Solids under Stress Flashcards
- What is a crystalline solid?
A crystalline solid is a solid material whose constituents—such as atoms, ions, or molecules—are arranged in a highly ordered, repeating pattern extending in all three spatial dimensions.
- What is an amorphous solid?
An amorphous solid is a solid in which the particles are not arranged in a long-range, orderly pattern; examples include glass and many polymers.
- What is stress in the context of solids under stress?
Stress is the force applied per unit area within a material (stress = force/area).
- What is strain?
Strain is the deformation or extension per unit length of a material under stress (strain = extension/original length).
- State the formula for stress.
Stress (σ) = Force (F) / Area (A).
- State the formula for strain.
Strain (ε) = Change in Length (∆L) / Original Length (L₀).
- What is Young’s Modulus?
Young’s Modulus is a measure of a material’s stiffness, defined as the ratio of stress to strain in the elastic (Hookean) region of a material’s stress-strain curve.
- How is Young’s Modulus calculated?
Young’s Modulus (E) = Stress (σ) / Strain (ε) within the elastic limit.
- What does a high Young’s Modulus indicate about a material?
A high Young’s Modulus indicates that the material is very stiff and resists deformation.
- Define elastic deformation.
Elastic deformation is a temporary change in shape or size of a material that is fully reversible when the applied stress is removed.
- Define plastic deformation.
Plastic deformation is a permanent change in shape or size of a material that occurs when the stress exceeds the elastic limit.
- What is the elastic limit?
The elastic limit is the maximum stress a material can withstand without undergoing permanent (plastic) deformation.
- What is yield strength?
Yield strength is the stress at which a material begins to deform plastically and permanent deformation occurs.
- Define tensile strength.
Tensile strength is the maximum stress that a material can withstand while being stretched or pulled before it breaks.
- Define compressive strength.
Compressive strength is the capacity of a material to withstand axially directed pushing (compressive) forces without failure.
- What is hardness in materials science?
Hardness is a measure of a material’s resistance to localized plastic deformation (e.g., indentation or scratching).
- What is toughness?
Toughness is the ability of a material to absorb energy and plastically deform without fracturing; it reflects a combination of strength and ductility.
- How does temperature generally affect the strength of a solid?
Increasing temperature usually decreases a material’s strength because the bonds become weaker, while lowering the temperature can make materials more brittle.
- What are dislocations, and how do they affect deformation in metals?
Dislocations are defects in the crystal structure of a material that allow layers of atoms to slide over one another, which facilitates plastic deformation and influences a metal’s ductility.
- Define brittle fracture.
Brittle fracture is a sudden breakage of a material without significant plastic deformation, often associated with little energy absorption.
- Define ductility.
Ductility is the ability of a material to undergo significant plastic deformation before rupture.
- What is malleability?
Malleability is the capacity of a material to be deformed under compressive stress, often measured by its ability to form a thin sheet without breaking.
- How does the crystal structure affect a solid’s strength?
The arrangement of atoms in a crystal lattice determines how easily dislocations move, which in turn affects the material’s strength and ductility.
- Compare covalent network solids and metallic solids in terms of bonding and mechanical properties.
Covalent network solids (e.g., diamond, SiO₂) have a continuous network of strong covalent bonds resulting in very high strength and hardness but brittleness, whereas metallic solids have delocalized electrons that provide ductility and malleability along with good electrical conductivity.
