CN215218341U - Measure combined material pipe hoop tensile properties's test device for structural engineering - Google Patents
Measure combined material pipe hoop tensile properties's test device for structural engineering Download PDFInfo
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Abstract
The utility model relates to a test device for measuring hoop tensile property of a composite material pipe for structural engineering, which comprises two stretching arc-shaped steel blocks, two fixed arc-shaped steel blocks, four screw rods, a connecting node, two connecting pieces, two supporting rods, a traction mechanism, an axial strain gauge and an annular strain gauge; the four screw rods are all fixed with the connecting nodes; the connecting pieces are in threaded connection with the fixed arc-shaped steel blocks and the screw rods, and the two connecting pieces are arranged in a straight line; the support rods are in threaded connection with the screw rods and abut against the inner side faces of the tensioning arc-shaped steel blocks, and the two support rods are arranged in a straight line; the traction mechanism is detachably connected with the two tensioning arc-shaped steel blocks; the axial strain gauge and the annular strain gauge are arranged on the outer surface of the annular sample. The utility model discloses measure the essence and lead to the height, the commonality is strong, belongs to structural material performance detection technical field among the civil engineering.
Description
Technical Field
The utility model relates to a structural material performance detection technique among the civil engineering, concretely relates to measure composite material pipe hoop tensile properties's test device for structural engineering.
Background
Fiber Reinforced Polymer (FRP) has excellent properties such as high strength and good corrosion resistance as a novel material, and has been widely used in the field of civil engineering in recent years, with the most typical application being a fiber reinforced composite pipe (hereinafter referred to as "composite pipe") reinforced concrete. The composite pipe can be manually manufactured by a wet laying method, and can also be directly manufactured by pultrusion or fiber winding. Under the effect of axial pressure, the lateral expansion of concrete can be effectively restrained by the fibers which are close to the annular arrangement, thereby greatly improving the strength and the ductility of the member. For the composite pipe confined concrete, the hoop tensile properties (including hoop ultimate tensile strain, hoop modulus of elasticity and poisson ratio) of the composite pipe, especially the hoop modulus of elasticity and the hoop ultimate tensile strain, have a crucial influence on the mechanical properties of the composite pipe. In the test method for measuring the tensile property of the composite material, besides a straight strip sheet tensile test and a traditional split-disk test, students in all countries around the world also put forward various test methods, but the existing methods have certain limitations in practical application and still have no accurate and convenient solution.
The measurement of tensile properties of fiber-reinforced composites by means of the straight-strip sheet tensile test method is well-described in test specifications of many countries and regions, for example, Standard test method for tensile properties of Polymer-based composites [ ASTM D3039/D3039M-14(2014) ], Standard test method for tensile properties of fiber-reinforced composites for civil engineering Reinforcement [ ASTM D7565/D7565M-10 (2017) ], Standard test method for tensile properties of oriented fiber-reinforced Polymer-based composites [ GB/T3354 (2014) ], test method for elastic constant of fiber-reinforced composites [ GB/T32376 (2015) ], and so on. However, the straight strip sheet tensile test method is mainly applicable to continuous unidirectional fiber reinforced composite flat plates. For a composite material pultrusion or winding pipe, an arc-shaped sample can only be cut out along the annular direction of the composite material pultrusion or winding pipe, and a straight strip-shaped sheet material tensile test method cannot be adopted; for the composite pipe manufactured by the manual wet laying method, although a straight strip-shaped sheet material sample which is made of the same material and has the same laying layer as the pipe material can be manufactured and subjected to a tensile test, due to the difference of the curvatures of the two and the difference of the manufacturing methods, the actual performance of the composite pipe is difficult to accurately calibrate by the result of the straight strip-shaped sheet material tensile test method.
Compared with a straight strip-shaped sheet material test method, the traditional split-disc test method adopts an annular test sample, relatively completely maintains the original shape of the pipe, and is widely applied to measuring the annular performance of the composite pipe, such as an apparent annular tensile strength standard test method for plastic or reinforced plastic pipes [ ASTM D2290-16(2016) ] and an apparent initial circumferential tensile strength test method for plastic pipeline systems-glass fiber reinforced thermosetting plastic pipes [ ISO 8521(2009) ]. However, in the conventional split disk test method, in order to reduce the adverse effect of the friction force between the annular test sample and the split disk on the test result, the test section of the annular test sample should be as close to the gap between the two semicircular split disks as possible. However, as the test is performed, the two split discs are gradually separated under the action of the tensile force, so that inevitable bending is generated on the test section of the annular test sample, and the test cannot finally acquire the accurate annular tensile elastic modulus of the composite pipe. In response to this problem, various measures for improving the split disk test are proposed, such as moving the test section of the ring-shaped test piece away from the gap of the split disk to eliminate the influence of the bending of the ring-shaped test piece on the test result, but such a measure brings another problem: the friction between the annular sample and the splitting disc enables the annular sample to generate a tensile stress gradient along the circumferential direction, so that accurate tensile stress of a test section cannot be obtained, and accurate performance of the composite pipe annular tensile material cannot be obtained. In addition, whether the composite material winding pipe is industrially produced or the composite material pipe is manufactured by a manual wet paving method, the pipe diameter and the wall thickness of the composite material winding pipe have certain dispersion, the dispersion degree adaptability of the splitting disc with fixed size to the pipe diameter of the composite material pipe is poor, and when the diameter difference between the splitting disc and the composite material pipe is larger, the measurement error caused by the bending of the test section is larger.
If the influence of adverse factors such as bending and friction on the determination of the annular performance of the composite pipe is to be eliminated, a novel split disc test method is the best choice. First, the annular test specimen of the novel split-disk test method ensures the integrity of the composite pipe. In addition, the novel split disc test method adjusts the distance between the two test section fixing arc-shaped steel blocks through the cross four-way screw, can be fine to adapt to the dispersion of the pipe diameter of the composite pipe, simultaneously considers the difference of the radian between the actual composite pipe and the test section fixing arc-shaped steel blocks, inserts the roller pin with gradually changed diameter at the gap between the actual composite pipe and the test section fixing arc-shaped steel blocks, and ensures that the test section of the annular sample can always keep the original radian in the test process and is in a stretching state without local bending. In addition, the gap between the tensioning arc-shaped steel block and the fixed arc-shaped steel block is close to the testing section of the annular test sample, and the friction force between the testing section of the annular test sample and the fixed arc-shaped steel block is eliminated as far as possible by smearing lubricating oil, so that the influence of the friction force on the testing result in the testing process can be ignored. According to the points, the hoop elasticity modulus and the hoop tensile ultimate strain of the composite pipe measured by the novel split disc test method are very reliable.
In summary, according to the analysis of the prior art, it can be known that the conventional test method for measuring the mechanical properties of the composite material mainly has the following two defects, which make it unsuitable for measuring the hoop tensile elastic modulus, poisson's ratio, hoop ultimate tensile strain and hoop tensile strength of the composite material pipe for structural engineering:
defect 1: the method for the tensile test of the straight strip-shaped sheet is only suitable for measuring the relevant performance of the composite flat plate and cannot solve the problem that the composite pipe has radian along the annular direction;
defect 2: the traditional split disc test method can not avoid the bending or friction problem, so that the measured annular elastic modulus error of the composite pipe is large, and the split disc with fixed size has poor adaptability to the pipe diameter deviation of the composite pipe;
in addition, according to the characteristics of the composite pipe for structural engineering, researchers also propose an internal pressure test method and an arc-shaped sample tensile test method for testing the annular performance of the composite pipe. However, the former is caused by the difficulty in sealing the lower end part of the composite pipe in a high-pressure state in the test, and the latter is caused by the need of straightening an arc-shaped test sample, so that the hoop tensile strength and the hoop ultimate tensile strain of the test sample cannot be measured by the two test methods; in addition, the two test methods cannot be applied to composite pipes with small diameters and thick pipe walls.
For solving the limitation of current test method, according to current technical condition, the utility model provides a to measuring simple and easy feasible, the result is reliable, extensive applicability's test method of compound tubular product hoop elastic modulus, poisson's ratio, hoop ultimate tensile strain and annular tensile strength for structural engineering.
SUMMERY OF THE UTILITY MODEL
To the technical problem who exists among the prior art, the utility model aims at: the test device for measuring the hoop tensile property of the composite pipe for the structural engineering is high in measurement accuracy and universality.
In order to achieve the above purpose, the utility model adopts the following technical scheme:
the test device for measuring the hoop tensile property of the composite material pipe for structural engineering comprises two tensioning arc-shaped steel blocks, two fixed arc-shaped steel blocks, four screw rods, a connecting node, two connecting pieces, two supporting rods, a traction mechanism, an axial strain gauge and an annular strain gauge; four screw rods are all fixed with the connecting node, and the four screw rods are distributed in a cross shape; one end of the connecting piece is a screw rod, and the other end of the connecting piece is a nut; the inner side surfaces of the two fixed arc-shaped steel blocks are respectively provided with a threaded hole, the screw end of the connecting piece is in threaded connection with the threaded holes of the fixed arc-shaped steel blocks, the nut end of the connecting piece is in threaded connection with the screw, and the two connecting pieces are arranged in a straight line; one end of each support rod is a nut, the other end of each support rod is a steel bar, the nut end of each support rod is in threaded connection with the corresponding screw, the steel bar end of each support rod abuts against the inner side face of the tensioning arc-shaped steel block, and the two support rods are arranged in a straight line; the traction mechanism for stretching the two tensioning arc-shaped steel blocks outwards is detachably connected with the two tensioning arc-shaped steel blocks; the outer side surfaces of the two tensioning arc-shaped steel blocks, which are attached to the inner wall of the annular sample, are convex arc-shaped surfaces; the outer side surfaces of the two fixed arc-shaped steel blocks, which are attached to the inner wall of the annular sample, are convex arc-shaped surfaces; the axial strain gauge and the annular strain gauge are arranged on the outer surface of the annular sample. After adopting this kind of structure, measurement accuracy is high, and the commonality is strong, has solved and the problem that the adaptability of the split disc of fixed size is poor to compound material pipe diameter deviation.
Preferably, the device further comprises a sliding baffle and a plurality of sets of needle rollers; the tensioning arc-shaped steel block is provided with two sliding grooves, and the two sliding grooves are respectively positioned on two side surfaces of the tensioning arc-shaped steel block which are inclined from inside to outside; the number of the sliding baffles is four, and in one tensioning arc-shaped steel block, two sliding chutes are matched with the two sliding baffles; the sliding chute is provided with a contraction position and an extension position, the end part of the sliding baffle is aligned with the end part of the outer side surface of the stretching arc-shaped steel block when the sliding baffle is positioned at the contraction position, and the end part of the sliding baffle is propped against the inner wall of the annular sample when the sliding baffle slides outwards from the contraction position to the extension position; enclose into the kingpin installation department between annular sample inner wall, stretch-draw arc steel billet lateral surface and the slide damper, each kingpin installation department sets up one set of kingpin, and each set of kingpin all includes many kingpins, and many kingpins are arranged according to the diameter from big to little in proper order. After the structure is adopted, the rolling needle with the proper diameter is selected and inserted into the rolling needle installation part formed by the annular sample, the stretching arc-shaped steel block and the steel baffle plate in a surrounding manner, the radian of the annular sample can be kept unchanged in the stretching process of the annular sample, and the problem that the measured annular elastic modulus error of the composite pipe is large due to the fact that the bending or friction problem cannot be avoided by the traditional split disc test method is solved
Preferably, the diameter of each set of roller pins is 0.5mm-5 mm; the difference between the diameters of two adjacent needle rollers is 0.5 mm.
Preferably, the traction mechanism comprises two steel chucks and two bolts; through holes are formed in the thickness direction of the two tensioning arc-shaped steel blocks, the steel chuck is provided with fixing holes corresponding to the through holes, the tensioning arc-shaped steel blocks are connected with the steel chuck through bolts, the bolts penetrate through the through holes, and two ends of the bolts are matched with the fixing holes; and an end rod connected with the tensile testing machine is arranged on the steel chuck.
Preferably, the connecting node is of a cubic structure, and the screw and the connecting node are of an integrally formed structure.
Preferably, the inner side face of the tensioning arc-shaped steel block is a plane, the head part of the steel rod end of the support rod is a plane, the steel rod end of the support rod props against the inner side face of the tensioning arc-shaped steel block, and the tail part of the steel rod end of the support rod is provided with a thread section which is in threaded connection with the nut end of the support rod.
Preferably, the annular sample is in an annular strip structure, the annular sample comprises two connecting sections with larger width and two testing sections with smaller width, and the connecting sections and the testing sections are alternately distributed; the two test sections are respectively aligned with the outer side surfaces of the two tensioning arc-shaped steel blocks; the axial strain gauge and the circumferential strain gauge are positioned in the middle of the test section.
A test method for measuring the hoop tensile property of a composite pipe for structural engineering adopts a test device for measuring the hoop tensile property of the composite pipe for structural engineering, and comprises the following steps:
(1) manufacturing an annular sample: the annular samples are taken from the composite material pipes in the same batch for test or engineering practice, and the total number of the annular samples is not less than 5;
(2) installing an annular sample:
a. respectively sticking 1 strain gage along the ring direction at the central position of two test sections of the ring-shaped sample, wherein the strain gage stuck along the ring direction is the ring-shaped strain gage, sticking 2 strain gages along the axial direction of the ring-shaped sample at the two ends of the ring-shaped strain gage, and the two axial direction sticks as the axial strain gage;
b. coating lubricating oil on the inner wall of the annular sample;
c. placing the two tensioning arc-shaped steel blocks and the two fixed arc-shaped steel blocks in the annular sample, and ensuring that arc tops of the two tensioning arc-shaped steel blocks and the two fixed arc-shaped steel blocks are in contact with the inner wall of the annular sample, wherein the tensioning arc-shaped steel blocks are aligned with a test section of the annular sample;
d. connecting two connecting pieces and two supporting rods with four screw rods respectively and placing the connecting pieces and the two supporting rods into an annular sample, adjusting the total length of the connecting pieces and the screw rods by rotating the nut ends of the connecting pieces, and adjusting the total length of the supporting rods and the screw rods by rotating the nut ends of the supporting rods; the screw rod ends of the two connecting pieces are screwed into the threaded holes of the fixed arc-shaped steel blocks, so that the positions of the fixed arc-shaped steel blocks are unchanged; the steel bar ends of the two support rods prop against the inner side surface of the tensioning arc-shaped steel block, and the position of the tensioning arc-shaped steel block is temporarily fixed;
e. a sliding baffle of the sliding tensioning arc-shaped steel block is abutted against the inner wall of the annular sample, and a roller pin mounting part is enclosed among the annular sample, the outer side surface of the tensioning arc-shaped steel block and the sliding baffle;
f. selecting a needle roller with the size corresponding to the size of the needle roller mounting part from the multiple sets of needle rollers, and inserting the needle roller into the needle roller mounting part;
g. installing a bolt and a steel chuck on the tensioning arc-shaped steel block;
h. the end rod on the steel chuck is connected with a tensile testing machine;
(3) loading: the tensile test is carried out at a constant speed of 3-5mm/min, and the tensile test is loaded until the annular sample is broken;
(4) selecting and calculating data: recording the maximum load value borne by the annular sample in the test process; selecting test data of the annular strain of the annular test sample in the test process, and calculating to obtain the annular tensile elastic modulus and Poisson ratio of each test section of the annular test sample; the failure modes required for the test method are: and the fracture surface appears in the middle of the annular sample testing section, only the test data when the fracture surface appears in the middle of the annular sample testing section is recorded, and the annular tensile strength and the annular ultimate tensile strain of the annular sample are obtained through calculation.
Preferably, in the step d, selecting test data of the annular strain of the annular test sample in the test process, and calculating to obtain the annular tensile elastic modulus and the Poisson ratio of the test section of the annular test sample;
the hoop tensile stress of the test section of the annular test specimen is calculated by the following formula:
in the formula:
σθthe hoop tensile stress of the test section of the annular sample is in MPa;
Ft-the tensile load of the annular specimen in N;
t is the average thickness of the test section of the annular sample, and the unit is mm;
h is the average width of the test section of the annular sample, and the unit is mm;
the modulus of elasticity in hoop tension of the test section of the annular test specimen is calculated by the following formula:
in the formula:
Eθthe modulus of elasticity in the circumferential direction of the test section of the annular sample is MPa;
εθthe annular strain of the test section of the annular test sample is the reading of the annular strain gauge on the test section;
Δεθthe annular strain increment of the annular sample testing section in the elastic range is at least 0.2 percent, and the range of 0.1 to 0.3 percent of the annular strain of the testing section is recommended to be selected;
Δσθand the incremental hoop strain of the test section Δ εθThe corresponding test section hoop tensile stress increment is in the unit of N;
the annular poisson ratio of the annular sample testing section is calculated by the following formula:
in the formula:
vθx-the annular poisson's ratio of the annular test specimen test section;
εxthe average axial strain of the test section of the annular test specimen is the average of the readings of the two axial strain gauges on the test section;
Δεxand the incremental hoop strain of the test section Δ εθThe corresponding test segment averaged the increase in axial strain.
Preferably, in the step d, selecting test data of a test section meeting the requirement of a failure mode, and calculating to obtain the hoop tensile strength and the hoop ultimate tensile strain value of the annular sample;
the hoop tensile strength of the ring specimen was calculated by the following formula:
in the formula:
Ptthe hoop tensile strength of the test section meeting the requirement of the failure mode is in MPa;
Ft，max-the maximum tensile load of the annular test specimen in N;
t is the average thickness of the test section of the annular sample meeting the requirement of the failure mode, and the unit is mm;
h is the average width of the test section of the annular sample meeting the requirement of the failure mode, and the unit is mm;
hoop ultimate tensile strain, ε, of an annular test specimenh，maxAnd the maximum strain value of the annular strain gauge on the test section meeting the requirement of the failure mode is measured at the fracture moment of the annular sample.
In general, the utility model has the advantages as follows:
(1) the utility model discloses the hoop tensile properties of measurement combined material pipe that can be accurate, including hoop tensile stress, hoop tensile elastic modulus, poisson's ratio, hoop tensile strength and hoop limit tensile strain.
(2) The utility model discloses a screw rod can be used to adjust the interval between the arc steel bloom, and the dispersion of adaptation combined material pipe diameter that stretch-draw arc steel bloom can be fine can be ensured to the kingpin.
(3) The utility model discloses extensive applicability has following aspect: a. besides the typical composite material pultrusion winding pipe, the utility model is also suitable for the composite material pipe which is manually manufactured by adopting a wet laying method; b. the method has high acceptance on the discrete level of the measured geometric dimension (diameter and thickness) of the composite pipe; c. the composite pipe is suitable for any fiber winding or laying angle; d. it is suitable for composite pipe of any diameter and thickness.
Drawings
FIG. 1a is a top view of a ring specimen;
FIG. 1b is a side view of a ring specimen;
FIG. 2 is a schematic view of a strain gage attached to the outside surface of an annular test specimen;
FIG. 3a is a perspective view of a tensioned arcuate steel block;
FIG. 3b is a top view of a tensioned arcuate steel block;
FIG. 4a is a perspective view of a fixed arc-shaped steel block;
FIG. 4b is a top view of the fixed arc-shaped steel block;
FIG. 5a is an exploded view of the connection node, screw, connector and support rod;
FIG. 5b is a schematic view of the connection node, screw, connector and support rod connection;
FIG. 6 is a perspective view of a set of needles;
FIG. 7 is a schematic view of the tensioned arc-shaped steel block and the fixed arc-shaped steel block installed inside the ring-shaped test sample;
FIG. 8 is a schematic view of the connection node, the screw, the connection member, the support rod, the tension arc-shaped steel block and the fixed arc-shaped steel block being mounted inside the annular sample;
FIG. 9 is an enlarged view of the slide damper;
FIG. 10a is a schematic view of the needle roller mounting;
FIG. 10b is an enlarged partial view of the needle roller mounting portion;
FIG. 11 is a schematic view of a steel collet installation;
FIG. 12 is a perspective view of a testing apparatus for measuring hoop tensile properties of a composite pipe for structural engineering;
FIG. 13a is a schematic view of a ring specimen meeting failure mode requirements;
FIG. 13b is a schematic view of a ring specimen not meeting the failure mode requirements;
figure 14 is a graph of hoop stress versus strain for the test.
Wherein, 1 is stretch-draw arc steel piece, 2 is fixed arc steel piece, 3 is the kingpin, 4 is the connecting piece, 5 is the bolt, 6 is the steel chuck, 7 is slide damper, 8 is annular sample, 9 is the hoop foil gage, 10 is the axial foil gage, 11 is the bracing piece, 12 is the connected node, 13 is the screw rod, and A is the maximum load point.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments.
The test device for measuring the hoop tensile property of the composite material pipe for structural engineering comprises two tensioning arc-shaped steel blocks, two fixed arc-shaped steel blocks, four screw rods, a connecting node, two connecting pieces, two supporting rods, a traction mechanism, an axial strain gauge and an annular strain gauge; four screw rods are all fixed with the connecting node, and the four screw rods are distributed in a cross shape; one end of the connecting piece is a screw rod, and the other end of the connecting piece is a nut; the inner side surfaces of the two fixed arc-shaped steel blocks are respectively provided with a threaded hole, the screw end of the connecting piece is in threaded connection with the threaded holes of the fixed arc-shaped steel blocks, the nut end of the connecting piece is in threaded connection with the screw, and the two connecting pieces are arranged in a straight line; one end of each support rod is a nut, the other end of each support rod is a steel bar, the nut end of each support rod is in threaded connection with the corresponding screw, the steel bar end of each support rod abuts against the inner side face of the tensioning arc-shaped steel block, and the two support rods are arranged in a straight line; the traction mechanism for stretching the two tensioning arc-shaped steel blocks outwards is detachably connected with the two tensioning arc-shaped steel blocks; the outer side surfaces of the two tensioning arc-shaped steel blocks, which are attached to the inner wall of the annular sample, are convex arc-shaped surfaces; the outer side surfaces of the two fixed arc-shaped steel blocks, which are attached to the inner wall of the annular sample, are convex arc-shaped surfaces; the axial strain gauge and the annular strain gauge are arranged on the outer surface of the annular sample. The connecting piece cooperates the distance between two fixed arc steel blocks of screw adjustment, and the bracing piece cooperates the distance between two stretch-draw arc steel blocks of screw adjustment to ensure that the lateral surface of two fixed arc steel blocks and two stretch-draw arc steel blocks all pastes the inner wall in annular sample.
The device also comprises a sliding baffle and a plurality of sets of needle rollers; the tensioning arc-shaped steel block is provided with two sliding grooves, and the two sliding grooves are respectively positioned on two side surfaces of the tensioning arc-shaped steel block which are inclined from inside to outside; the two side surfaces are connecting surfaces of two ends of the outer side surface (arc surface) and two ends of the inner side surface (plane) of the tensioning arc-shaped steel block, the number of the sliding baffles is four, and in one tensioning arc-shaped steel block, two sliding chutes are matched with the two sliding baffles; the sliding chute is provided with a contraction position and an extension position, the end part of the sliding baffle is aligned with the end part of the outer side surface of the stretching arc-shaped steel block when the sliding baffle is positioned at the contraction position, and the end part of the sliding baffle is propped against the inner wall of the annular sample when the sliding baffle slides outwards from the contraction position to the extension position; enclose into the kingpin installation department between annular sample inner wall, stretch-draw arc steel billet lateral surface and the slide damper, each kingpin installation department sets up one set of kingpin, and each set of kingpin all includes many kingpins, and many kingpins are arranged according to the diameter from big to little in proper order. In each set of roller pins, the diameter of the roller pins is 0.5mm-5 mm; the difference between the diameters of two adjacent needle rollers is 0.5 mm. The roller pin installation parts are formed at two ends of the outer side face of the stretching arc-shaped steel block, the roller pins installed on the roller pin installation parts are arranged in rows from the end part of the outer side face of the stretching arc-shaped steel block to the arc top, the length direction of the roller pins is consistent with the thickness direction of the stretching arc-shaped steel block, and the end part of the sliding baffle abuts against the inner wall of the annular sample when the sliding baffle slides outwards from the contraction position to the extension position, so that the roller pins are limited to slide from the outer side face of the stretching arc-shaped steel block.
The traction mechanism comprises two steel chucks and two bolts; through holes are formed in the thickness direction of the two tensioning arc-shaped steel blocks, the steel chuck is provided with fixing holes corresponding to the through holes, the tensioning arc-shaped steel blocks are connected with the steel chuck through bolts, the bolts penetrate through the through holes, and two ends of the bolts are matched with the fixing holes; and an end rod connected with the tensile testing machine is arranged on the steel chuck. The steel chuck comprises a transverse plate, two vertical plates and an end rod; two riser parallel arrangement are at the both ends of diaphragm, riser and diaphragm mutually perpendicular, and riser and diaphragm are integrated into one piece structure, and the riser is equipped with the fixed orifices that corresponds with the through-hole, and the fixed orifices size corresponds with the bolt, and end bar perpendicular to diaphragm, end bar are located the diaphragm middle part, and the end bar orientation is opposite with the riser orientation.
The connecting node is of a cubic structure, and the screw rod and the connecting node are of an integrally formed structure. The inner side surface of the tensioning arc-shaped steel block is a plane, the head part of the steel bar end of the supporting rod is a plane, the steel bar end of the supporting rod props against the inner side surface of the tensioning arc-shaped steel block, and the tail part of the steel bar end of the supporting rod is provided with a thread section which is in threaded connection with the nut end of the supporting rod.
The annular sample is of an annular strip structure and comprises two connecting sections with larger width and two testing sections with smaller width, and the connecting sections and the testing sections are alternately distributed; the two test sections are respectively aligned with the outer side surfaces of the two tensioning arc-shaped steel blocks; the axial strain gauge and the circumferential strain gauge are positioned in the middle of the test section. The axial strain gauge and the annular strain gauge are used for measuring the annular and axial strain of the annular sample in the annular stretching process. And calculating and obtaining the hoop tensile elastic modulus, Poisson's ratio, hoop tensile strength and hoop ultimate tensile strain of the annular sample according to the tensile data and the strain data measured in the test.
1 annular test specimen
1.1 annular sample pattern
The annular samples are taken from the composite pipes in the same batch for test or engineering practice, and the total number of the annular samples is not less than 5. The annular test sample is shown in figures 1a and 1b, and the smaller width of the annular test sample is the test section of the annular test sample. D is the inner diameter of the annular sample; t is the thickness of the annular sample; h is the width of the annular sample connecting section; h is the width of the test section of the annular sample; l is the arc length of the test section of the annular test specimen.
1.2 annular sample size
The width (h) of the test section should not exceed 35mm, and meanwhile, the width of the test section should not be less than 20mm in order to facilitate the sticking of the strain gauge; the width H of the connecting section of the annular sample is 20mm plus the width H of the testing section; the arc length (l) of the test section is not smaller than 20mm, and is not larger than 50mm in order to reduce the friction force of the test section. As shown in fig. 1a and b.
1.3 inner wall requirement of annular sample
In order to ensure that the inner wall of the annular sample is tightly attached to the outer side surfaces of the fixed arc-shaped steel block and the stretching arc-shaped steel block, the inner wall of the annular sample is smooth and free of layering, tearing and the like, and the rest surfaces of the inner wall of the annular sample are free of damage.
1.4 sticking of annular sample strain gauge
As shown in fig. 2, a unidirectional strain gauge is adhered to the center of the annular test sample testing section in the circumferential direction, the circumferentially adhered strain gauge is an annular strain gauge, two unidirectional strain gauges are respectively adhered to two sides of the annular strain gauge in the axial direction of the annular test sample, and the two unidirectional strain gauges are adhered in the axial direction. Preferably, a strain gage with a gauge length of 5mm to 20mm is used.
1.5 number of annular samples
Each group of the mechanical property annular samples is not less than 5, 5 effective annular samples are ensured to exist in the same batch, and the physical property annular samples are regulated according to corresponding standards.
2 conditions of the test
2.1 test environmental conditions
2.1.1 laboratory Standard environmental conditions
Temperature: (23 + -2) deg.C; relative humidity: (50. + -. 10)%.
2.1.2 laboratory non-Standard environmental conditions
If the standard environmental condition of the laboratory is not available, the environmental condition of the laboratory close to the standard environmental condition of the laboratory is selected.
2.2 test Condition adjustment
The test was carried out under the conditions of at least 23. + -. 2 ℃ and 50. + -. 10% relative humidity for 24 hours. The test was performed at ambient laboratory temperature without the conditions.
3 device and apparatus
3.1 test device
The test device of the test method for the annular tensile property of the composite material pipe consists of two tensioning arc-shaped steel blocks, two fixing arc-shaped steel blocks, four screw rods, a connecting node, two connecting pieces, two supporting rods, a traction mechanism, an axial strain gauge, an annular strain gauge, a roller pin and a sliding baffle; as shown in fig. 12. Wherein, the diameter of the arc section of the stretching arc-shaped steel block and the fixed arc-shaped steel block is D, the radius is r, the diameter D-2mm of the annular sample is 2r, and the width is H1The width of the annular sample is H +10mm (the width refers to the thickness of the tensioning arc-shaped steel block and the fixed arc-shaped steel block); the arc length of the stretching arc-shaped steel block is l1，l1The test section of the annular test piece has an arc length of l +20 mm.
3.2 test apparatus
The tensile apparatus tested may employ a tensile system equipped with a tension regulator and a hydraulic reservoir. The test equipment should meet the following requirements:
3.2.1 the tension system should have the ability to stretch the annular specimen uniformly and continuously.
3.2.2 the tension system needs to be connected with a tension sensor, and the relative error of the tension sensor is not more than 1% of the full scale.
3.2.3 necessary safety protection measures are required in the test process, and the tension system is subjected to safety inspection.
3.2.4 the test apparatus should be calibrated regularly via the metering department with the appropriate qualifications.
3.2.5 the test equipment for physical properties should meet the specifications of the corresponding standards.
3.3 drawing speed
The tensile test is performed at a constant rate of 3-5mm/min, and is loaded until the hoop specimen is snapped.
4 test procedure
4.1 Ring sample preparation as specified in 1.1, 1.2, 1.3 and 1.4.
4.2 the ring specimen is subjected to visual inspection and if there are defects and ring specimens which do not meet the requirements of size and preparation, they are discarded.
4.3 numbering qualified ring-shaped samples, and measuring the inner diameter of the ring-shaped samples and the thickness and the width of a test section of the ring-shaped samples to the accuracy of 0.01 mm. On two end faces of the ring-shaped sample, the inner diameters in two directions perpendicular to each other are measured, respectively, and the average value is taken as the average inner diameter. Measuring wall thickness and width at five equal intervals in the test section of the annular sample, discarding the maximum value and the minimum value, and taking the average value of the rest points as the average wall thickness and the average width
4.4 installation of annular test specimen:
4.4.1 respectively attaching 1 strain gage to the center positions of two testing sections of the annular sample along the annular direction, and then attaching 2 strain gages to the two ends of the annular strain gage along the axial direction of the annular sample, as shown in FIG. 2;
4.4.2 smearing lubricating oil on the inner wall of the annular sample to reduce the friction force between the annular sample and the arc-shaped steel block in the tensile test process;
4.4.3 placing the two tensioning arc-shaped steel blocks and the two fixed arc-shaped steel blocks in the annular sample to ensure that the arc tops of the two tensioning arc-shaped steel blocks and the two fixed arc-shaped steel blocks are contacted with the inner wall of the annular sample, wherein the tensioning arc-shaped steel blocks are aligned with the test section of the annular sample, as shown in fig. 7;
4.4.4 connecting two connecting pieces and two supporting rods with four screw rods respectively and placing the connecting pieces and the two supporting rods into an annular sample, adjusting the total length of the connecting pieces and the screw rods by rotating the nut ends of the connecting pieces, and adjusting the total length of the supporting rods and the screw rods by rotating the nut ends of the supporting rods; the screw rod ends of the two connecting pieces are screwed into the threaded holes of the fixed arc-shaped steel blocks, so that the positions of the fixed arc-shaped steel blocks are unchanged; the steel bar ends of the two support rods prop against the inner side surface of the tensioning arc-shaped steel block, and the position of the tensioning arc-shaped steel block is temporarily fixed, as shown in fig. 8.
4.4.5 sliding the sliding baffle of the tensioning arc-shaped steel block to abut against the inner wall of the annular sample, and a roller pin mounting part is enclosed among the annular sample, the outer side surface of the tensioning arc-shaped steel block and the sliding baffle; as shown in fig. 9;
4.4.6 selecting a roller pin with the size corresponding to the size of the roller pin mounting part from the multiple sets of roller pins, and inserting the roller pin into the roller pin mounting part; as shown in fig. 10a and 10 b;
4.4.7 installing a bolt and a steel chuck on the tensioning arc-shaped steel block; as shown in fig. 11;
4.4.8 connecting the end rod on the steel chuck with a tensile testing machine; the entire test apparatus was thus mounted on a tensile tester.
4.5 adjustment of the ring sample conditions as specified by 2.2.
4.6 the loading rate was 3.3, uniform and continuous stretching until the ring specimen broke.
4.7 during the test, the data to be collected and stored include: tensile load, strain and tensile time of the ring specimen.
Failure mode of 5 Ring test piece
The failure modes required for the test method are: and the fracture surface appears in the middle of the annular sample testing section, only the test data when the fracture surface appears in the middle of the annular sample testing section is recorded, and the annular tensile strength and the annular ultimate tensile strain of the annular sample are obtained through calculation.
Finally, the annular sample is pulled apart, fig. 13a and 13b show two typical failure modes of the annular sample, the fracture surface shown in fig. 13a appears in the middle of the test section, and in order to meet the requirements of the failure modes, the test data of the test section can be used for calculating the annular tensile strength and the annular ultimate strain of the annular sample; FIG. 13b shows the fracture surface at the end of the test segment, and in order not to meet the requirements for failure mode, the test segment data for the failure mode cannot be used to calculate the hoop tensile strength and hoop ultimate strain of the ring specimen.
6 calculation
6.1 FIG. 14 shows the hoop stress-strain curve over the entire course of a typical composite pipe hoop tensile property test for structural engineering. The above are all stated that the pulling is positive and the pressing is negative.
6.2 calculating the hoop tensile stress of the test section of the annular sample according to the formula (1):
in the formula:
σθthe hoop tensile stress of the test section of the annular sample is in MPa;
Ft-the tensile load of the annular specimen in N;
t is the average thickness of the test section of the annular sample, and the unit is mm;
h-average width of test section of annular sample, unit is mm.
6.3 calculating the hoop tensile elastic modulus of the test section of the annular sample according to the formula (2):
in the formula:
Eθthe modulus of elasticity in the circumferential direction of the test section of the annular sample is MPa;
εθannular sample measurementThe circumferential strain of the test section is the reading of a circumferential strain gauge on the test section;
Δεθthe annular strain increment of the annular sample testing section in the elastic range is at least 0.2 percent, and the range of 0.1 to 0.3 percent of the annular strain of the testing section is recommended to be selected;
Δσθand the incremental hoop strain of the test section Δ εθThe corresponding test section hoop tensile stress increment is expressed in MPa;
6.4 calculating the annular Poisson ratio of the annular sample testing section according to the formula (3):
in the formula:
vθx-the annular poisson's ratio of the annular test specimen test section;
εxthe average axial strain of the test section of the annular test specimen is the average of the readings of the two axial strain gauges on the test section;
Δεxand the incremental hoop strain of the test section Δ εθThe corresponding test segment averaged the increase in axial strain.
6.5 calculating the hoop tensile strength of the annular sample according to the formula (4):
in the formula:
Ptthe hoop tensile strength of the test section meeting the requirement of the failure mode is in MPa;
Ft，max-the maximum tensile load of the annular test specimen in N;
t is the average thickness of the test section of the annular sample meeting the requirement of the failure mode, and the unit is mm;
h-the average width of the test section of the annular sample meeting the requirement of the failure mode, and the unit is mm.
Circumferential direction of annular sampleUltimate tensile strain,. epsilonh，maxAnd the maximum strain value of the ring direction strain gage of the test section meeting the requirement of the failure mode is measured at the fracture moment of the ring-shaped test sample.
7 results of the test
The arithmetic mean, standard deviation, dispersion coefficient, etc. of the test results such as the hoop initial elastic modulus, the hoop initial poisson's ratio, etc. should be obtained. For larger dispersion coefficients, specific reasons should be analyzed. If the quality of the ring-shaped sample is poor, a batch of ring-shaped samples should be prepared again for testing.
7.1 Each test ring comprises two test segments, each having a performance value (divided by P)tAnd εh，maxExternal): x1，X2，X3，…,Xn(ii) a Hoop tensile strength P of each annular sampletAnd hoop ultimate strain epsilonh，max：X1，X2，X3，…,Xn. If necessary, the failure of each ring sample should be described.
7.2 calculate the arithmetic mean according to equation (5) to three significant figures:
in the formula:
Xifor the Performance parameter PtAnd εh，maxFor each ring sample performance value that meets failure mode requirements; for other performance values, for each test segment;
n-for the Performance parameter PtAnd εh，maxIn other words, the number of ring-shaped samples meeting the requirement of failure mode; for other performance values, is (number of ring samples × 2).
7.3 calculate the standard deviation S according to equation (6) to a two-digit significant figure:
in the formula:
s-standard deviation.
7.4 calculating the coefficient of dispersion C according to equation (7)vCalculate to two significant digits:
in the formula:
Cv-discrete coefficients.
7.5 confidence intervals for the mean.
Calculated according to ISO 2602: 1980.
The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be equivalent replacement modes, and all are included in the scope of the present invention.
Claims (7)
1. Measure composite material pipe hoop tensile properties's test device for structural engineering, its characterized in that: the tension device comprises two tension arc-shaped steel blocks, two fixed arc-shaped steel blocks, four screw rods, a connecting node, two connecting pieces, two support rods, a traction mechanism, an axial strain gauge and an annular strain gauge;
four screw rods are all fixed with the connecting node, and the four screw rods are distributed in a cross shape; one end of the connecting piece is a screw rod, and the other end of the connecting piece is a nut; the inner side surfaces of the two fixed arc-shaped steel blocks are respectively provided with a threaded hole, the screw end of the connecting piece is in threaded connection with the threaded holes of the fixed arc-shaped steel blocks, the nut end of the connecting piece is in threaded connection with the screw, and the two connecting pieces are arranged in a straight line; one end of each support rod is a nut, the other end of each support rod is a steel bar, the nut end of each support rod is in threaded connection with the corresponding screw, the steel bar end of each support rod abuts against the inner side face of the tensioning arc-shaped steel block, and the two support rods are arranged in a straight line; the traction mechanism for stretching the two tensioning arc-shaped steel blocks outwards is detachably connected with the two tensioning arc-shaped steel blocks; the outer side surfaces of the two tensioning arc-shaped steel blocks, which are attached to the inner wall of the annular sample, are convex arc-shaped surfaces; the outer side surfaces of the two fixed arc-shaped steel blocks, which are attached to the inner wall of the annular sample, are convex arc-shaped surfaces; the axial strain gauge and the annular strain gauge are arranged on the outer surface of the annular sample.
2. The test device for measuring the hoop tensile property of the composite pipe for structural engineering according to claim 1, characterized in that: the device also comprises a sliding baffle and a plurality of sets of needle rollers; the tensioning arc-shaped steel block is provided with two sliding grooves, and the two sliding grooves are respectively positioned on two side surfaces of the tensioning arc-shaped steel block which are inclined from inside to outside; the number of the sliding baffles is four, and in one tensioning arc-shaped steel block, two sliding chutes are matched with the two sliding baffles; the sliding chute is provided with a contraction position and an extension position, the end part of the sliding baffle is aligned with the end part of the outer side surface of the stretching arc-shaped steel block when the sliding baffle is positioned at the contraction position, and the end part of the sliding baffle is propped against the inner wall of the annular sample when the sliding baffle slides outwards from the contraction position to the extension position; enclose into the kingpin installation department between annular sample inner wall, stretch-draw arc steel billet lateral surface and the slide damper, each kingpin installation department sets up one set of kingpin, and each set of kingpin all includes many kingpins, and many kingpins are arranged according to the diameter from big to little in proper order.
3. The test device for measuring the hoop tensile property of the composite pipe for structural engineering according to claim 2, characterized in that: in each set of roller pins, the diameter of the roller pins is 0.5mm-5 mm; the difference between the diameters of two adjacent needle rollers is 0.5 mm.
4. The test device for measuring the hoop tensile property of the composite pipe for structural engineering according to claim 1, characterized in that: the traction mechanism comprises two steel chucks and two bolts; through holes are formed in the thickness direction of the two tensioning arc-shaped steel blocks, the steel chuck is provided with fixing holes corresponding to the through holes, the tensioning arc-shaped steel blocks are connected with the steel chuck through bolts, the bolts penetrate through the through holes, and two ends of the bolts are matched with the fixing holes; and an end rod connected with the tensile testing machine is arranged on the steel chuck.
5. The test device for measuring the hoop tensile property of the composite pipe for structural engineering according to claim 1, characterized in that: the connecting node is of a cubic structure, and the screw rod and the connecting node are of an integrally formed structure.
6. The test device for measuring the hoop tensile property of the composite pipe for structural engineering according to claim 1, characterized in that: the inner side surface of the tensioning arc-shaped steel block is a plane, the head part of the steel bar end of the supporting rod is a plane, the steel bar end of the supporting rod props against the inner side surface of the tensioning arc-shaped steel block, and the tail part of the steel bar end of the supporting rod is provided with a thread section which is in threaded connection with the nut end of the supporting rod.
7. The test device for measuring the hoop tensile property of the composite pipe for structural engineering according to claim 1, characterized in that: the annular sample is of an annular strip structure and comprises two connecting sections with larger width and two testing sections with smaller width, and the connecting sections and the testing sections are alternately distributed; the two test sections are respectively aligned with the outer side surfaces of the two tensioning arc-shaped steel blocks; the axial strain gauge and the circumferential strain gauge are positioned in the middle of the test section.
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