SIMULATION: Transactions of The Society for Modeling and Simulation International

Wang, Rujia; Wu, Shiping; Chen, Wei

doi: 10.1177/0037549718774842pmid: N/A

A unified wave equation of mechanical wave propagation during solidification of an alloy was established and the numerical solution of the wave equation was obtained. A three-element model (KSLS) used to describe the stress–strain constitutive relation of the alloy in the mushy zone was established by the analysis of rheological characteristics of molten melt during solidification. Based on the KSLS model, we could describe the constitutive relation of the liquid alloy, a Maxwell medium, and of the solidified alloy, an elastic medium, by the various Lame coefficients. The wave propagation during solidification was identified by a unified wave equation coming from a unified integral constitutive equation, to adapt to a variety of viscoelastic media. The wave equations could be solved succinctly by introducing a "memory factor" and the staggered grid finite difference method. The analytical results demonstrated that the unified wave equation could be perfectly applied to the numerical simulation of wave propagation during solidification. The propagation of the P-wave in a one-dimensional alloy was simulated during solidification, obtaining the propagation law of the mechanical wave: the wave with variable wavelength and amplitude propagated with attenuation during solidification; otherwise, as the source excitation force was fixed, the fluctuations caused by the mechanical wave could be more serious when the vibration was applied in the melt directly, which is more conducive to grain refinement.

Cristiá, Maximiliano; Hollmann, Diego A.; Frydman, Claudia

doi: 10.1177/0037549718765080pmid: N/A

Discrete Event System Specification (DEVS) is a modular and hierarchical formalism for system modeling and simulation. DEVS models can be mathematically described; simulation is performed by tools called concrete simulators. Concerning atomic DEVS models, each concrete simulator has its own input language which is, essentially, a general-purpose programming language (such as Java or C++). Hence, once engineers have written the mathematical model, they need to manually translate it into the input language of the concrete simulator of their choice. In this paper we present a multi-target compiler for atomic DEVS models written in CML-DEVS, a mathematics-based DEVS modeling language. This multi-target compiler is able to compile a CML-DEVS model to the input languages of the PowerDEVS and DEVS-Suite concrete simulators. In this way, the CML-DEVS compiler frees engineers from the manual translation of their mathematical models. In fact, the same mathematical model can be simulated on both simulators by simply recompiling the model. The CML-DEVS multi-target compiler can be easily extended to produce code for other concrete simulators.

A S, Sharan; Hiremath, Somashekhar S; Venkatesha, C S; Karunanidhi, S

doi: 10.1177/0037549718759187pmid: N/A

The torque motor is an intricate assembly in electro-hydraulic technology and plays a crucial role in converting the electrical signal into controlled mechanical output signal. It involves many precise components, such as the feedback spring, armature and its coil, permanent magnet, feed pipe, flexure shaft, jetpipe, and flexure support. The components are embedded together as a single operating component. Each component contributes to the effective dynamics of the system. The present paper proposes a novel approach to investigate the effect of critical parameters on the working design dynamics of the torque motor employed in the jetpipe electro-hydraulic servovalve. Based on the principles of mechatronics, a mathematical model is developed. The model-based design approach is employed to investigate the dynamics of the system. The required simulation parameters of the critical and precision components were obtained from solid and finite element (FE) models. The solid and FE models of the critical and precision components were first analyzed with suitable boundary and loading conditions to establish the stiffness. To validate the obtained FE results, experiments were carried out with a specially designed and fabricated test set-up. Based on the basic principle of electromagnetics, a nonlinear FE model of torque motor is analyzed for magnetic field distribution, the torque developed, and armature and jetpipe deflection for varied input current. From the results obtained, good agreement was observed between FE, simulated, and experimental values. The present novel approach enables one to improve the working design dynamics of the torque motor.

Mei, Zhenyu; Tan, Zhen; Zhang, Wei; Wang, Dianhai

doi: 10.1177/0037549718757651pmid: N/A

This paper presents the findings of a simulation study evaluating the potential benefits of implementing transit signal priority (TSP) combined with arterial signal coordination for an isolated intersection. Traffic signal coordination is usually implemented along corridors with bus lanes. Active transit signal priority (active TSP) is a traffic-responsive control that prioritizes transit vehicles at signalized intersections. Thus, implementing active TSP under a stable cycle length is necessary to meet the relative demand of the non-priority phase and to maintain system stability. A real key intersection on an artery is taken as the object, and TSP controlling logics with specific restrictions are realized by using the VISSIM vehicle actuated programming module. Simulation analysis reveals the effect of TSP strategies with flow variation on the optimal cycle, and also identifies a reasonable method for selecting the gap time and initial green time of the priority phase. Results show that under special flow combination, increasing the cycle time generated by the traditional transportation and road research laboratory approach can give rise to additional benefits. The volume influences both the gap time and initial green time of the TSP phase. Moreover, the efficiency of red truncation is slightly better than that of the green extension strategy.

Liu, Tingting; Liu, Zhen; Ma, Minhua; Chen, Tian; Liu, Cuijuan; Chai, Yanjie

doi: 10.1177/0037549717753294pmid: N/A

Simulation of behaviors in emergencies is an interesting subject that helps to understand evacuation processes and to give out warnings for contingency plans. Individual and crowd behaviors in the earthquake are different from those under normal circumstances. Panic will spread in the crowd and cause chaos. Without considering emotion, most existing behavioral simulation methods analyze the movement of people from the point of view of mechanics. After summarizing existing studies, a new simulation method is discussed in this paper. First, 3D virtual scenes are constructed with the proposed platform. Second, an individual cognitive architecture, which integrates perception, motivation, behavior, emotion, and personality, is proposed. Typical behaviors are analyzed and individual evacuation animations are realized with data captured by motion capture devices. Quantitative descriptions are presented to describe emotional changes in individual evacuation. Facial expression animation is used to represent individuals’ emotions. Finally, a crowd behavior model is designed on the basis of a social force model. Experiments are carried out to validate the proposed method. Results showed that individuals’ behavior, emotional changes, and crowd aggregation can be well simulated. Users can learn evacuation processes from many angles. The method can be an intuitional approach to safety education and crowd management.

Zhao, Zenghui; Ma, Qing; Tan, Yunliang; Gao, Xiaojie

doi: 10.1177/0037549718770284pmid: N/A

Mine disasters, such as large deformation, floor heave, and roof fall, occur extremely easily in weakly consolidated soft rock strata in western China, posing enormous challenges to traditional anchorage support design. To avoid tensile failure of bolts as a result of the superposition effect of stress accumulation, a segmentally yieldable anchorage support, taking into consideration the different failure zones in surrounding rock, is presented in this paper. First, load transfer mechanisms and the process of anchorage failure are analyzed for end anchorage, full-length anchorage, and segmentally yieldable anchorage based on numerical pull-out tests. Results show that the load transfer follows a multipeak chain-like trend in the case of multipoint segmental anchorage, and that the peaks of stress attenuate slowly. Therefore, the proposed anchorage type can leverage the shear strength effectively. Furthermore, numerical models for the applications of the aforementioned three different anchoring modes to weakly consolidated soft strata are established. Results indicate that segmentally yieldable anchorage can withstand larger tensile deformation and surrounding rock deformation. Moreover, the bolt shows higher strength reservation. A combination of these characteristics is conducive to controlling deformation and damage during roadway excavation.