DM308: Lecture 1 Properties of materials and materials processing Medium

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What is the purpose of stress-strain testing?

The purpose is to understand the behavior of materials under tension and compression, including elastic behavior, fracture strength, and strain recovery.

How is strain measured accurately in stress-strain testing?

Strain is measured accurately using a strain gauge or an extensometer.

What is the purpose of a Wheatstone bridge in stress measurement?

The Wheatstone bridge is used to measure strain in materials accurately.

What is Digital Image Correlation (DIC) used for?

DIC is used for contactless measurement of strain in complex parts of materials.

What is the elastic behavior exhibited by ideal brittle materials?

Ideal brittle materials exhibit purely elastic behavior before fracture, where all of the strain is recovered when the material is unloaded.

What is the elastic modulus also known as for brittle materials?

The elastic modulus for brittle materials is known as Young’s modulus.

What is the behavior of ductile materials up to the elastic limit?

Up to the elastic limit, ductile materials exhibit linear and reversible deformation.

What is the stress at which a ductile material fractures known as?

The stress at which a ductile material fractures is known as the tensile strength.

What are the three material families discussed in the text?

Metals and Alloys, Ceramics, Glasses, and Polymers.

What is the main focus of Materials Science and Engineering?

The main focus is the development of new materials through a holistic understanding of their behavior.

What is the transition stress between elastic and plastic behavior known as?

Yield strength

What is the maximum stress sustained by the material known as?

Ultimate Tensile Strength

What is the Vickers Hardness Test used to measure?

Hardness

What does the Charpy impact test measure?

Fracture toughness

What does DBTT stand for and what is its significance?

Ductile-to-brittle transition temperature; It is the temperature at which some materials may undergo a transition from ductile to brittle behavior.

What are the factors that stress intensity factors K depend on?

Crack opening mode, crack geometry, specimen/material geometry

What is fatigue and what does the S-N curve show?

Fatigue is the damage done to a material by a cyclic load. The S-N curve shows how the number of cycles to failure changes with the stress amplitude.

What is the difference between High cycle fatigue (HCF) and Low cycle fatigue (LCF)?

HCF involves high frequency, low stress amplitude, elastic deformation, and large number of cycles to failure, while LCF involves low frequency, high stress amplitude, some plasticity, and low number of cycles to failure.

What is the critical strain energy release rate a good measure of?

Fracture toughness

What led to the catastrophic hull tear of the Titanic during the iceberg collision?

Low-grade iron rivets becoming brittle in the icy waters of the Atlantic

What caused the breakage of Liberty ships during WW2?

Welds undergoing a ductile-brittle transition at low temperatures

What is the significance of stress concentration at window corners in the De Havilland Comet case study?

It led to catastrophic crack propagation and loss of three aircraft

What is the Paris’ law model used to predict?

Sub-critical crack growth rate

What is creep in materials and when does it become particularly problematic?

Creep is plastic deformation over a long period of time, and it becomes particularly problematic at higher temperatures.

What are the stages of creep?

Incubation period, Primary creep, Secondary creep, Tertiary creep, Failure

What factors are important to consider for materials design and selection in relation to the operating environment?

Chemical reactivity, temperature effects, sudden environmental changes

What is one of the problems associated with stress corrosion in materials?

Crack formation in the material

What is the relationship between plastic deformation and time in materials?

The amount of plasticity depends on the strain rate; given enough time and sufficient force, even brittle materials can flow.

What are the categories in which material properties are classified?

Structural or Functional

Why are fatigue properties important for materials subjected to cyclic loading?

Fatigue properties are important because they relate to cyclic loading, where materials may fail over time.

What does the Paris’ law model depend on?

The properties of the material, environment, and stress ratio

What happens during the Incubation period of creep?

No measurable deformation is observed as the defects needed for plastic deformation must first be generated in sufficient numbers.

What is the problem associated with thermal shock in materials?

Thermal shock can cause failure of the material

Why is it important to consider the operating environment when selecting materials?

To mitigate risks of oxidation, corrosion, and thermal degradation

What are Isotopes?

Isotopes are variants of a chemical element that have the same number of protons in their atomic nuclei but different numbers of neutrons. This means isotopes of a particular element have the same chemical properties but different atomic masses.

Why is everything past Iron on the periodic table hard to find?

The scarcity of elements beyond iron in the periodic table is primarily attributed to the process of stellar nucleosynthesis. Elements heavier than iron are generally formed through nucleosynthesis in stars, specifically during supernova explosions. Elements past Iron on the periodic table also tend to have a short lifespan

What finishes do Ductile and Brittle materials have at their breaking points when they are subjected in the elastic range.

Ductile materials have a fibrous finish and brittle materials have a smooth finish

Study Notes

  • Dr. Vassili Vorontsov is teaching DM308 Production Techniques 2 at the University of Strathclyde.
  • Lecture 1 focuses on the structural properties of materials.
  • Useful texts and books for the course include "Materials science and engineering" by Callister, "Engineering materials" by Ashby and Jones, and others.
  • The course consists of eight lectures and assessment includes a written exam, two pieces of coursework, and optional forum questions.
  • The coursework topics will not be covered in the exam.
  • To build an ATM, materials with specific properties would be used for different components such as LCD screens, CPUs, and cash dispensers.
  • Materials engineering is a discipline that deals with the development of new materials through understanding their behavior, structure, processing, and application.
  • Central to materials engineering is the scientific study of materials using experimental and theoretical techniques.
  • Materials authentication involves understanding the structure, processing, and properties of various material families, including metals and alloys, ceramics, glasses, polymers, and composite materials.
  • Materials engineering focuses on controlling structural and functional properties, while engineers have limited control over density, cost, scarcity, and toxicity.
  • Hooke's law is a fundamental concept in materials engineering, which states that the force applied to a material is proportional to the extension caused by that force.
  • Stress and strain are important concepts in materials engineering, with stress being the applied force and strain being the deformation caused by that force.
  • Tension and compression are two types of stress, with tension resulting in a positive strain and compression resulting in a negative strain.
  • Elastic and plastic deformation are two types of material behavior, with elastic materials exhibiting reversible deformation and plastic materials undergoing permanent deformation.
  • Young's modulus is a measure of the elasticity of a material, representing the ratio of stress to strain in the elastic regime.
  • The stress-strain curve for a material shows the relationship between stress and strain, with the elastic modulus representing the slope in the elastic region and the yield strength representing the transition from elastic to plastic behavior.
  • Finite element analysis is a computational method used to investigate stresses within complex components and assemblies, using the 3D description of Hooke's law.
  • Hardness is a measure of a material's resistance to indentation or scratching, with a correlation to the tensile yield strength in ductile materials.
  • Several hardness tests exist, with the Vickers Hardness Test being the most widely used.
  • Toughness is a measure of a material's ability to absorb energy during deformation, with the total energy being the sum of the elastic and plastic components.
  • The Charpy impact test is a common method for measuring fracture toughness, involving the breaking of a standardized notched specimen using a pendulum hammer.

Test your knowledge of stress, deformation, and material properties with this quiz. Questions cover concepts such as yield strength, ultimate tensile strength, Young’s modulus, and stress vs. strain curves.

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