苏里格气田泥页岩井壁水化损伤失稳周期确定

钻井过程中复杂的应力和固液作用,使围岩产生了水化扩散和水化膨胀,改变了其中的应力场和力学参数,从而导致泥页岩井壁失稳。通过试验研究,探讨了泥页岩井壁围岩水化随时间和空间的变化规律以及岩石弹性模量和抗压强度随含水率变化的损伤弱化规律,进而结合强度变形破坏理论推导出泥页岩遇水后的损伤演化方程、损伤演化极限方程和确定坍塌周期的方法。应用该方法,得出苏里格气田泥页岩井壁坍塌周期为6.8 d左右。

薄壁旋转叶片热屈曲失稳与损伤应用研究

作为发动机中最重要的部件之一,旋转叶片的结构特性和工作状态直接影响到航空发动机的正常运行。以应用于航空发动机中高速旋转叶片为研究对象,对其屈曲失稳响应进行研究。建立旋转叶片结构热屈曲分析模型,对比揭示温度场下约束叶片的线性与非线性热屈曲响应的失稳特性。通过对比线性/非线性热屈曲响应,发现了非线性屈曲失稳特性更接近真实损伤工况,分析出屈曲应力最大的部位位于叶根并与试验对比一致,由此获得了叶片的临界载荷及其失稳条件,这对降低热-结构耦合振动对叶片的损伤具有重要的意义。

基于损伤理论的混凝土构件裂缝的扩展研究

根据已有的资料和试验参数,分别采用三点弯曲梁和楔入式紧凑拉伸试件,利用有限元方法分析了混凝土裂缝尖端的应力、应变之间关系,以及裂缝口张开位移与试验结果进行对比分析,数据比较吻合,验证了模拟计算的合理性.根据以上结果,计算了带裂缝混凝土构件的损伤场,得到了裂缝发展中缝端的起裂损伤和失稳损伤.

超塑性板料的成形极限

根据超塑变形过程中的损伤演变方程和超塑性变形的特点，本文将基于粘塑性势的热粘塑性损伤势函数与Ｈｉｌｌ描述板料变形的各向异性材料屈服行为有机地结合起来，考虑了起塑变形过程中损伤与失稳的交互作用．将起塑变形全过程分为稳定变形。准稳定变形、应变路径飘移和集中性失稳发展四个阶段，用数值方法建立了超塑性板料的损伤失稳模型．然后在此基础上，以集中性失稳发生（ｄε２＝０）或临界空洞体积分数（ｆｃ）作为破坏判据，预测了板料超塑变形时的成形极限。

Damage failure of cemented backfill and its reasonable match with rock mass

In order to study the failure mechanism of backfill and the reasonable matches between backfill and rock mass, and to achieve the object of safe and efficient mining in metal mine, four types of backfills were tested under uniaxial compression loading, with cement?tailing ratios of 0.250:1, 0.125:1, 0.100:1 and 0.083:1, respectively. With the help of the stress?strain curves, the deformation and failure characteristics of different backfills with differing cement?tailing ratios were analyzed. Based on the experimental results, the damage constitutive equations of cemented backfills with four cement?tailing ratios were proposed on the basis of damage mechanics. Moreover, comparative analysis of constitutive model and experimental results were made to verify the reliability of the damage model. In addition, an energy model using catastrophe theory to obtain the instability criteria of system was established to study the interaction between backfill and rock mass, and then the system instability criterion was deduced. The results show that there are different damage characteristics for different backfills, backfills with lower cement?tailing ratio tend to have a lower damage value when stress reaches peak value, and damage more rapidly and more obviously in failure process after peak value of stress; the stiffness and elastic modulus of rock mass with lower strength are more likely to lead to system instability. The results of this work provide a scientific basis for the rational strength design of backfill mine.

Dynamic mechanical properties and instability behavior of layered backfill under intermediate strain rates

To obtain dynamic mechanical properties and failure rule of layered backfill under strain rates from10to80s-1,impactloading test on layered backfill specimens(LBS)was conducted by using split Hopkinson pressure bar system.The results indicatethat positive correlation can be found between dynamic compressive strength and strain rate,as well as between strength increasefactor and strain rate.Dynamic compressive strength of LBS gets higher as the arithmetic average cement-sand ratio increases.Compared with static compressive strength,dynamic compressive strength of LBS is enhanced by11%to163%.In addition,theenergy dissipating rate of LBS lies between that of corresponding single specimens,and it decreases as the average cement contentincreases.Deformation of LBS shows obvious discontinuity,deformation degree of lower strength part of LBS is generally higherthan that of higher strength part.A revised brittle fracture criterion based on the Stenerding-Lehnigk criterion is applied to analyzingthe fracture status of LBS,and the average relevant errors of the3groups between the test results and calculation results are4.80%,3.89%and4.66%,respectively.

腰椎间盘突出症患者PELD术后再次手术的影响因素分析

目的分析腰椎间盘突出症患者经皮内窥镜下腰椎间盘切除术(PELD)后再次手术的影响因素。方法选取2019年2月~2020年2月期间本院收治的腰椎间盘突出症患者80例,均进行手术治疗,术后完成为期6个月跟踪随访,记录术后生再手术例数,统计患者基线资料,分析腰椎间盘突出症患者PELD术后再次手术的影响因素。结果80例腰椎间盘突出症患者PELD术后再次手术6例,占7.50%;经单因素与多因素分析结果显示,椎管狭窄、腰椎失稳、马尾神经损伤、术后高强度运动是腰椎间盘突出症患者PELD术后再次手术的危险因素(OR>1,P<0.05)。结论年龄较大、腰椎失稳、马尾神经损伤、术后高强度运动均为腰椎间盘突出症患者PELD术后再次手术的影响因素,临床可据此实行针对性处理措施,以避免再次手术。