Significance of Creep-Fatigue Interactions in Strctural Integrity Assessment

Creep-fatigue interaction is a special phenomena that have a detrimental effect on the performance of metal parts of components operating at elevated temperatures. This paper deals with the simultaneous interactions between creep and fatigue. The effect of hold time, hold position, temperature and creep ductility on creep-fatigue interaction life and damage modes of several high temperature alloys are presented in detail. The inherent deficiencies and potentially serious consequences of over-or under- design by using the classical Linear Time and Cycle-Fraction rule for predicting structural durability under high temperature creep-fatigue conditions are presented. The potential of a strain based approach in accurately predicting creep-fatigue life for ensuring structural integrity is outlined

Gene expression profiling of canine osteosarcoma reveals genes associated with short and long survival times

<p>Abstract</p> <p>Background</p> <p>Gene expression profiling of spontaneous tumors in the dog offers a unique translational opportunity to identify prognostic biomarkers and signaling pathways that are common to both canine and human. Osteosarcoma (OS) accounts for approximately 80% of all malignant bone tumors in the dog. Canine OS are highly comparable with their human counterpart with respect to histology, high metastatic rate and poor long-term survival. This study investigates the prognostic gene profile among thirty-two primary canine OS using canine specific cDNA microarrays representing 20,313 genes to identify genes and cellular signaling pathways associated with survival. This, the first report of its kind in dogs with OS, also demonstrates the advantages of cross-species comparison with human OS.</p> <p>Results</p> <p>The 32 tumors were classified into two prognostic groups based on survival time (ST). They were defined as short survivors (dogs with poor prognosis: surviving fewer than 6 months) and long survivors (dogs with better prognosis: surviving 6 months or longer). Fifty-one transcripts were found to be differentially expressed, with common upregulation of these genes in the short survivors. The overexpressed genes in short survivors are associated with possible roles in proliferation, drug resistance or metastasis. Several deregulated pathways identified in the present study, including Wnt signaling, Integrin signaling and Chemokine/cytokine signaling are comparable to the pathway analysis conducted on human OS gene profiles, emphasizing the value of the dog as an excellent model for humans.</p> <p>Conclusion</p> <p>A molecular-based method for discrimination of outcome for short and long survivors is useful for future prognostic stratification at initial diagnosis, where genes and pathways associated with cell cycle/proliferation, drug resistance and metastasis could be potential targets for diagnosis and therapy. The similarities between human and canine OS makes the dog a suitable pre-clinical model for future 'novel' therapeutic approaches where the current research has provided new insights on prognostic genes, molecular pathways and mechanisms involved in OS pathogenesis and disease progression.</p

Діагностика банкрутства в системі антикризового управління

Розглянуто питання відповідності і значимості діагностики фінансового стану кожної стадії антикризового управління. Діагностику банкрутства визначено як ретроспективне, оперативне і перспективне дослідження господарської діяльності та процесу управління підприємством, направлене на виявлення параметрів кризового розвитку за допомогою реалізації комплексу дослідницьких процедур, виявлення слабких ланок і "вузьких місць".Рассмотрены вопросы соответствия и значимости диагностики каждой стадии антикризисного управления. Диагностика банкротства определена как ретроспективное, оперативное и перспективное исследование хозяйственной деятельности и процесса управления предприятием, направленное на выявление параметров кризисного развития с помощью реализации комплекса исследовательских процедур, выявления слабых зон и «узких мест».The article analyzes issues of adequacy and role of diagnostics in all stage of anti-crisis management. The diagnostics of bankruptcy is defined as a retrospective, operative and prospective study of enterprise’s economic activity and management process that is directed to identification of parameters of crisis development by using comprehensive researches and to finding weak spots and "bottlenecks"

On the band spectrum of mercurous iodide

This article does not have an abstract

Influence of temperature on the low cycle fatigue behaviour of a modified 9Cr-1Mo ferritic steel

Low cycle fatigue (LCF) behaviour of a modified 9Cr-1Mo steel under normalized and tempered conditions is reported. The alloy was normalized at 1313K for 1 h followed by tempering at 1033K for 1 h, which resulted in a tempered martensitic structure. Total axial strain controlled LCF tests were conducted at a constant strain rate of 3&#215;10-3 s-1 at different strain amplitudes varying from &#177;0.25 to &#177;1.0% in the temperature range of 300-873K. The cyclic stress response behaviour, in general, showed an initial brief hardening for the first few cycles, followed by a continuous and gradual softening regime that ended in a stress plateau that continued up to the specimen failure. The fatigue life decreased as the temperature increased. The temperature effect on life was more pronounced at low strain amplitudes. The metallography of the failed samples revealed that the fatigue failure at high amplitudes of testing was marked by extensive crack branching and the formation of secondary cracks. Oxidation was found to exert major influence on LCF life reduction at 873K

A comparative study of isothermal and thermomechanical fatigue on type 316L(N) austenitic stainless steel

Thermomechanical fatigue (TMF) behaviour of a nitrogen-alloyed type 316L austenitic stainless steel under in-phase (IP) and out-of-phase (OP) cycling conditions in different temperature domains has been reported. Tests were performed under mechanical strain control mode, at a fixed strain rate of 6.4 &#215; 10-5 s-1 and a strain amplitude of &#177;0.4%. It was observed that OP TMF yielded lower lives compared to IP TMF in the sub-creep regimes, whereas the reverse was found true in the creep temperature domain. The variations observed in cyclic lives and the cyclic stress response behaviour under isothermal and TMF were examined in relation to the dynamic strain ageing (DSA) effects occurring in the intermediate temperature ranges. The development of dislocation substructures under TMF cycling was evaluated and discussed in relation to the DSA and creep processes. Extensive carbide precipitation was observed under TMF cycling that contributed to an enhanced stress response compared to isothermal cycling at the peak temperature

Thermomechanical fatigue evaluation and life prediction of 316L(N) stainless steel

An attempt has been made to understand the thermomechanical fatigue (TMF) behaviour of a nitrogen-alloyed type 316L austenitic stainless steel under different temperature domains. Smooth, hollow specimens were subjected to in-phase (IP) and out-of-phase (OP) thermal-mechanical cycling in air under a mechanical strain control mode, at a strain rate of 6.4 &#215; 10-5 s-1 and a strain amplitude of &#177;0.4%. For the sake of comparison, total strain controlled low cycle fatigue (LCF) tests were also performed at the peak temperatures of TMF cycling on similar specimens employing the same strain rate and strain amplitude. Life was found to depend on the thermal/mechanical phasing and temperature. Creep was found to contribute to life reduction in IP tests when the peak temperature of cycling was above 600 &#176;C. A few TMF tests were performed in vacuum in order to assess environmental influence on life. Thermomechanical fatigue cycling led to the development of significant amounts of mean stresses and the stress response was generally higher compared to that of LCF tests at the peak cyclic temperatures. Also, the isothermal tests at the peak temperature of TMF cycling resulted in lower lives compared to those obtained under TMF. An attempt was made to predict the TMF life using the isothermal database and satisfactory predictions were achieved using the Ostergren's frequency modified damage function (FMDF) approach

Artificial neural network approch to low cycle fatigue and creep-fatigue interaction life prediction of modified 9Cr-1Mo ferritic steel

Low cycle fatigue (LCF) behaviour of normalized and tempered modified 9Cr-1Mo steel has been studied at various temperatures, strain amplitudes, increase in strain amplitude, decrease in strain rate and with an increase in the duration of hold time in tension. The capability of artificial neural network (ANN) approach of life prediction under LCF and creep-fatigue interaction conditions has been assessed by using the data from National Institute of Materials Science, Japan and that generated in our laboratory. It is demonstrated that the predictions are well within a factor of two

Effect of hold-time on low cycle fatigue behaviour of nitrogen bearing 316L stainless steel

Axial strain controlled low cycle fatigue (LCF) behaviour and creep-fatigue interaction behaviour of 316L(N) stainless steel (SS) in solution annealed condition has been investigated at various strain amplitudes. Creep-fatigue interaction behaviour of the material has been evaluated by employing tension and compression holds at peak strain. Tension holds up to 90 min were studied. Under all the testing conditions, the material showed initial hardening followed by stress saturation. Hold-time conditions generally showed lower cyclic stress response compared to continuous cycling. The decrease in cyclic stress response with hold-time is attributed to enhanced recovery of the substructure and increase in the grain boundary damage accumulated during the stress relaxation period. The fatigue life is observed to be lower in tensile-hold conditions and the endurance decreased with increase in the duration of the hold. The factors that contribute to the decrease in fatigue life with hold-time have been identified from metallographic studies as the development of creep cracks and cavities and crack initiation and propagation assisted by oxidation. Creep-fatigue damage values based on the damage summation rule have been computed and compared with the RCC-MR bi-linear creep-fatigue interaction diagram suggested for nitrogen alloyed 316L SS at 600°C