scholarly journals Investigations on Interface Shear Fatigue of Semi-Precast Slabs with Lattice Girders

2021 ◽  
Vol 11 (23) ◽  
pp. 11196
Author(s):  
Matthias Hillebrand ◽  
Maximilian Schmidt ◽  
Katrin Wieneke ◽  
Martin Classen ◽  
Josef Hegger
Keyword(s):  
Fatigue Behavior ◽  
Precast Concrete ◽  
Longitudinal Shear ◽  
Fatigue Tests ◽  
Vertical Shear ◽  
Experimental Investigations ◽  
Concrete Slabs ◽  
Interface Shear ◽  
Fatigue Design ◽  
Shear Fatigue

Due to their high cost efficiency and flexibility, semi-precast concrete slabs with lattice girders are widely used in constructions all over the world. Prefabricated concrete slabs, combined with in situ concrete topping, exhibit a quasi-monolithic structural behavior in which lattice girders serve as vertical shear reinforcement and ensure the transfer of longitudinal shear within the interface, acting in combination with concrete-to-concrete bonding mechanisms. To be applicable in industrial and bridge construction, semi-precast slabs need to have sufficient resistance against fatigue failure. To improve and expand the limits of application, theoretical and experimental investigations are conducted at the Institute of Structural Concrete (IMB), RWTH Aachen University. To investigate the fatigue behavior of lattice girders, small size tests with lattice girder diagonals were carried out. These test results have been used to derive an S–N curve (S: stress, N: number of load cycles) for lattice girders for a more refined fatigue design. Subsequently, the fatigue behavior of semi-precast slabs with lattice girders was investigated by fatigue tests on single-span slab segments. The fatigue design regulations of lattice girders according to technical approvals can generally be confirmed by this test program; however, they tend to be conservative. The use of the derived S–N curve leads to significantly improved agreement of fatigue behavior observed in tests and design expressions.

scholarly journals Evaluation of Estimation Methods for Shear Fatigue Properties and Correlations with Uniaxial Fatigue Properties for Steels and Titanium Alloys

2018 ◽  
Vol 165 ◽  
pp. 16012 ◽  
Author(s):  
Shahriar Sharifimehr ◽  
Ali Fatemi
Keyword(s):  
Titanium Alloys ◽  
Inconel 718 ◽  
Fatigue Behavior ◽  
Estimation Method ◽  
Fatigue Tests ◽  
Estimation Methods ◽  
Fatigue Properties ◽  
Modified Method ◽  
Shear Fatigue ◽  
Von Mises

The goal of this study was to evaluate the accuracy of different methods in correlating uniaxial fatigue properties to shear fatigue properties, as well as finding a reliable estimation method which is able to predict the shear fatigue behavior of steels and titanium alloys from their monotonic properties. In order to do so, axial monotonic as well as axial and torsion fatigue tests were performed on two types of steel and a Ti-6Al-4V alloy. The results of these tests along with test results of 23 types of carbon steel, Inconel 718, and three types of titanium alloys commonly used in the industry were analyzed. It was found that von Mises and maximum principal strain criteria were able to effectively correlate uniaxial fatigue properties to shear fatigue properties for ductile and brittle behaving materials, respectively. Also, it was observed that for steels and Inconel 718 obtaining shear fatigue properties from uniaxial fatigue properties which are in turn calculated from Roessle-Fatemi estimation method resulted in reasonable estimations when compared to experimentally obtained uniaxial fatigue properties. Furthermore, a modification was made to the Roessle-Fatemi hardness method in order to adjust it to fatigue behavior of titanium alloys. The modified method, which was derived from uniaxial fatigue properties of titanium alloys with Brinell hardness between 240 and 353 proved to be accurate in predicting the shear fatigue behaviors.

Corrosion Fatigue Behavior of Mooring Chain Steel in Seawater

2016 ◽  
Author(s):  
Alberto Arredondo ◽  
Jonathan Fernández ◽  
Elena Silveira ◽  
José Luís Arana
Keyword(s):  
Cathodic Protection ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Fatigue Design ◽  
Steel Grades ◽  
Integrity Management ◽  
Loading Modes ◽  
Actual Response ◽  
Fractographic Examination ◽  
Frequency Temperature

With a majority of the reported chain failures related to fatigue, this phenomenon is one of the main topics to be studied as part of Mooring Integrity Management. Present fatigue design is mainly based on fatigue curves for chains under tension-tension loads in seawater. However, the applicability of these curves for different loading modes and specific environments remains unclear. This paper studies the fatigue behavior of the material used on chains as it builds the baseline for the performance of these mooring components. It includes uniaxial fatigue tests that were undertaken on R4 and R5 steel grades obtained from actual chains after all their manufacturing steps. Samples were not only tested in air and in synthetic seawater but different corrosion related parameters were also studied: frequency, temperature and cathodic protection. From the results of these tests, separated SN curves were obtained. Subsequently, these curves were analyzed and compared against present recommended design curves for material. Fractographic examination was undertaken to assess the effect of corrosion and cathodic protection and comparison between material and component response was also addressed. Results showed the strong synergy between corrosion and fatigue. Also, the improvement from fatigue design curves to actual response of the materials was quantified.

scholarly journals From the fatigue properties of Ti6Al4V produced by ALM selective laser melting process to the mechanical design of an aeronautical part

2020 ◽  
Vol 321 ◽  
pp. 03032
Author(s):  
François Edy ◽  
Viet-Duc LE ◽  
Claudia BIERE ◽  
Monica Perez ◽  
Etienne Pessard ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Mechanical Design ◽  
Fatigue Behavior ◽  
Melting Process ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Laser Melting ◽  
Fatigue Design ◽  
Process Strategy

Selective laser melting SLM is investigated through a study of redesign and characterization of an aeronautic part made of titanium Ti6Al4V. The part must ensure an excellent static and fatigue behaviour. The methodology developed hereby follows 3 main steps: First, the influence of laser power, laser speed and hatch distance on the amount/rate of porosity is performed to define optimized process parameters. Then, the influence of building process strategy, i.e. building direction or as-built surface roughness on the static and fatigue behaviour are studied and understood by following a vast experimental campaign. Obtained properties are finally used in a topology optimization study to find the best compromise between part weight and fatigue behavior . 3 prototypes of simulated part are produced and then characterized. Fatigue tests are conducted on the component and confirm the fatigue design proposed. Obtained results are encouraging and illustrate the fatigue design optimization of a complex Additive Manufacturing component.

scholarly journals Low Cycle Fatigue Behavior of Steam Generator Tubes under Axial Loading

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1944 ◽  
Author(s):  
Xing He ◽  
Junfeng Chen ◽  
Wei Tian ◽  
Yuebing Li ◽  
Weiya Jin
Keyword(s):  
Stress Concentration ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Strain Curve ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Stress Strain Curve ◽  
Fatigue Design ◽  
Alloy 690 ◽  
Set Up

Compared with the fatigue properties of the material (Inconel Alloy 690), the real fatigue lives of tubes are more meaningful in the fatigue design and assessment of steam generator (SG) tube bundles. However, it is almost impossible to get a satisfactory result by conducting fatigue tests on the tube directly. A tube with a uniform and thin wall easily fails near the clamping ends under cyclic loading due to the stress concentration. In this research, a set-up for fatigue tests of real tubes is proposed to overcome the stress concentration. With the set-up, low cycle fatigue tests were conducted in accordance with an existing fatigue design curve for Alloy 690. Strain control mode was applied with fully reversed push–pull loading under different strain amplitudes (0.15%, 0.2%, 0.3%, and 0.4%). A favourable result was obtained, and the low cycle fatigue behavior was investigated. The results showed that the fatigue life tested by the real tube was below the strain–life curve of Alloy 690 which was fitted by conventional solid specimens. A cyclic hardening behavior was found by the cyclic stress–strain curve when compared with the monotonic stress–strain curve.

Correlation of Fatigue Limit and Crack Growth Threshold Value to the Nanobainitic Microstructure

2016 ◽  
Vol 258 ◽  
pp. 314-317 ◽  
Author(s):  
Inga Müller ◽  
Rosalia Rementeria ◽  
Francisca G. Caballero ◽  
Matthias Kuntz ◽  
Eberhard Kerscher
Keyword(s):  
Crack Growth ◽  
Fatigue Limit ◽  
Fatigue Behavior ◽  
Bainitic Ferrite ◽  
Block Size ◽  
Threshold Value ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Microstructural Parameters ◽  
Fatigue Design

The recently developed nanobainitic steels show high ultimate tensile strength (UTS) as well as high ductility. Although this combination seems to be desirable for fatigue design, fatigue limit of nanostructured bainite is often disappointingly low. To improve fatigue properties we tried to earn a fundamental understanding of the microstructural parameters governing fatigue behavior.Therefore our hypothesis to improve the fatigue behavior was not necessarily avoiding the initiation of a fatigue crack – which could lead to failure of the material – but to improve the ability of the present microstructure to slow down or stop growing cracks. Thus, the key to understand the fatigue behavior of nanostructured bainite is to understand the role of the microstructural features which could act as barriers for growing cracks.We tried to correlate our results of fatigue tests and analysis of fracture surfaces to the size of microstructural features like bainitic ferrite plates, crystallographic bainite blocks and packets or prior austenite grains, as well as cracks induced at nonmetallic inclusions. Thereby we found that the crystallographic bainite block size governs fatigue behavior. Additionally, threshold values were determined from crack growth experiments and related to the characteristic microstructural features.

scholarly journals S235JRC+C Steel Response Analysis Subjected to Uniaxial Stress Tests in the Area of High Temperatures and Material Fatigue

2021 ◽  
Vol 13 (10) ◽  
pp. 5675
Author(s):  
Josip Brnic ◽  
Marino Brcic ◽  
Sebastian Balos ◽  
Goran Vukelic ◽  
Sanjin Krscanski ◽  
...  
Keyword(s):  
High Temperatures ◽  
Room Temperature ◽  
Uniaxial Stress ◽  
Fatigue Tests ◽  
Experimental Investigations ◽  
Response Analysis ◽  
Stress Tests ◽  
Staircase Method ◽  
Mechanical Fatigue ◽  
Proper Material

Knowledge of the properties and behavior of materials under certain working conditions is the basis for the selection of the proper material for the design of a new structure. This paper deals with experimental investigations of the mechanical properties of unalloyed high quality steel S235JRC + C (1.0122) and its behavior under conditions of high temperatures, creep and mechanical fatigue. The response of the material at high temperatures (20–700 °C) is shown in the form of engineering stress-strain diagrams while that at creep behavior (400–600 °C) is shown in the form of creep curves. Furthermore, based on uniaxial fully reversed mechanical fatigue tests (R=−1), a stress-life (S-N) fatigue diagram has been constructed and the fatigue (endurance) limit of the material is calculated The experimentally determined value of tensile strength at room temperature is 534 MPa. The calculated value of the fatigue limit, also at room temperature, using the modified staircase method and based on the mechanical fatigue tests data, is 202 MPa. With regard to creep resistance, steel 1.0122 can be considered creep-resistant only at a temperature of 400 °C and at an applied stress not exceeding 50% of the yield strength corresponding to this temperature.

scholarly journals Influence of Shot Peening on the Isothermal Fatigue Behavior of the Gamma Titanium Aluminide Ti-48Al-2Cr-2Nb at 750 °C

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1083
Author(s):  
Christoph Breuner ◽  
Stefan Guth ◽  
Elias Gall ◽  
Radosław Swadźba ◽  
Jens Gibmeier ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Shot Peening ◽  
Elevated Temperatures ◽  
Stress Amplitude ◽  
Negative Impact ◽  
Fatigue Behavior ◽  
Surface Hardness ◽  
Fatigue Tests ◽  
Positive Effects ◽  
Isothermal Fatigue

One possibility to improve the fatigue life and strength of metallic materials is shot peening. However, at elevated temperatures, the induced residual stresses may relax. To investigate the influence of shot peening on high-temperature fatigue behavior, isothermal fatigue tests were conducted on shot-peened and untreated samples of gamma TiAl 48-2-2 at 750 °C in air. The shot-peened material was characterized using EBSD, microhardness, and residual stress analyses. Shot peening leads to a significant increase in surface hardness and high compressive residual stresses near the surface. Both effects may have a positive influence on lifetime. However, it also leads to surface notches and tensile residual stresses in the bulk material with a negative impact on cyclic lifetime. During fully reversed uniaxial tension-compression fatigue tests (R = −1) at a stress amplitude of 260 MPa, the positive effects dominate, and the fatigue lifetime increases. At a lower stress amplitude of 230 MPa, the negative effect of internal tensile residual stresses dominates, and the lifetime decreases. Shot peening leads to a transition from surface to volume crack initiation if the surface is not damaged by the shots.

Fatigue behavior of precipitation strengthened Cu–Ni–Si alloy modified by Cr and Zr addition

2020 ◽  
Vol 11 (6) ◽  
pp. 861-873
Author(s):  
Ş. Hakan Atapek ◽  
Spiros Pantelakis ◽  
Şeyda Polat ◽  
Apostolos Chamos ◽  
Gülşah Aktaş Çelik
Keyword(s):  
Design Methodology ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Lower Stress ◽  
Content Type ◽  
Hardened Alloy ◽  
Zr Addition ◽  
Nucleation Sites ◽  
The Matrix ◽  
Lower Stress Level

Purpose The purpose of this paper is to investigate the fatigue behavior of precipitation-strengthened Cu‒2.55Ni‒0.55Si alloy, modified by the addition of 0.25 Cr and 0.25 Zr (wt%), using mechanical and fractographical studies to reveal the effect of microstructural features on the fracture. Design/methodology/approach For strengthening, cast and hot forged alloy was subjected to solution annealing at 900°C for 60 min, followed by quenching in water and then aging at 490°C for 180 min. Precipitation-hardened alloy was exposed to fatigue tests at R=−1 and different stress levels. All fracture surfaces were examined within the frame of fractographical analysis. Findings Fine Ni-rich silicides responsible for the precipitation strengthening were observed within the matrix and their interactions with the dislocations at lower stress level resulted in localized shearing and fine striations. Although, by the addition of Cr and Zr, the matrix consisted of hard Ni, Zr-rich and Cr-rich silicides, these precipitates adversely affected the fatigue behavior acting as nucleation sites for cracks. Originality/value These findings contribute to the present knowledge by revealing the effect of microstructural features on the mechanical behavior of precipitation-hardened Cu‒Ni‒Si alloy modified by Cr and Zr addition.

Gigacycle Fatigue of Welded Joints of Structural Materials (A Review)

2016 ◽  
Vol 17 ◽  
pp. 14-30 ◽  
Author(s):  
Okechukwu P. Nwachukwu ◽  
Alexander V. Gridasov ◽  
Ekaterina A. Gridasova
Keyword(s):  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Testing Machine ◽  
Structural Materials ◽  
Fatigue Tests ◽  
Material Defects ◽  
Graphite Cast Iron ◽  
Ultrasonic Fatigue ◽  
Materials Used ◽  
Fatigue Failures

This review looks into the state of gigacycle fatigue behavior of some structural materials used in engineering works. Particular attention is given to the use of ultrasonic fatigue testing machine (USF-2000) due to its important role in conducting gigacycle fatigue tests. Gigacycle fatigue behavior of most materials used for very long life engineering applications is reviewed.Gigacycle fatigue behavior of magnesium alloys, aluminum alloys, titanium alloys, spheroid graphite cast iron, steels and nickel alloys are reviewed together with the examination of the most common material defects that initiate gigacycle fatigue failures in these materials. In addition, the stage-by-stage fatigue crack developments in the gigacycle regime are reviewed. This review is concluded by suggesting the directions for future works in gigacycle fatigue.

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.

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