scholarly journals High-Cycle Fatigue Properties and Sub-Surface Crack Initiation in Ti-5%Al-2.5%Sn ELI Alloy

2003 ◽  
Vol 67 (8) ◽  
pp. 391-397 ◽  
Author(s):  
Yoshinori Ono ◽  
Tetsumi Yuri ◽  
Hideshi Sumiyoshi ◽  
Saburo Matsuoka ◽  
Toshio Ogata
Keyword(s):  
Crack Initiation ◽  
Surface Crack ◽  
High Cycle Fatigue ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Surface Crack Initiation

High Cycle Fatigue Properties of Multi-Directionally Forged Commercial Purity Grade 2 Ti Plate

2018 ◽  
Vol 916 ◽  
pp. 166-169
Author(s):  
Ilhamdi ◽  
Toshifumi Kakiuchi ◽  
Hiromi Miura ◽  
Yoshihiko Uematsu
Keyword(s):  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Pure Titanium ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Commercially Pure Titanium ◽  
Cycle Fatigue ◽  
Subsurface Crack ◽  
Initiation Mechanism ◽  
Fish Eye

Tension-tension fatigue tests were conducted using ultrafine-grained commercially pure Titanium (Ti) plates fabricated by multi-directional forging (MDFing). The MDFed pure Ti plates with the thickness of 1 mm were developed aiming at dental implant application. The fatigue properties of MDFed pure Ti plates were superior to those of the conventional rolled pure Ti plates. The higher fatigue strengths in MDFed plates could be attributed to the much finer grains evolved by MDFing. Fatigue crack initiated from specimen surface, when number of cycles to failure was shorter than 106 cycles. In the high cycle fatigue (HCF) region, however, subsurface crack initiation with typical fish-eye feature was recognized in the MDFed pure Ti plate in spite of the thin thickness. Fractographic analyses revealed that no inclusion existed at the center of fish-eye. The subsurface crack initiation mechanism could be related to the inhomogeneity of microstructure with some coarse grains in the inner part of the plate.

Effect of the Rheocasting Process and of the SLS Layer on the Fatigue Behavior of 357 Aluminum Alloy

2014 ◽  
Vol 217-218 ◽  
pp. 227-234 ◽  
Author(s):  
Alain Abou Antoun ◽  
Myriam Brochu ◽  
Heinrich Möller
Keyword(s):  
Aluminum Alloy ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Initiation Mechanism ◽  
Liquid Segregation ◽  
Surface Liquid ◽  
Effect Of Surface

Two objectives were targeted: 1) compare the high cycle fatigue behavior of rheocast aluminum alloy 357 prepared by the swirl enthalpy equilibration device (SEED) and by the Council for Scientific and Industrial Research (CSIR) process, and 2) study the effect of surface liquid segregation (SLS) on the fatigue behavior of the CSIR material. Rectangular hourglass specimens machined from rheocast plates were tested at four stress amplitudes in axial fatigue with a stress ratio of R = -1 and a frequency of 20 Hz. Results obtained for SLS free specimens show that the SEED and the CSIR processes produce rheocast materials with comparable high cycle fatigue properties, 115 MPa at 107 cycles. In order to study the influence of surface liquid segregation, slightly polished specimens with a remaining SLS of nearly 750 microns thick were also tested. According to the results, the SLS reduces the average fatigue strength by approximately 5% (110 MPa vs. 115 MPa at 107 cycles). For SLS free specimens, the fatigue crack initiated at shrinkage cavities, oxide films or in the alpha globules. On the other hand, for specimens with SLS, no crack initiation in the alpha globules was observed. The main crack initiation mechanism was identified to be a deformation incompatibility between regions characterized by higher silicon content compared to nominal eutectic regions. The originality of the work is provided by the rigorous comparative analysis of the fatigue performance of components produced in two different rheocasting facilities, but tested in a single laboratory. It is also the first fundamental research published on the mechanical effect of surface liquid segregation. It confirms that SLS should be removed in critical areas in order to optimize the fatigue resistance of rheocast components.

Factors Affecting the Low Cycle Fatigue Behavior around the Weak Axis of Welded I-Section Bracing Members

2006 ◽  
Vol 324-325 ◽  
pp. 959-962
Author(s):  
Yao Chun Zhang ◽  
Wei An Lian ◽  
Wen Yuan Zhang
Keyword(s):  
Fatigue Life ◽  
Energy Dissipation ◽  
Crack Initiation ◽  
Surface Crack ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Loading History ◽  
Energy Dissipation Capacity ◽  
Surface Crack Initiation

The low cycle fatigue behavior and energy dissipation capacity around the weak axis of the welded I-section bracing members are investigated by 35 pinned-pinned bracing specimen tests under the axial cyclic loading with different characteristics. Particular attention is paid to the effects of loading amplitude, loading history and geometry properties of these members. It is found that the fatigue damage propagating to fracture in the flanges of the bracing members can be divided into 3 stages involving the macroscopic surface crack initiation, the penetrated crack formation and the penetrated crack propagation. Some empirical formulas to estimate the fatigue life and cyclic energy dissipation capacity of the bracing members are also presented based on the experimental data. The statistical analysis indicates that the fatigue life to surface crack initiation significantly depends on the inelastic local buckling and will increase with decreasing width-thickness ratio of the flanges and increasing slenderness ratios of the bracing members. Besides, it is found that the low cycle fatigue and energy dissipation of these members also depends on loading amplitude and loading history, and the effects of overloads and mean compression amplitude can improve the fatigue performance of bracing members. The test results show that the bracing members with better low-cycle fatigue resistance have the better energy dissipation capacities.

Enhancing Fatigue Properties of Nanostructured Metals and Alloys

2007 ◽  
Vol 29-30 ◽  
pp. 117-122 ◽  
Author(s):  
Terry C. Lowe
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Computational Methods ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Metals And Alloys ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Nanostructured Metals ◽  
Improve Fatigue

Recent research on the fatigue properties of nanostructured metals and alloys has shown that they generally possess superior high cycle fatigue performance due largely to improved resistance to crack initiation. However, this advantage is not consistent for all nanostructured metals, nor does it extend to low cycle fatigue. Since nanostructures are designed and controlled at the approximately the same size scale as the defects that influence crack initiation attention to preexisting nanoscale defects is critical for enhancing fatigue life. This paper builds on the state of knowledge of fatigue in nanostructured metals and proposes an approach to understand and improve fatigue life using existing experimental and computational methods for nanostructure design.

The Improvement of High Cycle Fatigue Properties of AC4CH Alloy with Shot Peening Treatment

2005 ◽  
Vol 297-300 ◽  
pp. 1919-1924
Author(s):  
Kiyotaka Masaki ◽  
Yasuo Ochi ◽  
Takashi Matsumura
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Shot Peening ◽  
High Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Crack Propagation Rate ◽  
Fatigue Properties ◽  
Fatigue Crack Propagation Rate ◽  
Cycle Fatigue

In order to investigate the effect of SP treatment on the high cycle fatigue properties such as fatigue strength, crack initiation and propagation behaviors, rotating bending fatigue tests on shot-peening (SP) treated AC4CH aluminum alloy were carried out. The fatigue properties of the SP-treated material were compared with fatigue properties of the non-peened material, the hot isostatic pressure (HIP) treated material and the semi-liquid (SL) die casting material. the main conclusions obtained were, (1) The fatigue properties of SP-treated material is most excellent in all materials. (2) The fatigue life property of AC4CH alloys is significantly affected by fatigue crack initiation behavior. The reason why the SP-treated material has longer fatigue life than those of other material is that it has no cast defects near the surface by the effect of SP treatment. (3) The reason of fatigue life improvement by SP treatment is decrease of fatigue crack propagation rate.

Review on Surface Failure Mode of Metallic Materials in Very High Cycle Fatigue Regime

2013 ◽  
Vol 652-654 ◽  
pp. 1295-1300
Author(s):  
Dong Ming Wang ◽  
Wei Li ◽  
Ping Wang ◽  
Wei Xian Chu
Keyword(s):  
Crack Initiation ◽  
Surface Crack ◽  
High Cycle Fatigue ◽  
Metallic Materials ◽  
Crack Initiation And Propagation ◽  
Surface Failure ◽  
Very High Cycle Fatigue ◽  
Initiation And Propagation ◽  
Very High ◽  
Surface Crack Initiation

With higher cleanness upgraded steadily, surface failure of metallic materials in very high cycle fatigue (VHCF) regime beyond 107 cycles has been reported one after another. The occurrence of surface crack initiation to failure in VHCF regime is closely related to the following factors: (i) surface finishing condition of specimen, i.e. whether some grinding scratches, grooves and cavities with a relatively larger size than the subsurface defect exist at the surface of specimen; (ii) type, size, location, distribution and density of metallurgical defects such as inclusion contained in the subsurface of material; (iii) degree of persistent slip band (PSB) deformation induced by surface roughening of specimen, mainly corresponding to the some ductile single-phase metallic materials. Furthermore, the effect of environment such as humidity also accelerates surface crack initiation and propagation in VHCF regime. In the present paper, the authors briefly reviewed surface failure modes of metallic materials in VHCF regime beyond 107 cycles, and analyzed the surface crack initiation and propagation mechanisms from the viewpoints of the fracture mechanics and statistics.

scholarly journals Effect of Microstructure on the High-Cycle Fatigue Behavior of Ti(43-44)Al4Nb1Mo (TNM) Alloys

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1043
Author(s):  
Bin Tang ◽  
Bin Zhu ◽  
Weiqing Bi ◽  
Yan Liu ◽  
Jinshan Li
Keyword(s):  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Crack Nucleation ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Subsurface Crack ◽  
Tial Alloys ◽  
Fracture Morphologies

To investigate the high-cycle fatigue (HCF) behavior of TNM alloys, three different microstructures were designed and obtained by different heat treatments. Staircase tests and fatigue tests in a finite life-region were performed to evaluate the fatigue properties. Then, the fracture surfaces were analyzed to study the fracture behavior of TNM alloys with different microstructures. Results showed that the TNM alloys with duplex microstructure possesses the highest fatigue strength and fatigue life, followed by near lamellar TiAl alloys. HCF failure exhibited cleavage fracture morphologies, and multiple facets were generated in the crack initiation region of different TNM alloys. Two different crack initiation modes, subsurface crack nucleation and surface origin, were observed. Both crack initiation modes appeared in near lamellar alloys, while only subsurface crack initiation were obtained in the duplex (DP) alloy. It contributes to the high scatter of S-N data. The HCF failure of TNM alloys was dominated by crack nucleation rather than crack propagation. These findings could provide guidance for optimizing the microstructure and improving the HCF properties of TiAl alloys.

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