Advanced experimental methods for the characterization of welded structures

Welding is one of the most prevalent techniques for mechanical fastening of metals. Recent developments in welding technology have led to welding techniques being more readily employed in safety-critical engineering structures. Since the existence of residual stresses and material property variation around welds affects the mechanical performance and thereby structural integrity, it is essential to improve our knowledge in understanding and modelling the mechanical response of the welded structures. The present work focuses on mechanical characterizations of such structures. This work can be broadly classified into two parts; the first part investigates the residual stress distribution in welded specimens of different metals and the second part presents investigations of mechanical properties in welded specimen using full field optical techniques. A newly invented destructive technique for residual stress measurement, the contour method, was used for the investigations of the residual stress in welded joints in this study. The principle of the contour method is based on a variation of Bueckner's superposition theory. By means of a single straight cut, the 2D residual stress component normal to the region of interest can be determined. In this work, first the numerical simulations of the contour method using two and three dimensional bodies have been demonstrated. The contour method was then applied to one-pass and three-pass groove weld specimens and the results obtained from the contour method were compared to those obtained by the neutron diffraction strain measurement technique. The capability of the contour method to measure multiple residual stress components was also investigated in this project. A recent development of the contour method of stress measurement, the multi-axial contour method, permits measurement of the 3D residual stress distribution in a body, based on the assumption that the residual stresses are due to an inelastic misfit strain (eigenstrain) that does not change when a sample containing residual stresses is sectioned. The eigenstrain is derived from measured displacements due to residual stress relaxation when the specimen is sectioned. By carrying out multiple cuts, the full residual stress tensor in a continuously processed body can then be determined. In this study, finite element simulations of the technique were carried out to verify the method numerically. The method was then used to determine the residual stresses in a VPP A-welded sample, and the results were validated by neutron diffraction measurements. As part of the characterization of the welded structures, a study was undertaken to develop a method of extracting local mechanical properties from weld metal by strain mapping using the digital image correlation (DIC) technique. The feasibility of determining local stress-strain behaviour in the weld zone of a 316H stainless steel pipe with a girth weld was investigated by tensile tests on miniature and standard tensile test specimens. In addition, electron speckle pattern interferometry (ESPI) was utilized to obtain the full-field strain maps of a standard tensile specimen during loading and compared to those obtained in the same specimen by digital image correlation in order to verify the DIC measurements

A CPFEM based study to understand the void growth in high strength dual-phase Titanium alloy (Ti-10V-2Fe-3Al)

Author is thankful to University of Aberdeen for the award of Elphinstone Scholarship which covers the tuition fee of PhD study of author. Thanks are also due to Professor R.M. McMeeking for useful discussions.Peer reviewedPostprin

Radyal yönde değişken ısı kaynağı, dış basınç ve ısı yayınım sınır koşulu etkisindeki kompozit tüplerin termoelastoplastik davranışı.

M.S. - Master of Scienc

Radyofrekans Termal Ablasyon Yönteminin Karaciğer Hidatik Kistlerinin Tedavisinde Kullanımı: Ex vivo Koyun Çalışması

Objective: Hydatid disease is a disease caused by parasites belonging to the echinococcus family. This disease is often caused byEchinococcus granulosus and rarely by echinococcus alveolaris.The parasite may cause illness anywhere in the human body, mainlyin liver. In this study, we aimed to destroy the hydatid cyst viability by Radiofrequency Thermal Ablation (RFTA) method whichhas been used in many areas in medicine.Methods: We used fresh sheep liver with hydatid cysts. Average diameter of cysts was 3.3 cm. The study was performed in 3groups, each of which involved 20 cysts. After more than half of the cyst fluid was drained, ablation was performed. When thecore temperature of the cyst exceeded 95C, ablation procedure was continued for 3 minute in 1st group and for 4 minutes in 2ndgroup. Third group was the control group. And then, cyst fluid and germinative membrane were collected for microbiologic andpathologic assessment.Results: In 1st group, the cysts could not be destroyed at the desired level. In 2nd group, it was observed that 100% of theprotoscolex died and 100% of the germinative membranes was degenerated. In control group, %13 of protoscolex died and %10of germinative membranes wasdegenerated.Conclusion: We destroyed all the protoscolex and germinative membranes by using RFTA in 2nd group.Amaç: Hidatik kist hastalığı, echinococcus ailesine mensup parazitlerin etken olduğu bir hastalıktır. Ülkemizde hastalığın etkenisıklıkla Echinococcus granulosus, nadiren de echinococcus alveolaris’tir. İnsanda başlıca karaciğer olmak üzere birçok yerde hastalıkoluşturabilir. Bu çalışmada, birçok alanda kullanılan Radyofrekans Termal Ablasyon (RFTA) yöntemiyle hidatik kistin canlılığınıyok etmeyi amaçladık.Yöntemler: Çalışmada yeni kesilmiş hidatik kistli taze koyun karaciğerleri kullanıldı. Kistlerin ortalama çapı 3,3 cm idi. Herbirinde 20 kist olan 3 grupta çalışma yapıldı. Kist içeriğinin yarısından fazlası boşaltılarak radyofrekans ablasyon iğnesi yerleştirilipişlemler uygulandı. Kist içi sıcaklığı 95ºC’nin üzerine çıktıktan sonra 1. gruba 3 dakika, 2. gruba 4 dakika daha ablasyon işlemiuygulandı. Üçüncü grup kontrol grubuydu. Kist sıvısı mikrobiyoloji, germinatif membran da patoloji değerlendirmesine gönderildi.Bulgular: Birinci grupta kist canlılığını yok etmek için amaçlanan etki sağlanamadı. İkinci grupta %100 protoskoleks ölümüve %100 germinatif membran dejenerasyonu tespit edildi. Kontrol grubunda % 13 ölü protoskoleks oranı ve %10 germinatifmembran hasarı izlendi.Sonuç: Grup 2’de uyguladığımız RFTA yöntemi ile prtoskoleksler tamamen öldürülmüş ve tam bir germinatif membrandejenerasyonu sağlanmıştır

Konya'da acil cerrahi kapasitesinin tahmini: Dokuz yıllık çok merkezli çalışma

Amaç: Cerrahi acillerin sayısının sürekli artmasına rağmen acil cerrahi yatışları hakkında kısıtlı veri bulunmaktadır. Bu çok merkezli çalışmanın amacı, Konya şehrinde acil genel cerrahi sonuçlarını değerlendirmektir.Gereç ve Yöntemler: Konya'da tüm genel cerrahi acil başvurularının dokuz yıllık sonuçları incelendi (Ocak 2003Ocak 2012). Tüm demografik veriler istatistiksel olarak değerlendirildi.Bulgular: Konya'da yer alan 4 hastaneden 21954 hasta çalışmaya alınmıştır. Konya Numune Hastanesi (7154), Konya Eğitim ve Araştırma Hastanesi (6654), Necmettin Erbakan Üniversitesi Meram Tıp Fakültesi (6400) ve Başkent Üniversitesi Konya Eğitim ve Araştırma Hastanesi (1390) verileri toplandı. Hastaların yaş ortalaması 59,6 ve ortalama hastanede kalış süresi 3,3 gündü. Hastaneye kabul edilen hastaların tanıları; akut apandisit (%59,57), bağırsak tıkanıklığı (%11,12), travma (%7,97), boğulmuş kasık fıtığı (%5,46), akut kolesistit (%4,87), peptik ülser perforasyonu (%4,09), mezenterik iskemi (%2,73), nekrotizan fasiit (%2,73), gastrointestinal sistem kanaması (%1,79) ve diğerleriydi (%1,1).Sonuç: Bu çalışma ile cerrahi kabullerin sürekli arttığı görülmüştür. Non-travmatik akut karın, genel cerrahi acillerinin en sık nedeniydi. Yaşlı hastaların sayısında artış olmasına rağmen, hastanede kalış süresi ve mortalite oranları azalmıştır.Objective: Although the number of surgical emergencies continues to increase, comprehensive data on emergency surgical admissions are scarce. The aim of this multicenter study was to evaluate the causes, management, and outcomes of the general surgical emergencies in the city of Konya, Turkey.Material and Methods: The relevant details of the cases admitted and considered to be general surgical emergencies in Konya over a nine-year period (January 2003-January 2012) were analyzed. All demographic data were analyzed statistically.Results: The study group comprised 21954 cases from 4 hospitals in Konya: 7154 from Konya Numune Hospital, 6,654 from Konya Education and Research Hospital, 6,400 from Necmettin Erbakan University Meram Medical Faculty, and 1,390 from Başkent University Konya Education and Research Hospital. Their mean age was 59.6 years, and the average hospitalization time was 3.3 days. The diagnoses of the admitted patients were as follows: acute appendicitis (59.57%), bowel obstruction (11.12%), trauma (7.97%), strangulated inguinal hernia (5.46%), acute cholecystitis (4.87%), peptic ulcer perforation (4.09%), mesenteric ischemia (2.73%), necrotizing fasciitis (2.73%), gastrointestinal system bleeding (1.79%), and others (1.1%).Conclusion: The findings of the study indicate a steady increase in surgical admissions to emergency units. Nontraumatic acute abdomen was the most common reason for general surgical emergencies. Although the number of elderly patients increased, the hospital stay and mortality rates decreased over the study period

Estimation of the capacity of emergency surgery in Konya: Nine-year multicenter study

Objective: Although the number of surgical emergencies continues to increase, comprehensive data on emergency surgical admissions are scarce. The aim of this multicenter study was to evaluate the causes, management, and outcomes of the general surgical emergencies in the city of Konya, Turkey. Material and Methods: The relevant details of the cases admitted and considered to be general surgical emergencies in Konya over a nine-year period (January 2003-January 2012) were analyzed. All demographic data were analyzed statistically. Results: The study group comprised 21954 cases from 4 hospitals in Konya: 7154 from Konya Numune Hospital, 6,654 from Konya Education and Research Hospital, 6,400 from Necmettin Erbakan University Meram Medical Faculty, and 1,390 from Baskent University Konya Education and Research Hospital. Their mean age was 59.6 years, and the average hospitalization time was 3.3 days. The diagnoses of the admitted patients were as follows: acute appendicitis (59.57%), bowel obstruction (11.12%), trauma (7.97%), strangulated inguinal hernia (5.46%), acute cholecystitis (4.87%), peptic ulcer perforation (4.09%), mesenteric ischemia (2.73%), necrotizing fasciitis (2.73%), gastrointestinal system bleeding (1.79%), and others (1.1%). Conclusion: The findings of the study indicate a steady increase in surgical admissions to emergency units. Nontraumatic acute abdomen was the most common reason for general surgical emergencies. Although the number of elderly patients increased, the hospital stay and mortality rates decreased over the study period

Nail Fold Capillary Abnormality and Insulin Resistance in Children with Familial Mediterranean Fever: Is There Any Relationship Between Vascular Changes and Insulin Resistance?

Objective: Nail fold capillary changes are accepted as early symptoms of several rheumatic disorders such as scleroderma and dermatomyositis. In adults, nail fold capillary abnormality (NCA) has been described in Familial Mediterranean Fever (FMF). However, there is not enough study in children with FMF. The aim of the present study was (1) to investigate whether children with FMF have NCA in both active and/or remission period or not and (2) to assess insulin resistance in children with FMF in both active and/or remission period of the disease compared with the control group