木材断裂解离分形特征与分形断裂力学模型研究

目的以椴木为研究对象,研究冲击载荷作用下椴木试件的断裂解离形貌特征和断裂力学特性,建立适用于木材原料断裂解离的分形断裂力学模型,并对其断裂解离力学行为进行描述。方法对椴木试件进行冲击加载试验,分析试件断口的形貌特征和断裂力学特性,构建适用于木材原料断裂解离的分形断裂力学模型。结果椴木试件横向冲击断裂断口裂纹形状和断口形貌特征比纵向冲击复杂,横、纵向冲击断裂断口均具有分形特征;椴木试件纵向冲击断裂韧性均值是横向冲击断裂韧性均值的1.112倍,椴木试件横、纵向冲击断口的分形维数均值分别为2.0635和2.0751,椴木试件横、纵向冲击韧性与其断口分形维数之间存在线性正相关关系,拟合优度分别为0.7787和0.8122;构建的木材原料断裂解离临界解离应力和断裂韧性的分形断裂力学模型也适用于脆性材料。结论在木材原料冲击断裂解离时,木材原料初始裂纹长度越短,断裂解离断口越粗糙复杂,木材原料断裂解离所需要的能量越大;当裂纹沿着与冲击加载力方向垂直成大约1.055 rad方向扩展时所需的能量最小,木材原料最易沿该方向进行断裂解离。

Cu－Ni－Al单晶的分形断裂与相变增韧

测定了Ｃｕ－Ｎｉ－Ａｌ单晶在２０—１２０℃温度范围的断裂韧性ＫＣ和断裂表面的分形维数Ｄｆ．裂纹前沿应力诱导相变使母相有较高的ＫＣ．在单一断裂机制下，ｌｎＫＣ与Ｄｆ之间有简单的线性关系：脆性断裂时斜率为正，韧性断裂时斜率为负．由断裂微观机制与分形概念对上述结果进行分析讨论．

惠民凹陷临南洼陷T_6反射层断裂分形特征与有利储层预测

断裂活动对于油气的运移与聚集至关重要,然而伴随断裂活动形成的大量裂缝对于储集空间的改善,及由此而形成的有利储层的预测却没有引起足够的重视.基于分形几何学的基本理论与方法,对惠民凹陷临南洼陷T6反射层（沙三段中亚段）断裂分形特征进行了定量分析,结合已知油气藏的分布及沉积相特征,探讨了断裂分维值的特征及其与油气储集空间分布之间的联系,并对由于断裂活动形成的有利储层的分布进行了预测.结果表明,研究区断裂构造在0.187 5-1.5 区间内具有良好的自相似性,相关系数大多大于0.970;且分维值越大,断裂发育的复杂程度越高.断裂分维值的变化特征与断裂的发育规律具有相关性,研究区中部洼陷的有利储层主要分布于分维值为1.1-1.4的等值线闭合圈内,南、北两侧有利储层分布于分维值大于1.2的等值线闭合圈内;断裂分维值为0.8-1.4的断裂构造部位是该区油气聚集的优势区,分维值大于1.4的部位是油气运移的区域;结合沉积相特征,预测夏224井区以西、夏53井区以南、街斜201井区以南等是目前油气勘探的有利区带.

东营凹陷沙三段断裂系统分形特征及构造储集层预测

断裂活动对于油气的运移与聚集至关重要，然而伴随断裂活动形成大量的裂缝，其对于储集空间的改善及断裂对改善油气储层的定量研究却没有引起足够的重视。基于分形几何理论，对东营凹陷沙三段上、中、下3个亚段的断裂体系分布特征进行了系统的定量研究，并对东营凹陷沙三段内可能发育的构造储集层进行了预测。结果表明，在0．5～8km的研究标定尺度范围内，东营凹陷沙三段断裂体系的平面分布具有良好的白相似性（相关系数0．98～1），即具有良好的分形特征；研究区已探明油气藏主要分布在油源断裂附近的砂岩和泥岩之中，其中，砂岩区断裂系统分维值介于0．6～1．3，泥岩区断裂系统分维值介于0．8～1．2。预测了沙三上、中、下3个亚段有利的构造储集层区域。

探讨大理岩损伤和动态断裂分形模型问题

分析了南岭大理岩的损伤特征 ,根据脆性损伤理论 ,得到了南岭大理岩损伤耗散能释放率与损伤变量的关系曲线 ,与实测曲线符合较好 ;

材料断口分形研究现状及发展前景

讨论了分形几何应用于断裂研究的几个基本问题,主要包括断面的分形特征与分形测量,分维与断裂韧性的关系以及金属断裂的多种分形模型。进一步阐述了分形理论在金属断裂方面的应用前景。

断面分形研究中的几个问题

本文讨论了分形几何应用于断裂研究的几个基本问题．主要内容包括断面的分形特征及分维测量，分维与宏观力学性能（如断裂韧性等）的关系，分形断裂模型及分形断裂的物理机理．

金湖凹陷阜二段断裂信息维特征与油气藏分布

金湖凹陷油气运移、聚集、成藏与断裂的展布、发育程度密切相关。为了认识断裂发育区油气分布规律以及断裂对油气富集程度的控制作用，运用分形理论对金湖凹陷断裂体系进行研究．利用研究区已落实的油气藏分布，分析断裂与油气分布关系。结果表明，断裂面积信息维在1．530～1．685之间有利于大油藏形成和保存；断裂信息维在1．655—1．832之间的高值区，断块被进一步分割复杂化，导致油气分布支离破碎，使得油气藏小而碎；有利于油气聚集成藏的分维下限值为1．483。应用信息维法对断裂体系分维计算结果表明，断裂面积信息维高值区与油气藏分布区吻合较好。在此基础上，分析预测了金湖凹陷下一步勘探优选区。

一种计算断裂信息维的方法及其应用

对断裂数据化处理,得到断裂控制点。以断裂控制点为约束,对断裂进行点插值,以单个统计单元为视窗,统计落入不同栅格内的插值点数目,进而求得插值点落入不同栅格的概率,对变量数据拟合,得到断裂信息维以及相关系数。将该思路应用在金湖凹陷阜二段断裂分形评价中,分别计算了断裂长度信息维、面积信息维。结果表明,90%以上的统计单元相关系数>0.9,断裂发育区具有较高的自相似性,断裂总体分形特征曲线的相关系数>0.999。金湖凹陷断裂的计算表明,该思路是测量断裂信息维的有效方法,能够提高工作效率,具有较好的应用前景。

渤海海域新近系明化镇组断裂控藏作用定量评价——以黄河口凹陷中央构造脊为例

渤海海域黄河口凹陷油气成藏条件复杂，系统分析断裂对油气成藏的控制作用有利于更好地指导研究区下步的油气勘探。对黄河口凹陷中央构造脊各级断裂的延伸长度、密度、各地质时期断距、活动速率、盖层断接厚度、分形分维值等参数进行统计对比，认为油气成藏期油源断裂活动速率决定油气的垂向输导能力，当油源断裂活动速率大于15m/Ma时，对油气的运移能力较强；盖层断接厚度影响油气的富集层位，当盖层断接厚度小于60m时，对油气的阻挡作用较小；断裂分形分维值调节浅层油气的运聚效率，当断裂分形分维值大于1.30时，对油气的运聚效率较高。在此基础上建立断裂控藏“速-盖-维”三因素定量评价方法，应用该方法对与黄河口凹陷中央构造脊相邻的渤中29构造区进行断裂控藏作用定量评价，并优选出浅层的6个有利圈闭作为研究区下步的油气勘探目标。

Fractal Analysis of Spatial Fault Distribution in the Southern South China Sea

Fractal geometry can effectively quantify naturally nonlinear or much complicated phenomena, and fractal dimension is the quantitative parameter. In this paper, we applied fractal geometry to analyze spatial fault distribution of the southern South China Sea. Calculation results indicate that the spatial fault distribution of this area have remarkable fractal features in a non-scale interval of 25 - 250 km, with fractal dimensions of 1.660 1, 1.387 5, and 1.269 3 for all faults, NE-trending faults and NW-trending faults, respectively. These dimensions （capacity dimensions）, obtained by box-counting method, represent well the characteristics of spatial fault distribution. Displayed by isoline-maps of fractal dimensions, faults in the study area arrange symmetrically along the spreading axis of the Southwest Sub-basin, and density of the NE-trending faults supplements to that of the NW-trending faults, revealing a property of mutual restriction between these two groups of faults. At last, by correlating the fractal features of spatial fault distribution with the evolution of the South China Sea and the distribution of oil or gas basins, we tried to reveal their relationships.

Fractal analysis of fracture surfaces in aluminum borate whisker-reinforced aluminum alloy 6061 composite

The effect of interface reaction on the fractal dimensions of fracture surface in aluminum borate whisker-reinforced aluminum alloy 6061 composite was investigated. The composite was fabricated by squeeze-casting technique. The fracture surfaces created in tensile test were measured by vertical sectioning method. Fractal phenomena were found in two plots, in which the measuring units were from 3 to 15 μm and 1 to 5 μm, respectively. The relation was established between the tensile properties and fractal dimension with measuring units of 3-15 μm. The results show that the ultimate tensile strength increases while the fracture surface roughness increases with fractal dimension increasing due to the change in fracture mode depending on the degree of interface reaction status induced by heat treatment. But when the measuring units are 1-5 μm, fractal dimension does not change with heat treatment.

Analytic Expression of Meso-Criterion on Dynamic Fracture

This study presents a meso-criterion of dynamic fracture, on the basis of stress in integral form In such way the difficulty due to the singularity of stress distribution at the crack tip is overcome. A micro-parameter, the atom radius, is introduced into the criterion.Meanwhile a characteristic time concept is taken into account for describing the inertia effect of material. The criterion reveals The criterion reveals the effects of loading rate, defect and sample geometry,material constants including the micro-structure parameter.

Molecular dynamics simulation of fracture behaviors of <110> tilt grain boundaries in γ-TiAl

Molecular dynamics(MD) simulations were carried out to study the fracture behaviors of several symmetric tilt grain boundaries in γ-Ti Al bicrystals with <110> misorientation axes. Tensile deformation along direction perpendicular to grain boundary was simulated under various strain rates and temperatures. The results indicate that the relative orientation of the grains and the presence of certain atom units are two critical factors of the interface structure affecting the stress required for dislocation nucleation. Dislocations nucleate and extend at or near the symmetric tilt grain boundaries during the tensile deformation of Σ3(111) 109.5°, Σ9(221) 141.1° and Σ27(552) 148.4° interfaces. For Σ27(115) 31.6° and Σ11(113) 50.5° interfaces, the interfaces fractured directly in a cleavage manner due to no dislocation emitted from the boundary. The tensile fracture mechanisms of the bicrystals are that micro-cracks nucleate at the grain boundary and propagate along the interface. The variance of crack propagation is whether there is accommodation of plastic region at the crack tips.

Simulation of failure process of jointed rock

A modified discontinuous deformation analysis (DDA) algorithm was proposed to simulate the failure behavior of jointed rock. In the proposed algorithm, by using the Monte-Carlo technique, random joint network was generated in the domain of interest. Based on the joint network, the triangular DDA block system was automatically generated by adopting the advanced front method. In the process of generating blocks, numerous artificial joints came into being, and once the stress states at some artificial joints satisfy the failure criterion given beforehand, artificial joints will turn into real joints. In this way, the whole fragmentation process of rock mass can be replicated. The algorithm logic was described in detail, and several numerical examples were carried out to obtain some insight into the failure behavior of rock mass containing random joints. From the numerical results, it can be found that the crack initiates from the crack tip, the growth direction of the crack depends upon the loading and constraint conditions, and the proposed method can reproduce some complicated phenomena in the whole process of rock failure.

Analysis of the blunting line in ductile fracture toughness J_(IC) test method

The blunting line equation is very important in J-integral testing because of its indispensability in the determination of valid data and JIC value. The blunting line equation in current standard has had a larger relative error in depiction of the crack blunting compared to the experimentally measured results. By analyzing the blunting process of the crack tip according to the D-B model, a new form of blunting line was obtained on the base of the path independence of J-integral, i.e., J=1.25(σs+Sf)/(1+n)·WSZ. Experimental results show that this equation is more precise to describe the crack blunting than those in current standards.

五沟煤矿10煤层小断层发育特征及其介质条件控制

五沟煤矿隶属淮北煤田临涣矿区,矿井构造较为复杂,小断层尤其发育且走向多变,以NE向为主,NNE向及NEE向次之,其次还发育有NS、EW以及为数不多的NW、NNW、NWW向小断层。笔者首先运用断裂分形理论,采用网格覆盖法计算了五沟煤矿10煤层的小断层断裂容量维值,绘制断裂容量维等值线,并对小断层发育复杂程度进行评价;其次,以10煤层顶底板岩石物理力学性质测试分析为基础,分析了顶底板岩性分布及岩层组合特征等介质条件对小断层发育的响应特征,并得出以下结论:顶底板为强岩层分布区域断裂构造较为发育,而弱岩层分布区域断裂构造发育较为微弱;泥岩比值小的区域小断层较为发育,比值较大的区域小断层发育较微弱;即强硬岩层占主体的岩层发育区域小断层较为发育,软弱岩层占主体的岩层发育区域小断层发育较少。

Combined fracture dislocation of the navicular bone along with cuboid, cuneiform and longitudinal split fracture of the lateral malleolus： a rare combination of fractures

Fracture dislocation of the navicular bone~ fracture of the cuboid, cuneiform, and longitudinal split fracture of the lateral malleolus is a rare combination of fractures. This is a high velocity injury fracture and can be caused by forcible plantar flexion and inversion of the foot at the time of impact onto the ground. Here we reported such a case in a 35-year-old male patient who was treated by open reduction and fixation with a partially threaded screw and two K-wires for the navicular bone,and two interfragmentary screws with a one third tubular plate for the lateral malleolus. K-wires were removed 6 weeks after surgery followed by partial weight bearing. After 6 months, the patient can walk normally with minimal pain and swelling of the foot.

Failure behavior and criteria of metallic glasses

Metallic glasses(MGs)constitute an emerging class of advanced structural materials due to their excellent mechanical properties.However,brittle failure at room temperature and the resultant complicated fracture behavior greatly limit their wide engineering applications.Over the past decades,the deformation and fracture in ductile or brittle mode referring to material compositions,load conditions,sample size,etc.,have been widely studied,and significant progress has been made in understanding the failure behavior of MGs.Micromechanisms of fracture have been revealed involving shear banding,cavitation and the nature of the crack tip field.The ductile-to-brittle transition and inherent governing parameters have been found.To well describe and predict the failure behavior of MGs,failure criteria for ductile and brittle MGs have been established empirically or based on atomic interactions.In this paper,we provide a detailed review of the above advances and identify outstanding issues in the failure of MGs that need to be further clarified.