Cavitation (elastomers)

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Cavitation is the unstable unhindered expansion of a microscopic void in a solid elastomer under the action of tensile hydrostatic stresses. This can occur whenever the hydrostatic tension exceeds 5/6 of Young's modulus. [1]

The cavitation phenomenon may manifest in any of the following situations:

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<span class="mw-page-title-main">Cavitation</span> Low-pressure voids formed in liquids

Cavitation in fluid mechanics and engineering normally refers to the phenomenon in which the static pressure of a liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, called "bubbles" or "voids", collapse and can generate shock waves that may damage machinery. These shock waves are strong when they are very close to the imploded bubble, but rapidly weaken as they propagate away from the implosion. Cavitation is a significant cause of wear in some engineering contexts. Collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion. This results in surface fatigue of the metal, causing a type of wear also called "cavitation". The most common examples of this kind of wear are to pump impellers, and bends where a sudden change in the direction of liquid occurs. Cavitation is usually divided into two classes of behavior: inertial cavitation and non-inertial cavitation.

In physics, a fluid is a liquid, gas, or other material that may continuously move and deform (flow) under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear force applied to them.

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<span class="mw-page-title-main">Spall</span> Fragments broken off a larger solid body of material

Spall are fragments of a material that are broken off a larger solid body. It can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure. Spalling and spallation both describe the process of surface failure in which spall is shed.

<span class="mw-page-title-main">Hydrostatic test</span> Non-destructive test of pressure vessels

A hydrostatic test is a way in which pressure vessels such as pipelines, plumbing, gas cylinders, boilers and fuel tanks can be tested for strength and leaks. The test involves filling the vessel or pipe system with a liquid, usually water, which may be dyed to aid in visual leak detection, and pressurization of the vessel to the specified test pressure. Pressure tightness can be tested by shutting off the supply valve and observing whether there is a pressure loss. The location of a leak can be visually identified more easily if the water contains a colorant. Strength is usually tested by measuring permanent deformation of the container.

<span class="mw-page-title-main">Pressure vessel</span> Vessel for pressurised gases or liquids

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<span class="mw-page-title-main">Hydraulic machinery</span> Type of machine that uses liquid fluid power to perform work

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Stress migration is a failure mechanism that often occurs in integrated circuit metallization. Voids form as result of vacancy migration driven by the hydrostatic stress gradient. Large voids may lead to open circuit or unacceptable resistance increase that impedes the IC performance. 'Stress migration is often referred as stress voiding, stress induced voiding or SIV.

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<span class="mw-page-title-main">Composite overwrapped pressure vessel</span> Pressure vessel with a non-structural liner wrapped with a structural fiber composite

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Cavitation is the formation of vapour cavities in a liquid.

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Alan Neville Gent was a professor at the University of Akron. He was recognized during his lifetime as a world-leading authority on the topics of adhesion physics, crystalline and glassy polymers, and the fracturing of rubber.

In metallurgy, peening is the process of working a metal's surface to improve its material properties, usually by mechanical means, such as hammer blows, by blasting with shot, focusing light, or in recent years, with water column impacts and cavitation jets. With the notable exception of laser peening, peening is normally a cold work process tending to expand the surface of the cold metal, thus inducing compressive stresses or relieving tensile stresses already present. It can also encourage strain hardening of the surface metal.

<span class="mw-page-title-main">Biaxial tensile testing</span> Testing a materials tensile strength along two perpendicular axes

In materials science and solid mechanics, biaxial tensile testing is a versatile technique to address the mechanical characterization of planar materials. It is a generalized form of tensile testing in which the material sample is simultaneously stressed along two perpendicular axes. Typical materials tested in biaxial configuration include metal sheets, silicone elastomers, composites, thin films, textiles and biological soft tissues.

References

  1. Gent, Alan N. (1990). "Cavitation in Rubber: A Cautionary Tale". Rubber Chemistry and Technology. 63 (3): 49–53. doi:10.5254/1.3538266.