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Testing method for dynamic crack arrest toughness of I-type crack under impact load

A technology of impact load and test method, applied in the field of geotechnical engineering, can solve problems such as neglect, and achieve the effect of convenient operation and simple method

Inactive Publication Date: 2017-01-04
SICHUAN UNIV
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Problems solved by technology

Dally JW used the configuration specimen proposed by the American Society for Experimental Materials ASTM to test the static crack arrest toughness of steel, but this method ignored the influence of dynamic effects

Method used

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  • Testing method for dynamic crack arrest toughness of I-type crack under impact load
  • Testing method for dynamic crack arrest toughness of I-type crack under impact load
  • Testing method for dynamic crack arrest toughness of I-type crack under impact load

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specific Embodiment

[0033] In the first step, the present invention adopts a specially designed side-opening single-crack semi-orifice plate, such as figure 2 As shown, the test piece is sandstone material; the sample size is: a=10mm, L 1 =15mm, L 2=130mm, H=40mm, D=30mm, specimen thickness B=30mm, dynamic bulk modulus 12GPa, dynamic shear modulus 7.2GPa; density ρ=3g / cm 3 Tensile strength σ t = 4MPa.

[0034] It should be noted that the dynamic crack arrest toughness tested in the present invention refers to the dynamic crack arrest toughness during the crack propagation process.

[0035] In the second step, impact loading is achieved by means of a large-diameter split Hopkinson strut system, such as image 3 As shown, the ultra-dynamic strain gauge supporting the system is used for data collection, and the sampling frequency is 20MHz. Stick it on the surface of the test piece, and the wire grid is perpendicular to the crack tip. When the crack propagates, it will cause the crack growth me...

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Abstract

The invention discloses a testing method for the dynamic crack arrest toughness of an I-type crack under the impact load, and belongs to the technical field of geotechnical engineering. The method includes the steps of conducting impact test research through a large-diameter separated type Hopkinson pressing rod and a test configuration designed by an inventor, determining the dynamic crack toughness of a sample through an experiment-numerical value method, calculating the load borne by the sample and the moment of crack arrest through strain signals obtained through a test, inputting an obtained time travel curve to a finite element program Ansys, calculating the near-field displacement of a crack tip through a 1 / 4 node unit, obtaining the time travel curve of the I-type dynamic rupture stress strength factor of the sample through a displacement extrapolation method, obtaining the strain strength factor value corresponding to the crack arrest moment as the dynamic crack arrest toughness of the material, and then obtaining the pure I-type crack dynamic crack arrest toughness under the effect of the impact load. The method is simple and convenient to operate and should have more practical application meaning in research of the dynamic crack arrest characteristic of rock under the impact dynamic load.

Description

technical field [0001] The invention belongs to the technical field of geotechnical engineering, in particular to a method for testing dynamic arrest toughness of type I cracks under impact load. Background technique [0002] In modern underground engineering construction, engineering methods such as percussion rock drilling, blasting, and piling are widely used, and it is an extremely complicated mechanical problem. [0003] The existing joints and cracks of different scales and sizes in the underground rock mass, under the action of dynamic load, these defects will expand, bifurcate and gather until the macroscopic destruction of the entire structure; among them, defects such as cracks or faults are particularly obvious, and the geometry of the crack itself The shape and the corresponding relationship with the spatial position of the excavation project have a significant impact on the crack propagation and penetration process. [0004] The test methods for the static frac...

Claims

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Application Information

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IPC IPC(8): G01N3/30G01N3/06
CPCG01N3/30G01N3/066
Inventor 王蒙朱哲明
Owner SICHUAN UNIV
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