1、 Host device of hydraulic universal material testing machine

Slowly adjust the loading speed according to the speed indicated by the test plate and the loading speed indicated by the torsion plate. Loading speed: the stress increase rate before yield is 10MPa / s. After yielding, the moving speed of the active chuck of the testing machine under load shall not exceed 0.5l/min.

When loading the material testing machine, sometimes it can not add a large load or unload during the loading process. This kind of fault often occurs and has many causes. The viscosity of the oil used is too low (there is always oil flowing out of the oil return pipe of the oil delivery valve during loading). Generally, mineral oil with medium viscosity is used, which does not contain water, acid and other mixtures. It does not decompose at room temperature and remains unchanged. If necessary, it can be measured with a viscometer. If the oil is used improperly, the valve and oil circuit will be blocked, and vibration or pipeline leakage may be caused. Oil shall be used according to the requirements of the manual.

If the oil cylinder and piston of the host device of the hydraulic universal material testing machine are not vertical, the indication deviation will be brought. If the host device is not aligned, the guide wheel on the column will tend to one side, because the spherical support rod in the piston will follow the tendency to one side, resulting in the difference between the upper and lower collets and the upper and lower pressing plates. During long-term application, the extrusion of the guide wheel will produce large friction, which will occasionally crush the guide wheel, the test bench will be guided, and the sample will not be disconnected in the central position. This problem affects the application and indication. Indication deviation caused by incorrect dynamometer device. If the dynamometer device tilts to the right, the included angle between the vertical line of the gear rod and the push rod increases, resulting in too small oil pressure, which affects the accuracy of the experimental machine. If the dynamometer device tilts to the left, the result is vice versa.

The oil pressure system has serious oil leakage. The oil leakage of the oil circuit system generally occurs at the connections of buffer valve, oil return valve, oil delivery valve, oil pump and pipeline. After padding, tighten the screws. If the sealing gasket is broken, it must be disassembled and replaced with a new one. Gaskets shall be made of red copper or aluminum alloy. The fuel tank is insufficient. When it is loaded to a certain load, there are "poof" and "poof" sounds on the oil return pipe of the oil delivery valve, with less oil and bubbles. When the load can no longer rise, no oil flows out of the oil return pipe. Troubleshooting: fill the oil tank of the testing machine until the oil level reaches half of the sight glass. The oil collector of the oil pump is not pressed on the pump body. In this way, each load can only reach a certain load, and the load can not rise again. There is no oil flowing out of the oil return pipe of the oil delivery valve. Troubleshooting: tighten the fixing screw at the rear of the oil pump with a wrench. If there are still problems, remove the oil collector and add a gasket between the oil collector and the pump body.

2、 Operating points of hydraulic universal material testing machine!

About the start-up sequence test of hydraulic universal material testing machine: after entering the online state, the test software is fully started. The machine runs easily (the oil pump starts easily). Therefore, it is necessary to start the measuring system before starting the tester. The startup sequence is: display → printer → computer → industrial control computer → start test software → hydraulic source. Selection and loading / unloading of test fixture: select a suitable test fixture to clamp the sample. Ensure the safety of the tensile testing machine and the accuracy of the test results. In order to avoid unreliable clamping, the sample will slip. Round clamps are usually used for round specimens and flat clamps are used for flat specimens. When the scale of the sample is at the critical scale of the clamping block, try to choose a smaller scale. When installing the fixture of the hydraulic universal material testing machine, the oil pump motor shall not be started, and the machine is in the shutdown state. Push the clamping block into the dovetail groove of the lining plate, and the chamfer side of the clamping block follows the direction of the sample force. Tighten the small diaphragms on both sides of the liner to prevent the clamping block from being crushed.

After clamping the test piece, load the test piece slowly and evenly. Using the automatic stretching device on the universal material testing machine, the relationship curve between external force and deformation is drawn. When the load increases to a point, the upper half of the hydraulic universal testing machine is a straight line, indicating this stage. The proportional relationship between internal load and deformation of the specimen conforms to the elastic deformation range of Hooke's law. When the load increases to the point, the dynamometer pointer remains stationary or suddenly drops to the point, and then swings in a small range. At this time, the deformation increases rapidly and the load increases very slowly; This indicates that the material produces a flow corresponding to this point. The stress is called the upstream limit, and the corresponding stress of the hydraulic universal testing machine is called the downstream limit. Because the lower flow limit is relatively stable, the flow limit of the material is usually specified as the value of the flow limit divided by the load value of the corresponding point divided by the original cross-sectional area of the sample, carbon steel with low flow limit, after the flow stage,

It is used to display sampling data. There is a sensor bar in the main interface of the software. The impact universal material testing machine can display the values of four sensors, namely test force, displacement, extensometer and peak force. Generally, after clamping the specimen and extensometer, the sensor needs to be cleaned before starting the operation test. However, the zero clearing of the force sensor is special. First clamp the chuck on the tension clamp, then adjust the lower beam to the right direction, define the force value, and clamp the lower chuck.