Data-driven casting defect prediction model for sand casting based on random forest classification algorithm

The complex sand-casting process combined with the interactions between process parameters makes it difficult to control the casting quality,resulting in a high scrap rate.A strategy based on a data-driven model was proposed to reduce casting defects and improve production efficiency,which includes the random forest(RF)classification model,the feature importance analysis,and the process parameters optimization with Monte Carlo simulation.The collected data includes four types of defects and corresponding process parameters were used to construct the RF model.Classification results show a recall rate above 90% for all categories.The Gini Index was used to assess the importance of the process parameters in the formation of various defects in the RF model.Finally,the classification model was applied to different production conditions for quality prediction.In the case of process parameters optimization for gas porosity defects,this model serves as an experimental process in the Monte Carlo method to estimate a better temperature distribution.The prediction model,when applied to the factory,greatly improved the efficiency of defect detection.Results show that the scrap rate decreased from 10.16% to 6.68%.

Mineral Processing of Silica Sand in Hanout Area/South of Jordan

White sandstone samples from Hanout area of Late Cambrian-Early Ordovician sandstone in south of Jordan were studied and assessed as a source of glass sand. Upgrading the sand included removing or reducing the content of the contaminant oxides and the heavy minerals. The aim of this research was to achieve this upgrading by examining the best-suited and cost-effective processing method(s) with sufficient product recovery. Following the initial sample characterisation at “bench scale”, a pilot study was performed. A high-grade Glass Sand product of 500 - 125 μm size fraction was produced by wet screening, attrition scrubbing and the separation of heavy minerals using spirals. The high quality Glass Sand product compared well with Grade-A of the British Standard for glass sand. Due to the relatively low level of impurities in the raw material, a substantial silica sand recovery was produced with a high silica grade. The silica sand product was capable to be used in the high quality glass industry and in many other applications where pure silica is required. The mass flowrate of the feeds and the products in the spiral was calculated for the bulk sample as well as the amount of water required operating the process.

Influence of core sand properties on flow dynamics of core shooting process based on experiment and multiphase simulation

The influence of core sand properties on flow dynamics was investigated synchronously with various core sands, transparent core-box and high-speed camera. To confirm whether the core shooting process has significant turbulence, the flow pattern of sand particles in the shooting head and core box was reproduced with colored core sands. By incorporating the kinetic theory of granular flow(KTGF), kinetic-frictional constitutive correlation and turbulence model, a two-fluid model(TFM) was established to study the flow dynamics of the core shooting process. Two-fluid model(TFM) simulations were then performed and a areasonable agreement was achieved between the simulation and experimental results. Based on the experimental and simulation results, the effects of turbulence, sand density, sand diameter and binder ratio were analyzed in terms of filling process, sand volume fraction(αs) and sand velocity(Vs).

Coating process of multi-material composite sand mold 3D printing

Sand mold 3 D printing technology is an advanced manufacturing technology which has great flexible manufacturing ability. A multi-material composite sand mold can control the temperature field of metallic parts during the pouring process, while the current sand mold 3 D printing technology can only fabricate a single material sand mold. The casting temperature field can not be adjusted by using single sand mold material with isotropous heat exchange ability during the pouring process. In this work, a kind of novel coating device was designed. Multi-material composite sand molds could be manufactured using the coating device according to the casting process demands of the final parts. The influences of curing agent content, coating velocity and scraper shape on compactness and surface roughness of the sand layer(silica sand and zircon sand) were studied. The shapes and sizes of transition intervals of two kinds of sand granules were also tested. The results show that, with the increase of the added volume of curing agent, the compactness of sand layer reduces and the surface roughness value rises. With the increase of the velocity of the coating device, the compactness of sand layer reduces and the surface roughness value rises similarly. In addition, the scraper with a dip angle of 72 degrees could increase the compactness value of the sand layer. The criteria of quality parmeters of the coating procedure are obtained. That is, the surface roughness(δ) of sand layer should be equal to or lesser than half of main size of the sand particles(Dm). The parameter H of the coating device which is the distance between the base of hopper and the surface of sand layer impacts the size of transition zone. The width of the transition zone is in direct proportion to the parameter H, qualitatively. Through the optimization of the coating device, high quality of multi-material sand layers can be obtained. This will provide a solution in manufacturing the multi-material composite sand mold.

A Numerical Model of Coastal Processes of Sand Beaches Based on Long-Term Wave Series

A numerical model of shoreline change of sand beaches based on long-term field wave data is proposed, the explicit and implicit finite difference forms of the model are described, and an application of the model is presented. Results of the application indicate that the model is sensitive to the order of the input wave data, and that the effects of long-term wave series and the effects of the mean annual wave conditions on the model are different. Instead of a single wave condition, the wave series will make the calibration and the verification of the model more practical and the results of the model more reasonable.

Effect of Vibrational Modes on Sand Pressure and Pattern Deformation in the EPC Process

During the EPC (expendable pattern casting) process, one of the essential requirements is to prevent pattern distortion duringsand filling and compaction. A new method which vibrates the system in a two-dimensional circular mode has been appliedto the EPC process. The molding properties of unbonded sand obtained by this new vibration mode are investigated andcompared with those in the one-dimensional vertical mode. For adequate compaction of sand. the circular vibration mode ismore effective than the vertical mode. Sand became more fluidized by the circular vibration and the particle pressure coefficientwas close to unity The particle pressure coefficient, which is defined as the ratio of horizontal to vertical sand pressure, isresponsible for the effectiveness of sand filling.

Migration process of ammonium ion in saturated silty sand and sandy loam

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Modeling of Deposition Process of Particulate Organic Matter (POM) with Sand on Vegetated Area in a River

The transport and deposition of particulate organic matter (POM) in river streams has recently received much attention as one of important ecological processes in rivers. We focused on interacted behaviors of sand particles in bed load and POM in vegetated area on sand bars. The purpose of this study is to clarify the characteristics of deposition of POM with bed load on sandbars with the riparian vegetation. A basic experiment on POM transport and deposition with vegetation is conducted in a laboratory flume. It demonstrates that several issues still remain to be future investigated. In particular, the shear due to the bed roughness in the vegetated area and the transport and deposition process of sand particles and POM are required to be described by the proper modeling which will be introduced into a simulation model of various fluvial processes. The main results of this study are that ripples are formed by bed load in riparian vegetation and POM deposition is promoted by ripple behavior. Based on these results, the POM deposition with ripples in vegetated area is described by a conceptual model which will affect various aspects in ecosystem management based on fluvial processes.

高液压射台前板球墨铸铁件铸造工艺设计

射台前板是注塑机中的关键部件之一,其油缸孔部位加工精度高且有承压要求。本文介绍了高液压球墨铸铁射台前板铸件的工艺难点,设计了分型方案、浇注系统及冷却系统,并借助软件模拟分析了缩孔与缩松缺陷,确定了型芯方案。通过合理选择铸件的化学成分,严格控制球化、孕育及浇注过程,铸件本体渗透检验(PT)达到EN1371标准的质量等级I级,附铸试块铸件的力学性能和金相组织均符合客户标准。

玄武岩纤维沙漠砂混凝土本构关系及损伤特性研究

为了有效提高沙漠砂资源化利用,研究了玄武岩纤维掺量(0、0.3%、0.4%、0.5%)对沙漠砂混凝土本构关系和损伤特性的影响。结合本构模型拟合了玄武岩纤维沙漠砂混凝土的应力-应变曲线,利用声发射事件数分析了玄武岩纤维沙漠砂混凝土损伤破坏过程,并借助速率过程理论对玄武岩纤维沙漠砂混凝土的损伤程度进行了评估。研究表明:掺入适量的玄武岩纤维(0.4%)可以减小沙漠砂混凝土构件的损坏;Carrerira J模型与试验数据具有较高的吻合度;同时还发现构件在到达峰值应力附近时,声发射事件数会急剧增加;基于速率过程理论以损伤变量D与相对荷载V之间的关系建立的损伤演化曲线,可用来评估玄武岩纤维沙漠砂混凝土的损伤破坏程度。

黄河上游高寒沙地生态经济型治沙植物筛选评价

为助推黄河上游高寒区乡村振兴工作,在调查黄河上游沙生植物种质资源的基础上,采用层次分析法,从适应能力、扩繁能力、生态价值和经济价值4个方面确定地带性乡土植物、自然分布海拔、自然分布坡向等21个评价指标,构建黄河上游高寒沙地生态经济型治沙植物筛选层次结构模型,从22种具有经济价值的乡土治沙植物中筛选出沙棘、金露梅、银露梅、变叶海棠、垂穗披碱草、高山羊茅、高山绣线菊和窄叶鲜卑花等8种优良生态经济型治沙植物,为黄河上游高寒沙地植被恢复治沙植物选择提供科学依据。

水电站砂石冲洗系统SS废水回用中絮凝剂的累积效应

水电站砂石骨料加工系统会产生大量含有固体悬浮物(SS)的废水,由于生产环境的要求,废水经过循环处理后需要回用,而絮凝剂的累积和离子溶出情况极大地影响了后续生产的混凝土的性能。以旭龙水电站的砂石骨料冲洗废水为研究对象,对聚合氯化铝(PAC)和阳离子型聚丙烯酰胺(CPAM)絮凝处理砂石骨料冲洗废水回用过程中的絮凝效果以及絮凝剂和离子的累积效应进行了研究。结果表明:回用过程中PAC、CPAM的累积导致体系Zeta电位快速增加,从原有的负电位(-9、-4 mV)逐渐增加到正电位(0、4 mV),增加的正电荷使溶液中SS难以结合而沉降,导致絮凝效果变差;絮凝剂及絮凝剂溶出的Cl^(-)在回用过程中均出现显著累积,Al3+、CPAM、Cl^(-)累积浓度分别在1.96~3.47、3.10~9.37、160~55 mg/L范围内波动;利用构建的絮凝剂累积效应模型,可对废水回用中絮凝剂的累积情况进行预测。该研究结果可为水电站砂石冲洗废水的回用工艺提供理论指导。

基于数值模拟的通海阀铜合金铸件工艺优化

针对某船舶通海阀在铸造过程中易产生缩孔、缩松等缺陷问题,以Cu-7Ni-7Al-4Fe-2Mn合金通海阀铸件为研究对象,使用三维制图软件UG构建了铸件3D模型,并结合通海阀铸件的结构特性,设计了底注式浇注系统。利用数值模拟软件模拟了铸件的砂型铸造过程,分析了可能出现缩孔、缩松缺陷的位置,优化了通海阀铸件的浇注系统。研究了浇注温度、浇注时间、铸型预热温度等参数对铸件缩孔、缩松率的影响规律,结合正交试验方法优化出匹配的铸造工艺参数。研究结果表明,工艺参数对通海阀铸件缩孔率的影响程度从大到小依次是浇注时间、铸型预热温度、浇注温度。优化后的工艺参数分别为浇注温度1 200℃,浇注时间30 s,铸型预热温度35℃。通过在铸造缺陷较多的部位增大冒口尺寸,有效减少了缩孔、缩松铸造缺陷的产生。

高压蒸汽室铸钢件砂型铸造工艺模拟研究

基于高压蒸汽室铸钢件的结构特点和铸造工艺要求,设计了该铸钢件的砂型铸造初步方案,并采用ProCAST软件进行了充型和凝固收缩数值模拟研究。结果表明:充型过程平稳,未出现浇不足现象,但在蒸汽室底座厚大部位、蒸汽室顶部凸台处出现了大体积缩孔,同时铸件中产生了分散的缩松缺陷。结合模拟结果,对缺陷部位增加了冒口和冷铁,改进后的模拟结果良好,没有缩孔缺陷。

基于离散元的颗粒性质标定及铺砂过程模拟

喷墨打印中,砂床质量的高低直接影响最终打印零件的质量,在砂层铺设过程中砂粒的颗粒性质是影响砂床质量的关键因素之一。为研究喷墨打印中颗粒性质对砂床质量的影响,以原砂为研究对象,通过实验和离散元仿真相结合的方法完成了砂粒间接触参数进行标定,并对覆膜砂接触参数进行研究,使用颗粒间的表面能来描述砂粒流动性的变化,通过实验与仿真结合的方法得到了催化剂含量和表面能之间的关系。在砂粒颗粒性质确定的基础上,构建了喷墨打印工艺中砂床铺设过程的离散元模型,完成了颗粒性质对铺砂质量影响的仿真实验,结果表明:催化剂含量的增加会降低砂床质量,但过低的催化剂含量会导致制件的尺寸精度和力学强度变差。因此,为了平衡固化效率和砂床质量,可将催化剂含量控制在0.4%到0.6%之间;在层厚和落砂质量一定的条件下,粒径系数是影响砂床质量的主要参数,粒径系数的减小会导致砂床质量的下降。

机制砂混凝土的力学性能与声发射特征研究

基于数字图像处理技术,测定了机制砂的形状参数。结合数值建模方法,重构了不同细观特征的机制砂混凝土模型,并通过离散元分析软件,定量化地研究了机制砂混凝土的力学与声发射规律。研究结论如下:(1)单轴压缩下不同细观特征机制砂混凝土呈现出同样的应力应变规律,可分为弹性阶段,屈服阶段和软化阶段。(2)机制砂圆润度越高,机制砂混凝土峰值应力越大,同时塑性承载能力越强,其整体力学性能越好。(3)机制砂混凝土模型声发射和能量演化可分为平静期,缓增期和活跃期3个时期;声发射事件带预示着试样内宏观裂纹的扩展路径;试样内部声发射事件数密集或高能量释放区域更容易产生张开型裂隙。

江西某锂云母尾矿制备高纯石英砂试验研究

随着半导体、光伏等战略新兴产业的高速发展,其关键基础原材料石英资源变得愈发紧缺,对尾矿中的低品质石英砂进行高效分选提纯,可有效缓解我国高纯石英资源短缺的局面。本试验对江西某锂云母尾矿中的石英砂进行选矿试验研究,采用“磁选-擦洗-浮选-酸浸”试验工艺流程,研究不同试验因素对石英砂提纯效果的影响。结果表明,石英砂中SiO_(2)含量(质量分数,下同)由原矿73.75%提至99.90%,精矿总杂质元素含量降至977.83μg/g,其中Fe_(2)O_(3)含量从0.42%降至87.21μg/g,Al_(2)O_(3)含量从14.28%降至584.12μg/g,去除率分别为97.91%与99.59%,提纯效果较好,满足JC/T 2314—2015《光伏玻璃用硅质原料》对光伏砂质量要求。本研究有利于提升锂云母伴生石英矿的综合利用,提高伴生石英矿的价值。

一种基于图像处理的铁轨积沙检测方法

针对积沙检测实时性差、易受天气因素影响、积沙量化指标不明确等问题,提出了一种基于图像处理的铁轨积沙检测方法,使用单尺度Retinex算法处理了沙尘天气条件下的铁轨积沙图像,通过铁轨未积沙区域特征提取和最大类间方差法对含有阴影的铁轨积沙图像进行了阈值分割,综合两次图像分割结果并获取了积沙信息。此外,基于铁路沙害等级划分指标对提取的积沙信息进行了沙害等级划分,最终实现了不同天气条件下的铁轨积沙检测。结果表明,该方法能够在晴天和沙尘天气下准确获得铁轨积沙状况并根据对应沙害等级提供预警。

基于机制砂棱角性表征的级配测量修正方法及实验研究

机制砂的形状特征和级配对混凝土性能有着重要影响,图像法可以同时测量颗粒的形态和级配。在机制砂的级配测量中,需要考虑颗粒的形态特征对级配的影响。因此,提出利用图像分析技术实现机制砂棱角性的表征和级配测量修正,分别进行了机制砂的棱角性对比实验,级配重复性实验,图像法与筛分法级配测量对比实验以及修正前后的对比实验。实验结果表明,拟合椭圆棱角性算法可以独立地表征棱角性,不受粒径大小的影响。等效Feret椭圆短径作为等效粒径,粒度区间最大重复性误差出现在1.18~2.36 mm的尺寸区间,为1.26%。图像法测量的最大级配误差从修正前的6.29%减少到修正后的1.01%,细度模数的最大误差从0.17降低到0.04。相比传统的筛分方法,该测量系统具有良好的稳定性和功能性,满足测量的标准和要求。

改进OTSU算法的砂土CT图像分割及组构分析

针对砂土各向异性的量化这一关键问题,以CT技术获取的砂土试样断面图为研究对象,首先采用直方图均衡化和中值滤波法对图像预处理,降低图像噪声、提高分辨率,其次运用数学形态学改进的OTSU算法有效克服了非均匀光照的影响,最后利用分水岭算法优化重叠颗粒之间的粘连情况,从而提高分割性能,得到清晰的二值化图像。结合环形测试线法对砂土颗粒内部孔隙的定向分布进行量化,并判断其宏观力学性。结果表明,经该方法处理后,提取的细观参数准确,能够清晰地展现砂土颗粒细观组构。验证了砂土颗粒确有典型的各向异性,证明了该方法的有效性和可靠性。