The Influence of Stress Ratio on the Fracture Behavior of Brittle Materials

2007 ◽  
Vol 353-358 ◽  
pp. 937-940
Author(s):  
Wei Hong Li ◽  
Xiong Chen ◽  
De Shen Zhao ◽  
Yi Wang Bao
Keyword(s):  
Stress State ◽  
Fracture Behavior ◽  
Stress Ratio ◽  
Process Analysis ◽  
Failure Process ◽  
Brittle Materials ◽  
Simulation Method ◽  
Critical Stress Intensity Factor ◽  
Complex Stress State ◽  
Biaxial Stress

The fracture behavior of brittle materials under different stress ratio has been investigated by means of numerical simulation method with software RFPA2D (Realistic Failure Process Analysis). The fracture dependence of brittle material on biaxial plane stress state was confirmed. The results show that the critical stress intensity factor under biaxial stress increases with the increase of biaxial stress ratio. The simulation tests reveal that the biaxial stresses have strong influence on the fracture properties of glass. The results confirmed that the strain criterion of fracture is feasible while brittle materials under complex stress state.

Numerical Approach to Fracture of Glass under Biaxial Stress

2005 ◽  
Vol 297-300 ◽  
pp. 1617-1622 ◽  
Author(s):  
Wei Hong Li ◽  
Li Jiu Wang ◽  
Chun An Tang ◽  
Yi Wang Bao ◽  
Li Ding Wang ◽  
...  
Keyword(s):  
Plane Stress ◽  
Fracture Behavior ◽  
Process Analysis ◽  
Crack Opening ◽  
Failure Process ◽  
Simulation Method ◽  
Plane Stress State ◽  
Numerical Approach ◽  
Biaxial Stress ◽  
Crack Plane

The fracture behavior of brittle materials under biaxial plane stress has been investigated by means of numerical simulation method with software MFPA2D (Material Failure Process Analysis). The aims of this study are to clarify the fracture dependence of brittle material on biaxial plane stress state. The observation of crack initiation and fracture behavior reveals that the biaxial stresses have strong influence on the fracture properties of glass. Thus, the fracture criterion by the stress intensity factor was questioned for the biaxial plane stress issues. It is confirmed that the tensile stress parallel to the crack plane is an important factor affecting crack arrest, while the compressive stress parallel to the crack plane contributes to crack opening.

Numerical Simulation on Fracture Formation on Surfaces of Bi-Layered Columnar Materials

2012 ◽  
Vol 446-449 ◽  
pp. 2929-2933
Author(s):  
Tian Hui Ma ◽  
Chun An Tang ◽  
Lian Chong Li ◽  
Zheng Zhao Liang ◽  
Yong Bin Zhang
Keyword(s):  
Principal Stress ◽  
Stress Ratio ◽  
Numerical Solutions ◽  
Process Analysis ◽  
Failure Process ◽  
Numerical Results ◽  
Numerical Code ◽  
Continuous Transition ◽  
Fracture Patterns ◽  
Fracture Formation

Parallel fracture formation on surfaces of bi-layered columnar materials like growing tree trunk has been previously studied numerically. In this paper, numerical results of a continuous transition from parallel to polygonal fracture patterns with principal stress ratio provides the clear convincing theoretical explanation for fracture spacing. We perform three-dimensional simulations of fracture growth in a bi-layered columnar model with an embedded heterogeneous layer under inner radial expansion and terminal tension by finite element approach. As a result of this expansion, the bark stretches until it reaches its limit of deformation and cracks. A novel numerical code, 3D Realistic Failure Process Analysis code (abbreviated as RFPA3D) is used to obtain numerical solutions. In this numerical code, the heterogeneity of materials is taken into account by assigning different properties to the individual elements according to statistical distribution function. Elastic-brittle constitutive relation with residual strength for elements and a Mohr-Coulomb criterion with a tensile cut-off are adopted so that the elements may fail either in shear or in tension. The discontinuity feature of the initiated crack is automatically induced by using degraded stiffness approach when the tensile strain of the failed elements reaching a certain value. Numerical results of a continuous transition from parallel to polygonal fracture patterns with principal stress ratio are obtained by varying simulation parameters, the thickness of the material layer. We find that, except for further opening of existing fractures after they are well-developed (saturation), new fractures may also initiate and propagate along the interface between layers, which may serve as another mechanism to accommodate additional strain for fracture saturated layers.

The Influence of Different Stress States on 16MnR Deformation Capacity

2013 ◽  
Vol 716 ◽  
pp. 590-594
Author(s):  
Shi Lei Zhao ◽  
Yi Liang Zhang ◽  
Gong Feng Jiang
Keyword(s):  
Plastic Deformation ◽  
Stress State ◽  
Equivalent Stress ◽  
Great Influence ◽  
Equivalent Strain ◽  
Complex Stress State ◽  
Biaxial Stress ◽  
Deformation Capacity ◽  
Engineering Structures ◽  
Stress States

16MnR is the typical material of pressure equipment which worked under complex stress state in engineering application. In order to be close to the actual combined tension-shearing stress state and explore the relationship of deformation capacity and different stress state, many groups of combined tension-torsion tests on 16MnR specimens were designed and the equivalent stress-strain relation under different stress state was obtained. The concept of stress triaxiaty (TS value) was cited to characterize the different stress state and the result showed different stress states have a great influence on the material plastic deformation capacity, TS value turns larger, the plastic deformation weakened; 16MnR has a strongest plastic deformation capacity in pure torsion; the level of tensile stress had no significant effect on the maximum stress in the biaxial stress state, but has a significant inverse relationship with the maximum equivalent strain .At last, the mathematical relationship between maximum equivalent-strain and stress triaxiaty could be found. If the stress state of one point in the engineering structures is certain, the maximum equivalent-strain can be estimated.

Fracture Behavior and Water Migration in Heterogeneous and Porous Rocks

2005 ◽  
Vol 297-300 ◽  
pp. 2636-2641
Author(s):  
Lian Chong Li ◽  
Leslie George Tham ◽  
Tian Hong Yang ◽  
Xia Li
Keyword(s):  
Fluid Flow ◽  
Fracture Behavior ◽  
Rock Sample ◽  
Process Analysis ◽  
Failure Process ◽  
Compressive Loading ◽  
Porous Rocks ◽  
Rock Failure Process ◽  
Strength Character ◽  
Weak Zones

Based on the heterogeneous and porous characteristics of rock materials, a flow-stressdamage (FSD) model, implemented with the Rock Failure Process Analysis code (RFPA2D), is used to investigate the behavior of fluid flow and damage evolution, and their coupling action in rock sample that are subjected to both hydraulic and uniaxial compressive loading. A highly heterogeneous sample, containing grains, grain boundaries and weak zones, is employed in the numerical simulation. The simulation results provide a deep insight in the physical essence of the evolutionary nature of fracture phenomena as well as the fluid flow in heterogeneous materials, especially when they are highly stressed. The simulation result suggests that the nature of fluid flow and strength character in rocks strongly depends upon the heterogeneity of the rocks.

The Influence of Multiaxial Stress Relaxation on Component Creep Damage Accumulation

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Nayden Matev ◽  
Robert A. Ainsworth ◽  
Meini Su ◽  
Mark Stevens ◽  
Alan Jappy
Keyword(s):  
Stress State ◽  
Stress Drop ◽  
Damage Accumulation ◽  
Stress Ratio ◽  
Equivalent Stress ◽  
Creep Damage ◽  
Biaxial Stress ◽  
Multiaxial Stress ◽  
Multiaxial Stress State

Abstract Unless inelastic analysis is used, high temperature codes base creep relaxation on the start-of-dwell equivalent stress, which relaxes according to a uniaxial creep law. Elastic follow-up is also included. This approach only evaluates equivalent stress and creep strain rate and the multiaxial stress state is assumed to remain at its initial value as the stress relaxes. Codes suggest that the stress drop is limited to a fraction (typically 20%) of the initial equivalent stress to ensure this assumption does not introduce significant inaccuracies. This article provides a numerical examination of creep relaxation of a cruciform plate subjected to displacement-controlled biaxial loading, with the aim to provide clarification of any required constraint on stress drop. The initial biaxial stress ratio, the plate geometry and the power in a power–law creep model are varied, leading to variations in the elastic follow-up describing the creep relaxation. The biaxial stress ratio is generally found to change with relaxation and a multiaxial ductility approach is used to evaluate the associated creep damage accumulation. This is compared with the damage estimated assuming relaxation is controlled by the equivalent stress with no change in multiaxial stress state. For biaxial plane stress with one principal stress initially being compressive and one tensile, it is found that significant equivalent stress drops (about 40% of the initial stress) can be allowed without the simplified equivalent stress approach becoming inaccurate. More care is required for tensile–tensile stress biaxiality where multiaxial stress changes depend on the initial stress biaxiality and the degree of elastic follow-up. The results will be used to propose improved guidance for simplified inelastic calculations.

Fracture Behavior under biaxial stress state of Unidirectional CFRP with a Cruciform Form

2020 ◽  
Vol 2020.58 (0) ◽  
pp. 02b4
Author(s):  
Sho NAKASAKI ◽  
Shoma NAKAMURA ◽  
Koichi GODA ◽  
Arnaud MACADRE
Keyword(s):  
Stress State ◽  
Fracture Behavior ◽  
Biaxial Stress ◽  
Biaxial Stress State

Analysis of Fracture Behavior of Metal/Ceramic Functionally Graded Materials under Thermal Stress

2013 ◽  
Vol 750-752 ◽  
pp. 2200-2205 ◽  
Author(s):  
Cheng Fan
Keyword(s):  
Functionally Graded Materials ◽  
Fracture Behavior ◽  
Crack Formation ◽  
Ceramic Coating ◽  
Process Analysis ◽  
Failure Process ◽  
Functionally Graded ◽  
Graded Materials ◽  
Crack Morphology ◽  
Metal Ceramic

In this presented work, a coupled thermo-mechanical model is employed to analyze the thermo-mechanical behavior of ceramic functionally graded materials (FGMs) and the crack formation and propagation process of ceramic coating was simulated step in step and step by step using the RFPA (Realistic Failure Process Analysis) 2D-Thermo code. The thermal shock fracture behavior is discussed based on the basis of the simulated crack morphology and elucidated the mechanism of crack deformation and crack propagation. The state change from compression to tension whose magnitude is large enough to exceed the tension strength of ceramic causes the vertical crack. The numerical results agreed well with the experimental results in the previous literature.

Three-Dimensional Material Failure Process Analysis

2005 ◽  
Vol 297-300 ◽  
pp. 1196-1201 ◽  
Author(s):  
Chun An Tang ◽  
Zheng Zhao Liang ◽  
Yong Bin Zhang ◽  
Tao Xu
Keyword(s):  
Process Analysis ◽  
Failure Process ◽  
Three Dimensional ◽  
Brittle Materials ◽  
Constitutive Law ◽  
Numerical Code ◽  
Material Failure ◽  
Fibrous Materials ◽  
Material Stiffness ◽  
Cracking Process

This paper introduces a newly developed three-dimensional Material Failure Process Analysis code, MFPA3D to model the failure processes of brittle materials, such as concrete, ceramics, fibrous materials, and rocks. This numerical code, based on a stress analysis method (finite element method) and a material failure constitutive law, can be taken as a tool in numerical modeling analysis to enhance our understanding of the failure mechanisms of brittle materials. Properties of material heterogeneity are taken into account. The material is discretized into numerous small elements with fixed size. Fracture behavior can be modeled by reducing the material stiffness and strength after the peak strength of the material has been reached. The evolution of the cracking process down to full fracture implies strain softening, which describes the post-peak gradual decline of stress at increasing strain. In the present study, a Mohr-Coulomb criterion envelop with a tension cut-off is used so that the element may fail either in shear or in tension. Simulated fracture or crack patterns of two examples are found quite realistic, and the results strongly depend on the heterogeneity level.

Evaluation of Biaxial Bending Strength in Damaged Soda-Lime Glass

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1329-1334 ◽  
Author(s):  
Sang Yeob Oh ◽  
Hyung Seop Shin ◽  
Chang Min Suh
Keyword(s):  
Stress State ◽  
Bending Strength ◽  
Axial Stress ◽  
Brittle Materials ◽  
Soda Lime ◽  
Uniaxial Stress ◽  
Biaxial Stress ◽  
Bending Test ◽  
Ring Test ◽  
Soda Lime Glass

In applications of brittle materials such as soda-lime glass and ceramics, they are usually subjected to a multi-axial stress state. Brittle materials with cracks or damage caused by foreign impacts are apt to fracture abruptly from cracks because of their low fracture toughness. Depending upon the crack pattern developed, the strength using a multi-axial stress state might be different from the one using a uniaxial stress. As a result, when a small size crack was introduced by Vicker's indentation, the residual strength using a biaxial stress state obtained by the ball-on-ring test was greater than that using a uniaxial stress by the 4-point bending test. In the case of the specimens cracked by a spherical impact, there was overall decrease in the bending strength with increasing an impact velocity.

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