检索结果-南通市图书馆

北京力学会第26届学术年会

作者： Xiang Li zhanli liu School of Aerospace Engineering Tsinghua University

With the steady development of computer science,deep learning and data science have made significant progress in recent *** techniques generally rely on a substantial amount of data samples to extract the inherent mapping *** recent years,these technologies have attracted the attention of researchers in the field of computational mechanics,and they have been applied to the solution of mathematical physics equations,fluid mechanics calculations,constitutive model establishment,mechanical properties prediction of complex materials,metamaterial design,*** studies have opened up new avenues for efficient and accurate online engineering calculations and precise design of new materials and *** paper explores the applications of deep learning in numerical computation and virtual material *** preliminary researches include the implementations of deep learning to finite element equation solution,heterogeneous material mechanical property prediction,and acoustic metamaterial design.A method based on artificial neural network framework is developed for solving finite element equations.A standard finite element equation is transformed into an optimization problem in this method.A unique convolutional neural network architecture for solving linear elastic finite element equations is *** numerical solution of the finite element equation is obtained by the back-propagation *** proposed method is verified by comparing with the numerical solution of a standard finite element program.A framework for predicting effective mechanical properties of heterogeneous materials based on deep learning is *** is employed in this paper as an example to illustrate the *** quantities of stochastic shale samples are generated using a stochastic reconstruction *** processing techniques are employed to transform the shale sample images to finite element models.A convolutional neural network is trained t

关键词： Deep learning numerical calculation virtual design heterogeneous materials phononic crystal finite element equation

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

页岩气高效开采的可压裂度和射孔簇间距预测

引用

力学学报 2022年第2期54卷 517-525页

作者：王涛柳占立庄茁北京理工大学爆炸科学与技术国家重点实验室北京100081 清华大学航天航空学院北京100084

页岩储层的可压裂性是影响页岩气产量的关键因素.本文基于断裂力学理论,以高围压下岩石层理弱面的剪切破坏为主要研究对象,依据岩石抗拉强度和层理弱面抗剪强度的比值关系,首先提出了可压裂度的概念,给出了无量纲的定性曲线图,涵盖了岩... 详细信息

页岩储层的可压裂性是影响页岩气产量的关键因素.本文基于断裂力学理论,以高围压下岩石层理弱面的剪切破坏为主要研究对象,依据岩石抗拉强度和层理弱面抗剪强度的比值关系,首先提出了可压裂度的概念,给出了无量纲的定性曲线图,涵盖了岩石脆性矿物质含量,黏性主导和韧性主导裂缝尖端流体压强、射孔簇分布间距的综合地质与工程因素.接着提出了一种新的表征高围压下页岩可压裂度的无量纲参数,在保证达到充分解吸附的最小压裂间距前提下,依据该参数可计算水平井压裂中的射孔簇间距,可作为工程参考指标.本文将断裂力学理论结合水力压裂高效开采页岩气工程,具有力学理论意义和工程应用前景.

关键词：页岩气水力压裂脆性矿物质含量剪切强度抗拉强度断裂韧性

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

纳米尺度摩擦过程的分子动力学模拟

引用

金属学报 2008年第9期44卷 1025-1030页

作者：刘小明由小川柳占立庄茁清华大学航天航空学院北京100084

利用分子动力学方法模拟了刚性金刚石压头在Ni单晶体上的滑动过程,讨沦了压入深度对摩擦力的影响(压入深度对滑动过程中压头下方的微结构演化(能否发射位错环)有很大影响).结合摩擦过程中的塑性行为和能量耗散机制,解释了产生摩擦力锯... 详细信息

利用分子动力学方法模拟了刚性金刚石压头在Ni单晶体上的滑动过程,讨沦了压入深度对摩擦力的影响(压入深度对滑动过程中压头下方的微结构演化(能否发射位错环)有很大影响).结合摩擦过程中的塑性行为和能量耗散机制,解释了产生摩擦力锯齿形曲线的原因,证实了位错的形核及湮灭是黏一滑机制的原因之一.不同滑动速度对摩擦力影响的模拟表明,压头的滑动速度决定了压头下方位错环的运动和演化形式:在高速滑动下,形成的位错环依次沿着滑移面很快向Ni单晶基体内扩展;在低速滑动下,压头下方产生的位错环互相发生作用,在材料的亚表面形成较低能量的大位错环,由此产生的塑性变形主要集中在材料的亚表面.

关键词：纳米尺度摩擦分子动力学黏-滑机制位错环

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Correction to: Numerical study on dynamic mechanism of brain volume and shear deformation under blast loading

引用

Acta Mechanica Sinica 2020年第4期36卷 981-982页

作者： Zhijie Li Zhibo Du Xiaochuan You zhanli liu Jian Cheng Chengcheng Luo Dongyang Chu Shaowu Ning Yue Kang Ce Yang Zhuo Zhuang School of Aerospace Engineering Tsinghua UniversityBeijing 100084China School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Daping Hospital Army Medical UniversityChongqing 400038China

In the original publication few errors have been identified in Fig.10a,*** correct version of Fig.10a,b are provided in this *** original article has been corrected[1].

关键词： corrected loading correct

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Study of fracture propagation in multi-phase composites using phase field method

Study of fracture propagation in multi-phase composites usin...

引用

北京力学会第二十四届学术年会

作者： Xiang Li Dongyang Chu zhanli liu School of Aerospace Engineering Tsinghua University

Multiphase composites are commonly used materials in various *** is of significant importance to study crack mechanism of multiphase *** traditional fracture mechanics,however,is established based upon homogeneous materials,and it appears both complex and arduous to be applied to the investigation of composite *** this paper,a phase field method is developed to study complex fracture propagation in composites.A strain energy criterion with threshold is introduced to the method to capture fracture *** assigning different damage initiation threshold onto different composite phases,the proposed method is endowed with the capability of fracture simulation in multiphase composites.

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Probing the constitutive behavior of microcrystals by analyzing the dynamics of the micromechanical testing system

引用

Acta Mechanica Sinica 2022年第3期38卷 26-37,I0001页

作者： Peng Wang zhanli liu Degang Xie Shaoxing Qu Zhuo Zhuang Danli Zhang Applied Mechanics Laboratory School of Aerospace EngineeringTsinghua UniversityBeijing 100084China Center for Advancing Materials Performance from the Nanoscale(CAMP-Nano) State Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an 710049China State Key Laboratory of Fluid Power&Mechatronic System Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceDepartment of Engineering MechanicsZhejiang UniversityHangzhou 310027China

The constitutive behavior of microcrystals remains mysterious since very little,or no information regarding plastic deformation in the measured stress-strain curve is available due to plastic ***,the measured stress-strain curves vary greatly under different control modes,while constitutive behavior should remain unaffected by test *** these reasons,probing the real constitutive behavior of microcrystals has long been a challenge because the nonlinear dynamical behaviors of micromechanical testing systems are ***,we perform and carefully analyze the experiments on singlecrystal aluminum micropillars under displacement control and load *** interpret these experimental results,a lumpedparameter physical model based on the principle of micromechanical testing is developed,which can directly relate nonlinear dynamics of the micromechanical testing system to the constitutive behavior of *** reveals that some stages of the measured stress-strain curve attributed to the control algorithm are not related to constitutive *** solving the nonlinear dynamics of the micromechanical testing system,intense plastic instability(large strain burst)starting from the equilibrium state is attributed to the strain-softening stage of *** studies are also performed to reduce the influence of plastic instability on the measured *** study provides critical insights for developing various constitutive models and designing a reliable micromechanical testing system.

关键词： Plastic instability Micromechanical testing Physical model Nonlinear dynamics Constitutive behavior

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Strain rate and size effect on dislocation plasticity in single crystalline pillar

Strain rate and size effect on dislocation plasticity in sin...

引用

2018年全国固体力学学术会议

作者： Jianqiao Hu Zhuo Zhuang Xiaoming liu zhanli liu State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Applied Mechanics Lab. School of Aerospace Engineering Tsinghua University

Dislocation plays an important role in the plastic deformation of crystalline materials. The deformation mechanism varies with strain rate, sample size and internal defects. In this work, discrete dislocation dynamics(DDD) are performed to clarify the dislocation controlled plasticity in single crystalline copper pillars with diameter ranging from 100 to 800 nm. It is founded that there is a transition from dislocation multiplication to surface nucleation when strain rate increases or sample size decreases. Two analytical models are established based on the surface nucleation mechanism and the single arm source dominated plasticity, respectively. The critical resolved shear stress at different sizes evaluated by the analytical models matches well with the experiment results. The critical size when the dominated dislocation mechanism transforms is predicted to be ～140 nm.

关键词： Surface nucleation strain rate submicron pillars discrete dislocation dynamic critical size

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

机器学习与计算力学的结合及应用初探

引用

科学通报 2019年第7期64卷 635-648页

作者：李想严子铭柳占立清华大学航天航空学院应用力学实验室北京100084

自20世纪50年代以来,随着计算机科学的不断进步,机器学习和数据科学得到了长足发展.这些技术一般依靠大量数据作支撑,通过训练过程提取出蕴藏在数据内部的抽象映射关系,目前已被成功应用于化学、生物等自然科学研究领域.近年来,这些技... 详细信息

自20世纪50年代以来,随着计算机科学的不断进步,机器学习和数据科学得到了长足发展.这些技术一般依靠大量数据作支撑,通过训练过程提取出蕴藏在数据内部的抽象映射关系,目前已被成功应用于化学、生物等自然科学研究领域.近年来,这些技术也逐渐受到计算力学领域研究者的关注.本文结合作者的相关研究成果介绍了机器学习、数据科学与计算力学相结合的3种形式:第一种是与有限元方程求解方面的结合,直接应用卷积神经网络算法求解线性有限元方程;第二种方式结合有限元计算和机器学习预测复杂材料结构与力学性能的关系.本文作者应用该方法基于细观页岩扫描照片和随机建模算法,成功训练出可以有效预测细观页岩样本等效模量的卷积神经网络;第三种方式是建立基于数据驱动的计算力学方法,比如直接利用真实的材料实验数据代替材料本构模型.这些工作显示了机器学习、数据驱动在处理材料的力学实验数据、设计新型材料以及创建更高效的计算力学模型方面的广阔前景.随着计算力学的发展,未来将可能出现更多将数据科学、机器学习与计算力学相结合的应用场景,进一步开发出更加强健、高效和保真的计算力学方法.

关键词：机器学习数据驱动人工神经网络计算力学有限单元法

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Discrete and continuum modeling of dislocations in crystal

Discrete and continuum modeling of dislocations in crystal

引用

中国计算力学大会2014暨第三届钱令希计算力学奖颁奖大会

作者： zhanli liu Yinan Cui Liyuan Wang Zhuo Zhuang Applied Mechanics Lab. School of AerospaceTsinghua University

The discrete dislocation plasticity in crystals is investigated by Discrete Dislocation Dynamics(DDD)and micro-scale continuum crystal plasticity theory,respectively,in this *** the DDD modeling,a unified computational model which directly combines 3D DDD and Finite Element Method(FEM)is developed to investigate the discrete dislocation plasticity in a finite *** this model,1)an initial internal stress field is introduced to represent the preexisting stationary dislocations in the crystal;2)the external boundary condition is handled by finite element method spontaneously;3)the constitutive relationship is based on the finite deformation theory of crystal plasticity,but the discrete plastic strains induced by the slip of dislocations are calculated by dislocation dynamics methodology instead of phenomenological constitutive equations used in conventional crystal *** processes,such as loop dislocation evolution,dislocation junction formation *** simulated to verify the reliability of this computational *** challenges in the current DDD modeling are also discussed,such as it is difficult to deal with dislocations in heterogeneous materials and to consider the evolution of more than one types of defects,*** solve these problems,it is useful to describe the defects in a continuum manner.A new method for modeling dislocations continuously is developed based on the continuum crystal plasticity *** with conventional crystal plasticity theory,the‘plastic slip’associated with each dislocation sweep is described by a continuous smooth field *** evolution of plastic slip field is described through Ginzburg-Laudau equation,similar to that used in phase field method(PFM).The advantage is the elastic interaction between dislocations as well as the interaction between dislocations and internal/external interfaces are automatically taken into account within a unified continuum mechanics *** examples are

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

CRC-AIDED TURBO EQUALIZATION FOR MIMO FREQUENCY SELECTIVE FADING CHANNELS

引用

Journal of Electronics(China) 2007年第1期24卷 69-74页

作者： liu zhanli Liang Xiao Zhao Chunming Wang Jing National Mobile Commun. Research Lab. Southeast Univ. Nanjing i10096 China SEUCOMM Corporation Ltd Nanjing 2100P6 China

This paper presents a CRC (Cyclic Redundancy Check)-aided turbo equalization approach to reduce the computational complexity. In this approach,CRC code bits are padded to the end of each transmit block,and a cyclic redundancy check is performed after decoding each block at the receiver end. If the check sum is zero,which means the receive block is correct,the corresponding LLRs (Log Likelihood Ratios) of this block are set high reliable values,and all the computations corresponding to this block can be cancelled for the subsequent outer iterations. With a lower computational complexity the proposed approach can achieve the same as or even better performance than the conventional non-CRC method.

关键词： Cyclic Redundancy Check (CRC) Turbo equalization Multi-Input Multi-Output (MIMO)

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：