The Penetration–Explosion Effects of Differently Distributed Inactive/Active Composite Shaped Charge Jets

An analysis of the penetration–explosion (PE) effects of four distributions of inactive/active composite jets shows that a well-designed inactive/active double-layer liner can promote composite jet damage. Penetration experiments were then carried out for shaped charge jets having a single inactive (Cu) liner or an inactive/active (Cu/Al) double-layer liner with variable liner height. The behaviors and firelight patterns of the different jets were captured by high-speed photography. The perforation, deformation area, and deflection were measured for each plate, showing that the Cu/Al jets have stronger PE effects. Numerical simulation shows that the tip of the composite jet generated from the full-height liner is only Cu, whereas for the other jet, from the double-layer liner, Cu is almost wrapped entirely by Al.

A Novel Method for Extracting Time Series Information of Deformation Area of a Single Landslide Based on Improved U-Net Neural Network

This paper proposed an improved U-Net fully convolutional neural network to automatically extract a single landslide deformation information under time series based on the physical model experiments. This method extracts time series information for three different landslide deformation ranges. Compared to U-Net and mainstream superpixel method, evaluation indicators of DSC, VOE and RVD verify the high recognition accuracy and strong robustness of our method.

Research on the key design and application of the device of opening cover and ring cutting and digging flesh of Mandari

Aiming at the problems of low efficiency and poor sanitation of manual cover opening and meat digging in the production of common orange tea, a multi station full-automatic meat digging machine for common orange tea is designed to realize the automatic cover opening and pulp separation device of green orange, so as to meet the production of common orange tea in Xinhui District of Jiangmen. The mechanism of peel stress and pulp separation damage of green citrus in the process of mechanical meat digging was studied. The state of peel contact deformation area of green Citrus under the extrusion of meat digging knife was analyzed by simulation, and the structural and operating parameters of de jacking and opening mechanism and meat digging mechanism were optimized. When the extrusion force was less than 35.6n, the peel damage rate could be minimized. Compared with manual operation, it reduces labor cost and production cost, saves processing time, and realizes automatic and rapid production.

Effect of ultrasonic surface deep rolling combined with oxygen boost diffusion treatment on fatigue properties of pure titanium

Ultrasonic surface deep rolling (USDR), oxygen boost diffusion (OBD), and their combination (USDR-OBD) were all used to improve the surface hardening of pure titanium. The microstructure, microhardness, and fatigue life of pure titanium treated by USDR, OBD, and USDR-OBD methods were analyzed. USDR treatment induced a severe deformation area, while OBD treatment produced a brittle oxygen diffusion zone. The USDR-OBD treated samples approached the highest hardness in comparison with other treated samples. The fatigue lives of USDR treated samples were improved, which was due to the high compressive residual stress and refined grains. However, the fatigue lives of both OBD treated samples and USDR-OBD treated samples were decreased due to premature crack initiation and rapid propagation in the oxygen diffusion zone. Finally, the fatigue fracture mechanisms of different samples were proposed.

Investigations of the Rockfall Impacts on the Flexible Protective Barriers under Seismic Loading

Rockfall triggered by earthquakes can cause severe infrastructure losses and even fatalities. The flexible protective barrier is an efficient rockfall protection system that has been widely used against rockfall. This studyproposed a novel approach to simulate a field test of rockfall impacting the flexible barrier, and the simulation results showed an excellent match with the field test results. Based on this approach, the seismic loading was applied to the numerical model, and four types of seismic loading were adopted, e.g., non-seismic, x-directional seismic, y-directional seismic, and z-directional seismic. This study aims at investigating the dynamic behavior of the flexible protective barrier under different seismic loading during the rockfall impact process. The following findings can be obtained from the simulation results. First of all, the seismic loading can increase the maximum elongation and decrease the final elongation of the flexible protective barrier comparing to non-seismic loading. Second, the largest deformation area of the protective barrier is at the diagonal position when x-directional seismic loading was applied, which is at the vertical bisector position when y-directional and z-directional seismic loading was applied. Third, the maximum elongation of the protective barrier decreased with the increasing seismic wave period. But in general, the amplitude and period of seismic waves have negligible effects on the elongation, maximum normal stress, and maximum shear stress of the flexible protective barrier.

Research on plastic deformation law and forming technology of rotary forging with multi-cone rolls

With the development of industrial technology, the application of large diameter-thickness ratio integral discs in various high precision vessels is becoming more and more important. At present, the forming processes of large-diameter disc mainly includes welding and multiple local upsetting, but these processes exhibit large defects and cannot meet the requirements of industry. Therefore, a new metal plastic forming technology, namely rotary forging with multi-cone rolls (MCRs) is proposed to integrally form large diameter and ultra-thin discs. The forming process was simulated by DEFORM-3D finite element analysis software, and the deformation characteristics of MCRs disc were revealed. The results show that the axial plastic deformation of disc can be divided into three stages. In the first stage, the plastic deformation area was basically symmetrical, and the deformation was relatively stable. In the second stage, the plastic deformation area on both sides was different, which was in the unstable stage and easy to produce defects. In the third stage, the plastic deformation area was approximately symmetrical for a long time, and the plastic deformation was stable. At the same time, the influence of process parameters on the form characteristics of MCRs, the main defects in the deformation process and the preventive measures were studied. The research results are helpful to better understand the metal plastic forming technology of MCRs and promote the further development of MCRs.

Geodetic benchmark displacement measurements following the 2020 Petrinja earthquake in Croatia

<p>The earthquake with magnitude ML=6.2 that occurred on 29th December 2020 has caused significant material damage to objects and infrastructure in the towns of Petrinja, Sisak,Glina and the surrounding area. According to the satellite interferometry data, the coseismic and postseismic deformation area covers around 500 square kilometers. The existing geodetic benchmarks have been set in the affected towns, and their coordinates have been determined based on previous GPS campaigns. The GPS network was set up and adjusted at the State Geodetic Administration's request for geodetic monitoring of infrastructure and cadastral projects. These points are not primarily intended for high accuracy measurements at the level of a few millimeters, so their accuracy and the absolute shift concerning geodynamic processes in the region should be taken into account. Nevertheless, the data obtained by their observation after the earthquake can provide valuable information about the horizontal and vertical displacements with a certain level of confidence. The field survey has detected disappearance of a large number of benchmarks and some valuable information has been lost. Still, 58 points were found and observed and it has been concluded that 52 points are reliable and can be used for future research. Because the network of benchmarks is not developed in rural areas, there is a gap in the distribution of benchmarks in affected area. Therefore, the additional data was collected using the benchmarks established for the engineering and cadastral projects and studies. From a total of 67 points that have been found and observed, 42 points will be used. Along with the data collected in urban areas, there will be a total of 94 benchmarks. The accuracy of the geodetic benchmark measurements is at the centimeter level, while the values of deformation are at the level of a few decimeters. Therefore, the obtained data can be used to better assess the displacement recorded during the 29 December 2020 event. In the future, field research will focus on finding additional benchmarks to reach a better spatial distribution.</p>

Explosion Resistance of Three-Dimensional Mesoscopic Model of Complex Closed-Cell Aluminum Foam Sandwich Structure Based on Random Generation Algorithm

According to the randomness of the spatial distribution and shape of the internal cells of closed-cell foam aluminum and based on the Voronoi algorithm, we use ABAQUS to model the random polyhedrons of pore cells firstly. Then, the algorithm of generating aluminum foam with random pore size and random wall thickness is written by Python and Fortran, and the mesh model of random polyhedral particles and random wall thickness was established by the algorithm read in by TrueGrid software. Finally, the mesh model is impo rted into the LS-DYNA software to remove the random polyhedron part of the pore cell. Compared with the results of scanning electron microscopy and antiknock test, the morphology and properties of the model are close to those of the real aluminum foam material, and the coincidence degree is more than 91.4%. By means of numerical simulation, the mechanism of the wall deformation, destruction of closed-cell aluminum foams, and the rapid attenuation of explosion stress wave after the interference of reflection and transmission of bubbles were studied and revealed. It is found that aluminum foam deformation can be divided into four areas: collapse area, fracture area, plastic deformation area, and elastic deformation region. Therefore, the explosion resistance is directly related to the cell wall thickness and bubble size, and there is an optimal porosity rule for aluminum foam antiknock performance.

Investigation of the Deformation Twins on the Bending Cross Section of TA2 Titanium Sheet

In order to determine the evolution features of deformation twins for TA2 commercial pure titanium (cp-TA2), the TA2 samples were bent under different bending angles in three-point bending tests via a universal testing machine. The electron backscatter diffraction (EBSD) technique was applied to identify the grain boundaries (GBs) and twin boundaries (TBs) in the bending areas. The results reveal that the type of deformation area would effect the evolution of different deformation twins. It is inferred that the state of stress would promote the multiplication of the same type of deformation twins.