bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Micro-Mechanical Constitutive Model to Predict Hygrothermal Aging of Cross-Linked Polymers
Authors: Bahrololoumi Amir , Ghaderi Aref , Shaafaey Mamoon , Dargazany Roozbeh 
Published: January 2022

Abstract
A multi-physics material model is presented to describe the effects of temperature, oxygen, and humidity on the constitutive response of cross-linked polymers. The effect of hygrothermal damage on the mechanical integrity of the polymer matrix can be considered as the result of damage accumulation of two independent aging mechanism namely, i) thermo-oxidative, and ii) hydrolytic aging. In order to capture the mutual effects of thermo-oxidative and hydrolytic aging, an assumption has been made that each of the aging phenomenon can be superposed to each other. In fact, each of them works independently and as a result, they can compete with each other. Utilizing the theory of network decomposition, all phenomena and their correlation were modeled and thus, the strain energy function of the polymer matrix is written with respect to four independent mechanisms, i) the shrinking original matrix that has neither been attacked by water nor oxygen, ii) conversion of the first network to two new network due to the reduction and formation of cross-links, and iii) energy loss from network degradation due to attack of the water molecules to polymer active agents. Moreover, the proposed model is micro-mechanically based and is mainly relevant on thin samples due to our underlying assumption of homogeneous diffusion of oxygen and water throughout the matrix. The model has been validated against extensive data-sets obtained from experiments we specifically designed for concept validation.
Hydrokinetic Turbine Performance and Wake Analysis Using a Data-Driven Actuator Line Model
Authors: Bowman J. , Bhushan S. , Burgreen G. , Dettwiller I. 
Published: January 2022

Abstract
A data-driven actuator line model was derived using a blade-resolved turbine DES simulation. Pressure and viscous forces were extracted from the blades and incorporated into an actuator line model framework implementation in OpenFOAM. The data-driven actuator line model attempts to address the limitations of the currently available actuator line model. The development of the data-driven actuator line model transformed the high-fidelity blade-resolved force data into force coefficients. The result is a finely tuned model that can replicate the turbine performance of the blade-resolved model for a fraction of the computational expense. The comparison between the data-driven actuator line model and the actuator line model reveals that at high tip speed ratios the actuator line model over predicts the thrust and power coefficient. The author discusses the limitations of the data-driven actuator line model in its current form and how the model will be advanced.
A Mixed-Mode Analysis of Two Parallel Non-Aligned Cracks in a Large Flat Plate Subjected to Remote Tension
Authors: Perl Mordechai , Levy Cesar , Ma Qin 
Published: January 2022

Abstract
The interaction of multiple cracks plays an important role in cracking behavior resulting from plant degradation, especially in the case of stress corrosion cracking (SCC) and fatigue. The Fitness-for-Service (FFS) standards require the characterization of multiple cracks to determine the structural integrity of cracked components using fracture mechanics concepts. Multiple cracks must first be classified as to whether they are located on the same cross-section plane for alignment purposes. Various codes and standards have been found to have differing crack alignment rules. Using these rules and standards, two parallel, non-aligned cracks have been previously simulated by various investigators in Fitness-for-Service evaluations based on Linear Elastic Fracture Mechanics (LEFM). However, all these studies focused on mode I fracture of cracks. The present study focuses on mixed-mode interaction between two parallel, non-aligned cracks subject to remote uniform tension. A parametric study of the dependence of the mixed-mode Stress Intensity Factors (SIFs), and the energy release rates (ERRs) of two parallel cracks on the intra-horizontal and vertical separation distances is conducted. The evaluation of the SIFs and ERRs was accomplished for a wide range of the normalized intra-vertical separation distances of H/2a1 = 0.4∼2, and normalized intra-horizontal separation distances of S/2a1 = −0.4∼2. It is found that for certain crack configurations mixed-mode analysis might be significant and should be carefully considered in the application of Fitness-for-Service rules.
Modeling the Effects of Surface Roughness Variations on Pressure Drop in Flow Minichannels
Authors: Alghamdi Abdulaziz , Alfaiz Suliman , Alsulami Marwan , Mortazavi Mehdi , Niknam Seyed A. 
Published: January 2022

Abstract
Research efforts are underway to understand the inherent surface roughness in additive manufacturing (AM) particularly in powder bed systems. It has been acknowledged that powder bed systems may suffer from layer variation due to sputtering effects or recoating mechanism. This lack of layer uniformity has negative effects on surface roughness. This research investigates the effect of layer variation on minichannels surfaces through which fluids flows for heat transfer applications. For this, a number of long stainless-steel flow channels with various cross sections were fabricated using selected laser melting technology. In addition, an experimental setup was developed to measure the pressure drop for different gas flow rates. This study provides insights into the relationship between surface roughness deviation along minichannels length and the pressure drop in the flow minichannels.
Virtual Surface Roughness Measurements From an ‘As-Built’ Virtual CAD Model for Bead Based Deposition Additive Manufactured Components
Authors: Kalami Hamed , Urbanic Jill 
Published: January 2022

Abstract
All additive manufacturing processes have a characteristic ‘staircase’ layering effect at the boundaries, as this process family fabricates components by stacking layers upon each other. This effect is noticeable at shallow angles and where there is significant surface curvature. Measuring the surface roughness from virtually modeled beads of an additive manufactured product helps to have an initial estimation of the surface quality during process planning. In this paper, three techniques are developed to measure the profile surface roughness from an ‘as-built’ CAD model generated from theoretical bead geometries. Two CAD files are needed as inputs: a model of the ideal part geometry and the model created based on the bead geometry, percent bead overlap, and the fill strategy. Developed solutions are projection, projection normal-line distance, and elongation method.
The results are verified by analytical calculations with less than one percent variation. The samples include flat faces, a curved surface, and an S shape (a double arc). Sensitivity studies for evaluation length are conducted as well.
Estimation of the surface roughness values before a component is being built will help designers to evaluate how much material stock is needed to be added if subsequent machining processes are required. Therefore, it is anticipated that this research will assist process planners in developing their desired build solutions for both AM and hybrid manufacturing.
Molecular Dynamic Simulation of Diffusion in the Melt Pool in Laser Additive Alloying Process of Co-Ni-Cr-Mn-Fe High Entropy Alloy
Authors: Farias Mathew , Hu Han , Zhang Shanshan , Li Jianzhi , Xu Ben 
Published: January 2022

Abstract
High entropy alloys (HEAs) can be manufactured in many conventional ways, but it becomes difficult of fabricating heterogeneous materials and structures. Selective Laser Melting (SLM) method generally melts pure elemental powders or prefabricated alloy powders without alloying process. In-situ alloying in SLM, which is also called Laser Additive Alloying (LAA), using pure elemental powders becomes a promising method for creating HEA with heterogeneous structures. However, the effect of the diffusion of elements in the molten pool on the formation of HEA remains unclear. In this paper, the well-discussed Cantor HEA was studied in an in-situ alloying situation, where pure elemental powders (Co, Cr, Mn, Ni, Fe) distributed on a powder bed were irradiated by laser and were subsequently allowed to cool back to room temperature. The diffusion of specific elements, with respect to their original clusters, was tracked via Mean Square Displacement (MSD) as well as the final composition of key locations. Our model was verified by showing a good agreement with the overall average diffusion rates of each element in the Cantor HEA qualitatively in other works from literature. Results initially showed that as the energy density increases, better diffusion was observed through a pixel overlay analysis about the mixing of different elements. The best-case scenario of diffusion from the pixel overlay map indicated a strong presence of 3 to 4 elements after the laser scanning. Given the conditions in the MD simulation, there was no apparent segregation of elements during the alloying process. In addition, we also conducted a simulation by implementing a 0.03 nm/ps laser scanning in a meander 2-track scan in order to completely melt the powder bed. After cooling and equilibration, Polyhedral Template Analysis was applied to analyze the crystal structure of the solidified powder bed in the presence of increasing components. When the powders of Cantor HEA were alloyed using LAA approach, all elements experienced a complex diffusion behavior, elements like Cr also experienced a relatively rapid diffusion compared to other elements. Despite this, Cr only diffused for a short period and diffused minimally during the in-situ alloying process. The analysis of element-specific behavior, such as diffusion, can provide a framework for the LAA production of HEA. This MD study provides a detailed analysis about the effect of diffusion on the formation of HEA system if in-situ alloying is adopted, the findings of this study can be used to guide the material design and the appropriate parameters for manufacturing process of new HEAs. This study can also be extended to analyze the effect of diffusion on the thermomechanical properties of HEAs.
Product Design Journey: Novel Tool Changer
Authors: Chagouri Tariq , Al-Darwish Fawziya , Sharif Abdulrahman , Al-Hamidi Yasser 
Published: January 2022

Abstract
This paper presents a product design journey for a group of undergraduate sophomore university students as part of their Geometrical Modeling for Mechanical Design course. The course project aimed to help students to use basic process of engineering design, use a computer aided design (CAD) tool to model their product, engineering analysis tools to evaluate their design, and understand the need for prototyping.
The students started their journey with ideas tournament to select an outstanding idea which would be of a great market value. After intensive consultation with the course instructor and implementing a stringent selection criterion, students chose to design a novel tool changer that incorporates two different grippers with varying performance specifications. The students followed a systematic approach that got them involved in doing very thorough literature review in which they classified most of the grippers and tool changers available in the market. They also sensed how their product could be demanded in industrial applications where the utilization of a single gripper would demonstrate inconvenience. Such industrial sectors would be surgical operations where the operator would require a gripper to hold the flesh and another for cutting or stitching or any other surgical tasks, another application would be welding where a gripper is required to hold the metallic parts and another for performing the welding task. The utilization of two grippers with various designs would also expands the range of tasks that could be accomplished, for instance, a lot of manufacturing facilities requires performing internal and external gripping operations as is the case in car manufacturing, the tool Cha design introduced in this paper would facilitate such tasks by enabling the capability of simultaneous utilization of an internal and an external gripper. This design will also be beneficial in the current global pandemic where human interaction would be a genuine menace.
The systematic approach helped the students also to establish target specifications for their product, decompose the product into different subsystems and explore the whole design space of each subsystem. All concept solutions (fragments) of all subsystems were then compiled in a combination table to select the product final concept and in turn finalize product specifications.
After selecting the preferred combination of concept solutions, a CAD model was established to run the necessary simulations prior to realizing it into a tangible product through either additive manufacturing (3d printing) or subtractive manufacturing (milling, turning, or EDM).
Realizing that many aspects of the product design journey cannot be covered in this course, the students were eager to see how other upcoming courses would help in letting them to carry out more sophisticated tasks in the product design process.
Characterization and Optimization of a Lower Extremity Exoskeleton Device for Leg Muscle Rehabilitation
Authors: Elahi Haadi , Perez Marvin , Viswanathan Vimal , Vemuri Aayush , Madireddy Indeever , Zaidi Sohail 
Published: January 2022

Abstract
Robotics-assisted rehabilitation has been one of the popular research areas in recent years. The increase in the elderly population and sports-related injuries, the high cost of physical therapy, and advances in Mechatronics have been crucial factors driving this research. The objective of this project is to provide supplementary motion in knee extension and flexion for lower extremity rehabilitation. The device incorporates pneumatic muscles that closely recreate human muscle movement and surface electromyography (EMG) sensors to activate motions. Recently, tests were carried out to characterize the unit and compare the performance of the pneumatic muscles against the theoretical values provided by the manufacturer. Results indicate limitations in the range of operation of the device, mainly due to the limited contraction ratio of commercially available fluidic muscles. Overall, the project provided vital insights that may be useful for researchers developing exoskeleton devices for rehabilitation. This paper reports the characterization of the EMG sensors and pneumatic-based fluidic muscles used in the ABJ system. To address the shortcomings of the commercially available fluidic muscle, custom muscles are designed and characterized. The results provide significant insights for a redesign of the device. Based on the characterization data, a redesign is proposed for a future generation of the device.
Corrosion Monitoring and Mitigation in Reinforced Concrete Structures Using Novel 3D-Printed Valves and Internet-of-Things Approach
Authors: Escarcega Mario , Bradley Savannah , Campos Gabriel , Randall Parker , Strebe Luke , Momeni Hamed , Ebrahimkhanlou Arvin 
Published: January 2022

Abstract
Reinforced concrete corrosion can be monitored by the acoustic emissions produced by transient mechanical waves of corrosion and damage events. This study aims to use 3D-printed one-way valves to relieve the corrosion-induced internal pressure on concrete structures. This valve is designed in such a way that it can be simply installed to existing structures to increase corrosion resistance in the concrete structure and extend the service life. The impressed current technique is a common technique used to rapidly corrode reinforced concrete samples. To corrode the concrete samples, current was passed through the internal steel strand and copper mesh. This study also investigated the use of an Internet-of-Things device to continuously monitor corrosion in steel-reinforced concrete samples in order to determine the effectiveness of the designed valves. Pressure testing revealed that the designed valves were against backflow and cracked at very low pressure. It was ideal that the valves cracked at a lower pressure so as to release pressure constantly while preventing further corrosion in backflow. This type of valve will prevent reinforced concrete surface cracking and extend the service life of concrete structures by releasing internal pressure build-up without allowing foreign materials to further corrode the steel reinforcement.
Effect of Morphological Changes in Reused AlSi10Mg Powder on the Formation of Defects in Components Manufactured by SLM
Authors: Orozco Sandoval María Guadalupe , Hinojosa Rivera Moisés 
Published: January 2022

Abstract
The continuous reuse of powder in powder bed additive manufacturing techniques is a common practice, however, research focused on morphological changes in the powder as reuse cycles accumulate is relatively scarce, especially if we consider that the quality of the powder is fundamental to obtain components that meet the requirements of demanding industries such as aeronautics, automotive and medical. The continuous reuses of powder offer two important advantages which are reducing manufacturing costs and waste, both fundamental to the continuity of companies. The repercussions of uncontrolled reuse of powder without understanding the impact on final parts is a growing problem for a common practice. The present study focuses on the morphological changes in the particles of reused powder in five cycles of AlSi10Mg and the resulting effects on the components manufactured by the Selective Laser Melting (SLM) technique, varying manufacturing parameters defined as critical by the literature. Scanning Electron Microscopy (SEM) images of the powder were evaluated following the Zingg methodology, categorizing the particles into four shapes: sphere, disc, rod and blade. 80% of the virgin powder particles showed a spherical morphology, unlike the powder reused in five cycles, where this percentage is reduced by 8%. Elongated particles (blade and rod shape) showed an 11% increase in reused after five cycles. The variation in manufacturing parameters had an impact on the relative density of the components manufactured with reused powder, obtaining a maximum value of 94.5% and a minimum of 86%. The variation in the surface defects of the components was mostly influenced by the power of the laser, the scanning speed and the location of the component in the powder bed, where the sample set with the highest percentage of surface defects was where a laser power of 200 W and a scanning speed of 1000 mm/s and the gas flow was lower due to its location in the powder bed. The results allowed to establish the critical manufacturing parameters for components manufactured with reused powder in five cycles of AlSi10Mg; however, the accumulation of reuse cycles requires further investigation.
Design Innovation of Bicycle Frames Exploiting Topology Optimization
Authors: Colombo Zefinetti Filippo , Rossoni Marco , Martinelli Carlo , Regazzoni Daniele 
Published: January 2022

Abstract
In recent years, the use and demand of bicycles have increased thanks to the growing attention to the environment and due to the COVID-19 pandemic situation. At the same time, the design of the bicycles has remained substantially unchanged, improving in materials and components technology. In the off-road sector, two diametrically opposed categories have emerged in terms of comfort and pedalling efficiency. The goal of this research is to introduce a first methodological approach for the optimization of a mountain bike frame. The behaviour of the developed frame aims to combine the pedalling benefits now available only in different and non-comparable bicycle configurations. The first step concerns the modelling of a generic off-road bicycle frame, then its behaviour has been simulated for specific load cases. Subsequently, the part of the bicycle that best performed the double function of compliance and rigidity has been sought through an analysis of the strain energy using FE simulations. Hence, the reference region has been topologically optimized to provide adequate chassis travel performance. The analysis scheme has been iteratively repeated also on other parts of the frame until an acceptable solution is obtained for the utilize presented. The final configuration permits a rear tube and bottom bracket displacement of 10.4 mm and 2.4 mm compared to the 0.5 mm and 0.4 mm of the original frame respectively. The approach described can be proposed as a support for the search for an innovative design for products with unchanged geometries due to the inertia of the designers. At the same time, this methodology aims to expand the possible use of topological optimization, moving away from the classic constraint schemes present in various software.
Solder Paste Additives for Thermal Expansion Control
Authors: Capela P. , Souza M. S. , Costa S. , Fernandes M. , Figueiredo H. , Alves R. , Delgado I. , Teixeira J. , Soares D. 
Published: January 2022

Abstract
Most electronic failures that occur in equipment are due to stresses induced by differences in the Coefficient of Thermal Expansion (CTE) of the different materials in a Printed Circuit Board Assemblies (PCBA). During a thermal cycle, the incompatibility of CTE between the PCB and the components induces shear fatigue that may affect the reliability of the solder interconnections on the PCB, which can eventually lead to fracture and failure of the joints and the PCB. Due to the advancement in the electronic components industry, interest from the researcher’s point of view has grown in studying the influence of additives in the solder alloys, in relation to microstructure, physical and mechanical properties and, mainly in the CTE.
In this work two types of additives (Bi and graphite powder) were tested in order to reduce the CTE of a lead-free solder (SAC305) solder paste for reflow soldering. Because the selected additives have different characteristics, namely different densities, a different method of SAC305 solder additivation was tested for each type of additive. For Bi addition in SAC305 alloy (up to 6.5 wt.%), after a mechanical mixing of it, with the solder paste, a fusion technique (with a thermal cycle similar to the used on the reflow soldering) was used. For composites with graphite (addition up to 0.1 wt.%) a double-printing method was used in order to achieve a homogeneous additive distribution, so that graphite remained in the final ingot.
These additivated solder alloys were chemically analyzed and characterized for thermogravimetric properties. Samples microstructure were characterized by SEM/EDS analysis, and also they were tested for their electrical resistivity.
With graphite addition there is a slight increase on the initial alloy melting temperature (∼1.5°C) and with Bi an almost linear decrease was obtained (∼16 °C for the higher tested Bi addition).
Composites with bismuth have a decrease trend, with the additive increase content until close to 5%. The CTE value decreases almost linearly ((from 25 to ∼14.5 μm/(m·°C); R2 = 0.9905). However, the sample of SAC305 + 6.5% Bi does not follow this trend, which may indicate that for these and higher amounts of bismuth, the composite CTE stabilizes. For composites with graphite there is a reduction of CTE (from 25 to ∼17 μm/(m·°C) for 0.04 wt. % graphite addition). For higher graphite additions the CTE seems to increase.
The obtained results show that both additives can be used in order to achieve a CTE target value close to the PCB copper PAD (17 μm/(m·°C). However, the mixing method used for graphite mixing on solder paste cannot be directly transposed to the reflow soldering technique.