bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiscale Analysis of Multifunctional Composite Structures
Authors: Bahei-El-Din Yehia , Micheal Amany 
Published: April 2014

In a truly multiscale analysis of multilayered composites, the underlying phenomena are represented and their effect on the overall behavior is determined considering the interaction between the different phases and between the laminas. The analysis gets more involved when multiple phenomena are considered since in this case not only the direct effects play a role but also the coupled effects contribute to the distribution of the local fields and the overall response. In a fibrous composite laminate reinforced with piezoelectric filaments, for example, passing an electric field in the fibers generates stresses and strains which propagate through the composite medium due to constraints that exist both at the micromechanical, ply level, and the macromechanical, laminate level. Pyroelectricity is another coupling phenomenon in which a temperature change is caused by an electric field, and hence leads to changes in the stress and strain fields throughout the composite medium.
The above phenomena have been considered by the authors in a unified, transformation field analysis (TFA) approach in which stresses and strains which cannot be removed by mechanical unloading are treated as transformation fields. Due to mutual constraints of the phases and the bonded plies, local transformations generate stresses at the micro and macro levels, which are computed by means of influence functions which depend on material geometry and properties. Treatment of damage follows the same scheme but the transformation fields are instead determined such that the local stresses in the affected phase are removed.
In the present paper, implementation of the TFA approach in a general purpose finite element code is described. This expands the multiscale analysis outlined above to composite structures where complex geometries can be modeled and the effect of local phenomena can be considered. This naturally comes at a much larger cost of the computations compared to finite element analysis with homogenized models but the benefit of obtaining a more realistic response is clear. Moreover, the availability of high performance computing and parallel processing overcomes the computation time barrier. In the present paper however, simple examples of laminated structures are given as proof of concept in which the results are compared to those of standalone routines. Since the TFA approach centers on treating the composite medium as elastic with induced local transformations, implementation in the finite element framework does not require generation of an overall instantaneous stiffness matrix, which saves tremendously on the computation time. Instead, overall transformation strains, or stresses, are computed through a multiscale model, which is implemented as a user routine, and treated in the general finite element solution as nonmechanical strains in the same way thermal strains are treated.
A Thermoplastic Constitutive Modeling and Geotechnical Centrifuge Simulation of Partially Saturated Soil Under Buried Explosive Loading
Authors: Yarahmadi Asghar , Brannon Rebecca , Lista Carlos Bonifasi 
Published: April 2014

In high-rate failure models for geological and rock-like materials, heating due to inelastic deformation is often neglected or accommodated incompletely through the use of an isentropic elastic response. However, for realistic prediction of geomaterials response to high-rate large deformations with significant released energy (such as buried explosive), dissipation caused by the initial mechanical work of the blast wave results in a non-negligible entropy generation that must be accounted for in constitutive modeling. In this study, thermal effects in the vicinity of a buried explosive in partially saturated soil are investigated using the Jones-Wilkins-Lee (JWL++) detonation model of High Explosive (HE) material, along with coupled multiphysics balance equations in an open-source massively parallel computational framework (Uintah) via Material Point Method (MPM) and Implicit, Continuous fluid, Eulerian (ICE) for compressible multi-material formulation of fluid-structure interactions (including highly pressurized explosive gaseous products). The temperature is allowed to evolve according to thermo-plasticity equations (derived from dissipation inequalities and basic conservation/thermodynamics laws) and thereafter, the state of internal variables (porosity, entropy, yield stress, etc) and stress in the partially saturated soil are determined for the obtained temperature. In order to account for material hardening from pore collapse, a yield surface based on Gurson’s upper bound theory evolves with stress, temperature, and internal state variables in plastic phase. Comparisons of soil response to blast loading are provided to quantify the importance of thermal effects.
Furthermore, geomaterials develop anisotropy in their response to deformation caused by prompt high-pressure shock waves. Thermodynamic admissibility implies that the fourth-order tangent stiffness tensor of geomaterials must develop a recoverable deformation-induced anisotropy (RDIA) even if the material is initially isotropic. This effect is significant for materials, like geomaterials, that have strongly pressure-sensitive strength. The degree of RDIA and the required additional terms in the form of deformation-induced anisotropy based on thermodynamics requirements in a high-temperature phenomenon are summarized for the region near the buried explosive source in partially saturated soil.
On Utilization of Material Failure Criterion in Modeling Pull-Out Failure of Spot-Welded Joints
Authors: Zeng Long , Xia Yong , Zhao He , Zhou Qing 
Published: April 2014

Two distinct failure modes of spot welds, interfacial and pull-out failure, are observed in impact of spot-welded structures. Automotive industries prefer pull-out as the predominant failure mode since it makes more use of load-bearing capacity of a joint. For the time being, finite element models for predicting pull-out failure of spot weld have not been well developed. The dependence of failure on the stress state, i.e., a locus in the space of failure strain and stress triaxiality, needs to be known for base metal sheets when modeling spot weld pull-out. Existing failure criteria, with or without physical base, were formulated to provide an effective way to utilize a limited number of tests to reconstruct the failure locus.
This paper is aimed to evaluate influence of failure criterion form for identifying failure parameters on modeling spot weld pull-out. As for material tests, various specimen configurations of metal sheets were designed to obtain stress states around a number of typical stress triaxialities. These test results constructed a set of test data for calibrating failure criterion. The spot-welded joints were also tested two different coupon configurations. The force-displacement curves were obtained, and the deformation fields around the spot weld nugget were achieved with DIC. These test results of joints were utilized to validate the model of spot weld pull-out.
Two prevailing failure criteria, shear-modified Gurson model and Modified Mohr-Coulomb model, were selected to predict the complicated spot weld pull-out failure. Parameters in each of the two failure criteria were identified with material test data. Various simulation results were thereafter obtained based on different failure criteria. The two criteria were evaluated in terms of their predictive capabilities for spot weld pull-out failure.
Accuracy Evaluation of the Coupled Eulerian-Lagrangian Method in Abaqus/Explicit Using a Passenger Airbag Model
Authors: Nandi Biswanath , Buettner Joerg 
Published: April 2014

Computer simulations are widely used in modern automotive industry to design effective restraint systems, such as airbags. Until recently, the uniform pressure method (UPM), which assumes uniform pressure distributions inside the airbag, is mostly used in the design of airbags. The uniform pressure method is appropriate with fully inflated airbags interacting with in-position or belted occupants. However, with recent safety regulations for protecting occupants of various sizes and seating positions as well as the implementation of side airbags, Out-of-Positions (OOP) simulations are becoming more and more important for airbag suppliers and the OEMs. To simulate OOP cases, gas flow approaches are implemented in various commercial finite element codes in different forms.
This paper discusses the recent developments in the Coupled Eulerian-Lagrangian (CEL) method for airbag deployment simulations available in Abaqus/Explicit. A passenger airbag model was selected for the evaluation of accuracy of the CEL method. This paper also discusses some advanced Coupled Eulerian-Lagrangian method features available in Abaqus/Explicit in order to facilitate efficient occupant safety simulations.
Bending Stiffness and Dynamic Characteristics of a Rotor With Spline Joints
Authors: Wu Fayong , Liang Zhichao , Ma Yanhong , Zhang Dayi 
Published: April 2014

Spline is a kind of typical joint structures widely used in the aero-engine rotor system. The stiffness distribution of the spool is affected by the spline joint’s stiffness directly. Therefore, it is significant to investigate the spline joint’s stiffness characteristics and its influences on the dynamic characteristics of the rotor system. To figure out the factors that affect the bending stiffness of the spline joint, a mechanical model which takes contact state into account was built based on the structure analysis and force state analysis. In addition, an actual rotor with a spline joint was established to measure the stiffness under different loads, and the results were compared with the analysis by three modeling methods. Furthermore, the natural frequencies of the rotor were tested.
Obtained results indicate that the structural discontinuity, the surface stiffness and the clearance fit cause the loss of local angular stiffness and linear stiffness. Meanwhile, the stiffness of the rotor with the spline joint is weaker along with the increase of the load/deformation, and become stable when undergoing the huge load/deformation. Besides, the local blending stiffness is presented as nonlinear and uncertainty subjected to an interval, which further affected the dynamic characteristics of rotor system.
Thermal Design of Alkaline Water Electrolysis Assisted by Combined Flash Binary Geothermal Power Plant
Authors: Kanoglu Mehmet , Yilmaz Ceyhun 
Published: April 2014

The purpose of this study is thermoeconomic performance evaluation of alkaline water hydrogen production assisted by geothermal energy. In this study energy, exergy and cost balances of combined systems of each component for hydrogen production assisted by geothermal energy will be written. Exergy of each involved stream will be calculated and the exergetic balance of each subsystem will be assessed, as well as the global system, identifying and quantifying losses. This will allow thermodynamic performances of combined systems and each component. This information will be relevant to optimize the system performance from an economical point of view.
We consider a geothermal resource at 230°C available at a rate of 230 kg/s. Under realistic operating conditions, 21545 kW power can be produced in a power plant. The produced power is used for the electrolysis process. The electrolysis water can be preheated to 67.6°C by the geothermal water leaving the power plant and hydrogen can be produced at a rate of 0.1125 kg/s. Also, combine flash binary geothermal power plant energy and exergy efficiencies are calculated to be 12.1% and 57.4% at this condition. Electrolysis system energy and exergy efficiencies are calculated to be 71.4% and 60.7% of geothermal water temperature at 230°C and geothermal water flow rate at 230 kg/s. We evaluated at unit exergetic cost of electricity combined flash binary system is 10.1$/GJ (0.0364 $/kWh) and unit exergetic cost of hydrogen is 34.6$/GJ (4.16 $/kg H2).
Operator Related Causes for Low Correlation Between CAT Simulations and Physical Results
Authors: Rosenqvist M. , Falck A-C. , Söderberg R. , Wärmefjord K. 
Published: April 2014

The objective of this study was to explore correlation between CAT (Computer Aided Tolerancing) simulation and physically measured results in running production with focus on operator dependant factors. Therefore, the manual assembly of 25 different system solutions (locating scheme, tolerances, fasteners etc for a part) was analyzed. The study has been performed in the automotive industry and the system solutions are from 3 different cars in 2 different factories, all manual assembly in a paced line.
The analysis shows several interesting results; in running production 33% of the measurements are not ok although 28% had their tolerance zone adjusted according to the measured results to make them ok. The conclusion is that the CAT simulations do not predict all the variation and therefore additional factors need to be included to enable accuracy improvement.
Further relationships between additional factors such as operator influence and bad geometrical quality can be proven.
A short term solution is suggested as well as a long term solution involving the need for development of additional functions in CAT tools, the overall goal being to decrease the difference between simulation results and actual physical results.
Modelling of Misaligned Rotor System in Aero-Engines and Interval Method Investigation
Authors: Wang Guihua , Ma Yanhong , Li Tianrang , Li Jun , Hong Jie 
Published: April 2014

Based on the structural and dynamic characteristics of aero-engine rotor system, we used Lagrange method to develop a two-bearing and a multi-bearing rotor model with misalignment. An equation of motion was derived with features of response examined. Due to the uncertainty of mechanical parameters, interval method was adopted to investigate the dynamic response of rotor system with misalignment. Dynamic response and influence of the key mechanical parameters will be obtained in further research.
The two times harmonic was found as a distinctive feature of misalignment and the magnitude of it in spectrum is closely related to some key mechanical factors. We also found interval method outstandingly performed in investigating dynamic response when some key parameters are uncertain.
Optimizing Machining of Machine Tool Casting Bodies by Means of Optical Scanning
Authors: Gessner Andrzej , Staniek Roman 
Published: April 2014

The hereby presented study reports on the results of research funded by the NCBiR improvement grant. The goal of the undertaken experimental effort was to eliminate the laborious process of marking out from the technological procedure of cast machining. Marking out, even in highly automatized machining enterprises, is performed manually. It assesses casting accuracy, as well as denotes surpluses on machining surfaces. The precision of marking out is, therefore, dependent on individual performance of a given worker. Moreover, gauging casts of cylindrical (non-perpendicular) shape is highly problematic. Incorrect marking out generates quantifiable material (cast iron) and machining losses, as well as production interruptions.
Herein, we present an innovative cast machining technology based on cast model scanning. Prior to machining, each body is scanned according to the technology guidelines. The subsequent comparison of the cast model and the model of the machined body affords geometrical accuracy assessment of the cast and the determination of optimal machining surpluses. The surplus verifying criteria include: machining volume minimization, tool working motions minimization, and idle tool motion minimization. Moreover, in special cases, high productive cutting (HPC) or high speed machining (HSM) optimization of cast technology, as well as elimination of superfluous procedures (e.g. milling of machining datum surfaces), are possible. The proposed comparative analysis of the aforementioned 3D models additionally affords acquisition of data for positioning (horizontal alignment) of the machined cast, e.g. the required length of technological supports.
The hereby presented experimental results (obtained in an industrial setting) confirm the proposed elimination of the marking out process, thereby affording time reduction of preparatory procedures, initial assessment, and positioning of the cast for machining, as well as a decrease of machining volume by approx. 10 % (for the investigated casts). Experimental simulation results allowed us to estimate the machining volume minimization reaching up to 25 % (depending on the cast shape and the machining process specifications). Moreover, our investigation indicated a possibility of detection of casting flaws caused by insufficient surface brushing down. As the casts are painted post-brushing, the interfering sand mold remains are easily overlooked and often cause cutting-tool damage leading to costly production interruptions.
Integrated Approach for System Oriented Analyses and Optimization of Complex Hybrid Powertrain Applications by Means of Vehicle-in-the-Loop Roller Test Bench
Authors: Albers Albert , Schwarz Alexander , Behrendt Matthias 
Published: April 2014

Central activity in the development process of automotive drive systems is the validation to meet the customers’ demands. Thereby the transmission topology as well as the operation and drive strategy and their independencies have a great influence on the comfort and the energy efficiency of the vehicle. Especially in modern drivelines, like in hybrid electric vehicles there are great independencies between those factors, which have to be considered and integrated in order to achieve a global optimum.
In this contribution an integrated validation and development environment with the focus on hybrid transmission applications is presented. This approach is capable to integrate and consider aspects of complex powertrain systems, as hybrid powertrains, and to cover the competing aspects of NVH, drivability as well as energy efficiency. The approach is an integral combination of new or already published as well as established individual methods that have been extended with challenging aspects of hybrid powertrain development. One integrated method is the time-efficient arrangement of measuring points in order to shorten the global needed conditioning phases. For gearshift evaluation of a dual clutch transmission, this reduces operation time on the roller test bench about 80% compared to an experienced test driver [1]. The integrated approach uses system identification to create time and cost efficient test runs for the test based optimization [2]. Thereby advanced methods for rating the drivability and for automatic identification of NVH-Phenomena [3] are used to optimize multi criteria objective functions. The measurement is done in the IPEK-X-in-the-Loop Framework (XiL) [4], which enables a transmission assessment on the complete vehicle level.
The Drift Flux Model After Fifty Years: A Personal, Problem Solving Survey
Authors: Toma Peter 
Published: April 2014

Offspring of the nuclear reactor industry and gas-oil production, multiphase fluids handling technology appears to have matured into an entirely new field of inquiry, most notably following broad acceptance of the drift flux and flow pattern concepts and their widespread integration into engineering calculations.
The drift flux model (DFM), first suggested by Nicklin in 1962 and, soon after, adapted and developed by Professor Zuber’s research group at General Electric, enables calculation of “locally averaged” phase velocity. Further progress made in selection of the flow patterns, calculated for each section of the pipe, provided the key to properly assessing the terminal velocity of the discrete phase and the local phase distributions.
The flow pattern concept was first introduced by Canadian Charles Govier to describe oil-water laboratory experiments, then by Hewitt-Roberts and Baker in 1954. A decade later, the team of Dukler-Taitel-Barnea developed the qualitative flow pattern concept into a quantitative roadmap procedure leading to rational calculations of the local (cross-section averaged) gas-liquid flow geometry, or flow pattern. The homogeneous gas-liquid flow, presuming the equality of gas and liquid velocities, a simplification broadly accepted during the early days of two-phase flow engineering, came to be regarded, due to Hinze’s work (Shell, 1955), as an identifiable region in the local flow map, reflecting turbulent and high-shear breakup of the discrete phase.
To illustrate the usefulness, validity, and importance of the DFM, and mechanistic modeling using the DFM, as well as the salient work of Prof. Zuber on boiling instability this paper discuses reduction of potential explosive droplet boiling risk during multiphase pumping of high–gas-oil ratio mixtures.
To assess critical operating conditions of the multiphase pumps, the Ishi-Zuber criteria developed during 1970 for assessing potential boiling instabilities were adapted to multiphase pumping/compression equipment and the results compared to field instability data.
The elucidation of this problem relies heavily on the DFM and on salient research performed during 70s by Prof. Zuber’s team.