# Collision Study on New Aluminum Alloy W-Beam Guardrail
## 4 Vehicle Collision Conditions and Evaluation Criteria  
During collisions between vehicles and traffic safety barriers, the collision energy is absorbed and dissipated in the deformation of the vehicle body and the protective barrier, mitigating the impact of the collision. Ideally, traffic safety barriers should possess controllable guiding properties and good cushioning characteristics, aiming to protect the safety of both the colliding vehicle and its occupants without posing a threat to other vehicles in traffic.  
In simulating car-barrier collisions, the collision angle, velocity, and position of the vehicle are fundamental collision conditions. In this context, at the same velocity, collision damage is directly proportional to the collision angle. Increasing the collision angle results in increased damage to both the vehicle and the barrier. Collision damage reaches its maximum in a 90-degree frontal collision. According to the \"Highway Guardrail Safety Performance Evaluation Standard\" (JTG/T F83-01-2004) [35], a collision angle of 20 degrees  
Figure 10: The localized finite element model of the guardrail.  
Figure 9: The constitutive relationship of Al 6061-T6 at room temperature and high strain rates.  
and the actual vehicle speed within the first 6 m of the collision point should be selected as the basic collision conditions. Additionally, the standard specifies the minimum total installation length of the guardrail and stipulates that the collision position should be one-third of the total length of the guardrail. In this simulation experiment, we followed this standard and selected a collision angle of 20 degrees and a collision speed of 100 km per hour, with the dimensions of the barrier being 7 \(\times\) 4 m and a total length of 28 m. The collision position was set at one-half of the total length of the barrier. The car-barrier collision model is depicted in Figure 11.  
When assessing the safety performance of barriers, consideration should be given to three aspects: human, vehicle, and barrier. For semi-rigid wave barriers, it is essential to ensure that their maximum dynamic deformation does not exceed the standard-specified maximum dynamic deformation of 1000 mm to guarantee their safety performance. In collision experiments without the use of crash test dummies, if the maximum accelerations experienced by occupants in the vehicle in the lateral, longitudinal, and vertical directions do not exceed 20 g, it is considered that occupants will not sustain fatal injuries in such collisions. Regarding vehicle collision trajectories, it is crucial to ensure that the collision vehicle model meets requirements and that phenomena such as vehicle intrusion or rollover do not occur during collisions with the barrier. Additionally, the barrier should exhibit good guidance properties to prevent vehicles from deviating at excessive angles and intruding into other lanes, thus avoiding secondary collisions.  
According to existing relevant research [36; 37; 38] and evaluation standards [35], the most commonly used evaluation indicators include the maximum dynamic deformation produced during the barrier-vehicle collision, the acceleration of the vehicle's center of mass, and the energy absorption curve of the barrier. These indicators can be used to assess the safety performance of the barrier. The LS-DYNA solver module is employed to solve the finite element model of the barrier-vehicle collision and obtain relevant data, thereby comprehensively evaluating the barrier's performance.