铝合金圆筒结构淬火残余应力形成及分布规律研究

发布时间：2018-06-28 08:41

本文选题：铝合金 + 圆筒结构　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：目前深潜结构无论从结构形式还是材料均已达到技术极限,表现为无法实现深潜结构在进一步提高极限潜深的同时具备长航时、高容重比的技术指标,是制约海洋工程规模探测和深海开发的关键技术瓶颈。“内拉外压的环向残余应力”在提高极限承载能力的同时有利于拓宽容重比,协调探测深度与作业能力之间的矛盾,有望实现现有技术条件下耐压壳技术的突破。基于这一现状,本文以铝合金圆筒结构为研究对象,提出一种利用淬火处理所形成的残余应力来提高圆筒结构综合性能的方法。淬火是温度、相变、应力相互影响的复杂非线性过程,传统方法对于测量淬火残余应力的分布有一定局限和不足,也难以精确跟踪应力场演变规律。针对目前铝合金淬火模拟大多从固溶温度开始的情况,本文利用有限元分析软件ABAQUS,建立了能揭示加热过程对铝合金圆筒淬火模拟影响的有限元模型,采用有限元模拟的方法对淬火过程进行了热固耦合分析。通过模拟计算,研究了圆筒在淬火过程中温度场、应力场的分布变化规律,淬火残余应力的形成历程与机制,关键参数对淬火残余应力的影响规律,以及淬火残余应力对圆筒几何形状的影响。基于残余应力释放引起加工变形的特征,对淬火残余应力的分布特点进行了测试,并对其导致的圆筒淬火变形进行了试验验证。研究结果表明:(1)加热过程对铝合金圆筒淬火模拟的温度场及残余应力影响很小,而对变形影响较大。(2)淬火初期,圆筒外层温度急剧下降,内外温差迅速增大;随着冷却进行,圆筒降温速度明显减慢,内外温差越来越小,筒体温度逐渐接近淬火介质温度。(3)淬火初期,圆筒外层快速收缩,受到内层牵制而产生拉应力,内层受外层收缩影响而产生压应力,淬火后期应力反向变化,最终形成了内拉外压的环向残余应力。(4)圆筒的径厚比越小,材料的屈服强度越小、弹性模量越大、塑性模量越小,淬火工艺的固溶温度越大、淬火水温越小、冷却速度越大,最终形成的环向残余应力就越大,长度对淬火环向残余应力的影响非常小。(5)试验结果与模拟结果有较好的一致性,圆筒经外表面喷淋淬火可形成内拉外压的环向残余应力,同时整体呈现双头喇叭形的微量变形趋势,对圆筒结构的承载性能影响很小。
[Abstract]:At present, the deep submersible structure has reached the technical limit in terms of structure form and material, which shows that it is impossible to realize the technical index of high bulk density ratio when the deep submarine structure can further improve the limit depth and have a high bulk weight ratio at the same time. It is the key technical bottleneck that restricts the scale exploration and deep-sea exploitation of ocean engineering. The "circumferential residual stress of internal and external pressure" can increase the ultimate bearing capacity and at the same time widen the volume-weight ratio and coordinate the contradiction between the detecting depth and the working ability, which is expected to achieve the breakthrough of the pressure-resistant shell technology under the existing technical conditions. Based on this situation, this paper takes the aluminum alloy cylinder structure as the research object, and puts forward a method to improve the comprehensive properties of the cylinder structure by using the residual stress formed by quenching treatment. Quenching is a complex nonlinear process in which temperature, phase transformation and stress affect each other. The traditional method has some limitations and shortcomings in measuring the distribution of quenching residual stress, and it is difficult to track the evolution of stress field accurately. In view of the fact that the quenching simulation of aluminum alloy mostly starts from the solution temperature, a finite element model which can reveal the effect of heating process on the quenching simulation of aluminum alloy cylinder is established by using the finite element analysis software Abaqus. The finite element method is used to analyze the heat-solid coupling of quenching process. Through simulation and calculation, the distribution and variation of temperature field and stress field, the formation history and mechanism of quenching residual stress, and the influence of key parameters on quenching residual stress are studied. And the effect of quenching residual stress on the geometry of cylinder. Based on the characteristics of machining deformation caused by residual stress release, the distribution characteristics of quenching residual stress are tested, and the quenching deformation caused by quenching deformation is verified. The results show that: (1) the effect of heating process on the temperature field and residual stress of aluminum alloy cylinder quenching is very small, but it has a great effect on deformation. (2) at the beginning of quenching, the temperature of the outer layer of the cylinder decreases sharply, and the temperature difference between inside and outside increases rapidly. The cooling rate of the cylinder obviously slows down, the temperature difference between inside and outside becomes smaller and smaller, and the temperature of the cylinder gradually approaches the quenching medium temperature. (3) at the beginning of quenching, the outer layer of the cylinder shrinks rapidly, resulting in tensile stress from the inner layer. Under the influence of outer layer shrinkage, the inner layer produces compressive stress, and the stress changes in reverse direction after quenching. (4) the smaller the diameter to thickness ratio of the cylinder, the smaller the yield strength of the material, the greater the elastic modulus and the smaller the plastic modulus. The larger the solution temperature of quenching process is, the smaller the quenching water temperature is, and the larger the cooling rate is, the greater the final circumferential residual stress is, and the effect of length on the annular residual stress of quenching is very small. (5) the experimental results are in good agreement with the simulation results. The circumferential residual stress of internal tension and external pressure can be formed by spray quenching on the outer surface of the cylinder, and the micro deformation trend of double head horn shape is presented as a whole, which has little effect on the bearing capacity of the cylinder structure.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U661.4;U663.91

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