本文關(guān)鍵詞：多軸隨機(jī)載荷下疲勞壽命預(yù)測(cè)方法的研究　出處：《東北大學(xué)》2012年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 多軸疲勞 應(yīng)力不變量 壽命預(yù)測(cè) 譜方法 功率譜密度

【摘要】：多軸隨機(jī)載荷是工程實(shí)踐中大量遇到的實(shí)際情況,經(jīng)典的疲勞理論遠(yuǎn)遠(yuǎn)滿足不了當(dāng)代機(jī)械產(chǎn)品強(qiáng)度和壽命設(shè)計(jì)要求,因此多軸隨機(jī)載荷作用下結(jié)構(gòu)構(gòu)件的疲勞強(qiáng)度分析和壽命估算是近年來國(guó)內(nèi)外疲勞研究的主要對(duì)象。從理論上對(duì)隨機(jī)載荷下的疲勞壽命預(yù)測(cè)方法進(jìn)行全面系統(tǒng)深入地研究,將會(huì)有效地提高疲勞壽命預(yù)測(cè)精度,保證機(jī)械設(shè)備安全可靠地運(yùn)行,減少事故的發(fā)生。同時(shí)也可以提高產(chǎn)品的設(shè)計(jì)水平、延長(zhǎng)使用壽命,增強(qiáng)機(jī)械產(chǎn)品在市場(chǎng)的競(jìng)爭(zhēng)力,不僅具有深遠(yuǎn)的理論意義,而且也具有重大的應(yīng)用價(jià)值和經(jīng)濟(jì)效益。 本文在綜述國(guó)內(nèi)外多軸疲勞研究發(fā)展概況的基礎(chǔ)上,根據(jù)目前已有的多軸疲勞理論研究成果,采用時(shí)域與頻域相結(jié)合的方法,對(duì)隨機(jī)載荷下多軸疲勞壽命預(yù)測(cè)方法進(jìn)行深入研究。 首先,建立根據(jù)載荷幅值的方差所確定的參考坐標(biāo)系,將偏量空間中的載荷路徑沿參考坐標(biāo)系各軸投影,原載荷等效成為多段單軸載荷歷程,依據(jù)向量范數(shù)的概念,定義和求解剪應(yīng)力的等效幅值。由于疲勞損傷與載荷幅值的方差密切相關(guān),所以通過這種方法求得的剪應(yīng)力的等效幅值反映了載荷對(duì)材料損傷的影響。 其次,考慮平均應(yīng)力的影響,計(jì)算等效的單軸載荷歷程造成的疲勞損傷。這個(gè)過程需要對(duì)兩段載荷時(shí)間歷程進(jìn)行同步計(jì)數(shù),基于此,給出了多軸隨機(jī)載荷的壓縮方法與多軸循環(huán)計(jì)數(shù)方法。本方法不但能夠有效地簡(jiǎn)化隨機(jī)載荷歷史,而且還能實(shí)現(xiàn)載荷取舍的同步性,使同時(shí)對(duì)兩段載荷進(jìn)行循環(huán)計(jì)數(shù)成為可能。 再次,利用修正S-N曲線方法,建立了時(shí)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(yàn)數(shù)據(jù)進(jìn)行驗(yàn)證,預(yù)測(cè)結(jié)果與試驗(yàn)結(jié)果的誤差較小,并偏于安全。 最后,在時(shí)域多軸疲勞壽命估算模型的基礎(chǔ)上,結(jié)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(yīng)力過程。經(jīng)過引用文獻(xiàn)中的試驗(yàn)數(shù)據(jù)進(jìn)行驗(yàn)證,預(yù)測(cè)結(jié)果均在2個(gè)因子范圍內(nèi),預(yù)測(cè)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(xué)位授予單位】：東北大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2012
【分類號(hào)】：TH114

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