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61.
层理岩层是石油钻井中经常遇到的一类地层,特别是在页岩气开采过程中,所钻页岩属于典型的层理岩层。研究层理岩层在钻齿作用下的破碎机理对于控制井眼轨迹、优化钻进参数、提高钻进效率都有很大指导作用。在以往岩石破碎机理研究中,一般多假设岩石介质为各向同性;但是对于层理岩层,由于其表现出强烈的强度各向异性特征,各项同性假设不再适用。本文利用离散单元方法(PFC2D)建立了钻齿与层理岩层相互作用模型。研究了层理岩层在钻齿切削和侵入过程中的破碎情况、裂纹的扩展情况以及钻齿受力情况。研究表明:切削力根据层理倾角分为高切削力区和低切削力区;液柱压力的存在对裂纹扩展有抑制作用,增大切削力;在岩石侵入过程中,层理的存在改变了裂纹的走向,当主裂纹扩展至层理处时,裂纹不再向岩石内部扩展,而是朝着层理的方向扩展。 相似文献
62.
Single Ni?P and Ni?Mo?P coatings as well as duplex Ni?P/Ni?Mo?P coatings with the same compositions were prepared by electroless plating. The residual stresses of the coatings on the surface and cross sections were measured by nanoindentation and AFM analysis, and the corrosion behaviour of the coatings in 10% HCl solution was evaluated by electrochemical methods, to establish the correlation between the residual stresses and corrosion behaviour of the coatings. The results showed that the single Ni?P and duplex Ni?P/Ni?Mo?P coatings presented residual compressive stresses of 241 and 206 MPa respectively, while the single Ni?Mo?P coating exhibited a residual tensile stress of 257 MPa. The residual compressive stress impeded the growth of the pre-existing porosity in the coatings, protecting the integrity of the coating. The duplex Ni?P/Ni?Mo?P coatings had better corrosion resistance than their respective single coating. In addition, the stress states affect the corrosive form of coatings. 相似文献
63.
纳米压痕和划痕法测定 TiO2 纳米薄膜的力学性能 总被引:2,自引:2,他引:0
目的研究相同工艺条件下阳极氧化法在不同钛合金基底(TA1,TC4,TC4F136)上生成的TiO2薄膜的力学性能差异。方法采用扫描电镜结合原子力显微镜观察3种薄膜的形貌和结构,用UNHT型纳米压痕仪测试TiO2纳米薄膜的力学性能,利用纳米划痕法测试3种钛合金表面生成的TiO2薄膜与基底的结合强度及摩擦性能,用纳米压痕技术测试TiO2的显微硬度和弹性模量。结果电解液及其它电化学条件相同时,不同钛合金基底上形成的TiO2薄膜结构(管直径、管壁厚及管长度)不同。结论阳极氧化法在钛合金基底上生成的TiO2纳米薄膜的力学性能,由TiO2微观结构及其与基底的结合强度决定,微观结构和结合强度归根到底由合金中元素决定。 相似文献
64.
微米压入技术已可实现延性金属材料力学性能的准无损检测,相对于传统力学性能测试手段,该技术不仅可实现焊接接头、增材修复界面等微尺度复杂结构力学性能的准无损评价,还可用于在役设备关键重要部件力学性能的在线监测,为其安全预警与寿命预测提供依据。系统总结基于微米压入的延性金属单轴拉伸性能及断裂韧性评价技术的研究及应用现状。首先,较完整地阐述各类评价模型的基本原理、技术路线及实际应用现状,深入讨论不同评价模型的优点及局限性,给出领域内规范、标准的制定进展;然后,分别从理论研究和工程应用两个角度论述了基于微米压入力学性能评价方法存在的问题和挑战;最后,对微米压入力学性能检测技术的发展与应用趋势进行了展望。 相似文献
65.
V. Le SauxY. Marco G. BlesS. Calloch S. MoyneS. Plessis P. Charrier 《Mechanics of materials : an international journal》2011,43(12):775-786
Micro-hardness testing is widely used to measure the materials local response and is very valuable to describe gradients of physical properties. For polymers, the most common use is to measure a scalar value (hardness or modulus), which gives access to useful qualitative information but can clearly not be used to identify local constitutive models, strongly needed to achieve the numerical simulation of heterogeneous massive parts. In this study, load/displacement curves obtained at a micro-scale are used to identify the parameters of an Edwards-Vilgis hyperelastic model. The protocol proposed is coupling FE simulations achieved with Abaqus and optimization procedures using the dedicated software Boss Quattro. In order to limit the microstructure and viscous effects, the material studied is an unfilled natural rubber which exhibits a behavior very close to perfect hyperelasticity. Several numerical parameters (indent geometry, friction, thickness, …) as well as experimental protocols were tested in order to check the protocol reliability. The identified parameters are used to simulate macroscopic tests (tensile, compression and pure shear tests). The agreement with experimental data is very good, which is rarely found in the literature and which validates several numerical assumptions. 相似文献
66.
采用压痕裂纹(IM)法测定了无压烧结ZrO2基陶瓷的断裂韧性(K1c),并引入相对偏差概念表征K1c值的精确度.结果表明,由于ZrO2基陶瓷的压痕裂纹具有巴氏裂纹特征,因而只能选择Niihara(P)方程(P表示巴氏裂纹)、Shetty方程、Laugier方程或Marshall方程等来计算K1c.其中,用Niihara(P)压痕方程计算的K1C值最符合实际,且具有最小的相对偏差.因此,正确判断压痕裂纹类型、选择合适的压痕方程及科学处理实验数据等,都将有利于提高压痕断裂韧性的测定精度. 相似文献
67.
《Journal of Adhesion Science and Technology》2013,27(8):813-836
The indentation test provides a simple means by which the adhesion of coatings can be qualitatively assessed. On the way to establishing a quantitative measurement of the adhesion strength of coatings and films, it is important that the mechanics of this test are clearly understood. To investigate the influence of factors such as the coating thickness, the indenter radius, and friction during the test, numerical simulations of the indentation of a typical polymeric coating, polymethylmethacrylate (PMMA), bonded to a rigid substrate were conducted by using the finite element method. The stress generated during the indentation test were obtained by employing an accurate constitutive model of the elastic-viscoplastic behaviour of the polymeric coating under consideration. The results of this analysis illustrate the effects of the factors mentioned above on the deformation of the coating during indentation, its confinement, and interfacial shear, and the normal, shear, and hoop stress distributions occurring during indentation. These results provide insight into the possible failure mechanisms operative during the indentation of thin coatings and the important effects of the coating thickness during such tests. 相似文献
68.
The diagram of penetration recorded in the course indentation is represented in the form of a quadratic function with the
origin of coordinates shifted to the left along the abscissa. This models the smooth character of penetration of an indenter
in its initial contact with the surface. The recorded depth of penetration increases by the length of the shift. The application
of the quadratic function and the corrected depth of penetration guarantees that the values of hardness are constant under
various loads.
Translated from Problemy Prochnosti, No. 2, pp. 43–54, March–April, 2009. 相似文献
69.
This paper aims to assess the applicability of the bonded–interface technique (BIT) that has been used for examining sub-surface damage in brittle materials. With the aid of the finite element method, the indentation stress fields in alumina specimens with and without a bonded–interface were analysed. It was found that the bonded–interface greatly alters the stress distribution in the neighbourhood of the interface. The high-stress zone shifts away from the interface, and extends to the surface. Both glue layer mechanical properties and bond thickness play a limited role in the overall stress field of the BIT alumina. Comparisons of theoretical predictions with experimental observations showed that, to a great extent, the BIT presents a different pattern of sub-surface damage. The study clarifies the applicability of the BIT and offers a useful guideline for practitioners. 相似文献
70.
Determining the Toughness of Ceramics from Vickers Indentations Using the Crack-Opening Displacements: An Experimental Study 总被引:1,自引:0,他引:1
Recently, a method for evaluating the fracture toughness of ceramics has been proposed by Fett based on the computed crack-opening displacements of cracks emanating from Vickers hardness indentations. To verify this method, experiments have been conducted to determine the toughness of a commercial silicon carbide ceramic, Hexoloy SA, by measuring the crack-opening profiles of such Vickers indentation cracks. Although the obtained toughness value of K o = 2.3 MPa·m1/2 is within 10% of that measured using conventional fracture toughness testing, the computed crack-opening profiles corresponding to this toughness display poor agreement with those measured experimentally, raising concerns about the suitability of this method for determining the toughness of ceramics. The effects of subsurface cracking and cracking during loading are considered as possible causes of such discrepancies, with the former based on direct observations of lateral subsurface cracks below the indents. 相似文献