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The purpose of this paper is to discretely model rockfill materials considering the irregular shape of the particles and their crushability. The scientific goal was to investigate the influence of particle crushability and shape on the mechanical behavior of rockfill materials.

The method of generating irregular-shaped particles was based on the observation that most rockfill grains can be approximately circumscribed by an ellipsoid. Two shape descriptors were used to make the virtual particles closely replicate the geometric features of natural rockfill grains. The combined finite-discrete element method (FDEM) was used to numerically simulate a drained, tri-axial compression test. The particle assemblies were subjected to tri-axial compression under strain controlled conditions while a constant confining pressure was maintained.

The non-breakable particles showed a remarkable ability to dilate as a result of a higher inter-particle locking effect. Dilation forces the particles to move from a lower potential energy state to a higher potential energy state, which causes the micro-structure to become less stable, resulting in a dramatic decline in the angle of friction from the peak state to the residual state. In addition, the elongated particles enhance the interlocking effect, but breakage is also more likely to occur. The net effect of those two mechanisms controls the overall shearing resistance of rockfill materials.

After calibration using a few micro-parameters, the combined FDEM was able to reproduce the typical behavior of rockfill materials without requiring a description of the complex relationship that exists between constituents; this relationship must be described in continuum mechanics. The simulation results showed that this approach is predictive. The combined FDEM also provides an opportunity for a quantitative study of the micro-structure of granular materials, and this study will help us to better understand the mechanical characteristics of rockfill materials.

Researchers are now designing a new generation of machines that can reason, make judgements, learn from experience ‐ intelligent machines. Already this technology is being incorporated into a new generation of machines and manufacturing processes. Explores the use of fuzzy logic, neural networks and genetic algorithms in the design of intelligent machines and explains their basic structure. Gives examples of how this technology can be incorporated into applications such as the design of robot end effectors, CNC machine tools and autonomous guided vehicles. Discusses the development of the intelligent machine and the impact that these will have on manufacturing in the future.

Hydroforming offers the potential to reduce parts count and significantly increase structural strength and stiffness, as demonstrated by the use of the process to produce A‐pillars and windshield headers for the BMW 3‐series.

This article presents an approach for assessing the damage resistance of H30 rigid foam subjected to local static loading. The main goal of the experimental part of this paper is to obtain the loaddisplacement response of foam beam specimens under static indentation by steel cylindrical indentors for both loading (indentation) and unloading stages. The instant residual dent magnitude is also measured in the testing. The nonlinear character of the mechanical behavior and the formation of a residual dent (after unloading) are attributed to local crushing of the foam in the zone directly under the indentation area. A visual inspection of a lateral surface of the foam specimens after indentation tests revealed that the local damage underneath the indentor consists of crushed and highly compacted foam, while the rest of the specimen is almost undeformed. A two‐dimensional numerical model is developed to simulate the static indentation response using the ABAQUS computer code. No overall bending of the foam specimens is assumed. The finite element modeling procedure takes into account both physical and geometrical non‐linearities. In order to simulate the plastic part of the response, the model employs the *CRUSHABLE FOAM and *CRUSHABLE FOAM HARDENING options. The modeling procedure is capable of analyzing indentation as well as unloading of foam beam specimens. Thus, the instant residual dent can be predicted. Results generated by this model exhibit good correlation with indentation tests data, thus substantiating its validity.

Discusses some of the stability, control and operational problems arising in the design of supersonic aircraft. The changes in the flow patterns about an aerofoil as a function of Mach number are reviewed and typical patterns are given for M 0·85, 0·95, 1·05 and 1·35. This forms a basis for discussion of the following problems: wing drop which occurs near the drag rise and is the result of compressibility effects and small differences in the manufacture of the wings; ‘pitch‐up’ in which the aircraft during pull‐out after a dive or during a turn suddenly operates under a load factor considerably higher than the pilot intended. Unaccelerated stability, high landing speeds, and approach and landing rates of descent are also discussed. These problems are all studied for transonic and supersonic aircraft and the differences between the two cases are indicated. A case of severe tail buffetting is discussed which occurred when testing the after‐burner of a high thrust jet engine in the bomb bay installation of a B‐45 aircraft used as an engine test‐bed.

IN RECENT issues (April, Stopwatch and Book Reviews, June) we referred to the possibility of a factory where the sole human was a person pressing buttons at a control centre. All else was done by automation.

This paper aims to propose a shape factor for granular materials based on particle shape. The scientific goal is to investigate the influence of particle shape on the mechanical properties of rockfill materials.

The method of generating four regular-shaped particles is based on the observation that most rockfill grains are regarded as like-triangle, like-rhombus, like-square and like-hexagon. A shape factor F that is developed using the Blaschke coefficient and a concave–convex degree is proposed. A biaxial compression test on rockfill materials under stress path is numerically simulated by discrete element method. The evolution of the shape factor F under the simulated stress paths is analyzed, and particle breakage rate, peak intensity and peak-related internal friction angle for rockfill materials are derived. A method of determining the shape factor F involved in the two functions is proposed.

A new micro-parameter is calibrated using the test data of one rockfill material. Particle shape greatly affects the particle breakage rate, peak intensity and peak-related internal friction angle for rockfill materials. The final experimental grading curves all approach the particle breakage grading curve proposed by Einav (the fractal dimension is 2.7).

This study proposes a shape factor F, which describes the geometric features of natural rockfill particles. The proposed shape factor F has a simple structure, and its parameters are easy to determine. The method provides an opportunity for a quantitative study on the particle shape of granular materials, and this study helps to better understand the influence of particle shape on the mechanical characteristics of rockfill materials.