A unified damage model for fibrous composite laminae subject to in-plane stress-state and having multi material-nonlinearity

2020 ◽  
Vol 29 (9) ◽  
pp. 1329-1344
Author(s):  
GA Abu-Farsakh ◽  
AM Asfa
Keyword(s):  
Energy Density ◽  
Plastic Strain ◽  
Strain Energy Density ◽  
Damage Evolution ◽  
Strain Energy ◽  
Fibrous Composite ◽  
Damage Model ◽  
Damage Propagation ◽  
Damage Response ◽  
Plastic Strain Energy

In the present study, a novel methodology of damage modeling is introduced to predict damage propagation in fibrous composite materials according to the plastic strain energy density induced in the lamina only. The importance of the new damage-model is the ability to assess damage-evolution in fibrous composite laminae irrespective of stress-state and fiber-orientation angle. An energy-based model called as a unified damage model, is proposed to evaluate damage in unidirectional fibrous composite laminae. The aforementioned damage model represents a unique relationship between damage-evolution and the resulting plastic strain energy density induced in the composite lamina, as verified through this study. Damage propagation under a state of in-plane-stress is investigated for three composite laminas; boron/epoxy, graphite/epoxy, and carbon/epoxy. The unified damage model represents a simplified mathematical relation of quantum-damage (or modified-damage) variables in terms of the induced plastic-strain-energy density induced in a composite lamina. The developed unified damage model confirms the results of Ghazi-Ahmad macro-mechanical damage model in which graphite/epoxy has the lowest damage response, whereas boron/epoxy has the highest possible damage response amongst the three composite materials. Also, it is noticed that quantum-damage propagates nonlinearly with the evolved plastic strain energy density in fibrous composite laminae.

Effect of plastic strain energy density on polymer optical fiber power losses

2006 ◽  
Vol 31 (7) ◽  
pp. 879 ◽  
Author(s):  
Yung-Chuan Chen ◽  
Jao-Hwa Kuang ◽  
Li-Wen Chen ◽  
Hua-Chun Chuang
Keyword(s):  
Energy Density ◽  
Plastic Strain ◽  
Optical Fiber ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Power Losses ◽  
Polymer Optical Fiber ◽  
Plastic Strain Energy

scholarly journals Low Cycle Fatigue Life Assessment Based on the Accumulated Plastic Strain Energy Density

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2372
Author(s):  
Yifeng Hu ◽  
Junping Shi ◽  
Xiaoshan Cao ◽  
Jinju Zhi
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Energy Density ◽  
Plastic Strain ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Fatigue Initiation ◽  
Plastic Strain Energy

The accumulated plastic strain energy density at a dangerous point is studied to estimate the low cycle fatigue life that is composed of fatigue initiation life and fatigue crack propagation life. The modified Ramberg–Osgood constitutive relation is applied to characterize the stress–strain relationship of the strain-hardening material. The plastic strain energy density under uni-axial tension and cyclic load are derived, which are used as threshold and reference values, respectively. Then, a framework to assess the lives of fatigue initiation and fatigue crack propagation by accumulated plastic strain energy density is proposed. Finally, this method is applied to two types of aluminum alloy, LC9 and LY12 for low-cycle fatigue, and agreed well with the experiments.

Plastic Strain Energy in Low-Cycle Fatigue of A356 (Al-7Si-0.4Mg) Aluminum Alloys

2011 ◽  
Vol 194-196 ◽  
pp. 1210-1216
Author(s):  
Mou Sheng Song ◽  
Mao Wu Ran
Keyword(s):  
Energy Density ◽  
Plastic Strain ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Low Cycle Fatigue ◽  
A356 Alloy ◽  
Cycle Fatigue ◽  
Plastic Strain Energy ◽  
Ti Content ◽  
Ti Addition

In this paper, the problem of plastic strain energy density as a evaluation of low-cycle fatigue (LCF) properties for A356 alloys with various Ti content and Ti-addition methods is considered. The experimental results reveal that it is not the Ti-addition methods but the Ti content that has played an important role in influencing on the plastic strain energy density, thus on the LCF life. Whether for the electrolytic A356 alloys or for the melted A356 alloys, the alloys with 0.1% Ti content can consume higher cyclic plastic strain energy during the cyclic deformation compared with the alloys with 0.14% Ti content due to the better plasticity, giving rise to a better fatigue resistance and a longer LCF life. Because of the different macro or micro deformation mechanism, the fracture surface of electrolytic A356 alloy exhibits the diverse microstructural morphologies under the various strain amplitude.

scholarly journals Strain energy-and stress-based approaches revisited in notch fatigue of ductile steels

2018 ◽  
Vol 165 ◽  
pp. 14009 ◽  
Author(s):  
Bruno Atzori ◽  
Mauro Ricotta ◽  
Giovanni Meneghetti
Keyword(s):  
Energy Density ◽  
Plastic Strain ◽  
Strain Energy Density ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Fatigue Behaviour ◽  
Strength Reduction Factor ◽  
Plastic Strain Energy ◽  
Elastic Strain Energy Density

The constant amplitude, zero-mean stress, axial-fatigue behaviour of plain and bluntly notched AISI 304 L stainless steel specimens is investigated in terms of strain energy density. Concerning plain material, it was found that at the fatigue knee the plastic strain energy density is 1.49 times higher than the elastic strain energy density. In the authors’ opinion, the presence of plasticity at the fatigue knee is responsible for the unsuitableness of classical stress - based approaches to synthesise the fatigue behaviour of this material. On the contrary, the elastic-plastic strain energy density was found an efficient parameter to rationalise in a single scatter band fatigue data of plain and bluntly notched specimens. Based on this result, the classic stress-and the point stress-based approaches were revisited taking into account the presence of plasticity at the fatigue knee, by introducing an equivalent fully elastic material having a linear elastic strain energy density at the fatigue knee equal to that of the actual material. Accordingly, a coefficient of plasticity Kp was successfully introduced to modify the classical definition of fatigue strength reduction factor, Kf.

scholarly journals Microstructure-sensitive critical plastic strain energy density criterion for fatigue life prediction across various loading regimes

2020 ◽  
Vol 476 (2236) ◽  
pp. 20190766 ◽  
Author(s):  
Ritwik Bandyopadhyay ◽  
Veerappan Prithivirajan ◽  
Alonso D. Peralta ◽  
Michael D. Sangid
Keyword(s):  
Fatigue Life ◽  
Energy Density ◽  
Plastic Strain ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Hysteresis Loops ◽  
Strain Range ◽  
Strain Ratio ◽  
Material Point ◽  
Plastic Strain Energy

In the present work, we postulate that a critical value of the stored plastic strain energy density (SPSED) is associated with fatigue failure in metals and is independent of the applied load. Unlike the classical approach of estimating the (homogenized) SPSED as the cumulative area enclosed within the macroscopic stress–strain hysteresis loops, we use crystal plasticity finite element simulations to compute the (local) SPSED at each material point within polycrystalline aggregates of a nickel-based superalloy. A Bayesian inference method is used to calibrate the critical SPSED, which is subsequently used to predict fatigue lives at nine different strain ranges, including strain ratios of 0.05 and −1, using nine statistically equivalent microstructures. For each strain range, the predicted lives from all simulated microstructures follow a lognormal distribution. Moreover, for a given strain ratio, the predicted scatter is seen to be increasing with decreasing strain amplitude; this is indicative of the scatter observed in the fatigue experiments. Finally, the lognormal mean lives at each strain range are in good agreement with the experimental evidence. Since the critical SPSED captures the experimental data with reasonable accuracy across various loading regimes, it is hypothesized to be a material property and sufficient to predict the fatigue life.

Damage Criteria Based on Plastic Strain Energy Intensity Under Complicated Stress State

2015 ◽  
Vol 07 (06) ◽  
pp. 1550089 ◽  
Author(s):  
Junping Shi ◽  
Xiaoshan Cao ◽  
Chao Shen
Keyword(s):  
Stress State ◽  
Energy Density ◽  
Plastic Strain ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Energy Intensity ◽  
Yield Condition ◽  
Uniaxial Tensile ◽  
Fracture Plane ◽  
Plastic Strain Energy

In this study, total strain theory and isotropic hardening model based on Mises yield condition are used to derive the expression for plastic strain energy density under complicated stress state. The normal and shear stress distributions of a solid cylindrical bar under a combination of tensile and torsional stresses as well as the equation and integral formula for plastic strain energy density are presented. The plastic strain energy density of critical point and the plastic strain energy intensity on the fracture plane of different materials under several typical stress states are obtained by measuring the fracture data of different materials. With the plastic strain energy intensity as the failure parameter, uniaxial tensile experiments were conducted to measure the final plastic strain energy intensity of the failure section. The plastic strain energy intensity failure criteria of the material under complex stress state are established. Combined tension–torsion tests were conducted on two types of materials, LC9 and LY12, to verify the validity and applicability of the criteria.

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