A contribution to research on the cause of axle assembly expansions of exploited freight wagons

Abstract

Željeznički kotač je zajedno s osovinom jedan od kritičnih dijelova koji su neophodni sigurnom pogonu teretnih vagona. U eksploataciji su kotači teretnih vagona izloženi velikim toplinskim zagrijavanjima koja su uzrok naprezanjima i mogućem mehaničkom lomu te geometrijskim trošenjima uslijed kočenja, posebno kad se ono izvodi izravno preko kočnih papuča. Ovaj rad daje prikaz rezultata istraživanja uzroka proširenja osovinskih sklopova vagona Hrvatskih željeznica. Rezultati pokazuju da proširenja razmaka kotača izvan dopuštenih granica ovise jednim dijelom o zaostalim vlačnim naprezanjima u samim kotačima te o promjeru kotača. Kao optimalna statistička metoda povezanosti ovih pojava pokazala se multiregresijska analiza. Analizirajući kvarove zbog proširenja kotača po serijama vagona, izdvojene su serije s najvećom frekvencijom kvarova, čiji je glavni uzročnik proizvođač kočne opreme A.A railway wheel, together with an axle, is one of the crucial parts that support the safe operation of freight wagons. In exploitation the wheels of freight cars are exposed to high heat warmings causing stresses and possible mechanical failures due to wear and geometric distance, especially when it runs directly over the break shoes. This paper gives an overview of the research on the cause of axle assembly expansions of Croatian Railways’ freight wagons. The results of the research show that the widening of the wheel distance outside the tolerant limits depends on the residual stresses within the wheels themselves, and on the diameter of the wheels. Multiple regression analysis has shown to be the optimal statistical method for linking these phenomena. By analysing malfunctions concerning wheel expansions on train wagon series, a series with most frequent malfunctions has been singled out, while the main cause of these malfunctions is the manufacturer of wheel equipment A