Determination of plasticity following deformation and welding of austenitic stainless steel

Intergranular strain has been associated with high-temperature cracking of welded pipework in 316H austenitic stainless steel material used in nuclear power plant heat exchangers. In this study, neutron diffraction has been used to study the development of intergranular strains in plastically-deformed and welded 316H stainless steel. Measurements have been made of the intergranular strain evolution with increasing plastic strain in base material, and correlated with further measurements made in samples extracted from welded pipes, where the pipes were welded following plastic deformation to different levels of plastic strain. Strong tensile strain evolution was seen on the compliant 200 grain family. The results were correlated with various proxy measures of plastic strain, including hardness and diffraction peak width, and excellent agreement was obtained

Spontaneous recovery of post-traumatic cerebrospinal fluid rhinorrhea following meningitis: A case report

The aim of the present report was to present the patient with an anterior cranial base fracture who developed post-traumatic cerebrospinal fluid rhinorrhea, which recovered after onset of meningitis complication. A 26-year-old male patient who had a traffic accident one week ago was sent to our clinic because of his rhinorrhea persisting for 4 days. On cranial computed tomography, fracture of the left frontal skull base and sinus walls, a fracture line on temporal bone, parenchymal bleeding in the vicinity of the frontal sinus, subarachnoidal bleeding and left temporal extradural hematoma were detected. Then he underwent sinus wall repair and extradural hematoma was drained through bifrontal craniotomy. However, rhinorrhea persisted which resulted a deterioration in consciousness and he entered into a deep somnolent state. When his symptoms of meningitis became apparent, rhinorrhea of the patient disappeared. The patient transferred in intensive care unit and re-connected to a lumbar drainage system. On cerebral magnetic resonance imaging, regression of contrast-enhanced lesions localized in the left anterotemporal and frontal and in the regions lateral to the right trigon and medial to the right thalamus and in the right posteroparietal regions was observed. Despite repair of the anterior cranial fracture and lumbar drainage, rhinorrhea may persist. Herein, development of meningitis caused disappearing of rhinorrhea symptoms without any need for surgical intervention

Effects of plastic strain history on the properties of stainless steel boiler tube welds

The subject of this dissertation is the study of the effects of fabrication history (prestraining, welding and heat treatment) on the mechanical properties of austenitic stainless steel thin wall boiler tubes. These tubes are usually cold bent to shape, and sometimes swaged, prior to interconnection by welding. The bends require solution heat treatment before welding. In addition, subsequent to welding, the residual stresses should be relieved. It is sometimes not practically feasible to follow these constructional practices strictly especially when a whole boiler is constructed as a single unit and becomes too large and complex and contains different tubing materials. As a result of this fabrication history, the mechanical properties of boiler tube materials can be significantly altered. Sample tubes simulating the fabrication steps were supplied by British Energy for this project. The primary aim of the study was to determine spatially resolved room-temperature tensile properties using digital image correlation (DIC) by testing cross-weld specimens machined from the thin wall welded tubes (with plain or prestrained base metal) before and after the heat treatment. The experimental procedure which is used to retrieve the tensile properties from these integrated tests was validated through finite element simulation. Digital image correlation, which is a full-field strain measurement technique, was implemented in order to obtain the local stress-strain curves from regions less than a square millimetre in area and to extract the corresponding local tensile properties such as offset proof strength. The variation of the 0.2% offset proof strength was successfully obtained along these specimens. Evidence of strain hardening due to constraint and weld thermomechanical cycles was found in the plain base metal near the weld pool and evidence of softening was seen in prestrained base metal. On the other hand, after the heat treatment, the effect of prestraining and welding is cleaned out and the strength along the specimen was almost homogenized. However, as- welded cross-weld specimens with prestrained base metal have demonstrated unusual local stress-strain behavior in the weld-affected region. For a better understanding of this behavior, tension test of a cross-weld specimen with a high strength mismatch between the weld metal and base metal was simulated using the finite element method. It was found that the strength mismatch in the specimen, in combination with the experimental procedure, may cause some anomalies in the local stress-strain curves. It was also confirmed that these anomalies are not very detrimental for the determination of the proof strength on the specimens with strength mismatch. Material characterization of the welds and detailed hardness surveys on cross- weld specimens were performed. Plastic strain is known to be detrimental for high temperature performance of austenitic stainless steel tubes, therefore, the degree of the plastic deformation should be known before these tubes enter service. DIe, hardness, electron back-scattered diffraction and neutron diffraction (peak width and anisotropy strain) were used to determine the amount of plastic strain in the as-welded tubes. It was observed that there is a good agreement between the predictions of plastic strain in 20% prestrained and welded tube.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Gastrocystoplasty in pigs and effect of selective antral vagotomy on acid secretion of the reconstructed bladder

Introduction: The aim of this study was to investigate the outcome of gastrocystoplasty and the effects of selective antral vagotomy (SAV) on the postprandial gastrin secretion from the antrum as well as on the acid secretion from the augmented bladder. Materials and Methods: In this study on 12 male pigs, we applied subtotal cystectomy plus gastric augmentation plus SAV to the study group and the same procedure without SAV to the control group. The animals were followed up for 3 months with respect to feeding, weight, and urine output. The urine pH levels and the gastrin levels of the pigs in the two groups were then followed up and compared. Results: The use of gastric segments in bladder reconstruction was found to be appropriate in terms of both gastric function and urinary system function. Nevertheless, regarding the effect of SAV, the differences between either the urinary pH levels or the gastrin levels of the pigs in the two groups were statistically significant. Conclusions: Although gastric segments in the bladder reconstruction were found to be appropriate in terms of both gastric function and urinary system function, SAV did not prevent postprandial gastrin secretion and the resulting increase of the urine acidity. Copyright (C) 2003 S. Karger AG, Basel