Seal Analysis for the Ares-I Upper-Stage Fuel Tank Manhole Covers

Seal Joint Analysis and Design for the Ares-I Upper Stage LOX Tank

“…The materials and properties used for the analyses are provided in Table 1. The modeling practices established for the LH2 tank manhole cover analyses that were previously anchored to ET test data (Phillips and Wingate, 2010) are employed for the LOX tank sump analyses. These modeling practices include element type and mesh refinement, boundary conditions and the use of shell-to-solid coupling, bolt modeling with beam elements, the use of "spider" constraints to simulate the effect of the washer bearing-surface size and bolt-to-insert engagement, and contact modeling at the seal primary and secondary sealing surfaces.…”

“…The solid elements are the ABAQLJS C3D8I elements, which are 8-node brick elements with additional internal degrees of freedom introduced as incompatible modes for improved bending behavior'. A mesh convergence study was performed during the previous ET analyses (Phillips and Wingate, 2010), and the mesh refinement for this LOX tank model is based on that study. The seal is used as the slave surface in the contact definitions (to be discussed later), and as such, the mesh refinement in the two non-thickness directions is twice the refinement of the end cap and sump.…”

“…The bolted connection is modeled as established by the previously mentioned ET test analyses (Phillips and Wingate, 2010). Beam elements are used to represent the bolt, and "spider" constraints are used to represent the interaction of the bolt with the connected parts.…”

“…The joint openings predicted for US are evaluated against the seal design specification for two-sided 4 flange deflection S2 sp,,-In addition, the specification control drawing requires that one-sided flange deflection not exceed (!) spec = Qspec/2 -Analysis results for the US LH2 tank manhole cover models subjected to flight environments showed that the one-sided flange deflections were predicted to be within the design specification: therefore, it was concluded that the US manhole cover design using the Naflex seal should perform adequately (Phillips and Wingate, 2010).…”

“…models for the ET LH2 tank manhole cover seal joints were correlated with historical ET seal test results (see Gillespie, 1988). The 3D FE modeling practices established with the ET models were then used to construct an Ares-I US LH2 tank model to assess the manhole cover seal performance under flight environments (Phillips and Wingate, 2010).…”