A new multi-level analysis method of introducing the super-element modeling method, derived from the multi-level analysis method first proposed by O. F. Hughes, has been proposed in this paper to solve the problem of ...A new multi-level analysis method of introducing the super-element modeling method, derived from the multi-level analysis method first proposed by O. F. Hughes, has been proposed in this paper to solve the problem of high time cost in adopting a rational-based optimal design method for ship structural design. Furthermore,the method was verified by its effective application in optimization of the mid-ship section of a container ship. A full 3-D FEM model of a ship,suffering static and quasi-static loads, was used as the analyzing object for evaluating the structural performance of the mid-ship module, including static strength and buckling performance. Research results reveal that this new method could substantially reduce the computational cost of the rational-based optimization problem without decreasing its accuracy, which increases the feasibility and economic efficiency of using a rational-based optimal design method in ship structural design.展开更多
Efficient transient analysis is critical in rotor dynamics.This study proposes the super-element(SE)differential-quadraturediscrete-time transfer matrix method(DQ-DT-TMM),a novel approach that eliminates the requireme...Efficient transient analysis is critical in rotor dynamics.This study proposes the super-element(SE)differential-quadraturediscrete-time transfer matrix method(DQ-DT-TMM),a novel approach that eliminates the requirement for initial componentaccelerations and effectively handles beam and solid finite element(FE)models with high-dimensional degrees of freedom(DOFs)in rotor systems.The primary methodologies of this approach include:(1)For the beam substructure FE dynamicequation,the Craig-Bampton method is employed for the order reduction of internal coordinates,followed by the differentialquadraturemethod for temporal discretization.Using SE technology,the internal accelerations are condensed into theboundary accelerations,and the transfer equation and matrix for beam SEs are derived.(2)For the solid substructureFE dynamic equation formulated in the rotating reference frame,in addition to applying the procedures used for beamsubstructures,rigid multipoint constraints are introduced to condense the boundary coordinates for hybrid modeling withlumped parameter components.The transfer equation is subsequently formulated in the inertial reference frame,enabling thederivation of the transfer matrix for solid SEs.Comparative analysis with full-order FE models in commercial softwaredemonstrates the advantages of the SE DQ-DT-TMM for linear rotor systems:(i)Accurately captures system dynamics usingonly a few primary modes.(ii)Achieves a 99.68%reduction in computational time for a beam model with 1120 elements and a99.98%reduction for a solid model with 75361 elements.(iii)Effectively recovers dynamic responses at any system node usingrecovery techniques.This research develops a computationally efficient framework for the transient analysis of large-scale rotorsystems,effectively addressing the challenges associated with high-dimensional DOF models in conventional DT-TMMs.展开更多
基于对单元能量投影(element energy projection,EEP)法误差项的直接推导及分析,用EEP简约格式的解计算出略掉的误差项,反补后得到比简约格式高一阶精度的EEP超收敛计算的加强格式。该文以一维Galerkin有限元为例,给出EEP加强格式的算...基于对单元能量投影(element energy projection,EEP)法误差项的直接推导及分析,用EEP简约格式的解计算出略掉的误差项,反补后得到比简约格式高一阶精度的EEP超收敛计算的加强格式。该文以一维Galerkin有限元为例,给出EEP加强格式的算法公式和数学证明。理论分析和算例验证表明:对于m (≥1)次单元,采用EEP加强格式计算的内点位移和内点导数都具有h^(min(m+3,2m))阶的收敛精度,对系数特例问题二者甚至可以分别达到h^(min(m+5,2m))和h^(min(m+4,2m))阶的收敛精度。并对该法的进一步拓展作了讨论。展开更多
目的建立超级微波消解-碰撞反应池电感耦合等离子体质谱法同时测定蔬菜中铅、砷、镉、铬等21种元素的方法。方法选择超级微波消解法进行样品预处理,以硝酸为消解液,运用具有八极杆反应池系统的电感耦合等离子体质谱仪,以铂锥作为采样锥...目的建立超级微波消解-碰撞反应池电感耦合等离子体质谱法同时测定蔬菜中铅、砷、镉、铬等21种元素的方法。方法选择超级微波消解法进行样品预处理,以硝酸为消解液,运用具有八极杆反应池系统的电感耦合等离子体质谱仪,以铂锥作为采样锥,使用He气碰撞模式(5 m L/min),通过动能歧视和碰撞诱导解离进行干扰的消除。此外,选择包括低、中、高质量范围的^(6)Li、^(45)Sc、^(72)Ge、^(103)Rh、^(115)In、^(159)Tb、^(175)Lu、^(209)Bi元素作为内标,使用在线添加内标的方式进行干扰消除,并在数据分析时采用虚拟内标校正模式。结果在优化后的实验条件下,21种元素在一定的质量浓度区间内,其对应的信号强度与质量浓度呈线性关系。标准曲线线性良好,相关系数在0.999~1.000之间。方法的检出限在0.005~1.200 mg/kg,定量限在0.015~3.600 mg/kg。方法通过加标回收测定回收率,加标回收率在85.2%~119.9%之间。对处理后的蔬菜样品加入低、中、高3种不同浓度的标准,每份平行测定7次,测定值的相对标准偏差在1.03%~4.60%之间。结论通过本研究方法对蔬菜样品中21种元素进行测定,满足国家标准对各项技术指标参数的要求。该方法检出限低,选择性好,结果准确可靠,为蔬菜样品中多种元素分析测定提供了新的参考方法。展开更多
Based on the experimental results of super-elastic NiTi alloy, a three-dimensional super-elastic constitutive model including both of stress-induced martensite transformation and plasticity is constructed in a framewo...Based on the experimental results of super-elastic NiTi alloy, a three-dimensional super-elastic constitutive model including both of stress-induced martensite transformation and plasticity is constructed in a framework of general inelasticity. In the proposed model, transformation hardening, reverse transformation of stress-induced martensite, elastic mismatch between the austenite and martensite phases, and temperature-dependence of transformation stress and elastic modulus of each phase are considered. The plastic yielding of martensite occurred under high stress is addressed by a bilinear isotropic hardening rule. Drucker-Prager-typed transformation surfaces are employed to describe the asymmetric behavior of NiTi alloy in tension and compression. The prediction capability of the proposed model is verified by comparing the simulated results with the correspondent experimental ones. Based on backward Euler＇s integration, a new expression of consistent tangent modulus is derived. The proposed model is then implemented into a finite element package ABAQUS by user-subroutine UMAT. Finally, the validity of such implementation was verified by some numerical samples.展开更多
基金Supported by the Project of Ministry of Education and Finance(No.200512)the Project of the State Key Laboratory of ocean engineering(GKZD010053-10)
文摘A new multi-level analysis method of introducing the super-element modeling method, derived from the multi-level analysis method first proposed by O. F. Hughes, has been proposed in this paper to solve the problem of high time cost in adopting a rational-based optimal design method for ship structural design. Furthermore,the method was verified by its effective application in optimization of the mid-ship section of a container ship. A full 3-D FEM model of a ship,suffering static and quasi-static loads, was used as the analyzing object for evaluating the structural performance of the mid-ship module, including static strength and buckling performance. Research results reveal that this new method could substantially reduce the computational cost of the rational-based optimization problem without decreasing its accuracy, which increases the feasibility and economic efficiency of using a rational-based optimal design method in ship structural design.
基金supported by the National Natural Science Foundation of China(Grant/Award No.92266201).
文摘Efficient transient analysis is critical in rotor dynamics.This study proposes the super-element(SE)differential-quadraturediscrete-time transfer matrix method(DQ-DT-TMM),a novel approach that eliminates the requirement for initial componentaccelerations and effectively handles beam and solid finite element(FE)models with high-dimensional degrees of freedom(DOFs)in rotor systems.The primary methodologies of this approach include:(1)For the beam substructure FE dynamicequation,the Craig-Bampton method is employed for the order reduction of internal coordinates,followed by the differentialquadraturemethod for temporal discretization.Using SE technology,the internal accelerations are condensed into theboundary accelerations,and the transfer equation and matrix for beam SEs are derived.(2)For the solid substructureFE dynamic equation formulated in the rotating reference frame,in addition to applying the procedures used for beamsubstructures,rigid multipoint constraints are introduced to condense the boundary coordinates for hybrid modeling withlumped parameter components.The transfer equation is subsequently formulated in the inertial reference frame,enabling thederivation of the transfer matrix for solid SEs.Comparative analysis with full-order FE models in commercial softwaredemonstrates the advantages of the SE DQ-DT-TMM for linear rotor systems:(i)Accurately captures system dynamics usingonly a few primary modes.(ii)Achieves a 99.68%reduction in computational time for a beam model with 1120 elements and a99.98%reduction for a solid model with 75361 elements.(iii)Effectively recovers dynamic responses at any system node usingrecovery techniques.This research develops a computationally efficient framework for the transient analysis of large-scale rotorsystems,effectively addressing the challenges associated with high-dimensional DOF models in conventional DT-TMMs.
文摘基于对单元能量投影(element energy projection,EEP)法误差项的直接推导及分析,用EEP简约格式的解计算出略掉的误差项,反补后得到比简约格式高一阶精度的EEP超收敛计算的加强格式。该文以一维Galerkin有限元为例,给出EEP加强格式的算法公式和数学证明。理论分析和算例验证表明:对于m (≥1)次单元,采用EEP加强格式计算的内点位移和内点导数都具有h^(min(m+3,2m))阶的收敛精度,对系数特例问题二者甚至可以分别达到h^(min(m+5,2m))和h^(min(m+4,2m))阶的收敛精度。并对该法的进一步拓展作了讨论。
文摘目的建立超级微波消解-碰撞反应池电感耦合等离子体质谱法同时测定蔬菜中铅、砷、镉、铬等21种元素的方法。方法选择超级微波消解法进行样品预处理,以硝酸为消解液,运用具有八极杆反应池系统的电感耦合等离子体质谱仪,以铂锥作为采样锥,使用He气碰撞模式(5 m L/min),通过动能歧视和碰撞诱导解离进行干扰的消除。此外,选择包括低、中、高质量范围的^(6)Li、^(45)Sc、^(72)Ge、^(103)Rh、^(115)In、^(159)Tb、^(175)Lu、^(209)Bi元素作为内标,使用在线添加内标的方式进行干扰消除,并在数据分析时采用虚拟内标校正模式。结果在优化后的实验条件下,21种元素在一定的质量浓度区间内,其对应的信号强度与质量浓度呈线性关系。标准曲线线性良好,相关系数在0.999~1.000之间。方法的检出限在0.005~1.200 mg/kg,定量限在0.015~3.600 mg/kg。方法通过加标回收测定回收率,加标回收率在85.2%~119.9%之间。对处理后的蔬菜样品加入低、中、高3种不同浓度的标准,每份平行测定7次,测定值的相对标准偏差在1.03%~4.60%之间。结论通过本研究方法对蔬菜样品中21种元素进行测定,满足国家标准对各项技术指标参数的要求。该方法检出限低,选择性好,结果准确可靠,为蔬菜样品中多种元素分析测定提供了新的参考方法。
基金supported by the New Century Excellent Talents in University (No.NCET05-0796)National Natural Science Foundation of China (No.50625515)the Innovation Foundation of Southwest Jiaotong University (2008)
文摘Based on the experimental results of super-elastic NiTi alloy, a three-dimensional super-elastic constitutive model including both of stress-induced martensite transformation and plasticity is constructed in a framework of general inelasticity. In the proposed model, transformation hardening, reverse transformation of stress-induced martensite, elastic mismatch between the austenite and martensite phases, and temperature-dependence of transformation stress and elastic modulus of each phase are considered. The plastic yielding of martensite occurred under high stress is addressed by a bilinear isotropic hardening rule. Drucker-Prager-typed transformation surfaces are employed to describe the asymmetric behavior of NiTi alloy in tension and compression. The prediction capability of the proposed model is verified by comparing the simulated results with the correspondent experimental ones. Based on backward Euler＇s integration, a new expression of consistent tangent modulus is derived. The proposed model is then implemented into a finite element package ABAQUS by user-subroutine UMAT. Finally, the validity of such implementation was verified by some numerical samples.
文摘通过焊接热模拟研究了在超大线能量下焊接时Al元素、Mg元素和Ti元素含量对EH36高强船板钢热影响区粗晶区组织、性能的影响规律,采用Thermo-Calc热力学计算与SEM,EDS测试相结合的方法揭示了Al元素、Mg元素和Ti元素含量与母材中氧化物类型、尺寸、数量及粗晶区相变的关系.结果表明,Al_(2)O_(3)无法诱导针状铁素体相变,当Al元素质量分数低于0.005%时,钢中可形成Mg元素、Ti元素或其复合氧化物,可促进粗晶区针状铁素体相变.Mg元素和Ti元素联合添加时,当Mg元素质量分数由0.0042%降低为0.0013%,氧化物类型由MgO转变为Mg_(2)TiO_(4),经统计20个视场内的氧化物数量由408个提高到503个,平均直径由1.37μm减小到1.10μm,显著提高了非均匀形核的比表面积,抑制了晶界铁素体的形成,使t8/5=300 s时粗晶区热模拟试样-20℃冲击吸收能量由43 J提升到127 J.
