scholarly journals ANALYSIS OF RHEOLOGICAL MODELS OF PROCESS OF SELF-FORMING OF GLUED WOODEN

2020 ◽  
Vol 16 (2) ◽  
pp. 94-100
Author(s):  
Vladislav Ponomarev ◽  
Galina Kashevarova
Keyword(s):  
Plastic Deformation ◽  
Numerical Modeling ◽  
Moisture Content ◽  
Rheological Model ◽  
Experimental Studies ◽  
Rheological Models ◽  
Model Experiments ◽  
Promising Technology ◽  
Expansion Coefficients ◽  
Elastic And Plastic Deformation

The article considers a promising technology for self-shaping glued wooden elements of curved forms. This method is based on rheological processes occurring in wood, such as dehumidification and swelling of wood and its anisotropic properties. To predict the final curved shape of the wooden structure, the authors analyzed existing rheological models of wood and concluded that the rheological model proposed by European researchers includes the most complete list of factors that affect the process of deformation of wood: elastic and plastic deformation, drying and swelling of wood, deformation of viscous-elastic creep and mechanical sorption deformation. Based on the results of experimental studies and numerical modeling of the change in the curvature of glued wooden elements, which were made by European researchers, it was found that the proposed rheological model of wood needs to be clarified, namely, the correction of hygro-expansion coefficients depending on the moisture content of wood. A further direction of the authors’ research will be aimed at conducting model experiments to determine the hygro-expansion coefficients of different grades of wood depending on the thickness of the wooden elements and the orientation of the layers in the glued structure.

scholarly journals The current state and tendencies of using rheological models for self-forming wooden structures

2020 ◽  
pp. 112-122
Author(s):  
V. S Ponomarev ◽  
G. G Kashevarova
Keyword(s):  
Rheological Model ◽  
Experimental Studies ◽  
The Self ◽  
Building Structures ◽  
Forming Process ◽  
Rheological Models ◽  
Factors Affecting ◽  
Wooden Structure ◽  
Shrinkage And Swelling ◽  
Wooden Structures

Wood is a natural and ecological material. Exceptional mechanical properties of wood allow it to be used in building structures subject to chemically active substances. However some changes in mechanical characteristics of wood under the influence of water and temperature, as well as its anisotropy, limit the application areas of this material. Based on the results of the research by S.P. Timoshenko, foreign scientists proposed a method that makes it possible to use these shortcomings of wood to create wooden structures of unique shapes. This article considers the self-forming process of glued layered wooden structures, which is based on various rheological processes taking place in wood. In order to predict the shape of a glued layered wooden structure obtained with the self-forming method, an accurate rheological model is required, which takes into account all wood deformation mechanisms. We analyzed the available rheological models of wood proposed or described both by Russian and foreign scientists, as well as the international experimental studies and numerical modeling results of the self-formed glued layered wooden structures. Based on the analysis results, it was found that the present rheological models do not take into account a number of factors that influence the process of self-forming of glued layered wooden structures. The rheological model, which includes a complete list of factors affecting wood deformation (elastic and plastic deformation, wood shrinkage or swelling, viscous-elastic creep deformation and mechanical and sorption deformation), is the most promising for creating unique architectural objects from glued wood. But it also has a number of shortcomings, mainly due to inconsideration of some factors and few experimental studies. Such factors include the geometric parameters of layers of the glued wooden structures, the surface treatment of layers, temperature, as well as wood species. These factors influence the process of wood shrinkage and swelling, thus the final shape of a wooden structure. It is necessary to have additional experimental and theoretical studies of the mechanical behavior of glued wooden structures which will take into account these factors, as well as to study other species of wood including their combinations.

scholarly journals Análise de um pavimento reforçado com geossintético a partir de resultados de ensaio em equipamento de grandes dimensões

TRANSPORTES ◽  
2011 ◽  
Vol 19 (3) ◽  
pp. 28
Author(s):  
Francis Massashi Kakuda ◽  
Alexandre Benetti Parreira ◽  
Glauco Tulio Pessa Fabbri
Keyword(s):  
Plastic Deformation ◽  
Numerical Modeling ◽  
Laboratory Tests ◽  
Resilient Modulus ◽  
Base Layer ◽  
Plastic Deformations ◽  
Elastic And Plastic Deformations ◽  
Back Calculation ◽  
Pavement Reinforcement ◽  
Elastic And Plastic Deformation

<p><strong>Resumo</strong>: O artigo analisa o beneficio do uso de uma geogrelha como reforço da camada de base de um pavimento. Seções do pavimento e subleito com dimensões próximas às reais submetidas a carregamentos cíclicos foram ensaiadas numa caixa metálica quadrada com lado de 1,5 m e altura de 1,2 m. Concluiu-se que a utilização da geogrelha proporciona a redução de deformações elásticas e permanentes, e que a eficiência do reforço posicionado na interface com o subleito é maior que a do reforço posicionado no horizonte médio da base. Foram ainda determinados os módulos de resiliência da base e do subleito a partir da retroanálise das bacias de deflexões obtidas nos ensaios. Finalmente, a análise numérica de um pavimento hipotético mostrou que a geogrelha pode proporcionar uma extensão expressiva na vida de fadiga do revestimento asfáltico.</p><p><strong>Palavras-chave</strong>: pavimentos reforçados com geosintéticos, geogrelha, ensaios de laboratório em verdadeira grandeza, deformações elásticas e plásticas sob carregamento cíclicos.</p><p><strong>Abstract</strong>: The article analyzes the benefits of the application of a geogrid as base layer pavement reinforcement. Cyclic loaded fullscale sections of pavement and subgrade were tested in a square metallic box with 1.5 m width and 1.2 m height. It was concluded that the geogrid reduces the elastic and plastic deformations and also that positioning the reinforcing at subgrade interface is more efficient than at base medium horizon. The base and subgrade resilient modulus were obtained by back calculation using the deflection basin results from the tests. Finally, a numerical modeling of a hypothetic pavement showed that the geogrid may conduct to an expressive increase of the bituminous surface life.</p><p><strong>Keywords</strong>: geosynthetic reforced pavement, geogrid, full-scale laboratory tests, elastic and plastic deformation under cyclic loadings.</p>

scholarly journals Simulation of plastic deformation and destruction in the process of chip formation

2018 ◽  
Vol 211 ◽  
pp. 17007
Author(s):  
Tanel Tärgla ◽  
Jüri Olt ◽  
Olga Liivapuu
Keyword(s):  
Plastic Deformation ◽  
Formation Process ◽  
Chip Formation ◽  
Rheological Model ◽  
Metal Cutting ◽  
Depth Of Cut ◽  
Key Factors ◽  
Local Zone ◽  
Complex Process ◽  
Relaxing Medium

Metal cutting is a complex process in which several mechanisms are at work simultaneously. The mathematical modelling allows carrying out research into the optimization of machining conditions. This work examines the simulation of chip formation during the process of cutting. The studies demonstrated that the chip formation process, taking into account the plastic deformation and destruction of metal in the local zone, is most appropriately represented by a rheological model in the form of a series connection of elasticductile- plastic relaxing medium of Ishlinskiy (reflecting the process of primary deformation of metal from the cut off layer) and the medium of Voigt with two elastic-dissipative elements (representing the process of deformation and frictions from the convergent shaving). The attained complex rheological model served as the basis for constructing a representative dynamic model for the chip formation process. The key factors that govern the chip formation have been taken into account, such as tool vibration frequency and amplitude, depth of cut, feed rate.

scholarly journals Biopolymer Drill-in Fluid Performance for Different Rheological Models using Statistical Characterisation

2019 ◽  
Vol 19 (1) ◽  
pp. 86-92
Author(s):  
M. Owusu ◽  
H. Osei
Keyword(s):  
Rheological Model ◽  
Rheological Behaviour ◽  
Primary Objective ◽  
Least Square ◽  
Model Parameters ◽  
Drilling Fluids ◽  
Cleaning Efficiency ◽  
Rheological Models ◽  
Least Square Regression ◽  
Best Fit

Appropriate selection of rheological models is important for hydraulic calculations of pressure loss prediction and hole cleaning efficiency of drilling fluids. Power law, Bingham-Plastic and Herschel-Bulkley models are the conventional fluid models used in the oilfield. However, there are other models that have been proposed in literature which are under/or not utilized in the petroleum industry. The primary objective of this paper is to recommend a rheological model that best-fits the rheological behaviour of xanthan gum-based biopolymer drill-in fluids for hydraulic evaluations. Ten rheological models were evaluated in this study. These rheological models have been posed deterministically and due to the unrealistic nature have been replaced by statistical models, by adding an error (disturbance) term and making suitable assumptions about them. Rheological model parameters were estimated by least-square regression method. Models like Sisko and modified Sisko which are not conventional models in oil industry gave a good fit. Modified Sisko model which is a four parameter rheological model was selected as the best-fit model since it produced the least residual mean square of 0.61 Ibf2/100ft4. There is 95% certainty that the true best-fit curve lies within the confidence band of this function of interest. Keywords: Biopolymer; Least-Square Regression; Residual Mean Squares; Rheologram

CORRELATION DEPENDENCES OF THE BENDING STRENGTH OF POLYMER COMPOSITE MATERIALS MODIFIED IN A MICROWAVE ELECTROMAGNETIC FIELD ON THE MOISTURE CONTENT DURING EXPOSURE IN FULL-SCALE CONDITIONS

2021 ◽  
pp. 3-9
Author(s):  
I. V. Zlobina ◽  
I. S. Katsuba
Keyword(s):  
Electromagnetic Field ◽  
Composite Materials ◽  
Carbon Fiber ◽  
Moisture Content ◽  
Bending Strength ◽  
Climatic Factors ◽  
Experimental Studies ◽  
Three Point Bending ◽  
Treated Carbon ◽  
Control Samples

Experimental studies of the influence of external climatic factors, taking into account exposure, on the change in the bending strength of control and microwave – treated carbon and fiberglass samples in the cured state were performed. An increase in the limit stresses of three – point bending of experimental carbon fiber samples compared to the control ones was found by 7…12 %, and fiberglassby 4…7 %. It is shown that with an increase in exposure to 14 months, the strength of control samples of carbon and fiberglass decreases by an average of 10 %. At the same time, the strength of the prototypes is reduced only by 4.4 %. With an increase in the moisture content of both control and experimental samples, a decrease in their strength is observed. In this case, the linear correlation is average (from– 0.44 to – 0.615). It is established that for experimental samples, the influence of the amount of absorbed moisture on the strength is manifested to a much lesser extent. For carbon fiber, the reduction is 16.6 %, for fiberglass – 12 %.

Deformation, Fracture, and Friction Processes

2020 ◽  
pp. 14-24
Author(s):  
Francois Louchet
Keyword(s):  
Plastic Deformation ◽  
Ductile Failure ◽  
Scientific Validity ◽  
Coulomb’S Friction ◽  
Dynamic Loadings ◽  
Triggering Mechanisms ◽  
The Difference ◽  
Elastic And Plastic Deformation ◽  
Physical Quantities ◽  
Rupture Criterion

The main mechanical and physical quantities and concepts ruling deformation, fracture, and friction processes are recalled, with particular attention paid to the simplicity of the analysis, but without betraying the scientific validity of the arguments. We particularly discuss the difference between between elastic and plastic deformation, and quasistatic and dynamic loadings, essential in avalanche triggering mechanisms. The physical origin of Griffith’s rupture criterion that rules both fracture nucleation and propagation, and the transition between brittle and ductile failure processes, is thoroughly discussed. We also explain the physical meaning of the classical Coulomb’s friction law, showing why it can hardly apply to a non-conventional porous, brittle, and healable solid like snow.

Effects of Compaction Moisture Content on Permanent Deformation of Soils Subjected to Repeated Triaxial Load Tests

2019 ◽  
Vol 2673 (2) ◽  
pp. 466-476 ◽  
Author(s):  
Caroline Dias Amancio de Lima ◽  
Laura Maria Goretti da Motta ◽  
Francisco Thiago Sacramento Aragão
Keyword(s):  
Moisture Content ◽  
Permanent Deformation ◽  
Tropical Soils ◽  
Asphalt Pavements ◽  
Design Guide ◽  
Compaction Curve ◽  
Triaxial Loads ◽  
Load Tests ◽  
Deformation Tests ◽  
Elastic And Plastic Deformation

Water content is one of the key parameters that can cause variations in the elastic and plastic deformation of pavement layers. More specifically, both the compaction moisture and the post-compaction moisture should be carefully controlled. The objective of this study is to analyze the effects of compaction moisture on the accumulation of permanent deformation when unbound materials are subjected to repeated triaxial loads. The moisture contents were defined according to the compaction curve of each soil, being one above and one below the optimum moisture content which has been typically considered for the design of asphalt pavements in Brazil. The four soils evaluated in the study are commonly used in flexible pavements and have different classifications according to the Brazilian Miniature, Compacted, Tropical (MCT) methodology tailored to classify tropical soils. Specimens were subjected to permanent deformation tests and the results obtained show that the moisture content can significantly affect the mechanical behavior of soils. That effect is significant on both sides of the compaction curve, but the permanent deformation increases as the compaction moisture content increases on the wet side. This work is part of a broader and comprehensive research project in progress in Brazil to continuously update the current version of the Brazilian mechanistic-empirical pavement design guide. The proper understanding and characterization of the resistance to permanent deformation of unbound materials is a key part of that design guide.

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