Fatigue Ratio Research Articles

821P - Tolerability associated with sunitinib (SU) 2-week on and 1-week off schedule (2/1 schedule) compared with its standard schedule in metastatic RCC (mRCC): Meta-analysis

SU is the 1st line standard treatment for mRCC and it requires 4-week on treatment and 2-week off as a standard schedule for mRCC. The treatment is associated with several adverse events (AEs), such as fatigue, hand-foot syndrome (HFS), neutropenia, thrombocytopenia etc. Schedule modifications of SU including 2/1 schedule are studied and the results provided the total number of treatment-related adverse events decreased in 2/1 schedule without compromising efficacy. However, the effect of 2/1 schedule on individual AEs was not clearly understood. This analysis included 1 randomized controlled trial (RCT): Lee et al. 2015 (RESTORE trial, NCT00570882) and 4 non-randomized controlled studies (non-RCT): Neri et al. 2013, Kondo et al. 2014, Bradarda et al. 2015 and Pan et al. 2015. The primary objective was to estimate risk of individual adverse events in SU 2/1 schedule versus standard one and secondary objectives were to evaluate efficacy outcomes. 7 AEs were evaluated with a standard data of RCT compared with the weighted meta-analysis data (non-RCT meta). Meta-analysis technique, including fixed effects modelling with Review Manager v5.3 was used to pool study-level data using the inverse-variance of each study as the weight. Data cut-off for this analysis: Apr 2015 The selected studies included a total of 484 patients with mRCC, which comprised 74 and 410 from RCT and non-RCTs, respectively. The risk ratio of fatigue and neutropenia for 2/1 schedule vs. standard significantly decreased in both RCT and non-RCT meta (risk ratio (RR) of fatigue: 0.69 [95% confidence intervals (CI) 0.51, 0.95] vs. 0.75 [0.63, 0.89]; RR of neutropenia 0.60 [0.37, 0.99] vs. 0.58 [0.41, 0.83]). Other AEs also tended to decrease in both sets except diarrhea and anorexia. Efficacy outcomes were comparable between 2/1 and standard schedule. This meta-analysis suggests that 2/1 schedule of SU compared to its standard one decreases risk of fatigue and neutropenia and also favoured to control other AEs without compromising efficacy even with limited sources of data. A patient-level meta-analysis to confirm these findings is warranted.

Al7075-T6의 압축잔류응력 및 피로 수명에 미치는 재피닝의 효과

The effects of re-peening on the compressive residual stress and fatigue life of Al7075-T6 were investigated. The compressive residual stress induced on the surface of components by shot peening is known to increase the fatigue life. However, the fatigue load relaxes the compressive residual stress of components. Re-peening is a technique to again induce the relaxed compressive residual stress and increase the total fatigue life of components. In this study, the re-peening process was applied to fatigue-loaded specimens. The compressive residual stress and fatigue life were examined for re-peened specimens with fatigue ratios of 30%, 50%, and 70%. The results showed that the compressive residual stress of the specimens was relaxed under the fatigue load. The re-peening process significantly increases the compressive residual stress and total fatigue life.

Intrinsic high cycle fatigue behavior of ultrafine grained pure Cu with stable structure

Ultrafine grained (UFG) materials have attracted considerable attention owing to their unique microstructure and mechanical properties. However, the easy formation of large-scale shear bands and severe grain coarsening during cyclic deformation gives rise to enormous difficulties when investigating the intrinsic fatigue behavior of UFG materials. Herein, we discuss the fabrication of an ideal model material, based on pure Cu, by friction stir processing (FSP), which exhibits equiaxed ultrafine grains, low dislocation density, and a high ratio of high-angle grain boundaries. This model material was used to investigate the intrinsic high cycle fatigue behavior of UFG material. It was found that an enhanced fatigue limit and fatigue ratio can be achieved by FSP Cu due to its uniform and stable UFG structure. Instead of traditional large-scale shear bands, protrusion was found to be the main surface damage morphology for FSP Cu during high cycle fatigue deformation, and no obvious grain coarsening was observed. Dislocation related activity also dominated, but was limited to the ultrafine grains without the formation of regular dislocation structures.

Optimizing Resistance During Multiple-Set Weight Training to Increase Training Volume for Rural Firefighters

PURPOSE:In this study, we hypothesized that a greater training volume would be produced using a training protocol where resistance is decreased with each set (DR) compared to a constant resistance (CR) protocol. In order to develop DRs, we used the subject’s fatigue ratio (using an individualized regression equation) from a CR training protocol where the number of repetitions declines with each set. METHODS:20 active-duty male firefighters (mean±SD, age = 32± 7yr, height = 180±5 cm, body mass = 96±16 kg, fire service = 9±7 yr) completed 4 sets at 65% of their 1RM CR and DR bench press, lat pulldown, and leg press exercises to failure with 30 second rest intervals. Exercise trials were performed in a random counterbalanced order. Data were analyzed using paired sample t-tests. RESULTS:There was a greater training volume (P<0.01) when subjects trained with DR sets compared to training with CR sets at all three exercises (table 1). CONCLUSIONS:In male firefighters, a greater training volume is attained using this DR method based on subject’s fatigue ratio than when using a CR training method suggesting that this may be a more effective training method.Table 1: Training volumes (kg, sets × reps × resistance) completed during 4 set exercises.

A Study of High Cycle Fatigue Fracture Behavior of Three Types of Steels Used in Automotive Industry

High cycle fatigue fracture behavior of three different steel grades used extensively in automotive industry i.e. Microalloyed (MA), Quench and Tempered (QT) and Bainitic steel (BS) were studied using Rotating Bending Fatigue test and were compared. The results indicated that the fatigue strength of BS is higher than that of QT and MA steel in both longitudinal and transverse direction. The Endurance strength obtained for BS is higher than that of QT and MA by 12 and 18.4 % in longitudinal direction and 3.2 and 33.3 % in transverse direction. But, fatigue ratio of MA steel in longitudinal direction is higher as compared to that of BS and QT steel and in transverse direction the same is lower than BS and similar to QT steel. Microstructural analysis revealed the presence of full Bainitic structure in case of BS as against the pearlite–ferrite plus Bainitic structure for QT steel and pearlite with grain boundary ferrite for MA steel. The presence of full Bainitic microstructure in BS may be the reason of its higher fatigue strength.

Compression Fatigue Crack Growth in Nacre and Its Implication on the Mechanical Performance of Orthopedic Implants

The aim of the present review is to present some phenomenological observations on compression fatigue crack propagation of nacre samples. The first part of the paper reviews the characteristics of hierarchical structure and the mechanical properties of nacre, which characterize its specific properties. We have investigated the main chemical constituents of nacre and determined their mineral elements. Electron microscopy studies revealed that nacre is composed of a single-crystal aragonite. In the second part of the paper samples of nacre have been tested in compression-compression fatigue under cyclic loading and a Paris curve have been constructed at a fatigue ratio of about 10, subjected to a 30 Hz sinusoidal compressive load. It has been demonstrated that two driving forces ΔK and Kmax mainly govern the overall fatigue crack growth of nacre. Nacre shows considerable ability to stop cracking. By means of axial compression tests, we identified a single elastic and inelastic property. Measurements based on experiments were first done. Mean values of compressive strength and modulus of elasticity were obtained for several samples. A three-point bending test was performed on polished nacre samples according to the international standards for Young’s modulus, bending strength. An attempt is made to explain qualitatively the mechanical behavior of nacre in terms of its submicroscopic structure. It is concluded that the precise geometric arrangement of the plates is highly important. The results obtained provide a director for the design of orthopedic implants.

Enhancing high-cycle fatigue properties of cold-drawn Fe–Mn–C TWIP steels

High-cycle fatigue properties of cold-drawn twinning-induced plasticity (TWIP) steel, a favored candidate for replacing fully pearlitic (FP) steels in wire applications, were investigated. The high-cycle fatigue tests were conducted on cold-drawn TWIP and FP steels that had comparable ultimate tensile strength for comparison. Fatigue strength of both TWIP and FP steels increased with the tensile strength, but the TWIP steel cold-drawn to a tensile strength of 1.5GPa exhibited a very low fatigue ratio (a ratio of fatigue strength to tensile strength) which deviated far from the predicted linear relationship. Fracture surface analysis showed that crack initiation mainly occurred at the ferrite matrix in FP steels, while either at grain or twin boundaries in TWIP steels where a large density of dislocations piled up during cold drawing. In the case of TWIP steels, the presence of inclusions at grain boundaries led to high local stress concentration and caused early intergranular fatigue cracking as notch sensitivity increased with tensile strength. Subsequent annealing after cold-drawing effectively increased fatigue strength of TWIP steels. It was suggested that TWIP steel revealing both high tensile strength and excellent high cycle fatigue strength could be a promising alternative for replacing conventional FP steels.

Adaptation and validation of stochastic limiting strain distribution and fatigue ratio concepts for perpetual pavement design

Traditional perpetual pavement thickness design is based, in part, on controlling strain levels at the bottom of the asphalt concrete layer below an endurance limit to prevent bottom-up fatigue cracking (FC). A field-based limiting strain threshold was developed from cumulative distributions of field-measured tensile strains in the 2003 and 2006 research cycles at the National Center for Asphalt Technology Pavement Test Track to understand the limiting strain necessary to control FC. Additionally, the fatigue ratio, the ratio of the nth percentile strain to the fatigue endurance limit, was developed. Both the tensile strain distributions and fatigue ratios showed a clear difference between sections that experienced bottom-up FC and those that did not. However, it is necessary to adapt these thresholds to strains predicted by perpetual pavement design tools. PerRoad, a stochastic perpetual pavement design programme, was used to predict strains for the same 2006 sections. Previously developed strain distributions and fatigue ratios were adjusted to reflect observed differences in predicted and measured strains. Cumulative distributions and fatigue ratios based on predicted strains for the 2009 research cycle validated the updated limiting strain distribution and maximum fatigue ratios for designing perpetual pavements to resist bottom-up FC.

Effect of heterogeneous precipitation caused by segregation of substitutional and interstitial elements on mechanical properties of a β-type Ti alloy

This study investigates the effect of heterogeneous precipitation induced by the segregation of substitutional and interstitial elements in Ti–29Nb–13Ta–4.6Zr alloy (TNTZ) on its mechanical properties. For this, samples both with and without segregation of substitutional elements were prepared, with only the latter being subjected to long-term homogenization. It was found that micro-scale segregation of substitutional elements such as Nb, Ta, and Zr does not significantly affect mechanical properties such as fatigue strength, not even if heterogeneous precipitation occurs as a result of this segregation. On the other hand, segregation of interstitial elements was achieved by controlling the aging time. The segregation of interstitial elements creates precipitate-free zones (PFZs), grain boundary (GB) plates, and Widmanstätten α phases with migrating O atoms that all significantly affect the mechanical properties. Specifically, the PFZs have the potential to improve fatigue life, while the Widmanstätten α phase increases the tensile strength and reduces the fatigue ratio, the GB-plates reduce elongation, These results indicate that the formation of a Widmanstätten α phase by the migration of interstitial elements has a varying influence on the tensile and fatigue properties.

A Descending Resistance Sets Produces Greater Training Volume than a Constant Resistance Sets

PURPOSE:When an experienced resistance-trained individual performs multiple sets with a short rest period, such as 1 minute and 30 seconds between sets, the resistance must be reduced to maintain the same number of repetitions (reps) until fatigue. Otherwise, the number of reps will be reduced if the same resistance is used. There is no standard method for optimizing resistance to maximize training volume when using multiple sets with short rest periods. In this study, we hypothesized that a greater training volume (sets × reps × resistance) would be produced using a four week training method where resistance is decreased with each set (DR) compared to a four week CR method. In order to develop DR sets, we used the subject’s fatigue ratio (using an individualized regression equation) from a CR protocol where the number of repetitions declines with each set. METHODS: Ten male subjects (mean±SD, age = 30±5 yr, height = 175±5 cm, body mass = 78±4 kg, 1RM = 127±9 kg, weight training experience = 6±2 yr) completed pre and post training volume tests of 4 sets at 80% and 75% of their 1RM CR bench press. During these pre and post tests, four week muscular endurance intensities equivalent to 80% and 75% 1RM CR or DR bench press exercise trainings were performed in counterbalanced order. Data was analyzed using paired sample t-tests. RESULTS: There were greater increases with training volume (p < 0.05) when subjects trained with DR sets compared to training with CR sets after a four week training period for each condition (table 1). CONCLUSIONS: In males, a greater training volume is attained using a four week DR method based on subject’s fatigue ratio than when using a four week CR training method. This suggests that DR training may be more effective than CR training.Table 1: Training volumes (kg, sets × reps × resistance) completed during 4 set exercises.

Fatigue behaviors of AISI 316L stainless steel with a gradient nanostructured surface layer

By means of surface mechanical rolling treatment (SMRT), a gradient nanostructured (GNS) surface layer was formed on AISI 316L stainless steel. The mean grain size is ∼30nm in the topmost surface layer and increases with depth. Tension–compression fatigue measurements were performed on the SMRT sample under the stress-controlled mode. In comparison with the coarse-grained sample, the fatigue strength of the SMRT sample is significantly enhanced in both the low- and high- cycling fatigue regimes. Meanwhile, the fatigue ratio is evidently elevated with an increasing tensile strength in the SMRT sample. The initiation and growth of cracks, the cyclic deformation behaviors, as well as effects of strength and residual stresses, have been investigated to clarify the fatigue mechanism of the SMRT sample. The results emphasized the GNS surface layer enhances the fatigue property by suppressing the initiation of cracks and accommodating a remarkable cyclic plastic strain amplitude.

Fatigue behaviour of clinched joints in a steel sheet

AbstractClinch joining has been used in sheet metal work owing to its simplicity and because it facilitates the joining dissimilar metal sheets. In this study, monotonic and fatigue tests were conducted using coach‐peel and cross‐tension type specimens to evaluate the fatigue strength of clinch joints in a cold‐rolled mild steel sheet. The monotonic experimental results reveal that the coach‐peel specimen exhibits the lowest monotonic strength among the three specimen configurations. The coach‐peel and cross‐tension specimen geometries exhibit very low fatigue ratios, compared with the tensile‐shear specimen. The maximum von Mises and principal stresses at the fatigue endurance limit are much higher than the engineering tensile strengths of the steel sheet used to determine the three specimen geometries. Compared with the effective stress and maximum principal stress, the Smith–Watson–Topper fatigue parameter can be used for an appropriate prediction of the current experimental fatigue life. With regard to the coach‐peel specimen geometry, all samples exhibit pull‐out failure mode in the fatigue testing range. However, for the cross‐tension specimen geometry, mixed (pull‐out and interface) and interface failure modes occurred, depending on the number of cycles to failure.

Correlation between fretting and plain fatigue using fatigue damage gradient

Fretting fatigue is correlated with plain fatigue in order to develop a method to estimate fretting fatigue life from plain fatigue data. Fretting fatigue experiments as well as plain ones were conducted to obtain fatigue life data at various conditions. Finite element analyses were conducted to evaluate the Smith-Watson-Topper (SWT) fatigue damage parameter around crack initiation location. It is revealed that the SWT in fretting fatigue decays exponentially away from the surface. Moreover, a correlation function exists that relates the gradient of normalized SWT at the surface to the maximum SWT ratio of plain fatigue to fretting fatigue at the same life. It is demonstrated that equivalent SWT for fretting fatigue, which is determined from the correlation function, can be compared directly with plain fatigue data for estimation of fretting fatigue life.

Fatigue behaviour of glass fibre reinforced epoxy composites enhanced with nanoparticles

Nanoparticle reinforcement of the matrix in laminates has been recently explored to improve mechanical properties, particularly the interlaminar strength. This study analyses the fatigue behaviour of nanoclay and multiwalled carbon nanotubes enhanced glass/epoxy laminates. The matrix used was the epoxy resin Biresin® CR120, combined with the hardener CH120-3. Multiwalled carbon nanotubes (MWCNTs) 98% and organo-montmorillonite Nanomer I30 E nanoclay were used. Composites plates were manufactured by moulding in vacuum. Fatigue tests were performed under constant amplitude, both under tension–tension and three points bending loadings. The fatigue results show that composites with small amounts of nanoparticles addition into the matrix have bending fatigue strength similar to the obtained for the neat glass fibre reinforced epoxy matrix composite. On the contrary, for higher percentages of nanoclays or carbon nanotubes addition the fatigue strength tend to decrease caused by poor nanoparticles dispersion and formation of agglomerates. Tensile fatigue strength is only marginally affected by the addition of small amount of particles. The fatigue ratio in tension–tension loading increases with the addition of nanoclays and multi-walled carbon nanotubes, suggesting that both nanoparticles can act as barriers to fatigue crack propagation.

Study on Wear Ratio Analysis of Materials by Computer Image Technology

Wear particles in lubricating grease used in ball grooves of a heavy load tracked vehicle’s master clutch’s release mechanism were observed and its digital photos were taken by a ferroscope. Those images were analyzed quantitatively via computer image technology by analyzing the configuration, size, color, and area percentage of wear particles. Wear ratio of abrasion, adhesion, contact fatigue and corrosion wear are quantificationally analyzed.

Analyzing the Effect of Fiber, Yarn and Fabric Variables on Bagging Behavior of Single Jersey Weft Knitted Fabrics

This research investigates the effect of fiber, yarn and fabric variables on the bagging behavior of single jersey weft knitted fabrics interpreted in terms of bagging fatigue percentage. In order to estimate the optimum process conditions and to examine the individual effects of each controllable factor on a particular response, Taguchi's experimental design was used. The controllable factors considered in this research are blending ratio, yarn twist and count, fabric structure and fabric density. The findings show that fabric structure has the largest effect on the fabric bagging. Factor yarn twist is second and is followed by fabric density, blend ratio and yarn count. The optimum conditions to achieve the least bagging fatigue ratio were determined.

A descriptive study on wrist and hand sensori-motor impairment and function following distal radius fracture intervention

Study designDescriptive cross-sectional design. IntroductionWrist and hand sensori-motor impairment have been observed after distal radius fracture (DRF) treatment. This impairment and its relationship to function lack research. Purpose of the studyThe primary aim of this exploratory study was to determine the magnitude of wrist and hand sensori-motor impairment following surgical and non-surgical treatment among older patients following DRF. Secondary aims were to determine the relationship between wrist and hand sensori-motor impairment with function and pain as well as the relationships among wrist and hand sensori-motor impairment and function and age following DRF. MethodsTen Test (TT), active joint position sense (JPS), electromyography (EMG), computerized hand-grip dynamometer (CHD), and the Patient-Rated Wrist Evaluation (PRWE) were used to assess twenty-four female participants 8 weeks following DRF treatment and their 24 matched-control healthy counterparts on wrist and hand sensibility, proprioception, muscle recruitment, grip force, muscle fatigue, and functional status. ResultsParticipants following DRF demonstrated significantly (p < .05) greater sensory (i.e., JPS, TT), and motor (i.e., EMG, CHD) deficits than their control counterparts. A significantly higher functional deficit (i.e., PRWE) also existed among participants following DRF than the control group. Participants following surgical and non-surgical DRF treatment were found to be statistically different only on total grip force. Group differences on JPS and total grip force revealed the strongest effect size with the highest correlations to PRWE. EMG and muscle fatigue ratio group differences revealed a weaker effect size with a fair degree of correlation to PRWE. Pain significantly correlated with sensori-motor function. Age did not correlate with any measured variable. ConclusionsSignificant wrist and hand sensori-motor impairment and functional deficits among older females 8 weeks following DRF surgical and non-surgical interventions were revealed. JPS and total grip force were the most clinically meaningful tests for assessing the sensori-motor status as well as explaining functional disability and pain levels for these patients. Level of evidence2c.

Four-point-bending-fatigue behavior of the Cu45Zr45Ag7Al3 bulk metallic glass

Four-point-bend fatigue experiments were conducted on Cu45Zr45Ag7Al3 bulk metallic glass, which was done by the use of an electrohydraulic machine, at a frequency of 10Hz (using a sinusoidal waveform) with an R ratio of 0.1, where R=σmin/σmax (σmin and σmax are the applied minimum and maximum stresses, respectively). This material shows a fatigue-endurance limit and fatigue ratio of 386±5MPa and 0.26±0.01, respectively, and the fracture toughness is estimated to be about 23–30MPa·m1/2. The fatigue-fracture morphology indicated that Cu45Zr45Ag7Al3 has a significantly brittle fracture mode. The fracture surface can be divided into four regions: crack initiation, crack propagation, fast fracture, and melting regions. The fracture mechanism is discussed.

The influence of cyclic shear fatigue on the bracket–adhesive–enamel complex: An in vitro study

ObjectivesTo describe the effect of fatigue on the strength of the bracket–adhesive–enamel complex and characterize the fatigue behavior of the materials tested. MethodsUpper central incisor brackets (Discovery®, Dentaurum) were bonded with a light-curing (Transbond XT™, 3M Unitek) and a chemically-curing adhesive (Concise™, 3M Unitek) on bovine teeth embedded in cylindrical resign bases and stored in water at 37(±2)°C for 24 (±2)h. The first 15 specimens were tested with a universal testing machine ZMART.PRO® (Zwick GmbH & Co. KG, Ulm, Germany) for ultimate shear bond strength according to the DIN-13990-2-standard. The remaining three groups of 20 specimens underwent fatigue staircase testing of 100, 1000 and 3000 cycles at 1Hz with a self-made testing machine. The survived specimens were subjected to shear strength testing. ResultsThe fatigued specimens showed decreased shear strength with both adhesives at all cycle levels. The shear strength after fatigue for 100, 1000 and 3000 cycles was in the Concise™-groups 34.8%, 59.0%, 47.3% and in the Transbond™ XT-groups 33.6%, 23.1%, 27.3% relative to the ultimate shear strength. The fatigue life of the Concise™-groups decreased with increasing stress and Transbond™ XT showed lower fatigue ratio with no obvious trend. The specimens bonded with Transbond™ XT showed typically favorable fracture modes in contrary to Concise™. SignificanceFatigue of the bracket–adhesive–enamel complex decreased its shear strength. The staircase method can provide a standardized experimental protocol for fatigue studies, however testing at various cycle numbers is recommended.

超音波疲労試験機を用いたZr&lt;sub&gt;&lt;font size="-1"&gt;55&lt;/font&gt;&lt;/sub&gt;Al&lt;sub&gt;&lt;font size="-1"&gt;10&lt;/font&gt;&lt;/sub&gt;Ni&lt;sub&gt;&lt;font size="-1"&gt;5&lt;/font&gt;&lt;/sub&gt;Cu&lt;sub&gt;&lt;font size="-1"&gt;30&lt;/font&gt;&lt;/sub&gt;金属ガラスの超高サイクル疲労特性

In this work, the ultra-high cycle fatigue behavior of Zr55Al10Ni5Cu30 metallic glass was investigated by using ultrasonic fatigue testing method. Test alloy rods with a diameter of 8mm were prepared by tilt-casting with copper mold. Test specimens were machined to hourglass shape type (the minimum diameter ; 2.0mm), and after machining the surface of specimens was manually polished with polishing paste. The specimens were tested at a frequency of 20kHz under a stress ratio of -1. The fatigue limit (σw) (half a total stress amplitude) and fatigue ratio (σw/σB) of the alloy showed 893MPa and 0.53, respectively. Furthermore, we did not see any fish-eye like crack-growth morphology on fracture surfaces. The initiation region of fatigue crack was always observed at the side surface of the specimens. A viscous-flow fracture region with large dimples between the fatigue crack-growth region and the final unstable fracture region was observed. This peculiar fracture morphology may be due to adiabatic heating of the metallic glass specimens during the fracture, resulting in transition to supercooled liquid, under extremely high frequency of fatigue stress using ultrasonic loading.