Method of the shortcut estimation of rails reliability by the fatigue strength criterion

The diagram of damage of structural steels under bending and contact loading has been constructed. The criterion of the critical state of steels is proposed, which corresponds to the formation of incipient surface cracks in the rolling friction zone. The methods of shortcut estimation of the damaged state of railway rails, which provide prediction of their reliability and life under service conditions, are proposed. A set of experimental studies is made with objectives to justify the proposed diagram, criterion and methods.Описана процедура построения диаграммы повреждаемости конструкционных сталей при нагружении изгибной и контактной на­грузками. Предложены критерий критичес­кого состояния для сталей, который соот­ветствует условию формирования поверх­ностных трещин в зоне трения качения, и методы ускоренной оценки поврежденного состояния железнодорожных рельсов, позво­ляющие прогнозировать их надежность и долговечность при эксплуатационном нагружении. Выполнена серия экспериментов, что дает возможность обосновать предло­женные диаграмму, критерий и методы

Dynamic experimental investigations of composites

Investigation of non-metallic and polymeric composite materials (FRP – fiber reinforced plastics) response to impact loading is now one of the most actual problems of experimental mechanics. This paper describes current results in the field of dynamic investigations, when magnitude of inertial force becomes near equal to resistance force of the test sample. Time of loading up to rupture becomes very small under high strain rates. These two factors mainly define peculiarities of material dynamic testing. For composites these problems become more complicated because of high anisotropy of material elastic and strength properties.
The paper contains basic classification of composite test methods according to strain rate and time of loading. To make this classification correctly it is necessary to take into account the specimen length, wave velocity and time factor. Among ail kinds of dynamic experiments only experimental investigations devoted to impact toughness are standardized now. The rest types of experimental methods have not yet normalized because of lack of metrological tounded demands to the methodic of testing. Present results of investigations in the field of dynamic loading of composites can be considered as definite basic step to the State Standard appearance. Some types of damage mechanics models are proposed and discussed