bluuebunny/crossref_metadata_2025 huggingface dataset:
On RCCC Linkage Motion Generation With Defect Elimination for an Indefinite Number of Precision Positions
Authors: Lee Wen-Tzong , Cosme Jose , Russell Kevin
Published: October 2017

A general optimization model for the dimensional synthesis of defect-free revolute-cylindrical-cylindrical-cylindrical joint (or RCCC) motion generators is formulated and demonstrated in this work. With this optimization model, the RCCC dimensions required to approximate an indefinite number of precision positions are calculated. The model includes constraints to eliminate order branch and circuit defects—defects that are common in dyad-based dimensional synthesis. Therefore, the novelty of this work is the development of a general optimization model for RCCC motion generation for an indefinite number of precision positions that simultaneously considers order, branch, and circuit defect elimination. This work conveys both the benefits and drawbacks realized when implementing the optimization model on a personal computer using the commercial mathematical analysis software package matlab.
Functional Synthesis of Manufacturing Systems Using Co-Platforming to Minimize Cost of Machines and System Changes
Authors: Abbas Mohamed , ElMaraghy Hoda
Published: October 2017

Manufacturing systems need to be designed to cope with products’ variety and frequent changes in market requirements. Switching between product families in different production periods often requires reconfiguration of the manufacturing system with associated additional cost and interruption of production. A mixed integer linear programing (MILP) model is proposed to synthesize manufacturing systems based on the co-platforming methodology taking into consideration machine level changes including addition or removal of machine axes and changing setup as well as system level changes such as addition or removal of machines. The objective is to minimize the cost of change needed for transition between product families and production periods. An illustrative numerical example and an industrial case study from tier I automotive supplier are used for verification. Finally, the effect of maintaining a common core of machines in the manufacturing system on the total capital and change cost is investigated. It has been demonstrated that synthesizing manufacturing systems designed using the co-platforming strategy reduces the total investment cost including initial cost of machines and cost of reconfiguration.
Low Order Static Load Distribution Model for Ball Screw Mechanisms Including Effects of Lateral Deformation and Geometric Errors
Authors: Lin Bo , Okwudire Chinedum E. , Wou Jason S.
Published: October 2017

Accurate modeling of static load distribution of balls is very useful for proper design and sizing of ball screw mechanisms (BSMs); it is also a starting point in modeling the dynamics, e.g., friction behavior, of BSMs. Often, it is preferable to determine load distribution using low order models, as opposed to computationally unwieldy high order finite element (FE) models. However, existing low order static load distribution models for BSMs are inaccurate because they ignore the lateral (bending) deformations of screw/nut and do not adequately consider geometric errors, both of which significantly influence load distribution. This paper presents a low order static load distribution model for BSMs that incorporates lateral deformation and geometric error effects. The ball and groove surfaces of BSMs, including geometric errors, are described mathematically and used to establish a ball-to-groove contact model based on Hertzian contact theory. Effects of axial, torsional, and lateral deformations are incorporated into the contact model by representing the nut as a rigid body and the screw as beam FEs connected by a newly derived ball stiffness matrix which considers geometric errors. Benchmarked against a high order FE model in case studies, the proposed model is shown to be accurate in predicting static load distribution, while requiring much less computational time. Its ease-of-use and versatility for evaluating effects of sundry geometric errors, e.g., pitch errors and ball diameter variation, on static load distribution are also demonstrated. It is thus suitable for parametric studies and optimal design of BSMs.
State of the Art Review on Process, System, and Operations Control in Modern Manufacturing
Authors: Djurdjanovic Dragan , Mears Laine , Niaki Farbod Akhavan , Haq Asad Ul , Li Lin
Published: October 2017

Dramatic advancements and adoption of computing capabilities, communication technologies, and advanced, pervasive sensing have impacted every aspect of modern manufacturing. Furthermore, as society explores the Fourth Industrial Revolution characterized by access to and leveraging of knowledge in the manufacturing enterprise, the very character of manufacturing is rapidly evolving, with new, more complex processes, and radically, new products appearing in both the industries and academe. As for traditional manufacturing processes, they are also undergoing transformations in the sense that they face ever-increasing requirements in terms of quality, reliability, and productivity, needs that are being addressed in the knowledge domain. Finally, across all manufacturing we see the need to understand and control interactions between various stages of any given process, as well as interactions between multiple products produced in a manufacturing system. All these factors have motivated tremendous advancements in methodologies and applications of control theory in all aspects of manufacturing: at process and equipment level, manufacturing systems level, and operations level. Motivated by these factors, the purpose of this paper is to give a high-level overview of latest progress in process and operations control in modern manufacturing. Such a review of relevant work at various scales of manufacturing is aimed not only to offer interested readers information about state-of-the art in control methods and applications in manufacturing, but also to give researchers and practitioners a vision about where the direction of future research may be, especially in light of opportunities that lay as one concurrently looks at the process, system and operation levels of manufacturing.
Innovating Safe Lithium-Ion Batteries Through Basic to Applied Research
Authors: Love Corey T. , Buesser Christopher , Johannes Michelle D. , Swider-Lyons Karen E.
Published: October 2017

This paper for inclusion in the special issue provides a brief synopsis of lithium-ion battery safety research efforts at the Naval Research Laboratory (NRL) and presents the viewpoint that lithium-ion battery safety is a growing research area for both academic and applied researchers. We quantify how the number of lithium-ion battery research efforts worldwide has plateaued while publications associated with the safety aspect of lithium-ion batteries are on a rapid incline. The safety challenge creates a unique research opportunity to not only understand basic phenomena but also enhance existing fielded system through advanced controls and prognostics. As the number of lithium-ion battery safety research contributions climbs, significant advancements will come in the area of modeling across multiple time and length scales. Additionally, the utility of in situ and in operando techniques, several performed by the NRL and our collaborators, will feed the data necessary to validate these models. Lithium-ion battery innovations are no longer tied to performance metrics alone, but are increasingly dependent on safety research to unlock their full potential. There is much work to be done.
Numerical Analysis of the Effect of Misaligned Guide Vanes on Improving S-Shaped Characteristics for a Pump-Turbine
Authors: Yexiang Xiao , Wei Zhu , Zhengwei Wang , Jin Zhang , Soo-Hwang Ahn , Chongji Zeng , Yongyao Luo
Published: October 2017

The S-shaped characteristic curves in pump-turbines complicate synchronization with the electrical grid and affect system safety. Misaligned guide vanes (MGVs) are one of the most effective solutions to avoid S-shaped characteristics. The internal flow mechanism with the MGV for improving S-shaped characteristics was studied by numerical analysis. Six operating conditions were modeled in the S-shaped region. Four guide vanes were arranged as the MGVs to qualitatively and quantitatively analyze the flow behavior. The internal flow was quite complex at the four operating points without the MGV; here, the attack angle and the flow behavior had no obvious difference at each vane. For the similar conditions with MGVs, attack angles and internal flow fields varied clearly at each vane, especially in the vaneless region and in the runner blade passages. For the same discharge rates, total openings, and rotating speeds, the internal flows were quite different between with and without the MGVs. The MGVs disrupt the high-speed circumferential water ring (appreciably faster compared to the main flow) in the vaneless region and maintain operation with higher unit speeds. Consequently, the unit speed is larger at the same unit discharge in the S-shaped region. Therefore, the MGV method can reduce S-shaped characteristics.
Fault Management System of LP-EGR Using In-Cylinder Pressure Information in Light-Duty Diesel Engines
Authors: Oh Junhyeong , Min Kyunghan , Han Manbae , Sunwoo Myoungho
Published: October 2017

Particulate matters (PM) accumulation through a low-pressure exhaust gas recirculation (LP-EGR) path may hinder to obtain the desired LP-EGR rate and thus causes an increase of nitrogen oxides (NOx). The degree of lack of the LP-EGR rate should be detected, i.e., an LP-EGR fault, and a remedy to compensate for the lack of LP-EGR rate should be a mandate to suppress NOx emission, i.e., a fault management. In order to accomplish those objectives, this paper proposes an LP-EGR fault management system, which consists of a fault diagnosis algorithm, fault-tolerant control algorithm, and an LP-EGR rate model. The model applies a combustion parameter derived from in-cylinder pressure information to the conventional orifice valve model. Consequently, the LP-EGR rate estimation was improved to the maximum error of 2.38% and root-mean-square-error (RMSE) of 1.34% at various operating conditions even under the fault condition compared to that of the conventional model with the maximum error of 7.46% and RMSE of 5.39%. Using this LP-EGR rate model as a virtual sensor, the fault diagnosis algorithm determines an LP-EGR fault state. Based on the state, the fault-tolerant control determines whether or not to generate the offset of the exhaust throttle valve (ETV) position. This offset combines with the look-up table (LUT)-based feedforward controller to control an LP-EGR rate. As a result of real-time verification of the fault management system in the fault condition, the NOx emission decreased by up to about 15%.
Quantifying the Direct Influence of Diffusive Mass Transfer in Rarefied Gas Mixing Simulations
Authors: Darbandi Masoud , Sabouri Moslem
Published: October 2017

This work utilizes the direct simulation Monte Carlo (DSMC) calculations and examines the influence of rarefication on the mixing length and effective diffusion coefficient in a two-species mixing problem. There have been efforts in past rarefied mixing flow studies to bridge between the mixing evolution rate and Knudsen number. A careful review of those efforts shows that the past derived relations did not determine the weights of Reynolds (or Peclet) number in the rarefaction influences. Although they indicated that an increase in Knudsen would decrease the mixing length, such reductions were primarily due to the Reynolds (or Peclet) reduction. Therefore, those studies could not explicitly appraise the contribution of rarefaction in the total mass diffusion magnitude. This work focuses specifically on the role of rarefaction in the total diffusive mass transfer magnitude in rarefied gas mixing problems. It excludes the contributions of momentum and heat to the mass diffusion via imposing suitable velocity, pressure, and temperature fields in the mixer domain. The results show that there will be some decreases in the diffusive mass fluxes and some increases in the mixing length as Knudsen increases. Using the Fick’s law, the effective diffusion coefficient is then calculated in the mixer zone. The results show that this coefficient may vary considerably throughout the mixer zone due to the local rarefaction level variation. The results of all investigated cases indicate that the trends of their effective diffusion coefficient variations approach to a limiting value as the rarefaction level decreases.
A Parametric Study of Hydrodynamic Cavitation Inside Globe Valves
Authors: Jin Zhi-jiang , Gao Zhi-xin , Qian Jin-yuan , Wu Zan , Sunden Bengt
Published: October 2017

Hydrodynamic cavitation that occurs inside valves not only increases the energy consumption burden of the whole piping system but also leads to severe damages to the valve body and the piping system with a large economic loss. In this paper, in order to reduce the hydrodynamic cavitation inside globe valves, effects of valve body geometrical parameters including bending radius, deviation distance, and arc curvature linked to in/export parts on hydrodynamic cavitation are investigated by using a cavitation model. To begin with, the numerical model is compared with similar works to check its accuracy. Then, the cavitation index and the total vapor volume are predicted. The results show that vapor primarily appears around the valve seat and connecting downstream pipes. The hydrodynamic cavitation does not occur under a small inlet velocity, a large bending radius, and a large deviation distance. Cavitation intensity decreases with the increase of the bending radius, the deviation distance, and the arc curvature linked to in/export parts. This indicates that valve geometrical parameters should be chosen as large as possible, while the maximal fluid velocity should be limited. This work is of significance for hydrodynamic cavitation or globe valve design.
Fast Fabrication of Superhydrophobic Titanium Alloy as Antibacterial Surface Using Nanosecond Laser Texturing
Authors: Patil Deepak , Aravindan S. , Kaushal Wasson Mishi , P. Vivekanandan , Rao P. V.
Published: October 2017

The method for fast fabrication of superhydrophobic surfaces was proposed to resist the formation of biofilm of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) for orthopedic and dental implants. Laser beam machining with nanosecond pulsed laser (Nd:YAG) was used to fabricate pit structure on Grade-5 Ti–6Al–4V alloy followed by annealing (at 300 °C with different time scales) in order to reduce the transition time from hydrophilic to superhydrophobic surface generation. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) techniques were used to characterize the textured samples. The surface wettability of plain and textured samples was measured by the sessile drop method using goniometer. The biofilm formation was qualitatively and quantitatively evaluated by FE-SEM and crystal violet binding assay, respectively. The biofilm formation was observed on plain (hydrophilic) surface for both the types of bacteria, whereas significantly less biofilm formation was observed on the laser textured (superhydrophobic) surfaces. The proposed method helps in reducing the risk of infection associated with implants without using cytotoxic bactericidal agents.
On Timescale Separation in Networked Systems With Intermittent Communication
Authors: Awad Armand , Narang-Siddarth Anshu
Published: October 2017

This paper studies the multiple timescale behavior that is induced by dynamic coupling between continuous-time and discrete-time systems, and that arises naturally in distributed networked systems. An order reduction method is proposed that establishes a mathematically rigorous separation principle between the fast evolution of the continuous-time dynamics and the slow updates of the discrete-time dynamics. Quantitative conditions on the discrete update rate are then derived that ensure the stability of the coupled dynamics based on the behavior of the isolated systems. The results are illustrated for a distributed network of satellites whose attitudes evolve continuously while communicating intermittently over the network.
Numerical Investigation of Air–Oil–Thermal Coupling Mechanism in Floating Ring Bearings
Authors: Yan Wang , Xiao-Dong Ren , Xue-Song Li , Chun-Wei Gu
Published: October 2017

Floating ring bearings (FRBs) are widely used in automobile turbochargers. However, there is no satisfying explanation of phenomenon that ring rotation speed levels off when the shaft speed reaches a certain value under low oil-supplied pressure condition. The traditional opinion that effective viscosity decreases with increasing temperature cannot completely explain this phenomenon. In this study, the air entrainment effect is introduced and evaluated using computational fluid dynamics (CFD). CFD results considering air entrainment, viscous heating, and heat transfer are compared with experimental results to evaluate each effect. The decrease in effective viscosity as a result of air–oil–thermal coupling effect is the mechanism behind the abovementioned phenomenon. This study provides calculated data and visual results of the air entrainment in low oil-supplied pressure FRB.
Wear Behavior and Mechanical Properties of TiO2 Coating Deposited Electrophoretically on 316 L Stainless Steel
Authors: Dhiflaoui Hafedh , Kaouther Khlifi , Larbi Ahmed Ben Cheikh
Published: October 2017

In this work, the TiO2 coatings were synthesized by electrophoretic deposition (EPD) of nanosized powder in order to improve the tribological properties. Several characterization methods were applied to the coated substrates. The surface topography of the EPD layers, their morphology, composition, and mechanical properties were investigated. The influence of heat treatment, which results in calcination, on the wear performance of coated films was also examined. It was noticed that the effect of the normal force and sliding velocity on the coefficients of instantaneous and stabilized friction was not the same in treated coatings and untreated ones. Moreover, the treated and uncoated films showed a close relation between the dissipated accumulated energy and the worn volume. The energetic wear coefficients of fretting wear were also studied. As expected, the treated coating reduced the energetic wear coefficient, which enhanced the resistance to fretting wear.
Bottom Supported Tension Leg Tower for Offshore Wind Turbines
Authors: Sarkar Arunjyoti , Gudmestad Ove Tobias
Published: October 2017

Power production from the high energy density offshore wind has now emerged as a potential source of renewable energy for the future of mankind. While the installed global cumulative offshore wind capacity in 2014 was around 8 GW [1], almost all of this came from the shallow water sites (water depths equal to 25m or less) where typical bottom founded structures (such as: monopole, jacket, concrete gravity type, etc.) are used to support the turbines.

Today, most of the shallow water sites are exhausted, and the industry is looking for setting up turbines at the deeper water sites, where the existing bottom founded structures tend to become massive and expensive. On the other hand, the floating wind turbine concept, apart from being expensive, is more suitable for water depth of 100 m or more.

It is expected that in the near future, the industry will primarily focus on concepts that may extend the application range of the existing bottom founded structures towards the deeper waters.

In this paper, a novel support structure concept termed “Bottom supported tension leg tower” is presented, and its preliminary technical feasibility is checked for a monopile type structure for 50 m water depth. The concept can also be used with a jacket or a gravity type support structure. The potential of using the monopile based structure at 100m water depth is also briefly addressed.
Development of Tsunami Design Provisions for the ASCE 7-16 Standard
Authors: Robertson Ian N.
Published: October 2017

Building design codes in the US do not include any consideration of tsunami design, even though past tsunamis have caused significant structural damage in coastal communities. In February 2011 the American Society of Civil Engineers (ASCE) formed a new Tsunami Loads and Effects subcommittee, which spent four years to develop a new chapter for inclusion in the ASCE7-16 Standard, Minimum Design Loads and Associated Criteria for Buildings and Other Structures. This new chapter has now been approved by the ASCE7 Main Committee and ASCE7-16 has been published with a new Chapter 6, Tsunami Loads and Effects. In December 2016, ASCE 7–16 was officially adopted by the International Code Council, with the new chapter on Tsunami Loads and Effects, for inclusion in the US model code, IBC 2018. The tsunami design provisions will apply to all coastal communities in California, Oregon, Washington State, Alaska and Hawaii. This paper presents an overview of the new ASCE7-16 Tsunami Loads and Effects design provisions and how they were developed based on field survey observations and laboratory experimentation.
Improvement of Side-by-Side LNG Offloading Operability Calculations Using Monte Carlo Simulations and Scattered Data Multidimensional Interpolation
Authors: Auburtin Erwan , Lefebvre Timothée , Paquet Stéphane
Published: October 2017

In order to properly design the mooring and offloading equipment, and assess the availability of Floating Liquefied Natural Gas (FLNG) units during the engineering phase, TechnipFMC has paid a particular attention to the operability prediction of LNG offloading operations. For the FLNG projects currently under construction, the chosen offloading solution is the Marine Loading Arms (MLA) technology with the LNG carrier (LNGC) moored in side-by-side (SBS) configuration.

In this paper, an improved methodology using Monte Carlo simulations is proposed to create a representative sample of a typical hindcast for North West Australia, assuming the case of a 147,000 m3 LNGC moored side-by-side to a TechnipFMC in-house design FLNG. It is shown that the random sampling is very well suited for large number of dimensions implied by the driving parameters (e.g. significant height, peak period, relative heading) of multiple wave partitions. In a second step, different multidimensional scattered data interpolation techniques are evaluated in order to further improve the accuracy. Since this would not be practical in time-domain and because the objective for this study is to compare the sampling and interpolation techniques to a benchmark on the whole hindcast, the vessels’ motions and SBS offloading operability are calculated in frequency-domain. The conclusions could also be applied to time-domain simulations. The paper also presents the sensitivity studies to the different interpolation methods and their key parameters and discusses the suitability of the proposed solutions.
Safety Challenges of LNG Offshore Industry and Introduction to Risk Management
Authors: Forte Karina , Ruf Diane
Published: October 2017

Over many years, onshore plants have been deployed to liquefy the gas extracted from offshore wells and regasify the liquefied gas before sending it to the consumer grid. Currently the LNG Offshore Industry crosses a new development period since LNG Offshore Floating Units are considered as good options to improve the viability of gas supply.

Nevertheless this paper will introduce the main safety challenges usually identified on LNG Offshore facilities, such as the space constraints on LNG Liquefaction Offshore Floating Units and injuries to personnel due to the cryogenic properties of the LNG. Moreover, it will be demonstrated that each hazard has a particular solution which has to be carefully assessed in order to ensure that the risks linked to an installation dealing with LNG are well understood and under control at the same time that the expectations of the project are achieved and compliance with recognized international health and safety standards is respected.

Gaining knowledge about the properties of hazardous substances processed and operations performed in the installations is crucial to ensure safety in LNG Industry. Therefore this paper also aims at ensuring the awareness and understanding concerning the issues that could compromise the safety in LNG installations. As previously mentioned, a great concern in the LNG Offshore Industry is related to the space constraints in the site, once in case of a gas release followed by ignition there is the probability of escalation occurrence through the whole installation, what would affect personnel, environment and assets. Despite the space constraints found on offshore installations, it is important to consider minimum safety distances among the LNG facility systems. Thus, control of major hazards is of key importance, and prevention of escalation from an initial incident is critical. Also, it is important to understand what conditions could cause physical effects such as a pool fires, rapid phase transitions and vapour cloud explosions. Since this paper details and compares the safety challenges related to LNG processes, it will be presented some examples of accidents occurred in LNG facilities. The lessons learned from previous accidents can enable the companies to justify the investment to improve the safety in the installation and develop an effective Risk Management, which provides several benefits for the LNG operations (i.e.: the fewer accidents so lower employee absence, lessened threat of legal actions against the company, better reputation and consequently, reduced costs, increased productivity and greater profit.).
Three Dimensional Numerical Study of Various Geometries of Breakwaters on Wave Energy Dissipation
Authors: Buruchenko Sergei K.
Published: October 2017

The application of smoothed particle hydrodynamics (SPH) to model the three-dimensional fluid-structure interaction for waves approaching a rigid mound breakwater is presented. The main purpose is to examine the influence of the forms of block sea breakwater on its overtopping. The problem includes extremely large deformations of the free surface fluid. To better understand such deformations, a three-dimensional SPH code is applied to analyze the dynamic responses of fluid-rigid structure interaction. In the classical SPH formulation, the Navier-Stokes equations are solved and the fluid is treated as weakly compressible. The numerical model is first validated against experimental data for two-dimensional and three-dimensional breakwater problems, it shows a fair agreement of overall fluid motions. The open-source GPU code, DualSPHysics, enables the simulation of millions of particles required for the accurate simulation of the run-up on a rigid structure. SPH has been proven to be a suitable method for practical applications in marine engineering. The aim is to investigate the reliability of this approach as a design tool.
Numerical Study of Forward-Speed Ship Motion and Added Resistance
Authors: Hong D. C. , Ha T. B. , Song K. H.
Published: October 2017

The added resistance of a ship was calculated using Maruo’s formula [1] involving the three-dimensional Kochin function obtained using the source and normal doublet distribution over the wetted surface of the ship. The density of the doublet distribution was obtained as the solution of the three-dimensional frequency-domain forward-speed Green integral equation containing the exact line integral along the waterline. Numerical results of the Wigley ship models II and III in head seas, obtained by making use of the inner-collocation 9-node second-order boundary element method have been compared with the experimental results reported by Journée [2]. The forward-speed hydrodynamic coefficients of the Wigley models have shown no irregular-frequencylike behavior. The steady disturbance potential due to the constant forward speed of the ship has also been calculated using the Green integral equation associated with the steady forward-speed free-surface Green function since the so-called mj-terms [3] appearing in the body boundary conditions contain the first and second derivatives of the steady potential over the wetted surface of the ship. However, the free-surface boundary condition was kept linear in the present study. The added resistances of the Wigley II and III models in head seas obtained using Maruo’s formula showing acceptable comparison with experimental results, have been presented. The added resistances in following seas obtained using Maruo’s formula have also been presented.
Numerical Investigation of the Effect due to Vessel Motion on Green Water Impact on Deck
Authors: Kudupudi Ravindra Babu , Datta Ranadev
Published: October 2017

The present paper focuses on modeling of green water loading on an oscillating body using CFD. The vessel motion is calculated a priory using time domain panel method code, then green water impact is computed based on that pre-calculated motion. The finite volume method is used to capture the green water impact, however in order to represent the free surface, volume of fluid method is used. A sophisticated dynamic mesh is used to handle the motion of the vessel in fluid domain. Several examples and case studies are considered to validate the present CFD model as well as to check the effect of global motion on green water loading such as effect of steepness and heading angle on green water impact. Results show that due to the motion, the impact loading phenomena changes significantly and there is a significant change in pressure on the deck after considering the motion effect and it deviates considerably with the results obtained from fixed vessel cases.
A Coupled CFD/Multibody Dynamics Analysis Tool for Offshore Wind Turbines With Aeroelastic Blades
Authors: Liu Yuanchuan , Xiao Qing , Incecik Atilla
Published: October 2017

Aero-elasticity is an important issue for modern large scale offshore wind turbines with long slender blades. The behaviour of deformable turbine blades influences the structure stress and thus the sustainability of blades under large unsteady wind loads. In this paper, we present a fully coupled CFD/MultiBody Dynamics analysis tool to examine this problem. The fluid flow around the turbine is solved using a high-fidelity CFD method while the structural dynamics of flexible blades is predicted using an open source code MBDyn, in which the flexible blades are modelled via a series of beam elements. Firstly, a flexible cantilever beam is simulated to verify the developed tool. The NREL 5 MW offshore wind turbine is then studied with both rigid and flexible blades to analyse the aero-elastic influence on the wind turbine structural response and aerodynamic performance. Comparison is also made against the publicly available data.
A Fundamental Study on the Dynamic Response of Hull Girder of Container Ships due to Slamming Load
Authors: Yamada Yasuhira , Kameya Kyoko
Published: October 2017

The purpose of the present study is to fundamentally investigate dynamic hull girder response due to slamming load. A series of time domain FE-simulation is carried out using a non-uniform finite element beam model of a 8000 TEU container ship where slamming load is applied at the bottom of the bow. The ship is modeled by elaso-plastic material with equivalent ultimate strength and strain rate effect is considered. Hull-girder vertical bending moment as well as deformation modes, bending stress are investigated by varying the time duration of the slamming load which is modeled by sinusoidal impulse. In order to obtain post vibration after the first slamming load explicit analysis is adopted instead of implicit analysis with considering gravity and buoyancy. Buoyancy is modeled by inelastic spring elements. It is found from the present study hull girder vertical bending moment is dependent on time duration of slamming load. Especially if time duration is smaller than natural period response bending moment may become smaller than applied bending moment. Moreover effect of inertia at fore and aft is also investigated in detail.
A Surrogate Model for Predicting Stress Intensity Factor: An Application to Oil and Gas Industry
Authors: Keprate Arvind , Ratnayake R. M. Chandima , Sankararaman Shankar
Published: October 2017

Evaluation of the stress intensity factor (SIF) for a crack propagating in a structural component is the analytical basis of linear elastic fracture mechanics (LEFM) approach. Handbook solutions give accurate SIF results for simple crack geometries. For intricate crack geometries and complex loading conditions finite element method (FEM), is used to predict SIF. The main drawback of FEM techniques is that they are prohibitively expensive in terms of computing cost and also very time consuming. In this manuscript, authors have presented a Gaussian Process Regression Model (GPRM), which may be used as an alternative to FEM for predicting SIF of a propagating crack. The GPRM is firstly trained using 70 SIF values obtained by FEM, and then validated by comparing the values of SIF predicted by GPRM and FEM for 30 data points (i.e. combination of crack size and loading). On comparing the aforementioned values the average residual percentage between the two is 2.57%, indicating good agreement between GPRM and FEM model. Also, the time required to predict SIF of 30 data points is reduced from 30 mins (for FEM) to 10 seconds with the help of proposed GPRM.
Thermal Analysis of Saline Droplet Motion With Cooling in Cold Regions
Authors: Dehghani-Sanij Alireza , Naterer Greg F. , Muzychka Yuri S. , Pope Kevin
Published: October 2017

In this paper, a theoretical approach is employed to analyze the thermal behaviour and study the cooling process of water droplets in cold regions. Additionally, the effect of several parameters, such as air temperature, droplet size, initial droplet temperature, relative humidity and droplet salinity on the cooling process is investigated. The model contains convection, evaporation, and radiation heat transfer from the droplet’s surface and a uniform temperature across the droplet. The results illustrate a good agreement between the theoretical predictions and previously measured data. Furthermore, droplet size, air temperature, initial droplet temperature, and droplet flight time have a substantial effect on the droplet cooling process. This model is a useful tool to investigate the thermal behaviour and the cooling process of water droplets.
Effect of Installation on Collapse Performance of Flexible Pipes
Authors: Caleyron Fabien , Le Corre Vincent , Paumier Laurent
Published: October 2017

This paper investigates the effect of installation on collapse performance of flexible pipes.

In the design of flexible pipelines for offshore field developments, one of the critical failure modes being associated with external pressure and bending loadings is the hydrostatic collapse. In accordance with standards, Technip methodology for flexible pipe collapse resistance determination ensures a robust and competitive design. The model has an analytical basis, leading to a fast and straightforward use. It has been validated with more than 200 tests performed on all possible pipe constructions on straight and curved configurations.

As the industry is moving to deeper and deeper water, there is a greater need to understand all factors which could affect collapse. This includes residual effects due to the high installation loads from the laying system. As a consequence, Technip has performed several collapse tests on samples previously submitted to a loading representative of installation conditions (tension and crushing). Moreover, Technip and IFP Energies Nouvelles have developed and improved over the past few years a Finite Elements model dedicated to collapse prediction. The model accounts for the detailed geometry of the wires (carcass, pressure vault, spiral), ovalization, cyclic plasticity, contacts and residual stresses due to manufacturing. It allows to evaluate the effect of installation on the ovalization and plasticity of each layer and the collapse performance of the flexible pipe.

The purpose of this paper is to present the collapse tests results and the corresponding calculations performed with the Finite Elements Model on several cases representative of Technip flexible pipes portfolio.
Calculating Arc Length and Curvature of Helical Elements in Bent Cables and Umbilicals Using Fourier Series
Authors: Komperød Magnus
Published: October 2017

Mechanical cable analyses range from simple hand calculations to complex, three-dimensional finite element analyses. This paper considers numerical calculations of analytical models as an attractive compromise between these extremities. The paper derives numerical calculations of the arc lengths and the local bending curvatures of helical elements in bent cables and umbilicals, and compares the results with analytical approximations found in the scientific literature. The numerical calculations are highly efficient, requiring only a very few function evaluations to give excellent accuracy. On today’s PCs and laptops the calculations require only a few milliseconds CPU time. The excellent convergence properties of Fourier series for smooth, periodic functions are used to achieve these favorable results. In addition to high accuracy, the numerical calculations disclose behaviors that are not captured by the analytical approximations.
Visualization of Relative Wind Profiles in Relation to Actual Weather Conditions of Ship Routes
Authors: Perera Lokukaluge P. , Mo Brage , Nowak Matthias P.
Published: October 2017

Ship performance and navigation data are collected by vessels that are equipped with various supervisory control and data acquisition systems (SCADA). Such information is collected as large-scale data sets, therefore various analysis tools and techniques are required to extract useful information from the same. The extracted information on ship performance and navigation conditions can be used to implement energy efficiency and emission control applications (i.e. weather routing type applications) on these vessels. Hence, this study proposes to develop data visualizing methods in order to extract ship performance and navigation information from the respective data sets in relation to weather conditions. The relative wind (i.e. apparent wind) profile (i.e. wind speed and direction) collected by onboard sensors and absolute weather conditions, which are extracted from external data sources by using position and time information a selected vessel (i.e. from the recorded ship routes), are considered. Hence, the relative wind profile of the vessel is compared with actual weather conditions to visualize ship performance and navigation parameters relationships, as the main contribution. It is believed that such relationships can be used to develop appropriate mathematical models to predict ship performance and navigation conditions under various weather conditions.
Comparison of Real-Time Hybrid Model Testing of a Braceless Semi-Submersible Wind Turbine and Numerical Simulations
Authors: Karimirad Madjid , Bachynski Erin E. , Berthelsen Petter Andreas , Ormberg Harald
Published: October 2017

In this paper, integrated analyses performed in SIMA are compared against experimental results obtained using real-time hybrid model testing (ReaTHM®) carried out in the ocean basin facilities of MARINTEK in October 2015. The experimental data is from a 1:30 scaled model of a semi-submersible wind turbine. Coupled aero-hydro-servo-elastic simulations are performed in MARINTEK’s SIMA software. The present work extends previous results from Berthelsen et al. [1] by including a blade element/momentum (BEM) model for the rotor forces in SIMA and comparing the coupled responses of the system to the experimental results. The previously presented hydrodynamic model is also further developed, and the importance of second order loads (and applicability of approximate methods for their calculations) is examined. Low-frequency hydrodynamic excitation and damping are seen to be important, but these loads include a combination of viscous and potential forces. For the selected concept, the second order potential flow forces have limited effects on the responses.
Solving 2D Fluid-Structure Interaction Problem by a Coupled Particle Method
Authors: Zha Ruosi , Qiu Wei , Peng Heather
Published: October 2017

It is important to predict wave impact and structural responses of ship and offshore structures in extreme sea conditions. There are advantages to apply Lagrangian particle methods to simulate highly nonlinear breaking free surface flow and fluid-structure interactions (FSI). In this paper, an improved moving particle semi-implicit (MPS) method was developed to solve the FSI problems. At each time step, the fluid motions and the structural responses are solved. For flow computations, a modified mixed source term method and an improved free surface identification method were adopted to suppress pressure oscillations. Moreover, a particle collision model was used to enhance the numerical stability and avoid nonphysical solutions. The discretized Poisson equations for pressure were solved by a parallel version of the bi-conjugate gradient stabilized method based on the message passing interface (MPI) approach. For structural responses, solids were treated as isotropic elastic particles. Validation studies were carried out for cases of 2D dam breaking and its interaction with a rubber gate. The numerical solutions are in good agreement with experimental data and other published numerical results.
Analytical Method of Buried Steel Pipelines Subjected to Strike-Slip Faults
Authors: Li Ying , Wang Bin , Li Xin
Published: October 2017

Based on the summary of the existing analytical methods of buried steel pipelines at crossings with active strike-slip faults, an improved analytical methodology herein is proposed. Based on Karamitros model, the Ramberg-Osgood stress-strain relationships of pipe steel and the effects of nonlinear soil-pipeline interaction in both the axial and transverse directions are taken into account. Compared with existing analytical methodologies and 3D nonlinear finite element analysis, the analytical methodology presented is suitable for engineering applications due to exact and conservative results.
Assessment of Welded Joints by Strain Energy Density Approach Accounting for Misalignments and Geometrical Imperfections
Authors: Gaiotti Marco , Rizzo Cesare Mario , Berto Filippo
Published: October 2017

Among recently introduced fatigue assessment approaches, the ones based on the notch stress intensity factor (N-SIF) concept appear to be very promising, both because of their theoretically soundness and because of the possibility of straightforward computation of parameters believed to govern the fatigue process. Actually, while such approaches can be considered in between stress-based approaches and crack propagation ones, quantities like N-SIF and strain energy density in a control volume can be evaluated by finite element analysis according to nowadays well-established procedures, mostly already implemented in commercial FEM software. The present study moves from a former one, dealing with butt joints between typical shipbuilding shell plates, and aims at assessing how the misalignment influences the fatigue strength estimation when applying the strain energy density approach. Eventually, the capabilities of such approach in accounting for misalignments is demonstrated and results are found in agreement with magnification factors currently recommended by guidelines and rules when applying other, stress based, fatigue assessment approaches.
UHB of Flexible Flowlines: Design and Analysis
Authors: Liu M. , Cross C.
Published: October 2017

The predictive upheaval buckling (UHB) for un-bonded flexibles can be challenging due to their complex multilayer structure and nonlinear properties. A combination of design data preparation and interpretation, in-place analysis methodologies, and installation can result in a varied UHB screening exercise and results. For flexible flowlines prone to UHB, pre-pressurisation is widely used prior to trenching and backfill to improve their UHB performance.

This paper is intended to present a study on the issues associated with the flexible UHB assessment. The solidity and veracity of the current UHB screening and analysis procedure is examined for pre-pressurised flexibles in particular. The initial effective tension induced by pre-pressurisation prior to backfill is investigated in detail. Pitfalls and inconsistencies in the methodologies are reviewed.

It is demonstrated that due to the neglect of nonlinearity, potential misuse of design parameters and assumptions made for the UHB design screening and analysis procedure can be compromised and open to rationalisation. The tangible benefit of initial pressurisation may be inaccurately evaluated for UHB mitigation. It is established that for the same flexible flowline, its UHB resistance performance can be either overpredicted or underestimated in certain conditions. An alternative approach is developed and proposed to redress some deficiencies. A case study is presented to show the key results and conclusions.
Acceptable Target Probability of Failure for Subsea Pipeline UHB Design
Authors: Liu M. , Cross C.
Published: October 2017

For subsea pipeline UHB design, it is essential to establish appropriate UHB load factors by undertaking a structural reliability analysis based on a target acceptable probability of failure. The current practice is to setup the acceptable probability of failure according to the best industrial practice coded in DNV OS F101 and ISO16708 but regardless of trench performance, imperfection details and inspection results.

This paper is intended to discuss the relationship between the UHB failure probability for the whole pipeline and the trench performance and imperfection frequency statistics. A detailed statistic and reliability analysis is undertaken to address some disparity in the current practice. It is shown that in order to achieve a specific reliability level required for the entire pipeline, it is paramount to calibrate the target probability of failure based on the survey data. The common practice for UHB is shown un-conservative giving rise to an insufficient safety level and non-compliant OOS design. An improved approach is outlined to address the critical issues allowing for a robust OOS assessment by means of case studies.
Effect of Elastic Properties of the Fluids on the Particle Settling Velocity
Authors: Arnipally Sumanth Kumar , Kuru Ergun
Published: October 2017

An experimental study was performed to investigate the influence of fluid elastic properties on the settling velocity of spherical particles in viscoelastic polymer fluids. The Particle Image Shadowgraph (PIS) technique was used to measure the settling velocity of the spherical particles (with average diameter of 2mm) in the hydrolyzed poly acrylamide (HPAM) polymer test fluids.

Test fluids were prepared by mixing 3 different grades of HPAM (with molecular weights of; 500,000; 8,000,000; and 20,000,000) at polymer concentrations of 0.09 and 0.1% by weight. Shear viscosity and oscillatory measurements were carried out to characterize the test fluids.

The test fluids were formulated in such a way that they had almost identical shear viscosity characteristics while showing significantly different elastic properties. The relaxation time was used to quantify the elastic characteristics of the fluids.

To quantify the impact of elasticity, the experimentally measured settling velocities were compared to the values calculated by using the model developed for predicting settling velocity of spherical particles in power law (visco-inelastic) fluids [1]. Experimental results indicated that the settling velocity of spherical particles in visco-elastic fluids decreased significantly with the increasing elasticity (measured in terms of relaxation times) of the fluids.