Computer aided engineering in the foundry industry

Refinement of design and increasing demands for accurate pattern, core box and die making haved caused both designers and manufacturers to see how the computer might be used to aid them in their problems. The system of computer aided engineering [CAD/CAM°)] both for design and for manufacture shown in the following, is now firmly established in British and German industry for the design and manufacture of complex shapes. This paper discusses some of the problems which are being solved by its use.     

提高铝合金压铸模使用寿命的途径

针对3Cr2W8V钢制铝合金压铸模,采用真空亚温淬火加浅层氮碳共渗改进的热处理工艺,并找出了适宜的工艺参数.结果表明,该工艺能明显提高模具的抗热疲劳性能和使用寿命.     

A RUNNER-GATE DESIGN SYSTEM FOR DIE CASTING

Various analytical finite element method (FEM) tools have been developed for flow processes, including die casting, but they only give information about whether the predetermined die design is correct. Current shop practice uses trial-and-error methods to determine new die designs. This article describes development of a computer-aided die design system for die casting. The computer-assisted design (CAD) system was written using Auto LISP with a personal computer. This system was developed to present algorithms for automation of die design, especially a runner-gate system using three-dimensional geometry. This system quantifies practical knowledge and experiences in die design as the formulating procedure. The system allows engineers to make automatic and efficient designs and it will result in reduction of required expenses and time. The system is composed of selection of cast alloy and product design, and uses the runner-gate design. In addition, specific rules and equations for the system are presented. An example is applied to a cap-shaped casting using the proposed system.     

Powder Deposition in Three Parallel-Oriented Dies of Different Shapes

Uniformity of bulk density distribution during the die filling process is required to minimize quality problems, such as distortion and cracking, for powder compacts. Understanding the die filling process is necessary in ensuring a uniform powder deposition. The second-generation pressure deposition tester (PDT-II) was used to investigate the deposition process and final pressure distribution of powder filling in toroidal, cylindrical, and E-shaped dies. All tests were conducted using a spray-dried free-flowing granular powder. The results indicated that for toroidal dies: (1) the area around 0° orientation (the leeward end) had the highest pressure values (1186.7 to 2498.0 Pa), with the average pressure values of the remaining area 353.7-648.0 Pa; (2) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; (3) the highest feed shoe speed (500 mm/s) led to the most nonuniform pressure distribution among the three speeds; (4) higher feed shoe speed did not always result in higher final pressure values; and (5) the right die tended to have higher final pressure values (215.0 to 2498.0 Pa) than the center die (95.4 to 2052.5 Pa). For E-shaped dies: (1) the final pressure values of the middle leg (308.9 to 760.7 Pa) were higher than those of the left and the right legs (148.9 to 530.3 Pa); (2) the area along the backside had the highest final pressure value (1054.6 to 1303.8 Pa); (3) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; and (4) neither the center die nor the right die always had higher pressure values than the other one at all locations. Comparison between cylindrical and toroidal dies indicated that: (1) neither of the two die shapes (cylinder and toroid) led to consistently higher or lower final pressure values at all locations and (2) for all three feed shoe speeds, the toroidal die had higher average final pressure values in the 0° orientation.     

Gating System Design for a Magnesium Alloy Casting

The gating system of a cylindrical magnesium casting has been designed by using multiple objective optimiza- tion and Taguchi method.Mold filling and solidification processes were simulated by using MAGMASOFT（？）. The simulation results indicate that the gating system design has a significant effect on the quality of magne- sium castings.In an effort to obtain the optimal design of gating system,the signal-to-noise （S/N） ratio was used to analyze the effect of various gating designs on cavity filling and casting quality by using a weighting method based on the design of an orthogonal array.Four gating system parameters,namely,ingate height, ingate width,runner height,runner width,were optimized with a consideration of multiple objective criteria including filling velocity,shrinkage porosity and product yield.     

Computer aided analysis of strain rosette data

In this paper a computer program has been developed for analysing the strain gauge rosettes by considering the transverse sensitivity of all gauges. The program is capable of calculating principal strains, maximum shear strain, principal stresses, maximum shear stress and principal directions from the data obtained by using strain gauge rosettes of various configurations. The gauge factor and transverse sensitivity of all gauges in the rosette must be the same.     

Neuro-Knowledge-Based Expert System (NKBES) for Optimal Scheming of Die Casting Process

We develop a neuro-knowledge-based expert system (NKBES) frame in this work. The system mainly concerns with decision of gating system and die casting machine based on a neuro-inference engine launched under the MATLAB software environment. For enhancement of reasoning agility, an error back-propagation neural network was applied. A rapidly convergent adaptive learning rate (ALR) and a momentum-based error back-propagation algorithm was used to conduct neuro-reasoning. The working effect of the system was compared to a conventional expert system that is based on a two-way (forward and backward) chaining inference mechanism. As the reference, the present paper provided the neural networks sum-squared error (S5E) and ALR vs iterative epoch curves of process planning case mentioned above. The study suggests that the neuro-modeling optimization application to die casting process design has good feasibility, and based on that a novel and effective intelligent expert system can be launched at low cost.     

镁合金及其铸造成形技术

镁合金是目前最轻的结构材料,在汽车、电子等诸多领域的应用日益增加。本文介绍了铸造镁舍金的性能及强化方法、镁合金熔炼的阻燃、镁合金的铸造成形技术和铸造缺陷及改进方法。     

流动注射——荧光法测定水样中敌敌畏含量

有机磷农药敌敌畏(DDVP)在过硼酸钠的作用下可将胺类化合物氧化成可发荧光的产物。本研究根据这一原理,建立了定量测定这类农药的流动注射——荧光分光光度法。该方法具有分析速度快、操作方便、重现性好、灵敏度较高等特点。     

Influences of Casting Pressure Conditions on the Quality and Properties of a Magnesium Cylinder Head Cover Die Casting

Casting pressure conditions have great influences on the casting defects, such as gas porosity, shrinkage porosity and gas holes. A Mg cylinder head cover die casting was used to experimentally study the influences of casting pressure, the loading time and the piston position of pressure intensification on the variation of pressure and the quality of casting. The results show that casting pressure, the loading time and the piston position of pressure intensification have great influences on the pressure variations in the mold, the quality and performance of casting. The external quality, the density and the tensile strength of casting were improved with the increase of casting pressure and the piston position of pressure intensification and the decrease of the loading time of pressure intensification.     

Effect of Cu addition on microstructures and tensile properties of high-pressure die-casting Al-5.5Mg-0.7Mn alloy

In this study, Cu was added into the high-pressure die-casting Al-5.5Mg-0.7Mn (wt%) alloy to improve the tensile properties. The effects of Cu addition on the microstructures, mechanical properties of the Al-5.5Mg-0.7Mn alloys under both as-cast and T5 treatment conditions have been investigated. Additions of 0.5 wt%, 0.8 wt% and 1.5 wt% Cu can lead to the formation of irregular-shaped Al₂CuMg particles distributed along the grain boundaries in the as-cast alloys. Furthermore, the rest of Cu can dissolve into the matrixes. The lath-shaped Al₂CuMg precipitates with a size of 15–20 nm × 2–4 nm were generated in the T5-treated Al-5.5Mg-0.7Mn-xCu (x = 0.5, 0.8, 1.5 wt%) alloys. The room temperature tensile and yield strengths of alloys increase with increasing the content of Cu. Increasing Cu content results in more Al₂CuMg phase formation along the grain boundaries, which causes more cracks during tensile deformation and lower ductility. Al-5.5Mg-0.7Mn-0.8Cu alloy exhibits excellent comprehensive tensile properties under both as-cast and T5-treated conditions. The yield strength of 179 MPa, the ultimate tensile strength of 303 MPa and the elongation of 8.7% were achieved in the as-cast Al-5.5Mg-0.7Mn-0.8Cu alloy, while the yield strength significantly was improved to 198 MPa after T5 treatment.     

Computer Aided Model for Casting Aluminium Using Die-Casting

Computer aided casting of aluminum using die-casting was developed. A piston, which is an automobile part and very important in internal combination engine, was chosen for the research. Pistons are made of aluminum alloy. Models of the products were developed to aid the casting process. Mathematical models that show the dimensions of the casting were also developed. Since the project is about using computer to aid casting process, a program using visual basic （VB） Language was developed. The program was used to incorporate die-casting process into computer system. The written program was tested and the model of the casting product （piston） was displayed. The result shows that computer which is faster with accurate result can be used as an aid in the production of aluminum piston using die-casting process, for accurate planning in the manufacture of the product.     

压铸模温度场与铸件质量关系的研究与应用

运用有限元分析软件ANSYS对薄壁铝合金压铸件的压铸过程进行温度场数值模拟分析,研究了浇注温度、模具预热温度对温度场分布的影响,分析了热应力集中的位置,从而有效控制了铸件因热应力引起的体积收缩,保证了铸件质量及其精度,优化了压铸工艺参数,为压铸模具的热应力分析奠定了基础。     

Review on the experimental studies of refrigerant flow mechanisms inside short-tube orifices

A short-tube orifice is a kind of an expansion device. The advantages of a short-tube orifice are simplicity, low cost, and low starting torque of the compressor as the pressures across the short-tube orifice equalise during the off-cycle. The two-phase flow mechanisms of refrigerant inside the short-tube orifice are very complicated although its physical configurations are simple. During the past decade, investigations of the mass flow rate of various refrigerants inside short-tube orifices, which is useful for selecting the proper size in practical applications, have been reported by many researchers. However, few researchers focused on the flow pattern, choked flow, and metastable flow phenomena inside short-tube orifices, which are necessary for a clear understanding of the flow behaviour and developing suitable calculation techniques. The aim of this paper is to summarise the evolution of the experimental research on refrigerant flow characteristics inside short-tube orifices to provide guidelines for future research.     

镍基高温合金调压铸造非线性压力曲线设计与验证

目的 针对变截面铸件在调压铸造充型阶段出现充型不稳定这一问题,结合数值模拟分析,提出非线性压力曲线的设计方法。方法 基于Pro CAST软件对不同壁厚和不同截面比的模型进行模拟,研究在不同加压速度和不同型壳预热温度下不同壁厚模型浇口速度的变化情况,以及在不同加压速度下不同截面比模型浇口速度的变化情况。针对数值模拟结果提出变截面模型工艺优化方法,设计特征模型进行数值模拟验证;推导在实际调压铸造充型过程中加压速度与充型速度的关系,并利用水力学模拟进行验证。结果 用非线性加压进行数值模拟,相对于线性加压充型过程,其浇口速度普遍呈下降趋势,其中最大浇口速度由0.29 m/s下降到0.2m/s,降幅为45%;在变截面前后,浇口速度呈周期性波动,说明非线性加压充型较为稳定;对推导出的加压速度计算公式进行了水力学模拟实验,从充型形态可以看出,在变截面处水流波动平稳,验证了加压速度计算公式的正确性。结论 通过研究变截面突变浇口速度的变化情况,提出了非线性加压方法,有效解决了调压铸造过程中出现的金属液飞溅、振荡、充型不稳定等问题,不仅提高了铸件的成品率,而且优化了调压设备的精准控压。     

连续流动注射法测定水中总磷的不确定度评估

本文从标准曲线拟合、磷标准溶液配制、重复性、标准系列溶液配制、示值误差、测量环境条件和操作人员影响等六个方面对连续流动注射法测定水中总磷的不确定度进行分析计算,合成标准不确定度（U）和扩展不确定度（U）。     

梯形槽中高聚物熔体压力流动的理论模型研究

以梯形槽中高聚物熔体为研究对象，基于塑料成型加工过程中熔体在梯形槽中的流动行为，推导了熔体压力流动的速度分布和体积流率的理论模型方程。结果表明：在不计黏温效应的前提下，影响其速度分布和体积流率的主要因素有熔体黏度、流动指数、梯形槽尺寸和两端压力差；梯形槽两侧壁对流率的修正因子是截面宽高比和熔体流动指数的函数。     

Computer aided diagnosis of brain abnormalities using texture analysis of MRI images

The drive of this study is to develop a robust system. A method to classify brain magnetic resonance imaging (MRI) image into brain-related disease groups and tumor types has been proposed. The proposed method employed Gabor texture, statistical features, and support vector machine. Brain MRI images have been classified into normal, cerebrovascular, degenerative, inflammatory, and neoplastic. The proposed system has been trained on a complete dataset of Brain Atlas-Harvard Medical School. Further, to achieve robustness, a dataset developed locally has been used. Extraordinary results on different orientations, sequences of both of these datasets as per accuracy (up to 99.6%), sensitivity (up to 100%), specificity (up to 100%), precision (up to 100%), and AUC value (up to 1.0) have been achieved. The tumorous slices are further classified into primary or secondary tumor as well as their further types as glioma, sarcoma, meningioma, bronchogenic carcinoma, and adenocarcinoma, which could not be possible to determine without biopsy, otherwise.     

Computer aided automated detection and classification of brain tumors using CANFIS classification method

The development of abnormal cells in human brain leads to the formation of tumors. This article proposes an efficient approach for brain tumor detection and segmentation using image fusion and co-active adaptive neuro fuzzy inference system (CANFIS) classification method. The brain MRI images are fused and the dual tree complex wavelet transform is applied on the fused image. Then, the statistical features, local ternary pattern features and gray level co-occurrence matrix features. These extracted features are classified using CANFIS classification approach for the classification of source brain MRI image into either normal or abnormal. Further, morphological operations are applied on the abnormal brain MRI image for segmenting the tumor regions. The proposed methodology is evaluated with respect to the performance metrics sensitivity, specificity, positive predictive value, negative predictive value, tumor segmentation accuracy with detection rate. The proposed image fusion based brain tumor detection and classification methodology stated in this article achieves 96.5% of average sensitivity, 97.7% of average specificity, 87.6% of positive predictive value, 96.6% of negative predictive value, and 98.8% of average accuracy.     

Computer aided teaching in civil engineering materials science at the University of Stuttgart

During the past five years the Institute of Construction Materials at the University of Stuttgart (IWB) has participated in different projects concerning e-teaching. Amongst other efforts co-workers of IWB have created a set of virtual content concerning concrete technology within a German e-teaching network in civil engineering materials science called “WiBA-Net” (). The content of this network consists of teaching material that is organized at four different levels of granularity. At the most basic level single items (“assets”) are collected. At the second level such assets are arranged into single pages filling one screen. Several pages dealing with aspects of a single topic are ordered into a teaching path at the third level and finally a set of teaching paths forms an entire course at level four. Virtual searching methods are offered on all four levels depending on the state of the user. Besides the mentioned teaching material also virtual communication facilities are offered within the network. During the work on WiBA-Net, which consists of six German Universities, questions concerning the reusability of virtual content, metadata enhancement techniques and the concept of Blended Learning were focused. Educational and didactic aspects have been closely taken into account and quality assuring evaluation methods have been applied. Meanwhile first experiences have been made in real life teaching and learning situations, which give us an idea of future needs and development in the field.