bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Tire Attributes on the Aerodynamic Performance of a Generic Car-Tire Assembly
Authors: Rath Shubham , Untaroiu Alexandrina , Fu Gen
Published: September 2022

The effect of tires on the overall aerodynamic drag in a car-tire assembly has been studied and deemed considerable from past studies. It has been shown that it is important to understand how the vehicle body and the tires influence the flow structures generated. Previous studies focused on the tire attributes that have an impact on the aerodynamic performance of the vehicle. These tire attributes, however, have not been studied to the extent where one can get a better understanding of the impact of each of these attributes. This paper studies the impact that specific tire attributes have on the overall aerodynamic drag on the vehicle. A thorough and systematic sensitivity study of the effect of tire attributes of a standalone tire was performed to better understand the flow structures around the car body and the improvement in the aerodynamic performance of the vehicle.

In this study, the DrivAer model is used due to the extensive research that has been done on the model. A baseline CFD model of the tire-vehicle assembly of the DrivAer model is simulated using Ansys FLUENT in the open road domain to understand the flow structures around the body of the vehicle. Simulations are done on the fastback configuration of the DrivAer model. A smooth underbody is chosen for this simulation in order to avoid complexities in the meshing. A cuboid shaped open road domain is created, keeping in mind the blocking ratio that is adequate to emulate the flow around the vehicle under open road conditions. Ground simulation and rotating wheel boundary conditions are used to simulate the vehicle moving on the road. The contribution of the tire towards the aerodynamic drag on the vehicle is studied. Coefficient of Drag and coefficient of pressure results from the simulation are validated from experimental data. This is used to create a simulation procedure with appropriate meshing techniques and solution methods in order to simulate for the baseline tire-vehicle assembly and the optimized tire-vehicle assembly. Data from these simulations are used to quantitatively compare the drag contribution of different parameters of the tires.

The sensitivity analysis of the tire-vehicle assembly model performed gives a better insight into the modelling techniques that can be used on a car-tire assembly, as well as the impact of the parameters that could be selected for future tire model optimization.
Impact of Aspect Ratio on Drag and Flow Structure for Cylinders With Two Free Ends
Authors: Shepard Thomas , Law Deify , Dahl Jacob , Reichstadt Rhett , Selvamani Arun Sriniwas
Published: September 2022

When examining the literature for flow effects on circular cylinders one can find many studies on infinite cylinders and cantilevered cylinders but minimal data related to cylinders with two free ends. The limited data available shows that the cylinder aspect ratio affects the drag and frequency content of flow within the wake however these studies were done at discreet Reynolds numbers. In order to better understand the combined impact of aspect ratio and Reynolds number a series of wind tunnel tests and numerical simulations has been conducted for cylinders with two free ends having aspect ratios of 2–15. Test were conducted in the subcritical regime with Reynolds numbers ranging 9300–105,000. Tip vortex effects, which vary with aspect ratio, are shown to impact the cylinder surface pressure, drag coefficient and wake Strouhal numbers though Reynolds number effects are minor for the conditions studied. The results are compared against existing historical data and show the trend of drag coefficient increasing with cylinder aspect ratio.
A Wall-Modeled Large Eddy Simulation Method for High-Order Spectral Element Solvers
Authors: Walters D. Keith , Bhushan Shanti , Strasser Wayne
Published: September 2022

A new method for implementation of wall-modeled large eddy simulation (WMLES) for use with high-order spectral element methods is introduced. Spectral element methods present unique challenges for wall modeling, specifically related to the application of appropriate wall boundary conditions and the specification of modeled fluxes in the near-wall region. The new method addresses these difficulties through the use of an assumed wall function velocity profile in the first layer of near-wall elements, which is used to determine the wall shear stress as well as appropriate pseudo-fluxes to be summed and implemented as source terms at each grid point located in the near-wall elements. Furthermore, the method ensures that the mean velocity field is C1 continuous at the interface between the wall-modeled region and the outer region. Simulations are performed using the spectral element solver Nek5000, and results are compared to high-fidelity DNS data. The test cases considered are fully developed channel flow and flow over a backward-facing step with separation and reattachment. Variations are investigated including different values of the subgrid stress model coefficients for the baseline LES method used. The results show that the new wall function methodology produces results in close agreement with more fully resolved LES for attached channel flow and produces good agreement with field quantities for the backward facing step. The magnitude of wall shear stress in the separated/reattaching flow is underpredicted, and potential reasons for this are discussed. Because WMLES provides a savings in computational cost that scales with Reynolds number, further improvements to the new wall-modeling strategy can potentially lead to significant savings in computational effort for scale-resolving simulations using spectral element numerical methods.
Development of a Finite Element Solver Including a Level-Set Method for Modeling Hydrokinetic Turbines
Authors: Hamada Ahmed A. , Fürth Mirjam
Published: September 2022

Hydrokinetic flapping-foil turbines in swing-arm mode have gained considerable interest in recent years because of their enhanced capability to extract power, and improved efficiency compared to foils in simple mode. The performance of foil turbines is closely linked to the development and separation of the Leading-Edge Vortex (LEV). To accurately model the formation and the separation of the LEV on flapping foils, a purpose-built 2D numerical model was developed. The model is based on weighted residual Finite Element Method (FEM); this is combined with an interface capturing technique, Level-Set Method (LSM), which was used to create a reliable and high-quality numerical solver suitable for hydrodynamic investigations. The solver was validated against well-known static and dynamic benchmark problems. The effect of the mesh density was analyzed and discussed. This paper further covers an initial investigation of the hydrodynamics of flapping-foil in swing-arm mode, by studying the structure of the vortex around a NACA0012 foil. The presented method helps to provide a better understanding of the relation between the Leading-Edge Vortex creation, growth, and separation over the flapping-foil in swing-arm mode and the extracted power from a hydrokinetic turbine.
Development of Three-Dimensional Velocity Vector Profiler Using Ultrasonic Pulsed Doppler Method
Authors: Shoji Naruki , Takahashi Hideharu , Kikura Hiroshige
Published: September 2022

In March 2011, the severe accident of the Fukushima Daiichi (1F) nuclear power plant was happened by the earth quack and massive tsunami in Tohoku, Japan. And then, fuel debris was generated within the primary containment vessels (PCVs) of units 1, 2, and 3, respectively. Recently, the decommissioning of 1F is underway to remove the fuel debris, and the inside inspection with robots was conducted so far. Optical techniques have been applied for inspecting the PCVs, but information of the contaminated water leakage has been not unveiled due to non-clear water causing poor visibility of the camera. Therefore, non-optical techniques are required to unveil the leakage location, and we focused on the ultrasonic measurement technique. In this study, we have developed the ultrasonic velocity profiler (UVP) system for the investigation of leaking locations. The UVP is based on the pulsed Doppler method, and it can measure instantaneous velocity profile along an ultrasonic beam path. In the original UVP principle, it can measure only one-dimensional velocity measurement. Therefore, we extended the UVP to multi-dimensional measurement. To achieve this, a transducer array was used and an algorithm of three-dimensional (3-D) velocity vector reconstruction was developed. The 3-D vector measurement is realized by simultaneous receiving Doppler signal at each ultrasonic element. The measurement performance was evaluated by the rigid rotating flow measurement. In addition, we checked the validity of the system for leakage detection by measuring the simulated leakage flow.
Fabrication of a Multi-Well Plate Channel Device With Reversible Seals
Authors: Zhang Haipeng , Emeigh Carson , Brooks Stephen , Wei Timothy , Ryu Sangjin , Chatzizisis Yiannis S. , Liu Xiang-der
Published: September 2022

Mechanical forces acting on cells have been recognized as an important aspect of cells’ environment because cells adjust their cellular functions in response to such forces, including fluid shear force. For studying such mechanobiological responses of cells, multi-well plate microchannel devices have been used to apply flow shear stress on a cell culture for a long duration. The device includes microfluidic channels attached to the bottom of a conventional multiple-well plate. Such readily available multi-well plate channel devices are costly, and they allow neither direct access to cells cultured in the channel nor easy modification of the device.

In this paper, we propose an easy-to-adopt, cost effective fabrication method for a multi-well plate channel device with reversible seals. This device consisted of two modules. For the top module, a conventional 24-well plate was modified as the base. An inlet/outlet layer and a channel layer were fabricated using polydimethylsiloxane (PDMS) and soft lithography, and they were permanently bonded to the bottom of the plate. The bottom module was a detachable flow chamber layer made with Ecoflex, PDMS, and transparent film using soft lithography. Since Ecoflex can form weak bonding to PDMS, the flow chamber layer could be easily attached to, and then detached from, the PDMS layer of the top module.

As a proof-of-concept, we fabricated a prototype device and tested it by flowing dyed water through the device. No leaking was observed. Then, the device was disassembled and then reassembled for further testing. The weak bonding between Ecoflex and PDMS could create leak-free, reversible seals for the device.

The proposed method has the following advantages. First, fabrication of the device is cost-effective because it can be easily created using common lab instruments and inexpensive materials. Second, the proposed method allows easy modification of the channel design. Last, the reversible seal between the two modules allows direct access to a cell culture for further analysis of the sample after flow stimulation.
Comparative Analysis of Step Change and Reduced Slew Rate Input on the Boundary Layer Response to Forcing by an Array of Plasma Actuator Vortex Generators
Authors: Varacalli Michael , Khanjari Hossein , Hanson Ronald E.
Published: September 2022

In this study, simulations of the laminar boundary layer response to forcing by an array of streamwise oriented plasma actuators are performed. The objective of this study is to evaluate a method to mitigate the non-minimum phase behaviour of the flow that occurs during the step response to input by the actuators. It was recently shown that when the actuators are abruptly started the non-minimum phase response of the wall shear and near-wall disturbance velocity is detected downstream of the actuators. This was shown to be caused by a secondary flow generated between the wall and the front of the tilted vortex structure that is advected downstream [1]. In the present study the step input response is compared to gradually applied inputs. For the step response, the actuators are abruptly activated for 0.2 s followed by a rest period for the flow to return to the undisturbed Blasius condition. For the gradually applied input, the body force of the actuators increases linearly from zero for either 0.005 s, 0.01 s, 0.02 s and 0.04 s to the same maximum value of the step, which simulates a reduced slew rate applied to the physical actuator. The value is held constant and then linearly decreases over a total duration of 0.2 s. It is shown the that inverse response remains for the gradually applied input. However, the peak magnitude is less for the lower ramp rates and the overall response appears more damped.
Deep Learning-Based Super-Resolution for the Finite Element Analysis of Additive Manufacturing Process
Authors: Zhang Yi , Freeman Elton
Published: September 2022

Finite element analysis (FEA) of fused deposition modeling (FDM) has recently been recognized in additive manufacturing (AM) for predictions in temperature gradient of three-dimensions (3D) printed components. These predictions can be invaluable for making corrections to the printing process to improve quality of printed components. However, FEA has its limitations. For example, models with fine mesh (small element size) yield more accurate results than ones with coarse mesh (large element size). Comparing with the coarse mesh model, a fine mesh model can take considerably longer computational times and discourages most manufacturers from using FEA. In this work, an innovative deep-learning (DL) based super-resolution approach is used to improve the result accuracy of a coarse mesh model to the higher accuracy level of a fine mesh model and reduce the computational time. The element in the FEA was treated as the physical pixel in an image, so the fine temperature grid and coarse temperature grid in the FEA were analogous to high resolution (HR) images and low resolution (LR) images, respectively. The result shows that the difference value HS between HR image and super resolution (SR) image is much smaller than the one HL between HR image and LR image, which demonstrated that our proposed DL-based super-resolution approach was effective to enhance the result accuracy of the coarse mesh model. Besides, both the increased Peak Signal-to-Nosie Ratio (PSNR) value and Structural Similarity Index (SSIM) value indicated that the quality of the images was also improved through the super-resolution approach.
A Crystal Plasticity Finite Element Method Modeling of Zircaloy With Hydride Phases Based on Scanning Electron Micrographs
Authors: Kulkarni Shank S. , Truster Timothy , Senor David J. , Devanathan Ram
Published: September 2022

This work developed a microstructure-based finite element model to predict the stress state of alloys with second phase inclusions. Quantitative microstructural details were extracted from scanning electron microscopy (SEM) images and were used to generate heterogeneous microstructures. Generation of digital microstructure was achieved through two steps of tessellations using software Neper and Matlab. This digital microstructure can be further used to perform multiple structural simulations as per the need. Such simulations are very useful in many applications as the manufacturing process can be altered to obtain the morphology resulting in desired overall material properties. The process is demonstrated using an example of Zircaloy material with secondary phases of hydrides dispersed within and stress-strain response of Zircaloy containing hydrides was predicted. Crystal plasticity based constitutive material model was used for Zircaloy whereas the hydrides were modeled as isotropic elasto-plastic material. A parametric study was conducted to understand the effect of volume fraction, and lamellae thickness of the hydride phase on the mechanical properties of the overall material. The introduction of the hydride phase was found to increase the yield stress of Zircaloy with an almost linear relationship between yield stress and hydride volume fraction. On the other hand, the width of hydride lamina was found to have a negligible effect on the yield stress of Zircaloy. These results can help designers to alter the manufacturing process to obtain the enhanced mechanical properties for components used in nuclear applications made by Zircaloy material.
Coupled Diffusion-Deformation-Damage Model for Polymers Used in Hydrogen Infrastructure
Authors: Kulkarni Shank S. , Choi Kyoo Sil , Simmons Kevin
Published: September 2022

The soft materials used in the infrastructure of hydrogen storage and distribution systems are vulnerable because exposure to high-pressure hydrogen can lead to mechanical damage and property degradation. Polymers are one of the widely used classes of soft materials within hydrogen infrastructure. Many small cavities exist within the polymer material due to their long molecular chains. When exposed to high-pressure hydrogen gas, the gas diffuses through the polymer material and occupies these cavities. When outside hydrogen pressure reduces suddenly, the hydrogen gas inside the cavities does not get enough time to diffuse out as diffusion is a much slower process. Instead, this trapped gas causes blistering or in extreme cases rapture of polymer material. This phenomenon is also known as rapid decompression failure.

In this study, a continuum mechanics-based fully coupled diffusion-deformation model with damage is developed to predict the stress distribution and damage propagation while the polymer undergoes rapid decompression failure. The hyperelastic material model, along with the maximum principal strain failure theory, was chosen for this study as it represents the nonlinear material response with sudden failure observed in uniaxial tensile tests perfectly. EPDM polymer was chosen for this study because of its commercial availability and common use in hydrogen storage and distribution system. It has superior mechanical properties, high and low-temperature resistance, and certain compounds work well in hydrogen gas. Stress concentration was observed on the periphery of the cavity at the point closest to the outside surface which lead to damage initiation at the same location. Also, this work showed that the coefficient of diffusion plays an important role in damage initiation. As the value of the coefficient of diffusion increases, the amount of damage decreases due to the higher coefficient of diffusion ensures a safe passage for trapped hydrogen to escape to the atmosphere. This work is useful for design engineers to alter the parameters while manufacturing polymer composites to increase their performance in a high-pressure hydrogen environment.
Analysis of Conduction Cooling Strategies for Wire Arc Additive Manufacturing
Authors: Heinrich Lauren , Feldhausen Thomas , Saleeby Kyle S. , Saldana Christopher , Kurfess Thomas R.
Published: September 2022

Metal additive manufacturing (AM) processing consists of numerous parameters which take time to optimize for various geometries. One aspect of the metal AM process that continues to be explored is the control of thermal energy accumulation during component manufacturing due to the melting and solidification of the feedstock. Excessive energy accumulation causes thermal failure of the component while minimal energy accumulation causes lack of fusion with the build plate or previous layer. The ability to simulate the thermal response of an AM component can increase research efficiency by reducing the time to optimize thermal energy accumulation. This paper presents an effective implementation of finite element analysis to determine the thermal response of a wire arc additive manufactured component with various build plate sizes and cooling methods including, integral build plate cooling, oversized build plates with passive cooling, and non-integral build plate cooling. The use of integral build plate cooling channels was shown to decrease the interpass temperature at the conclusion of the build process by 55% and build plate temperature by 96% compared to the conventionally deposited sample with 20 second dwell time. The use of a tall build plate with passive cooling was shown to reduce the interpass temperature by 32% as compared to the conventionally deposited sample with 20 second dwell time. Each cooling strategy evaluated decreased the interpass temperature within a range of 20–55% which enables higher deposition rates and decreased dwell times during depositions. The cooling strategies are designed to be implemented in a hybrid or retrofit AM platform to mitigate concerns of the thermal input from the additive process having detrimental effects on the precision of the machining process. This paper shows that accurate simulations of all strategies can be used to accurately predict the thermal response of the various strategies discussed. These cooling strategies will allow for increased deposition rates with comparable interpass temperature and decreased dwell time, increasing deposition efficiency. This model and these simulations are verified by experimental results. It is concluded that passive strategies, such as the over-sized tall build plate, can be used when liquid coolant in the AM environment could negatively affect the deposition process. Active cooling strategies, such as the integral build plate cooling could be used if low thermal conductivity materials are deposited or higher material deposition rates are desired. This paper discusses the use of active and passive cooling used during AM and shows how a simulation model can be used to make design choices for cooling strategies. The model also enables verification of select critical process parameters such as dwell times for a desired interpass temperature.
Solving the Open Route Capacitated Periodic Vehicle Routing Problem With Time Windows to Service Microgrids Powered by Uncertain Renewable Generation
Authors: Shawky Waleed , Azab Ahmed , Kassem Sally
Published: September 2022

Supply Chain and logistics operations are high-cost operations that require planning to keep costs minimum. One of the most crucial supply chain stages is the distribution stage, including delivering products to retailers and/or customers. The problem of products’ distribution consumes considerable amounts of time and money and is modeled in many situations as a Vehicle Routing Problem (VRP). In this paper, servicing and provision of power transactions to an electric micro-grid using a fleet of mobile energy storage systems (MESSs) during a specific time horizon is targeted using the developed model for the well-known Capacitated VRP with Time Windows (CVRPTW). The process of servicing power transactions of an electric micro-grid is repeated for each station periodically, which results in a problem known as periodic VRP (PVRP). The MESSs in the developed model do not necessarily return back to their original trip starting point (depot); hence, the problem at hand is considered as Open-Route as well. Therefore, the Open Route Capacitated Periodic VRP with Time Windows (OCPVRPTW) is studied in this paper. The model is formulated and solved using commercial software to obtain exact solutions to the tackled problem instances. For future work and due to the combinatorial nature of the problem, Ant Colony Optimization will be used to solve larger instances of the problem.
Laser Micro Machining Using an Oblique Photonic Nanojet With Focused Laser Beam Irradiation
Authors: Uenohara Tsutomu , Yasuda Makoto , Yamamoto Kosei , Mizutani Yasuhiro , Takaya Yasuhiro
Published: September 2022

Three-dimensional microstructures in the sub-micrometer scale exhibit unique properties. A flexible machining method to fabricate such structures is desired. Photonic nanojet (PNJ) is high intensity laser beam with sub-micrometer scale beam diameter and micrometer scale depth of focus. PNJs have a longer depth of focus than tightly focused laser beams with a high numerical aperture. In this study, we investigate the angular control of PNJs by controlling the propagation direction of incident light in order to realize flexible laser micro machining using PNJs. By controlling the position of the microsphere in the focused laser beam with a large defocus, the propagation direction of the laser beam incident on the microsphere is changed, and the angle of the PNJ can be controlled. Laser machining experiments on a silicon substrate showed that the PNJ angle can be controlled by incident laser angle. Furthermore, sub-micrometer scale laser machining was achieved even when using an oblique PNJ. The simulation results and experimental results are in good agreement. In conclusion, the angle control of the photonic nanojet can be applied to flexible multi-axis laser micro machining.
Fabrication of Nanowires Using Glancing Angle Deposition
Authors: Qu Chuang , McNamara Shamus , Walsh Kevin
Published: September 2022

This paper introduces the fabrication of wafer-long nanowires using glancing angle deposition (GLAD). GLAD is an advanced physical vapor deposition technique, and it has the unique advantage of creating three-dimensional nanofeature arrays, compared to conventional top-down nanofabrication techniques. Various nanofeatures created by GLAD have been reported, including pillars, springs, chevrons, ribbons, and those structures as templates for creating nanoporous membranes; this paper fills the gap by presenting the creation of nanowires by GLAD. This paper describes the fabrication process by introducing the seeding scheme of corrals. The seed design for GLAD adopts the design rules of corrals of line seeds, and the GLAD parameters are determined by the design of the corrals of line seeds. In the experiment, conventional photolithography is used for creating micro-level widths and heights and wafer-length of line seed corrals. Two GLAD sessions with the target material for the nanowires and the mask material are deposited on the substrate in sequence with different azimuth angles; the nanowires are obtainable by anisotropic etching and removal of the sacrificial layer of corrals of line seeds. The design of the corrals of line seeds and the control of the size of the nanowires are discussed. The nanowires created are potentially applied in sensing applications, for example, the palladium or platinum nanowires can be used for hydrogen sensing.
Establishment of Mode Shape Database for Machine Tool and its Application in Estimating System Dynamics
Authors: Liu Jiahui , Kizaki Toru , Yamaura Shogo , Sugita Naohiko
Published: September 2022

Machine tool dynamics has an important role in machine health monitoring, chatter prevention, machining process control, and improvement of manufacturing accuracy. For industrial applications, system dynamics vary with the machining process. To achieve this information during operation, the operational modal analysis (OMA) method, which can observe dynamic performance with output only, has rapidly developed and evolved into transmissibility function-based operational modal analysis (TOMA), with the ratio of outputs used for the estimation of system dynamics. However, this analysis is limited by excitation variance and nature of coherence deformation for the entire system when machining position or posture change. To precisely estimate machine dynamics in process, this study proposes the use of feature fitting from a mode shape database after collection by TOMA. By segmenting the continuous machining process, the variation in system dynamics during operation can be separated into domains under the requirement of machining accuracy. A numerical experiment was performed with a no-damping finite element model of one machining center to verify the feasibility and accuracy of the proposed method. Subsequently, the experimental performance of the mode shape with several accelerometers was evaluated, and the differences with finite element results were discussed with further consideration of application in practice.
Embrace the Imperfection: How Intrinsic Variability of Roll-to-Roll Manufactured Environmental Sensors Enable Self-Calibrating, High-Precision Quorum Sensing
Authors: Saha Ajanta , Gopalakrishnan Sarath , Waimin Jose , Sedaghat Sotoudeh , Mi Ye , Glassmaker Nicholas , Cakmak Mukkerem , Shakouri Ali , Rahimi Rahim , A. Alam Muhammad
Published: September 2022

Roll-to-Roll (R2R) process is well suited for manufacturing low cost, miniaturized, solid contact Ion-selective electrodes (ISEs) of potentiometric sensors to be used for continuous monitoring of various analytes in environmental, industrial, and health-care applications. It is presumed that the intrinsic thickness variability of the R2R process would limit the accuracy of the ISE-based sensors and would make them inferior to sensors fabricated by higher precision manufacturing processes. Instead, in this paper we propose to use the intrinsic variability of R2R process as a “resource” to achieve high-accuracy sensing even when the sensors are operated in uncontrolled field conditions. This is achieved by applying a fundamentally new physics-guided statistical approach involving: (i) ‘Self calibration’ where we calculate temperature from differential measurement of the ISEs induced by R2R variability to calibrate the sensors in uncontrolled temperature condition, and (ii) ‘Quorum sensing’ where we use a collection of R2R manufactured sensors to estimate the true concentration considering credibility of each sensor calculated by Bayesian Maximum Likelihood Estimation method. With these two new techniques, we demonstrate the use of “low-precision” R2R sensors to measure nitrate concentration of an agricultural field continuously over a period of 15 days within 10% of the ground-truth measured by the traditional high-precision commercial nitrate sensor.
3D Printed Pelvic Organ Prolapse (POP) Tissue Scaffolds
Authors: Zhu Yuxiang , Ravichandran Dharneedar , Song Kenan
Published: September 2022

Nearly 1 in 4 women undergo surgery for pelvic organ prolapse or urinary incontinence in the US. The weakened pelvic floor, which could be caused by childbirth injury, aging, or obesity, fails to support the pelvic organs, resulting in urinary incontinence, sexual difficulties, and pelvic organ prolapse (POP). Polypropylene (PP) meshes are often used in reconstructive surgeries as a reinforcement to provide long-term, durable support. However, commercial polypropylene meshes have a risk of complications, such as pain, mesh erosion, and infection. The United States Food and Drug Administration (FDA) has consequently re-classified the polypropylene mesh as a high-risk device. Therefore, the need for new meshes to cure POP with a rapid prototyping technique is urgent, especially for personalized medicine.

Therefore, we developed a new implantable mesh using biocompatible polymers (e.g., gelatin, polyvinyl alcohol (PVA), chitosan) with controlled bonding strength and tunable lifetime. Our group has leveraged additive manufacturing for porous scaffold structures beneficial for cell attachment and nutrition transmission. Our POP scaffold mesh has demonstrated high biocompatibility and controlled biodegradability. We will also leverage our manufacturing expertise and clinical partnerships to examine cell proliferation and differentiation for tissue regeneration. Our advanced manufacturing method is compatible with other materials and has potential use in layered structures for dental, heart, or bone engineering applications.
Estimating Milling Forces From Vibration Measurements
Authors: Joddar Manish , Ahmadi Keivan
Published: September 2022

Machining force and vibration signals are commonly used for process monitoring. While low-cost accelerometers are conveniently installed in machining setups, the direct measurement of machining forces in industrial applications is challenging. As an alternative to direct measurement, cutting forces can be estimated indirectly from vibration measurements, enabling the simultaneous monitoring of vibrations and forces from vibration signals only. In this paper, we two methods for estimating the dynamic milling forces from acceleration measurements during milling processes. The first method applies offline regularized deconvolution to the measured acceleration data to extract the forces causing them. The second method designs an online Augmented Kalman Filter to observe the forces as the augmented system states. The efficiency and performance of both methods are studied experimentally. The comparison between the indirectly estimated forces and the directly measured ones confirms the feasibility of using acceleration sensors to monitor the machining forces and the resulting vibrations simultaneously. Nevertheless, because the low-frequency contents of the forces are filtered in the resulting accelerations, only the dynamic component of the forces can be recovered. Experimental comparison of regularized deconvolution and augmented Kalman filter methods shows that the latter is more effective in recovering a larger portion of low-frequency content of the forces. Despite missing the low-frequency content, the reconstructed dynamic forces can still be used for process monitoring in applications where force sensors cannot be installed.
Exploring the Role of Mechanochemical Effects in Cutting of Aluminum Alloys With Alcohols
Authors: Sugihara Tatsuya , Nomura Takuma , Enomoto Toshiyuki , Udupa Anirudh , Viswanathan Koushik , Mann James
Published: September 2022

In metal cutting processes, a chemical ambient environment in the cutting zone can be a useful variable for process control and process performance improvement. In this work, we study how mechanochemical effects influence the chip formation process, especially focusing on a specific chemical reaction between aluminum alloys and alcohols as a model system. Using high speed in-situ imaging and particle image velocimetry, we demonstrate that the mechanochemical effect in cutting of annealed Al with use of isopropyl alcohol (IPA) is manifest in two different ways: a lubricating effect at the tool-chip interface and an embrittlement effect at the workpiece free-surface, depending on the undeformed chip thickness and cutting speed. Consequently, the highly unsteady chip flow seen in dry cutting of annealed Al, which is typically seen in cutting of ductile “gummy” metals, transitions to a laminar-type (smooth) chip-flow mode or a segmented, fracture-controlled chip flow, due to the Al-IPA reaction. In both cases, the modified chip flow modes lead to significant reduction in cutting forces and improvement of finished surface quality. The specific manifestation of the mechanochemical effect is found to be principally determined by the penetration capability of the alcohols into the tool-chip interface and the time required for the chemical reaction between aluminum and the alcohols. Also, we discuss some implications for improving the performance of practical Al cutting operations using alcohols as a fluid medium.
Effect of Alloying Elements of Al Alloy on the Interfacial Microstructure and Fracture Behaviour of Al Alloy/Steel Inertia Friction Welded Joint: A Comparative Study
Authors: Ma Hong , Geng Peihao , Qin Guoliang
Published: September 2022

The present study highlighted the effect of alloying elements in Al alloy on the interfacial microstructure, and the corresponding fracture behaviour of the Al alloy/steel inertia friction welded joint by selectively adopting two types of Al alloys. A strong texture of <111>//radial direction was formed on the Al alloy side in both types of joints, while no obvious changes were identified on the steel side. Different types of intermetallic compounds (IMCs) were formed at the weld interface. In the Al-Mg-Si alloy/steel joint produced at a low heat input, the interfacial microstructure was composed of a nanoscale amorphous layer and partially crystallised layer, while it turned into a fully crystallised Fe2Al5 phase with Si enriched when the heat input was enhanced. In the Al-Cu alloy/steel joint, Cu was enriched at the weld interface, with the possible formation of Fe-Al-Cu based IMCs. Moreover, a two-layered structure of IMC with different compositions of Cu appeared when the joint was prepared at a high heat input. Such distinct interfacial microstructure caused different fracture behaviours of joints. An interfacial reaction layer less than 130 nm thick led to the failure of Al alloy rather than the weld interface which easily happened at a thicker IMC.
Effect of Metal Mixing on Mechanical Performance of Laser Keyhole Welding of Nickel and Copper
Authors: Huang Wenkang , Tan Wenda , Cai Wayne , Bracey Jennifer
Published: September 2022

In laser keyhole welding of dissimilar metals, metal mixing in the molten pool is critical to the microstructure and mechanical performance of the welds. In this study, metal mixing and its effects on the mechanical performance of the miscible Nickel-Copper welds are investigated. Experiments were carried out to fabricate samples with different welding parameters. Energy-dispersive X-ray spectroscopy is used to characterize the metal distribution in the fusion zone of the post welds. Mechanical strength testing and fractographic analysis are performed to characterize the strength of the welds and the fracture mode. Two regions of different concentrations can be found in the welds, and the concentrations of these two regions vary significantly with welding parameters. The weld strength is dependent on the interfacial region concentration, and the welds undergo a mixture of shear fracture and tensile fracture during the mechanical strength testing process. The interfacial concentration and the weld strength can be controlled by tuning the concentration of the two concentration regions in the fusion zone and the location of the boundary between the two regions. This study provides insights for industries regarding the design and optimization of the laser welding process to achieve welds with optimal mechanical performance.
Thermal Analyses of Electrically Assisted Forming
Authors: Grimm Tyler J. , Mears Laine
Published: September 2022

Electrically assisted manufacturing (EAM) is defined as the direct application of electricity to a workpiece in situ with a manufacturing process. This is commonly used in forming to reduce the flow stress and increase the ductility of metals. Under certain conditions, there seem to be effects of the electricity that occur in addition to the inherent resistive heating in metals. This electroplastic effect is often deduced by estimating temperatures through analytical or numerical simulations and comparing this to the temperatures required to effect thermal stress reductions observed in experimental tests.

For tests which utilized pulsed or AC currents, an RMS current value may be used to simplify simulations since current transience can be averaged to a constant representative value. However, there is often no justification of this assumption and it is possible that assumption could lead to erroneous results. Various assumptions applied to EAM research are explicitly explored herein to determine their validity in thermal estimations. It was concluded that AC, square wave, and sawtooth currents at frequencies greater than 1 Hz, or pulses from power supplies with significant ripple, can be approximated with a DC current of similar RMS value to obtain similar thermal estimations. Simulation geometries should incorporate as much of the experimental setup as possible. An example from literature was used to test several other assumptions as well, including the use of analytical simulations, rather than numerical.
Product Life-Cycle Energy Framework in Friction Scenarios
Authors: Linke Barbara S. , Gupta Shivam
Published: September 2022

Manufacturers have great power to change the sustainability of products over the whole life cycle, but they need holistic life cycle models to guide those decisions. Challenges exist in connecting the product’s life cycle data to model-based sustainability metrics and in quantifying uncertainty in the product data. This study develops a life-cycle energy framework around two application cases to showcase informed and transparent decision-making. The case studies investigate additively manufactured parts in two friction scenarios, one where low friction is desired and one where high friction is preferred. The layer height is chosen as process parameter of additive manufacturing that changes the surface roughness of the sample parts, but also the manufacturing time and energy. The use phase energy in the first friction scenario is influenced by the user behavior, and by a random input function in the second scenario. The life-cycle energy framework is used to discuss total life cycle energy for each scenario. In general, this framework should be used to better connect product use phase and manufacturing phase, in particular by examining the interconnections of part design, manufacturing phase impacts, and use performance. Product quality is the central aspect of optimization. The framework can be used for engineering education and be expanded to study data uncertainty, user behavior, system complexity, process chains, machine learning, sustainability metrics, and more.
Synthesis and Fabrication of Single Walled Carbon Nanotube Microelectrode Arrays on Flexible Probes for Neurotransmitter Detection
Authors: Park Sei Jin , Ivanovskaya Anna , Yorita Allison
Published: September 2022

Implantable microelectrode arrays are an effective method for understanding neurotransmitter dynamics with high spatial resolution. In particular, carbon-based electrodes are efficient for electrochemical detection of dopamine, a neurotransmitter studied for its role in motor movement and reward-seeking behavior. However, very few options exist for arrayed carbon microelectrodes, specifically on flexible polymeric probes. We demonstrate fabrication of polyimide probes featuring single walled carbon nanotube (SWCNT) microelectrode arrays and characterize their dopamine detection performance. First, SWCNT synthesis parameters were optimized to grow high density SWCNT “forests” that have uniform height with electrode diameters ranging from 15 μm to 100 μm, as these dimensions are spatially relevant to chemical sensing in an animal model. These SWCNT microelectrodes were then incorporated into a microfabrication process involving deposition and patterning of polyimide substrate and metal traces. The process flow was designed such that the polyimide was not exposed to the high temperatures required to grow SWCNTs. Instead, a bottom-up approach was utilized, in which the SWCNT catalyst was first patterned, the SWCNTs were synthesized on a silicon substrate, then polyimide and trace metal layers were deposited and patterned. Prototype probes were fabricated containing the same range of electrode diameters as those used for SWCNT synthesis development to determine the effect of electrode diameter on ease of microfabrication. Microelectrodes ranging from 15 μm to 50 μm in diameter were found to release from the carrier wafer more easily, while larger electrodes demonstrated poor release. These probes demonstrate a concentration-dependent response to dopamine, with high sensitivity compared to microelectrode arrays consisting of bare metal. Further development of this electrode material will enable neuroscientists to study dopamine at higher spatial resolution, with the benefit of utilizing flexible probes.
Primary Chatter and Limiting Chip Load in Turning Under Negative Process Damping
Authors: Hsu Ming-Jen , Wang Jiunn-Jyh
Published: September 2022

This paper presents an analysis of primary chatter under velocity-induced negative process damping in the peripheral outer diameter turning of medium carbon steel. A first-order approximation model of the instant specific cutting force with respect to dynamic cutting speed was established and the slope was defined as the specific process damping coefficient (SPDC) to investigate the negative process damping with respect to cutting speed, depth of cut, and chip thickness. The process damping coefficient was defined as the product of the specific process damping coefficient and chip load. The total system damping coefficient as the sum of the process damping coefficient and structural damping coefficient determines the system stability and predict primary chatter. The SPDCs were obtained through experiments under various speeds, feeds, and depths of cut by using a tool system with force sensors and accelerometers. The SPDCs were insensitive to cutting speeds of 2.5 to 5.5 m/sec and ranged from −1514 and −716 MPa·s/m for feeds per revolution of 0.058 to 0.118 mm, respectively. The higher negative SPDC at smaller chip thickness reduces the limiting stable chip load. Equations for the limiting chip load and limiting depth of cut were derived and validated by experiments. Stability diagrams of limiting chip load and limiting depth with respect to feed per revolution were created to provide guidance on preventing primary chatter.
A Comparative Study on the Effects of an Advanced Scan Pattern and Intelligent Scan Sequence on Thermal Distribution, Part Deformation, and Printing Time in PBF Additive Manufacturing
Authors: He Chuan , Tsai Yueh-Lin , Okwudire Chinedum E.
Published: September 2022

Parts made using powder bed fusion (PBF) additive manufacturing often suffer from deformation, residual stresses, cracks, and other defects stemming from non-uniform thermal distribution during the printing process. Scan pattern (i.e., the geometric pattern of an infill) and scan sequence (i.e., the order in which features of a geometric pattern are scanned) are among the approaches that have been explored to achieve more uniform thermal distribution and reduce thermally-induced defects. The authors have recently proposed an intelligent approach (called SmartScan) for generating scan sequences. SmartScan is model-based and optimization-driven. However, it has only been applied to the most rudimentary scan patterns. This paper compares the separate and combined effects of an advanced scan pattern (the varying-helix pattern) and SmartScan on thermal distribution, part deformation, and printing time in PBF additive manufacturing. Simulations and experiments involving laser marking of AISI 316L stainless steel plates are employed for the comparison. Using SmartScan applied to a rudimentary pattern as a benchmark, the experimental results demonstrate that the application of the advanced pattern without SmartScan improved both temperature uniformity and reduced deformations by 20%, at the cost of 7% increase in printing time. The combination of the advanced pattern and SmartScan yielded 28% and 33% improvement in thermal uniformity and reduction in deformation, respectively, at the cost of 18% increase in scanning time.