Convective heat transfer in the study of thermal cracking of concrete samples under laser irradiation

Abstract

The research used a scheme for constructing a solution to an uncoupled problem of quasi-static thermoelasticity for a semi-infinite body under mixed boundary conditions, which is subject to heating in a limited region of the boundary surface by a heat flux, and based on the constructed solution, an approach to calculating the parameters of thermal separation was developed, which uses criterion levels. (Griffiths and McClintock-Welsh) mechanics of brittle fracture. The scheme was tested on concrete samples of two types with different compressive strengths.

The effect of forced cooling on the thermal stress state in deformable solids under the conditions of action of concentrated heat flows was studied in works, where the conditions under which the effect of cooling is significantly felt are established. Experimental studies of temperature regimes have shown that in the absence of forced cooling systems, the heat transfer in the process of short-term (with Fourier numbers less than ten) heating can be less than 5% of the total amount of heat received.

The general results can also be the basis for further research on the influence of different laser sources on the processes of heat treatment of building materials and structures.

A review of the works in which approaches to finding the non-stationary temperature and quasi-static temperature stresses in a half-space with a uniform thermal flow of heat were initiated show that the surface outside the contact area is thermally insulated. However, taking into account convective heat transfer shows the problem more precisely.

It is necessary to consider the general order of construction of the solution to the problem of quasi-static unbound thermoelasticity for a semi-infinite body heated by a uniformly distributed heat flux under mixed boundary conditions.

Next, on this basis, we will present an approach to the calculation of parameters of laser thermal cracking, which uses some criterion equations of the mechanics of brittle fracture.