Effect of Remanent Polarization on Electro-mechanical Fields Near an Elliptic Cavity or a Crack in Piezoelectric Ceramics
Effect of Remanent Polarization on Electro-mechanical Fields Near an Elliptic Cavity or a Crack in Piezoelectric Ceramics
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DOI：
10.4028/www.scientific.net/kem.183-187.821
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发表时间：
2000-04
期刊：
影响因子：
--
通讯作者：
Guoru Fu;Wei Su
中科院分区：
文献类型：
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作者：
Guoru Fu;Wei Su
焊接结构中焊接接头的疲劳强度远低于母材。大量试验表明，疲劳裂纹一般在焊趾处萌生，因此通过对焊趾进行喷丸处理可以显著提高疲劳强度。超声冲击是改善焊趾几何形状、消除焊趾缺陷、改变焊趾区域残余应力分布，改善焊接接头疲劳性能的有效方法之一。为了评价超声冲击的效果，对Q235B钢的对接接头和十字接头在焊态和冲击状态下进行了疲劳试验。结果表明，在不同应力水平下，接头的疲劳寿命均有显著提高。喷丸接头的疲劳寿命明显长于焊态接头，而且很多情况下疲劳裂纹是从母材而不是焊趾开始的。2.喷丸对接接头的疲劳强度比焊态接头提高了57%，十字接头的疲劳强度提高了-71%。两种类型的接头的疲劳强度都不低于母材：焊接接头不再是一个关键位置。TIG修整后的接头也与喷丸接头进行了比较：在高应力范围内，TIG修整效果更好，而在低应力范围内，超声喷丸效果更好。
The fatigue strength of welded joints in welded structures is much lower than that of the base metals. Many experiments show that the fatigue crack normally initiates at the weld toe, so that the fatigue strength can be dramatically increased by peening the weld toe. Ultrasonic peening is one of the most useful methods to improve the fatigue behavior of welded joints by improving the weld toe geometry, removing weld toe defects and modifying the residual stresses distribution in this region. To evaluate the ultrasonic peening, fatigue tests were performed on butt and cruciform joints of Q235B steel both in the as-welded and peened conditions. Results show that joints showed a significant increase in fatigue life at different stress levels. The fatigue life of peened joints was significantly longer than that of the as-welded joints, and in many cases fatigue cracks initiated in the base metal instead of the weld toe.2.The increase in fatigue strength of the peened butt joints compared to the as-welded joints was 57%, and for the cruciform joints the increase was 64 - 71%. The fatigue strength of both types of joints was not lower than that of the base metal: Welded joints are no longer a critical location. TIG dressed joints were also tested for comparison with peened joints: in the high stress range TIG dressing was more effective, whereas in the lower stress range ultrasonic peening was more effective.