Roll-bending brazing copper ring processing technology for high-power wind driven generator

Abstract

The roll bending brazing copper ring machining technology for the high-power wind driven generator comprises the following steps that S1, machining is conducted, specifically, the two ends of a copper bar are both machined, half-thickness connectors are obtained, each half-thickness connector sequentially comprises a first inclined section, a horizontal section and a second inclined section from outside to inside, and the two half-thickness connectors are spliced to form a lap joint section; s2, preliminary roll bending; and S3, induction brazing is conducted, specifically, a silver-copper-nickel soldering lug is placed on the horizontal section, and silver-copper-zinc soldering lugs are placed on the first inclined section and the second inclined section. The prepared copper ring has strength, hardness and toughness, has heat resistance and corrosion resistance, and can be safely used as a high-power wind driven generator.

Description

TECHNICAL FIELD

[0001] The application relates to a brazing processing technology field, in particular to a rolling-bending brazing copper ring processing technology for a high-power wind generator. BACKGROUND

[0002] Brazing refers to a welding method that simultaneously heats a filler metal and a welding piece below the melting point of the welding piece to the melting temperature of the filler metal, and fills the gap of the solid welding piece with the liquid filler metal to connect the metals.

[0003] Induction brazing is a welding method that uses an alternating magnetic field formed by an alternating high-frequency, medium-frequency or power frequency power source and an induction coil to generate an induced current in the part, and uses the resistance heat generated by the current as a heat source. The workpiece is placed in the induction coil, the frequency and power of the coil are adjusted to generate appropriate induced current in the workpiece, thereby heating the workpiece.

[0004] The copper ring of a high-power wind generator (usually referring to a megawatt-level, especially a land-based and offshore wind turbine with a capacity of more than 3 MW) is a core component of the slip ring system, responsible for transmitting large current and signals between the rotating generator rotor and the stationary system, and its strength and reliability are crucial. At present, the copper ring parts used on the stator and rotor of a high-power wind generator are generally formed into an open ring through a rolling-bending forming process from a copper bar or a copper busbar with a certain cross section, and then the joint of the open ring is welded by brazing. After welding, the circular ring is calibrated by a calibrating device to form a complete ring that meets the size requirements. For the joint brazing of the above-mentioned open ring, there are two common joint forms: butt joint brazing joint and full-thickness lap joint brazing joint. However, these two brazing joints have the following respective problems: Firstly, the butt joint brazing joint has a small brazing area, which can easily lead to low joint strength and unreliable welding.

[0005] Secondly, the full-thickness lap joint brazing joint has a bulky structure, which often causes inconvenience to the installation of the stator and rotor and affects the utilization rate of the internal space of the stator and rotor. SUMMARY

[0006] In view of the above problems, the application provides a rolling-bending brazing copper ring processing technology for a high-power wind generator.

[0007] The technical scheme of the application is as follows: A rolling-bending brazing copper ring processing technology for a high-power wind generator, comprising the following steps: S1, machining: select a copper bar with the same length as the length of the finished copper ring to be machined, machine both ends of the copper bar, and obtain a half-thickness joint, the half-thickness joint comprises, from the outside to the inside, a first inclined section, a horizontal section, and a second inclined section, the first inclined section and the second inclined section have the same inclination angle and the same length, and the two half-thickness joints are spliced together to form a lap joint section; S2, preliminary bending: place the machined copper bar in S1 on a bending device, and use a bending die to bend it to obtain an open copper ring, then place the lap joint section on a bending machine and perform flattening treatment; S3, induction brazing: place a silver copper nickel soldering sheet on the horizontal section of one of the half-thickness joints with the position facing upwards, place a silver copper zinc soldering sheet on the first inclined section and the second inclined section, coat the silver copper nickel soldering sheet and the silver copper zinc soldering sheet on both sides with flux, then align the two half-thickness joints with each other, fix the lap joint section with a clamping tool, place the lap joint section on a mica plate, place the mica plate on the induction coil of an induction heating device, press the lap joint section with a pneumatic pressing plate, keep the lap joint section, the mica plate, and the induction coil fixed relative to each other, set the induction heating current to 90-120 A, start heating, heat until the soldering sheets in the lap joint section completely melt and fill the weld, stop heating, and obtain the bending brazed copper ring after water cooling.

[0008] Further, in S1, the length of the horizontal section is 1.5-2 times the thickness of the copper bar.

[0009] Note: By constraining the length of the horizontal section and the thickness of the copper bar, the welding is firm.

[0010] Further, in S1, the length L of the copper bar is π(r1+r2) / 2+L ＇ , where L ＇ is the length of the lap joint section, r1 is the outer diameter of the finished copper ring, and r2 is the inner diameter of the finished copper ring.

[0011] Note: By determining the length of the copper bar in advance when selecting materials, errors can be reduced, and the prepared copper ring can be ensured to be the same as the requirements of the drawing.

[0012] Further, in S1, the inclination angles of the first inclined section and the second inclined section are determined according to the tensile strength of the copper bar material, and the calculation formula is as follows: ; wherein is the included angle between the first inclined section and the second inclined section and the horizontal section, and the unit is °; Rm is the tensile strength of the copper bar material, and the unit is MPa.

[0013] Description: By optimizing the inclination angles of the first inclined section and the second inclined section, the balance of strength, hardness and toughness is achieved.

[0014] Further, in S2, the roll bending die comprises upper and lower limiting rings, an upper backing ring below the upper limiting ring, a lower backing ring above the lower limiting ring, and an intermediate backing ring between the upper and lower backing rings, and the intermediate backing ring is in butt joint with the copper bar.

[0015] Description: By providing a dedicated roll bending die, the roll bending precision is improved, and at the same time, it is ensured that the roll bending process will not cause surface damage to the copper bar.

[0016] Further, in S3, the silver copper nickel solder sheet is GB / T 10046 BAg56CuNi, the silver copper zinc solder sheet is GB / T 10046 BAg45CuZn, BAg50CuZn or BAg60CuZn, the thickness of the silver copper nickel solder sheet and the silver copper zinc solder sheet is 0.2mm±0.05mm, the silver copper nickel solder sheet and the silver copper zinc solder sheet abut each other when placed, and the flux is QJ102 flux.

[0017] Description: By selecting appropriate silver solder sheets as brazing filler metals at different positions, the prepared copper ring can have strength, hardness and toughness.

[0018] Further, in S3, the pressure of the pneumatic pressing plate pressing the lap joint section is 0.4-0.6MPa.

[0019] Description: By reasonably controlling the pressure of the pneumatic pressing plate, it can be ensured that the brazing part always remains firm.

[0020] Further, in S3, the clamping tool comprises a main body, fastening clamps on both sides of the upper surface of the main body, the fastening clamps are fixedly connected with the main body through fastening bolts and fastening nuts, a placing groove for placing the copper bar is arranged on the upper surface of the main body below the fastening clamps, and the mica plate is fixedly arranged in the groove arranged in the middle of the main body.

[0021] Description: By the clamping tool, the overall stability of the lap joint section during brazing is maintained.

[0022] Further, it further comprises the following step S4: S4, roll bending and shaping: the welding scar, welding slag and excess welding height at the welded joint are polished flat by an angle grinder, the lap joint section is placed on a roll bending equipment, and the lap joint section in a flat state is roll bent to a required arc state of the copper ring by the roll bending die from inside to outside.

[0023] Description: By shaping, the copper ring for high-power wind turbine required by the drawing is finally obtained.

[0024] The beneficial effects of the present application are: (1) The present application optimizes the structure of the butt joint part of the copper ring, so that the butt joint part of the copper ring for high-power wind turbine is smoother, and the induction brazing process can complete the welding in a short time, wherein two different silver soldering sheets are preferred as the welding materials of the inclined section and the horizontal section, so as to further improve the welding strength, the lower brazing temperature of the silver copper zinc soldering sheet can make it melt into the internal gap of the lap joint section first, then the silver copper nickel soldering sheet melts, and the lower fluidity of the silver copper nickel soldering sheet can improve the strength and hardness of the lap joint section, so that the prepared copper ring has strength, hardness and toughness, and has heat resistance and corrosion resistance, and can be safely used as a high-power wind turbine; (2) The present application optimizes the internal length of the lap joint section according to the thickness of the copper ring, and optimizes the angle of the inclined section according to the different materials of the copper ring, when the tensile strength of the material is low, the angle of the inclined section is reduced as much as possible to avoid the length of the inclined section being too long, so as to appropriately reduce the coverage area of the silver copper zinc soldering sheet and ensure the overall strength of the copper ring, while the material with high strength can appropriately increase the angle and length of the inclined section to improve the toughness, so as to balance the strength, hardness and toughness; (3) The present application also provides a rolling bending die and a clamping tool, so as to provide protection for the rolling bending and brazing of the copper ring, and provide technical support for the development of the induction brazing process of the copper ring for high-power wind turbine. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a schematic view of the overall structure of the processed copper ring; Figure 2 is a side view of the processed copper ring; Figure 3 is a front view of the half-thickness joint; Figure 4 is a top view of the half-thickness joint; Figure 5 is a schematic view of the structure of the rolling bending die; Figure 6 is a schematic view of the structure of the open copper ring after preliminary rolling bending and the lap joint section after flattening treatment; Figure 7 is a schematic view of the structure of the clamping tool; Figure 8 is a schematic view of the structure of the induction coil; Figure 9 is a schematic view of the lap joint section after rolling bending and shape correction; Figure 10 is a photo of the lap joint of each group in the experimental example; Figure 11 is a brazing RT photo of the lap joint of each group in the experimental example; Figure 12 is a brazing copper ring lap joint RT photo in the experimental example.

[0026] Wherein, 1-copper row, 2-half-thickness joint, 21-first inclined section, 22-horizontal section, 23-second inclined section, 3-roller bending die, 31-limit ring, 32-upper gasket ring, 33-lower gasket ring, 34-intermediate gasket ring, 4-clamping tool, 41-main body, 42-fastening clamping plate, 43-fastening bolt, 44-fastening nut, 45-putting slot, 46-groove, 5-mica plate, 6-induction coil, 7-pneumatic pressing plate. DETAILED DESCRIPTION

[0027] Embodiment 1: A rolling and brazing copper ring processing technology for high-power wind turbine, comprising the following steps: S1, machining: according to the length of the finished copper ring to be machined, select a copper row 1 with the same length, machine both ends of the copper row 1 to obtain a half-thickness joint 2, as shown in Figure 3 and Figure 4 , the half-thickness joint 2 comprises, from outside to inside, a first inclined section 21, a horizontal section 22 and a second inclined section 23, the first inclined section 21 and the second inclined section 23 have the same inclination angle and the same length, the two half-thickness joints 2 are spliced with each other to form a lap joint section, the length of the horizontal section 22 is 1.8 times the thickness of the copper row 1, and the length L of the copper row 1 is π(r1+r2) / 2+L ＇ , wherein L ＇ is the length of the lap joint section, r1 is the outer diameter of the finished copper ring, and r2 is the inner diameter of the finished copper ring; the inclination angle of the first inclined section 21 and the second inclined section 23 is determined according to the tensile strength of the copper row 1 material, and the calculation formula is as follows: ; wherein, is the included angle between the first inclined section 21, the second inclined section 23 and the horizontal section 22, and the unit is °; Rm is the tensile strength of the copper row 1 material, and the unit is MPa; S2, preliminary rolling: as shown in Figure 5 , the copper row 1 machined in S1 is placed on the rolling equipment, and the rolling die 3 is used for rolling to obtain an open copper ring, and then the lap joint section is placed on the bending machine for flattening treatment, as shown in Figure 6 , the rolling die 3 comprises two upper and lower limit rings 31, an upper gasket ring 32 located below the upper limit ring 31, a lower gasket ring 33 located above the lower limit ring 31, and an intermediate gasket ring 34 located between the upper gasket ring 32 and the lower gasket ring 33, and the intermediate gasket ring 34 is in abutment with the copper row 1; S3, induction brazing: as shown in Figure 7 and Figure 8As shown in the figure, silver copper nickel soldering pieces are placed on the horizontal section 22 of the position-up one-half-thickness joint 2, silver copper zinc soldering pieces are placed on the first inclined section 21 and the second inclined section 23, and the silver copper nickel soldering pieces and the silver copper zinc soldering pieces are coated with flux on both sides, then the two half-thickness joints 2 are spliced and aligned with each other, the lap joint is fixed by the clamping tool 4, the lap joint is placed on the mica plate 5, the mica plate 5 is placed on the induction coil 6 of the induction heating device, the lap joint is pressed by the pneumatic pressing plate 7, the pressure of the pneumatic pressing plate 7 is 0.5 MPa, the relative fixation of the lap joint, the mica plate 5 and the induction coil 6 is maintained, the induction heating current is set to 100 A, heating is started, the soldering pieces in the lap joint are completely melted and the weld is filled, heating is stopped, the roll-bending brazed copper ring is obtained after water cooling, and the appearance of the weld is checked, the silver copper nickel soldering piece is GB / T10046 BAg56CuNi, the silver copper zinc soldering piece is GB / T 10046 BAg50CuZn, the thickness of the silver copper nickel soldering piece and the silver copper zinc soldering piece is 0.2 mm, the silver copper nickel soldering piece and the silver copper zinc soldering piece abut against each other when placed, and the flux is QJ102 flux; The clamping tool 4 includes a main body 41, fastening clamping plates 42 located on both sides of the upper surface of the main body 41, the fastening clamping plates 42 are fixedly connected with the main body 41 through fastening bolts 43 and fastening nuts 44, the upper surface of the main body 41 below the fastening clamping plates 42 is provided with a placing groove 45 for placing the copper bar 1, and the mica plate 5 is fixedly arranged in a groove 46 arranged in the middle of the main body 41; S4, roll-bending and shaping: as shown in the figure, Figure 9 the welding flash, welding slag and excess welding height at the welded joint are polished flat by an angle grinder, the lap joint is placed on a roll-bending device, the lap joint in the flat state is roll-bent to the required circular arc state of the copper ring from the inside to the outside by the roll-bending die 3, as shown in the figure, Figure 1 and Figure 2 and as shown in the figure, the diameter of the circular ring of the lap joint is checked after roll-bending.

[0028] The welded copper ring is placed on a specially-made circular ring diameter checking tool, which is generally made of ordinary carbon steel plate through processes such as plasma cutting, leveling, quenching heat treatment and machining of ring grooves. The carbon steel plate is subjected to quenching heat treatment to ensure that the hardness of the steel is within the range of HRC 45-50, the diameter of the ring groove on the checking tool is specially designed according to the diameter of the finished copper ring and its tolerance requirements, and the depth of the ring groove is generally 2 / 3 of the width of the copper ring.

[0029] If the welded copper ring can be smoothly placed into the ring groove on the checking tool, it is considered that the diameter, roundness and other dimensions of the welded copper ring meet the drawing requirements and no further shaping is required; if the welded copper ring cannot be smoothly placed into the ring groove on the checking tool, it is considered that the diameter, roundness and other dimensions of the welded copper ring do not meet the drawing requirements, and further shaping by knocking with a rubber hammer or other tools is required.

[0030] The copper ring after the correction is further polished, the surface defects such as scratches and pits are polished by a pneumatic polishing device, and then the copper ring surface is cleaned by a hundred-grit cloth and a copper brightener, such as shown in Fig. Figures 10-12

[0031] Embodiment 2: The difference between this embodiment and embodiment 1 is that, in S1, the length of the horizontal section 22 is 1.5 times the thickness of the copper bar 1.

[0032] Embodiment 3: The difference between this embodiment and embodiment 1 is that, in S1, the length of the horizontal section 22 is 2 times the thickness of the copper bar 1.

[0033] Note: The length of the horizontal section 22 should be controlled at a proper length, and is proportional to the thickness, that is, the thicker the thickness, the more appropriate the length of the horizontal section 22.

[0034] Embodiment 4: The difference between this embodiment and embodiment 1 is that, in S3, the pressure of the pneumatic pressing plate 7 pressing the lap joint section is 0.4 MPa, the lap joint section, the mica plate 5 and the induction coil 6 are kept relatively fixed, and the induction heating current is set to 90 A.

[0035] Embodiment 5: The difference between this embodiment and embodiment 1 is that, in S3, the pressure of the pneumatic pressing plate 7 pressing the lap joint section is 0.6 MPa, the lap joint section, the mica plate 5 and the induction coil 6 are kept relatively fixed, and the induction heating current is set to 120 A.

[0036] Note: The pressing pressure of the pneumatic pressing plate and the induction heating current can be reasonably adjusted within the range given in the present application.

[0037] Embodiment 6: The difference between this embodiment and embodiment 1 is that, in S3, the silver copper zinc soldering sheet is GB / T 10046 BAg45CuZn, and the thickness of the silver copper nickel soldering sheet and the silver copper zinc soldering sheet is 0.15 mm.

[0038] Embodiment 7: The difference between this embodiment and embodiment 1 is that, in S3, the silver copper zinc soldering sheet is GB / T 10046 BAg60CuZn, and the thickness of the silver copper nickel soldering sheet and the silver copper zinc soldering sheet is 0.25 mm.

[0039] Note: The three kinds of silver copper zinc soldering sheets given in the present application are all general-purpose brazing filler metals, which can be reasonably selected according to the cost and material strength requirements, and the thickness of the silver copper nickel soldering sheet and the silver copper zinc soldering sheet can be reasonably adjusted within the range given in the present application.

[0040] ​Experimental example: In order to verify the actual effect of the method of the present application, we designed several groups of comparative experiments for comparative analysis, wherein, Comparative Example 1 is a copper ring prepared by the way of butt brazing joint, Comparative Example 2 is a copper ring prepared by the way of full-thickness lap brazing joint, Comparative Example 3 is to use a continuous whole piece of silver copper nickel soldering sheet to press and braze in the inclined section and the horizontal section, Comparative Example 4 is to use a continuous whole piece of silver copper zinc soldering sheet GB / T 10046 BAg50CuZn to press and braze in the inclined section and the horizontal section, in Comparative Example 5, no inclined section and horizontal section is divided, but a pre-processed arc-shaped transition section is used at the position of the original inclined section and horizontal section, and then a continuous whole piece of silver copper zinc soldering sheet GB / T 10046 BAg50CuZn is used to press and braze, the rest of the steps in Comparative Examples 3-5 are the same as in Example 1, and the final test results are shown in Table 1.

[0041] Table 1 Performance table of copper rings prepared by different methods ;

[0042] From the data in the above table, it can be seen that in the three groups of examples of the present application, good tensile strength and toughness are achieved, and the structural integrity and performance stability can be better maintained when subjected to external force impact; In Comparative Examples 1 and 2, the butt brazing joint has a small brazing area itself, which can easily lead to low joint strength, poor welding reliability and other problems; the full-thickness lap brazing joint has a bulky structure, which often brings inconvenience to the installation of the stator and rotor, and affects the utilization rate of the internal space of the stator and rotor, so the tensile strength and toughness of both are relatively low; In Comparative Examples 3 and 4, a continuous whole piece of silver soldering sheet is used, when silver copper nickel soldering sheet is selected, the tensile strength is relatively high, but the temperature required for brazing is also relatively high, which requires higher power and time, and the toughness is generally low; when silver copper zinc soldering sheet is selected, the required temperature is relatively low, but the tensile strength and toughness are both generally low, which may be due to the fact that brittle phases are easily precipitated in the inclined section and the horizontal section; In Comparative Example 5, the arc-shaped smooth transition can achieve a technical effect close to that of Example 1, but the arc-shaped smooth transition section requires high machining requirements, which prolongs the overall working time.

[0043] In addition, the inclination angles of the first inclined section 21 and the second inclined section 23 are determined according to the tensile strength of the copper bar 1 material, for example, when the material of the copper bar 1 selected is chromium zirconium copper, the tensile strength is 480 MPa, then = 90 + 0.05 x 480 = 114°; When the material of the copper bar 1 selected is aluminum bronze, the tensile strength is 700 MPa, then = 90 + 0.05 x 700 = 125°; When the material of the copper bar 1 is tellurium copper and the tensile strength is 350 MPa, then = 90 + 0.05 x 350 = 107.5°; When the material of the copper bar 1 is pure copper and the tensile strength is 200 MPa, then = 90 + 0.05 x 200 = 100°.

Claims

1. A process for processing high-power wind turbine generator roll-bending and brazing copper rings, characterized in that, Includes the following steps: S1. Machining: Select a copper busbar (1) of the same length as the finished copper ring to be machined, and machine both ends of the copper busbar (1) to obtain a half-thickness joint (2). The half-thickness joint (2) includes a first inclined section (21), a horizontal section (22), and a second inclined section (23) from the outside to the inside. The first inclined section (21) and the second inclined section (23) have the same inclination angle and the same length. The two half-thickness joints (2) are spliced ​​together to form an overlapping section. S2, Preliminary rolling: Place the machined copper busbar (1) from S1 on a rolling bending machine and roll it with a rolling bending mold (3) to obtain an open copper ring. Then place the overlapping section on a bending machine for flattening. S3, Induction Brazing: Place silver-copper-nickel brazing sheets on the horizontal section (22) of one of the half-thickness joints (2) facing upwards, and place silver-copper-zinc brazing sheets on the first inclined section (21) and the second inclined section (23). Apply flux to both sides of the silver-copper-nickel brazing sheets and the silver-copper-zinc brazing sheets. Then, align the two half-thickness joints (2) together and fix the overlapping section with a clamping fixture (4). Place the overlapping section on a mica plate (5) and then place the mica plate (5) on the induction coil (6) of the induction heating device. Press down the overlapping section with a pneumatic pressure plate (7) to keep the overlapping section, mica plate (5) and induction coil (6) relatively fixed. Set the induction heating current to 90~120A and start heating. Heat until the brazing sheets in the overlapping section are completely melted and fill the weld. Stop heating and water-cool to obtain the rolled brazed copper ring.

2. The processing technology for a high-power wind turbine generator using a roll-bending and brazing copper ring as described in claim 1, characterized in that, In S1, the length of the horizontal segment (22) is 1.5 to 2 times the thickness of the copper busbar (1).

3. The processing technology for a high-power wind turbine generator using a roll-bending and brazing copper ring as described in claim 1, characterized in that, In S1, the length L of the copper busbar (1) is L = π(r1+r2) / 2 + L ＇ , where L ＇ R1 is the length of the overlap section, R2 is the outer diameter of the finished copper ring, and R2 is the inner diameter of the finished copper ring.

4. The processing technology for a high-power wind turbine generator using a roll-bending and brazing copper ring as described in claim 1, characterized in that, In S1, the inclination angles of the first inclined segment (21) and the second inclined segment (23) are determined based on the tensile strength of the copper busbar (1) material, and the calculation formula is as follows: ； in, The angle between the first inclined segment (21) and the second inclined segment (23) and the horizontal segment (22) is expressed in degrees. Rm The tensile strength of the copper busbar (1) material is expressed in MPa.

5. The processing technology for a high-power wind turbine generator using a roll-bending and brazing copper ring as described in claim 1, characterized in that, In S2, the bending die (3) includes upper and lower limiting rings (31), an upper pad ring (32) located below the upper limiting ring (31), a lower pad ring (33) located above the lower limiting ring (31), and an intermediate pad ring (34) located between the upper pad ring (32) and the lower pad ring (33), the intermediate pad ring (34) being connected to the copper busbar (1).

6. The processing technology for a high-power wind turbine generator using a roll-bending and brazing copper ring according to claim 1, characterized in that, In S3, the thickness of the silver-copper-nickel solder sheet and the silver-copper-zinc solder sheet is 0.2mm±0.05mm. The silver-copper-nickel solder sheet and the silver-copper-zinc solder sheet are placed in contact with each other. The flux is QJ102 flux.

7. The processing technology for a high-power wind turbine generator using a roll-bending and brazing copper ring as described in claim 1, characterized in that, In S3, the pressure of the pneumatic pressure plate (7) pressing down on the overlapping section is 0.4~0.6MPa.

8. The processing technology for a high-power wind turbine generator using a roll-bending and brazing copper ring as described in claim 1, characterized in that, In S3, the clamping fixture (4) includes a main body (41) and fastening clamps (42) located on both sides of the upper surface of the main body (41). The fastening clamps (42) are fixedly connected to the main body (41) by fastening bolts (43) and fastening nuts (44). The upper surface of the main body (41) below the fastening clamps (42) is provided with a placement groove (45) for placing copper busbars (1). The mica plate (5) is fixedly placed in a groove (46) provided in the middle of the main body (41).

9. The processing technology for a high-power wind turbine generator using a roll-bending and brazing copper ring as described in claim 1, characterized in that, It also includes step S4: S4. Rolling and bending: Grind the weld beads, slag and excess weld height at the welded joint with an angle grinder. Place the lap section on the rolling and bending equipment and use the rolling and bending mold (3) to roll the straight lap section from the inside to the arc state required by the copper ring from the inside to the outside.

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