weight.
Materials with high specific strength are ideal for applications needing high strength at reduced weight.
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Compressive strength is typically lower than tensile strength for brittle materials.
Compressive strength is typically lower than tensile strength for brittle materials.
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Cranes and pressure vessels are designed to fail by fracture.
Cranes and pressure vessels are designed to fail by fracture.
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Special steels are required to contain liquefied gases at temperatures below $0^{ ext{o}}C$.
Special steels are required to contain liquefied gases at temperatures below $0^{ ext{o}}C$.
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Temperatures of $100^{ ext{o}}C$ do not cause any issues for polymers like plastic cups and kettles.
Temperatures of $100^{ ext{o}}C$ do not cause any issues for polymers like plastic cups and kettles.
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The creep of materials can occur at temperatures as low as room temperature for certain materials.
The creep of materials can occur at temperatures as low as room temperature for certain materials.
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The maximum service temperature for materials is determined by measuring strength at multiple temperatures.
The maximum service temperature for materials is determined by measuring strength at multiple temperatures.
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Nickel alloys used in jet engines are affected by creep below $600^{ ext{o}}C$.
Nickel alloys used in jet engines are affected by creep below $600^{ ext{o}}C$.
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The maximum service temperature of materials is measured in Fahrenheit.
The maximum service temperature of materials is measured in Fahrenheit.
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Metals and ceramics are required for applications that operate at temperatures of $400^{ ext{o}}C$ or more.
Metals and ceramics are required for applications that operate at temperatures of $400^{ ext{o}}C$ or more.
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The range of maximum service temperature indicates the exact temperatures in which a material should be used.
The range of maximum service temperature indicates the exact temperatures in which a material should be used.
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Study Notes
Engineering Material Selection - CH 560
- Course taught by Dr. Yehia M. Youssef
- Relevant to engineering material selection
Material Properties - Definition
- Young's Modulus (E): Measures a material's resistance to elastic deformation under load.
- High Young's Modulus = Stiff material (e.g., diamond)
- Low Young's Modulus = Flexible material (e.g., rubbers)
- Stiffness of a component depends on material's Young's modulus, loading type (tension, bending), and component shape/size.
- Specific Stiffness = Young's Modulus / Density (more accurately, specific modulus)
- Important for comparing materials where units don't matter
Material Properties - Measurement
- Tensile testing: Used to determine material properties.
- Similar to compression testing, but stockier specimen used to prevent bending.
- Young's Modulus (E) is the initial gradient of the stress-strain curve.
- Elastic stretch is usually small (<0.1%).
Material Properties - Strength
- Strength: Resistance to failure by permanent deformation (yielding).
- Strong materials require high loads for permanent deformation.
- Strength in selection charts commonly refers to yield strength under tension.
- For brittle materials (e.g., ceramics), failure occurs by fracture, with variable tensile strength.
- Selection charts often show compressive strength instead.
- Specific Strength = Strength / Density
Material Properties - Toughness
- Toughness: Resistance to fracture (breaking in two) caused by a crack.
- More energy absorbed during fracture = tougher material.
- Amount of energy absorbed per unit crack area is constant for a given material.
- Tough materials (e.g., mild steel) have large plastic deformation during fracture.
- Brittle materials (e.g., glass) have small absorbed energy, fracturing easily.
Material Properties - Elongation
- Elongation: Measure of material ductility.
- Amount of strain a material can withstand before failure in tensile testing.
- Ductile materials (e.g., most metals, polymers) exhibit high elongation.
- Brittle materials (e.g., ceramics) show low elongation.
- Rubber stretches significantly before failure, mostly elastically.
Material Properties - Density
- Density: Mass of material per unit volume.
- Relatively unaffected by temperature changes, though size changes slightly with temperature.
- Gold and lead are examples of high-density materials.
- Density variation can be higher in materials with internal structural variation (e.g., wood).
Design Issues
- Stiffness/Specific Stiffness: Important in designs where deformation needs to be limited (bridges, springs).
- Strength/Specific Strength: Vital in applications needing high loads with reduced weight in transport (aircraft), structures (buildings).
- Toughness: Important in impact-prone components (cars, pressure vessels), where catastrophic failure should be avoided.
- Density: Critical for lightweight design in transport applications, and other areas requiring maximum strength/stiffness under lowest weigh.
- Maximum service temperature: Strength decreases with increased temperature, limiting the operating temperature.
- Creep: Deformation over long loading durations at high temperatures.
Material Properties - Measurements & Values
- Density: Measured in kg/m³. Sometimes reported relative to water density (=1000kg/m³).
- Strength: Measured in force/area (N/m² or Pascals).
- Toughness: Measured in energy per unit area (e.g., J/m²).
- Elongation: Often given as a percentage of strain (% strain).
- Maximum Service Temperature: Measured in Kelvin (K) or Celsius (°C).
- Units are important for direct comparison among materials
Material Selection Charts
- Visual representations showing properties' ranges for various materials (e.g., Young's modulus, strength, density, toughness, elongation, max. service temperature).
- Charts categorize materials in different properties ranges (e.g., “Rigid”, “Flexible”).
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Description
Explore key material properties crucial for engineering material selection with Dr. Yehia M. Youssef. This quiz covers fundamentals like Young's Modulus, tensile testing, and material strength. Enhance your understanding of how these properties influence material selection and application in engineering.
