粗糙集理论在注塑件熔接痕分析中的应用

采用粗糙集理沦中的决策分辨矩阵,分析了注射成型过程中工艺参数和结构参数对注塑件熔接痕的影响.利用决策分辨矩阵消除信息系统中的冗余属性,找出影响熔接痕的关键因素,通过值约简,提炼出判断熔接痕的决策规则.研究结果表明,这种新的判断方法可简化复杂的分析过程,具有一定的实际应用价值.     

基于粗糙集理论的肺癌细胞图像识别

肺癌细胞的早期诊断相当困难,肺癌细胞的特征选择依据难以把握.提出根据肺癌细胞的每个特征属性对粗糙集下、上近似集的影响程度作为属性约简的依据,根据约简的结果,再采用扩展的相近关系粗糙集对肺癌细胞进行识别诊断.利用下近似集中的结果进行判断可以提高识别的准确率,利用上近似集中的结果进行判断可以降低肺癌细胞识别的漏诊率.从识别的结果来看,方法行之有效.     

基于粗糙集-贝叶斯的电网故障诊断方法

提出了一种基于粗糙集-贝叶斯的电网故障诊断方法,采用粗糙集信息表约简方法对电网故障特征进行约简,获取了电网故障诊断最小决策表,然后针对最小诊断决策规则建立贝叶斯网络模型,利用贝叶斯网络节点之间的权重关系提高电网故障诊断的效率和正确率.     

基于粗集理论的数据挖掘应用

论述了粗集的基本理论和特点,并对其在旋转机械故障诊断中的应用进行了探索,提出了粗集理论在旋转机械故障诊断中的数据挖掘方法,运用这一方法对故障诊断决策表进行属性约简,去除其中不必要的属性,揭示出旋转机械故障诊断条件属性中的冗余性,最后得出了属性约简的结果以及决策规则。     

基于粗糙集的属性约简及其在高校就业数据分析中的应用

粗糙集理论是数据分析与知识发现的数学工具,近年来已被广泛应用于各个研究领域。本文利用粗糙集理论的属性约简算法,找出了影响高校数学专业学生就业的约简集。研究成果可以帮助高校学生更好地制定职业规划,为将来就业提供一定的帮助。     

注射成型缺陷的智能诊断

针对注射成型仿真软件提供的大量离散数值数据（如温度场、压力场）难于进行理解和直接用来指导模具设计的现象，提出基于知识（包括CAE仿真数据）的注射成型缺陷智能诊断方法，在阐述注射成型知识组成的基础上，描述了注射成型缺陷诊断原理、实现方法和实施框架，并以气泡缺陷为例，阐述了智能诊断的应用过程。     

固体催化剂成型工艺的研究进展

介绍了常用的固体催化剂成型方法,包括挤条成型、喷雾成型、压片成型,转动成型等。探讨了成型过程对催化剂性能的影响,分析了这些成型方法的成型原理和实际应用。     

波纹管成型凸模半径优化设计

成型凸模半径对波纹管下井后的膨胀性能有重要影响。针对成型凸模不同半径尺寸对波纹管成型过程中力学特性的影响,基于金属弹塑性力学、板材成型理论及有限单元法,建立了波纹管成型过程及力学行为的有限元模型,并利用有限元软件ABAQUS对该模型进行了仿真计算,从而得到了成型后的波纹管形状,并获得了成型凸模半径对成型过程残余应力和残余应变的影响,进一步求取了成型凸模半径的最优值为25mm。     

粉煤成型技术研究进展

综述了国内外型煤技术研究现状,针对我国煤炭机械化开采过程中的粉煤利用难问题,提出了粉煤成型利用的必要性。总结了粉煤成型影响因素、型煤粘结剂及粉煤成型机理研究进展,研究表明:粉煤的性质、成型水分、煤料粒度、成型工艺、成型压力、粘结剂性质及添加量等对粉煤成型有很大影响;提出了粉煤无粘结剂成型过程假说和粉煤有粘结剂成型理论,为粉煤成型利用技术开发提供了理论基础。     

浅谈气辅成型过程中工艺参数对制品性能的影响

本文结合国内外对气辅成型工艺的研究。比较了气辅成型和传统的注射成型成型制件的优缺点。通过讨论在气辅成型过程中,熔体预注射量、气体延迟时间和气体压力等工艺参数对制品性能的影响,揭示了影响制品性能的内在因素取向机理在气辅成型和传统的注射成型成型的不同及气辅成型技术研究发展的趋势。     

INCREASING FLOW LENGTH IN THIN WALL INJECTION MOLDING USING A RAPIDLY HEATED MOLD

Injection molded parts are driven down in size and weight especially for portable electronic applications. While gains are achieved via cost reduction and increased portability, thinner parts encounter more difficulty in molding due to the frozen layer problem. To increase moldability in thin wall molding, a rapid thermal response (RTR) mold was investigated. The RTR mold is capable of rapidly raising the surface temperature to the polymer melt temperature prior to the injection stage and then rapidly cooling to the ejection temperature. The resulting filling process is done inside a hot mold cavity and formation of frozen layer is prohibited. Concepts of scalable filling and low-speed filling are discussed in the article to address the benefit of this molding method. Simulation results showed that significant reduction in injection pressure and speed can be achieved in RTR molding. In contrast to the filling behavior in conventional molding, the injection pressure in RTR molding decreases as the injection speed decreases, and therefore, extremely thin parts can be molded at lower injection speeds. Filling lengths of both RTR and conventionally molded polycarbonate samples, with two levels of thickness, under two levels of injection speed were experimentally studied. The experimental results demonstrated the advantage of the new molding method.     

塑料注射成型技术的最新进展

阐述了近年来塑料注射成型的一些新技术,包括微型注射成型技术、振动气体辅助成型技术、节能降耗注射成型技术、水辅注射成型技术、簿壁超高速注射成型技术等,并对注塑成型技术的发展前景进行了展望。     

Molding of reprocessed thermoplastics with preplastication injection molding

The injection molding of reprocessed plastics with a preplastication plunger injection‐molding machine was investigated with a focus on the processing conditions. The process of the filling of the resin into the mold is much better controlled with preplastication than with processing in a conventional injection‐molding machine. Reprocessing of the resin leads to a reduction in molecular weight due to drastic changes in the resin morphology, thereby causing a reduction in melt viscosity. Direct experimental evidence for reduced viscosity was obtained from measurements of the filling pressure recorded on the machine and also with a melt‐flow indexer. The results of this study provide a practical solution for reducing the resin temperature when reprocessed resin is used in the injection molding of plastics. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1455–1461, 2001     

Processing enhancers for rotational molding of polyethylene

Rotational molding is a zero shear process used to manufacture hollow plastic parts. One disadvantage of this process is long cycle times, which are significantly affected by the sintering rates of thermoplastic powder. The objective of this work was to evaluate low molecular weight additives as sintering enhancers for polyethylene and to validate the results in rotational molding. The following additives were blended with linear low‐density polyethylene: mineral oil, glycerol monostearate and pentaerythritol monooleate. The additives resulted in decreased melt viscosity and/or elasticity at low shear rate. The reduction in melt elasticity was particularly significant. Sintering studies confirmed that the additives resulted in significantly faster coalescence. In uniaxial rotational molding, the decreased melt viscosity and elasticity obtained with mineral oil were observed to result in much faster densification and bubble removal. Part thickness was uniform and there was no warpage. Adding mineral oil to polyethylene reduced the cycle time in uniaxial rotational molding and the peak impact strength was identical to that obtained without any additive. Biaxial rotational molding experiments confirmed that the use of mineral oil resulted in shorter cycle time without sacrificing peak impact strength.     

NiO直接电化学还原制Ni制片条件对阴极片孔隙率影响研究

本文研究了NiO直接电化学还原制取Ni工艺过程中制片条件对阴极片孔隙率影响。设计正交实验研究了成型过程中粘结剂的浓度和用量、球磨时间和成型压力对阴极片孔隙率的影响。结果表明,其中成型压力影响最大。利用SEM、测定孔隙率等手段研究了成型压力、烧结时间和烧结温度对NiO片的影响。结果表明:三者对孔隙率影响程度由大到小依次为:烧结温度、成型压力、烧结时间;随着烧结温度压力和成型压力的增大,试样孔隙率逐渐减小;而烧结时间对试样孔隙率的影响不大。     

新能源汽车全塑车身先进制造技术

轻量化技术是当前汽车节能、减少污染的最有效途径之一,全塑车身成型方法是突破汽车轻量化的关键技术,应用旋塑成型工艺可以实现汽车车身塑化制造的整体成型。本文主要介绍全塑车身的整体轻量化设计、成型设备、车身模具、加工工艺的先进制造技术,并对其进行研究对比试验。结果表明：应用计算机辅助设计、机电控制和高分子材料等领域的先进技术,通过对旋塑设备进行热流分析与能效优化,采用模具内无线测温技术、模具单元分块快速开合模技术和微发泡技术可以满足全塑车身整体一次成型。     

Flow‐induced crystallization in the injection molding of polymers: A thermodynamic approach

The prediction of the crystallinity and microstructure that develop in injection molding is very important for satisfying the required specifications of molded products. A novel approach to the numerical simulation of the skin‐layer thickness and crystallinity in moldings of semicrystalline polymers is proposed. The approach is based on the calculation of the entropy reduction in the oriented melt and the elevated equilibrium melting temperature by means of a nonlinear viscoelastic constitutive equation. The elevation of the equilibrium melting temperature that results from the entropy reduction between the oriented and unoriented melts is used to determine the occurrence of flow‐induced crystallization. The crystallization rate enhanced by the flow effect is obtained by the inclusion of the elevated equilibrium melting temperature in the modified Hoffman–Lauritzen equation. Injection‐molding experiments at various processing conditions were carried out on polypropylenes of various molecular weights. The thickness of the highly oriented skin layer and the crystallinity in the moldings were measured. The measured data for the microstructures in the moldings agree well with the simulated results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 502–523, 2005     

Processing of short fiber reinforced polypropylene. II: Statistical study of the effects of processing conditions on the impact strength

Within the general objective of analyzing and modeling the processability of polypropylene and of its short fiber composites, a statistical analysis of the relationship between processing conditions and final properties has been performed applying modern experimental design concepts. In order to gather the largest amount of information with a manageable quantity of experiments, Taguchi methods were used for the design of injection molding tests and for the analysis of experimental fiber orientation and impact strength results. Two levels of each variable of interest were selected, and the results of the analysis not only show which of the processing variables are predominant but also show that interactions between variables must be taken into account. The approach presented here offers a viable route to the scaling-up of the injection molding process through the reduction of the number of variables in the prediction of the processing behavior of semicrystalline polymers and of their composites.     

Thin‐wall injection molding of polypropylene using molds with different laser‐induced periodic surface structures

In injection molding, high pressure is required to completely replicate the mold geometry, due to the viscosity of thermoplastic polymers, the reduced thickness of the cavity, and the low mold temperature. The reduction of the drag required to fill a thin‐wall injection molding cavity can be promoted by inducing the strong slip of the polymer melt over the mold surface, which occurs within the first monolayer of macromolecules adsorbed at the wall. In this work, the effects of different laser‐induced periodic surface structures (LIPSS) topographies on the reduction of the melt flow resistance of polypropylene were characterized. Ultrafast laser processing of the mold surface was used to manufacture nano‐scale ripples with different orientation and morphology. Moreover, the effects of those injection molding parameters that mostly affect the interaction between the mold surface and the molten polymer were evaluated. The effect of LIPSS on the slip of the polymer melt was modeled to understand the effect of the different treatments on the pressure required to fill the thin‐wall cavity. The results show that LIPPS can be used to treat injection mold surfaces to promote the onset of wall slip, thus reducing the injection pressure up to 13%. POLYM. ENG. SCI., 59:1889–1896, 2019. © 2019 Society of Plastics Engineers     

Automated Design for the Runner System of Injection Molds Based On Packing Simulation

Multiple injection cavities are automatically balanced by adjusting runner and gate sizes based on an iterative redesign methodology integrated with computer-aided engineering (CAE) packing simulation. For runner balancing, each cavity must be filled simultaneously at uniform pressure. In addition, the time-pressure history of the polymer melt over the entire molding cycle should be considered. Based on the proposed methodology, a multicavity mold with identical cavities is balanced to minimize entrance pressure differences among various cavities at discrete time steps of the molding cycle. The results have shown more than a 95% reduction of the entrance pressure differences over other related studies, and also have demonstrated increased searching performance over other optimization techniques. A family mold with different cavity volumes and geometries is also balanced to minimize pressure differences at the end of the melt flow path in each cavity on a basis of discrete time steps of the molding cycle. The methodology has shown uniform pressure distributions among the cavities during the entire molding cycle.