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101.
为了得到试件的粘聚力和内摩擦角随轴向塑性压应变变化的曲线提出本方法。试件的弹塑性本构关系遵循相关联的Mohr-Coulomb强度准则;对常规三轴试验,试件受力进入塑性状态后,处在棱椎状屈服面的棱上,加载过程遵循Koiter流动法则。按经典塑性力学理论,推导得到轴向塑性压应变与轴向应力与轴向应变的关系;在常规三轴试验机上获得不同围压下试件的全程应力-应变曲线,进而可得到各自围压下轴向塑性压应变随加载过程的变化曲线;把来自不同围压下对应同一轴向塑性压应变的应力分别代入屈服面方程,即可求得对应的粘聚力和内摩擦角。结果表明,Mohr-Coulomb材料的两个强度参数的变化由轴向塑性压应变确定。轴向塑性压应变可以作为塑性变形的状态参数,它和试件的受力过程可以唯一确定试件的变形过程。 相似文献
102.
Ordinal optimization (OO) has enjoyed a great degree of success in addressing stochastic optimization problems characterized by an independent and identically distributed (i.i.d.) noise. The methodology offers a statistically quantifiable avenue to find good enough solutions by means of soft computation. In this paper, we extend the OO methodology to a more general class of stochastic problems by relaxing the i.i.d. assumption on the underlying noise. Theoretical results and their applications to simple examples are presented. 相似文献
103.
《Current Applied Physics》2015,15(11):1397-1401
Capacitive deionization (CDI) is the next generation of water desalination and softening technology by using relatively low capacitive current of electrochemical double layer. Among various carbon-based materials used for making electrode, reduced graphene oxide (rGO) has been intensively studied due to its excellent electrical conductivity and high surface area. Although Hummer method for making graphene oxide (GO) and rGO is a simple process, it remains some impurities in inherent GO and rGO which affect negatively to the CDI performance. In this work, we successfully prepared ultra purified GO and rGO by modifying Hummer method in order to remove entirely excess elements degrading the CDI performance. The electrosorption capacity of ultra purified rGO is considerably better than that of previous rGO, and maximum removal achieves 3.54 mg g−1 at applied voltage of 2.0 V. Thus, this result could be comparable to other researches in CDI process. 相似文献
104.
Thermoplastic elastomers (TPEs) based on high-impact polystyrene (HIPS)/waste styrene–butadiene rubber powder (WSBRP) blends were prepared by melt-compounding; they were enhanced by incorporation of styrene–butadiene–styrene block copolymer (SBS) and aromatic oil (AO). The effects of SBS and AO dosage on the mechanical properties, Mullins effect and morphological properties of the blends were investigated. Experimental results showed that the incorporation of SBS and AO in the HIPS/WSBRP blends could improve the mechanical properties significantly. Compared with that of HIPS/WSBRP blends, the elongation at break had a maximum value with 9 phr SBS and 15 phr AO loading, being improved by about 220%. The Mullins effect results showed that a softening effect appeared obviously after the first loading–unloading cycle, while the residual deformation and internal friction loss of the HIPS/SBS/AO/WSBRP TPEs were much lower than those of the HIPS/WSBRP blends, indicating the improvement of elasticity. 相似文献
105.
The calcium carbonate crystallization from aqueous solutions in the presence of alkali additives such as sodium hydroxide and ammonium hydroxide has been researched. It is found CaCO3 crystallizes predominantly in the modification of aragonite in the presence of ammonium hydroxide. The calcium carbonate formation rate in an alkaline medium and the gaseous reaction products due to sorption of gas bubbles on crystal surfaces, affect the aragonite structure formation. It is shown use of ammonium hydroxide for water treatment can solve two urgent tasks such as water softening and exclusion sediment of deposits on the equipment surfaces by a calcium carbonate crystallization in the form of aragonite. 相似文献
106.
Q. H. Zhang Z. Zhai Z. H. Nie S. Harjo D. Y. Cong M. G. Wang J. Li Y. D. Wang 《Journal of Applied Crystallography》2015,48(4):1183-1191
Superelastic behavior is traditionally related to the martensitic transition with a collective transformation scenario in some shape memory alloys. A kind of quasi‐linear superelasticity accompanied by a finite avalanche or confined martensitic transformation was recently found in some alloy systems with strain glass state. Here, an in situ neutron diffraction technique was used to study the deformation behavior in an Ni43Fe18Ga27Co12 alloy with strain glass state in order to reveal the new intrinsic physical nature of the quasi‐linear superelasticity. A significant modulus softening prior to the stress‐induced martensitic transformation was observed during compression in the studied alloy, which is similar to the characteristics exhibited in the tweed precursor phenomena prior to temperature‐induced martensitic transformation. Moreover, the diffraction peak broadening was further shown during the elastic stage of deformation for both single‐crystal and polycrystalline samples, which mainly stems from the short‐range fluctuation in the strain field inside each grain based on Williamson–Hall analysis. The authors believe that there exists a spatial heterogeneity in the modulus of the confined martensitic transformation alloy. 相似文献
107.
Lei Yan David A. Dillard Robert L. West Loren D. Lower Glenn V. Gordon 《Journal of Polymer Science.Polymer Physics》2010,48(21):2207-2214
Particle‐filled elastomers often exhibit a reduction in peak stress after the initial extension under cyclic straining, a phenomenon known as the Mullins effect. In reported literature, long rest periods and elevated temperatures are often necessary conditions to even partially restore stiffness. The stress softening of the polymer nanoparticle composite discussed in this article appeared to be completely reversible in a comparatively short time span (less than 17 h) at room temperature. Although this material acted elastomeric at slow strain rates, significant stiffening, and a pronounced yielding behavior was observed during the first strain cycle at higher strain rates. Subsequent cycling of the material revealed much softer behavior and an absence of the yielding phenomenon, although relatively short rest periods allowed the material to regain its original behavior. The Mullins effect recovery phenomenon was investigated by introducing rest periods of various durations following loading and unloading cycles. Both single and multiple loadings were used in the tests conducted to evaluate recovery. A mechanism of stress recovery was proposed based on the reduction of entanglements and weakening particle‐matrix interactions. New entanglements and particle‐chain interactions were considered major contributors to the recovery of the stiffness. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010 相似文献
108.
Molecular dynamics simulations were performed to study void evolution subject to unidirectional self-bombardment and radiation-induced variation of mechanical properties in single crystalline vanadium. 3D simulation cells of perfect body-centered cubic (BCC) vanadium, as well as those with one, two, four, and six voids, were investigated. For the no void case, the maximum number of defects, maximum volumetric swelling, and the number of defects left in bulk after a sufficiently long recovery period increased with higher primary recoil energy. For the cases containing voids, a primary recoil energy was carefully assigned to an atom so as to initiate a dense collision spike in the voids center, where some self-interstitial atoms gained kinetic energy by secondary replacement collision sequence traveling along the ? 111? direction. It is found that the larger or the greater the number of voids contained initially in the box, the larger the normalized void volume, and the smaller the volumetric swelling after sufficient recovery of systems. In the single void case, the void became elongated along the bombarding direction; in the multiple void cases, the voids coalesced only when the intervoid ligament distance was short. After sufficient relaxation of the irradiated specimen, a hydrostatic tension was exerted on the box, where the voids were treated as dislocation sources. It is shown that with higher primary recoil energy, the yield stress dropped in cases with smaller or fewer voids but rose in those with larger or greater number of voids. This radiation-induced softening to hardening transition with increasing dislocation density can be attributed to the combined effects of the defect-induced dislocation nucleation and the resistance of defects to dislocation motion. Moreover, as the primary recoil energy increased, the ductility of vanadium in the no void case decreased, but was only slightly changed in the cases containing void. 相似文献
109.
在二维正方Heisenberg铁磁系统的基础上建立了磁振子-声子相互作用模型.利用Matsubara格林函数理论研究了系统的横向声频支声子激发,计算了布里渊区的主要对称点线上的横向声频支声子色散曲线,发现在第一布里渊区的Σ线上,小波矢区(Γ附近kxa＜0.2)横向声频支声子有硬化现象,但是在软化区(0.25＜kxa＜0.7)有横向声频支声子有软化现象,在M附近(0.75＜kxa)横向声频支声子有硬化现象.在Δ线上没有发生横向声频支声子有软化与硬化现象.在Z线上小波失区(X附近kxa＜0.65)横向声频支声子有软化现象,但是在M附近横向声频支声子有硬化现象.并且又讨论了各项参数对横向声频支声子激发的影响,发现磁振子-声子耦合与自旋波劲度常数对横向声频支声子软化起很大的作用.关键词：磁振子-声子相互作用横向声频支声子软化Matsubara格林函数理论铁磁系统 相似文献
110.
提出一个J2流的有限弹塑性本构方程来显式、全面地模拟了形状记忆合金（SMAs）在3个不同阶段加载并卸载所表现出来的应力-对数应变关系.这3个阶段包括变形完全恢复的伪弹性阶段、变形部分恢复的塑性阶段以及软化破坏阶段.该文的主要思想在于从实验数据的形函数出发,得到用形函数表达的多轴硬化函数,进而代入到本构方程,建立一个能模拟任意形状应力-对数应变关系,多轴有效的本构方程.该文方法的优势在于避免考虑微观到宏观的平均方法、相变条件等一系列复杂处理,大大减少了计算量.所得到的数值结果可以精确匹配实验数据. 相似文献