共查询到20条相似文献,搜索用时 78 毫秒
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通过不同的加工工艺制备具有不同晶粒尺寸和织构的AZ31镁合金板材,通过室温埃里克森试验研究了工艺因素对提高镁合金板材室温成形性能的影响。结果表明:增大晶粒尺寸,减弱基面织构,可以改善镁合金轧板在变形过程中产生的在轧制方向的硬取向,增大镁合金轧板的延伸率,从而提高镁合金室温成形性能;用异步轧制工艺(轧制和退火温度为400℃、异速比为1.5)制备的试样晶粒尺寸增大到20μm、(0002)极图最大极密度仅为2,室温杯突实验测得IE值达到了5.71,显著提高了材料室温成形性能。 相似文献
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通过挤压后再轧制的方法制备AZ61镁合金板材,利用动态再结晶产生局部剪切变形减弱挤压形成的{0002}基面织构,可以有效提高板材的塑性成形能力,对比分析了直接轧制75%变形量与挤轧复合轧制60%变形量的AZ61电磁半连铸镁合金板材.结果表明,两种工艺方法所得到的板材力学性能相近,前者抗拉强度σb=300 MPa,屈服强度σ0.2=230 MPa,延伸率δ=8.0%,后者σb=295 MPa,σ0.2=245 MPa,δ=8.2%.因此,可以通过挤轧复合的工艺方法利用较小的轧制变形量(60%)制备出与较大轧制变形量(75%)性能相近的镁合金板材. 相似文献
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累积叠轧工艺对AZ31镁合金板材组织和性能的影响 总被引:1,自引:0,他引:1
采用累积叠轧工艺对AZ31 镁合金薄板进行剧塑性变形,研究了累积叠轧变形过程中镁合金板材的组织及性能演变.实验结果表明,累积叠轧可以有效细化AZ31镁合金板材的晶粒组织,显著改善室温延伸率,是制备大尺寸、高性能细晶镁合金板材的一种有效、经济而且可以实现工业化生产的技术.累积叠轧5道次后AZ31镁合金板材组织均匀,晶粒尺寸为1~2μm左右,晶粒细化源于大的累积变形及表面剪切变形;室温抗拉强度和延伸率可达到349MPa和22.46%,可归因于晶粒细化对镁合金强度和塑性的改善.累积叠轧板材的道次间的加热使ARB组织粗化,减小了累积叠轧过程中晶粒持续细化的效果. 相似文献
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A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling. 相似文献
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An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a
rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate
agreement is demonstrated between the derived relations and experimental data. 相似文献
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水三相点是开尔文热力学温度的唯一基准点,也是ITS-90国际温标重要的定义固定点。因此,水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来,中国计量科学研究院研制出一系列高质量的水三相点容器,加强了水三相点的研究,为不确定度的分析提供了更为可靠的实验依据。同时,不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此,根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明,其扩展不确定度为0.16mK(k=2.69,P=0.99)。 相似文献
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Liebert A Wabnitz H Grosenick D Möller M Macdonald R Rinneberg H 《Applied optics》2003,42(28):5785-5792
A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue. 相似文献
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