Journal articles on the topic 'Shock (Mechanics) – Mathematical models'
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1
Qu, Zhi Ming. "Investigation of Damage Effect by Shock Wave on Structures in Excavation Roadway." Key Engineering Materials 439-440 (June 2010): 1438–43. http://dx.doi.org/10.4028/www.scientific.net/kem.439-440.1438.
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Using the theory of explosion mechanics and gas detonation dynamics and the conservation law of mass, momentum and energy, the physical and mathematical models of damage effect are set up in excavation roadway during gas explosion. In view of gas concentration, accumulation position, volumes and states of spaces, the shock wave damage on structures in the roadway during gas explosion. The damage effects are characterized of heat and mechanic damage. Meanwhile, the high temperature and pressure are formed in different degree. With the action of overpressure and impulse, the damage degree is different with different geometric structures in ventilation system. By means of basic condition, influential factors, procedure features and simulation, some unnecessary structures or barriers should be cleared in order to keep smooth the ventilation system.
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Chang, Juntao, Lei Wang, and Wen Bao. "Mathematical modeling and characteristic analysis of scramjet buzz." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 228, no. 13 (January 29, 2014): 2542–52. http://dx.doi.org/10.1177/0954410014521055.
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Buzz is an important issue for a scramjet engine. A mathematical model of buzz oscillations is necessary for control system design. Control-oriented models of hypersonic vehicle propulsion systems require a reduced-order model that is accurate to some extent but requires less than a few seconds of computational time. To achieve this goal, a reduced-order model of buzz oscillations for a scramjet engine is built by introducing the modeling idea of Moore–Greitzed model for compressors. The introduction of characteristic lines avoids the complex interactions in hypersonic inlet, such as shock–shock interactions and shock–boundary layer interaction. And the inlet characteristics are obtained from the pressure signal of combustor. Based on the established buzz model, we can predict the inlet performance, characterize the stability margin of inlet, reflect the oscillatory characteristics of inlet buzz including the dominant amplitude and frequency and describe the transition process of inlet buzz.
3
R., Krupych,, Nishchenko, I., Shevchuk, R., and Krupych, S. "Mathematical model of the system “manual vibration shock shaker – fruit branch”." Mehanization and electrification of agricultural, no. 9(108) (2019): 210–23. http://dx.doi.org/10.37204/0131-2189-2019-9-27.
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Purpose. Development of mathematical model of oscillating system “manual vibration shock shaker – fruit branch” for the purpose of theoretical substantiation of the parameters of the shaker. Methods. The basic positions of mathematics, theoretical mechanics, mathematical modeling, program development and numerical calculations on the PC using methods of constructing mathematical models of functioning of agricultural machines are used. Results. The paper proposes a mathematical system model “manual vibration shock shaker – fruit branch” of six differential equations describing the motion of five separate masses (the mass of branch and four masses of individual shaker strings) and differential equations of the transverse and rotational motion of the system as whole. The mathematical system model determines the regularity of the motion of all masses, as well as the reactions of the viscals of the oscillatory system to the impact and after the impact that is generated in the shock mechanism. The proposed nonlinear, complex system of differential equations solves the numerical Runge-Kutta method of the fourth order of accuracy. On the basis of the calculated data the theoretical regularities of change of movement, speed and acceleration of a branch in the place of capture are received, which confirm that in the case of interaction of the cups of the shock mechanism there is blow that is accompanied by an increase in the acceleration of the branch, which is 4–5 times greater than the acceleration of the vibration mode of operation. Conclusions 1. The mathematical model of oscillating system “manual vibration shock shaker – fruit branch” is proposed in the form of system of six differential equations that allows to theoretically substantiate the basic modes of work of the manual shaker in the vibration shock mode to provide the agrotechnical necessary extraction completeness. 2. The received theoretical regularities of change of displacement, speed and acceleration of branch at the place of capture confirm the effectiveness of the vibration shock mode of the shaker. Due to the vibration-shock mode, the acceleration of the branch at the point of transmission of disturbing forces is 4–5 times higher than the acceleration of the vibrational operation mode. Keywords: manual shakes, vibration shocking process, oscillation oscillators, mathematical model, fruit branch, harvesting.
4
Ucar, H., and I. Basdogan. "Dynamic characterization and modeling of rubber shock absorbers: A comprehensive case study." Journal of Low Frequency Noise, Vibration and Active Control 37, no. 3 (August 21, 2017): 509–18. http://dx.doi.org/10.1177/1461348417725954.
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Rubber or elastomeric materials are widely used for shock absorbers having elastic and viscous properties such as high inherent damping, deflection capacity, and energy storage. The dynamic properties of these components are of primary concern in designing rubber absorbers to reduce the shock loading given as well as the structure-borne noise transmissibility. Besides, the dynamic response of the mechanical systems, at where the rubber shock absorbers are used, is directly associated with the properties of the shock absorbers. In order to determine these properties of the rubber, mathematical models are created in terms of hyperelasticity and viscoelasticity. The hyperelastic and viscoelastic material models represent the nonlinear elastic and strain rate dependencies of the overall rubber behavior, respectively. Hyperelastic material model captures the material’s nonlinear elasticity with no-time dependence whereas viscoelastic model describes the material response which contains an elastic and viscous part depending on time, frequency, and temperature. This paper presents the dynamic characterization of rubber shock absorbers, having different shore hardness values, in terms of hyperelastic and viscoelastic constitutive models. The parameters of the constitutive models are determined from the uniaxial tensile and relaxation tests. These parameters are used for the numerical model of the rubber components and the accuracy of the characterization is presented by means of a numerical case study.
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Morozov, Victor A., Vsevolod I. Bogatko, and Andrey B. Yakovlev. "About mathematical simulation of processes for high-speed loading of materials on Department of Physical Mechanics of St. Petersburg State University." Vestnik of Saint Petersburg University. Mathematics. Mechanics. Astronomy 65, no. 4 (2020): 699–713. http://dx.doi.org/10.21638/spbu01.2020.411.
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The researches of shock-wave processes in the constructional materials are actual, but carrying out of natural experiments is extremely inconvenient and expensive, and sometimes it is even impossible to replicate. Therefore basically all researches of these problems are reduced to various cases of simulation of processes for high-speed loading of materials in the laboratory circumstances. In the paper we consider following directions of mathematical simulation of processes for high-speed loading of materials that were made on department of physical mechanics of St. Petersburg State University: the simulation of shock-loaded media by using of dynamics of dislocations; the simulation of high-speed loading of media with the account of the relaxation phenomena in a near-surface region; the simulation of propagation of the short elastoplastic impulse in medium under the condition of influence of a weak magnetic field; the generation of mathematical models of deformation and destruction of thin metal rings by a magnetic-pulse method; the simulation of crack propagation during the short-term pulse loading.
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Liu, Hongtuo, Fangwei Xie, Kai Zhang, Xinxing Zhang, Jin Zhang, Cuntang Wang, and Hao Li. "Effect of air chamber and oil properties on damping characteristics of single-tube pneumatic shock absorber." International Journal of Structural Integrity 9, no. 1 (February 5, 2018): 27–37. http://dx.doi.org/10.1108/ijsi-03-2017-0017.
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Purpose The shock absorber is an important component of vehicle suspension that attenuates the vehicle vibration. Its running state directly affects the performance of the vehicle suspension. The purpose of this paper is to quantitatively study the relationship between damping characteristics and air chamber and oil properties in single-tube pneumatic shock absorber. Design/methodology/approach Combined with the principle of fluid dynamics and hydraulic transmission technology, the rebound stroke and compression stroke mathematical models, and damping characteristics simulation model are established to investigate the effect of the air chamber and oil property on damping characteristics. Findings Research results show that the initial pressure of the air chamber is the key parameter which influences the damping characteristics of the shock absorber. The change of the initial pressure has more impact on damping force, and less impact on the speed characteristic; the initial volume of the air chamber almost has no effect on the damping characteristics. The density and viscosity of the oil have certain influence on the damping characteristics. Therefore, selecting suitable damping oil is very important. Originality/value Using Matlab/Simulink software to build simulation models, its results are very accurate. The conclusions can provide a theoretical reference for the structure design of a single-tube pneumatic shock absorber.
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Пятакович, В. А., В. Ф. Рычкова, and А. П. Пурденко. "Mathematical models for evaluating the effectiveness of shock-absorbing fasteners of vibro-active mechanisms of marine objects by vibrational power." MORSKIE INTELLEKTUAL`NYE TEHNOLOGII)</msg>, no. 4(54) (December 2, 2021): 13–20. http://dx.doi.org/10.37220/mit.2021.54.4.083.
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Для создания виброакустической защиты судового оборудования необходимо учитывать потоки колебательной энергии, распространяющиеся от источников как через опорные и неопорные связи, так и в виде воздушного шума. В работе представлены математические модели оценки эффективности амортизирующих креплений виброактивных механизмов морских объектов по колебательной мощности, учитываемые при обучении разрабатываемой нейросетевой системы классификации морских целей. Теоретические разработки в области виброзащиты и виброизоляции во многом имеют междисциплинарный характер и опираются на методы теории механизмов и машин, теоретической механики, теории колебаний, теории управления, используются методы инфорьт мационные технологии для оценки, поиска и выбора рациональных проектно-конструкторских решений. Создание амортизирующих устройств, способных защитить объекты от вибраций и ударов и, вместе с тем, обладающих ограниченными размерами, является сложной технической проблемой. В связи с этим первостепенное значение приобретают вопросы теории и расчета адаптивных виброзащитных систем. To create vibro-acoustic protection of ship equipment, it is necessary to take into account the flows of vibrational energy propagating from sources both through support and non-support connections, and in the form of air noise. The paper presents mathematical models for evaluating the effectiveness of shock-absorbing fasteners of vibro-active mechanisms of marine objects by vibrational power, which are taken into account when training the developed neural network system for classifying marine targets. Theoretical developments in the field of vibration protection and vibration isolation are largely interdisciplinary in nature and are based on the methods of the theory of mechanisms and machines, theoretical mechanics, vibration theory, control theory, information technology methods are used to evaluate, search and select rational design solutions. The creation of shock-absorbing devices that can protect objects from vibrations and shocks and, at the same time, have limited dimensions is a complex technical problem. In this regard, the issues of the theory and calculation of adaptive vibration protection systems are of paramount importance.
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Li, Jun, and Zhi Ming Qu. "Application of Much-Touted Stochastic Algorithm in Investigating Active Networks and World Wide Web." Advanced Materials Research 143-144 (October 2010): 62–66. http://dx.doi.org/10.4028/www.scientific.net/amr.143-144.62.
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Using the theory of explosion mechanics and gas detonation dynamics and the conservation law of mass, momentum and energy, the physical and mathematical models of damage effect are set up in excavation roadway during gas explosion. In view of gas concentration, accumulation position, volumes and states of spaces, the shock wave damage on structures in the roadway during gas explosion. The damage effects are characterized of heat and mechanic damage. Meanwhile, the high temperature and pressure are formed in different degree. With the action of overpressure and impulse, the damage degree is different with different geometric structures in ventilation system. By means of basic condition, influential factors, procedure features and simulation, some unnecessary structures or barriers should be cleared in order to keep smooth the ventilation system.
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SHPACHUK, Vladimir, Aleksandr CHUPRYNIN, Tatiana SUPRUN, and Andriy KOVALENKO. "MECHANICAL INTERACTION OF THE RAIL TRANSPORT CAR AND JOINT IRREGULARITY." Scientific Journal of Silesian University of Technology. Series Transport 113 (December 1, 2021): 173–89. http://dx.doi.org/10.20858/sjsutst.2021.113.14.
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Mechanical models of a transport system “carriage - track” while crossing a joint irregularity are proposed. An investigation was conducted on the peculiarities of static, shock and dynamic interaction between the four-axle car and the track, considering tram wheelsets motion features over joint irregularity. A method to solve the equations of a mathematical model of static, shock and dynamic interaction is developed. Numerical analysis is used to determine deflections of the facing rail under the first sleeper for each phase of motion depending on motion phases, and car load and speed.
10
Kou, Farong, Qiangqiang Jing, Chen Chen, and Jianghao Wu. "Endocrine Composite Skyhook-Groundhook Control of Electromagnetic Linear Hybrid Active Suspension." Shock and Vibration 2020 (February 29, 2020): 1–17. http://dx.doi.org/10.1155/2020/3402168.
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In order to effectively improve vehicle riding comfort, handling stability, and realize vibration energy recovery, a new kind of electromagnetic linear hybrid active suspension (EMLHAS) integrated with linear motor and solenoid valve shock absorber is put forward. Firstly, for the analysis of the suspension performance, a quarter dynamic model of EMLHAS is established. At the same time, the mathematical models of a linear motor, including the active state and energy-regenerative state, are found. The correctness of mathematical models for the linear motor in the active and energy-regenerative states is verified by means of characteristic tests. Moreover, the velocity characteristic tests of solenoid valve shock absorber are carried out to determine its mathematical polynomial model in the semiactive state. Then, a new kind of multimode endocrine composite skyhook-groundhook control strategy is proposed. The suspension motion is divided into four modes according to the driving conditions of the vehicle. An endocrine control with long feedback and short feedback is combined with the skyhook-groundhook control. The control laws of the skyhook-groundhook controller and endocrine controller are, respectively, designed. Finally, the simulation analysis of suspension dynamic performance and energy-regenerative characteristic is done. The results show the control effect of endocrine composite skyhook-groundhook control is better than that of skyhook-groundhook control, which improves vehicle riding comfort and handling stability. Moreover, part of vibration energy is recovered.
11
Dudko, Olga V., Victoria E. Ragozina, and Anastasia A. Lapteva. "Mathematical Modeling the Nonlinear 1D Dynamics of Elastic Heteromodular and Porous Materials." Materials Science Forum 945 (February 2019): 899–905. http://dx.doi.org/10.4028/www.scientific.net/msf.945.899.
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Approaches to mathematical modeling of nonlinear strain dynamics in heteromodular and porous materials are discussed; the mechanical properties of media are described in terms of the simple piecewise linear elastic models. Several nonstationary 1D boundary value problems show that the singularity of model relationships gives rise to shock waves and centered Riemann waves in generalized solutions. Nonstationary load modes leading to the listed nonlinear effects are indicated separately for heteromodular and porous media.
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Balandin, Dmitry V., Nikolai N. Bolotnik, Walter D. Pilkey, and Sergey V. Purtsezov. "Impact Isolation Limiting Performance Analysis for Three-Component Models." Journal of Dynamic Systems, Measurement, and Control 127, no. 3 (November 17, 2004): 463–71. http://dx.doi.org/10.1115/1.1978914.
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For the crashworthiness analysis of transport vehicles a three-component system that consists of a base, a container, and an object to be protected, connected by shock isolators, can be utilized as a model. An approach for a limiting performance analysis of shock isolation for such a model is proposed. This approach involves the reduction of the optimal control problem for the three-component system to an auxiliary optimal control problem for a two-component system. A detailed description of the technique for the determination of the absolute minimum of the performance index and construction of the optimal control is presented. A proposition that provides a mathematical substantiation for this technique is stated and proven. Example problems included in the paper demonstrate the effectiveness of the proposed technique.
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Safronov, Oleksandr, Bohdan Semon, Oleksandr Nedilko, and Yurii Bodryk. "Mathematical Models of Transonic Flatter of Aerody-namic Control Surfaces of Supersonic Aircraft." Advances in Military Technology 17, no. 2 (September 1, 2022): 195–209. http://dx.doi.org/10.3849/aimt.01543.
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In the article, the joint analysis of the Bernoulli equations for compressed gas, variations of the supersonic flow parameters of the Prandtl-Meyer expansion fan and the hypothesis of aerofoil dynamic curvature were used to develop a linear and a nonlinear mathematical models describing the occurrence of transonic flutter of aerodynamic control surfaces of supersonic aircraft. The analysis of the obtained mathematical models confirms a theoretical possibility of the occurrence of transonic flutter of aerodynamic control surfaces of supersonic aircraft that is due to the peculiarities of the interaction of shock waves with the angular velocity of elastic bending oscillations of aerodynamic control surfaces.
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Dzhamgarov, S. G., V. I. Oleynikov, V. A. Trudonoshin, and V. G. Fedoruk. "Simulation of Aircraft Landing." Mechanical Engineering and Computer Science, no. 8 (October 22, 2018): 1–10. http://dx.doi.org/10.24108/0818.0001405.
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The article proposes a mathematical model of the aircraft landing upon touchdown operation. The mathematical model can be used at the early design stages to select the rational parameters of shock absorbers to ensure soft landing. Unlike most of the papers in the field concerned, it describes the simulation of the aircraft's run-out process rather than the first touchdown impact or Dynamic Drop Testing. This is due to the use of three-dimensional mathematical models of mechanical systems, including the aircraft body. In addition to the forces on the aircraft, the article gives a sufficiently detailed representation of the forces that arise in the shock absorber. The simulation results obtained using the PA8 complex developed at the CAD Department in Bauman Moscow State Technical University are presented. The diagrams presented show the effect of the clearance in the chambers of recovery stroke on the operation of shock absorbers and, as a consequence, on ensuring the soft landing conditions. An object-oriented approach, implemented in the complex, allows us to evaluate the influence of each element on the system dynamics. The article presents the time diagrams of the force of a gas spring taking into account the dry friction and the hydraulic force in the shock absorber. In conclusion, a rational, in authors’ opinion, approach to designing shock absorbers is shown. One of the points of this approach is the validation of shock absorber parameters based on the results of Dynamic Drop Testing and, after that, simulation of the aircraft landing with validated parameters. Such a technique will allow us to minimize the number of field experiments, and as a result, will shorten the design time and put the product into operation.
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Chai, Yuzhen, Tingting Jia, Huiqin Hao, and Jianwen Zhang. "Exp-Function Method for a Generalized MKdV Equation." Discrete Dynamics in Nature and Society 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/153974.
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Under investigation in this paper is a generalized MKdV equation, which describes the propagation of shallow water in fluid mechanics. In this paper, we have derived the exact solutions for the generalized MKdV equation including the bright soliton, dark soliton, two-peak bright soliton, two-peak dark soliton, shock soliton and periodic wave solution via Exp-function method. By figures and symbolic computations, we have discussed the propagation characteristics of those solitons under different values of those coefficients in the generalized MKdV equation. The method constructing soliton solutions in this paper may be useful for the investigations on the other nonlinear mathematical physics model and the conclusions of this paper can give theory support for the study of dynamic features of models in the shallow water.
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Goncalves Da Silva, Eric, and Philippe Parnaudeau. "Comparison of multiphase models for computing shock-induced bubble collapse." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 8 (November 22, 2019): 3845–77. http://dx.doi.org/10.1108/hff-05-2019-0399.
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Purpose The purpose of this paper is to quantify the relative importance of the multiphase model for the simulation of a gas bubble impacted by a normal shock wave in water. Both the free-field case and the collapse near a wall are investigated. Simulations are performed on both two- and three-dimensional configurations. The main phenomena involved in the bubble collapse are illustrated. A focus on the maximum pressure reached during the collapse is proposed. Design/methodology/approach Simulations are performed using an inviscid compressible homogeneous solver based on different systems of equations. It consists in solving different mixture or phasic conservation laws and a transport-equation for the gas volume fraction. Three-dimensional configurations are considered for which an efficient massively parallel strategy was developed. The code is based on a finite volume discretization for which numerical fluxes are computed with a Harten, Lax, Van Leer, Contact (HLLC) scheme. Findings The comparison of three multiphase models is proposed. It is shown that a simple four-equation model is well-suited to simulate such strong shock-bubble interaction. The three-dimensional collapse near a wall is investigated. It is shown that the intensity of pressure peaks on the wall is drastically increased (more than 200 per cent) in comparison with the cylindrical case. Research limitations/implications The study of bubble collapse is a key point to understand the physical mechanism involved in cavitation erosion. The bubble collapse close to the wall has been addressed as the fundamental mechanism producing damage. Its general behavior is characterized by the formation of a water jet that penetrates through the bubble and the generation of a blast wave during the induced collapse. Both the jet and the blast wave are possible damaging mechanisms. However, the high-speed dynamics, the small spatio-temporal scales and the complicated physics involved in these processes make any theoretical and experimental approach a challenge. Practical implications Cavitation erosion is a major problem for hydraulic and marine applications. It is a limiting point for the conception and design of such components. Originality/value Such a comparison of multiphase models in the case of a strong shock-induced bubble collapse is clearly original. Usually models are tested separately leading to a large dispersion of results. Moreover, simulations of a three-dimensional bubble collapse are scarce in the literature using such fine grids.
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Zhang, Xue-bo, Jian-liang Gao, Jing-zhang Ren, and Chun-xia Wang. "Analysis of the Characteristics and Influencing Factors of Gas Explosion in Heading Face." Shock and Vibration 2020 (October 29, 2020): 1–11. http://dx.doi.org/10.1155/2020/8871865.
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In order to accurately grasp the characteristics and influencing factors of gas explosion in heading face, the mathematical model of gas explosion was determined. According to the actual size of a heading face of a coal mine, a 3D geometric model with a length of 100 m was established, and the effects of ignition energy and gas explosion equivalent on the gas explosion characteristics of the heading face were analyzed. The results show the following. (1) The mathematical models for numerical simulation of gas explosion can accurately simulate the gas explosion and its propagation process. The time-space step size has a great influence on the simulation results. The grid spacing for numerical simulation of mine gas explosion is determined to be 0.1 m and the time step length is determined to be 0.001 s. (2) The ignition energy has a limited effect on gas explosion characteristics. It only has a certain influence on the gas explosion process, but has little influence on the overpressure of shock wave. The larger the ignition energy is, the faster the explosion reaction speed is, and the maximum overpressure increases slightly. When the ignition energy increases to a certain value, the time of peak shock wave and the maximum overpressure both tend to be stable. The ignition energy has little effect on gas explosion characteristics when an explosion accident occurs underground with a large amount of gas accumulation. (3) The gas explosion equivalent has a great influence on the overpressure of gas explosion shock wave. The higher the explosion equivalent is, the greater the pressure is, and the peak value of the shock wave overpressure increases with the explosion equivalent as a power function. The research results have important guiding significance for the research and development of new technology for prevention and control of gas explosion.
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Tahani, Mojtaba, Mehran Masdari, Hamidreza Eivazi, and Massoud Tatar. "Assessment of turbulence models for transonic oscillating airfoil." International Journal of Numerical Methods for Heat & Fluid Flow 27, no. 11 (November 6, 2017): 2603–28. http://dx.doi.org/10.1108/hff-04-2016-0142.
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Purpose This paper aims to investigate numerical solution of transonic flow around NACA0012 airfoil under sinusoidal pitch oscillation. Accordingly, effects of the amplitude and frequency of oscillations on aerodynamic coefficients are evaluated and the efficiency of the turbulent models, K-ω shear-stress transport (SST), scale adaptive simulation (SAS) and delayed detached eddy simulation (DDES), in simulation of the nonlinear phenomena – i.e. the interaction between shock and boundary layer and the shock oscillations – is studied. Design/methodology/approach K-ω SST, SAS and DDES models are used as turbulence approaches. The numerical results are compared with available experimental and numerical information. Findings According to the results inside the buffet boundaries, the DDES turbulent model expresses results that are more appropriate; however, SAS and SST models are not efficient enough in evaluating the characteristics of nonlinear flow. Originality/value In this research study, hybrid RANS-LES turbulence model is engaged to simulate transonic flow around pitching NACA0012 airfoil, and results are compared to the SAS and Reynolds Average Navier–Stocks simulations as well as available numerical and experimental data. In addition, effects of the amplitude and frequency of oscillations on aerodynamic coefficients are evaluated in buffet regions.
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Semenov, A., A. Smirnov, M. Stepanov, N. Kharaldin, and A. Borovkov. "The simplified approach to numerical modeling of polyurethane foam shock absorbers of complex structure: determination of effective mechanical properties and preparation of mathematical models of a homogenized material." Journal of Physics: Conference Series 2131, no. 4 (December 1, 2021): 042056. http://dx.doi.org/10.1088/1742-6596/2131/4/042056.
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Abstract The first part of this paper is devoted to modeling foam taking into account the effect of strain rate on material behavior in the LS-Dyna software package for solving dynamic problems in a wide range of speeds. The MAT_083 material model was used, which analyzes the stress-strain state considering the dependence on the strain rate. The process of adaptation of experimental data for use in the MAT_083 material model is described. The second part of this study touches upon the homogenization of the properties of a shock absorber consisting of SKU-PFL-100 polyurethane (the modeling approach is described in the previous article) and polyurethane foam, the model of which is described in the first part of this paper. Homogenization of the shock absorber is carried out in order to reduce the number of elements in the problem and, accordingly, to improve the calculation performance. The stress-strain curves obtained during the compression of a shock absorber are used in the material MAT_083.
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Blickhan, Reinhard, Andre Seyfarth, Hartmut Geyer, Sten Grimmer, Heiko Wagner, and Michael Günther. "Intelligence by mechanics." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1850 (November 17, 2006): 199–220. http://dx.doi.org/10.1098/rsta.2006.1911.
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Research on the biomechanics of animal and human locomotion provides insight into basic principles of locomotion and respective implications for construction and control. Nearly elastic operation of the leg is necessary to reproduce the basic dynamics in walking and running. Elastic leg operation can be modelled with a spring-mass model. This model can be used as a template with respect to both gaits in the construction and control of legged machines. With respect to the segmented leg, the humanoid arrangement saves energy and ensures structural stability. With the quasi-elastic operation the leg inherits the property of self-stability, i.e. the ability to stabilize a system in the presence of disturbances without sensing the disturbance or its direct effects. Self-stability can be conserved in the presence of musculature with its crucial damping property. To ensure secure foothold visco-elastic suspended muscles serve as shock absorbers. Experiments with technically implemented leg models, which explore some of these principles, are promising.
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Li, Changping, Longchen Duan, Songcheng Tan, Victor Chikhotkin, and Xiaohui Wang. "An Electro Breakdown Damage Model for Granite and Simulation of Deep Drilling by High-Voltage Electropulse Boring." Shock and Vibration 2019 (November 29, 2019): 1–12. http://dx.doi.org/10.1155/2019/7149680.
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Electropulse rock breaking has wide application prospects in hard rock drilling and ore breaking. At present, there are no suitable physical mathematical models that describe electropulse boring (EPB) processes under confining pressures. In this paper, a high-voltage electropulse breakdown damage model is established for granite, which includes three submodels. It considers electric field distortions inside the rock, and an electric field distribution coefficient is introduced in the electro-breakdown model. A shock-wave model is also constructed and solved. To simulate the heterogeneity of rocks, EPB rock breaking in deep environments is simulated using the two-dimensional Particle Flow Code (PFC2D) program. The solved shock wave is loaded into the model, and confining pressure is applied by the particle servo method. An artificial viscous boundary is used in the numerical simulation model. Using this approach, a complete numerical simulation of electropulse granite breaking is achieved. Breakdown strength and the influences of physical and mechanical parameters on it are also obtained. Time-varying waveforms of electrical parameters are obtained, and the effect of confining pressure on EPB is also described.
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Tikhov-Tinnikov, Dmitry A. "METHODS FOR MONITORING THE TECHNICAL CONDITION OF THE SUSPENSION OF VEHICLE UNDER OPERATING CONDITIONS." International Journal of Advanced Studies 11, no. 4 (December 30, 2021): 18–30. http://dx.doi.org/10.12731/2227-930x-2021-11-4-18-30.
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Suspension faults can reduce wheel traction and therefore reduce vehicle stability. Existing diagnostic methods for the suspension do not take into account the stability of the vehicle. To control stability, it is proposed to use road and bench methods, characterized by suspension vibrations and constant lateral force. Theoretical studies were carried out using mathematical models based on the description of the functioning of sprung and unsprung vehicle masses, as well as elastic tires. Experimental studies include bench tests of tires, shock absorbers and silent blocks of various technical conditions, as well as road studies of the kinematic parameters of the M1 category vehicle. As a result, a road method for monitoring the technical condition of shock absorbers was developed, taking into account their influence on stability indicators.
Purpose – Theoretical substantiation and experimental confirmation of the method for diagnosing suspension systems by parameters related to the stability of the vehicle movement.
Methodology includes experimental methods, mathematical modeling methods and numerical methods for solving differential equations.
Results: experimental methods and mathematical apparatus were developed to study the influence of the parameters of the suspension system on the stability of the movement of vehicles.
Practical implications: the results can be used by organizations and institutions involved in the development of diagnostic methods for vehicles.
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Sebesan, Ioan, Gabriel Popa, and Marius Adrian Spiroiu. "Researches on the Behavior of the Supporting Structure of Railway Traction Vehicles under the Effect of Shock Dynamic Forces." Applied Mechanics and Materials 659 (October 2014): 237–42. http://dx.doi.org/10.4028/www.scientific.net/amm.659.237.
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During circulation the railway vehicle is subjected to the action of dynamic forces under the effect of shocks that appear in the driving system caused by stick slip phenomenon, dynamic forces arising from the rolling process when the wheelset is passing over accidental vertical unevenness of the track and also longitudinal dynamic forces occurring in the case of buffering, respectively those caused by frontal impact (the crash forces). The present paper presents the mechanical and mathematical models which are underlying the evaluation of the magnitude of these forces as well as their effects on the resistance of supporting structure of the vehicle and on traffic safety.
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Zimin, V. N., A. V. Krylov, G. N. Kuvyrkin, and A. O. Shakhverdov. "Development of a mathematical model of a force actuator for the opening of a space structure with transformable configuration." Journal of Physics: Conference Series 2231, no. 1 (April 1, 2022): 012029. http://dx.doi.org/10.1088/1742-6596/2231/1/012029.
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Abstract The prospects for the development of radio astronomy, solar energy, space communications, exploration of the Earth’s surface and other planets from space are currently associated with the creation of fundamentally new large-sized space structures. The inevitable complication of the design schemes of promising large-sized systems due to the increase in their operational functionality requires the development of mathematical models that adequately describe the mechanical properties of structures. When designing large-sized systems, the scheme of which allows for automatic configuration change of the structure, it is necessary to take into account shock loads. They inevitably arise when the working state of the structure fixes in orbit upon completion of the process of its opening. To ensure smooth, reliable and shock-free opening of large-sized space structures, it is proposed to use force actuators with active elements made of titanium nickelide material with a shape memory effect. During the tests of the active elements, the main parameters of the force actuator were determined: the generated force, the actuation time and the length of the working stroke. The length of the working stroke was determined by the change in the relative elongation of the active element of the force actuator during its heating. The conducted experimental and theoretical studies are aimed at developing a mathematical model of the functioning of an active element made of titanium nickelide with a shape memory effect for the opening of a space structure with transformable configuration.
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Zimin, V. N., A. V. Krylov, G. N. Kuvyrkin, and A. O. Shakhverdov. "Development of a mathematical model of a force actuator for the opening of a space structure with transformable configuration." Journal of Physics: Conference Series 2231, no. 1 (April 1, 2022): 012029. http://dx.doi.org/10.1088/1742-6596/2231/1/012029.
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Abstract The prospects for the development of radio astronomy, solar energy, space communications, exploration of the Earth’s surface and other planets from space are currently associated with the creation of fundamentally new large-sized space structures. The inevitable complication of the design schemes of promising large-sized systems due to the increase in their operational functionality requires the development of mathematical models that adequately describe the mechanical properties of structures. When designing large-sized systems, the scheme of which allows for automatic configuration change of the structure, it is necessary to take into account shock loads. They inevitably arise when the working state of the structure fixes in orbit upon completion of the process of its opening. To ensure smooth, reliable and shock-free opening of large-sized space structures, it is proposed to use force actuators with active elements made of titanium nickelide material with a shape memory effect. During the tests of the active elements, the main parameters of the force actuator were determined: the generated force, the actuation time and the length of the working stroke. The length of the working stroke was determined by the change in the relative elongation of the active element of the force actuator during its heating. The conducted experimental and theoretical studies are aimed at developing a mathematical model of the functioning of an active element made of titanium nickelide with a shape memory effect for the opening of a space structure with transformable configuration.
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Wu, Wangxia, Gaoming Xiang, and Bing Wang. "On high-speed impingement of cylindrical droplets upon solid wall considering cavitation effects." Journal of Fluid Mechanics 857 (October 30, 2018): 851–77. http://dx.doi.org/10.1017/jfm.2018.753.
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The high-speed impingement of droplets on a wall occurs widely in nature and industry. However, there is limited research available on the physical mechanism of the complicated flow phenomena during impact. In this study, a simplified multi-component compressible two-phase fluid model, coupled with the phase-transition procedure, is employed to solve the two-phase hydrodynamics system for high-speed cylindrical droplet impaction on a solid wall. The threshold conditions of the thermodynamic parameters of the fluid are established to numerically model the initiation of phase transition. The inception of cavitation inside the high-speed cylindrical droplets impacting on the solid wall can thus be captured. The morphology and dynamic characteristics of the high-speed droplet impingement process are analysed qualitatively and quantitatively, after the mathematical models and numerical procedures are carefully verified and validated. It was found that a confined curved shock wave is generated when the high-speed cylindrical droplet impacts the wall and this shock wave is reflected by the curved droplet surface. A series of rarefaction waves focus at a position at a distance of one third of the droplet diameter away from the top pole due to the curved surface reflection. This focusing zone is identified as the cavity because the local liquid state satisfies the condition for the inception of cavitation. Moreover, the subsequent evolution of the cavitation zone is demonstrated and the effects of the impact speed, ranging from $50$ to $200~\text{m}~\text{s}^{-1}$ , on the deformation of the cylindrical droplet and the further evolution of the cavitation were studied. The focusing position, where the cavitation core is located, is independent of the initial impaction speed. However, the cavity zone is enlarged and the stronger collapsing wave is induced as the impaction speed increases.
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Kassoy, D. R. "The Zeldovich spontaneous reaction wave propagation concept in the fast/modest heating limits." Journal of Fluid Mechanics 791 (February 22, 2016): 439–63. http://dx.doi.org/10.1017/jfm.2015.756.
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Quantitative mathematical models describe planar, spontaneous, reaction wave propagation (Zeldovich, Combust. Flame, vol. 39, 1980, pp. 211–214) in a finite hot spot volume of reactive gas. The results describe the complete thermomechanical response of the gas to a one-step, high-activation-energy exothermic reaction initiated by a tiny initial temperature non-uniformity in a gas at rest with uniform pressure. Initially, the complete conservation equations, including all transport terms, are non-dimensionalized to identify parameters that quantify the impact of viscosity, conduction and diffusion. The results demonstrate unequivocally that transport terms are tiny relative to all other terms in the equations, given the relevant time and length scales. The asymptotic analyses, based on the reactive Euler equations, describe both induction and post-induction period models for a fast heat release rate (induction time scale short compared to the acoustic time of the spot), as well as a modest heat release rate (induction time scale equivalent to the acoustic time). Analytical results are obtained for the fast heating rate problem and emphasize the physics of near constant-volume heating during the induction period. Weak hot spot expansion is the source of fluid expelled from the original finite volume and is a ‘piston-effect’ source of acoustic mechanical disturbances beyond the spot. The post-induction period is characterized by the explosive appearance of an ephemeral, spatially uniform high-temperature, high-pressure spot embedded in a cold, low-pressure environment. In analogy with a shock tube the subsequent expansion process occurs on the acoustic time scale of the spot and will be the source of shocks propagating beyond the spot. The modest heating rate induction period is characterized by weakly compressible phenomena that can be described by a novel system of linear wave equations for the temperature, pressure and induced velocity perturbations driven by nonlinear chemical heating, which provides physical insights difficult to obtain from the more familiar ‘Clarke equation’. When the heating rate is modest, reaction terms in the post-induction period Euler equations exhibit a form of singular behaviour in the high-activation-energy limit, implying the need to use a nonlinear exponential scaling for time and space, developed originally to describe spatially uniform thermal explosions (Kassoy, Q. J. Mech. Appl. Maths, vol. 30, 1977, pp. 71–89). Here again the result will be the explosive appearance of an ephemeral spatially uniform high-temperature, high-pressure hot spot. These results demonstrate that an initially weak temperature non-uniformity in a finite hot spot can be the source of acoustic and shock wave mechanical disturbances in the gas beyond the spot that may be related to rocket engine instability and engine knock.
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Shcherbakov, L. N., Yu P. Mansur, D. V. Verstakov, T. S. Kochkonyan, D. A. Domenyuk, E. N. Ivancheva, and S. D. Domenyuk. "Biomechanical virtual planning of the stress-strain state of the func-tional masticatory center." Medical alphabet, no. 34 (January 13, 2023): 44–52. http://dx.doi.org/10.33667/2078-5631-2022-34-44-52.
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A feature of mathematical modeling and study of a complex three-dimensional biomechanical object is the ability to achieve unity of geometric, physical, mechanical and biological indicators with the individual characteristics of the patient. A rather urgent problem of clinical dentistry is the development of recommendations on the distribution of masticatory pressure in patients with balanced occlusal-articulation relationships of the dentition. This paper considers one of the aspects of this problem associated with modeling the stress-strain state of the functional masticatory center, which is localized in the region of the first molars and the premolar groups of the upper and lower jaws during physiological occlusion. To determine the biomechanical parameters of the functional masticatory center, an analysis of the stress-strain state of mathematical models of this fragment of the dentition was carried out using the finite element method. When developing a model of a biomechanical system, the surrounding biological tissues were considered discretely in terms of structure and physical and mechanical properties: dentin, enamel, periodontium, bone, cement. A technique for analyzing models of the functional masticatory center is proposed, which makes it possible to establish the relationship between the magnitudes and directions of functional loads, as well as internal stresses and deformations. As a result of the analysis of the stress-strain state of geometric and finite element models, the distributions of maximum strains and stresses in a given section under the action of specified loads were obtained. It has been established that under the conditions of this mathematical model, the areas of the apical periodontium of the teeth have the maximum shock-absorbing properties, and the functional masticatory center is equated to a static system. The capabilities of modern computer software make it possible to expand the understanding of areas of stress concentration with varying load parameters in the functional masticatory center in order to determine the most “critical” zones in order to predict and prevent the development of long-term complications.
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Gomez, Q., and I. R. Ionescu. "Micro-mechanical fracture dynamics and damage modelling in brittle materials." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379, no. 2196 (March 15, 2021): 20200125. http://dx.doi.org/10.1098/rsta.2020.0125.
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This study explores the interplay between wave propagation and damage in brittle materials. The damage models, based on micro-mechanical fracture dynamics, capture any possible unstable growth of micro-cracks, introducing a macroscopic loss of stability. After stating the non-dimensional mathematical problem describing the wave propagation with damage, we introduce a non-dimensional number, called the microscopic evolution index, which links the micro and macro scales and discriminates the microscopic scale behaviour. For large values of microscopic evolution index, corresponding to a microscopic quasi-static process coupled with a macroscopic dynamic one, the macroscopic dynamic system could lose its hyperbolicity or become very stiff and generate shock waves. A semi-analytical solution to the one-dimensional wave propagation problem with damage, which could be very useful in the accuracy evaluation of the numerical schemes, was constructed. Concerning the asymptotic behaviour of the dynamic exact solution on the microscopic evolution index (or on the strain rate), an important strain rate sensitivity was found: the pulse loses its amplitude for decreasing strain rate and, starting with a critical value, the micro-scale model is rate independent. A possible regularization technique to smooth the shock waves at low and moderate strain rates is discussed. Finally, some numerical results analyse the role played by the the friction on the micro-cracks in the damage modelling of blast wave propagation. This article is part of the theme issue ‘Fracture dynamics of solid materials: from particles to the globe’.
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Suhir, E. "Could Shock Tests Adequately Mimic Drop Test Conditions?" Journal of Electronic Packaging 124, no. 3 (July 26, 2002): 170–77. http://dx.doi.org/10.1115/1.1487356.
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Drop tests are often substituted in qualification or life testing of microelectronic and optoelectronic products by shock tests. The existing (e.g., Telcordia) qualification specifications require that a short term load of the given magnitude and duration (say, an “external” acceleration with the maximum value of 500 g, acting for 0.001 s) is applied to the support structure of the product under test. The natural frequencies of vibration are not taken into account. The objective of our study is to develop simple analytical (“mathematical”) predictive models for the evaluation of the dynamic response of a structural element in a microelectronic or an optoelectronic product/package to an impact load occurring as a result of drop or shock tests. We use the developed models to find out if a shock tester could be “tuned” in such a way that the shock tests adequately mimic drop test conditions. We suggest that the maximum induced curvature and the maximum induced acceleration be used as suitable characteristics of the dynamic response of a structural element to an impact load. Indeed, the maximum curvatures determine the level of the bending stresses, and the maximum accelerations are supposedly responsible for the functional (electronic or photonic) performance of the product. We use the case of an elongated rectangular simply supported plate as an illustration of the suggested concept. We show that in order to adequately mimic drop test conditions, the shock test loading should be as close as possible to an instantaneous impulse, and that the duration of the shock load should be established based on the lowest (fundamental) natural frequency of vibrations. We show also that, for practical purposes, it is sufficient to consider the fundamental mode of vibrations only, and that the shock load does not have to be shorter than, say, half the quarter of the fundamental period. We demonstrate that, if the loading is not short enough, the induced curvatures and accelerations can exceed significantly the curvatures and accelerations in drop test conditions. Certainly, the results of such shock tests will be misleading. After the appropriate duration of the shock impulse is established, the time dependence and the maximum value of the imposed (“external”) acceleration in shock tests should be determined, depending on the most likely drop height, in order to adequately mimic drop test conditions. We demonstrate that the application of a probabilistic approach can be helpful in understanding the mechanical behavior and to ensure high short- and long-term reliability of an electronic or photonic device that might be or will be subjected to an accidental or expected impact loading. We conclude that although it is possible to “tune” the shock tester, so that the drop test conditions are adequately reproduced, actual drop tests should be conducted, whenever possible. The results of the analysis can be helpful in physical design and qualification testing of microelectronic and photonic products, experiencing dynamic loads of short duration.
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Galkin, V. S., and S. V. Rusakov. "Burnett models of the structure of a strong shock wave in a binary mixture of monatomic gases." Journal of Applied Mathematics and Mechanics 67, no. 1 (January 2003): 57–65. http://dx.doi.org/10.1016/s0021-8928(03)00016-9.
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Storm, J., B. Yin, and M. Kaliske. "The concept of Representative Crack Elements (RCE) for phase-field fracture: transient thermo-mechanics." Computational Mechanics 69, no. 5 (January 27, 2022): 1165–76. http://dx.doi.org/10.1007/s00466-021-02135-w.
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AbstractThe phase-field formulation for fracture based on the framework of representative crack elements is extended to transient thermo-mechanics. The finite element formulation is derived starting from the variational principle of total virtual power. The intention of this manuscript is to demonstrate the potential of the framework for multi-physical fracture models and complex processes inside the crack. The present model at hand allows to predict realistic deformation kinematics and heat fluxes at cracks. At the application of fully coupled, transient thermo-elasticity to a pre-cracked plate, the opened crack yields thermal isolation between both parts of the plate. Inhomogeneous thermal strains result in a curved crack surface, inhomogeneous recontact and finally heat flow through the crack regions in contact. The novel phase-field framework further allows to study processes inside the crack, which is demonstrated by heat radiation between opened crack surfaces. Finally, numerically calculated crack paths at a disc subjected to thermal shock load are compared to experimental results from literature and a curved crack in a three-dimensional application are presented.
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Li, Mingjun, and Li Zhu. "Interfacial instability of ferrofluid flow under the influence of a vacuum magnetic field." Applied Mathematics and Mechanics 42, no. 8 (July 24, 2021): 1171–82. http://dx.doi.org/10.1007/s10483-021-2758-7.
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AbstractThis study is to numerically test the interfacial instability of ferrofluid flow under the presence of a vacuum magnetic field. The ferrofluid parabolized stability equations (PSEs) are derived from the ferrofluid stability equations and the Rosensweig equations, and the characteristic values of the ferrofluid PSEs are given to describe the ellipticity of ferrofluid flow. Three numerical models representing specific cases considering with/without a vacuum magnetic field or viscosity are created to mathematically examine the interfacial instability by the computation of characteristic values. Numerical investigation shows strong dependence of the basic characteristic of ferrofluid Rayleigh-Taylor instability (RTI) on viscosity of ferrofluid and independence of the vacuum magnetic field. For the shock wave striking helium bubble, the magnetic field is not able to trigger the symmetry breaking of bubble but change the speed of the bubble movement. In the process of droplet formation from a submerged orifice, the collision between the droplet and the liquid surface causes symmetry breaking. Both the viscosity and the magnetic field exacerbate symmetry breaking. The computational results agree with the published experimental results.
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Chakroun, Moez, and Med Hédi Ben Ghozlen. "Simulation of Dynamic Rigidity Modulus of Brain Matter by that of Agar Gel." Biophysical Reviews and Letters 11, no. 04 (December 2016): 149–56. http://dx.doi.org/10.1142/s179304801650003x.
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Agar gel is a linear viscoelastic material with low deformations ([Formula: see text]). Here, characterization technique used is the rheometer-type Carri-Med “CSL 100”. This rheometer offers us the opportunity to study the gel in static and dynamic shear. The study is done at low frequencies ([Formula: see text]–[Formula: see text]). Mechanical characterization of the agar gel in terms of dynamic modulus is performed for different concentrations. The dynamic rigidity of the gel decreases with increasing concentration. The 8% agar gel simulates very well the dynamic rigidity of brain tissue at low frequency. The range of low frequencies is rarely studied for this material (brain) in the literature. Most tests done on brain tissue are in a frequency range between [Formula: see text] and [Formula: see text]. Yet, the Maxwell–Kelvin–Voigt model simulates very well the 8% agar gel. The instant elasticity derived from mathematical modeling of agar gel is similar to that measured in the literature for the brain tissue. Hence agar gel can be used in the construction of physical models of the human head used to analyze the dynamic response of the head to shock or to an inertial load.
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Kedrinskii, V. K. "Features of the dynamics of the heavy bubble magma state in explosive volcanic eruptions." Proceedings of the Mavlyutov Institute of Mechanics 9, no. 1 (2012): 104–9. http://dx.doi.org/10.21662/uim2012.1.020.
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The explosive eruption of a volcano that occurs when a volcanic canal is suddenly depressurized is one of the mysterious phenomena of nature, the mechanism of which is associated with the sudden decompression of a high-pressure magma containing dissolved gas and microcrystallites and with its transition to a multiphase state. With the obvious lack of the possibility to directly investigate these processes, the problem of experimental and numerical modeling, and creation of mathematical models that would allow describing the state of magma during various stages of eruption with a certain degree of adequacy are becoming topical. A model combining systems of equations of the mechanics of multiphase media is proposed. The model is formulated on the basis of the modified Iordansky–Kogarko–van Wijngaarden model with the Navier-Stokes equation for the variable viscosity, and the full range of kinetic relationships, including spontaneous nucleation and saturation dynamics of magma with cavitation nuclei. An analysis of a pre-explosive state of a number of volcanoes was carried out, which showed that the structural features of explosive volcanoes are analogous to the schemes of hydrodynamic shock tubes (UT), such as Glass-Heuckroth. Experimental modeling of the flow structure demonstrates the probability of the formation of the projectile regime as a consequence of coalescence of bubbles in the flow. A physical model of combined explosive volcanic eruptions is proposed; the process of formation in the magma flux of an independent flow of crystalline clusters (magmatic ”bombs“) moving with respect to the flow of cavitating magma at a much higher rate is experimentally studied.
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Xu, Jing-Lei, You-Fu Song, Yang Zhang, and Jun-Qiang Bai. "Study of the Shock Wave–Turbulent Boundary Layer Interaction Using a 3D von Kármán Length Scale." International Journal of Nonlinear Sciences and Numerical Simulation 18, no. 1 (February 1, 2017): 57–66. http://dx.doi.org/10.1515/ijnsns-2016-0018.
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AbstractTraditional turbulence models are initially formulated and calibrated under incompressible conditions. Thus, these models are always of low fidelity when extended to high speed, complex and compressible flows. In this work, a compressible von Kármán length scale is proposed for compressible flows considering the variable densities. The length scale is the ratio between the new vorticity and its gradient. The new length scale is actually based on phenomenological theory, which is then integrated into the KDO (turbulence Kinetic energy Dependent Only) turbulence model, arriving at a compressible model called CKDO (Compressible KDO). In the CKDO turbulence model, all the extra terms produced by compressibility are modeled as dissipation. Compression corners of 8, 16, 20 and 24 angles are studied within SST, SA, KDO and CKDO. These test cases are known as the typical shock wave–boundary layer interactions. The results show that the new length scale in CKDO is able to well capture the surface pressure and skin friction distributions. Besides, compared with the standard von Kármán length scale, the new length scale in CKDO can better capture the size and position of the separation bubble. With the increase of the corner angle, CKDO shows more prominent potential for describing compressible flows.
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Meshcheryakov, Viktor, Tatyana Sinyukova, Vladislav Gladyshev, Alexey Sinyukov, Lyudmila Solovieva, and Elena Gracheva. "Modeling and analysis of vector control systems for asynchronous motor." E3S Web of Conferences 220 (2020): 01075. http://dx.doi.org/10.1051/e3sconf/202022001075.
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At metallurgical enterprises, slab transfer devices are widely used, the principle of operation of which is to lift slabs in the steel casting area and transport them to the storage area. The article considers the existing control system of the slab transfer device. At the moment, the mechanism has a DC motor controlled by a thyristor Converter. This system is difficult to maintain and has a large size. As an upgrade, the installation of an asynchronous motor with a frequency Converter is proposed. In the Matlab environment, mathematical models of single-circuit and double-circuit DC motor control systems and a model of asynchronous motor with a short-circuited rotor have been developed. A vector control system is used as an AC motor control system. As a result of simulation performed analysis of the characteristics. As an optimization of the system with vector control, in order to reduce dynamic loads on the turntable, it is proposed to introduce an intensity setter into the system, the use of which provides the necessary restriction of accelerations and jerks, reduces shock loads on the mechanical components of the electric drive, including a reduction in the load on the turntable when lowering the slab.
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Costanzi, M., and D. Cebon. "An investigation of the effects of lorry suspension performance on road maintenance costs." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 221, no. 11 (November 1, 2007): 1265–77. http://dx.doi.org/10.1243/09544062jmes639.
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A mathematical model of the interaction between a fleet of heavy vehicles and a spraysealed road surface is developed and validated using field performance data. Key features of the model include: (a) modelling the dynamic performance of the vehicle fleet using an ensemble of ‘quarter car’ vehicle models; (b) careful accounting for the ‘spatial repeatability’ of tyre forces; (c) use of accelerated pavement performance test data to model the evolution of the road surface profile; (d) surface maintenance intervention based on permanent deformation (rutting), potholing and excessive surface roughness. The model is used to predict long-term road maintenance intervention costs and to compare the predicted road maintenance costs for various suspension scenarios in the vehicle fleet. The simulation results indicate that conversion of the heavy vehicle fleet from conventional leaf spring suspensions to ‘road-friendly’ suspensions would results in a reduction in road maintenance costs per tonne-km of 14 per cent. Increasing the freight load by 3.0 tonnes per vehicle would reduce this benefit to approximately 1 per cent. If the fleet was to have 50 per cent poorly maintained shock absorbers, the simulations show an increase in road maintenance expenditures per tonne-km: about 5 per cent higher than conventional suspensions at the lower weights and 21 per cent higher at the higher weights.
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Tirskii, G. A., and S. V. Utyuzhnikov. "A comparison of the models of a thin and a complete viscous shock layer in the problem of the supersonic flow of a viscous gas past blunt cones." Journal of Applied Mathematics and Mechanics 53, no. 6 (January 1989): 762–67. http://dx.doi.org/10.1016/0021-8928(89)90083-x.
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Shan, Hua, Jianzhong Su, Jiansen Zhu, and Leon Xu. "Three-Dimensional Modeling and Simulation of a Falling Electronic Device." Journal of Computational and Nonlinear Dynamics 2, no. 1 (August 4, 2006): 22–31. http://dx.doi.org/10.1115/1.2389039.
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This article focuses on a realistic mathematical model for multiple impacts of a rigid body to a viscoelastic ground and its comparison to theoretic results. The methodology is used to study impact on an electronic device. When an electronic device drops to the floor at an uneven level, the rapid successions of impact sequence are important for their shock response to internal structure of the devices. A three-dimensional, continuous contact, computational impact model has been developed to simulate a sequence of multiple impacts of a falling rigid body with the ground. The model simulates the impact procedure explicitly and thus is capable of providing detailed information regarding impact load, impact contact surface, and the status of the body during the impact. For the purposes of model verification, we demonstrate the numerical simulation of a falling rod problem, in which the numerical results are in good agreement with the analytic solutions based on discrete contact dynamics impact models. It is indicated by the numerical experiments that simultaneous impacts occurred to multiple locations of the body and that subsequent impacts might be larger than initial ones due to different angles of impact. The differential equation-based computational model is shown to be realistic and efficient in simulating impact sequence and laid a foundation for detailed finite element analysis of the interior impact response of an electronic device.
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SHCHERBAN, VOLODYMYR, JULY MAKARENKO, OKSANA KOLISKO, LUDMILA HALAVSKA, and YURYJ SHCHERBAN. "COMPUTER IMPLEMENTATION OF RECURSION ALGORITHM DETERMINATION OF THREAD TENSION DURING FORMATION OF MULTILAYER FABRICS FROM POLYETHYLENE THREADS." HERALD OF KHMELNYTSKYI NATIONAL UNIVERSITY 297, no. 3 (July 2, 2021): 204–7. http://dx.doi.org/10.31891/2307-5732-2021-297-3-204-207.
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Multilayer fabrics made of polyethylene threads are widely used for products of real property and tactical equipment of servicemen capable of protecting the human body from the influence of firearm, cold, cutting, spiny weapons, shock and shock-fractional influences. Optimization of the process of their manufacture is to optimize the tension of the main polyethylene threads in front of the formation zone. To do this, it is necessary to determine the change in relative tension on zones of filling of polyethylene threads on a loop. The execution of this complex task should be based on the use of specially designed computer programs. Taking into account the specifics of the processing of threads on a weaving machine, when determining the relative tension in each individual zone, it is necessary to use a recursion algorithm when the initial tension of the thread from the previous zone will be input for the next zone. Designing new and improvement of existing technological processes of processing polyethylene complex threads on weaving machines requires a change in relative tension on zones of refueling of basic threads. The execution of this complex task should be based on the use of specially designed computer programs using a recursion algorithm. Determination of the change in relative tension on zones of filling of polyethylene complex threads on weaving machines, taking into account the material of the guide, will improve the technology of manufacturing multilayer fabrics that are used to manufacture products of real property and tactical equipment of servicemen capable of protecting the human body from the influence of firearms, cold, cutting, spiny weapons, shock and shock-fractional influences. Improvement of existing technological processes of processing polyethylene complex threads on weaving machines will reduce the downtime that arise when breaking the threads. This negatively affects the productivity of weaving machine tools, reduces the quality of multilayer tissues. Minimization of tension in each line of refueling line of basic polyethylene complex threads will reduce the likelihood of a cliff of the thread, which is important for improving technological processes from the position of increasing the productivity of weaving machine tools and the quality of multilayer tissues. Mathematical provision of a computer program requires the development of thread interaction models with surfaces of scala, framing guides, holes of the remission framework taking into account the real physical and mechanical properties of complex threads and yarns and their real geometric and constructive parameters. The main factor affects the growth of the tension of polyethylene complex threads is the force of friction. It characterizes the friction properties of the threads and conditions of their interaction with the surfaces of the scala, framing guides, holes of the striped frames.
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Koshur, V. D. "Nonlinear discrete-structural models and calculation of the dynamic reaction of multilaminate composite panels under intensive distributed and localized shock loads." Mechanics of Composite Materials 23, no. 4 (1988): 463–68. http://dx.doi.org/10.1007/bf00611116.
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Hunt, Barry. "Knowledge-Based Nonlinear Boundary Integral Models of Compressible Viscous Flows Over Arbitrary Bodies: Taking CFD Back to Basics." Applied Mechanics Reviews 44, no. 11S (November 1, 1991): S130—S142. http://dx.doi.org/10.1115/1.3121345.
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The paper starts with a discussion of a knowledge-based CFD methodology. A new incompressible formulation known as SAVER is first introduced, employing a novel relaxation approach. This is then generalized through a modification of the boundary conditions to the GENESIS methodology, for analysis or design in compressible, rotational flow. A discussion is presented of how the basic causal nature of integral methods offers new insights into certain flow phenomena, such as shocks and separations, and facilitates aerodynamic sensitivity analysis. The paper presents a new class of vector fields approximating the Euler equations for transonic flows, and shows how GENESIS can be used to construct first an exact solution of these approximate fields, then a numerical solution of the residual error fields. The explicit representation of a shock discontinuity on the body boundary exploits its causal link with conditions at the sonic point to suppress, non-dissipatively, the mathematically-valid but physically-impossible formation of an expansion shock.
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Hu, Yumeng, Haiming Huang, and Zimao Zhang. "Numerical simulation of a hypersonic flow past a blunt body." International Journal of Numerical Methods for Heat & Fluid Flow 27, no. 6 (June 5, 2017): 1351–64. http://dx.doi.org/10.1108/hff-05-2016-0187.
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Purpose The purpose of this paper is to explore the characteristics of hypersonic flow past a blunt body. Design/methodology/approach The implicit finite volume schemes are derived from axisymmetric Navier–Stokes equations by means of AUSM+ and LU-SGS methods, and programmed in FORTRAN. Based on the verified result that a 2D axisymmetric chemical equilibrium flow has a good agreement with the literature, the characteristics of hypersonic flow past a sphere are simulated by using four different models which involve four factors, namely, viscous, inviscid, equilibrium and calorically perfect gas. Findings Compared with the calorically perfect gas under hypervelocity condition, the shock wave of the equilibrium gas is more close to the blunt body, gas density and pressure become bigger, but gas temperature is lower due to the effect of real gas. Viscous effects are not obvious in the calculations of the equilibrium gas or the calorically perfect gas. In a word, the model of equilibrium gas is more suitable for hypersonic flow and the calculation of viscous flow has a smaller error. Originality/value The computer codes are developed to simulate the characteristics of hypersonic flows, and this study will be helpful for the design of the thermal protection system in hypersonic vehicles.
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Curcio, Luciano, Laura D'Orsi, and Andrea De Gaetano. "Seven Mathematical Models of Hemorrhagic Shock." Computational and Mathematical Methods in Medicine 2021 (June 3, 2021): 1–34. http://dx.doi.org/10.1155/2021/6640638.
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Although mathematical modelling of pressure-flow dynamics in the cardiocirculatory system has a lengthy history, readily finding the appropriate model for the experimental situation at hand is often a challenge in and of itself. An ideal model would be relatively easy to use and reliable, besides being ethically acceptable. Furthermore, it would address the pathogenic features of the cardiovascular disease that one seeks to investigate. No universally valid model has been identified, even though a host of models have been developed. The object of this review is to describe several of the most relevant mathematical models of the cardiovascular system: the physiological features of circulatory dynamics are explained, and their mathematical formulations are compared. The focus is on the whole-body scale mathematical models that portray the subject’s responses to hypovolemic shock. The models contained in this review differ from one another, both in the mathematical methodology adopted and in the physiological or pathological aspects described. Each model, in fact, mimics different aspects of cardiocirculatory physiology and pathophysiology to varying degrees: some of these models are geared to better understand the mechanisms of vascular hemodynamics, whereas others focus more on disease states so as to develop therapeutic standards of care or to test novel approaches. We will elucidate key issues involved in the modeling of cardiovascular system and its control by reviewing seven of these models developed to address these specific purposes.
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Meirmanov, Anvarbek, and Irina Nekrasova. "Mathematical models of a hydraulic shock." Journal of Mathematical Analysis and Applications 408, no. 1 (December 2013): 76–90. http://dx.doi.org/10.1016/j.jmaa.2013.05.024.
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Singh, Kanwar Bharat, and Saied Taheri. "Piezoelectric Vibration-Based Energy Harvesters for Next-Generation Intelligent Tires." Tire Science and Technology 41, no. 4 (October 1, 2013): 262–93. http://dx.doi.org/10.2346/tire.13.410404.
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ABSTRACT Because of access limitations inside the tire, the use of batteries for sensor nodes embedded inside an intelligent tire is not practical. The high vibration levels inside a tire have the potential to generate electrical power using vibration-based energy-harvesting techniques. In this article, the feasibility of using an inertial vibrating energy harvester unit to power a sensor module for tire use is assessed. To predict the electrical power output of the generator, a generic analytical model based on the transfer of energy within the system has been derived. The vibration measurements taken from the test conducted using accelerometers embedded in the tire have been applied as an excitation to the model to predict the power output for a device of suitable dimensions and to study the feasibility of this concept. For the tire applications, a special compact harvester design has been proposed that is able to withstand large shocks and vibrations. Suitable mathematical models for different harvester configurations have been developed to identify the best configuration suited for use inside a tire. The harvester unit demonstrates power generation over a wide speed range and provides a distinct advantage in cost and flexibility of installation while extending the lifetime of the power supply for sensor data acquisition and communication. Results indicate the viability of the procedure outlined in the article.
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Liu, J. J. "Analytical Predictions of Strong Pseudo-Steady Mach Reflections for the Polyatomic Gas: SF6." Journal of Mechanics 17, no. 1 (March 2001): 1–12. http://dx.doi.org/10.1017/s1727719100002367.
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ABSTRACTStrong pseudo-steady Mach reflections in sulfur hexafluoride (SF6) are analyzed using the three-shock and local three-shock theories, where both the vibrationally-frozen (γ = 1.333) and -equilibrated (γ = 1.093) perfect-gas models are used to compare with existing experiments. The ranges of the incident shock Mach number and reflecting wedge angle studied are 1.49 ≤ Ms ≤ 5.95 and 10° ≤ θω ≤ 42°, respectively. It is found that predicted angles between the incident and reflected shocks from the local three-shock theory using the vibrationally-equilibrated fictitious perfect-gas model (i.e., γ = 1.093) agree closely with those, currently available in literature, measured experimentally; while these predicted angles obtained using the vibrationally-frozen perfect-gas model (i.e., γ = 1.333) differ significantly from the existing experiments. Taking the convex Mach stem curvature at the triple point into consideration, it is shown that both the triple point trajectory angle and the angle between the incident and reflected shocks of strong pseudo-steady Mach reflections in SF6 can be more accurately determined for wide ranges of Ms and θω from the three-shock theory using the vibrationally-equilibrated fictitious perfect-gas model than those without considering this effect.
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Green, W. A., and A. B. Tayler. "Mathematical Models in Applied Mechanics." Mathematical Gazette 71, no. 457 (October 1987): 241. http://dx.doi.org/10.2307/3616780.
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Tayler, A. B., and J. B. Keller. "Mathematical Models in Applied Mechanics." Journal of Applied Mechanics 55, no. 1 (March 1, 1988): 252. http://dx.doi.org/10.1115/1.3173653.
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