Corrosion behavior of dissimilar copper/brass joints welded by friction stir lap welding in alkaline solution

This study was done to evaluate the nugget zone(NZ)corrosion behavior of dissimilar copper/brass joints welded by friction stir lap welding(FSLW)in a solution of 0.015 mol/L borax(pH 9.3).To this end,dissimilar copper/brass plates were welded with two dissimilar heat inputs(low and high)during the welding procedure.The high and low heat inputs were conducted with 710 r/min,16 mm/min and 450 r/min,25 mm/min,respectively.Using open circuit potential(OCP)measurements,electrochemical impedance spectroscopy(EIS)and Tafel polarization tests,the electrochemical behavior of the specimens in borate buffer solution was assessed.With the help of scanning electron microscope(SEM),the morphology of welded specimen surfaces was examined after immersion in the test solution.According to the results,the NZ grain size and resistance improvement reduced due to the nugget zone corrosion with a decreased heat input.The results obtained from Tafel polarization and EIS indicated the improved corrosion behavior of the welded specimen NZ with a decrease in the heat input during the welding process unlike the copper and brass metals.Furthermore,an increased heat input during the welding process shows a reduction in the conditions for forming the passive films with higher protection behavior.

COMPLEX VARIABLE-VARIATIONALMETHOD OF SOLUTION FOR BI-METALLAMINATES WITH INTERFACE CRACKSAND ITS APPLICATION IN GLUED JOINTS

In this paper, the eigen function expansions of displacements and stresses of bi-metal laminates with interface cracks are obtained. Furthermore, the stress intensity factors are determined by the variational method to satisfy the boundary conditions and there are only line integrals in the variational equations due to the previous satisfaction of all basic equations. The computations show that this method of solution has the advantages of rapid convergency and time-saving. The results obtained by this method for homogeneous material agree with the known ones very well.

PATH INTEGRAL SOLUTION OF NONLINEAR DYNAMIC BEHAVIOR OF STRUCTURE UNDER WIND EXCITATION

A numerical scheme for the nonlinear behavior of structure under wind excitation is investigated. With the white noise filter of turbulent-wind fluctuations, the nonlinear motion equation of structures subjected to wind load was modeled as the Ito＇ s stochastic differential equation. The state vector associated with such a model is a diffusion process. A continuous linearization strategy in the time-domain was adopted. Based on the solution series of its stochastic linearization equations, the formal probabilistic density of the structure response was developed by the path integral technique. It is shown by the numerical example of a guyed mast that compared with the frequency-domain method and the time-domain nonlinear analysis, the proposed approach is highlighted by high accuracy and effectiveness. The influence of the structure non-linearity on the dynamic reliability assessment is also analyzed in the example.

Direct solution for fixed source location using well-posed TDOA and FDOA measurements

Based on the time differences of arrival(TDOA) and frequency differences of arrival(FDOA) measurements of the given planar stationary radiation source, the joint TDOA/FDOA location algorithm which solves the location of the target directly is proposed. Compared with weighted least squares(WLS) methods,the proposed algorithm is also suitable for well-posed conditions,and gets rid of the dependence on the constraints of Earth's surface. First of all, the solution formulas are expressed by the radial range. Then substitute it into the equation of the radial range to figure out the radial range between the target and the reference station. Finally use the solution expression of the target location to estimate the location of the target accurately. The proposed algorithm solves the problem that WLS methods have a large positioning error when the number of observation stations is not over-determined. Simulation results show the effectiveness of the proposed algorithm, including effectively increasing the positioning accuracy and reducing the number of observatories.

络合沉淀法—硫化沉淀法联合处理铜氰贫液试验研究

针对某黄金生产企业产生的铜氰贫液,采用络合沉淀法—硫化沉淀法联合进行回收处理。在络合沉淀法五水合硫酸铜投加量3.0 g/L、焦亚硫酸钠投加量2.0 g/L,硫化沉淀法九水合硫化钠加药量0.35 g/L条件下,铜氰贫液中总氰化合物、铜和硫氰酸盐质量浓度从150.84 mg/L、121.46 mg/L、252.65 mg/L降至0.44 mg/L、86.17 mg/L、1.23 mg/L,回收金、银、铜的产值为116.62元/m^(3),扣除药剂成本后产生经济效益55.44元/m^(3)。研究结果为类似氰化企业铜氰贫液的净化处理提供参考。

基于聚焦解决模式的护理干预对强直性脊柱炎患者情绪及治疗依从性的影响

目的:探讨强直性脊柱炎患者应用基于聚焦解决模式护理干预的效果及其对情绪及治疗依从性的影响。方法:选取2022年1—12月福建医科大学附属三明第一医院风湿内分泌科收治的58例强直性脊柱炎患者,按随机数字表法分为两组,给予对照组(n=29)患者常规护理,给予观察组(n=29)患者常规护理及基于聚焦解决模式的护理干预。观察比较两组心理状态、疼痛度、关节功能、自我效能及治疗依从性。结果:护理后,观察组抑郁自评量表(SDS)与焦虑自评量表(SAS)评分较对照组均显著更低(P<0.05);护理后,观察组Bath强直性脊柱炎功能指数量表(BASFI)与视觉模拟评分法(VAS)评估均显著低于对照组(P<0.05);观察组护理后一般自我效能感量表(GSES)评分及总依从率均显著高于对照组(P<0.05)。结论:强直性脊柱炎患者临床治疗中应用基于聚焦解决模式的护理,可明显改善患者不良情绪与疼痛感,并可提高其治疗依从性与自我效能,使患者能以积极心态主动配合治疗与护理,进而能有效提升其关节功能。

347H不锈钢焊接接头热处理后产生裂纹的分析及应对研究

347H不锈钢在稳定化及固溶化热处理后焊缝容易产生裂纹等缺陷,裂纹的产生增加了设备的制造成本、延长了制造周期。镍基焊材具有耐腐蚀性强,抗蠕变性好等优点。本文通过实验对347H不锈钢和镍基焊材在不同热处理方式下焊接接头的组织性能、耐腐蚀性能进行了研究,表明347H不锈钢采用镍基焊条焊接方法能有效避免焊接接头在稳定化或固溶热处理后易产生裂纹的倾向,解决了奥氏体不锈钢热处理后形成裂纹的问题,为实际生产提供了较好的参考。

固溶和稳定化热处理对TP347钢焊接接头组织的影响研究

对TP347钢管道焊接接头在经过1050℃固溶热处理和900℃稳定化热处理后不同区域显微组织的变化进行了研究。结果表明:在焊态下,热影响区晶粒长大,形成不同形态的铁素体,并有NbC和Cr的碳化物析出;在固溶处理后,观察到热影响区和焊缝区中铁素体含量明显减少,并且发现有分布更分散且尺寸更小的NbC;在先固溶处理再稳定化热处理后,观察到NbC在尺寸上进一步变小,表明这种热处理方法能够有效地分散NbC颗粒。研究结果表明,TP347钢经固溶热处理和稳定化热处理后铁素体转变、NbC形成以及降低焊接热循环引起的显微组织变化,可以有效提高材料的抗晶间腐蚀性能。

Joint TDOA and AOA location algorithm

For the joint time difference of arrival（TDOA） and angle of arrival（AOA） location scene,two methods are proposed based on the rectangular coordinates and the polar coordinates,respectively.The problem is solved perfectly by calculating the target position with the joint TDOA and AOA location.On the condition of rectangular coordinates,first of all,it figures out the radial range between target and reference stations,then calculates the location of the target.In the case of polar coordinates,first of all,it figures out the azimuth between target and reference stations,then figures out the radial range between target and reference stations,finally obtains the location of the target.Simultaneously,simulation analyses show that the theoretical analysis is correct,and the proposed methods also provide the application of the joint TDOA and AOA location algorithm with the theoretical basis.

基于自收敛同伦延拓法搜索七自由度机械臂零空间解集

针对七自由度机械臂零空间解集的无穷性,传统数值迭代只能求取单一解,解析法通用性较低,微分映射法精度较低的问题,本文在传统同伦延拓法的基础上采用同伦延拓参数自收敛的方式并加入关节限幅环节以优化延拓空间,并在此基础上,采用余弦函数作为同伦延拓辅助函数为方程组加入扰动。首先,根据改进DH参数法得到正运动学变换矩阵;其次,对自收敛同伦延拓法和传统同伦延拓法的求解时效、求解范围、对求解精度的适应性以及迭代限幅对求解的影响进行对比实验;最后,使用球形包围盒法结合加权取解的方式使得机械臂利用搜索到的零空间解集进行避障运动。经实验证明自收敛法的求解时效要优于传统法,加入关节限幅过程后,两种方法的时效性均有提升。

Stresses induced by post-tensioned anchor in jointed rock mass

A new analytical study on stresses around a post-tensioned anchor in rocks with two perpendicular joint sets is presented. The assumptions of orthotropic elastic rock with plane strain conditions are made in derivation of the formulations. A tri-linear bond-slip constitutive law is used for modeling the tendon-grout interface behavior and debonding of this interface. The bearing plate width is also considered in the analysis. The obtained solutions are in the integral forms and numerical techniques that have been used for evaluation. In the illustrative example given, the major principal stress is compressive in the anchor free zone and compressive stress concentrations of 815 k Pa and 727 k Pa(for the anchor load of 300 k N) are observed under the bearing plate and the bond length proximal end, respectively. However, large values of tensile stresses with the maximum of-434 k Pa are formed at the bond length distal end. The results obtained using the proposed solution are compared very those of numerical method(FEM).

磷酸盐-柠檬酸盐体系中Q235钢焊接接头磷化处理及耐蚀性

将柠檬酸钠添加到锌锰系磷化液中配成磷酸盐-柠檬酸盐磷化液体系,然后在该体系中对Q235钢焊接接头进行磷化处理。研究了磷化液体系中柠檬酸钠的质量浓度对Q235钢焊接接头表面磷化膜的微观形貌、成分、厚度和耐蚀性的影响。结果表明:磷化处理后焊接接头的外观呈黑灰色,磷化膜完整地覆盖母材和焊缝区域并且结合紧密。随着柠檬酸钠质量浓度的增加,磷化膜的微观形貌发生明显变化,厚度呈先增加后降低的趋势,导致耐蚀性先提高后下降。柠檬酸钠的质量浓度为2.5 g/L时获得的磷化膜表面结构较致密且厚度最大(约9.4μm),其腐蚀电流密度为1.36×10^(-6)A/cm^(2)且耐点滴时间达到186 s,可以起到较理想的防护作用。在此条件下磷化处理后的Q235钢焊接接头表现出良好的耐蚀性。

穿断层分段柔性接头隧道纵向地震响应解析解

地震发生伴随的断层错动是穿断层隧道灾变防控的重点和难点,目前比较有效的措施是通过设置柔性接头来适应断层的错动,但是对于柔性接头隧道的分段设计和参数取值缺少理论依据。以穿断层分段柔性接头隧道为研究对象,将分段隧道简化成有限长梁,隧道接头简化为剪切和弯曲弹簧元件,围岩简化为Pasternak双参数地基。为了合理考虑断层场地的不连续性,将断层带及上、下盘的非连续位移场等效为荷载施加在隧道梁上。基于建立的控制方程及边界条件,推导出分段柔性接头隧道在断层错动作用下的纵向地震响应解析解。通过与相同计算条件下的模型试验和数值计算结果对比分析,验证了解析方法的正确性。最后应用解析解对穿断层分段柔性接头隧道设计的关键参数进行敏感性分析,揭示了分段柔性接头布置方式和隧道本体-接头刚度比等因素对隧道结构内力响应的影响规律。结果表明:设置柔性接头可有效降低断层带影响区域内隧道结构纵向的内力响应,且柔性接头数量越多,隧道结构内力响应越小,若将柔性接头分别布置于断层错动面、断层与上/下盘交界面处,可以显著降低隧道结构的内力响应;而通过调整接头刚度来增大隧道本体-接头刚度比可以进一步降低隧道结构的内力响应。研究可为穿断层隧道抗震分析与分段柔性接头设计提供理论依据。

考虑环缝接头塑性变形的跨断层盾构隧道纵向响应解析解

本文基于Winkler地基Timoshenko梁理论,考虑水平地基摩阻力及盾构隧道环缝接头塑性变形特征,提出了一种跨断层盾构隧道纵向响应解析模型。首先,以正断层错动工况为例,采用数值模拟方法验证解析解的合理性。然后,分析了盾构隧道环缝接头的塑性变形特征,并通过参数分析讨论了影响隧道纵向变形响应的因素。研究结果表明:断层错动下盾构隧道环缝接头张开及错台变形均较为显著,解析模型计算得到的盾构隧道纵向力学响应特征与数值模型计算结果规律一致;在断层错动10 cm时,盾构隧道环缝接头已产生显著的塑性变形;在穿越活动断层工况中,地层对隧道纵向变形的限制作用更加明显,导致环缝接头变形量更大;地基刚度越大,盾构隧道纵向变形响应越显著。当不考虑断层破碎带宽度时,计算得到隧道纵向力学响应值是偏安全的;在隧道环缝接头弹性变形阶段,弹性弯曲刚度有效率越大,接头张开量越小;在环缝接头塑性变形阶段,盾构隧道二次塑性等效弯曲刚度比越大,盾构隧道环缝接头塑性变形越小。本文提出的解析模型可以预测跨断层盾构隧道环缝接头变形,同时可以为盾构隧道接缝防水设计提供理论指导。

汽车雷达多域联合调制波形

针对汽车雷达时分复用(time-division multiplexing,TDM)多输入多输出(multiple-input multiple-output,MIMO)波形中存在的时间空间利用率低及高速目标多普勒模糊等问题,提出一种多域联合调制的汽车雷达波形。该波形在时域上进行脉冲重复间隔参差抖动,利用奇偶序列之间相位差实现速度解模糊,在频域和空域上通过多天线间的多普勒频率调制实现波形正交,提高了时间空间发射效率。仿真实验及基于汽车雷达波形验证系统的实测结果均验证了所提波形的有效性,与传统TDM-MIMO波形对比,所提波形具有更大的不模糊测速范围和相参积累增益,不仅对汽车雷达工程实践具有较强的应用价值,而且对低成本导引或防撞探测系统同样具有指导意义。

一种基于航向估计的多平台纯方位目标转向机动检测算法

针对纯方位目标转向机动检测问题,提出一种基于航向估计的多平台纯方位目标机动检测算法。该算法通过选定假设机动点序列,解算假设机动点前后的两段目标运动要素,根据解算出的相邻段航向差序列变化来判别目标是否发生机动。基于Taylor级数要素解算模型,建立了两段运动要素联合解算模型和两段运动要素独立解算模型。通过对多种航路进行仿真计算,统计分析这两种解算模型下机动检测算法的虚警率、目标机动检测率、机动检测延迟时间以及机动时刻估计精度。仿真结果表明,两种解算模型下的机动检测算法能够有效地对转向机动目标进行机动检测。

固溶热处理对304L不锈钢焊接接头力学性能及微观组织的影响

304L不锈钢采用埋弧焊焊接方法焊接,焊后分别进行焊态和1060℃固溶热处理态的性能试验,通过对比试验研究固溶热处理对304L不锈钢焊接接头性能的影响。对两种状态下的焊接接头进行常温拉伸、弯曲、冲击、硬度、铁素体、微观组织等对比试验。试验结果表明,经过固溶热处理后的焊接接头常温抗拉强度及焊缝硬度、焊缝铁素体均有一定程度的下降,焊缝及热影响区的冲击韧性上升,焊缝中的柱状晶组织消失,形成新的奥氏体晶粒。

Multiscale microstructural consideration of enhanced shear strength in TiAl intermetallic/K4169 alloy composite joints prepared by vacuum brazing with(Ti,Zr)-Ni-based amorphous filler metal

TiAl intermetallic could be used to replace Ni-based alloy in assemblies to generate excellent specific strength.A(Ti,Zr)-Ni-based amorphous filler metal Ti_(21.25)Zr_(25)Ni_(25)Cu_(18.75)(at.%)was designed using a cluster-plus-glue-atom model to successfully vacuum braze K4169 and TiAl bimetallic assemblies.At various brazing temperatures and holding time,the quantitative relationships between lattice distortion,grain boundary,dislocation density,and hardness,elastic modulus,shear strength of the joints were investigated.Meanwhile,the fracture mechanism of the joints was revealed.The brazed seam mainly consisted of solid diffusion reaction layers(ZonesⅠandⅢ)and filler metal residue zone(ZoneⅡ).When the brazing temperature increased to 1030℃,grain refinement occurred in the brazed seam.ZoneⅠwas primarily composed of(Ni)ss[0-11]+TiNi[011]/(Cr,Fe,Ni)ss[0-11]/(Ti,Zr)Ni[0-1-1]+(Cr,Fe,Ni)ss[0-11].The(Ti,Zr)(Ni,Cu)[001]and(Ti,Zr)(Ni,Cu)[101]intermetallic compound-based solid solutions were formed in ZoneⅡ.And the lattice distortion of(Ti,Zr)(Ni,Cu)[101]and(Ti,Zr)(Ni,Cu)[001]was 32.05%and 14.82%,respectively.As a result,the proportion of low angle grain boundaries(LAGBs)and deformed grains in ZoneⅡrose to 38.6%and 38.7%.In ZonesⅠandⅢ,the proportion of LAGBs reduced to 8%and 3.4%,respectively.As the holding time increased,the long-range diffusion of Al in ZoneⅡcaused the(Ti,Zr)(Ni,Cu)[001]with cubic structure to transform into(Ti,Zr)(Ni,Cu,Al)[00-1]with hexagonal crystal system structure,where the lattice distortion was 4.42%and 10.49%for a and c.At 1030℃/10 min,the average geometrically nec-essary dislocation densities(GNDs)in ZonesⅠ,ⅡandⅢwere 9.87×10^(14)m^(-2),8.55×10^(14)m^(-2)and 11.4×10^(14)m^(-2),respectively.Therefore,the shear strength of joints reached 322 MPa due to the lattice distortion,dislocation strengthening and fine grain strengthening.Meanwhile,the plastic and brittle hard phases were generated in ZoneⅡand displayed a mechanical interlocking structure that contributed to the performance of the joint.Both(Ti,Zr)(Ni,Cu)[001]and(Ti,Zr)(Ni,Cu)[101]in ZoneⅡformed along differ-ent low-index cleavage planes during transgranular fracture.The cracks initiated in this region extended to the interface between Zones I andⅡand exhibited bimodal grain characteristics.

基于分块粒子滤波的多节点协同无源探测解算算法

多节点协同无源探测是实现对机动雷达快速定位的有效手段。在空间上分离的多个节点同时无源侦察雷达信号,获取信号到达不同节点的到达时间差(Time Difference of Arrival,TDOA)和频率差(Frequency Difference of Arrival,FDOA)。通过TDOA/FDOA联合解算,完成对目标雷达位置和速度的测量。粒子滤波是一种近似最优的非线性滤波方法,其借助蒙特卡洛模拟可实现对待求参数概率密度函数的近似最优估计。将粒子滤波应用于协同无源探测解算,可实现非参数化的递推贝叶斯滤波,大幅提升无源探测的位置、速度测量精度。此外,还提出一种分块粒子滤波解算算法,通过降低粒子状态矢量维度,提升粒子空间覆盖性,在粒子数量受限的情况下,可进一步提升探测精度。

面向地表三维形变解算的SOR迭代拟合推估GPS-InSAR联合模型应用研究

针对基于最小二乘法在GPS-InSAR联合拟合推估模型中,对小控制范围内地表三维形变联合解算中系数矩阵奇异且扰动大、结果精度低等问题,本文提出一种优化的拟合推估联合解算模型,使用逐次超松弛迭代法(SOR)控制解算模型系数矩阵的扰动,进而提高拟合推估模型联合解算的精度,且使用西宁市南山的GPS和InSAR数据进行直接法、最小二乘法和SOR优化的测试实验。实验结果表明,经SOR优化的拟合推估模型GPS-InSAR联合解算精度明显优于直接法、最小二乘法的解算精度,其中,SOR优化拟合推估模型解算平均误差和均方根误差优于最小二乘法拟合推估模型解算,精度约为64.35%、70.45%,因此更有利于后期地表三维形变的监测。