Topic
Fatigue limit
About: Fatigue limit is a research topic. Over the lifetime, 20489 publications have been published within this topic receiving 305744 citations. The topic is also known as: endurance limit & fatigue strength.
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TL;DR: In this paper, the authors examined the threshold condition for the fatigue limit of materials containing a small crack under cyclic torsion and reversed torsional fatigue tests were carried out on 0.47% C steel specimens containing an initial small crack.
Abstract: In order to examine the threshold condition for the fatigue limit of materials containing a small crack under cyclic torsion, reversed torsional fatigue tests were carried out on 0.47% C steel specimens containing an initial small crack. Initial small semi-elliptical cracks ranging from 200 to 1000 μm in length were introduced by the preliminary tension-compression fatigue tests using specimens containing holes of 40 μm diameter. The threshold condition for the fatigue limit of the specimens containing artificial small defects under rotating bending and cyclic torsion are also reviewed. Crack growth behaviour from an initial crack was investigated. The torsional fatigue limit for a semi-elliptical small crack is determined by the threshold condition for non-propagation of Mode I branched cracks. The torsional fatigue limit of specimens containing an initial small crack can be successfully predicted by the extended application of the √area parameter model in combination with the σ θmax criterion.
80 citations
TL;DR: In this article, a semicircular surface crack 100 μm in diameter was made on each sample, and the crack-healing behavior was systematically studied, as functions of crack healing temperature and healing time.
Abstract: Alumina/silicon carbide (Al 2 O 3 /SiC) composite ceramics with large self-crack-healing ability, high strength and high heat-resistance limit temperature for strength were developed and subjected to three-point bending. A semicircular surface crack 100 μm in diameter was made on each sample. Crack-healing behaviour was systematically studied, as functions of crack-healing temperature and healing time, and the fatigue strengths of the crack-healed sample at room temperature and 1373 K were investigated. Four main conclusions were drawn from the present study. (1) Al 2 O 3 /SiC composite ceramics have the ability to heal after cracking from 1273to 1673 K in air. (2) The heat-resistance limit temperature for strength of the crack-healed sample is ≅ 1573 K, and ≅68% of the samples fractured from outside the crack-healed zone in the testing-temperature range 873-1573 K. (3) The crack-healed sample exhibited very high fatigue limit at room temperature and also 1373 K. (4) The large self-crack-healing ability is a desirable technique for the high structural integrity of ceramic component.
80 citations
TL;DR: In this article, the authors performed fatigue tests on two common engineering materials, cast ductile iron and low carbon steel, using two stress states, cyclic torsion and cyclic Torsion with static axial and hoop stresses.
Abstract: Relatively simple fatigue tests have been performed on two common engineering materials, cast ductile iron and low-carbon steel, using two stress states, cyclic torsion and cyclic torsion with static axial and hoop stresses. Tests were designed to discriminate between normal stress and hydrostatic stress as the most suitable mean stress correction term for high cycle fatigue analysis. Microscopy shows that cracks in low-carbon steel nucleate and grow on maximum shear planes, while for cast iron pre-existing flaws grow on maximum normal stress planes. The data illustrate that tensile normal stress acting on a shear plane significantly reduced fatigue life and is an appropriate input for fatigue analysis of ductile materials. Static normal stresses did not significantly affect the fatigue life for the cast iron because the net mean stress on the maximum normal stress plane was zero. Mean torsion significantly reduced the fatigue strength of the cast iron. A critical plane long-life parameter for nodular iron which accounts for both stress state and mean stress is proposed, and is found to accurately correlate experimental data.
80 citations
TL;DR: In this article, two types of stage I fatigue crack initiation were observed, (a) along α/β interfaces and (b) transcrystalline initiation across α grains in partly transformed microstructures and across αβ interfaces in fully transformed micro structures.
Abstract: Fatigue deformation and stage I (shear mode) crack initiation in Ti-6Al-4V alloy test pieces have been studied using optical microscopy. Two types of stage I fatigue crack initiation were observed, (a) alongα/β interfaces and (b) transcrystalline initiation acrossα grains in partly transformed microstructures and acrossαβ interfaces in fully transformed microstructures. The α/β interface cracking occurred predominantly in the low stress regions of the test pieces. These observations suggested that a microstructure with a smallα grain size, to minimize the mean free slip path, and with minimum lengths ofα/β interface, would have a high fatigue strength. Such a microstructure, with anα grain size of < 10 μm, and spheroidal or near spheroidalβ particles, was produced by thermo-mechanical processing. The rotating cantilever fatigue strength of this microstructure, ± 670 MN m−2 at 10−7 cycles, compares with fatigue strengths in the range ± 480 to ± 590 MN m−2 for commercial Ti-6Al-4V bars.
80 citations
TL;DR: In this paper, the authors analyzed the relationship between the monotonic and cyclic behavior of cylindrical AlSi10Mg (CL31 AL) samples fabricated by Selective Laser Melting (SLM) to the build direction, the presence of manufacturing defects (pores, voids, oxides, etc.) and the beneficial effect of post-processing (T6 and hot isostatic pressing (HIP) treatments).
80 citations