Method for determining fracture toughness and tensile strength of quasi-brittle materials from two-point loaded specimens

A brittle material, fracture toughness technology, applied in the analysis of materials, strength properties, preparation of test samples, etc., can solve the problems of increasing the cost of test sample production and test workload, and difficulty in completing sample preparation and test work.

Active Publication Date: 2019-01-18
NORTH CHINA UNIV OF WATER RESOURCES & ELECTRIC POWER
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  • Application Information

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Problems solved by technology

[0006] In addition, in the fracture toughness test, there are strict restrictions on the specimen type, loading fixture, loading method, test system, etc., and it is difficult to complete the preparation and testing of the specimen under ordinary laboratory conditions, which makes The production cost and test workload of the test sample are greatly increased

Method used

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  • Method for determining fracture toughness and tensile strength of quasi-brittle materials from two-point loaded specimens
  • Method for determining fracture toughness and tensile strength of quasi-brittle materials from two-point loaded specimens
  • Method for determining fracture toughness and tensile strength of quasi-brittle materials from two-point loaded specimens

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Embodiment 1

[0041] Example 1: The concrete specimen of the two-point loading type used in the test of this example, the maximum particle size of the concrete aggregate d max = 13mm, L x B x W = 806.4 × 152 × 203.2 mm, initial seam height ratio α = a 0 / W = 0.30, 0.35, 0.40, 0.45, 0.50, W / d max =15.6.

[0042] see figure 1 , considering concrete as a quasi-brittle material, the peak load P The stress distribution when figure 1 As shown, the corresponding crack growth Δ a = β · d max . Based on formula (2), the nominal strength of each specimen can be calculated from the measured peak load σ n .

[0043] Think Statistically β= 1.0, the average value of concrete fracture toughness and tensile strength can be calculated, see figure 2 . Considering the discreteness of the concrete test results and solving it accurately, it can make β= 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4..., calculate the exact values ​​of the fracture toughness and tensile strength of concrete,...

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Abstract

The invention discloses a method for determining the facture toughness and the tensile strength of a brittle material through a two-point loading test piece. The method comprises the following steps: preparing a test piece, cutting a crack, performing two-point static force loading, recording peak load, calculating nominal strength sigma n, calculating an equivalent crack length ae, and the like; finally, performing regression analysis and simultaneously obtaining the tensile strength ft and the fracture toughness KIC of the brittle material. The method disclosed by the invention is simple in form; the test is easy to operate; the accuracy is enough; the result reasonability is easy to judge. The facture toughness KIC and the tensile strength ft of the brittle material can be determined at the same time by the peak load of a small-sized two-point loaded test piece which is loaded at two points.

Description

technical field [0001] The invention belongs to the technical field of civil engineering and water conservancy engineering, in particular to a method for determining the fracture toughness and tensile strength of quasi-brittle materials from a two-point loading test piece. Background technique [0002] A large number of studies have shown that there is an obvious size effect on the strength and fracture toughness of quasi-brittle materials (cement mortar, concrete or rock, etc.). To obtain real material parameters that are independent of the size of the specimen, larger specimens must be used. Therefore, the test results of small-scale quasi-brittle materials cannot be directly used to evaluate their real material properties. [0003] For the test of the fracture toughness of quasi-brittle materials, according to the US ASTM E399 standard, if the conditions of linear elastic fracture mechanics are met, and the fracture toughness of materials without size effect is measured,...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/00G01N1/28
CPCG01N1/286G01N3/00G01N2001/2873G01N2203/0067
Inventor 管俊峰姚贤华白卫峰胡晓智谢超鹏王强韩霄羽钱国双
Owner NORTH CHINA UNIV OF WATER RESOURCES & ELECTRIC POWER
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