Effects of Dimensional Tolerances on the Friction Power Loss of Hydrodynamic Journal Bearing System

According to the dimensional tolerances on hydrodynamic journal bearing system, a nonlinear oil film force model was established,and the Reynolds' equation was solved by adopting finite difference method. In order to fulfill different dimensional tolerances in the system,adopting 2kfactor design and using the eccentricity ratio corresponding to the stability critical curve,the effects of the friction power loss brought by the dimensional tolerances of the dynamic viscosity,bearing width,bearing diameter and journal diameter were analyzed. The effect on dynamic characteristics of the hydrodynamic journal bearing system was quantitatively analyzed,and the nonlinear dynamic analysis, modeling and calculation methods were studied while considering the manufacturing tolerances. The results show that in contrast to the impacts of the tolerances in journal diameter,dynamic viscosity and bearing width,the bearing diameter tolerance would lead to the rise in the power loss, and the dimensional tolerances have different degrees of impacts on the journal bearing system. The friction power loss decreased as the eccentricity ratio increased, and when the eccentricity ratio was 0. 695 the power loss came to the minimum.The investigation would find the best solution and reduce energy consumption,then control varieties of nonlinear dynamical behavior effectively,and provide a theoretical basis for hydrodynamic journal bearing system in parameter design.

Analysis and evaluation of effects of processing steps on dimensional tolerance of PIM parts

The factors affecting the dimensional tolerance of powder injection molding (PIM), such as the selection of the powder and binder, the feedstock homogeneity, the feedstock thermal properties, the feedstock rheologic behavior, the debinding schedule and atmosphere and sintering temperature gradient were discussed. An attempt was made to develop a model to estimate the influence of important variables. The results show that a better understanding of these factors can provide some useful theoretical instructions for large scale production.

Automatic generation of assembly dimension chain based on tolerance cell

In the process of generating assembly dimension chain automatically, there are many problems such as complex assembly relationship, variety of constraints of components and complex dimension and tolerance relations of components. These problems lead to many difficulties in search process and need lots of man-machine interaction. Because of these difficulties, this paper presents a method of automatic generation of assembly dimension chain based on tolerance cell. This method is realized through obtaining assembly tolerance cell and part tolerance cell first. These two types of tolerance cell are extracted and expressed in the form of linked list structure in computer further. Then assembly dimension chain is searched automatically based on obtained tolerance cell, and the correct assembly dimension chain is extracted finally. A system of generating assembly dimension chain automatically has been developed based on DELMIA and successfully deployed in aircraft assembly simulation in the engineerine practice.

Study on Dimension Chain Generation for Auto-body Tolerance Analysis

For auto-body product, assembly dimensional quality evaluation using tolerance analysis method is a challenging task because there are plenty of elements impacting on the variation stack-up and propagation during assembly process. Traditional method of dimension chain generation based on tolerance charting technique can not suit the case of auto-body assembly. This paper proposed a method to generate dimension chain based on developing a jot chain model of assembly, which can be integrated with important information needed for variation analysis, such as joints types and assembly sequences. The implementation of such a procedure will contribute to rapid evaluation of body dimensional quality in the design stage.

Active-passive radial-additive friction stir repairing of mechanical hole out of dimension tolerance of AZ31 magnesium alloy

In order to avoid the depth increasing of repaired hole and eliminate the super-fine grain band in stir zone by radial-additive friction stir repairing(R-AFSR), a solid-state repairing technique of active-passive radial-additive friction stir repairing(AP-RAFSR) assisted by the truncated cone-shaped filling material was proposed in this study. The mechanical hole out of dimension tolerance of AZ31 magnesium alloy was chosen as the repaired object. The results indicated that the AP-RAFSR process rather than the R-AFSR process avoided the kissing bond in the bottom of the repairing interface under the condition of the tool pin length equal to the height of the standard mechanical hole.The continuously-distributed and large-length super-fine grain bands were eliminated in the stir zone by AP-RAFSR. The maximum tensile and compressive-shear strengths of repaired hole by AP-RAFSR reached 190.6 MPa and 138.9 MPa at 1200 rpm respectively, which were equivalent to 97.7% and 89.6% of those of the standard mechanical hole. This AP-RAFSR process assisted by the truncated cone-shaped filling material provides a new technique to obtain a no-depth-increasing, defect-free and high-strength repaired mechanical hole.

GsMAPK4,a positive regulator of soybean tolerance to salinity stress

Salt stress is one of the major factors affecting plant growth and yield in soybean under saline soil condition. Despite many studies on salinity tolerance of soybean during the past few decades, the detailed signaling pathways and the signaling molecules for salinity tolerance regulation have not been clarified. In this study, a proteomic technology based on two-dimensional gel electrophoresis(2-DE) and mass spectrometry(MS) were used to identify proteins responsible for salinity tolerance in soybean plant. Real-time quantitative PCR(qRT-PCR) and Western blotting(WB) were used to verify the results of 2-DE/MS. Based on the results of 2-DE and MS, we selected glucosyltransferase(GsGT4), 4-coumarate, coenzyme A ligase(Gs4 CL1), mitogen-activated protein kinase 4(GsMAPK4), dehydration responsive element binding protein(GsDREB1), and soybean cold-regulated gene(GsSRC1) in the salinity tolerant soybean variety, and GsMAPK4 for subsequent research. We transformed soybean plants with mitogen-activated-protein kinase 4(GsMAPK4) and screened the resulting transgenics soybean plants using PCR and WB, which confirmed the expression of GsMAPK4 in transgenic soybean. GsMAPK4-overexpressed transgenic plants showed significantly increased tolerance to salt stress, suggesting that GsMAPK4 played a pivotal role in salinity tolerance. Our research will provide new insights for better understanding the salinity tolerance regulation at molecular level.

Computer-Aided Process Tolerance Design

A comprehensive survey of the state of the art, the projection of future trends of process dimension charts and mathematical models in computer-aided process tolerance are presented In the paper.

Adaptive Dimensional Learning with a Tolerance Framework for the Differential Evolution Algorithm

The Differential Evolution(DE)algorithm,which is an efficient optimization algorithm,has been used to solve various optimization problems.In this paper,adaptive dimensional learning with a tolerance framework for DE is proposed.The population is divided into an elite subpopulation,an ordinary subpopulation,and an inferior subpopulation according to the fitness values.The ordinary and elite subpopulations are used to maintain the current evolution state and to guide the evolution direction of the population,respectively.The inferior subpopulation learns from the elite subpopulation through the dimensional learning strategy.If the global optimum is not improved in a specified number of iterations,a tolerance mechanism is applied.Under the tolerance mechanism,the inferior and elite subpopulations implement the restart strategy and the reverse dimensional learning strategy,respectively.In addition,the individual status and algorithm status are used to adaptively adjust the control parameters.To evaluate the performance of the proposed algorithm,six state-of-the-art DE algorithm variants are compared on the benchmark functions.The results of the simulation show that the proposed algorithm outperforms other variant algorithms regarding function convergence rate and solution accuracy.

接触面尺寸公差对航空齿轮泵性能阈值的影响

接触面加工误差是影响航空齿轮泵性能的敏感因素,有必要研究接触面尺寸公差对航空齿轮泵外特性的影响规律。选取泵体内部3种主要接触面(泵腔内表面、齿顶面和齿面),分别建立存在尺寸公差的实际模型,并与无公差的理想模型进行对比。利用RNG k-ε湍流模型三维瞬态流场数值模拟,推导出基于公差的径向泄漏量数学模型,揭示不同接触面公差对泵外特性的影响规律。研究表明:接触面公差降低了容积效率,缓解了流量脉动与压力脉动,使得相邻腔室间压力梯度下降;其中齿面公差对泵的流量、压力特性最为敏感。齿面公差的存在使得容积效率、瞬时流量算术平均偏差及瞬时压力算术平均偏差分别下降4.7%、31.8%和39.3%。此外,齿面公差有效缓解困油区压力和减少齿轮激励力,而齿顶与泵腔接触面公差对其影响不大。

双维度视阈下家庭收入期望差距对消费的影响

消费是保持经济持续稳定增长最主要的需求来源,深入挖掘消费潜能、充分发挥消费对经济增长的驱动作用对经济复苏和持续发展至关重要。文章基于前景理论,采用中国家庭金融调查数据,从历史和社会双维度视阈探讨了家庭收入期望差距对消费行为的影响及作用机理。家庭收入期望差距对消费有显著影响,但具有不对称性,总体而言,收入期望顺差对消费的影响落差较大。家庭收入社会期望顺差显著促进消费,落差显著抑制消费;家庭收入历史期望顺差和落差均显著促进消费。收入社会期望顺差比历史期望顺差对当期消费促进作用更强,长期则反之。分析表明,收入期望顺差通过提升家庭风险容忍度进而促进消费,而在收入社会期望处于落差状态下家庭风险容忍度不易改变。研究为解释家庭消费行为和制定刺激消费需求相关政策提供了新的观点和实证依据。

熔体黏弹特性对模内微装配成型制造精度影响

针对微细万向球形转动运动副的功能自润滑液膜辅助模内微装配成型,明晰其微装配界面直径制造公差—黏弹性热流固耦合冲击载荷、连续相变演化区厚度、热黏弹塑性应力—熔体黏弹弹性的多场协同耦合演化规律,是实现精密调控其制造精度的关键技术问题。结果表明,微装配界面直径制造公差受控于二次注射成型充填熔体的黏弹特性,当参考黏度由2267 Pa·s增至15000 Pa·s时,微装配界面直径制造公差由11μm增至19μm,增幅为72.7%;而当松弛时间由0.05 s增至0.25 s,则由31μm减至19μm,减幅38.7%;为了满足行业规范的尺寸制造公差技术指标≤30μm的要求,不宜采用松弛时间小于0.05 s的高弹性熔体进行其功能自润滑液膜辅助模内微装配成型。

Radial Additive Friction Stir Repairing of Mechanical Hole Out of Dimension Tolerance of AZ31 Magnesium Alloy Assisted by Stationary Shoulder:Process and Mechanical Properties

Radial additive friction stir repairing(R-AFSR)assisted by stationary shoulder was put forward in the present study,which can be employed to repair the mechanical hole out of dimension tolerance of AZ31 magnesium alloy sheet.The results show that the stationary shoulder has sealed-barrier,heat-sink and extra-forging effects.The heat-sink effect improves the microstructure uniformity along the stir zone(SZ)thickness and the surface appearance of repaired hole,and the sealedbarrier and extra-forging effects eliminate the super-fine grain band in the SZ.Therefore,these three effects improve the formation quality of repaired region,thereby enhancing the mechanical properties of repaired mechanical hole compared with conventional R-AFSR.The tensile and compressive shear strengths of the repaired hole by stationary shoulder R-AFSR both increase first and then decrease when the rotating speed changes from 1200 to 1800 rpm,and these maximum values,respectively,reach 190±3 MPa and 64.5±2 MPa at 1400 rpm.The addition of stationary shoulder during R-AFSR can obtain a higher-quality repaired hole and broaden the repairing process window.

动力电池包装配式密封条的设计概况

以装配式密封条为例,介绍动力电池包密封条的设计要素,包括开发体系和分类、断面设计、性能要求、材料选择、定位精度和尺寸公差。密封条的上、下表面接触压力大于0.01 MPa,密封条即实现安全密封,密封等级达到IPX7。密封条橡胶材料的主体材料选用三元乙丙橡胶最佳,密封条的尺寸公差采用M1等级,定位采用分区定位法。

飞机复材主承力结构数字化高性能装配协调技术研究与应用

为满足新一代大型飞机复合材料主承力结构高精度、低损伤、低应力的装配性能与技术指标保证需求,本文以产品多种类关键特征耦合分析与控制为装配协调设计线索,以工程化应用研究为主线,系统地阐述了以关键特征识别、三维工艺容差仿真分析、装配过程变形预测、实测数据预装分析、高精度装配补偿等方法为主要技术路径的飞机复材主承力结构数字化高性能装配协调技术体系,并以典型复材外翼盒段部件装配为对象,对上述体系方法进行了全流程工程应用研究与试验验证,解决了复材外翼盒段部件装配协调设计与产品补偿策略设计问题,产品装配质量满足设计要求。

尺寸工程在白车身生产中的应用

汽车白车身的精度是整车生产的重要品质参数之一,好的白车身能体现企业的制造能力,提升车辆品质和消费者满意度。从汽车车身设计、品标图纸发布、测量设备和检具、工装夹具定位方案、试生产中的尺寸匹配、量产中的精度维持等角度出发,分析尺寸工程在白车身生产中的应用,归纳阐述白车身尺寸工程内容要点,以期能为白车身的良好生产提供系统性建议。

尺寸公差与形位公差混合优化分配

为解决尺寸公差与形位公差混合优化分配问题,提出了一种公差优化分配方法。根据成本—公差函数和尺寸公差与形位公差的关系,建立了以最小制造总成本为目标的非线性公差混合优化分配模型。该模型的约束包括装配尺寸链的功能要求和加工能力。求解该模型能同时得到优化的尺寸公差和形位公差。最后,分别用公差混合优化分配法和传统方法对一个实例进行公差分配,结果表明所提方法比传统方法更优越。

基于雅可比旋量理论的公差优化分配

以雅可比旋量理论为基础,建立了尺寸公差和形位公差综合优化分配模型。首先在公差模型中计算了空间尺寸链传递累积形成的装配误差,并以设计规定的装配功能要求作为公差优化分配的约束条件,以加工总成本最小为优化目标函数,采用遗传算法求解,得到优化的尺寸公差和形位公差。将此方法应用于某齿轮泵装配体的公差优化分配算例中,在保证装配质量的前提下实现了加工总成本最低的公差优化分配。

装配系统中零件公差的空间建模及应用

将装配系统分为宏观与微观信息结构，并对零件层内部的几何尺寸公差进行空间建模，将零件内尺寸公差信息和零件间装配关系信息用网络图的形式加以表示。以齿轮装配箱为例，对装配封闭环的公差链进行在三维方向的分析，例证上述表达思想。

三维片上网络故障及拥塞感知的容错路由器设计

三维片上网络中路由器的输入端口和交叉开关出现故障,将严重影响整个网络的性能,因此文章提出了一种故障及拥塞感知的容错路由器.通过增加一个冗余的输入端口和旁路总线,不仅能实现对输入端口和交叉开关容错的目的,而且还能在没有端口故障的情况下使用冗余端口有效地解决拥塞问题.实验表明此容错机制能够使得网络在故障路由器多、拥塞严重的情况下,仍然保持良好的性能.

三维结构可重构阵列在线自诊断与容错方法

目前传统的可重构阵列容错方法一般需要控制器来完成重构控制,容错重构控制算法复杂,资源利用率不高,因此提出一种面向三维结构的可重构阵列分布式自主容错方法。系统由相同的电子细胞以三维结构组成,每个细胞能进行故障定位且实现故障自修复;采用基于广度优先布线算法的重布线机制在三维细胞阵列中寻找最近冗余细胞;冗余细胞按比例均匀分布在三维阵列中,可增加容错重构控制过程的灵活性,缩短重构时间。以4位并行乘法器电路为例,对可重构阵列的功能和容错能力进行验证,实验结果表明该方法能够实现三维可重构阵列分布式自主故障诊断与修复,可容错多次故障且容错重构时间短,冗余资源利用率高。