2.3 Trdnost in elasticnost
2.3 Trdnost in elasticnost
2.3 Trdnost in elasticnost
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52 Poglavje 2. STATIKA - OBRAVNAVA MATERIALNIH TELES V MIROVANJU<br />
Primer:<br />
Nosilni element iz jekla prereza S obremenimo s silo F. Določiti želimo presek <strong>in</strong> raztezek za kvadratni<br />
<strong>in</strong> okrogli profil.<br />
S<br />
S<br />
a<br />
F<br />
l0 = 1m<br />
a<br />
d<br />
∆l<br />
F = 210N sila obremenitve<br />
σdop = k ′ = 140N/mm 2<br />
Ejeklo = 2 · 10 5 N/mm 2<br />
dopustna napetost<br />
elastični modul<br />
Presek:<br />
σ = F F<br />
→ S = = 1.5 mm2<br />
S σ<br />
�<br />
π d2 4S<br />
Sokrogel = → d = = 1.382 mm<br />
4 π<br />
Skvadraten = a 2 → a = √ S = 1.225 mm<br />
Raztezek:<br />
ǫ = ∆l<br />
l → ∆l = ǫ l0 = σ<br />
E l0 = 0.7 mm
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