Fengde Mechanical & Electrical Manufacturing Co., Ltd. , http://www.dieselgeneratores.com
1. Establishing the vibration model From the perspective of dynamics, the vibratory roller is a vibration system. According to the structural characteristics and working characteristics of the roller, it belongs to two-stage vibration reduction: the first vibration reduction between the vibration wheel and the frame, and the second vibration reduction between the frame and the cab. Since the stiffness and mass of the vibrating wheel and the upper frame are much larger than the stiffness and mass of the damping block, the vibrating wheel and the upper frame can be simplified into a concentrated mass, and the damping block is simplified as an ideal elastic element without mass; Level damping, because the quality of the cab is much smaller than the mass of the upper frame, the vibration of the cab has less impact on the vibration of the upper frame, simplifying the cab and damping block to a concentrated mass and spring unit. In Pro/MECHANICA, a five-degree-of-freedom vibration model of "Roller-Soil" is established, as shown in Figure 1. In fact, this is just the vibration model of the roller in the vertical direction. In fact, because the exciting force of the roller is a circular motion, this exciting force can theoretically be decomposed into the simple harmonic force in both the vertical and horizontal directions, which will not only produce Vertical vibration also produces horizontal vibration. For the horizontal vibration, for the first-order vibration, the vibration model is the same as the vertical vibration, and the vibration of the two vibrations is equal, but the phase difference is 90°. Here, for the vibration amount of the vibrating wheel and the upper frame, only vertical vibration must be considered. For the exciting force of 70KN/45Hz, since the amount of vibration caused by it is small, only the amplitude of the vibration wheel caused by it is calculated, and the others are not calculated.
The picture shows the vibration model to simplify and assume the relevant parameters and conditions of the model as follows: 1) In the model, the soil is assumed to be an elastic body with a certain stiffness, the stiffness is K1, the damping is C1; 2) the vibrating wheel of the vibratory roller, The quality of the frame and cab is reduced to a concentrated mass; 3) any one of the vibratory rollers working in the vibratory roller remains in contact with the ground.
In this model, the meanings of the parameters are as follows: F0—excitation force; K1, C1—soil stiffness and damping, or the stiffness and damping of the tire during the test; K2, C2—the damping block between the frame and the vibrating wheel Stiffness and damping; K3, C3—Stiffness and damping of the damping block between the frame and the cab.
The stiffness of the stiffness is measured here. The value is generally determined by the experiment. The stiffness coefficient of this paper is 1.5 (about 1.5 times the static stiffness); m1—vibration wheel mass; m2—front frame quality; m3—rear frame quality ;m4—cab quality; X1—vertical displacement of front vibrating wheel; X2—vertical displacement of rear vibrating wheel; X3—vertical displacement of front frame; X4—vertical displacement of rear frame; X5—vertical displacement of cab.
In this model, the values ​​of each parameter (data from the machine design calculation book): F0=110×sin(2π×37×t)/70×sin(2π×45×t); the test takes the tire stiffness K1=1500N /mm, compacted asphalt takes K1=18300N/mm; K2=2440×1.5=3600N/mm, K3=1920×1.2=2400N/mm (moving stiffness); C1=30N.S/mm; C2=C3= 5N.S/mm (obtained after consulting relevant data); m1=2250kg; m2=3500kg; m3=3950kg; m4=550kg.
2. Calculation of the vibration amount of the vibrating wheel and the upper frame Through the motion analysis of the model, the vibration amount of the vibrating wheel and the upper frame is calculated and compared with the inspection report of the road roller. It can be seen from Table 1 that the calculated value and the test value are relatively close, but the calculated values ​​of the parameters such as velocity and acceleration after vibration reduction of the vibration system are smaller than the test value. One reason is that the value of the dynamic stiffness coefficient is too large. In fact, the dynamic stiffness coefficient may be greater than 1.5, and the specific value is determined experimentally. Generally, the larger the dynamic stiffness coefficient is, the worse the vibration damping effect is. At the same time, considering the vibration wheel walking and the number of vibration damping blocks on both sides of the vibration wheel, the actual vibration quantity values ​​of the upper frame are greatly different.
Table 1 Calculation and test results of vibration model of vibratory roller Vibrational force 110KN/37Hz Calculation result K1=1500N/mm Calculation result K1=18300N/mm Test result Design value Vibration wheel amplitude mm0.941.090.850.8 Upper frame amplitude mm0.0250.03 ——(上架架)k=49.2Af[1]4.55.57.4—the vibration intensity of the upper frame Vrmsmm/S front 33.84.95—after 3.33.74.74—the acceleration of the upper frame m/S20.80.881.15 exciting force 70KN/45Hz vibration wheel amplitude mm0.390.430.380.35 Note: k-person withstand mechanical vibration load rate, A-amplitude mm, f-frequency Hz In the vibration model, the calculated and tested values ​​of the vibration wheel amplitude are larger than the design value. Under the same exciting force, the amplitude of the vibrating wheel is the largest when compacting the asphalt pavement, that is, the roller is compacted with the soil during the working process, and the amplitude is increased from 0.94 mm to 1.09 mm, which is larger than the design value. 17.5% and 36.3%; the other vibrations have the same trend and amplitude. In addition, the calculation and test results show that the vibration crack and amplitude of the upper frame are reduced after the first stage of vibration reduction of the roller, and the amplitude of the upper frame is 2.7% of the amplitude of the vibration wheel. The first-order damping effect is obvious. According to the relevant information, from the consideration of the mechanical vibration load rate - k value, the upper frame k value is 4-8, between 3 and 10. If only one level of vibration reduction is considered, then people tend to feel uncomfortable and have an impact on the work; in order not to affect the work, it is necessary to increase the first stage of vibration reduction, that is, increase the vibration reduction block under the cab.
3. Conclusions and improvement measures When the excitation force is 110KN/37Hz, the amplitude of the vibration wheel is too large, which is about 17.5~36.3% larger than the design value; due to the vibration wheel amplitude and the quality of the vibration wheel, the stiffness of the vibration damping block K2, The vibration force is related to the frequency. Therefore, reducing the mass of the vibrating wheel, the stiffness of the damping block K2, and the magnitude of the exciting force can effectively reduce the amplitude of the vibrating wheel.
Vibration System Analysis of YZC12 Vibratory Roller
Key words: motion simulation vibration model vibration quantity improvement measure YZC12 type vibration roller is a double frequency, double amplitude, double drum vibratory roller. In the process of use, there is poor damping effect of the cab, the driver is prone to fatigue, and under pressure. In the case of solid asphalt pavement, the compaction power is too large according to the designed performance parameters, and there are problems such as over-compaction and waste of raw materials. In order to solve the above problems, this paper applies the US PTC Pro/MECHANICA software to analyze its vibration system and proposes improvement measures.