CN114441354A

CN114441354A - Method for measuring wear and evaluating durability of rock cutting tool

Info

Publication number: CN114441354A
Application number: CN202110387330.0A
Authority: CN
Inventors: 曺政佑; 吴柱泳; 宋昌宪; 金大地; 金在元; 郑载一
Original assignee: Korea Institute of Industrial Technology KITECH
Current assignee: Korea Institute of Industrial Technology KITECH
Priority date: 2020-10-31
Filing date: 2021-04-09
Publication date: 2022-05-06
Also published as: KR102403509B1; KR20220058803A

Abstract

The invention relates to a method for measuring and evaluating the abrasion and durability of a rock cutting tool by using a rock test piece and a method for using the method as an accelerated life test, in particular to a fault-free accelerated test method for increasing at least one of cutting load and cutting speed and defining the reliable life by replacing a reliable time concept with a reliable excavation amount.

Description

Method for measuring wear and evaluating durability of rock cutting tool

The present application claims priority from korean patent application No. 10-2020-0143971 (filed on 10/31/2020), the specification and drawings of which are incorporated herein by reference in their entirety.

Technical Field

The present invention relates to a method for measuring wear and evaluating durability of a rock cutting tool. Specifically, the present invention relates to a method for performing a pin-on-disk (pin-on-disk) test specified by ASTM, (i) a method for forming an archimedes spiral trajectory at a constant speed during the alternately repeated inward and outward movements of a cutting tool on a rock specimen, (ii) a method for implementing the wear measurement and durability evaluation method of the above (i) on a hollow specimen, and (iii) a method for defining a reliable life by improving a cutting load and/or a cutting speed by using the above (ii) as an accelerated life test and replacing a reliable time concept with a reliable excavation amount concept, and designing and providing a method for a failure-free accelerated test.

Background

In general, the durability of the bedrock/resource cutting tools mounted on roadheader, shearer loader, TBM is directly related to the efficiency of the operation.

However, there has not been a standard test or accepted test that can quantitatively evaluate the durability performance of rock cutting tools. ASTM (American Society for Testing and Materials) discloses a pin-to-disk test and a pin-to-drum (pin-on-drum) test, both of which are used to test metal-to-metal wear and are therefore not suitable for direct application to heavy-cut rock specimens.

As shown in fig. 1, the pin-to-disk test is a test in which abrasion is caused during linear movement of a pin in a radial direction while a disk-shaped test piece is rotated about a vertical axis. In order to perform a pin-to-disk test, the cutting tool needs to form an archimedean spiral track on the test piece at a constant speed (constant velocity).

However, ASTM does not specifically describe the equation of motion and the method of controlling the pin and the test piece, but merely describes the basic principle and the drawing of the method of testing the wear of the metal test piece, and does not specifically describe the method of controlling the severely worn test piece such as rock and concrete, the equation of motion, the method of extracting data, and the like.

Disclosure of Invention

Technical problem

The present invention is intended to solve these problems, and an object of the present invention is to provide a method for measuring wear and evaluating durability of a rock cutting tool, comprising: the pin-to-disc test specified in ASTM can be applied to a rock cutting tool and a rock test piece, the cutting tool cuts the rock test piece while alternately repeating inward movement and outward movement and the cutting tool moves along different archimedes' spirals when moving inward and outward, the end point of the inward movement becomes the starting point of the outward movement, the end point of the outward movement becomes the starting point of the inward movement, and the rotation direction of the rock test piece when moving outward and inward is the same.

Another object of the present invention is to provide a method for measuring wear and evaluating durability of a rock cutting tool, which can be applied to a hollow type rock test piece so that the problems occurring when the above evaluation method is applied to a solid type rock test piece can be solved.

It is still another object of the present invention to provide a failure-free accelerated test method defined by a concept of a reliable excavation amount, which is capable of improving a cutting load and/or a cutting speed as an accelerated life test when a test is performed using a hollow rock specimen, instead of a concept of a reliable time in terms of reliability engineering.

Technical scheme

In order to solve the problems described in [ background art ], the present applicant disclosed a control equation for forming an archimedean spiral trajectory while a cutting tool moves at a constant speed on a solid rock specimen (an internal full-center rock specimen) as shown in fig. 2, and developed a measurement method using the control equation.

In the above-described measuring method, the cutting tool 10 cuts the rock specimen 1 while linearly moving from the center of the upper surface 3 of the rock specimen 1 to the outer periphery or linearly moving from the outer periphery to the center in a state where the rock specimen 1 rotates with the rotation shaft 112 as a reference, thereby forming a spiral-shaped trajectory on the upper surface 3.

Specifically, the rotational force of the driving motor 110 is transmitted to the test piece fixing part 130 via the rotary shaft 112, and the rock test piece 1 is rotated. The cutting tool 10 is linearly moved (in the direction of an arrow) from the center of the rock specimen 1 to the outer contour, or linearly moved from the outer contour of the rock specimen 1 to the center, or repeatedly reciprocated between the center and the outer contour in a state where the pressing or displacement is adjusted by a load cell (not shown). The cutting tool 10 may be linearly moved by a linear moving unit (not shown).

According to the measuring method, the radius (R) of the outermost portion of the spiral, the time (T) required for the cutting tool 10 to move once along the spiral trajectory, and the number (N) of spirals are received from the user, and the trajectory of the spiral, the distance (R) from the center to the cutting tool, the rotation angle (theta) of the rock specimen 1, the distance (L) of the cutting tool 10 moving along the spiral trajectory, and the speed (V) of the cutting tool 10 moving along the spiral trajectory are calculated by the following formula_L) And the like. Fig. 3 shows the definition of the radius (r) of the spiral versus the rotation angle (θ).

[ formula 1]

[ formula 2]

In the above formula, t: time, R: the radius of the outermost profile portion of the spiral,

n: number of helices (e.g., N ═ 5 in fig. 3), θ (t): the angle of rotation of the rock specimen is,

t: the time required for the cutting tool to move from the center to the profile or from the profile to the center along a spiral trajectory.

When the cutting tool 10 is linearly moved in the radial direction and the rock specimen is rotated based on the above calculation results, the cutting tool 10 forms an archimedes spiral trajectory at a constant speed on the upper surface 3. At this time, the interval between the spiral tracks is constant. Fig. 4 shows the archimedes' spiral trajectory formed by the cutting tool in the case of an outward spiral (outward ward forward).

However, since the trigonometric functions with respect to time (t) are included in equations 1 and 2, the radial velocity and the rotational velocity satisfying the constant velocity cannot be absolutely calculated (i.e., an accurate solution of the differential equation cannot be calculated) simply by reverse calculation (equation solution).

In addition, in the field of Atomic Force Microscopy (AFM) and Scanning Transmission Electron Microscopy (STEM), in order to improve Scanning quality, a method of moving an archimedean screw at a Constant speed (CLV) was studied as follows.

D Ziegler et al, Ideal Scan Path of high-speed atomic force microscope, IEEE/ASME Integrated mechatronics, 22(1),381-391,2016 (DOI:10.1109/TMECH.2016.2615327)

IA Mahmood and SO Reza moeimani, spiral scanning atomic force microscope: constant linear velocity method, proceedings of the tenth IEEE International conference on nanotechnology Union Nanocorticulation in 2010, KINTEX, Korea, 2010(DOI:10.1109/NANO.2010.5698063)

X Sangg et al, dynamic scan control in STEM: helical scanning, advanced structural and chemical imaging, 2(6), 2017 (DOI: 10.1186/s40679-016-

From the above-described results, in the path (Outward path) moving from the inner side to the outer side of the circle, the spiral radius (r) and the rotation angle (θ) can be expressed by the following

expressions

3 and 4.

[ formula 3]

r(t)＝R·f(t_*)

[ formula 4]

θ(t)＝2πN·f(t_*)

In the above formula, t_*：t/T

f (t;): f (t) when the cutting tool moves linearly from the center to the outer periphery of the rock specimen_*) To satisfy any function of f (0) being 0 and f (1) being 1. When the cutting tool moves linearly from the outer edge of the rock test piece toward the center, f (t) is an arbitrary function satisfying the condition that f (0) is 1 and f (1) is 0.

See the above study (paper), in the case of outward spiraling (outward spiraling), published

In the case of inward spiraling (inward spiraling)

Will be provided with

The

following equations

5 and 6 can be obtained by differentiating t in place of

equations

3 and 4.

[ formula 5]

[ formula 6]

Equation 5 shows the linear movement speed of the cutting tool in the case of the outward spiral. However, since the linear movement speed is too high when t is close to 0, for example, when t is 0 ≦ t ≦ 1, a constant linear movement speed may be input to the device in an actual test.

And, equation 6 shows the rotation speed of the rock specimen in the case of outward spiral. However, in the start stage of measurement at a time when t is around 0 (for example, in the case where 0 ≦ t ≦ 0.1 seconds), the rotational speed temporarily increases excessively and converges to a constant speed, and therefore, this portion needs to be considered when processing the result data after actual measurement. This part is an error of the approximate solution, occurring a small amount in a time period within 0.1 second, and is therefore an error of negligible degree.

In addition, the case of inward spiral will

Substituting the

expressions

3 and 4, differentiating t to obtain the expressions 7 and 8. Fig. 5 shows the archimedean spiral path formed by the cutting tool with the inward spiral.

[ formula 7]

[ formula 8]

Equation 7 shows the linear movement speed of the cutting tool in the case of the inward spiral. However, when T is near T, for example, when T is 100 seconds (sec), and when 99.9 seconds ≦ T ≦ 100 seconds, the linear moving speed is excessively increased and converges to a constant speed, and therefore, the user needs to take these into consideration during data processing. However, this is also an error that occurs in a very short time, to the extent that it is negligible for the user.

As described above, the present applicant has disclosed a governing equation for a cutting tool to move at a constant speed while forming an archimedean spiral trajectory on a solid rock specimen, and developed a measurement and evaluation method using the governing equation. This method has advantages of simple test and saving test time, compared to the existing linear cutting test (e.g., KR 701979B 1, korea, etc.).

In addition, the solid rock test piece has a problem that the cutting depth of the cutting tool cannot be adjusted at the center thereof. That is, as shown in FIG. 6, in the case of the inward spiral, the cutting depth (d) of the cutting tool is adjusted outside the test piece₁，d₂Etc.) into the outer contour of the test piece, the cutting depth can be adjusted, but it is difficult to adjust the cutting depth of the cutting tool at the center of the test piece, and thus there is a problem that the test can be performed only with an inward spiral, and it is difficult to perform the test with an outward spiral. As shown in fig. 7, there is also a problem that the tool holder interferes (collides) with the central portion of the test piece when the cutting is performed to a depth of a certain depth or more.

In order to solve these problems, a control equation for forming an archimedes spiral trajectory at a constant speed on a hollow test piece (a test piece having a hollow portion formed at the center) by a cutting tool has been newly proposed, and a wear measurement and durability evaluation method using the control equation has been developed. Further, a method of calculating a failure-free accelerated excavation volume using a reliable excavation amount instead of a reliable life by using such a method as an accelerated life test by increasing a cutting load and/or a cutting speed has been developed.

Technical effects

The present invention has the following effects.

First, there is provided a method for measuring wear and evaluating durability of a rock cutting tool, which is capable of applying a pin-to-disk test specified by AS TM to a rock cutting tool and a rock specimen, wherein the cutting tool cuts the rock specimen while alternately repeating inward movement and outward movement, and the cutting tool moves along different archimedes' spirals while moving inward and outward, an end point of the inward movement becomes a start point of the outward movement, an end point of the outward movement becomes a start point of the inward movement, and the outward movement and the inward movement are in the same rotational direction AS the rock specimen.

Second, a new control equation is provided to apply the above method to the empty test strip.

Thirdly, the test of the hollow test piece is used as an accelerated life test by improving the cutting load and/or the cutting speed, the reliable life is defined by reliable digging amount instead of the reliable time concept, and a fault-free accelerated measuring method is designed and provided.

Drawings

FIG. 1 is a perspective view showing an ASTM specified pin-to-disc test;

fig. 2 is a perspective view showing a rock wear test using a rock specimen of a solid type;

FIG. 3 is a diagram showing the definition of the spiral radius (r) and the rotation angle (θ) in an Archimedes spiral;

fig. 4 is a graph showing a trajectory in a case where a cutting tool moves from the center of a solid type rock specimen to the outer contour along an archimedean spiral (referred to as an outward spiral);

fig. 5 is a graph showing a trajectory in a case where the cutting tool moves from the outer periphery of the solid rock specimen to the center along the archimedean spiral (referred to as inward spiral);

fig. 6 is a sectional view showing the adjustment of the cutting depth in the case where a solid type rock specimen forms an inward spiral trajectory;

fig. 7 is a schematic view showing interference (collision) between the central portion of the rock specimen and the tool holder as cutting progresses in a case where a cutting test is performed on a solid rock specimen;

FIG. 8 is a schematic view of an inward spiral (left side), an outward spiral (center), and an inward and outward spiral (right side) of a first embodiment of the present invention;

fig. 9 is a perspective view showing an example of a hollow test piece (hollow specimen) used in the second embodiment of the present invention;

FIG. 10 shows the respective spacing distances (R)_offset) Schematic of the inward spiral path (left side) and the outward spiral path (right side);

FIG. 11 is a schematic view showing an inward spiral (a), an outward spiral (b) and a slope discontinuity (c) from the position where the inward spiral is connected to the outward spiral, respectively, formed in a hollow test piece;

FIG. 12 is a graph showing a region of s and R such that the difference in slope of the two spirals is less than 1 at the location of the connection of the inward spiral and the outward spiral;

FIG. 13 is a schematic view of a cutting knife and cutting track disposed on a cutting head;

fig. 14 (a), (b) are schematic views showing the length (Lc) of the outline of the cutting head and the interval(s) between the cutters, respectively;

fig. 15 is a schematic view showing the depth of penetration at the time of the cutting feed operation;

fig. 16 is a schematic view showing the operation speed and the penetration depth in the cutting operation;

fig. 17 is a graph showing a ratio (Rt) of contact time corresponding to a cutting depth (y) at the time of cutting work;

fig. 18 is a graph showing a relation between the cutting depth (d) and the cutting load (Fc);

fig. 19 is a graph showing a change tendency of the cutting load (Fc) and the vertical load (Fn) according to the Uniaxial Compressive Strength (UCS).

Detailed Description

[ first embodiment ]

In a first embodiment, the cutting tool alternately repeats inward movement and outward movement, the cutting tool cuts the rock specimen during movement along different archimedean spirals as it moves inward and outward, the end point of the inward movement becomes the starting point of the outward movement, the end point of the outward movement becomes the starting point of the inward movement, and the outward movement is in the same direction as the rotation of the rock specimen as it moves inward.

According to this method, the rock specimen continues to rotate in the same direction, and therefore, the load on the specimen-rotating motor is not imposed. In contrast, when the rotation direction of the rock specimen is instantaneously changed in the opposite direction between the end point of the inward spiral and the end point of the outward spiral, a load is imposed on the motor and the like.

Fig. 8 shows the spiral trajectory when the cutting tool is moved inward (left diagram, in w), the spiral trajectory when moved outward (middle diagram, outw), and the overlap of the inward spiral trajectory and the outward spiral trajectory (right diagram) in the first embodiment, respectively.

The inward spiral alternately repeats cutting from (R, 0) on the x-axis in an inward movement (inward spiral, inw) → an outward movement (outward spiral) → an inward movement (inward spiral) → an outward movement (outward spiral) → moving along different trajectories (paths), respectively, and the rotation direction of the rock test piece is the same.

The trajectory of the inward spiral is shown in formulas (A) to (E). [ T-0- (T-T)₀)]。

r_inw＝Bf_inw(t)..................(B)

θ_inw＝2πNf_inw(t)-θ_f..................(C)

P_xinw＝r_inw·cos(θ_inw)...................(D)

P_yinw＝r_inw·sin(θ_inw)..................(E)

The trajectory of the outward helix is shown in formulas (F) to (J). (t ═ t)₀～T)。

r_outw＝Rf_outw(t)...................(G)

θ_outw＝-(2πNf_outw(t)-θ₀)+(θ₀-θ_f)………………(H)

P_xoutw＝r_outw·cos(θ_outw)...................(I)

P_youtw＝r_outw·sin(θ_outw)...................(J)

In the above formula, R is the radius of the position of the cutting tool, R is the radius of the test piece, R is₀S is the interval between the spirals (see fig. 3) and v is the moving speed of the cutting tool moving along the spiral, which is the radius of the cutting start position when moving outward or the radius of the cutting end position when moving inward. The parameters in the above formula can be calculated by the formula (K). And inw denotes inward movement and outw denotes outward movement.

θ₀Is to make the radius (R) from the end point of the inward spiral₀) And the value used for the angle to coincide with the starting radius and angle of the outward spiral, theta_fIs a value (phase angle at the time point when the previous spiral ends) that is applied to start the inward spiral from (R, 0) on the x-axis.

The calculation is performed by setting constants in the following table as shown in fig. 8 (the function constants are the same although the trajectories (paths) of the two spirals are different). The outward spiral starts at the point where the inward spiral ends, so that the different spiral paths move in the same rotational direction.

[ TABLE ] examples of constants for Archimedes spiral path abrasion test of rock test pieces

R[mm]	R0[mm]	s[mm]	v[mm/s]
				200	40	20	10

As shown in the right graph of fig. 8, the instantaneous slope (dy/dx) of the spiral path at the time of transition from inward spiral to outward spiral is different, and thus (inward spiral is about-1.71, outward spiral is about-1.12), the connection between the spirals is not soft. (see the inside of the green circle (G) of fig. 8). In particular, such slope differences increase with increasing spiral spacing(s), because the slopes are different when different spirals have the same radius.

The slope difference can be calculated by the following formula.

Δθ＝|(dy/dx)_inw-(dy/dx)_outw

By adjusting the four constant values of the above table, it is preferable that the difference between the slope of the end point of the inward shift and the slope of the start point of the outward shift and the slope of the end point of the outward shift and the slope of the start point of the inward shift is 0.5 ° to 5 °, more preferably less than 1 °. If the difference in the slope is more than 5 °, the connection between the spirals is not soft and problems may occur in continuously acquiring data, and if the difference in the slope is less than 0.5 °, the intervals between the spirals are too close and thus problems may occur in terms of experiment and thus it is not preferable.

As described above, in the case of having different paths and the same rotational direction, the paths of the inward spiral and the outward spiral are different, and thus it is difficult to calculate the spiral. In particular, as the inward spiral/outward spiral is switched, the end position and angle are required to be input as the initial start position and angle to implement the path so that the end time point and the start time point of the spiral path coincide. For this purpose, the angle (formula C, formula H) is calculated as follows.

First inward movement: theta₁(t＝2πNf_inw(t)θ_f

First outward movement: theta₂(t)＝-(2πNf_outw(t)-θ₀)+θ₁(T-t₀)

On the second inward movement: theta₃(t)＝2πNf_inw(t)+θ₂(T)

On the second outward movement: theta₄(t)＝-(2πNf_outw(t)-θ₀)+θ₃(T-t₀)

When the h moves inwards for h (h is more than or equal to 3): theta_2h-1(t)＝2πNf_inw(t)+θ_2h-2(T)..............(L)

When the h moves outwards (h is more than or equal to 3): theta_2h(t)＝-(2πNf_outw(t)-θ₀)+θ_2h-1(T-t₀).....(M)

In the above formula, the first and second carbon atoms are,

t: time of day

N: number of spirals

f_inw(t): satisfy f_inw(0)＝1、f_inw(1) 0. For example

f_outw(t): satisfy f_outw(0)＝0、f_outw(1) 1-arbitrary function. For example

T: the time required for the cutting tool to move along a helical trajectory from the center to the profile or vice versa of the rock specimen

T-t₀: the time the cutting tool is moved along the helical track.

θ₀: in order to make the radius (R) at the end point of the inward movement₀) And a constant used with the angle coinciding with the starting radius and angle of the outward movement

According to the angle calculation method described above, the equation for calculating the angle in the course of repetition presents regularity, moving inward (inward spiral) → moving outward (outward spiral) → moving inward (inward spiral) → moving outward (outward spiral). That is, the angle is calculated reflecting the end angle of the previous spiral, and the method of calculating the angle of the inward spiral is different from that of the outward spiral. According to the above expression and regularity, a continuous spiral path in the same rotation direction can be generated.

[ second embodiment ]

1. Pin-to-disc for hollow rock test piece

(1) New intrinsic constant (R)_offset) Definition of (1)

Fig. 9 is a perspective view showing an example of a hollow test piece. As shown in the figure, the hollow test piece has a hollow (hollow space) formed in the center thereof in the vertical direction.

During a cutting test, after n times of abrasion is finished, n +1 times of abrasion needs to be executed after the cutting depth needs to be adjusted, and the cutting depth can be vertically adjusted only by going out to the outer side of the test piece or going out to the hollow side for a certain length. In this case, the radial length of the excess is defined as R_offset。

In the present invention, since it takes time to accelerate a motor (not shown) for rotating the rock specimen, the set constant speed cannot be satisfied from the beginning of the test. For this reason, it is necessary to set R_offsetTo ensure an acceleration interval. Corresponding to R in FIG. 9_offsetAcceleration time of t₁-t₀And T-T₂. This acceleration time needs to be set sufficiently compared to the specification of the motor to perform the wear test after reaching the constant speed.

(2) Arranging variables according to specimen shape

The variables required for the archimedes screw test (pin-to-disk test) for the preparation of hollow rock test pieces are as follows.

R: outside radius of hollow test piece [ mm ]

R₀: inside radius [ mm ] of hollow test piece]

R_offset: the length of the cutting tool (Pick cutter, etc.) extending out of the hollow specimen or the length of the cutting tool moving into the hollow interior [ mm ]]。

t₀: the cutting tool is moved from the center of rotation of the hollow test piece to (R0-R)_offset) Time required [ s ]]

t₁: the cutting tool is moved from the rotation center of the hollow test piece to R₀Time required [ s ]]

t₂: time required for the cutting tool to move from the center of rotation of the hollow test piece to R [ s ]]

T＝T_total: the cutting tool is moved from the rotation center of the hollow test piece to (R + R)_offset) Time required [ s ]]

T_move: the time taken for the cutting tool to actually move in the cutting test. I.e. from (R)₀-R_offset) To (R + R)_offset) Time taken [ s ]]

T_test: actual wear test time of hollow rock test piece (time of contact with test piece, t)₂-t₁)[s]

N(＝N_total): mathematically from the center of the test piece to (R + R)_offset) Total number of helices generated

N_move: number of actually realized spirals in cutting test

N_test: number of spirals formed in a region where the cutting tool contacts the hollow rock specimen

s: spacing between helices [ mm ]

v: the spiral movement of the cutting tool adds the velocity [ mm/s ]. I.e. the speed at which the cutting tool moves along the helix

In this test, intrinsic constants of the archimedean spiral test are defined as 5 as shown below, and the remaining test variables are dependent constants calculated from the intrinsic constants.

Table 1: archimedes spiral path abrasion test inherent constant of 5 hollow test pieces

R[mm]

R₀[mm]

R_offset[mm]

s[mm]

υ[mm/s]

(3) Collation of intrinsic constant relationships

The relationship between the dependent constant and the inherent constant is calculated by the following equation. Total number of helices (N ═ N)_total) Number of spirals (N) compared to actual movement_move) The number of helices formed by actual contact with the test piece (N)_test) Can be calculated as follows.

The relationship with respect to the movement time variable can be calculated as follows.

I.e. T ═ T_total，T_move＝T-t₀T_real＝t₂-t₁。

The movement distance variable can be calculated as follows.

Wherein L is_inwtotal、L_inwtest、L_outwtotal、L_outwtestThe total moving distance in the inward direction, the cutting test distance in the inward direction, the total moving distance in the outward direction, and the cutting test distance in the outward direction are shown, respectively.

And, the locus (P) of the inward spiral_xinw，P_yinw) Outward spiralTrack (P) of_xoutw，P_youtw) The equation of (c) is shown below.

P_xinw＝r_inw·cos(θ_inw)........................(12)

P_yinw＝r_inw·sin(θ_inw).......................(13)

P_xoutw＝r_outw·cos(θ_outw).......................(14)

P_youtw＝r_outw·sin(θ_outw).......................(15)

In the above formula, P_xinw，P_vinw: position coordinates of the cutting tool at a specific time (t) while moving inward

r_inw: radius of cutting tool position at a specific time (t) when moving inward

θ_inw: phase angle of cutting tool position at specific time (t) when moving inward

P_xoutw，P_youtw: position coordinates of the cutting tool at a specific time (t) while moving outward

r_outw: radius of cutting tool position at a specific time (t) when moving outward

θ_outw: phase angle of cutting tool position at specific time (t) when moving outward

The rotary motor for rotating the rock test piece and the linear motor device for linearly moving the cutting tool are all controlled by speed. Therefore, the path equations (equations 12-15) represent the current position of the cutting tool, and therefore the differential needs to be converted into linear velocity and RPM.

Consider R_offsetIn the case of (2), the radial velocity (v)_routw，v_rinw) And RPM (RPM)_outw，RPM_inw) As shown in the following formula.

In the above formula, V_routw: radial linear moving speed of cutting tool when moving outward

RPM_outw: the rotational speed of the rock specimen when moving outwards

V_rinw: speed of linear movement of cutting tool in radial direction when moving inward

RPM_inw: the rotational speed of the rock specimen while moving inwardly

(4) Design demonstration of spiral test

The movement path is simulated by the values of the inherent constants arbitrarily specified in table 2 below for the five helical wear tests. The calculation output table of the spiral function corresponding to the five constants is shown in table 3.

TABLE 2 five intrinsic constants for Archimedes spiral path abrasion test of hollow test pieces

R[mm]	R_o[mm]	R_offset[mm]	s[mm]	v[mm/s]
					300	40	40	10	10

TABLE 3 examples of the arrangement of the output values of the test variables

Serial number	Variables of	Unit of	Value of
				1	N(＝N_total)
2	N_move
				3	N_test
4	t₀	s
				5	t₁	s
6	t₂	s
				7	T(＝T_total)	s
8	T_move	s
				9	T_test	s
10	L_inwtotal	mm
				11	L_inwtest	mm
12	L_outwtotal	mm
				13	L_outwtest	mm

The locus (Re) of the inward spiral is shown by a graph in the left side of fig. 10, and the locus (B1) of the outward spiral is shown by a graph in the right side of fig. 10. In fig. 10, a gray path (gr) indicates an overall path, and red (Re) and blue (Bl) paths respectively indicate paths of actual cutting.

(5) Solving the problem of discontinuity of the spiral

Fig. 11 shows an inward spiral path (a), an outward spiral path (b), and a path (c) in the case of moving inward and then outward, respectively. In fig. 11 the inward movement is in the same direction as the rotation of the rock test piece when moving outward. When the test is continuously performed as described above, a discontinuous position of the spiral inclination occurs at a time point when the inward shape is changed to the outward shape, and when the discontinuous angle is excessively increased, a problem such as an excessive load applied to the equipment may occur, and therefore, it is necessary to consider these in the test design.

Empirically, the present applicant found that when the difference between the slope of the inward movement end point and the slope of the outward movement start point and the difference between the slope of the outward movement end point and the slope of the inward movement start point are smaller than a specific angle (δ °), the direction change at the time of the abrasion test can be softened, and the present applicant found that a preferable specific angle is 1 °. This is expressed by the numerical expression shown in the formula 20. If the difference in the slope is 1 ° or more, the connection between the spirals is not soft, and the motor movement is greatly changed, so that there is a possibility that a problem such as an excessive load on the device may occur, which is not preferable.

Therefore, the range of specimen radius (R) and spiral interval(s) in the region where the specimen is kept at less than 1 ° was examined and simulated as shown in fig. 12. It was found that the region smaller than 1 ° was almost linearly distinguished from the region above 1 °. The inequality at this time is shown in equation 21. Therefore, when the specific angle is set to 1 °, it is safe to set the test variable in the region of the numerical expression. The following inequality ranges are illustrative.

s＜0.003R-5.334(where，D_grad＜1°)...................(21)

2. Accelerated life wear test design

(1) Cutting condition calculation method

As shown in fig. 13 to 14, cones (pick) of the cutting head (an example of a cutting tool) have different rotation orbits. Therefore, the designed cutting interval(s) can be estimated by dividing the total length of the track by the number of cones arranged in the cutting head. That is, the cutting interval(s) is calculated by dividing the length (Lc) of the contour line of the drum end of the cutting head by the number (n) of cones. For reference, '+', 'x' in fig. 14 denote cones, respectively.

s＝L_c/_n...................(22)

The depth of penetration indicates the depth at which the cutting head cuts the rock at each rotation. The cutting operation of the cutting head can be divided into a cutting operation and a shearing operation.

Depth of penetration (d) during cutting operation_sump) Generally, the manual of the equipment is described. In FIG. 15, the value of X (X1, X2, etc.) is the depth of penetration (d) per revolution_sump)。

Depth of penetration (d) per turn in shearing operation_shear) As shown in fig. 16, depending on the lateral direction transfer speed of the cutting head (sliding or cutting speed: v. of_shear) Calculated from the rotational speed (rpm). d_shearThe equation of (c) is shown below.

(2) Conversion of cutting speed

The cutting speed is scaled according to the designed rotational speed (rpm) or linear speed (vl) value of the cutting head. This uses the linear velocity from the cutting head to the cone end point in conversion to the rotational speed, equation 24. In most cases, the radius of the drum is set to the value of r. Since the cones at the end portions of both sides of the cutting drum, i.e., the nose (nose) portions, are different in position on the radius of the drum, the r value needs to be set in consideration of the positions of the respective cones.

(3) Conversion of cutting distance

The cutting head continues to contact the bedrock while the apparatus is in operation, however, the cone only contacts the bedrock part of the time. The cutting time of the cone thus varies during operation with the contact angle with the contact surface. The operation is divided into feeding and cutting.

Cutting distance during feed operation

One can think of the interval where the feed starts to push half of the cutting head in. The drum type entry driving machine has an initial contact time of 0, and the maximum depth of cut is pressed into the drum to the radius (D/2: R). The ratio of contact time to working time (Rt) is therefore 50%, so 1/4 times the average contact cutting time can be assumed. The cutting distance (Lc) of an individual cone can thus be calculated using the working time (t) of the heading machine as follows.

Cutting distance during cutting operation

The tunneling machine is operated while keeping the vertical excavation depth (y) value of 1/2-1/4 of the drum diameter (D) at most except for the first cutting operation zone. This is because the excavation speed can be increased. Fig. 17 shows the results of the investigation of the working depth ratio (y/D) and the contact time ratio (Rt) of the cutting cylinder during the cutting operation. Since the following equation 26 is obtained by linear regression, the entire cutting distance of the shearing at the working time (t) is calculated as equation 27. (wherein Rt has a maximum value of 0.5)

Rt＝0.36+0.15(y/D)(where，R_t≤0.5).......................(26)

(4) Cutting load accelerated life test method

Method for adjusting cutting depth (d)

It is known that the cutting load (Fc) increases linearly with increasing depth of cut in the same rock. Therefore, the accelerated life test can be designed by adjusting the cutting depth (d) to increase the cutting load. Since the cutting load is also 0 when d is 0, it is reasonable to assume that the v-intercept of the linear regression equation is 0. The cutting load corresponding to the pressing depth can be predicted by the following linear function. Where a is the slope of the linear function and is a coefficient determined by experiment.

F_C＝ad...................(28)

The heading machine can dig into the initial area of hard rock. Therefore, the data were analyzed with the weakest soft rock set to 10MPa on the basis of the compressive strength and the hard rock initial region set to 100 MPa. The minimum-maximum range of the slope was 3 to 11, and the results were examined as shown in FIG. 18.

Method for comprehensively regulating rock physical property and cutting depth

There is a method of improving the accelerated life by improving the physical properties of the rock disk to be cut. Generally, Uniaxial Compressive Strength (UCS) of rock has a typical physical property tendency, and thus an accelerated life wear test can be performed by increasing the UCS. Where UCS and d are selected as input variables and the cutting load (Fc) is selected as output, the relationship between them can be regressed to a specific function. A typical example of the regression equation is shown below. Where Fc is the cutting load, UCS is the uniaxial compressive strength, d is the cutting depth, and a and b, m, and n are coefficients of regression equations, respectively.

F_C＝[a UCS+b]d...................(29)

F_C＝[m UCS⁽ⁿ⁾]d...................(30)

The power function of equation 30 is more accurate, however, the linear function shown in equation 29 is also largely used for convenience. The coefficient values for a, b can be determined in this equation to complete the model for weighting the cutting load. Accelerated life tests can be designed in this way. Experimental results according to the prior research (Bilgin, 2006) indicate a range from soft to hard Rock with values of the order a 0.83, b 21.8, m 2.3, n 0.8 (n. Bilgin et al, Journal of International Rock Mechanics and Mining science 43(2006) where major Rock properties affect the performance of conical picks and some experimental and theoretical results (dominent of Rock engineering & Mining sciences International Journal of concrete and mineral research 43(2006) 139.156).

The vertical load during cutting can be estimated by the following equation 31. It is reported that the vertical load can be estimated by n-1. And thus can be expressed by estimating the coefficient as one by the following linear numerical expression (see fig. 19). That is, as the strength of the bedrock increases, the vertical load increases more than the cutting load, and thus it is known that attention is required to cut more than hard rock.

F_N＝[m UCS⁽ⁿ⁾]d＝[m UCS]d...................(31)

Acceleration test of cutting speed

Accelerated life tests may also be performed by increasing the cutting speed. The cutting speed may be increased by increasing the added moving speed (vRe) of the tool. Which is shown below.

In the above formula, v_rRepresenting radial linear velocity, v, of the cutting tool_tRepresenting the tangential rotational speed of the tool. As a result, the moving speed is added to the final speed, and therefore, the acceleration test can be designed only by converting the speed.

(5) Setting an acceleration factor of an accelerated life test

(ii) load for accelerated life test

(i) Equivalent load

The evaluation value of the cutting load (Fc) described above may be defined as an equivalent load. Since the extraction of the average value of the cutting load cannot be realized by a real-time test, it is necessary to derive the average value based on data obtained by a linear cutting test or a rotational cutting test. Let the real-time test load extracted from the cutting test be fc (t), sample number: n, t 1: starting time (sec), t₂: end time (sec), f_s: the equivalent load at sampling frequency (Hz) is calculated as follows.

where，n＝f_s(t₂-t₁)

(ii) Acceleration load

Acceleration load (Fc)_a) Is a value determined at the time of experimental design, and is a ratio of acceleration load (a)_F) Calculated by the following formula 34. It is composed ofIn the formula, λ is a fatigue damage index, which is a value defining the degree of damage of each member corresponding to a load, and regression is calculated from an S-N curve obtained by a fatigue test or fatigue analysis. Typically, bearings, gear components, etc. take a value of 2.0.

② speed of accelerated life test

(i) Equivalent velocity

The equivalent speed represents the average resultant force speed during operation, and is calculated from the rotation radius of the machine and rpm as described above, and the formula is shown in equation 35.

(ii) Acceleration rate

Ratio of acceleration rates during the test (a)_v) By acceleration speed (v)_a) With equivalent velocity (v)_eq) The ratio is expressed by the following numerical expression. Where (λ v) is the fatigue damage index with respect to velocity. For a rock cutting tool where the effect of wear due to velocity differences is unknown, 1.0 is assumed.

Acceleration speed (v)_a) Is a value belonging to one of five intrinsic constants, and is set by an experimenter. For example, the equivalent speed (v) of the heading machine is measured_eq) At 1.5m/s, the user sets the acceleration rate 30 (v)_a) 3.0m/s, and an acceleration rate ratio of 2.0 when the fatigue damage index is 1.0. In this case, the radial velocity and the tangential velocity should be accurately controlled according to the above-mentioned equations.

Acceleration factor

By multiplication of a_FAnd a_vAnd calculating an Acceleration Factor (AF). Setting the acceleration factorIn the case of (3), the test time and excavation amount of the accelerated life test can be significantly reduced.

AF＝a_Fa_v....................(37)

Failure-free excavation measurement formula

The known failure-free test time is defined as the minimum time for which a product should operate without failure in an actual use environment in order to meet reliability targets. That is, Rx (%) of the product is C (%) reliable to Lx time without fail, and no failure should occur during the no-failure test time in the actual use environment. Also, a method for calculating the failure-free test time is known.

However, for rock cutting tools, it is more reasonable to target the excavation amount as a test target than to target the test time as a test target. This is because the equipment operation rate is typically less than 50%, and particularly depending on its operating scenario, the contact time of each rock cutting tool (e.g., cone) varies widely, and therefore in many cases the rock cutting tool operation time cannot be accurately estimated.

It is therefore preferable to replace the product reliable life (Lx) with the reliable excavation amount (Lv). In this case, the method is used to calculate the fault-free excavation amount and the fault-free accelerated excavation volume (Vc)_a) The formula (2) is shown below.

In the above formula, L_v: reliable excavation amount (reliable life, m)³)，V_c: fault free excavation volume (m)³)，

AF: acceleration coefficient, C: reliability level, n: number of samples, R_x: degree of reliability

C, n and Rx are dimensionless constants, so the units of the whole numerical expression are unified into volume units.

Wherein digging has no reasonObstacle acceleration excavation volume (Vc)_a) Meanwhile, if no trouble occurs in the case of performing a product test in an accelerated load cycle, Rx (%) of a specific tool product means reliable C (%) digging to L_vThe cutting volume position does not fail.

Claims

1. A method for measuring wear and evaluating durability of a rock cutting tool, characterized by comprising:

under the condition that the rock test piece rotates by taking the center of the rock test piece as a reference, the cutting tool alternately repeats inward movement of cutting the rock test piece in the process of linearly moving from the outer contour to the center of the upper surface of the rock test piece and outward movement of cutting the rock test piece in the process of linearly moving from the center to the outer contour,

the cutting tool forming a spiral path at a certain speed when moving inward and outward, the interval between the spirals being certain,

the rock test piece is a test piece with a hollow part vertically formed in the central part, the cutting tool moves towards the hollow part for at least a certain distance when moving inwards to adjust the press-in depth and then starts to move outwards, and the cutting tool moves outwards to the outer side of the rock test piece for a certain distance to adjust the press-in depth and then starts to move inwards.

2. The method of measuring wear and evaluating durability of a rock cutting tool according to claim 1, wherein:

the cutting tool being spaced R from the outside of the rock specimen on inward movement_offsetWhile moving spirally into the rock specimen,

the cutting tool being spaced R from the centre of the rock test piece when moved outwardly_o-R_offsetEnters the rock test piece in the process of spiral movement,

R_ois the radius of the hollow.

3. The method of measuring wear and evaluating durability of a rock cutting tool according to claim 1, wherein:

the radial direction moving speed of the cutting tool and the rotating speed of the rock test piece are calculated by the following formula,

[ formula ]

In the above formula, V_routw: the linear moving speed of the cutting tool in the radial direction when moving outward,

r: the radius of the test piece is greater than the radius of the test piece,

R_offset: the distance that the cutting tool moves to the outside of the rock test piece away from the rock test piece when moving outwards, or the distance that the cutting tool moves to the center of the rock test piece away from the rock test piece when moving inwards,

t: the time of day is,

t: when the cutting tool moves inward or outward, it moves from the center of the rock specimen to' R + R_offsetThe time required for the' production of the polymer,

RPM_outw: the rotation speed of the rock specimen when moving outwards,

n: from the center of the rock specimen to ` R + R `_offsetThe number of the spirals of (2) is,

Vr_inw: the linear moving speed of the cutting tool in the radial direction when moving inward,

RPM_inw: the rotational speed of the rock test piece when moving inwards.

4. The method of measuring wear and evaluating durability of a rock cutting tool according to claim 3, characterized in that:

the rotation directions of the rock test piece are the same when the rock test piece moves inwards and outwards, the difference between the spiral slope of the inward movement terminal point and the spiral slope of the outward movement starting point is less than 1 degree and satisfies the following formula,

[ formula ]

s＜0.033R-5.334

In the above formula, the first and second carbon atoms are,

s: the spacing between the spirals.

5. The method of wear measurement and durability evaluation of a rock cutting tool according to any one of claims 1 to 4, characterized in that:

the test method is realized by an accelerated life test by increasing cutting load (Fc) and cutting speed (v)_Re) At least any one implementation of (a).

6. The method of wear measurement and durability evaluation of a rock cutting tool according to claim 5, characterized in that:

the increase in cutting load (Fc) is achieved by increasing at least one of the cutting depth (d) and the Uniaxial Compressive Strength (UCS) of the rock specimen, as calculated by any one of the following equations,

[ formula ]

F_C＝a₁d

F_C＝[a₂UCS+b₂]d

F_C＝[mUCS⁽ⁿ⁾]d

a₁: the slope of a straight line representing the relationship between the cutting depth (d) and the cutting load (Fc),

a₂，b₂m, n: UCS and d are used as input variables, and Fc is used as a coefficient of a regression expression of the output.

7. The method of measuring wear and evaluating durability of a rock cutting tool according to claim 5, wherein:

the cutting speed (v) was calculated by the following formula_Re)，

[ formula ]

v_r: the radial direction moving speed of the cutting tool,

v_t: tangential velocity of the cutting tool.

8. The method of measuring wear and evaluating durability of a rock cutting tool according to claim 5, wherein:

reliable excavation amount (L) for the accelerated life test_v) Instead of the concept of reliable time defining the reliable lifetime,

the failure-free accelerated excavation volume (Vc) is calculated by the following formula_a)，

[ formula ]

In the form of a line-stitch,

vc: fault free excavation volume (m)³)，L_v: reliable excavation volume (═ reliable life, m)³) C: the reliability level is that the reliability of the system,

n: number of samples, Rx: reliability, β: failure characteristic index (shape parameter), AF: an acceleration factor.

9. The method of measuring wear and evaluating durability of a rock cutting tool according to claim 8, wherein:

the AF is calculated by the following formula,

[ formula ]

AF＝a_Fa_v

In the form of a line-stitch,

a_F: the ratio of the acceleration load to the acceleration load,

Fc_a(acceleration load): the values determined at the time of the experimental design,

Fc_eq(equivalent load): a certain time (t)₁～t₂) The average value of the internal cutting load (Fc),

where，n＝f_s(t₂-t₁)

fc (t): real time cutting load

λ (fatigue damage index): is a value defining the degree of damage of the components with respect to the load,

a_V: the ratio of the speeds of the acceleration is,

v_a: acceleration rate

v_eq: the speed of the motor is equivalent to the speed of the motor,

r: the radius at which the cutting tool is located,

rpm: the rotation speed of the rock test piece.

10. A method for measuring wear and evaluating durability of a rock cutting tool, characterized by comprising:

in the state that the rock test piece rotates by taking the center of the rock test piece as a reference, the cutting tool alternately repeats the inward movement of the cutting rock test piece in the process of linearly moving the cutting rock test piece from the outer contour of the upper surface of the rock test piece to the center and the outward movement of the cutting rock test piece in the process of linearly moving the cutting rock test piece from the center to the outer contour,

cutting the rock test piece during the inward movement and outward movement of the cutting tool along different spirals, the cutting tool moving along the spirals being moved at a certain moving speed with the same pitch between the spirals,

the end point of the inward movement becomes the starting point of the outward movement, the end point of the outward movement becomes the starting point of the inward movement, and the outward movement is in the same direction as the rotation of the rock specimen during the inward movement.

11. The method of measuring wear and evaluating durability of a rock cutting tool according to claim 10, wherein:

the cutting tool starts from the inward movement and repeats the inward movement and the outward movement alternately, the phase angle of the cutting tool at the time of the inward movement and the outward movement is as follows,

first inward movement: theta₁(t)＝2πNf_inw(t)-θ_f

First outward movement: theta₂(t)＝-(2πNf_outw(t)-θ₀)+θ₁(T-t₀)

On the second inward movement: theta₃(t)＝2πNf_inw(t)+θ₂(T)

When the h is moved inwards for the h time (h is more than or equal to 3): theta_2h-1(t)2πNf_inw(t)+θ_2h-2(T)

When the h moves outwards (h is more than or equal to 3): theta_2h(t)-(2πNf_outw(t)-θ₀)+θ_2h-1(T-t₀)

In the above formula, the first and second carbon atoms are,

t: the time of day is,

n: the number of the spiral is equal to the number of the spiral,

f_inw(t): satisfy f_inw(0)＝1，f_inw(1) As an arbitrary function of 0 or more,

f_outw(t): satisfy f_outw(0)＝0，f_outw(1) As an arbitrary function of 1, the number of bits,

t: the time required for the cutting tool to move along a spiral trajectory from the center of the rock specimen to the profile or from the profile to the center,

T-t₀: the time the cutting tool is moved along the helical path,

θ₀: radius (R) at end point for inward movement₀) And a constant of the angle in accordance with the starting radius and angle of the outward movement.

12. The method of wear measurement and durability evaluation of a rock cutting tool according to claim 11, characterized in that:

f_inw(t) and f_outw(t) satisfies the following formula,

[ formula ]

13. The method of measuring wear and evaluating durability of a rock cutting tool according to claim 12, wherein:

the difference between the slope of the end point of the inward movement and the slope of the start point of the outward movement and the difference between the slope of the end point of the outward movement and the slope of the start point of the inward movement are less than 1 °.