Art of Modeling in Contact Mechanics

International audienceIn this chapter, we will first address general issues of the art and craft of modeling-contents, concepts, methodology. Then, we will focus on modeling in contact mechanics, which will give the opportunity to discuss these issues in connection with non-smooth problems. It will be shown that the non-smooth character of the contact laws raises difficulties and specificities at every step of the modeling process. A wide overview will be given on the art of mod-eling in contact mechanics under its various aspects: contact laws, their mechanical basics, various scales, underlying concepts, mathematical analysis, solvers, identification of the constitutive parameters and validation of the models. Every point will be illustrated by one or several examples. 1 Modeling: the bases It would be ambitious to try to give a general definition of the concept either of a model itself or of model processing. Modeling relates to the general process of production of scientific knowledge and also to the scientific method itself. It could be deductive (from the general to the particular, as privileged by Aristotle) or inductive (making sense of a corpus of raw data). Descartes (38) saw in the scientific method an approach to be followed step by step to get to a truth. Modeling can be effectively regarded as a scientific method that proceeds step by step, but its objective is more modest: to give sense of an observation or an experiment, and above all to predict behaviors within the context of specific assumptions. This concept of " proceeding step by step " is fundamental in modeling. In this first section, we will examine the notion of model in the general context of mechanical systems

New innovations in pavement materials and engineering: A review on pavement engineering research 2021

Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges. In the past 10 years, the pavement infrastructure strongly supports the rapid development of the global social economy. New theories, new methods, new technologies and new materials related to pavement engineering are emerging. Deterioration of pavement infrastructure is a typical multi-physics problem. Because of actual coupled behaviors of traffic and environmental conditions, predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis. In order to summarize the current and determine the future research of pavement engineering, Journal of Traffic and Transportation Engineering (English Edition) has launched a review paper on the topic of “New innovations in pavement materials and engineering: A review on pavement engineering research 2021”. Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering, this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world. The content includes asphalt binder performance and modeling, mixture performance and modeling of pavement materials, multi-scale mechanics, green and sustainable pavement, and intelligent pavement. Overall, this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering

Third International Symposium on Space Mission Operations and Ground Data Systems, part 2

Under the theme of 'Opportunities in Ground Data Systems for High Efficiency Operations of Space Missions,' the SpaceOps '94 symposium included presentations of more than 150 technical papers spanning five topic areas: Mission Management, Operations, Data Management, System Development, and Systems Engineering. The symposium papers focus on improvements in the efficiency, effectiveness, and quality of data acquisition, ground systems, and mission operations. New technology, methods, and human systems are discussed. Accomplishments are also reported in the application of information systems to improve data retrieval, reporting, and archiving; the management of human factors; the use of telescience and teleoperations; and the design and implementation of logistics support for mission operations. This volume covers expert systems, systems development tools and approaches, and systems engineering issues

Parametric modelling of integral bridge soil spring reactions

Thesis (MEng)--Stellenbosch University, 2022.ENGLISH ABSTRACT: The integral bridge is a bridge structure in which the deck, piers and abutments are all made integral without the use of expansion joints. The joints would normally allow the expansion and contraction of the bridge deck, however now the flexibility inherent in the piers and abutments is utilized. The main design issue in an integral bridge is the effect of the temperature fluctuations and the corresponding movements in the bridge deck. By its nature, the integral bridge has ends that interact with the embankment soil, as the bridge is subjected to cycles of movement that result in changes in soil pressure from the active to the passive pressure state. Forces inherent in conventional bridge systems also act longitudinally against the backfill soil, however the magnitude of the soil-structure interaction is negligible since the cyclic forces that are created are minor in comparison with those acting on integral bridges. This makes the integral bridge design both a structural and a geotechnical problem of interest. The interaction between the bridge structure and the surrounding soil is a relatively intricate, three dimensional scenario that is simplified in analysis modelling. Engineers are interested in two different (but related) issues. The first is the deformation of the soil as load is applied to it by the structural system, the second is the load carrying capacity of the soil. These two phenomena can be described as soil stiffness and soil strength. Clearly, a greater soil stiffness should lead to larger axial forces and bending moments in the deck due to the longitudinal expansion or contraction of the bridge. Finite Element (FE) approaches to Soil-structure interaction (SSI) usually fall into approaches that characterize the soil using continuum elements and those that represent the soil through springs. In the spring method of analysis, the resistance of the soil lying adjacent to the piles and to the abutment is represented by springs which can be linear, compression only or non-linear in character. The theories used for the calculation of the spring stiffnesses are quite different between the abutments and the piles. In this thesis, the influence on SSI reactions of pertinent bridge geometry and load parameters was investigated. To this end, a series of parametrically varied 2D and 3D bridge models with soil springs were created and subsequently analysed. The parameters of span length, abutment height and soil condition for different percentages of live load and thermal expansion/contraction/gradient were investigated and their influence on SSI reactions were revealed through the series of parametric model testing. Pile lateral loading vs deflection relationships tend to be non-linear, however the spring reaction relationship for increasing span and load (once a pile is incorporated into an integral bridge system) was unknown prior to the analysis work captured in this thesis. The basic hypothesis for the thesis is that 3D models with realistic properties assigned to the springs will be required to capture the true behaviour of the integral bridge springs (which are suspected to be non-linear in nature), and that simplified 2D models can nonetheless provide some basic understanding of their behaviour and characteristics, but will not be able to completely model the bridge spring reaction behaviour. The model test results showed that the maximum spring reactions (for abutments, piles and footings) followed either a linear relationship with increasing span or tended towards more non-linear relationships. The results showed distinct and significant differences between the spring reaction vs span relationships for the abutments and the piles (for the same bridge types). Further interpretation of the test results also showed that as spans increase (irrespective of the abutment height), the maximum spring reaction ratio (abutment/pile reaction ratio) tends towards unity under live loading. In summary, the spring reaction results clearly demonstrated the influence of soil conditions, the bridge geometry and the applied loads on the spring reactions. It was also noted that significant increases or changes in spring reaction often occurred after the span length of 20m was exceeded. It is hoped that the model testing and analysis has added valuable knowledge to the study of integral bridges. Further model testing is recommended to determine the characteristics of the spring reactions for much longer lengths of span, typically found in multi-span bridges.AFRIKAANSE OPSOMMING: n Integrale se brugdek, kolomme en landhoofde vorm 'n geheel sonder die gebruik van uitsettingsvoë wat gewoonlik uitsetting en inkrimping van 'n brugdek toelaat. 'n Integrale brug struktuur benut die inherente buigsaamheid van die kolomme en landhoofde. Die hoof ontwerpskwessie in 'n integrale brug, is die effek van temperatuur skommelinge en ooreenstemmende bewegings in die brugdek. Die integrale brug se eindpunte is in wisselwerking met die grondwalle wanneer die brug onderwerp word aan die bewegingssiklusse wat gronddruk veranderinge vanaf die aktiewe na die passiewe druk toestand, teweeg bring. Kragte inherent aan die konvensionele brug sisteme, werk ook longitudinaal teen die hervul grond. Die omvang van die grondstruktuur interaksie, is egter weglaatbaar aangesien die sikliese kragte wat gekep word, gering is in vergelyking met die kragte wat op die integrale brug inwerk. Dit maak die integrale brug ontwerp beide 'n strukturele en geotegniese probleem van belang. Die interaksie tussen die brugstruktuur en die omliggende grond is 'n relatiewe ingewikkelde, drie dimensionele scenario wat vereenvoudig kan word deur analise-modellering. Ingenieurs stel belang in twee verskillende (maar verwante) verskynsels. Een aspek is die vervorming van die grond soos wat lading en druk van die struktuur daarop toegepas word. 'n Tweede aspek is die ladingskapasiteit van die grond. Hierdie twee aspekte kan as grondstyfheid en grondsterkte beskryf word. 'n Hoër grondstyfheid behoort duidelik tot groter aksiale kragte en buigmomente in die brugdek te lei, as gevolg van die longitudinale-uitsetting of -inkrimping van die brug. Finite Element (FE) benaderings tot Grondstruktuur Interaksie (SSI), verwys gewoonlik na die benutting van grondelemente en die gebruik van veerstelsels. Met die veermetode van analise, verteenwoordig vere (lineêr of nie- lineêr van aard, of bied slegs kompressie) die weerstand van die grond aangrensend tot die heipale en landhoofde. Die teorieë wat gebruik word vir die berekening van die veerstyfheid, verskil vir die landhoofde en die heipale. In hierdie proefskrif is n reeks parametriese 2D en 3D brugmodelle vir grondvere geskep. Die parameters vir spanlengte, landhoofhoogte en grondtoestand vir verskillende persentasies van die lewendige lading, asook termiese uitsetting/inkrimping/gradiënt, is ondersoek, en die veergedrag is waargeneem en ontleed deur 'n reeks van parametriese model toetsings. Die veerreaksies vir enkelportaal (enkelspan) integrale brûe is oorweeg, met 'n hipotese dat vir 2D modelle, lineêre gedrag waargeneem sal word as gevolg van die vereenvoudigde model aannames. Met die 3D modelle vir heipale, sal dan 'n nie-lineêre gedrag waargeneem word as gevolg van die nie-lineêre laterale heipaal gedrag karakteristieke, en die gebruik van nie-lineêre vere.Master

Cone Penetration Testing 2022

This volume contains the proceedings of the 5th International Symposium on Cone Penetration Testing (CPT’22), held in Bologna, Italy, 8-10 June 2022. More than 500 authors - academics, researchers, practitioners and manufacturers – contributed to the peer-reviewed papers included in this book, which includes three keynote lectures, four invited lectures and 169 technical papers. The contributions provide a full picture of the current knowledge and major trends in CPT research and development, with respect to innovations in instrumentation, latest advances in data interpretation, and emerging fields of CPT application. The paper topics encompass three well-established topic categories typically addressed in CPT events: - Equipment and Procedures - Data Interpretation - Applications. Emphasis is placed on the use of statistical approaches and innovative numerical strategies for CPT data interpretation, liquefaction studies, application of CPT to offshore engineering, comparative studies between CPT and other in-situ tests. Cone Penetration Testing 2022 contains a wealth of information that could be useful for researchers, practitioners and all those working in the broad and dynamic field of cone penetration testing

New innovations in pavement materials and engineering: A review on pavement engineering research 2021

Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges. In the past 10 years, the pavement infrastructure strongly supports the rapid development of the global social economy. New theories, new methods, new technologies and new materials related to pavement engineering are emerging. Deterioration of pavement infrastructure is a typical multi-physics problem. Because of actual coupled behaviors of traffic and environmental conditions, predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis. In order to summarize the current and determine the future research of pavement engineering, Journal of Traffic and Transportation Engineering (English Edition) has launched a review paper on the topic of “New innovations in pavement materials and engineering: A review on pavement engineering research 2021”. Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering, this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world. The content includes asphalt binder performance and modeling, mixture performance and modeling of pavement materials, multi-scale mechanics, green and sustainable pavement, and intelligent pavement. Overall, this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering

Routledge Handbook of Ocean Resources and Management

This comprehensive handbook provides a global overview of ocean resources and management by focusing on critical issues relating to human development and the marine environment, their interrelationships as expressed through the uses of the sea as a resource, and the regional expression of these themes. The underlying approach is geographical, with prominence given to the biosphere, political arrangements and regional patterns – all considered to be especially crucial to the human understanding required for the use and management of the world's oceans. Part one addresses key themes in our knowledge of relationships between people and the sea on a global scale, including economic and political issues, and understanding and managing marine environments. Part two provides a systematic review of the uses of the sea, grouped into food, ocean space, materials and energy, and the sea as an environmental resource. Part three on the geography of the sea considers management strategies especially related to the state system, and regional management developments in both core economic regions and the developing periphery. Chapter 23 of this book is freely available as a downloadable Open Access PDF under a Creative Commons Attribution-Non Commercial-No Derivatives 3.0 license. https://www.routledgehandbooks.com/doi/10.4324/9780203115398.ch2

Synthesis of new pyrazolium based tunable aryl alkyl ionic liquids and their use in removal of methylene blue from aqueous solution

In this study, two new pyrazolium based tunable aryl alkyl ionic liquids, 2-ethyl-1-(4-methylphenyl)-3,5- dimethylpyrazolium tetrafluoroborate (3a) and 1-(4-methylphenyl)-2-pentyl-3,5-dimethylpyrazolium tetrafluoroborate (3b), were synthesized via three-step reaction and characterized. The removal of methylene blue (MB) from aqueous solution has been investigated using the synthesized salts as an extractant and methylene chloride as a solvent. The obtained results show that MB was extracted from aqueous solution with high extraction efficiency up to 87 % at room temperature at the natural pH of MB solution. The influence of the alkyl chain length on the properties of the salts and their extraction efficiency of MB was investigated