Inelastic Region Research Articles

Cyclic behavior of shear walls with HPFRCCs in the inelastic deformation critical region

This study presents a structural application of high-performance fiber-reinforced cement composites in the inelastic deformation critical region of the shear wall to improve the performance and reduce the disadvantages of conventional reinforced concrete members. Six small-scale wall specimens with the same aspect ratio and various configurations were tested under reversed cyclic loading, and their cyclic behaviors were evaluated and compared. The fiber cementitious material examined in this study exhibited excellent pseudo strain-hardening behavior in tension and high tensile ductility. The results of the quasi-static cyclic tests revealed that the deformation compatibility between the steel reinforcements and high-performance fiber-reinforced cement composite (HPFRCC) matrix could maintain composite integrity. Accordingly, the damage tolerance of the wall specimens for high inelastic deformation could be improved. Furthermore, the ultimate deformation and energy dissipation capacities of the wall specimens were dominated by the ductility and stability of the longitudinal reinforcements. Consequently, the combination of highly ductile mixture material and buckling-restrained measures of steel reinforcement, such as the steel sleeve presented in this paper, was proposed for use in shear walls under moderate or even higher axial loads. Copyright © 2016 John Wiley & Sons, Ltd.

Toward a Solution of the Edwards Equation for the Vertex Function of Quantum Electrodynamics in the Region of Large Momenta

An asymptotic expression for the vertex function in the region of large momenta in quantum electrodynamics is investigated in the ladder approximation. To formulate a calculational model in the ladder approximation, an iterative scheme has been used to solve the Schwinger–Dyson equation in the formalism of a bilocal source of fields. For the chirally symmetric leading approximation, the Edwards equation for the electron–positron–photon vertex has been obtained in the case of arbitrary values of the photon momentum. Our primary task is to develop a method to solve the vertex equation in the region of large momenta. Nontrivial behavior of the vertex function in the deeply inelastic region of momenta has been revealed.

配管系の弾塑性応答時の履歴減衰推定

When piping systems respond under the elastic-plastic region, it is known that the increasing of hysteresis damping and the decreasing of the dominant frequency would occur due to the plastic deformation. But there are few studies that attempt to estimate them quantitatively from the actual excitation test data of piping systems. In this paper, the hysteresis damping ratios and the dominant frequencies under inelastic response behavior region are estimated based on the test data obtained by one-directional shaking table tests on a 3D piping system model. In addition, the strains which were caused on the piping system model are also checked, and correlated with the estimated hysteresis damping ratios. As a result, the estimated damping ratio was about 4% when the one elbow in the piping system model reached to the inelastic region, with about 0.6% strain range. The hysteresis damping ratio was up to more than 10% under the high input acceleration level, when the two main elbows reached to the inelastic region. The dominant frequency was decreased about 3~8% when the one elbow in the piping system model reached to the inelastic region. The decreasing ratio was about 14~18% under the higher input acceleration level.

Dark solitonic interaction and conservation laws for a higher-order [formula omitted]-dimensional nonlinear Schrödinger-type equation in a Heisenberg ferromagnetic spin chain with bilinear and biquadratic interaction

In this paper, a higher-order (2+1)-dimensional nonlinear Schrödinger-type equation is investigated, which describes the nonlinear spin dynamics of the (2+1)-dimensional Heisenberg ferromagnetic spin chain with bilinear and biquadratic interaction. Lax pair and infinite-number conservation laws are constructed, which could prove the existence of the multi-soliton solutions. Via the auxiliary function, bilinear forms and dark-soliton solutions are derived. Properties and interaction patterns for the dark solitons are investigated: (i) Effects on the dark solitons arising from the bilinear interaction, biquadratic interaction and lattice parameter are discussed. (ii) Through the asymptotic analysis, elastic and inelastic interaction between the two solitons is discussed analytically and graphically, respectively. Due to the elastic interaction, amplitudes and velocities of the two dark solitons remain unchanged with the distortion of the interaction area, except for certain phase shifts. However, in virtue of the inelastic interaction, amplitudes of the dark solitons reduce to zero, without the distortion. (iii) Elastic interaction among the three dark solitons is investigated, which implies that the properties of the elastic interaction among the three are similar to that between the two, except for the more complicated distortion. Inelastic–elastic interaction is also investigated, which implies that the interaction between the inelastic region and the dark soliton is elastic. (iv) Linear stability analysis is proposed, which is used to analyze the properties of modulation instability and proves that the dark solitons are modulationally stable.

Dynamic pseudoplastic behavior of laminated ceramics with soft and hard interbedded dense layers

Laminated ZrO–Zr2CN/Si3N4 ceramics with soft and hard interbedded dense layers were prepared via tape casting and reactive hot pressing. The dynamic compressive behavior was investigated at various high strain rates ranging from 1000 to 5000s−1 using a split Hopkinson bar, and the dynamic loading pattern was analyzed. With increasing the strain rate, the dynamic strength obtained a peak value, while the failure strain increased continuous. The compressive stress–strain curves exhibited universal four deformation regions, including inelastic deformation region, rapid loading region, pseudoplastic deformation region and failure region. The dynamic pseudoplastic behavior of the laminated ceramics was similar to that of some metal matrix composites.

Fabrication and dynamic compressive response of laminated ZrO–Zr2CN/Si3N4 ceramics

Laminated ZrO–Zr2CN/Si3N4 ceramics with soft and hard interbedded layers and an in-situ interface were prepared via tape casting and reactive hot pressing, and the dynamic compressive response was investigated using a Split Hopkinson pressure bar tester at a range of high strain rates from 1.1×103s−1 to 3.5×103s−1. With increasing the strain rates, the duration and energy of transmitted wave decreased, but that of reflected wave as well as the failure strain increased continuously. The energy absorptivity kept at a high stable level. The four characteristic stages of the stress–strain curves were inelastic loading region, stable loading region, pseudoplastic deformation region and failure region. The laminated ceramics possessed longer stable loading region but shorter pseudoplastic deformation region at higher high-strain-rates. The failure model consisting of a three-part process of multi-reflection of stress waves, crack initiation and crack deflection at the interfaces was established.

The Profile of Inelastic Collisions from Elastic Scattering Data

Using the unitarity relation in combination with experimental data about the elastic scattering in the diffraction cone, it is shown how the shape and the darkness of the inelastic interaction region of colliding protons change with increase of their energies. In particular, the collisions become fully absorptive at small impact parameters at LHC energies that results in some special features of inelastic processes. Possible evolution of this shape with the dark core at the LHC to the fully transparent one at higher energies is discussed that implies that the terminology of the black disk would be replaced by the black toroid. The approach to asymptotics is disputed. The ratio of the real to imaginary parts of the nonforward elastic scattering amplitude is briefly discussed. All the conclusions are only obtained in the framework of the indubitable unitarity condition using experimental data about the elastic scattering of protons in the diffraction cone without any reference to quantum chromodynamics (QCD) or phenomenological approaches.

Unitarization and low-energy scattering data

A procedure based on the well-known $\mathcal{K}$-matrix formalism is presented, which makes patterns in inelastic regions of low-energy scattering data considerably more transparent. It relies on the use of an empirical kernel, obtained by eliminating elastic loops from the experimental amplitude. This allows structures associated with resonances, such as locations, widths, and heights, to become visible with the naked eye. The method is illustrated with a study of the $P$-wave $K\ensuremath{\pi}$ amplitude.

Credit-Induced Boom and Bust

Can a credit expansion induce a boom and bust in house prices and real economic activity? This paper exploits the federal preemption of national banks in 2004 from local laws against predatory lending to gauge the effect of the supply of credit on the real economy. Specifically, we exploit the heterogeneity in the market share of national banks across counties and in state anti-predatory laws to instrument for an outward shift in the supply of credit. First, a comparison between counties in the top and bottom deciles of presence of national banks in states with anti-predatory laws suggests that the preemption regulation resulted in a 11% increase in annual lending in the 2004-2006 period. Our estimates show that this lending increase is associated with a 3.3% rise in annual house price growth rate and a 2.2% expansion of employment in the non-tradable sectors. These effects are followed by a decline in loan origination, house prices and employment of similar magnitude in subsequent years. Furthermore, we show that the increase in the supply of credit reduced mortgage delinquency rates during the boom years but increased them in bust years. Finally, these effects are stronger for subprime and inelastic regions.

Analyticity of $$\eta \pi $$ η π isospin-violating form factors and the $$\tau \rightarrow \eta \pi \nu $$ τ → η π ν second-class decay

We consider the evaluation of the \(\eta \pi \) isospin-violating vector and scalar form factors relying on a systematic application of analyticity and unitarity, combined with chiral expansion results. It is argued that the usual analyticity properties do hold (i.e. no anomalous thresholds are present) in spite of the instability of the \(\eta \) meson in QCD. Unitarity relates the vector form factor to the \(\eta \pi \rightarrow \pi \pi \) amplitude: we exploit progress in formulating and solving the Khuri–Treiman equations for \(\eta \rightarrow 3\pi \) and in experimental measurements of the Dalitz plot parameters to evaluate the shape of the \(\rho \)-meson peak. Observing this peak in the energy distribution of the \(\tau \rightarrow \eta \pi \nu \) decay would be a background-free signature of a second-class amplitude. The scalar form factor is also estimated from a phase dispersive representation using a plausible model for the \(\eta \pi \) elastic scattering \(S\)-wave phase shift and a sum rule constraint in the inelastic region. We indicate how a possibly exotic nature of the \(a_0(980)\) scalar meson manifests itself in a dispersive approach. A remark is finally made on a second-class amplitude in the \(\tau \rightarrow \pi \pi \nu \) decay.

초고강도 섬유보강 콘크리트 분절형 박스 거더의 휨거동

압축강도 160MPa과 길이 15.4 m를 가진 초고강도 섬유보강 콘크리트 분절박스 거더의 휨거동 실험을 수행하였다. 초고강도 섬유보강 콘크리트 분절 박스에 연성거동 특성을 보강하기 위한 강섬유와 종방향철근의 조합 효과를 두종류의 강섬유 혼입률로 제작된 초고강도 분절형 박스거더의 휨거동을 비교함으로써 평가하였다. 강섬유 혼입률이 1%이고 전단철근과 상부플랜지와 복부에 종방향철근으로 보강한 초고강도 콘크리트 박스거더 BF2의 거동은 탄성응력대에서 전단철근 없이 강섬유 혼입률 2%인 초고강도 섬유보강 콘크리트 박스거더와 유사한 연성거동을 보여준다. 그러나 비선형응력대에서는 BF1의 강성이 약간 더 크고 안정적인 연성거동 형태를 보여주고 있다. 초고강도 섬유보강 콘크리트 박스거더의 분절면은 휨파괴 시까지 균열이나 슬립이 발생하지 않았다.

Measurement of the structure function of the nearly free neutron using spectator tagging in inelasticH2(e,e′ps)Xscattering with CLAS

Much less is known about neutron structure than that of the proton due to the absence of free neutron targets. Neutron information is usually extracted from data on nuclear targets such as deuterium, requiring corrections for nuclear binding and nucleon off-shell effects. These corrections are model dependent and have significant uncertainties, especially for large values of the Bjorken scaling variable x. The Barely Off-shell Nucleon Structure (BONuS) experiment at Jefferson Lab measured the inelastic electron deuteron scattering cross section, tagging spectator protons in coincidence with the scattered electrons. This method reduces nuclear binding uncertainties significantly and has allowed for the first time a (nearly) model independent extraction of the neutron structure function. A novel compact radial time projection chamber was built to detect protons with momentum between 70 and 150 MeV/c. For the extraction of the free neutron structure function $F_{2n}$, spectator protons at backward angle and with momenta below 100 MeV/c were selected, ensuring that the scattering took place on a nearly free neutron. The scattered electrons were detected with Jefferson Lab's CLAS spectrometer. The extracted neutron structure function $F_{2n}$ and its ratio to the deuteron structure function $F_{2d}$ are presented in both the resonance and deep inelastic regions. The dependence of the cross section on the spectator proton momentum and angle is investigated, and tests of the spectator mechanism for different kinematics are performed. Our data set can be used to study neutron resonance excitations, test quark hadron duality in the neutron, develop more precise parametrizations of structure functions, as well as investigate binding effects (including possible mechanisms for the nuclear EMC effect) and provide a first glimpse of the asymptotic behavior of d/u as x goes to 1.

Relationship between boson heat capacity peaks and evolution of heterogeneous structure in metallic glasses

The dependence of boson heat capacity peaks of a typical Zr52.5Ti5Cu17.9Ni14.6Al10 metallic glass on different annealing time and quenching rates is studied. It is found that the boson heat capacity peak moves to higher temperatures and reduces intensity when the metallic glass is isothermally annealed or slowly quenched. We show that the intensity and position change of the boson heat capacity peak are associated with the evolution of heterogeneous structure and inelastic regions in metallic glasses. The results might help in understanding the structural features and evolution as well as their effects on boson peak of metallic glasses.

Reliability-analysis on damage of unidirectional composites matrix polymers

This work presents an analytical model to predict the strength of the unidirectional carbon epoxy composite using micromechanical techniques. This model supposes that a group of broken fibres surrounded by a number of intact fibres with hexagonal arrangement. The mathematical developments used are presented to justify the distribution form of the stresses around broken fibre and adjacent intact fibres. To follow the evolution of the damage in regions of debonding and local plasticity; we proceeded to a progressive increase in the fiber volume fraction and tensile external load. This, procedure enable us to evaluate the extension of the region locally plasticized, the ineffective region, the stress concentration and the longitudinal displacement of broken and intact fibres, in function of broken fibres number and specimen length. As fiber breaks are intrinsically random, the variability of input data allows us to describe the probabilistic model by using the Monte-Carlo method. The sensitivities of the mechanical response are evaluated regarding the uncertainties in design variables such as Young’s modulus of fibers and matrix, fiber reference strength, shear yield stress, fiber volume fraction and shear parameter defining the shear stress in the inelastic region.

Inelastic neutron scattering investigation of ball-milled FeSiB described as a magnetic nanoglass-like structure

An inelastic neutron scattering study has been carried out to assess the effects of mechanical milling treatments (10, 20 and 70h) on an amorphous melt-spun FeSiB ribbon. Faint traces of crystallization were observed after 10 and 20h milling by X-ray diffraction and Mössbauer spectroscopy and a minor fraction of bcc-Fe was clearly detected after 70h. Whilst the neutron spectrum S(E) of the 10h-milled sample, at temperature T=300K, does not differ from that of the precursor FeSiB ribbon, the area of the inelastic region of S(E) decreases more and more after 20 and 70h milling. Moreover, in the samples milled for 20 and 70h, also the area of the elastic region of the S(E) spectrum is definitely smaller than the one of the FeSiB ribbon. This is consistent with a reduction of the magnetic cross section upon milling and it agrees also with magnetization measurements. We interpret this behavior assuming that the milling treatment causes local alterations of the short-range atomic order within the amorphous phase, and hence of the precursor collinear ferromagnetic order, finally giving rise to a sort of magnetic nanoglass structure.

Investigation Stress-Strain Behaviors of Glass/Polymer Composites

In this paper, a micromechanical model based on Generalized Method of Cells(GMC) for predicting stress-strain behaviors of polymer-matrix composites is presented. Improved Bodner-Partom viscoplastic model is incorporated into GMC to describe nonlinear mechanical behavior of composites. On this basis, strain rate and fiber volume fraction(FVF) influence on nonlinear behaviors of composites are discussed. The results show that strain rate influences on stress-strain behaviors of composites in inelastic region can be clearly discerned. Moreover, FVF tends to clearly increase stiffness behaviors of polymer-composites.

Examining potential shortcomings in using phase shifts as a link between experiment and QCD

Luscher has shown that in single channel problem (elastic region below first inelastic threshold) there exists a direct link between the discrete value of the energy in a finite QCD volume and the scattering phase shift at the same energy. However, when the extension of the theorem is made to the baryon resonance sector (multi-channel situation in the inelastic region above first inelastic threshold), eigenphases (diagonal multi-channel quantities) replace phase shifts (single channel quantities). It is necessary to stress that the renowned pi/2 resonance criterion is formulated for eigenphases and not for phase shifts, so the resonance extracting procedure has to be applied with utmost care. The potential instability of extracting eigenphases from experimental data which occurs if insufficient number of channels is used can be reduced if a trace function which explicitly takes multi-channel aspect of the problem into account is used instead of single-channel phase shifts.

Model calculation of the asymptotics of the scattering amplitude in massive φ 4 theory

An asymptotic solution of an equation of Bethe–Salpeter type in the massive theory with λφ 4 interaction is investigated in the ladder approximation. The main problem is to work out a recipe to ground a concrete asymptotic solution of equations of Bethe–Salpeter type for amplitudes in models with 4-fermion interaction in different regions of variation of the momentum. An integral equation for the imaginary part of the forwardscattering amplitude with two-particle irreducible kernel is used. An explicit expression is found for the kernel, which consists of a simple bubble and comprises part of the kernel of the considered equation. The corresponding equation is solved in the deeply inelastic region of momenta in the form of a power-law function.

Within subject heterogeneity in tissue-level post-yield mechanical and material properties in human trabecular bone

The ability to determine patient-specific mechanical properties of trabecular bone is needed for a reliable estimation of fracture risks. Tissue mechanics and material composition are important factors that contribute to trabecular bone performance, but only a few studies have investigated the post-yield behaviour of human trabecular bone, and limited knowledge for modelling is available about ultimate properties needed.Aim of this paper was to investigate absolute values and deviation of mechanical and material properties of human trabecular bone at the tissue level, in a healthy and osteoporotic donor. A combination of tensile and bending tests of single trabeculae up to failure, μCT measurement of sample geometry and finite element analysis were incorporated to determine mechanical properties. The samples were analysed with Raman spectroscopy to evaluate the material composition. High within-subject variability was found, for both the healthy and osteoporotic donor. Nevertheless, the two donors could be separated by analysing the ultimate strain and post-yield work, as well as two of the material parameters (B-type carbonate substitution ratio and collagen cross-link ratio). It indicates that tissue level properties seem to be relevant also for macroscopic mechanical behaviour. These findings also suggest that the mechanical variability for the inelastic region at the tissue level may be associated with varying material properties, while until yielding occurs our data does not suggest any connection between the mechanical and the investigated material. Finally, a set of mechanical properties of human bone have been reported that are a relevant reference for computational studies and FE analysis.

Modeling a smooth elastic–inelastic transition with a strongly objective numerical integrator needing no iteration

Large deformation evolution equations for elastic distortional deformation and isotropic hardening/softening have been developed that model a smooth elastic---inelastic transition for both rate-independent and rate-dependent response with no need for loading---unloading conditions. A novel special case is a rate-independent overstress model. Specific simplified constitutive equations are proposed that capture the main effects of elastic-plastic and elastic-viscoplastic materials with only a few material parameters. Moreover, a robust and strongly objective numerical integrator for these simplified evolution equations has been developed which needs no iteration. Examples show the influence of the various parameters on the predicted material response. The smoothness of the elastic---inelastic transition in the proposed model, with the associated overstress, tends to spread the inelastic region. This side effect prevents severe deformation from being localized in an element region that continues to reduce in size with mesh refinement. However, preliminary calculations indicate the need for additional modeling of a material characteristic length that independently controls the size of a localized severely deformed region.