Several Vibration Roller Vibration Jumping Phenomenon and Solutions

Vibration jump 1: insufficient backup power

The fluctuation of working frequency and vibration pressure indicates that the system has not reached a stable state, the very low working frequency indicates that the system has not crossed the resonance area, the engine working at rated speed indicates that the engine power output is normal, and the overflow of the system indicates that the working roller of the system is beyond the design. The main reason for this problem is that the manufacturer pursues economy excessively, adopts small pump and motor, and the output power of vibration system is not enough to meet the compaction requirements.

The analysis is as follows: when the roller vibrates, the working frequency ω increases from 0 to the design value, and it needs to cross the resonance region where the first and second natural frequencies ω 1 and ω 2 are located. Generally, the starting time of the roller is about 3 seconds. If the back-up power of the vibration system is small, the starting speed is slow, and the time of staying in the resonance area is long. The greater the amplitude of the resonance point is, and the amplitude increases to a certain extent. If the full power operation of the vibration system is still not enough to support the vibration under this amplitude, the working frequency of the roller cannot cross the resonance area. Therefore, the vibration wheel is in the ultra-high amplitude and Vibration at very low frequency leads to vibration jump.

Solution: the manufacturer changes the system configuration and increases the backup power of the vibration system.

Vibration jump 2: unreasonable construction technology

If the working frequency is equal to the nameplate value (or the error is not more than 10%), it indicates that the system can reach a stable state, the roller itself is normal, the compaction condition is hard ground, and the vibration pressure is close to the overflow, indicating that the load is large. The main reason for this problem is that the construction technology is unreasonable and the large, small vibration or static pressure can not be switched in time.

The analysis is as follows: in the actual compaction process, with the increase of soil compactness, the stiffness of soil increases and the damping decreases, the second-order natural frequency of the system keeps close to the set working frequency, and the amplitude under the working frequency continuously deviates from the nominal amplitude, resulting in more and more ground reaction force, and the amplitude and ground reaction force continue to increase, resulting in the final vibration wheel jumping off the ground Now the vibration jumps. Therefore, the roller is generally set with two working modes of low-frequency high amplitude and high-frequency low amplitude. By switching the mode, the vibration amplitude under the nominal amplitude and working frequency of the vibration wheel is changed to reduce the ground reaction force. Therefore, the construction technology also puts forward the compaction requirements of "when the soil strength is enough to support the vibration compaction, first strong vibration and then weak vibration". If this requirement is not followed, high amplitude compaction is still adopted when the ground stiffness is very large, and all parts of the whole machine will vibrate violently.

Solution: adjust the compaction construction process, timely switch large, small vibration, static pressure.

Vibration jump 3: vibration frequency out of tolerance

When the compaction condition is hard ground and the vibration pressure is close to overflow, it means that the load is large and the working frequency is too high. The main reason for this problem may be that the vibration working frequency is not calibrated during maintenance or the user operates improperly.

The analysis is as follows: according to the two degree of freedom vibration mathematical model, if the soil can absorb the vibration energy infinitely and the working frequency exceeds the second-order natural frequency and continues to increase, the vibration amplitude of the upper car and the vibration wheel will become more and more constant, in which the vibration wheel amplitude tends to the nominal amplitude, and the system can still operate stably, but at this time the vibration acceleration amplitude of the vibration wheel will follow the working frequency The output energy of the vibration system will increase infinitely with the increase of the rate.

In the actual compaction process, on the premise of stable operation of the system, increasing the working frequency can increase the output power of the vibrating wheel, so as to make the soil quickly compact. At this time, continue to compact according to the normal construction process, which may lead to the vibration jump problem caused by the strong vibration compaction when the ground stiffness is very large as described in vibration jump 2.

Solution: correct the frequency to the factory condition (28hz).

Vibration jump 4: the damping system is damaged

Check that all items are normal, indicating that the system is relatively stable and can achieve continuous compaction. The abnormal vibration of the upper vehicle should be caused by the unreasonable rigidity of the vibration damper between the vibration wheel and the upper vehicle.

The analysis is as follows: after the shock absorber is aged or damaged, the rigidity of the damping system changes, and the damping effect can not meet the expected requirements. The vibration of the upper car is abnormal due to the poor damping effect.

Solution: regularly check and replace the failed damper.

If there is a problem with the new machine or the problem cannot be solved after replacing the shock absorber, it may be caused by the unreasonable design of the shock absorber system of the original vehicle. A typical example is that the shock absorber is just too large and the frame and the vibration wheel are nearly fixed. At this time, the first-order natural frequency may be raised to close to the vibration frequency. It can be seen that this problem only occurs when the design level is very low or the quality is completely out of control Life.

Solution: replace the damper with other rigidity.

Vibration jump 5: poor adaptability of roller or abnormal working conditions

Under some working conditions, it is abnormal; under some working conditions, it is normal; under some operating conditions, it is abnormal; under some operating conditions, it is normal Obviously, the problem is caused by the adaptability of roller itself or the changing external conditions, and may also be caused by the combination of the above factors.

Generally, there are some conventional requirements for roller compaction. For example, the compacted soil shall reach a certain strength, and vibration compaction cannot be carried out on rubber soil. The compaction process shall be determined in the test section, the engine speed shall be pulled to the rated speed, and the condition of the machine shall be checked regularly. If the adaptability of roller itself is poor or the compaction process can not meet these requirements, jumping may occur.

A typical example is that the roller is compacting the rubber soil, at this time, the soil becomes an elastic accumulator, and the compaction work cannot be applied to the deep soil, and the vibration compaction cannot be carried out, which results in the abnormal vibration of the roller.

Solution: first of all, it should be cut into many small pieces by convex block wheel to make it lose elasticity, and then it can be compacted by vibrating roller.

Another typical example is the vibration compaction when the engine is running at idle speed. At this time, the actual vibration frequency is reduced to 1 / 3 of the design vibration frequency, which is close to the natural frequency of the system, and the engine output power is insufficient. The system can not run stably, and will produce relatively violent vibration.

Solution: ensure that the engine works at the rated speed approximately.

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