Topic
Paris' law
About: Paris' law is a research topic. Over the lifetime, 13815 publications have been published within this topic receiving 224818 citations. The topic is also known as: Paris-Erdogan law.
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TL;DR: In this article, a fatigue crack model is proposed to address frictional contact along crack faces and multi-axial non-proportional sollicitations in linear elastic fracture mechanics framework (LEFM).
80 citations
TL;DR: In this paper, the effects of colony size, lamellar spacing, and volume fraction of equiaxed γ grains are analyzed in terms of their effects on resistance to the growth of large (>5 mm) cracks.
Abstract: Ambient-temperature fracture toughness and fatigue crack propagation behavior are investigated in a wide range of (γ+α 2) TiAl microstructures, including single-phase γ, duplex, coarse lamellar (1 to 2 mm colony size (D) and 2.0 µm lamellar spacing (λ)), fine lamellar (D ∼ 150 µm, λ=1.3 to 2.0 µm), and a powder metallurgy (P/M) lamellar microstructure (D=65 µm, λ=0.2 µm). The influences of colony size, lamellar spacing, and volume fraction of equiaxed γ grains are analyzed in terms of their effects on resistance to the growth of large (>5 mm) cracks. Specifically, coarse lamellar microstructures are found to exhibit the best cyclic and monotonic crack-growth properties, while duplex and single-phase γ microstructures exhibit the worst, trends which are rationalized in terms of the salient micromechanisms affecting growth. These mechanisms primarily involve cracktip shielding processes and include crack closure and uncracked ligament bridging. However, since the potency of these mechanisms is severely restricted for cracks with limited wake, in the presence of small (<300 µm) cracks, the distinction in the fatigue crack growth resistance of the lamellar and duplex microstructures becomes far less significant.
80 citations
TL;DR: The existence or non-existence of fatigue crack growth thresholds is of practical importance and scientific interest, as is knowledge of the stresses enabling crack formation at the surface and the interior of a specimen as discussed by the authors.
80 citations
TL;DR: In this article, the authors showed that the importance of a crack tip constraint parameter, the elastic T-stress, to irregular crack growth behavior that conventional LEFM fails to explain.
79 citations
TL;DR: In this article, a high energy laser beam is applied to melt a thin layer of the metallic powder according to the information provided by CAD files, which offers the opportunity to create complex parts for application areas e.g., aerospace and automotive industries where the lightweight design has been and still is a priority for material development.
Abstract: Selective Laser Melting (SLM ® ), an additive manufacturing (AM) technology, allows manufacturing of geometrically complex metallic parts directly. In the SLM technology, a high energy laser beam is applied to melt a thin layer of the metallic powder according to the information provided by CAD files. This layer-wise manufacturing offers the opportunity to create complex parts for application areas e.g., aerospace and automotive industries where the lightweight design has been and still is a priority for material development in recent years. Therefore, the materials such as aluminium alloys come into focus due to their low density and high mechanical characteristics. In view of these aspects, previously unused high strength aluminium alloy EN AW-7075 powder was produced by gas atomization and processed by SLM ® as presented in this paper. Initially, specimens were produced to examine monotonic and fracture mechanical properties in different building directions. The tensile tests and the fracture examinations show an anisotropic material behaviour. The fatigue crack growth curves have the double S shape, which is typical of aluminium. Mechanical characteristics obtained from the experiments are lower in comparison to the conventionally manufactured aluminium alloy properties.
79 citations