Bimetallic strips

Strip is heated, strip B wants to expand more than strip A, but they are bonded, so strip B causes the bimetallic strip to bendl This bending under a loading that would othenwise seem to cause only extension is our first (qualitative) example of the structural phenomenon of coupling between bending and extension that we will study in more detail in Chapter 4. 

Determine the extensional, bending-extension coupling, and bending stiffnesses of an equal-thickness bimetallic strip as shown in Figure 1-3 (a beam made of two different isotropic materials with E, v, a, E2, V2, and 02). Use the middle surface of the beam as the reference surface. 

Various types of detectors that recognize heat and/or smoke utilizing fused bimetallic strips, ionization chambers and the interruption of a light beam by smoke or other combustion products. It is important to select the most appropriate form of detector for the environment. Insurers give a modest discount from premiums if the alarm installation complies with the insurance rules. 

A device for maintaining a constant temperature. It may employ a bimetallic strip the twisting movement of which (due to the different coefficients of expansion of the two metals) switches heating elements on or off to maintain the specified temperature. 

In a modem, automatic kettle, an electric heater warms the water inside the kettle - we call it the element . The electric circuit stops when the water reaches 100 °C because a temperature-sensing bimetallic strip is triggered. But the energy for a more old-fashioned, whistling kettle comes from a gas or a coal hob. The water boils on heating and converts to form copious amounts of gas (steam), which passes through a small valve in the kettle lid to form a shrill note, much like in a football referee s whistle. 

Thermostats—bimetallic strip, snap-action disk, and thermostatic cable Continuous discrete conductors Thermistor sensors Rate of temperature rise Copper tubing heat-actuated devices (HADs) Thermoelectric Combined rate of rise/fixed temperature Rate compensation Oil mist ... 

Results. XPS spectra of the chromate films on the bimetallic strips, on pure silver and on pure gold showed no indication of a Cr+6 state (Fig. 11) suggesting that flaws in the chromate film would not heal and therefore would be susceptible to corrosive attack. This non-healing aspect of the chromate films on the Ag/Au contacts differs from the effect of chromate films on A1 (51) and was confirmed in field studies. Therefore, the chromate films formed on the Au/Ag/Be-Cu contact are protective, but will not heal over scrapes and other damage caused by usage. 

Under an applied voltage the stress-free filaments in a bent bimorph will be in two planes, one above and one below the central plane and at equal distances a from it. The centre plane is strain free because the stresses on opposite sides of the joining layer are equal and opposed to one another. The steps in the argument are illustrated in Fig. 6.29 and the stress system is similar to that set up in a heated bimetallic strip, as analysed by S. Timoshenko [20]. 

The principle of the expansion of a solid is employed in bimetallic-strip thermometers, which are comprised of strips of two different metals bonded together, side by side. Since the metals selected for this use have... 

Cantilever deflections are also caused by small changes in temperature, because the usual fabrication produces a bimetallic strip configuration. Thus the AFM arrangement could be used to measure tiny thermal changes that arise in electrochemical cells. Applications of this type are just emerging. 

Changes in dimension. With such devices, a change in physical dimension occurs with a change in temperature. In this category are liquid-in-glass or other fluid-expansion thermometers, bimetallic strips, and others. 

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