CN205844058U - Three point bending specimen for the test of rock I/III Mixed Mode Fracture toughness - Google Patents

Abstract

This utility model relates to a kind of three point bending specimen for the test of rock I/III Mixed Mode Fracture toughness.This utility model includes rectangular test specimen body, the bottom surface of test specimen body is provided through the otch of its thickness direction front-back, the cut sides of otch is perpendicular to the bottom surface of test specimen body, and otch central point on test specimen body bottom surface overlaps with test specimen body bottom center's point.Wherein, otch angle with test specimen body bottom thickness direction centrage on test specimen body bottom surface is preferably 0 °～60 °.This utility model can realize pure I type and I/III Mixed Mode Fracture, and the processing of required test specimen is simple, saves test specimen raw material, and loading experiment equipment is simple.

Description

Three point bending specimen for the test of rock I/III Mixed Mode Fracture toughness

Technical field

This utility model relates to a kind of three point bending specimen for the test of rock I/III Mixed Mode Fracture toughness, belongs to disconnected Split mechanical technology field.

Background technology

Crackle is broadly divided into opening mode (I type), slide type (II type), tearing mode (III by mechanical characteristic by fracture mechanics Type).I type and II type fault analysis is more and comparative maturity；But III type fracture is owing to tearing outside test specimen plane relatively difficult to achieve, with Less as research.Test specimen and the technology of fracture in existing research face (I type II type and compound) are the most perfect, such as Brazil Disk test specimen, three-point bending beam test specimen, semi-disc three point bending specimen etc..But it is the most less to realize the test specimen of fracture outside face, and The test specimen known is complex, requires higher to experimental facilities, and such as Antiplane Shear box needs special fixture and to commonly The carrier aircraft that adds transform.

Utility model content

Technical problem to be solved in the utility model is: provide one to test for rock I/III Mixed Mode Fracture toughness Three point bending specimen, simple in construction, convenient implement.

Be the technical scheme is that for rock I/III Mixed Mode Fracture by solving above-mentioned technical problem this utility model The three point bending specimen of toughness test, including rectangular test specimen body, the bottom surface of test specimen body is provided through its thickness side Otch the most below, the cut sides of otch is perpendicular to the bottom surface of test specimen body, otch central point on test specimen body bottom surface Overlap with test specimen body bottom center's point.

Further: otch angle with test specimen body bottom thickness direction centrage on test specimen body bottom surface is 0 ° ～60 °.

The beneficial effects of the utility model are: test specimen simple in construction, it is easy to utilize the fragile material cutting processing such as rock, keep away Exempt from coring processing on the sillar of finite size, less to material requested volume requirement.By adjusting otch at the bottom of test specimen body On face, angle with test specimen body bottom thickness direction centrage can realize I/ III Mixed Mode Fracture of pure I type and different situations, Load mode is simple.

Accompanying drawing explanation

Fig. 1 is structural representation of the present utility model；

Fig. 2 is perspective view during this utility model enforcement；

Fig. 3 is elevation during this utility model enforcement；

Fig. 4 is plane graph during this utility model enforcement；

Fig. 5 is Y in embodiment of the present utility model_IResult of calculation functional arrangement；

Fig. 6 is Y in embodiment of the present utility model_IIIResult of calculation functional arrangement；

Parts, position and numbering in figure: 1-test specimen body, 2-otch.

Detailed description of the invention

The utility model is described in further detail below in conjunction with the accompanying drawings.

As it is shown in figure 1, the three point bending specimen that this utility model is tested for rock I/III Mixed Mode Fracture toughness, including Rectangular test specimen body 1, the bottom surface of test specimen body 1 is provided through the otch 2 of its thickness direction front-back, cutting of otch 2 Actinal surface is perpendicular to the bottom surface of test specimen body 1, the otch 2 central point on test specimen body 1 bottom surface and test specimen body 1 bottom center point Overlap.Wherein, otch 2 angle with test specimen body 1 bottom thickness direction centrage on test specimen body 1 bottom surface be preferably 0 °～ 60°。

As shown in figs. 2 to 4, a length of L of test specimen body 1, height are B for W, thickness, and otch 2 is in test specimen body 1 bottom surface Upper and test specimen body 1 bottom thickness direction centrage angle is θ, and the degree of depth of otch 2 is a, and test specimen supporting span is 2S, test specimen Load is P.In the present embodiment, L:W:B is preferably arranged to 6:2:1,2S:L and is preferably arranged to 3:4.

Processing method of the present utility model: be the cuboid more bigger than pre-set dimension by required measurement Rock cutting, then make Polish with grinding machine, be polished to required size, it is ensured that the flat smooth of every, and adjacent surface has preferable perpendicularity, protect Card test specimen body 1 contacts with bearing and loading headline, prevents contact position stress concentration and causes contact point elder generation breakoff phenomenon. Fixing test specimen body 1, uses pigment pen to draw the line becoming angle theta with bottom center line in the bottom surface of test specimen body 1, and at test specimen The two sides of body 1, along the vertical line of a length of a of this line drawing, use milling machine to process otch 2, use scroll saw to make after machining The most advanced and sophisticated sharpening of otch 2.

I/III complex fracture experiment method: draw bearing in processing gained test specimen bottom surface respectively with end face and load pressure head Boost line.Adjust pole bearing span so that it is meeting span length's ratio, and be positioned on bearing by test specimen, boost line overlaps with bearing. Experimentation keeps bearing span constant, makes loading pressure head just contact with test specimen and overlap with upper surface boost line, it is ensured that Recording pressure in sensor is 0.Loading test specimen, loading speed is preferably lower than 0.2mm/min.Load until test specimen ruptures Peak load P occurs_cr, and load curve has bigger falling.Stop loading, and go up loading pressure head, change test specimen.

Fracture toughness computing formula is:

$K_I=\frac{P_{cr}\sqrt{\mathrm{\π}a}}{2WB}{Y}_I(\frac{a}{W},\frac{S}{L},\mathrm{\θ});$

$K_{III}=\frac{P_{cr}\sqrt{\mathrm{\π}a}}{2WB}{Y}_{III}(\frac{a}{W},\frac{S}{L},\mathrm{\θ});$

In formula: K_IIt is I type stress intensity factor, K_IIIIt is III type stress intensity factor, Y_IAnd Y_IIIFor dimensionless stress intensity The factor, is the function (a/W≤0.5) of test specimen geometric shape and tiltangleθ.Y_IAnd Y_IIIDesirable value can use finite element software meter Obtaining, the most as shown in Figure 5 and Figure 6, in figure, α is relative crack length α=a/W to result of calculation, will experiment gained load P_cr Substitute into above-mentioned formula and just can obtain test specimen fracture toughness.

Claims (2)

1. for the three point bending specimen of rock I/III Mixed Mode Fracture toughness test, including rectangular test specimen body (1), its It is characterised by: the bottom surface of test specimen body (1) is provided through the otch (2) of its thickness direction front-back, the cut sides of otch (2) It is perpendicular in the bottom surface of test specimen body (1), the otch (2) central point on test specimen body (1) bottom surface and test specimen body (1) bottom surface Heart point overlaps.

2. the three point bending specimen for the test of rock I/III Mixed Mode Fracture toughness as claimed in claim 1, its feature exists It it is 0 °～60 ° in: otch (2) angle with test specimen body (1) bottom thickness direction centrage on test specimen body (1) bottom surface.