Technical Glossary

RSL seismic isolation system

One of seismic isolation structures in which rubber, steel and lead are combined. Because each instrument (component) can be laid out depending in accordance with a building (a high degree of flexibility in designing), this system is highly reliable and specific cycles can be stretched.

Isolators

Components, instruments and mechanism which are used to insulate against vibrations. Isolators often mean the laminated seismic isolation rubber mounts. However, these sometimes mean the support parts of vibration isolation tables or vibration instruments.

Compressed permanent distortion

Compressed permanent distortion is the permanent distortion resulting from the heating compression of rubber materials. The smaller this number, the greater the restoration capability after being compressed for a long time. This can be evaluated by the test referred to the standard JIS K 6262

SI unit

This "SI" known worldwide as an abbreviation of "International System of Units" was determined in 1960 by the International Committee of Weights and Measures as a "practical system of units that all countries could implement. The international system of units consists of 7 basic units, 2 supplemental units, units derived from combinations of these units (these three types of units are collectively called the SI units), and integral multiplications of 10 of these units.

StFF

Vibration damping stage feed forward. Control by detecting movement of stage on the random springs.

FFKEAP control

This is a control system that cancels the vibration of the springs when there is a source of repeating vibrations on the springs such as a stage. This control is performed by estimating disturbances using disturbance estimation and learning functions of KEAP control and the feed-forward control of an actuator in accordance with the movement of stage.

FFT

FFT is an abbreviation of Fast Fourier Transform. Using FFT, the types of frequencies and amplitudes which consist of waveforms which synthesize the waveforms that sounds and vibrations have can be known (spectrum analysis).

Acceleration response scale factor

Ratio of acceleration of a floor in a seismically-isolated building and its foundation.

Exciting source

Cause of vibrations of pumps and motors.

Acceleration

Volume of change of speed per unit hour.

Audible sound

The sound which has specific frequencies that can be audible to people (it varies between individuals, however, it is about between 20 Hz and 15000 or 20000 Hz)

Vulcanization and forming

Rubber compounds which before vulcanization are formed into target shapes. These are then heated and pressurized for a certain period of time to have an elastic property.

Conversion factor

This is a factor to be multiplied to simplify the calculation of spring constants and permissible loads of rubber products at any hardness but using a hardness of 60 degrees as a reference.

Inertial weight

Specific volume of an object calculated by external force/acceleration, when an acceleration movement occurs due to an external force being applied to the object.

Sound absorption

Absorption of sound without reflecting it.

Resonance

This is a state in which an exciting frequency and a natural frequency of anti-vibration material are harmonized, therefore, the transmissibility of vibration becomes infinitely large (if damping is zero).

Permissible load

The maximum permissible load which products can be used safely without causing breakage when they are used for their intended purposes.

Permissible deflection

The maximum permissible volume of deflection which products can be used safely without causing breakage when they are used for intended purposes.

Air-borne sound

Sound that spreads using only air as a medium.

Damping

Reduction of kinetic energies. In the case of vibrations, most of them are transformed into thermal energies.

Rigid body

Rigid articles which do not deform at all.

Hardness

Hardness of rubber surface. The hardness measured using a hardness meter which satisfies the specifications described by JIS K 6253. This is also called "rubber hardness."

Solid sound

See "Solid-borne sound."

Solid-borne sound

Vibrations and impacts are directly applied to a structural body, such as a floor or a wall in a building. These vibrations spread using structural bodies (solid) and cause sounds as air in contact with the structural body is vibrated. This is also called the "solid sound."

Rubber hardness

See "Hardness."

Rubber compounding

The amount of polymer (raw rubber), plasticizer and other chemicals to be added to the raw material rubber to satisfy the functions which rubber products must meet.

Specific cycle

This is an inverse number of a natural frequency. The time required to make a reciprocal motion when an object vibrates freely.

3-axis compaction force

The material mechanics show that the maximum, intermediate and minimum 3-axis stresses which cross perpendicularly to each other are created in objects. This is the state in which all three of these are compression stresses. The state as if hydrostatic fluid pressure is applied.

Support load

This is the load that anti-vibration rubber mounts and instruments support when the anti-vibration rubber mounts and instruments to be isolated from vibration are installed.

Seismic waves

These are the waves which transmit through the ground during an earthquake. Depending on the way that the vibrations are transmitted, they are called P-wave, S-wave and surface area.

Sound insulation

Not to transmit sounds.

Stress concentration

If the shape of part is simple, like a round bar or a square panel, there is an even amount of stress in the part. However, if the part has slots, holes or steps, a high partial stress will be applied. This is the concentration of stress.

Degrees of freedom

This is the number of directions in which an object can move freely. A rigid body in a 3D space has six degrees of freedom; back and forth, to the right and left and up and down.

Frequency

The number vibrations repeated in one second.

Gravimetric unit

This is a unit which includes a weight (force) unit instead of a mass unit as a basic unit. The unit of force in the gravimetric unit is defined as gravity applied to the unit mass, and the word "gravity" is incorporated into the name of the mass unit. Currently, the unit SI has become common, therefore, the gravimetric unit is no longer used.

Sound muffling

This is to reduce sound energy by absorbing a sound or having sounds muffled by each other.

Vibration isolation

This is to reduce the force (acceleration) transmitted to instruments and equipment, through use of soft springs. The instruments and equipment influenced by external vibrations include measuring devices and semi-conductor equipment.

Vibration acceleration level

This is the volume which indicates the amount of physical energy in a vibration and the unit of measurement is the decibel (dB).

Vibration frequency

This is the frequency of vibrations repeated in a unit of time (in general 1 second). It is also called the frequency.

Transmissibility of vibration

This is the ratio between the exciting force which is created by instruments and equipment and the force transmitted to the foundation through anti-vibration materials when the instruments and equipment are supported elastically.

Amplitude

This is a distance from the center of a vibration to the maximum point of displacement when an object is vibrating. It is approximately half of the oscillating width.

Horizontal rigidity

Spring constant in the horizontal direction

Static-dynamic ratio

The force of vulcanized rubber causes an offset of phase from the displacement when the rubber is under the dynamic excited condition. The force at that time can be broken down into elements: An element of displacement, a coordinate phase and an element in which the phase is offset by 90 degrees. (Maximum value of the coordinate phase element of force) / (Maximum value of displacement) is called the dynamic (storage) spring constant and the ratio between the dynamic spring constant and the static spring constant is called the static-dynamic ratio.
On the other hand, (Maximum force) / (Maximum value of displacement) is called the absolute spring constant and the ratio between the absolute spring constant and the static spring constant is called the static-dynamic ratio in some cases.

Laminated structure

This is a structure in which two (or more) different types of materials are laminated alternatively (in a certain sequence).

Laminated rubber isolator

Laminated product of thin rubber and steel used in seismic isolation buildings. It has the function to support buildings in the vertical direction as hard materials are applied and a function to dampen the seismic force in the horizontal direction as soft materials are applied.

Shearing elastic modulus

The elastic modulus is a physical value which expresses the difficulty in deformation and it can be calculated in the formula "elastic modulus = stress ÷ distortion." The stress is the load per unit cross section and the distortion is the extent of elongation per unit length. If the load direction is the tensile direction, it is called the "tensile elastic modulus" and if the load direction is the shearing direction, it is called the "shearing elastic modulus."

Noise

Sound that is unpleasant to people. It is designated as a type of pollution in the Basic Environment Act. Sounds which could adversely influence measuring equipment may be identified as noise.

Loss factor

About the above item, (Maximum value of force of 90-degree phase-lead element) / (Maximum value of displacement) is called the loss spring constant.
Then, (Loss spring constant) / (storage spring constant) is called the loss factor and indicated by tanδ. This indicates how much energy the materials absorb during deformation (converted into energy). This is measured using a dynamic viscoelasticity tester.

Seismic resistance

Both safety and resistance against earthquake vibrations can be secured by achieving the minimal collapse of a building.

Elastic material

This is an object which deforms in proportion to the size of force when a force is applied and the regaining of its original shape when the application of the force stops. This is often used for the purpose of vibration isolation.

Transmission sound

When sounds collide with a wall, the sounds reflect or become absorbed by the wall. The sounds which last passed through the wall is called the transmission sound.

Secondary shape factor

This is defined as the value calculated by dividing the diameter of laminated rubber by the total thickness of laminated rubber. This indicates the degree of flattening of laminated rubber. The formula used to calculate this degree is: (Diameter of laminated rubber) / (Total thickness of laminated rubber).

Spring constant

This is the force required to deform an anti-vibration material for unit length.

Rebound resilience

This is an index showing the amount of energy that a material absorbs at the time of collision with an object. This can be indicated by the ratio of rebounding energy for the applied energy when a pendulum, whose striking end is sphere, collides with a test piece at a certain collision weight and speed.

Hysteresis

This is based on the load-deflection property of anti-vibration rubber. The phenomenon of energy consumption during a loading process of 1 cycle when values during the loading and unloading processes are different.

Strain

Strain is the change in material shape so called in material engineering. The strain which changes vertically is called the vertical strain and the strain which changes in a parallel direction is called the shearing strain. The strain is indicated by the ε code. Any materials which receive a load generate stress in them. Then, the materials change their shapes due to the stress.

Feed back

This is a means of control when a sensor detects vibrations in an object on the spring. Upon receiving a signal from the sensor, the deviation to the target is calculated and the controller operates the actuator based on the data of deviation to approximate the object to the target value.

Bloom (blooming)

The chemical agents blended with the rubber compound become crystallized like powders as they are precipitated and come out from the surface of the rubber. This phenomenon is called "bloom" or "blooming."

Permanent deformation

This is a phenomenon in which a load applied to rubber over time allows for the progressing of compression deformation. It is also called creeping.

Bench durability test

This is a durability test using a bench of tester. It is the opposite of the prototype durability test.

Soundproofing

This means to insulate occurrences of sound. There are some means for this, such as sound insulation, muffling and absorption.

Anti-vibration

Anti-vibration is a process to prevent vibrations to be transmitted to outside. This can be conducted by supporting vibrating machines and equipment with elastic materials.

Anti-vibration calculation

This is a method of calculation to be sure that anti-vibration materials satisfy the target natural frequency and do not cause any construction or equipment issues.

Surface pressure

This is the mean stress in the vertical direction calculated by dividing the axial force applied to the laminated rubber, such as an isolator, by the pressure-receiving area.

Seismic isolation

A type of structure. The articles in the building, equipment and instruments, and piping can be protected comprehensively by mounting soft laminated rubber mounts in the horizontal direction between the ground and the building and by preventing the impact of earthquake vibrations directly transmitted to the building.

Mode

Specific forms of vibrations exposed to a certain object.

Stabilizer

This is a tool to prevent an object from becoming inclined unnecessarily when an external force, such as strong wind, is applied.

Hot dip galvanizing

This is a process to apply zinc films to the surfaces of steel materials by immersing them in a zinc solution. This prevents rust and corrosion.

Linkage

This is a phenomenon in which a force applied in one free direction results in a motion in another free direction.

Rocking

This is one of the vibration modes of a rigid body in which the body shakes like a boat as the horizontal vibration and the rotational vibration are linked.