【摘要】：航空渦輪盤是航空發(fā)動(dòng)機(jī)的核心部件,制造中由于工藝參數(shù)波動(dòng)可能導(dǎo)致偏析、夾雜物、孔洞、裂紋等各類缺陷;服役過(guò)程受力復(fù)雜、條件嚴(yán)苛,往往產(chǎn)生疲勞裂紋缺陷,而航空渦輪盤即使存在微小缺陷也可能造成嚴(yán)重后果,因此對(duì)其進(jìn)行出廠和在役的無(wú)損檢測(cè)顯得十分必要。相控陣超聲檢測(cè)技術(shù)是一種可通過(guò)電子方法實(shí)現(xiàn)聲束變角、深度變焦的無(wú)損檢測(cè)技術(shù),避免了常規(guī)單晶探頭因移動(dòng)范圍、聲束角度有限而引起缺陷漏檢。此外,相控陣超聲檢測(cè)技術(shù)的聲場(chǎng)能控制能力強(qiáng)、檢測(cè)能量高,可有效提高檢測(cè)精度和檢測(cè)效率。根據(jù)相控陣超聲檢測(cè)技術(shù)的特點(diǎn),相控陣超聲檢測(cè)技術(shù)有望對(duì)復(fù)雜結(jié)構(gòu)的高溫合金航空渦輪盤中的各類缺陷進(jìn)行準(zhǔn)確、高效的無(wú)損檢測(cè)。相控陣超聲檢測(cè)技術(shù)在對(duì)航空渦輪盤進(jìn)行檢測(cè)時(shí),由于其體積大、結(jié)構(gòu)復(fù)雜且組織結(jié)構(gòu)粗大,當(dāng)微小缺陷位于航空渦輪盤近表面、底面、復(fù)雜結(jié)構(gòu)區(qū)域時(shí),由于缺陷信號(hào)容易混淆、信噪比低,缺陷檢測(cè)容易出現(xiàn)漏檢或誤檢。因此,分析相控陣超聲聲場(chǎng)分布特點(diǎn)及其影響因素以優(yōu)化檢測(cè)參數(shù)、分析檢測(cè)信號(hào)并提出相應(yīng)的信號(hào)處理算法對(duì)檢測(cè)信號(hào)及圖像進(jìn)行降噪處理是航空渦輪盤相控陣超聲檢測(cè)技術(shù)的主要研究?jī)?nèi)容。首先,理論分析陣元數(shù)、陣元間距、頻率等參數(shù)對(duì)航空渦輪盤相控陣超聲聲場(chǎng)的影響,結(jié)果表明:相控陣超聲聚焦聲場(chǎng)能量隨陣元數(shù)的增加、頻率的提高而增強(qiáng);相控陣超聲柵瓣幅度隨陣元間距的增大而增大。第二,試驗(yàn)分析盤件中超聲相控陣聲場(chǎng)特性,測(cè)量航空渦輪盤中相控陣超聲焦區(qū)寬度及信號(hào)幅值隨陣元數(shù)及聚焦深度的變化規(guī)律,結(jié)果表明:相控陣超聲焦區(qū)寬度隨陣元數(shù)的增加而減小,隨聚焦深度的增加而增大;采用相控陣超聲斜探頭對(duì)半徑為50mm圓弧上分布的間隔橫孔進(jìn)行檢測(cè)成像試驗(yàn),并分析陣元數(shù)、探頭布置位置對(duì)檢測(cè)分辨率的影響,結(jié)果表明:增加陣元數(shù)、適當(dāng)調(diào)整探頭位置使與橫孔圖像相交的掃查線角度間隔增大有利于提高檢測(cè)分辨率。第三,采用超聲相控陣斜探頭對(duì)航空渦輪盤中槽型缺陷進(jìn)行檢測(cè)成像試驗(yàn),深入分析航空渦輪盤中面型缺陷的超聲相控陣成像方法及其圖像特征,并根據(jù)窄槽衍射回波形成的相互分離條紋測(cè)量出窄槽缺陷的取向和尺寸,同時(shí)分析了陣元數(shù)、探頭布置位置對(duì)窄槽檢測(cè)精度的影響,結(jié)果表明:相控陣超聲測(cè)長(zhǎng)值總體要稍大于窄槽實(shí)際長(zhǎng)度;檢測(cè)近表面窄槽缺陷應(yīng)選擇少陣元數(shù),遠(yuǎn)距離檢測(cè)則應(yīng)采用多陣元檢測(cè)。第四,采用相控陣超聲斜探頭開(kāi)展了關(guān)于航空渦輪盤復(fù)雜區(qū)域微小缺陷的試驗(yàn)研究,優(yōu)化相控陣超聲檢測(cè)參數(shù),深入分析航空渦輪盤相控陣超聲檢測(cè)特征信號(hào),結(jié)果表明:采用5MHz頻率相控陣超聲斜探頭、激發(fā)32陣元、激勵(lì)信號(hào)脈沖寬度設(shè)置為100ns、聚焦深度為102mm(孔深)可有效檢測(cè)該缺陷。最后,為提高航空渦輪盤微小缺陷相控陣超聲檢測(cè)信號(hào)的信噪比以及扇掃圖像質(zhì)量,深入分析結(jié)構(gòu)檢測(cè)信號(hào)特征,并采用小波包分解技術(shù)觀察缺陷檢測(cè)信號(hào)的時(shí)頻特征,對(duì)比了小波閾值及小波基對(duì)檢測(cè)信號(hào)降噪效果的影響并對(duì)小波包閾值進(jìn)行優(yōu)化以獲得最優(yōu)小波包降噪?yún)?shù)。為進(jìn)一步提高圖像質(zhì)量,采用奇異值分解技術(shù)對(duì)經(jīng)小波包處理后的航空渦輪盤超聲相控陣檢測(cè)信號(hào)做進(jìn)一步處理,對(duì)比了Hankel矩陣維數(shù)如何選取以及奇異值如何處理時(shí)的降噪效果,從而得到最優(yōu)奇異值降噪?yún)?shù),結(jié)果表明:航空渦輪盤中微小缺陷信號(hào)緊鄰航空渦輪盤結(jié)構(gòu)信號(hào);缺陷特征信號(hào)并非集中在某一頻帶范圍內(nèi),因此,針對(duì)特定頻帶范圍進(jìn)行濾波將在濾除噪聲的同時(shí)可能造成缺陷特征信號(hào)的損失;根據(jù)小波包分析結(jié)果選擇部分分解信號(hào)并結(jié)合改進(jìn)的去噪閾值,可有效的提取檢測(cè)圖像的缺陷特征圖像、結(jié)構(gòu)特征圖像,甚至也可將材料組織結(jié)構(gòu)引起的噪聲條紋提取出來(lái);采用優(yōu)化參數(shù)后的奇異值分解技術(shù)對(duì)相控陣超聲檢測(cè)數(shù)據(jù)做進(jìn)一步處理并成像,缺陷信噪比以及分辨率得到進(jìn)一步提高。綜上,采用相控陣超聲檢測(cè)技術(shù)對(duì)高溫合金航空渦輪盤進(jìn)行安全、有效的無(wú)損檢測(cè)可保障渦輪盤質(zhì)量及安全性,在節(jié)約制造成本、提高渦輪盤性能、避免安全事故等方面具有重要意義。
[Abstract]:The air turbine disc is the core part of the aero-engine, and due to the fluctuation of process parameters, various defects such as segregation, inclusions, holes, cracks and the like can be caused, the service process is complex in force, and the condition is severe, and the fatigue crack defect is often generated, It is necessary to carry out the non-destructive testing of the air turbine disk in the factory and in-service even if there is a minor defect in the air turbine disk. Phased-array ultrasonic detection technology is a kind of non-destructive testing technology that can realize the variable angle and deep zoom of the acoustic beam through the electronic method, so as to avoid the defect of the conventional single crystal probe caused by the limited moving range and the limited sound beam angle. In addition, the sound field energy control capability of the phased array ultrasonic detection technology is strong, the detection energy is high, and the detection accuracy and the detection efficiency can be effectively improved. According to the characteristics of the phased array ultrasonic detection technology, the phased array ultrasonic detection technology is expected to carry out accurate and high-efficiency nondestructive testing on various defects in the high-temperature alloy aviation turbine disc of the complex structure. The phased array ultrasonic detection technology has the advantages of large volume, complex structure and coarse structure of the tissue structure when the aviation turbine disk is detected by the phased array ultrasonic detection technology, and when the micro defects are located in the near surface, the bottom surface and the complex structure region of the aviation turbine disk, the defect signal is easy to be confused, the signal-to-noise ratio is low, The defect detection is prone to missing or false detection. Therefore, the characteristics of the sound field distribution of the phased array and its influencing factors are analyzed to optimize the detection parameters, the detection signal is analyzed and the corresponding signal processing algorithm is proposed to noise reduction of the detection signal and the image, which is the main research content of the aviation turbine disk phased array ultrasonic detection technology. First, the influence of the parameters of the array element number, the array element distance and the frequency on the ultrasonic sound field of the aviation turbine disk phased array is analyzed. The results show that the energy of the phased array ultrasonic focusing sound field is enhanced with the increase of the number of the array elements and the increase of the frequency. The amplitude of the phased array ultrasonic grating increases with the increase of the array element pitch. Secondly, the characteristics of the ultrasonic phased array sound field in the disk device are analyzed, and the variation of the width of the phased array ultrasonic focal zone and the amplitude of the signal amplitude along with the number of the array elements and the focusing depth is measured. The results show that the width of the phased array ultrasonic focal zone decreases with the increase of the number of the array elements. The effect of the array element number and the position of the probe placement on the detection resolution is analyzed, and the results show that the number of the matrix elements is increased, the proper adjustment of the probe position increases the scan line angle spacing that intersects the cross-hole image to increase the detection resolution. thirdly, the ultrasonic phased array oblique probe is adopted to test the groove type defects in the aviation turbine disc, and the ultrasonic phased array imaging method and the image characteristic of the plane type defect in the aviation turbine disc are analyzed in detail, and the influence of array element number and probe arrangement position on the detection precision of the narrow groove is analyzed, and the result shows that the long value of the phased array ultrasonic measurement is slightly larger than the actual length of the narrow groove; In order to detect the defects of the near-surface narrow groove, the number of elements should be selected, and the multi-array element should be used for long-distance detection. In the fourth part, the experimental research on the micro-defect of the complex area of the aviation turbine disc is carried out by using the phased array ultrasonic oblique probe, and the ultrasonic detection parameters of the phased array are optimized, and the characteristic signals of the phased array ultrasonic detection of the aviation turbine disc are analyzed in detail. The results show that a 5MHz frequency phased array ultrasonic oblique probe is adopted, The excitation signal pulse width is set to 100ns, the focus depth is 102mm (hole depth), and the defect can be effectively detected. in that end, in order to improve the signal-to-noise ratio of the micro-defect phased array ultrasonic detection signal of the aviation turbine disk and the quality of the fan-scan image, the characteristic of the structure detection signal is deeply analyzed, and the time-frequency characteristic of the defect detection signal is observed by using the wavelet packet decomposition technique, The influence of the small wave threshold and the wavelet basis on the noise reduction effect of the detection signal is compared, and the wavelet packet threshold is optimized to obtain the optimal wavelet packet noise reduction parameter. In order to further improve the image quality, the ultrasonic phased array detection signal of the air turbine disk after the wavelet packet processing is further processed by using the singular value decomposition technique, and the noise reduction effect when the Hankel matrix dimension number is selected and the singular value is processed is compared, so as to obtain the optimal singular value noise reduction parameter, according to the wavelet packet analysis result, a partial decomposition signal is selected and combined with the improved de-noising threshold value, the defect characteristic image and the structural characteristic image of the detection image can be effectively extracted, and can even extract the noise fringes caused by the structure of the material, further processing and imaging the phased array ultrasonic detection data by using the singular value decomposition technology after the optimization parameters, and further improving the signal-to-noise ratio and the resolution of the defect. The high-temperature alloy aero-turbine disk is safe and effective by adopting the phased-array ultrasonic detection technology, and the quality and the safety of the turbine disk can be guaranteed, the manufacturing cost is saved, the performance of the turbine disk is improved, safety accidents are avoided, and the like.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：V263.6;TB559

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本文編號(hào)：2316444