scholarly journals Experimental Investigation of Second-Harmonic Lamb Wave Generation in Additively Manufactured Aluminum

2018 ◽  
Vol 1 (4) ◽  
Author(s):  
Benjamin Steven Vien ◽  
Wing Kong Chiu ◽  
L. R. Francis Rose
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Second Harmonic ◽  
Low Cycle Fatigue ◽  
Propagation Distance ◽  
Nonlinearity Parameter ◽  
Harmonic Amplitude ◽  
Cycle Fatigue ◽  
Fatigue Damage Accumulation

The correlation between the nonlinear acousto-ultrasonic response and the progressive accumulation of fatigue damage is investigated for an additively manufactured aluminum alloy AlSi7Mg and compared with the behavior of a conventional wrought aluminum alloy 6060-T5. A dual transducer and wedge setup is employed to excite a 30-cycle Hann-windowed tone burst at a center frequency of 500 kHz in plate-like specimens that are 7.2 mm thick. This choice of frequency-thickness is designed to excite the symmetric Lamb mode s1, which, in turn, generates a second-harmonic s2 mode in the presence of distributed material nonlinearity. This s1-s2 mode pair satisfies the conditions for internal resonance, thereby leading to a cumulative build-up of amplitude for the second-harmonic s2 mode with increasing propagation distance. Measurements of a nonlinearity parameter β derived from the second-harmonic amplitude are plotted against propagation distance at various fractions of fatigue life under constant amplitude loading, for three different stress levels corresponding to low-cycle fatigue (LCF), high-cycle fatigue (HCF), and an intermediate case. The results show both qualitative and quantitative differences between LCF and HCF, and between the additively manufactured specimens and the wrought alloy. The potential use of this nonlinearity parameter for monitoring the early stages of fatigue damage accumulation, and hence for predicting the residual fatigue life, is discussed, as well as the potential for quality control of the additive manufacturing (AM) process.

A Multi-Level Low Cycle Fatigue Damage Model for Forging Die Material

2006 ◽  
Vol 514-516 ◽  
pp. 804-809
Author(s):  
S. Gao ◽  
Ewald Werner
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Fatigue Loading ◽  
Cycle Fatigue ◽  
Die Material ◽  
Multi Level ◽  
Loading Sequence ◽  
Forging Die

The forging die material, a high strength steel designated W513 is considered in this paper. A fatigue damage model, based on thermodynamics and continuum damage mechanics, is constructed in which both the previous damage and the loading sequence are considered. The unknown material parameters in the model are identified from low cycle fatigue tests. Damage evolution under multi-level fatigue loading is investigated. The results show that the fatigue life is closely related to the loading sequence. The fatigue life of the materials with low fatigue loading first followed by high fatigue loading is longer than that for the reversed loading sequence.

scholarly journals Fatigue Damage Accumulation Modeling of Metals Alloys under High Amplitude Loading at Elevated Temperatures

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1030 ◽  
Author(s):  
Jarosław Szusta ◽  
Andrzej Seweryn
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Elevated Temperatures ◽  
Low Cycle Fatigue ◽  
High Amplitude ◽  
Metal Alloys ◽  
Damage State ◽  
State Variable ◽  
Fatigue Damage Accumulation

This article presents an approach related to the modeling of the fatigue life of constructional metal alloys working under elevated temperature conditions and in the high-amplitude load range. The article reviews the fatigue damage accumulation criteria that makes it possible to determine the number of loading cycles until damage occurs. Results of experimental tests conducted on various technical metal alloys made it possible to develop a fatigue damage accumulation model for the LCF (Low Cycle Fatigue) range. In modeling, the material’s damage state variable was defined, and the damage accumulation law was formulated incrementally so as to enable the analysis of the influence of loading history on the material’s fatigue life. In the proposed model, the increment of the damage state variable was made dependent on the increment of plastic strain, on the tensile stress value in the sample, and also on the actual value of the damage state variable. The model was verified on the basis of data obtained from experiments in the field of uniaxial and multiaxial loads. Samples made of EN AW 2024T3 aluminum alloy were used for this purpose.

Modeling, Simulation, and Experimentation of Fatigue Behavior in Amorphous Solids

2018 ◽  
Vol 774 ◽  
pp. 210-216 ◽  
Author(s):  
Thierry Barriere ◽  
Gang Cheng ◽  
Sami Holopainen
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Stress Reduction ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Amorphous Solids ◽  
Cycle Fatigue ◽  
Unified Approach ◽  
Structural Element ◽  
Modeling Simulation

Amorphous solids, such as certain polymers, alloys, and polymer-based composites,are increasingly used materials in engineering components and thus, their fatigue behavioris of utmost importance. The article presents a unified approach suitable for modeling bothisothermal high cycle and low cycle fatigue behavior. The emphasis is placed on the ductilefatigue in which fatigue damage represents the material degeneration during the creation ofmicro-cracks governing majority of the total fatigue life (up to 95%). The model’s capability fortechnologically important polycarbonate (PC) polymer is addressed. The results, in accordancewith experimental observations, favor ductile fatigue behavior, i.e. damage fields remain smallfor most of the fatigue life and do not cause the macroscopic stress reduction. Due to thisproperty, fatigue life of an entire structural element can be evaluated by exploiting singlelocations at which the fatigue damage decisively emerges.

Early Fatigue Damage of Magnesium Alloy On-Line Monitoring by Nonlinear Ultrasonic

2010 ◽  
Vol 139-141 ◽  
pp. 194-197
Author(s):  
Bing Sheng Yan ◽  
Bin Wu ◽  
Cun Fu He ◽  
Jing Pin Jiao
Keyword(s):  
Fatigue Life ◽  
Magnesium Alloy ◽  
Yield Stress ◽  
Fatigue Damage ◽  
Stress Level ◽  
Second Harmonic ◽  
Experimental Results ◽  
Nonlinearity Parameter ◽  
Acoustic Nonlinearity Parameter ◽  
On Line

This research develops a robust experimental procedure to monitor the evolution of early fatigue damage in AZ31 magnesium alloy with the acoustic nonlinearity parameter , and demons- trats its reliability by measuring the linear relationship between amplitudes of the second-harmonic waves and fundamental waves squared. Using this system, of two sets of specimens with different stress level is measured. The experimental results show that there is a significant increase in linked to fatigue degree in the early stages of fatigue life and reaches the maximum about 55%of fatigue life, when the stress level is ±60%of the yield stress, can characterize the early fatigue damage of magnesium alloy. However, when the stress level is ±70%of the yield stress, there is a regular fluctuation in linked to fatigue degree, this experimental results can’t be explained.

Cumulative Damage and Effect of Mean Strain in Low-Cycle Fatigue of a 2024-T351 Aluminum Alloy

1966 ◽  
Vol 88 (4) ◽  
pp. 801-810 ◽  
Author(s):  
Kiyotsugu Ohji ◽  
W. R. Miller ◽  
Joseph Marin
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Cumulative Damage ◽  
Strain Condition ◽  
Cycle Fatigue ◽  
History Of ◽  
Mean Strain ◽  
Strain Cycling ◽  
Cycling Behavior

By assuming a linear cumulative damage hypothesis for strain cycling, theories are developed in this paper for fatigue life under varying strain amplitude, residual ductility after a given history of strain cyling, and life under mean strain condition. These predictions are based on uniaxial completely reversed cycling behavior. The expressions obtained were compared with the experimental results on 2024-T351 aluminum alloy as well as other data available in the literature. The agreements between theories and experiments were found to be satisfactory.

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