Nanoscale Weibull Statistics

In this paper a modification of the classical Weibull Statistics is developed for nanoscale applications. It is called Nanoscale Weibull Statistics. A comparison between Nanoscale and classical Weibull Statistics applied to experimental results on fracture strength of carbon nanotubes clearly shows the effectiveness of the proposed modification. A Weibull's modulus around 3 is, for the first time, deduced for nanotubes. The approach can treat (also) a small number of structural defects, as required for nearly defect free structures (e.g., nanotubes) as well as a quantized crack propagation (e.g., as a consequence of the discrete nature of matter), allowing to remove the paradoxes caused by the presence of stress-intensifications

Fatigue of polycrystalline silicon under long-term cyclic loading

The long-term mechanical behavior of 3.5 µm thick and 50 µm wide polysilicon tensile specimens under tension-tension cyclic loading was investigated. The use of an external actuator allows the variation of the test frequency between 50 and 6000 Hz. It was shown, that the strength of the samples decreases with an increasing number of cycles. The tensile strength of ?c=1.1 GPa of virgin samples was reduced by about 35 % to a fatigue strength of ?f = 0.70 GPa after 109 cycles. No influence of frequency of the fatigue behavior in the range of 50 to 6000 Hz was observed

Solarmodul sowie Verfahren zur Herstellung eines Solarmoduls

(A1) Beschrieben wird ein Solarmodul sowie ein Verfahren zur Herstellung eines Solarmoduls mit einer elektrisch verschalteten, flaechig ausgebildeten Solarzellenanordnung, an deren Rueckseite eine Rueckseitenkonstruktion und an deren Vorderseite eine strahlungstransparente Frontseite vorgesehen sind, sowie mit einem die Solarzellenanordnung zwischen der Rueckseitenkonstruktion und der Frontscheibe umgebenden Einbettungsmaterial. Die Erfindung zeichnet sich dadurch aus, dass die Rueckseitenkonstruktion als separates Modul, mittels Spritzgiessen, Spritzpraegen oder Pressen hergestellter Kunststofftraeger ist, dass die Frontscheibe mit ihrer dem Kunststofftraeger zugewandten Oberflaeche ganzflaechig mittels einer erstarrungsfaehigen und mechanische Lasten uebertragbaren, strahlungstransparenten Vergussmasse mit dem Kunststofftraeger verbunden ist, die die Solarzellenanordnung zwischen der Frontscheibe und dem Kunststofftraeger umschliesst

Mechanical properties of glass frit bonded micro packages

Frit glass bonding is a widely used technology for encapsulation of surface micro-machined structures like inertial sensors or gyroscopes on wafer level. Since for sensors in automotive applications, a lifetime of 15-20 years has to be guaranteed for, a reliable lifetime prediction is necessary. Different material parameters have to be known for a lifetime estimation based on stress corrosion cracking, which determines the longterm strength behaviour of most bonded interfaces of microsystems. Parameters needed for lifetime prediction have to describe the material's resistance against crack propagation (fracture toughness KIC), the stress situation in a micro package and the long-term strength behaviour. Results for fracture toughness investigations presented in this paper were determined by the micro chevron test. The stress situation in a micro package was calculated by a thermo-mechanical Finite Element Analysis. Furthermore the residual stress in the glass layer and linear thermal expansion coefficient were determined by a crack width measurement in an environmental scanning electron microscope

Numerical simulations of thermo-mechanical stresses during the casting of multi-crystalline silicon ingots

Silicon is an important semiconductor substrate for manufacturing solar cells. The mechanical and electrical properties of multi-crystalline silicon (mc-Si) are primarily influenced by the quality of the feedstock material and the crystallization process. In this work, numerical calculations, applying finite element analysis (FEA) and finite volume methods (FVM) are presented, in order to predict thermo-mechanical stresses during the solidification of industrial size mc-Si ingots. A two-dimensional global model of an industrial multi-crystallization furnace was created for thermal stationary and time-dependent calculations using the software tool CrysMAS. Subsequent thermo-mechanical analyses of the silica crucible and the ingot were performed with the FEA code ANSYS, allowing additional calculations to define mechanical boundary conditions as well as material models. Our results show that thermal analyses are in good agreement with experimental measurements. Furthermor e we show that our approach is suitable to describe the generation of thermo-mechanical stress within the silicon ingot