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Modeling, Simulation, and Analysis of Electric Motors
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
In engineering practices, there are two major categories of failures in mechanical systems: material failure and structural instability. Buckling refers to a phenomenon that a part or component that is subjected to compression suddenly becomes unstable. As shown in Figure 14.37, a thin-walled sheet is subjected to compressive force F on its two ends. By increasing F until a certain value, the sheet will suddenly bend, indicating that it is no longer to withstand any loads. In this figure, δl and δo are load displacement and out-of-plane displacement, respectively. This phenomenon can also occur for other geometries such as columns, flanges, and shells. Because of its suddenness, bucking failure may cause catastrophic consequences.
Component Failure in Road Traffic Incidents and Accidents
Published in Colin R. Gagg, Forensic Engineering, 2020
Turning attention to the single broken wheel stud (Figure 10.8B), it had fractured at the root of the first thread in engagement, exactly where predicted by the FEA analysis shown in Figure 10.6. Beach markings were clearly evident on the surface, and indicative of crack propagation in discreet steps typical of a fatigue mode of failure. The growing crack had progressed some 60% across the section, at which point the reduced load-bearing area could not sustain the (cyclic) loading stresses generated by a normal wheel rolling action. Final failure immediately followed, with a tearing overload of the reduced sectional area (Figure 10.8B). These features are classic fingerprints of fatigue therefore it can be said with certainty that fatigue was the initiating failure mechanism responsible for the fracture of the one stud on the ambulance rear nearside axle. By definition, fatigue is a mechanical mode of failure, progressing over time with cyclically applied loading. As such, failure of the stud in question was entirely mechanical in nature, and not as a result of some traumatic overload event immediately prior to failure. Once a fatigue crack had been initiated in the stud, its final failure was inevitable.
An Introduction to Systems
Published in Joseph Eli Kasser, Systems Engineering, 2019
Sooner or later systems will fail or break down and exhibit abnormal behaviour. Failures may be: Total: the system stops working.Partial: some functionality is lost while the system can still operate. Failures due to wear and tear on parts can be predicted statistically and can often be prevented by a combination of proper maintenance and design for reliability. Failures due to external causes can often be compensated for by designing in redundancy. Contingency plans for dealing with failures and breakdowns need to be prepared and periodically updated.
Methodology for ranking internal corrosion-induced leakage susceptibility in oilfield pipelines
Published in Corrosion Engineering, Science and Technology, 2023
Pipeline integrity management programme includes periodic threat assessment in order to prioritise oilfield pipelines for risk from a variety of internal and external threats. Such risk ranking facilitates a timely deployment of predictive-maintenance action and provides reliable safeguards against unexpected leak failures. Failures do jeopardise mechanical integrity, operation, health, safety and environment, with significant financial consequences. During a period of 6 years, 22 internal-corrosion-induced leakage failures were recorded at KOC. An effective risk assessment process could have identified the conditions that led to such unexpected failures. In this context, risk management is the systematic application of policies, practices and resources to control risk and provide reliable safeguards against unanticipated failures and leaks, occasioned by internal and external threats.
Failure analysis of a low-pressure stage steam turbine blade
Published in Nondestructive Testing and Evaluation, 2023
LP turbine blades are prone to premature failure, and corrosion, erosion, fatigue, and their interactions are the principal causes [8]. Many researchers have done work in this area to find the root cause of failure of turbine components. They carried out the failure analysis in the form of chemical composition, microstructural degradation and mechanical tests. A low-pressure steam turbine blade failed after 13,200 service hours because of an environment-assisted fatigue fracture [2]. In a 210 MW plant, Corrosion fatigue initiated from pits was the reason for blade‘s failure in LP steam turbine [9]. Foreign particle erosion-corrosion was the reason for fatigue failure of a steam turbine blade after 72,000 h of working [10]. Damage to the steam turbine blade occurred after approximately 165,000 h of operation. Fatigue was found to be the primary cause of failure, followed by erosion and the development of notches [11]. A case study concluded that high cycle fatigue and impact of the brass ring was the reason for low-pressure turbine blade failure [1]. After 8000 h of operation at high temperatures, a failed investigation of 40 MW gas turbine blades was conducted. Because of the transformation, a continuous film of carbides was found in the base material’s grain boundaries. Intergranular cracks that developed as a result of high-temperature exposure are identified as the failure’s primary cause. When the cracks reached a threshold length after starting at the grain boundaries, catastrophic fracture resulted [12].
On the copula-based reliability of stress-strength model under bivariate stress
Published in International Journal of General Systems, 2023
Burcu Hudaverdi, Selim Orhun Susam
The relationship between stress-strength variables and system functions can be described in terms of reliability, functionality and structural integrity. In reliability, the strength variables should be chosen properly to ensure that the system functions reliably under various operating conditions. Through the process, the appropriate material properties and safety factors are determined in order to prevent unexpected failures and ensure long service life. In functionality, the selection of materials and their design should be considered to provide functional requirements of the system. For example, a high-loaded component must have a high-fatigue strength to be able to function properly. And for maintaining structural integrity, the stress variables must be within the allowable stress limits defined by the strength variables. Therefore, understanding the relationship between stress and strength variables is critical for maintaining the structural integrity of a system.