Intensity of stress singularity for the circumferential V‐shape corner front of a three‐dimensional diamond‐like defect

Three-dimensional diamond-like defects with circumferential V-shape corner fronts are often contained in engineering materials. In this paper, generalized stress intensity factors are calculated for this type of defect using a modified advanced finite element method. A super corner front element model in the global coordinates is established to capture the stress singularities along the circumferential corner front. Three-dimensional numerical series eigen-solutions in the element have been transformed from asymptotic expressions in the local curvilinear coordinates. The element is suitable for a sharp V-shape corner with arbitrary opening and inclination angle. Singular stress fields near various shapes of diamond-like defects are systematically investigated. The interaction of an embedded defect with free surface or another identical defect is also investigated. The numerical results can be used as stress intensity parameters to predict fatigue strength at circumferential corner front of a diamond-like defect.Agency for Science, Technology and Research (A*STAR)The authors acknowledge the support of National Natu-ral Science Foundation of China under grantno. 51975411 and 51365013, the Natural Foundation of Tianjin, China, under grantno. 18JCYBJC88500, and the Personnel Training Plan forYoung and Middle-aged Innovation Talents in Universi-ties in Tianjin, China. The work was finished when X. CPing visited Prof. Z.M. Xiao at School of Mechanical andAerospace Engineering in Nanyang Technological Uni-versity as a visiting Scholar. The support of SingaporeA*STAR SERC AME Programmatic Fund for the“Struc-tural Metal Alloys Programme”(project WBSM4070307.051) is also acknowledged

An overview of ceramic molds for investment casting of nickel superalloys

Accelerating advancements in technological systems have demonstrated a need for alloys with drastically improved thermomechanical and chemical properties, called superalloys. Ceramic molds are typically used in near-net shape investment casting processes of superalloy components due to their chemical inertness and high-temperature capabilities. Ceramic molds, however, often suffer from shortcomings in vital properties including flexural strength, thermal shock resistance, permeability, dimensional stability, corrosion resistance, and leachability, which have restricted their ability to adequately process modern alloy castings. This study analyses these limitations and illustrates how to address them, particularly regarding ceramic mold and slurry design, processing of shells and cores, material selection, and testing and characterization. By utilizing advanced processing methods including additive manufacturing and gel-casting, more dimensionally accurate and preferentially built molds can be formed. Additionally, by varying the mold composition to achieve more chemically inert structures, reactions with the mold can be mitigated to reduce chemically induced defects