TY - THES

T1 - About the wear assessment of valve train components using an experimental screening methodology

AU - Gussmagg, Jakob

N1 - embargoed until 18-11-2026

PY - 2021

Y1 - 2021

N2 - In order to improve the environment-friendliness and efficiency of the combustion engine, the continuous development of new technologies to reduce emissions and fuel consumption is necessary. From a tribological point of view, this development leads to increasing demands on various engine components. Engine and model tests can be used to evaluate engine oils and parts and to study their attrition. To test the tribological contact rocker arm - push rod, an experimental screening method was developed in the course of this work. This can be used to test engine oils in development. For validation of the obtained results, wear data and components of engine tests are available. The methodology was developed for a rotary tribometer. A swashplate adapter enabled the implementation of the oscillating motion of the rocker arm. Furthermore, carbon black served as a soot surrogate. The surface analysis of the specimens revealed a matching damage mechanism. To reproduce a correct oil ranking, different test strategies were used. Thus, the tests were evaluated according to gravimetric wear, soot clogging behaviour, and scuffing limits. The latter were defined by evaluating the measured AE-RMS signal. By stopping tests on the exceeding of defined thresholds, these AE-RMS limits were assigned to wear states, thus visualizing the stages of development. The developed screening method found validation by comparing an unalloyed base oil with a fully formulated oil. Furthermore, the calculation of the wear coefficients provided a basis for comparing the obtained tribometer data with the existing engine wear data. The results of the two types of tests are in the same order of magnitude, demonstrating a good replication of engine conditions by the screening method. The recorded AE-RMS data corresponded to the gravimetric wear values by means of an exponential function.

AB - In order to improve the environment-friendliness and efficiency of the combustion engine, the continuous development of new technologies to reduce emissions and fuel consumption is necessary. From a tribological point of view, this development leads to increasing demands on various engine components. Engine and model tests can be used to evaluate engine oils and parts and to study their attrition. To test the tribological contact rocker arm - push rod, an experimental screening method was developed in the course of this work. This can be used to test engine oils in development. For validation of the obtained results, wear data and components of engine tests are available. The methodology was developed for a rotary tribometer. A swashplate adapter enabled the implementation of the oscillating motion of the rocker arm. Furthermore, carbon black served as a soot surrogate. The surface analysis of the specimens revealed a matching damage mechanism. To reproduce a correct oil ranking, different test strategies were used. Thus, the tests were evaluated according to gravimetric wear, soot clogging behaviour, and scuffing limits. The latter were defined by evaluating the measured AE-RMS signal. By stopping tests on the exceeding of defined thresholds, these AE-RMS limits were assigned to wear states, thus visualizing the stages of development. The developed screening method found validation by comparing an unalloyed base oil with a fully formulated oil. Furthermore, the calculation of the wear coefficients provided a basis for comparing the obtained tribometer data with the existing engine wear data. The results of the two types of tests are in the same order of magnitude, demonstrating a good replication of engine conditions by the screening method. The recorded AE-RMS data corresponded to the gravimetric wear values by means of an exponential function.

KW - Verschleiß

KW - Ventiltrieb

KW - Tribometer

KW - Verschleißkoeffizienten

KW - Wear

KW - Valve train

KW - Tribometer

KW - Wear coefficients

M3 - Master's Thesis

ER -