Avaliação de danos de Sitophilus zeamais em pomares de pessegueiro.

O objetivo do trabalho foi avaliar o potencial de danos causados por S. zeamais em pêssego

Efeito da altura do resíduo sobre a produção e a estrutura de sorgo forrageiro.

O cultivo de sorgo forrageiro (Sorghum bicolor (L.) Moench.) tem crescido na região Noroeste do Rio Grande do Sul nos últimos anos. Os produtores rurais estão sendo orientados a manejar o sorgo forrageiro em pastejo rotacionado, respeitando uma altura de entrada dos animais acima de 70 cm e altura de saída (resíduo) em torno de apenas 5 cm.bitstream/item/63868/1/BP31.pd

Fatigue behavior of hybrid and bonded single lap joints made of composite material

Joining of composite materials can be performed with different techniques and, in particular, trough mechanical fasteners, bonding, hybrid solutions. In last years, hybrid (bolted/bonded) joints are attracting the interest of several companies and scientific community, since the use of both techniques permit to overcome some critical aspects connected to the separate usage of adhesive and bolts, i.e., negative effects of the environmental conditions on adhesive, localized stresses at the notch. This paper aims to improve the knowledge about the fatigue behavior of hybrid CFRP (Carbon Fiber Reinforced Polymer) joints. For the purpose, experimental fatigue and static tests are performed on hybrid and bonded joints and the results herein discussed. Results are post-processed with the main goal to highlight the benefits led to the hybrid technique with respect to the bonding one

Fatigue strength of austempered ductile iron-to-steel dissimilar arc-welded joints

Nowadays, the use of different classes of materials in the same structure is increased to keep pace with innovation and high structural performances. In this context, structural components made of different materials need to be joined together and a possible solution is given by arc welding. Dissimilar welded joints must often be able to withstand fatigue loads; however, Design Standards provide fatigue strength categories only for homogeneous welded joints. The aim of the present paper is to compare the fatigue behaviour of EN-GJS-1050 austempered ductile iron-to-S355J2 steel dissimilar joints to the categories of the corresponding homogeneous steel welded joints, as suggested in International Standards and Recommendations. For this purpose, experimental fatigue tests were performed on a selection of dissimilar welded details. First, the microstructure was identified by metallographic analysis; micro-hardness measurements were collected and residual stress profiles were obtained by using the X-ray diffraction technique on a selection of joints. Misalignments were quantified for all specimens. Then, experimental fatigue tests have been performed on a number of joint geometries subject to axial or bending fatigue loadings and tested in the as-welded conditions. The fracture surfaces of the joints have been analysed to locate fatigue crack nucleation sites

Tributyltin and Zebrafish: Swimming in dangerous water

Zebrafish has been established as a reliable biological model with important insertion in academy (morphologic, biochemical, and pathophysiological studies) and pharmaceutical industry (toxicology and drug development) due to its molecular complexity and similar systems biology that recapitulate those from other organisms. Considering the toxicological aspects, many efforts using zebrafish models are being done in order to elucidate the effects of endocrine disruptors, and some of them are focused on tributyltin (TBT) and its mechanism of action. TBT is an antifouling agent applied in ship's hull that is constantly released into the water and absorbed by marine organisms, leading to bioaccumulation and biomagnification effects. Thus, several findings of malformations and changes in the normal biochemical and physiologic aspects of these marine animals have been related to TBT contamination. In the present review, we have compiled the most significant studies related to TBT effects in zebrafish, also taking into consideration the effects found in other study models.This study was supported by Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (PP-SUS-FAPERJ E-26/110.282/2014; JCNE-FAPERJ, E-26/201.520/2014; APQ1-FAPERJ, E-26/111.485/2014), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES/Ciências sem Fronteiras/Pesquisador Visitante Especial/88881.062218/2014-0), and Conselho Nacional de Desenvolvimento Científico (CNPq, PQ-Nível 2, 305872/2016-8). Funding was obtained from FEDER-Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020-Operacional Programme for Competitiveness and Internationalization (POCI), Portugal 2020, and by Portuguese funds through FCT-Funda??o para a Ci?ncia e a Tecnologia/Minist?rio da Ci?ncia, Tecnologia e Inova??o in the framework of the project "Institute for Research and Innovation in Health Sciences" (POCI-01-0145-FEDER-007274) and by the project "Advancing cancer research: from basic knowledgement to application"; NORTE-01-0145-FEDER-000029; Projetos Estruturados de I&D&I, funded by Norte 2020-Programa Operacional Regional do Norte. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscrip

Material fragmentation as dissipative process of micro rotation sequence formation: Hybrid model of excitable cellular automata

The authors have developed a multi-level model of energy propagation along interfaces between the various structural elements of a solid with taking into account mutual energy transformations of various kinds. They have also designed a computer simulation tool based on the excitable cellular automaton (ECA) method. An algorithm for calculating the local moments of forces has been developed for the case of material rotation and torsion. The relationship for the accumulated elastic energy is supplemented with a dissipation term. Numerical experiments have been carried out on high-energy impact on polycrystalline copper specimens with different grain sizes. The paper shows that during the nanostructuring of material surface layer, the dissipation of elastic energy gives rise to the rotation of structural elements. This makes it possible to prevent the occurrence of stress concentrators with peak values typical of coarse-grained specimens and reducing their mechanical properties

Influence of stress concentrator shape and testing temperature on impact fracture regularities of pipeline steel

The structure and impact toughness of the pipeline 17Mn1Si steel have been studied. The main attention was paid to the analysis of various conditions of stress concentration under dynamic loadings. The process of strain localization with increasing stress state stiffness at the tip of the concentrator with decreasing testing temperature was investigated. Impact loading diagrams for specimens with various stress concentrator shapes were registered and analyzed

Influence of pre-strain and bake hardening on the static and fatigue strength of a DP600 steel sheet

The influence of pre-strain on the tensile and fatigue properties of a dual phase DP600 steel was studied. The material was pre-strained by uni-axial tension in rolling and transverse direction. Thereafter, specimens were cut from the deformed plates in parallel or orthogonal to pre-strain direction. It was found that pre-strain increases yield and tensile strength. Results suggested that strain path change primarily affects the elastic-plastic transition during early stage of reloading. Pre-strained specimens showed an increase in high cycle regimes as a consequence of yield strength increment, irrespective of imposed pre-straining direction. A modified stress life equation that accounts for pre-strain was proposed and showed good agreement with experimental data. Bake hardening enhanced both tensile and high cycle fatigue resistance. Walker equation was successfully fitted to account for tensile mean stress. In low cycle fatigue, negligible influence of pre-strain was observed due to cyclic softening and residual stress relaxation

On the interaction between corrosion and fatigue which determines the remaining life of bridges

This paper studies the combined effect of corrosion and fatigue on the growth of cracks that arise from natural corrosion in steel bridges. It is shown that if these two effects need to be simultaneously analysed. If not then the resulting life is not conservative. Consequently, to enable a better understanding of the remaining life of steel bridges this paper presents a simple methodology for performing this coupled analysis