FG Mechatronische Maschinendynamik

19 Items

Recent Submissions
Comparison of the dynamics of a Duffing equation model and experimental results for a bistable cantilever beam in magnetoelastic energy harvesting

Noll, Max-Uwe ; Lentz, Lukas ; Wagner, Utz von (2020-04-03)

Nonlinear energy harvesting systems, consisting of a piezo cantilever beam with two additional magnets placed near the beam’s free end, have received a lot of attention in the past decade. The most common approach to model this system is to discretize the beam in space with one modal ansatz function and to assume a cubic restoring force caused by the magnetic field. The magnets are positioned so...

Zum Einfluss von Dämpfung auf Bremsenschwingungen

Schmid, Dominik (2020)

Hörbare, selbsterregte Schwingungen bei Kraftfahrzeugen, die während des Bremsvorgangs aus dem Reibkontakt zwischen Belag und Bremsscheibe resultieren, stellen einen Qualitätsmangel dar und können zu Kundenreklamationen führen. Kompositstrukturen - in der Automobilwelt als Shims bezeichnet - werden bei Scheibenbremsen auf Belagrückenplatten appliziert, um die Belagdämpfung zu erhöhen und einem ...

On the influence of external stochastic excitation on linear oscillators with subcritical self-excitation and gyroscopic influence with application to brake squeal

Nguyen-Thai, Minh-Tuan ; Wulff, Paul ; Gräbner, Nils ; Wagner, Utz von (2020-06-17)

In a linear analysis for brake squeal, an unwanted type of sound in the kHz-range produced during the braking process of vehicles, usually only the stability of the system is examined. However, with the appearance of additional stochastic excitation, the vibration of a linear system with subcritical self-excitation, i.e. having self-excitation but due to damping still an asymptotically stable t...

On Artifacts in Nonlinear Dynamics

Wagner, Utz von ; Lentz, Lukas (2017)

Nonlinear oscillations are of permanent interest in the field of dynamics of mechanical and mechatronical systems. There exist several well-known semi-analytical methods like Harmonic Balance, perturbation analysis or multiple scales for such problems. We reconsider in our presentation the method of Harmonic Balance but add some additional steps in order to avoid artifacts and get information a...

On the influence of external stochastic excitation on linear oscillators with subcritical self-excitation applied to brake squeal

Nguyen-Thai, Minh-Tuan ; Wulff, Paul ; Gräbner, Nils ; Wagner, Utz von (2019)

A characteristic of linear systems with self-excitation is the occurrence of non-normal modes. Because of this non-normality, there may be a significant growth in the vibration amplitude at the beginning of the transient process even in the case of solely negative real parts of the eigenvalues, i.e. asymptotic stability of the trivial solution. If such a system is excited additionally with whit...

Energy Harvesting From Bistable Systems Under Random Excitation

Lentz, Lukas ; Nguyen, Huy The ; Wagner, Utz von (2017)

The transformation of otherwise unused vibrational energy into electric energy through the use of piezoelectric energy harvesting devices has been the subject of numerous investigations. The mechanical part of such a device is often constructed as a cantilever beam with applied piezo patches. If the harvester is designed as a linear resonator the power output relies strongly on the matching of ...

On some aspects of the dynamic behavior of the softening Duffing oscillator under harmonic excitation

Wagner, Utz von ; Lentz, Lukas (2016-02-26)

The Duffing oscillator is probably the most popular example of a nonlinear oscillator in dynamics. Considering the case of softening Duffing oscillator with weak damping and harmonic excitation and performing standard methods like harmonic balance or perturbation analysis, zero mean solutions with large amplitudes are found for small excitation frequencies. These solutions produce a ”nose-like”...

On artifact solutions of semi-analytic methods in nonlinear dynamics

Wagner, Utz von ; Lentz, Lukas (2018-05-29)

Nonlinear dynamics is a topic of permanent interest in mechanics since decades. The authors have recently published some results on a very classical topic, the dynamics of a softening Duffing oscillator under harmonic excitation focusing especially on low-frequency excitation (von Wagner in Arch Appl Mech 86(8):1383–1390, 2016). In this paper, it was shown that classical tools like harmonic bal...

On the detection of artifacts in Harmonic Balance solutions of nonlinear oscillators

Wagner, Utz von ; Lentz, Lukas (2018-09-06)

Harmonic Balance is a very popular semi-analytic method in nonlinear dynamics. It is easy to apply and is known to produce good results for numerous examples. Adding an error criterion taking into account the neglected terms allows an evaluation of the results. Looking on the therefore determined error for increasing ansatz orders, it can be evaluated whether a solution really exists or is an a...

On the modeling of a bistable beam with application to energy harvesting

Noll, Max-Uwe (2020)

The term energy harvesting refers to strategies to transform small amounts of ambient energy into a useful form. When the available energy is of a kinetic type, an energy harvester is often designed as a mechanical oscillator, made of a beam structure and attached piezoelectric patches to transform motion energy into electrical energy. One specific harvester has attracted a lot of attention, du...

On the discretization of a bistable cantilever beam with application to energy harvesting

Noll, Max-Uwe ; Lentz, Lukas ; Wagner, Utz von (2019)

A typical setup for energy harvesting is that of a cantilever beam with piezoceramics excited by ambient base vibrations. In order to get higher energy output for a wide range of excitation frequencies, often a nonlinearity is introduced by intention in that way, that two magnets are fixed close to the free tip of the beam. Depending on strength and position of the magnets, this can either resu...

Effect of vibrations on friction in the context of brake squeal

Nguyen, Thai Minh Tuan (2019)

Brake squeal is a case of friction-induced vibration that has not been fully understood yet due to difficulties in both experimental and theoretical approaches. Both approaches are considered in this research in order to contribute knowledge to this topic. Following the idea of the already existing Dynamic Compression Test Rig (DCTR), which shows that the dynamic stiffness of a pad specimen de...

Design, analysis, and control of a cable-driven parallel platform with a pneumatic muscle active support

Zhao, Xingwei ; Zi, Bin ; Qian, Lu (2017)

The neck is an important part of the body that connects the head to the torso, supporting the weight and generating the movement of the head. In this paper, a cable-driven parallel platform with a pneumatic muscle active support (CPPPMS) is presented for imitating human necks, where cable actuators imitate neck muscles and a pneumatic muscle actuator imitates spinal muscles, respectively. Analy...

Non-linear investigation of an asymmetric disk brake model

Spelsberg-Korspeter, G. ; Hochlenert, Daniel ; Hagedorn, P. (2011)

Among design engineers, it is known that breaking symmetries of a brake rotor can help to prevent squeal. From a modelling point of view, in the literature brake squeal is almost exclusively treated using models with a symmetric brake rotor, which are capable of explaining the excitation mechanism but yield no insight into the relation between rotor asymmetry and stability. In previous work, it...

A mathematical model in three-dimensional piezoelectric continuum to predict non-linear responses of piezoceramic materials

Samal, M. K. ; Seshu, P. ; Wagner, Utz von ; Hagedorn, P. ; Dutta, B. K. ; Kushwaha, H. S. (2008)

It has been experimentally observed that the piezoceramic materials exhibit different types of non-linearities under different combinations of electrical and mechanical fields. When excited near resonance in the presence of weak electric fields, they exhibit typical non-linearities similar to a Duffing oscillator such as jump phenomena and the presence of superharmonics in the response spectra....

Zur Modellbildung und Analyse von bistabilen Energy-Harvesting-Systemen

Lentz, Lukas (2018)

The subject of the thesis is the modeling and the analysis of a bistable energy-harvesting system. The energy-harvesting system consists of a bimorph beam that is made from a ferromagnetic substructure and piezoceramic layers on top. The beam is attached to a rigid frame which can be attached to a host structure. On the frame two permanent magnets are mounted in such a way, that the restoring f...

Theoretical and experimental investigations of the bifurcation behavior of creep groan of automotive disk brakes

Zhao, Xingwei ; Gräbner, Nils ; Wagner, Utz von (2018)

There are several low frequency vibration phenomena which can be observed in automotive disk brakes. Creep groan is one of them provoking noise and structural vibrations of the car. In contrast to other vibration phenomena like brake squeal, creep groan is caused by the stick-slip-effect. A fundamental investigation of creep groan is proposed in this paper theoretically and experimentally with ...

Theoretical and experimental investigations of creep groan in automotive disk brakes

Zhao, Xingwei (2018)

Due to the increasing comfort claims of customers, the study on low frequency creep groan has been receiving increasing attention currently. This thesis forces on the study of the fundamental mechanism of creep groan theoretically and experimentally. In order to understand creep groan step by step, the design of test rigs concentrating on creep groan are presented. A test rig with an idealized...

A novel excitation method for pyroshock simulation

Houshmand, Behnam ; Lacher, Alexander ; Juengel, Níkolas ; Prasol, Lukas ; Wagner, Utz von ; Uhlmann, Eckart (2016)

Pyroshocks are structural responses to transient excitation caused by the essential use of pyrotechnic devices in aerospace applications. In order to avoid damage in aerospace structures due to pyroshocks, tests are performed on earth prior to launching space modules. In these tests, explosive loads are often replaced by alternative excitation methods such as hammer pendulums or shakers simulat...