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The focus of the present study is to rigidize the toroidal member of an inflatable space antenna using a novel rigidization technique. This technique involves embedding heat-actuated Shape Memory Alloy (SMA) wires between laminated Kapton layers to provide structural strength. Finite Element Analysis (FEA) is performed to assess the strength of the torus under a heating environment. The analysis considers the approach of constraining torus deployment in all directions, simulating the conditions it would experience during deployment and operation. By subjecting the torus to a heating environment, the behavior of the SMA wires can be observed, which in turn affects the rigidity and strength of the structure. In addition to the numerical analysis, experiments are conducted to verify the feasibility of the design and strategy. The material properties of the involved materials, such as Kapton and SMA wires, have been determined through separate experimental investigations and incorporated into the FEA tool as input parameters. Furthermore, a parametric study is conducted to examine the impact of design and material parameters on the strength of the toroidal structure. The study demonstrates that a 1-meter diameter toroidal structure based on SMA wires can offer structural strength during partial or complete venting scenarios. [ABSTRACT FROM AUTHOR]

This study investigates the folding pattern design and deployment behavior of origami-based foldable conical structures. The geometric analysis is performed to design the six fold line pattern to obtain foldable conical structures. A single-story origami cone, modeled with pin-jointed framework, is selected for the analytical investigation. The axial strains, nodal forces, relative rotation of the fold polygons, and the strain energy during the deployment are obtained analytically. Moreover, the influence of design parameters ( m and α 1 ) on the deployment behavior of a single story cone is investigated. The results indicate that several fold configurations exhibit a bistable behavior during the motion, and these bistable configurations undergo lesser deformations than other singly stable fold configurations. Then, the folding and deployment process is simulated numerically using FE software to verify the accuracy of the analytical approach. The numerical results are completely consistent with the analytical results. The existence of bistability is verified using the variation of elastic strain energy during the motion. An analytical approach to obtain the bistability points for any conical folding pattern is presented and verified using numerical simulations. The influence of design parameters, materials, and scaling on the bistability point is also investigated. The results show that the bistability is solely a geometrical phenomenon, and scaling does not change the deformation behavior of the cone. Finally, the deployment dynamics of both singly stable and bistable multistory conical structures are discussed, with their potential applications. [ABSTRACT FROM AUTHOR]

Rolling element bearings are critical components of rotating machines since the failure of rolling element bearings may cease the functioning of the entire equipment. The damages observed due to bearing failures are expeditious in nature and hence the need to develop an effective prognostic methodology becomes a requisite to prevent the sudden machinery breakdown. The performance degradation assessment and accurate determination of remaining useful life are the two key issues in prognostics of rolling element bearings. This paper proposes a degradation indicator based on selforganising map for the performance degradation assessment of bearings and later support vector regression is utilised to estimate the remaining useful life of bearings. The time-domain and frequency domain features extracted from the raw bearing vibration signals are supplied to the self-organising map classifier to achieve the degradation index termed as self-organising map-minimum quantisation error evolution in the paper. For estimating the remaining useful life of bearings, first the central trend of minimum quantisation error is extracted to achieve the feature vector defined as bearing health index in this work. The bearing health index is then used as input and the life percentage of the bearing is set to output in order to build the support vector regression prediction model for remaining useful life estimation of bearings. The proposed method is validated on the vibration signatures collected in a bearing test rig. The results show that the advocated method can efficiently track the evolution of deterioration and predict the remaining useful life of bearings. [ABSTRACT FROM AUTHOR]

Minimal mass (ultra lightweight) and high packaging efficiency (stowage volume) are the most important factors associated with space technology and hence they become more attractive traits for getting larger bandwidth satellites on-orbit. Nowadays, maintaining the surface shape of pre-tension membranes to instrument precision has become a more challenging problem. Hence, membrane reflectors are receiving increasing attention for mission architectures that need extremely large in-space deployable antennas. This paper presents the finite-element investigation of a rectangular, flat thin membrane using polyvinylidene fluoride (PVDF) piezo-actuated material as an actuator/sensor. The passive effect of PVDF on the dynamics of an inflatable space-based rectangular shaped structure has been studied and trends in natural frequencies for various patch areas and thickness have been explored. Investigation shows that rather than using the various numbers of patches to the practical system for controlling their vibration behavior, the single patch with the appropriate thickness can easily control the desired vibration behavior. It can therefore be concluded that the discrete sensor/actuators devices are to be preferred to realize lower weight and effective control authority for the modest values of actuator voltages for active vibration control of practical structures. [ABSTRACT FROM PUBLISHER]

In this paper, the dynamic behavior of a high-speed rotating shaft under the combined localized defects on outer race, inner race and rolling element has been analyzed. An adaptive algorithm based on wavelet packet decomposition and Hilbert transform is used to extract the bearing fault characteristic component from the vibration signals. The reverse Biorthogonal wavelet 5.5 is considered as the most appropriate wavelet for decomposing the bearing vibration signal, on the basis of the maximum energy-to-Shannon entropy ratio criterion. The imperial trend suggested in diagnosing the combined localized defects of rolling bearing is based on experimental analysis at various rotor speeds. The results are presented in the form of envelope analysis, bifurcation diagrams and Poincaré maps that show the appearance nonlinearity in the dynamic response due to the rotor speed and the presence of combined localized defect. Significant peaks are reported at BPFO, BSF, FTF and modulation of BPFI with rotational frequency in envelope spectrum. Fundamental train frequency also shows noticeable excitation. A modified mathematical model shows good agreement with experimental results. [ABSTRACT FROM AUTHOR]