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Parametric equations for notch stress concentration factors of rib–deck welds under bending loading

《结构与土木工程前沿（英文）》 2021年 第15卷 第3期   页码 595-608 doi: 10.1007/s11709-021-0720-1

摘要： The effective notch stress approach for evaluating the fatigue strength of rib–deck welds requires notch stress concentration factors obtained from complex finite element analysis. To improve the efficiency of the approach, the notch stress concentration factors for three typical fatigue-cracking modes (i.e., root–toe, root–deck, and toe–deck cracking modes) were thoroughly investigated in this study. First, we developed a model for investigating the effective notch stress in rib–deck welds. Then, we performed a parametric analysis to investigate the effects of multiple geometric parameters of a rib–deck weld on the notch stress concentration factors. On this basis, the multiple linear stepwise regression analysis was performed to obtain the optimal regression functions for predicting the notch stress concentration factors. Finally, we employed the proposed formulas in a case study. The notch stress concentration factors estimated from the developed formulas show agree well with the finite element analysis results. The results of the case study demonstrate the feasibility and reliability of the proposed formulas. It also shows that the fatigue design curve of FAT225 seems to be conservative for evaluating the fatigue strength of rib–deck welds.

关键词： notch stress concentration factor     rib–deck weld     parametric analysis     regression analysis     parametric equation    

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A family of non-conforming crack front elements of quadrilateral and triangular types for 3D crack problems using the boundary element method

Guizhong XIE, Fenglin ZHOU, Hao LI, Xiaoyu WEN, Fannian MENG

《机械工程前沿（英文）》 2019年 第14卷 第3期   页码 332-341 doi: 10.1007/s11465-019-0540-3

摘要： This study focuses on establishing non-conforming crack front elements of quadrilateral and triangular types for 3D crack problems when the dual boundary element method is applied. The asymptotic behavior of the physical variables in the area near the crack front is fully considered in the construction of the shape function. In the developed quadrilateral and triangular crack front elements, the asymptotic term, which captures the asymptotic behavior of the physical variable, is multiplied directly by the conventional Lagrange shape function to form a new crack front shape function. Several benchmark numerical examples that consider penny-shaped cracks and straight-edge crack problems are presented to illustrate the validity and efficiency of the developed crack front elements.

关键词： Taylor expansion     crack front elements     stress intensity factors     dual boundary element method    

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强度理论与实验现象

刘大斌,韩文坝,蔡冰清,韩晓东

《中国工程科学》 2007年 第9卷 第12期   页码 44-52

摘要： 用四大经典理论、莫尔强度理论和质点平衡强度理论的准则和强度条件，对单向拉压、二向拉压、纯扭转等已被认定的实验现象进行对比，对低、中碳钢重新做了纯扭转求最大屈服剪应力实验。发现质点平衡强度理论的符合率较高，13个实验中的有12个符合。尤其是拉伸—剪切使剪切破坏试验变得容易，压缩—剪切使剪切破坏试验变得困难的实验现象与质点平衡强度理论完全符合；莫尔强度理论也只有当拉伸和压缩极限强度不同时才能符合；其他强度理论都与此实验不符合。特别是当三向等应力拉伸（或压缩）时第三强度理论出现相当应力为零；三向等应力拉伸（或压

关键词： 强度理论     实验现象     屈服现象     应力状态    

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液力传动箱上箱体强度分析与优化

刘传峰,田爱琴

《中国工程科学》 2008年 第10卷 第5期   页码 70-74

摘要：

计算机模拟模型分析法是机械设计开发的革命，运用有限元分析法可有效地规避设计风险和失误。对液力传动箱上箱体进行三维建模,提出了力学分析模型，将两个方案进行了有限元分析对比，指导设计方案的改进，提出最终解决方案，解决了设计难题。

关键词： 液力传动箱     力学模型     有限元分析     应力图     静强度     疲劳强度    

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Stress field near circular-arc interface crack tip based on electric saturation concept

Longchao DAI, Xinwei WANG

《机械工程前沿（英文）》 2009年 第4卷 第3期   页码 320-325 doi: 10.1007/s11465-009-0042-9

摘要： Within the framework of nonlinear electroelasticity, the anti-plane problem of a circular-arc interfacial crack between a circular piezoelectric inhomogeneity and an infinite piezoelectric matrix subjected to a far-field uniform loading is investigated by an electrical strip saturation model, the complex variable method, and the method of analytical continuation. Explicit closed form expressions for the complex potentials in both the matrix and the inclusion, and the stress intensity factor at the crack tip are presented. Comparison with some related solutions based on the linear electroelastic theory shows the validity of the present solutions

关键词： piezoelectric material     arc crack     strip saturation     stress intensity factor    

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Development of mix design method based on statistical analysis of different factors for geopolymer concrete

Paramveer SINGH; Kanish KAPOOR

《结构与土木工程前沿（英文）》 2022年 第16卷 第10期   页码 1315-1335 doi: 10.1007/s11709-022-0853-x

摘要： The present study proposes the mix design method of Fly Ash (FA) based geopolymer concrete using Response Surface Methodology (RSM). In this method, different factors, including binder content, alkali/binder ratio, NS/NH ratio (sodium silicate/sodium hydroxide), NH molarity, and water/solids ratio were considered for the mix design of geopolymer concrete. The 2D contour plots were used to setup the mix design method to achieve the target compressive strength. The proposed mix design method of geopolymer concrete is divided into three categories based on curing regime, specifically one ambient curing (25 °C) and two heat curing (60 and 90 °C). The proposed mix design method of geopolymer concrete was validated through experimentation of M30, M50, and M70 concrete mixes at all curing regimes. The observed experimental compressive strength results validate the mix design method by more than 90% of their target strength. Furthermore, the current study concluded that the required compressive strength can be achieved by varying any factor in the mix design. In addition, the factor analysis revealed that the NS/NH ratio significantly affects the compressive strength of geopolymer concrete.

关键词： geopolymer concrete     mix design     fly ash     response surface methodology     compressive strength     stress−strain    

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Mixed mode properties of CNT reinforced composites using Arcan test rig

Jacob MUTHU

《结构与土木工程前沿（英文）》 2015年 第9卷 第4期   页码 397-404 doi: 10.1007/s11709-015-0321-y

摘要： Composite materials reinforced with carbon nanotubes were mechanical tested using Arcan test rig under Mode-I, Mode-II and mixed mode loading conditions to obtain their fracture properties. The butterfly composite specimens were fabricated with 0.02, 0.05 and 0.1 wt % CNTs. The polyester/CNT composite was fabricated using VRTM (Vacuum Resin Transfer Molding) where the CNTs were first functionalised to reach an optimum properties. Arcan test rig was designed and fabricated to work with the Shimadzu testing machine. The results show that the functionalised CNTs have improved the fracture behavior by acting as bridge between the cracked face. In addition, the fracture properties were not improved for the higher weight fraction of 0.1 wt% CNTs.

关键词： CNT     composites     Arcan test rig     stress intensity factor    

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An investigation on prevalent strategies for XFEM-based numerical modeling of crack growth in porous media

《结构与土木工程前沿（英文）》 2021年 第15卷 第4期   页码 914-936 doi: 10.1007/s11709-021-0750-8

摘要： Crack growth modeling has always been one of the major challenges in fracture mechanics. Among all numerical methods, the extended finite element method (XFEM) has recently attracted much attention due to its ability to estimate the discontinuous deformation field. However, XFEM modeling does not directly lead to reliable results, and choosing a strategy of implementation is inevitable, especially in porous media. In this study, two prevalent XFEM strategies are evaluated: a) applying reduced Young’s modulus to pores and b) using different partitions to the model and enriching each part individually. We mention the advantages and limitations of each strategy via both analytical and experimental validations. Finally, the crack growth is modeled in a natural porous media (Fontainebleau sandstone). Our investigations proved that although both strategies can identically predict the stress distribution in the sample, the first strategy simulates only the initial crack propagation, while the second strategy could model multiple cracks growths. Both strategies are reliable and highly accurate in calculating the stress intensity factor, but the second strategy can compute a more reliable reaction force. Experimental tests showed that the second strategy is a more accurate strategy in predicting the preferred crack growth path and determining the maximum strength of the sample.

关键词： numerical modeling     extended finite element method     porous media     crack growth     stress intensity factor    

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Investigation of Generalized SIFs of cracks in 3D piezoelectric media under various crack-face conditions

Jaroon RUNGAMORNRAT, Bounsana CHANSAVANG, Weeraporn PHONGTINNABOOT, Chung Nguyen VAN

《结构与土木工程前沿（英文）》 2020年 第14卷 第2期   页码 280-298 doi: 10.1007/s11709-019-0586-7

摘要： This paper investigates the influence of crack geometry, crack-face and loading conditions, and the permittivity of a medium inside the crack gap on intensity factors of planar and non-planar cracks in linear piezoelectric media. A weakly singular boundary integral equation method together with the near-front approximation is adopted to accurately determine the intensity factors. Obtained results indicate that the non-flat crack surface, the electric field, and the permittivity of a medium inside the crack gap play a crucial role on the behavior of intensity factors. The mode-I stress intensity factors ( ) for two representative non-planar cracks under different crack-face conditions are found significantly different and they possess both upper and lower bounds. In addition, for impermeable and semi-permeable non-planar cracks treated depends strongly on the electric field whereas those of impermeable, permeable, and semi-permeable penny-shaped cracks are identical and independent of the electric field. The stress/electric intensity factors predicted by permeable and energetically consistent models are, respectively, independent of and dependent on the electric field for the penny-shaped crack and the two representative non-planar cracks. Also, the permittivity of a medium inside the crack gap strongly affects the intensity factors for all crack configurations considered except for of the semi-permeable penny-shaped crack.

关键词： crack-face conditions     intensity factors     non-flat cracks     permittivity     piezoelectric media     SGBEM    

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Global sensitivity analysis of certain and uncertain factors for a circular tunnel under seismic action

Nazim Abdul NARIMAN, Raja Rizwan HUSSAIN, Ilham Ibrahim MOHAMMAD, Peyman KARAMPOUR

《结构与土木工程前沿（英文）》 2019年 第13卷 第6期   页码 1289-1300 doi: 10.1007/s11709-019-0548-0

摘要： There are many certain and uncertain design factors which have unrevealed rational effects on the generation of tensile damage and the stability of the circular tunnels during seismic actions. In this research paper, we have dedicated three certain and four uncertain design factors to quantify their rational effects using numerical simulations and the Sobol’s sensitivity indices. Main effects and interaction effects between the design factors have been determined supporting on variance-based global sensitivity analysis. The results detected that the concrete modulus of elasticity for the tunnel lining has the greatest effect on the tensile damage generation in the tunnel lining during the seismic action. In the other direction, the interactions between the concrete density and both of concrete modulus of elasticity and tunnel diameter have appreciable effects on the tensile damage. Furthermore, the tunnel diameter has the deciding effect on the stability of the tunnel structure. While the interaction between the tunnel diameter and concrete density has appreciable effect on the stability process. It is worthy to mention that Sobol’s sensitivity indices manifested strong efficiency in detecting the roles of each design factor in cooperation with the numerical simulations explaining the responses of the circular tunnel during seismic actions.

关键词： shear waves     Sobol’s sensitivity indices     maximum principal stress     maximum overall displacement     tensile damage    

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Influence of sprinkler irrigation droplet diameter, application intensity and specific power on flower

Yisheng ZHANG, Delan ZHU

《农业科学与工程前沿（英文）》 2017年 第4卷 第2期   页码 165-171 doi: 10.15302/J-FASE-2017145

摘要： To determine the main parameters of droplet strike damage and avoid flower injury due to the unsuitable practices during sprinkler irrigation, an indoor experiment of irrigation droplet impact on cyclamen was conducted. The influences of different parameters such as droplet diameter, application intensity, specific power on flower strike damage was analyzed using Image Pro-Plus software to compute strike damage area and define damage level by sense-analysis. The results showed that a damage area of <1% represents a safe irrigation level, 1%–3% slight damage level, 3%–6% moderate damage level, and>6% heavy damage level. Equations of application intensity, specific power with sprinkler irrigation time and flower injury ratio were regressed against parameters which cause impact damages. The results indicated that specific power has a significant correlation with injury, and flower damage area increased as the increasing of the value of specific power for the same irrigation time. Application intensity was also correlated with injury when the droplet diameter was larger than 1 mm. When the duration of sprinkler irrigation was 1, 5 and 10 min, the threshold of impinging damage of application intensity was 25.30, 5.01 and 1.64 mm·h and the specific power was 0.467×10 , 9.340×10 and 3.110×10 W·m . These results provide a reference for determining the suitable values of sprinkler properties in operation design.

关键词： application intensity     damage     floriculture     flowers     specific power     sprinkler irrigation    

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Impact of inter-fuel substitution on energy intensity in Ghana

Boqiang LIN, Hermas ABUDU

《能源前沿（英文）》 2020年 第14卷 第1期   页码 27-41 doi: 10.1007/s11708-019-0656-5

摘要： Energy intensity and elasticity, together with inter-fuel substitution are key issues in the current development stage of Ghana. Translog production and ridge regression are applied for studying these issues with a data range of 2000–2015. The current energy dynamics reveal the expected inverse relationship: higher energy intensity and lower elasticity with economic growth. There are evidences of energy-economic challenges: high energy cost, inefficiency and backfire rebound effect. The implications are higher energy losses in the system, more consumption of lower-quality energy together with low energy technology innovation. Energy is wasted and directly not productive with economic activities. It is observed further that the higher energy intensity invariably increases CO emission because approximately 95% of total energy is derived from hydrocarbons and biomass. An inter-fuel substitution future scenario design was further conducted and the results were positive with growth, lower energy intensity, and improved energy efficiency. Therefore, government and energy policymakers should improve energy efficiency, cost, and productiveness. That is, they should change energy compositions and augment energy technology innovation, thus, increasing renewable share to 15% by 2026, reducing wood and charcoal by about 69%, and increasing natural gas to about 776%. Energy policymakers should enhance the installation of smart energy, cloud energy solution, tokenization of energy system and storage.

关键词： energy intensity     energy elasticity     inter-fuel substitution prospects     energy contribution     Translog production approach     ridge regression    

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Dynamic mechanism for the decline of China’s energy intensity during the 11th FYP (Five-Year Plan)

Minghui LI

《能源前沿（英文）》 2011年 第5卷 第3期   页码 237-249 doi: 10.1007/s11708-010-0130-x

摘要： From 2006 to 2009, the aggregate energy intensity of China fell by 14.38%, which means that China has made substantial progress towards its goal of achieving approximately a 20% reduction in energy intensity during the period of the 11th FYP (Five-Year Plan). This paper describes some new properties of the mechanism for the decrease in China’s energy intensity since the beginning of the 11th FYP. First, compared with the period of the 10th FYP, technical, structural, and residential energy-savings have been improved to a certain extent. Secondly, unlike the dynamic mechanism before 2000, technical energy savings have been the main driver of momentum since the beginning of the 11th FYP. Next, although structural energy savings are not the main factor, they are still a key factor for the decrease in energy intensity. Finally, residential energy savings are still a stable driver of momentum for the decline in China’s energy intensity.

关键词： energy intensity     structural energy savings     technical energy savings    

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Efficiency of scalar and vector intensity measures for seismic slope displacements

Gang WANG

《结构与土木工程前沿（英文）》 2012年 第6卷 第1期   页码 44-52 doi: 10.1007/s11709-012-0138-x

摘要： Ground motion intensity measures are usually used to predict the earthquake-induced displacements in earth dams, soil slopes and soil structures. In this study, the efficiency of various single ground motion intensity measures (scalar ) or a combination of them (vector ) are investigated using the PEER-NGA strong motion database and an equivalent-linear sliding-mass model. Although no single intensity measure is efficient enough for all slope conditions, the spectral acceleration at 1.5 times of the initial slope period and Arias intensity of the input motion are found to be the most efficient scalar for flexible slopes and stiff slopes respectively. Vector can incorporate different characteristics of the ground motion and thus significantly improve the efficiency over a wide range of slope conditions. Among various vector considered, the spectral accelerations at multiple spectral periods achieve high efficiency for a wide range of slope conditions. This study provides useful guidance to the development of more efficient empirical prediction models as well as the ground motion selection criteria for time domain analysis of seismic slope displacements.

关键词： seismic slope displacements     intensity measures     empirical prediction    

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Does financial development lower energy intensity?

Philip Kofi ADOM, Michael Owusu APPIAH, Mawunyo Prosper AGRADI

《能源前沿（英文）》 2020年 第14卷 第3期   页码 620-634 doi: 10.1007/s11708-019-0619-x

摘要： The growth-induced effects of financial development have been well-established in the empirical literature, as well as the significance of financial development to energy demand behavior. However, the empirical evidence on the relationship between financial development and energy intensity remains sparse in the literature. Given the multifaceted nature of the effects of financial development, the proposed relationship seems a complex one and warrants an empirical investigation. Using the case of Ghana, this study provides an empirical answer to the question: does financial development lower energy intensity? To provide solid grounds for either rejection or acceptance of the null hypothesis, this study performed several robustness checks. Generally, the evidence revealed that financial development lowers energy intensity. Further, the results revealed that the price of energy, trade liberalization and industry structure play significant roles. These results have important implications for the design of macro energy efficiency policies and the creation of a ‘Green Bank’.

关键词： financial development     energy intensity     energy efficiency     Ghana    

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标题 作者 时间 类型 操作

Parametric equations for notch stress concentration factors of rib–deck welds under bending loading

期刊论文

A family of non-conforming crack front elements of quadrilateral and triangular types for 3D crack problems using the boundary element method

Guizhong XIE, Fenglin ZHOU, Hao LI, Xiaoyu WEN, Fannian MENG

期刊论文

强度理论与实验现象

刘大斌,韩文坝,蔡冰清,韩晓东

期刊论文

液力传动箱上箱体强度分析与优化

刘传峰,田爱琴

期刊论文

Stress field near circular-arc interface crack tip based on electric saturation concept

Longchao DAI, Xinwei WANG

期刊论文

Development of mix design method based on statistical analysis of different factors for geopolymer concrete

Paramveer SINGH; Kanish KAPOOR

期刊论文

Mixed mode properties of CNT reinforced composites using Arcan test rig

Jacob MUTHU

期刊论文

An investigation on prevalent strategies for XFEM-based numerical modeling of crack growth in porous media

期刊论文

Investigation of Generalized SIFs of cracks in 3D piezoelectric media under various crack-face conditions

Jaroon RUNGAMORNRAT, Bounsana CHANSAVANG, Weeraporn PHONGTINNABOOT, Chung Nguyen VAN

期刊论文

Global sensitivity analysis of certain and uncertain factors for a circular tunnel under seismic action

Nazim Abdul NARIMAN, Raja Rizwan HUSSAIN, Ilham Ibrahim MOHAMMAD, Peyman KARAMPOUR

期刊论文

Influence of sprinkler irrigation droplet diameter, application intensity and specific power on flower

Yisheng ZHANG, Delan ZHU

期刊论文

Impact of inter-fuel substitution on energy intensity in Ghana

Boqiang LIN, Hermas ABUDU

期刊论文

Dynamic mechanism for the decline of China’s energy intensity during the 11th FYP (Five-Year Plan)

Minghui LI

期刊论文

Efficiency of scalar and vector intensity measures for seismic slope displacements

Gang WANG

期刊论文

Does financial development lower energy intensity?

Philip Kofi ADOM, Michael Owusu APPIAH, Mawunyo Prosper AGRADI

期刊论文