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M2D'2015 P. Delgada/Portugal 2015
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6th International Conference on MECHANICS AND MATERIALS IN DESIGN (Ponta Delgada/Azores, 26-30 July 2015) |
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Keynote Speakers The M2D'2015 program will include a number of Keynote Plenary Lectures by distinguished scientists in the different areas covered by the Main Topics and Symposia of the conference, to provide thematic presentations of their most recent findings. The names of the following Keynote Speakers and the titles of their presentations have already been confirmed (ordered by date of confirmation): Prof. Shaker A. Meguid (Canada) Prof. Noritsugu Umehara (Japan) Prof. José Reis Campos (Portugal)
Director, Mechanics and Aerospace Design Laboratory University of Toronto, CANADA Email: [email protected]
Title of Presentation:
ENERGY ABSORPTION IN AXIAL CRUSHING OF ULTRALIGHT STRUCTURES
ABSTRACT
The US National Highway Traffic Safety Administration reported 30,000 fatalities and over 1.5 million injuries resulting from motor vehicle crashes in 2010. Recent legislative pressure led automobile manufacturers to design lightweight vehicles to reduce cost, fuel consumption and gas emissions. There exist various energy absorbers that can be used to improve the crashworthiness of these vehicles, without drastically increasing their weight and cost. In particular, thin walled structures that experience progressive folding, as opposed to global buckling, are ideal shock absorbers, because they can undergo large displacements at near constant load. Furthermore, they are highly economical and easy to manufacture. It has also been proven that by filling thin-walled sections with foam, the energy absorption capacity can be improved significantly. The improvement is attributed to interaction effects between the foam and the tube walls. Comprehensive analytical, numerical (FEM) and experimental investigations are conducted to study the crush behaviour of foam-filled thin-walled circular tubes and frusta. Accordingly, three aspects of the work are considered. The first is concerned with the analytical modelling of the quasistatic crush behaviour of empty and foam-filled frusta. The analytical crush model is idealised into an axisymmetric multiple-fold mechanisms with the energy being dissipated in the formation of plastic hinges, the circumferential deformation of frusta walls and the interaction effects between the inside wall and the filler. The second deals with the nonlinear finite element modelling of the crush behaviour of foam-filled frusta accounting for the different contact surfaces and the nonlinear constitutive behaviour of the considered materials. The third deals with the experimental validation of the developed models via quasistatic crush tests of foam-filled and unfilled frusta. The analytical and numerical predictions are compared with the findings of the crush test results with a specific interest in the normalised load-deformation behaviour, the specific energy absorption and the mode of collapse. The influence of the wall thickness, the semi-apical angle and the density of foam filler are also investigated and the results highlight the advantages of using foam-filled frusta as energy absorbers. Overall, this research shows clearly that foam-filled frusta are superior to empty ones because of the greater specific energy absorption, the improved load ratio, the interaction effects, and the stability of the crush response. To take advantage of the interaction effects and the stability of the crush response, multi-frusta configurations are further developed and examined in this presentation.
Advanced Materials and Manufacturing Laboratory, Mechanical Science and Engineering Department, Graduate School of Engineering, Nagoya University, JAPAN Email: [email protected]
He began his carrier at the Tohoku University in 1988 as a research associate in the Department of Mechanical Engineering before coming assistant professor in 1993, associate professor in 1995 and move to Nagoya University as Professor in 2003. He received a Bachelor, a Master and a Doctor of Engineering from Tohoku University, Sendai, Miyagi in 1983, 1985 and 1988, respectively. He published more than 120 research papers in various journals, and holds 6 Patents on Magnetic Fluid Grinding. Professor. Umehara received the JSME Young Engineer Award in 1991, 1995 LaRoux K. Gillespie Outstanding Young Manufacturing Engineer Award from the Society of Manufacturing Engineers in 1995, F.W. Tayler Medal from the CIRP in 1995 and JSME paper award in 2010. He is member of the Japan Society of Mechanical Engineers (JSME), the Japan Society for Precision Engineering (JSPE), the Japan Society of Tribologist (JAST) and the Japan Society for Grinding Engineering. In view of his outstanding contribution to the fields of advanced materials, manufacturing and tribology for sustainable society, he has been invited to the Associate Editorship of the International Journal of Mechanics and Materials in Design, published by Springer. Professor Umehara is often invited to give keynote lectures in major meetings and is acknowledged as being highly innovative researcher, as evidenced by the large number of his patents.
Title of Presentation:
RECENT DEVELOPMENTS IN TRIBOLOGY FOR ENERGY SAVINGIN SUSTAINABLE SOCIETY
ABSTRACT The design requirement of ultra-energy saving of advanced internal combustion engines for automobiles for the next century will be dictated by the need for energy saving for sustainable society. For this purpose, the development of light-weight, compact, loss-reduction, for improving fuel economy and the protection of the environment against CO2 and NOx. Lubricant and surface treatment technologies will play major roles, in term of their direct and immediate effects for improving performance. Specifically, new technologies concerned with development of hard and lubricious coatings are of current interest to the automobiles companies and will be discussed in this presentation. The carbonaceous coatings, such as Diamond-Like Carbon (DLC) coating and amorphous Carbon Nitride (CNx) coatings, are promising coatings for high hardness, low friction losses and are highly cost effective. Though it is reported that the transformed layer is important in ensuring low friction, it is still unclear if that transformed layer produces ultra-low friction - less than 0.01 under dry contact conditions. To clarify the ultra-low friction mechanism of CNx, we proposed a technique to measure the thickness, sp2/sp3 ratio and density of free bonds of the transformed layer in-situ during of pin-disk relative sliding using reflectance spectrometer. The in-situ measuring system used to identify the friction area is composed of pin-on-disk friction tester and a reflectance spectrometer that can measure the optical properties of surface coatings as reflectance index and extinction coefficient through sapphire hemisphere. We used the system to estimate the thickness, sp2/sp3 ratio and density of free bonds of the coating in-situ. From the in-situ observation results, we obtained an accurate relationship between the thickness and the properties of the transformed layer and friction as well as developed an ultra-low friction model. Furthermore, we demonstrate that the ultra-low friction model can be applied to traditional oil lubrication for DLC. On the basis of these research achievements, carbonaceous hard coatings can be used as smart materials to reduce friction a leading to reduced energy loss for sustainable society.
Aerospace Engineering Division School of Mechanical and Aerospace Engineering Nanyang Technological University 50 Nanyang Avenue, Singapore 639798, Singapore Email: [email protected]
Title of Presentation:
EXTREME INSULATORS FOR EXTREME ENVIRONMENTS: UNDERSTANDING THE PROPERTIES OFULTRALIGHT AEROGELS AND 2D MATERIALS
ABSTRACT Aerogels are amazing materials, besides being the lightest solids on the planet; they also exhibit the lowest thermal conductivity of any known solid, making then one of the best thermal insulators available. On the other hand, novel 2D materials such as silicene and graphene possess very high thermal conductivities. These 2D materials are currently touted to revolutionize the electronics industry, and if they live up to their current hype, associated thermal management issues become most pertinent. In this presentation, we examine the thermal properties of these ultralight materials, namely silica aerogels and 2D graphene and silicene, which are investigated and established through classical molecular dynamics (MD) simulation. In addition, the construct and evolution of the atomic/molecular structures of these ultralight aerogels and 2D materials are explored and realized through various MD simulation schemes. The aerogel study involves two simulation steps, where the percolated structures of silica aerogel at various densities are first acquired using negative pressure rupturing, while reverse non-equilibrium molecular dynamics (RNEMD) is performed to determine the thermal conductivities of these aerogel samples. Two potential functions were employed in this study, namely the widely used Beest-Kramer-Santen (BKS), and the re-parameterized Tersoff. Results obtained based on the BKS potential followed the power-law variation reminiscent of sintered aerogel characteristics. To achieve a higher accuracy for bulk amorphous silica, the re-parameterized Tersoff potential was found to be superior to the BKS potential, when comparing the vibrational density of states with previous experimental studies. By fitting the results using a power-law variation, the trend of the thermal conductivities successfully mirrored power-law trends of experimental bulk aerogel. Due to finite sizes of pores that can be represented, where increasing simulation length scales leads to an increase in the largest pore size that can be modeled, current quantitative results are consistently higher but within the same order of magnitude as experimental bulk aerogel. For the analysis of 2D materials, graphene and silicene are considered. There are two major components in this 2D materials simulation study. Firstly, the exfoliation phenomenon of graphite is investigated. This is modeled through MD simulations, where the compression of AB-stacked graphite flakes between hydrogen-terminated silicon substrates leads to the exfoliation of graphene layers. It is shown that this phenomenon occurs through the activation of an inter-layer superlubricity regime, caused by torque-induced spontaneous rotations of the layers due to in-plane shear of graphite during compression. Secondly, the thermal properties of graphene and silicene are established through RNEMD simulations using the adaptive intermolecular reactive empirical bond order (AIREBO) potential. Of special interest in this study are the effects of defects, such as double vacancies and Stone-Thrower-Wales (STW) defects, on the thermal conductivities of graphene nanoribbons when compared with their pristine structures. It was found that thermal conductivities can fall by more than 80% with just 10% coverage of defect density, and these reductions occur over a wide temperature range of 100K to 600K. Finally, the thermal conductivity of nano- to micron-sized silicene and graphene monolayers are analyzed and compared. Across all length scales, silicene has significantly lower thermal conductivity than graphene, and this was found to be attributed to the lower phonon group velocities of the dominant acoustic modes in silicene.
Institute of Physical Chemistry University of Heidelberg, Im Neuenheimer Feld 253 D-69120 Heidelberg, Germany Email; [email protected]
Professor Peter Hess is Professor (Emeritus)of Physical Chemistry at University of Heidelberg since 1980. Previously, he studied for a diploma in chemistry at the Karlsruhe Institute of Technology (KIT) and for a PhD thesis (1968) and then for the habilitation thesis (1972) at Ruprecht-Karls-University in Heidelberg. He was research fellow at the Department of Chemistry, University of California, Berkely, USA (1974,1979) and after 1980 he was regularly visiting scientist at Almaden Research Laboratories, IBM, San Jose, California, USA for short time periods. Since 1995 he is head of the Steinbeis Technology-Transfer Center (STC) Heidelberg. He has been active in several research field. (1) Laser-based photoacoustics in gases: chemical relaxation and trace gas analysis. (2) Laser-based surface acoustic waves (SAWs) and wedge waves (WWs): all-optical nondestructive evaluation (NDE), linear and nonlinear elastic constants and mechanical properties of superhard materials, nonlinear behavior and fracture strength of solids and solitary surface waves. (3) Laser-induced desorption, ablation, and surface processing: laser-based time-of-flight mass spectrometry of specific surface reactions induced by pulsed laser irradiation and measurement of the thermal stability of surface end groups and functionalizations. (4) Silicon surface spectroscopy and chemistry: in situ and real-time diagnostics of surface reactions (e.g. functionalization, oxidation) on silicon with monolayer resolution (FTIR spectroscopy, IR-UV spectroscopic ellipsometry), and atomic force microscopy (AFM). He published some 290 papers in scientific journals, one worldwide and one European patent on functionalization and processing of silicon surfaces. He was editor or co-editor of 6 books (Springer 1987, 1989; Elsevier 1995, 1999; SPIE 1997, 2000), chairman or co-chairman of ten international conferences. He delivered many plenary and invited talks at international conferences and received the James Smith prize of the International Photoacoustic and Photothermal Association (IPPA) for the application of linear and nonlinear elastic waves in materials science.
Title of Presentation:
ON THE USE OF GUIDED WAVES IN NONDESTRUCTIVE DIAGNOSTICS AND FAILURE ANALYSIS
ABSTRACT
Nondestructive evaluation (NDE) and structural health monitoring (SHM) to evaluate materials properties without causing damage and the determination of critical fracture stresses or strengths of materials to avoid catastrophic structural failure play an ever increasing role in materials science and technology. One of the important experimental tools is laser ultrasonics, suitable for pulsed excitation and continuous detection of guided one-, two, and three-dimensional (1-3D) elastic waves. While for nondestructive evaluation the easy scanning of excitation and probe laser beams and the high spatial resolution obtainable by focusing are the most important features, destructive testing is based on the high laser power, allowing the generation of nonlinear elastic pulses with shock fronts leading to fracture. Even in well-established conventional applications of conventional ultrasonics with 3D waves to macroscopic objects such as rails or tubes, there is a tendency to use guided waves for industrial inspection, which is connected with reduced cost, less inspection time, and greater coverage. These guided ultrasonic waves are constrained by the boundaries of the particular geometric structure and include, for example, torsional waves in a tube or Lamb waves in a plate but also longitudinal or shear modes. Permanent sensor installation for long distance diagnostics by conventional transducers, e.g. in rails, is a new approach in SHM. A serious challenge of guided modes in complex geometries is their dispersive and multimode nature. In NDE applications, substantial computational effort is needed for data analysis under these conditions. For 3D applications laser ultrasonics is under development. Surface acoustic waves (SAWs), first discovered by Lord Rayleigh in 1885, can be characterized by a two-dimensional (2D) wave vector. The planar surface of an elastic half space is a 2D waveguide for these particular waves. Their displacement field decays to zero in the direction normal to the surface, e.g. exponentially within about one wavelength depth. SAWs or Rayleigh waves are non-dispersive in homogeneous media. In recent years laser photoacoustics opened the door to many new applications of linear SAWs, such as the determination of elastic coefficients of advances materials (e.g. nanodiamond), or in nondestructive evaluation (NDE) of surface-breaking cracks. Real partially closed surface cracks of micrometer size have been analyzed with this method. More recently also pulsed laser excitation of nonlinear solitary elastic surface pulses and their detection with a probe laser has been achieved, by generating dispersion with a thin film coating that introduces a length scale. In addition, such laser pump-probe experiments allow the excitation of short nonlinear SAW pulses with steep shock fronts that fracture brittle materials such as silica or silicon. With such a laser-based method it is possible to measure the fracture strength of materials and compare the critical failure stress with ab initio calculations of the theoretical strength of the corresponding single crystal, giving an upper limit of the mechanical strength. The acoustic edge or “wedge waves” were discovered in 1972 by numerical calculations. Theoretical approaches prove the existence of these 1D acoustic waves with 1D wave vector also in anisotropic crystals. The displacement field decays exponentially away from the tip in the plane normal to the edge. The selective excitation of these guided waves was performed with an optically-pumped angle-tunable transducer. The characteristic features of the non-dispersive linear wedge waves in ideal systems such as their small phase velocity below the Rayleigh velocity and the very high degree of localization of the displacement field at the wedge tip could be clearly verified. A number of possible applications have been discussed and feasibility studies have been carried out already but no commercial devices are on the market yet. Future applications of dispersive wedge waves in real systems include monitoring of defects of cutting tools or turbine blades, sensor applications measuring the velocity change upon tip and surface modifications. Owing to the large displacements involved, ultrasonic motors, stirring and acoustic streaming in fluidics, and aquatic propulsion can be realized.
College of Mechanical and Vehicle Engineering, Hunan University Changsha City, PR China 410082 Email: [email protected]
His research focuses on simulation-based design, inverse problems, and uncertainty optimization. He has authored over 150 papers in leading academic journals, and one research monograph on computational inverse techniques in non-destructive testing published by CRC Press. These works have been very well cited. His recent honors and awards include: the Second Prize of National Science and Technology Progress Award (2013), the First Prize of Hunan Science and Technology Progress Award (2010), the First Prize of China Machinery Industry Science and Technology Award (2012), the GM Automobile Industry Innovation Talent Award in Chinese Universities (2007), and the Instructor of National Excellent Doctoral Dissertation (2011), etc. His professional service includes: the general council member of International Society of Computational Mechanics, the general council member of the tenth Council of Chinese Society of Mechanics, the vice president of the Computational Mechanics Committee of Chinese Society of Mechanics, the executive director of Mechanical Design Branch of Chinese Mechanical Engineering Society. He is the Associate Editor of International Journal of Computational Methods and Inverse Problems in Science & Engineering.
Title of Presentation:
Convex-model-based non-probabilistic uncertainty analysis and reliability design for complex structures
ABSTRACT
Uncertainties associated with manufacturing imperfection, usage variation and imprecise knowledge widely exist in practical engineering problems, and quantifying and controlling their effects on the structural performance is of great importance for current product design. Since 1990, the non-probabilistic convex model has been developed for uncertainty analysis and reliability design, in which the variation bounds of the uncertain parameters are only required rather than their precise probability distributions. Thus, it provides a potential and promising way to conduct the reliability analysis and design for many complex problems with limited samples. In the past decade, we conducted a systematic study for the convex–model-based uncertainty analysis and reliability design, through which we expect to improve the engineering practicability of the convex model theory in complex structures: (1) An uncertainty modeling approach was proposed for ellipsoidal convex model based on a correlation analysis technique, through which the uncertainty domain of the multi-dimensional correlated parameters can be conveniently constructed based on the samples; (2) A non-probabilistic reliability model was developed based on the volume ratio, through which the safety degree of a structure with convex model uncertainty can be well described; (3) A new kind of convex model, namely the multidimensional parallelepiped model, was proposed for multi-source uncertainty quantification in which the independent and dependent uncertain parameters coexist, and a corresponding structural reliability model was also suggested; (4) A non-probabilistic convex model process was proposed for time-variant uncertainty analysis, which provides an effective mathematic tool for structural dynamic uncertainty modeling and reliability analysis for structures lacking experimental samples; (5) The above developed methods were also applied to the uncertainty analysis and design of many practical products or structures, such as vehicle body, engineering machinery, etc. Keywords: uncertainty analysis, reliability design, non-probabilistic convex model
Faculty of Dental Medicine, University of Porto Porto, Portugal Email: [email protected]
His research activities include mainly Biomechanics applied to Prosthodontics. This focus on Biomechanics was initiated with the research that conducted his PhD Thesis. He was pioneer in developing these interdisciplinary research activities between the Faculty of Dental Medicine and the Faculty of Engineering of the University of Porto. Presently he is the coordinator of several projects and the supervisor of a number of MSc. and PhD. students in the area of mechanics and materials applications to Prosthodontics and Dental Medicine. He is also a founder and member of the Executive Board of the Laboratory of Biomechanics of the University of Porto (LABIOMEP), which is a multidisciplinary laboratory involving different schools and research institutes within the University of Porto. Prof. Reis Campos is author/co-author of many papers published in national and international journals/proceedings, editor of a number of Proceedings of Bioengineering conferences and congresses, invited Speaker in national and international scientific events, member of the Editorial Committee of the Revista Portuguesa de Estomatologia, Medicina Dentária e Cirurgia Maxilofacial and Revista de Mecânica Experimental (Revista da Associação Portuguesa de Análise Experimental de Tensões - APAET) and member of different Organizing and Scientific Committees of numerous scientific conferences and congresses.
Title of Presentation:
Mechanics and Materials applications in Prosthodontics and Dental Medicine: Challenges and Opportunities
ABSTRACT
Nowadays, Dental Medicine is seen as a health science with a multidisciplinary scope. It is not only related to its medical field, but also to biomaterials, biomechanics and mechanical engineering, among different other subjects. Evolution in this health science is directly related to the application of mechanics and materials research. In the last two decades, intensive research and important developments have been achieved worldwide on biomechanics applications in the oral cavity, mostly related to the prosthodontics field and materials that are used in this area, like acrylic resins, metal alloys, titanium and the currently used dental ceramics, such as zirconia. By using the new technologies of CAD-CAM systems applied to Dentistry, together with experimental and numerical techniques, many studies have been reported on the stresses and strains of prosthodontic rehabilitations (fixed or removable), on teeth or dental implants, and on the supporting bones. In this keynote, we present a synopsis of the current research in this area and the new challenges ahead (eg. zirconia dental implants), highlighting the contribution of mechanics and materials sciences to obtain results that can improve the quality of the Dentist work and, most importantly, the oral health related quality of life of human beings.
Page created on 12 July 2013 / Last update on 19 December 2014 |
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