bluuebunny/crossref_metadata_2025 huggingface dataset:
A Finite Element Approach to Calculate Temperatures Arising During Cryogenic Turning of Metastable Austenitic Steel AISI 347
Authors: Becker Steven , Hotz Hendrik , Kirsch Benjamin , Aurich Jan C. , v. Harbou Erik , Müller Ralf
Published: September 2018

In this paper an inverse method is presented to evaluate the inner workpiece temperature distribution during cryogenic turning of metastable austenitic steel AISI 347 utilizing a FE representation of the process. Temperature data during the experiments is provided by thermocouples and a commercial thermo-graphy system. A constant cutting speed at two varying feeds are investigated. Inverse parameter verification by aligning simulated and experimental data in a least squares sense is achieved. A heat flux from tool to workpiece as well as heat transfer coefficients for forced convection by air and by carbon dioxide as cryogenic coolant are identified for each set of cutting parameters. Rigid body rotation in the model is considered applying convective time derivatives of the temperature field. Unphysical oscillations occurring in regions of high Péclet numbers are suppressed utilizing a streamline-upwind/Petrov-Galerkin scheme.
A Standards and Technology Roadmap for Scalable Distributed Manufacturing Systems
Authors: Hedberg Thomas , Helu Moneer , Sprock Timothy
Published: September 2018

The increasing decentralization of manufacturing has contributed to the growing interest in scalable distributed manufacturing systems (DMSs). The emerging body of work from smart manufacturing, Industrie 4.0, Industrial Internet of Things (IIoT), and cyber-physical systems can enable the continued development of scalable DMS, particularly through the digital thread. However, significant challenges exist in understanding how to apply the digital thread most appropriately for scalable DMS. This paper describes these major challenges and provides a standards and technology roadmap developed from the digital thread viewpoint and consensus-built industrial standards to realize scalable DMS. The goal of this roadmap is to guide research that enables manufacturers to take advantage of opportunities provided by scalable DMS, including improved agility, flexibility, traceability, dynamic decision making, and utilization of manufacturing resources.
Machine-Tool Error Observer Design With Application to Thermal Error Tracking
Authors: Ko Hua-Wei , Kapoor Shiv G. , Ferreira Placid M. , Bazzoli Patrick , Nisbett J. Adam , Bristow Douglas , Chen Yujie
Published: September 2018

A parameter identification procedure for identifying the parameters of a volumetric error model of a large and complex machine tool usually requires a large number of observations of volumetric error components in its workspace. This paper demonstrates the possibility of applying optimal observation/experimental design theories to volumetric error model parameter identification of a large 5-axis machine with one redundant axis. Several designs such as A-, D- and K-optimal designs seek to maximize the amount of information carried in the observations made in an experiment. In this paper, we adapt these design approaches in the construction of machine-tool error observers by determining locations in the workspace at which components of volumetric errors must be measured so that the underlying error model parameters can be identified.

Many of optimal designs tend to localize observations at either the center or the boundary of the workspace. This can leave large volumes of the workspace inadequately represented, making the identified model parameters particularly susceptible to model inadequacy issues. Therefore, we develop constrained optimization algorithms that force the distribution of observation points in the machine’s workspace. Optimal designs provide the possibility of efficiency (reduced number of observations and hence reduced measurement time) in the identification procedure. This opens up the possibility of tracking thermal variations of the volumetric error model with periodic quick measurements. We report on the design, implementation and performance of a constrained K-optimal in tracking the thermal variations of the volumetric error over a 5.5 hour period of operations with measurements being made each hour.
Characterization of Long Period Grating With a Screw Shape Fabricated by a Single-Path Scanning of Femtosecond Laser
Authors: Joe Hang-Eun , Yun Huitaek , Jun Martin B. G. , Cho Yonghyun , Ahmed Farid , Lee Patrick C.
Published: September 2018

We propose a manufacturing process for fabrication of long period grating (LPG) with a screw shape by a single-path scanning of femtosecond laser. The optical fiber was rotating in radial direction and traveled along the fiber-axis simultaneously while femtosecond laser irradiation. Several screw-shaped LPGs were fabricated under different parameters, such as laser power, index change length and grating period, and their transmission characteristics were investigated. Moreover, the screw-shaped LPG with complicated pitches of the screw were fabricated by adjusting the rotating speed and travelling speed. The screw-shaped LPG sensor with complex pitches had reverse bending effect that the transmission dip becomes deeper as bending curvature increases. Consequently, it was found that the screw-shaped LPG with multiple pitches of grating has a potential as the sensors for monitoring of the structural characteristics such as bending or curvature under harsh environment.
Lightweight Microlattice With Tunable Mechanical Properties Using 3D Printed Shape Memory Polymer
Authors: Yang Chen , Boorugu Manish , Dopp Andrew , Lee Howon
Published: September 2018

Metamaterials are architected artificial materials engineered to exhibit properties not typically found in natural materials. Increasing attention has recently been given to mechanical metamaterials with unprecedented mechanical properties including high stiffness, strength, or/and resilience even at extremely low density. These unusual mechanical performances emerge from the three-dimensional (3D) spatial arrangement of the micro-structural elements designed to effectively distribute mechanical loads. Recent advances in additive manufacturing in micro-/nano-scale have catalyzed the growing interest in this field.

This work presents a new lightweight microlattice with tunable and recoverable mechanical properties using a three-dimensionally architected shape memory polymer (SMP). SMP microlattices were fabricated utilizing our micro additive manufacturing technique called projection micro-stereolithography (PμSL), which uses a digital micro-mirror device (DMD™) as a dynamically reconfigurable photomask. We use a photo-crosslinkable and temperature-responsive SMP which can retain its large deformation until heated for spontaneous shape recovery. In addition, it exhibits remarkable elastic modulus changes during this transition. We demonstrate that mechanical responses of the micro 3D printed SMP microlattice can be reversibly tuned by temperature control. Mechanical testing result showed that stiffness of a SMP microlattice changed by two orders of magnitude by a moderate temperature shift by 60°C. Furthermore, the shape memory effect of the SMP allows for full restitution of the original shape of the microlattice upon heating even after substantial mechanical deformation. Mechanical metamaterials with lightweight, reversibly tunable properties, and shape recoverability can potentially lead to new smart structural systems that can effectively react and adapt to varying environments or unpredicted loads.
Voxel Based Cutting Force Simulation of Ball End Milling Considering Cutting Edge Around Center Web
Authors: Nishida Isamu , Nakamura Takaya , Sato Ryuta , Shirase Keiichi
Published: September 2018

A new method, which accurately predicts cutting force in ball end milling considering cutting edge around center web, has been proposed. The new method accurately calculates the uncut chip thickness, which is required to estimate the cutting force by the instantaneous rigid force model. In the instantaneous rigid force model, the uncut chip thickness is generally calculated on the cutting edge in each minute disk element piled up along the tool axis.

However, the orientation of tool cutting edge of ball end mill is different from that of square end mill. Therefore, for the ball end mill, the uncut chip thickness cannot be calculated accurately in the minute disk element, especially around the center web. Then, this study proposes a method to calculate the uncut chip thickness along the vector connecting the center of the ball and the cutting edge. The proposed method can reduce the estimation error of the uncut chip thickness especially around the center web compared with the previous method. Our study also realizes to calculate the uncut chip thickness discretely by using voxel model and detecting the removal voxels in each minute tool rotation angle, in which the relative relationship between a cutting edge and a workpiece, which changes dynamically during tool rotation.

A cutting experiment with the ball end mill was conducted in order to validate the proposed method. The results showed that the error between the measured and predicted cutting forces can be reduced by the proposed method compared with the previous method.
Machining Performance and Microstructure Evolution in Milling Advanced Low-Alloy Military-Grade Steel
Authors: Wolf Jason , Saldana Christopher , Maloney Tom , Quitter Jack , Von Roemer John
Published: September 2018

Next generation defense applications for structural steels require new alloys that eliminate or reduce critical materials from their composition, while maintaining or exceeding the high strength and toughness requirements for extreme shock or dynamic loading environments. A new alloy system has been developed for this purpose and characteristics of its manufacture and material response in component manufacturing must be understood. In the present study, the relative machinability of a new structural steel, denoted as AF9628, was evaluated relative to a surrogate steel benchmark (AISI4340). The effects of machining parameters employed in milling across a range of machining speeds, feed rates and cooling conditions was investigated by measurements of force signatures and surface roughness. Machined chips were collected and measured to determine the relative effects of these parameters on evolved microstructure. Changes in chip hardness and microstructure were observed due to the effect of cooling conditions in the milling process. Subsurface microstructure was measured using electron backscatter diffraction. The utility of these methods for understanding machinability for defense alloys and components is briefly discussed.
Visualization of Geometrical Deviations in Micro Grinding by Kinematic Simulations
Authors: Setti Dinesh , Kirsch Benjamin , Arrabiyeh Peter A. , Aurich Jan C.
Published: September 2018

In micro machining processes, achieving the required accuracy and surface quality in the first attempt is of utmost importance. Because, it is challenging to perform a secondary operation in a microscaled structure due to re-positioning inaccuracies. In the micro grinding process, geometrically deviated structures are common due to the low depth of cuts compared to the size of abrasive grits. Moreover, abrasive grits random distribution on the tool surface is also a factor. In most of the cases, the number of grits participating in the grinding process is countable, unlike macro grinding process. Hence, the position of every grit on the micro tool surface is important. In the micro grinding process, geometrically deviated structures are common due to the low depth of cuts compared to the size of abrasive grits. In this case, the depth of cut values will be less than the size of the abrasive grits. In that case, the abrasive grits located at the tool bottom surface highly influence the quality of the component produced. In the present work, a simulation study has been performed for micro grinding process to understand the influence of tool topography on the micro channel geometrical deviations, especially when the depth of cut is less than the size of the grits. Simulation results showed the importance of the number of grits, their protrusion heights and radial positions on the tool bottom surface at small depths of cuts to minimize the geometrical deviations.
Measuring and Modeling of Volumetric Errors for Vertical Machining Centers Based on Bi-Directional Laser Sequential Step Diagonal Measurement
Authors: Li Huimin , Xiang Sitong , Deng Ming , Zhu Mengrui , Du Zhengchun , Yang Jianguo
Published: September 2018

This paper proposes a bi-directional laser sequential step diagonal measuring method for three-axis vertical machining centers. Different measure paths are particularly designed for positive and negative directions, and corresponding error decoupling models are established. Based on the laser measuring data along these bi-directional paths, 18 geometric errors can be identified simultaneously, including 6 angular errors, 3 positioning errors, 6 straightness errors and 3 squareness errors. Compared with single directional step diagonal measurements, the proposed bi-directional mothed is more efficient and can identify more error items, namely 6 angular errors. Experimental tests were conducted on a three-axis vertical machining center. Decoupled error items obtained by the proposed bi-direction measurements coincide with those from direct measurements via a laser Doppler displacement meter, which verified the feasibility of the proposed method. Finally, the position error of the machine whole workspace was predicted by building volumetric error model and the machine accuracy was improved.
MOEA/D for Multi-Objective Hybrid Flowshop Rescheduling Problem
Authors: Zhang Biao , Pan Quan-ke , Gao Liang , Zhao Yao-bang
Published: September 2018

In this paper, a multi-objective hybrid flowshop rescheduling problem (HFRP) is addressed in a dynamic shop environment where two types of real-time events, namely machine breakdown and job cancellation, simultaneously happen. For the addressed problem, two objectives are considered. One objective concerning the production efficiency is minimizing the maximum completion time or makespan, while regarding with the instability, the total number of the jobs assigned to different machines between the revised and the origin schedule is considered. A multi-objective evolutionary algorithm based on decomposition (MOEA/D) is applied to solve this problem. In the algorithm, the weighted sum approach is used as the decomposition strategy. The algorithm is, then, rigorously compared with three state-of-the-art evolutionary multi-objective optimizers, and the computational results demonstrate the effectiveness and efficiency of the algorithm.
Improvement of Ionic Bonding Strength and Electrochemical Corrosion Resistance of Hydroxyapatite- Calcium Phosphate Pulsed Electrochemically Deposited In-Situ Coating Through Hydroxyl Ion Treatment
Authors: Chakraborty Rajib , Datta Susmita , Raza Mohammad Shahid , Saha Partha
Published: September 2018

Hydroxyl ion treatment of different hydroxyapatite-calcium hydrogen phosphate composite in-situ coatings synthesized through pulsed electro-deposition with varying amount of hydroxyapatite phase and degree of crystallinity were carried out with the help of highly basic solution in order to achieve a more chemically stable and corrosion resistance performance under contact with body fluid. The coatings exhibit altogether completely different behaviour in terms of bond formation, surface topography generation, phase transformation and corrosion behaviour. Detailed characterizations of formed top surface layer were carried out with the help of XRD, SEM and FTIR in order to correlate the results with their base surface characteristics. Transformation of <020> and <121> surface parallel planes of calcium hydrogen phosphate in to <002> and <112> planes of hydroxyapatite took place in all the coatings along with formation of nano-crystalline structure. Calcium-rich porous hydroxyapatite scaffold formation takes place in low current density coating which in general exhibits low stability in terms of chemical bonding strength vis-à-vis corrosion protection performance. 10 mA/cm2 coating, which come with optimum presence of hydroxyapatite phase and crystallinity post electro-deposition, showed significant improvement in terms of increasing hydroxyl and phosphate bond polarization strength of hydroxyapatite phase and the same lead to improvement in the overall corrosion resistance performance of the coating by two times. Despite of formation of highest amount of hydroxyapatite phase during hydroxyl ion treatment in 20 mA/cm2 coatings, the corrosion protection performance results are negative on account of dilution of mostly low bonding amorphous phases with high internal residual stress.
Laser Induced Forward Transfer: Topography Dependence of Laser Fluence and Thickness for Titanium Film
Authors: Zhao Jie , Hu Yongxiang , Yao Zhenqiang
Published: September 2018

Compared with other metals, titanium has a wide range of applications in laser induced forward transfer (LIFT) due to its unique properties of low thermal conductivity and high melting point. In general, the titanium film is used as a sacrificial layer or transferred material in LIFT with different laser fluence. In this study, four different topography types are classified under the laser irradiation of ultraviolet nanosecond pulses. For Ti films with different thicknesses, probability distribution of these types is provided to demonstrate how topographies evolve with the increasing laser fluence. Through the research, the understanding of the physical mechanism of titanium film would be deepened.
Characterization of Nanofinished WC-Co Coating Using Advanced 3D Surface Texture Parameters
Authors: Ghosh Gourhari , Sidpara Ajay , Bandyopadhyay P. P.
Published: September 2018

WC-Co coatings are extensively used in abrasion, sliding, and erosion resistance applications for its favourable mechanical properties. Nanofinishing of WC-Co coating is required for aircraft landing gear cylinder and diesel engine cylinder. Characterisation of surface topography becomes an important aspect in tribological applications as it has significant effect on the functional performance of the surfaces. In this present study, the motif analysis with 5% wolf pruning is applied to identify the significant hills for pattern reorganization of the surface texture generated by different finishing steps such as grinding, shape adaptive grinding (SAG) and chemical assisted SAG (CA-SAG). Several 3D advanced texture parameters are employed to characterize the coated surface before and after finishing in terms of surface roughness, third and fourth moments (skewness and kurtosis) of the probability density function, bearing area ratio curve and fluid retention properties of the surface. Furthermore, power spectral density (PSD) analysis is performed to analyse the unevenness and periodicity of the texture. It is observed that the fluid retention property and the bearing property of the surface improve with the subsequent finishing stage.
Parametric Optimization for Nano-Finishing of the External Cylindrical Surfaces Using Rotating Core Magnetorheological Finishing Process
Authors: Singh Manpreet , Singh Anant Kumar
Published: September 2018

A rotating core magnetorheological finishing process has been developed to finish the external cylindrical surfaces at nano-level as the conventional finishing processes like grinding cannot meet the extreme precise requirement. The quality of finished cylindrical components estimated through its geometrical accuracy, material assets, and mechanical features. The macaroni making machine driving shaft is made up of mild steel where high quality of surface finish is required. In plastic toy industries, the mild steel punches are used where a high level of surface finish is required to increase the appearance of the products and to improve its geometrical accuracy. The MR finishing process can improve the external surface quality of the cylindrical components very precisely. This result in the improvement of prolongs functional performance of the components. In the present work, the optimum process parameters are experimentally investigated for nano-finishing of the mild steel cylindrical external surfaces using the rotating core magnetorheological (MR) finishing process. The rotation of tool core, the rotation of the cylindrical workpiece, the current, and the working gap are the control process parameters which affect the finishing performance i.e. percentage change in surface roughness value. So, the effects of these process parameters on the process response such as percentage change in surface roughness value have been analyzed using signal-to-noise ratios and mean response data. The current and the rotational speed of the tool core have been found as a considerable role for increasing the percentage change in roughness value. Further, the optimum magnitude of the process parameters are predicted as the current 3A, the rotational speed of tool 500 rpm, the rotational speed of the cylindrical workpiece 80 rpm and the working gap of 0.6 mm. With the finishing of these optimum process parameters on the present developed process, the average roughness Ra value of the external surface of the mild steel cylindrical is reduced to 60 nm from the initial Ra value of 600 nm in 90 minutes of finishing. The results of scanning electron microscopy test, mirror images and roughness graphs of the finished surface have confirmed that the present finishing process can fulfil the extreme precise requirement of surface quality which is not possible by the conventional finishing processes. The extreme precise requirement of the surface quality of the external cylindrical workpieces are dealing with mild steel punches in plastic toy industries, dies, and molds, macaroni making driving shafts, armature shaft, and shafts used in gear etc.
High-Performance Computing Based Big Data Analytics for Smart Manufacturing
Authors: Yang Yuhang , Cai Y. Dora , Lu Qiyue , Zhang Yifang , Koric Seid , Shao Chenhui
Published: September 2018

With the rapid development of sensing, communication, and computing technologies and infrastructure, today’s manufacturing industry is marching towards a big data era and a new generation of digitalization and intelligence. The availability of big data provides us with a golden opportunity to promote smart manufacturing. Nevertheless, the deployment and popularization of big data analytics in manufacturing is still at its nascent stage. One critical challenge results from the lack of high-performance computing (HPC) capability, which is crucial for responsive and intelligent decision-making in the modern manufacturing industry. To address this challenge, this paper proposes a framework and some general guidelines for implementing big data analytics in an HPC environment. The details of the whole workflow, from the prototype to the final application, are high-lighted. A case study for intelligent 3D sensing with real-world manufacturing data is presented to demonstrate the effectiveness of the proposed framework.
Laser Engineered Net Shaping of Titanium-Silver Alloy for Orthopedic Implant
Authors: Hu Yingbin , Maharubin Shahrima , Cong Weilong , Tan George
Published: September 2018

Post-surgery infection is one of the major causes of orthopedic implantation failure. Silver has been widely used as a broad-spectrum antimicrobial component in medical instrument. This paper presents a pioneering study on laser engineered net shaping (LENS) of titanium-silver (Ti-Ag) alloy for implant-related infection control. Ti-Ag alloy coupons were 3D printed through LENS process and characterized by 3D microscopy. The biofilm resistance and biocompatibility of the alloy samples were investigated. Results showed that the alloy significantly reduced the bacterial attachment for both Gram-positive and Gram-negative strains, and has no cytotoxicity to human fibroblast cells. This study demonstrated a great potential of laser 3D printed Ti-Ag alloy for orthopedic implant.
Robotic Work Cell Test Bed to Support Measurement Science for Monitoring, Diagnostics, and Prognostics
Authors: Klinger Alexander , Weiss Brian A.
Published: September 2018

Industrial robotics users, integrators, and manufacturers are implementing advanced monitoring, diagnostics, and prognostics (collectively known as Prognostics and Health Management (PHM)) techniques and technologies. PHM can take many different forms when implemented, and measures of effectiveness are highly dependent on the techniques implemented. A test bed has been built, and a use case designed, to represent common manufacturing tasks performed in robot work cells where PHM can provide greater equipment and process health intelligence. The physical and functional relationships within the work cell are mapped using a hierarchical deconstruction method to gain a better understanding of the propagation of effects of both equipment and process degradation. The test bed has been built so PHM techniques and technologies can be integrated and tested in a realistic scenario. Data is recorded for post processing and analysis for the verification and validation (V&V) of the implemented PHM techniques. The test bed will serve as a platform to develop, test, verify, and validate PHM techniques at the National Institute of Standards and Technology (NIST), and provide industry participants a standard platform for testing their PHM technologies. Having a common testing platform will provide industry a foundation for sets of tests to evaluate PHM. This paper presents the test bed and use case, the relationships therein, and the data management and collection approaches used to enable future research.
Robotic Finishing of Interior Regions of Geometrically Complex Parts
Authors: Kabir Ariyan M. , Shembekar Aniruddha V. , Malhan Rishi K. , Aggarwal Rohil S. , Langsfeld Joshua D. , Shah Brual C. , Gupta Satyandra K.
Published: September 2018

Surface finishing is an important manufacturing process. Many parts with complex geometries require finishing of internal regions before they can be used. In small and medium volume productions most of the finishing tasks are non-repetitive in nature, and have to be performed manually. These finishing operations for parts with complex geometries can be quite labor intensive, and may pose risk to humans. We have developed a collaborative finishing system where human operators work on high level decision making, and the robot assistants carry out the labor intensive low level finishing tasks. The human operator guides the robotic system by transferring operator knowledge through a user interface. Our system generates instructions for the robots based on the user inputs and task requirements. We have also developed a planning algorithm that automatically computes the paths for the robots by using the CAD model of the part. This significantly reduces the robot programming time and improves the efficiency of the finishing system. If needed, the system seeks help from the human operator by generating notifications.
Current-Dependent Kinetics of Self-Folding for Multi-Layer Polymers Using Local Resistive Heating
Authors: Elsisy Moataz , Poska Evan , Bedewy Mostafa
Published: September 2018

The purpose of this paper is to characterize the kinetics and direction of self-folding of pre-strained polystyrene (PSPS) and non-pre-strained styrene (NPS), which results from local shrinkage using a resistively heated ribbon in contact with the polymer sheet. A temperature gradient across the thickness of this shape memory polymer (SMP) sheet induces folding along the line of contact with the heating ribbon. Varying the electric current changes the degree of folding and extent of local material flow. This method can be used to create practical 3D structures. Sheets of PSPS and NPS were cut to 10 × 20 mm samples and their folding angles were plotted with respect to time, as obtained from in situ videography. In addition, the use of polyimide tape (Kapton) was investigated for controlling the direction of self-folding. Results show that folding happens on the opposite side of the sample with respect to the tape, regardless of which side the heating ribbon is on, or whether gravity is opposing the folding direction. Given the tunability of fold times and extent of local material flow, heat-assisted folding is a promising approach for manufacturing complex 3D lightweight structures by origami engineering.
An Experimental Study of Wedge Indentation of Porous Solids: Implications for Cutting and Drilling Processes
Authors: Yadav Shwetabh , Murthy Tejas G. , Sagapuram Dinakar
Published: September 2018

An experimental study of mechanics of wedge indentation of porous solids is carried out under plane-strain conditions. A comparison is made between the porous ductile copper and porous brittle gypsum to study the influence of matrix material on the indentation behavior. Image-based measurement techniques are used to capture the evolution of deformation zone and obtain quantitative velocity, strain and volume change fields at high resolution. The results show that despite widely-different characteristics of the matrix material, the overall deformation zone evolves in a manner that is largely similar across material systems. Porous copper exhibits a smoothly-varying radial compression-type plastic flow within the deformation zone, while localized flow features (compaction bands) are typical of gypsum. Implications of our observations on wedge indentation for modeling complex machining geometries such as cutting and drilling are briefly discussed.
Maintenance Decision Model for a Two-Machine Production Line With Multistage Degradation Machines
Authors: Kang Yunyi , Ju Feng
Published: September 2018

In this work, we develop preventative maintenance policies on two-machine-and-one-buffer production systems with machines subject to multi-stage degradation. Condition-based maintenance policies are generated for both machines, with consideration on both the machine degradation stages and the buffer level. Moreover, the policies are flexible, allowing a machine to be recovered to any better operating state, while merely recovering to the best operating state is possible in many previous work. A Markov decision model is formulated to find the optimal maintenance policy and computational experiments show that the policies improve the performance of a system in finite production runs.
Experimental Study on the Electrosurgical Tissue Joining Process With Process Parameter Monitoring for Quality Control
Authors: Yang Che-Hao , Chen Roland K. , Phillips Scott , Ramsay Josh , Li Wei
Published: September 2018

Electrosurgical tissue joining is an effective way to create hemostasis, especially in surgical procedures performed in the minimally-invasive manner. The quality of tissue joints and potential thermal damage to the surroundings are the two main concerns when using electrosurgical tissue joining tools. A more robust method for quality control is still needed. In this study, we developed an experimental setup to join tissues and performed tensile tests to evaluate the quality of the tissue joint, while also monitoring the process parameters including voltage, current, impedance, temperature and thermal dose. Three joining times (4, 6, and 8 seconds) and three compression levels (80%, 90%, and 95%) were used to join porcine arterial tissues. It was found that 95% compression can form a strong joint with a shorter joining time and less energy, but the joint strength decreases when the joining time is extended to 8 seconds. A lower compression level can still form a quality joint but requires longer joining time and energy which could lead to more thermal damages. A new index, specific strength (mmHg/J), which is defined as the ratio between tensile strength and the consumed energy, is proposed. Specific strength offers a new way to estimate the required joining time to achieve sufficient joining strength while minimizing the energy consumption to reduce thermal damages.
Numerical Modeling of Thermo-Fluid Flow and Metal Mixing in Laser Keyhole Welding of Dissimilar Metals
Authors: Tan Wenda , Huang Wenkang
Published: September 2018

In laser keyhole welding of dissimilar metals, the thermo-fluid flow in the molten pool has decisive effects on the compositional mixing of different chemical elements and hence the formation of detrimental intermetallic compounds. A numerical model is developed in this work to investigate the composition mixing in laser keyhole welding of dissimilar metals. The model takes into account multiple important physics in the process, including dynamic keyhole evolution, laser matter-interaction, phase change, thermo-fluid flow, and composition diffusion/advection. The preliminary simulation results demonstrate that the keyhole behavior is strongly affected by the properties of the dissimilar metals, and the keyhole fluctuation causes an unstable flow in the molten pool that facilitates the compositional mixing through advection.
Characterization of Kinematic Error Model Consistency for Five-Axis Machine Tools
Authors: Ma Le , Bristow Douglas A. , Landers Robert G.
Published: September 2018

New metrology tools, such as laser trackers, are enabling the rapid collection of machine tool geometric error over a wide range of the workspace. Error models fit to this data are used to compensate for high-order geometric errors that were previously challenging to obtain due to limited data sets. However, model fitting accuracy can suffer near the edges of the measurable space where obstacles and interference of the metrology equipment can make it difficult to collect dense data sets. In some instances, for example when obstacles are permanent fixtures, these locations are difficult to measure but critically important for machining, and thus models need to be accurate at these locations. In this paper, a method is proposed to evaluate the model accuracy for five-axis machine tools at measurement boundaries by characterizing the statistical consistency of the model fit over the workspace. Using a representative machine tool compensation method, the modeled Jacobian matrix is derived and used for characterization. By constructing and characterizing different polynomial order error models, it is observed that the function behavior at the boundary and in the unmeasured space is inconsistent with the function behavior in the interior space, and that the inconsistency increases as the polynomial order increases. Also, the further the model is extrapolated into unmeasured space, the more inconsistent the kinematic error model behaves.
Surface Grinding of ZTA Parts Fabricated by Laser Engineered Net Shaping Process: Effects of ZrO2 Content and Ultrasonic Vibration
Authors: Hu Yingbin , Wang Hui , Li Yuanchen , Ning Fuda , Cong Weilong
Published: September 2018

The zirconia toughened alumina (ZTA) parts fabricated by laser engineered net shaping (LENS) process demonstrate problems resulted from poor surface quality. To improve surface quality and to reduce related problems, rotary ultrasonic machining (RUM) process, which combines both grinding process and ultrasonic machining process, has been introduced. In this investigation, the effects of ZrO2 content and ultrasonic vibration on flatness, surface roughness, microhardness, and cutting force in feeding direction of LENS-fabricated ZTA parts have been studied. Results showed that with the ZrO2 content increasing, the flatness value increased, the surface roughness value decreased, and the microhardness value firstly increased then decreased. Compared with LENS-fabricated parts, the parts processed by RUM machine exhibited better surface quality with significantly reduced flatness value and surface roughness value. In RUM process, the introduction of ultrasonic vibration was beneficial for reducing cutting force.
A Combined Experimental-Numerical Method to Evaluate Powder Thermal Properties in Laser Powder Bed Fusion
Authors: Cheng Bo , Lane Brandon , Whiting Justin , Chou Kevin
Published: September 2018

Powder bed metal additive manufacturing (AM) utilizes a high-energy heat source scanning at the surface of a powder layer in a pre-defined area to be melted and solidified to fabricate parts layer by layer. It is known that powder bed metal AM is primarily a thermal process and further, heat conduction is the dominant heat transfer mode in the process. Hence, understanding the powder bed thermal conductivity is crucial to process temperature predictions, because powder thermal conductivity could be substantially different from its solid counterpart. On the other hand, measuring the powder thermal conductivity is a challenging task. The objective of this study is to investigate the powder thermal conductivity using a method that combines a thermal diffusivity measurement technique and a numerical heat transfer model. In the experimental aspect, disk-shaped samples, with powder inside, made by a laser powder bed fusion (LPBF) system, are measured using a laser flash system to obtain the thermal diffusivity and the normalized temperature history during testing. In parallel, a finite element model is developed to simulate the transient heat transfer of the laser flash process. The numerical model was first validated using reference material testing. Then, the model is extended to incorporate powder enclosed in an LPBF sample with thermal properties to be determined using an inverse method to approximate the simulation results to the thermal data from the experiments. In order to include the powder particles’ contribution in the measurement, an improved model geometry, which improves the contact condition between powder particles and the sample solid shell, has been tested. A multi-point optimization inverse heat transfer method is used to calculate the powder thermal conductivity. From this study, the thermal conductivity of a nickel alloy 625 powder in powder bed conditions is estimated to be 1.01 W/m·K at 500 °C.
Printing Free-Form Free-Standing Glass Structures
Authors: Curtis Bret , Peters Daniel , Hostetler John , Landers Robert , Bristow Douglas , Kinzel Edward C.
Published: September 2018

Transparent, bubble-free glass structures can be printed using a filament-fed, laser-heated additive manufacturing process. In this process, a stationary CO2 laser beam is focused at the intersection of the filament and workpiece to locally heat the glass above its working temperature. Glass enters the molten region and is deposited on the workpiece as the workpiece is translated/rotated using a 4-axis stage. This paper studies creating free-form, free-standing objects which is facilitated by the glass rapidly achieving structural rigidity as it cools upon exiting the molten region. The effects of the process parameters and printing techniques are examined and optimized to print simple wall and truss structures.
Chip Morphology Studies Using Separate Fracture Toughness Values for Chip Separation and Serration in Orthogonal Machining Simulations
Authors: Patel Jaimeen , Cherukuri Harish P.
Published: September 2018

It is well known that the chip morphology predictions in machining simulations depend on the separation criteria used for modeling chip formation. In this paper, we propose to use two different criteria for chip separation and serration along with the Johnson-Cook damage model. The threshold value for chip separation is determined from machining experiments using the methodologies discussed in Patel et al. [1]. In addition, two separate damage evolution laws for chip separation and serration are used. Our results indicate that the choice of the evolution law and the threshold values of Gc used for chip separation and serration have a significant effect on chip shape and other field variables such as the equivalent plastic strain, cutting force, temperature, etc.
A State-of-the-Art Review on Solid-State Metal Joining
Authors: Cai Wayne , Daehn Glenn , Vivek Anupam , Li Jingjing , Khan Haris , Mishra Rajiv , Komarasamy Mageshwari
Published: September 2018

This paper aims at providing a state-of-the-art review of an increasingly important class of joining technologies called solid-state welding. Among many other advantages such as low heat input, solid-state processes are particularly suitable for dissimilar materials joining. In this paper, major solid-state joining technologies such as the linear and rotary friction welding, friction stir welding, ultrasonic welding, impact welding, are reviewed, as well as diffusion and roll bonding. For each technology, the joining process is first depicted, followed by the process characterization, modeling and simulation, monitoring/diagnostics/NDE, and ended with concluding remarks. A discussion section is provided after reviewing all the technologies on the common critical factors that affect the solid-state processes such as the joining mechanisms, chemical and materials compatibility, surface properties, and process conditions. Finally, the future outlook is presented.
Additive Manufacturing for Civil Infrastructure Design and Construction: Current State and Gaps
Authors: Bhardwaj Abhinav , Zou Na , Pei Z. J.
Published: September 2018

Additive manufacturing (AM) has applications in several fields ranging from aerospace and consumer goods to the medical industry. However, applications of AM in civil infrastructure design and construction are very limited. Based on information shared at the NSF workshop on Additive Manufacturing (3D Printing) for Civil Infrastructure Design and Construction in July 2017, this paper summarizes the current state of the field, gaps, and recommendations.
Fabrication of Efficient Electrodes for Dye-Sensitized Solar Cells Using Additive Manufacturing
Authors: James Sagil , Contractor Rinkesh , Veyna Chris , Jiang Galen
Published: September 2018

Dye-Sensitized Solar Cells (DSSC) are third generation solar cells used as an alternative to c-Si solar cells. DSSC are mostly flexible, easier to handle and are less susceptible to damage compared to c-Si solar cells. Additionally, DSSC is an excellent choice for indoor application as they perform better under diverse light condition. Most DSSCs are made of liquid medium sandwiched between two conductive polymer layers. However, DSSCs have significantly lower efficiencies compared to silicon solar cells. Also, use of liquid medium resulting in leaking of liquid, and occasional freezing during cold weather, and thermal expansion during hot weather conditions. DSSC can be manufactured in small quantities using relatively inexpensive solution-phase techniques such as roll-to-roll processing and screen printing technology. However, scaling-up the DSSC manufacturing from small-scale laboratory tests to sizeable industrial production requires better and efficient manufacturing processes. This research studies the feasibility of using additive manufacturing technique to fabricate electrodes of DSSC. The study aims to overcome the limitations of DSSCs including preventing leakage and providing more customized design. Experimental studies are performed to evaluate the effects of critical process parameters affecting the quality of electrodes for DSSC. Volume resistivity test is performed to evaluate the efficiency of the electrodes. In this study, the electrodes of DSSC are successfully fabricated using Fused Disposition Modeling (FDM) 3D printing technique. The results of this study would enable additive manufacturing technology towards rapid commercialization of DSSC technology.
Modeling for Prediction of Surface Roughness and Experimental Research in Ultra-Precision Flycutting Machining
Authors: Li Jiasheng , Jiao Yang , Liu Pinkuan
Published: September 2018

To improve the surface quality of the copper and reduce the diamond tool wear, a prediction model is established experimentally for the relationship between surface roughness and machining parameters. Based on the processing principle of flycutting machining, the prediction model for surface roughness is set up by response surface methodology. Then, a machining experiment for the copper is conducted under different cutting parameters designed by Taguchi method and the surface roughness is tested by 4D technology dynamic laser interferometer. After that, the prediction model is obtained by analyzing the experimental data, and the accuracy of the model is verified by analysis of variance (ANOVA), R2 value and residual analysis. Furthermore, the effect of cutting parameters upon the surface roughness is analyzed. Finally, validation tests are conducted to verify the model. Experimental results demonstrate that the prediction model is adequate at 95% confidence level. The output of prediction model helps to select cutting parameters to reduce surface roughness which ensures surface quality in ultra-precision fly cutting machining.
Prediction of fluid flow and acoustic field of a supersonic jet using vorticity confinement
Authors: Sadri M. , Hejranfar K. , Ebrahimi M.
Published: September 2018

In this study, the numerical simulation of the fluid flow and acoustic field of a supersonic jet is performed by using high-order discretization and the vorticity confinement (VC) method on coarse grids. The three-dimensional Navier-Stokes equations are considered in the generalized curvilinear coordinate system and the high-order compact finite-difference scheme is applied for the space discretization, and the time integration is performed by the fourth-order Runge-Kutta scheme. A low-pass high-order filter is applied to stabilize the numerical solution. The non-reflecting boundary conditions are adopted for all the free boundaries, and the Kirchhoff surface integration is utilized to obtain the far-field sound pressure levels in a number of observer locations. Comparisons of the jet mean flow and jet aeroacoustics results with the other numerical and experimental data at similar flow conditions are made and show a reasonable agreement. The study shows that the proposed solution methodology based on the high-order compact finite-difference scheme in conjunction with the VC method can reasonably predict the near-field flow and the far-field noise of high Reynolds number jets with a fairly coarser grid than that used in the large eddy simulations and, thus, the computational cost can be significantly decreased.
Social-Media-Based Antibrand Communities Opposing Sport-Team Sponsors: Insights From Two Prototypical Communities
Authors: Popp Bastian , Horbel Chris , Germelmann Claas Christian
Published: September 2018

This study investigated social-media-based anti-sponsor-brand communities and their impacts, not only on the sponsoring brand but also on the sponsored club and the sport itself. Guided by balance theory and social identity theory, the authors conducted a qualitative study of 2 distinctive, prototypical Facebook-based anti-sponsor-brand communities of teams from the German Football League (Bundesliga). The results reveal common findings for both cases, including members’ motivation to oppose a sponsor and, at the same time, to protect the sport. However, the communities differ in terms of their members’ relationships to the club. This results in different consequences for the sponsor and club brands, as well as for other actors in the sponsorship network. To managers of clubs, sponsors, and sport-governing bodies, the authors suggest concerted strategies like image campaigns and interaction with anti-sponsor-brand communities as responses to different community motivations.
Electrocardiographic Safety of Repeated Monthly Dihydroartemisinin-Piperaquine as a Candidate for Mass Drug Administration
Authors: Millat-Martínez Pere , Ila Rhoda , Laman Moses , Robinson Leanne , Karunajeewa Harin , Abel Haina , Pulai Kevin , Sanz Sergi , Manning Laurens , Moore Brioni , Bassat Quique , Mitjà Oriol
Published: September 2018

Mass drug administration (MDA) of sequential rounds of antimalarial drugs is being considered for use as a tool for malaria elimination. As an effective and long-acting antimalarial, dihydroartemisinin-piperaquine (DHA-PQP) appears to be suitable as a candidate for MDA.