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排序方式: 共有5111条查询结果,搜索用时 69 毫秒
71.
早期微裂纹的检测是结构失效分析的关键,该文利用电磁超声Lamb波混频检测的方法,综合考虑微裂纹界面呼吸作用的特点,以弹簧模型为基础并考虑微裂纹界面的迟滞效应和阻尼力,建立含有微裂纹的三维Lamb波混频非线性检测模型,模拟混频超声波作用下微裂纹的波动状况,分析混频超声波与微裂纹界面发生的非线性作用,研究微裂纹长度与深度的变化对混频调制效果的影响.最后搭建电磁超声混频非线性检测系统,根据差频非线性系数与和频非线性系数对微裂纹长度变化敏感性的不同定义了综合系数因子,量化分析微裂纹的长度.通过实验数据得到了综合系数因子与微裂纹长度之间的关系,并对微裂纹长度进行了预测.实验结果表明,利用综合系数因子可以对微裂纹长度进行有效的预测. 相似文献
72.
许多先进的检测技术已被证实能获取锂离子电池的荷电状态(SOC),然而目前的检测手段未能同时满足精度和效率方面的要求.利用超声波对SOC的表征已经得到初步的认可,该方法检测效率高、对电池损伤小,但存在单个声学指标与电池材料动力学特性不清晰的问题.该文在分析锂离子电池SOC声学表征研究现状的基础上,将振铃计数引入电池SOC评价中,明确SOC与振铃计数的相关性.基于Lemaitre等效应变原理推导了振铃计数与有效杨氏模量的对应关系,提出基于超声纵波的锂离子电池SOC在线检测方法,结合常规的声学指标研究了锂离子电池在充放电循环中有效杨氏模量演化规律.通过将常规的时域声学指标与振铃计数表征结果进行对比,验证了振铃计数对SOC表征的可行性. 相似文献
73.
Cu基Cu-Zr-Al块体非晶合金的成分设计 总被引:7,自引:0,他引:7
利用变电子浓度经验判据,从Cu—Zr亚组元体系中的最深共晶点Cu61.8Zr38.2和次深共晶点Cu56Zr44出发,连接第三组元Al,建立(Cu61.8Zr38.2)1-xAlx和(Cu56Zr44)1-xAlx变电子浓度线.电子浓度在1.24—1.30的(Cu61.8Zr38.2)1-xAlx合金可通过铜模吸铸法形成直径为3mm的块体非晶;对于(Cu56Zr44)1-xAlx系列合金,块体非晶形成的电子浓度区间为1.28-1.36.热分析结果表明,每条变电子浓度线上块体非晶合金的热稳定性和玻璃形成能力随电子浓度增大而增加.其中,(Cu61.8Zr38.2)1-xAlx变电子浓度线上的非晶合金Cu58.1Zr35.9Al6(e/α=1.3)具有最高的热稳定性和最大的玻璃形成能力,其特征参数Tg=760K,Tg/Tl=0.648,皆高于已报道的最优成分Cu55Zr40Al5(Tg=722K,Tg/Tl=0.614)。 相似文献
74.
Fault diagnosis of internal combustion engines using visual dot patterns of acoustic and vibration signals 总被引:3,自引:0,他引:3
An investigation of the fault diagnosis technique in internal combustion engines based on the visual dot pattern of acoustic and vibration signals is presented in this paper. Acoustic emissions and vibration signals are well known as being able to be used for monitoring the conditions of rotating machineries. Most of the conventional methods for fault diagnosis using acoustic and vibration signals are primarily based on observing the amplitude differences in the time or frequency domain. Unfortunately, the signals caused by damaged elements, such as those buried in broadband background noise or from smearing problems arising in practical applications, particularly at low revolution, are not always available. In the present study, a visual dot pattern technique is proposed to identify the acoustic emission and vibration signals for fault diagnosis in an internal combustion engine and drive axle shaft. Experiments are carried out to evaluate the proposed system for fault diagnosis under various fault conditions. The experimental results indicate that the proposed technique is effective in the fault diagnosis of an internal combustion engine and drive axle shaft. 相似文献
75.
Mechanisms of nanostructure and metastable phase formations in the surface melted layers of a HCPEB-treated D2 steel 总被引:1,自引:0,他引:1
This work investigates the mechanism of surface modification associated with the high-current pulsed electron beam (HCPEB) treatment of a D2 steel with increasing numbers of pulses. The surface layers were melted and resolidified but the treated surfaces showed very different features. This variation is essentially due to the different levels of homogeneity and carbide dissolution. It is demonstrated that the presence of carbides served as nucleation sites for the surface eruption phenomenon that creates craters on the surface. After a sufficient number of pulses, most of the carbides in the surface layer were dissolved and an almost crater-free homogeneous melted layer consisting of a very stable nano-austenite structure was formed. The HCPEB technique is thus demonstrated to be a versatile technique for surface microstructure modification involving, in the case of steels, austenite stabilization and ultrafine grain formation. 相似文献
76.
用透射电镜对Zr65Al7.5Ni10 Cu17.5块状非晶合金的晶化过程进行了研究。发现晶化过程的不同阶段相的组成是不同的。710K时 ,主要是tI CuZr2 相和tP Al2 Zr3 相 ,两者有固定的取向关系 :[0 10 ]tI∥ [0 10 ]tP,(10- 3) tI∥(2 0 2 ) tP。在 76 0K时 ,除了前面的两个相外 ,又出现了hP2 Al2 NiZr6相和hP3 α Zr相 ,两者也有固定取向关系 :[113]hP2 ∥ [0 0 1]hP3 ,(14- 1) hP2 ∥ (2 1- 0 ) hP3 。根据它们的晶格常数的相似性可以把晶化相归纳为两类 :tI ,oC ,hP3 和tP ,hP1,hP2 。这些相都是Zr基的 ,但前者富Cu和Ni,后者富Al。用电镜得到的结果来标定X射线衍射谱 ,结果吻合很好。 相似文献
77.
GAO Bo HAO Sheng-zhi ZOU Jian-xin JIANG Li-min ZHOU Ji-yang'''' DONG Chuang .State Key Lab. of Materials surface Modification by Laser Ion Electron Beams Dalian China .Department of Materials Engineering Dalian University of Technology Dalian China 《材料热处理学报》2004,25(5)
MAGNESIUM ALLOYS exhibit high strength toweight ratio and stiffness and are finding theirapplications in air,automobile and electronic industries.Despite the worldwide growing interests inmagnesium alloys,their inferior wear resistance is aserious impediment.Considering that wear is asurface-related behavior,surface modification canresolve the problem.Recently,intense and pulsed energetic beams areemerging as new and effective methods for surfacemodification.The High Current Pulsed Ele… 相似文献
78.
Zr-Al-Co块状非晶的成分优化 总被引:2,自引:0,他引:2
运用等电子浓度和变电子浓度线判据实现了Zr—Al—Co块状非晶合金的成分优化.在(Al50Co50)-Zr等电子浓度线(e/α=1.5)和(Zr9Co4)—Al及(Zr78.5Co21.5)—Al变电子浓度线上设计成分,并通过吸铸法制备块状合金.实验结果表明,在(Al50Co50)—Zr等电子浓度线和(Zr9Co4)—Al变电子浓度线上可形成块状非晶合金,且非晶合金的热稳定性与非晶形成能力随电子浓度的增大而单调递增.其中,(Al50Co50)-Zr等电子浓度线和(Zr9Co4)—Al变电子浓度线交点处形成的Zr53Al23.5Co23.5非晶合金,具有最大的热稳定性和非晶形成能力,特征热力学参数Tg=783K,Tx=849K,Tg/Tm=0.637,Tg/Ti=0.590。 相似文献
79.
T. L. Su L. C. Tsao S. Y. Chang T. H. Chuang 《Journal of Materials Engineering and Performance》2002,11(5):481-486
The interfacial reactions of liquid Sn and Sn-3.5Ag solders with Ag thick films are investigated in the temperature range
from 250–325 °C, and the morphology of intermetallic compounds formed after such soldering reactions is observed. In kinetics
analysis of the growths of intermetallic compounds, it was found that both Sn/Ag and Sn-3.5Ag/Ag reactions were interfacial-controlled,
and the growth rates for both cases were similar. The rate of Ag dissolution into liquid solder attendant on the formation
of interfacial intermetallic compounds after Sn/Ag reaction was about four times higher than that after Sn-3.5Ag/Ag reaction,
as evidenced by experimental results. 相似文献
80.
The surface modification of magnesium alloys (AZ31 and AZ91 HP) was studied by a high current pulsed electron beam(HCPEB). The results show that the cross-sectional microhardness of treated samples increases not only in the heat affected zone( HAZ), but also beyond HAZ, reaching over 250μm. This is due to the action of quasi-static thermal stress and the shock thermal stress wave with materials, which result in its fast deformation on the surface layer and so increases microhardness. For the AZ91HP alloy, a nearly complete dissolution of the intermetallic phase Mg17Al12 is observed, and a super-saturated solid solution forms on the re-melted surface, which is due to the solute trapping effect during the fast solidification process. Measurements on sliding wear show that wear resistance is improved by approximately 5.6 and 2.4 times for the AZ31 and AZ91HP respectively, as compared with as-received samples. 相似文献