本文關鍵詞：多軸隨機載荷下疲勞壽命預測方法的研究　出處：《東北大學》2012年碩士論文　論文類型：學位論文

  更多相關文章： 多軸疲勞 應力不變量 壽命預測 譜方法 功率譜密度

【摘要】：多軸隨機載荷是工程實踐中大量遇到的實際情況,經典的疲勞理論遠遠滿足不了當代機械產品強度和壽命設計要求,因此多軸隨機載荷作用下結構構件的疲勞強度分析和壽命估算是近年來國內外疲勞研究的主要對象。從理論上對隨機載荷下的疲勞壽命預測方法進行全面系統(tǒng)深入地研究,將會有效地提高疲勞壽命預測精度,保證機械設備安全可靠地運行,減少事故的發(fā)生。同時也可以提高產品的設計水平、延長使用壽命,增強機械產品在市場的競爭力,不僅具有深遠的理論意義,而且也具有重大的應用價值和經濟效益。 本文在綜述國內外多軸疲勞研究發(fā)展概況的基礎上,根據目前已有的多軸疲勞理論研究成果,采用時域與頻域相結合的方法,對隨機載荷下多軸疲勞壽命預測方法進行深入研究。 首先,建立根據載荷幅值的方差所確定的參考坐標系,將偏量空間中的載荷路徑沿參考坐標系各軸投影,原載荷等效成為多段單軸載荷歷程,依據向量范數(shù)的概念,定義和求解剪應力的等效幅值。由于疲勞損傷與載荷幅值的方差密切相關,所以通過這種方法求得的剪應力的等效幅值反映了載荷對材料損傷的影響。 其次,考慮平均應力的影響,計算等效的單軸載荷歷程造成的疲勞損傷。這個過程需要對兩段載荷時間歷程進行同步計數(shù),基于此,給出了多軸隨機載荷的壓縮方法與多軸循環(huán)計數(shù)方法。本方法不但能夠有效地簡化隨機載荷歷史,而且還能實現(xiàn)載荷取舍的同步性,使同時對兩段載荷進行循環(huán)計數(shù)成為可能。 再次,利用修正S-N曲線方法,建立了時域多軸疲勞壽命估算模型。該模型也適用于單軸、多軸比例、非比例,多軸變幅等加載情況。通過引用三種材料的試驗數(shù)據進行驗證,預測結果與試驗結果的誤差較小,并偏于安全。 最后,在時域多軸疲勞壽命估算模型的基礎上,結合頻域疲勞的研究方法,建立了頻域多軸疲勞壽命估算模型。該模型也適用于單軸、多軸平穩(wěn)高斯應力過程。經過引用文獻中的試驗數(shù)據進行驗證,預測結果均在2個因子范圍內,預測能力較好。
[Abstract]:Multi-axis random load is a large number of practical situations encountered in engineering practice. The classical fatigue theory can not meet the requirements of strength and life design of modern mechanical products. Therefore, fatigue strength analysis and life estimation of structural members under multiaxial random loads are the main objects of fatigue research at home and abroad in recent years. Ground study. It will effectively improve the prediction accuracy of fatigue life, ensure the safe and reliable operation of mechanical equipment, reduce the occurrence of accidents, improve the design level of products, and prolong the service life. Enhancing the competitiveness of mechanical products in the market not only has profound theoretical significance, but also has great application value and economic benefit. On the basis of summarizing the development of multiaxial fatigue research at home and abroad, this paper adopts the method of combining time domain and frequency domain according to the existing research results of multiaxial fatigue theory. The prediction method of multiaxial fatigue life under random load is studied. Firstly, the reference coordinate system is established according to the variance of the load amplitude. The load path in the offset space is projected along each axis of the reference coordinate system, and the original load is equivalent to the multi-section uniaxial load history. According to the concept of vector norm, the equivalent amplitude of shear stress is defined and solved. The fatigue damage is closely related to the variance of load amplitude. So the equivalent amplitude of shear stress obtained by this method reflects the effect of load on material damage. Secondly, considering the effect of average stress, the fatigue damage caused by the equivalent uniaxial load history is calculated. The compression method and the multiaxial cyclic counting method of multiaxial random loads are presented. This method not only simplifies the history of random loads effectively, but also realizes the synchronicity of load selection and selection. It is possible to carry out cyclic counting of two loads at the same time. Thirdly, using the modified S-N curve method, a time-domain multiaxial fatigue life estimation model is established, which is also applicable to uniaxial, multi-axial proportional and non-proportional. By using the test data of three kinds of materials for verification, the error between the prediction results and the test results is small, and it is more safe. Finally, based on the time-domain multiaxial fatigue life estimation model and the frequency-domain fatigue research method, a frequency-domain multiaxial fatigue life estimation model is established, which is also suitable for uniaxial fatigue. The multiaxial stationary Gao Si stress process is verified by citing the experimental data in the literature. The predicted results are within the range of two factors and the prediction ability is good.
【學位授予單位】：東北大學
【學位級別】：碩士
【學位授予年份】：2012
【分類號】：TH114

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本文編號：1362475