scholarly journals Simulation on tensile failure process of unidirectional hybrid FRP.

1985 ◽  
Vol 34 (378) ◽  
pp. 280-285 ◽  
Author(s):  
Isao KIMPARA ◽  
Tsuyoshi OZAKI ◽  
Shiro TAKADA
Keyword(s):  
Failure Process ◽  
Tensile Failure ◽  
Unidirectional Hybrid

Effects of Geometry, Temperature, and Test Procedure on Reported Failure Strains From Simulated Wide Plate Tests

2006 ◽  
Author(s):  
Yong-Yi Wang ◽  
Ming Liu ◽  
Yaoshan Chen ◽  
David Horsley
Keyword(s):  
Test Data ◽  
Failure Process ◽  
Test Procedure ◽  
Gage Length ◽  
Tensile Failure ◽  
Temperature Fields ◽  
Weld Strength ◽  
Width Ratio ◽  
Local Cooling ◽  
Linear Variable Displacement Transducer

Wide plate test is a valuable tool in the assessment of pipeline girth weld integrity. It has been used for welding procedure qualification and for the validation of theoretically based defect assessment procedures. Although the general form of the test has remained largely unchanged over the years, the size of the test specimen, strain measurement, and test procedure, has had some variations. The influence of these variables has not been adequately examined. While this might be acceptable for tests targeted for stress-based design in which a general pass/no-pass answer is desired, the requirements for data accuracy and consistency for strain-based design are much higher. Understanding the variability of the test data is critical for high strain applications. This paper examines the effects of test geometry, mainly the length to width ratio, on the reported failure strains, assuming material’s failure process remains the same. The influence of different strain measdurement procedures, such as the location and gage length of LVDTs (Linear Variable Displacement Transducer), is assessed for different materials and weld strength mismatch levels. The other consideration is the influence of temperature fields on the cold test data. The postulated cold tests use either local cooling at the location of the weld defect or uniform cooling. In the case of local cooling, the gage length of the LVDTs covers materials of different temperatures. Consequently the reported failure strains are affected by the distribution of the temperature fields. The effects of the temperature fields on the reported tensile failure strains are examined.

scholarly journals Failure Process Simulation of Interlayered Rocks under Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Chi Yao ◽  
Sizhi Zeng ◽  
Jianhua Yang
Keyword(s):  
Shear Failure ◽  
Failure Process ◽  
Strength Criterion ◽  
Tensile Failure ◽  
Strength Anisotropy ◽  
Rigid Block ◽  
Bedding Planes ◽  
Typical Experiment ◽  
Confining Pressures ◽  
Spring Method

Anisotropy in strength and deformation of rock mass induced by bedding planes and interlayered structures is a vital problem in rock mechanics and rock engineering. The modified rigid block spring method (RBSM), initially proposed for modeling of isotropic rock, is extended to study the failure process of interlayered rocks under compression with different confining pressures. The modified rigid block spring method is used to simulate the initiation and propagation of microcracks. The Mohr–Coulomb criterion is employed to determine shear failure events and the tensile strength criterion for tensile failure events. Rock materials are replaced by an assembly of Voronoi-based polygonal blocks. To explicitly simulate structural planes and for automatic mesh generation, a multistep point insertion procedure is proposed. A typical experiment on interlayered rocks in literature is simulated using the proposed model. Effects of the orientation of bedding planes with regard to the loading direction on the failure mechanism and strength anisotropy are emphasized. Results indicate that the modified RBSM model succeeds in capturing main failure mechanisms and strength anisotropy induced by interlayered structures and different confining pressures.

scholarly journals Research on Failure Characteristics of Concrete Three-Point Bending Beams with Preexisting Cracks in Different Positions Based on Numerical Simulation

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Liuqun Zhao ◽  
Li Zheng ◽  
Hui Qin ◽  
Tiesuo Geng ◽  
Yonggang Tan ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Bearing Capacity ◽  
Failure Modes ◽  
Failure Process ◽  
Engineering Application ◽  
Tensile Failure ◽  
Engineering Structures ◽  
Failure Characteristics ◽  
Three Point Bending ◽  
Wide Range

Concrete three-point bending beams with preexisting cracks are widely used to study the growth process of I-II mixed mode cracks. Studying the failure characteristics of preexisting cracks at different locations on concrete three-point bending beams not only has important scientific significance but also has a wide range of engineering application backgrounds in the safety assessment of engineering structures. In this paper, through several numerical experiments, the influence of preexisting cracks at different positions on the failure characteristics of concrete three-point bending beams is studied, and three typical failure modes are obtained. The failure process of the specimens with three typical failure modes is discussed in detail, and it is pointed out that the crack failure mode is tensile failure. The change trends of bearing capacity, acoustic emission quantity, and acoustic emission energy of three typical failure modes are analyzed. The maximum bearing capacity, the maximum acoustic emission quantity, and energy of three failure modes of concrete three-point bending beams generally show an increasing trend.

scholarly journals Numerical Studies on the Failure Process of Heterogeneous Rock Material with Preexisting Fracture under Uniaxial Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Qi Zhang ◽  
Dan Ma ◽  
Jiangfeng Liu ◽  
Kai Zhang ◽  
Zhiqiang Fan
Keyword(s):  
Shear Failure ◽  
Failure Process ◽  
Damage Model ◽  
Rock Material ◽  
Tensile Failure ◽  
Underground Engineering ◽  
Intact Specimen ◽  
Numerical Studies ◽  
Heterogeneous Rock ◽  
Reduced Parameters

It is of vital importance to understand the failure processes of the heterogeneous rock material with different kinds of preexisting fractures in underground engineering. A damage model was introduced to describe the initiation and propagation behaviors of the fractures in rock. Reduced parameters were applied in this work because the microcracks in the rock were neglected. Then, the numerical model was validated through comparing the simulation results with the laboratory observations. Finally, a number of numerical uniaxial compressive tests were performed on heterogeneous rock specimens with preexisting fracture, and the influence of the heterogeneity of the rock and the angle and length of the preexisting fractures was fully discussed. The results showed that the brittleness of the rock increased with the increase of the homogeneity index, and tensile failure was the main failure form for relatively heterogeneous rock, whilst shear failure was the main failure form for relatively homogeneous rock. The uniaxial compressive strengths of the specimens with the angles of 0, 30, 45, and 60 of the preexisting fracture dropped 62.7%, 54.7%, 46.6%, and 38.2% compared with that of the intact specimen; the tensile cracks were more difficult to form, and the required load was increasing with the increase of the angle of the preexisting fracture; besides, antiwing cracks were difficult to form than wing cracks because the tensile stress in wing cracks’ area was greater than that in antiwing cracks’ area. The uniaxial compressive strengths of the specimens with the lengths of 20 mm, 25 mm, 30 mm, and 35 mm of preexisting fracture dropped 38.6%, 46.6%, 53.4%, and 56.6% compared with that of the intact specimen, and the damage conditions of the samples with different lengths of preexisting fracture were similar.

scholarly journals Dynamic Tensile Strength of Dry and Saturated Hard Coal under Impact Loading

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1273
Author(s):  
Xianlei Zhu ◽  
Qing Li ◽  
Guihua Wei ◽  
Shizheng Fang
Keyword(s):  
Tensile Strength ◽  
High Speed ◽  
Shear Failure ◽  
Split Hopkinson Pressure Bar ◽  
Failure Process ◽  
Tensile Failure ◽  
Hard Coal ◽  
Control Group ◽  
Hopkinson Pressure Bar ◽  
Brazilian Disk

To evaluate the influence of water content on the hard coal dynamic behavior, the dynamic tensile properties of saturated coal Brazilian disk (BD) samples were studied using a split Hopkinson pressure bar system, and dry samples were also tested as a control group. In the range of impact speeds studied, the tensile strength of the saturated coal is lower than that of the dry specimen. A synchronized triggering high-speed camera was used to monitor the deformation and failure process of dry and saturated coal samples, allowing analysis of the failure stages and mechanism of dynamic BD test, the broken mode was classified into three types, which can be classified into unilateral tensile failure, bilateral or multilateral tensile failure, and shear failure. Finally, fragments smaller than 5 mm in diameter were statistically analyzed. There is less debris in range of 0–5.0 mm for the saturated coal sample than for the dry coal. This study provides some information about the dynamic response of the hard coal for the relevant practical engineering.

scholarly journals Numerical tests on thermal cracking characteristics of rocks with different scales

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879214 ◽  
Author(s):  
Yang Xiao ◽  
Rui Zhao ◽  
Qing-Xiang Huang ◽  
Jun Deng ◽  
Jun-Hui Lu
Keyword(s):  
Acoustic Emission ◽  
Thermal Destruction ◽  
Thermal Damage ◽  
Process Analysis ◽  
Failure Process ◽  
Acoustic Emissions ◽  
Thermal Cracking ◽  
Tensile Failure ◽  
Failure Patterns ◽  
Different Diameters

Realistic failure process analysis, a thermal software simulation, was used to explore the scale effect of thermal cracking of rock under the thermal–mechanical coupling loading. The patterns and characteristics of thermal destruction were analyzed by simulating the thermal cracking of rocks with the same diameter different lengths, the same length but different diameters, and the same size ratio but different sizes (same length/diameter ratio but with different diameters). The acoustic emission and energy changes were also studied during thermal destruction. The results represented that the main forms of thermal cracking are tensile failure and shear failure. The smaller the scale is (length, diameter, and size), the more complex the pattern of thermal damage exhibited as failure patterns of inverted “S” or “V.” With the increasing scale, thermal damage models were simpler. The elastic modulus was determined by the diameter of specimens, and the peak stress was determined by the length of specimens. Overall, as the scale increased, the stress intensity decreased, but the number of acoustic emissions and acoustic emission energy and the corresponding accumulation increased.

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