【摘要】：金屬材料在其加工過程中的塑性變形達(dá)到一定程度時(shí),會(huì)出現(xiàn)韌性斷裂和承載能力的損失。韌性斷裂是影響金屬材料可加工性和工程構(gòu)件安全的重要因素。在產(chǎn)品的設(shè)計(jì)和優(yōu)化過程中,對材料韌性斷裂的準(zhǔn)確預(yù)測起著至關(guān)重要的作用。工藝過程中,選用一種適用可靠的斷裂準(zhǔn)則顯得很有必要。從目前的研究來看,眾多韌性斷裂準(zhǔn)則和極限斷裂準(zhǔn)則被提出用于預(yù)測材料變形過程中裂紋的啟裂位置和時(shí)刻。不銹鋼作為一種綠色環(huán)保且綜合性能優(yōu)異的材料,已廣泛地應(yīng)用于各領(lǐng)域。近年來,對不銹鋼的力學(xué)性能、耐腐蝕等問題進(jìn)行了大量的研究,但對于不銹鋼成形過程中斷裂準(zhǔn)則的研究卻鮮有提及。本文以304不銹鋼為對象,研究了其成形過程中的斷裂準(zhǔn)則,并將該準(zhǔn)則應(yīng)用于精沖領(lǐng)域,用以評價(jià)304不銹鋼的精沖性能。文中設(shè)計(jì)了7組不同高徑比的304不銹鋼圓柱試樣,對其進(jìn)行平板鐓粗破裂實(shí)驗(yàn)。對實(shí)驗(yàn)過程中測量的數(shù)據(jù)進(jìn)行計(jì)算,建立了304不銹鋼在其變形過程中的斷裂準(zhǔn)則,即“平均應(yīng)力三軸度-等效應(yīng)變”斷裂準(zhǔn)則。結(jié)果表明,平均應(yīng)力三軸度存在一個(gè)極限值-1/3。在ABAQUS/Explicit平臺上建立304不銹鋼圓柱平板鐓粗有限元模型,基于實(shí)驗(yàn)建立的斷裂準(zhǔn)則應(yīng)用于有限元模擬中。將有限元模型中失效斷裂點(diǎn)的應(yīng)力、應(yīng)變變量提取出來并計(jì)算,通過曲線擬合的方法建立校準(zhǔn)后的斷裂準(zhǔn)則。結(jié)果表明,第4次校準(zhǔn)的模擬結(jié)果能夠較好地符合平板鐓粗實(shí)驗(yàn)現(xiàn)象。通過對3組不同尺寸系列的圓環(huán)試樣進(jìn)行壓縮實(shí)驗(yàn),將測量的實(shí)驗(yàn)數(shù)據(jù)應(yīng)用于圓環(huán)壓縮有限元模擬中。有限元模擬結(jié)果和圓環(huán)壓縮實(shí)驗(yàn)中試樣的破裂情況進(jìn)行對比,來驗(yàn)證校準(zhǔn)建立的斷裂準(zhǔn)則的適用性和可靠性。結(jié)果表明,基于第4次校準(zhǔn)建立的斷裂準(zhǔn)則能夠較好的預(yù)測圓環(huán)壓縮實(shí)驗(yàn)中試樣的破裂情況。為了研究304不銹鋼的精沖性能,設(shè)計(jì)開發(fā)了一種材料精沖性能實(shí)驗(yàn)裝置,同時(shí)給出了一種材料精沖性能評價(jià)方法。將建立的304不銹鋼斷裂準(zhǔn)則引入到精沖有限元模擬中,來預(yù)測精沖過程中裂紋的出現(xiàn)。通過對精沖模擬結(jié)果中試樣光潔帶l和毛刺高度t的測量,依據(jù)給出的標(biāo)準(zhǔn)評價(jià)了304不銹鋼的精沖性能。評價(jià)結(jié)果表明,304不銹鋼的精沖性能不好。
[Abstract]:When the plastic deformation of metal material reaches a certain degree, ductile fracture and loss of bearing capacity will occur. Ductile fracture is an important factor affecting the machinability of metal materials and the safety of engineering components. In the process of product design and optimization, it is very important to predict ductile fracture accurately. In the process, it is necessary to select a reliable fracture criterion. From the current research, many ductile fracture criteria and limit fracture criteria have been proposed to predict the location and time of crack initiation in the process of deformation of materials. Stainless steel has been widely used in various fields as a kind of green and comprehensive performance material. In recent years, the mechanical properties and corrosion resistance of stainless steel have been studied extensively, but the study of fracture criterion in the forming process of stainless steel is seldom mentioned. In this paper, the fracture criterion of 304 stainless steel during forming process was studied and applied to fine blanking field to evaluate the fine punching performance of 304 stainless steel. In this paper, seven groups of 304 stainless steel cylinder specimens with different aspect ratio were designed and the upsetting fracture test was carried out. The fracture criterion of 304 stainless steel during deformation is established by calculating the measured data during the experiment, that is, "average stress triaxial-equivalent strain" fracture criterion. The results show that the average stress triaxiality has a limit value of -1 / 3. The finite element model of 304 stainless steel column upsetting was established on ABAQUS/Explicit platform. The fracture criterion based on experiment was applied to finite element simulation. The stress and strain variables of the failure fracture point in the finite element model are extracted and calculated, and the calibrated fracture criterion is established by curve fitting method. The results show that the simulated results of the fourth calibration are in good agreement with the plate upsetting experiment. Three groups of annular specimens with different sizes were tested and the measured data were applied to the finite element simulation of ring compression. In order to verify the applicability and reliability of the proposed fracture criterion, the finite element simulation results are compared with the fracture conditions of the specimen in the annular compression test. The results show that the fracture criterion based on the fourth calibration can predict the fracture of the specimen in the annular compression test. In order to study the precision punching performance of 304 stainless steel, a material precision punching performance experimental device was designed and developed. At the same time, an evaluation method of material precision punching performance was given. The fracture criterion of 304 stainless steel is introduced into the finite-blanking finite element simulation to predict the crack occurrence in the fine blanking process. The fine punching properties of 304 stainless steel were evaluated according to the standard given by the measurement of the smooth strip l and the burr height t of the sample in the simulation results of fine blanking. The evaluation results show that the fine punching performance of stainless steel is not good.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG142.71

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