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991.
992.
D. Constales J. Ka
ur R. Van Keer 《International journal for numerical methods in engineering》2002,53(3):539-565
In this paper, we consider the inverse problem of determining the optimal cooling parameters for continuous casting under changing casting speed. We rely on automatic differentiation to support different search methods for the parameter values that will minimize a given cost functional, which can include a variety of criteria: surface temperature evolution and variation, interface position, full solidification point. In the direct problem we use a fixed‐domain transformation to solve the corresponding free‐boundary problem to high accuracy. Numerical experiments are provided to illustrate and support the effectiveness of the present concept. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
993.
连铸碱性中间包覆盖剂的实验室研究 总被引:1,自引:0,他引:1
本文介绍了包钢连铸中间包覆盖剂配方的设计思路及设计原则,并对所设计的碱性中间包覆盖剂的各种物化性能,测试方法作了介绍,表明这种碱笥覆盖剂保温性能好,同时具有较强的防止钢液二次氧化及吸收A12O3等非金属夹杂的能力,对中间包内衬及长水口侵蚀也较小。 相似文献
994.
一台设备中铸件质量一般占到30%-70%,铸件生产直接关系着机械行业的整体质量和水平。铸造生产中普遍存在单件小批量形式,其生产特点的八个方面是引起铸件质量不稳定的关键因素。从管理方式、人员素质要求、新技术应用三个方面,提出了如何控制单件小批量铸件质量的具体措施和方法。 相似文献
995.
论述了 B O P P 生产线铸片锟结垢类型及形成原因,介绍了铸片锟化学清洗的工艺流程.实践证明,用化学清洗方法清除结垢是提高换热效率非常有效的方法 相似文献
996.
Ductile irons are still important engineering materials due to their high strength and toughness, and relatively low price.
In the foundries, ductile irons suffer from shrinkage porosity formation during solidification, which is detrimental to the
mechanical properties. In order to minimize porosity formation, large risers are normally used in the design, which reduces
porosity level sometimes but leads to a low yield. In order to better understand the shrinkage behavior of ductile iron during
solidification, a micro model was developed to simulate the microstructure formation. The density change during solidification
and the room temperature mechanical properties can be calculated based on the microstructure. The simulation has been compared
with the experimental results and found to be in good agreement. 相似文献
997.
A new class of defects has been recently discovered, which are regarded as double oxide film defects. In this study, a number of Ni-based vacuum-cast test bars were investigated. The fractures in the broken test bars were observed by Scanning Electron Microscopy (SEM). Energy Dispersive Spectroscopy (EDS), as well as Wavelength Dispersive Spectroscopy (WDS) were used to characterize the chemical elements of the fracture's surface. Observation by SEM revealed the presence of inclusions identified as films that appeared to have initiated the growth of carbides. This study has added to the evidence that oxide film defects do exist in Ni-based super-alloy in certain vacuum casting conditions. It provides a reference for researchers' further study on the defects, and provides a possible direction for researchers to improve casting technology so as to remove these defects. 相似文献
998.
The aim of this paper was to study the reaction between a Ti-6Al-4V alloy and boron nitride based investment shell molds used for invest- ment casting titanium. In BN based investment shell molds, the face coatings are made of pretreated hexagonal boron nitride (hBN) with a few yttria (Y2O3) and colloidal yttria as binder. The Ti-6Al-4V alloy was melted in a controlled atmosphere induction furnace with a segment water-cooled copper crucible. The cross-section of reaction interface between Ti alloys and shell mold was investigated by electron probe micro-analyzer (EPMA) and microhardness tester. The results show that the reaction is not serious, the thickness of the reacting layer is about 30-50 μm, and the thickness of α-case is about 180-200 μm. Moreover the α-case formation mechanism was also discussed. 相似文献
999.
1000.
为解决立交地涵施工期混凝土的温控防裂问题,用三维温度场和应力场有限元法对淮安某立交地涵工程混凝土结构进行施工期的仿真计算分析,对结构施工分层、设置后浇带、部分整体浇筑和多种保温等混凝土防裂措施进行了计算和比较,了解这些防裂措施的效果,进而找出最有效的防裂措施,为工程混凝土结构的施工提供科学指导. 相似文献