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171.
This study is concerned with the mechanics of ductile fracture in bulk metal forming processes by a finite-element analysis and experiments. Developed is a computer program using conventional finite-element method such that the behavior of crack propagation after ductile fracture can be analyzed. The phenomenon of a material separating into two pieces upon shearing and tensile tests has been simulated using the developed computer program. Special attention is focused on the effect of various ductile fracture criteria on crack initiation and propagation during shearing and tensile tests. 相似文献
172.
In a previous article the authors introduced a Lagrange multiplier based fictitious domain method. Their goal in the present article is to apply a generalization of the above method to: (i) the numerical simulation of the motion of neutrally buoyant particles in a three-dimensional Poiseuille flow; (ii) study – via direct numerical simulations – the migration of neutrally buoyant balls in the tube Poiseuille flow of an incompressible Newtonian viscous fluid. Simulations made with one and several particles show that, as expected, the Segré–Silberberg effect takes place. To cite this article: T.-W. Pan, R. Glowinski, C. R. Mecanique 333 (2005). 相似文献
173.
We investigate the behavior of fluid–particle mixtures subject to shear stress, by mean of direct simulation. This approach is meant to give some hints to explain the influence of interacting red cells on the global behavior of the blood. We concentrate on the apparent viscosity, which we define as a macroscopic quantity which characterizes the resistance of a mixture against externally imposed shear motion. Our main purpose is to explain the non-monotonous variations of this apparent viscosity when a mixture of fluid and interacting particles is submitted to shear stress during a certain time interval. Our analysis of these variations is based on preliminary theoretical remarks, and some computations for some well-chosen static configurations. To cite this article: A. Lefebvre, B. Maury, C. R. Mecanique 333 (2005). 相似文献
174.
175.
Mathematical justifications are given for a simulation technique of multivariate non-Gaussian random processes and fields based on Rosenblatt's transformation of Gaussian processes. Different types of convergences are given for the approaching sequence. Moreover an original numerical method is proposed in order to solve the functional equation yielding the underlying Gaussian process autocorrelation function. 相似文献
176.
Synthesis of voiced sounds using low-dimensional models of the vocal cords and time-varying subglottal pressure 总被引:1,自引:0,他引:1
Edson Cataldo Fabiana R. Leta Jorge Lucero Lucas Nicolato 《Mechanics Research Communications》2006,33(2):250-260
The vocal cords play an important role on voice production. Air coming from the lungs is forced through the narrow space between the two vocal cords that are set in motion in a frequency that is governed by the tension of the attached muscles. The motion of the vocal cords changes the type of flow, that comes from the lungs, to pulses of air, and as the flow passes through the oral and nasal cavities, it is amplified and further modified until it is radiated from the mouth. This complex process can be modeled by a system of integral-differential equations. This paper considers two mechanical models previously used for explaining the dynamics of the vocal cords. It shows that the level of naturalness of the sound generated by these models is rather poor, and it proposes temporal variations of the parameters of the models to increase such level. Examples of synthetic vowels and diphthongs are given to assess the models. In general, the results show that, although the system of voice production is complex, we can achieve satisfactory results with relatively simple low-dimensional models, by suitable temporal variations of the aerodynamic parameters. 相似文献
177.
Actual melt temperatures are rarely measured directly when conducting rheological characterisations of materials in non-ambient
conditions despite the potentially large influence temperature may have on the rheological data. For rheometers that use only
a temperature-regulated lower plate, it is likely that the set point and true melt temperatures differ, an effect that becomes
significant when characterising melts or suspensions close to phase-change events like crystallisation. This work investigates
the magnitude of these effects for a controlled-stress rheometer featuring a temperature-controlled lower plate. The lower
plate was fitted with a serrated cover disc that was found to exacerbate temperature deviations from the desired set point.
Steady-state radial and vertical temperature profiles within the sample were measured and compared with the predictions of
a finite element analysis model. The deviations between set point and measured temperatures were successfully predicted by
the simulation for two typical gap heights for a thermoplastic, ceramic paste. The non-ideal heat transfer characteristics
were also investigated numerically for a representative polymer system that demonstrated the increased deviations from ideal
values for lower thermal conductivity materials.
相似文献
D. Ian WilsonEmail: |
178.
A numerical tool is developed for coupling natural convection in cavities with surface radiation and computations are performed for an air-filled square cavity whose four walls have the same emissivity. Compared to the adiabatic case without radiation, the top wall is cooled, the bottom wall is heated, air flow along the horizontal walls are reinforced and thermal stratification in cavity core is reduced. Detailed analysis shows that net radiative heat flux is linear with ΔT if , which is the case at low Rayleigh number, and that radiative Nusselt number is a linear function of the cavity height. Surface radiation induces an early transition to time-dependent flows: for and a cavity height of 0.335 m the critical Rayleigh number is equal to and the corresponding Hopf bifurcation is supercritical. Furthermore, multiple periodic solutions are observed between and . To cite this article: H. Wang et al., C. R. Mecanique 334 (2006). 相似文献
179.
Brahim El Khalil Hachi Said Rechak Mohamed Haboussi Mbarek Taghite 《Comptes Rendus Mecanique》2006,334(1):83-90
A method improving the evaluation of the stress intensity factor by hybridization of two weight functions is presented and applied to embedded elliptical cracks under various loadings. The hybridization consists in using one or the other function in the zone of the crack where it is the most efficient. The delimitation of the two zones is achieved after optimizing the axes ratio and the curvature radius of the crack. During this optimization we seek to reduce the effects of the singularities present in the weight functions as well as to take better into account the influence of the ellipse curvature. To cite this article: B. El Khalil Hachi et al., C. R. Mecanique 334 (2006). 相似文献
180.
Mohamed Maidi 《Comptes Rendus Mecanique》2006,334(5):285-291
An acoustic numerical code based on Ligthill's analogy is combined with large-eddy simulations techniques in order to evaluate the noise emitted by subsonic and supersonic round jets. We show first that, for centerline Mach number and Reynolds number , acoustic intensities compare satisfactorily with experimental data of the literature in terms of levels and directivity. Afterwards, high Reynolds number free and forced jets at Mach 0.7 and 1.4 are studied. Numerical results show that the jet noise intensity depends on the nature of the upstream mixing layer. Indeed, the subsonic jet is 4 dB quieter than the free jet when acting on this shear layer by superposing inlet varicose and flapping perturbations at preferred and first subharmonic frequency, respectively. The maximal acoustic level of the supersonic jet is, on the other hand, 3 dB lower than the free one with a flapping upstream perturbation at the second subharmonic. The results reported in this paper confirm previous works presented in the literature demonstrating that jet noise may be modified according to the inlet conditions. To cite this article: M. Maidi, C. R. Mecanique 334 (2006). 相似文献