航空发动机限寿件概率失效风险评估的等效应力转化

提出一种从整个飞行循环出发并基于全局的限寿件等效应力转化方法,将转化后的等效应力作为概率失效风险评估的输入条件,从而获得更为精确的失效风险结果。首先通过流固耦合数值模拟获得限寿件在整个飞行循环的瞬态应力,然后基于雨流计数法及线性累计损伤理论编制转换程序,将限寿件模型全部节点上的瞬态应力转化为等效应力,最后作为概率失效风险分析流程的输入条件确定寿命期内的概率失效风险。相同飞行循环条件下,与基于局部最大应力的转化方法相比,全局等效应力转化方法获得的失效风险更低。该方法的提出,为我国民机型号概率失效风险评估时作为关键输入数据应力的确定给出了定量参考,有力支撑了适航取证。

强电场下高聚物绝缘中的应力转化与补偿效应

研究了高分子聚合物绝缘材料在强电场下发生的应力转化与补偿现象。发现外加电场可以转化为材料耐受的机械应力,形成机械应变;反之,外加机械应力或残余应力又可以补偿电场作用,影响材料的击穿电压和场强。这种转化和补偿的定量关系与材料的松弛特性有关,由此导出的材料击穿场强公式可用于定量评估应力/应变以及杨氏模量对材料介电性能的影响。

Si/InP材料的应力转化特性分析

InP材料被广泛的应用于光电子领域,但其材料脆、工艺不成熟、成本高,而Si基外延InP材料能良好的改善该技术瓶颈。论文中对不同介质、不同厚度的介质键合制备Si/InP材料进行了分析。其中以SiO2键合制备的Si/InP材料应力转化率最高,且SiO2制备工艺简单、亲水,材料键合强度大,机械特性好,是键合制备Si/InP材料的首选。而且,SiO2键合介质越薄,其应力转化率越高,材料对力学信号就越敏感,制备的Si/InP材料的机械性能越好。

阜山金矿区构造应力场及其转化的恢复

本文估算了阜山金矿区成岩成矿期构造差应力值 ,获得近 2km2 内主压应力和差异应力的空间分布规律 ,结果表明矿体部位往往对应于应力应变强烈变化区段 ,而并非极高值或极低值处。通过应变测量和磁组构分析 ,得到阜山金矿成岩期和成矿期构造应变场特征 ,指出阜山金矿构造应力场在成矿期经历了由NW向挤压转为NE向挤压转化的特征 。

截面应力内力相互转化的初步研究

渡槽等水工建筑物的三维有限元力学分析结果为应力形式,不能直接用来进行配筋设计,研究应力内力相互转化的方法,通过对梁的边界条件、应力特点的研究,得出了适用于一般情况的转化公式,编制了转化程序,经典题目和工程实例验证了方法的可行性。

论高应力软岩巷道支护对策

高应力软岩系指在高应力状态下发生显著塑性变形的工程岩体。本文研究了高应力软岩的基本特征、变形力学机制及其支护力学对策技术，并以峰峰矿务局通二矿高应力软岩巷道的支护工程为例，展示了新理论、新技术的应用前景。

强电场下非线性阻性介质中的应力补偿效应

传统聚合物中添加掺杂颗粒构成的复合应力控制材料是目前世界范围内的一个热门研究领域,其特有的场致非线性电阻特性使其能应用于套管型绝缘结构中,从而改善电场集中分布,提高设备耐受电压。研究发现,这一类非线性电阻型电介质在改善电场集中的同时,会将超过临界电应力的电场转化为热应力,以补偿原电场改善的部分;反之,该过程也存在等效的逆向效应,即试样温度的升高会使发生同等程度转化的场强值降低。这种发生在电介质中的应力转化和补偿现象使试样的介质损耗角正切tanδ随场强E变化的关系曲线出现回线形式。研究结果表明,这种应力转化的定量关系与电介质的松弛时间特性有关。

有限元法在船闸结构设计中的应用

船闸结构设计过程中,精确计算结构内力是混凝土配筋的关键因素。文中利用通用大型有限元软件,结合某大型船闸工程,计算了闸室在最不利工况下的应力、应变分布情况,并将应力结果转成为结构内力,与传统算法进行了对比,结果表明传统算法偏保守。同时,基于混凝土塑性损伤模型,分析评价了有限元计算的配筋结果,分析结果显示,该配筋满足规范要求,可供类似工程参考。

窄长型充填体的拱架效应及其对目标强度的影响

利用Belem模型计算拱架效应对于充填体垂直应力的转化率,分析充填体3种应力状态下的目标强度(支撑围岩、侧向暴露自立、支撑设备),对比拱架效应引入前后充填体垂直应力降低比率。结果表明:谦比希铜矿窄长形充填体自重应力为0.4 MPa,拱架效应转化后,充填体所受垂直应力仅为0.055 MPa,转化率达到86.25%,最大主应力为充填体宽度方向上的水平应力0.289 MPa;支撑围岩与设备要求强度1 MPa,自立要求强度0.2 MPa。窄长型充填体的目标强度设计应考虑拱架效应对于垂直应力的转化,从而降低相关技术经济指标。

硅基外延GaAs材料的力学仿真分析

Si,GaAs,Si基异质外延GaAs三种材料的基本力学特性各有不同,通过理论计算和ANSYS仿真得出相同条件下Si基异质外延GaAs材料中GaAs应力转化率是Si和GaAs材料的1.26倍左右,应力造成的位移系数略小于Si,远远小于GaAs,同时经过计算得出Si基异质外延GaAs材料的量程是GaAs材料的5倍,说明Si基外延GaAs材料不仅机械特性良好,而且还明显优于Si和GaAs,有更好的力电耦合效应需要的机械特性。

构造物理化学成矿理论问题探讨

构造物理化学成矿研究涉及以下新的认识:构造体制下矿源岩系演化序列,构造动力热液淬取成矿机制,构造附加动力驱动热液成矿机制,构造应力场转化成矿机制,成矿流体水-岩反应的浓缩成矿机制以及构造物理化学场结构与界面成矿特点。

Mechanical model for failure modes of rock and soil under compression

The failure modes of rock and soil under compression are complex phenomena that have not been explained in a mechanical perspective. However, large amounts of studies indicate that the failure modes of rock and soil samples can be categorized into eight types. In this work, the inner tensile stress and the dissipation and conversion of energy of rock and soil under compression are analyzed, then the effective conversion coefficient of energy is deduced, thus the tensile failure criterion of rock and soil under compression is established. Combined with the shear strength criterion of Mohr–Coulomb, a tensile joint shear strength criterion for rock and soil under compression is built. Therefore, a mechanical criterion model concerning the failure modes of rock and soil under compression is established and verified by tests. This model easily explains the test results in the existing literature and many natural phenomena, such as collapse.

Siderite pyrolysis in suspension roasting:An in-situ study on kinetics,phase transformation,and product properties

Siderite,as an abundant iron ore,has not been effectively utilized,with a low utilization rate.In this study,the in-situ kinetics and mechanism of siderite during suspension magnetization roasting(SMR)were investigated to improve the selective conversion of siderite to magnetite and CO,enriching the theoretical system of green SMR using siderite as a reductant.According to the gas products analyses,the peak value of the reaction rate increased with increasing temperature,and its curves presented the feature of an early peak and long tail.The mechanism function of the siderite pyrolysis was the contraction sphere model(R_(3)):f(α)=3(1−α)2/3;E_(α)was 46.4653 kJ/mol;A was 0.5938 s^(−1);the kinetics equation was k=0.5938exp[−46.4653/(RT)].The in-situ HT-XRD results indicated that siderite was converted into magnetite and wüstite that exhibited a good crystallinity in SMR under a N_(2) atmosphere.At 620℃,the saturation magnetization(M_(s)),remanence magnetization(Mr),and coercivity(Hc)of the product peaked at 53.63×10^(-3)A·m^(2)/g,10.23×10^(-3)A·m^(2)/g,and 12.40×10^(3)A/m,respectively.Meanwhile,the initial particles with a smooth surface were transformed into particles with a porous and loose structure in the roasting process,which would contribute to reducing the grinding cost.

Investigation of Propene Oligomerization Catalyzed by Phosphotungstic Acid Catalysts

In this paper, the propene oligomerization reaction catalyzed by phosphotungstic acid supported on two kinds of silica gel was studied, it had been found out that the conversion of propene catalyzed by the type A silica gel-phosphotung- stic acid catalyst was 3.38 m%, while the conversion of propene catalyzed by the type B silica gel-phosphotungstic acid catalyst was 90.1 m% with a nonene selectivity of 42.33 m%, and a dodecene selectivity of 31.79 m%. The influence of reaction temperature, pressure and liquid hourly space velocity （LHSV） on the reaction catalyzed by the type B silica gel- phosphotungstic acid catalyst was investigated. It had been verified that when the reaction temperature increased from 170 ~C to 190 ~C, the conversion of propene increased while the selectivity of nonene and dodecene decreased; when the re- action pressure increased from 3.5 MPa to 4.5 MPa, the conversion of propene increased also, and the selectivity of nonene and dodecene changed very little. The conversion of propene at a space velocity of between 0.5 h-1 and 1.0 h-~ was higher than that achieved at 2.0 h-~, but the selectivity of nonene and dodecene did not show regular fluctuations. An optimum conversion of propene （91.05 m%） and an optimum selectivity of nonene and dodecene （89.51 m%） could be achieved at a reaction temperature of 170 ~C, a reaction pressure of 4.5MPa, and a LHSV of 1.0 fit. The experiments on catalyst life showed that the activity of the type B silica gel-phosphotungstic acid catalyst could be only maintained in 25 hours, and the reason was explained also.

Kinetics of celestite conversion to acidic strontium oxalate hydrate in aqueous solution of oxalic acid

Conversion of SrSO4 to acidic strontium oxalate hydrate(H[Sr(C2O4)1.5(H2O)]) in aqueous H2C2O4 solutions proceeds as a consecutive reaction. In the first step of the consecutive reaction, SrSO4 reacts with H2C2O4 and pseudomorphic conversion to SrC2 O4·H2O occurs. In the second step, SrC2 O4·H2O reacts with H2C2O4 to form H[Sr(C2 O4)1.5(H2O)]. Sr(HC2 O4)(C2 O4)0.5·H2 O crystallizes during cooling of the reaction mixture to room temperature if the solution reaches the saturation concentration of (H[Sr(C2O4)1.5(H2O)]. The aims of this study are the derivation of reaction rate equations and the determination of the kinetic parameters such as pre-exponential factor, apparent activation energy and order of H2C2O4 concentration for each reaction step.Fractional conversions of SrSO4 were calculated using the quantitative amounts of dissolved S and Sr. It was determined that the reaction rate increased at the initial time of reaction by increasing the temperature using solutions with approximately same H2C2O4 concentrations. The reaction extends very slowly after a certain time in solutions with low H2C2O4 concentration and ends by the formation of a protective layer of SrC2O4-H2O around the surfaces of solid particles. Fractional conversion of SrSO4 is increased by increasing concentration of H2C2O4 at constant temperature. Kinetic model equations were derived using shrinking core model for each step.

Inversion of the Volumetric Strain of Aquifer According to the Tidal Effect of Groundwater in North China

The change of the confined aquifer level reflects the pore pressure change,and the pore pressure change of the aquifer is closely related to the aquifer pressure. This paper uses the tidal response of the well water level data in the North China region to calculate the tidal factor of each well and extract the effective water trend information. Then,the volumetric strain of an existing confined aquifer well in the North China region is inverted,and the contour maps are plotted on a half-year scale from 2009 to 2012. Results show that it can reflect the state of stress and strain in deep crust to a certain extent in the North China region.

Research on the Applications of Advanced Mathematics on Mathematical Modeling and the Inner Connections with Linear Algebra and Probability Statistics

In this paper, we conduct research on the applications of advanced mathematics on the mathematical modeling and the inner connections with linear algebra and the probability statistics. Aiming at model in mathematical modeling and solving and model of evaluation and promotion of the two links, put forward the ＂bystander＂ and ＂the authorities＂ this two characters, and points out that excellent mathematical modeling participants should have ＂from a bystander to the authorities＂ and ＂from the authorities to return to bystanders＂ two-way role transformation ability. Great situation in mathematics teaching, by means of the mathematical modeling formed in the development of the teachers, as well as the teaching thought, teaching experience and achievements, the onward march of mathematical experiment should be faster than mathematical modeling. Our research provides the new paradigm for the math development which will be meaningful.

A Molecular Dynamic Modelling of Cross-Linked Epoxy Resin Using Reactive Force Field： Thermo-Mechanical Properties

The reactive force field was used to study the molecular dynamics of cross-linked EPON 862 （diglycidyl ether of bisphenol-F） and DETDA （diethylene toluene diamine） system in order to predict its thermo-mechanical behavior under different loading conditions. The approach for building the EPON 862/DETDA structures, cross-linking, and equilibration of the systems, and the evaluation of the models are presented. The mechanical properties such as Young＇s and shear moduli, Poisson ratio, and yields strength as well as thermal properties such as glass transition temperature and coefficient of thermal expansion are predicted. The results are in close agreement with both experimental data and simulated results in literature.

输水盾构隧洞复合衬砌结构设计计算研究

软土有压输水盾构隧洞采用管片外衬和整筑预应力内衬作复合式衬砌的设计计算中,为能较好考虑内衬与外衬管片的相互作用,以及内衬预应力荷载在隧洞施工和运营各阶段对复合衬砌结构受力的影响,本文提出了一种新的实体叠合计算模型。由于确定管片纵缝接头抗弯刚度的复杂性,文中建议对用数值模拟管片纵缝接头刚度采用了一种非线性耦合弹簧"接触对"的模拟系统。在采用实体单元建模的条件下,由于计入管片接头刚度的力学处理困难,文中研究了一种能以模拟管片接头刚度的简化计算方法。根据内、外衬砌接触界面处理方式的不同,文中提出了5种适合不同界面条件内、外层衬砌的相互作用模型。此外,本文还研制了内衬预应力荷载的一种转化程序,以解决采用等效荷载法施加预应力时的前处理问题。上述各点创意构思已在南水北调中线一期穿黄隧洞的结构设计研究中得到了具体反映和成功应用。

Transgenic barley with overexpressed PTrx increases aluminum resistance in roots during germination

A transgenic barley line(LSY-11-1-1) with overexpressed Phalaris coerulescens thioredoxin gene(PTrx) was employed to measure the growth,protein oxidation,cell viability,and antioxidase activity in barley roots during germination on the presence of 2 mmol/L AlCl3 on filter paper.The results show that(1) compared with the non-transgenic barley,LSY-11-1-1 had enhanced root growth,although both were seriously inhibited after AlCl3 treatment;(2) the degree of protein oxidation and loss of cell viability in roots of LSY-11-1-1 were much less than those in roots of non-transgenic barley,as reflected by lower contents of protein carbonyl and Evans blue uptakes in LSY-11-1-1;(3) activities of catalase(CAT) ,glutathione peroxidase(GPX) ,ascorbate peroxidase(APX) ,and glu-tathione reductase(GR) in LSY-11-1-1 root tips were generally higher than those in non-transgenic barley root tips,although these antioxidase activities gave a rise to different degrees in both LSY-11-1-1 and non-transgenic barley under aluminum stress.These results indicate that overexpressing PTrx could efficiently protect barley roots from oxidative injury by increasing antioxidase activity,thereby quenching ROS caused by AlCl3 during germination.These properties raise the possibility that transgenic barley with overexpressed PTrx may be used to reduce the aluminum toxicity in acid soils.