CN103970995A - Drill bit for CFRP machining and experimental determining method for structural parameters of drill bit - Google Patents

Abstract

The invention discloses an experimental determining method for structural parameters of a drill bit for CFRP machining. The method includes the steps of obtaining the distribution of cutting force and cutting temperature on a main cutting edge of the drill bit through a cutting experiment of prefabricated holes of different diameters, obtaining the function relationship between the cutting force, the cutting temperature and the structural parameters of the drill bit through an orthogonal free cutting experiment of CFRP, determining distribution parameter values of the angle of the rear corner of the drill bit and the radius of a blunt circle along the main cutting edge by the utilization of the known angle of a front corner of the drill bit according to the principle of the even distribution of the cutting force and the cutting temperature, and manufacturing the drill bit according to the determined parameter values. According to the drill bit for CFRP machining, in the actual production process of the CFRP, the cutting force and cutting temperature on the main cutting edge are evenly distributed, and drilling defects are reduced.

Description

For the drill bit of CFRP processing and the Experimental Determination Method of structural parameters thereof

Technical field

The present invention relates to a kind of drilling tool, be specifically related to a kind of drill bit for carbon fibre reinforced composite (CFRP) processing, and determine based on drill thrust and the control of drilling temperature and the experimental method of its structural parameters belong to Machining Technology field.

Background technology

Carbon fibre reinforced composite (Carbon Fiber Reinforced Polymer, be called for short CFRP) be a kind of novel polymer matrix composites taking carbon or graphite fiber as reinforcement, because of the advantage such as have that intensity is high, specific stiffness is high, fatigue performance is good and designability is strong, it is widely used in the main force support structure part of manufacturing on Advanced Aircraft, parts such as aircraft skin, wallboard, wing intermediate beam, fuselage bulkhead and hatch door.In the machine cut processing of CFRP, drilling is to use maximum, most widely used a kind of processing mode, and the quality of drilling drilling quality is directly connected to assembly quality and the service life of whole aircraft.Due to distinctive anisotropy and the feature such as interlayer contact intensity is low, CFRP becomes a kind of typical difficult-to-machine material.In CFRP boring procedure, its drilling is except can producing the common defect of traditional metal material drilling (scale error in hole, deviation from circular from, site error, the error of perpendicularity etc.), also can produce the distinctive defect of compound substance, main manifestations is: entrance is peeled off layering, outlet layering, interlayer layering, torn and burr, hole perimeter surface fiber extraction etc., and wherein delamination damage is topmost drilling defect.According to statistics, when aircraft is in the end assembled, because of scrapping up to more than 60% that boring layering causes.

CFRP laminate boring layering is by the excessive material causing with drilling excess Temperature of drilling axial force separating between layers, therefore in the drilling process of CFRP laminate, the control of drill thrust and drilling temperature is just seemed to particularly important.And in machine work, drill thrust and drilling temperature have 60% impact that derives from cutter geometry, therefore, are a kind of effective ways of controlling drilling quality for the special drilling tool of the fabrication design of compound substance.At present, in numerous compound substances, drill bit used is the method for sharp cutting edge by increase cut staple at cylindrical turning point place, reduces and in multiple material drilling process, produces burr and layering.But such structure has often only been optimized this very small region of cylindrical turning point to the impact in drilling process, global optimization effect is also not obvious.

Through the retrieval to existing document, find no so far the open report of definite method of closing carbon fibre reinforced composite Special drill tool structure parameter.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, a kind of drill bit for CFRP processing and the Experimental Determination Method of structural parameters thereof are provided, obtain by experiment basic data, set up the distributed model of cutting force and cutting temperature on main cutting edge, optimize accordingly relief angles and the blunt round radius of cutter, the object being evenly distributed to reach cutting force and cutting temperature, thereby the generation of minimizing drilling drilling mass defect.

The technical scheme that the present invention solves its technical matters is:

A kind of Experimental Determination Method of structural parameters of the drill bit for CFRP processing, the cutting force and the cutting temperature that obtain on drill bit main cutting edge by the drilling test of different-diameter pre-manufactured hole distribute, orthogonal free cutting experiment by carbon fibre reinforced composite obtains the funtcional relationship between cutting force and cutting temperature and the each structural parameters of drill bit, utilize known drill bit anterior angle angle, the principle being evenly distributed according to cutting force and cutting temperature, determine the parameter values that described drill bit back angle angle and blunt round radius distribute along main cutting edge, prepare described drill bit according to definite parameter values.

Further, described Experimental Determination Method comprises following concrete steps:

The first step, the a series of pre-manufactured hole that diameter increases progressively step by step with unit length is set on the laminate of carbon fibre reinforced composite, use the experiment of holing of selected drill bit on each pre-manufactured hole, and measure and record the cutting force and the cutting temperature that on the main cutting edge of described drill bit, produce, use same drill bit on described laminate without the experiment of holing of pre-manufactured hole place, and measure and record the cutting force and the cutting temperature that on the main cutting edge of described drill bit, produce, be following polynomial function by cutting force and cutting temperature along the fitting of distribution of described drill bit main cutting edge by data processing:

F (x)=a ₁x ³+ b ₁x ²+ c ₁x+d ₁, formula (4),

T (x)=a ₂x ³+ b ₂x ²+ c ₂x+a ₂, formula (5);

Second step, use has the orthogonal experiment that the drill bit of different anterior angles, relief angle and blunt round radius carries out free cutting on carbon fibre reinforced composite, each factor adopts respectively 5 levels, in experiment, measure and record the cutting force and the cutting temperature that on the main cutting edge of each drill bit, produce, by data processing, the relation between cutting force and cutting temperature and the each structural parameters of drill bit being fitted to following polynary quadratic function:

F _{γ, α}=a ₃γ ²+ b ₃γ+c ₃α ²+ d ₃α+e ₃, formula (6),

$T_{\mathrm{\γ},\mathrm{\α},R_0}=a_4{\mathrm{\γ}}^2+b_4\mathrm{\γ}+c_4{\mathrm{\α}}^2+d_4\mathrm{\α}+e_4{R}_0^2+f_4{R}_0+g_4,$ Formula (7);

The 3rd step, according to the anterior angle distribution function γ (x) of the formula being obtained by the first step (4) and formula (5), the formula (6) being obtained by second step and formula (7) and known described drill bit, redistribute cutting force and the cutting temperature on main cutting edge according to the principle being evenly distributed, thereby determine drill bit back angle angle as described below and the blunt round radius distribution function along main cutting edge, and according to this relief angles of calculating and the concrete numerical value of blunt round radius parameter:

$\mathrm{\α}\left(x\right)=\frac{-d_3\±\sqrt{d_3^2-{4c}_3(a_3\mathrm{\γ}{\left(x\right)}^2+b_3\mathrm{\γ}\left(x\right)+e_3-\frac{a_1}{4}-\frac{b_1}{3}-\frac{c_1}{2}-d_1)}}{{2c}_3},$ Formula (2),

$R_0\left(x\right)=\frac{-f_4\±\sqrt{f_4^2-{4e}_4(a_4\mathrm{\γ}{\left(x\right)}^2+b_4\mathrm{\γ}\left(x\right)+c_4\mathrm{\α}{\left(x\right)}^2+d_4\mathrm{\α}\left(x\right)+g_4-\frac{a_2}{4}-\frac{b_2}{3}-\frac{c_2}{2}-d_2)}}{{2e}_4},$ Formula (3),

In above-mentioned formula (2), formula (3), formula (4), formula (5), formula (6) and formula (7),

f is cutting force, and T is cutting temperature, and R is drill bit radius, and r is the radius value of measuring point on main cutting edge, and γ is drill bit anterior angle angle, and α is drill bit back angle angle, R ₀for drill bit blunt round radius,

A ₁, b ₁, c ₁, d ₁, a ₂, b ₂, c ₂, d ₂, a ₃, b ₃, c ₃, d ₃, e ₃, a ₄, b ₄, c ₄, d ₄, e ₄, f ₄, g ₄for matching gained constant;

γ (x) is the function that the anterior angle of known described drill bit distributes along main cutting edge;

The 4th step, the relief angles obtaining according to the 3rd step and the design parameter numerical value sharpening of blunt round radius are prepared described drill bit.

Further, described γ (x) is for obtaining by measuring.

Further, described drill bit is twist drill, and described γ (x) is following known function:

formula (1),

Wherein, the helix angle that β is drill bit, for the original sharp angle of drill bit, r ₀thick for boring core half, k is constant.

Another technical scheme of the present invention is:

For a drill bit for CFRP processing, the parameter values that its relief angles and blunt round radius distribute along main cutting edge adopts above-mentioned Experimental Determination Method to determine, meets following relational expression:

$\mathrm{\α}\left(x\right)=\frac{-d_3\±\sqrt{d_3^2-{4c}_3(a_3\mathrm{\γ}{\left(x\right)}^2+b_3\mathrm{\γ}\left(x\right)+e_3-\frac{a_1}{4}-\frac{b_1}{3}-\frac{c_1}{2}-d_1)}}{{2c}_3},$ Formula (2),

$R_0\left(x\right)=\frac{-f_4\±\sqrt{f_4^2-{4e}_4(a_4\mathrm{\γ}{\left(x\right)}^2+b_4\mathrm{\γ}\left(x\right)+c_4\mathrm{\α}{\left(x\right)}^2+d_4\mathrm{\α}\left(x\right)+g_4-\frac{a_2}{4}-\frac{b_2}{3}-\frac{c_2}{2}-d_2)}}{{2e}_4},$ Formula (3),

F (x)=a ₁x ³+ b ₁x ²+ c ₁x+d ₁, formula (4),

T (x)=a ₂x ³+ b ₂x ²+ c ₂x+d ₂, formula (5),

F _{γ, α}=a ₃γ ²+ b ₃γ+c ₃α ²+ d ₃α+e ₃, formula (6),

$T_{\mathrm{\γ},\mathrm{\α},R_0}=a_4{\mathrm{\γ}}^2+b_4\mathrm{\γ}+c_4{\mathrm{\α}}^2+d_4\mathrm{\α}+e_4{R}_0^2+f_4{R}_0+g_4,$ Formula (7),

Wherein, f is cutting force, and T is cutting temperature, and R is drill bit radius, and r is the radius value of measuring point on main cutting edge,

γ is drill bit anterior angle angle, and α is drill bit back angle angle, R ₀for drill bit blunt round radius,

A ₁, b ₁, c ₁, d ₁, a ₂, b ₂, c ₂, d ₂for matching gained constant after the experiment of the said method first step,

A ₃, b ₃, c ₃, d ₃, e ₃, a ₄, b ₄, c ₄, d ₄, e ₄, f ₄, g ₄for matching gained constant after the experiment of said method second step;

γ (x) is the function that the anterior angle of known described drill bit distributes along main cutting edge.

Further, described γ (x) is for obtaining by measuring.

Further, described drill bit is twist drill.

Further, described γ (x) is following known function:

formula (1),

Wherein, the helix angle that β is drill bit, for the original sharp angle of drill bit, r ₀thick for boring core half, k is constant.

Compared with prior art, beneficial effect of the present invention is: due to the principle based on cutting force and cutting temperature mean allocation in processing, in the situation that tool orthogonal rake angle parameter is known, combine by basic experiment method and data fitting, determine tool clearance angle and the blunt round radius parameter distribution numerical value along main cutting edge, thereby make the drill bit of manufacturing accordingly in the actual processing of carbon fibre reinforced composite (CFRP), reach cutting force and cutting temperature is evenly distributed, reduce the generation of boring defect.

Brief description of the drawings

The schematic diagram of different-diameter pre-manufactured hole in Fig. 1 first step of the present invention.

Fig. 2 first step gained of the present invention cutting force and cutting temperature are along the distribution schematic diagram of main cutting edge.

Fig. 3 cutter structure schematic diagram of the present invention.

In Fig. 4 the present invention, anterior angle angle, relief angles and blunt round radius are along the variation schematic diagram of main cutting edge.

Fig. 5 is the partial enlarged drawing of main cutting edge in Fig. 3.

Embodiment

The present invention is based on infrastest data, set up the distributed model of cutting force and cutting temperature on main cutting edge, and redistribute cutting force and the cutting temperature on main sword to be evenly distributed as principle, thereby relief angles and the cutter blunt round radius of determining drill bit, obtain the multiple material drilling cutters that drilling quality is higher.

The invention provides a kind of Experimental Determination Method of structural parameters of the drill bit for CFRP processing, the cutting force and the cutting temperature that obtain on drill bit main cutting edge by the drilling test of different-diameter pre-manufactured hole distribute, orthogonal free cutting experiment by carbon fibre reinforced composite obtains the funtcional relationship between cutting force and cutting temperature and the each structural parameters of drill bit, utilize known drill bit anterior angle angle, the principle being evenly distributed according to cutting force and cutting temperature, determine the parameter values that described drill bit back angle angle and blunt round radius distribute along main cutting edge, prepare described drill bit according to definite parameter values.

Experimental Determination Method of the present invention comprises following concrete steps:

The first step, use not reconditioning or carry out carbon-fiber-reinforcomposite composite material layer plywood drilling test through the drill bit of special reconditioning, experiment is adopted with the following method and is carried out: on CFRP laminate, prefabricated diameter is a series of pre-manufactured holes that increase progressively step by step with unit length such as 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, as shown in Figure 1.Use selected drill bit in the experiment of holing of each pre-manufactured hole same position, and in experiment, measure the cutting force and the cutting temperature that on the main cutting edge of described drill bit, produce, be recorded as respectively F1, F2, F3, F4, F5, F6, F7, F8 and T1, T2, T3, T4, T5, T6, T7, T8; And use same drill bit on described laminate without the experiment of holing of pre-manufactured hole place, and measure and record the cutting force and the cutting temperature that on the main cutting edge of described drill bit, produce, be recorded as F0 and T0.Through type F (n-1)-F (n) and T (n-1)-T (n) calculate cutting force and the cutting temperature that unit length (1mm) on this drill bit main cutting edge produces, and obtain the distribution curve of cutting force and cutting temperature on main cutting edge as shown in Figure 2.By the mode of data processing, the cutting force on drill bit main cutting edge and cutting temperature distribution are reduced to respectively to polynomial funtcional relationship, by the method for fitting of a polynomial, obtain following polynomial function:

F (x)=a ₁x ³+ b ₁x ²+ c ₁x+d ₁, formula (4),

T (x)=a ₂x ³+ b ₂x ²+ c ₂x+d ₂, formula (5),

Wherein, f is cutting force, and T is cutting temperature, and R is drill bit radius, and r is the radius value of measuring point on main cutting edge, a ₁, b ₁, c ₁, d ₁, a ₂, b ₂, c ₂, d ₂for matching gained constant.

Second step, the drill bit that use has different anterior angles, relief angle and a blunt round radius carries out the free cutting orthogonal experiment of CFRP, experiment adopts orthogonal experimental method, each factor adopts respectively 5 levels, in experiment, measure and record the cutting force and the cutting temperature that on the main cutting edge of each drill bit, produce, and adopt the mode of data processing, the relation between cutting force and cutting temperature and the each structural parameters of drill bit is fitted to following polynary quadratic function:

F _{γ, α}=a ₃γ ²+ b ₃γ+c ₃α ²+ d ₃α+e ₃, formula (6),

$T_{\mathrm{\γ},\mathrm{\α},R_0}=a_4{\mathrm{\γ}}^2+b_4\mathrm{\γ}+c_4{\mathrm{\α}}^2+d_4\mathrm{\α}+e_4{R}_0^2+f_4{R}_0+g_4,$ Formula (7),

Wherein, F is cutting force, and T is cutting temperature, and γ is drill bit anterior angle angle, and α is drill bit back angle angle, R ₀for drill bit blunt round radius, a ₃, b ₃, c ₃, d ₃, e ₃, a ₄, b ₄, c ₄, d ₄, e ₄, f ₄, g ₄for matching gained constant.

The 3rd step, using drill bit anterior angle as benchmark, determines relief angles and the blunt round radius of drill bit.

If drill bit is twist drill, its anterior angle is changing along main cutting edge always, and is determined by parameters such as cutter helix angle, original sharp angle, brill core thickness, after cutter moulding, often determine, and malleable not.Therefore, according to the traditional calculating formula of twist drill anterior angle:

formula (1)

Wherein, the helix angle that β is drill bit, for the original sharp angle of drill bit, r ₀thick for boring core half, k is constant.

Described γ (x) also can obtain by measuring.

By γ (x) substitution formula (6), can obtain F _{γ, α}(x)=a ₃γ (x) ²+ b ₃γ (x)+c ₃α ²+ d ₃α+e ₃.

Can think, the hole of the same degree of depth of the same diameter of drilling need to consume same merit, produces onesize average cutting force.Therefore can through type (4), according to equally distributed principle, redistribute cutting force

$F_{\mathrm{\γ},\mathrm{\α}}\left(x\right)={\∫}_0^{1}F\left(x\right)\mathrm{dx}=\frac{a_1}{4}+\frac{b_1}{3}+\frac{c_1}{2}+d_1,$

And determine that drill bit back angle angle as described below is along the distribution function of main cutting edge, and according to the concrete numerical value of this relief angles parameter of calculating:

$\mathrm{\α}\left(x\right)=\frac{-d_3\±\sqrt{d_3^2-{4c}_3(a_3\mathrm{\γ}{\left(x\right)}^2+b_3\mathrm{\γ}\left(x\right)+e_3-\frac{a_1}{4}-\frac{b_1}{3}-\frac{c_1}{2}-d_1)}}{{2c}_3}$ Formula (2)

Wherein, γ (x) is suc as formula shown in (1), or obtains by measuring.

By γ (x) and α (x) substitution formula (7), obtain again

$T_{\mathrm{\γ},\mathrm{\α},R_0}=a_4{\mathrm{\γ}}^2+b_4\mathrm{\γ}+c_4{\mathrm{\α}}^2+d_4\mathrm{\α}+e_4{R}_0^2+f_4{R}_0+g_4,$

Can think, the hole of the same degree of depth of the same diameter of drilling, produces the heat of as much, causes same temperature rise, therefore can through type (5), according to equally distributed principle, redistribute cutting temperature

$T_{\mathrm{\γ},\mathrm{\α},T_0}\left(x\right)={\∫}_0^{1}T\left(x\right)\mathrm{dx}=\frac{a_2}{4}+\frac{b_2}{3}+\frac{c_2}{2}+d_2,$

And determine that drill bit blunt round radius as described below is along the distribution function of main cutting edge, and according to the concrete numerical value of this blunt round radius parameter of calculating:

$R_0\left(x\right)=\frac{-f_4\±\sqrt{f_4^2-{4e}_4(a_4\mathrm{\γ}{\left(x\right)}^2+b_4\mathrm{\γ}\left(x\right)+c_4\mathrm{\α}{\left(x\right)}^2+d_4\mathrm{\α}\left(x\right)+g_4-\frac{a_2}{4}-\frac{b_2}{3}-\frac{c_2}{2}-d_2)}}{{2e}_4}$ Formula (3)

Wherein, γ (x) is suc as formula obtaining shown in (1) or by measuring, and α (x) is suc as formula shown in (2).

The 4th step, the relief angles obtaining according to the 3rd step and the design parameter numerical value sharpening of blunt round radius are prepared described drill bit.

Drill bit for CFRP processing of the present invention, the parameter values that its relief angles and blunt round radius distribute along main cutting edge adopts above-mentioned Experimental Determination Method to determine, it meets above-mentioned relation formula formula (2), formula (3), formula (4), formula (5), formula (6) and formula (7), wherein γ (x) can obtain by measuring, in the time that described drill bit is twist drill, described γ (x) is as shown in above-mentioned formula (1).

Below in conjunction with accompanying drawing, the invention will be further described, and the present embodiment is implemented as prerequisite taking technical solution of the present invention, provided detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

Embodiment

In the present embodiment, adopting diameter is the hard alloy twist drill drilling processing T800CFRP laminate of 12mm, measures cutting force and cutting temperature on its cutting edge and distributes as shown in Figure 2.Experimental data is processed, is obtained following fitting formula:

F(x)＝11.15x ³-12.76x ²-1.02x+10.84，

T(x)＝-37.77x ³+44.48x ²-10.35x+9.33。

Adopt cutting speed V=200m/min, cutting depth a _p=20 μ m are experiment parameter, carry out the orthogonal free cutting experiment of CFRP, wherein anterior angle adopts 5 °, 10 °, 15 °, 20 ° and 25 ° of five levels, relief angle adopts 5 °, 10 °, 15 °, 20 ° and 25 ° of five levels, blunt round radius adopts 5 μ m, 10 μ m, 15 μ m, 20 μ m and five levels of 25 μ m, measure cutting force and cutting temperature, cutting force and cutting temperature are obtained to cutting force and the cutting temperature of unit length divided by thickness of slab, then experimental data is carried out to matching, obtains relational expression:

F _γ，α＝0.004γ ²-0.264γ+0.0008α ²-0.332α+12.86,

$T_{\mathrm{\γ},\mathrm{\α},R_0}={0.0026\mathrm{\γ}}^2-0.25\mathrm{\γ}-{0.0001\mathrm{\α}}^2-0.237\mathrm{\α}+{0.0001R}_0^2+{0.103R}_0+11.23.$

As shown in Figure 3, its design feature is on the apex point of common twist drill, to grind two symmetrical inner edges in order to reduce chisel edge, and weaken near the negative rake phenomenon of boring core place to the twist drill that experiment adopts.Drill bit radius is 6mm, and brill core radius is 0.5mm, and original sharp angle is 119.5 °, and helix angle is 30 °, and the anterior angle of this drill bit changes function and is

While calculating α (x) according to formula (2), consider α ²the coefficient of item is minimum, gives up this, simplifies result of calculation and obtains

α(x)＝0.012γ(x) ²-0.795γ(x)+11.95。

Calculate R according to formula (3) ₀(x) time, consider α ²xiang He coefficient minimum, these two are given up, simplify result of calculation and obtain

R ₀(x)＝0.00233γ(x) ²+0.602γ(x)+10.97。

γ (x), α (x) and R ₀(x) variation as shown in Figure 4.

Calculate α (x) and R according to the method for the present embodiment ₀(x) relief angle to this drill bit and blunt circle carry out sharpening, obtain the dedicated tool for machining composite material, as shown in Figure 5.Although this drill bit can not reduce total cutting force and cutting temperature, can in boring procedure, make cutting force and cutting temperature be evenly distributed on main cutting edge, significantly improve drilling quality, reduce the defect producing in boring procedure.

The present invention is limited to the illustrative embodiments presenting in instructions and accompanying drawing never in any form.All combinations of the embodiment that instructions is described are interpreted as and fall in the scope of protection of present invention clearly.And in the scope of the present invention of being summarized as claims, a lot of distortion are possible.

Claims (9)

1. the Experimental Determination Method for the structural parameters of the drill bit of CFRP processing, it is characterized in that: the cutting force and the cutting temperature that obtain on drill bit main cutting edge by the drilling test of different-diameter pre-manufactured hole distribute, orthogonal free cutting experiment by carbon fibre reinforced composite obtains the funtcional relationship between cutting force and cutting temperature and the each structural parameters of drill bit, utilize known drill bit anterior angle angle, the principle being evenly distributed according to cutting force and cutting temperature, determine the parameter values that described drill bit back angle angle and blunt round radius distribute along main cutting edge, prepare described drill bit according to definite parameter values.

2. the Experimental Determination Method of the structural parameters of the drill bit for CFRP processing according to claim 1, is characterized in that: described Experimental Determination Method comprises following concrete steps:

The first step, the a series of pre-manufactured hole that diameter increases progressively step by step with unit length is set on the laminate of carbon fibre reinforced composite, use the experiment of holing of selected drill bit on each pre-manufactured hole, and measure and record the cutting force and the cutting temperature that on the main cutting edge of described drill bit, produce, use same drill bit on described laminate without the experiment of holing of pre-manufactured hole place, and measure and record the cutting force and the cutting temperature that on the main cutting edge of described drill bit, produce, be following polynomial function by cutting force and cutting temperature along the fitting of distribution of described drill bit main cutting edge by data processing:

F (x)=a ₁x ³+ b ₁x ²+ c ₁x+d ₁, formula (4),

T (x)=a ₂x ³+ b ₂x ²+ c ₂x+d ₂, formula (5);

Second step, use has the orthogonal experiment that the drill bit of different anterior angles, relief angle and blunt round radius carries out free cutting on carbon fibre reinforced composite, each factor adopts respectively 5 levels, in experiment, measure and record the cutting force and the cutting temperature that on the main cutting edge of each drill bit, produce, by data processing, the relation between cutting force and cutting temperature and the each structural parameters of drill bit being fitted to following polynary quadratic function:

F _{γ, α}=a ₃γ ²+ b ₃γ+c ₃α ²+ d ₃α+e ₃, formula (6),

$T_{\mathrm{\γ},\mathrm{\α},R_0}=a_4{\mathrm{\γ}}^2+b_4\mathrm{\γ}+c_4{\mathrm{\α}}^2+d_4\mathrm{\α}+e_4{R}_0^2+f_4{R}_0+g_4,$ Formula (7);

The 3rd step, according to the anterior angle distribution function γ (x) of the formula being obtained by the first step (4) and formula (5), the formula (6) being obtained by second step and formula (7) and known described drill bit, redistribute cutting force and the cutting temperature on main cutting edge according to the principle being evenly distributed, thereby determine drill bit back angle angle as described below and the blunt round radius distribution function along main cutting edge, and according to this relief angles of calculating and the concrete numerical value of blunt round radius parameter:

$\mathrm{\α}\left(x\right)=\frac{-d_3\±\sqrt{d_3^2-{4c}_3(a_3\mathrm{\γ}{\left(x\right)}^2+b_3\mathrm{\γ}\left(x\right)+e_3-\frac{a_1}{4}-\frac{b_1}{3}-\frac{c_1}{2}-d_1)}}{{2c}_3},$ Formula (2),

$R_0\left(x\right)=\frac{-f_4\±\sqrt{f_4^2-{4e}_4(a_4\mathrm{\γ}{\left(x\right)}^2+b_4\mathrm{\γ}\left(x\right)+c_4\mathrm{\α}{\left(x\right)}^2+d_4\mathrm{\α}\left(x\right)+g_4-\frac{a_2}{4}-\frac{b_2}{3}-\frac{c_2}{2}-d_2)}}{{2e}_4},$ Formula (3),

In above-mentioned formula (2), formula (3), formula (4), formula (5), formula (6) and formula (7),

f is cutting force, and T is cutting temperature, and R is drill bit radius, and r is the radius value of measuring point on main cutting edge, and γ is drill bit anterior angle angle, and α is drill bit back angle angle, R ₀for drill bit blunt round radius,

A ₁, b ₁, c ₁, d ₁, a ₂, b ₂, c ₂, d ₂, a ₃, b ₃, c ₃, d ₃, e ₃, a ₄, b ₄, c ₄, d ₄, e ₄, f ₄, g ₄for matching gained constant;

γ (x) is the function that the anterior angle of known described drill bit distributes along main cutting edge;

The 4th step, the relief angles obtaining according to the 3rd step and the design parameter numerical value sharpening of blunt round radius are prepared described drill bit.

3. the Experimental Determination Method of the structural parameters of the drill bit for CFRP processing according to claim 2, is characterized in that: described γ (x) is for obtaining by measuring.

4. the Experimental Determination Method of the structural parameters of the drill bit for CFRP processing according to claim 2, is characterized in that: described drill bit is twist drill.

5. the Experimental Determination Method of the structural parameters of the drill bit for CFRP processing according to claim 4, is characterized in that: described γ (x) is following known function:

formula (1),

Wherein, the helix angle that β is drill bit, for the original sharp angle of drill bit, r ₀thick for boring core half, k is constant.

6. for a drill bit for CFRP processing, it is characterized in that: described in the parameter values employing claim 2 that the relief angles of described drill bit and blunt round radius distribute along main cutting edge, Experimental Determination Method is determined, meets following relational expression:

$\mathrm{\α}\left(x\right)=\frac{-d_3\±\sqrt{d_3^2-{4c}_3(a_3\mathrm{\γ}{\left(x\right)}^2+b_3\mathrm{\γ}\left(x\right)+e_3-\frac{a_1}{4}-\frac{b_1}{3}-\frac{c_1}{2}-d_1)}}{{2c}_3},$ Formula (2),

$R_0\left(x\right)=\frac{-f_4\±\sqrt{f_4^2-{4e}_4(a_4\mathrm{\γ}{\left(x\right)}^2+b_4\mathrm{\γ}\left(x\right)+c_4\mathrm{\α}{\left(x\right)}^2+d_4\mathrm{\α}\left(x\right)+g_4-\frac{a_2}{4}-\frac{b_2}{3}-\frac{c_2}{2}-d_2)}}{{2e}_4},$ Formula (3),

F (x)=a ₁x ³+ b ₁x ²+ c ₁x+d ₁, formula (4),

T (x)=a ₂x ³+ b ₂x ²+ c ₂x+d ₂, formula (5),

F _{γ, α}=a ₃γ ²+ b ₃γ+c ₃α ²+ d ₃α+e ₃, formula (6),

$T_{\mathrm{\γ},\mathrm{\α},R_0}=a_4{\mathrm{\γ}}^2+b_4\mathrm{\γ}+c_4{\mathrm{\α}}^2+d_4\mathrm{\α}+e_4{R}_0^2+f_4{R}_0+g_4,$ Formula (7),

Wherein,

f is cutting force, and T is cutting temperature, and R is drill bit radius, and r is the radius value of measuring point on main cutting edge, and γ is drill bit anterior angle angle, and α is drill bit back angle angle, R ₀for drill bit blunt round radius,

A ₁, b ₁, c ₁, d ₁, a ₂, b ₂, c ₂, d ₂for matching gained constant after the experiment of claim 2 first step,

A ₃, b ₃, c ₃, d ₃, e ₃, a ₄, b ₄, c ₄, d ₄, e ₄, f ₄, g ₄for matching gained constant after the experiment of claim 2 second step;

γ (x) is the function that the anterior angle of known described drill bit distributes along main cutting edge.

7. the drill bit for CFRP processing according to claim 6, is characterized in that: described γ (x) is for obtaining by measuring.

8. the drill bit for CFRP processing according to claim 6, is characterized in that: described drill bit is twist drill.

9. the drill bit for CFRP processing according to claim 8, is characterized in that: described γ (x) is following known function:

formula (1),

Wherein, the helix angle that β is drill bit, for the original sharp angle of drill bit, r ₀thick for boring core half, k is constant.