CN112548854B

CN112548854B - Grinding clamp

Info

Publication number: CN112548854B
Application number: CN202011405629.6A
Authority: CN
Inventors: 王文权; 王苏煜; 张新戈; 徐宇欣; 戴華仁
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2020-02-12
Filing date: 2020-02-12
Publication date: 2022-04-05
Anticipated expiration: 2040-02-12
Also published as: CN111168240A; CN112548854A; CN111168240B

Abstract

The invention provides a grinding fixture, which comprises a base and a slide rail slidably connected with the base, a sample-carrying platform is arranged above the slide rail, one end of the sample-carrying platform is hinged with the slide rail, and the other end is connected to the slide rail through a strut A lower support frame is slidably connected to the sample stage. One end of the aluminum alloy sample and the plastic sample is placed on the sample stage, and the other end is placed on the lower support frame and protrudes from the end of the lower support frame. The upper pressure plate is placed on the alloy sample and the plastic sample. The width of the upper pressure plate, the lower support frame and the sample stage are all larger than the width of the aluminum alloy sample and the plastic sample. The upper pressure plate is provided with strips on both sides along the width direction. The end of the bar-shaped hole close to the strut is provided with a loose bolt matched with the upper end surface of the sample stage, and the end away from the strut is provided with a tight bolt matched with the end of the lower support frame. The grinding fixture performs grinding treatment on the surfaces to be welded of the aluminum alloy sample and the plastic sample.

Description

Grinding clamp

The invention is a divisional application of invention patents with application date of 2020.02.12, application number of 202010088544.3, and name of aluminum alloy and plastic laser welding method and grinding clamp and clamping clamp.

Technical Field

The invention relates to a grinding fixture, which is applied to laser connection in a lap joint and butt joint mixed joint mode between aluminum alloy and plastic dissimilar materials, and belongs to the technical field of welding and connection.

Background

With the increasing popularization of automobiles, the problem of environmental pollution is becoming more serious. Research shows that when the weight of the automobile is reduced by 10 percent, the fuel consumption can be reduced by 6 to 8 percent, and the improvement of the fuel economy means the corresponding reduction of the greenhouse gas emission. In order to meet the requirements of environmental protection and fuel saving, materials for reducing the quality of the vehicle body are required to reduce energy consumption and pollution. The aluminum alloy has relatively high specific strength, good plastic toughness and corrosion resistance, and is widely applied to automobiles. Thermoplastics, including various common engineering plastics, specialty plastics, and carbon fiber or glass fiber reinforced composites, which have received much attention recently, have almost unlimited processability, good fatigue and corrosion resistance, and lighter weight, and are increasingly used in vehicles, and it is possible to achieve the excellent properties of both materials if they can be reliably joined together. The more currently used connection processes for connecting aluminum alloy and plastic structures such as bumpers, steering wheels and the like in automobiles are mechanical connection and adhesive connection. The mechanical connection has no heat input, can effectively avoid the problem of joint embrittlement caused by heat action, but the joint form is complex, the weight and the design freedom of the joint are limited by the problems of pre-punching and the like, and serious stress concentration is easily caused. The adhesive connection can realize large-area connection and uniform stress distribution, but the problem of environmental pollution is inevitably caused because the adhesive is influenced by temperature in the pretreatment or use process. The laser welding process is a welding method with small heat input, high welding speed, concentrated energy and flexible joint form, and can effectively avoid a series of problems caused by gluing and mechanical connection.

At present, some scholars research the laser welding connection process of metal and nonmetal, and have published in various journals, see (1) script materials, 2008,59: 1247-; (2) journal of Materials Processing Technology,2016,229:668-677, and the like. Studies by the researchers at the laser processing center at osaka university indicate that the laser bonding process of plastic and stainless steel plate is reliably connected due to the bubble pressurization theory during welding, i.e. bubbles generated by pyrolysis of plastic during welding push the surrounding liquid plastic to spread and wet the metal surface. Most researchers have studied the treatment of metal and plastic surfaces to enhance the strength of the bond between the two materials. Among them, the laser etching process has received wide attention as a process with controllable structure density and high efficiency. The grooves vertical to the stretching direction are etched on the metal surface by nanosecond or picosecond laser, so that the mechanical resistance of the two plates in the horizontal direction can be effectively increased, meanwhile, partial oxidation of the metal surface caused by laser ablation can be better combined with oxygen-containing functional groups in the plastic aggregate, and the mechanical property of the joint is improved. Most scholars are limited to studying lap joint forms and few scholars have studied laser welding processes of aluminum alloys and plastics. No researchers have studied the butt joint type welding process of aluminum alloy and plastic at the present stage, because the butt joint area of the thin plates is small, and the wettability of metal and plastic is poor, so that reliable connection is difficult to form. The problem that needs to be solved at present is to improve the welding joint form, increase the butt joint area while avoiding as far as possible the phenomenon of joint stress concentration, make aluminium alloy and successful the linking together realization lightweight of plastics.

Disclosure of Invention

The invention aims to solve the technical problem of providing a grinding clamp aiming at the defects in the prior art, and the grinding clamp can clamp an aluminum alloy sample and a plastic sample and carry out grinding operation, so that the joint ends of the aluminum alloy sample and the plastic sample are ground to form inclined planes with the same inclination.

The scheme is realized by the following technical measures: the laser welding method of the aluminum alloy and the plastic comprises the following steps:

(1) surface grinding treatment of the joint end surfaces of the aluminum alloy sample and the plastic sample: the inclination of the joint end face in the ground aluminum alloy sample and the ground plastic sample is equal by adopting a lap joint and butt joint mixed joint mode;

(2) nanosecond laser pre-etching treatment of the end face of the aluminum alloy sample: etching the ground end face of the aluminum alloy sample by using a nanosecond laser;

(3) assembling the joint ends of the aluminum alloy sample and the plastic sample and welding by adopting a laser: and after the joint end surfaces of the plastic sample are arranged on the upper side and the aluminum alloy sample are arranged on the lower side and the two joint end surfaces are tightly attached, performing laser single-pass or multi-pass welding forming by a laser.

Preferably, the nanosecond laser has a laser power of 20-100W, a frequency of 15-40KHz, a scanning speed of 1000-.

Preferably, the laser welding power of the laser is 30-300W, the welding speed is 50-500mm/s, the welding times are 1-8 times, and the weld bead spacing is 1-3 mm.

Preferably, the aluminum alloy test sample and the plastic test sample are equal-thickness plates, and the thickness is 1-4 mm.

The invention also provides a grinding fixture, which comprises a base and a slide rail connected with the base in a sliding way, a sample carrying table is arranged above the slide rail, one end of the sample carrying table is hinged with the slide rail, the other end of the sample carrying table is inserted into the slide rail through a support rod, the sample carrying table is connected with a lower supporting frame in a sliding way, one end of the aluminum alloy sample and one end of the plastic sample are placed on the sample carrying table, the other end of the aluminum alloy sample and the other end of the plastic sample are placed on the lower supporting frame and extend out of the end part of the lower supporting frame, the upper pressure plate, the lower support frame and the sample carrying table are wider than the aluminum alloy sample and the plastic sample, the upper press plate is provided with strip-shaped holes along the two sides of the width direction respectively, one end of each strip-shaped hole, which is close to the supporting rod, is provided with a loose bolt matched with the upper end face of the sample carrying table, and one end of each strip-shaped hole, which is far away from the supporting rod, is provided with a tight bolt matched with the end part of the lower supporting frame.

Preferably, a plurality of limiting grooves matched with the lower ends of the support rods are arranged on the slide rails along the sliding direction of the lower support frame.

Preferably, the sample loading table has an articulation angle alpha, and the value range of the articulation angle alpha is more than or equal to 0 degrees and less than or equal to 6 degrees.

The invention also provides a clamping fixture, which comprises a substrate for placing the aluminum alloy test sample and the plastic test sample with at least one characteristic, wherein two parallel pressing plates are arranged above the substrate, the two pressing plates respectively press opposite ends of the aluminum alloy test sample and the plastic test sample, two ends of each pressing plate are respectively detachably and fixedly connected with the corresponding pressing plate through studs, and a welding operation space is reserved between the opposite side surfaces of the two pressing plates.

Preferably, the clamping fixture further comprises two stop blocks, the two stop blocks can be respectively spliced with the back of the body ends of the aluminum alloy sample and the plastic sample, mounting grooves are symmetrically formed in two ends of the outer side surfaces of the two stop blocks respectively, and an elastic connecting piece can be sleeved in the two mounting grooves corresponding to the upper positions of the two stop blocks.

Preferably, a long hole corresponding to the position of the welding seam is arranged in the upper end face of the base plate and between the two pressure plates.

The beneficial effects of the invention can be known from the description of the above scheme:

in the laser welding method of the aluminum alloy and the plastic, the welding joint is a composite joint form integrating overlapping and butt joint, and simultaneously, the problems of serious stress concentration of the overlapping joint and small effective stress area of the butt joint are solved. In addition, the aluminum alloy sample subjected to laser etching has large horizontal resistance on the surface, better chemical bonding with one side of the plastic sample and higher joint strength, and the processed aluminum alloy sample has large surface roughness, higher laser absorption rate and a certain protection effect on a laser head, wherein the direction of a laser beam is not vertical to an interface;

the grinding fixture can clamp and grind the aluminum alloy sample and the plastic sample, and grind the joint ends of the aluminum alloy sample and the plastic sample into inclined planes with the same inclination so as to better realize the bubble pressurization theory, and the grinding fixture adopts an assembly form of embedded grinding, and the pre-grinding inclination is adjustable;

the clamping fixture provided by the invention can avoid vertical deflection and horizontal displacement in the welding process by virtue of vertical bolt pressurization and horizontal spring pressurization, realizes more reliable welding, and is formed by adopting laser multi-pass welding.

In conclusion, the laser welding method breaks through the traditional lap joint form, the grinding fixture is utilized to grind the surfaces to be welded of the aluminum alloy sample and the plastic sample, the aluminum alloy sample and the plastic sample are enabled to obtain inclined end surfaces with the same inclination, nanosecond laser pre-etching treatment is carried out on the aluminum alloy surface, finally, the clamping fixture is adopted to clamp the surfaces and then laser multi-pass welding forming is carried out, the design freedom degree of the aluminum alloy sample and the plastic sample joint can be effectively improved, stress concentration caused by the lap joint form is reduced, the welding speed is high, the joint quality is good, the welded sample does not need post-treatment and has reliable strength. Therefore, compared with the prior art, the method has prominent substantive features and remarkable progress, and the beneficial effects of the implementation are also obvious.

Drawings

FIG. 1 is a schematic view of a grinding jig according to the present invention;

fig. 2 is a schematic structural view of the clamping fixture of the present invention.

FIG. 3 is a schematic diagram of the welding process and the welding structure of an aluminum alloy sample and a plastic sample in the laser welding method of aluminum alloy and plastic according to the present invention;

in the figure, a is a laser beam, b is a scanning path of the laser beam, 1 is an upper pressing plate, 2 is a tight bolt, 3 is an aluminum alloy sample, 4 is a hinged shaft, 5 is a sample carrying table, 6 is a lower supporting frame, 7 is a supporting rod, 8 is a sliding rail, 9 is a base, 10 is a stop block, 11 is a base plate, 12 is a plastic sample, 13 is a pressing plate, 14 is a stud, 15 is a strip-shaped hole, 16 is a loose bolt, 17 is a limiting groove, 18 is an installation groove and 19 is a strip-shaped hole.

Detailed Description

In order to clearly illustrate the technical features of the present solution, the following explains the present solution by way of specific embodiments and with reference to the accompanying drawings.

A laser welding method of aluminum alloy and plastic comprises the following steps:

(1) surface grinding treatment of joint end faces of aluminum alloy sample 3 and plastic sample 12: the aluminum alloy sample 3 and the plastic sample 12 are equal-thickness plates, the thickness is 1-4mm, the plastic sample 12 must have thermoplasticity, namely the plastic sample can be softened to flow after being heated, a lap joint and butt joint mixed joint mode is adopted, the grinding clamp is utilized to respectively carry out surface treatment on the aluminum alloy sample 3 and the plastic sample 12, the inclination of the joint end surfaces in the aluminum alloy sample 3 and the plastic sample 12 after grinding is equal, and the air bubble pressurization theory can be better realized due to the equal inclination;

(2) nanosecond laser pre-etching treatment of the 3 end surfaces of the aluminum alloy sample: etching the ground end face of the aluminum alloy sample 3 by using a nanosecond laser, wherein the depth direction of a laser etching groove is required to be parallel to the thickness direction of the aluminum alloy sample 3 and the plate of the plastic sample 12, namely the scanning direction is parallel to the surfaces of the aluminum alloy sample 3 and the plate of the plastic sample 12 and is vertical to the side face, the laser power of the nanosecond laser is 20-100W, the frequency is 15-40KHz, the scanning speed is 1000 plus materials 20000mm/s, the scanning interval is 50-500 mu m, and the scanning frequency is 2-8 times; the end face of the joint after etching treatment has certain roughness, and is partially oxidized, so that the etching process not only improves the laser absorption rate of the alloy, saves energy, but also can effectively improve the strength of the joint;

(3) the joint ends of the aluminum alloy sample 3 and the plastic sample 12 are assembled and welded by a laser: the joint ends of the aluminum alloy sample 3 and the plastic sample 12 adopt a lap joint and butt joint mixed mode, the joint end face of the plastic sample 12 is arranged on the upper side, the joint end face of the aluminum alloy sample 3 is arranged on the lower side, the end faces of the two joints are tightly attached and then clamped by the clamping fixture disclosed by the invention, the tight attachment and seamless connection of the two joint end faces are ensured, no lateral displacement exists, and finally, a laser is adopted for carrying out laser single-pass or multi-pass welding forming, wherein the laser welding power of the laser is 30-300W, the welding speed is 50-500mm/s, the welding frequency is 1-8 times, and the welding bead interval is 1-3 mm.

The laser welding method adopts a joint form of lapping and butt joint, and carries out laser pre-etching treatment on the end surface of the aluminum alloy sample 3, so that the surface of the joint is smooth, the stress concentration is small, the joint has a larger combination area than the joint, and the performance of the joint can be effectively improved. And (3) carrying out laser etching on the inclined surface of the joint of the aluminum alloy sample 3 to construct a groove, wherein the direction of the groove is vertical to the stress direction of the tensile test. During welding, bubbles generated by plastic pyrolysis promote liquid plastic to be slowly solidified after being filled into the metal groove, so that the resistance of the joint in the horizontal direction is effectively improved, meanwhile, partial oxidation exists on the surface of the aluminum alloy sample 3 subjected to laser etching, van der Waals force effect exists between the oxide and the oxygen-containing functional group in the plastic, the aluminum alloy sample 3 and the plastic sample 12 are better in chemical combination, and the strength is obviously improved. The roughness of the aluminum alloy surface after the laser etching treatment is larger, the absorptivity to laser is higher, and in the process of laser etching grooving and the process of laser welding, as shown in fig. 1, the direction of a laser beam is the Z-axis direction, the scanning direction of the laser beam is X → Y → X → Y → X → Y, and so on, the direction of the laser beam is not perpendicular to the surface to be welded of the aluminum alloy sample 3, preferably, the angle beta is formed between the direction of the laser beam and the surface to be treated and to be welded of the aluminum alloy sample 3, the value range of the angle beta is 84 degrees to 90 degrees, the radiation of the laser reflected by the aluminum alloy surface to the laser head is effectively avoided, and the laser head is protected to a certain extent.

The invention also provides a grinding fixture, as shown in fig. 2, which comprises a base 9 and a slide rail 8 connected with the base 9 in a sliding manner, wherein the slide rail 8 is in clearance fit with the base 9, so that the slide rail 8 can slide normally, and the slide rail 8 cannot move laterally due to overlarge clearance between the slide rail 8 and the base to ensure the grinding precision, the base 9 is kept still during grinding operation, the slide rail 8 slides relative to the base 9, the feeding of an aluminum alloy sample 3 and a plastic sample 12 is realized, and the abrasion of the whole fixture can be reduced. The utility model discloses a sample carrying platform, including slide rail 8, sample carrying platform 5, slide rail 8, hinge shaft 4, sample carrying platform 5's hinge angle is alpha, hinge angle alpha's value scope is 0 and is less than or equal to 6 for alpha, sample carrying platform 5's the other end passes through vaulting pole 7 and 8 pegs graft with slide rail, particularly, slide rail 8 is last to be provided with a plurality of spacing slot 17 with the lower extreme complex of vaulting pole 7 along under bracing frame 6's slip direction, and sample carrying platform 5 can rotate around hinge shaft 4, makes vaulting pole 7 insert and obtains different grinding inclinations in the spacing slot 17 of difference, guarantees that anchor clamps have certain angle degree of freedom, and grinding inclination can also be adjusted under the circumstances of guaranteeing stable support to this kind of structural style to the inclined plane requirement of adaptation aluminum alloy sample 3 and plastics sample 12 joint terminal surface. And the sample carrying table 5 is connected with a lower supporting frame 6 in a sliding manner, a sliding groove matched with the lower supporting frame 6 is formed in the sample carrying table 5, and the lower supporting frame 6 slides in the sliding groove so as to adjust the supporting length according to the lengths of the aluminum alloy sample 3 and the plastic sample 12. The one end of aluminum alloy sample 3 and plastics sample 12 is placed on carrying sample platform 5, the other end is placed in on lower braced frame 6 and is stretched out the tip of lower braced frame 6, top board 1 has been placed on aluminum alloy sample 3 and the plastics sample 12, top board 1, lower braced frame 6 and the width of carrying sample platform 5 all are greater than the width of aluminum alloy sample 3 and plastics sample 12 to guarantee that top board 1, lower braced frame 6 and carry sample platform 5 can cover aluminum alloy sample 3 and plastics sample 12 in the width direction, guarantee that aluminum alloy sample 3 and plastics sample 12 can be by firm compressing tightly. Strip-shaped holes 15 are respectively formed in two sides of the upper pressing plate 1 in the width direction (namely, in the direction perpendicular to the moving direction of the upper pressing plate 1), the strip-shaped holes 15 extend in the moving direction of the upper pressing plate 1, one end, close to the supporting rod 7, of each strip-shaped hole 15 is provided with a loose bolt 16 matched with the upper end face of the sample carrying table 5, one end, far away from the supporting rod 7, of each strip-shaped hole is provided with a tight bolt 2 matched with the end part of the lower supporting frame 6, the positions of the tight bolts 2 and the loose bolts 16 can be adjusted along the strip-shaped holes 15 according to different grinding gradients, the best effect of limiting deformation of the pre-ground aluminum alloy samples 3 and the plastic samples 12 is achieved, the whole grinding clamp can be adapted to the aluminum alloy samples 3 and the plastic samples 12 with different thicknesses by the bolt fixing mode, and the degree of freedom of the selected samples is better satisfied.

The aluminum alloy sample 3 and the plastic sample 12 are ground by using sand paper or abrasive belt, the sand paper can be cushioned by a flat surface article (such as a glass plate) to reduce the height difference, and the purpose of shortening the extending distance between the upper pressure plate 1 and the lower support frame 6 is achieved, so that the grinding stability is improved. The grinding fixture can clamp and fix the aluminum alloy sample 3 and the plastic sample 12, and can push the upper pressure plate 1, the aluminum alloy sample 3, the plastic sample 12 and the lower support frame 6 to perform continuous grinding on the aluminum alloy sample 3 and the plastic sample 12 along the sample carrying table 5 in a micro-motion mode. The lower supporting frame 6 drives the upper pressure plate 1 to slide along the sample carrying table 5, and along with the reduction of the pre-grinding angle, the upper pressure plate 1, the aluminum alloy sample 3, the plastic sample 12 and the lower supporting frame 6 can be integrally extended along the sample carrying table 5 to meet the pressing requirement, so that the deformation of the aluminum alloy sample 3 and the plastic sample 12 plate in the grinding process is prevented.

The invention also provides a clamping fixture, as shown in fig. 3, which comprises a substrate 11 for placing the aluminum alloy sample 3 and the plastic sample 12 with at least one of the above characteristics, wherein two parallel pressing plates 13 are arranged above the substrate 11, the two pressing plates 13 respectively press opposite ends of the aluminum alloy sample 3 and the plastic sample 12, two ends of the pressing plates 13 are respectively detachably and fixedly connected with the pressing plates 13 through studs 14, a welding operation space is reserved between opposite side surfaces of the two pressing plates 13 to facilitate welding operation, and the pressing plates 1 can ensure that the aluminum alloy sample 3 and the plastic sample 12 to be welded cannot generate vertical deflection. The clamping fixture further comprises two stop blocks 10, the two stop blocks 10 can be respectively inserted into opposite ends of the aluminum alloy sample 3 and the plastic sample 12, mounting grooves 18 are symmetrically formed in two ends of the outer side faces (namely the side faces opposite to the insertion faces) of the two stop blocks 10, an elastic connecting piece (not shown in the figure) can be sleeved in the two mounting grooves 18 corresponding to the two stop blocks 10, and preferably, the elastic connecting piece is a spring. And a long hole 19 corresponding to the position of a welding seam is arranged in the upper end surface of the base plate 11 and positioned between the two pressure plates 13, and the long hole 19 can prevent the aluminum alloy test sample 3 and/or the plastic test sample 12 to be welded from being welded with the base plate 11 due to overlarge welding power. After the structure is adopted, before welding, the two welding ends of the aluminum alloy sample 3 to be welded and the plastic sample 12 are pressed tightly through the two pressing plates 13, the opposite ends of the aluminum alloy sample 3 to be welded and the plastic sample 12 to be welded are respectively inserted into the two check blocks 10, and then the two ends of the two pressing plates 13 are elastically clamped through the two springs, so that the two aluminum alloy samples 3 to be welded and the two plastic samples 12 to be welded can not generate horizontal displacement.

In the clamping fixture, the pressing plate 13 can avoid the vertical deflection of the aluminum alloy sample 3 and the plastic sample 12 to be welded, and can eliminate the gap between the joints of the aluminum alloy sample 3 and the plastic sample 12, thereby better realizing the bubble pressurization theory. The opposite ends of the two aluminum alloy samples 3 to be welded and the opposite ends of the plastic sample 12 to be welded are respectively inserted into the two check blocks 10, and then the two ends of the two pressing plates 13 are elastically clamped through the two springs, so that the two aluminum alloy samples 3 to be welded and the plastic sample 12 cannot generate horizontal displacement. The pressure in the vertical direction and the pressure in the horizontal direction can make the positive stress on the inclined planes of the aluminum alloy sample 3 and the plastic sample 12 larger, reduce the friction force in the direction perpendicular to the inclined planes, limit the double-shaft displacement and deformation of the two plates and realize more reliable welding.

Technical features not described in the present invention can be implemented by the prior art, and are not described in detail herein. The present invention is not limited to the above-described embodiments, and variations, modifications, additions and substitutions which are within the spirit of the invention and the scope of the invention may be made by those of ordinary skill in the art are also within the scope of the invention.

Claims

1. The grinding clamp is characterized in that: it includes the base and with base sliding connection's slide rail, the top of slide rail is provided with carries the appearance platform, carry the one end of appearance platform articulated with the slide rail, the other end passes through the vaulting pole and pegs graft with the slide rail, carry the appearance bench sliding connection have lower supporting frame, and the one end of aluminum alloy sample and plastics sample is placed on carrying the appearance platform, the other end is placed in lower supporting frame and is stretched out lower supporting frame's tip, the top board has been placed on aluminum alloy sample and the plastics sample, the width of top board, lower supporting frame and year appearance platform all is greater than the width of aluminum alloy sample and plastics sample, the bar hole has been seted up respectively to the both sides along width direction of top board, the one end that is close to the vaulting pole in the bar hole is provided with the upper end complex loose bolt that carries the appearance platform, keep away from being provided with the tight bolt of lower supporting frame's tip complex in the one end of vaulting pole, be provided with a plurality of lower extreme complex spacing slot with the vaulting pole along lower supporting frame's slip direction on the slide rail.

2. A grinding jig according to claim 1 wherein: the sample carrying table is characterized in that the hinge angle of the sample carrying table is alpha, and the value range of the hinge angle alpha is more than or equal to 0 degree and less than or equal to 6 degrees.