Design, Analysis and Experimental Verification of the Self-Resonant Inverter for Induction Heating Crucible Melting Furnace Based on IGBTs Connected in Parallel

The object of this research was a self-resonated inverter, based on paralleled Insulated-Gate Bipolar Transistors (IGBTs), for high-frequency induction heating equipment, operating in a wide range of output powers, applicable for research and industrial purposes. For the nominal installed capacity for these types of invertors to be improved, the presented inverter with a modified circuit comprising IGBT transistors connected in parallel was explored. The suggested topology required several engineering problems to be solved: minimisation of the current mismatch amongst the paralleled transistors; a precise analysis of the dynamic and static transistors’ parameters; determination of the derating and mismatch factors necessary for a reliable design; experimental verification confirming the applicability of the suggested topology in the investigated inverter. This paper presents the design and analysis of IGBT transistors based on datasheet parameters and mathematical apparatus application. The expected current mismatch and the necessary derating factor, based on the expected mismatch in transistor parameters in a production lot, were determined. The suggested design was experimentally tested and investigated using a self-resonant inverter model in a melting crucible induction laboratory furnace.

HYDRAULIC MACHINES FOR SEPARATION OF WET DISPERSED SYSTEMS

Separation processes of wet dispersed systems are quite common in the food, processing and other industries. In particular, these include processes related to the production of fruit and vegetable juices, jams, sunflower and olive oil, the extraction of fat from meat rinds in meat production, the separation of whey from cheese mass in the production of cheese, the separation of grated cocoa into butter and pulp, dehydration of wet dispersed waste of food production (alcohol grain, beer pellets, beet pulp, coffee and barley sludge). These processes are quite energy-intensive and have low-productivity, therefore, much attention is paid for modernization of equipment for their implementation in the direction of improving the indicated efficiency characteristics, as well as increasing reliability and reducing material consumption, complexity and price of working machines. At the same time, the known hydraulic static presses do not provide of low final moisture content of the product and the required productivity of the working process. Vibratory pressing equipment is often quite complex, unreliable and generates intense noise and vibration during of operation. Screw presses with an electromechanical drive, despite of their advantages, do not allow to achieve of the necessary degree of separation of the components of the dispersed system, in addition, their actuators are structurally quite complex and wear out quickly. The authors propose improved schemes of hydraulic presses for separation of wet dispersed systems, which can provide high rates of efficiency of the working process and have a simple and reliable design. The article also presents equations for calculating of the main operating parameters of the proposed equipment.

Distinct Advantages of Circumferential Notch Tensile (CNT) Testing in the Determination of a Threshold for Stress Corrosion Cracking (KISCC)

Stress corrosion cracking (SCC) is a vexing problem for load-bearing equipment operating in a corrosive environment in various industries, such as aerospace, chemical and mineral processing, civil structures, bioimplants, energy generation etc. For safe operation, effective maintenance and life prediction of such equipment, reliable design data on SCC (such as threshold stress intensity for SCC, i.e., KISCC) are invaluable. Generating reliable KISCC data invariably requires a large number of tests. Traditional techniques can be prohibitively expensive. This article reviews the determination of KISCC using the circumferential notch tensile (CNT) technique, the validation of the technique and its application to a few industrially relevant scenarios. The CNT technique is a relatively recent and considerably inexpensive approach for the determination of KISCC when compared to traditional techniques, viz., double-cantilever beam (DCB) and compact tension (CT) that may be fraught with prohibitive complexities. As established through this article, the CNT technique circumvents some critical limitations of the traditional techniques.

DISCOVERING FAILURE CRITERIA OF COMPOSITES BY SPARSE IDENTIFICATION AND COMPRESSED SENSING

A reliable design of a composite structure needs to consider the failure of the composites. Hashin failure criterion is one of the most popular phenomenological models in engineering practice due to its simplicity of application. Although remarkable success has been achieved from the Hashin failure criterion, it does not always fit the experimental results very well. Over the past few years, a few experimental failure data have been collected. It would be of interest to leverage the existing data to improve the prediction of failure criteria. In this paper, we proposed to apply a framework that combines sparse regression with compressed sensing to discover failure criteria from data. Following the phenomenological failure models, we divided the failure of composites into tensile and compressive fiber modes, tensile and compressive matrix modes. Two examples were studied with the proposed framework. The first example was presented to demonstrate the capability of the framework. The data was generated by the Hashin failure criterion and added various magnitudes of noise. The proposed framework was implemented to discover the failure criterion from the noised data. For the second example, the proposed method was used to discover failure criteria from the experimental data which are collected from the first world wide failure exercise (WWFE I). Both examples show that the proposed method can discover the failure criteria accurately.

Research on Robust and Efficient Approach for Extreme Mooring Tension Estimation for FLNG and FOWT

Offshore floating production units such as FPSO, FLNG, etc. are stationed at operation sites for many years without stopping operation. The mooring systems are provided as permanent positioning system for the floaters and are designed based on conditions that normally assume way longer than their actual service life. The offshore industry, nevertheless, has experienced higher than expected failure rates of mooring systems in the past. [1] Therefore, more robust and pertinent design requirements are desired. On the other hand, while operators demand more reliable design procedures, mooring analysis needs to be performed for numerous load cases on actual projects, which require enormous cost and resources for simulation and analysis. This has resulted in the need by the industry for more efficient mooring analysis procedures while maintaining the required safety.

Fatigue assessment of additively manufactured AlSi10Mg structures using effective stress concepts based on the critical distance approach

In the last decade, Additive Manufacturing (AM) technologies have been considered by both the automotive and aerospace industries for the production of end-use metallic parts, with a main focus on Powder Bed Fusion – Laser Beam / metallic (PBF-LB/M) technologies. However, AM parts present features that are deleterious to their cyclic properties. For a reliable design in terms of fatigue strength, existing influencing variables must be identified and transferred to a numerical model. In particular, different types of defects, as well as their distribution, should be taken into account. In addition to the identification of relevant parameters based on literature data, an AlSi10Mg component-like structure is assessed based on results from notched specimens and a linear-elastic assessment concept using effective stresses.

Granular flow experiment using artificial gravity generator on International Space Station

Studying the gravity-dependent characteristics of regolith, fine-grained granular media covering extra-terrestrial bodies is essential for the reliable design and analysis of landers and rovers for space exploration. We performed a granular flow experiment under stable artificial gravity conditions generated by a centrifuge on the International Space Station. We also performed a discrete element simulation of the granular flow in both artificial and natural gravity environments. The simulation results verified that the granular flows in artificial and natural gravity are consistent. Further, regression analysis of the granular flow results revealed that the mass flow rate quantitatively follows a well-known physics-based law with some deviations under low-gravity conditions, implying that the bulk density of the granular media decreases with gravity. This insight also indicates that the bulk density considered in simulation studies of space probes under low-gravity conditions needs to be tuned for their reliable design and analysis.

Probabilistic Assessment of Fracture Toughness of Epoxy Resin EPOLAM 2025 Including the Notch Radii Effect

Many design scenarios of components made of polymer materials are concerned with notches as representative constructive details. The failure hazard assessment of these components using models based on the assumption of cracked components leads to over-conservative failure estimations. Among the different alternative approaches proposed that are based on the apparent fracture toughness, KcN is considered. In so doing, the current deterministic underlying concept must be replaced by a probabilistic one to take into account the variability observed in the failure results in order to ensure a reliable design. In this paper, an approach based on the critical distance principle is proposed for the failure assessment of notched EPOLAM 2025 CT samples with each different notch radii (ρ) including a probabilistic assessment of the failure prediction. First, each apparent fracture toughness is transformed into the equivalent fracture toughness for ρ=0 based on the critical distances theory. Then, once all results are normalized to the same basic conditions, a Weibull cumulative distribution function is fitted, allowing the probability of failure to be predicted for different notch radii. In this way, the total number of the specimens tested in the experimental campaign is reduced, whereas the reliability of the material characterization improves. Finally, the applicability of the proposed methodology is illustrated by an example using the own experimental campaign performed on EPOLAM 2025 CT specimens with different notch radii (ρ).