An experimental validation of load distribution in screw threads

The thread load distribution has been examined, as is known, in literature both theoretically and experimentally. in the present paper the load distribution is validated by strain-gage measurements. Starting from the theoretical load distribution the stresses on the outer surface of the female member of a threaded connection are calculated. The theoretical and experimental stress values obtained are reasonably close.     

Recent advances in notch analysis of fracture and fatigue

Summary Neuber's micro- and macrosupport effect theories are applied to obtain on expression for the plastic work required for crack extension. On this basis analytical predictions for fracture toughness, thickness effects and fatigue crack propagation threshold are made and found in very good agreement with experimental results.

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Übersicht Mit Hilfe der Neuberschen Theorie der Mikro- und Makrostützwirkung wird eine allgemeine Formulierung für die Rißerweiterungskraft bei nichtlinearem Werkstoffverhalten hergeleitet. Darauf aufbauend werden die Rißzähigkeit, Dickeneffekte und Rißstop bei Schwingbeanspruchung theoretisch behandelt und eine sehr gute Übereinstimmung mit Versuchsergebnissen festgestellt.

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Dedicated to o. Prof. Dr.-Ing. Dr. rer. nat. h. c. H. Neuber.     

High-temperature test facility for repeated pressure loading of cylinders

A test facility capable of subjecting cylindrical specimens to repeated pressure loadings at high temperatures is described. The loading rates range from 480 to 600 cycles per minute. The test pressures range from 310 to 447 MN/m² and the test temperatures are 260°C, 538°C and 816°C. Testing was performed at two strain rates. A “low” strain rate of about 4 per second and a “high” strain rate of about 9.6 per second. The uniqueness of the facility lies in the choice of a solid loading medium to transmit pressure to the specimen. Some typical results are presented.     

Flow of a binary gas mixture with arbitrary accommodation of the tangential momentum

The system of BGK (Bhatnagar, Gross, Krook) equations describing the isothermal flow of a binary gas mixture in a capillary with arbitrary accommodation of the tangential momentum is solved by the Bubnov-Galerkin method. General expressions are given for the kinetic thermodynamic coefficients which are valid in the whole range of Knudsen numbers and have the correct free-molecule and viscous limits. The diffusion-slip coefficients, calculated by using test values of the fraction of diffuse reflection, are compared with the experimental results.     

A goniometric-compensation technique using rotation of the polarizer

In certain polariscopes, it is inconvenient to disturb the position of elements on the viewing side of the model. This discussion presents an analysis of a goniometric-compensation technique where the polarizer alone is rotated.     

Generation of beams of three-dimensional periodic internal waves by sources of various types

The energy and force characteristics of periodic internal wave beams in a viscous exponentially stratified fluid are analyzed. The exact solutions of linearized problems of generation obtained by integral transformations describe not only three-dimensional internal waves but also the associated boundary layers of two types. The solutions not containing empirical parameters are brought to a form that allows a direct comparison with experimental data for generators of various types (friction, piston, and combined) of rectangular or elliptic shape. The stress tensor and force components acting on the generator are given in quadratures. In the limiting cases, the solutions are uniformly transformed to the corresponding expressions for the problems in a two-dimensional formulation. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 3, pp. 12–23, May–June, 2006     

Digital compensation of pressure sensors in the time domain

This contribution presents an innovative technique to determine the transfer function of pneumatic and fast-response pressure probes. The dynamic response is determined experimentally with pressure step-tests. In the case of conventional instrumentation fast-opening valves or balloon explosions are used. For the fast-response pressure sensors, shock tube tests are performed. The response of the probe is fitted in the time domain with the response of an m-order linear system. This numerical system is then used to correct the lag and dynamic error of the measurement chain. Received: 27 November 2000 / Accepted: 4 July 2001     

Field-induced gelation, yield stress, and fragility of an electro-rheological suspension

 Electro-rheological suspensions (ERS) are known to undergo liquid-to-solid transition under the application of an electric field. Long-range interaction between neighboring particles results in sample-spanning particulate structures which behave as soft solids. Here, we studied the rheological expression of this field-induced transition which has many similarities with chemical gelation. This similarity shows in mechanical spectroscopy on a suspension of monodisperse silica in PDMS as model ERS. Upon application of the electric field, dynamic moduli G′, G′′ grow by orders of magnitude and evolve in a pattern which is otherwise typical for gelation of network polymers (random chemical or physical gelation). At the gel point, the slow dynamics is governed by power-law relaxation behavior (frequency-independent tan δ). A low field strength is sufficient to reach the gel point and, correspondingly, the percolating particle structure at the gel point is still very fragile. It can be broken by the imposition of low stress. For inducing a finite yield stress, the field strength needs to be increased further until the long-range electrostatic interaction generates string-like particle alignments which become clearly visible under the optical microscope. The onset of fragile connectivity was defined experimentally by the tan δ method. The ERS was probed dynamically at low frequencies where the transition is most pronounced, and also in steady shear where the rate of structure formation equals the rate of internal breaking. Received: 1 May 2001 Accepted: 11 August 2001     

Conductor destruction in electrical explosion

Conductor damage has been examined when the current is switched off at various stages in electrical explosion. If the switching is fairly rapid, kink instability growth is accompanied by formation of vapor bubbles at the kinks within the volume of the liquid metal. Later switching results in vapor bubbles uniformly distributed along the conductor. Cumulative ejection occurs under certain conditions. A qualitative interpretation is given.