Dynamic fracture mechanics assessments by simultaneous magnetic emission and potential drop techniques

Modern structural integrity assessment procedures incorporate fracture mechanical concepts most of which rely on dynamic fracture mechanics parameter determination from experiments. In the case of dynamic loading conditions, various experimental methods have evolved for determining the loading parameters and load-displacement behaviour. Ductile structural steel has many applications and its properties are interesting for designing experiments that simulate ductile, brittle and mixed fracture behaviour. In this study are presented the results of fracture mechanics investigations of a ductile ferromagnetic low-alloy high strength steel, performed under dynamic loading conditions. Standard Charpy specimens are tested by simultaneous coupled magnetic emission (ME) and potential drop (PD) techniques for determining critical crack initiation properties and resistance curve determination of a ductile steel behaviour. Equivalent brittle, ductile, and mixed mode fracture behaviour may be simulated by choice of test temperature and impact velocity. Analysis of integrated ME and PD signal data, employed in deriving critical J integral, has been successful in interpreting unstable or stable crack initiation and propagation. Experimental results are discussed with respect to the characteristics and the physical interpretations of both of the independent experimental techniques. Some specific experimental difficulties in the reliable assessment of dynamic crack initiation parameters are outlined

Dynamic fracture mechanics assessments by simultaneous magnetic emission and potential drop techniques

Modern structural integrity assessment procedures incorporate fracture mechanical concepts most of which rely on dynamic fracture mechanics parameter determination from experiments. In the case of dynamic loading conditions, various experimental methods have evolved for determining the loading parameters and load-displacement behaviour. Ductile structural steel has many applications and its properties are interesting for designing experiments that simulate ductile, brittle and mixed fracture behaviour. In this study are presented the results of fracture mechanics investigations of a ductile ferromagnetic low-alloy high strength steel, performed under dynamic loading conditions. Standard Charpy specimens are tested by simultaneous coupled magnetic emission (ME) and potential drop (PD) techniques for determining critical crack initiation properties and resistance curve determination of a ductile steel behaviour. Equivalent brittle, ductile, and mixed mode fracture behaviour may be simulated by choice of test temperature and impact velocity. Analysis of integrated ME and PD signal data, employed in deriving critical J integral, has been successful in interpreting unstable or stable crack initiation and propagation. Experimental results are discussed with respect to the characteristics and the physical interpretations of both of the independent experimental techniques. Some specific experimental difficulties in the reliable assessment of dynamic crack initiation parameters are outlined

Magnetic emission technique in assessing dynamic fracture mechanics parameters of ductile steel

Novi izazovi u proceni integriteta konstrukcija, uključujući identifikaciju opuštanja i produžetak radnog veka konstrukcionih čelika putem kvalitativnog i kvantitativnog određivanja dinamičkih parametara mehanike loma, imaju veliki značaj. Problematika eksperimentalnih istraživanja u vezi je sa preciznim određivanjem otpornosti na lom u uslovima dinamički opterećenih konstrukcija, gde još uvek nisu definisane standardne procedure u slučaju šarpi epruveta sa zamornom prslinom. Izvedeno je instrumentirano šarpi ispitivanje upotrebom tehnike magnetne emisije (ME) radi određivanja osobina kritične inicijacije prsline kod čelika sa izrazitim duktilnim svojstvima. Ekvivalentno krto, duktilno i mešovito ponašanje loma dobijeno je izborom temperature ispitivanja i brzine udara. Uspešno je sprovedena analiza i odgovarajuća interpretacija snimljenih ME signala i integrisanih ME signala, koji su upotrebljeni za izračunavanje kritičnog dinamičkog J integrala u slučaju nestabilnog ili stabilnog razvoja prsline.Concerning new challenges in structural integrity assessment, the identification of relaxation and service life extension of structural steels by qualitative and quantitative determination of dynamic fracture mechanics parameters is highly significant. Problems in experimental research are in connection with precise determination of resistance to fracture in conditions of dynamic loading of structures, where standard procedures in the case of precracked Charpy specimens are yet to be defined. Instrumented Charpy testing is performed by magnetic emission (ME) technique for determining critical crack initiation properties in a steel of dominant ductile properties. The equivalent brittle, ductile, and mixed fracture behaviour is simulated by the choice of test temperature and impact velocity. Analysis of acquired ME and integrated ME signals, both employed in deriving the critical J integral, has been successful in interpreting the results for unstable or stable crack propagation

Magnetic emission technique in assessing dynamic fracture mechanics parameters of ductile steel

Novi izazovi u proceni integriteta konstrukcija, uključujući identifikaciju opuštanja i produžetak radnog veka konstrukcionih čelika putem kvalitativnog i kvantitativnog određivanja dinamičkih parametara mehanike loma, imaju veliki značaj. Problematika eksperimentalnih istraživanja u vezi je sa preciznim određivanjem otpornosti na lom u uslovima dinamički opterećenih konstrukcija, gde još uvek nisu definisane standardne procedure u slučaju šarpi epruveta sa zamornom prslinom. Izvedeno je instrumentirano šarpi ispitivanje upotrebom tehnike magnetne emisije (ME) radi određivanja osobina kritične inicijacije prsline kod čelika sa izrazitim duktilnim svojstvima. Ekvivalentno krto, duktilno i mešovito ponašanje loma dobijeno je izborom temperature ispitivanja i brzine udara. Uspešno je sprovedena analiza i odgovarajuća interpretacija snimljenih ME signala i integrisanih ME signala, koji su upotrebljeni za izračunavanje kritičnog dinamičkog J integrala u slučaju nestabilnog ili stabilnog razvoja prsline.Concerning new challenges in structural integrity assessment, the identification of relaxation and service life extension of structural steels by qualitative and quantitative determination of dynamic fracture mechanics parameters is highly significant. Problems in experimental research are in connection with precise determination of resistance to fracture in conditions of dynamic loading of structures, where standard procedures in the case of precracked Charpy specimens are yet to be defined. Instrumented Charpy testing is performed by magnetic emission (ME) technique for determining critical crack initiation properties in a steel of dominant ductile properties. The equivalent brittle, ductile, and mixed fracture behaviour is simulated by the choice of test temperature and impact velocity. Analysis of acquired ME and integrated ME signals, both employed in deriving the critical J integral, has been successful in interpreting the results for unstable or stable crack propagation

Analytical solution of elastic-plastic stresses in thin rotating disc made up of piezoelectric material

This paper presents an analytic solution of transitional and plastic stresses in a thin rotating disc made up of piezoelectric material under internal pressure. The stresses in the rotating disc are calculated by applying the transition theory. The transitional and fully plastic stresses are derived with the help of stress strain relations. A nonlinear differential equation is obtained by substituting the resultant relations into the equilibrium equation. The solution of the differential equation with applied boundary conditions gives stresses, pressure and electric displacement. The results obtained are presented graphically and analysed numerically. It has been concluded on the basis of the study that isotropic material is better than piezoelectric material

Repetitions

In 1994, after following a character in Peter Handke’s novel Repetition into what is now Slovenia and after traveling in landscapes of Handke’s youth, Žarko Radaković and Scott Abbott published a two-headed text in Belgrade, Ponavljane, now published in English by punctum as Repetitions. The possibility of narration in two voices, complicated by the third voice that is Peter Handke’s own narrator, is the main focus of deliberation while traveling and reading and writing. Repetitions begins with Abbott’s text, a fairly straightforward travel narrative. It ends with Radaković’s account of the same events, much less straightforward, more repetitious, more adventuresome. Two aspects make the double-book unique. First, it represents experiences shared by two authors whose native languages are Serbian and English respectively (German is their only common language). The authors’ perspectives contrast with and supplement one another: Radaković grew up in Tito’s Yugoslavia and Abbott comes from the Mormon American West; Radaković is the translator of most of Peter Handke’s works into Serbo-Croatian and Abbott translated Handke’s provocative A Journey to the Rivers: Justice for Serbia for Viking Press and his play Voyage by Dugout: The Play of the Film of the War for PAJ (Performing Arts Journal); Radaković was a journalist for Deutsche Welle in Cologne and Abbott is a professor of German literature at Utah Valley University; Radaković is the author of several novels and Abbott has published mostly literary-critical work; and so on. Two sets of eyes. Two pens. Two visions of the world

Quality of the blood sampled from surgical drainage after total hip arthroplasty

Several methods have been found to be successful in reducing the need for allogeneic transfusion among the patients undergoing total hip replacement. The purpose of this prospective study was to analyse the quality and evaluate the effect of postoperative autotransfusion on the need for allogeneic transfusion following total hip replacement. The prospective study was performed in two groups of patients undergoing total hip replacement. Before the operative procedure all patients in both groups predonated two doses of autologous blood. In GROUP 1. the system for postoperative collection and transfusion of shed blood was used. In GROUP 2. the patients underwent total hip replacement without blood salvage system. Standard suction collection sets were used postoperatively. In this group shed blood was not transfused to the patients. The samples of preoperative donated autologus blood, allogeneic blood and postoperative collected autologous blood were analysed for number of red cells, hemoglobin, hematocrit, platelets, white blood cells, values of potassium, sodium, free hemoglobin and acid base status. The postoperatively blood salvage significantly reduced the use of allogeneic transfusion among patients managed with total hip replacement (allogeneic transfusion received 12% patients in Group 1 and 80% patients in Group 2; p<0.001). The values of red blood cells are significantly lower in postoperative collected autotransfusion blood compared with preoperative collected autologous blood and allogeneic blood (p<0.001). The values of potassium and acid base status were in normal range in postoperatively collected autotransfusion blood. These values in preoperatively collected autologous blood and allogeneic blood were out of normal range; (p<0.001). In addition to reducing the risk of complications that are associated with allogeneic transfusion, postoperative blood salvage may offer benefits including reducing the need for allogeneic blood. Our study confirmed that postoperative collection and transfusion of drainaged blood is simple and safe method that significantly reduce the need for allogeneic transfusion in patients underwent total hip replacement. The blood collected and transfused postoperatively has lower values of red blood cells and normal values of potassium and acid base balance. The transfusion of this blood caused no complications in our patients

Klimatski signali u kronologijama ranog drva, kasnog drva i širini goda hrasta kitnjaka (Quercus petraea (Matt.) Liebl.) iz Majdanpeka, sjeveroistočna Srbija

In this article, the dependence of the sessile oak (Quercus petraea (Matt.) Liebl.) radial growth (tree-ring, earlywood, and latewood widths) on climate (the mean monthly temperature and precipitation totals) was studied in the Majdanpek area, north-eastern Serbia. The growth response of the oak trees to the prevailing climate conditions was dendroecologically investigated, by applying the correlation and response function, as well as by pointer years analysis. The site chronology covered 159 years (1855-2013). We found that latewood and total tree-ring width contain the imprinted positive response to the amount of precipitation in summer months (June and July) of the current growing season. The earlywood width showed no direct dependence on climate data, but it was significantly affected by the previous-year latewood width. Moreover, 40 % of the variation in the latewood width is explained by the earlywood variation in the same season. The temperature was not found to have any significant effect on the growth of oak at the study site. The use of pointer years, determined by applying several calculation procedures, has highlighted previous results, indicating that the precipitation in summer months was the deciding climate factor leading to the occurrence of the years with exceptionally wide or narrow tree-rings and latewood. To enhance our understanding of the response of the sessile oak growth at south-oriented sites with a shallow soil profile to precipitation and temperature variations, and expand the current database and knowledge, future studies should be undertaken.U radu je proučavana ovisnost radijalnog prirasta (širine goda, širine ranoga i kasnog drva) hrasta kitnjaka (Quercus petraea (Matt.) Liebl.) o klimi (srednjoj mjesečnoj temperaturi i količini oborina) na području Majdanpeka, u sjeveroistočnoj Srbiji. Odziv radijalnog rasta hrastovih stabala na prevladavajuće klimatske uvjete istražen je dendrokronološki, primjenom korelacijske i odzivne funkcije, kao i analizom pokaznih godina. Kronologija staništa obuhvatila je 159 godina (1855. – 2013.). Otkrili smo da kasno drvo i ukupna širina goda sadržavaju utisnut pozitivan odziv na količinu oborina u ljetnim mjesecima (lipnju i srpnju) tekuće sezone rasta. Širina ranog drva nije pokazala izravnu ovisnost s klimatskim uvjetima, ali je na nju značajno utjecala širina kasnog drva iz prethodne godine. Nadalje, 40 % varijacija širine kasnog drva objašnjava se varijacijama ranog drva iz iste sezone. Na istraživanom staništu nije utvrđeno da temperatura ima značajan utjecaj na rast hrasta. Primjena pokaznih godina, koje su određene primjenom nekoliko računskih postupaka, potvrdila je prethodne rezultate upućujući na to da je prevladavajući klimatski čimbenik koji je doveo do pojave izrazito širokih ili uskih godova i kasnoga drva u pojedinim godinama bila količina oborina u ljetnim mjesecima. Da bi se sveobuhvatno razumjela reakcija rasta hrasta kitnjaka na promjene temperature i količinu oborina na južnim ekspozicijama i s plitkim profilom tla, trebalo bi provesti dodatne studije kako bi se proširila baza podataka i spoznaja

Analytical solution of elastic-plastic stresses in thin rotating disc made up of piezoelectric material

This paper presents an analytic solution of transitional and plastic stresses in a thin rotating disc made up of piezoelectric material under internal pressure. The stresses in the rotating disc are calculated by applying the transition theory. The transitional and fully plastic stresses are derived with the help of stress strain relations. A nonlinear differential equation is obtained by substituting the resultant relations into the equilibrium equation. The solution of the differential equation with applied boundary conditions gives stresses, pressure and electric displacement. The results obtained are presented graphically and analysed numerically. It has been concluded on the basis of the study that isotropic material is better than piezoelectric material

MTHFR C 677T Mutation and 4G/5G PAI-1 Polymorphism in Patient With Polycystic Ovarian Syndrome

Combined oral contraceptives (Ocs) are the most commonly used androgen supresors and the treatment of choice for menstrual dysfunction in women with polycystic ovarian syndrome (PCOs). Although OCs have remained popular due to their convenience and effectiveness, there have been continuing concerns about adverse effects. The OCs have long been known to incur and increased risk of venous thromboembolism especially in carriers of common inherited thromboembolic defects. Factor V Leiden, prothrombin factor G20210A polymorphism, MTHFR (C677T) mutation and 4G/5G polymorphism of the PAI-1 gene account for the majority of thromboembolic events in association with oral contraceptive use. The aim of the article is to present woman with unrecognized inherited thrombophilia who was treated with OCs due to PCOs signs