基于射钉法的小方坯凝固过程数值模拟

结合方坯连铸机二冷各段的实际情况，在二冷各段末对铸坯进行射钉取样，利用硫印法测定方坯二冷区内目标点凝固壳的厚度，建立了方坯传热数学模型，并利用射钉结果修正数学模型中的各段的传热系数，提高数学模型的准确性。将射钉法确定的坯壳厚度与数学模型计算结果相比较，结果表明，利用修正过的数学模型可以模拟整个铸机的传热凝固过程。     

Effects of coating thickness and residual stresses on the bond strength of ASTM C633-79 thermal spray coating test specimens

Wire-arc-sprayed nickel-aluminum is widely used in the aircraft industry for dimensional restoration of worn parts and as a bond coat for thermal barrier coatings and other top coats. Some repair applications require thick coatings, which often result in lower bond strength. A mechanism being investigated to ex-plain this decrease in bond strength is the free edge effect, which includes both coating residual stresses and coating thickness. The layer-removal method was used to determine experimentally the residual stresses in wire-arc-sprayed nickel-aluminum coatings of different thicknesses. Bond strength evalu-ations were performed using an improved ASTM C 633-79 test specimen. Finite-element analysis and fracture mechanics were used to investigate the effects of coating thickness and residual stress state on coating bond strength.     

Oxide formation during etching of gallium arsenide

Characterisation of n-type GaAs, etched in a 5:1:1 mixture of H₂SO₄:H₂O₂:H₂O, was performed using X-ray photoelectron spectroscopy (XPS) and electrochemical AC impedance. Quantitative XPS analysis of GaAs indicated that the as-received wafers had a gallium-rich native oxide which was not affected by solvent degreasing treatments. Subsequent, oxidative etching formed a thinner arsenic-rich oxide. It is suggested that etching causes initial thinning of the native oxide; subsequently, transport of Ga and As ions occurs through the film by high-field ionic conduction. Arsenic enrichment in the resultant oxide film arises from the greater mobility of Ga³⁺ ions compared with As³⁺ ions as well as the relative solubility of Ga₂O₃ compared with As₂O₃. The as-received oxide film thickness, determined from the ratio of the oxide to substrate XPS peaks, was approximately 1.1 nm. After etching this was reduced to about 0.7 nm. This thickness is consistent with the driving voltage for oxide formation being provided by the electrochemical potential difference between hydrogen peroxide and the GaAs wafer (i.e. between 0.4 V, for As, and 1.2 V, for Ga, at a nm V⁻¹ ratio of 2). Capacitance measurements, derived from electrochemical impedance data, combined with film thickness data, gave a value of about 5 for the dielectric constant of As₂O₃.     

宽板弯曲成形过程中板厚变化精化模型

基于弹塑性力学基本理论,在考虑板材真实本构关系基础上建立了宽板板厚变化精细化模型。同时,借鉴分三层思想,较好地考虑了宽板在弯曲成形过程中部分纤维层应力反号过程,因此具有较好的精确性和较强的普适性。最后,以铝板为例进行分析,发现计算值和实验值吻合较好。本文研究成果为深入研究弯曲变形过程和科学制定弯曲成形工艺具有一定的理论价值和实用意义。     

热轧厚规格窄带钢厚度控制策略优化

针对某450 mm窄带钢生产线生产6.00 mm以上厚规格产品时带钢扭转导致测厚仪产生厚度测量偏差，严重影响厚度自动控制系统的正常投用，对产品厚度控制精度产生影响的问题，通过对轧件扭转前后轧件厚度的比较，实现了6.00 mm以上厚规格产品的厚度测量补偿，以此为基础实现了厚度的精确控制。现场实际生产应用表明，6.00 mm以上厚度规格96%以上达到了±50 μm的厚度控制精度，有效地保证了产品质量。     

拉深筋对板厚减薄量的影响

利用数值模拟的方法,着重研究了板料通过半圆形拉深筋和矩形拉深筋时板厚的变化规律和特点,分析了板料通过拉深筋时影响板厚减薄的主要因素,为探索板料通过拉深筋后的后续可成形性提供理论基础。研究结果表明,板料通过拉深筋时的弯曲变形是导致板厚减薄的根本原因,同时减薄量还受到板内张力及变形程度的影响。并指出累积等效应变不适于用来评价板料通过拉深筋后的变形程度。     

宝钢钢管全浮动芯棒连轧工艺的技术进步

全浮动芯棒连轧管生产线工艺的突出问题是钢管存在“竹节”现象和壁厚均匀度差。围绕提高钢管壁厚均匀度和消除“竹节”现象,进行持续的工艺技术改进,通过改善芯棒润滑条件,自主开发张力减径机非传统孔型,开发大规格孔型和高铬钢产品,提高生产线工艺自动控制水平等,使该生产线继续发挥能力,为用户提供高精度、高钢级的产品。     

半浮动芯棒连轧荒管壁厚不均的原因分析

介绍了半浮动芯棒连轧管机荒管壁厚不均的类型及特点,荒管壁厚不均有同批壁厚不均、纵向壁厚不均和横向壁厚不均等3种类型。分析了荒管壁厚不均产生的原因,穿孔毛管壁厚不均、连轧管机孔型形状变化、轧制中心线偏移均会造成荒管横向壁厚不均;芯棒尺寸波动会引起荒管纵向壁厚不均和同批壁厚差。提出了改善半浮动芯棒连轧荒管壁厚不均的有效措施。     

铝—钢双金属复合轧制层厚比及轧制力的研究

用实验方法研究了铝－钢双金属复合轧制时层厚比的变化规律。给出了双金属复合时轧制力的计算式。     

火箭发动机包覆层测厚时间延迟估计算法研究

用超声测量火箭发动机包覆层厚度时,当包覆层较薄时检测回波信号会出现时域混叠。为此提出一种时间延迟估计的新方法。该方法能对修正的检测信号能量谱的对数微商求逆傅里叶变换。实验结果表明,该方法能准确估计出时域混叠信号的延迟时间。提高了火箭发动机包覆层厚度测量精度。