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91.
刚性圆板自由落体在水面上的冲击压力 总被引:2,自引:0,他引:2
本文对一个刚性圆板自由落体在水面上的冲击过程建立了比较精确的理论模型,并建立了相应的数值格式。计算结果与已有的实验结果符合良好,通过计算进一步给出了下落质量和下落高度对冲击压力峰值的影响。 相似文献
92.
S. H. Ahmad 《Polymer International》1992,28(4):291-294
Measurement of the flow stress of high density polyethylene (HDPE) and nylon 66 at strain rates of 103 s?1 using a split Hopkinson pressure bar technique is discussed. The flow stress at a strain of 10% has been determined for both polymers at 20°C. The intrinsic errors involved in this technique are briefly reviewed. The results indicate that the flow stress of HDPE and nylon 66 were 50MPa and 150MPa, respectively, at strain rates of about 103s?1. 相似文献
93.
Nanoadhesives of epoxy resin are synthesized and evaluated. They are organically modified by multiwalled carbon nanotubes (MWCNT) (1% by weight) as reinforcement. Tensile tests are conducted on multiple identical unnotched and notched specimens to evaluate the overloading and fracture behavior of the nanoadhesives and are compared with the neat epoxy resin. In comparison with the neat epoxy, it is found that the 1% MWCNT reinforcement increased the ultimate and residual strength by about 29% and 56%, respectively. In comparison with the neat resin, there is a 265% increase in the fracture toughness of the MWCNT adhesive. Fracture surface analysis revealed the various mechanisms by which the MWCNT adhesives acquire their superior strength and toughness in comparison with the neat resin. 相似文献
94.
Flame retardant and the degradation mechanism of high impact polystyrene/Fe-montmorillonite nanocomposites 总被引:1,自引:1,他引:0
High impact polystyrene/Fe-montmorillonite (HIPS/Fe-MMT) nanocomposites were successfully prepared by melting intercalation.
The nanostructures of HIPS/Fe-MMT were testified by X-ray diffraction (XRD) and transmission electron microscope (TEM). Corresponding
to pure HIPS, the thermal stability of HIPS/Fe-MMT nanocomposites was notably improved. The peaks of heat release rate (PHRR)
and the mass loss rate (MLR) were significantly reduced after the formation of the HIPS/Fe-MMT nanocomposites from cone calorimetry.
And nanocomposites PHRR was further lower with the increase of Fe-MMT content in the range of 1 to 5 wt%. The degradation
mechanism of HIPS and HIPS/Fe-MMT nanocomposites was conducted by pyrolysis gas chromatography mass spectrometry (Py-GC-MS).
And the reason of the enhancement of thermal stability maybe is that structural iron is the operative site for radical trapping
in the Fe-MMT and the nanostructure enhances the interaction of the chains of the HIPS. 相似文献
95.
��Ȼ�����öԻ���Ӱ����������ڷ��� 总被引:11,自引:0,他引:11
将清洁燃料(天然气)的利用与环境结合起来进行研究,是当今世界的前沿科学技术。为了具体说明从天然气开采到使用整个过程中对环境产生的影响,采用生命周期分析的方法对天然气开采、运输、使用等三个阶段中所造成的废弃物排放进行了分析和计算,对整个过程中投入和产出的能量进行了计算,并对天然气合成氨、作为民用燃气、发电、热电联产等天然气利用方法进行了比较。结果表明:与煤、石油等传统能源相比,天然气在各个方面对环境的影响是最小的,是一种理想的清洁能源。 相似文献
96.
A. A. Korobkin 《Journal of Engineering Mathematics》2007,58(1-4):121-139
The paper deals with the two-dimensional unsteady problem of the impact of a liquid parabola onto a rigid flat plate at a
constant velocity. The liquid is assumed ideal and incompressible and its flow potential. The initial stage of the impact
is the main concern in this study. The non-dimensional half-width of the contact region between the impacting liquid and the
plate plays the role of a small parameter in this problem. The flow region is subdivided into four parts: (i) the main flow
region, the dimension of which is of the order of the contact-region width, (ii) the jet-root region, where the curvature
of the free surface is very high and the flow is strongly nonlinear, (iii) the jet region, where the flow is approximately
one-dimensional, (iv) the far-field region, where the flow is approximately uniform at the initial stage of impact. A second-order
solution in the main flow region has been derived and matched to the first-order inner solution in the jet-root region. The
matching conditions provide an estimate of the dimension of the contact region for small time. Pressure distributions in both
the main flow region and the inner region are derived. The accuracy of the obtained asymptotic formulae is estimated. The
second-order hydrodynamic force acting on the plate is obtained and compared with available experimental data. A fairly good
agreement is reported. 相似文献
97.
98.
为了研究飞机起落架受冲击载荷时的功量吸收状况,须在起落架落震试验中,对飞机着陆瞬间起落架机轮在空间三个方向上冲击位移的动态变化量进行测量。为此,本文设计了四自由度空间定位装置,并使其与计算机连接,实现了落震试验过程中,起落架在高速冲击状态下机轮三向位移的有效测量与记录。 相似文献
99.
Legal liabilities pertaining to the identification and selection of domain experts is an issue that could adversely impact expert systems developers. Problems pertaining to flawed knowledge, improperly defined expertise, and behavioural and psychological impediments are just some of the issues. This paper examines the torts of strict products liability and negligence that system developers could incur as a result of expert-related difficulties. Parallels from legal scholars and federal and state court decisions are discussed relevant to expert system projects and developers. The paper concludes with a presentation of steps that systems developers can take to minimize potential legal liability. 相似文献
100.
共混合金力学性能的研究 Ⅲ.CPP对PVC共混体系力学性能的影响 总被引:1,自引:0,他引:1
将PP氯化后作为PVC共混体系的刚性体分散相,旨在改善高分子合金的相容性,DSC实验表明,CPP(氯化聚丙烯)与PVC的相容性比PVC与PP的好。在用弹性体增韧的PVC/CPE和PVC/ABS共混体系中加入刚性体CPP后,随着CPE、ABS用量的增加,共混合金的冲击强度增加,并且由刚性的CPP的加入所产生的冲击强度最大值的幅度也有所提高,其趋势是CPE、ABS用量越多,共混合金冲击强度值达到最大值时所需CPP的量越多,增加的幅度也越大。CPP对共混合金的拉伸屈服强度和断裂伸长率的影响比较小。 相似文献