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Introduction
Published in Sumit Sharma, Composite Materials, 2021
Bimetals are laminates of two different metals that have significantly different coefficients of thermal expansion. When the temperature changes, bimetals warp or deflect, making these well suited for temperature-measuring devices. Figure 1.3 shows a simple thermostat made from a cantilever strip of two metals bonded together. Metal A (upper layer) has a coefficient of thermal expansion αA, and metal B (lower layer) has a coefficient of thermal expansion αB with αB > αA. When the temperature is increased, strip B wants to expand more than strip A but since they are bonded together, so strip B causes the bimetallic strip to bend.
Lexicon
Published in Samuel C. Sugarman, HVAC Fundamentals, 2020
bimetallic strip: (Electrical) A bimetallic strip is comprised of two metals having different temperature coefficients of expansion. The strip deflects when one side of the strip expands more than the other side. Bimetallic strip are used in thermal switches, thermometers and thermostats.
Fundamental Concepts
Published in Irving Granet, Jorge Luis Alvarado, Maurice Bluestein, Thermodynamics and Heat Power, 2020
Irving Granet, Jorge Luis Alvarado, Maurice Bluestein
Another device that is used to measure temperature or temperature differences depends on the expansion of materials and is called the bimetallic element. This element usually consists of two thin, flat strips placed side by side and welded together. The composite strip can be used flat or coiled into a helix or spiral. Changes in temperature cause the strip to change its curvature, and the motion produced can be used to move a pointer. The flat bimetallic strip is commonly used in room thermostats, where the motion of one end is used to close or open an electrical contact. The action of a bimetallic strip is shown in Figure 1.9.
Effect of electrode heating on performance of electrochemical micromachining
Published in Materials and Manufacturing Processes, 2019
The experimental EMM setup shown in Fig. 2(a) is used for conducting the experiments. The setup mainly consists of pulsed power supply unit, machining unit, electrode feed unit, electrolyte supply system and specially designed electrode heating unit. The electrode heating unit consists of power supply unit, heating coil, ceramic, thermostat and regulator unit. The heating unit is embedded in the tool electrode as shown in Fig. 2(b). During the experiment, the temperature of the tool electrode is set using the temperature regulator and heated using a AC power supply. The thermostat present in the system continuously senses the temperature and maintains the set temperature in the tool electrode. Thermostat consists of bimetallic strip made of two different dissimilar metals with different thermal expansion coefficients bonded together with a single unit. Once the temperature reaches the required temperature, the strip tends to bend toward the material with a lower coefficient of thermal expansion. The strip is therefore no longer physically connected to the contact point and the circuit opens and the current stops flowing. The circuit remains open until the temperature drops in electrode and then the strip regains its original shape and the current flows. If the tool electrode temperature exceeds the set temperature, the thermostat automatically cuts off the power supply to the coil responsible for heating the electrode. The temperature range varies from 20°C to 60°C.
Lift-off nulling and internal state inspection of multi-layer conductive structures by combined signal features in pulsed eddy current testing
Published in Nondestructive Testing and Evaluation, 2018
Pingjie Huang, Xuwei Luo, Dibo Hou, Zhaohe Yang, Ling Zhao, Guangxin Zhang
In the study of the classification of the test specimen, we simplified the specimen, in which the aluminium shell, the bimetal and the air layer between the shell and bimetal, together constitute a typical multi-layer conductive structure. Qualified thermostat had a positive place bimetallic strip (hereinafter referred to as sample 1, as shown in Figure 6(a)).The unqualified products primarily had the following three states: bimetallic anti-put (hereinafter referred to as sample 2, as shown in Figure 6(b)), did not put bimetal (hereinafter referred to as sample 3, as shown in Figure 6(c)), two pieces of bimetal stacked (hereinafter referred to as sample 4, as shown in Figure 6(d)). However, when the thermostat package was completed, inspectors could not directly distinguish these four different internal states by casual observation.
On the curvature and internal stresses in a multilayer strip due to uniform heating, electric field, or hydration
Published in Journal of Thermal Stresses, 2022
For example, if the curvature is maximized if the second layer has the thickness if E2 = E1 the thickness is while h2 = h1 for The normalized curvature is plotted versus the thickness ratio for the three selected values of in Figure 2a. Figure 2b shows the plot of the curvature maximizers versus the elastic moduli ratio For each pair of elastic moduli (E1, E2), the corresponding values of thermal expansion are assumed to be given. For bimetallic termostats, the copper/steel or brass/steel layers are often used. The thermoelastic properties in this case are ( GPa, ), ( GPa, ), ( GPa, ). In the case of copper/steel bimetallic strip () it readily follows that maximum curvature is obtained for while in the case of brass/steel bimetallic strip () the maximum curvature is obtained for If the temperature change is K, the corresponding radii of curvature are and If the length of a strip is L, the maximum deflection in the middle of the strip, relative to the ends of the strip, is (ignoring the end effects). One can also proceed to optimize the value of h2 by minimizing the maximum stress in a bimetallic strip.