Background
Statistical analysis has shown that fracture, wear and corrosion are the major failure modes of mechanical parts, where fractures are sudden and often cause serious accidents. According to theoretical research and practice, people realize that when mechanical parts bear alternating load, fatigue phenomena can occur, and when the alternating load is accumulated to a certain degree, the parts can be broken and damaged. Among the many factors that cause the mechanical parts to break, the failure of the mechanical parts to break due to metal fatigue accounts for over 80%.
The number of times of alternating load of mechanical parts is generally 106~107The number of times is a reference number, and the magnitude of the alternating load is defined as the fatigue strength. The fatigue strength is closely related to the material, processing mode, geometry and load type of the mechanical parts.
Therefore, it is very difficult to calculate the fatigue strength by a theoretical method for a structure having a complicated shape subjected to an alternating load, and therefore the fatigue of the structure is often measured by an experimental method. Generally speaking, firstly parameters of the alternating load are defined according to the service condition of the structure, and secondly 10 is applied according to the design service life of the structure and the frequency of the alternating load6~107And (5) secondary alternating load, and observing the fracture condition of the structure. If the structure does not have cracks, the structure is considered not to have fatigue fracture under the test alternating load, namely the fatigue strength of the structure is larger than the stress corresponding to the test alternating load.
In the tension type cathodic protection system, the cable is subjected to the action of cyclic load due to frequent impact movement of wind, wave and current in seawater, meanwhile, as the axial size of the auxiliary anode integrated on the cathodic protection system is far larger than the diameter of the cable, the difference between the rigidity and the rigidity of the cable is large, local fatigue damage is easy to occur at the contact position of the auxiliary anode and the cable, and meanwhile, the tension type cathodic protection system has pretension. Therefore, it is necessary for the fatigue testing equipment to be able to apply both pretension and alternating moment load to the cable components.
In the existing experimental equipment, how to ensure the direction of the bending load, conveniently calculate the bending moment applied to the end part and improve the loading frequency of the bending load is a difficult point.
Disclosure of Invention
An object of the utility model is to overcome the above-mentioned defect that prior art exists, provide a can improve the crooked load of reversal and apply frequency, measure convenient, the simple tired loading device of equipment.
In order to achieve the above purpose, the technical scheme of the utility model is as follows:
a fatigue loading device comprises a slide box and a pulley, wherein the slide box is of a box structure, a longitudinal pulley extending seam is formed in the center of the front side face of the slide box, a detachable baffle plate is arranged on the upper side face of the slide box, and two slide rails which are symmetrical about the pulley extending seam are arranged inside the front side face; the tackle comprises a tackle main body and a pulley, wherein a horizontal extension rod perpendicular to the plane of the tackle main body is installed at the center of the tackle main body, the tackle main body is tightly combined with the slide rail through the pulley, and the horizontal extension rod extends out of the slide box through the tackle extension seam and is connected with a test piece.
Preferably, the pulley main body is an i-shaped frame, the number of the pulleys is four, and the four pulleys are respectively mounted at four end points of the i-shaped frame through bearings.
Preferably, the rear side of the slide box is a square blind flange, and the size of the square blind flange is larger than that of the front side of the slide box.
Preferably, the cross section of the slide rail is a convex arc, the surface of the pulley, which is in contact with the slide rail, is a concave arc, and the radius of the convex arc is equal to that of the concave arc; or the cross section of the sliding rail is a concave arc, the surface of the pulley, which is in contact with the sliding rail, is a convex arc, and the radiuses of the concave arc and the convex arc are equal.
Preferably, the horizontally extending rod is connected to an actuator.
Preferably, the horizontal extension bar is also connected to a displacement meter.
According to the above technical scheme, the utility model discloses a design coaster and the tired loading device that the smooth case combines to slide rail through the smooth case and be connected between the pulley of coaster, guarantee that the coaster only produces the displacement of a direction, and reduce rolling friction power, can improve alternating load frequency, overall structure is simple, and the loading is convenient, and alternating load amplitude is measured portably. Therefore, the utility model has the characteristics of showing.
Detailed Description
The following describes the present invention in further detail with reference to the accompanying drawings.
In the following detailed description of the embodiments of the present invention, for the sake of clarity of the structure of the present invention, it is to be understood that the structure shown in the drawings is not drawn to scale, and is partially enlarged, deformed and simplified, and therefore the present invention is not limited thereto.
Referring to fig. 2, fig. 2 is a schematic structural diagram of the fatigue loading device in the present embodiment. The fatigue loading device is composed of a slide box 2 and a pulley 3, the slide box 2 is a box structure, the rear side 21 is fixed on the shear wall, specifically, the rear side 21 can be a square blind flange, the size is larger than that of the front side 22, the slide box is fixed on the shear wall by using bolts/nuts, the center position of the front side 22 is provided with a longitudinal pulley extending slit 23, two slide rails 24 (refer to fig. 3) symmetrical to the pulley extending slit 23 are arranged inside the front side 22, and in the embodiment, the cross section of each slide rail 24 is a convex arc. The upper side of the sliding box is a detachable baffle plate for installing the pulley, a gap with a certain width is reserved in the middle of the baffle plate, the pulley can be conveniently observed, and meanwhile, a lubricant is conveniently added to the pulley. Referring to fig. 3 to 5, the pulley 3 includes a pulley body 31 and four pulleys 32 with equal size, the pulley body 31 includes an i-shaped frame 34, and a horizontal extension bar 33 fixedly installed at the center of the i-shaped frame 34 and perpendicular to the plane of the i-shaped frame, the four pulleys 32 are respectively installed at four end points of the i-shaped frame through bearings, the pulley body 31 is tightly coupled with the slide rail 24 in the slide box 2 through the pulleys 32, and the horizontal extension bar 33 extends out of the slide box through the pulley extension slit 23. In the embodiment, the pulley 32 is a concave arc, the radius of the concave arc is equal to the radius of the convex arc of the slide rail 24, so that the pulley and the slide rail are tightly combined, and the arc structure has small rolling friction force, thereby facilitating the increase of loading frequency. Or the cross section of the sliding rail is a concave arc, the surface of the pulley, which is in contact with the sliding rail, is a convex arc, and the radiuses of the concave arc and the convex arc are equal.
When the fatigue loading device is used for a bending fatigue test, please refer to fig. 1, fig. 1 is a schematic structural diagram of a bending fatigue test device capable of applying an axial pretension in an embodiment of the present invention. As shown in FIG. 1, the bending fatigue testing device capable of applying axial pretension comprises a slide box 2, a pulley 3, a first connecting piece 4, an actuator 5, a test piece fixing and supporting device 6, a test piece 7, a second connecting piece 8, a force sensor 9, an axial force applying device and an axial force applying fixing and supporting device 11, wherein the slide box 2 and the pulley 3 form a bending fatigue loading device, and the slide box 2 is fixed on a shear wall 1.
In the embodiment, the test piece is an auxiliary anode 7 encapsulated on a composite cable 13, and the left end of the auxiliary anode 7 is fixed through the test piece fixing and supporting device 6. An axial pretension is provided at the left end of the test piece 7, specifically, the left end of the test piece 7 is connected with a force sensor 9 through a second connecting piece 8, the force sensor 9 is connected with an axial stressing device, in the embodiment, the axial stressing device is a T-shaped lead screw 14, a gasket and a nut 15, the axial pretension is applied through a tightening nut 15, the axial pretension can be accurately measured through the force sensor 9, the T-shaped lead screw 14 is fixed through an axial stressing fixed supporting device 11, in the embodiment, the axial stressing fixed supporting device 11 is a ground pier with a fixed supporting frame 10, a through hole baffle of the T-shaped lead screw 14 is fixed on the fixed supporting frame 10 through a bolt, and the ground pier is fixed on the ground through a horizontal platform. After a certain axial pretension is applied to the test piece, a bending fatigue load is applied to the right end of the test piece 7, and in the embodiment, the trolley 3 is driven by the actuator 5 to reciprocate up and down in the slide box 2, so that the test piece 7 is driven to generate a bending moment. The direction of the bending fatigue load can also be along the horizontal direction, and the fixed direction of the slide box can be changed.
The actuator 5 is installed below the horizontal extension bar 33, specifically, a ring structure with an opening is fixed at the end of the actuator, an extension part of a connecting bolt is arranged at the opening, the shape of the ring structure is matched with the cross section shape of the horizontal extension bar, and the ring structure is sleeved on the root part of the horizontal extension bar and is fixedly connected with the horizontal extension bar through a bolt. The actuator drives the pulley 3 to reciprocate through the horizontal extension rod 33. In order to accurately measure the displacement of the trolley 3, a displacement meter 12 may be further installed at the front end of the horizontally extending rod 33, as shown in fig. 1.
When the actuator 5 has no power output, the axis of the pulley 3, the axis of the horizontal extension rod 33, the axis of the test piece 7 and the axis of the axial force application device are positioned on the same straight line and are parallel to the horizontal plane.
The method for performing the bending fatigue test on the test piece applying the axial pretension by using the device mainly comprises the following steps:
s1: and mounting the test piece on the test piece fixing and supporting device.
In the embodiment, the test piece 7 is a component consisting of the cable 13 and the auxiliary anode 7, one end of the cable 13 is connected to the horizontal extension bar 33 of the pulley body through the first connecting piece 4, the other end of the cable is connected to the force sensor 8 through the second connecting piece 8, and the auxiliary anode 7 is fixed through the test piece fixing device 6; the force sensor 8 is connected to the axial force means.
S2: and applying axial pretension with a certain value to the test piece by using an axial force application device.
Specifically, the axial force application device is adjusted, and the data of the force sensor 8 is read, and the axial pretension is set to a specified value.
S3: and (4) giving the bending moment amplitude and the load cycle number of the test piece.
S4: and calculating the stroke of the actuator according to the axial pretension, the bending moment amplitude of the test piece, the size of the test piece and the position of the actuator, and applying bending moment to the test piece.
Specifically, the initial position of the pulley is adjusted, so that the axis of the horizontal extension rod of the pulley, the axis of the test piece and the axis of the axial force application device are positioned on the same straight line. The stroke of the actuator, the axial pretension, the set bending moment amplitude, the size of the test piece and the position of the actuator have the following relations:
wherein,vthe stroke of the actuator is M is the bending moment amplitude of the fixed end of the auxiliary anode, F is the applied pretension, and L1To assist anode length, L2To assist the length of the anode unsecured end to the actuator.
S5: and (4) setting an actuator according to the stroke of the actuator obtained in the step (S4), setting the frequency of the actuator, driving the bending fatigue loading device through the actuator, and performing a bending fatigue test.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the technical scope of the present invention.