發(fā)布時間：2018-03-16 17:07

  本文選題：空化水射流　切入點：沖擊強化　出處：《江蘇大學》2017年碩士論文　論文類型：學位論文

【摘要】：噴丸是一種常見的被用于提高金屬材料表面性能及其疲勞壽命的表面處理工藝,而空化水射流噴丸技術(shù)作為一種新型的表面處理工藝,其利用材料表面附近空化泡潰滅瞬間釋放的高壓沖擊反復(fù)作用于材料表面,使材料表層發(fā)生塑性形變,產(chǎn)生殘余壓應(yīng)力場,提高表面硬度,而粗糙度值卻不會明顯增大,從而有效提高材料表面性能。同時,該工藝所具有的一系列獨特優(yōu)勢,如綠色環(huán)保、通用性高以及易于實現(xiàn)自動化等,使其正日益成為表面處理技術(shù)領(lǐng)域中一個新的研究方向。本文以空化水射流技術(shù)為基礎(chǔ),以實現(xiàn)綠色高效的噴丸方式、提高金屬材料表面性能為出發(fā)點,采用理論分析的方法,對空化水射流噴丸工藝中空化泡的運動與動力學基礎(chǔ)、發(fā)展?jié)邕^程以及沖擊強化機理進行了分析。采用FLUENT數(shù)值模擬方法,對所設(shè)計噴嘴(收縮型、角型和風琴管噴嘴)的空化性能進行分析。通過對噴嘴在高壓水射流環(huán)境下的速度場、壓力場以及氣相體積分數(shù)分布進行對比分析后發(fā)現(xiàn):作為一種空化噴嘴,收縮型噴嘴的空化效果最不理想,風琴管噴嘴在一定程度上能夠滿足空化生成的需要,但角型噴嘴的空化性能最為突出,其內(nèi)外流場的空化泡群密度及分布廣度均要優(yōu)于其他兩種噴嘴,有利于空化水射流系統(tǒng)的穩(wěn)定輸出。同時,采用試驗研究的方法,利用相關(guān)設(shè)備組裝完成空化水射流噴丸裝置,選取廣泛應(yīng)用于對零部件表面綜合性能要求較高的航空、航天、汽車以及軍工等領(lǐng)域中的2A12鋁合金材料作為空化水射流噴丸試驗的試樣,檢測并比較分析了不同噴丸工藝參數(shù)下材料表面的各項性能,得出本試驗環(huán)境下的最佳噴丸工藝參數(shù)是入射壓力P=20MPa,靶距S=40mm,噴丸時間T=4min。經(jīng)過最佳噴丸工藝參數(shù)處理后的試樣表面的硬度值約為137HV,較原始試樣的表面硬度提高近48.9%;最大殘余壓應(yīng)力及其深度則分別達到320MPa、390μm,相對于噴丸前的原始試樣分別提升3.7倍、6.5倍;而表面粗糙度值只增加至1.29μm。并且通過觀察試樣表面的微觀形貌,可以明顯看到空化泡潰滅沖擊影響區(qū)的凹凸形貌過渡區(qū)連貫平滑,并沒有衍生出傳統(tǒng)噴丸中常見的尖銳棱邊、微裂紋等形變,避免了這些形變處的應(yīng)力集中,對空化水射流噴丸強化下的金屬材料表面性能夠起到較好的增益效果。
[Abstract]:Shot peening is a common surface treatment process used to improve the surface properties and fatigue life of metal materials, while cavitation water jet peening is a new surface treatment technology. The high pressure impact released by cavitation bubble collapsing near the surface of the material repeatedly acts on the surface of the material, resulting in plastic deformation of the surface of the material, resulting in residual compressive stress field and increasing the surface hardness, but the roughness value does not increase obviously. At the same time, the process has a series of unique advantages, such as green environmental protection, high versatility and easy to realize automation, etc. Therefore, it is becoming a new research direction in the field of surface treatment technology. Based on cavitation water jet technology, in this paper, the method of theoretical analysis is adopted to realize green and efficient shot peening and to improve the surface properties of metal materials. The motion and dynamics basis of cavitation water jet shot peening process, the development of collapse process and the mechanism of impact strengthening are analyzed. The designed nozzle (shrinkage type) is simulated by FLUENT numerical simulation method. By comparing the velocity field, pressure field and gas phase volume fraction distribution of the nozzle under the high pressure water jet environment, it is found that the nozzle is a cavitation nozzle. The cavitation effect of constrictive nozzle is the least, the organ nozzle can meet the need of cavitation to some extent, but the cavitation performance of angle nozzle is the most outstanding. The density and distribution of cavitation bubble group in the internal and external flow field are superior to those of the other two kinds of nozzles, which is beneficial to the steady output of cavitation water jet system. At the same time, the cavitation water jet shot peening device is completed by means of experimental study and related equipment. The aluminum alloy 2A12, which is widely used in aviation, aerospace, automobile and military industry, which is widely used in the field of air, aerospace, automobile and military industry, is selected as the sample of cavitation water jet shot peening test. The properties of the material surface under different parameters of shot peening were tested and compared. It is concluded that the optimum parameters of shot peening in this test environment are incident pressure P0 20 MPA, target distance 40 mm, shot peening time T4 min. The hardness of the sample surface treated by the best shot peening parameters is about 137 HVV, which is 48.9% higher than that of the original sample. The maximum residual compressive stress and its depth are respectively 320MPA ~ (390) 渭 m, which are 3.7 times and 6.5 times higher than those of the original sample before shot peening. The surface roughness was only increased to 1.29 渭 m. By observing the microscopic morphology of the sample surface, it can be seen that the transition zone of the concave and convex morphology of the affected area of cavitation bubble collapsing is smooth, and there is no derivation of the sharp edge commonly seen in the traditional shot peening. The microcracks and other deformation can avoid the stress concentration at these deformations and can improve the surface properties of metal materials strengthened by cavitation water jet shot peening.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG146.21;TG668

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本文編號：1620846