1 Overview According to the requirements of “introducing advanced technology, joint design and production, and building Chinese brandsâ€, CSR and CNR successfully introduced EMU technology with speeds of 200km/h and 300km/h from France, Japan, Canada, Germany and the United States. High-power electric power, diesel locomotive technology. A group of domestically produced EMUs and high-powered locomotives with world-class levels have been put into use. China's locomotive and rolling stock manufacturing industry has entered a period of technological upgrading, and the key production processes and equipment levels have been greatly improved, narrowing the gap with railway locomotive and rolling stock equipment in developed countries, and gradually establishing its own technology research and development system and production system. Most OEMs have gradually standardized the use of fasteners by learning from foreign experience. At the same time, it has promoted the transformation of fastener application technology and design ideas of various OEMs, standardized the installation method of fasteners, and improved the reliability of fastener application. Many fastener manufacturers have invested a lot of manpower and material resources, researched and developed various new types of locknuts, and some have contributed to the speed-up lines and facilities renovation of China's railways, and some have applied for patents. In addition, the national standards for fasteners have been comprehensively revised several times, and many standards have adopted ISO standard drafts: 2010-11-03: Chen Weijin, engineer 1 standard. However, it is undeniable that the design and use level of fasteners in China is still not high, and there is a deviation from the development trend of ISO fastener standardization. The design and selection of fasteners in China, especially the fasteners for rolling stock, still have a big gap compared with advanced industrial countries such as Germany. There are some problems in the application of fasteners, which need to be solved in the improvement of the standard system. strengthen. ISO fastener standards are almost identical to the German Standards Association DiN standard, and the European Community Standard EN also uses DIN fastener standards. The advancement and rationality of the DIN standard are basically reflected in the ISO fastener standard. The design guidelines for m.DIN 25201 railway vehicles and their components are bolted. As a professional guideline for the design and application of fasteners for railway vehicles, detailed The effectiveness of system theory and applied technology has been proved by many years of practical application and has a good reference. The design calculation of the fasteners referred to in DIN 25201 refers to Part 1 of the Design Guide for the calculation method of the VDI 2230 high-strength bolting system of the German Society of Engineers VdI, which has been widely used for more than 30 years. 2 Classification of bolted failures 25201 defines the possible hazards of bolting failure as three risk levels: high, medium and low. The different levels of risk, the requirements for the size of the bolted connections, the installation and documentation, and the tools used for installation are also different. (1 high risk level: when the bolt connection fails, it may cause direct or indirect physical and life hazard or vehicle operation danger. In the risk level: When the bolt connection fails, it causes a functional failure of the railway vehicle. (3 low risk level: when the bolt connection fails, it will cause passengers or staff to feel uncomfortable at most. In order to improve the quality of bolting of existing bogies and ensure the quality of bolted joints, some of the mainframes of CSR and CNR have gradually begun to try to formulate bolt connection specifications, performance grades, loading parts, etc. according to DIN 25201. The contents of the bogie bolt connection importance rating statistics table. For example, a main engine factory defines the connection between the gear box and the motor and the suspension seat in a bogie of a certain type of vehicle. The hex bolt M24X110 with a performance level of 8.8 is defined as a high risk level, and the performance level of the gear box is 8.8. The hexagon socket screw M20X40 is defined as the risk level, and Table 1 is an example of the bolt risk rating classification section. Table 1 Bolt risk rating grading part example serial number name specification performance level risk level installation part hex bolt M24X110 high gear box and motor, hanging hex bolt M30X110 high motor and hollow shaft hex bolt M24x45 high gear box hanging seat and motor hex Bolt M20X70 gearbox and gearbox hanger hex nut M20 gearbox and gearbox hanger hex bolt M20X45 gearbox sling and motor hex screw M20X40 gearbox hex bolt M10X16 connecting pin and connecting rod but At present, the idea and principle of judging the bolt risk level of each main engine factory are not unified, and the risk level defined by the bolts used in the same part is not. For example, for the bolts used for safe suspension of the gearbox in the bogie composition, different OEMs define different risk levels, which are defined as high risk levels and are also defined as risk levels. Due to the different levels of risk, the subsequent measures and means including design requirements, anti-loose requirements and installation methods and requirements are very different. Therefore, each OEM should combine the RAMS reliability work with the reliability of the RAMS, and the team consists of interdisciplinary and professional personnel to fully demonstrate the risks that may be caused by bolt failures in various parts, but not by individuals. The risk rating of the bolt is graded. Once the bolt risk rating is determined, a list of bolt risk levels should be issued at the company. In the case of uncertain risk levels, it is advisable to adopt a high-risk level and adjust the risk level through reasonable changes in the case of accumulating certain practical experience. 3 bolt connection design At present, the most widely used bolt connection design in China is still the bolt calculation method introduced in the mechanical design textbook. The introduction of EMU, high-power electric power and diesel locomotive technology has enabled the design of bolt fasteners in Germany, the United States and Sakamoto to be applied in China. 2230, the purpose is to recommend its calculation method to solve the problem of determining the bolt connection parameters. The design, calculation and installation conditions of the bolt connection are basically the same as the main ideas and methods of the VDI2230. The theory of the calculation method of the bolt stiffness of the American mechanical engineering design textbook is inconsistent with the VDI2230. The basic theory introduced in China's general mechanical design textbooks is similar to VDI 2230. It is developed on the basis of the general single bolt strength calculation method, but it is very different from VDI2230 in theory and application. The following four aspects are highlighted in VDI2230, but they are not involved in the bolt design of mechanical design textbooks in China: 1 Considering the reduction of the pre-tightening force caused by the depression after the tightening of the joint surface, the bolt head and the nut bearing surface 2; according to the tightening tool used, the range of variation of the tightening force is specifically considered in the calculation; 3 the calculation method is used to determine the flexibility of the bolt and the connected part according to the material and size of the part; The force ratio is introduced to introduce a load introduction factor. 2230 developed bolt design calculation procedures, mainly for foreign software, such as KISSSOFT, MIT-CALC and MDESIGN and other software have bolt calculation modules. 2230 is gradually being applied in China's wind power and automotive fields. In addition, the national standards developed on the basis of international standards have also introduced the calculation method of VDI2230, such as GB/Z194142003 industrial closed gear transmission. 3.1 Comparison of calculation methods In general, the load applied by bolts can be divided into axial load, lateral load and torsional moment. The following main comparisons are made with the design of the bolts for transverse loads in the rigid coupling connection of VDI 2230 example B2. For the calculation method of 2230, the final bolt specification of example B2 is M16-10.9, and the torque is tightened with a torque wrench. The tightening torque is MA=302Nm. According to the calculation method in the mechanical design, if the safety factor S=4 is taken, the final selected bolt The specification is M30-10.9; if the safety factor S=3.5, the final bolt size is M24-10.9. The diameter calculated by the mechanical design method is larger than the diameter calculated by VDI2230, mainly due to the lack of necessary on-site actual conditions. Data or test data. According to the mechanical design method, the safety factor is relatively conservative, and the result calculated by the mechanical design method is low in relation to the fastening method used in the actual installation. Therefore, it is inevitable that the tightening torque is too large or too small, resulting in bolts. The problem of connection failure. 3.2 Comparison of tightening torque calculation 3.2.1VDI 2230 tightening torque calculation The tightening torque of VDI2230 is mainly calculated according to the following formula: In formula 1, MA is the tightening torque, Nm; Fm is the pre-tightening force, N; P is the pitch , mm; d2 is the thread diameter, mm; iG is the thread friction coefficient; /iK is the bearing surface friction coefficient; DKm is the effective diameter of the friction moment in the bolt head or nut bearing area, mm. in the formula Q, U is the yield strength The utilization factor is generally 0.9; Rp.2 is the yield strength, MPa; A is the minimum cross section of the bolt. 3.2.2 Calculation of the tightening torque in China's mechanical design The calculation formula of the tightening torque in China's mechanical design and GB/T16823. 21997 thread fasteners are consistent, but the symbols are somewhat different. The calculation formula of tightening torque in GB/T16823.21997 is in formula 3, Tf is the tightening torque, N'm; K is the torque coefficient; Ft is the pre-tightening force, N; d is the nominal diameter of the thread, mm. Pre-tightening force Ft-like design selects 60%~80% of the bolt yield strength, and the safety factor is above 1.2. The torque factor K is related to the surface treatment, strength, geometrical tolerance, thread accuracy of the fastener, roughness and stiffness of the bearing surface of the fastened part. Among them, surface treatment is the key factor. In general, the surface torque is 0.13~0.18 when the surface is phosphating, and the torque coefficient is 0.26~0.3 when the surface is blackened. For the coarse steel bolts of M10~M68, when When the thread is not lubricated, the torque coefficient can be taken as 0.2. The torque coefficient recommended by the United States, Germany and Germany is 0.12~0.2. 3.2.32 kinds of tightening torque calculation comparison table 2 is the thread friction coefficient and the bearing surface friction coefficient are 0.10 The VDI2230 and the calculation method in China's mechanical design are used to calculate the comparison table of the tightening torque. Table 2 Comparison of two kinds of tightening torque calculation specifications performance level tightening torque / (Nm can be seen from Table 2, the comparison of the tightening torque calculated by GB/T16823.21997 compared with the result calculated by VDI2230 3.3 bolt connection strength verification 3.3.1 VDI2230 bolting strength verification method There are mainly six methods for checking the bolt joint strength in 2230. (1 The actual calculated pre-tightening force FMmax should not be greater than the maximum assembly pre-tightening force allowed by the bolt material. F. (2 Checking the working stress dB should satisfy SF=RpffiMlB>1.0, Sf is the safety factor to prevent exceeding the yield point. R is the stress when the non-proportional elongation is 0.2%, MPa; the torsional stress Kmx should satisfy SeRpcV1.0. SD=i1.0, Sd is the safety factor to prevent fatigue failure; as is the stress cross-sectional area Limit stress amplitude, MPa; indicates the heart or b. (4 check the surface pressure Pm and PBmx in the assembled state and working state, should satisfy the SpS", Sp is the safety factor to prevent surface crushing; PG is the ultimate surface pressure, N; P table FI Allowable shear stress of the tooth, MPa; skillfully the yield limit of the bolt material, MPa; ST is the safety factor. For cast iron, press p= b to determine. Among them, is the extrusion strength of the bolt rod and the hole wall, MPa; skill is the yield limit of the bolt material, MPa; p is the safety factor; is the tensile strength limit of the bolt material, MPa. 3.4VDI2230 application range limitation 2230 is mainly It is suitable for system calculation of a single common bolt connection, and the VDI 2230 part 2 calculated for the multi-bolt connection system has not been released. For the multi-bolt connection structure, in principle, it can be converted into several single-bolt connections for design and calculation. This concept has been embodied in foreign commercial software. 2230 is only suitable for the design and calculation of steel high-strength bolted joints. The angle of the teeth is 8.8~12.9. 2230 has strict limits on the size of the contact surface. If the limit value is exceeded, the method is no longer applicable; again, the standard does not apply to the strength calculation of the reaming bolt. The 2230 is subject to many limitations of the actual application conditions. For example, if the coefficient of friction of the thread and the friction coefficient of the bearing surface are not properly selected, a large calculation error will result. Therefore, for important bolting, an experimental or finite element analysis method is required to verify the calculation results. The loosening of the bolted bolts of the four bolts mainly includes creep, looseness caused by the indentation, and looseness caused by the relative movement of the contact faces. Variable loads, vibrations and shocks are the main causes of loose bolts. 4.1 Bolting method of bolting method In the bolting connection with high tightening force, the number of joint faces is small, and the ratio L5 of the tightening length Lk to the nominal diameter d of the bolt can be sufficiently strong and no other measures are required. If the anti-loosening gasket is added, the amount of the indentation is increased due to the increase in the number of joint faces, which can only play an adverse role. An additional anti-loose device is only used if a positive preload is not available due to work load or crushing. DIN25201 recommends to prevent creep due to increased surface pressure, reduced number of interfaces, increased tightening length, reduced surface roughness, proper shape and position tolerance, and high pre-stressing with high strength bolts. Looseness caused by indentation; prevention of relative movement of the contact surface by increasing the preload, increasing the flexibility of the bolt, increasing the friction on the bolt and nut support surface or in the thread, using locking elements, using adhesives, etc. The resulting bolt is loose. 4.2 Anti-loose performance test analysis Selecting several anti-loose methods, such as fixed snaps, spring washers, SPL nuts and Loctite adhesives, on the current rolling stock, the anti-loose performance test is carried out. The test plan is shown in Table 3. Table 3 Fastener anti-loose performance test program scheme nut anti-loose rubber tightening torque / remark type hex nut fine teeth M16x1.5 stop clasp type hex nut fine teeth M16x1.5 washer SPL6177.2 hex flange face nut fine teeth M16x1 .5 locking element stop clasp, SPL nut and adhesive can prevent the bolt from loosening. Spring washers reduce surface pressure or reduce crushing and prevent loose bolts. In general, ordinary spring washers do not work well because their maximum spring force often does not pre-tension the bolt to 70% yield strength. 104312008 Lateral vibration test method for fasteners. The lateral vibration test is carried out. The vibration source is from the eccentric wheel. The vibration frequency is 12.5 Hz and the number of cycles is 1500. The bolts used in the test are all GB/T57852000 hex head bolts full thread M16x1.5x110, the thread locking glue Loctite272 is used together with the accelerator 7471, the curing time is 3h. The ratio of the residual preload force to the initial preload force after the test is shown in the table. 4. Table 4 ratio of residual pre-tightening force to initial pre-tightening force sample number scheme 1 scheme 2 scheme 3 scheme 4 scheme 5 scheme 6 scheme 7 to determine whether the fastener is loose with the initial pre-tightening force of the fastener is reduced to 80% The standard of the removal, the test results of the schemes 1, 3, 4, 5, and 7 are qualified, and the test results of the schemes 2 and 6 are unqualified. The 10 sets of tests in Option 6 only the test results of samples 2 and 7 just reached the qualified line, and the lowest ratio was only 58.3%, indicating that the fastener has lost the anti-loosening effect. In addition, in the case where the mounting torque is substantially constant, since the axial force value of the fastener is too low, it is difficult to provide a fastening effect during use. The SPL nut used in Option 7 is a new SPL-type slotted nut developed by SPL to replace the company a few years ago and is now being used on the railway. The nut is loosened by mechanical deformation to change the internal thread structure, thereby changing the threaded connection and thus relaxing, and the test proves that the anti-loose effect is better. Comparing Scheme 2 and Scheme 3 found that the SPL-CO nut alone did not have a good anti-loosening effect, and even the test failed. When used in combination with anti-slack rubber, a better anti-loosening effect is achieved. Comparing Scheme 3 and Scheme 4 found that the SPL-CO nut did not exhibit superior anti-loosening properties than ordinary nuts. It can be found from the schemes 1, 3 and 4 that all the fasteners using the anti-loosening rubber have achieved good anti-loosening effect. However, the anti-slack adhesive must be used within the specified temperature range. The liquid adhesive specified in DIN 25201 is used at a temperature of -40 to 100 T:. At present, companies such as Loctite have developed locker products suitable for temperatures above 200 psi. 5Installation 5.1 Bolt fastening method Since the tightening torque required for the bolt increases with d3, the particularly small bolt is easily broken, and the large bolt is often insufficiently pre-tightened. In particular, when the number of bolts used is large, uneven tightening force will cause the load distribution of the parts to be uneven, thereby causing warping deformation. In this case, the best way is to use a torque wrench to pre-tighten the bolt or to pre-tighten it according to a predetermined extension or rotation angle. China's fastener standard system lacks specific requirements for the installation of bolt fasteners. At present, most OEMs have borrowed the methods and requirements for fastener installation by foreign companies in the process of technology introduction. Torque method, torque angle control method and elongation control method have been widely used. DIN 25201 proposes different installation requirements for bolted connections of different risk levels. For bolts with high risk and medium strength, the use of impact wrenches is prohibited during installation. Bolts installed using the control angle tightening method are not allowed to be reused. Bolts with a high level of risk should be installed by trained personnel. If the bolt is tightened with an impact wrench, the tightening torque will produce an error of more than 30%, causing the tightening torque to be too large or too small. In order to improve production efficiency, some OEMs have not completely banned the use of impact wrenches, but only for initial preloading. At the same time, after pre-tightening with an impact wrench, when tightening with a torque wrench, the bolt or nut should be able to rotate 1/ 4~1/3 circle. At present, the installation technology of bolt fasteners has gradually gained the attention of various OEMs. At the time of product development, there are bolted fastener installation instructions or general technical specifications for fasteners, but some irregular operation still exists. For example, if the fastener is not pre-screwed into the threaded hole of the base body, it will be screwed again with the impact wrench, causing the tooth of the thread to break or break the bolt; the part that needs to be tightened twice is only after the first tightening. The anti-loose mark prevents the torque requirement of this part. 5.2 Bolt installation quality inspection In order to ensure the installation quality of the bolts, DIN 25201 recommends that the bolt installation results be verified by measuring the loose torque and measuring the elongation. Or mark the initial position after tightening, then loosen the bolt and re-tighten it to the marked position. Then measure the torque and compare the torque value twice. The required torque value is within the range of the tightening torque value allowed by the torque wrench. This method is cumbersome, but the results are fair. 5.3 Bolt anti-loose marking DIN25201 stipulates that bolts with a size larger than M8 should be marked with a pen. For the contrasting color, the screw-in bolt connection on the nut and bolt head should be on the bolt head and the fastened parts sometimes on the attachment. Marked on. If you re-bolt the bolt, you should re-do the above mark. An example of a lockout requirement for a main plant bolt installation. Requirements: 1. Mark line E clear; 2! l Line width 2-4mm; 3. The line must not be installed with anti-loose marks on the bolts. Example 6 Conclusion From the aspects of bolt fastener risk level, design calculation, anti-loose method and installation requirements, it is pointed out that China and Germany are used in rolling stock. The gap in bolt technology. In order to narrow these gaps and effectively improve the application level of bolting applications for rolling stock in China, the CSR enterprise standards and railway industry standards released in recent years have borrowed the advanced concepts of the DIN25201 standard to varying degrees. However, the understanding and application of VDI 2230 by various OEMs is still difficult. In the future, it is necessary to make an in-depth study of its theory and software implementation methods, and conduct certain test verification. High Power Led,3Mm Red Hair Red Led,Green Double-Color Led,Red In-Line Lamp Bead Dongguan XINYUDA Technology Co., Ltd. , https://www.gdxige.com