发动机缸盖导管阀座压装技术分析

介绍汽油发动机缸盖导管阀座压装技术的发展和领先的压装技术,对传统压装技术和新压装技术分别做了详细的技术分析和对比。     

大通径止回阀的选材和结构设计

止回阀是一种自动阻止介质逆流的阀门,其结构简单,能自动启闭,因而广泛应用于各个领域。对大通径旋启式止回阀的选材和结构设计进行了研究。     

火箭多级筒燃气弹射动力学特性及影响因素

为提高火箭弹射的性能,研究一种新型改进火箭多级筒燃气弹射装置的安全性,对其弹射过程中结构的动力学特性及发射过程中的影响因素进行比较分析。使用有限元方法对该弹射装置的弹射过程进行仿真,将弹射出的火箭位移、速度、俯仰角等结果与实验结果进行对比,验证有限元计算模型的有效性。在有限元模型基础上分析筒节间隙、推力偏心和发射角度对多级筒弹射安全性的影响。分析结果表明：发射角度是弹射安全性的主要影响因素,筒节间隙和推力偏心是次要影响因素,火箭弹射偏转、筒节间相互作用力和横向最大位移增大都是这些因素影响弹射安全性的主要表现;当活塞筒筒节间隙扩大到0.3 mm或发射角度偏转到3°时,会对发射安全性产生较大的威胁。     

一种导弹电磁线圈弹射器方案设计与仿真分析

为解决电磁线圈弹射器弹射大质量载荷时存在的机械应力大和磁场强等问题,提出一种导弹电磁线圈弹 射器方案。以某型导弹为弹射目标,建立弹射器系统模型进行仿真分析。结果表明：该方案能通过增加驱动线圈的 放电次数,使弹射器在较短的加速距离上,以较小的加速力使导弹稳定加速,获得高初速度。     

Study on the design of ball valve based on elastic ring valve seat structure and fluid characteristics and fatigue strength

Aimed at the technical problems such as the influence of granular medium on spring pre-tightening force sealing, a new ball valve based on elastic ring valve seat structure is studied. The spring plate type valve seat structure is designed to cooperate with the ball core for sealing, and the blade spring coil is used to cooperate with the ball core for sealing in the spring plate type valve seat structure. Wherein the supporting back ring supports the blade leaf spring on the outer side to enhance and protect the role of the blade spring coil. The design without the spring cavity avoids the problem of sealing failure caused by medium entering into the spring cavity and affecting the compression spring, and avoids the situation that the valve seat can be sealed with the ball core by pre-tightening the compression spring, thus avoiding the problem of sealing failure caused by the valve seat sticking on the valve body. The mechanical and flow characteristics are studied and analyzed by the ball valve characteristic test system. The stem torque, unbalance torque, flow characteristics and flow coefficient variation at different nominal diameters are analyzed. The seal allowable squeeze stress and seal surface pressure are analyzed, and the seal is stable and reliable with the seal pressure meeting the seal design criteria. The fluid dynamics simulation analyzes the velocity, pressure and flow traces of the fluid flowing through the ball valve under three opening degrees: fully closed, half open and fully open, the maximum velocity-pressure and opening degree variation curves of the inlet and outlet, the maximum velocity-pressure and opening degree variation curves of the inlet and outlet under different nominal diameters and the flow resistance coefficient curves. Static strength analysis was done for the ball core and spring plate seat structure to obtain the stress, displacement, strain and safety factor. The fatigue strength of the ball spool and spring-loaded plate seat structure was analyzed, and the total number of lives (cycles) and load factors were obtained, and the results show that the fatigue strength of the ball spool and spring-loaded plate seat structure is safe and the fatigue strength meets the requirements. Ball valve pressure test, low pressure sealing test and high pressure sealing test, valve body strength and ball valve sealing performance all meet the requirements.     

汽轮机前轴承座滑销系统销孔加工方案解析

汽轮机滑销系统是保证汽轮机安全高效运行的重要部件之一,其中,Ф50_0＋015mm的骑缝销孔在滑销系统中起着关键的定位作用。由于此销孔特征为深孔加工,所定位的2个零件材质不同,成为汽轮机行业的加工难题。通过对改进加工工艺路线、设计外冷镗刀杆、选择合理的加工刀具和工装以及合理选择润滑油及润滑方式等方面进行综合分析,制定了一套合理的加工方案,有效保证了销孔的加工质量和精度,在同类产品制造中具有广泛的借鉴作用。     

大口径双向密封固定球球阀的阀座结构分析与设计

分析了石油和天然气管线用固定球球阀阀座的结构特点和性能,介绍了一种大口径双向密封固定球球阀的阀座优化设计。     

基于人机工程的汽车驾驶座椅舒适性设计研究

运用人机工程学原理,对影响汽车驾驶座椅的主要因素进行了分析,在此基础上从驾驶座椅舒适性和安全性的角度出发,对座椅的主要参数,结构,材料等方面进行设计研究.在汽车驾驶座椅设计中引入数字化建模、模拟仿真试验等先进技术及手段,将是以后的发展方向.     

冲击座铸造工艺设计及优化

介绍了冲击座铸件的结构及其工艺设计,包括每型件数、浇注系统形式及内浇道、横浇道和直浇道的截面积、浇注时间、冒口及冷铁设计等。初始铸造工艺只采用冒口补缩,模拟发现该工艺未能完全消除缩孔缺陷,据此对铸造工艺进行了改进,在孤立热节区设计冷铁。对改进后的铸造工艺进行模拟,结果显示,缩孔缺陷已完全可以消除。     

Kinematics of the trunk in sitting posture: An analysis based on the instantaneous axis of rotation

This paper presents a new approach for analysing trunk kinematics in sitting posture based on the characterisation of thorax and pelvis motion by means of ranges of motion and instantaneous axes of rotation (IAR). These variables are estimated from videophotogrammetric data. An experiment was carried out in order to analyse three motions associated with the flexion–extension movement: the absolute motions of the pelvis and thorax and the relative motion between the thorax and pelvis. The results obtained suggest a sequential activation of lumbar vertebrae in the flexion–extension motion. On the other hand, the location of the pelvis IAR shows that the movement of the pelvis on the seat is not just a rolling motion but a rolling with some level of sliding. Finally, the location of the IAR in the thorax-pelvis relative motion shows a mismatch between the trunk IAR and the backrest axis of rotation in several office chairs. The proposed technique provides a new approach for the kinematic analysis of sitting posture. The results can be applied to the improvement of biomechanical models of seated posture as well as to define some design criteria of work seats based on the fit between the trunk and backrest movements.