Cross-section distortion and springback characteristics of double-cavity aluminum profile in force controlled stretch-bending

3D elastic-plastic FE model for simulating the force controlled stretch-bending process of double-cavity aluminum profile was established using hybrid explicit−implicit solvent method.Considering the computational accuracy and efficiency,the optimal choices of numerical parameters and algorithms in FE modelling were determined.The formation mechanisms of cross-section distortion and springback were revealed.The effects of pre-stretching,post-stretching,friction,and the addition of internal fillers on forming quality were investigated.The results show that the stress state of profile in stretch-bending is uniaxial with only a circumferential stress.The stress distribution along the length direction of profile is non-uniform and the maximum tensile stress is located at a certain distance away from the center of profile.As aluminum profile is gradually attached to bending die,the distribution characteristic of cross-section distortion along the length direction of profile changes from V-shape to W-shape.After unloading the forming tools,cross-section distortion decreases obviously due to the stress relaxation,with a maximum distortion difference of 13%before and after unloading.As pre-stretching and post-stretching forces increase,cross-section distortion increases gradually,while springback first decreases and then remains unchanged.With increasing friction between bending die and profile,cross-section distortion slightly decreases,while springback increases.Cross-section distortion decreases by 83%with adding PVC fillers into the cavities of profile,while springback increases by 192.2%.

Accuracy profile理论在高效液相色谱法测定纺织品中3种有机溶剂残留中的应用

样品经超纯水机械振荡萃取,提取液在Spursil C_(18)色谱柱上分离,以甲醇-水-乙腈(25+70+5)混合液为流动相进行洗脱,检测波长为200nm。N,N-二甲基甲酰胺、N,N-二甲基乙酰胺和N-甲基吡咯烷酮的质量浓度在0.5~10 mg·L^(-1)内与峰面积呈线性关系,检出限(3S/N)为1.1~2.8mg·kg^(-1),测定下限(10S/N)为3.7~9.3mg·kg^(-1)。采用Accuracy profile理论验证方法的准确性,并评估了测定的不确定度,说明方法可满足3种有机溶剂的日常检测要求。

An analytical model for the prediction of cross-section profile and mean roll radius in alloy bar rolling

In a round-oval-round pass rolling sequence, the cross-section profile of an outgoing workpiece was predicted first after getting the maximum spread. The concept ＂critical point on the contact boundary＂ was proposed and the coordinates of the critical point were solved. The equivalent contact section area was represented and the mean roll radius was determined. The validity of this model was examined by alloy bar rolling experiment and rigid-plastic FEM simulation. Compared with the existing models, the mean roll radius obtained by this model is similar to experiment data.

The Study of In-Orbit Calibration Accuracy of NOAA Satellite Infrared Sounder and Its Effect on Temperature Profile Retrievals

The calibration accuracy of High Resolution Infrared Radiation Sounder Mod. 2 (HIRS / 2) on NOAA-10 satellite is analyzed in this paper. The non-linear effect in the linear calibration curve induces a deviation of 1.5 degrees (k) of brightness temperature in the tenth channel (8.3 um, water vapor absorption) of the HIRS/2 and the non-linear effect affects the other channels to a different extent. Based on analyzing non- linearity in two-point calibration curve, a tri-point calibration equation is given. A numerical test of effects of the linear and non-linear calibration models on the accuracy of atmospheric temperature retrievals is carried out.

0-10 KM TEMPERATURE AND HUMIDITY PROFILES RETRIEVAL FROM GROUND-BASED MICROWAVE RADIOMETER

Deviation exists between measured and simulated microwave radiometer sounding data. The bias results in low-accuracy atmospheric temperature and humidity profiles simulated by Back Propagation artificial neural network models. This paper evaluated a retrieving atmospheric temperature and humidity profiles method by adopting an input data adjustment-based Back Propagation artificial neural networks model. First, the sounding data acquired at a Nanjing meteorological site in June 2014 were inputted into the Mono RTM Radiative transfer model to simulate atmospheric downwelling radiance at the 22 spectral channels from 22.234 GHz to 58.8 GHz, and we performed a comparison and analysis of the real observed data; an adjustment model for the measured microwave radiometer sounding data was built. Second, we simulated the sounding data of the 22 channels using the sounding data acquired at the site from 2011 to 2013. Based on the simulated rightness temperature data and the sounding data, BP neural network-based models were trained for the retrieval of atmospheric temperature, water vapor density and relative humidity profiles. Finally, we applied the adjustment model to the microwave radiometer sounding data collected in July 2014, generating the corrected data. After that, we inputted the corrected data into the BP neural network regression model to predict the atmospheric temperature, vapor density and relative humidity profile at 58 high levels from 0 to 10 km. We evaluated our model's effect by comparing its output with the real measured data and the microwave radiometer's own second-level product. The experiments showed that the inversion model improves atmospheric temperature and humidity profile retrieval accuracy; the atmospheric temperature RMS error is between 1 K and 2.0 K; the water vapor density's RMS error is between 0.2 g/m^3 and 1.93 g/m3; and the relative humidity's RMS error is between 2.5% and 18.6%.

Semi-analytical method for calculating aeroelastic effect of profiled rod flying at high velocity

The key technique of a kinetic energy rod(KER) warhead is to control the flight attitude of rods. The rods are usually designed to different shapes. A new conceptual KER named profiled rod which has large L/D ratio is described in this paper. The elastic dynamic equations of this profiled rod flying at high velocity after detonation are set up on the basis of Euler-Bernoulli beam, and the aeroelastic deformation of profiled rod is calculated by semi-analytical method for calculating the vibration characteristics of variable cross-section beam. In addition, the aeroelastic deformation of the undeformed profiled rod and the aeroelastic deformation of deformed profiled rod which is caused by the detonation of explosive are simulated by computational fluid dynamic and finite element method(CFD/FEM), respectively. A satisfactory agreement of these two methods is obtained by the comparison of two methods. The results show that the semi-analytical method for calculating the vibration characteristics of variable cross-section beam is applied to analyze the aeroelastic deformation of profiled rod flying at high velocity.

THE INFLUENCE OF INHOMOGENEOUS WIND DISTRIBUTION ON DATA QUALITY FOR WIND PROFILING RADAR

Horizontal wind measured by wind profiling radar(WPR) is based on uniform wind assumption in volume of lateral beam. However, this assumption cannot completely meet in the real atmosphere. The subject of this work is to analyze the influence of atmospheric inhomogeneities for wind measurement. Five-beam WPR can measure two groups of horizontal wind components U and V independently, using the difference of horizontal wind components U and V can evaluate the influence of the inhomogeneity of the atmospheric motion on wind measurement. The influences can be divided into both inhomogeneous distribution of horizontal motion and vertical motion. Based on wind measurements and meteorological background information, a new means of coordinate rotation the two kinds of inhomogeneous factor was separated, and the impact in different weather background was discussed. From analysis of the wind measured by type of PB-II WPR(445MHz) during 2012 at Yanqing of Beijing, it is shown that the inhomogeneity of horizontal motion is nearly the same in U and V direction. Both the inhomogeneities of horizontal motion and vertical motion have influence on wind measurement, and the degrees of both influences are associated with changes of wind speed. In clear air, inhomogeneity of horizontal motion is the main influence on wind measurement because of small vertical velocity.In precipitation, the two influences are larger than that in clear air.

宜昌地基遥感垂直观测系统探测精度分析研究

宜昌地基遥感垂直观测系统能够实时监测本区域上空云、雾、弱降水、风速、风向、温度、相对湿度、液态含水量垂直廓线、气溶胶浓度等探测要素,增强突发性、灾害性天气监测能力.该文针对宜昌地基遥感垂直观测系统探测数据的准确性评估问题,提出了一种观测要素评估方法.方法使用了同址探空站的观测资料作为参考标准,通过对比时空匹配的垂直探测数据,分析宜昌垂直观测系统各类探测数据的准确性.通过该系统的垂直廓线产品联合观测2024年2月宜昌雨雪冰冻灾害天气过程,进行多条垂直廓线融合应用研究.定量分析结果表明:宜昌地基遥感垂直观测系统的数据质量全部满足评估指标要求,探测数据与探空资料相关性总体较好,可为气象监测提供精密的观测数据.

考虑梭口因素的积极式凸轮开口设计

为协调复杂机织物对不同梭口的适应性,将共轭凸轮、平面杆组与织机开口系统的设计开发相结合,形成了一种适用于半开梭口织造的积极式凸轮开口构型。利用MatLab开发具有非对称静止时长的摆臂运动规律,有效延长下层经纱的静停时间;在机构设计、梭口分析和程序编译基础上,实现极坐标条件下的主凸轮理论廓线精确反求与压力角校核;通过路径跟踪仿真生成副凸轮理论廓线,构建基于ADAMS/View的共轭凸轮开口数字功能样机。研究结果表明:主、副凸轮与滚子之间具有良好的几何封闭接触,凸轮实际轮廓曲线达到理想共轭精度;综框运动规律与摆臂从动件高度匹配,可满足半开梭口对于下层经纱的长停要求。该设计对高速织机的梭口创新和形式改造具有重要借鉴。

轮廓度误差对超声速压气机叶栅气动性能的影响

[目的]旨在评估轮廓度误差对压气机气动性能的影响,并为叶片鲁棒性设计提供参考。[方法]建立单峰值轮廓度误差分布数学模型,采用数值模拟方法,研究压力面和吸力面不同轮廓度组合误差对超声速压气机平面叶栅气动性能的影响。[结果]结果表明:吸力面轮廓度误差分布是影响叶栅总压损失的关键因素,随着吸力面轮廓度峰值误差位置向下游移动,总压损失系数逐渐降低;压力面和吸力面误差分布对气流折转角和静压升系数的影响趋势相反。对较低来流马赫数的叶栅,吸力面误差对气流折转角和静压升均起主导作用;对较高来流马赫数的叶栅,压力面误差对气流折转角和静压升影响明显。激波位置和激波强度、激波后扩张通道的流道型线综合决定了叶片表面和叶栅流道内的流动状态,使得近吸力面侧流动损失增大,近压力面侧流动损失减小,其综合效果决定了叶栅损失、气流折转角和静压升的变化。[结论]结果对指导跨声速压气机设计、加工和超差审理均具有重要意义。

粗粒度金刚石砂轮的放电赋能磨削修整试验研究

针对粗粒度金刚石砂轮磨粒出刃形貌难以控制的问题,提出了放电赋能磨削修整技术,旨在实现出刃磨粒的等齐性。系统研究了该复合修整技术的材料去除机理,建立脉冲放电传热数值模型,以金刚石热软化深度作为磨削深度,最大限度发挥放电赋能磨削的修整优势。探究了机床运动参数(待修砂轮转速、刀具轮转速、进给速度、磨削深度)对砂轮修整精度和刀具轮损耗深度的影响规律,并优化了工艺参数以实现粗粒度砂轮的高效高精修整。磨粒粒度为180目的金刚石砂轮修整后轮廓误差PV值为11.97μm。修整砂轮表面形貌检测结果表明,放电赋能磨削修整可将磨粒部分去除,使得砂轮表面磨粒具有较好的等齐性。磨削的碳化硅陶瓷工件表面粗糙度达412 nm,表明了修整砂轮具有优异的磨削性能。

基于线激光的化铣激光刻型在机精度检测方法

化铣激光刻型工艺是飞机蒙皮加工的重要方式,目前尚缺乏在机测量方法来检测激光刻型的精度与质量。针对此问题,提出了基于线激光的化铣激光刻型在机精度检测方法。首先,基于齐次坐标变换建立了五轴激光刻型机和线激光传感器的运动学模型,确定激光测量坐标系与工件坐标系之间的变换关系,据此获得刻型线扫描点云。然后,基于模板匹配提取单帧刻型槽截面轮廓特征,并通过Levenberg-Marquardt算法求解刻型线槽宽、槽深以及位置信息。再通过点云分割、轮廓匹配和轮廓误差计算方法得到激光刻型的轮廓误差。最后,通过激光刻型在机精度检测试验验证所提出方法的有效性,试验结果表明,该方法能够有效评估刻型线的均匀性和轮廓精度,为加工误差溯源、工艺改进和提高刻型线的轮廓精度提供了重要参考依据。

面向空中风力发电系统的高空风场观测

[目的]文章旨在研究空中风力发电系统(Airborne Wind Energy System,AWES)的测风需求及设备选型。[方法]以某空中风力发电示范工程为依托,开展测风激光雷达与风廓线雷达的对比观测试验,并对数据获取率、垂直廓线特征和时间变化特征进行分析。[结果]结果显示:在3 km高度范围内,测风激光雷达的数据获取率随高度递减至不足0.4,风廓线雷达的数据获取率则维持在0.98以上,具有更好的观测适应性;两种测风设备的风速、风向垂直廓线以及逐日、多日波动特征均具有一致性,并且能被再分析资料和高空气象站同期探空资料所验证。测风激光雷达观测结果的中位数、极差、标准差等统计特征与再分析资料更接近,相关性更好;风廓线雷达观测结果的极差和标准差整体偏大,测风精度不及测风激光雷达。[结论]文章研究表明,应根据项目所在地的气候状况,在空中风力发电站工程的不同设计阶段合理选择测风设备,科学设置测风方式。

深V型复材制件交联固化成型技术创新研究

复合材料具有比强度高、比模量高、比重小和抗疲劳性能优异等特点,在航空航天领域的应用占比日益增加。研究从实际工程应用角度出发,以开口角度小且深度大的深V型制件为研究对象,从产品厚度、内部质量、表面质量及固化变形控制等方面进行多方位攻关,分别采用阴模成型和阳模成型2种工艺方法制造试验件,通过理论分析和工艺试验论证,解决了深V型制件实际生产中出现的质量问题,为类似深V型结构零件的精确制造提供经验积累和技术支撑。

阵列持气率仪在大斜度井产气剖面监测中的应用

针对大斜度气井提高井筒内流体识别产气剖面精度,引进了阵列持气率仪(GAT),利用流体对光折射率的差异实现流体的识别。现场结果表明,GAT仪器能识别1 mm微小气泡,适合于不同流态产气识别,在大斜度井中与RAT响应一致性强,在套管井中产气识别效果好于筛管井;筛管完井多封隔器有利于提高产出剖面的解释精度,鉴于筛管完井方式的局限和筛管外窜流的存在,更加精细的解释剖面建议结合噪声测井等技术得到。

Simulation of temperature and stress in 6061 aluminum alloy during online quenching process

The cooling curves of 6061 aluminum alloy were acquired through water quenching experiment. The heat transfer coefficient was accurately calculated based on the cooling curves and the law of cooling. The online quenching process of complex cross-section profile was dynamically simulated by the ABAQUS software. The results suggest that the heat transfer coefficient changes during online quenching process. Different parts of the profile have different cooling velocity, and it was verified by water quenching experiment. The maximum residual stress of the profile was predicted using FEM simulation based on ABAQUS software The relations between the temperature and stress were presented by analyzing the data of key points.

国产风廓线雷达对比试验初步分析

根据2005年7月～10月风廓线雷达比对试验的资料,阐述了近几年我国主要风廓线雷达生产厂家研制的对流层风廓线雷达和边界层风廓线雷达的基本技术指标及其软硬件技术特点,计算并分析了这些风廓线雷达在试验期间观测所获得数据的数据获取率,以及与L波段雷达测风对比的结果,得到了目前国内自主研制的风廓线雷达的基本测量性能,为我国风廓线雷达网的建设提供选型依据。试验结果表明,我国风廓线雷达和相关器件的生产技术已较为成熟,基本达到业务应用需求。

钢轨轮廓全断面检测中轨廓动态匹配方法研究

钢轨轮廓匹配是钢轨廓形检测的关键步骤,决定轨道几何参数检测精度。在高速动态条件下实现检测钢轨轮廓与标准钢轨轮廓高精度自动匹配,是轨道几何参数高精度动态测量面临的重要问题。本文对钢轨轮廓高精度自动匹配方法进行了研究。首先,根据标准钢轨轮廓曲线曲率固有特征信息,对检测获取的轨腰和轨底廓形中不同圆弧、线段之间切点进行自动识别,实现不同圆弧、线段自动分割;然后,对获取的不同圆弧添加半径约束进行非线性拟合,准确提取各圆弧圆心坐标;最后,针对道岔处钢轨廓形复杂特点,提出采用Kalman滤波器对检测获取的标准轨腰和轨底特征点进行连续在线跟踪和预测,并根据结果构建道岔钢轨虚拟标准轨腰和轨底,以解决道岔处钢轨轮廓匹配问题。将该方法已在轨道检测车中进行实际应用,证明其是切实可行的。

分类精确性指数Entropy在潜剖面分析中的表现:一项蒙特卡罗模拟研究

本研究通过蒙特卡洛模拟考查了分类精确性指数Entropy及其变式受样本量、潜类别数目、类别距离和指标个数及其组合的影响情况。研究结果表明:(1)尽管Entropy值与分类精确性高相关,但其值随类别数、样本量和指标数的变化而变化,很难确定唯一的临界值;(2)其他条件不变的情况下,样本量越大,Entropy的值越小,分类精确性越差;(3)类别距离对分类精确性的影响具有跨样本量和跨类别数的一致性;(4)小样本(N=50~100)的情况下,指标数越多,Entropy的结果越好;(5)在各种条件下Entropy对分类错误率比其它变式更灵敏。

利用地基微波辐射计资料反演0～10km大气温湿廓线试验研究

实测与模拟的微波辐射计亮温存在偏差,导致基于BP神经网络模型的大气温湿廓线反演精度的降低。研究了一种基于资料订正后的BP神经网络反演大气温湿廓线的方法。首先,基于2014年6月南京江宁探空资料,利用MonoRTM模式,模拟中心频率在22.234 GHz^58.800 GHz范围内22通道亮温;对比模拟和实测南京站微波辐射计资料,建立实测微波辐射计资料订正模型。然后,以南京地区2011—2013年探空资料为输入,模拟22通道亮温数据,并基于模拟的22通道亮温数据和当地探空资料,利用BP神经网络算法,建立大气温度、水汽密度、相对湿度廓线反演模型。最后,利用构建的订正模型,对2014年7月试验获取的微波辐射计资料进行订正,并将订正后的微波辐射计资料输入BP神经网络反演模型,反演0~10 km高度58层的大气温度、水汽密度和相对湿度,对比实际探空资料以及微波辐射计二级产品,评估分析反演效果。实验结果表明:所建的反演模型提高了大气温湿廓线反演精度,大气温度、水汽密度和相对湿度均方根误差范围分别为1.0~2.0 K、0.20~1.93 g/m^3和2.5%~18.6%。