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International Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems (HAPTICS)

作者： Maximilian Kaluschke René Weller Niels Hammer Luigi Pelliccia Mario Lorenz Gabriel Zachmann Institute for Computer Graphics and Virtual Reality University of Bremen Department of Orthopedics University Hospital Leipzig Professorship Machine Tool Design and Forming Technology Chemnitz University of Technology

ISBN: (数字)9781728102344

ISBN: (纸本)9781728102351

We present a novel haptic rendering method to simulate material removal in medical simulations at haptic rates. The core of our method is a new massively-parallel continuous collision detection algorithm in combination with a stable and flexible 6-DOF collision response scheme that combines penalty- and constraint-based force computation. Moreover, a volumetric object representation of the 3D objects allows us to derive a realistic local material model from experimental human cadaveric data, as well as support real-time continuous material removal. We have applied our algorithm to a hip replacement simulator and two dentistry-related simulations for root-canal opening and caries removal. The results show realistic continuous forces and torques at haptic rates.

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The usage of grid-characteristic method for the simulation of flows with detonation waves

The usage of grid-characteristic method for the simulation o...

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International Conference on 50 years of the development of grid-characteristic method, GCM50 2018

作者： Lopato, Alexander I. Utkin, Pavel S. Institute of Computer Aided Design of the RAS 19/18 2-ya Brestskaya ul. Moscow123056 Russia 9 Institutskiy per. Dolgoprudny141701 Russia

ISBN: (纸本)9783030062279

The chapter is dedicated to the numerical investigation of the strongly unstable mode of pulsating gaseous detonation wave propagation using two approaches. In the first one, the problem is solved in the laboratory frame and the detonation is initiated near the closed end of the channel. In the second approach, the modeling is carried out in the shock-attached frame. For this purpose, we proposed the numerical algorithm for the integration of shock evolution equation using a grid-characteristic method. The algorithm is characterized by the second approximation order. The mechanisms of two qualitatively different regimes of pulsations are described. © 2019, Springer Nature Switzerland AG.

关键词： Detonation

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On the Complexity of Minimizing Quasicyclic Boolean Functions

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Journal of Applied and Industrial Mathematics 2018年第3期12卷 426-441页

作者： Chukhrov, I.P. Institute of Computer Aided Design Vtoraya Brestskaya ul. 19/18 Moscow123056 Russia

We investigate the Boolean functions that combine various properties: the extremal values of complexity characteristics ofminimization, the inapplicability of local methods for reducing the complexity of the exhaustion, and the impossibility to efficiently use sufficient minimality conditions. Some quasicyclic functions are constructed that possess the properties of cyclic and zone functions, the dominance of vertex sets, and the validity of sufficient minimality conditions based on independent families of sets. For such functions, we obtain the exponential lower bounds for the extent and special sets and also a twice exponential lower bound for the number of shortest and minimal complexes of faces with distinct sets of proper vertices. © 2018, Pleiades Publishing, Ltd.

关键词： Boolean functions

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Numerical method for calculating fatigue fracture using a multimode damage model

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AIP Conference Proceedings 2021年第1期2448卷

作者： I. S. Nikitin A. D. Nikitin B. A. Stratula B. V. Volkov Institute for Computer Aided Design of RAS 2nd Brestskaya st. 123056 Moscow Russia

The paper deals with the problem of fatigue failure and durability of structural elements in the process of cyclic loading. Previously, such problems were solved by calculating the stress state in a cycle using a multiaxial fatigue fracture criterion. Here we consider the initiation and development of the fatigue process based on the cyclic damage model. The model contains the evolution equation for the damage function depending on stress state. The algorithm is based on a special post proceeding of a numerical solution for an elastic solid mechanics problem that can be also applied for elastic-plastic case. The normal crack opening and shear crack mechanisms are taken into account in this model. On this basis, calculations of the initiation and development of crack-like fracture zones are carried out for an aircraft structure element of a disk with a blade in a flight loading cycle. The geometry of quasi-cracks in the vicinity of the contact zone of the disk and the blade and the assessment of durability are similar to those observed in real operation.

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Mathematical modeling of the VHCF resonance loadings with a progressive damage accumulation

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IOP Conference Series: Materials Science and Engineering 2021年第1期1191卷

作者： I S Nikitin A D Nikitin B A Stratula Institute for computer aided design of RAS 2nd Brestskaya st. 123056 Moscow Russia

One of the most critical in-situ loading modes is resonant. Such loading conditions may lead to premature fatigue damage accumulation and failure. The progressive fatigue damage changes the natural frequency of a structure and causes a permanent modification of loading conditions. This paper considers the model of fatigue damage accumulation regarding its evolution and resonant loading parameters. To describe the evolution of material degradation due to fatigue a complex kinetic model of damage development and numerical algorithm are introduced. The model contains the evolution equation for the damage function depending on stress state. The algorithm is based on a special post proceeding of a numerical solution for an elastic solid mechanics problem that can be also applied for elastic-plastic case. Different loading conditions can be considered by choosing the method of solution for solid mechanics problem. This paper is focused on the comparison between quasi-static and resonant loading conditions used for damage function calculation. It was shown that use of resonant loading solution leads an earlier crack initiation and shorter fatigue life results compared to quasi-static solution. A spatial development of the fatigue damage zone is also different for these two cases. The normal crack opening mechanism is discussing in this paper.

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Numerical effects in computer simulation of simplified hodgkin-huxley model 19

Numerical effects in computer simulation of simplified hodgk...

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2nd International Conference on Mathematics and Statistics, ICoMS 2019

作者： Ostrovskii, Valerii Y. Karimov, Timur I. Solomevich, Ekaterina P. Kolev, Georgii Y. Butusov, Denis N. Department of Computer-Aided Design Saint Petersburg Electrotechnical University "LETI" Saint Petersburg Russia Youth Research Institute Saint Petersburg Electrotechnical University "LETI" Saint Petersburg Russia

ISBN: (纸本)9781450371681

In this paper, we consider the impact of the discretization effects on the dynamical behaviour of the single-compartment neuron model represented by simplified Hodgkin-Huxley equations. In order to implement numerical simulation, one need to discretize the continuous model of the system or use the discrete operator preserving the main properties of the continuous prototype. However, discrete models can suffer from negative effects caused by the applied method, discretization step and round-off errors. This fact is particularly important for the analysis of nonlinear systems, e.g. the biological neuron models. Within this study, the impact of the application of the most common one-step integration methods is examined through the series of computational experiments, where the dynamical system is put into the resonant and chaotic oscillation modes. The results of the study are visualized as two-parameter dynamical maps and interspike interval histograms. © 2019 Association for Computing Machinery.

关键词： Dynamical systems

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On the Inherent Polycrystal Stress Concentration

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Journal of Physics: Conference Series 2021年第1期1945卷

作者： V V Gulin A D Nikitin Institute for Computer Aided Design of RAS 19/18 2nd Brestskaya 123056 Moscow Russia

When analyzing the structural integrity of a material or structural part, the mechanics of continuous media is traditionally used with the concept of the homogeneity and isotropy of material properties; with this approach, the fracture criteria are related to the integral characteristics of the material and are described by the invariants of the stress tensor. However, this approach does not consider the physical aspects of the occurrence of local areas of plastic deformation, which ultimately means the impossibility of predicting the fracture, and, consequently, the resource of the structure. This is especially evident in the conditions of cyclic loading, when the material can fail at stresses well below the traditional «fatigue limit». In the current work, an approach is proposed that allows to save traditional methods of design and resource forecasting by expanding the scale of modeling. The paper introduces the concept of inherent stress concentration in any structurally heterogeneous medium as its inherent attribute. A universal algorithm for determining this characteristic is presented.

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Mathematical modeling of the evolution of compact astrophysical gas objects

Mathematical modeling of the evolution of compact astrophysi...

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International Conference on 50 years of the development of grid-characteristic method, GCM50 2018

作者： Babakov, Alexander V. Lugovsky, Alexey Yu. Chechetkin, Valery M. Institute for Computer Aided Design of the RAS 19/18 Vtoraya Brestskaya ul. Moscow123056 Russia Keldysh Institute of Applied Mathematics of the RAS 4 Miusskaya pl. Moscow125047 Russia

ISBN: (纸本)9783030062279

In the current study, the vortex structures that occur in one of the most common astrophysical objects such as massive stars and accretion disks are investigated using mathematical modeling methods. Modeling of convective processes with the formation of vortex structures in massive stars of various masses, rotating and being possessed in the self-gravitation conditions is carried out. Modeling uses a gas-dynamic model of an inviscid perfect gas. The numerical technique is based on the finite-difference approximation of the conservation laws for the additive characteristics of the environment for a finite volume. Direct calculation of gravitational forces is used by summing up the interaction between all the finite volumes in the area of integration. For the objects with different mass and rotation speed, visualized pictures of the vortex structure are given. Modeling of the processes of formation of large-scale vortex structures in accretionary stellar disks with different disk thickness is also carried out. Self-gravitation of the matter of a disk rotating in the field of the gravity of a compact central object is not taken into consideration. The numerical technique is based on the explicit, conservative, and monotone in the linear approximation Godunov-type Roe-Einfeldt-Osher scheme, which approximates with order no higher than the third the conservation laws of the characteristics of the environment. For the disks with different thicknesses, visualized pictures of the vortex structure are given. Evolutionary calculations are carried out on the basis of parallel algorithms implemented on the computational complex of the cluster architecture. © 2019, Springer Nature Switzerland AG.

关键词： Numerical methods

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Complex theoretical and experimental investigations of flow structure near V-shaped wings

Complex theoretical and experimental investigations of flow ...

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International Conference on 50 years of the development of grid-characteristic method, GCM50 2018

作者： Maksimov, Fedor A. Ostapenko, Nikolai A. Zubin, Mikhail A. Institute of Computer Aided Design of the RAS 19/18 2-ya Brestskaya ul Moscow123056 Russia Institute of Mechanics Lomonosov Moscow State University 1 Michurinskii prosp Moscow119992 Russia

ISBN: (纸本)9783030062279

For estimating the supersonic flow near the V-shaped wings, the method and programs based on the Euler and Navier-Stokes equations were developed. The calculation results are compared with the experimental data obtained in the aerodynamic tunnel with the help of the unique optical direct-shadow method of the supersonic space gas flow visualization via the laser technology. As for the nonviscous flow, the vortex structures appear as the result of the Mach interaction of shock waves with the formation of the contact discontinuity of the certain intensity. When dealing with the viscous flow, the vortex structure appearance is based on the viscous layer formation near the surface of the object under the influence of the pressure fall or the pressure gradient in the external flow field. The comparison of the calculation results and experimental data revealed the vortex structures with the nonviscous and viscous origin. The chapter contains the examples of the calculations based on different programs to show the both possibility and impossibility to get the right solution using different mathematical models of the flow. © 2019, Springer Nature Switzerland AG.

关键词： Shock waves

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Constitutive equations of the semi-microscopic theory of plasticity for a multiaxial stress state

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Procedia Structural Integrity 2019年 23卷 119-124页

作者： Nikitin I.S. Nikitin A.D. Stratula B.A. Institute of Computer Aided Design of RAS 2-nd Brestskaya str. 19/18 Moscow 123056 Russia

A model of a plastic medium based on a plastic slip theory is presented in the paper. It is presumed that a micro-slip (i.e. a plastic shear) on any oriented plane occurs while a shear stress is exceeding some critical level at the same time with a rising of a local loading condition. In any other case a plastic shear does not occur. Under certain assumptions, one can integrate the increments of plastic shears over all possible slip planes in the case of an arbitrary three-dimensional stress state and obtain the constitutive relations for the plastic model, which is a version of the theory of plastic flow. For some particular loading paths in cases of two- and three-dimensional stress states ranges of orientation changes for slip planes are defined. Comparison between calculated plastic deformations and experimental ones is performed.

关键词： slip theory plasticity partial loading active loading

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