Plastic instability in complex strain paths predicted by advanced constitutive equations

The present paper aims at predicting plastic instabilities under complex loading histories using an advanced sheet metal forming limit model. The onset of localized necking is computed using the Marciniak-Kuczinslcy (MK) analysis [I] with a physically-based hardening model and the phenomenological anisotropic yield criterion Yld2000-2d [2]. The hardening model accounts for anisotropic work-hardening induced by the microstructural evolution at large strains, which was proposed by Teodosiu and Hu [3]. Simulations are carried out for linear and complex strain paths. Experimentally, two deep-drawing quality sheet metals are selected: a bake-hardening steel (BH) and a DC06 steel sheet. The validity of the model is assessed by comparing the predicted and experimental forming limits. The remarkable accuracy of the developed software to predict the forming limits under linear and non-linear strain path is obviously due to the performance of the advanced constitutive equations to describe with great detail the material behavior. The effect of strain-induced anisotropy on formability evolution under strain path changes, as predicted by the microstructural hardening model, is particularly well captured by the model.open1134Nsciescopu

Mechanical behaviour of TWIP steel under shear loading

Twinning induced plasticity steels (TWIP) are very good candidate for automotive industry applications because they potentially offer large energy absorption before failure due to their exceptional strain hardening capability and high strength. However, their behaviour is drastically influenced by the loading conditions. In this work, the mechanical behaviour of a TWIP steel sheet sample was investigated at room temperature under monotonic and reverse simple shear loading. It was shown that all the expected features of load reversal such as Bauschinger effect, transient strain hardening with high rate and permanent softening, depend on the prestrain level. This is in agreement with the fact that these effects, which occur during reloading, are related to the rearrangement of the dislocation structure induced during the pre-deformation. The homogeneous anisotropic hardening (HAH) approach proposed by Barlat et al. (2011) [1] was successfully employed to predict the experimental results.110Ysciescopu

The performance of Marciniak–Kuczinsky approach on prediction of plastic instability of metals subjected to complex loadings

The objective of the present paper is to analyse the performance of Marciniak-Kuczinsky (MK) theory on the prediction of formability of sheet metals subjected to complex loadings. Advanced constitutive equations taking into account isotropic and anisotropic hardening are applied to describe the material mechanical behaviour under linear and complex loadings. A comparative study on their accuracy on predicting the forming limits for the studied material is performed. Two deep-drawing quality sheet metals are selected. Several strain path changes are taken into account. A good agreement between the theoretical and experimental results was obtained. MK theory is an efficient and valuable tool on the prediction of plastic flow localization of sheet metals under complex loadings when proper constitutive equations are used.publishe

The study of the new distribution solutions of in medium voltage network

Fișierul atașat conține: Rezumat, Abstract, Cuprins, Introducere.Teza este structurată în 3 capitole și e formată dintr-un volum total de 64 pagini. Scopul lucrării constă în examinarea diferitor soluții tehnice de distribuție a energiei electrice, analiza lor comparativă întru argumentarea posibilelor direcții de diminuare a pierderilor de energie în rețelele de distribuție în Republica Moldova. Obiectivele generale: creșterea economică prin optimizarea pierderilor de energie și diminuarea consumului tehnologic în rețelele noi proiectate sau rețelele aflate în planul de modernizare. Primul capitol constă în descrierea funcțiilor operatorului sistemului de distribuție (OSD), principiilor și criteriilor la proiectarea, dimensionarea și construcția rețelelor de distribuție. Aici au fost analizate principalele clauze ce determină calitatea energiei electrice și au fost afișate măsuri și tehnologii noi de creștere a acesteia. Capitolul doi pune accent pe pierderile de putere și energie electrice, structura lor cât și metodele utilizate pentru determinarea și prognozarea acestora în rețelele de distribuție în funcție de datele inițiale prezente. Ultimul capitol e un studiu de caz care exemplifică determinarea pierderilor de putere și de tensiune în rețelele de distribuție pe baza unui singur feeder tipic cu 28 consumatori racordați la rețeaua de distribuție de 0,4 kV, direct la rețeaua de distribuție de 10 kV printr-un transformator monofazat și racordați la rețeaua de 10 kV printr-un transformator pe baza de elemente semiconductoare SST.The thesis is structured in 3 chapters and consists of a total volume of 64 pages.The purpose of the thesis is to examine different technical solutions for electricity distribution, their comparative analysis in order to argue the possible directions of diminishing the energy losses in the distribution networks in the Republic of Moldova. General objectives: economic growth by optimizing energy losses and reducing technological consumption in newly designed networks or networks in the modernization plan. The first chapter consists of the description of the functions of the distribution system operator (OSD), the principles and criteria for the design, dimensioning and construction of the distribution networks. Here were analyzed the main clauses that determine the quality of electricity and new measures and technologies for its growth. Chapter two focuses on the losses of power and electricity, their structure and the methods used to determine and predict them in the distribution networks according to the initial data presented. The last chapter is a case study that exemplifies the determination of power and voltage losses in distribution networks based on a single typical feeder with 28 consumers connected to the 0,4 kV distribution network, directly to the 10 kV distribution network through a single-phase transformer and connected to the 10 kV network through a transformer SST based on semiconductor elements

Cercetarea influenţei soluţiei de ventilare adoptată asupra pierderilor de căldură pentru clădirile de locuit

Fişierul ataşat conţine: Содержание, Rezumat, Summary.Lucrarea de diplomă este dedicată cercetării tipurilor sistemelor de ventilare pentru clădirile de locuit și influența sistemelor de ventilare adoptate asupra pierderilor de căldură în clădirile de locuit. În lucrarea de diplomă s-a efectuat analiza tipurilor sistemelor de ventilare pentru clădirile de locuit și influența sistemelor de ventilare a celor utilizate și recomandate. Sunt descrise principiile de lucru a sistemelor de ventilare, avantajele și dezavantajele acestora. S-a elaborat o clasificare contemporană a sistemelor de ventilare întrebuințate și s-a efectuat analiza echilibrului de caldură a clădirii. În lucrarea de diplomă s-a cercetat influența sistemelor de ventilare asupra echilibrului de caldură a clădirii . S-a efectuat analiza și determinarea factorilor decisivi a utilizării ventilației mecanice cu recuperator de căldură.The diploma thesis is devoted to research types of ventilation systems for residential buildings and the impact made on the ventilation heat loss from buildings. The thesis work has been carried aut the analysis used and recommended ventilation systems for residential buildings, describes the principles of operation of ventilation systems, their advantages and disadvantages. It developed the modern classification used types of ventilation systems for residential buildings, as well as conducted an analysis of the heat balance of the building. The thesis work was to study the effect of the accepted system of ventilation on the heat balance of the building. Analysis was made and to identify the appropriateness of supply and exhaust system with mechanical drive and heat recovery for residential buildings

Instalații de stingere a incendilor cu ajutorul sunetului și a aburului

Resursă electronicăÎn articol se abordează particularitățile utilizării stingerii incendiilor prin intermediul instalațiilor cu ajutorul sunetului și a aburului

The formability of twinning: induced plasticity steels predicted on the base of Marciniak-Kuczynski theory

The purpose of this work is to predict and analyze the formability of twinning – induced plasticity steels through the Marciniak-Kuczynski (MK) theory with emphasis on the solutions for improving the prediction results. The selected constitutive equations involve the Yld00-2d of Barlat et al. (2003) plane stress yield function, the Swift strain–hardening power law and the dislocation density based constitutive model proposed by Kim et al. (2013), taking into account the dislocation glide, twinning and dynamic strain aging. Three types of high manganese content TWIP steels sheet were selected. To understand the formability of the TWIP steel and the factors influencing it, a sensitive study on the effect of the mechanical properties of the TWIP steel on the MK theory concept and the predicted forming limits is performed. Using the dislocation density based microstructural model, the deformation twinning effect and the contribution of dynamic strain aging to the FLDs of TWIP steel is analyzed. The relevant influence of the sharpness of the yield surface in the biaxial stretching region in the prediction of FLDs of TWIP steels is highlighted. The extended MK model can be adapted to predict the forming limits of the TWIP steels by using an unusual high initial geometrical defect imposed by their high strain hardening. In this way it was showed that the MK theory cannot be applied for predicting the forming limits of TWIP steels unless by applying imperfection factors that are not physically reasonable. Therefore, new failure models are required for TWIP steel.publishe

The formability prediction of twinning-induced plasticity steels

The proposal of this work is to predict and analyse the formability of twinning-induced plasticity steels through the Marciniak-Kuczinsky approach with emphasis on the solutions for improving the prediction results. The selected constitutive equations involve the Yld2000-2d plane stress yield function and the Swift strain-hardening power law. To understand the formability of the TWIP steel and the factors influencing it, a sensitive study on the effect of the mechanical properties of the TWIP steel on the Marciniak-Kuczinsky (MK) theory concept and the predicted forming limits is performed.publishe

Analysis of the promotion of Xacobeo 21-22 as a transversal event between pilgrimage and tourism

RESUMEN: Este primer año de recuperación tras el impacto de la pandemia del Covid-19 coincide en Galicia con la celebración del Año Xacobeo 21-22 cuyo propósito es impulsar la movilidad social, cultural y económica en la comunidad a través del fomento de esta experiencia de origen milenario. En este TFM se procura estudiar el sentido y la evolución del Camino de Santiago, así como la relación que guarda con el turismo con el fin de esclarecer la intencionalidad de promoción turística del Xacobeo 21-22. En este contexto, el Camino es clave en la oferta turística de Galicia adquiriendo un enfoque emocional que invita al mundo a caminar este Año Santo con el objetivo de volver a llenar las rutas hacia Santiago. Además, se tienen en cuenta los efectos de la pandemia en el comportamiento del peregrino, así como su propia experiencia para determinar las nuevas tendencias y motivaciones que animan hoy en día a realizar el Camino.ABSTRACT: This first year of recovery after the impact of the Covid-19 pandemic coincides in Galicia with the celebration of the Xacobeo Year 21-22 whose purpose is to promote social, cultural and economic mobility in the community through the promotion of this experience of millenary origin. This TFM seeks to study the meaning and evolution of The Way of Saint James, as well as the relationship it has with tourism in order to clarify the intentionality of tourism promotion of Xacobeo 21-22. In this context, The Way is key in the tourist offer of Galicia acquiring an emotional approach that invites the world to walk this Holy Year with the aim of refilling the routes to Santiago. In addition, the effects of the pandemic on the pilgrim’s behavior are taken into account, as well as his own experience to determine the new trends and motivations that encourage today to realize The WayMáster en Dirección de Marketing (Empresas Turísticas