考虑初始椭圆度的套管抗载能力分析

针对套管的不同初始椭圆度建立了套管、水泥环、地层平面应变力学模型。分析认为,在非均匀地应力作用下,套管内壁的径向变形较大,抗载能力明显降低,破坏主要是由地下非均匀地应力引起的;随着初始椭圆度的增加,在地应力作用下套管各部位产生的应力分布不均程度增大,使得套管抗外载能力减弱。建议在生产和使用过程中应严格将套管椭圆度控制在规定的范围内,从而提高套管的抗载能力。

重载铁路桥上长枕埋入式无砟轨道混凝土轨枕的研制

长枕埋入式无砟轨道在重载铁路上应用优势明显,研制混凝土轨枕产品非常必要。根据长枕使用的特殊性进行特殊外形设计、配筋计算,特别对长枕截面的静载抗裂能力做了简化计算,确认其抗弯能力的储备情况,采用两种设计方案对比选出最优方案,通过检验静载试验抗弯能力、观测后期的收缩变形等,确认了设计产品能够满足重载铁路无砟轨道线路的使用。介绍轨枕生产的工艺流程和关键技术,产品外观质量、静载抗弯性能满足技术要求,可在重载铁路线路上推广使用。

TBR轮胎胎体帘线稀并线原因分析与对策

分析TBR轮胎胎体帘布稀并线异常的产生原因,并提出相应解决方案。胶料流动性、工艺工装磨损、帘布渗胶质量、压延张力波动、胶部件接头缺陷、帘布局部拉伸等因素均会造成胎体帘线间距排列异常,通过优化混炼工艺、工艺工装精细管理、提升帘布渗胶质量、稳定钢丝压延张力、严控压延机积胶均一性与部件接头质量等措施,可有效解决胎体稀并线异常问题。

AR-20沥青改性剂性能评价

介绍了沥青改性剂 AR-2 0的基本性能 ,考察了 AR-2 0对沥青性能的影响 ,以及对沥青混合料的抗车辙能力。

化工设备

XFG新型多功能粉体干燥机XFG新型多功能粉体干燥机是靖江市新思维石化设备厂近几年根据粉体行业的特殊要求进行独特设计的高效率粉体干燥机。该机结构紧凑,占地面积小;粉碎装置采用动静结构,运行平稳;旋转气流速度不受系统干扰,产品质量稳定;具有多种进料方式,可以无级变速来调整进料量;产品细度和水分易于调整,并可根据用户条件分别选用蒸气、电、燃油、燃气热风炉或烟道气等加热方式。

Influence of steel corrosion to flexural behavior of coral aggregate concrete beam

To study the flexural behavior and calculation model,8 coral aggregate concrete(CAC)beams with different types of steel were designed.The flexural behavior of CAC beam was tested.The failure mode,bearing capacity,the maximum crack width(ws)and average crack spacing(lm)were studied.A calculation model for the bearing capacity of CAC beam was proposed.The results indicated that with the steel strength increased,the cracking moment(Mcr)and ultimate moment(Mu)of CAC beam increased,and the development of the ws gradually slowed,which effectively inhibited the formation of cracks and improved the flexural behavior of CAC beam.For CAC structures in the ocean engineering,it is recommended to use organic new coated steel to extend its effective service life.In addition,considering the influence of steel corrosion,a calculation model for the Mcr,Mu,lm and ws of CAC beam was established.

Technology of load-sensitivity used in the hydraulic system of an all-hydraulic core rig

The existing hydraulic system always have problems of temperature rise,runningstability and anti-interference of the implementation components,reliability of hydrauliccomponents,maintenance difficulties,and other issues.With high efficiency,energysaving,reliability,easy operating,stable running,anti-interference ability,and other advantages,the load-sensitive hydraulic system is more suitable for coal mine all-hydrauliccore rig.Therefore,for the technical development of the coal mine all-hydraulic core rig,the load-sensitive technology employed by the rig should be of great significance.

A new PMSM speed modulation system with sliding mode based on active-disturbance-rejection control

A sliding mode and active disturbance rejection control(SM-ADRC)was employed to regulate the speed of a permanent magnet synchronous motor(PMSM).The major advantages of the proposed control scheme are that it can maintain the original features of ADRC and make the parameters of ADRC transition smoothly.The proposed control scheme also ensures speed control accuracy and improves the robustness and anti-load disturbance ability of the system.Moreover,through the analysis of a d-axis current output equation,a novel current-loop SM-ADRC is presented to improve the system’s dynamic performance and inner ability of anti-load disturbance.Results of a simulation and experiments show that the improved sliding-mode ADRC system has the advantages of fast response,small overshoot,small steady-state error,wide speed range and high control accuracy.It shows that the system has strong anti-interference ability to reduce the influence of variations in rotational inertia,load and internal parameters.

Design of micropiles to increase earth slopes stability

A methodology was proposed for the design of micropiles to increase earth slopes stability. An analytic model based on bearn-colurnn equation and an existing P-y curve method was set up and used to find the shear capacity of the micropile. Then, a step-by-step design procedure for stabilization of earth slope with rnicropiles was introduced, involving six main steps： 1） Choosing a location for the rnicropiles within the existing slope; 2） Selecting micropile cross section; 3） Estimating length of rnicropile; 4） Evaluating shear capacity of mieropiles; 5） Calculating spacing required to provide force to stabilize the slope; 6） Designing the concrete cap beam. The application of the method to an embankment landslide in Qinghai Province was described in detail. In the final design, three rows of rnicropiles were adopted as a group and a total of 126 rnicropiles with 0.23 m in diameter were used. The micropile length ranged between 15 and 18 m, with the spacing 1.5 m at in-row direction. The monitoring data indicate that slope movement has been effectively controlled as a result of the slope stabilization measure, which verifies the reasonability of the design method.

Moisture effect on compressive behavior of concrete under dynamic loading

The effect of moisture content upon compressive mechanical behavior of concrete under impact loading was studied. The axial rapid compressive loading tests of over 50 specimens with five different saturations were executed. The technique "split Hopkinson pressure bar"(SHPB) was used. The impact velocity was 10 m/s with corresponding strain rate of 50 s-1. The compressive behavior of materials was measured in terms of stress-strain curves, dynamic compressive strength, dynamic increase factor(DIF) and critical strain at a maximum stress. The data obtained from test indicate that both ascending and descending portions of stress-stain curves are affected by moisture content. However, the effect is noted to be more significant in ascending portion of the stress-strain curves. Dynamic compressive strength is higher at lower moisture content and weaker at higher moisture content.Furthermore, under nearly saturated condition, an increase in compressive strength can be found. The effect of moisture content on the average DIF of concrete is not significant. The critical compressive strain of concrete does not change with moisture content.

Design and energy absorption enhancement of vehicle hull under high dynamic loads

V-shape hulls are widely used in peacekeeping efforts such as demining vehicles in order to deflect the blast energy and reduce the effects of mine blast. Blast resistant design and energy absorption enhancement of V-shape plates were carried out using finite element analysis package ABAQUS. Various geometries of V-shape plates with and without interlayer of materials like Al-foams and honeycomb were employed to analyze their effects on the deformation of the plate and applied stresses and strains. The results obtained show that application of metallic foams leads to better response of the plate and consequently results in more energy dissipation, less dame to vehicle and enhances crew survivability.

Automatic Carrier Landing System with Gust-rejection Capability

A new direct-lift control carrier landing mode is advanced, and it is proved to be very effective to keep the attitude angle and path angle constant when the aircraft is in the blind area of tracking radar and the guidance system is shut off. The direct-lift control mode is achieved with the symmetric deflection of the flaps and dynamic decoupling for minor disturbance of the angle of attack. This mode changes an aircraft' s model from a short-period oscillation model to a non-oscillation one, which could evidently increase the gust-rejection capability of the aircraft.

Seismic failure mode improvement of RC frame structure based on multiple lateral load patterns of pushover analyses

The structural failure under severe ground motions is primarily caused by their unreasonable seismic failure mode (SFM). This paper provides a methodology aiming at the SFM improvement of reinforced concrete frame structure. An RC frame is modeled and three types of failure criterion are defined as the premise of SFM. Static pushover analysis is adopted to identify the SFM. The dominant failure modes and failure paths of the structure are obtained in three lateral load patterns (inverted trian- gular distribution, uniform distribution and adaptive distribution). Based on the pushover analysis, the sequential failure of components and the probability of the occurrence of plastic hinges are determined. By this, weak components of the structure are detected and herein are strengthened. The project cost of the proposed strengthening strategy increases by 2.4%. Capacity spectrum method is used to study the performance of the strengthening structure. Pushover analysis is conducted again to present the improvement of strength and ductility. Lateral drift and local response through IDA are also studied to indicate that the strengthening of some columns and beams can improve the SFM to enhance the seismic capacity of structure.

Navigation signal structure based on complex carrier modulation

Signal structure design is an important part of satellite navigation system research,which directly affects navigation performance.Signal performance parameters are analyzed and performances of BPSK modulated signals and BOC modulated signals are compared.Aiming at requirements of high navigation precision and high anti-jamming ability,a new navigation signal structure based on complex carrier modulation is proposed and performances of the signal are researched with different parameters.A synchronization algorithm is put forward according to the signal characteristics,and the synchronization performance is qualitatively analyzed.Next,the applications of the complex carrier modulated signal are discussed,which include anti-jamming,navigation enhancement,power combing and so on.Simulations and analysis show that the proposed navigation signal structure based on complex carrier modulation has good navigation capabilities and anti-jamming abilities,which deserves further study.

Advanced Unified Failure Model on Uniformly Reinforced Concrete Box Section Members

Based on the traditional Nielsen model,a unified failure model on the uniformly reinforced concrete box section members under combined forces was introduced by Luo and Liu.One of their contributions is adjustment of the shear carrying capacity of concrete at the member failure surface.In the unified failure model,the comparison with the experimental results verified this adjustment.Nevertheless,it should be pointed out that the adjustment factor of shear carrying capacity at member failure surface for the reinforced concrete members in the unified failure model is a fixed adjustment constant for all experiment data,which is basically determined by curve fitting.However,the adjustment factor should vary with the normal stress at the member failure surface.In this paper,an advanced theoretical model is introduced,in which the adjustment factor of shear carrying capacity at failure surface is a variable related to the normal stress at failure surface.Furthermore,the advanced unified failure model on the uniformly reinforced concrete box section member can still be expressed in a simple form.Finally,the comparison with several groups of test data has verified that this advanced model is more accurate and feasible to be used in design.