Fiber orientation in melt confluent process for reinforced injection molded part

Fiber orientation in reinforced polymer parts can greatly affect the appearance and mechanical properties. The fiber orientation process during a confluent process of two or more strands of melt in a mold cavity is discussed. Different from common polymer melts with no reinforced material, a novel model describing the confluent process for fiber-reinforced melt is established. Through finite element simulation, fiber orientation and its accumulation state in different layers of plastic parts are obtained. 3D surface morphologies of the confluent region caused by fiber orientation and distribution are tested in the laboratory, and the relationships between the mold temperature and the appearance of the confluent region are presented as well. By using SEM to observe the fiber orientation induced in different mold temperatures, the effect of the fiber orientation in confluent region process on the impact strength of the resultant parts is discussed. Testing results prove that the established model is effective in explaining the outcome of the confluent process for fiber-reinforced materials.     

Evaluation of inhomogeneous deformation and stress concentration in polymer composites injection weld by means of thermoelastic techniques

Fiber composite materials are widely used in aerospace industries due to their high specific strength and stiffness. Especially, the increasing use of polymer composite materials for injection of automobile components has led to a considerable interest in the application of stress pattern analysis by thermal emission to these composite materials. Therefore, in this study the microstructure of glass fiber orientation at the parent and weld line of polycarbonate is observed by a light transmission microscope. And we also investigate a stress concentration model of a notch including short glass fibers. Especially the polymer injection weld reorients the fiber to suggest a new method for the evaluation of inhomogeneous deformation.     

Experimental investigation of the factors influencing the polymer–polymer bond strength during two-component injection moulding

Two-component injection moulding is a commercially important manufacturing process and a key technology for combining different material properties in a single plastic product. It is also one of most industrially adaptive process chain for manufacturing so-called moulded interconnect devices (MIDs). Many fascinating applications of two-component or multi-component polymer parts are restricted due to the weak interfacial adhesion of the polymers. A thorough understanding of the factors that influence the bond strength of polymers is necessary for multi-component polymer processing. This paper investigates the effects of the process conditions and geometrical factors on the bond strength of two-component polymer parts and identifies the factors which can effectively control the adhesion between two polymers. The effects of environmental conditions on the bond strength are also investigated. Investigation shows that melt and mould temperatures are vital process parameters that influence the bond strength. Besides this, surface roughness of the first-shot part and environmental factors like moisture have profound influence on the bonding of the two materials. The selections of materials and environmental conditions were done based on the suitability of MID production, but the results could be useful for two-component polymer processing for a wide range of industrial applications. The results and discussion presented in this paper are only valid for the two-component plastic parts moulded by over moulding in cavity-transfer process.     

注射模的定位原理

生产实践中经常会遇到关于注射定位方式的选择,定位机构的设计等问题,注射模定位模外和模内定位,模具的定位不合理,在高锁模压力下会损坏模人。地对此问题,以注射模定位原理主基础,进行了探讨和系统性总结。     

离合器齿毂总成试验与焊接强度研究

对离合器齿毂总成试件进行焊接强度台架试验,得到离合器齿毂总成试件的破坏形式、焊缝处焊接极限强度.建立离合器齿毂总成有限元模型,并进行焊接强度仿真模拟分析.通过台架试验与仿真实验结果的对比,两者比较接近,验证了有限元仿真模型的有效性,为以后离合器齿毂的研发提供了参考.     

The development of simplified ultrasonic CT system and its application to the evaluation of weld metal

In this paper, as a new measurement method to estimate the change of material condition, the simplified ultrasonic CT system, which uses the information of three directions, that is, 90°, + 45° and −45° about inspection plane is proposed. Use of simplified CT system has two merits: Firstly, the measurement time is very short compared with general CT. Secondly, it can detect sensitively small defect in vertical or slant direction about inspection plane because the obtained image is CT image calculated from three directions. From these merits, this method can be considered as an effective method to evaluate material conditions. The basic performance of the proposed method was confirmed through several specimens with several simple defects. In order to confirm the applicability of actual NDT, several kinds of welded specimens are investigated. The result showed that the CT image obtained had good agreement with actual defect of specimens.     

Effect of gate dimension on micro injection molded weld line strength with polypropylene (PP) and high-density polyethylene (HDPE)

As a defect of micro injection molding parts, weld line is unfavorable since it will influence the surface quality and mechanical properties of micro parts. Therefore, the investigation on the developing process of weld line would be a significant issue for improving the quality of micro injection molded parts. In this study, one injection mold with four micro tensile sample cavities was designed and constructed. Every cavity responses to various gate dimensions, which is marked as Gate $ {\text{Nr}}.1\left( {1.5 \times 0.1 \times 0.{\text{5mm}},{\text{width}} \times {\text{depth}} \times {\text{length}}} \right) $ , $ {\text{Nr}}.2\left( {1.0 \times 0.1 \times 0.{\text{5mm}},{\text{width}} \times {\text{depth}} \times {\text{length}}} \right) $ , $ {\text{Nr}}.3\left( {1.0 \times 0.05 \times 0.{\text{5mm}},{\text{width}} \times {\text{depth}} \times {\text{length}}} \right) $ , and $ {\text{Nr}}.4\left( {0.5 \times 0.1 \times 0.{\text{5mm}},{\text{width}} \times {\text{depth}} \times {\text{length}}} \right) $ . The effects of gate dimension of the mold on mechanical properties of weld line have been studied by experiments in different processing parameters. The tensile test was used to characterize the micro injection molded weld line strength. The results for polypropylene show that with the changing of injection pressure and mold temperature, Gate Nr.3 is corresponding to the strongest weld strength; the next is Gate Nr.2; Gates Nr.4 and Nr.1 are in the end. The difference between them is not obvious. For high-density polyethylene, Gate Nr.1 is not able to be completely filled, which is due to the blocking of stick materials and dirt based on the simulation analysis. The investigation was only carried out for the other three gate sizes; results present that Gate Nr.3 always gives the best weld line strength whatever the processing parameters are, Gate Nr.4 is next and then Gate Nr.2. There are always middle optimal values for processing parameters leading to strongest weld line strength, when injection pressure is 80 MPa, injection speed is 90 cm³/s, melt temperature is 200°C, and mold temperature is 130°C. Higher and lower processing parameters result in reduced weld line strength.     

Effect of Lack of Penetration on the fatigue strength of high strength steel butt weld

Fatigue tests are performed to evaluate the fatigue strength of high strength steel containing partial penetration butt weld and full penetration butt weld. The influence of the unwelded ligament (Lack of Penetration) in the partial penetration welds on the fatigue life is analyzed for various LOP sizes. For full penetration welds, the fatigue crack initiated at the weld toe and propagated to the HAZ. For partial penetration welds, however, the fatigue cracks initiated at the LOP section and propagated to the weld metal (or weld toe) for the considered LOP sizes (from 2mm to 4mm) reducing the fatigue strength. Consequently, the increament of the LOP size yield in the fatigue life degradation by some extent.     

铝合金焊缝X射线底片智能评定技术

分析铝合金焊缝X射线底片的特点 ,阐述焊缝X射线自动化评片技术的发展 ,探讨焊缝X射线底片特征参数提取和模式识别技术 ,设计出铝合金焊缝X射线智能评片系统     

基于MSC.Fatigue的安全带固定支架焊缝的疲劳强度分析及优化

以某型号座椅为例,基于材料力学、断裂力学和局部应力应变法给出了汽车座椅安全带固定支架焊缝的静强度和疲劳强度的计算模型。通过MSC.patran建立其有限元模型,并进行了静力学分析,分析结果揭示了焊缝的应力集中部位。在静力学分析的基础上通过MSC.Fatigue进行了疲劳强度分析,结果表明应力集中部位的疲劳寿命最低,构件的疲劳寿命主要受薄弱环节的疲劳状况影响。根据有限元仿真分析结果,提出了"安全区域"的概念,基于"安全区域"对焊缝进行了优化设计,结果表明断续段焊缝相对于连续全焊缝更加符合工程实际要求。     

纺丝箱应力分析和强度评定

采用有限元法分析、计算纺丝箱的应力,并按分析设计原理进行强度评定。计算结果显示,在拉撑杆与侧板连接区、圆角区和长边侧板中部出现高应力。有限元法是一种有效、实用的方法,可方便地计算出复杂结构的应力。计算结果按线性处理简便、可靠。强度评定结果显示,纺丝箱安全。     

国内外规范中铝合金焊缝形式对强度及疲劳的影响分析

随着铝合金材料逐步用于重大结构件,对其安全性能分析日趋重视,特别是对于焊缝部位的关键设计尤为重要.文中基于国内外主要的铝合金设计规范,对铝合金结构的对接焊缝和角焊缝两种焊缝形式的构造进行比较,并对考虑热影响区软化作用下的焊接材料及铝合金构件强度及疲劳强度进行分析对比,说明不同规范对于铝合金结构焊缝形式设计计算的要点和区...     

Parametric study of injection molding and hot embossing in polymer microfabrication

In recent years, plastics have begun to show great commercial potential especially in manufacturing micro-structured parts. Injection molding and hot embossing are two major microfabrication methods. Replication accuracy was investigated for these two methods. Polymethyl methacrylate (PMMA) was used as the polymer substrate. The mold insert (or master) was fabricated by LIGA-type method. In this study, hot embossing was found to have better replication accuracy for microstructure than injection molding. Experiments were also conducted to study the effects of process parameters on the replication quality.     

基于熵带与DS理论的焊缝等级磁记忆量化评价

针对焊缝不同等级的磁记忆特征提取及定量评价难题,提出信息熵带与D-S理论联合的磁记忆定量评价模型。以Q235B焊接试件为实验材料,通过焊缝疲劳损伤试验,对照X射线定量评价标准,引入能够反映焊缝损伤程度的奇异谱熵、功率谱熵和小波空间能谱熵,分别提取不同损伤等级对应的这3种信息熵及其熵带的特征值,构建基于信息熵带数学期望的各等级贴近度公式,以信息熵贴近度作为证据体,建立基本可信度分配函数,通过D-S理论的证据组合原理将基本可信度进行信息融合,依据D-S诊断规则输出焊缝缺陷等级的定量识别结果,建立基于信息熵带和D-S证据理论联合的焊缝等级磁记忆评价模型。结果表明焊缝等级识别的不确定度为0.008,为实际工程中焊缝缺陷等级磁记忆定量化评定提供新的思路和方法依据。     

注塑模斜推杆机构强度分析及其结构尺寸研究

采用ANSYS有限元分析方法分析了圆形截面斜推杆和方形截面斜推杆的应力状况,通过试验数据对比分析了两者的强度性能.以单个几何参数为变量使用APDL语言建立了有限元参数化分析模型,研究了各个几何参数与方形截面斜推杆的强度关系,为模具设计制造过程中选用斜推杆类型和几何参数提供了理论参考.     

Influence of building orientation on the flexural strength of laminated object manufacturing specimens

This study aims to define the best building orientation for components produced via the Laminated object manufacturing (LOM) technique to enhance their flexural performance. Results of previous research show that components produced via LOM are capable of with-standing higher deflections than components produced through other layer manufacturing techniques. However, the relation between the building orientation and flexural strength of components has not yet been assessed. Four types of specimens have been manufactured using different building orientations for each type. The specimens have been tested in a machine with four loading points to evaluate their failure mode and identify the best building orientation toward flexural loading. The best building orientation in terms of maximum load before failure is 45°. Furthermore, a repetitive failure pattern is found for each tested condition. Building orientation is confirmed to be a relevant parameter in LOM manufacturing by influencing the mechanical properties of components.     

Techno-economic evaluation of reducing shielding gas consumption in GMAW whilst maintaining weld quality

A series of experimental trials have been conducted to investigate the effects of reducing the shielding gas consumption in gas metal arc welding (GMAW). A number of claims have been made as to potential shielding gas savings in the GMAW process when using gas-saving devices such as commercially available self-regulating valves. However, the literature and data available on weld quality obtained as a result of reducing the shielding gas flow rate is not readily available, so the thrust of this study is to present a new body of data to report on the technical and economic merits of controlling the shielding gas flow rate using (a) a conventional flow meter and (b) a ‘new to market’ self-regulating gas-saving device. It has been determined that, in a draft-free environment, the shielding gas flow rate can be reduced to 6?L/min without diminishing weld quality, although a lower flow rate was more susceptible to the effects of cross-drafts, and the weld quality level was compromised. In addition to the economic savings associated with reducing the shielding gas flow rate, there are several weld aspects that have been found to be influenced by the shielding gas flow rate including penetration, leg length, distortion and peak temperature, thus suggesting that the heat transfer efficiency is affected by the shielding gas flow rate. This significant finding supports the view that there is scope to increase the travel speed when implementing a lower flow rate and, consequently, enhance productivity.     

重型汽车前轴疲劳强度分析和评价

重型汽车前轴主要用于支撑车辆重量、转向机件和悬吊支架,其几何形状复杂,是汽车上承受载荷较大的重要部件.通过对某重型汽车前轴的三种结构(旧前轴、新前轴A、新前轴B)设计,选用I-DEAS软件,运用有限元的分析方法,建立模型、划分网格和约束边界条件,分别对其结构强度和疲劳寿命作了相关计算分析,实现了三种前轴结构在工况下的应...