發(fā)布時間：2018-06-24 22:18

  本文選題：彎曲 + 扭轉(zhuǎn)��； 參考：《吉林大學》2016年碩士論文

【摘要】：傳統(tǒng)的材料力學性能測試方法往往對被測材料樣品施加拉伸、彎曲或扭轉(zhuǎn)等單一載荷作用,結(jié)合檢測手段測量這類單一載荷作用下材料的基本力學參數(shù)與力學行為。隨著科技的進步,為保證材料服役過程中的可靠性、耐久性、學術(shù)界和工程界對材料性能測試要求不斷提高,傳統(tǒng)單一載荷的測試方法已不能滿足需求。同時,在測試過程中,研究人員希望通過掃描電子顯微鏡、金相顯微鏡、X射線衍射儀等材料性能表征手段動態(tài)監(jiān)測載荷作用下材料的力學行為和微觀組織結(jié)構(gòu)演化情況,即原位(In situ)測試。為此,開展復雜載荷條件下材料微觀力學性能原位測試技術(shù)的研究,顯得尤為重要且迫切。面向上述需求,本文以扭轉(zhuǎn)預載荷下原位三點彎曲測試裝置的設計分析與試驗研究作為選題開展研究。論文在對材料力學性能測試相關(guān)領域現(xiàn)狀進行綜述分析的基礎上,設計提出了能夠施加扭轉(zhuǎn)預載荷的原位三點彎曲測試裝置,再對被測試件施加扭轉(zhuǎn)預載荷的基礎上,通過大減速比減速機構(gòu)實現(xiàn)準靜態(tài)的彎曲加載。論文采用ABAQUS軟件對彎曲加載裝置的關(guān)鍵機構(gòu)與整機進行了靜力學分析和模態(tài)分析,仿真分析結(jié)果顯示所設計的裝置在剛度與強度方面基本滿足要求。針對研制的測試裝置,論文分別對彎曲力傳感器、扭轉(zhuǎn)力傳感器進行了標定試驗,通過激光位移傳感器標定了電機編碼器的輸出精度。在此基礎上,論文分別對裝置結(jié)構(gòu)機架柔度以及底座偏轉(zhuǎn)角度誤差進行了理論計算與仿真分析。通過對黃銅、7075鋁合金的重復性試驗驗證了彎曲測試裝置的穩(wěn)定性,通過誤差修正與產(chǎn)業(yè)化試驗機結(jié)果對比驗證了裝置的精確性。通過有限元仿真分析,研究了扭轉(zhuǎn)預載荷對材料彎曲力學響應的影響。針對6061鋁合金和45鋼樣品材料分別開展了扭轉(zhuǎn)彈性階段與扭轉(zhuǎn)塑性階段等預載荷條件下的彎曲性能測試分析。從彎曲彈性階段、彎曲強化階段以及被測試樣回彈能力三個方面進行研究。驗證了扭轉(zhuǎn)預載荷的增大會增強材料樣品的抗彎強度與回彈性能。針對脆性鑄鐵材料,論文不僅開展了扭轉(zhuǎn)預載荷的彎曲力學響應的研究,同時分析了鑄鐵斷口的宏觀失效形式。證明了彎曲載荷斷裂角度會隨預扭轉(zhuǎn)載荷的增大向軸線偏移。利用CCD顯微鏡對Q235材料的金相組織變化,分析扭彎復合應力對材料微觀組織失效機理,揭示了預扭轉(zhuǎn)載荷作用下材料樣品的金相組織變形更早進入微觀失效形式。
[Abstract]:The traditional testing methods of mechanical properties of materials often apply single load such as tensile bending or torsion to the samples under such a single load. The basic mechanical parameters and mechanical behaviors of the materials under this kind of single load are measured by means of testing. With the development of science and technology, in order to ensure the reliability and durability of the material in service, the academic and engineering circles have been increasing the requirements of material performance testing, the traditional method of single load testing can not meet the demand. At the same time, during the testing process, the researchers hope to dynamically monitor the mechanical behavior and microstructure evolution of the materials under loading by means of scanning electron microscope, metallographic microscope and X-ray diffractometer. In situ test. Therefore, it is very important and urgent to study the in-situ testing technology of material micromechanical properties under complex loading conditions. In order to meet the above requirements, the design, analysis and experimental study of the in-situ three-point bending test device under torsional preload are studied in this paper. On the basis of summarizing and analyzing the current situation in the field of material mechanical performance testing, this paper designs a three-point bending in-situ testing device which can apply torsional preload, and then applies torsional preload to the tested part. The quasi-static bending loading is realized by the deceleration mechanism of large deceleration ratio. The static analysis and modal analysis of the key mechanism and the whole machine of the bending loading device are carried out by Abaqus software. The simulation results show that the designed device basically meets the requirements in terms of stiffness and strength. In this paper, the bending force sensor and the torsional force sensor are calibrated, and the output precision of the motor encoder is calibrated by the laser displacement sensor. On this basis, the flexibility of the frame and the deflection angle error of the base are calculated and simulated respectively. The stability of the bending test device was verified by the repeatability test on the brass alloy 7075 aluminum alloy. The accuracy of the device was verified by comparing the error correction with the results of the industrial testing machine. The effect of torsional preload on bending mechanical response of materials was studied by finite element simulation. The bending properties of 6061 aluminum alloy and 45 steel samples were tested and analyzed under preloading conditions such as torsional elastic stage and torsional plastic stage respectively. In this paper, the springback ability of tested samples is studied from three aspects: bending elastic stage, bending strengthening stage and springback ability of tested samples. It is verified that the increase of torsional preload will enhance the flexural strength and springback of the material. For brittle cast iron, not only the bending mechanical response of torsional preload is studied, but also the macroscopic failure mode of cast iron fracture is analyzed. It is proved that the fracture angle of bending load deviates to the axis with the increase of pretorsion load. The microstructure of Q235 material was changed by CCD microscope, and the failure mechanism of torsional and flexural composite stress on microstructure of Q235 material was analyzed. It was revealed that the deformation of metallographic microstructure of the material under pretorsion load entered the microfailure mode earlier.
【學位授予單位】：吉林大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TH87

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本文編號：2063212