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开发了一种基于分形维数来表征纳米颗粒团聚行为的方法,通过对纳米SiO2颗粒的透射电子显微镜的图片进行分析,并借助冷冻切片技术对硅橡胶中的SiO2分布状态进行观测和分形维数的计算,探究了分形维数与吸油值、表面羟基数、力学性能等的关系。结果表明:纳米颗粒的团聚程度越大其分形维数越大;通过对纳米SiO2补强硅橡胶的超薄切片的分形维数的计算可知,在聚合物中的纳米颗粒的团聚也呈现相同的规律,即分形维数越大团聚程度越大;此外,分形维数越大,纳米SiO2的吸油值越小,表面羟基数越少,硅橡胶片的拉伸强度、撕裂强度及邵尔A硬度则越大。 相似文献
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本文应用高维分形理论,计算了颗粒复合材料ABS/TiO2的拉伸断口的分形维数,并对该材料的拉伸强度极限与其断口分形维数的关系进行了研究,得到了两者间的线性关系。 相似文献
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对聚酯玻璃钢进行实验室氙灯加速老化试验,测试了聚酯玻璃钢不同老化时间的弯曲强度。研究发现,弯曲强度与老化时间关系的现象是分形的,采用改变观察尺度计算方法对分形部分进行了分形维数的计算,得到聚酯的分形维数为1.24、含碳酸钙聚酯玻璃钢的分形维数为1.12、聚酯玻璃钢的分形维数为1.08,这说明氙灯加速老化下弯曲强度变化的复杂程度是按聚酯、含碳酸钙聚酯玻璃钢、聚酯玻璃钢顺序依次降低的。 相似文献
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针对搅拌过程中湍能耗散造成的能量损失问题,提出了一类新型分形几何涡轮桨,并基于计算流体动力学,对系列分形桨进行湍能耗散强度分布数值模拟实验。通过分析分形桨的湍能耗散分布强度规律,探究了分形维数及迭代次数对搅拌设备各部分湍能耗散以及搅拌功率的影响。结果表明:流场湍能耗散强度分布特征为横向呈风轮状,纵向呈扇状;相对于无迭代桨,分形迭代桨湍流耗散强度降低;分形维数增加会降低各处的湍能耗散强度。迭代次数增加会降低流场中湍能耗散,但会增大搅拌桨上的耗散强度;分形迭代桨会降低搅拌功率,并随着分形维数增大而效果加强。研究结果为高速离心搅拌桨设计提供新的设计思路。 相似文献
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混凝土梁在受弯过程中表面裂缝分布及演化的宏观特征可以反映其受弯性能,本文基于不同废旧轮胎钢纤维(WTSF)取代率的玄武岩纤维增强复合材料(BFRP)筋混杂钢纤维超高性能混凝土梁受弯试验结果,利用分形理论分析试验梁表面裂缝开展情况。结果表明,BFRP筋混杂钢纤维超高性能混凝土梁表面裂缝分布具有分形特征,满足自相似性,分形维数的变化区间为[0.892,1.064]。探讨了梁表面裂缝分形维数与施加荷载值、WTSF取代率、跨中挠度和最大裂缝宽度之间的关系,并分别拟合了WTSF取代率与完全破坏状态下全梁区和纯弯段分形维数的函数关系。分形维数与施加荷载值、跨中挠度和最大裂缝宽度均呈对数函数关系,完全破坏状态下,WTSF取代率变大会增大梁表面裂缝的分形维数,但总体来说不利影响并不明显,研究结果可为超高性能混凝土的工程实际应用提供参考。 相似文献
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运用分形理论获得了含多裂纹的有机玻璃的裂纹分形特征,并研究了分形维数与有效弹性模量及双裂纹聚合路径的关系。结果表明:有效弹性模量随分形维数的增大成比例减小趋势;双裂纹的聚合路径可以用分形维数判定。 相似文献
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Fei Qi Songhe Meng Fan Song Hao Guo Xianghong Xu Yingfeng Shao Yao Chen 《Journal of the American Ceramic Society》2019,102(6):3641-3652
This work utilized a combination of experimental evidence and fractal geometric method to assess the effect of crack extension concerning the thermal shock on residual strength of ceramics. Sintered alumina (Al2O3) ceramic slabs were bundled and quenched in water under different thermal shock temperatures. The fractal dimension of thermal shock crack patterns on the interior surface and the cooled surface was calculated by the Box-counting method. Fracture energy of a fractal pattern of microcracks in quasi-brittle solids was employed to explain the relationship between crack length and fractal dimensions. The results show that if the crack propagation has the same crack length but a larger fractal dimension, it will absorb more fracture energy. The thermal shock crack patterns of Al2O3 ceramics with different grain sizes were analyzed, and the smaller grain size ceramic had a higher fractal dimension of crack patterns than the larger one. 相似文献
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A quantitative study on the surface crack pattern of concrete with high content of steel fiber 总被引:1,自引:0,他引:1
The mechanical properties and digital image analysis of slurry-infiltrated fiber reinforced concrete (SIFCON) were investigated experimentally. Fractal dimension is used as a parameter to characterize the crack pattern on the surface of SIFCON. It is found that there exists fractal phenomenon for different fiber contents of SIFCON, fractal dimension can be a parameter to characterize crack pattern on the surface of SIFCON quantitatively, and there exists a good correlation between mechanical properties and fractal dimension. 相似文献
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《Drying Technology》2013,31(7):1555-1568
Abstract We examined in this work the drying characteristics of wastewater sludge, considering the weight loss using an electronic balance and the morphology change of drying cake by an X-ray micro-computerized tomography scanner (micro-CT). The drying rates for sludge cake was 50–60% of the pure water test. The corresponding micro-CT images were scanned to explore the change in cake volume and development of internal crack over drying. The Otsu's method was applied to bilevel the scanned images, based on which the three-dimensional model for crack's internal structure was reconstructed. The cake porosity and the geometric factors of cracks, such as the compactness, the boundary fractal dimension, and the Sierpinski carpet fractal dimension, were evaluated. The shrinkage of cake volume and the development of internal crack occurred simultaneously. The skin layer formed by the former mechanism retards further drying. On the other hand, the internal cracks were shown to exhibit zigzagging with a noncircular cross section and fractal-like boundary, which should be able to enhance local drying. A possible role of change in crack structure on the rate of drying was discussed. 相似文献
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以GAP(缩水甘油叠氮聚合物)、NEPE(硝酸酯增塑聚醚)和HTPB(端羟基聚丁二烯)推进剂为研究对象,对3种推进剂的扫描电镜(SEM)图像分形维数进行了研究.利用分形维数对固体推进剂裂纹定量表征以研究推进剂的力学性能,对阈值选取方法进行了分析,结果表明,利用全局阈值分割法选取图像适合的阈值可以对图像进行可靠的分割.固... 相似文献
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Local residual stress caused by impacts, machining and indentation results in a decrease in strength in most materials that fail in a brittle manner. The ratio of the critical crack size, c, and the fracture mirror size, r, also is affected by the existence of local residual stress. The global fracture toughness of non-R curve materials is not affected by the local residual stress. The fractal dimension of the fracture surface as characterized by the fractal dimensional increment, D*, is directly related to the square of the fracture toughness. This paper addresses the question of the effect of the local residual stress on the fractal dimension of the fracture surface. We derive a relationship between the fractal dimensional increment and the c/r ratio for materials fractured with and without local residual stress. We then compare the prediction with two cases of experimental results. We show the fractal dimension remains constant with the change in the c/r ratio for local residual stress conditions. 相似文献
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锂渣细度对锂渣混凝土早期抗裂性能影响及分形评价 总被引:3,自引:1,他引:2
锂渣作为一种工业废渣利用到混凝土中,可发挥锂渣的潜能,提高混凝土的性能。试验利用了锂渣优良的可磨性,通过平板法开裂试验研究了不同细度锂渣对混凝土塑性收缩、自缩收裂缝的影响,并应用分形理论测量并计算不同细度锂渣混凝土裂缝的分形维数。结果表明:锂渣混凝土早期裂缝的最大宽度、总长度以及总面积随锂渣细度的增大而增大,同时裂缝复杂化程度提高。 相似文献
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为研究钢纤维混凝土损伤破坏过程和裂纹发展演化机理,基于分形理论和扩展有限元法,建立钢纤维混凝土立方体抗拉试验细观有限元模型和切口梁三点弯曲试验有限元模型,以相关试验测试结果为基础,比较验证了所建有限元分析模型的可靠性。以裂纹分形维数表征钢纤维混凝土损伤演化过程,考察不同钢纤维体积掺量和长度、粗骨料形状等重要因素对钢纤维混凝土损伤演化过程的影响。结果表明,基于裂纹分形维数的损伤值可以较好地反映钢纤维混凝土的损伤演化过程及特征,钢纤维体积掺量、长度的增加和骨料形状的不规则化会延缓钢纤维混凝土立方体试件的损伤演化过程,钢纤维体积掺量、初始裂纹距跨中距离的增加和初始裂纹缝高比的减小可在较小程度上延缓钢纤维混凝土切口梁的损伤演化过程。 相似文献