Tracked vehicles are widely used in agriculture, military, construction and other fields because of their high passability, super climbing ability and high traction, and their dynamic performance directly determines the ride comfort and running stability of the vehicle. Identifying the sensitive factors that affect the dynamic characteristics of tracked vehicles has important engineering value in improving the dynamic performance of the vehicle. In this paper, the dynamic modeling and sensitive factor analysis of the tracked vehicle are carried out. Focus on the different flexibility treatment methods, road slope, speed and other parameters of the tracked body and balance elbow, and discuss the influence of different factors on the dynamic performance. The results show that the compliance of the balance bend and the body in the rigid-flexible coupled model will lead to changes in the equivalent stiffness and damping of the entire body, resulting in significant changes in the dynamic response. The acceleration response is greatly affected by the high frequency mechanism, and the pitch angle response is greatly affected by the low frequency mechanism.
Monitoring the damage of adhesive joining could avoid potential accidents in multimaterial lightweight vehicles. Different from the additional sensors, a kind of functional adhesives with hybrid fillers of carbon nanotubes (CNTs) and carbon black (CB) was developed, and verified by in-situ sensing of adhesion damage in single-lap shear joints (SLAJ) of composite-to-metal. The influences of the total weight percent of fillers and relative ratio of CNT-to-CB on the mechanical, piezoresistive and the microwave absorption performance of SLAJ were investigated experimentally. The addition of both CNTs and CB increases the cohesive shear strength but decreases the failure strain at the same time. For the formula of total 2wt.% fillers and CNT:CB = 1:3, the shear strength of SLAJ is nearly 37.50% higher than that of pure adhesives. Both CNT and CB lead to the reduction of electrical resistivity. When approaching the failure strain, the electric resistances for all CNT-to-CB ratios increase sharply. For this formula, the relative electric resistance ratio is 29% at strain 0.038, close to the failure strain. The adhesives with this formula also show a better microwave absorption. This research shows a potential application of adhesives with hybrid nanoparticles in lightweight and low-cost structural health monitoring.
Solving systems of nonlinear equations is perhaps one of the most difficult problems in all of numerical computations, especially in a diverse range of engineering applications. The convergence and performance characteristics can be highly sensitive to the initial guess of the solution for most numerical methods such as Newton’s method. However, it is very difficult to select reasonable initial guess of the solution for most systems of nonlinear equations. Besides, the computational efficiency is not high enough. Aiming at these problems, an improved particle swarm optimization algorithm (imPSO) is proposed, which can overcome the problem of selecting reasonable initial guess of the solution and improve the computational efficiency. The convergence and performance characteristics of this method are demonstrated through some standard systems. The results show that the improved PSO for solving systems of nonlinear equations has reliable convergence probability, high convergence rate, and solution precision and is a successful approach in solving systems of nonlinear equations.
Abstract Polymer‐matrix composites are widely used in various industries due to their high specific strength and specific stiffness. However, the void formation is inevitable as a by‐product during manufacturing processes, which may have negative effects on its mechanical properties. The purposes of this paper are to quantitatively evaluate the influence of voids on the anisotropic elastic properties of composites and to provide corresponding theoretical prediction models. Firstly, three‐dimensional representative volume elements (RVE) of fiber‐reinforced composite materials with different fiber contents (36.37%, 45.47%, 50.92%) and different void contents (1%, 3%, 5%, 7%) are established. To obtain the elastic properties in different directions, various periodic boundary conditions are applied to the RVE models and corresponding subroutines are developed by ABAQUS‐PYTHON. Secondly, a series of theoretical models are proposed to quickly predict the anisotropic elastic properties of unidirectional fiber/epoxy composites containing random‐sized void defects, which agree well with the finite element simulation results. Especially, the proposed models have concise expressions, which require only a few parameters to be input, and hence they are convenient for engineering application. Both theoretical and numerical results show that void defects have an obvious influence on the transverse modulus, major Poisson's ratio, and the out‐of‐plane shear modulus. When the void volume reaches 7%, all of the properties mentioned above decrease by more than 10% for the FRPs studied.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)