bluuebunny/crossref_metadata_2025 huggingface dataset:
Joint Maintenance and Production Planning by Maintenance-Optimal Swapping
Authors: Almuhtady Ahmad , Lee Seungchul , Ni Jun
Published: November 2013

Degradation is an inevitable course of any manufacturing tool, machine or system. The degradation of the health state of manufacturing tools results in some sort of an ineludible maintenance action which could be both costly and occurring during critical production time. In many manufacturing systems, a fleet of identical machines are assigned different tasks (or products) towards satisfying production requirements. We re-introduce the maintenance-optimal resource allocation planning scheme [1] (presented in MSEC2012) and focus on the solution of the generated mathematical model. The planning scheme, denoted as Degradation Based Optimal Swapping (DBOS), incorporates the optimal implementation of swapping scheduled tasks (or products) and allocating maintenance actions throughout a finite time horizon. The objective is to minimize projected maintenance costs and/or utilize the manufacturing productivity towards prescribed logistics and/or production goals. A DBOS-specific branch-and-bound-based optimization algorithm is developed to address the complexity in the generated model. Numerical results will demonstrate the effectiveness of the algorithm in comparison to standard optimization algorithms. DBOS planning scheme coupled with the proposed algorithm succeeds in establishing substantial savings in the simulated case studies which amount up to 70% of the estimated maintenance costs in comparison to the scenario where fixed scheduling is applied.
Study of the Effect of Anode/Cathode Geometry on the Yield Rate and Quality of the MWCNTs Synthesized by Submerged Arc Discharging
Authors: Awadallah Osama M. , Rashad Ragaie M. , Wifi Abdalla S.
Published: November 2013

The main objective of the present paper is to clarify the effect of anode/cathode geometry combinations on the yield rate and quality of the Multiwalled Carbon Nanotubes (MWCNTs) produced by submerged arc discharge technique. The effects of current intensity and the discharging medium (solvent) are also investigated. The morphology and crystalline perfection of the produced MWCNTs are confirmed by transmission electron microscopy (TEM) and Electron diffraction. Thermogravimetric analysis (TGA) is conducted to check the quality of the MWCNTs in a quantitative manner. The flat ended anode/cathode combination of diameters 4 and 12 mm respectively exhibited the highest yield at 70 A using deionized water as solvent. Through careful selection of the process parameters, the yield rate of MWCNTs obtained is found to be higher than most of the reported values in literature. However, the best quality of MWCNTs with purity as high as 95%, average thermal stability of 745°C as well as good batch homogeneity, is obtained with KCl solution and tapered male/female anode combination. The best quality MWCNTs is used successfully as reinforcement for A356 aluminum silicon composite.
A Comprehensive Model for Laser Hardening of Carbon Steels
Authors: Fortunato Alessandro , Ascari Alessandro , Liverani Erica , Orazi Leonardo , Cuccolini Gabriele
Published: November 2013

This article illustrates the development of a complete and exhaustive mathematical model for the simulation of laser transformation hardening of hypo-eutectoid carbon steels. The authors propose an integrated approach aimed at taking into consideration all the the phenomena involved in this manufacturing process, with particular attention to implementing easy mathematical models in order to optimize the trade-off between the accuracy of the predicted results and the computational times. The proposed models involve the calculation of the 3D thermal field occurring into the workpiece and predict the microstructural evolution of the target material exploiting an original approach based on the definition of thermodynamic thresholds which can be considered as a physical constant of the material itself. Several parameters and phenomena are taken into consideration in order to accurately simulate the process: laser beam characteristics, fast austenization of the steel and tempering effect due to mutually interacting beam trajectories.
Mechanical Behavior of Ti-6Al-4V Manufactured by Electron Beam Additive Fabrication
Authors: Ladani Leila , Roy Lalit
Published: November 2013

Additive Layer Fabrication, in particular Electron Beam Additive Fabrication (EBAF), has recently drawn much attention for its special usability to fabricate intricately designed parts as a whole. It not only increases the production rate which reduces the production lead time but also reduces the cost by minimizing the amount of waste material to a great extent. Ti6Al4V is the most common type of material that is currently being fabricated using EBAF technique. This material has been used in aerospace industry for several reasons such as excellent mechanical properties, low density, great resistance to corrosion, and non-magnetism. The effects of build direction of layers (namely, addition of layers along one of the x, y & z directions with respect to the build table) and the anisotropy effect caused by it has not been explored vigorously. This anisotropy effect has been investigated in this work. Different mechanical properties such as Yield Strength (YS), Ultimate Tensile Strength (UTS), and Modulus of Elasticity (E) of these three types of Ti6Al4V are determined using tensile tests and are compared with literature. The tensile test results show that YS and UTS for flat-build samples have distinguishably higher values than those of the side-build and top-build samples.
Fabrication of Chitosan Porous Structure and Applications on Artificial Photosynthesis Device
Authors: Ren Xiang , Yu Miao , Zhou Xiaohang , Zhang Qingwei , Zhou Jack
Published: November 2013

Research and development on artificial photosynthesis provide a new direction to obtain sustainable energy. To increase the artificial photosynthesis reaction rates and the efficiency of collecting the energy product, a novel artificial photosynthesis device was designed and developed to constrain the photosynthesis reactions in chitosan porous structure. Both 3D printing and molding-casting could be used in fabrication of chitosan structure on artificial photosynthesis devices. In molding and casting, the molds were made by acrylonitrile butadiene styrene (ABS) and polydimethylsiloxane (PDMS). Concurrently, 3D interconnected chitosan channels were built with a user-made heterogeneous 3D rapid prototyping machine, and the lyophilization method was used to generate the micro or nano pores inside the chitosan scaffold. After lyophilization, the pore size and porosity was generated by MATLAB image processing. CO2 absorption was simulated based on porous structures properties when import the chitosan into the artificial photosynthesis devices. The results suggested that chitosan porous structure is a good candidate to be an interface between atmosphere and micro-fluidic devices with biochemical reactions.
Multi-Zone Proportional Hazard Model for a Multi-Stage Degradation Process
Authors: Li Lin , Sun Zeyi , Xu Xinwei , Zhang Kaifu
Published: November 2013

Conditional-based maintenance (CBM) decision-making is of high interests in recent years due to its better performance on cost efficiency compared to other traditional policies. One of the most respected methods based on condition-monitoring data for maintenance decision-making is Proportional Hazards Model (PHM). It utilizes condition-monitoring data as covariates and identifies their effects on the lifetime of a component. Conventional modeling process of PHM only treats the degradation process as a whole lifecycle. In this paper, the PHM is advanced to describe a multi-zone degradation system considering the fact that the lifecycle of a machine can be divided into several different degradation stages. The methods to estimate reliability and performance prognostics are developed based on the proposed multi-zone PHM to predict the remaining time that the machine stays at the current stage before transferring into the next stage and the remaining useful life (RUL). The results illustrate that the multi-zone PHM effectively monitors the equipment status change and leads to a more accurate RUL prediction compared with traditional PHM.
Corotating or Codeforming Models for Thermoforming: Free Forming
Authors: Baek H. M. , Giacomin A. J.
Published: November 2013

Our previous work [J Pol Eng, 32, 245 (2012)] explores the role of viscoelasticity for the simplest relevant problem in thermoforming, the manufacture of cones. In this previous work, we use a differential model employing the corotational derivative [the corotational Maxwell model (CM)] for which we find an analytical solution for the sheet deformation as a function of time. This previous work also identifies the ordinary nonlinear differential equation corresponding to the upper convected Maxwell model (UCM), for which she finds no analytical solution. In this paper, we explore the role of convected derivative by solving this UCM equation numerically by finite difference. We extend the previous work to include sag by incorporating a finite initial sheet curvature. We treat free forming step in thermoforming and find that the convected derivative makes the free forming time unreasonably sensitive to the initial curvature. Whereas, for the CM model, we get a free forming time that is independent of initial sheet curvature, so long as the sheet is nearly flat to begin with. We cast our results into dimensionless plots of thermoforming times versus disk radius of curvature.
Experimental Investigation of Chip Formation and Surface Topology in Ultrasonic-Assisted Milling of X20Cr13 Stainless Steel
Authors: Abootorabi Zarchi M. Mahdi , Razfar M. R. , Abdullah A.
Published: November 2013

In the present paper, by using longitudinal one dimensional ultrasonic vibrations, characteristics of side milling of X20Cr13 martensitic stainless steel has been investigated. In order to experimentally investigate the chip formation and machined surface topology of workpiece, conventional milling (CM) and ultrasonic-assisted milling (UAM) processes have been applied and compared in certain cutting conditions. Imaging by digital microscope shows that applying ultrasonic vibrations on milling process leads to thinner and smaller formed chips and it also makes machined surface of workpece flatter. In both CM and UAM processes, as feed rate increases, chips become thicker and machine surface loses its flatness.
Fatigue Properties and Life Prediction of 8630 Cast Steel in the Presence of Weld Repair and Porosities
Authors: Shirazi Alireza , Ragai Ihab
Published: November 2013

The objective of the this work is to study the effect of weld repair and macro-porosities on fatigue properties and fatigue life of AISI 8630 cast steel subjected to bending cyclic loads. Test specimens were cut from a cast steel component that contains macro-porosities. To regain the structural integrity, the component is typically excavated and weld repaired.

In this study, weld repairs are simulated by machining a cylindrical groove across the width of the specimen then the groove is welded using different weld rods and various pre and post weld heat treatment conditions. All specimens were examined by radiography (X-Ray) in accordance with ASTM E446 before depositing the weld in order to verify the quality of the samples. After welding, the quality of the welded grooves was examined using ultrasonic testing (UT) and magnetic particle inspection (MPI) in accordance with ASTM A609 and ASTM E709 standards, respectively.

Qualified samples were then machines to the final dimensions. The fatigue test was performed under pure bending conditions using four-point bend set up. This set up allows localizing stresses at the sites where weld repairs were applied.

Experimental results show that specimens with stronger weld material tested under no heat treatment conditions have comparable fatigue performance to those heat treated specimens with lower strength weld material.

Furthermore, it was found that the fatigue test results are highly affected by the presence of micro-porosities within the cast steel material. Therefore, an analytical approach to predict the fatigue life is also presented in this work. A good agreement is achieved between the predicted fatigue lives and the experimental results.

Generally, the results show that for porosities with width to depth ratios between 0.25 to 1 and width size smaller than or equal to 1 mm the life is reduced by up to 1.5 orders of magnitude while the endurance limit was reduced by a factor of 1.57. Similarly for porosities with ratios between 1.5 and 2.5 and width greater than 1.5 mm the life was reduced by 2.5 orders of magnitude and the endurance limit was reduced by a factor of 2.2.
Finite Element Modeling on Dislocation Density and Grain Size Evolution in Machined Surface
Authors: Ding Liqiang , Zhang Xueping , Liu C. Richard
Published: November 2013

Machining process usually induces Severe Plastic Deformation (SPD) in the chip and machined surface, which will further lead to rapid increase of dislocation density and alteration of grain size in micro-scale. This paper presents a novel FE model to simulate the dislocation density and grain size evolution in the machined surface and subsurface generated from the orthogonal cutting process of Al6061-T6. A dislocation density model of microstructure evolution is implemented in the FE model as a user-defined subroutine written in FORTRAN. The model can predict the microstructure characteristic in a machined surface. The predicted chip thicknesses, cutting forces, distributions of dislocation density and grain size are verified by the experimental tests of the chip, forces, microstructure and micro-hardness. The predicted results show that the dislocation density decreases along the depths of machined surface; whereas the grain size shows an opposite tendency. Dislocation density in machined surface decreases and grain size increases when cutting speed increases. Higher cutting speeds are associated with thinner deformation layers. Dislocation density in a machined surface decreases initially and then increases with feed rates. Dislocation density increases significantly when cutting tool has a larger negative rake angle. The bigger negative rake angles further lead to the thicker deformation layers in machined surface.
Characterization of Sintered Ti-6Al-4V Powders in Electron Beam Additive Manufacturing
Authors: Gong Xibing , Chou Kevin
Published: November 2013

In the powder-based electron beam additive manufacturing (EBAM) process, preheating is applied, prior to the melting stage, to aggregate precursor powders and to reduce the residual stresses in the build parts. Preheating results in sintering of the powders, which serve as the initial work material for the subsequent melting stage. In this study, sintered Ti-6Al-4V alloy powders from preheating were obtained and studied. The specimens of sintered powders, also processed to prepare metallographic samples, were observed and characterized by optical microscopy (OM) and scanning electron microscopy (SEM). The results show that after preheating, some powders are partially “melted” and necks between adjacent particles are formed with metallurgical bonds. The sintering evidence, necking, can be noted on both the build plane and the side surface (normal to the build plane). The Baktetwave α-β structure is identified in the powders, while the martensitic structure is formed in the solid EBAM part.
Lifecycle Management of Knowledge in a Cloud Manufacturing System
Authors: Hu Anrui , Zhang Lin , Tao Fei , Hu Xiaohang
Published: November 2013

Cloud manufacturing is a new service-oriented intelligent manufacturing paradigm. Knowledge is a core part and the foundation to realize its intelligence. In this paper, the importance and functions of knowledge to cloud manufacturing was first investigated from the lifecycle of cloud service. Then a knowledge management system was designed and the layered architecture and key technologies were analyzed. A case study was conducted to demonstrate the feasibility of the proposed knowledge management system.
A Critical Factor in Enhancement of MQL Lubricants: Platelet Thickness
Authors: Nguyen Trung Kien , Kwon Patrick Y. , Park Kyung-Hee
Published: November 2013

The lamellar-type solid lubricants are readily available in a form of platelets. The diameter and thickness of these platelets are typically up to tens of microns and few microns, respectively, which are classified as micro-platelets. Some of these platelets are also available as nano-platelets whose thickness is well below a micron (even to few nanometers). In the previous work, the vegetable oil mixed with nano-platelets was enormously effective for Minimum Quantity Lubrication (MQL) machining. Clearly, the micro-platelets are not as inexpensive. In addition, the mixtures with the micro-platelets are not as stable as those with the nano-platelets. This paper intends to find the effect of the thickness differential on these platelets in MQL machining. The tribometer test shows that the nano-platelets are much more effective than the micro-platelets in reducing wear without changing the friction. With the MQL ball mill experiment, the micro-platelets present in MQL oil increased the tool wear, even compared to the traditional MQL with pure oil only. Thus, the thickness of the nano-platelets holds an important characteristic to enhance MQL-based machining.
Research Progress of Cloud Manufacturing in China: A Literature Survey
Authors: Lin Qun , Xia Kai , Wang Lihui , Gao Liang
Published: November 2013

Cloud manufacturing has been of considerable interest to Chinese academic researchers over the last decade. This paper presents a broad perspective of the research on cloud manufacturing in China. The topics studied mainly include design of cloud manufacturing architecture, resource and capability virtualization, combinatorial optimization of virtual resource and capability, design and collaboration of cloud manufacturing services, intelligent searching and matching method and trust evaluation. The present literature survey also includes two successful cases applying cloud manufacturing in China to verify the feasibility of the cloud manufacturing architecture and services. Potentially interesting directions for future research in this area are also identified.
Product-Oriented Sustainability Aspects of Abrasive Processes
Authors: Aurich Jan C. , Carrella Marina , Kirsch Benjamin
Published: November 2013

Sustainability in manufacturing became more and more important in the last years and, because of scarcity of resources, will become even more important in the future. In a process-oriented view, abrasive processes appear to be the worst manufacturing processes concerning sustainability due to their high required specific energies. In this paper a product-oriented view is proposed, taking the whole Life Cycle of the machined products into account. In doing so, it becomes evident that abrasive processes can enhance sustainability even when investing additional energy during machining.
Characterization of Fluid Film Produced by an Atomization–Based Cutting Fluid (ACF) Spray System During Machining
Authors: Hoyne Alexander C. , Nath Chandra , Kapoor Shiv G.
Published: November 2013

The atomization–based cutting fluid (ACF) spray system has recently been proposed as a cooling and lubrication solution for machining hard to machine materials (e.g. titanium alloys). On the tool rake face, the ACF spray system forms a thin film from cutting fluid that penetrates into the tool–chip interface to improve tool life. The objective of this work is to characterize this thin fluid film in terms of thickness and velocity for sets of ACF spray parameters. ACF spray experiments are performed by varying impingement angle in order to observe the nature of the spreading film, and to determine the film thickness at different locations after impingement of the droplets. It is observed that the film spreads radially outward producing three fluid film development zones (i.e. impingement, steady, unsteady). The steady zone is found to be between 3 and 7 mm from the focus (impingement point) of the ACF spray for the set of parameters investigated. An analytical 3D thin fluid film model for the ACF spray system has also been developed based on the equations for continuity of mass and momentum. The model requires a unique treatment of the cross–film velocity profile, droplet impingement and pressure distributions, as well as a strong gas–liquid shear interaction. The thickness profiles predicted by the analytical film model have been validated. Moreover, the model predictions of film velocity and chip flow characteristics during a titanium turning experiment reveal that the fluid film can easily penetrate into the entire tool–chip interface with the use of the ACF spray system.
Monitoring Multistage Surface Spatial Variations Using Functional Morphing
Authors: Suriano Saumuy , Wang Hui , Hu S. Jack
Published: November 2013

In multistage manufacturing processes, the machined surface shape of a part changes as it goes through each stage. Process monitoring at multiple stages is necessary for root cause diagnosis and surface variation reduction. However, due to measurement time and capacity constraints, it is challenging to collect sufficient surface measurements at all intermediate stages for monitoring. This paper proposes a functional morphing based algorithm to monitor the surface variation propagation using end of line multi-resolution measurements supplemented with low resolution measurements at intermediate stages. The surface changes over multiple stages are captured by a functional morphing model which integrates geometric transformations with engineering insights. The model estimates a morphed surface prediction at an intermediate stage of interest using end-of-line surface measurements. This morphed surface is combined with the low-resolution measurements at that stage to improve the surface prediction accuracy. The model can be further improved by incorporating the effects of correlated process variables. Based on the model, abnormal surface variations can be detected and located by a single-linkage cluster monitoring algorithm as developed in our previous work. The case study of a two-stage machining process demonstrates that the method successfully monitors multistage surfaces using reduced measurement resolution at intermediate stages.
Effect of Inter-Particle Interaction on Particle Deposition in a Cross-Flow Microfilter
Authors: Jubery Talukder Z. , Kapoor Shiv G. , Wentz John E.
Published: November 2013

Recent studies show that inter-particle interaction can affect particle trajectories and particle deposition causing fouling in the microfilters used for metal working fluids (MWFs). Inter-particle interaction depends on various factors: particle geometry and surface properties, membrane pore geometry and surface properties, MWF’s properties and system operating conditions, etc. A mathematical model with a Langevin equation for particle trajectory and a hard sphere model for particle deposition has been used to study the effect of particle’s size, particle’s surface zeta potential, inter-particle distance, and shape of membrane pore wall surface on particle trajectory and its deposition on membrane pore wall. The study reveals that bigger particles have a lesser tendency to be deposited on membrane pore walls than smaller particles. The shape of the membrane pore wall surface can also affect the particle deposition behavior.
Automated Part Inspection Using 3D Point Clouds
Authors: Wells Lee J. , Shafae Mohammed S. , Camelio Jaime A.
Published: November 2013

Ever advancing sensor and measurement technologies continually provide new opportunities for knowledge discovery and quality control (QC) strategies for complex manufacturing systems. One such state-of-the-art measurement technology currently being implemented in industry is the 3D laser scanner, which can rapidly provide millions of data points to represent an entire manufactured part’s surface. This gives 3D laser scanners a significant advantage over competing technologies that typically provide tens or hundreds of data points. Consequently, data collected from 3D laser scanners have a great potential to be used for inspecting parts for surface and feature abnormalities. The current use of 3D point clouds for part inspection falls into two main categories; 1) Extracting feature parameters, which does not complement the nature of 3D point clouds as it wastes valuable data and 2) An ad-hoc manual process where a visual representation of a point cloud (usually as deviations from nominal) is analyzed, which tends to suffer from slow, inefficient, and inconsistent inspection results. Therefore our paper proposes an approach to automate the latter approach to 3D point cloud inspection. The proposed approach uses a newly developed adaptive generalized likelihood ratio (AGLR) technique to identify the most likely size, shape, and magnitude of a potential fault within the point cloud, which transforms the ad-hoc visual inspection approach to a statistically viable automated inspection solution. In order to aid practitioners in designing and implementing an AGLR-based inspection process, our paper also reports the performance of the AGLR with respect to the probability of detecting specific size and magnitude faults in addition to the probability of a false alarms.
Laser Beam Forming: Experimental Investigation and Statistical Analysis of the Effects of Parameters on Bending Angle
Authors: Akinlabi Stephen , Shukla Mukul , Marwala Tshilidzi
Published: November 2013

Laser Beam Forming (LBF), a non-contact manufacturing process has become a viable manufacturing process for shaping of metallic components. The capability of LBF and bending demands more on experimental studies to identify optimized parameter settings and also establish the probable influence of process parameters on the response i.e. the resulting bending angles in the present work. The experiments on laser forming process of 3 mm steel plate were conducted using a 4.4 kW Nd: YAG laser (Rofin DY 044), at the Council for Science and Industrial Research - National Laser Centre (CSIR-NLC), Pretoria, South Africa. This paper investigates the effects of five important process parameters such as namely laser power, beam diameter, number of scan tracks, scan velocity and cooling effect on the resulting formed sample curvature. Statistical tools combined with the Taguchi robust Design of Experiment, based on the L-27 Taguchi Orthogonal array (TOA) have been used. The samples were successfully formed to different curvatures following the experimental design. Both the Taguchi analysis and Analysis of Variance (ANOVA) established that the number of scan irradiation had the maximum effect while cooling effect coolant flow had the least contribution on the bending angle of formed components. Regression analysis was also conducted on the experimental data and a linear model relating all the influencing parameters was developed with an R-square value of around 98% showing the goodness of fit of the model. The regression model confirms that the experimentally measured bending angles were in good agreement with the model predicted values. This model can ultimately be used to estimate the bending angle in LBF of 3 mm steel plate within the study range of parameters.
Bayesian-Based Probabilistic Force Modeling in Cold Rolling
Authors: Wendel John C. , Nelson Andrew W. , Malik Arif S. , Zipf Mark E.
Published: November 2013

A primary factor in manufacturing high-quality cold-rolled sheet is the ability to accurately predict the required rolling force. The rolling force directly influences roll-stack deflections, which correlate to the resulting flatness quality of the rolled sheet. Increasingly high demand for thin and ultra-thin gauge for cold-rolled sheet metals, along with the correspondingly larger sensitivity of flatness defects when rolling thin gauges, makes it more important to accurately and rapidly predict the rolling force before the rolling operation begins. Accurate rolling force predictions enable assignment of appropriate pass schedules and flatness mechanism set-points early in the rolling process, thereby reducing rolling time, improving quality, and reducing scrap. Traditionally, force predictions in cold rolling have employed two-dimensional analytical models such as those proposed by Roberts and by Bland & Ford. These simplified methods are prone to inaccuracy, however, because of several uncertain, yet influential, model parameters that are difficult to establish deterministically for wide-ranging products. These parameters include, for example, the average compressive yield strength of the rolled strip, frictional characteristics relating to low and high mill speeds, and the strain rate dependency of yield strength. Conventionally, these unknown parameters have been evaluated deterministically by comparing force predictions with actual rolling force data and using a best-fit regression approach. In this work, Bayesian updating using a probability mass function (PMF) is applied to identify joint posterior probability distributions of the uncertain parameters in rolling force models. It is shown that the non-deterministic Bayesian updating approach is particularly useful as new evidence becomes available in the form of additional rolling force data. The aim of the work is to incorporate Bayesian inference into rolling force prediction for cold rolling mills to create a probabilistic modeling approach which can also “learn” as new production data is added. The goal is a model that can better predict necessary mill parameters based on accurate probability estimates of the actual rolling force. The rolling force data used in this work for applying Bayesian updating is actual production data of grades 301 and 304L (low carbon) stainless steels, rolled on a 10-inch wide 4-high cold rolling mill. This force data was collected by observing and averaging load cell measurements at steady rolling speeds.
Simulation of Surface Roughness Effects on Residual Stress in Laser Shock Peening
Authors: Hasser Peter J. , Malik Arif S. , Langer Kristina , Spradlin Thomas J.
Published: November 2013

Laser peening (LP) has shown to be a viable method by which the fatigue life of metallic components can be extended. Although current commercial implementation of LP techniques has not developed much beyond a trial-and-error methodology to implement the process, researchers at several institutions have examined various parameters that affect residual stress fields induced by LP, using Finite Element Analysis (FEA) and semi-empirical eigenstrain methods. This research is a preliminary investigation of a potentially under-considered variable in laser peening — material surface roughness. The influence of surface roughness on laser peening has not previously been studied through finite element modeling. The main point of interest for this work is to discover the amount that surface roughness magnitude affects the residual stresses created by LP.

The FEA models, used in the exploration of surface roughness effects, had a simulated roughness produced by displacing surface nodes a pre-determined distance orthogonal to the original, smooth model surface. The amount that each node was moved was based on Kernel Density Estimation (KDE), a statistical method used to quantify uncertainties in random variables according to non-standard probability distribution functions. The KDEs were created from surface-roughness measurements taken from three separate 6061-T6 aluminum tubes. Two separate roughness sample sets were tested at magnifications of 1×, 10×, and 20× times the measured average roughness (Ra). Each roughness magnitude was simulated at peening pressures of 2, 2.5 and 3 times the Hugonoit Elastic Limit (HEL) for Al6061-T6. The 10× and 20× magnitude roughness samples produced significant changes in residual stress components relative to a smooth model, for all pressure loadings.
All Solution-Based Fabrication of CIGS Solar Cell
Authors: Vittoe Robert L. , Ho Tung , Shrestha Sudhir , Agarwal Mangilal , Varahramyan Kody
Published: November 2013

This paper presents fabrication of copper indium gallium di-selenide (CIGS) solar cells using all solution-based deposition processes. CIGS nanoparticles were synthesized through multi-step chemical process using copper chloride, indium chloride, gallium chloride, and selenium in oleyamine. CIGS thin films were constructed through layer-by-layer (LbL) self-assembly and spray-coating techniques. Chemical-bath-deposition and spray-coating methods were used for cadmium sulfide and zinc oxide film depositions, respectively. Initial thin film solar cell devices exhibited promising 0.3 mA short circuit current and 200 mV open circuit voltage. The solar cells fabricated through the all solution-based processes are cost-effective, thus, have potentials of providing a viable, renewable and sustainable energy source. The proposed processes can further be realized on flexible substrates, which may broaden the applications range for the solar cells.
Austenite-Martensite Phase Transformation of Biomedical Ni50.8Ti49.2 Alloy by Ball Burnishing
Authors: Fu C. H. , Guo Y. B. , Wei X. T.
Published: November 2013

Nitinol alloys have received considerable attentions in biomedical and aerospace applications. They can exhibit both austenite and martensite phases at room temperature. Austenite can transform to martensite by applied stress or temperature. Ball burnishing is a very promising technique to modify surface integrity via plastic deformation on the workpiece surface. Phase transformation of Nitinol by burnishing may occur at certain load, which results in the mechanical property change on the workpiece. A burnishing experiment has been conducted in this research at different burnishing loads. The burnishing tracks are characterized and microstructures in the subsurface are studied. A corresponding simulation is also performed to shed light on phase transformation mechanism of Nitinol in burnishing.
Modeling of Focused Ultrasound Propagation in Water Towards a Solid Target and Comparisons to Experimental Observations on Ultrasonic Cavitation
Authors: Dabir-Moghaddam Navid , Gao Yibo , Wu Benxin
Published: November 2013

A numerical model has been developed for focused ultrasound propagation in water towards a solid target, for which the previous modeling work in the literature has been limited. The model predications are reasonably consistent with experimental observations on the cavitation region size at the target surface in the given ultrasound transducer power range, which has provided a verification of the model. The model calculations show that the ultrasound-induced peak negative pressure is highly spatially non-uniform on the side surface of a studied cylindrical target under the investigated conditions. This implies that to uniformly peen the target with focused ultrasonic cavitation peening, a special process design and/or parameter selection may be needed, for which the developed model may provide a useful guiding tool.
A Product Configurator for Cloud Manufacturing
Authors: Yip Arthur L. K. , Corney Jonathan R. , Jagadeesan Ananda P. , Qin Yi
Published: November 2013

Product configurators have become an important enabler for enterprises to achieve product customization in order to address individual customers’ requirements. Despite adoption across a wide range of application domains from automotive to consumer goods, even state-of-the-art product configuration systems are limited in their ability to quickly respond to changes in the production systems that deliver the goods specified. Enabled by the emerging paradigm of cloud manufacturing, the authors propose a “configurable configurator” that is automatically updated to reflect changes in the supply chain. The paper reports the ongoing research and development towards a dynamically generated system that supports product configuration, visualization and assessment from the cloud manufacturing concept of Manufacturing-as-a-Service (MaaS). In addition to outlining the architecture of such a system, an overview of its modules and integration to the cloud manufacturing platform is described. Lastly, the case study of a customizable façade module is presented with two different scenarios to demonstrate the prototype implementation and validate the proposed approach.
Methodology for Ball Screw Component Health Assessment and Failure Analysis
Authors: Jin Wenjing , Chen Yan , Lee Jay
Published: November 2013

The ball screw system is one of the most critical components in advanced manufacturing and is expected to perform with high accuracy. However, any potential failures or degradation of mechanical parts in the system would affect its efficiency and position precision; even cause severe machining errors or breakdown. This paper mainly focuses on the fault diagnosis of ball screw system components. In order to classify multiple failure modes, one full size ball screw testing machine is set up to replicate different health conditions including four failure modes — lubrication starvation, preload loss, ball nut wear, and re-circulation system failure. In this paper, the first two failure modes are introduced. Time domain and frequency domain features have been extracted from the vibration and temperature signals. A classification modeling method is used to establish a ball screw system health map. The direction of the threads on the screw shaft causes different vibration patterns when ball nut travels forward and backward. Thus, failure signatures from both traveling directions are investigated in the paper. Based on the developed health map for the ball-screw, the health values can be calculated to quantify the failure severity. Furthermore, from the perspectives of accuracy and online application efficiency, three health assessment methods, Self-Organizing Map - Minimum Quantization Error (SOM-MQE), Mahalanobis distance (MD) and Gaussian Mixture Model (GMM) are compared in the study.
A Novel Hybrid Process for Drawing Operations
Authors: Pender Kyle , Ngaile Gracious
Published: November 2013

A novel hybrid process for drawing operations is proposed. This process combines the conventional drawing and hydroforming features. The hybrid drawing die assembly is designed to incorporate multiple die segments engraved with high pressure fluid channels. Preliminary results on drawn Al 6061 specimens under two fluid pressure levels showed that the drawing load can decrease significantly. The hybrid drawing process has also shown that varying the fluid pressure can alter the surface asperities at the tool-workpiece interface in real-time, promoting micro-pool lubrication. This was evidenced by distinct surface topographies observed via scanning electron micrographs and optical micrographs.
Modelling Long-Term Trends in Significant Wave Height and its Potential Impacts on Ship Structural Loads
Authors: Vanem Erik , Bitner-Gregersen Elzbieta M.
Published: November 2013

This paper presents the results from a statistical model for significant wave height in space and time. In particular, various model alternatives were applied to extract long-term temporal trends towards the year 2100. Future projections of the North Atlantic ocean wave climate based on two of these alternatives are presented, i.e. an extrapolated linear trend and trends based on regression on atmospheric levels of CO2 and assuming future emission scenarios proposed by IPCC.

It is further explored how such future trends can be related to the structural load calculations of ships. It will be demonstrated how the estimated future trends can be incorporated in joint environmental models to yield updated environmental contour lines that take possible changes in the ocean wave climate into account. In this way, the impact of climate change on the wave climate can be accounted for in stress and loads calculations and hence in the structural dimensioning of ships and offshore installations. The proposed approach is illustrated by an example showing the potential impact of the estimated long-term trends in the wave climate on the wave-induced structural loads of an oil tanker. Results indicate that the impact may be far from negligible, and that this may need to be considered in the future when performing loads calculations.
Dynamic Response of Different Types of TLPs in Liwan Gas Field
Authors: Song Linfeng , Sun Liping , Qian Jiayu , Liu Shengnan
Published: November 2013

Tension leg platform is an important compliant offshore structure used for oil exploration and drilling operations in deep water. This paper deals with the choice of four typical structural forms of the tension leg platform in harsh environmental conditions in the Liwan gas field of South China Sea. These platforms are designed based on a new principle of similarity in order to have the same similarity criterion. The three-dimensional radiation/diffraction theory is used for hydrodynamic analysis, and the far-field solution is used to get mean wave drift forces. The time-domain nonlinear dynamic responses are studied considering the couple between the mooring and the platform. The motion of the platform considers the coupled effect of TTRs, SCRs and the tendons. Wind, wave and current are assumed to be collinear. Considering the platform motion and the utilization ratio of tendon, the most suitable structure type is advised for the Liwan gas field.
Probabilistic FAD and Ductile Tearing Assessment
Authors: Maes Marc A. , Van Coile Ruben , Caspeele Robby , Gao Ming , Dann Markus R.
Published: November 2013

The assessment of cracks in pipelines is one of the key elements for the integrity verification and the remaining lifetime evaluation of pipelines. This crack assessment is commonly performed through Failure Assessment Diagram (FAD) methods in which two failure criteria are combined, i.e. brittle fracture and plastic collapse. FAD assessments are, however, highly deterministic and do not take into account the various uncertainties that affect cracking. A probabilistic FAD tool is developed that accounts for these uncertainties and determines the probability of failure as a function of the crack dimensions, steel grade and pipeline characteristics. The failure probabilities are associated with a reliability index β, which is commonly used to describe structural safety. The results allow an objective comparison of different cracks across a wide range of operating characteristics, and can be used to construct a reliability-based inspection plan. Multiple parameter studies are executed in which the influence of specific variables on the reliability level is quantified.
A New Method for Environmental Contours in Marine Structural Design
Authors: Huseby Arne Bang , Vanem Erik , Natvig Bent
Published: November 2013

The environmental contour concept is often applied in marine structural design in conjunction with the Inverse First Order Reliability Method (IFORM). It allows for the great advantage of considering the environmental loads independently of the structural response. In this way, design sea states may be identified along the contour and time consuming response calculations are only needed for a limited set of design sea states. The traditional way of establishing such environmental contour lines is by applying the Rosenblatt transformation and identify the circle (in two dimensions) with radius equal to the reliability index βr The points along this circle are then transformed back to the original environmental space, specifying the closed contour. In this paper, an alternative approach for establishing the environmental contour lines in the original environmental space is proposed, eliminating the need for any transformations. This approach utilizes Monte Carlo simulations of the joint environmental model and is generally found to perform well. Advantages are that it yields a more precise interpretation and allows for more flexible modelling of the environmental parameters. This makes it easier to modify the environmental models to account for effects such as climate change if this is desired. In addition, possible over- or underestimation of failure probabilities due to the Rosenblatt transformation inherent in the traditional approach can be avoided with the proposed method.
COSSARC: Concept Selection for Shipping in the Arctic
Authors: Valkonen Janne , Løvoll Grunde , Eide Magnus Strandmyr , Walter Erik Løkken
Published: November 2013

Increased global demand for oil, gas and minerals combined with melting sea ice opens new opportunities for shipping companies, both in the form of new Arctic shipping routes and extended use of existing ones. It can be challenging for a ship owner to make informed decisions and plan for Arctic operations, as it requires complex techno-economical assessments of information that has a high degree of uncertainty. To aid ship-owners in making decisions for operation in the Arctic, DNV has developed a prototype decision support tool to assess strategic options: COSSARC — Concept Selection for Shipping in the Arctic. The tool integrates detailed models for ship performance both in ice and in open water with port and route alternatives to simulate travel time, fuel consumption, emissions and overall economics. The tool makes use of stochastic models for wave and ice conditions, but specific historical data or model data from climate models can also be taken as input. In this paper, the COSSARC tool is described, including a case study demonstrating the capabilities of the tool.
Anchoring Strategy Suggested for the Mitigation of Pipeline Walking
Authors: Castelo Adriano , Galgoul Nelson Szilard , Tardelli Luciano , Barros Douglas
Published: November 2013

Short subsea pipelines when subjected to high internal pressures and high operational temperatures (HP/HT) might experience displacements of the whole line that may accumulate cyclically over their operational lifetime resulting in a phenomenon known as “pipeline walking”.

Three different mitigation strategies for this phenomenon have been investigated for a specific pipeline, which also had PLETs with sliding foundations at both ends, and results of this investigation were published recently — Castelo et al. (2012). The aforementioned strategies, however, have included only suggestions of different ways to anchor the pipeline subjected to the “pipeline walking” phenomenon.

This recent publication has presented the conclusion that it is advantageous to anchor the pipeline at an intermediate position along its length in order to try to cancel out the friction forces by having them occur in opposite directions, also considering the presence of the unbalanced forces caused by the sloped seabed.

In practical terms determining this intermediate position is not just choosing the pipeline midpoint because of forces built into the pipeline during installation and it is reminded also that no suggestions had been made on how to anchor.

In this paper, therefore, the authors have decided to provide some insight on how to investigate the position where the anchoring should take place in order to minimize the unbalanced forces and also on what structural details are more adequate to perform this anchoring.