冻融循环对路基土物理力学性质影响分析

本文选择了3种典型的东北三省路基粘土作为研究对象,在进行含水率试验、土的密度试验、土的颗粒大小分析试验、土的液、塑限试验、击实试验、土的回弹模量试验等基础上,制作静三轴试件进行试验。试验中,对3种土分别进行了0—8次冻融循环,对其静三轴试验数据进行整理分析发现：冻融作用后土的粘聚力和抗剪强度降低,摩擦角在3种土中变化不一致;随着冻融循环次数的增加,土的力学指标变化趋于平缓;横向来看,3种土由于基本属性参数的不同,受冻融影响在细节方面略有差异,但总体趋势相同。     

Optimal combined set-up and calibration policy

The optimal level to which the mean of a critical variable should be set-up, and the optimal number of repetitions until recalibration, has been jointly determined for the case where the variable is distributed normally and the mean changes linearly with the number of repetitions. It was proven that the optimal set-up level should be below the midpoint between the specification limits by a distance which depends on the slope of change of the mean and on the recalibration cycle, in such a manner that just prior to the recalibration the mean reaches the same distance above the midpoint. A method has been outlined for the numerical evaluation of the optimal number of cycle repetitions, and a general approximation formula was derived, which allows its closed-loop determination. A numerical example and sensitivity analysis are provided.     

On the issue of investigating the strength of the IVV.10M reactor vessel and internals

The questions of strength and seismic stability of a new water-moderated water-cooled research reactor are examined. A computational method is developed and numerical investigation of static capacity and stability, brittle fracture resistance, long-term static capacity, long-term cyclic strength, and seismic load response is carried out. The most loaded parts in the reactor vessel and internals are identified, and quantitative estimates of the deflected mode parameters in risk areas are obtained. The results of calculations are compared with normative documents applicable in the domestic nuclear power industry. The equivalence of new design solutions to the requirements of reactor plant trouble-free operation during the life cycle not only under normal operating conditions but also in an extreme situation, in particular, by an earthquake, is proved.     

旋转压实方法在沥青混合料配合比设计中的试验研究

分别采用马歇尔击实方法和旋转压实方法进行AC-13沥青混合料体积设计,并对两种方法得到的指标进行对比分析。结果表明,旋转压实方法所确定的最佳沥青用量比马歇尔击实方法所确定的最佳沥青用量明显降低,而且其动稳定度（次/mm）、冻融劈裂抗拉强度比、残留稳定度等路用性能都得到了很大的提高。     

Ⅲ类季节性冻土场地对圆柱形储液罐地震反应的影响

季节性冻土场地从未冻结状态过渡到冻结状态或反向循环,土体的物理力学性质将发生巨大变化,各种强度指标大幅度提高或衰减。中国东北、华北及西北大部分地区烈度在7度以上。立式圆柱形储液罐一旦在地震中遭受破坏,其损失不仅为罐体本身和所储存的介质,更为严重的是它所产生的次生灾害。以Ⅲ类季节性冻土场地上的八种立式储罐为研究对象,计算了场地在非冻结期和冻结期两种情况下储罐的地震反应,并对计算结果进行了对比分析。结果表明Ⅲ类季节性冻土场地上的储罐,冻结期的地震反应要比非冻结期的地震反应明显增大。     

Artefacts in the mechanical characterization of porcine articular cartilage due to freezing

Many experimental protocols for investigating articular cartilage mechanics have involved the use of a freeze-thaw cycle for storage or tissue manipulation. It was hypothesized that mechanical properties are altered due to freeze-thaw cycling. The aim of this study, therefore, was to examine the possibility of protocol-induced artefacts in the mechanical properties of porcine articular cartilage specimens related specifically to freeze-thaw events. Twenty-eight osteochondral specimens [14 from the femoral condyles (FCs) and 14 from the patella-femoral (PF) groove] were tested in confined compression before and after being frozen at -20 degrees C for 7 days. The fluid-independent and fluid-dependent mechanical properties (aggregate modulus of the solid phase and the half-life of stress relaxation respectively) were determined and compared. The aggregate modulus decreased by 13.5 per cent and 20.1 per cent for the PF and FC regions respectively (p = 0.002) and the half-life of the stress relaxation at 10 per cent strain decreased by 6.4 per cent and 12.6 per cent for the PF and FC specimens respectively (p = 0.0341). In conclusion, it has been shown that the protocol used, which involved freezing to -20 degrees C and thawing after 7 days, caused artefacts in the mechanical properties of porcine osteochondral specimens. It is suggested that protocols requiring freezing must be critically reviewed to eliminate such artefacts.     

适合于土压力测试的新型光纤光栅传感器性能研究

土压力测量是土力学研究要点,传统土压力传感器因不具备长期稳定、耐久性和抗电磁干扰等功能无法满足结构监测要求.光纤光栅,因有精度高、体积小、耐腐蚀等优点,被作为传感元件,设计了一种新型光纤光栅土压力传感器,理论分析其测压原理及可行性,并以实验方式对该传感器性能进行校核.研究表明:此光纤光栅土压力传感器的温度自补偿功能、线性度和重复性、总精度等都较好,满足工程需求,能用于岩土工程结构的长期健康监测.     

多通道疲劳试验加速实例

提供了一个在开发产品时如何使用疲劳编辑技术缩短疲劳试验时间的实际例子,特别说明了将疲劳分析和试验联系在一起的“一体化耐久性管理”过程所带来的好处,并突出了选择一种满足工程需要的方法的重要性。     

加载方式对深部人工冻结粘土力学参数影响试验研究

采用自行研制的W3Z-200型冻土三轴试验机,试验研究了加载方式对深部人工冻结粘土力学特性的影响,结果表明,加载方式不同对冻土的强度及力学参数影响明显,其中CTC试验所获得的冻结粘土剪切强度、内聚力及内摩擦角都比RTC试验所获得的相应指标大。无论何种试验加载方式,冻结粘土的剪切强度都与围压关系不大,只随着温度的降低而增大,而内摩擦角则有随着温度的降低而减小的趋势。     

当量屈服强度法在双层管液压成形中的应用

当量屈服强度法在工程中广泛应用。双层管液压成形理论分析中,以内层管真实应力应变曲线的计算过程相当复杂,很难得到准确的解析解且难以满足工程的需要。在总结分析前人工作的基础上,提出了适用于双层管液压成形的当量屈服强度法,给出了确定当量屈服强度的具体步骤。研究结果表明：应用该方法能有效地提高理论计算的精度,与试验值符合良好,计算数据与试验值之间的最大误差为1.02％,为液压成形双层管的工业生产提供较为科学的依据。     

Materials selection for environmentally conscious design via a proposed life cycle environmental performance index

Although product design methods are well developed, the recent rise of environmentally conscious design, which includes materials selection as a key element, mandates the development of new engineering tools for decision-making. In this investigation, a method for establishing a life cycle environmental performance index is developed; it is envisioned that the index can be integrated into an environmentally conscious design process. The method addresses such traditional design factors as structural constraints and incorporates an additional consideration, the life cycle environmental impact. The method is applied to the design of an air conditioner support plate. In this application, it is desired to select a material that provides minimal environmental impact, subject to stiffness and strength constraints. Pareto optimization is adopted to analyze the results. The case study shows that the decision-making analysis can provide design guidelines and a criterion for materials selection to achieve environmentally conscious design.     

基于广义延拓逼近的暂态稳定分析

在求解暂态稳定的问题中给迭代计算一个更好的初值,则能加速网络方程的迭代速度,减少迭代次数.提出了广义延拓算法,并应用于网络方程迭代求解的初值预测,最后通过仿真算例证明了它的有效性.研究结果同时表明,此算法和传统方法相比,能减少计算量,从而节省暂态稳定分析的时间,具有广阔的推广应用前景.     

Strength measurement and textural characteristics of tropical residual soil stabilised with liquid polymer

The stabilisation of soils with additives is a chemical process that can be used to improve soils that contain weak engineering properties. The effects of non-traditional additives on the geotechnical properties of soils have been the focus of much investigation in recent years. It has been well established that the plasticity index and also the size, shape, and arrangement of soil particles will affect the treatment process of natural soils with additives. In this study, a commercial liquid polymer (SS299) was used to improve the strength of Malaysian residual soil. Unconfined compressive strength (UCS), field emission scanning electron microscopy (FESEM), N₂-BET surface area, and particle size analysis tests were used to investigate the influence of SS299 and the plasticity index on the time-dependent compressive strength and textural characteristics of tropical residual soil. The UCS results showed that the addition of 6% (as the optimum amount) of the selected additive increased the compressive strength of laterite soil noticeably, after 7 days of curing period. In addition, the increased compressive strength of the treated samples with the curing time was evident. Based on the FESEM results, it was found that the stabilisation process modified the porous network of the laterite soil. Furthermore, new white layers of reaction products were formed on the surface of clay particles.     

Designing a control mechanism using earned value analysis: an application to production environment

Earned value analysis is a project performance method which simultaneously presents both cost and schedule performances. The purpose of this paper is to model the uncertainty associated with activity duration in earned value analysis. The approach incorporates to design a control mechanism, which would be applicable through production control as well as project management problems. The job processing times have been considered as triangular fuzzy number. Costs are assumed to be directly related to fuzzy activity time, which are estimated through a bottom up hierarchy process. Consequently, different earned value metrics have been achieved. Research findings provide an efficient control mechanism in earned value analysis, which would be highly applicable in production control area. This research also yields a novel approach for representing a production performance index during implementation of production processes. In addition to the above mentioned issues, forecasting features can be further performed for predicting completion time of products for delivery to the customer. The approach presented in this paper has been successfully implemented through a multi-period–multi-product production planning problems, which efficiently demonstrates the applicability of the proposed control mechanism.     

破碎带小岩体三轴试验方法探讨

在工程实践中,岩体的抗剪强度参数是评价工程稳定性的重要依据,三轴试验则是获取岩体抗剪强度参数最重要的方法之一。然而有些大型工程地基岩体中存在大量破碎带,该区域既无条件进行现场三轴试验,也没有办法取得足够岩样在室内进行常规三轴试验。在这种特殊情况下,需要寻找一种新的试验方法获得破碎小岩体的抗剪强度参数。本文对取自某水电站坝基破碎带小岩体进行了室内多点三轴试验（常规三轴试验）和单点三轴试验,利用莫尔库伦强度理论,计算小岩体的抗剪强度参数内聚力C值和内摩擦角φ值。通过对两种试验结果的分析和比较,得出单点试验方法是可行的,试验结果是可用的。本文研究结果对用室内方法获得破碎带小岩体的抗剪强度参数进行了有益探索,丰富了室内岩石试验方法。     

Supercooling release of micro-size water droplets on microporous surfaces with cooling

The gas diffusion layer (GDL) of polymer electrolyte membrane fuel cells plays a key role in controlling moisture in these cells. When the GDL is exposed to a cold environment, the water droplets or water nets in the GDL freeze. This work observed the supercooling and freezing behaviors of water droplets under low temperature. A GDL made of carbon fiber was coated with a waterproof material with 0%, 40%, and 60% PTFE (polytetrafluoroethylene) contents. The cooling process was investigated according to temperature, and the water droplets on the GDL were supercooled and frozen. Delay in the supercooling release was correlated with the size of water droplets on the GDL and the coating rate of the layer. Moreover, the supercooling degree of the droplets decreased as the number of freeze-thaw cycles in the GDL increased.

     

基于人的可靠性分析的防错设计研究

应用防错法预防制造过程差错是一种很好的方法,针对制造过程防错遇到的问题,提出面向制造质量的防错设计概念,给出面向制造质量防错设计的研究内容和体系结构;而面向制造质量的防错设计中最为关键的是制造过程差错的识别与预测,为了更为准确地识别和预测制造过程中的人为差错,首次将人的可靠性分析引入到制造过程,提出用成功似然指数法来识别产品制造中人为差错并预测其概率,最后以后轴销支座为例,对上述理论进行验证.     

基于多色集合的微线段齿轮表面工程技术工艺建模

针对产品零部件表面工程技术工艺建模复杂的问题,以多色集合理论为辅助对表面工程技术工艺建模进行深入研究。首先,运用多色集合理论选择表面工程技术方法并对工艺规划进行数学建模,建立表面功能需求映射矩阵和表面工程技术工艺需求围道矩阵。然后,将表面处理技术工艺需求划分为循环需求和线性需求,通过进化算法和多色图理论分别对两种需求对应的工艺路线进行求解。最后,以微线段齿轮的表面处理工艺过程作为验证,获得合理的表面处理工艺路线。     

预测铣削稳定性的隐式Adams方法

针对铣削加工过程中产生的振动现象,提出了一种隐式Adams方法（Implicit Adams method,IAM）来预测铣削加工过程的稳定性。考虑再生颤振的铣削加工动力学方程可以表示为时滞线性微分方程,将刀齿周期可分为自由振动阶段和强迫振动阶段,对强迫振动阶段进行离散,运用IAM方法构建状态传递矩阵,利用Floquet理论,判定系统的稳定性,获得系统的稳定性叶瓣图。Matlab软件仿真结果表明,IAM方法是预测铣削稳定性的一种有效方法。随着离散数的增加,IAM方法的收敛速度要快于一阶半离散法（First-order semi-discretization method,1st-SDM）和二阶全离散法（Second-order full-discretization method,2nd-FDM）,离散数较少的IAM方法能达到离散数较多的1st-SDM方法和2nd-FDM方法的局部离散误差。此外,在单自由度和双自由度动力学模型下,三种方法的稳定性叶瓣图显示,IAM方法预测铣削稳定性的预测精度均好于1st-SDM方法和2nd-FDM方法,计算效率远远高于1st-SDM方法,稍高于2nd-FDM方法。切削试验和仿真结果表明,IAM方法的预测精度和可靠度均好于1st-SDM方法和2nd-FDM方法。     

冻胀力测试的实验装置设计

冻土问题，一直被认为是建设冻土地区交通基础设施的一项世界难题。考虑到冻土的力学性质与环境的依赖关系，为掌握冻土的力学性质以及应力的真实分布情况，冻胀力的测试必须在现场完成。本实验装置以套孔应力解除法为原理，再充分地考虑了冻土层的特性后，设计了一机多用的应力测试装置。