CN101840447A - Finite element modeling method for predicting forging force in rotary swaging process - Google Patents

Abstract

The invention discloses a finite element modeling method for predicting forging force in the rotary swaging process and belongs to the technical field of plastic forming. The forging force is calculated by an empirical formula in the conventional rotary swaging industry, the calculation accuracy is low, and the change rule of the forging force along the rotary swaging technological parameters cannot be predicted. Due to complex motion track of the rotary swaging molds, a report for calculating the rotary swaging forging force by the finite element method is absent up to now. The finite element modeling method comprises the following steps of: calculating a motion track diagram of the rotary swaging mold relative to workpieces subjected to the rotary swaging by using mathematical software; establishing a finite element model of the rotary swaging by using universal finite software; and combining the motion track diagram of the rotary swaging mold which is obtained by the mathematical software to realize the simulation of the forging die motion process in the finite element simulation process. The finite element modeling method can solve the problems of high workload and high time consumption when commercial finite element software draws a complex motion track of an object, can precisely calculate the change rule of the forging force along the rotary swaging technological parameters to obtain the range of the reasonable rotary swaging technological parameters, and provides a basis for accurately designing the rotary swaging molds and rotary swaging technological parameters and selecting the models of rotary swaging machines.

Description

The finite element modeling method of prediction forging force in rotary swaging process

Technical field

The invention belongs to the plastic forming technology field, particularly a kind of finite element method of predicting forging force in rotary swaging process.

Background technology

Swaging is a kind of advanced Plastic Forming processing technology, is widely used in various materials, as silk bar forming technologies such as metal (aldary, iron and steel, tungsten, molybdenum, niobium etc.), metallic matrix composite, metal oxides.Its advantage is the production efficiency height, goods precision height, and quality is good, can save metal material again.

Swaging belongs to the multi-head spiral stretching, has pulse concurrently and forges and the multidirectional characteristic that forges.The accurate Calculation of forging force of swaging plays an important role to the design of the selection of swager model, the mould of swaging and the process parameters design of swaging.Factors such as the height of the complicacy of mould motion process and the deformation process of swaging is non-linear owing to swage are never used the report that Finite Element Method is calculated the forging force of swaging at present.Swage at present and extensively adopt in the industry experimental formula to calculate the forging force of swaging, computational accuracy is low, can not predict the Changing Pattern of forging force with the technological parameter of swaging of swaging.The present invention combines common finite element software with general software for mathematical computing, the accurate emulation relative motion process of mould and workpiece of swaging, the finite element modeling method that provides a kind of prediction to swage forging force.

Summary of the invention

When the present invention is directed to the compound movement track of drawing object in the commercial finite element software, workload is big, long problem expends time in, use general software for mathematical computing and calculate radially the reaching the axially-movable trajectory diagram and export of swaging mould with respect to the workpiece of being swaged with finite element input format file, utilize common finite element software to set up the finite element model of swaging, the mould movement locus figure that swages that utilizes general software for mathematical computing to export in FEM numerical simulation process realizes the emulation of forging die motion process, purpose is to swage forging force with the Changing Pattern of the technological parameter of swaging by the finite element analysis accurate Calculation, to reach the correct design mould of swaging, the purpose of technological parameter and the selection swager model of swaging.

Technical scheme of the present invention may further comprise the steps:

Step 1: gather the primitive technology parameter swage, comprising: the roller number in the swager speed of mainshaft, feeding speed, the head, supplied materials diameter, the diameter after swaging, circular cone angle of feed, compression zone length, calibrating strap length, the initial temperature of swaging;

Step 2: use the primitive technology parameter of swaging of being gathered, use general software for mathematical computing and calculate the .txt formatted file preservation that radially reaches axially-movable geometric locus figure and can discern of swaging mould according to formula with respect to the workpiece of being swaged with finite element software;

Described formula is

The mould of swaging opens the length S that once sends workpiece to

S＝V _ax/n _s＝V _ax/(n _f·p)＝V _ax/((1.0-0.4)n _A·p)

Forging once required time T is

T＝1/n _s＝1/(p·n _f)＝1/(p·(1.0-0.4)n _A)

Radially drafts H is

H＝ΔR＝(D-d)/2

V in the formula _AxBe feeding speed, n _sFor forging frequency, n _{T is}Effective rotating speed, n _ABe the rotating speed of main shaft, p is the roller number, and D is the supplied materials diameter, and d is the back diameter of swaging;

Step 3: set up the finite element model of swaging

1. according to the primitive technology parameter of swaging of being gathered, set up the finite element geometric model of swaging, the part model grid adopts 4 node axisymmetric elements of full integration, and the mould of swaging is defined as the rigidity contact that can conduct heat, input material constant and constitutive relation model;

2. the mould movement locus file of will swaging is read in the finite element model, and the motion of the relative workpiece of mould of swaging is set to displacement control, finishes the modeling work of the finite element model of swaging;

3. move the finite element analogy program, adopt the criterion of heavily dividing automatically as grid in the computation process based on the absolute error criterion of equivalent stress;

Step 4: operation finite element analogy program, from finite element result, extract the forging force data, analyze forging die and bear pressure

1. the pressure Q that the mould that the contact force addition of all contact nodes obtained swaging bears;

2. draw the suffered radial pressure Q of forging die and reach the change curve that pulse forges number of times in time, obtain the suffered maximum pressure Q of forging die _MaxCalculate forging die authorized pressure Q _c, compare Q _cWith Q _Max, judge the load-bearing capacity the restriction whether technological parameter of swaging of simulating satisfies swager;

Described forging die authorized pressure Q _cCalculate according to following formula:

$Q_c={\left(\frac{R_{\mathrm{cm}}}{60}\right)}^2\frac{{\mathrm{ld}}_{p}r}{d_p+2r}$

The technical parameter of the swager that wherein relates to is determined according to the swager instructions:

R _Cm---roller allow compressive stress, kgf/mm ²

The contact line length of l---roller and forging die, mm;

The arc radius of r---slide block, mm;

d _p---the diameter of roller, mm.

Step 5: change circular cone angle of feed, axially feeding speed, these three technological parameters of swaging of drafts radially, obtain the suffered maximum pressure Q of forging die _MaxChange curve with the technological parameter of respectively swaging; The technological parameter span of swaging that obtains the restriction of swager load-bearing capacity and must satisfy;

Benefit of the present invention and effect are, extensively adopt experimental formula to calculate the forging force method of swaging at the industry of swaging at present, computational accuracy is low, can not predict that the forging force of swaging with the problem of the changes in process parameters situation of swaging, provides a kind of finite element method of predicting forging force in rotary swaging process.In addition, when the present invention can effectively overcome the compound movement track of drawing object in the commercial finite element software, big, the long problem that expends time in of workload, the mould movement locus figure that swages that in FEM numerical simulation process, utilizes general software for mathematical computing to calculate gained realize the swaging emulation of mould motion process.The present invention can accurate Calculation forging force with the Changing Pattern of the technological parameter of swaging, obtain the technological parameter span of swaging that swager load-bearing capacity restriction institute must satisfy, for swage mould, swage technological parameter and selection swager model of correct design provides data.

Description of drawings

Fig. 1 process flow diagram of the present invention

Fig. 2 swaged relatively axially-movable geometric locus of workpiece of mould of swaging

Fig. 3 swaged relatively radial motion geometric locus of workpiece of mould of swaging

Fig. 4 finite element geometric model

Radially contact force cloud charts when Fig. 5 is out of shape 0.042s

When Fig. 6 is out of shape 0.042s radially contact force along the distribution of MN direction

Fig. 7 suffered radial pressure Q of mould that swages reaches the change curve that pulse forges number of times in time

The specific heat of Fig. 8 magnesium and the relation of temperature

The elastic modulus of Fig. 9 magnesium and the relation of temperature

The correlativity of suffered radial pressure Q of forging die and tg (α/2) when Figure 10 magnesium is swaged

Suffered radial pressure Q of forging die and the correlativity of drafts Δ R radially when Figure 11 magnesium is swaged

Suffered radial pressure Q of forging die and axial feeding speed V when Figure 12 magnesium is swaged _AxCorrelativity

Embodiment

Process flow diagram of the present invention is seen Fig. 1.Below in conjunction with accompanying drawing, the example that is predicted as with pure magnesium forging force in rotary swaging process specifies the inventive method, but protection scope of the present invention is not limited to following embodiment:

Step 1: gather the primitive technology parameter swage, comprising: the roller number in the swager speed of mainshaft, feeding speed, the head, supplied materials diameter, the diameter after swaging, compression zone length, calibrating strap length, circular cone angle of feed, the initial temperature of swaging, as table 1.

Table 1 calculates the required primitive technology parameter of forging force of swaging

Step 2: utilize mathematical software matlab to calculate and swage mould, undertaken by following order with respect to the curve map that radially reaches the axially-movable track of the workpiece of being swaged and with the .txt formatted file output that finite element software can be discerned:

1. according to the primitive technology parameter of swaging, be calculated as follows data:

The mould of swaging opens the length S that once sends workpiece to and is mm:

S＝V _ax/n _s＝V _ax/(n _f·p)＝V _ax/((1.0-0.4)n _A·p)＝0.675mm (1)

Forging once required time T is:

T＝1/n _s＝1/(p·n _f)＝1/(p·(1.0-0.4)n _A)＝0.009s (2)

Radially drafts H is:

H＝ΔR＝(D-d)/2＝0.5mm (3)

V in the formula _Ax---feeding speed, m/min;

n _s---forge frequency, inferior/min;

n _f---effective rotating speed, r/min;

n _A---the rotating speed of main shaft, r/min;

P---roller number, individual;

D---supplied materials diameter, mm;

D---the back diameter of swaging

2. according to above data in matlab, draw the mould of swaging swaged relatively workpiece axially and radial motion geometric locus figure, as Fig. 2, Fig. 3;

3. in matlab software Fig. 2, Fig. 3 are saved as .txt formatted file and the output that finite element software can be discerned, the axially-movable track name of the mould of swaging is zx.txt, and the radial motion track name is jx.txt.

Step 3: utilize the common finite element analysis software to set up the finite element model of swaging, and zx.txt, jx.txt file are read in the finite element model, finish the modeling work of the finite element model of swaging, operation finite element analogy program.Specifically undertaken by following order:

1. set up the finite element geometric model of swaging, divide grid, as Fig. 4.D is the supplied materials diameter among Fig. 4, and L is the Workpiece length of required simulation, is calculated as follows:

L＝L _d+(D-d)/2·ctg(α/2)＝13mm (4)

Wherein: L _dBe the mould calibrating strap length of swaging, α is the mould coning angle of swaging.

The material requested constant is imported by the ASM normal data: the thermal conductivity of magnesium sees Table 2, and the multicrystal thermal expansivity of magnesium sees Table 3, and the specific heat of magnesium and the relation of temperature are seen Fig. 5, and the elastic modulus of magnesium and the relation of temperature are seen Fig. 6.

The thermal conductivity of table 2 magnesium

The multicrystal thermal expansivity of table 3 magnesium

2. the motion of the relative workpiece of mould of swaging is set to displacement control, reads in zx.txt, jx.txt file in finite element software, and the mould of swaging is set to zx.txt at the displacement control curve of x direction, is set to jx.txt at the displacement control curve of y direction.

3. move the finite element analogy program.Be cyclical variation with load when swaging distortion, periodically stress raisers phenomenon can occur in the structure, thereby adopt the criterion of heavily dividing automatically as grid in the computation process based on the absolute error criterion of equivalent stress.Time increment step number in each period T is set at 32 and (gets 2 ⁿ(4≤n≤7) get higher value with the increase n value of decrement and feeding speed), just in time be an incremental step with the summit that guarantees each recurrence interval in the forging die movement locus (see figure 3).

4. the experimental verification of finite element model and analog parameter are proofreaied and correct: adopt the surfaceness of the magnesium silk of swaging of actual measurement and finite element analogy gained to compare, carry out the correction and the experimental verification of finite element analogy parameter.Difference is swaged, and the simulation of the magnesium silk surfaceness of preparation relatively sees Table 4 with the experiment measured value under the technological parameter.Visible error is in 9%, and finite element analogy method precision of the present invention is higher, satisfies the engineering application requirements.

The swage comparison of the magnesium silk surfaceness analogue value and measured value of table 4

Table is annotated: V _AxAxial feeding speed; α---circular cone angle of feed; Δ R---drafts radially; T _Initial---initial forging temperature;

---the surfaceness analogue value;

---the surfaceness measured value.

Step 4: from finite element result, extract the forging force data, analyze forging die and bear pressure.Carry out as follows:

1. calculate the pulse of a bit in the compression zone, experiencing arbitrarily in the workpiece and forge times N:

$N=\frac{L_Y}{S}=\frac{h\&CenterDot;\mathrm{Ctg}\frac{\mathrm{\&alpha;}}{2}}{S}=\frac{\frac{D-\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000054072700012.png,HSA00000054072700042.png"\; state="\{\{state\}\}">d</figure-callout>}}{2}\&CenterDot;\mathrm{Ctg}\frac{\mathrm{\&alpha;}}{2}}{V_{\mathrm{ax}}/n_s}=\frac{(D-d)\&CenterDot;\mathrm{Ctg}\frac{\mathrm{\&alpha;}}{2}}{2v/((1.0-0.4)n_A\&CenterDot;p)}=4.5---\left(5\right)$

L in the formula _Y---the length of compression zone, mm;

S---the mould of swaging opens the length of once sending workpiece to, mm

H a---drafts, mm;

D---the diameter of workpiece before swaging, mm;

D---the back diameter of work of swaging, mm;

α---circular cone angle of feed;

V _Ax---axial feeding speed, mm/min;

n _s---forge frequency, inferior/min

n _f---effective rotating speed, r/min

n _A---the rotating speed of main shaft, r/min

P---roller number, individual

2. be calculated as follows forging die authorized pressure Q _c:

$Q_c={\left(\frac{R_{\mathrm{cm}}}{60}\right)}^2\frac{{\mathrm{ld}}_{p}r}{d_p+2r}=\left(\frac{200}{60}\right)\&times;\frac{30\&times;25\&times;9.5}{25+19}=1800\&times;9.8\mathrm{kN}=17.64\mathrm{kN}---\left(6\right)$

The technical parameter of the swager that wherein relates to is determined according to the swager instructions:

R _Cm---roller allow compressive stress, determine according to the swager instructions, be 200kgf/mm ²

The contact line length of l---roller and forging die is 30mm;

The arc radius of r---slide block is 9.5mm;

d _p---the diameter of roller is 25mm.

That 3. life-span of swager (mainly being roller) is exerted an influence is the radial pressure Q ' that mould is subjected to that swages.The radial load Q that the radial pressure Q ' that the mould of swaging is subjected to and the workpiece of swaging are subjected to is reacting force each other, therefore tries to achieve the radial pressure that the mould of swaging bears by calculating the radial load that workpiece is subjected to.

From the finite element analogy result, be extracted in N pulse and forge each time point of cycle, the contact force distribution plan of all contact nodes (seeing Fig. 7, Fig. 8).Contact force summation to all contact nodes on each time point workpiece is the suffered radial pressure Q of each time point forging die.Draw N pulse and forge in the cycle, the suffered radial pressure Q of forging die reaches the change curve (see figure 9) that pulse forges number of times in time, obtains the suffered maximum pressure Q of forging die _Max=2.1kN.The suffered maximum pressure Q of forging die _MaxMuch smaller than forging die authorized pressure Q _c, the load-bearing capacity of swager allows to swage by the technological parameter shown in the table 1.

Step 5: change the technological parameter of swaging (comprise circular cone angle of feed, axially feeding speed, drafts etc. radially), obtain the suffered maximum pressure Q of forging die _MaxChange curve with each technological parameter.

Figure 10 is the correlativity of suffered radial pressure Q of forging die and tg (α/2), use the exponential function match, the facies relationship number average shows that more than 0.996 the suffered radial pressure Q of forging die reduces with the increase of circular cone angle of feed α, and is exponential relationship decline with the increase of tg (α/2).By Figure 10 also as seen, Q with α reduce and the speed that increases depends on radially drafts Δ R strongly.When Δ R=0.7mm, α=9 ° 40 ' times, Q _Max=24.6kN＞Q _c=17.64kN, the suffered radial pressure of forging die has exceeded its authorized pressure, and this technological parameter is irrational; And as Δ R=0.7mm, α is increased to 14 ° of 10 ' times, and Q has been reduced to 3.98kN, much smaller than Q _c=17.64kN becomes the reasonable process parameter that pure magnesium is swaged.So, when Reduction per draft is big, should increases the circular cone angle of feed rotary swaging process is carried out smoothly.

Figure 11 is Q under the different circular cone angle of feed _MaxWith the graph of a relation of Δ R, use the exponential function match, the facies relationship number average is more than 0.998.Thereby the suffered radial pressure Q of forging die is exponential increase with the increase of drafts Δ R radially.

Figure 12 is disalignment Q under feeding speed _MaxWith the graph of a relation of Δ R, with V _AxIncrease, Q _MaxAlso slightly increase, but different V _AxUnder Q _MaxVariation 0.7 in kN, V _AxVery little to the influence of Q power, under the commercial production condition, can ignore.

Thereby the suffered radial pressure Q of forging die is exponential relationship with the increase of Δ R and increases, and with tg (α/2) reduce be exponential relationship and increase.When technological parameter is swaged in industrial design, should be according to the present invention the curve (seeing Figure 10 and Figure 11) of match gained select rational Δ R and α, guarantee Q＜Q _c

Claims (4)

1. finite element modeling method of predicting forging force in rotary swaging process is characterized in that may further comprise the steps:

Step 1: gather the primitive technology parameter swage, comprising: the roller number in the swager speed of mainshaft, feeding speed, the head, supplied materials diameter, the diameter after swaging, circular cone angle of feed, compression zone length, calibrating strap length, the initial temperature of swaging;

Step 2: use the primitive technology parameter of swaging of being gathered, calculate the .txt formatted file preservation that radially reaches axially-movable geometric locus figure and can discern of swaging mould according to formula with respect to the workpiece of being swaged with finite element software;

Step 3: set up the finite element model of swaging, operation finite element analogy program

1. according to the primitive technology parameter of swaging of being gathered, set up the finite element geometric model of swaging, the part model grid adopts 4 node axisymmetric elements of full integration, and the mould of swaging is defined as the rigidity contact that can conduct heat, input material constant and constitutive relation model;

2. the mould movement locus file of will swaging is read in the finite element model, and the motion of the relative workpiece of mould of swaging is set to displacement control, finishes the modeling work of the finite element model of swaging;

3. move the finite element analogy program, adopt the criterion of heavily dividing automatically as grid in the computation process based on the absolute error criterion of equivalent stress;

Step 4: from finite element result, extract the forging force data, analyze forging die and bear pressure

1. the pressure Q that the mould that the contact force addition of all contact nodes obtained swaging bears;

2. draw the suffered radial pressure Q of forging die and reach the change curve that pulse forges number of times in time, obtain the suffered maximum pressure Q of forging die _MaxCalculate forging die authorized pressure Q _c, compare Q _cWith Q _Max, judge the load-bearing capacity the restriction whether technological parameter of swaging of simulating satisfies swager;

Step 5: change circular cone angle of feed, axially feeding speed, these three technological parameters of swaging of drafts radially, obtain the suffered maximum pressure Q of forging die _MaxChange curve with the technological parameter of respectively swaging; The technological parameter span of swaging that obtains the restriction of swager load-bearing capacity and must satisfy.

2. the finite element modeling method of prediction forging force in rotary swaging process according to claim 1 is characterized in that, the formula described in the step 2 is:

The mould of swaging opens the length S that once sends workpiece to

S＝V _ax/n _s＝V _ax/(n _f·p)＝V _ax/((1.0-0.4)n _A·p)

Forging once required time T is

T＝1/n _s＝1/(p·n _f)＝1/(p·(1.0-0.4)n _A)

Radially drafts H is

H＝ΔR＝(D-d)/2

V in the formula _AxBe feeding speed, n _sFor forging frequency, n _{F is}Effective rotating speed, n _ABe the rotating speed of main shaft, p is the roller number, and D is the supplied materials diameter, and d is the back diameter of swaging.

3. the finite element modeling method of prediction forging force in rotary swaging process according to claim 1 is characterized in that, the radial motion geometric locus of the relative workpiece of forging die in the step 2 is pressed swager collet segment shape drafting in the swager instructions.

4. the finite element modeling method of prediction forging force in rotary swaging process according to claim 1 is characterized in that, the forging die authorized pressure Q described in the step 4 _cCalculate according to following formula:

$Q_c={\left(\frac{R_{\mathrm{cm}}}{60}\right)}^2\frac{{\mathrm{ld}}_{p}r}{d_p+2r}$

The technical parameter of the swager that wherein relates to is determined according to the swager instructions:

R _Cm---roller allow compressive stress, kgf/mm ²

The contact line length of l---roller and forging die, mm;

The arc radius of r---slide block, mm;

d _p---the diameter of roller, mm.

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