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  • Crack Growth

All practical materials contain some small internal defects (cracks). If these cracks can grow easily, they will join up and the material will fail in a brittle way. As a crack grows, strain energy is released from the surrounding material. A crack will grow rapidly when the strain energy release rate due to crack growth is sufficient to cause the crack to grow further in length, so it becomes self propagating. This critical value of the strain energy release rate depends several factors, including the energy absorbed by plastic deformation. The greater the critical strain energy release rate , the more resistant a material will be to unstable crack growth.

  • Creep

The dimensional change with time of a material under load, following the initial instantaneous elastic deformation. Creep at room temperature is sometimes called Cold Flow.

  • Deflection Temperature (1)

The measurement of temperature at which a specimen deflects 0.01 inches under a load of 66 lb/in2.

  • Deflection Temperature (2)

The measure of temperature at which a specimen deflects 0.01 inches under a load of 264 lb/in2.

  • De-ionized (DI) Water

Deionized water, sometimes called demineralized water, is water that has had all minerals removed from it using an ion exchange process. Water is deionized by a process called ion exchange. Water is placed in a container with a special resin that is negatively charged. The resin attracts minerals, such as sodium and calcium, removing them from the water.

  • Density

Weight per unit volume of a substance, expressed in grams per cubic centimeter, pounds per cubic foot, etc.

  • Diaphragma Valve

Diaphragm valves offer many combinations of body materials and elastomeric diaphragm materials. The valve design is abrasion-resistant and non-clogging. When the diaphragm, which is connected to the stem of the valve by a compressor, is pulled away from the bottom of the valve body or weir, the path of the fluid has a smooth, streamlined flow. Slurries at low pressure that would normally clog most other valve designs easily pass through a diaphragm valve. The valve has a top-entry design, allowing in-line maintenance; it is suitable for throttling and on/off service in applications ranging from water treatment to chemical abrasion processes. Diaphragm valves are operated manually, electrically, or pneumatically.

  • Dielectric

Insulating material. In radio-frequency preheating, dielectric may refer specifically to the material which is being heated.

  • Dielectric Constant

Normally the relative dielectric constant; for practical purposes, the ratio of the capacitance of an assembly of two electrodes separated solely by a plastics insulating material to its capacitance when the electrodes are separated by air (ASTM D150-59T).

  • Dielectrical Loss Factor

is a measure of the loss of energy in a dielectric material through conduction, slow polarization currents, and other dissipative phenomena. The peak value for a dielectric with no direct-current conductivity occurs at the relaxation frequency which is temperature related

  • Dielectric Magnetic Field

Electomagnetic field : The field of force associated with electric charge in motion, having both electric and magnetic components and containing a definite amount of electromagnetic. Dielectric material is a substance that is a poor conductor of electricity, but an efficient supporter of electrostatic field s. If the flow of current between opposite electric charge poles is kept to a minimum while the electrostatic lines of flux are not impeded or interrupted, an electrostatic field can store energy. This property is useful in capacitor s, especially at radio frequencies. Dielectric materials are also used in the construction of radio-frequency transmission lines.

  • Dielectric Strength

The electric voltage gradient at which an insulating material is broken down or arced through, in volts per mil of thickness.

  • Diffusion

Process by which there is a net flow of matter from a region of high concentration to one of low concentration. It occurs fastest in liquids and slowest in solids.

  • Dimensional Stability

The ratio of the power loss in a dielectric material to the total power transmitted through the dielectric, the imperfection of the dielectric. Equal to the tangent of the loss angle (dimensionless). Most plastics have a low dissipation factor, a desirable property because it minimizes the waste of electrical energy as heat.

  • Dissipation Factor

The ratio of the power loss in a dielectric material to the total power transmitted through the dielectric, the imperfection of the dielectric. Equal to the tangent of the loss angle (dimensionless). Most plastics have a low dissipation factor, a desirable property because it minimizes the waste of electrical energy as heat.

  • Double Containment Piping Systems

Double pipe systems where an inner "carrier" pipe carries the fluid while an outer "containment" pipe surrounds the inner pipe and contains any leaks. Double containment pipe systems have long been employed by the chemical industry to prevent the potentially catastrophic consequences of leaks of corrosive chemicals.

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