Mechanical Properties of Porous Ceramics

It is widely known that increasing interest in porous ceramics is due to their special properties, which comprise high volumetric porosity (up to 90%) with open or closed pores, and a broad range of pore sizes (micropores: d  d > 2 nm and macropores: d > 50 nm). These properties have many uses comprehending macroscaled devices, mesoscaled materials and microscaled pieces. During their usage, these materials are usually submitted to thermal and/or mechanical loading stresses. Therefore, it is a premise to understand how these porous structures behave under thermomechanical stresses to design materials that show adequate properties for the required application. In this context, the aim of this chapter is to review the mechanical properties of macroporous ceramics

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

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

Alguns aspectos da camada superficial obtida por difusão do boro em aços carbono

Unavailable.Técnicas de difração de raio X e metalográficas foram aplicadas em aços SAE 1010 e SAE 1030, boretados pelo processo eletrolítico, com a finalidade de se determinar a constituição e a morfologia da camada superficial, obtida pela difusão do boro numa matriz y, até completa saturação da camada. As medidas dos parâmetros obtidas por difração de raio X nos conduziram a conclusões parciais em relação à constituição da camada de difusão, pois algumas raias que aparecem no filem de difração não foram identificadas. Por outro lado, no exame da morfologia encontramos: superficialmente uma camada de boretos com um aspecto nitidamente colunar, apresentando duas regiões distintas, uma clara e outra escura, identificando os compostos intermediários FeB w Fe2B, respectivamente. Mais internamente encontramos uma faixa contendo ferrita intergranular e Widmastatten, sob um fundo fortemente perlítico, que nos deu a impressão de que o carbono existente na superfície do espécime difundiu para o interior. Em seguida propomos o merecimento responsável pelo aumento do teor de carbono naquela faixa e detetamos a existência de "B" naquela região, com a finalidade de eliminarmos certa discrepância observada no exame da microtextura. Finalizando concluímos que essa faixa fortemente perlítica contribui para diminuir o gradiente de dureza ao longo da camada de boretos-material de suporte, com fortes implicações tecnológicas

ISOTHERMAL AND THERMOMECHANICAL FATIGUE OF A NICKEL-BASE SUPERALLOY

Thermal gradients arising during transient regimes of start-up and shutdown operations produce a complex thermal and mechanical fatigue loading which limits the life of turbine blades and other engine components operating at high temperatures. More accurate and reliable assessment under non-isothermal fatigue becomes therefore mandatory. This paper investigates the nickel base superalloy CM 247LC-DS under isothermal low cycle fatigue (LCF) and thermomechanical fatigue (TMF). Test temperatures range from 600°C to 1,000°C. The behavior of the alloy is strongly affected by the temperature variation, especially in the 800°C-1,000°C range. The Ramberg-Osgood equation fits very well the observed isothermal behavior for the whole temperature range. The simplified non-isothermal stress-strain model based on linear plasticity proposed to represent the thermo-mechanical fatigue behavior was able to reproduce the observed behavior for both in-phase and out-of-phase TMF cycling

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