Pub Date : 2017-11-03DOI: 10.2495/CMEM-V6-N4-827-834
H. Horii
{"title":"VEHICLE OCCUPANT RESTRAINT SYSTEM DESIGN UNDER UNCERTAINTY BY USING MULTI-OBJECTIVE ROBUST DESIGN OPTIMIZATION","authors":"H. Horii","doi":"10.2495/CMEM-V6-N4-827-834","DOIUrl":"https://doi.org/10.2495/CMEM-V6-N4-827-834","url":null,"abstract":"","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"33 4","pages":"827-834"},"PeriodicalIF":0.0,"publicationDate":"2017-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72596767","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}
Pub Date : 2017-11-03DOI: 10.2495/CMEM-V6-N4-691-702
M. Goto, Takaei Yamamoto, Seung-Zeon Han, J. Ahn, J. Kitamura, Kusno Kamil, T. Yakushiji, Toshiki Masuda, T. Iwamura, Sangshik Kim
The formation mechanism of inclined fatigue cracks in ultrafine-grained Cu processed by equal channel angular pressing was studied by using a smooth specimen with a small blind hole. The crack growth direc- tion depended on the location of drilling hole along the circumferential direction of the round bar specimen and on the applied stress amplitudes. Although the low-cycle fatigue crack growth paths inclined 45° and 90° to the loading-axis were observed in the different locations on the surface, crack faces in these cracks were extended along one set of maximum shear stress planes, corresponding to the shear plane of the final processing. To study the crack growth behaviour, surface damage around the crack paths formed by the two-step fatigue stress tests was observed. Profile of crack face was examined, showing the aspect ratios ( b / a ) of b / a = 0.38 and 1.10 for the cracks with 45° and 90° inclined path directions with respect to the loading axis, respectively. The role of the microstructure and deformation mode at the crack-tip areas on the formation of crack paths parallel to the shear plane of the final pressing was discussed in terms of the microstructural evolution caused by cyclic stressing and the mixed-mode stress intensity factor.
采用带小盲孔的光滑试样，研究了等径角挤压超细晶Cu材料倾斜疲劳裂纹的形成机理。裂纹扩展方向与钻孔沿圆杆试件周向的位置和外加应力幅值有关。虽然在表面不同位置观察到向加载轴倾斜45°和90°的低周疲劳裂纹扩展路径，但这些裂纹中的裂纹面沿一组最大剪应力面扩展，对应于最终加工的剪切面。为了研究裂纹扩展行为，对两步疲劳应力试验形成的裂纹路径周围的表面损伤进行了观察。对裂纹面剖面图进行了检测，结果表明，相对于加载轴，路径方向为45°和90°的裂纹长径比(b / a)分别为b / a = 0.38和1.10。从循环应力和混合模态应力强度因子的微观组织演化角度，讨论了裂纹尖端区域的微观组织和变形模式对平行于终压剪切面裂纹路径形成的影响。
{"title":"RELATIONSHIP BETWEEN SHEAR PLANE OF THE FINAL PRESSING AND FATIGUE CRACK GROWTH BEHAVIOUR OF ROUND-BAR SPECIMENS OF CU PROCESSED BY ECAP","authors":"M. Goto, Takaei Yamamoto, Seung-Zeon Han, J. Ahn, J. Kitamura, Kusno Kamil, T. Yakushiji, Toshiki Masuda, T. Iwamura, Sangshik Kim","doi":"10.2495/CMEM-V6-N4-691-702","DOIUrl":"https://doi.org/10.2495/CMEM-V6-N4-691-702","url":null,"abstract":"The formation mechanism of inclined fatigue cracks in ultrafine-grained Cu processed by equal channel angular pressing was studied by using a smooth specimen with a small blind hole. The crack growth direc- tion depended on the location of drilling hole along the circumferential direction of the round bar specimen and on the applied stress amplitudes. Although the low-cycle fatigue crack growth paths inclined 45° and 90° to the loading-axis were observed in the different locations on the surface, crack faces in these cracks were extended along one set of maximum shear stress planes, corresponding to the shear plane of the final processing. To study the crack growth behaviour, surface damage around the crack paths formed by the two-step fatigue stress tests was observed. Profile of crack face was examined, showing the aspect ratios ( b / a ) of b / a = 0.38 and 1.10 for the cracks with 45° and 90° inclined path directions with respect to the loading axis, respectively. The role of the microstructure and deformation mode at the crack-tip areas on the formation of crack paths parallel to the shear plane of the final pressing was discussed in terms of the microstructural evolution caused by cyclic stressing and the mixed-mode stress intensity factor.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"38 1","pages":"691-702"},"PeriodicalIF":0.0,"publicationDate":"2017-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73216242","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}
Pub Date : 2017-11-03DOI: 10.2495/CMEM-V6-N4-625-634
Y. Jaluria
This paper focuses on combined experimental and numerical approaches to model thermal processes and obtain accurate results on system behaviour and performance. Interest lies in obtaining repeatable and dependable inputs for choosing appropriate conditions and parameters for enhancing the efficiency and the desired output. These results can also form the basis for system design and optimization. Several fundamental and practical problems are considered and typical results presented to discuss the implications and applications of this methodology. Circumstances where experimental data are used to validate the model, provide greater physical insight and define the boundary conditions, thus allowing the numerical simulation to be carried out, are also presented. Results from a concurrent, or parallel, simulation and experimentation approach are also presented to indicate the usefulness of such a strategy. It is stressed that experimental data are indispensable in obtaining accurate and realistic results for complex practical problems involving thermal transport processes.
{"title":"COMBINED EXPERIMENTAL AND NUMERICAL APPROACH TO MODEL, DESIGN AND OPTIMIZE THERMAL PROCESSES","authors":"Y. Jaluria","doi":"10.2495/CMEM-V6-N4-625-634","DOIUrl":"https://doi.org/10.2495/CMEM-V6-N4-625-634","url":null,"abstract":"This paper focuses on combined experimental and numerical approaches to model thermal processes and obtain accurate results on system behaviour and performance. Interest lies in obtaining repeatable and dependable inputs for choosing appropriate conditions and parameters for enhancing the efficiency and the desired output. These results can also form the basis for system design and optimization. Several fundamental and practical problems are considered and typical results presented to discuss the implications and applications of this methodology. Circumstances where experimental data are used to validate the model, provide greater physical insight and define the boundary conditions, thus allowing the numerical simulation to be carried out, are also presented. Results from a concurrent, or parallel, simulation and experimentation approach are also presented to indicate the usefulness of such a strategy. It is stressed that experimental data are indispensable in obtaining accurate and realistic results for complex practical problems involving thermal transport processes.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"69 1","pages":"625-634"},"PeriodicalIF":0.0,"publicationDate":"2017-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74504839","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}
Pub Date : 2017-11-03DOI: 10.2495/cmem-v6-n4-785-796
Julian Belz, K. Bamberger, O. Nelles, T. Carolus
A methodology for goal-oriented active learning with local model networks (LMNs) is proposed. It is applied for the generation of training data for a computational fluid dynamics (CFD) metamodel. The used metamodel is an LMN trained with data originating from CFD simulations. This metamodel describes the total-to-static efficiency for a given design point, defined by the pressure rise at a specific volume flow rate, depending on geometrical parameters of an impeller of centrifugal fans. The goaloriented nature originates from three main targets that are addressed simultaneously during the active learning procedure. (I) The concentration on possibly optimal geometries and (II) the focus on areas in the input space where the metamodel’s performance is considered to be worst. Additionally, (III) new measurements should differ from already simulated geometries as much as possible. With these goals three important issues in modeling are addressed simultaneously: (I) optimality, (II) model bias, (III) model variance/uniformly space-filling property. In order to fulfill all goals, special properties of LMNs are utilized (embedded approach). Through the structure of LMNs, it is possible to assign local model errors to specific areas in the input space. New measurements are preferably placed in such high-error regions, while concentrating on presumably optimal geometries that differ most from the ones already available in the training data. In the field of fluid machinery, the range of achievable design points is usually identified by the Cordier diagram. While the design points obtained in the passive learning phase fairly agree with the standard Cordier diagram, an extension of achievable design points was observed due to the proposed goal-oriented learning strategy. In addition, the total-to-static efficiency could be improved in some areas of the Cordier diagram.
{"title":"GOAL-ORIENTED ACTIVE LEARNING WITH LOCAL MODEL NETWORKS","authors":"Julian Belz, K. Bamberger, O. Nelles, T. Carolus","doi":"10.2495/cmem-v6-n4-785-796","DOIUrl":"https://doi.org/10.2495/cmem-v6-n4-785-796","url":null,"abstract":"A methodology for goal-oriented active learning with local model networks (LMNs) is proposed. It is applied for the generation of training data for a computational fluid dynamics (CFD) metamodel. The used metamodel is an LMN trained with data originating from CFD simulations. This metamodel describes the total-to-static efficiency for a given design point, defined by the pressure rise at a specific volume flow rate, depending on geometrical parameters of an impeller of centrifugal fans. The goaloriented nature originates from three main targets that are addressed simultaneously during the active learning procedure. (I) The concentration on possibly optimal geometries and (II) the focus on areas in the input space where the metamodel’s performance is considered to be worst. Additionally, (III) new measurements should differ from already simulated geometries as much as possible. With these goals three important issues in modeling are addressed simultaneously: (I) optimality, (II) model bias, (III) model variance/uniformly space-filling property. In order to fulfill all goals, special properties of LMNs are utilized (embedded approach). Through the structure of LMNs, it is possible to assign local model errors to specific areas in the input space. New measurements are preferably placed in such high-error regions, while concentrating on presumably optimal geometries that differ most from the ones already available in the training data. In the field of fluid machinery, the range of achievable design points is usually identified by the Cordier diagram. While the design points obtained in the passive learning phase fairly agree with the standard Cordier diagram, an extension of achievable design points was observed due to the proposed goal-oriented learning strategy. In addition, the total-to-static efficiency could be improved in some areas of the Cordier diagram.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"21 1","pages":"785-796"},"PeriodicalIF":0.0,"publicationDate":"2017-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90839138","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}
Pub Date : 2017-11-03DOI: 10.2495/CMEM-V6-N4-764-771
J. Jiménez‐Alonso, A. Sáez, E. Caetano, Á. Cunha
In this paper a simplified biomechanical crowd-structure interaction model is proposed and validated in order to analyse the lateral lock-in phenomenon on real footbridges. The proposed crowd-structure interaction model is organized in three levels: (i) pedestrian-structure interaction; (ii) interaction among pedestrians in the crowd; and (iii) interaction between the crowd and the structure. To this end, first, the human-structure interaction of each pedestrian is modelled via a simplified two degrees of freedom system. Second, the interaction among pedestrians inside the crowd is simulated using a multi-agent model. The considered model simulates the movement of each pedestrian from the dynamic equilibrium of the different social forces that act on him/her. Finally, the crowd-structure interaction is achieved modifying the behaviour of the pedestrians depending on the comfort level experienced. For this purpose, the recommendations established by the French standards have been considered. The integration of the three levels in an overall model is achieved by the implementation of a predictive– corrective method. The performance of the proposed model is validated correlating the numerical and experimental dynamic response of the Pedro e Inês footbridge during the development of a lateral lock-in pedestrian test. As the first lateral natural frequency of the footbridge is inside the range that characterizes the walking pedestrian step frequency in lateral direction, numerical and experimental studies were performed to analyse its behaviour under pedestrian action. The agreement between the numerical and experimental results is adequate. However, further studies are recommended in order to generalize the proposed approach and facilitate its use during the design project of future footbridges.
本文提出了一种简化的生物力学人群-结构相互作用模型，并对其进行了验证，以分析实际人行天桥上的横向锁定现象。提出的人群-结构互动模型分为三个层次:(i)行人-结构互动;(ii)人群中行人之间的互动;(三)人群与建筑的互动。为此，首先，通过简化的二自由度系统对每个行人的人-结构相互作用进行建模。其次，利用多智能体模型模拟人群中行人之间的相互作用。所考虑的模型从作用于他/她的不同社会力量的动态平衡中模拟每个行人的运动。最后，实现了人群与结构的相互作用，根据体验的舒适度来改变行人的行为。为此目的，审议了法国标准所提出的建议。在一个整体模型中，三个层次的集成是通过预测校正方法的实现来实现的。通过Pedro e Inês人行桥横向锁定行人试验期间的数值和实验动态响应，验证了该模型的性能。由于人行桥的第一横向固有频率在行人横向行走频率的范围内，因此进行了数值和实验研究来分析其在行人作用下的行为。数值计算结果与实验结果吻合较好。然而，我们建议进行进一步的研究，以推广建议的方法，并方便日后行人天桥的设计项目使用。
{"title":"A CROWD-STRUCTURE INTERACTION MODEL TO ANALYZE THE LATERAL LOCK-IN PHENOMENON ON FOOTBRIDGES","authors":"J. Jiménez‐Alonso, A. Sáez, E. Caetano, Á. Cunha","doi":"10.2495/CMEM-V6-N4-764-771","DOIUrl":"https://doi.org/10.2495/CMEM-V6-N4-764-771","url":null,"abstract":"In this paper a simplified biomechanical crowd-structure interaction model is proposed and validated in order to analyse the lateral lock-in phenomenon on real footbridges. The proposed crowd-structure interaction model is organized in three levels: (i) pedestrian-structure interaction; (ii) interaction among pedestrians in the crowd; and (iii) interaction between the crowd and the structure. To this end, first, the human-structure interaction of each pedestrian is modelled via a simplified two degrees of freedom system. Second, the interaction among pedestrians inside the crowd is simulated using a multi-agent model. The considered model simulates the movement of each pedestrian from the dynamic equilibrium of the different social forces that act on him/her. Finally, the crowd-structure interaction is achieved modifying the behaviour of the pedestrians depending on the comfort level experienced. For this purpose, the recommendations established by the French standards have been considered. The integration of the three levels in an overall model is achieved by the implementation of a predictive– corrective method. The performance of the proposed model is validated correlating the numerical and experimental dynamic response of the Pedro e Inês footbridge during the development of a lateral lock-in pedestrian test. As the first lateral natural frequency of the footbridge is inside the range that characterizes the walking pedestrian step frequency in lateral direction, numerical and experimental studies were performed to analyse its behaviour under pedestrian action. The agreement between the numerical and experimental results is adequate. However, further studies are recommended in order to generalize the proposed approach and facilitate its use during the design project of future footbridges.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"81 1","pages":"764-771"},"PeriodicalIF":0.0,"publicationDate":"2017-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83406568","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}
Pub Date : 2017-11-03DOI: 10.2495/CMEM-V6-N4-772-784
Hsien-I Lin, Xuan-Anh Nguyen, Wei-Kai Chen
Understanding human intention is an important ability for an intelligent robot to collaborate with a human to accomplish various tasks. During collaboration, a robot with such ability can predict the successive actions that a human partner intends to perform, provide necessary assistance and support, and remind for the missing and failure actions from the human to achieve a desired task purpose. This paper presents a framework that allows a robot to automatically recognize and infer the action intention of a human partner based on visualization, in which an inverse-reinforcement learning (IRL) system is learnt based on the observed human demonstration and used to infer the human successive actions. Compared to other systems based on reinforcement learning, the reward of a Markov-Decision process (MDP) is directly learned from the demonstration. In our experiment, we provide some examples of the proposed framework which yields promising results with coffee-making and pick-and-place tasks. Regarding to the human-intention model based on IRL, the coffee-making experiment indicates that the action is globally predicted because the action of putting down the water pot is selected instead of pouring water when the cup is already filled with water.
{"title":"ACTIVE INTENTION INFERENCE FOR ROBOT-HUMAN COLLABORATION","authors":"Hsien-I Lin, Xuan-Anh Nguyen, Wei-Kai Chen","doi":"10.2495/CMEM-V6-N4-772-784","DOIUrl":"https://doi.org/10.2495/CMEM-V6-N4-772-784","url":null,"abstract":"Understanding human intention is an important ability for an intelligent robot to collaborate with a human to accomplish various tasks. During collaboration, a robot with such ability can predict the successive actions that a human partner intends to perform, provide necessary assistance and support, and remind for the missing and failure actions from the human to achieve a desired task purpose. This paper presents a framework that allows a robot to automatically recognize and infer the action intention of a human partner based on visualization, in which an inverse-reinforcement learning (IRL) system is learnt based on the observed human demonstration and used to infer the human successive actions. Compared to other systems based on reinforcement learning, the reward of a Markov-Decision process (MDP) is directly learned from the demonstration. In our experiment, we provide some examples of the proposed framework which yields promising results with coffee-making and pick-and-place tasks. Regarding to the human-intention model based on IRL, the coffee-making experiment indicates that the action is globally predicted because the action of putting down the water pot is selected instead of pouring water when the cup is already filled with water.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"45 1","pages":"772-784"},"PeriodicalIF":0.0,"publicationDate":"2017-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80650353","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}
Pub Date : 2017-11-03DOI: 10.2495/cmem-v6-n4-716-725
J. Lellep, A. Lenbaum
Free vibrations of beams and rods made of nano-materials are investigated. It is assumed that the dimensions of cross sections of nano-beams are piecewise constant and that the beams are weakened with cracks. It is expected that the vibrational behaviour of the nano-material can be described within the non-local theory of elasticity and that the crack induces additional local compliance. The latter is coupled with the stress intensity coefficient at the crack tip.
{"title":"FREE VIBRATIONS OF STEPPED NANO-BEAMS","authors":"J. Lellep, A. Lenbaum","doi":"10.2495/cmem-v6-n4-716-725","DOIUrl":"https://doi.org/10.2495/cmem-v6-n4-716-725","url":null,"abstract":"Free vibrations of beams and rods made of nano-materials are investigated. It is assumed that the dimensions of cross sections of nano-beams are piecewise constant and that the beams are weakened with cracks. It is expected that the vibrational behaviour of the nano-material can be described within the non-local theory of elasticity and that the crack induces additional local compliance. The latter is coupled with the stress intensity coefficient at the crack tip.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"44 1","pages":"716-725"},"PeriodicalIF":0.0,"publicationDate":"2017-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80855830","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}
Pub Date : 2017-11-03DOI: 10.2495/CMEM-V6-N4-679-690
D. Adair, M. Jaeger
The main purpose of this work is to employ the Adomian modified decomposition method (AMDM) to calculate free transverse vibrations of non-uniform cantilever beams carrying a transversely and axially eccentric tip mass. The effects of the variable axial force are taken into account here, and Hamilton’s principle and Timoshenko beam theory are used to obtain a single governing non-linear partial differential equation of the system as well as the appropriate boundary conditions. Two product non-linearities result from the analysis and the respective Cauchy products are computed using Adomian polynomials. The use of AMDM to make calculations for such a cantilever beam/tip mass arrangement has not, to the authors’ knowledge, been used before. The obtained analytical results are compared with numerical calculations reported in the literature and good agreement is observed. The qualitative and quantitative knowledge gained from this research is expected to enable the study of the effects of an eccentric tip mass and beam non-uniformity on the vibration of beams for improved dynamic performance.
{"title":"Simulation of the vibrations of a non-uniform beam loaded with both a transversely and axially eccentric tip mass","authors":"D. Adair, M. Jaeger","doi":"10.2495/CMEM-V6-N4-679-690","DOIUrl":"https://doi.org/10.2495/CMEM-V6-N4-679-690","url":null,"abstract":"The main purpose of this work is to employ the Adomian modified decomposition method (AMDM) to \u0000calculate free transverse vibrations of non-uniform cantilever beams carrying a transversely and axially \u0000eccentric tip mass. The effects of the variable axial force are taken into account here, and Hamilton’s \u0000principle and Timoshenko beam theory are used to obtain a single governing non-linear partial differential \u0000equation of the system as well as the appropriate boundary conditions. Two product non-linearities \u0000result from the analysis and the respective Cauchy products are computed using Adomian polynomials. \u0000The use of AMDM to make calculations for such a cantilever beam/tip mass arrangement has not, to \u0000the authors’ knowledge, been used before. The obtained analytical results are compared with numerical \u0000calculations reported in the literature and good agreement is observed. The qualitative and quantitative \u0000knowledge gained from this research is expected to enable the study of the effects of an eccentric tip \u0000mass and beam non-uniformity on the vibration of beams for improved dynamic performance.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"41 1","pages":"679-690"},"PeriodicalIF":0.0,"publicationDate":"2017-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86621861","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}
Pub Date : 2017-11-03DOI: 10.2495/CMEM-V6-N4-726-736
A. Tenza-Abril, Y. Villacampa, F. Baeza-Brotons, J. Navarro-Gonzalez, A. Solak
In this work, numerical models were obtained for describing the segregation phenomenon in lightweight aggregate concrete. To that end, a numerical methodology based on the generation of geometric models of finite elements has been applied, selecting those that describe better this phenomenon. The use of lightweight aggregate concretes (LWC) allows greater design flexibility and substantial cost savings. It is also well known that it contributes to a positive impact on the energy consumption of a building due to the high-thermal resistance values. However, lightweight concretes are susceptible to present aggregate segregation due to density differences between its components during concrete vibration. Segregation in concrete may strongly affect the concrete global properties. This fact justifies the needs for the identification and quantification of this phenomenon, in order to estimate the concrete segregation experimentally, a LWC was mixed in laboratory conditions. Controlled segregation was caused applying different times of internal vibration in a cylinder specimen. The specimens were horizontally sectioned in order to obtain the density in each section because the segregation index can be estimated obtaining a relation by comparing the densities of the upper and lower parts. Firstly, ANOVA test was performed to determine the statistical significance (p<0.05) of the differences in the density of the different sections, differences in the aggregate type and differences in the time of concrete vibration. Results show that there is a significant difference of each section and there is no significant difference of each lightweight aggregate used to mix the concrete in spite of their different density. In order to model the segregation in the LWC, at first, linear models were considered and rejected because for not explaining the phenomenon. However, the application of numerical models shows good results to describe the phenomenon of segregation in LWC.
{"title":"Numerical Model for Describing the Segregation Phenomenon in Lightweight Concrete Using Density Sections","authors":"A. Tenza-Abril, Y. Villacampa, F. Baeza-Brotons, J. Navarro-Gonzalez, A. Solak","doi":"10.2495/CMEM-V6-N4-726-736","DOIUrl":"https://doi.org/10.2495/CMEM-V6-N4-726-736","url":null,"abstract":"In this work, numerical models were obtained for describing the segregation phenomenon in lightweight aggregate concrete. To that end, a numerical methodology based on the generation of geometric models of finite elements has been applied, selecting those that describe better this phenomenon. The use of lightweight aggregate concretes (LWC) allows greater design flexibility and substantial cost savings. It is also well known that it contributes to a positive impact on the energy consumption of a building due to the high-thermal resistance values. However, lightweight concretes are susceptible to present aggregate segregation due to density differences between its components during concrete vibration. Segregation in concrete may strongly affect the concrete global properties. This fact justifies the needs for the identification and quantification of this phenomenon, in order to estimate the concrete segregation experimentally, a LWC was mixed in laboratory conditions. Controlled segregation was caused applying different times of internal vibration in a cylinder specimen. The specimens were horizontally sectioned in order to obtain the density in each section because the segregation index can be estimated obtaining a relation by comparing the densities of the upper and lower parts. Firstly, ANOVA test was performed to determine the statistical significance (p<0.05) of the differences in the density of the different sections, differences in the aggregate type and differences in the time of concrete vibration. Results show that there is a significant difference of each section and there is no significant difference of each lightweight aggregate used to mix the concrete in spite of their different density. In order to model the segregation in the LWC, at first, linear models were considered and rejected because for not explaining the phenomenon. However, the application of numerical models shows good results to describe the phenomenon of segregation in LWC.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"263 1","pages":"726-736"},"PeriodicalIF":0.0,"publicationDate":"2017-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73353375","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}
Pub Date : 2017-11-03DOI: 10.2495/cmem-v6-n4-737-748
P. Jadhav, J. Mallikarjuna
Performance and emission characteristics of a gasoline direct injection (GDI) engine are mainly influenced by the in-cylinder mixture preparation. However, in these engines, mixture formation depends upon many factors viz., fuel injection strategy and parameters, mode of operation, engine geometry, etc. Therefore, understanding the mixture formation, under various engine operating conditions and fuel system configurations, is very much essential. In this study, an attempt has been made to understand the effect of fuel injector-hole diameter and fuel injection timing on the mixture formation in a four-stroke, wall-guided GDI engine using computational fluid dynamics (CFD) analysis. The CFD simulations are carried out from inlet valve opening (IVO) to exhaust valve opening (EVO) period using the CONVERGE. The CFD models used are validated with the available data from the literature. The engine considered has a compression ratio (CR) of 11.5. All the CFD simulations are carried out at the engine speed of 2000 rev/min. Three fuel injector-hole diameters viz., 0.1, 0.14 and 0.18 mm and three fuel injection timings viz., 605, 620 and 635 crank angle degree (CAD) are considered for the analysis. The mixture formation is analyzed in the vicinity of the spark plug and at other parts of the combustion chamber. From the results, it is found that higher nozzle-hole diameter yielded very rich mixture zones near spark plug. Also, lower nozzle-hole diameter and retarded fuel injection timing showed higher indicated mean effective pressure (IMEP).
{"title":"EFFECT OF FUEL INJECTOR HOLE DIAMETER AND INJECTION TIMING ON THE MIXTURE FORMATION IN A GDI ENGINE - A CFD STUDY","authors":"P. Jadhav, J. Mallikarjuna","doi":"10.2495/cmem-v6-n4-737-748","DOIUrl":"https://doi.org/10.2495/cmem-v6-n4-737-748","url":null,"abstract":"Performance and emission characteristics of a gasoline direct injection (GDI) engine are mainly influenced by the in-cylinder mixture preparation. However, in these engines, mixture formation depends upon many factors viz., fuel injection strategy and parameters, mode of operation, engine geometry, etc. Therefore, understanding the mixture formation, under various engine operating conditions and fuel system configurations, is very much essential. In this study, an attempt has been made to understand the effect of fuel injector-hole diameter and fuel injection timing on the mixture formation in a four-stroke, wall-guided GDI engine using computational fluid dynamics (CFD) analysis. The CFD simulations are carried out from inlet valve opening (IVO) to exhaust valve opening (EVO) period using the CONVERGE. The CFD models used are validated with the available data from the literature. The engine considered has a compression ratio (CR) of 11.5. All the CFD simulations are carried out at the engine speed of 2000 rev/min. Three fuel injector-hole diameters viz., 0.1, 0.14 and 0.18 mm and three fuel injection timings viz., 605, 620 and 635 crank angle degree (CAD) are considered for the analysis. The mixture formation is analyzed in the vicinity of the spark plug and at other parts of the combustion chamber. From the results, it is found that higher nozzle-hole diameter yielded very rich mixture zones near spark plug. Also, lower nozzle-hole diameter and retarded fuel injection timing showed higher indicated mean effective pressure (IMEP).","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"55 4 1","pages":"737-748"},"PeriodicalIF":0.0,"publicationDate":"2017-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90092746","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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