Applied Mechanics and Materials Vols. 148-149

Abstract: In the aim at developing and utilizing ferrous mill tailing resources to save energy, protect environment and develop sustainable society, the research of replacing natural sand for ferrous mill tailing into concrete are carried out. Concrete mixed with ferrous mill tailing is called ferrous mill tailing concrete. The study results show the compressive strength of ferrous mill tailing concrete with grade from C20 to C40 is nearly equal to that of common concrete though its dump and divergence decrease little. Through adding in suitable volumes of water reducing mixture, fly ash and slag powder, its workability is improved and satisfies the practical requirement.

Abstract: The friction and wear behaviors of Al₂O₃/TiC ceramic tool materials were evaluated at temperature up to 800°C. The friction coefficient and wear rates were measured. The microstructural changes and the wear surface features were examined. Results showed that the temperature had an important effect on the friction and wear behaviors of Al₂O₃/TiC ceramics. The friction coefficient decreased with the increase of temperature, while the wear rates increased with the increase of temperature. The difference of the worn surface features of the Al₂O₃/TiC ceramics at different temperature is related to the chemical transformation during sliding wear tests. The wear mechanism of the composites at temperature less than 400°C was primary abrasive wear, and the mechanisms of oxidative wear dominated in the case of 800 °C sliding operation.

Abstract: In this paper, the ultrasonic infrared thermography (UIT) technique was applied to detect the composites damage. The frictional heating and thermal conductivity at the location of crack of the composites under ultrasonic excitation was simulated by finite element method (FEM). The excitation parameters including time, amplitude and frequency were studied. The composite involving delamination was detected by the ultrasonic generator. The results show that the UIT can identify the contacting interface-type damages at the surface or subsurface of composites rapidly, for example, delamination, fatigue crack et al.The excitation time, amplitude and frequency are impotent detection parameters. It can be seen accurately and intuitively of location of the damage, and there is no uniform heating problems from the experiment. Suitable coupling material can improve testing quality and eliminate “standing wave” effectively.

Abstract: In this paper, an actual system based on wavelet transform and artificial neural networks was established to diagnose different types of fault in a gearbox. As a key step, biorthogonal wavelet was used to denoise in feature extraction of signals because of its properties of compact support, high vanishing moment and symmetry. Consequently, a multi-layer perceptron network were designed to diagnose the fault status with feature vectors as inputs. In order to improve the network learning speed and stability, Levenberg-Marquardt algorithm was used to train the network. The present classification accuracy indicates the effectiveness of gearbox failure diagnosis.

Abstract: Scientific and practical crane evaluation index system is expected to obtain by screening of indices in this paper. The initial comprehensive evaluation indices are selected by stratification. Then the quantitative indices are screened by entropy method and Pearson correlation coefficient method, and the qualitative indices are screened by Delphi method and Spearman correlation coefficient method. The little effect indices on the evaluation result are deleted and the redundant information between the indices are got rid of. The index system simplified is comprehensiveness and representative, which is convenient to compare and evaluate cranes.

Abstract: The effects of positive and reverse working time, electroplating time, current density, duty cycle on the weight-gain rate were investigated. The optimized technical parameters were as follows: room temperature, 300 ms of positive working time, 30 ms of reverse working time, 40% of duty cycle, 8.20 ×10-5 A/mm2 of current density, 6 min of electroplating time. The quality of copper coating was checked with SEM. The adhesion between the coating and carbon fibers was tested by the method of psychro-thermal cycles. Additionally, comparison to pulse plating and direct current plating was made. The obtained results showed that a flat, detailed and well-crystalloid copper coating on the carbon fiber surface was obtained with the present conditions. The adhesion between the coating and carbon fibers was 450kPa.

Abstract: In this research, positive-pressure high velocity pneumatic conveying has been tested to determine the flow conditions such as minimum velocity, solid mass flow rate, and pressure drop per unit length of polypropylene (PP), recycled polyethylene (recycled PE), high-density polyethylene (HDPE), and low-density polyethylene (LDPE). The conveying efficiency (η ) of such two-phase flow was also experimentally investigated. During the course of the experimental conduct, the material sphericity ranged from 73.2 to 84.4 %. True density ranged from 904.5 to 1305.7 kg/m3, and bulk density covered the range of 493.7 to 783.4 kg/m3 .The tests were carried out on a pneumatic conveying test rig using a PVC pipes of 0.079-m inner diameter and total test length of 8.57 m. The results showed the minimum conditions to move the particles in dilute phase. For the conveying efficiency (η), the efficiency varies reversely with the air velocity in exponential function.

Abstract: This work investigated the weight loss profile and kinetic parameters during the pyrolysis process of the 1/3 coking coal samples from Dongshan (Jixi, Heilongjiang province) in inert gases with the help of thermal-gravimetry apparatus. The characteristic temperatures, the activation energy and the frequency factors gained from the experiment change regularly during the pyrolytic process of the sample coal. The activation energy change with the bulk density indicates that the increase of the bulk density of the coal is beneficial to the coking reaction process of the coking coal.

Abstract: The worst problem we are facing in the hydraulic system is the serious loss of energy, due to bad matching between the power components and the actuators and the large pressure loss when oil flowing though the various hydraulic elements, especially in speed governing system. However, Servo pump which is introduced in this paper can cover the problems mentioned above finely. The most difficult thing is its mathematical modeling, in the paper, it is established according to the actual situation. Here, the modeling between servo valve and cylinder, between cylinder and pump are established respectively, then these are connected by geometry relationship, finally ,the whole modeling is completed.

Abstract: Multi-crystalline silicon ingot was prepared by directional solidification method using metallurgical grade silicon as raw materials. The influence of impurities and crystalline defects in mc-Si on the minority carrier lifetime and resistivity was investigated. The results indicate that both grain boundary and impurities play important roles in the deterioration of the minority carrier lifetime.