Ata Mugan

Railroad passenger car collision analysis and modifications for improved crashworthiness

In this study, crashworthiness assessment and suggestions for the modification of a railroad passenger car are presented. To assess the crashworthiness, collision of the railroad passenger car onto a rigid wall is simulated by using finite element (FE) methods. A full-length, detailed passenger car model is used in FE analyses. In order to validate the FE model, simulation results obtained for different types of static loading conditions in compliance with various scenarios defined in UIC CODE OR 577 are compared with experimental measurements before running collision analyses of the railroad passenger car. The good agreement between static tests and FE analyses results indicates that the FE model accurately represents the real structure. Following the FE model validation, analysis of the collision behaviour of the railroad passenger car consists of two stages. In the first stage, the crashworthiness of the initial concept design of the railroad passenger car is analysed. It was observed that local buckling takes place at various points, which prevents the desired progressive damage behaviour in the railroad car body. Having revealed the structural weaknesses, the initial design was modified and simulated again under the same conditions. Using size optimisation, thickness of some sheet metal components is changed in order to obtain the intended progressive damage behaviour. As a result of the modifications, the passenger car design with better crashworthiness properties was obtained, in which large plastic deformations occur around the collision side of the car while mainly elastic deformations occur in the cars body away from the bumpers.

Effect of attachment types and number of implants supporting mandibular overdentures on stress distribution: a computed tomography-based 3D finite element analysis.

The objective of this study was to calculate stresses in bone tissue surrounding uncoupled and splinted implants that are induced by a bite force applied to the mandible and to determine whether the number of mandibular overdenture supporting implants in mandibular bone influence the stress distribution. A human adult edentulous mandible retrieved from a formalin fixed cadaver was used to define the geometry of finite element (FE) model and the FE model was verified with experimental measurements. Following the FE model validation, three different biting situations were simulated for the 2-, 3- and 4-implant retentive anchor as well as bar attachment overdentures under vertical loading of 100 N. As a result of the analyses, it was concluded that an increment in implant number and the splinted attachment type tended to cause lower stresses and the use of two single attachments seems to be a safe and sufficient solution for the treatment of mandibular edentulism with overdentures.

Design sensitivity analysis of structures based upon the singular value decomposition

The singular value decomposition (SVD) is employed for design sensitivity analysis of structures. As the squares of singular values are the bounds of power, energy and power spectral density ratios between the input and output vectors, shaping the singular values of a structure is equivalent to shaping the response of the structure. Comparison is made of the proposed sensitivity analysis based upon the SVD with the conventional techniques. The issues such as structural robustness, worst loading case and multiple load cases are studied. As shown, design sensitivity analysis based upon the SVD can give good insight into static and dynamic response characteristics of structures; it is more informative than eigenvalue design sensitivity analysis and, in particular, computationally advantageous in case of multiple load cases. Numerical examples are presented to illustrate the proposed approach.

Crash and structural analyses of an aluminium railroad passenger car

Crashworthiness, strength and vibrational features of a railroad passenger car, which is originally made of steel members and then converted to an aluminium design, are studied. The finite element (FE) method is utilised for the static analysis in compliance with various scenarios defined in UIC CODE OR 577, modal analysis and simulation of the crash into a rigid wall. Firstly, a full-length, detailed passenger car model made of steel is used in FE analyses and the model is verified for the steel car body by comparisons with strain measurements and experimental evaluation of natural frequencies. The agreement between test measurements and FE results indicates that the FE model of the railroad car accurately represents the original structure. Following, effects of material change on the structural behaviour can be accurately judged based on the outcomes of the analyses. It is observed that the stress values and natural frequencies of the aluminium structure are almost equal to those of the original steel structure. Moreover, the crash energy absorption characteristics are within the acceptable tolerances for both cases. The final aluminium design is found to be about one-third of the weight of the initial steel structure while it preserves stiffness values within acceptable limits. In addition, an equivalent spring-mass system is developed to model the crash of both steel and aluminium passenger cars, which can be used for occupant safety investigations in future.

Conversion of a conventional electric automobile into an unmanned ground vehicle (UGV)

In this study, conversion procedure of a conventional electric automobile into an unmanned ground vehicle (UGV) is illustrated. This conversion process is divided into two main parts as, mechanical and electrical modifications. Interface circuit, interface software, additional power system, selection of the sensors and computer hardware are given in electrical modifications part. Similarly, design of braking and steering system, their computer simulations and strength analysis are given in mechanical modifications part. All these applications are illustrated on a conventional electric vehicle during this study.

Multi-sensor data fusion of DCM based orientation estimation for land vehicles

In this paper, an algorithm estimating orientation is implemented using Direction Cosine Matrix (DCM) method, chosen due to its linear process model and ease of use. Two Kalman filters were used to estimate the rotation matrix elements where the Euler Angles are easily computed. A rule based decision structure is used to choose the best measurement available in the system from GPS and digital compass. Also the dynamic motion of the vehicle is considered to overcome the slow response of the digital compass. The algorithm is tested with real time logged data set and a decision structure is developed to have the best Information provided from the multiple sensors. The algorithm is also tested under artificial GPS outages, performs successfully for both attitude and heading angles.

Development of a design for a crash energy management system for use in a railway passenger car

A design approach for a crash energy management (CEM) system for a N13-type railway passenger car used by the Turkish State Railway Company is developed in this paper. The components of the CEM system are honeycomb-structured boxes, primary energy absorbers, shear bolts, a sliding sill mechanism and a fixed sill mechanism that are located in the passenger-free space at the end of the passenger car. In order to investigate the benefits provided by the CEM system, a full-scale railway passenger car collision with a rigid wall is simulated by using dynamic/explicit finite element (FE) methods. The crushing force, secondary impact velocity, acceleration and velocity curves, and deformation modes are computed to allow a comparison of the crashworthiness performance of a passenger car equipped with the proposed CEM system with that of a conventional passenger car. Comparisons of FE analysis results show that a passenger car incorporating the CEM system has a superior crashworthiness performance to that of the conventional passenger car.

Rollover crashworthiness analysis of a railroad passenger car

Rollover of railroad passenger cars is one of the most serious accidents having high rates of injuries and fatalities. Therefore, the railroad passenger car structures should satisfy the rollover crashworthiness requirements in order to protect the occupants. In this paper, rollover crashworthiness of a railroad passenger car called ‘N13-type’ used by Turkish State Railways is investigated. To assess the rollover crashworthiness, rollover simulations of the full scale and detailed passenger car models onto a rigid ground are completed by using a non-linear explicit finite element code, Abaqus. The numerical model is validated with static and modal experimental measurements before running rollover analyses of the railroad passenger car. Good agreement is observed between tests and finite element results, which indicate that the numerical model accurately represents the real structure. Simulations are performed in accordance with the regulation of ECE R66. Based on this standard, two different rollover scenarios are considered. In the first scenario, lateral rollover simulation is performed at the standard angular velocity due to ECE R66 regulation. The second scenario is performed at the double of this angular velocity to investigate the crashworthiness behaviour under exaggerated conditions. As a result of the analyses, it is observed that the residual space remains undamaged during and after the rollover, and passenger car is able to pass the required regulations.

Stop/Start System Integration to Diesel Engine and System Modelling & Validation

Abstract Hybrid and micro-hybrid systems became widespread due to fuel economy benefit and environmental concerns. Micro-hybrid systems such as Regenerative Braking and Stop/Start system are commonly used in automotive industry. This paper is based on integration of a Stop/Start (S/S) system to 1.5 liter diesel engine. General information is given about subsystems which are used by S/S system. For fuel consumption model, engine mapping data is obtained by using an engine dynamometer. The equations of motion are used for the torque model. By using calculated engine speed and engine inner torque, total fuel consumption is calculated. For NEDC, cycle fuel consumption benefit of S/S system is simulated as 0.165 liter per 100 km which is measured as 0.16 liter per 100 km. An approximate model is developed which is useful to use at early phases of a project. For NEDC cycle, CO 2 emissions benefit of S/S system is approximately 4 gr/100 km which is simulated as 4.5 gr/100km.

Active vibration control with piezoelectric actuator on a lathe machine with a gain controller

In this study, an active vibration control on a CNC lathe machine by the use of a stack piezoelectric actuator is accomplished. In the implementation of piezoelectric actuators, dSpace 1104 Control Card is used as the control unit. By using the acceleration feedback signals measured on the cutting tool, the control signal being out-of-phase with the acceleration measurements is applied to the piezo electric actuators. The system is implemented on a Mazak CNC lathe machine. The experimental results show that the implemented active control approach yields reduction on surface roughness of machined parts.