Simulation of semisolid diecasting process of four-way valve of HPb59-1 alloy for air-conditioner

There exist many problems in producing four-way valve of HPb59-1 alloy for an air-conditioner by traditional solid state hot forging,i.e.larger forming loads,lower material utilization,larger subsequent machining allowance and nonuniform microstructure.For this reason,based on the orthogonal test,the semisolid diecasting process of a certain type of four-way valve was simulated with FLOW-3D.The simulation results show that the optimized process parameters are:the pouring temperature of 897.25 ?C,the shot velocity of 2.0 m/s and the preheated die temperature of 260 C.The simulation results demonstrate that the cavity can be filled smoothly and completely,the surface defects are small,the temperature field and the pressure field are uniform,and the casting quality is satisfactory.The effectiveness and availability of applying this technology are well verified by the numerical simulation.

Theoretical Analysis and Experimental Verification on Valve-less Piezoelectric Pump with Hemisphere-segment Bluff-body

Existing researches on no-moving part valves in valve-less piezoelectric pumps mainly concentrate on pipeline valves and chamber bottom valves, which leads to the complex structure and manufacturing process of pump channel and chamber bottom. Furthermore, position fixed valves with respect to the inlet and outlet also makes the adjustability and controllability of flow rate worse. In order to overcome these shortcomings, this paper puts forward a novel implantable structure of valve-less piezoelectric pump with hemisphere-segments in the pump chamber. Based on the theory of flow around bluff-body, the flow resistance on the spherical and round surface of hemisphere-segment is different when fluid flows through, and the macroscopic flow resistance differences thus formed are also different. A novel valve-less piezoelectric pump with hemisphere-segment bluff-body （HSBB） is presented and designed. HSBB is the no-moving part valve. By the method of volume and momentum comparison, the stress on the bluff-body in the pump chamber is analyzed. The essential reason of unidirectional fluid pumping is expounded, and the flow rate formula is obtained. To verify the theory, a prototype is produced. By using the prototype, experimental research on the relationship between flow rate, pressure difference, voltage, and frequency has been carried out, which proves the correctness of the above theory. This prototype has six hemisphere-segments in the chamber filled with water, and the effective diameter of the piezoelectric bimorph is 30mm. The experiment result shows that the flow rate can reach 0.50 mL/s at the frequency of 6 Hz and the voltage of 110 V. Besides, the pressure difference can reach 26.2 mm H20 at the frequency of 6 Hz and the voltage of 160 V. This research proposes a valve-less piezoelectric pump with hemisphere-segment bluff-body, and its validity and feasibility is verified through theoretical analysis and experiment.

Body-temperature circadian rhythm in 67 patients after heart valve replacement surgery secondary to valvular heart disease

Purpose:Patient body temperature was monitored after cardiac valve replacement,in order to explore the characteristics of body-temperature circadian rhythm and the factors influencing that rhythm.Methods:A cohort of 67 patients who received cardiac valve replacement in a Fuzhou,Fujian province,China,general hospital underwent temperature measurements and analysis(by cosine curve)of their body-temperature circadian rhythm.A biological rhythm model was established through principal component analysis and evaluation of biological rhythm features.Multiple circadian parameters were included through linear regression analysis.Results:Patients’temperature after cardiac valve replacement exhibited circadian characteristics(p<0.05),among which the scores of temperature mesor,amplitude,and acrophase were respectively(37.61
0.08),(0.10
0.09),and33(e355,e119).Body-temperature rhythms were influenced by both gender and cardiopulmonary bypass time(p<0.05).Conclusion:Although some patients’circadian characteristics disappeared after cardiac valve replacement,circadian rhythms remained intact for most patients.Measures that were found to mitigate body-temperature circadian rhythm disruption included building a natural rhythm of light/darkness and decreasing cardiopulmonary bypass time.

Failure analysis of the needle valve body of R18CrNi8 steel

A needle valve is a key component of a diesel injector.The needle valve body of the diesel engine, made of R18CrNi8 steel, cracked and failed during the working process.The cracking failure reasons for the carburized injector valve body through chemical composition analysis, metallographic examination, scanning electron microscope(SEM) analysis, and energy spectrum analysis, were investigated.The results reveal that the original material of the needle valve is in conformity with the manufacturing requirement.Due to the high carburizing quenching temperature, the best carburized layer structure was not obtained, and the machining defect from which the crack emanated was not identified.The cracks expanded and eventually led to fracture under the action of altered stress and the high-temperature combustion environment during the operation of the engine.

Severe prelenticular membrane formation on the surface of a hydrophilic acrylic intraocular lens after cataract surgery in an eye with an Ahmed valve implant

【正】Dear Sir,Iam Yong-Sun Ahn,from the Department of Ophthalmology of St.Vincent Hospital of Suwon,Kyungki-do,South Korea.Cataracts are a common problem in eyes with a glaucoma drainage device(GDD),because tube shunt surgery increases the incidence and progression of cataracts[1].An Ahmed valve,the most commonly inserted GDD,is composed of a silicone tube connected to a flat plate sewn to the sclera,and aqueous humor flows from the

Valve replacement plus reconstruction of the annulus

Objective To investigate surgical technique and clinical outcomes of reconstruction of annulus and intervalvular fibrous body during valve replacements. Methods Fifty-nine patients underwent reconstruction of annulus or intervalvular fibrous body during valve replacement. Indications for operation were small

STC100valve数控阀门专用机床设计

针对阀门(闸阀)制造业阀门体的制造工艺要求,作者根据多年设计机床经验开发设计了一种高性能、高效率的数控阀门专用机床,并将模块化设计理念贯穿到专机设计中。该机床在分析市场需求及零件加工工艺的基础上进行设计,将镗床平旋盘技术成功地应用到车床上,可实现阀门行业阀门体零件的一次装夹,多工序复合化加工的要求。样机试制完成后,证明该数控专用机床可以很好地解决阀门加工效率和质量稳定性问题,设计是成功的。

体重指数对重度主动脉瓣狭窄患者经导管主动脉瓣置换术围术期及远期预后的影响

目的:探讨体重指数(BMI)对重度主动脉瓣狭窄患者经导管主动脉瓣置换术(TAVR)围术期及远期预后的影响。方法:回顾性收集2019年1月至2022年1月于福建省立医院行TAVR治疗的重度主动脉瓣狭窄患者180例,根据BMI分为低体重组(BMI<18.5 kg/m^(2),n=23)、体重正常组(18.5 kg/m^(2)≤BMI<24.0 kg/m^(2),n=65)、超重组(24.0kg/m^(2)≤BMI<28.0 kg/m^(2),n=57)和肥胖组(BMI≥28.0 kg/m^(2),n=35)。比较各组一般临床资料、影像学参数、围术期指标和随访期间的全因死亡及其他远期不良心血管事件发生率,同时评估TAVR围术期并发症及远期预后的影响因素。结果:肥胖组的高血压及糖尿病比例、左心室舒张末期内径、室间隔厚度以及左心室后壁厚度均高于正常组(P均<0.05)。低体重组的前白蛋白水平低于正常组(P<0.05),低体重组围术期总体并发症发生率高于正常组(60.9%vs.12.3%,P=0.042)。随访(18.0±6.8)个月期间,低体重组的全因死亡率明显高于体重正常组、超重组和肥胖组(17.4%vs.4.6%vs.3.5%vs.5.7%,P=0.003)。Kaplan-Meier生存分析显示,低体重组TAVR术后18个月的生存率明显降低(log-rank P<0.01)。多因素Cox回归分析结果显示,与正常体重组比较,低体重组远期不良心血管事件发生风险明显增加(HR=7.633,95%CI:1.012~57.564,P=0.049)。结论:低体重的重度主动脉瓣狭窄患者TAVR围术期并发症的发生率较高,远期预后较差。这类患者在行TAVR前应适当加强营养摄入,调整自身体重至正常水平。

电站调节阀阀体结构参数对流阻特性的影响

为了系统研究阀体结构参数对调节阀流阻特性的影响,采用数值模拟的方法,建立电站调节阀阀体模型,结合正交试验设计,研究调节阀阀体不同结构参数对流阻特性的影响。结果表明:调节阀阀体的结构参数对流阻系数的影响程度依次为上腔半径>下腔高度>上腔高度>阀体半长>下腔半径>中腔半径,同时再对阀体的入口角度进行优化分析,得到入口角度越小,流阻系数越小。通过正交实验优化和入口角度优化后得到的最优结构,其流阻系数与原结构相比降低了19.45%,且流量特性曲线也更加理想。研究成果能够为套筒式调节阀的结构优化提供理论支持。

某航空机轮气门嘴慢漏气故障分析

某航空机轮外场出现慢漏气现象,故障定位于气门嘴组件处,该机轮配装的专用气门嘴组件来自航标气门嘴组件的结构改进。通过故障核实、分解检查和进一步分析,发现漏气是由于气门嘴帽与气门芯、出现干涉,导致气门芯的芯座密封被异常打开所致,气门嘴帽内未装橡胶垫片并非核心因素,主要症结在于气门芯安装后高出气门嘴体端面超量。采取适度增大气门嘴体内锥直径(改动量最小),将气门芯安装后的位置限制在不高于气门嘴体端面,消除了干涉隐患,相关改进措施也被推广到了航标气门嘴组件。

Comparative analysis of multi criteria decision making techniques for material selection of brake booster valve body

Braking system is one of the most critical parts in a vehicle,and one of the main components of this system is brake booster valve body which plays a significant role in safety standards of the vehicle.The working conditions under the hood of the vehicle necessitate the valve body to have some special properties.This component should have high mechanical strength and the ability to maintain this strength at elevated temperatures.On the other hand,lower weight and lower cost are always desirable in industries.The material selection for the valve body is very important and should satisfy the aforementioned requirements.In order to select the best material for a large number of alternatives considering many different criteria,multi criteria decision making(MCDM) methods are used in this study.The weighting of criteria is carried out by entropy and analytic hierarchy process(AHP) methods and a combination of these two techniques are used as the final weights.MOORA,TOPSIS and VIKOR methods are used in this paper for selecting the best material for braking booster valve body.The alternative materials were ranked using these methods and the results of the analysis were compared using Spearman’s rank correlation.PET-gf35(PET reinforced with 35 wt% glass fiber) was found to be the best material for the valve body.Owing to the desirability of the results,the results of this study can be used in automotive industry in order to enhance the material selection process.

浅析低温仪表开关阀的特殊要求

低温仪表开关阀因为工作在极为苛刻的低温环境,在阀门的制造及设计过程有很多特殊的要求以保证低温下的功能,例如阀座和壳体的泄漏等级等。从阀型的选择、阀门安装类型、球阀设计、蝶阀结构等方面,分析了低温阀门专用的设计和制造标准以及特殊要求。介绍了阀体、内件及其材质、阀盖及填料、低温测试、防火等方面的特殊要求。对比分析了国外LNG项目低温阀门的特殊要求和国内低温阀门厂家的制造技术特点,以期提高国产阀门的质量,促进国产化的进程。

一种空气分配阀总阀体四轴加工方法

本文介绍了一种铁路货车空气分配阀总阀体的结构及工艺加工方法,简单介绍了分配阀的用途,分析了总阀体的结构及关键控制点,结合产品结构特点及材料加工特性,梳理了阀体的加工难点,根据已有加工设备和经验,制定了总阀体的加工工艺方案,运用数控四轴加工手段、工序定位及专用工装等解决措施,有效地完成了该型空气分配阀总阀体的加工,保证了加工质量,为类似复杂空间孔系,精度要求高的铝合金阀体在数控机床的加工提供了成功的参考案例。

工业阀门阀体自动化产线开发与应用

工业一体式阀门阀体加工存在多机床、多次装夹定位、多工序加工和多次转道等问题,使得阀体生产质量稳定性较差,生产效率较难满足自动化生产的需要。为此,在采用多种机床、配置复合式夹具及多工位转轴的基础上,应用自动平行料仓和自动控制技术,研究开发了可实现阀体两次装夹的多工序自动化加工产线。该项技术成果可以应用在阀门阀体及中小型机械零件自动化加工产线设计建设中,具有一定的参考借鉴价值。

气瓶阀阀体断裂原因分析

针对一起气瓶阀阀体断裂造成气瓶阀失效的案例,对气瓶阀阀体进行宏观检查、化学成分分析、名义Zn含量计算、显微组织分析、显微硬度分析、断口微观分析。结果表明:气瓶阀阀体断裂主要与显微组织中Pb相颗粒在晶界聚集及阀体内部结构产生的应力集中有关。Pb相颗粒在晶界聚集,引起晶界弱化,裂纹在晶界上萌生;阀体内部的应力集中加速了裂纹扩展。最终在气瓶阀多次使用后,气瓶阀阀体发生断裂。

一种进口连采机国产控制阀质量提升研究

针对进口连采机使用国产控制阀的过程中遇到的阀体高温、漏油故障,进行了试验测量与理论计算,经分析得出故障发生原因。针对故障发生原因进行了整改处理,试验证明整改效果良好,为进口连采机使用国产控制阀提供了质量保障。

基于STM32的物联网智能阀门系统设计

在STM32的基础上,使用设计的新型阀体并结合物联网技术,提出基于STM32的物联网智能阀门系统.该系统的各种传感器通信数据主要利用MQTT协议通过阿里云物联网平台提供的Topic机制来发布,并且可在手机第三方应用程序实时显示以上功能,实现了以低电压、小电流控制大流量的快速通断,且无需电网供电,降低了远程控制阀门使用成本,填补了远程控制阀门技术的空白.测试结果证明,该设备能显著提升农业灌溉用水效率,远程控制火车自动上水等危险场景,有效节约了人力资源.

柴油机高压共轨喷油器针阀体裂纹分析

为解决喷油器针阀体肩胛圆角处开裂故障,采用扫描电子显微镜、能谱分析仪、显微硬度检测、计算机断层扫描等方法分析故障原因及失效机理并提出解决方案。结果表明:失效位置表面含有S、Cl等腐蚀性元素,裂纹表面存在多处不规则腐蚀坑,裂纹处维氏硬度比肩胛处降低了28%,最小壁厚比正常件减小了47%,腐蚀性裂纹是导致针阀体失效的主要原因。可采用使用符合国家标准的燃油及在针阀体表面增加涂层等解决针阀体腐蚀失效问题。

变速箱液压阀体性能分析与常见故障模式

阀体作为自动变速箱的核心零部件,其性能好坏直接影响到汽车的行驶质量。文章以GF6自动变速箱液压系统为例,详细介绍了阀体的压力和泄漏量两项性能指标的计算方法,并通过实际故障案例,说明了如何利用这两项指标来分析常见的变速箱液压系统问题。文章为自动变速箱的阀体设计和阀体故障分析提供指导和参考。

球阀阀杆头部尺寸的研究与优化设计

针对球阀阀杆头部与球体接触部位的研究,通过理论计算的方式,采用等强度设计原则,提供了一个球阀阀杆头部尺寸的优化设计方法,确定主要尺寸对接触部位挤压应力的影响,给出了设计图表,对于不同的阀杆头部深度h,匹配一个最佳的扁身宽度值a,减少了阀杆头部与球体接触部位的挤压应力,优化了阀杆头部尺寸的设计,提高了阀门启闭动作性能,同时为设计者提供经验数值,可快速完成阀杆头部尺寸的最优设计。