A disc-slotted pulse water jet is a potential tool to break hard rock due to its special loading styles, such as the water hammer pressure, ultra-speed lateral jetting and pulse dynamic load etc. Aiming at investigating the flow filed of the jet, a two-phase-flow transient computational model, matching with the geometry and motion of the interrupted water jet generating device, was established to simulate the dynamic evolution and characteristics of a single pulsation within 100 mm standoff based on the volume of fluid (VOF) model and dynamic mesh theory. The results show that at the head of the pulsed jet forms a deflective slug structure which is consistent with the result from high-speed photography experiments. The slug head velocity is lower than that at the jet outlet and the jet turbulence is mainly distributed over boundary layers between jet and air and at the deflective side. Tile-shaped stereo-structure is yielded during the pulse formation process. It presents non-axisymmetric flow pattern when impacting target, which consists with the irregular erosion cavity obtained by hard rock fragmentation experiments.

The purpose of the current study was to analyze the influence of changes of the material of the human thoracic skeleton and soft tissues on the thorax responses under frontal impact loading conditions. A series of human thorax impact simulations were conducted based on a developed and validated human thorax finite element (FE) model. A number of thoracic response parameters were output to investigate the effect of material property changes on the predicted thoracic responses by using polynomial fitting analysis. The results of the simulations indicated that varying thoracic material properties affects the impact responses with different level. The impact force (Fmax) and chest deflection (Dmax) were obviously affected, and the number of rib fractures (NRF) and T12 accelerations (Gmax-T12) were additionally affected by the material properties. However, the influences of the material properties on the deflection rate (Vmax) and T1 acceleration (Gmax-T1) were small. Specifically, the Fmax, Dmax, and Gmax-T12 were mainly influenced by the soft tissue material properties, while the NRF was primarily determined by the thoracic skeletal structure material properties.

Here, the pedestrian lower extremity injury risk was studied using the real world accident data. For this purpose, 354 cases with pedestrian lower extremity injuries selected from the german in-depth accident study(GIDAS) database were used to conduct the one-way variance analysis to determine the effects of impact speed, pedestrian age, height and weight on the pedestrian serious lower extremity injuries risk. Then, the pedestrian serious lower extremity injury risk model was established. The results showed that the impact speed and pedestrian age are significant factors affecting pedestrian lower extremity serious injuries, but the pedestrian weight and height are not; the risk of injury is positively related to impact speed and pedestrian age; the pedestrian serious lower extremity injury risk reaches 50% when the impact speed is 43 km/h.

对轴对称腔体内淹没射流的空化流动特征进行了高速摄像观测和试验研究,得到了腔体内和下喷嘴出口管内流动的空化数与工作射流雷诺数(Re)的变化规律。试验研究发现,在一定的Re范围内,空化数随Re数发生跳跃变化,腔体内空化形态发生突变,空泡形态由突变前的小直径空泡剧变为突变后的大直径空泡。Re减小变化过程发生空化数跳跃的Rec小于Re增大变化过程发生空化数跳跃的Rec,两者存在滞后效应。在试验的腔长范围(6≤Lc/d1≤13)内,Re增大变化过程和Re减小变化过程的Rec均随腔长线性变化,但后者变化的斜率小于前者,滞后效应随着腔长的增长而扩大。

The structural performance and safety condition of the railway turnout has a significant impact on the running safety and operation quality of the trains,especially the high-speed trains,and it is therefore of great importance to conduct the research of damage detection and crack monitoring for the railway turnout. A fiber Bragg grating( FBG) sensing technology-based method for damage detection of turnout rail-tracks was proposed with the aid of the characteristics of reflection spectra of FBG sensors. The FBG sensors were installed on the turnout rail-track with cracks,and the static and dynamic experiments in the laboratory were carried out to verify the method of damage detection by analyzing the structure of reflection spectra of FBG sensors. The experimental results show that the proposed damage identification method based on the characteristics of FBG reflective spectra can effectively identify the cracks on the turnout rail-tracks.