The web crossed truss boom is one of the commonly used truss boom structures of crawler cranes. However, the existing calculations fail to consider the limiting effect of the web members' bending resistance on the chord members, and cannot give full play to the load-bearing capacity of the existing structure. This paper takes the top section of the Crawler crane truss boom as the research object. The single-span truss theoretical model is established according to Timoshenko's elastic stability theory. And the theoretical critical load of the variable cross-section boom is obtained with full consideration of the limitation of the web member's bending resistance on the chord members. The finite element method simulation model is compared and verified. Compared with a large number of simulation experiments and theoretical calculations, it can be concluded that the theoretical calculations in this article are highly consistent with the simulation results, verified the assumptions that the web members' bending resistance help to improve the bending resistance of the chord members, and this will provide certain reference to the engineering designers.

With the application of wireless sensor networks become widespread, supply energy for these wireless sensors proves to be a significant issue. Moreover, for the ambient vibration lies everywhere, the vibration can supply energy for the wireless sensor via energy harvester. The piezoelectric energy harvester becomes the research focus for the simple structure and higher energy conversion efficiency. Due to the transcendental equation in distributed parameter model, the numerical method is become powerful complement for theoretical and experimental method. This paper uses ANSYS to analyze the single piezoelectric cantilever in static analysis, model analysis, harmonic response analysis and mechanical-electrical coupling analysis. It analyzes the natural frequency and voltage effect from four aspects which are length to thickness ratio, length to width ratio, the substrate thickness to piezoelectric thickness ratio and seismic mass. Test and measurement for piezoelectric energy harvester is conduct on the testing platform. Macro cantilever beam piezoelectric energy harvester are tested and measured

The installation of a superlift device on the telescopic boom of a crane is the main method to improve the stress condition of the telescopic boom and to effectively improve the lifting performance of the crane. However, there is a lack of an effective and accurate numerical method to solve the critical force of a crane telescopic boom with a superlift device. Therefore, the telescopic boom with a superlift device is reasonably simplified as a stepped column and double cable model. Based on the longitudinal and transverse bending theory, the differential equations of the deflection of the n-stepped column with double cables model are established, the buckling characteristic equation and its recurrence formula of the n-stepped column with double cables model are derived, and the combined superlift equations are established. The Levenberg–Marquardt optimization algorithm is used to solve the critical force and length coefficient. A large amount of data were compared and analyzed between the numerical solution results and the ANSYS finite element simulation results. The error result analysis proved the correctness of the deduced buckling characteristic equation and its derived formula and the accuracy of the numerical solution. The numerical solution method in this paper can be used to calculate the critical force and length coefficient under any number of boom sections, boom section length, sectional moment of inertia, cable length, and included angle between the two cables of the telescopic boom with a superlift device. The numerical solution method can provide a technical support for the structural design of a telescopic boom with a superlift device in practical projects.

Statistical size and geometrical size are the main factors affecting the service life of mechanical structure calculation. To explore the reliability of the lifespan of beam structures, a probability lifespan numerical calculation method based on Vector Form Intrinsic Finite Element Method (VFIFEM) was proposed, and the method was verified through full lifespan experiments on I-beam welded structures. First, a fatigue fracture model that considers the coupling of residual stress (RS) and cyclic load variations was established. Based on this fatigue fracture model, a probability lifespan calculation model for beam elements was defined by proposing a cross-sectional shape correction coefficient and a position correction coefficient. The proposed probability lifespan model for beam elements was used to calculate the I-beam welded structure, and the calculated results were compared with the full lifespan experiment results, which were close in statistical results, with all experimental results falling within the [10%, 90%] interval except for one experiment. This method effectively couples the influence of statistical size and geometric size on probability lifespan, providing a new approach for the structure probability lifespan calculation in the future.