Showing papers by "Swedish Institute published in 1986"

The evaluation of large strains from industrial sheet metal stampings with a square grid

Abstract: A method to determine surface strains in industrially stamped sheet panels has been studied. The method incorporates a quadrilateral grid imposed to the blank and automatic image analysis. The quadrilateral grid makes it possible to analyze complex strain histories with rotations of the deformation system. The grid size can easily be increased from a minimum value upward during the analysis of a panel, for example, from one area to the next. In areas of the panel where cracking occurs, a small size grid is required because of the sharp strain gradients close to the crack. In relatively flat areas of the panel with low levels of strain attention is usually focused on strain variations over larger distances than in failure regions, and larger grids are used. Such long range strain variations are of interest in analyzing buckling, springback, or shape fixation. An inner auto body component was stamped in a high strength rephosphorized sheet steel and analyzed in some detail. Complex strain histories were identified with rotations of the deformation system. The distribution of strains in different areas of the stamping was determined. The analysis gives both the magnitude of the strains and the direction of the largest strain. Such information can be used by a die engineer in tooling development and in selecting blank holder pressure. Cracking occurred at one location of the stamping. The corresponding strain path was complex. The failure could be predicted with the present strain analysis and the forming limit diagram.

International dissemination of new drugs: A comparative study of six countries

Abstract: The times at which new drugs were licensed since 1960 have been compared for Sweden and five other countries, and the differences in licensing time between these countries have been evaluated statistically. Also, the time required for the Swedish authorities to process the licence applications has been studied and compared with the small number of similar studies available from other countries. A relationship between the delay in licensing and the processing time is discussed.

Influence of Combustion Atmospheres on the Phase Transformation of Zirconia

Abstract: Etude des transformations de phases et des modifications de la composition chimique de zircones stabilisees par MgO ou Y 2 O 3 et soumises a des traitements thermiques simulant des combustions a 700-900°C sous diverses atmospheres

Analysis of Air Change Rates in Swedish Residential Buildings

Abstract: Measurements of the rate of air exchange in residential buildings have been carried out by the Swedish Institute for Building Research since 1970. The results of an analysis of these measurements are presented in this paper for about 500 buildings not having mechanical ventilation. The studied buildings include one- and two-story, detached, single-family houses, row houses, and multifamily residential buildings built between 1900 and 1982 and of various design. In some cases, the buildings have been retrofitted by improving the insulation of the attic or the exterior walls. The building sites vary from freely exposed to a sheltered urban environment. Tracer gas measurements using the decay technique have been used for the determination of the rate of air exchange. In about 300 cases, the measurement of air change rates has been complemented by measurements using pressurization techniques. Data on 50 other parameters also have been collected. These parameters describe the building geometry, the building design, and the meteorological conditions at the time of measurement. The measurements have been performed with the outdoor temperature varying from -15 to +25°C and for wind speeds from 0 to 10 m/s. The calculation model used for the analysis includes two dimensionless variables and two parameters. The dependent variable is given by the measured air change rate and the geometric properties of the building, while the other variable is defined as the ratio of the aeromotive force to the buoyancy force. The two parameters of the model represent the degree of wind shelter and the leakage area of the building, respectively. For the analysis, the buildings have been divided into classes according to the building environment, the year of construction, and the type of building.

Some Fracture Properties of Alumina-Containing Electrical Porcelains

Abstract: The mechanical properties of electrical porcelains for high voltage insulators are important as the products are expected to serve for several decades at high tensile loads. The principles and test methods of linear elastic fracture mechanics are well established to explain and measure the long-term mechanical properties of glass as well as many high performance ceramics. These ideas could also be applied to traditional poly-crystalline ceramics but so far they have been used only to a minor extent in this field (1–8).

Numerical Simulation of Stretch Forming Processes

Abstract: Constitutive relations and finite element formulations for elastic-plastic and rigid-plastic materials in sheet metal forming analysis are reviewed. In the present study an elastic-plastic material model and a Total Lagrangian finite element formulation is used. Arbitrarily shaped punches and dies can be treated. The interface contact forces between the tools and the metal sheet are assumed to be either of Coulomb friction type or simply a constant shear stress. The effects of various material parameters and friction in the strain distribution in hemispherical punch stretching have been investigated numerically and are shown in diagrams. A few experimentally determined strain distributions are shown and are compared with results from finite element calculations.

On the mechanism of silicon nitridation in the presence of ZrO2

Abstract: The present work addresses the interaction between Si and ZrO which may occur during the nitridation stage of silicon and can affect t8e final reaction products. Using the thermoanalytical methods combined with Xray diffractometry it has been shown that the Si, parallel to the nitride formation, disproportionates in the presence of Zr02 forming ZrSi04 and ZrSi2-x according to 2Zr02 + (3-x)Si > ZrSi04 + ZrSi 2-x It is shown further that these reaction products form ZrN, Zr 0 N and Si N 0 2 2 during the nitridation. ZrO thus affects the nitridation so lh&! less desir2 able by-products are introduced (i.e. ZrN, Zr 0 N ) which may cause a decre7 11 2 ased oxidation resistance of the sintered body.

A fractographic study of electrical porcelains containing alumina

Abstract: Electrical porcelains have been studied using fractographic methods. Typical strength controlling defects were quartz grains for an extruded low-alumina porcelain and pores for an isostatically pressed high-alumina porcelain. The fracture mirror constant was measured to 1.0 ~ ~ / m 3 / 2 and the residual stress was estimated to approximately 90 MPa for the isostatically pressed porcelain. I INTRODUCTION Fractography is a well established method to characterize fracture surfaces of glasses as well as of high performance ceramics such as silicon nitride and silicon carbide /1,2/. The information about mode of failure and failure origin that can be obtained by fractography is of value, both for the designer of a ceramic component that has to bear a load, as well as for the material developer who wants to make stronger materials. Fractography can also be app1,ied to the traditional poly-crystalline ceramics even if the method is less used In this field /3,4/. Electrical porcelains for high voltage applications have to bear high tensile loads. Strength and slow crack growth are factors that affect the performance of such materials. In this paper the fracture of some electrical porcelains have been studied using fractographic methods.