{"id":16347,"date":"2022-07-12T13:55:21","date_gmt":"2022-07-12T12:55:21","guid":{"rendered":"https:\/\/mollificiovalli.it\/?p=16347"},"modified":"2022-10-20T08:54:56","modified_gmt":"2022-10-20T07:54:56","slug":"why-does-a-spring-break","status":"publish","type":"post","link":"https:\/\/mollificiovalli.it\/en\/why-does-a-spring-break\/","title":{"rendered":"WHY DOES A SPRING BREAK"},"content":{"rendered":"

With this article, we introduce you to our technical portal and we do so by talking about the main issue involved in springs, in other words spring breakage.<\/p>\n

Technically, the breakage of a spring<\/strong> occurs when there is an interruption in the continuity of the physical structure of the wire: in short, the wire breaks in two or more parts.<\/p>\n

Why does the spring break?<\/h2>\n

The theory of materials tells us that a material breaks when the breaking load is exceeded in any point of its section. Working backwards, as in the 5Why<\/em> problem solving technique, we go down one level and discover what the breaking load is: it is a physical quantity typical of each material, which has the dimensions of pressure (it is measured in Mpa<\/em> , mega Pascal). In fact, the force applied is divided by the area of \u200b\u200bthe section of the material.<\/p>\n

We meet this quantity by studying one of the first physical laws formulated at the beginning of the scientific revolution of the seventeenth century, Hooke’s law<\/em>.<\/p>\n

Given \u03c3<\/em> the stress and \u03b5<\/em> the elongation, Hooke’s law expresses the direct proportionality bond between \u03c3<\/em> and \u03b5<\/em> through the constant E<\/em>, which represents Young’s modulus<\/em>.<\/p>\n

Hence the relation is \u03c3 = E x \u03b5<\/em>.<\/p>\n

\"diagramma

This proportionality bond is valid only in the elastic part of the material, that is, when the stress suppression brings the material back to its original size (\u03b5 = 0)<\/em>. In the graph this area is the straight one.<\/p>\n

Successively the material enters the elastoplastic zone<\/em>, exceeds the yield strength (Rp0.2<\/em>, by convention the value obtained by intersecting the graph with a straight line parallel to that of the elastic zone, displaced by 0.2% of elongation), reaches the maximum load (Rm<\/em>) and shortly after it breaks.<\/p>\n

Conventionally, we use Rm<\/em> as the breaking load, even if the breaking occurs at a lower load, this happens to steel for springs.<\/p>\n

So, to go back to our story, if the system of forces applied to the spring leads the material to exceed the value of Rm<\/em>, there is first a permanent deformation (yield<\/em>) and then the breaking.<\/p>\n

But is this what happens in reality?<\/h2>\n

The answer is no, springs usually break before reaching the load Rm of the material they are made of. Indeed, they break even when far from reaching the yield strength.<\/p>\n

We are going into the field of resistance to fatigue. To understand what are the dynamics that determine the fatigue strength of a spring and what are also the factors that influence it, it is necessary to familiarize with the following concepts to which we will dedicate the next articles:<\/p>\n

    \n
  • \u00a0\u00a0\u00a0 Differences between static<\/em> and dynamic stress<\/em><\/li>\n
  • \u00a0\u00a0\u00a0 W\u00f6hler and Goodman diagram<\/em><\/li>\n
  • \u00a0\u00a0\u00a0 Materials and their structure (surface defects<\/em>)<\/li>\n
  • \u00a0\u00a0\u00a0 Shot peening<\/em><\/li>\n
  • \u00a0\u00a0\u00a0 Usage environment (aggressive environments and corrosion)<\/li>\n
  • \u00a0\u00a0\u00a0 Interference and risk factors<\/li>\n
  • \u00a0\u00a0\u00a0 Resonance<\/em><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"

    Tecnicamente la rottura di una molla si presenta quando avviene l\u2019interruzione di continuit\u00e0 della struttura fisica del filo che compone la molla: in poche parole il filo si spezza in due o pi\u00f9 parti.<\/p>\n","protected":false},"author":5,"featured_media":14888,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[318,332],"tags":[],"class_list":["post-16347","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news-en","category-technical-articles"],"_links":{"self":[{"href":"https:\/\/mollificiovalli.it\/en\/wp-json\/wp\/v2\/posts\/16347","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mollificiovalli.it\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mollificiovalli.it\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mollificiovalli.it\/en\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/mollificiovalli.it\/en\/wp-json\/wp\/v2\/comments?post=16347"}],"version-history":[{"count":0,"href":"https:\/\/mollificiovalli.it\/en\/wp-json\/wp\/v2\/posts\/16347\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mollificiovalli.it\/en\/wp-json\/wp\/v2\/media\/14888"}],"wp:attachment":[{"href":"https:\/\/mollificiovalli.it\/en\/wp-json\/wp\/v2\/media?parent=16347"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mollificiovalli.it\/en\/wp-json\/wp\/v2\/categories?post=16347"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mollificiovalli.it\/en\/wp-json\/wp\/v2\/tags?post=16347"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}