Research On Structure Strength And Fatigue Performance Of Vibrating Screen

Road construction machinery is very important in the construction of transportation projects,and the asphalt mixing plant is one of the necessary equipment for the production of road construction mixtures.The vibrating screen is the key mechanical equipment for evaluating the production quality of the asphalt mixing plant.The quality of the road surface is directly related to the screening work efficiency of the vibrating screen.However,there are often vibrating screens that have poor screening effects.The problems of wear or fracture of parts and short service life may be related to the complex stress environment and unreasonable design structure when the vibrating screen is working.Therefore,aiming at the fracture of the end pre-tensioned beam of a certain type of vibrating screen equipment,a space finite element model was established,and a series of structural mechanics analysis and dynamic response analysis were carried out on the finite element model of the vibrating screen structure.The reason for the fracture of the pre-tensioned beam at the end and the improvement plan have been proposed to increase the service life of the vibrating screen system.Here are the main contents:(1)A spatial finite element model was established with a certain type of vibrating screen as the research object,the structure of the vibrating screen is complex,and the load is affected by various factors.In order to ensure the accuracy and reliability of the model,the following model processing solutions were adopted for the key parts of the vibrating screen equipment:For important bolts,the bolt center was divided,and a rigid area was established through a coupling method to achieve force transmission;Using beam elements with the same cross-section as the screen to simulate the screen in order to apply the pre-tightening force of the screen;Simulating the eccentric mass of the vibration motor by adding a mass unit,and apply a nodal force on the mass unit to simulate the exciting force generated by the vibration motor;The mass element was used to simulate the screening of materials and the materials were evenly distributed on the screen,and the mass element and the corresponding screen were established in a rigid area to achieve force transmission.(2)The vibration characteristics of the vibrating screen structure are obtained through modal analysis.The result of the modal analysis shows that the difference between the natural frequency of the structure and the excitation frequency is less than 10%.According to the design standard of the vibrating screen,it indicates that the structure may resonate;The harmonic response analysis of the vibrating screen model was carried out,and the dynamic response of the vibrating screen’s pre-tightened beam structure under load was obtained.The first principal stress amplitude-spectrum graph and the stress cloud diagram of the pre-tightened beam structure were found to be the dynamic response of the vibrating screen pre-tensioned beam structure.The tight beam structure always shows instantaneous extreme stress at low frequencies(such as 0.6Hz,1.6Hz),indicating that the pre-tensioned beam structure of the vibrating screen will produce instantaneous extreme stress at the low frequency stage,which will cause cracks to initiate and expand;In order to accurately analyze the fracture location of the vibrating screen,a fine finite element model of the fracture location of the pre-tensioned beam structure of the vibrating screen(including weld details,process holes,and refined mesh)was established and transient response analysis was performed.The results show that the pre-tensioned beam structure stress value is greater than the allowable stress value of the material,and the structure is prone to fracture.(3)By analyzing the dynamic response of the vibrating screen,the pre-tightened beam structure at the end of the vibrating screen was improved,and a three-dimensional finite element model of the improved structure was established.The modal analysis and dynamic response analysis were completed.The results showed that the vibrating screen improved structure can effectively improve the natural frequency of the end pre-tightened beam structure and keep the natural frequency away from the working frequency of the vibrating screen;Establishing a fine finite element model of the welded joint of the pre-tensioned beam to improve the structure,analyze the transient response of the structure under the working frequency of the vibrating screen system,and obtain the time history of the first principal stress of the welded joint,and the result shows the stress status of the improved structure was effectively improved;The hot spot stress method was used to interpolate the weld toe of the improved structure,and the welding fatigue life of the vibrating screen pre-tightened beam structure was obtained.The result shows that the stress was significantly reduced.The hot spot stress in the weld area has a steady-state stress amplitude of 30 MPa,which satisfies the International Institute of Welding(IIW)requirement of fatigue level in the long-life zone,that is,the stress amplitude is less than 40 MPa,indicating that the improved structure has a certain effectiveness.