Establishment of Sheet Plastic Wrinkling Instability WLD and Study on Strain Distribution Characteristics in Instability Region

To investigate the deformation characteristics of protected coal seams, the numerical simulation of the mining of an upper protective coal seam was carried out in the present study. Based on the basic definition of strain, a method for the extraction of the strain data of the protected coal seam was proposed, and the strain distribution characteristics were obtained. It was found that the x -direction strain is mainly distributed near the coal pillars on both sides and inside the goaf, the y -direction strain is mainly distributed at the working face, the initial mining line, and inside the goaf, and the z -direction strain is mainly distributed at the working face, the initial mining line, the coal pillars on both sides, and inside the goaf. The distribution characteristics and the value of volumetric strain were found to be basically consistent with the z -direction strain. As the working face advances, the protected coal seam undergoes compression and damage expansion in turn. The turning point between compression and damage expansion is approximately 15 m in front of the working face. The variation law of gas drainage in the boreholes of the protected coal seam is closely related to the distribution characteristics of volumetric strain. The results of this research are of great significance for the comprehensive investigation of the effects of pressure relief and the permeability enhancement of protective coal seam mining.

Download Full-text

Damage Evolution and Circumferential Strain Distribution Characteristics of the Bolt-Supported Cavern under Multiple Explosion Sources

Shock and Vibration ◽

10.1155/2021/9985774 ◽

2021 ◽

Vol 2021 ◽

pp. 1-16

Author(s):

Taotao Wang ◽

Ansheng Cao ◽

Weiliang Gao ◽

Guangyong Wang ◽

Xiaowang Sun

Keyword(s):

Tensile Stress ◽

Stress Wave ◽

Strain Distribution ◽

Damage Evolution ◽

Circumferential Strain ◽

Circumferential Stress ◽

Surrounding Rock ◽

Distribution Characteristics ◽

Finite Element Software ◽

The Impact

The impact of multiple explosion sources on the safety of the underground cavern is enormous. Based on a similarity model test, the finite element software LS-DYNA3D was utilized to analyze the damage evolution and circumferential strain distribution characteristics of the bolt-supported cavern under the seven combinations of concentrated charge explosion sources in three places, including the side of the vault, side arch, and sidewall. The accuracy of the simulation results is verified by comparing them with test results. The research results indicate that the damage of the surrounding rock is mainly caused by the tensile stress wave reflected from the free surfaces and the superposition of the tensile stress wave. The damage of the surrounding rock in the cases of multiple explosion sources is not a simple superposition of that in the cases of a single explosion source. The peak circumferential stress and damage of the surrounding rock in the middle of two explosion sources are significantly greater than that of the cases of the corresponding single explosion source. In the seven cases, the peak circumferential strain of the cavern wall changes from tensile to compressive from the vault to the spandrel. When the explosion occurs on the sidewall, the peak circumferential strain of the floor is tensile.

Download Full-text

Study on 3D Strain Distribution Characteristics Using Etched Grid Method in Tube Bending

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.184-185.505 ◽

2012 ◽

Vol 184-185 ◽

pp. 505-509

Author(s):

Heng Li ◽

He Yang ◽

Kai Peng Shi

Keyword(s):

Strain Distribution ◽

Three Dimensional ◽

Grid Method ◽

Thickness Variation ◽

Distribution Characteristics ◽

Tube Bending ◽

Thickness Strain ◽

Bending Angle ◽

Maximum Value ◽

Wall Thickness Variation

Strain distribution is crucial for understanding tube bending and preventing defects. In this paper, taking 321 stainless steel as the objective, via etched grid method, the strain distribution characteristics during tube bending are studied, the effects of the bending velocity and the bending angle on the strain distribution are analyzed, and the consistency of thickness strain with wall thickness variation is verified. The results show that: (1) three-dimensional (3D) strain is symmetrically distributed about bending plane and reaches the maximum value at wall extrados and intrados; (2) absolute value of the 3D strain increases at first, then decreases in tube bending; (3) compared with bending angle, bending velocity has greater effect on spatial strain, and compared with tangent strain, thickness strain is more sensitive to bending velocity; (4) thickness strain distribution characteristics are generally consistent with distribution characteristics of wall thinning degree.

Download Full-text