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中文核心期刊

基于巴西盘试验的海冰拉伸强度研究

EXPERIMENTAL STUDY ON SEA ICE TENSILE STRENGTH BASED ON BRAZILIAN TESTS

  • 摘要: 海冰拉伸强度是其基本力学性能之一, 同时也是冰区船舶与海洋工程结构设计所需的重要参数. 对于脆性材料的拉伸强度测试, 巴西盘劈裂试验相比单轴拉伸试验在试样制备与加载上具有明显的优势. 为研究海冰的拉伸强度特征, 对渤海辽东湾沿岸的粒状冰开展了系统的巴西盘劈裂试验研究. 在加载过程中与试样破坏后, 分别对加载横梁的位移与加载力以及试样最终破坏模式进行了记录. 同时, 对试样的冰晶结构、盐度、温度以及密度进行了测量. 通过改变加载速率、试样厚度与试样温度以研究不同参数对试验结果的影响. 针对传统试验中试样的刚体假设, 考虑了试样变形对应力状态的影响并将其引入了理论模型. 试验过程中所有海冰试样均以劈裂模式破坏. 试验结果表明, 加载速率与试样厚度对拉伸强度的影响并不显著, 但孔隙率的影响较为明显. 当孔隙率由75‰降低至10‰时,拉伸强度由1.0 MPa升高至2.8 MPa. 与单轴拉伸试验所测得数据对比, 巴西盘劈裂试验所得到的拉伸强度随孔隙率的变化趋势相一致. 但该方法所得到的粒状冰拉伸强度要高于预期结果. 试验表明巴西盘劈裂试验中海冰试样的破坏模式与试验结果均较为合理, 可成为海冰拉伸强度的有效测试方法.

     

    Abstract: The tensile strength of sea ice is one of the fundamental mechanical properties as well as a key parameter for the design of ships and offshore structures in ice-infected waters. For the determination of the tensile strength of brittle materials, the Brazilian test has advantages on sample preparation and loading procedure compared with the traditional method of uniaxial tension tests. To study the tensile strength of sea ice, the Brazilian tests were carried out on the sea ice with granular structure, which was collected in the Liaodong Bay of Bohai Sea. The load and loading plate displacement were recorded while the final failure pattern was photographed. Besides, the ice texture, salinity, temperature and density were also measured. The tests were performed on the ice samples with various thicknesses, temperatures and loading speeds. To calculate the tensile strength with high precision, the ice deformation is considered to improve the conventional formula. In all the experiments the ice samples failed in splitting manner. It means that the ice sample failed by reaching its tensile strength and the method works as initial expectation. The results show that the tensile strength has weak dependency on the loading speed and sample thickness but strong dependency on the total porosity. The tensile strength increased from 1.0 MPa to 2.8 MPa when total porosity decreased from 75‰ to 10‰. The results were compared with the tensile strength from uniaxial tension tests. It shows that both results have a similar trend where the total porosity and the tensile strength are in a negative relationship. However, the values of tensile strength from granular ice samples were higher than expectation. This study has identified that all the samples failed in expected pattern and the experiments provided reasonable results. It is a potential alternative for the investigation of tensile strength of sea ice.

     

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