Structural Configuration Analysis of Crew Exploration Vehicle Concepts

Probabilistic structural and thermal analysis of a gasketed flange

Protecting Lunar Colonies From Space Radiation

During the development stage of a liquid rocket engine structural analyses are needed for increasing structural reliability and identify necessary design changes. These analyses need enormous efforts for detail modeling and cause large computational cost. With increasing computational power, the modeling can be more detailed than in the past. In this study, non-linear static structural and free vibration analyses taking into account the static loading as preloading are performed for a 750 kN class liquid rocket engine system. The finite element (FE) structural analyses are performed using the general purpose commercial code, Abaqus 2016. The effects of the static loadings on stress distributions and the free vibration results are analyzed. Additionally a simple kinematic model using rigid body elements is made up to investigate the elasticity effects on the rotation angles due to engine gimbaling. The strains measured from a ground firing test are converted to equivalent stresses to be compared with the FE analysis results. And a certain leakage problem solved using the FE analysis results is also presented.

Multidisciplinary design optimization of long-range slender guided rockets considering aeroelasticity and subsidiary loads

As more satellite wells are tied into existing subsea infrastructure, fluid flow velocities in subsea piping can be significantly higher than was anticipated during design. These higher velocities may lead to increased flow-induced vibration (FIV) as well as erosion due to sand transport. FIV is caused by flow-induced turbulence and associated pressure fluctuations, typically generated at piping geometry, such as bends or tees. These flow-induced fluctuating forces pose structural integrity concerns for subsea piping in terms of cyclic stressing and, over time, a threat of fatigue failure. Currently, a high-level screening approach for FIV exists as part of the Energy Institute (EI) Guidelines on the Avoidance of Vibration Induced Fatigue Failure (AVIFF). However, the EI AVIFF guideline does not provide a framework for the direct estimation of vibration levels, stress levels, or fatigue life. To address this gap, we have developed a comprehensive screening procedure for FIV in subsea piping. Assets which fail a screening based on published guidelines (e.g., EI AVIFF guidelines), may undergo a more detailed screening based on numerical simulation. The paper gives an overview of such a screening, based on computational fluid dynamics (CFD) and structural finite element analysis (FEA). CFD is a specialized field requiring specific expertise and a significant amount of computational resources. The CFD calculates the unsteady signature of flow-induced forcing on the piping for a given flow condition (i.e., multiphase flow). This forcing is then applied to a structural Finite Element (FE) model of the piping, with the output being displacement, acceleration, stress (among possible others) and ultimately a fatigue life estimate. FIV and erosion measurements are much more costly subsea than they are on topsides. Hence, advanced simulation techniques are valuable tools in determining the integrity status as well as the safe operating limits of subsea piping.

Structural modeling of HTS tapes and cables

The DPP-2 shipping package (DPP-2) has been under development by the Y-12 National Security Complex (Y-12), Oak Ridge, TN. The Transportation Technologies Group (TTG) of Oak Ridge National Laboratory (ORNL), at the request of the Y-12, performed physical testing of the DPP-2 as part of Y-12's effort to obtain US Department of Energy (DOE) Type B certification for this package. The certification testing included sequential drop and crush testing of several prototype units in many different orientations. Structural finite element analysis (FEA) was a heavily relied upon tool used during the design, development and certification of the DPP-2. Initially, FEA was used to rule out various design concepts. Once a more mature design had been arrived at, FEA was employed to determine testing orientations which would create maximum damage to the test units. Finally, FEA has been employed to answer certification reviewers' questions regarding items not explicitly covered by physical testing. Because current...

Dynamic characteristics and reliability of elastomeric pads are dominant components in the design methodology to satisfy the performance parameters under dynamic operations. The fatigue life of rubber pads fitted with elastomeric pads mainly depends upon elastomers; natural rubber, chloroprene, nitrile butadiene, silicon compounds, etc., additives, accelerators, activators, fillers, anti-degradants, and manufacturing processes. The performance of the elastomeric pad is evaluated based on service operation, simulation, and laboratory testing. New and failed elastomeric (EM) pads have been examined in the Indian Rubber Manufacturer’s Research Association IRMRA laboratory for detailed failure analysis of existing EM pads. Further, chemical and physical properties are also evaluated in M&C (Metallurgical and Chemical) and Testing Directorate of Research Designs and Standards Organization (RDSO), labs respectively. The fatigue life of the EM pad is estimated based on the results extracted from the Finite Element (FE) analysis of the EM pad. An attempt is made to modify the design of the EM pad by considering the results of detailed field trials, lab testing, and FE analysis. The modified design satisfies the dynamic characteristic during FE (Structural and Thermal) analysis and lab testing.

We present an optimization methodology to reduce magnetically induced vibrations of a spoke-type interior permanent magnet (IPM) motor that we developed by performing magnetic and structural finite element analyses and optimization. The magnetic forces acting on the teeth of the stator were calculated by magnetic finite element analysis and the Maxwell stress tensor method. The natural frequencies and mode shapes of the stator were calculated by structural finite element analysis and verified by modal testing. The vibration of the motor due to the rotating magnetic force was calculated by the mode superposition method, and it was compared with the measured vibration. Finally, two optimization problems were formulated and solved to reduce magnetically induced vibration: minimization of magnetic force and minimization of acceleration. We showed that minimization of acceleration was more effective than minimization of magnetic force at reducing magnetically induced vibrations, because the former method effectively decreased the amplitudes of the excitation frequencies of magnetic force by considering the transfer function of the motor.

Subdivision methods have been mainly used in computer graphics. This paper extends their applications to the integration of geometric design and Finite Element Analysis (FEA) for sheet metal structures, and fulfils the seamless integration of geometric design and FEA in the model and representation. A common model or a unified representation for geometric design and FEA was created with subdivision surfaces for sheet metal structures. Automatic mesh generation for geometric design and FEA was fulfilled through subdivision methods. The seamless integration can improve the accuracy in numerical analysis and shorten the cycle for the geometric design and the FEA of sheet metal structures.

Morphing wing ribs are essential for enabling adaptive aerodynamic performance, reduced fuel consumption, and operational flexibility in low-speed aircraft and UAVs. This study presents a comprehensive structural evaluation of trailing-edge morphing ribs fabricated from five engineering thermoplastics; Nylon, Polycarbonate, Polyethylene, Polypropylene, and Polystyrene across three rib topologies; 50:50, 60:40, 70:30 rigid-to-flexible ratios, three thicknesses; 2.5, 5.0, 7.5 mm, and three prescribed deflection angles; +5°, + 10°, + 15°. A linear-static finite element analysis was conducted in ANSYS Workbench to quantify total deformation, von Mises stress, and safety factor for 135 design configurations. Boundary conditions replicated spar attachment and controlled trailing-edge displacement, with isotropic, linear-elastic material properties applied. A composite performance index, integrating normalized stiffness and safety factor, facilitated comparative ranking of all configurations. Results indicate that rib thickness dominates stiffness, with 7.5 mm ribs showing a 200–220% increase over 2.5 mm ribs. Safety factor is strongly constrained by deflection and thickness, decreasing 40–70% at + 15° across all materials, while material choice modulates stress distribution and fine-tunes structural margin. Polycarbonate and Nylon consistently achieve the highest stiffness > 300 N/m and safety factors > 1.7 at + 5°, HDPE and Polypropylene exhibit intermediate performance, and Polystyrene experiences critical reductions ~ 0.4 at + 15° due to geometric softening. Topologies 2 and 3 provide 8–12% higher stiffness and improved stress distribution relative to 50:50 ribs. The study provides a systematic framework for polymer-based morphing rib design, enabling optimized material selection and structural configuration for lightweight, adaptive aerospace wings.

Herein is presented a design for a lightweight 5 m x 1 m radio-frequency (RF) reflector that can be flattened, folded, and coiled for compact stowage on board an ESPA-class spacecraft. The reflector is a reflectarray that operates at 3.2 GHz. Compared to state-of-the-art technologies for RF reflectors, the presented design has advantages in terms of areal density, stiffness, deployed stability, and scalability. Thermal and structural analysis is presented to demonstrate deployed stiffness and thermoelastic stability of the proposed design. Thermal analysis is used to predict in-space deployed temperatures in an operational condition, and structural finite element analysis is used to predict deployed vibration modes and frequencies, and the thermoelastic deformation of the deployed reflector. Also presented are the fabrication, assembly, and testing of two one-third-scale-length full-scale-width 1.7 m x 1 m test articles. These test articles are used to experimentally demonstrate RF functioning, stowage, deployment, and RF performance after deployment.

<abstract> <p>We propose an asymptotic concentration approach combined with isogeometric analysis (IGA) for the topology optimization of two-dimensional (2D) linear elasticity structures under the commonly-used framework of the solid isotropic materials and penalty (SIMP) model. Based on the SIMP framework, the B-splines are used as basis functions to describe geometric model in structural finite element analysis, which closely combines geometric modeling with structural analysis. Isogeometric analysis is utilized to define the geometric characteristics of the 2D linear elasticity structures, which can greatly improve the calculation accuracy. In addition, to eliminate the gray-scale intervals usually caused by the intermediate density in the SIMP approach, we utilize the asymptotic concentration method to concentrate the intermediate density values on either 0 or 1 gradually. Consequently, the intermediate densities representing gray-scale intervals in topology optimization results are sufficiently eliminated by virtue of the asymptotic concentration method. The effectiveness and applicability of the proposed method are illustrated by several typical examples.</p> </abstract>

A planar parallel compliant mechanism based on 3-RRR kinematic structure is designed to be used as a micro positioning stage. The position of the center is measured by using a laser position sensor and the mechanism is actuated by piezoelectric actuators. The stage displacements are analyzed by using structural Finite Element Analysis (FEA). However the experimental displacement results for the manufactured mechanism are not compatible with the FEA which means that we have errors due to manufacturing, assembly etc. A position control using Sliding Mode Control with Disturbance Observer is proposed for the reference tracking of the center of the stage. Piezoelectric actuator linear models are used for disturbance rejection. Finally, the position control of the mechanism is succeeded although it has inadmissible errors compared to FEA.

Computation of stress distribution in a Francis turbine runner induced by fluid flow