JPH0724534A - Method for bending metallic sheet by linear heating - Google Patents

Abstract

PURPOSE:To carry out bending of a metallic sheet by linear heating without a skilled engineer. CONSTITUTION:After inputting geometric information on an initial shape and target shape (step 1), the initial shape is mesh splitted by the finite element method (step 2) and the splitted shape is mapped on the target shape (step 3). The initial shape is forcibly elastically deformed in the target shape and the target intrinsic strain in each element is obtained (step 4). The obtained target intrinsic strain is heated by the analogy and the generated intrinsic strain is realized (step 5). A normal relation of heating condition and generated intrinsic strain is obtained so as the generated intrinsic strain is obtained when a heating condition is given (step 6). A work is bent by giving the target shape the generated intrinsic strain by the heating method obtained in the steps 5 and 6 (step 7, 8 and 9). A difference between a working shape and the target shape is required and, if a difference is obtained, the present shape is replaced by the initial shape, the data given to the step 4 are corrected and bending is carried out again (steps 10, 11, 12 and 13).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used to finish a curved member of a ship, a bridge, or other metal structure from an initial shape which has been subjected to primary processing such as a flat plate material or press to a desired curved shape. The present invention relates to a method for bending a metal plate by linear heating.

[0002]

2. Description of the Related Art In general, bending of a metal plate used for ships, bridges and the like is often performed by linear heating. This bending by linear heating uses linear heating at a predetermined position of a flat plate or a metal plate that is primarily processed by a press, and uses in-plane shrinkage and angular deformation of the plate due to the generated plastic strain. To create the desired three-dimensional shape.

In the bending process by the linear heating, the in-plane shrinkage amount and the angular deformation amount are determined by the heating position, the direction and the heating condition of the linear heating. Therefore, these heating position, direction and heating condition are important. is there.

At the current processing site, there is no technology based on a theoretical approach focusing on the distribution of the target intrinsic strain obtained by the calculation of forced deformation from the initial shape to the target shape. It is the actual situation that the heating position, direction, and heating condition are determined by the intuition and skill of an expert while detecting the deviation from the target shape by temporarily disposing it above.

However, in recent years, problems such as the aging of these skilled workers and the accompanying decrease in the number of workers have become remarkable.

Therefore, in view of the above circumstances, a method of bending a plate by linear heating which enables the linear heating work requiring skill to be performed without requiring special skill and the processing capacity can be improved recently. Has been proposed and a patent application has been filed (Japanese Patent Application No. 3-237948).

The recently proposed method is to determine the position, direction and generated intrinsic strain (concentrated strain distribution) of the linear heating wire based on the elastic analysis of the finite element method (FEM). As shown in FIG. 24, first, geometric information about the initial shape and the final molded shape is input (step I), and then the FEM mesh division corresponding to the initial shape is performed (step II). Next, after forcibly elastically deforming from the initial shape to the final shape and calculating the strain that occurs in the process, the calculated strain is separated into in-plane component and bending component, and the main strain distribution of each is displayed on the graphic screen. Display (step III). Next, paying attention to the in-plane strain distribution, select the region where the main strain of compression is large as the heating region, and set the heating direction at right angles to the direction of the principal strain (step IV), and also in the distribution of bending strain. Paying attention, a region having a large absolute value of bending strain is added to the heating region, and the heating direction is perpendicular to the main direction having the maximum absolute strain value (step V).

Next, in order to determine the magnitude of the intrinsic strain to be generated, the forced deformation FEM elastic analysis in which the rigidity of the element belonging to the heating region is made smaller than that of the remaining portion is performed again, and the strain concentrated in the heating region is re-executed. The value of the generated intrinsic distortion is calculated from the value of (step VI). Then, based on these calculations, linear heating is performed to generate an intrinsic strain, thereby processing into a predetermined final shape (step VII).

[0009]

In the case of the method proposed and applied recently, the plate can be easily bent by linear heating, which is advantageous in that it can be carried out without resorting to the intuition of a skilled person. However, in formulating the heating method, step IV and step V
By separating the target intrinsic strain into a pure in-plane component and a bending component, the direction of the heating line and the magnitude of the generated intrinsic strain are approximately determined.However, due to the gas flame and high frequency induction heating actually used, Depending on the heater, it is impossible to achieve pure in-plane shrinkage and bending independently, and no matter what heating condition is selected, it always contains both a constant ratio of in-plane strain component and bending strain component. I'm out. Therefore, even if two heating conditions of in-plane component predominance and bending component predominance are selected, it is considered difficult to realize the correct heating line direction and the intended intrinsic strain state. Forced deformation FEM as shown in (a) to (b) of FIG.
When performing elastic analysis, generally, the in-plane component of the target intrinsic strain may appear not only the contraction strain but also the extension strain as shown in FIG. Similarly, elongation strain may also appear in the forced deformation FEM elastic analysis in which the rigidity of the heating portion is lowered to determine the magnitude of the intrinsic strain. The bending work by linear heating is a method of working by utilizing the compressive plastic strain generated in the heating part, and the elongation strain (← → mark) seen in the lower part of FIG. 25C cannot be applied. Therefore, in order to be able to process the target shape only by linear heating, all the above FEM calculation results must be shrinkage strains (→ ← marks). FIG. 25.
In (c), it is necessary to apply a uniform contraction strain at least to the portion having elongation strain or as a whole.
This corresponds to shrinking the target shape or increasing the initial shape. Similarly, in order to achieve a certain amount of bending strain by heating from one side, some in-plane shrinkage is unavoidable. Due to these extra contractions, the finished target shape has insufficient in-plane dimensions. Although this is qualitatively known in the past, it is not possible to compensate them quantitatively, so at the present time, a sufficient margin based on an empirical rule is set in advance and the final There is a possibility that extra work for trimming and alignment, or in some cases, insufficient dimensions may occur. When linear heating is performed, it is well known that not only the contraction strain in the direction perpendicular to the heating line but also the contraction strain in the direction of the heating line is small, but it is well known. In addition, it is considered difficult to accurately realize the target intrinsic strain distribution. Further, since the quantitative relationship between the heating conditions and the generated intrinsic strain is not mentioned in the method recently proposed and applied, it is inferred from experience and intuition from the bending site and the initial shape, which is the current field technology. The heating condition that will generate the required deformation amount for each part is selected based on experience, and the method is adopted.However, as a result of accumulating multiple stages of estimation based on experience and intuition, difficult, error, There are problems such as large variation, limited number of people, and long learning time.

Therefore, the present invention eliminates the above-mentioned problems by further advancing the above-mentioned recently proposed and applied method of bending a plate by linear heating, and can be carried out by an amateur even if a target shape is given. , It is intended to realize the objective intrinsic strain only with desired heating conditions.

[0011]

In order to solve the above-mentioned problems, the present invention first bends a metal plate from an initial shape to a final target shape by first providing geometric information of the initial shape and the target shape. Input, perform mesh division of the finite element method based on the initial shape, map the divided shape onto the target shape, then forcibly deform from the initial shape to the target shape and calculate the target intrinsic strain distribution Then, the obtained target intrinsic strain distribution is expressed by the generated intrinsic strain generated by a plurality of heating lines, and at this time, the quantitative relationship between the heating conditions for the combination of the heating device and the work material and the generated intrinsic strain is expressed. After introducing the similarity rule and obtaining it, and then connecting the above heating wires in each element and setting and displaying the position, direction, and heating conditions of the heating wire of the entire plate, the heating conditions were given. Generation-specific when required After performing a linear simulation for confirming the curved shape by adding to the initial shape, the metal plate is heated and bent, and the shape of the heated metal plate is measured to obtain the target shape. If the error exceeds the allowable value, the shape at that time is replaced with the initial shape, and the distribution data of the intrinsic strain and elastic strain is corrected based on the above error and accumulated as the actual value. In this way, the bending process of the metal plate by linear heating is performed, wherein the bending process of the metal plate is performed again.

Further, when the quantitative relationship between the heating condition and the generated intrinsic strain for the combination of the heating device and the work material is determined by the similarity law, an axisymmetric heating source is used and the amount of heat input is controlled within each element. The heating conditions may be set as the heating.

Further, when the metal plate is heated and bent, it is preferable that a heating source is slid to follow the surface shape of the metal plate.

[0014]

[Function] After the metal plate is forcibly elastically deformed from the initial shape to the target shape to obtain the target intrinsic strain distribution in each element, the target intrinsic strain distribution is expressed as a generated intrinsic strain by a plurality of heating wires, In addition, when the generated intrinsic strain is given based on the quantitative relation obtained by introducing the similarity rule, the heating condition corresponding to it is obtained. Therefore, by giving this generated intrinsic strain to the initial shape, It suffices to predict in advance how the target shape will be achieved, and to perform heating with a plurality of heating wires under the required heating conditions, without having to rely on a skilled engineer. Furthermore, the error between the plate shape after heating and the target shape is fed back as the initial shape, and it is taken in as the actual data for the calculation of the target intrinsic strain distribution. can get.

Further, when introducing the similarity rule and determining the generated intrinsic strain based on the quantitative relationship, if a point heating is performed in each element using an axisymmetric heat source, the control parameter can be reduced. The calculation load is reduced and the efficiency can be improved accordingly.

Further, when the metal plate is heated and bent, when the heat source is slid along the plate surface, the heat source and the metal plate come into close contact with each other, so that the heating efficiency is not lowered. The curved surface accuracy can be accurately obtained.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a flat plate having an arbitrary peripheral shape, a steel plate having an initial shape of an arbitrary curved surface, or a metal plate other than steel, which is bent into a target shape (another arbitrary peripheral shape and curved surface shape). In the flowchart showing the method, geometric information about the initial shape and the target shape is input (step 1), and then, based on the initial shape of the metal plate P, as shown in FIG.
As shown in (a), mesh division of the finite element method (FEM) is performed (step 2), and the divided shape is converted into a metal as shown in FIG. 2 (b) by an appropriate mapping method that maps the initial shape to the target shape. Map onto the target shape of the plate P (step 3). Then, each element node position in the initial shape is forcibly elastically deformed to the corresponding element node position in the target shape by FEM calculation, and the strain distribution (target inherent strain distribution) in each element is calculated (step 4). . At this time, by appropriately selecting the mapping method when forcibly deforming, it is possible to obtain the target intrinsic strain distribution that is suitable for the processing method, and to determine the shrinkage allowance associated with the mapping method and the processing method.

Next, as a heating method, the target intrinsic strain distribution in the element obtained in step 4 is a concentrated strain distribution (generated intrinsic strain) generated by a plurality of heating lines.
Is approximately expressed by (step 5). In this case, when the target intrinsic strain distribution is realized by the generated intrinsic strain in step 5, for a given combination of the heater (gas flame, high frequency induction heater, laser light, etc.) and the work material, Since a quantitative relationship between the heating conditions (heat input amount per unit time, moving speed, etc.) and the generated intrinsic strain is required, this relationship should be obtained (step 6). The quantitative relationship between the heating condition and the generated intrinsic strain is generally obtained by accumulating experimental data or by giving a heat input condition (heat input distribution or temperature distribution that changes in time series) by a thermo-elasto-plastic FEM analysis. It is obtained by calculating the generated intrinsic strain on the metal plate when. A feature of the present invention is that when the relationship between the heating conditions and the generated intrinsic strain is calculated by using the thermo-elastic-plastic FEM program whose validity is confirmed by the proof experiment, the linear heating is performed as described later. By developing an efficient calculation method using the similarity law that holds for the thermo-elasto-plastic deformation problem due to the method and the governing parameters derived from it, and by arranging the calculated results in a generalized form with those parameters This is to provide a means capable of efficiently obtaining the generated intrinsic distortion when the condition is given.

Next, by connecting the heating wires in each of the above-mentioned elements, the positions and directions of the heating wires of the entire plate and the heating conditions are determined and displayed (step 7), and then the values are obtained in steps 5 and 6. By giving the generated intrinsic strain when the heating conditions are given to the initial shape, a linear simulation of the bent shape is performed and confirmed (step 8). Then, according to the heating method defined in step 6, linear heating is performed manually or using an NC-controlled heating device (step 9).

By applying the generated intrinsic strain to the metal plate by the heating method obtained by the procedure from step 1 to step 9 above, the metal plate can be bent into a target shape.

Further, the shape of the metal plate after being bent by linear heating is measured, and an error from the target shape of step 1 is confirmed (step 10). If the error is within an allowable value, the work is finished ( Step 11). On the other hand, when the error exceeds the permissible value, the current shape is replaced with the initial shape (step 12), and the feedback is made to step 1. or,
At this time, the distribution data of the intrinsic strain and the elastic strain sent to step 4 is corrected from the above error (step 13).
At the same time, the actual value is accumulated.

As a result, a heating plan is created and reworked in the same process as the first time. At this time, depending on the simulation result of step 8, if necessary, step 1
The distribution data of 3 will be further corrected.

The details will be described below.

Steps 1 to 3 correspond to steps I and II in FIG.

In step 4, the proper intrinsic strain distribution suitable for the processing method can be obtained by proper selection of the mapping method when forcibly deforming, and the shrinkage margin associated with the mapping method and the processing method can be determined. The simplest example of the method for quantitatively obtaining the shrinkage margin required in this bending process is as follows. First, in order to eliminate the portion of in-plane elongation strain, for example, x, y of the metal plate P shown in FIG. A contraction strain whose absolute value is equal to the maximum elongation strain in both directions is uniformly applied to the entire plate, that is, all elements. This uniform addition corresponds to the addition of a certain specific modification to the mapping method from the initial shape to the target shape when the shrinkage allowance is not taken into consideration. Accordingly, the shrinkage allowance in this case is easily calculated in a uniform manner along each side as shown in FIG. 3 by multiplying the applied uniform strain by the length of the plate. Regarding shrinkage due to bending, if the bending component ratio under the selected heating conditions is α, the maximum bending strain multiplied by α times the plate length becomes the shrinkage allowance (similarly If given). The overall shrinkage allowance is obtained by performing the same operation in the vertical and horizontal directions of the plate. That is, Δl _x = ε _mx ^max l _x + αε _bx ^max l _x Δl _y = ε _my ^max l _y + αε _by ^max l _y Next, when the heating method of step 5 is formulated, in order to realize the target intrinsic strain, The target intrinsic strain distribution of the metal plate P is divided into six independent components (in-plane strains ε _xu , ε _yu ,
γ _xyu and the in-plane strain of the lower surface ε _xl , ε _yl , γ _xyl )
Next, the intrinsic strain generated by one linear heating is shown in FIG.
In-plane shrinkage amount δ _m (= (δ _mu + δ _ml ) / 2) and angular deformation amount φ in the direction perpendicular to the heating line a as shown in the metal plate P in (b)
(Or a bending component ratio represented by α = (δ _u −δ _l ) / (δ _u + δ _l )). As a result, the above six strain components can be realized by appropriately arranging a plurality of heating wires or adjusting heating conditions. That is, six conditional expressions for determining the arrangement, directions, and heating condition characteristic values of a plurality of heating wires are obtained from the six target intrinsic strain components. From these, for example, the characteristic values of two types of generated intrinsic strains are obtained. It is possible to determine the spacing and the direction of the heating line when given. In the above description, the characteristic strain generated by one linear heating is expressed by two characteristic values of δ _m and α, but it is equivalent to the contraction deformation in the heating line direction. Total of 4 by adding the equivalent external force P _L and the equivalent moment M _L required to cause such deformation
If the generated intrinsic strain is aggregated by individual characteristic values and the same method as above is performed, the generated intrinsic strain corresponding to the arrangement, direction, or heating conditions of the heating wire will be considered in consideration of the effect of shrinkage in the heating direction caused by heating. Characteristic values can be set.

Now, with respect to the above-mentioned plurality of heating wires, as an example, when the target intrinsic strain is realized by two heating wires, that is, 6 of the target intrinsic strain in a certain element as shown in FIG.
The components (in-plane strains ε _xu , ε _yu , γ _xyu of the upper surface and in-plane strains ε _xl , ε _yl , γ _{xyl of the} lower surface) are realized by two heating lines a and b having different characteristic values. explain. If the S and L subscripts are used to represent the respective heating lines a and b, then 2
Characteristic values of the four generated intrinsic strains under each heating condition (δ _mS ,
δ _mL , α _S , α _L ), the angles θ _S and θ _L formed by the two heating lines a and b with the x-axis, respectively, and the heating line intervals d _S and d _L between the two heating lines a and b are summed up. The heating method can be determined by the eight parameters described above. In order to realize the objective intrinsic distortion, the following six conditional expressions are imposed (however, 2
Both books are heated on the top).

Ε _xu = −δ _mS / d _S (1 + α _S ) sin ² θ _S −δ _mL / d _L (1 + α _L ) sin ² θ _L (1-1) ε _yu = −δ _mS / d _S (1 + α _S ) cos ² θ _S −δ _mL / d _L (1 + α _L ) cos ² θ _L (1-2) γ _xyu = −δ _mS / d _S (1 + α _S ) sin ² θ _S −δ _mL / d _L (1 + α _L ) sin2θ _L (1-3) ε _xl = −δ _mS / d _S (1-α _S ) sin ² θ _S −δ _mL / d _L (1-α _L ) sin ² θ _L (1-4) ε _yl = −δ _mS / d _S (1-α _S ) cos ² θ _S −δ _mL / d _L (1-α _L ) cos ² θ _L (1-5) γ _xyl = −δ _mS / d _S (1-α _S ) sin2θ _S −δ _mL / d _L (1-α _L ) sin2θ _L (1-6) Therefore, two of the eight parameters can be freely selected, so they are specified in advance to specific values. However, the target intrinsic distortion can be realized by selecting the remaining six parameters so that the above six conditional expressions are satisfied.

When all of the above eight parameters are determined, the specific heating method within the element is determined.
In this way, for example, if the heating conditions are determined for all 16 elements as shown in FIG. 6, these can be heated continuously or intermittently to finish the entire plate into the desired shape. Furthermore, δ _mS , δ _mL
By adjusting the sizes of α _S and α _L by changing the heating conditions, it is possible to perform fine and smooth bending with a narrow heating interval d _S and d _L to simple rough bending.

In the present embodiment, for example, assuming that two types of heating devices are used, in FIG. 5, one heating is performed by linear heating by a gas flame (indicated by a suffix S) and the other heating is performed by another device ( The subscript L) is used. For other instruments, the heating condition is fixed, or the characteristic value data of the generated intrinsic strain is obtained only under the specific heating condition. Therefore, δ _mL and α _L of the 8 parameters must be specified in advance. In this case, in order to achieve the target intrinsic strain state, the above 6
The remaining six parameters θ _L , d _L , θ _S , d _S , δ _mS , and α _S are obtained from the conditional expressions (1-1) to (1-6). Of these, δ _mS and α _S are determined from the heating conditions of the gas flame, so for example, the heating conditions Q and v that result in δ _mS and α _S obtained using FIGS. 14 and 15 should be determined. You can

Next, FIG. 7 shows a case where the target intrinsic strain is realized by three different heating lines a, b, c as another embodiment of the case where the target intrinsic strain is realized by a plurality of heating wires. . The heating method is determined by 12 parameters, and 6 parameters out of 12 can be freely set in advance.

In the case of this embodiment, for example, the characteristic value δ _{mS of} the intrinsic strain generated by the three heating wires a, b and c,
Even if δ _mM , δ _mL , α _S , α _M , and α _L are fixed from the operating conditions of the device, the three heating line directions θ _S , θ _M ,
By properly selecting θ _L and heating line intervals d _S , d _M , and d _L so as to satisfy the six conditional expressions, the target intrinsic strain can be achieved.

FIG. 8 shows four heating wires a, b, as still another embodiment in the case where the target intrinsic strain is realized by a plurality of heating wires.
The case where the target intrinsic distortion is realized by c and d is shown.

In this case, there are many possible methods of implementation, but as an example, two types of heating conditions, heating lines a and b, are set, and two heating lines (each of which is mutually (Fixed angles ψ _S and ψ _L respectively intersect), the heating method is δ _mS , δ _mL ,
1 of α _S , α _L , θ _S , θ _L , d _S1 , d _S2 , d _L1 and d _L2
It is decided by 0 parameters, and 4 out of 10 parameters can be freely set in advance.

In this embodiment, for example, the characteristic values δ _mL and α _{L of} the generated intrinsic strain corresponding to one heating condition are designated, and only one of them is designated in that condition in the designated direction θ _L and interval d.
_If it is supposed to be constructed by _L1 , it can be achieved by correctly selecting the remaining parameters δ _mS , α _S , θ _S , d _S1 , d _S2 and d _L2 so as to satisfy the six conditional expressions.

Next, a specific embodiment for obtaining a quantitative relationship between the heating conditions in step 6 and the generated intrinsic strain will be described. (A) When the generated intrinsic strain is obtained by applying heating conditions When a plate with a plate thickness h = 16 mm is linearly heated at a heat source moving speed v = 15 mm / sec using a gas flame with an input heat quantity Q = 3115 cal / sec An example of obtaining δ _m and α will be shown. In this case, the following physical property values of steel should be used.

Λ = 0.160cal / mm · sec · ° C Cp = 0.098cal / g · ° C ρ = 0.00782g / mm ^{3 When the} heat penetration coefficient p and the thermal diffusion coefficient k are calculated, p = (λCpρ) ^{1 / 2 = 0.0035cal / mm 2 ·} ℃ k = λ / Cpρ = 20.9mm 2 / sec where, lambda: the thermal conductivity of the metal plate Cp: specific heat of the metal plate [rho: density of the metal plate thus the similarity rule The governing parameters β and ζ are β = Q / (P ² vh ³ ) ^1/2 = 4.4 × 10 ³ ζ = (vh / k) ^1/2 = 3.4. β is a parameter proportional to the maximum temperature of the surface of the plate heated by the heat source, and ζ is a parameter corresponding to the heat source moving speed.

From FIG. 14 showing changes in the amount of angular deformation due to the parameters β and ζ, and FIG. 15 showing changes in the amount of in-plane lateral contraction due to the parameters β and ζ, the angular deformation φ and the lateral contraction δ with respect to these parameters β and ζ. When reading the _m, it can be seen that the _{φ = 0.005 rad δ m = 0.001mm} . The angular deformation component ratio α is α = φh / 2δ _m = 40.

Introducing the similarity law of thermo-elasto-plastic deformation by a moving heat source, the shape of the target plate and the width of the heat source are geometrically similar, and the material of the metal plate is the same, and the thermal and mechanical properties are the same. Assuming that
It can be seen that if the values are the same, the temperature distributions at the similar time and the position are the same, and similar deformation occurs.

As an example of application of the similarity rule, FIG.
Table 1 compares the calculation results in which specific numerical values are set for the two cases shown in.

[0041]

[Table 1] In this example, the axisymmetric heat source (heat flux) 21 is shown as shown in the figure, but various methods are conceivable as the heat source. The method proposed here can be utilized corresponding to the shape of the heat source.

Here, the plate thickness of 8 mm and the width of 30 shown in FIG.
A model with 0 mm and a length of 300 mm is called M8, and a model with a plate thickness of 16 mm, a width of 600 mm and a length of 600 mm shown in FIG. 9B is called M16.

As can be seen from Table 1, the geometric shape is 2
In the case of double, in order to generate similar deformation, heat input Q
It can be seen that the heat source moving speed v must be twice and the heat source moving speed v must be half.

FIG. 10 and FIG. 11 show the temperature history associated with the movement of the heat source occurring on the heating line of each of the M8 and M16 plates, at the center in the plate length direction, and on the plate front and back surfaces.

The vertical axis of the graph shows the temperature of the part. The horizontal axis of the graph is the standardized relative time, but at the same time it corresponds to the position in the plate length direction, and τ = 0.5 is the center of the plate length direction (Y direction in FIG. 8), τ = 1. .0 is the end. β, ζ
It can be seen that the temperatures at the corresponding positions are the same for M8 and M16, which are equal to each other.

FIG. 12 shows the history of angular deformation due to the movement of the heat source in the transverse section at the center of the heating wire upper plate length direction of M8 and M16. The vertical axis is the deformation angle (radian), and the horizontal axis is the same as in FIGS.

FIG. 13 shows the history of shrinkage deformation of M8 and M16 in the plate width direction in the transverse cross section at the center of the plate length direction on the heating wire.

In FIGS. 12 and 13, it is clear that the state of change with time and the difference in deformation amount when the heat source moving speed is fast (ζ = 4.4) and slow (ζ = 1.9). Can be taken.

FIG. 14 is a graph summarizing the results of series calculations performed by changing β and ζ.

Β is 3.2 × 10 ³ (corresponding to the maximum temperature on the plate surface of about 445 ° C.) 4.4 × 10 ³ (corresponding to the maximum temperature on the plate surface of about 615 ° C.) 5.7 × 10 ³ ( (Corresponding to a maximum temperature of about 785 ° C on the plate surface).

The vertical axis represents the amount of angular deformation (radian), and the horizontal axis represents ζ.
It can be seen that (corresponding to the moving speed of the heat source), the larger β (the higher the surface temperature), the larger the amount of angular deformation.

Dotted lines connect points having the same Q / v (heat input amount per unit length). From this, it can be seen that even if the heat input amount per unit length is the same, the deformation amount is different if the heat input rate is different.

FIG. 15 shows the relationship between the amount of shrinkage in the lateral direction and the parameter in the transverse section at the center of the lengthwise direction of the plate on the heating line.

The vertical axis is the amount of shrinkage, the horizontal axis is the same as in FIG. 14, and the dotted line is the same as in FIG.

FIG. 16 shows the relationship between the shrinkage strain in the width direction and the parameter at the center position in the width direction on the same cross section as in FIG. The amount of bending strain is expressed by the difference in plastic strain between the plate surface and the center of plate thickness. 16 is shown in FIG.
It can be considered that the tendency shown in FIG.

FIG. 17 shows the relationship between the bending deformation (radian) and the lateral contraction (mm) when the concentration degree of the distribution is changed considering the axially symmetric heating source as shown in FIG. Assuming that the heating is given as the forced heat flux q from the plate surface, let q be the axisymmetric Gaussian distribution

[0057]

[Equation 1] However, r is the distance from the center of the heat source, qmax is the horizontal axis, and κ is the heat flux at the center of the heat source. in this case,
κ represents the spread of q (r), and the larger κ is, the more concentrated it is, and the smaller it is, the more diffuse it is.

The relation between q and Q is Q = πqmax / κ.

From this graph, even when the heat input amount and the heating rate are the same, the manner of deformation is different when the heat input distribution pattern of the heat source is different. That is, an important finding is given that the efficiency of bending significantly changes. (B) When obtaining the generated intrinsic strain by designating the maximum temperature. Obtain the heat source moving speed for heating while keeping the maximum temperature below 500 ° C under the same gas flame and plate thickness conditions as in (A). At that time, The characteristic value of the generated intrinsic strain of is obtained. As mentioned above, the temperature field is characterized by two parameters, β and ζ. FIG. 18 is a graph in which the maximum temperatures T _s and _max of the plate surface are arranged on the vertical axis based on the calculation results of the temperature distribution in which β and ζ are systematically changed. In the case of (A), v
= 15 mm / sec, β = 4.4 × 10 ³ , ζ = 3.
It was 4. The maximum temperature at this time is about 600 from FIG.
It can be seen that the temperature is ° C. In order to lower the maximum temperature to 500 ° C., it is necessary to increase v and lower β. From the figure, ζ
Since it can be seen that T _s and _max hardly depend on ζ in the region of> 3.0, only β needs to be adjusted. v = 2
If it is 2.6 mm / sec, β = 3.7 × 10 ³ , and T
_It can be seen that _s , _max = 500 ° C. Ζ at this time
Is

[0060]

[Equation 2] Becomes Applying these values of ζ and β to FIGS. 14 and 15, angular deformation φ = 2 × 10 ⁻³ rad, lateral contraction δ _m = 0.5.
It is about 10 ⁻³ mm. (C) When obtaining heating conditions from the generated intrinsic strain When the heating method is determined, the characteristic value of the generated intrinsic strain may not move for some reason (for example, δ in the first embodiment of the heating method determination method). _mS , α _S ). In this case, it is possible to know what heating conditions (Q, v) should be used for heating. It is assumed that the characteristic values of the generated intrinsic strain when the plate thickness is 16 mm are specified as δ _m = 10 × 10 ⁻³ mm and α = 7.2. The angular deformation φ is φ = 2αδ _m / h = 9 × 10 ⁻³ (rad.).

In FIG. 19 in which FIG. 14 is reproduced again, a line parallel to the horizontal axis is drawn so that the angular deformation is 9 × 10 ⁻³ rad.
Similarly, in FIG. 20 in which FIG. 15 is reproduced, the lateral contraction amount is 1
Draw a line parallel to the horizontal axis that gives ^{0x10 -3} mm. While changing the value of ζ, various lines parallel to the vertical axis are drawn, and a ζ position where β matches in FIGS. 19 and 20 is searched for at the intersection of the horizontal line and the vertical line. After all, when ζ = 2.1, the values of β at the intersections in both figures become equal, and β = 5.2 × 10 ³ or so.

[0062]

[Equation 3] Therefore, with a gas flame of 2805 cal / sec, 5.8 mm /
If linear heating is performed at a moving speed of sec, the required δ _m = 10 ×
10 ⁻³ mm, α = 7.2 will be achieved.

As described above, step 5 and step 6
In step 8, the inherent strain generated by the heating by the heating method obtained in step 3 is applied to the initial shape, and the linear shape simulation of the bent shape is performed for confirmation to bend the metal plate. Bending is performed to a target shape by giving the generated intrinsic strain in step 10. This shape is confirmed in step 10.

The difference from the target shape in step 10 is mainly the residual stress during material rolling and primary processing (by pressing etc.), variations in heating conditions, difference between calculation assumptions and actual conditions (simulation error), etc. Can be considered. If there is no error, the work is completed as in step 11, but
When the error exceeds the permissible value, the current shape is fed to step 12 and replaced with the initial shape value, and the bending process is performed again.

At this time, regarding the detected error distribution, the composition ratio of the intrinsic strain and the elastic strain is selected in step 13 by referring to the know-how accumulated in advance, and the variation of the heating condition is also verified. To do. That is, in step 13, the correction data generated as a result is accumulated, and the parameter accuracy of the calculation is gradually made closer to the actual value, so that it is possible to cope with the change of the target material and the drastic change of the required shape.

Next, FIG. 21 shows steps 5 and 7.
The heating line search and display in Fig. 9 can be simplified. By performing point heating with freely changing the heat input rate using an axially symmetric heating source as shown in Fig. 9, a plane of contraction deformation can be obtained. The directionality of the direction is eliminated, the degree of freedom when calculating the heating plan is reduced, and the calculation efficiency is improved. That is, FE
One heating is applied to each element lattice of M calculation. In FIG. 21, the mark ◯ shows an example of the amount of heat input during heating, and the larger the mark ◯, the greater the amount of heat input.

Generally, it is more efficient and easier to handle by changing the heat input rate by controlling the output of the heating device. Therefore, by controlling only the amount of input heat, the calculation load is greatly reduced. be able to.

Next, FIGS. 22 and 23 show an example of the NC-controlled heating device used in step 9, in which a gate-shaped frame 24 composed of the beam 22 and a pedestal 23 supporting the beam 22 is provided with an arrow. The guide beam 22 is provided with an arm 25 that is extendable and retractable in the vertical direction (Z direction) so that it can travel in the X direction, and can traverse in the Y direction orthogonal to the X direction. Further, the heating source 26 is attached so that it can be swung (turned), and the heating source 26 can be brought into close contact with the curved surface of the metal plate P to be slid.

When the metal plate P is heated by NC control, the frame 24 travels in the X direction and the arm 25 traverses in the Y direction.
The expansion and contraction of the arm 25 in the Z direction allows the heating source 26 to slide along the surface of the metal plate P. The control of the arm 25 in the Z direction is such that the reaction force from the surface of the metal plate P becomes constant.

In the above linear heating work, when a high frequency induction heating device is used as the heating source 26, the heating source 26
If a gap is formed between the metal plate P and the metal plate P, the heating efficiency sharply decreases, and the heating condition is significantly deviated from the premise of the calculation, which may deteriorate the curved surface accuracy. And using a heating device as shown in FIG.
Since the heating source 26 can be closely held and moved while being held vertically, it is possible to deal with a curved surface which is constantly continuously and complicatedly deformed by heating.

[0071]

As described above, according to the method for bending a metal plate by linear heating of the present invention, the following excellent effects can be obtained. (i) The target intrinsic strain distribution in each element is calculated, and the target intrinsic strain distribution in the obtained element is expressed by the generated intrinsic strain generated by a plurality of heating lines.
In general, when determining the heating method from the target shape or the target intrinsic strain, it usually becomes an inverse problem, and after sufficiently storing the data of the deformation state or the generated intrinsic strain when various heating methods are given, The procedure of finding the most suitable heating method among them must be taken. However, according to the present invention, even if an intended shape is given, even an amateur can find a bending method according to the flow shown in FIG. Even if the process which has the effect and adopts this heating method is adopted, if the characteristic value of the generated intrinsic strain to be given in the element is specified, the heating as shown in FIGS. 14 and 15 is performed. A data bank that gives the relationship between the condition and the generated intrinsic strain is necessary. Against this, the present invention also increases the number of heating wires to obtain the desired heating condition ( Eg to characteristic values of the product-specific strain made it possible to achieve the desired intrinsic distortion just previously Known heating conditions). (ii) The intrinsic strain generated by a specific heating condition includes the bending component and the in-plane component at the same time, so the required generated intrinsic strain is obtained (that is, it matches the values to obtain the bending component and the in-plane component, respectively). The problem is that you have to solve the inverse problem of finding the cause by knowing the result. However, in the present invention, since the quantitative relationship between the heating condition and the generated intrinsic strain is given over a wide range, an appropriate heating condition when the generated intrinsic strain is given is The optimum heating device can be designed as required. Furthermore, by introducing the similarity rule, when trying to obtain the generated intrinsic strain for various heating conditions, it is possible to infer a large object by a model experiment with a small dimension, and the range of application of calculation results is widened. , The amount of calculation for accumulating quantitative data covering the whole and the amount of experiments can be greatly reduced, and so on. (iii) The target shape can be realized with high accuracy by correcting the difference between the calculated heating instruction and the actually obtained shape, and at this time, the correction data generated as a result is accumulated. However, by making the calculation parameter accuracy closer to the actual one, it is possible to improve the accuracy of the next work and reduce the number of feedbacks, even if the physical properties of the workpiece material change or the curvature changes. , It will be possible to incorporate it as know-how, and it will be possible to flexibly respond to the required shape. (iv) When determining the quantitative relationship between the heating conditions and the generated intrinsic strain by the similarity rule, using an axially symmetric heating source, and setting the heating conditions as point heating with the input heat amount controlled in each element, Since the heating pattern can be simplified, the control parameters can be reduced and the calculation load can be reduced, so that the efficiency can be improved and other functional improvements can be dealt with. (v) When heating and bending a metal plate, if the heating source is made to slide following the surface shape of the metal plate, the heating source will be in close contact with the curved surface that changes as the heating progresses. Therefore, high frequency induction heating can be adopted. (vi) Due to (i), (ii), (iii), (iv), and (v) above, a linear phenomenon that had to rely on a skilled engineer because it was a complicated phenomenon that included many trial and error elements in the past. With regard to the heating and bending method, it has become possible to use a device or select the optimum processing method.

[Brief description of drawings]

1 is a flow chart showing an embodiment of the method of the present invention.

2A and 2B show mapping from an initial shape to a target shape and forced deformation. FIG. 2A is a diagram of FEM mesh division, and FIG. 2B is a state diagram mapped onto the target shape.

FIG. 3 is a diagram showing an example of how to take a shrinkage allowance.

4A and 4B show a state when linear heating is performed by one heating wire, in which FIG. 4A is a perspective view of a plate, and FIG. 4B is a cross-sectional view of FIG.

FIG. 5 is a diagram showing an example of a case where a target intrinsic strain is realized by two heating wires under different heating conditions.

FIG. 6 is a schematic diagram of heating wire connection for each element in the case of FIG.

FIG. 7 is a diagram showing an example of a case where a target intrinsic strain is realized by three heating wires under different heating conditions.

FIG. 8 is a diagram corresponding to FIGS. 5 and 7 in the case where there are two types of heating conditions and two heating lines corresponding to them.

9A and 9B show application examples of the similarity rule, in which FIG. 9A is a perspective view of a model M8, and FIG. 9B is a perspective view of a model M16.

FIG. 10 is a diagram showing a comparison of temperature histories at corresponding positions of the models M8 and M16 when the parameter ζ = 4.4.

FIG. 11 is a diagram showing a comparison of temperature histories at corresponding positions of the models M8 and M16 when the parameter ζ = 1.9.

FIG. 12 is a diagram showing a comparison of changes over time in angular deformation at corresponding positions of models M8 and M16.

FIG. 13 is a diagram showing in-plane lateral contraction amounts at corresponding relative positions in the plate width direction of models M8 and M16.

FIG. 14 is a diagram showing changes in the amount of angular deformation due to parameters β and ζ.

FIG. 15 is a diagram showing changes in in-plane lateral contraction amount due to parameters β and ζ.

FIG. 16 shows parameters β and ζ of plastic strain in the central cross section.
It is a figure which shows the change by.

FIG. 17 is a diagram showing the influence of the expansion of the heat source on the deformation.

FIG. 18 is a diagram showing changes in maximum temperature due to parameters β and ζ.

FIG. 19 is a diagram showing angular deformation and reading of β from a parameter ζ.

FIG. 20 is a diagram showing lateral contraction and reading β from a parameter ζ.

FIG. 21 is a diagram showing an example of a case where each element is point-heated by an axisymmetric heating source to realize a target intrinsic strain.

FIG. 22 is a schematic diagram showing an example of a heating device under NC control.

23 is a schematic sectional side view of FIG. 22. FIG.

FIG. 24 is a flowchart showing an example of a method of bending a plate by linear heating that has been recently applied.

FIG. 25 shows in-plane strain components when the initial shape is forcibly deformed to a target shape, where (a) shows the initial shape, (b) shows the target shape, and (c) shows the surface. It is an inner principal distortion vector diagram.

[Explanation of symbols]

 1 step 1 2 step 2 3 step 3 4 step 4 5 step 5 6 step 6 7 step 7 8 step 8 9 step 9 10 step 10 11 step 11 12 step 12 13 step 13 21 heat source 26 heating source a heating wire b heating wire c Heating wire d Heating wire P Metal plate

Claims (3)

[Claims] 1. In order to bend a metal plate from an initial shape to a final target shape, first, geometric information of the initial shape and the target shape is input, and mesh division of the finite element method is performed based on the initial shape. Then, the divided shape is mapped onto the target shape, then the target intrinsic strain distribution is calculated by forcibly deforming from the initial shape to the target shape, and the obtained target intrinsic strain distribution is generated by multiple heating lines. It is expressed by the generated intrinsic strain, and at this time, the quantitative relationship between the heating condition and the generated intrinsic strain for the combination of the heating device and the work material is obtained by introducing the similarity rule. By connecting the above-mentioned heating line in, and displaying the position, direction, and heating conditions of the heating line of the entire plate, by giving the generated intrinsic strain obtained when the heating condition is given to the initial shape Check the bent shape After performing a linear simulation for heating, the metal plate is heated to perform bending, and the shape of the metal plate after heating is measured to obtain the error from the target shape.The error exceeds the allowable value. Then, the shape at that time is replaced with the initial shape, and the distribution data of the intrinsic strain and the elastic strain is corrected based on the above error and accumulated as the actual value, and the metal plate is bent again. A method for bending a metal plate by linear heating, which is characterized by the above. 2. When a quantitative relationship between a heating condition and a generated intrinsic strain for a combination of a heating device and a work material is obtained by a similarity rule, an axisymmetric heating source is used and an input heat amount is controlled in each element. The method for bending a metal plate by linear heating according to claim 1, wherein heating conditions are set as heating. 3. The bending of a metal plate by linear heating according to claim 1, wherein a heating source is slid to follow the surface shape of the metal plate when the metal plate is heated and bent. Processing method.