Applied Mechanics and Materials Vol. 807

Abstract: This paper outlines a design process for the bolted joints of the drive train of sheet-fed offset printing presses incorporating statistical data and methods. Sheet-fed offset printing presses are driven by a continuous geared drive train along the length of the press. The bolted joints of the drive train connecting the gears to the cylinders of the press are subjected to high loads, especially during emergency stops. A nonlinear mechanical model of a printing press implemented in Matlab/Simulink is presented which is used to calculate the occurring loads. Measurements of linear and nonlinear system response are presented to support the quality of the mechanical model. The bolted joints between the main drive train gears and cylinders are designed according to current standards. Statistical information based on experimental data is considered during the application of the standardized method. Using the Monte Carlo technique, a more exact description of the joint’s strength is made possible. In this way, the maximum tolerable load for the screw connection is 16% higher than the same result from a standard worst-case calculation.

Abstract: Joints used to fasten different parts are the source of local non-linearity with predominance of contact damping in comparison to inherent material damping. The conventional numerical models can predict the dynamic behaviour to a good accuracy, but their implementation for the large system under real time dynamic excitations - like random vibration are encountered with problems of numerical convergence and high computational cost. This paper proposes an approach to model the contact interfaces using discrete elements, with a non-homogeneous definition for the equivalent contact stiffness and damping over the contact interface. The non-homogeneous definition captures the non-linear effects and the local linearisation provides the capability to perform the frequency domain analysis for non-deterministic excitations. The proposed model is validated with experimental results for a test structure excited with random white noise base excitation.

Abstract: Composite materials are created as a quite complex architecture which includes a fibre reinforcement structure and matrix material. Many material parameters play a role when composite structures are modelled, e.g. in finite element models. In addition to the properties of the raw fibre and matrix materials which are used, also geometrical parameters have a significant effect on structural characteristics. Fibre reinforcement geometry together with material properties of fibre and matrix determine homogenised material properties.The first part of the paper gives an overview of the most important processes which are used in composites processing industry. The factors which affect variability are also listed, and the effect of variability on material parameters is mentioned as well. The second part of the paper elaborates the identification of geometrical variability of the fibre reinforcement structure which is encountered with one particular type of composite material, namely a twill 2/2 carbon fibre weave with an epoxy matrix.

Abstract: To add reliability to numerical simulations, Uncertainty Quantification is considered to be a crucial tool for clinical decision making. This especially holds for risk assessment of cardiovascular surgery, for which threshold parameters computed by numerical simulations are currently being discussed. A corresponding biomechanical model includes blood flow, soft tissue deformation, as well as fluid-structure coupling. Thereby, structural material parameters have a strong impact on the dynamic behavior. In practice, however, particularly the value of the Young's modulus is rarely known in a precise way, and therefore, it reflects a natural level of uncertainty. In this work we introduce a stochastic model for representing variations in the Young's modulus and quantify its effect on the wall sheer stress and von Mises stress by means of the Polynomial Chaos method. We demonstrate the use of uncertainty quantification in this context and provide numerical results based on an aortic phantom benchmark model.

Abstract: The aim of this paper is to get insight into measurement uncertainties for thermomechanical measurements performed using a piezoresistive silicon-based stress sensor in a standard microelectronic package. All used sensors have the same construction, were produced in the same technological processes at the same time, yet the measurement results show significant distribution. The possible causes for this phenomenon are discussed in this paper. Additionally, Finite Element Method (FEM) model is created and validated, what enables a study of sensitive parameters influencing the measurement uncertainties.

Abstract: This paper presents two new technologies in order to optimize the operation of a con-ventional spring-damper-system. Therefore, the function structure such as the energy flow of a con-ventional system is investigated and optimized. The first resulting technology is the fluid dynamicabsorber (FDA) which is still a passive solution and improves the energy flow of the conventionalspring-damper-system with the help of an absorber with a hydraulic transmission. The second tech-nology is the active air spring damper (AASD) which is an active variant of a spring-damper-systemand optimizes the energy flow by using electrical energy. We use a quarter car model to examine theperformance of our technologies and compare them in the conflict diagram where driving comfort vs.driving safety is shown within the scope of uncertainty. The FDA improves the driving safety at almostthe same comfort. The driving comfort is improved by using the AASD. We also examine the systembehavior at uncertain loads. The results show that they are capable of controlling this uncertainty.

Abstract: Beams in lightweight truss structures are subject to axial and lateral loads that may lead to undesired structural vibration or failure by buckling. The axial and lateral forces may be transferred via the truss supports that offer possibilities for state control of single beams and larger structures. In earlier own studies, the concept of a piezo-elastic support for active buckling control and resonant shunt damping has been investigated. An elastic spring element is used to allow a rotation in the beam's bearing in any plane perpendicular to the beam's longitudinal axis. The rotation is laterally transferred to an axial displacement of piezoelectric stack transducers that are either used to generate active lateral forces for active buckling control or to attenuate vibrations with a resonant shunt. In this paper, the model verification and validation of the elastic properties of the piezo-elastic support for passive and active structural control of beams with circular cross-section is presented. The rotational and lateral spring element stiffness is investigated numerically and experimentally and the existing models are updated in the verification process. The model is validated by comparing the numerical results and experimental ability for vibration attenuation.

Abstract: The calculation of the structural intensity allows for a better understanding of the NVH behavior of complex structures as it shows vibratory energy flows between an excitation and radiating areas. However, the information gathered is underlying aleatory and epistemic uncertainties and needs to be dealt with carefully. In this paper two aspects are discussed: Firstly how the structural intensity calculation helps to reduce uncertainty in NVH design and secondly what currently existing uncertainties need to be considered and how they can be further reduced. This does not only include an improvement of the current calculation process itself but also an extension towards an integrated, holistic calculation of vibratory energetic quantities for structure-borne and air-borne sound.

Abstract: This paper gives an overview about how to locate uncertainty in product modelling within the development process. Therefore, the process of product modelling is systematized with the help of characteristics of product models and typical working steps to develop a product model. Based on that, it is possible to distinguish between product modelling uncertainty, mathematic modelling uncertainty, parameter uncertainty, simulation uncertainty and product model uncertainty.