The welding residual stress has different effects on the mechanical properties of aluminum alloy welded joints, such as size stability, fatigue strength and stress corrosion cracking. Therefore, it is very important to evaluate the welding residual stress accurately. In this paper, the residual stress of A7N01 aluminum alloy welded joints was measured by X-ray diffraction. In contrast to the traditional method, the cos[Formula: see text] method was used in this paper, the results were compared with those obtained by the conventional [Formula: see text] method. In addition, the influence of oscillation unit on the test results of the cos[Formula: see text] method was studied.
The influence of temperature, vibration time, amplitude, and other factors on the residual stress release effect was studied using the method of low-temperature heating and high-frequency ultrasonic vibration, and excellent control parameters were obtained. In addition, the influence of cutting weld reinforcement on the residual stress release was also studied. The results demonstrate that the highest relative residual stress release rate was 280.29%, the average release was over 150 MPa, and the efficiency was higher than that of the general stress release methods. After cutting the reinforcement, only a small part of residual stress was released, influencing the overall residual stress distribution relatively little. The experimental material was a butt-welded 316L stainless steel plate μ-X360s diffractometer, and this was used for measuring the residual stress.
A severe challenge resulting from the harsh climate and environment is the power supply to remote rail-side devices on the Tibetan plateau. Evolving renewable energy harvesting technologies offer a promising solution. This paper proposes and verifies a wind-solar energy harvester (WSEH) based on an airflow enhancement mechanism (AFEM) for powering rail-side devices. The proposed WSEH includes a vertical axis wind turbine (VAWT), flexible photovoltaic deflectors (FPVD), and energy conversion and storage devices. The AFEM is implemented based on the FPVD, which boosts the airflow energy blown to the VAWT due to the Venturi effect. The FPVD, based on an umbrella-like mechanism, unfolds as a PV panel for solar energy harvesting and folds as a deflector to boost the wind energy harvesting capacity for the VAWT. In CFD simulation, the maximum power coefficient of VAWT reaches 0.387, and the optimum gain effect of FPVD is 66.54%. The prototypes, including VAWT and FPVD, are tested in a wind tunnel to verify the practical effects demonstrated by no-load speed and load output of the VAWT. The case study indicates that the WSEH generates 1566.82 kWh of electrical energy per year, which is adequate for powering rail-side devices on the Tibetan Plateau.
A severe challenge resulting from the harsh climate and environment is the power supply to remote rail-side devices on the Tibetan plateau. Evolving renewable energy harvesting technologies offer a promising solution. This paper proposes and verifies a wind-solar energy harvester (WSEH) based on an airflow enhancement mechanism (AFEM) for powering rail-side devices. The proposed WSEH includes a vertical axis wind turbine (VAWT), flexible photovoltaic deflectors (FPVD), and energy conversion and storage devices. The AFEM is implemented based on the FPVD, which boosts the airflow energy blown to the VAWT due to the Venturi effect. The FPVD, based on an umbrella-like mechanism, unfolds as a PV panel for solar energy harvesting and folds as a deflector to boost the wind energy harvesting capacity for the VAWT. In CFD simulation, the maximum power coefficient of VAWT reaches 0.387, and the optimum gain effect of FPVD is 66.54%. The prototypes, including VAWT and FPVD, are tested in a wind tunnel to verify the practical effects demonstrated by the no-load speed and load output of the VAWT. The case study indicates that the WSEH generates 1566.82 kWh of electrical energy per year, which is adequate for powering rail-side devices on the Tibetan Plateau.
Equiatomic high-entropy alloys (HEAs) fabricated by additive manufacturing (AM) have gained increasing attention since they present superior mechanical properties over their counterparts made by traditional synthesis routes. However, few studies have investigated AM of non-equiatomic HEAs, although this type of HEAs showing excellent mechanical properties. In this paper, we additively manufactured a novel non-equiatomic FeCoCrNi HEA via in-situ alloying 316L stainless steel and CrCoNi medium-entropy alloy. Besides fine grains and high dislocation density, we observed unexpected high-intensity of hybrid crystal-amorphous precipitates, which have never been reported in NiCoCr-based alloys made by AM. These unique microstructures led to exceptional combination of mechanical properties exceeding those of additively manufactured equiatomic FeCoCrNi HEAs. Our observation from EBSD, TEM and atomistic simulations reveals a group of deformation mechanisms of stacking faults, deformation twins, TB-dislocation and dislocation-precipitates interactions. Our findings not only provide new insights into AM of non-equiatomic HEAs via in situ alloying, also shed lights on understanding the microstructure-properties relationship of non-equiatomic HEAs fabricated by AM.
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