How to choose the installation position of the hinge on the side of the body to prevent the hinge fr

With the development of society and the improvement of people's living standards, the demand for cars as a comfortable means of transportation has increased. Consumers are now paying more attention to safety and quality durability when purchasing cars, rather than just focusing on eye-catching novel shapes. In order to meet the needs of users within the useful life of a car, automotive reliability design aims to ensure that auto parts can perform their functions effectively. The strength and stiffness of the parts themselves play a vital role in determining the service life of the car.

One of the most important body components that car buyers often pay attention to is the engine cover. The engine cover serves multiple functions including facilitating maintenance of various parts in the engine compartment, protecting the components, isolating engine noise, and ensuring pedestrian safety. The hood hinge, a rotating structure for fixing and opening the hood, plays a crucial role in the functioning of the engine cover. The strength and rigidity of the hood hinge are of great significance for the smooth operation of the hood.

During a 26,000km vehicle reliability road test, a problem was identified with the body side bracket of the engine hood hinge. The bracket broke and the engine hood side hinge was separated from the body side hinge, causing the engine hood to be unable to be fixed properly and compromising driving safety.

The overall performance of a vehicle is achieved through the interrelationship and matching of its various parts. During the manufacturing and assembly processes, errors can occur due to factors such as manufacturing, tooling, and human operation. These errors accumulate and can lead to mismatching and problems during road tests. In the case of the broken hinge, it was found that the hood lock of the car had not been properly locked, resulting in vibrations along the X and Z directions during the road test, leading to fatigue effects on the body side hinges.

In engineering practice, parts often have holes or slotted structures due to structural or functional requirements. However, experiments have shown that sudden changes in the shape of a part can result in stress concentration and cracks. In the case of the broken hinge, the fracture occurred at the intersection of the shaft pin mounting surface and the hinge limit corner, where the shape of the part changes abruptly, leading to high stress concentration. Factors such as the strength of the part material and the structural design can also contribute to part breakage.

The body side hinge in question is made of SAPH400 steel material with a thickness of 2.5mm. The mechanical and technological properties of the steel plate are within the specified values, indicating that the material selection was appropriate. However, fatigue damage can occur in auto parts under road loads. The maximum stress value of the body side hinge was calculated to be 94.45MPa, which is below the lower yield strength of SAPH400. This suggests that the hinge material was suitable, and the stress concentration at the gap was the main reason for the hinge fracture.

The design of the hinge structure also played a role in the hinge failure. The angle between the hinge installation surface on the body side and the X axis was initially set at 30°, which made it difficult to adjust the gap between the hood and the fender after installation. Furthermore, the unbalanced support of the force increased the risk of fracture. The width and thickness of the mounting surface of the hinge shaft pin also affected the stress distribution. A comparison with similar structures indicated that the fracture occurred when the dimensions exceeded 6mm.

To address these issues, several design improvements were proposed. The hinge mounting surface on the body side should be installed as horizontally as possible, or at least within a controlled range of 15°. The installation points of the hinge and the shaft pin should be arranged in an isosceles triangle to optimize force transmission. The structure should be optimized to reduce stress concentration and fatigue effects. The mounting surface should have a wider width and a reduced curvature to improve the strength and durability of the hinge.

Through CAE strength analysis software, several design schemes were evaluated and compared. Scheme 3, which included removing the middle rib, increasing the fillet radius, and optimizing the limit mechanism, showed the best results in terms of stress distribution. It was further validated through road tests. The optimized design not only improved the strength and durability of the hinge but also ensured the pedestrian protection function of the engine hood.

In conclusion, the design of the hood hinge is crucial for the proper functioning and safety of the engine cover. Through careful analysis and optimization, the structural design of the hinge can be improved to reduce stress concentration and fatigue effects. This will increase