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本大板面散热器真空钎焊工艺参数复杂、焊接难度大、产品合格率较低,鉴于此钎焊接头的检测是生产过程中必不可少的一个环节,无损检测在不破坏钎焊接头或在不影响钎焊接头使用的前提下进行的焊接缺陷检验是验证产品焊接质量的重要手段.本文旨在针对大板面散热器钎焊质量有效控制与评估,对其无损检测方法进行探究. 相似文献
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由于焊接热过程的作用,焊接接头较容易产生组织性能劣化、残余应力、应力集中以及各种焊接缺陷。焊接缺陷的存在严重影响了焊接结构件的质量和安全使用,因此对含缺陷焊接接头进行安全性评估具有重要的工程应用价值。基于综合考虑含缺陷焊接接头的缺陷检测手段和BS 7910缺陷规则化表征处理的方法,对BS 7910中失效评估图的级别以及相应级别下针对含缺陷焊接接头评估点坐标确定过程中所涉及的应力种类和修正因子进行探讨,为工程实际利用BS 7910对焊接接头进行评估时的缺陷检测手段选择、缺陷规则化表征处理以及失效评估图级别的选择、评估点坐标的确定提供参考。 相似文献
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某高温换热类设备内件采用耐热低合金钢锻件和耐热低合金钢换热管作为换热介质的承压边界材料,由于产品为特殊的立式结构,管子-管板焊缝的焊接只能在仰焊位置操作.通过工艺研究发现,为了得到质量稳定、焊缝尺寸和形状满足设计和相关技术条件要求的管子-管板仰焊焊接接头,优先选用内缩填丝式管子-管板焊接坡口,合理配比自动钨极氩弧焊工艺... 相似文献
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1 焊接工艺评定的概念和目的是什么? 在引入焊接工艺评定的概念以前,焊制压力容器焊接接头的焊接质量是靠无损探伤和产品焊接试板来保证的。但无损探伤只能确定有无缺陷,产品焊接试板也是机率性的检验主要焊缝的性能。 相似文献
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《机械工程学报》2017,(12)
承压设备包括锅炉、压力容器和压力管道,其运行安全对保障国家经济运行和人民日常生活至关重要。在承压设备建造阶段,无损检测与评价技术被应用于原材料生产和焊接质量的检测与控制。在使用阶段,无损检测与评价技术被用于及时发现承压设备在运行过程中出现的各种材料劣化和损伤等缺陷,并可根据检测结果对承压设备的安全状况进行评价,并对承压设备的剩余寿命进行评估。首先,论述对承压设备进行无损检测与评价的重要性,给出目前已成熟和正在发展的无损检测与评价技术;然后,重点对辐射、声学、电磁以及其他领域的各个新的检测技术进行介绍,简述这些技术的原理、特点、适用范围,并指出其存在的不足和发展趋势;最后,对未来承压设备对无损检测与评价技术的需求进行总结,指出将来需进一步开展的主要研究领域和重点任务,以便更好地保障承压设备的运行安全。 相似文献
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针对自制垂直引入式飞行时间质谱仪(orthogonal extraction time-of-flight mass spectrometer, O-TOFMS)的需要,运用直接数字频率合成 (direct digital frequency synthesis,DDS)技术,研制了射频四极杆的高压射频驱动电路装置。该驱动器频率可调范围为0.5~2 MHz,幅度最高达到1 000 Vp-p。该射频四极杆驱动器(radio frequency quadrupole driver,RFQ Driver)可用于分子离子反应器(molecule ion reactor,MIR)和RFQ驱动,其结构简洁、成本低、性能稳定可靠。 相似文献
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光电容积描记图(PPG)是一种利用光学技术无创检测人体心血管脉搏波的方法。PPG信号来源于MIMIC数据库,它含有许多生理信息。本文提出了将集合经验模态分解(EEMD)、倒谱、快速傅里叶变化和过零点检测相结合的方法,从PPG中可靠地估算脉搏率(PR)、心率(HR)和呼吸频率(RR)。首先,将PPG信号通过EEMD分解为有限个固有模态函数(IMF)。因为EEMD有自适应滤波特性,所以估算不同的生理参数时,可以用不同的IMF分量来重构信号。其次,估算脉搏率时,舍去低频含有伪迹的IMF,再通过过零点检测可以得到瞬时脉搏率。然后,估算心率时,用1 Hz~1.67 Hz(60次/分钟~100次/分钟)的IMF来重构信号,再求倒谱,选取反映心脏活动的频带来得到心率。最后,估算呼吸率时,用0.05 Hz~0.75 Hz(3次/分钟~45次/分钟)的IMF来重构信号,然后对呼吸信号求快速傅里叶变化得到频谱图,寻找频谱图中的峰值得到呼吸率。对来自MIMIC数据库的53个成人PPG信号进行了仿真。仿真结果表明使用该综合信号处理方法提取的生理参数与实际生理参数一致,且该方法有运算量小,精确度高的优点(误差不超过1.17%)。 相似文献
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建立了二苯甲烷二异氰酸酯(MDI)的超高效液相色谱-串联质谱(UPLC-MS/MS)联用的分析方法。实验用甲醇作衍生试剂,将二苯甲烷二异氰酸酯衍生成二苯甲烷二氨基甲酸甲酯(MDC),通过测定二苯甲烷二氨基甲酸甲酯来确定二苯甲烷二异氰酸酯的含量。实验采用Waters Acquity BEH C18超高效液相色谱柱,甲醇-0.1%甲酸作为梯度洗脱液,二苯甲烷二氨基甲酸甲酯在1.5 min内与其他化合物进行完全分离,经四极杆质谱选择离子监测模式检测。线性范围为2~100 μg/L,检出限为1 μg/L,相关系数0.999 4。考察了水、甲酸、甲酸铵流动相体系,以及进样量大小对样品的分离效果,发现甲酸流动相体系的分离效果优于其他两种流动相体系,同时发现在进样量大时出现平头峰。并且在优化条件下,对实际样品中游离的二苯甲烷二异氰酸酯进行了测定。 相似文献
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Yang Sun Yongda Yan Yingchun Liang Zhenjiang Hu Xuesen Zhao Tao Sun Shen Dong 《Scanning》2013,35(5):308-315
Nanobundles patterns can be formed on the surface of most thermoplastic polymers when the atomic force microscope (AFM)‐based nanomechanical machining method is employed to scratch their surfaces. Such patterns are reviewed as three‐dimensional sine‐wave structures. In the present study, the single‐line scratch test is used firstly to study different removal states of the polystyrene (PS) polymer with different molecular weights (MWs). Effects of the scratching direction and the scratching velocity on deformation of the PS film and the state of the removed materials are also investigated. Single‐wear box test is then employed to study the possibility of forming bundle structures on PS films with different MWs. The experimental results show that the state between the tip and the sample plays a key role in the nano machining process. If the contact radius between the AFM tip and the polymer surface is larger than the chain end‐to‐end distance, it is designated as the “cutting” state that means the area of both side ridges is less than the area of the groove and materials are removed. If the contact radius is less than the chain end‐to‐end distance, it is designated as the “plowing” state that means the area of both side ridges is larger than the area of the groove and no materials are removed at all. For the perfect bundles formation on the PS film, the plowing state is ideal condition for the larger MW polymers because of the chains’ entanglement. SCANNING 35:308‐315, 2013. © 2012 Wiley Periodicals, Inc. 相似文献
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Y.L. Tu S.Q. Xie J.J. Kam 《The International Journal of Advanced Manufacturing Technology》2006,29(5):499-510
To shorten the product development cycle time and reduce the cost at the same time, which is very critical for the survival
of those small and mid-sized one-of-a-kind production (SMOKP) companies, various computer communication, simulation and computer
aided engineering and management techniques have been widely used in these SMOKP companies. However, according to our study,
the applications of these advanced computer technologies in these SMOKP companies are lack of system integration and synergy,
which result in communication errors, reworks, duplications and hence a longer product development lead time and a higher
cost. To solve this problem, an inter/intranet based computer aided rapid product development system is presented in this
paper. This system consists of a number of inter/intranet based computer models or sub-systems for supporting rapid development
of a one-of-a-kind product. It also employs a novel concurrent product development strategy called “prototype based incremental
product development strategy” and an integrated product data structure called “product production structure”. Some industrial
implementations of the proposed system, product development strategy and product data structure are also reported in the paper. 相似文献
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Y. L. Tu S. Q. Xie J. J. Kam 《The International Journal of Advanced Manufacturing Technology》2006,29(5-6):499-510
To shorten the product development cycle time and reduce the cost at the same time, which is very critical for the survival
of those small and mid-sized one-of-a-kind production (SMOKP) companies, various computer communication, simulation and computer
aided engineering and management techniques have been widely used in these SMOKP companies. However, according to our study,
the applications of these advanced computer technologies in these SMOKP companies are lack of system integration and synergy,
which result in communication errors, reworks, duplications and hence a longer product development lead time and a higher
cost. To solve this problem, an inter/intranet based computer aided rapid product development system is presented in this
paper. This system consists of a number of inter/intranet based computer models or subsystems for supporting rapid development
of a one-of-a-kind product. It also employs a novel concurrent product development strategy called “prototype based incremental
product development strategy” and an integrated product data structure called “product production structure”. Some industrial
implementations of the proposed system, product development strategy and product data structure are also reported in the paper. 相似文献
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全面准确地标定与测试是开发车辆电子稳定控制(electronic stability control,ESC)系统的关键环节。车辆控制过程是典型的强非线性系统,建立精确的车辆模型比较困难,驾驶员模型也很难准确模拟紧急工况下驾驶员的真实反应。在仿真系统中将难以精确建模的液压制动系统、ESC压力调节单元、转向及电子节气门装置采用真实硬件,并在试验平台中嵌入真实驾驶员,基于Matlab/Simulink/dSPACE环境和车辆动力学软件veDYNA,开发硬件在环(hardware-in-the-loop,HIL)和驾驶员在环(driver-in-the-loop,DIL)的仿真试验平台,并在此平台上对所设计的ESC系统进行仿真试验研究。试验结果表明,所设计的DIL/HIL仿真平台可以大幅提高ESC系统的开发效率和测试准确性。 相似文献
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R. K. Dutta S. Paul A. B. Chattopadhyay 《The International Journal of Advanced Manufacturing Technology》2006,31(5-6):434-442
Face milling is a process predominantly affected by dynamic variation of cutting forces, thermo-mechanical shocks and vibration leading to catastrophic tool failure along with gradual wear of the inserts. Keeping in view the industrial importance of this process, it is necessary to devise suitable methods to predict in advance the onset of tool failure without grossly impairing the machining set-up and the job. Hence, the applicability of back propagation neural network with delta bar delta learning rule for faster convergence has been studied with the above objective. The multi sensor based tool condition monitoring strategy shows that the learning rate adaptation scheme combined with the selection of suitable process parameters drastically reduces the training time of the artificial neural network without dispensing with the prediction accuracy. 相似文献
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A method developed to participate the pilot study of international comparison CCQM-P67 was introduced. Isotope dilution mass spectrometry (IDMS) was used in the detection of five PCB congeners in freeze-dried muscle tissue. Soxhlet Extraction is used for extraction of mussel, duplicate clean-up of GPS and SPE column were used, C-13 labeled PCB congeners were added as internal standard to avoid the error from sample preparation and diction. High resolution Mass spectrometer was used to give good result of detection. 相似文献