A method for calculating the interaction force between rock cutting teeth and rocks

Abstract

A method for calculating the interaction force between rock cutting teeth and rock in the field of dredging engineering and rock cutting technology includes the following steps: determining the rock type and the rock cutting teeth used; measuring the tensile and compressive strengths of the rock; measuring the radius of the tooth tip; determining parameters related to the cutting angle and cutting depth; conducting a linear rock cutting test with the teeth to determine the relationship between the cross-sectional area of ​​the cutting groove and the cutting depth; and calculating the interaction force between the rock cutting teeth and the rock, i.e., the cutting resistance, using a formula. The present invention establishes a model of the interaction force between the teeth and the rock using the cross-sectional area of ​​the cutting groove, the rock strength, and related cutting parameters, thereby estimating the cutting resistance of the rock cutting teeth. The method of the present invention is suitable for calculating the cutting resistance of rocks with a certain strength and has the advantages of unified dimensions, comprehensive consideration of various cutting parameters, and relatively accurate results.

Description

Technical Field

[0001] The present invention relates to a method for calculating the forces in the field of dredging engineering and rock cutting technology, in particular to a method for calculating the interaction forces between rock cutting teeth and rocks with unified dimensions and comprehensive consideration of various cutting parameters. Background Art

[0002] During dredging operations for port and waterway construction, rocky strata are often encountered. To meet navigational depth requirements and engineering construction requirements, underwater rock must be cut and crushed. Therefore, it's necessary to estimate the resistance experienced by the cutter teeth when cutting rock. Current formulas for calculating the interaction force between cutter teeth and rock are partly derived from two-dimensional cutting theory, significantly deviating from the actual cutting resistance. Others are empirical formulas based on experimental data, often applicable only to specific working conditions and often with inconsistent dimensions. Summary of the Invention

[0003] In response to the shortcomings of the existing technology, the present invention proposes a method for calculating the interaction force between rock cutter teeth and rocks. The present invention has the advantages of unified dimensions, comprehensive consideration of various cutting parameters and relatively accurate results. The method can more accurately estimate the resistance encountered by rock cutter teeth when cutting weathered rock, which is of great significance to the rock cutting and crushing problems encountered during the dredging process of port and waterway construction.

[0004] The present invention is achieved through the following technical solutions: The present invention provides a method for calculating the interaction force between a rock cutting tooth and a rock, comprising the following steps: Step 1, determining the rock type and the rock cutting tooth; Step 2, measuring the tensile and compressive strengths of the rock; Step 3, measuring the tooth tip radius; Step 4, determining parameters related to the cutting angle and cutting depth; Step 5, conducting a linear rock cutting test of the tooth to determine the relationship between the cross-sectional area of ​​the cutting groove and the cutting depth; Step 6, calculating the peak interaction force between the rock cutting tooth and the rock, i.e., the peak cutting resistance, using the following formula:

[0005]

[0006] Where, F p Cutting resistance, unit is kN; d is cutting depth, unit is mm; A(d) is the relationship between the cross-sectional area of ​​the cutting groove and the cutting depth, unit is mm 2 ; σ t is the tensile strength of rock, unit: MPa; σ c is the rock compressive strength, unit: MPa; α is the cutting angle, unit: (°); g(α) is the factor affecting the cutting angle on the rock strength; r is the tooth tip radius, unit: mm; r0 is the correction value of r, unit: mm; p is the constant coefficient.

[0007] Step 7: Calculate the average value of the interaction force between the rock cutter teeth and the rock, i.e., the mean cutting resistance, using the following formula:

[0008] F a =K·F p

[0009] Where, F a is the average cutting resistance, unit is kN; K is the constant coefficient.

[0010] Furthermore, in the present invention, the rock compressive strength σ c is the unconfined compressive strength, which is measured by the unconfined tensile strength test; the rock tensile strength σ t Measured by Brazilian split test.

[0011] Furthermore, in the present invention, g(α) is a quadratic function related to the cutting angle α. The specific functional relationship is related to the rock material and the cutter tooth material, and can be fitted based on the test results.

[0012] Furthermore, in the present invention, r0 is the correction value of r, which is F p The absolute value of the intersection of the -r relationship curve and the r axis, p = 0.7.

[0013] Furthermore, in the present invention, K is a constant coefficient, and its value ranges from 1.2 to 1.6 according to different rock types, and can be determined based on a test of linear rock cutting by a cutter tooth.

[0014] In the present invention, cutting groove is a quantity quadratically related to cutting depth and can be measured through linear rock cutting tests. A linear rock cutting test is performed using a rock cutting tool to obtain a cutting groove. Several cross sections are taken from the cutting groove, and the cutting depth and cross-sectional area are measured to obtain the relationship A(d) between the cross-sectional area and cutting depth.

[0015] Rock strength measurements include unconfined compressive strength σ c and tensile strength σ t There are two types, the unconfined compressive strength can be measured by the unconfined tensile strength test, and the tensile strength can be measured by the Brazilian splitting test.

[0016] The influence of rock strength on resistance also needs to consider the influence of cutting angle α, which is the angle between the cutter tooth cutting rock surface and the horizontal direction. The influence of cutting angle is used as the tensile strength σ t and unconfined compressive strength σ c The exponent of the ratio, its expression g(α) is a quadratic function related to the cutting angle α. The specific functional relationship is related to the rock material and the tooth material, and can be fitted through the test results.

[0017] The bluntness of the blade teeth is a quantity related to the fillet radius of the blade tooth tip. r is the fillet radius of the blade tooth tip. When the blade teeth are sharp, r = 0; when the blade teeth are blunt, the size of r is the fillet radius between the blade teeth. r0 is the correction value of r, which is F p The absolute value of the intersection of the -r relationship curve and the r-axis. p is a constant coefficient. In general construction environments, it is assumed that p = 0.7.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] First, the present invention comprehensively considers various parameters of the rock being cut by the cutter teeth, including rock parameters (e.g., unconfined compressive strength, shear strength, etc.), tooth parameters (e.g., bluntness, etc.), and parameters reflecting the interaction between the two (e.g., groove cross-sectional area, cutting angle, etc.). This comprehensive set of parameters allows the resulting cutting resistance to be closer to actual values.

[0020] Second, the present invention comprehensively considers the cutting failure process in three-dimensional conditions, and the tensile strength, groove cross-sectional area, etc. used in the present invention can reflect the three-dimensional characteristics of cutting.

[0021] Third, the dimensions of the left and right sides of the equation of the present invention are consistent. Compared with the existing empirical formula, the dimension of the resistance estimation model in the present invention is m 2 Pa, which is consistent with the dimension of force, N, is more practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of the present invention;

[0023] Figure 2 Schematic diagram of the rock crushing process in an embodiment of the present invention;

[0024] Figure 3 Schematic diagram of the blunt corner radius of the blade teeth in an embodiment of the present invention;

[0025] Figure 4 This is the correspondence between the theoretical value obtained by the calculation formula and the actual test value in the embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following describes an embodiment of the present invention in detail with reference to the accompanying drawings. This embodiment is based on the technical solution of the present invention and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiment.

[0027] Example

[0028] The specific implementation process is as follows Figure 1As shown in the figure, the test used weathered rock as the cutting rock sample, with a size of 100cm×45cm×10cm and a flat cutting surface. The measured rock tensile strength was 16.51MPa and the tensile strength was 1.47MPa. The test used sharp teeth with a tip width of 20mm. The tooth tip was basically sharp, r=0, as shown in the figure. Figure 3 As shown. A force sensor is installed on the cutter teeth to monitor the cutting resistance of the cutter teeth during cutting. The test adopts a constant cutting speed of 0.5m / s, and changes the cutting depth of the cutter teeth from 0.5cm to 3.0cm and the cutting angle from 40° to 60° (that is, the angle between the front cutting surface of the cutter teeth and the horizontal direction). Figure 2 α in ), monitor the changes of cutting force on the cutter teeth over time under different working conditions.

[0029] After the test, the cross-sectional area of ​​the grooves was measured. For each groove, an average of 5 sections were taken to measure the relationship between the area A and the depth d. For the weathered rock and cutter teeth used in this test, the relationship between the cross-sectional area A and the depth d is: A = d(3.75d + 20), and g(α) is g(α) = 0.0008α. 2 -0.0865α+4.0556. For the bluntness of the blade teeth, take r+r0=2.5, p=1.3. Peak cutting force F p and mean cutting force F a The ratio K is 1.2. In summary, the peak cutting force F p The expression is

[0030]

[0031] Mean cutting force F a The expression is

[0032] F a =F p / 1.2

[0033] The simulation results calculated using the peak cutting force formula are compared with the results obtained from the actual experiment. The comparison chart is as follows: Figure 4 The horizontal axis represents the experimental data, the vertical axis represents the simulated data, and the slash represents y = x. As can be seen from the figure, most of the data points are distributed near the slash, indicating that the formula fits the experimental results well.

[0034] The above describes the specific operation mode of the present invention. It should be understood that the present invention is not limited to the above specific operation mode, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for calculating the interaction force between rock cutting teeth and rocks, characterized in that: The following steps are involved: Step 1: Determine the rock type and the cutter teeth to be used for rock excavation; Step 2: Determine the tensile and compressive strength of the rock; Step 3, measuring the tooth tip radius of the blade; Step 4: Determine the parameters related to cutting angle and cutting depth; Step 5: Conduct a linear rock cutting test on the cutter teeth to determine the relationship between the cross-sectional area of ​​the cutting groove and the cutting depth; Step 6: Calculate the peak value of the interaction force between the rock cutter teeth and the rock, i.e., the peak cutting resistance, using the following formula: Where, F p is the peak cutting resistance, unit is kN; d is the cutting depth, unit is mm; A(d) is the relationship between the cross-sectional area of ​​the cutting groove and the cutting depth, unit is mm 2 ; σ t is the tensile strength of rock, unit: MPa; σ c is the rock compressive strength, unit MPa; α is the cutting angle, unit (°); g(α) is the factor affecting the cutting angle on rock strength; r is the chamfer radius of the cutter tooth tip, unit mm; r0 is the correction value of r, unit mm; p is a constant coefficient; Step 7: Calculate the average value of the interaction force between the rock cutter teeth and the rock, i.e., the mean cutting resistance, using the following formula: F a =F p / K Where, F a is the average cutting resistance, unit is kN; K is the constant coefficient.

2. The method for calculating the interaction force between rock cutting teeth and rock according to claim 1, characterized in that The rock compressive strength σ c is the unconfined compressive strength, which is measured by the unconfined tensile strength test; the rock tensile strength σ t Measured by Brazilian split test.

3. The method for calculating the interaction force between rock cutting teeth and rock according to claim 1, characterized in that The r0 is the correction value of r, which is F p The absolute value of the intersection of the -r relationship curve and the r axis, p = 0.7.

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