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Journal of Engineering publishes research in several areas of engineering, including chemical engineering, civil engineering, computer engineering, electrical engineering, industrial engineering and mechanical engineering.
Chief Editor, Professor Wang, is the Vice Deputy Dean of the School of Aerospace Engineering at Tsinghua University.
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Experimental Research on the Mechanical Properties of Heated Granite after Rapid Cooling
Understanding the mechanical properties of the reservoir rock under different temperatures after rapid thermal cooling is necessary for safe and effective deep geoengineering applications, including deep mining projects, deep geological disposal of nuclear waste, and geothermal energy extraction. This paper is devoted to investigating the effect of rapid cooling on the mechanical behavior of the granite rock. At first, high-temperature heating was conducted. The 24 samples were divided into six groups and were heated at 100, 200, 300, 400, 500, and 600°C, and once they had reached the chosen temperature, they were immediately cooled with a cold water container, and the temperature of water in the pan was 25°C. After the thermal treatment, the samples were measured using ultrasonic wave velocities, and then they were deformed under uniaxial and triaxial compression tests. The -wave velocity, damage characteristics, stress-strain curves, compressive strength, and Young’s modulus of the samples were presented considering different thermal temperatures. The results confirmed that the -wave velocities of the samples generally decrease with temperature. P-wave velocity can indirectly reflect the damage of the rock structure. These changes represent a negative exponential relationship between -wave velocity and hold temperature following cooling. As the samples experienced greater temperatures, the peak strength and elastic characteristics also significantly reduced. This is mainly due to thermally induced damage in the form of both intergranular and intragranular cracks. The stress-strain response revealed that the failure mode can change from brittle to quasi-brittle fracturing following treatment at increasingly greater temperatures.
Effect of Aggregate Roughness on Strength and Permeation Characteristics of Lightweight Aggregate Concrete
This paper aims to examine the effect of surface roughness of lightweight aggregate particles (LWA) on the strength and permeation characteristics of lightweight aggregate concrete (LWAC). Changing the smooth surface texture of LWA particles was achieved by applying surface polishing to make rough texture of the aggregate particle surface. LWAC mixes with different LWA surface roughness (smooth and rough) were produced, and their strength and permeation properties were investigated. Cut section method was adopted to measure the surface roughness of LWA particles. The surface profile was measured by using ImageJ software on images captured using the optical microscope (OM) and scanning electron microscope (SEM) with different magnifications. The ability of making the surface of LWA particles rough by polishing them was proved by means of 2D roughness measurements. From the results, it was found that using treated LWA with rough surface helped in enhancing the strength (compressive) and the permeation properties (water absorption and sorptivity) of lightweight aggregate concrete (LWAC). Making the LWA rough helped in improving the compressive strength by about 13.5% owing to enhancing the ITZ between the LWA particles and the cement paste as well as improving the chemical bonding and mechanical interlocking forces between them. In addition, using rough lightweight aggregate led to reduce the water absorption and cumulative volume of water absorbed by about 9% and 12%, respectively, compared to values of mix with original (smooth) LWA.
A Multiport Electric Energy Routing Scheme Applied to Battery Energy Storage System
In this paper, the research status of topology and control strategy of energy storage grid-connected system is analyzed, and aiming at the working characteristics of the repurposed battery, a cascade power electronic transformer (CPET) with independent DC output is proposed. The working principle of current fed isolated bidirectional DC-DC converter (CF-IBDC) and cascaded H-bridge (CHB) is analyzed, and the decoupling control strategy is designed. In this paper, a hierarchical control strategy is designed for the repurposed battery energy storage (RBES) grid-connected system based on CPET, which consists of three layers: energy layer, power layer, and state of charge (SOC) layer. The energy layer responds to active and reactive power scheduling instructions, the power layer controls the grid-connected current and tracks the grid voltage, and the SOC layer equates the charged state of repurposed batteries. A 3 MVA/12 kV three-phase grid-connected simulation system was established, and a 1 kW single-phase system experiment platform was designed. The simulation and experimental results can verify the correctness of the theoretical analysis and the feasibility of the control strategy.
Shear Strength of Reinforced Recycled Aggregate Concrete Corbels
This paper is related to a laboratory program for the shear strength of reinforced concrete corbels (RCC) cast with or without recycled aggregate (RA) by investigating the main parameters affecting the corbels behavior including the replacement aggregate recycling ratio, fcu, and shear span to effective depth ratio a/d. Eight specimens were cast and tested. The obtained results were compared with ACI and EC2 codes. It is found that the ACI code and E2 code give sensibly conservative results when compared with the findings of the present work for all tested specimens regarding RA, concrete strength, and a/d. Also, the experimental results show that the presence of recycled aggregate decreases slightly both cracking and failure loads. Furthermore, the failure load development due to the effect of compressive strength is more effective with the presence of recycled aggregate, and the 50% ratio of RA was the suitable ratio in elaborate crack and failure loads. Finally, the reduction of the span-depth ratio (from 0.50 to 0.35) increases the crack and failure load by 8.1% and 20.2%, respectively, leading to confirm that the corbel strength is much sensitive to decreasing span-depth ratio compared to the associated deflections.
Dynamic Characteristics of the Rotating Penetrating Missile for Attacking Warship Vertically
The paper aimed to analyze the dynamic response of a new type penetrating missile in rotary attacking warship. The dynamic response characteristics of the penetrator become more complex when attacking the ship target due to the special materials of the deck such as stiffeners. Therefore, different from attacking other targets, the article reveals the design rules of precession penetration ammunition and fuze. A physical model of the missile target is established to study the numerical simulation of the penetration process of rotating projectile into a stiffened target based on finite element analysis (FEA) software. We studied the dynamic response characteristics of different projectile positions, rotational speeds, and positions that act in precession penetration. As experimental results show, the residual velocity of the precession penetrator decreases with the distance between the projectile point and stiffener. When the projectile penetrates the second target plate, the acceleration is greater than that in the first layer. It is proved that the deflection angle of the shell body is affected by comprehensive factors. The rotational speed in the projectile has less contribution to precession penetration ammunition. In addition, the change of acceleration in the missile’s central section can be significantly perceived in the direction perpendicular to the penetration direction.
Torsional Behavior of High Strength Concrete Members Strengthened by Mixed Steel Fibers
Twelve mixing steel fibers-reinforced high strength concrete beams were experimentally tested under pure torsion to investigating the concrete member torsional behavior. The first cracking torque, ultimate torsional resistance, crack patterns, effect of steel fiber ratio, effects of shape and size of hollow cross-section, and effect of stirrups reinforcement were discussed. The ratio of mixing steel fiber, different shape and size of hollow cross-section, and ratio of stirrups reinforcement were considers as major parameters. The results are shown that the width of cracks decreases and the cracks number increases with mixing steel fibers ratio increased. The first cracking torque and ultimate torsion load increased with decrease in the hollow cross-section area of high strength concrete members strengthened by steel fibers.