Characteristics of pulsation fatigue testing machine and electro-hydraulic servo testing machine

Pulsation fatigue testing machine:

This type of testing machine uses a camshaft driven by a motor to drive a piston pump, which pumps hydraulic oil into the actuator cylinder to drive the piston to eject. The advantages are simple structure, low power consumption, loading frequency adjustment can be realized through the motor speed control. Such products belong to our country in the last century, the 1960s and 1970s products, limited to the technical development at that time, its shortcomings are obvious: due to manually adjusting the relief valve by observing the pointer pressure gauge to set the loading load, so it can not be accurately set fatigue loading of the upper and lower limits of the load, there is no force value feedback, completely open-loop control. The oil pump pumps out only a few hundred milliliters of oil each time (which is the most direct reason for the small power consumption of the pulsation fatigue testing machine), the piston stroke is very small, so the pulsation fatigue testing machine is basically used for construction engineering on the geotechnical, concrete, steel and other deformation of the specimen fatigue test is very small.And because the retraction of the pulsation head (unloading) is dependent on the spring tension on the pulsation head to pull back, and can not track the specimen's own rebound, it is very easy to cause the detachment of the actuator head from the surface of the specimen, so as to produce the phenomenon of the actuator head knocking the specimen. In the axle test, the deformation of the axle body is large (generally in the range of 10~15mm), requiring a high degree of loading simulation (otherwise, it will cause non-axle body's own factors generated by the specimen failure, losing the significance of the test). It can be seen that the pulsation fatigue testing machine due to its own operating principle of the limitations, it can be affirmed that this type of testing machine is not suitable for trailer axle performance test. Many domestic and foreign axle manufacturers almost no use of such equipment for axle testing, which also argues from another aspect of the above conclusion.

In the axle test, whether static or dynamic test, are required to have two balanced loading points on the specimen, the left and right loading point of the loading action and loading load must be the same, which is the fatal flaw of the pulsation fatigue testing machine in the axle test. A single pulsation fatigue testing machine does not have two points in the axle test loading capacity, such as to increase a loading point, must be in the oil circuit in parallel with a doer. But so increase the way to do the actuator, it is bound to half reduce the load and load stroke, completely unable to meet the needs of the axle test. Another way is to parallel the two sets of pulsation fatigue testing machine, synchronization, but the cost of doing so is to multiply the investment in equipment, and the synchronization of the two sets of equipment is very poor.Even if the loading action of the two machines can be synchronized, the loaded load will produce a large deviation, resulting in the left and right loading difference of the axle test, artificially causing non-normal failure of the axle specimen and unreliable test data. In the axle stiffness, strength test, two parallel pulsation fatigue testing machine is simply not possible by manual operation to complete the synchronization of loading (pulsation fatigue testing machine in the static test is completed by manual operation of the inlet and outlet valves). Pulsation fatigue testing machine manufacturers of 1000kN pulsation fatigue testing machine is connected in parallel with two 500kN pulsation fatigue testing machine, in the actual application of the fact that almost none of the successful cases that confirms the above inference.

Electro-hydraulic servo fatigue testing machine:

Electro-hydraulic servo system has many advantages, the most prominent of which is the fast response speed, high output power, high control accuracy, and thus has been widely used in the fields of aviation, aerospace, military, metallurgy, transportation, engineering machinery and so on. Electro-hydraulic servo technology is the best technical means to realize dynamic high-cycle fatigue, program-controlled fatigue and low-cycle fatigue, as well as static constant deformation rate, constant load rate, and a variety of analog simulation test system.

The use of electro-hydraulic servo valves to control the fatigue testing machine, can realize precise, continuous pressure control, not only can instantaneous output of the tip of the pulse, but also by the computer control of its output triangle wave, square wave or sine wave, so that the fatigue testing machine function can be greatly strengthened. Not only can do dynamic fatigue test, but also can do the static performance test of the specimen. Moreover, due to the use of electro-hydraulic servo valves for load control in the dynamic fatigue test, the output of the minimum and maximum test load can be accurately controlled, so that there will be no fatigue life measurement errors due to inaccurate load output.

With the current state of technological development, the only disadvantage of electro-hydraulic servo testing machine is that the price is relatively high, some users can hardly afford.