Zeitschriftenartikel: „Ultrasonic fatigue tests“

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XUE, H., D. WAGNER, N. RANC und E. BAYRAKTAR. „Thermographic analysis in ultrasonic fatigue tests“. Fatigue Fracture of Engineering Materials and Structures 29, Nr. 7 (Juli 2006): 573–80. http://dx.doi.org/10.1111/j.1460-2695.2006.01024.x.

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Kasap, S. O., S. Yannacopoulos, V. Mirchandani und J. R. Hildebrandt. „Ultrasonic Evaluation of Thermal Fatigue of Composites“. Journal of Engineering Materials and Technology 114, Nr. 2 (01.04.1992): 132–36. http://dx.doi.org/10.1115/1.2904151.

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Results are presented on the evaluation of thermally fatigued E-glass composite specimens using ultrasonic techniques. The changes of the acoustic velocity and the attenuation coefficient in the ultrasonic range have been examined as a function of accumulated damage in various thermally fatigued composites. Three types of E-glass fiber reinforced composites have been used in this study having the following fiberglass weaves: (a) randomly oriented short fiber, (b) uniaxial fiber mat with continuous fiber bundles, (c) bidirectional continuous glass fiber mat. Representative specimens were subjected to thermal fatigue by thermal cycling between 25°C and 75°C. The structural integrity of these specimens was evaluated by determining the flexural strength after a number of thermal cycles via three point bending tests. It was observed that both the acoustic velocity and the flexural strength decreased whereas the ultrasonic attenuation increased with the number of thermal cycles which have been attributed to an accumulation of defects in the material and especially to debonding at the fiber-matrix interface. It has been observed that the use of ultrasonics may be very appropriate in evaluating composites in service since a good correlation has been noted between changes in the flexural strength, acoustic velocity and the attenuation coefficient in thermally fatigued composites.

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Peng, Wen Jie, Bao Wen Qiu, Rong Feng Li und Huan Xue. „Ultrasonic Fatigue Tests on a High Strength Steel for Welded Structure“. Advanced Materials Research 503-504 (April 2012): 714–17. http://dx.doi.org/10.4028/www.scientific.net/amr.503-504.714.

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In this paper, the ultrasonic fatigue machine which works at frequency of 20kHz is utilized to conduct the ultrasonic fatigue tests on a high strength welding structural steel with symmetric cycle stress R=－1 at room temperature. Two typical specimen geometries are tested: smooth specimen and notch specimen. The fatigue tests of smooth specimen are also carried out on the electromagnetic resonance equipment at conventional frequency. A comparison is made between the fatigue test results at the ultrasonic and conventional frequency.

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Yamane, K., Norio Kawagoishi, Kazuhiro Morino und K. Fukada. „Ultrasonic Fatigue of Radical Nitrided Ni-Base Superalloy“. Key Engineering Materials 417-418 (Oktober 2009): 209–12. http://dx.doi.org/10.4028/www.scientific.net/kem.417-418.209.

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Ultrasonic and rotating bending fatigue tests were carried out for aged and nitrided Ni-base super alloys to investigate the effects of loading frequency and nitriding on fatigue strength. Loading frequencies were 19.5 kHz under ultrasonic and 50 Hz under rotating bending, respectively. Fatigue strength under ultrasonic was higher than that under rotating bending in both alloys. Moreover, in both tests, fatigue strength was improved by nitriding. The increase in fatigue strength by nitriding was large in ultrasonic fatigue. These results were discussed through the successive observation of fatigue process at specimen surface and fracture surface observation.

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Fukudome, T., Norio Kawagoishi und K. Kariya. „Effect of Humidity on Fatigue Strength of Age-Hardened Al Alloy“. Key Engineering Materials 417-418 (Oktober 2009): 373–76. http://dx.doi.org/10.4028/www.scientific.net/kem.417-418.373.

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Ultrasonic and rotating bending fatigue tests were carried out using plain specimens and specimens with a small blind hole for an extruded and age-hardened Al alloy 7075-T6 in different environments in order to investigate the effect of humidity on fatigue strength and fracture mechanism. Fatigue strength was decreased by high humidity under both tests. The effect of humidity on fatigue strength was larger in ultrasonic fatigue. The humidity affected both of crack initiation and propagation processes. Crack propagated in tensile mode then changed to shear mode macroscopically in all environments under ultrasonic fatigue, though it was only in tensile mode under rotating bending fatigue. These differences in fracture mechanism related to the difference in environmental effect on fatigue strength in both tests.

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Dominguez Almaraz, Gonzalo M., Manuel Guzmán Tapia und Alexiane Dominguez. „Ultrasonic Fatigue Tests on the Inconel Alloy 718“. Procedia Structural Integrity 26 (2020): 20–27. http://dx.doi.org/10.1016/j.prostr.2020.06.004.

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7

Fitzka, Michael, Bernd M. Schönbauer, Robert K. Rhein, Niloofar Sanaei, Shahab Zekriardehani, Srinivasan Arjun Tekalur, Jason W. Carroll und Herwig Mayer. „Usability of Ultrasonic Frequency Testing for Rapid Generation of High and Very High Cycle Fatigue Data“. Materials 14, Nr. 9 (27.04.2021): 2245. http://dx.doi.org/10.3390/ma14092245.

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Ultrasonic fatigue testing is an increasingly used method to study the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) properties of materials. Specimens are cycled at an ultrasonic frequency, which leads to a drastic reduction of testing times. This work focused on summarising the current understanding, based on literature data and original work, whether and how fatigue properties measured with ultrasonic and conventional equipment are comparable. Aluminium alloys are not strain-rate sensitive. A weaker influence of air humidity at ultrasonic frequencies may lead to prolonged lifetimes in some alloys, and tests in high humidity or distilled water can better approximate environmental conditions at low frequencies. High-strength steels are insensitive to the cycling frequency. Strain rate sensitivity of ferrite causes prolonged lifetimes in those steels that show crack initiation in the ferritic phase. Austenitic stainless steels are less prone to frequency effects. Fatigue properties of titanium alloys and nickel alloys are insensitive to testing frequency. Limited data for magnesium alloys and graphite suggest no frequency influence. Ultrasonic fatigue tests of a glass fibre-reinforced polymer delivered comparable lifetimes to servo-hydraulic tests, suggesting that high-frequency testing is, in principle, applicable to fibre-reinforced polymer composites. The use of equipment with closed-loop control of vibration amplitude and resonance frequency is strongly advised since this guarantees high accuracy and reproducibility of ultrasonic tests. Pulsed loading and appropriate cooling serve to avoid specimen heating.

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Furuya, Yoshiyuki, Kazuo Kobayashi, Masao Hayakawa, Masao Sakamoto, Yutaka Koizumi und Hiroshi Harada. „High-Temperature Ultrasonic Fatigue Testing at 1000°C“. Advanced Materials Research 891-892 (März 2014): 1413–18. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.1413.

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A high-temperature ultrasonic fatigue testing system was developed to evaluate the gigacycle fatigue properties of single-crystal superalloys used in aircraft engine turbine blades. In this development, a commercial ultrasonic fatigue testing machine was considerably modified to achieve high-temperature fatigue testing. The developed system took account of temperature dependency of Youngs modulus, and also had a function to evaluate the Youngs modulus. In order to protect the testing system from the heat of a specimen, straight and round rods were inserted between the testing system and the specimen. Other modifications achieved accurate control of temperature, edge displacement and resonance frequency, which were necessary for accurate control of stress amplitude. The testing system was first applied to a heat-resistant steel at 650 °C to check its accuracy, and next to SC superalloy samples at 1000 °C. In the conventional fatigue tests on the heat-resistant steel, the results were coincident in a frequency range from 1 Hz to 800 Hz, suggesting that comparable results would be obtained in ultrasonic fatigue testing at 20 kHz. In case of the SC superalloy samples, conventional fatigue tests were conducted at only 10 Hz, so the frequency effects were not clarified. In both cases, ultrasonic fatigue testing showed good agreement with conventional fatigue testing. The accuracy of the developed system is therefore high, even at 1000 °C. In these results, the SC superalloys showed no fatigue limit, indicating gigacycle fatigue tests to be necessary.

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SAKURAI, Keigo, Yuma MIYAI, Shota HASUNUMA, Takeshi OGAWA, Myunghun WOO und Masahiro TAKANASHI. „Fatigue Crack Growth Threshold of Ni Based Castalloys Using Ultrasonic Fatigue Tests“. Journal of the Society of Materials Science, Japan 66, Nr. 12 (2017): 879–86. http://dx.doi.org/10.2472/jsms.66.879.

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Peng, Wen Jie, Hui Cai Long, Li Yu, Huan Xue, Bao Wen Qiu und Yan Wen Zhang. „An Investigation of Size Effect on Fatigue Property of 3000 MPa-Class Mould Steel Under Ultrasonic Fatigue Testing“. Applied Mechanics and Materials 239-240 (Dezember 2012): 88–91. http://dx.doi.org/10.4028/www.scientific.net/amm.239-240.88.

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Ultrasonic fatigue testing was conducted for 3000 MPa-class mould steel to investigate the fatigue behavior. The fatigue specimen is designed particularly due to the ultra-high strength. Ultrasonic fatigue tests are conduced using two types of specimen sizes and the test results are compared to investigate the size effect on the fatigue property.

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Yan, Nu, Qing Yuan Wang, Q. Chen und J. J. Sun. „Influence of Loading Frequency on Fatigue Behavior of High Strength Steel“. Key Engineering Materials 353-358 (September 2007): 227–30. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.227.

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In order to investigate the influence of loading frequency on the fatigue behaviors of the high strength steel, ultrasonic fatigue tests were carried out for a high-carbon-chromium steel and the results were compared with those of fatigue tests using conventional rotary bending fatigue test machine with a frequency of 52.5Hz. The different of fatigue strength at ultrasonic frequency level and conventional frequency level is very small and the S-N curve obtained from 20 kHz or 52.5 Hz shows the step-wise shape. The fatigue crack occurred from inclusions on the subsurface site in the long life regime and the typical surface fracture occurred in the short life one though the loading frequency level is different. It is indicated that ultrasonic fatigue method is an effective method to investigate the fatigue properties in super-long life region.

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Peng, Wen Jie, Li Yu, Hui Cai Long, Huan Xue, Lan Xiang Kuang und Bao Wen Qiu. „An Investigation of the Fatigue Property of Ultra-High Strength Mould Steel at 130 Hz and 20 kHz“. Applied Mechanics and Materials 239-240 (Dezember 2012): 96–99. http://dx.doi.org/10.4028/www.scientific.net/amm.239-240.96.

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In this paper, the fatigue property of ultra-high strength mould steel is investigated. The fatigue specimen is designed particularly due to the ultra-high strength. Fatigue tests are conduced using ultrasonic and conventional fatigue testing machines respectively. The same geometry and size of the ultrasonic fatigue specimens and conventional fatigue specimens are adopted to overcome the size effects. The test results are compared to investigate the frequency effect.

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Li, Jiu Kai, Yong Jie Liu, Qing Yuan Wang und Fang Hou. „Effect of Temperature and Loading Frequency on the Fatigue Behavior of Ti-17“. Key Engineering Materials 664 (September 2015): 131–39. http://dx.doi.org/10.4028/www.scientific.net/kem.664.131.

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A high-temperature ultrasonic fatigue testing system was developed to evaluate the gigacycle fatigue properties of Ti-17. Ultrasonic (20 kHz) fatigue tests were performed at room temperature, 200°C and 350°C, respectively. The dynamic Young’s modulus and fatigue endurance limit decrease with increasing temperature linearly. Rotating bending (50 Hz) tests were performed to evaluate the influence of loading frequency at room temperature, 200°C and 350°C, respectively. There is an obviously loading frequency effect at elevated temperature, although no loading frequency effect at room temperature.

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Schneider, Norbert, Brita Pyttel, Christina Berger und Matthias Oechsner. „Influence of Frequency and Testing Technique on the Fatigue Behaviour of Quenched and Tempered Steel in the VHCF-Regime“. Advanced Materials Research 891-892 (März 2014): 1430–35. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.1430.

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Today in many cases ultrasonic testing machines with a frequency of f ≈ 20 kHz are used for investigations of the fatigue behaviour up to the very high cycle regime (VHCF-regime). A question that arises is if the results of these high frequency fatigue tests are comparable to conventional fatigue tests. This paper compares the fatigue behaviour of a quenched and tempered steel 50CrMo4 in two different tempered conditions investigated at low frequencies (f ≤ 400 Hz) on a servohydraulic testing machine and at a high frequency (f ≈ 20 kHz) on an ultrasonic fatigue testing machine. Effects which can occur because of the different testing techniques and testing frequencies are investigated. A concept is derived to describe the frequency effect caused by the strain rate. The estimations are compared with results of the fatigue tests.

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Zuñiga Tello, Ishvari F., Marijana Milković, Gonzalo M. Domínguez Almaraz und Nenad Gubeljak. „Ultrasonic and Conventional Fatigue Endurance of Aeronautical Aluminum Alloy 7075-T6, with Artificial and Induced Pre-Corrosion“. Metals 10, Nr. 8 (01.08.2020): 1033. http://dx.doi.org/10.3390/met10081033.

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Ultrasonic and conventional fatigue tests were carried out on the AISI-SAE AA7075-T6 aluminum alloy, in order to evaluate the effect of artificial and induced pre-corrosion. Artificial pre-corrosion was obtained by two hemispherical pitting holes of 500-μm diameter at the specimen neck section, machined following the longitudinal or transverse direction of the testing specimen. Induced pre-corrosion was achieved using the international standard ESA ECSS-Q-ST-70-37C of the European Space Agency. Specimens were tested under ultrasonic fatigue technique at frequency of 20 kHz and under conventional fatigue at frequency of 20 Hz. The two applied load ratios were: R = −1 in ultrasonic fatigue tests and R = 0.1 in conventional fatigue tests. The main results were the effects of artificial and induced pre-corrosion on the fatigue endurance, together with the surface roughness modification after the conventional fatigue tests. Crack initiation and propagation were analyzed and numeric models were constructed to investigate the stress concentration associated with pre-corrosion pits, together with the evaluation of the stress intensity factor in mode I from crack initiation to fracture. Finally, the stress intensity factor range threshold ΔKTH was obtained for the base material and specimens with two hemispherical pits in transverse direction.

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da Costa, Pedro R., Diogo Montalvão, Manuel Freitas und Luis Reis. „Ultrasonic fatigue experiments with biaxial cruciform specimens“. MATEC Web of Conferences 300 (2019): 18004. http://dx.doi.org/10.1051/matecconf/201930018004.

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Fatigue studies of materials in simple or complex loading systems for any given lifetime is object of continuous research. This is due to the advancements on mechanical and structural components, as well as for new and innovative materials, which implies the knowledge of a materials response to all dynamic loads. The fatigue failure regime beyond what was once considered to be the fatigue limit (infinite life) is characterized between 107 and 109, known as Very High Cycle Fatigue regime. Due to the time consuming and wide energy consumption of conventional fatigue testing for such regime, fatigue tests under ultrasonic actuators are being used, capable of applying the dynamic loads at around 20 kHz. Nowadays, several variants of ultrasonic fatigue tests were already proposed and tested but it is still a somewhat limited fatigue test if compared to the conventional servo-hydraulic fatigue testing machines of general use. In this study, biaxial in plane stresses are induced in specially designed cruciform specimens with ultrasonic fatigue testing resonant principals. Two geometries were numerically analysed, manufactured and experimentally tested, the in-phase tension-tension (T-T) specimen and the out-of-phase compression-tension (C-T) specimen. All specific designed geometries go under a thorough numerical and several experiments analysis for their validation. The specimens showing a correct and as intended behaviour are led to failure.

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Ebara, Ryuichiro, und Yuya Miyoshi. „Ultrasonic Corrosion Fatigue Behaviorof Duplex Stainless Steel“. Key Engineering Materials 577-578 (September 2013): 421–24. http://dx.doi.org/10.4028/www.scientific.net/kem.577-578.421.

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Ultrasonic Corrosion Fatigue Tests were Conducted for SUS329J3L in Air and 3%NaCl Aqueous Solution. Reduction of Giga-Cycle Corrosion Fatigue Strength was 12.5%. Corrosion Pit was Observed on Corrosion Fatigue Crack Initiation Area. Striation was Predominantly Observed on Crack Propagation Area both in Air and 3% Nacl Aqueous Solution. it can be Concluded that the Reduction of Corrosion Fatigue Strength of SUS329J3L is due to the Corrosion Pit Formation at Corrosion Fatigue Crack Initiation Area.

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Tridello, Andrea, Davide Salvatore Paolino und Massimo Rossetto. „Ultrasonic VHCF Tests on Very Large Specimens with Risk-Volume Up to 5000 mm3“. Applied Sciences 10, Nr. 7 (25.03.2020): 2210. http://dx.doi.org/10.3390/app10072210.

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The research on the size-effects in Very-High-Cycle Fatigue (VHCF) has recently drawn the attention of several scholars. The fatigue cracks in VHCF originate from the largest defect present within the loaded material volume (risk-volume) and the larger the risk-volume, the larger the probability of critical defects affecting the VHCF response (size-effect). Many models have been proposed in the literature to deal with size-effects in VHCF. However, the proposed models cannot be validated on full-scale components, since VHCF tests are typically carried out with ultrasonic fatigue testing machines. The authors have proposed a specimen geometry, the so-called Gaussian specimens, to enlarge as much as possible the risk-volume in ultrasonic VHCF tests. In this study, fully reversed tension–compression ultrasonic VHCF tests up to 109 cycles were carried out on AISI H13 steel Gaussian specimens with a risk-volume of 5000 mm3, two times larger than the largest tested in the literature. The stress distribution and the absence of bending loads were verified with strain gages, proving that VHCF tests on risk-volumes of 5000 mm3 can be reliably carried out. Ultrasonic VHCF tests were also carried out on small hourglass specimens, confirming that larger risk-volumes allow for a more reliable design against VHCF failures.

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Wagner, D., F. J. Cavalieri, C. Bathias und N. Ranc. „Ultrasonic fatigue tests at high temperature on an austenitic steel“. Propulsion and Power Research 1, Nr. 1 (Dezember 2012): 29–35. http://dx.doi.org/10.1016/j.jppr.2012.10.008.

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Wu, Liang Chen, und Dong Po Wang. „Effect of Welding Residual Stress on Fatigue Performance of the Welded Joints Treated by Ultrasonic Peening“. Advanced Materials Research 418-420 (Dezember 2011): 337–41. http://dx.doi.org/10.4028/www.scientific.net/amr.418-420.337.

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The fatigue tests of Q235B steel unload longitudinal fillet welded joints containing high welding residual stress were carried out. And the effect of welding residual stress on fatigue performance of the welded joints treated by ultrasonic peening has been studied. Specimens were divided into four groups: as welded, specimens treated by ultrasonic peening(UP), specimens treated by stress relief treatment(SRT) and specimens treated by both ultrasonic peening and stress relief treatment(UP+SRT). Test results show that the effect on fatigue performance of the welded joints treated by ultrasonic peening from welding residual stress is small. It is safe that using the small specimens treated by ultrasonic peening and not containing high welding residual stress to appraise the fatigue performance improvement on large-scale welded structures which are as the same junction style and thickness as the small.

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Cobb, A. C., J. E. Michaels und T. E. Michaels. „An integrated approach to local ultrasonic monitoring of fastener hole fatigue cracks“. Aeronautical Journal 113, Nr. 1150 (Dezember 2009): 775–88. http://dx.doi.org/10.1017/s0001924000003432.

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Abstract Ultrasonic nondestructive evaluation methods are routinely used to detect and size fatigue cracks near fastener holes in aircraft structures as a part of scheduled maintenance. In contrast, statistical crack propagation models provide an estimate of the expected fatigue life assuming a known crack size and future fatigue loadings. Here an integrated approach for in situ diagnosis and prognosis of fastener hole fatigue cracks is proposed and implemented that incorporates both ultrasonic monitoring and crack growth laws. The sensing method is an ultrasonic angle beam technique, and cracks are automatically detected from the ultrasonic response. An extended Kalman filter is applied to combine ultrasonically estimated crack sizes with a crack growth law, effectively using the time history of the ultrasonic results rather than only the most recent measurement. A natural extension of this method is fatigue life prognosis. Results from fatigue tests on 7075-T651 aluminium coupons show improved crack size estimates as compared to those obtained from ultrasonic measurements alone, and also demonstrate the capability of predicting the remaining life. This approach for fatigue crack detection, sizing and prognosis is an example of a general strategy for in situ monitoring of structural damage whereby improved results are achieved from the integration of noisy measurements with imperfect crack growth models.

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Fitzka, M., H. Rennhofer, D. Catoor, M. Reiterer, H. Lichtenegger, S. Checchia, M. di Michiel, D. Irrasch, T. A. Gruenewald und H. Mayer. „High Speed In Situ Synchrotron Observation of Cyclic Deformation and Phase Transformation of Superelastic Nitinol at Ultrasonic Frequency“. Experimental Mechanics 60, Nr. 3 (05.12.2019): 317–28. http://dx.doi.org/10.1007/s11340-019-00562-8.

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AbstractThe near equi-atomic intermetallic Ni Ti alloy Nitinol is used for medical implants, notably in self-expanding stent grafts and heart valve frames, which are subjected to several hundred million load cycles in service. Increasing the testing frequency to the ultrasonic range would drastically shorten the testing times and make the very-high cycle regime experimentally accessible. Such tests are, however, only meaningful if the material response at ultrasonic frequency is identical to that observed in conventional fatigue tests. A novel fatigue testing setup where superelastic Nitinol dog bone specimens are loaded at ultrasonic cycling frequency is presented. Loading conditions resemble in vivo loading (i.e., repeated cyclic loading with relatively small strain amplitudes, specimens in a pre-strained multi-phase state). Strains and phase transformations during ultrasonic frequency cycling are quantitatively measured in an X-ray diffraction (XRD) synchrotron experiment and compared to the material response at low frequency. The XRD experiment confirms that forward and reverse stress-induced phase transformation from austenite to martensite via the intermediate R-phase occurs during low frequency (0.1 Hz, strain rate $$ \dot{\varepsilon}\approx $$ε˙≈ 10−3 s−1) and ultrasonic frequency (20 kHz, $$ \dot{\varepsilon}\approx $$ε˙≈ 102 s−1) cycling. Since the same deformation mechanisms are active at low and ultrasonic frequency, these findings imply a general applicability of the ultrasonic fatigue testing technique to Nitinol.

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Dong, Hong Lei, Zhong Guo Huang, Qing Hua Yuan und Jia Fan. „Research on Fatigue Test of LZ20Mn2 Axle Pipe Steel“. Applied Mechanics and Materials 44-47 (Dezember 2010): 2152–56. http://dx.doi.org/10.4028/www.scientific.net/amm.44-47.2152.

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The core of ultrasonic accelerate fatigue test is resonance, and specimens need resonating with the system. The ultrasonic fatigue test method was used to investigate the high cycle fatigue properties of LZ20Mn2 axle pipe steel. Tests were conducted on cylindrical dog-bone specimens, and all fatigue loadings were controlled by inputting vibration amplitude. The results showed that the S-N curve of LZ20Mn2 axle pipe steel presented a slow-decline shape and subsurface crack initiation. The fatigue fracture was observed by SEM. Two different crack initiation mechanisms were observed which were the mixed inclusions and dislocation. Crack closure effect played an important role at fatigue crack propagation area and the fracture mechanism was a typical plastic fracture.

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Zhang, Wei Chang, Ming Liang Zhu und Fu Zhen Xuan. „Experimental Characterization of Competition of Surface and Internal Damage in Very High Cycle Fatigue Regime“. Key Engineering Materials 754 (September 2017): 79–82. http://dx.doi.org/10.4028/www.scientific.net/kem.754.79.

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Axially push-pull cyclic tests of a low strength rotor steel were performed up to the very high cycle fatigue regime at ambient environment under ultrasonic frequency. Fatigue tests were interrupted at selected number of cycles for surface morphology observation and roughness measurement with the help of a 3D surface measurement system (Alicona InfiniteFocusSL). The fatigue extrusions and slip band developed on the specimen surface were recorded. The influence of stress level on the number and morphology of slip band was discussed. The surface roughness of fatigue specimens was found to be increased with the increasing of fatigue cycles. The fatigued specimens were finally cracked from surface or interior micro-defects after observation of fracture surface by scanning electron microscopy. The internal damage behavior consists of crack initiation and early propagation from micro-defect, crack growth within the fish eye, and fast crack growth. It is observed that there exists a competition between surface and internal fatigue damage in the very high cycle fatigue regime, i.e., surface damage is gradually developed with the increasing of fatigue cycles, while the critical interior micro-defect can be dominant for fatigue cracking.

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Pirinu, Alessandra, und Francesco Panella. „Fatigue Damage Monitoring of CFRP Elements by Thermographic Procedure under Bending Loads“. Key Engineering Materials 873 (Januar 2021): 47–52. http://dx.doi.org/10.4028/www.scientific.net/kem.873.47.

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For structural health of mechanical structures, non-destructive detection and material defect characterization represent the main useful tools for mechanical decay prediction caused by local composite damage phenomena. In this work, internal delamination due to alternate bending were characterized in flat specimens, performing fatigue and static tests, coupled with thermographic, optical, and ultrasonic analysis for damage detection and evolution purposes. Damage to rupture behavior of CFRP material through mechanical tensile tests is performed on several samples and non-destructive inspection procedures are optimized during successive HCF tests to detect in real time local compliance variations and damage initiation. Thermographic continuous monitoring and occasional ultrasonic analysis are implemented to analyze composite anomalies during fatigue life and to elaborate a procedure for identification of delamination induced damage before failure. IRT and UT results are computed with MATLAB analysis for damage evaluation with strain and compliance data acquired during tests.

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Kim, Namgyu, Keunyoung Jang und Yun-Kyu An. „Self-Sensing Nonlinear Ultrasonic Fatigue Crack Detection under Temperature Variation †“. Sensors 18, Nr. 8 (02.08.2018): 2527. http://dx.doi.org/10.3390/s18082527.

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This paper proposes a self-sensing nonlinear ultrasonic technique for fatigue crack detection under temperature variations. Fatigue cracks are identified from linear (α) and nonlinear (β) ultrasonic parameters recorded by a self-sensing piezoelectric transducer (PZT). The self-sensing PZT scheme minimizes the data acquisition system’s inherent nonlinearity, which often prevents the identification of fatigue cracks. Also, temperature-dependent false alarms are prevented based on the different behaviors of α and β. The proposed technique was numerically pre-validated with finite element method simulations to confirm the trends of α and β with changing temperature, and then was experimentally validated using an aluminum plate with an artificially induced fatigue crack. These validation tests reveal that fatigue cracks can be detected successfully in realistic conditions of unpredictable temperature and that positive false alarms of 0.12% occur.

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Kawagoishi, Norio, Q. Chen, M. Oki und Qing Yuan Wang. „Crack Growth Behavior of Al Alloy under Ultrasonic Fatigue“. Key Engineering Materials 324-325 (November 2006): 327–30. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.327.

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In order to investigate the effect of frequency on the crack growth behavior, ultrasonic fatigue tests were carried out for an extruded age-hardened Al alloy, 7075-T6, and the results were compared with those in rotating bending fatigue. Fatigue strength in ultrasonic was higher than that in rotating bending. This was mainly caused by the retardation of crack initiation. Growth direction of a crack changed from a tensile mode to a shear one in ultrasonic fatigue, though fracture occurred by the growth of a tensile mode in rotating bending. The growth direction of a shear mode crack was inclined about 55 degrees to the tensile axis. The relation between an applied stress σa and a crack depth at transition of growth direction T was expressed by a nT=C, where C and n are constants. These results were discussed from the points of view of the time dependent environmental effect and the texture of material.

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Luo, Xing Wen, und Hai Lin Yao. „Deformation and Acoustics Parameters Feature of Recycled Concrete under Cyclic Loading“. Applied Mechanics and Materials 80-81 (Juli 2011): 213–16. http://dx.doi.org/10.4028/www.scientific.net/amm.80-81.213.

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Concrete demolition waste has been proved to be an excellent source of aggregates for new concrete production. Four types of recycled concrete specimens were made for cyclic loading tests in laboratory, in order to research the acoustics parameters and deformation feature of recycled concrete under cyclic loading. Acoustics parameters such as ultrasonic wave time, ultrasonic velocity and ultrasonic amplitude of recycled concrete were tested synchronously while recycled concrete were loaded. Test results show the evolution of fatigue total strain of recycled concrete undergoes three stages. The cycle times in the three stages accounted for 10%, 80% and 10% of the fatigue life respectively. These stages can be simulated by power function equations, first-order linear equations and exponential functions accordingly. Tests results show that wave time increased with the rise of cyclic times, while wave amplitude decreased in the same time.

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Costa, Pedro, Richard Nwawe, Henrique Soares, Luís Reis, Manuel Freitas, Yong Chen und Diogo Montalvão. „Review of Multiaxial Testing for Very High Cycle Fatigue: From ‘Conventional’ to Ultrasonic Machines“. Machines 8, Nr. 2 (13.05.2020): 25. http://dx.doi.org/10.3390/machines8020025.

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Fatigue is one of the main causes for in service failure of mechanical components and structures. With the development of new materials, such as high strength aluminium or titanium alloys with different microstructures from steels, materials no longer have a fatigue limit in the classical sense, where it was accepted that they would have ‘infinite life’ from 10 million (107) cycles. The emergence of new materials used in critical mechanical parts, including parts obtained from metal additive manufacturing (AM), the need for weight reduction and the ambition to travel greater distances in shorter periods of time, have brought many challenges to design engineers, since they demand predictability of material properties and that they are readily available. Most fatigue testing today still uses uniaxial loads. However, it is generally recognised that multiaxial stresses occur in many full-scale structures, being rare the occurrence of pure uniaxial stress states. By combining both Ultrasonic Fatigue Testing with multiaxial testing through Single-Input-Multiple-Output Modal Analysis, the high costs of both equipment and time to conduct experiments have seen a massive improvement. It is presently possible to test materials under multiaxial loading conditions and for a very high number of cycles in a fraction of the time compared to non-ultrasonic fatigue testing methods (days compared to months or years). This work presents the current status of ultrasonic fatigue testing machines working at a frequency of 20 kHz to date, with emphasis on multiaxial fatigue and very high cycle fatigue. Special attention will be put into the performance of multiaxial fatigue tests of classical cylindrical specimens under tension/torsion and flat cruciform specimens under in-plane bi-axial testing using low cost piezoelectric transducers. Together with the description of the testing machines and associated instrumentation, some experimental results of fatigue tests are presented in order to demonstrate how ultrasonic fatigue testing can be used to determine the behaviour of a steel alloy from a railway wheel at very high cycle fatigue regime when subjected to multiaxial tension/torsion loadings.

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Vaško, Alan, Juraj Belan und Eva Tillová. „Study of the fatigue behaviour of synthetic nodular cast irons at low and high frequency cyclic loading“. MATEC Web of Conferences 157 (2018): 07014. http://dx.doi.org/10.1051/matecconf/201815707014.

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The paper presents the results of low and high frequency fatigue tests carried out on nodular cast iron. The specimens of synthetic nodular cast irons from three different melts were studied in the high cycle fatigue region (from 105 to 108 cycles) using fatigue experimental equipments for low and high frequency cyclic loading. Low frequency fatigue tests were carried out at frequency f ≈ 120 Hz using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100. High frequency fatigue tests were carried out at frequency f ≈ 20 kHz using the ultrasonic fatigue testing device KAUP-ZU. Both of them were carried out at sinusoidal cyclic push-pull loading (stress ratio R = -1) at ambient temperature (T ≈ 20 °C). The relationship σa = f (N) and fatigue strengths were determined experimentally; mechanical properties, microstructures and fracture surfaces were investigated.

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Soares, H., P. Costa, M. Freitas und L. Reis. „Fatigue life assessment of a railway wheel material under HCF and VHCF conditions“. MATEC Web of Conferences 165 (2018): 09003. http://dx.doi.org/10.1051/matecconf/201816509003.

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Fatigue damage and life assessment is still an issue and a challenge nowadays. Many different tests can be performed for the assessment of fatigue properties of any given material. In the present study a worn out railway wheel goes under uniaxial fatigue analyses for the high cycle and very high cycle fatigue regimes through the use of a conventional hydraulic machine and an ultrasonic fatigue test, both with a stress ratio of R=-1. For every used specimen, a life cycle is obtained for the corresponding induced specimen and the data is afterwards plotted. All the fracture surfaces of all failed specimens were analysed. The study and initial application of multiaxial ultrasonic fatigue condition and the design of the corresponding specimen for evaluating the wheel material is also presented.

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Kim, Bum Joon, Byeong Soo Lim, Sung Jin Song und Young H. Kim. „Application of Ultrasonic Test on Creep-Fatigue Life Evaluation“. Key Engineering Materials 321-323 (Oktober 2006): 476–79. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.476.

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This work investigates the relationship between the creep-fatigue life and ultrasonic test of creep-fatigue damage. Under the creep-fatigue interaction, the main cause of life reduction is the initiation and growth of microvoid with increasing hold time. The number/size of microvoid/cavity, the fraction of cavity area varied with the hold time. Therefore, the life evaluation using the microvoid with the variation of hold time is very informative for safety of components in power plants. In this study, using the heat resisting alloy, P122 steel for USC (ultra super critical) power plant, the creep-fatigue tests with various hold times and their ultrasonic inspection were carried out for the purpose of evaluation for creep-fatigue life. The results obtained by Rayleigh surface wave of backscattered ultrasound were compared and analyzed with the experimental parameters. The good agreement between the experimental life and the predicted life was obtained.

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Heinz, Stefan, und Dietmar Eifler. „Very High Cycle Fatigue and Damage Behavior of Ti6Al4V“. Key Engineering Materials 664 (September 2015): 71–80. http://dx.doi.org/10.4028/www.scientific.net/kem.664.71.

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High frequency fatigue tests were carried out with a 20 kHz ultrasonic testing facility to investigate the cyclic deformation behavior of Ti6Al4V in the Very High Cycle Fatigue (VHCF) regime in detail. The S,Nf -curve at the stress ratio R = -1 shows a significant decrease of the stress amplitude and a change from surface to subsurface failures in the VHCF regime for more than 107 cycles. Microscopic investigations of the distribution of the α-and β-phase of Ti6Al4V indicate that inhomogeneities in the phase distribution are reasons for the internal crack initiation. Scanning electron microscopy as well as light microscopy were used to investigate the internal crack initiation phenomenon in the VHCF-regime. Beside the primary fatigue crack additional defects like micro cracks and crack clusters were observed in the fatigued specimens. SEM-investigations of specimens which were loaded up to 1010 cycles without failure show irreversible microstructural changes inside the specimens. Two step tests were performed to evaluate the influence of internal fatigue induced defects observed in specimens which did not fail within 1010 cycles.

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Tridello, A., D. S. Paolino, G. Chiandussi und Massimo Rossetto. „Gaussian Specimens for Gigacycle Fatigue Tests: Evaluation of Temperature Increment“. Key Engineering Materials 627 (September 2014): 85–88. http://dx.doi.org/10.4028/www.scientific.net/kem.627.85.

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Experimental tests investigating very-high-cycle fatigue (VHCF) properties of materials are commonly performed with ultrasonic testing machines, which allow for a significant reduction of testing time. In order to evaluate the effect of tested material volume (size-effect) on VHCF properties, the Authors recently proposed to adopt Gaussian specimens for VHCF tests. Investigation of size-effect with Gaussian specimen induces large mechanical power dissipation and temperature increment that must be taken into account. The present paper proposes an analytical model, which allows to approximately predict the dissipated mechanical power and the temperature increment in Gaussian specimens. The analytical model is also numerically verified through a Finite Element Analysis.

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Weibel, Dominic, Frank Balle und Daniel Backe. „Ultrasonic Fatigue of CFRP - Experimental Principle, Damage Analysis and Very High Cycle Fatigue Properties“. Key Engineering Materials 742 (Juli 2017): 621–28. http://dx.doi.org/10.4028/www.scientific.net/kem.742.621.

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Structural aircraft components are often subjected to more than 108 loading cycles during their service life. Therefore the increasing use of carbon fiber reinforced polymers (CFRP) as primary lightweight structural materials leads to the demand of a precise knowledge of the fatigue behavior and the corresponding failure mechanisms in the very high cycle fatigue (VHCF) range. To realise fatigue investigations for more than 108 loading cycles in an economic reasonable time a novel ultrasonic fatigue testing facility (UTF) for cyclic three-point bending was developed and patented. To avoid critical internal heating due to viscoelastic damping and internal friction, the fatigue testing at 20 kHz is performed in resonance as well as in pulse-pause control resulting in an effective testing frequency of ~1 kHz and the capability of performing 109 loading cycles in less than twelve days. The fatigue behavior of carbon fiber twill 2/2 fabric reinforced polyphenylene sulfide (CF-PPS) and carbon fiber 4-H satin fabric reinforced epoxy resin (CF-EP) was investigated. To study the induced fatigue damage of CF-PPS and CF-EP in the VHCF regime in detail, the fatigue mechanisms and damage development were characterized by light optical and SEM investigations during interruptions of constant amplitude tests (CAT). Lifetime-oriented investigations showed a significant decrease of the bearable stress amplitudes of CF-PPS and CFEP in the range between 106 to 109 loading cycles. The ultrasonically fatigued thermoset matrix composite showed a significantly different VHCF behavior in comparison to the investigated thermoplastic matrix composite: No fiber-matrix debonding or transversal cracks were present on the specimen edges, but a sudden specimen failure along with carbon fiber breakage have been observed. The fatigue shear strength at 109 cycles for CF-PPS could be determined to τa, 13 = 4.2 MPa and to τa, 13 = 15.8 MPa for the thermoset material CF-EP.

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DOMINGUEZ ALMARAZ, Gonzalo Mariano, Alexiane DOMINGUEZ und Necker J. ALONSO. „Granite stone subjected to ultrasonic fatigue tests under three point bending modality“. Frattura ed Integrità Strutturale 13, Nr. 48 (24.02.2019): 70–76. http://dx.doi.org/10.3221/igf-esis.48.09.

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37

AKINIWA, Yoshiaki, Hidehiko KIMURA, Hirotaka TSURU und Ayuko NAKAMURA. „Fatigue Tests of Thin Stainless Steel Sheets Under Bending at Ultrasonic Frequency“. Transactions of the Japan Society of Mechanical Engineers Series A 74, Nr. 742 (2008): 879–84. http://dx.doi.org/10.1299/kikaia.74.879.

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38

He, Chao, Yong Jie Liu und Qing Yuan Wang. „Very High Cycle Fatigue Properties of Welded Joints under High Frequency Loading“. Advanced Materials Research 647 (Januar 2013): 817–21. http://dx.doi.org/10.4028/www.scientific.net/amr.647.817.

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Very high cycle fatigue (VHCF) properties of welded joints under ultrasonic fatigue loading have been investigated for titanium alloy (TI-6Al-4V) and bridge steel (Q345). Ultrasonic fatigue tests of base metal and welded joints were carried out in ambient air at room temperature at a stress ratio R=-1. It was observed that the fatigue strength of welded joints reduced by 50-60% as compared to the base metal. The S-N fatigue curves in the range of 107~109 cycles of base metal and welded joints for both materials exhibited the characteristic of continually decreasing type. The fatigue failure still occurred after 107 cycles of loading, and the fatigue limit in traditional does not exist. The fatigue facture mainly located in the weld metal region at low cycle fatigue range, but in the fusion area in HCF and VHCF. Analysis of fracture surfaces analyzed by SEM revealed that the fatigue cracks initiated from welding defects such as pores, cracks and inclusions.

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Hasani Najafabadi, S. H., Stefano Zucca, D. S. Paolino, G. Chiandussi und Massimo Rossetto. „Numerical Computation of Stress Intensity Factors in Ultrasonic Very-High-Cycle Fatigue Tests“. Key Engineering Materials 754 (September 2017): 218–21. http://dx.doi.org/10.4028/www.scientific.net/kem.754.218.

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The correct computation of the Stress Intensity Factor (SIF) in ultrasonic Very-High-Cycle Fatigue (VHCF) loading conditions is a key issue when investigating the crack growth rate curve with pre-cracked specimens or when evaluating critical SIF values from fracture surfaces of failed specimens. Dynamic conditions related to the resonance of the vibrating specimen, contact nonlinearity between crack faces and stress singularity at the crack tip make the SIF computation difficult and cumbersome. Generally, numerical computation through Finite Element Models (FEMs) under non-linear dynamic conditions makes use of direct integration methods (implicit or explicit). However, in the high frequency regime of ultrasonic VHCF tests, the procedure may lead to an unacceptable computational time. In order to reduce the computational time, a hybrid procedure based on the Harmonic Balance Method (HBM) and on the Virtual Crack Closure Technique (VCCT) is originally presented and applied in this paper. The dynamic field parameters calculated with the HBM are used as input data for the computation of the SIF through the VCCT.

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Mahmood, Zeina Shaker, und Jumaa Salman Chiad. „Fatigue and Vibration Parameters Improvement of Steel DIN 41Cr4 by Ultrasonic Shock Peening Treatment“. Al-Nahrain Journal for Engineering Sciences 22, Nr. 3 (26.10.2019): 233–39. http://dx.doi.org/10.29194/njes.2203233.

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The effects of the ultrasonic peening treatment (UPT) on the rotating bending fatigue behavior and the behavior of the vibrations of alloy steel DIN 41Cr4 were studied. Hardness test, Tensile test, Constant amplitude fatigue tests, and the vibrations measurements have been carried out on the specimens. Also, the fracture surface was examined and analyzed by a Scanning Electron Microscope (SEM). The results of the investigations, e.g. stress to number of cycles to failure (S-N) curves, fatigue strength improvement factor was 7%. The decreasing percentage of maximum Fast Fourier Transform (FFT) acceleration of the ultrasonic peened condition compared to the untreated conditions was 45%.

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Takamori, Hiroyuki, und John W. Fisher. „Tests of Large Girders Treated To Enhance Fatigue Strength“. Transportation Research Record: Journal of the Transportation Research Board 1696, Nr. 1 (Januar 2000): 93–99. http://dx.doi.org/10.3141/1696-12.

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Two large-scale fatigue test studies of plate girders are reported on. One study involved a series of coverplated bridge girders with small fatigue cracks that were retrofitted in 1976 as described in NCHRP Report 206. The second study involved plate girders fabricated from HPS-485W (HPS-70W) steel with welded attachments. The Category E’ coverplated beams that were removed from the I-95 Yellow Mill Pond Bridge in 1997 had been retrofitted in 1976 by either air hammer peening or gas tungsten arc (GTA) remelting. All details had small fatigue cracks at the time of retrofit. No further fatigue cracking was observed at the coverplate ends after 20 years of service and an estimated 56 million truck passages. The beams were tested at a stress range of 69 MPa (10 ksi). Cracks developed from the root of the transverse end weld and propagated through the weld throat. The fatigue resistance of the treated weld toe details improved to Category C except for one GTA-remelted detail, which exceeded Category D. Another study was carried out on large-scale HPS-485W plate girders with as-welded and ultrasonic-impact treatment (UIT) details. UIT was applied to the weld toe of transverse stiffeners welded to the web and flanges (Category C) and to coverplated ends (Category E’). The as-welded details cracked at their expected fatigue resistance. The UIT transverse stiffeners improved to Category B fatigue resistance, whereas the UIT coverplated details improved to Category C fatigue resistance.

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Xu, Jun, Huahuai Sun, Weizhen Chen und Xuan Guo. „Experiment-Based Fatigue Behaviors and Damage Detection Study of Headed Shear Studs in Steel–Concrete Composite Beams“. Applied Sciences 11, Nr. 18 (07.09.2021): 8297. http://dx.doi.org/10.3390/app11188297.

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Many in-service bridges with steel–concrete composite beams are currently aging and experiencing performance deterioration. Under long-term cyclic loads from traffic on bridges, headed shear studs in steel–concrete composite beams are vulnerable to fatigue damage. The comprehensive understanding of fatigue behaviors and the feasible detection of fatigue damage of headed shear studs is, thus, crucial for the accurate numerical simulation of the fatigue crack propagation process. The paper, thus, experimentally investigates the fatigue behaviors of headed shear studs through push-out tests of three specimens. The fatigue failure modes and cyclic strain evolution of specimens are analyzed. The fatigue lives of headed shear studs are compared with the S–N curves of the AASHTO, Eurocode 4 and BS5400 codes. The fatigue crack details of shear studs in push-out tests are then detected using the ultrasonic non-destructive testing. The results show that the root fracture is the main fatigue failure mode of shear studs under fatigue loading. The fatigue life estimations based on the three current codes (i.e., AASHTO, Eurocode 4 and BS5400) can be safely guaranteed only with different safety redundancies. The strain at the shear stud with fatigue damage shows a consistent increasing trend followed by decreasing behavior after reaching the peak value with the loading cycles. Moreover, the feasibility of the ultrasonic non-destructive testing with the combination of a strain measurement for fatigue crack details detection of headed shear studs in composite beams is proved.

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Cheng, Li, Chao Gao, Jing Sheng Shen, Ning Li, Wei Chen und Quan Tong Li. „Investigation of Very High Cycle Fatigue Behavior of TC17 Alloy“. Advanced Materials Research 295-297 (Juli 2011): 1311–14. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.1311.

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According to the loading characteristics of engine blades, a vibration bending fatigue system by using the ultrasonic fatigue test technique has been developed and the specimen is designed by finite element method, fatigue tests of TC17 between 106and 109cycles have been completed in this paper. The results show that the fatigue life of specimen increases over 107cycles and the initiation of fatigue cracks transfers from only in the surface of specimen to both in the surface and the sub-surface with loading decreasing.

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Kikuchi, Shoichi, Stefan Heinz, Dietmar Eifler, Yuta Nakamura und Akira Ueno. „Evaluation of Very High Cycle Fatigue Properties of Low Temperature Nitrided Ti-6Al-4V Alloy Using Ultrasonic Testing Technology“. Key Engineering Materials 664 (September 2015): 118–27. http://dx.doi.org/10.4028/www.scientific.net/kem.664.118.

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Fatigue tests were carried out at the stress ratio R = -1 using a 20 kHz ultrasonic testing facility to investigate the effects of low temperature nitriding on the fatigue properties of Ti-6Al-4V alloy in the very high cycle fatigue (VHCF) regime in detail. The oscillation and fatigue behavior of the nitrided Ti-alloy were characterized by measuring parameters like the ultrasonic generator power, the displacement of the specimens and dissipated energy under ultrasonic cyclic load. Moreover, the surface microstructure of the nitrided Ti-alloy was characterized using a micro-Vickers hardness tester, an optical microscope, scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron backscatter diffraction technique (EBSD) to clarify the fatigue fracture mechanism. The Ti-alloy nitrided at the temperature of 873 K showed duplex S-N properties consisting of the respective fracture modes of the surface fracture and the subsurface fracture. The low temperature nitriding reduced the surface fatigue life of Ti-alloy in comparison to the un-nitrided one due to the formation of a brittle titanium nitride (Ti2N), whereas the subsurface fatigue life in the VHCF regime was increased by the low temperature nitriding. In addition, the fatigue fracture mechanisms of the low temperature nitrided Ti-alloy were discussed from viewpoints of fractography and fracture mechanics.

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Lee, WJ, BH Seo, SC Hong, MS Won und JR Lee. „Real world application of angular scan pulse-echo ultrasonic propagation imager for damage tolerance evaluation of full-scale composite fuselage“. Structural Health Monitoring 18, Nr. 5-6 (24.02.2019): 1943–52. http://dx.doi.org/10.1177/1475921719831370.

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Composite structures are assertively used for new airframe designs and manufacturing in military aircrafts because of superior strength-to-weight ratios and fatigue resistance. Because the composites have different fatigue failure characteristics compared with metals, it is necessary to develop different approaches for the composite fatigue design and testing. In this study, we propose an in situ damage evaluation technology with high spatial resolution during full-scale fatigue testing of composite aircraft structures. For real composite structure development considering composite fatigue characteristics, full-scale fatigue and damage tolerance tests of the composite fuselage structure were conducted to evaluate the structural characteristics. In the meantime, the laser ultrasonic nondestructive inspection method, called an angular scan pulse-echo ultrasonic propagation imager, which is fully noncontact, real-time, and portable to position it in between the complex test rigs, is used to observe in situ damage growth of the composite. Finally, the verification procedure assisted by the angular scan pulse-echo ultrasonic propagation imager assures no growth of the initial impact damages after lifetime operation and proves the damage tolerance capability of the developed composite fuselage structure.

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Shimamura, Yoshinobu, Reo Kasahara, Hitoshi Ishii, Keiichiro Tohgo, Tomoyuki Fujii, Toru Yagasaki und Soichiro Sumida. „Fretting Fatigue Behaviour of Alloy Steel in the Very High Cycle Region“. MATEC Web of Conferences 300 (2019): 18002. http://dx.doi.org/10.1051/matecconf/201930018002.

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It is well known that fretting fatigue strength is much lower than the fatigue strength of smooth specimens and the fatigue limit disappears. Many studies on fretting fatigue have been reported but most of the studies have not cover fatigue properties in the very high cycle regime more than 107 cycles. In this study, an accelerated fretting fatigue testing method was developed by using an ultrasonic torsional fatigue testing machine with a clamping fretting pad. Fretting fatigue tests of CrMo steel were conducted by using the developed method. Test results showed that fretting fatigue failure occurs in the very high cycle region.

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YAMADA, Koji, und Susumu MIYAKAWA. „Super-long Life Fatigue Properties of Al-Si-Cu Die Casting Alloy by Using Ultrasonic Fatigue Tests“. Transactions of the Japan Society of Mechanical Engineers Series A 72, Nr. 717 (2006): 749–56. http://dx.doi.org/10.1299/kikaia.72.749.

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48

Hasani Najafabadi, S. H., D. S. Paolino, A. Tridello, G. Chiandussi und Massimo Rossetto. „Experimental-Numerical Assessment of Critical SIF from VHCF Tests“. Key Engineering Materials 713 (September 2016): 62–65. http://dx.doi.org/10.4028/www.scientific.net/kem.713.62.

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The continuous enhancement of reliability and durability requirements for many machinery components is significantly pushing the experimental research on the Very-High-Cycle Fatigue (VHCF) response of metallic materials. In order to significantly reduce testing time, ultrasonic testing machines are widely adopted when carrying out VHCF tests. Several fundamental material properties can be estimated from the fracture surfaces of specimens failed during ultrasonic VHCF tests. In the VHCF literature the critical Stress Intensity Factor (SIF) is generally estimated by applying analytical SIF formulations to the typical semi-circular surface crack geometry revealed by fracture surfaces at final failure. However, when subjected to ultrasonic VHCF tests, analytical SIF formulations valid for static loading conditions could eventually lead to significant estimation errors. The present paper aims at comparing the critical SIF at failure estimated from conventional analytical formulations and from Finite Element Models (FEMs). The fracture surfaces of two specimens with different shapes (Hourglass and Gaussian) are taken into account for modeling crack geometry at final failure. Through an implicit solving procedure, the critical SIF in resonance condition at 20 kHz is computed from the 3D geometry of the cracked specimens and compared with the corresponding analytical prediction.

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Wang, Yuhua, und Hengchao Zheng. „Nonlinear Analysis Method of High-Strength Steel Based on Local Buckling Fiber Hinge“. Mathematical Problems in Engineering 2021 (24.04.2021): 1–12. http://dx.doi.org/10.1155/2021/5541772.

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Based on the analysis and summary of the research and application status of domestic and foreign high-strength steel local buckling fiber hinged rod stability and ordinary steel local buckling fiber hinged rod stability control, this paper proposes a fiber hinged rod suitable for spatial structures subject to local buckling. The new type is high-strength steel composite local buckling fiber hinged pressure rod. The influence of related parameters in the dislocation string model and the dislocation couple model on the ultrasonic nonlinear parameters is deeply analyzed. And, from the perspective of contact nonlinear acoustics, the mechanism of the ultrasonic nonlinear response of the crack is analyzed, and the finite element software ABAQUS is used to simulate it. The relationship between the nonlinear parameter and the internal crack shape of the material is simulated and analyzed, which proves the nonlinearity. A series of nonlinear ultrasonic testing was performed on three groups of FV520B high-strength steel fatigue specimens using a nonlinear testing system. Analyzing the results, it is found that the material has a good ultrasonic nonlinear cumulative effect, and the microcracks have a greater impact on the ultrasonic nonlinear response. The β-N curves under three sets of fatigue tests are obtained. The results show that the nonlinear parameters are very sensitive to the fatigue damage of FV520B high-strength steel, and the ultrasonic nonlinear parameters generally increase with the increase in the number of fatigue cycles.

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Liu, Lu, Yifan Ma, Shisen Liu und Shengnan Wang. „The Fatigue Behaviors of a Medium-Carbon Pearlitic Wheel-Steel with Elongated Sulfides in High-Cycle and Very-High-Cycle Regimes“. Materials 14, Nr. 15 (02.08.2021): 4318. http://dx.doi.org/10.3390/ma14154318.

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The effects of stress ratio (R), loading condition, and MnS inclusion on the fatigue behavior of a medium-carbon pearlitic wheel-steel were investigated by a combination of rotating (frequency of 52.5 Hz, 103–108) bending and ultrasonic (frequency of 20 kHz, 5 × 104–109) axial cycling tests in high-cycle and very-high-cycle regimes. All the S-N curves present horizontal asymptotic shapes and have clear fatigue limits. The fatigue limits (260–270 MPa) for R = −1 obtained by ultrasonic test are almost 140–150 MPa lower than that (400–410 MPa) obtained by rotating bending, and the limit values of R = 0.3 are almost in the range of 195–205 MPa. For rotating bending, the fatigue fractures were originated from the surface matrix of the specimen. Whereas for ultrasonic fatigue, both surface and interior crack initiation occurred, and cracks were all initiated from MnS inclusions regardless of stress ratios. The finite element method was employed to study the influence of MnS inclusions on crack initiation and propagation. The results show that high stress concentrates on the sides of the elliptical MnS inclusion rather than the tip of the inclusion.

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