采用机械应力分等法对天然林落叶松锯材进行动态弹性模量EMSR测定,依据美国标准ASTM D 4761-05测量其四点平弯与侧弯的弹性模量E4f、E4s和抗弯强度(MOR),并分析EMSR与E4f、E4s、MOR的相关性。结果显示,EMSR与E4f、E4s相关性存在较大差异...采用机械应力分等法对天然林落叶松锯材进行动态弹性模量EMSR测定,依据美国标准ASTM D 4761-05测量其四点平弯与侧弯的弹性模量E4f、E4s和抗弯强度(MOR),并分析EMSR与E4f、E4s、MOR的相关性。结果显示,EMSR与E4f、E4s相关性存在较大差异,且后者高于前者。相关系数分别为0.555、0.681。E4f、E4s与MOR相关性高于EMSR与MOR的相关性,E4s与MOR的相关性高于E4f与MOR的相关性。实验表明,采用机械应力分等法提高木材分等准确性还需进一步研究。展开更多
In order to improve the strength and stiffness of shield cutterhead, the method of fuzzy mathematics theory in combination with the finite element analysis is adopted. An optimal design model of structural parameters ...In order to improve the strength and stiffness of shield cutterhead, the method of fuzzy mathematics theory in combination with the finite element analysis is adopted. An optimal design model of structural parameters for shield cutterhead is formulated,based on the complex engineering technical requirements. In the model, as the objective function of the model is a composite function of the strength and stiffness, the response surface method is applied to formulate the approximate function of objective function in order to reduce the solution scale of optimal problem. A multi-objective genetic algorithm is used to solve the cutterhead structure design problem and the change rule of the stress-strain with various structural parameters as well as their optimal values were researched under specific geological conditions. The results show that compared with original cutterhead structure scheme, the obtained optimal scheme of the cutterhead structure can greatly improve the strength and stiffness of the cutterhead, which can be seen from the reduction of its maximum equivalent stress by 21.2%, that of its maximum deformation by 0.75%, and that of its mass by 1.04%.展开更多
文摘采用机械应力分等法对天然林落叶松锯材进行动态弹性模量EMSR测定,依据美国标准ASTM D 4761-05测量其四点平弯与侧弯的弹性模量E4f、E4s和抗弯强度(MOR),并分析EMSR与E4f、E4s、MOR的相关性。结果显示,EMSR与E4f、E4s相关性存在较大差异,且后者高于前者。相关系数分别为0.555、0.681。E4f、E4s与MOR相关性高于EMSR与MOR的相关性,E4s与MOR的相关性高于E4f与MOR的相关性。实验表明,采用机械应力分等法提高木材分等准确性还需进一步研究。
基金Project(51074180) supported by the National Natural Science Foundation of ChinaProject(2012AA041801) supported by the National High Technology Research and Development Program of China+2 种基金Project(2007CB714002) supported by the National Basic Research Program of ChinaProject(2013GK3003) supported by the Technology Support Plan of Hunan Province,ChinaProject(2010FJ1002) supported by Hunan Science and Technology Major Program,China
文摘In order to improve the strength and stiffness of shield cutterhead, the method of fuzzy mathematics theory in combination with the finite element analysis is adopted. An optimal design model of structural parameters for shield cutterhead is formulated,based on the complex engineering technical requirements. In the model, as the objective function of the model is a composite function of the strength and stiffness, the response surface method is applied to formulate the approximate function of objective function in order to reduce the solution scale of optimal problem. A multi-objective genetic algorithm is used to solve the cutterhead structure design problem and the change rule of the stress-strain with various structural parameters as well as their optimal values were researched under specific geological conditions. The results show that compared with original cutterhead structure scheme, the obtained optimal scheme of the cutterhead structure can greatly improve the strength and stiffness of the cutterhead, which can be seen from the reduction of its maximum equivalent stress by 21.2%, that of its maximum deformation by 0.75%, and that of its mass by 1.04%.
