scholarly journals Ultrasonic Fatigue Device and Behavior of High-Temperature Superalloy Inconel 718 with Self-Heating Phenomenon

2020 ◽  
Vol 10 (23) ◽  
pp. 8761
Author(s):  
Mengxiong Zhao ◽  
Tieying Wu ◽  
Zhenhua Zhao ◽  
Lulu Liu ◽  
Gang Luo ◽  
...  
Keyword(s):  
Inconel 718 ◽  
Initiation Site ◽  
Fatigue Tests ◽  
Test Method ◽  
Self Heating ◽  
Ductile Mode ◽  
Ultrasonic Resonance ◽  
Ultrasonic Fatigue ◽  
And Behavior ◽  
Very High

Ultrasonic resonance fatigue test method at 20 kHz related to the very high cycle fatigue (VHCF) aims to accelerate a time-consuming experiment. In this paper, an ultrasonic fatigue device with a data acquisition system was improved for monitoring and recording the data from fatigue tests in which self-heating phenomenon exists. Symmetric tension-compression sinusoidal vibrating mode (R = −1) was observed in this study. VHCF behavior and mechanism of Inconel 718 were carried out using this device. It was concluded that more than 99% of fatigue life is consumed in initiation duration. Specimen temperature increase was not a decisive factor in VHCF strength for Inconel 718, as long as it was far less than the design temperature limitation. A single initiation site existed at the subsurface facet or grain cluster, observed from scanning electron microscope (SEM) micrographs. Quasi-cleavage fracture in transgranular ductile mode emerged and then tended to trace grain boundaries in an intergranular manner by cleavage-dominated mixed mode.

Effect of shot peening on very high cycle fatigue of 2024-T351 aluminium alloy

2020 ◽  
Vol 10 (7) ◽  
pp. 1032-1039
Author(s):  
Renhui Tian ◽  
Jiangfeng Dong ◽  
Yongjie Liu ◽  
Qingyuan Wang ◽  
Yunrong Luo
Keyword(s):  
Fracture Surface ◽  
Crack Initiation ◽  
Shot Peening ◽  
High Cycle Fatigue ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Fatigue Strength Improvement ◽  
Ultrasonic Fatigue ◽  
Very High

To investigate the influence of shot peening (SP) on very high cycle fatigue (VHCF) performance of 2024-T351, the specimens with three surface conditions were performed under ultrasonic fatigue tests: mechanicallypolished without peening (NP), ceramic shot peening (SP1), steel and glass mixed shot peening (SP2). The roughness, microhardness, residual stress, fractography measurement and scanning electron microscopy (SEM) were applied before fatigue test to characterize the effective layer induced by the peening treatment. For the failed specimens, the fracture surface were analysed using SEM to study the mechanisms of fatigue crack propagation. In addition, the fatigue life curve in ultra-high cycle region continuously decreased in the three series of specimens. However, the experimental results revealed that fatigue strength improvement resulting from shot peening treatment was negligible in very high cycle regime. Furthermore, the stress intensity factor for the surface crack initiation (SCI) and interior crack initiation (ICI) was discussed based on quantitative analysis on the fracture surface. The average values of ΔKfish-eye for NP, SP1 and SP2 specimens are about 2.22, 1.48 and 1.61 MPa · m1/2, respectively.

scholarly journals Ultrasonic fatigue testing under multiaxial loading conditions on a railway wheel

2019 ◽  
Vol 300 ◽  
pp. 18003 ◽  
Author(s):  
Pedro R. da Costa ◽  
Henrique Soares ◽  
Luís Reis ◽  
Manuel Freitas
Keyword(s):  
Stress Ratio ◽  
Fatigue Testing ◽  
Fatigue Tests ◽  
Cycle Frequency ◽  
Railway Wheel ◽  
Material Specimen ◽  
Hydraulic Machines ◽  
Wide Range ◽  
Ultrasonic Fatigue ◽  
Very High

Ultrasonic fatigue testing is a relative recent fatigue methodology that uses resonant principles for the induction of stress cycles in a specific designed material specimen. This experimental method can apply very high cycle frequency, the most common frequency being 20 kHz, and was created with the main purpose of studying material fatigue life in the Very High Cycle Fatigue regime between 107 and 109 cycles with a higher performance of time and energy wise in comparison to conventional servo-hydraulic machines. In this study an improvement of an already built multiaxial ultrasonic fatigue machine in the Instituto Superior Técnico laboratories was carried out to specific designed specimens and afterwards a fatigue study was made for a material of a worn-out railway wheel. The particular design of the specimen was achieved by numerical and experimental analysis based on previous experiments and components. Thermographic imaging and the application of rosette strain gauges to the main throat of the specimens were conducted in order to validate the improved specimen design and to understand the real induced stresses on the specimen. Afterwards fatigue tests were conducted for several specimens for a wide range of stresses with a stress ratio R=-1 and an axial vs shear stress ratio of around 0.58. Results were analysed and fracture analysis was also carried out.

Damage Mechanisms of Initiating Micro-Pitting on 42CrMo4 Hardened and Tempered Steel

2007 ◽  
Vol 348-349 ◽  
pp. 869-872
Author(s):  
Fabrizio D'Errico ◽  
Marco Boniardi ◽  
Silvia Barella ◽  
Silvia Cincera
Keyword(s):  
Heat Treatment ◽  
Failure Mode ◽  
Contact Fatigue ◽  
Fatigue Tests ◽  
Treatment Choice ◽  
Test Method ◽  
Damage Mechanisms ◽  
Disc Surface ◽  
Very High ◽  
Electronic Microscope

A deep comprehension of the damage mechanisms involved in contact fatigue should optimize material and heat treatment choice for a specific application. In this work rolling disc-on-disc contact fatigue tests have been performed on a hardened and tempered UNI EN 42CrMo4 . The adopted test method creates the best conditions in order to develop micro-pitting on disc surface. Extensive micro-fractographic examinations have been carried out, on the damaged surfaces, through a scanning electronic microscope (SEM). For this steel, loaded with Hertzian pressure of 1000 MPa, the failure mode is always micro-pitting which begins at the surface, and it is not a sub-superficial damaging. If micro-pits develop, they will coalesce in larger craters. By this way, the probability that micropitting will degenerate into sub-superficial destructive pitting is very high.

scholarly journals Ultrasonic fatigue experiments with biaxial cruciform specimens

2019 ◽  
Vol 300 ◽  
pp. 18004
Author(s):  
Pedro R. da Costa ◽  
Diogo Montalvão ◽  
Manuel Freitas ◽  
Luis Reis
Keyword(s):  
Fatigue Testing ◽  
Complex Loading ◽  
Fatigue Tests ◽  
Dynamic Loads ◽  
Structural Components ◽  
Ultrasonic Fatigue ◽  
Innovative Materials ◽  
Wide Energy ◽  
Intended Behaviour ◽  
Very High

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.

scholarly journals Very High Cycle Fatigue Investigations on the Fatigue Strength of Additive Manufactured and Conventionally Wrought Inconel 718 at 873 K

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1682
Author(s):  
Alexander Schmiedel ◽  
Christina Burkhardt ◽  
Sebastian Henkel ◽  
Anja Weidner ◽  
Horst Biermann
Keyword(s):  
Crack Initiation ◽  
Inconel 718 ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Reference Conditions ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Fine Grained Structure ◽  
Very High

The fatigue lives of additively manufactured (AM) Inconel 718 (IN718) produced by selective electron beam melting and conventional wrought material as reference conditions were studied in the very high cycle fatigue regime under fully reversed loading (R = −1) at the elevated temperature of 873 K using an ultrasonic fatigue testing system. The fatigue lives of the AM material were significantly reduced compared to the wrought material, which is discussed in relation to the microstructure and a fractographical analysis. The additively manufactured material showed large columnar grains with a favoured orientation to the building direction and porosity, whereas the wrought material showed a fine-grained structure with no significant texture, but had Nb- and Ti-rich non-metallic inclusions. Crystallographic crack initiation as well as crack initiation from the surface or internal defects were observed for the AM and the wrought IN718, respectively.

Investigation of Very High Cycle Fatigue Behavior of TC17 Alloy

2011 ◽  
Vol 295-297 ◽  
pp. 1311-1314
Author(s):  
Li Cheng ◽  
Chao Gao ◽  
Jing Sheng Shen ◽  
Ning Li ◽  
Wei Chen ◽  
...  
Keyword(s):  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Test Technique ◽  
Bending Fatigue ◽  
Very High Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Very High ◽  
Ultrasonic Fatigue Test

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.

scholarly journals Review of Multiaxial Testing for Very High Cycle Fatigue: From ‘Conventional’ to Ultrasonic Machines

Machines ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 25
Author(s):  
Pedro Costa ◽  
Richard Nwawe ◽  
Henrique Soares ◽  
Luís Reis ◽  
Manuel Freitas ◽  
...  
Keyword(s):  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Cycle Fatigue ◽  
New Materials ◽  
Multiaxial Testing ◽  
Very High Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Very High

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.

scholarly journals Influence of Heat Treatment on Cyclic Response of Nickel-Based Superalloy Inconel 718 up to Very-High Cycle Regime

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5358
Author(s):  
Mengxiong Zhao ◽  
Zhenhua Zhao ◽  
Lulu Liu ◽  
Gang Luo ◽  
Wei Chen
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Crack Initiation ◽  
Inconel 718 ◽  
Fatigue Behavior ◽  
Initiation Mechanism ◽  
Cyclic Response ◽  
Self Heating ◽  
Average Grain Size ◽  
Very High

Cyclic response and fatigue behavior are sensitive to the microstructure of material induced by heat treatment. In this paper, three sets of high-temperature superalloy Inconel 718 with different heat treatment, namely annealed, aged, and directly aged high quality (DAHQ), are compared. Difference in grain size distribution, phase, and precipitate, etc., were investigated using an optical camera and scanning electron microscopy. Yield and ultimate strength were found to increase obviously after aging heat treatment. Self-heating phenomenon at 20 kHz was attenuated as grain size decreased. There was a transition from cyclic hardening to softening. Very-high cycle fatigue (VHCF) behavior of Inconel 718 was tested using an ultrasonic fatigue device. Crack initiation duration occupied greater than 99% of the total fatigue life. It concluded that average grain size influences VHCF strength and crack initiation mechanism, and that self-heating phenomenon is not a decisive factor on VHCF strength for Inconel 718.

scholarly journals Internal Crack Initiation and Growth Starting from Artificially Generated Defects in Additively Manufactured Ti6Al4V Specimen in the VHCF Regime

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5315
Author(s):  
Carsten Wickmann ◽  
Christopher Benz ◽  
Horst Heyer ◽  
Kerstin Witte-Bodnar ◽  
Jan Schäfer ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Fatigue Testing ◽  
Early Stage ◽  
Ion Beam ◽  
Fatigue Tests ◽  
Internal Crack ◽  
Very High Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Experimental Findings ◽  
Very High

The aim of the present work was to investigate the ‘fine granular area’ (FGA) formation based on artificially generated internal defects in additively manufactured Ti6Al4V specimens in the early stage of fatigue crack growth in the ‘very high cycle fatigue’ (VHCF) regime. Fatigue tests were performed with constant amplitude at pure tension-compression loading (R = −1) using an ultrasonic fatigue testing setup. Failed specimens were investigated using optical microscopy, high-resolution ‘scanning electron microscopy’ (SEM), and ‘focused ion beam’ (FIB) techniques. Further, the paper introduces alternative proposals to identify the FGA layer beneath the fracture surfaces in terms of the ‘cross section polishing’ (CSP) technique and metallic grindings with special attention paid to the crack origin, the surrounding microstructure, and the expansion of the nanograin layer beneath the fracture surface. Different existing fracture mechanical approaches were applied to evaluate if an FGA formation is possible. Moreover, the results were discussed in comparison to the experimental findings.

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