Papers by Keyword: Fracture Toughness

Abstract: Additive manufacturing gains ground on the production of high-precision metallic components with varying thickness. As the material thickness alters in the various locations of the product, it is eminent that the material mechanical properties might vary. In the present contribution, a preliminary study was performed to investigate the resistance to fracture of additively manufactured AlSi10Mg material with varying thicknesses. To this end, fracture toughness specimens of compact tension geometry with varying thicknesses from 3 to 15 mm were additively manufactured, machined and tested. The results showed that with increasing the specimen thickness, critical stress intensity factor K_cr decreases gradually from 38 MPa√m up till 31 MPa√m for the lower and higher investigated thicknesses, respectively. Finally, it was noticed that even the 15 mm thickness (higher investigated) does not satisfy the plane strain fracture mechanism and therefore all investigated specimens were in plane-stress condition.

Abstract: In this study, the bonding of WC-Co cermet to AISI 304L stainless steel was achieved through the flash spark plasma sintering (FSPS) process under a steady pressure of 5 MPa and ultra-short holding durations. The investigation focused on the impact of holding time on interfacial characteristics, diffusion behavior, and mechanical performance. The results demonstrated that prolonged holding times, particularly up to 12 seconds, led to pronounced interfacial deformation and significant diffusion of Co, Ni, and Fe elements across the joint interface. Toughness assessment of the WC-Co cermet near the bonded region was carried out using the Vickers indentation fracture (VIF) technique. The analysis revealed a decline in mechanical integrity with extended holding times, increasing the brittleness of the joint despite the enhanced elemental diffusion between the cermet and the stainless steel.

Abstract: Crack propagation behavior is a critical factor influencing the service life of thermal barrier coatings (TBCs). With the use of hydrogen as a fuel in a carbon-neutrality context, incomplete combustion of hydrogen gas will introduce potential new failure modes for TBCs. Therefore, it is crucial to evaluate the crack propagation behavior of TBCs subjected to a hydrogen environment. In this study, in-situ three-point bending tests were used to investigate the crack propagation behavior within the top coat after heat treatment under air and hydrogen environments. The results reveal that the sintering degree is reduced after heat treatment in hydrogen environments, accompanied by the formation of numerous microcracks before the displacement reaches 0.6mm. Conversely, heat treatment in air environments results in a higher sintering degree and promotes the propagation of main vertical cracks on the surface of the top coat as the displacement gradually increases to 0.8 mm. Additionally, this study discusses the effect of sintering on the fracture toughness of the top coat and further elucidates the effect of hydrogen fuel on the overall durability of TBCs.

Abstract: Water shortage is a major global issue affecting the construction industry. One possible solution is to use seawater instead of tap water in cement-based materials. However, this raises concerns about the impact on material properties. In addition, it is known that the use of volcanic pumice powder in cement mortar can improve its properties, but the combined effects of seawater and volcanic pumice powder have not been thoroughly investigated. This study aims to fill this gap by investigating the synergistic effects of seawater and volcanic pumice powder on the slump flow, compressive and flexural strengths, water absorption, and fracture toughness of cement mortar. The main variables in this study are the type of water (Mediterranean water and tap water) and the percentage of volcanic pumice powder (VPP). The volcanic pumice powder content is 0%, 10%, 20%, and 30%, replacing cement by mass. Based on investigation results, it was shown that the combination of seawater and volcanic pumice powder leads to less fluid and more viscous mortars compared to those made with tap water (TW). However, in the hardened state, seawater promoted the early precipitation of cement hydration, resulting in an increase in compressive strength from the second day until 28-days, along with an improvement in the transport properties of mortar at 28 days. Meanwhile, a noticeable decline in both strength and fracture toughness was recorded for ages more than 28 days and up to 90 days, compared to mortars cast and cured with tap water.

Abstract: The crack initiation and propagation in an aluminium alloy in a corrosive environment are complex because of the loading parameters and material properties, which may result in a sudden failure in real-time applications. This paper investigates the fracture toughness of aluminium alloy under varying environmental and corrosion conditions. The main objective of the work is to link the interdependencies of humidity and temperature for an AL6082-T651 alloy in a corrosive environment. This study investigates AL6082-T651alloy's fracture behaviour and mechanism through microstructure and fractographic studies. The results show that a non-corroded sample, at room conditions, provided more load-carrying capacity than a corroded sample. Additionally, an increase in temperature improves fracture toughness, while an increase in humidity results in a decrease in fracture toughness.

Abstract: In order to analyze the stress concentration impact, intensity close to the zone of the crack tip, this work examines the in-plane SIF(SIF) of composite plates utilizing measured crack tip opening displacement (CTOD). The test specimens' E-glass fiber mats were arranged in various ply configurations. The ASTM standards utilized for researching mode I fracture of composite materials served as the foundation for the compact tension (CT) specimen. The mode I, K_I Stress intensity factor (SIF), and critical stress, c, were calculated for each specimen along the fracture length propagation based on the experiments. It was found that the SIF is directly proportional with fracture length, or a/W, for all E-glass fiber laminate cases tested. The K_IC is often higher in thinner laminates. The presence of woven roving increases the SIF and hence the toughness of the laminate.

Abstract: The effect of tempforming on strength and fracture toughness of a 0.4%C-2%Si-1%Cr- 1%Mo-VNb steel was examined. Tempering at a temperature of 600°C followed by plate rolling at the same temperature results in the formation of lamellar structure with a spacing of 72 nm between longitudinal boundaries and a lattice dislocation density of ~10¹⁵ m⁻² that enhances fracture toughness in normal direction of tempformed plate. The increase in the absorbed impact energy is attributed to delamination, which occurs in plains intersecting the propagation path of main crack that blunts crack tip.

Abstract: In present work, a high Zn-containing Al-Zn-Mg-Cu alloy with different grain sizes was fabricated by extrusion and related precipitation characteristics and mechanical property were investigated after uniform heat treatments. The results showed that precipitation characteristics for the three alloys were almost the same. Matrix precipitates were GPII zone and η' phase and possessed small size and dense distribution while grain boundary precipitates exhibited discontinuous distribution. The rank of strength and fracture toughness for the three alloys are SG>MG>LG. Tearing ridges had been found on all the fracture surface while only LG alloy possess obvious dimple characteristics. The a-N curve showed that crack length list is MG>LG >SG under a same cycle number. The da/dN-ΔK curve also proved that fatigue crack propagation (FCP) rate of MG alloy is slightly larger than that of LG alloy, both were apparently larger than that of SG alloy. The width of fatigue striations on FCP fracture surface also backed it. Besides, obvious transgranular cracking characteristics and apparent secondary cracks were found on the FCP fracture surface.

Abstract: In the present work, the effect of cryo-rolling on the processed LM6 alloy samples has been studied. The solution treated (ST) sample of LM6 alloy has been processed through cryo-rolling with reduction of its thickness with values such as 30%, 40%, and 75%. One of the key material properties i.e., fracture toughness has been studied and equivalent energy fracture toughness ( ) is being evaluated according to the ASTM E 992 standard. The microstructure evolution after processing through cryorolling (CR) has been carried out with the help of optical microscopy and Scanning Electron Microscopy (SEM). Then, the calculated values of fracture toughness parameter i.e., equivalent energy fracture toughness ( is being correlated with the microstructure evolution after processing of LM6 alloy. It was found out that there is an improvement in equivalent energy fracture toughness ( ) as the reduction values increases. The 75% CR sample showed great increment of 67% as compared to ST alloy sample. The microstructure evolution also signifies the mix-mode fracture visualized through Scanning Electron Microscopy (SEM) and as the reduction values increase, the ductile fracture zone dominance increases on brittle fracture zone indicating there is improvement in fracture toughness of the ultra-fined grain LM6 alloy due to the grain refinement, dislocation strengthening and grain boundary strengthening.

Abstract: Present, artificial intelligence methods play a huge role in solving complex engineering problems such as the fracture toughness of materials, which is one of the parameters to be considered for engineering design. Fracture toughness tests can be prepared materials and test configured in a variety of ways, resulting in different fracture toughness depending on the preparation method. In this study, fracture toughness of PMMA under the effect of loading rate is one of the testing configs that can be adjusted according to the actual load characteristics of the material and the crack geometry (crack width and crack length ratio) according to crack preparation to test specimens and the effect of these factors was predicted with generalized regression neural network (GRNN) and Gaussian processes regression (GPR) models which are one of the artificial intelligence models, compared to traditional fracture toughness predictions. The results showed that artificial intelligence prediction was able to more accurately predict the effect of the factors studied on the fracture toughness of PMMA compared to the traditional fracture toughness prediction.