Stiffened panels are commonly used in aircraft structures in order to resist high compression and shear forces with minimum total weight. Minimization of the weight is obtained by combining the optimum design parameters. The panel length, the stringer spacing, the skin thickness, the stringer section type and the stringer dimensions are some of the critical parameters which affect the global buckling allowable of the stiffened panel. The aim of this study is to develop a design tool and carry out a geometric optimization for panels having a large number of stringers. The panel length and the applied compression-shear loads are assumed to be given. In the preliminary part, a simplified panel with minimized number of stringers is found. This panel gives the same equivalent critical buckling load of panels having larger number of stringers. Additionally, the boundary conditions to be substituted for the outer stringer lines are studied. Then the effect of some critical design parameters on the buckling behavior is investigated. In the second phase, approximately six thousand finite element (FE) models are created and analyzed in ABAQUS FE program with the help of a script written in Phyton language. The script changes the parametric design variables and analyzes each skin-stringer model, and collect the buckling analysis results. These design variables and analysis results are grouped together in order to create an artificial neural network (ANN) in MATLAB NNTOOL toolbox. This process allows faster determination of buckling analysis results than the traditional FE analyses.
{"title":"Development of Structural Neural Network Design Tool for Buckling Behaviour of Skin-Stringer Structures Under Combined Compression and Shear Loading","authors":"A. Okul, E. Gürses","doi":"10.1115/IMECE2018-87970","DOIUrl":"https://doi.org/10.1115/IMECE2018-87970","url":null,"abstract":"Stiffened panels are commonly used in aircraft structures in order to resist high compression and shear forces with minimum total weight. Minimization of the weight is obtained by combining the optimum design parameters. The panel length, the stringer spacing, the skin thickness, the stringer section type and the stringer dimensions are some of the critical parameters which affect the global buckling allowable of the stiffened panel. The aim of this study is to develop a design tool and carry out a geometric optimization for panels having a large number of stringers. The panel length and the applied compression-shear loads are assumed to be given. In the preliminary part, a simplified panel with minimized number of stringers is found. This panel gives the same equivalent critical buckling load of panels having larger number of stringers. Additionally, the boundary conditions to be substituted for the outer stringer lines are studied. Then the effect of some critical design parameters on the buckling behavior is investigated. In the second phase, approximately six thousand finite element (FE) models are created and analyzed in ABAQUS FE program with the help of a script written in Phyton language. The script changes the parametric design variables and analyzes each skin-stringer model, and collect the buckling analysis results. These design variables and analysis results are grouped together in order to create an artificial neural network (ANN) in MATLAB NNTOOL toolbox. This process allows faster determination of buckling analysis results than the traditional FE analyses.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133459488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cycloidal rotors have the inherent ability to provide vectorized thrust with fast reaction times. However, their present efficiency levels restricts their routinely use as propulsion elements for air-vehicles. Efforts have been made to improve the performance of cycloidal rotors through the optimal combination of its geometric parameters. In the present work the performance improvement of cycloidal rotors is demonstrated using a different approach, namely by imposing an unsteady change on the dynamics and structure of the vortices developed around the blades. This required change on the flow field, around the blades, was applied by adding an harmonic vibration to the traditional cycloidal movement of the blades, thus causing the blades to vibrate as they describe their oscillating pitch movement. This research on the effect of harmonic vibration, on lift and drag coefficients, was done first for a single blade profile, and later for a full cycloidal rotor, and is based on the Takens reconstruction theorem and Poincaré map. Therefore, diverse test cases and conditions were considered: a single static airfoil, an oscillating blade profile, and a complete cycloidal rotor. We concluded that the optimal combination of harmonic vibration parameters, specifically; amplitude, phase angle and vibration frequency, under adequately tuned design conditions, can have a beneficial effect on cycloidal rotor performance.
{"title":"Effects of Harmonic Vibration on Cycloidal Rotor Performance","authors":"Jakson Augusto Léger Monteiro, José C. Páscoa","doi":"10.1115/IMECE2018-87103","DOIUrl":"https://doi.org/10.1115/IMECE2018-87103","url":null,"abstract":"Cycloidal rotors have the inherent ability to provide vectorized thrust with fast reaction times. However, their present efficiency levels restricts their routinely use as propulsion elements for air-vehicles. Efforts have been made to improve the performance of cycloidal rotors through the optimal combination of its geometric parameters. In the present work the performance improvement of cycloidal rotors is demonstrated using a different approach, namely by imposing an unsteady change on the dynamics and structure of the vortices developed around the blades. This required change on the flow field, around the blades, was applied by adding an harmonic vibration to the traditional cycloidal movement of the blades, thus causing the blades to vibrate as they describe their oscillating pitch movement. This research on the effect of harmonic vibration, on lift and drag coefficients, was done first for a single blade profile, and later for a full cycloidal rotor, and is based on the Takens reconstruction theorem and Poincaré map. Therefore, diverse test cases and conditions were considered: a single static airfoil, an oscillating blade profile, and a complete cycloidal rotor. We concluded that the optimal combination of harmonic vibration parameters, specifically; amplitude, phase angle and vibration frequency, under adequately tuned design conditions, can have a beneficial effect on cycloidal rotor performance.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124005828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thermal Barrier Coatings have been widely used in modern turbine engines to protect the nickel based metal substrate from the high temperature service conditions, 1600–1800 K. In this study, some of the failure mechanisms of typical Air Plasma Sprayed Thermal Barrier Coatings (TBC) used in after-burner structures composed of three major layers: Inconel 718 substrate, NiCrAlY based metallic bond coat (BC) and Yttria Stabilized Zirconia (YSZ) based ceramic top coat (TC) are investigated. Investigation of the cracking mechanism of TBC in terms of design and performance is very important because the behavior of TBCs on ductile metallic substrates is brittle. To this end, four-point bending experiments conducted in Kütükoğlu (2015) is analyzed by using the Extended Finite Element Method (XFEM). All the analyses are conducted with the commercial finite element software ABAQUS. Three different models with varying TC and BC thicknesses are studied under four-point bending. It is observed that multiple vertical cracks are initiated in the TC. Cracks initiate at the top of YSZ and propagate through the whole TC. It is observed that the average crack spacing increases with the increasing thickness of the TC. Numerical results are found to be consistent with the experimental results. In other words, the average crack spacing for three different models are similar with the experimental results.
{"title":"Finite Element Modelling of TBC Failure Mechanisms by Using XFEM","authors":"Safa Mesut Bostancı, E. Gürses, D. Coker","doi":"10.1115/IMECE2018-86576","DOIUrl":"https://doi.org/10.1115/IMECE2018-86576","url":null,"abstract":"Thermal Barrier Coatings have been widely used in modern turbine engines to protect the nickel based metal substrate from the high temperature service conditions, 1600–1800 K. In this study, some of the failure mechanisms of typical Air Plasma Sprayed Thermal Barrier Coatings (TBC) used in after-burner structures composed of three major layers: Inconel 718 substrate, NiCrAlY based metallic bond coat (BC) and Yttria Stabilized Zirconia (YSZ) based ceramic top coat (TC) are investigated. Investigation of the cracking mechanism of TBC in terms of design and performance is very important because the behavior of TBCs on ductile metallic substrates is brittle. To this end, four-point bending experiments conducted in Kütükoğlu (2015) is analyzed by using the Extended Finite Element Method (XFEM). All the analyses are conducted with the commercial finite element software ABAQUS. Three different models with varying TC and BC thicknesses are studied under four-point bending. It is observed that multiple vertical cracks are initiated in the TC. Cracks initiate at the top of YSZ and propagate through the whole TC. It is observed that the average crack spacing increases with the increasing thickness of the TC. Numerical results are found to be consistent with the experimental results. In other words, the average crack spacing for three different models are similar with the experimental results.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122789250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Composite materials are becoming increasingly common in the aerospace industry. In order for simulation and modeling to accurately predict failure of composites, a material model based on observed damage mechanisms is required. Composites are commonly classified into four damage categories based on the composite constituents and their loading condition: fiber tension, fiber compression, matrix tension, and matrix compression. Previous work identified a compact compression (CC) specimen as a suitable option for isolating matrix compression damage. However upon continued testing, stable crack propagation in the specimen was limited to a relatively low material failure ratio (σCompressive/σTension). This paper presents specimen geometry that can isolate matrix compression damage in materials with a failure ratio greater than two, the limit of the compact compression specimens. Initial specimen selection used the compact compression specimens from previous research and added additional specimens based on commonly used compressions specimens for different materials. The added specimens included center notched compression (CNC), edge notch compression (ENC), and four-point bending (4PB). All specimens were evaluated experimentally with the success criteria of controlled propagation of a matrix compression crack. In addition to propagating a controlled matrix compression crack, specimens were required to have a visible region around the stress concentrator to allow for digital image correlation (DIC) image capture during the experiments. The specimens were manufactured from a carbon fiber reinforced polymer (CFRP) with a failure ratio greater than six. CC and 4PB specimens were unable to produce a compression crack before any other failure methods were present. CNC specimens produced an unstable compression crack that progressed from the notch to the edge of the specimen too rapidly to acquire meaningful crack propagation data. ENC specimens showed some ability to stably propagate a crack, however some tests resulted in an unstable crack propagation similar to the CNC specimens. In order to increase the test repeatability, a tapered thickness was added to the specimen around the notch tip. The resulting tapered ENC (TENC) produced repeatable controlled matrix compression crack propagation. Ultimately, the specimen fails when the crack has propagated through the entire width of the specimen. TENC specimens show promise for isolating matrix compression damage in materials with high failure ratios. Continued testing of CFRP with TENC specimens could be used to refine the material model for finite element analysis.
{"title":"Experimental Specimen for Classification of Matrix Compression Damage in Carbon Fiber Reinforced Polymers","authors":"Taylor J. Rawlings, K. Carpenter, J. Parmigiani","doi":"10.1115/IMECE2018-87132","DOIUrl":"https://doi.org/10.1115/IMECE2018-87132","url":null,"abstract":"Composite materials are becoming increasingly common in the aerospace industry. In order for simulation and modeling to accurately predict failure of composites, a material model based on observed damage mechanisms is required. Composites are commonly classified into four damage categories based on the composite constituents and their loading condition: fiber tension, fiber compression, matrix tension, and matrix compression. Previous work identified a compact compression (CC) specimen as a suitable option for isolating matrix compression damage. However upon continued testing, stable crack propagation in the specimen was limited to a relatively low material failure ratio (σCompressive/σTension). This paper presents specimen geometry that can isolate matrix compression damage in materials with a failure ratio greater than two, the limit of the compact compression specimens. Initial specimen selection used the compact compression specimens from previous research and added additional specimens based on commonly used compressions specimens for different materials. The added specimens included center notched compression (CNC), edge notch compression (ENC), and four-point bending (4PB). All specimens were evaluated experimentally with the success criteria of controlled propagation of a matrix compression crack. In addition to propagating a controlled matrix compression crack, specimens were required to have a visible region around the stress concentrator to allow for digital image correlation (DIC) image capture during the experiments. The specimens were manufactured from a carbon fiber reinforced polymer (CFRP) with a failure ratio greater than six. CC and 4PB specimens were unable to produce a compression crack before any other failure methods were present. CNC specimens produced an unstable compression crack that progressed from the notch to the edge of the specimen too rapidly to acquire meaningful crack propagation data. ENC specimens showed some ability to stably propagate a crack, however some tests resulted in an unstable crack propagation similar to the CNC specimens. In order to increase the test repeatability, a tapered thickness was added to the specimen around the notch tip. The resulting tapered ENC (TENC) produced repeatable controlled matrix compression crack propagation. Ultimately, the specimen fails when the crack has propagated through the entire width of the specimen. TENC specimens show promise for isolating matrix compression damage in materials with high failure ratios. Continued testing of CFRP with TENC specimens could be used to refine the material model for finite element analysis.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126548317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The recent introduction of spike in the frontal region of high speed reentry vehicles has brought a tremendous improvement in space activities in the world. The major issue that the spikes resolves is aero heating of re-entry vehicles. Moreover, it preserves structural integrity and avoids damage. Usage of spike is economical and effective over different kinds of thermal protection system. Previous investigation on spiked re-entry vehicles leads to a conclusion that the Blunt and Snap spikes resulted in better reduction of temperature at nose of re-entry vehicle. This paper deals with geometry optimization of blunt and snap spike specifically the length, which is varied as L/8, L/4 and 3L/8 respectively where L is the length of the vehicle. ANSYS 17.2 FLUENT solver is incorporated for analysis purpose and the results are compared among the three different length spike re-entry vehicles. Modal analysis has also been carried out and natural frequency of spikes are obtained. This would provide a way to accept the safe and economical design with better thermal protection of the high-speed space vehicle.
{"title":"Recent Advancements in Spikes Used in Hypersonic Re-Entry Vehicles by Using CFD","authors":"E. Madhukar, Harish Panjagala","doi":"10.1115/IMECE2018-86550","DOIUrl":"https://doi.org/10.1115/IMECE2018-86550","url":null,"abstract":"The recent introduction of spike in the frontal region of high speed reentry vehicles has brought a tremendous improvement in space activities in the world. The major issue that the spikes resolves is aero heating of re-entry vehicles. Moreover, it preserves structural integrity and avoids damage. Usage of spike is economical and effective over different kinds of thermal protection system. Previous investigation on spiked re-entry vehicles leads to a conclusion that the Blunt and Snap spikes resulted in better reduction of temperature at nose of re-entry vehicle. This paper deals with geometry optimization of blunt and snap spike specifically the length, which is varied as L/8, L/4 and 3L/8 respectively where L is the length of the vehicle. ANSYS 17.2 FLUENT solver is incorporated for analysis purpose and the results are compared among the three different length spike re-entry vehicles. Modal analysis has also been carried out and natural frequency of spikes are obtained. This would provide a way to accept the safe and economical design with better thermal protection of the high-speed space vehicle.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126402340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Detailed numerical investigations on the unsteady flow excitation characteristics and mechanical performance under unsteady surface pressure of last turbine stage long blade are conducted by applying sliding interface method and fluid-structure interaction approach. Unsteady aerodynamic performance of turbine stage is analyzed through solving the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solution and k-ε turbulent model using commercial CFD software ANSYS-CFX. The computational domains include last stage stator domain, rotor domain, shroud domain and curved diffusor. Unsteady pressure on long blade surfaces in every time step is transferred to the mechanical grids of long blade after interpolated in the fluid-solid interface. The mechanical performance of long blade with damper shroud and part-span connector (PSC) is obtained using finite element method (FEM) while considering the unsteady aerodynamic load and nonlinear contact between adjacent damping tip-shroud and PSC. The numerical results show that static pressure on long blade surface presents obvious periodic fluctuation; with the decrease of mass flow, blade loading reduces obviously and separation vortex appears in the diffusor and extends to the rotor passages; the frequency of separation vortex is about 126 Hz; the maximum displacement and maximum Von-Mises stress of long blade both show periodic features.
采用滑动界面法和流固耦合法对末级长叶片在非定常面压作用下的非定常流场激励特性和力学性能进行了详细的数值研究。利用商业CFD软件ANSYS-CFX，通过求解三维reynolds - average Navier-Stokes (RANS)解和k-ε湍流模型，分析了涡轮级的非定常气动性能。计算域包括末级定子域、转子域、叶冠域和弯曲扩散域。每个时间步长叶片表面的非定常压力在流固界面内插值后传递到长叶片的机械网格上。考虑非定常气动载荷和相邻阻尼叶冠与部分跨连接件之间的非线性接触，采用有限元法对带阻尼叶冠和部分跨连接件的长叶片进行了力学性能分析。数值计算结果表明，长叶片表面静压存在明显的周期性波动;随着质量流量的减小，叶片负荷明显减小，分离涡在扩压器内出现并向转子通道延伸;分离涡的频率约为126 Hz;长叶片的最大位移和最大Von-Mises应力均呈现周期性特征。
{"title":"Investigations on Unsteady Flow Excitation and Mechanical Performance of Last Turbine Stage Long Blade Using Fluid-Structure Interaction Method","authors":"Jun Li, Zhigang Li, Liming Song, Qinghua Deng","doi":"10.1115/IMECE2018-86950","DOIUrl":"https://doi.org/10.1115/IMECE2018-86950","url":null,"abstract":"Detailed numerical investigations on the unsteady flow excitation characteristics and mechanical performance under unsteady surface pressure of last turbine stage long blade are conducted by applying sliding interface method and fluid-structure interaction approach. Unsteady aerodynamic performance of turbine stage is analyzed through solving the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solution and k-ε turbulent model using commercial CFD software ANSYS-CFX. The computational domains include last stage stator domain, rotor domain, shroud domain and curved diffusor. Unsteady pressure on long blade surfaces in every time step is transferred to the mechanical grids of long blade after interpolated in the fluid-solid interface. The mechanical performance of long blade with damper shroud and part-span connector (PSC) is obtained using finite element method (FEM) while considering the unsteady aerodynamic load and nonlinear contact between adjacent damping tip-shroud and PSC. The numerical results show that static pressure on long blade surface presents obvious periodic fluctuation; with the decrease of mass flow, blade loading reduces obviously and separation vortex appears in the diffusor and extends to the rotor passages; the frequency of separation vortex is about 126 Hz; the maximum displacement and maximum Von-Mises stress of long blade both show periodic features.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115451406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Bertolino, Rocco Gentile, G. Jacazio, F. Marino, M. Sorli
Seals are widely used in hydraulic power systems to prevent fluid leakages. However, several types of degradation can decrease the performance of these components such as wear, which induces changes in the geometry of the cross-section area, influencing their sealing capability. Over the years, their behaviour has been primarily investigated with several theoretical and experimental researches. All these valuable results can be considered as a starting point for further investigations on the interaction between seals and the complete hydraulic equipment and on the root of seals degradation. This article proposes a physical model of performance degradation acting on dynamic seals of an electro-hydraulic servo-actuator (EHSA) ram for primary flight controls. In this article, a dynamic non-linear seals degradation model has been developed, based on the Hart-Smith hyperelasticity model, which physically describes the stress and strain of “rubber-like” materials. Similarly, wearing has been assessment by using the Archard’s equation. Furthermore, different operating temperatures have been considered to analyze the effect on seals performances. The integration between the mentioned seals degradation model and the high-fidelity model of the complete EHSA allows to evaluate the influence of various wear levels on the actuator behaviour. This research activity is inserted into a more extensive project of Prognostic and Health Management (PHM) of EHSAs. The results of the proposed simulations reveal how the performance of an EHSA can be affected by seals degradations.
{"title":"EHSA Primary Flight Controls Seals Wear Degradation Model","authors":"A. Bertolino, Rocco Gentile, G. Jacazio, F. Marino, M. Sorli","doi":"10.1115/IMECE2018-87080","DOIUrl":"https://doi.org/10.1115/IMECE2018-87080","url":null,"abstract":"Seals are widely used in hydraulic power systems to prevent fluid leakages. However, several types of degradation can decrease the performance of these components such as wear, which induces changes in the geometry of the cross-section area, influencing their sealing capability. Over the years, their behaviour has been primarily investigated with several theoretical and experimental researches. All these valuable results can be considered as a starting point for further investigations on the interaction between seals and the complete hydraulic equipment and on the root of seals degradation.\u0000 This article proposes a physical model of performance degradation acting on dynamic seals of an electro-hydraulic servo-actuator (EHSA) ram for primary flight controls. In this article, a dynamic non-linear seals degradation model has been developed, based on the Hart-Smith hyperelasticity model, which physically describes the stress and strain of “rubber-like” materials. Similarly, wearing has been assessment by using the Archard’s equation. Furthermore, different operating temperatures have been considered to analyze the effect on seals performances.\u0000 The integration between the mentioned seals degradation model and the high-fidelity model of the complete EHSA allows to evaluate the influence of various wear levels on the actuator behaviour. This research activity is inserted into a more extensive project of Prognostic and Health Management (PHM) of EHSAs. The results of the proposed simulations reveal how the performance of an EHSA can be affected by seals degradations.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115068300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A global-local approach has been developed for the elasto-plastic analysis of thin-walled metal structures, which interfaces between commercial finite element software and advanced structural theories based on the Carrera Unified Formulation (CUF). The structure is modeled in CUF using the Component-Wise approach where Lagrange polynomials enhance the cross-section kinematics of the beam element. The von Mises constitutive model with isotropic work hardening is used to describe the material nonlinearity. Two types of the global-local approach have been discussed: (1) elastoplasticity is considered in both global and local analyses, and (2) a linear global analysis is followed by a nonlinear local analysis. It is shown that the second version maintains the accuracy of the solution for cases where the plastic zone is localized within the structure. The described approach results in a significant reduction in the computational size of the problem, compared to standard 3D finite element analysis.
{"title":"A Global-Local Strategy for the Elastoplastic Analysis of Complex Metallic Structures via Component-Wise Approach","authors":"E. Carrera, I. Kaleel, M. Nagaraj, M. Petrolo","doi":"10.1115/IMECE2018-86564","DOIUrl":"https://doi.org/10.1115/IMECE2018-86564","url":null,"abstract":"A global-local approach has been developed for the elasto-plastic analysis of thin-walled metal structures, which interfaces between commercial finite element software and advanced structural theories based on the Carrera Unified Formulation (CUF). The structure is modeled in CUF using the Component-Wise approach where Lagrange polynomials enhance the cross-section kinematics of the beam element. The von Mises constitutive model with isotropic work hardening is used to describe the material nonlinearity. Two types of the global-local approach have been discussed: (1) elastoplasticity is considered in both global and local analyses, and (2) a linear global analysis is followed by a nonlinear local analysis. It is shown that the second version maintains the accuracy of the solution for cases where the plastic zone is localized within the structure. The described approach results in a significant reduction in the computational size of the problem, compared to standard 3D finite element analysis.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127341764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a systematic numerical investigation of guided wave generation, propagation, interaction with damage, and reception in anisotropic piezoelectric composite plates. This approach employs piezoelectric composite materials as both load bearing and sensing elements. Finite element modal analysis of a plate unit cell with Bloch-Floquet boundary condition is performed to understand the guided wave propagation characteristics in piezoelectric composite plates. The guided wave generation and tuning characteristics are investigated using the harmonic analysis model with absorbing boundary conditions. The relationship between the generated wave modes and the laminate layup orientations is studied. Subsequently, an impact damage is introduced and modeled as a group of cone shape delaminated layers and stiffness losses within the layers through the thickness direction. 2D and 3D transient dynamic coupled-field finite element models are constructed to simulate the procedure of guided wave generation, propagation, interaction with the impact damage, and reception in an orthotropic piezoelectric composite plate using the commercial finite element software (ANSYS). In addition, Contact Acoustic Nonlinearity (CAN) is simulated via time domain transient analysis. Advanced signal processing techniques are used to extract the distinctive nonlinear features. The frequency-wavenumber analysis is further adopted to decipher wave modes and frequency components in the scattered wave field. This paper finishes with concluding remarks and suggestions for future work.
{"title":"Guided Wave Generation and Propagation in Self-Sensing Piezoelectric Composite Plates for Structural Health Monitoring","authors":"Junzhen Wang, Yanfeng Shen","doi":"10.1115/IMECE2018-86229","DOIUrl":"https://doi.org/10.1115/IMECE2018-86229","url":null,"abstract":"This paper presents a systematic numerical investigation of guided wave generation, propagation, interaction with damage, and reception in anisotropic piezoelectric composite plates. This approach employs piezoelectric composite materials as both load bearing and sensing elements. Finite element modal analysis of a plate unit cell with Bloch-Floquet boundary condition is performed to understand the guided wave propagation characteristics in piezoelectric composite plates. The guided wave generation and tuning characteristics are investigated using the harmonic analysis model with absorbing boundary conditions. The relationship between the generated wave modes and the laminate layup orientations is studied. Subsequently, an impact damage is introduced and modeled as a group of cone shape delaminated layers and stiffness losses within the layers through the thickness direction. 2D and 3D transient dynamic coupled-field finite element models are constructed to simulate the procedure of guided wave generation, propagation, interaction with the impact damage, and reception in an orthotropic piezoelectric composite plate using the commercial finite element software (ANSYS). In addition, Contact Acoustic Nonlinearity (CAN) is simulated via time domain transient analysis. Advanced signal processing techniques are used to extract the distinctive nonlinear features. The frequency-wavenumber analysis is further adopted to decipher wave modes and frequency components in the scattered wave field. This paper finishes with concluding remarks and suggestions for future work.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122388483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An important role in the design of structure is represented by the buckling analysis. The loading and service conditions, in which structures usually work, may significantly afflict their equilibrium state. This aspect often forces the design engineers to perform an accurate buckling analysis, in order to calculate critical loads of the structure. In fact, this critical load causes a sudden change of the structure, leading to a radical decrease in the loadcarrying capability. For these reasons, buckling analysis of beam-columns has been widely investigated in the past and recent years. One of the most important experimental technology to calculate the critical buckling load of structures if represented by the Vibration Correlation Technique (VCT). It allows determining equivalent boundary conditions and buckling load for several types of structures and its strength is represented by the fact that it is a non-destructive methodology: essentially, the stability loads were determined by interpolating, until singularity, the natural frequency of the structure subjected to progressive higher loadings, without reaching the instability point. VCT is already widely used for beam, plate and shell structures. This paper intends to assess a numerical simulation of the experimental data needed for the Vibration Correlation Technique. The solution proposed is developed in the domain of the Carrera Unified Formulation (CUF), according to which theories of structures can degenerate into a generalized kinematics that makes use of an arbitrary expansion of the generalized variables. Moreover, in order to reproduce results obtained in an experimental way, when large displacement and rotations may occur, geometrical nonlineatities have been taken into account. Thus, a finite element approximation is used along with a path-following method to perform nonlinear analyses. Different types of structures have been analyzed, made with metallic and composite materials, and some results are compared with others found in the VCT literature. Results show how this methodology can well evaluate the natural frequencies on the structure in a geometrical nonlinear framework, and so also the critical buckling load.
{"title":"Virtual Vibration Correlation Technique (VCT) for Nonlinear Analysis of Metallic and Composite Structures","authors":"A. Pagani, R. Augello, E. Carrera","doi":"10.1115/IMECE2018-86674","DOIUrl":"https://doi.org/10.1115/IMECE2018-86674","url":null,"abstract":"An important role in the design of structure is represented by the buckling analysis. The loading and service conditions, in which structures usually work, may significantly afflict their equilibrium state. This aspect often forces the design engineers to perform an accurate buckling analysis, in order to calculate critical loads of the structure. In fact, this critical load causes a sudden change of the structure, leading to a radical decrease in the loadcarrying capability. For these reasons, buckling analysis of beam-columns has been widely investigated in the past and recent years.\u0000 One of the most important experimental technology to calculate the critical buckling load of structures if represented by the Vibration Correlation Technique (VCT). It allows determining equivalent boundary conditions and buckling load for several types of structures and its strength is represented by the fact that it is a non-destructive methodology: essentially, the stability loads were determined by interpolating, until singularity, the natural frequency of the structure subjected to progressive higher loadings, without reaching the instability point. VCT is already widely used for beam, plate and shell structures.\u0000 This paper intends to assess a numerical simulation of the experimental data needed for the Vibration Correlation Technique. The solution proposed is developed in the domain of the Carrera Unified Formulation (CUF), according to which theories of structures can degenerate into a generalized kinematics that makes use of an arbitrary expansion of the generalized variables. Moreover, in order to reproduce results obtained in an experimental way, when large displacement and rotations may occur, geometrical nonlineatities have been taken into account. Thus, a finite element approximation is used along with a path-following method to perform nonlinear analyses.\u0000 Different types of structures have been analyzed, made with metallic and composite materials, and some results are compared with others found in the VCT literature. Results show how this methodology can well evaluate the natural frequencies on the structure in a geometrical nonlinear framework, and so also the critical buckling load.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"85 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128619834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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