POE Lesson 2-3 Key Terms

Axial Stress

A force with its resultant passing through the centroid of a particular section and being perpendicular to the plane of the section. A force in a direction parallel to the long axis of the structure.

Breaking Stress

The stress required to fracture a material whether by compression, tension, or shear.

Compression

When a material is reduced in volume by the application of pressure; the reciprocal of the bulk modulus.

Deformation

Any alteration of shape or dimensions of a body caused by stresses, thermal expansion or contraction, chemical or metallurgical transformations, or shrinkage and expansions due to moisture change.

Destructive Testing

Test methods used to examine an object, material, or system causing permanent damage to its usefulness.

Elastic Limit

Maximum stress that a material will withstand without permanent deformation.

Elongation

The fractional increase in a material's length due to stress in tension or thermal expansion.

Factor of Safety

The ratio of actual strength to required strength.

Failure Point

Condition caused by collapse, break, or bending, so that a structure or structural element can no longer fulfill its purpose.

Fatigue

The loss of the load-bearing ability of a material under repeated load application, as opposed to a single load.

Hooke's Law

The law stating that the stress of a solid is directly proportional to the strain applied to it.

Modulus of Elasticity

The ratio of the increment of some specified form of stress to the increment of some specified form of strain, such as Young's modulus, the bulk modulus, or the shear modulus. Also known as coefficient of elasticity, elasticity modulus, elastic modulus.

Nondestructive Testing

Test methods used to examine an object, material, or system without impairing its future usefulness.

Problem Solving

The ability to get answers to questions through a conscious, organized process. The answers are usually, but not necessarily, quantitative.

Proportional Limit

Point at which the deformation is no longer directly proportional to the applied force. Hooke's Law no longer applies.

Quality Control

Operational techniques necessary to satisfy all quality requirements; includes process monitoring and the elimination of root causes of unsatisfactory product or service quality performance.

Reliability

The probability that a component part, equipment, or system will satisfactorily perform its intended function under given circumstances, such as environmental conditions, limitations as to operating time, and frequency and thoroughness of maintenance for a specified period of time.

Resilience

A mechanical property of a material that shows how effective the material is absorbing mechanical energy without sustaining any permanent damage.

Rupture Strength

Nominal stress developed in a material at rupture. Not necessarily equal to ultimate strength. Since necking is not taken into account in determining rupture strength, seldom indicates true stress at rupture.

Shear Stress

A measure of how easily a material can be twisted.

Standard Deviation

A statistical measurement of variability.

Statistics

The collection and analysis of numerical data in large quantities.

Strain

Change in the length of an object in some direction per unit.

Stress

The force acting across a unit area in a solid material resisting the separation, compacting, or sliding that tends to be induced by external forces.

Stress-Strain Curve

Graphical representation of a material's mechanical properties.

Tension

The condition of a string, wire, or rod that is stretched between two points.

Toughness

Mechanical property of a material that indicates the ability of the material to handle overloading before it fractures.

Ultimate Stress

Sometimes referred to as tensile strength; determined by measuring the maximum load a material specimen can carry when in the shape of a rectangular bar or cylindrical can.

Variance

The average of the squared differences from the mean