Low-frequency fatigue tensile loading equipment in marine environment

Abstract

The invention provides low-frequency fatigue tensile loading equipment in a marine environment, which comprises an environmental box system, the environmental box system comprises a test box, a circulating system and a temperature control system, a solution for simulating the marine environment is arranged in the test box, the circulating system is communicated with a solution area in the test box, and the temperature control system is used for controlling the temperature of the solution; the truss type loading equipment is arranged in the environment box system, the truss type loading equipment comprises an upper chord beam frame, a variable load structure is connected to the upper chord beam frame, lower chord clamping nodes are arranged on the lower portions of the two sides of the upper chord beam frame respectively, and a sample is clamped between the lower chord clamping nodes and located in a solution area in the test box. According to the invention, various acidic and alkaline marine environment working conditions can be simulated, and various corrosive solution environments can be simulated; environmental conditions such as dry-wet cycle and freeze-thaw cycle are simulated. The limitation that a traditional environment test box cannot apply variable loads is broken through. And a test condition closer to a service state is provided for a durability test.

Description

Technical Field

[0001] The present invention relates to the technical field of material mechanics test equipment, and particularly to a low-frequency fatigue tensile loading device in a marine environment. Background Art

[0002] Materials such as FRP and steel tend to be in a load-holding condition in ocean engineering, and their loads can be divided into two parts: static load and wind-wave dynamic load. In the scientific research field, when conducting durability tests on engineering materials, there is no standard for standardizing the load-holding device, and the load-holding methods can generally be divided into displacement control and load control.

[0003] The device for displacement control generally adopts the post-tensioning method, providing the required force by controlling the displacement. However, with the creep and performance deterioration of the material, its elastic modulus changes, and at this time, the applied displacement load changes, and the load shows a long-term decreasing trend.

[0004] The load control loading device generally uses the form of multi-stage lever amplification to provide tensile load for the specimen, and a water tank can be arranged in the tension area to provide a corrosive environment. However, this water tank is open-air, and its environmental variables are difficult to control; the load is relatively stable, but quantitative change of the load cannot be achieved.

[0005] The existing test equipment cannot fully simulate the variable loads in the marine conditions, nor can it easily simulate the dry-wet alternating marine environment, and its application scenarios are very limited. Summary of the Invention

[0006] The purpose of the present invention is to provide a low-frequency fatigue tensile loading device in a marine environment, which can simulate the variable loads in the marine conditions and the dry-wet alternating marine environment;

[0007] The present invention provides a low-frequency fatigue tensile loading device in a marine environment, including: an environmental chamber system, the environmental chamber system includes a test chamber, a circulation system and a temperature control system, there is a solution simulating the marine environment in the test chamber, the circulation system is communicated with the solution area in the test chamber, and the temperature control system is used to control the solution temperature; a truss-type loading device, the truss-type loading device is arranged in the environmental chamber system, the truss-type loading device includes an upper chord beam frame, a variable load structure is connected to the upper chord beam frame, and lower chord clamping nodes are respectively arranged on the lower parts of both sides of the upper chord beam frame, and the specimen is clamped between the lower chord clamping nodes and is located in the solution area in the test chamber.

[0008] Further, the circulation system includes a water return tank and a water pump system, and the water return tank is internally communicated with the test chamber through the water pump system.

[0009] Further, the water pump system includes a feed water pump and a return water pump. The return water tank is provided with a return water outlet and a first water outlet, and the test chamber is provided with a water inlet and a second water outlet. The first water outlet is communicated with the water inlet through a pipeline and the feed water pump, and the second water outlet is communicated with the return water outlet through a pipeline and the return water pump.

[0010] Further, the circulation system further includes a controller, which is signal-connected to the water pump system. The controller includes a dry-wet circulation control mode, and the dry-wet circulation control mode includes the following steps: S1, controlling the water pump system to be turned on for a time t1 at an interval of time T1, so that the solution is transferred from the test chamber to the return water tank; S2, controlling the water pump system to be turned on for a time t2 at an interval of time T2, so that the solution is transferred from the return water tank to the test chamber.

[0011] Further, the temperature control system is respectively arranged at the inner bottoms of the test chamber and the return water tank, and the temperature control system includes a temperature control switch and a heating rod.

[0012] Further, the variable load structure includes at least two turntables rotatably arranged on the upper chord beam frame. The two turntables rotate in opposite directions, and at least one load is arranged on the turntable. The loads on the two turntables are symmetrically arranged about the center.

[0013] Further, the variable load structure further includes a rotation driving device arranged at the center of the upper chord beam frame. A gear is arranged on the rotation driving device. The two turntables are symmetrically distributed on both sides of the rotation driving device. Gear teeth are arranged on the edges of the turntables. The gear of the rotation driving device meshes with the gear teeth on the two turntables on both sides.

[0014] Further, a height adjusting mechanism is arranged in the middle of the upper chord beam frame, and the variable load structure is connected to the upper chord beam frame through the height adjusting mechanism.

[0015] Further, the height adjusting mechanism includes a plurality of pin holes opened in the middle of the upper chord beam frame along the height direction. The height of the variable load structure is adjusted by inserting the upper chord pin shaft into different pin holes.

[0016] Further, the lower chord clamping node includes connection holes opened at the lower parts on both sides of the upper chord beam frame. A pulling member is connected in the connection holes through a length adjusting component. Both ends of the specimen are connected to the pulling member through clamping members.

[0017] The technical solution of the present invention forms an environmental chamber system through a test chamber, a circulation system and a temperature control system. Different solutions can be used to soak specimens to simulate various acidic and alkaline marine environmental conditions and various corrosive solution environments. And the injection and discharge of the solution in the test chamber are controlled by the circulation system, and the temperature of the solution is controlled by the temperature control system to realize the simulation of environmental conditions such as dry-wet cycles and freeze-thaw cycles. The load value is adjusted by a variable load structure and transmitted to the specimen through the upper chord beam frame, breaking through the limitation that traditional environmental test chambers cannot apply variable loads. Thus, the present invention realizes the combined action of load and corrosive environment at low cost, providing test conditions closer to the service state for durability tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 is the front view of the present invention;

[0020] Figure 2 is the schematic diagram of the top view and the turntable direction of the present invention;

[0021] Description of the reference numerals:

[0022] 1 - test chamber; 101 - water inlet; 102 - second water outlet; 2 - return water tank; 201 - return water inlet; 202 - first water outlet; 3 - feed pump; 4 - return pump; 5 - temperature control system; 6 - upper chord beam frame; 7 - lower chord clamping node; 701 - pulling member; 702 - nut; 703 - universal joint; 8 - turntable; 801 - gear tray; 9 - load; 10 - rotation driving device; 11 - gear; 12 - pin hole; 13 - pin shaft; 14 - solution, 15 - specimen. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0025] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined. In addition, the terms "install", "connect", and "couple" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] Embodiment 1

[0027] As Figure 1 - Figure 2 shown, the present invention provides a low-frequency fatigue tensile loading device in a marine environment, including: an environmental chamber system, which includes a test chamber 1, a circulation system, and a temperature control system 5. There is a solution 14 for simulating the marine environment in the test chamber 1. The circulation system is in communication with the solution 14 area in the test chamber 1, and the temperature control system 5 is used to control the temperature of the solution 14; a truss-type loading device, which is arranged in the environmental chamber system. The truss-type loading device includes an upper chord beam frame 6, a variable load structure is connected to the upper chord beam frame 6, and lower chord clamping nodes 7 are respectively arranged on the lower parts on both sides of the upper chord beam frame 6. The specimen 15 is clamped between the lower chord clamping nodes 7 and is located in the solution 14 area in the test chamber 1.

[0028] Specifically, the environmental chamber system is used to simulate the marine environment. The test chamber 1 is a sealed container, and its material can be changed to adapt to acidic, alkaline, and marine environment working conditions. Different property solutions 14 are filled in the chamber to meet the simulation of various corrosion environments. The circulation system can control the circulation time and the amount of the solution 14 in the test chamber 1, and the temperature control system 5 can adjust the temperature of the solution 14 to simulate environmental working conditions such as solution 14 immersion, wet-dry cycling, and freeze-thaw cycling.

[0029] Referring to the structure of the beam string structure, in the present invention, the upper chord beam frame 6 is symmetric about the left and right, including the top and the two side feet. The lower chord clamping nodes 7 are arranged on the two side feet, so the two lower chord clamping nodes 7 are symmetric about the left and right. The specimen 15, as the object to be loaded, is connected to the truss beam in a clamped state through the lower chord clamping nodes 7 on both sides. When a load 9 is applied to the top of the upper chord beam frame 6, the lower chord of the truss beam formed by the two side feet is in a tension state. The magnitude of the tensile force is related to the magnitude of the upper load 9, the acting position of the load 9, the span and the height of the truss beam. The magnitude, acting position and span of the load 9 determine the magnitude of the mid-span bending moment.

[0030] The span and width of the truss beam can be adjusted. For example, the truss beam can be extended by splicing flat plates through a plurality of pin shaft 13 holes at the mid-span to change the span.

[0031] The top of the beam frame is a horizontal plane, and an annular array of rollers and a central pin shaft 13 are arranged. The annular rollers are a group of ball bearings, and the central pin shaft is a round bar. The purpose is to ensure that the turntable rotates around the center, and the force is evenly dispersed to the top platform surface of the truss beam through the ball bearings. Or the top surface of the truss beam may not be a plane, but it is necessary to ensure that the top surface of the turntable 8 is a horizontal plane to ensure that no vertical interference force is generated during the rotation of the motor.

[0032] The temperature control system 5 can be a quartz electric heating rod, a Teflon electric heating rod, an air source heat pump or a compressor condenser, which can realize heating or refrigeration, and start and cut off the power through a temperature control switch to ensure that the temperature is controlled within the set range.

[0033] The materials of the truss beam and the environmental test chamber 1 can be steel, stainless steel, engineering plastics, etc. to cope with the corrosion conditions of acid, alkali and salt.

[0034] Embodiment 2

[0035] The circulation system includes a water return tank 2 and a water pump system. The water return tank 2 is internally connected to the test chamber 1 through the water pump system. The water pump system includes a water inlet pump 3 and a water return pump 4. The water return tank 2 is provided with a water return port 201 and a first water outlet 202, and the test chamber 1 is provided with a water inlet 101 and a second water outlet 102. The first water outlet 202 is connected to the water inlet 101 through a pipeline and the water inlet pump 3, and the second water outlet 102 is connected to the water return port 201 through a pipeline and the water return pump 4. The circulation system further includes a controller, and the controller is signal-connected to the water pump system. The controller includes a dry-wet circulation control mode, and the dry-wet circulation control mode includes the following steps: S1, controlling the water pump system to be turned on for t1 time at an interval of T1 time to transfer the solution 14 from the test chamber 1 to the water return tank 2; S2, controlling the water pump system to be turned on for t2 time at an interval of T2 time to transfer the solution 14 from the water return tank 2 to the test chamber 1.

[0036] Specifically, the test chamber 1 and the water return tank 2 are sealed containers with good heat preservation and airtightness, which can slow down the temperature change and prevent water evaporation and impurity intrusion. The test chamber 1 and the water return tank 2 are connected through a water pump system, which consists of a feed water pump 3, a return water pump 4, two pipes and a controller. The dry-wet cycle control mode is a set of timed power-on facilities, which are turned on once every 5 hours and 45 minutes (T1 time and T2 time), and each time it is turned on for 15 minutes (t1 time and t2 time), so that the solution 14 is transferred back and forth between the test chamber 1 and the water return tank 2, and a dry-wet cycle is completed every 12 hours in the test chamber 1.

[0037] Example 3

[0038] The temperature control systems 5 are respectively arranged at the inner bottoms of the test chamber 1 and the water return tank 2. The temperature control system 5 includes a temperature control switch and an electric heating rod.

[0039] Specifically, the temperature control system 5 is two sets of temperature control switches and quartz electric heating rods, so that the solution 14 in the test chamber 1 and the water return tank 2 is maintained constant in the range of 59°C to 61°C.

[0040] Example 4

[0041] The variable load structure includes at least two turntables 8 rotatably arranged on the upper chord beam frame 6. The two turntables 8 rotate in opposite directions. At least one load 9 is arranged on the turntable 8, and the loads 9 on the two turntables 8 are arranged centrally symmetrically. The variable load structure also includes a rotation driving device 10 arranged at the center of the upper chord beam frame 6. A gear 11 is arranged on the rotation driving device 10. The two turntables 8 are symmetrically distributed on both sides of the rotation driving device 10. Gear teeth are arranged on the edges of the turntables 8, and the gear 11 of the rotation driving device 10 meshes with the gear teeth on the two turntables 8 on both sides.

[0042] Specifically, the rotation driving device 10 is selected as a motor device. The motor can rotate at a constant speed or a variable speed, so that the axial force received by the clamped specimen 15 is presented in the form of a sine wave, a triangular wave or a square wave. The load 9 turntables 8 are a pair of symmetrically placed plane gear 11 turntables 8. Weights are placed on the turntables 8 as the load 9. When the motor drives the gear 11 and drives the turntables 8 to rotate in opposite directions, the loads 9 on both sides are always centrally symmetric. From the front view, the loads 9 symmetrically move away from the A / A' points simultaneously to the B / B' points and then move back and forth again, and their planar speed follows a sine function.

[0043] By adjusting the motor speed, the rotation speed of the load 9 turntables 8 can be adjusted, and thus the frequency of the fatigue load 9 can be controlled.

[0044] The external weight load 9 is F, C is the distance from the center of the turntable 8 to the support, R is the distance from the centroid of the weight to the axis of rotation of the turntable 8, ω is the angular velocity of the self-rotation of the turntable 8, H is the distance from the centroid of the upper chord pin shaft 13 to the centroid of the lower chord clamped specimen 15, and T0 is the initial tension of the structural self-weight on the specimen 15. Then the calculation formula for the axial force T of the specimen 15 is:

[0045]

[0046] Example 5

[0047] A height adjustment mechanism is provided in the middle of the upper chord beam frame 6, and the variable load structure is connected to the upper chord beam frame 6 through the height adjustment mechanism. The height adjustment mechanism includes a plurality of pin holes 12 opened in the middle of the upper chord beam frame 6 along the height direction, and the height H of the variable load structure is adjusted by inserting the upper chord pin shaft 13 into different pin holes 12.

[0048] Specifically, the position of the upper chord pin shaft 13 determines the effective height of the truss beam. There are three pin holes at the upper node in the middle of the truss beam, and their positions are fixed. By adjusting the pin shaft from top to bottom or from bottom to top, the adjustment of the distance H from the center line of the lower chord to the center line of the pin shaft can be realized, and the distance ratio is 1:1.5:2. By manually adjusting the position of the pin, the adjustment of the internal force of the lower chord member can be realized.

[0049] Example 6

[0050] The lower chord clamping node 7 includes connection holes opened at the lower parts on both sides of the upper chord beam frame 6. A pulling member 701 is connected in the connection holes through a length adjustment assembly, and both ends of the specimen 15 are connected to the pulling member 701 through clamping members.

[0051] Specifically, the pulling member 701 of the lower chord clamping node 7 can realize the coordination of rotational deformation in the forms of a universal joint 703, a ball shaft, a wire rope, etc., so that the clamped specimen 15 is in an axial tension state. The connection mode between the lower chord clamping node 7 and the upper chord beam frame 6 can realize the length adjustment function of the length adjustment assembly in ways such as bolt connection, wedge embedding, ratchet winch tightening, etc. The clamping member can adopt a mechanical self-tightening chuck or a cover plate bolt.

[0052] The present invention adjusts the amplitude and frequency of the applied load 9 by adjusting the support span, the position of the upper chord pin shaft 13, the size and position of the weights, and the motor speed, and the adjustment range of the load 9 is large.

[0053] The present invention can adapt to acidic, alkaline and marine environment working conditions by changing the material, and meet various corrosion environments. The temperature of the solution 14 and the circulation time can be adjusted to simulate environmental working conditions such as solution 14 immersion, dry-wet cycle, freeze-thaw cycle, etc., and the environmental adaptability is strong.

[0054] Generally speaking, the present invention overcomes the disadvantages of high cost in modifying a mechanical testing machine by adding an environmental chamber and a single simulated environment, and also breaks through the limitation that the traditional environmental test chamber 1 cannot apply variable loads 9. It realizes the combined action of the load 9 and the corrosion environment at low cost, providing test conditions closer to the service state for durability tests.

[0055] The usage method of the present invention:

[0056] 1. First, firmly clamp and connect the specimen 15 to be clamped and the two lower chord tie rods (tension members 701). Then, pass the screw part at the other end of the tie rod through the screw hole at the support of the truss beam and roughly screw on the nut to ensure that the lower chord does not fall off.

[0057] 2. Insert the upper chord pin shaft 13 of the truss beam to form a stable structure of three steel plates; then place the entire upper chord beam frame 6 on the roller supports in the test chamber 1 to release the lateral internal force through the roller supports, making the overall structure in a simply supported state; and adjust the lower chord nut 702 to change the length of the lower chord, so that the upper surface of the truss beam is adjusted to a horizontal state. During this process, simplify the two upper chord truss beams and one GFRP of the lower chord of the overall structure into an isosceles triangle at the connection points. The upper vertex angle of the triangle must be a fixed value so that the top surfaces of the two truss beams can be in a horizontal state. During the bonding process of the GFRP of the lower chord, it may be too long or too short, causing a change in the included angle between the two truss beams, which will cause the gear load turntable to squeeze the gear of the motor and cause damage.

[0058] 3. Place the turntable 8 on the upper surface of the truss beam and fasten the gear 11 tray 801, so that the motor gear 11 and the tray gear 11 are fastened. Subsequently, place the weights in the card slots of the tray.

[0059] 4. Pour the prepared solution 14 into the test chamber 1 and the water return tank 2, close the lid of the test chamber 1, and turn on the power of the temperature control device, the water pump system, and the motor to start the test of the combined action of load and environment.

[0060] The present invention can be a device for applying a constant or low-frequency sinusoidally varying tensile stress to various profiles, and its environment can be divided into two types: constant temperature immersion and wet-dry cycle.

[0061] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-frequency fatigue tensile loading device in a marine environment, characterized in that, Including: An environmental chamber system, which includes a test chamber, a circulation system, and a temperature control system. There is a solution simulating the marine environment in the test chamber. The circulation system is connected to the solution area in the test chamber, and the temperature control system is used to control the solution temperature; A truss-type loading device, which is arranged in the environmental chamber system. The truss-type loading device includes an upper chord beam frame. A variable load structure is connected to the upper chord beam frame. Lower chord clamping nodes are respectively arranged at the lower parts on both sides of the upper chord beam frame. The specimen is clamped between the lower chord clamping nodes and is located in the solution area in the test chamber.

2. The low-frequency fatigue tensile loading device in the marine environment according to claim 1, wherein The circulation system includes a water return tank and a water pump system. The water return tank is internally connected to the test chamber through the water pump system.

3. The low-frequency fatigue tensile loading device in a marine environment according to claim 2, wherein The water pump system includes a feed water pump and a return water pump. A water return port and a first water outlet are arranged on the water return tank. A water inlet and a second water outlet are arranged on the test chamber. The first water outlet is connected to the water inlet through a pipeline and the feed water pump. The second water outlet is connected to the water return port through a pipeline and the return water pump.

4. The low-frequency fatigue tensile loading device in a marine environment according to claim 2, wherein, The circulation system further includes a controller, which is signal-connected to the water pump system. The controller includes a dry-wet circulation control mode. The dry-wet circulation control mode includes the following steps: S1, controlling the water pump system to be turned on for t1 time at an interval of T1 time, so that the solution is transferred from the test chamber to the water return tank; S2, controlling the water pump system to be turned on for t2 time at an interval of T2 time, so that the solution is transferred from the water return tank to the test chamber.

5. The low-frequency fatigue tensile loading device in a marine environment according to claim 2, wherein The temperature control system is respectively arranged at the inner bottoms of the test chamber and the water return tank. The temperature control system includes a temperature control switch and an electric heating rod.

6. The low-frequency fatigue tensile loading device in a marine environment according to claim 1, wherein The variable load structure includes at least two turntables rotatably arranged on the upper chord beam frame. The two turntables rotate in opposite directions. At least one load is arranged on the turntable. The loads on the two turntables are symmetrically arranged about the center.

7. The low-frequency fatigue tensile loading device in a marine environment according to claim 6, characterized in that The variable load structure further includes a rotation driving device arranged at the center of the upper chord beam frame. A gear is arranged on the rotation driving device. The two turntables are symmetrically distributed on both sides of the rotation driving device. Gear teeth are arranged at the edges of the turntables. The gear of the rotation driving device meshes with the gear teeth on the two turntables on both sides.

8. The low-frequency fatigue tensile loading device in a marine environment according to claim 1, wherein A height adjustment mechanism is arranged in the middle of the upper chord beam frame. The variable load structure is connected to the upper chord beam frame through the height adjustment mechanism.

9. The low-frequency fatigue tensile loading device in a marine environment according to claim 8, wherein The height adjustment mechanism includes a plurality of pin holes opened in the middle of the upper chord beam frame along the height direction. The height of the variable load structure is adjusted by inserting the upper chord pin shaft into different pin holes.

10. The low-frequency fatigue tensile loading device in a marine environment according to claim 1, characterized in that, The lower chord clamping node includes connection hole positions opened at the lower parts on both sides of the upper chord beam frame. A pulling member is connected in the connection hole positions through a length adjustment component. Both ends of the specimen are connected to the pulling member through clamping members.

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