引发陶瓷裂纹测量断裂韧度的新方法

以单边切口梁法ＳＥＮＢ测量材料的断裂韧度ＫＩＣ为基础，用静态膨胀的方法ＳＥＳＢ预制瓷等脆材料的原生裂纹，代替一般常用的机械切口，再用三点弯曲法测试其ＫＩＣ值。     

碾压混凝土断裂韧度尺寸效应的试验研究

进行了不同尺寸碾压混凝土三点弯曲试件的断裂试验。对实验结果进行分析,得到了碾压混凝土断裂韧度的尺寸效应规律。将碾压混凝土断裂韧度试验结果与已有的普通混凝土断裂韧度尺寸效应公式结合,通过对几种模型的计算结果的分析比较,得到了碾压混凝土所适用的断裂韧度尺寸效应公式。     

GRAINREDUCTIONANDGROWTHINFAULTING

ＧＲＡＩＮＲＥＤＵＣＴＩＯＮＡＮＤＧＲＯＷＴＨＩＮＦＡＵＬＴＩＮＧＡＮＤＮＥＷＣＬＡＳＳＩＦＩＣＡＴＩＯＮＯＦＦＡＵＬＴＥＤＲＯＣＫＳＤｕａｎＪｉａｒｕｉＫｏｎｇＨｕａ（ＤｅｐａｒｔｍｅｎｔｏｆＧｅｏｌｏｇｙ，ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒｓｉ...     

STUDIES ON MECHANICS PROBLEM OF DYNAMIC WALKING OF ANTHROPOMORPHIC BIPED ROBOTS

ＳＴＵＤＩＥＳＯＮＭＥＣＨＡＮＩＣＳＰＲＯＢＬＥＭＯＦＤＹＮＡＭＩＣＷＡＬＫＩＮＧＯＦＡＮＴＨＲＯＰＯＭＯＲＰＨＩＣＢＩＰＥＤＲＯＢＯＴＳＴａｎＧｕａｎｚｈｅｎｇ；ＹａｎｇＨｏｎｇｚｈｉ（ＲｏｂｏｔｔｅｓＲｅｓｅａｒｃｈＣｅｎｔｒｅ，ＣｅｎｔｒａｌＳ...     

三点弯曲法测定砼断裂能的尺寸效应

对常用的三点弯曲法测定砼断裂能的尺寸效应进行分析，揭示了随试件尺寸增大，测试结果的正误差增大或负误差减小，这可能是三点弯曲法测试砼断裂能尺寸效应的主要原因之一。     

材料韧性断裂特征参数VGC的测试方法研究

介绍了一个新的材料韧性断裂特征参数ＶＧＣ及相应的临界的断裂判据。根据初步拟定的测试方案。对ＷＨ５３０高韧性压力容器钢和７４７５铝合金两种材料的ＶＧＣ进行了测试，测试结果表明，按照这种方法，不同测试者测得的结果存在一定差异。文中分析了造成这种差异的原因，并提出了一种改进方法，即多次加载法，用这种方法测试ＶＧＣ，可提高测试精度，不同测试者测得的结果基本无差异。     

FAULT DIAGNOSIS OF HYDRAULIC PUMPS USING IMPROVED NEURAL NETWORK~

ＦＡＵＬＴＤＩＡＧＮＯＳＩＳＯＦＨＹＤＲＡＵＬＩＣＰＵＭＰＳＵＳＩＮＧＩＭＰＲＯＶＥＤＮＥＵＲＡＬＮＥＴＷＯＲＫ~＋￥ＹａｎｇＨｏｎｇｚｈｉ；ＴａｎＧｕａｎｚｈｅｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＡｕｔｏｍａｔｉｃＣｏｎｔｒｏｌＥｎｇｉｎｅｅｒｉｎｇ，Ｃ?..     

混凝土断裂能的理论分析

针对采用三点弯曲法确定的混凝土断裂能具有明显的尺寸效应的问题,分析了三点弯曲法测量混凝土断裂能误差来源,指出荷载-挠度曲线下降段被截断的尾部曲线对断裂能测量结果影响较大．解释了断裂能测量结果的尺寸效应现象,其根本原因是断裂区以外的附加能耗随试件尺寸增大而递增;推导了断裂能的理论值,其值消除了尺寸效应的影响,可视为材料参数．     

海外需求

编号：Ａ９８１０３００２行业：机械设备国别／地区：ＲＥＰＵＢＬＩＣＯＦＫＯＲＥＡ（韩国）厂商：ＳＥＯＫＹＵＮＧＥＮＧＩＮＥＥＲＩＮＧＣＯＬＴＤ地址：＃４１０２ＴＲＡＤＥＴＯＷＥＲＫＷＴＣ１５９－１ＳＡＭＳＵＮＧＤＯＮＧ电话：００８２２５５１８７７１传...     

RESEARCH OF FILM THICKNESS DURING DRAWING PROCESS LUBRICATED WITH O／W EMULSIONS~＋

ＲＥＳＥＡＲＣＨＯＦＦＩＬＭＴＨＩＣＫＮＥＳＳＤＵＲＩＮＧＤＲＡＷＩＮＧＰＲＯＣＥＳＳＬＵＢＲＩＣＡＴＥＤＷＩＴＨＯ／ＷＥＭＵＬＳＩＯＮＳ~＋￥ＹａｎＨｅｎｇｚｈｉ；ＺｈｏｎｇＪｕｅ（ＤｅｐａｒｔｍｅｎｔｏｆＭｅｃｈａｎｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ?..     

Size effect of fracture characteristics for anisotropic quasi-brittle geomaterials

Understanding the size effect exhibited by the fracture mechanism of anisotropic geomaterials is important for engineering practice. In this study, the anisotropic features of the nominal strength, apparent fracture toughness, effective fracture energy and fracture process zone (FPZ) size of geomaterials were first analyzed by systematic size effect fracture experiments. The results showed that the nominal strength and the apparent fracture toughness decreased with increasing bedding plane inclination angle. The larger the specimen size was, the smaller the nominal strength and the larger the apparent fracture toughness was. When the bedding inclination angle increased from 0° to 90°, the effective fracture energy and the effective FPZ size both first decreased and then increased within two complex variation stages that were bounded by the 45° bedding angle. Regardless of the inherent anisotropy of geomaterials, the nominal strength and apparent fracture toughness can be predicted by the energy-based size effect law, which demonstrates that geomaterials have obvious quasi-brittle characteristics. Theoretical analysis indicated that the true fracture toughness and energy dissipation can be calculated by linear elastic fracture mechanics only when the brittleness number is higher than 10; otherwise, size effect tests should be adopted to determine the fracture parameters.     

Fracture toughness and fatigue crack growth analysis of 7050-T7451 alloy thick plate with different thicknesses

The strength,fracture toughness and fatigue crack growth resistance of 7050-T7451 aluminum alloy plate with different thicknesses(35 mm and 160 mm) were investigated by means of optical microscope,scanning electron microscope and transmission electron microscope.The results show that thicker plate has lower strength and fracture toughness but higher fatigue crack growth resistance,by comparison to the thinner plate.The drop of strength is mainly attributed to grain coarsening in the thicker plate,and the increased degree of recrystallization results in the loss of KIC.However,the coarsened grains in the thicker plate make cracks deflected and closure effect enhanced due to surface roughness increased.For both of plates,in the fracture surface subjected plain strain,a transition from transgranular dimpled fracture to intergranular dimpled fracture is observed during the fracture process.     

3D morphology and formation mechanism of fractures developed by true triaxial stress

As main part of underground rock mass, the three-dimensional (3D) morphology of natural fractures plays an important role in rock mass stability. Based on previous studies on 3D morphology, this study probes into the law and mechanism regarding the influence of the confining pressure constraints on 3D morphological features of natural fractures. First, fracture surfaces were obtained by true triaxial compression test and 3D laser scanning. Then 3D morphological parameters of fractures were calculated by using Grasselli’s model. The results show that the failure mode of granites developed by true triaxial stress can be categorized into tension failure and shear failure. Based on the spatial position of fractures, they can be divided into tension fracture surface, S-1 shear fracture surface, and S-2 shear fracture surface. Micro-failure of the tension fracture surface is dominated by mainly intergranular fracture; the maximum height of asperities on the fracture surface and the 3D roughness of fracture surfaces are influenced by σ₃ only and they are greater than those of shear fracture surfaces, a lower overall uniformity than tension fracture surface. S-1 shear fracture surface and S-2 shear fracture surface are dominated by intragranular and intergranular coupling fracture. The maximum height of asperities on the fracture surface and 3D roughness of fracture surface are affected by σ₁, σ₂, and σ₃. With the increase of σ₂ or σ₃, the cutting off of asperities on the fracture surface becomes more common, the maximum height of asperities and 3D roughness of fracture surface further decrease, and the overall uniformity gets further improved. The experimental results are favorable for selecting technical parameters of enhanced geothermal development and the safety of underground mine engineering.     

重复压裂技术在江汉低渗透油田的应用

初次支撑裂缝和天然裂缝的应力场分布,以及生产活动引起的孔隙压力变化,导致了井眼附近应力的变化,决定了重复压裂裂缝是否能重新定向。重复压裂选井选层至关重要,其中剩余可采储量和地层能量是重复压裂取得增油效果的前提。适合于江汉低渗透油田重复压裂主要工艺措施有:加大施工规模、提高施工砂比,选用比初次压裂强度高、导流能力好的支撑剂等。     

岩石粗糙裂隙大范围雷诺数条件下渗流特性

通过试验和理论分析,研究不同几何参数的岩石粗糙裂隙渗流的非达西系数β、临界雷诺数Re_c、非达西效应因子E等变化特性。研制裂隙渗流试验仪器,制作9个不同开度和裂隙粗糙度(joint roughness coefficient, JRC)的单裂隙模型,开展大范围雷诺数Re条件下粗糙裂隙渗流试验。根据渗流试验结果,得到了不同粗糙度(JRC=2~20)单裂隙的渗流特性,显示出粗糙度对裂隙的非线性渗流特性产生显著的影响。结合Forchheimer方程,从理论参数方面,对粗糙度的影响进行量化。研究显示:裂隙粗糙度越大,则越容易引起裂隙渗流的非线性,临界雷诺数越小,非线性作用越强。     

结构陶瓷断裂韧性测试方法的研究

准确测试陶瓷材料断裂韧性K_(IC)的关键是预制具有原生裂纹的试样。本文首先对桥压法预制原生裂纹进行了研究,然后针对桥压法存在的问题提出了一种简便而有效的陶瓷材料原生裂纹的预制方法——静态膨胀法。研究结果表明:静态膨胀法中裂纹的扩展是稳态的;通过调节影响膨胀剂压力的多种因素,可以准确地控制裂纹扩展的深度,预制出合适的原生裂纹,对几种陶瓷材料试验后得到了满意的结果。为准确评价结构陶瓷的断裂韧性提供了一种有效可行的方法。     

材料破坏理论进展综述

分析了从断裂理论的产生发展到细观损伤理论的衍生这一从宏观到细观不同尺度层面揭示材料破坏本质的进展过程,综述了这一研究领域的发展规律、动态及现存主要问题,预测了其发展和工程应用前景.     

分形和空间灰度共生矩阵联合评价断口形貌研究

为了全面描述断口形貌特征，采用分形和空间灰度共生矩阵结合的方法，对4个典型断口形貌进行定量分析．结果表明：分形维数与断口的粗糙度和复杂度相关；灰度共生矩阵的每一个二阶统计参数都可以精确地描述断口形貌的某一特征，具有较好的纹理表达能力；将灰度共生矩阵的二阶统计参数和分形维数相结合组成多维特征集可以较完整地描述断口图像的纹理特征．分形和空间灰度共生矩阵的联合评价方法，可望实现断口类型的自动分类识别，同时对处理其它纹理图像具有一定的借鉴作用．     

Fracture mechanism of TiAl intermetallics caused by hydride and atomic hydrogen

Hydrogen embrittlement (HE) of TiAl intermetallics was studied at room temperature. The results showed that there were two forms of HE in TiAl intermetallics, i.e. hydride HE and atomic HE. Most of hydrogen in TiAl intermetallics was transformed into hydrides at room temperature. The hydride exists as (TiAl)H_x for a low hydrogen concentration while it exists in several forms for a higher hydrogen concentration. Stress intensity factor K_(IC) decreased with increase in hydride concentration. K_(IC) decreased further when TiAl intermetallics were charged cathodically with hydrogen in 1 mol/L H_2SO_4 solution. Stress intensity factor during hydrogen charging K_(IH) was about 50％ K_(IC). 20％ of the decrease was caused by hydrides while 30％ was caused by atomic hydrogen. Mechanism of HE caused hydrides was the same as any other second phase in nature. Delayed fracture caused by atomic hydrogen resulted from hydrogen induced local plastic deformation.