Fretting Damage Analysis and Predicting of Engine Head and Block

<div class="section abstract"><div class="htmlview paragraph">The paper presents a numerical activity directed at the analysis and optimization of internal combustion engine water cooling jackets, with particular emphasis on the fatigue-strength assessment and improvement.</div><div class="htmlview paragraph">In the paper, full 3D-CFD and FEM analyses of conjugate heat transfer and load cycle under actual engine operation of a single bank of a current production V6 turbocharged diesel engine are reported.</div><div class="htmlview paragraph">A highly detailed model of the engine, made up of both the coolant galleries and the surrounding metal components, i.e., the engine head, the engine block, the gasket, the valve guides and valve seats, is used on both sides of the simulation process to accurately capture the influence of the cooling system layout under thermal and load conditions as close as possible to actual engine operations.</div><div class="htmlview paragraph">Concerning the CFD side, a 50-50 binary mixture of ethylene-glycol and water is used in order to correctly reproduce the coolant behavior, while boundary conditions are derived from a combination of experimental measurements and a CFD-1D model of the whole engine.</div><div class="htmlview paragraph">In order to find a proper CFD setup for the optimization of the thermal behavior of the engine, a preliminary comparison between experimental temperature distribution within the engine head and CFD forecasts is carried out. Eight thermocouples are used to measure the engine head local temperature at some critical locations.</div><div class="htmlview paragraph">Among the many competing numerical sub-models involved in the CFD simulations, particular attention is devoted to the modeling of phase transition and vapor nuclei formation within the coolant galleries.</div><div class="htmlview paragraph">Concerning the FEM side, thermo-mechanical analyses are carried out aiming at addressing the design optimization of the engine in terms of fatigue strength. In view of the wide range of thermal and load conditions, both high-cycle and low-cycle fatigue must be properly characterized by means of ad-hoc criteria. An energy-based criterion specifically suited for low-cycle fatigue regions is therefore superimposed to well-established S-N o ε-N criteria for the high cycle fatigue regions.</div><div class="htmlview paragraph">The proposed methodology shows very promising results in terms of point-wise detection of possible engine failures and proves to be an effective tool for the accurate thermo-mechanical characterization of internal combustion engines under actual life-cycle operations.</div></div>

<div class="htmlview paragraph">The effects of engine operating conditions on the octane requirement and the resulting knock-limited output were studied on a single cylinder engine using production cylinder heads. A 4-valve cylinder head with port deactivation was used to study the effect of fuel octane, inlet air temperature, coolant temperature, air/fuel ratio, compression ratio and exhaust back pressure. The effect of the thermal environment was studied in more detail using separate cooling systems for the cylinder head and engine block on a 2-valve cylinder head.</div> <div class="htmlview paragraph">The results of this study compared closely with results found in the literature even though the engine and/or operating conditions were quite different in many cases. Guidelines on the effect of various parameters on the octane requirement of an engine can be summarized as follows:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">Spark Advance: 1 ON/1° SA</div></li> <li class="list-item"><div class="htmlview paragraph">Intake Air Temperature: 1 ON/7 K</div></li> <li class="list-item"><div class="htmlview paragraph">Air/Fuel Ratio: peaks at 5% rich of stoichiometric, decreases by around 2 ON / air/fule ratio around peak</div></li> <li class="list-item"><div class="htmlview paragraph">Intake Pressure: 3-4 ON/10 kPa</div></li> <li class="list-item"><div class="htmlview paragraph">Compression Ratio: 5 ON/CR</div></li> <li class="list-item"><div class="htmlview paragraph">Exhaust Back Pressure: 1 ON/30 kPa</div></li> <li class="list-item"><div class="htmlview paragraph">Coolant Temperature: 1 ON/10 K (Similar effect of head and block temperature., Larger effect at low speed.)</div></li> </ul> </div>

<div class="htmlview paragraph">The effects of the swirl level on the fresh air charge distribution is studied by using a multidimensional computer code for a uniflow type two-cycle diesel engine geometry. The flow is assumed to be axisymmetric. The inlet ports are simulated as an annular opening around the liner, and the exhaust valves are simulated as an annular slot in the cylinder head. Calculations are performed from exhaust valve opening to TDC for a large range of inlet port angles (10-30°). Results are presented in terms of velocity vector plots together with swirl velocity, and fresh charge contour plots.</div> <div class="htmlview paragraph">During the valves open period, the calculations indicate the presence of two vortices in the radial-axial flow plane as previously observed by Diwakar. The first one is near the liner wall (named as wall vortex) and the other is near the symmetry axis (named as the backflow vortex). The incoming fresh air tends to flow toward the cylinder head between these two vortices with reverse flows on the liner wall and near the symmetry axis. Increasing the swirl increases the strength and the region covered by the backflow vortex, redirects the upward fresh charge to a larger radius, and restricts the short-circuiting of the fresh air to the exhaust valves. This increases the trapping of fresh charge and the scavenging efficiency.</div> <div class="htmlview paragraph">Calculations from the exhaust valve closing to TDC show that: <ol class="list nostyle"> <li class="list-item"><span class="li-label">1)</span> <div class="htmlview paragraph">The size of the backflow vortex is reduced as the port is closed and diminishes immediately thereafter. The wall vortex is present up to 60° CA BTDC when the squish effects generated by the piston motion becomes dominant.</div></li> <li class="list-item"><span class="li-label">2)</span> <div class="htmlview paragraph">Fresh charge is not completely mixed with the residual gases even at TDC. There is about 11-17% difference in the fresh charge concentrations at the highest and lowest fresh charge locations at TDC. The inlet port angle (engine swirl level) seems to increase the magnitude of this stratification slightly, but more importantly, it changes the location of this charge stratification considerably. At low swirl levels (port angle 10°), the low fresh charge region is located near the mid-radius of the bowl, and the maximum fresh charge is in the clearance volume between the piston and the bowl. At high swirl levels (port angle 30°), the maximum fresh charge is compressed toward the bowl belly, and the low concentration region is both in the clearance volume and on the cylinder head near the axis. At medium swirl levels (port angle 20), the fresh charge covers the midsection of the bowl, while the residual gases are restricted only within the clearance between piston and engine head.</div></li> </ol></div> <div class="htmlview paragraph">For the diesel engine application and to enhance the mixing of the fuel spray with the fresh air, the residual gas-fresh air stratification pattern of the medium swirl case is better than both the high swirl and low swirl cases.</div> <div class="htmlview paragraph">In addition to the wall vortex (generated by flow separation above the port) and the Backflow Vortex (generated by the swirl velocity field), a new vortex pattern named as the Head Vortex is identified. The mechanism for the Head Vortex development is recognized as the stagnation of the fresh air jet on the cylinder wall rather than on the engine head. The presence of the head vortex changes the mixing rate between the residual gases and the fresh air considerably. The development of the concentration profiles to these final shapes is demonstrated. The effects of the engine swirl level on the mixing of the fresh charge with the residual gases are investigated in terms of the mixing rates and the maximum concentration difference within the flow field.</div>

<div class="section abstract"><div class="htmlview paragraph">Fatigue failure is one of the major failure modes for internal combustion engines, especially with reduction in engine size and increase in combustion pressure and operating temperature. Dynamometer tests are devised to ensure engine durability for high and low cycle fatigue. With the advent of CAE technology, the dynamometer test behavior can be simulated using CAE analysis and engine durability can be assessed. The data generated in CAE analyses can be used to predict failure of the engines or future engine design modifications.</div><div class="htmlview paragraph">The present paper has two parts - first is running finite element analysis (FEA) to get stress, strain data and running high cycle fatigue analysis to get safety factors and second is creating a predictive tool to assess failures using data from the first part as inputs. Using advancements in the field of machine learning, the paper presents use of support vector machine (SVM) algorithm to predict failure of the engine based on inputs.</div><div class="htmlview paragraph">The paper discusses procedure to build the data driven model and its results. Such data driven model can be used as a tool to predict failure of engine arising from future design changes or as a variation tool to predict failure arising from changes in inputs.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Gasoline direct injection (GDI) engines usually emit higher levels of particulates in warm-up conditions of a driving cycle. Thus, sources of soot formation in these conditions were investigated by measuring particulate numbers (PN) emitted from a single-cylinder GDI engine and their sizes. The combustion was also visualized using an endoscope connected to a high-speed camera. Engine coolant and oil temperatures were varied between 15 and 90<sup>o</sup>C to mimic warm-up conditions. In addition, effects of delaying the start of ignition (SOI) on the emissions in these conditions were examined.</div><div class="htmlview paragraph">Coolant and oil temperatures were varied individually to identify which factor has most effect on PN emissions. While coolant temperature strongly influenced PN with cold oil, the oil temperature insignificantly affected PN at low coolant temperature. These findings indicate that PN emissions are heavily dependent on the engine block’s temperature, which is dominated by the coolant.</div><div class="htmlview paragraph">SOI plays a significant role in PN formation because it influences the wall film thickness on the piston top. In the experimental warm-up conditions, injecting fuel at a later SOI was found to decrease PN emissions. Visualization showed no occurrence of diffusion flames at late SOI timings due to the associated reduction in interaction between liquid fuel and the piston.</div><div class="htmlview paragraph">The integrated luminescence from combustion images was found to correlate closely with PN emission measurements. Thus, higher integrated luminescence, indicating higher soot formation due to pool fires on the piston top, was associated with higher PN levels. When coolant and oil temperatures were both varied, PN emissions were found to decline dramatically with increasing temperatures. At lower temperatures, diffusion combustion occurred on the piston due to persistence of a non-vaporized fuel film. At 15<sup>o</sup>C coolant and oil temperature, this phenomenon was strong, but it gradually declined as the temperature increased. When the temperature reached 60<sup>o</sup>C, diffusion flames started to disappear, resulting in a dramatic decrease in PN.</div></div>

<div class="section abstract"><div class="htmlview paragraph">This paper presents the results of an experimental analysis on a multi-cylinder diesel engine, in which in-cylinder pressure and accelerometer transducers are used with the purpose of developing and setting up a methodology able to monitor and optimize the combustion behavior by means of non-intrusive measurements.</div> <div class="htmlview paragraph">Previously published results have demonstrated the direct relationship existing between in-cylinder pressure and engine block vibration signals, as well as the sensitivity of the engine surface vibration to variation of injection parameters when the accelerometer is placed in sensitive location of the engine block. Moreover, the accelerometer trace has revealed to be able to locate in the crank-angle domain important phenomena characterizing the combustion process (the start of pre-mixed combustion, the crank angle value corresponding to the beginning of diffusive combustion and to the in-cylinder pressure maximum value).</div> <div class="htmlview paragraph">The objective of the present work is to quantify the strict relationship between the in-cylinder pressure signal and the accelerometer trace, in order to obtain information concerning both the pressure maximum value and the pressure rise rate from the accelerometer trace.</div> <div class="htmlview paragraph">In this paper, the previously developed steps of the research program are briefly presented. The processing technique is described and representative results are presented and discussed, in which different values of speed and load have been imposed on the engine.</div></div>

<div class="htmlview paragraph">A single-cylinder, two-valve engine was operated with independent cooling circuits for the engine block and cylinder head to investigate the effect of temperature distribution on HC emissions. The goal was to understand and quantify the mechanisms responsible for decreased HC emissions at elevated temperatures. Tests were run at a typical road load condition using two different fuels (a 97 RON blend and isopentane - to eliminate liquid fuel and oil layer absorption effects). The total HC emissions (97 RON fuel) decreased by 15-20% with an increase in either the cylinder head or engine block coolant temperature from 71 to 110 °C. When operating with isopentane the HC emissions decreased by 15-20% with an increase in the engine block temperature from 71 to 110 °C but were essentially unaffected by cylinder head temperature. This indicates that the cylinder head temperature primarily influenced the HC emissions from liquid fuel effects. The exhaust gas temperature did not change significantly with an increase in either the cylinder head or engine block temperature so it is believed that port oxidation was not significantly affected. The increased cylinder block coolant temperature produced decreased crevice loading (lower gas density) as the liner and piston temperatures increased. An increase in the liner temperature should also reduce the density of the wall layer gas which expands from the piston crevice and increase the diffusion into the hot burned gases, increasing in-cylinder oxidation. The results indicate that the effect of oil layer absorption on the HC emissions was not large since the liner temperature had a similar effect on the emissions when operating with either a soluble (97 RON) or a relatively insoluble (isopentane) fuel.</div>

<div class="htmlview paragraph">The production unit number of small diesel engine cars tends to decline except recreational vehicles in Japanese market in recent years, while the production unit number in Europe market keeps on increasing owing to the merits of the durability and the fuel consumption. The small diesel engines will have to be improved in the near future by solving major problems such as noise and vibration pollution, environmental pollution, improvement in performance of diesel engines, in order to expand the production of the engines.</div> <div class="htmlview paragraph">This paper refers to a basic study on the experimental and analytical methods for the reduction of resonant vibration in each vibration mode on some cylinder blocks of small high-speed diesel engines in rated engine speed range. Hammering test method, which is easy and useful for measuring frequency response functions, is carried out in the experiments. In this test, the cylinder blocks are directly excited with the impulse hammer, and more the main journals are excited via the newly-made force transmission parts in the next experiment. Two kinds of the engines which have been recently recognized as low noise and vibration engines are chosen in this study. The cylinder blocks of the engines are called of long skirt type and ladder frame type, respectively. The vibration characteristics of these cylinder blocks are obtained in the frequency range from 500 <i>Hz</i> to 2 <i>kHz</i> using the experimental modal analysis. This frequency range is chosen in consideration of the reliability of the vibration experiments. And the force transmission routes from the piston heads to the crank journals of each cylinder block are considered as mentioned in the latter experimental method. The experimental results are used to calculate the natural frequencies by the modal analysis and the calculated results are compared with the ones obtained from FEM analysis. Furthermore, the cylinder blocks are remodeled in order to reduce the vibrations of all modes using FEM analysis.</div> <div class="htmlview paragraph">Consequently, it has been shown that the vibration stress of the cylinder block can be reduced by higher rigidities and more lightening weights of the crankcase and the crank journals in the measured frequency range.</div> <div class="htmlview paragraph">The conclusions are described as follows;</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts is useful to measure the natural frequencies of a cylinder block. This method can be easy to get the equal results with the measured ones on running conditions without engine operation.</div> </li> <li class="list-item"> <span class="li-label">2</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts can easily analyze the natural frequencies at all the vibration modes on equal conditions with running ones. Then the method is a useful tool for improving the vibration characteristics.</div> </li> <li class="list-item"> <span class="li-label">3</span> <div class="htmlview paragraph">It has been proved from the analytical viewpoints that the cylinder block of the ladder frame type can be adopted as low-noise, small diesel engines with little increase of the engine weight while maintaining higher rigidity.</div> </li> </ol> </div>

<div class="htmlview paragraph">This paper presents several methods for reducing engine weight primarily through substitution with light-weight materials. The efficiency and performance of the engine were reviewed using a light-weight experimental engine (hereinafter called “weight-reduced engine”) constructed by the authors in order to investigate the possibility of practical use of the proposed weight reduction measures.</div> <div class="htmlview paragraph">The weight-reduced engine is based on an in-line 4-cylinder, 2.0 liter, gasoline engine with the base engine weight of 162 kg excluding engine oil and coolant and was reduced by 37 kg by applying alternative light-weight materiaLs and new manufacturing techniques. This corresponds to 23 % weight reduction.</div> <div class="htmlview paragraph">The materials used in the weight-reduced engine are 53 % steel, 33 % aluminum, 7 % plastics and 7 % other light-weight materials.</div> <div class="htmlview paragraph">It was found that by application of light-weight materials, the engine performance of the weight-reduced engine could be improved. That is improvements in response and friction loss. In particular, weight reduction of the major moving components, such as connecting rods, not only contributes to reduce friction loss but leads to a weight reduction for other components.</div> <div class="htmlview paragraph">The light-weight components have been put to various kind of testings which cover fatigue of components and bench testing with assembled engine by motoring and firing. These results were sufficient to confirm that these components are durable enough to operate in a practical environment.</div>

<div class="section abstract"><div class="htmlview paragraph">In-cylinder large scale and small scale structures are widely recognized to strongly influence the mixing process in HSDI Diesel engines, and therefore combustion and pollutant emissions. In particular, swirl motion intensity and temporal evolution during the intake and compression strokes must be correctly estimated to properly target the spray jets. The experimental characterization of the attitude of a valve/port assembly to promote swirl is traditionally limited to the steady flow bench, in which the analysis is carried out for fixed valve positions / fixed pressure drops and with no piston. Since flow bench analyses cannot reproduce the highly complex instantaneous flow conditions typical of actual engine operations, the use of fully-transient in-cylinder numerical simulations can become extremely useful to correctly address the engine ability to promote adequate flow structures and patterns.</div><div class="htmlview paragraph">CFD analyses of in-cylinder flow motion development and decay are usually carried out using relatively simple yet stable turbulence models, among which k-epsilon and RNG k-epsilon, in conjunction with near-wall algebraic functions, are probably the most popular ones. Nevertheless, it is widely recognized that such models show deficiencies in correctly capturing complex rotating flow structures such as those dominating in-cylinder flows of compression ignition engines. While waiting for the diffusion of more refined approaches such as Large Eddy Simulation (LES) or Detached Eddy Simulation (DES), the use of better performing RANS models such as Reynolds Stress and k-omega SST, in conjunction with adequate resolution of the near wall flow, would be recommendable.</div><div class="htmlview paragraph">The paper reports a numerical activity aiming at evaluating the influence of the turbulence model choice on the prediction of in-cylinder flow patterns in a HSDI Diesel engine for automotive applications. Three different engine operations are investigated, i.e. two part-load / low engine speeds ones and a full-load / peak power engine speed one. For each engine condition, both wall-function k-epsilon and low-Reynolds k-omega SST models are used, and for the last one two different near-wall grid refinements are adopted. In order to better assess the predictive capabilities of the models, analyses are preliminarily compared to experimental measurements for both a simplified engine-like geometry and flow structure available in literature and steady flow-bench operations of the actual engine head.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The following article describes the low frequency vibration analysis of aircraft piston engine Rotax 912 ULS. The results are based on the vibration signal made by the engine in the frequency range up to 400 Hz measured on the engine block in three axes. The aim of the research was to determine the method of detecting the misfire of individual cylinders based on the power spectrum of the selected frequencies analysis. Frequencies resulting from the periodicity of engine operation related to the frequency of the work cycle, rotational speed and ignition frequency were considered for the analysis. The tests were carried out in one point of operation. The highest levels of changes were recorded in the <i>Y</i> axis - the axis of piston movement. It was shown that the vibration level changes after switching off one of the cylinders. An indicator describing the vibration level was developed based on the value of amplitude of the power spectrum of vibrations two selected frequencies and it was shown that on its basis it is possible to detect misfires of individual cylinders. It was proven that it is feasible to use this method to diagnose misfire with the identification of a particular cylinder.</div></div>

<div class="htmlview paragraph">In undertaking any experimental work the first step is to plan carefully each successive step. Literature bearing on the subject should be examined to learn what work others have done on the problem and avoid needless duplication of effort. If the testing of only a simple accessory is involved, the results the device is intended to accomplish should be studied and an effort made to discover the designer's reason for believing that it will accomplish them. All conditions under which such a device must operate should be listed and the information needed from which to draw conclusions as to whether the device will meet them successfully should be determined. Before starting the actual work of testing, it is good policy to plan the necessary charts for presentation of the report.</div> <div class="htmlview paragraph">This preliminary work means that the investigator will start well prepared but not with his mind made up as to what the results will be. It is necessary to be very careful in all experimental or research work; otherwise preconceived ideas are likely to result in finding what one wants to find rather than the exact truth. Prejudice is not the result of careful thinking and planning but of lack of such forethought. If a problem involves the investigation of a device on an engine, as for example a manifold, it is well to remember that there are other functioning parts and to be on guard against the temptation to attribute a sudden falling off of engine-power to the manifold when it may, in fact, be due to improper functioning of one of the other parts. New problems are more than likely to arise within, the major one as the work progresses and must be solved before the original program can be continued. Each sub-problem should also be planned carefully.</div> <div class="htmlview paragraph">Methods to be followed in making an investigation are elucidated by examples of a study of adapting an existing carbureter to an existing engine and of a study of charge distribution by a manifold to the cylinders of a four-cylinder engine. It is necessary to do this with the use of numerical quantities taken from actual test results, but in the case of the carbureter tests the figures have no actual relation to one another and are not to be taken as representing achievements, as many were taken from experimental engines and other equipment. Before the effect of a given carbureter on the power and fuel economy of an engine can be studied, it is first necessary to learn what the engine is capable of doing when it is not influenced by the characteristics of the carbureter. After charts have been prepared from the ascertained data, the commercial-carbureter tests can be started. Each step for carrying these out is explained. All results are plotted in various ways for comparison and study.</div> <div class="htmlview paragraph">A method that is thought to be easiest and surest for studying charge distribution is by measurement of the maximum explosion-pressures in the several cylinders of a multiple-cylinder engine. The equipment used and the method of doing this are described and the results given. Curves produced from the study indicate that power loss due to poor distribution is incurred by reason of (<i>a</i>) too lean or too rich a mixture and (<i>b</i>) improper spark-advance.</div> <div class="htmlview paragraph">In planning the layout and equipment of a laboratory, a good way to begin is to make a study of the work that probably will have to be done in it and to realize that undoubtedly some problems will have to be undertaken that are not included in the survey, for which reason all equipment should be so designed that changes can be made easily, quickly and cheaply. Known essentials are that</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">(1)</span> <div class="htmlview paragraph">Equipment must be bolted to the floor</div> </li> <li class="list-item"> <span class="li-label">(2)</span> <div class="htmlview paragraph">Water must be drained away</div> </li> <li class="list-item"> <span class="li-label">(3)</span> <div class="htmlview paragraph">Sufficient working space must be available</div> </li> <li class="list-item"> <span class="li-label">(4)</span> <div class="htmlview paragraph">The entire space must be well lighted</div> </li> <li class="list-item"> <span class="li-label">(5)</span> <div class="htmlview paragraph">The room should have a high ceiling</div> </li> <li class="list-item"> <span class="li-label">(6)</span> <div class="htmlview paragraph">Good crane-transportation should be provided</div> </li> <li class="list-item"> <span class="li-label">(7)</span> <div class="htmlview paragraph">Provision must be made for conducting away exhaust-gas</div> </li> </ol> </div> <div class="htmlview paragraph">A model laboratory that answers all of these requirements is illustrated and described in considerable detail.</div>

<div class="section abstract"><div class="htmlview paragraph">The paper presents a combined experimental and numerical activity carried out to improve the accuracy of conjugate heat transfer CFD simulations of a high-performance S.I. motorbike engine water cooling jacket. The computational domain covers both the coolant jacket and the surrounding metal components (head, block, gasket, valves, valve seats, valve guides, cylinder liner, spark plug).</div><div class="htmlview paragraph">In view of the complexity of the modeled geometry, particular care is required in order to find a tradeoff between the accuracy and the cost-effectiveness of the numerical procedure. The CFD-CHT simulation of water cooling jackets involves many complex physical phenomena: in order to setup a robust numerical procedure, the contribution of some relevant CFD parameters and sub-models was discussed by the authors in previous publications and is referred to [<span class="xref">1</span>, <span class="xref">2</span>, <span class="xref">3</span>, <span class="xref">4</span>].</div><div class="htmlview paragraph">Among the formers, the effects of a proper set of boundary conditions and a detailed representation of the physical properties of the involved materials were evaluated. Among the latter, the contribution of a two-phase approach taking into account the effects of phase transition within the engine coolant was considered.</div><div class="htmlview paragraph">The CFD-CHT setup is now applied to investigate and understand the origin of a critical engine behavior occurring at the engine test bench under a severe reliability test. Additional sub-models are introduced and their impact on the results is discussed. Different engine operations are modeled and a detailed analysis of the many thermo-mechanical factors influencing the engine fatigue strength is carried out.</div><div class="htmlview paragraph">At the end of the process, CFD simulations are able to correctly capture and understand the origin of the engine failure, thus leading to a faster and more effective design modification.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Integrated controls for commercial dynamometers do not have appropriate characteristics to perform research and teaching tasks. These are developed to perform quick tests and its logic is prepared to obtaining the information in accordance with the technical standards.</div><div class="htmlview paragraph">This way, the use for research is hindered because it does not have an interface that allows a refinement to the desired data ranges, t data sampling and the type of load that is applied. Its use for teaching is limited because these "standard" controls does not allow to analyze or to determine engines characteristics that are not covered through tests specified by the standards, so the use of this tool as an important part in professional training formed by the institution.</div><div class="htmlview paragraph">The development of a system control to the electromagnetic brake and capture of torque and rotation data will allow better use of dynamometers for research and teaching, providing to the students the knowledge of the control system itself and data acquisition where parameters such as temperature and pressure can be added, improving the accuracy of torque and power measurements.</div><div class="htmlview paragraph">This system will be made available to other educational and research institutions interested in the use of a control and data acquisition system designed for teaching and research in the engine area, with a low cost of development and operation.</div></div>

<div class="htmlview paragraph">Fatigue strength of typical types of spot-welded joints made of high strength steel sheets was experimentally investigated, as a cooperative program of “Subcommittee on Strength of Spot-Welded Joint” of JSAE. The materials used were rephosphorized high-strength steel sheet (HSS) of 400 MPa class and low-carbon steel sheet (LCS); both were 0.8 mm, 1.2 mm and 1.6 mm thick. The types of loading were tensile-shear, cross-tension and plane bending.</div> <div class="htmlview paragraph">The results obtained are as follows; <ol class="list nostyle"> <li class="list-item"><span class="li-label">1)</span> <div class="htmlview paragraph">The fatigue strengths of joints of HSS in tensile-shear and plane bending were higher than those of LCS, respectively. But, in cross-tension, the strength of joints of HSS was exceeded by that of LCS beyond 10<sup>6</sup> cycles.</div></li> <li class="list-item"><span class="li-label">2)</span> <div class="htmlview paragraph">The fatigue strengths of joints of different materials in cross-tension and plane bending were found lower than those of the same materials.</div></li> <li class="list-item"><span class="li-label">3)</span> <div class="htmlview paragraph">The strain range - cycles to fracture (Δε-N) diagrams for the joints of sheets of different steels and thicknesses were obtained. These data are available for the evaluation of the fatigue life of spot-welded joints.</div></li> </ol></div>