The Experts below are selected from a list of 13668 Experts worldwide ranked by ideXlab platform
Ulrich Bohle - One of the best experts on this subject based on the ideXlab platform.
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finite element analysis of piezoceramic components taking into account ferroelectric hysteresis behavior
International Journal of Solids and Structures, 2001Co-Authors: Marc Kamlah, Ulrich BohleAbstract:Abstract A simplifying macroscopic constitutive law for ferroelectric and ferroelastic hysteresis effects of piezoceramics is presented. After summarizing the uniaxial formulation motivated elsewhere (Kamlah, M., Tsakmakis, C., 1999. Int. J. Solids Struct. 36, 669–695; Kamlah, M., Bohle, U., Munz, D., Tsakmakis, Ch., 1997. Smart Structures and Materials 1997: Mathematics and Control in Smart Structures, Proceedings of SPIE, vol. 3039, 144–155), it is generalized to a three-dimensional tensorial formulation. The model has been implemented in the public domain finite element code PSU of Stuttgart University. The finite element analysis is carried out in a two-step scheme: First the purely dielectric boundary value problem is solved for the history of the electric potential. Second, prescribing this electric potential, the electro-mechanical Stress analysis for the mechanical boundary conditions yields the electro-mechanical Fields as, for instance, the mechanical Stress Field. In order to verify the capabilities of our tool, a multilayer-like actuator geometry is analyzed. It is shown that the remanent polarization remaining after poling gives rise to a non-vanishing distribution of the electric potential even it is reduced to zero at the electrodes. Concerning the residual Stresses present after poling, a Tensile Stress Field perpendicular to the direction of the electrodes can be found in the passive region of the actuator where so-called poling cracks are known to occur. It is concluded that our finite element tool is suitable for studying the influence of geometry and material parameters on the Stresses in critical regions of piezoceramic devices.
Madhura B M - One of the best experts on this subject based on the ideXlab platform.
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Rajanna S, Damage tolerance evaluation of wing in presence of large landing gear cutout through Stress analysis using
2015Co-Authors: Madhura B M, N. G. S. Udupa, Rajanna SAbstract:Aircraft is symbol of a high performance mechanical structure, which has the ability to fly with a very high structural safety record. Aircraft experiences variable loading in service. Rarely an aircraft will fail due to a static overload during its service life. For the continued airworthiness of an aircraft during its entire economic service life, fatigue and damage tolerance design, analysis, testing and service experience correlation play a pivotal role. The present study includes the Stress analysis and damage tolerance evaluation of the wing through a stiffened panel of the bottom skin with a landing gear cutout. Wing bottom skin experiences Tensile Stress Field during flight. Cutouts required for fuel access and landing gear opening and retraction in the bottom skin will introduce Stress concentration. Fatigue cracks will initiate from high Tensile Stress locations. An integral stiffened panel consisting a landing gear cutout is considered for the analysis. Stress analysis will identify the maximum Tensile Stress location in the panel. In a metallic structure fatigue manifests itself in the form of a crack which propagates. If the crack in a critical location goes unnoticed it could lead to a catastrophic failure of the airframe. A critical condition will occur when the Stress intensity factor (SIF) at the crack tip becomes equal to fracture toughness of the material. SIF calculations will be carried out for a crack with incremental crack lengths using MVCCI method. Analytical evaluation of the crack arrest capability of th
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damage tolerance evaluation of wing in presence of large landing gear cutout through Stress analysis using fem
International Journal of Research in Engineering and Technology, 2014Co-Authors: Madhura B M, S RajannaAbstract:Aircraft is symbol of a high performance mechanical structure, which has the ability to fly with a very high structural safety record. Aircraft experiences variable loading in se rvice. Rarely an aircraft will fail due to a static overload during its service life. For the continued airworthiness of an aircraft duri ng its entire economic service life, fatigue and da mage tolerance design, analysis, testing and service experience correlatio n play a pivotal role. The present study includes t he Stress analysis and damage tolerance evaluation of the wing through a stiffene d panel of the bottom skin with a landing gear cuto ut. Wing bottom skin experiences Tensile Stress Field during flight. Cut outs required for fuel access and landing gear open ing and retraction in the bottom skin will introduce Stress concentration. Fa tigue cracks will initiate from high Tensile Stress locations. An integral stiffened panel consisting a landing gear cutout is considere d for the analysis. Stress analysis will identify tmaximum Tensile Stress location in the panel. In a metallic structure fatigue manifests itself in the form of a crack which p ropagates. If the crack in a critical location goes unnoticed it could lead to a catastrophic failure of the airframe. A critical c ondition will occur when the Stress intensity factor (SIF) at the crack tip becomes equal to fracture toughness of the material. SI F calculations will be carried out for a crack with incremental crack lengths usin g MVCCI method. Analytical evaluation of the crack arrest capability of the stiffening members ahead of the crack tip will be c arried out.
Daniel A. Buttry - One of the best experts on this subject based on the ideXlab platform.
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repassivation behaviour of Stressed aluminium electrodes in aqueous chloride solutions
Corrosion Science, 2012Co-Authors: Changwen Mi, Nishant Lakhera, Demitris Kouris, Daniel A. ButtryAbstract:Abstract The combined influence of mechanical Stress and chemical environment on the pitting susceptibility of aluminium electrodes was studied by integrating open circuit potential measurements and electrochemical repassivation modelling. The transient degradation of aluminium oxide owing to a Tensile Stress Field and its subsequent repassivation are observed as an abrupt negative potential excursion followed by a slow decay of the corrosion potential back towards its initial value prior to the mechanical loading. Experiments were performed and an electrochemical repassivation model was established to quantitatively describe the dependence of oxide dissolution rate and the reciprocal of cathodic Tafel slope on chloride concentration.
Marc Kamlah - One of the best experts on this subject based on the ideXlab platform.
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finite element analysis of piezoceramic components taking into account ferroelectric hysteresis behavior
International Journal of Solids and Structures, 2001Co-Authors: Marc Kamlah, Ulrich BohleAbstract:Abstract A simplifying macroscopic constitutive law for ferroelectric and ferroelastic hysteresis effects of piezoceramics is presented. After summarizing the uniaxial formulation motivated elsewhere (Kamlah, M., Tsakmakis, C., 1999. Int. J. Solids Struct. 36, 669–695; Kamlah, M., Bohle, U., Munz, D., Tsakmakis, Ch., 1997. Smart Structures and Materials 1997: Mathematics and Control in Smart Structures, Proceedings of SPIE, vol. 3039, 144–155), it is generalized to a three-dimensional tensorial formulation. The model has been implemented in the public domain finite element code PSU of Stuttgart University. The finite element analysis is carried out in a two-step scheme: First the purely dielectric boundary value problem is solved for the history of the electric potential. Second, prescribing this electric potential, the electro-mechanical Stress analysis for the mechanical boundary conditions yields the electro-mechanical Fields as, for instance, the mechanical Stress Field. In order to verify the capabilities of our tool, a multilayer-like actuator geometry is analyzed. It is shown that the remanent polarization remaining after poling gives rise to a non-vanishing distribution of the electric potential even it is reduced to zero at the electrodes. Concerning the residual Stresses present after poling, a Tensile Stress Field perpendicular to the direction of the electrodes can be found in the passive region of the actuator where so-called poling cracks are known to occur. It is concluded that our finite element tool is suitable for studying the influence of geometry and material parameters on the Stresses in critical regions of piezoceramic devices.
Gao Longyang - One of the best experts on this subject based on the ideXlab platform.
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Study on the long-term behaviour of glass fibre in the Tensile Stress Field
Ceramics International, 2019Co-Authors: Dapeng Wang, Qingzhao Wang, Wang Zhiming, Huanying Jiang, Zhang Zhao, Liu Peng, Xu Chao, Gao LongyangAbstract:Abstract Glass fibre is a random network structure composed of [SiO4] tetrahedra. The structure contains a large number of defects, which act as crack initiation points. Under Tensile Stress, cracks undergo crack initiation, stable propagation, failure propagation, and fracture, and the Stress that begins after unstable propagation is called the critical fracture Stress. When the Stress is less than the critical value, the crack is subject to the force of chemical bonds during the crack propagation process, and crack arrest occurs. When the Stress is greater than the critical value, the glass fibre will undergo destructive fracture. In this paper, long-term Tensile tests were carried out on glass fibre and a glass fibre composite under different constant Tensile Stress conditions. The fracture times of the glass fibre and glass fibre composite under different Tensile Stresses were obtained, the critical fracture Stress of glass fibre was inferred, and the fracture mechanism was explained.
