Aluminum Sleeve Research Articles

Anchorage performance of a new rebar bolt under different surrounding rock strength and borehole depth

The theory and technology of rock bolting are fundamental research topics for strata control in civil and mining engineering. Rebar bolts are commonly used for roadway primary support in underground coal mine. To adapt to deep resource mining, a new left threaded rebar bolt has been developed. Compared to conventional rebar bolts, the result of installation test showed that the new bolt reduced of 41.5% and 57.9% in stirring resistance force and torque, respectively. In laboratory pullout tests, PVC and aluminum sleeves were used to simulate weak and medium strength surrounding rocks. The average peak pullout force, displacement at the peak load and energy absorption increased by 27%, 107% and 108%, respectively, using PVC sleeve; and increased by 113%, 109% and 212%, respectively, using aluminum sleeve. Field tests were conducted under soft coal, hard coal and medium strength rock geo-conditions. Different borehole depths were selected to precisely calculate the average anchorage performance of the new bolt. Results showed that the average peak pullout force of the new bolt increased by 37%, 38% and 28%, respectively, under different surrounding rock conditions. Moreover, based on on-site test results, the pullout curves in field-testing were summarised and classified into 6 different patterns, which were discussed from a viewpoint of causality mechanism. The research findings validate that the newly developed bolt has better anchorage performance compared to conventional rebar bolts, making it a new anchorage material for deep resource mining.

NUMERICAL STUDY OF THE PERFORMANCE OF HEAT PIPE-BASED THERMAL MANAGEMENT SYSTEM FOR POWER LITHIUM BATTERY

The power battery thermal management system (BTMS) is a key component of an electric vehicle (EV) thermal management system. In this paper, a novel heat pipe-based temperature control system for power batteries is devised for a cylindrical battery pack. In this system, the battery is wrapped in an aluminum sleeve with heat pipes attached to the outside, and heat is removed from the heat pipe's evaporative end by the coolant. Effects of four different arrangements of heat pipes on the thermal properties of BTMS under different inlet flow conditions are studied numerically. The results show that when the flow rate reaches a certain value, the temperature of the battery module no longer decreases and even rises. Finally, based on the comprehensive consideration of energy consumption and cooling performance, the optimal heat pipe arrangement is concluded for the battery in different discharge rate scenarios. In conclusion, the cooling method of heat pipe plus liquid cooling can effectively control the battery temperature, and the temperature homogeneity of the system can be well improved by adjusting the position of the heat pipe arrangement. When the cell heat generation is 0.65 W/cell, the overall temperature difference of the battery pack is reduced by 15% by optimizing the heat pipe arrangement, and when the cell heat generation is 2 W/cell, the overall temperature difference is reduced by 19%.

Possibility for using a low-enriched target to produce 99Mo in the MAK-2 research channel of the VVR-ts reactor

Thermal-hydraulic calculations have been conducted with respect to the active part of the MAK-2 loop facility of the VVR-ts research reactor for the 99Mo production. The computational studies were undertaken both for the case of using a highly 235U enriched target and for a low-enriched target. The calculation was performed for the actual technical characteristics of the research channel. The power density for the two simulated cases was obtained in the course of a preliminary neutronic calculation and selected for the most heated channel. The problem is solved for the steady-state mode of the channel coolant flow and takes into account the dependence of the thermophysical parameters of materials on temperature. The volumetric temperature distribution in the channel was obtained in the process of the calculation. The calculation results present the maximum temperatures of the target materials for the 99Mo production. An analysis of the obtained results has shown that the maximum temperatures of the aluminum sleeve and the target filling materials do not exceed the critical values. For the analyzed calculation cases, the maximum coolant temperature is localized at a point near the sleeve wall surface and does not reach the boiling temperature for a given pressure. The study has therefore shown that it is possible to reduce the 235U enrichment of the target filling fissile material to 19.7%, provided the average density of the mixture and the amount of 235U in the target remain the same. At the same time, the amount of the medicinally important 99Mo generated will not practically change, which will lead to reduced capital costs for a highly enriched mixture of the target matrix.

High cycle fatigue behavior of bimetallic Al 7025/CP-Mg rods produced by rotary swaging

This study aims to investigate the monotonic uniaxial tensile/compressive properties and the high cycle fatigue behavior of aluminum alloy 7025 (Al 7025)/commercially pure magnesium (CP–Mg) bimetallic rods produced via rotary swaging method at ambient temperature. In these lightweight bimetallic rods, the outer layer of aluminum can protect the magnesium core from corrosion and improve the rods' mechanical properties. The microhardness and microstructure were studied in the cross-section of the rods to investigate the manufacturing process effects on the starting materials. Based on the obtained results, under the compressive loading, the ultimate strength of the Al/Mg sample increased by 34% compared with the pure magnesium sample. Furthermore, while only 31% of the bimetallic cross-section is composed of aluminum, the tensile and compressive yield strengths of Al/Mg specimens are closer to those of the aluminum specimens. Microhardness results and the microstructural evaluation indicate that no significant chemical interface is formed between the layers. According to the fatigue test results, adding the outer layer of aluminum can increase the fatigue life more than ten times, compared with the monolithic magnesium specimens. The aluminum layer acts as a deterrent agent, delaying crack initiation and causing such substantial life improvement. The aluminum layer plays a more significant role at the lower stress levels, where most of the fatigue life is spent on crack initiation. Based on the finite element analysis, compared to the monolithic magnesium specimen at the same position, adding an aluminum layer around the magnesium core causes a 46.8% reduction in the maximum stress at the surface of the magnesium core in the bimetallic specimen. The fractography shows that the cracks initiated at the surface and propagated through the aluminum sleeve are barricaded by Al/Mg interface, resulting in new crack initiation sites on the magnesium core.

Development of a new anchorage system for carbon fiber–reinforced polymer rods using extrusion process

Carbon fiber–reinforced polymer (CFRP) rods have been considered as a candidate material for prestressed concrete applications because of their superior properties. For current applications, successful use of CFRP rods is linked to an efficient anchorage system design. This paper presents a newly developed anchorage system for CFRP rods and the design concept that the extrusion process is used to generate gripping force. The proposed anchorage system consists of a steel barrel and an aluminum sleeve, and an extrusion region is designed on the outside of barrel to generate a suitable contact pressure distribution on the CFRP rod. A mathematical model was proposed to estimate the contact pressure on the CFRP rod and the capacity of anchorage system. The simulation of extrusion and loading process was conducted with a three-dimensional (3D) finite-element (FE) model. The key design parameters of anchorage system were analyzed to obtain an optimized parameter combination. The experimental validation showed that the new anchorage system is capable of allowing the CFRP rod to attain the ultimate tensile strength.

Dynamic experiment and numerical simulation of frozen soil under confining pressure

With the development of cold region engineering, it is crucial to study the mechanical properties of frozen soil. In practice, frozen soil is inevitably subject to impact loading, making the study of frozen soil under impact loading necessary for engineering in cold regions. The split–Hopkinson pressure bar (SHPB) is an important experimental means for obtaining the dynamic performance of materials. In this study, an SHPB experiment was conducted on frozen soil under confining pressure. The frozen soil exhibited an evident strain rate effect and temperature effect under confining pressure. The SHPB experiment on frozen soil under confining pressure was simulated numerically using LS-DYNA software and the Holmquist–Johnson–Cook (HJC) material model. A loading simulation with passive confining pressure and active confining pressure was completed by adding an aluminum sleeve and applying a constant load. The simulation results obtained using the above methods were in good agreement with the experimental results. The strength of the frozen soil under confining pressure was greater than that of the uniaxial impact, and there was an evident confining pressure effect. Furthermore, the confining pressure provided by passive confinement was larger than that provided by active confinement. The passive confining pressure energy absorption efficiency was higher than for the active confining pressure due to the need to absorb more energy under the same damage conditions. The frozen soil exhibited viscoplastic failure characteristics under confining pressure.

A numerical study on the performance of a thermal management system for a battery pack with cylindrical cells based on heat pipes

Thermal management system aims to control the operating temperature of power battery packs, which is of great significance for the safety and sustainability of the electric vehicle. In the present work, a novel thermal management system based on heat pipes is designed for a battery pack with cylindrical cells. The wave-shaped aluminum sleeves are employed to connect batteries with heat pipes and increase the contact area between them. Effects of the coolant flow rate, the length of heat pipe condenser section and the height of aluminum sleeve on thermal performance of the system are numerically investigated. The result shows that the coolant flow rate significantly influences the maximum temperature of the battery pack but affects the temperature uniformity slightly. When the battery pack discharges at 2 C, a coolant flow rate of 0.5 L⋅min−1 is recommended. Increasing both the length of heat pipe condenser section and the height of aluminum sleeve can reduce the maximum temperature of the battery pack and improve the temperature uniformity. When the height of aluminum sleeve is above 60 mm, the temperature difference of the battery pack can be kept under 5 °C. Using aluminum sleeves with different heights can further improve the temperature uniformity of the battery pack while reducing the system weight.

Performance characteristics of the digital uMI550 PET/CT system according to the NEMA NU2-2018 standard

BackgroundThe aim of this study is to conduct physical performance evaluation on the uMI550 whole-body PET/CT system according to the NEMA NU2-2018 standard.MethodsAccording to the NEMA NU2-2018, spatial resolution, sensitivity, scatter fraction, count-rate performance, accuracy of count losses and random corrections, image quality, and timing resolution were evaluated. Spatial resolution was measured by using a 22Na point source. System sensitivity was measured by inserting an 18F line-source in six concentric aluminum sleeves with varying diameters. Scatter fraction, count-rate performance, accuracy of count loss, and timing resolution were all calculated by analyzing dynamically acquired data of an 18F line-source inside a polyethylene cylinder in 20 cm diameter and 70 cm length. Image quality was assessed using a NEMA IEC body phantom with a 4:1 ratio of activity concentration of spheres to the warm background. Additionally, three patient studies were performed, with one brain scan and two whole-body scans, separately. The patient images were evaluated to get a visual first impression of uMI550.ResultsThe tangential, radial, and axial spatial resolutions were measured as 2.91 mm, 2.98 mm, and 2.97 mm FWHM, respectively, at 1 cm radial offset. The total system sensitivity to line source at center was 10.24 cps/kBq. A NECR peak was measured as 124.4 kcps at 18.85 kBq/mL. The scatter fraction at NECR peak was 36.65%, and the maximum count-rate error at and below NEC peak was 1.55%. Contrast recovery coefficients were from 46.5 (10 mm) to 83.9% (37 mm). The timing resolution was measured as 372 ps at low count rate.ConclusionNEMA NU-2 2018 testing was performed on the new SiPM-based uMI550 PET/CT system. The uMI550 shows a high-spatial resolution of less than 3 mm and a good timing resolution of 372 ps. It shows clinical significances on improving potentially diagnostic ability on small lesions.

The Performance of Clay Furnace with Variation in the Diameters of the Briquette Burning Chamber

Biomass fuel is an alternative energy source used in the form of briquettes using clay stoves. Utilization of clay as a briquette stove often results are not satisfactory as is the use of other fuel stoves, this is because the amount of air in the furnace burning chamber has not been determined and focused properly, so the purpose of this study is to determine the thermal efficiency of the furnace at variations in the diameter of the aluminum sleeve in the furnace burning chamber. The method used is to test 5 variations in diameter of the furnace burning chamber (cylinder). The results showed the best thermal efficiency was obtained at 52.87% at 180 mm slab diameter, boiling time at 9 minutes, with a heat loss of only 2.02 kW.

Confirmation of Nuclear Heating Rate for Installation of Cold Neutron Source at HANARO

In order to determine the capacity of the cold neutron source refrigerator of HANARO, the nuclear heating rate at CN vertical hole is measured by using the heat-flow calorimetric method and confirmed by the calculation. The heating rate measurement device of HANARO was composed of a calorimeter sensor, an air containing aluminum sleeve for fitting the sensor to the CN hole, aluminum weight and a lead wire assembly. The calorimeter sensor consists of a cylindrical Al sample and container, two thermocouples and the electric heater for the calibration of the calorimeter. The sample is separated by an air gap from the Al container surrounded by an air containing Al sleeve. After installation of the calorimeter at a measurement position of HANARO, the heat transfer inside the calorimeter was simulated by the electric heating for the sample. The nuclear heating rates at the CN hole were determined at three reactor powers of 1, 4 and 8 MW by using the calibration curve and the temperature measurements at each reactor power. The measured nuclear heating rate per unit mass of Al sample at 8 MW reactor power is 0.143 W/g and it is equivalent to the 0.494 W/g at 30 MW. The nuclear heating rate was calculated by using the MCNP code. The calculation model for the whole facility including the reactor core and the reflector tank were established. In the calculation procedure, the heat generations by various radiations were evaluated with considering the prompt, delayed and activation effects. The measured heating rate was reasonably well supported by the calculation using the cold neutron facility design code. It will be very useful for the moderator cell of cold neutron source of HANARO.

Characteristics and Analysis of an Eddy Current Shock Absorber Damper Using Finite Element Analysis

In the paper a model is developed for a proposed eddy current damper using finite element analysis. Several damper configurations are studied and its characteristics are analyzed. The steady state performance for the configurations is compared to reach a design with an acceptable performance for the eddy current damper. Furthermore, the proposed designs performance are compared with the traditional damper performance. It was found that the best two designs to achieve the targeted performance were to have an iron core damper or an iron core with an aluminum sleeve. Those two designs are economical and simple while achieving acceptable performance when compared to traditional dampers and other electromagnetic damping systems.

SHPB test analysis and a constitutive model for frozen soil under multiaxial loading

A split Hopkinson pressure bar is adopted to test the dynamic mechanical behavior of frozen soil at different temperatures and high strain rates. An aluminum sleeve is used as a passive confining pressure device. Comparing the results of this test with those under the uniaxial state shows that besides the temperature and strain rate effects, frozen soil exhibits obvious stress strengthening characteristics. In addition, the failure mode is viscoplastic instead of brittle. If frozen soil is regarded as a particle-reinforced composite material, then the debonding damage of ice particles and rate-dependent damage of soil matrix are taken into account. Based on this, a dynamic constitutive model of frozen soil under a multiaxial state is proposed. The theoretical results of the model agree well with the experimental results, verifying the rationality and applicability of the model.

Quality test of clamping connection of transmission lines across tensile line

This paper develops a new technology for the quality inspection of the transmission line that is important across the tensile clamp. The new technology mainly based on the ultrasonic pulse echo thickness measurement mechanism tests the thickness of the aluminum sleeve after crimping the tensile clamp to reflect the relative position of the aluminum sleeve and the steel anchor after the crimping, thereby judging whether there is a crimping positioning defect. At the same time, it is supplemented by steel anchor model comparison, crimping position length comparison, and crimping to margin detection to determine whether the transmission line crimping quality is qualified.

Forging of eccentric co-extruded Al-Mg compounds and analysis of the interface strength

Within the subproject B3 of the Collaborative Research Center 692 it has been shown that Al-Mg compounds with a good bonding quality can be produced by hydrostatic coextrusion. During processing by forging, the aluminum sleeve is thinned in areas of high strains depending on the component geometry. To solve this problem an eccentric core arrangement during co-extrusion was investigated. Based on the results of FE-simulations, the experimental validation is presented in this work. Rods with an offset of 0.25, 0.5 and 0.75 mm were produced by eccentric hydrostatic co-extrusion. Ultrasonic testing was used to evaluate the bonding quality across the entire rods. For the forging investigations the basic process Rising was chosen. The still good bonding quality after forging was examined by dye penetrant testing and optical microscopy.For an optimal stress transfer between the materials across the entire component, a sufficient bonding between the materials is essential. To evaluate the interface strength, a special bending test was developed. For the conception of the bending specimens it was required to analyze the Rising specimens geometry. These analyses were performed using a reconstruction of the geometrical data based on computer tomography (CT) investigations. The comparison with the numerically deter-mined Rising specimen geometry shows good correlation. Parametric Finite Element Analyses of the bending test were used to develop the load case and the specimen geometry. By means of iterative adaption of load application, bearing and specimen geometry parameters, an advantageous stress state and experimentally applicable configuration were found. Based on this conception, the experimental setup was configured and bending tests were performed. The interface strength was deter-mined by the calculation of the maximum interlaminar interfacial tension stress using the experimental interface failure force and the bending FE model.

A numerical criterion for quality prediction of bimetal strands

This paper describes the investigation of the hydrostatic co-extrusion process and the produced compounds. These compounds consist of an aluminum sleeve and a magnesium core. The quality of the produced Al–Mg compounds is of particular interest, especially the mechanical stability of the compound interface. This paper shows in detail the results of further investigations of the Al–Mg compounds, especially the advantages of a new die design and the description of the compound quality based on axial plastic strains during the production process. The axial plastic strain is a suitable numerical criterion for the evaluation and prediction of the quality of co-extruded compounds.

Simulation Research on Head Structure and Rod Components

In order to further optimize the structure of tube-rod extended penetrator, the author did numerical simulation to the penetration process of five different head structures and rod assembly of tube-rod extended penetrator to finite RHA603 target with LS-DYNA at a certain speed. Be drawn from the results of the numerical simulation, the penetration effect of truncated cone head structure is the best, because its top angle is small, the wave on the top is weak, the overpressure is small, and it is faster to open a pit on the target. 3mm aluminum sleeve rod attachment structure is the best. In the early penetrating stage, it can enhance the stiffness of the the rear rod, so that it will not deform under the stress wave in front penetration. In the late penetrating stage, due to the weak aluminum sleeve, it is easy to crash in contact with the target plate, so no excessive energy of the rod is used to open the pit.

Formability of Hybrid Aluminum-Magnesium Compounds

In the SFB 692 HALS (High-strength aluminum based lightweight materials for safety components), subproject B-3, the production of an aluminum magnesium compound by a hydrostatic co-extrusion process was investigated. The quality of these semi-finished products, especially the stability and robustness of the interface between the aluminum (AlMgSi1) sleeve and magnesium (AZ31) core, was of particular interest. Previous papers have described the first process optimization steps as the improvement of the die design as well as the numerical methods for identification of important process parameters and the development of a quality model for the interface. This paper describes the formability of such semi-finished products with subsequent forging processes, especially die forging. Therefore, two different die forging strategies were investigated. In the first approach the strand-shaped work piece, with a circular cross-section, was formed along its longitudinal axis with die forging. In the second approach the same geometry was radially formed with die forging. Thereby, the compound was formed in longitudinal direction up to an analytical equivalent strain value of 1.61 and in radial direction up to 1.38. First results showed that the interface of the aluminum magnesium compound is very stable and ductile enough to be forged. Dye penetration tests were performed to prove the stability of the interface in a first step. Then, micro sections were made to investigate the interface metallographically. No cracks or damages were detected with both test methods in the interface of the forged aluminum magnesium compound. Furthermore, numerical simulations were performed to analyze the forging processes in detail. Therefore, a full 3D simulation model was set-up with Forge2011 and the calibration was performed with the press force as well as the geometry aspects. The correlations between experiments and simulations are very well. By means of the calibrated simulation detailed analyses of interface section are performed and the stability of the interface was investigated. This shows that the compound quality reached by the hydrostatic co-extrusion process is very suitable for subsequent forming steps as die forging. The investigations show the potential of such hybrid compounds and clarify their application, especially in the automotive sector.

Beryllium liner implosion experiments on the Z accelerator in preparation for magnetized liner inertial fusion

Multiple experimental campaigns have been executed to study the implosions of initially solid beryllium (Be) liners (tubes) on the Z pulsed-power accelerator. The implosions were driven by current pulses that rose from 0 to 20 MA in either 100 or 200 ns (200 ns for pulse shaping experiments). These studies were conducted in support of the recently proposed Magnetized Liner Inertial Fusion concept [Slutz et al., Phys. Plasmas 17, 056303 (2010)], as well as for exploring novel equation-of-state measurement techniques. The experiments used thick-walled liners that had an aspect ratio (initial outer radius divided by initial wall thickness) of either 3.2, 4, or 6. From these studies, we present three new primary results. First, we present radiographic images of imploding Be liners, where each liner contained a thin aluminum sleeve for enhancing the contrast and visibility of the liner's inner surface in the images. These images allow us to assess the stability of the liner's inner surface more accurately and more directly than was previously possible. Second, we present radiographic images taken early in the implosion (prior to any motion of the liner's inner surface) of a shockwave propagating radially inward through the liner wall. Radial mass density profiles from these shock compression experiments are contrasted with profiles from experiments where the Z accelerator's pulse shaping capabilities were used to achieve shockless (“quasi-isentropic”) liner compression. Third, we present “micro-Ḃ” measurements of azimuthal magnetic field penetration into the initially vacuum-filled interior of a shocked liner. Our measurements and simulations reveal that the penetration commences shortly after the shockwave breaks out from the liner's inner surface. The field then accelerates this low-density “precursor” plasma to the axis of symmetry.

송전선로 직선슬리브 원격점검 방법 및 장치

Line sleeves, which used to connect ACSR cables when transmission lines were constructing, sometimes cause power transmission failure due to deterioration and corrosion. Therefore, power transmission line should be inspected regularly to prevent national disaster. Current inspection tool detects insertion length of transmission line on line sleeves, the inspection tool includes enormous error by operator. Moreover, the system is not controlled remotely, negligent accident would be caused while inspecting. To deal with those problems, KEPCO reviewed several ways to inspect line sleeves and proposes new method to inspect line sleeve by measuring magnetic flex which penetrate junction of steel and aluminum sleeve. The developed inspection tool is reliable enough to detect eccentric sleeves. Also, the developed inspection device was applied on actual transmission line and verified its effectiveness.

A Constitutive Model forIn SituComminuted Silicon Carbide

Cylindrical hot-pressed silicon carbide (SiC) ceramic targets were predamaged before ballistic testing. The SiC was thermally shocked to introduce noncontiguous cracks, then additional damage was induced by load–unload cycling in an MTS machine while the ceramic specimen was confined in a 7075-T6 aluminum sleeve. Long gold rod penetration was measured as a function of impact velocity vp over the approximate range of 1–3 km/s, with most data between 1.5 and 3 km/s. Penetration as a function of time was measured using multiple, independently timed flash X-rays. It was assumed that the penetration response of the damaged SiC could be represented by a Drucker–Prager constitutive model. Numerical simulations were used to estimate the constitutive constants. It was found that simulations could not be used to determine a unique set of constitutive constants within experimental data scatter.