大直径冲击反循环钻头疲劳寿命数值模拟

发布时间：2018-08-25 08:00

【摘要】：大直径冲击反循环钻机是一种用于钻孔的大型工程机械,目前被广泛应用在大型建筑物、桥梁等工程作业过程中,但与其配套使用的钻头因为长期遭受连续的冲击载荷作用,结构件断裂、焊缝开裂等现象时有发生,导致钻头使用寿命极低,因此对钻头进行疲劳破坏研究及疲劳寿命的预测十分必要。本文主要以YCJF-25型冲击反循环钻头为研究对象,对钻头进行了模态分析,获得了钻头的前几阶振型,以及钻头的固有频率,表明钻机不会因共振而产生破坏。采用ANSYS Workbench中的显式动力学模拟了钻头在不同工况下的冲击过程,对钻头在工作过程中的受力情况进行了分析,得到了钻头冲击过程中冲击参数、地层工况及钻头偏载对钻头应力分布的影响关系。分析表明,随着冲击高度的增加,钻头冲击过程所受应力逐渐增大,随着地层的变硬,应力值同样会变大。不论何种情况,钻头内圈3及其冲击阶梯面所受应力总是最大,内圈2次之;偏载导致与地层交界处接触的钻头端面应力集中,使所受应力大于正常工作条件下钻头所受应力。对钻头冲击过程中的冲击力进行了计算,利用ANSYS nCode Design Life疲劳分析软件分别对钻头在正常工作和偏载两种状态下的疲劳寿命进行了评估,获得了钻头的疲劳寿命和疲劳破坏的危险点。正常工作条件下钻头疲劳寿命预测为8.39×105,偏载状态下钻头疲劳寿命降低到原来的七分之一。进而研究了冲击频率对钻头疲劳寿命的影响。分析表明,冲击频率增加一倍的情况下,钻头寿命降低两个数量级,大大降低了寿命,验证了钻机工作频率的合理性。根据分析结果,从材料和施加筋板布置两个方面入手,对原有钻头进行了优化分析,钻头内圈2、3材料由Q235改为Q345使钻头疲劳寿命提高到原来的1.2倍,钻头整体材料全部改为Q345后疲劳寿命提高到原来的2.1倍,施加筋板使钻头疲劳寿命提高到原来的3.3倍,为大直径冲击反循环钻头的进一步改进提供了理论依据。
[Abstract]:Large diameter impact reverse circulation drilling rig is a kind of large engineering machinery used for drilling holes. At present, it is widely used in large buildings, bridges and other engineering processes, but the bits used with it are subjected to continuous impact loads for a long time. The breakage of structural parts and the cracking of welds occur from time to time, which leads to the extremely low service life of the bit. Therefore, it is necessary to study the fatigue failure and predict the fatigue life of the bit. This paper mainly takes YCJF-25 type impact reverse circulation bit as the research object, carries on the modal analysis to the bit, obtains the bit first several vibration modes, as well as the bit natural frequency, indicates that the drill rig will not be damaged by resonance. The explicit dynamics in ANSYS Workbench is used to simulate the impact process of bit under different working conditions. The stress of bit during operation is analyzed, and the impact parameters are obtained. The influence of formation condition and bit bias load on bit stress distribution. The analysis shows that with the increase of the impact height, the stress of the bit during the impact process increases gradually, and the stress value increases with the hardening of the formation. In any case, the stress on the drill inner ring 3 and its impact stepped surface is always the largest, followed by the inner ring 2, and the stress concentration on the end face of the bit in contact with the formation is caused by the bias load, which makes the stress greater than that of the bit under normal working conditions. The impact force during bit impact is calculated, and the fatigue life of bit under normal working and biasing load is evaluated by ANSYS nCode Design Life fatigue analysis software. The fatigue life of drill bit and the dangerous point of fatigue failure are obtained. Under normal working conditions, the prediction of bit fatigue life is 8.39 脳 10 ~ 5, and the bit fatigue life under biased load decreases to 1/7. Furthermore, the influence of impact frequency on bit fatigue life is studied. The analysis shows that the drill bit life is reduced by two orders of magnitude when the impact frequency is doubled, which greatly reduces the life span and verifies the reasonableness of the drilling rig's working frequency. Based on the analysis results, the optimization analysis of the original bit is carried out from the aspects of material and stiffening plate arrangement. The material of drill inner ring 2n3 is changed from Q235 to Q345, and the fatigue life of the bit is increased to 1.2 times as long as the original one. The whole material of the bit is changed to Q345 and the fatigue life of the drill is increased to 2.1 times of the original, and the fatigue life of the bit is increased to 3.3 times by applying the stiffening plate, which provides a theoretical basis for the further improvement of the large-diameter impact reverse circulation bit.
【学位授予单位】：山东建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU631

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