Analysis of Cracking Failure in NSK Bearing Blocks
Source: Bearing Network | Date: April 3, 2013
NSK bearing blocks are commonly used in heavy-duty machinery and industrial applications. However, cracking failures can occur due to various factors, including stress concentrations, material defects, and improper installation. Understanding the causes of such failures is essential for improving the durability and reliability of these components. In some cases, a deep compressive stress layer can be formed during manufacturing, which helps reduce tensile stresses that may lead to corrosion and fatigue damage. Induction heating is often employed to enhance surface hardness, with hardening depths typically ranging from 3 to 7 mm. For certain applications, the hardened layer depth should be at least 2.3 mm, while for larger components like 110mm and 120mm parts, it should reach 4 mm or more. In production, several drive axle half-shafts have shown uneven tooth arrangements and low insert hardness, which compromises the overall strength and wear resistance of the component. Crack sources are often found on the inner surface of the NSK bearing water jacket. These areas may show signs of corrosion, but fatigue arc traces are not always clearly visible. Scanning electron microscopy (SEM) analysis reveals that cracks often originate from corrosion pits and propagate through fan-shaped microstructures. The crack propagation area may display typical fatigue features, such as beach marks around the source region. Some corrosion pits may even connect to form continuous lines, indicating long-term exposure to corrosive environments. The NSK bearing water jacket is subjected to three main types of stress: explosion stress, installation stress, and thermal stress. The maximum stress occurs in the hoop direction, reaching approximately 128 MPa. At the same time, the inner wall of the water jacket experiences a lower stress level, around 98 MPa. These stresses can contribute to material degradation over time, especially if the component is exposed to harsh operating conditions. During production, issues such as misalignment between the workpiece and sensor can lead to noise and reduced performance. To mitigate these problems, high-reliability sintered bronze oil-impregnated NSK bearings are often used. Proper control of sintering conditions, alloy composition, and anti-corrosion treatments can also help improve the quality and lifespan of the bearing. In summary, the failure of NSK bearing blocks is often linked to stress concentrations, corrosion, and poor material properties. By addressing these factors through improved design, manufacturing, and maintenance practices, the service life of these critical components can be significantly extended. Recommended Reading: - KOYO Bearing Appearance View and Ferrule Processing Analysis - Tips for Proper Bearing Storage - How to Identify Fake Bearings - Preventing TIMKEN Bearing Issues For more information on bearings and related topics, visit China Bearing Network. Previous: KOYO Bearing Application Methods and Precautions Next: SKF Guide to Choosing and Using Bearings
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