This book is a contribution to the further development of gradient plasticity. Several open questions are addressed, where the efficient numerical implementation is particularly focused on. Thebook inspects an equivalent plastic strain gradient plasticity theory and a grain boundary yield model. Experiments can successfully be reproduced. The hardening model is based on dislocation densities evolving according to partial differential equations taking into account dislocation transport.

Dual-phase steels exhibit good mechanical properties due to a microstructure of strong martensitic inclusions embedded in a ductile ferritic matrix. This work presents a two-scale model for the underlying work-hardening effects; such as the distinctly different hardening rates observed for high-strength dual-phase steels. The model is based on geometrically necessary dislocations and comprises the average microstructural morphology as well as a direct interaction between the constituents.

Diese Arbeit beschäftigt sich mit der Vorhersage des elastischen Verhaltens von kurzfaserverstärkten Werkstoffen durch Mean-Field-Homogenizierungsmethoden, die experimentell ermittelte und künstlich Mikrostrukturinformationen in diskreter und gemittelter Form berücksichtigen. Die Vorhersagen werden mit Experimenten und mit voxelbasierten Vollfeldlösungen verglichen. Es wird untersucht, ob für solche Vorhersagen der Orientierungstensor zweiter Stufe die Mikrostruktur ausreichend beschreibt.
This work is focused on the prediction of elastic behavior of short-fiber reinforced composites by...

In experiments on metallic microwires, size effects occur as a result of the interaction of dislocations with, e.g., grain boundaries. In continuum theories this behavior can be approximated using gradient plasticity. A numerically efficient geometrically linear gradient plasticity theory is developed considering the grain boundaries and implemented with finite elements. Simulations are performed for several metals in comparison to experiments and discrete dislocation dynamics simulations.

The deep drawing of an aluminum alloy used in the packaging industry for the beverage can manufacturing process is investigated. In this work, the effective constitutive behavior is based on a crystal plasticity model in combination with a non-linear Hashin-Shtrikman type homogenization scheme in which a reference stiffness controls the stress and strain fluctuations. The simulation results are compared to experiments in terms of deep drawing earing profiles, texture evolution, and localization.

Dynamisch-mechanische Analyse wird verwendet um die temperaturabhängige, anisotrope viskoelastische Steifigkeit, Schädigungsinduzierte Steifigkeitsdegradation sowie physikalische Alterung von Polypropylen und dem im Fließpressverfahren hergestellten langfaserverstärkten Polypropylen zu untersuchen. Basierend auf Mikro-Computertomographiedaten wird die Approximation linear elastischer Eigenschaften unter Verwendung der Mori-Tanaka-Methode dargestellt. Dynamical mechanical analysis is used to investigate the temperature dependent, anisotropic visco-elastic stiffness, damage induced...

Hot stamping is a hot drawing process which takes advantage of the polymorphic steel behavior to produce parts with a good strength-to-weight ratio. For the simulation of the hot stamping process, a nonlinear two-scale thermomechanical model is suggested and implemented into the FE tool ABAQUS. Phase transformation and transformation induced plasticity effects are taken into account. The simulation results regarding the final shape and residual stresses are compared to experimental findings.

This work approaches the fields of homogenization and of materials design for the linear and nonlinear mechanical properties with prescribed properties-profile. The set of achievable properties is bounded by the zeroth-order bounds (which are material specific), the first-order bounds (containing volume fractions of the phases) and the second-order Hashin-Shtrikman bounds with eigenfields in terms of tensorial texture coefficients for arbitrarily anisotropic textured materials.

The focus of this work lies on the microstructure-based modeling and characterization of a discontinuous fiber-reinforced thermoset in the form of sheet molding compound (SMC). A microstructure-based parameter identification scheme for SMC with an inhomogeneous fiber orientation distribution is introduced. Different cruciform specimen designs, including two concepts to reinforce the specimens' arms are evaluated. Additionally, a micromechanical mean-field damage model for the SMC is introduced.

A single-crystal plasticity model as well as a gradient crystal plasticity model are used to describe the creep behavior of directionally solidified NiAl based eutectic alloys. To consider the transition from theoretical to bulk strength, a hardening model was introduced to describe the strength of the reinforcing phases. Moreover, to account for microstructural changes due to material ux, a coupled diffusional-mechanical simulation model was introduced.