This paper presents the results of numerical analysis of aerodynamic characteristics of a sports car equipped with movable aerodynamic elements. The effects of size, shape, position, angle of inclination of the moving flaps on the aerodynamic downforce and aerodynamic drag forces acting on the vehicle were investigated. The calculations were performed with the help of the ANSYS-Fluent CFD software. The transient flow of incompressible fluid around the car body with moving flaps, with modeled turbulence (model Spalart-Allmaras or SAS), was simulated. The paper presents examples of effective flap configuration, and the example of configuration which does not generate aerodynamic downforce. One compares the change in the forces generated at different angles of flap opening, pressure distribution, and visualization of streamlines around the body. There are shown the physical reasons for the observed abnormal characteristics of some flap configurations. The results of calculations are presented in the form of pressure contours, pathlines, and force changes in the function of the angle of flap rotation. There is also presented estimated practical suitability of particular flap configurations for controlling the high-speed car stability and performance.
This paper presents a three-dimensional model of an airbag located outside of a small city car at the front bumper, which is intended to protect the vehicle against the effects of road traffic collisions. Results of numerical simulations of airbag operation in case of collision with two types of obstacles are presented: a flat, vertical wall and a circular pillar with a diameter of 200 mm. The paper presents the physical model, which is the subject of simulation, along with its mathematical description and the numerical calculation scheme used.
The paper presents the simulation analysis determining the effect of tyre energy efficiency class on fuel consumption of a passenger car. Calculations were made assuming the wheel movement on a dry and smooth asphalt road surface. The tests based on a simulation model were performed on 61 types of tyres, being characterised by different sizes and energy efficiency classes. Different values of rolling resistance coefficient were adopted (in accordance with energy efficiency classes), also, the values of basic and additional resistance to motion were determined. Based on them, engine speeds and load torque corresponding to respective specific fuel consumption were estimated. This parameter allowed the relationship between average mileage fuel consumption and tyre energy efficiency class to be determined on the basis of the NEDC test.
Brain-computer interface (BCI) is a device which allows paralyzed people to navigate a robot, prosthesis or wheelchair using only their own brains reactions. By creating a direct communication pathway between the human brain and a machine, without muscles contractions or activity from within the peripheral nervous system, BCI makes mapping persons intentions onto directive signals possible. One of the most commonly utilized phenomena in BCI is steady-state visually evoked potentials (SSVEP). If subject focuses attention on the flashing stimulus (with specified frequency) presented on the computer screen, a signal of the same frequency will appear in his or hers visual cortex and from there it can be measured. When there is more than one stimulus on the screen (each flashing with a different frequency) then based on the outcomes of the signal analysis we can predict at which of these objects (e.g., rectangles) subject was/is looking at that particular moment. Proper preprocessing steps have taken place in order to obtain maximally accurate stimuli recognition (as the specific frequency). In the current article, we compared various preprocessing and processing methods for BCI purposes. Combinations of spatial and temporal filtration methods and the proceeding blind source separation (BSS) were evaluated in terms of the resulting decoding accuracy. Canonical-correlation analysis (CCA) to signals classification was used.
The process of wheel - rail interaction is largely determined by dynamic properties of the car, improvement of which is possible by improving design of the bogie and its basic elements. The article analyses and discusses the problems that have arisen in recent years in the course of operation of bogie 18-100. Tribological and mechanical properties of a friction wedge-type oscillation damper are studied.
Sound propagation from the vehicles moving on the city roundabout, with taking into account the wind is investigated. Solution of the problem for one moving sound source is found by means of the integral Fourier transforms extended over space variables and time. Inverse transforms are calculated approximately, using a stationary phase method and iterative technique. The solution for a general problem is obtained as a superposition of many partial solutions. The numerical analysis of noise characteristics is performed for the three-way Korfanty roundabout case in Łódź.
This paper defines the concept of simple strategy and introduces three kinds of simple strategies: wealth-invariant, scale-invariant and "wealthier-accept more". For three commonly used utility function families: CARA, CRRA and DARA equivalent characterizations are obtained in terms of the corresponding simple strategy, in terms of the buying and selling price properties, and in terms of the utility function properties as expressed by Cauchy functional equations. Moreover, an extension of famous Pratt (1964) theorem is proved which involves buying price for a lottery as an alternative measure of comparative risk aversion. Additionally a number of propositions on both selling and buying price for a lottery and CRRA utility class are proved.
The paper presents optimization of 5-rod (5-link) suspension mechanism used in passenger cars for independent guiding of the wheels. Selected stiffness coefficients defined for five elastomeric bushings installed in joints of the suspension rods are considered as design variables. Two models with lumped parameters (i.e. elastokinematic and dynamic) of wheel-suspension-car body system are formulated to describe relationships between the design variables and the performance indexes including car active safety and ride comfort, respectively. The multi-criteria goal function is minimized using a deterministic algorithm. The suspension with optimized bushings rates fulfils desired elastokinematic criteria together with a defined dynamic criterion, describing the so-called rolling comfort. An event of car passing over short road bump is considered as dynamic conditions. The numerical example deals with an actual middle-class passenger car with 5-rod suspension at the front driven axle. Estimation of the models parameters and their verification were carried out on the basis of indoor and outdoor experiments. The proposed optimization procedure can be used to improve the suspension design or development cycle.
This paper deals with the prevention of failure of structural elements made of reinforced concrete. It discusses preservice cracks in the concrete decks of an underground parking facility. The cracks were assessed by analyzing their morphology. The results were used to determine the crack causes and the mechanisms of their initiation and growth. Some design solutions to prevent or reduce the occurrence of pre-service cracks are also presented.
The paper presents a Car Sequencing Problem, widely considered in the literature. The issue considered by the researchers is only a reduced problem in comparison with the problem in real automotive production. Consequently, a newconcept, called Paint Shop 4.0., is considered from the viewpoint of a sequencing problem. The paper is a part of the previously conducted research, identified as Car Sequencing Problem with Buffers (CSPwB), which extended the original problem to a problem in a production line equipped with buffers. The new innovative approach is based on the ideas of Industry 4.0 and the buffer management system. In the paper, sequencing algorithms that have been developed so far are discussed. The original Follow-up Sequencing Algorithm is presented, which is still developed by the authors. The main goal of the research is to find the most effective algorithm in terms of minimization of painting gun changeovers and synchronization necessary color changes with periodic gun cleanings. Carried out research shows that the most advanced algorithm proposed by the authors outperforms other tested methods, so it is promising to be used in the automotive industry.
The paper presented the model of a problem of choosing the location of a car crane for the installation of prefabricated elements in a given assembly situation with the solution proposal. The issue relates to the situation, in which the dimensions of the shielding structure (assembled) are specified, sizes and weights of the prefabricated elements with their location on the structure. The solution seeks the best location of a crane from the point of view of the parameters of the crane, scope and height of the lift.
The introduction of the sustainable development elements in the construction industry leads to finding new ways of using waste minerals that are difficult in storage and recycling. Coal combustion products have been already introduced into building materials as a part of cement or concrete but they have been thought insufficiently compatible with the polymer-cement binders . The paper presents results of the mechanical properties of polymer-cement composites containing two types of mineral additives: waste perlite powder that is generated during the perlite expanding process, and calcium fly ash which is the byproduct of burning coal in conventional furnaces. Mechanical tests of polymer-cement composites modified with wastes were carried out after 28 and 90 days of curing. As a part of preliminary study specific surface area and particle size distribution of mineral wastes were determined.