Counter-intuitive breathing mode response of an elastic–plastic circular ring subjected to axisymmetric internal pressure pulse

Counter-intuitive phenomena have been observed in a range of structural elements such as beams and plates. It has been realised that the elastic–plastic non-linearity and the compressive instability are responsible for the occurrence of the observed counter-intuitive phenomena. Forrestal et al. [A counterintuitive region of response for elastic–plastic rings loaded with axisymmetric pressure pulses. Int J Impact Eng 1994;15(3):219–23] reported counter-intuitive response in an elastic–plastic circular ring subjected to axisymmetric internal pressure pulse. In this paper, it is shown that the counter-intuitive response observed by Forrestal et al. [A counterintuitive region of response for elastic–plastic rings loaded with axisymmetric pressure pulses. Int J Impact Eng 1994;15(3):219–23] is due to the combined effects of the plastic energy dissipation and the kinematic hardening of the ring material, which is totally different from the one responsible for the counter-intuitive responses observed in beams and plates. A single degree of freedom model and a corresponding FE model are employed for the breathing mode response of an elastic–plastic circular ring subjected to axisymmetric internal pressure pulse in this study.     

国产S30408奥氏体不锈钢应变强化低温容器许用应力及应变确定

对奥氏体不锈钢低温压力容器常规设计与应变强化设计进行比较,可知应变强化技术可大幅提高奥氏体不锈钢材料的许用应力,减薄简体壁厚,减轻容器重量。根据预应变拉伸试验确定国产S30408奥氏体不锈钢应变强化压力容器的应变上限值,并建立国产S30408奥氏体不锈钢材料的ASME和双线性这两种应力应变曲线,对两者进行比较后,以ASME应力应变曲线为计算依据,考虑抗拉强度的影响,确定了国产S30408奥氏体不锈钢材料制造应变强化低温容器时的许用应力及其对应的应变。     

An improved vacuum-steam pulsed blanching machine design and garlic scape blanching verified experiment

Vacuum-steam pulsed blanching (VSPB) is an emerging blanching method resulting in high efficiency and product quality. However, inconvenient loading, small loading capacity, uneven rinsing and imprecise control hinder its application in food industry. Therefore, the current work aimed to design a VSPB machine, including selection of components, building a control system and designing a steam nozzle in order to increase the load capacity and improve device control. For this purpose, a horizontal blanching chamber with internal nozzle was designed and optimized using CFD method. The vacuum chamber design required a more evenly distributed steam inlet. A water-sealing vacuum pump, a cooling device and a hardware system were developed. The distribution of steam released from the nozzle in the chamber was numerically investigated by solving the three-dimensional Reynolds-averaged Navier-Stokes equations, with a velocity uniformity index value of 0.448. The validation blanching test was conducted using garlic scape as the test material. The steam holding time and the number of cycles significantly affected (p < 0.05) the color of the garlic scapes. Peroxidase (POD) activity decreased with the increase of blanching cycles until the enzymes were completely inactivated. VSPB significantly decreased (p < 0.05) the lignin content of the garlic scapes. The findings indicate that the best results were obtained after 2 cycles of VSPB and steam holding time of 30 s.Industrial relevanceHot water and steam thermal blanching are the two most frequently used blanching methods in food processing. Generally, they are used as a pretreatment before drying, freezing or canning of different fruits and vegetables. In current work, an improved vacuum-steam pulsed blanching machine was designed and the validation blanching test with garlic scape as the material indicated that VSPB operation was effective in preventing the synthesis of lignification in garlic scapes. By considering enzyme inactivation, lignification, color, and other quality attributes, 2 cycles of VSPB and steam holding for 30 s were proposed as the optimal VSPB conditions.     

防波板对罐车在制动时的安全稳定性的影响

充液罐车在制动时,液体晃动对罐车的安全稳定性影响很大。对罐体进行全尺寸建模模拟,通过与试验结果的对比验证了计算方法的可靠性,并且对比研究了罐车在带有防波板和未带防波板两种情况下,液体的晃动分析、罐车的压强和受力变化以及在不同加速度、充装率下防波板的作用。结果表明,防波板能够使晃动液体分流,减小了冲击力峰值,使压强分布得更加均匀,有效地降低液体的晃动程度。这对罐车的安全运行,尤其是装有化学试剂的罐车具有重要的参考价值。     

Finite element analysis of postbuckling and delamination of composite laminates using virtual crack closure technique

The two-dimensional and three-dimensional parametric finite element analysis (FEA) of composite flat laminates with two through-the-width delamination types: 0₄/(±θ)₆//0₄ and 0₄//(±θ)₆//0₄ (θ = 0°, 45°, and “//” denotes the delaminated interface) under compressive load are performed to explore the effects of multiple delaminations on the postbuckling properties. The virtual crack closure technique which is employed to calculate the energy release rate (ERR) for crack propagation is used to deal with the delamination growth. Three typical failure criteria: B-K law, Reeder law and Power law are comparatively studied for predicting the crack propagation. Effects of different mesh sizes and pre-existing crack length on the delamination growth and postbuckling properties of composite laminates are discussed. Interaction between the delamination growth mechanisms for multiple cracks for 0₄//(±θ)₆//0₄ composite laminates is also investigated. Numerical results using FEA are also compared with those by existing models and experiments.     

Combined composites layup architecture and mechanical evaluation of type IV pressure vessels: A novel analytical approach

Strict requirements for cost and reliability of compressed gaseous pressure vessels as on-board hydrogen storage necessitates in-depth understanding on the mechanical responses of the composite structure. General numerical methodology to assess this involves a two-step setup: composite layup generation and mechanical property calculation, which becomes highly time and resource-consuming, particularly if multiple designs are scanned for optimization. This study presents a multi-functional analytical tool, combining both aforementioned steps in a single modeling framework. The model enables quick prediction of the strain/stress distribution in correlation with uncomplicated inputs describing the layup design, i.e. stacking sequence with desired winding angles. Additionally, the mechanical evaluation specially focuses on the dome region whose calculation has hardly been inspected analytically in the literature. The results are validated against a three-dimensional finite element calculation implemented in Ansys Workbench, showing qualitative and quantitative agreement. Overall, the study paves the way for composite tank design using analytical approaches, with easy implementation, minimum computational cost and great transparency.     

Surface reconstruction of defective SrTi0.7Cu0.2Mo0.1O3-δ perovskite oxide induced by in-situ copper nanoparticle exsolution for high-performance direct CO2 electrolysis

Solid oxide electrolysis cell (SOEC) provides an effective solution to electrochemically convert CO₂ into valuable products with high efficiency, which is also developed as a promising way for the electricity utilization. However, the poor catalytic activity of the electrode material results in slow cathode kinetics for this technology. In this work, we propose a series of Sr_xTi_0.7Cu_0.2Mo_0.1O_3-δ (S_xTCM, x = 1, 0.975, 0.95) perovskite oxides as the cathodes of SOEC. By tuning the defects of the materials, abundant oxygen vacancies are stimulated in the perovskite lattice, which effectively improves the oxygen ion transport capacity and also act as the receptors of CO₂ molecule. Uniformly dispersed Cu nanoparticles on STCM substrate are in-situ generated after reduction treatment, leading to the formation of abundant active sites for CO₂ reduction reaction (CO₂RR). The results of this work demonstrate a general strategy for developing promising catalysts for efficient CO₂RR.     

Metal-organic framework derived Ni/Mo2C/Mo2TiC2Tx@NC as an efficient electrocatalyst for enhanced hydrogen production

Metal-organic framework's (MOF) shortcomings, such as poor conductivity, poor stability, and easy aggregation, impede its development in various application fields. Ni/Mo₂C/Mo₂TiC₂T_x@NC, a high-performance electrocatalyst for hydrogen evolution reaction, was prepared by incorporating a Mo₂TiC₂T_x MXene conductive matrix into MOF (namely C–Y). The Ni/Mo₂C/Mo₂TiC₂T_x@NC electrocatalyst demonstrates a remarkable HER ability with an overpotential of 105 and 134 mV and Tafel slope of 58 and 75 mV dec⁻¹ at a current density of 10 mA cm⁻² in 0.5 M H₂SO₄ and 1.0 M KOH, respectively. The outperformed HER activity of Ni/Mo₂C/Mo₂TiC₂T_x@NC catalyst is ascribe to the introduction of conductive Mo₂TiC₂T_x MXene as a carrier to improve the poor conductivity of MOF, the synergistic effect of Ni and Mo₂C nanoparticles, and the protective effect of the carbon layer. The work not only provides an experimental approach to address the problem of poor conductivity of MOF, but also provides a high-performance electrocatalyst for HER reactions. By utilizing MOFs and MXene as the precursor and the conducting carrier, our work provides some experimental reference for fabrication of multi-component inexpensive electrocatalysts.     

Regulating surface wettability and electronic state of molybdenum carbide for improved hydrogen evolution reaction

Molybdenum carbide (Mo₂C) is a cost-effective transition metal carbides (TMCs) electrocatalyst for hydrogen evolution reaction (HER) due to its electronic structure similar to Pt-group noble metal. Herein, we report that an effective strategy of regulating the surface wettability and electronic state of Mo₂C by ammonia and hydrothermal co-treatment to enhance its HER activity. The electrochemical results demonstrate that Mo₂C undergoing ammonia and hydrothermal co-treatment (Mo₂C-wh) exhibits remarkably improved electrocatalytic HER activity as compared to the pristine Mo₂C (Mo₂C-p) catalyst. The activity-structure relationship studies manifest that ammonia and hydrothermal co-treatment increases the content of hydroxyl group and pyridinic-N, thus endowing Mo₂C-wh with lower charge transfer resistance, larger electrochemical active surface area and higher surface wettability. DFT calculations reveal that ammonia and hydrothermal co-treatment enhances the Mo 3d-band center and reduces the hydrogen adsorption free energy. These changes in electronic states of Mo sites and physical properties of Mo₂C positively contribute to the improvement of electrocatalytic HER activity.     

Graphene-based catalysts for carbon monoxide oxidation: Experimental and theoretical insights

Graphene-based catalysts are important in various applications ranging from hydrogen production to fuel cells and gas conversion reactions, due to their high surface area, low density, great mechanical properties, and rich electron density. Carbon monoxide oxidation (CO) is among the hottest research themes, due to its significant role in fundamental industrial, and environmental remediation applications. Graphene-based catalysts are highly promising for CO oxidation, due to their accessible surface area, low-cost, and ease of preparation. However, to the best of our knowledge, there are no review papers on graphene-based catalysts for CO oxidation. Therefore, it is important to provide a timely update on this area of research. This review provides a brief synopsis of the relevant milestones and highlights of graphene-based catalysts for experimental and theoretical CO oxidation reaction. This includes self-standing, doped, and metal nanoparticles supported graphene rooting from the preparation methods to the thermal CO oxidation and their related parameters and mechanisms. The CO oxidation reaction fundamentals (i.e., measurements, calculations, and mechanisms) and the effects of CO on the environment are also highlighted. Finally, the current challenges and drawbacks are discussed for further deployment of novel graphene-based catalysts for efficient CO oxidation under ambient conditions.