熱再生瀝青混合料間接拉伸試驗離散元數(shù)值模擬研究
發(fā)布時間：2018-12-28 20:41
【摘要】：再生瀝青混合料屬于組分復雜的非連續(xù)介質(zhì)材料,其宏觀性能與細觀結(jié)構息息相關,但當前關于再生瀝青混合料細觀結(jié)構特性的研究較少。從細觀角度闡釋破損過程,剖析再生瀝青混合料損傷規(guī)律,實現(xiàn)細觀結(jié)構力學響應與宏觀表象的統(tǒng)一,不僅使得細觀力學模擬方法成為傳統(tǒng)室內(nèi)試驗的有效補充,而且還能理論指導室內(nèi)試驗方法的選擇。因此運用離散單元法構建再生瀝青混合料細觀結(jié)構模型,實現(xiàn)宏細觀相結(jié)合的方法對再生瀝青混合料的損傷規(guī)律研究具有重要的理論指導意義。論文通過采用化學染色劑預處理新集料,成型不同回收瀝青路面材料(簡稱RAP)摻配率的再生瀝青混合料馬歇爾標準試件進行室內(nèi)間接拉伸試驗,測試劈裂強度。借助數(shù)碼相機拍照獲取試件橫切面圖,應用圖像均衡、圖像銳化、邊緣檢測和圖像分割等數(shù)字圖像處理技術實現(xiàn)圖像細節(jié)凸顯和各顆粒邊緣清晰可辨等目的,并完成集料圖像粒徑分類。然后利用體視學方法完成橫切面圖像從二維實體向三維實體轉(zhuǎn)換,計算圖像顆粒的均勻性系數(shù)。最后根據(jù)上述分析結(jié)果合理確定二維離散元數(shù)字試件級配,在二維顆粒流程序基礎上進行二次開發(fā),數(shù)字重構再生瀝青混合料細觀模型,使用實際邊界信息并合理進行材料細觀參數(shù)比選,運用伺服機制控制荷載施加,實現(xiàn)間接拉伸試驗數(shù)值模擬,分析再生瀝青混合料細觀力學特性。研究結(jié)果表明:(1)0%、10%、20%和40%RAP摻配率下的劈裂強度分別為1.57MPa、1.43MPa、1.38MPa和1.33MPa,劈裂強度隨摻配率增加呈下降趨勢,對于新拌瀝青混合料劈裂強度而言,10%、20%和40%RAP摻配比例的試件強度下降率分別為8.9%、12.1%和15.3%;(2)利用體視學方法修正集料圖像級配,得到骨料修正系數(shù)=π/4,=0.86,使得集料圖像級配與設計級配基本吻合;(3)集料均勻性系數(shù)達到0.9左右,表明其橫向分布均勻,新舊料空間分布的卡方擬合趨勢圖呈直線關系,證明新舊集料空間分布達到均勻狀態(tài);(4)通過細觀參數(shù)校準后建立的再生瀝青混合料間接拉伸試驗數(shù)字試件模型的模擬結(jié)果與室內(nèi)試驗值之間雖然存在一定的誤差,但是可從細觀角度闡釋再生瀝青混合料速度矢量圖及力鏈發(fā)育規(guī)律,證明了再生瀝青混合料力學試驗虛擬化模擬室內(nèi)試驗的有效性。
[Abstract]:Recycled asphalt mixture is a kind of discontinuous material with complex components, and its macroscopic performance is closely related to its meso-structure. However, there is little research on the meso-structure characteristics of recycled asphalt mixture at present. The damage process of recycled asphalt mixture is explained from the point of view of meso, the damage law of recycled asphalt mixture is analyzed, and the unity of mechanical response and macroscopic appearance of micro structure is realized, which not only makes the meso-mechanical simulation method an effective supplement to the traditional indoor test. It can also guide the selection of indoor test methods theoretically. Therefore, using discrete element method to construct the meso structure model of recycled asphalt mixture and realizing the method of combining macro and micro view have important theoretical guiding significance for the research of damage law of recycled asphalt mixture. In this paper, through pretreatment of new aggregate with chemical dye agent and formation of recycled asphalt mixture Marshall standard specimen with different recycled asphalt pavement material (RAP) blending ratio, indirect tensile test is carried out in laboratory to test the splitting strength. With the help of digital camera, the cross-sectional images of the samples are obtained, and the digital image processing techniques such as image equalization, image sharpening, edge detection and image segmentation are applied to realize the purpose of image detail highlighting and the distinct and discernible edges of each particle. The particle size classification of aggregate image is completed. Then the horizontal section image is transformed from two dimensional solid to three dimensional entity by stereology method, and the uniformity coefficient of image particle is calculated. Finally, according to the above analysis results, the gradation of two-dimensional discrete element digital specimen is reasonably determined, and the secondary development is carried out on the basis of two-dimensional particle flow program, and the mesoscopic model of recycled asphalt mixture is reconstructed digitally. Using the actual boundary information and reasonably selecting the meso-parameters of the material, the servo mechanism is used to control the load applied to realize the numerical simulation of indirect tensile test, and the meso-mechanical properties of recycled asphalt mixture are analyzed. The results show that: (1) the splitting strength is 1.57 MPA and 1.33 MPA, respectively, and the splitting strength is 1.57 MPA and 1.33 MPA, respectively, and the splitting strength tends to decrease with the increase of the blending ratio, and the results show that: (1) the splitting strength is 1.57 MPA, 1.43 MPA and 1.33 MPA, respectively, and the splitting strength decreases with the increase of the blending ratio. For the split strength of fresh asphalt mixture, the drop rate of strength of 10% or 20% and 40%RAP ratio is 8.9% and 15.3%, respectively. (2) the aggregate image gradation is corrected by stereology method, and the aggregate correction coefficient = 蟺 / 4 / 0.86 is obtained, which makes the aggregate image gradation basically coincide with the design gradation; (3) the uniform coefficient of aggregate is about 0.9, which indicates that the horizontal distribution is uniform, and the chi-square fitting trend diagram of spatial distribution of new and old materials is linear, which proves that the spatial distribution of new and old aggregates is uniform; (4) although there is a certain error between the simulation results of the digital specimen model of indirect tensile test of recycled asphalt mixture and the indoor test value, However, the velocity vector diagram and the law of force chain development of recycled asphalt mixture can be explained from the viewpoint of meso, which proves the validity of virtualization simulation laboratory test of recycled asphalt mixture mechanical test.
【學位授予單位】：長安大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U414
本文編號：2394410
[Abstract]:Recycled asphalt mixture is a kind of discontinuous material with complex components, and its macroscopic performance is closely related to its meso-structure. However, there is little research on the meso-structure characteristics of recycled asphalt mixture at present. The damage process of recycled asphalt mixture is explained from the point of view of meso, the damage law of recycled asphalt mixture is analyzed, and the unity of mechanical response and macroscopic appearance of micro structure is realized, which not only makes the meso-mechanical simulation method an effective supplement to the traditional indoor test. It can also guide the selection of indoor test methods theoretically. Therefore, using discrete element method to construct the meso structure model of recycled asphalt mixture and realizing the method of combining macro and micro view have important theoretical guiding significance for the research of damage law of recycled asphalt mixture. In this paper, through pretreatment of new aggregate with chemical dye agent and formation of recycled asphalt mixture Marshall standard specimen with different recycled asphalt pavement material (RAP) blending ratio, indirect tensile test is carried out in laboratory to test the splitting strength. With the help of digital camera, the cross-sectional images of the samples are obtained, and the digital image processing techniques such as image equalization, image sharpening, edge detection and image segmentation are applied to realize the purpose of image detail highlighting and the distinct and discernible edges of each particle. The particle size classification of aggregate image is completed. Then the horizontal section image is transformed from two dimensional solid to three dimensional entity by stereology method, and the uniformity coefficient of image particle is calculated. Finally, according to the above analysis results, the gradation of two-dimensional discrete element digital specimen is reasonably determined, and the secondary development is carried out on the basis of two-dimensional particle flow program, and the mesoscopic model of recycled asphalt mixture is reconstructed digitally. Using the actual boundary information and reasonably selecting the meso-parameters of the material, the servo mechanism is used to control the load applied to realize the numerical simulation of indirect tensile test, and the meso-mechanical properties of recycled asphalt mixture are analyzed. The results show that: (1) the splitting strength is 1.57 MPA and 1.33 MPA, respectively, and the splitting strength is 1.57 MPA and 1.33 MPA, respectively, and the splitting strength tends to decrease with the increase of the blending ratio, and the results show that: (1) the splitting strength is 1.57 MPA, 1.43 MPA and 1.33 MPA, respectively, and the splitting strength decreases with the increase of the blending ratio. For the split strength of fresh asphalt mixture, the drop rate of strength of 10% or 20% and 40%RAP ratio is 8.9% and 15.3%, respectively. (2) the aggregate image gradation is corrected by stereology method, and the aggregate correction coefficient = 蟺 / 4 / 0.86 is obtained, which makes the aggregate image gradation basically coincide with the design gradation; (3) the uniform coefficient of aggregate is about 0.9, which indicates that the horizontal distribution is uniform, and the chi-square fitting trend diagram of spatial distribution of new and old materials is linear, which proves that the spatial distribution of new and old aggregates is uniform; (4) although there is a certain error between the simulation results of the digital specimen model of indirect tensile test of recycled asphalt mixture and the indoor test value, However, the velocity vector diagram and the law of force chain development of recycled asphalt mixture can be explained from the viewpoint of meso, which proves the validity of virtualization simulation laboratory test of recycled asphalt mixture mechanical test.
【學位授予單位】：長安大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U414
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