Elastodynamics of piston compression rings

The piston ring pack accounts for a disproportionate amount of the total engine frictional losses. The frictional behaviour of piston rings is significantly affected and governed by its flexible dynamics. The dynamically changing shape of the ring determines its contact geometry with the cylinder liner and hence affects the frictional losses. The compression ring undergoes a multitude of complex motions during the engine cycle prescribed by the gas pressure, contact reaction, ring tension, friction between the ring and its groove and inertial forces that excite a plethora of the ring’s modal responses. This adversely compromises the functionality of the ring through a number of undesired phenomena such as ring flutter, twist, rotation and jump. Therefore, a prerequisite for improving the prediction of tribological conditions is an accurate determination of the ring’s elastodynamic response. This paper presents a methodology to directly solve the governing differential equations of motion for different forms of beam cross-section, where the shear and mass centres are not coincident, typical of the complex cross-sections of a variety of different piston compression rings. Combined numerical and experimental investigations are undertaken to determine the dynamic behaviour of the compression ring

Nonlinear tribodynamics of an elastic shaft with a flexible bearing outer race

In this paper a mathematical model of a rotor-bearing system is presented. The model includes modal elastodynamics of a flexible rotor as well as the in-plane radial dynamics of the bearing with a flexible outer race. Elastodynamics of the flexible shaft utilises a solution based on Green’s function to provide a computationally efficient approach. The flexible bearing outer race is modelled using Timoshenko beam theory. The system model also includes detailed lubricated contact mechanics of balls-to-races contacts with viscous friction. Therefore, the rotor-bearing analysis represents a detailed multi-physics tribodynamics and modal elastodynamic responses of the system which closely represents broad-band vibration response of such systems in practice, an approach not hitherto reported in the literature. It is also demonstrated that the outer race flexibility changes the location of the stability orbital centres, as well as the spread of limit cycle vibrations. Furthermore, it accentuates the occurrence of multiples of ball pass frequency. The importance of integrated system dynamics and lubricated contact mechanics is highlighted, showing that although the elastodynamic response of the rotor’s flexible elements may not be clear in the acquired vibration signal, its effect on energy efficiency of the system can be quite important.</p

Least squares means and standard errors of means for fatty acids of back fat from dairy steers grazed on winter rye and winter wheat.

<p>Least squares means and standard errors of means for fatty acids of back fat from dairy steers grazed on winter rye and winter wheat.</p

Results from the principal component analysis for the first 5 principal components.

<p>Results from the principal component analysis for the first 5 principal components.</p

Least squares means and standard errors of means for carcass quality measurements, WBSF, and objective color scores for steers grazed on winter rye and winter wheat and for HOL, MVH crossbred, and NJV crossbred dairy steers.

<p>Least squares means and standard errors of means for carcass quality measurements, WBSF, and objective color scores for steers grazed on winter rye and winter wheat and for HOL, MVH crossbred, and NJV crossbred dairy steers.</p

Least squares means and standard errors for sensory attributes of steaks for steers grazed on winter rye and winter wheat and for HOL, MVH crossbred, and NJV crossbred dairy steers.

<p>Least squares means and standard errors for sensory attributes of steaks for steers grazed on winter rye and winter wheat and for HOL, MVH crossbred, and NJV crossbred dairy steers.</p

Correlation of coefficients between select meat quality variables.

<p>Correlation of coefficients between select meat quality variables.</p

Least squares means and standard errors of means for fatty acids of back fat for HOL, MVH crossbred, and NJV crossbred dairy steers.

<p>Least squares means and standard errors of means for fatty acids of back fat for HOL, MVH crossbred, and NJV crossbred dairy steers.</p

Least squares means and standard errors for amino acids of meat from steers grazed on winter rye and winter wheat cover crops and for HOL, MVH crossbred, and NJV crossbred dairy steers.

<p>Least squares means and standard errors for amino acids of meat from steers grazed on winter rye and winter wheat cover crops and for HOL, MVH crossbred, and NJV crossbred dairy steers.</p