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The Cumulative Damage Division of the SAE Fatigue Design and Evaluation Committee recently finished an extensive fatigue test program. This test program involved one Keyhole test specimen, two different materials, three loading spectrums and the cooperation of eight test laboratories to run the 58 specific fatigue tests. The objective of the overall division program was to determine the state-of-the-art of cumulative damage life prediction capability using the experimental data for correlation. This work reports a finite element and damage analysis of the Keyhole test specimen. The calculated notch root strain was compared with the experimental strain. The calculated stress and strain were used in a cumulative damage procedure to predict life for both materials subjected to various load levels for each of three loading spectrums. The results of the theoretical life predictions are compared to the experimental results.

Three computer programs are presented for predicting the fatigue life of notched members undergoing complex load histories. The programs, while differing in terms of required information, employ a common approach involving the determination of the material response at the notch root, an assessment of damage based on closed hysteresis loops, and a linear damage summation to predict life. Agreement between predictions and experimental results generated by the SAE Fatigue Design and Evaluation Committee is reasonably good. The programs have purposely been kept simple to allow for easy modification. Applications and limitations of the three programs are discussed.

Results of the SAE Fatigue Design and Evaluation Committee, Cumulative Damage Division test program are reported. This includes a description of the test specimen geometry, variable amplitude load histories, material properties and fatigue data. The data set produced can be used to generally evaluate methods of fatigue life prediction and laboratory simulation.

By calculating the cooling rate during quenching and calculating Ms temperatures from measured carbon contents and carbide quantities in depth, curves indicating the time at which transformation began in cylindrical specimens were determined. Using these curves, measured residual stress distributions were analyzed. Transformation started at a depth near the carburized case-core boundary, determined by the carbon gradient and cooling rate. It then proceeded out to the case and into the core, generating high internal stresses in these areas. The sequence of transformation was responsible for oscillations in the final residual stress distribution, with maximum compression occurring outside the case-core boundary.

A TRIAXIAL AUTOMOTIVE WHEEL FORCE AND MOMENT TRANSDUCER A transducer capable of simultaneously measuring the dynamic forces and moments acting on the front or rear wheel of an automotive vehicle has been jointly developed by Ford Motor Company and GSE, Inc. This transducer was designed to be used on passenger cars with 13, 14, or 15 inch wheels. It is adaptable to laboratory wheel and tire testing machines. An instrumentation package that provides electrical excitation, signal conditioning, and cross-talk compensation for the transducer was also developed. The operational features of the transducer and the transducer instrumentation package as well as an assessment of some of its applications will be presented using functional block diagrams. Specifications for the system are listed and calibration data and road evaluation data will also be presented.

The effect of prestraining on the tensile properties and uniaxial low cycle fatigue behavior of SAE 1008 hot rolled low carbon steel strip has been investigated using a prestraining technique which simulates a press forming operation. Preliminary data for the case of a 40% balanced biaxial prestrain show a considerable increase in fatigue resistance in the long life regime. The reduced ductility as a result of prestraining, however, causes degradation of the short life fatigue resistance. Therefore, for component operation in the long life regime where the strains are mainly elastic, SAE 1008 may have considerably greater fatigue resistance than a designer would anticipate based on the yield and ultimate strength levels or fatigue data of the as-received material.

Two cycle counting algorithms, based on Range Pair and Rainflow methodologies, are quantitatively compared using three typical automotive load histories. Both algorithms were found to produce essentially equivalent counted spectra based on the resultant amplitude exceedance data. Because of the output format, the range pair algorithm is generally recommended for applications requiring damage accumulation calculations and spectrum analysis. The rainflow algorithm is recommended for applications involving cycle counting of arbitrary duration field load histories.

Using linear elastic fracture mechanics concepts, two steels quenched and tempered to Rockwell C 40-47 were evaluated for application in crawler tractor main frames. These high strength steels were D6-B and an experimental steel whose chemistry was optimized using a digital computer procedure referred to as the CHAT system, an acronym standing for Computer Harmonized-Application Tailored. Fatigue crack growth rate da/dN versus ΔK for constant amplitude loading and plane strain fracture toughness KIc parameters were determined from compact specimens. These parameters together with approximate stress intensity calculations were utilized to estimate component fatigue crack growth life assuming various initial crack sizes. These estimations were compared with accelerated component fatigue life, which included both crack initiation and crack growth.

This paper presents predictions of fatigue crack initiation life for three distinctly different, irregular load histories, each applied to keyhole-notched compact tension specimens at several maximum load levels and using two different structural steels. Work leading to this paper was done in conjunction with the cooperative research program of the SAE Fatigue Design and Evaluation Committee. Three computerized prediction methods (Landgraf, Wetzel, and a Nominal Stress Range approach) are used. All predictions are based on load histories condensed to 10% of their original number of reversals by the “Racetrack Method.” This method, which is described in detail, selects the most damaging overall ranges in an irregular load history while preserving the sequence of the original loading. Predictions are compared with test data for the two dozen combinations of loading type and level and steel used. Comments are made on the relative merits of the different prediction methods.

Severe corrosion was observed in the neck area of Inconel 751 material exhaust valves operated in an ebulient-cooled natural gas engine. The type of corrosion was identified as sulfidation attack. Deposits removed from the valves consisted mainly of calcium sulfate (CaSO4) from oil additives and carbon (C) residue from combustion products. Experimentation showed that the presence of C was a necessary pre-requisite for attack. Based on this information, the corrosion mechanism must involve the reduction of the sulfate by C. The reduction of the sulfate results in a high sulfur chemical potential at the alloy surface making transport of sulfur into the substrate a highly favored step. Aluminizing the Inconel 751 material proved to be an effective deterrent against sulfidation attack.

THREE SIMPLIFIED PROCEDURES for predicting fatigue life are compared with actual test results. The part geometry, load histories, material properties, and test results used in these analyses were obtained from the SAE Fatigue Design and Evaluation Committee's Cumulative Fatigue Damage Test Program (1)*. The purpose of this effort is to evaluate the relative accuracy and applicability of these frequently used methods.

Single-cylinder experiments were conducted with a 3-valve carbureted pre-chamber stratified charge engine in comparison with a conventional engine. The pre-chamber engine operation is governed by many design and operating variables. This investigation was limited to determining the effect of overall air/fuel ratio, ignition timing and EGR on emissions and fuel economy at a single road load test condition. It was found that, as for the conventional engine, these operating variables are also significant for the pre-chamber engine and that a compromise must be made between good fuel economy and low emissions. The main virtue of the pre-chamber engine was found to be the ability to operate at leaner overall air-fuel ratio. This resulted in lower nitrogen oxide (NO) emissions than the conventional engine without EGR. The unburned hydrocarbons (HC) were found to be higher for the pre-chamber engine up to the conventional engine lean misfire A/F ratio.

Experimental work is carried out to investigate the importance of the connecting nozzle between the auxiliary and the main chambers and the ignition point location to the performance of a stratified charge spark ignition engine using Broderson's method of charge stratification. Thre different nozzle configurations and two ignition point locations were used in the present experiment. The study shows that the fuel economy obtained with this approach is dependent upon the nozzle geometry which also plays an important role in the combustion noise generation, a characteristic of this method. The results show good fuel consumption over the entire range; the analytical work on the combustion of the mixture in the auxiliary chamber indicates that flame initiation near the center of the nozzle opening has a potential of restricting the flow of unburned mixture in the main chamber.

The purpose of this paper is to contribute to knowledge of the behavior of the stratified charge engine with prechamber injection by experimental investigation of several important parameters. Special attention is given to degree of charge stratification, position of injection nozzle and spark plug in the prechamber, construction of the injection nozzle, start of injection, timing of ignition, and throttling of the intake air. These parameters have a more or less significant influence on output, fuel consumption, and exhaust emission. Finally, the combustion system was adjusted partly by optimizing and partly by compromising. Comparison with a conventional spark ignition engine is made. Using a mathematical model of the process, the possible causes of the significant improvements in NO emissions are discussed.

A historical review of the patents and literature pertaining to 3-valve stratified charge engines is presented in this paper. This very old invention appears to be a practical approach for the “clean engine” being sought for vehicular use since it has the intrinsic capability of simultaneously giving good fuel economy and producing minimal objectionable exhaust emissions. The prime requisites of this engine are a rich prechamber charge and a very lean main chamber charge regardless of prechamber volume, nozzle diameter, valving and spark plug location. Fuel-air equivalence ratios of the charges in the two combustion chambers are significantly important in order to achieve the proper optimization. These ratios should be about 15% rich for the prechamber and 15 to 30% lean for the main chamber at the moment of ignition.

Combustion in model eddy combustion chamber was investigated in order to obtain insight into the combustion mechanism. High-speed schlieren cinematography and recording of the ionization current were used in the experiments. It was established theoretically and experimentally that the flame kernel formed by ignition at periphery moved towards the rotation axis and reached it in a time of the order of that for the mixture rotatory cycle at the periphery, irrespective of the circular speed of gas rotation and of the chamber size. After reaching the rotation axis, the kernel acquired the form of rotating body. The radial spread of this body can be lower than the visible rate of the immobile gas burning, due to the fast elongation of the rotating body along the axis. The results obtained are essential for understanding the phenomena occurring in eddy chamber of diesel engine and engines with spark ignition at an eddy motion.

Experimental work of the torch ignited engine demonstrated that this engine provided stable engine performance and low exhaust emissions using an overall lean mixture. Some combustion characteristics of the torch ignited engine were compared with those of a conventional one. Experimental analysis was performed to determine the influence of a number of prechamber inlet air-fuel ratios and nozzle diameters. These are respectively a main operating factor and a main design factor of the torch ignited engine. These factors control the torch combustion process and determine engine performance and emission characteristics.

This paper describes work done to separate and further define the effects of volume and temperature on the effectiveness of exhaust thermal reactors operating at lean (18-22:1) A/F ratios. Thirty feet of stainless tubing with a volume of over 1200in3 was added to the exhaust manifold of a 4 cylinder engine. The entire assembly was insulated to serve as a constant temperature “lean reactor”. Exhaust emission and temperature measurements at various points along the “reactor” provided data on the extent of the HC and CO oxidation reactions as a function of reactor volume. Mass flow calculations were made to calculate eahaust gas residence times. The data are presented as percent HC and CO rreacted versus gas residence time in the reactor and are plotted to show the effect of reactor temperatures ranging from 1275°F to 1675°F at various inlet HC concentrations. Limited data are also presented on the effect of exhaust flow rate on mixing.

The first engine dynamometer test results are presented for a modified fuel system based on hydrogen enrichment for a V-8 I.C. engine. The engine burns mixtures of gasoline and hydrogen under ultralean conditions to yield extreme low NOx emissions with increased engine efficiency. The hydrogen is produced in a compact onboard generator from gasoline and air. The hydrogen-rich product gas is cooled and mixed with the normal combustion air in a modified carburetor. The engine then operates in the conventional manner on atomized gasoline with spark ignition, but with hydrogen-enriched air and with a high spark advance of 40-50° BTDC. The engine thus receives two charges of fuel: a charge of gaseous fuel from the hydrogen generator, and the normal gasoline charge. The results on hydrogen enrichment are compared with the 1973 V-8 baseline stock engine with emission controls, and the same engine without controls and operated at a maximum efficiency under lean conditions.

The flow and combustion processes of a three-valve, stratified charge engine with small prechamber are examined for exhaust emissions. The exhaust emissions from a single-cylinder version of this engine are shown to depend on the internal flow processes as well as mixture supply stoichiometry. A theoretically-based simulation model of the engine flow and combustion processes is described. Model predictions are compared with time-resolved prechamber air-fuel ratio measurements made during intake and compression strokes. These comparisons are used to illustrate and describe the complex flow phenomena which take place in this engine. The combustion process is then examined with the aid of calculations using the simulation model. The complexity of the combustion process is illustrated by showing that, in addition to burned gas temperatures, the cylinder and prechamber burned gas air-fuel ratios change with time.