Dynamic Response of Electro-Mechanical Properties of Cement-Based Piezoelectric Composites

By employing ordinary Portland cement as a matrix and PZT-5H piezoelectric ceramic as the functional body, 1-3 and 2-2 cement-based piezoelectric composites were prepared. Quasi-static compression tests were performed along with dynamic impact loading tests to study the electro-mechanical response characteristics of 1-3 and 2-2 cement-based piezoelectric composites. The research results show that both composites exhibit strain rate effects under quasi-static compression and dynamic impact loading since they are strain-rate sensitive materials. The sensitivity of the two composites has a non-linear mutation point: in the quasi-static state, the sensitivity of 1-3 and 2-2 composites is 157 and 169 pC/N, respectively; in the dynamic state, the respective sensitivity is 323 and 296 pC/N. Although the sensitivity difference is not significant, the linear range of the 2-2 composite is 24.8% and 61.3% larger than that of the 1-3 composite under quasi-static compression and dynamic impact loading, respectively. Accordingly, the 2-2 composite exhibits certain advantages as a sensor material, irrespective of whether it is subjected to quasi-static or dynamic loading.

Energy Absorbing Properties Analysis of Layers Structure of Titanium Alloy Ti6Al4V during Dynamic Impact Loading Tests

This paper presents the testing methodology of specimens made of layers of titanium alloy Ti6Al4V in dynamic impact loading conditions. Tests were carried out using a drop-weight impact tower. The test methodology allowed us to record parameters as displacement or force. Based on recorded data, force and absorbed energy curves during plastic deformation and sheet perforation were created. The characteristics of the fractures were also analyzed. The impact test simulation was carried out in the ABAQUS/Explicit environment. Results for one, two, and three layers of titanium alloy were compared. The increase in force required to initialize the damage and the absorbed energy during plastic deformation can be observed with an increase in the number of layers. The increase in absorbed energy is close to linear. In the simulation process, parameters such as Huber–Mises–Hencky stress value, equivalent plastic strain, temperature increase, and stress triaxiality were analyzed.

3D Physical Modelling Study of Shield-Strata Interaction under Roof Dynamic Loading Condition

The dynamic hazards in the open face area caused by the impact load of the massive strong roof become increasingly severe with the increase in the cutting height of the longwall face and its depth of cover. Understanding the strata-shield interaction under the dynamic impact loading condition may relieve the dynamic hazards. In this paper, a 3D physical modelling platform is developed to study the interaction between the roof strata and the longwall shield under the dynamic impact load conditions. A steel plate is dropped to the coal face wall at a certain height above the immediate roof to simulate the free fall of the main roof and the dynamic impact loading environment. The occurrence of major roof falls is modelled at different height above the model and at different positions relative to the longwall faceline. The large-cutting-height and top-coal-caving mining methods are modelled in the study to include the nature of the immediate roof. The results show that the level of face and roof failures depends on the magnitude of the dynamic impact load. The position and height of the roof fall have an important influence to the stability of the roof and face. The pressures on the shield and the solid coal face are relieved for the top-coal-caving face as compared to the large-cutting-height face.

AN ANALYTICAL APPROACH AGAINST PROGRESSIVE COLLAPSE AFTER EXPLOSION RC BUILDING

Reinforced concrete structures may be subjected to uncontrolled sudden loads such as weight or rock fall, industrial or transport accidents, military or terrorist activities, controlled or bottled gas, natural gas, fuel tanker or fuel station explosion. It is difficult to predict how the structure will react under dynamic impact loading. However, creating scenarios taking measures against dynamic loading is a simple solution for behavior impact prediction. In this study was investigated to remove of the middle column in the reinforced concrete structure after the internal explosion. Static analyzes were carried out with IdeCAD Static software according to the load distributions after the carrier element removed in the typical building. In this study, load distribution principles are reviewed in accordance with ASCE 7-10, GSA 2016 and ACI 318 recommendations after subtracting elements. As a result, element remove scenarios are required as a design principle for structures.

Comparative Shear Tests of Bolt Rods Under Static and Dynamic Loading

This article presents the methodology and results of single shear tests of bolt rods under dynamic impact loading generated by means of a drop hammer. Comparative analysis was also performed for bolt rod load capacity, stress and shear work under static and dynamic (impact) loading. The developed method of single shear testing of bolt rods under impact loading makes it possible to obtain repeatable test results concerning maximum bolt rod shearing force, shear stress and shear work values.Comparative shear tests of four types of bolt rods under static and impact loading showed that the APB-type bolt rods made of AP770 steel, which was characterised by having the highest strength, exhibited the greatest shear work. AM22-type bolt rods exhibited a very similar work value. Though the AM22-type bolt rods made of A500sh steel demonstrated lower strength than the APB-type bolts, as well as a smaller diameter and cross section, they dissipated the impact energy better thanks to their higher plasticity. This could indicate the direction of optimisation for bolt rods in order to increase their impact strength.Mathematical relationships were also formulated for selected tests, describing the real single shear courses F d =f(t) of bolts under impact loading. The obtained relationships could be applied in the load assessment process of bolt rods intended for use under roof caving, tremor and rock burst conditions.