Effect of Pre-Strain on Fatigue Properties of NHH Rail

2004 ◽  
Vol 261-263 ◽  
pp. 1239-1244
Author(s):  
Wen Xian Sun ◽  
S. Nishida ◽  
Nobusuke Hattori ◽  
X.L. Yue
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Fatigue Test ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Slip Lines ◽  
Propagation Behavior ◽  
Strain Process ◽  
Initiation And Propagation

In the present study, fatigue tests have been performed to study the effect of pre-strain on fatigue properties of NHH (New Head-Hardened) rail. The objectives of this study were: (1) to observe the microscopic behavior of specimens during pre-strain process, (2) to research the influence of pre-strain on fatigue strength of NHH rail and (3) to investigate initiation and propagation behavior of the fatigue crack. The results showed that plastic pre-strain decreased the fatigue strength of NHH rail; fatigue limits had no obvious variation among the different pre-strain ratios. Fatigue cracks initiated in the microscopic cracking or slip lines that were originated in the pre-strain process and propagated from these sites in the later fatigue test.

Retrofitting for Fatigue Cracks at Connection between the Main Girder Web and Lateral Girder Flange Using the Bolting-Stop-Hole Method with Attached Plates

2014 ◽  
Vol 891-892 ◽  
pp. 130-135
Author(s):  
Takeshi Mori ◽  
Kazuya Sasaki ◽  
Mitsuru Nakanuma
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Fatigue Cracks ◽  
High Strength ◽  
Fatigue Tests ◽  
Steel Plates ◽  
Small Scale ◽  
Bolted Connections ◽  
Repair Method ◽  
Main Girder

For the purpose of clarifying the fatigue strength of a main girder web connected to a lateral girder flange which is repaired by bolting-stop-hole method with attached steel plates, fatigue tests have been performed on girder specimens. In addition, fatigue tests have been also carried out on small scale plate specimens modeling the repaired parts in order to investigate the fatigue crack origin and fatigue strength of the repaired parts. Furthermore, the effect of the repair method has been compared with those of stop-hole method and/or bolting-stop-hole method through the fatigue tests. It has been confirmed that the fatigue strength of the repaired parts is considerably high and almost equal to that of friction type of high strength bolted connections.

Effect of Radical Nitriding on Fatigue Strength of Ni-Base Superalloy

2009 ◽  
Vol 417-418 ◽  
pp. 205-208 ◽  
Author(s):  
Kazuhiro Morino ◽  
Norio Kawagoishi ◽  
K. Yamane ◽  
K. Fukada
Keyword(s):  
Fatigue Strength ◽  
Base Alloy ◽  
Compound Layer ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Propagation Behavior ◽  
Initiation And Propagation ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
Base Superalloy

In order to investigate the effect of nitriding on the crack initiation and propagation behavior of Ni-base super alloy, Alloy 718, rotating bending fatigue tests were carried out until 108 cycles at room temperature. By nitriding at 500°C for 12h, compound layer of about 5μm in thickness was formed and the initiation of a fatigue crack was strongly suppressed causing the increase in fatigue strength. A crack initiated in brittle manner at the compound layer in all of fractures. However the crack propagated in ductile manner controlled by the property of the base alloy. That is, there is no or little influence of nitriding on the crack growth rate of the alloy.

INITIATION AND PROPAGATION BEHAVIOR OF A FATIGUE CRACK OF ALLOY 718

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2857-2862 ◽  
Author(s):  
NORIO KAWAGOISHI ◽  
MASAHIRO GOTO ◽  
XISHU WANG ◽  
QINGYUAN WANG
Keyword(s):  
Fatigue Strength ◽  
Fatigue Tests ◽  
Alloy 718 ◽  
Aged Material ◽  
Propagation Behavior ◽  
Peak Aged Condition ◽  
Initiation And Propagation ◽  
High Fatigue ◽  
Rotating Bending Fatigue ◽  
Peak Aged

Rotating bending fatigue tests were carried out at room temperature and 500°C for alloy 718 with nearly the same static strength but different precipitated particles, i.e. a peak aged condition (720°C-10h) and a double aged one (720°C-8h, 620°C-8h), in order to investigate the effect of precipitated particles on crack initiation and propagation behavior. Fatigue strength was higher in the double aged material than in the peak one at both temperatures. The main reason for high fatigue strength of the double aged material was that the propagation of a small crack with a few grain sizes was suppressed by the carbide particles precipitated in a grain.

Fatigue Properties of Non-Loosening Bolt with Double Screw Mechanism

2005 ◽  
Vol 297-300 ◽  
pp. 2525-2532
Author(s):  
Shinichi Nishida ◽  
Nobusuke Hattori ◽  
H. Iwakiri ◽  
A. Uchisako
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Fatigue Failure ◽  
Strength Characteristics ◽  
Fatigue Properties ◽  
Initiation And Propagation ◽  
Bolt Failure ◽  
Screw Mechanism ◽  
Thread Root

Prevention of slack in fastening bolt has been an important researching subject since fatigue failure can be generally caused by loosening nut. According to the above reason, the super lock bolt with double screw mechanism, which is non-loosening, has been developed for preventing such kind of bolt failure. The objects of the present study are as follows: (1) To clarify the fatigue strength characteristics. (2) To investigate the initiation and propagation behaviour of fatigue crack regarding to the thread root of first pitch. In addition, the mechanism of “fatigue strength of super lock bolt” is also discussed in this paper and it is confirmed that this bolt shows excellent fatigue strength and non-loosening properties.

Fatigue Properties Improvement of Notched Structural Steel Sheets

2008 ◽  
Vol 385-387 ◽  
pp. 553-556
Author(s):  
Nobusuke Hattori ◽  
Kazuhiko Nakayama ◽  
Mian Zhang ◽  
Shinichi Nishida
Keyword(s):  
Fatigue Strength ◽  
Early Stage ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Plastic Working ◽  
Notched Specimen ◽  
Mechanical Parts ◽  
Steel Sheets ◽  
Initiation And Propagation

Nearly 90% of failures of machines and mechanical parts are caused at the area of stress concentrated in the structural components. Hence, it is important to investigate the method of improving fatigue strength for notched parts. In this paper, the fatigue tests have been performed to investigate the effect of the plastic-working on fatigue strength of specimens with notch. The main results obtained in this study are as follows: (1) The fatigue limit of notched specimen chamfered by the plastic-working increases by 45% than that of specimen without chamfer. (2) The reason of enhancing the fatigue strength may be to attributed to the work-hardening and compressive residual stress which suppress the fatigue crack initiation and propagation in early stage.

PREDICTION FOR FATIGUE CRACK GROWTH IN NOTCHED PLATES

2012 ◽  
Vol 06 ◽  
pp. 269-274
Author(s):  
K. SHOJIMA ◽  
K. YANASE ◽  
M. ENDO
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Crack Growth Behavior ◽  
Plastic Behavior ◽  
Short Cracks ◽  
Major Factors

The notch is usually unavoidable in designing various mechanical components. As well known, those notches significantly influence the fatigue life and fatigue strength of materials. In addition, most fatigue cracks spend the vast majority of their lives as short cracks, and the behavior of such flaw is of significant importance in determining the fatigue lifetime of notched components. Correspondingly, in this research, we investigate the fatigue crack growth behavior and fatigue strength of notched plates. For the proposed method, the elastic-plastic behavior, the Kitagawa effect and the crack closure are taken into account as the major factors responsible for the peculiar behavior of small fatigue cracks emanating from notches. Regarding the experiment, the fatigue tests were conducted using the plates with a circular notch under uniaxial loading condition. The proposed approach is validated by comparing the predicted results to the experimental data.

Fatigue Properties of Surface-Micromachined Al-3%Ti Thin Films

2007 ◽  
Vol 353-358 ◽  
pp. 299-302
Author(s):  
Jun Hyub Park ◽  
Man Sik Myung ◽  
Yun Jae Kim
Keyword(s):  
Thin Film ◽  
Fatigue Strength ◽  
Fatigue Test ◽  
Rf Mems ◽  
Type Specimen ◽  
Fatigue Tests ◽  
Measuring System ◽  
Fatigue Properties ◽  
Test Machine ◽  
Ti Alloy

This paper describes new structure of specimen easy to manipulate, align and grip a thin-film and test machine for a fatigue test. High cycle fatigue test has been performed on tensile type specimen of Al-3%Ti alloy using the newly developed fatigue test machine. The material used in this study was Al-3%Ti thin film, which was used in RF MEMS switch. The structure of the suggested specimen has two holes and several bridges. The holes at centre of grip end are able to make alignment and gripping easy. The bridges are to remove the side support strip easily and extract specimen from wafer without sawing. The test machine was developed using the voice coil of speaker. The new tensile loading system has a load cell with maximum capacity of 0.5N and a non-contact position measuring system based on the principle of capacitance micrometry with 0.1nm resolution for displacement measurement. Fatigue tests was performed on 7 specimens. The thickness and width of the thin film of specimen are 1.0μm and 150μm, respectively. The fatigue strength coefficient and the fatigue strength exponent of Al-3%Ti alloy micro-sized specimen are determined to be 164MPa and -0.01322, respectively

Thermal Fatigue Properties of the Fin in the Boilers

2007 ◽  
Vol 353-358 ◽  
pp. 315-318 ◽  
Author(s):  
Yukihiro Tokunaga ◽  
Nu Yan ◽  
Daisuke Yonekura ◽  
Riichi Murakami
Keyword(s):  
Heat Transfer ◽  
Fatigue Test ◽  
Thermal Fatigue ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Test Machine ◽  
Element Analysis ◽  
Heat Transfer Efficiency ◽  
Heating And Cooling

In order to improve the heat transfer efficiency, the fins are commonly used in the industrial boiler in Japan. In actual application, the thermal fatigue due to the cyclic change of temperature usually occurs in the fins. The thermal fatigue tests were carried out by using the thermal fatigue apparatus designed. The designed testing apparatus can apply thermal load to the fin by giving heating and cooling alternatively. The fatigue cracks can be observed in the vicinity of the toe in the thermal fatigue test. The heat transfer coefficient and the thermal stress were calculated by using Finite Element Analysis (FEA) method. The fatigue experiments of the fins were also conducted using electro-hydraulic servo fatigue test machine in the laboratory. The results of thermal fatigue experiments were discussed by comparing with those of the mechanical fatigue experiments.

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