{"id":62991,"date":"2022-08-29T04:35:25","date_gmt":"2022-08-29T09:35:25","guid":{"rendered":"https:\/\/www.bjultrasonic.com\/piezo-ceramics-how-to-define-strain\/"},"modified":"2025-01-27T06:14:53","modified_gmt":"2025-01-27T11:14:53","slug":"piezo-ceramics-how-to-define-strain","status":"publish","type":"post","link":"https:\/\/www.bjultrasonic.com\/cs\/piezo-ceramics-how-to-define-strain\/","title":{"rendered":"Piezokeradika: Definice a m\u011b\u0159en\u00ed deformace"},"content":{"rendered":"<p>Piezokeradika jsou materi\u00e1ly, kter\u00e9 vykazuj\u00ed piezoelektrick\u00fd efekt \u2013 schopnost generovat elektrick\u00e9 nap\u011bt\u00ed v reakci na mechanick\u00e9 nap\u011bt\u00ed (tlak, tah) a naopak, m\u011bnit sv\u00e9 rozm\u011bry v reakci na aplikovan\u00e9 elektrick\u00e9 pole.  Definice deformace (strain) v kontextu piezokeradiky je kl\u00ed\u010dov\u00e1 pro pochopen\u00ed jejich chov\u00e1n\u00ed a aplikac\u00ed, a\u0165 u\u017e se jedn\u00e1 o generov\u00e1n\u00ed ultrazvuku,  senzory tlaku, nebo aktu\u00e1tory.  P\u0159esn\u00e1 definice a m\u011b\u0159en\u00ed deformace v\u0161ak vy\u017eaduje hlub\u0161\u00ed pochopen\u00ed.<\/p>\n<h3>Definice deformace v line\u00e1rn\u00ed pru\u017enosti<\/h3>\n<p>V line\u00e1rn\u00ed pru\u017enosti je deformace definov\u00e1na jako zm\u011bna d\u00e9lky vzta\u017een\u00e1 k p\u016fvodn\u00ed d\u00e9lce.  Pro jednoosou deformaci plat\u00ed vztah:<\/p>\n<p>\u03b5 = \u0394L \/ L\u2080<\/p>\n<p>kde:<\/p>\n<ul>\n<li>\u03b5 je deformace (strain) \u2013 bezrozm\u011brn\u00e9 \u010d\u00edslo<\/li>\n<li>\u0394L je zm\u011bna d\u00e9lky<\/li>\n<li>L\u2080 je p\u016fvodn\u00ed d\u00e9lka<\/li>\n<\/ul>\n<p>Tento jednoduch\u00fd vztah je v\u0161ak platn\u00fd pouze pro mal\u00e9 deformace.  U piezokeradik, zejm\u00e9na p\u0159i pou\u017eit\u00ed vysok\u00fdch elektrick\u00fdch pol\u00ed, se m\u016f\u017eeme setkat s neline\u00e1rn\u00edm chov\u00e1n\u00edm, a proto je nutn\u00e9 pou\u017e\u00edt sofistikovan\u011bj\u0161\u00ed metody.<\/p>\n<h3>M\u011b\u0159en\u00ed deformace v piezokeradik\u00e1ch<\/h3>\n<p>M\u011b\u0159en\u00ed deformace v piezokeradik\u00e1ch vy\u017eaduje pou\u017eit\u00ed specifick\u00fdch metod, kter\u00e9 zohled\u0148uj\u00ed jejich k\u0159ehkost a malou velikost deformace.  \u010casto pou\u017e\u00edvan\u00e9 metody zahrnuj\u00ed:<\/p>\n<ul>\n<li><strong>Interferometrie:<\/strong> Tato optick\u00e1 metoda umo\u017e\u0148uje velmi p\u0159esn\u00e9 m\u011b\u0159en\u00ed i extr\u00e9mn\u011b mal\u00fdch deformac\u00ed.<\/li>\n<li><strong>Extenzometry:<\/strong>  Tyto senzory se lep\u00ed na povrch piezokeradiky a m\u011b\u0159\u00ed zm\u011bnu d\u00e9lky s vysokou p\u0159esnost\u00ed.<\/li>\n<li><strong>Laserov\u00e9 Dopplerovsk\u00e9 vibrometry:<\/strong>  Tato bezkontaktn\u00ed metoda m\u011b\u0159\u00ed rychlost vibrac\u00ed a umo\u017e\u0148uje tak odvodit deformaci.<\/li>\n<\/ul>\n<p>Volba metody z\u00e1vis\u00ed na po\u017eadovan\u00e9 p\u0159esnosti, velikosti vzorku a typu aplikace.<\/p>\n<h3>Vliv elektrick\u00e9ho pole na deformaci<\/h3>\n<p>Piezoelektrick\u00fd efekt umo\u017e\u0148uje ovliv\u0148ovat deformaci piezokeradiky aplikac\u00ed elektrick\u00e9ho pole.  Tento efekt se popisuje pomoc\u00ed piezoelektrick\u00fdch koeficient\u016f, kter\u00e9 ud\u00e1vaj\u00ed vztah mezi elektrick\u00fdm polem a deformac\u00ed.  Tyto koeficienty se li\u0161\u00ed v z\u00e1vislosti na krystalov\u00e9 struktu\u0159e a slo\u017een\u00ed materi\u00e1lu.<\/p>\n<table class=\"table table-striped table-bordered\">\n<thead>\n<tr>\n<th>Piezoelektrick\u00fd koeficient<\/th>\n<th>Jednotka<\/th>\n<th>Typick\u00fd rozsah pro piezokeradiku<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>d33<\/td>\n<td>m\/V<\/td>\n<td>100 &#8211; 600 pm\/V<\/td>\n<\/tr>\n<tr>\n<td>d31<\/td>\n<td>m\/V<\/td>\n<td>-100 &#8211; -300 pm\/V<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>d33 reprezentuje deformaci ve sm\u011bru aplikovan\u00e9ho elektrick\u00e9ho pole, zat\u00edmco d31 reprezentuje deformaci kolmo na aplikovan\u00e9 elektrick\u00e9 pole. Znam\u00e9nko m\u00ednus u d31 indikuje kontrakci materi\u00e1lu p\u0159i aplikaci kladn\u00e9ho pole.<\/p>\n<h3>Neline\u00e1rn\u00ed chov\u00e1n\u00ed a hystereze<\/h3>\n<p>U v\u011bt\u0161\u00edch deformac\u00ed se projevuje neline\u00e1rn\u00ed chov\u00e1n\u00ed piezokeradik a hystereze. Hystereze znamen\u00e1, \u017ee deformace z\u00e1vis\u00ed nejen na aktu\u00e1ln\u00ed velikosti elektrick\u00e9ho pole, ale i na jeho historii.  To je d\u016fle\u017eit\u00e9 zohlednit p\u0159i n\u00e1vrhu a modelov\u00e1n\u00ed aplikac\u00ed.<\/p>\n<h3>Z\u00e1v\u011br<\/h3>\n<p>Definice a m\u011b\u0159en\u00ed deformace v piezokeradik\u00e1ch je komplexn\u00ed \u00faloha, kter\u00e1 vy\u017eaduje znalost materi\u00e1l\u016f a m\u011b\u0159ic\u00edch technik.  Porozum\u011bn\u00ed neline\u00e1rn\u00edmu chov\u00e1n\u00ed a hysterezi je kl\u00ed\u010dov\u00e9 pro \u00fasp\u011b\u0161n\u00fd n\u00e1vrh a aplikaci t\u011bchto materi\u00e1l\u016f v r\u016fzn\u00fdch oblastech, od generov\u00e1n\u00ed ultrazvuku a\u017e po p\u0159esn\u00e9 polohovac\u00ed syst\u00e9my.  P\u0159esn\u00e9 m\u011b\u0159en\u00ed deformace, \u010dasto s vyu\u017eit\u00edm sofistikovan\u00fdch metod, je nezbytn\u00e9 pro optimalizaci jejich vlastnost\u00ed a efektivn\u00edho vyu\u017eit\u00ed jejich potenci\u00e1lu.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Piezokeradika jsou materi\u00e1ly, kter\u00e9 vykazuj\u00ed piezoelektrick\u00fd efekt \u2013 schopnost generovat elektrick\u00e9 nap\u011bt\u00ed v reakci na mechanick\u00e9 nap\u011bt\u00ed (tlak, tah) a naopak, m\u011bnit sv\u00e9 rozm\u011bry v reakci na aplikovan\u00e9 elektrick\u00e9 pole. Definice deformace (strain) v kontextu piezokeradiky je kl\u00ed\u010dov\u00e1 pro pochopen\u00ed jejich chov\u00e1n\u00ed a aplikac\u00ed, a\u0165 u\u017e se jedn\u00e1 o generov\u00e1n\u00ed ultrazvuku, senzory tlaku, nebo aktu\u00e1tory.<\/p>\n","protected":false},"author":1,"featured_media":5007,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6415],"tags":[],"class_list":["post-62991","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","prodpage-classic"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.bjultrasonic.com\/cs\/wp-json\/wp\/v2\/posts\/62991","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.bjultrasonic.com\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bjultrasonic.com\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bjultrasonic.com\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bjultrasonic.com\/cs\/wp-json\/wp\/v2\/comments?post=62991"}],"version-history":[{"count":0,"href":"https:\/\/www.bjultrasonic.com\/cs\/wp-json\/wp\/v2\/posts\/62991\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.bjultrasonic.com\/cs\/wp-json\/wp\/v2\/media\/5007"}],"wp:attachment":[{"href":"https:\/\/www.bjultrasonic.com\/cs\/wp-json\/wp\/v2\/media?parent=62991"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bjultrasonic.com\/cs\/wp-json\/wp\/v2\/categories?post=62991"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bjultrasonic.com\/cs\/wp-json\/wp\/v2\/tags?post=62991"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}