Study On Fatigue Life Of LZ Type Vertical Rolled-steel Pallet Of Baotou Iron And Steel Group

With the development of the national economy and the rapid improvement of the level of science and technology,Chinese demand for basic industrial products rolled-steel is also increasing.Due to the characteristics of long distance,heavy weight,and inland areas of rolled-steel transportation,railway transportation has become the most important way for rolled-steel transportation.Therefore,the loading and securement of rolled-steel also determines the safety and security,fast and efficient of railway transportation.Due to the advantages of high safety,fast loading and unloading,environmental protection,and reusability,the rolled-steel pallet has been widely used in rolled-steel railway transportation.The current rolled-steel loading methods of Chinese railways are divided into vertical loading and horizontal loading.The vertical loading method has the advantages of high transportation efficiency,less difficulty in transportation organization,and more reasonable and effective rolled-steel placement.However,Chinese current simulation research on the rolled-steel pallet is only for the horizontal rolled-steel pallet,while the research on the vertical rolled-steel pallet is very few.Therefore,the paper chooses the LZ vertical rolled-steel pallet designed and manufactured by Baotou Iron and Steel Group as the object of simulation research.In order to ensure transportation safety,the rolled-steel pallet will undergo regular strength tests.The current rolled-steel pallet strength tests generally use the maximum instantaneous stress value method to determine their safety,that is,the maximum instantaneous stress of each measurement point is collected in the railway freight car impact test.After data processing,the measured stress value of each measuring point and the allowable stress of the material are compared to determine the safety of the rolled-steel pallet.But in fact,during the transportation process,the rolled-steel pallet hardly bear the maximum instantaneous stress during the test and the vehicle vibration caused by the track irregularity makes the rolled-steel pallet subjected to changing alternating most of the time The alternating load causes fatigue damage to the pallet,and the rolled-steel pallet gradually reaches the fatigue life.In this thesis,the LZ type vertical rolled-steel pallet designed and manufactured by Baotou Iron and Steel Group is selected as the research object,and predicting the fatigue life of the pallet according to the following steps and the optimization plan of the pallet is proposed.（1）SIMPACK dynamics simulation software was used to establish the car-cargo dynamics model of the C₇₀ universal gondola with two pieces of vertical steel coils.Set up operating conditions according to the actual railway line conditions of Baotou Iron and Steel Group transports rolled-steel,the load-time series of the LZ-type vertical rolled-steel pallet during the rolled-steel transportation process is obtained by simulation calculation.（2）According to the Auto CAD drawing of the LZ type vertical rolled-steel pallet,the Solid Works 3D modeling software is used to establish the 3D model of the pallet,and the model is imported into the Hyper Mesh software to mesh and set the relevant parameters.Use the Optistruct solver to carry out the finite element strength simulation calculation.After the calculation,the stress distribution cloud diagram of the LZ vertical rolled-steel pallet and the stress value of each position of the pallet under a certain pressure can be obtained in Hyper View.Compare the simulated stress value and the measured stress value of each measuring point in the field test to verify the reliability of the finite element model of the pallet.Then,select the fatigue evaluation points on the LZ type vertical rolled-steel pallet by analyzing the structure of the pallet,the stress distribution law of the pallet,and the simulated stress value at each position of the pallet.（3）According to the load-time series and the finite element strength simulation calculation result of the LZ type vertical rolled-steel pallet,the stress-time series of each fatigue evaluation point can be obtained.Based on the rain flow counting method,the stress spectrum of each evaluation point is statistically obtained in the ANSYS n Code Designlife software,and according to the British standard BS7608:1993 fatigue design and assessment of steel structure,predict the fatigue damage value and the fatigue life mileage of each evaluation point under different line level conditions.Then the safe operation times and safe service life of the LZ type vertical rolled-steel pallet on the selected railway section in this paper are estimated.（4）Propose several commonly used methods to extend the fatigue life of parts by analyzing several factors that affect the fatigue life of parts.Analyze the feasibility and advantages and disadvantages of the methods separately,and select the most economical and effective weak point securement method to optimize the LZ type vertical rolled-steel pallet,and calculate its optimization effect.In this paper,dynamic simulation software is used to simulate the vehicle-cargo dynamics simulation model to obtain the load-time series of the LZ type vertical rolled-steel pallet during transportation;Use 3D modeling and finite element strength simulation to determine the fatigue evaluation points of the pallet and perform fatigue life analysis and prediction,which provide scientific guidance and theoretical basis for the design,production,maintenance and inspection,as well as the safe and full use of the seat frame during the life cycle of various types of vertical rolled-steel pallet in the future.