Measurement Method of Thermal Conductivity of Multilayer Composite Materials Based on Conjugate Gradient Method

Abstract

The invention discloses a conjugate gradient method based heat conduction coefficient measurement method for a multilayer composite material. The method comprises that a thermal impact is applied to the front side of the multilayer composite material, a back side temperature value of the multilayer composite material is obtained, a one-dimensional dimensionless unstable nonlinear thermal conduction control equation is established to solve a direct problem, dimensionless temperature distribution is obtained, an adjoint problem of the material m to be identified is solved to obtain Lagrange multiplier distribution, a derivative and a conjugation coefficient of an objective function of the material m to be identified and an iteration direction coefficient of a heat conduction coefficient of the material to be identified are calculated, the sensitivity problem of the material m to be identified is solved, the iteration step size of the heat conduction coefficient of the material to be identified is calculated, the heat conduction coefficient of the material to be identified is updated, a dimensionless temperature field is substituted into the objective function of the material to be identified, and if a function value satisfies the need for precision of a user, an identification result of the heat conduction coefficient of the material to be identified represents a measurement value of the heat conduction material of the material to be identified in the multilayer composite material.

Description

technical field [0001] The invention belongs to the field of heat transfer, in particular to a method for measuring thermal conductivity of multilayer composite materials based on a conjugate gradient method. Background technique [0002] In the field of aerospace, due to the extreme and complexity of the application environment, the outer walls of hypersonic vehicles are mostly made of high heat-resistant multilayer composite materials. Multilayer composites are laminated and pressed from several materials with different properties and have excellent mechanical and thermal insulation properties. Accurately obtaining the thermophysical properties of each layer of material is a necessary prerequisite for the use of multilayer composites. In order to accurately obtain the thermal insulation performance of typical multi-layer composite materials in different use environments, and to evaluate the application of supporting materials, it is necessary to carry out arc wind test an...

AI Technical Summary

Problems solved by technology

When the existing measurement technology measures the thermal conductivity of a layer of a multilayer composite material, it is necessary to disassemble the multilayer composite material or insert a detector into the material, which will cause damage to the multilayer composite material

Or, when a certain layer of material is taken out separately and the thermal conductivity is measured, the measurement result will be inaccurate due to excessive radiation heat dissipation

Images