Overlap Zone Research Articles

Multi-component Parallel Endografts at Complex TEVAR May Be Prone to Modular Dislocation Causing Novel Endoleaks: A Tale of Two Cases

Introduction We report two cases of complex thoracic endovascular aneurysm repair (TEVAR) with endoleakage due to modular dislocation of multi-component left subclavian parallel endografts in periscope configuration. Report First, a 67-year-old female patient presented with a 75-mm thoracic aortic aneurysm that was treated by right-to-left carotid–carotid bypass, and TEVAR with a two-piece left subclavian arterial periscope. This was complicated by modular disconnection of the periscope components and also proximal migration of the upper component of the periscope, resulting respectively in endoleaks due to modular disconnection and partial loss of seal. Second, a 65-year-old man presented with a chronic type B aortic dissection with combined true and false lumen diameter of 65 mm, treated by TEVAR and a three-piece left subclavian arterial periscope, which was complicated by modular dislocation of only the upper overlap. These were successfully treated by percutaneous endografting to bridge the disconnected segments, and to also achieve a seal in the left subclavian artery for the first patient. Discussion These cases indicate multi-component parallel endografts at TEVAR may be prone to modular disconnection, possibly due to distracting forces contributed by the configuration of the main thoracic endograft in conjunction with flow haemodynamics. They also highlight the need for longer overlap zones for the stent-grafts used in chimney–periscope–snorkel techniques and use of single long pieces whenever possible. We would also suggest review of the current endoleak classification in this context.

Closure of small and medium size umbilical hernias with the Proceed Ventral Patch in obese patients: a single center experience.

Obesity is a risk factor for the development of umbilical hernia. Open hernia closure could be challenging in obese patients leading to high rates of recurrence. The aim of this study was to investigate the effectiveness and safety of hernia patches in the management of obese patients with umbilical hernias. All the patients included in this study were managed in the department of surgery of a primary care hospital in Germany. The data of patients undergoing umbilical hernia repair within a two-year period was retrospectively reviewed. Patients managed with the PVP were included for analysis. 24 obese patients were analyzed. Small and medium size patches were used in 15 and 9 patients respectively. The median duration of surgery was 40 min and the median length of hospital stay was 4d. The mean length of follow-up was 12 ± 9 months (range: 6–30 months). The rate of recurrence was 4.1% and the rate of complication was 8.3%. Obese patients presenting with small and medium size umbilical hernias could be safely and effectively managed with prosthetic patches like the Proceed Ventral Patch. However, the limited overlap zone following hernia closure with such a patch can be an issue.

Advising patients on visual fitness to drive: implications of revised DVLA regulations

AimTo examine the relationship between the two UK vision standards for driving: the ability to read a number-plate at 20 m and achieving 6/12 (+0.30 logMAR).Methods120 participants were assessed without...

Using Species Distribution Modeling to Assess Factors that Determine the Distribution of Two Parapatric Howlers (Alouatta spp.) in South America

Through presence-only data, ecological niche modeling can use environmental variables to generate maps of areas that are potentially suitable for the presence of a species, improving our knowledge of its niche requirements and extending our understanding of its geographic distribution. We used the ecological niche model MaxEnt to predict the potential distribution of black-and-gold howlers (Alouatta caraya) and brown howlers (Alouatta guariba clamitans) in South America, as well as the potential sympatry area between both species. We modeled distributions of Alouatta caraya (196 presence localities, 8 bioclimatic variables) and A. guariba clamitans (74 presence localities, 13 bioclimatic variables) using bioclimatic variables from WorldClim with habitat suitability categorized as low, moderate, or high. Alouatta caraya showed a broader potential distribution, occupying a wide variety of habitats in a broad range of temperatures. Temperature annual range (Bio 7) was the bioclimatic variable with most influence in modeling the potential distribution of this species. Alouatta guariba clamitans was more restricted to rainy areas of mature forests at higher altitudes with low minimum temperatures. Mean temperature of coldest quarter (Bio 11) was the bioclimatic variable with the highest influence in this model. The predicted area of potential sympatry of both species was a relatively small area in the interior Atlantic Forest ecoregion, and a new syntopy locality occurred within the predicted area of sympatry. This narrow zone of overlap could be maintained, among other causes, by the role of the Paraná River as a natural barrier for dispersion, differences in niche requirements, potential interspecific competition, and hybridization.

Control of an overlap-type proportional directional control valve using input shaping filter

In a hydraulic control system (herein, termed a major control loop), a proportional directional control (PDC) valve with spool position feedback may work in a minor (or inner) control loop. In this study the authors propose control designs to improve the performance of the PDC valve control loop (a minor control loop). At first, the mathematical model for the PDC valve is developed through an experimental identification process. Then, a dead-zone compensator that facilitates jumping of the overlap zone in spool/sleeve combination is devised and applied. A reference input following controller (including PI-D and feed-forward controller) that enables robust control of the PDC valve under disturbances is devised using the pole placement method and the zero placement method. Subsequently, an input shaping filter is incorporated into the devised control system to improve the reference following characteristic in high frequency range. Finally, the effectiveness of the proposed control design is verified experimentally.

분자동역학과 확률회전동역학을 결합한 멀티스케일 모델링 기법 개발

Multiscale modeling is a new simulation approach which can manage different spatial and temporal scales of system. In this study, as part of multiscale modeling research, we propose the way of combining two different simulation methods, molecular dynamics(MD) and stochastic rotation dynamics(SRD). Our conceptual implementations are based on LAMMPS, one of the well-known molecular dynamics programs. Our prototype of multiscale modeling follows the form of the third party implementation of LAMMPS. It added MD to SRD in order to simulate the boundary area of the simulation box. Because it is important to guarantee the seamless simulation, we also designed the overlap zones and communication zones. The preliminary experimental results showed that our proposed scheme is properly worked out and the execution time is also reduced.

Spatial organization of cytokinesis signaling reconstituted in a cell-free system.

During animal cell division, the cleavage furrow is positioned by microtubules that signal to the actin cortex at the cell midplane. We developed a cell-free system to recapitulate cytokinesis signaling using cytoplasmic extract from Xenopus eggs. Microtubules grew out as asters from artificial centrosomes and met to organize antiparallel overlap zones. These zones blocked the interpenetration of neighboring asters and recruited cytokinesis midzone proteins, including the chromosomal passenger complex (CPC) and centralspindlin. The CPC was transported to overlap zones, which required two motor proteins, Kif4A and a Kif20A paralog. Using supported lipid bilayers to mimic the plasma membrane, we observed the recruitment of cleavage furrow markers, including an active RhoA reporter, at microtubule overlaps. This system opens further approaches to understanding the biophysics of cytokinesis signaling.

Refinement of collagen–mineral interaction: A possible role for osteocalcin in apatite crystal nucleation, growth and development

Mineralization of vertebrate tissues such as bone, dentin, cementum, and calcifying tendon involves type I collagen, which has been proposed as a template for calcium and phosphate ion binding and subsequent nucleation of apatite crystals. Type I collagen thereby has been suggested to be responsible for the deposition of apatite mineral without the need for non-collagenous proteins or other extracellular matrix molecules. Based on studies in vitro, non-collagenous proteins, including osteocalcin and bone sialoprotein, are thought to mediate vertebrate mineralization associated with type I collagen. These proteins, as possibly related to mineral deposition, have not been definitively localized in vivo. The present study has reexamined their localization in the leg tendons of avian turkeys, a representative model of vertebrate mineralization. Immunocytochemistry of osteocalcin demonstrates its presence at the surface of, outside and within type I collagen while that of bone sialoprotein appears to be localized at the surface of or outside type I collagen. The association between osteocalcin and type I collagen structure is revealed optimally when calcium ions are added to the antibody solution in the methodology. In this manner, osteocalcin is found specifically located along the a4–1, b1, c2 and d bands defining in part the hole and overlap zones within type I collagen. From these data, while type I collagen itself may be considered a stereochemical guide for intrafibrillar mineral nucleation and subsequent deposition, osteocalcin bound to type I collagen may also possibly mediate nucleation, growth and development of platelet-shaped apatite crystals. Bone sialoprotein and osteocalcin as well, each immunolocalized at the surface of or outside type I collagen, may affect mineral deposition in these portions of the avian tendon.

Cytonuclear discordance and the species status of Myotis myotis and Myotis blythii (Chiroptera)

We used both highly variable mitochondrial and nuclear loci to investigate the large mouse‐eared bat species complex in the Western Palaearctic to clarify their systematic position. Although mitochondrial lineages show no species segregation and some haplotypes are shared between Myotis myotis and Myotis blythii sensu lato, Bayesian clustering methods based on multilocus genotypes indicate highly concordant nuclear and morphological species assignment. These multilocus, nuclear analyses detected only a single putative F1 hybrid in the extensive areas of sympatry sampled, thus confirming the biological species status of M. myotis and M. blythii s.l. We propose that the strong cytonuclear discordance in these species complex results from a combination of prior spatial isolation of the two species in different glacial refugia, followed by a succession of mitochondrial introgression events that occurred during the eastward and westward expansions of M. myotis and of M. blythii, respectively. The nuclear markers further indicate the presence of a notable genetic discontinuity within M. myotis that broadly separates populations into an eastern and a western component with an overlap zone in the Balkans. This eastern and western discontinuity is also apparent in the mitochondrial lineages with the D haplogroup largely confined to samples found in Thrace and Asia Minor. None of these genetic discontinuities correspond to the distribution of the two commonly recognized M. myotis subspecies (myotis and macrocephalicus). We also show that distinct morphological subspecies within M. blythii (oxygnathus, omari, risorius and lesviacus) in Europe and the near‐East do not correlate with significant evolutionarily units, whether identified by mitochondrial or nuclear data and thus only represent local morphological variants with little taxonomic relevance.

Feature-constrained registration of building point clouds acquired by terrestrial and airborne laser scanners

Point-cloud registration is usually accomplished on the basis of several corresponding features to compute the parameters of the transformation model. However, common point features are difficult to select because airborne laser scanner (ALS) and terrestrial laser scanner (TLS) point clouds of the same object have be aligned due to the different sensing positions and sampling modes. Taking building profile features as objects, a registration method based on feature constraints is proposed here. The standard six-parameter rigid-body transformation adopted for alignment of laser scans is replaced by a two-step transformation: horizontal registration based on a two-dimensional similarity transformation and vertical registration based on a simple vertical shift. First, the feature-line and feature-plane equation parameters are obtained from both the airborne and terrestrial point clouds. Second, the plane transformation parameters are computed after projecting the extracted features onto a horizontal reference plane. Finally, the elevation transformation parameter is calculated by comparing the heights of flat features. The ALS and TLS datasets of two buildings (Shanghai Pudong International Conference Center and Shanghai Ocean Aquarium, China) were used to evaluate the robustness and accuracy. The results show that the proposed feature-constrained method works well for registration between two datasets. Five checkpoints and one overlap zone for the Pudong International Conference Center were selected to evaluate the accuracy and resulted in accuracies of 0.15 to 0.5 m in the horizontal direction and 0.20 m in the vertical direction.

Investigating the Performance of Four Empirical Cross-Calibration Methods for the Proposed SWOT Mission

The proposed surface water and ocean topography (SWOT) mission aims at observing short scale ocean topography with an unprecedented resolution and accuracy. Its main proposed sensor is a radar interferometer, so a major source of topography error is the roll angle: the relative positions of SWOT’s antennas must be known within a few micrometers. Because reaching SWOT’s stringent requirements with onboard roll values is challenging, we carried out simulations as a contingency strategy (i.e., to be ready if roll is larger than anticipated) that could be used with ground-based data. We revisit the empirical calibration algorithms with additional solving methods (e.g., based on orbit sub-cycle) and more sophisticated performance assessments with spectral decompositions. We also explore the link between the performance of four calibration methods and the attributes of their respective calibration zones: size and geometry (e.g., crossover diamonds), temporal variability (e.g., how many days between overlapping SWOT images). In general, the so-called direct method (using a single SWOT image) yields better coverage and smaller calibrated roll residuals because the full extent of the swath can be used for calibration, but this method makes an extensive use of the external nadir constellation to separate roll from oceanic variability, and it is more prone to leakages from oceanic variability on roll (i.e., true topography signal is more likely to be corrupted if it is misinterpreted as roll) and inaccurate modeling of the true topography spectrum. For SWOT’s baseline orbit (21 days repeat and 10.9 days sub-cycle), three other methods are found to be complementary with the direct method: swath crossovers, external nadir crossovers, and sub-cycle overlaps are shown to provide an additional calibration capability, albeit with complex latitude-varying coverage and performance. The main asset of using three or four methods concurrently is to minimize systematic leakages from oceanic variability or measurement errors, by maximizing overlap zones and by minimizing the temporal variability with one-day to three-day image differences. To that extent, SWOT’s proposed “contingency orbit” is an attractive risk reduction asset: the one-day sub-cycle overlaps of adjoining swaths would provide a good, continuous, and self-sufficient (no need for external nadirs) calibration scheme. The benefit is however essentially located at mid to high-latitudes and it is substantial only for wavelengths longer than 100 km.

Quantitative assessment of primary mitral regurgitation using left ventricular volumes: a three-dimensional transthoracic echocardiographic pilot study.

To investigate the value of assessment of mitral regurgitant fraction (RF) using left ventricular (LV) volumes obtained by three-dimensional echocardiography (3DE) to quantify primary mitral regurgitation (MR). Sixty patients with primary MR in sinus rhythm were prospectively enrolled. RF was calculated using either 2DE or 3DE LV volumes obtained as follows: (LV total stroke volume - LV forward stroke volume by Doppler)/LV total stroke volume. Severity of MR was graded independently by two cardiologists blinded to LV volumetric data using an integrative approach, as recommended by current guidelines. Sixty patients with LV ejection fraction >50% and no MR were also studied. In patients without MR, 3D total LV stroke volume was more strongly correlated with LV forward stroke volume than 2D total LV stroke volume (r = 0.75, P < 0.0001 vs. r = 0.62, P < 0.0001, respectively). The 3D method had a feasibility of 90% in patients with MR. Inter-reader concordance for MR grading (four grades) was excellent with a Kappa-value of 0.90, P < 0.0001. A significant correlation was observed between grade of MR severity and 3D RF (r = 0.83, P < 0.0001) and 2D RF (r = 0.74, P < 0.0001). Comparisons between individual grades for 3D RF were significant (P < 0.05) except for 3+ vs. 4+ MR (P = 0.213). All patients with 3D RF ≥40% had ≥3+ or 4+ MR and those with 3D RF ≤30% had 1+ or 2+ MR with a 'grey' overlap zone between 30 and 40%. RF can be routinely determined using 3D LV volumes with a high feasibility in patients with primary MR and is reliable for identification of Grade 3+ or Grade 4+ MR. The incorporation of this parameter into the currently recommended multiparametric integrative approach might be helpful to discriminate significant MR.

Mate recognition and reproductive isolation in the sibling species Spodoptera littoralis and Spodoptera litura

Mate recognition is crucial for reproductive isolation and for maintaining species integrity. Chemosensory-mediated sexual communication with pheromones is an essential component of mate recognition in moths. Confronted with sex pheromone stimuli released from conspecific and closely related heterospecific females, which partially overlap in chemical composition, male moths are under strong selection to recognize compatible mates. Here, we investigated the role of pheromone signals in premating communication in the sibling species Spodoptera littoralis and S. litura (Lepidoptera, Noctuidae). Further, we measured the reproductive consequence of conspecific vs. heterospecific matings. Both species use Z9,E11-14:Ac as the major pheromone compound, and the 11-component blend found in pheromone glands of S. littoralis comprises the compounds found in S. litura. Accordingly, S. littoralis and S. litura males readily responded to conspecific and heterospecific calling females in no-choice behavioural tests. In contrast, in a dual-choice test, S. littoralis males choose conspecific calling females, whereas S. litura males did not discriminate between conspecific and heterospecific females. In S. littoralis females, heterospecific matings had a negative fitness effect as compared to conspecific matings. Female longevity, egg-laying and hatching of larvae were significantly reduced by matings with heterospecific males. Reciprocal crossings, between S. litura females and S. littoralis males, were prevented by genital morphology, which is consistent with reduced heterospecific attraction of S. littoralis males in a dual-choice assay. On the other hand, matings between S. littoralis females and S. litura males, under a no-choice situation, show that interspecific matings occur in zones of geographical overlap and corroborate the idea that mate quality, in these closely related species, is a continuous and not a categorical trait.

Structural evolution of the Mount Wall region in the Hamersley province, Western Australia and its control on hydrothermal alteration and formation of high-grade iron deposits

The discovery of two relatively small but high-grade iron ore deposits near Mt Wall, an intensely faulted part of the southwestern Hamersley province provides unique insights into the structural control on ore formation in this region. The deposits have many geological features typical of the high grade microplaty hematite group which also contains the much larger Mt Tom Price, Paraburdoo and Mt Whaleback deposits. The deposits are structurally controlled along early normal faults and contain abundant microplaty hematite and martite, and are largely confined to the Dales Gorge member of the Brockman Iron Formation. In addition to the microplaty hematite-martite ore, there are martite-goethite ores and rare magnetite-goethite or magnetite-hematite ores. Below the modern weathering surface, hydrothermally altered zones in wallrock BIF from the Lower Dales Gorge member contain magnetite, hematite and carbonate/talc bearing mineral assemblages. A staged ore genesis model involving early extension and fluid circulation along normal faults, hypogene silica leaching and carbonate alteration, followed by deep meteoric oxidation with microplaty hematite formation and finally weathering can explain most features of the Mt Wall deposits. The role of deformation was to provide pathways for mineralising fluids and initiate the seed points for the mineralised systems.High grade iron in the Wellthandalthaluna deposit is situated between the NW to NNW trending Boolgeeda Creek fault and a synthetic joining splay, the Northern fault. Both are high angle normal faults and formed during early extension in this part of the province. Faults are characterised by localised small scale deformation and brecciation, deep carbonate alteration and oxidation. Recent weathering has penetrated deeply into the fault zones, converting the carbonate-rich assemblages into goethite. Mineralisation in the Arochar deposit is situated in the overlap or relay zone between two segments of the Mt Wall fault zone, a moderately to steeply southerly dipping normal fault system which at Arochar is intruded by dolerite dykes. At both locations, the ore controlling faults are offset by later NW trending dextral and normal faults.Fault relay zones or fault splay zones were likely zones of increased permeability and fluid flow during fault development or reactivation and may also have been important in initiating mineralisation in larger deposits such as Mt Tom Price and Mt Whaleback. However structural controls on the largest iron ore deposits are often obscured due to the intensity and scale of ore development, whereas they are better preserved in the smaller deposits.Recognition that carbonate bearing protores at Mt Wall survived for nearly two billion years until intense recent weathering converted them to martite-goethite or magnetite-goethite ores may imply that more of the giant hematite-goethite deposits of the Hamersley province had hydrothermal precursors and were not formed by supergene processes alone.

Phylogeny and phylogeography of the Tuber brumale aggr.

The Tuber brumale (winter truffle) is a black truffle reported from most European countries, belonging to the Melanosporum group. Its significance in the economy is ambivalent as the winter truffle has been shown to be a frequent contaminant species in the orchards of the Perigord truffle and occasionally in those of the summer truffle, yet owing to its delicate fragrance, its trade is worthy of note. The phylogeny and phylogeography of economically important truffles are relatively well-explored; however, no thorough research has been published on these aspects of the winter truffle. Therefore, here, we report the first phylogeographic analyses based on samples representing the entire distribution of the species. ITS sequences were used in this survey for haplotype and coalescent analyses, while phylogenetic analyses were based on the ITS, LSU and PKC loci. According to all loci, the samples clustered into two big clades imply the existence of two phylogenetic species. Based on our results, one of these appears to be endemic to the Carpathian Basin. In the other more widespread species, two main phylogeographic groups can be distinguished that show east-west separation with a zone of overlap in the Carpathian Basin, suggesting that they survived the latest glacial period in separate refugia.

Environmental filtering of foraging strategies mediates patterns of coexistence in the fire antsSolenopsis geminataandSolenopsis xyloni, and their interspecific hybrids

Tradeoffs in functional traits facilitate species coexistence within communities and are important contributors to community assembly. Two aspects of a life‐history tradeoff known to structure ant communities include foraging efficiency (i.e. resource discovery and retrieval) and competitive dominance (territoriality and survivorship following competition).This work examined these aspects in workers of two fire ant species (Solenopsis xyloniandSolenopsis geminata) and theirF1hybrids using laboratory experiments.Parental foraging strategies were consistent with a tradeoff between discovery efficiency and competitive territorial dominance. Desert‐adaptedS. xyloniwas the most efficient forager but the least effective territory defender; mesic‐adaptedS. geminatawas a less efficient forager, but fared best in competition trials. Hybrid workers were generally intermediate, leading to increased survival by hybrids in competitive encounters withS. geminatacompared with the performance ofS. xyloni.These findings suggest that traits associated with foraging and competitive ability in the parental species are subject to environmental filtering; across habitats, species with a similar dominance rank in their respective communities differ in their placement along the discovery–dominance axis.Interspecific hybridisation may play a role in extending eastern range limits ofS. xylonivia shifting colony allocation towards the strategy of its competitor. In the overlap zone,S. xyloniwith hybrid workers may be sufficiently competitive to persist withS. geminata, while colonies withS. xyloniworkers cannot, providing a substantial selective advantage to hybridisation forS. xyloniqueens that may explain the unusual hybridogenetic social structure of this population.

Receiver function constraints on crustal seismic velocities and partial melting beneath the Red Sea rift and adjacent regions, Afar Depression

The Afar Depression is an ideal locale for the investigation of crustal processes involved in the transition from continental rifting to oceanic spreading. To provide relatively high resolution images of the crust beneath the Red Sea rift (RSR) represented by the Tendaho graben in the Afar Depression, we deployed an array of 18 broadband seismic stations in 2010 and 2011. Stacking of about 2300 receiver functions from the 18 and several nearby stations along the ~200 km long array reveals an average crustal thickness of 22±4 km, ranging from ~17 km near the RSR axis to 30 km within the overlap zone between the Red Sea and Gulf of Aden rifts. The resulting anomalously high Vp/Vs ratios decrease from 2.40 in the southwest to 1.85 within the overlap zone. We utilize theoretical Vp and melt fraction relationships to obtain an overall highly reduced average crustal Vp of ~5.1 km/s. The melt percentage is about 10% beneath the RSR while the overlap zone contains minor quantities of partial melt. The observed high Vp/Vs values beneath most of the study area indicate widespread partial melting beneath the southwest half of the profile, probably as a result of gradual eastward migration of the RSR axis. Our results also suggest that the current extensional strain in the lower crust beneath the region is diffuse, while the strain field in the upper crust is localized along narrow volcanic segments. These disparate styles of deformation imply a high degree of decoupling between the upper and lower crust.

Microstructural evolution at the overlap zones of 12Cr martensitic stainless steel laser alloyed with TiC

Abstract Multiple track laser alloying is characterised by additional heat treatment and differences in the amount of powder deposited at the overlap regions. These result in different microstructural and phase evolution at these regions, which are not obtainable in the single tracks. X12CrNiMo steel has been laser alloyed with TiC using a 4.4 kW continuous wave (CW) Nd:YAG laser. The process parameters were first optimised after which they were kept constant for overlap ratios of 50% and 75%. The depths of the alloyed zone, the mcrostructural evolution, metallurgical structures and compositions are different for the 50% and 75% overlap. The 75% overlap sample has an alloying depth of 4233 µm (about two times that of the 50% overlap). The XRD of the 50% overlap sample reveals the presence of complex carbides, which are absent in that of the 75% overlap. Although both overlap samples have retained martensite, diffractographs show that the martensite of the 75% is richer in carbide. These are attributed to differences in powder catchment, heat build-up and depth of alloying.

Fatigue Life Analysis of Crane K-Type Welded Joints Based on Non-Linear Cumulative Damage Theory

There are large numbers of welds on cranes’ lattice booms. Due to notably complicated force conditions, the fatigue life analysis of the lattice boom is difficult when designing the limit life. The fatigue cycle of the utilization level of a lattice boom crane is in the overlap zone of low-cycle fatigue and high-cycle fatigue. The poor accuracy of measurement of the fatigue life of lattice booms indicates that the calculation dispersion of the linear Palmgren-Miner (PM) rule was high. To obtain real crane stress spectra inexpensively and conveniently, a new stress spectra acquisition method based on the ‘measured & simulated & compared & statistics’ integrated strategy of crane K-type welded joints is proposed. The errors of the maximum stress amplitudes between the measured stress spectra and the simulated stress spectra were less than 10%. The fatigue test results also indicated that errors of the test fatigue life were less than 10% under both the simulated and the measured stress spectra. A new, simplified Huffman non-linear cumulative damage theory is proposed to calculate the fatigue life of crane K-type welded joints based on the notch stress and strain approaches. The calculation results indicated that the accuracy of the non-linear damage accumulation was higher than that of the PM rule, although the calculation result based on the non-linear damage accumulation method was slightly un-conservative when the initial damage was not considered in the calculation. By setting different initial damage conditions, various results were analysed, which revealed that the calculation errors of fatigue life based on the non-linear theory were less than 10% when the initial damage levels were set from 0.02 to 0.04. Such results are appropriate for engineering applications. When the fatigue life calculation needs to be more conservative, the initial damage levels may be set from 0.04 to 0.07; the resulting calculation errors could be less than 25%. As the Huffman non-linear cumulative damage theory requires data from only a few material properties, such as the cyclic stress-strain curve and the constant amplitude strain-life curve, it could therefore be more suitable for engineering applications with higher calculation accuracy and fewer costs.

Strength of spline joints assembled by forming

In this paper, a new assembling method of spline joints that enables tight fitting in a simple manner by allowing slight plastic deformation at the spline teeth was introduced. Experiments were carried out for the spline joints of medium carbon steel varying the overlap zone between the male and the female spline teeth. Axial joining strength was increased with increase in the overlap length due to the residual compressive stress by forming. The joint by the proposed method also showed higher torsional strength than the conventional joint. Improvement in the torsional strength was explained based on the deformation and hardness distribution around the spline teeth. With respect to the shape of overlap zone, better results were obtained when using the specimen having a uniform overlap length along the axial direction.