The tomography technique is an effective way to quantitatively evaluate damage from reconstruction imaging in structure health monitoring (SHM). The reconstruction algorithm for the probabilistic inspection of damage (RAPID) algorithm based on the signal difference coefficient (SDC) feature is a promising approach due to its superior performance. This paper focuses on the influence of different patterns of PZT (Lead Zirconate Titanate) sensor array configurations, i.e., the circular, square, and parallel array, on reconstruction image qualities for evaluating hole and crack damage. Variable shape parameters are applied to account for the unequal damage distances of different actuator-sensor pairs. Considering the directionality scattering fields of cracks, the angular scattering pattern of the SDC values are studied by simulation. The SDC variations for different groups of sensing paths at the same actuator are applied to predict the crack orientation. An improved RAPID algorithm is proposed by defining an additional SDC value of 1 in the path along the predicted crack orientation, which is determined by the point of the actuator causing the minimal SDC variation and the center point of the initial reconstruction image of the crack. The results show that the improved RAPID algorithm is effective for the evaluation of crack damage. Reconstruction image qualities with three PZT sensor array configurations for both holes and cracks are compared. The research is significant for selecting the PZT sensor array configuration in SHM.

The cavitation flow of the cartridge pilot-operated relief valve’s main valve port was numerically simulated and studied using Computational Fluid Dynamics (CFD) in our research, and the relief valve structure was modified to decrease cavitation noise. These findings indicate that cavitation in the relief valve occurs primarily downstream of the main valve port and is linked to the wall. The cavitation generation is influenced by the jet at the valve port. The closer the high-speed jet at the valve port is to the valve’s inner wall, the more readily cavitation occurs. Conversely, less cavitation is observed. This paper reports the effects of the forms and parameters of the main port structure on the jet angle and morphology of cavitation. The annular groove structure of the spool has a considerable influence on the cavitation attached to the spool and the valve sleeve wall, whereas the outlet position of the relief valve mostly affects the intensity of cavitation near the valve sleeve wall. Based on this, an optimized structure of the relief valve was designed, with which the maximum vapor volume fraction and total vapor volume of the cavitation flow were considerably decreased for various inlet pressures and spool openings. The experimental results show that, following optimization, the noise of the relief valve drops dramatically, confirming that optimizing the structure has a beneficial impact on decreasing cavitation noise.

Hydraulic vibration excitation has been widely regarded as a promising method of excitation because of its high power density and large output force. However, the alternating pressure in the hydraulic vibration exciter could cause the pilot-operated relief valve (PRV) to open abnormally, which presents a new challenge to the normal operation of the PRV. To determine the abnormal opening characteristics of the PRV under alternating pressure, the effects of structure parameters of the PRV (including diameters of orifices 1 and 2, volume of the pilot valve inlet, volume of the main valve spring chamber, area ratio of the main spool, and main spring pre-compression force and stiffness) on its abnormal opening displacement under alternating pressure were numerically investigated. The calculation results indicate that the abnormal opening of the PRV will be effectively decreased by appropriately increasing the diameter of orifice 1, decreasing the pilot valve inlet and main valve spring chamber volumes, and increasing the area ratio of the main spool and the main spring pre-compression force. The influence of the orifice 2 diameter on the abnormal opening of the PRV is dependent on the diameter range of orifice 1. The reasonable diameters of orifices 1 and 2 are in the range of 0.8–1.2 mm. The influence of the main valve spring chamber volume is more significant than the pilot valve inlet volume. The influence of the main spring stiffness is not significant.

The numerical calculation method is used to analyze the wear of the liner of the general structure of a semi-autogenous mill in the axial direction, and the non-uniform wear of each area of the liner is studied to explore the reasons for said wear. The liner is divided into areas along the axial direction, and the discrete element method (DEM) is used to analyze the relationship between the wear volume of each area and the total mass of particles. The composition ratio of the rocks and steel balls in each area, and its relationship with time, are also studied. The results show that the total mass of the particles in the area has a significant effect on the wear of the liner. When the particles are affected by the conical end cover on both sides during the operation of the mill, they will be stratified along the axial direction. The particles with large masses will accumulate on both sides of the mill, and the particles with small masses will be concentrated in the middle of the mill. As a result, the difference between the density and impact energy of rocks and steel balls in each area is caused, and eventually, the mill liner appears to have non-uniform wear.

With an increase of suction efficiency of fresh concrete pumping in confined spaces, the laminar flow state will be damaged by the return flow caused by distribution value direction changes and concrete gravity. This is a fact, but one which is rarely studied. In this work, the flow state, flow velocity, and suction efficiency of fresh concrete pumping are simulated using the coupled smooth particle hydrodynamics and Discrete Elements Method (SPH-DEM). The rheological parameters and Herschel-Bulkley-Papanastasiou (HBP) rheological model are adopted to simulate fresh concrete in the numerical simulation model. The study reveals that the error between the slump experimental result and that obtained by the HBP model is negligible. A model is therefore established for numerical simulations of the suction efficiency of fresh concrete pumping. An experimental concrete pumping platform is built, and the pressure and efficiency data during pumping are collected. A comparison of the numerical simulation with experimental results shows that the error is less than 10%.

In contrast to traditional approaches to simulating fresh concrete, the model applied here allows issues such as liquid phase and the motion of sub-scale particles to be considered. The rheological behavior of fresh concrete materials was investigated, and the slump test and pumping process of fresh concrete were simulated by combining the smooth particle hydrodynamics coupled with discrete element method. Based on Bi-viscosity model and Bingham model, linear and nonlinear fitting of rheometer data and the derivation equations were educing. Bi-viscosity model and the Bingham model were compared in slump test. The results show that the Bi-viscosity model is more accurate in simulation, and the error percentage is less than 10%. The Bi-viscosity model was used to simulate and predict the results of slump experiment, and the influence of rheological parameters on the slump velocity and shape was obtained. The simulation analysis model of concrete single-cylinder pumping is established, and the experimental and simulation analysis models are compared. The results show that the SPH-DEM pumping pressure prediction is very close to the experimental results.