Werner Mack

Thermal assembly of an elastic-plastic hub and a solid shaft

SummaryBased on Trescas yield criterion and the associated flow rule, the thermal assembly of an elastic-plastic hollow cylinder and a solid shaft is investigated. The transient stress distribution in the shrink fit is discussed and illustrated by numerical results.ÜbersichtUnter Zugrundelegung der Trescaschen Fließbedingung und der zugeordneten Fließregel wird das thermische Fügen eines elastisch-plastischen Hohlzylinders und einer Vollwelle behandelt. Die instationäre Spannungsverteilung im Querpreßverband wird untersucht und durch numerische Ergebnisse illustriert.

Rotating elastic-plastic solid shaft with fixed ends

Abstract Based on Trescas yield condition and the flow rule associated with it, the distribution of stress, strain, and displacement in a rotating elastic-perfectly plastic solid cylinder with fixed ends is discussed. Special attention is paid to the behavior in the fully plastic state.

Rotating elastic-plastic tube with free ends

Abstract Based on Trescas yield condition and the associated flow rule, the distribution of stress, strain and displacement in a rotating hollow cylinder of elastic-plastic material under generalized plane strain is discussed.

Transient heating of a rotating elastic–plastic shrink fit

The stress distribution in a rotating shrink fit with solid shaft subject to a temperature cycle is investigated. It is presumed that both components are in a state of generalized plane strain and exhibit the same elastic-perfectly plastic material behavior. Applying Trescas yield condition and the flow rule associated with it, the problem is accessible to a quasi-analytical treatment. It is found that the interface pressure and therefore the transferable moment show a permanent reduction due to plastic deformation as well as a temporary reduction due to the thermal expansion of the hub; these effects may lead to a failure of the device.

NONPARAMETRIC SHOCK ABSORBER MODELLING BASED ON STANDARD TEST DATA

Summary The possibility of improving the results of a rough road simulation by a - compared to the classic forcevelocity relation - more complex, but still an easy-to-handle shock absorber model based only on standard harmonic excitation test data is investigated. While a force-displacement-velocity relation proves not well suited for the problem under consideration, a force-velocity-acceleration relation yields a noticeable gain of accuracy with little effort. Special attention is given to the problems arising particularly in a full vehicle simulation.

STRESS DISTRIBUTION IN AN ELASTIC PLASTIC DISK SUBJECTED TO A CIRCULAR HEAT SOURCE

Abstract Stress distribution in a perfectly plastic disk caused by a circular heat source of constant output is investigated. It is shown that, dependent on the ratio of the radius of the disk to the radius of the heat source, Trescas yield condition assumes different forms. In certain cases, the plastic zone is composed of two parts associated with different branches of the yield condition. The critical time for avoiding secondary plastic flow is discussed.

On the performance of rheological shock absorber models in full vehicle simulation

A comparative study of the performance of three rheological automotive shock absorber models as well as of an extended force–velocity relation in full vehicle simulation is performed. Simulation results for both the shock absorber test rig and a full vehicle crossing a single obstacle are compared with measured data. While the gain of accuracy by the extended force–velocity relation is marginal, the rheological models in general yield a noticeable improvement, which, however, in full vehicle simulation is less significant than in test rig simulation. Among the rheological models studied here, the one consisting of a nonlinear spring–dashpot element with an element modelling friction by a continuous transition from the compression to the extension range in parallel and a quadratic approximation of the static gas force exhibits the best global performance.

Residual stresses in an elastic-plastic solid shaft with fixed ends after previous rotation

The subject of this paper is the distribution of the residual stresses in an elastic-perfectly plastic solid cylinder with fixed ends after previous rotation. Special attention is paid to the occurrence of secondary plastic flow during unloading. All the results are based on Tresca yield condition and the flow rule associated with it.

On the scattering of test data and the significance of the standard coefficients ‘dynamic stiffness’ and ‘loss angle’ for hydraulic engine mounts

Based on the test results, a study on the scattering of the standard coefficients c dyn and δ within the test cycles on a standard testing machine as well as within the samples of a batch of hydraulic engine mounts is performed; furthermore, an estimate for the systematic error caused by the testing machine is given. By a simulated example, the pronounced sensitivity of the response of the engine to the scattering of c dyn and δ as well as to even small deviations of the hysteresis curves for otherwise identical values of the standard coefficients is demonstrated. As a main result, it is found that the most important source of uncertainty is scattering within the batch, which, in conjunction with the observed sensitivity of the response of the engine, raises the question for the meaningful level of sophistication of a model for predictive purposes.

Effects of non-linear modelling of a hydromount in full vehicle simulation

The effects of different levels of model complexity for a hydromount in full vehicle simulation are investigated. In particular, the performances of the classical Kelvin-Voigt model, a standard linear lumped parameter (lever) model and an amplitude-dependent non-linear physical model with respect to their predictive capabilities are studied; thereby special attention is paid to the step from a linear to a non-linear model. The evaluation is based on comparisons with test results for crossing a single obstacle, driving on a motorway and on a rough road, respectively. Assessments in the time domain as well as by statistical means show that the non-linear model is capable of capturing high-amplitude oscillations more precisely, but that the overall differences between the simulation results are not very pronounced.