Ice resistance prediction is a critical issue in the preliminary design of ships navigating brash ice conditions, which is closely related to the safety of a ship to navigate encounter brash ice, and has significant e...Ice resistance prediction is a critical issue in the preliminary design of ships navigating brash ice conditions, which is closely related to the safety of a ship to navigate encounter brash ice, and has significant effects on the kinds of propellers and motor power needed. In research on this topic, model tests and full-scale tests on ships have thus far been the primary approaches. In recent years, the application of the finite element method(FEM) has also attracted interest. Some researchers have conducted numerical simulations on ship–ice interactions using the fluid–structure interaction(FSI) method. This study used this method to predict and analyze the resistance of an ice-going ship, and compared the results with those of model ship tests conducted in a towing tank with synthetic ice to discuss the feasibility of the FEM. A numerical simulation and experimental methods were used to predict the brash ice resistance of an ice-going container ship model in a condition with three concentrations of brash ice(60%, 80%, and 90%). A comparison of the results yielded satisfactory agreement between the numerical simulation and the experiments in terms of both observed phenomena and resistance values, indicating that the proposed numerical simulation has significant potential for use in related studies in the future.展开更多
The surface of lotus leaves has a hierarchical micro–nano-rough structure.We determined that the papillary structure also possesses hierarchical features on the microscale.We used alumina particles as rough structure...The surface of lotus leaves has a hierarchical micro–nano-rough structure.We determined that the papillary structure also possesses hierarchical features on the microscale.We used alumina particles as rough structure building units to construct a Hierarchical Papillary microrough Structure(HPS)on a ceramic surface.The effects of the spatial distribution of HPS on the abrasion resistance and mechanical stability of hydrophobic coatings were investigated.Furthermore,for each HPS,the falling sand abrasion process was analyzed using finite element fluid mechanics analysis.A denser or more two-dimensional HPS implied that more area was impacted by the falling sand and that the abrasion amount and rate were higher.This is contrary to the common belief that when there are more wear-resistant substances on the surface,the abrasion resistance is better;thus,abrasion resistance does not necessarily depend entirely on the concentration of wear-resistant substances on the surface,but it is also influenced by the abrasion mode and the spatial distribution structure of the wear-resistant substances.The 3D stacked HPS(3D-HPS)with excellent abrasion resistance and rich pore structure considerably enhanced the mechanical stability of the hydrophobic coatings.These findings provide novel insights and a theoretical basis for designing spatial structures on high abrasion-resistant superhydrophobic ceramic surfaces.展开更多
Usually, the action of sea ice on offshore engineering structures is one of the controlling loads in cold waters engineering structure design. The reasonable selection of environmental condition and the physical mecha...Usually, the action of sea ice on offshore engineering structures is one of the controlling loads in cold waters engineering structure design. The reasonable selection of environmental condition and the physical mechanical properties of ice in the region are directly related to the structure design, operation and safety. In this paper, the sea ice force acting on the structure, the physical mechanical properties of ice and the selection of parameters in calculation are discussed. Some suggestions are proposed as to the calculation of various kinds of ice loads acting on the structure.展开更多
In this paper, using the theory of stochastic analysis of the response to earthquake load, a stochastic analysis method of the response of piled platforms to earthquake load has been established. In the method, the st...In this paper, using the theory of stochastic analysis of the response to earthquake load, a stochastic analysis method of the response of piled platforms to earthquake load has been established. In the method, the strong ground motion is considered as three dimensional stationary white noise process and the pile-soil interaction and water-structure interaction are considered. The stochastic response of a typical platform to earthquake load has been computed with this method and the results compared with those obtained with the response spectrum analysis method. The comparison shows that the stochastic analysis method of the response of piled platforms to earthquake load is suitable for this kind of analysis.展开更多
根据ST12钢的双点及三点拉剪电阻点焊试件的恒幅疲劳测试结果,分别使用缺口应力法和等效结构应力法进行疲劳寿命预测。在使用缺口应力法时,按试件的实际尺寸和国际焊接学会(International institute of welding, IIW)推荐标准,分别建立...根据ST12钢的双点及三点拉剪电阻点焊试件的恒幅疲劳测试结果,分别使用缺口应力法和等效结构应力法进行疲劳寿命预测。在使用缺口应力法时,按试件的实际尺寸和国际焊接学会(International institute of welding, IIW)推荐标准,分别建立了双点和三点拉剪试件的三维实体有限元模型进行弹性应力分析,从有限元分析结果提取von Mises最大应力变化值,结合IIW推荐标准中的S-N曲线对试件进行疲劳寿命分析预测;在使用结构应力法时则采用梁壳混合单元进行有限元应力分析,并且根据主S-N曲线进行疲劳寿命预测。结果表明,在低周疲劳范围内,缺口应力法和等效结构应力法预测的结果相对于试件的实际寿命有较好地相关性,其中等效结构应力法的结果更接近实验寿命结果。展开更多
船舶在冰区海域中航行会受到冰水环境阻力的影响,是冰区船舶快速性研究中的重要影响因素。为合理分析冰区船舶的快速性能,该文采用基于离散元(discrete element method,DEM)和光滑粒子流体动力学(smoothed particle hydrodynamics,SPH)...船舶在冰区海域中航行会受到冰水环境阻力的影响,是冰区船舶快速性研究中的重要影响因素。为合理分析冰区船舶的快速性能,该文采用基于离散元(discrete element method,DEM)和光滑粒子流体动力学(smoothed particle hydrodynamics,SPH)方法的流固耦合模型模拟船舶冰区航行过程,获得不同航速下的船舶阻力和推进力,进一步计算出螺旋桨的推力、扭矩以及定速航行所需的螺旋桨转速等参数。为研究船体结构、海冰与海水之间的流固耦合作用,文中通过SPH粒子与固定粒子边界相对运动的拟合项直接计算固体与流体之间的相互作用力,建立船体结构、海冰与海水耦合的DEM-SPH模型,并基于该模型分别对船舶在冰区的航行阻力和推进力进行模拟,通过拟合的方式匹配航行阻力和推进力,并考虑尾部流场导致的船体阻力增额,从而预报船舶在特定航速下实现自航所需的螺旋桨转速。此外,文中还模拟了DTMB 5415船模在浮冰区和层冰区中航行的阻力和不同螺旋桨转速下的推力,对船模在不同工况下实现特定航速航行所需的螺旋桨转速进行了预报。计算结果表明:DEM-SPH耦合模型对船-冰、桨-冰作用中的流固耦合过程模拟效果出色,可完整描述船体及尾部伴流场对海冰的拖曳作用;通过文中所述阻力-推力模拟算例及强制力的拟合分析,所形成的基于数值模拟方法的船舶自航下螺旋桨转速预报,可为进一步的试验验证和工程应用推广奠定基础。展开更多
采用大型商用有限元软件MSC MARC Mentat研究了钢结构柱所受轴向约束的刚度对抗火性能的影响,对无保护层钢结构柱的抗火性能进行有限元分析,分析结果与试验结果吻合较好。结果表明:在室温情况下,轴向约束有利于提高钢结构柱的极限承载力...采用大型商用有限元软件MSC MARC Mentat研究了钢结构柱所受轴向约束的刚度对抗火性能的影响,对无保护层钢结构柱的抗火性能进行有限元分析,分析结果与试验结果吻合较好。结果表明:在室温情况下,轴向约束有利于提高钢结构柱的极限承载力,但在高温情况下,约束刚度的增大对钢结构柱的抗火承载力却具有负面影响,轴向约束的提高降低了高温下钢结构柱的极限承载力,并降低了钢结构柱的极限温度承载力;在温度达到450°C之前,由于钢材的弹性模量改变与构件的热膨胀,导致构件的承载力降低,温度超过450°C之后,弹性模量与屈服强度的折减及构件的热膨胀所导致的约束反力共同作用,使得构件更早失效。展开更多
采用大型有限元软件M SC.M ARC.M en tat,对具有轴向约束且无保护层的钢结构柱进行了非线性有限元分析,研究了不同轴向约束对钢结构柱抗火能力的影响,给出了典型约束钢结构柱的有限元网格划分和受压后的变形图,以及不同温度、不同约束...采用大型有限元软件M SC.M ARC.M en tat,对具有轴向约束且无保护层的钢结构柱进行了非线性有限元分析,研究了不同轴向约束对钢结构柱抗火能力的影响,给出了典型约束钢结构柱的有限元网格划分和受压后的变形图,以及不同温度、不同约束刚度情况下的荷载-位移曲线,有限元数值模拟结果与试验进行对比,吻合较好.研究表明:室温下,轴向约束有利于提高柱子的极限承载能力,但在高温情况下,约束刚度的大小对柱子的抗火承载力却具有负面影响,轴向约束的提高降低了高温下柱子的极限承载力,并降低了柱子的极限温度承载力;在温度达到450℃之前,由于钢材的弹性模量改变与构件热膨胀而导致承载力的降低,温度超过450℃之后,弹性模量与屈服极限的折减,以及构件热膨胀所导致的约束反力共同作用使得构件更早失效.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.51679052)the Natural Science Foundation of Heilongjiang Province of China(Grant No.E2018026)the Defense Industrial Technology Development Program(Grant No.JCKY2016604B001)
文摘Ice resistance prediction is a critical issue in the preliminary design of ships navigating brash ice conditions, which is closely related to the safety of a ship to navigate encounter brash ice, and has significant effects on the kinds of propellers and motor power needed. In research on this topic, model tests and full-scale tests on ships have thus far been the primary approaches. In recent years, the application of the finite element method(FEM) has also attracted interest. Some researchers have conducted numerical simulations on ship–ice interactions using the fluid–structure interaction(FSI) method. This study used this method to predict and analyze the resistance of an ice-going ship, and compared the results with those of model ship tests conducted in a towing tank with synthetic ice to discuss the feasibility of the FEM. A numerical simulation and experimental methods were used to predict the brash ice resistance of an ice-going container ship model in a condition with three concentrations of brash ice(60%, 80%, and 90%). A comparison of the results yielded satisfactory agreement between the numerical simulation and the experiments in terms of both observed phenomena and resistance values, indicating that the proposed numerical simulation has significant potential for use in related studies in the future.
基金supported by the National College Students Innovation and Entrepreneurship Training Program(No:202110895003,China)Pingxiang City Science and Technology Plan Project(No:2021C0102,China)National Natural Science Foundation of China(Nos.5217020839,52001175,China).
文摘The surface of lotus leaves has a hierarchical micro–nano-rough structure.We determined that the papillary structure also possesses hierarchical features on the microscale.We used alumina particles as rough structure building units to construct a Hierarchical Papillary microrough Structure(HPS)on a ceramic surface.The effects of the spatial distribution of HPS on the abrasion resistance and mechanical stability of hydrophobic coatings were investigated.Furthermore,for each HPS,the falling sand abrasion process was analyzed using finite element fluid mechanics analysis.A denser or more two-dimensional HPS implied that more area was impacted by the falling sand and that the abrasion amount and rate were higher.This is contrary to the common belief that when there are more wear-resistant substances on the surface,the abrasion resistance is better;thus,abrasion resistance does not necessarily depend entirely on the concentration of wear-resistant substances on the surface,but it is also influenced by the abrasion mode and the spatial distribution structure of the wear-resistant substances.The 3D stacked HPS(3D-HPS)with excellent abrasion resistance and rich pore structure considerably enhanced the mechanical stability of the hydrophobic coatings.These findings provide novel insights and a theoretical basis for designing spatial structures on high abrasion-resistant superhydrophobic ceramic surfaces.
文摘Usually, the action of sea ice on offshore engineering structures is one of the controlling loads in cold waters engineering structure design. The reasonable selection of environmental condition and the physical mechanical properties of ice in the region are directly related to the structure design, operation and safety. In this paper, the sea ice force acting on the structure, the physical mechanical properties of ice and the selection of parameters in calculation are discussed. Some suggestions are proposed as to the calculation of various kinds of ice loads acting on the structure.
文摘In this paper, using the theory of stochastic analysis of the response to earthquake load, a stochastic analysis method of the response of piled platforms to earthquake load has been established. In the method, the strong ground motion is considered as three dimensional stationary white noise process and the pile-soil interaction and water-structure interaction are considered. The stochastic response of a typical platform to earthquake load has been computed with this method and the results compared with those obtained with the response spectrum analysis method. The comparison shows that the stochastic analysis method of the response of piled platforms to earthquake load is suitable for this kind of analysis.
文摘根据ST12钢的双点及三点拉剪电阻点焊试件的恒幅疲劳测试结果,分别使用缺口应力法和等效结构应力法进行疲劳寿命预测。在使用缺口应力法时,按试件的实际尺寸和国际焊接学会(International institute of welding, IIW)推荐标准,分别建立了双点和三点拉剪试件的三维实体有限元模型进行弹性应力分析,从有限元分析结果提取von Mises最大应力变化值,结合IIW推荐标准中的S-N曲线对试件进行疲劳寿命分析预测;在使用结构应力法时则采用梁壳混合单元进行有限元应力分析,并且根据主S-N曲线进行疲劳寿命预测。结果表明,在低周疲劳范围内,缺口应力法和等效结构应力法预测的结果相对于试件的实际寿命有较好地相关性,其中等效结构应力法的结果更接近实验寿命结果。
文摘采用大型商用有限元软件MSC MARC Mentat研究了钢结构柱所受轴向约束的刚度对抗火性能的影响,对无保护层钢结构柱的抗火性能进行有限元分析,分析结果与试验结果吻合较好。结果表明:在室温情况下,轴向约束有利于提高钢结构柱的极限承载力,但在高温情况下,约束刚度的增大对钢结构柱的抗火承载力却具有负面影响,轴向约束的提高降低了高温下钢结构柱的极限承载力,并降低了钢结构柱的极限温度承载力;在温度达到450°C之前,由于钢材的弹性模量改变与构件的热膨胀,导致构件的承载力降低,温度超过450°C之后,弹性模量与屈服强度的折减及构件的热膨胀所导致的约束反力共同作用,使得构件更早失效。
文摘采用大型有限元软件M SC.M ARC.M en tat,对具有轴向约束且无保护层的钢结构柱进行了非线性有限元分析,研究了不同轴向约束对钢结构柱抗火能力的影响,给出了典型约束钢结构柱的有限元网格划分和受压后的变形图,以及不同温度、不同约束刚度情况下的荷载-位移曲线,有限元数值模拟结果与试验进行对比,吻合较好.研究表明:室温下,轴向约束有利于提高柱子的极限承载能力,但在高温情况下,约束刚度的大小对柱子的抗火承载力却具有负面影响,轴向约束的提高降低了高温下柱子的极限承载力,并降低了柱子的极限温度承载力;在温度达到450℃之前,由于钢材的弹性模量改变与构件热膨胀而导致承载力的降低,温度超过450℃之后,弹性模量与屈服极限的折减,以及构件热膨胀所导致的约束反力共同作用使得构件更早失效.
