Limited by the vibrator structure, there are some problems such as low down-going earth energy and shallow down-going depth of shear-wave signals when the shear-wave vibroseis is excited. Therefore, the influence of different combinations of shear-wave vibroseis vibrators on the excitation effect was innovatively studied through the three-dimensional finite element numerical simulation. Firstly, based on three-dimensional nine-component data and two types of combinations,eight modes of vibration excitation of combined shear-wave vibroseis were considered, a vibrator-earth finite element model was established, and an evaluation system of the vibration excitation effect of the combined shear-wave vibroseis was constructed. Secondly, based on this evaluation system, the influence of the various combined excitation modes of the shear-wave vibroseis on the downward energy of the earth, the downward depth of shear-wave signals and the mutual interference between combined excitation waves was analyzed in detail. The results show that, compared with a single shear-wave vibroseis, when two SHY shear-wave vibroseises are arranged side by side for the normal excitation, the incoming earth energy is increased by 86.36%, and the displacement amplitude of earth particles is increased by 73.40% on average. When two SHX shear-wave vibroseises are excited in the normal direction, the incoming earth energy increases by 97.48%, and the displacement amplitude of earth particles increases by 58.61% on average, which greatly improves the excitation effect. The research results can provide the guidance for improving the excitation effect of the shear-wave vibroseis and the reference for the design of combined excitation mode of the shear-wave vibroseis.

An improved northern goshawk optimization (INGO) algorithm was proposed to address the local optimization problem that swarm intelligence algorithms often encounter when optimizing support vector machine (SVM) models, and it was applied to fault diagnosis of rolling bearings. By introducing an adaptive inertia weight factor based on the cosine variation and a Cauchy mutation strategy, the northern goshawk optimization (NGO) algorithm was improved, and an INGO-SVM fault diagnosis model was constructed using SVM. In order to evaluate the performance of the improved algorithm,firstly, benchmark testing functions were used for experiments, and the improved algorithm was compared with existing optimization algorithms such as NGO, particle swarm optimization (PSO), sparrow search algorithm (SSA), etc. The results show that the performance of the improved algorithm is improved to a certain extent. At the same time, the original diagnostic signals were feature extracted through wavelet packet decomposition and divided into 10 categories. The energy of each frequency band in the 3rd layer was used as the feature vector and input into the fault diagnosis model. Finally, the performance of the improved algorithm was compared with the other three algorithms in optimizing SVM parameters for fault classification. The results show that the improved algorithm can effectively and accurately achieve different fault classifications, with an accuracy rate of 99.39%, verifying the effectiveness and feasibility of this method.

The creep behavior of 7050-T7451 aluminum alloy under different temperatures and stresses was studied by the uniaxial tensile creep test. Based on continuum damage mechanics, a constitutive model describing the creep behavior of aluminum alloy at high temperature was established. The model took into account the precipitation coarsening, dislocation multiplication/annihilation and microvoid formation during the creep process, and introduced the corresponding damage factor evolution formula to reflect these three damage processes. In addition, the model took into account the additional damage caused by stress increase to reveal the effect of stress on the creep damage. Based on the comparative analysis of the test results and the predicted results, it was verified that the established physical constitutive model can accurately describe the creep behavior of 7050 aluminum alloy under different temperatures and stresses.

Low-cycle fatigue is a typical failure mode of engine pistons. In order to study the influence of multi-source uncertainty factors on the reliability of low-circumference fatigue of pistons and improve the efficiency of the reliability analysis, a new reliability calculation method is constructed based on the polynomial-chaos-based Kriging (PC-Kriging) model and the Monte Carlo simulation (MCS), and the accuracy and efficiency of this method are proved by numerical examples.Taking the piston group structure of a certain diesel engine as the research object, a finite element model of the piston is established based on the thermal-mechanical coupling analysis, and the reliability analysis of the piston for low-cycle fatigue is carried out by using this method, taking into account the critical dimensions, the material properties, and the uncertainty of the load. The results of the reliability analysis show that, compared with the same type of method, this method is more efficient in calculation, requiring only 20+93 finite element calculations, and the probability of fatigue failure is 1.053% when the expected design life of the piston is 1.4×10⁴. The sensitivity analysis shows that, the height of the piston, the piston diameter,the elasticity modulus of the material, and the parameters of the fatigue calculation model have a greater influence on the reliability. The analysis results can provide a guidance for the reliability design of the piston.

In order to clarify the dynamic response, damage situation, and failure mode of titanium/steel corrugated composite plates and interfaces under impact loads, small energy (53 J）impact experiments were conducted on titanium/steel corrugated composite plates using a light air cannon. On the basis of verifying the effectiveness of the numerical calculation model, numerical simulations were conducted on composite plates under various velocities to study the impact mechanical response of composite plates and their interfaces under various energies. The results show that, under low energy impact conditions, the front of the corrugated composite plate shows plastic expansion damage, and the back plate has protrusions with cracks at the raised areas. The corrugated interface layer is tightly bonded and overall concave; cut the target plate along the impact center and observe that there are no cracks, delamination, or other damages on the cross-section. This is different from fiber reinforced composite laminates. There will generally be obvious delamination inside when there is barely visible damage on the impact surface. In numerical simulation, the cohesive force interface damage area of the corrugated composite plate under impact is less than that of the planar interface composite plate. When subjected to low energy impact, the absorption of bullet kinetic energy by the corrugated plate is mainly dominated by overall deformation energy absorption, and the damage to the titanium/steel composite plate at the corrugated interface is relatively small. Under various energy impacts,corrugated interface composite plates have tighter interface bonding, better structural integrity, and are less prone to damage compared to planar interface composite plates.

Single tube towers are widely used as the foundation for carrying 5G communication equipments. Due to construction needs, the mounted equipments often changes with the changes in 5G construction. Due to the small damping of the single tube tower, the increase of mounted equipments may cause an excessive vibration, reducing its load capacity.Therefore, the control of tower top vibration is particularly crucial. A particle damping tuned mass damper (PDTMD) method was proposed to control the problem of excessive vibration at the top of 5G communication towers. Based on a collision theory, a mathematical model using PDTMD to control the vibration of the communication tower was established. The vibration response of the tower under effects of PDTM was verified by the detailed calculation, and the damping mechanism of PDTMD was analyzed. The damping effectiveness of PDTMD was compared with the traditional tuned mass damper (TMD).The results show that the particle damping has good energy dissipation ability. Compared with traditional tuned mass dampers,PDTMD has better damping effect and higher robustness. Finally, based on the actual signal tower, the usage parameters of PDTMD in complex environments were optimized. Effects of gaps between damping particles and honeycomb structures,particle materials, and particle mass ratios on the damping effect of dampers were analyzed.

Since the fault vibration data collected in the real engineering may be accompanied by noise, traditional diagnostic models are difficult to identify fault categories. To address this problem, a rolling bearing fault diagnosis research method based on channel and spatial reconstruction and progressive convolutional neural networks (CSRP-CNN) was proposed.The model utilized channel and spatial reconstruction convolution（CSConv）to reduce the redundant information of channels and space in fault features, and reduced the complexity and computation to improve the performance; using the convolutional block attention module (CBAM), attention enhancement operation was carried out in the channel and spatial dimensions to make the model pay attention to the important fault feature information; and the progressive convolutional network structure was used in the shallow layer of the network, which would fuse the previous fault feature information with the current input to obtain the richer feature information. The performance of CSRP-CNN was evaluated by two different datasets of Case Western Reserve University (CWRU) and machinery fault simulator magnum (MFS-MG). After the noise and ablation tests, it is verified that CSRP-CNN has strong robustness and the effects of CSConv, CBAM and progressive convolutional neural network (PCNN) on the model noise immunity performance.

Under the medium and high speed of spherical hybrid sliding bearings, the dynamic pressure effect causes the fluid in the wedge space to whirl, and the vibration characteristics of the rotor may be affected by the oil whirl, so the rotation accuracy of the main shaft is reduced. The spherical hybrid sliding bearings with the orifice throttle was divided into cylindrical and conical whirl. The lubrication mathematical model and rotor dynamic model were established and solved simultaneously, the journal center trajectory and vibration amplitude were obtained. The influence of the centroid offset distance and initial deflection angle on the vibration characteristics of the rotor system were studied.The results show that,compared with the pure cylindrical whirl, the stability of the journal center trajectory decreases and the vibration amplitude increases after considering the conical whirl.With the increase of the centroid offset distance, the stability and vibration amplitude of the journal center trajectory decrease greatly.With the increase of the initial deflection angle, the stability and vibration amplitude of the journal center trajectory decrease only slightly.It can be concluded that changing the distance of the centroid offset has more influence on the stability of the journal center trajectory and the vibration characteristics of the rotor system than changing the initial deflection angle.

To achieve quantitative detection of bolt loosening angles through single frame images, a method based on color segmentation and connected domain feature processing was designed. Firstly, a method for performing nonlinear stretching, normalization and optimal threshold segmentation on a component successively in the Lab color space was designed to segment and represent the red anti-loosening line image of the bolt loosening angle. Secondly, the morphological operations were performed on the image by using the open operation. Then, the orientation vector of the connected domain in the anti-loose line image was determined by computing the geometric moments. Finally, the bolt loosening angle was determined through the four-quadrant arctangent function. The results demonstrate that the precise measurement of the bolt loosening angle through a single frame image can be achieved by this detection algorithm, with a maximal relative error of 1.80%, its accuracy meets the needs of engineering practice and has strong engineering application value.

Aiming at the problem of nonlinear vertical vibration control during the dynamic rolling of strip mills, a nonlinear vibration absorber with the disc spring was designed. Firstly, considering the constraints of dynamic rolling force of the rolling mill in the vertical direction, the mathematical model of the rolling mill under the control of the nonlinear vibration absorber was established, the amplitude-frequency characteristic curve equation of the system was solved by the multi-scale method, and the influence of damping, excitation amplitude and nonlinear stiffness on the vibration suppression effect of nonlinear dynamic vibration absorber was discussed. Secondly, by analyzing the spectrum curve and time domain curve, the vibration absorber device could increase the distance between the resonance frequency and the main resonance frequency, and shorten the time of the rolling mill system from the unstable state to the stable cycle was concluded. The results show that the addition of nonlinear vibration absorber can effectively increase the anti-vibration ability of the system and suppress the vertical vibration of the system.