Model Test Study on Ice Induced Vibration of A Compliant Conical Structure

The problem of ice induced vibration is common to ocean engineering of cold region countries. To study the ice induced vibration of a compliant conical structure, a series of model tests have been performed and some breakthrough progresses made. The ice sheet before the compliant conical structure is found to fail by two-time breaking in the tests. The process of two-time breaking behaves in two modes, and the general control of the ice and structural conditions determine the mode in which the ice force would behave. Two dynamic ice force functions are established respectively for the two modes of two-time breaking process in this paper. The numerical simulation results are in good agreement with the measured results, indicating that the dynamic ice force functions given in this paper can fully reflect the real situation of the dynamic ice force on a compliant conical structure.

Model Test Study on Ice-Induced Vibrations of Compliant Multi-Cone Structures

For the study on the ice-induced vibration of a compliant mono-cone structure,a series of model tests were performed from 2004 to 2006.In these tests,the ice sheet before the compliant conical structure was found to be failed in two-time breaking.Based on this important finding,model tests study of the ice force on a compliant multi-cone structure were performed from 2006 to 2007.In these tests,the ice sheet broke before each single cone non-simultaneously.The exciting energy of the total ice force was found to be in a wide range of frequencies,and the structure can be easily excited with nonlinear resonance.

Establishmen and vertification of an improved similitude law for dynamic ice force model test

To study the similitude laws for dynamic ice force model test which is a hot problem in ice mechanics.In this paper,a new modified similitude law for dynamic ice force model test is proposed based on ice-induced virbration theory and two reasonable assumptions.And the new law is vertified with an ice-induced pier virbration example.The numerical calculation results show that,firstly,the error of frequency factor between test value and theory value is small as well as that of displacement and velocity;Secondly,the time scale completely meet the similitude relation,the waveforms anastomotic well,and the phenomenon of offset and omit do not occur;Thirdly,as the damping ratio between prototype and model is nearly equal,the improved similitude law will still be applied.Therefore,the new modified similitude law is feasible to study dynamic ice force model test and can provide reference for the ice mechanics.

Model Test Study of Dynamic Ice Force on Compliant Conical Structures

To study ice-induced vibration of a compliant conical structure, a series of model tests were performed from 2004 to 2005. In the tests, the ice sheet before the compliant conical structure was found to fail in two-time breaking. From 2005 to 2006, this type of ice failure was studied through more groups of tests. The tests show that two-time breaking is the typical failure of ice before steep conical structures, and is controlled by other factors at the same time, such as ice speed and the angle of the cone.

IC测试插座选型与技术要求

对于IC电路测试而言,测试插座不可缺少,测试插座的质量直接关系到测试指标的准确性,该文简单介绍了测试插座的基本知识,详细介绍了插座材料的特性以及选型的技术要点,并给出了测试对比的结果,希望对IC测试工程师插座选型有一定的参考意义。

The Shielding Effect of Multi-Pile Structures on Ice Force

The shielding effect of the front pile-row on the ice force acting on the back pile-row is studied by ice force model tests. In the tests, the front pile-row is designed to model jacket legs and the back pile-row to model the water resisting pipe-phalanx within the jacket. The shielding factor for ice force corresponding to different conditions are given in this paper. The research indicates that there are many factors, including the longitudinal and lateral spacing between the front and back pile-row, ice attacking angle and the ratio of pile diameter to ice thickness, that influence the shielding effect on ice force.

Dynamic ice loads on conical structures

Two series of model tests were performed to observe the dynamic ice loads on conical structures.The variable testing parameters include the water line diameter of the model cone and ice parameters.During small water line diameter tests,two-time breaking is found to be the typical failure of ice on steep conical structure,and also be controlled by other factors,such as ice speed and the cone angle.During big water line diameter tests,the ice sheet failed nonsimultaneously around the cone.Several independent zones of bending were found in the nonsimultaneous failure process of ice.With the increase of the ratio of D/h and the number of independent zones,the total ice force was found being gradually reduced.

Experiments on the Resistance of a Large Transport Vessel Navigating in the Arctic Region in Pack Ice Conditions

In this study, we carried out model tests to investigate the ice failure process and the resistance experienced by a transport vessel navigating in the Arctic region in pack ice conditions. We tested different navigation velocities, ice plate sizes, and ice concentrations. During the tests, we closely observed several phenomena, including the modes of interaction of the ice ship and the moving and failure modes of ice. We also measured the vessel resistances under different conditions. The test results indicate that the navigation velocity is a significant determinant of the moving and failure modes of ice. Moreover, vessel resistance is remarkably dependent on the ice concentration and navigation velocity. The variances of the mean and maximum resistance are also compared and discussed in detail.

风力发电机叶片防除冰涂层(二):温升数值计算及防除冰性能

针对电热超疏水涂层覆冰过程中表现出的三类不同冰层形貌,该文建立了电加热融冰数值计算模型,并对仿真计算结果进行了相应的试验验证,验证结果与仿真结果基本一致,该模型能有效模拟融冰过程和温度分布。临界融冰功率的计算结果表明,电热超疏水涂层融冰所需功率大于非超疏水电热涂层,尤其在乳突状冰层出现后,融冰功率将大幅增加。电热超疏水涂层防冰试验结果表明,在雨凇覆冰环境中,超疏水性能单独作用时,叶片在覆冰前期能延缓覆冰;电热性能与超疏水性能共同作用时,叶片无覆冰形成。电热超疏水涂层用于风力发电机防覆冰具有较好的效果,但用于覆冰后的融冰时将需要更多的能量。

基于含冰量的冻结砂土-混凝土接触面蠕变特性

保证高含冰量冻土区桩基础的长期稳定性是多年冻土区桥梁桩基础安全服役中的关键问题,为研究含冰量对冻土-混凝土接触面蠕变特性的影响,采用自行研制的大型蠕变剪切仪,在−2℃条件下开展含冰量为6%、12%、16%、23%、36%、60%、80%的冻结砂土与混凝土接触面蠕变试验.试验结果表明:在恒定的剪应力作用下,除含冰量为6%试样出现加速蠕变外,其他试样仅出现衰减蠕变及稳定蠕变2个阶段;随含冰量的增大,试样黏性变形占比增大,含冰量为80%试样的黏性变形超过总变形量的80%;稳定蠕变速率受到干密度及含冰量的综合影响,含冰量为16%时稳定蠕变速率最小;Burgers黏弹性模型能较好地模拟高含冰量冻结砂土-混凝土接触面蠕变曲线;随着含冰量的增大,初始剪切模量和稳定蠕变阶段黏滞系数先增大后减小,初始蠕变阶段的渐进剪切模量呈幂函数减小,初始蠕变阶段黏滞系数呈幂函数增大.

基于有限元模型的IC卡芯片受力分析研究

在智能卡三轮测试中,失效表现为芯片受损,本文基于有限元模型来研究智能IC卡(Integrated circuit card)芯片受力分析与强度提升方法,针对其结构尺寸参数变化时对芯片的机械强度影响做了相关有限元仿真,分析芯片的受力情况,从芯片大小、芯片厚度、芯片偏转角度、EMC层厚度、PVC厚度、Lead frame厚度、芯片粘接胶厚七个因素,对比了IC卡单因素尺寸参数变化对芯片应力的影响,并依据正交设计表分析IC卡的七个因素的参数变化时芯片的受力情况,得到EMC层厚度、Lead frame和PVC卡片厚度的变化对芯片承受的最大应力影响显著,且随着这三个部件厚度的增加芯片所受最大应力减小的结论,为有效提升IC卡芯片的机械强度提供了方法。

层冰作用下直立圆柱结构冰载荷研究

层冰是冰区海工结构作业时遭遇的主要冰况之一,直立结构是海工结构的常见构型,因此,开展层冰作用下直立结构冰载荷研究对海工结构抗冰强化设计和安全评估具有重要意义。本文首先对层冰与直立结构作用过程进行概括分析。然后开展直立圆柱结构冰载荷的机理性试验,研究层冰的失效行为以及结构冰载荷的特征。最后基于黏聚单元模型和海冰软化本构开发层冰与结构作用模拟的数值仿真模型,对层冰的裂纹扩展和破碎过程进行模拟,同时利用试验数据对数值仿真模型的正确性进行验证。本研究工作可为结构冰载荷的数值和试验研究奠定重要基础,为冰区海工结构的设计建造提供技术参考。

中高密集度浮冰区船体冰水动力试验研究

船冰作用力的预报是冰区船航行性能评估环节的重点。本文针对某冰区航行船开展操纵性斜航模型试验研究,采用以聚丙烯为主材的圆形非冻结模型冰,通过模型试验给出船在无冰水域和中高密集度浮冰区的船体受力,研究船体在不同航速和漂角下的船体受力特性,并基于典型工况分析试验数据的重复性,发展冰区航行船的非冻结模型冰模型试验技术。研究结果表明:浮冰密集度、航速和漂角的增大会使船体受力增大,高密集度和大漂角下船冰接触区域更大,试验数据重复性也较好。

寒区隧道衬砌渗水挂冰试验研究

为揭示寒区隧道衬砌渗水挂冰发育规律,研制出一套模拟地表水补给条件下寒区隧道衬砌渗水挂冰发育的模型试验装置,实时监测渗水断面围岩温度和挂冰发育过程;采用Image-J软件测量挂冰图像截面积和线性回归分析方法分析挂冰发育过程,研究不同风速和围岩初始温度条件下渗水点围岩温度和挂冰堵塞率演变规律。结果表明:1)挂冰开始发育时刻,随着风速的增大和围岩初始温度的升高,渗水点围岩临界温度逐渐升高;渗水点围岩温度随冷却时间逐渐降低,近似呈对数函数关系;风速越小、围岩初始温度越高,平均降温速率越慢,挂冰发育持续时间越长;当风速分别为0.6 m/s和1.2 m/s时,由于渗水断面围岩冻结圈的形成和衬砌内壁冰体封堵渗水点导致衬砌挂冰停止发育。2)挂冰堵塞率与时间近似呈线性关系,风速越小、围岩初始温度越高,挂冰开始发育的时间越晚,冻害严重程度越高,而紧急程度越低。

冰雪砖抗弯抗压实验测试装置的设计与仿真分析

针对不同冰雪砖强度参数无法准确测定的问题,设计了一种冰雪砖实验测试装置,论文给出了装置的整体设计方案,对核心工作单元进行了理论公式推导,并运用软件SolidWorks Motion以及SolidWorks Simulation实现仿真分析验证。该装置能够对冰雪砖的强度进行参数测试,且符合测试标准。

碎冰航道航行船舶的冰阻力数值模拟方法研究

为准确模拟船舶在碎冰航道中航行时船-冰相互作用现象及评估船体所受碎冰阻力大小,以拉格朗日-欧拉法为基础,采用离散元方法对某天然液化气加注船在碎冰航道内航行的冰阻力开展数值模拟方法研究,并通过数值模拟结果与冰池船模试验结果对比评估数值模拟方法的可行性与可靠性。结果表明,本文提出的数值模拟方法可以描绘出航道内碎冰粒子与船体相互作用时的运动状态,且阻力计算精度在5%以内,满足工程应用的要求,可直接应用于相似碎冰区航行船的冰阻力计算及冰区船线型的优化设计工作。

冰力模型实验

本文首先简述了冰力模型实验的概况,然后介绍了在国内第一座冰池实验中进行的首次冰力模型实验——渤海辽东湾抗冰平台冰力模型实验的设备、模型冰制取技术和实验结果。实验中,冰排的破坏符合一般规律,它预示了现场冰的破坏现象;冰力值稍低于计算值,但更合理,可供设计参考;冰力谱中存在着明显的主频率,它集中于0.8HZ左右。

冰模拟实验与水利工程

冰及冰凌的威胁是与人民生命财产安全密切相关的重大问题。由于冰问题的复杂性,可靠地确定冰荷载的方法应该是:理论(包括公式计算)的方法与室内模型实验或现场观测密切结合,因此冰模拟实验已成为工程设计及工程论证不可缺少的工具。通过对冰模拟实验以及低温冷冻模型冰特性的论述和水工结构物冰荷载模拟实验的实例,阐述了冰模拟实验技术对水工建筑物冰问题研究的必要性和适用性。

碎冰条件下冰区船阻力性能试验研究

为了探究碎冰条件下冰区船试验方法和实船阻力预报方法 ,研究碎冰条件下冰区船舶阻力随速度变化规律,以及阻力随密集度变化规律,采用非冻结模型冰在拖曳水池中开展了4种密集度(60%、70%、80%、90%)工况下阻力试验。试验结果表明:随着碎冰密集度的增加,船模与碎冰的遭遇频率向更高速度点转移;碎冰密集度不同,船模总阻力不稳定区也不同;船模总阻力随着碎冰密集度的增加而增加;根据加拿大海洋技术研究所的Colbourne实船转换方法,预报了实船在1.05 m和2.0 m冰厚时的总阻力。

闸墩冰荷载及过冰能力的模型试验研究

本文针对我国东北地区某航电枢纽设计中泄洪闸闸墩的冰荷载以及流冰期排冰的问题进行了对应的物理模拟试验。通过孤立闸墩和双闸墩的冰荷载试验,证实了边界条件对冰荷载的影响,获得了边界影响系数.不同冰速的试验也证明,冰速对于冰力具有明显的影响。文中将试验结果与理论公式计算进行了比较并提出了作者的看法,可供工程设计人员参考。根据现场实测资料,进行了三种江面冰排不同分布和密度的闸墩过冰能力的定性物理模拟试验,阐述了现有工况下闸墩间流冰通过的可能性。