聚氨酯橡胶摩擦轮有限元及疲劳寿命分析

针对汽车滑板输送机聚氨酯橡胶摩擦轮的开裂问题,对摩擦轮与滑板之间的相互作用进行预压紧力和接触摩擦驱动有限元分析,获得摩擦轮的应力和变形分布等结果.在获得摩擦轮周向应力分布的基础上,根据疲劳裂纹扩展公式对聚氨酯橡胶部分进行疲劳寿命分析,验证是否满足设计要求.分析过程和结果能为聚氨酯橡胶摩擦轮的详细设计提供参考.     

刹车盘结构对车轮及整车流场的影响

为研究车轮刹车盘结构对旋转车轮和整车流场气动特性的影响,针对是否存在刹车盘两种情况分别建立等比例模型,采用可实现的k-ε两方程模型计算,对比分析气动升、阻力因数,表面压力因数及整体与局部流场,发现刹车盘结构在简化车体上对车轮局部和整车流场都具有突出影响,指出在整车气动特性模拟中刹车盘存在的必要性.进一步进行计算模型选择的研究,发现旋转壁面模型与多坐标参考系(Multiple Reference Frame,MRF)模型对旋转车轮的流场特性模拟结果有差异,在近车轮区域表现尤为明显.     

Brillouin-Scattering Study of the Elastic Constants of ErVO4

The room-temperature elastic constants of ErVO₄ were considerably smaller than those of isostructural silicate and phosphate analogs. The generally "less-rigid" crystalline lattice and weaker metal-oxygen bond-strength in the RVO₄ (R = rare earth elements) phases indicates that these materials are of interest for potential applications as an interphase component in toughened oxide ceramic composites.     

等强条件下橡胶微粒混凝土抗压特性及弹性模量研究

掺加橡胶微粒可以明显改善混凝土的力学特性。采用橡胶微粒等体积取代细骨料的方法,通过不断调整配合比,反复试验配制出橡胶微粒体积掺量分别为0%、10%和15%的等强度(30 MPa)橡胶微粒混凝土,探讨橡胶微粒混凝土的抗压强度变化规律,以及在等强条件下不同橡胶微粒掺量对混凝土弹性模量的影响。结果表明:掺入橡胶后,混凝土的前期强度(3 d和7 d)发展较基准混凝土变缓,7 d以及14 d后强度出现较大幅度的增长,28 d后各个配比混凝土立方体抗压强度增幅不大;掺入一定量的橡胶后,混凝土的抗裂性能得到了一定程度的改善,橡胶微粒体积掺量越大,试件受压破坏后的完整性越好;掺入橡胶后,混凝土的弹性模量呈现出近乎线性的大幅下降趋势。     

动力试验模型用橡胶集料微粒混凝土力学性能初步试验研究

大型跨海桥梁结构模型试验材料的选择对于模型动力试验至关重要。试验室可实现的微粒混凝土的弹性模量限制了模型的几何比尺。采用橡胶集料等质量比例代替微粒混凝土中砂骨料的方法,通过控制变量法,研究了多种因素影响下的橡胶集料微粒混凝土的抗压强度和弹性模量。试验结果表明:对于骨料含量不变的微粒混凝土,水灰比的增大可显著降低其抗压强度和弹性模量。橡胶集料微粒混凝土的抗压强度和弹性模量随橡胶集料代替微粒混凝土中砂骨料质量比的增加而呈现一定规律降低。研究成果可用于大型跨海桥梁工程大比尺动力试验模型材料相似关系设计和结果分析。     

Intrinsic Elastic, Dielectric, and Piezoelectric Losses in Lead Zirconate Titanate Ceramics Determined by an Immittance-Fitting Method

The material coefficients of "soft" and "hard" lead zirconate titanate (PZT) ceramics were determined as complex values by the nonlinear least-squares-fitting of immittance data measured for length-extensional bar resonators. The piezoelectric d -constant should be a complex value to obtain a best fitting between observed and calculated results. Because the elastic, dielectric, and piezoelectric losses determined in this process were not "intrinsic" losses, a calculation process to evaluate the "intrinsic" losses was proposed. It was confirmed that the intrinsic losses were smaller than the corresponding extrinsic losses. The intrinsic piezoelectric loss existed in both soft and hard PZTs; ∼50% of the loss of piezoelectric d -constant was derived from the elastic and dielectric losses. The most notable difference between the soft and hard PZTs was observed in their elastic losses.     

Dynamic response of Ti3SiC2 under shock compression up to 112 GPa

Ti₃SiC₂ is of interest due to its unique dual nature reminiscent of both brittle ceramics and ductile metals at ambient conditions. In this work, plate-impact experiments have been performed to study the dynamic behavior of Ti₃SiC₂ under shock compression up to 112 GPa by using laser velocity interferometer and electric pin techniques. Hugoniot elastic limits (HEL), spall strength, and Hugoniot equations of state have been obtained based on measured particle velocity profiles and shock wave velocities. The ratio of spall strength to HEL for Ti₃SiC₂ is larger than brittle ceramics but smaller than metals. This result indicates that the dual nature of Ti₃SiC₂ remains at least up to 10 GPa. On the other hand, the linearity of the Hugoniot equation of state, $D=6.9\text{0}1(22)+1.153(53)u_{\text{p}}$, suggests that the initial structure of Ti₃SiC₂ should be stable up to 112 GPa, in contrast to the result reported by Jordan et al. [J. Appl. Phys., 93 (2003) 9639].     

浅谈汽车四轮定位检测与调整技术

四轮定位对汽车的正常行驶起着十分重要的作用。对汽车四轮定位参数进行检测和调整,不仅能确保汽车的正常行驶,还能延长轮胎的使用寿命,同时节省油耗。重点研究了汽车四轮定位的检测方法和调整技术。