Bearing Failure Mode Research Articles

The effect of a fiber reinforced cavity configuration on load bearing capacity and failure mode of endodontically treated molars restored with CAD/CAM resin composite overlay restorations

ObjectivesTo evaluate the fracture strength and the mode of failure of endodontically treated molars restored with CAD/CAM overlays with fiber reinforced composite build-up of the pulp chamber. Methods40 Devitalized molars were cut over the CEJ and divided into five groups (n=8). The pulp chamber area was filled with: group 0 (control), no resin build-up; group 1, hybrid composite build-up (G-aenial posterior, GC); group 2, as in group 1 but covered with 3 nets of bi-directional E-glass fibers (EverStickNET, Stick Tech Ltd.); group 3, a FRC resin (EverX posterior, GC); group 4, as in group 3 but covered by the bi-directional fibers. The crowns were restored with CAD–CAM composite restorations (Lava Ultimate, 3M ESPE). Maximum fracture loads were recorded in Newton and data were analyzed using Kruskal–Wallis test (p<0.05). Fragments were analyzed using SEM. ResultsThe mean static loads in Newton were: group 0: 2448 (546); group 1: 2817 (873); group 2: 2128 (952); group 3: 2429 (1091); group 4: 2577 (833). No significant differences were found between the groups (p>0.05). All specimens fractured in a catastrophic way, under the CEJ. The main crack evolved in the corono-apical direction. In groups 2 and 4 secondary fracture paths with apico-coronal direction were detected close to the bi-directional fibers’ layer. ConclusionsFor the restoration of endodontically treated molars, the incorporation of FRCs did not influence the load-bearing capacity of the tooth–restoration complex. The SEM analysis showed a low ability of the bi-directional fibers net in deviating the fracture but this effect was not sufficient to lead more favorable fracture patterns, over the CEJ. Clinical significanceThe use of FRCs to reinforce the “core” of devitalized molars against vertical fractures under static loads seems useless when the thickness of the CAD/CAM composite overlay restoration is high.

On the thermally-induced seizure in bearings: A review

This paper presents a state-of-the-art survey of papers reported on the nature of a troublesome failure mode in bearings known as seizure. This mode of failure is thermally-induced and it occurs in both journal and rolling element bearings. To gain insight, particular attention is given to reported experimental observation, various mechanisms involved, and available prediction methodologies.

Characterisation of white etching crack damage in wind turbine gearbox bearings

White etching cracks (WECs) have been identified as a main failure mode of wind turbine gearbox bearings (WTGBs). This study reports an investigation of the destructive sectioning of a failed low speed planetary stage WTGB and the damage found at manganese sulphide (MnS) inclusions. The bearing inner raceway was sectioned through its circumferential and axial directions in order to compare the damage around inclusions in different directions. 112 damage initiating inclusions were catalogued and their properties were investigated.WECs were found attached to MnS inclusions of lengths 3–45µm at depths of up to 630µm from the bearing raceway surface and at a wide range of angles of orientation. Damage at MnS inclusions included internal cracking of the inclusions, separation from the surrounding steel matrix, crack initiation and WEC initiation. Evidence has been found to support the theory that WECs are subsurface-initiated by MnS inclusions, but that butterfly cracks with wings propagating at 30–50° from parallel to the raceway surface are not necessarily the same features as MnS inclusion-initiated WECs. Shorter inclusions were found to initiate longer WECs, as were the inclusions that were closer to parallel to the raceway surface in axially sectioned samples.

Influence of stamping on the compressive behavior and the damage mechanisms of C/PEEK laminates bolted joints under severe conditions

Bolted joint tests have been performed in order to evaluate the influence of stamping on the behavior of thermoplastic-based woven-ply laminates subjected to structural loadings under severe service conditions (120 °C after hygrothermal aging). Compressive tests have been carried out on carbon fabrics reinforced PolyEtherEtherKetone (PEEK) laminates to investigate fibers buckling due to changes induced by stamping on the non-planar interply structure of woven-ply laminates. As compressive strength decreases by 13% in stamped laminates, it facilitates the plastic buckling of 0° and ±45° oriented fibers due to compressive loads in bolted joints. Contrary to double-lap joints, stamping does not affect the strength of single-lap joints, as the geometry of single-lap joints is non-symmetric. Stamping modifies the damage mechanisms of PEEK-based laminates under bolt-bearing loadings, such as the failure of stamped bolted joints is dominated by bearing failure mode.

An Experimental Investigation on the Failure Behavior of a Notched Concrete Beam Strengthened with Carbon Fiber-Reinforced Polymer

This paper presents an experiment investigation on the failure behavior of a notched concrete beam reinforced with CFRP, by exploring the influences of the length, thickness, and CFRP bonding methods on the ultimate bearing capacity and failure mode. The interfacial shear stress has first been analytically derived and parametric analyses are then made to predict the failure mode. The experiment observation finds that failure mode significantly depends on CFRP length. The brittle fracture occurs only for nonstrengthened beams; the shear failure I mode mainly occurs when CFRP laminate is 100 mm long; the shear failure II mode mainly occurs when CFRP laminate is 200 mm long; and the delamination failure mode mainly occurs when CFRP laminate is 350 mm long. Meanwhile, the thickness and the bonding methods of CFRP also influence the final failure modes in terms of CFRP length. The measurement on ultimate load shows that an increase in the length of CFRP up to 200 mm significantly improves the bearing capacity of the reinforced beam. A comparison between a theoretical analysis and the experimental observation shows a good agreement in terms of failure modes indicating the accuracy and the validity of the experiment.

Research on Magnetic Loading in Reliability Enhancement Testing of Low Viscosity Lubricated Bearings

In order to provide a load environment for the reliability enhancement testing of half-size water-lubricated bearing in the reactor coolant pump, enhanced test principle based on water-lubricated bearing failure mode is researched, and an axial and radial magnetic loading system is developed. Three typical failure modes, including wear, lubrication and vibration, are selected, and their test programs are given to research reliability enhancement testing principle. The qualitative and quantitative relations between load and failure are analyzed. On the basis, the static and dynamic load requirements for the enhanced test of half-size water-lubricated bearing are proposed. A magnetic loading system including structure module and control module is built. The static and dynamic load structures of axial loading component are independent. The radial loading component uses an 8-pole scheme. And the control module supports two kinds of control strategy of open-loop and closed-loop. The performances of loading system are verified by the special experiments. The results show that, the wear loss of tile will increase from 1.0 to 1.2 times, and the start-stop times will reduce by 50% to 54% while the load increases 20% in samples. The axial load module can generate static load, impulse and sinusoidal excitation, and static load can be 100 k N when the gap is 2 mm and the current is 1.2 A. Static load,amplitude of impulse excitation and sinusoidal excitation generated by radial load components are 3.7 k N,500 N and 115 N respectively. The feasibility of magnetic loading technique introduced in reliability enhancement test is initially verified. Open-loop control strategy realized by the artificial adjustment of current is more effective for the multi-field coupling bearing test system with loading device.

RESEARCH OF DEFORMATION OF CLAY SOIL MIXTURES MIXTURES / MOLINIŲ GRUNTŲ MIŠINIŲ DEFORMACIJŲ TYRIMAS

The aim of this article is to determine clay soils and clay soils mixtures deformations during drying. Experiments consisted from: a) clay and clay mixtures bridges (height ~ 0,30 m, span ~ 1,00 m); b) tiles of clay and clay, sand and straw (height, length, wide); c) cylinders of clay; clay and straw; clay, straw and sand (diameter; height). According to the findings recommendations for clay and clay mixtures drying technology application were presented. During the experiment clay bridge bearing capacity and failure mode were determined. For investigations Vilnius Gediminas Technical University Civil Engineering Scientific Research Center infrastructure was used. Tyrimo tikslas – nustatyti molinio grunto mišinių džiūvant atsirandančias deformacijas. Eksperimentams buvo naudojama: a) moliniai ir molio mišinių tiltai (aukštis ~0,30 m, tarpatramis ~1,00 m, plotis 0,07–0,1 m); b) plytelės iš molio; molio, smėlio ir šiaudų (l; b; h); c) cilindrai iš molio; molio ir šiaudų; molio, šiaudų, smėlio (d; h). Pagal gautus bandymo rezultatus pateiktos rekomendacijos molinių gruntų mišinių džiovinimo technologijai taikyti. Nustatyta molinių tiltų laikomoji galia ir suirimo pobūdis. Atliekant tyrimus buvo pasinaudota Vilniaus Gedimino technikos universiteto Civilinės inžinerijos mokslo centro MTEP infrastruktūra.

Multiphysics computational analysis of white-etch cracking failure mode in wind turbine gearbox bearings

Wind energy is currently one of the most promising and the fastest-growing installed alternative-energy production technologies. It is anticipated that by 2030, at least 20% of the US energy needs will be provided by this form of energy. The economics of wind energy require that wind turbines (convertors of wind energy into electrical energy) be able to operate for at least 20 years, with only regular maintenance. Unfortunately, many wind turbines require major repairs after only 3–5 years in service, mainly due to the failure of their gear boxes. It is this lack of gear box reliability which is currently compromising wind energy economics. In the present work, a multiphysics computational methodology has been developed and used to analyze the problem of white-etch cracking, one of the key processes responsible for the premature failure of gearbox roller bearings. The multiphysics methodology includes: (a) quantum-mechanical calculations of the hydrogen dissolution and the accompanying grain boundary embrittlement phenomena; (b) atomistic-level kinetic Monte Carlo analysis of hydrogen diffusion from the crack wake into the adjacent unfractured material; (c) cohesive zone type modeling of the intergranular fracture processes; and (d) a conventional displacement-based finite element analysis of the kinematic and structural response of the bearing under service loading conditions. The results obtained clearly revealed the operation of the white-etch cracking phenomena and their possible interaction with the conventional rolling-contact fatigue damage processes.

Brazilian Tests on Transversely Isotropic Rocks: Laboratory Testing and Numerical Simulations

The dominant anisotropy (foliation and bedding) of geological materials, especially of foliated metamorphic rocks such as slates, gneisses, phyllites or schists, and sedimentary rocks with bedding planes, leads to complex fracture mechanical behavior. A series of Brazilian tests on Mosel slate were conducted considering different foliation-loading angles. Fracture patterns and strength of samples were analyzed. In addition, the deformation process and failure behavior of the foliated rock samples during the Brazilian tests were simulated using the discrete element method. The influence of anisotropic strength parameters of weak planes was studied numerically. A diagram of failure mode distribution marked with typical failure fracture patterns for Brazilian tests of transverse isotropic rocks was developed, which results in better understanding of failure modes of Brazilian tests on foliated rocks and allows a more reliable interpretation of strength parameters. It reveals, how the microparameters influence the bearing capacity and failure modes of Brazilian tests for anisotropic rocks.

Analysis and Experimental Study on Mechanical Performance of the Extruded Forming Channel Type Embedded Part

A kind of channel type embedded part which has been disposed through extrusion forming new technology needed to extensive apply in engineering. Theoretical analysis and experimental research have been carried out on shear properties of bolt and one-way static pull-out performance of channel. Got the ultimate bearing capacity, deformation and failure mode, compared the results between test and finite element analysis, fit a formula for calculating the bearing capacity of channel. Experimental result shows that embedded parts working performance is good. It has higher strength than work load and the expected ultimate load according to the theoretical calculation. Meantime, specimens has relatively good ductility before failure. The test results have provided the experimental basis for the application of embedded parts in engineering.

Numerical Simulation on the Mechanical Performance of the Wind Generator Latticed Concrete-Filled Steel Tubular Tower

Nonlinear finite element parameters analysis on the lattice type steel pipe concrete wind turbine tower, it shows the entire process of load bearing, failure mode and ultimate bearing capacity, researches on the influence law of aspect ratio, form of tower webs, tower diameter to thickness ratio and web member stiffness to tower column stiffness ratio on the ultimate bearing capacity and tower failure mode. The finite element analysis results shows that the tower aspect ratio λ, the diameter-thickness ratio γ of tower columns and the increase of stiffness ratio β between web members and tower columns has great influence on ultimate bearing capacity and failure mode, while the form of webs has small influence on that. with the increase of tower aspect ratio λ, the decrease of diameter-thickness ratio γ of tower columns and the increase of stiffness ratio β between web members and tower columns, the ultimate bearing capacity of this kind of latticed towers increase, the failure mode changed from Web local buckling to The combined damage of Web local buckling and the tension tower yield. This paper suggests that in the design of wind turbulent generator tower, the tower aspect ratio λ should be best controlled at 1/9, the bottom layers of this kind of tower should best use the re-divided web members, and other web member forms used on above layers, the diameter-thickness ratio γ of tower column should be taken less than 30, and the stiffness ratio β between webs and columns should be controlled less than 0.05 in order to avoid damage occurring on the tower columns earlier than the webs. The results can provide evidence for the engineering design.

Effect of Loading Direction on the Bearing Capacity of Cold-Reduced Steel Sheets

AbstractThis study is concerned with double-shear bolted connections in cold-reduced steel sheets that undergo the pure bearing failure mode of the inside sheet. Compared to the published test results of bolted connections failing in the net section fracture, those involving the bearing failure mode had very wide scatter in the ultimate test loads of specimens having seemingly similar configurations. This technical note presents the laboratory test results of 51 specimens composed of G2 and G450 steel sheets, which have very different ductility properties. One new and significant finding is that the absolute bearing capacity can be considerably higher in the rolling direction of the cold-reduced steel sheet than in the perpendicular direction, even though the tensile strength has the opposite trend. Another result is that material ductility has a much greater effect on the bearing capacity than on the net section tension capacity. It was also found that snug tightening had little effect on the bearing cap...

Failure Modes and Reliability Analysis of Motor Driving System in ITER Remote Handling Transfer Cask

For remote handling in a far distance and toxic substances leakage must be considered, International Thermonuclear Experimental Reactor has put forward higher requirement for the failure modes and reliability analysis of remote handling system. Based on the actual working condition of motor driving system when transfer cask remote handling the in-vessel components, all the failure modes of the motor driving system were analyzed and distinguished by software Isogragh, the main failure patterns and weak links were the control circuit failure mode, bearing failure mode, electrolytic capacitor and the insulation failure mode. Motor driving system reliability model in series was established, the reliability and mean time between failures were estimated by the component stress analysis method. The above-mentioned methods and results provide the basic references for the system reliability assessment, optimization design, making rapid and accurate judgment for potential failure when systems operating.

The Mechanical Behavior of a Pin-Loaded Hole in a Thermoplastic Composite Laminate

The paper deals with the structural response of mechanically fastened fiber-reinforced laminated thermoplastic composite joints. An experimental investigation was carried out to analyze the behavior of single-pinned joints made with woven glass-reinforced polypropylene composite laminates. A detailed experimental analysis was performed in order to predict the bearing response, failure strength, and failure mode of composite laminates containing a pin-loaded hole. The results obtained allow one to evaluate the influence of geometric parameters and the stacking sequence of laminates on the behavior of such joints.

Experimental Study on Flexural Capacity of Prestressed RC Hollow Slabs Strengthened by CFRP

Based on the experiment of prestressed concrete hollow slab flexural capacity, it obtained CFRP prestressed concrete hollow slab Ultimate bearing capacity, failure mode and load - displacement curve, and analyzed the influence of Mechanical performance and reinforcement effect caused by the paste way and paste amount of CFRP. Based on the test results to determine the most optimal paste way and paste amount of CFRP for the different damage (slight damage, moderate damage and severe damage) prestressed concrete hollow slab to meet their safety requirements.

Composite hollow truss with multiple vierendeel panels

The aim of this study was to evaluate through analytical calculation, two-dimensional elastic modeling, and three-dimensional plastic modeling, the bearing capacity and failure modes of composite hollow trusses bi-supported with a 15 meter span, varying the number of central Vierendeel panels. The study found the proportion span/3 - span/3 - span/3, as the ideal relationship for the truss - Vierendeel - truss lengths, because by increasing the proportion of the length occupied by the central Vierendeel panels, the new system loses stiffness and no longer supports the load stipulated in the project. Furthermore, they can start presenting excessive vertical displacements and insufficient resistance to external shear forces acting on the panels.

Failure analysis of the ball bearings of dental air turbine handpieces

The aim of this study was to identify the nature and causes of deterioration and failure in dental handpiece ball bearings and thus provide guidance for clinical handling for service longevity. The bearings of 36 turbine assemblies were dismantled for visual inspection, documented using a digital camera, and examined using scanning electron microscopy, as appropriate. For the metal parts of the ball bearing assembly, defects observed were mainly wear arising from the running load and corrosion. This was in the form of scratches and discoloured circumferential bands on the balls, and dull or worn surfaces extending around the circumference of the raceways. Cage damage including cracking, fracture, surface rubbing and distortion occurred, in varying degrees, in every failed turbine. Dental ball bearing failure modes have been identified. Cumulative effects of damage from corrosion and mechanical factors lead to handpiece deterioration. The cage was found to be very vulnerable to damage, and this may be the key limitation on bearing lifetime. Autoclaving may contribute to that, as it does to corrosion in the absence of adequate lubrication, but this seems to be minor in comparison to the effects of abuse. There is no justification for failing to observe usage and sterilization instructions.

Analysis of Mechanical Behaviour of the Concreat Filled Double Skin Steel TubesK-Joint

In recent years, a new kind struct of concreat-filled skin steel tubesConcrete-Filled Double Skin Steel Tubes (CFDST),are more used in transmission line constructions. It is a kind of hollow structs, which concentric placed the double skin steel tubes, and filling with concrete between the two steel tubes[.CFDST K-joints on power transmission tower must be finite element simulated to research the capacity of bond-slip between the steel and concrete by the finite element analysis software-ANSYS 10.0 in this paper, and finally gets the ultimate bearing capacity and failure modes of K-joints.

Bearing diagnostics using image processing methods

In complex machines, the failure signs of an early bearing damage are weak compared to other sources of excitations (e.g. gears, shafts, rotors, etc.). The task of emphasizing the failure signs is complicated by the fact that changes in operating conditions influence vibrations sources and change the frequency and amplitude characteristics of the signal, making it non-stationary. As a result, a joint time-frequency representation is required. Previous vibration based diagnostic techniques focused on either the time domain or the frequency domain.The proposed method suggests a different solution that applies image processing techniques to time-frequency or RPM-order representations (TFR) of the vibration signals in the orders-RPM domain.In the first stage, TFRs of healthy machines are used to create a baseline. The TFRs can be obtained using various methods (Wigner-Ville, wavelets, STFT, etc).In the next stage, the distance TFR between the inspected recording and the baseline is computed. In the third stage, the distance TFR is analyzed using ridge tracking and other image processing algorithms. In the fourth stage, the relations between the detected ridges are compared to the characteristic patterns of the bearing failure modes and the matching ridges are selected.The different stages of analysis: baselines, distance TFR, ridges detection and selection, are illustrated with actual data of damaged bearings.

A new method to model a localized surface defect in a cylindrical roller-bearing dynamic simulation

The main failure mode of cylindrical roller element bearings is localized surface defects such as spalls and pits on the surfaces of its races or rollers.1 However, it is difficult to describe the time-varying deflection excitation generated by a defect and the time-varying contact stiffness excitation due to the changes in contact conditions between a roller and the defect when the roller passes over the defect by using the previous defect models for the cylindrical roller bearing. In this work, a new dynamic analysis method is proposed to formulate a localized surface defect more accurately for a cylindrical roller bearing dynamic modeling. A two-degree of freedom dynamic model for a cylindrical roller bearing with a localized surface defect on its races is proposed, which considers both the time-varying deflection excitation and the time-varying contact stiffness excitation produced by the defect. The load-deflection relationship between the roller and the race is considered as non-Hertzian one, which can be used to determine the load-deflection relationship between the logarithmic-profile roller and the races of the cylindrical roller bearing. The numerical results are compared with the available results from the previous defect models in the literature. The effects of the defect width, depth, and types are investigated. To validate the proposed model, an experiment is also presented. The results show that the proposed method describes a more accurate in describing the real excitation produced by the defect and provides a new method to simulate the effects of a localized surface defect on the vibration response of a cylindrical roller bearing.