CN109883819B - Dynamic drawing method for bonding force of fiber cement-based composite material and combined clamp - Google Patents
Dynamic drawing method for bonding force of fiber cement-based composite material and combined clamp Download PDFInfo
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- CN109883819B CN109883819B CN201910165389.8A CN201910165389A CN109883819B CN 109883819 B CN109883819 B CN 109883819B CN 201910165389 A CN201910165389 A CN 201910165389A CN 109883819 B CN109883819 B CN 109883819B
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Abstract
The invention discloses a dynamic drawing method aiming at the bonding force of a fiber cement-based composite material and a combined clamp, and relates to the technical field of fiber stretching clamps. The clamp belongs to a fiber dynamic tensile clamp, and can be matched with a drop hammer impact tester to detect the interface bonding performance of a cement-based material. The combined clamp is reasonable in structural design and good in coordination of all links, can be used for various dynamic tensile tests by combining with a drop hammer impact testing machine, can improve the testing efficiency, and guarantees the testing accuracy.
Description
Technical Field
The invention discloses a dynamic bonding force drawing method of a fiber cement-based composite material and a combined clamp, belonging to the technical field of clamps and use methods.
Background
The fiber concrete is a novel composite material taking fiber as a reinforcing material and concrete as a matrix, the fiber has a reinforcing effect on the cement matrix in the concrete, the toughness of the fiber concrete can be greatly improved after the fiber is added into the cement matrix, and the physical and mechanical properties, such as compression strength, tensile strength, flexural strength and the like, of the fiber concrete are improved to different degrees. Because the fibers are distributed in the concrete uniformly in a large amount in unit volume, and the fibers and the cement matrix are interacted through the interface of the two materials, the deformation performance of the concrete is essentially changed by the fibers, and the fibers are added as if a large amount of fine ribs are doped in the concrete. When load acts on concrete, the fiber and the cement matrix are stressed and deformed together, and interface binding force generated by strain difference exists between the cement matrix and the fiber on an interface, so that the effects of preventing the initiation and the diffusion of concrete cracks and absorbing a large amount of energy are achieved, the binding strength between the fiber and the cement matrix is improved, the toughening effect of the fiber on the concrete is improved, and the deformation performance of the concrete is improved.
The fibers are classified into rigid fibers typified by steel fibers and flexible fibers typified by carbon fibers, glass fibers, basalt fibers, and the like. In actual engineering, the damage of fiber concrete is caused by the failure of the bonding performance of the fiber and a cement-based interface to a great extent, so that the bonding force of the fiber and a cement matrix directly influences the reinforcing, toughening and crack-resisting effects of the fiber on the concrete, and the quantitative characterization of the bonding strength of the interface is very important. And the methods for representing the interfacial mechanics are various, wherein the monofilament drawing method is an important means for evaluating the bonding performance of the fiber and cement-based interface. Many scholars at home and abroad perform monofilament drawing tests on fiber concrete and obtain a large number of meaningful results, but most researches are in the field of statics at present. The research on the mechanical property of the fiber concrete in the process of drawing the dynamic monofilament by the interface property is few and less.
In recent years, with the demand of people on the dynamic tensile properties of various materials and the development of dynamic tensile technology, many colleges and scientific research units in China have developed the dynamic tensile test research on various materials, wherein high-strength fibers are used as important components of high-strength composite materials, and the dynamic mechanical properties of the high-strength composite materials gradually attract the attention of people with the real demand. Since the dynamic tensile mechanical properties of the fibers are greatly different from the static tensile properties, the analysis of the dynamic mechanical response of the fibers by directly taking the static strength test results of the fibers has a bias, and therefore, the testing of the dynamic mechanical properties of the fiber bundles and the fiber monofilaments and the obtaining of the impact tensile stress-strain curve are very critical. The clamp provided by the invention is used for testing the interface bonding performance of the fiber and the cement base by considering the dynamic monofilament drawing test aiming at the fiber body and the fiber cement base under the action of dynamic load.
Disclosure of Invention
In order to solve the defects in the prior art, the invention discloses a dynamic bonding force drawing method of a fiber cement-based composite material and a combined clamp, wherein the clamp is reasonable in design and good in coordination of all links, and the method can be used for various dynamic tensile tests by combining a drop hammer impact testing machine, so that the testing efficiency can be improved, and the testing accuracy can be ensured.
The invention is realized by the following technical scheme:
the dynamic bonding force drawing combined clamp for the fiber cement-based composite material comprises a punched force bearing steel plate, a force transmission rod, a spring positioning guide rod, a spring pre-tightening clamping block, an outer frame, a test piece fixing frame, a force sensor, an annular clamping tool, a laser displacement sensor and a wire winding roll shaft; the outer frame comprises an outer frame top plate and an outer frame bottom plate which are horizontally arranged, a plurality of outer frame support rod screw holes are formed in the symmetrical positions of the outer frame top plate and the outer frame bottom plate, and the outer frame support rods penetrate through the outer frame support rod screw holes to connect the outer frame top plate and the outer frame bottom plate into a whole;
two spring positioning guide rod screw holes and a plurality of threaded rod supporting holes are formed in the middle of the outer frame bottom plate in a centrosymmetric manner, and threaded rod supports are arranged in the threaded rod supporting holes in a penetrating manner;
two dowel bar screw holes are symmetrically formed in the center of the impacted force-bearing steel plate, two dowel bar holes are symmetrically formed in the center of the outer frame top plate, and the positions of the dowel bar screw holes, the dowel bar holes and the spring positioning guide rod screw holes are symmetrical; the two dowel bar holes are internally and movably penetrated with dowel bars in the vertical direction, the dowel bars are double-headed screw bars with high rigidity, the upper ends of the two dowel bars are connected with dowel bar screw holes in the stressed force steel plate through screws, and the lower ends of the two dowel bars are connected with the upper parts of the spring pre-tightening clamping blocks through screws;
the lower part of the spring pre-tightening fixture block is connected with a spring positioning guide rod, the spring positioning guide rod is a vertically arranged high-rigidity double-end screw rod and is positioned on the same vertical axis with the dowel bar, the upper end of the spring positioning guide rod is connected with the spring pre-tightening fixture block through a screw, and the lower end of the spring positioning guide rod penetrates through a screw hole of the spring positioning guide rod and is connected with a leveling nut through a screw; a spring is sleeved outside the rod body of the spring positioning guide rod, and two ends of the spring respectively elastically press the spring to pre-tighten the fixture block and the outer frame bottom plate; in the vertical direction, the spring pre-tightening clamping block and the leveling nut provide a certain pre-tightening force for the spring together;
horizontal screw holes are symmetrically formed in the opposite inner side surfaces between the two spring pre-tightening clamping blocks, the two horizontal screw holes are respectively connected with one end of a wire winding roll shaft, the wire winding roll shaft is a double-end threaded rod, fastening nuts are further arranged at two ends of the wire winding roll shaft, and the fastening nuts are arranged on the inner sides of the horizontal screw holes; in the horizontal direction, the two spring pre-tightening clamping blocks are matched as a support of the wire winding roll shaft and provide support for the wire winding roll shaft through the horizontal screw hole; an annular fixture is movably sleeved outside the wire winding roll shaft, the cross section of the annular fixture is C-shaped and is attached to the wire winding roll shaft, a locking bolt is arranged on the annular fixture, and the wire winding roll shaft is tightly pressed by the annular fixture through the locking bolt;
the test piece fixing frame comprises a test piece fixing frame top plate and a test piece fixing frame bottom plate which are horizontally arranged, a force sensor screw hole I is formed in the center of the upper end face of the test piece fixing frame top plate, and the force sensor screw hole is connected with a force sensor; a fiber preformed hole is formed in the center of the base plate of the test piece fixing frame and is used for fiber yarns to pass through; fixing frame pull rod screw holes are symmetrically formed near four vertexes of the panel of the test piece fixing frame top plate and the test piece fixing frame bottom plate, and the fixing frame pull rods penetrate through the fixing frame pull rod screw holes to connect the test piece fixing frame top plate and the test piece fixing frame bottom plate into a whole; the pull rod of the fixing frame is a high-rigidity double-end screw rod;
a force sensor screw hole II is formed in the center of the top plate of the outer frame, the force sensor is a dynamic tension sensor and is positioned between the top plate of the outer frame and the top plate of the test piece fixing frame, and the upper end and the lower end of the force sensor are respectively connected with the top plate of the outer frame and the top plate of the test piece fixing frame through screws;
and a laser reflection sheet is adhered to the outer side of the spring pre-tightening clamping block, and a laser displacement sensor is arranged in a matching manner with the laser reflection sheet.
The laser displacement sensor may be replaced by a non-contact displacement sensor having a similar function.
The threaded rod support is a high-rigidity single-head threaded rod, the upper end of the threaded rod support is connected with the outer frame bottom plate through threads, and the bottom of the lower end of the threaded rod support is processed into a flat horn mouth shape.
The punched force bearing steel plate is a large-rigidity square steel plate with screw holes symmetrically formed in two ends and is used for directly bearing a dynamic load given by a falling weight of the testing machine.
And an elastic rubber layer is arranged on the inner wall of the annular fixture.
The method for carrying out the dynamic drawing test of the bonding force of the fiber cement-based composite material by using the clamp comprises the following steps:
step one, preparing a fiber cement base material test piece: configuring fiber cement-based test pieces with various strengths according to the strengths of the standard fiber cement bases;
step two, the clamp is completely assembled, and the laser reflection sheet is adhered to the outer side surface of the spring pre-tightening clamping block;
before the test, the wire winding roll shaft is in a horizontal position by screwing the leveling nut, meanwhile, the leveling nut is screwed to apply proper pretightening force to the spring, the fiber cement base material test piece is placed in a corresponding position of the test piece fixing frame, the long fiber is positioned in the fiber preformed hole, the long fiber for drawing downwards penetrates out of the fiber preformed hole in the center of the bottom plate of the test piece fixing frame, the end part of the long fiber is wound at the corresponding position of the wire winding roll shaft, the positioned fiber gauge length section and the pulling force action line of the drawing equipment are superposed on the same straight line, after the wire winding is finished, the fastening nuts at the screw threads at the two ends of the wire winding roll shaft are screwed, the ring-shaped fiber winding part of the clamp ring on the wire winding roll shaft is moved, and then the locking bolt is screwed by hand to lock the ring-shaped clamp;
and step four, during testing, the combined fixture is arranged below a drop hammer impact testing machine, a laser displacement sensor is arranged along the length direction of the fiber along the impact force action line of the drop hammer head, an upward laser is made to shoot a laser reflection sheet positioned on the outer side surface of the spring pre-tightening fixture block, the drop hammer is released to impact a punched force bearing steel plate of the combined fixture, and relevant data are recorded.
Compared with the prior art, the invention has the following beneficial effects:
(1) the clamp can obtain the dynamic tensile strength of the fiber simultaneously
Dynamic elongation at break of fiber epsilon and fiber breakCan W0Waiting for multiple dynamic mechanical indexes;
(2) the device can change the length L of the gauge length of the fiber by selecting the lengths of the springs with different lengths so as to carry out test measurement on the fibers with different lengths, and the original length L of the gauge length can be about 3mm-20 mm;
(3) as the diameter micron-sized flexible fiber can not be directly clamped in a test, the fiber is usually broken in the clamping process due to the brittleness of the fiber, even if the clamping is successful, the clamping end can damage the fiber, the breakage of the fiber is caused at the jaw, and the measured data can not reflect the real characteristics of the fiber. Aiming at the problems, the clamp adopts a winding clamping mode, so that the phenomena of fiber yarn slippage and clamp port fiber early breakage in the test process of the traditional flat plate clamping mode can be avoided.
The novel clamp has the characteristics of orderly winding, encircling extrusion, smooth winding and the like; the orderly arranged winding can ensure that the fiber winding rings are not stacked and extruded, and the fastening device can be locked; the annular fixture is internally provided with the thin-layer rubber gasket, and the annular fixture realizes encircling extrusion on the basis of orderly arranging and winding, so that the large friction resistance between the fixture and the fiber can be realized more efficiently, and the fiber and a rolling shaft are prevented from generating relative slippage in the experimental process; the arc line is smoothly wound out, so that the shearing damage of the fiber caused by the stress concentration of the chuck position in the stretching process can be avoided; this device be equipped with the shoulder hole on the test piece mount bottom plate, play the fixed action to the test piece, prevent that the test piece from taking place to slide in the experimentation to in the high allowed limit of test piece mount, can realize measuring the fibre adhesion of the different height dimensions of cement base test piece, thereby reduce experimental error through the contrast.
Drawings
The invention is further described below with reference to the accompanying drawings.
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic view of an opening in a top plate of the outer frame;
FIG. 3 is a schematic view of an opening of the bottom plate of the outer frame;
FIG. 4 includes FIGS. 4A and 4B, in which FIG. 4A is a schematic view of the ring-type jig being mounted, and FIG. 4B is a sectional view taken along line A-A of FIG. 4A;
FIG. 5 is a flow chart of the experimental operation.
In the figure, 1-a force bearing steel plate, 2-a force transmission rod, 3-a spring positioning guide rod, 4-a spring, 5-a spring pre-tightening fixture block, 6-a leveling nut, 7-a test piece fixing frame top plate, 8-a test piece fixing frame bottom plate, 9-a fixing frame pull rod, 10-a force sensor, 11-an outer frame top plate, 12-an outer frame bottom plate, 13-an outer frame support rod, 14-a ring-shaped fixture, 16-a laser reflection sheet, 17-a wire winding roll shaft, 18-a threaded rod support, 19-a fastening nut, 21-a force transmission rod screw hole, 22-a force transmission rod hole, 23-a cement-based test block, 24-a monofilament fiber, 31-a spring positioning guide rod screw hole, 80-a fiber preformed hole, 101-a force sensor screw hole I, 102-a force sensor screw hole II, 131-outer frame support rod screw holes, 141-locking bolts, 142-elastic rubber layers and 181-threaded rod support holes.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the scope of the present invention is not limited to these examples, and all changes or equivalent substitutions that do not depart from the spirit of the present invention are intended to be included within the scope of the present invention.
1.1 embodiment of a dynamic pulling combination jig for adhesion of fiber cement-based composites
A dynamic bonding force drawing combined clamp for a fiber cement-based composite material comprises a punched force bearing steel plate 1, a force transmission rod 2, a spring positioning guide rod 3, a spring 4, a spring pre-tightening fixture block 5, an outer frame, a test piece fixing frame, a force sensor 10, an annular fixture 14, a laser displacement sensor and a wire winding roll shaft 17; the outer frame comprises an outer frame top plate 11 and an outer frame bottom plate 12 which are horizontally arranged, a plurality of outer frame support rod screw holes 131 are formed in symmetrical positions on the outer frame top plate 11 and the outer frame bottom plate 12, and the outer frame support rods 13 penetrate through the outer frame support rod screw holes 131 to connect the outer frame top plate 11 and the outer frame bottom plate 12 into a whole;
two spring positioning guide rod screw holes 31 and a plurality of threaded rod supporting holes 181 are centrally and symmetrically arranged in the middle of the outer frame bottom plate 12, and threaded rod supports 18 are arranged in the threaded rod supporting holes 181 in a penetrating manner;
two dowel bar screw holes 21 are symmetrically arranged in the center of the impacted force-bearing steel plate 1, and dowel bars 2 are respectively fixed in the two dowel bar screw holes 21; two force transmission rod holes 22 are symmetrically arranged in the center of the outer frame top plate 11, and the positions of the force transmission rod screw holes 21, the force transmission rod holes 22 and the spring positioning guide rod screw holes 31 are symmetrical; a dowel bar 2 is movably arranged in the two dowel bar holes 22 in a vertical direction in a penetrating manner, the dowel bar 2 is a high-rigidity double-end screw rod, the upper ends of the two dowel bars are connected with a dowel bar screw hole 21 on the impacted force bearing steel plate 1 through screws, and the lower ends of the two dowel bars are connected with the upper part of a spring pre-tightening clamping block 5 through screws;
the lower part of the spring pre-tightening fixture block 5 is connected with a spring positioning guide rod 3, the spring positioning guide rod 3 is a vertically arranged high-rigidity double-end screw rod and is positioned on the same vertical axis with the dowel bar 2, the upper end head of the spring positioning guide rod 3 is connected with the spring pre-tightening fixture block 5 through a screw, and the lower end head of the spring positioning guide rod penetrates through a screw hole 31 of the spring positioning guide rod and is connected with a leveling nut 6 through a screw; a spring 4 is sleeved outside the rod body of the spring positioning guide rod 3, and two ends of the spring 4 respectively elastically press the spring pre-tightening fixture block 5 and the outer frame bottom plate 12; in the vertical direction, the spring pre-tightening clamping block 5 and the leveling nut 6 provide a certain pre-tightening force for the spring 4 together;
horizontal screw holes are symmetrically formed in the opposite inner side surfaces between the two spring pre-tightening clamping blocks 5, the two horizontal screw holes are respectively connected with one end of a wire winding roller shaft 17, the wire winding roller shaft 17 is a double-end threaded rod, fastening nuts 19 are further arranged at two ends of the wire winding roller shaft 17, and the fastening nuts 19 are arranged on the inner sides of the horizontal screw holes; in the horizontal direction, the two spring pre-tightening clamping blocks 5 are matched together to serve as a support of the wire winding roll shaft 17 and provide support for the wire winding roll shaft 17 through horizontal screw holes; an annular fixture 14 is movably sleeved outside the wire winding roller shaft 17, the cross section of the annular fixture 14 is C-shaped and is attached to the wire winding roller shaft 17, a locking bolt 141 is arranged on the annular fixture, and the wire winding roller shaft 17 is pressed tightly by the annular fixture 14 through the locking bolt 141; as shown in fig. 4, a in fig. 4 shows a cross section of the ring fixture and the wire winding roller shaft, and B shows a positional relationship of a fastening nut and the wire winding roller shaft.
The test piece fixing frame comprises a test piece fixing frame top plate 7 and a test piece fixing frame bottom plate 8 which are horizontally arranged, a force sensor screw hole I101 is formed in the center of the upper end face of the test piece fixing frame top plate 7, and the force sensor screw hole is connected with a force sensor 10; a fiber preformed hole 80 is formed in the center of the test piece fixing frame bottom plate 8 and is used for fiber yarns to pass through; fixing frame pull rod screw holes are symmetrically formed near four vertexes of the panel of the test piece fixing frame top plate 7 and the test piece fixing frame bottom plate 8, and the fixing frame pull rod 9 penetrates through the fixing frame pull rod screw holes to connect the test piece fixing frame top plate 7 and the test piece fixing frame bottom plate 8 into a whole; the fixed frame pull rod 9 is a high-rigidity double-end screw rod;
a second force sensor screw hole 102 is formed in the center of the outer frame top plate 11, the force sensor 10 is a dynamic tension sensor and is located between the outer frame top plate 11 and the test piece fixing frame top plate 7, and the upper end and the lower end of the force sensor 10 are respectively connected with the outer frame top plate 11 and the test piece fixing frame top plate 7 through screws;
and a laser reflection sheet 16 is adhered to the outer side of the spring pre-tightening clamping block 5, and a laser displacement sensor is arranged in cooperation with the laser reflection sheet 16.
The laser displacement sensor may be replaced by a non-contact displacement sensor having a similar function.
The threaded rod support 18 is a high-rigidity single-head threaded rod, the upper end of the threaded rod support 18 is connected with the outer frame bottom plate 12 through threads, and the bottom of the lower end of the threaded rod support is processed into a flat horn mouth shape.
The punched force bearing steel plate 1 is a large-rigidity square steel plate with screw holes symmetrically formed in two ends and is used for directly bearing a dynamic load given by a drop hammer of the testing machine.
The inner wall of the annular fixture 14 is provided with an elastic rubber layer.
The threaded rod supports 18 are four in number.
The number of the outer frame support rods 13 is four.
1.2 measurement principle:
in the test process, the drop hammer head impacts the stressed force bearing steel plate 1 of the combined clamp, the impact effect causes the compression and the wire winding of the spring 4 through the rigid dowel bar 2The roll shaft 17 is displaced to extract the fibers in the cement matrix, and the dynamic drawing load of the fibers changes along with the time (
Curve) can be measured and recorded by the force sensor 10 connected to the specimen holder, from which the peak dynamic load is measured and recorded
The ratio of the surface area A of the fiber monofilament can obtain the peak bonding strength of the fiber monofilament
(ii) a The change rule (s-t curve) of the relative slippage s of the fiber and the cement-based test block along with the time t can be obtained through a laser displacement sensor; finally, the dynamic constitutive relation of fiber monofilament drawing can be obtained, namely
Full curve.
1.3 the method for carrying out the dynamic drawing test of the bonding force of the fiber cement-based composite material by using the clamp is realized by the following steps:
step 1, connecting four threaded rod supports 18 with an outer frame bottom plate 12, screwing the upper ends and the lower ends of four outer frame support rods 13 into outer frame support rod screw holes 131 respectively, and connecting an outer frame top plate 11 and the outer frame bottom plate 12 to an outer frame of an integrally formed clamp;
3, the force bearing steel plate 1 is positioned above the outer frame top plate 11, the upper ends of the two force transmission rods 2 are connected with the force bearing steel plate 1, the lower ends of the force transmission rods 2 downwards penetrate through the force transmission rod holes 22 of the preformed holes in the outer frame top plate 11, and then the lower ends of the force transmission rods 2 are respectively screwed into the upper ends of the spring pre-tightening fixture blocks 5 for connection;
the upper ends of the two spring positioning guide rods 3 sequentially penetrate through the spring positioning guide rod screw holes 31 and the springs 4 reserved in the outer frame bottom plate 12 and then are connected with the lower ends of the spring pre-tightening clamping blocks 5, the lower ends of the spring positioning guide rods 3 are screwed into the leveling nuts 6, and the leveling nuts 6 are located below the outer frame bottom plate 12;
and 5, screwing the upper end of a force sensor 10 into a screw hole in the lower part of the outer frame top plate 11 through a screw, connecting the lower end of the force sensor 10 with a screw hole in a test piece fixing frame top plate 7 through a screw, and connecting the test piece fixing frame top plate 7 with a test piece fixing frame bottom plate 8 through four fixing frame pull rods 9.
And 6, adhering the laser reflection sheet 16 to the outer side surface of the spring pre-tightening fixture block 5.
And 7, before the test, screwing the leveling nut 6 to enable the wire winding roller shaft 17 to be in a horizontal position, simultaneously screwing the leveling nut 6 to apply proper pretightening force to the spring 4, putting the adhesion force test piece into a corresponding position of the test piece fixing frame, downwards penetrating long fibers for drawing out from a fiber preformed hole 80 in the center of the bottom plate 8 of the test piece fixing frame, winding the end parts of the long fibers at the corresponding position of the wire winding roller shaft 17, enabling the positioned fiber gauge length section and a pulling force action line of drawing equipment to be superposed on the same straight line, screwing the fastening nuts 19 at the thread parts at two ends of the wire winding roller shaft 17 after the wire winding is completed, moving the annular clamping tool 14 at the fiber winding part on the wire winding roller shaft 17, and screwing the locking bolt 141 by hand to lock the annular clamping tool.
And 8, during testing, placing the combined fixture below a drop hammer impact testing machine, ensuring that an impact force action line of a drop hammer head is along the length direction of the fiber, installing a laser displacement sensor 15, enabling an upward laser to shoot a laser reflection sheet 16 positioned on the outer side surface of the spring pre-tightening fixture block 5, releasing the drop hammer to impact a punched force bearing steel plate 1 of the combined fixture, and recording related data.
The present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. The dynamic bonding force drawing combined clamp for the fiber cement-based composite material is characterized by comprising a stressed force steel plate (1), a force transfer rod (2), a spring positioning guide rod (3), a spring (4), a spring pre-tightening clamping block (5), an outer frame, a test piece fixing frame, a force sensor (10), a ring-shaped clamping block (14), a laser displacement sensor (15) and a wire winding roll shaft (17);
the outer frame comprises an outer frame top plate (11) and an outer frame bottom plate (12) which are horizontally arranged, a plurality of outer frame support rod screw holes (131) are formed in the symmetrical positions of the outer frame top plate (11) and the outer frame bottom plate (12), and outer frame support rods (13) penetrate through the outer frame support rod screw holes (131) to connect the outer frame top plate (11) and the outer frame bottom plate (12) into a whole;
two spring positioning guide rod screw holes (31) and a plurality of threaded rod supporting holes (181) are arranged in the middle of the outer frame bottom plate (12) in a centrosymmetric manner, and threaded rod supports (18) are arranged in the threaded rod supporting holes (181) in a penetrating manner;
two dowel bar screw holes (21) are symmetrically formed in the center of the thrust bearing steel plate (1), two dowel bar holes (22) are symmetrically formed in the center of the outer frame top plate (11), and the positions of the dowel bar screw holes (21), the dowel bar holes (22) and the spring positioning guide rod screw holes (31) are symmetrical; the two force transmission rod holes (22) are internally and vertically movably penetrated with force transmission rods (2), the force transmission rods (2) are large-rigidity double-end screw rods, the upper ends of the two force transmission rods are connected with force transmission rod screw holes (21) in the impacted force bearing steel plate (1) through screws, and the lower ends of the two force transmission rods are connected with the upper parts of spring pre-tightening clamping blocks (5) through screws;
the lower part of the spring pre-tightening fixture block (5) is connected with a spring positioning guide rod (3), the spring positioning guide rod (3) is a vertically arranged high-rigidity double-head screw rod and is positioned on the same vertical axis with the dowel bar (2), the upper end head of the spring positioning guide rod (3) is connected with the spring pre-tightening fixture block (5) through a screw, and the lower end head of the spring positioning guide rod penetrates through a spring positioning guide rod screw hole (31) and is connected with a leveling nut (6) through a screw; a spring (4) is sleeved outside the rod body of the spring positioning guide rod (3), and two ends of the spring (4) respectively press the spring pre-tightening fixture block (5) and the outer frame bottom plate (12) in an elastic manner; in the vertical direction, the spring pre-tightening clamping block (5) and the leveling nut (6) provide a certain pre-tightening force for the spring (4) together;
horizontal screw holes are symmetrically formed in the inner side face, opposite to the inner side face, of each spring pre-tightening clamping block (5), the two horizontal screw holes are respectively connected with one end of a wire winding roller shaft (17), the wire winding roller shaft (17) is a double-end threaded rod, fastening nuts (19) are further arranged at two ends of the wire winding roller shaft (17), and the fastening nuts (19) are arranged on the inner sides of the horizontal screw holes; in the horizontal direction, the two spring pre-tightening clamping blocks (5) are matched as supports of the wire winding roll shaft (17) and provide support for the wire winding roll shaft (17) through horizontal screw holes; an annular fixture (14) is movably sleeved outside the wire winding roll shaft (17), the cross section of the annular fixture (14) is C-shaped and is attached to the wire winding roll shaft (17), a locking bolt (141) is arranged on the annular fixture, and the wire winding roll shaft (17) is pressed tightly by the annular fixture (14) through the locking bolt (141);
the test piece fixing frame comprises a test piece fixing frame top plate (7) and a test piece fixing frame bottom plate (8) which are horizontally arranged, a force sensor screw hole I (101) is formed in the center of the upper end face of the test piece fixing frame top plate (7), and the force sensor screw hole is connected with a force sensor (10); a fiber preformed hole (80) is formed in the center of the base plate (8) of the test piece fixing frame and used for fiber yarns to pass through; fixing frame pull rod screw holes are symmetrically formed near four vertexes of a panel of the test piece fixing frame top plate (7) and the test piece fixing frame bottom plate (8), and a fixing frame pull rod (9) penetrates through the fixing frame pull rod screw holes to connect the test piece fixing frame top plate (7) and the test piece fixing frame bottom plate (8) into a whole; the fixed frame pull rod (9) is a high-rigidity double-end screw rod;
a force sensor screw hole II (102) is formed in the center of the outer frame top plate (11), the force sensor (10) is a dynamic tension sensor and is positioned between the outer frame top plate (11) and the test piece fixing frame top plate (7), and the upper end and the lower end of the force sensor (10) are respectively connected with the outer frame top plate (11) and the test piece fixing frame top plate (7) through screws;
a laser reflection sheet (16) is adhered to the outer side of the spring pre-tightening clamping block (5), and a laser displacement sensor (15) is arranged in a matching manner with the laser reflection sheet (16);
the method for the clamp to carry out the dynamic drawing test of the bonding force of the fiber cement-based composite material comprises the following steps that in the test process, a drop hammer head impacts a stressed force bearing steel plate of the combined clamp, and through a rigid dowel bar, the impact effect causes the compression of a spring and the displacement of a wire winding roll shaft, so that the fiber in the cement base is pulled out;
law of change of dynamic drawing load of fiber with time FdThe t-curve is measured and recorded by a force sensor connected to the specimen holder, from which the peak dynamic load FdpThe ratio of the surface area A of the fiber monofilament to the surface area A of the fiber monofilament is obtained to obtain the bonding force peak strength tau of the fiber monofilamentdp；
Obtaining a change rule s-t curve of relative slippage s of the fiber and the cement-based test block along with time t through a laser displacement sensor; finally, the dynamic constitutive relation of the fiber filament drawing, namely tau, is obtainedd-s-holocurve; the method comprises the following steps:
step one, preparing a fiber cement base material test piece: configuring fiber cement base material test pieces with various strengths according to the strengths of the standard fiber cement bases;
step two, the clamp is completely assembled, and the laser reflection sheet is adhered to the outer side surface of the spring pre-tightening clamping block;
before the test, the wire winding roll shaft is in a horizontal position by screwing the leveling nut, meanwhile, the leveling nut is screwed to apply proper pretightening force to the spring, the fiber cement base material test piece is placed in a corresponding position of the test piece fixing frame, the long fiber is positioned in the fiber preformed hole, the long fiber for drawing downwards penetrates out of the fiber preformed hole in the center of the bottom plate of the test piece fixing frame, the end part of the long fiber is wound at the corresponding position of the wire winding roll shaft, the tensile force action lines of the positioned fiber gauge length section drop hammer impact experiment machine suspension drop hammer are coincided on the same straight line, after the wire winding is completed, the fastening nuts positioned at the threads at the two ends of the wire winding roll shaft are screwed, the annular clamp is moved to be positioned at the fiber winding part on the wire winding roll shaft, and the locking bolt is screwed by hand to lock the annular clamp;
and step four, during testing, the combined clamp is placed below a drop hammer impact testing machine, a laser displacement sensor is mounted on the combined clamp to ensure that the impact force action line of the drop hammer head is along the length direction of the fiber, an upward laser is made to irradiate a laser reflection sheet positioned on the outer side surface of the spring pre-tightening clamping block, the drop hammer is released to impact a stressed steel plate of the combined clamp, and relevant data are recorded.
2. The bonding force dynamic pulling assembly jig of fiber cement based composite material according to claim 1, characterized in that the laser displacement sensor (15) can be replaced by a non-contact displacement sensor with similar functionality.
3. The dynamic fiber cement-based composite material bonding force drawing combined clamp as claimed in claim 1, wherein the threaded rod support (18) is a high-rigidity single-head threaded rod, the upper end of the threaded rod support (18) is connected with the outer frame bottom plate (12) through threads, and the bottom of the lower end of the threaded rod support is processed into a flat horn mouth shape.
4. The dynamic bonding force drawing combined clamp for the fiber cement-based composite material as claimed in claim 1, wherein the stressed steel plate (1) is a large-rigidity square steel plate with screw holes symmetrically formed at two ends and is used for directly bearing the dynamic load given by a drop hammer of a testing machine.
5. The dynamic fiber cement based composite material bonding force drawing combination fixture according to claim 1, wherein the inner wall of the ring fixture (14) is provided with an elastic rubber layer.
6. The dynamic fiber cement based composite bond pulling assembly fixture of claim 1, wherein the number of threaded rod supports (18) is four.
7. The dynamic fiber cement-based composite material bonding force drawing combined clamp according to claim 1, wherein the number of the outer frame support rods (13) is four.
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Inventor after: Ma Gang Inventor after: Zhang Lijun Inventor after: Zhao Hui Inventor after: Deng Kezhao Inventor after: Zhang Yu Inventor after: Wang Zhiyong Inventor after: Du Sizhe Inventor before: Ma Gang Inventor before: Zhao Hui Inventor before: Deng Kezhao Inventor before: Zhang Yu Inventor before: Wang Zhiyong Inventor before: Du Sizhe |