Показана актуальность проблемы повышения пожарной безопасности автотранспортных средств. Приведены результаты исследования на растровом электронном микроскопе JSM-6390LV образцов медной контактной пластины автомобильного монтажного блока, используемого в электрической сети с напряжением 12 В и подвергшегося внешнему воздействию высоких температур и сверхтока. Даны снимки поверхностей оплавления медной контактной пластины автомобильного блока предохранителей после воздействия сверхтока и высоких температур. Приведены характерные диагностические признаки, позволяющие идентифицировать причину повреждения при пожаре (воздействие высоких температур, электродуговой процесс) медной контактной пластины автомобильного блока предохранителей. Установлено, что выявленные признаки являются устойчивыми и не подвержены изменениям в естественных условиях хранения автомобиля. Показано, что при выборе автомобильных предохранителей необходимо учитывать не только номинальное значение силы тока, но и материал изготовления, чтобы избежать образования недопустимой гальванической пары.
Introduction. The data covered in the present article evidence that a problem of improvement of fire safety of motor vehicles is very important. The aim of the article is to develop a scientifically-based method of examination of copper contact plates of car fuse blocks, which could be employed during fire-technical examination in order to identify causes of their damages. Materials and methodology. Researches have been conducted with the use of JSM-6390LV scanning electron microscope equipped with an add-on device for energy dispersive spectroscopy. Surfaces of failure of parts of the copper contact plate of the car fuse block have been analyzed without prior sample preparation. Results and discussion. Based on analysis of practical data it has been proven that temperature of fire of a light motor vehicle in the range of 850-950 °C does not cause change in form of the copper contact plate of the car fuse block. It has been shown in a laboratory environment that contacts of the copper plate of the car fuse block have signs of overcurrent flow caused by high transient resistance. Transient resistance, in turn, is caused by inadmissible copper - zinc galvanic pair. The paper provides results of examination of parts of the copper contact plate of the car fuse block, which have different modes of failure. It has been proven that not only nominal value of current intensity shall be used for selection of car fuses, but also material of manufacture. Conclusion. A method of differentiation of failures caused by fire (high-temperature impact, arc process) of the copper contact plate of the car fuse block has been proposed. The arc process is characterized by such indicators as straight or beveled cut, craters, swelling, ball-like meltback, or mass-transfer. It has been determined that signs identified at surfaces of failure of the copper contact plate of the car fuse block are persistent and are not exposed to changes under natural conditions of storage. The information given in the article could be useful for specialists performing expert studies of car copper contact plates sampled from places of fires of motor vehicles, for identification of nature of their failures and, eventually, for identification of causes of fires of motor vehicles.
The authors declare that there are no conflicts of interest present.