A simple and effective method for analyzing the stress distribution in a Functionally Gradient Material(FGM) layer on the su;face of a structural component is proposed in this paper. Generally, the FGM layer is very t...A simple and effective method for analyzing the stress distribution in a Functionally Gradient Material(FGM) layer on the su;face of a structural component is proposed in this paper. Generally, the FGM layer is very thin compared with the characteristic length of the structural component, and the nonhomogeneity exists only in the thin layer. Based on these features, by choosing a small parameter I which characterizes the stiffness of the layer relative to the component, and expanding the stresses and displacements on the two sides of the interface according to the parameter lambda, then asymptotically using the continuity conditions of the stresses and displacements on the interface, a decoupling computing process of the coupling control equations of the layer and the structural component is realized. Finally, two examples are given to illustrate the application of the method proposed.展开更多
A virtual Taylor impact of cellular materials is analyzed with a wave propagation technique, i.e. the Lagrangian analysis method, of which the main advantage is that no pre-assumed constitutive relationship is require...A virtual Taylor impact of cellular materials is analyzed with a wave propagation technique, i.e. the Lagrangian analysis method, of which the main advantage is that no pre-assumed constitutive relationship is required. Time histories of particle velocity, local strain, and stress profiles are calculated to present the local stress-strain history curves, from which the dynamic stress-strain states are obtained. The present results reveal that the dynamic-rigid-plastic hardening （D-R-PH） material model introduced in a previous study of our group is in good agreement with the dynamic stress-strain states under high loading rates obtained by the Lagrangian analysis method. It directly reflects the effectiveness and feasibility of the D-R-PH material model for the cellular materials under high loading rates.展开更多
This paper includes descriptions of the stress distribution regularities in the tight joint parts, regularities of the stress state changes in the contact region along coupling length, stress concentration factors, le...This paper includes descriptions of the stress distribution regularities in the tight joint parts, regularities of the stress state changes in the contact region along coupling length, stress concentration factors, levels of additional stresses caused by press fitting. Distributions of stress intensity, axial stress, contact pressure, tangent stress in parts and in contact zone along coupling length are considered. Calculation results obtained by three approaches: Lame relationships, FEM without considering assembly method, FEM with considering press fitting process are analyzed and compared. The adequacy of research carried out is confirmed.展开更多
The seepage property of low-permeability rock is of significant importance for the design and safety analysis of underground cavities. By using a self-developed test system, both permeability and porosity of granite f...The seepage property of low-permeability rock is of significant importance for the design and safety analysis of underground cavities. By using a self-developed test system, both permeability and porosity of granite from an underground oil storage depot were measured. In order to study the influence of rock types on permeability, a tight sandstone was selected as a contrast. The experimental results suggested that the porosity of this granite is less than 5% and permeability is low to 10–20 m^2 within the range of effective stress. During the loading process, both exponential relationship and power law can be utilized to describe the relationship between effective stress and permeability. However, power law matches the experimental data better during the unloading condition. The stress dependent porosity of granite during loading process can be described via an exponential relationship while the match between the model and experimental data can be improved by a power law in unloading paths. The correlation of permeability and porosity can be described in a power law form. Besides, granite shows great different evolution rules in permeability and porosity from sandstone. It is inferred that this difference can be attributed to the preparing of samples and different movements of microstructures subjected to effective stress.展开更多
高强螺栓作为关键零部件,广泛应用于悬索桥、风电塔筒等重要结构中,其安装质量对整体结构的稳定性和安全性具有至关重要的影响。然而,传统的扭矩法难以准确测量螺栓的轴向预紧力,从而难以有效评估结构的稳定性。为解决这一问题,基于声...高强螺栓作为关键零部件,广泛应用于悬索桥、风电塔筒等重要结构中,其安装质量对整体结构的稳定性和安全性具有至关重要的影响。然而,传统的扭矩法难以准确测量螺栓的轴向预紧力,从而难以有效评估结构的稳定性。为解决这一问题,基于声弹性效应,设计了高压激励和压控增益等电路,研制了一套螺栓轴力检测系统。系统通过激励压电传感器接收回波信号,并采用互相关算法计算渡越时间差以表征螺栓的应力状态,最后对风电螺栓进行了应力-渡越时间标定实验及超声法与扭矩法的对比实验。实验结果表明,当螺栓轴向预紧力达到其额定值的40%时,该系统的应力测量误差率≤2.81%,且分辨率可达0.2507 k N,能够有效满足螺栓轴向预紧力的测量要求。与传统扭矩法相比,超声法在螺栓服役状态下的应力测量误差控制与分辨率均具有显著优势,为工业领域关键部件的应力测量提供了可靠的技术方案。展开更多
文摘A simple and effective method for analyzing the stress distribution in a Functionally Gradient Material(FGM) layer on the su;face of a structural component is proposed in this paper. Generally, the FGM layer is very thin compared with the characteristic length of the structural component, and the nonhomogeneity exists only in the thin layer. Based on these features, by choosing a small parameter I which characterizes the stiffness of the layer relative to the component, and expanding the stresses and displacements on the two sides of the interface according to the parameter lambda, then asymptotically using the continuity conditions of the stresses and displacements on the interface, a decoupling computing process of the coupling control equations of the layer and the structural component is realized. Finally, two examples are given to illustrate the application of the method proposed.
基金supported by the National Natural Science Foundation of China(11372308 and 11372307)the Fundamental Research Funds for the Central Universities(WK2480000001)
文摘A virtual Taylor impact of cellular materials is analyzed with a wave propagation technique, i.e. the Lagrangian analysis method, of which the main advantage is that no pre-assumed constitutive relationship is required. Time histories of particle velocity, local strain, and stress profiles are calculated to present the local stress-strain history curves, from which the dynamic stress-strain states are obtained. The present results reveal that the dynamic-rigid-plastic hardening （D-R-PH） material model introduced in a previous study of our group is in good agreement with the dynamic stress-strain states under high loading rates obtained by the Lagrangian analysis method. It directly reflects the effectiveness and feasibility of the D-R-PH material model for the cellular materials under high loading rates.
文摘This paper includes descriptions of the stress distribution regularities in the tight joint parts, regularities of the stress state changes in the contact region along coupling length, stress concentration factors, levels of additional stresses caused by press fitting. Distributions of stress intensity, axial stress, contact pressure, tangent stress in parts and in contact zone along coupling length are considered. Calculation results obtained by three approaches: Lame relationships, FEM without considering assembly method, FEM with considering press fitting process are analyzed and compared. The adequacy of research carried out is confirmed.
基金Projects(11172090,51479049,11272113,11572110,51209075)supported by the National Natural Science Foundation of ChinaProject(BK2012809)supported by the Natural Science Foundation of Jiangsu Province,ChinaProject(201406710042)supported by China Scholarship Council
文摘The seepage property of low-permeability rock is of significant importance for the design and safety analysis of underground cavities. By using a self-developed test system, both permeability and porosity of granite from an underground oil storage depot were measured. In order to study the influence of rock types on permeability, a tight sandstone was selected as a contrast. The experimental results suggested that the porosity of this granite is less than 5% and permeability is low to 10–20 m^2 within the range of effective stress. During the loading process, both exponential relationship and power law can be utilized to describe the relationship between effective stress and permeability. However, power law matches the experimental data better during the unloading condition. The stress dependent porosity of granite during loading process can be described via an exponential relationship while the match between the model and experimental data can be improved by a power law in unloading paths. The correlation of permeability and porosity can be described in a power law form. Besides, granite shows great different evolution rules in permeability and porosity from sandstone. It is inferred that this difference can be attributed to the preparing of samples and different movements of microstructures subjected to effective stress.
文摘高强螺栓作为关键零部件,广泛应用于悬索桥、风电塔筒等重要结构中,其安装质量对整体结构的稳定性和安全性具有至关重要的影响。然而,传统的扭矩法难以准确测量螺栓的轴向预紧力,从而难以有效评估结构的稳定性。为解决这一问题,基于声弹性效应,设计了高压激励和压控增益等电路,研制了一套螺栓轴力检测系统。系统通过激励压电传感器接收回波信号,并采用互相关算法计算渡越时间差以表征螺栓的应力状态,最后对风电螺栓进行了应力-渡越时间标定实验及超声法与扭矩法的对比实验。实验结果表明,当螺栓轴向预紧力达到其额定值的40%时,该系统的应力测量误差率≤2.81%,且分辨率可达0.2507 k N,能够有效满足螺栓轴向预紧力的测量要求。与传统扭矩法相比,超声法在螺栓服役状态下的应力测量误差控制与分辨率均具有显著优势,为工业领域关键部件的应力测量提供了可靠的技术方案。
