Strain rate sensitivity of the commercial aluminum alloy AA5182-O

The mechanical behavior of the commercial aluminum alloy AA5182-O is investigated at temperatures ranging from −120 to 150 °C and strain rates from 10⁻⁶ to 10⁻¹ s⁻¹. The strain rate sensitivity parameter is determined as a function of temperature and plastic strain, and the strain rate and temperature range in which dynamic strain aging leads to negative strain rate sensitivity is mapped. The effect of dynamic strain aging on ductility and strain hardening is investigated. The sensitivity of the measured quantities to the experimental method employed and their dependence on grain shape are discussed. The experimental data are compared with the predictions of a model constructed based on a recently proposed mechanism for dynamic strain ageing. The mechanism is based on the effect solute clustering at forest dislocations has on the strength of dislocation junctions. The model is shown to reproduce qualitatively the experimental trends.     

复杂变形中单一应变因素的测量

以薄壁管受力变形为例，介绍了一种对扭转引起的应变的测量方法。     

钢管混凝土的等效本构关系研究

在总结现有钢管混凝土本构关系分析的基础上,将钢管混凝土简化为同一尺度的横观各向同性体来研究,并在弹性条件下利用应变能相等原理得到了宏观弹性系数,同时根据试验结果假设进入弹塑性阶段后各模量为二次抛物线变化,建立了钢管混凝土这种组合结构新的等效本构关系.并结合具体算例研究了弹性条件下材料强度变化和含钢率对各模量的影响,同时与前人的研究结果进行了比较,结果表明,该本构关系具有理论依据明确,参数易确定,能很好地反映组合构件材料物理性能的优点,为钢管混凝土结构进一步进行数值分析奠定了基础.     

Generalized Deformation Curve for High-Strength Steel over a Wide Range of Strain Rates

Test results for different high-strength steel specimens in static and impact tension and compression over a wide range of strain rates were summarized. These data were used to calculate the generalized deformation curve. The calculations based on this curve were compared with the experimental data on impact indentation with the conical indenter to evaluate the applicability of this method for studying the behavior of metals at high strain rates.     

Effect of Ion Dose on Growth of Relaxed SiGe Layer on Ion Implantation Si Substrate

Thin strain-relaxed Si0.8Ge0.2 films (57.6 nm) on the 30 keV Ar ion implantation Si substrates for different dose (1 × 1014, 5 × 1014, 3 × 1015 cm-2) were grown by ultra high vacuum chemical vapor deposition (UHVCVD) system.Rutherford backscattering/ion channeling (RBS/C), high resolution X-ray diffraction (HRXRD), Raman spectra as well as atomic force microscopy (AFM) were used to characterize these SiGe films. Investigations by RBS/C as well as HRXRD demonstrate that these thin Sio.8Geo.2 films could indeed epitaxially grow on the Ar ion implantation Si substrates. Under low dose ( 1 × 1014 cm-2) and medium dose (5 × 1014 cm-2) implantation conditions, the relaxation extents of SiGe films are 60.6% and 63.6%, respectively. However, high dose implantation (3 × 1015 cm-2) prompt the strain in epitaxial SiGe film to be close to full relaxation status (relaxation extent of 96.6% ). On the other hand, determinations of RBS/C also indicate the crystalline quality of SiGe film grown on high dose implantation Si substrate is nearly identical to that grown on low dose (1 × 1014 cm-2) implantation Si substrate.     

基于ABAQUS软件的微米级金属材料性能研究

为工程实践中迫切需要解决微米和亚微米量级的设计与制造问题,文章中运用MSG塑性理论利用Abaqus软件对铝合金的强度及均匀延伸率进行了比较系统的研究;运用有限单元法分析了MSG应变梯度本构方程和经典的弹塑性本构方程对不同晶粒尺寸的铝合金的应力应变关系;模拟不同晶粒尺寸的铝合金的强度及均匀延伸率。结果表明随着晶粒尺寸的减小,屈服强度、应变硬化明显增加,延伸率却往往越小。对于该问题的研究探索,将是解决材料强度与均匀伸长率这对矛盾体的问题关键,同时,为科研工作者提供了新方法和新途径。     

双屋架卧位对顶现场检测试验的技术与方法

文章以一个大型屋架的力学性能检测实例为工程背景,介绍在实验室空间条件受限制的情况下,改用在现场对大型屋架采取平卧状态下检测的技术与方法     

Critical State of Granular Materials Based on the Sliding-Rolling Theory

By representing the assembly by a simplified column model, a constitutive theory was recently developed for a two-dimensional assembly of rods. This theory, referred to as the sliding-rolling theory, is extended in this paper to represent the triaxial stress-strain behavior of granular materials. The sliding-rolling theory provides a dilatancy rule and an expression for the slope of the line of zero dilatancy in the stress space. These rules are then combined with triaxial observations to provide a microstructural interpretation of the critical state of granular materials. According to the theory, the slope of the critical state line in the stress space depends on the interparticle friction angle and the degree of contact normal anisotropy. To verify the basic ideas of the sliding-rolling theory, numerical experiments are conducted using the discrete-element method on three-dimensional assemblies of spheres.     

Strain hardening of porous iron under uniaxial compression

A series of experiments was carried out with powder iron of 1–40% porosity including deformation by compression to various degree of deformation, and strain hardening curves were calculated. It was established that change in the loading sign relative to uniaxial tension had practically no effect on the strain hardening laws of the solid phase, although it basically changed the porosity contribution to the loading curve formation. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(411), pp. 106–112. January–February, 2000.     

产电微生物对SMFC产电及降解性能的影响

目的在以含油污泥为阳极底泥的沉积型微生物燃料电池(SMFC)体系中,通过改变产电微生物种类和分布方式,探究产电微生物对SMFC产电及降解性能的影响。 方法通过采集输出电压、功率密度、表观内阻来检测石油去除率,比较了不同单菌-SMFC、不同混合菌-SMFC的产电性能和降解性能,考查了菌种分布对SMFC性能的影响。 结果在单菌-SMFC中,弗氏柠檬酸杆菌-SMFC的产电及降解性能均优于其他5种单菌构筑的SMFC;混合菌-SMFC的产电及降解性能较单菌-SMFC有较大提升,且其中蜡样芽孢杆菌+中间苍白杆菌-SMFC的产电及降解性能最优,输出电压可达到515.30 mV;菌种分布在阳极材料中和阳极底泥中都可以降解含油污泥中的有机物,但是菌种分布在阳极材料中更有利于SMFC产电性能及降解性能的发挥。 结论混合菌相对于单菌能够显著提升SMFC的产电及降解性能,而且菌种分布在阳极材料中更有益于SMFC产电性能及降解性能的发挥。 