bluuebunny/crossref_metadata_2025 huggingface dataset:
First-Order Size Effects in the Mechanics of Miniaturized Components
Authors: Hoefnagels J.P.M. , Janssen P.J.M. , de Keijser T.H. , Geers M.G.D.
Published: March 2009

This work analyses those size effects that are encountered first upon downscaling,
including grain boundary effects, free surface effects, grain statistics effects. The separate influence
of first-order effects was carefully investigated from uniaxial tensile tests on high-purity aluminum
specimens with a well-defined microstructure of through-thickness grains, whereby the total number
of grains in the cross-section was reduced towards a single grain in a cross-section by, first,
decreasing the film thickness and, second, for specimens with through-thickness grains decreasing
the specimen width. In addition, 3D dislocation-field strain gradient plasticity simulations were
employed to analyze the intrinsic size effects, using the grain size and texture as measured
experimentally.
The work shows that for miniaturized structures with a limited number of columnar grains a unique
Hall-Petch relation does not exist, even though a grain boundary effect, i.e. a decrease in stress level
(at a given strain) for decreasing grain boundary area per unit volume, is clearly present. When the
microstructure is kept constant upon miniaturization, the free surface per unit area increases causing
the stress level of the structure to decrease, the effect of which increases towards a single grain in
the cross-section. In addition, the work shows that grain statistics effects also contribute to observed
weakening, due to insufficient compensation of local (weaker) material properties by the
surrounding material (i.e. grains). Finally, grain statistics also significantly increase the statistical
variation in mechanical properties for small-sized structures, an effect that is especially important
for the reliability of miniature components. The separate influence of these first-order effects as well
as their interplay are explained in terms of the movement of the dislocations upon plastic flow.
Plastic General Instability of Ring-Stiffened Conical Shells under External Pressure
Authors: Ross Carl T.F. , Andriosopoulos G. , Little Andrew P.F.
Published: March 2009

The paper describes experimental tests carried out on three ring-stiffened circular conical shells that
suffered plastic general instability under uniform external pressure. The cones were carefully
machined from EN1A mild steel to a very high degree of precision. The end diameters of the cones,
together with their thicknesses were the same, but the size of their ring stiffeners was different for
each of the three vessels. In the general instability mode of collapse, the entire ring-shell
combination buckles bodily in its flank.
The paper also provides three design charts using the results obtained from these three vessels,
together with the results obtained for twelve other vessels from other tests. All 15 vessels failed by
general instability. One of these design charts was based on conical shell theory and two of the
design charts were based on the general instability of ring-stiffened circular cylindrical shells, using
Kendrick’s theory, which were made equivalent to ring-stiffened circular conical shells suffering
from general instability under uniform external pressure. The design charts allowed the possibility
of obtaining plastic knockdown factors, so that the theoretical elastic buckling pressures, for perfect
vessels, could be divided by the appropriate plastic knockdown factor, to give the predicted
buckling pressure. The theoretical work is based on the solutions of Kendrick, together with the
finite element program of Ross, namely RCONEBUR and the commercial finite element package
ANSYS. This method can also be used for the design of full-scale vessels.
Modelling of a Cervical Plate and Human Cervical Section C3 – C5 under Compression Loading Conditions Using the Finite Element Method
Authors: Beltrán-Fernández Juan Alfonso , Hernández-Gómez Luis Héctor , Rodríguez-Cañizo R.G. , Merchán-Cruz E.A. , Urriolagoitia-Calderón G. , González-Rebatú A. , Dufoo-Olvera M. , Urriolagoitia-Sosa G.
Published: March 2009

This paper presents the modelling of the effects due to load conditions on the cervical
section defined between C3 and C5 after a cervical plate implant is used to transfer the
compression loads from C3 to C5 as C4 is considered to be damaged as a result of a medical
condition. For this study, three different scenarios which describe the common motion condition of
the head-neck system are modelled. The first one refers to the effect of the head weight over the
considered section. In the second case the average patient weight is supported by C3 and C5
vertebrae. The last case simulates extreme loading conditions as vertebrae lesions occur when
these are compressed beyond its failure limit; the ultimate stress to compression load failure value
is applied to C3. The stability and mechanical behaviour of cervical plates under compression
loading conditions is evaluated using the Finite Element Method (FEM). Cervical plates are useful
to restore stability of the spine by improving the inter-vertebral fusion, particularly when the
cervical body has been damaged. The results show that the stresses on the plate and fixation
screws, for the three cases, are within the elastic range. Conversely, it has to be considered that
cortical and trabecular bone densities vary from one patient to another due to a number of factors,
which can influence the fixation conditions of the screws. In the case of this analysis, healthy bone
conditions were considered and the obtained results show that the risk of the integrity of the screwimplant-
vertebrae system is not compromised.
Nonlinear Stress and Deformation Behaviour of Composite Sandwich Beams
Authors: Gdoutos E.E. , Daniel I.M.
Published: March 2009

The nonlinear load-displacement and normal stress distribution in composite sandwich
beams made of unidirectional carbon/epoxy facings and PVC foam cores under bending was
studied. The carbon/epoxy after an initial linear response exhibits a stiffening nonlinearity in tension
and a softening nonlinearity in compression with the longitudinal strength in tension higher than
that in compression. The foam core also presents a nonlinear stress-strain response. It was obtained
that the load-displacement behaviour of the beam, after an initial linear part, is not linear. This
behavior was modeled by an incremental strength of materials nonlinear analysis. The theoretical
predictions were in good agreement with the experimental results. Furthermore, it was obtained that
the neutral axis of sandwich beams under bending does not pass through the centroid of the cross
section, but is displaced toward the tensile side of the beam. Experimental results by moiré
measurements of the in-plane horizontal displacements of the core material corroborated the
analytical predictions. These findings imply higher compressive and smaller tensile stresses in the
core, than those predicted for facings with identical stress-strain behaviour in tension and
compression, and should be taking into consideration in the failure analysis of sandwich beams.
Experimental Measurement of the Deformation in Hot Rolling of Aluminium 1% Mn: The Grid Technique
Authors: Boldetti C. , Pinna C. , Howard I.C. , Gutierrez G.
Published: March 2009

The grid technique is an experimental method for measuring the deformation in hot rolling. An AA3004 sample -fitted with an insert - was rolled in a single hot rolling pass at 400 oC. The insert was hand engraved with a 1x1 mm grid and the analysis of the image of the deformed grid enabled the calculation of the components of the deformation gradient tensor. In order to prevent relative motion between the insert and the work-piece, four steel pins were used; after the test no detachment was observed between insert and sample. The temperature was monitored during rolling using two embedded thermocouples, one close to the surface and the other on the centre-line of the slab. The commercial finite element (FE) code ABAQUS was used to build a threedimensional model of the rolling process. The recorded temperature was compared with the FE values evaluated after tuning the heat transfer coefficient. The FE model was run several times with different friction coefficients and the deformation gradient checked against the experimental measurement of the deformed grid in order to obtain the optimum friction coefficient. The experimentally determined deformation gradient and the measured temperature agreed well with the numerical values.
Experimental and Finite Element Study of Welded T-Joints
Authors: Wu A. , Mellor B.G. , Syngellakis S.
Published: March 2009

Suitable testing arrangements are made for assessing the strength of welded T-joint specimens and providing input for the validation of finite element simulations of their behaviour under load. Material characterisation across the various weld areas is carried out through tensile and hardness tests as well as standard metallographic procedures for examining the microstructure. Strain is measured at critical locations identified through initial FEM analysis. Failure mechanisms are monitored, failure loads recorded and linked to the joint material and geometric characteristics. The consistency of FEM predictions with these measurements and observations provide a reasonable degree of confidence that the developed model can yield reliable stress and strain distributions for failure analysis.
Mechanical Testing of Dual Alloy Inertia Friction Welded Shafts
Authors: Robotham William S. , Hyde Thomas H. , Williams Edward J. , Brown Paul , McColl Ian R. , Kong C.J.
Published: March 2009

The development of aeroengines with increasing thrust capabilities requires the development of shaft technology to deal with this greater power transmission, whilst still restricting their dimensions and weight. Modern aerospace drive shafts are predominantly of a single-alloy design and significant benefits could be obtained from using a dual alloy shaft, where a high temperature alloy is used at the turbine, i.e. hot, end of the shaft and a high strength alloy is used for the spline end of the shaft, where high strength is required, rather than high temperature performance. Whilst the processes of joining dissimilar materials are widely used the evolution of the joint and its strength characteristics are not fully understood. A program of research has been instigated to lead to an improved understanding of friction welds and their behaviour under monotonic and cyclic loadings with the overall objective to establish confidence in the welding parameters for these material combinations and the associated post-weld heat treatments. This paper presents an overview of the mechanical testing program and the aims of this work, illustrated with some examples from the monotonic and cyclic test work carried out on inertia friction welded dual alloy shaft components.
Investigation on the Influence of the Surface Resin Rich Layer on the Thermoelastic Signal from Different Composite Laminate Lay-Ups
Authors: Pitarresi G. , Conti A. , Galietti U.
Published: March 2009

This work presents a set of experimental results based on the measured thermoelastic signal from GRP composite coupons adopting different lay-ups. A comparison is made with the thermoelastic signal predicted by two different analytical models: one based on the classical law of the thermoelastic effect for orthotropic materials, and the other based on a novel theory accounting for the presence of a resin layer on the external surface of the composite structure. The composite coupons were designed such to determine a significant difference in the predictions made by the two theoretical models. Experimental results have shown a far better match with the predictions based on the novel theory accounting for the presence of a surface resin rich layer.
Interlaminar Shear Strength and Fractographic Evaluation with Varying Temperature and Moisture Content of Thermoplastic Composites
Authors: Franco L.A.L. , de Alencastro Graça Mario Lima , Silva F.S.
Published: March 2009

This paper is related to the understanding of the relationship between the apparent interlaminar shear strength and the temperature-moisture content by the analysis of the dominant failure mode. It assesses the fracture mode of laminates with carbon fiber fabrics in (0, 90, 45)S ply orientation reinforced Polyphenylenesulphide (PPS) polymer matrix, tested for Interlaminar Shear Strength by the Short Beam method. Tests were conduced at different temperatures: (+20°C), (+0°C), and (-55°C), under various moisture-absorbed contents, namely Dry, 25%, 50%, and 75% of the saturated condition. Fractographic analyses were made and reveal, by the analysis of the fracture surface, the dominant mode of failure in every temperature-moisture content pair. As expected it is verified that temperature is a degradation factor. It is also found that humidity is not a degradation factor and, above the water freezing temperature, the moisture content even becomes a strengthening factor on this thermoplastic composite
Phase-Shifting Method with Unknown Intervals in Phase-Shifting Digital Holography
Authors: Kita T. , Morimoto Yoshiharu , Fujigaki Motoharu , Matui Toru
Published: March 2009

Displacement measurement can be performed with high accuracy using phase-shifting method. In phase-shifting method, it is often used four steps of phase-shifting for one cycle. In conventional method, to measure the displacement of an object by an interferometer, the phase of a reference beam should be shifted by every π/2 in the four-step phase-shifting. In this paper, a phase-shifting method with unknown intervals is proposed. This method does not need to shift a phase by every π/2. It can detect an intensity distribution and a phase distribution from five fringe images with equal intervals even if the phase-shift amount is unknown. Using this method, we propose a displacement measurement of phase-shifting digital holographic interferometry using spherical wave as reference wave.
Semi Empirical Stress Analysis of a Brittle Material in a Vicinity of a Stress Concentrator
Authors: Chabaat M. , Djouder S. , Touati M.
Published: March 2009

In this study, interaction of a main crack with its surrounding damage, which consists of continuous lines of discontinuities, is analysed. To solve this complex problem, a Semi-Empirical Approach (SEA), which relies on experimentally measured crack opening displacements as the solution to this multiple crack interaction problem is suggested. The solution procedure is illustrated, first, for a particular case of the interaction of an array of horizontal and vertical crazes with a main crack, and second, for the generalized case to include the whole damage of crazing patterns surrounding the main crack. The results show that the crack Damage Zone (DZ) or the socalled Process Zone (PZ) interaction may either amplify or suppress the resulting stress field depending on the crack damage configuration. Green’s function for the Stress Intensity Factor (SIF) is employed to quantify the effects on a crack of the damage of continuous patterns of discontinuities. It follows from the analysis that an increase in the number of crazing patterns will amplify the stress at the main crack. It is also shown throughout this study that the overall effect of the damage is identified, as being an amplifying one and that the resulting local stress field would direct the propagation of the main crack since there is no toughening.
Locating Defects Using Dynamic Strain Analysis and Artificial Neural Networks
Authors: Hernández-Gómez Luis Héctor , Durodola J.F. , Fellows N.A. , Urriolagoitia-Calderón G.
Published: March 2009

An inverse artificial neural network (ANN) assessment for locating defects in bars with or without notches is presented in the paper. Postulated void defects of 1mm x 1mm were introduced into bars that were impacted with an impulse step load; the resultant elastic waves propagate impinging on the defects. The resultant transient strain field was analyzed using the finite element method. Transient strain data was collected at nodal points or sensors locations on the boundary of the bars and used to train and assess ANNs. The paper demonstrates quantitatively, the effects of features such as the design of ANN, sensing parameters such as number of data collection points, and the effect of geometric features such as notches in the bars.
Evaluation of Rugged 'Smart Patch' Fibre-Optic Strain Sensors
Authors: Doyle Crispin , Quinn S. , Dulieu-Barton Janice M.
Published: March 2009

Fibre-optic sensors have advantages over existing electrical sensors in many strain and stress monitoring applications. However, bare optical fibres are fragile and packaging techniques must be developed before these sensors can be used more widely. One such method is the Smart Patch, in which the fibre Bragg grating is encapsulated between plies of glass-reinforced epoxy where rugged cables are anchored. This forms a flat flexible patch in which the fibre is protected from mechanical and environmental damage. However, it is important that the mechanical strength of the patch is not achieved at the expense of good strain transfer characteristics. To confirm this, fibre Bragg gratings with acrylate and polyimide coatings were embedded in a glass-epoxy patch that was bonded to an aluminium tensile specimen. An electrical strain gauge was also bonded to the specimen to provide a strain reference. Tests were carried out at different loading rates and at temperatures from -30°C to +80°C. There was good agreement between the fibre-optic sensors and the electrical strain gauge demonstrating that the patch performed in a practically identical manner to the conventional gauges. A second experiment on a representative part of ship structure demonstrated the versatility of the patch.
On the Feasibility of Thermoelastic Stress Analysis on Rapid Prototyping Models
Authors: Carella Giuseppe , Galietti U. , Modugno D.
Published: March 2009

This work discusses application of the thermoelastic technique to the stress analysis of Rapid Prototyping (RP) models. The aim is to evaluate the possibility of conducting complete and effective structural tests on prototypes made by means of stereolithography (SLA). The analyzed material is an RP Cure 600 ND epoxy resin. A statistical approach was followed to evaluate the sensitivity of the thermoelastic behaviour of the material to some SLA characteristic parameters. In addition, the effect of load cycle frequency on thermoelastic signal was also analyzed. The experimental work included forty-eight tests on ASTM standardized specimens. A new testing procedure was developed for resin-made models. The new method is based on the application of a loading ramp to SLA standard specimens and on the acquisition of the infrared signal. The thermoelastic constant K is determined using the thermographic signal temporal slope. Results for an engine bracket are presented in the paper.
Ultrasonic Compression Tests on Aluminium
Authors: Daud Y. , Lucas Margaret , Huang Zhi Hong
Published: March 2009

A study is presented into the effect of ultrasonic activation of the platen on the stressstrain relationship in compression tests on aluminium specimens. The aim is to gain some insights into the reported beneficial effects of ultrasonically excited tools in metal forming operations. The paper investigates the compression of aluminium specimens using a variety of different lubricants under conditions of constant crosshead velocity and superimposed longitudinal ultrasonic excitation of the platen. The study shows that the changes in the stress-strain relationship under ultrasonic excitation can be explained in terms of the superimposed oscillatory stress condition and that there is some evidence of small changes in the interfacial friction condition.
Effect of Laminate Configurations on Impact Properties of GFRP Composite in Seawater
Authors: Srivastava S.K. , Singh I.P.
Published: March 2009

Hybrid laminates of glass fibre reinforced plastics (GFRP) are being increasingly used
for marine structures under multidirectional loadings, due to their anisotropic behavior, corrosion
resistance, high specific strength and stiffness. Therefore appropriate laminate configuration for
marine environment applications is an important field of study. Five types of fibre epoxy laminates
configurations, resulting from different combinations of three layers of chopped strand mats (CSM)
and woven roving (WR) were fabricated using the vacuum resin transfer moulding (VRTM)
technique. These were investigated for the effect of seawater on its impact properties. The results
showed a significant reduction in the impact strength in all types of wet specimens. This behavior
may be attributed to penetration of water molecules in the composites. The impact properties of
hybrid laminates using a mixture of CSM and WR were found to be better than combination of
laminates comprising only CSM and WR under both dry and wet conditions for marine structure.
The Application of an Active Vibration Regulation System to Improving Driving Comfort in Convertible Vehicles: A Comparative Study of Regulator Design Methodologies
Authors: Mahinzaeim Mahyar , Hale Jack M. , Swailes D.C. , Schmidt Reinhard , Johanning B.
Published: March 2009

This paper considers the development of an active vibration regulation (AVR) system on
a convertible car equipped with a hydraulic actuation system. Experimental modal analysis is used
to identify a model from the measured dynamic response of the car body and the hydraulic
actuators. Two different methods are used to design the AVR system in the presence of process and
measurement uncertainties, namely optimal feedback regulation and proportional-integralderivative
(PID) compensation. With the aim of reducing the amplitude of the first eigenmode of
the system considered, the AVR algorithms are digitally implemented and real-time experiments
involving a hydro-pulse four poster rig are conducted. The results from these are evaluated and it is
shown that the AVR systems achieve a significant vibration reduction in the first eigenmode, which
is important for passenger comfort.
Dynamic Mechanical Properties of Polypropylene Syntactic Foam with Polymer Microballoons
Authors: Mae Hiroyuki , Omiya Masaki , Kishimoto Kikuo
Published: March 2009

The main objective of this study is to measure and characterize the mechanical properties of the thermoplastic syntactic foams at the intermediate and high strain rates. The syntactic foam consists of the elastically deformable microballoons in the polypropylene matrix. The four types of syntactic foams and one polypropylene bulk specimen are prepared at same manufacturing process: 0, 20, 30, 40 and 50 volume percent of microballoons. Tensile tests are conducted at nominal strain rates ranging from 10-1 to 102 (1/sec). Elastic modulus, yield stress and rupture strain are measured and the effects of microballoons on the mechanical properties are studied. In addition, fracture surfaces are observed with ESEM (Environmental Scanning Electron Microscopy). Finally, the changes of fracture mode due to microballoons are discussed.
Techniques for Experimental Measurement of Fatigue Crack Closure
Authors: Nowell David
Published: March 2009

Fatigue crack closure is an important phenomenon which needs to be taken into account in the development of models for crack propagation. This paper presents an overview of techniques for measuring crack closure. The moiré interferometry approach is described in more detail and some experimental results are presented and compared with the predictions of closure models.
Software Implementation of the Virtual Fields Method
Authors: Tran V. , Avril Stephane , Pierron Fabrice
Published: March 2009

The virtual fields method is a tool dedicated to the identification of the mechanical properties of
materials from full-field deformation measurements. It is now validated in elasticity and
plasticity but one of the remaining problems is the fact that researchers wanting to use the
method must invest significant time in order to programme the routines. To help them, a
software called CamFit has been developed. The purpose of this paper is to present this software.
It is based on MATLAB® and uses a graphical pre-processing interface to produce the
geometry, the conditions on the virtual fields, to choose the type of behaviour etc... Then, series
of displacement maps are uploaded and the identification is launched. Since no iterative solution
of the direct problem is required, computation times are very small compared to updating
techniques. An important step in the procedure is the smoothing of the displacement
measurements to produce strains. FE based approximations are presently available in the
software. The final purpose is to introduce the software onto the market. This will be done in the
very near future.
An Internal Variable Update Procedure for the Treatment of Inelastic Material Behavior within an ALE-Description of Rolling Contact
Authors: Ziefle M. , Nackenhorst U.
Published: March 2009

Arbitrary Lagrangian Eulerian (ALE) methods provide a well established basis for
the numerical analysis of rolling contact problems, the theoretical framework is well developed
for elastic constitutive behavior. Special measures are necessary for the treatment of history
dependent and explicitly time dependent material behavior within the relative–kinematic ALE–
picture. In this presentation a fractional step approach is suggested for the integration of the
evolution equation for internal variables. A Time–Discontinuous Galerkin (TDG) method is
introduced for the numerical solution of the related advection equations. The advantage of
TDG–methods in comparison with more traditional integration schemes is studied in detail.
The practicability of the approach is demonstrated by the finite element analysis of rolling tires.
Dynamics of Continuous Systems Subjected to Traveling Loads
Authors: Bogacz Roman
Published: March 2009

We studied several cases of dynamical problems, where the motion is driven by a concentrated force or distributed load applied at a moving position. The velocity of motion is assumed as constant. In particular, we studied interactions with periodic structure of the medium. Earlier results on one-dimensional structuresare extended to the case of an array of plates.
Mechanics of Track Structure with Y-Shaped Steel Sleepers in Sharp Curves
Authors: Czyczuła Włodzimierz , Bogacz Roman
Published: March 2009

Certain analytical elastic solution for curvilinear track section under uniform thermal
loading has been proposed. Track section is composed of circular arc, transition curves and straight
lines. Next step is the analysis of two-dimensional model of the track structure (stress plane,
without vertical direction). The rails and the sleepers are assumed as elastic bodies. The fasteners
and ballast are modeled as elastic-plastic elements. Non-linear properties of these elements are
determined by comparison of numerical data with experimental results. Cyclic uniform thermal
field is applied as the load of the system. Pre-buckling analysis is the basic part of the
considerations. Certain remarks on the track stability, based on the previous author analyses, are
also presented. It is shown that track structure with Y-shaped steel sleepers gives the possibility to
use of continuous welded rail (CWR) track practically in any radius of curvature.
Research for a Flexible Production of Lightweight Space Frame Structures
Authors: Klaus Alexander , Kleiner Matthias
Published: March 2009

This paper presents the focus of research and the structure of the Collaborative Research Centre SFB/TR10 „Integration of Forming, Cutting, and Joining for the Flexible Production of Lightweight Structures” funded in 2003 by the German Research Foundation (DFG). Driven by the demands of low volume production. The aim of the Research Centre is to investigate the scientific basis and methods to design integrated process chains for the flexible manufacture of space frame
structures.
Seam Weld Positioning for Composite Extrusion
Authors: Schikorra Marco , Kleiner Matthias
Published: March 2009

The production of continuously reinforced profiles by use of aluminium as base material and a reinforcement made of steel or carbon offers a great potential for modern lightweight constructions. Within this scope, they present the potential for an increase in usage of space frame constructions in automotive or aerospace engineering. But with the insertion of reinforcement in the material flow of the extrusion process some problems can occur that are negligible in thee
conventional extrusion processes: in the composite development area a significant local perturbation of the material flow is induced that can lead to the induction of high tensile stresses into the reinforcement. Due to this, failures like cracking of the reinforcement elements during the extrusion process has been detected in experimental investigations. A second problem occurring is the
necessity of prediction of the seam weld position and prediction of the seam weld quality. The reinforcement can only be induced by bridge dies between two strands and due to this it is always positioned in a seam weld. While in conventional extrusion the seam weld positions is often only an aesthetical problem, now this position mainly influences the extruded profiles properties like moment of inertia.
This paper deals with the problem of determination of seam weld position on the example of a double-t-profile extrusion. By use of a coupled thermo-mechanical finite element simulation with the commercial FE code HyperXtrude from Altair the velocity fields of an extrusion process with and without reinforcement were calculated and the resulting material flow was analysed. The numerical results went along with experimental investigations to verify the calculated results.
Composite Extrusion – Determination of the Influencing Factors on the Positioning of the Reinforcing Elements
Authors: Kleiner Matthias , Klaus Alexander , Schomäcker Michael
Published: March 2009

In order to manufacture a workpiece fulfilling specified requirements with the lowest possible weight, it is crucial to be able to work with a variety of materials and to combine them accordingly. The production of profiles based on hybrid materials demonstrates such an approach. The continuous and selective reinforcement of aluminum profiles with metallic elements like steel wire and steel wire ropes by composite extrusion is being investigated within the scope of research of the Transregional Collaborative Research Center (SFB/TR10). A stable production process for composite profiles with embedded continuous reinforcing elements was developed during the research work. In this paper, the process principle is shown and an overview of the special tools is given. Furthermore, the temperature and the strand speed as influencing factors on the final state of the composite are analyzed, based on real size experiments using a 2.5MN and a 10 MN extrusion press.
Structural Behavior of an EN AW-6060 Profile during and Immediately after Welding by a Laser-Laser-Hybrid System
Authors: Zäh Michael F. , Roeren Sven
Published: March 2009

This paper describes the analysis of thermal and mechanical effects during welding and the following cooling-phase on a welded structure. An off-the-shelf aluminum-profile, as used in other simulation sub-projects of the research center, was chosen as a sample part for the simulation tests. Taking up an important production scenario of lightweight-production, the frontal closing of two profiles is modeled. The development of residual stresses and the distortion is investigated by a thermo-mechanical FE-simulation. The virtually examined process is provided by a hybrid, bifocal laser system consisting of both an Nd:YAG-laser and a high power diode laser (HPDL). For comparison, a single Nd:YAG-process was simulated, too. The theoretically different generation of residual stresses can be verified within the simulation.
Qualitative Knowledge and Manufacturing Considerations in Multidisciplinary Structural Optimization of Hybrid Material Structures
Authors: Huber Martin , Baier Horst
Published: March 2009

An optimization approach is derived from typical design problems of hybrid material structures, which provides the engineer with optimal designs. Complex geometries, different materials and manufacturing aspects are handled as design parameters using a genetic algorithm. To take qualitative information into account, fuzzy rule based systems are utilized in order to consider all relevant aspects in the optimization problem. This paper shows results for optimization tasks on
component and structural level.
Flexible and Intelligent Gripping Technology for Machining and Handling of Spatially Curved Extruded Aluminum Profiles
Authors: Lanza G. , Fleischer Jürgen , Ruch Daniel
Published: March 2009

With a novel extrusion process which is investigated in the Collaborative Research Center Transregio 10 (SFB/TR10), it is possible to manufacture spatially curved aluminum profiles. This process is the base for an automated small and medium size batch production of light-weight frame structures. For the handling and machining of the spatially curved profiles, highly flexible machines and manufacturing equipment are needed. Today’s automated process chains do not reach a sufficient flexibility. This article introduces a new approach to handle and machine spatially curved profiles using a flexible gripping and clamping system. Firstly, the requirements concerning the process comprehensive gripping technology, which have to be fulfilled for a flexible small and medium batch production of light-weight frame structures, are specified. Subsequently, the function and design of a flexible gripping and clamping system are described. Furthermore, metrological processes to maintain a once reached condition of order during the entire process chain are depicted.
Three-Dimensional Curved Profile Extrusion – First Results on the Influence of Gravity
Authors: Klaus Alexander , Becker Dirk , Kleiner Matthias
Published: March 2009

This paper presents and discusses the latest achievements in the manufacture of threedimensionally curved aluminum profiles using an integrated bar extrusion process. While the conventional process chain lacks applicability and quality especially in low volume production, the new technology is promising, but still needs research to understand the correlation between the product to be manufactured and the contour accuracy to be achieved. This paper shows first results on the manufacture using a robot-guided second guiding tool and direct air quenching. The results will have an impact on further processing steps
Investigation of the Influence of Process Parameters on the Structure and the Mechanical Properties of Joints Produced by Electromagnetic Compression
Authors: Schulze Volker , Barreiro Pablo , Löhe Detlef
Published: March 2009

Electromagnetic Compression of tubular profiles with high electrical conductivity is an
innovative joining process for light weight structures. The components are joined using pulsed magnetic fields which apply radial pressures of up to 200 MPa to tubular work pieces causing a symmetric reduction of the diameter with typical strain rates of about 104 sec-1. This process avoids any surface’s damage of the workpiece because there is no contact between the components and the forming tool. The load, which the joints can transmit, strongly depends on the process parameters. Of them, the charging energy and initial gap between components
are the most important. In the present article, the influence of these two parameters on the joint’s characteristics, material’s microstructure and the mechanical properties is analyzed. The strength of the joint is determined by tensile tests and by measurements of the residual stresses. Finally, conclusions for the joint design are given.
Processing and Ferroelectric Property of Lead-Free KBa2Nb5O15 Piezoceramics
Authors: Yoshifuji T. , Kakimoto Kenichi , Ohsato Hitoshi
Published: March 2009

Dense KBa2Nb5O15 ceramics have been first prepared from the accurate treatment of
powder mixing under ordinary pressure-less sintering. The sample prepared by the calcined powder
mixed by a planetary ball-milling showed a relatively high density of 94.7% and a homogeneous
microstructure resulting from the inhibition of abnormal grain growth. The electric properties of
KBa2Nb5O15 ceramics was controlled by the preferential crystallographic orientation. The remanent
polarization (Pr) of the sample cut parallel to the pressing direction demonstrated above two times
larger (2.9 μC/cm2) than that of the perpendicular-cut sample (1.3 μC/cm2) at 150°C.
Development of H2/O2 Fuel Cell Based on Proton Conducting P2O5-SiO2-PMA Glasses as Electrolyte
Authors: Uma Thanganathan , Nogami Masayuki
Published: March 2009

Sol-gel derived high proton conducting P2O5-SiO2-PMA (phosphomolybdic acid, H3PMo12O40 nH2O) glasses as electrolyte were used for the H2/O2 fuel cell performance at 30 °C under humidification with H2- based gas at the anode and O2- based gas at the cathode. The performance of the electrode was evaluated by the measurement of cell potential-current density plots. While the polarization curve yields data related to basic cell performance, more detailed information can be found by electrochemical measurements with an impedance analyzer. The power density shows a similar pattern to current density. The maximum power density value of 16.2 mW/cm2 was achieved with 0.1 mg/cm2 of Pt/C loading electrode and P2O5-SiO2-PMA (4-92-4 mol %) at 30°C with 30 % humidity. The glass membrane here plays a key role as electrolyte medium for proton transport and barrier to avoid the direct contact between fuel and oxygen.
Nano-Crystallized Glass Fibers with Second-Order Optical Nonlinearity
Authors: Iwafuchi N. , Mizuno S. , Benino Yasuhiko , Fujiwara Takumi , Komatsu Takayuki , Koide M. , Matsushita K.
Published: March 2009

Transparent nano-crystallized glass fibers with 300μm diameter were successfully
fabricated in tellurite (TeO2) based glass systems. Structure of crystallized glass fibers and orientation
of nano-size crystals were quantitatively investigated by microscopic Raman spectroscopy and X-ray
diffraction. Second harmonic generation was measured in the nano-crystallized optical fibers.
Hydrothermal Synthesis and Structure Characterization of Nanocrystalline Barium Titanate Powders
Authors: Lei Ji Xia , Liu Xiao Lin , Chen Jian Feng
Published: March 2009

Nano-sized barium titanate powders were prepared by the high-gravity reactive
precipitation (HGRP)-hydrothermal method. The properties and defects of hydrothermal barium
titanate crystallites were investigated by TEM, XRD and FTIR. The mean particle size of the
hydrothermal barium titanate was about 70 nm with narrow particle size distribution. The crystallite
phases and OH defects were focused. The results show that the powders without heat treatment
were crystallized as cubic-BaTiO3 and the absence of tetragonal with increasing calcined
temperature to 1100°C. The IR results exhibited the OH defect content in the crystallites was to
increase the heat treatment temperature and reduced the probability of forming barium vacancies.
Sintering Behavior and Mechanism of Pure BaTiO3 Ceramic Prepared by High-Gravity Reactive Precipitation
Authors: Wang Xiao Hui , Liu Xiao Lin , Chen Jian Feng
Published: March 2009

Sintering behavior and mechanism of barium titanate powders prepared by high-gravity
reactive precipitation (HGRP) process has been investigated by a dilatometer. The mean particle
size of barium titanate powders prepared by HGRP was about 80 nm. Pure BaTiO3 pellets were
sintered at a constant heating rate of 2.0 K/min and the temperature of shrinkage-onset for pellet
was 1060°C. The maximal shrinkage was 165um and the maximum of shrinkage rate was 8.0 x 10-3
/ min at 1170°C. The sintering mechanism for the initial stages of sintering was determined by
isothermal dilatometric measurements and was found to be viscous flow.
Tentative Mechanisms for In Situ Polymerization of Metanilic Acid Intercalated in MgAl Layered Double Hydroxide under Nitrogen Atmosphere
Authors: Tian Xiao Fei , Wei Min , Evans David G. , Rao Guo Ying , Duan Xue
Published: March 2009

A new route has been developed to prepare polyaniline (PANI)/ layered double hydroxides (LDHs) nanocomposites through in situ chemical oxidative polymerization of metanilic acid (m-NH2C6H4SO3H) intercalated in MgAl LDH under nitrogen atmosphere by using the pre-intercalated nitrate as the oxidizing agent. The whole process involves the synthesis of the precursor LDHs [Mg2Al (OH)6](NO3)·nH2O, the intercalation of the monomer metanilic acid into LDH and its in situ polymerization between the layers by thermal treatment under nitrogen atmosphere. The interlayer polymerization was monitored by thermogravimetry (TG)-differential thermal analysis (DTA) - mass spectrometry (MS), UV-vis spectroscopy and in situ high temperature X-ray diffraction (HT-XRD). UV-vis spectroscopy give strong evidence on the polymerization of the intercalated metanilic acid, with the increase of the interlayer distance and broadening of the diffraction peaks. It has been found by the in situ technologies that the co-intercalated nitrate anions act as the oxidizing agent which participate in the polymerization of the interlayer monomers under nitrogen atmosphere by heating from 300 oC to 350 oC.
Thermal Shock Test for Porous Ceramics Using Water Flow Cooling Method
Authors: Xian Cheng Ji , Awaji Hideo
Published: March 2009

Thermal shock test for porous SiC ceramics heated up to testing temperature was
performed by a water flow cooling method. In order to find the influence of the penetration for the
porous material under the thermal shock, transient temperature distribution was simulated with taking
account of the infiltration of the cooling media into the specimen. Thermal stress distributions in the
specimens were also calculated from the estimated temperature distributions. In this study, it was
evident that the temperature variation of the porous ceramics was more rapid than that of the ceramics
without taking account of the penetration.
One-Dimensional Multiplexed Anisotropic Gratings in Photoreactive Polymer Liquid Crystals
Authors: Emoto Akira , Ono Hiroshi , Kawatsuki Nobuhiro
Published: March 2009

One-dimensional multiplexed anisotropic gratings were fabricated in photoreactive
polymer liquid crystals (PPLCs), and the diffraction properties were characterized. Based on the
holographic technique, the overwriting process is combined with the highly-stable and –controllable
molecular alignment of the PPLCs. As a result, 1st- and 2nd-order diffraction intensities variable
gratings dependent on the polarization direction of probe beam were obtained without significant
changing their total diffraction intensity. The multiplexed gratings can be used as
polarization-selective diffractive optical elements.
Relation between Porosity and Permeability of Ceramic Membrane Supports
Authors: Liang Long , Li Jian Bao , Lin Hong , Yang Xiao Zhan , Guo Gang Feng , He Ming Sheng
Published: March 2009

A membrane support provides mechanical strength to a membrane top layer to withstand
the stress induced by the pressure difference applied over the entire membrane and must
simultaneously have a low resistance to the filtrate flow. Due to their low thermal-expansion
coefficient and good thermal-shock resistance as well as excellent mechanical and chemical stability
at elevated temperatures, porous SiC ceramics have been widely used as catalyst supports and hot-gas
or molten-metal filters. In this work, the influence of the particle size, sintering time and sintering
temperature on the porosity and permeability of supports made by dry-pressing of micron-sized SiC
powders is investigated. The present work presents a comparison of properties and performance data
for samples made with different particle size. The effects of sintering time and temperature were
analyzed in view of overall porosity and permeability. From calculations it becomes clear that
optimum values exist for the material properties of the support.
Relationship between Flame-Retardant Property and Structure of Cyclomatrix Phosphazene Polymer
Authors: Zhang Teng , Jin Ri Guang
Published: March 2009

A novel phosphazene cyclomatrix network polymer was synthesized via nucleophilic
displacement of activated nitro groups of tri(4-nitrophenoxy)tri(phenoxy) cyclotriphosphazene with
the hydroxyls of bisphenol A. Then, thermal properties of the polymer was investigated using
dynamic thermogravimetric analysis (TGA) in air, pyrolysis and combustion experiments.
According to the relation among the pyrolysis residue (CR) at 850°C, the char-forming tendency
(CFT) of every structural unit in polymer and the limiting oxygen index (LOI), CFT of the
structural unit (-P=N-)3 and the LOI of the polymer were calculated as 35.04 and 34.3 respectively,
which provided theoretical parameter for designing the cyclomatrix- or cyclo- phosphazene
polymers with highly thermal and flame-retardant properties.
Precipitate Microstructures of High Strength Mg-Gd-Y-Zn-Zr Alloys
Authors: Yamada Kentaro , Okubo Yoshiyuki , Kamado Shigeharu , Kojima Yo
Published: March 2009

Precipitate microstructures in Mg-2.0Gd-1.2Y-0.75Zn-0.2Zr alloy were investigated and
the characteristic and mechanism of microstructure evolution in the alloy were discussed. Specific
long-period 14H ordered stacking structure was formed at grain boundary of Mg matrix crystals by
solution heat treatment at 773K and metastable β’ phase was formed during subsequent aging
treatment at 498K in the Zn-added Mg-Gd-Y alloys. These structure and phase exist simultaneously at
the peak-aged condition in the microstructure. Precipitate free zone (PFZ) of β’ phase does not exist at
an interface between a 14H structure and Mg matrix inside the grain, however, PFZ exist near the
edge of 14H structure at grain boundary. These results strongly suggest that high diffusion rate of
solute atoms at grain boundary promotes the nucleation and growth of 14H structure.
Consolidation of h-BN/Feldspar Composites in Air
Authors: Kume Shoichi , Saklar Saruhan , Watari Koji
Published: March 2009

Attempts have been made to sinter hexagonal boron nitride (h-BN) by
pressureless-sintering in air. In order to achieve this purpose, feldspar has been selected as a sintering
aid to produce sintered compacts at a temperature above the melting point of feldspar. Even though
h-BN was not wetted by the molten feldspar in nitrogen, the wettability was significantly improved in
air. Through the heating process, the h-BN powder disappeared owing to the oxidation of the powder
followed by sublimation of the boron oxide. The decomposition of BN was prevented effectively by
the presence of molten feldspar in the h-BN/feldspar (30 vol.%) compact. It was shown that
h-BN/feldspar composite can be sintered in air under normal pressure, although the bulk density of
h-BN/feldspar composites (1.40 to 1.51 g/cm3) was not satisfactory enough.