Bending fatigue testing methods for sheet metal at normal and elevated temperatures

Several standard fatigue testing methods are used to determine the fatigue stress-life prediction model (S-N curve) and the endurance limit of Reinforced Concrete (RC) beams, including the application of constant cyclic tension-tension loads at different stress or strain ranges. The standard fatigue testing methods are time-consuming and expensive to perform, as a large number of specimens is needed to obtain valid results. The purpose of this paper is to examine a fatigue stress-life predication model of RC beams that are developed with an accelerated fatigue approach. This approach is based on the hypothesis of linear accumulative damage of the Palmgren–Miner rule, whereby the applied cyclic load range is linearly increased with respect to the number of cycles until the specimen fails. A three-dimensional RC beam was modeled and validated using ANSYS software. Numerical simulations were performed for the RC beam under linearly increased cyclic loading with different initial loading conditions. A fatigue stress-life model was developed that was based on the analyzed data of three specimens. The accelerated fatigue approach has a higher rate of damage accumulations than the standard testing approach. All of the analyzed specimens failed due to an unstable cracking of concrete. The developed fatigue stress-life model fits the upper 95% prediction band of RC beams that were tested under constant amplitude cyclic loading.

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Magnesium Sheet Metal Forming Considering its Specific Yield Behavior

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.6-8.771 ◽

2005 ◽

Vol 6-8 ◽

pp. 771-778 ◽

Cited By ~ 2

Author(s):

M. Redecker ◽

Karl Roll ◽

S. Häussinger

Keyword(s):

Sheet Metal ◽

Elevated Temperatures ◽

Flow Behavior ◽

Specific Yield ◽

Forming Limit ◽

Forming Process ◽

Local Flow ◽

Yield Behavior ◽

Magnesium Sheet ◽

Testing Procedures

In recent years very strong efforts have been undertaken to build light weight structures of car bodies in the automotive industry. Structural technologies like Space Frame, tailored blanks and relief-embossed panels are well-known and already in use. Beside that there is a large assortment of design materials with low density or high strength. Magnesium alloys are lighter by approximately 34 percent than aluminum alloys and are considered to be the lightest metallic design material. However forming processes of magnesium sheet metal are difficult due to its complex plasticity behavior. Strain rate sensitivity, asymmetric and softening yield behavior of magnesium are leading to a complex description of the forming process. Asymmetric yield behavior means different yield stress depending on tensile or compressive loading. It is well-known that elevated temperatures around 200°C improve the local flow behavior of magnesium. Experiments show that in this way the forming limit curves can be considerably increased. So far the simulation of the forming process including temperature, strain rates and plastic asymmetry is not state-of-the-art. Moreover, neither reliable material data nor standardized testing procedures are available. According to the great attractiveness of magnesium sheet metal parts there is a serious need for a reliable modeling of the virtual process chain including the specification of required mechanical properties. An existing series geometry which already can be made of magnesium at elevated temperatures is calculated using the finite element method. The results clarify the failings of standard calculation methods and show potentials of its improvement.

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Tracked Changes. Metallic materials � Rotating bar bending fatigue testing

10.3403/30404147 ◽

2021 ◽

Keyword(s):

Fatigue Testing ◽

Metallic Materials ◽

Bending Fatigue

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Small‐sized specimen design with the provision for high‐frequency bending‐fatigue testing

Fatigue & Fracture of Engineering Materials & Structures ◽

10.1111/ffe.13589 ◽

2021 ◽

Author(s):

Hamed Ghadimi ◽

Arash P. Jirandehi ◽

Saber Nemati ◽

Shengmin Guo

Keyword(s):

High Frequency ◽

Fatigue Testing ◽

Bending Fatigue

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Fatigue of Metal Free Reed due to Self-Excited Oscillation

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.33-37.267 ◽

2008 ◽

Vol 33-37 ◽

pp. 267-272

Author(s):

Yoshinobu Shimamura ◽

Keiichiro Tohgo ◽

Hiroyasu Araki ◽

Yosuke Mizuno ◽

Shoji Kawaguchi ◽

...

Keyword(s):

Fatigue Testing ◽

The Self ◽

Fatigue Properties ◽

Bending Fatigue ◽

Metal Free ◽

Mass Damper ◽

Excited Oscillation ◽

Analytical Research ◽

Fatigue Characteristics ◽

Good Agreement

Metal free reeds are used for musical instruments like harmonica. Free reeds are small, thin cantilevers, and oscillate by blowing air. It is reported that free reeds break due to fatigue during play. In order to elongate the life of free reeds, the fatigue properties should be investigated and a motion analysis method should be developed. The experimental and analytical research on metal free reed, however, has been rarely reported. In this study, two types of fatigue testing machines were developed to obtain basic fatigue characteristics. The fatigue testing machines are designed for bending fatigue of actual free reeds whose thickness is less than 400 μm. An S-N diagram is successfully obtained up to 107 cycles by using the developed fatigue testing machines. The fracture surfaces of fatigued specimens are in good agreement with those of free reeds failed in use. Then, an analytical method for the self-excited oscillation of free reeds was developed based on a mass-damper-spring model. The proposed method can take account for the shape of free reed. The self-excited oscillation of free reeds with different shape are analyzed and in good agreement with experimental results.

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Improvement of Fatigue Behaviour of High Strength Aluminium Alloys by Fluidized Bed Peening (FBP)

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.344.87 ◽

2007 ◽

Vol 344 ◽

pp. 87-96 ◽

Cited By ~ 2

Author(s):

M. Barletta ◽

F. Lambiase ◽

Vincenzo Tagliaferri

Keyword(s):

Fatigue Life ◽

Fluidized Bed ◽

Fatigue Testing ◽

Fatigue Behavior ◽

Maximum Amplitude ◽

High Strength ◽

Operational Parameters ◽

Bending Fatigue ◽

Rotating Bending Fatigue ◽

Rotating Bending

This paper deals with a definition of a relatively novel technique to improve the fatigue behavior of high strength aluminum alloys, namely, Fluidized Bed Peening (FBP). Fatigue samples made from AA 6082 T6 alloy were chosen according to ASTM regulation about rotating bending fatigue test and, subsequently, treated by varying FBP operational parameters and fatigue testing conditions. First, a full factorial experimental plan was performed to assess the trend of number of cycles to rupture of fatigue samples varying among several experimental levels the factors peening time and maximum amplitude of alternating stress applied to fatigue samples during rotating bending fatigue tests. Second, design of experiment (DOE) technique was used to analyze the influence of FBP operational parameters on fatigue life of AA 6082 T6 alloy. Finally, ruptures of FB treated samples and untreated samples were discussed in order to evaluate the influence of operational parameters on the effectiveness of FBP process and to understand the leading process mechanisms. At any rate, the fatigue behavior of processed components was found to be significantly improved, thereby proving the suitability of FBP process as alternative mechanical technique to enhance fatigue life of components made from high strength aluminum alloy.

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