TY - CONF
A1 - Eberle, Arno
A1 - Sievert, Rainer
T1 - Numerical analysis of an electronic structure bearing deep cracks
N2 - The successive fatigue failure process, i.e. crack initiation and growth up to electrical failure, has been investigated for a flip chip configuration. A cracked and uncracked solder bump was analysed using an unified viscoplastic constitutive model (Chaboche). The electrical failure of a bump seems to be reached in general not before a deep crack has grown into the bump. In order to update the actual loading situation two different cracked structures were calculated.
T2 - MicroMat 2000 - 3rd International conference and poster exhibition Micro Materials
CY - Berlin, Germany
DA - 17.04.2000
PY - 2000
SN - 3-932434-15-3
SP - 582
EP - 585
AN - OPUS4-33827
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Eberle, Arno
A1 - Sievert, Rainer
A1 - Schubert, A.
ED - Winkler, T.
ED - Schubert, A.
T1 - On the influence of two different underfill materials on the inelastic thermo-cyclic response of a flip-chip solder bump
N2 - The finite element method was used to simulate the thermo-mechanical behaviour of a solder bump configuration on Al2O3 substrate under thermo-cyclic loading between -55 °C and 125 °C. Chaboche's viscoplastic material model was used to describe the Bauschinger effect and the creep/plasticity interaction for the tin-lead solder material. The influence of two different viscoelastic underfill materials (Epoxy+50 % SiO2, Epoxy+70 % SiO2) on the inelastic deformation of the tin-lead solder was analyzed and compared. It may be shown that the thermally matched 'hard' underfiller (Epoxy+70 % SiO2) significantly reduces the accumulated inelastic strain in the bump compared to 'soft' underfiller or no underfill material. On the other hand, the maximum lateral normal stress will increase slightly.
PY - 2015
SP - 471
EP - 480
AN - OPUS4-33859
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Eberle, Arno
A1 - Sievert, Rainer
ED - Michel, B.
ED - Winkler, T.
T1 - Viscoplastic analysis of a solder-bump-configuration at thermo-cyclic loading
T2 - Micro Mat '97 - International conference and exhibition micro materials
CY - Berlin, Germany
DA - 1997-04-16
KW - Hardening and creep
KW - Constitutive modeling
KW - Determination of material parameters
KW - Hysteresis loops
KW - Relaxation behaviour
PY - 1997
SN - 3-932434-05-6
SP - 283
EP - 286
AN - OPUS4-33714
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Eberle, Arno
A1 - Sievert, Rainer
A1 - Schiller, Wolfgang Arno
T1 - Numerical investigation on the influence of different substrate materials on the viscoplastic behaviour of flip chip solder bumps
N2 - The finite element method was used to simulate the thermo-mechanical behaviour of a flip chip under thermocyclic loading between -55°C (-67°F) and 125°C (257°F). In order to simulate realistically the inelastic material response of the solder bump, Chaboche's viscoplastic material model instead of a classical ORNL-theory was implemented into the finite element code ABAQUS and applied to a flip chip configuration. This so-called unified constitutive model is able to describe the Bauschinger effect as well as the creep/plasticity interaction. Herewith the influence of the substrate material on the inelastic deformation behaviour of a tin-lead solder bump was analysed. A comparison is given with respect to the influence of the two substrate materials namely Al2O3 and our self-developed Low Temperature Co-fired Ceramics (LTCC) on the inelastic response of the Sn60Pb40 eutectic solder material. It may be shown that the thermoelastic behaviour of the LTCC substrate significantly reduces the cyclic stresses in the bump compared to Al2O3 as well as the cumulative inelastic strain which is responsible for the development of damage and hence flip chip failure
T2 - International symposium on advanced packaging materials 2000
CY - Braselton, Georgia, USA
DA - 06.03.2000
PY - 2000
SN - 0-930815-59-9
DO - https://doi.org/10.1109/ISAPM.2000.869253
SP - 112
EP - 117
AN - OPUS4-33716
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Sommitsch, C.
A1 - Sievert, Rainer
A1 - Wlanis, T.
A1 - Redl, C.
T1 - Lifetime evaluation of two different hot work tool steels in aluminium extrusion
N2 - During aluminium extrusion, the die experience cyclic thermo-mechanical loads that can lead to materials degradation and failure. For a process optimization and a comparison of different hot work tool steels, the finite element method is an appropriate means. Local inelastic strains result from the interaction of the applied temperature and stress loading and can be computed by suitable inelastic constitutive equations. Stress amplitudes and dwell times during extrusion result in creep-fatigue damage. A lifetime consumption model sums increments of a damage variable over time and defines materials failure as the accumulation of the resulting damage variable to a critical value. The procedure for the identification of the material parameters for both the constitutive and the damage model is described in detail, including the material parameters for the description of time-effects, and applied to the hot work tool steel Böhler W300 ISOBLOC (EN 1.2343). The lifetime consumption for two different hot work tool steels is compared on the basis of an example in aluminium extrusion.
KW - Extrusion
KW - Creep
KW - Fatigue
KW - Viscoplasticity
KW - Aging
KW - Failure
PY - 2008
DO - https://doi.org/10.1016/j.commatsci.2007.07.054
SN - 0927-0256
VL - 43
IS - 1
SP - 82
EP - 91
PB - Elsevier
CY - Amsterdam
AN - OPUS4-17585
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Krumphals, F.
A1 - Wlanis, T.
A1 - Sievert, Rainer
A1 - Wieser, V.
A1 - Sommitsch, C.
T1 - Damage analysis of extrusion tools made from the austenitic hot work tool steel Böhler W750
N2 - During hot extrusion of copper alloys, extrusion tools have to withstand cyclic thermal and mechanical loads. To enhance the service life of the tools, materials with high temperature strength are designed as well as an optimised process control is performed. To characterise the tool damage evolution during service and to improve process guiding, modelling and simulation are appropriate means. The extrusion process of copper billets at three different temperatures was simulated by an FE-program to obtain the temporal boundary conditions, i.e. stress and temperature distributions at the interface billet-liner. Those boundary conditions were used to simulate the elastic–viscoplastic behaviour of the tool steel Böhler W750 in service by means of Abaqus Standard v.6.8-3 software in conjunction with Z-Mat package. A lifetime rule was added in order to compute the lifetime consumption and the cycles to failure.
KW - Hot work tool steel
KW - Damage evolution
KW - Lifetime prediction
KW - Copper extrusion
PY - 2011
DO - https://doi.org/10.1016/j.commatsci.2010.04.022
SN - 0927-0256
VL - 50
IS - 4
SP - 1250
EP - 1255
PB - Elsevier
CY - Amsterdam
AN - OPUS4-23215
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Levkovitch, Vladislav
A1 - Sievert, Rainer
A1 - Svendsen, B.
T1 - Application of extended crystal plasticity to the modeling of glide and kink bands and of crack opening in single crystals
N2 - In this work, the influence of the development of geometrically necessary dislocations (GNDs) at a crack tip in single crystals on the hardening and crack propagation behaviour is investigated. In particular, we are interested in examining the effect of such additional hardening on the development of glide and kink bands at the crack tip as well as on the process of crack opening. To this end, following Nye and many others, local deformation incompatibility in the material is adopted as a measure of the density of GNDs. Their development results in additional energy being stored in the material, leading to additional kinematic-like hardening. A thermodynamic formulation of the model in the context of the dissipation principle facilitates the derivation of the corresponding hardening relation. Results suggest that this additional hardening retards kink-band development, but has little or no influence on glide-band development. It also influences the crack tip opening displacement (CTOD). It turns out that the simulated CTOD correlates well with experimentally determined crack-propagation rates for different crack growth direction in the crystal.
KW - Thermodynamics
KW - Single crystal plasticity
KW - Geometrically necessary dislocations
KW - Hardening
KW - Glide and kink bands
KW - Crack-opening displacement
PY - 2005
SN - 0927-0256
VL - 32
IS - 3-4
SP - 426
EP - 434
PB - Elsevier
CY - Amsterdam
AN - OPUS4-7067
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Levkovitch, Vladislav
A1 - Sievert, Rainer
A1 - Svendsen, B.
T1 - Simulation of Fatigue Crack Propagation in Ductile Metals by Blunting and Re-Sharpening
N2 - Laird and Smith [(1962). Philosophical Magazine 8, 847857] proposed a plastic sliding-off mechanism for the stage II fatigue crack growth via striation formation. In their view, the fatigue crack extension results solely from the changing character of deformation at the crack tip during loading and unloading. In particular, the crack tip blunts during the loading stage and folds into a double notch during the unloading stage, resulting in striation formation. In order to verify Lairds plastic blunting mechanism for ductile polycrystals as well as for ductile fcc single crystals, FE calculations were performed for a rectangular plate with an initially sharp crack under plane strain conditions. The plate was subjected to a fully reversed tension-to-pressure cyclic load perpendicular to the crack plane (Mode 1). In the single crystal case the crack propagation simulations were carried out for cracks with crack plane (001) for two different crack growth orientations [110] and [100]. No initial radius for the crack tip was assumed. The actual shape of the crack tip followed from an initially sharp crack by repeated remeshing. To model the constitutive behavior typical for polycrystalline ductile metals, J2 hypo-elasto-plasticity model with ArmstrongFrederick kinematic hardening was used. To model the constitutive behavior typical for ductile fcc single crystals, a geometrically nonlinear version of Cailletauds model based on the multiplicative elasto-plastic decomposition of the deformation gradient was implemented into the FE program ABAQUS. For simplicity, only octahedral slip systems were considered. Using repeated remeshing for severely distorted elements at the advancing crack tip, deformation patterns in the sense of Lairds mechanism for fatigue crack propagation with striation formation were obtained in the case of the polycrystal simulation as well as in the case of the single crystal simulation for [110] crack growth direction. The simulation for [100] crack growth direction with the same stress level as for [110] direction also yielded crack extension by progressive large deformations but without striation formation. The dependence of the fatigue striation formation on the crack growth direction as predicted by the simulation of crack propagation in single crystals is verified by the experimental results of Neumann [(1974). Acta Metallurgica 22, 11551165] on pure copper single crystals.
KW - Fatigue
KW - Crack Propagation
KW - Viscoplastic Constitutive Model
KW - Finite-Element-Simulation
KW - Fatigue
KW - FE modeling
KW - Laird
KW - Plastic blunting and re-sharpening
KW - Remeshing
KW - Single crystal
KW - Striations
PY - 2005
SN - 0376-9429
SN - 1573-2673
VL - 136
IS - 1-4
SP - 207
EP - 220
PB - Kluwer Academic Publ.
CY - Dordrecht
AN - OPUS4-10631
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Levkovitch, Vladislav
A1 - Sievert, Rainer
A1 - Svendsen, B.
T1 - Life Analysis of a fcc Single Crystal and Simulation of Crack Propagation by Blunting and Re-Sharpening
T2 - International Conference on Computational and Experimental Engineering and Science 2003 (ICCES '03)
CY - Corfu, Greece
DA - 2003-07-25
PY - 2003
CY - Tokyo
AN - OPUS4-2619
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Levkovitch, Vladislav
A1 - Sievert, Rainer
A1 - Svendsen, B.
ED - Portella, Pedro Dolabella
T1 - Simulation of Low Cycle Fatigue Failure of FCC Single Crystals
T2 - 5th International Conference on Low Cycle Fatigue (LCF-5)
CY - Berlin, Germany
DA - 2003-09-09
KW - Single crystal
KW - Viscoplasticity
KW - Simulation
KW - Fatigue
KW - Lifetime
KW - Crack propagation
KW - Blunting and resharpening
KW - Laird
KW - Striations
KW - Re-meshing
PY - 2003
VL - 5
SP - 415
EP - 420
PB - DVM, Deutscher Verband für Materialforschung und -prüfung
CY - Berlin
AN - OPUS4-3819
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Sievert, Rainer
A1 - Österle, Werner
A1 - Olschewski, Jürgen
A1 - Ziebs, Josef
T1 - Physical interpretation of a viscoplastic model applied to high temperature performance of a nickel-base superalloy
T2 - 7th International Conference on Mechanical Behaviour of Materials
CY - The Hague, Netherlands
DA - 1995-01-01
PY - 1995
SP - 557
EP - 558
CY - Den Haag
AN - OPUS4-2507
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Sievert, Rainer
A1 - Österle, Werner
A1 - Olschewski, Jürgen
A1 - Ziebs, Josef
T1 - Physical interpretation of a viscoplastic model applied to high temperature performance of a nickel-base superalloy
PY - 1997
SN - 0179-4841
SN - 0044-3093
VL - 88
SP - 416
EP - 424
PB - Hanser
CY - München
AN - OPUS4-2547
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Forest, S.
A1 - Sievert, Rainer
A1 - Aifantis, E. C.
T1 - Strain gradient crystal plasticity: Thermomechanical formulations and applications
PY - 2002
SN - 0334-8938
VL - 13
IS - 3-4
SP - 219
EP - 232
PB - Freund Publ.
CY - London
AN - OPUS4-2858
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Forest, S.
A1 - Boubidi, Pascal
A1 - Sievert, Rainer
T1 - Strain Localization Patterns at a Crack Tip in Generalized Single Crystal Plasticity
KW - Crack
KW - Single crystal
KW - Crystal plasticity
KW - Cosserat medium
KW - Strain localization
PY - 2001
DO - https://doi.org/10.1016/S1359-6462(00)00684-9
SN - 1359-6462
SN - 1872-8456
VL - 44
IS - 6
SP - 953
EP - 958
PB - Elsevier
CY - Oxford
AN - OPUS4-3972
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Levkovitch, Vladislav
A1 - Sievert, Rainer
A1 - Svendsen, Robert F.
T1 - Simulation of deformation and lifetime behavior of a fcc single crystal superalloy at high temperature under low-cycle fatigue loading
N2 - This work deals with the formulation of a three-dimensional crystallographic time-incremental lifetime rule for face-centered cubic (fcc) single crystals used for gas-turbine blade applications. The damage contribution rate of each slip system to the total damage is governed by the current values of the resolved shear stress and the slip rate on the corresponding slip system. The damage rule is combined with a crystallographic viscoplastic deformation model. For the nickel-base single-crystal superalloy CMSX4 at 950 °C, various strain- and stress-controlled uniaxial cyclic tests with and without hold-times can be described for different crystal orientations by one set of material parameters. For verification, simulation results for a single-crystal specimen with a notch have been compared with corresponding experimental results. The predicted lifetime is within the factor of two of the measured one.
KW - Single crystal
KW - High temperature
KW - Viscoplastic constitutive model
KW - Lifetime rule
KW - Low-cycle fatigue
KW - Superalloy
PY - 2006
DO - https://doi.org/10.1016/j.ijfatigue.2005.12.006
SN - 0142-1123
VL - 28
IS - 12
SP - 1791
EP - 1802
PB - Elsevier
CY - Oxford
AN - OPUS4-13198
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Forest, S.
A1 - Sievert, Rainer
T1 - Nonlinear microstrain theories
N2 - A hierarchy of higher order continua is presented that introduces additional degrees of freedom accounting for volume changes, rotation and straining of an underlying microstructure. An increase in the number of degrees of freedom represents a refinement of the material description. In addition to available nonlinear Cosserat and micromorphic theories, general formulations of elastoviscoplastic behaviour are proposed for microdilatation and microstretch continua. A microstrain theory is introduced that is based on six additional degrees of freedom describing the pure straining of the microstructural element. In each case, balance equations and boundary conditions are derived, decompositions of the finite strain measures into elastic and plastic parts are provided. The formulation of finite deformation elastoviscoplastic constitutive equations relies on the introduction of the free energy and dissipation potentials, thus complying with requirements of continuum thermodynamics. Some guidelines for the selection of a suitable higher order model for a given material close the discussion.
KW - Continuum mechanics
KW - Higher order continua
KW - Micromorphic
KW - Cosserat
KW - Elastoviscoplasticity
KW - Finite deformation
PY - 2006
DO - https://doi.org/10.1016/j.ijsolstr.2006.05.012
SN - 0020-7683
VL - 43
IS - 24
SP - 7224
EP - 7245
PB - Elsevier
CY - New York, NY
AN - OPUS4-13734
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Sommitsch, C.
A1 - Sievert, Rainer
A1 - Wlanis, T.
A1 - Günther, Burkhard
A1 - Wieser, V.
T1 - Modelling of creep-fatigue in containers during aluminium and copper extrusion
N2 - During hot extrusion of aluminium alloys, extrusion dies experience cyclic temperature changes as well as multiaxial loadings. To improve the service life of the dies, cleaner and high hot strength materials are designed as well as an optimised process control is performed. For the improvement of the process guiding and a comparison of lifetime behaviour of different hot work tool steels, modelling and simulation are appropriate means. The extrusion process has been simulated using the FE-program Deform to find the stress and temperature history at the inner diameter of the liner, i.e. the boundary conditions for the subsequent cyclic simulation of the container during service. Inelastic constitutive equations have been implemented into Abaqus Standard to describe strain hardening and time recovery effects. They include the Norton viscoplastic flow rule, thermo-mechanical isotropic hardening and two non-linear kinematic hardening laws. A damage-rate model predicts failure and thus the lifetime of the container. The procedure for the identification of material parameters for both the constitutive and the damage model is described in detail for the hot work tool steel Böhler W400 VMR (EN 1.2343).
KW - Extrusion
KW - Hot work tool steels
KW - Creep-fatigue
KW - Lifetime
KW - Damage
PY - 2007
SN - 0927-0256
VL - 39
IS - 1
SP - 55
EP - 64
PB - Elsevier
CY - Amsterdam
AN - OPUS4-14530
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Sievert, Rainer
T1 - A geometrically nonlinear elasto-viscoplasticity theory of second grade
N2 - A general concept for the consideration of the influence of strain gradients on elasto-viscoplastic material behaviour at finite deformation is presented that does not need to account for an additional flow rule for the plastic strain gradient. The balance of momentum including the representation of the stresses, the power of work at contact for the formulation of boundary conditions as well as the nonlocal form of the total power of deformation are derived via the dissipation inequality for the investigated nonpolar continuum model of second grade. In addition to the gradient of the elastic strain tensor, energy storage with gradients of different internal variables is considered: gradient of (i) the plastic strain Tensor itself, (ii) an internal strain tensor induced by viscoplastic straining, by which energy due to hardening is stored also with ist gradient, and (iii) scalar internal variables like the accumulated viscoplastic strain or an internal time variable of damage. Finally, for the simulation of the damage behaviour during a strain hold-time period at a crack tip the responses of a ratedependent and a quasi-rate-independent gradient-enhanced damage model are compared in finite element studies.
KW - Viscoplasticity
KW - Plasticity
KW - Strain-gradient
KW - Finite deformation
PY - 2011
UR - http://www.uni-magdeburg.de/ifme/zeitschrift_tm/2011_Heft2/01_Sievert.pdf
SN - 0232-3869
VL - 31
IS - 2
SP - 83
EP - 111
PB - Institut für Mechanik
CY - Magdeburg
AN - OPUS4-24166
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Boubidi, Pascal
A1 - Sievert, Rainer
ED - Fuentes, M.
T1 - Analysis of low-cycle fatigue at notches in a single crystal superalloy at high temperature
T2 - 13th European Conference on Fracture
CY - San Sebastián, Spain
DA - 2000-09-06
KW - LCF
KW - Kerben
KW - Einkristalle
KW - Turbinenschaufeln
PY - 2000
SN - 0-08-043699-4
SN - 1566-1369
N1 - Serientitel: ESIS publication – Series title: ESIS publication
IS - 26
PB - Elsevier
CY - Amsterdam
AN - OPUS4-1074
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Boubidi, Pascal
A1 - Sievert, Rainer
ED - Biallas, G.
T1 - Experimental and Numerical Investigations of Macro-Crack Initiation under Low-Cycle Fatigue Loading at Notches in a Single Crystal Superalloy at High Temperature
T2 - CAMP 2002
CY - Bad Lippspringe, Germany
DA - 2002-04-03
KW - Single crystal
KW - Notched specimens
KW - Cracks
KW - Lifetime
KW - Turbine blades
PY - 2002
SN - 3-00-009254-4
SP - 127
EP - 141
PB - Inst. für Prozess- und Werkstofftechnik
CY - Paderborn
AN - OPUS4-1436
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -