Shock (mechanics) - Citizendia

Mechanical failure modes
Buckling
Corrosion
Creep
Fatigue
Fracture
Impact
Melting
Mechanical overload
Thermal shock
Wear
Yielding
This box: view • talk • edit

A mechanical or physical shock is a sudden acceleration or deceleration caused, for example, by impact, drop, earthquake, or explosion. In Engineering, buckling is a failure mode characterized by a sudden failure of a structural member subjected to high Compressive stresses where Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings Creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses It occurs as a result of long term exposure to levels of A fracture is the (local separation of an object or material into two or more pieces under the action of stress. An impact force is a high Force or shock applied over a short time period Melting is a process that results in the phase change of a substance from a Solid to a Liquid. The failure or fracture of a product or component in a single event is known as mechanical overload. Thermal shock is the name given to cracking as a result of rapid temperature change In Materials science, wear is the erosion of material from a Solid Surface by the action of another substance The yield strength or yield point of a Material is defined in Engineering and Materials science as the stress at which a material An earthquake is the result of a sudden release of energy in the Earth 's crust that creates Seismic waves Earthquakes are recorded with a Seismometer An explosion is a sudden increase in Volume and release of Energy in an extreme manner usually with the generation of high Temperatures and the release Shock is a transient physical excitation.

Shock is usually measured by an accelerometer. An accelerometer is a device for measuring Acceleration and gravity induced reaction forces This describes a shock pulse as a plot of acceleration versus time. Acceleration can be reported in units of metre per second squared. Often, for convenience, the magnitude of a shock is stated as a multiple of the standard acceleration due to free fall in the Earth's gravity, a quantity with the symbol g having the value 9. Gravitation is a natural Phenomenon by which objects with Mass attract one another 80665 m·s^-2. Thus a shock of "20g" is equivalent to about 196 m/s². A shock can be characterized by the peak acceleration, the duration, and the shape of the shock pulse (half sine, triangular, trapezoidal, etc). The Shock response spectrum is a method for further evaluating a mechanical shock. A Shock Response Spectrum (SRS is a graphical representation of an arbitrary transient acceleration input such as shock in terms of how a Single Degree Of Freedom It is sometimes used as a defense standard for military equipment. A United States Defense Standard, often called a military standard, " MIL-STD " or " MIL-SPEC " is used to help achieve standardization

1 Effects of Shock
2 Considerations
3 See also
4 Further reading

Effects of Shock

Mechanical shock has the potential for damaging an item (e. g. , an entire light bulb) or an element of the item (e. The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric Light that works by Incandescence, (a general g. a filament in an Incandescent light bulb):

A brittle or fragile item can fracture. The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric Light that works by Incandescence, (a general For example, two crystal wine glasses may shatter when impacted against each other. A shear pin in an engine is designed to fracture with a specific magnitude of shock. A shear pin is the mechanical analogue of an electric fuse. Installed in a drive train, it is designed to break in the case of a mechanical overload preventing other
A ductile item can be bent by a shock. Ductility is a mechanical property used to describe the extent to which materials can be deformed plastically or "stretched" into "wires" without For example, a copper pitcher may bend when dropped on the floor.
Some items may not be damaged by a single shock but will experience fatigue failure with numerous repeated low-level shocks.
A shock may result in only minor damage which may not be critical for use. However, cumulative minor damage from several shocks will eventually result in the item being unusable.
A shock may not produce immediate apparent damage but might cause the service life of the product to be shortened: the reliability is reduced.
A shock may cause in item to become out of adjustment. For example, when a precision scientific instrument is subjected to a moderate shock, good metrology practice may be to have it recalibrated before further use. Metrology (from Ancient Greek metron (measure and logos (study of is the Science of Measurement. Calibration is the process of establishing the relationship between a measuring device and the units of measure
Some materials such as primary high explosives may detonate with mechanical shock or impact. An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied Detonation is a process of Supersonic Combustion in which a Shock wave is propagated forward due to energy release in a reaction zone behind it

Considerations

When laboratory testing, field experience, or engineering judgement indicates that an item could be damaged by mechanical shock, several courses of action might be considered:

Reduce and control the input shock at the source.
Modify the item to improve its toughness or support it to better handle shocks. Toughness, in Materials science and Metallurgy, is the resistance to Fracture of a material when stressed.
Use shock absorbers or cushions to control the shock transmitted to the item. A shock absorber in common parlance (or damper in technical use is a mechanical device designed to smooth out or dampen shock impulse and dissipate Cushioning reduces the peak acceleation by extending the duration of the shock. Package cushioning is used to help protect fragile items during shipment
Plan for failures: accept certain losses. Have redundant systems available, employ insurance, etc.

Contents

Effects of Shock

Considerations

See also

Further reading