超声波探伤仪的线性误差测试方法分析

介绍了超声波探伤仪的工作原理，得出水平线性和垂直线性对缺陷定位和定量的影响。对超声检定装置(含脉冲信号发生器和标准衰减器)和参考试块这两种测量器具进行探讨，同时用两种测试方法分别进行试验，得出这两种测试结果的优劣，分析影响因素，并给出相应的使用建议。     

轮槽形状对铜母线连续挤压影响的有限元分析

分析了在连续挤压初始喂料阶段,坯料在圆轮槽中的稳定性.通过理论计算和模拟研究得出,圆轮槽中的凸台对于铜的连续挤压建立一个稳定的挤压过程起关键作用.并在此基础上提出了针对圆杆形坯料的几种新的轮槽形状,将这几种轮槽对铜母线连续挤压扩展成形的影响进行了有限元数值模拟.就轮槽形状对铜扩展成形中金属的成形性、挤压轮的扭距以及成形金属流动的均匀性的影响进行了分析讨论.最后得出,带凸台的扩口形轮槽是连续挤压扩展成形中最优的轮槽形状.     

不同变质剂对液态模锻Al-Zn-Mg合金组织和性能的影响

以实验为基础,分别采用稀土钇(Y)和三元变质剂(25%NaF+62%NaCl+13%KCl,质量分数),并结合液态模锻工艺,对Al-Zn-Mg合金的成形性进行了研究;对比分析了两种变质剂在不同压力下成形试样的组织和力学性能,得出了变质剂和压力对该铝合金组织及力学性能的影响规律.     

多元醇改性呋喃树脂合成工艺研究

在现有脲醛呋喃树脂合成工艺基础上,选用山梨醉和芳烃聚醋多元醉两种多羟基化合物改性呋喃树脂,研究其添加量与添加位置对树脂砂强度影响,得出两种多元醇改性吠喃树脂最佳工艺条件,并通过红外光谱对它们改性过程的反应机理进行研究,从而得出它们的改性反应机理.并从反应机理上解释它们改性效果上差异.     

高线控冷冷却器流场仿真研究

采用有限元模拟软件Fluent对Morgan-5代、Morgan-6代冷却器进行了三维流场仿真,研究了冷却器结构变化对其压力场、速度场的影响,通过仿真获得两种冷却器的换热系数,进而对冷却器的冷却能力和冷却均匀性进行评估,得出在相同流量、相同内腔尺寸d=Φ17. 5mm的条件下,Morgan-5代冷却器的冷却能力高于Morgan-6代冷却器,在冷却均匀性方面,Morgan-6代冷却器表现更优。     

汽车铝合金轮毂辐条力学性能的统计学分析及预测

用多元统计方法对从大量汽车轮毂辐条中间部位取样测得的抗拉强度、屈服强度和伸长率等三个力学量进行了因子分析,找出了影响这些力学量的本质因素.由因子分析获知,影响辐条抗拉强度、屈服强度和伸长率三个变量的因子主要有两个:Si相和Mg2Si相.同时推出了这两相存在形态对轮毂辐条力学性能影响规律的定量分析表达式,由此可以评估这两相的强化效果,并对相应工艺流程进行评估.通过这三个力学量对轮毂形状参数进行主成分回归分析,得出了影响这些力学量的轮毂形状因素,并给出了轮毂辐条力学性能的预测区间.     

磷对超低碳冷轧钢带性能的影响

阐述在冷轧汽车钢的生产中,为了提高IF钢强度采用超低碳钢加磷的方法。为了解磷对超低碳钢性能的影响,试制了含磷和不含磷的两种超低碳冷轧钢带。通过对这两种冷轧钢带的力学性能、组织织构的对比分析,得出P使得超低碳钢的强度大幅度增加的同时,保持了良好的变形性,使得钢板在汽车厂加工后具有良好的使用性。     

线性摩擦焊接头焊合率的超声检测

论述了Ti-17线性摩擦焊接头焊合率的超声透射法检测原理、检测过程;分析了近场区对检测结果的影响,并对试件作了解剖验证,发现用超声透射法从正、反两个方向进行检测时,最大波幅高度之和∑Amax与焊合率近似成正比关系.     

焊后热处理对TC4钦合金线性摩擦焊接头组织和性能的影响

在前期焊接试验参数优化基础上,通过自行研制的线性摩擦焊机焊接了两组TC4钛合金试件,其中对一组试件焊后进行630℃x3h的热处理,然后对焊态和热处理态焊接接头的组织和力学性能进行了对比分析.结果表明.焊态下接头组织更为细小;热处理态接头组织中析出了次生a相,且晶粒发生球化长大现象,接头组织更加均匀.对两种接头在室温和400℃条件下进行拉伸试验,接头拉伸断裂位置均在母材处,且室温拉伸条件下热处理接头的抗拉强度和屈服强度均较焊态接头的高,高温拉伸条件下两种接头拉伸性能相差不大.400℃、570MPa条件下两种接头的持久时间均超过100h.     

酸洗材料对轮辐成形质量的影响

为避免钢制轮辐在拉深和反拉深过程中易出现拉裂或局部减薄等缺陷的问题,以某酸洗材料不同成分体系的两种原材料为试验材料,以材料的力学性能为基础,基于Autoform软件对以上两种材料进行仿真分析,从主次应变和厚度减薄对比研究两种材料的成形性,比较应变硬化指数n值和塑性应变比r值对成形质量的影响。对比轮辐实际生产中成形状态,得出塑性应变比r值较大时在厚度减薄上有利于零件的成形,3个方向的r差值应尽量较小,且保证3个r值在0. 8左右;当n值大于或等于0. 13时主应变量较小,破裂风险较低,有利于成形,组织均匀且伸长率更高的产品成形性优异。     

声速差计算方法及其在对外加非均匀应力评价中的应用

为了研究超声波对7050铝合金非均匀应力场的响应规律，利用Abaqus有限元软件计算不同应变状态下试样中的非均匀应力场，再根据声弹性理论计算得到该模型中试样复杂应力场对应的声速极差。为验证仿真的准确性，对7050?T7451铝合金试样施加同等程度应变的的外加应力，通过超声扫查获得超声速度分布图。结果发现，仿真和超声法获得的应力分布结果都符合应力分布的一般规律，超声法表征结果与仿真表征结果具有相关性，但是由于超声法评价的是样品全厚度方向应力的叠加效果，所以二者又存在一定的差异性。非均匀应力场仿真所得声速极差与实测较为一致，声速差异与外加变形量具有非线性递增关系，二者所得的变形量与声速极差曲线基本一致。     

基于激光超声的铝合金搅拌摩擦焊典型缺陷检测及分析

利用不同搅拌摩擦焊(FSW)工艺参数获得2219铝合金薄板根部未焊合、隧道孔两种典型缺陷,对比X射线检测结果,采用激光超声对这两种典型FSW缺陷进行检测. 从时域上对采样信号峰值点及幅值进行分析,并进一步运用PSD-welch功率谱法进行频域分析,提取频域不同频段的能量,结合时域最大幅值作为特征,利用支持向量机建模并训练,识别率达到85%. 结果表明,基于激光超声检测的时、频域特征能够有效对铝合金FSW两种典型缺陷进行分类识别,从而为铝合金FSW缺陷检测提供一种技术途径.     

Ultrasonic evaluation of the bonding strength of dissimilar metal bonds

Diffusion bonding of steel plates to titanium plates was carried out, and shear testing and ultrasonic measurement of bonds were performed to obtain the relationships between bonding strength, state of bonding interface and ultrasonic parameters. Fourier spectra of the ultrasonic wave reflected from the bonding interface were dependent on the state of the bonding interface; when an interlayer did not melt the spectrum showed a simple profile with one peak, and when the interlayer melted, the spectrum showed a profile with large irregularity. Transfer functions obtained from the spectrum were analysed with the subspace method (a kind of principal component analysis) and were represented by two major components. The bonding strength was quantitatively evaluated by two major components and a diameter estimated from the ultrasonic measurement.     

Fatigue behaviour and life estimation of Mg/Al ultrasonic spot weld bonding welds

Mg/Al dissimilar joints with favourable static and dynamic mechanical properties were obtained utilising ultrasonic spot welding and ultrasonic spot weld bonding technology. The fatigue behaviour, fatigue failure mode, and typical fatigue fracture surface morphology of Mg/Al ultrasonic spot welding and ultrasonic spot weld bonding joints were compared and observed to get a better understanding of the fatigue failure mechanism. In general, the Mg/Al ultrasonic spot weld bonding joint exhibited better fatigue performance than the ultrasonic spot welding joint. The two kinds of joints presented different fatigue failure modes with decreasing applied load level. A fatigue life prediction model was established, and the fatigue life prediction results were in good agreement with the experimental fatigue results.     

Production and bond strength of similar-titanium ultrasonic welded joints

The joinability of unalloyed titanium and the bond strength of similar titanium welded joints by ultrasonic welding were investigated. It turned out that sound welded joints of similar titanium were obtained by using the jig for fixing both base metals. In the case of non-fixing and fixing the lower base metal, sound welded joints were not usually obtained due to the slip between the two base metals. Producing welded joints having sufficient bond strength required a certain threshold value of the ultrasonic energy. When the ultrasonic welding was carried out under the condition where the ultrasonic energy was higher than a threshold value (approximately 2000 W s), the welded joints were fractured within the titanium base metal but not at the interface. The values of the bond strength were associated with the fixing method and the surface roughness of the base metals. The bond interface was joined metallurgically for the most part, although some small voids were observed on the bond interface by SEM and EPMA observation.     

低碳钢晶粒尺寸的超声无损评价技术

研究了超声纵波声速和低碳钢Q235平均晶粒直径的关系。通过热处理改变碳钢试件的晶粒尺寸。其结果表明，用5N14探头测得的纵波声速和晶粒直径之间有很好的线性关系；选择合适的超声波探头及频率测量超声纵波声速，能够无损地评价低碳钢的晶粒尺寸。     

超声椭圆振动切削技术及装置应用研究现状及进展

首先,阐述了超声椭圆振动切削技术、原理及其装置特点,着重论述了装置各构成部分的特点及其主要应用类型与材料。其次,分析了国内外学者在双激励、单激励方式下实现纵弯、纵扭、双弯曲和弯扭等复合超声振动装置结构设计及其优化方面的研究成果与进展,并且比较了超声椭圆振动切削与传统加工在加工性能、工件表面质量和加工精度等方面的加工优势与适用范围,以及不同超声振动装置在各切削加工中所能获得的加工效果。最后,对超声椭圆振动切削装置的发展趋势进行了总结和展望,指出该装置发展将朝着结合能场的方向发展。     

Influences of tensile direction and plastic strain on ultrasonic parameters measured with rolled brass plates

Cu-40 wt% Zn alloy plates were pulled parallel or perpendicular to the rolling direction and ultrasonic measurements were carried out with a probe generating shear wave of 4 MHz in frequency polarizing parallel or perpendicular to the tensile direction to examine the relationship between ultrasonic parameters, tensile direction and plastic strain. Ultrasonic echoes reflected from the bottom of specimens were Fourier transformed and an inverse transfer function was obtained as a ratio of the Fourier spectra of the first two echoes. The inverse transfer function changed complicatedly with plastic strain, and was analyzed with the subspace method to obtain a major parameter called the primary component. The primary component changed with the plastic strain, and was dependent on combination of the polarization direction of the shear wave, the rolling direction and the tensile direction. Specimens with curved sides were pulled and the primary component was obtained by the ultrasonic measurement to estimate the plastic strain distribution in specimens with the ultrasonic parameter. The estimated plastic strain was in good agreement with the measured plastic strain.     

Effects of ac arc ultrasonic on plasma arc in situ welding of SiCp/6061Al MMCs

Abstract

The isolation coupling device is designed based on the principle of high pass filter circuit, which can achieve isolation and coupling between ac welding power and ultrasonic frequency excitation source. In addition, ac arc ultrasonic vibration is obtained successfully. The plasma arc in situ welding of SiCp/6061Al was performed using two different processes. The first process is that the plasma gas is argon nitrogen mixture and the filler material is flux cored wire (Al–5Ti–5Si); the other process is that the plasma gas is argon and the filler material is flux cored wire (Al–15Ti–3Si). The two joints are respectively enhanced by nitride and Al₃Ti, which were obtained in these processes. After arc ultrasonic vibrations were imposed on the two welding processes, it was revealed that arc ultrasonic improved the distribution of the new nitride phases and optimised the morphology of Al₃Ti to improve the mechanical properties of joints that reached 246 and 263 MPa. Fracture analysis showed that the improvement of the mechanical properties resulting from Al₃Ti is better than that from nitride under the effect of arc ultrasonic.