ISO 18437-2:2005 機械的振動と衝撃—粘弾性材料の動的機械的特性の特性評価—パート2：共振法 | ページ 6

3.1

Young's modulus

E*

quotient of normal stress (tensile or compressive) to resulting normal strain, or fractional change in length

Note 1 to entry: Unit is the pascal (Pa).

Note 2 to entry: Young's modulus for visco-elastic materials is a complex quantity, having a real part E′ and an imaginary part E″.

Note 3 to entry: Physically, the real component of Young's modulus represents elastic-stored mechanical energy. The imaginary component is a measure of mechanical energy loss. See 3.2.

3.2

loss factor

ratio of the imaginary part of the Young's modulus of a material to the real part of the Young's modulus (the tangent of the argument of the complex Young's modulus)

Note 1 to entry: When there is energy loss in a material, the strain lags the stress by a phase angle, δ. The loss factor is equal to tan δ.

3.3

time-temperature superposition

principle by which, for visco-elastic materials, time and temperature are equivalent to the extent that data at one temperature are superposed upon data taken at a different temperature merely by shifting the data curves along the frequency axis

3.4

shift factor

measure of the amount of shift along the logarithmic (base 10) axis of frequency for one set of constant-temperature data to superimpose upon another set of data

3.5

glass transition temperature

T_g

temperature at which a visco-elastic material changes state from glassy to rubbery, and corresponds to a change in slope in a plot of specific volume against temperature

Note 1 to entry: Unit is degrees Celsius (°C).

Note 2 to entry: The glass transition temperature is typically determined from the inflection point of a specific heat vs. temperature plot and represents an intrinsic material property.

Note 3 to entry:T_g is not the peak in the dynamic mechanical loss factor. That peak occurs at a higher temperature than T_g and varies with the measurement frequency; hence is not an intrinsic material property.

3.6

resilient material

visco-elastic material intended to reduce the transmission of vibration, shock or noise

Note 1 to entry: It is sometimes referred to as an elastic support, vibration isolator, shock mounting, absorber or decoupler.

Note 2 to entry: The reduction may be accomplished by the material working in tension, compression, torsion, shear, or a combination of these.

3.7

linearity

property of the dynamic behaviour of a resilient material if it satisfies the principle of superposition

Note 1 to entry: The principle of superposition is stated as follows: if an input x₁(t) produces an output y₁(t) and in a separate test an input x₂(t) produces an output y₂(t), superposition holds if the input αx₁(t) + ßx₂(t) produces the output + ßy₂(t). This holds for all values of α, ß and x₁(t), x₂(t) ここで, α and ß are arbitrary constants.

Note 2 to entry: In practice, the above test for linearity is impractical. Measuring the dynamic modulus for a range of input levels can provide a limited check of linearity. For a specific preload, if the dynamic transfer modulus is nominally invariant, the system measurement is considered linear. In effect this procedure checks for a proportional relationship between the response and the excitation.