Numerical simulation and experimental validation of a ductile damage model for DIN 1623 St14 steel

St14 steel (DIN 1623) is widely used in sheet metal forming industries because of its remarkable formability and also its low price. In this paper, damage behaviour of St14 steel is studied in order to be used in complex forming conditions with the goal of reducing the number of costly trials. Damage parameters of St14 steel have been determined by using standard tensile and Vickers micro-hardness tests. A fully coupled elastic-plastic-damage model has been developed and implemented into an explicit code. With this model, damage propagation and crack initiation, and ductile fracture behaviour of drilled and notched specimens are predicted. The model can quickly predict both deformation and damage behaviour of the part because of using plane stress algorithm, which is valid for thin sheet metals. Experiments are also carried out to validate the results. It is concluded that finite element analysis (FEA) in conjunction with continuum damage mechanics (CDM) can be used as a reliable tool to predict ductile damage and fracture of St14 steel.     

一种新型石油射孔弹的数值模拟分析

为了提高油气井的产量及保护油气层,需要对射孔弹的设计理论及射孔机理进行大量的研究与分析,从而设计出一系列针对不同岩层,能够达到不同射孔要求的射孔弹.根据已有的射孔弹壳体要求,设计了一种由两层药型罩组合而成的新型双层复合罩.这种新型药型罩是由一个主装药和两个药型罩组成,应用Truegrid建立有限元模型,对不同药型罩模型进行数值分析,比较两种不同模型金属射流参数,为新型石油射孔弹的设计提供有力依据.     

一种新型热翅板式电子散热器的模拟研究

由于现代电子设备及元器件不断向高集成度、高紧凑性发展,其散热量也不断增大,威胁到其正常工作的安全性和可靠性.为此,一种新型的热翅板式散热器结构被提出,并针对高散热量的电子元件(CPU芯片)进行了散热能力的研究.通过数值模拟分析了该新型散热器的散热性能,得到不同热功率下芯片的温度分布,分析了冷却温度、冷却风量等对散热性能的影响,最终得到了正常工况下的最佳风量.     

Numerical simulation and experimental research on passive hydrodynamic bearing in a blood pump

The current research of hydrodynamic bearing in blood pump mainly focuses on the bearing structure design.Compared with the typical plane slider bearing and Rayleigh step bearing,spiral groove bearing has excellent performance in load-carrying capacity.However,the load-carrying capacity would decrease significantly with increasing flow rate in conventional designs.In this paper,the special treatment is made to the upper spiral groove bearing to make sure that both the circulatory flowing and load-carrying capacity are high.Three-dimensional computational fluid dynamics(CFD) models in the space between rotor and shaft are developed by using FLUENT software.Effects of groove number,film height and groove depth on load-carrying capacity of the spiral groove bearings are investigated by orthogonal experiment design.The experimental results show that film height is the most remarkable factor to the load-carrying capacity.The variation tendency of load-carrying capacity reveals that the best combination of geometry is the one with groove number of 8,film height 0.03 mm and groove depth 0.08 mm.The velocity and pressure distributions in spiral groove bearings are also analyzed,and the analysis result shows that the distributions are in conformity with the design of the blood pump based on the principle of hydrodynamic bearing.The displacement of the rotor with the best combination parameters is tested by using laser displacement sensors,the testing result shows that the suspending performance is satisfactory both in axial and radial directions.This research proposes a bearing design method which has sufficient load-carrying capacity to support rotor as an effective passive hydrodynamic bearing.     

Fault induction dynamic model,suitable for computer simulation: Simulation results and experimental validation

The study of induction motor behavior under not normal conditions and the ability to detect and predict these conditions has been an area of increasing interest. Early detection and diagnosis of incipient faults are desirable for interactive evaluation over the running condition, product quality guarantee, and improved operational efficiency of induction motors. The main difficulty in this task is the lack of accurate analytical models to describe a faulty motor. This paper proposes a dynamic model to analyze electrical and mechanical faults in induction machines and includes net asymmetries and load conditions. The model permits to analyze the interactions between different faults in order to detect possible false alarms. Simulations and experimental results were performed to confirm the validity of the model.     

Combinatorial electrochemical cell array for high throughput screening of micro-fuel-cells and metal/air batteries

An electrochemical cell array was designed that contains a common air electrode and 16 microanodes for high throughput screening of both fuel cells (based on polymer electrolyte membrane) and metal/air batteries (based on liquid electrolyte). Electrode materials can easily be coated on the anodes of the electrochemical cell array and screened by switching a graphite probe from one cell to the others. The electrochemical cell array was used to study direct methanol fuel cells (DMFCs), including high throughput screening of electrode catalysts and determination of optimum operating conditions. For screening of DMFCs, there is about 6% relative standard deviation (percentage of standard deviation versus mean value) for discharge current from 10 to 20 mAcm(2). The electrochemical cell array was also used to study tin/air batteries. The effect of Cu content in the anode electrode on the discharge performance of the tin/air battery was investigated. The relative standard deviations for screening of metal/air battery (based on zinc/air) are 2.4%, 3.6%, and 5.1% for discharge current at 50, 100, and 150 mAcm(2), respectively.     

The delay & sum algorithm applied to microphone array measurements: Numerical analysis and experimental validation

The experimental validation of the beamforming technique applied to microphone array measurements is investigated in this paper. At first the method theoretical background is presented, highlighting the main parameters affecting its performances and studying their influence with the aim of producing an instrument useful in designing an efficient experimental set-up. Then, in order to prove the theory assessment and to give a first estimation of the method uncertainty, an experimental campaign is carried out to validate the exposed theory under controlled and repeatable conditions.The obtained results highlight a very good correspondence between the theoretical model and the “in field” tests, giving the possibility to correctly design microphones array for future experimental campaigns.     

Numerical simulation of the failure process for an experimental sample with a concentrator under plane bending conditions

The results of the numerical simulation of elastic-plastic deformation, crack nucleation, and propagation in a sample are presented. The simulation is performed using the laws of mechanics of a damaged medium by considering different variants of the accumulation of faults. The obtained results are in good agreement with the experimental data for the case when during the simulation both plastic and brittle failures are taken into account.     

Rotordynamic analysis and experimental validation of a high speed induction motor made by copper die casting process

A copper die casting induction motor can obtain an energy saving effect of about 2–3% compared to previous aluminum die casing induction motors. In addition, copper die casting motors can reduce the size of motors and reduce material costs. The critical speed and unbalance response of high speed machines need to be verified by rotordynamic analysis for dynamic stability of the rotors. The critical speed analysis, harmonic analysis and transient analysis by unbalance are performed for dynamic stability. The unbalance analysis results are compared with the experiment considering allowable vibration displacement (API 611) and balancing grade (ISO 1940-1). This paper dealt with the design, analysis and experimental validation of a high speed induction motor. The dynamic stability of the prototype is verified successfully, and two experimental methods by ISO 10816-3 are suitable and reliable for the allowable vibration evaluation of rotating machine.     

双离合变速器敲击噪声的仿真分析与实验评价

针对某变速器在车辆一挡起步工况实验中出现敲击噪声的问题,利用LMS Virtual.Lab软件搭建了包含轴、齿轮、同步器、轴承、差速器、壳体等部件的双离合变速器刚柔耦合模型.考虑输入轴转速波动、轴承刚度非线性、齿轮啮合时变刚度和阻滞力矩,以再现敲击噪声发生时壳体的振动响应.仿真计算与实验结果的良好一致性,验证了仿真分析方法的有效性.     

Numerical and experimental study of a thermal probe for measuring groundwater velocity

A thermal method for a rapid measurement of groundwater velocity, particularly in aquifers with preferential flow where groundwater velocities over tenths of (m/d) are expected, was studied. Some instruments for measuring groundwater velocity are based on the application of heat. Those consisting of a central heater surrounded by several thermistors seem adequate for the above purpose, but their measuring range lies below 30 md (meters per day) and there are few works about their theory. Based on the diffusion-convection-dispersion equation, an electrical model is proposed for representing this type of instruments and a theoretical study is presented in an attempt to extend their measuring range. The model can be excited with any shape of power or temperature signals, allows the signals to be feedbacked for controlling the heater's excitation, and includes the thermal features of the heater and thermistors. The model was validated through laboratory tests with velocities of up to 100 md and extrapolated up to 1000 md. Numerical results suggest that exciting the heater with constant temperature allows the measuring range of these probes to be extended.     

On a new sectionalized motion control strategy for automated guided vehicles: modeling and simulation validation

As key equipment in logistics system of modern manufacturing factories, the automated guided vehicle (AGV) plays an increasingly important role. Although many strategies for AGV motion control are available, in most cases, only a single control method is utilized during the entire process, which inevitably leads to the lack of flexibility in dealing with problems encountered in various stages of the AGV motion. In this paper, a new approach called sectionalized motion control (SMC) was proposed in order to achieve superb comprehensive performance (i.e., high precision, low energy consumption, and good stability) for the entire AGV tracking process. In this method, considering AGV’s various characteristics in different motion stages (early, middle, and terminal), the neural dynamics-based tracking, energy-efficient tracking, and model predictive control technologies were adopted. Furthermore, a simulation using Matlab software was performed in order to verify the proposed approach. The simulated results showed that the SMC is capable of providing smooth, energy-efficient, robust, and globally stable control for the AGV system.     

Numerical simulation and experimental study of the accelerating structure with on-axis coupling cells for a double-sided CW racetrack microtron at an energy of 1.5 GeV

A numerical simulation of a biperiodic accelerating structure with on-axis coupling cells at a frequency of 2450 MHz for the double-sided cw race-track microtron with an energy of 1.5 GeV now being built at the Institute for Nuclear Physics, Johannes Gutenberg University (Mainz, Germany), was performed. On the basis of these calculations, test cells have been manufactured that are used to develop and refine the methods for measuring and tuning the accelerating structure. The final geometry of cells is established.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 24–35.Original Russian Text Copyright ¢ 2004 by Alimov, Vetrov, Ishkhanov, Kosarev, Pakhomov, Chubarov, Shvedunov, Euteneur, Jankowiak.     

面向节能高效的电弧焊工艺参数多目标优化方法

为降低电弧焊加工过程的能量消耗、减少环境排放,对电弧焊加工节能高效工艺参数优化问题进行了研究。建立了电弧焊加工过程电能消耗目标函数及热效率目标函数,在考虑焊接质量及设备、工艺对等实际约束的基础上,建立了以焊接电流和焊接速度为优化变量,以最小电能消耗(节能)和最大热有效利用率(高效)为优化目标的多目标优化模型;利用自适应进化梯度小生境遗传算法对模型进行了寻优求解;通过某阀座密封面手工电弧焊加工实例对所建模型及方法的可行性和有效性进行了验证,并将优化结果与实际结果及传统遗传算法的结果进行了比较分析。     

Fabrication and efficiency evaluation of a hybrid NiCrAl pressure cell up to 4 GPa

A hybrid NiCrAl pressure cell was fabricated to measure magnetic quantities under high pressure above 3 GPa. A pressure of 4.0 GPa was achieved and the pressure cell was found to be reusable even after a pressurizing trial up to 4.0 GPa. Pressure was monitored using (63)Cu nuclear quadrupole resonance of Cu(2)O and ruby fluorescence. The pressure efficiency of a fresh cell was maintained at 96%, and no appreciable deformation was observed at pressures below 3 GPa; on the other hand, the efficiency after pressurizing trials decreased gradually and reached 75% at 4 GPa accompanied by a maximum expansion inside the cylinder of 2%.     

Moving EM: the Rapid Transfer System as a new tool for correlative light and electron microscopy and high throughput for high-pressure freezing

In this paper, the Rapid Transfer System (RTS), an attachment to the Leica EMPACT2 high‐pressure freezer, is described as a new tool for special applications within the cryofixation field. The RTS is an automated system that allows for fast processing of samples (<5 s) that make it possible for the first time to use high‐pressure freezing in combination with high time resolution correlative light and electron microscopy. In addition, with a working cycle of 30 s this rapid turn over time allows one to acquire more samples of biopsy material before it deteriorates than with other HPF machines with longer cycle times. With the use of the RTS it was possible to obtain three samples each of four different tissues in 6 min. Together with the finding that 90% of samples of cells grown on sapphire discs were well frozen, the RTS was both fast and reliable. Most important, together with other newly developed accessories, the RTS made it possible to capture specific events occurring live in the cell as observed by light microscopy, to cryofix that sample/event within 4 s, and then to analyze that event at high resolution in the electron microscope with excellent preservation of ultra‐structure. These developments should give us the tools to unravel intracellular processes that can be observed by live cell imaging but are too rare or fast to be picked up by routine EM methods or where the history of a structure is necessary to be able to discern its nature.     

Numerical simulation and metal flow analysis of hot extrusion process for a complex hollow aluminum profile

The most important way to improve the quality of aluminum profiles is to assure the material flow through die land exit with the same velocity. In this paper, a numerical model was developed to investigate metal flow behavior during aluminum profile extrusion. Firstly, the numerical model for a complex hollow aluminum profile was built based on the arbitrary Lagrangian–Eulerian program HyperXtrude. Then, with the numerical model, metal flow behavior at each stage during the whole extrusion process was analyzed and dead zones in the die cavity were also investigated by means of the particle tracking method. Finally, the numerical results were validated by comparing with the nose ends of two extrudates in practice, and the comparison showed that the numerical model developed in this work could provide the effective guidance for practical production.     

Improvement and experimental validation of a multi-zone model for combustion and NO emissions in CNG fueled spark ignition engine

This article reports the experimental and theoretical results for a spark ignition engine working with compressed natural gas as a fuel. The theoretical part of this work uses a zero-dimensional, multi-zone combustion model in order to predict nitric oxide (NO) emission in a spark ignition (SI) engine. The basic concept of the model is the division of the burned gas into several distinct zones for taking into account the temperature stratification of the burned mixture during combustion. This is especially important for accurate NO emissions predictions, since NO formation is strongly temperature dependent. During combustion, 12 products are obtained by chemical equilibrium via Gibbs energy minimization method and nitric oxide formation is calculated from chemical kinetic by the extended Zeldovich mechanism. The burning rate required as input to the model is expressed as a Wiebe function, fitted to experimentally derived burn rates. The model is validated against experimental data from a four-cylinder, four-stroke, SI gas engine (EF7) running with CNG fuel. The calculated values for pressure and nitric oxide emissions show good agreement with the experimental data. The superiority of the multizone model over its two-zone counterpart is demonstrated in view of its more realistic in-cylinder NO emissions predictions when compared to the available experimental data.