Ultimate strength analysis of structural components using the continuum damage mechanics approach

In this study, an analytical model is developed to include the effect of material fracture on the overall behavior of a structure. The continuum damage mechanics approach is used to describe the continuous deterioration of the material stiffness that leads to total failure. The damage evolution is assumed to be anisotropic and the effect of the triaxiality of stress on the fracture criterion is included in the analysis. The above modifications were applied to an existing finite element program which is capable of including both geometric and material nonlinearities in the analysis. The program was used to analyze a welded tubular connection (T-joint). This joint was chosen because fracture was shown experimentally to control its ultimate behavior. Solid finite elements were used to model the chord and the branch in the intersection region, wedge elements were used for the weld profile, and the rest of the geometry was modeled using shell elements. The joint was subjected to an increasing amount of displacement at the far end of the branch. The loading was continued until total failure. During this process, the evolution of the damage and its propagation were monitored. Divergence of the solution was obtained at a failure load of 42.4 kips compared to 44.0 kips obtained experimentally. In addition, the failure mode of the joint predicted by the analysis was identical to that observed experimentally.     

Gamma sensitivity of ionization chambers

Translated from Atomnaya Énergiya, Vol. 66, No. 6, pp. 421–423, June, 1989.     

Error of measurement of coolant temperature in VVÉR-440 reactor

Translated from Atomnaya Énergiya, Vol. 67, No. 5, pp. 358–359, November, 1989.     

Pulse surface wave generator of millimeter band wavelength

Theoretical and experimental studies of high-power, relativistic surface-wave microwave Cherenkov generators are briefly considered. Some simulation and experiment results included, the experimentation being made in mm-wave region.     

Integrating heterogeneous distributed COTS discrete-event simulation packages: an emerging standards-based approach

This paper reports on the progress made toward the emergence of standards to support the integration of heterogeneous discrete-event simulations (DESs) created in specialist support tools called commercial-off-the-shelf (COTS) discrete-event simulation packages (CSPs). The general standard for heterogeneous integration in this area has been developed from research in distributed simulation and is the IEEE 1516 standard The High Level Architecture (HLA). However, the specific needs of heterogeneous CSP integration require that the HLA is augmented by additional complementary standards. These are the suite of CSP interoperability (CSPI) standards being developed under the Simulation Interoperability Standards Organization (SISO-http://www.sisostds.org) by the CSPI Product Development Group (CSPI-PDG). The suite consists of several interoperability reference models (IRMs) that outline different integration needs of CSPI, interoperability frameworks (IFs) that define the HLA-based solution to each IRM, appropriate data exchange representations to specify the data exchanged in an IF, and benchmarks termed CSP emulators (CSPEs). This paper contributes to the development of the Type I IF that is intended to represent the HLA-based solution to the problem outlined by the Type I IRM (asynchronous entity passing) by developing the entity transfer specification (ETS) data exchange representation. The use of the ETS in an illustrative case study implemented using a prototype CSPE is shown. This case study also allows us to highlight the importance of event granularity and lookahead in the performance and development of the Type I IF, and to discuss possible methods to automate the capture of appropriate values of lookahead.     

A stacking mechanism for setting bills upright in an automated teller machine

 To deal with circulated bills in various conditions regarding size, shape, and rigidity, we have developed a new bill-stacking cassette that can accept and re-dispense various-sized bills. This cassette stacks the bills upright by using deforming guides and sheet rollers under our newly developed “phase control”. It was experimentally verified by stacking tests that the cassette can handle bills in various conditions; thus, we conclude that the new cassette is practical for stacking circulated bills and re-dispensing them securely. Received: 14 August 2001/Accepted: 11 December 2001     

Al-Cu-Fe QUASICRYSTALLINE PHASE FORMATION BY MECHANICAL ALLOYING

Al-Cu-Fe alloys were prepared from elemental powders in a high-energy planetary ball mill. A sequence of solid state reactions resulting in quasicrystal (QC) phase formation takes place during heating of the as-milled powder. These reactions were studied by both differential scanning calorimetry and x-ray diffraction methods. Mechanically alloyed powders were consolidated by cold and hot pressing, as well as by explosive compaction. After annealing at sufficiently high temperatures, the consolidated samples are single-phase QC, except the ones consolidated by explosion. The high reactivity of the as-milled alloys causes the appearance of high porosity of the consolidated samples after the annealing.     

Hybrid gas-to-particle conversion and chemical vapor deposition for the production of porous alumina films

Porous alumina films can be found in a wide variety of materials, including filters, thermal insulation components, dielectrics, biomedical and catalyst supports, coatings and adsorbents. Production methods for these films are as equally diverse as their applications. In this work, a hybrid process based upon chemical vapor deposition and gas-to-particle conversion is presented as an alternative technique for producing porous alumina films, with the main advantages of solvent-free, low substrate-temperature operation. In this process, nanoparticles were produced in the vapor phase by reaction of aluminum acetylacetonate in the presence of oxygen. Downstream of this reaction zone, these nanoparticles were collected via thermophoresis onto a cooled substrate, forming a porous film. Some deposited films were subjected to post-processing in the form of annealing in air. Fourier-transform infrared spectra and X-ray energy-dispersive spectroscopy analysis confirmed the production of alumina at processing temperatures above 973 K. X-Ray diffraction revealed that the films were amorphous. Film thickness, ranging from 30 to 250 μm, and the average deposition rate were determined from scanning electron microscopy results. From transmission electron microscopy, the average primary particle size was determined to be approximately 18 nm and the formation of nanoparticle aggregates was evident. Annealing of the films at temperatures ranging from 523 to 1173 K in the presence of air did not have an effect on particle size. The specific surface area of the powder composing the films ranged from 10 to 185 m² g⁻¹, as determined from nitrogen gas adsorption by the Brunauer–Emmett–Teller method.     

Durability of hygrothermally aged graphite/epoxy woven composite under combined hygrothermal conditions

The objective of this study was to examine the effects of hygrothermal aging on the durability of a graphite/epoxy woven composite material system. The study was part of a larger project in which the objective was to evaluate and model the effects of moisture, temperature, and combined hygrothermal conditions on the strength and life of a graphite/epoxy woven composite material system. The results presented here represent an extension of the work by Patel and Case (Int. J. Fatigue 22 (2000) 809).

The hygrothermal aging consisted of cyclical temperature and moisture variations which were meant to simulate mission conditions for an advanced subsonic aircraft. Durability studies were carried out on the aged material system in the form of fatigue and residual strength testing under humid and elevated temperature environments. Damage mechanisms and failure modes were determined through fatigue testing, residual strength testing, and nondestructive evaluation.

Changes in physical appearance, thermal analysis results, fracture surfaces, and moisture diffusion behavior all supported the idea that the material was affected by the aging process. However, experimental testing also showed that the initial and residual tensile properties of the aged material were virtually unaffected by the imposed environmental aging (as compared to unaged material testing results), except when tested at elevated temperature. At elevated temperature, both the dynamic stiffness and residual strength were noticeably reduced from that at room temperature.