MAGNESIUM ALLOY AZ31B FORMING LIMIT CURVE USING THE NAKAZIMA TEST

The behaviour of a metal sheet when forming can be predicted with accuracy if the forming limit curve is known (FLC). Generating an FLC is a two-step process that involves forming the material blanks and measuring the strain. This can be done by using the Marciniak or Nakazima tests. In this experimental paper, the Nakazima test was used and is conducted using a hemispherical punch, retaining plate, and draw beads, to prevent the blank from slipping, along with the ARAMIS digital image correlation (DIC) system, used for measuring. Metal sheets of magnesium alloy AZ31B were used, with thicknesses of 0.5 mm and 1.0 mm. The settings of the testing equipment have been selected to allow the material to break at different strains: from uniaxial to biaxial stretches. Each specimen represents specific stress in the strain limit diagram. The geometries of the material and its thicknesses have the same leading role in creating tensions. Compared to the tensile compression test, this test confirms better formability of sheets with a thickness of 0.5 mm

STRETCH FORMING USING HEATED DIE

The stretch forming process implies stretching and drawing into shape a sheet of material onto a die. This method is used, among other sectors, in the construction of aeroplane fuselage, as significant, complex parts can be obtained in one piece. In essence, stretch forming implies working with materials that have medium to high spring back effects, such as aluminium or magnesium alloys. Different approaches are used in manufacturing due to this phenomenon, ranging from incremental processes to multipoint dies. Another critical aspect of this process is to know how the material behaves under severe plastic deformation, as different alloys require different approaches that vary from step by step forming to in-process chemical treatments to manual pounding the metal sheet. However, all these alloys have in common that, when heated, their machinability properties improve. In this experimental study, a heated die approach was taken into consideration. 6x60 mm 100W heating elements along with temperature sensors were fitted into the die. The USB/OC326009 metal sheet is in direct contact with the die, thus assuring the heat transfer, as the temperatures reach 200 °C. The die temperature is software controlled so that maximum temperature and thermal inertia could be controlled with ease. The data indicate that this method offers significantly improved results compared to a normal room-temperature process

STUDY REGARDING THE INFLUENCE OF CORROSIVE AGENTS ON THE SURFACE OF METALLIC MATERIAL LIKE STEEL

Corrosion is a process that involves the action of different agents on material surfaces. Corrosive agents in corrosion field can be ambient, saline and microbiological mediums. These agents can influence the mechanical properties of metallic material like steel. The aim of this research is to present the mechanic properties of sheet steel submitted at the action of corrosive agents. The metallic samples were analyzed in order to determinate the resistance at corrosion by stress-strain curves, deformation limit curves and (Atomic Force microscopy) AFM images. Relative results are obtained in the case of saline medium corrosion, meaning that the saline medium corrosion influences the metallic sample, in proportion to the degree of salinity. Also, the AFM images and topographies of metallic surface confirm this conclusion

MAGNESIUM ALLOY AZ31B FORMING LIMIT CURVE USING THE NAKAZIMA TEST

The behaviour of a metal sheet when forming can be predicted with accuracy if the forming limit curve is known (FLC). Generating an FLC is a two-step process that involves forming the material blanks and measuring the strain. This can be done by using the Marciniak or Nakazima tests. In this experimental paper, the Nakazima test was used and is conducted using a hemispherical punch, retaining plate, and draw beads, to prevent the blank from slipping, along with the ARAMIS digital image correlation (DIC) system, used for measuring. Metal sheets of magnesium alloy AZ31B were used, with thicknesses of 0.5 mm and 1.0 mm. The settings of the testing equipment have been selected to allow the material to break at different strains: from uniaxial to biaxial stretches. Each specimen represents specific stress in the strain limit diagram. The geometries of the material and its thicknesses have the same leading role in creating tensions. Compared to the tensile compression test, this test confirms better formability of sheets with a thickness of 0.5 mm

An Advanced Decision Support Platform in Energy Management to Increase Energy Efficiency for Small and Medium Enterprises

The paper presents a new vision on the energy consumption management in the case of the small and medium enterprises (SMEs), integrated into an advanced decision support platform, with technical and economic benefits on increasing the energy efficiency, with four modules for database management, profiling, forecasting, and production scheduling. Inside each module, artificial intelligence and data mining techniques were proposed to remove the uncertainties regarding the dynamic of technological flows. Thus, the data management module includes the data mining techniques, that extract the technical details on the energy consumption needed in the development of production scheduling strategies, the profiling module uses an original approach based on clustering techniques to determine the typical energy consumption profiles required in the optimal planning of the activities, the forecasting module contains a new approach based on an expert system to forecast the total energy consumption of the SMEs, and production scheduling module integrates a heuristic optimization method to obtain the optimal solutions in flattening the energy consumption profile. The testing was done for a small enterprise from Romania, belonging to the domain of trade and repair of vehicles. The obtained results highlighted the advantages of the proposed decision support platform on the decrease in the intensity of energy consumption per unit of product, reduction of the purchase costs, and modification of the impact for which energy bills have on the operational costs

Optimal Phase Load Balancing in Low Voltage Distribution Networks Using a Smart Meter Data-Based Algorithm

In the electric distribution systems, the “Smart Grid” concept is implemented to encourage energy savings and integration of the innovative technologies, helping the distribution network operators (DNOs) in choosing the investment plans which lead to the optimal operation of the networks and increasing the energy efficiency. In this context, a new phase load balancing algorithm was proposed to be implemented in the low voltage distribution networks with hybrid structures of the consumption points (switchable and non-switchable consumers). It can work in both operation modes (real-time and off-line), uploading information from different databases of the DNO which contain: The consumers’ characteristics, the real loads of the consumers integrated into the smart metering system (SMS), and the typical load profiles for the consumers non-integrated in the SMS. The algorithm was tested in a real network, having a hybrid structure of the consumption points, on a by 24-h interval. The obtained results were analyzed and compared with other algorithms from the heuristic (minimum count of loads adjustment algorithm) and the metaheuristic (particle swarm optimization and genetic algorithms) categories. The best performances were provided by the proposed algorithm, such that the unbalance coefficient had the smallest value (1.0017). The phase load balancing led to the following technical effects: decrease of the average current in the neutral conductor and the energy losses with 94%, respectively 61.75%, and increase of the minimum value of the phase voltage at the farthest pillar with 7.14%, compared to the unbalanced case

MANAGEMENT OF ORBITAL TUMORS PRESENTING AS UNILATERAL EXOPHTHALMOS

Aim of the study. We aim to present our experience regarding the management of exophthalmos as the first clinical manifestation of a space-occupying orbital lesion. Material and methods. We performed a retrospective review, selecting 17 patients with orbital tumors that initially presented for proptosis. Results. Following multidisciplinary clinical and imaging evaluation, three primary orbital tumors were diagnosed, one mass pertaining to the lacrimal gland, and 13 secondary tumors. Surgical treatment was performed in 11 patients. Complete excision was performed in three benign tumors, complete removal and orbital content preservation was achieved in eight patients, orbital exenteration was necessary in two cases of orbital malignancies, and extended orbital exenteration was performed in one patient. Four cases did not have indication of surgery due to internal carotid artery invasion or extensive intracranial invasion. Two patients were diagnosed with lymphoma following biopsy and underwent oncologic treatment. Conclusion. An early diagnosis of an orbital mass presenting as proptosis involves multidisciplinary evaluation for the exclusion of other causes of exophthalmos. Orbital content and function preservation are the main goals of the surgical treatment

Coordinated Control of Single-Phase End-Users for Phase Load Balancing in Active Electric Distribution Networks

In the paper, a coordinated control methodology of single-phase (1-P) end-users switching operations on the phases of an active electric distribution network (AEDN) has been proposed to obtain a minimum unbalance degree at the coupling common point (CCP) level with the main distribution system. The phase load balancing (PLB) process considers the smart devices that switch the 1-P end-users (consumers and prosumers) from one phase to another to compensate for the phase load unbalance. The proposed methodology has been tested successfully in an AEDN belonging to a Romanian Distribution Network Operator (DNO) containing 114 end-users (104 consumers/10 prosumers) integrated into the Smart Metering System (SMS). The optimal solution leads to a value of the objective function by 1.00, represented by the unbalance factor (UF), which could be identified with the ideal target. A comparative analysis was conducted considering other possible PLB cases (the consumer-level PLB and prosumer-level PLB), obtaining similar values of the UF (1.027 vs. 1.028), slightly higher than in the hybrid-level PLB. Additionally, the significant technical benefits were quantified through an energy-saving of 58.73% and decreasing the phase voltage unbalance rate by 91% compared to the initial case (without PLB). These results emphasized the positive impact of the proposed coordinated control methodology on the PLB process and evidenced its effectiveness and applicability in the AEDNs

Contributions to Power Grid System Analysis Based on Clustering Techniques

The topic addressed in this article is part of the current concerns of modernizing power systems by promoting and implementing the concept of smart grid(s). The concepts of smart metering, a smart home, and an electric car are developing simultaneously with the idea of a smart city by developing high-performance electrical equipment and systems, telecommunications technologies, and computing and infrastructure based on artificial intelligence algorithms. The article presents contributions regarding the modeling of consumer classification and load profiling in electrical power networks and the efficiency of clustering techniques in their profiling as well as the simulation of the load of medium-voltage/low-voltage network distribution transformers to electricity meters

Lung Ultrasound-Guided Fluid Management versus Standard Care in Surgical ICU Patients: A Randomised Controlled Trial

The value of lung ultrasound (LU) in assessing extravascular lung water (EVLW) was demonstrated by comparing LU with gold-standard methods for EVLW assessment. However, few studies have analysed the value of B-Line score (BLS) in guiding fluid management during critical illness. The purpose of this trial was to evaluate if a BLS-guided fluid management strategy could improve fluid balance and short-term mortality in surgical intensive care unit (ICU) patients. We conducted a randomised, controlled trial within the ICUs of two university hospitals. Critically ill patients were randomised upon ICU admission in a 1:1 ratio to BLS-guided fluid management (active group) or standard care (control group). In the active group, BLS was monitored daily until ICU discharge or day 28 (whichever came first). On the basis of BLS, different targets for daily fluid balance were set with the aim of avoiding or correcting moderate/severe EVLW increase. The primary outcome was 28-day mortality. Over 24 months, 166 ICU patients were enrolled in the trial and included in the final analysis. Trial results showed that daily BLS monitoring did not lead to a different cumulative fluid balance in surgical ICU patients as compared to standard care. Consecutively, no difference in 28-day mortality between groups was found (10.5% vs. 15.6%, p = 0.34). However, at least 400 patients would have been necessary for conclusive results