Vehicle and Automotive Engineering

Rolling element bearings can be found widely in domestic and industrial applications. They are important components of most machinery and their working conditions influence the operation of the entire machinery directly. Bearing failures may cause machine breakdown and might even lead to catastrophic failure or even human injuries. In order to prevent unexpected events, bearing failures should be detected as early as possible. Different methods are used for the detection and diagnosis of bearing defects. These techniques can be classified as noise analysis, acoustic measurements, wear debris detection, temperature monitoring, vibration analysis etc. Vibration signals collected from bearings carry detailed information on machine health conditions. This paper deals with a bearing test procedure which based on vibration analysis.

In the chapter the floor structure of a truck produced by a company in Hungary has been investigated. The structure consists of steel members, or extruded Al-alloy longitudinal and cross members as well as a tread deck plate. Using an optimum design process, namely the Hillclimb optimizer, significant mass and cost savings may be achieved by decreasing the deck plate thickness and changing the profile, dimensions and number of cross members. Comparison is made using the combination of the steel and aluminium, or using only steel alone. Design constraints relate to fatigue stress range of welded joints, to local buckling of extruded or normal profiles and to fabrication size limitations. A special loading case is also considered when a wheel is staying on a curb and the floor is distorted.

Automotive radiator is one of the most important devices of the engine cooling system. The function of this equipment is to remove heat from the engine and to keep the engine operating at the most efficient temperature. Nowadays, in the automotive industry, one of the most important project is decreasing the mass. This chapter focuses on calculation and optimization of finned-tube heat exchanger using several methods.

The Department of Fluid and Heat Engineering, established as the Department of Machine Operation in 1952, hosts research and teaching in engines for vehicles. In the first two decades after the foundation of the department, besides engines in vehicles, steam engines still played an important role as they were used in locomotives. At that time the department owned several dynamometers and besides teaching about engines, the department carried out research and development for the national production of engines. After a decade of transition, in the second half of the 1990s the production of internal combustion engines started to flourish again. This was manifested first in teaching, but from 2010 in research as well. The replacement of the old laboratory equipment with modern measuring instruments and engines and the construction of a full departmental laboratory for engine diagnostics contributed to this. All of these factors explain why the Department of Fluid and Heat Engineering is in charge of teaching internal combustion engines in the new (starting from 2016) Vehicle Engineering B.Sc programme.

For the drive technology tasks are used different system drives. One of these drives is the well-known direct-current hydraulic drive (DCH). The hydraulic drives can be classified among a new version of the new hydraulic drives: the alternating-current hydraulic drive (ACH). The spread of the drive innovation problems hinder, in turn it has many favourable features, which influence positively the transmission properties of the drive. With the development of this type of drive is dealt at the Department of Machine Tools the leadership of Dr. János Lukács about 40 years. The subject in the field of several doctoral dissertations, patents, scientific articles and student papers have been written. I got into the research work within the framework of doctoral training. My task was within the topic of alternating-current hydraulic drives: the transmission properties of the synchronous alternating-current hydraulic drive. I would like to introduce on the Department of Machine Tools that I built help of alternating-current hydraulic drive, this drive is advantageous and disadvantageous features, knowing that they these transmission properties can be used advantageously machines of the automotive industry.

It is well known that residual stress is introduced within solid materials during many types of processing methods, including heat treatments, machining, grinding, casting, etc. The type and magnitude of the formed stress state can be various depending on the type and conditions of the treatment and the geometry of the sample. The presence of residual stress can either be harmful or useful. If undesired residual stress is arisen within a machine component during its manufacturing steps, it can lead to deformation. Since the geometry of automotive components must be kept strictly within tolerances, more and more attention is given to the importance of residual stress in the field of the automotive industry. Many methods have been developed to characterise the residual stress. In the present study, the results of a destructive and non-destructive residual stress measuring methods for induction hardened automotive rack bar semi-products were compared. The theory of non-destructive method associated with the distortion of the crystal lattice, from which, residual stress can be quantitatively calculated, while the destructive method that we have developed specially to test this product at the Lech-Stahl Veredelung GmbH is very fast, suitable for qualification, and easily inserted into the manufacturing line.

This chapter deals with a dynamical modelling of autonomous vehicle, including different manoeuvrings. Solution of the state-space form was performed using the Runge-Kutta method. A special purpose program has been written in the Scilab software system. Manoeuvrings of different cornering and overtaking are simulated.

The paper deals with the development of a new internal combustion engine having a rotary piston. The introduction presents the short history of the evolution of the rotary combustion engines. The main part of the paper introduces the new patented internal combustion engine structure that has three rotational parts only: the rotary piston—rotor—, the rotary housing—rotary chamber—and the synchronizing gears. After the description of the structure, the work of the engine is discussed, compared to the usual internal combustion engines and the advantages and disadvantages are analyzed. Those properties that make possible the high speed operation are emphasized. Besides the constructional characteristics some manufacturing tasks are also presented, especially the very important precision finishing manufacturing of the working surfaces of the rotor and the rotary chamber.

The chapter introduces the simulation methods (MBS, FEM, SEA) which are generally used in the vehicle NVH. Alongside also hybrid methods will be introduced. An overview will be given about the usage of the methods depending on the frequency range for the simulation and prediction of the NVH behaviour of full vehicle and its components.

Through the case study of a simple mechanical system (mass, springs, damper) we analyse the effect of the damper coefficients on the output variance. The system described by a continuous differential equation is substituted with a discrete time (sampled) autoregressive moving average ARMA (3, 2) time series model. The displacement input (road profile) also characterized by an ARMA (p, q) stationary stochastic process. A variance transformation formula is derived which uses the (simulated) discrete impulse response function and the autocorrelations of the input signal. This formula is applied to the mechanical system searching the optimal damping which gives the minimal output variance.

In the recent years, it can be observed that the products are launched by rapidity and short time. The lifecycles of user equipment has been shortened, the flow of information accelerated, the freely available information more widely accessible. One of the conditions of competitiveness for the arisen problems is the rapid and optimal solutions. Using a software or system, which supports the knowledge based design (KBD) the time and costs of the product development phase can be reduced. In this chapter the results of a product design and development process implemented in a PLM system will be presented on a ball screw drive mechanisms focusing on its returning guide.

The traction drives requires initial tension. Let us imagine such kind of epicyclic drive or harmonic drive. In both cases the annular wheel is made of spring steel and its load is bending. The stiffness of the ring is large enough to produce the required normal force between the annular and the planetary wheels or between the ring and the flexible, cup shaped wheel. The transmission ratio depends on the ratio of planetary and sun wheel in the planetary drive, or the difference between the circumferences of ring wheel and the cup shaped wave wheel on the harmonic drive. Both the deflection of ring wheel and the number of planetary wheels or the number of deflection wave increase the load carrying capacity and decrease the bending moment. The problem of deflection can be managed by differential equation or any kind of energy method. The analysis of equivalence of the outcomes closes the paper.

Within the framework of the research a position- and speed-dependent, power-absorbing hydraulic cylinder were constructed based on laboratory tests and finite element numerical simulation studies. The elaborated cylinder construction has a mathematically predictable characteristics and based on this feature can be used for different applications in the field of kinetic energy absorbing.

Vehicles often operate in rather harsh and even extreme environmental conditions, so their many parts all should resist well against corrosion, wear and other outer impacts, which surface phenomena need continuous developments and frequent testing. One rather fast and quite effective surface analytical technique is the Glow Discharge Optical Emission Spectrometry (GD OES), the applicability of which is demonstrated here by its several laboratory uses to detect the elementary composition in depth of some contaminated then plasma cleaned, pre-treated then metal and/or organic coated (painted or varnished) or just properly surface modified samples originating from different segments of automotive manufacturing or disassembled cars put under maintenance and/or repair.

Nowadays diamond burnishing, which belongs to the cold plastic manufacturing procedures, is used more frequently for final finishing operations of parts. By its application, the surface roughness and the micro-hardness in the sub-layers of the components can be increased. The procedure of diamond burnishing can be performed for final finishing manufacturing of outer and inner cylindrical surfaces, and shaped surfaces (e.g. conical, spherical and even statue like) too. The parameters which effect to the surface features during manufacturing are burnishing speed, feed rate, burnishing force, the number of passes, material and geometrical data of the working part of the burnishing tool, furthermore the lubricant applied to burnishing. During our experiments we have chosen from the above mentioned parameters the burnishing speed, the feed rate and the burnishing force and we examined what is the effect of these parameters to the surface topography when manufacturing outer surface of cylindrical components by burnishing tool having given geometrical dimensions. The experiments were executed by the Factorial Experiment Design method. On the base of the evaluated experiment data the improvement ratio of surface roughness was determined by empirical formulas. The technological parameter and burnishing force values were shown out, which provided the highest improvement ratio of surface roughness.

The field of vehicle tyres is a key pillar to the Vehicle Engineering BSc launched in September 2016 at the Faculty of Mechanical Engineering and Informatics of the University of Miskolc and the Tyre manufacturing postgraduate course in the technological specialisation on which work is in progress. Generating a yearly amount of several 100 millions of tyres as waste of the automotive industry is, almost 80% of them as passenger car tyres and 20% as truck tyres, whose management creates a huge load to bear on society. These days a relevant task of this field is to find a solution that is reducing environmental loads and sustainable to the solution. Vehicle tyres contain many organic and inorganic compounds: natural and artificial caoutchoucs (NR, SBR, BR, IIR, EPDM), silica, zinc oxide, sulphur, steel and artificial fibres, anti-ageing agents, carbon black etc. whose production requires a significant use of fossil energy carriers. There are several ways of recycling tyres lost their original function: incineration, recycling in its material (rubber-based pavements, roads, sporting grounds) or chemical conversion (energy carrier, chemical raw material), respectively. These days cracking in combined material flow embodies one of the main research directions of chemical conversion. The bottom line is that several raw materials are decomposed in parallel during catalyst-assisted thermal cracking: blends of different ratios of biomass, plastics, rubber tyre. This publication presents options of chemical conversion and its optimisable parameters. We investigated thermo-catalytic thermal cracking (cracking) of rubber and polystyrene waste producing thereby valuable petrol- and gas oil-type hydrocarbon products.

The global need for energy and raw materials is constantly on the rise as mankind’s technology progresses. Due to more and more environmental load and fossil energy carriers exhausted, processes designed for thermo-catalytic conversion of various hydrocarbon-based wastes (plastics- and rubber waste, biomasses) and fuels with a low calorific value (lignite, brown coal) have come into focus in the last decades. The essence of these processes is that solid raw materials forming long carbon chains can be converted at medium-high temperatures (410–450 °C) by means of a special reactor system into more valuable hydrocarbon fractions of liquid and gas state such as petrol-, gas oil-, fuel gas-type products. We examined in our work, how low-quality rubber waste and/or brown coal, plastic waste raw materials can be converted into better quality products—of primarily liquid state. The problem raising a number of open points is a complicated optimisation issue as various heterogeneous components and their content in aggressive contaminants (sulphur, chlorine, nitrogen, oxygen, oxides, carbonates etc.) can largely affect decomposition kinetics thus the quality and quantity of hydrocarbon products formed so as well. This publication covers the system modelling techniques in detail that can be used as a foundation for the basis of mathematical modelling of high-complexity technical systems.

The aim of our research is to develop an economic material combination exhibiting good wetting with solder alloy melts and enhanced lifetime against erosion in lead-free soldering applications. Iron-nitrides have strong bonds compared to metals, therefore they are expected to have increased resistance against erosion in solder melts compared to iron soldering tools. The first step of our research is to find the proper substrate material for nitride coating to obtain the desired wetting behaviour. The present paper focuses on the substrate material selection through wetting examinations of nitrided W302, 42CrMo4 and C45 steels with SAC 305 solder alloy melt. It was found that the substrate composition strongly affects the wetting contact angle. The best wetting was achieved with the C45 type steel substrate. The correlation between substrate composition, compounds formed during nitriding and wetting behaviour is discussed.

The importance of dual phase (DP) steels in the automotive industry was continuously spreading in the last decade. With their special microstructure—containing ferrite and martensite in particular ratio—high strength and increased formability is available. That’s the reason why the application of DP steels is providing to exceed the 50% in a modern car body structure, according to the European program of Ultra-Light Steel Auto Body Advanced Vehicle Technology. This paper presents the experimental results of hemispherical dome tests and uniaxial tensile tests of three types of DP steels: DP 600, DP 800 and DP 1000. The effect of the tensile strength on the formability was investigated. It was described by the total and the ultimate tensile elongation, the average anisotropy and the limiting dome height (LDH). Based on our results it can be concluded that both the total and the uniform elongations are nearly linearly decreasing as the tensile strength is increasing. The slope of total elongation is more sensitive to the strength growth. However, it is no longer true for the plastic anisotropy. The reduction rate of average anisotropy stops over 800 MPa, and does not change until 1100 MPa. According to the dome tests results, the formability is also influenced by the sample geometry—through the deformation path—besides the tensile strength. The LDH values in biaxial stretch strain conditions are less dependent on the tensile strength. They are within a 3 mm interval for all three strength classes. In plane or stretch-press strain conditions, higher reduction can be observed. The characteristics of dome height curves are similar for all samples, regardless of their strength.

We performed a comparison between two laser interferometric methods. One of the methods is used by our modernized Michelson type laser interferometric motion analyser (LIMA), which measures primarily the displacement, while the other method is the one used by an LDV (Laser Doppler Vibrometer) device, which primarily measures the velocity on the basis of the Doppler effect. The motion that is measured is the vibration of the corner cube reflector (retroreflector) of the measuring arm of the LIMA. During the measurements the LDV measured the back plate of the house of the retroreflector. These simultaneous analyses of the vibrations made possible the comparison of these two methods for the precise velocity studies. In general, it was found that the velocity values, obtained by the two methods correspond to each other within 2% accuracy.

Nowadays have developed more and more such materials, which mechanical and physical properties are extremely better compared to commonly used materials. These composite materials, which were used before a few years ago just in the construction industry for stiffening or as a decorative element, are used also often is the automotive industry. This fact opened a new way in machining, where we must comply to increasingly stringent precision and visual requirements. The burr as attendant phenomenon is known as conventional metal cutting, is also present at machining of special materials (e.g. composites) as well. For high time for piece deburring increase the costs of parts production, therefore industry places much emphasis on reduction of it. The article investigates various options of deburring after machining of metal and polymer-based composite materials.

Vehicle industry plays an important role in the GDP production and employment of present-day Hungary. In the June of 2016 the share of vehicle manufacturing subsection within processing industry was 31.4% [1] and the sector employed 135 thousand persons in 2014 [2]. Thus higher education takes a significant role in the provision of adequately trained students and the co-operation with the industry has also a great role. The author reviews the training of internal combustion engines, which is the most frequently applied resource today—related to his own narrower field within vehicle industry and the joint research at the Department of Energy Engineering of BME. The author presents the Department in the field, the present areas of research, the industrial co-operations and the available infrastructure. Finally the further plans are being outlined.

In this paper the concept of a new turning method for helical surfaces will be demonstrated. In mechanical engineering several types of surfaces can be mentioned, which are difficult to machine for example the thread of a ball-nut or small workpieces with high pitch threads or helical surfaces. The main difficulty with these surfaces is that they can’t be machined with a tool that generates the desired surfaces, because we can’t assure the rigidity for these machining conditions. These surfaces are similar to threads in a certain respect. But we cannot use the exact threading cycle, because in the threading cycle the geometry of the tool defines the geometry of the surface of the thread. This new method is based on the threading NC cycle, but in this case the tool geometry won’t be copied to the surface. The surface geometry will be defined by the start points (and/or start angles) of the thread, which can be computed by an appropriate computer program.

Intelligent transportation systems (ITS) include both the traffic stream control and the intelligent vehicles. Cell phone networks and global positioning systems (GPS) enable the use of geographical information (GI) so that individual vehicles can locate themselves and global transportation systems can be enhanced taking advantages of new information technology solutions and algorithms. One of the major parts of ITS research is the assignment, routing and scheduling of vehicles in global transportation processes. This paper proposes an integrated engineering optimization algorithm to support the solution of assignment and scheduling problems of vehicles in intelligent transportation systems. This novel approach combines the available hardware and software components of an ITS with an algorithm to optimize the transportation processes of a global supply chain. To gain insight into the complexity of the logistic problem, the new model of supply chain including ITS is also described.

This paper shows the modeling and solving of a special production fine scheduling problem of the automotive industry. A new scheduling software has been developed to create execution plans to the production activities that satisfy the customers’ demands. The main characteristic of the scheduling problem is that different types of shared resources (e.g. production lines, attachment points, mold carriers, tools) have to be allocated simultaneously, and multi-processing tasks have to be scheduled to meet production orders within strict time limits. To solve the problem we consider not only the primary technological processes but also the tool-preparation processes. This inbuilt sub-problem is converted to a special resource environment by using a problem space transformation procedure. To minimize the tardiness, we schedule the jobs in the given resource environment. We elaborated a new solving algorithm that can create the optimal solution for the sub-problem in polynomial running time. This solution for the sub-problem is applied to meet the tool-preparation constraints of the full production fine scheduling problem. An advanced multi-objective searching algorithm solves the full problem. The paper presents the approach of the developed solving method, the defined objective functions and the applied neighbouring operators. In the solving process, all the decision making sub-tasks (assigning, sequencing and timing) are managed simultaneously. The concrete values of the decision variables are set by a multi-operator and multi-objective local searching algorithm. The fine scheduling software can also support inventory control by using special objective functions that can help to optimize the manufacturing from the point of view of the product type dependent stock levels. The scheduling problem comes from the plant of Fehrer Hungaria Járműipari Kft., specialized in vehicle seat products (Mór, Hungary).

In order to optimize the stockpile management costs, the suppliers of car manufacturers answer by building up a safety stock of different extents to avoid uncertainties arising from the fluctuation of demands and to minimize their impact. During the calculation of the safety stock in the case of both the periodic and the continuous review models, the relations proceed from the system of conditions, according to which the average level of forecasted demands does not change with the progress of time. In practice, however, we can see a certain shift, thus, during the definition of safety stocks and the order of purchased parts, the historical data can only be used by knowing the direction and the extent of the shift. During our analysis, we examine the impact of shifts of different directions and extents on the stock of purchased parts, and we build up a model that predicts the probability of the occurrence of a stock shortage of an unplanned extent and of an overstocking.

Vehicles, whose functions are enriched with attributes to increase safety, environmental awareness, effectiveness, comfort level and prestige, so that they can play a key role in creating optimal mobility, are now being invented, planned and manufactured for general use. Throughout the full spectrum of transport, vehicles will soon exempt people from the routine of driving. If people do not need to drive their cars, will their driving skills deteriorate or will they entirely fail to develop this skill later on? Is this threatening us in the near future? What are the latest research results and regulations on autonomous vehicles? What are the actual advantages of vehicle automation? We are trying to find the answers to these questions in our article, while analysing and systematizing information from the national and international literature on the development of intelligent vehicles by examining the interaction between various ground transport vehicles, and the related developments on the subject. Our goal is to create automatic intelligent vehicle systems, within the concept of intelligent infrastructures and smart cities. The paper provides an FMEA analysis of intelligent vehicles. To decrease the explored deficiencies in the present system, applicable proposals are formulated about development areas, such as forming a communication between vehicular traffic and railed vehicles. We feel that such developments are important steps in increasing traffic safety, and we regard them as elements of intelligent transport.

Using software became a part of our everyday life, in the last few decades. Software is widely used in areas, such as national defence, aeronautics and astronautics, medicine or even transport. There are 100 million lines of codes in a modern high-end car’s engine control unit. In comparison, the Space Shuttle needs 400 000, the F22 fighter jet needs less than 2 million, the Boeing 787 airplane needs 14 million and the Facebook needs more than 60 million lines of codes to function. Even a smaller error can lead to devastating consequences in safety-critical systems, such as those operating in vehicles. There have been several examples in recent years, when an automotive recall was necessary due to dangerous software, and there were cases when these errors presumably caused fatal accidents. Definition of software reliability is the error-free working probability of software for a specified period of time under well-defined environment. Usage of software is inevitable. It can be found in every vehicle to control almost everything. Therefore software can be considered as a critical success factor and it has a strong effect on the reliability of the whole system. The software systems are getting more and more complex. Known fact is a more complex system has more possibility to have errors. The most difficult problem is that the traditional methods of reliability cannot be used. For example fatigue and wearing of mechanical parts or features of lubricant systems can be calculated quite well, since we have enough prior knowledge on their features. Unfortunately, in case of software systems this knowledge is missing. This paper deals with the question of software reliability. In the first part it lists the problems and the second part gives some mathematical issues to calculate working probability.

In autonomous robotic control it is necessary to measure the exact tracks of the robot and then calculate the best route for it. This article is about to introduce a method which can be used to measure the route of an Unmanned Ground Vehicle to help the controller software to guide the vehicle. For now, the most popular way to measure and track of a vehicle or a robot’s movement is the incremental or absolute encoder installed on the vehicle’s wheels. This method measures movement in an indirect way because there can be gear system on its motor or in omnidirectional systems, there can be a slip between the wheel and the ground so the data of these sensors could be easily tampered. With this method we install an optical flow sensor (or sensors) to the undercarriage of the robot. This way the system measures the movement in a fully direct way because the sensors detect the movement between the robot and the ground and there is no mechanical or electrical connection between the sensor and the reference.

For the purpose of determining the position and orientation of a moving robot and autonomous vehicle, inertial sensors and magnetometer data are computed in order to enhance GNSS (Global Navigation Satellite System) data accuracy. This paper presents a method called hybrid localization that combines absolute localization, using exteroceptive data, and dead reckoning technique, using proprioceptive data. A positioning method based on dead reckoning technique is developed in this paper.

The paper describes the application of the QFD method, a technique used for the evaluation and proper realization of the different customer expectations, in the quality management of logistics systems. Both the theoretical basics of the method, as well as the main steps of its implementation are introduced. The implementation itself is presented with the help of a practical example that is strongly related to both the logistics and the automotive industries, as the latter especially relies on complex supply chains that require the extensive utilization of quality management tools. Besides the previous, the paper also provides an overview of all the possible areas of utilization for the QFD in the logistics industry. Therefore, the described method can have a great value from both the academic and the industrial perspectives.

This paper presents a sensorless method for determination of the load current of an automotive generator applying a neural-fuzzy implementation. We developed a simulation model of the automotive generator and its voltage regulator in order to get information about its behaviour at different operating conditions. The model takes into consideration the nonlinearity caused by the saturation of the magnetic flux and the effect of the shaft speed on to the internal impedance. The simulated results are compared to those that are available in the literature and to the results gained from real system measurements. A laboratory test rig was developed to study the operation of the automotive generator and voltage regulator in different conditions. In contrast to general spread methods in this area the measurement results are plotted in 3D to emphasize the hidden operation fields. In the operation of the system the parameters of the DFM—Digital Field Monitoring—signal have important roles. Both the frequency and even more the duty of the DFM signal carry on important information about the condition of operation of the automotive generator and its voltage regulator, especially about the load current. This has an important influence on the whole system of the electric circuit of a car starting from battery to end consumers, different ECUs—Electronic Control Units—fuel consumption and emission of the ICE—Internal Combustion Engine. Applying neural-fuzzy theory, we could realize a sensorless method for this aim.

This article focuses on CompactRIO based driver assistance system and the goal was a completely autonomous operation. By the development our vehicle had to be able to realize several intelligent driving assistance functions, such as adaptive cruise control, lane keeping, predictive emergency braking, brake energy regeneration, automated parallel- and cross parking and GPS navigation, and we also had to design hybrid drive on the go-kart. For implementing the intelligent functions mentioned above, we chose NI cRIO during the development. By taking the advantages provided by the developing environment and the modularity of the system, we could solve the scheduled tasks.

To detecting the nearly objects and walls is very important for a mobile robot or an autonomous vehicle to collision avoidance. It needs many of sensors for wide range detection. The results are better with more type of sensors for example infrared sensors, ultrasonic sensors, laser distance sensors. Because of the number of sensors it needed to use sensor fusion. It is a relatively easy way by using the FRI based Behaviour Description Language or the Bayes-classifier.

The growing market globalization, increasing global competition, more and more complex products require new technologies, methods and processes. The shorter life cycle and the complexity of final products and new customer requirements require efficient operation of supply chains (SC). Optimization of supply chains results new models, concepts of value chains and new organization and cooperation forms of members. Reduction of total cost and lead time of the chains, and higher customer service level can be the objectives of the supply chain optimization.

In this paper spot-welding technology of sheets made of Dual-Phase (DP) steel, which are one of the most important materials in the automotive industry, has been analyzed with experimental research and finite element modelling. Besides conventional mild steels that have been dominant for decades in automobile production, the application of advanced high-strength steels (AHSS) comes into focus. Among the first generation AHSS, DP steels are of the utmost importance concerning their automotive use. In Hungary a lot of small and medium sized enterprises function as the suppliers of the big automakers settled in our country. Nowadays these enterprises, besides the welding of conventional mild steel parts, often have the task of joining ferrite-martensitic DP steels with spot welding. During the spot welding of DP steels, when using the technology familiar with mild steels, the risk of hardening, the unfavourable failure of the joint or even cracking during operation must be taken into account, therefore welding technology must be planned on different theoretical bases. The traditional, continuous energy input and the symmetric double pulse as the non-continuous energy input were compared for resistance spot welding, focused on the advantages of pulsed energy input. For numerical analysis an axisymmetric coupled finite element model (FEM) is developed to study the effect of welding time and current intensity on nugget size and thermal history in resistance spot welding process using MSC.Marc software package. The cross-section macrostructures of the welded specimens are examined and compared to the predicted size of the weld nugget and heat affected zone (HAZ). Shear testing, cross tension testing, peel testing and hardness measurements are also performed on specimens for each welding process to examine the effect of the changes in different welding parameters on the load bearing capacity of the joint.

The design of railway vehicle structures is a complex task requiring absolute care, well-founded theoretical knowledge and significant practical experience. The requirements related to the vehicle structures make it necessary to manufacture structures that have the right amount of stiffness and are adequate also in terms of fatigue resistance, but have the lowest weight possible and can economically be manufactured, and at the same time are simple and easy to maintain. The main aspects of designing for modern welded vehicle structures are, as follows: suitable load-bearing capability and safety, the correct construction, according the welding technology, and the same, the cost-effectiveness, as well. We can achieve significant reduction of weight by increasing of the strength of elements and by reduction of the thickness of plates and construction elements. The minimum of the necessary thickness of plates can be calculated by optimization of sizes. In our lecture we will present the weight reduction design approach, and new innovative design methods and technologies for lightweight welded railway structures of the modern passenger coach by the examples of new IC+type railway passenger couch family, developed by MÁV-START Ltd.

For welding of aluminium alloys with Harms and Wende medium frequency inverters (1000 Hz) we developed a special control mode AMC (Aluminium Mode Classic) and its extension AMF to handle aluminium alloys (mainly 5000th and 6000th alloys). These modes have been made to handle the alloy groups. The new methods cover every day issues as undefined oxide layers or other coatings. From the commercial side a standard inverter is used to reduce investments. Internal monitoring while welding is another important topic of this mode as well as constant weld time. The last item is the key topic for high volume production customers. Examples are shown for several surface conditions. Methods are suggested to preserve against crackles and cracks. In advance first tendencies in quality monitoring are presented using the force signal during the current phase of the welding process. In this paper we give the solution first before showing the background.

High cycle fatigue tests were performed on two strength categories of high strength steels, on quenched and tempered (S690 and S960) and thermomechanical (S960) types, on base materials and their gas metal arc welded joints, and on different matching conditions. The planning and optimization of welding technologies based on investigations under cyclic loading conditions were built upon a large number of investigations and statistical evaluation of the test results. Statistical approach was already applied during the preparation of the investigations, which have been allowed the expansion of the scope of the results and the increasing of their reliability. The article demonstrates and evaluates the results comparing with each other and with literary data.

Based on the welding heat cycle models physical simulators are capable for the creation of critical heat-affected zones (HAZ). The simulated HAZ areas can be examined by various material testing methods (e. g. Charpy V-notch impact test) due to their increased homogeneous volume compared to their extension in real welding experiments. In our research work relevant technological variants (t_8.5/5 = 2.5…30 s) for gas metal arc welding technology were applied during the HAZ simulation of S960QL steel (EN 10025-6), and the effect of cooling time on the coarse-grained HAZ was analysed. In thermo-mechanical simulators the achievable cooling rate is always the function of specimen geometry and the presence of external cooling. Therefore a special drilled specimen with external cooling was developed for performing a shorter (t_8.5/5 = 2.5 s) cooling than 5 s, which cannot be realized on the conventional Gleeble specimen. Heat cycles were determined according to the Rykalin 3D model. The properties of the selected coarse-grained (CGHAZ) zone were investigated by scanning electron microscope, hardness test and Charpy V-notch impact test.

Determination of the residual stress state in a loaded automotive component is highly important because of its strong effect on the lifetime of the element. Nowadays, the residual stress characterization of products became an everyday requirement in the automotive industry, and the quality control is impossible to imagine without it. Forasmuch as every producing process (casting, heat treating, different kinds of metal deformation processes and surface compressing methods, etc.) influences the residual stress state, therefore it can be very complex and various within the materials. If we conscious in the effect of these processes it is possible to reach such a state in the material which can enhance its lifetime and quality, and with an optimized process, the costs could be reduced. Several methods exist for measuring the residual stress and each of them has its own advantage and disadvantage. With this paper our purpose is to introduce nowadays’ available stress measuring methods such as X-ray diffraction, magnetic Barkhausen noise and the hole drilling methods and a few more alternatives. Some useful results from the practice are also presented.