Development Of Repeated Impact Testing Machine And Dynamics Response Analysis Of The System

Repeated impact is the common operation condition in engineering. The failure mechanism of the parts under repeated impact is very little known to people at present. In the current status of lacking of special repeated impact fatigue testing machine, the DCP-2 type large energy repeated impact fatigue testing machine has been developed to simulate the working principle of repeated impact in different working condition. The main characteristic parameters of the machine: punch mass: 10kg, maximum impact velocity: 8m/s, the greatest impact energy: 320J; The testing machine can achieve the stepless adjustment of impact frequency 0-10Hz and impact distance 0-30mm. HB72 type intelligent counter is employed to record the impact times and control the auto-stop of the machine according to the set times;The data of repeated impact load is acquired by means of these instruments, such as LC0502 type piezoelectric quartz sensor, LC0601 type charge amplifier, TDS3000 series multi-function digital fluorescence oscilloscope and personal computer;A kind of special endoscope which can be cooperated with high-speed CCD has been designed for the specimens'on-line observing, imaging, graphics display and processing.In order to realize the specimens impacting with high frequency and velocity, a high frequency and large flow rate rotary reversal valve has been developed especially. The maximum reversing frequency of the valve is 10Hz and it can be much greater theoretically through adjusting the parameter of the speed governor of the motor. The greatest returning flow is up to 707 L/min. Because of valve port being processed on circumference surface, the flow rate demand can be met through increasing the opening area. The core rotates relative to the seat of the valve. Therefore, we can adjust the area of passage between the core and the seat to fulfill the testing machine's matching motion demand. The article also accomplishes the kinematical analysis of rotary reversal valve and gets corresponding characteristic curve. In addition, cam-cartridge combination valve, another kind of high frequency and large flow rate valve, is also designed in this paper. The impact process of the punch is analyzed. Using wave mechanics theory, the mathematical models are established and the influence of the parameters of the piston rod is discussed. The modal of frame structure is analyzed by using general FEA software, and its simulation results shows the front ten order natural frequency and front four order modal shapes. The results can be used to select suitable experimental frequency for avoiding the occurrence of resonance, and improve the design of the frame structure.The testing machine, using string and ring shaped specimens with different size and load-applying mechanism of hydraulic-spring system, controls the impact force value by changing the compressive deformation of the spring. The impact contact stress is between 30 to 800 MPa, which is within the scope of repeated impact parts in actual working condition. The test results shows that the machine operates stability, controls reliably, and is approximate to simulate the actual working condition of the parts under repeated impact load. The machine can accomplish the repeated impact experiments for materials or parts under repeated impact load, and provide experimental equipment for the study on failure mechanism of repeated impact, further more for the impact-resistant design of materials or parts, as well as provide experimental equipment and methods for the study on the system of repeated impact of different working condition, particularly for the liquid-solid coupling system under repeated impact load.