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• Failure analysis of bearings over the past 20 years are summarized and reviewed. • Different failure modes and mechanisms of bearings are classified and introduced. • It is described in details based on the corresponding characteristics of the failure mechanisms. • Wear and fatigue are the most common failure modes of bearings. • The main causes of failure are summarized. This work reviews the failure modes, mechanisms and causes of bearings in mechanical equipment. Bearings are among the most important basic mechanical components. Their operating conditions directly affect the safety and stability of mechanical equipment. In industries, users have very high requirements for the quality, accuracy, and service life of bearings and pay much attention to the selection, installation, use, and maintenance of bearings. However, bearing failures during operation has not been eliminated. Possible failure modes of bearings include fracture, corrosion, deformation and wear have been reviewed. Failure analysis is crucial for the safe operation of bearings. By identifying the modes and causes of failure, effective measures can be proposed to improve the service life of the bearings and eliminate potential accidents. Herein, the contributions of various researchers to bearing failure analysis over the past 20 years are reviewed. The failure modes and mechanisms of the bearings are classified and discussed. Typical bearing failure cases are discussed. According to statistical results, wear and fatigue are the most common failure modes of bearings, as bearings are affected by cyclic loads, friction, and lubrication during operation. Incorrect assembly, use, and maintenance is the main causes of bearing failure. The aim of this review is to provide information on systematic failure analysis of bearings, identify the failure mechanisms under different conditions, and propose an effective plan to improve the bearing reliability, reducing the occurrence of similar bearing failures. [ABSTRACT FROM AUTHOR]

• Failure analysis was performed to find out the failure cause of the crankshaft. • Evidences indicated the mechanism of the premature failure was fatigue failure. • Fatigue fracture initiation was induced by the dense inclusions. A sport utility vehicle crankshaft was premature failure after a short service life of about 3 years. The fracture took place at the transition arc between the crankpin and the journal. The fracture surface has an angle of 45° inclination with the axial direction of the crankshaft, which is in accordance with the maximum primary stress plane caused by the torsion. A fractographic study indicates that the fracture surface exhibits a brittle fracture morphology reflective of a low toughness of the material. Macro beach marks and micro striations indicate that the failure mechanism of the crankshaft is fatigue failure. Metallographic analysis shows that flake pearlite and reticular ferrite are the characteristics of the microstructure near the fracture surface, which may lead to the lower plasticity of the material. Reticular ferrite is induced by the heterogeneous inclusion with a chemical structure of CaO-MnS complex. The weaker ferrite destroys the continuous matrix material and reduces the plasticity of the material, resulting in a brittle fracture. Collected evidence reveal that a series of manganese sulfide inclusions are distributed near the crack initiation. According to the quantification analysis of inclusion distribution, the density of inclusions is great enough to act as the initiation of cracks. Moreover, finite element analysis indicates the stress concentration induced by the geometry structure is less than the inclusion. Given all of that, the failed crankshaft is supposed to be initiated by the harmful inclusions. Therefore, it is recommended that rigorous testing of the inclusions and improving the heat treatment quality of crankshafts are effective ways to solve the problem. [ABSTRACT FROM AUTHOR]

• The present literature survey reviewed and summarized failure analysis of shafts over the past 20 years. • The different failure modes and mechanisms are classified, and prevention and corrective actions are listed. • The bearing life, service load, macroscopic fracture characteristics and service environment of shafts are introduced in detail. • The main causes of fatigue failure are summarized. Shafts are core mechanical components of equipment. These play a key role in supporting the rotating device and transmitting motion, torque, or bending moment. The quality and performance of shafts are of high significance for the normal and safe operation of the equipment. Failure analysis is of high significance for the safe operation of mechanical equipment and accident prevention. By identifying the modes and causes of failure, effective measures can be proposed to improve the service life of shafts and eliminate potential accidents. In this work, failure analysis cases reported for shafts in the past 20 years are reviewed. Typical failure modes including fracture, corrosion, wear, and deformation failures are summarized. Fatigue fracture is the most common failure mechanism of shafts owing to the influence of cyclic loads on shafts under normal working conditions. The fatigue failure characteristics, environmental factors, wear fatigue, and causes of fatigue failure of shafts are described in detail. The objective of this review is to provide systematic failure analysis information of shafts and thereby, aid engineering communities to identify the failure mechanisms of shafts under different conditions. [ABSTRACT FROM AUTHOR]

Premature failure of headspan suspensions was mainly attributed to the fracture failure of the droppers. Various experiments were conducted to explore the fracture failure mechanism of the droppers used in headspan suspensions. Four notches along the axial direction of the dropper, corrosion pits and corrosion products were observed by visual examination. Although the axial cracks have little effect on the structural strength, they make it easier to form corrosion environment in the notches than on the exposed outer surfaces. Furthermore, energy spectrum analysis indicated the presence of chlorine and sulfur both in the corrosion products inside of axial cracks and corrosion pits. Meanwhile, typical microstructural features of intergranular cracking and corrosion products were observed by the scanning electron microscopy. Finally, finite element analysis was conducted to characterize the stress distribution near the corrosion pits. The simulation results showed that obvious stress concentration was formed near the corrosion area. All the results indicated that the droppers failed due to the combination of pitting corrosion and stress corrosion cracking. [ABSTRACT FROM AUTHOR]

• The fractured spring due to bending fatigue crack propagation were analyzed. • The failed spring has obvious external defects. • The precise characterization of the defects was measured by CT. • The effect of the defect on the stress distribution was analyzed. The torsion spring is an important component for vehicle steering system. The torsion spring in this study was manufactured using high quality carbon structural steel. In order to study the failure mechanism of the spring, a series of experiments were carried out. All the collected evidences indicated that the spring fracture was due to fatigue crack propagation. At the same time, an obvious machining defect was observed on the inner surface of the ring. There are two crack initiation regions which are located at the areas near and opposite side of the machining defect. Under the cyclic loading induced by the repeated turning, the crack propagated and fractured finally. In order to analyze the effect of the machining defect on the fatigue failure, a computed tomography experiment was conducted. The precise characters of the defect were measured by computed tomography experiments. Then a finite element model was established according to the actual defect size and the stress distribution of the torsion spring was analyzed. The results showed that the local stress of the spring and the area of stress concentration are closely related to the machining defect and the gap between the spring and the two cylindrical objects. Under the actual condition of the torsion spring in service, the severe stress was located on the fracture location, which indicating that the machining defect is the efficient cause of spring failure. [ABSTRACT FROM AUTHOR]