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Purpose: This study aims to investigate the compression characteristics of the 3D-printed polylactic acid (PLA) samples at temperatures below the glass transition temperature (Tg) with varying strain rates and develop a thermo-mechanical viscoplastic constitutive model to predict the finite strain compression response using a single set of material parameters. Also, the micro-mechanical damage processes are linked to the global stress–strain response at varied strain rates and temperatures through scanning electron microscopy (SEM). Design/methodology/approach: Tg of PLA was determined using a dynamic mechanical analyzer. Compression experiments were conducted at strain rates of 2 × 10–3/s and 2 × 10–2/s at 25°C, 40°C and 50°C. The failure mechanisms were examined using SEM. A finite strain thermo-mechanical viscoplastic constitutive model was developed to analyze the deformations at the considered strain rates and temperatures. Findings: Tg of PLA was determined as 55°C. While the yield and post-yield stresses drop with increasing temperature, their trend reverses with an increased strain rate. SEM imaging indicated plasticizing effects at higher temperatures, while filament fragmentation and twisting at higher strain rates were identified as the dominant failure mechanisms. Using a non-linear regression analysis to predict the experimental data, an overall R2 value of 0.98 was achieved between experimental and model prediction, implying the robustness of the model's calibration. Originality/value: In this study, a viscoplastic constitutive model was developed that considers the combined effect of temperature and strain rate for FDM-printed PLA experiencing extensive compression. Using appropriate temperature-dependent modulus and flow rate properties, a single set of model parameters predicted the rise in the gap between yield stress and degree of softening as strain rates and temperatures increased. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to experimentally investigate the large deformation compression characteristics of fused deposition modelling (FDM)-printed poly lactic acid (PLA), considering the combined effect of infill density and strain rate, and to develop a constitutive viscoplastic model that can incorporate the infill density to predict the experimental result. Design/methodology/approach: The experimental approach focuses on strain rate-dependent (2.1 × 10−4, 2.1 × 10−3, and 2.1 × 10−2 s−1) compression testing for varied infill densities. Scanning electron microscopy (SEM) imaging of compressed materials is used to investigate deformation processes. A hyperelastic-viscoplastic constitutive model is constructed that can predict mechanical deformations at different strain rates and infill densities. Findings: The yield stress of PLA increased with increase in strain rate and infill density. However, higher degree of strain-softening response was witnessed for the strain rate corresponding to 2.1 × 10−2 s−1. While filament splitting and twisting were identified as the damage mechanisms at higher strain rates, matrix crazing was observed as the primary deformation mechanism for higher infill density (95%). The developed constitutive model captured yield stress and post-yield softening behaviour of FDM build PLA samples with a high R2 value of 0.99. Originality/value: This paper addresses the need to analyse and predict the mechanical response of FDM print polymers (PLA) undergoing extensive strain-compressive loading through a hyperelastic-viscoplastic constitutive model. This study links combined effects of the printing parameter (infill density) with the experimental parameter (strain rate). [ABSTRACT FROM AUTHOR]

The present investigation highlights the development of a suitable and novel deep neural network-based learning model for accurately predicting the weld quality and mechanical properties of difficult-to-join dissimilar materials. Optimized experimental welding parameters in the available literature were taken as input in the deep neural network (DNN). A feed-forward and back-propagated DNN was developed to apprehend the high non-complexity present in friction stir welding of dissimilar materials. Unlike most neural networks, activation functions were altered between layers, effectively capturing non-linearity. The developed model was used to design an experimental condition for dissimilar friction stir welding of aluminum and titanium. Microstructural characterization of the weld was performed to comprehend the influence of parameters on the quality of the joint produced. A close correlation between the machine-learning model and the experimental results was established. The coefficient of determination R 2 between the predicted strength and the actual strength was 0.95 on the training dataset and 0.9 on the testing dataset. Similarly, R 2 between the predicted strength and the actual strength for the experimental dataset was 0.91, thus making the model suitable for predicting experimental conditions and corresponding mechanical properties with the highest accuracy for any unknown dissimilar friction stir welds. [ABSTRACT FROM AUTHOR]

Ball end magnetorheological finishing (BEMRF) is a process employed for precision finishing of flattened, intricate form complex 3D surfaces up to the nano level. Roughness of a surface determines the quality of results produced, which is usually measured by stylus-based instruments, with some optical methodologies also being adopted. These conventional methods when used for BEMRF tend to introduce errors in the part, which have to be removed from its fixture for measurement, and it is not feasible to remount it in the exactly same orientation again. Applications such as insular finishing (i.e., confined to a narrow region on the workpiece) demand the workpiece to be kept in the same orientation throughout, leading to requirement of measuring roughness in situ during the BEMRF process. A confocal sensor fits the requirement because of its confined design and lightweight capabilities. This work presents integration of a confocal sensor into the BEMRF setup for in situ roughness measurement. An initial Ra value of 352 nm was reduced to 289 nm just by insular finishing before finishing the full surface down to 78 nm in the case of a grinding error, from 420 nm to 342 nm by insular finishing, and finally down to 142 nm in the case of lapping error. [ABSTRACT FROM AUTHOR]

The potential use of copper as metallic mirrors in a wide variety of industries has put an onus on producing super-finished surfaces of copper of different shapes and sizes. However, with un-controlled normal forces in traditional finishing process, it is difficult to finish copper to the order of nanometers. Moreover the diamagnetic nature of copper limits its finishing capability by several advanced magnetic-assisted finishing methods. In this research work, a novel approach of finishing nonplanar copper mirrors is explored using magnetorheological polishing fluid. A finishing tool based on electromagnet with solid rotating core and having an efficaciously slotted tip has been developed and mounted on a five-axis CNC setup. The solid spindle core and multiple slots at the tip improve the magnetic flux density, essential for finishing of diamagnetic copper workpieces, and grip the polishing fluid firmly during the finishing operation. The electromagnet-based finishing tool also aids in in-process control of finishing forces acting on the copper workpiece. During the finishing process, forces acting on the workpiece were recorded using dynamometer and analyzed to understand the material removal mechanism and the process physics associated with it. Two nonplanar copper workpieces (convex and concave samples) were finished using the new tool to produce mirror-like reflective surfaces. In two finishing cycles with varying magnetizing current, the surface roughness of two samples were reduced from initial values of 120.1 and 129.2 nm to final values of 40.3 and 43.2 nm for convex and concave samples respectively. [ABSTRACT FROM AUTHOR]

Ball end magnetorheological finishing (BEMRF) is a novel method for nanofinishing of ferromagnetic as well as nonmagnetic materials. With increasing demands of precision finished products in various markets, the quality of surface finish and production rate are of prime importance. For products having complex geometries, this need intensifies as the manual finishing methods are incapable of producing uniform finish throughout the complex geometry of the surface. This paper describes the finishing of 3D surfaces using five-axis CNC BEMRF process in a fully automated manner such that a uniform finish is obtained throughout the workpiece. This eliminates the labor-intensive efforts and the subjective errors involved in manual finishing operations and increases the production rate of the finished products. A customized five-axis CNC controller is developed that enables the sequential and precise control of motion as well as process parameters in the BEMRF machine. The magnetizing current which governs the forces responsible for finishing in BEMRF process is controlled in-process through CNC part program using a specially defined "E" code for magnetizing current. A dedicated graphical user interface is also developed in Visual C# for the control of BEMRF process, enabling the user to make use of BEMRF machine without going into the complexities of the system. Using the customized five-axis CNC controller, automated finishing of a freeform mild steel workpiece is done. The finishing results obtained by the automated five-axis BEMRF machine shows uniformly finished surface profile (up to order of nanometer) on the mild steel test specimen. [ABSTRACT FROM AUTHOR]

Fused deposition modeling (FDM) is among the extensively used and the most economical additive manufacturing processes. Currently, the surface finish obtained for FDM additive manufactured parts are not at par with the current industrial application. To overcome the limitation of high surface roughness of 3D printed parts, a novel finishing technique has been proposed which includes primary and secondary finishing processes. While facing and lapping has been used as primary finishing technique, the secondary finishing involves the use of ball end magnetorheological finishing (BEMRF) process. BEMRF process is an unconventional finishing process which utilizes an advanced approach to impart finish on magnetic as well as non-magnetic materials that may be flat or freeform in shape. This article presents the experimental and analytical study to finish a polylactic acid (PLA) workpiece material manufactured by FDM process and finished using the BEMRF technique. The surface roughness of the FDM component has been reduced from initial surface roughness Ra = 20 µm to final value of Ra = 81 nm by combined primary and secondary finishing processes. The effect of magnetorheological polishing (MRP) fluid's composition and finishing time is discussed and is followed by optimization of MRP fluid for maximum percentage reduction in surface roughness. [ABSTRACT FROM AUTHOR]

Ball end magnetorheological finishing is a unique process that utilizes a magnetically controlled ball of polishing fluid at the tip of the rotating tool to finish workpiece of different materials and shapes. The aim of this research is to study the effect of polishing fluid volume on finishing spot size and the surface finish associated with it. A magnetostatic simulation is done to find the variation of flux density in the working gap and on the workpiece surface. The maximum limit of the polishing fluid volume is selected on the basis of area of threshold magnetic flux density (minimum value required for finishing) region on the workpiece surface. The surface characteristics and the diameter of the finished spot are analyzed by varying the fluid volume. The surface obtained with high fluid volume is poorly finished and has scratch marks as the excess fluid flows out from the working gap and forms a thick ring at the periphery of the tool tip. Contrary to this, if the fluid volume is too less, then it merely rotates over the workpiece surface without causing any finishing action. An optimum range of fluid volume produces a good quality surface finish with constant finished spot size. [ABSTRACT FROM AUTHOR]

Ball end magnetorheological finishing is a unique process that utilizes a magnetically controlled ball of polishing fluid at the tip of the rotating tool to finish workpiece of different materials and shapes. The aim of this research is to study the effect of polishing fluid volume on finishing spot size and the surface finish associated with it. A magnetostatic simulation is done to find the variation of flux density in the working gap and on the workpiece surface. The maximum limit of the polishing fluid volume is selected on the basis of area of threshold magnetic flux density (minimum value required for finishing) region on the workpiece surface. The surface characteristics and the diameter of the finished spot are analyzed by varying the fluid volume. The surface obtained with high fluid volume is poorly finished and has scratch marks as the excess fluid flows out from the working gap and forms a thick ring at the periphery of the tool tip. Contrary to this, if the fluid volume is too less, then it merely rotates over the workpiece surface without causing any finishing action. An optimum range of fluid volume produces a good quality surface finish with constant finished spot size. [ABSTRACT FROM AUTHOR]

An electrically conducting 'organic-inorganic' composite material polyaniline Ce(IV) molybdate was prepared by incorporating electrically conducting polymer, i.e., polyaniline into inorganic precipitate of polyvalent metal acid salts i.e., Ce(IV) molybdate. The temperature dependence of electrical conductivity of this composite system with increasing temperatures was measured on compressed pellets by using a 4-in-line-probe dc electrical conductivity-measuring instrument. The values of conductivity lies in the semiconductor region, i.e., they are of the order of 10-10 S cm and obey the Arrhenius equation. The thermal stability of this composite material in terms of dc electrical conductivity retention was studied under isothermal and cyclic techniques and electrical conductivity of composite was found to be sufficiently stable under ambient temperature conditions. The dependence of the electrical conductivity prepared with different concentrations of aniline monomers, on the concentration of conducting phases i.e., polyaniline was showed that electrical conductivity increase followed the percolation threshold. [ABSTRACT FROM AUTHOR]

There was an unprecedented growth of SHP (small hydropower) in Japan during recent years because the government has provided a high FIT (USD 0.32/kWh) for SHP development projects of less than 200 kW. The public and private sectors are committed to harnessing this natural energy to achieve the renewable energy goal as well as to improve local communities social and economic conditions. This paper will discuss about renewable energy initiatives by a food corporation enterprise (FCOOP) based in Fukuoka prefecture of Japan to reduce their net carbon emissions. A detailed approach for social enterprises-based SHP development has been discussed which will be a role model concept for other social enterprises in Japan and in the world that are willing to reduce CO2 emissions. Also, this kind of project connects urban stake holders with local community where resources are available and it leads to development of the local community living standards. As a demonstrated example, a case study of a 20 kW SHP installed in Japan by a FCOOP has been discussed. [ABSTRACT FROM AUTHOR]

It has been proposed that mitochondrial dysfunction and excitotoxic mechanisms lead to oxidative damage in the brain of Huntington;s disease patients. We sought evidence that increased oxidative damage occurs by examining postmortem brain material from patients who had died with clinically and pathologically diagnosed Huntington's disease. Oxidative damage was measured using methods that have already demonstrated the presence of increased oxidative damage in Parkinson's disease, Alzheimer's disease, and senile dementia of the Lewy body type. No alterations in the levels of lipid peroxidation (as measured by lipid peroxides and thiobarbituric acid-malondialdehyde adducts) were found in the caudate nucleus, putamen, or frontal cortex of patients with Huntington's disease compared with normal controls. Similarly, there were no elevations in the levels of 8-hydroxyguanine or of a wide range of other markers of oxidative DNA damage. Levels of protein carbonyls in these tissues were also unaltered. Our data suggest that oxidative stress is not a major component of the degenerative processes occurring in Huntington's disease, or at least not to the extent that occurs in other neurodegenerative disorders. [ABSTRACT FROM AUTHOR]

Energy is the prerequisite for social and economic development of a community and country. In Japan, national government is promoting small hydropower (SHP) through a renewable energy policy by providing a high FIT price of 34 yen (≒0.32 US$/kWh) on energy generated from an SHP of less than 200 kW. Until now, the energy generation was controlled by national government agencies, but now independent power generation businesses are growing at the local community level in rural Japan. For the future growth of SHP, it is necessary to make electricity generation at the local community level. Therefore, these local communities will install and manage their renewable electricity by themselves. It will help to make the community self-sustainable and independent from the national government, and at the same time, it will also lead them to achieve the Sustainable Developments Goals (SDGs) target from community-based action. This paper aimed to discuss an SHP development business model in which local community will become the business owner of the SHP. It means "of the community, by the community and for the community". The community identifies their renewable energy potential and needs, they borrow money from the financial organization or banks, install the power plant and do necessary maintenance and management by themselves. The revenue earned by selling electricity is used to repay the loan, and the rest is used for community development directly (such as local roads construction, agriculture land improvements, community hall maintenance, waterways maintenance, welfare, etc.). This paper also discussed a community-based 50 kW SHP installed in Miyazaki prefecture of Japan as a case study. This SHP is one of the best examples of a community ownership model (Community-based business model). A detailed explanation from planning to investment has been discussed. The local community is getting approximately 112,000 USD per year by selling the electricity, and 162-ton CO2 is estimated to decrease yearly, which will support the achievement of SDGs. Finally, installing this kind of SHP in remote areas will provide managerial skills to the local community directly, plant operation knowledge, and education to local students. Local communities learn the problem-solving skills, which lead them to solve the local problem on a community level by themselves. [ABSTRACT FROM AUTHOR]