Wang Hui, Lu Ping, Wu Yunyu, Du Hongguang
, Jinan 250061)
Abstract: In order to quantify the life of a ring die, the failure modes, failure mechanisms and the structural factors affecting the die life of the ring die are analyzed. Based on the fatigue life test data of the material, the SN curve of ring die fatigue failure is established by Weibull formula, The fatigue life of the ring die is studied. Finally, the fatigue life of the ring die is quantified by finite element software COS-MOS. The rain flow counting method is used to calculate the ring die under different structural parameters. The results show that the ring die Fatigue life data, and to determine the die hole diameter of 10mm, the die holes are alternately arranged and the die hole number of 720 ring die for the ideal ring mode.
0 Preface
At present, although the research on the life cycle of the ring mold of biomass solid particle molding machine is mostly in the experimental stage, the analysis of the life cycle of the biomass ring mold has not been quantified.This paper will analyze the failure mode, failure mechanism and The structural factors that affect the life of ring die and the S-N curve of ring die fatigue failure are established to study the fatigue life of the ring die.Finally, with COSMOSWorks finite element software, the rain flow count method is used to numerically evaluate the ring die under different structural parameters Calculated to obtain ring die fatigue life.
1 ring mode failure characteristics
1.1 failure form
Forming machine ring mold porous ring parts, poor working conditions, the use of long-term pressure roller to withstand the cycle of extrusion and material friction, resulting in periodic bending stress and contact compressive stress, the main failure form of fatigue failure. Ring mode failure in the actual use of coincidence.
1.2 Failure mechanism
In this paper, we will analyze the failure of the forming machine from the structural features of the ring die - the failure mechanism of plastic deformation, contact fatigue and abrasive wear.
1) ring die hole plastic deformation [1]The low mechanical strength of the porous ring die and the excessively large tension force during the adjustment of the pressure roller lead to partial microcracks in the ring die and eventually lead to fatigue failure.
2) Contact fatigue: When the ring die is working, it rotates at a low speed, and at the same time, it undergoes large alternating contact compressive stress. After a period of time, fatigue cracks will occur in the ring die, which eventually leads to fatigue failure of the ring die.
3) Abrasion failure: First, the pressure roller is too tight and the gap with the ring mold is small, friction with each other; second, the angle of the screwdriver is not appropriate, leading to partial wear of the ring mold due to the uneven distribution of materials and fatigue cracks And failure.
The above analysis shows that the ultimate failure mode of the ring die is fatigue failure, therefore, this study mainly studies the service life of the ring die by analyzing the fatigue life of the ring die.
1.3 affect the ring die fatigue failure structural parameters
Ring-shaped structure of the main parameters for the mold hole diameter, aspect ratio, die hole arrangement and the number of holes.
2 ring mode failure mathematical model
Based on the study of the fatigue properties of 42CrMo steel by Wang Weiqiang and Chen Juhua, combined with the fatigue characteristics of the above-mentioned metal materials, the S-N curve of 42CrMo steel is finally established [4-6], As shown in Fig. 2. It can be seen from Fig. 2 that the fatigue life curve 2 (a) obtained from the experiments basically matches the shape of the theoretical fatigue life curve 2 (b) of the universal metal material and belongs to the correct fatigue curve , Which is in line with the research needs.The curve is the important data and theoretical basis for analyzing fatigue life of ring die in this study.
Numerical Simulation of Ring Die Fatigue Life
In this research, the fatigue life of ring die will be simulated by using SolidWorks 3D modeling and COSMOSWorks finite element software.Firstly, a parametric model of biomass ring die is established by SolidWorks.Secondly, the fatigue of ring die is simulated by COSMOSWorks finite element software Finally, using the related theory of elastic-plastic mechanics and the mechanism of fatigue damage, the fatigue life of different ring holes, the arrangement of different ring holes and the fatigue life of different ring holes are analyzed and simulated. Quantitative.
3.1 ring die fatigue geometric model of the establishment
Representation cloud [2]The study of the ring mold properties of biomass particles found that when the aspect ratio of the ring die hole is 5: 1, the stress on the ring die is the minimum, so I only ring die in the aspect ratio of 5: 1 Die hole shape, die hole diameter (d), arrangement of fatigue life under the conditions of research.
The material used in this study was 42CrMo, and the parameters of the base material were as follows[7]:
3.2 ring die structure static analysis
3.2.1 Constraints, loads and boundary conditions
According to the actual working condition of ring die, load, constraint and boundary conditions are applied to the simulated ring die.On the two sides of the ring die, fixed constraints are imposed on both sides of the circumferential die, Z and so on all three directions of freedom of movement and all rotational degrees of freedom for fixed positioning; applied to the inner wall of the die hole average pressure perpendicular to the inner surface to simulate the circumferential pressure of biomass material on the ring die hole; the same time, Friction force is applied to the inner surface of the die hole in the axial direction of the die hole to simulate the friction force '3' of the biomass raw material to the inner wall of the die hole as shown in FIG. 4.
3.2.2 static analysis results
The results of Mises stress analysis and die hole displacement field analysis of die hole are shown in Fig. 5 and Fig. 6, respectively.
3.3 ring die life analysis
3.3.1 life parameter settings
Based on the structural static analysis of the ring die, the fatigue life of the ring die can be analyzed.
When using COSMOSWorks software to analyze the fatigue life of the ring die, the parameters of the software need to meet the needs of the static analysis of the structure, and the fatigue parameter parameters need to be set according to the above study of the die fatigue theory.Firstly, Of the SN curve, and set the strength reduction factor for the S-N curve caused by the ring mode structure. The fatigue cumulative damage theory is set as the Palmgren-Miner linear cumulative damage theory (Miner theory), and the calculation method of the software calculator Set to rain flow cycle counting method.
3.3.2 life simulation results analysis
To measure the service life of the ring die, it is necessary to take into account the fatigue life of the ring die, but also take into account the production of ring die. The number of ring die has a greater impact on the ring die production, under the same life conditions, The higher the number of rings, the higher the yield.The analysis of life-span simulation results will focus on these two factors.When the temperature is 120 ℃, the die life data are shown in Tab.1.
From the data analyzed in Table 1, it can be seen that under the condition of aperture 10mm, aspect ratio 5: 1 and temperature 120 ℃:
1) The ring die with the same arrangement of die holes, the fatigue life decreases with the increase in the number of die holes, because as the number of die holes increases, the mechanical strength of ring die decreases.
2) When the number of the die holes is equal, the die life of the die holes arranged alternately is much longer than that of the die die arranged in parallel with the die holes. For example, the die life of an alternating 800 die holes is 2.15 × 107Times, the die life of the parallel 864 die holes is 5.46 × 106Times.Compared with the two, the life of alternate hole ring die is 4 times of the life of parallel hole ring die, while the ratio of die holes is about 1: 1. This is because the ring die holes alternate to make the ring die force more uniform, Enhanced mechanical strength.
120 ℃ ring die life curve shown in Figure 8. Can be seen from Figure 8, under the same life conditions, the die hole diameter of 10mm alternately arranged ring die life than the die hole diameter 15mm ring die yield large In the case of the same arrangement of the die hole, die hole number is small, the ring die life is higher.
In engineering, the fatigue life of mechanical parts is generally considered as N = 106~ 107The fatigue life of the parts is considered as infinitely long.According to the production of ring-shaped particle machine, according to the data of the ring die life analysis and the correlation curve, the die holes are alternately arranged with a hole diameter of 10 mm, The total number of holes for the 720 ring mode selected as the benchmark.
4 Conclusion
1) The paper concluded that the main failure mode of the biomass particle machine ring die is fatigue failure, and the failure mechanism of the ring die is analyzed.
2) The S-N curve of ring die is established, which provides important data and theoretical basis for the analysis of ring die fatigue life.
3) By means of COSMOS finite element software, the fatigue life of the ring die is quantified, and the fatigue life data of the ring die under different structural parameters are obtained. It is found that the die hole diameter is 10 mm, the die holes are alternately arranged, Ideal ring mode.
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