Yazar "Atahan, Ali Osman" seçeneğine göre listele
Listeleniyor 1 - 8 / 8
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Biomechanical comparison of fixation of two-part osteoporotic neck fracture of the proximal humerus using uni-planar and multi-planar Kirschner wire(2009) Esen, Erdinç; Doğramacı, Yunus; Kömürcü, Mahmut; Kanatlı, Ulunay; Bölükbaşı, Selçuk; Atahan, Ali OsmanObjectives: The stability and effectiveness of uni-planar Kirschner wire (K-wires) was compared to multi-planar K-wires osteosynthesis combined with tension band wiring for fixation of two-part osteoporotic surgical neck fracture of the proximal humerus. Materials and methods: Two groups each with eight cadaveric elderly (mean age 72.6; range 70 to 80 year) frozen human humeri were used in the study. Transverse osteotomy of the proximal humerus was performed using a thin oscillating saw. The first group (group A) was fixed using two anterograde smooth K-wires, sent from lateral cortex, combined with tension band wiring. The second group (group B) was fixed using multi-planar (anterograde and retrograde) four smooth K-wires combined with tension band wiring on the lateral cortex. Biomechanical tensile properties for 3 mm displacement (gap load) and maximum load were assessed. Results: The mean value for the gap load was 1045.0±45.4 N (Newton) for group A and 1238.1±115.8 N for group B. Gap load values of groups were similar (p=0.01). The maximum load was 1261.8±52.4 N in group A and 1471.1±107.3 N in group B. The maximum load values were statistically higher in the multiplanar fixation technique (group B) when compared to that of the uniplanar fixation technique (group A), (p=0.004). Conclusion: Fixation in osteoporotic two-part surgical neck fractures of the proximal humerus using multiplanar K-wires combined with tension band wire provides substantially more effective stability compared to that of uniplanar fixation.Öğe Collision behaviour of double W-beam transition(Inderscience Enterprises Ltd, 2012) Atahan, Ali Osman; Arslan, TuranVehicle collisions result in many injuries and fatalities every year all around the world. A significant number of those incidents occur outside the roadway, partly owing to the incompatibility between the roadside safety hardware and impacting vehicles. Although the purpose of using roadside safety hardware is safely to contain impacting vehicles and reduce impact severity, use of inadequate safety hardware can have serious consequences. In this study, the crash behaviour of a currently used double W-beam transition barrier was analysed and its adequacy is evaluated using a series of five vehicular impacts. Finite element simulations were used to perform the analysis, and a full-scale crash test result was used to validate the finite element models used in the study. Results of the analysis predict that double W-beam transition can safely contain and redirect vehicles ranging from compact automobiles to high centre of gravity heavy trucks up to 10,000 kg in mass. Occupant injury risk values obtained from all five cases are also calculated and presented. Further use of computational tools in safety evaluation of the existing roadside safety hardware is strongly recommended.Öğe Crash testing and evaluation of a new generation L1 containment level guardrail(Pergamon-Elsevier Science Ltd, 2014) Atahan, Ali Osman; Yucel, Ayhan Oner; Erdem, Muhammet MusabGuardrails are one of the widely used passive safety devices designed to absorb loads applied by impacting vehicles. In this paper, development process of a new lightweight L1 containment level steel guardrail, called AG04-2.0, is explained. A series of full-scale crash tests were performed for the crashworthiness evaluation of AG04-2.0 system. AG04-2.0 failed to meet the EN1317 criteria at 10,000 kg truck test, called TB42. In the subsequent TB42 test when another brand truck was used the identical system successfully met the criteria. Additional crash tests, TB11 and TB32, were performed on AG04-2.0 system with 900 and 1500 kg passenger cars, respectively. To determine the effect of rail type on crash test performance both A and B type rails were utilized in the tests. Based on the extensive evaluations AG04-2.0 successfully passed all six crash tests and met L1 containment level requirements for both A and B type rails. Test results show that the difference in performance for the guardrail incorporating either A or B rail is fairly small. Moreover, it was concluded that variation in properties of 10,000 kg truck plays an important role in crash test outcome and thus a more detailed vehicle selection criteria in EN1317 are recommended. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Development of a 30,000 kg heavy goods vehicle for LS-DYNA applications(Inderscience Enterprises Ltd, 2007) Atahan, Ali Osman; Bonin, Guido; Karacasu, MuratIn this paper, a finite element model of a 30,000 kg Heavy Goods Vehicle (HGV) was developed and validated against full-scale crash test data. Since this vehicle is a standard test vehicle in the European crash test standards, EN1317, development of an accurate vehicle model was deemed to be a positive contribution to the evaluation of roadside safety hardware. The vehicle model reproduces a FIAT-IVECO F 180 truck, a vehicle with four axles and a mass of 30,000 kg when fully loaded. The model consisted of 12,337 elements and 11,470 nodes and was built for and is ready to use with LS-DYNA finite element code from Livermore Software Technology Corporation. Data available from two previously performed full-scale crash tests, one on a steel bridge rail and the other on a portable concrete barrier, were used to validate the accuracy of the HGV model. Results of the finite element simulation study show that the developed HGV model shows promise and can accurately replicate the behaviour of an actual HGV in a full-scale crash test. Improvements such as the steering mechanism in the front axles and the suspension system are currently underway to make model more realistic.Öğe Double plate osteosynthesis provides better biomechanical stabilization than double tension band technique in distal humerus fractures(2010) Doğramacı, Yunus; Esen, Erdinç; Kürklü, Mustafa; Kırıcı, Yalçın; Atahan, Ali Osman; Kömürcü, MahmutObjectives: In this study we evaluated the stability and effectiveness of the double tension band osteosynthesis technique compared to the double plate osteosynthesis technique used for fixation of distal humerus fractures. Materials and methods: The study was performed on two groups, and in each group eight cadaveric, elderly (mean age 70-80) human humeri was used. An osteotomy was performed in the supracondylar region using a manual saw. The first group (group 1) was fixed with double 3.5 mm reconstruction plates, while the second group (group 2) was fixed with the double tension band technique, using crossing Kirschner wires. The osteotomy was designed so that the distal fragment would allow only a single screw per plate. The constructs were evaluated using a material testing machine. A linear non-cyclic load was applied until the failure of the constructs. The force which produced a 3 mm gap (3 mm gap strength), as detected visually with the aid of operating loupes, and the maximum load prior to failure of the fixation (maximum force) were measured from all tests. Results: The mean value for the 3 mm gap strength was 1356.29±226.97 N for group 1 and 882.63±305.21 N for group 2. The mean value of the maximum load strength was 1487.13±298 N for group 1 and 1232±107.62 N for group 2. There were significant differences in 3 mm gap strengths of the two groups (p=0.005). There was also a significant difference in the maximum load between the two groups (p=0.016). Conclusion: Double plate osteosynthesis technique is superior to double tension band osteosynthesis for the fixation of distal humerus fractures.Öğe Effect of permanent jersey-shaped concrete barrier height on heavy vehicle post-impact stability(Inderscience Enterprises Ltd, 2009) Atahan, Ali OsmanJersey-shaped permanent concrete barriers are extensively used at narrow medians, bridge decks and at roadsides where lateral barrier deformations are not allowed. It is well documented that the crash performance of concrete barriers depends mainly on the barrier geometry, such as shape and top height. In most US applications, the height of jersey-shaped concrete barriers is 8 10 mm, whereas in Europe, concrete barriers as tal I as 1000 mm are used. According to European EN1317 crash test guidelines, concrete barriers should demonstrate acceptable crash test performances against 10, 30 and 38 ton heavy vehicle impacts. In this paper, the effect of permanent jersey-shaped concrete barrier height on post-impact stability of 10 and 30 ton heavy vehicles is investigated. A versatile finite clement program LS-DYNA capable of representing crash test behaviour of roadside safety hardware is used for the analysis. A total of five simulations, four with a 30 ton vehicle and one with a 10 ton vehicle, are performed. Permanent jersey-shaped barriers with 810, 950, 1000 and 1050 mm top heights are modelled and subjected to 30 ton vehicle impact. Only one simulation is performed on 8 10 mm tall barrier using 10 ton vehicle. Simulation results predict that a minimum of 1050 mm concrete barrier height is necessary to achieve post-impact stability for the 30 ton vehicle. For the 10 ton vehicle, a conventional 810 mm tall barrier is found to be adequate to provide stable vehicle redirection. As always, full-scale crash testing is recommended to verify the acceptability of simulation findings.Öğe Numerical analysis of an H4a heavy containment level transition(Inderscience Enterprises Ltd, 2006) Atahan, Ali Osman; Bonin, GuidoIt is fact that European highway safety personnel are not aware of the significance of transition barriers. As a result, most countries do not use transition designs on their highways. On the other hand, the ones that are currently in use lack adequate detailing and do not provide the required level of protection during a collision event. In this paper, the impact performance of a standard US flared-back guardrail-to-bridge rail transition is evaluated using a 30,000 kg heavy goods vehicle according to European EN1317 test TB71 requirements. A highly acceptable and versatile non-linear finite element code, LS-DYNA, is used for the analysis. Simulation results show that the transition fails to contain the vehicle. The vehicle overrides the transition due to insufficient rail height. To upgrade the impact performance of the transition to H4a, high containment level, an additional rail element was added to the current design to increase the rail height from 8 10 mm to 1050 mm. Subsequent simulation results show that the modified transition design meets the EN1317 test TB71 requirements. It is therefore recommended that the current US standard flared back guardrail-to-bridge rail transition design should have a minimum of 1050 mm rail height to satisfy European crash testing guidelines for H4a, heavy containment level transition.Öğe A recommended specification for heavy vehicle rear underrun guards (vol 39, pg 696, 2007)(Pergamon-Elsevier Science Ltd, 2008) Atahan, Ali Osman[Abstract Not Available]
