The topology optimization problem for the synthesis of compliant mechanisms has been formulated in many different ways in the past 15years, but there is not yet a definitive formulation that is universally accepted. Furthermore, there are two unresolved issues in this problem. In this paper, we present a comparative study of five distinctly different formulations that are reported in the literature. Three benchmark examples are solved with these formulations using the same input and output specifications and the same numerical optimization algorithm. A total of 35 different synthesis examples are implemented. The examples are limited to desired instantaneous output direction for prescribed input force direction. Hence, this study is limited to linear elastic modeling with small deformations. Two design parametrizations, namely, the frame element-based ground structure and the density approach using continuum elements, are used. The obtained designs are evaluated with all other objective functions and are compared with each other. The checkerboard patterns, point flexures, and the ability to converge from an unbiased uniform initial guess are analyzed. Some observations and recommendations are noted based on the extensive implementation done in this study. Complete details of the benchmark problems and the results are included. The computer codes related to this study are made available on the internet for ready access.
In this paper, Acoustic Emission (AE) based damage mode identification of Glass Fibre Reinforced Plastic (GFRP) lap joints is detailed using laboratory scale experiments. Bonded single lap joint specimens are fabricated from GFRP laminates. These specimens are subjected to tensile test with on-line AE monitoring. The study of failure mechanisms is facilitated by the choice of different oriented lap joint specimens in which one or two such mechanisms predominate. Range of peak frequencies in each orientation is investigated using frequency analysis. Fast Fourier Transforms enabled calculating the frequency content of each damage mechanism. Parametric plots are used to discriminate the different stages of occurrence of failure mechanism in lap joints. Results have shown that predominate of failure modes in each orientation is used as a key in the study of discrimination of failure modes from AE data in lap joints.
Non-contacting static seals are intended to provide high pressure drop at different leakage flow rates for better sealing. In special applications such as cryogenic engines and nuclear reactors which have high sealing requirements, conventional annular seals and circular-grooved square cavity labyrinth seals often do not meet the demand. This paper investigates newer configurations like circular-grooved triangular cavity labyrinth seals and sinusoidal-grooved triangular cavity labyrinth seals which can provide improved sealing than conventional seals. For these seals, pressure drop data over a wide range of water flow rates has been obtained using computational simulations and experiments. The pressure drops for the triangular seals are observed to be marginally more than those for square labyrinth seals and markedly higher than those for annular seals. The numerical results are also in good agreement with experimental and available analytical results. In order to highlight the effects of cavity shape and seal configuration, optimisation of a circular-grooved triangular labyrinth seal has been carried out using Artificial Neural Network (ANN), in association with a semi-theoretical model. The pressure drop for the identified optimal triangular labyrinth seal is 16% higher than that of the optimal square labyrinth seal. Among the seals tested, the sinusoidal-grooved triangular labyrinth seal exhibits the highest pressure drop, exceeding that of the optimal circular-grooved triangular labyrinth seal by 57%, at the rated flow rate.
Over the years, application of composite materials has got wider. So there is a necessity for development of new materials to satisfy the environmental requirements. It is viable through the process of hybridization of natural fibers to synthetic fibers. This investigation is carried out to determine the tensile and flexural strength of hybrid composites with various fiber combinations and stacking sequence. Thus it is easy to identify the natural fiber hybrid combination with high mechanical properties under static and varying thermal load conditions. The various fiber materials are meticulously chosen and three conventional and six different hybrid laminates were fabricated with various stacking sequences of selected fibers using hand layup technique. The tensile and flexural properties are determined through mechanical testing and compared with conventional materials. The failure morphologies are captured and investigated with zoom optical cameras. On analyzing the results, it is observed that carbon-flax hybrid composites exhibit nearly equivalent specific strength at a reduced cost compared to the carbon/glass fiber hybrid composites and also the effect of the stacking sequence in mechanical properties is elucidated through this study. Varying thermal load analysis reveals that there is a considerable loss in mechanical properties due to thermal exposure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.