Method for the interlayer interface fracture toughness of ballastless track
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A fracture toughness, ballastless track technology, applied in the preparation of test samples, the use of stable tension / pressure test material strength, measuring devices, etc.
Inactive Publication Date: 2020-05-22
CHINA RAILWAY ERYUAN ENG GRP CO LTD +1
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Among them, the stress intensity factor method uses the stress intensity factor as a characteristic quantity to describe the stress field at the crack tip, and most of the corresponding calculation theories and test standards are applicable to a single material, and have obvious limitations for the determination of the K factor of cracks at the interface of two materials
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Embodiment 1
[0052] (1) Test piece production: pouring such as figure 1 The double cantilever beam (DCB) test block shown. Make 5 groups of concrete C40-C20 DCB specimens with interlayer cracks, 15 in total. First, mix C40 concrete according to the mix ratio requirements, take the amount of concrete required for 1 / 2 the height of the test piece and put it into the test mold, put it in the curing room to cure the test pieces at the required interval, and then carry out layer treatment according to the construction requirements. Mix C20 concrete according to the mix ratio requirements, put it into the remaining 1 / 2 test mold, and maintain it to the age required by the test.
[0053] (2) When the test age is reached, the specimen is taken out from the curing room, and the cross-sectional dimension B of the specimen is measured to an accuracy of 1mm. Such as Figure 4 As shown on the right side of the middle, measure the cross-sectional dimension B of the test piece and the height h of the ...
Embodiment 2
[0059] 1. Production of test pieces
[0060] The test piece manufacturing process and load loading test process are the same as in Example 1, and the load loading instrument and equipment selection is as follows:
[0061] (1) Testing machine: 10kN tensile testing machine or servo program-controlled universal testing machine, the stretching distance is not less than 300mm.
[0062] (2) Mold test: the length of the test piece is 400mm, the interface width is B=50mm, and the initial crack length is a 1 =50, 65, 80, 95, 110mm, the thickness of the upper test piece is h 1 =50mm, the thickness of the lower specimen is h 2 = 50mm. Dimensions of molded specimens such as Figure 4 shown. In order to prevent the specimen from cracking along the vertical direction and provide a loading position for the application of the load, certain steel bars are configured for the specimen.
[0063] (3) Force block: length is 50mm, width is 50mm, thickness is 25mm, and the diameter of the round...
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Abstract
The invention relates to a method for testing the interlayer interface fracture toughness of a ballastless track. The method comprises the following steps: (1) manufacturing a concrete test block of adouble-layer concrete layer structure containing interlayer cracks; (2) mounting the concrete test block on a testing machine, and mounting at least one of a displacement sensor, a strain gauge and the like, pre-pulling the concrete test block, and the pre-pulling load being a failure load with the value range of (0-20%); (3) adjusting a measuring instrument, carrying out formal testing, controlling the load speed to be 0.1-1mm / min until the test piece is damaged, and recording the damage load and the fracture position; and (4) processing a test result, and solving the fracture toughness. Thetest result is processed according to a formula, and the toughness of the concrete interlayer crack is calculated and is accurate to 0.1 J / mm < 2 >. According to the method, the fracture toughness ofthe interlayer interface of the ballastless track is measured based on an energy method, the method is suitable for elastoplasticity and different material combinations, and a judgment basis can be provided for the interlayer hydraulic splitting opportunity of the CRTS I-type double-block ballastless track in a tunnel.
Description
technical field [0001] The invention relates to the field of railway engineering, in particular to a method for testing the fracture toughness of an interface between layers of a railway ballastless track. Background technique [0002] my country's terrain and geological conditions are complex and diverse. In railway engineering, ballastless tracks are prone to fractures and other damages under the long-term effects of various factors such as train loads and environmental factors because they have been exposed to complex environments. [0003] The CRTSI double-block ballastless track in the tunnel section is composed of steel rails, elastic fasteners, double-block sleepers, ballastless ballast bed, base or cushion, etc. Under the action of the interlayer interface, the damage is more serious. The reason is that the interlayers of the ballastless track are mostly composed of two materials. Due to the difference in mechanical properties of the two materials, a singular stress...
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