Kemal Çalışkan

Non-parametric modelling of damper top mounts

This paper details a new non-linear damper top-mount model, and the processes utilized to identify the constituent parameters. The damper top-mount model parameters are extracted from experimental data on commercial damper top mounts. The non-parametric restoring-force-mapping technique is used to construct the damper top-mount model. A damper top-mount model that consists of three elements, which are the non-linear elastic element, the non-linear friction element and the non-linear viscous element, is developed. The amplitude dependence of the top-mount characteristics is modelled by using the friction element and the elastic element, while the frequency dependence of the top mount is modelled by using the restoring-force-mapping technique. In order to obtain and optimize the required model parameters, a new procedure based on a two-stage optimization routine using two different sets of the measurement data for the amplitude-dependent parameters and the frequency-dependent parameters, is proposed. The model is validated by comparing the measured and simulated forces for three different damper top mounts. Good agreement between the measured force and the simulated force is obtained. Furthermore, the proposed model is found to be superior to the existing rubber isolator models.

Optimization of Damper Top Mount Characteristics to Improve Vehicle Ride Comfort and Harshness

A novel optimization technique for optimizing the damper top mount characteristics to improve vehicle ride comfort and harshness is developed. The proposed optimization technique employs a new combined objective function based on ride comfort, harshness, and impact harshness evaluation. A detailed and accurate damper top mount mathematical model is implemented inside a validated quarter vehicle model to provide a realistic simulation environment for the optimization study. The ride comfort and harshness of the quarter vehicle are evaluated by analyzing the body acceleration in different frequency ranges. In addition, the top mount deformation is considered as a penalty factor for the system performance. The influence of the ride comfort and harshness weighting parameters of the proposed objective function on the optimal damper top mount characteristics is studied. The dynamic stiffness of the damper top mount is used to describe the optimum damper top mount characteristics for different optimization case studies. The proposed optimization routine is able to find the optimum characteristics of the damper top mount which improve the ride comfort and the harshness performances together.

Product Based Material Testing for Hyperelastic Suspension Jounce Bumper Design with FEA

The basic problem in the finite element analysis of parts made of hyperelastic materials is the identification of mathematical material model coefficients. Furthermore, selection of a suitable mathematical hyperelastic material model may not be straightforward. In this study, a systematic design methodology is presented for hyperelastic suspension jounce bumpers. The presented methodology involves a critical examination of material testing procedures, material model selection, and coefficient identification. The identified material model coefficients are verified through comparison of the finite element analysis results with actual tests.

Effects of damper failure on vehicle stability

The general approach in vehicle dynamics analysis is to use mint state characteristics of the chassis components in vehicle simulation models. However, some of the chassis components are vulnerable to damage which might induce drastic changes in component characteristics. A comprehensive vehicle stability analysis should, therefore, account for the changing characteristics of the components. In the literature, such analyses exist only for slowly-developing damper wear cases. In recent years, there has been an increase in the popularity of controlled dampers. These dampers include an increased number of structural elements and their characteristics depend on the control current supplied by a complex control system. In this study, the effect of sudden shifts in controlled damper characteristics on the stability of the vehicles is examined in detail. Two different types of damper-characteristic shifts are taken into account; the first one is a soft-to-hard transition that takes place due to control current cut-off and the other is a hard-to-soft transition originating from failure of the mechanical components in the damper. A detailed vehicle simulation model is developed, verified and used to simulate different driving manoeuvres where damper failure might affect vehicle stability. The analysis is extended to a vehicle configuration employing a simple ESP structure in order to observe the effects of chassis control systems in minimizing the effects of the damper failure. The results obtained in this study show that the failure of a damper might lead to vehicle instability in some critical driving situations for vehicles lacking advanced chassis control systems.

Advanced parameter analysis for damper influence on ride dynamics

The conflicting objectives related to damping characteristics of vehicle suspensions promote further development of new damper concepts. The effort is no longer limited to finding the optimal damper velocity–force characteristics for a vehicle suspension system. Besides this basic design parameter, the amplitude- and frequency-dependent characteristics of dampers are also taken into consideration. The first step in adjustment of the velocity, displacement, and frequency-dependent damper characteristics is to understand the effect of these characteristics on the dynamics of the vehicle. Therefore, in this study, the interaction between the damper characteristics and vehicle ride response is analyzed by using a detailed mathematical damper model together with a verified full vehicle simulation model. A semi-parametric detailed damper model is first verified through physical testing of different dampers and then it is fully parameterized and implemented inside the full vehicle simulation model. A parameter variation analysis is performed to show the effect of the different damper characteristics on vehicle ride comfort.

Product-oriented material testing and FEA for hyperelastic suspension jounce bumper design

The basic problem in the finite element analysis of parts made of hyperelastic materials is the identification of mathematical material model coefficients. Furthermore, selection of a suitable mathematical hyperelastic material model may not be straightforward. In this study, a design methodology is presented for hyperelastic suspension jounce bumpers. The commonly used traditional trial-and-error method for jounce bumper design results in high mould costs for prototype production and prolongs the time required. The design methodology presented in this study involves a critical examination of material testing procedures, material model selection, and coefficient identification. The identified coefficients are verified through finite element analysis and actual test results.