Criteria of failure for a cantilever subjected to repeated shock loading

1968 ◽  
Vol 3 (4) ◽  
pp. 245-253 ◽  
Author(s):  
P Srinivasan ◽  
I S Rau
Keyword(s):  
Fatigue Life ◽  
Shock Loading ◽  
Testing Machine ◽  
Sine Wave ◽  
Fatigue Tests ◽  
Cumulative Damage ◽  
Wave Form ◽  
Shock Testing ◽  
Tip Mass ◽  
Damage Criteria

The results of a theoretical and experimental invetigation to determine the fatigue life of a cantilever (with tip mass) subjected to repeated shock loading of the half-sine-wave form are presented. From a simple law of fatigue-crack propagation cumulative damage criteria for predicting fatigue life under variable-amplitude loading are developed. The unknown constants in these criteria are determined from conventional constant-amplitude fatigue tests on a repeated-bending testing machine. From the response of the shock-excited structure determined from linear single-degree-of-freedom theory and the cumulative damage criteria developed, relations for predicting fatigue life under repeated shock loading are developed. The theoretical predictions are then compared with the experimental dau obtained by actually conducting the repeated shock test on a specially designed shock testing machine. The agreement between theory and experiment is fairly good for steel, the material for which the test results are reported.

Effects of Strain Holding and Continuously Changing Strain Rate on Fatigue Life Reduction of Structural Materials in Simulated LWR Water

2007 ◽  
Author(s):  
Makoto Higuchi ◽  
Katsumi Sakaguchi ◽  
Yuichiro Nomura
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
Sine Wave ◽  
Fatigue Tests ◽  
Wave Form ◽  
Peak Strain ◽  
Strain Wave ◽  
Strain Rate Change ◽  
Thermal Transients ◽  
Fatigue Life Reduction

The fatigue life reduces remarkably with reduction in strain rate in simulated light water reactor (LWR) water but the effects of strain wave form on this reduction are still not clear. This paper provides fatigue life data obtained from stepwise strain rate change tests, sine wave tests and strain holding tests. The effects of varying strain rate on fatigue life reduction can be estimated very well by the modified rate approach (MRA) method in the case of the step wise strain rate changing as shown in authors’ previous papers [1, 2, 3, 4, 5]. In the case of sine wave, however, the fatigue life reduction is much less compared to that predicted by the MRA method. The mechanism of such difference is not clear and the quantitative assessment of the fatigue life reduction caused by irregular strain wave form in actual transient seems impossible. The current MRA method gives always conservative assessment for sine wave straining and thus it is judged that this method need not be revised any more. The fatigue life reduction caused by strain holding at the peak of straining cycle in simulated BWR water had been reported in the previous paper [6]. In actual thermal transients, however, strain is not usually held at the peak of straining cycle but at the point somewhat reduced from the peak after the stabilization of temperature. In considering this phenomenon, additional fatigue tests in which the strain was held at the point somewhat reduced from the peak were carried out. In such conditions, the fatigue life reduction caused by strain holding disappeared. The similar fatigue tests with peak strain holding were also carried out in simulated PWR water and no fatigue life reduction can be observed. Considering the effects of strain holding on fatigue, the model for evaluating fatigue life reduction in LWR water was revised.

Effects of Continuous Strain Rate Changing on Environmental Fatigue for Stainless Steels in PWR Environment

2010 ◽  
Author(s):  
Yuichiro Nomura ◽  
Seiji Asada ◽  
Takao Nakamura ◽  
Masakazu Tanaka
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
Water Environment ◽  
Sine Wave ◽  
Fatigue Tests ◽  
Integral Model ◽  
Strain Rates ◽  
Test Results ◽  
Approach Method ◽  
The Difference

The strain rates in actual transients of operating plants are not constant and changing momentarily. A large number of fatigue tests under stepwise strain rate changing conditions were performed to develop a method for evaluating fatigue life under varying strain rate conditions. Based on these test results, a strain base integral model known as the named the modified rate approach method was developed and verified. However it was reported recently that in the case of sine wave fatigue tests in BWR environment, the fatigue life was two to six times longer than the fatigue life predicted by the modified rate approach method. For this paper, in order to confirm whether the same tendency is observed in PWR environment, fatigue tests of sine wave were performed of SS316 in simulated PWR water environment. As the result, the difference of fatigue life by sine wave test reported in BWR environment was not observed between experimental and predicted life in PWR environment and the modified rate approach method was applicable under continuous strain rate changing condition.

Fatigue Evaluation Under Continuous Strain Rate Changing Condition of Carbon Steel in BWR Environment

2014 ◽  
Author(s):  
Akihiko Hirano ◽  
Satoko Mizuta
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
Strain Rate ◽  
Fatigue Test ◽  
Fatigue Tests ◽  
Wave Form ◽  
Strain Wave ◽  
Water Reactor ◽  
Component Size ◽  
Fatigue Evaluation

Fatigue evaluation methods have been proposed based on environmental fatigue test results regarding parameters selected for simulating Boiling Water Reactor (BWR) and Pressurized Water Reactor (PWR) conditions. The effects of strain wave form have been discussed by comparing experimental fatigue life with predicted fatigue life evaluated by modified rate approach (MRA) method. The applicability of the MRA method has been verified extensively by the environmental fatigue tests with strain rate changing conditions consisting of combined constant strain rates. However, different results have been obtained for a sine strain wave in simulated BWR and PWR conditions. More study for evaluating the applicability of MRA method was required by evaluating with continuous strain rate conditions such as a sine wave. For the purpose of verification, two approaches were applied. One is performing the environmental fatigue tests with the sine strain wave in simulated BWR condition. The other is to evaluate the low cycle thermal fatigue test performed in simulated BWR condition because the wave form of this test contains continuous strain rate changing condition. MRA method was indicated to be applicable to predict fatigue lives under these kinds of continuous strain rate changing conditions. All of the studies including this study verifying the applicability of the MRA method were performed with small specimens having the well polished surfaces in the gage length. These results indicate that the evaluation by the MRA method includes the synergistic effect between the water environment and the transient. However, the synergistic effects with the surface roughness and the component size are not known. Design margin derived by the multiplication of the sub-factors of environment, surface roughness and component size may be conservative. The evaluation of the conservatism is considered to be beneficial.

Plastic Work Interaction Damage Rule Applied to Narrow-Band Gaussian Random Stress Situations

1988 ◽  
Vol 110 (1) ◽  
pp. 88-90 ◽  
Author(s):  
R. G. Lambert
Keyword(s):  
Fatigue Life ◽  
Narrow Band ◽  
Mathematical Expression ◽  
Fatigue Tests ◽  
Plastic Work ◽  
Wave Form ◽  
Work Interaction ◽  
Parameter Values ◽  
Life Parameter ◽  
Damage Rule

Fatigue life estimates that use a structural material’s constant amplitude stress life data values and a linear cumulative damage rule are always nonconservative for stress histories containing numerous subcycles and only a few large-amplitude cycles. Conservative fatigue life estimates were previously achieved by others with a plastic work interaction damage rule using the material’s overstrain fatigue life parameter values. Verification fatigue tests were run on laboratory specimens of 1020 steel using four selected variable amplitude stress wave form profiles. This paper extends the application of the plastic work interaction damage rule to narrowband Gaussian random stress situations. The derived stress life mathematical expression is of a power law form. The predicted fatigue life is more accurate than that predicted using a conventional linear damage rule.

scholarly journals IMPROVEMENT OF FATIGUE LIFE OF A HOLED SPECIMEN OF ALUMINUM-ALLOY 2024-T3 BY INDENTATION AND HOLE EXPANSION

2012 ◽  
Vol 06 ◽  
pp. 336-342 ◽  
Author(s):  
MD. SHAFIUL FERDOUS ◽  
CHOBIN MAKABE ◽  
TATSUJIRO MIYAZAKI ◽  
NOBUSUKE HATTORI
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Crack Growth ◽  
Testing Machine ◽  
Fatigue Tests ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Local Plastic ◽  
Aluminum Alloy 2024 ◽  
Pull Tests

A method of improving the fatigue life and crack growth behavior of a center holed specimen was investigated. Local plastic deformation was applied around the hole by indentation to achieve the purpose. A series of fatigue tests was conducted on aluminum-alloy 2024-T3. Push-pull tests were performed under a stress ratio of R= -1 and a frequency of 10Hz. The observations of the crack initiation and growth were performed with a microscope, and hardness around the hole was measured by Vickers hardness testing machine. In the present study, the longest fatigue life was observed in the case of an indentation specimen with the highest load. The indentation was performed on both sides of the hole edges. The crack growth rate was decreased by indentation or expansion of the material around the hole. From the experimental results, it is found that the fatigue life and crack growth behavior of a holed or notched specimen can be improved by a simple technical method that is related to the local plastic working.

A Study on Fatigue Behavior of SM490A Steel under Low Temperature

2007 ◽  
Vol 353-358 ◽  
pp. 142-145 ◽  
Author(s):  
Ki Weon Kang ◽  
Byeong Choon Goo ◽  
J.H. Kim ◽  
Heung Seob Kim ◽  
Jung Kyu Kim
Keyword(s):  
Fatigue Life ◽  
Low Temperature ◽  
Test Temperature ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Testing Machine ◽  
Fatigue Tests ◽  
Static Strength ◽  
Experimental Results ◽  
Railway Vehicle

This paper deals with the fatigue behavior and its statistical properties of SM490A steel at various temperatures, which is utilized in the railway vehicle. For these goals, the tensile ad fatigue tests were performed by using a servo-hydraulic fatigue testing machine at three temperatures: +20°C, -10°C and -40°C. The static strength and fatigue limits of SM490A steel were increased with decreasing of test temperature. The probabilistic properties of fatigue behavior are investigated by means of probabilistic stress-life (P-S-N) curve and they are well in conformance with the experimental results regardless of temperature. Also, based on P-S-N curves, the variation of fatigue life is investigated and as the temperature decreases, the variation of fatigue life increases moderately.

scholarly journals Effect of Fatigue Life of Dissimilar Aluminium Alloy (AA 5083 - AA 6062) Joining by Friction Stir Welding

2019 ◽  
pp. 314-319
Author(s):  
Sunit Yadav ◽  
Kamal Kanaujia ◽  
Ravi Shukla ◽  
Reetesh Shukla
Keyword(s):  
Friction Stir Welding ◽  
Testing Machine ◽  
Rolling Direction ◽  
Tensile Tests ◽  
Processing Parameters ◽  
Sine Wave ◽  
Fatigue Tests ◽  
Control Mode ◽  
Amplitude Control ◽  
Friction Stir

The effect of processing parameters on the mechanical and microstructural properties of dissimilarAA5083–AA6062 joints produced by friction stir welding was analysed in this study. Different samples were produced by varying the advancing speeds of the tool as 5 mm/min and by varying the alloy positioned on the advancing side of the tool. In all the experiments the rotating speed is fixed at1200 RPM. All the welds were produced perpendicularly to the rolling direction for both the alloys. Microhardness (HV) and tensile tests performed at room temperature were used to evaluate the mechanical properties of the joints. For the mechanical fatigue tests, a resonant electromechanical testing machine was employed under constant loading control up to 10 Hz sine wave loading. The fatigue tests were conducted in the axial total stress–amplitude control mode, with R = rmin/rmax = -1. In order to analyse the microstructural evolution of the material, the welds’ cross-sections a SEM observation was made of the fracture surfaces.

scholarly journals Flexural Fatigue Behaviors of Silicon Carbide Recycled Concrete in Corrosive Environments

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Jinzhi Zhou ◽  
Tiantian Fu ◽  
Chuheng Zhong ◽  
Kun Peng ◽  
Ziyang Shuang
Keyword(s):  
Silicon Carbide ◽  
Fatigue Life ◽  
Failure Probability ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Fatigue Tests ◽  
Recycled Concrete ◽  
Flexural Fatigue ◽  
Corrosive Environments ◽  
The Relationship

An experimental study on the flexural fatigue behaviors of recycled concrete (RC) and silicon carbide recycled concrete (SiCRC) was conducted. The immersion time was 0 d, 30 d, 60 d, and 90 d in 5% NaCl solution for these two kinds of recycled concrete specimens, respectively, and then, four-point flexural fatigue tests were performed by MTS fatigue testing machine. The fatigue life for varying stress levels ranging from 0.9 to 0.6 was obtained. The fatigue life was given considering the failure probability according to the fatigue life and stress level of the specimen via the logarithmic normal distribution and Weibull distribution, respectively. The relationship between fatigue life and failure probability was also obtained. The fatigue life with failure probability of 1% and 50% was further predicted. The results showed that the fatigue life of RC and SiCRC increased in corrosive environments. The fatigue life of SiCRC is higher than that of RC, and the incorporation of SiCRC can improve the fatigue life of recycled concrete.

Spalling Fatigue Life Assessment of Surface Hardened Sintered Gears Based on Fracture Mechanics

2003 ◽  
Author(s):  
Yuji Ohue ◽  
Akira Yoshida ◽  
Masanori Seki
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Testing Machine ◽  
Fem Analysis ◽  
Induction Hardening ◽  
Fatigue Tests ◽  
Rolling Contact ◽  
Life Assessment ◽  
Hertzian Contact ◽  
Ion Nitriding

In order to evaluate the surface durability of surface-hardened sintered gears, the fatigue lives of 5 kinds of sintered gears and 28 kinds of sintered rollers under sliding-rolling contact conditions were examined and estimated based on the fracture mechanics. The sintered gears and rollers were surface-hardened by induction-hardening and ion-nitriding. The fatigue tests were conducted using a power circulating gear testing machine and two cylinder testing machines. The pore distributions included in the sintered materials were observed and were analyzed statistically. The failure mode of the sintered gears and roller was mainly spalling. The stress intensity factor obtained by FEM analysis for the mode II under a condition of Hertzian contact became larger as the crack length became longer. The estimation of fatigue life of the sintered gears and rollers was attempted using the pore distributions and the fracture mechanics. The estimated fatigue lives were almost the same as the tested fatigue ones. Therefore, it could be said that the crack propagation of the sintered gears and rollers depended on the pore size and hardness.

scholarly journals Bending and Torsion Fatigue-Testing Machine Developed for Multiaxial Non-Proportional Loading

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1115 ◽  
Author(s):  
Fumio Ogawa ◽  
Yusuke Shimizu ◽  
Stefano Bressan ◽  
Takahiro Morishita ◽  
Takamoto Itoh
Keyword(s):  
Fatigue Life ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
304 Stainless Steel ◽  
Testing Time ◽  
Loading Conditions ◽  
Proportional Loading ◽  
Bending Loading

A new fatigue-testing machine was developed to perform high-cycle multiaxial fatigue tests at 50 Hz, in order to reduce testing time. The developed machine can combine bending and torsion loading and perform fatigue tests at a high frequency, under proportional and non-proportional loading conditions, where the principal stress direction changes during a cycle. The proportional loading is cyclic bending loading, and the non-proportional loading is cyclic, combining bending and reversed torsion loading. In this study, the effectiveness of the testing machine was verified by conducting tests under these loading conditions, using specimens of type 490A hot-rolled steel and type 304 stainless steel. The fatigue life linked to bending loading obtained using the new testing machine was slightly extended compared with that obtained using the conventional fatigue-testing machine. The fatigue life derived as a result of a combination of bending and torsion was comparable to that obtained using the conventional fatigue-testing machine, although a fatigue limit reduction of 100 MPa was observed compared to the former study. The feasibility of tests using the developed multiaxial fatigue-testing machine was confirmed.

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