本文選題：超高周疲勞 + FV520B�。� 參考：《山東大學(xué)》2015年博士論文

【摘要】：離心壓縮機(jī)葉輪屬于高速回轉(zhuǎn)類零件,由于尾流激振、機(jī)組振動(dòng)等原因,其往往承受高頻低應(yīng)力幅循環(huán)載荷作用,疲勞壽命要求遠(yuǎn)遠(yuǎn)超過107周次,進(jìn)入超高周疲勞范圍。離心壓縮機(jī)葉輪重要材料FV520B的超高周疲勞行為與機(jī)理研究不僅為離心壓縮機(jī)葉輪的長壽命疲勞設(shè)計(jì)與疲勞失效預(yù)防提供了指導(dǎo),也為后續(xù)離心壓縮機(jī)葉輪可再制造臨界閾值的判定提供了有力支持。作者首先對(duì)某離心壓縮機(jī)葉輪力學(xué)特性進(jìn)行了分析,在此基礎(chǔ)上研究了高低溫時(shí)效處理、試樣尺寸、表面粗糙度、焊接對(duì)FV520B超高周疲勞行為與機(jī)理的影響。利用有限單元法,對(duì)空分空壓機(jī)組H418低壓缸一級(jí)葉輪及磨損致葉片局部減薄后該葉輪的相關(guān)力學(xué)特性進(jìn)行了分析。結(jié)果表明：(1)僅承受離心載荷時(shí),葉根中部應(yīng)力最大。(2)葉輪在額定轉(zhuǎn)速附近運(yùn)行時(shí),應(yīng)力集中主要發(fā)生在葉片前緣中部,與該葉輪服役時(shí)的疲勞斷裂部位吻合。(3)磨損導(dǎo)致的葉片局部減薄為“小失諧”,葉輪失諧前后的結(jié)構(gòu)拓?fù)湫问交静蛔?失諧葉輪模態(tài)頻率和各階振型與諧調(diào)葉輪相比變化不大。(4)尾流激振引起葉輪共振時(shí),葉片前緣中部最危險(xiǎn),可作為葉輪疲勞試驗(yàn)的重點(diǎn)考察部位,此位置的最大交變載荷幅值為33.3MPa,葉片前緣的振動(dòng)與一端為滑動(dòng)質(zhì)量塊的懸臂梁的彎曲振動(dòng)相似。研究了高低溫時(shí)效處理對(duì)FV520B超高周疲勞行為與機(jī)理的影響。通過對(duì)稱拉壓超聲疲勞試驗(yàn)方法對(duì)FV520B經(jīng)過不同溫度時(shí)效處理后得到的FV520B-I、 FV520B-S的超高周疲勞性能進(jìn)行測(cè)試,獲得超高周疲勞S-N曲線,并通過斷口形貌觀察和特征區(qū)域尺寸測(cè)量,對(duì)其超高周疲勞機(jī)理進(jìn)行研究。FV520B-I與FV520B-S的超高周疲勞行為與機(jī)理存在較大差異。FV520B-I的S-N曲線在109周次試驗(yàn)范圍內(nèi)呈持續(xù)下降的趨勢(shì),起裂模式的不同導(dǎo)致曲線分為斜率明顯不同的兩部分。FV520B-S的S-N曲線大幅低于FV520B-I,甚至從106循環(huán)周次處便出現(xiàn)“傳統(tǒng)疲勞極限”。在超高周疲勞階段,FV520B-I裂紋主要萌生于內(nèi)部夾雜物,少數(shù)裂紋萌生于表面基體或內(nèi)部較軟的鐵素體。FV520B-I超高周疲勞斷口魚眼區(qū)的形成與裂紋源距試樣表面距離有關(guān),裂紋源距試樣表面越近,內(nèi)部裂紋轉(zhuǎn)變?yōu)楸砻媪鸭y越快,魚眼區(qū)內(nèi)外裂紋擴(kuò)展速率差別越大,魚眼區(qū)邊界越明顯。FV520B-I超高周疲勞壽命隨GBF (granular bright facet)區(qū)直徑的增大而增大,而與其他特征區(qū)域尺寸的關(guān)系并不明顯。夾雜物處起裂裂紋的萌生壽命不是超高周疲勞壽命的主要部分,超高周疲勞壽命主要消耗在GBF區(qū)的形成上。夾雜物直徑對(duì)GBF區(qū)直徑有一定影響,夾雜物直徑顯著減小時(shí),GBF區(qū)直徑也會(huì)顯著減小。在Murakami模型的基礎(chǔ)上,通過斷裂力學(xué)分析考察了夾雜物形狀對(duì)疲勞強(qiáng)度預(yù)測(cè)的影響。考慮夾雜物形狀時(shí),修正模型的超高周疲勞強(qiáng)度預(yù)測(cè)值比Murakami模型預(yù)測(cè)值略高2%,修正模型對(duì)FV520B-I超高周疲勞強(qiáng)度的預(yù)測(cè)更接近試驗(yàn)結(jié)果。基于Paris公式和腐蝕疲勞裂紋萌生壽命模型對(duì)FV520B-I超高周疲勞壽命進(jìn)行擬合,基于腐蝕疲勞裂紋萌生壽命模型的擬合結(jié)果明顯優(yōu)于基于Paris公式的擬合結(jié)果。通過對(duì)稱拉壓超聲疲勞試驗(yàn)方法對(duì)FV520B-I試樣尺寸增大時(shí)的超高周疲勞性能進(jìn)行測(cè)試,考察試樣尺寸對(duì)FV520B-I超高周疲勞行為與機(jī)理的影響。試樣尺寸增大后,試樣中夾雜物尺寸增大,試樣熱效應(yīng)更明顯,S-N曲線下移,相同應(yīng)力水平下,疲勞壽命縮短,109循環(huán)周次下的疲勞強(qiáng)度降低,但FV520B-I超高周疲勞機(jī)理未發(fā)生本質(zhì)變化。與小尺寸試樣試驗(yàn)結(jié)果相似,大尺寸試樣的超高周疲勞壽命與裂紋源距試樣表面距離、魚眼區(qū)直徑?jīng)]有明顯關(guān)系。載荷一定時(shí),超高周疲勞壽命隨夾雜物直徑的減小總體上呈增大的趨勢(shì),隨GBF區(qū)直徑與夾雜物直徑比值的增大而增大。對(duì)于大尺寸試樣,夾雜物處起裂裂紋的萌生壽命同樣不是超高周疲勞壽命的主要部分,超高周疲勞壽命主要消耗在GBF區(qū)的形成上。采用統(tǒng)計(jì)極值方法對(duì)不同尺寸試樣中可能的最大夾雜物尺寸進(jìn)行預(yù)測(cè),并進(jìn)一步通過Murakami模型以及考慮夾雜物形狀影響后的修正模型對(duì)超高周疲勞強(qiáng)度進(jìn)行估算,相較于對(duì)小尺寸試樣試驗(yàn)結(jié)果的預(yù)測(cè),上述模型特別是修正模型對(duì)大尺寸試樣超高周疲勞強(qiáng)度的預(yù)測(cè)更接近試驗(yàn)結(jié)果。利用腐蝕疲勞裂紋萌生壽命模型對(duì)大尺寸試樣的超高周疲勞壽命進(jìn)行擬合,相較于對(duì)小尺寸試樣超高周疲勞壽命的擬合,擬合效果有所下降。采用對(duì)稱拉壓超聲疲勞試驗(yàn)方法測(cè)試了接近葉輪真實(shí)表面粗糙度情況下FV520B-I在109周次范圍內(nèi)的超高周疲勞性能,并與前兩組光滑試樣的試驗(yàn)結(jié)果進(jìn)行對(duì)比,分析了表面粗糙度對(duì)FV520B-I超高周疲勞行為與機(jī)理的影響。隨著試樣表面粗糙度的增大,S-N曲線下移,表面裂紋向內(nèi)部裂紋轉(zhuǎn)變的應(yīng)力幅值降低,直至出現(xiàn)“傳統(tǒng)疲勞極限”。將試樣危險(xiǎn)截面處的最深溝槽作為一條單獨(dú)裂紋處理,預(yù)測(cè)得到的表面疲勞極限相較于Murakami模型預(yù)測(cè)值與試驗(yàn)結(jié)果更為接近。對(duì)于Ra≈0.05,Ra≈0.2的試樣,應(yīng)力幅值較高時(shí),很多試樣中的裂紋未能充分?jǐn)U展,測(cè)試得到的疲勞壽命偏小,試驗(yàn)結(jié)果小于平行層模型預(yù)測(cè)值。對(duì)于Ra≈0.6的試樣,應(yīng)力幅值較高時(shí),裂紋能充分?jǐn)U展,測(cè)試結(jié)果較為準(zhǔn)確,平行層模型預(yù)測(cè)值與試驗(yàn)結(jié)果吻合較好。試樣從表面或內(nèi)部起裂是由表面裂紋或內(nèi)部裂紋進(jìn)入到擴(kuò)展階段的先后決定的,GBF區(qū)內(nèi)裂紋生長極慢,該區(qū)域的形成與裂紋萌生相近,可采用參數(shù)D*=NG/NS表征裂紋起裂模式的競(jìng)爭(zhēng)。采用漏斗形試樣著重對(duì)表面粗糙度不同時(shí)FV520B-I焊縫的超高周疲勞行為與機(jī)理進(jìn)行研究。相較于母材,FV520B-I焊縫試樣的起裂模式更多,焊接過程中產(chǎn)生的氣孔和藥皮夾渣都能引起疲勞開裂。FV520B-I焊縫高周疲勞裂紋主要萌生于表面,超高周疲勞裂紋主要萌生于熔池冶金反應(yīng)形成的復(fù)雜非金屬氧化物。GBF區(qū)存在C富集,佐證了GBF區(qū)形成的碳化物彌散減聚機(jī)制。GBF區(qū)的形成是裂紋由短裂紋群體行為逐漸演化為單條長裂紋行為的過程�？拷鼕A雜物,應(yīng)力集中越大,有效短裂紋密度越高,斷面粗糙度越大；遠(yuǎn)離夾雜物,應(yīng)力集中越小,有效短裂紋密度越低,斷面粗糙度越小。FV520B-I光滑焊縫具有明顯的超高周疲勞特征,疲勞壽命高于107周次時(shí),裂紋主要在內(nèi)部萌生。表面粗糙度增大后,S-N曲線有所下降,裂紋傾向于表面萌生。Murakami模型對(duì)表面疲勞極限的預(yù)測(cè)遠(yuǎn)大于試驗(yàn)值,平行層模型則能較好的預(yù)測(cè)表面起裂高周疲勞裂紋的疲勞壽命。夾雜物(氣孔)處起裂裂紋的萌生壽命不是超高周疲勞壽命的主要部分,超高周疲勞壽命隨夾雜物(氣孔)直徑的減小而增大,隨GBF區(qū)直徑與夾雜物(氣孔)直徑比值的增大而增大。夾雜物(氣孔)直徑減小導(dǎo)致應(yīng)力集中降低,減緩了有效短裂紋密度的增加,GBF直徑的增大增加了主導(dǎo)有效短裂紋的擴(kuò)展距離�？傊�,通過離心壓縮機(jī)葉輪的力學(xué)特性分析,確定了葉輪典型的高頻低幅疲勞載荷及危險(xiǎn)部位,為后續(xù)離心壓縮機(jī)葉輪材料FV520B的超高周疲勞試驗(yàn)提供了參考。通過對(duì)FV520B的超高周疲勞行為與機(jī)理進(jìn)行研究,揭示了熱處理狀態(tài)、試樣尺寸、表面粗糙度、焊接對(duì)FV520B超高周疲勞行為與機(jī)理的影響規(guī)律,為離心壓縮機(jī)葉輪的剩余壽命估算以及可再制造臨界閾值的判定提供了支持。然而,由于時(shí)間和試驗(yàn)條件的限制,FV520B-I母材狗骨型試樣與FV520B-I焊接接頭狗骨型試樣的超高周疲勞試驗(yàn)有待繼續(xù)開展。
[Abstract]:Centrifugal compressor impeller is a high speed rotary part. Due to the wake excitation and vibration of the unit, it often bears the function of high frequency and low stress amplitude cycle load. The fatigue life requirement is far more than 107 weeks and enters the ultra high cycle fatigue range. The ultra high cycle fatigue behavior and mechanism of the important material FV520B of centrifugal compressor impeller is not only used for the study of the fatigue behavior and mechanism of the centrifugal compressor impeller. The long life fatigue design and fatigue failure prevention of centrifugal compressor impeller provide guidance, and provide strong support for the determination of the critical threshold for the remanufacture of the centrifugal compressor impeller. First, the author analyses the mechanical characteristics of a centrifugal compressor impeller. On this basis, the high and low temperature aging treatment, the sample size, and the table are studied. The effect of surface roughness and welding on the high cycle fatigue behavior and mechanism of FV520 B ultrasonic. The finite element method was used to analyze the mechanical properties of the impeller after the partial reduction of the first stage impeller and the worn blade of the H418 low pressure cylinder of air separation air compressor unit. The results showed that (1) the maximum stress in the middle part of the blade root was the maximum. (2) the impeller was in the amount. When the fixed speed is running, the stress concentration occurs mainly in the middle of the blade front, which is consistent with the fatigue fracture site when the impeller is in service. (3) the local thinning of the blade is reduced to "small detuning", and the structure topology of the impeller is basically unchanged before and after the detuning, and the frequency of the mode state of the detuning impeller and the modes of each order have little change compared with the harmonic impellers. (4) when the wake excited vibration causes the impeller resonance, the central part of the blade front is the most dangerous. It can be used as the key site of the impeller fatigue test. The maximum amplitude of the alternating load is 33.3MPa. The vibration of the front edge of the blade is similar to the bending vibration of a cantilever beam with a sliding mass. The high and low temperature aging treatment has been studied for the high cycle fatigue of FV520 B ultrasonic. The ultra high cycle fatigue performance of FV520B-I and FV520B-S obtained by FV520B after different temperature aging treatment was tested by symmetrical tension pressure ultrasonic fatigue test. The ultra high cycle fatigue S-N curve was obtained. The ultrahigh cycle fatigue mechanism was studied by the fracture morphology observation and the characteristic regional scale measurement. There is a great difference between the ultra high cycle fatigue behavior and mechanism of FV520B-I and FV520B-S. The S-N curve of.FV520B-I has a tendency to decline continuously within the range of 109 weeks. The S-N curve of the curve divided into a distinct slope with different slopes is significantly lower than that of FV520B-I, and the "tradition" appears even from the 106 cycle. In the stage of ultra high cycle fatigue, the FV520B-I cracks mainly erupt in the internal inclusions, a few cracks occur on the surface of the surface or the soft ferrite in the.FV520B-I ultra high cycle fatigue fracture area, which is related to the distance between the crack source and the sample surface. The crack source is closer to the specimen surface, and the internal crack is transformed into a surface crack. The faster the difference in the rate of crack propagation in the fish eye area, the more obvious the.FV520B-I ultra high cycle fatigue life of the fish eye area increases with the increase of the diameter of the GBF (granular bright facet) region, but the relationship with the other characteristic region size is not obvious. The ultrahigh cycle fatigue life is mainly consumed in the formation of the GBF region. The diameter of inclusions has a certain effect on the diameter of the GBF region, the diameter of the inclusion is significantly reduced, and the diameter of the GBF region will be reduced significantly. On the basis of the Murakami model, the influence of the inclusion shape on the fatigue strength prediction is investigated by the fracture mechanics analysis. The prediction value of ultra high cycle fatigue strength of the modified model is slightly higher than that of the Murakami model. The modified model is closer to the test results for the prediction of FV520B-I ultra high cycle fatigue strength. Based on the Paris formula and the corrosion fatigue crack initiation life model, the ultra high cycle fatigue life of the FV520B-I is fitted and the fatigue crack initiation life model is based on the corrosion fatigue crack initiation life model. The fitting results are obviously superior to the fitting results based on the Paris formula. The ultra high cycle fatigue performance of the FV520B-I specimen is tested by the symmetrical tension pressure ultrasonic fatigue test, and the effect of the sample size on the ultra high cycle fatigue behavior and mechanism of FV520B-I is investigated. The size of the inclusions in the sample increases after the sample size increases, and the sample size increases. The thermal effect is more obvious, the S-N curve moves down, the fatigue life shortens under the same stress level, and the fatigue strength decreases under the 109 cycle cycle, but the ultra high cycle fatigue mechanism of FV520B-I does not change essentially. When the load is fixed, the ultra high cycle fatigue life increases with the decrease of the inclusion diameter, and increases with the increase of the ratio of the diameter of the GBF area to the inclusion diameter. For large size specimens, the initiation life of the crack crack at the inclusion is not the main part of the ultra high cycle fatigue life, and the ultra high cycle fatigue life is the same. It is mainly consumed in the formation of the GBF region. The maximum inclusion size in different size samples is predicted by the statistical extremum method, and the super high cycle fatigue strength is estimated by the Murakami model and the modified model considering the influence of the inclusion shape, compared with the prediction of the test results for small size samples. The model, especially the modified model, is more close to the test results for the prediction of the ultra high cycle fatigue strength of large size specimens. Using the corrosion fatigue crack initiation life model to fit the super high cycle fatigue life of large size specimens, compared with the fitting of the ultra-high cycle fatigue life of small size specimens, the fitting effect is reduced. The ultrasonic fatigue test method was used to test the ultra high cycle fatigue performance of FV520B-I in the 109 week range near the actual surface roughness of the impeller, and compared with the test results of the previous two groups of smooth samples. The effect of surface roughness on the ultra high cycle fatigue behavior and mechanism of FV520B-I was analyzed. With the increase of the surface roughness of the sample, S-N When the curve moves down, the stress amplitude of the change of the surface crack to the internal crack is reduced until the "traditional fatigue limit" appears. The most deep groove at the dangerous section of the specimen is treated as a single crack. The predicted surface fatigue limit is closer to the predicted value of the Murakami model than the test result. For the test of Ra 0.05, the test of Ra 0.2 When the stress amplitude is high, the cracks in many samples are not fully expanded, the fatigue life of the test is smaller and the test results are less than the predicted value of the parallel layer model. For the sample of Ra 0.6, the crack can be fully expanded, the test result is more accurate, the prediction value of the parallel layer model is in good agreement with the test result. The crack from surface or inside is determined by the entry of the surface crack or the internal crack to the expansion stage. The crack growth in the GBF region is very slow. The formation of the region is similar to the crack initiation. The competition of the crack initiation mode can be characterized by the parameter D*=NG/NS. The use of the funnel-shaped specimen is focused on the super high surface roughness of the FV520B-I weld. The behavior and mechanism of the cycle fatigue are studied. Compared with the parent material, the crack initiation mode of the FV520B-I welds is more. The pores produced in the welding process and the dregs can cause the fatigue cracking.FV520B-I weld high cycle fatigue crack initiation on the surface, and the ultra high cycle fatigue crack mainly originated from the complex non-metal formed by the metallurgical reaction of the weld pool. The presence of C enrichment in the oxide.GBF region shows that the formation of the carbide dispersion reduction mechanism of the GBF zone is the process of the crack evolution from the short crack group behavior to the single long crack. The greater the stress concentration is near the inclusion, the higher the density of the effective short crack, the greater the roughness of the section, and the smaller the stress concentration away from the inclusions. The lower the effective short crack density is, the smaller the cross section roughness is, the.FV520B-I smooth weld has obvious ultra high cycle fatigue characteristics. The fatigue life is higher than 107 weeks, and the crack is mainly in the interior. After the surface roughness increases, the S-N curve decreases, and the crack tends to the surface initiation.Murakami model to predict the surface fatigue limit far greater than the test. The parallel layer model can better predict the fatigue life of the high cycle fatigue crack on the surface. The initiation life of the crack in the inclusion (air hole) is not the main part of the ultra high cycle fatigue life. The ultra high cycle fatigue life increases with the decrease of the diameter of the inclusions (the pores), and increases with the ratio of the diameter of the GBF area to the inclusion (air hole) diameter. The decrease of the diameter of the inclusions (holes) leads to the decrease of the stress concentration and the increase of the effective short crack density. The increase of the GBF diameter increases the extended distance of the dominant and effective short crack. In a word, the typical high frequency and low amplitude fatigue load and dangerous part of the impeller are determined by the analysis of the mechanical characteristics of the impeller of the centrifugal compressor. The ultra high cycle fatigue test of the centrifugal compressor impeller material FV520B provides a reference. Through the study of the ultra high cycle fatigue behavior and mechanism of FV520B, the effect of heat treatment state, sample size, surface roughness, welding on the behavior and mechanism of FV520 B ultrasonic high cycle fatigue is revealed, and the residual life of the centrifugal compressor impeller is estimated. Support is provided for the determination of the remanufacturing critical threshold. However, due to time and test conditions, the ultra high cycle fatigue test of the FV520B-I parent dog bone specimen and the FV520B-I welded joint dog bone specimen needs to be carried out.

【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TH452

【引證文獻(xiàn)】

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1 王志明;尚爾峰;薛松海;王亞勤;;立空壓機(jī)一級(jí)葉輪葉片斷裂失效分析[A];2009年全國失效分析學(xué)術(shù)會(huì)議論文集[C];2009年

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