Sensitivity Analysis of Effect Related with Material Process and Assembly Variations to Loads Deformation and Stress on HSS Stamping Die

During stamping process, the material properties, process design parameters and production environments inevitably have variation and noisy factors, which possibly affect the sheet metal formability and the deformation of the die structure.After gaining a success in applying sheet metal forming numerical simulation analysis to get the forming loads during stamping process, a methodology of die structure analysis based on sheet metal forming simulation was proposed and validated by experiments.Based on these results, the effect related with initial blank thickness, blank holder force, blank positioning error and die alignment error variations to a DP600 hyperbolic bottomed cup drawing die's forming loads(especially unbalanced loads), and deformation and stress was studied numerically.The influence level of these variations to the die's forming loads, deformation and stress was disclosed.The findings can guide die design, die tryout and process control for high-strength steel(HSS) stamping with increased forming load and decreased sheet metal formability.     

Computer Simulation on Temperature Rise in Process of Wire Drawing

IntroductionTheuseofhighspeedinwire-drawingprocesstomeetthedemandsforincreasedPfOductivityhasagrCateffectontheheatgeneratedduetoplasticdeformationandfrictionbetweenthewireanddrawingtools.MostofmechanicalenergyconvertstoheatandresultsintemperatUrerisesofhundredsofdegrees.Therisetemperaturerisesgreatlyaffectionlubricationconditions,toollife,andproPotiesoffinialproduct.Energysavinginwire-drawingbecameanimportantissueinacompetitivemarket.Inordertoachieveminimumenergyconsumption,wecansetupamathe…     

模拟深海环境砂土地层的材料配比试验研究

为了研究可近似模拟琼州海峡深海环境下砂土地层的相似材料,基于正交试验法,以重晶石粉/标准砂、黏结剂浓度、凡硅比和石膏含量作为4个控制因素,对不同配比相似材料的物理力学参数的变化规律进行了分析. 首先确定标准砂、重晶石粉作为骨料,凡士林和硅油作为黏结剂,石膏粉作为调节剂,其次基于正交试验原理设计25组相似材料配比,分别进行密度试验、直剪试验、压缩试验以及渗流试验,得到了重度、内摩擦角、黏聚力、压缩模量以及渗透系数等物理力学指标,通过极差和显著性分析,研究了各个控制因素对材料参数的影响规律,并对25组试验结果进行了去异常点的多元线性回归分析. 研究结果表明:相似材料重度受重晶石粉/标准砂比值的影响最大,石膏的比例是控制压缩模量的主要因素,内摩擦角和黏聚力无主要控制因素,重晶石粉的比重主要控制着渗透系数的大小;适用于深海环境砂土地层条件下的相似材料配比为重晶石粉/标准砂0.4,黏结剂浓度4.5%,凡硅比3∶1,石膏含量3%.      

A new fractal model of elastic,elastoplastic and plastic normal contact stiffness for slow sliding interface considering dynamic friction and strain hardening

The deflection properties of elastic stage, elastoplastic stage and plastic stage of elastomer were analyzed. Taking account of the kinetic friction force in friction interface and strain hardening in slow sliding interface, the elastic, elastoplastic and plastic normal contact stiffness model for harsh surface was established, which revised the Majumdar-Bhushan fractal model and made it more perfect. In the combination of macro and micro perspective, the effects of coarse surface fractal variables, kinetic friction force in the friction interface, material characters of the friction couples on the contact status and contact property were discussed by the study of digital analysis. Results imply that the normal contact stiffness improves with the increasing real contact area and normal contact load, and reduces with the augment of kinetic friction coefficient. When the kinetic friction coefficient is smaller than 0.3, the normal contact stiffness comprises a linear decrease with the increment of kinetic friction coefficient. When the kinetic friction coefficient is bigger than 0.3, the normal contact stiffness has an exponential decrease with the increasing kinetic friction coefficient.     

Study on Factors Affecting Springback and Application of Data Mining in Springback Analysis

Springback of sheet metal induced by elastic recovery is one of major defects in sheet metal forming processed. Springback is influenced by many factors including properties of the sheet material and processing conditions. In this paper, a springback simulation was conducted and comparisons between the results based on different processing variables were illustrated. The discovery of knowledge of the effects of geometry and process parameters on springback from FEM results becomes increasingly important, as the number of numerical simulation has grown exponentially. Data mining is an effective tool to realize knowledge discovery in simulation results. A datamining algorithm, rough sets theory (RST), was applied to analyze the effects of process parameters on springback in U-bending.     

基于FPGA的GMM说话人辨认系统

目前基于GMM的说话人辨认系统主要在微机上由软件实现,难以胜任大语音流的多路实时处理任务。鉴于FPGA强大的流水和并行处理能力,提出了一种以FPGA为应用平台,基于GMM的与文本无关说话人实时辨认系统的硬件实现方法。抽取NIST2003语音库的语料进行试验,结果表明,与在PC上的软件实现相比,识别率几无差别,但实时处理速度提高了约90倍。     

Friction characteristics in green drilling titanium alloy Ti6Al4V

Titanium alloy Ti6Al4V, as difficult-to-cut material, has poor machinability. Conventional cutting fluid serves as a coolant and lubricant. In green drilling, water vapor is recognized as an effective coolant; however, its lubrication properties are not well known in drilling. This paper investigates the friction characteristics between chip and tool in green drilling Ti6Al4V, compared with that in sliding and turning process. A friction evaluation model is developed based on the equivalent model of drilling, then is used to calculate the effective friction coefficient. Results indicate that the friction coefficient on the tool-chip interface is considerably reduced in drilling by water vapor, so the drilling forces decrease, too. The friction coefficient decreases as velocity increases in drilling, which is different from the law of sliding tests; the friction coefficient increases when the distance to chisel edge increases.     

拧紧速度对螺栓转矩系数的影响分析

为了研究拧紧速度对螺栓拧紧特性的影响,利用多功能螺栓紧固分析系统对紧固件进行转矩——夹紧力试验,通过试验分析得出摩擦系数随着拧紧速度的增大而减小并逐渐趋于稳定;同时摩擦系数是影响转矩系数的主要因素,转矩系数是摩擦系数的增函数,在一定范围内,转矩系数与摩擦系数呈同增减趋势;紧固件的拧紧过程,摩擦会产生高温,温度变化是使摩擦系数发生变化的重要因素.     

斜拉索内平行钢丝间摩擦系数的确定

准确识别斜拉索内平行钢丝间的摩擦系数值是确定拉索局部弯曲应力大小的必要条件之一.在摩擦理论的基础上,考虑外荷载、金属表面膜、工况等影响摩擦系数大小的因素,提出了试验室测定和进一步修正镀锌高强钢丝间摩擦系数的方法,为进一步分析斜拉索内钢丝间联合工作情况提供了较为可靠的试验依据.     

二硫化钼填充乙烯基树脂的摩擦学性能

研究了不同质量分数的二硫化钼（MoS2）填充乙烯基树脂（VER）复合材料及所成转移膜在不同转速、载荷下的摩擦学性能,并对摩擦表面形貌进行了分析．结果表明：MoS2含量低于15％和高于35％时主要磨损机制分别为粘着磨损和轻微犁削式的磨粒磨损,且都不随转速的变化而改变;但MoS2含量处于15％～35％时主要磨损机制为粘着磨损、疲劳剥落式的磨粒磨损,且随转速的增加而减弱．另外,MoS2含量低于25％时摩擦系数随载荷增加而增大,高于25％时却随载荷增加而减小,磨损率均变化不大．对偶盘上形成的转移膜能有效降低摩擦磨损,随着MoS2含量的增加,转移膜的减摩时问逐渐延长,而摩擦系数基本不变;随着载荷的增加,转移膜的摩擦系数逐渐降低,减摩时间则大幅度缩短．     

高速铁路制动区间钢轨摩擦自激振动研究

为了探究高速铁路制动区间的典型钢轨波磨现象,基于轮轨摩擦自激振动诱导钢轨波磨的观点展开了研究,通过武广高速铁路制动区段的现场调研,掌握该区段的波磨特征并采集相应的轨道不平顺;基于轮轨摩擦自激振动诱导钢轨波磨的观点分别建立制动区段高速列车的动/拖车轮对-轨道-制动系统的有限元模型,并利用复特征值法进行动/拖车轮轨系统的摩擦自激振动分析,比较动/拖车轮轨系统在制动和非制动工况下系统发生摩擦自激振动的可能性,以及在制动工况下动车轮轨和拖车轮轨系统的摩擦自激振动情况;使用控制变量法研究了制动系统摩擦系数和扣件垂向刚度对动/拖车轮轨系统摩擦自激振动的影响规律.研究结果表明：制动工况更容易引起系统的摩擦自激振动;拖车轮轨系统更容易引起系统摩擦自激振动;控制制动装置摩擦系数约为0.30,扣件垂向刚度约为50 MN/m时能一定程度降低轮轨系统发生摩擦自激振动的可能性,进而抑制钢轨波磨的产生.     

沥青跑道抗滑性能分析

为了提高机场沥青跑道的抗滑性能,保证飞机滑跑安全,分析了沥青道面防滑性能要求,研究了沥青道面摩擦系数、粗糙度、抗滑耐久性等防滑性能指标,参照国际民航的规定和中国沥青道面抗滑标准,提出了考虑飞机滑跑安全的道面技术参数,并对材料性质、沥青混合料类型与级配、沥青用量等因素对抗滑性能的影响进行了分析。分析结果表明:当沥青道面摩擦系数摆式仪测定值控制在45以上,构造深度大于0.4 mm时,飞机滑跑是安全的;通过选择坚硬石料作为沥青混合料的集料,采用沥青玛蹄脂碎石混合料作为面层材料,设计合理的坡度,及时清除道面积雪等设计与使用维护措施,可增强沥青道面抗滑性能。     

Influence of high frequency vibration on deep drawing process of AZ31 sheet at room temperature

Quasi-ultrasonic vibration with a frequency of 15 kHz and a maximum output of 2 kW was imposed on the deep drawing process of AZ31 magnesium alloy sheet at room temperature, in order to reveal the effect of high frequency vibration on deformation behavior of AZ31 during the process. From the drawn results and the observation of the microstructure within the large deformation area, high frequency vibration has a great influence on the formability, the forming load and the failure mode of AZ31 sheet during the deep drawing process; the influence is a comprehensive result of so-called ??volume effect?? and ??surface effect??, and relies on the vibrating amplitude. Total forming load decreased significantly as soon as the vibration superimposed. According to the tensile test results of AZ31 bars under ultrasonic vibration, the formability of AZ31 sheet increases firstly with the increase of stimulating energy, then decreases and finally becomes brittle. Under the combined influence of ??surface effect?? and the ??softening?? in the ??volume effect?? near the relative low amplitude of 25%A in the experiment (A is the maximum amplitude), the formability of AZ31 reaches the largest value, and the samples possess the same distribution trend of cracks as those added with lubricating oil. With the increase of excitation energy, the ??volume effect?? gradually becomes apparent, and finally the ??hardening?? of the ??volume effect?? occupies a dominant position.     

凝冰条件下沥青路面与轮胎接触摩擦动力响应分析

综合考虑轮胎材料超弹性和路面材料的粘弹性、轮胎与路面间的瞬态接触摩擦作用,利用有限元软件ANSYS/LS-DYNA建立凝冰条件下轮胎与沥青路面接触的有限元模型,分析沥青路面动力响应规律。结果表明：凝冰条件下沥青路面路表弯沉在轮胎作用的区域明显增大,在没有直接作用的区域弯沉逐渐减小,且路表弯沉随着摩擦系数的增大而逐渐增大;路表水平剪应力以轮胎作用区域为中心呈反对称分布,且最大水平剪应力在轮胎经过前随着摩擦系数的增大而减小,而在轮胎经过后随摩擦系数的增大而增大。路表竖向应力在轮胎作用的瞬间出现应力集中现象,在非作用区域则很小,竖向应力随着摩擦系数的增大而减小;同时阻尼对凝冰沥青路面力学响应也有着重要的影响。     

充填粗糙节理直剪数值模拟宏细观分析

利用颗粒流数值计算方法对岩石充填节理直剪作用下力学性质进行研究,从细观角度分析不同法向荷载下粗糙节理面的损伤情况;探讨充填节理粗糙程度、充填物强度参数、充填物与围岩接触面强度以及充填厚度对节理剪切强度的影响,结果表明:（1）随着法向荷载的增大,上下节理面接触状态及粘结力分布规律发生转变,充填节理面粘结破坏明显增加;（2）节理粗糙度系数（JRC）对峰值剪切应力的影响较大;随JRC的增加节理峰值剪切强度增大;节理面粘结力呈类线性增长,而内摩擦角随JRC的增大而呈明显的非线性变化;（3）随节理充填物粘结强度比的增加,峰值剪切应力增大;随充填物强度比的增加,节理面粘结力出现明显的增长,而内摩擦角呈现先下降后增加的趋势;（4）当法向荷载较小时,峰值剪切应力受接触面粘结强度比的影响较大;当法向荷载较大时,其对峰值剪切应力的影响程度明显降低.节理面粘结力和内摩擦角随接触面粘结的增加分别呈现出非线性增长和下降的趋势.（5）节理剪切力学形式随充填后的增加呈现降低的趋势,然而随着厚度的不断增加,所带来的剪切力学参数变化程度逐渐减小.      

铜基陶瓷强化摩擦材料的摩擦磨损性能

采用粉末冶金技术,制备了铜基陶瓷强化摩擦材料.通过定速摩擦试验机,测试了摩擦压力、摩擦速度和干湿条件对材料摩擦磨损性能的影响.结果表明:在干摩擦条件下,系数大于0.3,摩擦系数稳定.摩擦压力在0.5~0.6 MPa范围时,摩擦系数处于较低值.随摩擦压力的变化,磨损率变化不大.当摩擦速度为2 000 r/m in时,摩擦系数最大.湿摩擦条件下摩擦系数低于干摩擦条件下的摩擦系数.     

一种基于深度学习的离散化交通状态判别方法

在智能交通信号控制和交通流诱导系统中,交通环境状态的有效判别是影响交通控制决策的先决条件,本文针对交通流产生的大数据信息,结合深度学习算法提出一种离散化交通状态的判别方法.给出了包括交通状态数据采集、状态数据描述、状态深度学习和判别等功能模块的系统架构,构建了一种离散交通状态编码方法,为深度学习交通状态特征提供了数据基础.模型训练阶段,对采集到的二值和连续值交通状态数据,分别构建了两种不同的深度置信网络实现交通状态特征的无监督学习;模型微调阶段,在整合形成的高层抽象特征向量顶端增加softmax分类器,采用反向传播算法实现参数微调.最后,该方法基于VISSIM微观交通软件进行仿真,实验结果表明,离散交通状态编码方法可有效表达交通状态,基于深度学习的交通状态判别方法相对传统方法具有较高的准确度.     

五河口斜拉桥索塔环向预应力筋张拉试验研究

针对环向预应力筋张拉伸长值比理论伸长值偏大这一现象,对环向预应力筋的张拉控制进行了研究．测试了6束预应力筋的摩阻系数,同时,还对初始张拉控制应力进行了试验分析,提出了相应的张拉控制程序。最后．对索塔锚固区共290柬环向预应力筋实测张拉伸长值结果进行了概率统计分析,证实了理论伸长值修正算法中各项修正的必要性。     

The Size Effects on Process Design of Micro Deep Drawing

This paper suggested to reformulate cylindrical deep drawing parameters with dimensionless form. A diagram, in which a feasible zone is drawn to bound both the maximal allowable tension and compression stress during the deep drawing process, was established. Since it is presented in a dimensionless form, it may be applied for both conventional and micro deep drawing. Cylindrical cup deep drawing was taken as an example to show the dimensionless process design method. In addition, the size effects should be taken into account. Two kinds of size effects on micro deep drawing were investigated, which can be explained by surface layer model and strain gradient model. Numerical simulations were carried out to compare the strain distribution with or without consideration of size effect.     

Field Tests for Investigating the Extraction Rate of Piles Using a Vibratory Technique

Factors directly affecting the extraction rate of the piles pulled out by a vibratory pulling system are summarized and classified into five categories (excitation force, resistance, vibration amplitude, pile plumbness keeping, and slowing down at the later stage) from the mechanics and engineering practice. Field tests on steel sheet piles extracted by vibratory technique in different soil conditions are conducted to ascertain how these factors affect the extraction rate of a pile with regard to three major actors of vibratory pile pulling: the pile to be extracted, the selected pulling system, and the imposed soil conditions. The extraction rates of three different sheet pile types (having up to four different lengths) pulled out by two different vibratory pulling systems are documented. The piles with different lengths and types, pulled out with or without a clutch, have different extraction rates. The working parameters governing the vibratory hammer, such as excitation force and vibration amplitude, exert significant influences on the rate of pile extraction, especially in the early stages of up-lift process. The extraction rate of the piles driven in different soil conditions is uniform because different extraction resistances mainly refer to shaft friction. The properties of the pile-soil interface influence the extraction rate of the piles, and the extraction rate decreases with the time for which the piles have been buried in the earth.