The energy industry, transportation and even the smallest consumer electronics benefit from the practical applications of rechargeable batteries. Expectations of battery performance are greatly related to capacity, power output and available lifetime. However, the lifetime is affected by gradual chemical and mechanical degradation of the internal battery structure that cannot easily be predicted prior to installation. The reduction in performance is closely related to a particular usage pattern which is unique to the user and application, and is thus difficult to predict. Reliable real-time prediction of the remaining battery life therefore remains an important research topic. In this paper we show that fading battery performance under cyclic loading can be effectively and continuously followed by introducing the concept of the damage parameter derived from mechanical durability modelling approaches. The damage parameter is calculated continuously by the novel macro-scale hysteresis damage operator model. The hysteresis model is formed by a system of constitutive spring-slider modelling elements, here bridging the complex relation between the battery load and the durability data. The spring and the slider properties are individually calibrated for lithium nickel manganese cobalt oxide (NMC) batteries, however other battery structures can also be used. The durability data is obtained experimentally under controlled steady thermal and cyclic loading (constant charge/discharge...
COBISS.SI-ID: 35666179
One of the challenging tasks related to lithium-ion batteries (LIBs) remains a comprehensive approach for battery behaviour modelling. An approach is presented that enables modelling the voltage-capacity response of LIBs that are subjected to variable temperature and current load histories. A detailed presentation of the developed macro-scale phenomenological model embedding the mechanistic properties of the Prandtl type hysteresis operator and the concept of the force-voltage analogy is made. The necessary input data preparation for the model calibration is also presented. Accuracy of the model is confirmed with experimental observations for both nested current load history at two different temperatures and for arbitrary current load history. The same measured data is used to calibrate and to simulate response of the first order Thevenin equivalent circuit topology in order to amply compare the obtained results.
COBISS.SI-ID: 16771099
The paper introduces a method for calculating the strain energy dissipated during cyclic loading based on Prandtl-Ishlinskii hysteresis operators. The dissipated strain energy is cal- culated continuously throughout the loading procedure, the main advantage of the method being independence from the incremental step size. The Prandtl-Ishlinskii energy model is applied to a rheological model for magnesium alloy AZ31 that correctly simulates the material's complex response when subjected to arbitrary uniaxial loading at room temperature. This approach gives a fast and accurate value of the dissipated strain energy which in turn can be used for estimating the fatigue life of magnesium alloys.
COBISS.SI-ID: 22466563
Magnesium is one of the lightest metals for structural components. It has been used for producing various lightweight cast components, but the application of magnesium sheet plates is less widespread. There are two reasons for this: (i) its poor formability at ambient temperatures; and (ii) insufficient data on its durability, especially for dynamic loading. In this article, an innovative approach to predicting the fatigue life of the AZ31 magnesium alloy is presented. It is based on an energy approach that links the strain-energy density with the fatigue life. The core of the presented methodology is a comprehensive new model for tensile and compressive loading paths, which makes it possible to calculate the strain-energy density of closed hysteresis loops. The model is universal for arbitrary strain amplitudes. The material parameters are determined from several low-cycle fatigue tests. The presented approach was validated with examples of variable strain histories.
COBISS.SI-ID: 16894235
In product design, the focus is increasingly shifting towards optimizing and increasing the efficiency of the development process. This can be achieved with advanced numerical tools, but these methods require precise knowledge of material properties. One of the desired properties is the dynamic load behavior of the material. The research is directly related with the company that developed the slender wooden beams used in industry to produce windows of larger dimensions (height over 3 m). For the testing of wooden beams, the pneumatic four-point bending fatigue test rig was developed. In this paper, the whole structure of the test rig is described in detail. Based on the performed experiments of dynamic strength, the Woehler curve was determined, which serves as a necessary input for further numerical simulation of the fatigue process of wood-based beams. Knowledge of the response of wood to dynamic loads is very important to predict its life expectancy in various products.
COBISS.SI-ID: 36773379