基于有限体积模拟的模锻优化设计

在锻造等金属大变形的工艺设计中,相关参数的确定很大程度上依赖于经验公式,而有限元法在金属大变形过程数值模拟中有明显的局限性,且模拟结果难以验证。本文基于有限体积法模拟了一典型开式模锻过程,并在通用经验值允许的范围内,根据模拟结果调整工艺设计中的参数设置,有效避免了一种锻件常见缺陷。通过分析变形过程特定时段的变形区形状、分流面的变化及变形力分布曲线,结合相关塑性理论验证了模拟结果的正确性,实现了工艺优化设计。研究证明理论预测与数值模拟相“拟合”的方法可以代替实验用于指导生产实践。     

Constitutive equations and finite element implementation of strain localization in sand deformation

A recently proposed model coupling with the solid-fluid of the saturated sand was utilized to study the deformation band. Based on the critical state plasticity model by Borja and Andrade, the hydraulic conductivity tensor was naturally treated as a function of the spatial discretization matrix about the displacement and the stress field, allowing a more realistic representation of the physical phenomenon. The fully Lagrangian form of the Darcy law was resolved by Piola algorithm, and then the flow law was gained, leading to the implementation of a modified model of the saturated sand. Then the criterion for the onset of localization was derived and utilized to detect instability. The constitutive model was implemented in a finite element program coded by FORTRAN, which was used to predict the formation and development of shear bands in plane strain compression of saturated sand. At last, the formation mechanism of the shear band was discussed. It is shown that the model works well, and the simulation sample bifurcates at 1.18% axial strain, which is in a good qualitative agreement with the experiment. The pore pressure greatly affects the onset and development of the deformation band, and it obviously increases around the localization-prone regions with the direction toward the outer side of the normal of the shear band, while the pore stress flows nearly horizontally and is distributed equally far away the shear band region. Foundation item: Project(2006G007-C) supported by the Foundation of the Science and Technology Section of Ministry of Railway of China; Project(77206) supported by the Excellent PhD Thesis Innovation Foundation of Central South University, China     

Comprehensive assessment on dynamic roof instability under fractured rock mass conditions in the excavation disturbed zone

The damage process of fractured rock mass showed that the fracture in rocks induced roof collapse in Yangchangwan Coal Mine,China.The rock mass was particularly weak and fractured.There occurred 6 large-scale dynamical roof falls in the excavation disturbed zone (EDZ) with the collapsing volume of 216 m3.First,the field detailed geological environment,regional seismic dy-namics,and dynamic instability of roadways were generally investigated.Second,the field multiple-index monitoring measurements for detecting the deep delamination of the roof,convergence deformation,bolt-cable load,acoustic emission (AE) characteristic pa-rameters,total AE events,AE energy-releasing rate,rock mass fracture,and damage were arranged.Finally,according to the time-space-strength relations,a quantitative assessment of the influence of rock-mass damage on the dynamic roof instability was accomplished.     

Chaotic characteristics of electromagnetic emission signals during deformation and fracture of coal

Electromagnetic emission (EME) is a kind of physical phenomenon accompanying the process of deformation and frac-ture of loaded coal and rock and it is of importance in quantitatively analyzing its characteristics. This will reveal the process of deformation and fracture of coal and predicting dynamic disasters in coal mines. In this study, the G-P (Grassberger and Procaccia) algorithm, calculation steps of the (if only 1 dimension) correlation dimension of time series and the identification standards of chaotic signals are introduced. Furthermore, the correlation dimensions of EME and the acoustic emission (AE) signals of time series during deformation and fracture of coal bodies are calculated and analyzed. The results show that the time series of pulses number of EME and the time series of AE count rate are chaotic and that the saturation embedding dimensions of a K3 coal sample are, respectively, 5 and 6. The results can be used to provide basic parameters for predicting of EME and AE time series.     

Deformation characteristics of surrounding rock of broken and soft rock roadway

A similar material model and a numerical simulation were constructed and are described herein. The deformation and failure of surrounding rock of broken and soft roadway are studied by using these models. The deformation of the roof and floor, the relative deformation of the two sides and the deformation of the deep surrounding rock are predicted using the model. Measurements in a working mine are compared to the results of the models. The results show that the surrounding rock shows clear rheological features under high stress conditions. Deformation is unequally distributed across the whole section. The surrounding rock exhibited three deformation stages: displacement caused by stress concentration, rheological displacement after the digging effects had stabilized and displacement caused by supporting pressure of the roadway. Floor heave was serious, accounting for 65% of the total deformation of the roof and floor. Floor heave is the main reason for failure of the surrounding rock. The reasons for deformation of the surrounding rock are discussed based on the similar material and numerical simulations.     

江西金山金矿控矿韧性剪切带的递进变形成矿机理：显微构造证据

在对江西金山金矿控矿韧性剪切带内岩石和矿石的显微构造分析基础上,对剪切带的递进变形与成矿机理进行探讨。研究发现,金山韧性剪切带在韧性—韧脆性递进剪切变形过程中发育3类石英脉透镜体或石香肠构造;剪切压溶和缝合线构造在金山韧性剪切带内强烈发育;扩散蠕变机制是金山韧性剪切带重要的变形机制。大量缝合线构造的形成增强了岩石的孔隙度和渗透率,有利于流体的迁移和沉淀。金山剪切带内变形和成矿作用经历了漫长复杂的地质过程,粗略估算至少跨过了72Ma。在递进剪切变形过程中经历多种构造变形机制,如经历了以透人性片理为代表的韧性剪切变形机制到以“次级剪切面”构造网络为代表的韧-脆性剪切变形机制的转换。剪切带的递进剪切变形自始至终控制着金的成矿作用过程,没有递进剪切变形也就没有金山金矿的形成。     

江西浒坑钨矿含矿韧性剪切带及其^40Ar-^39Ar年代学约束

江西省浒坑钨矿是一个大型石英脉黑钨矿矿床,含矿石英脉除了块状石英脉以外,还大量发育条带状石英脉。本文针对条带状石英脉进行了专门研究,认为条带状石英脉实质上是韧性剪切带,以透入性发育的剪切面理和拉伸线理、剪切透镜体、剪切分异条带普遍发育为特色。剪切带岩石以石英质糜棱岩为主,具有丰富的塑性变形显微构造特征。显微剪切指向构造统计表明,东西向和北西向脉组的运动方式均以左旋正滑为主,近水平脉组则以正滑为主。北西向韧性剪切带的新生绢云母^40Ar-^39Ar坪年龄为140．3±1．0Ma,相应的等时线年龄为139．6±2．4Ma;而东西向韧性剪切带绢云母^40Ar-^39Ar坪年龄则比较复杂,高温阶段年龄可能受到成矿期白云母残斑的影响,中温阶段的表观年龄和总气体年龄更接近前一样品的坪年龄。据此认为韧性剪切变形的年龄为140Ma左右,韧性变形发生在成岩和成矿之后。条带状石英脉系块状石英脉韧性剪切改造而成,推测其形成主要与晚期补充岩体的斜向上侵作用有关,但更为合理的模式需要更多资料的进一步证实。     

地下连续墙施工变形监测与结果分析

以抚州市电力大厦为例,监测其地下连续墙的水平位移和沉降监测。从水平位移监测值来看,北侧的水平位移较大,D8的位移达到预警值,D5临近预警值,为此,在1层开挖位移增加值较大处（深度为4．2m）加大对部分观测点的观测频数,并加强北面的支护体系,增加角支撑,并在长边增加2根对撑。沉降变化曲线表明：地下连续墙墙顶在整个开挖过程中存在一个波浪式的抬升现象。除第V阶段开挖过程因开挖面积及土方量均较小、反应不明显外,伴随着每次挖土过程地下连续墙墙顶均有一次明显的抬升过程,在楼板的制作和养护期间,墙顶先下沉后逐渐趋于稳定,大底板浇筑后墙顶又逐渐下沉。     

直接甲酸燃料电池阳极催化剂的研究进展

介绍了直接甲酸燃料电池（DFAFC）阳极电催化机理,以及Pt基、Pd基附载型和非附载型阳极催化剂的发展状况,分析了金属合金d-带能级移动和金属表面偏析对直接甲酸燃料电池催化活性的影响,对筛选阳极催化剂合金材料具有一定的指导作用.     

凝析气藏注气过程中露点压力变化特征研究

在凝析气藏循环注气和注气吞吐解除近井带反凝析堵塞的注气过程中,凝析气流体的露点压力变化较大,而在目前的凝析气藏开发过程中,对凝析气露点压力变化考虑较少.作者利用Nemeth.L.K和Kennedy.H.T.的露点压力计算经验公式,研究了向凝析气中注入N2、甲烷、CO2和丙烷等介质的过程中露点压力变化规律,并分析了衰竭式开发和注气过程中凝析气井近井带露点压力变化特征.结果表明,注甲烷使露点压力有较小幅度的减小;注入CO2和丙烷均可使凝析气露点压力有较大幅度降低;而注入N2将使露点压力升高.在凝析气藏衰竭式开发过程中,当近井带压力下降至露点压力以下时,距井筒越近,凝析气中重质组分含量越低,露点压力也越低.在注气吞吐的焖井阶段,反蒸发作用会引起凝析气中重质组分增加,露点压力将升高.