Engineering Failure Analysis最新文献

Study on failure mechanism and seismic performance of RC Frame-Infilled walls structures reinforced by CFRP CFRP 加固的 RC 框架填充墙结构的破坏机理和抗震性能研究

IF 4.4 2区工程技术 Q1 ENGINEERING, MECHANICAL

Engineering Failure Analysis

Pub Date : 2024-11-24 DOI: 10.1016/j.engfailanal.2024.109114

Xuetan Zhang, Yang Zhou, Xiangyu Liu, Changda Wang, Zhiguo Sun

The reinforced concrete (RC) frame structure with continuous half-height infilled walls is a common structural form. However, the existence of infilled walls alters the structure’s force mechanism and failure mode, making the frame columns susceptible to brittle failure and adversely affecting the overall seismic performance. To enhance the seismic capacity of such systems, quasi-static tests were conducted on RC frame-infilled wall models reinforced with different CFRP methods. Based on the test results, numerical analysis models of RC frame-infilled walls were established to perform parametric studies and quantitatively assess the impact of various CFRP reinforcement methods on seismic performance. The results indicate that both full wrapping and strip reinforcement methods can improve the failure mode and enhance the seismic capacity of the frame-infilled wall structure, but the degree of improvement varies significantly. Compared to the unreinforced frame, the ductility, ultimate bearing capacity, initial stiffness, and energy dissipation of the fully wrapped and strip-reinforced frames increased by 42.86% and 58.76%, 30.43% and 10.65%, 68.76% and 9.55%, 298.01% and 340.92%, respectively. Considering the overall seismic demand and CFRP utilization rate, the strip reinforcement method is more suitable for the seismic strengthening of half-height infilled wall frame structures. When using the same amount of CFRP without other improvement measures, it is recommended that the ratio of strip spacing to strip width be between 1.1 and 1.25.

带有连续半高填充墙的钢筋混凝土（RC）框架结构是一种常见的结构形式。然而，填充墙的存在改变了结构的受力机制和破坏模式，使框架柱容易发生脆性破坏，对整体抗震性能产生不利影响。为了提高此类系统的抗震能力，对采用不同 CFRP 方法加固的 RC 框架填充墙模型进行了准静力试验。根据试验结果，建立了 RC 框架填充墙的数值分析模型，以进行参数研究并定量评估各种 CFRP 加固方法对抗震性能的影响。结果表明，全包和条带加固方法都能改善框架填充墙结构的破坏模式，提高其抗震能力，但改善程度差异显著。与未加固的框架相比，全包裹和条状加固框架的延性、极限承载力、初始刚度和耗能分别提高了 42.86% 和 58.76%、30.43% 和 10.65%、68.76% 和 9.55%、298.01% 和 340.92%。考虑到整体抗震要求和 CFRP 利用率，条带加固法更适合半高填充墙框架结构的抗震加固。在不采取其他改进措施的情况下，使用相同数量的 CFRP 时，建议带间距与带宽度之比介于 1.1 与 1.25 之间。

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引用次数: 0

Numerical investigation on bending characteristic and ductile fracture of AA7075 thin-walled beam using advanced orthotropic plasticity and fracture models 利用先进的正交塑性和断裂模型对 AA7075 薄壁梁的弯曲特性和韧性断裂进行数值研究

IF 4.4 2区工程技术 Q1 ENGINEERING, MECHANICAL

Engineering Failure Analysis

Pub Date : 2024-11-24 DOI: 10.1016/j.engfailanal.2024.109122

Tianyu Xu , Duquan Zuo , Ti Ye , Guohao Zhang , Yufeng Zhang

Thin-walled structures manufactured from the 7075 aluminum alloy are gaining tremendous attention in the automotive industry for their potential to reduce vehicle weight. However, the bending characteristics and rupture behavior of the AA7075 thin-walled beams under unexpected collision events have not been extensively studied. This study aims to fill that gap through a detailed numerical investigation of the bending deformation and failure mechanism of AA7075 thin-walled beams under quasi-static three-point bending at room temperature. Full-size, three-dimensional numerical simulations of laboratory-scale AA7075-T6 hat-shaped beam were conducted using the ABAQUS/Explicit solver. The material elastic–plastic response is described by a rate-independent constitutive description, incorporating advanced non-quadratic orthotropic plasticity and anisotropic ductile fracture criteria via VUMAT subroutines. Results indicate that the simulations accurately reproduced experimental observations, including the loading-displacement curves and deformation patterns. The bending behavior of the AA7075-T6 thin-walled beams aligns with typical bending collapse mechanisms, consistent with Kecman’s theory. The rupture process exhibits ductile fracture characteristics, with heterogeneous stress distribution across the material thickness affecting crack initiation rates between the upper and lower surfaces. Notably, the stress state at the fracture’s half-thickness section approximates an equi-biaxial tension condition. These findings provide essential insights into the bending deformation and failure mechanisms of AA7075 thin-walled structures under unexpected impact loading.

用 7075 铝合金制造的薄壁结构因其减轻汽车重量的潜力而受到汽车行业的极大关注。然而，AA7075 薄壁梁在意外碰撞事件下的弯曲特性和断裂行为尚未得到广泛研究。本研究旨在通过对 AA7075 薄壁梁在室温准静态三点弯曲下的弯曲变形和断裂机理进行详细的数值研究来填补这一空白。使用 ABAQUS/Explicit 求解器对实验室规模的 AA7075-T6 帽形梁进行了全尺寸三维数值模拟。材料的弹塑性响应由与速率无关的构成描述来描述，并通过 VUMAT 子程序纳入了先进的非四元正交塑性和各向异性韧性断裂准则。结果表明，模拟准确地再现了实验观察结果，包括加载-位移曲线和变形模式。AA7075-T6 薄壁梁的弯曲行为符合典型的弯曲塌陷机制，与 Kecman 理论一致。断裂过程表现出韧性断裂特征，整个材料厚度上的异质应力分布影响了上下表面之间的裂纹萌发率。值得注意的是，断口半厚度部分的应力状态近似于等轴拉伸状态。这些发现为了解 AA7075 薄壁结构在意外冲击载荷作用下的弯曲变形和破坏机制提供了重要启示。

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引用次数: 0

Dynamic analysis of cutting RC structure with shield disc-cutter: Insights from the coupled simulation and laboratory test verification 使用盾构圆盘切割机切割 RC 结构的动态分析：耦合模拟和实验室测试验证的启示

IF 4.4 2区工程技术 Q1 ENGINEERING, MECHANICAL

Engineering Failure Analysis

Pub Date : 2024-11-23 DOI: 10.1016/j.engfailanal.2024.109112

Yidong Guo , Dalong Jin , Dajun Yuan , Zheng Mou

During shield tunneling in densely populated urban areas, shield machines may unexpectedly encounter obstacles such as reinforced concrete (RC) structure. Cutting through RC structure with a shield machine presents significant challenges due to potential cutter damage and reduced cutting efficiency. In this study, dynamic analyses of cutting RC structure via disc-cutter were performed based on the finite element method-discrete element method (FEM-DEM) coupled approach. In FEM-DEM coupled model, the mechanical behaviour of concrete is represented using DEM, while the influence of the rebar in the concrete is accounted for through FEM. And the precision and dependability of the simulation results were validated through the laboratory experiments. Overall, the numerical outcomes agreed well with the experimental data. Furthermore, a parametric study was conducted, and the effects of the shield working parameters and the geometric configurations of disc-cutter on the cutting performance of the disc-cutter were investigated, respectively. Through the parametric analysis, it is recommended that the shield machine adopts a tunneling pattern with low penetration and medium rotational speed in actual project when cutting the RC structure. The findings of this study may serve as valuable references for cutting RC obstacles with disc-cutters in future applications.

在人口稠密的城市地区进行盾构掘进时，盾构机可能会意外地遇到钢筋混凝土（RC）结构等障碍物。由于潜在的刀盘损坏和切割效率降低，使用盾构机切割 RC 结构面临巨大挑战。本研究基于有限元法-离散元法（FEM-DEM）耦合方法，对通过圆盘切割机切割 RC 结构进行了动态分析。在 FEM-DEM 耦合模型中，使用 DEM 表示混凝土的力学行为，同时通过 FEM 考虑混凝土中钢筋的影响。模拟结果的精确性和可靠性通过实验室实验得到了验证。总体而言，数值结果与实验数据非常吻合。此外，还进行了参数研究，分别研究了盾构工作参数和圆盘切削机几何配置对圆盘切削机切削性能的影响。通过参数分析，建议盾构机在实际工程中切割 RC 结构时采用低穿透、中转速的掘进模式。本研究的结果可为今后使用圆盘切割机切割 RC 障碍物提供有价值的参考。

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引用次数: 0

Performance research and effect evaluation of a high-grade damping fastener in subway line 地铁线高等级阻尼扣件的性能研究与效果评估

IF 4.4 2区工程技术 Q1 ENGINEERING, MECHANICAL

Engineering Failure Analysis

Pub Date : 2024-11-23 DOI: 10.1016/j.engfailanal.2024.109098

Xiaogang Gao , Haidong Yan , Qingsong Feng , Yufei Ma , Maojin Du

In recent years, some subway lines have been upgraded with vibration and noise reduction technology. As the only component connecting rail and sleeper, the fastener system has been the primary solution to vibration and noise reduction in subways. However, due to the mismatch between the structure design and material selection of the fastener system, the performance decay and aging failure of the fastener elastic pad occurred in less than one year of service in the line. In this paper, we choose a high-grade damping fastener with low vertical and high lateral stiffness as the research object, and explore the design method of fastener system to control the failure of stiffness aging and rail wear. Following that, theoretical analysis and experimental research are conducted on structural components of the higher damping fastener. The main conclusions are as follows: First, the stiffness of the damping fastener is adjustable in real time. By adjusting the nut installation height, optimizing the thickness of the elastic pad under the plate, and alerting the lateral block contact angle can change the vertical stiffness of fastener system by 19.4 %, 27.1 %, and 28.6 %, respectively. Second, before the line replacement, the rail roughness under the Egg type damper (Egg damper) is increasing exponentially. After replacing with the ZK type high-grade damping fastener (ZK fastener), the average roughness of high and low rails decreases at a rate of −0.3 dB/month. Third, hammering test results indicate that the vertical support stiffness of the ZK fastener is significantly lower than that of the Egg damper, while the lateral stiffness is 2.55 times greater than that of the Egg damper. Fourth, compared to the Egg damper before replacement, the maximum vertical vibration at the tunnel wall with the ZK fastener is reduced by 6.9 dB, and the dynamic twisting at the rail head is only half of the original. Application of the new damping fastener system in subway line replacement over the past two years not only reflects a clever stiffness design principle but also demonstrates good track stability, making it a preferred high-grade damping modification measure for controlling subway vibration and noise.

近年来，一些地铁线路采用了减振降噪技术进行升级改造。作为连接轨道和枕木的唯一部件，扣件系统一直是地铁减振降噪的主要解决方案。然而，由于扣件系统的结构设计和材料选择不匹配，扣件弹性垫在线路上使用不到一年就出现了性能衰减和老化失效。本文选择垂直刚度低、横向刚度高的高等级阻尼扣件作为研究对象，探索控制刚度老化和钢轨磨损失效的扣件系统设计方法。随后，对高等级阻尼扣件的结构部件进行了理论分析和实验研究。主要结论如下：首先，阻尼扣件的刚度可实时调节。通过调整螺母安装高度、优化板下弹性垫厚度、提醒侧向块接触角，可使紧固件系统的垂直刚度分别改变 19.4%、27.1% 和 28.6%。其次，线路更换前，蛋型阻尼器（Egg damper）下的钢轨粗糙度呈指数增长。更换为 ZK 型高级阻尼扣件（ZK 扣件）后，高低轨的平均粗糙度以-0.3 分贝/月的速度下降。第三，锤击试验结果表明，ZK 扣件的垂直支撑刚度明显低于 Egg 阻尼器，而横向刚度则是 Egg 阻尼器的 2.55 倍。第四，与更换前的 Egg 阻尼器相比，使用 ZK 扣件后隧道壁的最大垂直振动降低了 6.9 分贝，轨头的动态扭曲仅为原来的一半。近两年来，新型阻尼扣件系统在地铁线路更换中的应用，不仅体现了巧妙的刚度设计原理，而且表现出良好的轨道稳定性，是控制地铁振动和噪声的首选高级阻尼改造措施。

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引用次数: 0

Modeling and analysis of internal excitation and vibration characteristics of gears with early-stage crack and 3D tooth surface error 具有早期裂纹和三维齿面误差的齿轮内激和振动特性建模与分析

IF 4.4 2区工程技术 Q1 ENGINEERING, MECHANICAL

Engineering Failure Analysis

Pub Date : 2024-11-22 DOI: 10.1016/j.engfailanal.2024.109116

Lantao Yang , Kun Yue , Liming Wang , Fengshou Gu , Andrew Ball

Affected by the tooth surface errors, the vibration characteristics of early crack failures are usually various under different tooth surface precision level. Therefore, to reveal the influence of three-dimensional (3D) tooth surface error (TSE) on the internal excitation and vibration characteristics of gears with early-stage crack (ESC), a coupling internal excitation model of gears with ESC and 3D errors is proposed based on a double-layer iterative method. In this model, the influence of meshing phase between tooth pair and along tooth width direction (TWD) on the time-varying mesh stiffness (TVMS) are simultaneously considered, which overcomes the limitations of traditional models that are only suitable for characterizing the coupled excitation of the two-dimensional tooth profile errors and TVMS. Based on verifying the proposed model, the effects of TSE type, parameters, and load on the TVMS, loaded static transmission error (LSTE), load distributions, and torsional deformation of the cracked gear teeth are investigated, and the vibration characteristics of ESC failures under the effects of 3D TSE are also explored. The research results show that the distribution parameters of 3D TSE have a significant effect on the internal excitation and vibration characteristics of gears with ESC, and thus measuring and evaluating the distribution parameters of TSE can help improve the accuracy of gear fault identification and diagnosis methods.

受齿面误差的影响，在不同的齿面精度水平下，早期裂纹失效的振动特性通常各不相同。因此，为了揭示三维（3D）齿面误差（TSE）对早期裂纹（ESC）齿轮内部激励和振动特性的影响，基于双层迭代法，提出了一种具有 ESC 和 3D 误差的齿轮耦合内部激励模型。在该模型中，同时考虑了齿对之间和沿齿宽方向（TWD）的啮合相位对时变啮合刚度（TVMS）的影响，克服了传统模型仅适用于表征二维齿廓误差和 TVMS 耦合激励的局限性。在验证所提模型的基础上，研究了 TSE 类型、参数和载荷对开裂轮齿的 TVMS、加载静态传输误差 (LSTE)、载荷分布和扭转变形的影响，并探讨了三维 TSE 作用下 ESC 故障的振动特性。研究结果表明，三维 TSE 分布参数对带 ESC 的齿轮的内部激励和振动特性有显著影响，因此测量和评估 TSE 分布参数有助于提高齿轮故障识别和诊断方法的准确性。

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引用次数: 0

Local stress/strain field analysis of die-casting Al alloys via 3D model simulation with realistic defect distribution and RVE modelling 通过三维模型模拟与现实缺陷分布和 RVE 建模对压铸铝合金进行局部应力/应变场分析

IF 4.4 2区工程技术 Q1 ENGINEERING, MECHANICAL

Engineering Failure Analysis

Pub Date : 2024-11-22 DOI: 10.1016/j.engfailanal.2024.109104

Jian Yang , Bo Liu , Dongwei Shu , Qin Yang , Tiegang Hu

The deformation and fracture behavior of die-casting aluminium (Al) alloys is very complex. Due to local variations in properties, the microstructure and mechanical behavior of materials are highly anisotropic. In this paper, an attempt has been made to quantitatively study the defect characteristics of high pressure cast Al alloy parts using experimental and finite element calculation methods, and to analysis the effect of local porosity and pore size on plasticity. Three-dimensional solids with real defect distribution are obtained by using 3D X-ray computed tomography, and used as an input for building a finite element model. The damage initiation of cast Al alloys under complex stress states is analyzed from micro to macro scales. Crack propagation occurs through two modes of microporous agglomeration: aggregated pores produce cracks from internal necking and stress concentration. Then, they expand in the same direction, agglomerate in a specific direction and eventually fracture. Subsequently, the effect of porosity on non-homogeneity was elucidated by obtaining local stress/strain behavior through digital image correlation measurements. Additionally, a theoretical framework of elasto-plastic deformation of microstructures and a 3D representative volume element model are developed to simulate the deformation and damage processes under cyclic boundary conditions of materials. The simulation results show that the local stress/strain around the pores evolves gradually with deformation. During the die casting process, the method demonstrates the ability to predict the mechanical behavior of Al alloys.

压铸铝（Al）合金的变形和断裂行为非常复杂。由于性能的局部变化，材料的微观结构和机械行为具有高度各向异性。本文尝试使用实验和有限元计算方法定量研究高压铸造铝合金零件的缺陷特征，并分析局部孔隙率和孔隙大小对塑性的影响。通过三维 X 射线计算机断层扫描获得了具有真实缺陷分布的三维实体，并将其作为建立有限元模型的输入。从微观到宏观尺度分析了铸铝合金在复杂应力状态下的损伤起始。裂纹扩展通过微孔聚集的两种模式发生：聚集的孔隙通过内部缩颈和应力集中产生裂纹。然后，它们向同一方向扩展，在特定方向聚集，最终断裂。随后，通过数字图像相关测量获得了局部应力/应变行为，从而阐明了孔隙率对非均质性的影响。此外，还建立了微结构弹塑性变形理论框架和三维代表性体积元素模型，以模拟材料在循环边界条件下的变形和损伤过程。模拟结果表明，孔隙周围的局部应力/应变随变形逐渐演变。在压铸过程中，该方法展示了预测铝合金机械行为的能力。

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引用次数: 0

Analysis of short-circuit failure paths and causes of high-reliability tungsten-copper electrode gas discharge tubes 高可靠性钨铜电极气体放电管的短路故障路径和原因分析

IF 4.4 2区工程技术 Q1 ENGINEERING, MECHANICAL

Engineering Failure Analysis

Pub Date : 2024-11-22 DOI: 10.1016/j.engfailanal.2024.109092

Hefei Cao , Tongze Xin , Congying Han , Pengcheng Cai , Guohua Zhang , Min Wang

In engineering practice, it has been found that as the number of surge discharges increases, gas discharge tubes exhibit short-circuit failure, significantly affecting the normal operation of the protected system. This study obtained gas discharge tubes failure short-circuit samples at a current of (235–240 A) through a self-built discharge testing platform. By combining multiple characterization methods and based on the classification of failed insulation resistance, it was determined that the main short-circuit failure paths are conductive tube walls and conductive electrodes, both caused by stacked or free electrode matrix particles. Through non-destructive disassembly, it was found that the failed samples exhibited significant differences compared to new samples. Specifically, the anode electrode and tube wall showed material stacking and growth, while the cathode electrode exhibited degradation and erosion, with the severity increasing as the insulation resistance progressively decreased. After the completion of cathode electron powder splashing, the tungsten copper electrode accelerates dissociation under the dual effects of maintaining arc discharge and melting splashing. Droplets splash onto the side of the anode or tube wall, solidify, and adhere, gradually accumulating to form surface particles. Some molten droplets bounce back when they come into contact with the electrode or wall, solidify into free tiny particles. These free particles accumulate in the grooves of the tube wall under the influence of gravity or energy waves. When a circuit is formed inside the gas discharge tube by these tungsten-copper particles, the gas discharge tube short-circuits and fails.

在工程实践中发现，随着浪涌放电次数的增加，气体放电管会出现短路故障，严重影响受保护系统的正常运行。本研究通过自建的放电测试平台获得了电流为（235-240 A）的气体放电管故障短路样本。结合多种表征方法，并根据失效绝缘电阻的分类，确定短路失效的主要途径是导电管壁和导电电极，二者均由堆叠或游离的电极基体颗粒引起。通过非破坏性拆解发现，失效样品与新样品相比有显著差异。具体来说，阳极电极和管壁出现了材料堆积和增长，而阴极电极则出现了退化和侵蚀，其严重程度随着绝缘电阻的逐渐降低而增加。阴极电子粉飞溅完成后，钨铜电极在维持电弧放电和熔融飞溅的双重作用下加速解离。液滴飞溅到阳极侧面或管壁上，凝固并附着，逐渐累积形成表面颗粒。一些熔滴在接触到电极或管壁时会反弹，凝固成游离的微小颗粒。在重力或能量波的作用下，这些游离微粒在管壁的凹槽中积聚。当这些钨铜颗粒在气体放电管内形成回路时，气体放电管就会短路并失效。

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引用次数: 0

Optimization of 3D-printed reinforced concrete beams with four types of reinforced patterns and different distances 优化四种加固模式和不同间距的 3D 打印钢筋混凝土梁

IF 4.4 2区工程技术 Q1 ENGINEERING, MECHANICAL

Engineering Failure Analysis

Pub Date : 2024-11-22 DOI: 10.1016/j.engfailanal.2024.109096

Mohammad Hematibahar , Amirali Milani , Roman Fediuk , Mugahed Amran , Amir Bakhtiary , Makhmud Kharun , Mir Sharif Mousavi

The enhancement of mechanical properties in reinforced concrete beams remains a pivotal focus in modern structural engineering. In the pursuit of innovative solutions, recent studies have explored the potential of 3D-printing technology to reinforce cementitious materials. However, challenges persist in optimizing this approach. This study investigates the reinforcement of cement beams using four distinct 3D-printed patterns: Honeycomb, 3D-Honeycomb, Grid, and Triangle. Each pattern was strategically positioned at varying distances from the neutral axis to assess its impact on the beam’s flexural strength. The findings reveal that the Honeycomb pattern, when placed 10 mm from the bottom of the beam, enhanced flexural strength by over 25 %. The 3D-Honeycomb pattern, positioned at 5 mm, demonstrated similar improvements. Notably, the Grid pattern, also placed 5 mm from the bottom, resulted in a remarkable 46 % increase in flexural strength, while the Triangle pattern contributed to a 30 % enhancement. Further optimization was achieved by combining two reinforcement patterns. The Honeycomb pattern exhibited strain-hardening behavior and increased flexural strength by over 76 %. The 3D-Honeycomb and Grid patterns further augmented flexural strength by 76 % and 72 %, respectively. The most significant improvement was observed with the Grid pattern, which boosted flexural strength by more than 118 %. This study underscored the transformative potential of 3D-printed reinforcement in cement beams. The strategic use of Honeycomb, 3D-Honeycomb, Grid, and Triangle patterns not only enhances flexural strength but also induces strain-hardening behavior, leading to strength gains between 76 % and 118 % compared to the control sample. These findings offer valuable insights for the development of advanced construction materials and techniques.

提高钢筋混凝土梁的机械性能仍然是现代结构工程的一个关键重点。为了寻求创新的解决方案，最近的研究探索了三维打印技术加固水泥基材料的潜力。然而，优化这种方法仍面临挑战。本研究采用四种不同的 3D 打印模式对水泥梁进行加固：蜂窝状、3D-蜂窝状、网格状和三角形。每种图案都与中轴线保持不同距离，以评估其对梁抗弯强度的影响。研究结果表明，蜂窝状图案放置在距离横梁底部 10 毫米的位置时，抗弯强度提高了 25% 以上。三维蜂窝图案在距离梁底 5 毫米处也有类似的改善。值得注意的是，同样放置在离底部 5 毫米处的网格图案显著提高了 46% 的抗弯强度，而三角形图案则提高了 30%。通过将两种加固模式相结合，实现了进一步的优化。蜂巢图案表现出应变硬化行为，抗弯强度提高了 76% 以上。三维蜂窝和网格图案进一步提高了抗弯强度，分别提高了 76% 和 72%。网格图案的改善最为明显，抗弯强度提高了 118% 以上。这项研究强调了三维打印加固技术在水泥梁中的变革潜力。战略性地使用蜂窝、3D-蜂窝、网格和三角形图案不仅能提高抗弯强度，还能诱导应变硬化行为，与对照样本相比，强度提高了 76% 到 118%。这些发现为先进建筑材料和技术的开发提供了宝贵的启示。

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引用次数: 0

Microstructural characteristics and erosion resistance of laser cladding Stellite 6 alloy on an 1Cr11Ni2W2MoV steel surface 在 1Cr11Ni2W2MoV 钢表面激光熔覆 Stellite 6 合金的微观结构特征和抗侵蚀性

IF 4.4 2区工程技术 Q1 ENGINEERING, MECHANICAL

Engineering Failure Analysis

Pub Date : 2024-11-22 DOI: 10.1016/j.engfailanal.2024.109093

Meng Chen , Yinmin An , Quanbo Wang , Youwei Xu , Yu Shi

The cladding process conditions adopted naturally when laser cladding Stellite alloy surface strengthening for key positions of complex components need to be accurately adjusted because of significant differences in the heating rate and heat dissipation conditions in each region of the components. We observed that stress-relief annealing must be supplemented to effectively avoid the generation of cracks when treating small-diameter parts of 1Cr11Ni2W2MoV steel piston rods when the thickness of the cladding layer formed by laser cladding Stellite 6 alloy exceeds 2 mm. In this step, the cracks can be significantly reduced by setting the annealing temperature at 650 °C, holding for 2 h, and then cooling with the furnace to ensure the quality of the cladding layer is stable and reliable. We systematically analyzed the microstructure, crack defects, phase composition, and microhardness of the Stellite 6 cladding layer under different process conditions and focused on the performance of the substrate and cladding layer when subjected to erosion to understand the effect of this process on the material properties. This study not only provides an important basis for optimizing the laser cladding process but also provides a useful reference for improving the surface strengthening effect and durability of complex components.

在对复杂部件的关键位置进行激光熔覆 Stellite 合金表面强化时，由于部件各区域的加热速率和散热条件存在显著差异，自然需要对熔覆工艺条件进行精确调整。我们观察到，在处理 1Cr11Ni2W2MoV 钢活塞杆的小直径部件时，当激光熔覆 Stellite 6 合金形成的熔覆层厚度超过 2 毫米时，必须辅以去应力退火，以有效避免裂纹的产生。在这一步骤中，通过将退火温度设定在 650 ℃，保温 2 小时，然后用熔炉冷却，可显著减少裂纹，确保熔覆层质量稳定可靠。我们系统分析了不同工艺条件下 Stellite 6 堆焊层的微观结构、裂纹缺陷、相组成和显微硬度，并重点研究了基体和堆焊层在受到侵蚀时的性能，以了解这一工艺对材料性能的影响。这项研究不仅为优化激光熔覆工艺提供了重要依据，也为提高复杂部件的表面强化效果和耐用性提供了有益参考。

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引用次数: 0

Lack of fusion-induced cracking effect on tensile and fatigue behaviours of laser powder-bed fusion-processed Ti-6Al-4V implant 激光粉末床熔融加工 Ti-6Al-4V 植入体的拉伸和疲劳行为缺乏熔融诱导裂纹效应

IF 4.4 2区工程技术 Q1 ENGINEERING, MECHANICAL

Engineering Failure Analysis

Pub Date : 2024-11-22 DOI: 10.1016/j.engfailanal.2024.109095

Abdul Azeez Abdu Aliyu , Chedtha Puncreobutr , Junji Shinjo , Surasak Kuimalee , Thanawat Phetrattanarangsi , Thanachai Boonchuduang , Pariwat Taweekitikul , Chinnapat Panwisawas , Wanming LI , Kitti Poungsiri , Boonrat Lohwongwatana

In the laser powder-bed fusion (L-PBF) of Ti-6Al-4 V (Ti64) alloy, cracking defects often caused by lack-of-fusion (LoF) defects cannot be avoided. These defects strongly impact the structural stability of Ti64 implants. In this work, the influence of LoF defects on the tensile and fatigue behaviours of Ti64 implants at different energy densities is evaluated. Three primary approaches were used to characterise the LoF defects in the 10 mm gauge volume of near-net-shaped produced hourglass samples: Image-J software, scanning electron microscopy (SEM), and X-ray computed tomography (µ-CT). A low-cycle fatigue (LCF) test at a stress ratio of −1 and an extensive fractography study of the fractured Ti64 samples were used to investigate the LoF porosity-induced cracking and fatigue effect. The tensile properties of Ti64 samples processed by the L-PBF are generally more affected by microstructural changes resulting from variations in energy density than by LoF defects. A fine microstructure enhances tensile strength, while a coarser microstructure favours ductility. This is evident in samples LPBF-AD and LPBF-BD1, which demonstrate finer and coarser microstructures but show the lowest (8.31 %) and highest ductility (17.58 %), respectively. The best and worst fatigue performance samples were LPBF-AD (600 MPa) and LPBF-BD2 (200 MPa), respectively, and LoF defects significantly impacted this finding. Moreover, it has been demonstrated that cracks originate and propagate faster from the surface than the internal sites. As a result, the former demonstrates a negative effect on the fatigue life of L-PBF-processed Ti64 samples under cyclic loading. The sub-surface morphologies and pore formation with different energy densities are rationalised by high-fidelity thermal-fluid dynamics simulations.

在 Ti-6Al-4 V（Ti64）合金的激光粉末床熔化（L-PBF）过程中，通常无法避免由熔化不足（LoF）缺陷引起的开裂缺陷。这些缺陷严重影响了 Ti64 植入物的结构稳定性。本研究评估了 LoF 缺陷对不同能量密度下 Ti64 植入体的拉伸和疲劳行为的影响。我们主要采用了三种方法来表征近网状沙漏样品 10 毫米量规体积中的 LoF 缺陷：Image-J 软件、扫描电子显微镜 (SEM) 和 X 射线计算机断层扫描 (µ-CT)。应力比为-1 的低循环疲劳（LCF）试验和对断裂 Ti64 样品的大量断口研究用于研究 LoF 孔隙率引起的裂纹和疲劳效应。与 LoF 缺陷相比，采用 L-PBF 工艺加工的 Ti64 样品的拉伸性能通常更多地受到能量密度变化引起的微观结构变化的影响。精细的微观结构可提高拉伸强度，而较粗的微观结构则有利于延展性。这一点在 LPBF-AD 和 LPBF-BD1 样品中很明显，这两个样品的微观结构较细和较粗，但延展性分别最低（8.31%）和最高（17.58%）。疲劳性能最好和最差的样品分别是 LPBF-AD（600 兆帕）和 LPBF-BD2（200 兆帕），LoF 缺陷对这一结果有显著影响。此外，研究还表明，裂纹从表面产生和扩展的速度要快于内部。因此，在循环加载下，前者对 L-PBF 加工的 Ti64 样品的疲劳寿命有负面影响。高保真热流体动力学模拟合理地解释了不同能量密度下的次表面形态和孔隙形成。

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