To determine the stress spectra of a vehicle frame under random road excitations, A mathematical model was been established using the Euler-Bernoulli beam elements and spring-damper elements for the multiple-degree-of-freedom (MDOF) vibration of the vehicle frame with a finite element method, and adopted a virtual excitation method to construct virtual road excitations based on four points, i.e., front and rear wheels, thus we offered a method for calculating the statistical characteristic of the random vibration response of the vehicle frame based on the virtual excitation method, and realized stress spectrum analysis of the random vibration of the vehicle frame. The results show that combining the virtual excitation method and the finite element method for random vibration analysis, maintained the theoretical precision and greatly simplified the calculation , thus provided a feasible way for stress spectrum calculation in fatigue analysis of a vehicle frame under random excitations.
The dump is the important part in the open colliery. Slope should bring the huge loss without effective forecast during the work. Many methods have been used in the slope stability analysis to escape the slope. In this paper, the methods used in the analysis have been list and forecast reasearch should be discuss.
Since boom-type aerial equipment has complex dynamic characteristic under the action of random wind loads, traditional methods are hard to reflect its dynamic response. We put forward an analysis method for wind-induced random vibration response of aerial working arms based on finite element and pseudo-excitation methods. In this analysis, the pulse-wind-load-induced vibration was regarded as a random vibration under multi-point coherent steady random excitation, and Davenport wind speed spectra invariant with height were adopted with consideration of multi-point wind excitation correlation. We analyzed the wind-induced random vibration of the working arm of a folding-arm-type aerial operation vehicle. The analysis results confirm the reliability of the analysis method, so as to offer a feasible way for analyzing the dynamic wind-induced vibration response of large boom-type aerial equipment.
By means of resistance strain gauge and multifunctional test bench of materials mechanics, the relation curve between the axial compressive forces of the two-ends hinged column with a rectangular cross-section and total bridge strain was obtained by the resistance strain measurement method, accordingly, by the horizontal asymptote of this relation curve the critical load of compression column was obtained. The study indicates that the critical load obtained respectively by the resistance strain measurement method and Euler formula theory fits very well, and the research results verified the reliability of the experimental method.
The mechanical models with and without thimble constraints for the turning work-piece are built respectively, applying ABAQUS software to analyze the modes of work-piece, then the law of the influence that different turning depth on the bending modes of work-piece is obtained. The study indicates that each-order natural frequency increase gradually in linear form for the work-piece without thimble constraint, while for the work-piece with thimble constraint, the natural frequency of the first four orders decrease linearly with the increase in the turning depth, but the change of high order frequency is relatively complicated.
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