THERMAL LOADS IDENTIFICATION TECHNIQUE FOR MATERIALS AND STRUCTURES IN REAL-TIME

In experimental development of thermal protection materials and therma lly stressed structures of flight vehicles the necessity arises to mon itor the transient thermal loads and heat transfer parameters on the h eated surfaces in real time. Usually, this is connected with control o f heating intensity of the material specimens or structure samples dur ing tests to simulate heat transfer rate time-dependencies predicted f or a real flight, as well as temperature monitoring of the materials a nd structures in the most heated zones to avoid local overheating. The technique of aerothermo- dynamic parameter estimation is based on sol ving the corresponding inverse heat conduction problems (IHCPs) when t he required parameters of external heat transfer are calculated from d ata of thermocouples imbedded in the thermal protection or structural materials. A new technique of high response has been developed that re constructs transient heat fluxes at the surface of structural members from solving an MCP. An algorithm is suggested for solving a nonlinear MCP based on the formation of an unknown heat flux as a sequence of p oint estimates obtained in the result of solving a nonlinear boundary- retrospective problem in the sliding local time interval, where the in itial temperature distribution is also considered along with the bound ary condition as an unknown function. The solution of nonlinear bounda ry-retrospective problem is reduced to a sequence of corresponding lin ear problems. The solution of a linear MCP is recorded in the explicit form via a regularized operator of the inverse problem. A special rul e for sampling of a regularization parameter value in case of short ob servation intervals and a rule for terminating the iterative process a re suggested. The estimates of response time and accuracy for this tec hnique as well as the fields of its practical application are given. T he solution results of model problems solving and experimental data pr ocessing are presented. (C) 1998 International Astronautical Federatio n. Published by Elsevier Science Ltd.