Recent Studies of Corrosion - Fatigue Crack Growth on the 7081-T73511 Aluminium Alloy

This work aims to evaluate the effect of localized corrosion on the fatigue crack growth (FCG) resistance of the 7081-T73511 aluminium alloy. The understanding of this complex combined process was explained by the dissolution of adjacent 7081-T73511 aluminium matrix promoted by the Al7Cu2Fe second-phase particle and the crack tip interaction time with the aggressive medium. Fracture surfaces produced in air and in sea water fog at the testing conditions applied here, basically present the same appearance, with a transgranular, cleavage-like cracking mode for 8 <DK< 30 values

Lean development methodology for durability homologation of steel components considering biaxial fatigue reliability prediction models

Product development tools have been extensively used to accelerate the final homologations and release\ud launch with required reliability in order to minimize risks of damages for society and industry. This work explores a\ud project context for a suspension structural component with high safety requirements in an objective manner, proposing\ud a systematic lean planning approach, considering the value added technical deliverables, using available engineering\ud tools from best architecture definition throughout the detailing design, prototype and testing phases. Aiming an earlier\ud release for final manufacturing tools production compared to traditional development methods, a selection of\ud deliverables from modeling, simulation and testing for technological, manufacturing and economics purposes was\ud conducted to find the main crucial information to be part of a decision making process that involves a high amount of\ud monetary value. For speeding release, proposals were explored for accessing the structural integrity of a new\ud component considering materials selection, influence of manufacturing in the mechanical properties, characterization\ud and fatigue testing on samples subjected to measured service loads. The methodology was validated with data from\ud similar component evaluation and the reliability for the new product could be proved by dismissing additional on-road\ud durability tests

Corrosion Fatigue of Aluminum-Copper-Lithium Alloy 2050-T84 Submitted at Salt Spray and Aqueous Saline Solution

Interest in the improvement of the structural performance of aircraft has begun in the substitution of aluminum alloys due to the possibility of reduction of density, an increase of stiffness, high fracture toughness, greater resistance to the propagation of cracks by fatigue and greater resistance to corrosion. In these issues, the aluminum-copper-lithium alloy 2050-T84 is outstanding, which presents excellent mechanical properties even when subjected to aggressive atmospheres. The failure of structural components of aircraft occurs due to several factors that may arise from microstructural defects and/or applied static or cyclic stresses associated with atypical environments such as cryogenic or corrosive. In this sense, the results have evidenced the presence of precipitates that influence in the increase of the mechanical strength, behavior of fracture toughness, fatigue life, and corrosion fatigue, in different temperatures and aggressive means. Tensile and fracture toughness tests at 23 and −60°C the material showed ductility retention without a significant difference in the results. Fatigue crack growth in air and corrosion fatigue with 3.5 and 5% NaCl and aqueous solution with 3.5% NaCl showed a meaning difference in the threshold region; however, for the Paris region at the saline environment, fatigue crack growth (FCG) rates are similar

Application of the small punch test to evaluate hydrogen embrittlement in steels and nickel alloys

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Influence of phosphorus content and quenching/tempering temperatures on fracture toughness and fatigue life of SAE 5160 steel

This study investigates the influence of quenching/tempering temperatures on the fracture toughness and fatigue life of SAE 5160 steel, considering different phosphorus contents. Quenching and tempering treatments were applied to samples removed from different bars of commercial SAE 5160 steel with different P content. Three different austenitizing temperatures for quenching: 850, 900 and 1000 ºC and a constant holding time of 15 minutes were used. The oil temperature for quenching was kept at 66 ºC and the tempering conditions were 470, 500 and 530 ºC with the necessary time for a final hardness of 45 ± 3 HRC. Therefore, the heat treatments cycles were applied to specimens containing low (0.012 wt. (%)), medium (0.017 wt. (%)) and high (above 0.025 wt. (%)) phosphorus contents, in order to observe the effects of this element on the susceptibility of these steels to enhance quench and tempering embrittlements. The Charpy tests results showed that the phosphorus content analyzed in this work has caused embrittlement, even in the bars with the lowest P content, leading to intergranular fracture. However, if the nucleation life is taken into consideration, this embrittlement has no effect on the nucleation fatigue life of the component

Influencia do processo de prensagem isostática em multiplos passos nas propriedades mecânicas do PTFE sinterizado

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From Numerical Calculations to Materials Testing Homologation: A Biaxial Fatigue Reliability Prediction Methodology for Structural Components

This article investigates a fatigue approach conducted from the design phase to testing approval. It considerers modern analytical and experimental tools for structural durability assessment over each development phase for two reference components aiming an early approval methodology validation for a new design. A Finite element analysis procedure was used to set critical spots for measurements minimizing the data acquisition efforts. Based on measured data, strain life calculation was done for two reference components in order to set the release goals for a new design submitted to this approach. An innovative fatigue experimental technique is proposed using component extracted specimens and an edited input cycle loads. Considering the random data from a standard test track and signal proportionality evaluation, while assuming the Brown Miller equation for bi-axial fatigue together with Ramberg-Osgood model, equivalent damage load blocks were edited and used as input for durability assessment on specimens representing the component material. The results for the three parts materials were plotted as Weibull diagram for B10 life estimation. Fatigue life results showed good correlation with the reference parts structural performance thus validating the method as well as approving the new design for production without additional on-vehicle durability testing. The methodology and the fatigue testing proposal is therefore recommended for future applications on similar developments