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The local and global buckling capacity of the thin-walled box-section members formed by cold bending of ten BS700 high-strength steel (HSS) specimens are experimentally determined through an axial compression test. The mechanical properties of the materials are evaluated through material performance test, and a material model suitable for finite element analysis is proposed. The initial geometric imperfection of the members is measured, and it is found that the maximum initial deflection can be 1/1000 of the length of the members, as specified in the Chinese code. Based on the test, the ultimate bearing capacity and failure modes of the component with local and global interactive buckling are obtained. Further, a finite element model is established, and the corresponding results are compared with the test results. Furthermore, the test results are compared with those obtained using the existing specifications. The results show that the failure modes of the specimens are primarily local and global buckling failure. The influence of residual stress and initial geometric imperfection is considered in the proposed finite element model. Comparing the ultimate bearing capacity and load-displacement curves with the corresponding test results, it is found that the finite element model can effectively reproduce the test results. By comparing the test results with those obtained based on the steel structure design codes of China, the United States, and Europe, it is found that the test results are all higher than the existing code results, and the Chinese and European codes are relatively conservative with a difference of more than 20%, while the difference between the test results and the American code results is nearly 10%. Therefore, it is necessary to further improve the calculation methods of local and global buckling capacity of thin-walled box-section members of BS700 HSS under axial compression.

Fillers can improve the tensile performance of ductile tubes. Mechanical analyses of tensile tubes with filler have generally focused on experimental and numerical studies on concrete-filled steel tube (CFST) components, while mechanical performance of tensile tubes with flexible supporting fillers has rarely been investigated. In the current research, we have proposed a “steel tube+pre-stressed flexible internal support” structure. Meanwhile, strengthening of tensile thin-walled tubes with internal supports was studied in terms of stress and deformation. The trends of yield strength and ultimate strength of tensile tubes were determined and calculation equations of yield strength and normal ultimate strength of tensile tubes with internal support were derived. Strengthening coefficient variations as functions of radius-thickness ratios of steel tubes and elastic moduli of internal supports as well the optimized internal support p corresponding to maximum increment of tensile performance of tubes were also determined. It was experimentally verified that the initial supporting pre-stress of internal support on steel tubes could be achieved by cold shrink fitting technique. Experimental results revealed that the developed composite structure significantly enhanced the mechanical performance, fracture toughness, and energy consumption characteristics of tensile tubes. Hence, the proposed structure was confirmed to have promising applications.

In this work, the interface morphology and formation mechanism of TC1/1060/6061 composite plates prepared by explosive welding are examined by experiments and numerical simulation. The experimental results show that the non-welded area exists only at the edge of the composite plate, while all the other positions have higher bonding quality. Due to the boundary effect, the morphology of the two interfaces changes continually along the detonation direction, which is reproduced in numerical simulation. Smoothed particle hydrodynamics (SPH) is adopted in the simulation and the interface morphology and vortex structure observed in the experiment is successfully reproduced. Further, the transformation from the initial unstable stage of detonation to the stable stage is clearly revealed by using SPH simulation, and the formation mechanism of the straight TC1/1060 interface and wavy 1060/6061 interface is effectively explained. The straight interface is obtained by direct welding process causing by the violent plastic deformation, while the wavy interface originates from the periodic interaction between jetting and metal plates. [ABSTRACT FROM AUTHOR]

Cantilever beams with axial extension and contraction functions as time-varying parameter systems have attracted extensive research due to their prevalence in engineering structures. In this paper, the dynamic characteristics of the flat-push bridge mechanism are investigated from the theoretical aspect, firstly, it is simplified into a cantilever beam model with axial motion, and the transverse vibration equations of the cantilever beam are established based on the Euler–Bernoulli beam theory and D’Alembert’s principle, and the transverse displacements of the beam are discretized using the Galerkin truncation method and solved numerically by using the Newmark-β method for the second-order vibration differential equations with variable coefficients; second-order vibration differential equations were solved numerically by the Newmark-β method; then the structural examples in the existing literature are verified numerically, and the calculation results are consistent with the literature results, indicating that the transverse vibration equations derived in this paper are solved effectively; then a parametric analysis of the speed of the cantilever beam during axial extension/contraction was done, which showed that the faster the speed of axial motion, the faster the rate of change of the dynamic characteristics of the beam and the more pronounced the vibration; finally, the power signal is decomposed in the time-frequency domain by using the Choi–Williams Distribution (CWD), and the time-frequency characteristics of the system under different speeds are analyzed, and the results show that the use of CWD technique can accurately reflect the system’s transient vibration frequency and vibration energy with the change rule of time and speed, and the axial motion speed of ±0.05m/s, the transient frequency of the theoretical prediction and the average relative deviation between the finite element modal frequencies are kept within 5% and the recognition accuracy is high. This analysis provides flexible technical guidance for vibration control in engineering structures. [ABSTRACT FROM AUTHOR]