Steps for testing of hydraulic universal testing machine

a) The test machine takes the gauge distance at the middle section of the specimen or uses a foot gauge to mark both ends as a mark. Use a vernier caliper to measure the diameters at the middle and both ends within the gauge distance range of the specimen to take a small value as a calculation of the cross-sectional area of ​​the specimen.

b) Preparation of the test machine: First understandHydraulic universal testing machineThe basic structural principles and operating methods of the test machine are learned. According to the strength limit of low carbon steel and the cross-sectional area of ​​the specimen, the load required for tensile specimen is initially estimated, the appropriate velocity measurement dial is selected, and the corresponding pendulum is installed, the machine is activated, the force measurement pointer is adjusted to "zero point", and then the position of the lower chuck of the test machine is adjusted, and the specimen clip is installed in the chuck.

c) Perform experiment: After the test piece is clamped, the test piece is loaded slowly and evenly. Use the automatic drawing device on the universal material test machine to draw the relationship curve between external force and deformation when the load increases to the point. The upper section of the stretching diagram is a straight line indicating the proportional relationship between the load and the specimen in this stage, that is, the elastic deformation range that conforms to Hook's law. When the load increases to the point, the dynamometer pointer stays still or suddenly drops to the point and then swings within a small range. The deformation increases very quickly and the load increases very slowly. This shows that the material produces a stress corresponding to the flow point and the corresponding stress is called the lower flow limit. Because the lower flow limit is relatively stable, the flow limit of the material generally stipulates that the value of the lower flow limit is divided by the load value corresponding to the point by the original cross-sectional area of ​​the specimen to obtain the flow limit of the low carbon steel. After the flow stage,

The hydraulic universal testing machine test pieces must bear greater external forces before they can continue to deform. To increase the plastic deformation, the load must be increased, such as the point to point in the figure is the strengthening stage. When the load reaches the value point, the plastic deformation of the specimen is concentrated in a small section at a certain section. This section shrinks in cross-section, which means "necking" occurs. Turn off the machine, remove the broken specimens and tightly match the broken specimens together, use a vernier caliper to measure the length between the gauges of the specimens after breaking, and calculate the elongation of the low carbon steel according to the following formula.

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