Materials

Engineering Stress-strain Diagrams

In which the engineering strain and stress are plotted as abscissa and ordinate.

Twinning

Is a process that results in an alteration of the orientation of one part of crystal in relation to the other part of the same crystal

Plasticity

Is a property of a material by virtue of which permanent deformation can occur.

Ductility

Is a quality of a material by virtue of which maybe it is plastically elongated

Testing device

Is nothing more than a device in which the specimen can be elongated and which the forces required to causes elongation can be measured.

Hardness

Is usually resistance to scratch and penetration.

Toughness

It usually implies resistance to shock. Difficult to break.

Mechanical Test

May be defined as one in which all of the variables affecting a given property are controlled and the variable in question is measured under fixed conditions.

Modulus of resilience

Quantitatively the amount of enrgy per unit volume which the material will possess when subjected to the elastic limit stress.

3 types of stress

Tension, Compression, Shear

Reduction of Area

The ________ is expressed as the ratio of the decrease in area of the necked down section of the test specimen to the original area on a percentage basis.

Modulus of Rapture

The _________ of a material is a computed strength which provides the value from which the maximum twisting moment in torsion or the maximum bending moment in bending a cylindrical shaft or a beam can resist.

Strain

The change in length divided by the original length. Unit deformation to which a material is subjected. Caused by an external force.

Chemical Properties

The characteristics of a material that relate to its behavior in chemical reactions.

Percentage Elongation

The ductility of a material can be expressed in terms of ____________.

Block Slip

The force necessary to initiate plastic deformation

Tension

The forces act directly in an attempt to pull the material apart.

Compression

The forces acts so as to tend to shorten the member carrying the load

Proportional Limit

The maximum stress to which a material can be subjected without any deviation from the proportionality of stress and strain (Hooke's Law).

Elastic Limit

The maximum stress to which a material can be subjected without the occurence of any permanent strain remaining upon complete release of stress.

Ultimate Strength

The maximum stress to which a material may be subjected before failure occurs

Twinning Plane

The plane that separate the parts of diff. orientation

Elasticity

The property of regaining the original shape upon the removal of the external load

Malleability

The quality of a material by virtue of which it may be physically compressed.

Poisson's Ratio

The ratio of the lateral strain to the longitudinal strain.

Young's Modulus

The ratio of the stress to strain within the limit of proportionality. Also known as modulus of elasticity

Shear

There is an attempt to move one portion of the body with respect to the other so that two surfaces will tend to move over one another.

Modulus of toughness

This is the measure of the total energy-absorbing capacity of the material and includes the energy of both the elastic and plastic deformation.

Hooke's Law

This relation of linearity which states formally that within the elastic range of material, stress is proportional to strain.

Physical Properties

Those distinguishing qualities or characteristics that are used to describe a substance in the absence of external forces

Stress

Those internally distributed forces w/c tend to resist deformation may be defined qualitatively as.

Mechanical Properties

Those properties which describe the behavior of material under the application of force.

Inches per inch

Unit of strain

Upper Yield Point

A material continues to elongate ncreased for a time without the increase in load

Lower Yield Point

A stress reaches a relatively constant value while deformation continues

Flow Curve

Also known as the physical stress strain diagram. True stress is plotted against true strain.

Bulk Modulus of Elasticity

Also known as volume modulus. It is the ratio of the uniform, triaxial stress to the change in volume

Resilience

Capacity of the material to absorb energy within elastic range.

Extensometer

Extention of the test specimen

Stress

Force per unit area

Malleable

If the material can be severely deformed plastically in compression without fracture, the material is said to be _________.

Dislocation

Imperfection in a crystal structure