CN111044358A

CN111044358A - Testing device and testing method for stringer cut-off end test with free side edge

Info

Publication number: CN111044358A
Application number: CN201911175201.4A
Authority: CN
Inventors: 尚海江; 李星; 温顺达; 李程辉; 李梦琳
Original assignee: Commercial Aircraft Corp of China Ltd; Beijing Aeronautic Science and Technology Research Institute of COMAC
Current assignee: Commercial Aircraft Corp of China Ltd; Beijing Aeronautic Science and Technology Research Institute of COMAC
Priority date: 2019-11-26
Filing date: 2019-11-26
Publication date: 2020-04-21
Anticipated expiration: 2039-11-26
Also published as: CN111044358B

Abstract

The invention relates to the technical field of composite material mechanical property testing, and provides a testing device and a testing method for a stringer cut-off end test with free side edges, wherein a test piece comprises a skin, a stringer, a dummy rib and a test piece end reinforcing gasket; the dummy ribs are arranged on the rib station surfaces, the stringers are symmetrically arranged on two sides of the dummy ribs, the stringers are stopped at the rib station positions, and the end part reinforcing gaskets of the test piece are arranged at the end parts of the stringers; the skin is provided with a transverse reinforcing member; the test fixture comprises an end fixture, a dummy rib supporting fixture and a skin surface external supporting fixture; the end clamp is used for clamping the end of the test piece, the dummy rib supporting clamp is used for clamping the dummy rib, and the skin surface outer supporting clamp is used for restraining displacement and rotation of the skin surface outer direction. The test fixture is designed to be matched with the test piece, the test piece and the test fixture are simple and reasonable, and the manufacturing cost is low; the testing device is novel and simple, has high practicability and has high popularization and application values.

Description

Testing device and testing method for stringer cut-off end test with free side edge

Technical Field

The invention relates to the technical field of composite material mechanical property testing, in particular to a testing device and a testing method for a stringer cut-off end test with free side edges.

Background

At present, the composite material reinforced wall plate structure is widely applied to an airplane structure. For fuselage, wing or empennage structures, T-shaped, I-shaped, hat-shaped stringer stiffened panel structures are generally adopted, and the stringers and skins are generally formed by co-curing, co-bonding, secondary connection and the like.

The stringers inevitably need to be terminated at a certain location on the skin, depending on the requirements of the actual structure in terms of function, connection, etc., and therefore stringer termination ends may occur in the stiffened panel structure. Stress concentration at the stringer termination end can occur at the section due to changes in structural configuration and stiffness, resulting in debonding or delamination failures at the stringer termination end. Significant attention is therefore required at the stringer cutoff in the structural design.

According to the requirements of physical dimension, connection, function and the like of actual components, a plurality of patents exist for patenting the design form of the stringer cut-off end, wherein the number of the patents is 3 in a relatively representative way:

one Stringer termination design method is from Stringer stiff air composite structures patent No. EP3040268a 1. The design of the supporting structure at the ends of the stringers and the ends adopts a mode of directly connecting with the web of the supporting structure. The configuration enables loads to be directly transferred from the stringers to the web locations of the support structure, and force transfer is more efficient.

The second Stringer end design is from Load Transfer Devices at Stringer Run-out patent number US20120234978A 1. The configuration contemplates a sleeve that completely encases the stringer ends and connects the stringer webs and stringer tapes to the sleeve, respectively. According to the design scheme, the end load can be transferred to the skin from the web and the edge strip respectively, the load transfer path is increased, so that the load transfer is uniform, and the stress concentration of the end is avoided.

The third Stringer end design is from Optimized Stringer Run-out Zones in Aircraft Components patent No. US 2013/0101801A 1. The retrieval patent optimizes the stringer end area, and the force transfer of the stringer end is optimized through different shapes and different bevel angle designs of the stringer end.

The stringer cut-off end test device and method are less patented, and several typical schemes are examined as follows:

scheme I, a test scheme aiming at a metal stringer end is mentioned in the research on the tensile test of the metal wing stringer end (from civil aircraft design and research 2015 03, Koshiqiang by authors). According to the test scheme, a single stringer typical end structure is selected to design a test piece, and the test piece consists of a stringer and a skin. The test pieces are divided into three groups, namely a test piece A-1, a test piece A-2 and a test piece A-3, and the corresponding bevel angles are respectively 15 degrees, 30 degrees and 45 degrees;

the experiment designed a boundary support jig to simulate two boundary conditions:

(a) two side edges of the covering are supported. And the out-of-plane deformation of the side edge of the skin is limited by clamping the side edge of the skin of the test piece by the clamp.

(b) And supporting the wing ribs. The out-of-plane deformation of the test piece at the rib connection area was limited by bolting against the stringer tape at the rib connection area, simulating the out-of-plane stiffness of the rib at that location.

And in the second scheme, the wing stringer end selection test of a certain wing project in China. Five different stringer ends are selected respectively, and different beveling angles and beveling modes of the stringers are selected respectively for type selection tests. In order to ensure the reality of boundary conditions of two side edges of a test examination area, a three-stringer test piece is adopted.

The test is carried out on a wallboard tension-compression test platform, the test piece is connected to the transition end of the platform through clamping plates arranged at two ends, and the test piece is connected with the dummy piece of the rib of the test piece by adopting lateral support, so that the out-of-plane displacement of the wing skin at the rib position is limited, meanwhile, the test piece can axially move along a sliding rail, and the axial deformation of the test piece cannot be limited during loading. The installation height of the 2 hydraulic actuating cylinders is consistent with that of a rigid center of the test piece, and the condition that an axial tensile/compressive load is applied to the test piece to avoid causing additional bending moment is guaranteed. And during the compression test, knife edges are applied to two sides of the non-clamping end of the test piece to prevent buckling.

And a third scheme is that the stringer cut-off end test of a certain fuselage customs clearance project in China. The test adopts a single stringer configuration, and different clamps are respectively arranged aiming at the tensile test and the compression test. The end part of the tensile test piece is connected with the test piece through a loading clamp and a bolt, and a lateral supporting clamp simulating rib is arranged in the middle of the stop end of the stringer to support the test piece from the surface.

For the compression test piece, the end part adopts an encapsulation structure, the test piece is directly placed on a test bed for loading, and lateral supporting clamps are respectively arranged at the middle positions of the two stringer stop ends and the stringer side skin to limit the displacement of the middle part of the test piece.

The deficiencies of the above 3 experimental protocols:

the first scheme is as follows: the skin side support clamp is not connected with an external structure, and is insufficient for the skin side support structure.

Scheme II: the multi-stringer test piece is large in size, high in requirement on loading equipment, low in fatigue loading efficiency and high in difficulty.

The third scheme is as follows: different clamps are respectively arranged for the hat-shaped stringer structure and for the tensile test and the compression test, and the manufacturing cost is higher.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a testing device and a testing method for a stringer cut-off end test with free side edges.

The invention adopts the following technical scheme:

a testing device for a stringer cut-off end test with free side edges comprises a test piece and a test clamp;

the test piece comprises a skin, a stringer, a false rib and a test piece end reinforcing gasket; the dummy ribs are arranged at rib station surfaces, the stringers are symmetrically arranged on two sides of each dummy rib, the stringers are stopped at the rib station positions, and the test piece end reinforcing gaskets are arranged at the ends of the test pieces;

the test fixture comprises an end fixture, a dummy rib supporting fixture and a skin surface external supporting fixture; the end clamp is used for clamping the end reinforcing gasket of the test piece at the end part of the stringer, the dummy rib supporting clamp is used for clamping the dummy rib, and the skin surface outer supporting clamp is used for restraining displacement and rotation of the skin surface outer direction.

Further, the test piece comprises a test examination area and a non-test examination area; the stringer webs are cut off at rib stations, and the first stringer cut-off ends and the second stringer cut-off ends on the two sides of the dummy ribs are both stringer cut-off ends in the test examination area; the long truss web plate is stopped in the clamping area, and the stopping end of the first clamping area and the stopping end of the second clamping area are non-test checking area stopping ends; the end reinforcing gasket is grooved at the cut-off end of the clamping zone, and the end clamp is clamped on the end reinforcing gasket through hydraulic pressure.

Further, the end clamp comprises an end clamping block and a U-shaped groove arranged on the end clamping block; the U-shaped groove avoids clamping a stringer web and simulates the real stress of a segmented stringer structure. .

Furthermore, the width of the skin of the assessment area is the stringer distance of the actual structure, and the skin of the clamping area close to the end part is widened.

Further, the end reinforcing gasket is adhered to the skin at the end of the test piece.

Furthermore, the dummy rib supporting clamp comprises a supporting upright post, a sliding rail, a supporting cross beam, a dummy rib clamping block and a spring; 2 supporting cross beams are arranged among the supporting upright columns, sliding rails are arranged among the 2 supporting cross beams, and the false rib clamping blocks are arranged on the sliding rails; a spring is arranged between the dummy rib clamping block and the supporting cross beam, and the dummy rib clamping block can slide up and down along the slide rail (the spring balances the gravity of the dummy rib supporting clamp, so that the dummy rib is kept at the middle position of the dummy rib in a free state, and additional load is prevented from being added to the dummy rib); the false rib can move along the axial direction of the stringer through the sliding rail under the clamping of the false rib clamping block.

Further, the skin out-of-plane support fixture comprises a skin reinforcing member, a connecting structure and a support structure; the skin reinforcing member is arranged in a non-test examination area of the skin to reinforce the transverse rigidity of the test piece so as to prevent the skin from being unstable; the connecting structure is used for fixedly connecting or detachably connecting the skin reinforcing member and the supporting structure.

Further, the skin reinforcing member is provided in the skin width direction.

The invention also provides a testing method for the stringer cut-off end test with free side edges, which is carried out by using the testing device for the stringer cut-off end test with free side edges and comprises the following steps:

s1, clamping a test piece end reinforcing gasket on the upper part of the test piece by an upper end clamp to enable the test piece to be naturally vertical;

s2, adjusting the position of the clamp at the lower end part, centering the lower end part of the test piece, clamping the reinforced gasket at the end part of the test piece at the lower part, and finishing clamping the lower part of the test piece;

s3, adjusting the position of the skin surface external clamp to complete the fixation of the skin surface external clamp;

and S4, adjusting the position of the dummy rib supporting clamp to enable the clamping middle surface and the dummy rib middle surface to be positioned on the same horizontal plane, and clamping the dummy rib.

Further, in step S4, the dummy rib is clamped between the clamp blocks of the dummy rib supporting jig and the dummy ribs by tightening the bolts.

The invention has the beneficial effects that: the test piece is novel and reasonable in design, the cut-off end of the clamping area of the stringer web is reinforced through the end part reinforcing gasket, and the strength of the end part of the test piece is improved; the skin is widened near the clamping area at the end part of the test piece, so that the clamping area is prevented from being damaged in advance; the skin is provided with a skin reinforcing member in the width direction, so that the skin is prevented from being unstable in the direction out of the skin surface; the test fixture is designed to be matched with the test piece, the test fixture is simple and reasonable, and the manufacturing cost is low; the test device is novel and simple, has high practicability and has high popularization and application values.

Drawings

Fig. 1 is a schematic view of an overall structure of a testing apparatus for a stringer cut-off end test with free side edges according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a split of the test apparatus for testing the cut-off end of a stringer with free side edges in the example.

FIG. 3 is a schematic structural view of a test piece in the example.

FIG. 4 is a schematic structural view (back side) of a test piece in the example.

FIG. 5 is a schematic structural diagram of an outer skin surface support clamp in the embodiment.

FIG. 6 is a detail view of the skin out-of-plane support clip of FIG. 5.

Fig. 7 is a schematic structural view of an end clamp in the embodiment.

FIG. 8 is a schematic structural view of a dummy rib supporting jig according to an embodiment.

FIG. 9 is a schematic view showing the mounting step of the test jig in the embodiment.

In the figure: 1-a support column; 2-test piece; 3-a skin out-of-plane support fixture; 4-end clamp; 5-dummy rib support jig; 201-test piece end reinforcing gasket; 202- (non-test examination area) first clamping area cut-off end; 203-stringer webs; 204- (test examination area) first stringer cutoff end; 205-false ribs; 206- (test examination area) second stringer cut-off end; 207-skin; 208- (non-test examination region) second clamping region cut-off; 301-skin stiffening members; 302-a connecting structure; 303-a support structure; 401-end clamp block; 402-a U-shaped slot; 501-a slide rail; 502-a support beam; 503-false rib clamp block; 504-spring.

Detailed Description

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that technical features or combinations of technical features described in the following embodiments should not be considered as being isolated, and they may be combined with each other to achieve better technical effects. In the drawings of the embodiments described below, the same reference numerals appearing in the respective drawings denote the same features or components, and may be applied to different embodiments.

As shown in fig. 1-2, the testing device for testing the stringer stopping end with free side edges according to the embodiment of the invention comprises a test piece 2 and a test fixture. The test piece 2 comprises a skin 207, a stringer, a false rib 205 and a test piece end reinforcing gasket 201; the dummy rib 205 is provided at a rib station face, the stringers are symmetrically arranged on both sides of the dummy rib 205, the stringers are terminated at the rib station face, and the test piece end reinforcing shims 201 are provided at the ends of the stringers to prevent premature breakage of the nip cut ends (202 and 208); the test fixture comprises an end fixture 4, a dummy rib supporting fixture 5 and a skin surface external supporting fixture 3; the end clamp 4 is used for clamping the end reinforcing gasket 201 of the test piece at the end of the stringer, the dummy rib supporting clamp 5 is used for clamping the dummy rib 205, and the skin out-of-plane supporting clamp 3 is used for restraining displacement and rotation of the skin out-of-plane direction. Preferably, in order to reinforce the transverse rigidity of the test piece 2 and prevent the skin 207 from being unstable, a skin reinforcing member 301 is added to the skin 207 non-assessment area of the test piece 2.

Preferably, as shown in FIGS. 3-4, the test piece 2 includes a test examination region and a non-test examination region; the stringer webs 203 are cut off at rib stations, and the first stringer cut-off ends 204 and the second stringer cut-off ends 206 on two sides of the dummy ribs 205 are both the test check area stringer cut-off ends; the stringer web 203 is cut off in the clamping area, and both the first clamping area cut-off end 202 and the second clamping area cut-off end 208 are non-test examination area cut-off ends; the end reinforcing gasket 201 is grooved at the cut-off end of the clamping zone and the end clamp 4 is clamped hydraulically on the end reinforcing gasket 201.

Preferably, the width of the skin 207 in the test area is the stringer pitch of the actual structure, the skin 207 in the clamping area is subjected to widening treatment, and the reinforcing gasket 201 is adhered.

The test fixture is shown in fig. 5-8. Due to the loaded nature of the cut ends of the segmented stringers, the end clamps are U-shaped to avoid clamping stringer webs 203 while avoiding interference between stringer webs 203 and skin 207 during testing. Clamping the dummy rib 205 with a clamp for rib station positions constrains the out-of-plane displacement of the dummy rib 205. To constrain skin 207 out-of-plane displacement to prevent side skin buckling, skin stiffening members 301 were added to skin 207 of trial 2.

As shown in fig. 5-6, skin out-of-plane support fixture 3 includes skin stiffening members 301, connecting structures 302, and support structures 303, where skin stiffening members 301 are disposed in the non-test core region of skin 207 to stiffen test piece 2 in the lateral direction to prevent skin 207 from buckling; connecting structure 302 fixedly connects or detachably connects skin stiffening member 301 to support structure 303.

As shown in fig. 7, the end clamp 4 comprises an end clamp block 401, a U-shaped slot 402; the U-shaped channel 402 avoids clamping the stringer web 203.

As shown in fig. 8, the dummy rib supporting jig 5 includes a supporting column 1, a slide rail 501, a supporting beam 502, a dummy rib block 503, and a spring 504; 2 supporting cross beams 502 are arranged among the supporting upright columns 1, a sliding rail 501 is arranged among the 2 supporting cross beams 502, and the sliding rail 501 is provided with the false rib clamping blocks 503; a spring 504 is arranged between the false rib clamping block 503 and the supporting beam 502, and the false rib clamping block 503 can slide up and down along the slide rail 501; the dummy rib 205 can be moved axially along the stringer by the slide rail 501 under the clamping of the dummy rib clamp block 503.

When the test testing device is used for carrying out experiments, firstly, a test piece needs to be prepared, and then, a test fixture is installed, wherein the specific steps are as shown in fig. 9:

s1, the upper end clamp 4 clamps the test piece end reinforcing gasket 201 on the test piece 2 to enable the test piece to be vertical naturally;

s2, adjusting the position of the lower end clamp 4, centering the lower end of the test piece 2, clamping the lower test piece end reinforcing gasket 201, and finishing clamping the lower part of the test piece 2;

s3, adjusting the position of the skin surface outer clamp 3 to complete the fixation of the skin surface outer clamp 3;

and S4, adjusting the position of the dummy rib supporting clamp 5 to enable the clamping middle surface and the dummy rib 205 middle surface to be positioned on the same horizontal plane, and clamping the dummy rib clamping block 503 and the dummy rib 205 of the dummy rib supporting clamp 5 through tightening bolts.

Compared with the traditional continuous stringer cut-off end test scheme, the invention has the following innovation points:

1. the test piece 2 is of a single stringer configuration and is symmetrical along the rib standing surface. A dummy rib 205 is arranged on the rib station surface, and the stringer webs 203 on the two sides are cut off at the dummy rib 205 to form stringer cutting ends serving as test examination core areas;

2. the stringer cut-off end test piece 2 is widened in the clamping area and a test piece end reinforcing gasket 201 is adhered. The stringer webs 203 on two sides of the dummy rib 205 are cut off in a clamping area, the test piece end reinforcing gasket 201 is grooved at the cut-off end of the clamping area, the end clamp 4 is clamped on the test piece end reinforcing gasket 201 through hydraulic pressure, and the clamping area comprises a groove area of the test piece end reinforcing gasket 201;

3. the dummy rib 205 is clamped by a dummy rib clamping block 503, and the dummy rib 205 can move along the axial direction of the stringer in the loading process by a sleeve sliding rail 501;

4. a reinforcing structure along the width direction is arranged on the test piece skin 207, and is connected with the support upright 1 through a clamp to restrain the displacement of the skin 207 in the out-of-plane direction and the rotation around the central point.

While several embodiments of the present invention have been presented herein, it will be appreciated by those skilled in the art that changes may be made to the embodiments herein without departing from the spirit of the invention. The above examples are merely illustrative and should not be taken as limiting the scope of the invention.

Claims

1. A testing device for testing a stringer cut-off end with free side edges is characterized by comprising a test piece and a test clamp;

the test piece comprises a skin, a stringer, a false rib and a test piece end reinforcing gasket; the dummy ribs are arranged on rib station surfaces, the stringers are symmetrically arranged on two sides of each dummy rib, the stringers are stopped at the rib station positions, and the test piece end reinforcing gaskets are arranged in the test piece end clamping areas;

the test fixture comprises an end fixture, a dummy rib supporting fixture and a skin surface external supporting fixture; the end part clamp is used for clamping the end part of the test piece, the false rib supporting clamp is used for clamping the false rib, and the skin surface outer supporting clamp is used for restraining displacement and rotation of the skin surface outer direction.

2. The free-sided stringer end-stop test device of claim 1, wherein said test piece includes a test-check region and a non-test-check region; the stringer webs are cut off at rib stations, and the first stringer cut-off ends and the second stringer cut-off ends on the two sides of the dummy ribs are both stringer cut-off ends in the test examination area; the long truss web plate is stopped in the clamping area, and the stopping end of the first clamping area and the stopping end of the second clamping area are non-test checking area stopping ends; the end reinforcing gasket is grooved at the cut-off end of the clamping zone, and the end clamp is clamped on the end reinforcing gasket through hydraulic pressure.

3. The free-sided stringer end-stop test apparatus of claim 2, wherein said end clamp includes an end clamp block and a U-shaped slot disposed on said end clamp block; the U-shaped groove avoids clamping a long truss web, and simulates real force transfer of the segmented long truss.

4. The free-side stringer end-stop test apparatus of claim 2, wherein the width of the skin in the test audit area is taken as the stringer pitch of the actual structure, and the skin is widened near the end clamp area.

5. The free-side stringer end-stop test apparatus of claim 2, wherein said end reinforcing spacers are adhered to the skin of the test piece end clamping area.

6. The free-sided stringer end-stop test apparatus of any of claims 1-5, wherein said dummy rib support fixture comprises a support column, a slide rail, a support beam, a dummy rib clamp block, a spring; 2 supporting cross beams are arranged among the supporting upright columns, sliding rails are arranged among the 2 supporting cross beams, and the false rib clamping blocks are arranged on the sliding rails; a spring is arranged between the dummy rib clamping block and the supporting beam, and the dummy rib clamping block can slide up and down along the slide rail; the false rib can move along the axial direction of the stringer through the sliding rail under the clamping of the false rib clamping block.

7. The free-side stringer end-stop test apparatus of any of claims 1-5, wherein said skin out-of-plane support fixture comprises a skin stiffening member, a connecting structure, and a support structure; the skin reinforcing member is arranged in a non-test examination area of the skin to reinforce the transverse rigidity of the test piece so as to prevent the skin from being unstable; the connecting structure is used for fixedly connecting or detachably connecting the skin reinforcing member and the supporting structure.

8. The free-side stringer cutoff testing apparatus of claim 7 wherein said skin stiffening members are disposed along the width of the skin.

9. A method of testing a free-sided stringer cut-off end using the free-sided stringer cut-off end test apparatus of any of claims 1-8, comprising the steps of:

10. The method of testing a cutoff end of a free-sided stringer of claim 9, wherein in step S4, the dummy rib is clamped between the clamp blocks of the dummy rib supporting jig and the dummy ribs by tightening bolts.