共查询到20条相似文献,搜索用时 93 毫秒
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本文对工业用5CrMnMo钢超塑性变形特性进行了研究。测定了不同晶粒尺寸的lgσ—lgε关系曲线。研究了温度,应变速率与延伸率之间的关系。在晶粒尺寸为8.53μm的试样上、在700℃下、以4.9×10~(-4)s~(-1)的应变速率拉伸时,获得了最大延伸率、其值为582%。对变形后试样的组织分析结果表明:5CrMnMo钢在超塑性变形时有扩散蠕变、晶界滑移和位错滑移三种变形机制同时发生。晶界滑移为主要变形机制。 相似文献
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目的 研究Nb47Ti合金在变形温度为600~750℃、应变速率为0.001~1s?1条件下的热变形行为和微观组织。方法 采用Gleeble-3500型热/力模拟试验机进行等温恒应变速率压缩实验,获得Nb47Ti合金热变形的真应力应变曲线,并利用EBSD技术手段分析热变形后的微观组织。结果 Nb47Ti合金在变形温度小于650℃、应变速率小于0.1s?1下热变形的真应力-应变曲线为动态再结晶型曲线,变形温度大于等于700℃时呈现为动态回复型曲线;峰值应力随变形温度的升高和应变速率的减小而减小;在变形温度为650℃、应变速率为0.001 s?1下热变形组织以再结晶晶粒和亚晶粒为主,随着应变速率的增大,动态再结晶晶粒不断减少,而亚晶粒和变形晶粒增多,晶粒得到显著细化。当应变速率为0.1 s?1时,随着变形温度的增加,晶粒尺寸增大,变形温度升高至750℃,热变形组织中亚晶粒所占比例高达50.5%。结论 Nb47Ti合金是温度和正应变速率敏感材料,随变形温度的升高和应变速率的增大,变形过程中动态回复软化机制更为显著,低温、高应变速率下变形获得的再结晶晶粒尺寸小。 相似文献
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本文研究了硬化态铍青铜(QBe~2)的超塑性与动态再结晶。试验表明,合金在550℃和ε=1.75×10~(-4)s~(-1)条件下拉伸变形,获得最高延伸率780%,流动应力为0.075kg/mm~2。合金通过动态再结晶(ε≈0.3)形成等轴晶粒(等轴比1.12~1.22)。高速变形时晶粒尺寸会超细化,这可能是发生连续动态再结晶所致,但延伸率不高。第二相粒子会促进动态再结晶形核和通过钉扎晶界来保持细晶粒组织。 相似文献
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目的研究高温变形对合金动态再结晶晶粒尺寸的影响。方法利用Gleeble 3500热模拟试验机对Aermet100超高强度钢进行了热模拟压缩,分析了动态再结晶晶粒在变形温度为800~1040℃、应变速率为0.01~10 s-1条件下的演变行为。结果研究发现,Aermet100钢动态再结晶晶粒随变形温度的升高而增大,随应变速率的增大而减小,高温、低应变速率变形后获得的动态再结晶晶粒尺寸较大,再结晶充分;低温、高应变速率获得的动态再结晶晶粒尺寸细小,但再结晶不完全。结论根据实验数据,建立了动态再结晶晶粒尺寸随Zener-Hollomon参数变化的理论模型,为Aermet100钢锻造工艺优化提供了理论依据。 相似文献
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本研究运用动态再结晶诱发超塑性的原理,对未经细化晶粒预处理的常规生产热轧态2091Al-Li合金直接进行高温拉伸,试验结果表明合金在470~530℃温度范围和2×10~(-4)~1×10~(-3)应变速率范围内具有超塑性,最大断裂延伸率达405%。根据光镜和电镜组织观察和真应力—真应变曲线的单一峰值和变形激活能随应变量增大而下降等特征,讨论了动态再结晶诱发超塑性的机制。 相似文献
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利用Sans CMT4104型拉伸试验机、光学显微镜、电子显微镜研究变形温度、应变速率对2060铝锂合金热变形行为与显微组织的影响,分析合金在不同热变形条件下的真应力-真应变曲线,并结合Zener-Hollomon方程得到合金的热变形参数。通过对合金第二相、空洞、断口形貌的观察,研究了合金热拉伸显微组织的演变规律。结果表明:高温拉伸时合金的峰值应力随变形温度的升高和应变速率的减小而下降。合金的延伸率随变形温度的升高而提高,随应变速率的减小先提高后降低,在500℃/0.01 s-1条件下延伸率最佳,达到170%。通过计算,得到合金的变形激活能为227.28 kJ/mol。显微组织显示,随着变形温度的升高和应变速率的减小,空洞的数量增多、尺寸增大;在变形温度为475~500℃时,合金析出了第二相并发生了几何动态再结晶。 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa. 相似文献
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On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.…… 相似文献
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Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß. 相似文献
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C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill. 相似文献
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Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ... 相似文献
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《中国标准化(英文版)》2014,(4)
正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from 相似文献
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《中国标准化(英文版)》2014,(5)
正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively. 相似文献