铝材冷轧变形区油膜形成机理及影响因素

通过计算分析与轧制实验，探讨了名材冷轧变形区油膜形成机理及影响因素结果表明：流劝动力学成膜机理主要依赖于润滑剂粘度和轧制速度，特别是润滑剂粘度较氏时，轧制速度必须达到一定值，否则无法形成有效的油膜，而机械夹带作为低粘，低速条件下变形区主要成膜机理，其膜厚度依赖于轧辊与轧件粗糙度和夹带系数ｍ，０．１〈ｍ〈０．５，且随润滑剂粘度提高而增大。     

特细长轴球头端面的加工

提出了一种用摩擦打磨和搓削相结合加工特细长轴球头端面的新方法。并设计了搓削加工中的设备。该球头端面加工方法易于操作，加工效率高，成本低。     

3D Analysis of cold rolling using a constitutive model for interface friction

Full three-dimensional numerical analyses are carried out for the cold rolling of plates of finite width, to study the effect of the width spread during rolling. The contact and friction between roll and plate is modeled in terms of an interface constitutive model that accounts for the friction forces in the rolling direction as well as those in the transverse direction that give resistance to the width spread. At low normal pressures Coulomb friction is represented while at high normal pressure a yield stress limitation of the maximum tangential stress is incorporated, and slip as well as no slip is accounted for. Finite strain elasto-plasticity is applied for the plate material, using mostly isotropic hardening or in a few cases kinematic hardening to represent the effect of a rounded vertex on the yield surface. In addition, for a given plate thickness and degree of reduction the effect of different values of the roll radius and the effect of different values of the plate width are analysed.     

Elucidating white-etching matter through high-strain rate tensile testing

A form of damage in bearing steels subjected to rolling contact fatigue is the formation of localised regions of white material just below the contact surface. These ‘white-etching regions’ are strikingly visible signs of damage during metallographic examination. One mechanism proposed to explain their formation is adiabatic shear localisation. Experiments are reported here using high-strain rate (250?s^?1) tensile testing to show that this is not the case.     

A hybrid fault diagnosis approach based on mixed-domain state features for rotating machinery

To make further improvement in the diagnosis accuracy and efficiency, a mixed-domain state features data based hybrid fault diagnosis approach, which systematically blends both the statistical analysis approach and the artificial intelligence technology, is proposed in this work for rolling element bearings. For simplifying the fault diagnosis problems, the execution of the proposed method is divided into three steps, i.e., fault preliminary detection, fault type recognition and fault degree identification. In the first step, a preliminary judgment about the health status of the equipment can be evaluated by the statistical analysis method based on the permutation entropy theory. If fault exists, the following two processes based on the artificial intelligence approach are performed to further recognize the fault type and then identify the fault degree. For the two subsequent steps, mixed-domain state features containing time-domain, frequency-domain and multi-scale features are extracted to represent the fault peculiarity under different working conditions. As a powerful time-frequency analysis method, the fast EEMD method was employed to obtain multi-scale features. Furthermore, due to the information redundancy and the submergence of original feature space, a novel manifold learning method (modified LGPCA) is introduced to realize the low-dimensional representations for high-dimensional feature space. Finally, two cases with 12 working conditions respectively have been employed to evaluate the performance of the proposed method, where vibration signals were measured from an experimental bench of rolling element bearing. The analysis results showed the effectiveness and the superiority of the proposed method of which the diagnosis thought is more suitable for practical application.     

K60、X70管线钢奥氏体晶粒长大及再结晶的对比分析

通过金相观察的方法,研究了K60、X70管线钢在不同加热温度下奥氏体晶粒长大的规律及在不同变形量和变形温度下奥氏体晶粒再结晶的规律。结果表明:加热温度分别达到1 150℃和1 200℃时,K60、X70晶粒尺寸急剧增大;随着变形温度的提高,K60、X70奥氏体再结晶的临界变形量均降低;变形温度在1 150℃,变形量分别为50%和30%时,K60、X70再结晶程度可达90%以上。相比K60,X70未再结晶区狭小,为避免混晶的产生,轧制过程应尽量避开部分再结晶区。     

Predicting Beijing's tertiary industry with an improved grey model

In the context of the growth slowdown in China, it is important to accurately forecast the future economic trend to guide policy-makers the direction of adjusting their current economic policies. In this paper, we intend to predict Beijing's tertiary industry, whose datasets are small, irregular and non-stationary, leading to a difficulty of building an accurate prediction model. To this end, we present an improved grey model, named PRGM(1,1), which extends the grey prediction model by integrating two techniques, i.e., the particle swarm optimization algorithm for parameter optimization and the exponential preprocessing method for data cleaning. The experimental results show that PRGM(1,1) outperforms other variants of the grey prediction model in predicting Beijing's tertiary industry, and is viable to do reasonable prediction over short and fluctuated economic data sequences. In addition, we employ PRGM(1,1) in the economic prediction of Beijing's tertiary industry in the next five years, and conclude that the growth rate will decelerate. Our prediction result seems to be in line with the economic slowdown in China this year.     

Effect of cold rolling on mechanical properties and ballistic performance of nitrogen-alloyed austenitic steels

In this paper, the effects of different amount of cold rolling on mechanical properties, microstructure and ballistic resistance of nitrogen containing austenitic stainless steel in two different conditions have been presented. The ballistic performance was measured in terms of energy absorption against deformable projectiles. It is found that increased percentage of cold reduction increases the strength and hardness with loss of ductility and decreases the energy absorption of material. The nature of failures and damages of the targets has been studied and also the microstructural characterization has been carried out.     

Effect of annealing treatments on the anisotropy of a magnesium alloy sheet processed by severe rolling

The effect of annealing treatments on the normal plastic anisotropy (r-value) of a magnesium alloy, AZ61, processed by severe rolling was investigated. The various annealing treatments produce two effects on microstructure: grain coarsening and slight weakening of the texture. In addition, these treatments produce a noticeable decrease of the anisotropy that was correlated with an increase in strain rate sensitivity and a decrease of work hardening rate. It is concluded that an enhanced contribution of basal slip occurs as a consequence of the annealing treatments.