Stiffness

Stiffness is the rigidity of an object — the extent to which it resists deformation in response to an applied force.

The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is.

Calculations

The stiffness, k, of a body is a measure of the resistance offered by an elastic body to deformation. For an elastic body with a single degree of freedom (DOF) (for example, stretching or compression of a rod), the stiffness is defined as

where,

In the International System of Units, stiffness is typically measured in newtons per meter. In Imperial units, stiffness is typically measured in pounds(lbs) per inch.

Generally speaking, deflections (or motions) of an infinitesimal element (which is viewed as a point) in an elastic body can occur along multiple DOF (maximum of six DOF at a point). For example, a point on a horizontal beam can undergo both a vertical displacement and a rotation relative to its undeformed axis. When there are M degrees of freedom a M x M matrix must be used to describe the stiffness at the point. The diagonal terms in the matrix are the direct-related stiffnesses (or simply stiffnesses) along the same degree of freedom and the off-diagonal terms are the coupling stiffnesses between two different degrees of freedom (either at the same or different points) or the same degree of freedom at two different points. In industry, the term influence coefficient is sometimes used to refer to the coupling stiffness.

Flexibility (personality)

Flexibility is a personality trait — the extent to which a person can cope with changes in circumstances and think about problems and tasks in novel, creative ways. This trait is used when stressors or unexpected events occur, requiring a person to change their stance, outlook, or commitment. Flexible personality should not be confused with cognitive flexibility, which is the ability to switch between two concepts, as well as simultaneously think about multiple concepts. Researchers of cognitive flexibility describe cognitive flexibility as the ability to switch one’s thinking and attention between tasks. Flexibility, or psychological flexibility as it is sometimes referred to, is the ability to adapt to situational demands, balance life demands, and commit to behaviors.

Measures/assessments

Due to the different facets of the definition of psychological flexibility, many problems exist in measuring it. There are multiple questionnaires that attempt to do so.

Flexibility (disambiguation)

Flexibility may refer to:

See also