Optimum Design of Structures at Elevated Temperatures

Adelman, Howard M.; Sawyer, P.; Shore, C. P.

doi:10.2514/3.61186

Cited by 11 publications

(5 citation statements)

References 9 publications

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“…Investigations into this possibility are currently being conducted. 13 Finally, turbulent heating has not been considered in this study. The possibility of tailoring entry trajectories to limit turbulent heating and the resulting impact on the TPS/structure mass requires further investigation.…”

Section: Study Limitationsmentioning

confidence: 98%

Lifting entry vehicle mass reduction through integrated thermostructural/trajectory design

Wurster

1983

Journal of Spacecraft and Rockets

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The study described in this paper examines the impact of thermostructural/trajectory design integration on advanced-winged entry vehicle mass. A variety of thermal protection system (TPS) concepts are considered, and entry trajectories tailored specifically to each concept in terms of peak heat rate and total heat load are used in conjunction with an aerodynamic heating/thermal analysis program to determine the TPS requirements. Results indicate that for an aluminum structure, either the reusable surface insulation (RSI) or the hybrid TPS (RSI forward, Ren£ 41 metallic standoff aft) has the potential to yield the lowest mass system. The metallic standoff system is, however, quite competitive and, with the 25% reduction in the panel mass anticipated, could surpass the RSI system. Results also indicate that significant improvements in hot-structure design are necessary before such a system can become competitive. An assessment is made of the potential impact of higher temperature structure materials on combined TPS/structure mass. Results indicate that the greatest reduction in mass is obtained with the first 200K increase in temperature capability over that of aluminum and, thus, the potential for the lowest mass system appears to lie with either a graphite/polyimide or a titanium structure.Nomenclature lift coefficient specific heat at constant pressure, J/kg • K acceleration due to gravity, m/s 2 altitude, km thermal conductivity, W/m-K vehicle length, m lift-to-drag ratio reference heat rate, kW/m 2 reference heat load, MJ/m 2 thickness, cm temperature, K Earth-relative velocity, m/s body centerline location, m angle of attack, deg density, kg/m 3 ultimate tensile strength, kN/m 2

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Section: Study Limitationsmentioning

confidence: 98%

Lifting entry vehicle mass reduction through integrated thermostructural/trajectory design

Wurster

1983

Journal of Spacecraft and Rockets

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“…The function F(F) can be expanded with respect to the intervening variable 7, = Xf, as (-1 J (ID (12) where /?, and H are constants to be determined based on the information of the previous point. It will be shown that s(X) would uncouple /?, and H in the equations to compute them, which will make them easier to calculate.…”

Section: New Two-point Approximationmentioning

confidence: 99%

“…A logical improvement to the existing thermal/structural design methods is the incorporation of temperature constraints and the recalculation of temperatures during resizing. Adelman et al 12 and Adelman and Sawyer 13 solved coupled thermal/ structural optimization directly by applying the sequence of unconstrained minimization techniques and optimality criteria algorithms. Haftka and Shore 14 presented two approximation concepts for combined thermal/structural design.…”

Section: Introductionmentioning

confidence: 99%

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Structural Optimization with Thermal and Mechanical Constraints

Grandhi

1999

Journal of Aircraft

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This paper reports on the testing of the adaptability of the new approximation tools for thermal structural optimization. A finite element based procedure is proposed for obtaining a minimum mass design of structures subjected to stress, displacement, and temperature constraints. The optimization is based on a new two-point approximation method for the function. The coupling between thermal and structural sensitivities is taken into account to ensure the convergence. The direct or adjoint method is used for the sensitivity analysis. The two-point approximation is the incomplete second-order Taylor series expansion in terms of the intervening variables. The exponent of each design variable and the unknown constant in the second-order terms can be obtained in a closed form. This two-point approximation is used for temperature, displacement, and internal force approximations. Stress constraints are calculated by using approximated internal forces. Finally, the optimization procedure is demonstrated by two examples: the first example is the design of a titanium plate with aluminum bars and the second example is a structural wing box. These examples are subjected to external heating and mechanical loads, with temperature, strength, and minimum gauge constraints.

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“…1 coupled thermal/structural optimization problems are solved by directly applying mathematical programming and optimality criteria algorithms to sequential thermal and Structural analysis. In Ref, 2 it was shown that approximation concepts could be used to reduce the number of actual analyses required for structural optimization problems.…”

mentioning

confidence: 99%