Analysis of Strain Energy Behavior throughout a Fatigue Process

Scott‐Emuakpor, Onome; George, Tommy; Cross, Charles; Shen, M.-H. Herman

doi:10.1007/978-1-4419-9792-0_70

Cited by 3 publications

(4 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…3 Fatigue failure assessment based on hysteresis energy and thermal response [21][22][23][24] has been under extensive study during past decades. Both plastic strain energy [25][26][27][28][29][30] and total strain energy [31][32][33][34] have been the focus of a number of studies. It was postulated by Feltner and Morrow 35 that total non-recoverable plastic work measured from the hysteresis loop would be constant at the point of failure.…”

mentioning

confidence: 99%

Thermodynamic entropy generation in the course of the fatigue crack initiation

Ontiveros

Amiri

Kahirdeh

et al. 2016

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

Evolution of the thermodynamic entropy generation during fatigue crack initiation life of notched specimens is studied. A set of experimental results of AA7075‐T651 is examined to determine applicability of the thermodynamic entropy generation as an index of fatigue crack initiation. Entropy accumulation is calculated from hysteresis energy and temperature rise. An increasing trend of entropy accumulation with the number of cycle to failure is observed on macroscale measurements. Results also determine that the entropy generations from the samples under the same operating conditions are similar as the crack grows. Scanning electron microscope analysis is performed on the fractured surfaces to observe the fatigue striations, and persistent slip bands are observed employing an optical microscope. A discussion is presented regarding the length scales on which crack initiation occurs and entropy calculation is made.

show abstract

mentioning

confidence: 99%

Thermodynamic entropy generation in the course of the fatigue crack initiation

Ontiveros

Amiri

Kahirdeh

et al. 2016

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

show abstract

“…8,9 The cyclic energy attained from those previous tests showed that there is minimal energy variation in a small number of cycle samples (~20 cycles) at strain amplitudes greater than 3500 a ; the results also show the energy variation increasing drastically for strain amplitudes below 3000 a . 8 Since low strain ranges are necessary for assessing damping, especially for non-linear materials, the hysteretic energy variation through 300 cycles at low strain amplitudes were analyzed. The analysis observes the consistency of energy from specimen-to-specimen, and the energy repeatability of individual specimens after several tests.…”

Section: Results and Analysismentioning

confidence: 86%

“…Of these 500 cycles, the first 200 were discarded to avoid potential cyclic hardening (transient displacement amplitude) that could skew the stastistical results of dissipated energy. 8 For the 300 remaining cycles, load, displacement and strain were recorded at a sampling rate of 20Hz. The load was recorded from a calibrated load cell, and displacement was attained from the linear variable displacement transformer (LVDT).…”

Section: Methodsmentioning

confidence: 99%

“…This strain value was chosen arbitrarily because it was significantly lower than the strain amplitude analyzed in Ref. 8. Though strain amplitude was the targeted test parameter, the test was load controlled at a corresponding value that was chosen based on published elastic modulus data and the cross-sectional area of the specimen.…”

Section: A Analysis On Hysteretic Energy Variationmentioning

confidence: 99%

See 1 more Smart Citation

A Hysteretic Energy Method for Determining Damping Properties of Hard Coatings

Scott‐Emuakpor¹,

Runyon²,

George³

et al. 2012

53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials ConferenceSelf Cite

3
0
0
0

View full text Add to dashboard Cite

The following manuscript investigates the use of dissipated and stored energies to extract mechanical damping properties from an axially loaded system. This method is observed for three reasons that will benefit the process for determining the damping capacity of hard coatings: 1) it is capable of determining damping properties at larger strain amplitude levels than conventional methods, 2) small strain ranges at stress ratios greater than -1 can be observed to accurately assess damping properties of strain-dependent materials, and 3) the method for extracting damping properties can be automated by using simplified energy calculations. Despite the pros of the hysteretic energy method, there are some limitations that may make its use impractical. One of the major limitations was explored in this study: inconsistency of the hysteretic energy measurement. The hysteretic energy results were observed for several Aluminum 6061-T6 specimens, where a large sample size was averaged to determine if there was consistency in the mean quality factors (a damping parameter) and the relative standard deviations of the sampled energies. Though the results of this study showed consistency in both observed parameters, the resulting values of the quality factors were too low to assess the storage moduli values seen in typical hard coatings, which are in the range of 20-200GPa. The experimental results of this study brings forth the need to address another limiting factor of the hysteretic energy method. In other words, the mitigation of frictional energy losses at the boundary conditions will be explored in future work. NomenclatureD s = system dissipated energy E = elastic storage modulus E b = elastic storage modulus -substrate E c = elastic storage modulus -coating E l = loss modulus h = substrate thickness P a = force amplitude P c = compressive force equation P t = tensile force equation Q = quality factor R = alternating stress/strain ratio R-STD = relative standard deviation t = coating thickness U s = system stored energy  = displacement  a = displacement amplitude  = strain a = strain amplitude  = loss factor 2 Figure 1. Hysteresis loop schematic for energy calculation. c = coating loss factor  s = system loss factor

show abstract

Analysis of Hysteresis Damage Accumulation and the Effect on Fatigue Life
Scott‐Emuakpor
¹
,
George
²
,
Cross
³

et al. 2011
Experimental and Applied Mechanics, Volume 6
0
0
0
0
View full text Add to dashboard Cite

Analysis of Strain Energy Behavior throughout a Fatigue Process

Cited by 3 publications

References 7 publications

Thermodynamic entropy generation in the course of the fatigue crack initiation

Thermodynamic entropy generation in the course of the fatigue crack initiation

A Hysteretic Energy Method for Determining Damping Properties of Hard Coatings

Analysis of Hysteresis Damage Accumulation and the Effect on Fatigue Life

Contact Info

Product

Resources

About