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1

Octupole deformation properties of the Barcelona-Catania-Paris energy density functionals  

CERN Document Server

We discuss the octupole deformation properties of the recently proposed Barcelona-Catania-Paris (BCP) energy density functionals for two sets of isotopes, those of radium and barium, where it is believed that octupole deformation plays a role in the description of the ground state. The analysis is carried out in the mean field framework (Hartree- Fock- Bogoliubov approximation) by using the axially symmetric octupole moment as a constraint. The main ingredients entering the octupole collective Hamiltonian are evaluated and the lowest lying octupole eigenstates are obtained. In this way we restore, in an approximate way, the parity symmetry spontaneously broken by the mean field and also incorporate octupole fluctuations around the ground state solution. For each isotope the energy of the lowest lying $1^{-}$state and the $B(E1)$ and $B(E3)$ transition probabilities have been computed and compared to both the experimental data and the results obtained in the same framework with the Gogny D1S interaction, which...

Robledo, L M; Schuck, P; Viñas, X

2010-01-01

2

Octupole deformation properties of actinide isotopes within a mean field approach  

CERN Document Server

We discuss the octupole deformation properties of many even-even actinide isotopes. The analysis is carried out in the mean field framework (Hartree-Fock-Bogoliubov approximation) by using the axially symmetric octupole moment as a constraint. A one-dimensional octupole collective Hamiltonian is used to obtain properties like excitation energies or $E1$ and $E3$ transition probabilities of the negative parity band-heads associated to the lowest lying $1^{-}$ and $3^{-}$ states. The evolution of these values with neutron number is discussed and a comparison with available experimental data is made. In order to minimize the uncertainties associated to the energy density functional used, the calculations have been carried out for an assorted set ranging from the BCP1 functional to the finite range Gogny interaction with the D1S, D1N and D1M parametrization.

Robledo, L M; 10.1088/0954-3899/39/10/105103

2012-01-01

3

Octupole deformation properties of actinide isotopes within a mean-field approach  

Science.gov (United States)

We discuss the octupole deformation properties of many even-even actinide isotopes. The analysis is carried out in the mean-field framework (Hartree-Fock-Bogoliubov approximation) by using the axially symmetric octupole moment as a constraint. A one-dimensional octupole collective Hamiltonian is used to obtain properties such as excitation energies or the E1 and E3 transition probabilities of the negative-parity band-heads associated with the lowest lying 1- and 3- states. The evolution of these values with neutron number is discussed and a comparison with available experimental data is made. In order to minimize the uncertainties associated with the energy density functional used, the calculations have been carried out for an assorted set ranging from the BCP1 functional to the finite-range Gogny interaction with the D1S, D1N and D1M parametrization.

Robledo, L. M.; Rodríguez-Guzmán, R. R.

2012-10-01

4

Octupole deformation in odd-odd nuclei  

International Nuclear Information System (INIS)

Experimental evidence for octupole deformation in odd-odd nuclei is examined in both the rare earth and actinide regions. Extensive existing experimental data on 154Eu and 152Eu suggest the existence of octupole deformation, while the evidence is less clear for 156Eu. 224Ac and 220Fr have been studied experimentally following the alpha decay of accelerator produced and isotope separated 228PaF+4 and 220AcF+2 ions, respectively. Clear evidence of octupole deformation is found in both cases. Unusually small parity doublet splitting energies are found for the K = O± and K = 3± bands of 224Ac. The experimental Newby shifts of the K = 0± bands in 224Ac have opposite sign but approach the same absolute magnitude as theoretically expected for an octupole deformed system

5

Octupole deformation in sup 223 Ac  

Energy Technology Data Exchange (ETDEWEB)

The level structure of {sup 223}Ac has been obtained from a study of the alpha-decay of mass separated {sup 227}Pa. Two levels connected by a fast E1 transition and with spin and parity 5/2{sup +} and 5/2{sup -} were found: They form a parity doublet suggestive of octupole deformation in this nuclei. The Coriolis matrix element obtained for the mixing between the low-lying states is found to be attenuated, in agreement with theoretical expectations for stable octupole deformation. (orig.).

Ahmad, I.; Holzmann, R.; Janssens, R.V.F. (Argonne National Lab., IL (USA)); Dendooven, P.; Huyse, M.; Reusen, G.; Wauters, J.; Duppen, P. van (Leuven Univ. (Belgium). LISOL)

1989-12-11

6

Octupole Deformed Nuclei in the Actinide Region  

CERN Multimedia

% IS322 \\\\ \\\\ The aim of the present study is to investigate the limits of the "island" of octupole deformation in the mass region A=225. It is of particular importance to demonstrate experimentally the sudden disappearance of the stable octupole deformation in the presence of a well developed quadrupole field. \\\\ \\\\In order to establish the upper border line the $\\beta$ decay chains of $^{227}$Rn $\\rightarrow ^{227}$Fr $\\rightarrow ^{227}$Ra and $^{231}$Fr $\\rightarrow ^{231}$Ra $\\rightarrow ^{231}$Ac were studied at PSB-ISOLDE using advanced fast timing and $\\gamma$-ray spectroscopy techniques. The lifetimes of the excited states have been measured in the picosecond range using the time-delayed $\\beta\\gamma\\gamma$(t) method.

Thorsteinsen, T; Rubio barroso, B; Simpson, J; Gulda, K; Sanchez-vega, M; Cocks, J; Nybo, K; Garcia borge, M; Aas, A; Fogelberg, B; Honsi, J; Smith, G; Naumann, R; Grant, I

2002-01-01

7

Octupole Correlations and Deformation In Ba, La and Pr  

International Nuclear Information System (INIS)

Stable octupole deformation was predicted and subsequently found to occur centered around the reinforcing shell gaps at Z=56 and N=88 for ?3?0.15. Evidence for stable octupole deformation is reviewed. New results in 145Ba and 141Ba are presented. Rotational enhancement of octupole deformation is found at intermittent spins in Ba and La nuclei and the quenching of such deformation at higher spins in 146Ba but not in 144Ba. Symmetric and asymmetric shapes coexist in 145Ba and 145La. Evidence for octupole correlation is found in 147Pr but only h11/2 bands are found in 149,151Pr. The new 141Ba levels have two sets of two intertwined bands of levels with the characteristics of octupole deformation as found in 143,145Ba, however, a problem occurs with the assignment of parities in 141Ba. (author)

8

NUCLEAR PHYSICS: Octupole Deformations of Even-Even Rn, Th, and U Nuclei in Relativistic Mean Field Theory  

Science.gov (United States)

The octupole deformations and other ground state properties of even-even Rn, Th and U isotopes are investigated systematically within the framework of the reflection asymmetric relativistic mean field (RAS-RMF) model. The calculation results reproduce the binding energies and the quadrupole deformations well. The calculation results indicate these nuclei at ground states evolve from nearly-spherical (N = 130) shape to quadrupole deformation shape with the increase of the neutron number. It is also found that among the Rn isotopes, only 222,224Rn are octupole deformed and the octupole deformations for them are small. However, more nuclei (N notsimeq 134-148) in Th and U isotopes are octupole deformed and the octupole deformations for some of them are significant (|?3| ~ 0.1 or even larger).

Wang, Nan; Meng, Jie; Zhao, En-Guang

2010-06-01

9

Experimental tests for stable octupole deformation in actinium-227  

International Nuclear Information System (INIS)

The question of intrinsic reflection asymmetry or stable-octupole deformation in 227Ac was studied by the single-proton stripping reactions 226Ra(3He,d)227Ac with E/sub 3He/ = 30 MeV and 226Ra(?,t)227Ac with E/sub ?/ = 30 MeV and by measuring the magnetic moment of the first excited 3/2+ state at 27.38 keV by a differential perturbed angular correlation (DPAC) experiment. Theoretical differential cross sections were determined using calculated nuclear structure factors with and without octupole-deformed Woods-Saxon model wave functions. Theoretical values for the magnetic moments of the ground state and first excited state with and without octupole deformation were determined using calculated intrinsic g-factors from folded Yukawa model wave functions. The results of the proton-stripping cross sections are inconclusive. No how comparison of the measured values for the magnetic moment of the first excited state with a previous measurement for the ground state seems to support stable octupole deformation in 227Ac. Therefore, the energy ordering of orbitals and the magnetic moment results are consistent and they seem to support a stable-octupole deformed shape for the ground state parity doublet in 227Ac. Furthermore, the results are consistent with the branching ratio determination of the magnetic moment of the first excited state in 227Ac which is in agreement with the stable-octupole model prediction

10

Search for octupole deformation in neutron rich Xe isotopes  

Energy Technology Data Exchange (ETDEWEB)

A search for octupole deformation in neutron rich Xe isotopes has been conducted through gamma-ray spectroscopy of primary fragments produced in the spontaneous fission of {sup 248}Cm. The spectrometer consisted of the Eurogam array and a set of 5 LEPS detectors. Level schemes were constructed for Xe isotopes with masses ranging from 138 to 144. Except for {sup 139}Xe, none of them exhibit an alternating parity quasimolecular band, {alpha} feature usually encountered in octupole deformed nuclei. Substantial evidence for reflection asymmetric shape in the intrinsic system of the nucleus exists for the light actinide nuclei.

Bentaleb, M.; Schulz, N.; Lubkiewicz, E. [Universite Louis Pasteur, Strasbourg (France). Centre de Recherches Nucleaires] [and others

1994-07-01

11

Experimental tests for stable octupole deformation in actinium-227  

Energy Technology Data Exchange (ETDEWEB)

The question of intrinsic reflection asymmetry or stable-octupole deformation in /sup 227/Ac was studied by the single-proton stripping reactions /sup 226/Ra(/sup 3/He,d)/sup 227/Ac with E/sub 3He/ = 30 MeV and /sup 226/Ra(..cap alpha..,t)/sup 227/Ac with E/sub ..cap alpha../ = 30 MeV and by measuring the magnetic moment of the first excited 3/2/sup +/ state at 27.38 keV by a differential perturbed angular correlation (DPAC) experiment. Theoretical differential cross sections were determined using calculated nuclear structure factors with and without octupole-deformed Woods-Saxon model wave functions. Theoretical values for the magnetic moments of the ground state and first excited state with and without octupole deformation were determined using calculated intrinsic g-factors from folded Yukawa model wave functions. The results of the proton-stripping cross sections are inconclusive. No how comparison of the measured values for the magnetic moment of the first excited state with a previous measurement for the ground state seems to support stable octupole deformation in /sup 227/Ac. Therefore, the energy ordering of orbitals and the magnetic moment results are consistent and they seem to support a stable-octupole deformed shape for the ground state parity doublet in /sup 227/Ac. Furthermore, the results are consistent with the branching ratio determination of the magnetic moment of the first excited state in /sup 227/Ac which is in agreement with the stable-octupole model prediction.

Martz, H.E. Jr.

1986-01-01

12

Studies of Stable Octupole Deformations in the Radium Region  

CERN Multimedia

The purpose of the present project is to locate and identify states in the atomic nuclei possessing stable pearshaped octupole deformation. Such states, formally related to the structures known in molecular physics, manifest themselves as families of parity doublets in odd nuclei.\\\\ \\\\ The best possibilities for observing stable octupole deformations are offered in the Ra-region. Both theoretical calculations and experimental indications support such expectations. Such indications are the non-observation of two-phonon octupole vibrational states in the ISOLDE studies of the even-even radium nuclei, and the reversed sign of the decoupling factor of the ground state band in |2|2|5Ra observed in the single-neutron transfer reactions. In order to establish the predicted strong E1 and E3-transitions between the parity doublets in odd nuclei with stable octupole deformations it is proposed to study conversion electrons in odd-mass francium radium and radon isotopes following the @b-decay of francium and astatine. \\...

2002-01-01

13

Total Routhian surface calculations of octupole properties in neutron-deficient U isotopes  

Science.gov (United States)

Octupole properties in even-even 220-230U isotopes have been investigated using improved total Routhian surface calculations with the inclusion of reflection-asymmetric deformations. We pay attention to the evolution of octupole properties with increasing nucleon and rotational frequency. 222U is predicted to have static octupole deformation up to high spins. A shape transition from reflection-symmetry to reflection-asymmetry happens across 22892U136 with decreasing neutron number in uranium isotopes or decreasing proton number in N = 136 isotones. Our calculations were compared with previous calculations and available experiments.

Wang, Hua-Lei; Liu, Hong-Liang; Xu, Fu-Rong

2012-09-01

14

Aligned rotation of octupole-vibrational states in deformed nuclei  

International Nuclear Information System (INIS)

Analysis of level energies in aligned octupole bands in even-even deformed nuclei using the VMI-model expressed in terms of the rotational angular momentum R, show that almost complete alignment is reached at low spin values. It is shown that the alignment is almost spin independent. Using the ground-state band VMI-parameters only a renormalization of the alignment parameter is enough to reproduce the level energies of the NPB's. (orig.)

15

Collective T- and P- Odd Electromagnetic Moments in Nuclei with Octupole Deformations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Parity and time invariance violating forces produce collective P- and T- odd moments in nuclei with static octupole deformation. Collective Schiff moment, electric octupole and dipole and also magnetic quadrupole appear due to the mixing of rotational levels of opposite parity and can exceed single-particle moments by more than a factor of 100. This enhancement is due to two factors, the collective nature of the intrinsic moments and the small energy separation between membe...

Auerbach, N.; Flambaum, V. V.; Spevak, V.

1996-01-01

16

NUCLEAR AND HEAVY ION PHYSICS: Influence of angular momentum in axially symmetric potentials with octupole deformation  

Science.gov (United States)

The chaotic classical single-particle motion in an oblate octupole deformed potential with a nonzero z-component of angular momentum Lz is investigated. The stability analysis of the trajectories shows that with increasing rotation of the system, the unstable negative curvature regions of the effective potential surface decrease, which converts the chaotic motion of the system into a regular one.

Jin, Hua; Sun, Zhen-Wu; Zheng, Ren-Rong

2009-09-01

17

Incipient octupole deformation and parity doublets in the odd mass light actinides  

International Nuclear Information System (INIS)

A non-perturbative method is used to investigate the existence of octupole deformations in the light, odd mass, actinides. Calculated level schemes and B(E3) values are presented for serveral nuclides. Serveral, almost degenerate, parity doublets are found in the calculations. (orig.)

18

Competition between axial and non-axial octupole deformations in heavy nuclei  

International Nuclear Information System (INIS)

The macroscopic-microscopic method is applied to calculate the energies of heavy nuclei (A>220) in a multidimensional deformation space (??,?) including axial and non-axial quadrupole (?=2,?=0,2), axial and non-axial octupole (?=3,?=0,2) and axial hexadecapole (?=4,?=0) degrees of freedom. Shell and pairing corrections are calculated from the single-particle energies of the Woods-Saxon potential with the universal parameters and added to the macroscopic energy of the newest Lublin-Strasbourg Drop (LSD) model to obtain the total deformation energy. (author)

19

Low-energy E1 transitions and octupole softness in odd-A deformed nuclei  

International Nuclear Information System (INIS)

It is found that B(E1) values for yrast spectroscopy of deformed odd-A rare-earth nuclei calculated by using a model in which one quasiparticle is coupled to a rotor are more than an order of magnitude too small. Therefore, measured B(E1) values for 169Lu were analyzed by introducing parameters which effectively took octupole softness into account. Some preliminary results of the theoretical analysis which are presented in this paper still give do not agree completely with experiment. 4 refs., 1 tab., 5 figs

20

? decay of 227Pa and 225Pa and octupole deformation in 223Ac  

International Nuclear Information System (INIS)

The level scheme of actinide nuclei with 130 ? N ? 140 and 85 ? Z ? 92 shows features originating from a reflection asymmetric intrinsic shape. In odd-mass nuclei this gives rise to parity doublets - pairs of levels with the same spin but opposite parity, having the same intrinsic structure - and enhanced E1 transition rates within these parity doublet bands. A summary of the experimental data can be found and models in terms of stable ground state octupole deformation, octupole vibrations, ? clustering and the interacting boson model have been developed. In this paper the authors report on an ?decay study of 227Pa and 225Pa populating levels in 223Ac and 221Ac. These nuclei are expected to show static quadrupole-octupole deformation. Using the LIGISOL facility the authors produced 227Pa via a (p,6n)-reaction on 223Th and 225Pa via a (p,6n)-reaction on 230Th. A number of experiments were performed in order to get level-scheme information. In case of 227Pa multiscaled ?-singles spectra (using PIPS detectors), (?, ?, t)- (?, X, t) coincidences (using a LEGe-type detector) and (?, e-, t) coincidences (using a cooled Si(li) detector) were taken. In addition, a fast timing setup of an ?-detector and a plastic or BaF2 scintillator was used to determine the halflife of 223Ac levels. In case of 225Pa only ?-singles spesup>Pa only ?-singles spectra were accumulated. The construction of a more complete level scheme compared to ref. 5 is in progress. Due to the short halflife of the E1 (65 keV) transition between the 5/2+ - 5/2- parity doublet, compared to the time resolution of the setup (about 840 ps), only an upper limit on its halflife has been set (t1/2 < 250 ps)

 
 
 
 
21

The microscopic description of the collective states of rotating octupole-quadrupole deformed nuclei. The RPA equations and the probability of electric transitions  

International Nuclear Information System (INIS)

The equations of the model formulated early for the description of collective states of the rotating nuclei with intrinsic reflection symmetry are analysed in the random phase approximation. The well-known solutions for vibrational states of positive and negative signature for both parity values are reproduced in the absence of octupole deformation. In the case of nonzero octupole deformation the collective states are possible to classify with the quantum number of a generalized signature. The breaking of intrinsic reflection symmetry of the nucleus causes the appearance of collective E2-l, E1- and E3-transitions in rotational band

22

Enhanced E1 transition rates and octupole deformation in 225Ac  

International Nuclear Information System (INIS)

The levels of 225Ac are reliably assigned by detailed measurements of the radiations associated with the ? decay of 229Pa and the ? decay of 225Ra. Extremely large enhancements of E1 transition rates are found in 225Ac. The adequacy of a single-particle description of strong octupole correlations is examined

23

Identification of excited states and evidence for octupole deformation in sup 2 sup 2 sup 6 U  

CERN Document Server

Excited yrast states in the neutron-deficient nucleus sup 2 sup 2 sup 6 U have been identified in two experiments performed at the Accelerator Laboratory of the University of Jyvaeskylae, Finland. In the first, the technique of recoil-decay tagging was employed using the JUROSPHERE plus RITU device, where the reaction channel of interest is selected through correlation with a characteristic decay. In the second, the RITU device was employed to study the alpha decay of sup 2 sup 3 sup 0 Pu. Through these experiments the level scheme of sup 2 sup 2 sup 6 U was deduced for the first time. Interleaved bands of positive- and negative- parity states suggest the octupole nature of this nucleus, and the behaviour of the difference in aligned angular momentum between the negative- and positive- parity states with rotational frequency is consistent with that expected of a rotating reflection-asymmetric shape. This represents an extension of the known octupole-deformed nuclei to Z = 92. The interleaved bands of alternat...

Greenlees, P T

1999-01-01

24

High-spin study of octupole-deformed 222Th and reduction of the background from prompt fission  

International Nuclear Information System (INIS)

High-spin states have been studied in the octupole-deformed 222Th nucleus using the 208Pb(18O,4n) reaction. De-excitation gamma rays were detected using the Euroball-IV gamma-ray spectrometer. The large background of gamma rays from prompt fission fragments, which generally hampers the spectroscopy of actinide nuclei in fusion-evaporation reactions, has been reduced using the Euroball-IV inner BGO ball as a sum-energy filter. With the requirement that the summed gamma-ray energy detected in the reaction is less than 10 MeV, the intensity of 222Th gamma-rays, relative to the prompt fission background is significantly improved. The experiment and data analysis are discussed, and preliminary spectroscopic results are presented

25

Investigation of octupole deformations in the Fr217 nucleus by yrast spectroscopy  

International Nuclear Information System (INIS)

The spectroscopic characteristics of the yrast levels of Fr217 are determined. The level scheme up to a value of J = (39/2+) for angular momentum and parity is established. The production of the Fr217 nucleus in a heavy ion collision reaction was only possible by using a radioactive Pb210 target. The method for preparing the target is described. The Fr217 nucleus belongs to the category of nuclei showing octupole effects. Mass A = 217 seems to be the lower limit of the region where these effects occur

26

Identification of Excited States in 226U: Evidence for Octupole Deformation  

International Nuclear Information System (INIS)

The level scheme of 226U has been deduced from the results of two experiments carried out at the University of Jyvaskyla, Finland. Both ?- and ?-ray-spectroscopic techniques have been employed. The interleaved states of positive- and negative-parity indicate the octupole nature of this nucleus, and the behavior of the difference in aligned angular momentum between the positive- and negative-parity bands as a function of rotational frequency is consistent with that expected for a rotating reflection-asymmetric shape

27

Observation of K=1/2 octupole deformed bands in 227Th  

International Nuclear Information System (INIS)

High-spin states in 227Th have been populated using the reaction 226Ra(?,3n)227Th at a bombarding energy of 33 MeV. The high-spin rotational structures of this nucleus have been refined and extended. In addition, the linking of these structures with the low-spin states known from 231U ? decay has allowed a comprehensive decay scheme of this nucleus to be assembled for the first time. Four previously known rotational bands are interpreted as Coriolis coupled K?=1/2+ and K?=1/2- bands, in agreement with predictions using a reflection-asymmetric mean field approach. The determination of decoupling parameters for these bands is consistent with the a(K?=1/2+)=-a(K?=1/2-) rigid octupole rotor expectation. A further rotational band is interpreted as having K?=3/2-. Measured D0/Q0 ratios are consistent with an interpolation of the values given for neighboring even-even nuclei, providing further evidence for the significance of strong octupole correlations in this nucleus

28

Study of octupole-deformed K=1/2 bands in 227Th  

International Nuclear Information System (INIS)

High spin states in 227Th have been populated using the reaction 226Ra(?,3n)227Th at a bombarding energy of 33 MeV. The high-spin rotational structures of this nucleus have been refined and extended. In addition, the linking of these structures with the low-spin states known from 231U ? decay has allowed a comprehensive decay scheme of this nucleus to be assembled for the first time. Four previously known rotational bands are interpreted as Coriolis-coupled K? = 1/2+ and K? = 1/2- bands, in agreement with predictions using a reflection-asymmetric mean-field approach. The determination of decoupling parameters for these bands is consistent with the a(K? = 1/2+) = -a(K? = 1/2-) rigid-octupole-rotor expectation. A further rotational band is interpreted as having K? = 3/- . Measured D0/Q0 ratios are consistent with an interpolation, of the values given for neighbouring even-even nuclei, providing further evidence for the significance of strong octupole correlations in this nucleus. (author)

29

Coupling of the giant dipole resonance to low lying octupole modes - generator coordinate method study  

Science.gov (United States)

The effect on the properties of low lying octupole modes of the coupling with the giant dipole resonance is studied within the Generator Coordinate Method. Results are presented for 152Sm which is deformed in its ground state and for the superdeformed state of 190Hg. A basis is first generated by Hartree-Fock+BCS calculations with constraints on the octupole and dipole moments. The same Skyrme SkM ? effective interaction used in the mean field is then diagonalised by the GCM. For the octupole K = 0 mode, the effect of the coupling is marginal and the dipole properties of low lying states are satisfactorily described by pure octupole calculations. For the K = 1 mode, the dipole-octupole coupling slightly reduces the E1 transition strength.

Heenen, P.-H.; Skalski, J.

1996-02-01

30

'Staggering' effect in even-even nuclei with quadrupole and octupole deformations  

International Nuclear Information System (INIS)

Full text: The odd-even staggering effect is known as a zigzagging behaviour of the nuclear inertial parameter between the odd and even angular momentum states of a rotational band. It is characterized by a relative displacement of the odd angular momentum levels with respect to the even ones. The analysis and the interpretation of this effect are of current interest since it carries detailed information about the fine structure of the nuclear collective spectrum in different regions of the nuclear chart. The odd-even staggering patterns can be determined as Stag(I)=6?E(I) - 4?E(I-1) - 4?E(I+1)+?E(I+2)+?E(I-2) here ?E(I)=E(I+1) - E(I), E(I)-energy levels [1], I-spin of the excited states of even-even nuclei. Stag (I) is very sensitive to the fine structure of rotational spectra and provides spectacular ?I=1 staggering patterns (zigzagging behaviour of the function Stag (I) with clearly defined zero reference) in various rotational bands. On this basis we propose a relevant theoretical analysis of the ?I=1 staggering effects in nuclear octupole bands in reference to the underlying reflection-asymmetric shape characteristics of the nuclear collective motion. The behaviour of the odd-even (?I=1) staggering effect in the nuclei 152,154Sm, 154,156,158Gd, 156Dy, 162,164Er, 228Th, 236,238U has been considered and shown that the odd-even staggering patterns do not vanish in the observed regio not vanish in the observed region of angular momentum. (author) Reference: 1. Sh. Sharipov, M. S. Nadirbekov, G. A. Yuldasheva Ukrainian Journal of Physics, 53,11(2008)

31

Influence of shell effects and stable octupole deformation on the E1 and E2 transition rates in the heavy-Ba region  

International Nuclear Information System (INIS)

Lifetimes were measured for the 21+, 41+, 02+, 11-, and 31- levels in 142,144,146Ba using a recently developed ?-?-? fast timing method. In 146Ba, the Q0 moment for the negative parity band was slightly larger than that for the positive parity band. The isovector E1 rates which were very small in 146Ba and large in 144Ba can be explained in terms of shell effects on the electric dipole moment. The new data are interpreted by both the spdf interacting boson and the reflection-asymmetric deformed shell models and provide compelling evidence for a static octupole deformation near 146Ba

32

Microscopic analysis of the octupole phase transition in Th isotopes  

CERN Document Server

A shape phase transition between stable octupole deformation and octupole vibrations in Th nuclei is analyzed in a microscopic framework based on nuclear density functional theory. The relativistic functional DD-PC1 is used to calculate axially-symmetric quadrupole-octupole constrained energy surfaces. Observables related to order parameters are computed using an interacting-boson Hamiltonian, with parameters determined by mapping the microscopic energy surfaces to the expectation value of the Hamiltonian in the boson condensate. The systematics of constrained energy surfaces and low-energy excitation spectra point to the occurrence of a phase transition between octupole-deformed shapes and shapes characterized by octupole-soft potentials.

Nomura, K; Lu, B -N

2013-01-01

33

Study of octupole-deformed K=1/2 bands in {sup 227}Th[High spin states  

Energy Technology Data Exchange (ETDEWEB)

High spin states in {sup 227}Th have been populated using the reaction {sup 226}Ra({alpha},3n){sup 227}Th at a bombarding energy of 33 MeV. The high-spin rotational structures of this nucleus have been refined and extended. In addition, the linking of these structures with the low-spin states known from {sup 231}U {alpha} decay has allowed a comprehensive decay scheme of this nucleus to be assembled for the first time. Four previously known rotational bands are interpreted as Coriolis-coupled K{sup {pi}} = 1/2{sup +} and K{sup {pi}} = 1/2{sup -} bands, in agreement with predictions using a reflection-asymmetric mean-field approach. The determination of decoupling parameters for these bands is consistent with the a(K{sup {pi}} = 1/2{sup +}) = -a(K{sup {pi}} = 1/2{sup -}) rigid-octupole-rotor expectation. A further rotational band is interpreted as having K{sup {pi}} = 3/{sup -} . Measured D{sub 0}/Q{sub 0} ratios are consistent with an interpolation, of the values given for neighbouring even-even nuclei, providing further evidence for the significance of strong octupole correlations in this nucleus. (author)

Hammond, Neil

2002-07-01

34

Extension of the multiphonon method to odd mass deformed nuclei  

Science.gov (United States)

The multiphonon method based on the collective K=0- octupole state is applied to the study of the low energy spectroscopic properties of223 225 227Ac. Special attention is paid to various arguments usually invoked to assert that these isotopes have stable octupole deformation. A new criterium is proposed.

Piepenbring, R.

1986-09-01

35

Chaotic motion of a nucleon in mean field potential with octupole deformation. Pt.2: Characteristics of expectation values and uncertainty measures of canonical variables in space-temporal variation of initial coherent states  

International Nuclear Information System (INIS)

Coherent states of two dimensional asymmetrical harmonic oscillator, which propagate in additional octupole deformation potentials, are used to investigate the characteristics of expectation values and uncertainty measures of canonical variables in space-temporal variations. The quantum chaotic system shows varying behaviors as the corresponding classical chaotic system does. Thus the characteristics of quantum chaos are associated with the geometric symmetry of the potential surface, specifically, the existence of the negative curvature and the magnitude of the curvature in the potential surface

36

Octupole deformation in /sup 227/Ac by single-proton stripping reactions: /sup 226/Ra(?, t)/sup 227/Ac and /sup 226/Ra(3He,d)/sup 227/Ac  

International Nuclear Information System (INIS)

A radioactive /sup 226/Ra (t/sub 1/2/ = 1600 yr) target was used to study the /sup 226/Ra(?,t)/sup 227/Ac and /sup 226/Ra(3He,d)/sup 227/Ac reactions at an incident energy of 30 MeV for both the ? and 3He particles. These measurements have confirmed most levels observed in earlier decay-scheme studies, and give evidence for 11 additional levels. Several of the new levels were used in the tentative assignment of two K/sup ?/ = (5/2/sup +- / bands. The experimental data are compared with results from the Nilsson model and a nonadiabatic, rigid, reflection-asymmetric rotor (octupole) model. Although the order and spacing of levels in this mass region can be explained better by models that include an octupole deformation, the spectroscopic strengths in /sup 227/Ac are in better agreement with those calculated for the reflection-symmetric potential

37

Simultaneous quadrupole and octupole shape phase transitions in Thorium  

Science.gov (United States)

The evolution of quadrupole and octupole shapes in Th isotopes is studied in the framework of nuclear Density Functional Theory. Constrained energy maps and observables calculated with microscopic collective Hamiltonians indicate the occurrence of a simultaneous quantum shape phase transition between spherical and quadrupole-deformed prolate shapes, and between non-octupole and octupole-deformed shapes, as functions of the neutron number. The nucleus 224Th is closest to the critical point of a double phase transition. A microscopic mechanism of this phenomenon is discussed in terms of the evolution of single-nucleon orbitals with deformation.

Li, Z. P.; Song, B. Y.; Yao, J. M.; Vretenar, D.; Meng, J.

2013-11-01

38

Simultaneous quadrupole and octupole shape phase transitions in Thorium  

International Nuclear Information System (INIS)

The evolution of quadrupole and octupole shapes in Th isotopes is studied in the framework of nuclear Density Functional Theory. Constrained energy maps and observables calculated with microscopic collective Hamiltonians indicate the occurrence of a simultaneous quantum shape phase transition between spherical and quadrupole-deformed prolate shapes, and between non-octupole and octupole-deformed shapes, as functions of the neutron number. The nucleus 224Th is closest to the critical point of a double phase transition. A microscopic mechanism of this phenomenon is discussed in terms of the evolution of single-nucleon orbitals with deformation

39

Simultaneous quadrupole and octupole shape phase transitions in Thorium  

CERN Document Server

The evolution of quadrupole and octupole shapes in Th isotopes is studied in a fully microscopic framework based on nuclear Density Functional Theory. The constrained potential energy maps and observables calculated with microscopic collective Hamiltonians, indicate the occurrence of a simultaneous quantum shape phase transition between spherical and quadrupole-deformed prolate shapes, and between non-octupole and octupole-deformed shapes, as functions of the nucleon number. $^{224}$Th is predicted closest to the critical point of the double phase transition. A microscopic mechanism of this phenomenon is discussed in terms of the evolution of single-nucleon orbitals with deformation.

Li, Z P; Yao, J M; Vretenar, D; Meng, J

2013-01-01

40

Octupole deformation in 226Th  

Science.gov (United States)

Sources of 230U were prepared using the ?- decay of 230Pa produced in the reaction 232Th (p,3n) with 34-MeV protons. These sources were used to determine the half-life of the 1- state at 230.4 keV in 226Th using the Doppler shift method following ? decay of 230U. An average value of the half-life of 3.5+/-1.2 ps was observed. The half-life of the 226.4-keV 4+ state in 226Th was also measured to be 145+/-20 ps. The absolute transition probabilities in Weisskopf units of the 230- and 158-keV transitions depopulating the 1- state were determined as (2.50+/-0.86)×10-3 and (4.54+/-1.55)×10-3, respectively. These experimental values are compared with experimental values of 223Ra and theoretical calculations. Finally, experimental values of the intrinsic dipole moment D0 and the ratio of the intrinsic dipole moment to the intrinsic quadrupole moment D0/Q0 were determined as 0.27+/-0.05 e fm and (3.5+/-1.0)×10-4 fm-1 respectively, and compared with various theories and experiments.

Liang, C. F.; Paris, P.; Sheline, R. K.; Trubert, D.; Le Naour, C.; Vergnes, M.

1998-03-01

 
 
 
 
41

Octupole instability in the heavy barium region  

Energy Technology Data Exchange (ETDEWEB)

Quasi-molecular rotational bands characterized by spin states of alternating parity connected by enhanced E1 transitions have recently been observed in several transitional nuclei around /sup 224/Th. The appearance of such bands can easily be understood by assuming the absence of intrinsic parity symmetry in these nuclei. Another likely region on the chart of nuclides to find octupole-unstable nuclei is the region of nuclei around /sup 146/Ba. In fact, in several Xe, Ba and Ce isotopes with n approximately equal to 88, calculations yield octupole-unstable ground states. The main goal of the present study was to calculate equilibrium deformations of doubly-even Xe, Ba, Ce, Nd, Sm and Gd nuclei with neutron numbers between 84 and 94. The method used was the Woods-Saxon-Bogolyubov cranking model method combined with the shell correction approach. The results of these calculations confirm previous expectations of octupole deformed mean fields at low and medium spins in Xe-Sm nuclei with neutron numbers around N = 86. Recent experimental data support theoretical results. 8 refs., 1 fig. (DWL)

Nazarewicz, W.; Leander, G.A.; Tabor, S.

1987-01-01

42

Octupole Effects of Nuclei Near 11256Ba56  

Science.gov (United States)

Octupole instabilities in even-even nuclei near 11256Ba56 nucleus have been investigated by means of improved total-Routhian-surface calculations with the inclusion of reflection-asymmetric deformations. It is found that the shape evolutions of mirror nuclei are similar between Z = 56 isotopes and N = 56 isotones in the ground-states. As an example, 10852Te56, which has reflection-symmetric shape at low spins, is predicted to be octupole deformed at certain high rotational frequencies. The prediction is confirmed by experiment.

Wang, Hua-Lei; Jiang, Jin-Ge; Liu, Hong-Liang; Xu, Fu-Rong

2013-11-01

43

Chromaticity dependence on octupole strength  

CERN Document Server

The first measurements of the dependence of the chromaticity on the lattice octupole strength were performed at the LHC in a machine development session on Wednesday 20 June 2012. This chromaticity change is non negligible and needs to be taken into account when changing the octupole strength, e.g. for beam stabilization purposes. We report on the results of such measurements and later ones, along with some predictions and some first estimates of systematic horizontal and vertical misalignments of the octupoles.

Herr, W; Metral, E; Mounet, N; Papotti, G; Tomas Garcia, R; Wenninger, J

2012-01-01

44

Improvements on the present theoretical understanding of octupole correlations  

Directory of Open Access Journals (Sweden)

Full Text Available Some intriguing results, obtained in a recent survey of octupole properties for all even-even nuclei, are reanalyzed in order to understand the origin of the strong disagreement with experimental data and/or the strange behaviours observed. The limitations of the rotational formula to describe E1 and E3 transition strengths are discussed as well as the role played by octupole-quadrupole coupling in some specific nuclei.

Robledo L.M.

2014-03-01

45

Magnetic properties of cyclically deformed austenite  

Science.gov (United States)

In meta-stable austenitic stainless steels, low cycle fatigue deformation is accompanied by a partial stress/strain-induced solid state phase transformation of paramagnetic ?(fcc) austenite phase to ferromagnetic ?/(bcc) martensite. The measured characteristic of magnetic properties, which are the saturation magnetization, susceptibility, coercivity, retentivity, and the area under the magnetic hysteresis loop are sensitive to the total strain amplitude imposed and the corresponding material behaviour. The morphologies and nucleation characteristics of deformation induced martensites (i.e., ?(hcp), ?/(bcc)) have been investigated through analytical transmission electron microscope. It has been observed that deformation induced martensites can nucleate at a number of sites (i.e., shear band intersections, isolated shear bands, shear band-grain boundary intersection, grain boundary triple points, etc.) through multiple transformation sequences: ?(fcc)??(hcp), ?(fcc)??(hcp)??/(bcc), ?(fcc)? deformation twin ??/(bcc) and ?(fcc)??/(bcc).

Das, Arpan

2014-06-01

46

Magnetic properties of deformed superconductors  

International Nuclear Information System (INIS)

This communication concerns the geometric effect on magnetic properties of superconductors. The metric description for quantum particles holds only in limited class of medium and the screw-dislocated medium is considered. When the Ginzburg-Landau equation with Maxwell's equations was solved based on this description, it was shown that self-adjointness of the operator is guaranteed by specified solutions. As a result, isolated vortex exists at dislocation line. -- Highlights: ? The screw-dislocated superconductors with tight-binding approximation. ? The quantum singularity is removed by specific solution. ? Isolated vortex exists at dislocation line.

47

Band structures and octupole correlation effects in 151Sm  

International Nuclear Information System (INIS)

Excited states in 151Sm were populated through the 150Nd(?,3n) reaction at a beam energy of 35 MeV using a 9 mg/cm2 thick 150Nd target. An array of twenty Compton-suppressed germanium detectors was used to detect ?? and triple-? coincidences. The prime aim of this work was to investigate the effects of octupole correlations in odd-A nuclei in the A?150, N?88 region. A total of fifteen bands has been observed in 151Sm and their decay patterns followed up to spins near 20 h. Four ?I=2 bands have some characteristics associated with parity-doublet structures. However, the evidence overall suggests that octupole correlations in 151Sm are too weak to produce stable octupole deformation. (orig.)

48

Octupole state properties in /sup 168/Er and the two-neutron /(521 (1/2))(633 (7/2))/ configurational pair  

Energy Technology Data Exchange (ETDEWEB)

Detailed spectroscopy measurements have been made of the gamma rays that follow the deexcitation of /sup 168/Er levels populated in the electron capture decay of /sup 168/Tm. These results, when combined with a reanalysis of Coulomb excitation and inelastic scattering data, provide level lifetime information and support octupole-state Coriolis-coupling calculations. The /(521 (1/2))(633 (7/2))/ two-neutron configurational pair deexcitation rates are compared and some evidence for K mixing among the octupole bands is presented.

Meyer, R.A.; Nethaway, D.R.; Prindle, A.L.; Yaffe, R.P.

1987-04-01

49

Optical properties of plastically deformed copper  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Pure copper (99.99), prepared in the sample of square cross-section (10 x 10 mm2) and length about 50 mm, was extremely plastically deformed with the repeated application of Equal Channel Angular Pressing (ECAP). ECAP was applied as an effective technique for producing bulk nano-scaled structures. Optical properties of the sample were investigated using Raman spectroscopy. Two types of lines: narrow (with width of 7 cm¡1) and wide ( 40 cm¡1) are registered. Existence of two types of lines i...

Trajic?, J.; Rudolf, Rebeka; Anz?el, Ivan; Romc?evic?, M.; Lazarevic?, N.; Miric?, M.; Lazarevic?, Z.; Hadz?ic?, B.; Romc?evic?, Nebojs?a

2012-01-01

50

The strength of octupole correlations in neutron-rich Xe isotopes  

International Nuclear Information System (INIS)

Excited levels in 140Xe and 142Xe nuclei, populated in the spontaneous fission of 248Cm, were studied by means of prompt ?-ray spectroscopy, using EUROGAM2 array. We report the first observation of an octupole band in 142Xe and extend the octupole band in 140Xe. Level schemes of 140Xe and 142Xe obtained in this work show patterns characteristic of octupole-vibrational bands. Properties of octupole bands in Xe isotopes indicate that octupole correlations in these nuclei are lower than in the corresponding Ba nuclei. The electric dipole moment of 142Xe was found to be larger than in other Xe isotopes, contrary to theoretical predictions. This may be due to the special role of the N=88 neutron number. (orig.)

51

Stable and Vibrational Octupole Modes in Mo, Xe, Ba, La, Ce and Nd  

International Nuclear Information System (INIS)

Evidence is presented for stable octupole deformation in neutron-rich nuclei, bounded by Z = 54-58 and N = 85-92. To either side of this region negative parity bands built on more vibrational type octupole modes are observed in 140Ba and 152,154Nd. The largest stable octupole deformation (?s ? 0.1) is found in 144Baas. The theoretically predicted quenching (?s ? 0) of stable octupole deformation at higher spins is found in 140Ba. There is good agreement between theory and experiment for the strongly varying electric dipole moments as a function of mass for 142-141Ba. In odd-A 142Ba and odd-Z 140La, we observe parity doublets, two pairs of positive and negative parity bands with opposite spins. In 145La a strong coupled ground band with symmetric shape coexists with the asymmetric octupole shape which stabilizes above about spin 19/2. In 145,147La a strong reduction in E2 strength around 25/2 from band crossing is observed. The isotope 109Mo was identified and a new region of stable uctpole deformation is identified in 107,108Mo centered around N = 64-66 as earlier predicted. This is the first case of stable uctpole deformation involving only one pair of orbitals

52

Magnetic octupole scattering of neutrons  

International Nuclear Information System (INIS)

The cross section for the magnetic octupole scattering of neutrons by rare-earth ions is estimated. These scattering events can change the magnetic quantum number of the ions by up to three units. For high momentum transfers and a proper scattering geometry, the cross sections for magnetic octupole modular ?M = 2 and 3 transitions are comparable with those for magnetic dipole modulus ?M = 1 transitions. If a beam of polarized neutrons is used, modulus ?M 2 excitations, i.e. quadrupolar waves, can be produced without exciting spin waves modulus ?M = 1. Examples are quoted where this scattering is expected to be of particular interest. (author)

53

Toroidal discharges in an octupole field  

International Nuclear Information System (INIS)

Experimental results from the Extrap T1 device are reported. The Extrap T1 machine has a toroidal stainless steel below vessel, R/a=0.5/0.06 m, covered with a segmented shell. A special character of the device is a coil system which produces an octupole magnetic field. The application of the octupole field produce an equilibrium with four poloidal field nulls. Three modes of operation are considered; 1) toroidal field only, 2) toroidal field and octupole field, 3) octupole field only. The purpose of the present experiment was to study the effect of the octupole field. (author) 4 refs., 5 figs

54

Reflection asymmetric shell model for octupole rotation  

International Nuclear Information System (INIS)

The reflection asymmetric shell model approach has been introduced for the description of octupole bands. The Q·Q forces of quadrupole, octupole and hexadecapole as well as the monopole and quadrupole pairings are included in the hamiltonian. The shell model space is spanned by a selected set of the projected axial and octupole Nilsson plus BSC basis. The calculated results for the octupole bands in the A=220 region are in a good agreement with the experimental data. The experimental SD bands 1 and 3 in 194Hg are well reproduced by the present calculation and interpreted as the parity partner octupole SD bands with K? = 0+ and K? = 0- respectively. (author)

55

Global systematics of octupole excitations in even-even nuclei  

CERN Document Server

We present a computational methodology for a theory of the lowest octupole excitations applicable to all even-even nuclei beyond the lightest. The theory is the well-known generator-coordinate extension (GCM) of the Hartree-Fock-Bogoliubov self-consistent mean field theory (HFB). We use the discrete-basis Hill-Wheel method (HW) to compute the wave functions with an interaction from the Gogny family of Hamiltonians. Comparing to the compiled experimental data on octupole excitations, we find that the performance of the theory depends on the deformation characteristics of the nucleus. For nondeformed nuclei, the theory reproduces the energies to about 20 % apart from an overall scale factor of about 1.6. The performance is somewhat poorer for (quadrupole) deformed nuclei, and for both together the dispersion of the scaled energies about the experimental values is about 25 %. This compares favorably with the performance of similar theories of the quadrupole excitations. Nuclei having static octupole deformations...

Robledo, L M

2011-01-01

56

Structure and properties of copper deformed by severe plastic deformation methods  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: The main object of this study is to establish the influence of severe plastic deformation on the microstructure evolution and properties of polycrystalline copper Cu99.99.Design/methodology/approach: Polycrystalline copper Cu99.99 was deformed by cyclic extrusion compression (CEC, equal channel angular pressing (ECAP and hydrostatic extrusion (HE. Additionally the combination of these methods were applying to the sample deformations. The microstructure and properties of samples after different kinds of severe mode of deformations (SPD were examined and compared as well as their properties. The microstructure was investigated by optical (MO and transmission electron microscopy (TEM. The microhardness was measured by PMT3 microhardness tester.Findings: It was found that increase of deformation diminishing the microstructure and leads to the increase of microhardness of samples.Practical implications: The results may be utilized for determination of a relation between microstructure and properties of the copper deformed in the severe plastic deformation process.Originality/value: The results contribute to evaluation properties of the polycrystalline copper deformed to very large strains exerting the typical range of deformations.

M. Richert

2011-01-01

57

The octupoles take pole position  

CERN Multimedia

The first preseries octupole magnet was delivered to CERN in December 2001. Hooked up to a main quadrupole magnet, its function will be to correct imperfections in the beams. The LHC will be fitted with about 5000 corrector magnets, whose task it will be to provide maximum precision in beam collisions.

2002-01-01

58

High spin core-excited isomers and octupole coupling in sup 213 Rn  

Energy Technology Data Exchange (ETDEWEB)

The structures of some recently observed high-spin isomers in {sup 213}Rn are considered. Octupole-mixed configurations are shown to account for the measured energies and electromagnetic properties of these levels.

Stuchbery, A.E.; Dracoulis, G.D. (Department of Nuclear Physics Research School of Physical Sciences, Australian National University, GPO Box 4, Canberra, Australian Capital Territory (Australia))

1990-08-01

59

Studies of electric dipole moments in the octupole collective regions of heavy Radiums and Bariums  

CERN Multimedia

%IS386 %title\\ \\It is proposed to study the electric dipole moments in the regions of octupole collective Ra-Th and Ba-Ce nuclei by means of Advanced Time-Delayed (ATD) $\\beta\\gamma\\gamma(t)$ method with a primary goal to provide new and critical data on the properties of E1 moments. The proposal focuses on the nuclei of $^{225,226,229}$Ra, $^{229,233}$Th and $^{149,150}$Ba.\\ \\The ATD $\\beta\\gamma\\gamma$(t) method was first tested at ISOLDE as part of the IS322 study of Fr-Ra nuclei at the limits of octupole deformation region. The results have greatly increased the knowledge of electric dipole moments in the region and demonstrated that new and unique research capabilities in this field are now available at ISOLDE. Based on the experience and new systematics, we propose a specialized study with the aim to determine the missing key aspects of the E1 moment systematics. We propose : \\begin{enumerate}[a)] \\item to measure the lifetimes of the 1$_{1}^{-}$ and 3$_{1}^{-}$ states in $^{226}$Ra with $\\sim$15\\% prec...

Hoff, P; Kaczarowski, R

2002-01-01

60

Octupole bands of Gd isotopes  

International Nuclear Information System (INIS)

Excited states in 154,156,158,160Gd have been populated through the multiple coulomb excitation process by 32S, 48Ti, 58Ni ions. The ground band, ?-band and octupole K?=0- band were extended to I?=16+, (12+), and (11-) state respectively in 160Gd. The octupole K?=1- band was extended to I?=9- state in 158Gd. Excitation cross sections of individual levels relative to that of the I?=4+ state in the ground band in each nucleus were compared with the simulation by the computer code GOSIA within the framework of the pure rotational model. From these comparisons the matrix elements for both intra-band and inter-band transitions were deduced. (orig.)

 
 
 
 
61

Deformation effect on structure and properties of cast nickel alloys  

International Nuclear Information System (INIS)

The effect of deformation at 1000-2200 deg C on the properties of precipitation hardening cast KhN62MKYuTB (with tantalum) and KhN64KYuVMT alloys, are investigated. It is shown that the deformation of cast nickel alloys with a high content of hardening ?-phase brings about a sharp decrease of heat resistance. Low creep resistance of deformed material is conditioned by a more developed intergrain surface and rough heterophase intragrain metal structure

62

Permanent deformation properties of asphalt concrete mixtures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Rutting is recognized to be the major distress mechanism in flexible pavements as a result of increase in tire pressures and axle loads. Rutting is caused by the accumulation of permanent deformation in all or some of the layers in the pavement structure. The accumulation of permanent deformation in the asphalt surfacing layer is now recognized to be the major component of rutting in flexible pavements. This is a consequence of increased tire pressures and axle loads, which subjects the aspha...

Garba, Rabbira

2002-01-01

63

Mechanical Properties and Deformation Behavior of Bulk Metallic Glasses  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Metallic glasses demonstrate unique properties, including large elastic limit and high strength, which make them attractive for practical applications. Unlike crystalline alloys, metallic glasses, in general, do not exhibit a strain hardening effect, while plastic deformation at room temperature is localized in narrow shear bands. Room-temperature mechanical properties and deformation behavior of bulk metallic glassy samples and the crystal-glassy composites are reviewed in the present paper.

Alexander Yu. Churyumov; Louzguine-luzgin, Dmitri V.; Louzguina-luzgina, Larissa V.

2012-01-01

64

Mechanical Properties and Deformation Behavior of Bulk Metallic Glasses  

Directory of Open Access Journals (Sweden)

Full Text Available Metallic glasses demonstrate unique properties, including large elastic limit and high strength, which make them attractive for practical applications. Unlike crystalline alloys, metallic glasses, in general, do not exhibit a strain hardening effect, while plastic deformation at room temperature is localized in narrow shear bands. Room-temperature mechanical properties and deformation behavior of bulk metallic glassy samples and the crystal-glassy composites are reviewed in the present paper.

Alexander Yu. Churyumov

2012-12-01

65

Structure properties of even-even actinides at normal and super deformed shapes analysed using the Gogny force  

International Nuclear Information System (INIS)

Mean field and beyond mean field methods implemented with the D1S force are used in large scale calculations to study the structure properties of fifty five even-even actinides at normal and isomeric potential deformations. The mass region covered is spanned by the 226-236Th, 228-242U, 232-246Pu, 238-250Cm, 238-256Cf, 242-258Fm and 250-262No nuclides. Hartree-Fock-Bogolyubov (HFB) calculations performed with constraints placed on axial and triaxial quadrupole deformations as well as octupole deformations serve to build tensors of inertia and potential energy landscapes up to very large elongations. Long lived spin isomers are investigated through blocking calculations performed with and without breaking time reversal symmetry. Configuration mixing calculations are performed to make predictions for shape isomers and ?=+ vibrations in the isomeric potentials and to calculate moments of inertia at low spin. Moments of inertia are also investigated through cranking HFB calculations to high frequency so as to explore in this regime pairing properties of the D1S force in the heavy mass region. The WKB method is adopted in half-life calculations for the ?-back and fission decay modes of shape isomers. All these predictions are challenged through extensive comparisons with measurements for multipole moments, moments of inertia, spin and shape isomers as well as superdeformed phonons, inner and outeas superdeformed phonons, inner and outer potential barrier heights, and shape isomer lifetimes. Most predictions match the experimental data. Finally we predict a shallow minimum on top of the triaxial inner barriers of N?154 nuclei. This topological property offers a possible explanation for the unexpected structures observed in fission transmissions measured a long time ago for 252Cf and neighboring nuclei

66

Investigation of octupole vibrational states in medium mass nuclei  

Energy Technology Data Exchange (ETDEWEB)

The experimental and theoretical evidence for the presence of octupole vibrational states in {sup 146}Sm and {sup 150}Nd is presented. The first nucleus which is located only two neutrons and two protons away from the N=82 shell and Z=64 subshell closures has been investigated by means of the {sup 143}Nd({alpha},n) and {sup 144}Nd({alpha},2n) fusion-evaporation reactions. The structure of the possible candidates for a 2{sup +} x 3{sup -} quadrupole-octupole multiplet are discussed in terms of the harmonic vibrational model and interpreted in terms of the Interacting Boson Approximation in the spdf boson space (IBA-spdf). The latter nucleus which is a quadrupole deformed nucleus was investigated via inelastic proton scattering which is an excellent method to excite natural parity states. Using this method, B(E1) ratios of the decaying transitions for the octupole vibrational states were determined and compared to the Alaga rule and with the IBA-spdf model. A general good agreement was found between experimental data and theoretical calculations.

Pascu, Sorin; Elvers, Michael; Endres, Janis; Hennig, Andreas; Pickstone, Simon; Zilges, Andreas [Institut fuer Kernphysik, Universitaet Koeln (Germany)

2012-07-01

67

Investigation of octupole vibrational states in medium mass nuclei  

International Nuclear Information System (INIS)

The experimental and theoretical evidence for the presence of octupole vibrational states in 146Sm and 150Nd is presented. The first nucleus which is located only two neutrons and two protons away from the N=82 shell and Z=64 subshell closures has been investigated by means of the 143Nd(?,n) and 144Nd(?,2n) fusion-evaporation reactions. The structure of the possible candidates for a 2+ x 3- quadrupole-octupole multiplet are discussed in terms of the harmonic vibrational model and interpreted in terms of the Interacting Boson Approximation in the spdf boson space (IBA-spdf). The latter nucleus which is a quadrupole deformed nucleus was investigated via inelastic proton scattering which is an excellent method to excite natural parity states. Using this method, B(E1) ratios of the decaying transitions for the octupole vibrational states were determined and compared to the Alaga rule and with the IBA-spdf model. A general good agreement was found between experimental data and theoretical calculations.

68

Octupole magnet for expansion of irradiation area  

Energy Technology Data Exchange (ETDEWEB)

An octupole magnet for experiments is designed to prove a scheme for expanding beam irradiation area with good flatness. The length and maximum strength of the octupole field 1/3{exclamation_point} B``` are 0.6 m and 4000 T/m{sup 3}, respectively. (author)

Morita, Akio; Inoue, Makoto; Noda, Akira; Iwashita, Yoshihisa; Shirai, Toshiyuki; Urakabe, Eriko [Kyoto Univ., Uji (Japan). Inst. for Chemical Research; Hiramoto, Kazuo; Noda, Kouji

1997-12-31

69

Octupole degree of freedom for nuclei near 152Sm in a reflection-asymmetric relativistic mean-field approach  

International Nuclear Information System (INIS)

The potential energy surfaces of even-even isotopes near 152Sm are investigated within the constrained reflection-asymmetric relativistic mean-field approach using parameter sets PK1 and NL3. It is shown that the critical-point candidate nucleus 152Sm marks the shape/phase transition not only from U(5) to SU(3) symmetry, but also from the octupole deformed ground state in 150Sm to the quadrupole deformed ground state in 154Sm. The important role of the octupole deformation driving pair (?2f7/2, ?1i13/2) is demonstrated based on the components of the single-particle levels near the Fermi surface. In addition, the patterns of both the proton and the neutron octupole deformation driving pairs (?2f7/2, ?1i13/2) and (?2d5/2, ?1h11/2) are investigated.

70

Observation of an octupole circle-times quasiparticle band in 175Lu using photon scattering experiments  

International Nuclear Information System (INIS)

A nuclear resonance fluorescence (NRF) study was performed on the heavy deformed nucleus 175Lu. We observe the beginning of a rotational band built on the coupling of the unpaired proton to the K?=0- octupole vibration in the neighboring nucleus 174Yb. The dipole strength distribution is also discussed in terms of the scissors mode. copyright 1997 The American Physical Society

71

Some properties of deformed $q$-numbers  

CERN Document Server

Nonextensive statistical mechanics has been a source of investigation in mathematical structures such as deformed algebraic structures. In this work, we present some consequences of $q$-operations on the construction of $q$-numbers for all numerical sets. Based on such a construction, we present a new product that distributes over the $q$-sum. Finally, we present different patterns of $q$-Pascal's triangles, based on $q$-sum, whose elements are $q$-numbers.

Lobão, Thierry C Petit; Pinho, Suani T R; Borges, Ernesto P

2009-01-01

72

Corneal biomechanical properties from air-puff corneal deformation imaging  

Science.gov (United States)

The combination of air-puff systems with real-time corneal imaging (i.e. Optical Coherence Tomography (OCT), or Scheimpflug) is a promising approach to assess the dynamic biomechanical properties of the corneal tissue in vivo. In this study we present an experimental system which, together with finite element modeling, allows measurements of corneal biomechanical properties from corneal deformation imaging, both ex vivo and in vivo. A spectral OCT instrument combined with an air puff from a non-contact tonometer in a non-collinear configuration was used to image the corneal deformation over full corneal cross-sections, as well as to obtain high speed measurements of the temporal deformation of the corneal apex. Quantitative analysis allows direct extraction of several deformation parameters, such as apex indentation across time, maximal indentation depth, temporal symmetry and peak distance at maximal deformation. The potential of the technique is demonstrated and compared to air-puff imaging with Scheimpflug. Measurements ex vivo were performed on 14 freshly enucleated porcine eyes and five human donor eyes. Measurements in vivo were performed on nine human eyes. Corneal deformation was studied as a function of Intraocular Pressure (IOP, 15-45 mmHg), dehydration, changes in corneal rigidity (produced by UV corneal cross-linking, CXL), and different boundary conditions (sclera, ocular muscles). Geometrical deformation parameters were used as input for inverse finite element simulation to retrieve the corneal dynamic elastic and viscoelastic parameters. Temporal and spatial deformation profiles were very sensitive to the IOP. CXL produced a significant reduction of the cornea indentation (1.41x), and a change in the temporal symmetry of the corneal deformation profile (1.65x), indicating a change in the viscoelastic properties with treatment. Combining air-puff with dynamic imaging and finite element modeling allows characterizing the corneal biomechanics in-vivo.

Marcos, Susana; Kling, Sabine; Bekesi, Nandor; Dorronsoro, Carlos

2014-02-01

73

Plastic properties of cold-deformed ironbased sintered materials  

Directory of Open Access Journals (Sweden)

Full Text Available Cold plastic forming of sintered metal powders has limited practical application because of, among others, the deformation degree andinitial porosity of preforms. Cold forming is combined with a very drastic drop of plastic properties observed in final products. One of the methods that enable regaining the lost plasticity is annealing of sinters after deformation at temperatures above the recrystallisation point. The results of the investigations were presented which aimed at the determination of an effect that the annealing conditions of colddeformed sintered metal powder can have on its structure and mechanical properties. Special attention was drawn to a combined effect of the deformation degree and heat treatment temperature on final plastic properties of the sinters and on their ultimate tensile strength.

K. Zar?bski

2010-07-01

74

In-situ studies of bulk deformation structures: Static properties under load and dynamics during deformation  

DEFF Research Database (Denmark)

The main goal of the study presented in this thesis was to perform in-situ investigations on deformation structures in plastically deformed polycrystalline copper at low degrees of tensile deformation (<5%). Copper is taken as a model system for cell forming pure fcc metals. Anovel synchrotron-radiation based technique High Angular Resolution 3DXRD has been developed at the 1-ID beam-line at the Advanced Photon Source. The technique extents the 3DXRD approach, to 3D reciprocal space mapping with a resolution of ? 1 · 10?3Å?1 and allows for in-situmapping of reflections from deeply-embedded individual grains in polycrystalline samples during tensile deformation. We have shown that the resulting 3D reciprocal space maps from tensile deformed copper comprise a pronounced structure, consisting of bright sharp peaks superimposed on a cloud of enhanced intensity. Based on the integrated intensity, the width of the peaks, and spatial scanning experiments it is concluded that the individual peaks arise from individual dislocation-free regions (the subgrains) in the dislocation structure. The cloud is attributed to the dislocation rich walls. Samples deformed to 2% tensile strain were investigated under load, focusing on grains that have the tensile direction close to the h100i direction. It was found that the individual subgrains, on average, are subjected to a reduction of the elastic strain with respect to the mean elastic strain of the grain. The walls are equivalently subjected to an increased elastic strain. The distribution of the elastic strains between the individual subgrains is found to be wider than the distribution of strains within the individual subgrains. The average properties are consistent with a composite type ofmodel. The details, however, show that present understanding of asymmetrical line broadening have to be reconsidered. Based on continuous deformation experiments, it is found that the dislocation patterning takes place during the deformation, and that a subgrain structure appears from the moment where plastic deformation is detected. By investigating samples under stress relaxation conditions, and unloading, it is found that the overall dislocation structure only depends on the maximum obtained flow stress. However, some changes in orientation and internal strain distribution between the subgrains were observed after the unloading. An in-situ stepwise straining experiment of a pre-deformed sample was performed, allowing for investigation of individual subgrains during straining. The result indicates that the cell refinement process generally does not take place through simple subgrain breakups. Surprisingly, the dislocation structure shows intermittent behavior, with subgrains appearing and disappearing with increasing strain, suggesting a dynamical development of the structure.

Jakobsen, Bo

2006-01-01

75

Deformation properties of the BCP energy density functional  

CERN Document Server

We explore the deformation properties of the newly postulated BCP energy density functional (EDF). The results obtained for three isotope chains of Mg, Dy and Ra are compared to the available experimental data as well as to the results of the Gogny-D1S force. Results for the fission barrier of $^{240}$Pu are also discussed.

Robledo, L M; Schuck, P; Viñas, X

2008-01-01

76

Examination of different strengths of octupole correlations in neutron-rich Pr and Pm isotopes  

Science.gov (United States)

Recent prompt ?-ray spectroscopy studies of 149,151Pr have revealed weak octupole correlations. These are manifested by the absence of strong intraband E1 transitions between bands of opposite parities. On the other hand, in their isotones 151,153Pm, which have only two additional protons, the E1 transition rates are several orders of magnitude stronger, indicating enhanced octupole correlations. The quasiparticle phonon model combined with the particle-rotor model, which allows octupole correlations and Coriolis mixing to be taken into account, has been applied to calculate the E1 transition rates between low-lying states of the nuclei 149,151Pr and 151,153Pm. The dependence of the E1 rates on the magnitude of the quadrupole deformation, the magnitude and sign of the hexadecapole deformation parameter, the Coriolis and recoil attenuation parameters, the energies of the vibrational bandheads, and the parameters of the Nilsson Hamiltonian have been thoroughly investigated. From this investigation an overall conclusion can be drawn that, even if the intrinsic quasiparticle structure of the bandheads and the octupole correlations vary as the parameters of the model are changed, the octupole correlations in the odd Pr isotopes are much weaker than those in the odd Pm isotopes. Moreover, the experimental E1 transition rates can be satisfactorily described with the values of the quadrupole and hexadecapole deformation parameters expected in this region. In the case of 151Pr, two possible dominant configurations have been assigned to the 35.1-keV isomeric state, namely, the 3/2[422] and 1/2[420] orbitals. Our calculations show that the first assignment provides an E1 value closer to the experimental observations.

Thiamova, Gabriela; Alexa, Petr; Hons, Z.; Simpson, G. S.

2012-10-01

77

Magnetic dipole properties in deformed nuclei  

Science.gov (United States)

The magnetic dipole response in deformed nuclei is investigated. Spurious states due to the rotation of the whole nucleus are removed by restricting the residual interaction in such a way that it commutes with the total angular momentum as a ground state expectation value in the quasi-particle random phase approximation. By this one guarantees that the spurious state due to rotations lies at energy zero and that it is a solution of the quasi-particle random phase equation (QRPA) and can easily be removed. The Hamiltonian is chosen to be a deformed Saxon Woods potential with a pairing force and an isoscalar and isovector generalized quadrupole-quadrupole and spin-spin interaction. The generalized isoscalar quadrupole operator is defined as the commutator of the independent quasi-particle Hamiltonian with the total angular momentum. The restoration of rotational symmetry mentioned above determines the isoscalar coupling constant. The generalized isovector quadrupole-quadrupole force does not commute with the total angular momentum. But one can find a linear “isovector” combination of the proton and the neutron total angular momentum which produces by a commutator with the independent quasiparticle Hamiltonian an “isovector” quadrupole operator which yields an isovector quadrupole-quadrupole force which always commutes with the total angular momentum. Thus one gets no restriction of the isovector quadrupole-quadrupole force constant. We fit it to the isovector giant quadrupole resonance ( E(E2) = {130}/{A {1}/{3}}MeV). The Hamiltonian contains in addition a spin-spin force, which always commutes with the total angular momentum and therefore does not spoil the restoration of rotational symmetry. The proton-proton, neutron-neutron and proton-neutron spin force constant is determined by solving the nuclear matter problem with the Reid soft core interaction within the Brückner theory and translating the result with the help of the Migdal force into finite nuclei. This yields an almost pure repulsive isovector spin-spin force. This Hamiltonian predicts a high lying ?N = 2 scissors mode which lies between 17 and 26 MeV. It is spread over very many 1 + states with an average spacing of 15 keV. This highlying scissors mode consists of several hundred states and the overlap with an artificially constructed scissors mode is of the order of 38%, while the low lying scissors mode which shows up as 1 + states around 3 MeV has an overlap with the scissors mode of more than 50 %. In the same energy range as the high lying scissors mode lies also the isovector giant quadrupole resonance. Even at 180°, that means at completely backward angles, the E2 is comparable with the M1 excitation. This is due to the transversal quadrupole transition probability which is not disappearing in electron scattering at 180°. The same Hamiltonian is nicely describing the low lying scissors mode around 3 MeV in the rare earth and the transuranic nuclei. It gives the energies and the reduced magnetic dipole transition probabilities. It also can reproduce the formfactors measured by inelastic electron scattering. The Hamiltonian also reproduces the spin-flip states between 5 and 9 MeV excitation energy, which can be measured by inelastic proton scattering. One obtains in this region two maxima. The lowest one around 6 MeV is mainly of isoscalar nature and is weaker than the spin flip maximum at 7 to 8 MeV, which is mainly of isovector nature. The detailed form of this two-spin flip maxima depend very sensitively on the ratio of the isoscalar and isovector strength of the spin-spin force. In conclusion one can say: There exist a high lying scissors mode, but it is strongly fragmented over several hundred 1 + states between 17 and 26 MeV and even in electron scattering at backward angles the cross section for the excitation of the isovector giant quadrupole resonance is of comparable size. Thus it will be difficult to establish experimentally the existence of this high lying scissors mode.

Faessler, A.

78

Structure and properties changes in heterogeneous tungsten alloys under deformation  

International Nuclear Information System (INIS)

Changes in structure and properties of a carbidehardened low alloy under tensile deformation in the 300-1700 deg C temperature range were studied. Intense softenning of the alloy ceasing under further heating is stated to take place near the upper range of brittle-ductile transition (300-500 deg C). The minimum of plasticity associated with strain ageing is observed at 1000 deg C. 1400-1500 deg C is shown to be the optimum deformation range as a result of thermally activated processes of transverse slipping and climb of dislocations resulting in alloy softening

79

Deformation bands in porous sandstones their microstructure and petrophysical properties  

Energy Technology Data Exchange (ETDEWEB)

Deformation bands are commonly thin tabular zones of crushed or reorganized grains that form in highly porous rocks and sediments. Unlike a fault, typically the slip is negligible in deformation bands. In this dissertation the microstructure and petrophysical properties of deformation bands have been investigated through microscopy and numerical analysis of experimental and natural examples. The experimental work consists of a series of ring-shear experiments performed on porous sand at 5 and 20 MPa normal stresses and followed by microscopic examination of thin sections from the sheared samples. The results of the ring-shear experiments and comparison of them to natural deformation bands reveals that burial depth (level of normal stress in the experiments) and the amount of shear displacement during deformation are the two significant factors influencing the mode in which grains break and the type of shear zone that forms. Two end-member types of experimental shear zones were identified: (a) Shear zones with diffuse boundaries, which formed at low levels of normal stress and/or shear displacement; and (b) Shear zones with sharp boundaries, which formed at higher levels of normal stress and/or shear displacement. Our interpretation is that with increasing burial depth (approximately more than one kilometer, simulated in the experiments by higher levels of normal stress), the predominant mode of grain fracturing changes from flaking to splitting; which facilitates the formation of sharp-boundary shear zones. This change to grain splitting increases the power law dimension of the grain size distribution (D is about 1.5 in sharp boundary shear zones). Based on our observations, initial grain size has no influence in the deformation behavior of the sand at 5 MPa normal stresses. A new type of cataclastic deformation band is described through outcrop and microscopic studies; here termed a 'slipped deformation band'. Whereas previously reported cataclastic deformation bands are characterized by strain hardening, these new bands feature a central slip surface, which indicates late strain softening. They lack the characteristic compaction envelop, and are typified by higher porosity and lower permeability than previously-described cataclastic deformation bands. Intense background fracturing of the host rock and significant initial porosity are considered to be important in creating these newly-discovered deformation bands. In a related study, we investigate, for millimeter- wide deformation bands, the scale limitation inherent in laboratory measurements of porosity and permeability. The scale limitations imposed by the deformation band relative to the physical sample size motivated us to develop a new method for determining porosity and permeability based on image processing. While plug measurements measure the effective permeability across a 25.4 mm (1 inch) long sample, which includes both host rock and deformation band, the method presented here provides a means to estimate porosity and permeability of deformation band on microscale. This method utilizes low-order (one- and two orders) spatial correlation functions to analyze high-resolution, high-magnification backscatter images, to estimate the porosity and specific surface area of the pore-grain interface in the deformed sandstones. Further, this work demonstrates the use of a modified version of the Kozeny-Carmen relation to calculate permeability by using porosity and specific surface area obtained through the image processing. The result shows that permeability difference between the band and the host rock is up to four orders of magnitude. Moreover, the porosities and permeabilities estimated from image processing are lower than those obtained from their plug measurements; hence the traditional laboratory measurements have been overestimating permeability because of the previously-unrecognized scale problem. In addition, the image processing results clearly show that, as a result of microstructural variation, both porosity and permeability vary along the leng

Torabi, Anita

2007-12-15

80

Nanomechanical properties of poly(l-lactide) nanofibers after deformation.  

Science.gov (United States)

Atomic force microscopy (AFM) technique was used to investigate the nanomechanical properties of poly(l-lactide) (PLLA) nanofibers produced by the thermally induced phase separation (TIPS) method. Firstly, AFM-based nanolithography was employed to produce localized deformations on the surface of single PLLA nanofiber, in which the AFM tip served as a nanoscale burin to draw a scratch longitudinally along the nanofiber. Secondly, the morphology and physical properties of the nanofiber before and immediately after the deformation were characterized with AFM and force spectroscopy measurement. During the initial stage of TIPS process, the crystallization of PLLA resulted in a regular arrangement of crystalline domains along the thinner fibrils which then assembled laterally into larger nanofibers. The deformation due to the nanoindentation and plowing with the probe induced structural variation of PLLA nanofibers and led to a functional consequence in their nanomechanical properties. The region after deformation had a higher adhesion force and elastic modulus, probably because the polymer chains became more compact and ordered under both compression and shear stresses. PMID:24905683

Shao, Jundong; Wang, Yingjun; Chen, Xiaofeng; Hu, Xiaomeng; Du, Chang

2014-08-01

 
 
 
 
81

Octupole correlations in $^{229}Ra$  

CERN Document Server

The structure of /sup 229/Ra has been studied in the beta /sup -/ decay of /sup 229/Fr. Spins and parities have been determined from the conversion electron measurements, while half-lives for the 137.5, 142.7, 168.8, 213.0 and 479.0 keV levels have been measured in the ps and ns ranges via the fast timing beta gamma gamma (t) method. Our data confirm the previous results and enrich the knowledge of the structure of this nucleus by 25 new states and several strong transitions. Structural similarities are established between /sup 229 /Ra and its N=141 isotone /sup 231/Th. The experimental results are compared with the theoretical predictions of the quasiparticle-phonon model with inclusion of Coriolis coupling. The reduced transition probabilities, and especially the moderately fast B(E1) rate for the 137.5 keV transition connecting the band-heads of the K/sup pi /=5/2 /sup +or-/ parity doublet bands, reveal the presence of significant octupole correlations in /sup 229/Ra. (44 refs).

Fraile-Prieto, L M; García-Borge, M J; Fogelberg, B; García-Raffi, L M; Grant, I S; Gulda, K; Hagebø, E; Kurcewicz, W; Kvasil, J; Løvhøiden, G; Mach, H; Mackova, A; Martínez, T; Rubio, B; Taín, J L; Teijeiro, A G; Tengblad, O; Thorsteinsen, T F

1999-01-01

82

Octupole correlations in 229Ra  

International Nuclear Information System (INIS)

The structure of 229Ra has been studied in the ?- decay of 229Fr. Spins and parities have been determined from the conversion electron measurements, while half-lives for the 137.5, 142.7, 168.8, 213.0 and 479.0 keV levels have been measured in the ps and ns ranges via the fast timing ???(t) method. Our data confirm the previous results and enrich the knowledge of the structure of this nucleus by 25 new states and several strong transitions. Structural similarities are established between 229Ra and its N = 141 isotone 231Th. The experimental results are compared with the theoretical predictions of the quasiparticle-phonon model with inclusion of Coriolis coupling. The reduced transition probabilities, and especially the moderately fast B(E1) rate for the 137.5 keV transition connecting the band-heads of the K? = ((5)/(2±)) parity doublet bands, reveal the presence of significant octupole correlations in 229Ra

83

Octupole correlations in 143 Ba and 147 Pr  

International Nuclear Information System (INIS)

High spin states in neutron-rich odd-Z 143,145 Ba nuclei have been investigated from the study of prompt ?-rays in the spontaneous fission of 252 Cf. Alternating parity bands are identified for the first time in 145 Ba and extended in 143 Ba. A new side band with equal, constant dynamic and kinematic moments of inertia equal to the rigid body value, as found in superdeformed bands, is discovered in 145 Ba. Enhanced E1 transitions between the negative- and positive-parity bands in these nuclei give evidence for strong octupole deformation in 143 Ba and in 145 Ba. These collective bands show competition and co-existence between symmetric and asymmetric shapes in 145 Ba. The first evidence is found for crossing M1 and E1 transitions between the s = +i and s = -i doublets in 143 Ba. Neutron-rich 147 Pr also was studied in the spontaneous fission of 252 Cf. Possible parity doublets observed in 147 Pr with N = 88 indicate that neutron-rich 59147 Pr88 nucleus exhibits strong octupole correlations like those observed in the 58146 Ce88 core. (authors)

84

Microscopic description of octupole shape-phase transitions in light actinides and rare-earth nuclei  

CERN Document Server

A systematic analysis of low-lying quadrupole and octupole collective states is presented, based on the microscopic energy density functional framework. By mapping the deformation constrained self-consistent axially symmetric mean-field energy surfaces onto the equivalent Hamiltonian of the $sdf$ interacting boson model (IBM), that is, onto the energy expectation value in the boson condensate state, the Hamiltonian parameters are determined. The study is based on the global relativistic energy density functional DD-PC1. The resulting IBM Hamiltonian is used to calculate excitation spectra and transition rates for the positive- and negative-parity collective states in four isotopic chains characteristic for two regions of octupole deformation and collectivity: Th, Ra, Sm and Ba. Consistent with the empirical trend, the microscopic calculation based on the systematics of $\\beta_{2}$-$\\beta_{3}$ energy maps, the resulting low-lying negative-parity bands and transition rates show evidence of a shape transition be...

Nomura, K; Niksic, T; Lu, Bing-Nan

2014-01-01

85

Nuclear Schiff moment in nuclei with soft octupole and quadrupole vibrations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nuclear forces violating parity and time reversal invariance (${\\cal P},{\\cal T}$-odd) produce ${\\cal P},{\\cal T}$-odd nuclear moments, for example, the nuclear Schiff moment. In turn, this moment can induce the electric dipole moment in the atom. The nuclear Schiff moment is predicted to be enhanced in nuclei with static quadrupole and octupole deformation. The analogous suggestion of the enhanced contribution to the Schiff moment from the soft collective quadrupole and oct...

Auerbach, N.; Dmitriev, V. F.; Flambaum, V. V.; Lisetskiy, A.; Sen Kov, R. A.; Zelevinsky, V. G.

2006-01-01

86

Enhanced octupole correlation due to unpaired nucleons in actinide K-isomeric states  

Science.gov (United States)

Configuration-constrained potential-energy-surface calculations with reflection asymmetry show enhanced octupole correlations in the K?=6- states with configuration ?5/2+[633]??7/2-[743] in N=142,144 isotones, where a 33.5-?s isomer has been observed in 234U. High-K isomeric states in other nuclei around 240Pu are calculated to have reflection-symmetric deformations with excitation energies, in agreement with available data.

Liu, H. L.; Xu, F. R.

2013-06-01

87

Strength and Deformation Properties of Tertiary Clay at Moesgaard Museum  

DEFF Research Database (Denmark)

The tertiary clay at Moesgaard Museum near Aarhus in the eastern part of Jutland in Denmark is a highly plastic, glacially disturbed nappe of Viborg Clay. The clay is characterised as a swelling soil, which could lead to damaging of the building due to additional heave of the soil. To take this characteristic, as well as the strength and deformation properties, into account during the design phase, two consolidation tests and one triaxial test have been conducted. This paper evaluates the results of the laboratory tests leading to the preconsolidation stress, the deformation parameters consisting of the swelling pressure, the constrained modulus and the compression index, and the strength parameters comprising the undrained shear strength, the drained shear strength and the effective angle of internal friction

Kaufmann, Kristine Lee; Nielsen, Benjaminn Nordahl

2010-01-01

88

Octupole states in the SO(6) limit  

International Nuclear Information System (INIS)

In this paper we treat the octupole states in even-even nuclei using a system consisting of f- boson and N-1 s+, d+ bosons. The SO(6) limiting case is emphasized and the analytic relations for energies and electromagnetic transition rates are derived. Finally the two-particle states are briefly discussed

89

Enhancement of nuclear Schiff moments and time-reversal violation in atoms due to soft nuclear octupole vibrations  

International Nuclear Information System (INIS)

Parity and time invariance violating (P,T-odd) nuclear forces produce P,T-odd nuclear moments, for example, the nuclear Schiff moment. In turn, this moment can induce electric dipole moments (EDMs) in atoms. We estimate the contribution to the Schiff moment from the soft collective octupole vibrations existing in many heavy nuclei. Two possible mechanisms are considered, mixing of the ground state of an odd-A nucleus with the octupole phonon state, and P,T-odd admixture to the single-particle wave function of the valence nucleon. We found practically the same contribution to the Schiff moment as that of the static octupole deformation calculated earlier. This confirms a suggestion that the soft octupole vibrations can replace the (controversial) static octupoles in development of the collective Schiff moments. The values of atomic EDM predicted for 223,225Ra and 223Rn are enhanced by factors 102-103 compared to experimentally studied spherical nuclei 199Hg and 129Xe

90

Rock mass deformation properties of closely jointed basalt  

International Nuclear Information System (INIS)

The deformational behavior of the Columbia River basalt is being investigated as part of a comprehensive site characterization program intended to determine the feasibility of constructing a nuclear waste repository in basalt at Hanford, Washington. Direct field measurements were conducted in a 2-m cube of basalt to obtain truly representative rock mass deformation properties. Load was applied to the test block in three orthogonal directions through the use of flat jacks in two perpendicular planes and a cable anchor system in the third. This configuration allowed the block to be placed in a simulated triaxial stress state at stress levels up to 12.5 MPa. The deformation at the center of the test block was monitored through the use of an optical measurement system developed for this project. The results indicate that the vertically oriented columnar joints have a significant influence on the deformation behavior of the basalt. The modulus in the direction parallel to the column axis was approx. 30 GPa, while the modulus value perpendicular to the columns was approx. 20 GPa. Laboratory measurements of intact specimens taken from this area yielded a value of 80 GPa with no indication of anisotropy. Hysteresis was observed in all loading cycles, but was distinctly more pronounced perpendicular to the column axis, indicative of significant joint displacement in this direction. The results of this test represent the first true rock mass modulus data obtained in closely joi mass modulus data obtained in closely jointed rock on a large scale. These measurement methods have eliminated many of the ambiguities associated with borehole jacking and surface measurement techniques

91

Fission fragment properties at scission with the Gogny force  

International Nuclear Information System (INIS)

Two-dimensional Hartree-Fock-Bogoliubov (HFB) calculations have been performed from spherical shapes to large deformations with constraints on axial quadrupole and octupole deformations in U-238, Fm-256-260 and Th-226 actinides. Scission configurations have then been identified in this subspace of collective coordinates and many nuclear properties of the nascent fragments have been derived, such as deformation, deformation energy or prompt neutron multiplicity. The HFB states have then served as basis states for time-dependent collective calculations based on the Time-Dependent Generator Coordinate Method and the Gaussian Overlap Approximation to derive fission fragment yields. (authors)

92

Evidence for octupole vibration in the superdeformed well of {sup 190}Hg from eurogam  

Energy Technology Data Exchange (ETDEWEB)

Gammasphere experiments in 1993-94 brought to light the existence of an excited superdeformed (SD) band in {sup 190}Hg with the unusual property of decaying entirely to the lowest (yrast) SD band over 3-4 transitions, rather than to the normally deformed states as is usually the case in the A {approximately} 150 and A {approximately} 190 regions of superdeformation. Although M1 transitions between signature-partner SD bands were previously observed in {sup 193}Hg, no such mechanism was available to explain the situation in the even-even nucleus {sup 190}Hg, whose yrast SD band has no signature partner. The best explanation appears to lie in long-standing theoretical predictions that the SD minimum in the potential energy surface would be quite soft with respect to octupole vibrations. This would lead to enhanced E1 transitions connecting the one-phonon and zero-phonon states. The data and this interpretation were published. A shortcoming of the Gammasphere experiments was that they did not allow the definitive measurement of the energies of the gamma-ray transitions connecting the two bands, due to the very weak population of the excited band ({approximately}0.05% of the {sup 190}Hg channel) and also partly, we believed, to the angular distributions of the transitions, which were peaked near 90 degrees, where Gammasphere had few detectors.

Crowell, B.; Carpenter, M.P.; Janssens, R.V.F. [and others

1995-08-01

93

Effects of coupled structural and diagenetic processes on deformation localization and flow properties of deformation bands in sandstone  

Science.gov (United States)

Deformation bands tend to restrict flow perpendicular to the bands through the combined effects of porosity reduction, mechanical grain size reduction, and preferred cementation relative to the adjacent host rock. Thus, deformation bands may impart a permeability anisotropy to reservoir rocks. Deformation bands that occur in association with reservoir scale faults can impact reservoir-scale fluid flow and fault seal behavior. Using a combination of textural imaging including SEM-based cathodoluminescence imaging, compositional analysis, and lab petrophysics, this study is designed to (1) assess the effects of coupled chemical and mechanical processes leading to deformation localization in deformation bands and (2) to quantify the effect of these processes on single and multiphase fluid flow. While the effects of mechanical processes including grain translation, rotation, and breakage have been described in detail, chemical reactions affecting flow properties have received less attention. Such chemical reactions include the precipitation of carbonate and quartz cement, dissolution and albitization of feldspar, and the neoformation and infiltration of clay minerals. It is shown that the mechanical process of deformation localization is strongly controlled by chemical processes including pre-kinematic pore-filling cement, syn-kinematic cement filling intra- and transgranular fractures, and stress-enhanced dissolution reactions. Prekinematic cements reduce the strength contrast between grain and aggregate thus favoring deformation localization into narrow, well defined deformation bands. Prekinematic cementation and compaction may even favor thoroughgoing opening mode fractures and prevent localization of deformation into deformation band. Synkinematic cements within deformation bands will result in local strain hardening of bands and thus oppose further deformation localization with increasing strain. Examples will be presented from the Mesozoic clastic sequence of the western US to illustrate these processes.

Elliott, Sara; Eichhubl, Peter; Landry, Chris

2014-05-01

94

Observation of octupoles states in the fission probability of different thorium isotopes  

International Nuclear Information System (INIS)

Sharp resonances are observed in the fission probability of 230Th, 231Th and 233Th, measured in the (n,f) and (d,pf) reactions below the fission threshold. A simultaneous analysis of these resonances and of the associated fission fragment angular distributions concludes to the presence of two superimposed bands of levels, with a very large moment of inertia. These levels are interpreted as the lower levels in the ''third well'', predicted by the calculations to occur, at large quadrupole deformation and non-vanishing octupole deformation, in the potential energy surface of the light actinides

95

High-K isomers as probes of octupole collectivity in heavy nuclei  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The influence of the octupole deformation on the structure of high-K isomeric states in the region of heavy even-even actinide nuclei is studied through a reflection asymmetric deformed shell model (DSM). Two-quasiparticle states with high-K val- ues are constructed by taking into account the pairing effect through a DSM+BCS procedure with constant pairing interaction. The behaviour of two-quasiparticle ener- gies and magnetic dipole moments of K = 6+, 6? and 8? configurations, applicable...

Walker, Pm; Minkov, N.

2010-01-01

96

Observation of Octupole Structures in Radon and Radium Isotopes and Their Contrasting Behavior at High Spin  

International Nuclear Information System (INIS)

Multinucleon transfer reactions have been used, for the first time, to populate high-spin bands of alternating parity states in 218,220,222Rn and 222,224,226Ra. The behavior of the angular momentum alignment with rotational frequency for the Rn isotopes is very different when compared with Ra and Th isotopes with N?134, indicating a transition from octupole vibrational to stable octupole deformation. Throughout the measured spin range the values of |D0/Q0| remain constant for 222Ra and 226Ra and have a very small value for 224Ra, suggesting that the charge and mass distributions are not affected appreciably by rotations. copyright 1997 The American Physical Society

97

Lifetimes in the yrast and an octupole-vibrational superdeformed band in 196Pb  

International Nuclear Information System (INIS)

Lifetimes have been measured for states in the yrast (band 1) and an excited superdeformed band (band 2) in 196Pb. The excited band is thought to be built on an octupole vibration, rather than a quasiparticle excitation. Centroid shifts and line shapes of transitions in ?-ray coincidence spectra measured with the EUROBALL spectrometer have been analyzed. The transition quadrupole moments deduced from these data for the yrast and the excited superdeformed band are identical within the experimental uncertainties. This result shows that the excited band is not built on different deformation-driving orbitals compared to band 1. It is compatible with the previous suggestion of an octupole-vibrational excitation for the signature partner bands 2 and 3

98

Spin assignment of the lowest octupole bandhead in 236U  

International Nuclear Information System (INIS)

Measurements carried out to determine the nature of the octupole bandhead in 236U led in the past to considerable confusion concerning its spin assignment. To see whether penetration effects are important in the conversion electron decay of the octupole band, a high resolution measurement was carried out at the #betta#-spectrometer of the ILL. Relative intensities have been determined for the transitions from the octupole bandhead to the O+, 2+ and 4+ members of the ground state rotational. (U.K.)

99

High ? studies in the Wisconsin Toroidal Octupole  

International Nuclear Information System (INIS)

A wide range of MHD stable high ? plasmas is produced in the Wisconsin Levitated Octupole. At or near the single fluid regime we obtain, in the bad curvature region, ? = nk(T/sub e/ + T/sub i/)8?/B2 approx. = 8%, twice the theoretical single fluid ballooning instability limit of 4%. We also obtain stable plasmas at ? approx. = 35%, 9 times the theoretical limit, in a regime in which both finite ion gyroradius and gyroviscosity effects are important

100

Transient deformation properties of Zircaloy for LOCA simulation. Final report  

International Nuclear Information System (INIS)

The creep/creep rupture anisotropic properties of Zircaloy were determined and compared by analytical techniques with ramp-pressure and ramp-temperature test results. Tests were performed over the temperature range of 6000F (5890K) to 22000F (14770K) with the emphasis on the 8000F (7000K) to 20000F (13660K) temperature levels in low pressure air (6.5 x 10-5 atm) and in a 1 atm mixture of 20% oxygen, 80% argon. Stress levels of 60 to 95% of the ultimate tensile stress were used for the majority of the tests at each of the temperature levels tested, with selected tests performed as low as 30% of the ultimate tensile stress. Biaxial and uniaxial testing modes were used to evaluate the anisotropic deformation behavior. The combination of test results and predictive analysis techniques developed as part of this program make it possible to predict the transient deformation of reactor fuel cladding during simulated LOCA conditions. Results include creep/creep rupture strain numerical constitutive relationships out of 120 seconds, computer codes and ramp test data

 
 
 
 
101

Fluid and ionic transport properties of deformed salt rock  

International Nuclear Information System (INIS)

This is a final report on work done on the transport properties of salt during the period 1 January 1984 to 30 June 1985. This work was directed largely at the measurement of creep-induced permeability in salt rock, at determining the permeability persistence/decay characteristics of creep-dilated salt rock under hydrostatic conditions, and at ion migration/retention experiments on both deformed and undeformed material. The permeability work was carried out using both gas (argon) and brine, and involved the design and construction of corresponding permeametry systems for use in conjunction with dilatometric triaxial testing apparatus. Ion migration/retention studies involved the use of contaminant species such as Sr2+, Cs+, Fe3+ and TcO4

102

Properties of highly deformed tungsten alloys for vacuum technology  

International Nuclear Information System (INIS)

The powder metallurgical production and applications of tungsten alloys are briefly reviewed with emphasis on wires containing dispersed thoria for applications under vacuum. The properties of pure and Al-K-Si doped tungsten wire, of doped tungsten wire with 1 and 2% thoria added as powder and as thorium hydrosol, of undoped W2Th02, W2Th02 sol, and of W5Re are compared and discussed. The tensile strength, elongation and brittle-ductile transition temperature are given for W2Th02 as a function of deformation history up to 14000C. The effect of annealing in hydrogen at up to 24000C on the mechanical properties of 06. mm diameter wire of tungsten and eight tungsten materials has been determined. In addition to the determination of recrystallisation temperatures and electric conductivities, the results of creep tests are discussed. Sag tests were carried out on the wires and creep curves were recorded at 24500C in hydrogen and in vacuum. The results are correlated with scanning electron micrographs. Finally, the mechanical properties of 0.1 mm thick foil of pure and Al-K-Si doped tungsten, W10Re, and W2Th02 are described. (author)

103

Deformation-induced microstructures: analysis and relation to properties  

International Nuclear Information System (INIS)

The formation of microstructures is a unifying theme in the wide spectrum of materials behaviour associated with plastic deformation. Thus microstructures are generated during monotonic and cyclic deformation at low and high temperatures as well as during creep. Microstructures forming locally at crack fronts play critical roles in fatigue and fracture. It is becoming increasingly clear that deformation-induced microstructures are far more diversified than previously assumed. These deformation-induced microstructures define the theme of the present symposium. (LN)

104

Some Electronic Properties of Metals through q-Deformed Algebras  

CERN Document Server

We study the thermodynamics of metals by applying q-deformed algebras. We shall mainly focus our attention on q-deformed Sommerfeld parameter as function of q-deformed electronic specific heat. The results revealed that q-deformation acts as a factor of disorder or impurity, modifying the characteristics of a crystalline structure and thereby controlling the number of electrons per unit volume.

Tristant, Damien

2013-01-01

105

Influence of Plastic Deformation on the Properties of 6066 Heat Treatable Aluminum Alloys  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aims of this work are to (1) study the influence of plastic deformation on the properties of 6066 aluminum alloy; (2) study the effect of deformation on the age hardening of these alloys; (3) study the recovery of these defects from the samples. These effects were investigated in terms of microstructure using positron annihilation spectroscopy (PAS) analysis and mechanical properties by hardness measurements. Dislocations facilitate nucleation of precipitates. At first sight, deformed spe...

Ahmed, Alaa Aldeen; Abdel-naser, Mmdouh; Badawi, Emad Abdelraouf

2013-01-01

106

Effect of Degree of Deformation on the Mechanical Properties of High Temperature Thermomechanically Treated Steel  

Directory of Open Access Journals (Sweden)

Full Text Available The development of high strength materials, coupled with good formability, has always been the aim of material scientists. The effect of degree of deformation on the mechanical properties of high temperature themomechanically treated steel (HTMT has been investigated in this study. It has shown that an increase in percent deformation results in improvement in mechanical properties. In order to have maximum strengthening, heavy deformation and low finishing temperature should be chosen.

J.A. Omotoyinbo

2006-01-01

107

Microstructure and mechanical properties of precipitation hardened aluminum under high rate deformation  

International Nuclear Information System (INIS)

This chapter attempts to correlate the shock compression and quasistatic deformation of 6061-T6 aluminium. Examines recovered specimens which have been shock loaded, and compares results with both static and dynamic mechanical property measurements. Discusses experimental procedures (reshock and unloading experiments, shock recovery techniques, metallographic techniques and coldwork experiments); dynamic strength and wave-profile properties (strength and shear-stress states on the Hugoniot, steady-wave risetime and viscosity); quasistatic and shock metallography studies (metallography of quasistatically deformed material; metallography of shock deformed specimens; comparison of static and shock deformation; correlation of hardness and dynamic strength measurements); and thermal trapping calculations in shocked aluminium (heterogeneous deformation and adiabatic heating in shock-wave loading; energy and risetime relations under steadywave shock compression; heterogeneous temperature calculations in aluminium). Concludes that heterogeneous shear deformation appears to play a role in the dynamic deformation process

108

Physicomechanical properties and gravitational deformation of metallic asteroids  

Science.gov (United States)

A review is given of the mineralogical and chemical composition of iron meteorites and the problems associated with their origin. A detailed discussion is presented of the physical and mechanical properties of iron meteorites and their dependence on the structure, chemical composition, and temperature. Iron meteorites are shown to characterize, with no distortions, the physical and mechanical properties of their parent bodies (metallic asteroids). The population of M-type asteroids and the main characteristics of the identified metallic asteroids are examined. Compared with iron meteorites, metallic asteroids have a different shape and are not fragments of larger metallic parent bodies. The estimates for the current deviatoric stress in metallic asteroids show that, since their formation, asteroids have not been heated to over 600°C and certainly have not been subjected to partial or complete melting. An empirical dependence is found of the critical dimensions of small metallic objects (which allow for gravitational deformation) on the yield strength at temperatures below 300 K. It is shown that the physical and mechanical data are also a strong argument against the hypothesis of the origin of iron meteorites and metallic asteroids from the iron core of a differentiated parent body.

Slyuta, E. N.

2013-04-01

109

Double and triple octupole excitations in the A?150 region  

International Nuclear Information System (INIS)

The results of recent experiments performed at L.N.L. on multiple octupole excitations in the N=84 isotones are reviewed. In particular, the results on B(E3) strengths in 146Sm are discussed and expectations for higher-order octupole excitations are compared with the present experimental situation

110

Indication of an octupole shape revealed in the (tau,?) population of high-spin states in 225Ra  

International Nuclear Information System (INIS)

High spin states in 225Ra have been populated in the (tau,?) reaction with a 30 MeV3 He beam. Levels associated with the jsub(15/2) intruder orbital are given special attention. The peculiar population pattern observed for such states, located at excitation energies of 274 and 538 keV in 225Ra, is predicted in a model calculation where an octupole deformation is assumed. (orig.)

111

Nonclassical Properties of Q-Deformed Superposition Light Field State  

Science.gov (United States)

In this paper, the squeezing effect, the bunching effect and the anti-bunching effect of the superposition light field state which involving q-deformation vacuum state and q-Glauber coherent state are studied, the controllable q-parameter of the squeezing effect, the bunching effect and the anti-bunching effect of q-deformed superposition light field state are obtained.

Ren, Min; Shenggui, Wang; Ma, Aiqun; Jiang, Zhuohong

1996-01-01

112

Deformation properties of the projected spherical single particle basis  

Science.gov (United States)

Deformed single particle energies obtained by averaging a particle-core Hamiltonian with a projected spherical basis depend on a deformation parameter and an arbitrary constant defining the canonical transformation relating the collective quadrupole coordinates and momenta with the boson operators. When the mentioned basis describes the single particle motion of either protons or neutrons the parameters involved are isospin dependent. An algorithm for fixing these parameters is formulated and then applied for 194 isotopes covering a good part of the nuclide chart. Relation with the Nilsson deformed basis is pointed out in terms of deformation dependence of the corresponding single particle energies as well as of the nucleon densities and their symmetries. The proposed projected spherical basis provides an efficient tool for the description of spherical and deformed nuclei in a unified fashion.

Raduta, A. A.; Budaca, R.

2014-08-01

113

Influence of Plastic Deformation on the Properties of 6066 Heat Treatable Aluminum Alloys  

Directory of Open Access Journals (Sweden)

Full Text Available The aims of this work are to (1 study the influence of plastic deformation on the properties of 6066 aluminum alloy; (2 study the effect of deformation on the age hardening of these alloys; (3 study the recovery of these defects from the samples. These effects were investigated in terms of microstructure using positron annihilation spectroscopy (PAS analysis and mechanical properties by hardness measurements. Dislocations facilitate nucleation of precipitates. At first sight, deformed specimens had lower hardness as compared to non-deformed ones, and as the deformation increase, the hardness decreases. Another output of the mechanical test was the increase in hardness in the specimens after artificial aging with an increase in percent deformation.

Emad Abdelraouf BADAWI

2013-06-01

114

Octupole focusing in transport and acceleration systems  

International Nuclear Information System (INIS)

The radio-frequency quadrupole (RFQ) linac is capable of accelerating high-current, low-velocity ion beams. In accelerator systems comprising an RFQ and higher velocity accelerating structures, the current bottleneck still typically occurs within the RFQ. This limiting current is quite high in most cases, but linacs with even higher currents may be required in the future. We have begun a study of higher multipole systems to determine their capability for focusing and accelerating very high currents. We have chosen first to examine a radio-frequency octupole (RFO) transport system, and have developed a smooth-approximation analytical description that includes the conditions for input radial matching of a zero space-charge beam. Further, we have constructed a multiparticle beam-dynamics simulation program that accepts the low-current matched beam and gradually increases the beam current as it is transported. This results in a matched high-current beam, and the procedure can be used to determine the saturation-current limit of a periodic octupole system. As expected, at high currents the beam develops a hollow radial distribution that reduces the space-charge defocusing; initial results show that high currents can be transported. For acceleration, we have formulated the design parameters for a section of RFO linac, including the potential function, acceleration, and focusing efficiencies, and the geometry of the radially modulated pole tips

115

Octupole focusing in transport and accelerator systems  

International Nuclear Information System (INIS)

The radio-frequency quadrupole (RFQ) linac is capable of accelerating high-current, low-velocity ion beams. In accelerator systems comprising an RFQ and higher velocity accelerating structures, the current bottleneck still typically occurs within the RFQ. This limiting current is quite high in most cases, but linacs with even higher currents may be required in the future. We have begun a study of higher multipole systems to determine their capability or focusing and accelerating very high currents. We have chosen first to examine a radio-frequency octupole (RFQ) transport system, and have developed a smooth-approximation analytical description that includes the conditions for input radial matching of a zero space-charge beam. Further, we have constructed a multiparticle beam-dynamics simulation program that accepts the low-current matched beam and gradually increases the beam current as it is transported. This results in a matched high-current beam, and the procedure can be used to determine the saturation-current limit of a periodic octupole system. As expected, at high currents the beam develops a hollow radial distribution that reduces the space-charge defocusing; initial results show that high currents can be transported. For acceleration, we have formulated the design parameters for a section of RFQ linac, including the potential function, acceleration, and focusing efficiencies, and the geometry of the radially modulated

116

Persistence of octupole correlations in $^{231}/Ra$  

CERN Document Server

The structure of /sup 231/Ra, the heaviest odd Ra nucleus currently accessible for detailed spectroscopic investigation, has been studied in the beta /sup -/ decay of /sup 231/Fr. The main purpose has been to verify whether fast B(E1) rates and significant octupole correlations recently established in /sup 229/Ra persist in /sup 231 /Ra, The excited states in /sup 231/Ra have been determined for the first time. Spins and parities have been deduced from conversion electron measurements, while level half-lives in the ps and ns ranges have been measured with the Advanced Time Delayed beta gamma gamma (t) method. The moderately fast B(E1) rates found for transitions connecting the lowest-lying K/sup pi /=5/2/sup +or-/ and K/sup pi /=1 /2/sup +or-/ bands, reveal the persistence of octupole collective effects in /sup 231/Ra, although the B(E1) rates are lower than in /sup 229/Ra. These findings reinforce the differences in the B(E1) systematics between isotonic Ra and Th nuclei. (42 refs).

Fraile-Prieto, L M; Mach, H; Boutami, R; Aas, A J; Fogelberg, B; Gracía-Raffi, L M; Grant, I S; Gulda, K; Hagebø, E; Kurcewicz, W; Kvasil, J; López, M J; Løvhøiden, G; Martínez, T; Rubio, B; Taín, J L; Tengblad, O

2001-01-01

117

Convergence properties of the q-deformed binomial distribution  

Directory of Open Access Journals (Sweden)

Full Text Available We consider the $q$-deformed binomial distribution introduced by{sc S. C. Jing:} {it The {$q$}-deformed binomial distribution and its asymptotic behaviour,}J. Phys. A {f 27} (2 (1994, 493--499and{sc W. S. Chung} et al: {it {$q$}-deformed probability and binomial distribution,} Internat. J. Theoret. Phys.{f 34} (11 (1995, 2165--2170and establish several convergence results involvingthe Euler and the exponential distribution; some of them are $q$-analogues of classical results.

Martin Zeiner

2010-03-01

118

Large ferroquadrupole moment induced in the octupole-ordered Ce0.7La0.3B6 revealed by high-resolution x-ray diffraction  

Science.gov (United States)

We carried out a high-resolution x-ray diffraction experiment on Ce0.7La0.3B6 that exhibits staggered order of 4f octupole moments below TO=1.4 K. Theoretically, ferroquadrupole moments that accompany the antiferro-octupole order and a resultant rhombohedral deformation of the cubic lattice were predicted. In contrast, experimentally, no direct evidence of the rhombohedral lattice has been obtained. We observe the splitting of Bragg peaks below TO and find that the unit cell is a rhombohedron being elongated along the [111] axis. The response of rhombohedral domains to magnetic fields also well agrees with theoretical calculations. A particular outcome of this experiment is that the magnitude of the induced quadrupole moments is precisely evaluated from the obtained shear strain. Using this result, the magnitude of the hidden octupole moments is also discussed.

Inami, T.; Michimura, S.; Hayashi, Y.; Matsumura, T.; Sera, M.; Iga, F.

2014-07-01

119

Beam-Profile Control Using an Octupole Magnet  

Science.gov (United States)

For medical irradiation, beams with a uniform distribution have been required. We have proposed a method to control the beam profile using an octupole magnet. We have installed an octupole magnet and confirmed its effectiveness at the Heavy Ion Medical Accelerator in Chiba (HIMAC) beam-transport line. A beam efficiency of 91% can be realized with a flatness of ±4% over the range of ±15 mm. The beam offset at the position of the octupole magnet is required to be within ±0.2 mm to realize this condition. This method is expected to have a beam efficiency higher than that of the ordinary method using wobbler magnets and a scatterer system.

Urakabe, Eriko; Fujita, Yuzo; Hiramoto, Kazuo; Inoue, Makoto; Iwashita, Yoshihisa; Kanazawa, Mitsutaka; Morita, Akio; Nishi, Masatsugu; Norimine, Tetsuro; Noda, Akira; Noda, Koji; Ogawa, Hirotsugu; Shirai, Toshiyuki; Torikoshi, Masami; Umezawa, Masumi; Yamada, Satoru

1999-10-01

120

Octupole correlations in neutron rich, odd-A lanthanum nuclei  

International Nuclear Information System (INIS)

Neutron-rich, odd-Z nuclei 145La and 147La populated in spontaneous fission of 248Cm were studied using the EUROGAM array. The experiment indicates the presence of similar octupole correlations in the studied La isotopes as found in the barium core nuclei. Alternating-parity structures were found in 145La, indicating enhanced octupole correlations, as observed in 144Ba, while in 147La octupole effects are weakened by alignment phenomena, as seen in the core nucleus 146Ba. copyright 1996 The American Physical Society

 
 
 
 
121

Plastic deformation effect on structure and mechanical properties of 15Kh2NMFA steel  

International Nuclear Information System (INIS)

A study was made on the effect of plastic deformation on microstructure and mechanical properties of 15Kh2NMFA steel. It is shown that phase composition, dispersion degree, carbide distribution and the fracture mode of impact samples are independent of bending technology. Plastic deformation temperature dictates the character of dislocation structure of 15Kh2NMFA steel and therefore the character of change of its mechanical properties during temperings

122

Effect of deformation rate on the mechanical properties of arteries  

Directory of Open Access Journals (Sweden)

Full Text Available Pig aorta samples were tested uniaxially and equi- biaxially at deformation rates from 10 to 200 %/s. Under uniaxial and biaxial testing, loading forces were reduced up to 20% when the deformation rate was increased from 10 to 200 %/s, which is the opp- osite to the behaviour seen in other biological tissues. A rate-dependent isotropic hyperelastic constitutive equation, derived from the Mooney-Rivlin model, was fitted to the experimental results (e.g. aorta specimens using an inverse finite element technique. In the proposed model, one of the material par- ameters is a linear function of the deformation rate. The inverse relationship between stiffness and defo- rmation rate raises doubts on the hypothesized rel- ationship between intramural stress, arterial injury, and restenosis.

Savvas G. Hatzikiriakos

2010-03-01

123

Alternating parity bands and octupole effects in 221Th and 223Th?  

Science.gov (United States)

Level structures of the two neutron deficient odd- A nuclei 221Th and 223Th have been investigated by means of the reactions 208Pb( 16O, 3n) 221Th and 208Pb( 18O, 3n) 223Th. In-beam conversion electron and ?-ray spectroscopy in coincidence with the recoiling evaporation residues (R) has been carried out, including ??R-, e -?R- and e -e -R-coincidence measurements, as well as the determination of ?-ray angular distributions and ?-ray multiplicities using the Nal crystal ball. Level schemes could be established up to 13? above the ground state in 221Th and up to {33+}/{2} in 223Th. In 221Th one band of alternating parity states is observed, whereas in 223Th two such bands with equal intensity are seen. The level schemes are interpreted in terms of an octupole deformed core with an unpaired nucleon. From the {E1}/{E2} branching ratio the electric dipole moments can be deduced; for 221Th one finds ¦ D¯0¦ = 0.33 ± 0.06 e .fm and for 223Th ¦ D¯0¦ = 0.44 ± 0.09 e .fm, the largest value observed so far in this mass region. The alignments of the different bands in 223Th with simplex quantum number s = ± i are approximately equal and amount to octupole deformation.

Dahlinger, M.; Kankeleit, E.; Habs, D.; Schwalm, D.; Schwartz, B.; Simon, R. S.; Burrows, J. D.; Butler, P. A.

1988-07-01

124

Nonaxial-octupole Y_{32} correlations in N = 150 isotones from multidimensional constrained covariant density functional theories  

CERN Document Server

The non-axial reflection-asymmetric $\\beta_{32}$ shape in some transfermium nuclei with N=150, namely $^{246}$Cm, $^{248}$Cf, $^{250}$Fm, and $^{252}$No are investigated with multidimensional constrained covariant density functional theories. By using the density-dependent point coupling covariant density functional theory with the parameter set DD-PC1 in the particle-hole channel, it is found that, for the ground states of $^{248}$Cf and $^{250}$Fm, the non-axial octupole deformation parameter $\\beta_{32} > 0.03$ and the energy gain due to the $\\beta_{32}$ distortion is larger than 300 keV. In $^{246}$Cm and $^{252}$No, shallow $\\beta_{32}$ minima are found. The occurrence of the non-axial octupole $\\beta_{32}$ correlations is mainly from a pair of neutron orbitals $[734]9/2$ ($\

Zhao, Jie; Zhao, En-Guang; Zhou, Shan-Gui

2012-01-01

125

Tensile Properties and Deformation Characteristics of a Ni-Fe-Base Superalloy for Steam Boiler Applications  

Science.gov (United States)

Ni-Fe-base superalloys due to their good manufacturability and low cost are the proper candidates for boiler materials in advanced power plants. The major concerns with Ni-Fe-base superalloys are the insufficient mechanical properties at elevated temperatures. In this paper, tensile properties, deformation, and fracture characteristics of a Ni-Fe-base superalloy primarily strengthened by ?' precipitates have been investigated from room temperature to 1073 K (800 °C). The results showed a gradual decrease in the strength up to about 973 K (700 °C) followed by a rapid drop above this temperature and a ductility minimum at around 973 K (700 °C). The fracture surfaces were studied using scanning electron microscopy and the deformation mechanisms were determined by the observation of deformed microstructures using transmission electron microscopy. An attempt has been made to correlate the tensile properties and fracture characteristics at different temperatures with the observed deformation mechanisms.

Zhong, Zhihong; Gu, Yuefeng; Yuan, Yong; Shi, Zhan

2014-01-01

126

Mechanical properties of hot deformed Inconel 718 and X750  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: Variations of a flow stress vs. true strain illustrate behavior of material during plastic deformation. Stress-strain relationship is generally evaluated by a torsion, compression and tensile tests.Design/methodology/approach: Compression tests were carried out on precipitations hardenable nickel based superalloys of Inconel 718 and X750 at constant true strain rates of 10-4, 4x10-4s-1 within temperature through which precipitation hardening phases process occurred (720-1150°C using thermomechanical simulator Gleeble and dilatometer Baehr 850D/L equipped with compression unit. True stress-true strain curves analysis of hot deformed alloys were described.Findings: On the basis of received flow stress values activation energy of a high-temperature deformation process was estimated. Mathematical dependences (?pl -T i ?pl - ? and compression data were used to determine material’s constants. These constants allow to derive a formula that describes the relationship between strain rate (?, deformation temperature (T and flow stress ?pl.Research limitations/implications: Study the flow stress will be continued on the samples after the aging process.Practical implications: The results of high-temperature deformation of the examined Inconel alloys may possibly find some practical use in the workshop practice to predict a flow stress values, but only within particular temperature and strain rate ranges. The results of the study can be used in the aerospace industry to produce blades for jet engines.Originality/value: The results of the study can be used in the aerospace industry to produce blades for jet engines.

A. Nowotnik

2012-02-01

127

Plastic deformation and magnetic properties of yttrium ferrite garnet monocrystals  

International Nuclear Information System (INIS)

The method of selective chemical etching is used to determine conditions of plastic deformation of single crystals of Y3Fe5O12. The nature of the dislocation structure appearing under concentrated load and fourpoint bending is studied. The polarization-optical technique is used to study the effect of introduced dislocations on the domain structure of crystals. The plastic deformation is shown to substantially alter microscopic characteristics of magnetization of yttrium-iron garnet. The total magnetic permeability of a crystal sharply increases with the density rho of introduced dislocations, while the coercive force varies proportionally to ?rho, that is consistent with theoretical predictions for the case of chaotic distribution of dislocations

128

Mechanical properties of hot deformed Inconel 718 and X750  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Purpose: Variations of a flow stress vs. true strain illustrate behavior of material during plastic deformation. Stress-strain relationship is generally evaluated by a torsion, compression and tensile tests.Design/methodology/approach: Compression tests were carried out on precipitations hardenable nickel based superalloys of Inconel 718 and X750 at constant true strain rates of 10-4, 4x10-4s-1 within temperature through which precipitation hardening phases process occurred (720-1150°C) usin...

Nowotnik, A.; Pe?drak, P.; Sieniawski, J.; Go?ral, M.

2012-01-01

129

Influence of deformation temperature on the structure and mechanical properties of tungsten base alloys  

International Nuclear Information System (INIS)

Low-alloyed tungsten alloys were obtained by melting with subsequent thermomechanical treatment under different conditions. The structure and substructure were studied by optical and electron microscopy methods. The width of X-ray diffraction lines was also determined to characterize microdistortions of the crystal lattice. The strength properties, plastic characteristics and ductile brittle transition temperature were determined in a 100-600 deg C temperature range under mechanical tensile tests. It is shown that in a high-deformed metal (degree of reduction approximately equal to 80% and more) the dislocation cell size governs some mechanical properties as well as the grain size determines there properties in a recrystallized state. It is shown that the structure parameters and mechanical properties of different tungsten alloys vary in dependence on t (deformation) in a similar way. The investigation also shows that the dispersed particle presence in a deformed tungsten alloy induces an indirect rather than direct strengthening

130

Effect of High-Temperature Severe Plastic Deformation on Microstructure and Mechanical Properties of IF Steel  

Science.gov (United States)

Extensive research work has been carried out on interstitial-free steel to understand its response to deformation; particularly, the behavior during severe plastic deformation (SPD). However, most of these studies were mainly undertaken in the ferritic regime. The present investigation reports the initial results of our attempt to employ accumulative roll bonding (ARB), one of the variants of SPD, at a high temperature (950 °C). A considerable grain refinement has been observed, which may be attributed to the severity of deformation and recrystallisation at high temperatures. Nanoindentation tests have been performed at various stages of ARB process to understand the evolution of mechanical properties.

Jindal, Vikas; Rupa, P. K. P.; Mandal, G. K.; Srivastava, V. C.

2014-06-01

131

D-deformed Wess-Zumino model and its renormalizability properties  

CERN Document Server

Using the methods developed in earlier papers we analyze a new type of deformation of the superspace. The twist we use to deform the N=1 SUSY Hopf algebra is non-hermitian and is given in terms of the covariant derivatives $D_\\alpha$. A SUSY invariant deformation of the Wess-Zumino action is constructed and compared with results already known in the literature. Finally, by calculating divergences of the two-point Green functions a preliminary analysis of renormalizability properties of the constructed model is done. As expected, there is no renormalization of mass and no tadpole diagrams appear.

Dimitrijevic, Marija

2009-01-01

132

D-deformed Wess-Zumino model and its renormalizability properties  

International Nuclear Information System (INIS)

Using the methods developed in earlier papers we analyze a new type of deformation of the superspace. The twist we use to deform the N = 1 SUSY Hopf algebra is non-hermitian and is given in terms of the covariant derivatives D?. A SUSY invariant deformation of the Wess-Zumino action is constructed and compared with results already known in the literature. Finally, by calculating divergences of the two-point Green functions a preliminary analysis of renormalizability properties of the constructed model is done. As expected, there is no renormalization of mass and no tadpole diagrams appear.

133

The impact of cold deformation, annealing temperatures and chemical assays on the mechanical properties of platinum  

Directory of Open Access Journals (Sweden)

Full Text Available In order to form the necessary data base on platinum and platinum metals, certain tests were carried out on platinum samples of different purity of 99.5%, 99.9% and 99.99%. The degree of cold deformation, annealing temperature and chemical assays were tested as well as their impact on the mechanical properties of platinum. The Vickers hardness (HV values were determined with different deformation degree, starting from annealing temperatures for platinum of different purity and tensile strength (Rm, flow limit (Rp0,2 and elongation (A in the function of annealing temperatures and annealing time at a constant deformation degree.

Trumi? B.

2010-01-01

134

Effect of cold plastic deformation on the properties of semihard-magnetic alloys  

International Nuclear Information System (INIS)

The effect of pass and overall reduction during cold plastic deformation on magnetic properties of the 25KKh15 and 25KFN14 iron-cobalt alloys has been studied. It has been found out that gamma-? transformation which intensity id defined by the deformation temperature occurs during the 25KFN14 and 25KKh15 alloy cold rolling. The pass reduction decrease fostering complete proceeding of #betta#-? transformation is equivalent to the increase of overall reduction

135

Improvement of research methods and testing equipment for deformation properties of clay  

Digital Repository Infrastructure Vision for European Research (DRIVER)

One of the most challenging areas of geotechnical engineering is the prediction of deformations of soft soils such as clays. Strength and deformation properties of clays have been studied over centuries resulting in development of different testing techniques and interpretation methods. As a result different types of material models have been developed in order to describe the behavior of clays. Recently developed material models require additional parameters compared with the simple models d...

Laaksonen, Samuli

2014-01-01

136

Mathematical description of properties of a weakly deformed Gauss peak. 1  

International Nuclear Information System (INIS)

The properties of the weakly deformed Gaussian peak are described by given formulas. The moment generating function and all the higher moments of this weakly deformed Gaussian peak density function are calculated by closed integrations. The density function is useful for the design of Maximum-Likelihood peak shape parameter estimators and the application of spectral techniques with multi-channel spectra. Numerical calculations use the well known Gaussian error integral and can be done by programmable microcomputers or programmable pocket calculators. (author)

137

INFLUENCE OF EXTREME PLASTIC DEFORMATION ON THE MICROSTRUCTURE AND PROPERTIES OF METAL MATERIALS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work deals with the influence of plastic deformation on microstructural evolution of dispersion strengthened copper with the aim of uniting the mechanism of dispersion and deformation strengthening to produce nanostructured composite with improved properties. Within the work the possibility of achieving greater depths of internal oxidation zone was studied. With the modified Rhines package a sufficient depth of internal oxidation zone was reached to study the behaviour of dispersion str...

Kos, Matija

2014-01-01

138

Estimating the mechanical properties of the brittle deformation zones at Olkiluoto  

International Nuclear Information System (INIS)

In rock mechanics modelling to support repository design and safety assessment for the Olkiluoto site, it is necessary to obtain the relevant rock mechanics parameters, these being an essential pre-requisite for the modelling. The parameters include the rock stress state, the properties of the intact rock and the rock mass, and the properties of the brittle deformation zones which represent major discontinuities in the rock mass continuum. However, because of the size and irregularity of the brittle deformation zones, it is not easy to estimate their mechanical properties, i.e. their deformation and strength properties. Following Section 1 explaining the motivation for the work and the objective of the Report, in Sections 2 and 3, the types of fractures and brittle deformation zones that can be encountered are described with an indication of the mechanisms that lead to complex structures. The geology at Olkiluoto is then summarized in Section 4 within the context of this Report. The practical aspects of encountering the brittle deformation zones in outcrops, drillholes and excavations are described in Sections 5 and 6 with illustrative examples of drillhole core intersections in Section 7. The various theoretical, numerical and practical methods for estimating the mechanical properties of the brittle deformation zones are described in Section 8, together with a Table summarizing each method's advantages, disadvantages and utility in estimating the mechanical properties of the zones. We emphasise that the optimal approach to estimating the mechanical properties of the brittle deformation zones cannot be determined without a good knowledge, not only of each estimation method's capabilities and idiosyncrasies, but also of the structural geology background and the specific nature of the brittle deformation zones being characterized. Finally, in Section 9, a Table is presented outlining each method's applicability to the Olkiluoto site. A flowchart is included to indicate the proposed structure for a brittle deformation zone mechanical property estimation campaign, noting that the exact nature of future work will depend on the results of the ONKALO Prediction-Outcome studies and decisions on the rock mechanics work required to support the repository design. (orig.)

139

Cyclic deformation and dynamic compressive properties of copper bicrystals  

International Nuclear Information System (INIS)

Cyclic deformation and dynamic compressive tests of three copper bicrystals were carried out on a Shimadzu servo-hydraulic testing machine and a split Hopkinson pressure bar (SHPB) apparatus respectively. The post-deformation dislocation structures, grain boundary (GB) serrations and adiabatic shear bands (ASBs) were examined using electron channeling contrast (ECC) imaging in a scanning electron microscope (SEM). After cyclic straining the secondary slip bands were activated near the GB forming a GB affected zone (GBAZ). Microstructures beneath it are dislocation labyrinth or irregular persistent slip bands (PSBs). The saturation stress at GBAZ was calculated to be higher than that in the grain interior. In dynamic compression, the formation of ASBs, was found to be promoted by the GB. Dynamic stress-strain curves were compared with each other for single crystals, bicrystals and polycrystals. Microstructures were also characterized with orientation imaging microscopy (OIM) by electron backscattering diffraction (EBSD) technique. It was found that relatively larger lattice rotations occurred across the ASBs than in the other regions, which can be deduced by the localization of simple shear along ASBs. No recrystallization was found in the ASBs or along GBs in the present circumstance

140

Determination of the deformation properties of Søvind Marl  

DEFF Research Database (Denmark)

A serie of tests were made to determine the preconsolidation stresses, ??pc, and the consolidation modulus, K, of Søvind Marl, a fissured plastic tertiary clay. The fissures causes a decrease in the stiffness of the Søvind Marl, which can be mistaken for the decrease that happens when the effective stresses in the soil, ??, passes ??pc. The effects of the fissures are assessed, and an estimate of the stress level at which they will compress are made. During the consolidation tests, the effective stress level is raised to more then 24,000 kPa to get a comprehensive description of the preconsolidation of the soil. It is important to know how a strongly preconsolidated soil will deform when reloaded. The deformation parameters of the strongly preconlidated Søvind Marl is determined by unloading/reloading testing. It is found that the stiffness of the Søvind Marl depends of the plasticity index, and one conclusive expression of the consolidation modulus of the Søvind Marl can therefor not be given.

GrØnbech, Gitte; Nielsen, Benjaminn Nordahl

2010-01-01

 
 
 
 
141

Nonaxial-octupole Y32 correlations in N=150 isotones from multidimensional constrained covariant density functional theories  

Science.gov (United States)

The nonaxial reflection-asymmetric ?32 shape in some transfermium nuclei with N=150, namely, 246Cm, 248Cf, 250Fm, and 252No, are investigated with multidimensional constrained covariant density functional theories. By using the density-dependent point-coupling covariant density functional theory with the parameter set DD-PC1 in the particle-hole channel, it is found that, for the ground states of 248Cf and 250Fm, the nonaxial octupole deformation parameter ?32>0.03 and the energy gain due to the ?32 distortion is larger than 300 keV. In 246Cm and 252No, shallow ?32 minima are found. The occurrence of the nonaxial octupole ?32 correlations is mainly from a pair of neutron orbitals, [734]9/2 (?j15/2) and [622]5/2 (?g9/2), which are close to the neutron Fermi surface, and a pair of proton orbitals, [521]3/2 (?f7/2) and [633]7/2 (?i13/2), which are close to the proton Fermi surface. The dependence of the nonaxial octupole effects on the form of the energy density functional and on the parameter set is also studied.

Zhao, Jie; Lu, Bing-Nan; Zhao, En-Guang; Zhou, Shan-Gui

2012-11-01

142

Structure properties of 226Th and 256,258,260Fm fission fragments: Mean-field analysis with the Gogny force  

International Nuclear Information System (INIS)

The constrained Hartree-Fock-Bogoliubov method is used with the Gogny interaction D1S to calculate potential energy surfaces of fissioning nuclei 226Th and 256,258,260Fm up to very large deformations. The constraints employed are the mass quadrupole and octupole moments. In this subspace of collective coordinates, many scission configurations are identified ranging from symmetric to highly asymmetric fragmentations. Corresponding fragment properties at scission are derived yielding fragment deformations, deformation energies, energy partitioning, neutron binding energies at scission, neutron multiplicities, charge polarization, and total fragment kinetic energies

143

Ground-state properties of the heaviest nuclei analyzed in a multidimensional deformation space  

International Nuclear Information System (INIS)

Ground-state properties of the heaviest nuclei are analyzed in the three-dimensional deformation space {??}, ?=2, 4, 6. Effects of using even larger spaces are explored. Deformation, mass, alpha-decay energy and half-life of even-even nulcei with proton number Z=90-114 and neutron number N=136-168 are studied. The ground-state energy of the nuclei is treated in the macroscopic-microscopic approach. It is found that the use of a larger deformation space (in particular, a proper inclusion of the deformation ?6 in this space) significantly improves the description of experimental results and, also significantly, changes the predictions for nuclei not yet observed. (orig.)

144

Ground-state properties of the heaviest nuclei analyzed in a multidimensional deformation space  

International Nuclear Information System (INIS)

Ground-state properties of the heaviest nuclei are analyzed in the three-dimensional deformation space {??}, ?=2, 4, 6. Effects of using even larger spaces are explored. Deformation, mass, alpha-decay energy and half-life of even-even nuclei with proton number Z=90-114 and neutron number N=136-168 are studied. The ground-state energy of the nuclei is treated in the macroscopic-microscopic approach. It is found that the use a larger deformation space (in particular, a proper inclusion of the deformation ?6 in this space) significantly improves the description of experimental results and, also significantly, changes the predictions for nuclei not yet observed. (orig.)

145

Crystallization of ion clouds in octupole traps: Structural transitions, core melting, and scaling laws  

International Nuclear Information System (INIS)

The stable structures and melting properties of ion clouds in isotropic octupole traps are investigated using a combination of semianalytical and numerical models, with a particular emphasis at finite-size scaling effects. Small-size clouds are found to be hollow and arranged in shells corresponding approximately to the solutions of the Thomson problem. The shell structure is lost in clusters containing more than a few thousands of ions, the inner parts of the cloud becoming soft and amorphous. While melting is triggered in the core shells, the melting temperature follows the rule expected for three-dimensional dense particles, with a depression scaling linearly with the inverse radius.

146

Crystallization of ion clouds in octupole traps: structural transitions, core melting, and scaling laws  

CERN Document Server

The stable structures and melting properties of ion clouds in isotropic octupole traps are investigated using a combination of semi-analytical and numerical models, with a particular emphasis at finite size scaling effects. Small-size clouds are found to be hollow and arranged in shells corresponding approximately to the solutions of the Thomson problem. The shell structure is lost in clusters containing more than a few thousands of ions, the inner parts of the cloud becoming soft and amorphous. While melting is triggered in the core shells, the melting temperature unexpectedly follows the rule expected for three-dimensional dense particles, with a depression scaling linearly with the inverse radius.

Calvo, Florent; Yurtsever, Ersin

2009-01-01

147

Spectroscopy and octupole coupling of high-spin states in 213Rn  

International Nuclear Information System (INIS)

Excited states of 213Rn, up to spins of ? 55/2 ? and an excitation energy of ? 6 MeV, have been studied using ?-ray and electron spectroscopy following the reactions 208Pb(9Be,4n) and 204Hg(13C,4n). Eight isomeric states were identified and g-factors for five of these measured by the TDPAD technique. Several of the isomeric states decay by enhanced E3 transitions. The level scheme and electromagnetic properties of the isomers are compared with the results of semi-empirical shell-model calculations including calculations which explicitly account for the particle-octupole vibration coupling

148

Beam-profile control using an octupole magnet  

Energy Technology Data Exchange (ETDEWEB)

For medical irradiation, beams with a uniform distribution have been required. We have proposed a method to control the beam profile using an octupole magnet. We have installed an octupole magnet and confirmed its effectiveness at the Heavy Ion Medical Accelerator in Chiba (HIMAC) beam-transport line. A beam efficiency of 91% can be realized with a flatness of {+-}4% over the range of {+-}15 mm. The beam offset at the position of the octupole magnet is required to be within {+-}0.2 mm to realize this condition. This method is expected to have a beam efficiency higher than that of the ordinary method using wobbler magnets and a scatterer system. (author)

Urakabe, Eriko [Nuclear Science Research Facility, ICR, Kyoto University, Uji, Kyoto (Japan); Fujita, Yuzo; Hiramoto, Kazuo (and others)

1999-10-01

149

Beam-profile control using an octupole magnet  

International Nuclear Information System (INIS)

For medical irradiation, beams with a uniform distribution have been required. We have proposed a method to control the beam profile using an octupole magnet. We have installed an octupole magnet and confirmed its effectiveness at the Heavy Ion Medical Accelerator in Chiba (HIMAC) beam-transport line. A beam efficiency of 91% can be realized with a flatness of ±4% over the range of ±15 mm. The beam offset at the position of the octupole magnet is required to be within ±0.2 mm to realize this condition. This method is expected to have a beam efficiency higher than that of the ordinary method using wobbler magnets and a scatterer system. (author)

150

B(E1) rates in 229Ra and traces of octupole correlations at the upper border of the A=225 island  

Science.gov (United States)

The introduction of the fast timing ???(t) method at ISOLDE (CERN) has opened the heavy actinide region to lifetime measurements down to tenths of picoseconds, providing a direct experimental means of measuring the E1 rates. Recently, this method has been successfully applied to 229Ra, located at the border of the A=225 island of octupole deformation. In the light of the new results, structural similarities are established between 229Ra and its N=141 isotone 231Th, investigated with the same technique. The comparison shows that some collective aspects of both nuclei are related, but that the strength of the E1 transitions presents interesting differences. The collective B(E1) rates are also discussed in comparison with neighboring nuclei in the upper border of the island of octupole deformation at A=225.

Fraile, L. M.; Aas, A. J.; Borge, M. J. G.; Fogelberg, B.; García-Raffi, L. M.; Grant, I. S.; Gulda, K.; Hagebø, E.; Kurcewicz, W.; Løvhøiden, G.; Mach, H.; Martínez, T.; Rubio, B.; Taín, J. L.; Tengblad, O.; Thorsteinsen, T. F.

1999-11-01

151

B(E1) rates in $^{229}Ra$ and traces of octupole correlations at the upper border of the A=225 island  

CERN Document Server

The introduction of the fast timing beta gamma gamma (t) method at ISOLDE (CERN) has opened the heavy actinide region to lifetime measurements down to tenths of picoseconds, providing a direct experimental means of measuring the E1 rates. Recently, this method has been successfully applied to /sup 229/Ra, located at the border of the A=225 island of octupole deformation. In the light of the new results, structural similarities are established between /sup 229/Ra and its N=141 isotone /sup 231/Th, investigated with the same technique. The comparison shows that some collective aspects of both nuclei are related, but that the strength of the El transitions presents interesting differences. The collective B(E1) rates are also discussed in comparison with neighbouring nuclei in the upper border of the island of octupole deformation at A=225. (8 refs).

Fraile-Prieto, L M; García-Borge, M J; Fogelberg, B; García-Raffi, L M; Grant, I S; Gulda, K; Hagebø, E; Kurcewicz, W; Løvhøiden, G; Mach, H; Martínez, T; Rubio, B; Taín, J L; Tengblad, O; Thorsteinsen, T F

1999-01-01

152

High-spin states in sup(224,226,228)Th and the systematics of octupole effects in even Th isotopes  

International Nuclear Information System (INIS)

High-spin states in sup(224,226,228)Th were investigated using conversion-electron and ?-ray spectroscopic methods following 226Ra(?,xn) reactions. The Ksup(?)=0+ and 0- rotational bands are observed, which in sup(224,226)Th merge into a single band characteristic for reflection asymmetric shape. The systematics of the level energies and E1 transition rates of 220-230Th are discussed in terms of a stable octupole deformation. (orig.)

153

Deformation and Fracture Properties of Semicrystalline-Glassy Block Copolymers: The Effect of Microdomain Orientation  

Science.gov (United States)

We investigate the influence of polyethylene (PE) cylinder orientation on the deformation and fracture properties of poly(cyclohexylethylene)-poly(ethylene)- poly(cyclohexylethylene) (CEC) triblock copolymers. Large amplitude oscillatory shear was used to macroscopically orient cylindrical PE microdomains in a glassy matrix. The micromechanical deformation behavior was investigated by using so-called fragility test, where thin polymer films are tested in tension using copper grids as a support. We found that deformation and fracture properties of CEC depend significantly on the PE cylinder domain orientation. When PE-cylinders are oriented perpendicular to applied strain, films are brittle and crazes breakdown to form cracks at very low strains. On the contrary, when the PE-cylinders are oriented parallel to strain, stable craze growth is observed and films show ductile behavior. Additionally, CEC films are ductile if the PE cylinder orientation is random with respect to applied strain, as is the case for unoriented spin cast films.

Ruokolainen, Janne; Fredrickson, Glenn H.; Kramer, Edward J.; Magonov, Sergei; Hahn, Steve

2002-03-01

154

Self-similarity properties of nafionized and filtered water and deformed coherent states  

CERN Document Server

By resorting to measurements of physically characterizing observables of water samples perturbed by the presence of Nafion and by iterative filtration processes, we discuss their scale free, self-similar fractal properties. By use of algebraic methods the isomorphism is proved between such self-similarity features and the deformed coherent state formalism.

Capolupo, A; Elia, V; Germano, R; Napoli, E; Niccoli, M; Tedeschi, A; Vitiello, G

2013-01-01

155

Self-Similarity Properties of Nafionized and Filtered Water and Deformed Coherent States  

Science.gov (United States)

By resorting to measurements of physically characterizing observables of water samples perturbed by the presence of Nafion and by iterative filtration processes, we discuss their scale free, self-similar fractal properties. By use of algebraic methods, the isomorphism is proved between such self-similarity features and the deformed coherent state formalism.

Capolupo, A.; Del Giudice, E.; Elia, V.; Germano, R.; Napoli, E.; Niccoli, M.; Tedeschi, A.; Vitiello, G.

2014-11-01

156

Collective properties of deformed atomic clusters described within a projected spherical basis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Several relevant properties of the Na clusters were studied by using a projected spherical single particle states.The proposed model is able to describe in an unified fashion the spherical and deformed clusters. Photoabsorbtion cross section is realistically explained within an RPA approach and a Shiff dipole moment as a transition operator

Raduta, A. A.; Raduta, Al H.; Budaca, R.

2011-01-01

157

Deformation properties of the Barcelona-Catania-Paris (BCP) energy density functional  

International Nuclear Information System (INIS)

We explore the deformation properties of the newly postulated Barcelona-Catania-Paris (BCP) energy density functional (EDF). The results obtained for three isotope chains of Mg, Dy, and Ra are compared to the available experimental data as well as to the results of the Gogny-D1S force. Results for the fission barrier of 240Pu are also discussed

158

PROPERTIES AND NANOSTRUCTURES OF NANO-MATERIALS PROCESSED BY SEVERE PLASTIC DEFORMATION (SPD).  

Energy Technology Data Exchange (ETDEWEB)

Metallic materials usually exhibit higher strength but lower ductility after being plastically deformed by conventional techniques such as rolling, drawing and extrusion. In contrast, nanostructured metals and alloys processed by severe plastic deformation (SPD) have demonstrated both high strength and high ductility. This extraordinary mechanical behavior is attributed to the unique nanostructures generated by SPD processing. The combination of ultrafine grain size and high-density dislocations appears to enable deformation by new mechanisms not active in coarse-grained metals and alloys. These results demonstrate the possibility of tailoring the microstructures of metals and alloys by SPD to obtain superior mechanical properties. Nanostructured metals and alloys processed by SPD techniques have unique nanostructures not observed in nanomaterials synthesized by other techniques such as the consolidation of nanopowders. The SPD-generated nanostructures have many features related to deformation, including high dislocation densities, and high- and low-angle grain boundaries in equilibrium or nonequilibrium states. Future studies are needed to investigate the deformation mechanisms that relate the unique nanostructures with the superior mechanical properties exhibited by SPD-processed metals and alloys.

Zhu, Y. T. (Yuntian Theodore)

2001-01-01

159

Effect of mechanical scheme of deformation on mechanical properties and structure of superplasticity alloys Zn+22%Al and VT9  

International Nuclear Information System (INIS)

The effect of mechanical deformation scheme on mechanical properties and structure of fine-crystalline superplastic materials, is investigated. The effect of deformation mechanical scheme on the flow stress and integral value of optimum deformation rates in the case of superplastic flow of Ln+22% and VT9 alloys, is established. At low and high deformation rates, flow stresses for upsetting and tension are equal. In the range of optimum deformation rates for sagging, flow stresses during tension is somewhat higher than during upsetting. For deformation schemes characterized by the presence of positive hydrostatic pressure (primary effect of compression stresses); in the range of optimum deformation rates, the increase in grain growth of phases in Ln+22% and VT9 alloys is observed as compared with deformation by tension

160

Analysis of plastic properties of titanium alloys under severe deformation conditions in machining  

Directory of Open Access Journals (Sweden)

Full Text Available The present paper presents a method of analysis of titanium alloys plastic properties under severe deformation conditions during milling with registration of the cutting force components Fx, Fy, Fz in real time using a special stand. The obtained constitutive relations in the form the Johnson-Cook law for stresses and dependence for a friction coefficient describing the titanium alloy VT9 plastic properties under simulate operating conditions.

Alexander I. Khaimovich

2014-10-01

 
 
 
 
161

Large-deformation properties of wheat dough in uni- and biaxial extension. Part I. Flour dough  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Rheological and fracture properties of optimally mixed flour doughs from three wheat cultivars which perform differently in cereal products were studied in uniaxial and biaxial extension. Doughs were also tested in small angle sinusoidal oscillation. In accordance with previously published results the linear region was found to be very small. The rheological properties at small deformations hardly depended on the cultivar. A higher water content of the dough resulted in a lower value for the ...

Sliwinski, E. L.; Kolster, P.; Vliet, T.

2004-01-01

162

Application of Severe Plastic Deformation Techniques to Magnesium for Enhanced Hydrogen Sorption Properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we review the latest developments in the use of severe plastic deformation (SPD) techniques for enhancement of hydrogen sorption properties of magnesium and magnesium alloys. Main focus will be on two techniques: Equal Channel Angular Pressing (ECAP) and Cold Rolling (CR). After a brief description of these two techniques we will discuss their effects on the texture and hydrogen sorption properties of magnesium alloys. In particular, the effect of the processing temperature in E...

Daniel Fruchart; Jacques Huot; Nataliya Ye. Skryabina

2012-01-01

163

Fifth-order aberrations in magnetic quadrupole-octupole systems  

International Nuclear Information System (INIS)

Explicit integral expressions are given for the fifth-order geometrical aberration coefficients in rectilinear magnetic quadrupole-octupole systems used for the transport of nonrelativistic charged particle beams. The numerical values of the fifth-order geometrical aberration coefficients for a rare earth cobalt (REC) quadrupole doublet are given as an example. 26 refs., 5 figs., 4 tabs

164

Cryogenically cooled octupole ion trap for spectroscopy of biomolecular ions.  

Science.gov (United States)

We present here the design of a linear octupole ion trap, suitable for collisional cryogenic cooling and spectroscopy of large ions. The performance of this trap has been assessed using ultraviolet (UV) photofragmentation spectroscopy of protonated dipeptides. At the trap temperature of 6.1 K, the vibrational temperature of the ions reaches 9.1 K, although their estimated translational temperature is ~150 K. This observation suggests that, despite the significant translational heating by radio-frequency electrical field, vibrational cooling of heavy ions in the octupole is at least as efficient as in the 22-pole ion traps previously used in our laboratory. In contrast to the 22-pole traps, excellent radial confinement of ions in the octupole makes it convenient for laser spectroscopy and boosts the dissociation yield of the stored ions to 30%. Overlap of the entire ion cloud by the laser beam in the octupole also allows for efficient UV depletion spectroscopy of ion-He clusters. The measured electronic spectra of the dipeptides and the clusters differ drastically, complicating a use of UV tagging spectroscopy for structural determination of large species. PMID:24689562

Boyarkin, Oleg V; Kopysov, Vladimir

2014-03-01

165

Cryogenically cooled octupole ion trap for spectroscopy of biomolecular ions  

Science.gov (United States)

We present here the design of a linear octupole ion trap, suitable for collisional cryogenic cooling and spectroscopy of large ions. The performance of this trap has been assessed using ultraviolet (UV) photofragmentation spectroscopy of protonated dipeptides. At the trap temperature of 6.1 K, the vibrational temperature of the ions reaches 9.1 K, although their estimated translational temperature is ˜150 K. This observation suggests that, despite the significant translational heating by radio-frequency electrical field, vibrational cooling of heavy ions in the octupole is at least as efficient as in the 22-pole ion traps previously used in our laboratory. In contrast to the 22-pole traps, excellent radial confinement of ions in the octupole makes it convenient for laser spectroscopy and boosts the dissociation yield of the stored ions to 30%. Overlap of the entire ion cloud by the laser beam in the octupole also allows for efficient UV depletion spectroscopy of ion-He clusters. The measured electronic spectra of the dipeptides and the clusters differ drastically, complicating a use of UV tagging spectroscopy for structural determination of large species.

Boyarkin, Oleg V.; Kopysov, Vladimir

2014-03-01

166

Effect of deformation and heat treatment on phase transformations and properties of titanium alloys  

International Nuclear Information System (INIS)

Effects of deformation and heat treatment on phase transformations in VT22 and VT22M alloys were studied to reveal the structural factors controlling high strength of titanium alloys and to determine deformation and heat treatment conditions providing satisfactory plastic properties. It is recommended to work the materials in (?+?) phase field at 860 deg C before hardening heat treatment to prevent loss of ductility. It is found that the strength of both alloys is connected with a quantity ratio of ?- and ?-phases and is determined by their structure state

167

Mechanical properties and microstructure of resistance spot welded severely deformed low carbon steel  

International Nuclear Information System (INIS)

Highlights: ? Resistance spot welding is successfully used for severely deformed steel sheet. ? Microstructures of FZ and HAZ are refined to lower sizes at higher pass number. ? Mechanical properties in FZ and HAZ are increased with increasing the pass number. ? Electrode dip and nugget diameter are increased with increasing the pass number. - Abstract: The welding of nanostructured low carbon steel sheets produced by severe plastic deformation (SPD) has been considered in the present paper. Constrained groove pressing (CGP) method is used for imposing the severe plastic deformation to the steel sheets as a large pre-strain. The SPDed sheets are joined using resistance spot welding (RSW) process. The results show that severe plastic deformation can effectively increase the electrical resistivity of steel sheets; therefore it can affect the microstructure and mechanical properties of spot welds. Microstructure and mechanical properties of fusion zone, heat affected zone (HAZ), recrystallized zone and base metal of SPDed sheets are investigated and the results are compared with those of as-received specimens. The results show that with increasing the large pre-strain in sheets, at constant welding parameters (welding current and time), the fusion zone size, electrode indentation and nugget diameter are increased. Thus, peak load and hardness in fusion zone and HAZ are increased with increasing the CGP pass number. Also, the microstructures of fusion zone and HAZ are refined to lower sizes for larger pre-strained specimens.

168

Mechanical properties of mammalian cells in suspension measured by electro-deformation  

Science.gov (United States)

We describe a planar, micro-fabricated device for generating fringing non-uniform electric fields. We used it to measure the mechanical properties of individual mammalian cells in suspension by deforming them in time-varying, non-uniform electric fields. Electrical stresses generated by the planar microelectrodes were used to trap and stretch cells, while cell deformation was observed using optical microscopy. Two distinct cell types were compared after fitting strain data with a three-parameter 'standard linear solid' model of visco-elasticity, and with a two-parameter power-law method. Chinese hamster ovary (CHO) cells were approximately twice as stiff as U937 human promonocytes, and CHO cells displayed an elastic behaviour with recovery of initial shape, while U937 strain data bore witness to plastic deformation. Our results demonstrate that electrical stresses generated by micro-fabricated electrodes permit mechanical characterization of distinct mammalian cell types.

MacQueen, Luke A.; Buschmann, Michael D.; Wertheimer, Michael R.

2010-06-01

169

The effect of ultrasonics on the strength properties of carbon steel processed by cold plastic deformation  

Science.gov (United States)

A study was made of the influence of ultrasounds on the mechanical properties of OLT 35 carbon steel tubes cold-drawn on a plug ultrasonically activated by longitudinal waves. Experimental results indicate that: 1. The reduction in the values of the flow limit and tensile strength is proportional to the increase in acoustic energy introduced into the material subjected to deformation. 2. The diminution in influence of ultrasounds on tensile strength and flow rate that is due to an increased degree of deformation is explained by a reduction in specific density of the acoustic energy at the focus of deformation. 3. The relations calculated on the basis of the variation in the flow limit and tensile strength as a function of acoustic energy intensity was verified experimentally.

Atanasiu, N.; Dragan, O.; Atanasiu, Z.

1974-01-01

170

Effect of viscosity of petroleum products on deformation properties of concrete  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the results of studies of the effect of petroleum products, impregnating in concrete, on its deformation properties. Petroleum products, impregnating in concrete and reinforced concrete structures, have a negative impact on their strength and deformation characteristics. The negative impact of petroleum products on concrete and reinforced concrete is associated with changes in the hydration process of cement, as well as changes in the structure of the concrete. Strength and deformation characteristics of concrete change due to hydraulic pressure of petroleum products in the pores exerted on the skeleton of cement stone. In this aspect, the crucial point is the porosity of concrete as a permeability factor for petroleum products. One of the most important factors affecting the physical and mechanical characteristics of oil-impregnated concrete is their viscosity. In this paper, the mathematical description of the change of deformation depending on the relative viscosity of impregnating of petroleum products, the value of the axial load and the concrete class was proposed. The obtained results allow assessing changes in deformation characteristics of load-bearing concrete and reinforced concrete of industrial buildings, where petroleum products are used in the technological processes.

A.P. Svintsov

2014-11-01

171

Deformation Properties of Forest Soils in Karelia Affected by "Freeze-Defrost" Cycles  

Directory of Open Access Journals (Sweden)

Full Text Available The impact of “freeze-defrost” cycles on the deformation properties of forest soils has been little studied. The layout of technological schemes of harvesting sites development in off-season periods (spring, fall depends a lot on the formation of ruts when wood harvesting machinery passes. The study of processes occurring in forest soils affected by “freeze-defrost” cycles enables to justify the method of calculating rut depth depending on the number of machinery passes. The compression modulus of deformation, compressibility coefficient and relative compressibility coefficient of clay loam which was collected in the forest of the Republic of Karelia were determined in laboratory conditions. Forest soil samples underwent three “freeze-defrost” cycles. It has been determined clay loam deformation modulus after the first cycle reduces by 16% and after the second and third cycles it reduces by 18% and 25% respectively in relation to the value of deformation modulus before freezing. Compressibility coefficient increases by 18% after the first cycle, it increases by 22% after the second cycle and by 33% after the third one. The decrease of deformation modulus and the increase of clay loam compressibility coefficient are due to changes in the structure of forest soils under the influence of “freeze-defrost” cycles.

Ratjkova E. I.

2013-07-01

172

Microstructure and properties on nano-metals obtained by severe plastic deformation  

International Nuclear Information System (INIS)

The present study provides the review of the structures and properties of nano-metals obtained by service plastic deformation (SPD). The authors also analyze the methods of examining the microstructure and properties of nano-crystalline materials. The size and shape of the grains and the degree of the microstructure homogeneity of the nano-metals produced by SPD were analysed quantitatively. The strength properties were examined by measuring the microhardness and the tensile tests. The temperature stability of the microstructure was determined by examining the recovery and recrystallization kinetics. (author)

173

Effects of plastic deformations on microstructure and mechanical properties of ODS-310 austenitic steel  

International Nuclear Information System (INIS)

Highlights: ? We fabricated a 310 type ODS austenitic steel by the process of MA and HIP. ? Plastic deformations, including forging and hot rolling, were applied to samples. ? Fine Y-Ti-O particles dispersed in a relatively uniform way after forging. ? Ductility increased greatly after deformations, while strength decreased slightly. - Abstract: ODS-310 austenitic steel (Fe–25Cr–20Ni–0.35Y2O3–0.5Ti) was fabricated by the process of mechanical alloying and hot isostatic pressing. Plastic deformations, including forging and hot rolling, were applied to the as-hipped samples to improve the ductility. Microstructural evolutions in samples under different fabrication conditions were characterized by TEM. Tensile properties were tested at 23 °C and 700 °C. Dispersed oxide particles with sizes between 10 nm and 50 nm were characterized to be rich in Y–Ti–O. UTS and elongation of the as-hipped sample were 904 MPa and 11% respectively at 23 °C. Elongation increased two times after plastic deformations while there was only slight decrease in strength properties.

174

Optical and electrical properties of dislocations in plastically deformed GaN  

Science.gov (United States)

Optical and electrical properties of fresh dislocations in GaN bulk crystals deformed plastically at elevated temperatures were reviewed. A dislocation band model was proposed. The fresh dislocations of (a/3) [12bar10]-type edge dislocations on the (101bar0) prismatic plane induced several photoluminescence peaks at around 1.8, 1.9 and 2.4 eV, which implies the formation of radiative recombination centers of the dislocations. Simultaneously, near-band-edge (3.48 eV) photoluminescence intensity decreased remarkably for a high-density of non-radiative recombination centers originating in deformation-induced abundant Ga-vacancy related clusters. The intensity variation of yellow luminescence with plastic deformation and subsequent annealing did not relate to the native property of dislocations. Variation of optical absorption dependent on the strain in plastically deformed GaN was understood in a model of the Franz-Keldysh effect by the electric fields associated with charged dislocations (~5.8 e/nm). Scanning spreading resistance microscopic images showed many spots with high conductivity around the induced dislocations, showing electrical conduction along dislocations according to the Frenkel-Poole mechanism.

Yonenaga, I.; Ohno, Y.; Yao, T.; Edagawa, K.

2014-10-01

175

Effect of Nb content on deformation behavior and shape memory properties of Ti–Nb alloys  

International Nuclear Information System (INIS)

Highlights: ? Reorientation of martensite variants occurred by the deformation of the {1 1 1} type I and ?2 1 1? type II twins. ? Magnitude of twinning shear in Ti–20Nb is larger than that in Ti–23Nb. ? Ti–20Nb exhibited a higher stress for the reorientation of martensite variants when compared with Ti–23Nb. -- Abstract: Deformation behavior and shape memory properties of Ti–(20, 23) at.% Nb alloys in a single ?? martensite state were investigated. The Ti–20Nb alloy exhibited a higher stress for the reorientation of martensite variants when compared with the Ti–23Nb alloy. The recovery strain due to the shape memory effect in the Ti–20Nb alloy was smaller than that in the Ti–23Nb alloy. Transmission electron microscope (TEM) observation revealed that the reorientation of martensite variants occurred by the deformation of {1 1 1} type I and ?2 1 1? type II twins. The Nb content dependence of the deformation behavior and shape memory properties was discussed considering the magnitude of twinning shear of the twins

176

Effect of Nb content on deformation behavior and shape memory properties of Ti–Nb alloys  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? Reorientation of martensite variants occurred by the deformation of the {1 1 1} type I and ?2 1 1? type II twins. ? Magnitude of twinning shear in Ti–20Nb is larger than that in Ti–23Nb. ? Ti–20Nb exhibited a higher stress for the reorientation of martensite variants when compared with Ti–23Nb. -- Abstract: Deformation behavior and shape memory properties of Ti–(20, 23) at.% Nb alloys in a single ?? martensite state were investigated. The Ti–20Nb alloy exhibited a higher stress for the reorientation of martensite variants when compared with the Ti–23Nb alloy. The recovery strain due to the shape memory effect in the Ti–20Nb alloy was smaller than that in the Ti–23Nb alloy. Transmission electron microscope (TEM) observation revealed that the reorientation of martensite variants occurred by the deformation of {1 1 1} type I and ?2 1 1? type II twins. The Nb content dependence of the deformation behavior and shape memory properties was discussed considering the magnitude of twinning shear of the twins.

Tobe, H. [Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Kim, H.Y., E-mail: heeykim@ims.tsukuba.ac.jp [Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Inamura, T.; Hosoda, H. [Precision and Intelligence Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Nam, T.H. [School of Materials Science and Engineering and ERI, Gyeongsang National University, 900 Gazwadong, Jinju, Gyeongnam 660-701 (Korea, Republic of); Miyazaki, S., E-mail: miyazaki@ims.tsukuba.ac.jp [Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); School of Materials Science and Engineering and ERI, Gyeongsang National University, 900 Gazwadong, Jinju, Gyeongnam 660-701 (Korea, Republic of); Center of Excellence for Advanced Materials Research, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia)

2013-11-15

177

Semiclassical analysis of the lowest-order multipole deformations of simple metal clusters  

CERN Document Server

We use a perturbative semiclassical trace formula to calculate the three lowest-order multipole (quadrupole $\\eps_2$, octupole $\\eps_3$, and hexadecapole $\\eps_4$) deformations of simple metal clusters with $90 \\le N \\le 550$ atoms in their ground states. The self-consistent mean field of the valence electrons is modeled by an axially deformed cavity and the oscillating part of the total energy is calculated semiclassically using the shortest periodic orbits. The average energy is obtained from a liquid-drop model adjusted to the empirical bulk and surface properties of the sodium metal. We obtain good qualitative agreement with the results of quantum-mechanical calculations using Strutinsky's shell-correction method.

Pashkevich, V V; Brack, M; Unzhakova, A V

2002-01-01

178

Simultaneous estimation of material properties and pose for deformable objects from depth and color images  

DEFF Research Database (Denmark)

In this paper we consider the problem of estimating 6D pose, material properties and deformation of an object grasped by a robot gripper. To estimate the parameters we minimize an error function incorporating visual and physical correctness. Through simulated and real-world experiments we demonstrate that we are able to find realistic 6D poses and elasticity parameters like Young's modulus. This makes it possible to perform subsequent manipulation tasks, where accurate modelling of the elastic behaviour is important.

Fugl, Andreas Rune; Jordt, Andreas

2012-01-01

179

The effect of aluminum alloying on strength properties and deformation mechanisms of the Hadfield steel single crystals  

Science.gov (United States)

The role of aluminum alloying on strength properties and deformation mechanisms (slip, twinning) of single crystals of Hadfield steel under tensile loading at T = 300 K is demonstrated. It is found out that aluminum alloying suppresses twinning deformation in the single crystals and, during slip, results in a dislocation structure change from a uniform dislocation distribution to a planar dislocation structure.

Astafurova, E. G.; Tukeev, M. S.; Chumlyakov, Yu. I.

2007-10-01

180

Strength and high fatigue properties of ultrafine-grained titanium rods produced by severe plastic deformation  

Science.gov (United States)

The formation of an ultrafine-grained structure (UFGS) in titanium by severe plastic deformation significantly increases its mechanical properties, among them fatigue strength. In this work, high mechanical properties of titanium long rods are achieved using a combination of equal-channel angular pressing and subsequent thermal and thermomechanical treatment. The formation of a homogeneous UFGS in a rod of commercial titanium is found to increase the fatigue limit by a factor of about 1.5. Moreover, the fatigue strength of UFGS titanium estimated on notched specimens is higher than that of coarse-grained titanium, which is important for its structural application in medicine.

Semenova, I. P.

2010-09-01

 
 
 
 
181

The effect of carbon concentration and plastic deformation on ultrasonic higher order elastic properties of steel  

Science.gov (United States)

The behavior of higher order elastic properties, which are much more sensitive to material state than are second order properties, has been studied for steel alloys AISI 1016, 1045, 1095, and 8620 by measuring the stress derivative of the acoustic natural velocity to determine the stress acoustic constants (SAC's). Results of these tests show a 20 percent linear variation of SAC's with carbon content as well as even larger variations with prestrain (plastic deformation). The use of higher order elastic characterization permits quantitative evaluation of solids and may prove useful in studies of fatigue and fracture.

Heyman, J. S.; Allison, S. G.; Salama, K.

1985-01-01

182

Experiment and analysis on elastic deformation properties of graphite and carbon materials for HTTR core components  

International Nuclear Information System (INIS)

Fine-grained isotropic graphite grade IG-110, medium-grained near-isotropic graphite grade PGX and coarse-grained baked carbon grade ASR-ORB are employed as structural materials for the High Temperature Engineering Test Reactor (HTTR). The material properties for design are specified in Structural Design Code for Graphite Components of HTTR. This report describes in detail the experiment on deformation behavior including stress-strain relationship, elastic modulas and Poisson's ratio of each grade. An analytical method for linear elastic approximation leads to the property values contained in the Code. (author)

183

Examination of different strengths of octupole correlations in neutron-rich Pr and Pm isotopes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Recent prompt ?-ray spectroscopy studies of 149,151Pr have revealed weak octupole correlations. These are manifested by the absence of strong intraband E1 transitions between bands of opposite parities. On the other hand, in their isotones 151,153Pm, which have only two additional protons, the E1 transition rates are several orders of magnitude stronger, indicating enhanced octupole correlations. The quasiparticle phonon model combined with the particle-rotor model, which allows octupole cor...

Thiamova?, Gabriela; Alexa, Petr; Hons, Zdene?k; Simpson, G. S.

2012-01-01

184

Conflicting results for the deformation properties of forsterite, Mg2SiO4  

International Nuclear Information System (INIS)

Deformation properties of forsterite have been deduced simultaneously from X-ray diffraction data affected by extinction in Bonn-Pittsburgh (B), and in Groningen (G). For the G crystals, GI and GII, extinction is anisotropic and considerably larger than for crystal B. Measurements were made with Mo radiation for B, and with Mo and Ag radiation for GI and GII. As the Becker and Coppens extinction model is not exact, the deformation properties had to be filtered from the data with refinement models. The flexible B model [?'s and populations for single exponential functions (SEF's) refined for l=0-4] and the more rigid G model (SEF's populations refined for l=0-3 and ? for l=0; further ?'s and n's fixed at standard values) yield different results. Refinement of ? makes the majority of the SEF's notably diffuse, presumably due to correlation with incorrect extinction corrections. The order of the deformation potentials at the Mg(1) and Mg(2) sites is reversed for B and G. Maxima on the Si-O bonds, which are polarized towards O, are smaller for G (0.20-0.25 e A-3) than for B (0.25-0.45 e A-3). Although each of the two sets of deformation properties looks acceptable by itself, the present comparison shows that neither of them may be sufficiently close to the truth. The diffraction data are available on request from the Electron Density Data Bank (Professor H. Burzlaff, Institut fuer Angewandte Physik, Bismarckstrasse 10, D-8520 Erlangen, Federal Republic of Germany). Details of the measurements are described in the paper. (orig.)

185

Octupole excitations at high spins in A ˜ 160 nuclei  

Science.gov (United States)

The yrast and yrare states of 162Yb are studied within the cranked Nilsson model and random phase approximation. Special attention is paid to the analysis of experimental crossing points between different bands that form the yrast band. We found that, at the rotational frequency ?? > 0.3 MeV, there is onset of strong octupole correlations. The results of calculations demonstrate good agreement with available experimental data.

Kvasil, J.; Nazmitdinov, R. G.; Sitdikov, A. S.; Veselý, P.

2007-08-01

186

Octupole vibration in the superdeformed 196Pb nucleus  

International Nuclear Information System (INIS)

The study of the superdeformed (SD) 196Pb nucleus has been revisited using the EUROGAM phase 2 spectrometer. All the three observed excited SD bands were found to decay to the Yrast SD band through, presumably, E1 transitions, allowing relative spin and excited energy assignments. Comparisons with calculation using the random phase approximation suggests that all three excited bands can be interpreted as octupole vibrational structures. (authors)

187

Tests of octupole band structures using proton scattering and gamma-ray spectroscopy  

International Nuclear Information System (INIS)

In many even-even nuclei, bands of negative parity states have been interpreted as open-quotes octupole bandsclose quotes, which are sequences of vibrational or rotational excitations coupled to a low energy octupole phonon. Careful experimental examination of these structures is of interest because octupole phonons are generally considered to be unstable at high angular momentum. Results from experimental studies of octupole band structures in three nuclei are presented. Two of these nuclei, 144,146Nd, have been studied via inelastic scattering of 35 MeV protons. The third nucleus, 74Se, has been examined using the techniques of high spin gamma-ray spectroscopy

188

Mechanical properties and deformation behavior of Al/Al7075, two-phase material  

Energy Technology Data Exchange (ETDEWEB)

In the present study, mechanical properties and deformation behavior of Al/Al7075, two-phase material were investigated. The two-phase materials were fabricated by mixing commercially pure Al powder with Al7075 chips and consolidating the mixture through hot extrusion process at 500 {sup o}C. Mechanical properties and deformation behavior of the fabricated samples were evaluated using tensile and compression tests. A scanning electron microscope was used to study the fracture surface of the samples including different amount of Al powder, after they were fractured in tensile test. The results of the tensile and compression tests showed that with decreasing the amount of Al powder, the strength increases and ductility decreases. Calculation of work hardening exponent (n) indicated that deformation behavior does not follow a regular trend. In a way that the n value was approved to be variable and a strong function of strain and Al powder wt% of the sample. The results of the fractography studies indicate that the type of fracture happened changes from completely ductile to nearly brittle by decreasing the wt% of Al powder from 90% to 40%.

Sherafat, Z. [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Paydar, M.H., E-mail: paaydar@shirazu.ac.i [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Ebrahimi, R.; Sohrabi, S. [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of)

2010-07-16

189

Mechanical properties and deformation behavior of Al/Al7075, two-phase material  

International Nuclear Information System (INIS)

In the present study, mechanical properties and deformation behavior of Al/Al7075, two-phase material were investigated. The two-phase materials were fabricated by mixing commercially pure Al powder with Al7075 chips and consolidating the mixture through hot extrusion process at 500 oC. Mechanical properties and deformation behavior of the fabricated samples were evaluated using tensile and compression tests. A scanning electron microscope was used to study the fracture surface of the samples including different amount of Al powder, after they were fractured in tensile test. The results of the tensile and compression tests showed that with decreasing the amount of Al powder, the strength increases and ductility decreases. Calculation of work hardening exponent (n) indicated that deformation behavior does not follow a regular trend. In a way that the n value was approved to be variable and a strong function of strain and Al powder wt% of the sample. The results of the fractography studies indicate that the type of fracture happened changes from completely ductile to nearly brittle by decreasing the wt% of Al powder from 90% to 40%.

190

Influences of surface effects and large deformation on the resonant properties of ultrathin silicon nanocantilevers  

International Nuclear Information System (INIS)

The purpose of the present work is to quantify the influences of the discrete nature, the surface effects, and the large deformation on the bending resonant properties of long and ultrathin silicon nanocantilevers. We accomplish this by using an analytical semi-continuum Keating model within the framework of nonlinear, finite deformation kinematics. The semi-continuum model shows that the elastic behaviors of the silicon nanocantilevers are size-dependent and surface-dependent, which agrees well with the molecular dynamics results. It also indicates that the dominant effect on the fundamental resonant frequency shift of the silicon nanocantilever is adsorption-induced surface stress, followed by the discrete nature and surface reconstruction, whereas surface relaxation has the least effect. In particular, it is found that a large deformation tends to increase the nonlinear fundamental frequency of the silicon nanocantilever, depending not only on its size but also on the surface effects. Finally, the resonant frequency shifts due to the adsorption-induced surface stress predicted by the current model are quantitatively compared with those obtained from the experimental measurement and the other existing approach. It is noticed that the length-to-thickness ratio is the key parameter that correlates the deviations in the resonant frequencies predicted from the current model and the empirical formula. (condensed matter: structural, mechanical, and thermal properties)

191

Quantification of local matrix deformations and mechanical properties during capillary morphogenesis in 3D.  

Science.gov (United States)

Reciprocal mechanical interactions between cells and the extracellular matrix (ECM) are thought to play important instructive roles in branching morphogenesis. However, most studies to date have failed to characterize these interactions on a length scale relevant to cells, especially in three-dimensional (3D) matrices. Here we utilized two complementary methods, spatio-temporal image correlation spectroscopy (STICS) and laser optical tweezers-based active microrheology (AMR), to quantify endothelial cell (EC)-mediated deformations of individual ECM elements and the local ECM mechanical properties, respectively, during the process of capillary morphogenesis in a 3D cell culture model. In experiments in which the ECM density was systematically varied, STICS revealed that the rate at which ECs deformed individual ECM fibers on the microscale positively correlated with capillary sprouting on the macroscale. ECs expressing constitutively active V14-RhoA displaced individual matrix fibers at significantly faster rates and displayed enhanced capillary sprouting relative to wild-type cells, while those expressing dominant-negative N19-RhoA behaved in an opposite fashion. In parallel, AMR revealed a local stiffening of the ECM proximal to the tips of sprouting ECs. By quantifying the dynamic physical properties of the cell-ECM interface in both space and time, we identified a correlation linking ECM deformation rates and local ECM stiffening at the microscale with capillary morphogenesis at the macroscale. PMID:22281872

Kniazeva, Ekaterina; Weidling, John W; Singh, Rahul; Botvinick, Elliot L; Digman, Michelle A; Gratton, Enrico; Putnam, Andrew J

2012-04-01

192

Influence of materials properties on stress and deformation states of a prestressed concrete vessel  

International Nuclear Information System (INIS)

The influence of changes in some material parameters on relevant operational states is studied for a vessel with a concrete liner temperature of 700C. The results are given for the following material properties: thermal conductivity, thermal expansion coefficient, young's modulus, temperature dependency of the creep, steel tendon relaxation. The influence of changes in the initial strain due to deformation of the vessel also gets a mention. As the behaviour at 700C does not deviate significantly from the behaviour described in the extensive studies on a vessel of 500C, the calculations in this paper are essentially confined to two final operational states which illustrate the influence of the material parameters on the strains and deformations which are of interest for the layout of the vessel. (orig./AK)

193

Effect of large plastic deformation on microstructure and mechanical properties of a TWIP steel  

Science.gov (United States)

The effect of cold rolling on the microstructure evolution and mechanical properties of a cold rolled Fe-0.3C-17Mn-1.5AI TWIP steel was studied. The plate samples were cold rolled with reductions of 20, 40, 60 and 80%. The structural changes were associated with the development of deformation twinning and shear bands. The average spacing between twin boundaries in the transverse section of the rolled plates decreased from ~190 to 36 nm with an increase in the rolling reduction from 20 to 40%. Upon further rolling to 80% reduction the twin spacing remained at about 30 nm. The cold rolling resulted in significant increase in strength as revealed by tensile tests at an ambient temperature. The offset yield stress approached 1440 MPa, and the ultimate tensile strength increased to 1630 MPa after rolling reduction of 80%. Such significant strengthening was attributed to the development of specific structure consisting of deformation nanotwins with high dislocation density.

Yanushkevich, Z.; Belyakov, A.; Kaibyshev, R.; Molodov, D.

2014-08-01

194

Optimisation by plastic deformation of structural and mechanical uranium alloys properties  

International Nuclear Information System (INIS)

Structural and mechanical properties evolution of rich and poor uranium alloys are investigated. Good usual properties are obtained with few metallic additions with a limited effect giving a fine and isotrope grain structure. Amelioration is observed with heat treatment from ? and ? phases high temperature range. However, dynamic recrystallisation, related to hot working, is the better phenomena to maximize the usual mechanical and structural properties. So high temperature behaviour of rich and poor uranium alloys in ?, ? and ? crystalline structure is studied: - dynamic recrystallisation phenomena begins only in ?, and ? phases high temperature range; - high strength and brittle ? phase shows a very large ductility above 700 deg C. Recrystallisation is a thermal actived phenomena localised at grain boundary, dependant with alloys concentration and crystalline structure. ? phase activation energy and deformation rate for dynamic recrystallisation beginning are most important, than ? and ? phases in relation with quadratic structure complexity. Both temperature and deformation rate are the main dynamic recrystallisation factors. Optimal usual mechanical and structural properties obtained by hot working (forging, milling) are sensible to hydrogen embrittlement

195

Designing electronic properties of two-dimensional crystals through optimization of deformations  

Science.gov (United States)

One of the enticing features common to most of the two-dimensional (2D) electronic systems that, in the wake of (and in parallel with) graphene, are currently at the forefront of materials science research is the ability to easily introduce a combination of planar deformations and bending in the system. Since the electronic properties are ultimately determined by the details of atomic orbital overlap, such mechanical manipulations translate into modified (or, at least, perturbed) electronic properties. Here, we present a general-purpose optimization framework for tailoring physical properties of 2D electronic systems by manipulating the state of local strain, allowing a one-step route from their design to experimental implementation. A definite example, chosen for its relevance in light of current experiments in graphene nanostructures, is the optimization of the experimental parameters that generate a prescribed spatial profile of pseudomagnetic fields (PMFs) in graphene. But the method is general enough to accommodate a multitude of possible experimental parameters and conditions whereby deformations can be imparted to the graphene lattice, and complies, by design, with graphene's elastic equilibrium and elastic compatibility constraints. As a result, it efficiently answers the inverse problem of determining the optimal values of a set of external or control parameters (such as substrate topography, sample shape, load distribution, etc) that result in a graphene deformation whose associated PMF profile best matches a prescribed target. The ability to address this inverse problem in an expedited way is one key step for practical implementations of the concept of 2D systems with electronic properties strain-engineered to order. The general-purpose nature of this calculation strategy means that it can be easily applied to the optimization of other relevant physical quantities which directly depend on the local strain field, not just in graphene but in other 2D electronic membranes.

Jones, Gareth W.; Pereira, Vitor M.

2014-09-01

196

Application of Severe Plastic Deformation Techniques to Magnesium for Enhanced Hydrogen Sorption Properties  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper we review the latest developments in the use of severe plastic deformation (SPD techniques for enhancement of hydrogen sorption properties of magnesium and magnesium alloys. Main focus will be on two techniques: Equal Channel Angular Pressing (ECAP and Cold Rolling (CR. After a brief description of these two techniques we will discuss their effects on the texture and hydrogen sorption properties of magnesium alloys. In particular, the effect of the processing temperature in ECAP on texture will be demonstrated. We also show that ECAP and CR have produced different textures. Despite the scarcity of experimental results, the investigations up to now indicate that SPD techniques produce metal hydrides with enhanced hydrogen storage properties.

Daniel Fruchart

2012-08-01

197

Ambipolar electric fields and turbulence studies in the Wisconsin levitated toroidal octupole  

Energy Technology Data Exchange (ETDEWEB)

Detailed studies of hot ion plasmas (T/sub i/ > T/sub e/) in the poloidal field octupole show that the ambipolar electric field which is perpendicular to the flux surfaces is well explained by the observed properties of the microturbulence structures in the plasma. The turbulence structure has been measured by correlation techniques which are carefully described. In these experiments, signals were studied which are aperiodic in time and space, short lived compared to the decay times of the bulk plasma parameters, short ranged compared to the machine size, and are therefore classified as microturbulence structures. The resulting spatial and temporal correlation functions (CFs) are well fitted to a Gaussian function and the associated correlation lengths or times are the half width at half maximum of the CFs. The correlation length is measured to be the ion gyro radius for the hot hydrogen plasma and somewhat less for the helium plasma.

Armentrout, C.J.

1977-01-01

198

Deformation properties of highly plastic fissured Palaeogene clay - Lack of stress memory?  

DEFF Research Database (Denmark)

The geological preconsolidation of the Palaeogene clays in Denmark is estimated to 5-8 MPa or more, whereas laboratory and field experiences indicate values between 100 and 3000 kPa. Presumably, the high plasticity clay loses its memory of earlier preloads due to swelling, or as an effect of fissuring or debonding. Based on a large amount of high quality tests on Palaeogene clay partly encountered at Fehmarn Belt the typical deformational behaviour during unloading and swelling is discussed and evaluated with focus on stress states. K0-OCR relations are established and the relations are evaluated based on the degree of debonding caused by natural processes insitu as compared to processes induced during severe loading and unloading in laboratory. A long term oedometer test on Lillebælt Clay with a series of loading and unloading cycles was carried out. The test results are used to evaluate deformation properties, and to help explain the large primary and secondary swelling indices measured in Palaeogene claysand how they are related to preconsolidation stress. It is proven that the Palaeogene clay tends to “forget” the preconsolidation stress and the consequence is that OCR is not always a suitable parameter to estimate deformation and strength parameters from, unless additional information on structure of the clay is included. This is not solved yet.

KrogsbØll, Anette; Hededal, Ole

2012-01-01

199

Effect of deformation rate on characteristics of mechanical properties of heat treated titanium alloys  

International Nuclear Information System (INIS)

Effect of the deformation rate on strength and plasticity of industrial VT3-1 and VT23 alloys after hardening heat treatment has been investigated. Change in the deformation rate in mechanical tests from the minimum (3.3x10-1 s-1) to the maximum (1.67x10-4 s-1) admissible by the All-Union State Standard is shown to cause the increase of timing resistance of VT3-1 and VT23 alloys by 40...50 MPa, and relative elongation of the VT3-1 alloy decreases by 3%, VT23 alloy does not change practicallyy, relative contraction increases by 8% (VT3-1) and 15% (VT23). The VT23 alloy by virtue of composition and structure peculiarities with strength being practically equal to the VT3-1 alloy has higher values of ductile characteristics. Increase of the deformation rate of the VT3 alloy leads to substantial localization of plastic flow in the sample neck with conservation of high relative elongation. Increase of the strain rate in the range of 3.3x10-5...3.3x10-1 s-1 leads to increase in dipression of mechanical properties of VT3-1 and VT23 alloys in the heat treated state

200

Determination of the B(E3, 0+ ? 3-) strength in the strongly octupole correlated nucleus 224Ra using Coulomb excitation at REX-ISOLDE  

International Nuclear Information System (INIS)

Exploiting the unique capabilities of REX-ISOLDE to provide intense post-accelerated 224Ra radioactive ion beams we were able to Coulomb excite low-lying, low-spin levels of 224Ra. The previously accessible observables, such as the excitation energies of negative parity levels, and theoretical calculations using various models locate this nucleus to be situated in a mass-region with enhanced octupole correlations. Our collaboration was for the first time capable to Coulomb excite opposite parity levels in a post-accelerated radioactive nucleus. Indeed, apart from quasi-stable Uranium isotopes, 224Ra is the so far heaviest post-accelerated nucleus ever. A first, preliminary, B(E3, 0+ ? 3-) value provides quantitative information about the octupole correlations in this nucleus. The results will be discussed within the context of a possible stable octupole deformation in the ground state of this nucleus. An observation, that is implicating a CP-violating nuclear Schiff moment. The latter has a strong impact on the search for CP-violating physics in the atomic system of the neighbouring odd-mass Ra-isotopes. Financial support by the BMBF under grant 06DA9036I, HIC for FAIR and the ENSAR programme is gratefully acknowledged.

 
 
 
 
201

Processing of metals by severe plastic deformation (SPD – structure and mechanical properties respond  

Directory of Open Access Journals (Sweden)

Full Text Available SPD methods are used to convert coarse grain metals and alloys into ultrafine grained (UFG materials. Obtained UFG materials then possess improved mechanical and physical properties which destine them for a wide commercial use. This paper, in one direction, looks into historical development of SPD processes and their effect at obtaining fine crystalline structure, and on the other side also partially focuses on development of UFG structure and its stability in commercial pure aluminium as a function of strain and post-deformation annealing applied.

J. Zrnik

2008-07-01

202

Effect of cryogenic deformation on the structure and properties of chromium-nickel steels  

Science.gov (United States)

The effect of rolling at a temperature of 77 K and subsequent tempering on the structure and properties of chromium-nickel 05Kh14N14T2 and 15Kh14N14Yu1 steels is investigated. The formation of a nanocrystalline martensite phase in an austenitic matrix has been established. It is shown that additional hardening of the metal occurs due to the precipitation of intermetallic phases during heat treatment. The steels under study are high-strength and hard-magnetic after cryogenic deformation and heat treatment.

Glezer, A. M.; Rusanenko, V. V.; Zhukov, O. P.; Libman, M. A.; Klippenshtein, A. D.

2012-10-01

203

Change of mechanical properties of 1201 welding alloy under deformation and gamma-irradiation action  

International Nuclear Information System (INIS)

The effect of #betta#-irradiation and strain on mechanical properties of the aged 1201 alloy has been studied. It has been shown that the 1201 aluminium alloy straining by a single-axis stretching with the deformation degree of epsilon=3-5% after quenching before artificial ageing leads to the 20-30% strength growth and to 1.5-2 times ductility growth. The process of #betta#-irradiation between strain and artificial ageing increases the alloy strength up to epsilon=9% within the high ductility. The above regularities are also true for welded joint metal

204

Structural Properties and Deformation Patterns of Evolving Strike-slip Faults: Numerical Simulations Incorporating Damage Rheology  

Science.gov (United States)

We present results on evolving geometrical and material properties of large strike-slip fault zones and associated deformation fields, using 3-D numerical simulations in a rheologically-layered model with a seismogenic upper crust governed by a continuum brittle damage framework over a viscoelastic substrate. The damage healing parameters we employ are constrained using results of test models and geophysical observations of healing along active faults. The model simulations exhibit several results that are likely to have general applicability. The fault zones form initially as complex segmented structures and evolve overall with continuing deformation toward contiguous, simpler structures. Along relatively-straight mature segments, the models produce flower structures with depth consisting of a broad damage zone in the top few kilometers of the crust and highly localized damage at depth. The flower structures form during an early evolutionary stage of the fault system (before a total offset of about 0.05 to 0.1 km has accumulated), and persist as continued deformation localizes further along narrow slip zones. The tectonic strain at seismogenic depths is concentrated along the highly damaged cores of the main fault zones, although at shallow depths a small portion of the strain is accommodated over a broader region. This broader domain corresponds to shallow damage (or compliant) zones which have been identified in several seismic and geodetic studies of active faults. The models produce releasing stepovers between fault zone segments that are locations of ongoing interseismic deformation. Material within the fault stepovers remains damaged during the entire earthquake cycle (with significantly reduced rigidity and shear-wave velocity) to depths of 10 to 15 km. These persistent damage zones should be detectable by geophysical imaging studies and could have important implications for earthquake dynamics and seismic hazard.

Finzi, Yaron; Hearn, Elizabeth H.; Ben-Zion, Yehuda; Lyakhovsky, Vladimir

2009-10-01

205

Effect of simultaneous deformation and artificial ageing on the mechanical properties of an Al-Mg-Si alloy  

Energy Technology Data Exchange (ETDEWEB)

Tensile tests have been carried out on a commercial Al-Mg-Si-alloy after simultaneous deformation and artificial ageing. Extruded and solution heat treated specimens were deformed 2 %, 5 % and 10 % (engineering strain) and simultaneously artificially aged at two different temperatures (175 and 190 C) for various times (depending on the strain rates used for pre-deformation) before tensile testing. A comparison with previously obtained tensile properties following sequential pre-deformation and artificial ageing shows that the simultaneous mode generally displays better mechanical strength and after shorter ageing times. The best performing alloy has been obtained by using a split artificial ageing procedure for 10 % deformed sample simultaneously aged for 40 min at 175 C followed by additional ageing for 60 min at the same temperature. (orig.)

Kolar, Michal; Marthinsen, Knut [Norwegian Univ. of Science and Technology (NTNU), Trondheim (Norway). Dept. of Materials Science and Engineering; Pedersen, Ketill Olav [SINTEF Materials and Chemistry, Trondheim (Norway); Gulbrandsen-Dahl, Sverre [Norwegian Univ. of Science and Technology (NTNU), Trondheim (Norway). Dept. of Materials Science and Engineering; SINTEF Raufoss Manufacturing AS, Raufoss (Norway)

2012-08-15

206

Effects of deformation on the electronic properties of B-C-N nanotubes  

Energy Technology Data Exchange (ETDEWEB)

We apply first-principles methods, using density functional theory, to investigate the effects of flattening deformation on the electronic properties of BC{sub 2}N and C-doped BNNTs. Four different types of BC{sub 2}N structures are considered. Two of them are semiconductors, and the radial compression produces a significant reduction of the energy band gap. The other two types of structures are metallic, and the effect of radial compression is quite distinct. For one of them it is found the opening of a small band gap, and for the other one no changes are observed. For C-doped tubes, it is also found that the electronic properties undergo significant modifications when subjected to radial compression. - Graphical Abstract: We apply first-principles methods, using density functional theory, to investigate the effects of flattening deformation on the electronic properties of BC{sub 2}N and C-doped BNNTs. Four different types of BC{sub 2}N structures are considered. Two of them are semiconductors, and the radial compression produces a significant reduction of the energy band gap. The other two types of structures are metallic, and the effect of radial compression is quite distinct. For one of them it is found the opening of a small band gap, and for the other one no changes are observed. For C-doped tubes, it is also found that the electronic properties undergo significant modifications when subjected to radial compression. Highlights: Black-Right-Pointing-Pointer We investigated electronic properties of flattened BC{sub 2}N nanotubes. Black-Right-Pointing-Pointer The electronic states depend strongly on compression. Black-Right-Pointing-Pointer It is studied flattened BN nanotubes doped with a carbon atom. Black-Right-Pointing-Pointer The flattened C-doped structures, presents a significant reduction of the gap.

Azevedo, S., E-mail: sazevedo@fisica.ufpb.br [Departamento de Fisica, Universidade Federal da Paraiba, Caixa Postal 5008, 58059-900 Joao Pessoa-PB (Brazil); Rosas, A. [Departamento de Fisica, Universidade Federal da Paraiba, Caixa Postal 5008, 58059-900 Joao Pessoa-PB (Brazil); Machado, M. [Departamento de Fisica, Universidade Federal de Pelotas, Caixa Postal 354, 96010-900 Pelotas-RS (Brazil); Kaschny, J.R. [Instituto Federal da Bahia-Campus Vitoria da Conquista, Av. Amazonas 3150, 45030-220 Vitoria da Conquista-BA (Brazil); Chacham, H. [Departamento de Fisica, ICEX, Universidade Federal de Minas Gerais, Caixa Postal 702, 30123-970 Belo Horizonte-MG (Brazil)

2013-01-15

207

Particle octupole-vibration coupling near 208Pb  

International Nuclear Information System (INIS)

High-spin states in nuclei around 208Pb were populated in deep inelastic collisions of 136Xe and 208Pb projectiles with 208Pb targets at beam energies about 12% above the Coulomb barrier. New states in nuclei in the vicinity of 208Pb have been found that result from the coupling of one and two quasi particles to the lowest 3- excitation of the 208Pb core. They show the influence of particle octupole-vibration coupling in a pronounced and clear way and verify the validity of this concept. (orig.)

208

Particle octupole-vibration coupling near {sup 208}Pb  

Energy Technology Data Exchange (ETDEWEB)

High-spin states in nuclei around {sup 208}Pb were populated in deep inelastic collisions of {sup 136}Xe and {sup 208}Pb projectiles with {sup 208}Pb targets at beam energies about 12% above the Coulomb barrier. New states in nuclei in the vicinity of {sup 208}Pb have been found that result from the coupling of one and two quasi particles to the lowest 3{sup -} excitation of the {sup 208}Pb core. They show the influence of particle octupole-vibration coupling in a pronounced and clear way and verify the validity of this concept. (orig.)

Rejmund, M. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, Orsay Campus (France); Maier, K.H. [Hahn-Meitner-Institut, Berlin (Germany); Broda, R.; Fornal, B.; Lach, M.; Wrzesinski, J. [Niewodniczanski Institute of Nuclear Physics, Cracow (Poland); Blomqvist, J. [Royal Institute of Technology, Physics Department Frescati, Stockholm (Sweden); Gadea, A. [Instituto de Fisica Corpuscular, Valencia (Spain); Gerl, J.; Grawe, H.; Kaspar, M.; Schaffner, H.; Schlegel, C.; Schubart, R.; Wollersheim, H.J. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Gorska, M. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Nuclear Physics Division, Institute of Experimental Physics, Warsaw University (Poland)

2000-06-01

209

Microstructure and properties of ceramics and composites joined by plastic deformation  

Energy Technology Data Exchange (ETDEWEB)

A review is presented of the design of suitable materials systems for joining by high-temperature plastic deformation, details of the joining techniques, microstructures and properties of the resulting composite bodies, and prospects and limitation for this type of joining technology. Joining parameters and resulting forms are discussed for Al{sub 2}O{sub 3}/mullite particulate composites, Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} particulate/Al{sub 2}O{sub 3} particulate and whisker-reinforced composites, hydroxyapatite bioceramics, La{sub 0.85}Sr{sub 0.15}MnO{sub 3} electronic ceramics, MgF{sub 2} optical ceramics, and Ni{sub 3}Al intermetallics. Results are contrasted with those obtained by other methods of joining brittle, high-temperature materials, with special focus on durability and mechanical properties.

Goretta, K.C. [Argonne National Laboratory, Argonne, IL 60439-4838 (United States)], E-mail: ken.goretta@aoard.af.mil; Singh, D.; Chen Nan [Argonne National Laboratory, Argonne, IL 60439-4838 (United States); Gutierrez-Mora, F.; Cinta Lorenzo-Martin, M. de la [Argonne National Laboratory, Argonne, IL 60439-4838 (United States); University of Seville, Seville 41080 (Spain); Dominguez-Rodriguez, A. [University of Seville, Seville 41080 (Spain); Routbort, J.L. [Argonne National Laboratory, Argonne, IL 60439-4838 (United States)

2008-12-20

210

Microstructure and properties of ceramics and composites joined by plastic deformation  

International Nuclear Information System (INIS)

A review is presented of the design of suitable materials systems for joining by high-temperature plastic deformation, details of the joining techniques, microstructures and properties of the resulting composite bodies, and prospects and limitation for this type of joining technology. Joining parameters and resulting forms are discussed for Al2O3/mullite particulate composites, Y2O3-stabilized ZrO2 particulate/Al2O3 particulate and whisker-reinforced composites, hydroxyapatite bioceramics, La0.85Sr0.15MnO3 electronic ceramics, MgF2 optical ceramics, and Ni3Al intermetallics. Results are contrasted with those obtained by other methods of joining brittle, high-temperature materials, with special focus on durability and mechanical properties

211

Structure and properties of deformed alloys of tungsten-rich corner of W-Mo-Re-Hf-C system  

International Nuclear Information System (INIS)

Main regularities of structure formation and mechanical properties changing are established for deformation of vacuum-melted low alloys in W-Mo-Re-Hf-C system. It is shown that during hot deformation a fibrous structure is formed which provides a dec-- crease of ductile-brittle transition temperature. All the alloys investigated after a 95% reduction are ductile at room temperature. Hot deformation in the range 1450-1350 deg C with 92-93% re-- duction in area does not result in a visible increase of alloy ultimate strength

212

Effects of pre-deformation on the martensitic transformation and magnetocaloric property in Ni-Mn-Co-Sn ribbons  

International Nuclear Information System (INIS)

This paper investigates the martensitic transformation and magnetocaloric effect in pre-deformed Ni-Mn-Co-Sn ribbons. The experimental results show that the reverse martensitic transformation temperature TM increases with the increasing pre-pressure, suggesting that pre-deformation is another effective way to adjust TM in ferromagnetic shape memory alloys. Large magnetic entropy changes and refrigerant capacities are obtained in these ribbons as well. It also discusses the origin of the enhanced martensitic transformation temperature and magnetocaloric property in pre-deformed Ni-Mn-Co-Sn ribbons

213

Influence of plastic deformation and diffusion annealing on the properties of on copper plated VT9 titanium alloy  

International Nuclear Information System (INIS)

The phase composition, microhardness, wear- and erosion resistance of the surface layers of the VT9 titanium alloy which is plated with copper when combining plastic deformation and diffusional annealing are investigated. It is established that plastic deformation of the copper plated samples of the VT9 alloy combined with diffusional annealing results in the acceleration of mutual diffusion processes which is manifested in the formation of a wider diffusion zone with the improved physico-mechanical properties. The highest strengthening H 600-650 is observed on the samples plastically deformed both before plating and after it

214

Octupole correlation effects in 151Pm  

International Nuclear Information System (INIS)

Excited states of 151Pm have been observed using the 150Nd(?,p2n) reaction at a beam energy of 35 MeV. Levels with spin up to 19/2 have been seen in a positive parity band built on the 5/2+ ground state, and up to 21/2 in a negative parity band built on the 5/2- level at 117 keV excitation energy. Levels of the same spin but opposite parity are nearly degenerate and there are strong (?1.1x10-3 W.u.) electric dipole transitions between members of the two bands. The energy staggering of levels and their electromagnetic decay properties are somewhat different for the two bands

215

Octupole correlations in neutron-rich 143,145Ba and a type of superdeformed band in 145Ba  

International Nuclear Information System (INIS)

High spin states in neutron-rich odd-Z 143,145Ba nuclei have been investigated from the study of prompt ? rays in the spontaneous fission of 252Cf by using ?-?- and ?-?-?- coincidence techniques. Alternating parity bands are identified for the first time in 145Ba and extended in 143Ba. A new side band, with equal, constant dynamic, and kinetic moments of inertia equal to the rigid body value, as found in superdeformed bands, is discovered in 145Ba. Enhanced E1 transitions between the negative- and positive-parity bands in these nuclei give evidence for strong octupole deformation in 143Ba and in 145Ba. These collective bands show competition and coexistence between symmetric and asymmetric shapes in 145Ba. Evidence is found for crossing M1 and E1 transitions between the s=+i and s=-i doublets in 143Ba. copyright 1999 The American Physical Society

216

Microstructural evolution and mechanical properties of a copper-zirconium alloy processed by severe plastic deformation  

Science.gov (United States)

A copper alloy, Cu-0.1% Zr, has been processed at room temperature by different techniques of severe plastic deformation (SPD), namely equal-channel angular pressing (ECAP), high-pressure torsion (HPT) and a combination of both processing (ECAP + HPT). The experiments were conducted to evaluate the microstructural evolution and mechanical properties for each of the processed and their combination. A transmission electron microscopy (TEM) and an electron backscatter diffraction (EBSD) techniques were employed to measure the microstructural features, grain size distributions and the distribution of the misorientation angles. The mechanical properties of the processed samples were examined and compared both at a room temperature using microhardness measurements and at an elevated temperature using tensile testing. Using TEM and EBSD techniques, it is demonstrated that these three SPD procedures have a potential for producing an ultrafine-grain structure containing reasonably equiaxed grains with high-angle boundary misorientations. However, microstructures are refined in different level depending on the processing operation. The grain refinement mechanisms are primarily governed by dislocation activities. Microhardness distribution of the strained samples shows that there is a non-uniform of this distribution in the early stages of deformation where the lower hardness values were measured near the bottom of samples for ECAP and at the central region for HPT. This inhomogeneity is gradual decreased with increasing imposed strain and ultimately the microhardness distribution is reasonably homogeneous when the sufficient strain is subjected to the sample. The tensile results demonstrate that the samples after SPD processing exhibit superior mechanical properties with the combination of high strength and ductility compared to the as-received materials where the maximum elongation to failure of ˜240% at 723 K using a strain rate of 1.0 x 10 -4 s-1 is achieved in a sample processed by HPT. This elongation however does not fulfilled the requirements for true superplastic flow where the measured elongation in tension should be at least 400%.

Wongsa-Ngam, Jittraporn

217

Strength and deformational properties of concrete at elevated temperatures up to 5000C  

International Nuclear Information System (INIS)

Mechanical property tests of concrete at elevated temperatures had been performed. The experimental results obtained by the strength tests, were shown at each strength test. Compressive strength: sigmacu(T)/sigmacu, room = 1.00(normal temp. 0C), sigmacu(T)/sigmacu, room = -0.00195T + 1.544(280 0C -6T2 + 4.813 x 10-5T + 1.0(normal temp. 0C); Modulus of Rupture: sigmabu(T)/sigmabu, room = -0.0021T + 1.402(100 0C 0C); Young's Modulus: Esub(c)(T)/Esub(c), room = -0.00124T + 0.802(100 0C 0C); Relationship between Decrease rates of Young's Modulus(W) and Weight of Test Specimen(G): W = 0.047G + 2.88(100 0C 0C); compressive Strain at the Maximum Stress: R strain = 0.00263T + 0.932(normal temp. 0C), which means the ratio of the compressive strain at maximum stress at high temperature to that at normal temperature. It was made clear by the past researches that the thermal expansion coefficients of deformed bars increase according to temperature rise. The experimental results obtained by the free expansion tests using D16 deformed bars in Civil Engineering Laboratory supported the general tendency described above. Further, the strengths as well as Young's modulus of concrete at es well as Young's modulus of concrete at elevated temperatures were discussed. (Kubozono, M.)

218

Nanostructure formation under severe plastic deformation by rolling and annealing and enhancement of functional properties of Ti-Ni alloys  

International Nuclear Information System (INIS)

One carried out the comparison study of the following processes: structure formation, change of the functional properties and deformation behaviour of Ti-50%Ni alloy with shape memory in response to low-temperature thermal and mechanical treatment (LTTMT) with e=0.30-1.9 true deformation by rolling followed by annealing within 200-700 deg C range. The nanocrystalline structure with 50-80 nm grain size resulting from the LTTMT, e=1.9 and annealing under 400 deg C ensures simultaneously the best complex of the functional properties: 8% maximum recoverable strain and 1420 MPa maximum reaction pressure

219

Experimental deformation of synthetic magnetite-bearing calcite sandstones - Effects on remanence, bulk magnetic properties, and magnetic anisotropy  

Science.gov (United States)

The simultaneous effects of deformation on the magnetic remanence, bulk magnetic properties, and magnetic anisotropy of magnetite-bearing calcite sandstones were investigated in a set of synthetic magnetite-bearing samples prepared as described by Borradaile and Alford (1987). Experimental deformations of synthetic sandstone analogs containing 40-micron magnetite were found to produce significant changes in the orientation of anhysteretic remanence, in bulk magnetic properties, and in magnetic anisotropy. These changes proceeded slowly for shortening strains below about 10 percent, but much more rapidly at higher strains.

Jackson, Mike; Borradaile, Graham; Hudleston, Peter; Banerjee, Subir

1993-01-01

220

Quasi-instantaneous and Long-term Deformations of High-Performance Concrete with Some Related Properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This report outlines an experimental and numerical study on quasi-instantaneous and long-term deformations of High-Performance Concrete, HPC, with some related properties. For this purpose about two hundred small cylinders and about one thousand cubes of eight types of HPC were cast. The age at loading varied between 18h and 28 days. Other principal properties of HPC were studied up to 4 years' age. Creep deformations of the HPC were studied from 0.01 s of loading time until 5 years' ...

Persson, Bertil

1998-01-01

 
 
 
 
221

Formation of structure and properties of commercial titanium with nanocrystalline structure after deformation and subsequent heating  

International Nuclear Information System (INIS)

The influence of shear deformation degree on grain size and mechanical properties of titanium VT1-0 alloy was investigated. it is revealed that the structure with mean grain size of 100 nm can be produced by way of intense torsion. As this takes place some areas with grain size of 20-30 nm can exist. Postdeformation heating results in two main stages of structural transformations. The low temperature transformation (below 250 deg C) proceeds with a fairly high rate and involves stress and dislocation redistribution. Transformations above 300 deg C proceed by recrystallization mechanism. Nanocrystalline commercial titanium exhibits the best combination of strength and plasticity being annealed at 250 deg C

222

Temperature dependence of deformation vs. strength properties of radiation-crosslinked polyethylene  

International Nuclear Information System (INIS)

The authors have studied the deformation vs. strength properties of radiation-crosslinked low-density polyethylene irradiated by ? irradiation up to doses from 5.0 sm-bullet 104 to 1.0 sm-bullet 106 Gy. The authors present the elongation diagrams taken at temperatures below and above the melting point of the polymer. The authors have obtained the dependences of the breaking stress and the pre-break elongation of the polymer on the irradiation doses and the testing temperature. Based on the kinetic lifetime equation, The authors calculated the values of the activation energy for mechanical fracture and the structure-sensitive coefficient ?. The authors show that in the crystalline state the strength of radiation-crosslinked polyethylene is determined by the chemical interactions along the chain of polymer macromolecules; and in molten polyethylene, by the crosslinks between the macromolecules. 8 refs., 4 figs., 1 tab

223

Temperature dependence of deformation vs. strength properties of radiation-crosslinked polyethylene  

Energy Technology Data Exchange (ETDEWEB)

The authors have studied the deformation vs. strength properties of radiation-crosslinked low-density polyethylene irradiated by {gamma} irradiation up to doses from 5.0{sm_bullet}10{sup 4} to 1.0{sm_bullet}10{sup 6} Gy. The authors present the elongation diagrams taken at temperatures below and above the melting point of the polymer. The authors have obtained the dependences of the breaking stress and the pre-break elongation of the polymer on the irradiation doses and the testing temperature. Based on the kinetic lifetime equation, The authors calculated the values of the activation energy for mechanical fracture and the structure-sensitive coefficient {gamma}. The authors show that in the crystalline state the strength of radiation-crosslinked polyethylene is determined by the chemical interactions along the chain of polymer macromolecules; and in molten polyethylene, by the crosslinks between the macromolecules. 8 refs., 4 figs., 1 tab.

Matusevich, Yu.I.; Krul`, L.P.

1992-09-01

224

Electronic and transport properties of radially deformed double-walled carbon nanotube intramolecular junction  

Energy Technology Data Exchange (ETDEWEB)

The electronic and transport property of a radially deformed double-walled carbon nanotube (DWNT) intramolecular junction (IMJ) has been studied by the tight-binding (TB) model combined with the first-principle calculations. The geometrical structures of the DWNT IMJ have been first optimized in energy by the universal force field (UFF) method. It is found that when heavily squashed, the DWNT will become an insulator-coated metallic wire, and the conductance near the Fermi level has been significantly changed by the radial squash. Specially, several resonance conductance peaks appear at some energies in the conduction band of the squashed DWNT IMJ. Finally, we have also investigated the conductance variation due to change of the length of the central semiconductor in the squashed DWNT IMJ. Furthermore, a promising pure carbon nanoscale electronic device is proposed based on the DWNT IMJ.

Yang Xiaoping [Group of Computational Condensed Matter Physics, National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China) and Department of Physics, Huainan Normal University, Huainan, Anhui 232001 (China)]. E-mail: bunnyxp@hotmail.com; Dong Jinming [Group of Computational Condensed Matter Physics, National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China)

2004-09-20

225

Transient deformation properties of Zircaloy for LOCA simulation. Final report, Volume 1  

International Nuclear Information System (INIS)

The creep/creep rupture anisotropic properties of Zircaloy were determined and compared by analytical techniques with ramp pressure and ramp temperature test results. Tests were performed over the temperature range of 6000F (589 K) to 22000F (1477 K) with the emphasis on the 8000F (7000K) to 20000F (13660K) temperature levels in low pressure air (6.5 x 10-5 atm) and in a 1 atm mixture of 20% oxygen, 80% argon. Stress levels of 60 to 95% of the ultimate tensile stress were used for the majority of the tests at each of the temperature levels tested, with selected tests performed as low as 30% of the ultimate tensile stress. Biaxial and uniaxial testing modes were used to evaluate the anisotropic deformation behavior. Results include creep/creep rupture strain numerical constitutive relationships out to 120 seconds, computer codes and ramp test data

226

Effect of collective octupole vibration on single-particle states in zirconium region  

International Nuclear Information System (INIS)

There seems to be a correlation between the energies of the 3- states in even zirconium nuclei A = 90-96 and the single-particle energies of protons in psub(1/2) and gsub(9/2) orbits in neighbouring odd mass niobium nuclei A = 91-97. An attempt has been made to give a theoretical explanation of this systematic shift in the single-particle levels in niobium nuclei as arising due to the coupling of single-particle motion to the collective octupole vibration. An octupole-octupole interaction and the random phase approximation are used in calculating the energy shifts. (author)

227

Rare-earth nuclei: Radii, isotope-shifts and deformation properties in the relativistic mean field theory  

International Nuclear Information System (INIS)

A systematic study of the ground-state properties of even-even rare earth nuclei has been performed in the framework of the Relativistic Mean-Field (RMF) theory using the parameter set NL-Sh. Nuclear radii, isotope shifts and deformation properties of the heavier rare-earth nuclei have been obtained, which encompass atomic numbers ranging from Z=60 to Z=70 and include a large range of isospin. It is shown that RMF theory is able to provide a good and comprehensive description of the empirical binding energies of the isotopic chains. At the same time the quadrupole deformations ?2 obtained in the RMF theory are found to be in good agreement with the available empirical values. The theory predicts a shape transition from prolate to oblate for nuclei at neutron number N=78 in all the chains. A further addition of neutrons up to the magic number 82 brings about the spherical shape. For nuclei above N-82, the RMF theory predicts the well-known onset of prolate deformation at about N-88, which saturates at about N-102. The deformation properties display an identical behaviour for all the nuclear chains. A good description of the above deformation transitions in the RMF theory in all the isotopic chains leads to a successful reproduction of the anomalous behaviour of the empirical isotopic shifts of the rare-earth nuclei. The RMF theory exhibits a remarkable success in providing a unified and microscopic description of various empirical data. (orig.)

228

Plasma resistivity measurements in the Wisconsin levitated octupole  

Energy Technology Data Exchange (ETDEWEB)

Resistivity measurements parallel to the magnetic field were made on gun injected plasmas ranging in density from 10/sup 9/cm/sup -3/ to 10/sup 1/parallelcm/sup -3/ in the Wisconsin levitated octupole with toroidal and poloidal magnetic fields. The 10/sup 9/cm/sup -3/ plasma was collisionless with lambda/sub mfp/ > 100 mirror lengths, had T/sub e/ = 10 eV, T/sub i/ = 30 eV and was found to have anomalous resistivity scaling like eta = ..sqrt..T/sub e//n/sub e/ when E/sub parallel/ > E/su c/ is the Dreicer critical field. The 10/sup 12/cm/sup -3/ plasma was collisional with lambda/sub mfp/ < mirror length, had T/sub e/ = T/sub i/ approx. = .2 eV and was found to have Spitzer resistivity when E/sub parallel/ < E/sub c/.

Brouchous, D. A.

1980-11-01

229

Plasma resistivity measurements in the Wisconsin levitated octupole  

International Nuclear Information System (INIS)

Resistivity measurements parallel to the magnetic field were made on gun injected plasmas ranging in density from 109cm-3 to 101parallelcm-3 in the Wisconsin levitated octupole with toroidal and poloidal magnetic fields. The 109cm-3 plasma was collisionless with lambda/sub mfp/ > 100 mirror lengths, had T/sub e/ = 10 eV, T/sub i/ = 30 eV and was found to have anomalous resistivity scaling like eta = ?T/sub e//n/sub e/ when E/sub parallel/ > E/su c/ is the Dreicer critical field. The 1012cm-3 plasma was collisional with lambda/sub mfp/ < mirror length, had T/sub e/ = T/sub i/ approx. = .2 eV and was found to have Spitzer resistivity when E/sub parallel/ < E/sub c/

230

Detailed investigation of octupole vibrational states in 168Yb  

International Nuclear Information System (INIS)

The experimental evidence for the presence of octupole vibrational states in 168Yb is presented. In order to populate the excited states in this nucleus, the 166Er(?,2n?)168Yb fusion evaporation reaction was used with a beam energy of 24 MeV. Using the coincidence method, the level scheme was corrected and extended up to 3 MeV, both for the positive and negative parity states. In a second step, the lifetimes of five excited states were measured by using the fast timing method with the Bucharest HPGe and LaBr3:Ce detector array using the triple-? coincidence method. Reduced E1 and E2 transition probabilities were extracted from the measured lifetimes and compared, when possible, with similar observables in neighboring isotopes, showing a smooth behavior with increasing mass. The positive and negative-parity states revealed by this experiment are compared with the Interacting Boson Model and are found to be in good agreement.

231

Experimental study of dynamic compressive properties of rigid polyurethane foams under high deformation velocities using an impulsive shock technique  

International Nuclear Information System (INIS)

This paper presents an experimental study on dynamic compressive properties of rigid urethane foams under high deformation velocities realized by means of an impulsive shock device. Two kind of rigid foams are studied within the impulse range: 500 pa. s to 1.200 pa.s. Experimental results are analysed and a comparison between static and dynamic behaviour is made

232

Deformation Mapping and the Role of Carbides on the Microstructure and Properties of Evolved Adiabatic Shear Bands  

Science.gov (United States)

Impacting hardenable steel such as 4340, results in the formation of adiabatic shear bands (ASBs). Previous studies have shown that the presence of carbides/second-phase particles in the pre-deformation microstructures of 4340 steel increases their susceptibility to the formation of ASBs. The current study examines the role of carbides on the microstructure and properties within evolved ASBs in 4340 steel after impact. Geometric phase analysis was used to map local deformation fields within the evolved ASBs. It was observed that carbide fragmentation due to plastic deformation of carbides produces both residual carbides and residual carbide particles in regions away from the shear bands. Extensive carbide fragmentation produces fine residual carbide particles which are redistributed within the ASBs. This is attributed to strain localization within the ASBs which result in higher local strain and strain rates within the shear bands than in regions outside the bands. In addition, it is observed that the residual carbide particles trap and pin dislocations within the shear bands and contribute to an increase in local hardening. A more homogenous distribution of narrower and shorter rotational and shear-strain fields were revealed by the local deformation maps within the evolved ASBs. Lattice deformation mapping revealed that the ferrite matrix, prior to impact, had broader and longer rotational and shear-strain fields perpendicular to the direction of impact. This is attributed to lattice-invariant deformation and shape deformation processes that occur on specific crystallographic planes during martensitic transformation. It is concluded that strain localization during high strain rate deformations does not occur on specific crystallographic planes. This results in a more regular distribution of internal lattice rotational and strain fields within the evolved ASBs.

Boakye-Yiadom, Solomon; Khan, Abdul Khaliq; Bassim, Nabil

2014-11-01

233

Effect of Tempering Time on Microstructure, Tensile Properties, and Deformation Behavior of a Ferritic Light-Weight Steel  

Science.gov (United States)

In the present study, a ferritic light-weight steel was tempered at 973 K (700 °C) for various tempering times, and tensile properties and deformation mechanisms were investigated and correlated to microstructure. ?-carbides precipitated in the tempered band-shaped martensite and ferrite matrix, and the tempered martensite became more decomposed with increasing tempering time. Tempering times for 3 days or longer led to the formation of austenite as irregular thick-film shapes mostly along boundaries between the tempered martensite and the ferrite matrix. Tensile tests of the 1-day-tempered specimen showed that deformation bands were homogeneously spread throughout the specimen, and that the fine carbides were sufficiently deformed inside these deformation bands resulting in high strength and ductility. The 3-day-tempered specimen showed a small amount of boundary austenite, which readily developed voids or cracks and became sites for fracture. This cracking at boundary austenites became more prominent in the 7- and 15-day-tempered specimens, as the volume fraction of boundary austenites increased with increasing tempering time. These findings suggested that, when the steel was tempered at 973 K (700 °C) for an appropriate time, i.e., 1 day, to sufficiently precipitate ?-carbides and to prevent the formation of boundary austenites, that the deformation occurred homogeneously, leading to overall higher mechanical properties.

Han, Seung Youb; Shin, Sang Yong; Lee, Byeong-Joo; Lee, Sunghak; Kim, Nack J.; Kwak, Jai-Hyun

2013-01-01

234

THE EFFECTS OF HYDROGEN, TRITIUM, AND HEAT TREATMENT ON THE DEFORMATION AND FRACTURE TOUGHNESS PROPERTIES OF STAINLESS STEEL  

Energy Technology Data Exchange (ETDEWEB)

The deformation and fracture toughness properties of forged stainless steels pre-charged with tritium were compared to the deformation and fracture toughness properties of the same steels heat treated at 773 K or 873 K and precharged with hydrogen. Forged stainless steels pre-charged with tritium exhibit an aging effect: Fracture toughness values decrease with aging time after precharging because of the increase in concentration of helium from tritium decay. This study shows that forged stainless steels given a prior heat treatment and then pre-charged with hydrogen also exhibit an aging effect: Fracture toughness values decrease with increasing time at temperature. A microstructural analysis showed that the fracture toughness reduction in the heat-treated steels was due to patches of recrystallized grains that form within the forged matrix during the heat treatment. The combination of hydrogen and the patches of recrystallized grains resulted in more deformation twinning. Heavy deformation twinning on multiple slip planes was typical for the hydrogen-charged samples; whereas, in the non-charged samples, less twinning was observed and was generally limited to one slip plane. Similar effects occur in tritium pre-charged steels, but the deformation twinning is brought on by the hardening associated with decay helium bubbles in the microstructure.

Morgan, M.; Tosten, M.; Chapman, G.

2013-09-06

235

Simulations of octupole compensation of head-tail instability at the Tevatron  

International Nuclear Information System (INIS)

The proton lifetime in the Tevatron depends sensitively on chromaticities. Too low chromaticities can make the beam unstable due to the weak head-tail instability. One way to compensate this effect is to introduce octupoles to create a larger amplitude dependent betatron tune spread. However, the use of octupoles will also introduce additional side effects such as second order chromaticity, differential tune shifts and chromaticities on both proton and anti-proton helices. The non-linear effects may also reduce the dynamic aperture. There are 67 octupoles in 4 different circuits in the Tevatron which may be used for this purpose. We report on a simulation study to find the best combinations of polarities and strengths of the octupoles

236

Spectroscopy on a single trapped ¹³?Ba? ion for nuclear magnetic octupole moment determination.  

Science.gov (United States)

We present precision measurements of the hyperfine intervals in the 5D3/2 manifold of a single trapped Barium ion, ¹³?Ba?. Measurements of the hyperfine intervals are made between mF = 0 sublevels over a range of magnetic fields allowing us to interpolate to the zero field values with an accuracy below a few Hz, an improvement on previous measurements by three orders of magnitude. Our results, in conjunction with theoretical calculations, provide a 30-fold reduction in the uncertainty of the magnetic dipole (A) and electric quadrupole (B) hyperfine constants. In addition, we obtain the magnetic octupole constant (C) with an accuracy below 0.1Hz. This gives a subsequent determination of the nuclear magnetic octupole moment, ?, with an uncertainty of 1% limited almost completely by the accuracy of theoretical calculations. This constitutes the first observation of the octupole moment in ¹³?Ba? and the most accurately determined octupole moment to date. PMID:23037261

Lewty, Nicholas C; Chuah, Boon Leng; Cazan, Radu; Sahoo, B K; Barrett, M D

2012-09-10

237

Mechanical properties and constitutive relations for tantalum and tantalum alloys under high-rate deformation  

International Nuclear Information System (INIS)

Tantalum and its alloys have received increased interest as a model bcc metal and for defense-related applications. The stress-strain behavior of several tantalums, possessing varied compositions and manufacturing histories, and tantalum alloyed with tungsten, was investigated as a function of temperature from -196 C to 1,000 C, and strain rate from 10-3 s-1 to 8,000 s-1. The yield stress for all the Ta-materials was found to be sensitive to the test temperature, the impurity and solute contents; however, the strain hardening remained very similar for various ''pure'' tantalums but increased with alloying. Powder-metallurgy (P/M) tantalum with various levels of oxygen content produced via different processing paths was also investigated. Similar mechanical properties compared to conventionally processed tantalums were achieved in the P/M Ta. This data suggests that the frequently observed inhomogeneities in the mechanical behavior of tantalum inherited from conventional processes can be overcome. Constitutive relations based upon the Johnson-Cook, the Zerilli-Armstrong, and the Mechanical Threshold Stress models were evaluated for all the Ta-based materials. Parameters were also fit for these models to a tantalum-bar material. Flow stresses of a Ta bar stock subjected to a large-strain deformation of var-epsilon = 1.85 via multiple upset forging were obtained. The capabilities and limitations of each model for large-strain applications are examined. The deformation mechanisms controlling high-rate plasticity in tantalum are revisited

238

Phase stability, deformation mechanisms, and mechanical properties of Nb-Al-Ti alloys  

International Nuclear Information System (INIS)

The phase stability, deformation mechanisms and mechanical properties of two alloys based on Nb3Al containing additions of Ti have been studied. These two alloys, with nominal compositions (in at.%) of Nb-15Al-10Ti (alloy 1) and Nb-15Al-40Ti (alloy 2), have the B2 crystal structure in as cast form. The ALCHEMI technique has been employed to assess qualitatively the distribution of atom types over the two sublattices of the B2 compounds. It is found that Ti and Al occupy different sublattices in alloy 2. Heat-treatment of alloy 1 at 1,100 C results in the precipitation of an A15 phase in the B2 matrix. Annealing at 900 C for short time introduces an w-phase. Prolonged annealing of alloy 1 at 700 C reveals the presence of an orthorhombic phase. The same orthorhombic phase is also found to exist between 800 and 1,000 C in alloy 2. Specific orientation relationships exist between the matrix phase and precipitates. The yield strength in compression of Alloy 1 and 2 were determined at various temperatures. Alloy 1 is strong compared to superalloy IN 718 over a range of temperatures up to 950 C. Both alloys with the B2 crystal structure are deformed by one or more of the following slip systems, namely (110), (112) and (123). Dislocations with Burgers vector, b, given by b= are present in the form of dissociated superpartial pairs, each with b=1/2. The inherent ductility of both alloys is indicated by the active slip systems and illustratedby the active slip systems and illustrated by 20% elongation to failure obtained in alloy 2 under room temperature tensile test. A trend of increasing tensile yield stress with increasing antiphase domain size was found. No evidence of interaction between dislocations and antiphase boundaries has been found to account for this increase of strength

239

Comparative studies of constitutive properties of nanocrystalline and bulk iron during compressive deformation  

International Nuclear Information System (INIS)

Highlights: ? Yield strength of nano-Fe (2.0 GPa) is 15 times higher than that of micron-Fe (0.13 GPa). ? Compressive deformation does not build up additional dislocations in nano-Fe. ? Pressure induced dislocation annihilation in micron-Fe during compression. ? Dislocation annihilation is a dominant mechanism for plastic energy dissipation. - Abstract: We present a comparative study of the mechanical properties of body-centered cubic nanocrystalline iron (nano-Fe) and microcrystalline iron (micro-Fe) by in situ high-pressure synchrotron X-ray diffraction under triaxial compression. For nano-Fe with a starting high dislocation density of 1016 m-2, the peak broadening is almost reversible upon unloading from 8.6 GPa to atmospheric pressure, indicating that no additional dislocations are built up during compressive deformation inside grains, at grain boundaries or twin boundaries. Furthermore, an orientation-dependent surface strain is found to be stored in the surface layer of the bcc nano-Fe, which is in agreement with the core-shell model of the nanocrystals. For micro-Fe, a significant and continuous peak sharpening and the associated work softening were observed after the sample is yielded at pressures above 2.0 GPa, which can be presumably attributed to a pressure-induced dislocation annihilation. This finding/interpretation supports the hypothesis that the annihilation of dislocations is one of the dominant mechanisms underlying the ominant mechanisms underlying the plastic energy dissipation. The determined yield strength of 2.0 GPa for nano-Fe is more than 15 times higher than that for micro-Fe (0.13 GPa), indicating that the nanoscale grain-size reduction is a substantially more effective strengthening mechanism than conventional carbon infusion in iron.

240

Understanding the tune, coupling, and chromaticity dependence of the LHC on Landau octupole powering.  

CERN Document Server

During the 2012 LHC run several observations were made of shifts to tune, coupling and chromaticity which were correlated with changes in the powering of Landau octupoles. Understanding the chromaticity dependence is of particular importance given its influence on instabilities. This note briefly summarizes the observations and describes our understanding to-date of the relationship between Q, Q?, |C?| and the Landau octupole powering.

Maclean, E H; Persson, T; Tomas, R; Wenninger, J

2013-01-01

 
 
 
 
241

On the chemistry, microstructure, and deformation properties of cement pastes: Towards a new strategy for controlling drying shrinkage  

Science.gov (United States)

The research reported in this thesis covers a number of topics that include aspects of chemistry, microstructure, deformation of cement pastes. An overall goal has been to develop a materials science basis for controlling drying shrinkage. This goal is ambitious and there is a great deal of research still required. However, progress has been made and it is reported here. First, a new phase diagram believed to be consistent with the cement hydration process has been developed. This diagram assumes that a metastable C-S-H phase, analogous to jennite but without polymerized silicate chains, is responsible for the induction period, and that the final hydration reaction is a eutectic solidification reaction consisting of layered calcium silicate hydrate and calcium hydroxide. Second, the effects of chemical admixtures on the rheological behavior of cement in its fluid state was explored. It was found that steric hindrance must play a role in the mechanism behind the dispersing properties of these chemicals. Third, new deformation mapping technique used to investigate the drying shrinkage behavior of neat cement pastes has been developed. This technique requires only two digital images; the source of the images and the source of the deformation does not affect this analysis. A dynamic new picture of drying shrinkage deformation has emerged. Both rarefactions and compactions are found to develop within the microstructure under all drying conditions, and these deformed regions interact to control the overall deformation of the material. Finally, a finite element model was used to further explore drying shrinkage in cement pastes and mortars. It was found that the drying shrinkage of neat cement pastes appears to be controlled by only a subset of calcium silicate hydrate; this subset is detectable by nitrogen sorption techniques. This relationship is perhaps the second microstructure-property relationships known for cement pastes and can be used as a design tool for developing new materials with optimum drying shrinkage properties.

Neubauer, Christopher Michael

242

Effect of cold deformation on structure and properties of aluminium alloy 1441 sheets  

International Nuclear Information System (INIS)

The influence of tensile deformation on the 1441 alloy (Al-Cu-Mg-Li-Zr) in four states: quenched; quenched, straightened and naturally aged; annealed; quenched, straightened and artificially aged one, has been studied. It has been ascertained that deformation after quenching results in a considerable growth of yield strength. Artificial aging makes an insignificant contribution to stregthening of deformed sheet. 2 refs.; 4 figs

243

Numerical and experimental investigation of deformation and strength properties of lithophysae-rich tuff and analog materials  

Science.gov (United States)

Portions of the high-level nuclear waste repository in Yucca Mountain will be located in lithophysae-rich tuff formations. Understanding the mechanical properties of the lithophysae-rich tuff, including deformation modulus, deformation ratio and compressive strength, is an important issue for design and the performance of the repository tunnels. These properties are expected to be significantly affected by lithophysal porosity. Two different research directions are implemented in this dissertation. First, uniaxial compression testing is simulated using finite difference technique on models containing circular holes in order to investigate the effect of porosity on deformation parameters. Numerical results are compared with biaxial test results of urethane specimens containing circular tubes to verify the numerical analysis results. Second, an experimental program that consists of uniaxial compression tests on analog models and tuff is conducted. Two different configurations are implemented to model porosity using gypsum plaster as an analog material. In the first configuration analog models containing uniformly and randomly distributed open ended cylindrical tubes are produced. In the second configuration spherical cavities are introduced into the analog models. Both models are tested under uniaxial compression and their deformation moduli and compressive strength are compared with lithophysae-rich tuff specimens that are obtained from outcrops of lithophysal tuff units. Numerical modeling and testing are combined to assess that the deformation modulus of tuff where the porosity has a vital effect on mechanical behavior of the rock. Both numerical analysis and uniaxial testing on analog materials show that in deformation modulus exponentially decrease with increasing porosity. The deformation moduli and compressive strength of gypsum plaster specimens containing open ended cylindrical tubes are slightly lower than those containing spherical cavities due to confinement effects. The deformation moduli and compressive strengths of the tuff specimens fall between the values determined for the plaster specimens with two different porosity configuration. Distribution of data for both analog and tuff specimens is very similar at low porosities. At higher porosities, a greater decrease in deformation modulus is observed in tuff due to larger and nonspherical cavities indicating that shape of the cavities is a factor affecting the modulus.

Avar, Bahri Burcin

244

Effect of superplastic deformation on the bonding property of 00Cr25Ni7Mo3N duplex stainless steel  

Science.gov (United States)

The superplastic deformation diffusion bonding of 00Cr25Ni7Mo3N duplex stainless steel was performed on a hot simulator. The microstructure of the bonding interface was characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The mechanical properties of the specimen were investigated by a shear strength test. The results indicated that the shear strength was improved with the increase of superplastic deformation reduction. When the deformation reduction was up to 50%, the shear strength of the specimen achieved 417 Mpa, approaching to that of the base metal. In addtion, the superplastic diffusion bonding technique was not very sensitive to surface roughness levels. When the surface roughness of the bonding specimen surpassed 0.416 ?m (level G2), the shear strength achieved at least 381 MPa.

Chen, Xiao-hui; Ren, Xue-ping; Xu, Hui; Tong, Jian-guo; Zhang, Hai-yan

2012-04-01

245

Reduced electric-octupole transition probabilities, B(E3;O1+ ? 31-), for even-even nuclides throughout the periodic table  

International Nuclear Information System (INIS)

Adopted values for the excitation energy, Ex(31-), of the first 3- state of the even-even nuclei are tabulated. Values of the reduced electric-octupole transition probability, B(E3;O1+ ? 31-), from the ground state to this state, as determined from Coulomb excitation, lifetime measurements, inelastic electron scattering, deformation parameters ?3 obtained from angular distributions of inelastically scattered nucleons and light ions, and other miscellaneous procedures are listed in separate Tables. Adopted values for B(E3; O1+ ? 31-) are presented in Table VII, together with the E3 transition strengths, in Weisskopf units, and the product Ex(31-) x B(E3; O1+ ? 31--) expressed as a percentage of the energy-weighted E3 sum-rule strength. An evaluation is made of the reliability of B(E3; O1+ ? 31-) values deduced from deformation parameters ?3. The literature has been covered to March 1988

246

The effects of severe plastic deformation on some properties relevant to Ti implants  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english In some types of surgical implants, such as bone screws and plates, Grade 2 Ti is seriously considered as a replacement for the Ti-6Al-4V alloy. Advantages are lower cost and the absence of Al and V, which have been identified as potentially harmful to human health. The present paper shows that the [...] lower strength of the commercially pure metal can be enhanced by Severe Plastic Deformation followed by conventional cold rolling, so as to reach a strength level higher than the technical requirements applicable to the alloy. This was ascertained by tensile and Vickers hardness tests from which it was concluded that the best combination of properties are obtained by submitting the metal to Equal Channel Angular Pressing (four passes at 300 °C) followed by a 70% thickness reduction by cold rolling. Although the present results are valid for the material only, and not for the product considered, that is, bone screws, it appears that this solution is a step towards the replacement of the Ti6-4 alloy by Grade 2 Ti, at least for some types of metallic medical implants.

Anibal Andrade, Mendes Filho; Vitor Luiz, Sordi; Maurizio, Ferrante.

2012-02-01

247

Microstructure and mechanical properties of fine grain seamless Nb tube by a novel shear deformation process  

Science.gov (United States)

The objective of this work is to demonstrate a seamless tube fabrication method for obtaining uniform fine grained microstructures by a novel shear deformation process for tubular metal products. The manufacture of fine grained RRR Nb superconducting radio frequency (SRF) cavities, and other tubular Nb products requires strict microstructure control with respect to grain size and texture for good formability. The major challenges in SRF cavity fabrication and performance stems from: a) the high cost of pure Nb, b) a poor and inconsistent microstructure in the starting material, and c) seam welding to manufacture multi-cell cavities. The approach presented by the authors indicates a possible strategy to obtain fine grain Nb tube by an innovative shear process. Grain size less than 30?m and tensile ductility greater than 40 percent in the orthogonal direction are achieved. The tensile properties correlate with the strongest texture component in the processed tube. Based on preliminary results, the proposed methodology maybe a viable and cost effective approach to fabricating a seamless Nb tube with good hydroformability.

Balachandran, S.; Seymour, N.; Mezyenski, R.; Barber, R.; Hartwig, K. T.

2014-01-01

248

Comparison of mechanical and microstructural properties of conventional and severe plastic deformation processes  

Science.gov (United States)

The effect of the deformation processes on yield stress, Vickers microhardness and dislocation density were investigated using commercial purity (A1050) and alloyed aluminum (Al 6082). For the evolution of the dislocation density X-ray line profile analysis was used. In the large plastic strain range the variation of mechanical and microstructure evolution of A1050 and of Al 6082 processed by equal channel angular pressing are investigated using route BC and route C. In the plastic strain range up to 3 plane strain compression test was used to evaluate mechanical properties. The hardness and the yield stress showed a sharp increase after the first pass. In the case of A1050 it was found that the two examined routes has not resulted difference in the flow stress. In the case of Al 6082 the effect of the routes on the yield stress is significant. The present results showed that in the comparable plastic strain range higher yield stress values can be achieved by plane strain compression test than by ECAP.

Szombathelyi, V.; Krallics, Gy

2014-08-01

249

The effects of severe plastic deformation on some properties relevant to Ti implants  

Directory of Open Access Journals (Sweden)

Full Text Available In some types of surgical implants, such as bone screws and plates, Grade 2 Ti is seriously considered as a replacement for the Ti-6Al-4V alloy. Advantages are lower cost and the absence of Al and V, which have been identified as potentially harmful to human health. The present paper shows that the lower strength of the commercially pure metal can be enhanced by Severe Plastic Deformation followed by conventional cold rolling, so as to reach a strength level higher than the technical requirements applicable to the alloy. This was ascertained by tensile and Vickers hardness tests from which it was concluded that the best combination of properties are obtained by submitting the metal to Equal Channel Angular Pressing (four passes at 300 °C followed by a 70% thickness reduction by cold rolling. Although the present results are valid for the material only, and not for the product considered, that is, bone screws, it appears that this solution is a step towards the replacement of the Ti6-4 alloy by Grade 2 Ti, at least for some types of metallic medical implants.

Anibal Andrade Mendes Filho

2012-02-01

250

Interplay of inertia and deformability on rheological properties of a suspension of capsules  

CERN Document Server

The interplay of inertia and deformability has a substantial impact on the transport of soft particles suspended in a fluid. However, to date a thorough understanding of these systems is still missing and only a limited number of experimental and theoretical studies is available. We combine the finite-element, immersed-boundary and lattice-Boltzmann methods to simulate three-dimensional suspensions of soft particles subjected to planar Poiseuille flow at finite Reynolds numbers. Our findings confirm that the particle deformation and inclination increase when inertia is present. We observe that the Segr\\'e-Silberberg effect is unstable with respect to the particle deformability. Depending on the deformability and strength of inertial effects, inward or outward lateral migration of the particles takes place. In particular, for increasing Reynolds numbers and strongly deformable particles, distinct flow focusing emerges which is accompanied by a non-monotonic behaviour of the apparent suspension viscosity and th...

Krueger, Timm; Harting, Jens

2013-01-01

251

Micromechanical modeling of the normal deformation of rough-walled fractures: The influence of local damage events on macroscopic properties  

Science.gov (United States)

Quantifying fluid flow through rocks in the subsurface is critical to problems such as geothermal energy production and geologic CO2 sequestration. Often, these processes impose large stress perturbations, which can alter permeability, particularly when fractures are present. Predicting fluid flow through fractures under changing stress conditions requires improved understanding of the deformation of contacting fracture surfaces. Under normal loading, fractures deform elastically due to stresses induced at contacting asperities. Previously developed models calculate normal deformation of fracture surfaces using a semi-analytical approach that superimposes the solutions for the deformation of two elastic half-spaces caused by the independent elastic asperities between the two half spaces. These models reproduce elastic deformation of fractures reasonably well, but experimental observations often show hysteretic, or inelastic, response to cyclic loading. It is likely that this hysteretic behavior is due to damage to contacting asperities due to large local stresses. We present a modified model of fracture deformation that explicitly includes asperity damage and allows us to reproduce the hysteretic response of rock fractures caused by cyclical normal loading. Using our modified model, we explore the relative sensitivity of normal deformation to the statistical properties of fracture surfaces (i.e. standard deviation of roughness heights and Hurst exponent) and the compressive strength of asperities. Synthetic fractures are created by laterally offsetting two identical self-affine fractal surfaces, where asperities are modeled as a series of sub-millimeter-scale cylindrical posts constrained between two deforming half spaces. The results suggest that more asperities are damaged as the shear offset of the surfaces increases. It is also observed that the effect of damaged asperities is more pronounced in fractures with rougher surfaces (smaller Hurst exponent). This model provides a tool that can be employed to predict the relationship between fracture deformation, transmissivity and flow paths. This approach is particularly useful for improving our understanding of the response of newly created fractures, where the hysteretic response of the stress-strain relationship has implications on the evolution of fracture transmissivity.

Ameli, P.; Detwiler, R. L.

2010-12-01

252

Detailed investigation of octupole vibrational states in {sup 168}Yb  

Energy Technology Data Exchange (ETDEWEB)

The experimental evidence for the presence of octupole vibrational states in {sup 168}Yb is presented. In order to populate the excited states in this nucleus, the {sup 166}Er(?,2n?){sup 168}Yb fusion evaporation reaction was used with a beam energy of 24 MeV. Using the coincidence method, the level scheme was corrected and extended up to 3 MeV, both for the positive and negative parity states. In a second step, the lifetimes of five excited states were measured by using the fast timing method with the Bucharest HPGe and LaBr{sub 3}:Ce detector array using the triple-? coincidence method. Reduced E1 and E2 transition probabilities were extracted from the measured lifetimes and compared, when possible, with similar observables in neighboring isotopes, showing a smooth behavior with increasing mass. The positive and negative-parity states revealed by this experiment are compared with the Interacting Boson Model and are found to be in good agreement.

Pascu, Sorin; Derya, Vera; Endres, Janis; Hennig, Andreas; Netterdon, Lars; Pickstone, Simon G.; Spieker, Mark; Zilges, Andreas [Institut fuer Kernphysik, Universitaet Koeln (Germany)

2013-07-01

253

High power ICRH experiments on the Wisconsin levitated octupole  

International Nuclear Information System (INIS)

Preliminary ICRH experiments have begun on the Wisconsin Levitated Octupole. In order to study heating, energy confinement, and high ? plasmas, a 1.8 to 3 MHz oscillator and antenna have been installed. The oscillator and antenna have been installed. The oscillator is capable of delivering 2 MW of RF power for 10 msec, and to date up to 0.5 MW has been coupled into the plasma. At a density of approx. 6 x 1012 cm-3, T/sub e/ reaches a maximum of 30 eV as measured by Langmuir probes and VUV spectroscopy. Charge exchange measurements of T/sub i/ show Maxwellian components at 95 and 190 eV, with an energy confinement time of approx. 1 msec. Electron energy confinement is limited by impurity radiation, and several methods of impurity control are being tested. Current experiments also include direct measurement of the RF electric field, antenna loading measurements, variation of the oscillator frequency, and ohmic heating of the electrons

254

Ion-cyclotron-resonance heating in the Wisconsin Levitated Octupole  

International Nuclear Information System (INIS)

Ion-cyclotron-resonance heating has been investigated, both experimentally and theoretically, on the Wisconsin Levitated Octupole. Heating of both ions and electrons has been observed. Typically, a two-component ion energy distribution is produced (300 eV and 50 eV) with 500 kW of rf power coupled into a 5 x 1012 cm-3 plasma. Power is coupled to the plasma with an antenna that also serves as the inductor of an oscillator tank circuit. The oscillator is tunable from 1 to 3 MHz and can be applied for periods up to 10 msec. The experiments were performed with hydrogen, gun-injected plasmas. Most of the theortical work presented deals with a calculation that predicts the plasma loading. A slab model is used, and the questions of accessibility, polarization, and damping of the radio-frequency electromagnetic fields are addressed. It is found that cold-plasma theory cannot account for the heating and, therefore, hot-plasma theory is invoked to explain the results. The loading measurements and theoretical predictions are found to be in reasonable agreement

255

Frequency standard based on the octupole transition in 171Yb+  

International Nuclear Information System (INIS)

W present our results on the development of a new optical frequency standard based on the electric octupole (E3) transition 2S1/2(F=0) ? 2F7/2(F=3) of a single trapped laser-cooled 171Yb+ ion at 467 nm. In comparison with a previously realized optical frequency standard in 171Yb+ this E3 transition benefits from smaller systematic level shifts due to external fields and its negligible natural linewidth. Another important aspect of the new standard is its strong dependence on variations of the fine structure constant ?. A recently built probe laser system and the use of a new efficient repump scheme allows to observe Fourier transform-limited linewidths below 7 Hz and a resonant excitation probability of more than 90 %. We lock the probe laser frequency to the resonance signal of the E3 transition and use a real-time extrapolation scheme to eliminate the huge light shift induced by the probe field. The unperturbed transition frequency was measured by a comparison to a caesium fountain clock using a frequency comb generator. The resulting uncertainty was mainly limited by the systematic uncertainty of the fountain clock.

256

Ion cyclotron resonance heating in the Wisconsin Levitated Octupole  

Energy Technology Data Exchange (ETDEWEB)

Ion cyclotron resonance heating has been investigated, both experimentally and theoretically, on the Wisconsin Levitated Octupole. Heating of both ions and electrons has been observed. Typically, a two component ion energy distribution is produced (300 and 50 eV) with 500 kW of R.F. power coupled into a 5 x 10/sup 12/ cm/sup -3/ plasma. Power is coupled to the plasma with an antenna that also serves as the inductor of an oscillator tank circuit. The oscillator is tunable from 1 to 3 MHz and can be applied for periods up to 10 ms. The experiments were performed with hydrogen, gun-injected plasmas. Most of the theoretical work presented deals with a calculation that predicts the plasma loading. A slab model is used, and the questions of accessibility, polarization and damping of the evanescent radio frequency electromagnetic fields are addressed. It is found that cold plasma theory cannot account for the heating, and therefore hot plasma theory is invoked to explain the results. The loading measurements and theoretical predictions are found to be in reasonable agreement.

Fortgang, C.M.; Sprott, J.C.; Strait, E.J.

1984-04-01

257

Microstructure, mechanical properties, deformation, and fracture of V-4Ti-4Cr alloys  

International Nuclear Information System (INIS)

Full text of publication follows: The effect of the mode of thermomechanical treatment (TMT) on the microstructure, mechanical properties, mechanisms of plastic deformation, and fracture of V-4Ti-4Cr alloys has been studied. For these alloys, the TMT modes that provide a volumetrically uniform distribution of superfine particles of oxy-carbonitride phases, a substantial growth of their density, and an increase in recrystallization temperature have been substantiated. Interrelations have been found between the microstructure of the alloys and the features of their mechanical behavior, such as the level of strength and plasticity, discontinuous yielding, and an abnormal temperature dependence of strength. It has been shown that these phenomena are underlined by the high thermodynamic instability of the V-4Ti-4Cr alloys after TMT which is due to the presence of supersaturated solid solutions of titanium with interstitial elements, local inhomogeneities in composition, and superfine particles of oxy-carbonitride phases. The great variety of thermally activated obstacles that appear during TMT and mechanical tests at elevated temperatures are responsible for the significantly extended range of the anomalous temperature dependence of yield strength and the conservation of high values of strength up to T ?850 deg. C. The phenomenon of strain localization has been revealed whose temperature range coincides with the range of discontinuous yielding. The conclusion has been made that this phenomenon can be a direct reason for the discontinuous yielding that testifies to local mechanical instabilities in strain localization bands. Analysis of possible mechanisms and important features of the structural and stream instabilities of plastic flow in these bands has been performed. The TMT modes have been substantiated that provide high thermal stability of the microstructure and a significant increase in short-time strength of the V-4Ti-4Cr alloys over a wide temperature range (from 20 to 1000 deg. C), leaving rather much margin for plasticity. (authors)

258

Thermo-mechanical properties of a deformable mirror with screen printed actuator  

Science.gov (United States)

This paper reports on the thermo-mechanical modeling and characterization of a screen printed deformable mirror. The unimorph mirror offers a ceramic LTCC substrate with screen printed PZT layers on its rear surface and a machined copper layer on its front surface. We present the thermo-mechanical model of the deformable mirror based on Ansys multiphysics. The developed mirror design is practically characterized. The homogeneous loading of the optimized design results in a membrane deformation with a rate of -0.2 ?m/K, while a laser loading causes a change with a rate of 1.3 ?m/W. The proposed mirror design is also suitable to pre-compensate laser generated mirror deformations by homogeneous thermal loading (heating). We experimentally show that a 35 K pre-heating of the mirror assembly could compensate an absorbed laser power of 1.25 W.

Bruchmann, C.; Appelfelder, M.; Beckert, E.; Eberhardt, R.; Tünnermann, A.

2012-03-01

259

Effect of non-uniform deformation on properties of forged circular kilns  

International Nuclear Information System (INIS)

Non-uniformity of deformation was studied in model conditions in circular forged products from austenitic stainless steels. An extensive area with small local deformations was observed around forging edges. The study of samples from the edges and the central part of forgings showed significant differences in the microstructure, yield point and the resistance to intergranular corrosion. The results are shown in tables and graphs. (J.B.)

260

Formation of ultrafine-grained (UFG) structure and mechanical properties by severe plastic deformation (SPD)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Commercial pure cooper (99,9% Cu) was deformed by equal channel angular pressing (ECAP) using up to 10 passes, route C. The evolution of microstructure and fracture character were observed by OM, SEM and TEM. The mean grain size decreased with increasing deformation, after 10 passes to 100 – 300 nm. TEM analysis suggested the possible nanostructure formation mechanism by the formation of cellular structure in grains, forming of subgrains and then forming of high angle nanograins with random...

Besterci, M.; Kvac?kaj, T.; Koc?is?ko, R.; Bacso?, J.; Sulleiova?, K.

2008-01-01

 
 
 
 
261

Prior thermo-mechanical processing to modify structure and properties of severely deformed low carbon steel  

Science.gov (United States)

The article focuses on the severe plastic deformation (SPD) of low carbon steel AISI 1010 performed at increased temperature. The grain refinement of ferrite structure is monitored and described with respect to different initial steel structure modified by thermal and thermomechanical (TM) treatment (TM) prior severe plastic deformation. The refinement of coarse initial ferrite structure with grain size in range of 30 - 50 gm resulted from solutioning was conducted then in two steps. Preliminary structure refinement has been achieved due to multistep open die forging process and quite uniform ferrite structure with grain size of the order of gm was obtained. The further grain refinement steel structure was then accomplished during warm Equal Channel Angular Pressing (ECAP phi = 120°) at 300°C, introducing different strain in range of ?ef = 2.6 -4. The change of microstructure in dependence of the effective strain was evaluated by SEM and TEM study of thin foils. The high straining of steel resulted in extensive deformation of ferrite grains and formation of mixture of submicron grains structure in banded deformed structure with dense dislocation network and subgrains. The dynamic polygonization process, due to increased ECAP temperature, modified the submicrocrystalline structure formation. There was only indistinctive difference observed in structure refinement when considering different initial structure of steel. The tensile behaviour was characterized by strength increase followed by softening. None work hardening phenomenon appeared at tensile deformation of deformed bars.

Zrnik, J.; Lapovok, R.; Raab, G. I.

2014-08-01

262

Octupole correlations in neutron-rich 145,147La nuclei: Coriolis-limit-coupling bands with aligned h11/2 proton  

International Nuclear Information System (INIS)

Several new high-spin states are observed in the prompt ?-rays emitted from the neutron-rich, odd-Z 145,147La fragments produced in the spontaneous fission of 252Cf. Alternating parity bands are extended up to spins 41/2 and 43/2 in 145,147La, respectively. A new band completes the evidence for two sets of parity doublets expected for octupole correlations. Eight B(E1)/B(E2) ratios (four new) between two bands in 145La are all essentially constant and somewhat larger than similar ratios in 143,144Ba, where stable octupole deformation and/or correlations are reported. The new ratios out of the 31/2- levels in both nuclei show a sharp spike compared to other states, presumably from a strong reduction in E2 strengths in this backbending region. In 145La, collective bands show competition and coexistence between symmetric and asymmetric shapes. Band crossings occur in both nuclei around ???0.26 - 0.30 MeV. Their backbends are associated with the alignment of two i13/2 neutrons according to cranked shell model calculations. copyright 1999 The American Physical Society

263

Determination of the B(E3, 0{sup +} {yields} 3{sup -}) strength in the strongly octupole correlated nucleus {sup 224}Ra using Coulomb excitation at REX-ISOLDE  

Energy Technology Data Exchange (ETDEWEB)

Exploiting the unique capabilities of REX-ISOLDE to provide intense post-accelerated {sup 224}Ra radioactive ion beams we were able to Coulomb excite low-lying, low-spin levels of {sup 224}Ra. The previously accessible observables, such as the excitation energies of negative parity levels, and theoretical calculations using various models locate this nucleus to be situated in a mass-region with enhanced octupole correlations. Our collaboration was for the first time capable to Coulomb excite opposite parity levels in a post-accelerated radioactive nucleus. Indeed, apart from quasi-stable Uranium isotopes, {sup 224}Ra is the so far heaviest post-accelerated nucleus ever. A first, preliminary, B(E3, 0{sup +} {yields} 3{sup -}) value provides quantitative information about the octupole correlations in this nucleus. The results will be discussed within the context of a possible stable octupole deformation in the ground state of this nucleus. An observation, that is implicating a CP-violating nuclear Schiff moment. The latter has a strong impact on the search for CP-violating physics in the atomic system of the neighbouring odd-mass Ra-isotopes. Financial support by the BMBF under grant 06DA9036I, HIC for FAIR and the ENSAR programme is gratefully acknowledged.

Scheck, Marcus [TU Darmstadt (Germany); University of Liverpool (United Kingdom); Gaffney, Liam Paul; Butler, Peter Anthony [University of Liverpool (United Kingdom); Kroell, Thorsten [TU Darmstadt (Germany); Collaboration: IS475-Collaboration

2012-07-01

264

Deformational Structures on Smooth Manifolds  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Deformational structures, in many aspects generalizing standard elasticity theory, are investigated in abstract form. Within free deformational structures we define algebra of deformations, classify them by its special properties, define motions and conformal motions together with deformational decomposition of manifolds, generalizing isometry of Riemannian spaces and consider some physical examples. In frame of dynamical deformational structures we formulate variational pro...

Kokarev, Sergey S.

2002-01-01

265

Oxide dispersion strengthened ferritic alloys. 14/20% chromium: effects of processing on deformation texture, recrystallization and tensile properties  

International Nuclear Information System (INIS)

The ferritic oxide dispersion strengthened alloys are promising candidates for high temperature application materials, in particular for long life core components of advanced nuclear reactors. The aim of this work is to control the microstructure, in order to optimise the mechanical properties. The two ferritic alloys examined here, MA956 and MA957, are obtained by Mechanical Alloying techniques. They are characterised by quite anisotropic microstructure and mechanical properties. We have investigated the influence of hot and cold working processes (hot extrusion, swaging and cold-drawing) and recrystallization heat treatments on deformation textures, microstructures and tensile properties. The aim was to control the size of the grains and their anisotropic shape, using recrystallization heat treatments. After consolidation and hot extrusion, as-received materials present a extremely fine microstructure with elongated grains and a very strong (110) deformation texture with single-crystal character. At that stage of processing, recrystallization temperature are very high (1450 degrees C for MA957 alloy and 1350 degrees C for MA956 alloy) and materials develop millimetric recrystallized grains. Additional hot extrusion induce a fibre texture. Cold-drawing maintains a fibre texture, but the intensity decreases with increasing cold-work level. For both materials, the decrease of texture intensities correspond to a decrease of the recrystallization temperatures (from 1350 degrees C for a low cold-work level to 750 degrees C for 60 % cold-deformation, case of MA956 alloy) and a refinement of the grain size (from a millimetric size to less than an hundred of micrometer). Swaging develop a cyclic component where the intensity increases with increasing deformation in this case, the recrystallization temperature remains always very high and the millimetric grain size is slightly modified, even though cold-work level increases. Technologically, cold-drawing is the only way that permits the decreasing of the recrystallization temperature of several hundred degrees and giving the best compromise between mechanical strength and ductility. (author). 72 refs., 6 appends

266

Interseismic deformation along the Mexican Subduction Zone: GPS-constrained coupling, and relationships with seismic and aseismic fault behavior, long term deformation and fault properties  

Science.gov (United States)

Recent observations have shown that a large diversity of mechanisms accommodates the deformation on subduction zones interfaces, especially with the discovery of slow slip events. Our study aims at comparing Oaxaca and Guerrero areas in the Mexican subduction zone. In these two areas, slow slip events have been discovered in the vicinity of seismic gaps, as well as tremor activity. We derive a regional, interseismic coupling map based on continuous GPS. It reveals lateral variations of coupling at shallow depth (0-25 km, offshore), with two well coupled zones (coupling > 0.7) alternating with two low coupled zones (coupling 0.7 as well), with a down dip, northern limit between coupled and uncoupled areas that is laterally homogeneous, at a distance of 170 km from the trench. Coupling spatial variations are first analyzed with respect to the spatial extension of Slow Slip Events, Tremors and Earthquakes. The analysis of the long-term morphology (bathymetry, topography, sedimentation, gravity) also highlights longitudinal variations, consistent in overall with the GPS-derived coupling variations. This suggests that these coupling variations are, to the first order, persistent over geological time scales (10^6 yr), and representative of fault plane properties that influence the building of the morphology. A mechanical analysis based on the critical tapper theory aims at reconciling geodetic observations and long term observations by determining lateral variations of frictional properties on critical areas of the subduction interface.

Rousset, B.; Graham, S. E.; Cubas, N.; Radiguet, M.; Lasserre, C.; Socquet, A.; Campillo, M.; Walpersdorf, A.; Cotte, N.; DeMets, C.

2013-12-01

267

The effect of post-deformation aging on superelastic properties of Ni50.9Ti thin wires attaining micro and nano-substructure  

International Nuclear Information System (INIS)

Highlights: ? Precipitation of Ni4Ti3 during aging at 450 °C is hindered after severe cold work. ? Nanostructure formation improves the superelastic behavior of Ni-rich NiTi. ? Deformations less than 0.4 result in work hardening and reduce plateau strain. ? Deformations more than 0.4 yield in high stress and strain values of upper plateau. -- Abstract: Superelastic properties of Ni50.9Ti shape memory wires were studied after cold drawing and post-deformation annealing at 450 °C. Characteristic transformation temperatures were determined using differential scanning calorimetry. Microstructural investigations were performed using optical and transmission electron microscopy. Results indicate that deformations more than 0.4 of true strain yield in high stress and high strain values of upper plateau. On the other hand, deformations less than 0.4 result in work hardening and reduce plateau strain. Post-deformation heat treatment at 450 °C leads to precipitation of Ni4Ti3 particles and development of recovered microstructure in slightly cold drawn wires. Post-deformation annealing of wires with cold work value of 0.6 in true strain develop nanocrystalline microstructure and hindered the formation of Ni4Ti3 precipitates. Precipitation of Ni4Ti3 particles improves the superelastic properties of not cold drawn wires. However, in comparison with annealed and aged wires, severely deformed wires attain better superelastic properties after annealing at 450 °C without any Ni4Ti3 precipitates

268

Effect of multiaxial deformation Max-strain on the structure and properties of Ti-Ni alloy  

Science.gov (United States)

The severe plastic deformation (SPD) forming ultrafine-grained (nanocrystalline or nanosubgrained) structure is one of the most effective ways to improve the functional properties of Ti-Ni-based shape memory alloys [1, 2]. In the present work, the SPD of near-equiatomic Ti-Ni alloy was carried out using the multi-axial deformation module Max-strain, which is a part of the physical simulation system "Gleeble 3500". The deformation was performed at a constant temperature of 400°C with speed of 0.5 mm/s in six passes without interpass pauses. The accumulated true strain was about 3. As a result, a mixed ultrafine-grained/subgrained structure with grain/subgrain sizes from 50 to 300 nm and a high density of free dislocations formed. The resulting structure is close to a nanoscale region and provides a significant advantage in the basic functional property - completely recoverable strain - as compared with a conventional recrystallized structure: 7% versus 2%.

Khmelevskaya, I. Yu; Kawalla, R.; Prokoshkin, S. D.; Komarov, V. S.

2014-08-01

269

Cold deformation effect on the microstructures and mechanical properties of AISI 301LN and 316L stainless steels  

International Nuclear Information System (INIS)

As austenitic stainless steels have an adequate combination of mechanical resistance, conformability and resistance to corrosion they are used in a wide variety of industries, such as the food, transport, nuclear and petrochemical industries. Among these austenitic steels, the AISI 301LN and 316L steels have attracted prominent attention due to their excellent mechanical resistance. In this paper a microstructural characterization of AISI 301LN and 316L steels was made using various techniques such as metallography, optical microscopy, scanning electronic microscopy and atomic force microscopy, in order to analyze the cold deformation effect. Also, the microstructural changes were correlated with the alterations of mechanical properties of the materials under study. One of the numerous uses of AISI 301LN and 316L steels is in the structure of wagons for metropolitan surface trains. For this type of application it is imperative to know their microstructural behavior when subjected to cold deformation and correlate it with their mechanical properties and resistance to corrosion. Microstructural analysis showed that cold deformation causes significant microstructural modifications in these steels, mainly hardening. This modification increases the mechanical resistance of the materials appropriately for their foreseen application. Nonetheless, the materials become susceptible to pitting corrosion.

270

Minus-I quadrupole system for containing aberration-correction octupoles  

International Nuclear Information System (INIS)

Octupoles may be used to correct the third order spherical aberration of quadrupole transport systems. Crosstalk in the coupling of an octupole placed at a given point causes it to add a term with the wrong sign in the y-channel if it has the right sign in the x-channel, thus severely reducing efficiency. It is often convenient to utilize a special correcting section insertion which is seen as a +I transfer matrix by the first order focusing. Within point-to-point thin lens optics we give two-parameter systems with 16 magnets having locations with large S/sub x/ where S/sub y/ = 0 and vice versa for octupole placement

271

Influence of Nekhoroshev's criterion on dynamical aperture of circular accelerator with octupole lenses families  

International Nuclear Information System (INIS)

Soviet mathematician N.Nekhoroshev has shown that if the Hamiltonian of a system satisfies definite conditions (Nekhoroshev's criterion) then this system is stable (in Nekhoroshev's sense). This paper is devoted to study of Nekhoroshev's criterion influence on dynamical aperture (DA) of the ring including two families of octupole lenses for increase of betatron tunes spread and suppressing of transverse coherent instabilities. Two lattices have been designed: one lattice with strong modulation of beta-functions (which allows us to satisfy Nekhoroshev's criterion for octupole families) and the second lattice where this criterion is not satisfied. For both lattices the dependence of DA on octupole families current was calculated with account of systematic and random errors of magnetic field. The calculations have shown that for both lattices the DA is decreased with increase of the current; for the first lattice (where Nekhoroshev's criterion is satisfied) this effect is weaker than for the second one

272

Mechanical properties and local mobility of atactic-polystyrene films under constant-shear deformation.  

Science.gov (United States)

We have performed molecular-dynamics simulations of atactic polystyrene thin films to study the effect of shear rate, pressure, and temperature on the stress-strain behaviour, the relevant energetic contributions and non-affine displacements of polymer chains during constant-shear deformation. Under this deformation sliding motion is observed at high shear rates between the top substrate and top polymer layer, which disappears when the shear rate decreases. At low shear rates stick-slip motion of the whole film with respect to the bottom substrate takes place. We found that at low shear rates the yield stress logarithmically depends on the shear rate; this behaviour can be explained in terms of the Eyring model. It was also observed that an increase in the normal pressure leads to an increase in the yield stress in agreement with experiments. The contributions to the total shear stress and energy are mainly given by the excluded-volume interactions. It corresponds to a local translational dynamics under constant shear in which particles are forced to leave their original cages much earlier as compared to the case of the isotropic, non-sheared film. Moreover, it was observed that under constant-shear deformation the polymer glass is deformed non-affinely. As a result, the middle part of the film is much more deformed than the layers close to the supporting substrates, meaning that the well-known effect of shear-banding occurs. PMID:23020347

Hudzinskyy, D; Michels, M A J; Lyulin, A V

2012-09-28

273

Deformation and energy absorption properties of powder-metallurgy produced Al foams  

Energy Technology Data Exchange (ETDEWEB)

Highlights: {yields} Porous Al fabricated via a dissolution and sintering method using raw cane sugar. {yields} Different deformation mode depending on the relative density of the foams. {yields} Enhanced energy absorption by reducing pore size and relative density of the foam. {yields} Pore size uniformity and sintering temperature affect energy absorption. - Abstract: Al-foams with relative densities ranging from 0.30 to 0.60 and mean pore sizes of 0.35, 0.70 and 1.35 mm were manufactured by a powder metallurgy technology, based on raw cane sugar as a space-holder material. Compressive tests were carried out to investigate the deformation and energy absorbing characteristics and mechanisms of the produced Al-foams. The deformation mode of low density Al-foams is dominated by the bending and buckling of cell walls and the formation of macroscopic deformation bands whereas that of high density Al-foams is predominantly attributed to plastic yielding. The energy absorbing capacity of Al-foams rises for increased relative density and compressive strength. The sintering temperature of Al-foams having similar relative densities has a marked influence on both, energy absorbing efficiency and capacity. Pore size has a marginal effect on energy efficiency aside from Al-foams with mean pore size of 0.35 which exhibit enhanced energy absorption as a result of increased friction during deformation at lower strain levels.

Michailidis, N., E-mail: nmichail@eng.auth.gr [Physical Metallurgy Laboratory (PML), Mechanical Engineering Department, Aristotle University of Thessaloniki, GR 54124 Thessaloniki (Greece); Stergioudi, F. [Physical Metallurgy Laboratory (PML), Mechanical Engineering Department, Aristotle University of Thessaloniki, GR 54124 Thessaloniki (Greece); Tsouknidas, A. [Mechanical Engineering Department, Technical University of Western Macedonia, 50100 Kozani (Greece)

2011-09-15

274

Deformation and energy absorption properties of powder-metallurgy produced Al foams  

International Nuclear Information System (INIS)

Highlights: ? Porous Al fabricated via a dissolution and sintering method using raw cane sugar. ? Different deformation mode depending on the relative density of the foams. ? Enhanced energy absorption by reducing pore size and relative density of the foam. ? Pore size uniformity and sintering temperature affect energy absorption. - Abstract: Al-foams with relative densities ranging from 0.30 to 0.60 and mean pore sizes of 0.35, 0.70 and 1.35 mm were manufactured by a powder metallurgy technology, based on raw cane sugar as a space-holder material. Compressive tests were carried out to investigate the deformation and energy absorbing characteristics and mechanisms of the produced Al-foams. The deformation mode of low density Al-foams is dominated by the bending and buckling of cell walls and the formation of macroscopic deformation bands whereas that of high density Al-foams is predominantly attributed to plastic yielding. The energy absorbing capacity of Al-foams rises for increased relative density and compressive strength. The sintering temperature of Al-foams having similar relative densities has a marked influence on both, energy absorbing efficiency and capacity. Pore size has a marginal effect on energy efficiency aside from Al-foams with mean pore size of 0.35 which exhibit enhanced energy absorption as a result of increased friction during deformation at lower strain levels.

275

? decay of 227Pa and 225Pa and octupole deformation in 223Ac  

International Nuclear Information System (INIS)

An ?-decay study of 227Pa populating levels in 223Ac and 221Ac is reported. Using the LIGISOL facility we produced 227Pa via a (p,6n)-reaction on 232Th and 225Pa via a (p,6n)-reaction on 230Th. Many experiments were performed in order to get level-scheme information. In case of 227Pa multiscaled ?-singles spectra (using PIPS detectors),(?,?,t)- (?,X,t) coincidences (using a LEGe-type detector) and (?,e-,t) coincidences (using a cooled Si(Li) detector) were taken. In addition, a fast timing setup of an ? detector and a plastic or BaF2 scintillator were used to determine the halflife of 223Ac levels. In case of 225Pa only ?-singles spectra were accumulated. (author)

276

Plasma Confinement in a Toroidal Octupole Magnetic Field  

International Nuclear Information System (INIS)

The confinement of low-density (n = 109 cm-3) collisionless plasmas with Ti ? 40 eV, Te ? 10 eV produced by gun injection or with Te ? 1 eV. Ti -3of the Bohm diffusion coefficient which was not large enough to produce the observed radial loss. Studies were also made to determine the importance of low-frequency fluctuations or convective cells which may have been produced by injection, magnetic field perturbations or azimuthal density variations. The addition of a toroidal magnetic field decreased the lifetime slightly and generated large-scale convective cells in the shearless layer near the plasma surface. Currents parallel to the magnetic field have been observed which must be considered in determining the cause of increased fluctuation with the increase of the toroidal field. The mechanical supports were also guarded with magnetic dipoles in the manner proposed by Lehnert. The plasma flux to one of the supports was reduced for the hot ion plasma by an order of magnitude when there was one ion gyroradius between the mechanical support and the guard field separatrix. However, the plasma flux along the guard field separatrix increased to the value of the original support flux and there was a negligible ( ? 20%) improvement of the lifetime. An inductively excited, magnetically force-free octupole is being assembled with transiently withdrawn supports to eliminate the plasma loss to hoop supports. The device will provide at least 10 msec of experimental time during which only 5% of the magnetic flux diffuses into the internal hoops. 100 eV protons will have 15 gyroradii on each side of the separatrix. (author)

277

f-Deformed Squeezed Vacuum and First Excited States, Their Superposition and Corresponding Nonclassical Properties  

Science.gov (United States)

In this paper, we introduce two new classes of nonlinear squeezed states that we name as f-deformed squeezed vacuum state |?, f>even and f-deformed squeezed first excited state |?, f>odd, which according to their production processes, essentially include only even and odd bases of Fock space, respectively. In the continuation, we introduce the superposition of these two distinct nonlinear squeezed states with a respective phase ?. Then, some of the criteria which imply the nonclassicality of the states, such as Mandel parameter, second-order correlation function, quadrature squeezing, amplitude-squared squeezing, Husimi and Wigner-Weyl quasi-distribution functions, are numerically examined. At last, by considering a well-known nonlinearity function associated with a nonlinear physical system, we present our results which outcome from the numerical calculations. It is shown that, the introduced f-deformed states can reveal high nonclassical features.

NoormandiPour, A.; M. K., Tavassoly

2014-04-01

278

Properties of heterogeneous energetic materials under high strain, high strain rate deformation  

Science.gov (United States)

Heterogeneous energetic materials have many applications. Their dynamic behavior and microstructural evolution upon plastic deformation have remained not fully understood. The following heterogeneous materials were investigated in the this study: the pure PTFE (usually a mixture of crystalline and amorphous phases), PTFE-Sn, PTFE-Al, PTFE-Al-W, and carbon fibers filled Al alloy. Sample manufacturing processes involving ball milling and Cold Isostatic Pressing were employed. Quasi-static and Hopkinson bar tests were carried out to obtain the compressive strengths of composites. The Conventional Thick-walled Cylinder (TWC) method and newly developed small-scale Hopkinson bar based TWC experiments were conducted to investigate single shear bands and their assembly. Conventional and "soft" drop-weight tests were performed to examine the mechanical properties and the initiation of chemical reactions. Scanning Electron Microscopy was used to detect the details of the microstructures and failure mechanisms of heterogeneous materials. New features in the dynamic behavior of heterogeneous materials were observed. They include the following: (1) Strain softening, instead of thermal softening, is the main mechanism in the initiation of shear bands in explosively driven TWC tests of solid PTFE. (2) Cold isostatically pressed PTFE-Sn samples were more stable with respect to shear localization than solid PTFE. (3) The dynamic collapse of solid PTFE-Al samples with different particle sizes was accomplished with the shear localization bands and cracks. (4) Force chains in the fine W and Al particles were attributed to the high strength of the porous PTFE-Al-W composite containing fine W particles in comparison with composites with coarse W particles. (5) Debonding of metal particles from the PTFE matrix and the fracture of the matrix were identified to be two major mechanisms for the failure of the PTFE-Al-W composites. (6) The formation of PTFE nano-fibers during high strain flow was detected. (7) The orientation of carbon fibers did not influence the strength and reaction of carbon fibers filled Al alloys, but the strength of carbon fibers did.

Cai, Jing

279

Steel Processing Properties and Their Effect on Impact Deformation of Lightweight Structures  

Energy Technology Data Exchange (ETDEWEB)

The objective of the research was to perform a comprehensive computational analysis of the effects of material and process modeling approaches on performance of UltraLight Steel Auto Body (ULSAB) vehicle models. The research addressed numerous material related effects, impact conditions as well as analyzed the performance of the ULSAB vehicles in crashes against designs representing the current US vehicle fleet. This report is organized into three main sections. The first section describes the results of the computational analysis of ULSAB crash simulations that were performed using advanced material modeling techniques. The effects of strain-rate sensitivity on a high strength steel (HSS) intensive vehicle were analyzed. Frontal and frontal offset crash scenarios were used in a finite element parametric study of the ULSAB body structure. Comparisons are made between the crash results using the piece-wise-linear isotropic plasticity strain-rate dependent material model, and the isotropic plasticity material model based on quasi-static properties. The simulation results show the importance of advanced material modeling techniques for vehicle crash simulations due to strain-rate sensitivity and rapid hardening characteristics of advanced high strength steels. Material substitution was investigated for the main frontal crush structure using the material of similar yield stress a significantly different strain-rate and hardening characteristics. The objective of the research presented in Section 2 was to assess the influence of stamping process on crash response of ULSAB vehicle. Considered forming effects included thickness variations and plastic strain hardening imparted in the part forming process. The as-formed thickness and plastic strain for front crash parts were used as input data for vehicle crash analysis. Differences in structural performance between crash models with and without forming data were analyzed in order to determine the effects and feasibility of integration of forming processes and crash models. Computational analysis of vehicle-to-vehicle crashes between ULSAB and conventional car designs is reported in Section 3. The study involved vehicles of comparable weights and dimensions to assess the compatibility of the ULSAB with existing designs. Deformation and acceleration data for crashed vehicles were analyzed. Vehicle-modeling approaches have strong influence on computational results and the requirements for compatibility of models were identified for future research on vehicle-to-vehicle crash modeling.

Simunovic, S

2003-09-23

280

Formation of ultrafine-grained (UFG structure and mechanical properties by severe plastic deformation (SPD  

Directory of Open Access Journals (Sweden)

Full Text Available Commercial pure cooper (99,9% Cu was deformed by equal channel angular pressing (ECAP using up to 10 passes, route C. The evolution of microstructure and fracture character were observed by OM, SEM and TEM. The mean grain size decreased with increasing deformation, after 10 passes to 100 – 300 nm. TEM analysis suggested the possible nanostructure formation mechanism by the formation of cellular structure in grains, forming of subgrains and then forming of high angle nanograins with random orientation. Fractures of ECAP Cu material after 10 passes had transcrystalline ductile character with dimple morphology.

M. Besterci

2008-10-01

 
 
 
 
281

Specifications of the octupole magnets required for the ATF2 ultra-low ß* lattice  

Energy Technology Data Exchange (ETDEWEB)

The Accelerator Test Facility 2 (ATF2) aims to test the novel chromaticity correction for higher chromaticity lattices as the one of CLIC. To this end the ATF2 ultra-low ß* lattice is designed to vertically focus the beam at the focal point or usually referred to as interaction point (IP), down to 23 nm. However when the measured multipole components of the ATF2 magnets are considered in the simulations, the evaluated spot sizes at the IP are well above the design value. The designed spot size is effectively recovered by inserting a pair of octupole magnets. In this note we address the technical specifications required for these octupole magnets.

Marin, E.; /SLAC; Modena, M.; /CERN; Tauchi, T.; Terunuma, N.; /KEK, Tsukuba; Tomas, R.; /CERN; White, G.R.; /SLAC

2014-05-28

282

Octupole correlations in superdeformed mercury and lead nuclei: A generator-coordinate method analysis  

Science.gov (United States)

Axial and non-axial octupole excitations built on superdeformed states of zero spin in 192,194Hg and 194Pb nuclei are studied within the fully microscopic generator-coordinate method using selfconsistent Hartree-Fock BCS states as a basis. Results with the effective interaction SkM ? predict vibration energies of 1.9-2.5 MeV, B(E3) values of 15-37 single-particle units and unusually large B(E1) transition rates up to 0.02 W.u. Calculations including both octupole modes with K = 0 and K = 2 indicate that these modes couple weakly.

Skalski, J.; Heenen, P.-H.; Bonche, P.; Flocard, H.; Meyer, J.

1993-01-01

283

Octupole correlations in superdeformed mercury and lead nuclei: A generator-coordinate method analysis  

International Nuclear Information System (INIS)

Axial and non-axial octupole excitations built on superdeformed states of zero spin in 192,194Hg and 194Pb nuclei are studied within the fully microscopic generator-coordinate method using selfconsistent Hartree-Fock BCS states as a basis. Results with the effective interaction SkM* predict vibration energies of 1.9-2.5 MeV, B(E3) values of 15-37 single-particle units and unusually large B(E1) transition rates up to 0.02 W.u. Calculations including both octupole modes with K=0 and K=2 indicate that these modes couple weakly. (orig.)

284

Effect of various mechanical deformation on the properties of silver-clad bi-2223 composites  

International Nuclear Information System (INIS)

While the wire processing method was found to produce no noticeable difference in the silver/core interface, the tape forming technique resulted in significantly different interface. Pressing produced more wavy silver/core interface (sausaging) than flat-rolling and transverse rolling. Cracks were also found common in pressed samples, but rare in flat-rolled and transverse-rolled samples. Furthermore, the direction of sausaging was found to be dependent on the mechanical deformation technique used, i.e., along the length of tape in pressed and transverse-rolled samples and along the width of tape in flat-rolled tapes. The green tapes were heat treated using a thermomechanical process consisting of alternate mechanical deformation and sintering. For comparison, a control tape in which no deformation was used between sinterings was also prepared using the same sintering conditions. After each step of heat treatment, tapes were characterised in terms of high-Tc phase fraction, microstructure and critical current density (Jc). The results indicated that the mechanical deformation accelerated the Bi-2223 phase formation rate, in particular, the pressed samples showed the fastest Bi-2223 phase formation rate. For the Jc, pressing yielded the highest value, probably due to the high density and excellent grain alignment in the pressed tapes

285

Study on the testing method and procedures for engineering properties of NPP site : compressive strength and rock mass deformation modulus  

International Nuclear Information System (INIS)

This study have been carried out for attempting to develop the minimum requirements of testing methods and procedures for determining engineering properties for foundation bedrock at NPP site. As a first phase study, for the compressive strength and deformation modulus of rock important to the safety evaluation of the bearing capacity and settlement of the foundation, the testing methods and procedures for determining the two characteristic values were reviewed and comparison between each value of the sites under studying was carried out. The data originated from Wolsong 1 spent fuel dry storage site and the NPP sites of Yonggwang 3 · 4, Wolsong 2·3·4, and Ulchin 3·4. Also, re-evaluation was made for the data excluded from original analysis, and especially re-calculation of rock mass deformation modulus of Wolsong unit 2 was conducted by using the settlement data. The analysis result show that the uniaxial compressive and point load tests had been conducted for compressive strength and the jack test, hydraulic pressure meter test, and correlation methods using RQD, RMR, and velocity index were conducted for rock mass deformation modulus. It is also found that there was a tendency to decide characteristic values by selecting the lower value among various test results rather than considering the credibility of the test results

286

Thermal-deformation effect of welding on A 1 reactor pressure vessel weld joints properties and state of stress  

International Nuclear Information System (INIS)

The methods are compared of electroslag welding and of arc welding with a view to their possible application in welding the Bohunice A-1 reactor pressure vessel. Considered are the thermal deformation effects of welding on the physical properties and the stress present in welded joints. For testing, plates were used having the dimensions of 1100x2300x200 mm and rings with 4820 mm outer diameter, 1800 mm height and 170 mm thickness made of steel CSN 413O30 modified with Ni, Al+Ti. The deformation effect of welding on the residual surface and triaxial stress, the specific stored energy, the initiation temperature of brittle crack and the critical size of the initiation defect corresponding to the thermal deformation effect of welding were determined. It was found that for electroslag welding, there is a low probability of crack formation in the joints, a low level of residual stress and a low level of specific stored energy in a relatively wide joint zone. For arc welding there is a considerable probability of defect formation in the vicinity of the sharp boundary of the joint, a high level of the triaxial state of stress in the tensile region, and a high level of specific stored energy concentrated in the narrow zone of weld joints. The recommended thermal process is given for welding pressure vessels made of the CSN 413030 steel modified with Ni, Al+Ti, and 150 to 200 mm in thickness. (J.P.)

287

Scale effects of nanomechanical properties and deformation behavior of Au nanoparticle and thin film using depth sensing nanoindentation.  

Science.gov (United States)

Nanoscale research of bulk solid surfaces, thin films and micro- and nano-objects has shown that mechanical properties are enhanced at smaller scales. Experimental studies that directly compare local with global deformation are lacking. In this research, spherical Au nanoparticles, 500 nm in diameter and 100 nm thick Au films were selected. Nanoindentation (local deformation) and compression tests (global deformation) were performed with a nanoindenter using a sharp Berkovich tip and a flat punch, respectively. Data from nanoindentation studies were compared with bulk to study scale effects. Nanoscale hardness of the film was found to be higher than the nanoparticles with both being higher than bulk. Both nanoparticles and film showed increasing hardness for decreasing penetration depth. For the film, creep and strain rate effects were observed. In comparison of nanoindentation and compression tests, more pop-ins during loading were observed during the nanoindentation of nanoparticles. Repeated compression tests of nanoparticles were performed that showed a strain hardening effect and increased pop-ins during subsequent loads. PMID:24991519

Maharaj, Dave; Bhushan, Bharat

2014-01-01

288

Atomic structure and magnetic properties of the Ni50Mn50 alloy disordered by shear deformation under pressure  

International Nuclear Information System (INIS)

A comprehensive study is made into structural and phase transformations and physical properties of ordered equiatomic nickel-manganese alloy subjected to high shear strains under high pressure. The state of the alloy is investigated using methods of EXAFS-spectroscopy, neutron and X-ray diffraction analyses, transmission electron microscopy, metallography and magnetometry. It is revealed that severe deformations result in chemical disordering of components on formation of nanocrystalline structure with grain size of the order of 20 nm. As it takes place an initially antiferromagnetic ordered BCT phase transforms into a disordered antiferromagnetic FCC phase with Neel temperature of 280 K

289

Tailoring the Mechanical Properties of a Twinning-Induced Plasticity Steel by Retention of Deformation Twins During Heat Treatment  

Science.gov (United States)

The relation between microstructure and mechanical properties of a 30 pct cold-rolled, recovery-annealed, and recrystallization-annealed Fe-23Mn-1.5Al-0.3C twinning-induced plasticity (TWIP) steel was studied. The thermal stability of deformation-induced twin boundaries along with a reduced dislocation density due to annihilation during recovery annealing at 903 K (630 °C) was found to be a simple, promising processing route to overcome the shortcoming of low yield strength usually associated with TWIP steels.

Haase, Christian; Barrales-Mora, Luis Antonio; Molodov, Dmitri A.; Gottstein, Günter

2013-10-01

290

New level schemes and octupole correlations of light neutron-rich lanthanum isotopes {sup 143,144}La  

Energy Technology Data Exchange (ETDEWEB)

The yrast and near-yrast level scheme of light neutron-rich {sup 143}La (Z=57, N=86) is reinvestigated and expanded and that of {sup 144}La (N=87) is proposed for the first time by measuring prompt {gamma} rays from the spontaneous fission of {sup 252}Cf at Gammasphere. Spins/parities are assigned to the lowest-lying levels of {sup 143,144}La based on the early studies of {beta}{sup -} decay, and the assignments for high-spin levels of {sup 143,144}La are made by measuring internal conversion coefficients and following the level systematics of the neighboring heavier La isotopes and even-even Ba and Ce nuclei. The B(E1)/B(E2) ratios, energy displacements {delta}E(I) and rotational frequency ratios {omega}{sup -}(I)/{omega}{sup +}(I) of the new parity-doublets of {sup 143,144}La indicate that octupole deformations/correlations also develop in these nuclei. The band-crossings observed in a rotational frequency range of 0.31 to 0.34 MeV for the two even-parity bands in {sup 143}La but being absent in {sup 144}La are interpreted as due to alignment of a pair of i{sub 13/2} neutrons in {sup 143}La.

Luo, Y.X. [Physics Department, Vanderbilt University, Nashville, TN 37235 (United States); Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Hamilton, J.H. [Physics Department, Vanderbilt University, Nashville, TN 37235 (United States); Rasmussen, J.O. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)], E-mail: jorasmussen@lbl.gov; Ramayya, A.V.; Goodin, C. [Physics Department, Vanderbilt University, Nashville, TN 37235 (United States); Zhu, S.J. [Physics Department, Vanderbilt University, Nashville, TN 37235 (United States); Physics Department, Tsinghua University, Beijing 100084 (China); Hwang, J.K.; Li, Ke; Fong, D. [Physics Department, Vanderbilt University, Nashville, TN 37235 (United States); Stefanescu, I. [Department of Chemistry and Biochemistry, University of Maryland, MD 20742 (United States); Lee, I.Y. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Ter-Akopian, G.M. [Flerov Laboratory for Nuclear Reactions, JINR, Dubna (Russian Federation); Daniel, A.V. [Physics Department, Vanderbilt University, Nashville, TN 37235 (United States); Flerov Laboratory for Nuclear Reactions, JINR, Dubna (Russian Federation); Joint Institute for Heavy Ion Research, Oak Ridge, TN 37831 (United States); Stoyer, M.A. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Donangelo, R. [Universidade Federal do Rio de Janeiro, CP 68528, RG (Brazil); Ma, W.C. [Mississippi State University, Drawer 5167, Mississippi State, MS 39762 (United States); Cole, J.D. [Idaho National Laboratory, Bldg. IRCPL, MS2114, Idaho Falls, ID 83415 (United States)

2009-03-01

291

Creation of freestanding wrinkled nano-films with desired deformation properties by controlling the surface morphology of a sacrificial layer  

Science.gov (United States)

Various wrinkle patterns can be formed due to the buckling of a stiff thin film on a compliant substrate. However, most wrinkled films previously reported were fixed on a large deformable substrate and thereby the potential deformability of the film was mechanically constrained by the substrate. In this study, we developed a technique for forming various wrinkled structures on the surface of a sacrificial resin layer. Since the sacrificial layer can be subsequently removed with a solvent, freestanding wrinkled films are created using the sacrificial layer. We found that a wrinkled structure is formed on the surface of the layer by applying a compressive strain to the resin layer at the appropriate moment during the hardening process. The wrinkle pattern depends on the curing time and the timing of the straining in two in-plane orthogonal directions. In addition to conventional stripe and labyrinth patterns by simple uniaxial and equi-biaxial strains, respectively, it was found that independent biaxial strains induce interesting structures, such as an orthogonally ordered wrinkle pattern and a nonsymmetrical buckling structure, in which the stripe array produced by the first straining remains and many finer wrinkles appear in each stripe by the second straining in the orthogonal direction. We conducted tensile experiments for 300-nm-thick freestanding Cu films having these wrinkled structures. The wrinkled nano-films have a variety of mechanical properties: the stripe structure has extremely high deformability (more than 10% strain) and reversibility, the labyrinth structure shows planar isotropic deformation, and the nonsymmetrical buckling structure has an anisotropic modulus and strength. Finite element analysis on the wrinkle structures revealed that the local stress concentration dominates the fracture limits.

Hirakata, Hiroyuki; Maruyama, Tomohiro; Yonezu, Akio; Minoshima, Kohji

2013-05-01

292

Mechanical properties and deformation micromechanics of rubber-toughened acrylic polymers  

Energy Technology Data Exchange (ETDEWEB)

The tensile and impact properties of a range of rubber toughened acrylic polymers has been investigated. The effects of acrylic-matrix properties and toughening-particle composition, morphology, size, and level of inclusion on mechanical properties and fracture properties are discussed.

Lovell, P.A.; Sherratt, M.M.; Young, R.J. [Univ. of Manchester (United Kingdom)

1996-12-31

293

Nanocrystalline structures and tensile properties of stainless steels processed by severe plastic deformation  

Science.gov (United States)

The development of nanocrystalline structures in austenitic stainless steels during large strain cold rolling and their tensile behavior were studied. The cold rolling to total equivalent strains above 2 was accompanied by the evolution of nanocrystalline structures with the transverse grain size of about 100 nm. The development of deformation twinning and martensitic transformation during cold working promoted the fast kinetics of structural changes. The development of nanocrystalline structures resulted in significant strengthening. More than fourfold increase in the yield strength was achieved. The strengthening of nanocrystalline steels after severe plastic deformation was considered as a concurrent operation of two strengthening mechanisms, which were attributed to grain size and internal stress. The contribution of internal stresses to the yield strength is comparable with that from grain size strengthening.

Belyakov, A.; Odnobokova, M.; Kipelova, A.; Tsuzaki, K.; Kaibyshev, R.

2014-08-01

294

Effect of deformation on the thermoluminescent properties of LiF and TLD 100 dosimeter crystals  

International Nuclear Information System (INIS)

The response to ionizing radiation of LiF and TLD 100 dosimeter grade LiF, following various amounts of plastic deformation, has been investigated. The decrease in thermoluminescence with increasing plastic strain has been interpreted in terms of two models: (a) the thermoluminescence traps are destroyed by intersection or interaction with dislocation lines; (b) new thermoluminescence traps are created by dislocation intersections which then compete with the previously existing traps. The latter model is considered the more likely. (author)

295

Effect of vacuum-treatment on deformation properties of PMMA bone cement.  

Science.gov (United States)

Deformation behavior of polymethyl methacrylate (PMMA) bone cement is explored using microindentation. Two types of PMMA bone cement were prepared. Vacuum treated samples were subjected to the degassing of the material under vacuum of 270 mbar for 35 s, followed by the second degassing under vacuum of 255 mbar for 35 s. Air-cured samples were left in ambient air to cool down and harden. All samples were left to age for 6 months before the test. The samples were then subjected to the indentation fatigue test mode, using sharp Vickers indenter. First, loading segment rise time was varied in order to establish time-dependent behavior of the samples. Experimental data showed that viscous part of the deformation can be neglected under the observed test conditions. The second series of microindentation tests were realized with variation of number of cycles and indentation hardness and modulus were obtained. Approximate hardness was also calculated using analysis of residual impression area. Porosity characteristics were analyzed using CellC software. Scanning electron microscopy (SEM) analysis showed that air-cured bone cement exhibited significant number of large voids made of aggregated PMMA beads accompanied by particles of the radiopaque agent, while vacuum treated samples had homogeneous structure. Air-cured samples exhibited variable hardness and elasticity modulus throughout the material. They also had lower hardness values (approximately 65-100 MPa) than the vacuum treated cement (approximately 170 MPa). Porosity of 5.1% was obtained for vacuum treated cement and 16.8% for air-cured cement. Extensive plastic deformation, microcracks and craze whitening were produced during indentation of air-cured bone cement, whereas vacuum treated cement exhibited no cracks and no plastic deformation. PMID:22100087

Zivic, Fatima; Babic, Miroslav; Grujovic, Nenad; Mitrovic, Slobodan; Favaro, Gregory; Caunii, Mihaela

2012-01-01

296

Influence of Hot Deformation on Mechanical Properties and Microstructure of a Twin-Roll Cast Aluminium Alloy EN AW-6082  

Science.gov (United States)

Thin strips of medium- and high-strength age-hardening aluminium alloys are widely used in the automotive industry. Reducing their production costs caused by high energy consumption is an actual challenge. The implementation of the twin-roll casting technology is promising. However, mechanical properties of directly cast high-alloyed thin aluminium strips are oftentimes inadequate to standard specifications. In this work, the influence of a hot deformation following a twin-roll cast strip process on the mechanical properties and microstructure is investigated. For this study strips of age-hardening aluminium alloy EN AW-6082—manufactured at a laboratory scaled twin-roll caster—were single-pass rolled at temperatures of 420 °C and true strains of up to 0.5. The mechanical properties of the as-cast and by different strains hot deformed material in the soft-annealed and age-hardened states were characterized by tensile tests. The results reveal that the twin-roll cast material features the necessary strength properties, though it does not meet the standard requirements for ductility. Furthermore, the required minimum strain during hot rolling that is necessary to ascertain the standard specifications has been determined. Based on micrographs, the uniformity of the mechanical properties and of the microstructure as a result of recrystallization due to hot metal forming and heat treatment were determined. A fine-grain microstructure and satisfactory material ductility after prior rolling with a true strain above 0.41 for the age-hardened state T6 and above 0.1 for the soft-annealed state O have been established.

Grydin, O.; Stolbchenko, M.; Nürnberger, F.; Schaper, M.

2014-03-01

297

Convective cells and their relationship to vortex diffusion in the Wisconsin Levitated Octupole  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this thesis is two-fold: first, to present floating potential structure for different plasmas and operating parameters in the Wisconsin Levitated Octupole. Second, to show how the observed potential structure can be used, within the framework of vortex diffusion, to account for enhanced diffusion in the appropriate parameter regimes.

Ehrhardt, A.B.

1978-01-01

298

Multiparticle octupole coupling and magnetic moments of hn9/2 isomers in N=126 isotones  

International Nuclear Information System (INIS)

The influence of particle-vibration coupling on the g-factors of the (h9/2)n > isomers in the N = 126 isotones is assessed using the multiparticle octupole coupling model. According to the model, admixtures of the configuration (h9/2)n-1 f7/2> in the yrast 8+ and 21/2-states, nominally associated with the configuration (h9/2)n >, increase with n. On its own, the octupole mixing mechanism therefore predicts g-factors for these states that increase with the number of valence protons. This trend is the opposite of that predicted by core-polarization blocking. Combining multiparticle octupole coupling and first order core-polarization blocking significantly reduces the discrepancy between the experimental and theoretical g-factors of these states. It is concluded that the observed breakdown in additivity for the g-factors of the (h9/2)n > isomers in the N = 126 isotones arises primarily from first order core-polarization blocking and the combination of configuration mixing due to multiparticle octupole coupling and shell model residual interactions. 40 refs., 5 tabs., 3 figs

299

Single-beam measurements of LHC instability threshold in terms of octupole current  

CERN Document Server

This note summarizes two machine development (MD) studies aimed at determining the octupole current needed in the LHC in order to stabilize all headtail instabilities at 4TeV/c, before and after the squeeze, with tight collimator settings, and when a single beam (beam 2) at maximum intensity (1380 bunches, 2.1 1014 protons) is present in the machine. The MDs followed the normal physics operation procedure, at the notable exception that a single beam was used, the other beam containing only one non-colliding nominal bunch. Octupole current (with negative polarity in the focusing octupoles and the opposite in the defocusing ones) was decreased by small steps until the instability threshold was reached. This was performed in two distinct MDs, one before the squeeze and the other after it, testing also several chromaticity values and the effect of the transverse damper in the latter case. Octupole thresholds are shown in each case studied, as well as the rise times of the instabilities observed.

Mounet, N; Buffat, X; Burov, A; Hemelsoet, G; Metral, E; Papotti, G; Pieloni, T; Pojer, M; Salvant, B; Trad, G

2012-01-01

300

Possible discontinuity in octupole behaviour in the Pt-Hg region  

International Nuclear Information System (INIS)

Values of B(E3;O1+ ? 31-) have been determined for the nuclei 194,196,198Pt by Coulomb excitation, giving 0.125(8), 0.102(4), and 0.084(18) e2b3, respectively. The results are discussed within the context of a previously suggested discontinuity in octupole behaviour in the Pt-Hg region

 
 
 
 
301

Measurements of low energy hydrogen ion effective sticking coefficients on titanium in the Wisconsin Levitated Octupole  

International Nuclear Information System (INIS)

The effective sticking coefficient for low energy (2 effective sticking coefficient for the same conditions is less than 0.01. Seventy-four percent of the wall area of the Octupole is gettered. The effects of recycling on plasma parameters is also discussed

302

Possible discontinuity in octupole behavior in the Pt--Hg region  

International Nuclear Information System (INIS)

Values of B(E3; 01+?31-) have been determined for the nuclei /sup 194,196,198/Pt by Coulomb excitation, giving 0.125(8), 0.102(4), and 0.084(18) e2b3, respectively. The results are discussed within the context of a previously suggested discontinuity in octupole behavior in the Pt--Hg region

303

Modelling the deformation mechanisms, structure-property relationships and applications of auxetic nanomaterials  

Science.gov (United States)

Analytical and Molecular Mechanics methods have been used to study the structure and deformation mechanisms acting at the molecular level in the auxetic polymorph of crystalline silica (-cristobalite). The Molecular Mechanics simulations indicate a stress-induced phase transition from -cristobalite to ordered -cristobalite occurs for uniaxial loading along the x3 direction. This is in reasonable agreement with the previous prediction from an analytical model assuming deformation is by concurrent dilation and cooperative rotation (about axes in the x1-x2 plane, passing through the midpoints of opposing edges - the a-axes) of the SiO4 tetrahedral molecular sub-units, previously shown to predict the Poisson's ratio for loading in the x3 direction. The analytical models have been extended to include cooperative rotation of each tetrahedron about its axis (the c-axis) mostly closely aligned with the principal unit-cell x3-axis. The new models enable significantly improved prediction of the Poisson's ratios of -cristobalite when loaded in one of the transverse (x1 or x2) directions. Parametric fitting of the analytical models indicate that the deformation mechanism for transverse uniaxial loading of -cristobalite is by concurrent dilation and cooperative rotation about the local a and c-axes of the SiO4 tetrahedra.

Alderson, A.; Alderson, K. L.; Evans, K. E.; Grima, J. N.; Williams, M. R.; Davies, P. J.

2005-03-01

304

Shear-wave splitting unmasks deformation properties in the Eastern Himalayan Syntaxis and Namcha Barwa region  

Science.gov (United States)

The Himalayan orogen and the Tibetan Plateau resulted from the collision between the Indian Plate and Eurasian Plate. This young and active orogenic system provides excellent opportunities to examine the lithospheric deformation and various dynamic processes during continental collision. Of particular interest is the Eastern Himalayan Syntaxis, where the structures of the Himalayan range change abruptly, developing an 'indenter corner' at the edge of the two colliding plates. Previous GPS measurements in the broad areas of Tibet and the adjacent Sichuan Basin reveal a clockwise deformation pattern. These observations have led to the crustal flow model, among others, suggesting that the lower crust beneath Tibet is weak and thus moving toward southeast during the collision. However, it is unclear to what extent the surface deformation detected by GPS can represent the deformation and flow pattern in the underlying lithosphere. Seismic anisotropy, on the other hand, offers an effective means to infer the lithospheric deformation. The past decade has seen a series of deployments of broadband seismic arrays in the Himalaya-Tibet and surrounding regions that yield shear-wave splitting measurements indicating complexities in anisotropic parameters in this region. In this study, we perform shear-wave splitting analysis of teleseismic waveform data from 25 recently deployed broadband stations in the Namcha Barwa region. The analysis was operated on the SKS phase that travels through the Earth's core from the mantle, which is then radially polarized upon reentry. We apply a particle motion test with the cross-correlation method, in which the values of the rotation direction (phi) and the time lag (dt) are selected when the cross-correlation coefficient attains its maximum. Our preliminary results show a general NE-SW (61-66 degrees) fast axis of polarization direction to the west of Yarlung-Tsangpo River. The polarization direction appears to be roughly parallel to that of the Indian absolute plate motion. To the farther east, the fast axis wraps around the edge of the Himalayan syntaxis with a NW-SE orientation. Most of the stations yield delay times between 0.10 and 0.425 s, much lower compared to those obtained in the surrounding regions, suggesting possibly weaker anisotropy in this region. Nevertheless, our observations may argue for a mechanically coupled crust and lithospheric mantle at the suture region.

Chen, C.; Chen, H.; Chuang, Y. L.; Chan, W. W.; Jiang, M.; Liang, W.

2013-12-01

305

Note on a search for the two-octupole phonon 2+ state in 208 Pb with resonant photon scattering  

International Nuclear Information System (INIS)

Results of a 208 Pb (?,?') experiment are presented aiming at an identification of the 2 + member of the long-sought two-octupole phonon multiplet. Four E2 excitations have been observed below 6.5 MeV excitation energy, two of them for the first time. However, in contrast to new results of calculations within the quasiparticle-phonon nuclear model (QPM), no obvious candidate for the two-octupole phonon vibration could be found in the present study. We discuss the J?=2+ states detected in this as well as previous experiments with respect to their possible two-octupole phonon structure

306

Effect of V and Nb additions on microstructure, properties, and deformability of Ti-45Al-9 (V, Nb, Y alloy  

Directory of Open Access Journals (Sweden)

Full Text Available Ti-45Al-9(V, Nb, Y alloys with four different x=V/Nb (atomic ratio x = 1, 1.5, 2 and 3.5 have been prepared, and the microstructures, properties and hot deformation behaviors were investigated. SEM, XRD and TEM results showed that Ti-45Al-9(V, Nb, Y alloys were mainly composed of ?, ?2, and ? phase, and the volume fraction of ? phase increased with the increase of the atomic ratio of V/Nb. The alloys were featured with lamellar microstructure with ? and ? phases locating at the colony boundaries, and some ? precipitates appearing at ?/? interfaces. It was found that the colony size decreased with the increase of x. The alloys exhibited moderate mechanical properties at room temperature, with a yield strength of over 600 MPa, and fractures showed mainly translamellar character. The alloy with x=3.5 exhibited the best deformability at elevated temperature and that with x=1 had superior oxidation resistance at 800 ?.

Yang Fei

2010-11-01

307

The long-term strength and deformation properties of crystalline rock in a high level nuclear waste repository  

International Nuclear Information System (INIS)

The time-dependent phenomena which can affect the strength and deformation properties of hard crystal line rock are clarified. Suitable measuring methods for field conditions are also summarized. The significance of time is evaluated around a shaft in a high level nuclear waste repository. According to the investigation it is generally held that creep and cyclic fatigue are the most important phenomena. They arise from subcritical crack growth which is most affected by stress intensity, chemical environment, temperature, and microstructure. There are many theoretical models, which can be used to analyse creep and cyclic fatigue, but they are defective in describing the triaxial stress condition and strength criteria. Additionally, the required parameters are often too difficult to determine with adequate accuracy. The joint creep rate depends on the affecting stress regime, on the water conditions, and on the properties of filling material. The acoustic emission method is suited to observe long-term microcrack development in field conditions. The computer program developed by Atomic Energy of Canada Limited (AECL) is used to evaluate the time-dependent de-formation around a main shaft. According to the model the enlargement of the shaft radius by 30 cm takes millions of years. The possible reduction of shaft radius by 3 mm will happen during 200 years. The model is very sensitive to changes in stress state, in the uniaxial compressive strength, and in the stress corrosion index

308

Symmetry of the CMB sky as a new test of its statistical isotropy. Non cosmological octupole?  

International Nuclear Information System (INIS)

In this article we propose a novel test for statistical anisotropy of the CMB ?T( n-circumflex = (?,?)). The test is based on the fact, that the Galactic foregrounds have a remarkably strong symmetry with respect to their antipodal points with respect to the Galactic plane, while the cosmological signal should not be symmetric or asymmetric under these transitions. We have applied the test for the octupole component of the WMAP ILC 7 map, by looking at a3,1 and a3,3, and their ratio to a3,2 both for real and imaginary values. We find abnormal symmetry of the octupole component at the level of 0.58%, compared to Monte Carlo simulations. By using the analysis of the phases of the octupole we found remarkably strong cross-correlations between the phases of the kinematic dipole and the ILC 7 octupole, in full agreement with previous results. We further test the multipole range 2 < l < 100, by investigating the ratio between the l+m = even and l+m = odd parts of power spectra. We compare the results to simulations of a Gaussian random sky, and find significant departure from the statistically isotropic and homogeneous case, for a very broad range of multipoles. We found that for the most prominent peaks of our estimator, the phases of the corresponding harmonics are coherent with phases of the octupole. We believe, our test would be very useful for detections of various types of residuals of the foreground and systematic effects at a very broad range of multipoles 2 ? l ? 1500?3000 for the forthcoming PLANCK CMB map, before any conclusions about primordial non-Gaussianity and statistical anisotropy of the CMB

309

Evaluation of Tensile Deformation Properties of Friction Stir Processed Pure Copper: Effect of Processing Parameters and Pass Number  

Science.gov (United States)

In this work, the tensile behavior of pure copper including ultimate tensile stress, yield stress, and elongation in the specimens friction stir processed under different processing parameters and pass adding was investigated in detail. The effect of strain hardening, grain refinement, and heat input on the tensile properties of these specimens was explained as well. It was observed that, regarding the aforementioned factors, the processing parameters and pass number could have considerable effects on the tensile deformation properties of the pure copper such as 300 and 47% enhancements in elongation and ultimate strength, respectively. It was demonstrated that higher passes resulted in the development of ultrafine grains (up to 700-800 nm) in the specimens. The fracture surface morphology was also used to further support the elongation results.

Barmouz, Mohsen; Besharati Givi, Mohammad Kazem; Jafari, Jalal

2014-01-01

310

Anisotropy of seismic and mechanical properties of opalinus clay during triaxial and shear deformation  

International Nuclear Information System (INIS)

mechanical properties of argillaceous rocks on the transport properties with respect to the bedding plane. The points of interest are subdivided in the following tasks: (1) Anisotropy of mechanical and transport properties referred to the bedding plane (2) Onset of dilatancy and its evolution (healing and damage) (3) Mechanical strength of the bedding plane direct shear strength testing. (authors)

311

Systematics of nuclear densities, deformations and excitation energies within the context of the generalized rotation-vibration model  

International Nuclear Information System (INIS)

We present a large-scale systematics of charge densities, excitation energies and deformation parameters for hundreds of heavy nuclei. The systematics is based on a generalized rotation-vibration model for the quadrupole and octupole modes and takes into account second-order contributions of the deformations as well as the effects of finite diffuseness values for the nuclear densities. We compare our results with the predictions of classical surface vibrations in the hydrodynamical approximation.

312

Geometrical and mechanical properties of the fractures and brittle deformation zones based on the ONKALO tunnel mapping, 2400 - 4390 m tunnel chainage  

International Nuclear Information System (INIS)

In this report, the rock mechanics parameters of fractures and brittle deformation zones have been estimated in the vicinity of the ONKALO area at the Olkiluoto site, western Finland. This report is an extension of the previously published report: Geometrical and Mechanical properties if the fractures and brittle deformation zones based on ONKALO tunnel mapping, 0-2400 m tunnel chainage (Kuula 2010). In this updated report, mapping data are from 2400-4390 m tunnel chainage. Defined rock mechanics parameters of the fractures are associated with the rock engineering classification quality index, Q', which incorporates the RQD, Jn, Jr and Ja values. The friction angle of the fracture surfaces is estimated from the Jr and Ja numbers. There are no new data from laboratory joint shear and normal tests. The fracture wall compressive strength (JCS) data are available from the chainage range 1280-2400 m. Estimation of the mechanics properties of the 24 brittle deformation zones (BDZ) is based on the mapped Q' value, which is transformed to the GSI value in order to estimate strength and deformability properties. A component of the mapped Q' values is from the ONKALO and another component is from the drill cores. In this study, 24 BDZs have been parameterized. The location and size of the brittle deformation are based on the latest interpretation. New data for intact rock strength of the brittle deformation zones are not available. (orig.)

313

Geometrical and mechanical properties of the fractures and brittle deformation zones based on the ONKALO tunnel mapping, 2400 - 4390 m tunnel chainage  

Energy Technology Data Exchange (ETDEWEB)

In this report, the rock mechanics parameters of fractures and brittle deformation zones have been estimated in the vicinity of the ONKALO area at the Olkiluoto site, western Finland. This report is an extension of the previously published report: Geometrical and Mechanical properties if the fractures and brittle deformation zones based on ONKALO tunnel mapping, 0-2400 m tunnel chainage (Kuula 2010). In this updated report, mapping data are from 2400-4390 m tunnel chainage. Defined rock mechanics parameters of the fractures are associated with the rock engineering classification quality index, Q', which incorporates the RQD, Jn, Jr and Ja values. The friction angle of the fracture surfaces is estimated from the Jr and Ja numbers. There are no new data from laboratory joint shear and normal tests. The fracture wall compressive strength (JCS) data are available from the chainage range 1280-2400 m. Estimation of the mechanics properties of the 24 brittle deformation zones (BDZ) is based on the mapped Q' value, which is transformed to the GSI value in order to estimate strength and deformability properties. A component of the mapped Q' values is from the ONKALO and another component is from the drill cores. In this study, 24 BDZs have been parameterized. The location and size of the brittle deformation are based on the latest interpretation. New data for intact rock strength of the brittle deformation zones are not available. (orig.)

Moenkkoenen, H.; Rantanen, T.; Kuula, H. [WSP Finland Oy, Helsinki (Finland)

2012-05-15

314

Influence of degree of deformation on anisotropy in mechanical properties in wrought magnesium alloy ZK60  

International Nuclear Information System (INIS)

A direct-chill (DC) cast magnesium alloys ZK60 has been forward-extruded at 300 deg. C in a single pass at two extrusion ratios (ER) 12 and 44, which correspond to a total degree of deformation (f) of 2.5 and 3.8, respectively. The as-extruded microstructure in both cases consists of two colonies of grain sizes, i.e. about 15 mu m and 25 mu m) at higher extrusion ratios give significantly weaker strength differential effect (difference in tensile yield stress and compressive yield stress). (author)

315

Contribution of the disturbed dislocation slip planes to the electrical properties of plastically deformed silicon  

International Nuclear Information System (INIS)

The deep-level centers introduced by the plastic deformation at 680 deg. C in p-type silicon are quantitatively studied by the electron beam induced current (EBIC) and DLTS techniques. It is shown that the DLTS signal is higher than that could be ascribed to the centers located at (or close to) dislocations. In opposite, the number of electrically active defects in the dislocation trails, which is estimated from the EBIC contrast, easily explains the DLTS signal. The possible nature of defects in the dislocation trails is discussed

316

Influence of severe plastic deformation on the structure and properties of ultrahigh carbon steel wire  

Energy Technology Data Exchange (ETDEWEB)

Ultrahigh-carbon steel wire can achieve very high strength after severe plastic deformation, because of the fine, stable substructures produce. Tensile strengths approaching 6000 MPa are predicted for UHCS containing 1.8%C. This paper discusses the microstructural evolution during drawing of UHCS wire, the resulting strength produced and the factors influencing fracture. Drawing produces considerable alignment of the pearlite plates. Dislocation cells develop within the ferrite plates and, with increasing strain, the size normal to the axis ({lambda}) decreases. These dislocation cells resist dynamic recovery during wire drawing and thus extremely fine substructures can be developed ({lambda} < 10 nm). Increasing the carbon content reduces the mean free ferrite path in the as-patented wire and the cell size developed during drawing. For UHCS, the strength varies as {lambda}{sup {minus}5}. Fracture of these steels was found to be a function of carbide size and composition. The influence of processing and composition on achieving high strength in these wires during severe plastic deformation is discussed.

Leseur, D R; Sherby, O D; Syn, C K

1999-07-01

317

Investigation of mechanical properties and operative deformation mechanism in nano-crystalline Ni-Co/SiC electrodeposits  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer The tensile properties of Ni-Co and Ni-Co/SiC deposits were investigated. Black-Right-Pointing-Pointer The SiC particles enhanced tensile strength and ductility of nano-structured composites. Black-Right-Pointing-Pointer The deformation mechanism at low and high strain rates were studied. - Abstract: Ni-Co/SiC nano-composites were prepared via electrodeposition from a modified Watts bath containing SiC particles with average particle size of 50 nm, SDS as surfactant and saccharin as grain refiner in appropriate amounts. The effect of nano-particle incorporation on microstructure, mechanical properties and deformation mechanism of electrodeposits were investigated. The mechanical properties of electrodeposits were investigated by Vickers microhardness and tensile tests. The results indicated that incorporation of SiC particles into a 15 nm Ni-Co matrix had no considerable effect on its microhardness and yield strength, that is, dispersion hardening did not operate in this range of grain size. However it was observed that co-deposition of uniform distributed SiC particles can significantly improve the ultimate tensile strength and elongation to failure of the deposits. Calculation of apparent activation volume from tensile test results at different strain rates proved that incorporation of SiC nano-particles are responsible for stress-assisted activation of GB atoms mechanism that can significantly increase the plasticity. Nano-crystalline Ni-Co matrix showed a mixed mod behavior of ductile and brittle fracture whereas incorporation of SiC particles and increasing the strain rate promoted ductile fracture mode.

Lari Baghal, S.M. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Amadeh, A., E-mail: amadeh@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Heydarzadeh Sohi, M. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of)

2012-04-30

318

Investigation of mechanical properties and operative deformation mechanism in nano-crystalline Ni–Co/SiC electrodeposits  

International Nuclear Information System (INIS)

Highlights: ? The tensile properties of Ni–Co and Ni–Co/SiC deposits were investigated. ? The SiC particles enhanced tensile strength and ductility of nano-structured composites. ? The deformation mechanism at low and high strain rates were studied. - Abstract: Ni–Co/SiC nano-composites were prepared via electrodeposition from a modified Watts bath containing SiC particles with average particle size of 50 nm, SDS as surfactant and saccharin as grain refiner in appropriate amounts. The effect of nano-particle incorporation on microstructure, mechanical properties and deformation mechanism of electrodeposits were investigated. The mechanical properties of electrodeposits were investigated by Vickers microhardness and tensile tests. The results indicated that incorporation of SiC particles into a 15 nm Ni–Co matrix had no considerable effect on its microhardness and yield strength, that is, dispersion hardening did not operate in this range of grain size. However it was observed that co-deposition of uniform distributed SiC particles can significantly improve the ultimate tensile strength and elongation to failure of the deposits. Calculation of apparent activation volume from tensile test results at different strain rates proved that incorporation of SiC nano-particles are responsible for stress-assisted activation of GB atoms mechanism that can significantly increase the plasticity. Nano-crystalline Ni–Co matrix showed a mixed mod behavior of ductile anmod behavior of ductile and brittle fracture whereas incorporation of SiC particles and increasing the strain rate promoted ductile fracture mode.

319

Enhancement of nuclear Schiff moments and time reversal violation in atoms due to soft nuclear octupole vibrations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Parity and time invariance violating (${\\cal P},{\\cal T}$-odd) nuclear forces produce ${\\cal P},{\\cal T}$-odd nuclear moments, for example, the nuclear Schiff moment. In turn, this moment can induce electric dipole moments (EDMs) in atoms. We estimate the contribution to the Schiff moment from the soft collective octupole vibrations existing in many heavy nuclei. Two possible mechanisms are considered, mixing of the ground state of an odd-$A$ nucleus with the octupole phonon...

Flambaum, V. V.; Zelevinsky, V. G.

2002-01-01

320

Electrical and magnetic properties of hot-deformed Nd-Fe-B magnets with different DyF3 additions  

Science.gov (United States)

The effect of deformation and DyF3 additions on the electrical resistivity and the magnetic performance has been studied in hot-deformed Nd-Fe-B melt-spun ribbons and correlated with respective microstructures. Despite the nanocrystallinity of hot-compacted magnets, the specific electrical resistivity measured by four-point-method was shown to be comparable with that of sintered magnets. Die-upsetting reduces electrical resistivity within the magnetically hard plane because of an enhanced shape anisotropy of the grains. The addition of DyF3 overcompensates this reduction due to the presence of electrically insulating Dy-F rich inclusions and thus reduces eddy current losses within the magnet. Magnetic measurements reveal an increase in coercivity without a change in remanence for die-upset magnets with a total height reduction of 63% and 1.2 wt. % Dy (1.6 wt. %DyF3). Both properties, remanence and coercivity, demonstrate an effective reduction in heavy rare earth Dy for Nd-Fe-B magnets.

Sawatzki, Simon; Dirba, Imants; Schultz, Ludwig; Gutfleisch, Oliver

2013-10-01

 
 
 
 
321

[The deformation-strength properties of the vertebral and common carotid arteries in fetuses and newborn infants].  

Science.gov (United States)

General carotid and vertebral arteries of 51 corpses of foetuses and newborns with 28-40 weeks gestation were studied. The entire material was divided into 3 groups: 28-32 weeks, 33-36 weeks and 37-40 weeks. The thickness of the wall and its certain layers and connective tissue fibres architectonics were studied. General tensile strength, its limit, maximum relative deformation and the arterial wall Junge module were studied at longitudinal tension on ZM-40 tension machine. General carotid artery wall of foetuses and newborns is more tensile and has greater strength and less rigidity than that of the vertebral artery. The wall of the arteries studied has tensility reserve, safe for its structure in account of its fibroarchitectonics peculiarities. All the tensile strength parameters of the vessels investigated, with the exception of general carotid artery relative deformation, significantly change with the gestation increase. Tensile strength properties change depending on gestation term and body weight of foetuses and newborns may be approximated with linear function Y = A + B x X + C x Z (X--gestation term, Z--body weight). PMID:7550910

Kalmin, O V

1995-01-01

322

Elastic Deformation Properties of Implanted Endobronchial Wire Stents in Benign and Malignant Bronchial Disease: A Radiographic In Vivo Evaluation  

International Nuclear Information System (INIS)

Purpose: To evaluate the long-term mechanical behavior in vivo of expandable endobronchial wire stents, we imaged three different prostheses in the treatment of tracheobronchial disease. Methods: Six patients with bronchial stenoses (three benign, three malignant) underwent insertion of metallic stents. Two self-expandable Wallstents, two balloon-expandable tantalum Strecker stents and two self-expandable nitinol Accuflex stents were used. Measurements of deformation properties were performed during voluntary cough by means of fluoroscopy, at 1 month and 7-10 months after implantation. The procedures were videotaped, their images digitized and the narrowing of stent diameters calculated at intervals of 20 msec. Results: After stent implantation all patients improved with respect to ventilatory function. Radial stent narrowing during cough reached 53% (Wallstent), 59% (tantalum Strecker stent), and 52% (nitinol Accuflex stent) of the relaxed post-implantation diameter. Stent compression was more marked in benign compared with malignant stenoses. In the long term permanent deformation occurred with the tantalum Strecker stents; the other stents were unchanged. Conclusion: Endobronchial wire stents can be helpful in the treatment of major airway collapse and obstructing bronchial lesions. However, evidence of material fatigue as a possible effect of exposure to recurrent mechanical stress on the flexible mesh tube may limit their long-term use. This seems to be predomina long-term use. This seems to be predominantly important in benign bronchial collapse

323

Magnetorheological and deformation properties of magnetically controlled elastomers with hard magnetic filler  

Energy Technology Data Exchange (ETDEWEB)

Viscoelastic and deformational behavior of soft magnetic elastomers with hard magnetic fillers under the influence of a magnetic field is studied by different experimental techniques. The magnetic elastomers used in this work were synthesized on the basis of silicone rubber filled with FeNdB particles and were magnetized in a field of 3 and 15 kOe. We have shown that due to high residual magnetization the materials demonstrate well pronounced non-elastic behavior already in the absence of any external magnetic field. In particular, in contrast to magnetic elastomers based on soft magnetic fillers their elastic modulus is strain-dependent. Under the influence of external magnetic field the storage and loss moduli of magnetic elastomers with hard magnetic filler can both increase and decrease tremendously.

Stepanov, G.V., E-mail: gstepanov@mail.ru [Institute of Chemistry and Technology of Organoelement Compounds, Sh. Entuziastov 128, Moscow 111123 (Russian Federation); Chertovich, A.V. [Physics Department, Moscow State University, Moscow 119991 (Russian Federation); Kramarenko, E.Yu., E-mail: kram@polly.phys.msu.ru [Physics Department, Moscow State University, Moscow 119991 (Russian Federation)

2012-10-15

324

Mechanical Properties of Nano- and Submicrocrystalline Iron Subjected to Severe Plastic Deformation by Friction  

Directory of Open Access Journals (Sweden)

Full Text Available By using nanoindentation technique relationship between microstructure and mechanical parameters such as nanohardness Hh, plasticity characteristic, and Young’s modulus E were found to be dependent on the grain size of the bcc-Fe subjected to severe plastic deformation by friction (SPDF with argon atmosphere. Unlike fcc-metals in which the decreasing of grain size to 20 nm results in hardness growth accompanied by decreasing the plasticity, it was found the reverse effect in bcc-Fe, i.e. decreasing the grain size from 50 to 20 nm caused the decrease of hardness and increase of plasticity. Moreover, the decrease of Young’s modulus E with decreasing the grain size down to 20 nm was detected in nanoindentation experiments.

Yurkova A.I.

2012-08-01

325

The effect of aluminium on mechanical properties and deformation mechanisms of hadfield steel single crystals  

Science.gov (United States)

On single crystals of Hadfield steel (Fe-13Mn-1.3C, Fe-13Mn-2.7Al-1.3C, wt.%) the systematical investigations of deformation mechanisms - slip and twinning, stages of plastic flow, strain hardening coefficient depending on orientation of tensile axis have been carried out by methods of optical and electron microscopy, x-ray analysis. Is has been shown that the combination of low stacking fault energy (?{SF}=0.03J/m^2) with high concentration of carbon atoms in aluminium-free steel results in development of the mechanical twinning at room temperature in all crystal orientations. The new type of twinning with formation of extrinsic stacking fault has been found out in [001] single crystals. Experimentally it has been established that alloying with aluminium leads to increase of stacking fault energy of Hadfield steel and suppresses twinning in all orientations of crystals at preservation of high values of strain-hardening coefficients ?.

Zakharova, E. G.; Kireeva, I. V.; Chumlyakov, Y. I.; Shul'Mina, A. A.; Sehitoglu, H.; Karaman, I.

2004-06-01

326

Magnetorheological and deformation properties of magnetically controlled elastomers with hard magnetic filler  

International Nuclear Information System (INIS)

Viscoelastic and deformational behavior of soft magnetic elastomers with hard magnetic fillers under the influence of a magnetic field is studied by different experimental techniques. The magnetic elastomers used in this work were synthesized on the basis of silicone rubber filled with FeNdB particles and were magnetized in a field of 3 and 15 kOe. We have shown that due to high residual magnetization the materials demonstrate well pronounced non-elastic behavior already in the absence of any external magnetic field. In particular, in contrast to magnetic elastomers based on soft magnetic fillers their elastic modulus is strain-dependent. Under the influence of external magnetic field the storage and loss moduli of magnetic elastomers with hard magnetic filler can both increase and decrease tremendously.

327

Some Properties of an Infinite Family of Deformations of the Harmonic Oscillator  

CERN Document Server

In memory of Marcos Moshinsky, who promoted the algebraic study of the harmonic oscillator, some results recently obtained on an infinite family of deformations of such a system are reviewed. This set, which was introduced by Tremblay, Turbiner, and Winternitz, consists in some Hamiltonians $H_k$ on the plane, depending on a positive real parameter $k$. Two algebraic extensions of $H_k$ are described. The first one, based on the elements of the dihedral group $D_{2k}$ and a Dunkl operator formalism, provides a convenient tool to prove the superintegrability of $H_k$ for odd integer $k$. The second one, employing two pairs of fermionic operators, leads to a supersymmetric extension of $H_k$ of the same kind as the familiar Freedman and Mende super-Calogero model. Some connection between both extensions is also outlined.

Quesne, C

2010-01-01

328

Bulk crustal properties in NE Tibet and its implication for deformation model  

Science.gov (United States)

The crust beneath the northeastern (NE) Tibetan Plateau records far field effects of collision and convergence occurring between the Indian and Eurasian plates. A better structural understanding of the crust beneath NE Tibet can improve our understanding of Cenozoic deformation resulting from the India-Eurasia collision. Taking advantage of the relatively dense coverage in most areas in NE Tibet except for the Qaidam basin by regional seismic networks of Gansu and Qinghai Provinces, we isolate receiver functions from the teleseismic P wave data recorded from 2007 to 2009 and resolve the spatial distribution of crustal thickness and Vp/Vs ratio beneath NE Tibet from H-K scanning. Our results can be summarized as: (1) NE Tibet is characterized by ~ 60-km-thick crust beneath the Nan Shan, Qilian Shan thrust belts and the Anyemaqen Shan, and 45-50 km-thick crust beneath the Tarim basin, the Alashan depression and the Ordos basin; the crust thins gradually from west to east in addition to the previously observed pronounced thinning from south to north; (2) the crust of NE Tibet exhibits a relatively lower Vp/Vs ratio of 1.72 than the north China block and a decrease in average crustal Vp/Vs ratio with increasing crustal thickness; and (3) the crustal thicknesses are less than the values predicted by the simple isostatic model of throughout Tibetan plateau in where the elevation is larger than 3.0 km. Our observations can be explained by the hypothesis that deformation occurring in NE Tibet is predominated by upper-crustal thickening or lower-crust extrusion.

Tian, Xiaobo

2014-05-01

329

Analysis of the mechanical properties and deformation behavior of nanostructured commercially pure Al processed by equal channel angular pressing (ECAP)  

International Nuclear Information System (INIS)

In the present paper commercially pure Al was processed by equal channel angular pressing (ECAP) up to 8 passes using route BC. For ECAP processing a proper die set was designed and constructed. Transmission electron microscope (TEM) and electron backscatter diffraction (EBSD) were used to evaluate the microstructure of the pressed materials. Mechanical properties and the deformation behavior of the ECAP processed material were investigated by the hardness and compression tests. The significant increase in hardness and yield stress after ECAP was discussed by two strengthening mechanisms. Based on these mechanisms, variations of the hardness and yield stress as a function of the pass numbers were related to the calculated dislocation densities and the average boundary spacing. Also it was suggested that the absorption of the dislocations into grain boundaries would be an effective recovery process for the absence of the strain hardening

330

Geometrical and physical properties of the 1982-84 deformation source at Campi Flegrei - Italy  

Science.gov (United States)

Deformation of the ground surface in volcanic areas is generally recognized as a reliable indicator of unrest, possibly resulting from the intrusion of fresh magma within the shallow rock layers. The intrusion process is usually represented by a deformation source such as an ellipsoidal pressurized cavity, embedded within a homogeneous and elastic half-space. Similar source models allow inferring the depth, the location and the (incremental) volume of the intrusion, which are very important parameters for volcanic risk implications. However, assuming a homogeneous and elastic rheology and, assigning a priori the shape and the mechanism of the source (within a very restricted 'library' of available solutions) may bias considerably the inference of source parameters. In complete generality, any point source deformation, including overpressure sources, may be described in terms of a suitable moment tensor, while the assumption of an overpressure source strongly restricts the variety of allowable moment tensors. In particular, by assuming a pressurized cavity, we rule out the possibility that either shear failure may precede magma emplacement (seismically induced intrusion) or may accompany it (mixed tensile and shear mode fracture). Another possibility is that a pre-existent weakness plane may be chosen by the ascending magma (fracture toughness heterogeneity). We perform joint inversion of levelling and EDM data (part of latter are unpublished), collected during the 1982-84 unrest at Campi Flegrei caldera: a 43% misfit reduction is obtained for a general moment source if the elastic heterogeneities computed from seismic tomography are accouted for. The inferred source is at 5.2 km depth but cannot be interpreted as a simple pressurized cavity. Moreover, if mass conservation is accounted for, magma emplaced within a shallow source must come from a (generally deeper) reservoir, which is usually assumed to be deep enough to be simply neglected. At Campi Flegrei, seismic tomography indicates that the 'deep' magma source is rather shallow (at 7-8 km depth), so that its presence should be included in any thorough attempt to source modeling. Taking into account a deflating source at 7.5 km depth (represented either as a horizontal sill or as an isotropic cavity) and an inflating moment source, the fit of both levelling and EDM data improves further (misfit reduction 80%), but still the best fitting moment source (at 5.5 km depth) falls outside the range of pressurized ellipsoidal cavities. The shallow moment source may be decomposed in a tensile and a shear dislocation. No clue is obtained that the shear and the tensile mechanisms should be located in different positions. Our favourite interpretation is in terms of a crack opening in mixed tensile and shear mode, as would be provided by fluid magma unwelding pre-stressed solid rock. Although this decomposition of the source is not unique, the proposed solution is physically motivated by the minimum overpressure requirement. An important implication of this new interpretation is that the magma emplaced in the shallow moment source during the 1982-84 unrest was not added to already resident magma at the same position.

Bonafede, Maurizio; Trasatti, Elisa; Giunchi, Carlo; Berrino, Giovanna

2010-05-01

331

Role of deformation on giant resonances within the QRPA approach and the Gogny force  

CERN Document Server

Fully consistent axially-symmetric-deformed Quasi-particle Random Phase Approximation (QRPA) calculations have been performed, in which the same Gogny D1S effective force has been used for both the Hartree-Fock-Bogolyubov mean field and the QRPA approaches. Giant resonances calculated in deformed $^{26-28}$Si and $^{22-24}$Mg nuclei as well as in the spherical $^{30}$Si and $^{28}$Mg isotopes are presented. Theoretical results for isovector-dipole and isoscalar monopole, quadrupole, and octupole responses are presented and the impact of the intrinsic nuclear deformation is discussed.

Peru, S

2008-01-01

332

Design, fabrication and cold tests of a super ferric octupole corrector for the LHC  

International Nuclear Information System (INIS)

In the corrections scheme of the LHC it is planed to install octupole corrector magnets in the short straight section of the lattice. Initially these correctors were distributed windings on the cold bore tube nested in the tuning quadrupoles. The latter being suppressed a new compact super ferric design was chosen for the octupole prototype, suitable for a two-in-one configuration. This prototype was designed by CERN and CEDEX/Spain, built at INDAR/Spain and tested at CEDEX. The paper reports on the design of the prototype, describes the fabrication and assembly and presents the measurement results. Special interest has been taken to design a simple and compact magnet, easy to fabricate and training free below nominal field. First results show the feasibility of the solution wich will be finally confirmed by magnetic measurement. (Author) 4 refs

333

Design, fabrication and cold tests of a superferritic octupole corrector for the LHC  

International Nuclear Information System (INIS)

In the correction scheme of the LHC it is planned to install octupole corrector magnets in the short straight section of the lattice. Initially these correctors were distributed windings on the cold bore tube nested in the tuning quadrupoles. The latter being suppressed a new compact superferric design was chosen for the octupole prototype, suitable for a two-in-one configuration. This prototype was designed by CERN and CEDEX/Spain, built at INDAR/Spain and tested at CEDEX. The paper reports on the design of the prototype, describes the fabrication and assembly and presents the measurement results. Special interest has been taken to design a simple and compact magnet, easy to fabricate and training free below nominal field. First results show the feasibility of the solution which will be finally confirmed by magnetic measurements

334

Design, fabrication and cold tests of a superferritic octupole corrector for the LHC  

Energy Technology Data Exchange (ETDEWEB)

In the correction scheme of the LHC it is planned to install octupole corrector magnets in the short straight section of the lattice. Initially these correctors were distributed windings on the cold bore tube nested in the tuning quadrupoles. The latter being suppressed a new compact superferric design was chosen for the octupole prototype, suitable for a two-in-one configuration. This prototype was designed by CERN and CEDEX/Spain, built at INDAR/Spain and tested at CEDEX. The paper reports on the design of the prototype, describes the fabrication and assembly and presents the measurement results. Special interest has been taken to design a simple and compact magnet, easy to fabricate and training free below nominal field. First results show the feasibility of the solution which will be finally confirmed by magnetic measurements.

Laurent, G.; Russenschuck, S.; Siegel, N.; Traveria, M. [CERN, Geneva (Switzerland); Garcia-Tabares, L.; Calero, J. [CEDEX-MOPTMA, Madrid (Spain); Aguirre, P.; Etxeandia, J.; Garcia, J. [INDAR, Beasain (Spain)

1996-07-01

335

High spin octupole correlations in the N=85, 139Xe and 141Ba isotones  

International Nuclear Information System (INIS)

High spin states in 139Xe and 141Ba have been investigated using ?-? - and ?-?-?-coincidence studies of spontaneous fission of 252Cf. Alternating parity bands built on a 7/2-level are assigned up to spin I=(37/2) and I=(29/2) in 139Xe and 141Ba, respectively. Another possible octupole band based on ?i132(f7/2)2 multiplet with spin up to (29/2) also is observed in both nuclei. Cascades of enhanced E1 transitions and B(E1)/B(E2) ratios indicate strong octupole correlations. Systematics of the ?(f7/2)3, ?(f7/2)3x3- and ?u13/2(f7/2)2 multiplets and bands in N 85 isotones are presented. (author). Letter-to-the-editor

336

Octupole excitations in vibrational nuclei and the sdf interacting boson model  

International Nuclear Information System (INIS)

Proton and deuteron inelastic scattering experiments, performed with an energy resolution of 12-15 keV, have been used to study negative-parity states of vibrational and transitional nuclei with mass between 98 and 150. The analysis has been focussed on the isovector components, on the quadrupole-octupole two-phonon states and on the fragmentation of the octupole strength. This latter displays a regular dependence on the product of proton and neutron valence particle numbers and is satisfactorily reproduced by IBM-1+f-boson calculations. Other features of the experimental spectra, as the relative positions of the 3- states, exhibit a dependence on the ratio of valence particle numbers and indicate that a IBM-2 approach might be more appropriate. (orig.)

337

Lower hybrid heating associated with mode conversion on the Wisconsin octupole  

International Nuclear Information System (INIS)

This thesis addresses the following key issues in the lower hybrid frequency range: (1) what are the important physics aspects of wave propagation and heating in an experimental situation; (2) how effective is plasma heating in the complex magnetic field configuration of the octupole. Experimental work is accomplished by launching 1-10 ms pulses of up to 40 kW of radio frequency power at 140 MHz corresponding to the hot plasma lower hybrid resonance in the octupole. A dipole antenna which is moveable radially and is also rotatable couples wave power to the plasma. Coupling efficiencies greater than 95% are achieved by proper antenna placement near the edge of the plasma radial density profile

338

Investigation of octupole vibrational states in 150Nd via inelastic proton scattering (p,p'?)  

International Nuclear Information System (INIS)

Octupole vibrational states were studied in the nucleus 150Nd via inelastic proton scattering with 10.9-MeV protons, which are an excellent probe to excite natural parity states. For the first time in 150Nd, both the scattered protons and the ? rays were detected in coincidence, giving the possibility to measure branching ratios in detail. Using the coincidence technique, the B(E1) ratios of the decaying transitions for 10 octupole vibrational states and other negative-parity states to the yrast band were determined and compared to the Alaga rule. The positive and negative-parity states revealed by this experiment are compared with interacting boson approximation calculations performed in the spdf boson space. The calculations are found to be in good agreement with the experimental data, for both positive and negative-parity states.

339

Small deformation rheological properties of single and mixed Maltodextrin - Milk protein systems  

DEFF Research Database (Denmark)

Small deformation dynamic oscillation was used to investigate the structural behaviour of conformationally dissimilar maltodextrin and milk protein macro-molecules in a mixture, with the view of identifying the state of phase separation and the pattern of solvent distribution between the two constituent phases. The enthalpic nature of the maltodextrin network produced a sigmoidal transition in the development of storage modulus (G') during cooling and substantial thermal hysteresis upon heating of the gel. By contrast, the entropically-driven build up of structure in milk protein samples yielded linear and overlapping cooling and heating scans of G' with networks reverting into solutions at relatively low temperatures. These differences in the viscoelastic functions of the two polymers in combination with theoretical analysis (isostress-isostrain models, Kerner equation) have documented the reinforcing effect of strong and spherical maltodextrin inclusions on the weaker and continuous milk protein phase. However, at concentrations of maltodextrin beyond the phase inversion point, the binary assembly comprises a strong and continuous maltodextrin network surrounding the weaker milk protein inclusions. Finally, the sharp change in the pattern of water partition between the two polymeric components, as a result of phase inversion in the system, was rationalised on the basis of kinetically-influenced co-gels comprising phase separated networks which are trapped away from the state of thermodynamic equilibrium. Copyright (C) 1996 Published by Elsevier Science Ltd.

Chronakis, Ioannis S.; Kasapis, I.S.

1996-01-01

340

Ground state properties and Coulomb dissociation of the deformed halo nucleus 31Ne  

International Nuclear Information System (INIS)

The recently observed large cross sections for the Coulomb dissociation of 31Ne nucleus indicate that this nucleus takes a halo structure in the ground state. We analyze these experimental data using the particle-rotor model that takes into account the rotational excitation of the core nucleus 30Ne. We show that the experimental data can be well reproduced when the quadrupole deformation parameter of 30Ne is around ?2=0.2?0.3, at which the ground state takes the spin and parity of I?=3/2-. This state corresponds to the Nilsson level [330 1/2] in the adiabatic limit of the particle-rotor model. On the other hand, the state corresponding to the Nilsson level [321 3/2] with ?2?0.55 can be excluded when the finite excitation energy of the core is taken into account, even though this configuration is a candidate for the ground state of 31Ne in the Nilsson model analysis. We discuss briefly also a possibility of the I?=1/2+ configuration with ?2?1 and ?2?-0.4.

 
 
 
 
341

Radiation and helium effects on microstructures, nano-indentation properties and deformation behavior in ferrous alloys  

International Nuclear Information System (INIS)

Accelerated ion irradiation, especially 'dual-beam' irradiation, is a useful technique for experimental exploration of irradiation effects and validation of irradiation effect models, because of the unique controllability in irradiation conditions including the helium production rate. In this work, the effects of irradiation and helium implantation on microstructural evolution, hardness and plastic deformation behavior in Fe-15Cr-20Ni model austenitic ternary alloy and Fe-8 ? 9Cr-2W reduced-activation martensitic steels were studied through combined applications of ion irradiation, nano-indentation, focused ion-beam microprocessing and transmission electron microscopy. Systematic data on irradiation hardening are presented for broad irradiation conditions. Influences of helium implantation on irradiation-induced microstructural and nano-indentation hardness changes were not detected in the Fe-8 ? 9Cr-2W steels, while they were significant in the Fe-15Cr-20Ni alloy. The interaction behavior of dislocation loops with moving dislocations and the strength of the loops as obstacles to dislocation motion are also discussed for these two material classes based on the hardness, and the irradiated and indented microstructures

342

Creep Properties and Deformation Mechanisms of a FGH95 Ni-based Superalloy  

Science.gov (United States)

By means of full heat treatment, microstructure observation, lattice parameters determination, and the measurement of creep curves, an investigation has been conducted into the microstructure and creep mechanisms of FGH95 Ni-based superalloy. Results show that after the alloy is hot isostatically pressed, coarse ?' phase discontinuously distributes along the previous particle boundaries. After solution treatment at high temperature and aging, the grain size has no obvious change, and the amount of coarse ?' phase decreases, and a high volume fraction of fine ?' phase dispersedly precipitates in the ? matrix. Moreover, the granular carbides are found to be precipitated along grain boundaries, which can hinder the grain boundaries' sliding and enhance the creep resistance of the alloy. By x-ray diffraction analysis, it is indicated that the lattice misfit between the ? and ?' phases decreases in the alloy after full heat treatment. In the ranges of experimental temperatures and applied stresses, the creep activation energy of the alloy is measured to be 630.4 kJ/mol. During creep, the deformation mechanisms of the alloy are that dislocations slip in the ? matrix or shear into the ?' phase. Thereinto, the creep dislocations move over the ?' phase by the Orowan mechanism, and the < { 1 10 } rangle super-dislocation shearing into the ?' phase can be decomposed to form the configuration of (1/3) < { 1 12 } rangle super-Shockleys' partials and the stacking fault.

Xie, Jun; Tian, Su-gui; Zhou, Xiao-ming

2013-07-01

343

Detailed spectroscopy of the doubly closed shell nucleus 132Sn: First observation of octupole collectivity  

International Nuclear Information System (INIS)

The angular momenta and parities of the low-lying states of 132Sn have been firmly determined through studies of the ? decay of 132In. The lowest lying state with a negtive parity is shown to have a collective octupole character. Several particle-hole multiplets have been identified, including the lowest lying proton excitation. More than about 20% of the theoretically estimated bound states of 132Sn have been identified

344

Evidence for high energy giant octupole resonance in medium and heavy mass nuclei  

International Nuclear Information System (INIS)

Inelastic scattering of 3He-particles at 110 - 140 MeV on medium and heavy mass nuclei reveals the presence of a new resonance at Ex -- 118A sup(1/3) MeV with a width of about 7 MeV. Angular distribution of the resonance prefers an L = 3 transition and an octupole energy-weighted sum-rule fraction of 47 - 95% is exhausted. (author)

345

Towards a measurement of the nuclear magnetic octupole moment of barium-137  

Science.gov (United States)

A 2051 rim wavelength laser system designed and built for use in a number of proposed experiments is presented. The laser is shown to have a sub-kilohertz linewidth. Results of spectroscopic measurements of the 6S1/2 to 5D3/2 transition in 138Ba + are discussed. A proposed measurement of the nuclear magnetic octupole measurement of 137Ba is reviewed. The prospects for developing this laser system into a barium ion optical frequency standard are discussed.

Kleczewski, Adam

346

Effect of Temperature and Deformation Rate on the Tensile Mechanical Properties of Polyimide Films  

Science.gov (United States)

In order to study the structure-property relationships of different processed oriented polyimide films, the mechanical properties will be identified by using tensile tester Instron 4505 and structural information such as the 3-dimensional birefringence molecular symmetry axis and 3-dimensional refractive indices will be determined by using wave guide coupling techniques. The monoaxial drawing techniques utilized in this research are very useful for improving the tensile mechanical properties of aromatic polyimide films. In order to obtain high modulus/high strength polyimide films the following two techniques have been employed, cold drawing in which polyimide films are drawn at room temperature at different cross head speeds and hot drawing in which polyimide films are drawn at different temperatures and cross head speeds. In the hot drawing process the polyimide films are drawn at different temperatures until the glass transition temperature (Tg) is reached by using the environmental chamber. All of the mechanical and optical property parameters will be identified for each sample processed by both cold and hot drawing techniques.

Moghazy, Samir F.; McNair, Kevin C.

1996-01-01

347

Mechanical properties and deformation behavior of as-cast Ti-Sn alloys  

International Nuclear Information System (INIS)

In this study, the mechanical properties of as-cast Ti-Sn alloys with Sn content ranging from 1 to 30 wt.% prepared using a dental cast machine were investigated and compared with commercially pure titanium (c.p. Ti), which was used as a control. Experimental results indicated that the diffraction peaks of all the Ti-Sn alloys matched those for ? Ti, and no ? phase peaks or any intermediate phases were found. All the Ti-Sn alloys had higher bending strengths, bending moduli and elastic recovery angles than those of c.p. Ti. For example, the bending strength of the Ti-1Sn alloy was higher than that of c.p. Ti by 68%, its bending modulus was higher than that of c.p. Ti by 43% and its elastically recoverable angle was higher than that of c.p. Ti by as much as 240%. Additionally, the Ti-1Sn, Ti-5Sn and Ti-10Sn alloys exhibited ductile properties. When the Sn content was 20 wt.% or greater, the alloys showed brittle properties. Our research suggested that Ti-1Sn alloy had the most favorable mechanical properties of all the metals in this study, making it the best candidate for prosthetic dental applications.

348

A deformable shell model study of the properties of CsCl  

International Nuclear Information System (INIS)

The deformable shell model has been put to a stringent test by calculating the transition temperature for transition of CsCl crystal from the CsCl-to the NaCl-structure. Because of the very small heat of transition this calculation is a very sensitive test of the model. Einstein approximation is used for estimating the thermal part of free energy. The transition temperature has been obtained by equating the Helmholtz free energy for the two phases at transition since the volume change accompanying transition is very small and the transition takes place at atmospheric pressure. The static lattice energy expression used for computing the free energy is obtained from the effective interaction including the many body interaction. The equation of state has also been calculated using the relation -P = (deltaF/deltaV)sub(T), as a further test of the validity of the model. Finally, the same model has been used to improve upon the lattice dynamical calculation by incorporating the effect of the polarizability of Cs+ ion on the phonon dispersion curves. The nearest neighbour distance at room temperature and at transition point in the CsCl-phase comes out within 0.1% of the experimental values. These have been determined for any particular temperature by minimizing the Helmholtz free energy at that temperature. The transition temperature has been reproduced almost exactly and in the calculation of the equation of state, the agreement with experiment is within 8% even at the highest compression. It has also been found that the inclusion of the positive ion polarizability improves the phonon dispersion curves of Ghosh and Basu remarkably with relatively a few number of parameters. The only remaining notable discrepancy is reported at the zone boundary along (110) direction for both the L.O. and T.O. branches and those too are found to be 5.2% and 4.6% respectively. (K.B.)

349

The mechanical properties, deformation and thermomechanical properties of alkali treated and untreated Agave continuous fibre reinforced epoxy composites  

International Nuclear Information System (INIS)

Research highlights: ? New renewable and biodegradable Agave americana fibre. ? Environmentally free materials. ? Good mechanical properties of Agave fibre reinforced epoxy composite materials. ? Surface modification of the fibre (Alkali treatment) imported good mechanical properties. ? Future scope in light weight materials manufacture. -- Abstract: The mechanical properties such as tensile, compressive, flexural, impact strength and water absorption of the alkali treated continuous Agave fibre reinforced epoxy composite (TCEC) and untreated continuous Agave fibre reinforced epoxy composite (UTCEC) were analysed. A comparison of the surfaces of TCEC and UTCEC composites was carried out by dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The thermomechanical properties of the composite reinforced with sodium hydroxide (NaOH) treated Agave fibres were considerably good as the shrinkage of the fibre during alkali treatment had facilitated more points of fibre resin interface. The SEM micrograph and FTIR spectra of the impact fracture surfaces of TCEC clearly demonstrate the better interfacial adhesion between fibre and the matrix. In both analyses the TCEC gave good performance than UTCEC and, thus, there is a scope for its application in light weight manufacture in future.

350

Influence of plastic deformation on structure and mechanical properties of stainless steel type X5CrNi18-10  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: The paper analyzes the influence of the degree of cold deformation on the structure and mechanical properties of austenitic stainless steel X5CrNi18-10.Design/methodology/approach: The investigations included observations of the structure on a light microscope, researches of mechanical properties in a static tensile test and microhardness measurements. The analysis of the phase composition was carried out on the basis of X-ray researches. In the qualitative X-ray analysis the comparative method was applied.Findings: Plastic deformation in deep drawing process of container from investigated austenitic stainless steel induced in its structure martensitic transformation ? ? ?’.Research limitations/implications: The X-ray phase analysis in particular permitted to disclose and identify the main phases on the structure of the investigated steel after its deformation within the range 10%÷50%.Practical implications: The analysis of the obtained results permits to state that the degree of deformation has a significant influence on the structure and mechanical properties of the investigated steels. Besides, a good correlation was found between changes of the structure and the effects of investigations of the mechanical properties.Originality/value: The analytic dependence of the yield point of the investigated steel on the draft degree in deep pressing process has been confirmed. Revealing this relation is of essential practical importance for the technology of sheetmetal forming of austenitic steel.

W. Ozgowicz

2008-07-01

351

High-temperature mechanical properties and deformation behavior of high Nb containing TiAl alloys fabricated by spark plasma sintering  

Science.gov (United States)

A high Nb containing TiAl alloy was prepared from the pre-alloyed powder of Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y (at%) by spark plasma sintering (SPS). Its high-temperature mechanical properties and compressive deformation behavior were investigated in a temperature range of 700 to 1050°C and a strain rate range of 0.002 to 0.2 s-1. The results show that the high-temperature mechanical properties of the high Nb containing TiAl alloy are sensitive to deformation temperature and strain rate, and the sensitivity to strain rate tends to rise with the deformation temperature increasing. The hot workability of the alloy is good at temperatures higher than 900°C, while fracture occurs at lower temperatures. The flow curves of the samples compressed at or above 900°C exhibit obvious flow softening after the peak stress. Under the deformation condition of 900-1050°C and 0.002-0.2 s-1, the interrelations of peak flow stress, strain rate, and deformation temperature follow the Arrhenius' equation modified by a hyperbolic sine function with a stress exponent of 5.99 and an apparent activation energy of 441.2 kJ·mol-1.

Lu, Xin; Zhao, Li-hua; Zhu, Lang-ping; Zhang, Bin; Qu, Xuan-hui

2012-04-01

352

Contribution to the study of mechanical properties of nuclear fuel: atomistic modelling of the deformation of uranium dioxide  

International Nuclear Information System (INIS)

Mechanical properties of nuclear fuel are a complex problem, involving many coupled mechanisms occurring at different length scales. We used Molecular Dynamics models to bring some light on some of these mechanisms at the atomic scale. We devised a procedure to calculate transition pathways between some UO2 polymorphs, and then carried out dynamics simulations of these transitions. We confirmed the stability of the cotunnite structure at high pressure using various empirical potentials, the fluorite structure being the most stable at room pressure. Moreover, we showed a reconstructive phase transition between the fluorite and cotunnite structures. We also showed the importance of the major deformation axis on the kind of transition that occur under tensile conditions. Depending on the loading direction, a scrutinyite or rutile phase can appear. We then calculated the elastic behaviour of UO2 using different potentials. The relative agreement between them was used to produce a set of parameters to be used as input in mesoscale models. We also simulated crack propagation in UO2 single crystals. These simulations showed secondary phases nucleation at crack tips, and hinted at the importance thereof on crack propagation at higher length-scales. We then described some properties of edge dislocations in UO2. The core structures were compared for various glide planes. The critical resolved shear stress was calculated for temperatures up to 2000 K. These calculations showed a link between lattice disorder at the dislocations core and the dislocations mobility. (author)

353

Influence of Microstructure, Produced by Heat Treatment and Sever Plastic Deformation, on Tribological Properties of Low-carbon Steel  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the results of tribological investigations conducted on steel 20 with the carbon content of up to 0.2%. The steel was studied in the three conditions: initial (hot-rolled, after heat-treatment (quenching+tempering and after heat treatment with subsequent severe plastic deformation (SPD performed by equal channel angular pressing technique (ECAP. It was stated that after various treatments the material acquires various structural conditions and possesses various strength properties and has a considerable difference in oxygen content in the surface layer. This influences the tribological properties during the contact with tool steel. The lowest values of adhesive bond shear strength, friction coefficient and wear rate are demonstrated in the material after martempering with subsequent SPD by ECAP technique. The surface of the investigated material after SPD treatment by the ECAP technique possesses a highest bearing capacity and requires more time for wearing-in in friction assemblies. Oxygen content increase in the form of metal oxides on the surface of low-carbon steels is accompanied by a decrease of the adhesive component of friction coefficien.

V. I. Semenov

2011-06-01

354

Carbon deposition during brittle rock deformation: Changes in electrical properties of fault zones and potential geoelectric phenomena during earthquakes  

Energy Technology Data Exchange (ETDEWEB)

To investigate potential mechanisms for geoelectric phenomena accompanying earthquakes, we have deformed hollow cylinders of Sioux quartzite to failure in the presence of carbonaceous pore fluids and investigated the resulting changes in electrical conductivity and carbon distribution. Samples were loaded at room temperature or 400 C by a hydrostatic pressure at their outer diameter, increasing pressure at a constant rate to {approx}290 MPa. Pore fluids consisted of pure CO, CO{sub 2}, CH{sub 4} and a 1:1 mixture of CO{sub 2} and CH{sub 4}, each with pore pressures of 2.0 to 4.1 MPa. Failure occurred by the formation of mode II shear fractures transecting the hollow cylinder walls. Radial resistivities of the cylinders fell to 2.9 to 3.1 M{Omega}-m for CO tests and 15.2 to 16.5 M{Omega}-m for CO{sub 2}:CH{sub 4} tests, compared with >23 M{Omega}-m for dry, undeformed cylinders. Carbonaceous fluids had no discernable influence on rock strength. Based on mapping using electron microprobe techniques, carbon occurs preferentially as quasi-continuous films on newly-formed fracture surfaces, but these films are absent from pre-existing surfaces in those same experiments. The observations support the hypothesis that electrical conductivity of rocks is enhanced by the deposition of carbon on fracture surfaces and imply that electrical properties may change in direct response to brittle deformation. They also suggest that the carbon films formed nearly instantaneously as the cracks formed. Carbon film deposition may accompany the development of microfracture arrays prior to and during fault rupture and thus may be capable of explaining precursory and coseismic geoelectric phenomena.

Mathez, E A; Roberts, J J; Duba, A G; Kronenberg, A K; Karner, S L

2008-05-16

355

Ab initio calculations of the magnetic properties of perovskites under deformation  

International Nuclear Information System (INIS)

Materials with perovskite and perovskite-like structures demonstrate a broad spectrum of physical properties. Colossal magnetoresistance, ferroelectricity, multiferroicity, superconductivity, charge ordering, metal-insulator transition, Jahn-Teller and other effects are observed in perovskites. These properties of the mentioned materials with the common formula ABO3 are very sensitive to the type of the cations A and B. La2/3Sr1/3MnO3 (LSMO) is a strongly correlated 3d transition metal oxide with a Curie temperature (TC) above RT (370 K). For other La/Sr ratios different types of antiferromagnetism are observed. Other perovskite, ruthenate SrRuO3 (SRO) is a 4d ferromagnet with TC = 160 K. Here we perform ab initio calculations for LSMO and SRO in ideal cubic, tetragonally distorted, and different orthorhombic structures. We focus on magnetic order and Curie temperature of the above mentioned structures in the different structural phases.

356

Mechanical and corrosion properties of aluminium alloy EN AW 6082 after severe plastic deformation (SPD  

Directory of Open Access Journals (Sweden)

Full Text Available The aim had been to study changes in the properties of aluminium alloy AlSiMgMn. Influence of SPD of the mechanical properties had increased (Rm by 86 MPa, Ro0,2 by 175 MPa, while A had decreased to 20 %. The corrosion potentials had been evaluated in the environment of H2O and in SARS. After SPD was observed in the environment of H2O, that resistance had increased by -218 mV and after exposure up to 1 000 min there was a slight deterioration of resistance in SARS. On the surface specimens after SPD were observed higher quantities of corrosion products. After SPD was observed fatigue characteristics in torsional stress in the oblique branches Wohler curves showed favourable characteristics of about 35 %.

P. Lacková

2015-01-01

357

Influence of strong uniaxial deformation on the properties of ?-irradiated neutron-doped silicon  

International Nuclear Information System (INIS)

In order to determine the origin of the anisotropy of high tensoresistivity of ?-irradiated usually doped Czochralski n-Si(P) crystals, the measurements of transport properties have been made for uniaxially strained, neutron-doped, and ?-irradiated n-Si(P) crystals. We observed the absence of a high anisotropy of the tensoresistivity in the latter even for the higher degree of the compensation of donor states by radiation-induced acceptor states as compared with the phosphorus-doped and ?-irradiated crystals. The comparative examination of the tensoresistivity properties of both kinds of doped and ?-irradiated crystals permits to determine that the mentioned above anisotropy may be connected with the striated distribution of phosphorus atoms and the subsequent nonhomogeneous compensation which emerges after ?-irradiation

358

Petrophysical Properties of Sandstones Containing Deformation Bands Versus Those With Fractures: the Importance of Grain Contact Strength to Fault-Zone Structure  

Science.gov (United States)

In upper crustal fault zones, the majority of slip accumulates within a fault core, which is surrounded by a less deformed damage zone. Both the width and structural character of the damage zone affect its mechanical and hydrologic properties. Fault-related deformation can change rock mechanical properties, causing stress orientations to rotate in fault damage zones, and affecting seismicity over time. In addition, the types, densities, and orientations of structures in fault zones exert a first-order control on fault-zone permeability structure, permeability anisotropy, and flow pathways. For example, open-fracture damage zones enhance fault-parallel flow, whereas cataclastic deformation band networks slow flow in every direction except parallel to the line of intersection between bands. To improve our understanding of controls on damage zone character, we explored relationships between fault-zone structure and lithologic characteristics such as porosity and cement mineralogy in faulted quartz-rich sandstones. The sandstones chosen from fault sites in the Jurassic Navajo and Entrada sandstones in Utah, and the Cretaceous Mesaverde sandstone in Wyoming, exhibit a wide range in porosity. Samples collected include even greater variability in cements, from clay coatings on grains to patchy carbonate cement to grain-bridging quartz overgrowths and iron oxide cements. These variables demonstrably influence damage zone character, resulting in fractures in some locations and deformation bands in others (even within a single fault zone) and affecting deformation-band damage zone width. They likely influenced grain-contact strength also. Because ultrasonic velocity and related elastic moduli also vary with grain-contact strength, we measured P and S wave velocities as a function of confining pressure to 20 MPa as a sensitive proxy for grain-contact strength. More than 40 samples, including both host rock and rock with deformation bands, have been analyzed. Samples containing deformation bands display different ultrasonic velocities than adjacent samples lacking deformation bands. These data are used to evaluate the relative importance of the variables affecting deformation in clastic rocks. Establishing a quantitative link between fault structures, cements, porosity, and lithology and ultrasonic velocity will ultimately allow results to be directly applied to borehole geophysics and seismic reflection studies to improve prediction of fault-zone characteristics and fluid flow properties in quartz-rich sandstone reservoirs.

Schneider, J. R.; Tobin, H. J.; Goodwin, L. B.

2010-12-01

359

Tensile properties and deformation mechanisms of a 14Cr ODS ferritic steel  

Science.gov (United States)

The search for a new cladding material is part of the research studies carried out at CEA to develop a sodium-cooled fast reactor meeting the expectations of the Generation IV International Forum. In this study, the tensile properties of a ferritic oxide dispersion strengthened steel produced by hot extrusion at CEA have been evaluated. They prove the studied alloy to be as resistant as and more ductile than the other nano-reinforced alloys of literature. The effects of the strain rate and temperature on the total plastic strain of the material remind of diffusion phenomena. Intergranular damage and intergranular decohesion are clearly highlighted.

Steckmeyer, A.; Praud, M.; Fournier, B.; Malaplate, J.; Garnier, J.; Béchade, J. L.; Tournié, I.; Tancray, A.; Bougault, A.; Bonnaillie, P.

2010-10-01

360

Mechanical and service properties of low carbon steels processed by severe plastic deformation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The structure and properties of the 0,09% C-Mn-Si-Nb-V-Ti, 0,1% C-Mn-V-Ti and 0,09% C-Mo-V-Nb low-carbon steels were studied after cold equal-channel angular pressing (ECAP). ECAP leads to the formation of partially submicrocrystalline structure with a grain size of 150 – 300 nm. The submicrocrystalline 0,09% C-Mn-Si-Nb-V-Ti steel compared with the normalized steel is characterized by Re higher more than by a factor of 2 and by the impact toughness higher by a factor of 3,5 at a test temper...

Zrnik, J.; Ilija Mamuzi?; Dobatkin, S.

2009-01-01

 
 
 
 
361

Microstructure and mechanical properties of power beam weld superalloys during cyclic deformation  

Energy Technology Data Exchange (ETDEWEB)

In the current study investigations in the range of finite life were carried out at laser beam welds of the superalloys X5NiCrTi26-15 and NiCr19Nb5Mo3 in solution annealed as well as precipitation hardened condition. Within the scope of these examinations a characterisation of the material condition by light- and electron-microscopy and the investigation of mechanical properties are shown. The results of constant amplitude tests at room temperature show, that the cyclic properties of the base material are much better than those of the welded joint, because of the notch effect of the weld. This notch effect could be reduced by precipitation hardening. After realisation constant amplitude tests at room temperature a investigation of the fracture surfaces of the specimen under cyclic conditions by light- and electron-microscopy occurs. The failure of laser beam welded specimen occurs with crack initiation and crack propagation at the HAZ and finished with the forced fracture which could be located at the base material, the HAZ as well as the weld metal. The aim of further research is to understand the influence of the microstructure on the physical failure mechanisms during cyclic loading. (orig.)

Spirowski, T.; Weiss, S.; Fischer, A. [Univ. GH Essen (Germany). Werkstofftechnik

2000-07-01

362

Mechanical properties and microstructure evolution of 1050 aluminum severely deformed by ECAP to 16 passes  

International Nuclear Information System (INIS)

Variation of mechanical properties and microstructure evolution in 1050 aluminum processed by equal channel angle pressing are investigated using Route BC and up to 16 passes. Micro hardness and compression testing were used to evaluate mechanical properties, whereas electron back scattered diffraction (EBSD) was used to document the variation of cell size and misorientation angle with number of passes. The hardness and yield strength exhibited an instant increase by a factor of about 2.75 and 2.96, respectively, compared to the annealed state, after only the first pass. It was found that the cell size gradually decreased with number of passes and attained an average value of about 0.6 ?m in the face plane (normal to the extrusion direction), and 0.85 ?m in the flow plane (parallel to the extrusion direction) after the sixteenth pass. The average misorientation angle evolved in both the face and flow planes ended up to about 27 deg. and 26 deg., respectively

363

Geometrical and mechanical properties of the fractures and brittle deformation zones based on the ONKALO tunnel mapping, 4390-4990 m tunnel chainage and the technical rooms  

International Nuclear Information System (INIS)

In this report, the rock mechanics parameters of fractures and brittle deformation zones have been estimated in the vicinity of the ONKALO underground research facility at the Olkiluoto site, western Finland. This report is an extension of two previously published reports describing the geometrical and mechanical properties of the fractures and brittle deformation zones based on ONKALO tunnel mapping from tunnel chainages 0-2400 m (Kuula 2010) and 2400-4390 m (Moenkkoenen et al. 2012). This updated report makes use of mapping data from tunnel chainage 4390-4990 m, including the technical rooms located at the -420 m below the sea level. Analysis of the technical rooms is carried out by dividing the premises according to depth into three sections: the demonstration tunnel level, the technical rooms level and the -457 level. The division is executed in order to define the fracture properties in separate areas and to compare the properties with other technical rooms levels. Drillhole data from holes OL-KR1...OL-KR57 is also examined. This report ends the series of three parameterization reports. The defined rock mechanics parameters of the fractures are based on the rock engineering classification quality index, Q', which incorporates the RQD, Jn, Jr and Ja values. The friction angle of the fracture surfaces is estimated from the Jr and Ja numbers. No new data from laboratory joint shear and normal tests was available at the time of the report. The fracture wall compressive strength (JCS) data is available from the chainage range 1280-2400 m. New data for fracture wall compressive strength is not available although new Schmidt hammer measurements were performed in order to obtain the ratio of the intact rock mass vs. an intact brittle deformation zone. Estimation of the mechanical properties of the 23 brittle deformation zones (BDZ) is based on the mapped Q' value, which is converted into the GSI value in order to estimate the strength and deformability properties. Components of the mapped Q' values are either from the ONKALO or the drill cores depending on the availability of intersections. The location and size of the brittle deformation zones are based on the latest interpretation (Aaltonen et al. expected in 2014). New laboratory data for the intact rock strength of the brittle deformation zones is not available. (orig.)

364

Changes in the structure and mechanical properties of submicrocrystalline titanium during deformation in a temperature range of (0.15-0.45) Tm  

International Nuclear Information System (INIS)

Specific features of VT1-0 titanium in a submicrocrystalline (SMC) state are studied along with structural changes and mechanical properties on deformation in a temperature range of (0.15-0.45) Tmelt. It is established that the formation of SMC-structure in titanium by means of warm intensive plastic deformation (IPD) is accompanied by dynamic strain aging (DSA). The evolution of the process within a temperature range of 300-425 Deg C results in an anomalous change of titanium mechanical properties: a ductility decrease, an yield stress growth, an increase of strain hardening rate. Based on the data on mechanical properties and of energy activation analysis a conclusion is made that SMC VT1-0 shows evidence of superplasticity in a narrow temperature-strain rate range. A lower temperature boundary is limited by DSA development, and an upper one is determined by SMC-structure instability

365

Anharmonicities in the vibrational spectra in deformed nuclei  

International Nuclear Information System (INIS)

Several experimental results have recently raised again the problem of the description of the anharmonicities of the vibrations observed in even-even deformed nuclei. They are very briefly recalled together with some of their interpretations. The multiphonon method has been developed to improve two approaches in two aspects: the Pauli principle is properly treated and exact diagonalisation within collective space is used. A sketch of this method is given. It is illustrated by the description of octupole vibrations in the Ra - Th region. Other possible applications are also indicated

366

Confined crystallization, crystalline phase deformation and their effects on the properties of crystalline polymers  

Science.gov (United States)

With the recent advances in processing and catalyst technology, novel morphologies have been created in crystalline polymers and they are expected to substantially impact the properties. To reveal the structure-property relationships of some of these novel polymeric systems becomes the primary focus of this work. In the first part, using an innovative layer-multiplying coextrusion process to obtain assemblies with thousands of polymer nanolayers, dominating "in-plane" lamellar crystals were created when the confined poly(ethylene oxide) (PEO) layers were made progressively thinner. When the thickness was confined to 25 nanometers, the PEO crystallized as single, high-aspect-ratio lamellae that resembled single crystals. This crystallization habit imparted more than two orders of magnitude reduction in the gas permeability. The dramatic decrease in gas permeability was attributed to the reduced diffusion coefficient, because of the increase in gas diffusion path length through the in-plane lamellae. The temperature dependence of lamellar orientation and the crystallization kinetics in the confined nanolayers were also investigated. The novel olefinic block copolymer (OBC) studied in the second part consisted of long crystallizable sequences with low comonomer content alternating with rubbery amorphous blocks with high comonomer content. The crystallizable blocks formed lamellae that organized into space-filling spherulites even when the fraction of crystallizable block was so low that the crystallinity was only 7%. These unusual spherulites were highly elastic and recovered from strains as high as 300%. These "elastic spherulites" imparted higher strain recovery and temperature resistance than the conventional random copolymers that depend on isolated, fringed micellar-like crystals to provide the junctions for the elastomeric network. In the third part, positron annihilation lifetime spectroscopy (PALS) was used to obtain the temperature dependence of the free volume hole size in propylene/ethylene copolymers over a range in comonomer content. Above the glass transition temperature (Tg), the reduced free volume hole size and the densification of the amorphous phase were attributed to constraint imposed on rubbery amorphous chain segments by attached chain segments in crystals. However constant free volume fraction was found at Tg, across the crystallinity range of the copolymers, in agreement with the iso-free volume concept of glass transition.

Wang, Haopeng

367

Mechanical properties and constitutive relations for molybdenum under high-rate deformation  

Energy Technology Data Exchange (ETDEWEB)

Molybdenum and its alloys have received increased interest in recent years for ballistic applications. The stress-strain behavior of several molybdenums possessing various compositions, manufacturing sources, and the degree of pre-straining, were investigated as a function of temperature from 77 to 1,273 K, and strain rate from 10{sup {minus}3} s{sup {minus}1} to 8,000 s{sup {minus}1}. The yield stress was found to be sensitive to the test temperature and strain rate, however, the strain hardening remained rate-insensitive. The constitutive response of a powder-metallurgy molybdenum was also investigated; similar mechanical properties compared to conventionally wrought processed molybdenums were achieved. Constitutive relations based upon the Johnson-Cook, the Zerilli-Armstrong and the Mechanical Threshold Stress (MTS) models were evaluated and fit for the various Mo-based materials. The capabilities and limitations of each model for large-strain applications were examined. The differences between the three models are demonstrated using model comparisons to Taylor cylinder validation experiments.

Chen, S.R.; Maudlin, P.J.; Gray, G.T. III

1998-01-01

368

A 3D-RBS study of irradiation-induced deformation and masking properties of ordered colloidal nanoparticulate masks  

Energy Technology Data Exchange (ETDEWEB)

The 500 keV Xe{sup 2+} irradiation-induced anisotropic deformation of ordered colloidal silica nanoparticulate masks is followed using 2 MeV {sup 4}He{sup +} Rutherford Backscattering Spectrometry (RBS) with different measurement geometries and the improved data analysis capabilities of the RBS-MAST spectrum simulation code. The three-dimensional (3D) geometrical transformation from spherical to oblate ellipsoidal and polygonal shape and the decrease of the mask's hole size is described. The masking properties of the silica monolayer and the depth distribution of Xe in the underlying Si substrate vs. the irradiated Xe{sup 2+} fluence are discussed. Field Emission Scanning Electron Microscopy (FESEM) is applied as complementary characterization tool. Our results give contribution to clarify the impact of ion-nanoparticle interactions on the potentials and limits of nanosphere lithography. We also show the capability of the conventional RBS technique to characterize laterally ordered submicron-sized three-dimensional structures.

Zolnai, Z., E-mail: zolnai@mfa.kfki.h [Research Institute for Technical Physics and Materials Science, P.O.B. 49, H-1525 Budapest (Hungary); Deak, A.; Nagy, N.; Toth, A.L. [Research Institute for Technical Physics and Materials Science, P.O.B. 49, H-1525 Budapest (Hungary); Kotai, E. [Research Institute for Particle and Nuclear Physics, P.O.B. 49, H-1525 Budapest (Hungary); Battistig, G. [Research Institute for Technical Physics and Materials Science, P.O.B. 49, H-1525 Budapest (Hungary)

2010-01-01

369

Mechanical properties and microstructure of 6061 aluminum alloy severely deformed by ARB process and subsequently aged at low temperatures  

Science.gov (United States)

In order to clarify the aging behavior in ultrafine grained (UFG) Al alloys, a commercial Al-Mg-Si alloy was severely deformed by accumulative roll-bonding (ARB) process and subsequently aged at 100°C or 170°C. The age-hardening behavior and microstructure change during aging were investigated. At 170 °C, age-hardening was observed in solution treated (ST) specimens, but solution-treated and ARB-processed specimens were not hardened by aging. On the other hand, the hardness of the both ST specimen and ARB-processed specimen increased by aging at 100°C. From TEM observation, it was found that the ARB- processed specimen had an ultrafine lamellar boundary structure and the structure was kept during aging at 170°C and 100°C. In the ST specimen aged at 170°C, fine precipitates were observed within coarse grains. In the specimen ARB-processed and subsequently aged at 170°C, coarser precipitates were observed within ultrafine grains and on grain boundaries. It was considered that the reason why the hardness of the specimens ARB-processed and subsequently aged did not increase was coarsening of precipitates. In the specimens aged at 100°C, obvious precipitates were not observed, but clusters Mg and Si seemed to form during the aging, leading to the increase in the hardness of the specimen. From the results, it was suggested that aging at low temperatures could improve mechanical properties of Al alloys through combining grain refinement and precipitation hardening.

Terada, Daisuke; Kaneda, Yoma; Horita, Zenji; Matsuda, Kenji; Hirosawa, Shoichi; Tsuji, Nobuhiro

2014-08-01

370

Electrical and optical properties of stacking faults introduced by plastic deformation in 4H-SiC  

International Nuclear Information System (INIS)

The electrical and optical properties of stacking faults (SFs) introduced by plastic deformation in 4H-SiC were studied by Electron Beam Induced Current (EBIC) and cathodoluminescence (CL) methods. Partial dislocations and stacking faults in the (0001) glide planes perpendicular to the surface were introduced in n-type 4H-SiC under a well-controlled state of stress by cantilever bending at 550°C. CL measurements allow determining the multiplicity of the SFs (single or double). It is observed that the overwhelming majority of stacking faults are double Shockley type SFs (CL emission at 504 nm) that correlates well with previously published high resolution transmission electron microscopy (HRTEM) investigations. However, single Shockley type SFs (CL emission at 422 nm) of much smaller lengths are also observed in some areas near the scratched region from where the defects are nucleated. This suggests that the velocity of partial dislocation pairs under a given applied stress could be higher than that of single partial dislocations. It is also shown that in the EBIC mode, SFs produce a strong bright contrast, which can be explained by considering the SFs in 4H-SiC to be quantum wells of II type

371

Electrical and optical properties of stacking faults introduced by plastic deformation in 4H-SiC  

Energy Technology Data Exchange (ETDEWEB)

The electrical and optical properties of stacking faults (SFs) introduced by plastic deformation in 4H-SiC were studied by Electron Beam Induced Current (EBIC) and cathodoluminescence (CL) methods. Partial dislocations and stacking faults in the (0001) glide planes perpendicular to the surface were introduced in n-type 4H-SiC under a well-controlled state of stress by cantilever bending at 550°C. CL measurements allow determining the multiplicity of the SFs (single or double). It is observed that the overwhelming majority of stacking faults are double Shockley type SFs (CL emission at 504 nm) that correlates well with previously published high resolution transmission electron microscopy (HRTEM) investigations. However, single Shockley type SFs (CL emission at 422 nm) of much smaller lengths are also observed in some areas near the scratched region from where the defects are nucleated. This suggests that the velocity of partial dislocation pairs under a given applied stress could be higher than that of single partial dislocations. It is also shown that in the EBIC mode, SFs produce a strong bright contrast, which can be explained by considering the SFs in 4H-SiC to be quantum wells of II type.

Pichaud, B.; Regula, G. [Aix-Marseille Université, CNRS, IM2NP, UMR 7334, 13397, Marseille, France and Université de Toulon, CNRS, IM2NP, UMR 7334, 83957, La Garde (France); Yakimov, E. B. [Institute of Microelectronics Technology RAS, 142432, Chernogolovka (Russian Federation)

2014-02-21

372

Electrical and optical properties of stacking faults introduced by plastic deformation in 4H-SiC  

Science.gov (United States)

The electrical and optical properties of stacking faults (SFs) introduced by plastic deformation in 4H-SiC were studied by Electron Beam Induced Current (EBIC) and cathodoluminescence (CL) methods. Partial dislocations and stacking faults in the (0001) glide planes perpendicular to the surface were introduced in n-type 4H-SiC under a well-controlled state of stress by cantilever bending at 550°C. CL measurements allow determining the multiplicity of the SFs (single or double). It is observed that the overwhelming majority of stacking faults are double Shockley type SFs (CL emission at 504 nm) that correlates well with previously published high resolution transmission electron microscopy (HRTEM) investigations. However, single Shockley type SFs (CL emission at 422 nm) of much smaller lengths are also observed in some areas near the scratched region from where the defects are nucleated. This suggests that the velocity of partial dislocation pairs under a given applied stress could be higher than that of single partial dislocations. It is also shown that in the EBIC mode, SFs produce a strong bright contrast, which can be explained by considering the SFs in 4H-SiC to be quantum wells of II type.

Pichaud, B.; Regula, G.; Yakimov, E. B.

2014-02-01

373

Influence of the pearlite fineness on the mechanical properties, deformation behavior, and fracture characteristics of carbon steel  

Science.gov (United States)

Specific features of plastic deformation and tensile failure of a plain carbon ( C = 0.62%) pearlitic-ferritic steel with various pearlite fineness have been investigated. It is shown that the steels with coarse lamellar pearlite and fine lamellar pearlite have similar strain-hardening coefficients, but the relative elongation of the former steel is higher. Deformation results in a uniform dislocation distribution in the fine pearlite and in the formation of a cellular substructure in the coarse pearlite. It is established that the fine pearlite undergoes plastic deformation and ductile failure as a single structure, while the coarse pearlite exhibits a structure discontinuity upon deformation. A model of microplastic pearlite deformation and the initial stage of macroplastic pearlite deformation is proposed. It is established that the strain-hardening coefficient of pearlite at the initial deformation stage does not depend on its dispersity. A size effect, which manifests itself in the dependence of the dislocation structure formed in the ferrite interlayers on their thickness, is shown to be characteristic of pearlite deformation.

Izotov, V. I.; Pozdnyakov, V. A.; Luk'yanenko, E. V.; Usanova, O. Yu.; Filippov, G. A.

2007-05-01

374

Joint Probability Distribution Function for the Electric Microfield and its Ion-Octupole Inhomogeneity Tensor  

International Nuclear Information System (INIS)

From experiments, see e.g. [W. Wiese, D. Kelleher, and D. Paquette, Phys. Rev. A 6, 1132 (1972); V. Helbig and K. Nich, J. Phys. B 14, 3573 (1981).; J. Halenka, Z. Phys. D 16, 1 (1990); . Djurovic, D. Nikolic, I. Savic, S. Sorge, and A.V. Demura, Phys. Rev. E 71, 036407 (2005)], results that the hydrogen lines formed in plasma with Ne ? 1016 cm-3 are asymmetrical. The inhomogeneity of ionic micro field and the higher order corrections (quadratic and next ones) in perturbation theory are the reason for such asymmetry. So far, the ion-emitter quadrupole interaction and the quadratic Stark effect have been included in calculations. The recent work shows that a significant discrepancy between calculations and measurements occurs in the wings of H-beta line in plasmas with cm-3. It should be stressed here that e.g. for the energy operator the correction raised by the quadratic Stark effect is proportional to (where is the emitter-perturber distance) similarly as the correction caused by the emitter-perturber octupole interaction and the quadratic correction from emitter-perturber quadrupole interaction. Thus, it is obvious that a model of the profile calculation is consistent one if all the aforementioned corrections are simultaneously included. Such calculations are planned in the future paper. A statistics of the octupole inhomogeneity tensor in a plasma is necessarily needed in the first step of such calculations. For the first time the distribution functions of the octupole inhomogeneity have been calculated in this paper using the Mayer-Mayer cluster expansion method similarly as for the quadrupole function in the paper [J. Halenka, Z. Phys. D 16, 1 (1990)]. The quantity is the reduced scale of the micro field strength, where is the Holtsmark normal field and is the mean distance defined by the relationship, that is approximately equal to the mean ion-ion distance; whereas is the screening parameter, where is the electronic Debye radius. (author)

375

Octupole contributions to the generalized oscillator strengths of discrete dipole transitions in noble-gas atoms  

Science.gov (United States)

The generalized oscillator strengths (GOS’s) of discrete excitations np?nd and np?(n+1)s,d , both dipole (L=1) and octupole (L=3) , are studied. We demonstrate that although the relevant transitions in the same atom are closely located in energy, the dependence of their GOS’s on the momentum transfer squared q2 is remarkably different; viz., the GOS’s corresponding to L=3 have at least one extra maximum as a function of q2 and dominate over those of the L=1 , starting from about q2=1.5a.u. Peculiarities are noted in the GOS of only the Ne dipole 2p?3s transition in contrast to the rest of the atoms; viz., the characteristic minimum and the maximum are not obliterated by the dominance of 2p?3d GOS dipole and octupole sum as in the other atoms. The depth of the minimum of the GOS for the dipole 2p?3s transition is reduced considerably by the 2p?3d dipole and octupole GOS sums, while the corresponding maximum is enhanced. In the GOS sum both the minimum and maximum are still identifiable, permitting experimental observation. The calculations were performed in the one particle Hartree-Fock (HF) approximation and with account of many-electron correlations via the random phase approximation with exchange (RPAE). The GOS’s are studied for values of q2 up to 50a.u. Our calculated RPAE GOS’s for the Ar3p?4s dipole transition compare very well with the recently measured data of Zhu [Phys. Rev. A 73, 042703 (2006)].

Amusia, M. Ya.; Chernysheva, L. V.; Felfli, Z.; Msezane, A. Z.

2007-06-01

376

Octupole contributions to the generalized oscillator strengths of discrete dipole transitions in noble-gas atoms  

International Nuclear Information System (INIS)

The generalized oscillator strengths (GOS's) of discrete excitations np?nd and np?(n+1)s,d, both dipole (L=1) and octupole (L=3), are studied. We demonstrate that although the relevant transitions in the same atom are closely located in energy, the dependence of their GOS's on the momentum transfer squared q2 is remarkably different; viz., the GOS's corresponding to L=3 have at least one extra maximum as a function of q2 and dominate over those of the L=1, starting from about q2=1.5 a.u. Peculiarities are noted in the GOS of only the Ne dipole 2p?3s transition in contrast to the rest of the atoms; viz., the characteristic minimum and the maximum are not obliterated by the dominance of 2p?3d GOS dipole and octupole sum as in the other atoms. The depth of the minimum of the GOS for the dipole 2p?3s transition is reduced considerably by the 2p?3d dipole and octupole GOS sums, while the corresponding maximum is enhanced. In the GOS sum both the minimum and maximum are still identifiable, permitting experimental observation. The calculations were performed in the one particle Hartree-Fock (HF) approximation and with account of many-electron correlations via the random phase approximation with exchange (RPAE). The GOS's are studied for values of q2 up to 50 a.u. Our calculated RPAE GOS's for the Ar 3p?4s dipole transition compare very well with the recently measured data of Zhu et al. [Phys. Rev. A 73, 042703 (2006)]s. Rev. A 73, 042703 (2006)

377

Role of deformation on giant resonances within the quasiparticle random-phase approximation and the Gogny force  

International Nuclear Information System (INIS)

Fully consistent axially-symmetric-deformed quasiparticle random phase approximation (QRPA) calculations have been performed, in which the same Gogny D1S effective force has been used for both the Hartree-Fock-Bogolyubov mean field and the QRPA approaches. Giant resonances calculated in deformed 26-28Si and 22-24Mg nuclei as well as in the spherical 30Si and 28Mg isotopes are presented. Theoretical results for isovector-dipole and isoscalar monopole, quadrupole, and octupole responses are presented and the impact of the intrinsic nuclear deformation is discussed

378

Progress Towards A Permanent Octupole Magnetic Ultra-Cold Neutron Trap for Lifetime Measurements  

CERN Document Server

The current knowledge of the neutron $\\beta$-decay lifetime has come under scrutiny as of late due to large disagreements between recent precise measurements. Measurements using magnetically trapped Ultra-Cold Neutrons (UCNs) offer the possibility of storage without spurious losses which can provide a reliable value for the neutron lifetime. The progress towards realizing a neutron lifetime measurement using a Ioffe-type trap made with a Halbach-type permanent octupole magnet is presented here. The experimental procedure extracts a gas of UCNs into vacuum, which reduces many known channels of neutron losses, and detects the neutron decays via in-situ detection of the produced protons.

Leung, Kent

2008-01-01

379

Dipole octupole correlations in a boson model and evidence for their existence in nuclei  

International Nuclear Information System (INIS)

The interacting multi boson model (IMBM) introduced earlier, in its spdf boson case, is applied to a new experiment on the vibrational nucleus 21888Ra130. It is shown to describe in a ntural way, with the essential participation of pf bosons, both the ground yrast bands with positive and negative parity, and the peculiar side yrare bands with the same space ? and opposite spin (-(1 parity. So this experiment together with its boson interpretation can be viewed as evidence for the existence of combined dipole octupole correlations in nuclei

380

Dipole-octupole correlations in a boson model and evidence for their existence in nuclei  

Energy Technology Data Exchange (ETDEWEB)

The interacting multiboson model (IMBM) introduced earlier, in its spdf boson case, is applied to a new experiment on the vibrational nucleus /sub 88//sup 218/Ra/sub 130/. It is shown to describe in a natural way, with the essential participation of pf bosons, both the ground yrast bands with positive and negative parity, and the peculiar side yrare bands with the same space ..pi.. and opposite spin (-)/sup I/ parity. So this experiment together with its boson interpretation can be viewed as evidence for the existence of combined dipole-octupole correlations in nuclei.

Mikhailov, I.N.; Nadjakov, E.G.; Aiche, M.; Schulz, N.; Vanin, V.; Briancon, Ch.

1989-02-01

 
 
 
 
381

Electric-dipole transitions and octupole softness in odd-A rare-earth nuclei  

International Nuclear Information System (INIS)

It is found that B(E1) values calculated by using a model, in which one quasiparticle is coupled to a rotor, are more than an order of magnitude too small compared with measured B(E1) values in low-energy transitions observed in the yrast spectroscopy of odd-A rare-earth nuclei. Thus, the measured B(E1) values are analyzed by introducing the parameters which effectively take into account the octupole softness. An estimate of the parameters based on a microscopic model is made, and a discrepancy between the estimated values and the values necessary for reproducing data is found. (au)

382

Spectroscopy on a single trapped 137Ba+ ion for nuclear magnetic octupole moment determination  

CERN Document Server

We present precision measurements of the hyperfine splittings in the 5D3/2 manifold of a single trapped Barium ion, 137Ba+ . Measurements of the hyperfine splittings are made between mF = 0 sublevels over a range of magnetic fields allowing us to interpolate to the zero field splittings with an accuracy below 10 Hz. Our results, in conjunction with theoretical calculations, allow the determination of the hyperfine coupling constant, C, with an accuracy below 0.1 Hz. This gives a subsequent determination of the nuclear magnetic octupole moment with an uncertainty limited almost completely by the accuracy of theoretical calculations.

Lewty, Nicholas C; Cazan, Radu; Barrett, M D

2012-01-01

383

A novel antiproton radial diagnostic based on octupole induced ballistic loss  

CERN Document Server

We report results from a novel diagnostic that probes the outer radial profile of trapped antiproton clouds. The diagnostic allows us to determine the profile by monitoring the time-history of antiproton losses that occur as an octupole field in the antiproton confinement region is increased. We show several examples of how this diagnostic helps us to understand the radial dynamics of antiprotons in normal and nested Penning-Malmberg traps. Better understanding of these dynamics may aid current attempts to trap antihydrogen atoms.

Andresen, G B; Bowe, P D; Bray, C C; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Fajans, J; Fujiwara, M C; Funakoshi, R; Gill, D R; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jørgensen, L V; Kurchaninov, L; Lambo, R; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Page, R D; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Seif El Nasr, S; Silveira, D M; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y

2008-01-01

384

Experimental determination of the nuclear magnetic octupole moment of $^{137}$Ba$^+$ ion  

CERN Document Server

We perform precision measurements on the 5D$_{5/2}$ manifold hyperfine intervals of a single trapped ion, $^{137}$Ba$^+$. RF spectroscopy is used to measure the hyperfine intervals to an accuracy of a few Hz. Our results provide a three orders of magnitude improvement in accuracy over previous work and also provide a 10-fold improvement in the value of $g_J$ for this level. These results complement our previous work on the 5D$_{3/2}$ manifold of $^{137}$Ba$^+$, providing an independent measurement of the nuclear octupole, and a consistency check on atomic structure calculations.

Lewty, Nicholas C; Cazan, Radu; Sahoo, B K; Barrett, M D

2013-01-01

385

Octupole Contributions to the Generalized Oscillator Strengths of Discrete Dipole Transitions in Noble Gases  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The generalized oscillator strengths (GOS) of discrete excitations np-nd, both dipole (L=1) and octupole (L=3) are studied, the latter for the first time. We demonstrate that although the relevant transitions in the same atom are closely located in energy, the dependence of their GOS on the momentum transfer q squared, is remarkably different, so that the GOS corresponding to L=3 have at least one extra maximum as a function of q squared and dominate over those of the L=1, s...

Amusia, M. Ya; Chernysheva, L. V.; Felfli, Z.; Msezane, A. Z.

2007-01-01

386

Observation of the high-energy octupole giant resonance with 800-MeV protons  

International Nuclear Information System (INIS)

Inelastic scattering of 800-MeV protons from 40Ca, 116Sn, and 208Pb shows a broad giant resonance at an excitation energy of 110/A/sup 1/3/ MeV. The angular distributions are consistent only with scalar-isoscalar l=3 transfer. The excitation energy and width of this high-energy octupole giant resonance are in reasonable accord with theory. However its energy-weighted sum-rule strength (approx.20%) is only about one-half that predicted by random- phase-approximation calculations

387

Predictability of hydraulic head changes and characterization of aquifer-system and fault properties from InSAR-derived ground deformation  

Science.gov (United States)

evaluate the benefits of space-derived ground deformation measurements for basin-wide characterization of aquifer-system properties and groundwater levels. We use Interferometric Synthetic Aperture Radar (InSAR) time series analysis of ERS, Envisat, and ALOS SAR data to resolve 1992-2011 ground deformation in the Santa Clara Valley, California. T-mode principal component analysis successfully isolates temporally variable deformation patterns embedded in the multidecadal time series. The data reveal uplift at 0.4 cm/yr between 1992 and 2000 and illustrating the end of the aquifer-system's poroelastic rebound following recovery of hydraulic heads after the 1960s low stand. In addition, seasonal elastic deformation with amplitude of up to 3 cm, in phase with head fluctuations, is observed over the confined aquifer sharply partitioned by the Quaternary Silver Creek Fault (SCF). Integration of this deformation with hydraulic head data enables characterization of the aquifer-system storativity and elastic skeletal specific storage. Modeling of the deformation partitioning across the SCF constrains the fault's last tectonic activity, hydraulic conductivity, and material composition. The SCF likely cuts the shallow confining clays and was last active since ~140 ka, it has a horizontal hydraulic conductivity several orders of magnitude lower than the surrounding aquifer-system, and is likely composed of clays, making it an effective barrier to across-fault fluid flow. Finally, we show that after a period of calibration, InSAR can be used to characterize basin-wide water level changes without well measurements with an accuracy of 70%, which demonstrates that it provides useful data for groundwater management.

Chaussard, E.; Bürgmann, R.; Shirzaei, M.; Fielding, E. J.; Baker, B.

2014-08-01

388

Deformation resistance of metals as a result of self-organization of a system. Communication 1. On a role of grain boundaries in formation of metal properties  

International Nuclear Information System (INIS)

A new approach to the estimation of grain boundary contribution to formation of metal and alloy properties if proposed. The metal, both deformed and annealed, is considered as a self-organized system. Dissipative structures grain boundaries included exist in the material in initial undeformed state. Evaluation technique for interface induced stresses is suggested. Possible reasons for serrated yielding are discussed. Comparison of calculated and experimental data is made for nickel and austenitic steel. 16 refs., 2 figs

389

Preseismic and Postseismic Deformations Associated with Tohoku Earthquake and the Mechanical Properties of the Asthenosphere and of the Subduction Interface  

Science.gov (United States)

The postseismic and preseismic deformations preceding and following Tohoku earthquake have been recorded by the GPS stations of the GSI network and also far-field stations in far-East Russia, Korea and China. Using a 3D finite element model, we show that postseismic motions in the far-field can only be explained by relaxation in asthenosphere. We believe important to take into account this relaxation to interpret the data in the middle-field (over Japan). It can for example explain most of the postseismic velocities over southern Japan. However, the velocity pattern over Honshu, and in particular the postseismic uplift on the east coast of Honshu cannot be explained by this relaxation. Relaxation in a low viscosity wedge extending below the volcanic arc and viscous relaxation or aseismic slip on the bottom part of the interface are potential candidates for explaining uplift over the eastern part of Tohoku. While simple newtonian creep in a subduction channel and in the wedge or aseismic slip on the deep portions of the interface can both be compatible with the observed horizontal and vertical postseismic motions in front of the earthquake epicenter, the direction and large amplitude of motions further south (around 35°N) are only compatible with aseismic slip. This aseismic slip is going on since Tohoku earthquake and it clearly relaxes not only the stresses induced by Tohoku earthquake but rather stresses accumulated on the interface, at intermediate depths (around 45km depth), long before the megathrust earthquake which only triggered this aseismic slip. An interface with brittle asperities imbedded in a low viscosity material (serpentine?) are shown to have the appropriate properties to explain the observations, in particular to account for accumulation of stresses and relaxation on a time-scale of several years.

Trubienko, O.; Fleitout, L.; Garaud, J.; Shestakov, N.

2013-12-01

390

THE EFFECT OF SUPERPLASTIC DEFORMATION ON THE TENSILE AND FATIGUE PROPERTIES OF Al-Li (8090) ALLOY  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Superplastic deformation of the new generation of aerospace aluminium-lithium alloys has generated considerable interest in the aerospace industry not only with the potential savings in component weight and manufacturing costs but also for development of novel designs. Even though many papers have addressed the superplastic deformation characteristics of these alloys it is essential for their exploitation to determine and to understand the effect of the forming process on their mechanical pro...

Mcdarmaid, D.; Shakesheff, A.

1987-01-01

391

High spin octupole correlations in the N=85, {sup 139}Xe and {sup 141}Ba isotones  

Energy Technology Data Exchange (ETDEWEB)

High spin states in {sup 139}Xe and {sup 141}Ba have been investigated using {gamma}-{gamma} - and {gamma}-{gamma}-{gamma}-coincidence studies of spontaneous fission of {sup 252}Cf. Alternating parity bands built on a 7/2-level are assigned up to spin I=(37/2) and I=(29/2) in {sup 139}Xe and {sup 141}Ba, respectively. Another possible octupole band based on {nu}i{sub 132}(f{sub 7/2}){sup 2} multiplet with spin up to (29/2) also is observed in both nuclei. Cascades of enhanced E1 transitions and B(E1)/B(E2) ratios indicate strong octupole correlations. Systematics of the {nu}(f{sub 7/2}){sup 3}, {nu}(f{sub 7/2}){sup 3}x3{sup -} and {nu}u{sub 13/2}(f{sub 7/2}){sup 2} multiplets and bands in N 85 isotones are presented. (author). Letter-to-the-editor.

Zhu, S.J. [Physics Department, Tsinghua University, Beijing, 100084 (China); Department of Physics, Vanderbilt University, Nashville, TN 37235 (United States); Joint Institute for Heavy Ion Research, Oak Ridge, TN 37831 (United States); Hamilton, J.H.; Ramayya, A.V.; Jones, E.F.; Hwang, J.K.; Babu, B.R.S.; Ginter, T.N.; Kormicki, J. [Department of Physics, Vanderbilt University, Nashville, TN 37235 (United States); Wang, M.G.; Long, G.L.; Li, M.; Zhu, L.Y.; Deng, J.K. [Physics Department, Tsinghua University, Beijing, 100084 (China); Ma, W.C. [Department of Physics, Mississippi State University, MS 39762 (United States); Cole, J.D.; Aryaeinejad, R.; Dardenne, Y.K.; Drigert, M.W. [Idaho National Engineering Laboratory, Idaho Falls, ID 83415 (United States); Ter Akopian, G. [Department of Physics, Vanderbilt University, Nashville, TN 37235 (United States); Flerov Laboratory for Nuclear Reaction, Joint Institute for Nuclear Research, Dubna (Russian Federation); Oganessian, Yu.Ts. [Flerov Laboratory for Nuclear Reaction, Joint Institute for Nuclear Research, Dubna (Russian Federation); Daniel, A. [Department of Physics, Vanderbilt University, Nashville, TN 37235 (United States); Rasmussen, J.O.; Stoyer, M.A.; Chu, S.Y.; Gregorich, K.E.; Mohar, M.F. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Lee, I.Y. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Prussin, S.G. [Department of Nuclear Engineering, University of California, Berkeley, CA (United States); Johnson, N.R.; McGowan, F.K. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

1997-09-01

392

Persistence of octupole correlations in sup 2 sup 3 sup 1 Ra  

CERN Document Server

The structure of sup 2 sup 3 sup 1 Ra, the heaviest odd Ra nucleus currently accessible for detailed spectroscopic investigation, has been studied in the beta sup - decay of sup 2 sup 3 sup 1 Fr. The main purpose has been to verify whether fast B(E1) rates and significant octupole correlations recently established in sup 2 sup 2 sup 9 Ra persist in sup 2 sup 3 sup 1 Ra. The excited states in sup 2 sup 3 sup 1 Ra have been determined for the first time. Spins and parities have been deduced from conversion electron measurements, while level half-lives in the ps and ns ranges have been measured with the Advanced Time Delayed beta gamma gamma(t) method. The moderately fast B(E1) rates found for transitions connecting the lowest-lying K suppi=5/2 sup+- and K suppi=1/2 sup+- bands, reveal the persistence of octupole collective effects in sup 2 sup 3 sup 1 Ra, although the B(E1) rates are lower than in sup 2 sup 2 sup 9 Ra. These findings reinforce the differences in the B(E1) systematics between isotonic Ra and Th ...

Fraile-Prieto, L M; Mach, H; Boutami, R; Aas, A J; Fogelberg, B; García-Raffi, L M; Grant, I S; Gulda, K; Hageboe, E; Kurcewicz, W; Kvasil, J; López, M J; Løvhøiden, G; Martínez, T; Rubio, B; Taín, J L; Tengblad, O

2001-01-01

393

Construction and Operational Experience with a Superconducting Octupole Used to Trap Antihydrogen  

Energy Technology Data Exchange (ETDEWEB)

A superconducting octupole magnet has seen extensive service as part of the ALPHA experiment at CERN. ALPHA has trapped antihydrogen, a crucial step towards performing precision measurements of anti-atoms. The octupole was made at the Direct Wind facility by the Superconducting Magnet Division at Brookhaven National Laboratory. The magnet was wound with a six-around-one NbTi cable about 1 mm in diameter. It is about 300 mm long, with a radius of 25 mm and a peak field at the conductor of 4.04 T. Specific features of the magnet, including a minimal amount of material in the coil and coil ends with low multipole content, were advantageous to its use in ALPHA. The magnet was operated for six months a year for five years. During this time it underwent about 900 thermal cycles (between 4K and 100K). A novel operational feature is that during the course of data-taking the magnet was repeatedly shut off from its 950 A operating current. The magnet quenches during the shutoff, with a decay constant of 9 ms. Over the course of the five years, the magnet was deliberately quenched many thousands of times. It still performs well.

Wanderer P.; Escallier, J.; Marone, A.; Parker, B.

2011-09-06

394

High-Accuracy Optical Clock Based on the Octupole Transition in Yb+171  

Science.gov (United States)

We experimentally investigate an optical frequency standard based on the 467 nm (642 THz) electric-octupole reference transition S1/22(F=0)?F7/22(F=3) in a single trapped Yb+171 ion. The extraordinary features of this transition result from the long natural lifetime and from the 4f136s2 configuration of the upper state. The electric-quadrupole moment of the F7/22 state is measured as -0.041(5)ea02, where e is the elementary charge and a0 the Bohr radius. We also obtain information on the differential scalar and tensorial components of the static polarizability and of the probe-light-induced ac Stark shift of the octupole transition. With a real-time extrapolation scheme that eliminates this shift, the unperturbed transition frequency is realized with a fractional uncertainty of 7.1×10-17. The frequency is measured as 642 121 496 772 645.15(52) Hz.

Huntemann, N.; Okhapkin, M.; Lipphardt, B.; Weyers, S.; Tamm, Chr.; Peik, E.

2012-03-01

395

Multi-dimensional potential energy surfaces and non-axial octupole correlations in actinide and transfermium nuclei from relativistic mean field models  

Science.gov (United States)

We have developed multi-dimensional constrained covariant density functional theories (MDC-CDFT) for finite nuclei in which the shape degrees of freedom ??? with even ?, e.g., ?20, ?22, ?30, ?32, ?40, etc., can be described simultaneously. The functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the non-linear or density-dependent couplings. For the pp channel, either the BCS approach or the Bogoliubov transformation is implemented. The MDC-CDFTs with the BCS approach for the pairing (in the following labelled as MDC-RMF models with RMF standing for "relativistic mean field") have been applied to investigate multi-dimensional potential energy surfaces and the non-axial octupole Y32-correlations in N = 150 isotones. In this contribution we present briefly the formalism of MDC-RMF models and some results from these models. The potential energy surfaces with and without triaxial deformations are compared and it is found that the triaxiality plays an important role upon the second fission barriers of actinide nuclei. In the study of Y32-correlations in N = 150 isotones, it is found that, for 248Cf and 260Fm, ?32 > 0.03 and the energy is lowered by the ?32 distortion by more than 300 keV; while for 246Cm and 252No, the pocket with respect to ?32 is quite shallow.

Lu, Bing-Nan; Zhao, Jie; Zhao, En-Guang; Zhou, Shan-Gui

2014-03-01

396

One-phonon octupole vibrational states in 211At, 212Rn, 213Fr and 214Ra with N = 126  

International Nuclear Information System (INIS)

Excited high spin states in 211At, 212Rn, 213Fr and 214Ra with N = 126 are reorganized and interpreted in terms of the stretched weak coupling of an octupole 3- phonon. Nearly identical sequences of levels with ?I = 3 and the parity change are found, for the first time, up to 25- for 20 states of 214Ra, up to 35- for 36 states of 212Rn and up to 53/2+ for 16 states of 213Fr. The stretched weak coupling of an octupole phonon is extended up to the highest excitation energy of 11355 keV for 212Rn which has the largest experimental B(E3) value of 44.1(88) W.u. for the 11- ? 82+ transition. The stretched weak coupling of an octupole 3- phonon needs to be considered when single particle configurations are assigned to high spin states. Average octupole excitation energies of 657(51) keV for 211At, 1101(28) keV for 212Rn, 667(25) keV for 213Fr, and 709(25) keV for 214Ra are obtained. The calculated level energies are in a good agreement with the experimental level energies within the error limit of 4.3%. (orig.)

397

Multiparticle-octupole coupling and magnetic moments of h9/2n isomers in N=126 isotones  

International Nuclear Information System (INIS)

The influence of particle-vibration coupling on the g-factors of the vertical stroke (h9/2)n rightangle isomers in the N=126 isotones is assessed using the multiparticle-octupole-coupling model. According to the model, admixtures of the configuration vertical stroke (h9/2)n-1f7/2 rightangle in the yrast 8+ and 21-/2 states, nominally associated with the configuration vertical stroke (h9/2)n rightangle , increase with n. On its own, the octupole mixing mechanism therefore predicts g-factors for these states that increase with the number of valence protons. This trend is the opposite of that predicted by core-polarization blocking. Combining multiparticle-octupole coupling and first-order core-polarization blocking significantly reduces the discrepancy between the experimental and theoretical g-factors of these states. We conclude that the observed breakdown in additivity for the g-factors of the vertical stroke (h9/2)n rightangle isomers in the N=126 isotones arises primarily from first-order core-polarization blocking and the combination of configuration mixing due to multiparticle-octupole coupling and shell-model residual interactions. (orig.)

398

Effect of high-pressure torsion deformation on surface properties and biocompatibility of Ti-50.9 mol. %Ni alloys.  

Science.gov (United States)

Ti-50.9 mol. %Ni was subjected to high-pressure torsion (HPT) deformation for different number of rotations (N) of 0.25, 0.5, 1, 5, and 10. The structural changes induced by HPT were analyzed using x-ray diffractometer (XRD). The surfaces of the samples before and after cell culture were characterized using x-ray photoelectron spectroscopy (XPS). The biocompatibility of the samples was evaluated based on a colony formation assay, nickel ion release, and protein adsorption behavior. XRD analysis revealed the occurrence of grain refinement, phase transformation, and amorphization in the TiNi samples by HPT deformation due to high dislocation density. The changes in chemical composition and thickness of the passive film formed on the surface observed in XPS analysis reveals improvement in the stability of the passive film by HPT deformation. The microstructural change due to the deformation was found to influence the biocompatibility behaviors of TiNi. Plating efficiency and protein adsorption were found to be higher when the samples are in stress-induced martensitic or amorphous state. HPT deformation was found to alter the surface behavior of the TiNi, which effectively reduced the Ni ion release and improved its biocompatibility. PMID:24985211

Awang Shri, Dayangku Noorfazidah; Tsuchiya, Koichi; Yamamoto, Akiko

2014-06-01

399

Microstructures and mechanical properties of pure copper deformed severely by equal-channel angular pressing and high pressure torsion  

Energy Technology Data Exchange (ETDEWEB)

Pure Cu of 99.98 wt.% purity has been processed at room temperature by diverse techniques of severe plastic deformation, namely equal-channel angular pressing (ECAP), high pressure torsion (HPT) and a combination of both in order to find out the evolution on the microstructural homogeneity for each of the processes and their combination. Starting with a grain size of {approx}60 {mu}m, severe plastic deformation has been introduced to the material while maintaining the sample dimensions unchanged through the processes of ECAP and HPT. A significant decrease in grain size was observed by transmission electronic microscopy (TEM). Microtensile and microhardness tests were carried out on the deformed material in the three processing conditions. A significant improvement of the tensile strength was promoted with admissible penalization on ductility.

Lugo, N. [Department of Materials Science and Metallurgical Engineering, ETSEIB, Polytechnic University of Catalonia, Av. Diagonal 647, 08028 Barcelona (Spain)], E-mail: nayar.lugo@upc.edu; Llorca, N. [Department of Materials Science and Metallurgical Engineering, University of Barcelona, C/Marti i Franques 1-11, 08028 Barcelona (Spain)], E-mail: nullorca@ub.edu; Cabrera, J.M. [Department of Materials Science and Metallurgical Engineering, ETSEIB, Polytechnic University of Catalonia, Av. Diagonal 647, 08028 Barcelona (Spain); CTM Technical Center, Av. Bases de Manresa 1, 08242 Manresa (Spain)], E-mail: jose.maria.cabrera@upc.edu; Horita, Z. [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395 (Japan)], E-mail: horita@zaiko.kyushu-u-ac.jp

2008-03-25

400

Microstructures and mechanical properties of pure copper deformed severely by equal-channel angular pressing and high pressure torsion  

International Nuclear Information System (INIS)

Pure Cu of 99.98 wt.% purity has been processed at room temperature by diverse techniques of severe plastic deformation, namely equal-channel angular pressing (ECAP), high pressure torsion (HPT) and a combination of both in order to find out the evolution on the microstructural homogeneity for each of the processes and their combination. Starting with a grain size of ?60 ?m, severe plastic deformation has been introduced to the material while maintaining the sample dimensions unchanged through the processes of ECAP and HPT. A significant decrease in grain size was observed by transmission electronic microscopy (TEM). Microtensile and microhardness tests were carried out on the deformed material in the three processing conditions. A significant improvement of the tensile strength was promoted with admissible penalization on ductility

 
 
 
 
401

Boron nitride nanotubes reinforced aluminum composites prepared by spark plasma sintering: Microstructure, mechanical properties and deformation behavior  

International Nuclear Information System (INIS)

Boron nitride nanotubes (BNNT) reinforced aluminum based composites are synthesized by spark plasma sintering (SPS). The concentration of BNNT is varied as 0, 2 and 5 vol% in the aluminum matrix. Micro-pillar compression testing revealed that Al–5 vol% BNNT has yield strength and compressive strength as 88 MPa and 216 MPa respectively, which is more than 50% improvement over unreinforced Al. BNNT play an active role in strengthening Al matrix through effective load bearing and transfer by crack bridging and sword in sheath mechanisms. Cold rolling of Al–5 vol% BNNT with 75% thickness reduction in a single pass exhibited high deformability without cracking or disintegration. The deformation is dominated by slip signifying ductile behavior in sintered Al with and without BNNT. BNNT survives the extreme temperature and pressure conditions during SPS processing and heavy deformation during cold rolling

402

Effect of Radial and Axial Deformation on Electron Transport Properties in a Semiconducting Si-C Nanotube  

Directory of Open Access Journals (Sweden)

Full Text Available We study the bias voltage dependent current characteristic in a deformed (8, 0 silicon carbide nanotube by applying self consistent non-equilibrium Green’s function formalism in combination with the density-functional theory to a two probe molecular junction constructed from deformed nanotube. The transmission spectra and electron density of states at zero bias shows a significant reduction in threshold in the case of both radially compressed and axially elongated nanotube. However, semiconductor to metal transition was not observed, though the results show large differences in current characteristic compared to a perfect nanotube.

S. Choudhary

2011-01-01

403

The influence of severe plastic deformation by high pressure torsion on structure and mechanical properties of Hadfield steel single crystals  

Energy Technology Data Exchange (ETDEWEB)

Hadfield steel single crystals have been deformed by high pressure torsion at room temperature (P=5GPa) for 1, 2, 3 revolutions. The resulting microstructure has been studied by means of transmission electron microscopy (TEM) and X-ray analysis. The size of fragments decreases with increasing number of revolutions due to interaction of slip dislocations, microbands and thin twins. As a result of severe plastic deformation, the microhardness of the Hadfield steel has been increased, and a portion of {epsilon}, {alpha}' martensite has been found.

Zakharova, G G; Astafurova, E G, E-mail: galinazg@yandex.r [Institute of Strength Physics and Materials Science, Siberian Branch of Russian Academy of Sciences, Akademichesky prospect 2/4, 634021, Tomsk (Russian Federation)

2010-07-01

404

The influence of severe plastic deformation by high pressure torsion on structure and mechanical properties of Hadfield steel single crystals  

Science.gov (United States)

Hadfield steel single crystals have been deformed by high pressure torsion at room temperature (P=5GPa) for 1, 2, 3 revolutions. The resulting microstructure has been studied by means of transmission electron microscopy (TEM) and X-ray analysis. The size of fragments decreases with increasing number of revolutions due to interaction of slip dislocations, microbands and thin twins. As a result of severe plastic deformation, the microhardness of the Hadfield steel has been increased, and a portion of epsilon, ?' martensite has been found.

Zakharova, G. G.; Astafurova, E. G.

2010-07-01

405

The influence of severe plastic deformation by high pressure torsion on structure and mechanical properties of Hadfield steel single crystals  

International Nuclear Information System (INIS)

Hadfield steel single crystals have been deformed by high pressure torsion at room temperature (P=5GPa) for 1, 2, 3 revolutions. The resulting microstructure has been studied by means of transmission electron microscopy (TEM) and X-ray analysis. The size of fragments decreases with increasing number of revolutions due to interaction of slip dislocations, microbands and thin twins. As a result of severe plastic deformation, the microhardness of the Hadfield steel has been increased, and a portion of ?, ?' martensite has been found.

406

Plastic deformation of Fe-Al polycrystals strengthened with Zr-containing Laves phases Part II. Mechanical properties  

Energy Technology Data Exchange (ETDEWEB)

Fe-10 at.% Al-2.5 at.% Zr and Fe-20 at.% Al-2.5 at.% Zr alloys were deformed between room temperature and 700 deg. C. The materials show a flow stress plateau at about 300 MPa up to 600 deg. C for the material with 10 at.% Al and above 600 MPa up to 400 deg. C for the alloy with 20% Al. The high flow stresses compared to Fe-Al reference materials are partly due to the addition of Zr. The strain rate sensitivity of the flow stress was measured by stress relaxation and strain rate cycling tests. It is low up to 400 deg. C and high between 450 and 600 deg. C, i.e. in the range of the flow stress decrease. The microstructures of the undeformed materials are described in Part I of this paper. Micrographs of the deformed specimens taken in a high-voltage electron microscope reveal that the deformation occurs mainly within the soft Fe-Al grains and in the Fe-Al component of the grain boundary eutectic. The deformation data are interpreted in terms of solution hardening from the Al solute, dynamic strain ageing due to the Cottrell effect of the same defects, the athermal stress component of elastic dislocation interactions, the Hall-Petch contribution from the grain size, and the strengthening effect of the grain boundary layers.

Wasilkowska, A.; Bartsch, M.; Stein, F.; Palm, M.; Sauthoff, G.; Messerschmidt, U

2004-09-15

407

Mechanical properties of Fe -10Ni -7Mn martensitic steel subjected to severe plastic deformation via cold rolling and wire drawing  

Science.gov (United States)

Fe-Ni-Mn martensitic steels are one of the major groups of ultra-high strength steels that have good mechanical properties and ductility in as annealed condition but they suffer from severe inter-granular embitterment after aging. In this paper, the effect of heavy shaped cold rolling and wire drawing on the mechanical properties of Fe-Ni-Mn steel was investigated. This process could provide a large strain deformation in this alloy. The total strain was epsilon ~7. Aging behavior and tensile properties of Fe-10Ni-7Mn were studied after aging at 753 K. The results showed that the ultimate tensile strength and ductility after cold rolling, wire drawing and aging increased up to 2540 MPa and 7.1 %, respectively, while the conventional steels show a premature fracture stress of 830 MPa with about zero ductility after aging.

Ghasemi-Nanesa, H.; Nili-Ahmadabadi, M.; Shirazi, H.

2010-07-01

408

Mechanical properties of Fe -10Ni -7Mn martensitic steel subjected to severe plastic deformation via cold rolling and wire drawing  

International Nuclear Information System (INIS)

Fe-Ni-Mn martensitic steels are one of the major groups of ultra-high strength steels that have good mechanical properties and ductility in as annealed condition but they suffer from severe inter-granular embitterment after aging. In this paper, the effect of heavy shaped cold rolling and wire drawing on the mechanical properties of Fe-Ni-Mn steel was investigated. This process could provide a large strain deformation in this alloy. The total strain was ? ?7. Aging behavior and tensile properties of Fe-10Ni-7Mn were studied after aging at 753 K. The results showed that the ultimate tensile strength and ductility after cold rolling, wire drawing and aging increased up to 2540 MPa and 7.1 %, respectively, while the conventional steels show a premature fracture stress of 830 MPa with about zero ductility after aging.

409

Is nucleon deformed?  

International Nuclear Information System (INIS)

The surprising answer to this question Is nucleon deformed? is : Yes. The evidence comes from a study of the quark model of the single nucleon and when it is found in a nucleus. It turns out that many of the long standing problems of the Naive Quark Model are taken care of if the nucleon is assumed to be deformed. Only one value of the parameter PD ?1/4 (which specifies deformation) fits gA (the axial vector coupling constant) for all the semileptonic decay of baryons, the F/D ratio, the pion-nucleon-delta coupling constant fsub(?N?), the double delta coupling constant1 fsub(???), the Ml transition moment ??N and g1p the spin structure function of proton2. All this gives strong hint that both neutron and proton are deformed. It is important to look for further signatures of this deformation. When this deformed nucleon finds itself in a nuclear medium its deformation decreases. So much that in a heavy nucleus the nucleons are actually spherical. We look into the Gamow-Teller strengths, magnetic moments and magnetic transition strengths in nuclei to study this property. (author). 15 refs

410

Near-yrast spectroscopy of 164Yb and neighbouring nuclei: Systematics of octupole bands and bandcrossings  

International Nuclear Information System (INIS)

High-spin states in 164Yb have been populated in the 152Sm(16O,4n) and 150Sm(18O,4n) reactions. From studies of ?? coincidences, ?-ray angular distributions and conversion electron measurements the level scheme has been constructed. The g-band and the S-band have been established to spin and parity 22+ and 26+', respectively, and the rotational sequences (?,?)=(-,1)1, (-,0)1 and (-,0)2 to 23-, 24- and 18-, respectively. Constructed two-quasineutron configurations and cranked shell model calculations are compared with the experimental results. Residual interactions between quasiparticles are extracted from data. The side-bands in sup(162,164)Er and sup(164,166)Yb are discussed, putting a special emphasis on the octupole bands and their interaction with the two-quasiparticle bands. Crossing frequencies and the gain in alignment are summarized for the Yb isotopes and the main features are discussed. (orig.)

411

Gyromagnetic ratios and octupole collectivity in the structure of the 90-96Zr isotopes  

International Nuclear Information System (INIS)

Shell model calculations have been performed for low-excitation states in the Zr isotopes between 90Zr and 96Zr with an emphasis on the g factors and electromagnetic decay rates for the lowest 2+ and 3- states. Overall the 2+ states are reasonably well described. In contrast, the 3- states present a puzzle because the measured g factors imply a single-particle configuration whereas the experimental E3 transition rates imply collective structures that cannot be explained by shell model calculations. A consistent description of the 3- states in 90Zr and 96Zr is sought in terms of coupling between the single-particle structure and a collective octupole vibration

412

Octupole magnet for soft X ray magnetic dichroism experiments: Design and performance  

International Nuclear Information System (INIS)

An octupole magnet endstation for soft x-ray magnetic dichroism measurements has been developed at the Advanced Light Source. The system consists of an eight pole electromagnet that surrounds a small vacuum chamber. The magnet provides fields up to 0.9 T that can be applied in any direction relative to the incoming x-ray beam. High precision magnetic circular and linear dichroism spectra can be obtained reversing the magnetic field for each photon energy in an energy scan. Moreover, the field dependence of all components of the magnetization vector can be studied in detail by choosing various angles of x-ray incidence while keeping the relative orientation of magnetic field and sample fixed