注塑成型工艺参数对含熔接痕的PP改性塑件冲击性能的影响

通过正交试验来确定含有熔接痕的改性聚丙烯(PP)塑件抗冲击性能注塑生产工艺参数,得出了成型工艺参数(熔体温度、充模速度、注射时间、注射压力、保压压力等)对熔接痕的外观及性能的影响程度,并得出可能更优的注塑工艺参数。     

蒸气辅助快速热循环注塑技术及模温响应模拟

快速热循环注塑采用动态模温控制新策略,可以彻底解决常规注塑工艺存在的短射、喷射痕、缩痕、流动痕、熔接痕、浮纤等缺陷。文中通过对快速热循环注塑工艺与常规注塑工艺的比较,深入研究了蒸气辅助快速热循环注塑工艺的原理,制定了相应的工艺流程,提出了一套新的利用蒸气加热和冷凝水冷却的动态模温控制方案。利用ANSYS模拟了快速热循环注塑工艺和常规注塑工艺的模温响应过程,分别获得了两种注塑工艺的模具加热速率和冷却速率,讨论了快速热循环注塑对塑件成型周期的影响规律。     

基于CAE的大型LCD注塑面板变模温设计与分析

研究了一种利用蒸汽加热和冷却水冷却的变模温注塑工艺,制定了其工艺流程.以LCD面板为例,通过构建变模温注塑工艺分析模型,利用ANSYS对其加热、冷却过程进行了数值模拟,研究了加热、冷却过程中型腔表面和聚合物熔体的热响应规律,为优化变模温注塑工艺参数提供理论依据.最后,通过构建LCD面板变模温注塑实验生产线,并将分析结果应用于实验生产,验证了模拟分析的有效性和准确性.结果表明,利用本工作提出的变模温注塑工艺,可在不降低生产效率的同时,彻底消除塑件表面熔接痕和提高塑件表面光泽度.     

复杂塑料包装箱熔接痕疵病分析及工艺改进

目的 解决熔接痕疵病问题,降低废品率,提高生产效率。方法 通过熔接痕疵病成型机理及原因分析,采取在注塑模具上增加排气装置、改进分流道分布、增加冷却水道组数等工艺改进措施,改进后进一步优化注塑工艺参数。结果 工艺改进后,熔接痕疵病问题得以解决,产品质量提高,经过自由跌落工艺试验验证,工艺改进后加工的产品满足GJB 4403—2003和产品图样的相关要求,废品率由3%降低到0.78%以下,生产效率提高23%。结论 改进效果明显,解决了熔接痕疵病问题,提高了产品的外观质量,降低了废品率,保证了产品的使用性能,缩短了生产周期,也为今后生产提供了技术保障。     

顺序控制技术在复杂塑料制品注射成型中的应用

采用传统热流道注射技术成型大型复杂的塑料产品,由于熔接痕数目多,使产品在涂装过程中频繁出现色兰.针对这一问题,提出了顺序控制注射技术的新方法,通过在原有注塑机上加装可控制的液压回路,实现多浇口顺序控制,从而减少或消除熔接痕.建立了某轿车前保险杠顺序控制注射成型数值模拟模型,运用控制机理及数值模拟技术,对其成型过程进行了分析.通过比较,表明采用顺序控制注射方法可以较好地控制大型注射产品成型中的熔接痕,生产试验验证所提出模型和方法的有效性和可靠性.     

热流道计算机辅助工程(CAE)在洗衣机面板成型中的应用

热流道由于其多方面的优势而越来越被用于塑料的注射成型。文中以某款洗衣机面板为例,利用Moldflow软件对普通热流道和针阀式顺序注塑过程进行了优化模拟。通过对两者成型结果的定性分析和比较,可以得出,后者成型过程中,需要的最大注射压力和最大锁模力均小于前者成型的值,而制件的气穴和熔接痕的位置和数量明显优于前者成型的效果,制件总体质量和力学性能得到明显提高。同时也提出了顺序注塑模拟中应注意的问题。     

圆环形塑件熔接痕消除方法

圆环形塑件在注射成型中,由于其本身结构特点,往往会在制件表面形成熔接痕,对外观要求高的制件来说,就会影响其表面质量,因此对于此类制件来说,熔接痕问题成为影响其质量的关键因素,也是此类制件成型中比较难于解决的问题。本文以一圆环形塑件为例,提出解决熔接痕缺陷的办法,从而提高制品外观质量。通过研究,对此类制品的成型具有借鉴意义。     

模内微装配成型微装配界面熔接黏附脱黏剥离特性

如何准确预测和调控微装配界面熔接黏附脱黏剥离特性是聚合物模内微装配成型制备高性能微型机械运动的关键科学与技术问题。针对这一关键科学与技术问题,构建了模内微装配成型微型机械运动副界面熔接黏附脱黏剥离行为的模拟仿真平台和注射温度-材料副界面脱黏剥离断裂韧性参数-界面熔接黏附脱黏剥离特性的关联关系。研究表明,运动副微装配界面的启裂应力、临界应变能释放率和完全脱黏剥离驱动力与二次成型熔体注射温度呈正相关关系,降低二次成型注射温度,可以明显减小界面的启裂应力和临界应变能释放率,抑制微装配界面的熔接黏附,有利于降低微装配界面熔接黏附脱黏剥离的驱动力,提高微装配界面的可运动性能。     

分型面为曲面的套类注射制品的有限元分析

根据塑件开口端的特殊形状,为了让推件板与曲面端吻合,推件板的形状依照塑件顶端的曲边而设计成曲面。运用Moldflow有限元软件,在模具制造之前,通过CAE软件的分析结果选择合理的成型工艺条件和冷却方法。结果表明,CAE与Pro/E的有机结合,可以预测可能产生熔接痕、气穴等缺陷的位置,避免了传统方法的反复试模、修模所引起的成本上升。从根本上提高了设计的准确性和高效性,大大缩短了设计周期。     

基于Moldflow和UG的活动盖板数值仿真分析及模具设计

目的 为了提高开模成功率,提出一种数值仿真与模具设计相结合的方法,使模具关键参数的设计具有科学依据。方法 根据经验设计几种进浇方案,然后从模流分析仿真结果中选出一种较好的方案作为预选方案;对预选方案的重要参数进行验证,如缩水性、填充时间、填充等值线、流动前沿温度、熔接痕和气穴等,在验证通过后,使用三维设计软件UG进行模具设计。结果 进浇方案2的翘曲变形量较小,为0.61 mm,可作为预选方案。对方案2进行验证可知,产品无缩水情况,填充均匀,熔体流动前沿速度一致,没有出现流痕和虎皮纹现象,熔接痕出现在非外观表面且数量较少,气穴仅出现在产品边缘。待模具冷却系统设计完毕后进行仿真分析,结果表明,凸凹模模温温差小于10 ℃,产品内应力较小,无翘曲变形风险,方案2可作为最终方案。结论 提出的数值仿真与模具设计相结合的方法,准确预测了产品成型质量,为模具设计提供了科学依据,极大提高了开模一次性成功率。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...