Gauge Part Research Articles

Investigation and microstructural analyses of massive LSP impacts with coverage area on crack initiation location and tensile properties of AM50 magnesium alloy

The influence of massive laser shock peening (LSP) impacts with coverage area on tensile properties of AM50 magnesium alloy was investigated using MTS880-10 servo-hydraulic material testing machine system. Microstructure in the surface layer and fracture morphologies of as-machined and LSPed tensile specimens were also characterized and analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cross-sectional optical microscopy (OM). Special attention is paid to the crack initiation location as a function of LSPed coverage area in the gauge part of tensile specimen. Experimental results and analysis indicate that coverage area significantly influenced tensile properties of the tensile specimen. In addition, the grain refinement process in the top surface layer of AM50 magnesium alloy caused by massive LSP impacts is presented. Furthermore, the underlying influence mechanism of LSPed coverage area on tensile properties and crack initiation location of tensile specimen was clearly revealed.

Stress Corrosion Cracking of Sensitized 304 Stainless Steel Under MgCl2 Droplets

Stainless steels have been widely applied in the building, chemical plants and other industries due to their excellent weldability, superior anticorrosion properties, and so on. However, stainless steels suffer from localized corrosion in chloride-containing environments. Especially, in an atmospheric environments near the seashore, localized corrosion can be initiated easily because a very severe corrosion condition, a thin water-layer containing very high concentration of chloride ions, can be made on stainless steels. Moreover, local corrosion sites such as pits can become initiation sites for crack initiation of stress corrosion cracking (SCC) when the steels are subjected to tensile stress. Therefore, it can be considered that atmospheric SCC is one of the most severe degradations for stainless steels in atmospheric corrosion environments. There are some researches to investigate SCC in the atmospheric corrosion environments with chloride deposits1, 2. This study is aimed at investigating initiation and propagation of stress corrosion cracking of sensitized 304 stainless steel under tensile stress in MgCl2droplets. Austenitic 304 stainless steel sheet of 1 mm in thickness were used as a material. Tensile specimens with a gauge part of L15 mm x W8 mm were cut out from the sheet. The specimens were heated for 90 min at 700 oC and followed by furnace cooling for sensitization. The sensitized specimens were abraded to JIS #1000 grit with SiC papers. Then they were degreased with ethanol in an ultrasonic bath and rinsed with Milli-Q water (18 MWcm). SCC behavior under MgCl2 droplets was investigated by a constant strain tensile test with a horizontal tensile test machine. In the test, a specimen was first elongated to a certain stress value and then kept at a constant strain. After applying the constant strain, 20 mL droplets of 250 mM MgCl2 were placed on the gauge part of the specimen. The gauge part with the droplets was exposed to an environment at 50 OC and ca. 35 RH% for 3 days in a small chamber. During the test, in-situ surface observation was carried out with a digital microscope. After the test, surface of the specimen was observed by SEM-EDX. Fig. 1 shows surface and cross-sectional images of sensitized 304 stainless steel with 8.5% strain under MgCl2droplets. When the droplets are place on the gauge part of the specimen, the droplets evaporate and reach to an equilibrium state with the concentration of 10 M at 35%RH. At this time, the thickness of the solution film of the droplets can be estimated to be 70 mm. Actually pitting corrosion was initiated within 1 h after the droplets were applied. As shown in Fig. 1(a), which is taken at 12 h after a pit is formed in a droplet, some tiny cracks initiate from the edge of the pit. As the test time advances, the cracks propagate in the normal direction to the tensile axis and reach ca. 600 mm after 72 h. During the propagation of the cracks, hydrogen bubbles gushing from the inside of the cracks were observed. Cross-sectional observation in Fig. 1(d) reveals that cracks initiate from the bottom of the pit and propagate in the bulk direction both with transgranular and intergranular cracking modes. In the presentation, crack propagation mechanism of sensitized 304 stainless steel will be discussed.

Gauge Invariance, Lorentz Covariance and Canonical Quantization in Nucleon Structure Studies

There are different operators of quark and gluon momenta, orbital angular momenta, and gluon spin in the nucleon structure study. The precise meaning of these operators are studied based on gauge invariance, Lorentz covariance and canonical quantization rule. The advantage and disadvantage of different definitions are analyzed. A gauge invariant canonical decomposition of the total momentum and angular momentum into quark and gluon parts is suggested based on the decomposition of the gauge potential into gauge invariant (covariant) physical part and gauge dependent pure gauge part. Challenges to this proposal are answered. \keywords{Physical and pure gauge potentials; Gauge invariant canonical quark and gluon momenta, orbital angular momenta and spins; Homogeneous and non-homogeneous Lorentz transformations; Gauge invariant decomposition and gauge invariant extension; Classical and quantum measurements.

CARBON-EPOXY COMPOSITE FATIGUE STRENGTH – EXPERIMENT AND FEM NUMERICAL ESTIMATION

The development of composite materials characterized by the constant amelioration of their mechanical properties (stiffness and strength) has widened their application for structural elements, mainly in aeronautical, naval and automobile industries. The possibility of tailoring the composite’s properties appropriately to the applied load (by changing the direction of the fibre alignment and applying a corresponding matrix) results in the growing importance of the design process. The paper presents a numerical technique of determining the fatigue strength of the laminated carbon–epoxy composite. The experimental investigations were carried out to determine the complete set of the stiffness characteristics E ij , G ij , �� ij , the strength characteristics �1 i,n , �0 i,n . and the S-N fatigue curves. The static and fatigue numerical calculations were carried out for the material anisotropic model of the particular composite layers. Eight-node 3D finite elements with the composite’s properties were used to develop the specimen’s numerical model. The contact problem between the composite layers enabling the reflection of a mutual interaction was taken into account. The numerical investigation also included the state of effort analysis and the fatigue life assessment of the composite. The assessment of the composite’s fatigue life was performed using the MSC.Fatigue code. The verification of models and numerical analysis was carried out for composite specimens made of the CE 8201-24545/120 prepreg. The experimental verification confirmed that the places of the lowest fatigue life, found out in numerical analysis, are located in the area of the gauge part.

Notoph-Graviton-Photon Coupling

In the sixties Ogievetskii and Polubarinov proposed the concept of notoph, whose helicity properties are complementary to those of photon. Later, Kalb and Ramond (and others) developed this theoretical concept. And, at the present times it is widely accepted. We analyze the quantum theory of antisymmetric tensor fields with taking into account mass dimensions of notoph and photon. It appears to be possible the description of both photon and notoph degrees of freedom on the basis of the modified Bargmann-Wigner formalism for the symmetric second-rank spinor.Next, we proceed to derive equations for the symmetric tensor of the second rank on the basis of the Bargmann-Wigner formalism in a straightforward way. The symmetric multispinor of the fourth rank is used. It is constructed out of the Dirac 4-spinors. Due to serious problems with the interpretation of the results obtained on using the standard procedure we generalize it, and we obtain the spin-2 relativistic equations, which are consistent with the general relativity. The importance of the 4-vector field (and its gauge part) is pointed out.Thus, we present the full theory which contains the photon, the notoph (the Kalb-Ramond field) and the graviton. The relations of this theory with the higher spin theories are established. In fact, we deduced the gravitational field equations from relativistic quantum mechanics. The relations of this theory with scalar-tensor theories of gravitation and f(R) are discussed. We estimate possible interactions, fermion-notoph, graviton-notoph, photon-notoph, and we conclude that they will be probably seen in experiments in the next few years.

Investigation of Plastic Instability in TWIP Steels by <i>In Situ</i> Diffraction of High Energy X-Rays

We investigate the non uniform plastic deformation of a TWIP FeMnC steel by diffraction of high energy synchrotron X-rays. In particular, we observe the propagation of bands of plastic strain localisation. Debye-Scherrer rings are recorded in situ during tensile tests at two different strain rates. Discontinuous initial rings characteristic of unstrained polycristals with no texture become rapidly continuous after several percents of plastic strain due to strain gradients within the grains and a strong texture develops. The crystallographic dependence of the Young’s modulus is estimated and is consistent with the elastic anisotropy of a cubic crystal. A delay between the serrations on the macroscopic tensile curve and the stepwise variations of the diffracted peak’s position and width are consistent with propagating bands nucleating outside the X-ray beam. Slower and thinner bands are observed at the lowest strain rate. A tensile test interrupted to perform a few minute relaxation leads to a displacement of the nucleation site of the bands from one end to the middle of the gauge part.

Microstructural Evolution of X20CrMoV12.1 Steel upon Short-term Creep Rupture Test

In this work, microstructural and hardness evolution of the X20 steel upon short-term creep test (<TEX>$550^{\circ}C$</TEX> to <TEX>$650^{\circ}C$</TEX>, <TEX>$180^{\circ}C$</TEX> to 60 MPa) was studied by using scanning electron microscope, electron backscattered diffraction, and transmission electron microscope, microhardness tester. After creep rupture, gauge and grip part of the specimens were microstructurally analyzed. Creep at the <TEX>$650^{\circ}C$</TEX>/60 MPa resulted in a rupture at 1,460 hours with growth of lath width from 1.31 to <TEX>$2.87{\mu}m$</TEX> and a grain growth with a more equiaxed feature. There is a close relationship between Microhardness and lath width. The formation and coarsening of Laves phase, which was observed up to <TEX>$600^{\circ}C$</TEX> of creep temperature, was accelerated by the applied stress. Slight coarsening of the <TEX>$M_{23}C_6$</TEX> was observed in the <TEX>$550^{\circ}C$</TEX> and <TEX>$600^{\circ}C$</TEX> crept or aged specimens. The coarsening of <TEX>$M_{23}C_6$</TEX> depended on the temperature, where specimens crept at <TEX>$650^{\circ}C$</TEX> showed higher growth rate. The microstructural evolution of X20 after short-term creep test was extensively discussed in relation to the long-term creep/aging test reported in literatures.

Error compensation method for improving the accuracy of biomodels obtained from CBCT data

This paper presents a method of improving the accuracy of the tridimensional reconstruction of human bone biomodels by means of tomography, with a view to finite element modelling or surgical planning, and the subsequent manufacturing using rapid prototyping technologies. It is focused on the analysis and correction of the results obtained by means of cone beam computed tomography (CBCT), which is used to digitalize non-superficial biological parts along with a gauge part with calibrated dimensions. A correction of both the threshold and the voxel size in the tomographic images and the final reconstruction is proposed. Finally, a comparison between a reconstruction of a gauge part using the proposed method and the reconstruction of that same gauge part using a standard method is shown. The increase in accuracy in the biomodel allows an improvement in medical applications based on image diagnosis, more accurate results in computational modelling, and improvements in surgical planning in situations in which the required accuracy directly affects the procedure's results. Thus, the subsequent constructed biomodel will be affected mainly by dimensional errors due to the additive manufacturing technology utilized, not because of the 3D reconstruction or the image acquisition technology.

Gauge invariant descriptions of gluon polarizations revisited

We examine the feasibility of gauge invariant descriptions of the gluon polarization following the proposal that a gauge field can be decomposed into its physical part and its pure gauge part. We show that gauge invariant angular momentum currents can be constructed from summations of gauge variant Noether currents. We present novel expressions of the pure gauge field, which are used to formulate gauge invariant descriptions of the gluon spin and the photon spin. We show that the gauge invariant extension of the Chern-Simons current can describe the spins of the Laguerre-Gauss laser modes. We also discuss the relation of gauge invariant operators and the parton distributions constructed from Dirac variables.

1408 スリット入りつば付き試験片のクリープ変形特性と変形一様性(OS15-2 諸観点からの物質・材料の特性評価II,OS15 諸観点からの物質・材料の特性評価)

Since numerical analyses under elevated temperature usually depend on a constitutive equation of creep, it is necessary to derive a high-precision equation. Creep properties on deformation can be normally obtained using constant load creep machines, but constant stress creep tests are more suitable to acquire high-precision creep data. Conventional uniaxial creep specimens have ridges attached on both sides of gauge length. However, even if the constant stress creep testing machines are used, these ridges prevent area reduction around them, and cause unequal deformation in the gauge part. Authors have proposed cutting slits into the ridge to release the specimen from the circumferential constraint by extensometer ridges. In this study, taking into account a realistic analytic condition, the authors carried out elastic-plastic creep Finite Element (FE) analyses to investigate the performance of uniform deformation. Subsequently, a series of interrupted constant stress creep, tests using SUS304 steel were conducted to examine the effect of introducing slits. The analytical and the experimental results showed that the introduction of these slits into the ridges would affect the deformation during creep, but not improve the uniformity of deformation along the gauge part.

Tensile Plastic Deformation Behavior of Zr&lt;sub&gt;70&lt;/sub&gt;Ni&lt;sub&gt;16&lt;/sub&gt;Cu&lt;sub&gt;6&lt;/sub&gt;Al&lt;sub&gt;8&lt;/sub&gt; Bulk Metallic Glass at Cryogenic Temperature

A hypoeutectic Zr­Ni­Cu­Al bulk metallic glass (BMG) shows a clear tensile plastic deformation under a high strain rate condition at room temperature. In this study, the effect of cryogenic temperature and strain rate on the tensile plastic deformation behavior of the hypoeutectic Zr­Ni­Cu­Al BMG was investigated. Tensile tests were performed for the hypoeutectic Zr­Ni­Cu­Al BMG specimen with gauge part dimensions of 2.3mm in length and 0.8mm in diameter at cryogenic temperature (133K) under different strain rate conditions (1014 and 1011 s11). As the results, the tensile plastic deformation occurs under both strain rate conditions. Especially, in low strain rate condition (1014 s11), the amount of plastic deformation is clearly larger than that under the high strain rate condition (1011 s11). Furthermore, it was found that there is no positive correlation between the amount of tensile plastic deformation and the number of shear band. In addition, it was inferred that the tensile plastic deformation of the hypoeutectic Zr­Ni­Cu­Al BMG at cryogenic temperature was induced by specimen sliding along only one major shear band. [doi:10.2320/matertrans.M2012102]

Characteristics of Uniform Deformation in Uniaxial Creep Specimen with Slits Introduced in the Extensometer Limbs

Constant stress creep test instead of conventional constant load one should be performed to create an accurate constitutive equation of creep at designing modern high temperature machines and structures. However constant stress creep testing machines have not been widely employed yet because of their complex structures. Furthermore even if the constant stress creep machine were employed, constraint of limbs attached on a gauge part of the creep specimen for measuring creep strain would be another inevitable issue. These extensometer limbs on the uniaxial creep specimen usually prevent uniform deformation along the gauge part. In order to release the deformation of circumferential constraint by extensometer limbs, 24 slits were introduced in each limb. After these slits were machined in the limb of the uniaxial creep specimen, uniaxial tensile tests were firstly carried out to measure the strain distribution along the gauge part employing low alloy and austenitic stainless steels. Subsequently Finite Element Analyses were performed to examine the validity of introducing these slits into the extensometer limb. The analytic results showed that the uniaxial specimen with slits could release the circumferential constraint and raise the uniform deformation along the gauge part. It was also found that there was an optimum depth of the slit to deform uniformly for each material and that its depth depended on the work hardening property of the material.

THE MODIFIED BARGMANN-WIGNER FORMALISM FOR HIGHER SPIN FIELDS AND RELATIVISTIC QUANTUM MECHANICS

On the basis of our recent modifications of the Dirac formalism we generalize the Bargmann-Wigner formalism for higher spins to be compatible with other formalisms for bosons and fermions. Connections with dual electrodynamics, with the Ogievetskii-Polubarinov notoph and the Weinberg 2(2 S +1) theory are found. Next, we proceed to derive the equations for the symmetric tensor of the second rank on the basis of the Bargmann-Wigner formalism in a straightforward way. The symmetric multispinor of the fourth rank is used. It is constructed out of the Dirac 4-spinors. Due to serious problems with the interpretation of results we generalize the standard procedure and we obtain the spin-2 relativistic equations, which are consistent with the Einstein-Hilbert equation. We introduce the dual analogues of the Riemann tensor and we derive corresponding dynamical equations in the Minkowski space. Connections with the Marques-Spehler chiral gravity theory are discussed. The importance of the 4-vector field (and its gauge part) is pointed out. The spin-3/2 case is briefly discussed too.

The group structure of non-Abelian NS-NS transformations

We study the transformations of the worldvolume fields of a system of multiple coinciding D-branes under gauge transformations of the supergravity Kalb-Ramond field. We find that the pure gauge part of these NS-NS transformations can be written as a U(N) symmetry of the underlying Yang-Mills group, but that in general the full NS-NS variations get mixed up non-trivially with the U(N). We compute the commutation relations and the Jacobi identities of the bigger group formed by the NS-NS and U(N) transformations.

Influence of Specimen Geometry of Hot Torsion Test on Temperature Distribution During Reheating Treatment of API-X70

The commercial finite element package ANSYS™ was utilized for prediction of temperature distribution during reheating treatment of hot torsion test (HTT) samples with different geometries for API-X70 microalloyed steel. Simulation results show that an inappropriate choice of test specimen geometry and reheating conditions before deformation could lead to non-uniform temperature distribution within the gauge section of specimen. Therefore, assumptions of isothermal experimental conditions and zero temperature gradient within the specimen cross section appear unjustified and led to uncertainties of flow curve obtained. Recommendations on finding proper specimen geometry for reducing temperature gradient along the gauge part of specimen will be given to create homogeneous initial microstructure as much as possible before deformation in order to avoid uncertainty in consequent results of HTT.

Creep Behavior and Microstructure of 8Cr Oxide Dispersion Strengthened Martensitic Steel

In international thermonuclear experimental reactor (ITER), reduced activation ferritic/martensitic steels will be used for plasma-facing materials. However, it is necessary to raise the temperature of operation in order to elevate efficiency of electric power generation by using the material which is more excellent in strength at elevated temperature. Oxide dispersion strengthened (ODS) steels are promising candidate for high temperature materials of a nuclear fusion reactor. There are many reports that ODS steels show very high creep strength, but there are few reports on creep deformation mechanism. In this work, creep deformation behavior of 8 wt% Cr ODS steel was investigated. This ODS steel had high density of fine dispersed Y2Ti2O7 particles and -ferrite grains elongated along the hot-rolling direction. The creep curve showed a low creep strain rate until specimen ruptured. Vickers hardness of the gauge part of specimens in interrupted creep tests decreased with increasing the loading time. However, that of the grip part did not change significantly. Accordingly, although dynamic recovery occurred in the ODS steel, it had not affected the creep deformation rate.

Relation between local necking and cavitation during high-temperature tensile deformation of polycrystalline pure aluminum

For polycrystalline aluminum with grain size of 170 and 346μm, tensile deformation was carried out at a true strain rate of 1×10−2/s and a temperature of 553K (=0.59Tm, Tm: melting temperature in K). Onset and progress of local necking during the deformation were investigated by measurements of small-angle X-ray scattering (SAXS) from a viewpoint of cavity formation on grain boundaries. The cavitation was observed in the change of the SAXS intensities as a function of local strain along the gauge part of specimen. The intensities increase rather slowly during the beginning uniform deformation. However, it increases rapidly in the gauge part where the local necking has occurred. The degree of cavitation is found to be more remarkable for a specimen with smaller grain size. Cavity size and size distribution are evaluated from the SAXS profiles. The local necking phenomenon is discussed from a viewpoint of cavitation.

Prediction of Distortion of Airframe Components Made from Aluminum Plates

A mathematical model formulated for the prediction of distortion of airframe components manufactured from 7050-T7451 aluminum plates, caused by residual stresses introduced by the manufacturing process of the plate, was tested in validation experiments. The results indicate that distortion in thin gauge parts is caused primarily by machining-induced residual stresses. The residual stresses introduced by the plate manufacturing process, which includes hot rolling, quenching stretching, and aging operations, have a minor effect on distortion, consistent with the predictions based on the mathematical model described herein.

Fields of stored energy associated with localized necking of steel

This paper describes an experimental procedure for the simultaneous determination of heat sources and mechanical energy involved locally during a heterogeneous tensile test. This procedure involves two complementary imaging techniques: digital image correlation (DIC) and infrared thermography (IRT). The first technique gives displacement fields from which strains are derived while the second provides temperature fields with which the heat sources are estimated using a local form of the heat equation. Moreover, a method based on integration of equilibrium equations under the plane stress assumption is used to determine the stress distribution during the test. The distribution of the local deformation energy developed by the material is then assessed using stress and strain-rate fields. Tensile tests were performed on thin flat steel samples. The results revealed early and gradual development of strain localization within the gauge part of the specimen. Energy balances were performed inside and outside the necking zone based on the assumption that the thermoelastic part of the behaviour remains linear and isotropic. Finally, indirect estimate of the stored energy led us to compute the time course of the local Taylor-Quinney coefficient. mechanical energy involved locally during a heterogeneous tensile test. This procedure involves two complementary imaging techniques: digital image correlation (DIC) and infrared thermography (IRT). The first technique gives displacement fields from which strains are derived while the second provides temperature fields with which the heat sources are estimated using a local form of the heat equation. Moreover, a method based on integration of equilibrium equations under the plane stress assumption is used to determine the stress distribution during the test. The distribution of the local deformation energy developed by the material is then assessed using stress and strain-rate fields. Tensile tests were performed on thin flat steel samples. The results revealed early and gradual development of strain localization within the gauge part of the specimen. Energy balances were performed inside and outside the necking zone based on the assumption that the thermoelastic part of the behaviour remains linear and isotropic. Finally, indirect estimate of the stored energy led us to compute the time course of the local Taylor-Quinney coefficient.

Classical limits of scalar and tensor gauge operators based on the overlap Dirac matrix

It was recently proposed by the second author to consider lattice formulations of QCD in which complete actions, including the gauge part, are built explicitly from a given Dirac operator D. In a simple example of such theory, the gauge action is proportional to the trace of Ginsparg-Wilson operator D chosen to define the quark dynamics. This construction relies on the proposition that the classical limit of lattice gauge operator trD(x,x) is proportional to trF{sup 2}(x) (up to an additive constant). Here we show this for the case of the overlap Dirac operator using both analytical and numerical methods. We carry out the same analysis also for the tensor component of D, which is similarly related to the field-strength tensor F, and obtain results identical to our previous derivation that used a different approach. The corresponding proportionality constants are computed to high precision for a wide range of the negative mass parameter values, and it is verified that they are the same in finite and infinite volumes.