Temperature distribution and deflection in a bimetal Prepared by: Shubham soni

title Behavior of a bimetal heated directly by the current passing through it. OBJECTIVES Temperature distribution within a bimetal -used as a triggering mechanism in a domestic circuit breaker Deflection at the end of the bimetal due to difference in coefficient of thermal expansions in a bimetal under the influence of temperature distribution calculated above

Material selection Bimetal selected- KANTHAL 200 R 108 This bimetal consist of two metals one with Lower expansion material (invar- 36% Ni) and another with Higher expansion material (72 MnNiCu) LEM HEM CTE- 1.6 @ 93 ºCelsius CTE- 27.0 @ 93 ºCelsius Thermal conductivity- 6 W/m ºC Electrical resistivity- 1.08Ω.mm².m­ˉ¹ Isotropic material properties Same young’s Modulus, Tensile strength as well as poisons ratio

Bimetal dimensions Modelling bimetal that reflects the actual dimensions- 32mmX4mmX0.8mm Thickness of LEM = Thickness of HEM= 0.4mm Bonding of two strips in a bimetal- face to face bond, No slip, No friction , Zero gap

HEAT GENERATION The bimetal is directly heated when the current passes through it ; as bimetal offers some resistance to the flow of current, therefore I have selected internal heat generation as a source of heat input in my model Internal Heat generation = I²RT Let us assume internal heat generation of magnitude 0.0019 W/mm³ is generated through current passing through it

COVECTION HEAT TRANSFER Free convection is selected as a source of heat transfer to the still air with ambient temperature 22ºC. That is how ANSYS automatically generates film coefficient. meshing Fine meshing is chosen to get accurate Results 50% Proximity

TEMPERATURE DISTRIBUTION IN A BIMETAL Results of Steady state Thermal Analysis

CONCLUSION Maximum temperature within a bimetal when an internal heat generation of 0.0019 W/mm³ applied is 146.41ºCelsius and appears at the middle of the bimetal Minimum temperature within a bimetal when an internal heat generation of 0.0019W/mm³ applied is 145.51ºCelsius and appears at the edges of the bimetal

Coupled steady state thermal and structural analysis Results of Steady state thermal analysis gives temperature distribution within a bimetal, which is then applied as the input to structural analysis through IMPORT LOAD TEMPERATURE feature which gives us deflection within a bimetal; due to different coefficients of thermal expansion in a bimetal.

Importing temperature distribution from steady state thermal to structural analysis

Boundary conditions One end of the bimetal is constrained through a fixed support so that it acts as cantilever beam with one fixed end Again fine meshing is applied with 50% proximity to get accurate results

Simulation video

Deflection within a bimetal Time=4.44 sec Time=6.667 sec Time=8.889 sec Time=7.778 sec Time=10 sec

conclusion Maximum deflection appears at the free end of bimetal Maximum deflection = 3.1438 mm

Thank you