Many researchers that have carried out fretting wear tests have presented results which show a variation (usually an increase) in the friction force during the sliding phase of individual cycles. ...This phenomenon is contrary to the Amontons/Coulomb model of friction which predicts a constant friction force as sliding proceeds. An in-line fretting test involving an abrupt increase in amplitude was used to show that the effect is a result of wear scar interaction effects. A pair of rotational fretting tests were then carried out to determine whether these interaction effects originate from interaction of the wear scar ends, or whether such interaction occurs throughout the nominal contact area. A new experimental rig designed to adapt conventional in-line test machines for rotational fretting was designed and built for this purpose. Results show that the friction variation occurs whether or not wear scar ends are present. After testing, the worn surface topography of each fretting pair was scanned using a focus variation microscope, and these surface images revealed the existence (and size) of many distributed local peaks and troughs distributed throughout the contact area. In conclusion, the friction variation commonly observed in the literature arises predominantly from the interaction of local wear scar features distributed over the contact region.
A computational model is developed to predict elastic and elastic-plastic stress distribution in a nonlinearly hardening cooling fin of variable thickness subject to centrifugal force. The model is ...based on a realistic conduction-convection mechanism, von Mises yield criterion, Henky's deformation theory and a Swift-type strain hardening law. Temperature dependency of modulus of elasticity, uniaxial yield limit, coefficient of thermal expansion, and thermal conductivity of the fin material is taken into account.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Hydrogen Embrittlement, Stress Corrosion Cracking, Deformation, Plasticity, void growth (ProQuest: ... denotes formulae omitted.) 1.INTRODUCTION Austenitic stainless steels have widespread ...application in the energy, nuclear, automobile, chemical, oil and gas production, refining and medical industries showing a superior strength range, ductility and corrosion resistance when compared to other types of steels 5. ...austenitic stainless steels are vulnerable to Stress Corrosion Cracking (SCC) in specific environmental conditions including when exposed to hydrogen 1. Plastic deformation has been found to precede cracking in many failure cases for austenitic stainless steel and there has been a lot of commentary on the Hydrogen Enhanced Localised Plasticity (HELP) mechanism which has been used to explain this phenomenon 8910. Material specimens with dislocation trapping characteristics related to austenitic stainless steel were shown to fail predominantly by internal shear failure in the presence of hydrogen especially at low stress triaxiality.
A study has been performed using a crystal plasticity based finite element method to understand the effect of various stress states and crystal orientations with respect to loading direction for FCC ...single crystals in both hydrogenated and non-hydrogenated environment. Simulations have been performed for a variety of stress triaxilaities, Lode parmeters, crystal orientations and hydrogen concentrations. It is observed that crystal orientation has a varied effect on the influence hydrogen has on plastic deformation and void growth. Hydrogen in trap distribution at various stages of the deformation process was also found to be influenced by crystal orientation. From analyses performed, an analytical relationship between normalised void fraction and equivalent strain has been derived.
Ductile metals undergo a considerable amount of plastic deformation before failure. Void nucleation, growth and coalescence is the mechanism of failure in such metals. {\alpha}/{\beta} titanium ...alloys are ductile in nature and are widely used for their unique set of properties like specific strength, fracture toughness, corrosion resistance and resistance to fatigue failures. Voids in these alloys were reported to nucleate on the phase boundaries between {\alpha} and {\beta} phase. Based on the findings of crystal plasticity finite element method (CPFEM) based investigation of the void growth at the interface of {\alpha} and {\beta} phases 1, 2, a void nucleation, growth, and coalescence model has been formulated. An existing single-phase crystal plasticity theory is extended to incorporate underlying physical mechanisms of deformation and failure in dual phase titanium alloys. Effects of various factors (stress triaxiality, Lode parameter, deformation state (equivalent strain), and phase boundary inclination) on void nucleation, growth and coalescence are used to formulate the constitutive model while their interaction with a conventional crystal plasticity theory is established. An extensive parametric assessment of the model is carried out to quantify and understand the effects of the material parameters on the overall material response. Performance of the proposed model is then assessed and verified by comparing the results of the proposed model with the RVE study results. Application of the constitutive model for utilisation in the design and optimisation of the forming process of {\alpha}/{\beta} titanium alloy components is also demonstrated using experimental data.
Abstract The frequency of amyotrophic lateral sclerosis (ALS) mutations has been extensively investigated in several populations; however, a systematic analysis in Turkish cases has not been reported ...so far. In this study, we screened 477 ALS patients for mutations, including 116 familial ALS patients from 82 families and 361 sporadic ALS (sALS) cases. Patients were genotyped for C9orf72 (18.3%), SOD1 (12.2%), FUS (5%), TARDBP (3.7%), and UBQLN2 (2.4%) gene mutations, which together account for approximately 40% of familial ALS in Turkey. No SOD1 mutations were detected in sALS patients; however, C9orf72 (3.1%) and UBQLN2 (0.6%) explained 3.7% of sALS in the population. Exome sequencing revealed mutations in OPTN , SPG11 , DJ1 , PLEKHG5 , SYNE1 , TRPM7 , and SQSTM1 genes, many of them novel. The spectrum of mutations reflect both the distinct genetic background and the heterogeneous nature of the Turkish ALS population.
This study aimed to determine physical activity levels and understand the factors influencing an active lifestyle among patients with primary Sjögren's syndrome (pSS).
Ninety-seven patients ...participated in this multicentric study. Physical activity levels were assessed using the International Physical Activity Questionnaire-Short Form (IPAQ-SF). The Inflammatory Arthritis Facilitators and Barriers (IFAB) questionnaire was used to evaluate perceived barriers and facilitators to physical activity.
Forty-six patients were physically inactive and the rest of them were moderately active. Commonly identified barriers included a lack of motivation, fatigue, and pain. Conversely, knowledge of the health and mood benefits for physical activity emerged as a key motivator. Patients with better scores on facilitators and lower scores on barriers exhibited higher physical activity levels (p < 0.05). Notably, a high level of perceived facilitators of physical activity (odds ratio OR: 1.02; 95% confidence interval CI, 1.00 – 1.05) and reduced pain (OR: 0.81; 95% CI: 0.69 – 0.95) were linked to an active lifestyle.
This study emphasizes the role of motivation and awareness of the benefits of physical activity for health and mood in driving physical activity for patients with primary Sjögren’s syndrome. Tailored physical activity programs that address psychological aspects and disease-related pain, and fatigue should be designed to counter sedentary lifestyles in pSS patients.
Background: The skin is one of the most affected organs in tuberous sclerosis complex and angiofibromas are seen in almost 80% of such patients. These benign tumors impose a great psycho-social ...burden on patients. Objective: The aim of the study was to evaluate the effectiveness and tolerability of topical sirolimus for facial angiofibromas in patients with tuberous sclerosis complex. Methods: This was a prospective, single-blinded, cross-over study which involved twelve patients. We investigated the effect and safety of topical 0.1% sirolimus, which was obtained by crushing sirolimus tablets and mixing it with petrolatum. The patients were asked to apply the cream to one side of their face, and vaseline to the other side. The effect of topical sirolimus was evaluated using the "facial angiofibroma severity index." Results: There was a significant improvement in the redness and extension of the tumors on the sides to which the active ingredient was applied. Some side effects such as itching and irritation occurred in three patients, which were treated with topical hydrocortisone cream. Conclusion: Topical sirolimus appears to be a promising, fairly well tolerated treatment for facial angiofibromas in patients with tuberous sclerosis complex. Although its efficacy diminishes with time, repetitive usage is effective.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The study was planned to determine the efficacy and safety of adding rosiglitazone to a combination of glimepiride and metformin therapy with insufficiently controlled type 2 diabetes. This was an ...open-label study with a follow-up period of 26 weeks. Thirty patients were taking 3 mg glimepiride two times and 850 mg metformin two times per day. Patients were told to take one rosiglitazone 4 mg tablet before breakfast additionally. The primary efficacy measure was the mean change in HbA1c from baseline to the end of the study. Secondary efficacy parameters included the mean changes from baseline to the end of the study in fasting plasma glucose (FPG) and insulin levels, as well as total cholesterol, HDL-C, LDL-C, triglycerides, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Mean HbA1c levels decreased significantly from 7.54 ± 0.9% to 6.57 ± 0.7% (p<0,001) at 26th week. FPG levels fell from 169.39 ± 37.8 mg/dl to 135.69 ± 28.0 mg/dl (p<0.001), respectively. Insulin levels decreased from 19.60 ± 9.8 U/L to 14.66 ± 11.6 U/L (p = 0,026) at 26th week. No one experienced elevations of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels greater than 2.5 times the upper limit of the reference range. This study confirms that the addition of rosiglitazone (4 mg/day) to sulphonylurea and metformin treatment for patients with type 2 diabetes improves glycemic control, is safe, and generally well tolerated.
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