Vibration at the stern area is generally the most severe of the entire ship hull,which has always attracted special attention by ship designers and researchers.With reference to a real ship structural layout,a scaled ...Vibration at the stern area is generally the most severe of the entire ship hull,which has always attracted special attention by ship designers and researchers.With reference to a real ship structural layout,a scaled stern model of steel structure was innovatively designed to carry out the mode and response tests.Corresponding finite element(FE)model representing the tested structure was established for verification of commonly-used calculation methods of modal parameters and response.Good agreement between experimental and numerical results demonstrates the credibility of FE method,and some key points of modeling and calculating are discussed.In addition,with the combination of the experiment and calculation,some vibration characteristics of ship stern structure are summarized for future ship design guideline.展开更多
A model to describe the hysteresis damper character of rubber material is presented in this paper. It consists of a parallel spring and damper, whose coefficients change with vibration frequencies. In order to acquire...A model to describe the hysteresis damper character of rubber material is presented in this paper. It consists of a parallel spring and damper, whose coefficients change with vibration frequencies. In order to acquire these relations, the force decomposition is carried out according to some sine vibration measurement data about nonlinear forces changing with deformations of the rubber material. The nonlinear force is decomposed into a spring force and a damper force, which are represented by a frcquency-dependent spring and damper coefficient, respectively. Repeating this step for different measurements will give different coefficients corresponding to different frequencies. Then, application of a parameter identification method will provide the requested functions over frequency. Using those formulae, as an example, the dynamic character of a hollow shaft system supported by rubber rings is analyzed and the acceleration response curve in the centroid position is calculated. Comparisons with sine vibration experiments of the real system show a maximal inaccuracy of 8. 8 %. Application of this model and procedure can simplify the modeling and analysis of mechanical systems including rubber materials.展开更多
提出了一种简便计算镶嵌在无限大障板上的周界固定的含人工裂纹圆板在水中振动频率的计算方法。在假定流体不可压、圆板小振幅振动、水中模态挠度近似为真空模态挠度的条件下,利用瑞利积分得到了因流体压而引起的附加质量密度。进而应...提出了一种简便计算镶嵌在无限大障板上的周界固定的含人工裂纹圆板在水中振动频率的计算方法。在假定流体不可压、圆板小振幅振动、水中模态挠度近似为真空模态挠度的条件下,利用瑞利积分得到了因流体压而引起的附加质量密度。进而应用瑞利方法得到了圆板水中振动频率与真空中振动频率、量纲-附加虚质量增量(Nondimensionalized added virtual mass incremental)之间的关系。在真空中模态的有限元法分析数据以及采用适当方法处理奇点积分的基础上,应用离散积分计算了量纲一附加虚质量增量的值。从真空中模态特征频率出发用迭代法直到水中频率收敛为止而得到水中裂纹圆板的特征频率。方法的有效性通过周界固定圆板的量纲-附加虚质量增量与参考文献结果对比的一致性来验证。展开更多
文摘Vibration at the stern area is generally the most severe of the entire ship hull,which has always attracted special attention by ship designers and researchers.With reference to a real ship structural layout,a scaled stern model of steel structure was innovatively designed to carry out the mode and response tests.Corresponding finite element(FE)model representing the tested structure was established for verification of commonly-used calculation methods of modal parameters and response.Good agreement between experimental and numerical results demonstrates the credibility of FE method,and some key points of modeling and calculating are discussed.In addition,with the combination of the experiment and calculation,some vibration characteristics of ship stern structure are summarized for future ship design guideline.
文摘A model to describe the hysteresis damper character of rubber material is presented in this paper. It consists of a parallel spring and damper, whose coefficients change with vibration frequencies. In order to acquire these relations, the force decomposition is carried out according to some sine vibration measurement data about nonlinear forces changing with deformations of the rubber material. The nonlinear force is decomposed into a spring force and a damper force, which are represented by a frcquency-dependent spring and damper coefficient, respectively. Repeating this step for different measurements will give different coefficients corresponding to different frequencies. Then, application of a parameter identification method will provide the requested functions over frequency. Using those formulae, as an example, the dynamic character of a hollow shaft system supported by rubber rings is analyzed and the acceleration response curve in the centroid position is calculated. Comparisons with sine vibration experiments of the real system show a maximal inaccuracy of 8. 8 %. Application of this model and procedure can simplify the modeling and analysis of mechanical systems including rubber materials.
文摘提出了一种简便计算镶嵌在无限大障板上的周界固定的含人工裂纹圆板在水中振动频率的计算方法。在假定流体不可压、圆板小振幅振动、水中模态挠度近似为真空模态挠度的条件下,利用瑞利积分得到了因流体压而引起的附加质量密度。进而应用瑞利方法得到了圆板水中振动频率与真空中振动频率、量纲-附加虚质量增量(Nondimensionalized added virtual mass incremental)之间的关系。在真空中模态的有限元法分析数据以及采用适当方法处理奇点积分的基础上,应用离散积分计算了量纲一附加虚质量增量的值。从真空中模态特征频率出发用迭代法直到水中频率收敛为止而得到水中裂纹圆板的特征频率。方法的有效性通过周界固定圆板的量纲-附加虚质量增量与参考文献结果对比的一致性来验证。
基金国家自然科学基金项目资助(50579008)Support of the Foundation for Polish Science through TEAM Programme‘Smart&Safe’co-financed by the EUEuropean Regional Development Fund
