Study on the Thermal Cracking Processes of Composite Subjected to Thermal Loading

2012 ◽  
Vol 256-259 ◽  
pp. 2867-2870
Author(s):  
Shi Bin Tang ◽  
Zheng Zhao Liang ◽  
Ya Fang Zhang
Keyword(s):  
Thermal Expansion ◽  
Thermal Loading ◽  
Coefficient Of Thermal Expansion ◽  
Process Analysis ◽  
Failure Process ◽  
Thermal Cracking ◽  
The Matrix ◽  
Rock Failure Process ◽  
High Or Low Temperature ◽  
Radial Cracks

A numerical method RFPA-T (Thermal Induced Rock Failure Process Analysis) code is used to study the thermal cracking processes of quasi-brittle materials subjected to high or low temperature. The numerical results indicate that thermal stress concentrating along the interface between the matrix and the embedded grains due to their different coefficient of thermal expansion (CTE). The modeling results indicate that θ-crack is generated during temperature increment as the CTE of the embedded grain is smaller than that of the matrix. However, radial-cracks emerged when the temperature decrease. The results obtained from RFPA-T code show a good agreement with experimental evidence of crack patterns caused by thermal expansion mismatch.

Modelling of Thermal Cracking Behaviours of Fiber-Reinforced Composites

2007 ◽  
Vol 334-335 ◽  
pp. 237-240
Author(s):  
Tao Xu ◽  
Shan Yong Wang ◽  
Chun An Tang ◽  
Li Song ◽  
Shi Bin Tang
Keyword(s):  
Process Analysis ◽  
Failure Process ◽  
Damage Model ◽  
Mechanical Damage ◽  
Thermal Cracking ◽  
Model Material ◽  
Thermal Mismatch ◽  
Failure Patterns ◽  
Damage And Fracture ◽  
The Matrix

In this paper, a coupled thermal-mechanical-damage model, Material Failure Process Analysis for Thermo code (abbreviated as MFPA-thermo), was applied to investigate the formation, extension and coalescence of cracks in FRCs, caused by the thermal mismatch of the matrix and the particles under uniform temperature variations. The effects of the thermal mismatch between the matrix and fibers on the stress distribution and crack development were also numerically studied. The influences of the material heterogeneity, the failure patterns of FRCs at varied temperatures are simulated and compared with the experimental results in the present paper. The results show that the mechanisms of thermal damage and fracture of the composite remarkedably depend on the difference between the coefficients of thermal expansion of the fibers and the matrix on a meso-scale. Meanwhile, the simulations indicate that the thermal cracking of the FRCs at uniform varied temperatures is an evolution process from diffused damage, nucleation, and finally linkage of cracks.

scholarly journals Fabrication and Characterization of the Modified EV31-Based Metal Matrix Nanocomposites

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 125
Author(s):  
Seyed Kiomars Moheimani ◽  
Mehran Dadkhah ◽  
Mohammad Hossein Mosallanejad ◽  
Abdollah Saboori
Keyword(s):  
Thermal Expansion ◽  
Mechanical Strength ◽  
Metal Matrix ◽  
Coefficient Of Thermal Expansion ◽  
Structural Effect ◽  
Metal Matrix Nanocomposites ◽  
Mechanical Stirring ◽  
Specific Strength ◽  
The Matrix ◽  
Matrix Nanocomposites

Metal matrix nanocomposites (MMNCs) with high specific strength have been of interest for numerous researchers. In the current study, Mg matrix nanocomposites reinforced with AlN nanoparticles were produced using the mechanical stirring-assisted casting method. Microstructure, hardness, physical, thermal and electrical properties of the produced composites were characterized in this work. According to the microstructural evaluations, the ceramic nanoparticles were uniformly dispersed within the matrix by applying a mechanical stirring. At higher AlN contents, however, some agglomerates were observed as a consequence of a particle-pushing mechanism during the solidification. Microhardness results showed a slight improvement in the mechanical strength of the nanocomposites following the addition of AlN nanoparticles. Interestingly, nanocomposite samples were featured with higher electrical and thermal conductivities, which can be attributed to the structural effect of nanoparticles within the matrix. Moreover, thermal expansion analysis of the nanocomposites indicated that the presence of nanoparticles lowered the Coefficient of Thermal Expansion (CTE) in the case of nanocomposites. All in all, this combination of properties, including high mechanical strength, thermal and electrical conductivity, together with low CTE, make these new nanocomposites very promising materials for electro packaging applications.

Role of Out-of-Plane Coefficient of Thermal Expansion in Electronic Packaging Modeling

1999 ◽  
Vol 122 (2) ◽  
pp. 121-127 ◽  
Author(s):  
Manjula N. Variyam ◽  
Weidong Xie ◽  
Suresh K. Sitaraman
Keyword(s):  
Thermal Expansion ◽  
Electronic Packaging ◽  
Thermal Loading ◽  
Coefficient Of Thermal Expansion ◽  
Plane Deformation ◽  
Three Dimensional ◽  
Dissimilar Materials ◽  
3D Models ◽  
Material Behavior ◽  
Element Analysis

Components in electronic packaging structures are of different dimensions and are made of dissimilar materials that typically have time, temperature, and direction-dependent thermo-mechanical properties. Due to the complexity in geometry, material behavior, and thermal loading patterns, finite-element analysis (FEA) is often used to study the thermo-mechanical behavior of electronic packaging structures. For computational reasons, researchers often use two-dimensional (2D) models instead of three-dimensional (3D) models. Although 2D models are computationally efficient, they could provide misleading results, particularly under thermal loading. The focus of this paper is to compare the results from various 2D, 3D, and generalized plane-deformation strip models and recommend a suitable modeling procedure. Particular emphasis is placed to understand how the third-direction coefficient of thermal expansion (CTE) influences the warpage and the stress results predicted by 2D models under thermal loading. It is seen that the generalized plane-deformation strip models are the best compromise between the 2D and 3D models. Suitable analytical formulations have also been developed to corroborate the findings from the study. [S1043-7398(00)01402-X]

Numerical Analysis of Faults on Deep-Buried Tunnel Surrounding Rock Damaged Zones

2011 ◽  
Vol 90-93 ◽  
pp. 74-78 ◽  
Author(s):  
Jun Hu ◽  
Ling Xu ◽  
Nu Wen Xu
Keyword(s):  
Numerical Analysis ◽  
Mechanical Response ◽  
Progressive Failure ◽  
Process Analysis ◽  
Failure Process ◽  
Water Inrush ◽  
Surrounding Rock ◽  
Factors Affecting ◽  
Rock Failure Process ◽  
Tunnel Instability

Fault is one of the most important factors affecting tunnel instability. As a significant and casual construction of Jinping II hydropower station, when the drain tunnel is excavated at depth of 1600 m, rockbursts and water inrush induced by several huge faults and zone of fracture have restricted the development of the whole construction. In this paper, a progressive failure progress numerical analysis code-RFPA (abbreviated from Rock Failure Process Analysis) is applied to investigate the influence of faults on tunnel instability and damaged zones. Numerical simulation is performed to analyze the stress distribution and wreck regions of the tunnel, and the results are consistent with the phenomena obtained from field observation. Moreover, the effects of fault characteristics and positions on the construction mechanical response are studied in details. Some distribution rules of surrounding rock stress of deep-buried tunnel are summarized to provide the reasonable references to TBM excavation and post-support of the drain tunnel, as well as the design and construction of similar engineering in future.

Numerical Simulation on Failure Patterns of Rock Discs and Rings Subject to Diametral Line Loads

2004 ◽  
Vol 261-263 ◽  
pp. 1517-1522 ◽  
Author(s):  
Wan Cheng Zhu ◽  
K.T. Chau ◽  
Chun An Tang
Keyword(s):  
Tensile Strength ◽  
Standardized Test ◽  
Process Analysis ◽  
Failure Process ◽  
Brazilian Test ◽  
Rock Failure ◽  
Numerical Code ◽  
Failure Patterns ◽  
Rock Failure Process ◽  
Indirect Tensile

Brazilian test is a standardized test for measuring indirect tensile strength of rock and concrete disc (or cylinder). Similar test called indirect tensile test has also been used for other geomaterials. Although splitting of the disc into two halves is the expected failure mode, other rupture modes had also been observed. More importantly, the splitting tensile strength of rock can vary significantly with the specimen geometry and loading condition. In this study, a numerical code called RFPA2D (abbreviated from Rock Failure Process Analysis) is used to simulate the failure process of disc and ring specimens subject to Brazilian test. The failure patterns and splitting tensile strengths of specimens with different size and loading-strip-width are simulated and compared with existing experimental results. In addition, two distinct failure patterns observed in ring tests have been simulated using RFPA2D and thus this verifies the applicability of RFPA2D in simulating rock failure process under static loads.

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.

Numerical Investigation for Fracture Saturation in Multilayer Sedimentary Rock in Unsymmetrical Case

2013 ◽  
Vol 690-693 ◽  
pp. 3050-3053
Author(s):  
Feng Shan Han ◽  
Li Song
Keyword(s):  
Numerical Simulation ◽  
Layer Thickness ◽  
Sedimentary Rock ◽  
Process Analysis ◽  
Failure Process ◽  
Bottom Layer ◽  
Thickness Ratio ◽  
Fracture Spacing ◽  
Layer Thickness Ratio ◽  
Rock Failure Process

Opening mode fractures in multilayer sedimentary rock often are periodically distributed with fracture spacing scaled to the thickness of the fractured layer. In this paper, based on Rock Failure Process Analysis Code RFPA2D, a three layer model with a central layer and with the different thickness top and bottom layer, progressive formation in multilayer sedimentary rock at fracture saturation in unsymmetrical case is simulated. We investigate the change of the critical fracture spacing to layer thickness ratio as a function of the thickness of the top layer where the bottom layers is much thicker (5 times) than the fractured layer called the unsymmetrical case, in this unsymmetrical case, fracture saturation is simulated. By numerical simulation of RFPA2D, the critical spacing to layer thickness ratio decreases and tend to the same constant value as the thickness of the top layer increases. Numerical simulation shown that for the unsymmetrical case, if the adjacent layers are thicker than 1.5 times the thickness of the fractured layer, the multilayer sedimentary rock can be treated approximately as a system with infinitely thick top and bottom layers at fracture saturation.That should be useful in the design of engineering systems and in the prediction of fracture spacing in hydrocarbon reservoirs and groundwater aquifers.

scholarly journals Numerical Analysis on Failure Modes and Mechanisms of Mine Pillars under Shear Loading

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Tianhui Ma ◽  
Long Wang ◽  
Fidelis Tawiah Suorineni ◽  
Chunan Tang
Keyword(s):  
Failure Modes ◽  
Process Analysis ◽  
Failure Process ◽  
Effective Means ◽  
Shear Loading ◽  
Shear Stresses ◽  
Planning And Design ◽  
Rock Failure Process ◽  
Damage Process ◽  
Dip Angle

Severe damage occurs frequently in mine pillars subjected to shear stresses. The empirical design charts or formulas for mine pillars are not applicable to orebodies under shear. In this paper, the failure process of pillars under shear stresses was investigated by numerical simulations using the rock failure process analysis (RFPA) 2D software. The numerical simulation results indicate that the strength of mine pillars and the corresponding failure mode vary with different width-to-height ratios and dip angles. With increasing dip angle, stress concentration first occurs at the intersection between the pillar and the roof, leading to formation of microcracks. Damage gradually develops from the surface to the core of the pillar. The damage process is tracked with acoustic emission monitoring. The study in this paper can provide an effective means for understanding the failure mechanism, planning, and design of mine pillars.

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