This paper presents a posteriori residual error estimator for the new mixed el-ement scheme for second order elliptic problem on anisotropic meshes. The reliability and efficiency of our estimator are established with...This paper presents a posteriori residual error estimator for the new mixed el-ement scheme for second order elliptic problem on anisotropic meshes. The reliability and efficiency of our estimator are established without any regularity assumption on the mesh.展开更多
Time?varying mesh stiffness(TVMS) and gear errors include short?term and long?term components are the two main internal dynamic excitations for gear transmission. The coupling relationship between the two factors is u...Time?varying mesh stiffness(TVMS) and gear errors include short?term and long?term components are the two main internal dynamic excitations for gear transmission. The coupling relationship between the two factors is usually neglected in the traditional quasi-static and dynamic behaviors analysis of gear system. This paper investigates the influence of short?term and long?term components of manufacturing errors on quasi?static and dynamic behaviors of helical gear system considering the coupling relationship between TVMS and gear errors. The TVMS, loaded static transmission error(LSTE) and loaded composite mesh error(LCMS) are determined using an improved loaded tooth contact analysis(LTCA) model. Considering the structure of shaft, as well as the direction of power flow and bearing location, a precise generalized finite element dynamic model of helical gear system is developed, and the dynamic responses of the system are obtained by numerical integration method. The results suggest that lighter loading conditions result in smaller mesh stiffness and stronger vibration, and the corresponding resonance speeds of the system become lower. Long?term components of manufacturing errors lead to the appearance of sideband frequency components in frequency spectrum of dynamic responses. The sideband frequency components are predominant under light loading conditions. With the increase of output torque, the mesh frequency and its harmonics components tend to be enhanced relative to sideband frequency components. This study can provide effective reference for low noise design of gear transmission.展开更多
针对齿轮箱的振动噪声问题,提出了一种基于齿轮载荷静态传递误差(load static transfer error,LSTE)优化的减振降噪方法。通过建立齿廓修形齿轮的时变啮合刚度解析模型,并采用Timoshenko梁单元构建齿轮-转子-轴承耦合动力学模型,系统揭...针对齿轮箱的振动噪声问题,提出了一种基于齿轮载荷静态传递误差(load static transfer error,LSTE)优化的减振降噪方法。通过建立齿廓修形齿轮的时变啮合刚度解析模型,并采用Timoshenko梁单元构建齿轮-转子-轴承耦合动力学模型,系统揭示了不同修形量和修形曲线下齿轮LSTE与系统动力学响应之间的关系。在此基础上,采用遗传算法对齿轮LSTE相对峰峰值进行优化,获得最优修形参数组合。最后结合有限元/边界元法,分析了修形优化前后齿轮箱的噪声辐射特性。研究结果表明,经遗传算法优化后的修形参数可使主动轮位移幅频响应幅值与加速度幅频响应幅值相较其他修形参数均显著降低,齿轮箱辐射声功率级均方根值由未修形时的38.66 dB降至修形优化后25.32 dB,降幅达34.51%,降噪效果显著。研究成果为齿轮传动系统的低噪声设计提供了理论依据。展开更多
The combined hybrid finite element method is of an intrinsic mechanism of enhancing coarse-mesh-accuracy of lower order displacement schemes. It was confirmed that the combined hybrid scheme without energy error leads...The combined hybrid finite element method is of an intrinsic mechanism of enhancing coarse-mesh-accuracy of lower order displacement schemes. It was confirmed that the combined hybrid scheme without energy error leads to enhancement of accuracy at coarse meshes, and that the combination parameter plays an important role in the enhancement. As an improvement of conforming bilinear Q(4)-plane element, the combined hybrid method adopted the most convenient quadrilateral displacements-stress mode, i.e.,the mode of compatible isoparametric bilinear displacements and pure constant stresses. By adjusting the combined parameter, the optimized version of the combined hybrid element was obtained and numerical tests indicated that this parameter-adjusted version behaves much better than Q(4)-element and is of high accuracy at coarse meshes. Due to elimination of stress parameters at the elemental level, this combined hybrid version is of the same computational cost as that of Q(4)-element.展开更多
A goal-oriented adaptive finite element（FE） method for solving 3D direct current（DC） resistivity modeling problem is presented. The model domain is subdivided into unstructured tetrahedral elements that allow for ...A goal-oriented adaptive finite element（FE） method for solving 3D direct current（DC） resistivity modeling problem is presented. The model domain is subdivided into unstructured tetrahedral elements that allow for efficient local mesh refinement and flexible description of complex models. The elements that affect the solution at each receiver location are adaptively refined according to a goal-oriented posteriori error estimator using dual-error weighting approach. The FE method with adapting mesh can easily handle such structures at almost any level of complexity. The method is demonstrated on two synthetic resistivity models with analytical solutions and available results from integral equation method, so the errors can be quantified. The applicability of the numerical method is illustrated on a resistivity model with a topographic ridge. Numerical examples show that this method is flexible and accurate for geometrically complex situations.展开更多
The similarity property of conformal parameterization makes it able to locally preserve the shapes between a surface and its parameter domain, as opposed to common parameterization methods. A parametric tool path plan...The similarity property of conformal parameterization makes it able to locally preserve the shapes between a surface and its parameter domain, as opposed to common parameterization methods. A parametric tool path planning method is proposed in this paper through such parameterization of triangular meshes which is furthermore based on the geodesic on meshes. The parameterization has the properties of local similarity and free boundary which are exploited to simplify the formulas for computing path parameters, which play a fundamentally important role in tool path planning, and keep the path boundary-conformed and smooth. Experimental results are given to illustrate the effectiveness of the proposed methods, as well as the error analysis.展开更多
Given the framework of incremental mesh simplification based on edgecollapse, the paper proposes a mesh simplification algorithm using an improved approach formeasuring simplification error. The algorithm uses edge co...Given the framework of incremental mesh simplification based on edgecollapse, the paper proposes a mesh simplification algorithm using an improved approach formeasuring simplification error. The algorithm uses edge collapse to simplify the trianglemesh andmaintains surface error approximations using c-error for the faces which have changed after edgecollapse and d-crror for the faces which become degenerated after edge collapse. Also, we reportsome results using a variety of computer graphics models, which can show that the algorithm canachieve the desired simplification effect.展开更多
A new method for estimating the posterior error of linear triangular element is presented. According to the specified accuracy, the element size and node spacing function of adaptive h-version mesh refinement are pred...A new method for estimating the posterior error of linear triangular element is presented. According to the specified accuracy, the element size and node spacing function of adaptive h-version mesh refinement are predicted. The main domain is divided by the isolines of node spacing into subregions in which mesh regeneration is realized. This remeshing refinement process implements mesh subdivision and mesh de-refinement in onecycle.展开更多
文摘This paper presents a posteriori residual error estimator for the new mixed el-ement scheme for second order elliptic problem on anisotropic meshes. The reliability and efficiency of our estimator are established without any regularity assumption on the mesh.
基金Supported by Key Project of National Natural Science Foundation of China(Grant No.51535009)111 Project(Grant No.B13044)
文摘Time?varying mesh stiffness(TVMS) and gear errors include short?term and long?term components are the two main internal dynamic excitations for gear transmission. The coupling relationship between the two factors is usually neglected in the traditional quasi-static and dynamic behaviors analysis of gear system. This paper investigates the influence of short?term and long?term components of manufacturing errors on quasi?static and dynamic behaviors of helical gear system considering the coupling relationship between TVMS and gear errors. The TVMS, loaded static transmission error(LSTE) and loaded composite mesh error(LCMS) are determined using an improved loaded tooth contact analysis(LTCA) model. Considering the structure of shaft, as well as the direction of power flow and bearing location, a precise generalized finite element dynamic model of helical gear system is developed, and the dynamic responses of the system are obtained by numerical integration method. The results suggest that lighter loading conditions result in smaller mesh stiffness and stronger vibration, and the corresponding resonance speeds of the system become lower. Long?term components of manufacturing errors lead to the appearance of sideband frequency components in frequency spectrum of dynamic responses. The sideband frequency components are predominant under light loading conditions. With the increase of output torque, the mesh frequency and its harmonics components tend to be enhanced relative to sideband frequency components. This study can provide effective reference for low noise design of gear transmission.
文摘The combined hybrid finite element method is of an intrinsic mechanism of enhancing coarse-mesh-accuracy of lower order displacement schemes. It was confirmed that the combined hybrid scheme without energy error leads to enhancement of accuracy at coarse meshes, and that the combination parameter plays an important role in the enhancement. As an improvement of conforming bilinear Q(4)-plane element, the combined hybrid method adopted the most convenient quadrilateral displacements-stress mode, i.e.,the mode of compatible isoparametric bilinear displacements and pure constant stresses. By adjusting the combined parameter, the optimized version of the combined hybrid element was obtained and numerical tests indicated that this parameter-adjusted version behaves much better than Q(4)-element and is of high accuracy at coarse meshes. Due to elimination of stress parameters at the elemental level, this combined hybrid version is of the same computational cost as that of Q(4)-element.
基金supported by the National Natural Science Foundation of China (No. 41204055)the National Basic Research Program of China (No. 2013CB733203)the Opening Project (No. SMIL-2014-06) of Hubei Subsurface Multi-Scale Imaging Lab (SMIL), China University of Geosciences, Wuhan, China
文摘A goal-oriented adaptive finite element（FE） method for solving 3D direct current（DC） resistivity modeling problem is presented. The model domain is subdivided into unstructured tetrahedral elements that allow for efficient local mesh refinement and flexible description of complex models. The elements that affect the solution at each receiver location are adaptively refined according to a goal-oriented posteriori error estimator using dual-error weighting approach. The FE method with adapting mesh can easily handle such structures at almost any level of complexity. The method is demonstrated on two synthetic resistivity models with analytical solutions and available results from integral equation method, so the errors can be quantified. The applicability of the numerical method is illustrated on a resistivity model with a topographic ridge. Numerical examples show that this method is flexible and accurate for geometrically complex situations.
基金supported by the National Program on Key Basic Research Project of China (No. 2011CB302400)the National Natural Science Foundation of China (No. 51175495)
文摘The similarity property of conformal parameterization makes it able to locally preserve the shapes between a surface and its parameter domain, as opposed to common parameterization methods. A parametric tool path planning method is proposed in this paper through such parameterization of triangular meshes which is furthermore based on the geodesic on meshes. The parameterization has the properties of local similarity and free boundary which are exploited to simplify the formulas for computing path parameters, which play a fundamentally important role in tool path planning, and keep the path boundary-conformed and smooth. Experimental results are given to illustrate the effectiveness of the proposed methods, as well as the error analysis.
基金Supported by the Key Science Technology Project of China (2001BA102A04 02 03)
文摘Given the framework of incremental mesh simplification based on edgecollapse, the paper proposes a mesh simplification algorithm using an improved approach formeasuring simplification error. The algorithm uses edge collapse to simplify the trianglemesh andmaintains surface error approximations using c-error for the faces which have changed after edgecollapse and d-crror for the faces which become degenerated after edge collapse. Also, we reportsome results using a variety of computer graphics models, which can show that the algorithm canachieve the desired simplification effect.
文摘A new method for estimating the posterior error of linear triangular element is presented. According to the specified accuracy, the element size and node spacing function of adaptive h-version mesh refinement are predicted. The main domain is divided by the isolines of node spacing into subregions in which mesh regeneration is realized. This remeshing refinement process implements mesh subdivision and mesh de-refinement in onecycle.
