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71.
In this paper, one-dimensional compression behavior of uniformly graded fine sand is studied with the use of oedometer test
at elevated stress levels. To reach the elevated stress levels, testing is performed in a strain controlled manner. In addition,
standard stress controlled testing method is also used at lower stress levels for the purpose of comparison. Specimens prepared
with initial relative densities ranging from loose to dense are subjected to normal loading as well as hysteretic and repeated
loading patterns. Results showed that there is a linear relationship between compressibility index and relative density. The
magnitude of compression is mainly influenced by inundation where the compressibility behavior is found to be depending on
the initial formation density. Regardless of the initial formation density, convergence to a similar compression index is
observed with the hysteretically loaded samples whereas a continuous modification was obtained with repetitively loaded reformed
specimens. 相似文献
72.
钻井井架力学性能分析 总被引:7,自引:7,他引:0
钻井井架作为钻机系统设备中的关键部分,其力学性能直接关系到整套钻机系统的安全生产。文章推导了常用于分析钻井井架力学性能的理论,即线性屈曲、几何非线性和双重非线性理论。提出同时用这三种理论对钻井井架进行综合比较分析,从而合理地预见井架力学性能的方法。以A形钻井井架为例,进行了详细的分析,得到了井架的失稳形式、极限承载、破坏特征及薄弱部位,为钻井井架的设计、优化与评定提供了参考。 相似文献
73.
LOW-CYCLE FATIGUE UNDER NON-PROPORTIONAL LOADING 总被引:4,自引:0,他引:4
X. Chen Q. Gao X.-F. Sun 《Fatigue & Fracture of Engineering Materials & Structures》1996,19(7):839-854
A series of strain-controlled, low-cycle fatigue experiments have been conducted on 42CrMo steel under various loading paths including circular, square, cruciform, and rectangular paths. Present experiments have shown that there is additional hardening under non-proportional cyclic loading. Non-proportional cyclic additional hardening also results in a shorter life for multiaxial low cycle fatigue. A non-proportionality measure of strain path based on both a physical basis and macromechanical phenomena is proposed. The loading path effect on additional hardening is also described well. Low-cycle fatigue damage accumulation and the evolution process under non-proportional loading is analysed via the Continuum Damage Mechanics Model of Chaboche. A non-proportinality measure is introduced in the damage evolution equation and a modified Coffin-Manson type formula is derived. A novel fatigue life prediction approach based on the critical-plane concept of Brown and Miller is proposed. 相似文献
74.
75.
碳化硅加热元件的电性能和使用 总被引:2,自引:0,他引:2
本文介绍碳化硅加热元件的电特性、表面负荷以及工作气氛对它的影响,并对它设计和使用要点举例予以说明。 相似文献
76.
在复兴大桥超高吨位灌注桩的静载试验,预应力混凝土反力装置替代了传统的钢梁反力系统。这套装置主要包括预应力锚桩、预应力承台与预应力反力梁。试验结果表明,直接获得超高吨位大直径嵌岩桩的极限承载力相当不易,而对这类问题预应力混凝土反力装置是值得考虑的。 相似文献
77.
78.
新型梳形电缆防火墙的应用 总被引:2,自引:0,他引:2
通过新型梳形电缆防火墙的实施,有效地限制了电缆火灾范围,增强了电缆防火、隔火能力,并详细地介绍了梳形电缆防火墙的原理结构、安装使用和注意事项。 相似文献
79.
The convective batch drying of Western Hemlock hog fuel-sized particles in fixed beds under various operating conditions quantiatively established the effect of factors which govern the drying process. A correlation was obtained for the Nusselt number during the heat transfer controlled period. Under specific conditions, the existence of a unified characteristic drying rate curve was confirmed. Drying behaviour as described by the receding plane model provided a mathematical expression for such a curve. The existence of an inversion point temperature was experimentally confirmed. 相似文献
80.
Thomachan.A. Kattakayam Sumanta Khan Kandadai Srinivasan 《Solar Energy Materials & Solar Cells》1996,44(1):25
This article describes the development of an instrumentation system for characterizing photovoltaic panels. It uses an add on card (which contains DAC, ADC and digital input/output ports) in conjunction with a PC-AT. The panels in a field are selected in succession through a set of relays actuated by the digital output port. The selected panel is loaded in discreet steps by a transistor loading circuit which is activated by the digital to analog convertor to trace the most significant portion of the I-V curve. The data shows that the power output is invariably lower than that specified by the manufacturer. The reasons for drop in output have been analyzed. It is shown that these effects can be represented by the curvature of I-V characteristic at the maximum power point (OP). The loss of power due to accumulation of dust and the increase in temperature of the panels can be significant. 相似文献