bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Moisture Absorption on the Tensile and Flexural Properties of Glass Fiber Reinforced Composite Materials
Authors: Prakash Raghu V. , Viswanath Vishnu 
Published: January 2022

Abstract
The use of Glass fiber reinforced plastics (GFRP) in underwater applications has been increasing in recent times, due to its superior durability and chemical stability in corrosive environments compared to metals. However, penetration of moisture in to the polymer matrix can adversely affect the mechanical properties of composite materials. In this study, the effect of exposure to plain water and simulated sea water (3.5% by weight NaCl salt) water on the mechanical properties of GFRP specimens has been analyzed. Tensile and three point bend tests were conducted on composite specimens with different moisture contents to characterize the mechanical degradation due to moisture absorption. Gravimetric tests were conducted on specimens to calculate the moisture absorption parameters. The results indicate that plain water is absorbed at a faster rate compared to salt water. Using these parameters, a transient moisture diffusion model was developed using commercial finite element software ABAQUS®. The results of tensile and three point bend testing indicate that both tensile and flexural properties of glass fiber reinforced epoxy composites degrade with exposure to plain water and salt water. Further, a coupled hygro-mechanical model was developed in ABAQUS® and the simulation results were compared with actual test results. Scanning electron Microscopy was used to examine the fracture surface of failed specimens. The cause for mechanical degradation seems to be the deterioration of fiber-matrix interface due to the penetration of water molecules.
A Study on the Performance of Solar Driven Absorption Chiller in Terms of Coefficient Of Performance and Exergy Efficiency
Authors: Nitsas M. T. , Koronaki I. P. 
Published: January 2022

Abstract
Thermally driven chillers also known as sorption heat pumps have drawn considerable attention in recent years. They can be divided into two main categories: absorption (liquid-vapor) and adsorption (solid-vapor) systems. Even though sorption cycles have relatively lower coefficient of performance compared to conventional refrigeration cycles, however they prevail in terms of heat source, electric consumption for moving parts, mechanical wear etc. In order to enhance their environmentally friendly operation, sorption chillers can be driven by solar power.
In this study a solar driven absorption chiller which utilizes evacuated tubes collectors and intermediate heat exchanger is simulated. The model’s governing equations derived from the energy balance on each component of the system are solved numerically. The COP, the solar COP, the overall exergy efficiency, the required collectors’ surface and the collectors and tank normalized cost are calculated for various heat source temperatures. Moreover, all calculations are repeated for various values of heat exchanger effectiveness in order to determine the maxima and minima of the system’s operation. It is proved that the maxima are reached at lower inlet temperatures for higher values of the intermediate heat exchanger.
A Comparative Study of Various Deep Learning Techniques for Spatio-Temporal Super-Resolution Reconstruction of Forced Isotropic Turbulent Flows
Authors: Venkatesh T. S. Sachin , Srivastava Rajat , Bhatt Pratyush , Tyagi Prince , Singh Raj Kumar 
Published: January 2022

Abstract
Super-resolution is an innovative technique that upscales the resolution of an image or a video and thus enables us to reconstruct high-fidelity images from low-resolution data. This study performs super-resolution analysis on turbulent flow fields spatially and temporally using various state-of-the-art machine learning techniques like ESPCN, ESRGAN and TecoGAN to reconstruct high-resolution flow fields from low-resolution flow field data, especially keeping in mind the need for low resource consumption and rapid results production/verification. The dataset used for this study is extracted from the ‘isotropic 1024 coarse’ dataset which is a part of Johns Hopkins Turbulence Databases (JHTDB). We have utilized pre-trained models and fine tuned them to our needs, so as to minimize the computational resources and the time required for the implementation of the super-resolution models. The advantages presented by this method far exceed the expectations and the outcomes of regular single structure models. The results obtained through these models are then compared using MSE, PSNR, SAM, VIF and SCC metrics in order to evaluate the upscaled results, find the balance between computational power and output quality, and then identify the most accurate and efficient model for spatial and temporal super-resolution of turbulent flow fields.
Elliptical Machines Using Adjustable Linkages
Authors: Naif Ali Safdar , Zhou Hong 
Published: January 2022

Abstract
Elliptical machines are exercising or training machines that are used to imitate walking, jogging, running or climbing exercises. Different from treadmill machines, elliptical machine users never leave their feet away from the pedals, which reduces the pressures to the ankle, knee, and hip joints, and significantly lowers the impact injuries of users’ joints. The configurations of the elliptical motion commonly mimic the natural paths of the ankle, knee, and hip joints for walking, jogging or running, which further decreases the strains and stresses on users’ joints. In addition to low joint impact, another feature of elliptical machines is their integrated leg and arm movements that provide the dual lower and upper body exercises. Users of elliptical machines not only exercise their legs, but also push and pull the handlebars to strengthen their arms. Unlike treadmills, ellipticals are self-powered by user-generated motion and have no need for motor and belt conveyance. The closed trajectories of elliptical machines are generated through their linkages. The shapes and sizes of the closed trajectories depend on the linkage dimensions. The trajectory of an elliptical machine needs to meet the requirements for different exercises, and various short and tall people with a wide range of arm or leg sizes. If an elliptical machine has fixed linkage dimensions, its elliptical trajectory has only one shape and size, which does not provide flexibility. In order for an elliptical machine to have flexibility, its linkage has to be adjustable. Adjustable linkages are more difficult to design than linkages without adjustability. This research is motived by surmounting the challenges facing elliptical machines. Different types of elliptical machines (rear, front, and central drives) without and with adjustability are analyzed. Their elliptical output motions are simulated. The research results will provide useful guidelines for developing and promoting elliptical machines.
Acceleration Mechanism of Intergranular Cracking of SUS316L Under Creep-Fatigue Loading at Elevated Temperatures
Authors: Takahashi Yukako , Suzuki Ken , Miura Hideo 
Published: January 2022

Abstract
Austenitic stainless steels are used as heat-resistant steels because of their high corrosion resistance and strength at elevated temperatures. However, the fracture life of alloys under creep conditions at elevated temperatures was found to significantly decrease due to the acceleration of intergranular cracking. The drastic reduction in fracture life was caused by a change in the crack propagation path from transgranular to intergranular. It was also found that intergranular cracking occurred only by the interaction between temperature and mechanical stress even when the specimen was not in a corrosive environment. However, the mechanism of the acceleration of intergranular cracking is still unclear. Therefore, in this study, an intermittent creep and creep-fatigue tests were applied to SUS316L to visualize the degradation process of their micro textures. The degradation process of the crystallinity around grain boundaries in the alloy was investigated by EBSD (Electron Back-Scatter Diffraction) analysis. KAM (Kernel Average Misorientation) and IQ (Image Quality) value were used for the evaluation of the crystallinity and local plastic deformation, in other words, the total density of dislocations. It was found that the accumulation of fine voids started to appear around grain boundaries in the early stage of the lifetime and all the initial cracks were found to appear around grain boundaries perpendicular to the loading direction of the applied stress. It was confirmed that the intergranular cracks started to occur when dislocations accumulated around a grain boundary and the difference in the dislocation density between nearby grains reached a critical value. As a result of the analysis of the Schmid factor, it was confirmed that cracks occurred around grain boundaries composed of a grain with large absolute value of Schmid factor and the large difference in the Schmid factor with the nearby grain.
Influence Of Laser Induced Plasma on Material Removal in Micro-Drilling Underwater
Authors: Zheng Changlong , Shen Hong 
Published: January 2022

Abstract
Water-assisted ultrafast laser processing was proposed to solve the problem of surface quality in metal during laser micro-hole drilling. The percussion drilling process with different single pulse energies was tested under 10 mm water layer and in air. The morphologies of the laser induced plasma (LIP) were observed and recorded. The drilling depth and micro-hole radius were characterized by microscope and 3D surface profilometer. Experimental results show that the debris, spatter recast or others caused by the laser energy deposition are quickly transferred away, but the material removal performance caused by LIP under water is different from that in air. It is noteworthy that the drilling depth has been significantly reduced at all pulse energies owing to the shielding effect of water and LIP. But the micro-hole radius has increased several times after a sufficient pulse number, which is attributed to the defocusing effect of LIP. In order to explain the mechanism of underwater ablation characteristics, a model combining the LIP formation and evolution was developed to analyze the energy attenuation effect and the beam refraction effect by LIP underwater. Moreover, the annular morphology at the hole bottom under high pulse energy can also be explained by these two effects of LIP.
Establishment of the Off-Center Embedded Crack Stress Intensity Factor Database for Probabilistic Risk Assessment Based on Universal Weight Function
Authors: Xu Tongge , Ding Shuiting , Li Guo 
Published: January 2022

Abstract
Probabilistic failure risk analysis is important in recent development of airworthiness. In the fracture mechanics module of probabilistic failure risk analysis, efficient and accurate stress intensity factor (SIF) solutions are vital. Universal weight function (UWF) is a method that has a remarkable computational efficiency and high accuracy in SIF calculation. However, the concrete coefficients in the UWF remain unknown, and the rules of the geometric parameters and these coefficients have not been clarified. This limitation hinders the subsequent application of the method. This article discusses general off-center embedded cracks. The response surface method (RSM), as a means of database establishment, is used to construct the relations between the coefficients in the UWF and geometric parameters. The mean absolute percentage errors of the SIFs between UWF and finite element method are less than 4% within a certain range. Gaussian process regression is adopted to better fit the data, especially when the crack is near the plate boundary and the R-square is over 0.96. In addition, the effect of the offset distance on SIFs is discussed for a certain embedded crack in a given plate. Results show that changes in the SIFs are dependent on the plate boundary in the uniform stress field. However, stress predominates the changes in the SIFs when the crack is not very close to the plate boundary in the nonuniform distributed stress fields. The databases and discussion that followed can provide some reference and inspiration for further research.
EBSD Investigation of Ti6Al4V Alloy Processed by Constrained Groove Pressing and Heat Treatment
Authors: Bhardwaj A. , Gohil N. , Sharma A. , Lakshman Rao K. , Gupta A. K. , Kumar S. S. Satheesh 
Published: January 2022

Abstract
Ti6Al4V sheet metal has found significant applications in the aerospace, defence and biomedical sectors due to its high strength-to-weight ratio and excellent corrosion resistance. The texture plays an important role in tailoring the mechanical properties which can be modified via thermo-mechanical processing. Constrained groove pressing (CGP) is a well-known sheet metal severe plastic deformation (SPD) technique for grain refinement and enhancement of mechanical properties. In this work, high temperature CGP has been performed successfully on Ti6Al4V alloy at 550°C followed by heat treatment at 500°C. CGP and heat treatment led to grain refinement and formation of submicron size grains. The inverse pole figure (IPF) reveals the decrease in texture intensity of basal planes from 5.9 to 4.5 in CGPed Ti6Al4V. Heat treatment further reduced the IPF texture intensity to 3.5. Enhancement in mechanical properties such as YS, UTS and microhardness is also observed. Although slight enhancement is observed in yield strength, ultimate tensile strength has been improved by 21% after CGP and heat treatment. Up to 20% improvements in microhardness have also been observed in processed samples. CGP and heat treatment together can serve as an efficient technique for tailoring microtexture and mechanical properties of Ti6Al4V and other HCP alloys.
Conventional and Advanced Exergetic Analysis for the Combined Cycle of Power Plant With Gas Turbine of a Refinery
Authors: Fajardo Juan , Guette Dawing , Barreto Deibys , Cardona Camilo , Baldiris Ildefonso 
Published: January 2022

Abstract
This article shows the results of the performance study of a combined cycle plant made up of a Siemens STG-800 gas turbine and a MACCHI heat recovery boiler (HRSG) designed to produce 47.5 MW of electricity and 81908 kg / h of steam operating under ISO conditions (15 ° C and 60% relative humidity and 1 atm), the system is part of the steam and electric power generation section of a crude oil refinery in the city of Cartagena de Indias.
The objective of this research is to quantify the real inefficiencies in each of the equipment applying conventional and advanced exergetic analysis, to achieve this the investigation has been ordered as follows: first, the basic thermodynamics at the equipment boundaries is defined, define performance parameters that compare the adjustment of the thermodynamic model with the values provided by the manufacturer, the rate of exergy destruction and exergy efficiency are obtained from conventional analysis, advanced exergetic analysis allows obtaining avoidable, unavoidable, endogenous, exogenous exergies and the combined, finally, the mexogenous exergetic analysis allows to know the amount of energy that is lost due to the interactions between the equipment.
The thermodynamic model is adjusted with an average error of 2% using design KPIs such as net power, heat rate and thermal efficiency, it was obtained that the exergy destruction reaches 83.5MW, 15% is avoidable and the 8% is avoidable endogenous, the mexogenous analysis shows that inefficiencies in the compressor refer to all equipment, by focusing efforts on improving its conditions, up to 25% of the total exergy destruction can be recovered.
Do Long Aorta Branches Impact on the Rheological Properties?
Authors: Al-Rawi Mohammad , Al-Jumaily Ahmed , Belkacemi Djelloul 
Published: January 2022

Abstract
Current studies dispute the effect of the aorta geometry and branches on how the hemodynamics parameters develop along the branches in 3D models. In constructing and modelling the aorta geometry, it is necessary to incorporate the different lengths of the bifurcation and branches. Previous studies modelled the aorta with simplified assumptions (idealized model) which gave rise to some differences between the model and clinical outcomes. However, these differences are minimal, and the results can still be validated against clinical trials. The Computational Fluid Dynamics (CFD) methods can also accurately simulate the stresses affecting the artery wall and the dynamic behavior of the blood flow in its pulsatile form. Therefore, the outputs from CFD analysis can be used to reduce the risk of disease complications and enable a better understanding of the effects of hemodynamic stresses. A comparison of the behavior of the Time-Average Wall Shear Stress (TAWSS), Oscillatory Shear Index (OSI), and Relative Residence Time (RRT) against two lengths of bifurcations and in the presence of Non-Newtonian Power Law blood flow properties is presented in this work. This study investigates the cardiac cycle transient analysis using the Laminar inviscid flow in FLUENT, ANSYS 2020R2. The results are promising and give ample support for further development of new diagnostic tools based on the relationship between the Wall Shear Stress (WSS) derivatives: TAWSS and the OSI and the branches lengths.
Transitional Flow and Heat Transfer on the Pressure Surface of a C-D Compressor Blade
Authors: Katiyar S. , Sarkar S. 
Published: January 2022

Abstract
A large-eddy simulation (LES) is used here to investigate the laminar-turbulent transition on the pressure surface of a controlled-diffusion (C-D) compressor stator blade at a Reynolds number (Re) of 2.1 × 105. The objective of the present study is focused upon the transition mechanism on the pressure surface and associated heat transfer. Flow features appear laminar at the beginning, followed by the undulation of velocity fluctuations, attributing to the development of elongated streamwise streaks at 27% of the chord. These streaks undergo breakdown at the mid-chord region via a secondary instability. Resolved flow structures also elucidate the formation of abundant small-scale eddies via the appearance of hairpin structures an increase of the turbulent heat flux. The decay of these structures occurs as flow further evolves downstream, attributing to local flow acceleration.
Numerical Simulation of the Effect of Bonded Patch Repair on the Internal Stress Distribution
Authors: Sreenath A. M. , Prakash Raghu V. 
Published: January 2022

Abstract
Composite materials are used extensively in high-performance applications due to their superior mechanical properties and lower density. The composite materials are susceptible to impact damage, and repair of the damaged components is inevitable. Bonded patch repairs are used extensively in the aerospace industry to repair the low-velocity impact damage. Low-velocity impact on quasi-isotropic, carbon fiber reinforced polymer (CFRP) composites was numerically simulated using finite element analysis ev (FEA). Damage evolution and the failure of the repaired composite laminates under a monotonous uniaxial loading were evaluated using FEA for various patch repair configurations. Load displacement characteristics of pristine, impacted, and repaired specimens were simulated. The analysis indicates that impacted specimen has a lower load-bearing capacity than the pristine one. The specimen with the double-patch displayed superior load-bearing capacity and stiffness compared to the other repair configurations among the repaired specimens. Variation of stress and strain along the longitudinal and transverse directions were evaluated. The stress distribution in the pristine specimen was more uniform than the impacted one. The peak strain values of impacted and repaired specimens were significantly higher than that of pristine ones at the impacted location. A reduction of stress at the impacted location was noticed for the impacted and repaired specimen compared to the pristine one. The current study indicated comparable strength and rigidity for the repaired component and the pristine component. However, the localized stress distributions observed for the pristine, impacted, and repaired specimens were significantly different even though the overall load-bearing characteristics were comparable.
Load Path Analysis and Design for Stiffness of Bolted Electro-Magnetic Mass Drivers
Authors: Goyal Gaurav , Mehta Nagendra Kumar , Khatait Jitendra Prasad , Mukherjee Sudipto 
Published: January 2022

Abstract
Electro-magnetic mass drivers (EMD) are linear payload accelerators at the forefront of multi-physics technology that find use in various applications. In a homopolar variant of EMD, two electrically conductive rails are clamped at a set separation apart in an electrically insulating chamber formed of housing and elastic support. Preloaded bolts and clamping plates are used to minimize the rail deformation during operation. In literature, EMD is treated similarly to a T-shaped, bi-material bolted joint subjected to tensile loading. The difference is that, unlike in a bolted T-joint, two load paths are available during the bolting phase, and bolt preload gets distributed between housing and elastic support. However, during operation, the housing is not subjected to tensile loading. Therefore, the purpose of bolt preload taken up by the housing must be analyzed. This issue has not been addressed in any literature concerned with the design of bolted EMD. The load path in the initial clamping state and that in operation as a function of housing height H and clamp separation distance S is determined. It is observed that stiffness increases from 70.6 MN/m to 231 MN/m as H/S decreases. However, there is a slight decrease in EMD stiffness when the housing carries no preload. Reasons in support of eliminating the housing are provided, and consequences are discussed. The clamp plates suffer adverse bending effects when housing is removed. The EMD section is altered, and the material is aligned in the load path direction to reduce the bending effect of loading. Shape-optimized clamping plates provide improved stiffness while minimizing the peak stress levels by 36%, and EMD section mass is reduced by 10%. The analysis and design method proposed in this paper provides a theoretical basis for designing ultra-stiff and lightweight EMD.
Evaluation of Hydraulic and Thermal Characteristics of Interconnected Parallel Flow Mini Heat Sink
Authors: Uddin Md Wasi , Ayon Hassan Shahriar , Mehrab Tahmid Mohammad , Sifat Najmus Saquib 
Published: January 2022

Abstract
This study represents a numerical investigation of the compatibleness of mini-channel heat sink with high heat dissipation rate and the fluid flow patterns inside mini-channels for integrating secondary channel (or interconnector). A novel shape, rectangular fin with rounded ends, mini-channel heat sink was proposed to compare with the thermal performance of rectangular finned and oblique finned mini-channel heat sink. In this study, hydrodynamic characteristics of water as coolant was considered in the single-phase regime, and the flow was considered under laminar flow conditions at Reynolds numbers range of 150 to 1050 with a constant heat flux of 200 KW/m2 at the bottom surface of the mini-channel heat sink. Thereafter, a Performance Evaluating Criteria (PEC) was implemented for all cases to compare with the conventional mini-channel heat sink. The results showed that the overall Nu number for newly proposed rectangular fin with rounded ends shape mini-channel heat sink increases slightly with Re number when compared with the conventional mini-channel heat sink. The slight increment of Nu number was recorded at Re = 1050 for the newly proposed mini-channel heat sink up to ∼8% as compared to the conventional parallel flow mini-channel heat sink.