A novel phenomenological model for predicting hysteresis loss of rubber compounds obtained from ultra-large off-the-road tires

The objective of this study was to develop a novel phenomenological model that can predict the hysteresis loss of rubber compounds obtained from ultra-large off-the-road (OTR) tires under typical operating conditions at mine sites. To achieve this, first, cyclic tensile tests were conducted on tire tread compounds to derive the experimental results of hysteresis curves, peak stress, residual strain, and hysteresis loss at 6 strain levels, 8 strain rates, and 14 rubber temperatures. Then, referring to these experimental results, a phenomenological model was developed – the HLSRT model (a hysteresis loss model considering strain levels, strain rates, and rubber temperatures). This HLSRT model was generated based on a novel strain energy function that was modified from the traditional Mooney-Rivlin (MR) function, and the model was used to predict the hysteresis loss of rubber compounds in OTR tires. The prediction results show that the HLSRT model estimated the hysteresis loss of tire tread compounds with average and maximum mean absolute percent errors (MAPEs) of 11.2% and 18.6%, respectively, at strain levels ranging from 10% to 100%, strain rates from 10% to 500% s−1, and rubber temperatures from −30°C to 100°C. These MAPEs were relatively low when compared with previous studies, showing that the HLSRT model has higher prediction accuracy. For the first time, the HLSRT model derived from this study has provided a new approach to predicting the hysteresis loss of OTR tire rubbers to guide the use of OTR tires in truck haulage at mine sites.

Contact resistance, coupling and hysteresis loss measurements of ITER Poloidal Field joint in parallel applied magnetic field

The inter-strand contact resistance and AC losses were measured on an ITER PF Coil joint in a parallel applied AC magnetic field. In addition, the hysteresis loss was measured as a function of the angle with the applied magnetic field on a NbTi strand of the same type as in the joint with a Vibrating Sample Magnetometer (VSM). The AC loss measurements were performed at four applied field conditions for combinations of 0 or 1 T offset field and 0.2 or 0.4 T sinusoidal amplitude. The hysteresis loss of the joint was compared with the measured AC loss density of the NbTi strand for the same field conditions as the joint AC loss measurement but with varying the angle of the applied field. The subsequent cable twist angles affect the hysteresis loss since the critical current and penetration field depend on the angle of the applied field. It is found that 15.5° is an effective angle for the calculation of the hysteresis loss of joint when compared to the single strand measurement. The inter-strand contact resistance measurements cover all the typical strand combinations from the five cabling stages of the individual conductors, as well as the strand combinations across the two conductors to characterize the inter-strand including the copper sole resistivity. It’s the first time to measure the contact resistances and AC losses of the full-size ITER PF joint. By comparing the measured and simulated data in the JackPot-ACDC model, it’s also the first time to obtain the accurate inter-strand, inter-petal and strand to copper sole contact resistivities, which are the main input parameters for the further quantitative numerical analysis of the PF joints, in any current and magnetic field conditions.

Effective Method to Measure and Inspect the Hysteresis Loss of a Transformer

<p class="Abstract"><span lang="EN-US">This paper presents a study on the significance of source side harmonics and their effects on transformers. Source side harmonics are typically present in power electronic sources which are commonly used in renewable applications. The continued outcome of source side harmonics is observed on the hysteresis curve of a transformer. Single-phase transformers are used in the proposed study to determine the effect of harmonics on magnetization and demagnetization cycles using an electronic operational amplifier-based integrator circuit. A technique is also presented for effectively storing and plotting the hysteresis curve from the measured data. After the hysteresis curve is obtained, it is compared with standard data and a conclusion is obtained from the results about the presence of harmonics in the source. The hysteresis curve is thus found without removing the transformer from operation. The study also proposes a modified hysteresis model for the transformer considering the effect of source harmonics. The proposed study is an effective tool for easy measurement and detection of harmonics. The <em>MATLAB/Simulink</em> based simulations with suitable experiments validate the proposed study.<em></em></span></p>

On the Practical Evaluation of the Switching Loss in the Secondary Side Rectifiers of LLC Converters

The switching loss of the secondary side rectifiers in LLC resonant converters can have a noticeable impact on the overall efficiency of the complete power supply and constrain the upper limit of the optimum switching frequencies of the converter. Two are the main contributions to the switching loss in the secondary side rectifiers: on the one hand, the reverse recovery loss (Qrr), most noticeably while operating above the series resonant frequency; and on the other hand, the output capacitance (Coss) hysteresis loss, not previously reported elsewhere, but present in all the operating modes of the converter (under and above the series resonant frequency). In this paper, a new technique is proposed for the measurement of the switching losses in the rectifiers of the LLC and other isolated converters. Moreover, two new circuits are introduced for the isolation and measurement of the Coss hysteresis loss, which can be applied to both high-voltage and low-voltage semiconductor devices. Finally, the analysis is experimentally demonstrated, characterizing the switching loss of the rectifiers in a 3 kW LLC converter (410 V input to 50 V output). Furthermore, the Coss hysteresis loss of several high-voltage and low-voltage devices is experimentally verified in the newly proposed measurement circuits.

Influence of Silica Specific Surface Area on the Viscoelastic and Fatigue Behaviors of Silica-Filled SBR Composites

This work aimed at studying the effect of a silica specific surface area (SSA), as determined by the nitrogen adsorption method, on the viscoelastic and fatigue behaviors of silica-filled styrene–butadiene rubber (SBR) composites. In particular, silica fillers with an SSA of 125 m2/g, 165 m2/g, and 200 m2/g were selected. Micro-computed X-ray tomography (µCT) was utilized to analyze the 3D morphology of the fillers within an SBR matrix prior to mechanical testing. It was found with this technique that the volume density of the agglomerates drastically decreased with decreasing silica SSA, indicating an increase in the silica dispersion state. The viscoelastic behavior was evaluated by dynamic mechanical analysis (DMA) and hysteresis loss experiments. The fatigue behavior was studied by cyclic tensile loading until rupture enabled the generation of Wöhler curves. Digital image correlation (DIC) was used to evaluate the volume strain upon deformation, whereas µCT was used to evaluate the volume fraction of the fatigue-induced cracks. Last, scanning electron microscopy (SEM) was used to characterize, in detail, crack mechanisms. The main results indicate that fatigue life increased with decreasing silica SSA, which was also accompanied by a decrease in hysteresis loss and storage modulus. SEM investigations showed that filler–matrix debonding and filler fracture were the mechanisms at the origin of crack initiation. Both the volume fraction of the cracks obtained by µCT and the volume strain acquired from the DIC increased with increasing SSA of silica. The results are discussed based on the prominent role of the filler network on the viscoelastic and fatigue damage behaviors of SBR composites.

Hysteresis loss of ultra-large off-the-road tire rubber compounds based on operating conditions at mine sites

The objective of this study is to investigate the hysteresis loss of ultra-large off-the-road (OTR) tire rubber compounds based on typical operating conditions at mine sites. Cyclic tensile tests were conducted on tread and sidewall compounds at six strain levels ranging from 10% to 100%, eight strain rates from 10% to 500% s−1 and 14 rubber temperatures from −30°C to 100°C. The test results showed that a large strain level (e.g. 100%) increased the hysteresis loss of tire rubber compounds considerably. Hysteresis loss of tire rubber compounds increased with a rise of strain rates, and the increasing rates became greater at large strain levels (e.g. 100%). Moreover, a rise of rubber temperatures caused a decrease in hysteresis loss; however, the decrease became less significant when the rubber temperatures were above 10°C. Compared with tread compounds, sidewall compounds showed greater hysteresis loss values and more rapid increases in hysteresis loss with the rising strain rate.