0 Preface The wheel is one of the worst working conditions in the load-bearing components of railway rolling stock. The fatigue failure of the wheel has catastrophic consequences. Therefore, the evaluation of the fatigue strength is very important. According to UIC510- 5 [1] standard, for axisymmetric wheels, using uniaxial fatigue criteria for evaluation; for non-axisymmetric wheels with perforated plates, multiaxial fatigue criteria (such as Crossland and Dang Van multiaxial fatigue criteria) are recommended for webs. The hole area is evaluated. At present, many scholars at home and abroad have discussed the methods for assessing the fatigue strength of wheels. In [2], the uniaxial fatigue criterion and the Dang Van multi-axis high-cycle fatigue criterion were used to analyze the wheel of a moving car, and the safety factors of the key points of the wheel under two evaluation criteria were compared. The literature [3] used the Crossland criterion to evaluate the plate holes. The literature [4] uses the Sines criterion and the von_Mises criterion to calculate the wheel. The wheels analyzed in this paper use wheel brakes. The installation of the brake discs affects the wheel web area, the web and hub transition area, and the stress state of the web and rim transition area. The bolt preload of the brake disc is installed. Stress state of the bolt hole area of ​​the wheel web Health impact. The author will use the uniaxial fatigue criterion, the Crossland criterion and the Dang Van criterion to evaluate the wheel web area and study the effect of wheel mounting and bolt preload on the fatigue strength of the wheel web. 1 Uniaxial fatigue criteria in the UIC510-5 standard The average stress σm and the stress amplitude σa of each node satisfy the following relationship: The wheel manufacturing material is ER8, and the yield limit of the web area is 355 MPa. According to the UIC510-5 standard, the stress amplitude of the wheel web area is less than 180 MPa. The Haigh-Goodman curve is used for evaluation with a safety factor μ of: 2 Crossland and Dang Van multi-axis fatigue criteria The Crossland criterion [5-7] is a correction to the Sines criterion. The effect of hydrostatic stress on fatigue is expressed in the form of its maximum value in the Crossland criterion. The equivalent stress amplitude σeqc is: According to Dang Van [5], most of the metal crystals are easy to change with the microscopic fluctuation of the load. The reflection of the external load of the grain is a kind of elastic adjustment. The fatigue criterion based on the mesoscale is proposed for the first time. The Dang Van criterion [2,8] considers the characteristics of the plane of the maximum shear stress amplitude in the cycle. The hydrostatic stress σH and the shear stress amplitude τa are based on the Lin-Taylor homogenization assumption and the elastic Shakedown principle on the mesoscale. Linearly combined, the equivalent stress amplitude σeqd is: 3 finite element model and load conditions The high-speed EMU power wheel pair wheels analyzed in this paper are the whole X-ray steel wheels. The wheels are straight-spoke plate structures. The straight-radial plates and the hub and rim area are transitioned through a circular arc. There are 6 positioning pin mounting holes on the wheel web. And 12 bolt holes, the wheel wear limit finite element model is shown in Figure 1, where Figure 1a shows the brake disc model, the brake disc is in contact with the wheel web, and the brake discs on both sides of the web pass through 12 Bolt and 6 locating pins Mounted on the wheel, Figure 1b shows the finite element model without the brake disc wheel. The entire wheel can be seen as consisting of 12 structures shown in Figure 2, where A, B, C, and D represent the cross-section through the center of the wheel. The preload force FP of the bolt is: FP = TP /( KPd) ( 10) Where: TP is the bolt tightening torque; KP is the torque coefficient; d is the nominal diameter of the bolt. The bolt tightening torque is TP = 100N·m, the torque coefficient is 0.11 to 0.15 as specified in GB /T 1231 [9], and the nominal diameter of the bolt is 14 mm. Therefore, the bolt pre-tightening force FP = 47.62 to 64.94 kN. According to the UIC510-5 standard, the following six load cases are selected: 1) Straight running condition: Load vertical load P1, interference is Δ, and the maximum running speed is running. 2) Curve running condition: Load vertical load P2, lateral load H2, interference amount is Δ, and run at the highest running speed. 3) Turnout pass condition: Load vertical load P3, lateral load H3, interference amount Δ, maximum running speed. 4) Linear braking condition: Load vertical load P1, the interference is Δ, the highest running speed, the wheel reaches the highest temperature during braking. 5) Curve braking condition: Load vertical load P2, transverse load H2, interference amount is Δ, run at the highest running speed, and the wheel reaches the highest temperature during braking. 6) Turnout brake condition: Load vertical load P3, lateral load H3 The interference is Δ, the maximum running speed is running, and the wheel reaches the highest temperature during braking. 6 loaders In the case, the interference is 0.297mm. The wheel rolls along the track. Considering the non-axis symmetry of the wheel structure, multiple calculated sections (sections A, B, C, and D) are selected for loading on the wheel. Taking section A as an example, the rail acts on the wheel. The direction and position are shown in Figure 3. 4 Temperature field analysis The maximum running speed of the train is vmax = 380km/h. The common braking method first uses electric braking. When the train speed is reduced to a certain value (usually 5 to 15km/h), it is switched to air brake. Insufficient power, insufficient braking force is supplemented by air brakes. Assume that the electric braking force is insufficient, and when the train speed is greater than 15km/h, the electric braking force is 70% of its maximum braking force, and the air brake provides its maximum braking force. 30%; When the train speed is less than 15km/h, only air brake is used, and the braking force is the maximum air braking force. The temperature distribution at the highest temperature of the brake disc is shown in Figure 4. The maximum temperature of the brake disc during braking is 278. At 1 ° C, the corresponding braking time is 68 s; the temperature on the friction surface is higher, the highest temperature is generated inside the friction surface away from the bolt hole, and the temperature on the side where the brake disc is in contact with the wheel web is lower. The temperature distribution at the highest temperature of the wheel is shown in Figure 5. The maximum temperature of the wheel web is 93.9 °C, which occurs at the end of braking. The area where the web is in contact with the brake disc is at a higher temperature, the highest temperature is at the edge of the web, and the other areas of the web are cooler. 5 Fatigue strength of the web area The wheel material is ER8, and its symmetrical bending fatigue limit W-1 = 245 MPa [2]. For steel materials, the ratio of the symmetrical torsional fatigue limit N-1 to the symmetrical bending fatigue limit W-1 is between 0.48 and 0.75. Taking the average value, that is, N - 1 /W - 1 = 0.615, then N - 1 = 150.675 MPa. According to the recommendations of the UIC510-5 standard, the cross-section of the wheel web is evaluated using the Crossland and Dang Van multi-axis fatigue criteria, and the non-porous area is evaluated using the uniaxial fatigue criterion. The finite element models with and without brake discs were used for analysis. The bolt preload force in the model with brake disc was taken as 47. 62kN and 64. 94kN, the minimum safety factor for the non-porous area of ​​the web and the area of ​​the web hole are shown in Tables 1 and 2. Taking the section D in Figure 2 as an example, the safety factors of the inner and outer nodes of the wheel web are shown in Figures 6 and 7. From the analysis results of Table 1, Table 2 and Figure 6, Figure 7, it can be seen that the installation of the brake disc and the increase of the bolt pre-tightening force increase the safety factor of the transition zone between the straight web and the hub (see Table 1). But the bolt preload is increasing Large (from 47.62kN to 64.94kN) The effect of increasing the safety factor of this area is much less than the effect of increasing the brake disc. After the brake disc is installed, the transition between the straight web and the rim on the inner side of the web (the radial position is The safety factor of 375mm or so is reduced (see Figure 6, the dashed line value is less than the solid line value); the safety factor of the transition between the straight web and the rim of the outer surface of the web (the radial position is about 375mm) increases (see Figure 7). The dashed line value is greater than the solid line value). Overall, the installation of the brake disc increases the minimum safety factor of the transition zone between the web and the rim. The pre-tightening force of the brake disc mounting bolts is safe for the transition between the web and the hub and the web and the rim The coefficient has a small effect, which is consistent with the Saint-Venant principle. For the spoke hole area (see Table 2), the safety factor is increased after the brake disc is installed, and the bolt pre-tightening force is increased to make the safety factor of this area increase less. Use Dang The safety factor assessed by the Van criterion is less than the safety factor assessed using the Crossland criteria. The fatigue strength of the wheel web area is satisfactory (the minimum safety factor is greater than 1). Figure 7 Section D Spoke outside node safety factor 6 Conclusion In this paper, the finite element model of wheel strength calculation without brake disc and brake disc is established respectively. The influence of the installation of the brake disc and the preload force of the bolt on the fatigue strength of the wheel web area is studied. according to GB / T 1231, the pre-tightening force of the bolts in the finite element model with brake disc is taken as 47. 62kN and 64. 94kN, the non-porous area of ​​the wheel web was evaluated using the uniaxial fatigue criterion, and the area of ​​the web was evaluated by the Crossland and Dang Van multiaxial fatigue criteria. The results are as follows. 1) The installation of the brake disc increases the minimum safety factor of the web hole area, the web-to-hub transition area, and the web-to-rim transition area. In order to reduce the finite element calculation scale and calculation time, for safety reasons, the fatigue strength of the wheel brake wheel can be evaluated using the brakeless disk finite element model. 2) The pre-tightening force of the brake disc mounting bolt is 47. 62kN increased to 64. 94kN, all areas of the wheel web The safety factor changes little. 3) For the fatigue strength assessment of the spoke hole area, the Dang Van criterion is used to estimate a lower safety factor than the Crossland criterion, and it is safer to use the Dang Van criterion for evaluation. references: [1] International Union of Railways. UIC510-5 Technical approval of monobloc wheels[S]. Paris: International Union of Railways, 2007. [2] Liu Xu, Zhang Kailin, Yao Yuan, et al. Analysis of wheel fatigue strength under two evaluation criteria [J]. Electric Drive for Locomotives, 2012( 4) : 23 - 25. [3] Wang Jun, Li Yonghua, Zhang Yonghui. Fatigue strength analysis of HXD3B high-power locomotive wheels [J]. Science and Technology Innovation Herald, 2011(10) : 113 - 115. [4] Tang Daowu. Research on safety assessment of train wheel fatigue strength [J]. Electric Drive for Locomotives, 2008( 5) : 31 - 33. [5] Zhu Zhengyu, He Guoqiu, Chen Chengyu, et al. Research progress on multi-axis non-proportional loading high cycle fatigue [J]. Journal of Tongji University, 2006, 34( 9) : 1221 - 1225. [6] PAPADOPOULOS IV, DAVOLI P, GORLA C, et al. A Comparative Study of Multiaxial High-cycle Fatigue Criteria for Metals [J]. International Journal of Fatigue, 1997, 19 (3) : 219 - 235. [7] Crossland B. Effect of Large Hydrostatic Pressure on the Torsional Fatigue Strength of an Alloy Steel. Proceedings of the International Conference on Fatigue of Metals [C]. London: Institution of Mechanical Engineers, 1956: 138 - 149. [8] CHARKALUK E. Revisiting the Dang Van Criterion [J]. Pricedia Engineering, 2009( 1) : 143 - 149. [9] General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, China National Standardization Administration Committee. GB/T 1231 High-strength large hex head bolts, large hex nuts and washers for steel structures [S]. Beijing: China Standard Press, 2006. [10] KAKUNO H, KAWADA Y. A New Criterion of Fatigue Strength of a Round Bar Subjected to Combined Static and Repeated Bending and Torsion [J]. Fatigue Fract Engng Mater Struet, 1979( 2) . Sun-Shade Net,Shade Nets for Garden,Sun Shade Cover Netting Oushijia Hardware Wire Mesh Products Co., Ltd. , http://www.wiremesh-hb.com
