Simulation of shale gas transport and production with complex fractures using embedded discrete fracture model

The goal of this study is to develop a new model to simulate gas and water transport in shale nanopores and complex fractures. A new gas diffusivity equation was first derived to consider multiple important physical mechanisms such as gas desorption, gas slippage and diffusion, and non‐Darcy flow. For complex fractures, a state‐of‐the‐art embedded discrete fracture model (EDFM) was implemented. Numerical model is verified against a commercial reservoir simulator for shale gas simulation with multiple planar fractures. After that, a series of simulation studies was performed to investigate the impacts of complex gas transport mechanisms and various fracture geometries on well performance. The critical parameters controlling well performance are identified. The simulation results reveal that modeling of gas production from complex fractures as well as modeling important gas transport mechanisms in shale gas reservoirs is extremely significant. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2251–2264, 2018     

Mechanical and fracture behavior of an artificially ultraviolet‐irradiated poly(ethylene‐carbon monoxide) copolymer

In this work, 1 wt % carbon monoxide (CO) poly(ethylene‐carbon monoxide) (ECO) copolymer sheets were artificially exposed to ultraviolet (UV) light with a power density of 3 mW/cm² for up to 130 h. A thorough mechanical characterization of the irradiated material was conducted, in which both the stress–strain data and the values of the quasistatic crack initiation and growth toughness were measured and correlated with companion uniaxial tensile tests and single‐edge‐notched fracture tests. Average values of the elastic modulus, failure strain, and failure stress were determined from the tensile tests. The full‐field optical technique of digital image correlation was used to quantify in‐plane deformation (displacements and displacement gradients) during the fracture experiments and to extract values of the crack initiation and growth fracture toughness. The elastic modulus increased monotonically with UV irradiation for the exposure times used in this investigation. In addition, for low irradiation times of less than 5 h, both the failure strain and failure stress of ECO decreased, and this caused a corresponding decrease in the crack initiation and growth toughness. However, for longer irradiation times, the failure strain remained almost invariable, whereas the failure stress increased by about 25% over that of unirradiated ECO. As a result, for longer irradiation times (>5 h), 1 wt % CO ECO became not only stiffer but also stronger and tougher, as quantified by companion fracture experiments. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 139–148, 2004     

连续玻纤增强聚丙烯预浸带熔融浸渍过程纤维断裂研究

为提高连续玻纤增强聚丙烯预浸带（PP/GF）性能,采用熔融浸渍法制备连续玻璃纤维增强聚丙烯预浸带,研究了PP熔体浸渍连续GF束过程。基于Weibull分布函数建立了纤维断裂数学模型,预测预浸带生产过程中纤维断裂率并描述实验结果。结果表明,模型与实验数据吻合较好,能够为工业化生产提供指导;纤维束在浸渍模具中受到树脂熔体的作用,及纤维与设备之间的摩擦是影响纤维断裂的主要因素,适当提高浸渍模具温度,降低纤维束牵引速度,增大浸渍模具间隙能有效降低纤维断裂率,提高工艺稳定性。     

高掺量煤矸石固废微晶玻璃结构与性能研究

本文通过XRD、SEM、TG-DSC、耐腐蚀性、密度、硬度、断裂韧性等测试,研究不同热处理制度和煤矸石掺量对微晶玻璃晶体结构、微观形貌、物化性能的影响。结果表明,该体系煤矸石微晶玻璃析出的主晶相为钙长石相(CaAl₂Si₂O₈),随着热处理晶化温度的升高,析出的主晶相数量变多,尺寸变大,但主晶相种类并未改变。当热处理制度为核化温度750 ℃保温1 h、晶化温度1 000 ℃保温1 h时,主晶相晶体尺寸大小约300~400 nm。在优化热处理制度下,当煤矸石掺量从44%(质量分数)增加到70%时,4种不同煤矸石掺量微晶玻璃的物化性能相差不大。综合考虑煤矸石固废利用率和样品的物化性能指标,煤矸石掺量为70%的样品综合性能最佳。本文设计的煤矸石微晶玻璃体系,对煤矸石固废的包容性好,消纳性强,可实现煤矸石固废的大掺量高值化利用,为解决煤矸石固废堆积、环境污染等问题提供了理论基础和实验依据。     

Temperature and rate dependent debonding behaviors of precision glass molding interface

The glass-to-mold adhesion in precision glass molding could severely degrade the quality of molded optics and shorten the lifespan of the precious molds. Since the consequences of adhesion take effect during the separation between glass and molds, it is important to investigate the debonding behaviors of a typical glass molding interface. To this end, here we perform a probe tack test procedure for borosilicate glass BK7, where debonding is conducted at molding temperature and specific velocity. We fully characterize the debonding behaviors using the peak adhesion stress σ_max and the work of debonding W_deb. Experiments show that when temperature is decreased from 690°C to 655°C at 10 μm/s, σ_max continuously increases, while W_deb first increases but then sharply decreases. When the debonding velocity is increased from 10 to 50 μm/s at 680°C, σ_max also increases while W_deb overall decreases. Therefore, the debonding behaviors are highly temperature and rate dependent. More importantly, depending on the debonding conditions, three debonding types are identified, that is, the cohesive bulk deformation, the cohesive-interfacial transition and the interfacial fracture. The cohesive type can be converted into the interfacial fracture, by either decreasing temperature or increasing the debonding velocity. Based on the W_deb criterion, the three debonding regimes can be clearly distinguished. Finally, analyses on the temperature and velocity experimental results are unified by incorporating the reduced crack velocity a_Tv_c. The dependences of both viscoelasticity and W_deb on a_Tv_c qualitatively explain the transition condition for different debonding types. Concerning these findings, the work of debonding not only supplements the characterization of adhesion strength, but also throws insightful light on revealing the debonding mechanisms.     

高聚物黏结炸药的冲塞试验研究

用冲塞试验评价大药量装药在撞击、剪切、绝热加热等综合作用条件下的安全性.用火药加速装置对试件加速,并通过高速摄像机拍摄炸药试验件跌落撞靶、点火等试验过程,利用冲击波压力传感器测试冲击波超压表征炸药试验件的反应程度.结果表明,PBX-1炸药在撞靶速度高达37.6 m/s时没有发生反应,且PBX-2炸药在撞靶速度为27.7 m/s时发生了爆燃反应,在撞击速度低于25.5 m/s时未发生反应,说明PBX-2炸药的冲塞试验撞击感度高于PBX-1炸药.     

炸药爆炸残留物颗粒飞散运动过程的简化分析

采用空气流场中的球形颗粒一维稀疏二相流动力学模型对具有初始飞散速度的炸药残留物颗粒在空气中的受力情况及运动过程进行分析,获得了炸药残留物颗粒的速度衰减及水平飞散距离公式。对公式的定性分析结果表明,在初始抛散速度相等的前提下得出:(1)颗粒粒径越大的残留物其在水平方向的抛散速度衰减越慢,抛散距离也越远,但都存在一个水平分布极限距离xm ax(ds);(2)密度越大的炸药,其残留物水平方向分布区域越远;(3)炸药残留物颗粒水平方向的运动特性与炸药量无关。     

汽车发动机曲轴断裂失效分析

采用断口分析、显微组织检验、低倍组织检验、能谱分析和化学成份分析等方法对某汽车发动机曲轴断裂进行了失效分析,判断断裂失效的主要原因是非金属夹杂和次表面的原始微裂纹,建议改进热处理工艺,保证组织的均匀性,选用非金属夹杂物含量小的钢材。     

时效时间对Al-Cu-Li-Zr-Ce合金断裂机制影响的半定量研究

以Al-Cu-Li-Zr-Ce合金为研究对象,采用半定量分析统计方法,研究其断裂韧性机制,重点讨论时效时间和裂尖应力状态对合金分层开裂机制的影响。结果表明:随时效时间延长,起始区分层开裂特征所占比例越大,韧窝比例越小,甚至出现准解理特征;稳态扩展区,分层开裂为主要开裂机制;近失稳扩展区,分层比例下降,准解理逐渐成为主要断裂特征。随时效时间延长和裂纹扩展,分层厚度减小。分层裂纹的产生及扩展与主裂纹扩展及合金的时效时间有密切的关系。断裂韧性试样断口上分层比例较高时,合金可以获得较高的强度,同时保持相对较高的韧性。     

冷却速度对快冷Ti合金组织与力学性能的影响

通过铜模铸造法制备出了阶梯形的Ti66.7Ni20Cu13.3合金圆柱棒,直径分别为φ2mm、φ3mm、φ4mm和φ6mm。利用x射线衍射（XRD）仪和扫描电子显微镜（SEM）等研究了不同冷却速度对Ti66.7Ni20Cu13.3（原子百分比）合金组织与力学性能的影响。结果表明：合金形成Ti基非晶复合材料,直径为西3mm时塑性应变量最大为4．8％,直径为西4mm时最大强度达到1774MPa;随着直径的增大析出较多脆性相,导致试样破坏性脆断。