Optimum Design for Shrink-fit Multi-layer Vessels under Ultrahigh Pressure Using Different Materials

Multi-layer pressure vessels are widely used in every field of high pressure technology.For the purpose of enhancing a vessels＇ load bearing capacity,a beneficial process like shrink-fit is usually employed.However,few documents on optimum design for multi-layer shrink-fit vessels made of different strength materials can be found,available data are mainly on two-layer vessels.In this paper,an optimum design approach is developed for shrink-fit multi-layer vessels under ultrahigh pressure by using different materials.Maximum shear stress theory is applied as design criteria.The inner and outer radii of a multi-layer vessel,as well as the material of each layer,are assumed to be known.The optimization mathematical model is,thereby,built.Lagrange multipliers method is required to obtain the optimal design formula of wall ratio（ratio of outer to inner radii） of each layer,from which the optimum formulas of shrinkage pressure and radial interference are derived with the superposition principle employed.These formulas are applicable for the optimization design of all multi-layer vessels made of different materials,or same materials.The formulas of the limit working pressure and the contact pressure show that the optimum wall ratio of each layer and limit working pressure are only related to all selected material strength and unrelated to the position of the layer placement in the vessel.However,shrinkage pressure is related to the position of the layer placement in the vessel.Optimization design of an open ended shrink-fit three-layer vessel using different materials and comparisons proved that the optimized multi-layer vessels have outstanding characteristics of small radial interference and are easier for assembly.When the stress of each layer is distributed more evenly and appropriately,the load bearing capability and safety of vessels are enhanced.Therefore,this design is material-saving and cost-effective,and has prospect of engineering application.

High temperature and high pressure rheological properties of high-density water-based drilling fluids for deep wells

To maintain tight control over rheological properties of high-density water-based drilling fluids, it is essential to understand the factors influencing the theology of water-based drilling fluids. This paper examines temperature effects on the rheological properties of two types of high-density water-based drilling fluids （fresh water-based and brine-based） under high temperature and high pressure （HTHP） with a Fann 50SL rheometer. On the basis of the water-based drilling fluid systems formulated in laboratory, this paper mainly describes the influences of different types and concentration of clay, the content of a colloid stabilizer named GHJ-1 and fluid density on the rheological parameters such as viscosity and shear stress. In addition, the effects of aging temperature and aging time of the drilling fluid on these parameters were also examined. Clay content and proportions for different densities of brine-based fluids were recommended to effectively regulate the rheological properties. Four theological models, the Bingham, power law, Casson and H-B models, were employed to fit the rheological parameters. It turns out that the H-B model was the best one to describe the rheological properties of the high-density drilling fluid under HTHP conditions and power law model produced the worst fit. In addition, a new mathematical model that describes the apparent viscosity as a function of temperature and pressure was established and has been applied on site.

Progressive fracture processes around tunnel triggered by blast disturbances under biaxial compression with different lateral pressure coefficients

To investigate the progressive fracture processes around a tunnel triggered by static stress and dynamic disturbance,experiments and numerical simulations were performed.The results show that the spatial distributions of acoustic emission(AE)events become very different as lateral pressure coefficients change.The combined effect of static stress and dynamic disturbance causes the damage around the tunnel,and initial stress conditions control the damage morphology.The blast disturbance cannot fundamentally change the damaged area but will deepen the extent of damage and accelerate the failure speed.The more significant the difference between the vertical and horizontal stresses is,the higher the impact on the tunnel by the dynamic disturbance is.The AE activity recovers to a relatively stable state within a short time after the blast and conforms to power-law characteristics.

Effect of internal pressure on strength of hydraulically expanded joints

To analyze the effect of internal pressure on the connection strength of hydraulically expanded joints,a hydraulic expanding and push-out process of a joint of tube to sleeve was simulated by using FEM and validated by experiments at various internal pressure values.The stress and residual stress in the joined pair during the joining process illustrates that the contact pressure on the interface is not uniform along the longitudinal direction.The research reveals that if the sleeve does not experience any plastic deformation,the connection strength increases with the internal pressure linearly.For sleeve material with yield point elongation,if the sleeve experiences some degree of plastic deformation,there is an internal pressure interval in which the connection strength decreases slightly as internal pressure increases.Therefore,the internal pressure should be controlled depending on the deformation of the sleeve,but not as high as possible.The simulated results are in good agreement with those from experiments.

Radial Grip Rigidity of the Matching of Lengthened Shrink-fit Holder and Cutter in High-speed Milling

Though the lengthened shrink-fit holder (LSFH) is widely applied in high speed milling of the parts characterized by deep cavities at present, its design and selection mainly depends on the experience and lacks a correct theoretical guidance. In this paper, attention is focus on the radial grip rigidity of the matching of LSFH and cutter in high speed milling. Based on the experiment modal analysis (EMA) technique, an accurate finite element model of the matching of LSFH and cutter is established firstly. Subsequently, the influence of different interference, grip length and spindle speed on the grip rigidity of LSFH are analyzed. The analysis results show that there is a reasonable interference and grip length between the LSFH and cutter so that to have a steepless grip and have a good radial grip rigidity and at the same time to avoid the strength of LSFH to exceed it’s yield limit which will reduce the precision and service life of LSFH, besides when spindle speed reach a extension the weakening influence of the centrifugal force on the radial grip rigidity of the matching of LSFH and cutter should been taken into account. Finally, the finite element analysis results are verified based on the construction of measurement method of the grip rigidity and the results fit very well. The studies provide a theoretical basis for the design, selection and the serialization and standardization of the matching of LSFH and cutter.

Experimental Study on Spray Cooling Performance of Pressure Atomizing Nozzle

Aiming at the problem of air-cooled condenser output limit, a spray humidification system was presented to reduce the inlet air temperature. The pressure atomizing nozzle TF8 was chosen for inlet air spray cooling, and the spray cooling experiment with different layouts of nozzles were conducted. Through heat and mass transfer analysis, the cooling effect fitting correlation was acquired with evaporative cooling being the major cooling mechanism. The experimental results under different nozzle layouts show that when the product of dry ball and wet ball temperature difference and spray rate is smaller than 75 ~C-m3/h, opening the TF8 nozzles in row 1 and row 2 （row distance is 500 mm） has better cooling effect than those in row 1 and row 3 （row distance is 1 000 mm）, while when the product is larger than 75 ~C＇m3/h, opening the TF8 nozzles in row 1 and row 3 is superior in cooling effect to those in row 1 and row 2.

The study on the shrink-fit multi-ring flywheel with fall-off function

Structural integrity of the flywheel of reactor coolant pump is important for safe operation of a nuclear power plant. A shrink-fit multi-ring flywheel is designed with a fall-off function, i.e., it will separate from the shaft at a designed fall-off rotation speed, which is determined by the assembly process and the gravity. However, the two factors are ignored in the analytical method based on the Lame's equation. In this work, we conducted fall-off experiments to analyze the two factors and used the experimental data to verify the validity of the analytical method and the finite element method(FEM). The results show that FEM performs better than the analytical method in designing the falloff function of the flywheel, though FEM cannot successfully predict the strain variation with the rotational speed.

四阶Runge—Kutta公式在新工艺ShrinkFit可靠性设计和分析中的应用

基于Runge—Kutta方法能够精确而有效的对曲线趋势进行动态的仿真，它不仅提高了精度，同时提高了计算效率。运用Runge—Kutta方法能很好的解决“收缩配合”强度计算的问题，并且与有限元分析计算结果具有一致性，进一步证明Runge-Kutta方法的求解方案具有高稳定性能，为更好的实现对于，“收缩配合”可靠性设计和分析提供了新的求解思路。

Determination of interference fit value on entire roller embedded shapemeter roll

For entire roller embedded shapemeter roll, the relationship between the value of interference fit and the sensor pre-pressure, and the pressure transfer performance of shapemeter roll were analyzed by elasticity theory during the cold reversible rolling process. Considering the influence of strip temperature on the interference fit, the distributions of contact pressure of the framework's top surface and the sensor pre-pressure on different values of interference fit were analyzed by the finite element technology. The results show that the contact pressure of the framework's top surface and the sensor pre-pressure increase with the increase of the value of interference fit. When the value of interference fit is between 0.05 mm and 0.09 mm, roll body's inner hole surface, the framework and pressure magnetic sensitive component don't separate from each other, and the sensor works in the linear segment of characteristic curve, so the normal operation of shapemeter roll is guaranteed.

Real and Fitted Spherical Indentations

Spherical indentations that rely on original date are analyzed with the physically correct mathematical formula and its integration that take into account the radius over depth changes upon penetration. Linear plots, phase-transition onsets, energies, and pressures are algebraically obtained for germanium, zinc-oxide and gallium-nitride. There are low pressure phase-transitions that correspond to, or are not resolved by hydrostatic anvil onset pressures. This enables the attribution of polymorph structures, by comparing with known structures from pulsed laser deposition or molecular beam epitaxy and twinning. The spherical indentation is the easiest way for the synthesis and further characterization of polymorphs, now available in pure form under diamond calotte and in contact with their corresponding less dense polymorph. The unprecedented results and new possibilities require loading curves from experimental data. These are now easily distinguished from data that are “fitted” to make them concur with widely used unphysical Johnson’s formula for spheres (“P = (4/3)h3/2R1/2E∗”) not taking care of the R/h variation. Its challenge is indispensable, because its use involves “fitting equations” for making the data concur. These faked reports (no “experimental” data) provide dangerous false moduli and theories. The fitted spherical indentation reports with radii ranging from 4 to 250 μm are identified for PDMS, GaAs, Al, Si, SiC, MgO, and Steel. The detailed analysis reveals characteristic features.

Thermodynamic Fit Functions of the Two-Phase Fluid and Critical Exponents

Two-phase fluid properties such as entropy, internal energy, and heat capacity are given by thermodynamically defined fit functions. Each fit function is expressed as a temperature function in terms of a power series expansion about the critical point. The leading term with the critical exponent dominates the temperature variation between the critical and triple points. With β being introduced as the critical exponent for the difference between liquid and vapor densities, it is shown that the critical exponent of each fit function depends (if at all) on β. In particular, the critical exponent of the reciprocal heat capacity c﹣1 is α=1-2β and those of the entropy s and internal energy u are?2β, while that of the reciprocal isothermal compressibility?κ﹣1T is γ=1. It is thus found that in the case of the two-phase fluid the Rushbrooke equation conjectured α +?2β + γ=2 combines the scaling laws resulting from the two relations c=du/dT and?κT=dlnρ/dp. In the context with c, the second temperature derivatives of the chemical potential μ and vapor pressure p are investigated. As the critical point is approached, ﹣d2μ/dT2 diverges as c, while?d2p/dT2 converges to a finite limit. This is explicitly pointed out for the two-phase fluid, water (with β=0.3155). The positive and almost vanishing internal energy of the one-phase fluid at temperatures above and close to the critical point causes conditions for large long-wavelength density fluctuations, which are observed as critical opalescence. For negative values of the internal energy, i.e. the two-phase fluid below the critical point, there are only microscopic density fluctuations. Similar critical phenomena occur when cooling a dilute gas to its Bose-Einstein condensate.

Increasing silver leaching rate from leaching-resistant zinc residues by thiourea leaching method with pressurized preoxidation process

As for the leaching-resistant zinc residues, the silver leaching rate can be over 98% through the process of pressurized preoxidation and thiourea leaching. Compared with the method of extracting the silver directly from the leaching-resistant zinc residues, the silver leaching rate is greatly improved. The optimum preoxidation conditions are: particle size range 4060 μm, oxygen partial pressure 10 6 Pa, temperature 8090 ℃, pH=1.0, and leaching time 5 h. After pretreatment, the time of thiourea leaching silver is shortened to 1.5 h, and the thiourea consumption is reduced greatly. The oxidation mechanism and the thiourea leaching kinetics were also explored.

过盈配合工况下收缩管吸能特性分析及结构参数优化

轨道车辆收缩管在轴向冲击载荷及过盈配合下的吸能特性是吸能结构研究中的重要课题,其吸能过程依靠收缩管与锥形衬套之间的摩擦做工及收缩管的塑性变形实现,过盈配合通过影响收缩管与衬套间的接触力提高收缩管的能量耗散。为提高收缩管的吸能特性,研究过盈配合对吸能能力的影响,采用试验与有限元模型相结合的方法,基于多目标优化算法获取包括过盈量在内的收缩管最优结构参数。进行空心轴与轴套过盈静压试验,验证接触力理论公式的正确性;利用台车冲击试验研究收缩管碰撞过程中的吸能特性,构建有限元模型进行验证;推导过盈配合条件下收缩管接触表面压力的理论模型;使用全因子和Hammersley设计方法对过盈配合工况下收缩管结构参数进行研究,包括厚度(T)、过盈量(I_(ntf))、锥角长边(α_(x))和收缩比(R_(atio))。基于此,利用移动最小二乘法(MLSM)构建峰值力(PCF)、比吸能(SEA)和平均力(MCF)的近似模型。主效应分析表明,收缩比对PCF、SEA和MCF的影响最为显著。以获取最小PCF、最大SEA以及MCF最接近设计要求650 kN为优化目标,进行全局响应面(GRSM)优化,获得最优结构配置,与初始设计相比,SEA提高28.54%,PCF降低12.37%。代理模型最优解得出的MCF与有限元模型误差为2.01%,证明构建的代理模型具有较高的精度,可用于优化计算。优化后的结构有效提高了收缩管的吸能能力,降低了碰撞的初始峰值力。

不同缩口下闸阀介质流动特性研究

阀门的缩口比是阀门使用单位及生产单位关注的重要因素,直接关系到机组运行性能参数。文中分别以DN100和DN350闸阀,以缩口比0.75、0.8、0.85、0.90、0.95及1.0建立三维模型,并利用FLUENT软件进行流场模拟分析,模拟不同缩口的闸阀内介质的流动状态,获取其速度场和压力场,并计算出不同缩口下阀门的流阻系数。根据流阻系数计算出工况参数下阀门压力损失,为阀门使用单位及生产制造单位提供选型参考方案。

血流限制训练对上肢肌肉适能效益的影响

背景:血流限制训练在提高肢体肌肉力量方面有广阔的应用前景,其中上肢应用血流限制训练的效果较为理想,且具体应用方案具有较高的研究价值。目的:阐述血流限制训练对上肢肌肉适能效益的影响,总结上肢应用血流限制训练的具体方案,试图依据现有研究给出应用方案的建议。方法:检索中国知网(CNKI)、万方、维普、CBM、PubMed、Embase、EBSCO、Cochrane Library及Web of Science数据库中发表的上肢应用血流限制训练的相关文献,中文检索词为“血流限制,血流限制训练,加压训练,上肢,上臂,前臂,手臂,小臂”,英文检索词为“Blood Flow Restriction Training,Blood Flow Restriction Exercise,Blood Flow Restriction Therapy,BFR Therapy,Occlusion training,KAATSU training,BFRT,Upper Extremity,Upper Limb,Arm,Forearm”。选择各数据库建库至2022年12月收录的上肢应用血流限制训练的相关文章,并根据纳入标准和排除标准对所得文献进行筛选。结果与结论:①目前血流限制训练在上肢应用的人群以健康人、专项运动员和上肢损伤人群为主;②血流限制训练对上肢肌肉适能的影响主要体现在增加上肢的肢体围度、肌肉的力量、肌肉耐力、肌肉厚度、肌肉横截面积以及上肢爆发力,其次是引起上肢出现交叉迁移现象;③上肢应用血流限制训练多使用充气型的血流限制装置,袖带宽度为3-5 cm,加压位置在大臂上1/3处,限制压力为40%-60%动脉闭塞压(AOP)或80-160 mmHg,训练负荷为20%-30%1RM,训练量为4组(30-15-15-15次),间歇时间为30-60 s,训练频率为每周两三次。

不合脚鞋类对青年女性足底压力分布的影响

以往鞋类合脚性研究主要集中在鞋楦尺寸与穿着者脚型尺寸吻合性方面,受个人脚型尺寸变化、穿鞋习惯及设计因素制约,高度匹配脚型的鞋类产品很难实现。有研究已证实了不合脚的鞋类是足部受压和皮肤摩擦的主要原因,同时也会造成行走姿态发生改变。为了进一步探讨鞋类合脚性与人体穿着行走的影响,尤其是与足底压力分布的关系,研究设计了不同尺码的实验样鞋,通过问卷调查询问了9名实验对象穿鞋合脚性的主观感受,并进一步使用X光机确认实验对象足部与鞋类的匹配状态,使用Footscan足底压力平板采集实验对象在鞋偏小、偏大和合脚三种状态下的足底压力峰值和足底压力中心轨迹,结果发现:鞋类尺寸发生变化时,足底压力峰值和足底压力中心轨迹均发生改变,在鞋偏小状态、偏大状态与合脚状态相比,足部脚趾、第一跖趾关节,第五跖趾关节、足弓和足跟部位的足底压力峰值存在显著差异(p<0.05)。鞋类尺寸变化显著影响足底压力的分布。

台阶式斜篦齿封严压降与风阻温升数值分析

为研究转速、进口压力及齿隙和齿宽的比对斜篦封严压降与风阻温升特性的影响,建立二维阶梯式斜篦齿封严模型,对台梯式斜篦齿封严进行数值仿真计算,获得不同转速、进口压力及齿隙和齿宽的比下的进出口压差和风阻温升,以及最后一级齿隙处射流的温度和压力。结果表明:斜篦齿的背风面存在高温带,主要是由于旋转的摩擦效应、阶梯几何结构和2个大尺寸涡相遇处的掺混效应所导致;贴壁大尺寸涡与主流的动量交换随着转速的增加而增强,主流与齿腔大尺寸涡的动量交换随着转速的增加而减弱;风阻温升随着齿隙和齿宽的比的增大而降低,随着转速的增加而升高,但与进口压力的关系不明显;进出口压差随着转速的增加而增大,随着齿隙和齿宽的比的增大而减小;出口射流的压力随着进口压力的增加而增加。分别得到压差比和风阻温升系数的拟合式,拟合效果符合预期。

不同气流量下气泡帷幕对水下冲击波衰减特性研究

为了研究不同气流量下气泡帷幕对水下冲击波的衰减特性,采用高速摄像探究气泡帷幕在受到冲击波冲击后形态变化,结合冲击波压力时程曲线进行分析。结果表明,气泡帷幕中的气泡受到冲击波作用后会发生数次膨胀收缩行为,随着气流量增加,气泡膨胀的最大直径增大,第一次膨胀收缩周期变长;且气泡帷幕对水下冲击波压力有很强的衰减作用,气流量上升幅度越大,冲击波压力峰值衰减越明显,在气流量40 L/min下,冲击波峰值衰减高达88.98%;气流量大于20 L/min后,冲击波冲量衰减幅度均大于50.00%。针对气流量大小与压力峰值下降幅度的关系进行曲线拟合,提出适用于该工况下的经验方程,以期指导实际工程。

止口结构影响下的螺栓组装配工艺研究

螺栓-止口连接结构在航空航天、机床、高铁、掘进装备等工业产品中有着广泛的应用。但是止口结构的存在,影响了最终螺栓预紧力分布的一致性,而且针对止口影响下的螺栓预紧力变化规律缺乏相关的理论与工艺试验研究这一现状,本文开展了止口结构影响下的螺栓预紧力变化规律理论分析与工艺试验研究。定性分析了止口结构影响下的预紧力变化规律,建立了止口结构影响下的螺栓预紧力变化的理论模型,并开展含有24颗螺栓的螺栓连接试件与螺栓-止口连接试件的对比试验,试验结果表明,热装工艺完成后,止口结构会对上连接件产生一个“撬力”作用,造成连接界面出现不均匀的缝隙,在这种情况下,输入的扭矩需要先克服止口对上连接件作用的“撬力”,输入能量会有所损失,造成了平均预紧力的下降;同时,止口结构的存在同时会减小螺栓预紧力的分散性,针对这种现象设计了一种压板并提出了均压工艺,试验结果表明,采用均压工艺以后再对螺栓组进行拧紧不仅可以抵消止口结构“撬力”的影响,使螺栓组的平均预紧力有所提高,还能使螺栓预紧力分散性降低,提高装配质量。相关研究结果对螺栓-止口连接结构的工艺设计具有积极意义。

燃气发生器头腔吹除乳化过程压降特性及出流均匀性数值研究

气体吹除乳化技术可以大幅提高燃料流经燃气发生器时产生的压降,从而满足变工况下燃料的雾化及燃烧需求。目前气体吹除后燃气发生器内压降变化的定量规律还不清晰,为此,采用数值模拟的方法,对某型号燃气发生器全域及局部喷嘴进行了变工况计算,得到了氮气吹除过程中燃气发生器内煤油的相、速度以及压力分布规律,并针对喷嘴处的单相流及多相流压降特性进行拟合分析。结果显示:不同喷嘴处的煤油相分布具有不均匀性,喷嘴间流量差距可达66%;使用氮气吹除后的喷嘴处压降相较于煤油单相流可提升1.64倍以上,且喷嘴处的气体单相流压降特性系数随背压呈现线性变化规律,而煤油单相流阻力系数则与流量呈现幂函数规律;基于马尔基涅利公式提出了燃气发生器喷嘴处压降特性的集总参数模型,与数值计算结果及实验结果的平均误差为3.93%,具有较好的预测性。