The effects of tensile stresses on isothermal bainitic transformation were studied in the case of a 35MV7 steel. The modification of transformation kinetics and the presence of transformation plasticity is shown in a first step. Furthermore the effect of stress on the morphological modifications of the ferrite laths is illustrated. The role of the stress on these changes is analysed.

No abstract

The tightness of retail packagings and of their closures is of primary importance both for domestic and industrial products. For this reason, a research programme designed t o establish proper testing methods for a wide range of 'packaging + product' combinations, i n order t o check their tightness or permeability, was set up.All the available testing methods were reviewed, the most reliable ones selected and their sensitivity determined. More than 200 combinations of 'packaging + product' belonging t o five families of consumer products were examined and their tightnesdpermeability problems noted.Finally, specific testing methods were assigned t o each combination of 'packaging + product'. All these examples are currently in use in the packaging laboratory as a guideline for the testing of every kind of packaging.

The shrink films used to fix t h e loads on pallets are subjected to outdoor exposure and, particularly, t o temperature changes and light. The resistance t o photodegradation of these films must be taken into account in the design o f a quality certificate.The natural degradation o f the films was carried out in the natural environmental testing station in Bandol (south o f France). The climate o f this area represents the conditions encountered around the Mediterranean (moisture, temperature and radiant energy), which are as severe as those in most temperate countries.The accelerated tests were made at 60°C in a Sairem-Cepap 12/24 cabinet comprising four mercury gas-filled arc lamps o f the mean pressure type. The quality o f the light is representative o f natural photoageing. Any radiation o f wavelength lower than 290 nm, which is absent f r o m the solar spectrum, is carefully eliminated. The light sources radiate light rich in photons that have wavelengths between 290 and 450 nm, and provide one of the main factors o f degradation. The intensity o f emission and the spectral composition were constant during 5000 h.Three kinds o f films o f 120pm thickness were tested:(i) four films with 'medium' protection against sunshine (6 months resistance in a(ii) four films with 'high' protection against sunshine (12 months resistance in a very sunny country); (iii) one reference film without any protection.A film was considered acceptable if its mechanical properties (tensile strength and elongation) did not fall more than 50% after exposure t o natural radiations for 6 or 12 months, respectively. Comparative tests have shown that for these particular kinds o f polyethylene films, exposure t o natural radiations at Bandol for 6 or 12 months is equivalent t o an accelerated ageing in a Sairem-Cepap cabinet o f 350 or 500 h, respectively.