scholarly journals ANÁLISE DO COMPORTAMENTO MECÂNICO DE MACIÇOS ROCHOSOS CONTENDO DESCONTINUIDADES ATRAVÉS DO MÉTODO DAS DIFERENÇAS FINITAS VIA IMPLEMENTAÇÃO COMPUTACIONAL [ Analysis of the mechanical behavior of rocky mass with discontinuities through the finite differences method via computational implementation ]

2018 ◽  
Vol 15 (1) ◽  
Author(s):  
Luma Alvarenga Carvalho de Vasconcelos ◽  
Pedro Guilherme Cipriano Silva ◽  
Pedro Ivo Amaro Alves
Keyword(s):  
Rock Mass ◽  
Mechanical Behavior ◽  
Numerical Solutions ◽  
Compressive Force ◽  
Shear Stiffness ◽  
Relative Displacement ◽  
Shear Stresses ◽  
Linear Elastic ◽  
Finite Differences Method ◽  
Fortran 90

RESUMO: Neste trabalho é realizada uma análise computacional por meio da resolução de equações diferenciais para a modelagem de soluções analíticas e numéricas (MDF) do comportamento mecânico de um maciço rochoso contendo descontinuidades. Realizou-se simulações adotando um bloco composto por um material homogêneo, isotrópico e linear elástico sob atuação de uma força externa compressiva aplicada na sua extremidade livre e confinado entre duas descontinuidades rígidas, nas superfícies inferior e superior. A descontinuidade inferior apresenta rugosidade, caracterizada por um módulo de rigidez ao cisalhamento que conduz a uma distribuição de tensão cisalhante e a um deslocamento relativo entre o bloco e a base. Os resultados foram gerados através da compilação dos dados no programa computacional FORTRAN 90, e, com isso, pode-se verificar o deslocamento relativo entre o bloco e a descontinuidade, bem como as tensões atuantes em cada ponto previamente definido; e ainda realizar uma comparação entre as soluções analítica e numérica. Como principal contribuição do trabalho para a área da geotecnia, cita-se a possibilidade de uma análise de deslocamento de descontinuidades presentes em maciços rochosos mais próxima da realidade já que considera o meio como descontínuo. Além disso apresenta-se uma solução computacional de fácil implementação e entendimento.ABSTRACT: In this work a computational analysis is performed by solving differential equations for the modeling of numerical (MDF) and analytical solutions of the mechanical behavior of a rock mass with discontinuities. Simulations were carried out by adopting a block composed of a homogeneous, isotropic and linear elastic material under the action of an external compressive force applied at its free end and confined between two rigid discontinuities on the lower and upper surfaces. The lower discontinuity presents roughness characterized by a shear stiffness modulus leading to a shear stress distribution and a relative displacement between the block and the base. The results were generated through the compilation of the data in the FORTRAN 90 computer program, and with this, it is possible to verify the relative displacement between the block and the discontinuity, as well as the shear stresses acting at each previously defined point; and also perform a comparison between analytical and numerical solutions. The main contribution of the work to the area of geotechnics is the possibility of an analysis of discontinuity displacement present in rock mass closer to reality since it considers the environment as discontinuous. In addition, a computational solution is presented that is easy to implement and understand.

Tire Treadwear — A Comprehensive Evaluation of the Factors: Generic Type, Aspect Ratio, Tread Pattern, and Tread Composition Part IV: Laboratory Measurement of Mechanical Properties and Mechanical Actions of Tires Relating to Treadwear

1986 ◽  
Vol 14 (4) ◽  
pp. 264-291
Author(s):  
K. L. Oblizajek ◽  
A. G. Veith
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Contact Zone ◽  
Flexural Rigidity ◽  
Comprehensive Evaluation ◽  
Shear Stiffness ◽  
Shear Stresses ◽  
Lateral Shear ◽  
Band Bending ◽  
Tread Rubber

Abstract Treadwear is explained by specific mechanical properties and actions of tires. Rubber shear stresses in the contact zone between the tire and the road become large at large slip angles. When normal stresses are insufficient to prevent sliding at the rear of the footprint, wear occurs at a rate that depends on test severity. Two experimental approaches are described to relate treadwear to tire characteristics. The first uses transducers imbedded in a simulated road surface to obtain direct measurements of contact stresses on the loaded, freely-rolling, steered tires. The second approach is developed with the aid of a simple carcass, tread-band, tread-rubber tire model. Various tire structural configurations; characterized by carcass spring rate, edgewise flexural band stiffness, and tread rubber shear stiffness; are simulated and lateral shear stress response in the contact zone is determined. Tires featuring high band stiffness and low carcass stiffness generate lower lateral shear stress levels. Furthermore, coupling of tread-rubber stiffness and band flexural rigidity are important in determining level of shear stresses. Laboratory measurements with the described apparatus produced values of tread-band bending and carcass lateral stiffness for several tire constructions. Good correlation is shown between treadwear and a broad range of tire stiffness and test course severities.

Linear and non-linear elastic stability of beams by higher order beam theories

2019 ◽  
Author(s):  
Αμαλία Αργυρίδη
Keyword(s):  
Elastic Stability ◽  
Higher Order ◽  
Linear Elastic ◽  
Non Linear ◽  
Fortran 90 ◽  
Beam Theories

Στην παρούσα διδακτορική διατριβή διερευνάται η γραμμική και μη γραμμική ελαστική ευστάθεια ράβδων διαμέσου θεωριών δοκού ανώτερης τάξης. Προκειμένου να υλοποιηθεί αυτό, το πρώτο βήμα της παρούσας διδακτορικής διατριβής είναι η εξέταση του στρεπτοκαμπτικού λυγισμού σύμμικτων δοκών λαμβάνοντας υπόψη τα φαινόμενα της στρέβλωσης (εκτός επιπέδου παραμόρφωση) και την διατμητικής υστέρησης (διαφοροποίηση της κλασσικής κατανομής ορθών τάσεων) λόγω κάμψης και στρέψης. Στο δεύτερο βήμα της παρούσας διδακτορικής διατριβής, μορφώνεται το πρόβλημα της γραμμικής κα μη γραμμικής στατικής ανάλυσης ομογενών δοκών λαμβάνοντας υπόψη τα φαινόμενα της αξονικής στρέβλωσης και της διαστρέβλωσης (εντός επιπέδου παραμόρφωση) επιπρόσθετα σε εκείνα λόγω της καμπτικής και στρεπτικής συμπεριφοράς της δοκού διαμέσου του σχήματος διαδοχικής ισορροπίας που υιοθετείται (πλεονεκτήματα έναντι προβλημάτων ιδιοτιμών). Κύριο τμήμα του δεύτερου βήματος αποτελεί η διατύπωση, η αρχικοποίηση και η επίλυση των προβλημάτων συνοριακών τιμών που αφορούν στον υπολογισμό των αξονικών μορφών στρέβλωσης και διαστρέβλωσης διαμέσου του σχήματος διαδοχικής ισορροπίας. Στο προτελευταίο βήμα της παρούσας διδακτορικής διατριβής, οι προηγούμενα αναπτυγμένες αξονικές μορφές στρέβλωσης και διαστρέβλωσης μαζί με τις αντίστοιχες καμπτικές και στρεπτικές χρησιμοποιούνται προκειμένου να μορφωθεί και να επιλυθεί το πρόβλημα της γραμμικής ελαστικής ευστάθειας δοκών. Στο τελευταίο βήμα της παρούσας διδακτορικής διατριβής, διεξάγεται μη γραμμική ανάλυση λαμβάνοντας υπόψη τα φαινόμενα της στρέβλωσης και της διαστρέβλωσης λόγω αξονικής, διατμητικής, καμπτικής και στρεπτικής δομικής συμπεριφοράς και πραγματοποιείται σύγκριση με τα αντίστοιχα αποτελέσματα που λαμβάνονται στην περίπτωση όπου λαμβάνεται υπόψη μόνο η στρέβλωση και η διατμητική υστέρηση λόγω κάμψης και στρέψης. Αξίζει να σημειωθεί ότι σε όλες τις παραπάνω περιπτώσεις η διατομή της δοκού είναι τυχούσα, ενώ ο λόγος του Poisson λαμβάνεται υπόψη στον υπολογισμό των αξονικών, καμπτικών και στρεπτικών μορφών στρέβλωσης και διαστρέβλωσης. Στην παρούσα διδακτορική διατριβή χρησιμοποιούνται δύο αριθμητικές μέθοδοι. Η πρώτη είναι η μέθοδος των συνοριακών στοιχείων που χρησιμοποιείται για την επίλυση των προβλημάτων συνοριακών τιμών που αφορούν στον υπολογισμό των αξονικών, καμπτικών και στρεπτικών μορφών στρέβλωσης και διαστρέβλωσης και των γεωμετρικών σταθερών. Η δεύτερη μέθοδος είναι η μέθοδος των πεπερασμένων στοιχείων που χρησιμοποιείται για τη διακριτοποίηση των και την επίλυση των καθολικών εξισώσεων ισορροπίας της δοκού. Στη βάση των αναλυτικών και αριθμητικών μεθόδων που παρουσιάζονται στην παρούσα διδακτορική διατριβή έχουν γραφτεί προγράμματα σε FORTRAN 90/95 και έχουν μελετηθεί αντιπροσωπευτικά αριθμητικά παραδείγματα. Επιπρόσθετα, έχουν γραφτεί scripts σε MATLAB προκειμένου να ερμηνευθούν τα αποτελέσματα διαμέσου δισδιάστατων και τρισδιάστατων γραφημάτων της δοκού. Η ακρίβεια και η αξιοπιστία των προτεινόμενων μεθόδων επιβεβαιώνονται μέσω αριθμητικών παραδειγμάτων που αντλούνται από τη βιβλιογραφία και αποτελεσμάτων που εξάγονται από αναλύσεις τρισδιάστατων και επιφανειακών πεπερασμένων στοιχείων.

Mechanical response of double-stranded DNA to dynamic excitation

2021 ◽  
pp. 107754632110458
Author(s):  
Hamze Mousavi ◽  
Moein Mirzaei ◽  
Samira Jalilvand
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Actual Condition ◽  
Dimensional System ◽  
One Dimensional ◽  
Linear Elastic ◽  
Dynamic Excitation ◽  
Double Stranded Dna ◽  
Elastic Forces ◽  
Mass Spring

The present work investigates the vibrational properties of a DNA-like structure by means of a harmonic Hamiltonian and the Green’s function formalism. The DNA sequence is considered as a quasi one-dimensional system in which the mass-spring pairs are randomly distributed inside each crystalline unit. The sizes of the units inside the system are increased, in a step-by-step approach, so that the actual condition of the DNA could be modeled more accurately. The linear-elastic forces mimicking the bonds between the pairs are initially considered constant along the entire length of the system. In the next step, these forces are randomly shuffled so as to take into account the inherent randomness of the DNA. The results reveal that increasing the number of mass-spring pairs in the crystalline structure decreases the influence of randomness on the mechanical behavior of the structure. This also holds true for systems with larger crystalline units. The obtained results can be used to investigate the mechanical behavior of similar macro-systems.

Mathematical modelling of shallow flows: Closure models drawn from grain-scale mechanics of sediment transport and flow hydrodynamicsThis paper is one of a selection of papers in this Special Issue in honour of Professor M. Selim Yalin (1925–2007).

2009 ◽  
Vol 36 (10) ◽  
pp. 1605-1621 ◽  
Author(s):  
Rui M. L. Ferreira ◽  
Mário J. Franca ◽  
João G. A. B. Leal ◽  
António H. Cardoso
Keyword(s):  
Sediment Transport ◽  
Mathematical Modelling ◽  
Conceptual Models ◽  
Numerical Solutions ◽  
Shear Stresses ◽  
Shallow Flows ◽  
River Modelling ◽  
Morphologic Evolution ◽  
Sediment Mixtures ◽  
Selection Of

Mathematical modelling of river processes is, nowadays, a key element in river engineering and planning. River modelling tools should rest on conceptual models drawn from mechanics of sediment transport, river mechanics, and river hydrodynamics. The objectives of the present work are (i) to describe conceptual models of sediment transport, deduced from grain-scale mechanics of sediment transport and turbulent flow hydrodynamics, and (ii) to present solutions to specific river morphology problems. The conceptual models described are applicable to the morphologic evolution of rivers subjected to the transport of poorly sorted sediment mixtures at low shear stresses and to geomorphic flows featuring intense sediment transport at high shear stresses. In common, these applications share the fact that sediment transport and flow resistance depend, essentially, on grain-scale phenomena. The idealized flow structures are presented and discussed. Numerical solutions for equilibrium and nonequilibrium sediment transport are presented and compared with laboratory and field data.

Investigation of the Mechanical Behavior of 3D Printed Polyamide-12 Joints for Reduced Scale Models of Rock Mass

2020 ◽  
Vol 53 (6) ◽  
pp. 2687-2705
Author(s):  
Jana Jaber ◽  
Marianne Conin ◽  
Olivier Deck ◽  
Mohamed Moumni ◽  
Olivier Godard ◽  
...  
Keyword(s):  
Rock Mass ◽  
Mechanical Behavior ◽  
Polyamide 12 ◽  
Scale Models ◽  
3D Printed ◽  
Reduced Scale

scholarly journals Numerical Modeling on Hydraulic Fracturing in Coal-Rock Mass for Enhancing Gas Drainage

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Zhigang Yuan ◽  
Yaohua Shao
Keyword(s):  
Mathematical Model ◽  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Gas Flow ◽  
Numerical Solutions ◽  
Fracture Initiation ◽  
Engineering Practice ◽  
Gas Drainage ◽  
Fracturing Process ◽  
Coal Rock

The mechanism of how hydraulic fracturing influences gas drainage in coal-rock mass is still not clear due to its complex mechanism. In this work, statistical distributions are firstly introduced to describe heterogeneity of coal-rock mass; a novel simultaneously coupled mathematical model, which can describe the fully coupled process including seepage-damage coupling during hydraulic fracturing process and subsequent gas flow during gas drainage process, is established; its numerical implementation procedure is coded into a Matlab program to calculate the damage variables, and it partly uses COMSOL solver to obtain numerical solutions of governing equations with damage-flow coupling; the mathematical model and its implementation are validated for initial damage pressure and mode of a single solid model without considering flow-damage coupling, as well as fracture initiation pressure and influence of heterogeneity on damage evolution of hydraulic fracturing considering flow-damage coupling; and finally, based on an engineering practice of hydraulic fracturing with two boreholes, the mechanism of how hydraulic fracturing influences gas drainage is investigated, numerical simulation results indicate that coal-rock mass pore-fissure structure has been improved, and there would exist a gas migration channel with characteristics of higher porosity and lower stresses, which demonstrates significant effects and mechanism of hydraulic fracturing on improving coal-rock permeability and enhancing gas drainage. The research results provide a guide for operation of hydraulic fracturing and optimal layout of gas drainage boreholes.

scholarly journals Effect of Process Orientation on the Mechanical Behavior and Piezoelectricity of Electroactive Paper

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 204
Author(s):  
Sean Yoon ◽  
Jung Woong Kim ◽  
Hyun Chan Kim ◽  
Jaehwan Kim
Keyword(s):  
Mechanical Behavior ◽  
Process Orientation ◽  
Linear Elastic ◽  
Strong Shear ◽  
Performance Deterioration ◽  
Alignment Angle ◽  
Anisotropic Elastic ◽  
Stretching Ratio ◽  
Orientation Dependency ◽  
Piezoelectric Charge

This paper reports the effect of process orientation on the mechanical behavior and piezoelectricity of electroactive paper (EAPap) made from natural cotton pulp. EAPap is fabricated by a casting and wet drawing of cellulose film after dissolving cotton with LiCl and DMAc solvent. During the fabrication, permanent wrinkles, a possible factor for performance deterioration, were found in the films. Finite element method was introduced to identify the formation mechanism behind the wrinkles. The simulation results show that the wrinkles were caused by buckling and are inevitable under any conditions. The tensile and piezoelectric tests show that the orientation dependency of the stretched EAPap gives the anisotropic characteristics on both mechanical and piezoelectric properties. In this research, the anisotropic elastic moduli and Poisson’s ratios are reported. The piezoelectric charge constant of EAPap in the linear elastic is calculated. The piezoelectric charge constants of EAPap are associated with the alignment angle in the order of 45° > 0° > 90° due to the strong shear effect. The higher stretching ratio gives the higher piezoelectricity due to the alignment of the molecular chains and the microstructure in EAPap. The highest piezoelectric charge constant is found to be 12 pC/N at a stretching ratio of 1.6 and aligning angle of 45°.

scholarly journals Mechanical behavior of ballasted railway track stabilized with polyurethane: A finite element analysis

2018 ◽  
Vol 251 ◽  
pp. 04056 ◽  
Author(s):  
Zelimkhan Khakiev ◽  
Alexander Kruglikov ◽  
Georgy Lazorenko ◽  
Anton Kasprzhitskii ◽  
Yakov Ermolov ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mechanical Behavior ◽  
Finite Element Simulation ◽  
Elasticity Modulus ◽  
Railway Track ◽  
Binding Agent ◽  
Element Analysis ◽  
Linear Elastic ◽  
Element Simulation

Analysis of mechanical behavior of ballast shoulder of railway track reinforced by polyurethane binding agent has been performed by the method of finite-element simulation Limitation of the model of linear-elastic properties of geocomposite has been displayed. Dependence of elasticity modulus of geocomposite on deformation value has been suggested. Influence of penetration depth of polyurethane binding agent on behavior of railway track construction under different train loads has been studied.

The Distribution of Shear Stresses in an I Section Beam

1961 ◽  
Vol 65 (603) ◽  
pp. 198-201
Author(s):  
W. G. Wood
Keyword(s):  
Shear Stiffness ◽  
Bending Stiffness ◽  
Combined Effect ◽  
Transverse Load ◽  
Substantial Part ◽  
Shear Stresses ◽  
Short Beam ◽  
Bending Stresses

When a Beam is subjected to a static transverse load acting through its flexural centre, the resulting deflection may be considered as the combined effect of the deflection due to bending stresses and the deflection due to shear stresses. In a majority of cases, where the span of the beam is large, or where the shear stiffness is large compared with the bending stiffness, the bending component only need be considered. However, for a short beam, the shear deflection can account for a substantial part of the total deflection. This is especially so in the case of a deep I section beam with a thin web, where the bending stiffness is large compared with the shear stiffness.

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