scholarly journals Study on Shear Mechanism of Bolted Jointed Rocks: Experiments and CZM-Based FEM Simulations

2019 ◽  
Vol 10 (1) ◽  
pp. 62 ◽  
Author(s):  
Shubo Zhang ◽  
Gang Wang ◽  
Yujing Jiang ◽  
Xianlong WU ◽  
Genxiao Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Failure Mechanism ◽  
Laboratory Experiments ◽  
Shear Failure ◽  
Cohesive Zone Model ◽  
Rock Fracture ◽  
High Strength ◽  
Simulation Method ◽  
Jointed Rock ◽  
Zone Model

Based on the underground jointed rock of the Huangdao water sealed oil depot in China, the shear failure mechanism of bolted jointed rock is studied through laboratory experiments and numerical simulation. Laboratory experiments are performed to explore the shear behavior of bolted jointed rock with different joint roughness. Our results show that using high strength bolts is beneficial to improving the shear strength of the jointed rock, but the high strength of bolts can also lead to the rock fracture, which should be avoided. For this particular project site, experimental results indicate that 15% elongation is the best. In addition, a new numerical simulation method with CZM (cohesive zone model) used for modeling the shearing process of bolted jointed rock is proposed. It can reasonably describe the characteristics of jointed rock as a discontinuous medium, and bolt as a continuous medium, that replicate well the shearing process. The numerical model is then verified by comparing the experiment results, and it can be effectively be applied to the simulation of joint shearing process. Finally, we use this simulation method to explore the shear failure mechanism of bolted joints, and find that the root cause of rock failure is the deformation mismatch between the bolt and the surrounding rock. The tensile stress between them eventually causes the rock to fracture near the bolt hole.

Failure Mechanism of Tungsten Heavy Alloy for Mould

2011 ◽  
Vol 341-342 ◽  
pp. 432-435
Author(s):  
Wei Huang ◽  
Ya Feng Li ◽  
Kai Wen Tian ◽  
Fu Jun Shang ◽  
Yong Liu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Failure Mechanism ◽  
Matrix Composite ◽  
External Load ◽  
High Strength ◽  
Strength Level ◽  
Heavy Alloy ◽  
Theoretical Strength ◽  
Tungsten Heavy Alloy ◽  
The Real

The failure mechanism of tungsten matrix composite was studied with microscale numerical simulation. The results show that high strength tungsten particles are the real loading elements of composite, its strength level embodies the whole property of the composite to some extent. The real stress in tungsten particles is much higher than the external load, so failure may take place when the external load is less than the theoretical strength of tungsten particles.

Numerical simulation of single-lap adhesive joint of composite laminates

2018 ◽  
Vol 37 (8) ◽  
pp. 520-532 ◽  
Author(s):  
Zhang Taotao ◽  
Luo Wenbo ◽  
Xiao Wei ◽  
Yan Ying
Keyword(s):  
Numerical Simulation ◽  
Cohesive Zone Model ◽  
Tensile Load ◽  
Zone Model ◽  
Composite Joints ◽  
Universal Method ◽  
Continuum Damage Mechanic ◽  
Damage Mechanic ◽  
Damage Initiation ◽  
Ultimate Failure

A universal method is established to research the various possible damage modes of adhesive bond of laminated composites with or without z-pin reinforcements under tensile loads through numerical simulation. A Continuum Damage Mechanic model based on Hashin damage criterion as a user-defined subroutine is developed to simulate the damage of laminates and Z-pins. The Cohesive Zone Model is used to simulate the damage of adhesive damage, interlayer delamination, and Z-pin slipping-out phenomenon. The numerical simulation method is validated for simulating the various damage modes of the usual composite joints through comparing the simulated results and experiments. The research shows that different ply sequences induce different damage modes and ultimate failure loads of composite joints. The ultimate failure load of joint under tension is not affected obviously whether the joints are reinforced with or without z-pins. The reason is that the damage initiation usually locates at the two sides of adhesive zone and z-pins do not react on the reinforcement under tensile load of joint.

Modeling of Crack Growth in Thin Sheet Aluminum

1999 ◽  
Author(s):  
T. Siegmund ◽  
W. Brocks ◽  
J. Heerens ◽  
G. Tempus ◽  
W. Zink
Keyword(s):  
Crack Growth ◽  
Cohesive Energy ◽  
Cohesive Zone Model ◽  
Plastic Material ◽  
Thin Sheet ◽  
High Strength ◽  
Cohesive Strength ◽  
Zone Model ◽  
Additional Material ◽  
Center Crack

Abstract The present study reports on the application of a cohesive zone model to the analyses of crack growth in thin sheet specimen of a high strength aluminum alloy. In addition to the elastic-plastic material properties, the two parameters cohesive strength and cohesive energy describe material separation. For the sheet specimen under investigation the cohesive energy is determined via a numerical-experimental approach using tests on notched tensile specimens as well as a damage indicator. The cohesive energy is found to be close to the corresponding value of plane strain fracture toughness. The cohesive strength is approximately twice the yield strength. With these two additional material parameters being determined crack growth experiments in center crack panels are analyzed. Good agreement with experimental records is found. Finally the applicability of the model to study complex crack configurations as in multi-site damaged specimens is demonstrated.

Research on Stability Bearing Capacity for Pole and Tower Compression Members with Two Legs Connection

2012 ◽  
Vol 214 ◽  
pp. 315-319
Author(s):  
Xian Lei Cao
Keyword(s):  
Numerical Simulation ◽  
Analytical Solution ◽  
Bearing Capacity ◽  
Analytical Method ◽  
High Strength ◽  
Simulation Method ◽  
Elastic Theory ◽  
Numerical Simulation Method ◽  
Stability Bearing Capacity ◽  
Compression Members

In order to research the stability bearing capacity of high strength pole and tower compression members, analytical method and numerical simulation method were used to study stability on high strength axial compression members. Researched the impact of different slenderness ratio, different cross-section factors on the bearing capacity; energy relationship was using in analytical method, the boundary conditions issue is simplified according to different end restraint capacity; the failure modes and stability bearing capacity of members were studied by numerical simulation. Compared with the experimental results show that the numerical simulation and elastic theory analytical solution overestimate the capacity of members, but the numerical results have better agreement than the elastic theory analytical solution, which can show the numerical simulation method is right. Experiment method can obtain more secure mechanical behavior of high-strength angle steel member with axial loading.

scholarly journals Analysis on Failure Mechanism of Scarf Joints With Brittle-Ductile Adhesives Subjected to Uniaxial Tensile Loads

2013 ◽  
Author(s):  
Lijuan Liao ◽  
Toshiyuki Sawa ◽  
Chenguang Huang
Keyword(s):  
Failure Mechanism ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Adhesive Layer ◽  
Uniaxial Tensile ◽  
Zone Model ◽  
Displacement Curve ◽  
Failure Energy ◽  
Complete Failure ◽  
Scarf Joints

The failure mechanism of scarf joints with a series of angles and brittle-ductile adhesives subjected to uniaxial tensile loads is analyzed by using a numerical method which employs a cohesive zone model (CZM) with a bilinear shape in mixed-mode (mode I and II). The adopted methodology is validated via comparisons between the present simulated results and the existing experimental measurements, which illustrate that the load-bearing capacity increases as the scarf angle decreases. More important, it is observed that the failure of the joint is governed by not only the ultimate tensile loads, but also the applied tensile displacement until complete failure, which is related to the brittle-ductile properties of the adhesive layer. In addition, failure energy, which is defined by using the area of the load-displacement curve of the joint, is adopted to estimate the joint strength. Subsequently, the numerical results show that the strength of the joint adopting ductile adhesive with higher failure energy is higher than that of the joint using brittle adhesive with lower failure energy.

scholarly journals Combined Numerical-Statistical Analyses of Damage and Failure of 2D and 3D Mesoscale Heterogeneous Concrete

2015 ◽  
Vol 2015 ◽  
pp. 1-12
Author(s):  
Xiaofeng Wang ◽  
Andrey P. Jivkov
Keyword(s):  
Cohesive Zone Model ◽  
Volume Fraction ◽  
Simulation Method ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Zone Model ◽  
Generation Process ◽  
Cohesive Elements ◽  
Damage And Failure ◽  
2D And 3D

Generation and packing algorithms are developed to create models of mesoscale heterogeneous concrete with randomly distributed elliptical/polygonal aggregates and circular/elliptical voids in two dimensions (2D) or ellipsoidal/polyhedral aggregates and spherical/ellipsoidal voids in three dimensions (3D). The generation process is based on the Monte Carlo simulation method wherein the aggregates and voids are generated from prescribed distributions of their size, shape, and volume fraction. A combined numerical-statistical method is proposed to investigate damage and failure of mesoscale heterogeneous concrete: the geometrical models are first generated and meshed automatically, simulated by using cohesive zone model, and then results are statistically analysed. Zero-thickness cohesive elements with different traction-separation laws within the mortar, within the aggregates, and at the interfaces between these phases are preinserted inside solid element meshes to represent potential cracks. The proposed methodology provides an effective and efficient tool for damage and failure analysis of mesoscale heterogeneous concrete, and a comprehensive study was conducted for both 2D and 3D concrete in this paper.

Failure Mechanism of Laser Welds in Lap-Shear Specimens of a High Strength Low Alloy Steel

2010 ◽  
Author(s):  
Kamran Asim ◽  
Jaewon Lee ◽  
Jwo Pan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Failure Mechanism ◽  
Shear Failure ◽  
High Strength ◽  
Yield Function ◽  
Element Analysis ◽  
Lap Shear ◽  
Laser Welds ◽  
The Finite Element Analysis

In this study, the failure mechanism of laser welds in lap-shear specimens of a high strength low alloy (HSLA) steel under quasi-static loading conditions is examined based on the experimental results. Optical micrographs of the welds in specimens before tests were examined to understand the microstructure near the weld. A micrographic analysis of the failed welds in lap-shear specimens indicates a ductile necking/shear failure mechanism near the heat affected zone. Micro-hardness tests were conducted to provide an assessment of the mechanical properties of the joint area which has varying microstructure due to the welding process. A finite element analysis was also carried out to identify the effects of the weld geometry and different mechanical properties of the weld and heat affected zones on the failure mechanism. The computational results of the finite element analysis indicate that the material inhomogeneity and geometry of the weld bead play an important role in the ductile necking/shear failure mechanism. The computational results match well with the experimental observations of the necking/shear failure and its location. A finite element analysis with consideration of void nucleation and growth based on the Gurson yield function was also carried out. The results of the finite element analysis based on the Gurson yield function are in good agreement with the experimental observations of the initiation of ductile fracture and its location.

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