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  • Author: M. Graba x
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Limit Load Solutions for SEN(T) Specimens – 2D and 3D Problems

Abstract

This paper deals with the limit load solutions for SEN(T) specimens under plane stress and plane strain conditions. The existing solutions are verified using the Finite Element Method and extended to 3D cases. The numerical results can be used to assess the strength of a structural element with a defect. This paper is a verification and extension of the author’s previous paper [2].

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Numerical Analysis of the Influence of In-Plane Constraints on the Crack Tip Opening Displacement for SEN(B) Specimens Under Predominantly Plane Strain Conditions

Abstract

This paper presents a numerical analysis of the relationship between in-plane constraints and the crack tip opening displacement (CTOD) for single-edge notched bend (SEN(B)) specimens under predominantly plane strain conditions. It provides details of the numerical model and discusses the influence of external load and in-plane constraints on the CTOD. The work also reviews methods for determining the CTOD. The new formula proposed in this paper can be used to estimate the value of the coefficient dn as a function of the relative crack length, the strain hardening exponent and the yield strength - dn(n, σ0/E, a/W), with these parameters affecting the level of in-plane constraints. Some of the numerical results were approximated using simple mathematical formulae.

Open access
The Characterization of the Stress Fields Near a Crack Tip for a Compact Specimen for Elastic-Plastic Materials Dominated by the Plane Strain State

Abstract

The paper presents a comprehensive analysis of the stress field near a crack tip for a compact specimen dominated by the plane strain state using the finite element method. The analysis also includes the calculation of some parameters of in-plane constraints, both for small and large strain assumptions. It discusses the influence of the material characteristic, relative crack length and external load for the stress field, and the in-plane constraint parameter. The approximation formulas for some in-plane constraint parameters are presented.

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A Numerical Analysis of Selected Elastic-Plastic Fracture Parameters for DEN(T) Plates under Plane Strain Conditions

Abstract

This paper provides a numerical analysis of selected parameters of fracture mechanics for double-edge notched specimens in tension, DEN(T), under plane strain conditions. The analysis was performed using the elastic-plastic material model. The study involved determining the stress distribution near the crack tip for both small and large deformations. The limit load solution was verified. The J-integral, the crack tip opening displacement, and the load line displacement were determined using the numerical method to propose the new hybrid solutions for calculating these parameters. The investigations also aimed to identify the influence of the plate geometry and the material characteristics on the parameters under consideration. This paper is a continuation of the author’s previous studies and simulations in the field of elastic-plastic fracture mechanics [4, 6, 16, 17, 31].

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On The Parameters of Geometric Constraints for Cracked Plates under Tension – Three-Dimensional Problems

Abstract

This paper provides a comparative analysis of selected parameters of the geometric constraints for cracked plates subjected to tension. The results of three-dimensional numerical calculations were used to assess the distribution of these parameters around the crack front and their changes along the crack front. The study also involved considering the influence of the external load on the averaged values of the parameters of the geometric constraints as well as the relationship between the material constants and the level of the geometric constraints contributing to the actual fracture toughness for certain geometries.

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Experimental and Numerical Analysis of Fracture in 41Cr4 Steel – Issues of the Stationary Cracks

Abstract

This paper analyzes the process of fracture in 41Cr4 steel on the basis of experimental and numerical data obtained for non-propagating cracks. The author’s previous and latest experimental results were used to determine the apparent crack initiation moment and fracture toughness for the material under plane strain conditions. Numerical simulations were carried out to assess changes in the J-integral, the crack tip opening displacement, the size of the plastic region and the distribution of stresses around the crack tip. A complex numerical analysis based on the true stress-strain curve was performed to determine the behavior of 41Cr4 steel under increasing external loads.

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Device for Control the Valvetrain and Cylinder Pressure of a Spark-Ignition Engine

Abstract

This article describes the method of controlling an electric magnetic linear actuator that moves an inlet valve of an internal combustion engine. Thanks to the use of the electric control of the inlet valve of the internal combustion engine, it was possible to implement a variable effective compression ratio of the operating power unit, adapting it to the current needs and engine load. In this design, valvetrain was modified by introducing an autonomous intake valve operation with the use of a specially designed electromagnetic actuator. The introduction of this system necessitated an additional modification of the intake camshaft. The control was carried out with the use of a real-time controller with a built-in FPGA unit. The proposed design of a system with an electromagnetic actuator will allow obtaining an additional degree of freedom in the control unit. Particular attention should be paid to registered values or air pressure in the intake stroke for a closed or partially opened throttle, which generates significant pumping losses. The use of an electromagnetic actuator in the intake can help reduce said losses.

Open access
Possibilities of Using a Wireless Telemetry System of a Recreational Vehicle (Off-Road)

Abstract

The development of electronic systems has significantly contributed to the rapid increase in the number of controllers working in vehicles, and thus the amount of data transferred between them. The large amount of information sent prevents the driver from directly mastering or understanding them, hence it was necessary to limit the displayed parameters on the instrument cluster to the most important ones, so that the driver can focus on driving. However, in motor sports and in various types of road tests or research, where the driver is supported by an additional team of engineers, information sent between vehicle controllers can prove extremely valuable. Most often, the whole staff of people responsible for conducted traction tests does not occupy the vehicle, so as not to disturb the conditions. Their analysis usually takes place in a designated service spot, in which case the parameters from the on-board data transmission network are usually transmitted by radio from the vehicle to the archiving system. Therefore, research into the development of wireless data transmission systems from vehicle controllers is also carried out at the Opole University of Technology. This article describes the possibilities of using a system built at the Opole University of Technology for wireless conduction of diagnostics and analysis of current operating parameters of a recreational All-Terrain Vehicle (ATV). In addition, in the designed system, it is also possible to connect external sensors to analyse parameters normally not registered during the course on normal vehicle operation.

Open access
Comparative Analysis of the Fuel Consumption of Vehicles Equipped with Various Types of Automatic Transmissions

Abstract

The growing number of vehicles moving on Polish roads equipped with various types of automatic transmissions prompted the authors of this publication to carry out research to assess the impact of the use of this type of transmission on the fuel consumption of these vehicles. The presented article presents a comparative analysis of the fuel consumption of vehicles of different manufacturers equipped with automatic transmissions moving in specially prepared driving cycles for research purposes. In the developed driving cycle, the vehicle speed was gradually increased every 10 km/h, maintaining each speed for a period of at least 30 seconds in order to stabilize the measurement results. The tests were carried out for various load stages of the drive system. Load differentiation was made by simulating driving in the prepared cycle for simulated different slopes of the road. The tests were carried out on the MAHA MSR500 chassis dynamometer, and the obtained results for the vehicle moving in automatic mode, where the transmission controller selected the gear ratio according to the programmed algorithm, were compared with the vehicle's fuel consumption for the vehicle gear selected by the driver in the driving cycle. The control software used to test the chassis dynamometer allows taking into account the increasing resistance of traffic along with the increase of vehicle speed, which greatly approximates the simulated conditions in the laboratory to the conditions on the road. The main purpose of this publication is to check whether using automatic transmissions or other control algorithm of these gears can achieve a reduction in fuel consumption.

Open access
Comparative Analysis of the Operating Indexes of Manually and Automatically Controlled Passenger Car Powertrain System at Variable Load States

Abstract

This article reports the results of a study into operating parameters of a system consisting of an SI engine and a powertrain in a Fiat Panda passenger car in the conditions of a variable load. The analysis was primarily concerned with the variability of fuel consumption resulting of the changing load applied to the driving wheels in the conditions of a test performed on chassis dynamometer for manual and automatic controlled transmission gear change The test bench included a dedicated driving cycle, which was developed as cycle with periodically changed constant linear speed of the car every 10 km/h. According to the vehicle set speed, the load on its wheels was determined by the basic resistance as rolling resistance, air resistance and resistance corresponding to road inclination. Each period of a drive cycle corresponding to steady state driving gave the average instantaneous values of drive system performance indicators. The waveforms of these indicators were recorded and then averaged and presented as representative points of the powertrain system that were analysed. The focus of the study involved the identification of the points characterized with the minimum specific fuel consumption and impact of type of powertrain control on emission of CO2 from passenger car SI engines.

Open access