Thermomechanical Analysis of a Damaged Thermal Protection System

Ng, W. R.; Friedmann, Peretz P.; Waas, Anthony M.

doi:10.2514/6.2005-2301

Cited by 9 publications

(23 citation statements)

References 22 publications

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“…In the previous studies, (2,3) the transient heat flux profile, q ATS (t) shown in Fig. 7(a), is applied to the outer surface of the TPS.…”

Section: Heat Transfer and Thermal Stress Analysis In Previous Studiementioning

confidence: 99%

“…For the damaged configurations, there is considerable uncertainty regarding the effect of damage on the flow field and the heat flux induced by it on the TPS. To account for this uncertainty, two 'uniform' thermal loading conditions, and , representing lower and upper bounds on the heat flux, were applied as discussed in Ng et al (3) . On the surface of the damaged region, in Fig.…”

Section: Heat Transfer and Thermal Stress Analysis In Previous Studiementioning

confidence: 99%

“…In addition to the experimental validation of the FE model, the interaction between hypersonic flow and damage, which modifies the heat flux on the damaged TPS, is examined in this paper using a refined simulation capability. The FE analyses in the previous studies (1,2,3) were simplified by assuming that the aerodynamic heating through the damaged region is spatially uniform. However, the presence of damage modifies the flow field and thus the heat flux acting on the TPS.…”

Section: Introductionmentioning

confidence: 99%

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Thermomechanical behaviour of a damaged thermal protection system: experimental correlation and influence of hypersonic flow

Friedmann

Waas

et al. 2011

Aeronaut. j.

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undamaged surfaces (5,6) . Thus, the flow conditions in the damaged region must also be taken into account.Based on the background provided, the specific objectives of this study are: (a) to describe the experimental facility, and the experiments conducted to validate the FE thermomechanical models, and (b) to determine the heat flux on the damaged tile by considering the hypersonic flow past a cavity, and incorporate the refined thermal loading into the FE thermomechanical analysis in order to determine the effects of damage on TPS response. The numerical results obtained with the combined fluid and structural model, represent in more accurate manner the actual behaviour of the damaged TPS, and illustrate the importance of testing the TPS in a facility that can replicate the actual flow and its interactions with the cavity in the damaged region. DESCRIPTION OF THE TEST FACILITY AND EXPERIMENTSThe experiments were conducted in the Thermal Structure Testing Laboratory at the Department of Aerospace Engineering of the University of Michigan. Specimens used for the experiments consisted of undamaged and damaged configurations with three different sizes of damage, D = 25·4mm, 38·1mm and 46·6mm. The damage is illustrasted schematically in Fig. 2, it is idealised as a cylindrical hole ending in a spherical cap. The total depth of the dmaged region D is equal to the diametrer of the spherical cap. Due to the limited number of specimens available, only two tests were conducted for each configuration. Test facilityThe test facility resembles a somewhat similar facility at NASA Langley (7) . The precise re-entry conditions for testing TPS are difficult to duplicate. An alternative is to apply a transient temperature boundary condition that may exist during re-entry on the surface of the TPS test specimen, and simulate re-entry static pressure in the vacuum chamber. A major limitation of such a facility is the inability to account for the important interactions that exist between high speed flow and vehicle. An overview of the facility is shown in Fig. 3. It consists of the vacuum chamber, pressure control system, radiant heater system, and data acquisition system.The cylindrical steel vacuum chamber has a diameter of 851mm and a length of 940mm. The chamber is equipped with feed-through for power, gas, and instrumentation for 20 pairs of type K thermocouples and 12 pairs of strain gages. A vacuum of 5·33Pa can be achieved when equipped with a 0·0113m 3 /s dual-stage rotary vacuum pump. Nitrogen is bled into the chamber at a controlled rate to simulate re-entry pressures. This is accomplished by a control system which includes a control module and a servo-controlled leak

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“…In the previous studies, (2,3) the transient heat flux profile, q ATS (t) shown in Fig. 7(a), is applied to the outer surface of the TPS.…”

Section: Heat Transfer and Thermal Stress Analysis In Previous Studiementioning

confidence: 99%

Section: Heat Transfer and Thermal Stress Analysis In Previous Studiementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermomechanical behaviour of a damaged thermal protection system: experimental correlation and influence of hypersonic flow

Friedmann

Waas

et al. 2011

Aeronaut. j.

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“…al. 12 In a recent study 13 , the authors of this paper examined the thermomechanical behavior of a TPS that consists of the LI-900 high temperature reusable surface insulation tile and a strain isolation pad (SIP) attached to the underlying structure, which resembles approximately a portion of the space shuttle TPS as depicted in Figure 1.…”

mentioning

confidence: 99%

“…Two configurations: a square configuration ( Figure 2) which resembles the actual configuration and an axisymmetric configuration ( Figure 3) were considered in Ref. 13. The damage profile shown in Figure 3, is based on the so-called "hypervelocity impact" 14 which produces an actual damage profile illustrated in Figure 4.…”

mentioning

confidence: 99%

Thermomechanical Analysis of a Thermal Protection System with Defects and Heat Shorts

Friedmann²,

Waas³

2006

47th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials ConferenceSelf Cite

12
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10
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The thermomechanical behavior of damaged space shuttle tile thermal protection system is determined using the finite element method. The relative effects of damage on the thermal protection capability and the induced thermal stresses in the TPS are determined by comparing the thermal and structural response of the damaged configurations with the undamaged configurations. The TPS, consisting of 3 components (the LI-900 tile, the strain isolation pad and the underlying structure), is modeled as a discrete three-layer structure. The TPS is subjected to the re-entry heating and pressure profile of the Access to Space vehicle, and the transient temperature distribution and the resultant thermal stresses in the system are computed. Three different sizes of damage having diameters 0.5", 1" and 1.5", based on hypervelocity impact, are considered. The validity of the simplifying assumptions used in a recent study is systematically examined. Some of these assumptions are relaxed and their effects on the system response are studied in the present work. The effect of damage location on the overall behavior of the TPS is also examined. Damage changes the surface properties of the tile and increases the surface area exposed to heating. It significantly reduces the radiation heat loss from the surface of the tile, resulting in elevated temperatures in the TPS. The elevated temperatures, with the stress concentrations introduced by the damage increases the thermal stresses significantly. Results suggest that the damage considered is capable of raising the maximum temperature in the tile to beyond its melting point and may cause structural failure.

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Thermomechanical Behavior of a Damaged Thermal Protection System: Finite-Element Simulations
Ng
¹
,
Friedmann
²
,
Waas
³

2012
J. Aerosp. Eng.
11
0
8
0
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Thermomechanical Analysis of a Damaged Thermal Protection System

Cited by 9 publications

References 22 publications

Thermomechanical behaviour of a damaged thermal protection system: experimental correlation and influence of hypersonic flow

Thermomechanical behaviour of a damaged thermal protection system: experimental correlation and influence of hypersonic flow

Thermomechanical Analysis of a Thermal Protection System with Defects and Heat Shorts

Thermomechanical Behavior of a Damaged Thermal Protection System: Finite-Element Simulations

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