Dynamic Fatigue Tests Research Articles

Influence of different movement kinematics on cyclic fatigue resistance of nickel-titanium instruments designed for retreatment

Aim: The objective of this study was to investigate the effect of different types of movement kinematics on the resistance of the ProTaper D3 retreatment file to cyclic fatigue. Materials and Methods: Eighty ProTaper Universal D3 (20.07) files were utilized in this study. The cyclic fatigue tests were performed using a specially manufactured dynamic cyclic fatigue testing device, which has an artificial stainless steel canal having 60° of curvature angle and 5 mm of curvature radius. The files were randomly divided into four groups (Group 1: Rotary motion [RM]; Group 2: Adaptive motion [AM]; Group 3: Reciprocating motion [RCM]; Group 4: WaveOne motion [WM]). The movements of files until the files broke were recorded in “MOV” format using a device employing a slow-motion camera. The number of cycles to failure was calculated for each group. The data were analyzed statistically using one-way ANOVA and Tukey's honestly significant difference test (P Results: The cyclic fatigue resistance of the AM group (3357.9 ± 88.5) was significantly higher than that of the other groups (P Conclusion: Within the limitations of the present study, resistance of ProTaper Universal D3 file to the cyclic fatigue significantly increased in the AM group when compared to the RCM and WM groups.

Effect of adaptive motion on cyclic fatigue resistance of a nickel titanium instrument designed for retreatment.

ObjectivesThe aim of this study was to evaluate the cyclic fatigue resistance of the ProTaper Universal D1 file (Dentsply Maillefer) under continuous and adaptive motion.Materials and MethodsForty ProTaper Universal D1 files were included in this study. The cyclic fatigue tests were performed using a dynamic cyclic fatigue testing device, which had an artificial stainless steel canal with a 60° angle of curvature and a 5 mm radius of curvature. The files were randomly divided into two groups (Group 1, Rotary motion; Group 2, Adaptive motion). The time to failure of the files were recorded in seconds. The number of cycles to failure (NCF) was calculated for each group. The data were statistically analyzed using Student's t-test. The statistical significant level was set at p < 0.05.ResultsThe cyclic fatigue resistance of the adaptive motion group was significantly higher than the rotary motion group (p < 0.05).ConclusionWithin the limitations of the present study, the ‘Adaptive motion’ significantly increased the resistance of the ProTaper Universal D1 file to cyclic facture.

Highly flexible InSnO electrodes on thin colourless polyimide substrate for high-performance flexible CH3NH3PbI3 perovskite solar cells

Abstract We fabricated high-performance flexible CH3NH3PbI3 (MAPbI3) perovskite solar cells with a power conversion efficiency of 15.5% on roll-to-roll sputtered ITO films on 60 μm-thick colourless polyimide (CPI) substrate. Due to the thermal stability of the CPI substrate, an ITO/CPI sample subjected to rapid thermal annealing at 300 °C showed a low sheet resistance of 57.8 Ω/square and high transmittance of 83.6%, which are better values than those of an ITO/PET sample. Outer and inner bending tests demonstrated that the mechanical flexibility of the ITO/CPI was superior to that of the conventional ITO/PET sample owing to the thinness of the CPI substrate. In addition, due to its good mechanical flexibility, the ITO/CPI showed no change in resistance after 10,000 cycle outer and inner dynamic fatigue tests. Flexible perovskite solar cells with the structure of Au/PTAA/MAPbI3/ZnO/ITO/CPI showed a high power conversion efficiency of 15.5%. The successful operation of these flexible perovskite solar cells on ITO/CPI substrate indicated that the ITO film on thermally stable CPI substrate is a promising of flexible substrate for high-temperature processing, a finding likely to advance the commercialization of cost-efficient flexible perovskite solar cells.

Structural behaviour of prestressed concrete sleepers produced with high performance recycled aggregate concrete

© 2016, RILEM.A comparative analysis of the structural behaviour of prestressed concrete sleepers made with high performance concrete (HPC) and high performance recycled aggregate concrete (HPRAC) is presented in this study. Two types of HPRAC sleepers were tested, using 50 and 100% of recycled concrete aggregate (RCA) in replacement of coarse natural aggregates. The RCA employed in this research was sourced from crushing rejected HPC sleepers. The aim of this study was to determine through analysis if the HPRAC sleepers’ behaviour fulfilled the European minimum requirements standards for prestressed concrete sleepers and compare their experimental behaviour with that of the HPC sleepers. The three types of prestressed concrete sleepers were subjected to static load tests at rail-seat and centre section (positive and negative load). In the centre section tests a comparative study between the experimental results and the proposed values of four assessment methods of ultimate capacity was carried out. Dynamic load and fatigue tests were also performed at the rail-seat section. The HPRACs and HPC sleepers met all the structural requirements for prestressed concrete sleepers. The experimental results determined the satisfactory performance of the HPRAC-50 and the HPRAC-100, which was very similar to that of the HPC sleepers. The load–strain behaviour recorded via the use of strain gauges on the prestressing bars revealed slightly higher stiffness of the HPC sleepers. The values obtained from the four assessment methods of ultimate capacity were also accurate when applied to HPRAC.

Association of Muscle Endurance, Fatigability, and Strength With Functional Limitation and Mortality in the Health Aging and Body Composition Study.

Mobility limitation is highly prevalent among older adults and is central to the loss of functional independence. Dynamic isokinetic muscle fatigue testing may reveal increased vulnerability to disability and mortality beyond strength testing. We studied community-dwelling older adults enrolled in the Health Aging and Body Composition study (age range: 71-82) free of mobility disability and who underwent isokinetic muscle fatigue testing in 1999-2000 (n = 1,963). Isokinetic quadriceps work and fatigue index was determined over 30 repetitions and compared with isometric quadriceps maximum torque. Work was normalized to leg lean mass accounting for gender-specific differences (specific work). The primary outcome was incident persistent severe lower extremity limitation (PSLL), defined as two consecutive reports of either having a lot of difficulty or being unable to walk 1/4 mile or climb 10 steps without resting. The secondary outcome was all-cause mortality. There were 608 (31%) occurrences of incident PSLL and 488 (25%) deaths during median follow-up of 9.3 years. After adjustment, lower isokinetic work was associated with significantly greater risks of PSLL and mortality across the full measured range. Hazard ratios per standard deviation lower specific isokinetic work were 1.22 (95% CI 1.12, 1.33) for PSLL and 1.21 (95% CI 1.13, 1.30) for mortality, respectively. Lower isometric strength was associated with PSLL, but not mortality. Fatigue index was not associated with PSLL or mortality. Muscle endurance, estimated by isokinetic work, is an indicator of muscle health associated with mobility limitation and mortality providing important insight beyond strength testing.

예인 음탐기용 케이블 개발

Cables for Towed Array Sonar System(TASS) were developed. In order to verify the performance of cables, environmental and operational conditions as well as functional requirements were investigated during design stage. Double armored high and low voltage integrated cable for towed body and two kinds of cables, armored and light weight power and optic hybrid cables for towed array sensor system were developed by modeling and simulation. Customized manufacturing process and test method, such as foam extrusion and dynamic fatigue test were applied to this development. In conclusion, underwater towed hybrid cable with high tensile strength and compact structure were developed.

Roll-to-roll slot-die coating of 400 mm wide, flexible, transparent Ag nanowire films for flexible touch screen panels.

We report fabrication of large area Ag nanowire (NW) film coated using a continuous roll-to-roll (RTR) slot die coater as a viable alternative to conventional ITO electrodes for cost-effective and large-area flexible touch screen panels (TSPs). By controlling the flow rate of shear-thinning Ag NW ink in the slot die, we fabricated Ag NW percolating network films with different sheet resistances (30–70 Ohm/square), optical transmittance values (89–90%), and haze (0.5–1%) percentages. Outer/inner bending, twisting, and rolling tests as well as dynamic fatigue tests demonstrated that the mechanical flexibility of the slot-die coated Ag NW films was superior to that of conventional ITO films. Using diamond-shape patterned Ag NW layer electrodes (50 Ohm/square, 90% optical transmittance), we fabricated 12-inch flexible film-film type and rigid glass-film-film type TSPs. Successful operation of flexible TSPs with Ag NW electrodes indicates that slot-die-coated large-area Ag NW films are promising low cost, high performance, and flexible transparent electrodes for cost-effective large-area flexible TSPs and can be substituted for ITO films, which have high sheet resistance and are brittle.

Biomechanical Analysis of Individual All-Ceramic Abutments Used in Dental Implantology

Abstract The paper presents the results of finite element analysis and experimental testing under simulated physiological loading conditions on issues shaping the functional properties of individual all-ceramic abutments manufactured by CAD/CAM technology. The conducted research have cognitive significance showing the all-ceramic abutment behavior, as a key element of the implantological system, under the action of cyclic load. The aim of this study was evaluation the fatigue behavior of yttria-stabilized zirconia abutment submitted to cyclic stresses, conducted in accordance with EN ISO 14801 applies to dynamic fatigue tests of endosseous dental implants.

Magnetic memory signals of ferromagnetic weldment induced by dynamic bending load

Metal magnetic memory testing is a novel method for evaluating the fatigue damage of ferromagnetic weldments. To promote a further understanding of the impact of fatigue loads on magnetic memory signals of weldments, the normal component of magnetic signals, Hp(y), on the centre-notched welding specimens were measured during dynamic bending fatigue tests. The variation of peaks–troughs differential value ΔHp(y) of magnetic signals and its maximum gradient Kmax at the welded joint were also investigated. Results indicated that the ΔHp(y) on scanning line near the notch increased sharply when stress concentration and crack initiation appeared in the specimens. The microstructures on scanning lines were also examined. It shows that there was an increase in intragranular slips with the increase in loading cycles, and the change in crystallographic textures and movement of dislocations contributed to the magnetic signals varying significantly. The maximum gradient Kmax was found to increase exponentially with the increase in crack length, which is well coincident with the analytic result of the magnetic dipole model. The research provides a potential possibility of quantitative evaluation on stress concentration and crack in weldments under dynamic bending loads.

Self-gradient mechanism, morphology and damping analysis of a thickness continuous gradient epoxy–polyurethane interpenetrating polymer network

A simple and affordable gradient-distributing interpenetrating polymer network (IPN) composite was created that takes advantage of the relatively poor compatibility and the curing rate discrepancy between epoxy (EP) and polyurethane (PU) resins. Organic element content analysis (CHNS/O) and attenuated total reflection infrared spectroscopy (ATR-FTIR) reveal that the PU content is a gradient that changes along the direction of the thickness. Morphology analysis by scanning electron microscopy (SEM) and atomic force microscopy (AFM) proves that it has a continuously changing modulus with no stratified structure. Dynamic thermomechanical analysis (DMA) and fatigue testing demonstrate that the composite has better performances than traditional homogeneous IPNs with the same compositions.

Effects of Dental Implant-abutment Interfaces on the Reliability of Implant Systems

In this paper, by analyzing the effects of two different kinds of implant-abutment connection interfaces under the same working condition on the mechanical and fatigue performances of the implant system as well as on the surrounding bones, we intend to study such effects on the reliability of the implants and provide a theoretical basis for the design and clinical application of dental implant systems. For the purpose, we adopt a 3-D modeling method to establish the model, and use FEA (finite element analysis) to carry out static mechanic and fatigue analysis on the implant system and its surrounding bones; then we make the two implant systems, and carry out fatigue tests on a dynamic fatigue testing machine to verify the FEA results. After comparing the results from the two different systems, we find that the stress distribution and fatigue safety factor of the system which has deeper axial matching of the taper connection are better than those of the other system, that is to say, between the two major elements of a implant system, the axial length of the connecting taper and the size of the hexagon, the former has greater effects than the latter. When the axial matching is deeper, the stress distribution of the implant system will be better, the fatigue safety factor will be higher, and the implant system will be more reliable.

Slow crack growth behavior of silicon nitride ceramics in cryogenic environment

The slow crack growth behavior of Si3N4 ceramics in ambient and cryogenic environment had been investigated by dynamic fatigue testing. The fracture strength was principally dependent on stress rate at 293K while the fracture strength was comparatively independent of stress rate at 77K. The morphologies of the fracture surface and the crack tip region were examined to correlate with the slow crack growth behavior. The experimental results revealed that the Si3N4 ceramics exhibits a very high resistance to slow crack growth (SCG) in cryogenic environment. The reasons for such high resistance are likely related to the local residual stress associated with either the thermal anisotropies arising from the presence of the grain boundary glass phase, or from the crack tip shielding mechanism.

Experimental evaluation of asphalt material for interlayer in rigid–flexible composite pavement

Bond condition between layers in a rigid–flexible composite pavement is a key factor affecting the durability and maintenance of the pavement. High-temperature properties and viscosity of four interlayer asphalt materials were tested by rotational rheometer. Dynamic mechanical temperature sweep tests and shear fatigue tests were also carried out. The results indicated that AR (asphalt with rubber) and SBS modified asphalt are better asphalt materials for an interlayer, as their pavement performances are overall better than those of matrix asphalt A-50 (asphalt of penetration 50) and A-70 (asphalt of penetration 70). Compatibility of matrix asphalt and modifying agent has significant impact on fatigue properties of SBS polymer modified asphalt. SBS modified asphalt is recommended for an interlayer, for its excellent pavement performance and construction convenience. The optimum dosage of SBS modified asphalt is determined by interlayer bond test. The findings of this study could provide an important reference for choosing interlayer asphalt material for rigid–flexible composite pavements.

Detection of Non-Metallic Inclusions in Quenched and Tempered Steel Bars by XCT and after Fatigue Life Testing

Non-metallic inclusions (NMIs) determine to a high degree the quality and cleanness of steel and are often the reason for functional failure, especially in dynamic-stressed components. Therefore, it is important to have accurate, fast, and reliable characterization methods for these unwanted material inhomogeneities. In this paper, two different methods for the detection of NMIs are compared: X-ray-computed tomography (XCT) and fatigue life testing. XCT allows the detection and analysis of material inhomogeneities and their positions in a 3D volume. The evaluation of XCT-data of Fe-based materials can be rather difficult, since the results are usually prone to image noise, offer poor contrast, and the interpretation is affected by artifacts. Suitable evaluation strategies for detection and classification are presented. The degradation of steel samples by dynamic fatigue testing is a destructive way of determining the existence of harmful NMIs. If there is an NMI of critical size in the sample, a functional failure may occur. The fracture surface is investigated by scanning electron microscopy (SEM), equipped with an energy dispersive X-ray (EDX) spectroscopy unit in order to identify shape, type, and chemical composition of the harmful NMI.

Analysis of Static Stress in an Alloy Wheel of the Passengercar

The vehicle may be towed without the engine but it is not possible without the wheels. Road wheel is a significant structural member of the vehicular suspension system that supports the static and dynamic loads encountered during vehicle operation. As in the case of an automobile wheel maximum load is applied on the alloy wheel. Proper analysis of the alloy wheel plays a significant role for the safety of the passenger cars. Alloy wheels which are intended for normal use on passenger cars, undergo three tests and have to pass before going into the production: Dynamic Cornering Fatigue Test, Dynamic Radial Fatigue Test and Impact Test. Most of aluminium alloy wheels manufacturing companies have done several testing of their product however information of their method on simulation test is often kept limited. During a part of research a static and fatigue analysis of aluminum alloy wheel A356.0 was carried out using FEA package. The 3-D model was imported from CATIA into ANSYS using the appropriate format. Finite element analysis (FEA) is carried out by simulating the test conditions to analyze stress distribution and fatigue life of the aluminium alloy wheel rim of passenger car. Experimental analyses are carried out by radial fatigue testing machine for evaluation of fatigue life under influence of camber angle. The test indicates that integrating FEA and nominal stress method is a good and efficient method to predict alloy wheels fatigue life. In this paper by observing the results of both static and dynamic analysis the aluminium alloy is suggested as better material.

Synergistic effects of carbon nanotubes and carbon black on the fracture and fatigue resistance of natural rubber composites

ABSTRACTThe quasi‐static fracture and dynamic fatigue behaviors of natural rubber composites reinforced with hybrid carbon nanotube bundles (CNTBs) and carbon black (CB) at similar hardness values were investigated on the basis of fracture mechanical methods. Mechanical measurement and J‐integral tests were carried out to characterize the quasi‐static fracture resistance. Dynamic fatigue tests were performed under cyclic constant strain conditions with single‐edged notched test pieces. The results indicate that synergistic effects between CNTBs and CB on the mechanical properties, fracture, and fatigue resistance were obtained. The composite reinforced with 3‐phr CNTBs displayed the strongest fatigue resistance. The synergistic mechanisms and dominating factors of quasi‐static and dynamic failure, such as the dispersion state of nanotubes, hybrid filler network structure, strain‐induced crystallization, tearing energy input, and viscoelastic hysteresis loss, were examined. The weakest fatigue resistance of the composite filled with 5‐phr CNTBs was ascribed to its strikingly high hysteresis, which resulted in marked heat generation under dynamic fatigue conditions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42075.

Influence of Antioxidant-Enhanced Polymers in Bitumen Rheology and Bituminous Concrete Mixtures Mechanical Performance

This paper evaluates the effect of polymer enhancement with antioxidant in the rheological properties of bitumen and mechanical properties of bituminous concrete mixture (BCM). In this study, two antioxidant-enhanced polymers were utilized in mitigating bitumen hardening due to aging. The rheological testing consists of temperature sweep using Dynamic Shear Rheometer at various aging conditions. Critical stiffness temperature data from the sweep test suggested that enhanced polymer exhibits less long-term hardening and brittleness compared to standard polymer. The mechanical testing consists of dynamic modulus, indirect tensile, flow number, and beam fatigue tests on BCM exposed to short-term aging. Hamburg wheel tracking test was also performed to assess moisture-damage susceptibility. It is found that the enhanced-polymer BCM exhibited higher modulus, higher tensile strength ratio, improved rutting resistance, lower moisture-damage susceptibility, and slightly increased fatigue life as compared to standard-polymer BCM.

A review on reliability of electronic packaging in micro/nano manufacturing

Electronic packaging is a critical part of products such as computers, smart phones, automotive components and other electronic devices. Along with the development of society and economy, the demand for electronic devices and its quality has increased rapidly in recent years. Thus, it is necessary to research the reliability of electronic packaging. This paper presents a review of recent investigations on the reliability of electronic packaging components. The dynamic characteristics and fatigue test under different loading conditions are discussed, including vibration loading, thermal loading and combined loading. Finite element method (FEM) is used frequently in the studies as well as experimental test. Finally, it is significant to emphasise the importance of electronic packaging.

Innovations in Testing Material Applied to Elastomer Crack Propagation and Light Composite Vibrational Fatigue

Means of experimentation are developed, first for a specific application, and are then implemented on products such as dynamic testing machines and fatigue tests rigs. Two examples illustrate this way of introducing innovative development.First, in order to characterize elastomers’ resistance to tearing, a new methodology was defined and tested on a fatigue test machine for crack propagation analysis. This functionality was then implemented on standard products.Second, a fatigue testing machine was modified in order to characterize the vibration fatigue of a light composite structure at high temperature without any added mass or rigidity. The fatigue test was achieved by exciting a test beam at natural frequency with constant maximal strain.

Simulation Method Based on the Stress Circle for the Moment Output of Car Wheel Dynamic Bending Fatigue Testing Machine

Simulation Method Based on the Stress Circle for the Moment Output of Car Wheel Dynamic Bending Fatigue Testing Machine