The dynamic characteristics of hydrodynamic journal bearings lubricated with micropolar fluids are presented. The modified Reynolds equation is obtained using the micropolar lubrication theory. Applying the first order perturbation of the film thickness and steady state film pressure, the dynamic characteristics in terms of the components of stiffness and damping coefficients, critical mass parameter and whirl ratio are obtained with respect to the micropolar property for varying eccentricity ratios and slenderness ratios. The results show that micropolar fluid exhibits better stability in comparison with Newtonian fluid. 相似文献
In the present study the SERR technique has been reformulated to deal with extrusion of sections with/without re-entrant corners. A comprehensive computational model has been developed for this reformulated technique. The model has been used to analyse extrusion of I-section bars and the computed results have been compared with experimental values available in literature. 相似文献
High stress abrasive wear behaviour of aluminium alloy (ADC-12)–SiC particle reinforced composites has been studied as a function of applied load, reinforcement size and volume fraction, and has been compared with that of the matrix alloy. Two different size ranges (25–50 and 50–80 μm) of SiC particles have been used for synthesizing ADC-12–SiC composite. The volume fraction of SiC particles has been varied in the ranges from 5 to 15 wt%. It has been noted that the abrasive wear rate of the alloy reduced considerably due to addition of SiC particle and the wear rate of composite decreases linearly with increase in SiC content. It has also been noted that the wear resistance of composite varies inversely with square of the reinforcement size. The wear rate of the alloy and composite has been found to be a linear function of applied load but invariant to the abrasive size; at critical abrasive size, transition in wear behaviour is noted. This has been explained through analytically derived equations and wear–surface examination. 相似文献
Direct metal laser sintering process (DMLS) was chosen to develop cBN particulates reinforced SS316 based Metal matrix composite (MMC) with 5 %, 7.5 % and 10 % cBN in the nitrogen gas atmosphere using continuous wave fibre laser of 400 W output capacity. Effects of process parameters such as laser power, beam scanning speed and the mixing ratio of powder on different physical properties of the developed MMC were investigated. It was found that the physical and mechanical properties such as friction and wear behavior, micro hardness and density come up with improved results. FESEM images indicate the microstructure of the composite and evidently confirms the presence of cubic boron nitride in the SS316 matrix where chromium nitride acted as a binder in the presence of nitrogen atmosphere. The Vickers hardness values of the developed MMCs with laser power 60 W and 65 W were found in the range of 276-478 HV0.2 and 297-460 HV0.2, respectively. It was found that Vickers hardness is directly proportional to the % of cBN in the powder mixture and the laser beam power. The wear resistance of the sintered MMCs increased with increasing cBN content in powder mixture and results show that wear of MMCs are much lower than that of SS316. X-Ray diffraction (XRD) analysis of the fabricated MMC confirms the presence of different phases such as cBN, CrN, CrB2, Cr2N and Fe3N as a consequence of a series of chemical reaction between cBN and different elements of SS316 in nitrogen atmosphere. 相似文献
In this paper, a multi hybrid decode-amplify-forward relay cooperative network with perfect CSI in flat Rayleigh fading channel is considered. Using moment generating function based approach, the closed form of symbol error rate (SER) with asymptotic approximation is derived. Based on the lower bound of SER (Olfat and Olfat in IET Commun 5(4):2018–2027, 2011), Lagrange multiplier method and differential evolution (DE) algorithm based power allocation schemes are proposed. With fixed source power, the relay powers are optimized with the proposed schemes by the power allocation factor. Further the SER performance of proposed power allocation schemes is investigated by varying the location of the relays. The performance gain of proposed power allocation schemes depends on the channel quality of source to relay and relay to destination links. It is observed that the proposed power allocation schemes outperform the equal power allocation scheme and DE based power allocation provides SER response close to power allocation with Lagrange multiplier method. In order to achieve the target SER (quality of service) minimum power allocation is introduced as minimum relay power allocation and minimum source and relay power allocation.