共查询到19条相似文献，搜索用时 156 毫秒
1.
加载速率对裂隙岩体的力学性质及变形破坏均有重要影响。利用二维颗粒流程序PFC2D开展了不同倾角非贯通单裂隙砂岩试件的单轴压缩试验,研究了中等应变率对裂隙砂岩应力-应变曲线特征、裂隙尖端应力状态、特征应力状态、岩体损伤及裂隙扩展等力学响应的影响规律。裂隙岩体应力-应变曲线呈现明显的波动性,定义应力突变指标 对应力突变型波动剧烈程度进行了定量统计分析：随应变率的增加,曲线应力突变波动越剧烈,且峰后明显大于峰前;随裂隙倾角的增大,波动幅度峰前增大,而峰后减小。裂隙尖端破裂应力随应变率增大均有所提高,随裂隙倾角的增大,切向剪应力 总体上呈增加变化,而法向应力 明显减小。尖端破裂时岩样加载应力 、岩样临界扩容应力 及峰值应力 均随应变率增大而增大。裂隙尖端的破裂可立即引起岩体扩容,一般应变率越低,岩体裂隙尖端破裂点 和扩容点 越接近峰值强度 。随着应变率的提高,损伤裂纹及宏观裂隙类型越多,岩体试件损伤破裂程度越强,特别是试件端部效应愈显著。裂隙首先以I型翼裂纹在其尖端起裂,而I型翼裂纹的扩展长度与加载速率与裂隙倾角具有较强的相关性。 相似文献
2.
《岩土力学》2021,(2)
粗糙交叉节理广泛存在于实际岩体中,含不同角度粗糙交叉节理试样的力学破裂演化特性研究对岩体工程具有重要的指导意义。基于Barton节理轮廓曲线,通过3D打印技术制作不同角度粗糙交叉节理模型,浇筑成试样后进行单轴压缩试验,并采用DIC技术对试样表面的变形特征进行了处理与分析。结果表明:主节理倾角较大试样的单轴强度基本小于主节理倾角较小试样,主次节理夹角γ在45°～60°之间时对试样的单轴抗压强度和弹性模量影响最大;通过对DIC应变云图、节理尖端全程应变和应变率激增点分析可知,起裂主要发生在主节理上下端和次节理上端,起裂应力在峰值应力的90%至峰值阶段,屈服阶段裂隙扩展速度缓慢,快速扩展主要发生在峰后阶段;粗糙交叉节理试样的起裂方向与平直节理试样不同,节理尖端裂隙多以剪切形式存在,远端在最大主应力的作用下多演化为张拉裂隙;主节理下端的应力强度因子基本大于次节理上端,说明主节理对试样的破裂起主要作用,节理尖端的K_Ⅱ多大于K_Ⅰ,说明起裂扩展受剪切作用大于张拉作用。 相似文献
3.
目前数字图像相关方法在岩石力学领域的应用主要集中于获取变形场云图,缺乏结合一些指标对变形数据进行定量分析。采用数字图像相关方法对裂隙砂岩试件压缩加载过程进行非接触式、实时变形测量,结合方差量化描述应变场分异特征;而后对应变场方差变化曲线进行有限差分求导,量化描述应变场分异速率,分析应变场演化规律及前兆特征。研究结果表明:裂隙砂岩试件的变形破裂过程可划分为压密、弹性变形、裂纹稳定扩展、裂纹快速扩展及破坏等4个阶段。加载过程中裂隙砂岩试件的裂纹萌生和扩展行为,在应变场上表现为应变局部化带的产生与发展,进而导致应变场方差和分异速率发生变化。应变场方差-轴向应变曲线表现出阶段性特征,可划分为稳定分异、加速分异以及加加速分异等3个阶段。应变场分异速率-轴向应变曲线在张拉裂纹起裂时均出现第一个尖峰,可作为裂隙岩体失稳破坏前的前兆信号,对应的前兆应力与峰值应力之比为0.80～0.96。研究成果对工程岩体失稳预测具有较好的理论参考价值。 相似文献
4.
利用颗粒流程序（PFC) 对直切槽式圆盘试样进行巴西试验模拟,分析了不同的裂隙倾角和裂隙长度对直切槽式圆盘试样裂纹扩展规律的影响。根据起裂位置的不同,主裂纹可分为从裂隙尖端萌生的Ⅰ型主裂纹和从裂隙尖端一定距离处萌生的Ⅱ型主裂纹;次生裂纹可分为从加载点附近萌生的Ⅰ型次生裂纹和从远离加载点的一侧萌生的Ⅱ型次生裂纹。当裂隙长度保持不变而增大裂隙倾角时,主裂纹从Ⅰ型过渡为Ⅱ型,次生裂纹则从Ⅰ型转变为Ⅰ型和Ⅱ型共存,最后又变为Ⅰ型。当裂隙角度保持不变而增大裂隙长度时,主裂纹保持不变,次生裂纹则由Ⅰ型逐渐过渡为Ⅰ型和Ⅱ型共存。另外,当径向应力达到峰值应力之后,试样内会有大量的微裂纹萌生、扩展,造成了圆盘试样的破坏。从力链和能量角度来看,巴西圆盘试样的破裂过程是试样内部拉应力集中产生的颗粒间黏结破裂以及应变能释放的过程。 相似文献
5.
断续三裂隙砂岩强度破坏和裂纹扩展特征研究 总被引：4，自引：0，他引：4
利用岩石力学伺服试验机,对尺寸为80 mm×160 mm×30 mm的断续三裂隙砂岩试样进行了单轴压缩试验,研究了岩桥倾角? 2对断续三裂隙砂岩（? = 30°和? 1 = 60°）强度破坏和裂纹扩展特征的影响规律。与完整砂岩试样相比,断续三裂隙砂岩试样应力-应变曲线显示了较多的应力跌落,其峰值强度也呈显著降低趋势,但降低程度与? 2密切相关,随着? 2从75°增加到90°,峰值强度从82.04 MPa 降低到77.82 MPa,而当? 2从90°增加到120°,其峰值强度无明显变化。完整砂岩试样呈现轴向劈裂脆性破坏,而断续三裂隙砂岩试样是由许多从裂隙尖端产生的裂纹扩展与汇合,导致了其失稳破坏。通过照相量测技术,探讨了? 2对断续三裂隙砂岩试样裂纹扩展特征的影响：? 2为75°、90°和105°的断续三裂隙试样中裂隙①、③和②、③之间均出现了贯通,而裂隙①、②之间无任何贯通;? 2为120°的断续三裂隙试样中裂隙①、③和①、②之间均出现了贯通,而②、③之间无任何贯通。最后给出了断续三裂隙砂岩试样宏观变形特性与裂纹扩展过程之间的关系。 相似文献
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交叉节理普遍存在于实际岩体中,但其对岩体力学破裂特性的影响至今未有全面深入的研究。制作了含3D打印交叉节理试样,采用声发射、CT扫描技术和数字图像相关技术(DIC)分析手段对单轴条件下含交叉节理试样的力学及破裂特性进行了研究。研究结果表明:(1)主节理倾角较小时裂隙的分形维数DB与单轴强度、弹性模量和泊松比之间的变化关系比主节理倾角较大时的一致性更好,前者破裂模式的规律性好于后者。(2)主节理倾角较大时压密和弹性阶段节理和块体之间在张拉作用下会产生聚集性微破裂声发射事件,主节理倾角较小时不会产生这种现象。DIC应变云图中裂隙扩展路径上的微应变先于宏观破裂,可通过计算压缩条件下微应变最大区域预测破裂模式。(3)主节理对起裂角和裂隙扩展模式起主要作用,且声发射和分形特性具有统一性。次节理平行最大主应力时,总损伤主要由主节理扩展造成,累积声发射事件数量AAEE和DB均最大。AAEE和DB越大,破裂模式越复杂。(4)三维破裂模式以节理端部扩展产生的2~3个张拉翼裂隙面为主,内部三维宏观裂隙面上存在由不完全张拉破裂引起的非连续结构。 相似文献
7.
含交叉裂隙岩体相似材料试件力学性能单轴压缩试验 总被引：3，自引：0，他引：3
以相似材料制作含交叉裂隙岩体试件,考虑主裂隙与加载方向之间角度变化及主、次裂隙之间角度变化制作20组试件,对试件进行单轴压缩试验,研究交叉裂隙对岩体破坏模式及力学特性的影响。研究表明,主裂隙与加载方向呈0°及90°时,试件破坏主要为沿次裂隙扩展的剪切型破坏;当主裂隙与加载方向呈30°及45°时,试件破坏主要是沿主裂隙扩展所致的剪切型破坏;主裂隙角度一致情况下,大部分含交叉裂隙岩体破坏强度高于含单向裂隙岩体,含交叉裂隙岩体试件应力-应变曲线峰后下降斜率比含单向裂隙岩体大;主裂隙角度一致情况下,当次裂隙与主裂隙呈45°夹角左右时,岩体试件强度较低,当次裂隙与主裂隙呈30°及90°夹角左右时,岩体试件强度较高。 相似文献
8.
既有的巴西劈裂试验与模拟研究多集中在宏观破坏模式与细观演化规律上,对劈裂渐进过程的能量演化特征的分析较少。结合数字图像相关技术(DIC)与声发射实时监测,开展花岗岩的巴西劈裂实验。首先分析实验过程中,岩石破裂模式与破裂尺度的演化规律。在此基础上,采用颗粒流程序(PFC2D)对劈裂试验过程进行数值模拟,分析实验过程中内部裂纹演化过程的能量特征。试验与数值模拟对比结果表明:加载过程中岩样的损伤变化一共经历了4个阶段,即裂隙压密阶段(Ⅰ)、裂纹萌生阶段(Ⅱ)、裂纹扩展阶段(Ⅲ)、峰后破坏阶段(Ⅳ)。试样在裂隙萌生和裂纹扩展阶段以拉张型微破裂为主,裂纹扩展阶段后期产生剪切型破裂,并在加载直径方向形成大尺度裂纹并贯穿整个圆盘形成宏观破坏;试样在裂隙压密和萌生阶段几乎无耗散能,外力所做功几乎都转为岩体内可释放应变能,在破裂扩展后期应变能快速释放,声发射能量在峰值应力附近时达到最大值,峰后破坏阶段试件的可释放应变能快速减小,能量通过形成大量新裂面被耗散掉。 相似文献
9.
岩体内部赋存的裂隙很多表现为折线型,为探究这类岩体的断裂机制,制备含折线型裂隙砂岩试件并对其进行单轴压缩试验。采用数字图像相关(DIC)方法计算加载过程中的变形场演化,根据新生裂纹两侧的位移差异识别裂纹类型;运用扩展有限元法(XFEM)模拟断裂过程,根据应力分布特征解释翼型裂纹起裂与扩展机制。DIC计算结果表明,新生裂纹处出现应变局部化带,裂纹两侧发生相对分离;含直线型和折线型裂隙砂岩试件的翼型裂纹分别萌生于预制裂隙端部以及折角处,这是因为裂隙几何形态会改变拉应力集中位置;含折线型裂隙砂岩试件的起裂应力小于含直线型裂隙砂岩试件,这是因为相同加载条件下前者的最大拉应力值更大;这2类试件的裂纹扩展均是由于裂纹尖端集中的拉应力引起的,裂纹依然呈张开状态;裂隙几何形态未改变试件的最终破坏模式,均表现为对角剪切破坏。 相似文献
10.
微裂纹萌生、扩展和聚结模式的识别是研究岩体灾害孕育演化过程的基础。为探究裂隙岩石微裂纹发育过程及机制,采用主动超声测量和数字图像相关（digital image correlation,简称DIC）技术同步监测单轴压缩下预制裂隙砂岩的损伤破裂过程,分析了表面应变场演化及超声衰减特征。结果表明：小倾角预制裂隙尖端的局部拉应力集中利于裂纹更早萌生;随裂隙倾角增加,预制裂隙试样由较为稳定的渐进性破裂转变为突发性破坏,其脆性特征也更明显,表面应变场可实时追踪裂纹的萌生和扩展。P波波速、振幅谱和超声振幅的衰减与微裂纹的发育和宏观裂纹的形成密切相关,可将超声波主频的明显衰减视为宏观裂纹形成的直接证据;不同射线路径P波速度及振幅衰减的差异,是轴向应力和预制裂隙诱导损伤累积各向异性的结果。此外,采用改进谱比法分析了超声衰减的时移特征,发现超声波衰减比P波波速对岩石介质中微裂纹的发育更敏感,进一步对比发现超声振幅、表面应变、P波波速对岩石损伤识别的敏感性依次降低。该研究结果表明,主动超声衰减和DIC表面应变同步监测是识别和量化岩石损伤和裂纹扩展先兆信息的有力工具。 相似文献
11.
为了准确表征不同角度预制节理岩石在单轴压缩下的变形破坏模式,基于3D打印技术制作了节理模型用于模拟岩体中的结构面,通过水泥砂浆的浇筑得到含不同角度预制节理的岩石试件并进行单轴压缩试验,同时采用数字图像相关技术（DIC）观测、分析试验过程中试件裂纹产生、扩展以及贯通过程。结果表明：随着预制节理从0°增加到90°,试件强度与峰值应变均呈现先降低后升高的变化趋势,0°和45°试件弹性模量相对于完整试件有所降低。基于DIC检测结果,0°、30°、45°及60°试件裂纹皆从预制节理尖端部位起裂,各角度试件的起裂应力与试件强度变化规律一致。各角度试样起裂时在剪应力控制下以剪切翼型裂纹形式起裂,0°与45°试件裂纹在扩展过程由剪切发展为张拉型裂纹,30°和60°试件以剪切裂纹形式贯穿始终,90°试件从底部起裂并最终表现为张拉破坏。研究还发现,下翼起裂角θ2和上翼起裂角θ1之间存在明显的线性正相关关系,关系式为θ2 =0.828 6θ1 +12.185,且起裂应力大小变化与峰值应力变化一致,皆随节理角度的增加先减小后增大。 相似文献
12.
Three-dimensional surface crack initiation and propagation in two kinds of heterogeneous rocks were numerically investigated via parallel finite element analysis using a supercomputer. Numerically simulated rock specimens containing a pre-existing flaw were subjected to uniaxial compression until failure. The initiation and propagation of wing cracks, anti-wing cracks, and shell-like cracks were reproduced by numerical simulations. The numerically simulated results demonstrate that the further propagation of wing cracks and shell-like cracks stop due to their wrapping (curving) behavior in three-dimensional spaces, even if the applied loads continue to increase. Furthermore, rock heterogeneity could significantly influence crack propagation patterns and the peak uniaxial compressive strengths of rock specimens. Moreover, anti-wing cracks only appeared in relatively heterogeneous rocks, and the peak uniaxial compressive strengths of the specimens were observed to depend on the inclination of the pre-existing flaw. Finally, the mechanism of surface crack propagation is discussed in the context of numerically simulated anti-plane loading tests, wherein it was identified that Mode III loading (anti-plane loading) does not lead to Mode III fracture in rocks due to their high ratio of uniaxial compressive strength to tensile strength. This finding could explain the lateral growth of an existing flaw in its own plane, which is a phenomenon that has not been observed in laboratory experiments. 相似文献
13.
泥页岩单轴抗压破裂特征及UCS影响因素 总被引：2，自引：0，他引：2
正确认识泥页岩单轴抗压破裂特征及UCS影响因素对探究泥页岩破裂机制、钻完井设计、压裂评价、微裂缝预测、测井解释及地震响应等方面均具有重要参考价值。本文在对国内外近些年有关泥页岩单轴抗压及UCS研究系统调研及近期研究成果全面分析基础上,对泥页岩破裂特征及UCS影响因素进行了综合分析。研究结果表明,泥页岩单轴加载曲线的非弹性段变形机制受微裂缝的滑动、新微裂缝的产生、扩展及孔隙坍塌的综合影响。泥页岩单轴抗压破裂呈张性或张剪性,张性破裂易发生于刚度较高、固结程度较强的部位;而剪性破裂易发生于刚度较低、固结程度较弱的部位。S型破裂准则可以较为准确的描述泥页岩从单轴到三轴发生破裂时所对应的强度变化。从地质学角度,对影响泥页岩UCS的因素进行了归纳,分别为矿物组成、层理面角度、分选性、微组构、有机质含量及分布、孔隙度、水分、微裂缝8方面因素,详细分析了不同影响因素的影响机制。在这些影响因素中,微裂缝由于分布特征复杂,其对泥页岩单轴抗压破裂及UCS的影响机制研究尚不深入。因此建议未来应加强泥页岩微裂缝参数的定量化研究,从微观尺度研究微裂缝对泥页岩单轴抗压破裂的具体影响机制,该研究可以为页岩油气勘探、开发提供科学指导。 相似文献
14.
Zhaohui Chong Xuehua Li Qiangling Yao Ji Zhang Tian Chen 《Arabian Journal of Geosciences》2016,9(12):592
Particle flow code (PFC2D) software was adopted to investigate the anchorage behaviour and the characteristics of crack initiation, propagation and coalescence of reinforced specimens containing a single fissure (RSCSF). The microscopic parameters of the specimens in the numerical simulation were first validated by experimental outcomes of intact specimens, while the microscopic parameters of the rock bolts were validated based on the results of the RSCSF tests. Then, the mechanical parameters as well as the failure modes in the physical experiments were compared with those derived by the numerical simulation; the results showed good agreement between the simulated macroscopic mechanical properties and failure modes and those obtained in the laboratory experiments. The peak strength, number of cracks and the failure mode varied considerably as the anchorage angle α and fissure angle β increased. Three types of stress–strain curves, types I to III, were obtained from the RSCSF. Shear cracks were observed for all three categories of curves, but the tensile cracks were dominant. The number of cracks and the rate of bond failures decreased as the curve changed from type II to type I to type III. RSCSF failure can be classified into three failure modes: (1) tip crack propagation mode, (2) midpoint crack propagation mode and (3) rock bolt crack propagation mode. These failure modes are primarily differentiated by relations between α and β, and the ratio UCSS/UCSI between the uniaxial compressive strength (UCS, σ max) of the RSCSF (UCSS) and the uniaxial compressive strength of the intact specimen (UCSI). 相似文献
15.
Cheng Zhao Yimeng Zhou Qingzhao Zhang Chunfeng Zhao Hiroshi Matsuda 《国际地质力学数值与分析法杂志》2020,44(3):353-370
To deeply understand the cracking mechanical behavior of brittle rock materials, numerical simulations of a rock specimen containing a single preexisting crack were carried out by the expanded distinct element method (EDEM). Based on the analysis of crack tips and a comparison between stress- and strain-based methods, the strain strength criterion was adopted in the numerical models to simulate the crack initiation and propagation processes under uniaxial and biaxial compression. The simulation results indicated that the crack inclination angle and confining pressure had a great influence on the tensile and shear properties, peak strength, and failure behaviors, which also showed a good agreement with the experimental results. If the specimen was under uniaxial compression, it was found that the initiation stress and peak strength first decreased and then increased with an increasing inclination angle α. Regardless of the size of α, tensile cracks initiated prior to shear cracks. If α was small (such as α ≤ 30°), the tensile cracks dominated the specimen failure, the wing cracks propagated towards the direction of uniaxial compression, and the propagation of shear cracks was inhibited by the high concentration of tensile stress. In contrast, if α was large (such as α ≥ 45°), mixed cracks dominated the specimen failure, and the external loading favored the further propagation of shear cracks. Analyzing the numerical results of the specimen with a 45° inclination angle under biaxial compression, it was revealed that lateral confinement had a significant influence on the initiation sequence and the mechanical properties of new cracks. 相似文献
16.
脆性岩石材料在压应力作用下常出现两类裂纹：翼型张拉裂纹和次生剪切裂纹。近场动力学是一种新型的无网格数值计算方法。在近场动力学理论中,采用积分形式的控制方程代替微分形式的控制方程使得该数值算法在断裂问题上具有独特的优势。将Mohr-Coulomb准则和最大主应力准则引入非普通“态”基近场动力学理论中,分别用于模拟材料常见的压剪和张拉破坏。这种扩展的非普通“态”基近场动力学可以有效地模拟脆性岩石材料在多种受力状态下的裂纹起裂、扩展和连接问题。通过5个不同的数值算例说明该数值算法在处理脆性岩石材料断裂问题的有效性和准确性。首先,通过模拟含圆孔的弹性板拉伸数值试验说明该数值算法的有效性和准确性。其次,数值模拟了简单三点弯曲试验以及不使用其他外部准则条件下动荷载作用下裂纹的分叉试验,所得结果与其他试验结果或数值结果相吻合,从而验证了该理论的有效性。然后,模拟了包含斜裂纹的巴西圆盘试验,裂纹扩展路径和计算所得的断裂韧度同样吻合于试验结果。最后,模拟了单轴压缩状态下,预制裂纹试样的裂纹扩展和连接问题。将该数值算法与试验结果对比表明,所提出的数值方法可以模拟和预测岩石类材料的张拉和压剪裂纹的起裂、扩展和连接行为。 相似文献
17.
炭质页岩巴西劈裂载荷下破坏过程的时空特征研究 总被引：1，自引：0，他引：1
页岩在加载过程中的破裂时机及其空间位置研究对于页岩气探测及储层评价具有重要意义,为此开展了不同层理倾角条件下页岩的巴西圆盘劈裂载荷下的破坏过程试验,采用数字图像相关技术（DIC）,全程跟踪页岩裂纹萌生、扩展和贯通全过程的变形场实时演化特征,同时记录力-位移曲线,利用扫描电镜获得炭质页岩的破裂面特征及微观结构,采用宏、细观相结合的手段,研究不同层理方向炭质页岩微裂缝起裂时间、空间位置和扩展规律及其破裂机制。结果表明：页岩的巴西劈裂强度随层理方向与加载方向角度的增大而逐渐增大;随加载方向与层理面夹角的增加,裂缝萌生的时间逐渐增加,而裂缝从萌生、扩展到贯通所用时间逐渐减少。所有角度试件基本从试件端部萌生裂缝并沿层理面扩展,除90°试件外,不同层理倾角试样主裂缝破裂的位置逐渐偏离中心位置而向试件外侧发展。各角度试件主破坏类型存在一定差异性,除90°试件竖向主裂缝为张拉破坏外,随加载方向与层理面夹角的增加,各加载角度试件的主破裂模式从张拉剪切破坏逐渐过渡为剪切滑移破坏。 相似文献
18.
不同加载速率条件下岩石的力学特性,对于其动载下破裂内在机制的研究具有积极的意义。基于颗粒流理论,通过黏结颗粒模型（bonded particle model,简称BPM）虚拟实现不同加载速率0.001～0.500 m/s下花岗岩单轴压缩和巴西劈裂试验,定量分析加载速率对应力-应变、破裂形态、应变能率及声发射的影响。结果表明：单轴抗压强度和抗拉强度及其对应峰值应变随加载速率增加而非线性增长;单轴压缩作用下,随加载速率增加,试样由单一斜截面破坏向多斜截面破坏转变,且主控裂隙带宽度急剧增大,由裂纹数量及水平向高应变率区域变化规律可明显看出,试样破坏程度随着加载速率增加而逐渐加剧;巴西劈裂作用下试样从一条主控裂隙向多条主控裂隙转变,且裂纹向圆盘试样两侧边缘部分延伸,破坏程度加剧;单轴压缩和巴西劈裂作用下,声发射事件及应变能率均随加载速率增加而呈现出非线性增长趋势。 相似文献
19.
Cracking processes have been extensively studied in brittle rock and rock-like materials. Due to the experimental limitations and the complexity of rock texture, details of the cracking processes could not always be observed and assessed comprehensively. To contribute to this field of research, a numerical approach based on the particle element model was used in present study. It would give us insights into what is happening to crack initiation, propagation and coalescence. Parallel bond model, a type of bonded-particle model, was used to numerically simulate the cracking process in rock-like material containing a single flaw under uniaxial vertical compression. The single flaw’s inclinations varied from 0° to 75° measured from the horizontal. As the uniaxial compression load was increased, multiple new microcracks initiated in the rock, which later propagated and eventually coalesced into longer macrocracks. The inclination of the pre-existing flaw was found to have a strong influence on the crack initiation and propagation patterns. The simulations replicated most of the phenomena observed in the physical experiments, such as the type, the initiation location and the initiate angle of the first cracks, as well as the development of hair-line cracks, which later evolved to macrocracks. Analyses of the parallel bond forces and displacement fields revealed some important mechanisms of the cracking processes. The first cracks typically initiated from the tensile stress concentration regions, in which the tensile stress was partially released after their initiation. The tensile stress concentration regions subsequently shifted outwards close to the propagating tips of the first cracks. The initiation and propagation of the first cracks would not significantly influence the compressive stress singularity at the flaw tips, which was the driving force of the initiation of secondary cracks. The initiation of microcracking zone consisting almost exclusively of micro-tensile cracks, and that of microcracking zone consisting of micro-tensile cracks and mixed micro-tensile and shear cracks, were found to be correlated with two distinct types of displacement fields, namely type I (DF_I) and type II (DF_II), respectively. 相似文献