Fatigue Resistance of Laser Welded S355 Steel Sheet

2015 ◽  
Vol 665 ◽  
pp. 69-72 ◽  
Author(s):  
Ivo Černý ◽  
Jiří Sís ◽  
Pavel Zháňal
Keyword(s):  
Fatigue Resistance ◽  
Steel Sheet ◽  
High Cycle Fatigue ◽  
Endurance Limit ◽  
Fatigue Tests ◽  
Basic Material ◽  
Welding Parameters ◽  
Laser Weld ◽  
Cycle Fatigue ◽  
Self Consistent

The paper contains results of fatigue resistance investigation of laser welded 10 mm thick sheets of a carbon structural S355 steel. High cycle fatigue tests were performed to verify fatigue strength of the sheet containing laser weld performed with optimised laser welding parameters. Though the thickness of the sheet was quite big, resulting endurance limit of the welds and heat affected zone was comparable with that of basic material. In addition, some characteristics of the laser weld like hardness were very self-consistent. As expected, fatigue results were characteristic by quite high scatter. Different damage mechanisms were shown. The results are discussed on the basis of fractographical analyses, which provided some quite interesting details about crack initiation mechanisms.

Fatigue Strength and Damage Mechanisms of Laser Welded Structural Carbon Steel Sheets

2015 ◽  
Vol 662 ◽  
pp. 201-204 ◽  
Author(s):  
Ivo Černý ◽  
Jiří Sís
Keyword(s):  
Laser Welding ◽  
Fatigue Resistance ◽  
Fatigue Tests ◽  
Basic Material ◽  
Welding Parameters ◽  
Damage Mechanisms ◽  
Steel Sheets ◽  
Welding Processes ◽  
Structural Carbon ◽  
Structural Carbon Steel

Laser welding is one of advanced and promising joining technologies of metallic materials, characteristic by numerous advantages in comparison with conventional welding processes. The technology still can be considered as fairly new and so, investigations are needed to reach optimum properties of welds in specific application cases, depending on welding parameters. Certification welding procedures usually require to demonstrate sufficient microstructure, mechanical, impact loading and other characteristics, but not fatigue resistance, which is essential for welded dynamically loaded structures. The paper contains results of fatigue resistance investigation of laser welded 10 mm thick sheets of a carbon structural S 355 steel. High cycle fatigue tests were performed after optimizing laser welding parameters. Resulting endurance limit of the welds and heat affected zone was higher than that of basic material. However, high scatter of results and different damage mechanisms were shown for different load amplitudes. The results are discussed on the basis of fractographical analyses, which provided some quite interesting details about crack initiation mechanisms.

scholarly journals Very-High-Cycle Fatigue Behavior of Inconel 718 Alloy Fabricated by Selective Laser Melting at Elevated Temperature

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1001
Author(s):  
Zongxian Song ◽  
Wenbin Gao ◽  
Dongpo Wang ◽  
Zhisheng Wu ◽  
Meifang Yan ◽  
...  
Keyword(s):  
Elevated Temperature ◽  
Selective Laser Melting ◽  
Fatigue Resistance ◽  
Inconel 718 ◽  
High Cycle Fatigue ◽  
Cycle Fatigue ◽  
Laser Melting ◽  
Inconel 718 Alloy ◽  
Very High Cycle Fatigue ◽  
Very High

This study investigates the very-high-cycle fatigue (VHCF) behavior at elevated temperature (650 °C) of the Inconel 718 alloy fabricated by selective laser melting (SLM). The results are compared with those of the wrought alloy. Large columnar grain with a cellular structure in the grain interior and Laves/δ phases precipitated along the grain boundaries were exhibited in the SLM alloy, while fine equiaxed grains were present in the wrought alloy. The elevated temperature had a minor effect on the fatigue resistance in the regime below 108 cycles for the SLM alloy but significantly reduced the fatigue strength in the VHCF regime above 108 cycles. Both the SLM and wrought specimens exhibited similar fatigue resistance in the fatigue life regime of fewer than 107–108 cycles at elevated temperature, and the surface initiation mechanism was dominant in both alloys. In a VHCF regime above 107–108 cycles at elevated temperature, the wrought material exhibited slightly better fatigue resistance than the SLM alloy. All fatigue cracks are initiated from the internal defects or the microstructure discontinuities. The precipitation of Laves and δ phases is examined after fatigue tests at high temperatures, and the effect of microstructure on the formation and the propagation of the microstructural small cracks is also discussed.

Effect of corrosion and sandblasting on the high cycle fatigue behavior of reinforcing B500C steel bars

2017 ◽  
Author(s):  
Marina C. Vasco ◽  
Panagiota Polydoropoulou ◽  
Apostolos N. Chamos ◽  
Spiros G. Pantelakis
Keyword(s):  
Mass Loss ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Salt Spray ◽  
Fatigue Tests ◽  
Tensile Behavior ◽  
Loading Frequency ◽  
Reinforcing Steel ◽  
Cycle Fatigue ◽  
Steel Bars

In a series of applications, steel reinforced concrete structures are subjected to fatigue loads during their service life, what in most cases happens in corrosive environments. Surface treatments have been proved to represent proper processes in order to improve both fatigue and corrosion resistances. In this work, the effect of corrosion and sandblasting on the high cycle fatigue behavior reinforcing steel bars is investigated. The investigated material is the reinforcing steel bar of technical class B500C, of nominal diameter of 12 mm. Steel bars specimens were first exposed to corrosion in alternate salt spray environment for 30 and 60 days and subjected to both tensile and fatigue tests. Then, a series of specimens were subjected to common sandblasting, corroded and mechanically tested. Metallographic investigation and corrosion damage evaluation regarding mass loss and martensitic area reduction were performed. Tensile tests were conducted after each corrosion exposure period prior to the fatigue tests. Fatigue tests were performed at a stress ratio, R, of 0.1 and loading frequency of 20 Hz. All fatigue tests series as well as tensile test were also performed for as received steel bars to obtain the reference behavior. The results have shown that sandblasting hardly affects the tensile behavior of the uncorroded material. The effect of sandblasting on the tensile behavior of pre-corroded specimens seems to be also limited. On the other hand, fatigue results indicate an improved fatigue behavior for the sandblasted material after 60 days of corrosion exposure. Martensitic area reductions, mass loss and depth of the pits were significantly smaller for the case of sandblasted materials, which confirms an increased corrosion resistance.

High-cycle fatigue tests of pretensioned concrete beams

PCI Journal ◽  
2022 ◽  
Vol 67 (1) ◽  
Author(s):  
Jörn Remitz ◽  
Martin Empelmann
Keyword(s):  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Concrete Beams ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Design Methods ◽  
Test Results ◽  
Cycle Fatigue ◽  
Pretensioned Concrete ◽  
Current Design

Pretensioned concrete beams are widely used as bridge girders for simply supported bridges. Understanding the fatigue behavior of such beams is very important for design and construction to prevent fatigue failure. The fatigue behavior of pretensioned concrete beams is mainly influenced by the fatigue of the prestressing strands. The evaluation of previous test results from the literature indicated a reduced fatigue life in the long-life region compared with current design methods and specifications. Therefore, nine additional high-cycle fatigue tests were conducted on pretensioned concrete beams with strand stress ranges of about 100 MPa (14.5 ksi). The test results confirmed that current design methods and specifications overestimate the fatigue life of embedded strands in pretensioned concrete beams.

High Cycle Fatigue Resistance and Reliability Assessment of Flexible Printed Circuitry

2002 ◽  
Vol 124 (3) ◽  
pp. 254-259 ◽  
Author(s):  
Elena Martynenko ◽  
Wen Zhou ◽  
Alexander Chudnovsky ◽  
Ron S. Li ◽  
Larry Poglitsch
Keyword(s):  
Fatigue Resistance ◽  
High Cycle Fatigue ◽  
Failure Mechanisms ◽  
Three Dimensional ◽  
Reliability Assessment ◽  
Core Layer ◽  
High Strength ◽  
Multiple Cracks ◽  
Material System ◽  
Cycle Fatigue

Flexible printed circuitry (FPC) is a patterned array of conductors supported by a flexible dielectric film made of high strength polymer material such as polyimide. The flexibility of FPC provides an opportunity for three dimensional packaging, easy interconnections and dynamic applications. The polymeric core layer is the primary load bearing structure when the substrate is not supported by a rigid plate. In its composite structure, the conductive layers are more vulnerable to failure due to their lower flexibility compared to the core layer. Fatigue data on FPCs are not commonly available in published literature. Presented in this paper is the fatigue resistance and reliability assessment of polyimide based FPCs. Fatigue resistance of a specific material system was analyzed as a function of temperature and frequency through experiments that utilized a specially designed experimental setup consisting of sine servo controller, electrodynamic shaker, continuity monitor and temperature chamber. The fatigue characteristics of the selected material system are summarized in the form of S-N diagrams. Significant decrease in fatigue lifetime has been observed due to higher displacements in high cycle fatigue. Observed temperature effect was however counter-intuitive. Failure mechanisms are discussed and complete fracture analysis is presented. In various FPC systems, it has been found that the changes take place in FPC failure mechanisms from well-developed and aligned single cracks through the width at low temperature to an array of multiple cracks with random sizes and locations at high temperature.

Effect of Plasma Nitriding on Ultra-High Cycle Fatigue Behaviors of Ti-6Al-4V

2011 ◽  
Vol 295-297 ◽  
pp. 2386-2389 ◽  
Author(s):  
Ren Hui Tian ◽  
Qiao Lin Ouyang ◽  
Qing Yuan Wang
Keyword(s):  
High Cycle Fatigue ◽  
Plasma Nitriding ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Ultra High Cycle Fatigue ◽  
Stress Ratios

In order to investigate the effect of plasma nitriding treatment on fatigue behavior of titanium alloys, very high cycle fatigue tests were carried out for Ti-6Al-4V alloy using an ultrasonic fatigue machine under load control conditions for stress ratios of R=-1 at frequency of ƒ=20KHz. Experiment results showed that plasma nitriding treatment played the principal role in the internal fatigue crack initiation. More importantly, plasma nitriding treatment had a detrimental effect on fatigue properties of the investigated Ti-6Al-4V alloy, and the fatigue strength of material after plasma nitriding treatment appeared to be significantly reduced about 17% over the untreated material.

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