Thermal ratcheting of a P91 steel cylinder under an axial moving temperature distribution

International audienceThe progressive inelastic deformation, commonly referred as ratchetting, is a major concern in the design of components and structures submitted to mechanical and thermal cyclic loads in the plastic range. In the RCC-MRx code, the design assessment against ratcheting is performed by applying a simplified method based on the elastic analysis of the structure. The design rule uses a diagram, called efficiency diagram, elaborated essentially on the basis of the results of tension/torsion experiments.In this work the application of the RCC-MRx efficiency diagram to P91 steel has been investigated. It has been considered the thermal ratcheting of a cylinder subjected to a moving axial temperature gradient with no primary stresses applied. The thermal loads have been produced via hot liquid thermal shocks, by dipping a cylindrical mock-up in a molten eutectic mixture of sodium and potassium nitrates. The experimental results show that the present efficiency diagram in RCC-MRx is not suited for P91 steel. Its use for the design would foresee cumulative strains lower than those observed experimentally which is clearly not conservative. This result confirms the results obtained in previous tension-torsion ratcheting tests and provides additional data for the development of a modified efficiency diagram suited for 9Cr steel

Fosfitos para o controle de podridões pós-colheita em maçãs ‘Fuji’ durante o armazenamento refrigerado Use of phosphites for rot control during cold storage of ‘Fuji’ apples

Foi conduzido um experimento com o objetivo de avaliar o efeito da aplicação de adubos foliares contendo fosfitos de potássio e fosfitos de cálcio mais boro sobre o controle de podridões em maçãs ‘Fuji’ durante a frigoconservação. O delineamento experimental utilizado foi o inteiramente casualizado com quatro repetições de 25 frutos. Foram realizadas quatro lesões distribuídas de forma eqüidistante na região equatorial dos frutos, com 3mm de diâmetro e 5mm de profundidade. Os frutos foram submersos em uma solução com suspensão de esporos, onde permaneceram por 20 segundos. Após, foram aplicados os tratamentos: 1 - Testemunha (água); 2 - Iprodione (75g 100L-1); 3 - cloreto de cálcio( CaCl2) a 2%; 4 - fosfito de potássio (250mL 100L-1) + CaCl2 (2%); 5 - fosfito de potássio (250mL 100L-1); 6 - fosfito de cálcio mais boro (300mL 100L-1); e 7 - fosfito de potássio (250mL 100L-1) na suspensão de esporos por uma hora. Os frutos foram armazenados em ambiente refrigerado à temperatura de 0&deg;C durante 14 dias. As avaliações foram realizadas na saída da câmara e aos 2, 4, 6 e 8 dias a 20&deg;C. Verificou-se que os frutos tratados com fosfito de potássio (250mL 100L-1) + CaCl2 (2%) apresentaram a menor incidência de podridões e o menor diâmetro de lesão. Esses resultados foram semelhantes aos obtidos com a aplicação do fungicida padrão Iprodione e superiores à aplicação de fosfito de potássio isoladamente. O uso de fosfito de cálcio mais boro não foi eficiente.<br>This experiment aimed to evaluate the effectiveness of potassium (K) phosphite and calcium (Ca) + borum (B) phosphite to control rot during cold storage of ‘Fuji’ apples. Four equidistant lesions were made in the central region of the fruits, measuring 5mm wide and 3mm deep. After the treatments, fruits were submerged for 20 seconds in a spore suspension, except for the last treatment, in wich the immersion lasted one hour. The treatments were as follow: 1. control (water); 2. fungicide Iprodione (75g 100L-1); 3. CaCl2 (2%); 4. potassium phosphite (250mL 100L-1) plus CaCl2 (2%); 5. potassium phosphite (250mL 100L-1); 6. Ca + B phosphite (300mL 100L-1); and 7. potassium phosphite (250mL 100L-1) in spore suspension for one hour. Fruits were refrigerated at 0&deg;C during 14 days and evaluated at removal from cold room and after 2, 4, 6 and 8 days at 20&deg;C. Fruits treated with potassium phosphite (250mL 100L-1) combined with CaCl2 (2%) had less decay and smallest lesion diammeter. These results were similar to those obtained with the fungicide Iprodione. Potassium phosphite alone was not as effective as in combination with CaCl2, and Ca + B phosphite was not effective to control apple rot