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激光熔化沉积工艺对超声检测的影响研究
Alternative TitleResearch on the effect of Ultrasonic Inspection on Laser Melting Deposition
孙长进
Department工艺装备与智能机器人研究室
Thesis Advisor赵吉宾
Keyword激光熔化沉积 超声检测 超声声速 超声灵敏度 小波降噪
Pages60页
Degree Discipline机械工程
Degree Name专业学位硕士
2020-05-26
Degree Grantor中国科学院沈阳自动化研究所
Place of Conferral沈阳
Abstract随着我国新型航空器的快速发展,在设计层面对多功能大型结构部件的需求也与日俱增,传统的制造工艺已经难以满足需求,以钛合金等为原材料的激光熔化沉积工艺逐渐得到人们的重视。如何使用无损检测技术来控制激光熔化沉积产品质量是该技术规模化应用面临的难题之一。在常见无损检测方法中,相控阵超声检测凭借其检测缺陷种类多、检测缺陷深度范围大、检测速度快、适合自动化检测等优点,符合航空大型结构激光熔化沉积制品的无损检测要求。因此使用该无损检测方法展开对TA15钛合金激光熔化沉积工艺制品的无损检测方法研究。本文以提高缺陷检测位置精度、当量精度和缺陷检出率为目标,分别从超声声速标定、超声灵敏度标定以及缺陷信号降噪三个方面展开研究。首先,以现有激光熔化沉积制造系统为基础,通过增加惰性保护气及相应密封装置,并增加氧含量检测以优化制造设备;其次,搭建一套适用于本研究的超声无损检测系统,为后续的研究打下基础。通过分析加工过程中各工艺参数对成型质量的影响,确定激光功率及扫描间距作为研究对象,制造两组对比试块,再结合其他试块共同进行超声检测。通过分析上下表面回波时间差,得出该工艺下不同成型方向、激光功率、扫描间距之间超声声速和超声灵敏度的变化关系,提高了TA15钛合金在该工艺的超声检测缺项定位、定量精度。通过分析反射超声波的声学模型,确定了离散小波在超声波降噪方面的可行性,并提出了一种参数可调的阈值函数。通过预制气孔类缺陷、裂纹缺陷、平底孔缺陷等类型缺陷试块,采集缺陷波形并使用本文算法进行降噪处理,通过信噪比及均方根误差验证本文算法性能,证实本文算法可以有效减小超声检测中的结构噪声,并对各缺陷类型有效;可以有效提高超声检测缺陷检出率。因此对激光熔化沉积工艺制品进行超声检测时,需针对具体检测路径及制造工艺参数编制检测方法;若对检测精度要求较高使用本文降噪算法可有效提高缺陷检出率。
Other AbstractWith the increasing performance requirements of new generation aircraft, the demand for multi-functional large-scale structural components at the design level is also increasing, which traditional manufacturing process has been hard to satisfy. The laser melting deposition process using titanium alloys as raw materials has gradually received more attention. How to use non-destructive testing technology to control the quality of laser melting deposition products is one of the problems faced by the large-scale application of this technology. Among the common non-destructive testing methods, phased array ultrasonic testing meets the requirements of non-destructive testing of aerospace large-scale laser melting deposition products due to its flaw adaptation of many types, large depth of flaw detection, fast detection speed, and suitable for automated testing. Therefore, this non-destructive testing method was used to develop a non-destructive testing method for TA15 titanium alloy laser fusion deposition process products. In this paper, we aim to improve the detection accuracy of flaw position, ultrasonic sensitivity compensation accuracy and the successful ratio of flaw detection, and conduct research from three aspects: ultrasonic sound velocity calibration, ultrasonic sensitivity compensation calibration and defect signal noise reduction. At first, based on the existing laser melting deposition manufacturing system, by adding inert protective gas and corresponding vaccum plant, and adding the oxygen content detection to optimize the manufacturing equipment. Secondly, a set of ultrasonic non-destructive testing system has been built for this study, as the foundation of follow-up research. By analyzing the influence of various process parameters on the forming quality during the processing, the laser power and the scanning distance were determined as the research objects. Two sets of comparative test blocks were manufactured, and then combined with other test blocks for ultrasonic testing. By analyzing the length of time between the upper and lower surface echoes, the relationship between the ultrasonic sound velocity and ultrasonic sensitivity compensation between different forming directions, laser power, and scanning distances under this process is obtained, which improves the positioning and quantitative accuracy of TA15 titanium alloy in the ultrasonic testing of this process. By analyzing the acoustic model of reflected ultrasonic waves, the feasibility of discrete wavelet in ultrasonic noise reduction was determined, and a threshold function with adjustable parameters was proposed. Through prefabricating test blocks simulate air hole defects, crack defects, flat bottom hole defects and other types of defects, the echo waveforms were collected and noise reduction processing was performed with the algorithm of this paper. The performance of the algorithm in this paper was verified by the signal-to-noise ratio and the root mean square error, and it is confirmed that the algorithm in this paper can effectively reduce the structural noise in ultrasonic inspection and also effective for each type of flaw, which can effectively improve the successful ratio of ultrasonic flaw inspection. Therefore, when performing ultrasonic testing on laser melting deposition process products, it is necessary to compile testing methods for specific testing paths and manufacturing process parameters; if the detection accuracy was high, the noise reduction algorithm in this article can effectively improve the successful ratio of ultrasonic flaw inspection.
Language中文
Contribution Rank1
Document Type学位论文
Identifierhttp://ir.sia.cn/handle/173321/27151
Collection工艺装备与智能机器人研究室
Affiliation中国科学院沈阳自动化研究所
Recommended Citation
GB/T 7714
孙长进. 激光熔化沉积工艺对超声检测的影响研究[D]. 沈阳. 中国科学院沈阳自动化研究所,2020.
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