持久强度试验数据处理

持久强度试验数据处理的传统方法有等温直线法和Larson-Miller法。等温直线法需在每个试验温度下建一个方程,比较繁琐,Larson-Miller法需要商榷,为此开发了多元回归法。多元回归法是利用温度、断裂时间和应力之间的统计关系建立多元回归方程,用方程预测持久强度的方法。多元回归法预测持久强度的误差小、精度高;可进行温度和时间的外推预测;不需计算对数或使用对数坐标,方便直观。     

金属材料高温持久强度的预测模型

在Larson-Miller方程基础上，利用全微分和状态函数特征，建立了金属材料在给定温度条件下持久强度与高温瞬时强度之间关系的数学模型，并成功用于T91耐热钢和GH2871高温合金持久强度的预测。     

圆筒混合机滚圈与托辊强度计算

大型混料设备滚圈与托辊间接触应力很大,校核钢制托辊与滚圈的接触应力是大型混合机设计成功与否的重要因素之一。本文就接触应力进行详细计算,验证设计参数是合理的。     

蠕变持久统一方程

建立了一种蠕变持久统一方程和热强参数统一方程,它不但将目前常用的拉森－米勒（L－M）方程、葛一唐吾（G－D）方程、曼森－索柯普（M-S)方程和曼森－哈弗特（M－H）方程综合统一表达为一个方程,而且能很好地表征工程中许多用上述四种方程无法描述的材料蠕变断裂时间,应力和温度之间的关系,所以,与现行夫范中推荐的这上种蠕变持入方程相比,统一方程具有对试验数据的拟合精度高,适用经等优点。     

预测持久强度的Larson-Miller法不正确

通常采用Larson-Miller法或等温直线法预测钢的持久强度,但该两种方法的预测结果相差较大。究其原因,发现是由于Larson-Miller法不正确造成的。计算和分析结果表明:LarsonMiller法的原理和结果都不正确。     

用新方法检定高温蠕变及持久强度试验机

用一只应力应变传感器,通过不同的组桥方法,可以同时检定高温蠕变及持久强度试验机试验力和同轴度两个技术指标,提高了检定效率。     

GH36合金材料高温持久强度断裂时间分布研究

采用数理统计方法，对ＧＨ３６合金材料试验数据进行高温持久强度断裂时间的概率特性分析，研究其分布规律。为进一步可靠性分析和持久强度外推提供理论基础。     

计算圆筒动态应力强度因子的有限元方法与叠加积分方法

本文计算了厚壁筒的动态应力强度因子,研究了有限单元法计算动态应力强度因子的几个主要问题,提供了合理计算方案,本文还提供了计算厚壁筒动态应力强度因子的叠加积分法,方便于各种动态内压下的动态应力强度因子的计算。     

泡沫铝夹芯圆筒抗爆性能研究

在验证了所用方法有效性的基础上,采用有限元软件LS-DYNA分析了重量相同、由A3钢和闭孔泡沫铝制成的夹芯圆筒与由A3钢制成的实体圆筒在3种不同爆炸载荷作用下的动力响应,同时分析了5种不同夹芯圆筒的抗爆性能。结果表明,在相同爆炸载荷的条件下,无论是在变形还是在能量吸收方面,夹芯圆筒都优于相同重量的实体圆筒;对于夹芯圆筒,内面板厚度应不大于外面板厚度,这样能在降低夹芯圆筒整体变形的同时发挥泡沫铝芯层的吸能优势。     

Creep and Low Cycle Fatigue Investigations of Light Aluminium Alloys for Engine Cylinder Heads

Abstract: An influence of the chemical composition, porosity and ageing on mechanical behaviour of light, multifunctional aluminium alloys (AlSi8Cu3 and AlSi7MgCu0.5) subjected to creep and low cycle fatigue (LCF) was investigated. The materials were tested to verify their applicability as the cylinder heads in car engines. During creep tests, a strain response of the materials was observed under a range of the step‐increased stresses and different temperatures. The LCF tests were carried out under strain control in three blocks of 100 cycles each with a constant strain amplitude. The results of creep and LCF tests were analysed with regard to chemical composition, type of porosity and ageing of the materials tested. An influence of porosity on the creep resistance and lifetime was considered. The results of the LCF tests were compared for the materials in the as‐received state and after ageing. An experimental evaluation of cyclic behaviour because of the LCF was carried out to check whether the hardening or softening effects can be observed in the materials. Taking into account the various history of loading, a stress response of the materials was investigated.     

GH864合金在超温条件下碳化物含量与持久强度的关系

采用物理化学相分析、X射线衍射、金相检验和持久试验等分析方法研究了烟汽轮机叶片合金（GH864）在不同超温试验条件下显微组织中的碳化物含量与持久强度的关系。结果表明：随着GH864合金中碳化物含量的增加,尤其是M23C6量的增多,其持久强度下降,从而缩短了其剩余寿命。     

人工神经网络法在镍基变形合金蠕变断裂寿命预测中的应用

在试验数据的基础上,利用人工神经网络建立不同成分镍基变形合金的不同温度,外应力与蠕变断裂寿命之间关系模型,并进行网络训练,对合金的蠕变断裂寿命进行模拟.结果表明,模拟结果与实测结果吻合良好,采用人工神经网络方法可以为镍基变形合金蠕变断裂寿命的预测提供一种有效的手段.     

高强度铝合金的氢脆

氢脆是高强度铝合金在腐蚀环境中应用遇到的突出问题。本文简要介绍了高强度铝合金中的氢脆现象，氢脆特点，影响氢脆敏感性的因素以及氢脆理论等，并对这一研究领域的未来进行了展望。     

Nb对HP合金组织与蠕变断裂强度的影响

随 Nb 含量的增加,HP 合金蠕变断裂强度的变化表现出极大值特征。在含碳0.4(wt%)的HP 合金中添加0.5(wt%)以下的 Nb,主要起固溶强化作用;当 Nb 量约1.5(wt%)时,可以获得最佳的蠕变断裂强度。其原因是在共晶组织中形成了形态复杂的共晶 NbC,在晶内析出了高度弥散的二次 NbC,以及由于 Nb 的加入提高了组织稳定性;当 Nb 量进一步提高时,由于共晶 NbC 形成了片层状共晶团以及晶内 M_(23)C_6大量减少使蠕变断裂强度下降。     

Steady‐State Creep Analysis of Functionally Graded Rotating Cylinder

Axi‐symmetric component like cylinder etc. has to operate under severe thermo‐mechanical loads, which cause significant creep. It, thus, reduces its service life. The present study investigates the steady‐state creep in a functionally graded rotating cylinder at constant angular speed. The cylinder is made up of aluminium matrix and reinforced with silicon carbide particles. The thermal gradient in the functionally graded rotating cylinder is estimated by performing finite element analysis on ANSYS software (ANSYS Inc., Canonsburg, USA). The creep behaviour of the cylinder has been described by threshold stress‐based creep law. The creep parameters are obtained by conducting regression analysis. The mathematical models have been developed to describe steady‐state creep in the cylinder. The study reveals that the radial, tangential, axial and effective stresses in the cylinder are significantly affected by the presence of particle gradient alone as well as with the presence of particle & thermal gradient both. It has been found that the creep rates have been reduced significantly by imposition of particle and thermal gradients together and thus increases the service life of cylinder.     

Procedure of Determining Creep and Creep-Rupture Strength Parameters for Isotropic Materials under Nonisothermal Loading

A procedure has been developed for determining the parameters of creep and creep-rupture strength that appear in constitutive equations of thermoviscoplasticity for describing nonisothermal processes of deformation and damage accumulation in isotropic materials due to creep. The procedure is tried out using a high-temperature chromium-nickel alloy ÉI437.     

基于Z_c参数的HP耐热合金高温蠕变及持久寿命的预测方法

通过研究HP耐热合金的高温蠕变实验数据,提出一种基于Zc参数的高温蠕变变形预测方法,并且利用该方法对HP耐热合金的高温蠕变性能进行预测和分析。结果表明:在1000,980℃和930℃下,蠕变应变分别为0.5%和1%时,预测数据与HP耐热合金的蠕变实验数据符合较好。同时利用基于Zc参数的高温蠕变变形预测方法对HP耐热合金的高温持久寿命进行了评估,结果表明由该方法得到的预测主曲线与耐热合金的持久实验数据吻合较好。     

Ag颗粒增强复合钎料钎焊接头蠕变断裂及强化机理研究

测定了不同应力和温度下Ag颗粒增强复合钎料及基体钎料63Sn37Pb钎焊接头蠕变寿命,分析了Ag颗粒增强复合钎料及基体钎料钎焊接头蠕变断裂机理.表明:Ag颗粒增强复合钎料钎焊接头蠕变寿命优于基体钎料;Ag颗粒表面Ag-Sn金属间化合物形成及Ag颗粒对富Pb层阻碍作用是复合钎料钎焊接头蠕变性能提高的主要因素;钎焊接头Cu基板上一薄层富Pb相区形成是蠕变裂纹主要原因.     

Creep of polymer composites

A model incorporating a modified thermal activation theory is presented to model and predict creep of polymer composites. Results are presented of the successful application of this model to predict creep of a unidirectional, continuous-carbon-fiber-reinforced polymer composite (AS4/3501-6) and its epoxy matrix, over a wide range of stress (10–80% of ultimate tensile strength) and temperature (295–433 K). From an analysis of model parameters, it is concluded that the reinforcing carbon fibers do not alter the creep mechanism but do alter the creep behavior of the epoxy matrix, resulting in reductions in creep rate and in the magnitude of creep.