针对一些形状复杂、具有局部特征的难变形薄壁构件的成形问题,提出固体颗粒介质成形(Solid granules medium forming,SGMF)技术。并以薄壁的抛物线壳体零件为例,分析零件的特征及成形难点;基于ABAQUS平台,自行编制程序对抛物线壳体SGMF...针对一些形状复杂、具有局部特征的难变形薄壁构件的成形问题,提出固体颗粒介质成形(Solid granules medium forming,SGMF)技术。并以薄壁的抛物线壳体零件为例,分析零件的特征及成形难点;基于ABAQUS平台,自行编制程序对抛物线壳体SGMF成形过程进行有限元法(Finite element method,FEM)和离散元法(Discrete element method,DEM)耦合仿真分析,探究不同摩擦因数对工件SGMF的影响。研究表明,FEM-DEM耦合分析技术兼顾离散颗粒介质与连续体板材各自的变形特点,能较准确模拟金属板材SGMF成形过程,并采用该耦合分析技术确定该抛物线壳体零件的最佳成形工艺参数;最后在模拟结果的基础上,开展抛物线壳体零件的颗粒介质成形试验研究,并成功试制出合格工件,试验结果与FEM-DEM耦合模拟结果基本吻合。展开更多
Cone penetration test(CPT)is an appropriate technique for quickly determining the geotechnical properties of lunar soil,which is valuable for in situ lunar exploration.Utilizing a typical coupling method recently deve...Cone penetration test(CPT)is an appropriate technique for quickly determining the geotechnical properties of lunar soil,which is valuable for in situ lunar exploration.Utilizing a typical coupling method recently developed by the authors,a finite element method(FEM)-discrete element method(DEM)coupled model of CPTs is obtained.A series of CPTs in lunar soil are simulated to qualitatively reveal the flow of particles and the development of resistance throughout the penetration process.In addition,the effects of major factors,such as penetration velocity,penetration depth,cone tip angle,and the low gravity on the Moon surface are investigated.展开更多
Rockslides are one of the most common geological hazards in mountainous areas and can pose significant threats to the safety of human lives and infrastructures. Studying the dynamic fragmentation process, and fragment...Rockslides are one of the most common geological hazards in mountainous areas and can pose significant threats to the safety of human lives and infrastructures. Studying the dynamic fragmentation process, and fragment characteristics of rock blocks during rockslides is of great significance. In this study,the influences of the slope angle on the dynamic fragmentation process, damage and energy evolution,and the fragments’ flying velocity and flying angle were systematically investigated using a coupled 3D FEM-DEM method. An improved fragment search algorithm was first proposed to more effectively extract the information of the fragments after impacting. The input parameters in the numerical modeling were carefully calibrated based on the quasi-static uniaxial compression tests and the rockimpact tests. The complex fragmentation process of rock block sliding along an inclined slope was simulated. The results indicate that the fragmentation intensity gradually increases with increasing the slope angle, and the fragmentation intensity of the front region of the rock block is always higher than that of the rear region. Additionally, the slope angle can significantly affect the damage ratio, energy dissipation, and the ratio of tensile crack to shear crack during the rockslides. The number of the fragments having higher flying velocities and larger flying angles increases with increasing the slope angle,which contributes to a larger spreading distance and a wider deposition area.展开更多
We present recent developments in the coupling of the finite element method(FEM)and the discrete element method(DEM)for the analysis of rock blasting operations in tunnels.The coupled FEM-DEM technique has been proven...We present recent developments in the coupling of the finite element method(FEM)and the discrete element method(DEM)for the analysis of rock blasting operations in tunnels.The coupled FEM-DEM technique has been proven to be an efficient procedure for pre-dicting the multiple fractures of rock induced by the loads generated in blasting.The coupled FEM-DEM procedure is applied in tunnel construction,as well as to gas pressure blasting pyrotechnics to break rocks for the excavation of the tunnel front.In the latter case,the effect of gas explosion is modeled by solving the equations of gas dynamics in the analysis domain using FEM.The effect of gas forces in the underlying rock mass is modeled via an embedded fluid-structure interaction method.The efficiency of the coupled FEM-DEM tech-nique is demonstrated in several examples of fracture tests and rock blasting problems related to tunnel engineering.The examples pre-sented indicate that the combination of the DEM with simple three-node linear triangular elements(for two-dimensional problems)captures the onset of fractures and their evolution accurately,accounting for the penetration of gas in the failure domain(Zarate&Onate,2015;Zarate,Cornejo,&Onate,2018).展开更多
为了模拟喷丸强化过程,实现喷丸强化效果快速预测,基于Abaqus软件采用离散元法-有限元法(Discrete Element Method-Finite Element Method,DEM-FEM)耦合建立随机多丸粒喷丸强化模型,并以TC4钛合金为研究对象,通过喷丸强化试验来验证耦...为了模拟喷丸强化过程,实现喷丸强化效果快速预测,基于Abaqus软件采用离散元法-有限元法(Discrete Element Method-Finite Element Method,DEM-FEM)耦合建立随机多丸粒喷丸强化模型,并以TC4钛合金为研究对象,通过喷丸强化试验来验证耦合模型的准确性。采用Box-Behnken设计(Box-Behnken Design,BBD)法,针对弹丸大小、喷丸速度和喷丸覆盖率3个工艺参数设计了三因素三水平的喷丸仿真试验方案,采用仿真分析获得表面残余应力值及表面粗糙度值,并通过Design-Expert软件进行数值拟合,最终得到喷丸工艺参数与表面残余应力和表面粗糙度之间的函数模型,采用响应面法分析弹丸大小、喷丸速度、喷丸覆盖率三因素之间的交互作用以及对喷丸强化效果的影响规律。结果表明,响应面预测模型结果与仿真计算结果误差低于5%,所建立的响应面预测模型具有较高的近似精度和可靠性,利用此模型可实现喷丸强化效果的有效预测。展开更多
沙湾大沟泥石流位于云南省昆明市寻甸县,发育历史悠久,活动性强,有过多次大规模爆发记录,其原有阶梯型导流槽磨蚀损毁严重,几近失效。因此,为减缓泥石流对原有结构的磨蚀效应,在三期治理工程中提出将导流槽底面设计为“曲面跌水”的特...沙湾大沟泥石流位于云南省昆明市寻甸县,发育历史悠久,活动性强,有过多次大规模爆发记录,其原有阶梯型导流槽磨蚀损毁严重,几近失效。因此,为减缓泥石流对原有结构的磨蚀效应,在三期治理工程中提出将导流槽底面设计为“曲面跌水”的特殊形式,该结构实际运行后效果良好,为进一步研究沙湾大沟泥石流对导流设施的冲击过程及动力响应特征规律,该文引入光滑粒子流体动力学-离散单元法-有限单元法耦合方法(smoothed particle hydrodynamics-discrete element method-finite element method,SPH-DEM-FEM),构建沙湾大沟泥石流导流系统流固耦合模型,对泥石流冲击“曲面跌水”导流设施进行运动过程分析,并与二期原有阶梯型导流槽开展对比研究。结果表明,泥石流冲击“曲面跌水”导流设施过程中导流槽右侧积聚和爬升现象明显,左右两侧峰值速度分别为24.96、17.38 m/s,不同坡度衔接段及出口处水平段受冲击较大,等效应力峰值为722.3 kPa。在相同的工程条件下,曲面型导流槽对泥石流颗粒的减速消能效果更好,在保证排导功能基础上,其使用寿命优于阶梯型导流槽,研究成果为该类型导流槽的设计及应用提供了一定的参考依据及理论支撑。展开更多
高位滑坡对建筑集群的冲击破坏时常导致严重的人员伤亡,基于光滑粒子流体动力学-离散元法-有限元法(smoothed particle hydrodynamics-discrete element method-finite element method,SPH-DEM-FEM)耦合的数值模型,开展了高位滑坡对框...高位滑坡对建筑集群的冲击破坏时常导致严重的人员伤亡,基于光滑粒子流体动力学-离散元法-有限元法(smoothed particle hydrodynamics-discrete element method-finite element method,SPH-DEM-FEM)耦合的数值模型,开展了高位滑坡对框架结构建筑群的冲击过程、建筑结构破坏机理、冲击力时程与框架柱关键点应力和弯矩等动力机制研究。研究结果表明:SPH-DEM-FEM耦合数值方法能够有效地模拟碎石土滑坡中土(SPH)石(DEM)混合物的抛射弹跳、爬高绕流冲击运动过程。考虑了常规建筑垂直、平行于滑坡流向的三排建筑组合布局,位于滑坡近端的纵向排列建筑表现为连续性倾倒破坏,横向排列的建筑则呈现整体倾倒破坏;因前排建筑群对滑坡冲击能量的耗散及滑坡自身摩擦耗能,位于滑坡后端建筑表现为引流面墙体和前排柱发生局部破坏,结构保持稳定,损毁程度依次为上游无建筑缓冲耗能的建筑>有横向排列的建筑>有纵向排列的建筑;纵向、横向排列的建筑冲击力衰减幅度分别31%、21%。横向框架建筑整体倾倒的损毁机制表现为框架柱的直接剪断或节点塑形铰链失效;纵向框架建筑连续性倾倒的损毁机制表现为前排框架柱的失效引起后排框架柱轴向压力和极限弯矩增加,持续冲击荷载超过其极限弯矩致使后排框架柱发生弯曲破坏,最终结构倾倒。系统能量在动能、内能和摩擦耗能间转化,其中摩擦耗能占65.5%,结构耗能占23.6%,动能快速下降与内能急剧增加是建筑破坏的关键特征。展开更多
文摘针对一些形状复杂、具有局部特征的难变形薄壁构件的成形问题,提出固体颗粒介质成形(Solid granules medium forming,SGMF)技术。并以薄壁的抛物线壳体零件为例,分析零件的特征及成形难点;基于ABAQUS平台,自行编制程序对抛物线壳体SGMF成形过程进行有限元法(Finite element method,FEM)和离散元法(Discrete element method,DEM)耦合仿真分析,探究不同摩擦因数对工件SGMF的影响。研究表明,FEM-DEM耦合分析技术兼顾离散颗粒介质与连续体板材各自的变形特点,能较准确模拟金属板材SGMF成形过程,并采用该耦合分析技术确定该抛物线壳体零件的最佳成形工艺参数;最后在模拟结果的基础上,开展抛物线壳体零件的颗粒介质成形试验研究,并成功试制出合格工件,试验结果与FEM-DEM耦合模拟结果基本吻合。
基金Project(51278451) supported by the National Natural Science Foundation of ChinaProject(LZ12E09001) supported by the Zhejiang Natural Science Foundation,China
文摘Cone penetration test(CPT)is an appropriate technique for quickly determining the geotechnical properties of lunar soil,which is valuable for in situ lunar exploration.Utilizing a typical coupling method recently developed by the authors,a finite element method(FEM)-discrete element method(DEM)coupled model of CPTs is obtained.A series of CPTs in lunar soil are simulated to qualitatively reveal the flow of particles and the development of resistance throughout the penetration process.In addition,the effects of major factors,such as penetration velocity,penetration depth,cone tip angle,and the low gravity on the Moon surface are investigated.
基金supported by the National Natural Science Foundation of China (Grant Nos.52004182, 51908431)。
文摘Rockslides are one of the most common geological hazards in mountainous areas and can pose significant threats to the safety of human lives and infrastructures. Studying the dynamic fragmentation process, and fragment characteristics of rock blocks during rockslides is of great significance. In this study,the influences of the slope angle on the dynamic fragmentation process, damage and energy evolution,and the fragments’ flying velocity and flying angle were systematically investigated using a coupled 3D FEM-DEM method. An improved fragment search algorithm was first proposed to more effectively extract the information of the fragments after impacting. The input parameters in the numerical modeling were carefully calibrated based on the quasi-static uniaxial compression tests and the rockimpact tests. The complex fragmentation process of rock block sliding along an inclined slope was simulated. The results indicate that the fragmentation intensity gradually increases with increasing the slope angle, and the fragmentation intensity of the front region of the rock block is always higher than that of the rear region. Additionally, the slope angle can significantly affect the damage ratio, energy dissipation, and the ratio of tensile crack to shear crack during the rockslides. The number of the fragments having higher flying velocities and larger flying angles increases with increasing the slope angle,which contributes to a larger spreading distance and a wider deposition area.
基金the Tunel project funded by the Spanish Ministry of Science and Innovation.(2015-2019)via the subprogram CIEN(IDI-20150705)the EZUANA project(BIA2016-78544-R),funded by the Spanish Ministry of Education and Science of Spain.
文摘We present recent developments in the coupling of the finite element method(FEM)and the discrete element method(DEM)for the analysis of rock blasting operations in tunnels.The coupled FEM-DEM technique has been proven to be an efficient procedure for pre-dicting the multiple fractures of rock induced by the loads generated in blasting.The coupled FEM-DEM procedure is applied in tunnel construction,as well as to gas pressure blasting pyrotechnics to break rocks for the excavation of the tunnel front.In the latter case,the effect of gas explosion is modeled by solving the equations of gas dynamics in the analysis domain using FEM.The effect of gas forces in the underlying rock mass is modeled via an embedded fluid-structure interaction method.The efficiency of the coupled FEM-DEM tech-nique is demonstrated in several examples of fracture tests and rock blasting problems related to tunnel engineering.The examples pre-sented indicate that the combination of the DEM with simple three-node linear triangular elements(for two-dimensional problems)captures the onset of fractures and their evolution accurately,accounting for the penetration of gas in the failure domain(Zarate&Onate,2015;Zarate,Cornejo,&Onate,2018).
文摘为了模拟喷丸强化过程,实现喷丸强化效果快速预测,基于Abaqus软件采用离散元法-有限元法(Discrete Element Method-Finite Element Method,DEM-FEM)耦合建立随机多丸粒喷丸强化模型,并以TC4钛合金为研究对象,通过喷丸强化试验来验证耦合模型的准确性。采用Box-Behnken设计(Box-Behnken Design,BBD)法,针对弹丸大小、喷丸速度和喷丸覆盖率3个工艺参数设计了三因素三水平的喷丸仿真试验方案,采用仿真分析获得表面残余应力值及表面粗糙度值,并通过Design-Expert软件进行数值拟合,最终得到喷丸工艺参数与表面残余应力和表面粗糙度之间的函数模型,采用响应面法分析弹丸大小、喷丸速度、喷丸覆盖率三因素之间的交互作用以及对喷丸强化效果的影响规律。结果表明,响应面预测模型结果与仿真计算结果误差低于5%,所建立的响应面预测模型具有较高的近似精度和可靠性,利用此模型可实现喷丸强化效果的有效预测。
文摘沙湾大沟泥石流位于云南省昆明市寻甸县,发育历史悠久,活动性强,有过多次大规模爆发记录,其原有阶梯型导流槽磨蚀损毁严重,几近失效。因此,为减缓泥石流对原有结构的磨蚀效应,在三期治理工程中提出将导流槽底面设计为“曲面跌水”的特殊形式,该结构实际运行后效果良好,为进一步研究沙湾大沟泥石流对导流设施的冲击过程及动力响应特征规律,该文引入光滑粒子流体动力学-离散单元法-有限单元法耦合方法(smoothed particle hydrodynamics-discrete element method-finite element method,SPH-DEM-FEM),构建沙湾大沟泥石流导流系统流固耦合模型,对泥石流冲击“曲面跌水”导流设施进行运动过程分析,并与二期原有阶梯型导流槽开展对比研究。结果表明,泥石流冲击“曲面跌水”导流设施过程中导流槽右侧积聚和爬升现象明显,左右两侧峰值速度分别为24.96、17.38 m/s,不同坡度衔接段及出口处水平段受冲击较大,等效应力峰值为722.3 kPa。在相同的工程条件下,曲面型导流槽对泥石流颗粒的减速消能效果更好,在保证排导功能基础上,其使用寿命优于阶梯型导流槽,研究成果为该类型导流槽的设计及应用提供了一定的参考依据及理论支撑。
文摘高位滑坡对建筑集群的冲击破坏时常导致严重的人员伤亡,基于光滑粒子流体动力学-离散元法-有限元法(smoothed particle hydrodynamics-discrete element method-finite element method,SPH-DEM-FEM)耦合的数值模型,开展了高位滑坡对框架结构建筑群的冲击过程、建筑结构破坏机理、冲击力时程与框架柱关键点应力和弯矩等动力机制研究。研究结果表明:SPH-DEM-FEM耦合数值方法能够有效地模拟碎石土滑坡中土(SPH)石(DEM)混合物的抛射弹跳、爬高绕流冲击运动过程。考虑了常规建筑垂直、平行于滑坡流向的三排建筑组合布局,位于滑坡近端的纵向排列建筑表现为连续性倾倒破坏,横向排列的建筑则呈现整体倾倒破坏;因前排建筑群对滑坡冲击能量的耗散及滑坡自身摩擦耗能,位于滑坡后端建筑表现为引流面墙体和前排柱发生局部破坏,结构保持稳定,损毁程度依次为上游无建筑缓冲耗能的建筑>有横向排列的建筑>有纵向排列的建筑;纵向、横向排列的建筑冲击力衰减幅度分别31%、21%。横向框架建筑整体倾倒的损毁机制表现为框架柱的直接剪断或节点塑形铰链失效;纵向框架建筑连续性倾倒的损毁机制表现为前排框架柱的失效引起后排框架柱轴向压力和极限弯矩增加,持续冲击荷载超过其极限弯矩致使后排框架柱发生弯曲破坏,最终结构倾倒。系统能量在动能、内能和摩擦耗能间转化,其中摩擦耗能占65.5%,结构耗能占23.6%,动能快速下降与内能急剧增加是建筑破坏的关键特征。
