Material Design & Processing Communications最新文献

Among the mechanical properties already evaluated in ductile iron, could be mentioned tensile strength, bend, impact Charpy, fracture toughness and fatigue. However, an aspect no longer explored over the mechanical properties of these materials is concerned with the behavior under compressive loads. In this work, compressive properties are evaluated on quenched ductile iron, which is considered at first as an appropriate alternative for mechanical applications with this kind of load. The evaluation was performed by means of compression tests on cylindrical samples. Further application of compressive loads was explored using the tests known as the Brazilian test, which involves the use of a disc compressed along the diameter line. The results obtained are the first attempt of a complete study involving the different choices of ductile iron.

Additive manufacturing allows high complexity of manufactured structures, permitting entirely new design capabilities. In the context of complex design, lattice structures hold the most promise for high complexity, tailorable and ultra-lightweight structures. These unique structures are suitable for various applications including light-weighting, energy absorption, vibration isolation, thermal management amongst many others. This new complexity leads to new manufacturing quality control and metrology challenges. Traditional metrology tools cannot access the entire structure, and the only reliable method to inspect the inner details of these structures is by X-ray computed tomography (CT). This work highlights the challenges of this process, demonstrating a novel workflow for dimensional metrology of coupon lattice samples—using a combination of surface and internal metrology using tactile probe and CT. This dual combined approach uses traditional surface coordinate measurement on exterior accessible surfaces, which is followed by internal lattice measurements. The results show a clear method and workflow for combining these technologies for a holistic dimensional inspection. The confidence gained by inspection of such lattice coupons will support the application of these lattices in end-use parts.

Nodular cast iron contains about 10 vol% of graphite particles, which debond easily and thus act as nucleation sites of voids. When an elastic–plastic porous material is subjected to cyclic loading, voids grow with each load cycle due to so-called void ratchetting until the micro-ligaments between the graphite particles begin to neck. The cyclic necking leads to void coalescence and finally to the formation of a macroscopic crack. This mechanism is modeled in this study to explain fatigue failure under stress-controlled loading. For this purpose, an axisymmetric cell model is developed and cycle by cycle simulations are performed until final failure. From the simulation results, stress-life curves are extracted and compared with experimental data collected from literature. The effects of the shape of graphite particle, type of matrix material hardening, and mean stress on the fatigue life of nodular cast iron are studied.

At present, due to the unclear understanding of the mixed proportion of stone powder in the manufactured sand, the quality of finished concrete is affected. In this study, the concrete was mixed with manufactured sand containing 0%, 5%, 10%, and 15% stone powder and poured into standard models. The compressive strength of the concrete was obtained by measuring the pressure; the dry shrinkage rate of the concrete was obtained by measuring the volume; the impermeability was evaluated by the seepage height method. The results demonstrated that the increase of stone powder content resulted in the enhancement of concrete compressive strength and impermeability, but blindly adding stone powder led to the deterioration of concrete anti-shrinkage performance. Finally, the comparison of the overall experimental data showed that 10% of stone powder could make all aspects of the performance of the concrete optimal.

Through various examples, this short review presents the main X-ray-based techniques that are available to characterize nodular cast iron at the microstructural level. Emphasis is placed on the enormous potential offered by the recent developments in X-ray tomography, X-ray diffraction, and digital volume correlation, which allow collecting microstructural and micromechanical information in 4D (3D plus time) during both casting and subsequent mechanical loading. The goal is to demonstrate that for nodular cast iron, which has an inherently three-dimensional, composite microstructure, X-ray-based techniques provide some significant advantages over conventional microscopy. For this reason, these techniques can be instrumental in unveiling the mechanisms controlling both the formation of the microstructure as well as its micromechanical behavior during in-service loading, thus paving the way to the development of improved process–structure–property relations.

Recent studies on Co–Cr–Fe–Ni–Nb_x (x = molar ratio) high-entropy alloys (HEAs) have revealed that high-pressure torsion (HPT) induced severe straining improves the load-bearing ability of eutectic HEAs. Nanoindentation using a Berkovich indenter was employed to investigate the influence of severe straining on the rate-dependent strength responses in eutectic, proeutectic, and single-phase Co–Cr–Fe–Ni–Nb_x HEAs. The results reveal that the nature of the microstructure evolution after severe straining significantly affects Young's modulus and the yield strength in eutectic Co–Cr–Fe–Ni–Nb_0.65. The excellent combination of high strength with lower Young's modulus is crucial for opening new sights in lamellar eutectics for possible application as next-generation advanced materials.

Ductile cast iron (DCI) structural components are commonly employed in a wide range of industrial applications. The increasing use of DCI is justified by the good combination of mechanical and technological properties. Another advantage, not negligible, is the low production cost. The goal of the present paper is to estimate the lifetime of ductile cast iron smooth specimens under multiaxial fatigue loading, by using the multiaxial critical plane-based criterion proposed by Carpinteri and others. The obtained results in terms of fatigue life are quite satisfactory, because they fall into the scatter band 3 in almost all loading conditions examined. Finally, the accuracy of the criterion is compared with that obtained by using two stress invariant-based criteria.

The aim of this investigation is to characterize the mechanical properties at the microstructural level in ferritic ductile iron. The analysis involves microstructural characterization, nanoindentation testing, atomic force microscopy analysis, and the application of an inverse algorithms proposed in the literature.

The results show that, because of microsegregation, different regions of a single-phase ferritic matrix have different elastic-plastic behavior. The methodology developed in this work becomes useful to evaluate the mechanical properties along the metallic matrix of other ductile iron microstructures.

The nonlinear displacement on an embankment occurs owing to nonlinear dynamic loadings, design unsuitable geometry for a geo-structure, and using inhomogeneous construction materials for construct subsoil or embankment. In this study, the embankment was modeled with three types of geometries and installed on one type of subsoil. The cross-section of all three models has equal dimensions, and it selected from that was reported in the literature, and the length of 24, 48, and 72 m were designed for the embankment-subsoil model. The single type soil was used for modeling embankment and subsoil. The seismic load was applied to the model for assessment nonlinear displacement and vibration mechanism of the embankment-subsoil model. To assess the developed nonlinear displacement, statistical model was applied on the results of the numerical simulation. The results of the statistical model reveal the R² and root-mean-square error (RMSE) support selection suitable for the geometry of the embankment-subsoil. On the other hand, displacement mechanism associates with the vibration mechanism of the model. With attention to geomorphology of a territory that governs embankment-subsoil model geometry, the appropriate recognition of the impact of model geometry on differential displacement of the embankment-subsoil leads to design an embankment with higher seismic resistance.

Austempered ductile iron is a metallic alloy of technological interest. Currently, the part design is added by means of simulations performed by using different types of models. This work aims at comparing three models respectively based on the Avrami's equation, spherical representative volume elements, and cellular automata; all of them are able to compute the phase evolutions during the ausferritic and martensitic transformations. The models are employed to reproduce the experimental heat treatments where their strongness and weakness are discussed.