Hoofdstuk 8 samenvatting
- Key mechanical design properties are stiffness, strength, hardness, ductility, and toughness.
- Three principal ways in which a load may be applied: namely, tension, compression, and
shear.
- With increasing temperature, the modulus of elasticity decreases
- Theoretically the Poisson’s ratio for isotropic materials should be 0.25
- Hardness is a measure of a material’s resistance to localized plastic deformation.
Three factors should be considered in designing laboratory tests to assess the mechanical
characteristics of materials for service use are the nature of the applied load (i.e. tension,
compression, shear), load duration, and environmental conditions.
For loading in tension and compression: engineering stress is defined as the instantaneous load
divided by the original specimen cross-sectional area. Engineering strain is expressed as the change in
length (in the direction of load application) divided by the original length.
On an atomic scale, macroscopic elastic strain is manifested as small changes in the interatomic
spacing and the stretching of interatomic bonds. As a consequence, the magnitude of the modulus of
elasticity is a measure of the resistance to separation of adjacent atoms, that is, the interatomic
bonding forces.
Many materials are elastically anisotropic; that is, the elastic behaviour (i.e. the magnitude of E)
varies with crystallographic direction.
Both tensile strength and hardness are indicators of a metal’s resistance to plastic deformation.
Consequently, they are roughly proportional.
Green words:
Engineering stress: (σ) is defined by the relationship in which F is the instantaneous load applied
perpendicular to the specimen cross section, in units of newtons, and A 0 is the original cross-sectional
area before any load is applied.
Engineering strain: (ϵ) is defined according to … formula ….
Modulus of elasticity: constant of proportionality E, or Young’s modulus. Magnitude for most metals
ranges between 45 GPa for magnesium and 407 GPa for tungsten. Stiffness, or a material’s resistance
to elastic deformation.
Elastic deformation: deformation in which stress and strain are proportional, a plot of stress versus
strain results in a linear relationship. The greater the modulus, the stiffer the material or the smaller
the elastic strain that results from the application of a given stress. Elastic deformation is
nonpermanent, which means that when the applied load is released, the piece returns to its original
shape.
Anelasticity: the property of a solid in which deformation depends on the time rate of change of
stress as well as on the stress itself. (time-dependent elastic behaviour).
- Key mechanical design properties are stiffness, strength, hardness, ductility, and toughness.
- Three principal ways in which a load may be applied: namely, tension, compression, and
shear.
- With increasing temperature, the modulus of elasticity decreases
- Theoretically the Poisson’s ratio for isotropic materials should be 0.25
- Hardness is a measure of a material’s resistance to localized plastic deformation.
Three factors should be considered in designing laboratory tests to assess the mechanical
characteristics of materials for service use are the nature of the applied load (i.e. tension,
compression, shear), load duration, and environmental conditions.
For loading in tension and compression: engineering stress is defined as the instantaneous load
divided by the original specimen cross-sectional area. Engineering strain is expressed as the change in
length (in the direction of load application) divided by the original length.
On an atomic scale, macroscopic elastic strain is manifested as small changes in the interatomic
spacing and the stretching of interatomic bonds. As a consequence, the magnitude of the modulus of
elasticity is a measure of the resistance to separation of adjacent atoms, that is, the interatomic
bonding forces.
Many materials are elastically anisotropic; that is, the elastic behaviour (i.e. the magnitude of E)
varies with crystallographic direction.
Both tensile strength and hardness are indicators of a metal’s resistance to plastic deformation.
Consequently, they are roughly proportional.
Green words:
Engineering stress: (σ) is defined by the relationship in which F is the instantaneous load applied
perpendicular to the specimen cross section, in units of newtons, and A 0 is the original cross-sectional
area before any load is applied.
Engineering strain: (ϵ) is defined according to … formula ….
Modulus of elasticity: constant of proportionality E, or Young’s modulus. Magnitude for most metals
ranges between 45 GPa for magnesium and 407 GPa for tungsten. Stiffness, or a material’s resistance
to elastic deformation.
Elastic deformation: deformation in which stress and strain are proportional, a plot of stress versus
strain results in a linear relationship. The greater the modulus, the stiffer the material or the smaller
the elastic strain that results from the application of a given stress. Elastic deformation is
nonpermanent, which means that when the applied load is released, the piece returns to its original
shape.
Anelasticity: the property of a solid in which deformation depends on the time rate of change of
stress as well as on the stress itself. (time-dependent elastic behaviour).
