Stanje napona i deformacija u elementima skretnice

Abstract

U uvodu istradivari ja izloženi su osnovni pojmovi o skretnica- ma i osobenosti rada skretnica pod točkovima šinskog vozila i usled temperaturnih promena. Ispitivanje stabilnosti skretnice zavarene u dugi šinski trak usled temperaturnih promena putem proracunskog modela sa neli- nearnim vezama otpora i pomeranja pokazuje porast aksijalnih sila u šinama na pocetku skretnice. Tu se javlja kritični ta­ las izvijanja pri temperaturnoj promeni t^r=70K, te je sigur- nost skretnice protiv izvijanja dovoljna. Preporučuju se pri ekstremno visokim temperaturama odredjene mere pri održavanju skretnica, kao i konstruktivne mere za povećanje bočnih i po- dužnih otpora na kritičnim mestima. Rešenje problema proširenja koloseka u menjalici pri naletu točka vozila kod vožnje u odvojak analizirano je na dva pri­ mera i dokazuje: jezičak profila Zul-60 pokazuje proširenje koloseka u granicama dozvoljenih, a jezičak domaće proizvod- nje od ojačane šine prekoračuje dozvoljeno proširenje kolose­ ka. Proračun sila udara točka o skretničko srce sproveden je na dinamičkom modelu sa dva stepena slobode rešavanjem sistema nelinearnih diferencijalnih jednacina. Maksimalna sila udara iznosi 737 kN i daje kontaktne napone iznad granice plastično- sti. Takvo udarno opterećenje izaziva oštećenje srca skretni- ce, te se preporučuje upotreba manganskog čelika. Na taj nacin je ispitivanjem naponskog i deformacijskog sta- nja kritičnih delova skretnice ova disertacija doprinela po- boljšanju skretničke konstrukcije u cilju osposobljavanja za povećane brzine i opterećenja.

In the introduction of this investigation the main notions ab­ out the turnouts and their working characteristics under the vehicle wheels and the temperature changes are presented. The investigation of the welded turnout stability under the temperature increase by means of the mathematical model with nonlinear relationship between the resistances and the displa­ cements shows the increase of the axial forces in the rails at the turnout begininning. The critical hackling wave is po­ inted out at the same place under the temperature increase tcr=70K and the turnout security toward the hackling is suffi­ cient. Under the extremal high temperature the sertain measu­ res for increasing the lateral and longitudinal resistance at the critical parths are recommended. The solution of the track gage widening in the switch under the wheel attack during the diveding drive is analysing thro­ ugh the examples: tongue profile Zul-60 gives the track gage widening below the limited velue and the tongue made of enla­ rge rail profile shows the exeeding track gage widening. The calculation of the forces on the switch frog under the wheel impact is carried out by means of dynamic system of two degrees of freedom that leads to two differential equations. The maximum impact force is 737kN and gives the contact stre­ sses that can couse fatigue of the switch frog material and excessive damage through the time. So the manganese steel for the frog is recommended. In that way, the stress and strain state in critical parths of the turnout, investigated in this thesis, contributs to the improvement of the turnout structure for the increase speed and axle load in modern railroad track.