Development of an Operational Digital Twin of a Locomotive Parking Brake for Fault Diagnosis

Abstract In recent years, a growing role in digital technologies has been filled by model-based digital twinning. A digital twin produces a one-to-one mapping of a physical structure, operating in the digital domain. Combined with sensor technology and analytics, a digital twin can provide enhanced monitoring, diagnostic, and optimization capabilities. This research harnesses the significant capabilities of digital twining for the unmitigated challenge of fault type classification of a locomotive parking brake. We develop a digital twin of the locomotive parking brake and suggest a method for fault type classification based on the digital twin. The diagnostic ability of the method is demonstrated on a large experimental dataset

Experimental Investigation of the Spall Propagation Mechanism in Bearing Raceways

This article investigates the spall propagation mechanism for ball bearing raceways by focusing on an experimental investigation of cracks that evolve in the vicinity of the spall edge. Understanding the spall propagation mechanism is an important step towards developing a physics-based prognostic tool for ball bearings. This research reflects an investigation of different spall sizes that propagate naturally both in laboratory experiments and in the field. By using a combined model of a rigid body dynamic model and a finite element model that simulates the rolling element–spall edge interaction, our results shed light on the material behavior (displacements, strains, and stresses) that creates an environment for crack formation and propagation. With the support of the experimental results and the rolling element–spall edge interaction model results, three stages of the mechanism that control fragment release from the raceway were identified. In Stage one, sub-surface cracks appear underneath the spall trailing edge. In Stage two, cracks appear in front of the trailing edge of the spall and, in Stage three, the cracks propagate until a fragment is released from the raceway. These stages were observed in all the tested bearings. In addition, other phenomena that affect the propagation of the cracks and the geometry of the fragment were observed, such as blistering and plastic deformation. We include an explanation of what determines the shape of the fragments

Spall Evolution in a Rolling Element Bearing

International audienceRolling element bearing (REB) is one of the basic mechanical components in rotating machinery. It is common to divide the REB wearinto two stages,damage initiation and damage propagation. There hasbeen a growing awareness of the need to understand the damage mechanism during the propagation phase. The current work includes a discussion on the ongoing research and the methodology for the development of the prognostic method for damage propagation. The methodology integrates experiments, diagnostic methods, and physics-based models. Endurance tests were conducted in order to learn about the damage propagation processand model validation. Furthermore, Finite Element model of the spalled bearing was developedand validated. The FE model aims to investigate and simulate the damage propagation process. The simulation results are in good agreement with the experimental observation

New Damage Accumulation Model for Spall Propagation Mechanism in Bearing Raceways

The aim of this study was to investigate the spall propagation mechanism in ball bearing raceways using physics-based models. Spalling is one of the most common types of bearing failures that can lead to catastrophic failure. This research takes a step forward toward developing a prognostic tool for ball bearings. It is first necessary to understand the spall progression process in order to formulate a constitutive law of spall deterioration and to estimate the amount of remaining useful life. Fragment formation in the vicinity of the spall edge was found to consist of surface and sub-surface cracks that eventually coalesce, and a fragment is released from the raceway, based on naturally-developed spalls. Here, we describe a physics-based model, integrating a dynamic model with a finite element one to simulate this process. A continuum damage mechanics (CDM) approach and fracture mechanics tools were embedded into the finite element model to simulate the damage propagation. The formation of cracks in the vicinity of the spall (surface and sub-surface cracks) were studied using this effective stress CDM model, and the propagation of the cracks was examined using two approaches: a fracture mechanics approach and an accumulated inelastic hysteresis energy CDM approach. The latter also predicts the overall process of a single fragment release. The simulation results of the spall propagation models are supported by experimental results of spalls from both laboratory experimental bearings and an in-service Sikorsky CH-53 helicopter swashplate bearing. The results obtained show that the impact of the ball on the spall edge affects the crack propagation and the appearance of the surface and sub-surface cracks. Both release the residual stresses and cause crack propagation until a fragment is released

Probability-Based Algorithm for Bearing Diagnosis with Untrained Spall Sizes

Bearing spall detection and predicting its size are great challenges. Model-based simulation is a well-known traditional approach to physically model the influence of the spall on the bearing. Building a physical model is challenging due to the bearing complexity and the expert knowledge required to build such a model. Obviously, building a partial physical model for some of the spall sizes is easier. In this paper, we propose a machine-learning algorithm, called Probability-Based Forest, that uses a partial physical model. First, the behavior of some of the spall sizes is physically modeled and a simulator based on this model generates scenarios for these spall sizes in different conditions. Then, the machine-learning algorithm trains these scenarios to generate a prediction model of spall sizes even for those that have not been modeled by the physical model. Feature extraction is a key factor in the success of this approach. We extract features using two traditional approaches: statistical and physical, and an additional new approach: Time Series FeatuRe Extraction based on Scalable Hypothesis tests (TSFRESH). Experimental evaluation with well-known physical model shows that our approach achieves high accuracy, even in cases that have not been modeled by the physical model. Also, we show that the TSFRESH feature-extraction approach achieves the highest accuracy

Mechanical Response and Fracture of Pultruded Carbon Fiber/Epoxy in Various Modes of Loading

Pultrusion is a continuous process of forming constant cross-sections of unidirectional composites with a significant long length. This unique process is implemented widely in the composites industry due to its continuous, automated, and highly productive nature. The current research focused on mechanical response characterization at three modes of loading: tensile, compression, and shear loading of coupons made from a graphite/epoxy 1 mm sheet. In addition, the effects of holes and notches were examined in terms of mechanical properties. The mechanical behavior was assessed through stress–strain curves with careful attention on the curve profile, macroscopic fracture modes observations, and optical microscopic tracking with continuous video records. The mechanical tests follow standards with some critiques on the shear test. Finite element analysis (FEA) was used to accurately determine the shear modulus, and for other mechanical investigations. By nature, under tension, the unidirectional fiber composite at 0° orientation exhibits high strength (2800 MPa), with very low strength at 90° orientation (40 MPa). Both orientations display linear mechanical behavior. Under compression, 0° orientation exhibits low strength (1175 MPa), as compared to tension due to the kinking phenomena, which is the origin in the deviation from linear behavior. Under shear, both orientations exhibit approximately the same shear strength (45 MPa for 0° and 47 MPa for 90°), which is mainly related to the mechanical properties of the epoxy resin. In general, in the presence of holes, the remote fracture stress in the various modes of loading did not change significantly, as compared to uniform coupons; however, some localized delamination crack growth occurred at the vicinity of the holes, manifested by load drops up to the final fracture. This behavior is also attributed to the tension of notched coupons. FEA shows that the shear values were unaffected by manufacturing imperfections, coupon thickness, and by asymmetrical gripping up to 3 mm, with minor effect in the case of a small deviation from the load line. Selected experimental tests support the FEA tendencies