Ultimate response of stainless steel bolted connections

The use of stainless steels in structural applications has been steadily growing for decades with most research focusing on the structural behaviour of stainless steel members. However, the material behaviour of stainless steels has essential differences from that of carbon steel, as it exhibits significant strain hardening and an absence of a well-defined yield plateau. Moreover, the design provisions of EN 1993-1-8 (2005) which was originally developed for carbon steel joints are currently applicable to design of stainless steel connections with only minor modifications, thereby leading to unduly conservative strength predictions and hence inefficient design. To provide more efficient design rules, assess and improve the current design guidance for stainless steel connections, extensive experimental and numerical studies have been performed and are reported in this thesis. Firstly, an experimental programme on the determination of fracture properties and explicit fracture modelling of stainless steel bolts in tension has been performed. A predictive equation relating the equivalent plastic strain at fracture initiation and stress triaxiality for A4-80 stainless steel bolts was obtained experimentally and utilised within the phenomenological fracture model for ductile metals available in the FE code ABAQUS. Subsequently, an advanced FE model was developed in which the fracture of the bolts was incorporated utilising a ductile damage model with a damage initiation criterion and fracture propagation parameters. The developed FE model was validated against available experimental data published in the literature and was shown to accurately predict the available ductility and overall response of stainless steel joints failing by bolt fracture under predominantly tensile load. Subsequently, an experimental study on the ultimate behaviour of ferritic stainless steel bolted T-stubs under monotonic tension was carried out and 17 T-stubs employing a wide range of geometric configurations, which were designed to fail in a ductile mode were tested to failure. The obtained ultimate and plastic resistances with corresponding displacements and material characteristics including material anisotropy have been reported in detail. It was observed that the ferritic stainless steel T-stubs exhibit significant anisotropy and overstrength which can be defined as the ultimate over the plastic resistances. The effect of membrane action on the ultimate resistance of the T-stubs has been experimentally observed and quantified and a recently proposed predictive equation was assessed based on the obtained results. This immense strength reserve may be relied upon to mitigate progressive collapse under a column loss. Following the experimental investigations on ferritic stainless steel bolted T-stubs, an advanced FE model was developed and validated against the available test data. The FE models predicted the ultimate and plastic forces, and failure modes very accurately and the full force-displacement curves of each test specimen were obtained. Moreover, an extensive parametric study was conducted to reveal the effect of different parameters on the ultimate response of the stainless steel T-stubs and the results are reported comprehensively. Based on the obtained experimental and numerical results, the EN 1993-1-8 (2005) was assessed. It was concluded that the plastic resistance predictions of EN 1993-1-8 (2005) are overly conservative for austenitic and duplex stainless steel T-stubs, but satisfactory for ferritic stainless steel bolted T-stubs. This was attributed to the similarity of the strain-hardening characteristics between ferritic stainless steels and carbon steel, which are markedly inferior to those of the austenitic and duplex stainless steel grades. A recently proposed design formula for estimating the ultimate resistances of carbon steel bolted T-stubs was applied to the stainless steel T-stubs. It was concluded that the proposed formula can predict the ultimate resistances of stainless steel bolted T-stubs with a significant accuracy. Finally, conclusions have been made and future research suggestions are given in the final chapter of the thesis

The Effects of Out-of-School Learning Settings Science Activities on 5th Graders’ Academic Achievement

The purpose of this study was to investigate the effect of lessons conducted in out-of-school learning settings on 5th graders science achievement within the scope of a guidance material that was prepared to be used in out-of-school learning settings in accordance with the “Let’s Solve the Riddle of Our Body” chapter objectives. The pretest / posttest equalized control group design, which is one of the quasi-experimental designs, was used in this study. The sample of this study was composed of a total of 31 5th grade students (15 were in experimental group, 16 were in control group) that were selected from secondary schools in the first semester of the 2015-2016 academic year in Tokat Province. Let’s Solve the Riddle of Our Body Chapter Achievement Test (LeSROBAT) was administered before and after the implementation of the guidance material to measure the students’ achievements and retention. The lessons were conducted as suggested by the current curriculum in the control group. The data were analyzed using independent samples t-test and covariance analysis (ANCOVA). As a result of the analyses, it was found that the LeSROBAT post-test scores of experimental group were significantly higher than the control group. Within this context, it was concluded that the out-of-school learning settings positively contributed to academic achievement and the guidance material that was developed within the scope of this study was effective. The results of retention test analyses didn’t reveal any significant difference between the posttest and retention test scores of experimental and control groups. When the LeSROBAT retention test scores were examined, it was observed that the scores of experimental group was higher than the control group

The Serological and Virological Investigation of Canine Adenovirus Infection on the Dogs

Two types of Canine Adenovirus (CAVs), Canine Adenovirus type 1 (CAV-1), the virus which causes infectious canine hepatitis, and Canine Adenovirus type 2 (CAV-2), which causes canine infectious laryngotracheitis, have been found in dogs. In this study, blood samples taken from 111 dogs, which were admitted to the Internal Medicine Clinic of Selcuk University, Faculty of Veterinary Medicine, with clinical symptoms. Seventy-seven dogs were sampled from Isparta and Burdur dog shelters by random sampling, regardless of the clinical findings. Dogs showed a systemic disease, characterized by fever, diarrhea, vomiting, oculonasal discharge, conjunctivitis, severe moist cough, signs of pulmonary disease and dehydration. Two dogs had corneal opacity and photophobia. In serological studies, 188 serum samples were investigated on the presence of CAV antibodies by ELISA. Total 103 (103/188–54.7%) blood samples were detected to be positive for CAV antibodies by ELISA. However, 85 (85/188–45.2%) blood samples were negative. Blood leukocyte samples from dogs were processed and inoculated onto confluent monolayers of MDCK cells using standard virological techniques. After third passage, cells were examined by direct immunoflourescence test for virus isolation. But positive result was not detected. In conclusion, this study clearly demonstrates the high prevalence of CAV infection in dogs

POTENTIAL OF A CATALYZED (D,D) FUSION-DRIVEN HYBRID REACTOR FOR THE REGENERATION OF LWR SPENT FUEL

The potential of a catalyzed (D, D) fusion-driven hybrid blanket is investigated for the regeneration of light water reactor spent fuel. Total enrichment grade is 2.172 % at beginning of regeneration. The hybrid blanket has excellent neutronic performance and is investigated to achieve different cumulative fission fuel enrichment (CFFE) grades. A regeneration period of up to 36 months is investigated by a plant factor of 75% under a first wall catalyzed (D, D) fusion neutron current load of 10 14. Neutron (14.1 MeV)/cm 2. s and 10 14 neuton (2.45 MeV)/cm 2. s. This corresponds to a first wall load of 2.64 MW/m 2. Regeneration periods of 12, 20, 28 and 36 months are considered, resulting in final enrichment grades of 3.0, 3.5, 4.0, and 4.5 %, respectively. The blanket energy multiplication M is quite high and increases only by ~ 30 % in 36 months. The electricity production remains fairly constant during this period. Consequently, this power exploits the non-nuclear island very well. At the same time, the peak-to-average fission power density ratio ? decreases by ~10 %

Numerical analysis of heat transfer through a circular pipe with porous-ring turbulators

A numerical study has been carried out of heat transfer enhancement and flow characteristics through artificial porous materials in the form of ring turbulators on heated wall of a circular pipe for turbulent flow (Reynolds number range 16 000-64 000). In the study, uniform heat flux of 2500 W/m2 from a circular pipe wall surface has been assumed. A significant enhancement of heat transfer in the porous-ring turbulators is observed compared with that in a smooth surface. Four various shapes of porous-ring turbulators (0 (solid), 0.2, 0.4 and 1 (smooth circular pipe) porosity) have been examined using the RNG k-e turbulence model, and compared based on heat transfer enhancement and friction characteristics. Heat transfer decreases with increasing porosity. Using porous-ring turbulators in the pipe gives an increase in the Nusselt number and heat transfer enhancement. Therefore, such turbulators may be used in heat exchangers to increase heat transfer and energy saving

Neutronic analysis of a moderated (D, T) fusion driven hybrid blanket

In this study, neutronic effects on (D-T) driven hybrid reactor fuelled with different mixtures of 45.5% fertile fuels, vary from 0 to 100% for uranium components and from 100 to 0% for the thorium component in the fuel mixtures. These mixtures are UF4 + THF4, UO2 + ThO2 UC2 + ThC2. The coolants are selected as flibe (Li2BeF4), natural lithium and air for the heat transfer out of the fuels zones and the clad material is selected as SS-316 stainless steel with a volume fraction ratio of 9%. The fuel zones of the hybrid reactor are investigated to obtain fissile fuel breeding (U-233 and/or Pu-239). A regeneration period of up to 48 months is investigated by a plant factor of 75% under a first wall neutron flux (phi(w)) of 2.2210(14) (14.1 MeV) n/ cm(2).s for a conventional (D,T) driven hybrid reactor. These correspond to a first wall neutron load of 5 MW/m(2). At the end of the operation periods, cumulative fissile fuel enrichment (CFFE) value varies between 6.7% in pure UF4 with flibe coolant and 3.5% in pure ThO2 with natural lithium coolant. At the beginning of the operation, the tritium breeding ratio (TBR) is higher than unity in air coolant and natural lithium coolant cases. In flibe coolant cases the TBR value can reach nearly 55% uranium component + 45% thorium components. Therefore, the hybrid blanket is self-sufficient with respect to the TBR for these cases. It is important to follow the non-prolific level of the plutonium fuel during operation because of the nuclear weapons hazard. Nuclear quality of the plutonium increases linearly during the operation period. Pu-240 content has to be higher than 5% for safety. Pu-240 content is higher than 5% in UF4 + ThF4, UC2, + ThC2 and (UO2 > 20%) + (ThO2 < 80%) with flibe coolant. This is very important criteria for safety. In natural lithium and air coolant cases Pu-240 content is lower than 5%. In these cases, the operation period must be increased for safety. U-233 is used as a fuel in thermal reactors and can be separated from the Thourium component. But this separation is too difficult in the thorium component + uranium component mixtures. Therefore, investigated hybrid blanket is safer than 100% Th component. (C) 2000 Elsevier Science Ltd. All rights reserved