共查询到20条相似文献,搜索用时 250 毫秒
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沥青混合料的细观结构是复杂且高度不均匀混合物。这种不均匀性严重影响着沥青混合料整体的实体力学行为和开裂行为性能,而且细观结构模型的建立也极具挑战性。本研究将基于多重二维细观结构的有限元模型对沥青混合料粘弹体粘聚破坏响应进行预测。首先,为了模拟裂缝的产生和扩展,利用沥青混合料的扫描结构的图像,借助组成相的分割方法分离颗粒与胶浆,有效的生成多个二维的图像,并赋予混合料粘聚区域内的微观结构的材料属性,进而提出一种新的数值算法。建立模型时沥青胶结料具有粘弹特性和也是开裂区,集料被看作弹性体。其次,通过利用间断级配混合料的三点弯曲和密级配的半圆弯曲试验的结果与有限元模拟结果进行统计和对比分析,对提出的多重二维图像分析方法进行验证。结果表明,通过多重二维细观结构的模拟结果可以获取沥青混合料粘弹体的开裂行为,但是当粗骨料的含量越高和分布越复杂时预测能力将有所下降。当这些局限性得到进一步解决时,就可以仅仅通过获取扫描二维图像的细观结构就可以预估沥青混合料粘弹体的粘聚破坏行为,大幅度降低做实验消耗的成本。 相似文献
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铝合金焊接接头力学性能不均匀加大了焊接结构变形及开裂失效预测的难度。通过特殊样件拉伸试验,结合有限元反求方法获得了铝合金焊接接头焊缝、热影响区局部材料参数,建立从细观损伤力学角度预测铝合金焊接结构变形开裂的GTN(Gurson-Tvergaard-Needlemen)损伤模型。将焊接接头按照材料性能差异进行分区,构建精细有限元模型,采用Ls-dyna软件结合GTN损伤模型对铝合金拼焊薄壁梁结构轴向压溃变形及开裂失效进行了预测,预测结果与试验吻合很好,验证了该方法的有效性。 相似文献
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裂缝是沥青混凝土路面的主要病害之一。通常,对沥青混合料的裂缝研究没有考虑沥青混合料细观结构的各向异性,对于裂缝尖端的塑性特征也研究不足。采用数字图像处理技术,实现沥青混合料细观结构的有限元二维建模,采用内聚力模型对单调加载情况下半圆弯拉试验裂缝的动态扩展进行数值模拟,此研究可以进一步发展到疲劳特性研究。 相似文献
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J. M. Lee N. W. Sung G. B. Cho K. O. Oh 《International Journal of Automotive Technology》2010,11(3):307-316
An analytical study of the performance of a radial-type, metal foam diesel particulate filter is reported. A mathematical
model for the filtration and regeneration of soot in a metal foam filter was developed. Nickel foam was selected for the filter
medium due to its large specific area, high porosity, and high thermal resistance. For various metal foams, the filtration
efficiency and the pressure drop through the filter were calculated, as was the deposition of soot. The results from the analytical
model were compared with experimental data. In comparison with a conventional wall flow filter, the metal foam diesel particulate
filter (DPF) is effective in utilizing the volume of material, due to the porous structures. As the size of the metal foam
pores in the DPF increases from 580 μm to 800 μm, the filtration efficiency decreases from 90% to 50%, and the pressure drop
decreases from 380 mbar to 20 mbar. The metal foam DPF with a large pore size is effective in utilizing the volume of material
with a small pressure drop. The regeneration is completed within four minutes by the flow of hot exhaust gases under full
load conditions. 相似文献
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介绍了有限元强度折减法的基本原理,结合建立的二维边坡模型,基于有限元强度折减法,运用有限元软件Midas/GTS对该边坡进行了数值分析,得出边坡在自重作用下的水平位移等值云图、应力与应变云图及安全系数指标,依此确定了最危险滑面位置和形状以及整体失稳的安全系数。 相似文献
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为了揭示金属主簧-复合材料副簧的变形机理并快速预测其复合刚度,综合应用板弹簧设计理论、复合材料层合板理论及有限差分法建立了金属主簧-复合材料副簧复合刚度的理论计算模型,并编写了相应的MATLAB计算程序。采用ABAQUS软件建立了某金属主簧-复合材料副簧总成的有限元模型并对其刚度特性进行有限元模拟。有限元模拟刚度与理论计算刚度之间的误差低于3%,从而验证了理论计算模型的正确性。建立的理论计算模型不但阐明了金属主簧-复合材料副簧的变形机理,而且适宜编程计算,能准确快速地预测金属主簧-复合材料副簧的复合刚度,这对复合材料板簧的推广应用具有重要意义。 相似文献
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《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(1):122-138
The efficiency of a seat in reducing vibration depends on the characteristics of the vibration, the dynamic characteristics of the seat, and the dynamic characteristics of the person sitting on the seat. However, it is not known whether seat cushions influence the dynamic response of the human body, whether the human body influences the dynamic response of seat cushions, or the relative importance of human body nonlinearity and seat nonlinearity in causing nonlinearity in measures of seat transmissibility. This study was designed to investigate the nonlinearity of the coupled seat and human body systems and to compare the apparent mass of the human body supported on rigid and foam seats. A frequency domain model was used to identify the dynamic parameters of seat foams and investigate their dependence on the subject-sitting weight and hip breadth. With 15 subjects, the force and acceleration at the seat base and acceleration at the subject interface were measured during random vertical vibration excitation (0.25–25 Hz) at each of five vibration magnitudes, (0.25–1.6 ms?2 r.m.s.) with four seating conditions (rigid flat seat and three foam cushions). The measurements are presented in terms of the subject's apparent mass on the rigid and foam seat surfaces, and the transmissibility and dynamic stiffness of each of the foam cushions. Both the human body and the foams showed nonlinear softening behaviour, which resulted in nonlinear cushion transmissibility. The apparent masses of subjects sitting on the rigid seat and on foam cushions were similar, but with an apparent increase in damping when sitting on the foams. The foam dynamic stiffness showed complex correlations with characteristics of the human body, which differed between foams. The nonlinearities in cushion transmissibilities, expressed in terms of changes in resonance frequencies and moduli, were more dependent on human body nonlinearity than on cushion nonlinearity. 相似文献
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