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1.
The object of this note is the formulation of a simple elastoplastic model for the behavior of smooth sand-steel interfaces. The model is derived from a series of constant normal stiffness direct shear tests between a siliceous sand and a smooth steel plate. These tests highlight the importance of the shear stress degradation on the final value of the shear resistance and can be seen as the elementary mechanism that models in the laboratory the pile shaft-soil interaction. The goal of the presented model is to represent the observed behavior in a very simple way by using a reduced number of constitutive parameters. 相似文献
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Constitutive Behavior of Geosynthetic Interfaces 总被引:1,自引:0,他引:1
Jacob J. B. Esterhuizen George M. Filz J. Michael Duncan 《Canadian Metallurgical Quarterly》2001,127(10):834-840
New displacement-softening and work-softening models were developed to describe the sliding of geosynthetic interfaces, such as those in landfill liners. The displacement-softening formulation is based on the assumption that strength reduction at the interface can be related to nonrecoverable (plastic) shear displacement. The model uses three relationships: (1) the peak strength envelope; (2) the residual strength envelope; and (3) the residual factor versus displacement ratio relationship, which is a nondimensional expression of the rate at which displacement-softening occurs. The displacement-softening model is accurate for shearing when the normal stress stays constant. When normal stress increases during shearing, the displacement-softening formulation overpredicts damage to geosynthetic interfaces. The work-softening model was developed to compute interface softening during conditions of increasing normal stress. This formulation is based on the assumption that the postpeak reduction in shear strength can be attributed to plastic shear work rather than plastic shear displacement. By calculating an equivalent plastic shear displacement for a given amount of plastic shear work, the work-softening model can be formulated using the same basic relationships as the displacement-softening model. The work-softening model significantly outperformed the displacement-softening model when simulating laboratory tests under conditions of increasing normal stress. 相似文献
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Srinivasan Swaminathan Keiichiro Oh-Ishi Alexander P. Zhilyaev Christian B. Fuller Blair London Murray W. Mahoney Terry R. McNelley 《Metallurgical and Materials Transactions A》2010,41(3):631-640
The stir zone (SZ) temperature cycle was measured during the friction stir processing (FSP) of NiAl bronze plates. The FSP
was conducted using a tool design with a smooth concave shoulder and a 12.7-mm step-spiral pin. Temperature sensing was accomplished
using sheathed thermocouples embedded in the tool path within the plates, while simultaneous optical pyrometry measurements
of surface temperatures were also obtained. Peak SZ temperatures were 990 °C to 1015 °C (0.90 to 0.97 T
Melt) and were not affected by preheating to 400 °C, although the dwell time above 900 °C was increased by the preheating. Thermocouple
data suggested little variation in peak temperature across the SZ, although thermocouples initially located on the advancing
sides and at the centerlines of the tool traverses were displaced to the retreating sides, precluding direct assessment of
the temperature variation across the SZ. Microstructure-based estimates of local peak SZ temperatures have been made on these
and on other similarly processed materials. Altogether, the peak-temperature determinations from these different measurement
techniques are in close agreement. 相似文献
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Conventional construction materials used in foundations can encounter serious durability problems in contaminated subsurface or marine environments. Fiber-reinforced polymer (FRP) composites are potentially suitable for these harsh environments due to their chemical and corrosion resistant properties. Quantification of the interface behavior between FRP composites and soils is a necessary precursor to the adoption of these new materials in geotechnical engineering practice. This paper describes the results of an experimental study that was conducted to investigate the behavior of sand-FRP interfaces. Tests showed that the interface shear behavior between FRP composites and granular materials depended on the relative roughness (surface roughness∕particle mean size), the normal stress level, the initial density of the soil mass, and the angularity of the particles. The soil specimen preparation method, the rate of shearing, and the thickness of the soil specimen had little influence on the measured interface friction coefficients. The characteristics of FRP-sand and steel-sand interfaces were compared. 相似文献
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Behavior of Dilative Sand Interfaces in a Geotribology Framework 总被引:2,自引:0,他引:2
Frictional resistance along the exterior of an embedded structure or structural element develops through relative displacement at the interface. An understanding of how surface topography influences interface strength and deformation behavior is required to develop comprehensive interface models for soil-structure analyses, to develop interface design methods and for producing enhanced construction materials. This paper presents the results of an investigation to quantify the influence of surface topography on shear stress and volume change behavior of dilative granular material interface systems. The root spacing, asperity spacing, asperity height, and asperity angle of machined, idealized surfaces are systematically varied. Direct interface shear test results using Ottawa 20/30 sand and glass microbeads show that maximum interface efficiency for these materials is achieved for a asperity spacing to median grain diameter ratio between 1.0 and 3.0, and an asperity height to median grain diameter ratio greater than 0.9. An asperity angle of 50 degrees or greater yields maximum efficiency for any given asperity spacing or height. The results suggest that interface behavior is governed by predictable geometric and mechanical relationships that are applicable to more complex manufactured surfaces. 相似文献
7.
在MPX-2000型摩擦磨损试验机上考察了不同载荷下氟金云母玻璃陶瓷与碳钢对摩时的摩擦磨损性能,用金相显微镜观察和分析磨损表面形貌,测试了摩擦系数和玻璃陶瓷的磨损率,并探讨了材料的磨损机理。结果表明,随着载荷的增加,摩擦副的摩擦系数明显增大,有较大波动。 相似文献
8.
Evaluation of Flow Resistance in Smooth Rectangular Open Channels with Modified Prandtl Friction Law
Nian-Sheng Cheng Hoai Thanh Nguyen Kuifeng Zhao Xiaonan Tang 《Canadian Metallurgical Quarterly》2011,137(4):441-450
Flow resistance in open channels is usually estimated by applying the approach that is developed originally for pipe flows. Such estimates may be useful for engineering applications but always differ from measurements to some extent. This paper first summarizes empirical approaches that have been proposed in the literature to reconcile the resistance difference. These include various modifications of the pipe friction for applications to rectangular ducts and open channel flows. An improved friction equation is then derived for evaluating flow resistance of smooth rectangular open channels. Comparisons are made with experimental data reported by previous researchers and those collected in the present study. It is shown that the new proposed equation is applicable for both narrow and wide channels and is more accurate than those available in the literature. 相似文献
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Yo Tomota Shin Daikuhara Shun Nagayama Masanori Sugawara Norihiko Ozawa Yoshitaka Adachi Stefanus Harjo Shigeo Hattori 《Metallurgical and Materials Transactions A》2014,45(13):6103-6117
Three-dimensional microstructure observations, macro- to micro-scopic residual stress measurements by three methods and creviced bent beam SCC tests were performed for Inconel/low alloy steel (LAS) weld samples. The possible reasons for the suppression of SCC crack propagation near the weld interface found at a nuclear power plant were estimated to include the crack branching at the grain boundary (GB) parallel to the interface, i.e., Type II GB, compressive residual stresses in the LAS region and crack tip oxidation in the LAS at the interface. The formation mechanism of Type II GB and stress gradient in individual grains in the Inconel are also discussed. 相似文献
11.
研究了不同试验条件下对两种毛化钢板冲压摩擦行为的影响,结果表明,润滑条件将影响冲压过程中的摩擦行为,润滑油种类对凹模圆角处摩擦因数影响不大,而对冲头圆角处摩擦因数的影响较大;一般随冲程的增加,钢板的凹模、冲头圆角处摩擦因数都降低,而且凹模处的摩擦因数低于冲头圆角处的摩擦因数;在同一润滑条件下,激光板的表面具有较低的摩擦因数。 相似文献
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J. Yang D. R. Ni D. Wang B. L. Xiao Z. Y. Ma 《Metallurgical and Materials Transactions A》2014,45(4):2101-2115
Strain-controlled low-cycle fatigue (LCF) behavior of friction stir-welded (FSW) AZ31 joints, produced at rotation rates of 800 and 3500 rpm, was studied. The joints exhibited symmetric hysteresis loops, whereas asymmetric loops were observed for the parent material (PM). The fatigue resistance of the FSW joints was slightly improved as the rotation rate increased, and both the FSW joints possessed a fatigue life similar to that of the PM at the low strain amplitude of 0.1 pct. The obtained fatigue data for the PM and FSW joints can be well described using the Coffin–Manson and Basquin’s relationships. For the FSW joints, during LCF deformation, the $ \left\{ {10\bar{1}2} \right\} $ twinning originated from the nugget zone (NZ)/thermomechanically affected zone (TMAZ) boundary and then propagated to the NZ interior. This was attributed to different textures in these regions: the center of the NZ exhibited a hard orientation, whereas a soft orientation was observed in the region around the NZ/TMAZ boundary. The fatigue cracks initiated at the bottom of the joints and propagated along the NZ/TMAZ boundary or the NZ adjacent to the NZ/TMAZ boundary. 相似文献
14.
Chen Xiaowen Liao Dandan Zhang Defen Jiang Xuan Zhao Pengfei Xu Ruosi 《Transactions of the Indian Institute of Metals》2020,73(1):73-80
Transactions of the Indian Institute of Metals - To improve wear resistance of the titanium alloy micro-arc oxidation (MAO) coatings, this work explores the influence mechanism of graphene on the... 相似文献
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Jian-Guo Dai Hiroshi Yokota Mitsuyasu Iwanami Ema Kato 《Canadian Metallurgical Quarterly》2010,14(6):834-844
The effects of moisture on the initial and long-term bonding behavior of fiber reinforced polymer (FRP) sheets to concrete interfaces have been investigated by means of a two-year experimental exposure program. The research is focused on the effects of (1) moisture at the time of FRP installation, in this paper termed “construction moisture,” consisting of concrete substratum surface moisture and external air moisture; and (2) moisture, in this paper termed “service moisture,” which normally varies throughout the service life of concrete. Concrete beams with FRP bonded to their soffits were prepared. Before bonding, concrete substrates were preconditioned with different moisture contents and treated with different primers. The FRP bonded concrete beams were then cured under different humidity conditions before being subjected to combined wet/dry (WD) and thermal cycling regimes to accelerate the exposure effects. Adhesives with different elastic moduli were used to investigate the long-term durability of each adhesive when subjected to accelerated WD cycling. Pull-off tests and bending tests were conducted at the beginning of the cycling and then again after 8 months, 14 months, and 2 years of exposure so as to evaluate the tensile and shear performance of the FRP-to-concrete interfaces. It was found that the effect of the concrete substrate moisture content on short-term interfacial bond performance could be eliminated if an appropriate primer was used. All FRP-to-concrete bonded joints failed at the interface between the primer and concrete after exposure while those not exposed usually failed within the concrete substrate. After exposure to an environment of accelerated WD cycles, it was also found that the interfacial tensile bond strength degraded asymptotically with the exposure time while the flexural capacity of the FRP sheet bonded plain concrete beams even increased. The mechanism behind the above, which is an apparently contradictory phenomenon, is discussed. 相似文献
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DENGChen-hong CHENGuang-zhi GEQi-lu 《钢铁研究学报(英文版)》2005,12(4):50-53,59
Copper alloyed powder composites containing nanoparticles were developed by hot pressing. Effects of nanoscale activated sintering aid and fine ceramic particles Al2O3 on hardness, working quality, and behaviors of friction and wear of the composites have been studied, compared with the composites including mieroscale activated sintering aid and microscale ceramic particles. The microstructures of the samples were analyzed by SEM. The resuits show that the materials with nanoscale sintering aid and fine ceramic particles have better mechanical properties and abrasive resistance than the materials with microscale activated sintering aid and microceramic particles. Moreover, element mutual transfer occurs between samples (strip) and abrasive wheel (ring). 相似文献
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《钢铁研究学报(英文版)》2016,(10):1119-1126
Effects of friction stir processing (FSP)parameters and reinforcements on the wear behavior of 6061-T6 based hybrid composites were investigated.A mathematical formulation was derived to calculate the wear volume loss of the composites.The experimental results were contrasted with the results of the proposed model.The influ-ences of sliding distance,tool traverse and rotational speeds,as well as graphite (Gr)and titanium carbide (TiC) volume fractions on the wear volume loss of the composites were also investigated using the prepared formulation. The results demonstrated that the wear volume loss of the composites significantly increased with increasing sliding distance,tool traverse speed,and rotational speed;while the wear volume loss decreased with increasing volume fraction of the reinforcements.A minimum wear volume loss for the hybrid composites with complex reinforcements was specified at the inclusion ratio of 50% TiC+50% Al2 O3 because of improved lubricant ability,as well as resist-ance to brittleness and wear.New possibilities to develop wear-resistant aluminum-based composites for different in-dustrial applications were proposed. 相似文献