Finite element dynamic analysis of laminated composite beams under moving loads

Kahya, Volkan Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.5

This study presents dynamic analysis of laminated beams traversed by moving loads using a multilayered beam element based on the first-order shear deformation theory. The present element consists of N layers with different thickness and material property, and has (3N + 7) degrees of freedom corresponding three axial, four transversal, and 3N rotational displacements. Delamination and interfacial slip are not allowed. Comparisons with analytical and/or numerical results available in literature for some illustrative examples are made. Numerical results for natural frequencies, deflections and stresses of laminated beams are given to explain the effect of load speed, lamina layup, and boundary conditions.

Series tuned mass dampers in train-induced vibration control of railway bridges

Volkan Kahya,Onur Araz 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.61 No.4

This paper presents the series multiple tuned mass dampers (STMDs) to suppress the resonant vibrations of railway bridges under the passage of high-speed trains (HSTs). A STMD device consisting of two spring-mass-damper units connected each other in series is installed on the bridge. In solution, bridge is modeled as a simply-supported Euler-Bernoulli beam with constant cross-section, and vehicle is simulated as a series of moving forces with constant speed. By the assumed mode method, the governing equations of motion of the beam-TMD device coupled system traversed by a moving train are obtained. The optimum values for the parameters of the STMD device are obtained for the criterion based on the minimization of the maximum dynamic displacement of the beam at its midspan. Single TMD and multiple TMDs in parallel are also considered for demonstration of the STMD device\'s performance. The results show that STMDs are effective in bridge vibration suppression and robust to parameters\' change in the main system and the absorber itself.

Vibration and buckling of laminated beams by a multi-layer finite element model

Volkan Kahya,Muhittin Turan 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.28 No.4

This paper presents a multi-layer finite element for buckling and free vibration analyses of laminated beams based on a higher-order layer-wise theory. An N-layer beam element with (9<i>N</i> + 7) degrees-of-freedom is proposed for analyses. Delamination and slip between the layers are not allowed. Element matrices for the single- and multi-layer beam elements are derived by Lagrange's equations. Buckling loads and natural frequencies are calculated for different end conditions and lamina stacking. Comparisons are made to show the accuracy of proposed element.

Shear-deformable finite element for free vibrations of laminated composite beams with arbitrary lay-up

Volkan Kahya,Sebahat Karaca,Thuc P. Vo 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.4

A shear-deformable finite element model (FEM) with five nodes and thirteen degrees of freedom (DOFs) for free vibrations of laminated composite beams with arbitrary lay-up is presented. This model can be capable of considering the elastic couplings among the extensional, bending and torsional deformations, and the Poisson's effect. Lagrange's principle is employed in derivation of the equations of motion, and thus the element matrices are obtained. Comparisons of the present element's results with those in experiment, available literature and the 3D finite element analysis software (ANSYS®) are made to show its accuracy. Some further results are given as referencing for the future studies in vibrations of laminated composite beamst.

Finite element dynamic analysis of laminated composite beams under moving loads

Volkan Kahya 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.5

This study presents dynamic analysis of laminated beams traversed by moving loads using a multilayered beam element based on the first-order shear deformation theory. The present element consists of N layers with different thickness and material property, and has (3N + 7) degrees of freedom corresponding three axial, four transversal, and 3N rotational displacements. Delamination and interfacial slip are not allowed. Comparisons with analytical and/or numerical results available in literature for some illustrative examples are made. Numerical results for natural frequencies, deflections and stresses of laminated beams are given to explain the effect of load speed, lamina layup, and boundary conditions.

The effectiveness of wax secretion on chemical control in some mealybug species

ULUSOY Selcuk,KAHYA Dogancan,BILGIN Mustafa Gokhan,APALAK Alaittin 한국응용곤충학회 2022 Journal of Asia-Pacific Entomology Vol.25 No.3

The wax structure of mealybugs can be seen on the body naturally, causing natural resistance and decreasing the efficacy of insecticides. This study was conducted to determine effectiveness of wax structure on chemical control by removing with isoamyl alcohol(ISO) for Planococcus citri Risso (Hemiptera: Pseudococcidae), Phenacoccus solenopsis Tinsley (Hemiptera:Pseudococcidae) and Phenacoccus madeirensis Green (Hemiptera: Pseudococci dae). Before and after the occurrence of wax, LC 50 levels with bioassay were detected for Buprofezin (BP), sulfoxaflor (SF), chlorpyrifos ethyl (CH), dimethoate (DM), spirotetramat (SP), Lambda- Cyhalothrin (LC), pyr iproxyfen (PY) insecticides. The effectiveness of PY increased 10.6 and 6.5 times for P. Citri and P. solenopsis, the efficacy of BP increased 3 times for P. Madeirensis with the dissolution of the wax structure after the application of ISO. The lowest increase of efficacy was found 1.6 and 1.4 times for P. maderiensis and P. solenopsis for SF,1.1 times for BP on P. citri. The reproduction of the wax for adult female mealybugs was seen 72 h later after the ISO application. It has been revealed that the mealybug wax structure significantly reduced the effectiveness of some insecticides and this factor can provide remarkable contributions in chemical control.

Can tumor recurrence be reduced with plasma-kinetic vaporization of the area around the tumor in nonmuscle invasive bladder cancer?

Yüksel Yılmaz,Mehmet Cemal Kahya,Fatma Hüsniye Dilek,Osman Köse,Serkan Özcan,Ertan Can,Yiğit Akın,Batuhan Ergani,Ahmet Selçuk Dindar 대한비뇨의학회 2018 Investigative and Clinical Urology Vol.59 No.4

Purpose: To investigate the effect on recurrence of vaporization of the tumor surroundings and suspicious areas with a plasma-kinetic (PK) system after transurethral resection (TUR) of nonmuscle invasive bladder cancer. Materials and Methods: The study included 121 patients with a primary superficial bladder tumor who were randomized as those who underwent TUR with the PK system (Group 1, n=62) and those who underwent TUR with the monopolar system (Group 2, n=59). The vaporization procedure was performed by suppressing the cutting option of the PK system for a period, which would accumulate energy sufficient to make swelling-waves on the mucosa very close to the area of the loop to be vaporized. Results: A total of 121 patients who met the study criteria were included for evaluation. Recurrence was determined in 21 patients in Group 1 (33.87%) and in 29 patients in Group 2 (49.15%) (p=0.088). Recurrence was close to the old resection site in 6 of 21 patients in Group 1, and in 13 patients in Group 2 (p=0.028); the difference was statistically significant. No statistically significant difference was determined between the two groups with respect to age, gender, number of tumor foci, rate or range of additional treatments applied, cigarette smoking rate, repeat TUR rate and rate of tumor en- countered in repeat TUR, T-stage, and tumor grade. Conclusions: The effect of vaporization on recurrence by the PK system may seem similar to the effect of standard TUR, the recurrence- lowering effect surrounding nonmuscle invasive bladder cancers is better.

Modeling and analysis of surface roughness of microchannels produced by µ-WEDM using an ANN and Taguchi method

Rahim Jafari,Müge Kahya,Samad Nadimi Bavil Oliaei,Hakkı Özgür Ünver,Tuba Okutucu Özyurt 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11

Microchannel heat exchangers are used to remove the high heat fluxes generated in compact electronic devices. The roughness of the microchannels has a significant effect on the heat transfer characteristics, especially the nucleate boiling and pumping power. Therefore, development of predictive models of surface texture is of significant importance in controlling heat transfer characteristics of these devices. In this study, micro-Wire electrical discharge machining (µ-WEDM) was employed to fabricate metal-based microchannel heat sinks with different surface textures. First, experiments were conducted to achieve the desired surface roughness values. Oxygen-free copper is a common material in the cooling systems of electronic devices because of its high thermal conductivity and low cost. Design of experiment approach based on the Taguchi technique was used to find the optimum set of process parameters. An analysis of variance is also performed to determine the significance of process parameters on the surface texture. An artificial neural network model is utilized to assess the variation of the surface roughness with process parameters. The predictions are in very good agreement with results yielding a coefficient of determination of 99.5 %. The results enable to determine µ-WEDM parameters which can result in the desired surface roughness, to have a well-controlled flow and heat transfer characteristics for the microchannels.

Graphene-P(VDF-TrFE) Multilayer Film for Flexible Applications

Bae, Sang-Hoon,Kahya, Orhan,Sharma, Bhupendra K.,Kwon, Junggou,Cho, Hyoung J.,Ö,zyilmaz, Barbaros,Ahn, Jong-Hyun American Chemical Society 2013 ACS NANO Vol.7 No.4

<P>A flexible, transparent acoustic actuator and nanogenerator based on graphene/P(VDF-TrFE)/graphene multilayer film is demonstrated. P(VDF-TrFE) is used as an effective doping layer for graphene and contributes significantly to decreasing the sheet resistance of graphene to 188 ohm/sq. The potentiality of graphene/P(VDF-TrFE)/graphene multilayer film is realized in fabricating transparent, flexible acoustic devices and nanogenerators to represent its functionality. The acoustic actuator shows good performance and sensitivity over a broad range of frequency. The output voltage and the current density of the nanogenerator are estimated to be similar to 3 V and similar to 0.37 mu Acm(-2), respectively, upon the application of pressure. These values are comparable to those reported earlier for Zn0- and PIT-based nanogenerators. Finally, the possibility of rollable devices based on graphene/P(VDF-TrfE)/graphene structure is also demonstrated under a dynamic mechanical loading condition.</P>

Series tuned mass dampers in vibration control of continuous railway bridges

Onur Araz,Volkan Kahya 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.2

This paper presents the applicability of series tuned mass dampers (STMDs) to reduce the multiple resonant responses of continuous railway bridges under high-speed train. The bridge is modeled by two-span Bernoulli-Euler beam with uniform cross-section, and a STMD device consisting of two TMD units installed on the bridge to reduce its multiple resonant vibrations. The system is assumed to be under the action of a high-speed train passage which is modeled as a series of moving forces. Sequential Programming Technique (SQP) is carried out to find the optimal parameters of the STMD that minimizes the maximum peak responses of the bridge. Comparisons with the results available in the literature are presented to demonstrate the effectiveness and robustness of STMD system in reducing the multiple resonant responses of the continuous railway bridges under high-speed trains.