Isothermic growth of one spherulite around circular obstacles in a polypropylene foil

Growth of one spherulite within a thin foil of polypropylene around one circular obstacle or around combinations of circular obstacles is investigated. For each obstacle there exists a region of shadow, seen from the nucleus of the spherulite, which influences the growth of the spherulite. Within any region of shadow the growth fronts are evolvents of the obstacle's boundary, because the spherulite grows isotropically. When two growth fronts belonging to one spherulite meet each other inside the shadow, an intrinsic grain boundary is formed for each obstacle. Additionally, growth of one spherulite around a rectangular obstacle and a spherical obstacle is investigated.     

Creep-induced local lattice parameter changes in a monocrystalline nickel-base superalloy

The γ-γ lattice mismatch of specimens of the monocrystalline nickel-base superalloy SRR 99 has been measured by a high-resolution X-ray diffraction technique for the undeformed state and after high-tem-perature creep deformation. During creep deformation beyond the minimum creep rate (total strain =0.5%), the lattice mismatches, measured in and perpendicular to the [001] stress axis, respectively, un-dergo changes in opposite directions. This reflects the buildup of a complex deformation-induced triaxial state of internal stress in the phases y and γ. The overall resolved shear stresses that act in γ and y due to the combined action of the external and internal stresses are estimated, and the conditions under which cutting of the γ phase by dislocations should occur are discussed.     

Produkte der thermischen En-Reaktion von ungesättigten Fettstoffen und Maleinsäureanhydrid

Products of the Thermal Ene-Reaction of Unsaturated Fatty Compounds and Maleic Anhydride The thermal ene reaction of the methylates of unsaturated fatty acids 10-undecenoic acid, oleic acid and (E)-10-eicosendioic acid with maleic anhydride was carried out at 190°C. The mono addition products were isolated and their stereochemistry was deduced from ¹HNMR- and ¹³C-NMR-spectroscopy.     

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Processing and Damping Properties of Sputtered NiTi Thin Films for Tools in Machining Processes

Nowadays, many manufacturing processes require the machining of complex forms with a high aspect ratio or cavities. Tools with a long overhang length are a common method to meet these requirements. Typical examples for this are boring bars for bore-turning and the milling with very long cutters. These tools tend to vibrate strongly due to their slender shape. The stress-induced transformation of austenite to martensite and the distinctive hysteresis loop allow the NiTi shape memory alloys (SMA) to absorb vibration energy. This article describes the innovative approach to dampen process vibrations by coating the tool shafts of cutting tools with long overhang with NiTi thin films. It explores how these thin films can be applied on polished tungsten carbide shafts and how their modal parameters are modified by these coatings. In a further step, this knowledge is used to calculate stability charts of corresponding machining processes. The study reported in this article identified the stabilizing effects of coatings with a thickness of 2-4 ??m on milling processes. The minimum stability limit was increased by up to 200%.     

Determination of Some Parameters for Fatigue Life in Welded Joints Using Fracture Mechanics Method

In this work, the parameters stress intensity factor (SIF), initial and final crack lengths (a _i and a _f), crack growth parameters (C and m), and fatigue strength (FAT) are investigated. The determination of initial crack length seems to be the most serious factor in fatigue life and strength calculations for welded joints. A fracture mechanics approach was used in these calculations based on SIF which was calculated with the finite element method (FEM). The weld toe crack was determined to be equal to 0.1 mm, whereas the weld root crack’s length was varied depending on the degree of the weld penetration. These initial crack length values are applicable for all types of joints which have the same crack phenomenon. As based on the above calculated parameters, the new limits of FAT for new geometries which are not listed yet in recommendations can be calculated according to the current approach.     

具备更强机械性能的高功率IGBT模块——采用最新3．3kV IGBT3芯片技术

本文介绍了新一代IHM．B具备更强机械性能的高功率IGBT模块，其融合了最新的设计、材料、焊接和安装技术。首批IHMB模块将搭载最新的、采用沟槽栅单元设计的3．3kV IGBT3芯片，在保持机械兼容性的同时，极大地提高了器件的热效率和电气效率。本文还对宇宙射线以及功率循环试验进行了研究。