In order to realize the loading speed of the cement pressure testing machine, there are two methods:
1. General pressure testing machine. It is equipped with a readout panel and press the heart, fixed speed dial with logo to guide when press boot, constant speed plate will turn its angular velocity (value + hard just for the purpose of pressure test, the operator through the fuel valve, let the press pressure indicating needle always follow a point on speed dial, the specimen compressive loading speed can meet the requirements of regulations.
2. A pressure testing machine composed of pressure sensor, pressure automatic control unit and pressure system. The loading speed is free to choose, and the loading speed is always at the selected speed when the test is selected.
Ii. The significance of specifying the speed of loading:
According to the study of modern fracture mechanics, the stress-strain relation of the cement sand specimens in the constant strain rate loading is a curve. The relationship curve of normal cement sand in chaohu lake. It can be seen that the increase of strain is faster than the increase of stress for nonlinear relation. Because the hydration of cement is a process related to time, the relationship between different types of cement and different curing ages is different. At the same time, the relationship of the same specimen under different strain rate will change obviously. The strain rate of figure A is) if the strain rate becomes larger or smaller, the relationship curve will appear at the top or bottom of the existing curve and its ultimate stress (strength + will also be different. We determine the ultimate strength value of cement sand test in order to establish a comparative system of cement mechanical properties. This system is not only comparable to different varieties, grades and ages, but also can be comparable in different regions. So according to the cement mortar test piece! ! "The relationship is characterized by a comparable intensity value, must be in! And "select" a parameter, and fix its increase rate. If fixed strain increase rate of the currently used press will be difficult for us to do, and testing requirements are very high so that all countries in the world using relatively simple fixed stress increase rate to limit strength values. The latest specification of concrete strength test in China has also stipulated that the strength test should be carried out with the increase rate of fixed stress.