共查询到19条相似文献,搜索用时 109 毫秒
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目的研究某产品关键零件用壳体823钢在冲拔过程中,毛坯内膛出现侧壁拉裂和底部缩孔疵病的原因。方法通过理论分析毛坯在冲拔过程中的变形机理和金属流动规律,结合理化检测和工艺试验等手段,对该疵病产生的原因进行了系统分析与验证。结果准确找到了该疵病产生的原因。结论 823钢原材料存在缩孔残余及二次缩孔,是造成弹体毛坯底部缩孔疵病和侧壁拉裂疵病的根本原因;通过靶场射击动态考核试验和增加超声波探伤检验工序的产品,即使存在缩孔残余及二次缩孔,也不影响产品使用性能。 相似文献
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目的 为了避免铝合金盖板低压铸造过程产生的缩孔缺陷,对盖板结构进行分析。方法 采用数值分析技术,对盖板低压铸造过程进行数值模拟,将模拟结果与实际铸件缺陷进行对比,分析缩孔缺陷的产生原因。为消除铸件缩孔缺陷,在模具内增设冷却水道,并对该工艺进行模拟分析。结果 铸件凝固过程中,当合金固相率达到75%时,铸件特征位置处的补缩通道开始陆续关闭,形成了孤立液相区,导致凝固结束时形成缩孔缺陷。当模具内增设冷却水道后,铸件的缩孔体积分数由3.5%下降到0.8%。结论 通过在模具内增设合理的冷却水道,能加快铸件厚大部位的凝固速度,有利于实现顺序凝固,从而避免缩孔缺陷,提高铸件质量。 相似文献
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目的 研究分析两种铸造模拟软件在钛合金铸件模拟方面的差异及准确性。方法 利用华铸CAE和ProCast软件对某钛合金铸件的温度场、流场和缩孔缺陷进行数值模拟。为了验证模拟结果的准确性,进行实际浇注验证实验,并通过X射线探伤,检测缩孔缺陷的位置。结果 华铸CAE网格剖分简单、计算时间快,但是模型边界拟合较差,ProCast软件网格划分复杂、计算时间较长,但是网格可以较好地反映模型形状,模型边界拟合较高。结论 两种软件对温度场的模拟差异不大,凝固顺序基本一致,两种模拟软件的缩孔预测结果和实际缩孔位置吻合性都较好,说明两种数值模拟软件可以很好地预测钛合金铸件内缩孔分布。 相似文献
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为研究孤立波作用下跨海桥梁桥墩受到的波浪荷载以得到孤立波波浪力的简化计算方法,利用计算流体力学软件OpenFOAM模拟海洋孤立波,在不同来流波高和初始水深下,开展了2组仿真试验,三维数值模拟用于直接计算圆柱体上的波浪力,二维数值模拟用于推导Morison方程所需的速度场。对比现有文献,讨论原始Morison方程应用于孤立波波浪力计算的适用性以及孤立波非线性的变化规律,并验证了引入非线性项的修正Morison方程预测孤立波荷载的适用性。研究结果表明:在计算孤立波荷载时,非线性影响不可忽视,随着波高和水深的比值H/d的增大,孤立波的非线性越来越强;相比原始Morison方程,考虑非线性影响的修正Morison方程可以更准确地预测孤立波与圆柱桩间的相互作用;应用修正Morison方程进行孤立波荷载预测时,波浪力参数C D,C M的取值与波高H、水深d、圆柱桩直径D的绝对值无关,仅与H/d有关;基于多组仿真试验结果,给出了0.15≤H/d≤0.65内波浪力参数的取值,可为孤立波荷载的快速计算提供参考。 相似文献
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本文针对ZL105合金平板铸件,在最佳铸铁端部冷铁及冒口的作用下,运用回归分析方法,探讨了热参数与铸件致密性和二次枝晶间距以及二次枝晶间距,孔洞率与铸件抗拉强度之间的关系,研究结果表明:凝固指数是控制铸件致密性的最有用的热参数;用凝固时间来控制二次枝晶间距较其它热参数更为有效;二次枝晶间距与铸件抗拉强度之间存在着较好的线性关系。通过测定二次枝晶间距来预测铸件的抗拉性能是可行的,但是孔洞率对抗拉强度的影响不可忽视。 相似文献
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金属注射成形坯冷凝过程中缩孔生成的预测 总被引:1,自引:0,他引:1
本文用有限差分法模拟了金属注射成形坯件的凝却凝固过程,以预测坯件内部缩孔的生成,计算结果与实验结果基本相符。同时,作者还对模型中存在的误差的主要原因作了探讨,为进一步优化模型提供了可行途径。 相似文献
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目的优化发动机活塞裙铸件铸造工艺。方法采用UG等软件设计活塞裙铸件浇注系统以及采用MAGMA铸造仿真软件对铸造工艺进行仿真预测,分析铸件凝固温度场,预测缩孔、疏松等铸造缺陷,进一步优化铸造工艺。结果铸件整体上实现了自下而上的顺序凝固,虽然通过冒口获得了一定程度的补缩,但凝固温度梯度不明显,冒口疏松缺陷依然延伸至铸件上端面。通过合理设置冷铁,增加冒口和内浇口数量,从而实现铸件顺序凝固,使补缩效果更为明显,可有效降低缩孔、疏松缺陷。结论采用MAGMA铸造仿真软件分析凝固过程并预测缺陷,通过改进和优化工艺,可以有效预防活塞裙铸件缺陷的产生,提高铸件合格率。 相似文献
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FengjunLI HoufaSHEN BaichengLIU 《材料科学技术学报》2003,19(5):395-397
Based on the characteristics of the lost foam casting (LFC) and the artificial neural network technique, a mathematical model for the simulation of the melt-pattern interface movement during the mold filling of LFC has been proposed and experimentally verified. The simulation results are consistent with the experiments in both the shapes of melt front and filling sequences. According to the calculated interface locations, the fluid flow and the temperature distributions during the mold filling and solidification processes were calculated, and the shrinkage defect of a lost foam ductile iron casting was predicted by considering the mold wall movement in LFC. The simulation method was applied to optimize the casting design of lost foam ductile iron castings. It is shown that the model can be used for the defects prediction and for casting design optimization in the practical LFC production. 相似文献
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Solidification simulation of manufacturing shaped casting which plays an important role in asSuring the soundness and quality of castings, in minimizing the trial production time and in reducing the manufacturing cost becomes one of the hottest topics of the new research frontiers of foundry technology at home and abroad. Practical three dimensional computer numerical simulation system for temperature distribution during solidification as well as shrinkage cavity and porosity prediction has already been put into application all over the world. Further fundamental researche5 on fluid flow, thermal stress and micro-modeling as well as practical approaches of numerical simulation of solidification process of shaped castings for routine analysis of foundry industry are still underway. 相似文献
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采棉机凸轮盘作为采棉机采摘头的重要零件,其加工工艺和技术要求非常高,要求工作表面粗糙度比较低,而且在内部不允许有气孔、缩孔、缩松等缺陷,而生产实践中影响凸轮盘铸造工艺过程的因素较多,经常发生以上铸造缺陷,直接影响产品质量。通过传统的铸造工艺设计与现代设计方法,对设计过程和生产过程进行优化。分析并提出通过设计合理冒口、采用外冷铁工艺以及控制合金化学成分可以帮助减小热节的影响,消除缩孔和缩松缺陷。 相似文献
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铸件凝固过程的宏观及微观模拟仿真研究进展 总被引:39,自引:0,他引:39
面向市场经济,迎接全球化竞争的挑战,为国民经济的发展作贡献,就要十分重视制造业特别是铸造行业的发展。但是,我国铸造行业与国外相比有很大差距,它制约着国民经济的发展。世界各国在铸造成形加工技术的发展趋势方面,认识是一致的,即:一是大型工程中特大型铸件的关键铸造技术;二是向精确成形技术方向发展;三是用计算机模拟仿真逐步代替传统的经验性研究方法。铸造过程计算机模拟仿真是改造传统铸造产业的必由之路,是当今世界各国专家学关注的热点。铸造充型凝固过程的数值模拟可以帮助工程技术人员优化工艺设计,缩短试制周期、降低生产成本、确保铸件质量,已成为铸造领域最热门的研究课题之一。目前,凝固过程的流场、温度场数值模拟及缩孔缩松预测已应用于实际生产,应力分析、微观组织模拟等方面的基础研究及实用化进程都取得了很大进展。 相似文献
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A practical prediction model is proposed for predicting the shrinkage of steel fibre reinforced concrete (SFRC) from the composition of concrete mix, strength, age when drying begins, conditions of environment, size and shape of structures, fibre volume, aspect ratio of fibre, etc. The formulas were developed according to an extension of the well-recognized BP prediction model for the shrinkage of plain concrete (OPC). All important features of the BP prediction model, such as the diffusion-type size dependence of humidity effects and the square-root hyperbolic law for shrinkage, are automatically adopted for SFRC. In order to supplement the insufficient test data collected from the literature, a recently finished experimental series was used to expand the databank and hence the authors have a better command of the prediction formulas. Results of shrinkage from the literature and from the test series are reported, together with comparisons with predictions using the proposed model. 相似文献
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实验研究了挤压铸造条件下A390过共晶铝硅合金的金相组织与性能。结果表明,经过挤压铸造后,A390合金的组织致密度提高,缩松、缩孔等缺陷减少,初晶硅晶粒细化。与铁模铸造件比较,A390挤压铸造件的维氏硬度能提高15.2%,室温拉伸强度增幅为25.2%,相对耐磨性能为1.18,高温(300℃)拉伸强度能够达到183MPa。 相似文献
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Justification and refinements of model B3 for concrete creep and shrinkage 2. Updating and theoretical basis 总被引:3,自引:0,他引:3
Following statistical evaluation in part 1, this part deals with the improvement of prediction by updating one or two parameters
of the model on the basis of short term tests and theoretical derivation of some formulae. The updating of model parameters
is particularly important for high strength concretes and other special concretes containing various admixtures, superplasticizers,
water-reducing agents and pozzolanic materials. For the updating of shrinkage prediction, a new method is presented in which
the shrinkage half-time is calibrated by simultaneous measurements of water loss. This approach circumvents the ill-posedness
of the shrinkage extrapolation problem. Theoretical justifications of various aspects of the model are given and a new formula
for the additional creep due to drying (or stress-induced shrinkage) is derived. The new model should allow a more realistic
assessment of the creep and shrinkage effects in concrete structures, which significantly affect durability and long term
serviceability of civil engineering infrastructure. 相似文献