To enhance the high-temperature adaptability of copper-based composite materials and C–C/SiC discs,this article innovatively introduces a method of replacing graphite with sepiolite,resulting in the successful fabric...To enhance the high-temperature adaptability of copper-based composite materials and C–C/SiC discs,this article innovatively introduces a method of replacing graphite with sepiolite,resulting in the successful fabrication of samples with exceptional mechanical and friction properties.The results reveal that moderate incorporation(less 6%)of sepiolite provides a particle reinforcement effect,resulting in an improvement of mechanical properties.Interestingly,the addition of sepiolite causes a change in the traditional saddle-shaped friction curve due to high temperature lubrication.Meanwhile,the primary advantage of sepiolite lies in its superior abrasion resistance,evident in the increased friction coefficient and altered wear mechanisms with higher sepiolite content.The wear resistance is optimal at 200 Km/h(400℃).Particularly,the unique composition of the friction layer(outermost layer:a composite film consisting of B2O3,sepiolite,graphite,and metal oxide films;intermediate layer:metal oxide films)plays a pivotal role in improving friction stability.Finally,there are significant optimizations in the GA algorithm,especially GA-GB model has the best prediction effect on the maximum friction temperature.展开更多
A frequency and amplitude dependent model is used to describe the complex behavior of rail pads. It is implemented into the dynamic analysis of three dimensional coupled vehicle-slab track （3D-CVST） systems. The veh...A frequency and amplitude dependent model is used to describe the complex behavior of rail pads. It is implemented into the dynamic analysis of three dimensional coupled vehicle-slab track （3D-CVST） systems. The vehicle is treated as a 35-degree- of-freedom multi-body system, and the slab track is represented by two continuous Bernoulli-Euler beams supported by a se- ries of elastic rectangle plates on a viscoelastic foundation. The rail pad model takes into account the influences of the excita- tion frequency and of the displacement amplitude through a fractional derivative element, and a nonlinear friction element, re- spectively. The Granwald representation of the fractional derivatives is employed to numerically solve the fractional and non- linear equations of motion of the 3D-CVST system by means of an explicit integration algorithm. A dynamic analysis of the 3D-CVST system exposed to excitations of rail harmonic irregularities is primarily carried out, which reveals the dependence of stiffness and damping on excitation frequency and displacement amplitude. Subsequently, sensitive analyses of the model parameters are investigated by conducting the dynamic analysis of the 3D-CVST system subjected to excitations of welded rail joint irregularities. Following this, parameters of the rail pad model are optimized with respect to experimental values. For elu- cidation, the 3D-CVST dynamic model incorporated with the rail pads model is used to calculate the wheel/rail forces induced by excitations of measured random track irregularities. Further, the numerical results are compared with experimental data, demonstrating the reliability of the proposed model.展开更多
基金the National Key Research and Development Program of China(Grant No.2021YFB3703803)National Natural Science Foundation of China(Grant No.52075555)for their financial support.
文摘To enhance the high-temperature adaptability of copper-based composite materials and C–C/SiC discs,this article innovatively introduces a method of replacing graphite with sepiolite,resulting in the successful fabrication of samples with exceptional mechanical and friction properties.The results reveal that moderate incorporation(less 6%)of sepiolite provides a particle reinforcement effect,resulting in an improvement of mechanical properties.Interestingly,the addition of sepiolite causes a change in the traditional saddle-shaped friction curve due to high temperature lubrication.Meanwhile,the primary advantage of sepiolite lies in its superior abrasion resistance,evident in the increased friction coefficient and altered wear mechanisms with higher sepiolite content.The wear resistance is optimal at 200 Km/h(400℃).Particularly,the unique composition of the friction layer(outermost layer:a composite film consisting of B2O3,sepiolite,graphite,and metal oxide films;intermediate layer:metal oxide films)plays a pivotal role in improving friction stability.Finally,there are significant optimizations in the GA algorithm,especially GA-GB model has the best prediction effect on the maximum friction temperature.
基金supported by the National Basic Research Program of China("973"Project)(Grant Nos.2013CB036202 and 2013CB036206)the Science and Technology Development Program of China Railway Corporation(Grant No.2014G002-B)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2682013CX029)the 2013 Cultivation Program for the Excellent Doctoral Dissertation of Southwest Jiaotong University
文摘A frequency and amplitude dependent model is used to describe the complex behavior of rail pads. It is implemented into the dynamic analysis of three dimensional coupled vehicle-slab track （3D-CVST） systems. The vehicle is treated as a 35-degree- of-freedom multi-body system, and the slab track is represented by two continuous Bernoulli-Euler beams supported by a se- ries of elastic rectangle plates on a viscoelastic foundation. The rail pad model takes into account the influences of the excita- tion frequency and of the displacement amplitude through a fractional derivative element, and a nonlinear friction element, re- spectively. The Granwald representation of the fractional derivatives is employed to numerically solve the fractional and non- linear equations of motion of the 3D-CVST system by means of an explicit integration algorithm. A dynamic analysis of the 3D-CVST system exposed to excitations of rail harmonic irregularities is primarily carried out, which reveals the dependence of stiffness and damping on excitation frequency and displacement amplitude. Subsequently, sensitive analyses of the model parameters are investigated by conducting the dynamic analysis of the 3D-CVST system subjected to excitations of welded rail joint irregularities. Following this, parameters of the rail pad model are optimized with respect to experimental values. For elu- cidation, the 3D-CVST dynamic model incorporated with the rail pads model is used to calculate the wheel/rail forces induced by excitations of measured random track irregularities. Further, the numerical results are compared with experimental data, demonstrating the reliability of the proposed model.
