scholarly journals The influence of pavement degradation caused by cyclic loading on its failure mechanisms

2016 ◽  
Vol 11 (3) ◽  
pp. 179-187 ◽  
Author(s):  
Marcin Gajewski ◽  
Stanisław Jemioło
Keyword(s):  
Yield Condition ◽  
Limit Load ◽  
Flow Rule ◽  
Smooth Approximation ◽  
Simple Method ◽  
Plastic Properties ◽  
The Road ◽  
Plastic Materials ◽  
Number Of Cycles ◽  
Elastic Plastic Materials

In this paper, a simple method is proposed to estimate capacity of multilayered road structure including the degradation of the elastic and plastic properties of the constituent materials. In the study boundary value problem modeling interaction of wheels with road surface layer in the frame of large deformation theory for elastic-plastic materials was formulated. Plastic properties of the material were described by the flow rule un-associated with yield condition. The Coulomb-Mohr yield condition was assumed and the potential for plasticity is its smooth approximation. In addition, in constitutive modeling the dependence of the Young’s modulus and cohesion of the material from the number of cycles is taken into account. This paper presents qualitative findings in relation to mechanical behavior of the road structure, i.e., for example, the development of plastic zones with increasing load for un-degraded and degraded materials. In addition, a parametric study of the influence of the degradation ratio of the elasticity and plasticity properties for road structure failure mechanism (limit load value) was made.

Relationship between Indenter Calibration and Measured Mechanical Properties of Elastic-Plastic Materials

2015 ◽  
Vol 662 ◽  
pp. 27-30 ◽  
Author(s):  
Jaroslav Čech ◽  
Petr Haušild ◽  
Jiri Nohava
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Plastic Behavior ◽  
Calibration Function ◽  
Simple Method ◽  
Area Function ◽  
Elastic Plastic ◽  
Plastic Materials ◽  
Pile Up ◽  
Elastic Plastic Materials

Calibration of Berkovich indenter area function was performed on materials with different elastic-plastic behavior resulting in pile-up and sink-in, respectively. Experimentally obtained results were compared with the results obtained by the application of theoretical area function. The values of Young’s modulus and hardness were significantly affected by the calibration function used. Since the effects of pile-up and sink-in are already included in the used area function, this simple method can lead to more accurate results of Young’s modulus and hardness measurements.

Constraints on Moving Strong Discontinuity Surfaces in Dynamic Plane-Stress or Plane-Strain Deformations of Stable Elastic-Ideally Plastic Materials

1990 ◽  
Vol 57 (3) ◽  
pp. 569-576 ◽  
Author(s):  
Yinong Shen ◽  
W. J. Drugan
Keyword(s):  
Plane Strain ◽  
Plane Stress ◽  
Yield Condition ◽  
Strong Discontinuity ◽  
Dynamic Crack Propagation ◽  
Small Displacement ◽  
Flow Rule ◽  
Dynamic Crack ◽  
Plastic Materials ◽  
Discontinuity Surfaces

For dynamic deformations of compressible elastic-ideally plastic materials in the practically important cases of plane stress and plane strain, we investigate the possible existence of propagating surfaces of strong discontinuity (across which components of stress, strain, or material velocity jump) within a small-displacement-gradient formulation. For each case, an explicit proof of the impossibility of such a propagating surface (except at an elastic wave speed) is achieved for isotropic materials satisfying a Huber-Mises yield condition and associated flow rule, and we show that our method of proof can be generalized to a large class of anisotropic materials. Nevertheless, we demonstrate that moving surfaces of strong discontinuity cannot be ruled out for all stable (i.e., satisfying the maximum plastic work inequality) materials, as in the case of a material whose yield surface contains a linear portion. A clear knowledge of the conditions under which dynamically propagating strong discontinuity surfaces can and cannot exist is crucial to the attainment of correct and complete solutions to such practical elastic-plastic problems as dynamic crack propagation, impact and rapidly moving load problems, high-speed forming, cutting, and other manufacturing processes.

Optimization of Stepped Elastic Plastic Plates

2013 ◽  
Vol 742 ◽  
pp. 209-214 ◽  
Author(s):  
Jaan Lellep ◽  
Boriss Vlassov
Keyword(s):  
Algebraic System ◽  
Yield Condition ◽  
Necessary Optimality Conditions ◽  
System Of Equations ◽  
Elastic Plastic ◽  
Plastic Materials ◽  
Differential Algebraic System ◽  
Theory Of Optimal Control ◽  
Von Mises ◽  
Elastic Plastic Materials

A method of analysis and optimization of stepped plates made of elastic plastic materials is developed. The stress-strain of the plate is defined for the initial elastic and subsequent elastic plastic stages of deformation. Necessary optimality conditions are derived with the aid of variational methods of the theory of optimal control. This results in a differential-algebraic system of equations. The latter is solved numerically. The effectivity of the design established is assessed in the cases of one-and multi-stepped plates assuming the material obeys the Tsai-Wu or von Mises yield condition.

Fractals in elastic-hardening plastic materials

2009 ◽  
Vol 466 (2114) ◽  
pp. 603-621 ◽  
Author(s):  
J. Li ◽  
M. Ostoja-Starzewski
Keyword(s):  
Fractal Dimension ◽  
Two Dimensions ◽  
Square Lattice ◽  
Homogeneous Material ◽  
Flow Rule ◽  
Simple Method ◽  
Elastic Plastic ◽  
Plastic Materials ◽  
Fractal Patterns ◽  
Smooth Transitions

Plastic grains are found to form fractal patterns in elastic-hardening plastic materials in two dimensions, made of locally isotropic grains with random fluctuations in plastic limits or elastic/plastic moduli. The spatial assignment of randomness follows a strict-white-noise random field on a square lattice aggregate of square-shaped grains, whereby the flow rule of each grain follows associated plasticity. Square-shaped domains (comprising 256×256 grains) are loaded through either one of three macroscopically uniform boundary conditions admitted by the Hill–Mandel condition. Following an evolution of a set of grains that have become plastic, we find that it is monotonically plane filling with an increasing macroscopic load. The set’s fractal dimension increases from 0 to 2, with the response under kinematic loading being stiffer than that under mixed-orthogonal loading, which, in turn, is stiffer than the traction controlled one. All these responses display smooth transitions but, as the randomness decreases to zero, they turn into the sharp response of an idealized homogeneous material. The randomness in yield limits has a stronger effect than that in elastic/plastic moduli. On the practical side, the curves of fractal dimension versus applied stress—which indeed display a universal character for a range of different materials—offer a simple method of assessing the inelastic state of the material. A qualitative explanation of the morphogenesis of fractal patterns is given from the standpoint of a correlated percolation on a Markov field on a graph network of grains.

An energy-based method to extract plastic properties of metal materials from conical indentation tests

2005 ◽  
Vol 20 (5) ◽  
pp. 1194-1206 ◽  
Author(s):  
Yan Ping Cao ◽  
Xiu Qing Qian ◽  
Jian Lu ◽  
Zhen Han Yao
Keyword(s):  
Stable Solution ◽  
Strain Hardening Exponent ◽  
Simple Method ◽  
Plastic Properties ◽  
Representative Strain ◽  
Plastic Materials ◽  
Wide Range ◽  
Indentation Tests ◽  
Elastoplastic Materials ◽  
Conical Indentation

Based on dimensional analysis and finite element computations, an energy-based representative strain for conical indentation in elastoplastic materials has been proposed to establish an explicitly one-to-one relationship between the representative stress σr, the indentation loading curvature C, and the ratio of reversible work We to total work Wt performed by the indenter, i.e., σr/C = F0(We/Wt), where σr is the flow stress corresponding to the representative strain. The relationship provides a very simple method to evaluate the representative stress σr from the three directly measurable quantities We, Wt, and C. Numerical examples and further theoretical analysis reveal that a unique, stable solution can be obtained from the present method for a wide range of material properties, including both highly plastic materials (e.g., Ni for which E/σy = 1070) and highly elastic materials (e.g., materials for which E/σy = 25 and n = 0.5), using indenters with different tip apex angles. Based on the representative strains and stresses given by two indenters with different tip apex angles, e.g., (σr,80, ϵr,80) and (σr,65, ϵr,65), the plastic properties of materials, i.e., the yield strength σy and strain hardening exponent n can be further determined.

Effects of Torsion on Equivalent Bending Moment for Limit Load and EPFM Circumferential Pipe Flaw Evaluations

2010 ◽  
Author(s):  
Phuong H. Hoang ◽  
Kunio Hasegawa ◽  
Bostjan Bezensek ◽  
Yinsheng Li
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Large Strain ◽  
Bending Moment ◽  
Limit Load ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Weighted Factor ◽  
Elastic Perfectly Plastic ◽  
Elastic Plastic Materials

The circumferential flaw evaluation procedures in ASME Boiler and Pressure Vessel Code, Section XI non-mandatory Appendix C are currently limited to straight pipes under pressure and bending loads without consideration of torsion loading. The Working Group on Pipe Flaw Evaluation of the ASME Boiler and Pressure Vessel Code is developing guidance for considering the effects of torsion by a mean of an equivalent bending moment, which is a square root of sum square (SRSS) combination of bending moment and torsion load with a weighted factor for torsion moment. A torsion weighted factor for, Ce is established in this paper using large strain finite element limit load analysis with elastic-perfectly plastic materials. Planar flaws and non-planar flaws in a 10.75 inch OD pipe are investigated. Additionally, a finite element J-integral calculation is performed for a planar through wall circumferential flaw with elastic plastic materials subjected to bending and torsion load combinations. The proposed Ce factor for planar flaws is intended for use with the ASME B&PV Section XI, Appendix C for limit load and EPFM circumferential planar flaw evaluations.

scholarly journals S-N Curve Characterisation for Composite Materials and Prediction of Remaining Fatigue Life Using Damage Function

2021 ◽  
Vol 5 (3) ◽  
pp. 76
Author(s):  
Ho Sung Kim ◽  
Saijie Huang
Keyword(s):  
Fatigue Life ◽  
Composite Materials ◽  
Loading Rate ◽  
Theoretical Method ◽  
Damage Function ◽  
Simple Method ◽  
Arbitrary Choice ◽  
Number Of Cycles ◽  
First Time ◽  
Remaining Fatigue Life

S-N curve characterisation and prediction of remaining fatigue life are studied using polyethylene terephthalate glycol-modified (PETG). A new simple method for finding a data point at the lowest number of cycles for the Kim and Zhang S-N curve model is proposed to avoid the arbitrary choice of loading rate for tensile testing. It was demonstrated that the arbitrary choice of loading rate may likely lead to an erroneous characterisation for the prediction of the remaining fatigue life. The previously proposed theoretical method for predicting the remaining fatigue life of composite materials involving the damage function was verified at a stress ratio of 0.4 for the first time. Both high to low and low to high loadings were conducted for predicting the remaining fatigue lives and a good agreement between predictions and experimental results was found. Fatigue damage consisting of cracks and whitening is described.

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