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13 pages, 5904 KiB

Open AccessFeature PaperArticle

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

by Fumio Ogawa, Yusuke Shimizu, Stefano Bressan, Takahiro Morishita and Takamoto Itoh

Metals 2019, 9(10), 1115; https://doi.org/10.3390/met9101115 - 18 Oct 2019

Cited by 10 | Viewed by 5497

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Multiaxial Fatigue: Testing and Modelling)

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13 pages, 7314 KiB

Open AccessArticle

Fatigue Crack Growth Rate of the Long Term Operated Puddle Iron from the Eiffel Bridge

by Grzegorz Lesiuk, José A. F. O. Correia, Michał Smolnicki, Abílio M. P. De Jesus, Monika Duda, Pedro A. Montenegro and Rui A. B. Calcada

Metals 2019, 9(1), 53; https://doi.org/10.3390/met9010053 - 08 Jan 2019

Cited by 14 | Viewed by 3596

Abstract

The paper summarises an experimental study on the fatigue crack propagation and cracks paths in ancient steel—19th-century puddle iron from the Eiffel bridge. The tests were performed with the load R-ratio equal to 0.05 and 0.5. All tests were performed under different notch [...] Read more.

The paper summarises an experimental study on the fatigue crack propagation and cracks paths in ancient steel—19th-century puddle iron from the Eiffel bridge. The tests were performed with the load R-ratio equal to 0.05 and 0.5. All tests were performed under different notch inclinations (mode I + II). The fatigue crack growth rate in the tested material is significantly higher than its “modern” equivalent—low carbon mild steel. The crack closure phenomenon occurs in specimens during the process of crack growth. Understanding this aspect is crucial for the examination of a stress R-ratio influence on kinetic fatigue fracture diagram (KFFD) description. Both the experimental and numerical approach, using the HP VEE environment, has been applied to the crack closure as well as the crack opening forces’ estimation. These analyses are based on the deformation of the hysteresis loop. The algorithm that was implemented in the numerical environment is promising when it comes to describing the kinetics of fatigue crack growth (taking into consideration the crack closure effect) in old metallic materials. Full article

(This article belongs to the Special Issue Multiaxial Fatigue: Testing and Modelling)

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14 pages, 6350 KiB

Open AccessArticle

High-Temperature Low Cycle Fatigue Life Prediction and Experimental Research of Pre-Tightened Bolts

by Qingmin Yu, Honglei Zhou, Xudong Yu and Xiangjin Yang

Metals 2018, 8(10), 828; https://doi.org/10.3390/met8100828 - 15 Oct 2018

Cited by 6 | Viewed by 3532

Abstract

Bolted connections are widely used in various mechanical structures due to their superior fastening properties. However, vibration and fatigue loads in the structure are likely to cause fatigue failure of the bolted joints, especially those under high temperature, such as in aero-engines. This [...] Read more.

Bolted connections are widely used in various mechanical structures due to their superior fastening properties. However, vibration and fatigue loads in the structure are likely to cause fatigue failure of the bolted joints, especially those under high temperature, such as in aero-engines. This paper mainly studies the low-cycle fatigue life of the pre-tightened bolts working at a high temperature. A novel test fixture is designed for fatigue tests, and low cycle fatigue tests of pre-tightened bolts are conducted at the temperatures of 550 °C and 650 °C, respectively. Furthermore, a new low cycle fatigue model that is based on the Von Mises equivalent stress/strain criterion is proposed. Meanwhile, the proposed model is used to predict the high-temperature low cycle fatigue life of pre-tightened bolts according to the stress/strain results obtained by finite element analysis. There is good agreement between the experimental results and those obtained by theoretical prediction, which validates the accuracy of the proposed fatigue model. Research results will provide a theoretical basis for the low cycle fatigue life prediction of pre-tightened bolts. Full article

(This article belongs to the Special Issue Multiaxial Fatigue: Testing and Modelling)

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