bluuebunny/crossref_metadata_2025 huggingface dataset:
Load and Geometry Effect on Failure Mode Initiation of Composite Sandwich Beams
Authors: Gdoutos E.E. , Konsta-Gdoutos M.S.
Published: March 2009

Facing compressive failure, facing wrinkling and core shear failure are the most commonly encountered failure modes in sandwich beams with facings made of composite materials. The occurrence and sequence of these failure modes depends on the geometrical dimensions, the form of loading and type of support of the beam. In this paper the above three failure modes in sandwich beams with facings made of carbon/epoxy composites and cores made of aluminum honeycomb and two types of foam have been investigated. Two types of beams, the simply supported and the cantilever have been considered. Loading included concentrated and uniform. It was found that in beams with foam core facing wrinkling and core shear failure occur, whereas in beams with honeycomb core facing compressive failure and core shear crimping take place. Results were obtained for the dependence of failure mode on the geometry of the beam and the type of loading. The critical beam spans for failure mode transition from core shear to wrinkling failure were established. It was found that initiation of a particular failure mode depends on the properties of the facing and core materials, the geometrical configuration and loading of composite sandwich beams.
Spar Corner Radius Integrity for the A400M Wing
Authors: Edwards Tim , Thompson Jeremy
Published: March 2009

The paper focuses on the structural integrity of the corner radius of the carbon fibre composite, ‘C’-section spar for the Airbus A400M wing. The corner radius is subject to opening moments generated by internal wing box fuel pressures. The low inter-lamina strength of composites makes de-lamination of the corner of prime concern.
The paper describes initial development of analytical techniques to calculate the through-thickness tensile stresses and inter-lamina shear stresses developed in a corner radius under applied bending moments and transverse shear forces. A test programme is also described, aimed at the determination of the failure moment of curved laminates under pure bending moments. Using the analytical expressions developed, a through-thickness failure stress is calculated from the failure moments. A variation of the failure stress with specimen thickness is indicated, showing that thicker specimens fail at higher inter-lamina stresses – a characteristic that must be exploited in the design of the spar.
Using finite element analysis of the test configuration, in conjunction with virtual crack extension techniques, it is demonstrated that, at the failure load, a constant rate of strain energy release accompanies inter-lamina crack growth in the different test specimens. A critical energy release rate for uncontrolled crack growth is thus established, which is used, in conjunction with further finite element analysis, to predict the failure stress of specimens with different values of thickness and corner radius.
It is concluded that this fracture mechanics approach to integrity can be applied to the A400M spar corner and to similar aircraft structures. Recommendations for further testing and correlation with analysis are proposed to strengthen the theoretical basis for such integrity assessments.
Measurement of Stokes Parameters by Quarter-Wave Plate and Polarizer
Authors: Kihara T.
Published: March 2009

Formulations of the theory of automated photoelasticity are expressed simply by use of the Stokes parameters. In the automated photoelasticity, the measurement of the total relative phase retardation must often be performed over a wide wavelength range. The Stokes parameters (S0, S1, S2 and S3) need to be measured over a wide wavelength range. The Stokes parameters of monochromatic light can be measured by the adjustable azimuth settings of a retarder and analyzer (ARA) method. When undertaking the measurement of the Stokes parameters of light of an arbitrary wavelength over a wide wavelength range, the measurement of S3 by the conventional ARA method is dependent on the phase difference error ρ i of a quarter-wave plate mismatch as well as Stokes parameter S2. The measurement of S3 by a judicious choice of azimuth settings of a quarter-wave plate and a polarizer (JCAQP) as in the method proposed can be obtained by considering ρ I . The JCAQP method is clarified by employing the Poincaré sphere. It is shown that application of the JCAQP method yields the principal axis and the relative phase retardation of the birefringent plate free from the ρ i of the quarter-wave plate for incident elliptically polarized light of an arbitrary wavelength.
Dissipative Behaviour of Metallic Materials in Low Stress Cyclic Loading
Authors: Maquin Francois , Pierron Fabrice
Published: March 2009

In order to fully understand the thermomechanical phenomena involved in high-cycle fatigue, a method for determining the dissipative thermal sources in a loaded metallic specimen from the spatio-temporal integration of the heat diffusion equation is proposed. Temperature fields obtained through a focal array infra-red camera are processed with this technique. After a refined analysis of the sensitivity of the method, preliminary tests have shown that it is possible to detect a burst of heat sources within the first couple of cycles for the specimen tested above a certain level of tensile stress. This behaviour is thought to be related to the microplasticity level.
An Experimental and Finite Element Study of the Ductile Tearing Characteristics of High-Toughness Gas Pipeline Steel
Authors: Ayvar S.S. , Hashemi S.H. , Howard I.C. , Yates J.R.
Published: March 2009

This paper reports recent results from a set of experimental and computational studies of ductile flat fracture in modern gas pipeline steel. Experimental data from plain and notched cylindrical tensile bars and standard C(T) specimens together with damage mechanics theories have been used to capture the flat fracture characteristics of a gas pipeline steel of grade X100. The modelling was via finite element analysis using the Gurson-Tvergaard modified model (GTN) of ductile damage development. The assumption of effective material damage isotropy was sufficiently accurate to allow the transfer of data from the notched bars to predict, in a 2D model, the crack growth behaviour of the C(T) specimen. This was in spite of the considerable ovalisation of the bars at the end of their deformation. However, it was not possible to obtain similar accuracy with a 3D model of the C(T)test, even after a large number of attempts to adjust the values of the GTN parameters. This, and the anisotropic shape change in the tensile bars, suggests very strongly that the damage behaviour is so anisotropic that conventional models are not good enough for a full engineering description of the flat fracture behaviour. Suitable averaging (of shape) in the modelling of the notched bar data, and the companion averaging associated with the 2D model of the C(T) data provide a relatively fast way of transferring engineering data in the tests. There is a discussion of potential ways in which to incorporate 3D effects into the modelling for those purposes where the considerable increase in computational time (due to the microstructurally-sized finite elements needed to capture the damage behaviour) is acceptable in order to include through-thickness effects.
Elastic-Plastic Behaviour of a Plate with a Central Hole by Photoelastic Coating Method
Authors: Matsumoto N. , Ohtaki S. , Ohira M. , Kasayama H.
Published: March 2009

An application of the elastic-plastic problem by the photoelastic coating method is presented in this paper. A general procedure of this experiment, such as image processing and separation of the difference of principal strain to obtaine stresses from isochromatic fringes is referred. The methodology to extract centre lines of coloured isochromatic fringes is explained. Experiments are conducted with cross-shaped aluminum specimens with a circular hole subjected to uniaxial tension and equi-biaxial tension. Results of image processing are shown, and the distribution of difference of principal strains and separated principal strain are shown in the case of equi-biaxial tension.
Design and Development of Lifeboats - Damage Evaluation and Repair of Composite Structures
Authors: Cripps R.M.
Published: March 2009

The RNLI has been using composites for the construction of some of its lifeboats since the early 1970s and in the late 1980s a decision was taken to adopt a newer advanced form of composite construction with a view to saving overall structural weight whilst maintaining the requisite structural strength. This paper presents a broad discussion of the history of the use of composites in the RNLI, the structural design and development of lifeboats and the challenges currently faced in the identification of damage and repair methods for fibre-reinforced plastic sandwich structures, operating in the marine environment.
High-Resolution Neutron Diffraction for Nondestructive Analysis of Residual Stresses in Polycrystalline Materials
Authors: Mikula Pavol , Lukáš Petr , Vrána Miroslav
Published: March 2009

The performance of an unconventional high-resolution neutron diffractometer using Bragg diffraction optics that can be efficiently employed in strain/stress diffractometers are reported. Presented results demonstrate their experimental abilities for powder diffraction, namely for residual strain/stress measurements. In addition to the macrostrain scanning capability, the device can also be used for microstrain/stress studies by suitable analysis of the diffraction profiles. Two examples of the strain measurements are presented.
Experimental Studies of the Behaviour at High Strain Rates of Unfilled and Filled Polypropylenes
Authors: Temimi N. , Billon Noelle
Published: March 2009

Thermo mechanical behaviour of unfilled and filled polypropylenes are studied in tension from 10-4 to 102 s-1. Complementary low velocity compression and shear tests are also performed. A high-speed video camera (up to 2500 frames/s) combined with image analysis, image correlation and an infra red pyrometer allow measuring 3D-strain fields and temperature during tests. Thus, data can be processed without restrictive assumptions. Beside usual (for polymers) temperature and strain rate sensitivities it is found that plastic deformation in these materials does not obey incompressibility assumption. Voiding damage is evidenced in the polymer matrix by SEM observations that result in volume change and significant decrease in Young modulus for both materials. Moreover, an increase in the temperature of more than 10 °C is observed and is likely to modify the behaviour of each material at high strain rates. Shear and compression measurements demonstrate that yield criteria and constitutive equation depend on loading. It is concluded that apparent yield stress in semi-crystalline polypropylene can be a result of a combination of “non strain rate sensitive” “non-cohesive mechanisms” and “strain rate sensitive” “cohesive mechanisms”. Experimental characterisation on polymers should then be revisited as most of the usual assumptions are invalid and non monotonic tests should be generalized.
Plastic Response of Nested Systems under Static and Dynamic Loading Conditions Using FE and Experimental Techniques
Authors: Morris Edmund , Olabi Abdul Ghani , Hashmi M.S.J.
Published: March 2009

This paper presents the study of nested rings crushed laterally between rigid platens at 2 different velocities. In this investigation two different types of nested ring configurations are analysed: (A) In-Plane; where three rings of varying diameter are placed within each other and their axes are parallel. (B) Out of-Plane; where the rings have a 90 degree orientation. Material used was cold finished, drawn over mandrel (DIN 2393 ST 37-2) and is referred throughout the paper as mild steel. The Cowper-Symonds relation was used to predict the dynamic yield stress of the rings and this was included in the FE material model. The results obtained from experiments were compared to that of finite element method using the software package Ansys. Discussion is made on the post – collapse behaviour of these systems. It was found that the Out of-Plane ring system exhibited a more desirable force-deflection response due to its 90 degree orientation.
A New Measurement and Testing Procedure Based on Thermoelasticity for Motorcycle Frame Prototype Development
Authors: Marsili R. , Moretti Michele , Pirisinu J. , Rossi Gian Luca
Published: March 2009

Motorcycle frames are mechanical components that need to be optimised in terms of
performance and costs but with a limited amount of resources compared to, for example, car frames. Fatigue testing of the component is required for qualification and this is typically performed by using rotating drums with steps or servo-controlled hydraulic actuator based test benches. Therefore a fast and simple measurement and testing technique that operates during the fatigue tests will be a very useful tool. In this paper the possibility of analysing these components by measuring the stress levels and stress concentration in critical parts by thermoelasticity is investigated. The development of a multibody model, useful to simulate the typical working conditions of the motorcycle frame, is also described.
Measurement of the Large Strain Behaviour of Aircraft Tyre Rubber
Authors: Mines Robert A.W. , Birch R.S. , McKown S. , Karagiozova D.
Published: March 2009

The paper describes mechanical property tests on a Concorde aircraft tyre rubber. The tyre rubber is taken from the tyre tread, and consists of nylon reinforcement, laid up in an angle ply form. The constitutive behaviour of the rubber is characterised using the Mooney Rivlin approach, in which deformation is expressed in terms of strain energy. Static and dynamic tensile tests are conducted along the major reinforcement and minor reinforcement axes in the plane of the tread, and compression tests are conducted through the tread thickness. This data is then input into a finite element model of the tyre, using DYNA.
In Situ Measurement of Internal Stress in Electroless Plating by Television Holographic Interferometry
Authors: Kakunai S. , Hayashihara H. , Sakamoto T. , Matsuda H.
Published: March 2009

Electroless plating can uniformly plate a material on irregular and non-conducting surfaces. Consequently, it has been utilized widely for printed circuit boards in the electronics industry. During the plating process, internal stress is frequently incorporated into the film and this often results in detachment from the substrate. In order to investigate the origins of stress in the films, measurements of film stress are required during the early stages of growth. In this study, TV holography, which can capture holographic images at TV frame rates, was used to sensitively measure the deflection of the cantilever beam during deposition. By substituting the deformation data in Stoney’s equation, it is possible to calculate internal stresses in-situ. The internal stress created by electroless plating from a Cu plating solution on a Be-Cu substrate is discussed. It is assumed that the internal stress is generated in the initial stage in which the plating grains with a thickness of about 0.01µm deposit. This paper shows that the present method can be very useful for in-situ measurement of initial internal stress.
FE Simulation of Laser Ultrasonic Surface Waves in a Biomaterial Model
Authors: L'Etang A. , Huang Zhi Hong
Published: March 2009

This paper describes a study of laser generated ultrasonic waves in an 2-layer elastic, isotropic biomaterial model, in order to establish a modelling technique to simulate the thermoelastic response of high-power short pulse laser beams in human skin. The theory proposed in this paper takes into consideration the fundamental understanding of the laser/material interface. A finite element model using the commercial finite element code ANSYS is used to study the effects of laser pulse duration and energy flux contribution to the surface waves. The simulation comprises a set of boundary conditions that approximate a heat flux point source located on top of the surface of the material. Because of the time scale of interest, the elastic effects do not feed back into the thermal problems, so that a sequential coupled-field analysis was performed where the thermal and elastodynamic fields are uncoupled and treated separately. The initial finite element analysis involves a transient thermal analysis using a heat flux with Gaussian spatial variation to simulate the laser pulse heating. The results from the thermal analysis were read and applied to the structural analysis where the out-of-plane displacements histories are analyzed in the skin model with varying thicknesses
Mode I and Mode II Fracture Toughness Testing for a Coarse Grain Marble
Authors: Aliha M.R.M. , Ashtari R. , Ayatollahi Majid R.
Published: March 2009

A series of fracture toughness tests have been conducted on a type of coarse grain
marble. The tests were carried out either in pure mode I or in pure mode II conditions by using the
cracked chevron notched Brazilian disc (CCNBD) specimen. A total number of 44 CCNBD
specimens were tested, half in pure mode I and the rest in pure mode II, to obtain reliable values for
mode I and mode II fracture toughness (KIc and KIIc) of the tested marble. The average value of KIc
for this marble was approximately about 1.12 MPa m showing a good agreement with those reported
for similar coarse grain marbles. The mode II fracture toughness was found to be 2.25 MPa m in
average which is approximately twice the mode I fracture toughness. However, the conventional
fracture criteria suggest that the mode I fracture toughness should be higher than the mode II
fracture toughness, (KIc>KIIc). According to these criteria, the ratio of KIIc / KIc is a figure typically
between 0.63 and 0.96. It is shown in this paper that enhanced mode II fracture toughness of
CCNBD specimen could be due to the effects of highly negative T-stress when the specimen is
subjected to mode II. It is also shown that an improved prediction for the ratio KIIc / KIc can be
achieved when the effect of T-stress is taken into account.
Mathematical Models of Gear Rattle in Roots Blower Vacuum Pumps
Authors: Mason Joanna F. , Homer Martin E. , Wilson R.E.
Published: March 2009

This paper is concerned with the modelling of gear rattle in Roots blower vacuum
pumps. Analysis of experimental data reveals that the source of the noise and vibration problem
is the backlash nonlinearity due to gear teeth losing and re-establishing contact.We develop non-
smooth ordinary differential equation models for the dynamics of the pump. The models include
a time-dependent forcing term which arises from the imperfect, eccentric mounting of the gears.
We use a combination of explicit construction, asymptotic methods and numerical techniques
to classify complicated dynamic behaviour in realistic parametric regimes. We first present a
linear analysis of motions where the gears do not lose contact, and develop upper bounds on
eccentricity for quiet operation. We then develop a nonlinear analysis of ‘backlash oscillations’,
where the gears lose and re-establish contact, corresponding to noisy pump operation. It is
found that noisy solutions can coexist with silent ones, explaining why geared systems can rattle
intermittently. We then consider several possible design solutions, and show their implications
for pump design in terms of the existence and stability of silent and noisy solutions. Finally,
we present conclusions and possibilities for future work.
Superposition of Manoeuvres and Load Spectra Extrapolation
Authors: Cerrini Angela , Johannesson P. , Beretta Stefano
Published: March 2009

To face the increasing demand for long lasting, versatile and performing machines, a
detailed analysis of the load conditions is required especially when structural integrity assessment
has to be achieved. Usually acquisitions of load histories are shorter than the machine working life
and an extrapolation of the signal for the total service life is needed. Traditional methods for load
spectra extrapolation are based on conservative choices in terms of worst case scenario. Methods
based on extreme value statistics have been developed.
The problem addressed in this paper concerns the extrapolation of load histories on a welded
boom in which different manoeuvres are superimposed. Different ways of extrapolating the load
measurement have been derived, both in time domain and in Markov domain, in order to account
for the superposition of bigger and more damaging cycles and smaller cycles caused by two
different service operations.
Nonlinear Response of an Oscillator with a Magneto-Rheological Damper Subjected to External Forcing
Authors: Borowiec M. , Litak Grzegorz , Friswell Michael I.
Published: March 2009

This paper examines the dynamics of a single degree of freedom nonlinear model,
representing a quarter of an automobile with a semi-active, nonlinear suspension. Assuming that
the kinematic excitation caused by the road surface profile is harmonic, the principal resonance
and frequency entrainment are obtained for regions of the model parameters. Changing the
excitation frequency and road profile amplitude we analyze possible chaotic vibrations and
bifurcations of the system.
A Meta-Heuristic Based Weight Optimisation for Composite Wing Structural Analysis
Authors: Sahadevan Vijay , Bonnefon Yoann , Edwards Tim
Published: March 2009

This paper presents a two-stage meta-heuristic approach to producing weight-optimised
solutions needed prior to the detailed finite element analysis of composite wing. Composite wing
covers are assumed to take the form of a group of stiffened sub-panels with varying skin and
stiffener geometries according to the wing layout and loads. A population of limited solutions
satisfying various design constraints was created using layout (skin and stiffener geometry),
selected lay-ups, rule based stacking sequence and various assumed loads. The closed form
analytical solutions of flat stiffened orthotropic plates are used for calculating buckling reserve
factors and strength margins. For each sub-panel, a meta-heuristic rule was imposed to search for a
suitable combination of skin and stiffener geometry. The criterion used was minimum weight
satisfying laminate continuity accounting for manufacturability. Later, the optimised solutions for
each sub-panel are converted into a format supported by the conventional finite element tool
(NASTRAN). The use of meta-heuristic approach and their automation in Visual Basic for
Applications resulted in fast convergence and potential time-saving compared to genetic algorithms.
On Approximate Analytical Solutions for Vibrations in Cracked Plates
Authors: Israr A. , Cartmell Matthew P. , Krawczuk Marek , Ostachowicz Wiesław M. , Manoach Emil , Trendafilova Irina , Shishkina E.V. , Palacz Magdalena
Published: March 2009

Recent NATO funded research on methods for detection and interpretation
methodologies for damage detection in aircraft panel structures has motivated work on low-order
nonlinear analytical modelling of vibrations in cracked isotropic plates, typically in the form of
aluminium aircraft panels. The work applies fundamental aspects of fracture mechanics to define an
elliptical crack, and the local stress field and loading conditions, arbitrarily located at some point in
the plate, and then derives an analytical expression for this that can be incorporated into the PDE for
an edge loaded plate with various possible boundary conditions. The plate PDE is converted into a
nonlinear Duffing-type ODE in the time domain by means of a Galerkin procedure and then an
arbitrarily small perturbation parameter is introduced into the equation in order to apply an
appropriate solution method, in this case the method of multiple scales. This is used to solve the
equation for the vibration in the cracked plate for the chosen boundary conditions, which, in turn,
leads to an approximate analytical solution. The solution is discussed in terms of the perturbation
approximations that have been applied and highlights the phenomenology inherent within the
problem via the specific structures of the analytical solution.
Vibration of a Coupled Plate/Fluid Interacting System and its Implication for Modal Analysis and Vibration Health Monitoring
Authors: Gorman Daniel G. , Trendafilova Irina , Mulholland A.J. , Horáček Jaromír
Published: March 2009

When carrying out a vibration modal analysis of a structure it is usually assumed that the
structure is in vacuo. However as structures become increasingly light and thin walled due to the
development of high grade corrosion resistant alloys, this fundamental assumption is becoming
increasingly strained. In this paper we will highlight the analysis and the implications of
structural/fluid interaction on modal analysis for the purpose of prediction of dynamic response and
for vibration health monitoring.
Three-Dimensional Elasticity Analysis of Thick Rectangular Laminated Composite Plates Using Meshless Local Petrov-Galerkin (MLPG) Method
Authors: Alavi S.M.R. , Aghdam Mohammad Mohammadi , Eftekhari A.
Published: March 2009

This article presents apparently the first application of Meshless local Petrov-Galerkin
(MLPG) method for 3-D elasticity analysis of moderately thick rectangular laminated plates. As
with other Meshless methods, the problem domain is represented by a set of spread nodes in all
three dimensions of the plate without configuration of elements. The Moving Least-Squares (MLS)
method is applied to construct the required shape functions. A local asymmetric weak formulation
of the problem is developed and MLPG is applied to solve the governing equations. Direct
interpolation method is employed to enforce essential boundary conditions. Details of formulation,
numerical procedure, convergence and accuracy characteristics of the method are investigated.
Results are compared, where possible, with other analytical and numerical methods and show good
agreement.
Analysis of Stress Distribution in SnAgCu Solder Joint
Authors: Gong J. , Liu C. , Conway Paul P. , Silberschmidt Vadim V.
Published: March 2009

SnAgCu solder is a promising lead-free material for interconnections in electronic
packages. However, its melting temperature (490°K) is considerably higher than that of the
traditional SnPb solder (456°K). At the same time, SnAgCu has much better creep resistance at high
temperature. These properties may cause large residual stresses during manufacturing processes due
to the mismatch of thermal properties of electronic components that can influence the reliability of
solder joints in electronic packages. This paper studies the residual stresses in solder joints in a flip
chip package under different cooling conditions and their influence on the subsequent cyclic test by
means of a finite element approach. The results show that the initial temperature of 453°K is high
enough to induce residual stresses due to manufacturing procedures. Simulations, based on
traditional creep-fatigue models, demonstrate that the residual stresses affect the mechanical
behaviour of solder joints in several initial thermal cycles but have little effect on their reliability.
Modelling of the Deburring Process
Authors: Dumitraş C. G.
Published: March 2009

Due to robotic deburring development, the research gains a new orientation and focused
on the cutting forces and the chip control. The present paper will emphasize the main difference
which occurs between the normal cutting process and the deburring process, the way it develops and
the parameters which characterize this process. Also the dynamics of the process are considered.
Based on a central composite design one determine a relation between the geometry of the tool,
workpiece hardness and cutting force.
Time-Frequency Feature Extraction of a Cracked Shaft Using an Adaptive Kernel
Authors: Behzad M. , Ghias A.R.
Published: March 2009

Adaptive time-frequency representations have many advantages compared with
conventional methods. In this paper, a new method is proposed to adapt Smoothed Pseudo Wigner-
Ville distribution to match signal’s time-frequency content. It is based on maximizing a local timefrequency
concentration measure for different time and frequency smoothing window lengths.
Subsequently, the optimized values are used for constructing an adaptive kernel over time. The
proposed transform is then applied to vibration signals of healthy and cracked shafts which are
acquired through run-up, and the crack signature is obtained. Results show that enhanced
improvement in resolution is obtained while the computational cost is not very high.
Experimental Determination of Stress Concentrations in Composite Laminates and their Effects on Damage Evolution
Authors: Katerelos D.T.G. , Galotis Costas
Published: March 2009

Composite laminates are used for the construction of a wide range of products; from civil
infrastructure to aeronautical or space structures. Since all these structures cannot be built at once,
but they are composed by several structural elements connected in various patterns, the problem of
stress concentrations strikes importantly. Additionally, the structures are often designed in a “fail
safe” manner, which bespeaks the damage tolerance of the material. This means that the structural
element and the structure are called to operate in the presence of various forms of damage. Damage
locations within a structural element or a structure cause stress rising. In the present paper
experimental investigation of the stress concentration arising in composite laminates, (a) around a
circular notch and (b) due to damage onset and growth during their lifetime, is presented. The
experimental results are compared to analytical model predictions.
Nonlinear Models of Cable-Stayed Bridges
Authors: Massow C. , Vidal Veronica , Champneys Alan R. , Macdonald John H.G.
Published: March 2009

Cable-stayed bridges frequently experience vibrations due to a variety of mechanisms,
exacerbated by their very low inherent damping. A research group of the University
of Bristol has focused lately on the study of cable-stayed bridges, some advances have led to
the identification of vortex-induced deck vibrations occurring at the Second Severn Crossing
(SSC) and improved methods of analysis of field vibration data. Based on such experience,
it aims to study the autoparametric excitation which, due to very great amplitudes, can seriously
damage the structure. It has been suggested that this may have been the mechanism
of excitation of some large amplitude cable vibrations on real bridges, but the details of the
behaviour are not very well understood and several cases of large cable vibrations on full
scale bridges have not been fully explained. In this paper we examine a previously established
cable-deck model and compare it to a new, more exact model in a different coordinate
basis.
A Nonlinear and Non-Ideal Wind Generator Supporting Structure
Authors: Brasil Reyolando Manoel Lopes Rabelo da Fonseca , Feitosa L.C.S. , Balthazar José Manoel
Published: March 2009

We present a simple mathematical model of a wind turbine supporting tower. Here, the
wind excitation is considered to be a non-ideal power source. In such a consideration, there is
interaction between the energy supply and the motion of the supporting structure. If power is not
enough, the rotation of the generator may get stuck at a resonance frequency of the structure. This
is a manifestation of the so-called Sommerfeld Effect. In this model, at first, only two degrees of
freedom are considered, the horizontal motion of the upper tip of the tower, in the transverse
direction to the wind, and the generator rotation. Next, we add another degree of freedom, the
motion of a free rolling mass inside a chamber. Its impact with the walls of the chamber provides
control of both the amplitude of the tower vibration and the width of the band of frequencies in
which the Sommerfeld effect occur. Some numerical simulations are performed using the equations
of motion of the models obtained via a Lagrangian approach.
Studies of the Sensitivity of Brake Squeal
Authors: Butlin T. , Woodhouse J.
Published: March 2009

The problem of ‘brake squeal’ in the automotive industry remains despite over 70 years of research:
the phenomenon is still surprisingly unpredictable and poorly understood. The literature has moved from
very simple lumped parameter models to ever more sophisticated finite element models, but testing theory
against measurements has been hindered by the difficulty in obtaining repeatable results. It would seem the
phenomenon is extremely sensitive to changes in parameters beyond an experimenter’s control.
This paper describes recent results from a project to identify and quantify the sources of uncertainty within
sliding contact systems and to determine the sensitivity of the friction-coupled system to uncertain parameters.
The theoretical approach taken is to use a linear analysis based on the uncoupled transfer functions of two
general subsystems to predict stability when they are coupled by a sliding point contact. The model is tested
using a pin-on-disc rig whose uncoupled transfer functions can be measured.
Using a stability criterion based on the roots of the characteristic equation of the system, the sensitivity
of model predictions to parameter variations is investigated numerically. It is shown that using a realistic
range of parameters the root locations change considerably and enough to change stability predictions. As the
complexity of the model is increased reliable results become harder to achieve as the characteristic equation
becomes more ill-conditioned. This is not simply a result of the high order of the system, but is thought to
be a result of particular mode combinations. Experimental work shows uncoupled transfer functions vary over
time and by enough to significantly affect squeal predictions. These results suggest reasons for the difficulty in
obtaining repeatable measurements and for the unreliability of squeal prediction theories developed so far. If
the reasons for the sensitivity of squeal can be understood it may be possible to design sliding contact systems
that are more robust.
An Investigation of Residual Stress Effects due to the Anodic Bonding of Glass and Silicon in MEMS Fabrication
Authors: Sadaba I. , Fox Colin H.J. , McWilliam Stewart
Published: March 2009

Anodic bonding is widely-used in the fabrication of Micro-Electro-Mechanical Systems
(MEMS) devices to join silicon and glass components. The process involves the application of
temperature, moderate pressure and an electric field. This paper investigates residual stresses arising
during anodic bonding, focusing on the resulting induced distortions. Components of a MEMS
silicon rate sensor, in which a silicon wafer is anodically bonded to Pyrex™ glass, were used as the
vehicle for the investigation. Distortions generated by the anodic bonding process when using two
different electrode configurations (point and planar) were measured using a surface optical profiler.
These showed a particular pattern across the wafers for both configurations.
An efficient FEM study was carried out to model the qualitative effect of the following residual
stress sources; thermal stress, glass shrinkage due to structural relaxation and compositional
gradients due to ion migration. Importantly, the FE model takes account the actual multi-device
wafer-level configuration, as opposed to a single device. The results demonstrate that compositional
gradients can make a significant contribution to the observed pattern of distortions.
Development of the Humanoid Robot LOLA
Authors: Ulbrich Heinz , Buschmann T. , Lohmeier S.
Published: March 2009

This paper presents the performance enhanced humanoid robot LOLA which is currently being manufactured. Hardware design, controllers and simulation are based on ex- perience gained during the development of the robot JOHNNIE. The objective of the current research project is to realize a fast, human-like and autonomous walking motion. To enable an optimal design of the robot with respect to lightweight construction, motor and drive sizing, an appropriate simulation model is required. Dynamics simulation is a key tool to develop the hardware and control design properly. For hardware design and detailed dynamic analysis a comprehensive model including motor and gear dynamics is required, while for controller de- sign and stability analysis a simplified model for global system dynamics is sufficient. Both robots are characterized by a lightweight construction. In comparison to JOHNNIE, the new robot LOLA has a modular, multi-sensory joint design with brushless motors. Moreover, the previously purely central electronics architecture is replaced by a network of decentral joint controllers, sensor data acquisition and filtering units and a central PC. The fusion of motor, gear and sensors into a highly integrated mechatronic joint module has several advantages for the whole system, including high power density, good dynamic performance and reliability. Ad- ditional degrees of freedom are introduced in elbow, waist and toes. Linear actuators are used for the knee joints to achieve a better mass distribution in the legs.
Structural Optimisation using a Hybrid Cellular Automata (HCA) Algorithm
Authors: Chia C.M. , Rongong Jem A. , Worden Keith
Published: March 2009

The Hybrid Cellular Automata (HCA) algorithm has been used by several researchers to optimise structures during the last decade. Close observation of their work shows that the proposed optimisation algorithms are sensitive to the controller (local rule), the design variable and the field variable used. The aim of this work is to identify and understand the important parameters when using the HCA algorithm to optimise structures. For static loading, it is shown that the most important parameters are the design variable, the constraints on the design variable, the local rule, and the mesh density of the structure. The choice of the design variable affects the selection of the target value and the homogeneity of the resulting optimum structure. With constraints on the design variable, it is shown that the algorithm cannot always drive the structure to an optimum solution, as stresses in the resulting structure can be significantly higher than expected. Besides, the choice of the local rule and the mesh density of the structure can affect the convergence rate and may cause the algorithm to arrive at a local optimum rather than the global optimum solution.
The Application of the Hole Drilling Method to Define the Residual Stress of Dissimilar Laser Welded Components
Authors: Anawa E.M. , Olabi Abdul Ghani
Published: March 2009

Dissimilar metal welds between Ferritic steel and Austenitic steel (F/A)are commonly used
in power plants, food industry, pharmaceutical industry and many other applications. There are
many issues/problems associated with the joining of dissimilar materials, depending on the
materials being joined and the process selected. During the laser welding process, residual stresses
are introduced by a rise in temperature during the melting or heating process followed by a very
quick cooling of the weld and the surrounding material.
In this study, CO2 continuous laser welding has been successfully applied for joining 316
stainless steel with AISI 1009 low carbon steel F/A. Design of Experiment techniques (DOE) has
been used for some of the selected welding parameters (laser power, welding speed, and focus
position) to model the dissimilar F/A joints in terms of its residual stresses. The Hole-Drilling
Method technique was use for measuring the residual stress of dissimilar welded components.
Taguchi approach for selected welding parameters was applied and the output response was
the residual stresses. The results were analysed using analysis of variance (ANOVA) and signal-tonoise
(S/N) ratios for the effective parameters combination.
Evaluation of Sub-Surface Stresses Using Thermoelastic Stress Analysis
Authors: Sathon Nuttaphon , Dulieu-Barton Janice M.
Published: March 2009

Thermoelastic stress analysis (TSA) is a well established technique for stress analysis.
Recent studies have revealed that the technique can be used to detect sub-surface defect effectively.
In this study, the technique has been used to examine the thermoelastic response to sub-surface
damage in simple bar specimens. The non-adiabatic thermoelastic response from areas close to the
damage has been studied. The study shows that the phase of the response along with the thermal
diffusion can provide a parameter that will help reveal subsurface stresses.
Reconstruction of Impact Loads within Fibre Reinforced Polymers
Authors: Koenig Ch.R. , Mueller D.H. , Focke O. , Calomfirescu Mircea
Published: March 2009

Fibre reinforced polymers (FRP) offer a high potential to reduce kinetic energy. As a consequence
of this, fibre reinforced polymers often have a higher risk of being exposed to impact loads. The
knowledge of the mechanisms and of the material loading during and shortly after an impact load is
essential for an ‘impact-load-monitoring-system’ to predict possible structural failures. Especially a
prognosis of structural failures caused by – often unrecognized - barely visible impacts is an
important factor. Primary impact damages often leads to a sudden structural failure. These
unheralded failures seems to be one of the most important problems in product development for the
aircraft industry. By measuring the structural response at several discrete measurement points an
impact can be detected, reconstructed and also rated.
Strain Rate Effects in Crushable Structural Foams
Authors: Mines Robert A.W.
Published: March 2009

Structural foams are used as cores in sandwich construction. In the application of foreign object impact loading of sandwich structures, the core will suffer dynamic multi axial deformation and crush. This means that experimental study is required for the crush behaviour of structural foams at various strain rates, and numerical simulation foam models need to be calibrated with dynamic data. A number of foams are considered, namely Divinycell PVC foam, Rohacell PMI foam and Alporas aluminium foam. Also, new generation metallic micro lattice structures are discussed
Modelling the Uniaxial Impact Response of a Nonlinear Sandwich Structure with Interlaminar Buckling
Authors: Sek Michael A.
Published: March 2009

This paper describes the development of a software simulation tool of discrete elements
which has been developed for the purpose of investigating the dynamic response of multilayer
sandwich structures that incorporate highly nonlinear crumple (buckling) elements. These structures
are to be optimised as cushions in order to minimise the transmission of shocks when exposed to
transient excitation, such as in a free fall. Presented results are for multilayer corrugated
paperboard.
A single layer was modelled as a nonlinear 2-DOF system with an additional elastoplastic
element to reflect contact conditions. Numerical models of the platen and the exciter with either
acceleration or displacement control were developed and applied to perform numerical compression
tests of the sandwich layer at various strain rates to validate the model of a single layer. Sandwich
structures were then numerically assembled and subjected to simulated impacts. The model
predicted inter- and intralaminar forces, displacements, velocities and accelerations. The shock
attenuation characteristics were obtained and presented as the time-acceleration-static stress maps.
A postprocessor was developed to produce animations to reveal complex dynamic interactions
within modelled sandwich structures.
Experimental Study on the Material Response of Laser Weldment under Dynamic Loading
Authors: Fang Jian
Published: March 2009

The materials response of a laser beam welded joint from hot rolled DP600 steel plate to the dynamic loading has been experimentally studied by instrumented Charpy impact testing. Based on the impact force-displacement curve, Critical Crack Length, i.e. CCL and dynamic crack extension resistance curve, i.e. J-a were determined, describing the welding joint’s crack formation toughness and the dynamic crack behavior. It is shown that the difference of crack initiation and propagation between the HAZ and BM is not significant. In addition, the CCL of Welding Area, i.e. WA is multiple higher than that of HAZ and BM, which is also less dependent of low temperature. Moreover, the J-a curve of WA consists of two segments, the initial sudden ascending with linear feature and the subsequent slow rising. Furthermore, tearing module derived from the slope of J-a curve was discussed, indicating the material microstructure mechanism affected by the thermodynamic process of laser beam welding.
Theoretical and Experimental Working Life Comparison for a Helical Gear under Linear Pitting Failure
Authors: Khan Muhammed Ali , Starr Andrew G.
Published: March 2009

For machine components like gears and bearings, working life calculation is one of the complex issues to deal with. This is because the mechanics of their operation is dependent on many parameters, like loading, friction and lubrication etc. Also the influence of these parameters on the component failure modes cannot be perfectly idealized. But in this regard, standards like AGMA (American Gear Manufacturers Association); ISO (International Standard Organization) and BS (British Standards) are quite useful on the basis of which theoretical working life for machine components under a specific failure mode can be predicted. In this paper with linear pitting failure mode assumptions, theoretical working life calculation has been made for a helical gear. BS-ISO 6336-2 standard is used for the gear theoretical life calculations. Furthermore, a wear debris analysis based experiment has been performed for the validation of theoretical calculation. A back to back gear testing rig has been used for the experimental validation. The experimental results show that the theoretical life calculation made on the basis of BS-ISO 6336-2 standards is fairly accurate.
Simulation of Guided Waves Propagation in Axial Transmission Measurements in Human Radius
Authors: Pieczonka Łukasz , Uhl Tadeusz , Martowicz Adam
Published: March 2009

This paper is a brief review of the axial transmission measurements methodology. Theoretical background and description of the methodology is presented. Simulations made to verify some of the statements found in the scientific literature about the subject matter are described. Simulation performed were meant to be a basis for specifying parameters of the experimental set up to be used in the future. Three dimensional finite difference code was used to simulate wave propagation in human radius. Two models have been prepared to compare the results. One was an idealized geometry of the diaphysis of human radius and second was a reconstructed anatomical geometry from scans acquired with Computed Tomography (CT). Conclusions about the wave propagation character and feasibility of low frequency measurements in medical diagnostics are discussed.
In-Process Simulation of Multi-Axis Milling in the Production of Lightweight Structures
Authors: Ungemach Eduard , Odendahl Sven , Stautner Marc , Mehnen Jörn
Published: March 2009

Lightweight structures are an important element in today’s production industry. For the multi-axis milling of these structures some aspects have to be considered to achieve a good surface quality and to prevent damaging the milling machine during the machining process. In this article methods to determine suitable feed rates for the milling process, to identify parts of the workpiece with too much heat build-up, and to avoid collisions between workpiece and machine parts are presented. For this purpose a milling simulation based on a multi-dexel field workpiece model has been developed, in which two types of feed rate adaptation have been integrated. Work on a built-in temperature development simulation and collision control is in progress.