Michael Budnitzki

Forschungszentrum Jülich · Institute for Advanced Simulation (IAS)

Diamond wire sawing (DWS) of silicon wafers has replaced loose abrasive sawing (LAS) within a very short time, mainly due to the enormous cost pressure in the photovoltaic industry. However, the LAS process is still much better investigated and understood from a mechanics point of view. This lack of micromechanically substantiated process knowledge...

A multiscale approach is presented here to investigate the effect of the ferrite-pearlite microstructure after annealing on the subsequent machining process of steel gears. The case-hardening steel 18CrNiMo7-6 and a cost efficient alternative with reduced Cr and Ni content have been studied. After detailed microstructure characterization, three dif...

In classical elasticity theory the stress-field of a dislocation is characterized by a $1/r$-type singularity. When such a dislocation is considered together with an Allen-Cahn-type phase-field description for microstructure evolution this leads to singular driving forces for the order parameter, resulting in non-physical (and discretization-depend...

So-called microcracks are crucial for material removal during diamond wire sawing of silicon. But they also reduce the strength of silicon substrates after sawing due to the remaining subsurface damage. In order to investigate the influence of microcracks on strength of diamond wire sawn silicon substrates, more than 180 specimens of {100}-silicon...

A novel Calphad coupled mechano-chemical phase-field model is presented which in addition to chemo-elastic contributions to the driving force further includes mechano-chemical effects on diffusion (stress-driven diffusion), equilibrium compositions and driving force. These effects have their origin in the concentration dependency of the eigenstrain...

In classical elasticity theory the stress-field of a dislocation is characterized by a 1/r-type singularity. When such a dislocation is considered together with an Allen-Cahn-type phase-field description for microstructure evolution this leads to singular driving forces for the order parameter, resulting in non-physical (and discretization-dependen...

So-called Microcracks are crucial for material removal during diamond wire sawing of silicon. But they also reduce the strength of silicon substrates after sawing due to the remaining subsurface damage. In order to investigate the influence of microcracks on strength of diamond wire sawn silicon substrates, more than 180 specimens of {100}- silicon...

The mechanical behavior of TRIP-steels (TRansformation Induced Plasticity) under monotonic loading conditions has been extensively studied both experimentally and by continuum mechanical modeling. The cyclic response received far less attention so far, although the mechanically induced martensitic phase transformation highly affects the cyclic defo...

Transformation Induced Plasticity (TRIP) steels undergo a diffusionless phase transformation from austenite to martensite, resulting in a material exhibiting desireable material properties such as exceptional balance of strength and ductility as well as good fatigue behavior. Computational modeling at the mesoscale is potentially a suitable tool fo...

The understanding of how the microstructure influences the mechanical response is an essential pre-requisite for materials tailored to match specific requirements. The aim of this chapter is to further this understanding in the context of Mg-PSZ-TRIP-steel composites on three different scales using a set of methods ranging from phase-field simulati...

The aim of this chapter is to give insight into the continuum mechanics based modeling of high alloy TRIP-steels. A powerful thermomechanical framework is presented, which incorporates finite viscoplasticity, the TRIP-effect, complete thermomechanical coupling, and non-local damage. Based on this, different variants of material models are developed...

Diamond wire sawing (DWS) is the dominant manufacturing process for thin silicon substrates. The understanding of micromechanical damaging and material removal mechanisms is essential for improving the reliability of the processes and the quality of the products. Due to the lack of models that are capable to predict subsurface damage during diamond...

The martensitic tetragonal-to-monoclinic ( t → m ) phase transformation is the primary inelastic deformation mechanism in zirconia ceramics. In this study, a Ginzburg-Landau type phase-field model is utilized to simulate phase transformations in MgO-partially stabilized zirconia, clearly distinguishing between the effects of undercooling and stress...

Nanoscale scratching of silicon surfaces is the elementary abrasive event for various machining techniques including fixed abrasive wire saw slicing, grinding, elliptical ultrasonic cutting and single-point diamond turning. The understanding of this process is essential for improving the surface quality and reducing sub-surface damage. Nanoscratchi...

Silicon has a tremendous importance as an electronic, structural and optical material. Modeling the stress driven phase transitions during the interaction of a silicon surface with a pointed asperity at room temperature is a major step towards the understanding of various phenomena related to brittle as well as ductile regime machining of this semi...

Silicon has a tremendous importance as an electronic, structural and optical material. Modeling the interaction of a silicon surface with a pointed asperity at room temperature is a major step towards the understanding of various phenomena related to brittle as well as ductile regime machining of this semiconductor. If subjected to pressure or cont...

This work focuses on micromechanical modeling of the tetragonal to monoclinic phase transformation (t-m transformation) in partially stabilized zirconia (PSZ). Tetragonal particles dispersed in a cubic matrix may transform into the monoclinic phase under sufficiently high mechanical loading or if the material is cooled down below a critical tempera...

Most of the technologically relevant abrasive machining techniques for silicon (Si) such as lapping, sawing and grinding are based on the interaction of the silicon surface with a hard particle or asperity. It has been long established that the governing deformation mechanism for Si under such contact loading conditions is stress induced phase tran...

Technologically relevant abrasive machining techniques (lapping, sawing, grinding) for silicon (Si) are based on (sub-)surface crack formation triggered by contact events. Therefore, the understanding of the inelastic deforma-tion of Si under contact (indenter-)loading is essential to improve machining results. It has been long established that Si...

Silicon (Si) remains the most important semiconductor material to date. The understanding of its deformation behavior under contact (indenter-) loading is crucial to improving technologically relevant abrasive machining techniques (lapping, sawing, grinding). While it has been long established that Si undergoes a series of stress driven phase trans...

Micromachined, kHz-frequency resonators are now routinely employed as testing structures to characterize the fatigue degradation properties of thin film materials such as polycrystalline silicon (polysilicon). In addition to stress-life (S-N) fatigue curves, important properties such as crack propagation rates may be inferred from proper resonant f...

Previous studies on very high-cycle fatigue behavior of thin silicon (Si) films suggest a strong environmental dependence of the degradation mechanism, the precise nature of which is still the subject of debate. This is partly due to contradictory evidence on the presence of thick post-cycling surface oxides. In the present study, 2 μm thick polycr...

The influence of atomic-layer-deposited alumina surface coatings on the fatigue of polycrystalline silicon thin films was investigated. Tests were performed on 2-μm-thick notched cantilever-beam structures actuated at resonance ( ∼ 40 kHz) that were coated with ∼ 20 nm of alumina deposited at 100 °C. The coated devices show a drastically different...

Previous studies on very high-cycle fatigue behavior of thin silicon films suggest a strong environmental dependence of the degradation mechanism, the precise nature of which is still subject to debate. In the present study, 2-micron-thick polycrystalline Si notched cantilever beam structures were used to investigate fatigue degradation in a high-t...