Alleviation of Thermal Stresses in Bi‐metallic Spar Webs Available to Purchase

Results of an Investigation to Determine the Effectiveness of a Bi‐metallic Construction on Four Three‐spar Box Specimens Subjected to Simulated Aerodynamic Heating. The maximum thermal stresses in a stainless steel skin‐web combination subjected to aerodynamic heating may be greatly reduced by the addition of a thin layer of aluminium or copper to the stainless steel web. Such bi‐metallic construction increases the rate of conduction of heat from the structural parts (skins) exposed to the aerodynamic heating to the non‐exposed parts (webs) and consequently this produces a reduction in temperature gradients and thermal stresses. This paper presents the results of an investigation to determine the effectiveness of a bi‐metallic construction on a three‐spar box specimen subjected to simulated aerodynamic heating. The tests confirmed the feasibility of the method and indicated that the theoretical calculations give sufficient accuracy for design studies, provided an estimate of the joint conductance can be made. The method is effective only for relatively low heating rates and shallow wing structures. The work reported in this paper was sponsored by the Aerospace Research Laboratories, Wright‐Patterson Air Force Base, Ohio, under project No. 7063, Task 706302.