Browsing by Author "Malmi, Olli"

Now showing 1 - 3 of 3

Dynamic properties of wire rope isolator
(2022-08-22) Malmi, Olli
Insinööritieteiden korkeakoulu | Master's thesis
In the context of heavy machinery, vibration isolation is often necessary because vibration excited by the machine could be harmful for the machine itself or its sur- roundings. Rubber isolators are usually used for the vibration isolation due to their well isolation capacity and low-cost. A wire rope isolator (WRI) is a passive isolator, which properties differ from the properties of rubber isolators. WRIs have non-lin- ear dynamic properties, which depend on the direction and the magnitude of the loading. Due to the strong non-linear behavior, modelling of the dynamic proper- ties of WRIs is complicated. Thus, they are determined experimentally. In this thesis, dynamic properties of three sizes of wire rope isolators are deter- mined experimentally with two methods. The methods are determined in ISO 10846 standard. Measurement setups are made and verified for both methods. The dynamic properties are determined in relation to the excitation amplitude because it is known to have major influence. In addition to the effect of the excitation am- plitude, the influence of the static preloading is measured. For the comparison, rub- ber isolators, which are used for similar purpose as the investigated wire rope iso- lators, are tested experimentally. The comparison is reasonable because behaviors of wire rope isolators and rubber isolators differ strongly. In addition to experimental investigation, mathematical models of wire rope iso- lators are studied. Two mathematical models, which have similar properties with wire rope isolators, are tested. They are fitted to the measurement data of wire rope isolators. Results of the models are compared to the experiment results. Two independent methods were used for measuring the dynamic properties of the wire rope isolators. The methods gave compatible results. Therefore, the exper- imental results could be considered reliable. The effect of the excitation amplitude was noticed to be significant, which was assumed based on the previous research by others. The influence of the static preloading was minor, but consistent. The ex- perimental tests confirmed the assumption that the excitation frequency has insig- nificant effect on the dynamic properties of wire rope isolators. The investigated mathematical models have partly similar behavior with wire rope isolators, but their damping differed clearly from the measurement results. Stiffness and damping of the models are connected to each other, and therefore fit- ting both properties to the measurement results was found out to be difficult. Anal- ysis of the models showed that by developing the models, closer fit of the model to the measurements could be achieved.
Kiihtyvyyden mittaaminen
(2019-04-21) Malmi, Olli
Insinööritieteiden korkeakoulu | Bachelor's thesis
Wire rope isolator identification and dynamic modeling for small amplitude vibrations
(2024-11-01) Rytömaa, Samuli; Malmi, Olli; Laine, Sampo; Keinänen, Jarkko; Viitala, Raine
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Wire rope isolators are used in variety of applications to protect sensitive equipment from vibration. The nonlinear hysteretic behavior of steel wires provides advantages when compared to linear vibration isolators. This study proposes an amplitude dependent stiffness and damping model for low amplitude vibrations under axial loading, where the parameters can be determined with an experimental procedure. Comprehensive experimental results of forced vibration tests with varying loading, frequency and preload were considered in the model identification. Amplitude dependent stiffness and loss energy models were determined from the test data, and the effect of the preload and loading frequency on the model parameters were studied. It is shown, that the effect of preload and frequency is not evidently clear, while the effect of vibration amplitude is more significant. The mathematical model was further verified against measurements from base excitation loading. The proposed model can be used to study the effectiveness of the selected wire rope isolator configurations in chosen application, and to effectively perform dynamic design studies.