不同处理工艺轴承套圈的近表层硬度及残余应力

对M50钢轴承套圈、M50NiL钢渗碳轴承套圈及M50NiL钢渗碳+渗氮复合化学热处理轴承套圈的显微组织、硬度及残余应力进行了测试及分析,并对M50钢轴承套圈和M50NiL钢渗碳轴承套圈进行了硬度、应力和寿命耐久性试验。结果表明:复合化学热处理后,M50NiL钢轴承套圈的表面及心部硬度比M50NiL钢渗碳轴承套圈的有所提高,其表面应力尤其是次表层应力有了极大提高,因此耐磨性和抗疲劳性能也得到极大的改善;M50NiL钢渗碳轴承套圈的抗疲劳性能及使用寿命比M50钢轴承套圈的提高了3~5倍。

离子交换法对建筑陶瓷力学性能的影响及强化机理研究

建筑陶瓷板的强度对于提高装饰材料寿命和节能环保有重大意义。离子交换法能通过有效增强陶瓷表层的面向挤压应力来提高陶瓷的断裂阻力和抗弯强度。影响陶瓷强化工艺的两个关键因素是离子交换温度和离子交换时间。本文采用KNO_(3)熔盐对建筑陶瓷板作离子交换强化处理,分析离子交换温度和离子交换时间对陶瓷样品力学性能的影响,并进一步探讨强化机理。结果表明,离子强化处理后陶瓷的抗弯强度、断裂韧性和表面硬度得到大幅提升,同时弹性模量和质量密度几乎不变。离子交换法通过KNO_(3)熔盐的K+与陶瓷表面的Na^(+)之间的置换反应在陶瓷表层形成预压应力抵消了部分破坏载荷。试验得出,在600℃下处理20h,样品的抗弯强度达到最大值216.10MPa,相比原始样品提升103.20%。

基于逆焊接技术的T122/P122钢环焊缝残余应力消除工艺

采用ABAQUS有限元软件生死单元技术针对逆焊接消除残余应力的工艺方法进行分析,模拟计算了T122/P122钢环焊缝的逆焊接消除焊接残余应力的工艺过程,分析了逆焊接消除残余应力的操作工艺中不同热处理温度、冷却速率、冷却范围、冷却时间对消残余应力效果的影响.结果表明,经过逆焊接处理后,Mises残余应力及环向残余应力均明显降低,且热处理温度对残余应力的消除影响最为显著,其次是冷却时间和冷却速率.当热处理温度为400℃,冷却时间为20 s时不仅可以消除焊接残余应力,还可以在处理表面形成1.3 mm厚的压应力层.

油井合理井底流压综合判定方法

合理井底流压是充分发挥油井产能、提高油田开发效益的保证,但现在缺乏一种合理的综合性判定方法。在分析生产气油比、产层出砂、应力敏感和层间干扰等4个因素对合理井底流压影响规律的基础上,根据模糊变换原理建立了油井合理井底流压综合判定数学模型。利用该数学模型,可定量计算考虑不同因素、不同因素权值影响下的合理井底流压。实例计算表明,所建立的油井合理井底流压综合判定数学模型具有较高的计算精度,可为油井设计合理流压、配产提供理论指导;利用实例的数据分析了合理井底流压对渗透率变异系数、生产气油比、泊松比等参数的敏感性,结果表明:渗透率变异系数越大,为维持储层的渗流能力,需要保持越高的井底流压;生产气油比越高,为确保抽油泵泵效,需要保持越高的井底流压;对于泊松比较大的疏松砂岩储层,为防止地层出砂,需要保持较高的井底流压。

二步法化学强化屏幕保护玻璃组成和工艺发展及展望

碱铝硅酸盐玻璃(R2O-Al2O3-Si O2,R为Li/Na/K任一或几种组合)是显示终端重要屏幕保护材料.为进一步提升和改善屏幕保护玻璃的耐划伤和抗冲击性能,采用二步法化学强化工艺已成为新的技术发展趋势,围绕不同玻璃体系和化学组成分析比较表面压应力(compressive stress,CS)和离子交换层深度(depth of layer,DOL)特点,结果表明:不含Li2O的碱铝硅酸盐玻璃进行二步法化学强化后,玻璃表面的CS较第1步化学强化会有所减小,最大应力值向玻璃内部迁移,阻止了玻璃微裂纹向内部扩展的趋势;含Li2O的玻璃在进行二步法化学强化后,玻璃表面CS与DOL同时增加,表明2种玻璃化学强化机理不同.不含Li2O的玻璃在进行第1步化学强化时,纯KNO3熔盐中的K+交换了玻璃表面的Na+,这时CS达最大值,而进行第2步化学强化时,由于熔盐中加入一定比例的Na NO3降低了K+浓度梯度,使得第1步化学强化在玻璃表面积累的K+又被熔盐中的Na+交换出来;而含有Li2O的玻璃,第1步交换时采用KNO3与Na NO3的混合熔盐,主要目的是使熔盐中的Na+与玻璃中的Li+交换,到达一定深度,而后第2步采用比例更高的KNO3熔盐或者纯KNO3熔盐进行化学强化,使K+与第1步时进入玻璃表面的Na+交换,这样K+就可以到达玻璃更深处,从而达到增加CS与DOL的目的.同时从工艺和成本展望碱铝硅酸盐玻璃的化学强化工艺应回归到一步法二元离子交换工艺.

Nonlinear static characteristics of piezoelectric unimorph bending micro actuators

The nonlinear static characteristic of a piezoelectric unimorph cantilever micro actuator driven by a strong applied electric field is studied based on the couple stress theory.The cantilever actuator consists of a piezoelectric layer,a passive（elastic）layer and two electrode layers.First,the nonlinear static characteristic of the actuator caused by the electrostriction of the piezoelectric layer under a strong applied electric field is analyzed using the Rayleigh-Ritz method.Secondly,since the thickness of the cantilever beam is in micro scale and there exists a size effect,the size dependence of the deformation behavior is evaluated using the couple stress theory.The results show that the nonlinearities of the beam deflection increase along with the increase of the applied electric field which means that softening of the micro beam rigidity exists when a strong external electric field is applied.Meanwhile,the optimal value of the thickness ratio for the passive layer and the piezoelectric layer is not around 1.0 which is usually adopted by some previous researchers.Since there exists a size effect of the micro beam deflection,the optimal value of this thickness ratio should be greater than 1.0 in micro scale.

On the dissipation of negative excess porewater pressure induced by excavation in soft soil

Unloading induces negative excess porewater pressure in soil mass around a foundation pit during excavation. In this work, the dissipation rule of negative excess porewater pressure after excavation was studied. Analytical formulas for calculating the negative excess porewater pressures and the effective stresses were derived based on one-dimensional consolidation theory and Terzaghi’s effective stress principle. The influence of the dissipation of negative excess porewater pressure on earth pressure inside and outside a foundation pit and the stability of the retaining structure were analyzed through a numerical example. It was indicated that the dissipation of negative excess porewater pressure is harmful to the stability of the retaining structure and that rapid construction can make full use of the negative porewater pressure.

Buckling of un—stiffened cylindrical shell under non—uniform axial compressive stress

This paper provides a review of recent research advances and trends in the area of stability of unstiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses.Only the more important and interesting aspects of the research,judged from a personal viewpoint,are discussed.They can be crudely classified into four categories:(1) shells subjected to non-uniform loads;(2) shells on discrete supports;(3) shells with intended cutouts/holes;and (4) shells with non-uniform settlements.

In-situ stress measurements and stress change monitoring to monitor overburden caving behaviour and hydraulic fracture pre-conditioning

A coal mine in New South Wales is longwall mining 300 m wide panels at a depth of 160–180 m directly below a 16–20 m thick conglomerate strata. As part of a strategy to use hydraulic fracturing to manage potential windblast and periodic caving hazards associated with these conglomerate strata,the in-situ stresses in the conglomerate were measured using ANZI strain cells and the overcoring method of stress relief. Changes in stress associated with abutment loading and placement of hydraulic fractures were also measured using ANZI strain cells installed from the surface and from underground. Overcore stress measurements have indicated that the vertical stress is the lowest principal stress so that hydraulic fractures placed ahead of mining form horizontally and so provide effective pre-conditioning to promote caving of the conglomerate strata. Monitoring of stress changes in the overburden strata during longwall retreat was undertaken at two different locations at the mine. The monitoring indicated stress changes were evident 150 m ahead of the longwall face and abutment loading reached a maximum increase of about7.5 MPa. The stresses ahead of mining change gradually with distance to the approaching longwall and in a direction consistent with the horizontal in-situ stresses. There was no evidence in the stress change monitoring results to indicate significant cyclical forward abutment loading ahead of the face. The forward abutment load determined from the stress change monitoring is consistent with the weight of overburden strata overhanging the goaf indicated by subsidence monitoring.

Pressure relief, gas drainage and deformation effects on an overlying coal seam induced by drilling an extra-thin protective coal seam

Numerical simulations and field tests were used to investigate the changes in ground stress and deformation of, and gas flow from, a protected coal seam under which an extra-thin coal seam was drilled. The geological conditions were: 0.5 meter mining height, 18.5 meter coal seam spacing and a hard limestone/fine sandstone inter-stratum. For these conditions we conclude: 1) the overlying coal-rock mass bends and sinks without the appearance of a caving zone, and 2) the protected coal seam is in the bending zone and undergoes expansion deformation in the stress-relaxed area. The deformation was 12 mm and the relative defor- mation was 0.15%. As mining proceeds, deformation in the protected layer begins as compression, then becomes a rapid expansion and, finally, reaches a stable value. A large number of bed separation crannies are created in the stress-relaxed area and the permeability coefficient of the coal seam was increased 403 fold. Grid penetration boreholes were evenly drilled toward the protected coal seam to affect pressure relief and gas drainage. This made the gas pressure decrease from 0.75 to 0.15 MPa, the gas content decrease from 13 to 4.66 m3/t and the gas drainage reach 64%.

Evaluation of residual stress and corrosion behaviour of electroless plated Ni-P/Ni-Mo-P coatings

Single Ni-P and Ni-Mo-P coatings as well as duplex Ni-P/Ni-Mo-P coatings with the same compositions were prepared by electroless plating.The residual stresses of the coatings on the surface and cross sections were measured by nanoindentation and AFM analysis,and the corrosion behaviour of the coatings in10%HCl solution was evaluated by electrochemical methods,to establish the correlation between the residual stresses and corrosion behaviour of the coatings.The results showed that the single Ni-P and duplex Ni-P/Ni-Mo-P coatings presented residual compressive stresses of241and206MPa respectively,while the single Ni-Mo-P coating exhibited a residual tensile stress of257MPa.The residual compressive stress impeded the growth of the pre-existing porosity in the coatings,protecting the integrity of the coating.The duplex Ni-P/Ni-Mo-P coatings had better corrosion resistance than their respective single coating.In addition,the stress states affect the corrosive form of coatings.

30CrMoA车轴材料超声表面挤压强化技术研究

为了提高车轴疲劳强度,本文基于超声挤压强化技术,研究了其对列车专用30CrMoA车轴钢加工表面的影响.对比分析了超声挤压强化前后工件表面外观、表面粗糙度、残余应力等特征的变化,绘制了残余压应力沿层深分布的曲线.结果表明:超声强化后的试件表面达到了很好的镜面效果,表面光滑且具有光泽,消除了前道工序残留的环状纹路;表面粗糙度得到改善,粗糙度数值由原来的3.746μm降低到0.2μm左右,在前道工序的基础上下降了95%左右;原来的残余拉应力可以被调节成为压应力,残余压应力层的深度可以达到近2mm,阻止了疲劳裂纹的萌生和扩展,有利于提高金属材料的疲劳强度和使用寿命.

Distribution pattern of front abutment pressure of fully-mechanized working face of soft coal isolated island

The front abutment pressure of a fully-mechanized workface of 11061 soft coal isolated island of Liangbei Coal Mine was measured and studied using a self-developed mining-induced stress monitoring system associated with electromagnetic radiation technology, and the effects of abutment pressure distribution on strata behavior we discussed. The results indicate that the miningdnduced influencing distance advanced at the fully-mechanized working face of soft coal isolated island is larger than that at the gen- eral working face at the isolated island, besides the fracture zone in front of working face was widened to some extent, and the influencing range caused by relaxations on both roadways became bigger with the advancing working face. Moreover, it can be indicated that mining has significant effect on strata behav- ior of fully-mechanized working face of soft coal isolated island, which is mostly distributed in the area of stress concentration. The research results have an important reference value for revealing the distribution pattern of the front abutment pressure of a fully-mechanized working face of soft coal isolated island, and controlling the coal-rock dynamic disaster occurrence under similar mining conditions.

Study on determination method of in-situ stress using formation fracturing test and Kaiser effect method

A new method, which is based on formation fracturing test and Kaiser effect method, has been developed for confirming the oilfield in-situ stress in this paper. The new method has been used in a certain oilfield of China and the determined oilfield in-situ stresses is more accurate than that based on one single method.

Research into comprehensive gas extraction technology of single coal seams with low permeability in the Jiaozuo coal mining area

For a low permeability single coal seam prone to gas outbursts, pre-drainage of gas is difficult and inefficient, seriously restricting the safety and efficiency of production. Radical measures of increasing gas extraction efficiency are pressure relief and infrared antireflection. We have analyzed the effect of mining conditions and the regularity of mine pressure distribution in front of the working face of a major coal mine of the Jiaozuo Industrial （Group） Co. as our test area, studied the width of the depressurization zone in slice mining and analyzed gas efficiency and fast drainage in the advanced stress relaxation zone. On that basis, we further investigated and practiced the exploitation technology of shallow drilling, fan dril- ling and grid shape drilling at the working face. Practice and our results show that the stress relaxation zone is the ideal region for quick and efficient extraction of gas. By means of an integrated extraction technology, the amount of gas emitted into the zone was greatly reduced, while the risk of dangerous outbursts of coal and gas was lowered markedly. This exploration provides a new way to control for gas in working faces of coal mines with low permeability and risk of gas outbursts of single coal seams in the Jiaozuo mining area.

高速公路改扩建工程路面搭接宽度有限元分析

改扩建项目由于路面接缝的存在,容易造成接缝处出现应力集中使得加铺层层底受到过大的拉应力或者竖向剪应力而出现破坏。路面各层不同的搭接宽度与新老路面结构接缝的位置设置互相影响,本文根据新建部分的路面结构与旧路加铺结构进行有限元分析,根据路面在受到车辆荷载作用下的破坏模式来分析特定点位。

The fracturing pressure prediction model for hydraulic fracturing treatment

The accurate prediction of fracturing pressure for pay zone is the very important guidance to hydraulic fracturing design and operation. The pore pressure around the wellbore happens to change variously as the fracturing fluid entering the pay zone. The change of pore pressure affects the stress-state and the fracturing pressure around the wellbore. In this paper, a new concept of the effective membrane pressure coefficient is presented according to the wall building capacity of the fracturing fluid, then the change of pore pressure around the wellbore is studied, and it is proven that the prediction model for fracturing pressure is improved.

Ecological Security Assessment of the Yancheng National Nature Reserve based on GIS

This study used remote sensing and GIS to analyze the landscape pattern changes in the Yancheng Nature Reserve from 1983 to 2018,established an evaluation index system based on the regional natural-socio-economic complex ecosystem security pattern,and then analyzed the spatial characteristics of ecological security changes and discusses reasons for these changes.The results show that the landscape pattern changed dramatically from natural landscape to a mixture of natural landscape and artificial landscape from 1983 to 2018 due to the intensification of human activities.At present,the ecological security status of the protected areas is not optimistic.From the perspective of the survival status of red-crowned cranes,the protected areas are suitable.However,due to the increase of human activities and policy adjustments,the habitat of red-crowned cranes is fragmented.The red-crowned crane currently gathers in localized areas such as the core area and the buffer zone.We should pay more attention to management,policy development and the environmental awareness of local residents.At the same time,it is necessary to reduce the intensity of human activities within the reserve.

Assessing the Health of Inland Wetland Ecosystems over Space and Time in China

Wetland is a unique natural landscape pattern,which provides a variety of important functions and services for human societies.With the rapid develop of the economy and accelerated urbanization,the inland wetlands are faced with series of problems,including reduced area,weakened wetland functions,and deterioration of the wetland ecosystem environment.Therefore,it is necessary to quantitatively assess the ecological health of China’s inland wetlands,which is key to the sustainable development of ecosystems.However,most assessments of wetland ecosystems only examine single wetlands or watershed wetlands,and there are few assessments of wetland health at the national level.In this paper,based on land cover data,climate data,and social and economic data,an assessment system of inland wetland health is established by using the Pressure-State-Effect-Response(PSER)model,which includes 15 assessment indicators.Analytic hierarchy process(AHP)was used to define the indicator weights.Then we assessed the ecosystem health of the inland wetlands of China in 2010 and 2018,which produced three main results.(1)Unlike ecosystem health evaluated by administrative districts,wetland ecosystem health(WEH)evaluation based on the grid could provide additional details of wetland health.(2)The area of inland wetlands increased by 16328 km^(2) in 2018 compared to 2010,and the average wetland ecosystem health index in 2018 was 3.45,compared to an index value of 3.24 in 2010.(3)In 2018,wetlands in the better,good,moderate and poor conditions represented about 26.3%,46.4%,26.9%and 0.5%of the total,respectively.These results provide a practical guide for protecting and managing wetland system resources and reliable information for land use planning and development.

Thickness effects on magnetoelectric coupling for Metglas/PZT/Metglas laminates

Thickness effects on the ME coefficient αME and electromechanical resonance frequency of Metglas/PZT/Metglas tri-layered laminates are investigated. The thickness of the magnetic plate is changed by assembling different numbers of the Metglas thin sheets （30μm for each layer） while the PZT plate is maintained at constant thickness （0.5 mm）. At 1 kHz of the applied alter- nating magnetic field, only one peak presents in the ME coefficient （OCME） versus static magnetic field （Hs） curve. As the thickness ratio n increases, the peak value of αME first increases and reaches a maximum at approximately n = 0.519, and then decreases afterward. The peak position （Hoptim） moves steadily toward a higher value as n increases. It is suggested that the re- laxation factor k of the magnetic phase is reduced as n increases, causing the decrease of the piezomagnetic coefficient d11,m and the increase of Hoptim. By employing the micromechanics model and considering the degradation of dll,m with n, an opti- mized thickness ratio of 0.5 is predicted, which is in agreement with the experimental observations. The resonance frequency of the laminate increases with n, which is consistent with the calculation using a straightforward mixture law.