a p\u0159edstav\u00edme jejich v\u00fdpo\u010det na n\u011bkolika p\u0159\u00edkladech.<\/em><\/p>\n\n\n\n
Rezidu\u00e1ln\u00ed nap\u011bt\u00ed <\/h4>\n\n\n\n
Rezidu\u00e1ln\u00ed nap\u011bt\u00ed jsou mechanick\u00e1 nap\u011bt\u00ed vznikaj\u00edc\u00ed ve v\u00fdst\u0159iku bez p\u016fsoben\u00ed vn\u011bj\u0161\u00edch sil. Z\u016fst\u00e1vaj\u00ed ve v\u00fdst\u0159iku i po vyhozen\u00ed z dutiny formy, kdy se v\u00fdst\u0159ik ochlazuje na teplotu Rezidu\u00e1ln\u00ed tokov\u011b indukovan\u00e1 nap\u011bt\u00ed d\u00edky viskoelastick\u00e9 povaze polymern\u00ed taveniny p\u0159edstavuj\u00ed orientaci makromolekul a p\u0159\u00edp. vl\u00e1knit\u00e9ho plniva a jsou atributy smykov\u00fdch a norm\u00e1lov\u00fdch nap\u011bt\u00ed, kter\u00e1 jsou generov\u00e1na v pr\u016fb\u011bhu plnic\u00ed f\u00e1ze. Tato nap\u011bt\u00ed zcela nerelaxuj\u00ed, ale jsou zmra\u017eena ve v\u00fdst\u0159iku, proto\u017ee relaxa\u010dn\u00ed \u010dasy za\u010dnou rapidn\u011b nar\u016fstat v pr\u016fb\u011bhu chlazen\u00ed. Tato nap\u011bt\u00ed jsou relativn\u011b mal\u00e1, ale zp\u016fsobuj\u00ed velkou orientaci \u0159et\u011bzc\u016f molekul. Orientace ovliv\u0148uje mechanick\u00e9 a optick\u00e9 vlastnosti v\u00fdst\u0159iku a tak\u00e9 r\u016fzn\u00e1 smr\u0161t\u011bn\u00ed ve sm\u011bru a kolmo na sm\u011br toku taveniny.<\/p>\n\n\n\n Teplotn\u00ed nap\u011bt\u00ed se objevuje p\u0159i vst\u0159ikov\u00e1n\u00ed b\u011bhem f\u00e1ze dotlaku a chlazen\u00ed, jako d\u016fsledek teplotn\u00edho gradientu, kter\u00fd je sou\u010dasn\u011b p\u0159\u00edtomen i b\u011bhem f\u00e1ze tuhnut\u00ed. Rezidu\u00e1ln\u00ed teplotn\u00ed nap\u011bt\u00ed jsou v\u00fdsledkem prudk\u00e9ho nehomogenn\u00edho ochlazov\u00e1n\u00ed polymern\u00ed taveniny, jak proch\u00e1z\u00ed p\u0159es teplotu skeln\u00e9ho p\u0159echodu. Potom v pr\u016fb\u011bhu chlazen\u00ed povrchov\u00e9 vrstvy tuhnou d\u0159\u00edve ne\u017e v oblasti j\u00e1dra v\u00fdst\u0159iku. Tahov\u00e9 a tlakov\u00e9 slo\u017eky nap\u011bt\u00ed jsou tvo\u0159eny n\u00e1sledn\u00fdm ztuhnut\u00edm a teplotn\u00edm smr\u0161t\u011bn\u00edm j\u00e1dra v\u00fdst\u0159iku. Vysoce neuniformn\u00ed rozd\u011blen\u00ed teploty po pr\u016f\u0159ezu st\u011bny v\u00fdst\u0159iku zap\u0159\u00ed\u010di\u0148uje, \u017ee ka\u017ed\u00fd element polymeru ztuhne v r\u016fzn\u00e9m \u010dase. To vede k r\u016fzn\u00e9mu smr\u0161t\u011bn\u00ed vyvol\u00e1vaj\u00edc\u00edmu teplotn\u011b indukovan\u00e9 rezidu\u00e1ln\u00ed nap\u011bt\u00ed. Pon\u011bvad\u017e elastick\u00e9 vlastnosti a relaxa\u010dn\u00ed charakteristiky se v\u00fdznamn\u011b m\u011bn\u00ed s teplotou b\u011bhem tuhnut\u00ed, tato nap\u011bt\u00ed p\u0159etrvaj\u00ed a p\u0159etvo\u0159\u00ed se na rezidu\u00e1ln\u00ed teplotn\u00ed nap\u011bt\u00ed.<\/p>\n\n\n\n Na ob\u011b\u017en\u00e9m kole \u010derpadla vznikaj\u00ed trhliny, a to nejen p\u0159i provozn\u00edm zat\u00ed\u017een\u00ed, ale i p\u0159i dlouhodob\u00e9m skladov\u00e1n\u00ed (6). Ob\u011b\u017en\u00e9 kolo je vyrobeno vst\u0159ikov\u00e1n\u00edm PP pln\u011bn\u00e9ho 30% CaCO3. Do ob\u011b\u017en\u00e9ho kola je pro zv\u00fd\u0161en\u00ed tuhosti zast\u0159\u00edknuta ocelov\u00e1 vlo\u017eka (Obr. 6). Trhliny vznikaj\u00ed vlivem rozd\u00edln\u00e9ho koeficientu teplotn\u00ed rozta\u017enosti oceli a PP. Rozd\u00edln\u00e9 koeficienty teplotn\u00ed rozta\u017enosti vedou k rozd\u00edln\u00fdm objemov\u00fdm zm\u011bn\u00e1m a generuj\u00ed vysok\u00e9 hodnoty rezidu\u00e1ln\u00edch nap\u011bt\u00ed, kter\u00e1 p\u0159ekro\u010d\u00ed mez pevnosti PP a doch\u00e1z\u00ed ke vzniku trhlin (7).<\/p>\n\n\n\n Teplotn\u00ed anal\u00fdza ukazuje pr\u016fb\u011bh teploty PP matrice a ocelov\u00e9 vlo\u017eky po dobu chladnut\u00ed. Anal\u00fdza byla provedena pro dobu chladnut\u00ed 10 minut (8). Teplotn\u00ed gradient m\u00e1 za n\u00e1sledek rozd\u00edln\u00e9 objemov\u00e9 zm\u011bny, kter\u00e9 d\u00edky ocelov\u00e9mu z\u00e1st\u0159iku nemohou prob\u011bhnout. Doch\u00e1z\u00ed pak ke vzniku nap\u011bt\u00ed v polymern\u00ed matrici.<\/p>\n\n\n\n Jak je vid\u011bt z barevn\u00e9ho spektrogramu, ke vzniku nap\u011b\u0165ov\u00fdch \u0161pi\u010dek doch\u00e1z\u00ed v n\u00e1boji ob\u011b\u017en\u00e9ho kola. Srovn\u00e1vac\u00ed Von Misesovo nap\u011bt\u00ed dosahuje \u0161pi\u010dkov\u00e9 hodnoty 80 MPa (9). Tato hodnota daleko p\u0159ekra\u010duje hodnotu nap\u011bt\u00ed na mezi pevnosti PP pln\u011bn\u00e9ho 30% uhli\u010ditanu v\u00e1penat\u00e9ho, kter\u00e1 je 30 MPa. Proto\u017ee PP vykazuje vysokou hodnotu studen\u00e9ho toku, nap\u011bt\u00ed relaxuje a ke vzniku trhlin doch\u00e1z\u00ed a\u017e po \u010dase.<\/p>\n\n\n\n P\u0159i nalisov\u00e1n\u00ed kulov\u00e9ho \u010depu do pouzdra p\u0159i mont\u00e1\u017ei doch\u00e1z\u00ed k vylomen\u00ed dvou segment\u016f kle\u0161tiny pouzdra. P\u0159i lisov\u00e1n\u00ed doch\u00e1z\u00ed k elastick\u00e9 deformaci t\u011bchto t\u0159\u00ed segment\u016f a kl\u00ednov\u00e9 D\u00edky mal\u00e9mu pr\u016f\u0159ezu spojovac\u00edho kr\u010dku nep\u016fsob\u00ed v m\u00edst\u011b kritick\u00e9ho pr\u016f\u0159ezu efektivn\u011b dotlak p\u0159i vst\u0159ikov\u00e1n\u00ed, co\u017e zp\u016fsobuje vznik lunkr\u016f. D\u00e1le velk\u00e9 rozd\u00edly v tlou\u0161\u0165k\u00e1ch st\u011bn kle\u0161tiny zp\u016fsobuj\u00ed rozd\u00edln\u00e1 objemov\u00e1 smr\u0161t\u011bn\u00ed. Velk\u00e9 rozd\u00edly v objemov\u00e9m smr\u0161t\u011bn\u00ed (11) negativn\u011b ovliv\u0148uj\u00ed pevnost segment\u016f kle\u0161tiny a p\u0159isp\u00edvaj\u00ed ke vzniku vysok\u00fdch hodnot rezidu\u00e1ln\u00ed napjatosti v kritick\u00e9m m\u00edst\u011b (12). Ze stejn\u00e9ho d\u016fvodu doch\u00e1z\u00ed k velk\u00e9 deformaci segmentu kle\u0161tiny sm\u011brem dovnit\u0159 (13), tedy ke zmen\u0161en\u00ed jmenovit\u00e9ho pr\u016fm\u011bru. P\u0159i mont\u00e1\u017ei se pak segment elasticky deformuje sm\u011brem ven od st\u0159edu, aby mohla proj\u00edt kulov\u00e1 plocha \u010depu do pouzdra. Tyto deformace se s\u010d\u00edtaj\u00ed, co\u017e m\u016f\u017ee m\u00edt za n\u00e1sledek p\u0159ekro\u010den\u00ed meze pevnosti polymeru, kter\u00e1 u\u017e je sn\u00ed\u017eena lunkry, a t\u00edm i zlomen\u00ed segment\u016f (11).<\/p>\n\n\n\n Simula\u010dn\u00ed software Autodesk Simulation Moldflow Insight umo\u017e\u0148uje \u0159e\u0161it tzv. \u201emal\u00e9 a velk\u00e9 deformace\u201c (Small Deflection, Large Deflection). \u201eVelk\u00e9 a mal\u00e9 deformace\u201c je n\u00e1zev typu Vliv rezidu\u00e1ln\u00edch nap\u011bt\u00ed na kvalitu vst\u0159ikovan\u00fdch d\u00edl\u016f Autor: ing. Petr Hala\u0161ka, SMARTPLAST s.r.o. Rezidu\u00e1ln\u00ed nap\u011bt\u00ed jsou p\u0159\u00edtomna ve v\u0161ech v\u00fdst\u0159ic\u00edch po celou dobu jejich \u017eivotnosti a maj\u00ed z\u00e1sadn\u00ed vliv na kvalitu v\u00fdst\u0159iku a jeho chov\u00e1n\u00ed. Vysv\u011btl\u00edme si, jak rezidu\u00e1ln\u00ed nap\u011bt\u00ed vznikaj\u00eda p\u0159edstav\u00edme jejich v\u00fdpo\u010det na n\u011bkolika p\u0159\u00edkladech. Rezidu\u00e1ln\u00ed nap\u011bt\u00ed Rezidu\u00e1ln\u00ed nap\u011bt\u00ed jsou mechanick\u00e1 nap\u011bt\u00ed vznikaj\u00edc\u00ed ve v\u00fdst\u0159iku bez p\u016fsoben\u00ed vn\u011bj\u0161\u00edch sil. Z\u016fst\u00e1vaj\u00ed ve v\u00fdst\u0159iku i po vyhozen\u00ed z dutiny formy, kdy se v\u00fdst\u0159ik ochlazuje na teplotuokol\u00ed. Rezidu\u00e1ln\u00ed nap\u011bt\u00ed zp\u016fsobuj\u00ed deformaci a smr\u0161t\u011bn\u00ed v\u00fdst\u0159iku a maj\u00ed tak\u00e9 vliv na nap\u011b\u0165ov\u00e9 trhliny p\u016fsoben\u00edm prost\u0159ed\u00ed. Rezidu\u00e1ln\u00ed nap\u011bt\u00ed jsou p\u0159\u00edtomna ve v\u0161ech v\u00fdst\u0159ic\u00edch. Jsouindukov\u00e1na v pr\u016fb\u011bhu vst\u0159ikovac\u00edho procesu jako v\u00fdsledek rozd\u00edln\u00e9ho smr\u0161t\u011bn\u00ed a omezen\u00e9ho toku taveniny uvnit\u0159 dutiny formy. Rezidu\u00e1ln\u00ed nap\u011bt\u00ed ve v\u00fdst\u0159ic\u00edch jsou v\u00fdsledkemtokov\u00e9, teplotn\u00ed a tlakov\u00e9 historie a jsou klasifikov\u00e1na do dvou z\u00e1kladn\u00edch typ\u016f: tokov\u011b indukovan\u00e9 nap\u011bt\u00ed a teplotn\u011b indukovan\u00e9 nap\u011bt\u00ed. Tokov\u011b indukovan\u00e1 rezidu\u00e1ln\u00ed nap\u011bt\u00ed Rezidu\u00e1ln\u00ed tokov\u011b indukovan\u00e1 nap\u011bt\u00ed d\u00edky viskoelastick\u00e9 povaze polymern\u00ed taveniny p\u0159edstavuj\u00ed orientaci makromolekul a p\u0159\u00edp. vl\u00e1knit\u00e9ho plniva a jsou atributy smykov\u00fdch a norm\u00e1lov\u00fdch nap\u011bt\u00ed, kter\u00e1 jsou generov\u00e1na v pr\u016fb\u011bhu plnic\u00ed f\u00e1ze. Tato nap\u011bt\u00ed zcela nerelaxuj\u00ed, ale jsou zmra\u017eena ve v\u00fdst\u0159iku, proto\u017ee relaxa\u010dn\u00ed \u010dasy za\u010dnou rapidn\u011b nar\u016fstat v pr\u016fb\u011bhu chlazen\u00ed. Tato nap\u011bt\u00ed jsou relativn\u011b mal\u00e1, ale zp\u016fsobuj\u00ed velkou orientaci…<\/p>\n","protected":false},"author":2,"featured_media":23146,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/posts\/23132"}],"collection":[{"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/comments?post=23132"}],"version-history":[{"count":9,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/posts\/23132\/revisions"}],"predecessor-version":[{"id":23156,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/posts\/23132\/revisions\/23156"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/media\/23146"}],"wp:attachment":[{"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/media?parent=23132"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/categories?post=23132"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/tags?post=23132"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
okol\u00ed. Rezidu\u00e1ln\u00ed nap\u011bt\u00ed zp\u016fsobuj\u00ed deformaci a smr\u0161t\u011bn\u00ed v\u00fdst\u0159iku a maj\u00ed tak\u00e9 vliv na nap\u011b\u0165ov\u00e9 trhliny p\u016fsoben\u00edm prost\u0159ed\u00ed. Rezidu\u00e1ln\u00ed nap\u011bt\u00ed jsou p\u0159\u00edtomna ve v\u0161ech v\u00fdst\u0159ic\u00edch. Jsou
indukov\u00e1na v pr\u016fb\u011bhu vst\u0159ikovac\u00edho procesu jako v\u00fdsledek rozd\u00edln\u00e9ho smr\u0161t\u011bn\u00ed a omezen\u00e9ho toku taveniny uvnit\u0159 dutiny formy. Rezidu\u00e1ln\u00ed nap\u011bt\u00ed ve v\u00fdst\u0159ic\u00edch jsou v\u00fdsledkem
tokov\u00e9, teplotn\u00ed a tlakov\u00e9 historie a jsou klasifikov\u00e1na do dvou z\u00e1kladn\u00edch typ\u016f: tokov\u011b indukovan\u00e9 nap\u011bt\u00ed <\/strong>a teplotn\u011b indukovan\u00e9 nap\u011bt\u00ed<\/strong>.<\/p>\n\n\n\n![\"\"](\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2024\/03\/2013-cl.2_obr.-1.png\")
Tokov\u011b indukovan\u00e1 rezidu\u00e1ln\u00ed nap\u011bt\u00ed <\/h6>\n\n\n\n
![\"\"](\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2024\/03\/2013-cl.-2_obr.2.png\")
Teplotn\u011b indukovan\u00e1 rezidu\u00e1ln\u00ed nap\u011bt\u00ed <\/h6>\n\n\n\n
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P\u0159\u00edklad \u010d. 1: Vznik trhlin na povrchu ob\u011b\u017en\u00e9ho kola \u010derpadla<\/em><\/h5>\n\n\n\n
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Teplotn\u00ed a nap\u011b\u0165ov\u00e1 anal\u00fdza<\/h6>\n\n\n\n
![\"\"](\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2024\/03\/2013-cl.-2_obr8.png\")
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P\u0159\u00edklad \u010d. 2: L\u00e1m\u00e1n\u00ed segment\u016f kle\u0161tiny p\u0159i nalisov\u00e1n\u00ed kulov\u00e9ho \u010depu<\/em><\/h5>\n\n\n\n
z\u00e1padky, um\u00edst\u011bn\u00e9 proti segment\u016fm (10). Jak uk\u00e1zala zevrubn\u011b proveden\u00e1 anal\u00fdza vst\u0159ikovac\u00edho procesu a m\u011b\u0159en\u00ed, k l\u00e1m\u00e1n\u00ed segment\u016f kle\u0161tiny p\u0159i nalisov\u00e1n\u00ed kulov\u00e9ho \u010depu m\u016f\u017ee doch\u00e1zet jak z d\u016fvod\u016f procesn\u00edch, tak i z d\u016fvod\u016f mont\u00e1\u017en\u00edch.<\/p>\n\n\n\n![\"\"](\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2024\/03\/2013-cl.-2_obr10.png\")
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„Velk\u00e9 deformace“<\/h6>\n\n\n\n
anal\u00fdzy, kter\u00fd p\u0159\u00edmo nesouvis\u00ed se skute\u010dnou velikost\u00ed deformace. Anal\u00fdzou \u201emal\u00fdch deformac\u00ed\u201c je my\u0161lena line\u00e1rn\u011b elastick\u00e1 deformace ortotropn\u00edho materi\u00e1lov\u00e9ho modelu. Ten je pou\u017eit v p\u0159\u00edpad\u011b polymeru pln\u011bn\u00e9ho sklen\u011bn\u00fdmi vl\u00e1kny. V p\u0159\u00edpad\u011b polymeru bez vl\u00e1ken je pou\u017eit isotropn\u00ed materi\u00e1lov\u00fd model. V p\u0159\u00edpad\u011b \u201evelk\u00fdch deformac\u00ed\u201c jsou pou\u017eity stejn\u00e9 materi\u00e1lov\u00e9 modely, ale po\u010d\u00edt\u00e1 se zde se ztr\u00e1tou stability st\u011bny a deformace vst\u0159ikovan\u00e9ho d\u00edlu tak mohou b\u00fdt o \u0159\u00e1d vy\u0161\u0161\u00ed (14). Tento v\u00fdpo\u010dtov\u00fd model je vhodn\u00fd zejm\u00e9na pro dut\u00e9 tvary vyztu\u017een\u00e9 \u017eebrov\u00e1n\u00edm, kdy doch\u00e1z\u00ed ke ztr\u00e1t\u011b stability st\u011bny vst\u0159ikovan\u00e9ho d\u00edlu vlivem rezidu\u00e1ln\u00edho nap\u011bt\u00ed po vyhozen\u00ed z dutiny formy.<\/p>\n\n\n\n![\"\"](\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2024\/03\/2013-cl.-2_obr14-1024x251.png\")