Search | Engineering

订阅投稿

首页工程期刊工程焦点工程成就工程前沿关于我们 English

资源类型

期刊论文 313

会议视频 5

年份

2024 1

2023 20

2022 35

2021 29

2020 30

2019 30

2018 21

2017 9

2016 9

2015 15

2014 10

2013 13

2012 9

2011 8

2010 9

2009 7

2008 13

2007 15

2006 5

2005 5

展开︾

关键词

可拓集合 5

可拓学 4

混凝土 4

抗生素 3

医学 2

反渗透 2

可拓方法 2

可持续发展 2

小麦 2

物元变换 2

非线性有限元 2

2型糖尿病 1

6016 铝合金 1

Heterodera glycines 1

Pm21 1

Pm40 1

ABC-F家族蛋白 1

ANSYS 1

Al₂O₃-M_xO_y 1

展开︾

检索范围：

排序：展示方式：

Correlation between tension softening relation and crack extension resistance in concrete

Xiufang ZHANG , Shilang XU ,

《结构与土木工程前沿（英文）》 2009年第3卷第3期页码 323-329 doi: 10.1007/s11709-009-0041-2

摘要： Changes of the material fracture energy consumption with crack propagation can be described by a crack extension resistance curve, one of the fundamental fracture criteria in crack mechanics. Recently, experimental observation of the fracture behavior in concrete was used to develop a new fracture criterion, the crack extension resistance curve, to analyze crack propagation during the entire concrete fracture process. The variation of the crack extension resistance is mainly associated with the energy consumption in the fracture process zone ahead of the stress-free crack tip. The crack extension resistance is then a function of the softening curve, which is a basic mechanical property in the fracture process zone. The relationship between the softening curve and the crack extension resistance curve is then analyzed based on results of three-point bending beams tests. The results indicate that the characteristic points of the crack extension resistance curve is closely related to the characteristic point on used tension softening curve.

关键词： concrete fracture process zone crack extension G_R resistance tension softening curve

HTML PDF 收藏

Fracture resistance on aggregate bridging crack in concrete

ZHANG Xiufang, XU Shilang

《结构与土木工程前沿（英文）》 2007年第1卷第1期页码 63-70 doi: 10.1007/s11709-007-0006-2

摘要： Fracture toughening exhibited in quasi-brittle materials such as concrete is often mainly related to the action of aggregate bridging, which leads to the presence of a fracture process zone ahead of stress-free cracks in such materials. In this investigation, the fracture resistance induced by aggregate bridging, denoted by GI-bridging, is the primary focus. In order to quantitatively determine it, a general analytical formula is firstly developed, based on the definition of fracture energy by Hillerborg. After this, we further present the calculated procedures of determining this fracture resistance from the recorded load vs. crack opening displacement curve. Then, both numerical simulations and fracture experiments are performed on concrete three-point bending beams. Utilizing the obtained load against crack opening displacement curve, the value of G at any crack extension as well as the change of G with the crack extension is examined. It is found that G will firstly increase with the development of crack and then stay constant once the initial crack tip opening displacement reaches the characteristic crack opening displacement w0. The effects of material strength and specimen depth on this fracture resistance are also investigated. The results reveal that the values of G of different specimens at any crack propagation are strongly associated with the values of fracture energy of specimens. If the values of fracture energy between different specimens are comparable, the differences between G are ignored. Instead, if values of fracture energy are different, the G will be different. This shows that for specimens with different strengths, G will change greatly whereas for specimens that are different in depth, whether GI-bridging exhibits size effect depends on whether the fracture energy of specimens considered in the calculation of G is assumed to be a size-dependent material parameter.

HTML PDF 收藏

Influence of welding residual stresses on the ductile crack growth resistance of circumferentially cracked

Xiaobo REN, Odd M. AKSELSEN, B?rd NYHUS, Zhiliang ZHANG

《结构与土木工程前沿（英文）》 2012年第6卷第3期页码 217-223 doi: 10.1007/s11709-012-0169-3

摘要： Welding residual stress is one of the main concerns for fabrication and operation of steel structures due to its potential effect on structural integrity. This paper focuses on the effect of welding residual stress on the ductile crack growth resistance of circumferentially cracked steel pipes. Two-dimensional axi-symmetry model has been used to simulate the pipe. Residual stresses were introduced into the model by using so-called eigenstrain method. The complete Gurson model has been employed to calculate the ductile crack growth resistance. Results show that residual stresses reduce the ductile crack growth resistance. However, the effect of residual stresses on ductile crack growth resistance decreases with the increase of crack growth. The effect of residual stress has also been investigated for cases with different initial void volume fraction, material hardening and crack sizes.

关键词： residual stress ductile crack growth resistance complete Gurson model eigenstrain method

HTML PDF 收藏

Agricultural extension approach: evidence from an Integrated Soil Fertility Management Project in Ethiopia

Gerba LETA, Steffen SCHULZ, Girum GETACHEW ALEMU

《农业科学与工程前沿（英文）》 2020年第7卷第4期页码 427-439 doi: 10.15302/J-FASE-2020331

摘要：

Agricultural extension is an approach to rural development and agricultural transformation in which training, demonstration and technology transfer are key to reducing rural poverty, ensuring food security, and sustainably managing natural resources. During recent decades, different extension approaches have been tested and validated by the Ethiopian government and non-governmental organizations to stimulate in the agricultural extension system (AES). The most recent was a German-funded project entitled “Integrated Soil Fertility Management Project” (ISFM ), which employed a novel approach to piloting and upscaling proven technology and best practice. The purpose of this study was to analyze and document the modalities of ISFM and illustrate its effects on technology uptake and dissemination. The study used a mixed methods approach to collect data. ATLAS.ti and SPSS were used for data management and analysis. Farmer Research and Extension Groups and Farmer Field Schools were found to be central to the participation process. Also, the ISFM was found to aid technology transfer and helped to increase grain and residue yields as well as farmer livelihoods. Based on these empirical findings, it is argued that the ISFM approach and technology should be integrated and institutionalized in the mainstream AES in order to promote their extensive application.

关键词： Ethiopia Farmer Field School Farmer Research and Extension Group governance institutionalization ISFM⁺ ambassador participation

HTML PDF 收藏

挖掘变化知识的可拓数据挖掘研究

陈文伟

《中国工程科学》 2006年第8卷第11期页码 70-73

摘要：

规范了可拓信息与可拓知识基本概念，即在信息和知识的概念上扩充了变化的信息和变化的知识。明确了可拓数据挖掘概念以及可拓推理新概念。证明了可拓数据挖掘两个定理和可拓推理公式。提出的从挖掘静态知识的数据挖掘扩展到挖掘变化知识的可拓数据挖掘，为数据挖掘开辟了新的研究方向，并通过实例进行了说明。

关键词：可拓信息可拓知识可拓数据挖掘可拓推理

HTML PDF 收藏

可拓策划研究

杨春燕,张拥军

《中国工程科学》 2002年第4卷第10期页码 73-78

摘要：

可拓策划是从处理矛盾问题的角度，应用可拓学的方法而进行的策划。文章简介了可拓策划的基本思想、理论和方法，试图用形式化的方法告诉人们，在遇到矛盾问题时，如何生成策划创意，如何进行全面的资源分析、寻找可拓资源，以化不相容为相容，化对立为共存。在可拓策划的实务操作部分，介绍了资源整合的可拓策划、项目的可拓策划、市场开拓的可拓策划及危机防范与处理的可拓策划。

关键词：可拓策划矛盾问题可拓方法创意生成可拓资源

HTML PDF 收藏

基于滑模控制的可拓控制器设计

陈珍源,翁庆昌

《中国工程科学》 2001年第3卷第9期页码 48-51

摘要：

根据滑模控制概念，提出一种新的可拓控制器。在控制策略设计上分为两个部分，第一个部分是根据系统已知部分设计滑模控制的等效控制，另一部分为鲁棒控制以解决系统的不确定性因素及外部干扰问题。首先，构造一基本可拓控制器，用所定可拓集的关联函数作为系统状态信息的评价指针，并在其中植入一组待调增益参数，经参数修正来综合滑模可拓控制的鲁棒控制（滑模的撞击控制），以保证系统的稳定性。最后以一个非线性控制系统的仿真为例来说明所设计的可拓控制器的控制性能。

关键词：可拓集合可拓控制滑模控制系统稳定性

HTML PDF 收藏

Dynamic crack propagation in plates weakened by inclined cracks: an investigation based on peridynamics

A. SHAFIEI

《结构与土木工程前沿（英文）》 2018年第12卷第4期页码 527-535 doi: 10.1007/s11709-018-0450-1

摘要： Peridynamics is a theory in solid mechanics that uses integral equations instead of partial differential equations as governing equations. It can be applied to fracture problems in contrast to the approach of fracture mechanics. In this paper by using peridynamics, the crack path for inclined crack under dynamic loading were investigated. The peridynamics solution for this problem represents the main features of dynamic crack propagation such as crack bifurcation. The problem is solved for various angles and different stress values. In addition, the influence of geometry on inclined crack growth is studied. The results are compared with molecular dynamic solutions that seem to show reasonable agreement in branching position and time.

关键词： peridynamics inclined crack dynamic fracture crack branching

HTML PDF 收藏

可拓工程研究

杨春燕,蔡文

《中国工程科学》 2000年第2卷第12期页码 90-96

摘要：

介绍可拓工程研究的基本思想、工具和方法及其在检测、控制、管理、信息和计算机等领域的应用研究概况。

关键词：矛盾问题可拓集合可拓性可拓工程

HTML PDF 收藏

基于可拓学的设计方案进化推理方法

赵燕伟,,刘海生,张国贤

《中国工程科学》 2003年第5卷第5期页码 63-69

摘要：

在分析现有概念设计求解策略的基础上，提出了基于可拓学理论与遗传算法相结合的概念设计求解模型。利用遗传算法模拟物元变换过程，建立了产品方案物元描述的内部模型和外部模型，探讨了内、外模型的转换关系并通过关联函数将内、外部模型联系起来。根据内部模型给出了遗传算法的编码形式以及与之相适应的交叉、变异策略，并通过可拓评价方法建立了遗传算法的适应值函数，基本解决了产品概念设计中的知识组合爆炸和矛盾冲突问题。最后通过求解减速器方案验证了该方法的可行性。

关键词：概念设计物元变换遗传算法进化推理可拓评价

HTML PDF 收藏

可拓检测的方案生成

余永权,张吉文

《中国工程科学》 2002年第4卷第1期页码 64-68

摘要：

以可拓学理论为基础，论述了可拓检测的有关定义和概念，提出了可拓检测的方案生成方法及过程，同时探讨了检测方法的优化和评价方法。

关键词：检测物元检测元拓集可拓树

HTML PDF 收藏

Peridynamics versus XFEM: a comparative study for quasi-static crack problems

Jinhai ZHAO, Hesheng TANG, Songtao XUE

《结构与土木工程前沿（英文）》 2018年第12卷第4期页码 548-557 doi: 10.1007/s11709-017-0434-6

摘要： Peridynamics (PD) is a nonlocal continuum theory based on integro-differential equations without spatial derivatives. The fracture criterion is implicitly incorporated in the PD theory and fracture is a natural outcome of the simulation. However, capturing of complex mixed-mode crack patterns has been proven to be difficult with PD. On the other hand, the extended finite element method (XFEM) is one of the most popular methods for fracture which allows crack propagation with minimal remeshing. It requires a fracture criterion which is independent of the underlying discretization though a certain refinement is needed in order to obtain suitable results. This article presents a comparative study between XFEM and PD. Therefore, two examples are studied. The first example is crack propagation in a double notched specimen under uniaxial tension with different crack spacings in loading direction. The second example is the specimens with two center cracks. The results show that PD as well as XFEM are well suited to capture this type of behaviour.

关键词： XFEM peridynamic bilateral crack parallel double cracks nonlocal theory

HTML PDF 收藏

非线性系统的自适应可拓控制器设计

翁庆昌,陈珍源

《中国工程科学》 2001年第3卷第7期页码 54-58

摘要：

探讨可拓控制器的设计方法,利用自适应控制的设计策略来修正可拓控制器的增益参数,以近似获得所期望的最佳控制。所提出的控制器结构仅需调整单一参数,故易于实现。另外,引入最大值控制以保证所设计的可拓控制系统的稳定性，并将该控制器应用在非线性系统的控制上,以验证它的有效性及控制能力。

关键词：可拓理论自适应控制可拓控制器鲁棒稳定性

HTML PDF 收藏

可拓检测技术

余永权

《中国工程科学》 2001年第3卷第4期页码 88-94

摘要：

检测技术是目前多种学科的关键技术，检测中有两个难题：一个是无法检测的问题，另一个是检测精度提高的问题。基于可拓学矛盾转化的思想方法，提出了一种与传统检测技术不同的新技术--可拓检测，这种检测技术利用可拓学的物元概念及相关方法，从矛盾转化去研究检测技术，以解决无法检测的物理量检测问题。文章给出了可拓检测的有关概念，基本原理及结构，并且提出了有关的实施方法和应用实例。

关键词：可拓检测可拓学物元变换

HTML PDF 收藏

Stability and dynamics of rotor system with 45° slant crack on shaft

Yanli LIN, Xiaohui SI, Fulei CHU

《机械工程前沿（英文）》 2011年第6卷第2期页码 203-213 doi: 10.1007/s11465-011-0131-4

摘要：

Crack on a shaft is one of the common damages in a rotor system. In this paper, transverse vibrations are calculated to compare the influences of transverse crack and slant crack on the rotor system. Results show that the vibration amplitude of the rotor system with a 45° slant crack on the shaft is larger than that with a transverse crack when the two types of crack have the same depth and the rotor system runs in the same condition. Stability and dynamic characteristics of the rotor system with a 45° slant crack on the shaft under torsional excitation are analyzed by considering opening and closing of the crack. It is shown that the instability of the transverse vibration of the rotor system increases with increasing difference between the bending stiffness in two main directions, and the vibration is stable when the two bending stiffness are identical. The spectrum analysis of the steady-state response reveals that the gravity and the eccentricity produce different frequency components, and when the two bending stiffness are identical, the multiple frequency components of the torsional excitation disappear. Further investigation shows that the vibration amplitudes in combined frequencies increase rapidly in transversal, torsional, and axial vibration with increasing slant crack depth. The results are helpful for the understanding the dynamic behavior of a rotor system with a slant crack on a shaft and can be used for the detection of the slant crack on a shaft.

关键词： rotor dynamics slant crack stability torsional excitation open and close