AT-16井钻杆NC50内螺纹接头胀大原因分析

通过宏观分析、尺寸测量以及材质分析,对AT-16井钻杆NC50内螺纹接头胀大失效原因进行了详细的调查分析,分析结果表明:钻杆内螺纹接头胀大失效主要是在钻井过程中钻杆接头所承受的扭转载荷过大所致。有限元计算结果和双台肩接头钻杆在塔里木油田实际使用效果表明:双台肩接头钻杆的抗扭性能要优于单台阶螺纹接头钻杆,为有效地防止在深井和超深井钻井过程中钻杆内螺纹接头发生胀大失效,建议采用双台肩接头钻杆。     

钻杆接头粘扣原因分析

通过对油田现场粘扣钻杆接头粘扣形貌进行分析和钻杆接头上部扣试验,对某油田钻杆螺纹接头粘扣原因进行了分析。结果表明:该批钻杆在使用过程中发生粘扣,既与接头本身抗粘扣性能差有关,也与使用操作不当有关,钻杆接头在安装时存在偏斜对扣、没有引扣、高速上扣等问题。最后通过对现有标准和钻具使用条件进行分析,提出了评价钻具螺纹接头抗粘扣性能的上卸扣次数的建议。     

石油钻杆接头螺纹粘扣原因分析及预防措施

在钻井过程中接头螺纹粘扣是最常见的损伤失效形式,由于部分钻杆因螺纹卸不开扣,严重时不得不采取用气割割开的办法,严重影响了钻井生产,造成了一定的经济损失。提高钻杆接头螺纹的抗粘扣性和预防螺纹粘扣具有重要意义。     

S135钻杆内螺纹接头胀扣失效分析

本文对某油井发生的Ф127mmS135钻杆内螺纹接头胀扣失效事故进行了调研，并对其胀扣失效原因进行分析。结果表明，钻杆接头的材质符合行业标准要求；钻杆内螺纹接头胀扣失效的原因是外螺纹接头密封台肩面倒角直径过小，井下钻柱扭矩过大。内螺纹接头密封台肩面承受的接触压力超过材料屈服强度，导致内螺纹接头密封台肩面下陷，外螺纹接头密封台肩面进入内螺纹接头镗孔段，致使内螺纹接头发生胀扣失效。     

钻杆接头断裂原因分析

通过断口分析、金相检验、化学成分分析和力学性能测试等方法对钻杆接头断裂原因进行了分析。结果表明:钻杆接头在使用过程中受到了环境中硫化氢的腐蚀,发生了硫化氢应力腐蚀开裂,随着裂纹扩展最终导致断裂。     

5-1/2FH双台肩钻杆内螺纹接头断裂原因分析

采用宏观检验、化学成分分析、力学性能测试、金相检验和断口分析等方法对某5-1/2FH双台肩钻杆内螺纹接头的断裂原因进行了分析。结果表明:此双台肩钻杆内螺纹接头在副台肩第一完整螺纹根部发生了疲劳断裂失效。断裂具有多源特征,起源于内螺纹根部并向外壁扩展,当穿透壁厚形成通道时发生了刺漏,从而使断口表面形成了冲刷痕迹。上扣扭矩不足,同时接头承受的弯曲应力较大是造成接头疲劳断裂失效的主要原因,另外FH型螺纹固有的螺纹根部半径较小、应力集中较大,使接头失效的风险增大。     

某井钻杆接头断裂原因

在对某油气井的钻探过程中,钻杆接头发生断裂。采用宏观观察、化学成分分析、扫描电镜分析、力学性能测试、金相检验等方法对该钻杆接头的断裂原因进行分析。结果表明：该钻杆接头的断裂性质为疲劳断裂,钻杆钻进过程中频繁发生跳钻、憋钻现象,使其瞬时载荷较大,在钻杆大端螺纹根部萌生了疲劳裂纹,在复杂的交变载荷作用下,裂纹快速扩展,最终导致钻杆接头发生断裂。     

某井特殊螺纹套管脱扣和粘扣原因分析

对某井φ177.8mm×10.36mm 110特殊螺纹接头套管脱扣和粘扣原因进行了分析,认为套管是在严重粘扣之后才发生脱扣的,套管严重粘扣主要与下井操作不当有关。在套管起吊过程中没有螺纹保护器保护的套管接头螺纹、扭矩台肩和密封面容易被损伤,不使用对扣器直接对扣容易导致偏斜对扣;不引扣而直接开动套管钳高速上扣很容易导致粘扣和错扣;一旦严重粘扣和错扣,套管接头连接强度就会大幅度下降,最终导致套管在上提过程中发生脱扣事故。     

S135钻杆接头失效及腐蚀特征

通过化学成分分析、力学性能测试、组织结构分析和高温高压模拟试验,对127mm（5”）S135钻杆接头内壁出现划痕、凹槽和腐蚀三种失效形式,钻杆的腐蚀速率和腐蚀产物进行分析研究。结果表明：该钻杆接头的材料性能符合相关标准要求,钻杆接头腐蚀机理是氧腐蚀,腐蚀产物主要是Fe3O4和FeOOH,划痕和凹槽是由于使用不当和卡槽所致。     

钻杆接头倒角台肩面裂纹产生原因分析

某石油钻具公司在钻杆焊区超声波探伤工序中发现,一接头在其倒角台肩面存在横向裂纹。通过宏观观察、金相检验、化学成分分析和能谱分析等方法,对钻杆接头倒角台肩面横向裂纹产生的原因进行了分析。结果表明:接头材料成分不均匀,原材料局部区域存在严重的元素偏析、疏松等冶金缺陷,破坏了基体的连续性;在后续的接头加工工序中,冶金缺陷进一步扩展,最终产生裂纹。最后提出了相关建议以避免此类缺陷造成的损失。     

热采锅炉炉管异种钢焊接接头失效原因分析

利用光谱分析仪、光学显微镜和扫描电镜等测试手段,测试了炉管材料的化学成分和显微硬度,观察了失效接头的金相组织和断口形貌。发现焊接接头处存在魏氏组织、夹杂物严重聚集及局部区域出现熔合不良。分析结果表明,炉管接头焊接工艺参数过大,焊接材料选择不当,是引起炉管焊接接头失效的主要原因。     

Elucidation of fatigue characteristics and fracture mechanism of friction stir spot‐welded tension–shear joint steels

The fatigue life and fracture mechanism of friction stir spot welded tension–shear joints using 590‐MPa class steel as a base material under constant‐amplitude conditions were investigated with focus on welding dimension variations caused by tool wear. The fatigue limit of the friction stir spot welding (FSSW) joint used for this study is significantly low compared with the static tensile strength of the joint itself. It was clarified that the FSSW joint in this study exhibited two different failure morphologies regardless of the applied load level: base metal fracture and weld area fracture. Although the welding state changes due to the tool wear phenomenon that produce two types of fracture modes in relation to the welding rip diameter, they have no effect on the fatigue strength, regardless of the applied load.     

Dissimilar titanium/aluminum friction stir welding lap joints by experiments and numerical simulation

Dissimilar lap joints were produced by friction stir welding (FSW) out of Ti6Al4V titanium alloy and AA2024 aluminum alloy sheets. The joints, welded with varying tool rotation and feed rate, were studied by analyzing the maximum shear strength, Vickers microhardness and optical observations. A dedicated numerical model, able to take into account the presence of the two different alloys, was used to highlight the effects of the process parameters on temperature distribution, strain distribution, and material flow. The combined analysis of experimental measurements and numerical predictions allowed explaining the effects of tool rotation and feed rate on the material flow. It was found that tool rotation had a larger impact on the joint effectiveness with respect to feed rate. A competition between material mixing and heat input occurs with increasing tool rotation, resulting in higher joint strength when lower values of tool rotation are used.     

Ti6Al_4V人工膝关节的腐蚀疲劳破坏

针对一实际病例,通过具体人工膝关节的受力分析和断口SEM观察及金相观察,说明和解释了该人工膝的失效型式和原因,估算了寿命并提出了改进措施。     

铝/钢异种金属的超声振动强化搅拌摩擦焊接工艺

采用新型超声振动强化搅拌摩擦焊接工艺实现了6061-T6铝合金以及QP980高强钢的搭接焊, 对比分析了有无超声作用下, 接头的宏观形貌、微观组织和拉伸剪切性能, 同时研究了超声振动对焊接载荷的影响。结果表明: 焊接前对母材施加超声振动, 可以起到软化母材的作用, 促进了材料的塑性流动, 扩大了铝/钢界面区和焊核区, 使更多的钢颗粒随搅拌针旋转进入铝合金侧, 在界面区边缘形成钩状结构, 进而提高了接头的失效载荷; 超声改变了FSW接头断裂位置和断口形貌, 提高了接头力学性能, 在本实验工艺参数范围内, 接头最大的平均失效载荷为4.99 kN; 当焊接速度为90 mm/min, 下压量为0.1 mm时, 施加超声振动使接头的平均失效载荷提高了0.98 kN, 拉剪性能提升28.24%;施加超声振动后轴向力F_z、搅拌头扭矩M_t和主轴输出功率分别下降2.46%, 6.44%和4.59%。     

Analysis of adhesively bonded joints: a finite element method and a material model with damage

This paper deals with the derivation of a finite element (FE) method for an adhesively bonded joint which consists of two relatively thin bodies, joined by an even thinner adhesive layer. It is based on a model of the compound joint where the three bodies involved are described as material surfaces. A geometrically two‐dimensional model, where the middle surfaces of the upper and lower body are represented as geometrically coinciding surfaces, is obtained. An elastic–plastic material model with damage is used for the adhesive layer, and an important implication is that the (quasi‐static) propagation of the local failure zone in the adhesive layer in a structure can be simulated. Consequently, the failure load is obtained as a computational result and no failure criterion is needed. The problem is discretized, and a surface model, where only a single surface needs to be FE‐meshed, is obtained. A single‐lap joint is analysed and good agreement is obtained when compared to an analysis using a fine mesh with brick element. Furthermore, the failure load is computed and compared with experiments. The derived FE method opens up the possibility to efficiently model and analyse the mechanical behaviour of large bonded structures. Copyright © 2005 John Wiley & Sons, Ltd.     

Strength prediction of bolted joints in graphite/epoxy composite laminates

A parametric finite element analysis was conducted to investigate the effect of failure criteria and material property degradation rules on the tensile behaviour and strength of bolted joints in graphite/epoxy composite laminates. The analysis was based on a three-dimensional progressive damage model (PDM) developed earlier by the authors. The PDM comprises the components of stress analysis, failure analysis and material property degradation. The predicted load–displacement curves and failure loads of a single-lap single-bolt joint were compared with experimental data for different joint geometries and laminate stacking sequences. The stiffness of the joint was predicted with satisfactory accuracy for all configurations. The predicted failure load was significantly influenced by the combination of failure criteria and degradation rules used. A combination of failure criteria and material property degradation rules that leads to accurate strength prediction is proposed. For all the analyses performed, the macroscopic failure mechanism of the joint and the damage progression were also predicted.     

复合材料螺接修理结构参数化建模分析工具开发及验证

螺接修理在复合材料结构的临时性修理,尤其是战伤修理中应用较广泛。然而其修理设计过程较复杂,建模分析难度较大,难以满足工程快速定参的需要。本文针对含穿透损伤复合材料层合板的螺接修理问题,采用VB.NET结合p型有限元技术,开发了一套参数化的建模分析工具。分析工具通过界面读取修理结构的几何参数、螺栓布局、螺栓大小、载荷、材料属性等参数,自动创建有限元模型并进行求解。根据求解结果,分析工具可为用户提供修理结构的螺栓载荷、钉载比例、危险孔孔边应力等。另外,通过引入有限断裂力学,结合两级模型分析技术可预测得到修理结构的失效强度和失效位置。最后,采用典型算例对分析工具的有效性进行了验证。     

Microstructure and mechanical properties of dissimilar friction stir welding of 6061-to-7050 aluminum alloys

In this work, the microstructure and mechanical properties of friction stir welded dissimilar butt joints of 6061-to-7050 aluminum alloys were evaluated. Microstructure analysis of the cross-section of the joints revealed distinct lamellar bands and various degrees of intermixing that were correlated with tool rotational speed. Due to the distinct mechanical properties of the two alloys, microhardness measurements showed a consistent asymmetric hardness distribution profile across the weld nugget, regardless of tool rotational speed. Under monotonic tensile loading, an increase in the joint strength was observed with the increase in the tool rotational speed. Regarding fracture, the joints consistently failed on the 6061 aluminum alloy side. Furthermore, two modes of failure were observed, one through the stir zone and the other through the heat-affected zone. Inspection of the fracture surfaces suggested that inadequate material intermixing produced at low tool rotational speeds was the cause for the low mechanical strength and failure through the stir zone. On the other hand, the failure observed through the heat-affected zone at high rotational speeds was produced due to the material softening as confirmed by the microhardness measurements.     

Simultaneous topology and fastener layout optimization of assemblies considering joint failure

This article provides a method for the simultaneous topology optimization of parts and their corresponding joint locations in an assembly. Therein, the joint locations are not discrete and predefined, but continuously movable. The underlying coupling equations allow for connecting dissimilar meshes and avoid the need for remeshing when joint locations change. The presented method models the force transfer at a joint location not only by using single spring elements but accounts for the size and type of the joints. When considering riveted or bolted joints, the local part geometry at the joint location consists of holes that are surrounded by material. For spot welds, the joint locations are filled with material and may be smaller than for bolts. The presented method incorporates these material and clearance zones into the simultaneously running topology optimization of the parts. Furthermore, failure of joints may be taken into account at the optimization stage, yielding assemblies connected in a fail-safe manner.