Dynamic Testing of Elastic Modulus,Shear Modulus,and Poisson’s Ratio of Bamboo Scrimber

The bamboo scrimber is an anisotropic material.The elastic constant values of the bamboo scrimber specimens measured by the dynamic and static methods are consistent,and the dynamic test method has the advantages of rapidity,simplicity,good repeatability,and high precision.Bamboo scrimber has strong potential as a building material,and its elastic constant is an important index to measure its mechanical properties.To quickly,simply,non-destructively,and accurately detect the elastic constant of the bamboo scrimber,they were dynamically tested by the free plate transient excitation method and cantilever plate torsional vibration method.The static four-point bending method was used to verify the accuracy and reliability of the dynamic elastic modulus,shear modulus,and Poisson’s ratio of the bamboo scrimber.The mechanism analysis and evaluation of the quality grade,homogeneity,and size effect of the bamboo scrimber whole board were carried out.The main results show that the dynamic elastic modulus,shear modulus,and Poisson’s ratio of the bamboo scrimber are 12 GPa,1500 MPa,and 0.31,respectively,which meet the requirements of GB/T 40247-2021 for structural bamboo scrimber.

Research on Dynamic and Static Test Methods for Evaluating the Poisson's Ratio of Orien ted Strand Board

In this article,dynamic method and static method of testing Poisson's ratio of OSB(Oriented Strand Board)were proposed.Through modal and static numerical analyses,the position where the transverse stress is equal to zero was determined.The binary linear regression method was applied to express the gluing position of the strain gauge as a relational express ion that depended on the length-width ratio and width-thickness ratio of the canti-lever plate.Then the longitudinal and transverse Poisson's ratios of OSB were mea sured by the given dynamic and static methods.In addition,the test results of OSB Poisson's ratio were analyzed with the probability distribution of random variables.The results showed that using the proposed dynamic method and static method,the test results for longitudinal and transverse Poisson's ratios of OSB were quite consistent,despite the gluing position of the strain gauges being different.And these OSB Poisson's ratios were accorded with that obtained by the axial tensile method and the four-point bending method.OSB longitudinal and transverse Poisson's ratios followed Weibull distribution.

Fuzzy Model Free Adaptive Control for Rotor Blade Full-Scale Static Testing

To eliminate the node traction coupling during wind turbine blade full-scale static testing,a model free adaptive control algorithm is presented based on fuzzy control performance function compensation. Based on the universal model theory,the fuzzy model free adaptive control( FMFAC) algorithm is designed by configuring the spot static testing experiences as compensation function F( ·). Then the algorithm implementation process is provided and its quick convergence is proved. Using software to establish static load coupling model of multi-nodes,simulate and verify the validity of FMFAC algorithm,which is applied to wind turbines blade full-scale static testing. The results show that the adaptive decoupling ability of FMFAC is better. The traction of four load points can stay steady and change coordinately. Process error is not over ± 6 k N. The error rate is lower than 1% in special phase.This algorithm effectively eliminates the traction coupling of the static testing process,and makes wind turbine blade testing steadily.

Comparative study on three dynamic modulus of elasticity and static modulus of elasticity for Lodgepole pine lumber

The dynamic and static modulus of elasticity （MOE） between bluestained and non-bluestained lumber of Lodgepole pine were tested and analyzed by using three methods of Non-destructive testing （NDT）, Portable Ultrasonic Non-destructive Digital Indicating Testing （Pundit）, Metriguard and Fast Fourier Transform （FFT） and the normal bending method. Results showed that the dynamic and static MOE of bluestained wood were higher than those of non-bluestained wood. The significant differences in dynamic MOE and static MOE were found between bulestained and non-bluestained wood, of which, the difference in each of three dynamic MOE （Ep. the ultrasonic wave modulus of elasticity, Ems, the stress wave modulus of elasticity and El, the longitudinal wave modulus of elasticity） between bulestained and non-bluestained wood arrived at the 0.01 significance level, whereas that in the static MOE at the 0.05 significance level. The differences in MOE between bulestained and non-bluestained wood were induced by the variation between sapwood and heartwood and the different densities of bulestained and non-bluestained wood. The correlation between dynamic MOE and static MOE was statistically significant at the 0.01 significance level. Although the dynamic MOE values of Ep, Em, Er were significantly different, there exists a close relationship between them （arriving at the 0.01 correlation level）. Comparative analysis among the three techniques indicated that the accurateness of FFT was higher than that of Pundit and Metriguard. Effect of tree knots on MOE was also investigated. Result showed that the dynamic and static MOE gradually decreased with the increase of knot number, indicating that knot number had significant effect on MOE value.

Mechanical properties of rock under coupled static-dynamic loads

Rock drilling machine,INSTRON testing system,and SHPB device are updated to investigate the characteristics of rocks at great depth,with high loads from overburden,tectonic stresses and dynamic impacts due to blasting and boring.It is verified that these testing systems can be used to study the mechanical properties of rock material under coupled static and dynamic loading condition and give useful guidance for the deep mining and underground cavern excavation.Various tests to determine the rock strength,fragmentation behavior,and energy absorption were conducted using the updated testing systems.It is shown that under coupled static-dynamic loads,if the axial prestress is lower than its elastic limit,the rock strength is higher than the individual static or dynamic strength.At the same axial prestress,rock strength under coupled loads rises with the increasing strain rates.Under coupled static and dynamic loads,rock is observed to fail with tensile mode.While shear failure may exist if axial prestress is high enough.In addition,it is shown that the percentage of small particles increases with the increasing axial prestress and impact load based on the analysis of the particle-size distribution of fragments.It is also suggested that the energy absorption ratio of a specimen varies with coupled loads,and the maximum energy absorption ratio for a rock can be obtained with an appropriate combination of static and dynamic loads.

Optimal Reordering Trace Files for Improving Software Testing Suitcase

An invariant can be described as an essential relationship between program variables.The invariants are very useful in software checking and verification.The tools that are used to detect invariants are invariant detectors.There are two types of invariant detectors:dynamic invariant detectors and static invariant detectors.Daikon software is an available computer program that implements a special case of a dynamic invariant detection algorithm.Daikon proposes a dynamic invariant detection algorithm based on several runs of the tested program;then,it gathers the values of its variables,and finally,it detects relationships between the variables based on a simple statistical analysis.This method has some drawbacks.One of its biggest drawbacks is its overwhelming time order.It is observed that the runtime for the Daikon invariant detection tool is dependent on the ordering of traces in the trace file.A mechanism is proposed in order to reduce differences in adjacent trace files.It is done by applying some special techniques of mutation/crossover in genetic algorithm(GA).An experiment is run to assess the benefits of this approach.Experimental findings reveal that the runtime of the proposed dynamic invariant detection algorithm is superior to the main approach with respect to these improvements.

Application of signal sparse decomposition in dynamic test

In dynamic test,sampling rate is high and noise is strong,so a signal sparse decomposition method based on Gabor dictionary is put forward.This method iteratively decomposes the signal with the matching pursuit(MP)algorithm and takes the coherence ratio of the threshold as a condition of iteration termination.Standard MP algorithm is time-consuming,thus an adaptive genetic algorithm is introduced to MP method,which makes computation speed accelerate effectively.Experimental results indicate that this method not only can effectively remove high-frequency noise but also can compress the signal greatly.

Status of Developers’ Testing Process

Even if recent methodologies bring more recognition to developers’ testing process, we still have little insight into its status within the industry. In this paper, we study the status of developers’ testing process at Nomadic Software. Our results show that the process is not uniformly executed. The company suffers from lack of control over the methods used, lack of formal communication on requirements, lack of static testing practice, and lack of testing process documentation.

基于离散元法的面粉颗粒接触参数标定试验

为设计和优化面粉输送设备,应用离散元法对面粉进行准确地工程建模和分析,需要对其接触参数进行必要的标定。该研究依据颗粒缩放理论,用“Hertz-Mindlin with Johnson-Kendall-Roberts”接触模型表征面粉颗粒间黏性的影响,提出了一种基于静/动态休止角的接触参数标定方法。运用正交试验方法,对接触参数的敏感性和方差分析,表明面粉颗粒间的滚动摩擦系数、面粉颗粒与不锈钢表面间的静摩擦系数、表面能对静态休止角的影响极显著(P<0.01),并且多组接触参数都可以模拟出与试验相同的静态休止角。进一步研究表明,面粉颗粒与不锈钢表面间的静摩擦系数的合理取值范围为0.2~0.4。通过2种填充率、4种转速下基于动态休止角的参数标定,将其中与试验最为吻合的一组参数作为标定结果,其值如下:面粉颗粒之间恢复系数为0.6、面粉颗粒之间静摩擦系数为0.2、面粉颗粒之间滚动摩擦系数为0.1、面粉颗粒与不锈钢容器表面之间恢复系数为0.6、面粉颗粒与不锈钢容器表面之间静摩擦系数为0.6、面粉颗粒与不锈钢容器表面之间滚动摩擦系数为0.5、表面能为0.12 J/m^(2)。使用该组参数对矩形容器中物料自由坍塌试验进行仿真,其结果与试验结果相符,验证了该标定方法的有效性。该研究提出的标定方法简单、易执行,对粉料输送设备的设计及优化具有一定的工程应用价值。

地下管廊抗震研究现状综述

针对地下管廊工程建设高速发展、抗震减灾需求愈发凸显的现状,综述地下管廊抗震研究现状.首先,通过国内外以往的震害实例,对地下管廊的震害形式、震害影响因素及震害机理进行了系统性总结.其次,从拟静力试验和振动台试验两个方面总结了地下管廊抗震性能的试验研究现状.再次,总结了地下管廊抗震分析的简化分析方法、动力时程方法、地震易损性评估及减隔震技术的研究现状.最后,基于文献综述提出了目前地下管廊抗震研究亟待解决的问题并做出展望,以期促进地下管廊抗震研究的发展.研究表明:地下管廊在地震作用下的破坏形式主要有混凝土剥落、裂缝贯通、接缝错位或张开、管廊受剪断裂等;地震作用下地下管廊穿越非均匀场地时动力响应的放大效应显著,地下管廊穿越软硬交互等非均匀场地时的抗震性能研究值得重视;交叉节点是地下管廊的薄弱环节,交叉管廊的抗震设计方法研究值得关注;预制管廊接头易受到地震破坏,不同类型预制管廊接头的抗震性能研究需深入探索;城市大型地下管廊系统抗震性能受到不同交叉节点和不同管廊之间的交互影响,高效的地下管廊系统建模方法和高效的简化分析方法亟待研究;城市大型地下管廊系统地震易损性分析是重要的发展方向;地下管廊的减隔震技术值得发展.

浮选颗粒条栅结构表面润湿行为特性研究

矿物颗粒间表面润湿性差异是浮选成功的关键,受表面化学性质与物理形貌结构的双重影响。为进一步明确表面物理形貌结构对液滴在矿物颗粒表面上润湿行为的影响,采用光刻显影技术制备了5种具有不同粗糙度系数和表面面积分数的条栅结构聚二甲基硅氧烷(PDMS)表面,并利用自制的动/静态接触角测量系统及润湿三相接触线行为测试系统对液滴在PDMS表面上的润湿行为进行了测试。动/静态接触角测试结果表明:当表面粗糙度系数相同时,固体表面面积分数增加,条栅结构表面不同润湿方向上的接触角均呈减小趋势,而当表面面积分数相同时,条栅结构表面不同润湿方向上的接触角则与固体表面粗糙度系数呈正相关;此外,各样品表面垂直于条栅结构方向的动/静态接触角均大于平行方向(即θ_(⊥)>θ_(∥)),且不同润湿方向上接触角的差异随样品表面润湿性的增强而减小。动态接触角测试结果还表明:表面接触角滞后(Δθ=θ_(a)-θ_(r))与表面面积分数呈正相关,而与表面粗糙度系数呈负相关,且前进与后退接触角的预测值与试验值基本吻合,说明动态接触角能够真实地反映固体表面润湿性;此外,在液滴滚动时,其运动行为总是周期性地发生后端接触线先从固体表面分离,而后液滴重新与固体表面发生黏附形成新的前端接触线的过程,这种运动特性在不同条栅结构表面上完全相同。润湿三相接触线行为测试结果表明:液滴在条栅结构表面优先沿着条栅结构方向润湿或去润湿,而跨越条栅结构润湿时,受表面微结构的“钉扎”作用,润湿半径远小于平行润湿方向,且三相接触线在不同条栅结构表面的移动均呈现“解钉—钉扎—再解钉—再钉扎”的一种断续周期性过程。研究结果深化了矿物颗粒表面物理形貌结构对其润湿行为特性的影响,可为后续通过表面形貌调控颗粒表面润湿性起到一定的理论支撑作用。

Reconstruction of shock wave pressure field based on distributed test system

A new distributed test system composed of multiple test nodes was designed by adopting storage test technology to test shock waves in explosion field. The advantage of the system is the application of sensor lattice whose rise time is microsecond level, which can quickly response to transient shock wave signals. In order to reduce dynamic response error, shock tube is employed to conduct dynamic calibration on the system. The overpressure peak values of the explosion shock wave collected by sensor lattice were used to construct a shock wave pressure field with B-spline interpolation algorithm.

舰载飞机着舰撞击载荷实测技术研究

针对国内飞机起落架载荷测量中普遍存在的静标动测问题,从理论和机理上分析了静标定的应变法实测动态载荷存在问题的原因。同时,考虑到舰载飞机因定点着舰方式遭受严重的动态载荷,重点研究了舰载飞机着舰撞击载荷的静标动测问题。通过动态落震试验模拟飞机着舰过程,根据测力平台的实测载荷分析,获取了应变法实测载荷精度受动态影响的程度,提出一种改进的惯性修正方法,即:通过落震试验数据辨识质量矩阵,通过辨识的质量矩阵和实测加速度修正应变法的实测载荷。试验结果表明,改进的惯性修正方法进一步提高了垂向载荷的测量精度,显著提高了航向和侧向载荷的实测精度。

基础加固施工对重载铁路桥梁静动力性能影响研究

铁路桥梁墩台基础加固施工会改变桥墩约束状态,影响结构稳定和列车运营安全。以某重载铁路轻型桥墩基础加固工程为背景,采用数值模拟和试验测试手段,研究各关键施工环节对桥墩和桥跨结构稳定性、刚度和振动响应的影响规律。研究结果表明,基础加固施工分为钻孔桩施工、基础侧土体开挖、基础混凝土浇筑、墩身连接等4个关键施工步骤,其中土体开挖会导致桥墩稳定性和横向刚度降低,随开挖深度增加,两者均逐渐降低,而混凝土浇筑则引起桥墩刚度和稳定性逐渐增加,桥墩横向连接加固则引起墩身刚度显著增大,增幅达到32%;整个施工阶段中,土体开挖引起桥梁结构振动响应显著增大,其他加固环节对桥梁振动响应不明显;施工过程中,列车轴重、速度、桥墩高度是影响桥梁动力响应的最敏感因素,随列车轴重和速度以及桥墩高度增加,桥梁动力响应增大明显。

基于动态阈值和差异性检验的自训练算法

针对自训练算法在迭代训练分类器的过程中存在难以有效选取高置信度样本以及误标记样本错误累积的问题,本文提出了基于动态阈值和差异性检验的自训练算法。引入样本的局部离群因子,据此剔除有标签样本中的离群点以及分类标注无标签样本,依据标注分批次处理无标签样本,以使模型更易选取到高置信度的无标签样本;根据新增伪标签样本的数量和对比隶属度的变化,设计一种动态隶属度阈值函数,提升高置信度样本的质量;定义密集距离度量样本间的差异性,分别计算伪标签样本与同类和不同类样本之间的密集距离之和,从而找出不确定度高的伪标签样本,并将此类样本并入下轮训练的无标签样本集中,缓解误标记样本错误累积的问题。实验结果表明,该算法在12个UCI基准数据集上均取得理想效果。

冶金高频响高精度伺服液压缸性能测试系统软件开发

采用LabVIEW与MATLAB函数结合的方法,开发了冶金高频响高精度伺服液压缸性能测试系统。根据生产冶金高频响高精度伺服液压缸对其动静态性能指标要求,该测试系统功能模块包含最低起动压力测试模块、带载动摩擦力测试模块、阶跃响应测试模块、频率响应测试模块、偏摆测试模块,各项测试结果通过研华数据采集卡PCI-1742U、PCI-1723与SSI-RS485电流变送器转换采集MST位移传感器信号与AB相脉冲传感器信号;该测试系统能够对测试的数据进行实时跟踪显示、存储或查询;此外,该系统还具有数据导出、打印实验报告等辅助功能。实验证明,该测试系统具有较高的实时性与可操作性,填补了其他系统所空缺的针对于大直径冶金高频响高精度伺服液压缸的偏摆测试模块,同时该测试系统具有更高的稳定性,解决了技术人员对原有测试系统操作复杂的难题,实现“傻瓜式”操作,更加智能化、可视化、及时化。

融合改进哈里斯鹰和改进动态窗口的机器人动态路径规划

针对动态环境的移动机器人路径规划问题,提出了一种改进哈里斯鹰算法(IHHO)与改进动态窗口算法(IDWA)的融合算法(IHHO-IDWA)。首先,针对哈里斯鹰算法后期搜索性能不足等问题,提出了融合自适应混沌和核心种群动态划分策略、融合黄金正弦策略以及动态云最优解扰动策略来提高算法的性能。其次,针对动态窗口算法存在规划的路径长和易陷入死锁等问题,提出了三个改进策略:增加子函数,保证算法能够规划出更短的路径;提出自适应权重策略,平衡算法局部避障能力和全局搜索性能;设定初始航向角,避免路径冗余。最后,通过测试函数、CEC2014函数的数值实验和静态、动态路径规划实验,验证了IHHO和IDWA性能有明显提升;通过50×50大型动态地图验证了融合算法较对照组算法规划的路径缩短了11.51%,证明了该方法的优越性。

Dynamic finite element model updating of prestressed concrete continuous box-girder bridge

The dynamic finite element model （FEM） of a prestressed concrete continuous box-girder bridge, called the Tongyang Canal Bridge, is built and updated based on the results of ambient vibration testing （AVT） using a real-coded accelerating genetic algorithm （RAGA）. The objective functions are defined based on natural frequency and modal assurance criterion （MAC） metrics to evaluate the updated FEM. Two objective functions are defined to fully account for the relative errors and standard deviations of the natural frequencies and MAC between the AVT results and the updated FEM predictions. The dynamically updated FEM of the bridge can better represent its structural dynamics and serve as a baseline in long-term health monitoring, condition assessment and damage identification over the service life of the bridge .

可兼容四种March系列算法的PMBIST电路设计

存储器是系统级芯片(System on chip,SoC)中最重要的组成部分之一,也是最容易出现故障的部件。存储器故障可能会导致整个SoC失效,对存储器进行充分的测试和验证是至关重要的。目前,主流的存储器测试方法是采用存储器内建自测试(Memory build-in-self test,MBIST)技术,传统的可测性技术采用单一的测试算法进行测试,为了满足不同类型存储器的测试需求以及不同工艺制造阶段的测试强度,需要使用不同类型的测试算法进行测试。结合存储器常见的故障模型以及多种测试算法,设计了具有较高灵活性和可扩展性的可编程存储器内建自测试(Programmable memory built-in-self test,PMBIST)电路,可兼容四种不同的March系列算法进行存储器内建自测试,采用寄存器传输语言(Reigster transfer language,RTL)级代码的编写方式,针对静态随机存储器(Static random-access memory,SRAM)采用不同March系列测试算法进行仿真,并以常用的March C+算法为例进行说明。仿真结果表明,所设计的PMBIST电路可对四种不同的March算法进行测试,满足不同类型存储器的内建自测试需求。

DBI-Go:动态插桩定位Go二进制的非法内存引用

Go语言,也称Golang,由于其语法简单、原生支持并发、自动内存管理等特性,近年受到很多开发者的欢迎.Go语言期望开发者不必了解变量或对象是分配在栈上还是在堆中,而由Go编译器的逃逸分析来决定分配位置,再由Go垃圾收集器自动回收无用的堆对象.Go的逃逸分析必须正确决定对象的分配位置以保证内存状态的正确性.然而,目前Go社区中逃逸相关问题频发,潜在导致程序崩溃等致命问题,而目前对该方面的研究缺失.为有效检测编译器生成的代码是否存在可能引起运行时崩溃的非法内存引用,填补研究空白,对Go程序执行进行抽象建模,并提出两条判定写入违例的规则.基于这两条规则,克服Go二进制中高层语义缺失、运行时信息不便获取等挑战,设计一个轻量化的分析工具DBI-Go.DBI-Go采用静态分析加动态二进制插桩的分析方式,基于动态二进制分析框架Pin来实现,可以识别Go二进制中违例的store指令.实验结果表明,DBI-Go可以检测出Go社区中所有已知的逃逸相关Issues;DBI-Go还发现一个目前Go社区未知的问题,该问题已经得到确认.在实际项目上的应用则表明DBI-Go可以帮助开发人员找出逃逸算法的错误.测试结果还表明DBI-Go采取的措施可以有效降低误报率且在93.3%的情况下带来的额外运行时开销小于原先的2倍.同时,DBI-Go无需修改Go的编译运行时,可以适配不同版本的Go,有较高的适用性.