{"id":21250,"date":"2022-07-23T16:07:37","date_gmt":"2022-07-23T08:07:37","guid":{"rendered":"https:\/\/www.meetyoucarbide.com\/?p=21250"},"modified":"2022-07-27T11:24:16","modified_gmt":"2022-07-27T03:24:16","slug":"august-wohlers-experiment-statics-showing-you-how-the-4-elements-impact-on-fatigue-crack","status":"publish","type":"post","link":"https:\/\/www.meetyoucarbide.com\/zh\/%e5%85%ab%e6%9c%88-wohlers-experiment-statics-showing-you-how-the-4-elements-impact-on-fatigue-crack\/","title":{"rendered":"August W\u00f6hler \u7684\u5b9e\u9a8c\u9759\u529b\u5b66\u5411\u60a8\u5c55\u793a 4 \u79cd\u5143\u7d20\u5982\u4f55\u5f71\u54cd\u75b2\u52b3\u88c2\u7eb9"},"content":{"rendered":"
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Fatigue cracks are generally the result of periodic plastic deformation in local areas. Fatigue is defined as “failure under repeated load or other types of load conditions, and this load level is not sufficient to cause failure when applied only once.” This plastic deformation occurs not because of the theoretical stress on the ideal component, but because the component surface can not be actually detected.<\/a><\/a><\/a><\/a><\/a><\/a><\/p>\n\n\n\n

August W\u00f6hler \u662f\u75b2\u52b3\u7814\u7a76\u7684\u5148\u9a71\uff0c\u4ed6\u63d0\u51fa\u4e86\u4e00\u79cd\u7ecf\u9a8c\u65b9\u6cd5\u3002 1852 \u5e74\u81f3 1870 \u5e74\u95f4\uff0c\u6c83\u52d2\u7814\u7a76\u4e86\u94c1\u8def\u8f66\u8f74\u7684\u6e10\u8fdb\u5f0f\u6545\u969c\u3002\u4ed6\u5efa\u9020\u4e86\u56fe 1 \u6240\u793a\u7684\u8bd5\u9a8c\u53f0\u3002\u8be5\u8bd5\u9a8c\u53f0\u4f7f\u4e24\u4e2a\u94c1\u8def\u8f66\u8f74\u80fd\u591f\u540c\u65f6\u65cb\u8f6c\u548c\u5f2f\u66f2\u3002 W\u00f6hler \u7ed8\u5236\u4e86\u6807\u79f0\u5e94\u529b\u4e0e\u5bfc\u81f4\u5931\u6548\u7684\u5faa\u73af\u6b21\u6570\u4e4b\u95f4\u7684\u5173\u7cfb\uff0c\u8fd9\u5c31\u662f\u540e\u6765\u7684 SN \u56fe\u3002\u6bcf\u6761\u66f2\u7ebf\u4ecd\u79f0\u4e3a aw\u00f6hler \u7ebf\u3002 Sn \u6cd5\u4ecd\u7136\u662f\u5f53\u4eca\u4f7f\u7528\u6700\u5e7f\u6cdb\u7684\u65b9\u6cd5\u3002\u8be5\u66f2\u7ebf\u7684\u4e00\u4e2a\u5178\u578b\u4f8b\u5b50\u5982\u56fe 1 \u6240\u793a\u3002<\/p>\n\n\n\n

<\/a><\/p>\n\n\n\n

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\u56fe1 W\u00f6hler\u7684\u65cb\u8f6c\u5f2f\u66f2\u75b2\u52b3\u8bd5\u9a8c<\/figcaption><\/figure>\n\n\n\n

<\/a><\/p>\n\n\n\n

Several effects can be observed through the w \u00f6 hler line. First, we note that the SN curve below the transition point (about 1000 cycles) is invalid because the nominal stress here is elastoplastic. We will show later that fatigue is caused by the release of plastic shear strain energy. Therefore, there is no linear relationship between stress and strain before fracture, and it cannot be used. Between the transition point and the fatigue limit (about 107 cycles), the Sn based analysis is valid. Above the fatigue limit, the slope of the curve decreases sharply, so this region is often referred to as the “infinite life” region. But this is not the case. For example, aluminum alloy will not have infinite life, and even steel will not have infinite life under variable amplitude load.<\/a><\/p>\n\n\n\n

\u968f\u7740\u73b0\u4ee3\u653e\u5927\u6280\u672f\u7684\u51fa\u73b0\uff0c\u4eba\u4eec\u53ef\u4ee5\u66f4\u8be6\u7ec6\u5730\u7814\u7a76\u75b2\u52b3\u88c2\u7eb9\u3002\u6211\u4eec\u73b0\u5728\u77e5\u9053\uff0c\u75b2\u52b3\u88c2\u7eb9\u7684\u4ea7\u751f\u548c\u6269\u5c55\u53ef\u4ee5\u5206\u4e3a\u4e24\u4e2a\u9636\u6bb5\u3002\u5728\u521d\u59cb\u9636\u6bb5\uff0c\u88c2\u7eb9\u4ee5\u4e0e\u65bd\u52a0\u8f7d\u8377\u6210\u7ea6 45 \u5ea6\u7684\u89d2\u5ea6\uff08\u6cbf\u6700\u5927\u526a\u5e94\u529b\u7ebf\uff09\u6269\u5c55\u3002\u5728\u7a7f\u8fc7\u4e24\u4e2a\u6216\u4e09\u4e2a\u6676\u754c\u540e\uff0c\u5176\u65b9\u5411\u53d1\u751f\u53d8\u5316\uff0c\u5e76\u6cbf\u76f8\u5bf9\u4e8e\u65bd\u52a0\u8f7d\u8377\u6210\u7ea6 90 \u5ea6\u7684\u65b9\u5411\u5ef6\u4f38\u3002\u8fd9\u4e24\u4e2a\u9636\u6bb5\u79f0\u4e3a\u2160\u671f\u88c2\u7eb9\u548c\u2161\u671f\u88c2\u7eb9\uff0c\u5982\u56fe2\u6240\u793a\u3002<\/a><\/a><\/a><\/a><\/p>\n\n\n\n

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\u56fe2 I\u9636\u6bb5\u548cII\u9636\u6bb5\u88c2\u7eb9\u6269\u5c55\u793a\u610f\u56fe<\/figcaption><\/figure>\n\n\n\n

If we observe a stage I crack at high magnification, we can see that the alternating stress will lead to the formation of a continuous slip band along the maximum shear plane. These slip bands slide back and forth, much like a deck of cards, resulting in uneven surfaces. The concave surface finally forms a “budding” crack, as shown in Figure 3. In phase I, the crack will expand in this mode until it meets the grain boundary and will stop temporarily. When enough energy is applied to the adjacent crystals, then the process will continue.<\/p>\n\n\n\n

<\/a><\/p>\n\n\n\n

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\u56fe3 \u8fde\u7eed\u6ed1\u5e26\u793a\u610f\u56fe<\/figcaption><\/figure>\n\n\n\n

<\/a><\/a><\/a><\/a><\/a><\/a><\/p>\n\n\n\n

\u7a7f\u8fc7\u4e24\u4e2a\u6216\u4e09\u4e2a\u6676\u754c\u540e\uff0c\u88c2\u7eb9\u6269\u5c55\u65b9\u5411\u73b0\u5728\u8fdb\u5165\u7b2c\u4e8c\u9636\u6bb5\u6a21\u5f0f\u3002\u5728\u8fd9\u4e2a\u9636\u6bb5\uff0c\u88c2\u7eb9\u6269\u5c55\u7684\u7269\u7406\u6027\u8d28\u53d1\u751f\u4e86\u53d8\u5316\u3002\u88c2\u7eb9\u672c\u8eab\u6784\u6210\u4e86\u5e94\u529b\u6d41\u52a8\u7684\u5b8f\u89c2\u969c\u788d\uff0c\u5bfc\u81f4\u88c2\u7eb9\u5c16\u7aef\u7684\u9ad8\u5851\u6027\u5e94\u529b\u96c6\u4e2d\u3002\u5982\u56fe 4 \u6240\u793a\u3002\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u5e76\u4e0d\u662f\u6240\u6709\u7684 I \u671f\u88c2\u7f1d\u90fd\u4f1a\u53d1\u5c55\u5230 II \u671f\u3002<\/a><\/p>\n\n\n\n

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\u56fe4<\/figcaption><\/figure>\n\n\n\n

In order to understand the propagation mechanism of stage II, we need to consider the situation of crack tip cross-section during the stress cycle. As shown in Figure 5. The fatigue cycle begins when the nominal stress is at point “a”. As the stress intensity increases and passes through point “B”, we notice that the crack tip opens, resulting in local plastic shear deformation, and the crack extends to point “C” in the original metal. When the tensile stress decreases through the “d” point, we observe that the crack tip closes, but the permanent plastic deformation leaves a unique serration, the so-called “cut line”. When the whole cycle ends at the “e” point, we observe that the crack has now increased the “Da” length and formed additional section lines. It is now understood that the range of crack growth is proportional to the range of applied elastic-plastic crack tip strain. A larger cycle range can form a larger Da.<\/a><\/p>\n\n\n\n

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\u56fe 5 \u7b2c\u4e8c\u9636\u6bb5\u88c2\u7eb9\u6269\u5c55\u793a\u610f\u56fe<\/figcaption><\/figure>\n\n\n\n

<\/p>\n\n\n\n

\u5f71\u54cd\u75b2\u52b3\u88c2\u7eb9\u6269\u5c55\u901f\u7387\u7684\u56e0\u7d20<\/h2>\n\n\n\n

\u5bf9\u4e0b\u5217\u53c2\u6570\u5bf9\u75b2\u52b3\u88c2\u7eb9\u6269\u5c55\u901f\u7387\u7684\u5f71\u54cd\u8fdb\u884c\u4e86\u7814\u7a76\u548c\u6982\u5ff5\u89e3\u91ca\uff1a<\/p>\n\n\n\n

1\u526a\u5e94\u529b<\/h3>\n\n\n\n

From the diagram, we can see that a certain “amount” of shear stress is released during the periodic change of the strength of the nominal stress. And the larger the range of stress changes, the greater the energy released. Through the SN curve shown in Figure 1, we can see that the fatigue life decreases exponentially with the increase of the stress cycle range.<\/a><\/p>\n\n\n\n

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\u56fe 6 \u6cbf\u6ed1\u52a8\u9762\u548c\u88c2\u7eb9\u6839\u90e8\u7684\u5f39\u5851\u6027\u5e94\u529b\u5e94\u53d8<\/figcaption><\/figure>\n\n\n\n

<\/a><\/p>\n\n\n\n

2 \u5e73\u5747\u538b\u529b<\/h3>\n\n\n\n

\u5e73\u5747\u5e94\u529b\uff08\u6b8b\u4f59\u5e94\u529b\uff09\u4e5f\u662f\u5f71\u54cd\u75b2\u52b3\u5931\u6548\u7387\u7684\u4e00\u4e2a\u56e0\u7d20\u3002\u4ece\u6982\u5ff5\u4e0a\u8bb2\uff0c\u5982\u679c\u5411 II \u76f8\u88c2\u7eb9\u65bd\u52a0\u81a8\u80c0\u5e94\u529b\uff0c\u5219\u88c2\u7eb9\u5c06\u88ab\u8feb\u5f20\u5f00\uff0c\u56e0\u6b64\u4efb\u4f55\u5e94\u529b\u5faa\u73af\u90fd\u4f1a\u4ea7\u751f\u66f4\u663e\u7740\u7684\u5f71\u54cd\u3002\u76f8\u53cd\uff0c\u5982\u679c\u65bd\u52a0\u5e73\u5747\u538b\u5e94\u529b\uff0c\u88c2\u7eb9\u5c06\u88ab\u8feb\u95ed\u5408\uff0c\u4efb\u4f55\u5e94\u529b\u5faa\u73af\u90fd\u9700\u8981\u514b\u670d\u9884\u538b\u5e94\u529b\uff0c\u88c2\u7eb9\u624d\u80fd\u7ee7\u7eed\u6269\u5c55\u3002\u7c7b\u4f3c\u7684\u6982\u5ff5\u4e5f\u9002\u7528\u4e8e\u7b2c\u4e00\u9636\u6bb5\u7684\u88c2\u7f1d\u3002<\/p>\n\n\n\n

3 \u8868\u9762\u5904\u7406<\/h3>\n\n\n\n

\u56e0\u4e3a\u75b2\u52b3\u88c2\u7eb9\u901a\u5e38\u9996\u5148\u51fa\u73b0\u5728\u6709\u7f3a\u9677\u7684\u90e8\u4ef6\u8868\u9762\uff0c\u8868\u9762\u8d28\u91cf\u4f1a\u4e25\u91cd\u5f71\u54cd\u88c2\u7eb9\u53d1\u751f\u7684\u6982\u7387\u3002\u5c3d\u7ba1\u5927\u591a\u6570\u6750\u6599\u6d4b\u8bd5\u6837\u54c1\u90fd\u5177\u6709\u955c\u9762\u5149\u6d01\u5ea6\uff0c\u56e0\u6b64\u5b83\u4eec\u4e5f\u4f1a\u8fbe\u5230\u6700\u4f73\u7684\u75b2\u52b3\u5bff\u547d\u3002\u4e8b\u5b9e\u4e0a\uff0c\u5927\u591a\u6570\u90e8\u4ef6\u65e0\u6cd5\u4e0e\u6837\u54c1\u8fdb\u884c\u6bd4\u8f83\uff0c\u56e0\u6b64\u6211\u4eec\u9700\u8981\u4fee\u6539\u75b2\u52b3\u7279\u6027\u3002\u8868\u9762\u5149\u6d01\u5ea6\u5bf9\u627f\u53d7\u4f4e\u632f\u5e45\u5e94\u529b\u5faa\u73af\u7684\u90e8\u4ef6\u7684\u75b2\u52b3\u5f71\u54cd\u66f4\u5927\u3002<\/p>\n\n\n\n

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\u56fe7 \u5faa\u73af\u987a\u5e8f\u7684\u5f71\u54cd\u793a\u610f\u56fe \u8868\u9762\u5149\u6d01\u5ea6\u7684\u5f71\u54cd\u53ef\u4ee5\u901a\u8fc7\u5efa\u6a21\u6765\u8868\u793a\uff0c\u5373\u5728\u75b2\u52b3\u6781\u9650\u5904\u5c06SN\u66f2\u7ebf\u4e58\u4ee5\u8868\u9762\u4fee\u6b63\u53c2\u6570\u3002<\/figcaption><\/figure>\n\n\n\n

4 \u8868\u9762\u5904\u7406<\/h3>\n\n\n\n

\u8868\u9762\u5904\u7406\u53ef\u7528\u4e8e\u589e\u5f3a\u90e8\u4ef6\u7684\u6297\u75b2\u52b3\u6027\u3002\u8868\u9762\u5904\u7406\u7684\u76ee\u7684\u662f\u5728\u8868\u9762\u5f62\u6210\u6b8b\u4f59\u538b\u5e94\u529b\u3002\u5728\u4f4e\u632f\u5e45\u5468\u671f\u4e0b\uff0c\u8868\u9762\u5e94\u529b\u660e\u663e\u8f83\u4f4e\uff0c\u751a\u81f3\u4fdd\u6301\u538b\u7f29\u72b6\u6001\u3002\u56e0\u6b64\uff0c\u53ef\u4ee5\u663e\u7740\u5ef6\u957f\u75b2\u52b3\u5bff\u547d\u3002\u7136\u800c\uff0c\u6b63\u5982\u6211\u4eec\u6240\u6307\u51fa\u7684\uff0c\u8fd9\u79cd\u60c5\u51b5\u4ec5\u9002\u7528\u4e8e\u53d7\u5230\u4f4e\u632f\u5e45\u5e94\u529b\u5faa\u73af\u7684\u7ec4\u4ef6\u3002\u5982\u679c\u5e94\u7528\u9ad8\u632f\u5e45\u5468\u671f\uff0c\u9884\u538b\u7f29\u5c06\u88ab\u9ad8\u632f\u5e45\u5468\u671f\u514b\u670d\uff0c\u5176\u4f18\u52bf\u5c06\u4e27\u5931\u3002\u4e0e\u8868\u9762\u8d28\u91cf\u4e00\u6837\uff0c\u8868\u9762\u5904\u7406\u7684\u5f71\u54cd\u53ef\u4ee5\u901a\u8fc7\u5efa\u6a21\u6765\u663e\u793a\u3002<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

Fatigue cracks are generally the result of periodic plastic deformation in local areas. Fatigue is defined as “failure under repeated load or other types of load conditions, and this load level is not sufficient to cause failure when applied only once.” This plastic deformation occurs not because of the theoretical stress on the ideal component, but…<\/p>","protected":false},"author":2,"featured_media":21253,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[79],"tags":[],"jetpack_featured_media_url":"https:\/\/www.meetyoucarbide.com\/wp-content\/uploads\/2022\/07\/\u56fe\u72472.png","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.meetyoucarbide.com\/zh\/wp-json\/wp\/v2\/posts\/21250"}],"collection":[{"href":"https:\/\/www.meetyoucarbide.com\/zh\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.meetyoucarbide.com\/zh\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.meetyoucarbide.com\/zh\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.meetyoucarbide.com\/zh\/wp-json\/wp\/v2\/comments?post=21250"}],"version-history":[{"count":0,"href":"https:\/\/www.meetyoucarbide.com\/zh\/wp-json\/wp\/v2\/posts\/21250\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.meetyoucarbide.com\/zh\/wp-json\/wp\/v2\/media\/21253"}],"wp:attachment":[{"href":"https:\/\/www.meetyoucarbide.com\/zh\/wp-json\/wp\/v2\/media?parent=21250"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.meetyoucarbide.com\/zh\/wp-json\/wp\/v2\/categories?post=21250"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.meetyoucarbide.com\/zh\/wp-json\/wp\/v2\/tags?post=21250"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}