Preparation and application of carbon nanotubes/conductive carbon black/ethylene-propylene-diene rubber composite

Addition of conductive fillers such as conductive carbon black(CCB)and carbon nanotubes(CNTs)could significantly improve the electrical conductivity of rubber.However,that would result in the deterioration of processing properties for rubber compound and the rapid increase in hardness of vulcanizates,which affected seriously the preparation of conductive rubber composites and thus limits the application in the field of flexible conductive rubber materials.

Impact of the equivalent center of mass separating from the sliding surface on the isolation performance of friction pendulum bearings

A new equivalent center of mass model of FPBs (friction pendulum bearings) is introduced, and based on this model, coefficient j of the equivalent center of mass separating from the sliding surface is defined. It is thought in theory that j has a significant impact on the isolation parameter of FPBs, since the equivalent post-yielding stiffness and friction coefficients are not simply determined by sliding radius and sliding friction pairs. The results of numerical simulation analysis using ABAQUS conducted on two groups of FPBs support this viewpoint. For FPBs with the same sliding radius and sliding friction pairs, the FPB modules of structural analysis software such as ETABS could only distinguish the equivalent transformation using j one by one. The seismic response data obtained in a base isolation calculation example of FPBs are very different, which reveals that j’s impact on the isolation effectiveness of FPBs cannot be ignored. The introduction of j will help improve the classical structural theory of FPBs and the weak points of structural analysis software based on this theory, which is important in achieving more accurate analyses in structural design.

Enhanced Potassium‑Ion Storage of the 3D Carbon Superstructure by Manipulating the Nitrogen‑Doped Species and Morphology

Potassium-ion batteries(PIBs)are attractive for gridscale energy storage due to the abundant potassium resource and high energy density.The key to achieving high-performance and large-scale energy storage technology lies in seeking eco-efficient synthetic processes to the design of suitable anode materials.Herein,a spherical sponge-like carbon superstructure(NCS)assembled by 2D nanosheets is rationally and efficiently designed for K+storage.The optimized NCS electrode exhibits an outstanding rate capability,high reversible specific capacity(250 mAh g^(−1) at 200 mA g^(−1) after 300 cycles),and promising cycling performance(205 mAh g^(−1) at 1000 mA g^(−1) after 2000 cycles).The superior performance can be attributed to the unique robust spherical structure and 3D electrical transfer network together with nitrogen-rich nanosheets.Moreover,the regulation of the nitrogen doping types and morphology of NCS-5 is also discussed in detail based on the experiments results and density functional theory calculations.This strategy for manipulating the structure and properties of 3D materials is expected to meet the grand challenges for advanced carbon materials as high-performance PIB anodes in practical applications.

Synthesis and Characterization of Long Chain Semiaromatic Polyamides based on Undecanediamine

Long chain semiaromatic polyamides with high molecular weight were synthesized by the reactions of undecanediamine with various aromatic diacids,and characterized by fourier transform infrared spectra（FT-IR） and nuclear magnetic resonance（1H-NMR）.The thermal behaviors were determined by differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA）.The solubility,dynamic mechanical,physical and mechanical properties of the polyamides were also investigated.The experimental results show that the polyamides with high molecular weights are obtained only the PH value of the polyamides salt are in the range of 7.2-7.4.The melting temperatures and the glass transition temperatures of the polyamides increase with the increase of the rigidity of aromatic diacids,and are near to those of poly（nonamethylenetere-phthalamide）（PA9T）.

Numerical Analysis of the Hydrodynamic Lubrication of Micro-grooved Friction Pair

A growing interest is given to the hydrodynamic lubricated friction pair with surface textured. Because of its relatively simple processing methods and low manufacturing costs,micro-groove has become the most valuable form of surface texture,and definitely has broad application prospects in mechanical engineering. Based on numerical simulation,the present study aims to examine the effects of surface forms and cross-section types of micro-groove on the hydrodynamic lubrication performance,and to find out the optimal structural parameter for designing logical micro-grooves. Different surface form and cross-section types are designed to maximize the texture hydrodynamic effect. The average pressure of such microgrooved surface is evaluated in detail,and the variation trends with changes of the length of micro-groove,lp,or the depth,hp,are discussed. The theoretical results show that micro-grooves with rational design contribute to the improvement of hydrodynamic lubrication performance of friction pair largely. For a specific micro-grooved friction pair,the optimal surface form and crosssection type make the lubrication performance best.

Mechanical-Delay Dynamic Model of Magnetorheological Damper

In the dynamic characteristic experiment of magnetorheological( MR) damper, a strange feature which the improved Bouc-Wen model based on tanh function cannot accurately describe has been shown when MR damper is reversing or at a low speed. In order to describe this phenomenon,a new mechanicaldelay dynamic model based on the improved Bouc-Wen model has been proposed for MR damper. This new model comprehensively considers the coupling effect on the structural flexibility of MR damper and the MR effect of MR fluid. The identification results show that the new mechanical-delay dynamic model for MR damper has a good coherence with experiment whenever at low or high speed.

Torsional stiffness modeling and optimization of the rubber torsion bushing for a light tracked vehicle

Taking the rubber torsion bushing of a certain type of all-terrain tracked vehicle as the research object,a theoretical model of torsional stiffness was proposed according to the non-linear characteristics of rubber components and structural feature of the suspension. Simulations were carried out under different working conditions to obtain root mean square of vertical weighted acceleration as the evaluation index for ride performance of the all-terrain tracked vehicle,with a dynamics model of the whole vehicle based on the theoretical model of the torsional stiffness and standard road roughness as excitation input. Response surface method was used to establish the parametric optimization model of the torsional stiffness. The evaluation index showed that ride performance of the vehicle with optimized torsional stiffness model of suspension was improved compared with previous model fromexperiment. The torsional stiffness model of rubber bushing provided a theoretical basis for the design of the rubber torsion bushing in light tracked vehicles.