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**Special Overview of the Control and Prevention of Brittle Failure in Crane Steel Structures: Dalian Heavy Industry Lifting Group Co., Ltd.**
By Zou Sheng, Xu Hongze
Avoiding brittle failure in crane steel structures is a critical concern during both design and manufacturing. This article explores the key factors that contribute to brittle failure and outlines practical measures to control and prevent it. Brittle failure occurs suddenly, often under safe load conditions, making it particularly dangerous. It can lead to catastrophic consequences if not properly addressed.
Crane steel structures are subjected to dynamic loads, requiring careful consideration of material selection, structural design, and manufacturing processes. The primary goal is to avoid stress concentrations, cracks, and other defects that could initiate brittle failure. Inadequate rigidity or strength in the design can lead to rapid structural damage, which must be considered from the outset.
Material selection plays a crucial role in preventing brittle failure. Factors such as the type of stress, loading conditions, plate thickness, and ambient temperature all influence the choice of steel. High-strength steels may increase costs without necessarily improving performance, while unsuitable materials can lead to serious accidents. Impact toughness and environmental temperature are more important than stress levels in determining the risk of brittle failure.
Plate thickness also affects material behavior. Thicker plates tend to have lower impact energy values and are more prone to stress concentration. Standards provide mechanical properties for specific thicknesses, but real-world applications require additional testing and verification. For example, plates thinner than 12 mm generally do not pose a problem, while those over 26 mm should be carefully selected.
Environmental temperature significantly impacts the performance of steel. If the ambient temperature is below the transition temperature of the steel, brittle fracture becomes more likely. Understanding the plastic and failure shape transformation temperatures helps in selecting appropriate materials for different operating conditions.
In design, avoiding stress concentrations and ensuring proper weld quality are essential. Poor welding practices, such as lap joints and intersecting welds, can introduce cracks and reduce structural integrity. Butt welds are preferred over lap welds, and weld parameters must be carefully controlled to minimize defects.
Manufacturing processes, including shearing, punching, and flame heating, can introduce flaws that lead to brittle failure. Residual stresses must be minimized through proper heat treatment or preheating. Vibration techniques may help, but their effectiveness is limited.
In conclusion, preventing brittle failure requires a holistic approach that includes proper material selection, sound structural design, and rigorous manufacturing controls. Although modern steel technology has reduced the occurrence of brittle failures, the potential consequences remain severe. Therefore, this issue must remain a top priority in crane design and management.
Author: Zou Sheng
Address: 169 Bayi Road, Xigang District, Dalian
Reference: "Material Handling Equipment" 2004 (8)