Al-Cu-Li-xMg合金时效初期微结构演变的Monte Carlo模拟

采用基于Multi-States Ising Model的Monte Carlo算法,模拟研究了Al-Cu-Li-xMg合金时效初期微观结构的演变过程,结果表明:时效早期,在Al-1.2Cu-5.7Li合金中微结构的主要形态是Li原子团簇、Li-Cu原子对和空位团簇,且空位团簇的出现多出现在Li原子团簇附近,形成共生形态;而Al-1.2Cu-5.7Li-xMg合金中,出现明显的Cu-Clusters,而Li原子的偏聚过程则受到抑制,且空位团簇的形态也发生了变化,多与Cu-Mg原子团簇形成共生形态;微量Mg的作用是通过Mg/Li原子间存在强烈的相互作用调整Li原子团簇的偏聚形态,导致大量被Li原子Clustering过程锁定的Cu原子和空位被置换出来,进而影响Li、Cu原子团簇的形态和空位的分布形态,并影响随后的析出相分布形态.     

Kinetic Monte Carlo simulation of microalloying effect in Al-Ag alloys

The kinetic Monte Carlo method, which based on the Multi-States Ising Model, was applied to simulate the effect of microelements on the microstructural evolution of Al-Ag alloys during initial aging stage. The simulation results suggest that the microelements In, Sn and Be have a dramatic depression effect on the Ag clustering because of their strong tendency to co-existed with vacancies. There are no significant effects on the process of Ag clustering in Al-Ag alloys containing Li or Cd, because of little interaction between Li/Cd and Ag/vacancies. Microelements can influence the aging by interacting with vacancies and the atoms of precipitated composition, in which the former seems more important. In this model, ＂vacancy-locking＂ and ＂vacancy clusters＂ are two important mechanisms in the aging process.     

焙烧过程晶粒生长的Monte Carlo模拟

基于Monte Carlo（MC）方法,根据晶粒生长机理建立改进的转换概率模型,在不同焙烧温度、焙烧时间和激活能条件下可实现晶粒生长过程结构演化的计算机模拟,对模拟和实验数据进行分析,结果表明：当晶粒生长指数为2.17时,模拟与实验具有较好的一致性,从而得出焙烧过程晶粒的生长动力学模型;该模型能够较好地解释焙烧过程晶粒的生长过程,对晶粒生长动力学研究等具有一定的指导意义。     

Mg和Cu在Al-Zn-Mg合金时效初期的Monte Carlo模拟

采用Monte Carlo方法模拟研究Al-6Zn-(2Mg)和Al-10Zn-1.9Mg-(1.7Cu)合金时效初期微观结构的演变过程,并分析Mg和Cu的基本作用。结果表明:时效初期,Al-6Zn合金中的Zn原子有较强的团聚倾向,形成了明显的Zn原子簇;而在Al-6Zn-2Mg合金中出现明显的Zn原子簇、Zn-Mg原子簇及少量的Mg原子簇。Mg的作用是通过Mg和Zn原子间强烈的相互作用形成Zn、Mg原子交替排布的短程有序结构。含铜的Al-10Zn-1.9Mg-1.7Cu合金中,不仅形成了Zn原子簇、Mg原子簇和Zn-Mg原子簇,还形成了少量Zn-Cu原子簇、Mg-Cu原子簇和Zn-Mg-Cu原子簇。Cu的存在促进Zn原子和Zn-Mg原子团簇化,但对Mg原子的团簇化影响不大。     

Monte Carlo simulation of extrusion die life

Due to the high cost of metal forming tools (especially in hot extrusion), one of the major goals in tool design is a longer service life. Estimation and prediction of tool life thus becomes critically important for performance evaluation of the tools. The two most dominant failure mechanisms for extrusion dies (solid, hollow, and semi-hollow dies all taken together) are fracture and wear. In the first part of the paper, a fracture mechanics based fatigue life prediction model is described. A similar treatment is then presented for wear-related failures. Fracture and wear usually coexist as failure modes, and final die breakdown occurs due to the mechanism that becomes dominant. Therefore, a competing fracture–wear model has been later developed to represent the complete die failure situation. Attempt has been made to correlate the stochastic nature of various fatigue and wear related die parameters to die life. Monte Carlo simulation has been used to predict the life distribution of a die for a given set of manufacturing conditions and mechanical properties. In comparison with actual life data from the industry, the simulated life yields very realistic predictions.     

晶粒长大介观尺度Monte Carlo方法实时模拟

提出了一个用于晶粒长大Monte Carlo模拟的实时计算新模型,基于该模型以及作者已提出的“择优转换原则”、“新结点再取向转换概率公式”等改进措施构建了一个Monte Carlo实时模拟程序,用于纯铝正常晶粒长大过程实时模拟。结果表明,Monte Carlo实时模拟程序有效地模拟了纯铝晶粒长大过程;实际时间treal与模拟时间tC。呈指数关系;模拟的晶粒长大速率与实际长大速率接近。     

Kinetic Monte Carlo simulation of physical vapor deposition of thin Cu film

A two-dimensional Kinetic Monte Carlo method has been developed for simulating the physical vapor deposition of thin Cu films on Cu substrate. An improved embedded atom method was used to calculate the interatomic potential and determine the diffusion barrier energy and residence time. Parameters, including incident angle,deposition rate and substrate temperature, were investigated and discussed in order to find their influences on the thin film morphology.     

蒙特卡洛模拟厄洛替尼漏服及补服方案评价

目的:根据厄洛替尼群体药动学(PPK)模型,应用蒙特卡洛模拟(MCS)评价肿瘤患者厄洛替尼漏服及补服方案。方法:根据厄洛替尼PPK模型,以口服150 mg qd为给药方案,应用非线性混合效应动力学模型(NONMEM)软件对患者漏服及不同时间段补服方案(6 h,12 h,18 h,24 h双倍剂量补服)进行10 000次MCS,计算漏服及补服方案下个体治疗窗(ITW)外人群比例和ITW外持续时间(>5%人群),评估各场景下补服方案的合理性。结果:患者漏服厄洛替尼时,血药浓度持续下降至下次用药时间,且影响次日的血药浓度,ITW以下持续时间分别为25.1 h和6.6 h;随着补服时间的延长,ITW以下人群比例从6.82%增加到14.55%,持续时间从5.9 h增加到23.6 h;ITW以上人群比例从5.99%增加到10.74%,持续时间从3.7 h增加到9.7 h。结论:根据MCS结果,患者应提高厄洛替尼用药依从性,避免漏服。一旦出现漏服,可考虑尽快补服,但不建议接近下次给药时间时进行补服或加倍剂量补服,以免增加药物不良反应。     

矿井提升机故障树的蒙特卡罗法仿真

为了研究矿井提升机的可靠性问题,提出了一种基于蒙特卡罗算法的仿真运算。采用蒙特卡罗抽样方法,建立了故障树仿真模型,利用MATLAB对故障树的仿真模型进行了编程,最后对故障树进行了定量分析。通过计算,得出了故障树可靠性曲线、累积失效概率及基本单元模式重要度。结果表明：基于故障树的蒙特卡罗仿真可以作为预防矿井提升机故障的一种新的安全方法。     

一种ELC-BH钢板退火组织演变的Monte Carlo模拟

基于Monte Carlo方法所建立的退火模型,以一种含Nb的冷轧超低碳高强度烘烤硬化钢板(简称ELC-BH钢板)为研究对象,进行了退火组织演变的模拟和实验研究。结果表明:模拟结果较好地反映了ELC-BH实验板退火组织演变过程,特别是展示了回复阶段再结晶孕育期,证实了该模型的合理性和实用性;考虑升温、亚晶形成、析出相粒子等影响来进一步改进模型,可改善其实用效果。     

用SAS迭代及蒙特卡罗模拟优化美罗培南的使用

目的:筛选出针对临床上不同MIC值细菌时美罗培南的最优的药物剂量和点滴方式,同时比较传统、延长及优化两步点滴法的药效学。方法: 首先用SAS迭代的方法筛选出在不同的MIC值时美罗培南两步点滴法时最优的药物剂量和点滴方式,然后使用蒙特卡罗模拟计算传统、延长及优化两步点滴法时的%T>MIC的值和达标概率。结果: 在SAS迭代时,MIC为1、2、4 μg/mL 及CL和V_d取均数时,分别按 500 mg,0.25 h/100 mg+2.75 h/400 mg;500 mg,0.25 h/250 mg+2.75 h/250 mg 和 1000 mg;0.25 h/400 mg+2.75 h/600 mg 的优化两步点滴法的模型最优。在不同的MIC时,蒙特卡罗模拟均显示出在延长点滴和优化两步点滴法比传统点滴法有更高的%T>MIC和达标概率,优化两步点滴法比延长点滴法的达峰时间更短。结论:SAS迭代可以用来筛选出最优的药物剂量和点滴方式,同时蒙特卡罗模拟可以用来比较不同点滴方式的药效学。结果显示优化两步点滴法是更好的治疗临床严重感染的方法。     

基于蒙特卡罗方法的铝/钢熔钎焊界面金属间化合物层生长分析

针对铝/钢熔钎焊界面金属间化合物在SEM,EDS,XRD界面测试研究的基础上,确立了界面由Fe₂Al₅、FeAl₃等金属间化合物组成. 在此基础上采用蒙特卡罗方法,建立了铝/钢界面铝、铁扩散及Al-Fe化合物生长模型,并进行了数值分析和对比研究. 结果表明,所建立的模型能够很好地反映钢侧Fe₂Al₅的生长,铝侧FeAl₃离散存在,且金属间化合物层的厚度接近试验测量结果.     

CAD model based virtual assembly simulation,planning and training

This paper reviews the state-of-the-art methodologies for developing computer-aided design (CAD) model based systems for assembly simulation, planning and training. Methods for CAD model generation from digital data acquisition, motion capture, assembly modeling, human–computer interface, and data exchange between a CAD system and a VR/AR system are described. Also presented is an integrated methodology for designing, planning, evaluating and testing assembly systems. The paper further describes the implementation of these methods and provides application examples of CAD model based simulation for virtual assembly prototyping, planning and training. Finally, the technology gaps and future research and development needs are discussed.     

Three dimensional Monte Carlo simulation of grain growth during GTA welding of titanium

The work reported here represents significant advancement in the modeling of grain structure evolution in metallic systems. Utilizing computed temperature fields from a well tested heat transfer and fluid flow model, the evolution of grain structure was simulated for the first time using a three dimensional (3D) Monte Carlo model of grain growth in the heat affected zone of commercially pure titanium welds. The computed weld geometry and the simulated mean prior β grain size for different heat inputs agreed well with the corresponding experimental results when turbulence in the weld pool was considered. The grain sizes at various locations equidistant from the fusion line were different, indicating that the results of previous 2D calculations need to be reexamined. The computed grain size distribution agreed well with the corresponding experimental data. The agreement indicates significant promise for understanding grain growth in the entire heat-affected zone using a comprehensive phenomenological model.     

织构诱发异常晶粒长大的Monte Carlo模拟

利用欧拉角表示晶粒取向的Monte Carlo方法,模拟了异常晶粒长大过程。通过Voronoi模型产生了晶粒尺寸近似符合Lognormal分布且具有立方织构的初始组织,比较了该组织中不同织构半峰宽和体积分数对晶粒长大过程的影响。模拟结果表明:随着半峰宽变大,异常晶粒长大可能性和平均晶粒尺寸都变大;织构体积分数对异常晶粒长大的影响相对较小,只在半峰宽较小且体积分数很大时,才抑制异常晶粒长大,模拟结果与实验吻合。另外,模拟组织中平均晶粒长大速度不仅受到晶界迁移率的影响,而且受到异常晶粒长大数量的影响。     

一种基于关键特性识别的综合成本公差优化模型

当前基于制造成本与质量损失的公差优化模型缺乏对制造成本与产品质量间复杂关系的考虑以及对关键特性的控制。针对这一问题,提出一种引入制造成本与质量损失的权重系数和组成环灵敏度系数的装配公差优化模型。该模型的权重系数由设计、工艺、制造以及市场调研等相关领域专家进行评判打分确定,灵敏度系数依据关键特性识别的数学模型获取。最后以某型飞机外襟翼接头为例,验证该模型的可行性和有效性。     

A multiscale coupled Monte Carlo model to characterize microstructure evolution during hot rolling of Mo-TRIP steel

A multiscale modelling framework has been proposed to characterize microstructure evolution during hot strip rolling of transformation-induced plasticity (TRIP) steel. The modelling methodology encompasses a continuum dislocation density evolution model coupled with a lumped parameter heat transfer model which has been seamlessly integrated with a mesoscale Monte Carlo (MC) simulation technique. The dislocation density model computes the evolution of dislocation density and subsequently constitutive flow stress behaviour has been predicted and successfully validated with the published data. A lumped-parameter transient heat transfer model has been developed to calculate the average strip temperature in the time domain. The heat transfer model incorporates the effect of plastic work for different strain rates in the energy conservation formulation. A coupled initial value problem solver has been developed to integrate the system of stiff ordinary differential equations in the time domain to predict dislocation density and temperature profiles simultaneously. The temporal evolution of microstructure during hot rolling of TRIP steel is simulated by the MC method incorporating thermal and dislocation density data from the continuum models. Simulated microstructural maps, kinetics of recrystallization and grain size evolution have been generated in a 200 × 200 lattice system at different strain rates and temperatures. The simulation code has been implemented in a high-performance grid computing network. The predicted temporal evolution of grain size, recrystallized fractions and flow stress have been validated with the published literature and found to be in good agreement, confirming the predictive capability of the integrated model.     

基于蒙特卡洛法的3D打印机定位精度分析

为了研究在各种误差源综合作用的条件下,FDM桌面3D打印机挤出机头相对于热床的定位精度情况,通过蒙特卡洛法对其定位精度进行评估。根据多刚体系统理论,建立3D打印机的拓扑结构模型;基于仪器精度理论,对误差向量进行综合分析,分析步进电机在运动过程中,各种误差源在x,y,z方向引入的误差向量,建立3D打印机的误差传递模型;通过蒙特卡洛法对在各种误差源综合作用的情况下打印机挤出机头的定位精度进行仿真计算。结果表明:在置信概率95%情况下,挤出机头相对于热床在x,y,z 3个方向上的定位输出及其扩展不确定度分别为x=(70±0.099)mm,y=(50±0.100)mm,z=(20±0.518)mm。该方法可用于分析影响定位精度的主要因素,进行误差补偿,提高定位精度;也可应用到精密仪器设计中用于精度分配计算,合理分配多刚体结构各环节的精度指标。