Internal Inclusions Research Articles

Very high cycle fatigue of nitrided 18Ni maraging steel sheet

Thin sheets of nitrided 18Nimaraging steel are tested under cyclic tension (load ratio R=0.1) in the very high cycle fatigue (VHCF) regime. The ultrasonic fatigue testing method with a cycling frequency of about 20kHz has been further developed for these experiments. Sheet specimens with 0.35mm thickness are mounted on a carrier specimen, they are pre-stressed and are forced to vibrate jointly. Between 107 and 109 cycles, fatigue cracks are initiated exclusively at internal TiN inclusions. The areas of the crack initiating inclusions projected perpendicular to the applied tensile stress are evaluated. The square root of inclusion areas, (areaINC)1/2 lies between 2.5μm and 5.3μm. Considering inclusions as cracks, their stress intensity range is between ΔKINC=1.3MPam1/2 and 2.4MPam1/2. The sizes of crack initiating inclusions influence fatigue lifetimes. This is considered in a crack propagation model and by presenting lifetimes versus the stress amplitudes multiplied by (areaINC)1/12. A mean lifetime of 109cycles is found at a stress amplitude of 22% of the tensile strength, which is comparable to other high strength steels tested under cyclic tension.

Accurate simulation of the optical properties of atmospheric ice crystals with the invariant imbedding T-matrix method

The invariant imbedding T-matrix method (II-TM) is employed to compute the optical properties of randomly oriented ice crystals of various shapes including hexagonal columns, hollow columns, droxtals, bullet rosettes and aggregates. The II-TM is shown to be numerically stable and capable of obtaining the single-scattering properties of hexagonal ice crystals with size parameters up to 150. The 22° and 46° halo peaks in the phase function of compact hexagonal ice crystals begin to emerge at a size parameter of approximately 80 and tend to become insensitive to particle size as the corresponding size parameter approaches 150. Furthermore, the II-TM solutions are shown to be in agreement with their counterparts based on the discrete dipole approximation (DDA) method and the pseudo-spectral time-domain (PSTD) method. In addition, the accuracy of the improved geometric-optics method (IGOM) is examined for randomly oriented hexagonal ice crystal cases over a wide size-parameter range from the resonant to geometric-optics regimes. The II-TM is also used to study the effects of particle surface roughness and internal inclusions on the single-scattering properties of ice particles.

Deformation behavior of a composite drop in a simple shear flow

The hydrodynamics of disperse liquid mediaattracts increased attention, first of all, owing to theirnumerous applications in various industries (chemical, medical, pharmaceutical, processing of polymers,etc.). The theoretical analysis of such systems is basedon studying the dynamic behavior of an isolated dropin a flow for determining the strain, orientation, andstability of the drop in various flow modes. To date, anextensive body of experimental data on the mechanisms of deformation and breakup of homogeneousdrops has been accumulated [1–6]. However, thehydrodynamic behavior of composite drops containing one or several internal inclusions (cores) remainslittle studied. At the same time, such objects have adiversity of applications: from increasing the impactresistance of mixed polymer composites to targeteddrug delivery [5, 6]. Therefore, the comprehensiveinvestigation of composite drops is of fundamental andpractical interest.Studying the hydrodynamic behavior of such dropsis complicated by a number of difficulties related to thenecessity of taking into account a large number ofparameters and also the dynamic changes in theshapes of both inner and outer interfaces. In the simplest case, a composite drop consists of a single coreand a shell, which are immersed in a dispersion liquid(Fig. 1). In this case, features of the deformation andshaping of the drop are determined by the relative values of the surface tensions at the interfaces betweenthe components of the medium, their viscosities, andalso the core size as compared to the shell size.It was previously shown that, in a shear flow, a corewith low viscosity and low surface tension takes theshape of an extended dumbbell rotating in the direction of the flow [7]. In this work, we studied the hydrodynamic behavior of a twodimensional compositedrop in which the viscosity of the core is much higherthan that of the shell and also the core–shell interfacial tension significantly increases the surface tensionat the interface between the shell and the dispersionliquid. In such a formulation, the main contribution tothe total strain and orientation of the composite dropIs made by the transformation of the shape of the shell.The deformation and dynamic structuring of this typeare also characteristic of swollen microgels immersedin a thermodynamically incompatible liquid [8–10].Comparison of the hydrodynamic behaviors of composite and homogeneous drops enabled one to understand the effect of flow perturbations caused by thepresence of the viscous core on the deformationbehavior of the composite drop.

Total reflection infrared spectroscopy of water-ice and frozen aqueous NaCl solutions

Liquid-like and liquid water at and near the surface of water-ice and frozen aqueous sodium chloride films were observed using attenuated total reflection infrared spectroscopy (ATR-IR). The concentration of NaCl ranged from 0.0001 to 0.01 M and the temperature varied from the melting point of water down to 256 K. The amount of liquid brine at the interface of the frozen films with the germanium ATR crystal increased with salt concentration and temperature. Experimental spectra are compared to reflection spectra calculated for a simplified morphology of a uniform liquid layer between the germanium crystal and the frozen film. This morphology allows for the amount of liquid observed in an experimental spectrum to be converted to the thickness of a homogenous layer with an equivalent amount of liquid. These equivalent thickness ranges from a nanometer for water-ice at 260 K to 170 nm for 0.01 M NaCl close to the melting point. The amounts of brine observed are over an order of magnitude less than the total liquid predicted by equilibrium thermodynamic models, implying that the vast majority of the liquid fraction of frozen solutions may be found in internal inclusions, grain boundaries, and the like. Thus, the amount of liquid and the solutes dissolved in them that are available to react with atmospheric gases on the surfaces of snow and ice are not well described by thermodynamic equilibrium models which assume the liquid phase is located entirely at the surface.

Very high cycle fatigue of VDSiCr spring steel under torsional and axial loading

AbstractVery high cycle fatigue (VHCF) properties of VDSiCr spring steel are investigated with ultrasonic equipment under fully reversed cyclic torsion loading and under cyclic axial loading at load ratios R = –1, R = 0.1 and R = 0.5. Shot‐peened specimens with surface finish similar to valve springs in combustion engines are tested until limiting lifetimes of 1010 cycles. Under cyclic torsion loading, specimens either fail below 106 cycles with crack initiation at the surface or they do not fail. Under cyclic axial loading, failures above 109 cycles were found for all load ratios with crack initiation at the surface or at internal inclusions. Ratio of mean endurance limit (50% failure probability at 1010 cycles) under fully reversed cyclic torsion and cyclic tension‐compression loading is 0.86. Cyclic torsion loading slightly below the endurance limit leads to cyclic softening first followed by cyclic hardening whereas cyclic stability is found for tension‐compression loading. Cyclic torsion reduces surface compression stresses whereas they are hardly affected by cyclic tension‐compression loading. Mean endurance limit at 1010 cycles for R = 0.1 is 61% of the endurance stress amplitude at load ratio R = –1, and for R = 0.5 it is 44% of the tension‐compression endurance limit. Endurance limits for cyclic torsion and cyclic tension‐compression loading are comparable, if effective stress amplitude is used that considers cyclic normal stresses and residual compression stresses at the surface.

OS1307 放射光μCTイメージングを用いたTi-6Al-4V内部に発生する微小疲労き裂の検出

Very high cycle fatigue is mainly characterized by sub-surface fracture in the long regime over 10^7-10^8 cycles. However, since the detection of internal cracks is extremely difficult, the mechanism of very high cycle fatigue has not been clarified yet. In recent researches, small internal inclusions in steel were detected by using synchrotron radiation μCT imaging in the Super Photon ring-8 GeV (SPring-8). These results suggest a possibility that small cracks initiating inside metal material are observable. Focusing on the possibility, the present work conducted non-destructive observations of internal cracks by using the X-rays μ CT imaging in SPring-8 on Ti-6Al-4V alloy m which fatigue damage was accumulated. In order to open the internal crack during observations, a tensile load was given to the specimen. As a result of the series of observations, small internal fatigue cracks with a size of about 30 μm were successfully detected under the optimum tensile load necessary to open and identify those cracks. In addition, it was revealed that multi-cracks initiated inside the specimen and the fatigue life was determined by the competition of those propagations. The results obtained in this study showed that non-destructive inspection technique to detect small internal fatigue cracks was established.

Variations in carbon isotopic composition in the subcontinental lithospheric mantle beneath the Yangtze and North China Cratons: Evidence from in-situ analysis of diamonds using SIMS

The components and evolution of subcontinental lithospheric mantle beneath the North China Craton and the Yangtze Craton is a current topic in the geological study of China and the carbon isotopic composition of diamond is one of the most direct probes into cratonic lithospheric mantle processes. In this paper, in-situ SIMS (Secondary Ion Mass Spectrometry) techniques were used to analyze the carbon isotope compositions at different internal growth zones of diamonds from Shandong and Liaoning in the North China Craton and Hunan in the Yangtze Craton. It was found that the carbon isotopic range of diamonds from the North China Craton are rather distinct from those of the Yangtze Craton; the former has a range of −6.0/‰ to −2.0‰ (relative to VPDB) with an average value of −3.0‰ in their core areas, which is consistent with global peridotitic diamonds; the diamonds from the Yangtze Craton, however, have a carbon isotopic range from −8.6‰ to −3.0‰ with an average value of −7.4‰ in their core areas, being more consistent with global eclogitic diamonds. The variations of carbon isotope ratios between different internal growth zones in individual diamonds were different in the three diamond localities studied. There was a clear correlation between changes in carbon isotopic composition and phases of diamond dissolution and new growth, while no correlation was observed between δ 13C and internal inclusions. The variations suggest that the carbon isotopic compositions of mantle fluids were changing during the process of diamond crystallization, and that the heterogeneity of the carbon isotopic composition in mantle carbon reservoirs was a more important factor than carbon isotope fractionation in controlling the carbon isotopic compositions and their variation in diamonds. In addition, the preliminary results of in-situ nitrogen analyses demonstrated that the variation of carbon isotopic compositions between the core and outer growth zones does not correlate with nitrogen abundances, implying either that diamonds crystallized in an open environment or that the carbon isotopic composition and nitrogen contents in mantle fluids were controlled by other, not yet understood factors. The experimental results provide hints that the isotopic composition of carbon and its original sources were different in metasomatic fluids controlling diamond formation in the mantle beneath the North China Craton and the Yangtze Craton.

Inclusion size evaluation and fatigue strength analysis of 35CrMo alloy railway axle steel

The axial loading fatigue tests of 35CrMo alloy railway axle steel were carried out with the untreated specimens and those treated by nitrocarburization. It is found that the untreated 35CrMo steel specimens fracture from surface, while those of the treated specimens fracture from internal inclusions. In order to investigate the inclusion size in the material, the ultrasonic fatigue tests were conducted for the 35CrMo steel by applying large risk volume specimens with straight section after nitrocarburization. The results show that the cracks of all the specimens initiate from the internal inclusion. The statistics of extreme values (SEV) method was applied to evaluate the maximum inclusion size in the large volume material and the full-scale axle. Based on the evaluated maximum inclusion sizes and the fracture mechanics, different fracture behaviors of axial loading specimens and full-scale axle as well as the effect of inclusion size on fatigue strength of full-scale axles were analyzed based on the fracture mechanics.

A New Nonmetallic Inclusion Rating Method by Positive Use of Hydrogen Embrittlement Phenomenon

A new inclusions rating method using hydrogen embrittlement of a tensile test specimen is proposed. This method is essentially based on the statistics of extremes for inclusion rating where the maximum inclusion size is determined by simple tensile testing of a hydrogen-precharged (H-precharged) specimen. Tensile tests were conducted using two bearing steels (SAE52100 HV 346, HV 447, HV 559, HV 611, HV 678 and ASTM-A485-1 HV 706, HV 715) and one spring steel (SAE5160, HV 651). Fatigue tests were conducted using SAE52100 bearing steel (HV 682). All H-precharged tensile specimens (SAE52100, ASTM-A485-1 and SAE5160) were fractured from internal inclusions except the SAE52100 tensile specimens with a Vickers hardness of HV 346. It was confirmed that the distribution of extreme values of inclusion sizes obtained by SAE52100 tensile testing with H-precharged specimens coincided with those obtained by SAE52100 fatigue testing. From these results, it is presumed that the inclusion rating method by fatigue testing can be replaced by simple tensile testing with H-precharged specimens. The proposed method is more convenient and reliable than other existing inclusion rating methods, i.e., fatigue testing and optical microscopy. The proposed method can be applied to specimens with a Vickers hardness of higher than HV 447.

Numerical simulation of Gaussian beam scattering by complex particles of arbitrary shape and structure

An efficient numerical method based on the surface integral equations is introduced to simulate the scattering of Gaussian beam by complex particles that consist of an arbitrarily shaped host particle and multiple internal inclusions of arbitrary shape. In particular, the incident focused Gaussian beam is described by the Davis fifth-order approximate expressions in combination with rotation defined by Euler angles. The established surface integral equations are discretized with the method of moments, where the unknown equivalent electric and magnetic currents induced on the surfaces of the host particle and the internal inclusions are expanded using the Rao–Wilton–Glisson (RWG) basis functions. The resultant matrix equations are solved by using the parallel conjugate gradient method. The proposed numerical method is validated and its capability illustrated in several characteristic examples.

Scattering of Gaussian beam by arbitrarily shaped particles with multiple internal inclusions

In this paper, we introduce an efficient numerical method based on surface integral equations to characterize the scattering of an arbitrarily incident Gaussian beam by arbitrarily shaped particles with multiple internal inclusions. The incident Gaussian beam is described by the Davis-Barton fifth-order approximation in combination with rotation Euler angles. For numerical purposes, the surfaces of the host particle and the inclusions are modeled using small triangular patches and the established surface integral equations are discretized with the method of moments. The resultant matrix equation is solved by using a parallel implementation of conjugate gradient method on distributed-memory architectures. Some numerical results are included to illustrate the validity and capability of the developed method. These results are also expected to provide useful insights into the scattering of Gaussian beam by composite particles.

Gathering and deploying tourism destination intelligence

Software intelligence approaches have application to tourism destination managers seeking tourist-related information relevant to specific customer requests. Such approaches are framed by physically gathering business intelligences about each tourist-specific destination. These processes may be paper or computer-based to capture particular tourism stakeholder requirements. Small tourism destination businesses using lowest cost approaches may adopt destination-specific manual analysis approaches. Larger operators targeting broader destination tourist requirements may opt for more costly and but faster intelligent software approaches. Such internal and external intelligence gathering inclusions also offer improved business strategic positioning within a competitive tourism destination.

Fatigue life assessment of a high strength steel 300 M in the gigacycle regime

The fatigue behavior of a high strength steel 300 M in the gigacycle regime was investigated. Fully reversed tension — compression fatigue tests at ambient temperature were performed using an ultrasonic fatigue system operating at 20 kHz. The staircase test method was employed to obtain accurate values of the mean fatigue strength corresponding to fixed numbers of cycles up to 109. These results were compared to the curve which is estimated by the data tested in the mid-long life regime on conventional servo hydraulic test machine at 20 Hz. Results indicate that the fatigue strength determined from ultrasonic fatigue testing is lightly higher than conventional testing in the range of 106–107 cycles. It is obvious that nucleations of fractures tend to occur below the surface, if fractures happen after more than 107 cycles. All the fractured specimens fails from internal SiO2 inclusions or smaller carbides and carbide clusters.

Scanning electron microscopy and energy-dispersive X-ray investigations of gold grains in quartz veins from the Seiga gold mine, south Egypt

Seiga Au mineralization is located in the Wadi Seiga which intersected the Wadi Allaqi in Southeast Egypt. It has had a long history of ancient Au working since 4000B.C. and discontinzuous mining until 1950s. This study presents a detailed microchemical characterization of Au grains in quartz veins and veinlets, aiming to obtain further understanding of Au occurrences, chemistry of Au bearing phases, their internal structure, inclusions and genesis, and type of source mineralization for evaluation and exploration purposes. The scanning electron microscope fitted with energy dispersive X-ray spectrometer techniques has been applied to achieve this paper.The results revealed that the Au mineralization is considered as a single major episode of mineralization formed by hydrothermal ore bearing fluid rich in sulfides, epithermal character and metamorphic origin. It formed through four stages, including four mineral phases varied in their dimensions, distribution and composition. The first two phases were homogeneous and included Au+Ag and Au+Ag±Cs±Rb phases that derived from two separated homogeneous ore bearing fluids. They existed as discrete individual grains in quartz veins and veinlets, caged in secondary iron oxides pseudomorphed after early formed Au bearing pyrites and as zoned Au grains including the cores of Au+Ag phase and the rims of younger Au+Ag±Cs±Rb phase. The third phase was represented by pyrites and chalcopyrites, whereas the fourth phase included carbonate (ankerite and calcite) and muscovite minerals. Both the last two phases were barren and free of Au signals. Seiga Au mineralization has been subjected to dissolution, remobilization and re-precipitation processes that control the dimension and distribution of both Au phases. The obtained results give a complete image of quantitative and qualitative characterization of Au alloy phases and their associated minerals for genetic history of Au mineralization.

The effect of plasma nitriding on the fatigue behavior of DIN 1.2210 cold work tool steel

Plasma nitriding is an important thermo-chemical surface treatment which is widely used in order to enhance the surface hardness, fatigue strength and wear and corrosion resistance of steels. In this research, the effects of plasma nitriding parameters including temperature and time on the microstructure and fatigue strength of quenched and tempered DIN 1.2210 cold work tool steel were investigated. The microstructures of base material and nitrided layer were examined in details by optical microscopy and X-ray diffraction (XRD) analysis. Micro-hardness measurements were used to determine surface hardness and case depth. Fatigue tests were performed using a rotating bending machine. The results indicated that the plasma nitriding process led to a considerable increase in the micro-hardness and fatigue strength values. Furthermore, the maximum fatigue strength was attained after plasma nitriding at 550°C for 6h, which increased the fatigue life of the specimens by about 67%. It was also found that the dominant fatigue crack initiation mechanism in the plasma nitrided specimens was subsurface ‘fish eye’ type crack formation originated from internal nonmetallic inclusions.

Fabrication of composite microcapsules by drop-on-demand inkjet: Effect of precursor composition on the process limits

The feasibility of using drop-on-demand inkjet technology for the fabrication of calcium alginate hydrogel microcapsules containing dispersed sub-micron solid particles (TiO 2 photocatalyst) was demonstrated. The influence of the printed solution viscosity on the micro-droplet size has been investigated and a study of the effect of solids fraction in the suspension on its printability was carried out. It was found that solutions with viscosities of up to 28 mPa s and solids content of up to 7.8 vol% can be reproducibly printed, resulting in droplets ranging from 45 to 105 μm depending on the inkjet operating conditions. In order to ensure stable and reproducible droplet formation, a pressure difference ranging from −200 to −1800 Pa had to be maintained in the nozzle. A uniform distribution of dispersed solids in the resulting microcapsules was achieved by adjusting pH and viscosity. The relationship between the printhead operating pressure, the fluid viscosity, the solids loading and the final size of the obtained microcapsules was established, allowing rapid prototyping of artificial cell-like structures with internal solid inclusions by the inkjet method.

Impairment of mitochondrial tRNAIle processing by a novel mutation associated with chronic progressive external ophthalmoplegia

We report a sporadic case of chronic progressive external ophthalmoplegia associated with ragged red fibers. The patient presented with enlarged mitochondria with deranged internal architecture and crystalline inclusions. Biochemical studies showed reduced activities of complex I, III and IV in skeletal muscle. Molecular genetic analysis of all mitochondrial tRNAs revealed a G to A transition at nt 4308; the G is a highly conserved nucleotide that participates in a GC base-pair in the T-stem of mammalian mitochondrial tRNAIle. The mutation was detected at a high level (approx. 50%) in muscle but not in blood. The mutation co-segregated with the phenotype, as the mutation was absent from blood and muscle in the patient's healthy mother. Functional characterization of the mutation revealed a six-fold reduced rate of tRNAIle precursor 3′ end maturation in vitro by tRNAse Z. Furthermore, the mutated tRNAIle displays local structural differences from wild-type. These results suggest that structural perturbations reduce efficiency of tRNAIle precursor 3′ end processing and contribute to the molecular pathomechanism of this mutation.

A fracture mechanics approach to fatigue of heavily drawn steel wires

Heavily drawn steel wires, used in applications such as radial tires, have to withstand a high number of fatigue cycles, typically > 108. Such steel wires have diameters as small as 175μm. High cycle fatigue failure in such wires is initiated by either surface defects or internal non-metallic inclusions. The former leads to shorter fatigue lives than the latter. A methodology has been developed to measure the fatigue threshold Stress Intensity Factor (SIF) for long cracks in these heavily drawn steel wires. Then, the SIF's of the non-metallic inclusions, at which the high cycle fatigue cracks initiate, were compared to the threshold value for long crack growth. It was shown that the defect size that should be used to calculate the SIF is larger than the inclusion size itself. This is validated using Scanning Electron Microscopy in combination with a Focused Ion Beam, proving that the region around non-metallic inclusions is characterized by alterations in the microstructure. In this intermediate region between the inclusion and the start of the long cracks, the crack growth rate is very slow and can be described by a Paris’ law like relationship. Hence, a bi-linear Paris law has been proposed, enabling to predict the fatigue life of heavily drawn steel wires containing any size of inclusions.

Psychotopologies: Closing the Circuit between Psychic and Material Space

In this paper we present an argument for a psychoanalytic understanding of space. While Freud struggled to move away from his own early prepsychoanalytic attempts at mapping the psyche through cerebral localization, he nevertheless found himself compelled to use spatial language and topographical models throughout his career. In his ambivalence, Freud emphasized that the space of the psyche should be read as no more than metaphorical. We argue that the topographical models that Freud struggled with were constrained by the metrics of Euclidean space. The psyche is spatial, just not in topographical terms. For Jacques Lacan many of the psychic operations that Freud described (such as the transference) are better understood in terms of topological operations. Lacan uses such figures as the torus, the cross-cap, and the Möbius strip to demonstrate how the subject is formed through internal exclusions and external inclusions. Using Freud's famous case of the Rat Man, we argue that the neurotic's journey shows him seeking to overcome a psychospatial problem, one that resembles a topological conundrum. Through the Rat Man's story, we demonstrate how Lacan's topology of the subject (the R-schema as cross-cap) accounts for the Möbius twist that allows the neurotic to situate people, events, and places that are apparently separated in time and space in the same place. Ultimately, we consider the usefulness of topology over Euclidean space for building an understanding of space that is at once psychic and material.

Influence of the load ratio on the threshold stress intensity factor range for heavily drawn steel wires

The fatigue behavior of heavily drawn steel wires with a diameter of 175 μm and total strain of 3.5 has been studied. A new approach is used to estimate the threshold stress intensity factor range for crack growth (Δ K th, R ) which is based on fatigue crack initiations at internal non-metallic inclusions. At these internal crack initiations a characteristic area is formed around the inclusion (in literature this region is called optical dark area, granularly bright facet or facet). This area corresponds to the short crack growth regime. The transition between short and long crack growth, which can be seen clearly by fractography, is used to estimate Δ K th, R . Δ K th, R is estimated for different stress amplitudes ( σ a ) and load ratios ( R). It is observed that Δ K th, R is independent of σ a and that the fatigue crack growth is K max controlled for R < 0.15 and Δ K controlled for R > 0.15. The two asymptotes of the (Δ K, K max) graph, Δ K th ∗ and K max ∗ , are calculated to be 3.82 ± 0.09 and 4.47 ± 0.16 MPa √m respectively.