The Fatigue Behavior of NiCr22Co12Mo9 Under Low-Frequency Thermal-Mechanical Loading and Superimposed Higher-Frequency Mechanical Loading

2008 ◽  
pp. 195-195-15 ◽  
Author(s):  
M Moalla ◽  
K-H Lang ◽  
D Löhe
Keyword(s):  
Mechanical Loading ◽  
Fatigue Behavior ◽  
Low Frequency

Effects of Electrical Characters on Electrical Fatigue Behavior in PLZT Ferroelectric Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 159-162 ◽  
Author(s):  
Zhi Wu Chen ◽  
Zhen Ya Lu ◽  
Xu Ming Chen ◽  
Ying Zhang ◽  
Xuan Cheng
Keyword(s):  
Domain Switching ◽  
Fatigue Behavior ◽  
Low Frequency ◽  
Quantitative Information ◽  
Sine Wave ◽  
Sem Analysis ◽  
Fatigue Tests ◽  
Ferroelectric Ceramics ◽  
Electrical Field ◽  
Field Magnitude

Electrical fatigue tests have been conducted on PLZT ferroelectric ceramics. It was found that the higher the applied electrical field magnitude, the faster the Pr decreases; the samples under the same electrical field magnitude but with square wave have higher fatigue rate than that of sine wave. It was observed that at low frequency of applied field (50Hz and 500Hz), the polarization decreased very quickly and dropped below 70% of the original value within 106.2 switching cycles, however, when fatigue test were conducted at high frequencies of 100kHz and 300kHz, the polarization did not change significantly even after 109 cycles. The SEM analysis indicated that the facture mode was mainly of trans-granular for the virgin non-fatigued sample, while of inter-granular for the fatigue sample. The quantitative information on the 90° domain switching was measured in situ using X-ray diffraction. The effects of electrical characters on electrical fatigue behavior were explained according to the mechanism of electrical fatigue in PLZT ferroelectric ceramics.

scholarly journals Modelling and Laboratory Studies on the Adhesion Fatigue Performance for Thin-Film Asphalt and Aggregate System

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Dongsheng Wang ◽  
Junyan Yi ◽  
Decheng Feng
Keyword(s):  
Thin Film ◽  
Fatigue Behavior ◽  
Asphalt Binder ◽  
Low Frequency ◽  
Test System ◽  
Silica Content ◽  
Fatigue Performance ◽  
Adhesion Performance ◽  
Aggregate System

Adhesion between asphalt and aggregate plays an important role in the performance of asphalt mixtures. A low-frequency adhesion fatigue test was proposed in this paper to study the effect of environment on the asphalt-aggregate adhesion system. The stress-based fatigue model had been utilized to describe the fatigue behavior of thin-film asphalt and aggregate system. The factors influencing the adhesion fatigue performance were also investigated. Experiment results show that asphalt has more important effect on the adhesion performance comparing with aggregate. Basalt, which is regarded as hydrophobic aggregates with low silica content, has better adhesion performance to asphalt binder when compared with granite. The effects of aging on the adhesion fatigue performance are different for PG64-22 and rubber asphalt. Long-term aging is found to reduce the adhesion fatigue lives for rubber asphalt and aggregate system, while the effect of long-term aging for aggregate and PG64-22 binder system is positive. Generally the increased stress amplitude and test temperature could induce greater damage and lead to less fatigue lives for adhesion test system.

Effect of Frequency on the Fatigue Behavior of IN718 Superalloy

2017 ◽  
Vol 1142 ◽  
pp. 23-30 ◽  
Author(s):  
Jin Hui Du ◽  
Xu Dong Lu ◽  
Qun Deng
Keyword(s):  
Grain Size ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Low Frequency ◽  
Initiation Site ◽  
Fatigue Properties ◽  
Crack Initiation Site

IN718 alloy possesses excellent mechanical properties at high temperatures, good process ability, therefore, it has been widely used in aero engine turbine disks, compressor disks, and power turbine shafts (i.e., rotating components). The fatigue properties of the alloy are a key factor that determines the safety and reliability of the engine. In this paper, the fatigue properties of IN718 alloy are investigated under low-and middle-frequency conditions at 600 °C and 455 °C, the initiation of fatigue cracks, and the relation between fatigue life and grain size are discussed. The results show that the carbides response as a crack initiation site at low-frequency fatigue condition (1 Hz), and string-type or heap-type carbides distribution promotes crack propagation and shortens fatigue life, the twin boundaries in large grains are act as a crack initiation site at middle-frequency fatigue condition (10 Hz). The grain size is smaller, and the low cycle fatigue properties of the alloy are better.

Mechanical Properties of Piezoelectric Stack Actuators under Electro-Mechanical Loading

2007 ◽  
Vol 336-338 ◽  
pp. 331-334 ◽  
Author(s):  
Shao Ze Yan ◽  
Kai Zheng ◽  
Jian Xun
Keyword(s):  
Mechanical Loading ◽  
Piezoelectric Coefficient ◽  
Strong Dependence ◽  
Dynamic Test ◽  
Low Frequency ◽  
Input Voltage ◽  
Experimental Results ◽  
Phase Lag ◽  
Driving Frequency ◽  
Piezoelectric Stack Actuator

The responses of the piezoelectric stack actuator under electro-mechanical loading are investigated. Two types of tests are performed: influences of the preload on characteristics of the stack and dynamic test. Experimental results indicate strong dependence of the stack properties on the electro-mechanical loading conditions. The displacement output is initially enhanced with an increase of the mechanical preload, and the maximum value is obtained at the preload of about 0.4 kN. But much higher preload will cause the decrease of the displacement output. The effective piezoelectric coefficient and the hysteresis degree are employed to describe the variations of the stack’s performances caused by the mechanical preload. The effective piezoelectric coefficient under different preloads can be calculated by using experimental results of the displacement output and input voltage. Within low frequency band of about 400 Hz, the displacement magnitude of the stack is nearly constant, and the phase lag increases with the increase of the driving frequency at the applied sine sweep voltage with the amplitude of 150V.

scholarly journals Optimizing Mechanical Stretching Protocols for Hypertrophic and Anti-apoptotic Responses in H9c2 Cardiomyocytes

2020 ◽  
Author(s):  
Evangelos Zevolis ◽  
Anastassios Philippou ◽  
Athanasios Moustogiannis ◽  
Antonis Chatzigeorgiou ◽  
Michael Koutsilieris
Keyword(s):  
Mechanical Loading ◽  
Low Frequency ◽  
Signaling Proteins ◽  
Mechanical Stimuli ◽  
Elastic Membranes ◽  
H9c2 Cardiomyocytes ◽  
H9c2 Cardiomyoblasts ◽  
Mechanical Stretching ◽  
Strain Frequency

Abstract Background: Cardiomyocytes are sensitive to mechanical loading, possessing the ability to respond to mechanical stimuli by reprogramming their gene expression. In this study, signaling as well as expression responses of myogenic, anabolic, inflammatory, atrophy and pro-apoptotic genes to different mechanical stretching protocols were examined in differentiated cardiomyocytes.Methods: H9C2 cardiomyoblasts were cultured on elastic membranes up to their 5th day of differentiation (myotubes) and then subjected to three different stretching protocols by altering their strain, frequency and duration characteristics, using an in vitro cell tension system. cells were harvested and lysed 24 hours after the completion of each stretching protocol and Real Time-PCR was used to monitor changes in mRNA expression of myogenic regulatory factors (MyoD, Myogenin, MRF4), the IGF-1 isoforms (IGF-1Ea, IGF-1Eb), as well as atrophy (Atrogin-1), pro-apoptotic (FoxO, Fuca), and inflammatory (IL-6) factors in response to the different mechanical loading conditions. The activation of Akt and Erk 1/2 signaling proteins following the various stretching protocols was also evaluated by Western blot analysis.Results: We documented that the low strain (2.7% elongation), low frequency (0.25 Hz) and intermediate duration (12 hrs) stretching protocol was overall the most effective in inducing beneficial responses in differentiated cardiomyoblasts as it increased the expression of IGF-1 isoforms and phosphorylation of Akt and Erk1/2 (p<0.05), while it provoked the downregulation of all the other factors examined (p<0.05-0.001). Conclusion: These findings demonstrated that a low strain, low frequency of intermediate duration stretching protocol is the most effective in inducing a hypertrophic and anti-apoptotic response in H9C2 cardiomyotubes, in vitro.

scholarly journals Potential Relevance of Altered Muscle Activity and Fatigue in the Development of Performance-Related Musculoskeletal Injuries in High String Musicians

2018 ◽  
Vol 33 (3) ◽  
pp. 147-155 ◽  
Author(s):  
Dirk Möller ◽  
Nikolaus Ballenberger ◽  
Bronwen Ackermann ◽  
Christoff Zalpour
Keyword(s):  
Muscle Fatigue ◽  
Frequency Spectrum ◽  
Muscle Activity ◽  
Muscle Activation ◽  
Fatigue Behavior ◽  
Low Frequency ◽  
The Body ◽  
Trial Duration ◽  
Muscle Activation Patterns ◽  
Chromatic Scale

BACKGROUND: Muscle fatigue seems to be a risk factor in the development of performance-related musculoskeletal disorders (PRMDs) in musicians, but it is unclear how muscle activity characteristics change between musicians with and without PRMDs over a prolonged playing period. PURPOSE: To investigate muscle activity patterns in muscles of the arms, shoulder, and back of high string musicians during prolonged performance. METHODS: Fifteen professional or university high string musicians were divided into PRMD and non-PRMD groups. All musicians played a chromatic scale, then an individual “heavy” piece for 1 hr, and finally the chromatic scale again. Surface electromyography (sEMG) data were recorded from 16 muscles of the arm, shoulder, and trunk on both sides of the body. Two parameters were analyzed: the percentage load in relation to the respective maximum force during the chromatic scale, and the low-frequency spectrum to determine the fatigue behavior of muscles during the 1-hr play. RESULTS: Changes in muscle activation patterns were observed at the beginning and end of the trial duration; however, these varied depending on whether musicians had PRMDs or no PRMDs. In addition, low-frequency spectrum changes were observed after 1 hr of playing in the PRMD musicians, consistent with signs of muscular fatigue. CONCLUSION: Differences in muscle activity appear between high string musicians with and without PRMDs as well as altered frequency spectrum shifts, suggesting possible differential muscle fatigue effects between the groups. The applied sEMG analysis proved a suitable tool for detailed analysis of muscle activation characteristics over prolonged playing periods for musicians with and without PRMDs.

scholarly journals In vivo assessment of the effect of controlled high- and low-frequency mechanical loading on peri-implant bone healing

2012 ◽  
Vol 9 (72) ◽  
pp. 1697-1704 ◽  
Author(s):  
Xiaolei Zhang ◽  
Katleen Vandamme ◽  
Antonia Torcasio ◽  
Toru Ogawa ◽  
G. Harry van Lenthe ◽  
...  
Keyword(s):  
Mechanical Loading ◽  
Bone Healing ◽  
Ex Vivo ◽  
Low Frequency ◽  
Constant Strain Rate ◽  
Titanium Implants ◽  
Cortical Level ◽  
Bone Response ◽  
Custom Made ◽  
40 Hz

The aim of this study was to investigate the effect of controlled high- (HF) and low-frequency (LF) mechanical loading on peri-implant bone healing. Custom-made titanium implants were inserted in both tibiae of 69 adult Wistar rats. For every animal, one implant was loaded by compression through the axis of tibia (test), whereas the other one was unloaded (control). The test implants were randomly distributed among four groups receiving different loading regimes, which were determined by ex vivo calibration. Within the HF (40 Hz) or LF (2 Hz) loading category, the magnitudes were chosen as low- (LM) and high-magnitude (HM), respectively, leading to constant strain rate amplitudes for the two frequency groups. This resulted in the four loading regimes: (i) HF-LM (40 Hz–0.5 N); (ii) HF-HM (40 Hz–1 N); (iii) LF-LM (2 Hz–10 N); and (iv) LF-HM (2 Hz–20 N) loading. Loading was performed five times per week and lasted for one or four weeks. Tissue samples were processed for histology and histomorphometry (bone-to-implant contact, BIC; and peri-implant bone fraction, BF) at the cortical and medullar level. Data were analysed statistically with ANOVA and paired t -tests with the significance level set at 0.05. For the one-week experiments, an increased BF adjacent to the implant surface at the cortical level was exclusively induced by the LF-HM loading regime (2 Hz–20 N). Four weeks of loading resulted in a significant effect on BIC (and not on BF) in case of HF-LM loading (40 Hz–0.5 N) and LF-HM loading (2 Hz–20 N): BIC at the cortical level significantly increased under both loading regimes, whereas BIC at the medullar level was positively influenced only in case of HF-LM loading. Mechanical loading at both HF and LF affects osseointegration and peri-implant BF. Higher loading magnitudes (and accompanying elevated tissue strains) are required under LF loading to provoke a positive peri-implant bone response, compared with HF loading. A sustained period of loading at HF is needed to result in an overall enhanced osseointegration.

Investigation of High Cycle and Low Cycle Fatigue Interaction on Fatigue Behavior of Welded Joints

2012 ◽  
Vol 217-219 ◽  
pp. 2101-2106
Author(s):  
Liang Chen Wu ◽  
Dong Po Wang
Keyword(s):  
Adverse Effect ◽  
Fatigue Life ◽  
Welded Joints ◽  
High Frequency ◽  
Stress Ratio ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Low Frequency ◽  
Cycle Fatigue

Samples of Q345 steel welded joints were tested to failure under low cycle fatigue(LCF),high cycle fatigue(HCF) and combined fatigue(CCF) using an apparatus that is capable of providing interactive LCF/HCF loading. The stress ratio R is 0.5 and the frequency of HCF is about 19kHz. The result indicates that not only high frequency minor cycles superimposed on low frequency major cycles , but also low frequency minor cycles superimposed on high frequency major cycles can do remarkable damage to fatigue performance of welded joints. The CCF strength is characterized by amplitude envelope. If CCF fatigue life is characterized by LCF life, adverse effect of HCF component is underestimated. If CCF fatigue life is characterized by HCF life, adverse effect of LCF component is overrated.

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