不同饱水强度灰岩应变特性及劣化损伤本构模型研究

为研究饱水强度作用下灰岩的物理力学特性,对不同饱水强度的灰岩试样进行单轴压缩试验,分析其典型的应力-应变特征,并基于损伤力学理论建立损伤本构模型。结果表明,饱水强度加剧了灰岩的软化效应,高强度饱水灰岩的压密阶段相对延长,而弹性变形阶段相对缩短;随着饱水强度的增加,灰岩峰值强度呈线性降低,但饱水作用未对灰岩的破坏类型造成较大影响,仍以剪切破坏为主;损伤本构模型曲线和试验曲线高度吻合,说明建立的损伤本构模型是可靠的;随着饱水强度的增加,灰岩脆性和强度弱化,参数m和F₀分别呈二次函数和三次函数降低。     

基于能耗理论的岩石三维蠕变本构模型及临界分段

目前对岩石加速蠕变阶段的启动判定仍是一个难点。为了反映岩石蠕变全过程,基于能量耗散理论,结合蠕变速率特征,以耗散率值作为蠕变三阶段的控制阈值,对蠕变阶段进行临界分段。引入Perzyna黏弹塑性理论,应用到Cvisc元件模型中,建立一种新的加速蠕变启动判定方式的蠕变本构模型,并将其拓展为三维情形。开展砂岩三轴压缩蠕变试验,分析蠕变速率变化特征,研究等时应力-应变关系,提取模型临界分段参数。引用相关文献中泥岩和冻结软岩蠕变试验数据,通过所建模型对3种岩石蠕变试验数据进行辨识,对比试验曲线和预测曲线,验证所建模型描述岩石加速蠕变阶段的优越性,充分显示出所建模型表征蠕变力学行为的合理性和适用性。研究成果为岩石蠕变阶段的划分及力学行为的模拟提供一种新思路。     

Synthesis,structures, and properties of side‐chain cholesteric liquid‐crystalline polysiloxanes

The synthesis of three cholesteric monomers and side‐chain liquid‐crystalline polymers was described. The structure–property relationships of monomers IM–IIIM and polymers IP–IIIP were discussed. Their phase behavior and optical properties were investigated by differential scanning calorimetry, thermogravimetric analyses (TGA), and polarizing optical microscopy. Monomers IM–IIIM exhibited cholesteric oily‐streak texture and focal‐conic texture. Polymers IIP and IIIP revealed smectic A fan‐shaped texture and cholesteric grandjean texture, respectively. Experimental results demonstrated that the selective reflection of IM–IIIM shifted to the short‐wavelength region with increasing the flexible spacer length or decreasing the rigidity of the mesogen. Polymers with a longer flexible spacer had lower glass‐transition temperatures and wider mesomorphic temperature ranges. TGA showed that the temperatures at which 5% weight loss occurred were greater than 300°C for all the polymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3944–3950, 2003     

Swelling behaviors of a three‐component copolymer (starch graft sodium acrylate and 2‐acrylamido‐2‐methyl‐propanosulfonic acid) synthesized by microwave polymerization

A superabsorbent of starch, 2‐acrylamido‐2‐methyl‐propanosulfonic acid (AMPS), and sodium acrylate was synthesized by microwave irradiation, and the effect of AMPS on the performance of the polymer was investigated. The best mass fraction of the three components was determined (starch/acrylic acid/AMPS = 2 : 5 : 3). The structure of the polymer was characterized by Fourier transform infrared, ¹³C cross‐polarization/magic‐angle spinning NMR, and scanning electron microscopy, and the morphology of the surface of the sample was studied. The results showed that the morphology of the polymer was changed to some extent under microwave irradiation, and the swelling rate of the polymer synthesized by microwave polymerization was faster than the swelling rate of a polymer synthesized by a traditional method. The best absorbent capacities of the product in distilled water and a 0.9% sodium chloride solution were 450 and 53 g/g, respectively. Meanwhile, the introduction of AMPS to a superabsorbent resin was an effective method for improving the performance of the polymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1050–1054, 2005     

Synthesis of thermoplastic polyurethane and its physical and shape memory properties

In this article, thermoplastic polyurethane (PU) with a shape memory property was synthesized. First, the PU prepolymer was prepared by reacting poly(tetramethylene glycol) with 4,4′‐diphenylmethane diisocyanate, then extended with various extenders such as linear aliphatic 1,4‐butanediol, benzoyl‐type 4,4‐bis(4‐hydroxyhexoxy)‐isopropylane and naphthalate‐type bis(2‐phenoxyethanol)‐sulfone or naphthoxy diethanol. The experimental results showed that the tensile strength, elongation at break, and initial modulus at 300% of these copolymer films were in the range of 31–64 Mpa, 42%–614%, and 8.26–11.5 MPa, respectively. Thermal analysis showed that the glass‐transition temperature of these copolymers was in the range of ?73°C to ?50°C for the soft segment (T_gs) and 70°C–106°C for the hard segment (T_gh) and that the melting point was in the range of 14.6°C–24.2°C for the soft segment and 198°C–206°C for the hard segment. The extender with a benzoyl or naphthalate group was better able to promote its shape memory property than was the regular polyurethane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 607–615, 2006     

圆钢管轻骨料混凝土轴压短柱的力学性能分析

分析现有钢管轻骨料混凝土轴压短柱力学性能实验结果,提出轻骨料混凝土轴对称三轴受压轴向应力-应变关系,应用连续介质力学,确立圆钢管轻骨料混凝土同心圆柱体共同受压时的计算模型,建立了圆钢管轻骨料混凝土组合弹性模量理论计算公式和组合应力-应变关系的理论表达式,编制相应计算程序.结果表明,核心混凝土由于受钢管约束,其纵向应力有较大提高,延性得到显著改善,钢管在为轻骨料混凝土提供径向约束的同时,其纵向应力大幅降低;钢管对轻骨料混凝土的约束效果要低于对普通混凝土的约束效果.通过大量参数分析,得到钢管轻骨料混凝土轴压短柱极限承载力计算公式和组合应力-应变关系全曲线,计算与实验结果吻合良好.     

Unidirectional hemp and flax EP‐ and PP‐composites: Influence of defined fiber treatments

In some technical areas, mainly in the automotive industry, glass fiber reinforced polymers are intended to be replaced by natural fiber reinforced polymer systems. Therefore, higher requirements will be imposed to the physical fiber properties, fiber‐matrix adhesion, and the quality assurance. To improve the properties of epoxy resins (EP) and polypropylene (PP) composites, flax and hemp fibers were modified by mercerization and MAH‐PP coupling agent was used for preparing the PP composites. The effects of different mercerization parameters such as concentration of alkali (NaOH), temperature, and duration time along with tensile stress applied to the fibers on the structure and properties of hemp fibers were studied and judged via the cellulose I–II lattice conversion. It was observed that the mechanical properties of the fibers can be controlled in a broad range by using appropriate mercerization parameters. Unidirectional EP composites were manufactured by the filament winding technique; at the PP matrix material, a combination with a film‐stacking technique was used. The influence of mercerization parameters on the properties of EP composites was studied with hemp yarn as an example. Different macromechanical effects are shown at hemp‐ and flax‐PP model composites with mercerized, MAH‐PP‐treated, or MAH‐PP‐treated mercerized yarns. The composites' properties were verified by tensile and flexural tests. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2150–2156, 2004     

含中间幂等元的拟富足半群的结构

将Green关系推广到#-Green关系,拓展了含中间幂等元的富足半群,给出了一类具有中间幂等元的拟富足半群的结构.     

砌体本构关系的研究进展

介绍国内外砌体结构本构关系的研究现状和发展趋势,归纳砌体本构关系的各种类型及影响因素．根据实验数据的回归分析,得到混凝土多孔砖砌体受压本构关系的表达式．通过对国内外学者提出的不同本构关系进行比较和分析,给出了各本构关系的实用价值及存在问题,这是砌体结构内力分析、强度计算及有限元分析时必不可少的依据．最后,提出了砌体本构关系研究中存在的一些问题以及需要进一步完善的地方．     

论新时期矿区和谐劳动关系的构建

以大红山矿区为例,提出面对新时期矿区的生产现状和未来发展需要,必须严格执行法律法规,加快矿区生产发展,创新管理模式,保证安全生产,打造矿区和谐文化,探索新型劳动用工形式,才能构建起矿区和谐劳动关系。