JP4372534B2 - Joint strength estimation method, deformation state estimation method, and joint condition determination method - Google Patents

Description

  The present invention relates to a joining strength estimation method for estimating the joint strength of a joint subjected to friction stir welding, a deformation state estimation method for estimating a deformation state, and a joining condition determination method for determining a joining condition that satisfies a required joining quality. .

  As a technique for joining a plurality of members to be joined, a friction stir welding method has been proposed (see, for example, Patent Document 1). In the friction stir welding, a rotating welding tool is pressed against a workpiece on which the members to be joined are overlapped to be immersed. The joining tool partially fluidizes each member to be joined by frictional heat in an unmelted state, and stirs the fluidized member to join each member to be joined.

JP 2000-310995 A

  The mechanism of friction stir welding has not been fully elucidated. Therefore, in the past, in order to obtain the joint strength of a joint that has been friction stir welded, it was necessary to actually perform a strength test. Conventionally, a strength test is performed on each of the joints joined under different joining conditions, and the joining conditions capable of obtaining a target joining strength are determined by trial and error. The joining conditions include, for example, the number of rotations of the joining tool, the pressure of the joining tool, the joining time, the amount of pushing, and the shape of the joining tool.

  In this case, in order to obtain the target strength, it was necessary to repeat the strength test while changing the joining conditions, and the joining conditions could not be determined in a short time. In addition, every time the joining conditions are changed, a test piece to be a joint is necessary, and the cost for determining the joining conditions is large.

  Even if the joining conditions capable of obtaining the required strength are determined, if the materials and plate thicknesses of the members to be joined are different, it is necessary to determine the optimum joining conditions again by trial and error. As described above, conventionally, the bonding strength can be obtained only by the strength test, and the efficiency is poor in terms of time and cost.

  Accordingly, an object of the present invention is to provide a joint strength estimation method and a joint condition determination method for a joint that can estimate the joint strength of the joint without performing a strength test in friction stir welding.

In the present invention, when a rotating welding tool is immersed along a immersing direction in an object to be bonded in which two members to be bonded are arranged in a predetermined immersing direction, and the two members to be bonded are friction stir bonded, 2 A joint strength estimation method for estimating the joint strength of a joint formed by joining two members to be joined,
In accordance with a predetermined be joining conditions, the portions thus the object to be bonded to the friction stir is deformed, the sectional shape after deformation in a plane containing the axis of the welding tool extending immersion direction, physical properties of the object to be bonded, thickness, bonding A shape calculation step for calculating the shape, pressing force, rotation speed, joining time, and immersion amount of the tool and calculating by numerical analysis,
And a strength calculation step of calculating a joint strength of the joint based on the cross-sectional shape after deformation calculated in the shape calculation step.

Even if the welding conditions such as the number of rotations of the welding tool, the pressure of the welding tool, the welding time, the push-in amount, and the shape of the welding tool are different, Same joint strength. In this invention, the cross-sectional shape after deformation | transformation of a to-be-joined object is calculated by numerical analysis, and the joining strength of a to-be-joined object is computed based on the joining state after the deformation | transformation of the to-be-joined thing calculated. Accordingly, the bonding strength of the bonded article can be obtained without actually performing friction stir welding.

The present invention, the shape calculation process, the cross-sectional shape after the deformation, the junction length corresponding to the outer diameter of the fluidized region object to be joined by frictional heat during the friction stir is partially fluidized Sato,
Extending perpendicular to the immersion direction to the hook point which is the most upstream point in the immersion direction of the boundary line extending between the two members to be joined, and the portion of the boundary line not affected by the immersion of the welding tool out calculated expressed by the bonding height corresponding to immersion direction dimension between the reference point away from each direction,
The strength calculating step is characterized in that the bonding strength of the bonded object is calculated based on the calculated bonding length and bonding height.

  The fracture form of the joint in the strength test is divided into a fracture form that occurs when the joint length is short and a fracture form that occurs when the joint height is long. The inventors have confirmed this by experiments. The bonding strength is closely related to the bonding length and the bonding height. In the present invention, the joint strength and the joint height related to the joint strength are calculated by numerical analysis, and the joint strength can be accurately estimated by obtaining the joint strength based on the joint length and the joint height. . For example, the bonding strength includes peeling strength and shear strength.

Further, the present invention provides a tool indentation analysis stage in which the shape calculation step is performed when the welding tool is immersed in the workpiece and the cross-sectional shape of the workpiece is calculated by numerical analysis when rotation is not performed. ,
Rotation analysis stage for calculating the strain distribution of the workpiece when the welding tool is further rotated from the cross-sectional shape of the workpiece calculated by the tool indentation analysis stage by numerical analysis,
And a fluidization region calculation step of calculating a fluidization region in which the workpiece is partially fluidized based on the strain distribution of the workpiece calculated by the rotation analysis step.

When trying to model friction stir welding strictly, it is necessary to consider the high speed rotation of the welding tool. However, since the amount of calculation becomes enormous, numerical analysis using such a strict model is difficult. In the present invention, numerical analysis is performed when the welding tool is immersed in the workpiece without rotating, and then numerical analysis is performed when the welding tool is rotated using the numerical analysis data when the welding tool is immersed. . By calculating the fluidization region in this way, the calculation can be simplified and the cross-sectional shape after deformation of the workpiece can be calculated.

According to the present invention, in the tool indentation analysis stage, the welding tool is pressed in the immersion direction with a pressurizing force according to a predetermined joining condition, and the heat input according to the joining condition is applied to the object to be joined. The cross-sectional shape and temperature distribution of the joined product are calculated by numerical analysis.

According to the present invention, the cross-sectional shape after deformation of the workpiece can be calculated in consideration of the frictional heat generated by friction stir welding by giving the workpiece a heat input amount according to the joining conditions. This makes it possible to calculate a cross- sectional shape that approximates the cross-sectional shape after deformation of the bonded product when the friction stir welding is actually performed. For example, when two members to be joined are made of an aluminum alloy, the strength related to deformation greatly changes due to a temperature rise due to frictional heat. In such a case, the cross-sectional shape after deformation of the workpiece can be accurately calculated by considering the strength change of the workpiece due to frictional heat as in the present invention.

Further, according to the present invention, in the rotation analysis stage, the contact portion of the workpiece to be contacted with the welding tool is forcibly rotated based on the cross-sectional shape of the workpiece and the temperature distribution calculated by the tool indentation analysis stage. The strain distribution of the workpiece is calculated by numerical analysis.

  In order to model the friction stir welding strictly, it is necessary to consider the dynamic recrystallization phenomenon in the fluidization region and the large plastic flow on the welding tool side in the fluidization region. However, since a specific mechanism in friction stir welding has not been elucidated, it is difficult to perform numerical analysis using such a strict model. In the present invention, numerical analysis can be performed in consideration of the frictional heat of friction stir welding by giving an amount of heat input according to the bonding conditions to the workpiece. Even if the specific mechanism is not clarified by this, the fluidization region approximated to the fluidization region when the friction stir welding is actually performed can be calculated.

Further, in the present invention, the shape calculation step includes a joining length calculation step of calculating a joining length corresponding to the outer diameter dimension of the fluidization region based on the fluidization region calculated by the fluidization region calculation step;
Based on the cross-sectional shape calculated by the tool indentation analysis stage, the hook point that is the most upstream point in the immersion direction among the boundary lines extending between the two members to be joined , and the influence of the immersion of the joining tool among the boundary lines A joining height calculation step for calculating a joining height corresponding to a dimension in the immersive direction between the reference point separated in the extending direction perpendicular to the immersive direction , up to a portion not subjected to
The strength calculation step is characterized by calculating the joint strength of the joint based on the joint length calculation result and the joint height calculation result.

  There are two types of fractures in the strength test: a fracture mode that occurs when the junction length is short, and a fracture mode that occurs when the junction height is long. Therefore, the bonding strength is closely related to the bonding length and the bonding height. In the present invention, based on the fluidization region calculated in the fluidization region calculation step, the joint length and the joint height related to the joint strength are calculated by numerical analysis. By determining the bonding strength based on the bonding length and the bonding height, the bonding strength can be accurately estimated.

Further, according to the present invention, the shape calculation step is based on the cross-sectional shape of the workpiece calculated by the tool indentation analysis stage and the fluidization region of the workpiece calculated by the fluidization region calculation step. Numerical analysis of the cross-sectional shape of the object to be joined when the pressing structure having the fluidized region and the member to be welded upstream in the immersion direction is pressed against the member to be welded downstream in the immersion direction according to predetermined joining conditions. The method further includes a step of pushing the member to be joined to calculate,
The joining height calculation step is characterized in that the joining height is calculated based on the cross-sectional shape of the article to be joined, which is calculated in the joined member pushing step.

  According to the present invention, the state in which the pressing structure is pressed against the member to be joined on the downstream side in the immersion direction is numerically analyzed. When the pressing structure presses the member to be welded downstream in the immersion direction, the member to be welded downstream in the immersion direction is partially raised in the vicinity of the fluidization region and radially outward and partially upstream in the immersion direction. To do. By calculating the hook point based on this uplift phenomenon, the following effects can be obtained. That is, the hook point can be calculated easily and with high accuracy, and the joining height can be obtained with high accuracy.

Further, the present invention is based on the cross-sectional shape after deformation of the article to be joined calculated by the shape calculating step, and the thickness dimension of the joined member on the upstream side in the immersion direction and the thickness dimension of the joined member on the downstream side in the immersion direction. The method further includes a plate thickness calculating step of calculating.

  According to the present invention, the plate thickness of each member to be joined can be estimated without actually measuring the plate thickness by calculating the plate thickness of each member to be joined by the plate thickness calculating step.

Further, in the present invention, in the case where two members to be bonded are aligned in a predetermined immersion direction, a rotating welding tool is immersed along the immersion direction, and when these two members to be bonded are subjected to friction stir welding, A deformation state estimation method for estimating a cross-sectional shape after deformation of a joint formed by joining two members to be joined,
The cross-sectional shape in the plane including the axis of the welding tool extending in the immersion direction of the portion where the workpiece is deformed when the welding tool is immersed in the workpiece and not rotating is determined . Enter the physical property value, thickness dimension, welding tool shape, pressure, number of rotations, welding time and immersion amount, and calculate the tool indentation analysis stage by numerical analysis,
Rotation analysis stage for calculating the strain distribution of the workpiece when the welding tool is further rotated based on the cross-sectional shape of the workpiece calculated by the tool indentation analysis stage, by numerical analysis,
Deformation of a joint comprising a fluidization region calculation step for calculating a fluidization region in which the workpiece is partially fluidized based on the strain distribution of the workpiece calculated by the rotation analysis step. It is a state estimation method.

  According to the present invention, when trying to model friction stir welding strictly, it is necessary to consider the high speed rotation of the welding tool. However, since the amount of calculation becomes enormous, numerical analysis using such a strict model is difficult. In the present invention, numerical analysis is performed when the welding tool is immersed in the workpiece without rotating, and then numerical analysis is performed when the welding tool is rotated using the numerical analysis data when the welding tool is immersed. . By calculating the fluidization region in this way, the calculation can be simplified and the bonded state after deformation of the workpiece can be calculated. For example, the bonded state after the deformation of the object to be bonded includes the above-described bonding length and bonding height.

According to the present invention, in the tool indentation analysis stage, the welding tool is pressed in the immersion direction with a pressurizing force according to a predetermined joining condition, and the heat input according to the joining condition is applied to the object to be joined. Calculate the cross-sectional shape and temperature distribution of the joint by numerical analysis,
The rotation analysis stage is based on the cross-sectional shape and temperature distribution of the workpiece to be calculated in the tool indentation analysis stage, and the distortion of the workpiece when the contact part of the workpiece with the welding tool is forcibly rotated. The distribution is calculated by numerical analysis.

According to the present invention, the cross-sectional shape after deformation of the workpiece can be calculated in consideration of the frictional heat generated by friction stir welding by giving the workpiece a heat input amount according to the joining conditions. As a result, it is possible to calculate a cross-sectional shape that approximates the bonded state after deformation of the bonded product when the friction stir welding is actually performed. For example, when two members to be joined are made of an aluminum alloy, the strength related to deformation greatly changes due to a temperature rise due to frictional heat. In such a case, the joined state after deformation of the article to be joined can be accurately calculated by considering the strength change of the article to be joined due to frictional heat as in the present invention.

  In order to model the friction stir welding strictly, it is necessary to consider the dynamic recrystallization phenomenon in the fluidization region and the large plastic flow on the welding tool side in the fluidization region. However, since a specific mechanism in friction stir welding has not been elucidated, it is difficult to perform numerical analysis using such a strict model. In the present invention, numerical analysis can be performed in consideration of the frictional heat of friction stir welding by giving an amount of heat input according to the bonding conditions to the workpiece. Even if the specific mechanism is not clarified by this, the fluidization region approximated to the fluidization region when the friction stir welding is actually performed can be calculated.

Further, in the present invention, in the case where two members to be bonded are aligned in a predetermined immersion direction, a rotating welding tool is immersed along the immersion direction, and when these two members to be bonded are subjected to friction stir welding, A joining condition determining method for determining a joining condition in which a joining strength of a joined article formed by joining two members to be joined is within a predetermined range,
A joining length calculation step for calculating a joining length corresponding to the outer diameter of the fluidized region where the workpiece is partially fluidized by frictional heat at the time of friction stirring, by numerical analysis for each predetermined joining condition; ,
Extending perpendicular to the immersion direction to the hook point which is the most upstream point in the immersion direction of the boundary line extending between the two members to be joined, and the portion of the boundary line not affected by the immersion of the welding tool A joint height calculating step for calculating a joint height corresponding to a dimension in the immersive direction between the reference points separated in the direction by numerical analysis for each predetermined joint condition;
A strength calculation stage for calculating the joint strength of each joint based on the joint length calculation result and the joint height calculation result calculated for each predetermined joining condition;
A joining condition determining method comprising: a joining condition extracting step of extracting a joining condition having a joining strength that falls within a predetermined joining strength range based on a calculation result calculated by the strength calculating step.

  According to the present invention, it is possible to determine bonding conditions that fall within a predetermined bonding strength range. As a result, it is possible to select optimum construction conditions after ensuring the required bonding strength, and to improve convenience.

According to the present invention, the cross-sectional shape after deformation of the workpiece is calculated by numerical analysis, and the bonding strength is calculated based on the bonded state after deformation. By calculating the bonding strength of the bonded article after bonding from the calculated bonded state of the bonded article, it is not necessary to perform a strength test on the bonded article. Further, by obtaining the cross-sectional shape after deformation by numerical analysis, it is not necessary to experimentally measure the joint state after deformation of the joint. That is, it is possible to determine the joint strength of the joint without actually performing friction stir welding. Therefore, since the joining strength when the joining conditions are changed can be easily obtained, the joining conditions that achieve the target joining strength can be easily obtained, and the time and cost spent for setting the joining conditions can be reduced. it can.

  According to the present invention, the joining length and the joining height are calculated, and the joining strength is determined based on the computed joining length and the joining height. As a result, the bonding strength can be accurately estimated.

Further, according to the present invention, in order to calculate the cross-sectional shape after deformation of the object to be joined when the rotating welding tool is pushed into the object to be joined, the numerical analysis is divided into the tool indentation analysis stage and the rotation analysis stage. I do. By calculating the fluidization region in this manner, it is not necessary to perform numerical analysis of the high-speed rotation of the welding tool, and the cross-sectional shape after deformation of the workpiece can be calculated by simplifying the calculation. Further, by simplifying the calculation, the fluidization region can be calculated in a short time.

Further, according to the present invention, by giving a heat input corresponding to the frictional heat to the object to be bonded, it is possible to obtain a bonded state after the deformation of the object to be bonded in consideration of the frictional heat. The cross-sectional shape approximated to the cross- sectional shape after deformation in the case can be calculated. Thus, the calculated cross-sectional shape can be brought close to the actual cross-sectional shape after deformation, and the deformed shape can be calculated with higher accuracy.

Further, according to the present invention, the fluidization region is calculated based on the deformed cross-sectional shape considering the temperature distribution corresponding to the frictional heat. As a result, it is possible to calculate a fluidization region that approximates the fluidization region when the friction stir welding is actually performed, and it is possible to calculate the fluidization region with higher accuracy.

  According to the invention, the joining length and the joining height are calculated based on the fluidizing region calculated in the fluidizing region calculating step. Accordingly, the joining length and the joining height can be calculated with higher accuracy, and as a result, the joining strength can be calculated with higher accuracy.

  Further, according to the present invention, the pressed member is pressed against the member to be welded downstream in the immersion direction, so that the member to be welded downstream in the immersion direction partially rises upstream in the immersion direction. By calculating the hook point based on this uplift phenomenon, the hook point can be easily and accurately calculated. As a result, the bonding strength can be calculated with higher accuracy.

Moreover, according to this invention, the plate | board thickness of each to-be-joined member can be calculated by a plate | board thickness calculation process. Moreover, the plate | board thickness of each to-be-joined member cannot be measured from the external appearance of a joining thing, and it is difficult to obtain | require it by a test. In the present invention, the plate thickness of each workpiece can be estimated without performing a test. As a result, the thickness of each member to be joined, which is one measure of the joining quality, can be obtained and used for estimation of joining strength, and convenience can be improved.
Further, according to the present invention, the numerical analysis is performed when the welding tool is immersed in the workpiece without rotating, and then the welding tool is rotated using the numerical analysis data when the welding tool is immersed. Numerical analysis. By calculating the fluidization region in this way, the calculation can be simplified and the bonded state after deformation of the workpiece can be calculated. For example, the bonded state after the deformation of the object to be bonded includes the above-described bonding length and bonding height.
Further, according to the present invention, the cross-sectional shape after deformation of the workpiece can be calculated in consideration of the frictional heat generated by friction stir welding by giving the workpiece the amount of heat input according to the joining conditions. As a result, it is possible to calculate a cross-sectional shape that approximates the bonded state after deformation of the bonded product when the friction stir welding is actually performed. For example, when two members to be joined are made of an aluminum alloy, the strength related to deformation greatly changes due to a temperature rise due to frictional heat. In such a case, the joined state after deformation of the article to be joined can be accurately calculated by considering the strength change of the article to be joined due to frictional heat as in the present invention.

  Further, according to the present invention, it is possible to determine a joining condition that falls within a predetermined joining strength range. As a result, it is possible to select optimum construction conditions after ensuring the required bonding strength, and to improve convenience.

  FIG. 1 is a flowchart showing an estimation procedure of a bonding strength estimation method according to an embodiment of the present invention. The joint strength estimation method of the present invention is a method for estimating the joint strength of a joint that has been friction stir welded without actually performing friction stir welding. In general, a joining condition relating to friction stir welding is obtained in the joining condition obtaining step s1. Next, the deformation state of the objects to be joined at the time of joining is calculated by numerical analysis in the shape calculating step s2. Next, in the strength calculation step s3, the joint strength of the joint that will be joined by friction stir welding is calculated.

  FIG. 2 is a cross-sectional view showing a joining procedure of friction stir welding, and proceeds in the order of FIG. 2 (1) to FIG. 2 (4). Friction Stir Welding (abbreviated as FSW) joins two members 1 and 2 arranged in a predetermined reference direction A. The two members to be bonded 1 and 2 before bonding constitute the object to be bonded 3. The friction stir welding method is used for spot joining in which the members to be joined 1 and 2 are locally joined using a friction stir welding apparatus 10 described later.

  Friction stir welding is performed using a cylindrical welding tool 4. The joining tool 4 has a main body portion 5 formed in a substantially cylindrical shape, and a pin portion 6 that protrudes from the main body portion 5 in one axial direction and is formed in a substantially cylindrical shape. The main body 5 has a shoulder surface 7 which is an end surface on the one A1 side in the axial direction. The shoulder surface 7 is formed substantially perpendicular to the axis L <b> 1 of the welding tool 4. The pin portion 6 projects vertically from the shoulder surface 7. The main body portion 5 and the pin portion 6 are formed coaxially, and the outer shape of the pin portion 6 is smaller than the outer shape of the main body portion 5.

  When the welding tool 4 is immersed in the workpiece 3 while rotating, the workpiece 3 is partially fluidized by frictional heat with the welding tool 4 and the fluidized region is agitated. The fluidized members 1 and 2 that are fluidized in the object 3 are mixed together. Thereafter, the joined members 1 and 2 are joined by solidifying the fluidized portion. The members 1 and 2 are made of, for example, an aluminum alloy.

  For example, as for the joining tool 4, the diameter of the pin part 6 is set to 5 mm, the diameter of the main-body part 5 is set to 10 mm, and the protrusion amount which the pin part 6 protrudes from the main-body part 5 is set to 3 mm. Further, the joining tool 4 is chamfered.

  FIG. 3 is a perspective view showing the friction stir welding apparatus 10. The friction stir welding apparatus 10 (hereinafter simply referred to as a joining apparatus 10) includes a tool holding portion 11, a rotation driving means 12, a displacement driving means 13, a receiving base 14, a base 15, and a control means 16. Consists of. The joining apparatus 10 is set with a predetermined reference axis L1. The tool holding part 11 hold | maintains the joining tool 4 so that attachment or detachment is possible. The attached tool holder 11 is arranged such that its axis is coaxial with the reference axis L <b> 1 of the joining device 10. The rotation driving unit 12 drives the tool holding unit 11 to rotate around the reference axis L1. The displacement driving unit 13 drives the tool holding unit 11 in the reference directions A1 and A2 extending along the reference axis L1.

  The cradle 14 is provided at a position facing the tool holding portion 11 in the reference direction A, and supports the workpiece 3 from the side opposite to the welding tool 4. The base 15 is connected to the distal end portion of the robot arm 17 and directly or indirectly supports the tool holding unit 11, the driving units 12 and 13, and the cradle 14. The base 15 is a so-called C gun and is formed in a substantially C shape. The cradle 14 is provided at one end 15a in the circumferential direction of the base 15 formed in a C shape. Moreover, the tool holding | maintenance part 11 is provided in the circumferential direction other end part 15b of the base 15 formed in C shape. The control unit 16 controls the rotation driving unit 12 and the displacement driving unit 13. The control means 16 is realized by a microcomputer or the like, and the rotation driving means 12 and the displacement driving means 13 are realized by servo motors.

  The friction stir welding method is performed according to the procedure shown in FIG. First, an operator or the like attaches the welding tool 4 to the tool holding unit 11. Further, the workpiece 3 is held at a predetermined holding position. When such preparation for joining is completed, the control means 16 starts the joining operation.

  The control means 16 displaces and moves the base 15 to the predetermined joining standby position by the robot arm 17. When the base 15 is placed at the joining standby position, the joining tool 4 is placed at an interval in the reference direction A with respect to the target joining position set on the workpiece 3. The cradle 14 comes into contact with the workpiece 3 from the side opposite to the welding tool 4. Further, the direction in which the members 1 and 2 are lined up coincides with the reference direction of the bonding apparatus 10.

  Next, the control unit 16 controls the rotation driving unit 12 to rotate the tool holding unit 11 around the reference axis L1. Further, the control means 16 controls the displacement driving means 13 to move the tool holding portion 11 in one reference direction A1. As a result, as shown in FIG. 2 (1), the welding tool 4 moves toward the workpiece 3 while rotating, and enters the workpiece 3 as shown in FIG. 2 (2).

  The welding tool 4 is immersed in the workpiece 3 and then slides against the workpiece 3 while rotating as shown in FIG. Due to this frictional heat, a fluidized region 8 that partially fluidizes is formed in the workpiece 3. The fluidizing region 8 mixes the two members 1 and 2 to each other. In this way, the workpiece 3 is so-called solid phase agitation.

  When a predetermined stirring time elapses after the welding tool 4 comes into contact with the workpiece 3, the control unit 16 controls the displacement driving unit 13 to move the tool holding unit 11 in the other reference direction A <b> 2. Thereby, as shown in FIG. 2 (4), the welding tool 4 is separated from the workpiece 3. Further, the control means 16 controls the rotation driving means 12 to stop the rotation of the tool holding unit 11, and the control means 16 ends the joining operation.

  When the welding tool 4 is detached from the workpiece 3, the fluidized region 8 is hardened as the temperature of the workpiece 3 decreases. As a result, a joined product in which the two members 1 and 2 are joined is formed. In the present invention, the two members to be bonded 1 and 2 before joining are collectively referred to as an object 3 to be bonded, and the two members to be bonded 1 and 2 after bonding are collectively referred to as a bonded object.

  FIG. 4 is a block diagram showing an arithmetic unit 20 that executes the bonding strength estimation method of the present invention. The joint strength estimation method of the present invention is performed by the arithmetic unit 20. The computing device 20 includes an input means 21, an output means 22, a computing means 23, and a storage means 24. The input means 21 receives a welding condition and calculation start command regarding friction stir welding from an operator or the like. The output unit 22 outputs the bonding strength calculated by the calculation unit 23. The storage unit 24 temporarily stores a calculation program to be executed by the calculation unit 23 and data calculated at the time of calculation. The calculation means 23 reads the calculation program memorize | stored in the memory | storage means 24, and performs each procedure of a joining strength estimation method one by one by executing the calculation program.

Such an arithmetic unit 20 is realized by a computer. For example, the input means 21 is realized by a keyboard and a pointing device. The output means 22 is realized by a display device such as a display. The storage means 24 is a RAM (Random
The arithmetic means 23 is realized by an arithmetic circuit realized by a microcomputer or the like, for example, a CPU (Central Processing Unit).

The outline of the procedure for calculating the bonding strength will be described. As shown in FIG. 1, when the operator operates the input means 21 to give a calculation command for the bonding strength, the calculation means 23 estimates the bonding strength. The operation is started and the process proceeds to the joining condition acquisition step s1. In the joining condition obtaining step s <b> 1, the calculation unit 23 acquires a joining condition related to friction stir welding from the input unit 21. For example, Table 1 shows examples of joining conditions.

  As shown in Table 1, the given joining conditions include physical property values corresponding to the materials of the members to be joined, the thickness direction dimensions of the members to be joined, and friction stirring conditions.

  The friction stir conditions include the shape of the welding tool, the pressing force that pressurizes the object to be joined by the welding tool, the number of rotations of the welding tool, the bonding time that is the immersion time of the welding tool, and the amount of immersion of the welding tool. .

  The physical property values according to the material of the member to be joined include longitudinal elastic modulus, Poisson's ratio, yield stress, stress strain relationship, friction coefficient, density, thermal expansion coefficient, specific heat, and thermal conductivity. Including. The stress-strain relationship indicates the amount of plastic true strain that deforms the bonded member when a predetermined true stress is applied. In the present embodiment, A6N01-T5 defined in Japanese Industrial Standard (JIS) is used as each member to be joined.

  In the present embodiment, among the physical property values of each member to be joined, the property value for each temperature is given for the physical property value having temperature dependency. Therefore, the characteristics for each temperature in the longitudinal elastic modulus, the yield stress, and the stress-strain relationship are shown in Tables 2 to 4, respectively.

When the calculation means 23 acquires the joining conditions shown in Tables 1 to 4, the process proceeds to the shape calculation step s2.
In the shape calculation step s2, the calculation means 23 calculates the deformation state of the workpiece 3 by numerical analysis based on the joining condition acquired in the joining condition acquisition step s1, and proceeds to the strength calculation step s3. In the strength calculation step s3, the computing unit 23 calculates the joint strength of the joined object based on the deformation state of the article 3 to be joined calculated in the shape calculating step s2, and proceeds to the end step s4. In the end step, the calculation means 23 causes the output means 22 to output the calculated joining strength, and the joining strength calculating operation is finished. Numerical analysis is performed using a finite element method.

  When the given joining conditions are different, the deformation state of the article to be joined 3 changes. However, even if the joining conditions are different, it has been clarified by experiments that when the joined state after deformation of the article to be joined 3 is the same, the joining strength is almost the same. Therefore, as described above, the deformation state of the article to be bonded 3 is calculated by numerical analysis, and based on the bonding state after the deformation, the bonding strength of the bonded object after bonding can be calculated regardless of the bonding conditions. .

  FIG. 5 is an enlarged cross-sectional view of the workpiece 3. In the present invention, the direction in which the welding tool 4 is immersed in the workpiece 3 is defined as an immersion direction B, and the direction perpendicular to the immersion direction B is defined as an extending direction C. Further, when the welding tool 4 is immersed, the axis line L1 of the welding tool 4 that will pass through the workpiece 3 is referred to as the central axis line L1, and the position to be bonded is referred to as the bonding position 30. Further, the member 1 to be joined on the upstream side in the immersion direction is referred to as a first member 1 and the member 2 to be joined on the downstream side in the immersion direction is referred to as a second member 2.

  The fluidized region 8 is formed in a portion adjacent to the welding tool 4 when the rotating welding tool 4 is immersed in the workpiece 3. The fluidizing region 8 is formed in a ring shape centered on the central axis L1. Of the boundary lines 31 between the first bonded member 1 and the second bonded member 2, the boundary line 31 a in the vicinity of the fluidizing region 8 is located upstream in the immersion direction along the outer peripheral surface 32 of the fluidizing region 8. Raise.

  Further, the plate thickness of each of the members 1 and 2 at the separation position 33 sufficiently separated from the joining position 30 in the extending direction C is not affected by the immersion of the joining tool 4 and is the same as that before joining. In the present invention, one point among the boundary lines 31 where the members 1 and 2 are not affected by the immersion of the welding tool 4 is referred to as a reference point P1. In other words, the reference point P1 is a point at a position away from the joining direction in the extending direction C with respect to the joining position where the joining tool 4 is immersed in the boundary line 31. Further, the point on the boundary line 31a in the vicinity of the fluidization region 8 and the most upstream in the immersion direction is referred to as a hook point P2.

  In one embodiment of the present invention, the joining length D and the joining height H are calculated as indices indicating the deformation state of the article 3 to be joined. The joining length D corresponds to the outer diameter of the fluidized region 8 where the workpiece 3 is partially fluidized by frictional heat during friction stirring. As shown in FIG. 5, when the workpiece 3 is cut by a virtual plane that includes the reference point P1 and extends along the central axis L1, as shown in FIG. Of the boundary line 31 between the two points n1 and n2 that are located downstream of the hook point P2 in the immersion direction and that are on both sides of the reference axis L1 in the extending direction C and closest to the reference axis L1. Directional dimension.

  In other words, when the workpiece 3 is cut by the virtual plane, it proceeds along the boundary line 31 from a position far from the reference axis L1 in the extending direction one side, and before reaching the hook point P2. A point n1 that is closest to the reference axis L1 and a point n2 that is closest to the reference axis L1 before reaching the hook point P2 after traveling along the boundary line 31 from a position that is far from the reference axis L1 in the other extending direction. The dimension in the extending direction therebetween is the joint length D. The joining height H is a dimension in the immersion direction between the reference point P1 and the hook point P2 described above.

  FIG. 6 is a graph showing the relationship between the peel strength and the bonded state after deformation according to experiments. In FIG. 6, the vertical axis represents the peel strength. The horizontal axis indicates the bonding area and hook ligament. The bonding area increases as it goes to the right along the horizontal axis. Further, the hook ligament becomes smaller along the horizontal axis toward the right side.

The bonding area is determined based on the bonding length D. Specifically, the junction area A is represented by (D / 2) ² · π−r ² · π where D is the junction length and r is the radius of the pin portion 6. In this equation, multiplication is represented by an arithmetic symbol “·”. The hook ligament is obtained based on the joining height H. Specifically, the hook ligament represents the thickness Tu of the first member to be joined at the hook point P2. The hook ligament is represented by T1-H, where H is the joining height and T1 is the thickness of the first joined member 1 before joining.

  The peel strength is a force that can be withstood until the members 1 and 2 are separated from each other when the members 1 and 2 are separated from each other and in a direction parallel to the central axis L1. It is. As shown in FIG. 6, the peel strength and the bonding area are in a correspondence relationship. The larger the bonding area, that is, the bonding length D, the greater the peel strength. Based on the experimental results, when plot points 32 indicating the peel strength corresponding to the bonding area are plotted on the graph, the plot points 32 are arranged along a first approximate line 30 that is predetermined on the graph.

  Similarly, hook ligament and peel strength are in a corresponding relationship. The larger the hook ligament, that is, the smaller the joint height, the greater the peel strength. When plot points 33 indicating the peel strength corresponding to the hook ligament are plotted on the graph based on the experimental results, the plot points 33 are arranged along a second approximate line 31 that is predetermined on the graph.

  Such a relationship shows a certain tendency regardless of the number of rotations of the tool 4, the applied pressure, the joining time, and the like. Therefore, the peel strength, which is one of the joining strengths, is determined by the joining state after deformation of the joined article after joining, specifically, the joining length D and the joining height H, regardless of joining conditions.

  FIG. 7 is a cross-sectional view showing a fractured form of the bonded article in the peel strength test. As the amount of heat applied to the workpiece 3 increases, the bonding area increases and the hook ligament decreases. That is, as a tendency, the bonding area and the hook ligament have an inversely proportional relationship.

When the hook ligament is small (indicated by reference numeral 34 in FIG. 6), the fracture form shown in FIG. In this case, since the joining height H is large, the crack extends from the hook point P toward the surface 36 on the upstream side in the immersion direction of the first joined member 1, so that the first joined member 1 becomes the fluidized region 8 and Separated from the second bonded material 2. If the peel strength at this time is defined as the first peel strength, the first peel strength can be obtained experimentally. For example, the first peel strength P ₁ can be approximated as α ₁ · (F · D · π). In the above equation, α ₁ indicates a first coefficient determined according to the joining condition, and is, for example, 135. F represents a hook ligament, D represents a joining length, and π represents a circumference. Note that this approximate expression is an example, and another approximate expression may be used.

When the joining area is small (denoted by reference numeral 35 in FIG. 6), the fracture form shown in FIG. 7 (2) is shown. In this case, a crack extends from the hook point P toward the central axis L <b> 1, and the first member 1 and the fluidized region 8 are separated from the second member 2. If the peel strength at this time is the second peel strength, the second peel strength can also be obtained experimentally. For example, the second peel strength P ₂ can be approximated as α ₂ · A. In the previous equation, α ₂ indicates a second coefficient determined according to the joining condition, and is 216, for example. A represents the bonding area. Note that this approximate expression is an example, and another approximate expression may be used.

  The breaking form in the peel strength test is the breaking form shown in either FIG. 7 (1) or FIG. 7 (2). In order to increase the peel strength, it is preferable to increase the joint area and the hook ligament. However, since both relations are inversely related, both cannot be achieved. Therefore, the joint area and the hook ligament where the peel strength is maximized are determined in consideration of the combination of both. Specifically, the joint area and hook ligament where the peel strength is maximized are the joint area and hook ligament represented by the intersection P3 between the first approximate curve 30 and the second approximate curve 31 shown in FIG.

Further, when the joining length D and the joining height H are given, the actual peel strength P of the object to be joined is represented by Min (P ₁ , P ₂ ). That is, the first peel strength P ₁ is calculated, of the second peeling strength P _2, smaller becomes the peel strength of the actual object to be bonded.

  FIG. 8 is a graph showing the relationship between the experimental shear strength and the bonded state after deformation. In FIG. 8, the vertical axis represents the shear strength. The horizontal axis indicates the bonding area and hook ligament. The bonding area increases as it goes to the right along the horizontal axis, and the hook ligament decreases as it goes to the right along the horizontal axis. The definition of the bonding area and the hook ligament is the same as described above. The shear strength is a force that can be withstood until the members 1 and 2 are separated from each other when the force is applied to the members 1 and 2 in a direction away from each other and perpendicular to the central axis L1. It is.

  As shown in FIG. 8, the bonding area and the shear strength are in a correspondence relationship. The greater the joining area, that is, the joining length D, the greater the shear strength. When plot points 39 indicating the shear strength corresponding to the joint area are plotted on the graph based on the experimental results, the plot points 39 are arranged along a third approximate line 37 that is predetermined on the graph.

  Similarly, hook ligament and shear strength are in a corresponding relationship. The greater the hook ligament, that is, the smaller the joint height, the greater the shear strength. However, after the hook ligament exceeds a predetermined boundary value, the shear strength becomes a substantially constant value. When plot points 40 indicating the shear strength corresponding to the hook ligament are plotted on the graph based on the experimental results, the plot points 40 are arranged along a fourth approximate line 38 that is predetermined on the graph.

  Such a relationship shows a certain tendency regardless of the number of rotations of the tool 4, the applied pressure, the joining time, and the like. Therefore, the shear strength, which is one of the joining strengths, is determined by the joining state after deformation of the joined article after joining, specifically, the joining length D and the joining height H, regardless of joining conditions.

  FIG. 9 is a cross-sectional view showing a fractured form of the bonded product in the shear strength test. As the amount of heat applied to the workpiece 3 increases, the bonding area increases and the hook ligament decreases. That is, as a tendency, the joint area and the hook ligament have an inversely proportional relationship.

When the hook ligament is small (indicated by reference numeral 34 in FIG. 9), the fracture form shown in FIG. 9 (1) is shown. In this case, the fracture state differs on both sides in the shear direction. On one side 41 in the shear direction, a crack extends from the hook point P toward the upstream surface 36 in the immersion direction of the first member 1 to be joined, so that the first member 1 is joined to the fluidized region 8 and the second joint. Separate from material 2. On the other side 42 in the shear direction, a crack extends from the hook point P toward the central axis L <b> 1, and the first member 1 and the fluidized region 8 are separated from the second member 2. If the shear strength at this time is the first shear strength, the first shear strength can be obtained experimentally. For example, the first shear strength S ₁ can be approximated to β ₁ · F + γ. In the previous equation, β ₁ and γ indicate a third coefficient and a fourth coefficient determined according to the joining condition, respectively. For example, β ₁ is 1576 and γ is 3296. F indicates a hook ligament. Note that this approximate expression is an example, and another approximate expression may be used.

When the joining area is small (denoted by reference numeral 35 in FIG. 9), the fracture form shown in FIG. 9 (2) is shown. In this case, a crack extends from the hook point P toward the central axis L <b> 1, and the first member 1 and the fluidized region 8 are separated from the second member 2. If the shear strength at this time is the second shear strength, the second shear strength can also be obtained experimentally. For example, the second shear strength S ₂ can be approximated to β ₂ · A. In the previous equation, β ₂ represents a fifth coefficient determined according to the joining condition, and is, for example, 177. Note that this approximate expression is an example, and another approximate expression may be used.

  The fracture mode in the shear strength test is the fracture mode shown in either FIG. 9 (1) or FIG. 9 (2). In order to increase the shear strength, it is preferable to increase the joint area and the hook ligament. However, since both relations are inversely related, both cannot be achieved. Therefore, the joint area and the hook ligament where the shear strength is maximized are determined in consideration of the combination of both. Specifically, the joint area and hook ligament where the shear strength is maximized are the joint area and hook ligament represented by the intersection P4 of the third approximate curve 37 and the fourth approximate curve 38 shown in FIG.

Further, when the joining length D and the joining height H are given, the shear strength can be obtained based on the following formula. The actual shear strength S of the article to be joined is represented by Min (S ₁ , S ₂ ). That is, the smaller one of the calculated first shear strength S ₁ and second shear strength S ₂ is the actual shear strength of the article to be joined.

  In the shape calculation step s1, the joining length D and the joining height H are calculated by numerical analysis. Based on the calculated joining length D and joining height H, the joining strength of the joined product after joining can be obtained. Specifically, the shape calculating means s1 includes a tool indentation analysis stage a1, an indentation analysis result acquisition stage a2, a tool rotation analysis stage a3, a rotation analysis result acquisition stage a4, a fluidization region calculation stage a5, It includes a length calculation step a6, a joined member pushing step a7, and a joining height calculation step a8.

  Note that the friction stir welding model for performing numerical analysis is performed by an axisymmetric model with respect to the central axis L1. The shape calculating step s2 can be realized by executing a calculation program based on the joining condition given to the input unit 21 by the calculation unit 23.

  FIG. 10 is a diagram illustrating a simulation result in the tool indentation analysis stage a1. Tool indentation analysis is performed in the order of FIGS. 10 (1) to 10 (6). In the tool indentation analysis stage a1, based on the joining conditions given in the joining condition acquisition step s1, the deformation state when the joining tool 4 is pushed into the workpiece 3 without rotating is calculated by numerical analysis.

  In the numerical analysis, an axially symmetric model including the joining tool 4, the members 1 and 2 to be joined, and the cradle 14 is used. Further, the joining tool 4 and the cradle 14 are rigid bodies, and the strength of each of the members 1 and 2 to be joined is determined based on the material given according to the joining conditions. Further, the pressing force with which the welding tool 4 presses the workpiece 3 is given according to the bonding conditions.

  In the embodiment of the present invention, the welding tool 4 is pressed against the workpiece 3 and the amount of heat input according to the welding conditions is given to the contact portion 3 a of the workpiece 3 that contacts the welding tool 4. The amount of heat input q per unit time given to the contact portion 3a is expressed by the following equation.

Here, π is a circumferential ratio, μ is a friction coefficient, P is a pressure (N / mm ² ) applied to the contact interface between the welding tool 4 and the workpiece 3, and N is the welding tool 4. The number of revolutions per second (rev / sec), and R is the radius from the central axis L1 to the contact interface. Such an amount of heat input is sequentially given according to the time change of the indentation of the workpiece. In addition, each to-be-joined member 1 and 2 is set so that the intensity | strength may change based on the intensity | strength change by the temperature according to the material. For example, when the members 1 and 2 are made of an aluminum alloy, the strength is set to be lower than that of the room temperature portion in the portion that is hotter than the room temperature portion according to the strength-temperature characteristics of the aluminum alloy.

  In FIG. 10, the temperature distribution of each member 1 and 2 is shown in gray. FIG. 11 is a graph showing the temperature change of each member 1 and 2 over time. In FIG. 11, the solid line 43 indicates the temperature change on the upstream surface of the first member 1 to be joined in the immersion direction. A change in temperature inside the second member 2 is indicated by a broken line 44. Further, a change in temperature of the surface of the second joined member 2 on the downstream side in the immersion direction is indicated by a one-dot chain line 45.

  The temperatures of the members 1 and 2 increase with time. Further, the temperatures of the members 1 and 2 are increased as they approach the welding tool 4. As shown in FIGS. 10 (1) to 10 (6), numerical calculation is sequentially repeated, and when the deformation state and temperature distribution of the workpiece 3 when the welding tool 4 reaches a predetermined immersion amount are obtained, indentation analysis is performed. The process proceeds to the result acquisition stage a2. In the indentation analysis result acquisition stage a2, data indicating the deformation state and temperature distribution of the workpiece 3 calculated in the tool indentation analysis stage a1 is extracted.

  Next, a tool rotation analysis stage a3 is performed. In the tool rotation analysis stage a3, the strain distribution of the article 3 around the central axis L1 is obtained by using the deformation state and temperature distribution of the article 3 acquired in the indentation analysis result acquisition stage a2.

  FIG. 12 is a diagram illustrating a simulation result in the tool rotation analysis stage a3. Specifically, in the axially symmetric model, the strain distribution of the workpiece 3 is calculated when a stress is applied to rotate the contact portion of the workpiece 3 that contacts the welding tool 4 around the central axis L1. In FIG. 13, the distorted area | region 51 among the 1st to-be-joined members 1 is shown by gray display.

  FIG. 13 is a diagram illustrating plastic strain that rotates around the central axis L <b> 1 of a portion at an arbitrary distance from the pin portion 6 in the first bonded member 1. FIG. 13 (1) and FIG. 13 (2) show a case where numerical analysis is performed when the joining conditions are different. In FIG. 13, a solid line 46 indicates a case where the contact portion is displaced by 360 degrees. A case where the angle is displaced by 180 degrees is indicated by a broken line 47, and a case where the angle is displaced by 90 degrees is indicated by a dashed line 48. As shown in FIG. 13, the amount of strain decreases as the distance from the welding tool 4 in the extending direction C decreases, and when the distance from the welding tool 4 sufficiently extends in the extending direction C, distortion due to the rotation of the welding tool 4 disappears.

  FIG. 14 is a graph showing the width of the strain critical region 50 where the strain around the central axis L1 becomes zero and the angle at which the contact portion is forcibly rotated. The width of the strain critical region 50 is the outer peripheral diameter of the critical surface in the region where the shear strain is generated. Those having the same shape of the plot points in FIG. 14 indicate the same joining conditions. As shown in FIG. 14, in the numerical analysis, the position in the extending direction C where the strain around the central axis L1 is eliminated does not change regardless of whether the angle for forcibly rotating the contact portion is 90 degrees or 360 degrees. Therefore, even if the welding tool 4 is rotated 360 degrees or more, the strain critical region 50 does not change greatly. Therefore, the position in the extending direction C in which the distortion around the central axis L1 is eliminated is almost constant regardless of the rotation angle, and 90 degrees is sufficient for rotating the contact portion in order to reduce the calculation amount. .

  FIG. 15 is a diagram showing a case where the maximum width of the fluidized region 8 is obtained by experiment for the fluidized region and a case where the width of the strain critical region 50 is calculated under the same joining condition as the joining condition in the experiment. The maximum width of the fluidization region 8 means the maximum outer diameter of the fluidization region 8. As shown in FIG. 15, the width of the strain critical region 50 obtained by numerical calculation is almost the same as the maximum width of the actual fluidized region 8 that was tested under the same joining conditions, and corresponds to one to one. Therefore, by performing such numerical analysis and calculating the width of the strain critical region 50, the actual maximum width of the fluidized region 8 can be estimated.

  FIG. 16 is a diagram showing the maximum width of the fluidized region 8 based on experimental values and the joining length D based on experimental values. The maximum width of the fluidized region 8 based on the experimental value and the joining length D based on the experimental value are almost the same and correspond one-to-one. Therefore, the joining length D can be estimated based on the width of the strain critical region 50 calculated by numerical analysis.

  In the strength estimation procedure, the shear plastic strain distribution of the workpiece 3 is calculated in the tool rotation analysis stage a3, and data indicating the shear plastic strain distribution calculated in the tool rotation analysis stage a3 is extracted in the rotation analysis result acquisition stage a4. To do. Next, in the fluidization region calculation step a5, the width of the strain critical region 50 is obtained based on the data indicating the strain distribution extracted in the rotation analysis result acquisition step a4, and the width of the strain critical region 50 is set to the maximum of the fluidization region. Calculate as large. As the calculated width of the fluidized region, the calculated width of the strain critical region 50 may be used as it is. Alternatively, the calculated width of the strain critical region 50 may be obtained by adding / subtracting / dividing a coefficient based on the correspondence obtained by experiments.

  Next, in the joining length calculation step a6, the joining length D is calculated based on the maximum width of the fluidization region 8 calculated in the fluidization region calculation step a5. As the calculated joining length D, the calculated maximum width of the fluidized region 8 may be used as it is. Alternatively, the calculated maximum width of the fluidized region 8 may be obtained by adding / subtracting / dividing a coefficient based on the correspondence obtained by experiments. In this way, the joining length D corresponding to the given joining condition can be calculated in the joining length calculation step a6.

  FIG. 17 is a diagram illustrating a simulation result in the indentation indentation analysis stage a7. When the fluidization region calculation step a5 is completed, the bonded member pushing step a7 is performed independently of the joining length calculation step a6. In the to-be-joined object pushing step a7, the deformation of the second member to be joined 2 is deformed using the deformation state and temperature distribution acquired in the indentation analysis result acquisition step a2 and the fluidization region calculated in the fluidization region calculation step a5. Find the state.

  In the joined member pushing step a7, a pressing structure constituted by the joining tool 4, the fluidized region 8 and the first joined member 1 is set, and the second joined member 2 is moved downstream in the immersion direction by the pressing structure. Numerical analysis of the deformation state when pressed. At this time, an initially set pressure is applied only to the welding tool 4. As shown in FIG. 17, when the pressing structure is pushed into the second bonded member 2, the second bonded member 2 protrudes upstream in the immersion direction in the vicinity of the fluidizing region 8 and radially outward. The hook point P2 formed in the actual article 3 is formed. Next, when the joined push-in step a7 is completed, a joining height calculating step a8 is performed. In the joining height calculation step a8, the immersion direction dimension between the hook point P2 and the reference point P1 is obtained based on the deformation state of the second joined member calculated in the joined push-in step a7, and the joining height H Calculate as

  FIG. 18 is a graph showing the joint height obtained by experiment and the joint height H obtained by the joint height calculation step a8. As shown in FIG. 18, the joint height H obtained by numerical calculation is substantially the same as the actual joint height H that is an experiment conducted under the same joint conditions, and corresponds to one to one. Therefore, by performing such numerical analysis and calculating the joint height H, the actual joint height can be estimated. As the calculated joining height H, the dimension in the immersion direction between the hook point P2 and the reference point P1 obtained by the indentation object push-in analysis a7 may be used as it is. Further, the calculated hook point P2, the reference point P1, and the dimension in the immersion direction may be obtained by adding, subtracting, and dividing by a coefficient based on the correspondence obtained by experiments.

  FIG. 19 is a flowchart specifically showing the intensity calculating step s3. The strength calculation step s3 is obtained, for example, by a fracture simulation by a finite element method. In the strength calculating step s3, a fracture simulation is performed based on the joining length D and the joining height H calculated in the shape calculating step s2. In this fracture simulation, the form of force applied to the joint is set, and a numerical analysis of the fracture form of the joint according to this form of force is performed. Based on the analysis result, the strength of the bonded product is obtained.

  Specifically, in the strength calculation step s3, first, in the destruction criteria setting stage b1, the destruction resistance value of the joint is set by the operator. This destruction resistance value is input by the operator. Next, in the fracture mode numerical analysis step b2, when a force is applied to the joint based on the joint state after deformation including the joint length D and the joint height H calculated by the shape calculation step s2. Analyze the state numerically. For example, stress analysis or crack growth analysis is performed as a numerical analysis for calculating a force form.

  Next, in the strength calculation stage b3, based on the state of force calculated in the fracture mode numerical analysis stage b2 and the fracture resistance value of the joint set in the fracture criteria setting stage b1, the joint strength of the joint is determined. calculate. That is, the point of time when the force applied to the joint becomes equal to the fracture resistance value of the joint is defined as the breaking point, and the force applied to the joint at that time is defined as the joint strength. As the calculated strength, static ductile strength, fatigue strength, and the like can be calculated. When the joint strength b3 is calculated in this way, the process proceeds to an end step s4, the joint strength estimated by the output means is displayed, and the joint strength estimation operation is finished. The strength calculation step s3 can be realized by the calculation means 23 executing a calculation program based on the joining length D and the joining height H.

  FIG. 20 is a flowchart showing another estimation procedure. In the flowchart shown in FIG. 19, the fracture simulation is performed by the finite element method. However, without performing the fracture simulation, the joint strength is obtained based on the joint strength approximate expression related to the joint length D and the joint height H. Also good. That is, when the joining length D and the joining height H are obtained by the shape calculating step s2, the process proceeds to the strength calculating step s3.

  In the strength calculating step s3, the peel strength or shear strength is calculated based on the approximate expression shown in the graph of FIG. 6 or FIG. Then, the bonding strength calculated in the end step s4 may be displayed by the output means. The calculation means 23 acquires in advance a correspondence relationship between the joining length D and the joining height H and the joining strength using a database or an approximate line. Accordingly, in the strength calculation step s3, the calculation means 23 can easily obtain the bonding strength by referring to the database or the approximate line based on the calculated bonding length D and bonding height H. By calculating the joint strength in this manner, it is not necessary to perform numerical analysis related to the strength calculation, and the joint strength can be calculated in a shorter time.

  FIG. 21 is a graph showing the peel strength between the experimental result and the analysis result under the same joining condition, and FIG. 22 is a graph showing the shear strength between the experimental result and the analysis result under the same joining condition. When the peeling strength and the shear strength are estimated by the estimation method described above, a strength substantially equal to the experimental result can be obtained as shown in FIGS.

  As described above, according to the embodiment of the present invention, the deformation state of the article 3 is calculated by numerical analysis, and the bonding strength of the object is calculated based on the deformation state. As a result, it is not necessary to actually perform friction stir welding and obtain a bonding strength by a strength test, so that the bonding strength can be easily estimated in a short time. Therefore, since the joining strength when the joining conditions are changed can be easily obtained, the joining conditions that achieve the joining strength satisfying the required joining strength range can be easily obtained, and the time spent for setting the joining conditions and Cost can be reduced. Although it is difficult to directly calculate the joint strength by numerical analysis, it is relatively easy and accurate to calculate the deformation state of the joint by numerical analysis as in the present invention. it can.

  Further, the bonding strength is closely related to the bonding length and the bonding height, and the fracture form differs depending on whether the bonding length is small or the bonding height is long. In the present embodiment, the joint length and the joint height are calculated as indices representing the joint state after deformation, and the joint strength is calculated based on the joint length and the joint height. As a result, any fracture mode can be handled, and the bonding strength can be calculated with higher accuracy.

  Further, numerical analysis is performed when the welding tool 4 is immersed in the workpiece 3 without rotating, and then numerical analysis is performed when the welding tool 4 is rotated using numerical analysis data when the welding tool 4 is immersed. . As a result, the fluidized region can be estimated well without numerically modeling the friction stir welding, and the numerical analysis can be simplified. Furthermore, in the tool indentation analysis stage, a deformation state that approximates the deformation state of the joint when the friction stir welding is actually performed can be calculated by giving an amount of heat input that takes frictional heat into consideration. As a result, the deformation state can be calculated with higher accuracy.

  Further, by pressing the pressing structure against the member to be joined on the downstream side in the immersion direction, the member to be joined on the downstream side in the immersion direction is partially raised on the upstream side in the immersion direction. By calculating the hook point based on this uplift phenomenon, the hook point can be easily and accurately calculated. As a result, the bonding strength can be calculated with higher accuracy.

  Furthermore, in one embodiment of the present invention, the numerical analysis can be performed two-dimensionally by realizing the numerical analysis with an axisymmetric model, and the numerical analysis can be simplified. Further, in the rotation analysis stage a3, an angle of 90 degrees or less is sufficient for rotating the contact portion of the workpiece 3 that is in contact with the tool 4. Even if the rotation angle is reduced in this way, the strain critical region 50 does not change greatly, and the calculation time can be shortened.

  Moreover, in one Embodiment of this invention, although joining strength was output, you may output the deformation | transformation state of the to-be-joined object 3 to others. For example, it further includes a plate thickness calculating step for calculating the thickness dimension of the first bonded member 1 and the thickness dimension of the second bonded member 2 based on the deformation state of the workpiece 3 calculated by the shape calculating step s2. But you can.

  FIG. 23 is a cross-sectional view showing two joints having the same total thickness at a joining position by an experiment. FIG. 23 (1) shows a first bonded product in which the plate thickness H1 of the first member 1 is large and the plate thickness H2 of the second member 2 is small. FIG. 23 (2) shows a second bonded product in which the plate thickness H1 of the first member 1 is small and the plate thickness H2 of the second member 2 is large. Table 5 shows the dimensions and shear strength of each joint shown in FIG.

  As shown in Table 5, the joint strength may be different even if the total thickness H3 is the same. Specifically, the bonding strength is higher in the bonded product in which the plate thickness H1 of the first member to be bonded 1 is small and the plate thickness H2 of the second member to be bonded 2 is large. That is, rather than measuring the total plate thickness that can be measured from the outside after bonding, it is more effective in managing the bonding strength to measure the plate thicknesses of the first member 1 and the second member 2 individually by numerical analysis. It may be. According to the present invention, the plate thicknesses H1, H2, and H3 of the objects to be joined can be calculated by the plate thickness calculation step, so that convenience can be improved.

  The first and second workpieces 3 have substantially the same joining length D. Moreover, since the 2nd to-be-joined object 3 has small joining height compared with the 1st to-be-joined object 3, the relationship shown to the graph of FIG. 6 is satisfy | filled. The plate thickness calculation step calculates the plate thickness of each of the members 1 and 2 to be joined, and based on the calculated plate thicknesses H1 and H2, the joint length D, and the joint height H, the joint strength is further increased. It can be estimated accurately.

  In this embodiment, the tool rotation analysis stage a3, the rotation analysis result acquisition stage a4, and the fluidization area calculation stage a5 are sequentially performed to calculate the fluidization area 8. However, the fluidization area 8 is calculated using another method. May be calculated.

FIG. 24 is a graph showing the relationship between the heat input parameter given to the workpiece 3 and the maximum width of the fluidized region 8. The amount of heat given to the object to be bonded 3 is represented by the following equation, where q is the amount of heat input per unit time given to the contact portion of the object to be bonded 3.
Q / U = q · t / U

Here, q is the amount of heat input (W) per unit time given to the contact portion 3a of the workpiece 3 that contacts the welding tool 4, t is the bonding time (sec), and U is the workpiece 3 The total plate thickness (mm).

  As shown in FIG. 24, the maximum width of the fluidized region and the heat input parameter have a one-to-one relationship, and can be associated by one approximate curve shown on the graph. Therefore, the maximum width of the fluidization region 8 may be obtained based on the heat input parameter calculated from the joining conditions, and the joining length may be obtained from the maximum width of the fluidization region 8. In this case, the bonding height H is determined by setting the pressing structure with the first member 1 and the bonding tool 4 in the deformed state calculated by the tool indentation analysis stage a1. By simply obtaining the maximum width of the fluidized region 8 in this way, the numerical analysis can be further simplified, and the time taken to calculate the bonding strength can be shortened.

  The above-described embodiment of the present invention is merely an example of the present invention and can be realized by other methods. For example, in the present invention, the joint length D and the joint height H are calculated as indices indicating the joint state after deformation, but other deformation states may be calculated. For example, only the plate thickness that is the dimension in the immersion direction of each of the members 1 and 2 to be joined at the joining position may be calculated. As for the plate thickness of each of the members 1 and 2, the experiment is performed such that the smaller the plate thickness H1 of the first member 1 and the larger the plate thickness H3 of the second member 2 are, the smaller the joint height H is. Therefore, the joining strength may be estimated by calculating the plate thicknesses H1 and H2 of the members 1 and 2 to be joined.

  The material of each of the members 1 and 2 may be other than an aluminum alloy, or may be a different material. Also, the number of members to be bonded constituting the workpiece 3 may be two or more.

  FIG. 25 is a flowchart showing a joining condition calculation procedure using the strength estimation method of the present invention. The joining condition calculation procedure is performed by, for example, the arithmetic unit 23 described above. In step c0, when an instruction for calculating the joining condition is given to the input means 21, the operation proceeds to step c1, and the computing means 23 starts an operation for estimating the joining condition.

  In step c1, the constrained conditions among the bonding conditions, the target bonding strength to be targeted, the priority of the bonding conditions, etc. are acquired, and the process proceeds to step c2. In step c2, a joining condition that satisfies the constrained condition is set, and the process proceeds to step c3. In step c3, the bonding strength corresponding to the set bonding condition is calculated. For the bonding strength calculation procedure, the above-described method for estimating the bonding strength is used.

  That is, the process of step c3 includes a joining length calculation stage for calculating the joining length by numerical analysis for each joining condition, a joining height calculating stage for calculating the joining height by numerical analysis for each joining condition, and a predetermined step. A strength calculation step of calculating the bonding strength calculated for each bonding condition is included. When the joining condition in the set joining condition is calculated, the process proceeds to step c4.

  In step c4, it is determined whether or not the bonding strength calculated in step c3 is equal to or higher than the target strength. If it is equal to or higher than the target bonding strength, the process proceeds to step c5, and if not, the process proceeds to step c10. In step c5, the joining conditions and the joining strength are stored in association with each other, and the process proceeds to step c6. In step c6, when the joining condition can be changed among the restricted conditions, the process proceeds to step c7. In step c7, the joining condition is changed and the process returns to step c3.

  In step c6, when the constraint conditions are satisfied and the bonding strength is obtained for all the bonding conditions, the process proceeds to step c8. In step c8, the optimum joining condition is extracted from the joining conditions stored in step c5 in accordance with a predetermined priority order, the optimum joining condition is determined, and the process proceeds to step c9. The process of step c8 includes a joining condition extraction stage for extracting joining conditions that provide joining strength that falls within a predetermined joining strength range. In step c9, the optimum joining condition is output by the output means, and the joining condition determining operation is terminated.

  In step c10, if the joining condition can be changed among the restricted conditions, the process returns to step c3. In step c10, if the joining condition cannot be changed, the process proceeds to step c11. In step c11, the target intensity is changed, and the process returns to step c1.

  In this way, it is possible to extract a joining condition that is equal to or higher than the target connection strength. As a result, it is possible to select optimum construction conditions after ensuring the required bonding strength, and to improve convenience. Therefore, it is not necessary to determine an optimum joining condition by trial and error as in the prior art, and the efficiency can be improved in terms of time and cost. Thus, for example, even when the material and dimensions of the members to be joined are changed, the joining conditions capable of joining with the target joining strength can be quickly determined.

It is a flowchart which shows the estimation procedure of the joining strength estimation method which is one Embodiment of this invention. It is sectional drawing which shows the joining procedure of friction stir welding. 1 is a perspective view showing a friction stir welding apparatus 10. It is a block diagram which shows the arithmetic unit 20 which performs the joining strength estimation method of this invention. It is sectional drawing which expands and shows the to-be-joined object 3. FIG. It is a graph which shows the relationship between the peeling strength by experiment, and the joining state after a deformation | transformation. It is sectional drawing which shows the fracture | rupture form of the joined article in a peeling strength test. It is a graph which shows the relationship between the shear strength by experiment, and the joining state after a deformation | transformation. It is sectional drawing which shows the fracture | rupture form of the joined material in a shear strength test. It is a figure which shows the simulation result in the tool indentation analysis step a1. It is a graph which shows the temperature change by the time passage of each to-be-joined member 1,2. It is a figure which shows the simulation result in the tool rotation analysis stage a3. It is a figure which shows the plastic strain which rotates around the central axis line L1 of the part in the arbitrary distance from the pin part 6 among the 1st to-be-joined members 1. It is a graph which shows the width | variety of the strain critical area | region 50 from which the distortion | strain around the center axis line L1 becomes zero, and the angle which forcibly rotates a contact part. It is a figure which shows the case where the maximum width | variety of the fluidization area | region 8 is calculated | required by experiment for a fluidization area | region, and the case where the width | variety of the strain critical area | region 50 is calculated on the same joining conditions as the joining conditions in experiment. It is a figure which shows the maximum width of the fluidization area | region 8 by an experimental value, and joining length D by an experimental value. It is a figure which shows the simulation result in the to-be-joined object indentation analysis step a7. It is a graph which shows the joining height by experiment, and the joining height calculated | required by the joining height calculation step a8. It is a flowchart which shows the intensity | strength calculation process s3 concretely. It is a flowchart which shows another estimation procedure.

It is a graph which shows the peeling strength of an experimental result and an analysis result on the same joining conditions. It is a graph which shows the shear strength of an experimental result and an analysis result on the same joining conditions. It is sectional drawing which shows two joined objects with the same total plate | board thickness of the joining position by experiment. It is a graph which shows the relationship between the heat input parameter given to the to-be-joined object 3, and the maximum width of a fluidization area | region. It is a flowchart which shows the joining condition calculation procedure using the intensity | strength estimation method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st to-be-joined member 2 2nd to-be-joined member 3 To-be-joined object 4 Joining tool s1 Joining condition acquisition process s2 Shape calculation process s3 Strength calculation process a1 Tool indentation analysis stage a2 Indentation analysis result acquisition stage a3 Tool rotation analysis stage a4 Rotation Analysis result acquisition stage a5 Fluidization region calculation stage a6 Joining length calculation stage a7 Joined member indentation analysis stage a8 Joining height calculation stage

Claims (11)

In the case where a rotating joining tool is immersed in an immersion direction into an object to be bonded in which two members to be bonded are arranged in a predetermined immersion direction, and these two members to be bonded are friction stir bonded, two members to be bonded Is a bonding strength estimation method for estimating the bonding strength of a bonded product,
In accordance with a predetermined be joining conditions, the portions thus the object to be bonded to the friction stir is deformed, the sectional shape after deformation in a plane containing the axis of the welding tool extending immersion direction, physical properties of the object to be bonded, thickness, bonding A shape calculation step for calculating the shape, pressing force, rotation speed, joining time, and immersion amount of the tool and calculating by numerical analysis,
A strength calculation step of calculating a joint strength of the joint based on the cross-sectional shape after deformation calculated in the shape calculation step. Shape calculating step, the cross-sectional shape after the deformation, the junction length corresponding to the outer diameter of the fluidized region object to be joined by frictional heat during the friction stir is partially fluidized Sato,
Extending perpendicular to the immersion direction to the hook point which is the most upstream point in the immersion direction of the boundary line extending between the two members to be joined, and the portion of the boundary line not affected by the immersion of the welding tool out calculated expressed by the bonding height corresponding to immersion direction dimension between the reference point away from each direction,
The method for estimating the joint strength of a joint according to claim 1, wherein the strength calculation step calculates the joint strength of the joint based on the calculated joint length and joint height. The shape calculation step is a tool indentation analysis stage that calculates the cross-sectional shape of the object to be joined by numerical analysis when the joining tool is immersed in the object to be joined and is not rotated .
Rotation analysis stage for calculating the strain distribution of the workpiece when the welding tool is further rotated from the cross-sectional shape of the workpiece calculated by the tool indentation analysis stage by numerical analysis,
2. A fluidization region calculation step of calculating a fluidization region in which the workpiece is partially fluidized based on the strain distribution of the workpiece calculated by the rotation analysis step. Of joining strength estimation for joints. The tool indentation analysis step is a cross-sectional shape of the object to be joined when the welding tool is pressed in the immersion direction with a pressure according to a predetermined joining condition and the heat input according to the joining condition is given to the object to be joined. The joint strength estimation method according to claim 3, wherein the temperature distribution and the temperature distribution are calculated by numerical analysis. The rotation analysis stage is based on the cross-sectional shape and temperature distribution of the workpiece to be calculated in the tool indentation analysis stage, and the distortion of the workpiece when the contact part of the workpiece with the welding tool is forcibly rotated. The joint strength estimation method according to claim 4, wherein the distribution is calculated by numerical analysis. The shape calculation step includes a joining length calculation step of calculating a joining length corresponding to the outer diameter dimension of the fluidization region based on the fluidization region calculated by the fluidization region calculation step;
Based on the cross-sectional shape calculated by the tool indentation analysis stage, the hook point that is the most upstream point in the immersion direction among the boundary lines extending between the two members to be joined , and the influence of the immersion of the joining tool among the boundary lines A joining height calculation step for calculating a joining height corresponding to a dimension in the immersive direction between the reference point separated in the extending direction perpendicular to the immersive direction , up to a portion not subjected to
The strength calculation step calculates the joint strength of the joint based on the joint length calculation result and the joint height calculation result, The joint according to any one of claims 3 to 5, Bond strength estimation method. The shape calculation step is based on the cross-sectional shape of the workpiece calculated in the tool indentation analysis stage and the fluidization area of the workpiece calculated in the fluidization area calculation stage. The member to be joined that calculates the cross-sectional shape of the object to be joined when the pressing structure having the member to be joined on the upstream side in the direction is pressed against the member to be joined on the downstream side in the immersion direction according to predetermined joining conditions. And further comprising an indentation stage
The joining height calculating step calculates the joining height based on the cross-sectional shape of the object to be joined, which is calculated by the member-to-be-joined member pushing step, The joining according to any one of claims 3 to 6, A method for estimating the bonding strength of objects. Thickness for calculating the thickness dimension of the bonded member upstream of the immersion direction and the thickness dimension of the bonded member downstream of the immersion direction based on the cross-sectional shape after deformation of the workpiece calculated by the shape calculation step The method for estimating the bonding strength of a bonded article according to any one of claims 1 to 7, further comprising a calculating step. In the case where a rotating joining tool is immersed in an immersion direction into an object to be bonded in which two members to be bonded are arranged in a predetermined immersion direction, and these two members to be bonded are friction stir bonded, two members to be bonded A deformation state estimation method for estimating a cross-sectional shape after deformation of a joined product formed by joining,
The cross-sectional shape in the plane including the axis of the welding tool extending in the immersion direction of the portion where the workpiece is deformed when the welding tool is immersed in the workpiece and not rotating is determined . Enter the physical property value, thickness dimension, welding tool shape, pressure, number of rotations, welding time and immersion amount, and calculate the tool indentation analysis stage by numerical analysis,
Rotation analysis stage for calculating the strain distribution of the workpiece when the welding tool is further rotated based on the cross-sectional shape of the workpiece calculated by the tool indentation analysis stage, by numerical analysis,
Deformation of a joint comprising a fluidization region calculation step for calculating a fluidization region in which the workpiece is partially fluidized based on the strain distribution of the workpiece calculated by the rotation analysis step. State estimation method. The tool indentation analysis step is a cross-sectional shape of the object to be joined when the welding tool is pressed in the immersion direction with a pressure according to a predetermined joining condition and the heat input according to the joining condition is given to the object to be joined. And temperature distribution by numerical analysis,
The rotation analysis stage is based on the cross-sectional shape and temperature distribution of the workpiece to be calculated in the tool indentation analysis stage, and the distortion of the workpiece when the contact part of the workpiece with the welding tool is forcibly rotated. 10. The deformation state estimation method for a bonded article according to claim 9, wherein the distribution is calculated by numerical analysis. In the case where a rotating joining tool is immersed in an immersion direction into an object to be bonded in which two members to be bonded are arranged in a predetermined immersion direction, and these two members to be bonded are friction stir bonded, two members to be bonded A bonding condition determination method for determining a bonding condition in which the bonding strength of a bonded product formed by bonding is within a predetermined range,
A joining length calculation step for calculating a joining length corresponding to the outer diameter of the fluidized region where the workpiece is partially fluidized by frictional heat at the time of friction stirring, by numerical analysis for each predetermined joining condition; ,
Extending perpendicular to the immersion direction to the hook point which is the most upstream point in the immersion direction of the boundary line extending between the two members to be joined, and the portion of the boundary line not affected by the immersion of the welding tool A joint height calculating step for calculating a joint height corresponding to a dimension in the immersive direction between the reference points separated in the direction by numerical analysis for each predetermined joint condition;
A strength calculation stage for calculating the joint strength of each joint based on the joint length calculation result and the joint height calculation result calculated for each predetermined joining condition;
A joining condition determining method, comprising: a joining condition extracting step of extracting a joining condition having a joining strength that falls within a predetermined joining strength range based on a calculation result calculated by the strength calculating step.

Images