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IN an earlier article dealing with the general aspects of clastic distortion phenomena, which appeared in an issue of Aeronautics, mention was made of the various factors which tend either to promote, or to damp out and eliminate the onset of the aerodynamic inertia elastic vibration phenomena known as flutter, and it was pointed out that in this respect the provision of an adequate measure of rigidity, both as regards to twisting and flexure of the wing or tail surface structure is one of the most effective safeguards against the occurrence of torsional‐flexural flutter.

MOST previous methods for predicting moments of resistance of beams subjected to pure bending beyond the limit of proportionality involve somewhat complicated and cumbersome calculations and are usually confined to specific materials and cross‐sections.

THE force couples, including moments due to inertia masses, which acting at different points on a crankshaft cause an elastic distortion, as a result of which points disposed in the axial plane are subject to an angular displacement in relation to one another in the form of a phase advance and retard movement, and it follows that each will possess a different degree of cyclic variation.

AN outstanding feature relevant to the consideration of shaft whip phenomena is that intermediate bearings cannot be depended upon to eliminate whip by reducing the free shaft length, for under these conditions the forces tending to produce whip are still present and are transmitted to the bearings in the form of shocks which are likely to coincide with the maximum inertia load positions and result in overloading. Apart from this, an absolutely rigid bearing supporting structure is a practical impossibility (even if it were desirable) and flexing of the shaft is inevitably communicated to the structure so that if this be excessive, vibration, fatigue and rapid general deterioration must result.

A FEATURE of many of the light alloys now in common use is that the stress and strain curve often does not evidence any well defined region in which the elastic strain becomes plastic strain, and a linear portion of the diagram from the origin, which in the case of so many metals represents a region of proportionality, is sometimes almost non‐existent, the diagram being curved right from the origin so that it is not possible to define any region or limit of proportionality, and the proof stress; by standard definition, has accordingly a relatively low value compared with the ultimate tensile stress of the alloy concerned. (Fig. 1).

THIS issue of AIRCRAFT ENGINEERING might without excess of exaggeration almost be described as a special number for inspectors and ground engineers—for, indeed, that elusive individual, to whom we have on occasion referred before, the “practical man.”

THE article derives expressions for the position of the neutral axis and the failing moment of resistance of symmetrical and unsymmetrical I‐sections and channel sections, angles, solid circular sections and thick and thin tubes for materials for which the stress‐strain curve is non‐linear and is different in tension and compression.

This study describes the preparation of an eco‐balance to document the materials and energy which are part of the beer production process of the Hasseröder Brewery Ltd. A general introduction to eco‐balances and material flow networks is followed by the description of the concrete case study. The modelling of material flows and the derivation of eco‐balances is illustrated with the help of a selected process from beer production. Finally, the possibilities and limitations of the balance evaluation is discussed with the aid of performance measurement systems. The article closes with a preview of future studies.