| With the increasing number of motor vehicles in our country and the wide application of the central isolation barrier of urban roads in the country,the collision accidents between vehicles and barriers are on the rise obviously.In the collision accident between the vehicle and the central barrier of the urban road,the thin-walled long bar structure formed by the damage of the barrier is an important factor causing the windshield penetration.At present,there are few studies on the collision between vehicles and the central barrier of urban roads at home and abroad.There is a lack of research on the collision mechanism of thin-walled long bars with openings and the penetration mechanism of vehicle windshield.In this paper,we choose the finite element algorithm based on the updated Lagrangre formula.By simulating the impact process of three different connection forms of rectangular tube guardrail,the formation mechanism of open thin-walled long bar structure and the influence of different connection forms on the open form of open thin-walled long bar structure are obtained.Simplified the physical model and established the finite element model of two different kinds of open thin-walled long rod structures,and simulated the process of their impacting on the front windshield and side window of a car.The deformation of the open thin-walled long rod structure,the deformation and stress distribution of the windshield glass of a car were observed and analyzed.The occurrence mechanism of the open thin wall long rod structure penetrating the car windshield is obtained.The collision process between the open thin-walled long rod structure and the front windshield of a car with different openings,different collision speeds and angles is simulated.The deformation of the open thin-walled long rod structure and the penetration of the front windshield of a car under different constraints are observed.The influence of collision speed and angle on the penetration is pointed out.Based on this,the evaluation method of the open thin wall long rod structure for the penetration of car windshield is put forward.Through the analysis of the simulation results,we get the following conclusions:(1)The formation mechanism of the open thin-walled long bar structure is that the connection between the guardrail beam and the column fails during the collision,and the top end of the column separates from the front end of the beam under the collision,resulting in the exposure of the front end of the beam,thus forming the open thin-walled long bar structure.The connection between the beam and the column determines the form of the opening.(2)The mechanism of opening thin-walled long rod structure penetrating car windshield glass at low speed is the stress concentration caused by the tip angle of opening end impacting the glass,and the resulting breakage and cracks.The more sharp the opening shape is,the greater the stress concentration is,and the easier to penetrate.(3)The impact velocity has an obvious effect on the penetration of the open-ended thin-walled long rod structure.With the increase of impact velocity,the penetration time of the open-ended thin-walled long rod structure to the car windshield glass is shortened,and the deformation of the open-ended thin-walled long rod structure is smaller and the penetration is more serious.The structural penetration effect did not show obvious regularity.When the contact form is point contact,the penetration occurs more easily.The sharper the contact position,the more concentrated the impact stress,and the more serious the penetration.The response relationship between the maximum deformation and time and the contact-penetration time of the long thin-walled rod with an opening are selected as the evaluation method for the penetration of the windshield of a car.The shorter the contact-penetration time and the smaller the maximum deformation of the open thin-walled long rod structure,the more serious the windshield penetration will be.Finally,the structural optimization design and performance evaluation of the central barrier fence of urban roads are carried out.The evaluation results show that the optimized central isolation barrier can meet the relevant requirements of the GB50688-2011 anti-collision barrier,and can effectively prevent the formation of open thin-walled long bar structure in the collision.The research results reveal the formation mechanism of thin-walled long rod structure with guardrail opening and the mechanism of guardrail penetrating through car windshield glass,provide reference for the improvement of subsequent guardrail structure and the formulation of relevant national standards and regulations,provide new ideas for the simulation model establishment and simulation study of car windshield glass,and provide new ideas for vehicle windshield glass penetration.It provides a reference basis for evaluation of penetration and damage. |
