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排序方式: 共有162条查询结果,搜索用时 15 毫秒
141.
E. Fekete Sz. Molnár G.-M. Kim G. H. Michler B. Pukánszky 《Journal of Macromolecular Science: Physics》2013,52(5-6):885-899
Polypropylene/CaCO3 composites were homogenized in a twin-screw compounder and then injection molded into tensile bars. Six different fillers were used in a wide range of average particle sizes between 0.08 and 12 μm. Tensile and flexural properties were measured by standard techniques, while impact resistance was determined by instrumented impact testing. Structure was characterized by light and electron microscopy, while failure initiation and propagation was studied with in situ high-voltage electron microscopy. The results showed that aggregation of particulate fillers occurs when their particle size is smaller than a critical value. This critical size depends on component properties and processing conditions. Strength and impact resistance usually decrease with increasing number of aggregates. The presence of aggregation can be detected by the use of a simple semiempirical model. Comparison of samples prepared by two different technologies showed that twin-screw extrusion and injection molding leads to relatively homogeneous composites, which was indicated by smaller deviations of the properties from theoretical predictions. In spite of the acceptable dispersion, impact resistance showed a large standard deviation, probably determined by the local variation of structure. In composites containing relatively large particles, the dominating micromechanical deformation process is debonding, while in the presence of extensive aggregation of small particles, cracks are initiated inside and propagate through aggregates. Mixed-mode failure may also occur at certain intermediate panicle sizes. 相似文献
142.
P. K. Govindan Potti B. N. Rao V. K. Srivastava 《Theoretical and Applied Fracture Mechanics》2000,33(2)
The point stress criterion and the average stress criterion are applied for evaluating the notched tensile strength of injection-moulded plates with machined and moulded-in notches. Use is made of a characteristic length which is found to be geometry and material dependent. 相似文献
143.
The elastic modulus and failure behavior of poly(urea-formaldehyde) shelled microcapsules were determined through single-capsule
compression tests. Capsules were tested both dry and immersed in a fluid isotonic with the encapsulent. The testing of capsules
immersed in a fluid had little influence on mechanical behavior in the elastic regime. Elastic modulus of the capsule shell
wall was extracted by comparison with a shell theory model for the compression of a fluid filled microcapsule. Average capsule
shell wall modulus was 3.7 GPa, regardless of whether the capsule was tested immersed or dry. Microcapsule diameter was found
to have a significant effect on failure strength, with smaller capsules sustaining higher loads before failure. Capsule size
had no effect on the modulus value determined from comparison with theory. 相似文献
144.
Fei Ma Lianzhu Zhou Yang Luo Jiaqing Wang Bing Ma Binbin Qian Jun Zang Yueyang Hu Xuehong Ren 《印度化学会志》2022,99(8):100602
The high autogenous shrinkage of geopolymers hampers their application as building materials. In this study, pristine steel slag was used as an expansion material to mitigate shrinkage in geopolymers. The influence of pristine steel slag on the chemical deformation of alkali-activated fly ash-based geopolymers is investigated. The microstructure of the expanded system was studied by X-ray diffraction (XRD), FTIR measurement, thermogravimetric measurement (TGA), scanning electron microscopy with energy dispersive X-ray (SEM/EDS) and mercury intrusion porosimetry (MIP). Finally, the mechanisms of expansion were elucidated. The experimental results show that the shrinkage of the geopolymer is eliminated with the addition of steel slag. Fly ash was replaced by 0, 5, 10, and 15% of steel slag, and the expansion rate ranged from ?0.29% to 20.24%. Increased steel slag content reduced the bulk density of geopolymer. The incorporation of steel slag not only provided calcium for the information of C-A-S-H but also filled the pores. Steel slag produces different expansion effects in different porous media and thus refines the pore structure. Therefore, expansion by means of steel slag is an efficient approach for mitigating shrinkage in fly ash-based geopolymers. 相似文献
145.
146.
This study focuses on the characterisation of strength, density, and size of granules produced in various scales of a high shear granulator. Calcium carbonate (Durca165) was used as the feed powder and aqueous polyethylene glycol (PEG 4000) as the binder. The dried granules were analysed for their strength, density, size distribution, and wall make-up. Granules were produced in granulators with four scales, 1, 5, 50, and 250 L under three scale-up rules of constant tip speed, constant shear stress, and constant Froude number. The results show that regardless of equipment scale, increasing the impeller speed has a great effect on crushing strength and stress. The underlying cause is an increase in granule density due to more consolidation at higher impeller speeds. Wall make-up is significantly reduced to less than 5% as the scale is increased from 1 to 250 L. The results of this study corroborate our previous findings that the constant tip speed rule is the best criterion for scale-up of high shear granulators. 相似文献
147.
运用灰色系统方法,对原丝性能与碳纤维强度之间的关系进行了灰色关联分析。结果表明,原丝弹性与原丝强度对碳纤维强度影响较大,而原丝纤度与原丝伸度对碳纤维强度影响较小。 相似文献
148.
A biaxial hysteretic model for a structural system incorporating strength deterioration and pinching phenomena 总被引:2,自引:0,他引:2
Shu-Hsien Chao 《International Journal of Non》2009,44(7):745-756
A biaxial hysteretic model is developed to take into account the commonly observed hysteretic characteristics of strength and stiffness degradation, pinching and biaxial interaction. The concept of zero force point is proposed to develop the biaxial hysteretic model. Two non-linear inelastic springs and one linear elastic spring are connected in parallel to define the cyclic behavior of the proposed biaxial hysteretic model. The proposed biaxial hysteretic model is rate-independent and capable of simulating not only global (such as story shear force versus story drift response of the whole structure) but also the local hysteretic behavior of structural member (such as moment versus curvature or plastic rotation response of a structural element). The biaxial cyclic loading test data of six reinforced concrete columns, which are designed for flexural failure and shear failure, are used to validate the proposed biaxial hysteretic model. 相似文献
149.
It is discovered that there are two important characters, local-world character and weight-driven character, in many real-life complex networks. Motivated by this fact, a weight-driven local-world network model is proposed, which incorporates the weight dynamics and the fixed local-world property. By means of mathematical analysis and numerical simulation, the strength distribution of the network model has been obtained. The results are applied to epidemic spreading theory. 相似文献
150.
The main objective of the current study was to gain a detailed understanding on the rate-dependent strength behavior under ramp and shock wave loading. A forward, numerical-simulation-based cause and effect analysis was used to address the research objective. The apparent strength associated with shock and ramp wave loadings with different risetimes and shapes was investigated. It was shown that intrinsic material strength could vary with pressure, temperature, and deformation history, but the apparent strength, which was larger than the intrinsic strength, was a result of the interaction between the rate sensitivity of the strength and the rate of the external loading. The degree of interaction led to different levels of mechanical and thermal dissipations and their partition, which was manifested by different temperature, stress, and deformation histories. 相似文献