点热阻法在铸钢工艺CAD上的应用

提出了点热阻几何系数的概念,建立了点热阻法的数学模型,确定了几种热节的模数增大系数.经对300MW汽轮机高压主汽阀铸造工艺模拟计算及生产验证表明,点热阻法能够方便地计算出热节处的模数值,提高工艺设计精度.     

用模数法确定铸钢件保温冒口尺寸

作者叙述了用模教法计算冒口的原理、有效模数的概念及影响因素,给出了几种保温材料的模数增大系数,按模数法确定保温冒口尺寸的方法和步骤,提出了最佳保温套厚度与冒口模数的关系,并列出了计算保温冒口及保温套尺寸的表格。     

NY型内齿棘轮扳手的设计计算

在棘轮扳手的计算方法中引入了模数的概念,并且建立了NY型内齿棘轮扳手各几何参数与模数之间的数学关系,为棘轮扳手的设计计算提供了基本方法。     

大模数齿轮齿条的非线性接触强度分析

基于非线性的思想对大模数直齿渐开线轮齿啮合的非线性接触问题进行了研究。在分析大模数轮齿啮合过程中影响接触强度的相关因素的基础上,建立了精确的Pro/E三维参数化实体模型,应用ABAQUS的力学分析模块对轮齿啮合静、动力学强度进行了分析,获取了齿面接触应力的分布状况,并与赫兹理论的计算结果进行了对比。结果显示:利用ABAQUS有限元方法得出的大模数轮齿啮合接触应力分布状况的计算结果与理论计算的结果误差在允许范围内,可以作为大模数齿轮齿条啮合的强度计算依据。     

铸钢件冒口模数和重量的简化计算

近年来应用“模数法”计算铸钢件冒口越来越普遍。但各种类型的胃口的模数和重量的计算却比较麻烦。尽管有些标准冒口表中也列有胃口模数和重量的数值,但毕竞档次有限,对于某些铸件,标准冒口往往满足不了要求。这时工艺人员就不得不按照模数和重量的基本公式进行繁琐的计算,这不仅影响工作效率,而且给模数法的应用带来许多不便。本文针对这一问题。将最常用的四种冒口的模数(M)和重量(W)     

大模数变位齿轮的齿形参数计算

本文介绍了大模数变位齿轮的齿形参数计算方法,对于大模数或超大模数变位齿轮的制作具有实用价值,其铸造齿形精度可达Dc—9或10级,在某种程度上可代替切削加工齿轮。供参考。     

大型铝板轧机机架的铸造工艺设计与制造

介绍了用模数梯度法计算铸件凝固过程进行铸造工艺设计的方法。按照这种工艺设计方法,设计了大型铝板轧机机架的铸造工艺。生产实践表明,应用模数梯度法计算大型铸钢件的工艺参数,有利于实现外冷铁铸造工艺,能够生产出高质量的大型铸钢件。     

船用汽轮机后汽缸下半铸件的铸造工艺设计

船用汽轮机后汽缸下半铸件结构复杂,质量要求高,有较高的生产难度.采用ProCAST铸造模拟软件计算铸件模数,根据模数计算设置冒口;模拟浇注过程,确保充型过程快速平稳;对铸件凝固过程模拟优化,实现顺序凝固,保证了铸件致密度.     

基于三维的铸钢件模数计算

对ＡｕｔｏＣＡＤ－ＡＭＥ建造的铸钢件三维几何图形进行模数计算的方法及其软件的编制，以计算铸件的整体模数和体积及各部分的模数和体积。此方法为进行基于三维的铸造工艺ＣＡＤ／ＣＡＥ的一体化研究起到积极的作用。     

铸钢件的顺序凝固和冒口的计算(续)

四、运用模数法设计计算冒口1．冒口颈铸件和边冒口之间必须造成顺序凝固,凝固应从铸件开始,经过冒口颈再到边冒口,即冒口应该最后凝固。因此冒口颈的模数应该比铸件的模数大,边冒口的模数又应该比冒口颈的模数大,它们之间应为如下关系,     

Precipitation and dissolution peaks of hydride in Zr–2.5Nb during quasistatic thermal cycles

Two internal friction peaks and corresponding discontinuity (‘knee’) points of elastic modulus have been observed in hydride-forming metals upon heating and cooling, respectively. In the present work, measurements of Young’s modulus as functions of temperature and hold time during a quasistatic thermal cycle were made in Zr–2.5Nb samples containing hydrogen using a composite oscillator technique. The increment of modulus during an isothermal hold is proportional to the decrease in hydrogen concentration in solid solution of the Zr alloy. As a result, elastic modulus measurements provide a means to determine the amount of transformed hydride during the transition. It is confirmed experimentally that the two peaks reflect the variation of the hydride transformation rate during heating or cooling. It is demonstrated by the present work that the maximum-slope point of each peak, on the high temperature side, is coincident with the knee point on the curve of modulus versus temperature and this point provides the most reliable and physically sensible indicator of the end of hydride dissolution during heating, or the beginning of hydride precipitation during cooling.     

Ti-Mo-Zr-Fe合金的微观结构与纳米压入特性的关系

通过不同的热处理制度控制TMZF合金中的相组成和含量，利用XRD分析确定各种相结构。利用纳米压入测量仪测试了不同组织结构下的硬度和弹性模量。结果表明，当合金中存在ω相时，合金的的硬度和弹性模量最高，随着热处理温度的提高，合金中的ω相消失，代之而来的是α相，而且越接近β转变温度，α相含量越少，对应的弹性模量和硬度越来越低。对于Ti—Mo—Zr-Fe合金来说压入性能（硬度、弹性模量）与相成分之间存在着良好的匹配关系。     

CMAS对热障涂层界面裂纹和残余应力的影响

随着航空发动机涡轮叶片工作温度的提升,使得一种主要由CaO,MgO,Al₂O₃和SiO₂组成的玻璃态物质(CMAS)对热障涂层的危害越来越严重,从而对热障涂层的性能和耐久性有了更高的要求。本文以电子束物理气相沉积热障涂层为研究对象,利用有限元方法研究了CMAS的渗入对界面裂纹扩展及CMAS对陶瓷层(TC)内部残余应力的影响规律。采用波长固定、振幅变化的正弦曲线表示不同粗糙度的涂层界面,同时考虑了CMAS的弹性模量变化的影响及不同界面形貌与CMAS之间的相互作用。结果表明：CMAS弹性模量的增加对界面裂纹具有抑制作用,并且TGO幅值和厚度越小,抑制作用越明显。CMAS弹性模量对TC层最大残余应力S₂₂的影响存在临界点,在临界点之前,CMAS弹性模量的变化对TC层最大残余应力的影响较大,随着CMAS弹性模量的增加,TC层最大残余应力大幅度减小;在临界点之后,TC层最大残余应力基本不受CMAS弹性模量变化的影响。这些结果对电子束物理气相沉积喷涂的热障涂层失效机理的研究具有重要意义,可以为热障涂层界面的优化提供指导。     

回火处理对Fe-Mn基合金剪切模量的影响SCIEI

研究了回火温度和时间对两种成分Fe-Mn基合金剪切模量的影响。结果指出,附加Cr,Ti的合金在回火状态下ΔG G-T曲线有极小和极大两个极值,而附加Cr,Ni,W,C的合金只呈现极大值特征。这是由于Ni,W,C降低反铁磁转变点T_N造成的, 随着回火温度升高或回火时间增加,ΔG_λ效应逐渐增加。     

The Influence of Fe Content on the Mechanical Properties of NiAl Coatings Processed In-Situ

NiAl Plasma Transferred Arc coatings can be processed by in-situ synthesis of the aluminide during the deposition of mixtures of Ni and Al powders. This procedure allows to deposit compositions that otherwise would exhibit low weldability. The strong metallurgical bond of coatings involves the formation of a weld pool. It is therefore expected for the composition of the processed coatings to be influenced both by the deposited and base material, besides processing parameters. This study analyzed the impact of the deposition current on the point defect structure in the B2NiAl-ordered structure and consequently on the coating hardness and indentation modulus. Mixtures of 65 at.%Ni and 35 at.%Al were prepared and deposited on carbon steel and stainless steel plates. Deposition current ranging from 70 to 150 A was used to induce different Fe content in the coatings. Results showed that increasing deposition current increased dilution with substrate but contrary to observations on metallic coatings, an increase of hardness and indentation modulus was measured. The hypothesis that the measured behavior is related to the point defect structure of the ordered phase, B2-NiAl, is put forward. The Fe content determined the density and type of point defects: vacancies, anti-sites Al or Ni. A better understanding on the mechanisms controlling the properties of the aluminide PTA coatings with increasing deposition current is achieved: hardness exhibiting a direct correlation with the point defect structure and the indentation modulus a strong dependence on the microstructure.     

小电流脉冲TIG弧的谐振现象及其交流阻抗特性分析

采用直流叠加高频正弦的方法对小电流TIG弧的交流阻抗特性进行了研究,发现随频率的增大,电弧阻抗的模量先增大随后又减小;而其复角随频率的增大持续减小,在模量的最大值减小为零,很显然,电弧阻抗存在谐振点.经过对不同频率的激励电流和响应电压进行数据分析,得到了小电流TIG弧的高频动态阻抗电路模型以及传递函数.应用数学分析软件...     

Damage evolution in compacted graphite iron during thermomechanical fatigue testing

Thermomechanical fatigue properties of a compacted graphite iron in an out of phase configuration are investigated for different maximum temperatures and mechanical strain ranges. Furthermore, the stress–strain hysteresis loops are analysed, and, in particular, the unloading modulus, i.e. the elastic modulus measured during specimen unloading, is obtained from each cycle. This material parameter has earlier been explicitly related to the amount of microcracking in cast irons. The results show that the unloading modulus linearly declines with the numbers of cycles in all tests performed. In addition, the rate of change of the unloading modulus is closely related to the number of cycles to failure. Accordingly, it is concluded that microcracks are independently propagated by fatigue until a point of rapid crack linking resulting in ultimate failure. This is supported by microstructural analyses consisting of optical microscope images taken at different stages throughout the life of a specimen.     

Strength and modulus of a molybdenum-coated Ti-25Al-10Nb-3V-1 Mo intermetallic

The three- point bend strength, Young’s modulus, and vibrational damping of a plasma- sprayed molybdenum-coated Ti- 25Al- 10Nb- 3V- lMo intermetallic were measured. The bend strength of the intermetallic samples was significantly reduced as a result of the molybdenum coating. This decrease in the strength was attributed to cracks formed in the molybdenum coating during the plasma spraying process. Experimental measurements done using the piezoelectric ultrasonic composite technique (PUCOT) indicated that the modulus and vibrational damping of the coated samples were significantly higher than for the uncoated substrates. Thermal cycling of the molybdenum- coated intermetallic between 600 °C and room temperature revealed a saturation increase in the modulus with a corresponding decrease in the mechanical damping. This behavior was attributed to crack healing occurring in the molybdenum coating during the thermal cycling process.     

碳化硅复合材料与碳钢钎焊接头的抗剪强度及微观结构

在以往超重力场合成梯度材料的基础上,制备出组分含量TiB₂-TiC-Fe呈连续梯度变化的TiB₂基陶瓷/42CrMo合金梯度材料. 对材料进行XRD,SEM,硬度测试以及三点弯曲强度测试,并采用电测法获取陶瓷基体部分的弹性模量,并在此基础上,对中间过渡区的弹性模量进行拟合,最后再采用解析方法计算梯度材料的应力应变分布. 结果表明,TiB₂基陶瓷/42CrMo合金相界呈连续梯度变化,硬度自陶瓷顶部至合金底部呈梯度递减.三点弯曲测试发现TiB₂基陶瓷/42CrMo合金材料具有类似于金属的塑性变形特征,从而出现明显的失效延迟行为. 采用电测法得出纯陶瓷组分的弹性模量约为560 GPa,参数拟合得出中间过渡区的弹性模量变化形式更趋近于三角函数,计算得出的应力表示自金属底部出现损伤,而后裂纹向陶瓷顶部方向扩展,与该材料试验现象契合.     

TiB2基陶瓷/42CrMo合金层状梯度材料力学测试与结构设计

在以往超重力场合成梯度材料的基础上，制备出组分含量TiB₂-TiC-Fe呈连续梯度变化的TiB₂基陶瓷/42CrMo合金梯度材料. 对材料进行XRD，SEM，硬度测试以及三点弯曲强度测试，并采用电测法获取陶瓷基体部分的弹性模量，并在此基础上，对中间过渡区的弹性模量进行拟合，最后再采用解析方法计算梯度材料的应力应变分布. 结果表明，TiB₂基陶瓷/42CrMo合金相界呈连续梯度变化，硬度自陶瓷顶部至合金底部呈梯度递减.三点弯曲测试发现TiB₂基陶瓷/42CrMo合金材料具有类似于金属的塑性变形特征，从而出现明显的失效延迟行为. 采用电测法得出纯陶瓷组分的弹性模量约为560 GPa，参数拟合得出中间过渡区的弹性模量变化形式更趋近于三角函数，计算得出的应力表示自金属底部出现损伤，而后裂纹向陶瓷顶部方向扩展，与该材料试验现象契合.