基于紅外熱成像法5A06鋁合金疲勞行為各向異性研究
發(fā)布時(shí)間：2018-07-16 12:08
【摘要】：鋁合金由于其自身的優(yōu)點(diǎn)在車輛、化工、機(jī)械工程等眾多領(lǐng)域具有廣泛的應(yīng)用，這些領(lǐng)域的結(jié)構(gòu)往往承受疲勞載荷作用，其在應(yīng)用過程中不可避免地存在疲勞問題，由于傳統(tǒng)試驗(yàn)方法存在耗時(shí)長(zhǎng)等缺點(diǎn)，紅外熱像法以其實(shí)時(shí)、快速、非接觸、無(wú)損等一系列的優(yōu)勢(shì)，被應(yīng)用到材料的疲勞研究中；此外金屬材料在不同方向力學(xué)性能所表現(xiàn)出來(lái)的各向異性會(huì)限制其應(yīng)用，性能相對(duì)較差的加工成型方向往往作為工程設(shè)計(jì)的依據(jù)。因此基于紅外熱成像法研究5A06鋁合金高周疲勞性能的各向異性具有重要的現(xiàn)實(shí)意義。 本文采用紅外成像儀記錄了平行軋制方向和垂直軋制方向的5A06鋁合金在室溫下拉伸和高周疲勞斷裂過程及疲勞裂紋擴(kuò)展過程中的溫度演化，研究了5A06鋁合金的疲勞性能及產(chǎn)熱機(jī)制；對(duì)比分析兩個(gè)方向的拉伸和疲勞斷裂過程中的溫度場(chǎng)信息，并用紅外熱像法對(duì)兩個(gè)方向的疲勞強(qiáng)度進(jìn)行預(yù)測(cè)，與傳統(tǒng)的疲勞試驗(yàn)方法所得的結(jié)果進(jìn)行對(duì)比；采用電子背散射衍射(EBSD)的方法測(cè)量5A06鋁合金母材的織構(gòu)，研究其對(duì)平行軋制方向和垂直軋制方向5A06鋁合金疲勞性能及疲勞裂紋擴(kuò)展性能各向異性的影響。 結(jié)果表明：5A06鋁合金平行軋向和垂直軋向表現(xiàn)出明顯的塑性各向異性。傳統(tǒng)試驗(yàn)方法測(cè)得的平行軋向和垂直軋向5A06鋁合金的疲勞強(qiáng)度分別為113MPa和61MPa。采用紅外熱像法測(cè)得的平行軋向和垂直軋向的5A06鋁合金的疲勞強(qiáng)度分別為114.6MPa和64MPa，與傳統(tǒng)試驗(yàn)方法的相對(duì)誤差分別為1.4%和4.9%。紅外熱像法對(duì)于疲勞強(qiáng)度的預(yù)測(cè)與傳統(tǒng)試驗(yàn)方法測(cè)得的疲勞強(qiáng)度具有很好的一致性。 5A06鋁合金施加高于疲勞強(qiáng)度的載荷時(shí)，平行軋向和垂直軋向具有相同的溫度演化趨勢(shì)，即試件表面的溫度變化均分為四階段：初始溫升階段，溫度緩慢下降階段，溫度快速升高階段，溫度最終下降階段。在拉伸試驗(yàn)和同應(yīng)力下的疲勞測(cè)試過程中，垂直軋向的斷裂溫升值要高于平行軋向。由此發(fā)現(xiàn)，垂直軋向的試件斷裂時(shí)，其釋放的能量更多。同時(shí)，，也可以發(fā)現(xiàn)，在相同的應(yīng)力下，平行軋向的疲勞壽命明顯高于垂直軋向的疲勞壽命，這是由于平行軋向試件的阻止疲勞裂紋萌生的能力更強(qiáng)。 對(duì)平行軋向和垂直軋向的標(biāo)準(zhǔn)拉伸緊湊(CT)試件施加相同的載荷時(shí)，裂紋沿平行軋制方向的擴(kuò)展速率明顯大于垂直軋制方向的速率。疲勞裂紋擴(kuò)展過程中，采用紅外熱像儀觀察平行軋向和垂直軋向CT試件表面的溫度演化，發(fā)現(xiàn)鋁合金在疲勞裂紋擴(kuò)展過程中分為三個(gè)階段：初始的緩慢溫升階段、試件斷裂時(shí)的急劇溫升階段和試件斷裂后的自然降溫階段。在相同應(yīng)力下，垂直軋向的試件斷裂溫升值要高于平行軋向。 采用電子背散射衍射(EBSD)方法，得到沿軋制方向和垂直軋制方向的極圖與反極圖，平行和垂直軋向取向密度最高值分別達(dá)到7.79和8.14。說明5A06鋁合金母材晶粒中存在擇優(yōu)取向，即有強(qiáng)織構(gòu)存在。垂直軋向的取向極密度值較大，表明垂直軋向的晶粒更容易轉(zhuǎn)動(dòng)，其塑性變形能力相對(duì)于平行軋向更強(qiáng)。強(qiáng)度和塑性有相反的對(duì)應(yīng)關(guān)系，這與之前做的拉伸和疲勞試驗(yàn)結(jié)果具有很好的一致性。 施密特(Schmid)因子的峰值指數(shù)和平均值指數(shù)，平行軋制方向均低于垂直軋制方向，即垂直軋向的塑性性能要要優(yōu)于平行軋向，相應(yīng)的力學(xué)性能，平行軋制方向要優(yōu)于垂直軋制方向，這與拉伸試驗(yàn)結(jié)果與疲勞試驗(yàn)結(jié)果具有很好的一致性。
[Abstract]:Because of its own advantages, aluminum alloys are widely used in many fields, such as vehicle, chemical engineering, mechanical engineering and so on. The structure of these fields is often subjected to fatigue load, and the fatigue problem inevitably exists in the application process. Because of the disadvantages of the traditional test method, the infrared thermal image method is in fact, fast and non contact. A series of advantages, such as lossless and so on, are applied to the fatigue study of materials. In addition, the anisotropy of the mechanical properties of metal materials in different directions will limit its application. The processing direction of relatively poor performance is often used as the basis for engineering design. Therefore, the high cycle fatigue of 5A06 aluminum alloy is studied based on the infrared thermal imaging method. The anisotropy of energy has important practical significance.
In this paper, the temperature evolution of 5A06 aluminum alloy in parallel rolling direction and vertical rolling direction at room temperature and high cycle fatigue fracture and fatigue crack propagation are recorded by infrared imager. The fatigue property and heat production mechanism of 5A06 aluminum alloy are studied, and the tensile and fatigue fracture processes of the two directions are compared and analyzed. The fatigue strength of two directions was predicted by infrared thermal image method and compared with the results obtained from the traditional fatigue test method. The texture of 5A06 aluminum alloy was measured by electronic backscatter diffraction (EBSD), and the fatigue properties and fatigue properties of 5A06 aluminum alloy in parallel rolling and vertical rolling were studied. The effect of anisotropy on crack propagation properties of fatigue.
The results show that the parallel rolling and vertical rolling of 5A06 aluminum alloy show obvious plastic anisotropy. The fatigue strength of the parallel rolling and vertical rolling 5A06 aluminum alloy measured by the traditional test method is 113MPa and 61MPa., respectively, and the fatigue strength of the parallel rolled and vertical rolled 5A06 aluminum alloy measured by the infrared thermal image method is 114., respectively. 6MPa and 64MPa, the relative error of the traditional test method is 1.4% and the 4.9%. infrared thermal image method is in good agreement with the fatigue strength predicted by the traditional test method.
When the load of 5A06 aluminum alloy is higher than the fatigue strength, the parallel rolling and vertical rolling have the same temperature evolution trend. That is, the temperature change on the surface of the specimen is divided into four stages: the initial temperature rise stage, the slow decline stage of the temperature, the stage of rapid temperature rise, the final stage of temperature decline. During the test, the fracture temperature of vertical rolling is higher than that of parallel rolling. It is found that when the vertical rolling specimen is broken, it releases more energy. At the same time, it can be found that the fatigue life of parallel rolling is obviously higher than that of the vertical rolling fatigue life under the same stress, which is due to the prevention of fatigue crack in the parallel rolled specimen. The ability to grow is stronger.
When the same load is applied to the standard tensile compact (CT) specimen with parallel rolling and vertical rolling, the propagation rate of crack along the parallel rolling direction is obviously greater than that in the vertical rolling direction. In the process of fatigue crack propagation, the temperature evolution of the surface of parallel rolling and vertical rolling to the surface of CT is observed by infrared thermograph, and the aluminum alloy is found in the process of fatigue crack propagation. The fatigue crack propagation process is divided into three stages: the initial slow temperature rise stage, the rapid temperature rise stage of the specimen fracture and the natural cooling stage after the specimen fracture. Under the same stress, the fracture temperature appreciation of the vertical rolled specimen is higher than that of the parallel rolling.
The electron back scattering diffraction (EBSD) method is used to get the polar and reverse pole maps along the direction of rolling and vertical rolling. The highest orientation density of the parallel and vertical rolling direction is 7.79 and 8.14., respectively, indicating that the preferred orientation exists in the grain of 5A06 aluminum alloy, that is, the strong texture exists. The rolled grain is easier to rotate, and its plastic deformation ability is stronger than that of parallel rolling. There is a opposite relationship between the strength and the plasticity, which is in good agreement with the previous tensile and fatigue test results.
The peak index and average value index of Schmidt (Schmid) factor are lower in parallel rolling direction than in vertical rolling direction. That is, the plastic properties of vertical rolling are better than parallel rolling, and the corresponding mechanical properties are better than the vertical rolling direction. This is in good agreement with the results of tensile test and fatigue test.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG146.21
[Abstract]:Because of its own advantages, aluminum alloys are widely used in many fields, such as vehicle, chemical engineering, mechanical engineering and so on. The structure of these fields is often subjected to fatigue load, and the fatigue problem inevitably exists in the application process. Because of the disadvantages of the traditional test method, the infrared thermal image method is in fact, fast and non contact. A series of advantages, such as lossless and so on, are applied to the fatigue study of materials. In addition, the anisotropy of the mechanical properties of metal materials in different directions will limit its application. The processing direction of relatively poor performance is often used as the basis for engineering design. Therefore, the high cycle fatigue of 5A06 aluminum alloy is studied based on the infrared thermal imaging method. The anisotropy of energy has important practical significance.
In this paper, the temperature evolution of 5A06 aluminum alloy in parallel rolling direction and vertical rolling direction at room temperature and high cycle fatigue fracture and fatigue crack propagation are recorded by infrared imager. The fatigue property and heat production mechanism of 5A06 aluminum alloy are studied, and the tensile and fatigue fracture processes of the two directions are compared and analyzed. The fatigue strength of two directions was predicted by infrared thermal image method and compared with the results obtained from the traditional fatigue test method. The texture of 5A06 aluminum alloy was measured by electronic backscatter diffraction (EBSD), and the fatigue properties and fatigue properties of 5A06 aluminum alloy in parallel rolling and vertical rolling were studied. The effect of anisotropy on crack propagation properties of fatigue.
The results show that the parallel rolling and vertical rolling of 5A06 aluminum alloy show obvious plastic anisotropy. The fatigue strength of the parallel rolling and vertical rolling 5A06 aluminum alloy measured by the traditional test method is 113MPa and 61MPa., respectively, and the fatigue strength of the parallel rolled and vertical rolled 5A06 aluminum alloy measured by the infrared thermal image method is 114., respectively. 6MPa and 64MPa, the relative error of the traditional test method is 1.4% and the 4.9%. infrared thermal image method is in good agreement with the fatigue strength predicted by the traditional test method.
When the load of 5A06 aluminum alloy is higher than the fatigue strength, the parallel rolling and vertical rolling have the same temperature evolution trend. That is, the temperature change on the surface of the specimen is divided into four stages: the initial temperature rise stage, the slow decline stage of the temperature, the stage of rapid temperature rise, the final stage of temperature decline. During the test, the fracture temperature of vertical rolling is higher than that of parallel rolling. It is found that when the vertical rolling specimen is broken, it releases more energy. At the same time, it can be found that the fatigue life of parallel rolling is obviously higher than that of the vertical rolling fatigue life under the same stress, which is due to the prevention of fatigue crack in the parallel rolled specimen. The ability to grow is stronger.
When the same load is applied to the standard tensile compact (CT) specimen with parallel rolling and vertical rolling, the propagation rate of crack along the parallel rolling direction is obviously greater than that in the vertical rolling direction. In the process of fatigue crack propagation, the temperature evolution of the surface of parallel rolling and vertical rolling to the surface of CT is observed by infrared thermograph, and the aluminum alloy is found in the process of fatigue crack propagation. The fatigue crack propagation process is divided into three stages: the initial slow temperature rise stage, the rapid temperature rise stage of the specimen fracture and the natural cooling stage after the specimen fracture. Under the same stress, the fracture temperature appreciation of the vertical rolled specimen is higher than that of the parallel rolling.
The electron back scattering diffraction (EBSD) method is used to get the polar and reverse pole maps along the direction of rolling and vertical rolling. The highest orientation density of the parallel and vertical rolling direction is 7.79 and 8.14., respectively, indicating that the preferred orientation exists in the grain of 5A06 aluminum alloy, that is, the strong texture exists. The rolled grain is easier to rotate, and its plastic deformation ability is stronger than that of parallel rolling. There is a opposite relationship between the strength and the plasticity, which is in good agreement with the previous tensile and fatigue test results.
The peak index and average value index of Schmidt (Schmid) factor are lower in parallel rolling direction than in vertical rolling direction. That is, the plastic properties of vertical rolling are better than parallel rolling, and the corresponding mechanical properties are better than the vertical rolling direction. This is in good agreement with the results of tensile test and fatigue test.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG146.21
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