[0024]Combine belowfigure 1 withfigure 2The specific implementation of the metal pipe bending fatigue test device capable of online control of the stress level of the present invention will be further described.
[0025]Such asfigure 1 withfigure 2Shown is the invented metal tube bending fatigue test device with online stress control. The drive motor 1 is fixedly installed on the left side of the platform plate on the frame 5. The output shaft end is connected to the drive shaft 3.11 through the coupling 2; the drive shaft 3.11 The middle part is supported by the auxiliary support base 3.10, and the end is connected with the internal rotating head 3.4 of the driving eccentric part 3, so that the output end mechanism can rotate with the motor 1 at a high speed; a servo motor 4 is placed on the side of the central axis and fixed in The frame platform board 5 is synchronously connected and driven by the synchronous belt 3.9 and the synchronous belt wheel 3.9 on the driving eccentric assembly 3, and the nut sleeve 3.8 is driven to rotate, and the screw sleeve 3.7 matched with it is driven to expand and contract in the axial direction; 3.7 is connected to the telescopic rod 3.5 on the rotating head 3.4; at the output end of the rotating part, there is a sliding plate seat 3.3 in the center of the rotating head 3.4. The end of the rotating head is fixed with a perforated pressure plate to seal the sliding plate seat inside the rotating head. It rotates inside the rotating head driven by the rotating head, and can slide radially along the shaft in the rotating head (specifically, it can be realized by the track or limit groove structure), and it is composed of the spring pin 3.6 and the side telescopic rod 3.5 in the middle part. Eccentric adjustment mechanism, the spring pin pops out under the action of spring force, and the slide seat is pushed up through the inclined plane (withfigure 2Take the middle direction as an example). At the same time, the slide seat moves downward under the action of the telescopic rod, so that the radial position of the slide seat can be adjusted according to the needs, and then the position of the rotating support and the fixture The axis of the drive shaft and the chuck support assembly are offset, which increases the stress of the test piece, and vice versa. There is a radially movable rotating support 3.2 on the slide seat 3.3, which is located on the outside of the pressure plate and is supported by bolts. The limit is fastened on the sliding plate 3.3, which is completed when the test piece 8 is installed. According to the index plate and the indicating arrow, the stress value is adjusted in advance to reach the specified test stress value, reducing the amount of online adjustment.
[0026]According to the monitoring of the acquisition system of the dynamic strain system, the internal characteristics of the structure realize that under the drive of the servo motor, under the normal operation of the test, the slide base 3.3 is driven to move radially to adjust the stress value of the specimen 8. Meet the standard requirements and record the displacement, which effectively ensures that the test is carried out under a constant stress, the results are accurate and reliable, and the online stress value is automatically adjusted to ensure that the test piece is tested in an ideal stress range.
[0027]The invention also discloses a fatigue test method for on-line control of bending stress of a metal pipe, which is carried out by using the above-mentioned device, and the test steps are as follows:
[0028]1. Adjust the eccentric mechanism to return to the origin; rotate the rotating head 3.4 to return to the origin, that is, the fixture 3.1 and the drive shaft 3.11 are coaxial;
[0029]2. Install the test piece, connect one end of the tested piece 8 with the strain gauge attached to the fixture 3.1 on the rotating head 3.4, and connect one side to the chuck support assembly 9;
[0030]3. Turn on the machine, turn on the dynamic stress detection system, and adjust the radial position of the rotating seat 3.2 on the slide seat 3.3 according to the test requirements, and observe the monitoring interface stress value, which is close to the stress value range specified by the test piece 8;
[0031]4. Set the rotation frequency, specify the stress value and other parameters, start the rotating motor, and start the test;
[0032]5. During the test, according to the feedback signal of the strain gauge, judge the size of the bending stress of the test piece 8 and the deviation from the set test stress value, control the movement of the servo motor, and drive the nut sleeve 3.8 forward and reverse rotation through the synchronous pulley 3.9 The movement drives the central screw sleeve 3.7 to move back and forth, push and pull the telescopic rod 3.5 inserted into the rotating head 3.4, so that the sliding plate seat 3.3 mechanism matched with it will move radially under the force of its hand telescopic rod 3.5 and spring pin 3.6. The strain size of the test piece, keep the test piece within the specified stress range for fatigue test in real time;
[0033]6. Judge the fatigue life of the test piece according to the stress monitoring and internal pressure monitoring of the test piece.
[0034]In the structure of the present invention, the servo motor is disposed on the side of the main device rotation mechanism, and the synchronous pulley is connected to the synchronous pulley in the eccentric regulating mechanism of the embedded rotation structure, and the nut is driven to rotate in which the nut is fixed to the housing is rotated. The screw sleeve is sleeve in the axial direction; the telescoping rod in the end and the rotating mechanism of the rear end is connected to each other, and there is no interference freely rotatable and telescopic functional transmission; driving the mounting portion outputted at the rotating portion When the eccentric slide, the telescopic rod is extended when the telescopic rod moves in the direction of radial direction, so that the test piece should be smaller, the stress value is small; when the screw is rotated, the slide holder is in the spring pin and heart force. Under the action, the movement of the radial deviation is made to make the test piece strain becomes large, and the stress value is large. During the test, the stress monitoring system is passed to the strain sheet on the tested member, and the stress value is transmitted to the system, and the output signal control servo motor is transmitted to the system, and the stress value of the test piece is adjusted according to the real-time situation. The mating of a small pin rod and a large deceleration ratio is formed here in this point in which a non-contact high precision adjustment mechanism is used. The drive motor is fixed to the platform plate on the rack, and the output terminal is connected to the rear drive shaft; the intermediate portion of the drive shaft is connected to the auxiliary support bearing frame, the end is connected to the internal rotation output member inside the drive eccentric component, so that the output terminal mechanism The motor can be rotated with the motor; there is a radially movable slewing seat on the skateboard, and the bolt limit is fastened to the skateboard, and there is a circumferential separation disk on the outer ring housing, and there is an indicator arrow on the rotating head. When installing the test piece, you can accurately ensure the horizontal direction of the test piece and the offset, so that the preset stress value reaches the specified test stress value. A sliding moving support is placed on the rear side of the drive eccentric assembly, and the center chuck is mounted on the mount, with a fixed test piece to ensure concentric with the front side. There is a guide slide on the lower side of the support, and the manual lock restriction movement is provided, and the length compensation of the test piece is realized, and the length of the test piece length is machined.
[0035]In the scheme of the present invention, all fixed test piece devices on the platform have a centering structure, and when various components can be curved, the horizontal center position can be accurately identified, especially the shaft component, and can accurately regulate. The fixed end of the test piece and the bending stress applied end balanced position coaxial, reducing the material bending stress caused by the external force during installation, and it is realized that the initial state stress of the test piece meets the requirements. The present invention has been monitored by a dynamic strain collection system, and the feedback stress should be monitored in real time, so that the stress strain can be controlled in the same stress strain test conditions in accordance with the requirements. The present invention enables the test piece fixed to the rotating end by a rotational motion to generate a corresponding stress and strain to the root of the test piece fixed to the test piece fixed end. The shift size of the rotational motion generated by the rotational motion can be adjusted during the rotational motion by mechanical transmission, and the measuring method of the online adjustment is achieved without using the electric slip ring or the shutdown to adjust the offset adjustment. The power of online adjustment relies on the servo motor control system with a large deceleration ratio reduction machine and the small pin rod transmission, the adjustment is eccentric, and the precision is high. Relying on the dynamic strain gauge and the servo motor control system to achieve closed-loop control, maintain constant bending stress and strain during the test. The test equipment is high, high frequency, can perform high frequency bending life test, maximum frequency of 60 Hz.
