{"id":23418,"date":"2025-02-11T11:11:00","date_gmt":"2025-02-11T11:11:00","guid":{"rendered":"https:\/\/kvalitnivystrik.cz\/?p=23418"},"modified":"2025-02-10T13:26:12","modified_gmt":"2025-02-10T13:26:12","slug":"predikce-mechanickeho-chovani-plastovych-dilu","status":"publish","type":"post","link":"https:\/\/kvalitnivystrik.cz\/index.php\/2025\/02\/11\/predikce-mechanickeho-chovani-plastovych-dilu\/","title":{"rendered":"Predikce mechanick\u00e9ho chov\u00e1n\u00ed plastov\u00fdch d\u00edl\u016f"},"content":{"rendered":"\n<ol type=\"1\"><li><strong>Rozd\u00edly mezi strukturou plast\u016f a kov\u016f<\/strong><\/li><\/ol>\n\n\n\n<p>Aby bylo mo\u017en\u00e9 navrhnout plastov\u00fd d\u00edl s&nbsp;co nejmen\u0161\u00edm objemem materi\u00e1lu a tedy s nejmen\u0161\u00edm minim\u00e1ln\u00edm ekologick\u00fdm dopadem, je nutno m\u00edt k dispozici co nejv\u00edce materi\u00e1lov\u00fdch, technologick\u00fdch, a technick\u00fdch informac\u00ed.<\/p>\n\n\n\n<p>Polymery jsou makromolekul\u00e1rn\u00ed l\u00e1tky, jejich struktura a chov\u00e1n\u00ed jsou rozd\u00edln\u00e9 ve srovn\u00e1n\u00ed s&nbsp;kovy. Struktura kov\u016f je tvo\u0159ena krystalick\u00fdmi m\u0159\u00ed\u017ekami. Jednotliv\u00e9 atomy (ionty), tvo\u0159\u00edc\u00ed uzly m\u0159\u00ed\u017eky, jsou navz\u00e1jem sv\u00e1z\u00e1ny pevn\u00fdmi kovov\u00fdmi vazbami, kter\u00e9 jsou p\u0159\u00ed\u010dinou jejich typick\u00e9 pevnosti a teplotn\u00ed odolnosti. Ozna\u010den\u00ed kovov\u00e1 vazba vych\u00e1z\u00ed z p\u0159edstavy modern\u00ed <a href=\"https:\/\/cs.wikipedia.org\/w\/index.php?title=Teorie_kov%C5%AF&amp;action=edit&amp;redlink=1\">teorie kov\u016f<\/a>, podle kter\u00e9 jsou <a href=\"https:\/\/cs.wikipedia.org\/wiki\/Valen%C4%8Dn%C3%AD_elektron\">valen\u010dn\u00ed elektrony<\/a> <a href=\"https:\/\/cs.wikipedia.org\/wiki\/Atom\">atom\u016f<\/a> tvo\u0159\u00edc\u00ed kov voln\u011b sd\u00edlen\u00e9 mezi v\u0161emi atomy, tak\u017ee kovov\u00e9 <a href=\"https:\/\/cs.wikipedia.org\/wiki\/Ion\">ionty<\/a> jsou obklopeny a prostoupeny jak\u00fdmsi \u201eelektronov\u00fdm <a href=\"https:\/\/cs.wikipedia.org\/wiki\/Plyn\">plynem<\/a>\u201c. P\u0159\u00edtomnost takov\u00fdch voln\u00fdch elektron\u016f velmi dob\u0159e vysv\u011btluje vysokou <a href=\"https:\/\/cs.wikipedia.org\/wiki\/Tepeln%C3%A1_vodivost\">tepelnou<\/a> a <a href=\"https:\/\/cs.wikipedia.org\/wiki\/Elektrick%C3%A1_vodivost\">elektrickou vodivost<\/a>, kovov\u00fd lesk, pravidelnou krystalickou m\u0159\u00ed\u017eku. Polymery jsou naproti tomu tvo\u0159eny zapleteninami makromolekul\u00e1rn\u00edch \u0159et\u011bzc\u016f o r\u016fzn\u00fdch d\u00e9lk\u00e1ch. Makromolekul\u00e1rn\u00ed \u0159et\u011bzce jsou slo\u017eeny z opakuj\u00edc\u00edch se z\u00e1kladn\u00edch strukturn\u00edch jednotek, naz\u00fdvan\u00fdch mery. Mery jsou tvo\u0159eny atomy nebo skupinami atom\u016f r\u016fzn\u00fdch prvk\u016f. P\u0159evl\u00e1d\u00e1 C, H, O. Pokud jsou \u0159et\u011bzce spolu spojeny slab\u00fdmi Van der Vaalsov\u00fdmi vazbami a vod\u00edkov\u00fdmi m\u016fstky, pak hovo\u0159\u00edme o <em>termoplastech<\/em>. Nebo \u0159et\u011bzce mohou b\u00fdt spojeny chemick\u00fdmi kovalentn\u00edmi vazbami, v&nbsp;tomto p\u0159\u00edpad\u011b se jedn\u00e1 o <em>termosety<\/em>.<\/p>\n\n\n\n<p>D\u00e1le se v&nbsp;tomto p\u0159\u00edsp\u011bvku budeme zab\u00fdvat pouze termoplasty. Termoplasty podle struktury d\u011bl\u00edme na <em>amorfn\u00ed<\/em>, u kter\u00fdch jsou \u0159et\u011bzce vlivem tepeln\u00e9ho, Brownova pohybu, nepravideln\u011b uspo\u0159\u00e1d\u00e1ny a <em>semikrystalick\u00e9,<\/em> kdy jsou makromolekul\u00e1rn\u00ed \u0159et\u011bzce \u010d\u00e1ste\u010dn\u011b uspo\u0159\u00e1d\u00e1ny do pravideln\u00fdch lamel, kter\u00e9 pak vytv\u00e1\u0159\u00ed sf\u00e9rolity. P\u0159i zvy\u0161ov\u00e1n\u00ed teploty plastu se Brownov\u00fdm pohybem rozkmitaj\u00ed nejprve men\u0161\u00ed \u00faseky makromolekul a za\u010d\u00edn\u00e1 se sni\u017eovat pevnost polymeru. P\u0159i dal\u0161\u00edm dod\u00e1n\u00ed tepeln\u00e9 energie se rozkmitaj\u00ed v\u011bt\u0161\u00ed \u00faseky a d\u00e1le dojde rozru\u0161en\u00ed v\u00fd\u0161e uveden\u00fdch soudr\u017en\u00fdch sil do t\u00e9 m\u00edry, \u017ee se \u0159et\u011bzce od sebe odpoutaj\u00ed a z&nbsp;tuh\u00e9ho polymeru se st\u00e1v\u00e1 visk\u00f3zn\u011b tekut\u00e1 tavenina. V&nbsp;tomto stavu se daj\u00ed polymery zpracov\u00e1vat ve form\u011b. <em>Polymery<\/em> se modifikuj\u00ed r\u016fzn\u00fdmi plnivy, kter\u00e9 se sm\u00edchaj\u00ed s&nbsp;polymerem ve visk\u00f3zn\u00edm stavu, pak hovo\u0159\u00edme o <em>plastech<\/em>.<\/p>\n\n\n\n<ul><li><strong>Materi\u00e1lov\u00e9 vlastnosti v pevnostn\u00edm v\u00fdpo\u010dtu plastov\u00fdch d\u00edl\u016f<\/strong><\/li><\/ul>\n\n\n\n<p>P\u0159i pevnostn\u00edch v\u00fdpo\u010dtech kovov\u00fdch d\u00edl\u016f p\u0159edpokl\u00e1d\u00e1me a po\u017eadujeme, aby materi\u00e1l byl nam\u00e1h\u00e1n pouze v&nbsp;r\u00e1mci elastick\u00fdch (vratn\u00fdch) deformac\u00ed, tj. v&nbsp;mez\u00edch Hookova z\u00e1kona, kde pom\u011brn\u00e9 prodlou\u017een\u00ed, nar\u016fst\u00e1 \u00fam\u011brn\u011b se zat\u011b\u017euj\u00edc\u00edm nap\u011bt\u00edm. Na tomto p\u0159edpokladu je zalo\u017eena v\u011bt\u0161ina \u00faloh. Hovo\u0159\u00edme zde o chov\u00e1n\u00ed kov\u016f p\u0159i teplot\u00e1ch do 100 a\u017e 150\u00b0C. Tento zjednodu\u0161en\u00fd p\u0159\u00edstup dovoluje struktura atomov\u00e9 m\u0159\u00ed\u017eky.<\/p>\n\n\n\n<p>U plast\u016f, zejm\u00e9na pak vst\u0159ikovan\u00fdch je situace odli\u0161n\u00e1. Plasty vykazuj\u00ed v\u011bt\u0161inou velmi \u00fazkou oblast line\u00e1rn\u00edho chov\u00e1n\u00ed v&nbsp;r\u00e1mci Hookova z\u00e1kona. Plasty maj\u00ed proti kov\u016fm modul pru\u017enosti asi o dva \u0159\u00e1dy ni\u017e\u0161\u00ed, kde\u017eto pevnost je ni\u017e\u0161\u00ed jen asi o jeden \u0159\u00e1d. M\u016f\u017ee doj\u00edt k&nbsp;tomu, \u017ee p\u0159i zat\u011b\u017eov\u00e1n\u00ed plastov\u00e9ho v\u00fdrobku vzniknou tak velk\u00e9 deformace, kter\u00e9 jsou nep\u0159\u00edpustn\u00e9 z&nbsp;hlediska funkce v\u00fdrobku (prohnut\u00ed, net\u011bsnost, odchl\u00edpen\u00ed, zkroucen\u00ed apod.), i kdy\u017e je\u0161t\u011b nebyly p\u0159ekro\u010deny dovolen\u00e9 hodnoty pom\u011brn\u00e9ho prodlou\u017een\u00ed <em>e<\/em><em>dov<\/em> nebo nap\u011bt\u00ed <em>s<\/em><em>dov<\/em>. D\u00e1le pak modul pru\u017enosti, co\u017e je vlastn\u011b konstanta \u00fam\u011brnosti ve vztahu mezi nap\u011bt\u00edm a pom\u011brn\u00fdm prodlou\u017een\u00edm, p\u0159est\u00e1v\u00e1 b\u00fdt d\u00edky viskoelastick\u00e9mu chov\u00e1n\u00ed plast\u016f konstantou a z\u00e1vis\u00ed v\u00fdrazn\u011b tak\u00e9 na teplot\u011b a u navlhav\u00fdch plast\u016f tak\u00e9 na vlhkosti vzduchu. To jsou <em>materi\u00e1lov\u00e9 vlastnosti<\/em>, kter\u00e9 je nutno zohlednit v&nbsp;materi\u00e1lov\u00e9m modelu plast\u016f p\u0159i pevnostn\u00edch v\u00fdpo\u010dtech. (Obr. 1)<\/p>\n\n\n\n<ul><li>Viskoelastick\u00e9 chov\u00e1n\u00ed<\/li><\/ul>\n\n\n\n<p>Viskoelastick\u00e9 chov\u00e1n\u00ed plast\u016f se projevuje tokem za studena (creepem) a relaxac\u00ed nap\u011bt\u00ed. Tok za studena se projevuje pohybem nadmolekul\u00e1rn\u00ed struktury plastu v&nbsp;\u010dase, p\u0159i konstantn\u00edm zat\u00ed\u017een\u00ed a m\u016f\u017ee b\u00fdt zp\u016fsoben i vlastn\u00ed t\u00edhou plastov\u00e9ho d\u00edlu. P\u0159\u00edkladem m\u016f\u017ee b\u00fdt prota\u017een\u00ed plastov\u00e9 struny v&nbsp;\u010dase, kdy na ni zav\u011bs\u00edme z\u00e1va\u017e\u00ed. Relaxace nap\u011bt\u00ed je pokles stavu napjatosti v&nbsp;\u010dase. Jako p\u0159\u00edklad m\u016f\u017ee poslou\u017eit sn\u00ed\u017een\u00ed axi\u00e1ln\u00ed s\u00edly \u0161roubov\u00e9ho spojen\u00ed, po ur\u010dit\u00e9m \u010dase, p\u0159i pou\u017eit\u00ed plastov\u00e9 matice. Viskoelastick\u00e9 chov\u00e1n\u00ed plastu mus\u00edme zahrnout do pevnostn\u00edho v\u00fdpo\u010dtu p\u0159i \u010dasov\u00e9m p\u016fsoben\u00ed zat\u00ed\u017een\u00ed.<\/p>\n\n\n\n<ul><li>Z\u00e1vislost pevnosti plastu na teplot\u011b (Obr. 1)<\/li><\/ul>\n\n\n\n<p>Pevnost plast\u016f je v\u00fdrazn\u00fdm zp\u016fsobem z\u00e1visl\u00e1 na teplot\u011b. P\u0159i zv\u00fd\u0161en\u00ed teploty d\u00edlu na teplotu nad 60 \u00b0C dojde z\u00e1sadn\u00edm zp\u016fsobem ke sn\u00ed\u017een\u00ed pevnosti u v\u011bt\u0161iny komoditn\u00edch a konstruk\u010dn\u00edch plast\u016f. Naopak p\u0159i sn\u00ed\u017een\u00ed teploty pod -10 \u00b0C pevnost plastu naroste, ale sn\u00ed\u017e\u00ed se ta\u017enost a r\u00e1zov\u00e1 hou\u017eevnatost. Stejn\u011b tak je na teplot\u011b z\u00e1visl\u00e9 i viskoelastick\u00e9 chov\u00e1n\u00ed.<\/p>\n\n\n\n<ul><li>Z\u00e1vislost pevnosti plastu na vlhkosti prost\u0159ed\u00ed (Obr. 1)<\/li><\/ul>\n\n\n\n<p>N\u011bkter\u00e9 plasty nap\u0159. PA, PU jsou siln\u011b navlhav\u00e9. Jsou schopny absorbovat a\u017e 5% vzdu\u0161n\u00e9 vlhkosti. Molekuly vody mezi makromolekul\u00e1rn\u00edmi \u0159et\u011bzci sni\u017euj\u00ed t\u0159en\u00ed a zvy\u0161uj\u00ed voln\u00fd objem. T\u00edm se zv\u00fd\u0161\u00ed ohebnost nadmolekul\u00e1rn\u00ed struktury a z\u00e1rove\u0148 naroste objem plastu. V\u00fdsledkem je pokles pevnosti a n\u00e1rust ta\u017enosti a r\u00e1zov\u00e9 hou\u017eevnatosti. N\u00e1rust objemu vede ke zv\u011bt\u0161en\u00ed rozm\u011br\u016f d\u00edlu. Pevnost i rozm\u011bry se pak m\u011bn\u00ed podle relativn\u00ed vlhkosti vzduchu, podle toho v&nbsp;jak\u00e9m prost\u0159ed\u00ed se d\u00edl pr\u00e1v\u011b nach\u00e1z\u00ed.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"470\" src=\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_1-1024x470.jpg\" alt=\"\" class=\"wp-image-23419\" srcset=\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_1-1024x470.jpg 1024w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_1-300x138.jpg 300w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_1-768x352.jpg 768w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_1-1536x705.jpg 1536w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_1-1200x551.jpg 1200w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_1-120x55.jpg 120w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_1-81x37.jpg 81w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_1.jpg 1580w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p><em>Obr. 1: Vliv teploty, relativn\u00ed vlhkosti a rychlosti zat\u011b\u017eov\u00e1n\u00ed na pevnost plastu.<\/em><\/p>\n\n\n\n<ul><li><strong>Vliv vst\u0159ikovac\u00edho procesu na pevnost plastov\u00fdch d\u00edl\u016f<\/strong><\/li><\/ul>\n\n\n\n<p>Vst\u0159ikovac\u00ed proces a sn\u00edm spojen\u00fd technologick\u00fd design d\u00edlu mohou z\u00e1sadn\u00edm zp\u016fsobem ovlivnit pevnost plastov\u00e9ho d\u00edl\u016f. Z\u00e1sadn\u00ed vliv na mechanick\u00e9 chov\u00e1n\u00ed plastov\u00e9ho d\u00edlu m\u016f\u017ee m\u00edt p\u0159\u00edtomnost studen\u00fdch spoj\u016f a lunkr\u016f. P\u0159i pln\u011bn\u00ed dutiny formy doch\u00e1z\u00ed k\u00a0orientaci nadmolekul\u00e1rn\u00ed struktury a p\u0159\u00edpadn\u011b vl\u00e1knit\u00e9ho plniva. V\u00a0pr\u016fb\u011bhu vst\u0159ikovac\u00edho procesu se v\u00a0plastov\u00e9m d\u00edlu indukuj\u00ed rezidu\u00e1ln\u00ed nap\u011bt\u00ed generovan\u00e1 vnit\u0159n\u00edmi silami. Pevnost plastu vst\u0159ikovan\u00e9ho d\u00edlu z\u00e1vis\u00ed tak\u00e9 na hodnot\u011b a \u010dase dotlaku. Dal\u0161\u00ed ovlivn\u011bn\u00ed mechanick\u00e9ho chov\u00e1n\u00ed d\u00edlu je ovlivn\u011bno teplotou formy, resp. pr\u016fb\u011bhem teplotn\u00edho pole v\u00a0cyklu. Tyto v\u00fd\u0161e uveden\u00e9 nehomogenity dok\u00e1\u017eeme velmi dob\u0159e predikovat pomoc\u00ed CAE Moldflow anal\u00fdzy.<\/p>\n\n\n\n<p><\/p>\n\n\n\n<ul><li>Studen\u00e9 spoje (Obr. 2)<\/li><\/ul>\n\n\n\n<p>Studen\u00e9 spoje vznikaj\u00ed p\u0159i pln\u011bn\u00ed dutiny formy, kdy\u017e se setkaj\u00ed dv\u011b \u010dela proud\u00edc\u00ed taveniny v&nbsp;dutin\u011b formy. K&nbsp;t\u00e9to situaci dojde, kdy\u017e se proud taveniny rozd\u011bl\u00ed p\u0159i obt\u00e9k\u00e1n\u00ed nap\u0159. tv\u00e1rn\u00edku ve form\u011b na dv\u011b \u010d\u00e1sti a ty se op\u011bt spoj\u00ed v&nbsp;jeden proud za tv\u00e1rn\u00edkem. Podobn\u00e1 situace nastane, kdy\u017e je dutina formy pln\u011bna v\u00edce vtokov\u00fdmi \u00fast\u00ed, kter\u00e1 nejsou \u0159\u00edzena. Studen\u00fd spoj vznikne na soutoku jednotliv\u00fdch proud\u016f. Sn\u00ed\u017een\u00ed mechanick\u00fdch vlastnost\u00ed ve studen\u00e9m spoji z\u00e1vis\u00ed na odvzdu\u0161n\u011bn\u00ed dutiny formy v&nbsp;dan\u00e9m m\u00edst\u011b, na teplot\u011b \u010dela taveniny, lok\u00e1ln\u00edm tlaku a na p\u0159\u00edtomnosti vl\u00e1knit\u00e9ho plniva. Predikce exaktn\u00edch mechanick\u00fdch vlastnost\u00ed ve studen\u00e9m spoji je v&nbsp;re\u00e1ln\u00e9 situaci velmi obt\u00ed\u017en\u00e1, ale v&nbsp;ka\u017ed\u00e9m p\u0159\u00edpad\u011b by m\u011bla b\u00fdt zahrnuta do pevnostn\u00edho v\u00fdpo\u010dtu, by\u0165 jen posouzen\u00edm p\u0159\u00edpadn\u00fdch nap\u011b\u0165ov\u00fdch \u0161pi\u010dek ve studen\u00e9m spoji. Na tomto m\u00edst\u011b stoj\u00ed tak\u00e9 za zm\u00ednku jetting efekt (voln\u00fd proud taveniny z&nbsp;vtokov\u00e9ho \u00fast\u00ed), kter\u00fd tak\u00e9 vytv\u00e1\u0159\u00ed studen\u00fd spoj.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"304\" src=\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_2-1-1024x304.jpg\" alt=\"\" class=\"wp-image-23421\" srcset=\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_2-1-1024x304.jpg 1024w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_2-1-300x89.jpg 300w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_2-1-768x228.jpg 768w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_2-1-1536x456.jpg 1536w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_2-1-1200x357.jpg 1200w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_2-1-120x36.jpg 120w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_2-1-81x24.jpg 81w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_2-1.jpg 1841w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p><em>Obr. 2: Predikce studen\u00fdch spoj\u016f, anal\u00fdza nap\u011bt\u00ed, lom d\u00edlu a orientace kr\u00e1tk\u00fdch sklen\u011bn\u00fdch vl\u00e1ken ve studen\u00e9m spoji.<\/em><\/p>\n\n\n\n<ul><li>Lunkry (Obr. 3)<\/li><\/ul>\n\n\n\n<p>Lunkry jsou vakuoly, ostr\u00fdmi hranami ohrani\u010den\u00e9 dutiny, vznikaj\u00ed nedostate\u010dn\u00fdm p\u016fsoben\u00edm dotlaku. Nej\u010dast\u011bji jsou zp\u016fsobeny \u0161patn\u00fdm technologick\u00fdm designem plastov\u00e9ho d\u00edlu, p\u0159\u00edp. nevhodn\u00fdm um\u00edst\u011bn\u00edm vtokov\u00e9ho \u00fast\u00ed. Lunkr p\u0159edstavuje sn\u00ed\u017een\u00ed pr\u016f\u0159ezu st\u011bny plastov\u00e9ho d\u00edlu a z\u00e1rove\u0148 na ostr\u00fdch hran\u00e1ch doch\u00e1z\u00ed k vrubov\u00e9 koncentraci nap\u011bt\u00ed. Z&nbsp;t\u011bchto m\u00edst se pak mohou \u0161\u00ed\u0159it mikrotrhliny, kter\u00e9 vedou zejm\u00e9na p\u0159i cyklick\u00e9m nam\u00e1h\u00e1n\u00ed k&nbsp;destrukci d\u00edlu. Potenci\u00e1ln\u00ed vznik lunkr\u016f dok\u00e1\u017eeme pomoc\u00ed Moldflow velmi dob\u0159e predikovat.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"398\" src=\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_3-1024x398.jpg\" alt=\"\" class=\"wp-image-23422\" srcset=\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_3-1024x398.jpg 1024w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_3-300x117.jpg 300w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_3-768x299.jpg 768w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_3-1536x598.jpg 1536w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_3-1200x467.jpg 1200w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_3-120x47.jpg 120w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_3-81x32.jpg 81w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_3.jpg 1843w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p><em>Obr. 3: Predikce vzniku lunkr\u016f, lom d\u00edlu a anal\u00fdza nap\u011bt\u00ed<\/em><\/p>\n\n\n\n<ul><li>Rezidu\u00e1ln\u00ed nap\u011bt\u00ed (Obr. 4)<\/li><\/ul>\n\n\n\n<p>Rezidu\u00e1ln\u00ed nap\u011bt\u00ed je indukov\u00e1no v&nbsp;plastov\u00e9m d\u00edlu po celou dobu vst\u0159ikovac\u00edho procesu. Nejvy\u0161\u0161\u00ed hodnoty jsou pak indukov\u00e1ny ve f\u00e1zi dotlaku a chlazen\u00ed. Velikost rezidu\u00e1ln\u00edho nap\u011bt\u00ed z\u00e1vis\u00ed na velikosti rozd\u00edl\u016f hodnot tlaku a teplot, resp. rovnom\u011brnosti tlakov\u00e9ho a teplotn\u00edho pole jak v&nbsp;objemu d\u00edlu, tak v&nbsp;\u010dase, a to i po vyhozen\u00ed d\u00edlu z&nbsp;dutiny formy. Po vyhozen\u00ed d\u00edlu doch\u00e1z\u00ed k&nbsp;ochlazov\u00e1n\u00ed d\u00edlu na teplotu okol\u00ed bez vazeb dutiny formy. \u010c\u00e1st rezidu\u00e1ln\u00edho nap\u011bt\u00ed se realizuje na deformaci plastov\u00e9 ho d\u00edlu a \u010d\u00e1st nap\u011bt\u00ed relaxuje po celou dobu \u017eivotnosti plastov\u00e9ho d\u00edlu.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"359\" src=\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_4-1024x359.jpg\" alt=\"\" class=\"wp-image-23423\" srcset=\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_4-1024x359.jpg 1024w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_4-300x105.jpg 300w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_4-768x269.jpg 768w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_4-1536x538.jpg 1536w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_4-1200x420.jpg 1200w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_4-120x42.jpg 120w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_4-81x28.jpg 81w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_4.jpg 1762w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p><em>Obr. 4: Poprask\u00e1n\u00ed d\u00edlu z PP se z\u00e1liskem, p\u016fsoben\u00edm rezidu\u00e1ln\u00edho nap\u011bt\u00ed. Anal\u00fdza Moldflow rezidu\u00e1ln\u00edho nap\u011bt\u00ed.<\/em><\/p>\n\n\n\n<ul><li>Orientace<\/li><\/ul>\n\n\n\n<p>P\u0159i pln\u011bn\u00ed dutiny formy a \u010d\u00e1ste\u010dn\u011b tak\u00e9 p\u0159i dotlaku doch\u00e1z\u00ed k&nbsp;orientaci nadmolekul\u00e1rn\u00ed struktury polymeru ve sm\u011bru toku taveniny. Tento fakt se projevuje u semikrystalick\u00fdch polymer\u016f, u amorfn\u00edch polymer\u016f nen\u00ed v\u00fdznamn\u00fd. Mnohem v\u00fdznamn\u011bj\u0161\u00edm faktorem orientace je plnivo v&nbsp;podob\u011b vl\u00e1ken. Vl\u00e1kna se p\u0159i pln\u011bn\u00ed dutiny orientuj\u00ed ve sm\u011bru toku taveniny a pevnost v\u00fdsledn\u00e9 struktury z\u00e1vis\u00ed na sm\u011bru orientace vl\u00e1ken. (Obr. 5) Ve sm\u011bru orientace vl\u00e1ken je pevnost v\u00fdrazn\u011b vy\u0161\u0161\u00ed ne\u017e pevnost kolmo na sm\u011br orientace. Vl\u00e1kna mohou b\u00fdt kr\u00e1tk\u00e1 0,4-0,8mm nebo dlouh\u00e1 8-12mm d\u00e9lky. V&nbsp;p\u0159\u00edpad\u011b dlouh\u00fdch vl\u00e1ken je nutno po\u010d\u00edtat se zkracov\u00e1n\u00edm&nbsp;vl\u00e1ken l\u00e1m\u00e1n\u00edm p\u0159i pr\u016fchodu plastika\u010dn\u00ed jednotkou, vtokov\u00fdm syst\u00e9mem a dutinou. Orientaci vl\u00e1ken i l\u00e1m\u00e1n\u00ed m\u016f\u017eeme predikovat pomoc\u00ed CAE Moldflow a stejn\u011b tak m\u016f\u017eeme analyzovat zm\u011bnu pevnosti plastu v&nbsp;objemu vst\u0159ikovan\u00e9ho d\u00edlu. Tuto ortotropn\u00ed materi\u00e1lovou charakteristiku m\u016f\u017eeme namapovat na s\u00ed\u0165 kone\u010dn\u00fdch prvk\u016f ur\u010denou pro pevnostn\u00ed anal\u00fdzu nap\u0159. v&nbsp;Abaqus CAE.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"298\" src=\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_5-1024x298.jpg\" alt=\"\" class=\"wp-image-23424\" srcset=\"https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_5-1024x298.jpg 1024w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_5-300x87.jpg 300w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_5-768x224.jpg 768w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_5-1536x447.jpg 1536w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_5-1200x350.jpg 1200w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_5-120x35.jpg 120w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_5-81x24.jpg 81w, https:\/\/kvalitnivystrik.cz\/wp-content\/uploads\/2025\/02\/Obr_5.jpg 1854w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p><em>Obr. 5: Orientace sklen\u011bn\u00fdch vl\u00e1ken, zm\u011bna pevnosti v&nbsp;d\u016fsledku orientace, nap\u011bt\u00ed p\u0159i zat\u00ed\u017een\u00ed<\/em><\/p>\n\n\n\n<ul><li>Tlak v&nbsp;dutin\u011b formy a teplota formy<\/li><\/ul>\n\n\n\n<p>Tlak v&nbsp;dutin\u011b formy p\u0159i dotlaku m\u016f\u017ee tak\u00e9 ovlivnit pevnost plastu. S&nbsp;vy\u0161\u0161\u00edm tlakem se zv\u011bt\u0161uje tak\u00e9 pevnost plastu. Tzn., \u017ee oblasti vtokov\u00e9ho \u00fast\u00ed m\u00e1 d\u00edl v\u011bt\u0161\u00ed pevnost ne\u017e na konci tokov\u00e9 dr\u00e1hy, kde je p\u016fsoben\u00ed tlaku men\u0161\u00ed. Teplota formy ovliv\u0148uje u semikrystalick\u00fdch polymer\u016f pod\u00edl krystalick\u00e9 f\u00e1ze. S&nbsp;vy\u0161\u0161\u00ed teplotou formy nar\u016fst\u00e1 i pod\u00edl krystalick\u00e9 f\u00e1ze. Vy\u0161\u0161\u00ed pod\u00edl krystalick\u00e9 f\u00e1ze znamen\u00e1 vy\u0161\u0161\u00ed pevnost plastu, ale ni\u017e\u0161\u00ed ta\u017enost a r\u00e1zovou hou\u017eevnatost.<\/p>\n\n\n\n<ul><li><strong>Pevnostn\u00ed anal\u00fdza vst\u0159ikovan\u00fdch d\u00edl\u016f<\/strong><\/li><\/ul>\n\n\n\n<p>Jak u\u017e bylo \u0159e\u010deno v&nbsp;\u00favodu, plasty jsou slo\u017eit\u00e9 na popis materi\u00e1lov\u00e9ho modelu pro pevnostn\u00ed anal\u00fdzu. Je nutno m\u00edt k&nbsp;dispozici materi\u00e1lov\u00e1 data, zahrnuj\u00edc\u00ed co nejv\u00edce nam\u011b\u0159en\u00fdch parametr\u016f zp\u0159es\u0148uj\u00edc\u00edch v\u00fdpo\u010det.<\/p>\n\n\n\n<p>Aby pevnostn\u00ed anal\u00fdza co nejv\u011brn\u011bji popisovala realitu, mus\u00edme do v\u00fdpo\u010dtu zahrnout tak\u00e9 nehomogenity vznikl\u00e9 v&nbsp;pr\u016fb\u011bhu vst\u0159ikovac\u00edho procesu. Velmi dob\u0159e um\u00edme zahrnout do pevnostn\u00ed anal\u00fdzy orientaci vl\u00e1ken, studen\u00e9 spoje, rezidu\u00e1ln\u00ed nap\u011bt\u00ed a \u010d\u00e1ste\u010dn\u011b tak\u00e9 lunkry a orientaci krystalick\u00e9 struktury. Analytickou \u00falohu pak \u0159e\u0161\u00edme jako spojen\u00ed \u00falohy Moldflow a pevnostn\u00ed anal\u00fdzy.<\/p>\n\n\n\n<ul><li>Charakter zat\u00ed\u017een\u00ed<\/li><\/ul>\n\n\n\n<p>Zat\u00ed\u017een\u00ed plastov\u00e9ho d\u00edlu m\u016f\u017ee b\u00fdt p\u016fsoben\u00edm vn\u011bj\u0161\u00edch sil a prost\u0159ed\u00ed. Vn\u011bj\u0161\u00ed s\u00edly mohou p\u016fsobit staticky, cyklicky nebo dynamicky. P\u0159i statick\u00e9m zat\u00ed\u017een\u00ed se hodnota a sm\u011br zat\u00ed\u017een\u00ed nem\u011bn\u00ed v&nbsp;\u010dase. Je to nap\u0159. t\u00edha, mont\u00e1\u017en\u00ed zat\u00ed\u017een\u00ed. P\u0159i cyklick\u00e9m nebo m\u00edjiv\u00e9m zat\u00ed\u017een\u00ed se hodnota a sm\u011br zat\u00ed\u017een\u00ed m\u011bn\u00ed v&nbsp;\u010dase. Jsou to nap\u0159. ped\u00e1ly, zav\u00edrac\u00ed a zamykac\u00ed mechanismy dve\u0159\u00ed, \u010d\u00e1sti vyp\u00edna\u010d\u016f. V&nbsp;tomto p\u0159\u00edpad\u011b prov\u00e1d\u00edme v\u00fdpo\u010det na \u00fanavu. Dynamick\u00e9 zat\u00ed\u017een\u00ed p\u0159edstavuje velmi rychl\u00fd n\u00e1rust zat\u00ed\u017een\u00ed v&nbsp;d\u016fsledku n\u00e1razu, p\u00e1du, impaktu. Pro dynamick\u00e9 zat\u00ed\u017een\u00ed mus\u00edme pou\u017e\u00edt explicitn\u00ed \u0159e\u0161i\u010de a materi\u00e1lov\u00e9 modely zahrnuj\u00edc\u00ed zpevn\u011bn\u00ed p\u0159i rychl\u00e9m n\u00e1rustu hodnoty zat\u00ed\u017een\u00ed. (Obr.1)<\/p>\n\n\n\n<ul><li>P\u016fsoben\u00ed prost\u0159ed\u00ed<\/li><\/ul>\n\n\n\n<p>Vlivy prost\u0159ed\u00ed jsou hlavn\u011b zv\u00fd\u0161en\u00e1 teplota do 100\u00b0C a naopak sn\u00ed\u017een\u00e1 teplota pod -10\u00b0C. V&nbsp;tomto p\u0159\u00edpad\u011b je nutno upravit materi\u00e1lov\u00fd model odpov\u00eddaj\u00edc\u00ed dan\u00e9 teplot\u011b. Podobn\u011b je nutno upravit materi\u00e1lov\u00fd model u hygroskopick\u00fdch plast\u016f, u kter\u00fdch p\u0159i n\u00edzk\u00e9 relativn\u00ed vlhkosti kles\u00e1 ta\u017enost a r\u00e1zov\u00e1 hou\u017eevnatost. (Obr.1) P\u0159i p\u016fsoben\u00ed zv\u00fd\u0161en\u00e9 teploty je nutno tak\u00e9 br\u00e1t v&nbsp;\u00favahu relativn\u011b vysok\u00fd koeficient teplotn\u00ed rozta\u017enosti u plast\u016f, kter\u00fd je 5x vy\u0161\u0161\u00ed ne\u017e u oceli.<\/p>\n\n\n\n<ul><li><strong>Post<\/strong> <strong>procesn\u00ed zat\u00ed\u017een\u00ed<\/strong><\/li><\/ul>\n\n\n\n<p>Post procesn\u00ed zat\u00ed\u017een\u00ed p\u016fsob\u00ed p\u0159i povrchov\u00e9 \u00faprav\u011b, kdy je d\u00edl zah\u0159\u00edv\u00e1m p\u0159i vytvrzov\u00e1n\u00ed, galvanick\u00e9 pokoven\u00ed. V&nbsp;tomto p\u0159\u00edpad\u011b m\u016f\u017ee doch\u00e1zet ke zm\u011bn\u00e1m rezidu\u00e1ln\u00edch nap\u011bt\u00ed relaxac\u00ed p\u0159\u00edp. rekrystalizac\u00ed u n\u011bkter\u00fdch typ\u016f plast\u016f s&nbsp;vysok\u00fdm pod\u00edlem krystalick\u00e9 f\u00e1ze. K&nbsp;dal\u0161\u00ed zm\u011bn\u00e1m rezidu\u00e1ln\u00edho nap\u011bt\u00ed m\u016f\u017ee doj\u00edt p\u0159i sva\u0159ov\u00e1n\u00ed v&nbsp;d\u016fsledku p\u016fsoben\u00ed lok\u00e1ln\u00edho oh\u0159evu.<\/p>\n\n\n\n<ul><li><strong>Z\u00e1v\u011br<\/strong><\/li><\/ul>\n\n\n\n<p>Aby pevnostn\u00ed anal\u00fdza co nejv\u011brn\u011bji popisovala realitu, mus\u00edme do v\u00fdpo\u010dtu zahrnout co nejv\u00edce specifick\u00fdch charakteristik v\u00a0chov\u00e1n\u00ed plast\u016f. Je to hlavn\u011b viskoelastick\u00e9 chov\u00e1n\u00ed, a vliv teploty prost\u0159ed\u00ed, kde bude d\u00edl exponov\u00e1n. Krom\u011b toho je nutno po\u010d\u00edtat tak\u00e9 s\u00a0nehomogenitami vznikl\u00fdmi v\u00a0pr\u016fb\u011bhu vst\u0159ikovac\u00edho procesu. Jsou to studen\u00e9 spoje, jetting efekt, lunkry, orientace a rezidu\u00e1ln\u00ed nap\u011bt\u00ed. Dal\u0161\u00ed informace na <em>www.smartplast.cz<\/em><\/p>\n\n\n\n<p><\/p>\n\n\n\n<p>V<a href=\"https:\/\/youtu.be\/t_T83Tz9woc?si=Tvh4nsmyDJCA80gO\">ideo z p\u0159edn\u00e1\u0161ky najdete zde.<\/a><\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"Formy a plasty 2019 010 Smartplast - Chov\u00e1n\u00ed mechanicky nam\u00e1han\u00fdch d\u00edl\u016f\" width=\"1200\" height=\"675\" src=\"https:\/\/www.youtube.com\/embed\/t_T83Tz9woc?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Rozd\u00edly mezi strukturou plast\u016f a kov\u016f Aby bylo mo\u017en\u00e9 navrhnout plastov\u00fd d\u00edl s&nbsp;co nejmen\u0161\u00edm objemem materi\u00e1lu a tedy s nejmen\u0161\u00edm minim\u00e1ln\u00edm ekologick\u00fdm dopadem, je nutno m\u00edt k dispozici co nejv\u00edce materi\u00e1lov\u00fdch, technologick\u00fdch, a technick\u00fdch informac\u00ed. Polymery jsou makromolekul\u00e1rn\u00ed l\u00e1tky, jejich struktura a chov\u00e1n\u00ed jsou rozd\u00edln\u00e9 ve srovn\u00e1n\u00ed s&nbsp;kovy. Struktura kov\u016f je tvo\u0159ena krystalick\u00fdmi m\u0159\u00ed\u017ekami. Jednotliv\u00e9 atomy (ionty), tvo\u0159\u00edc\u00ed uzly m\u0159\u00ed\u017eky, jsou navz\u00e1jem sv\u00e1z\u00e1ny pevn\u00fdmi kovov\u00fdmi vazbami, kter\u00e9 jsou p\u0159\u00ed\u010dinou jejich typick\u00e9 pevnosti a teplotn\u00ed odolnosti. Ozna\u010den\u00ed kovov\u00e1 vazba vych\u00e1z\u00ed z p\u0159edstavy modern\u00ed teorie kov\u016f, podle kter\u00e9 jsou valen\u010dn\u00ed elektrony atom\u016f tvo\u0159\u00edc\u00ed kov voln\u011b sd\u00edlen\u00e9 mezi v\u0161emi atomy, tak\u017ee kovov\u00e9 ionty jsou obklopeny a prostoupeny jak\u00fdmsi \u201eelektronov\u00fdm plynem\u201c. P\u0159\u00edtomnost takov\u00fdch voln\u00fdch elektron\u016f velmi dob\u0159e vysv\u011btluje vysokou tepelnou a elektrickou vodivost, kovov\u00fd lesk, pravidelnou krystalickou m\u0159\u00ed\u017eku. Polymery jsou naproti tomu tvo\u0159eny zapleteninami makromolekul\u00e1rn\u00edch \u0159et\u011bzc\u016f o r\u016fzn\u00fdch d\u00e9lk\u00e1ch. Makromolekul\u00e1rn\u00ed \u0159et\u011bzce jsou slo\u017eeny z opakuj\u00edc\u00edch se z\u00e1kladn\u00edch strukturn\u00edch jednotek, naz\u00fdvan\u00fdch mery. Mery jsou tvo\u0159eny atomy nebo skupinami atom\u016f r\u016fzn\u00fdch prvk\u016f. P\u0159evl\u00e1d\u00e1 C, H, O. Pokud jsou \u0159et\u011bzce spolu spojeny slab\u00fdmi Van der Vaalsov\u00fdmi vazbami a vod\u00edkov\u00fdmi m\u016fstky, pak hovo\u0159\u00edme o termoplastech. Nebo \u0159et\u011bzce mohou b\u00fdt spojeny chemick\u00fdmi kovalentn\u00edmi vazbami, v&nbsp;tomto p\u0159\u00edpad\u011b se jedn\u00e1 o termosety. D\u00e1le se v&nbsp;tomto p\u0159\u00edsp\u011bvku budeme zab\u00fdvat pouze termoplasty. Termoplasty&#8230;<\/p>\n","protected":false},"author":1,"featured_media":23422,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[34,40],"tags":[59,60,78],"_links":{"self":[{"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/posts\/23418"}],"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\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/comments?post=23418"}],"version-history":[{"count":3,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/posts\/23418\/revisions"}],"predecessor-version":[{"id":23428,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/posts\/23418\/revisions\/23428"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/media\/23422"}],"wp:attachment":[{"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/media?parent=23418"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/categories?post=23418"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kvalitnivystrik.cz\/index.php\/wp-json\/wp\/v2\/tags?post=23418"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}