Meng Yang, Qing Jiang, Xiang Zhang, Ming Wu, Tao Zhang, Rui Pan, Peng Li, Sumei Wang, Jin Yang
The ultrashort pulsed (USP) laser microwelding of sapphire/lnvar36 alloy controlled by the surface roughness of metal was investigated for the first time. The surface roughness (Sa) of Invar alloys gradually decreased from 0.944 to 0.029 μm from the prime surface to grounded and polished surface. However, the joint shear strength first increased and then decreased with the lowered Sa, the maximum shear strength reached 107.87 MPa at the Sa ∼ 0.131 μm. Compared to other surfaces with low Sa, the relatively high surface roughness enhanced the interfacial thermal deposition both spatially and temporally which in turn promoted the diffusion of interface elements and the formation of jagged mechanical interlocking structures. Therefore, the appropriate rough metal surface was beneficial for the enhancement of sapphire/metal dissimilar joints. This report is of great significance in simplifying the surface preparation process in the USP laser microwelding of transparent hard and brittle materials with metals, therefore promoting this technique from lab to industry.
首次研究了由金属表面粗糙度控制的蓝宝石/英瓦尔 36 合金的超短脉冲 (USP) 激光微焊接。英瓦尔合金的表面粗糙度 (Sa) 从原始表面到研磨抛光表面从 0.944 μm 逐渐降低到 0.029 μm。然而，随着 Sa 的降低，接头剪切强度先升高后降低，当 Sa ∼ 0.131 μm 时，最大剪切强度达到 107.87 MPa。与其他低 Sa 表面相比，相对较高的表面粗糙度在空间和时间上都增强了界面热沉积，进而促进了界面元素的扩散和锯齿状机械互锁结构的形成。因此，适当粗糙的金属表面有利于增强蓝宝石/金属异种接合。本报告对于简化美国药典激光微焊接透明硬脆材料与金属的表面制备过程具有重要意义，从而将这项技术从实验室推广到工业领域。
{"title":"Effects of surface roughness on the microstructure and mechanical properties of dissimilar sapphire/Invar36 alloy joints made by ultrashort pulsed laser micro-welding","authors":"Meng Yang, Qing Jiang, Xiang Zhang, Ming Wu, Tao Zhang, Rui Pan, Peng Li, Sumei Wang, Jin Yang","doi":"10.2351/7.0001513","DOIUrl":"https://doi.org/10.2351/7.0001513","url":null,"abstract":"The ultrashort pulsed (USP) laser microwelding of sapphire/lnvar36 alloy controlled by the surface roughness of metal was investigated for the first time. The surface roughness (Sa) of Invar alloys gradually decreased from 0.944 to 0.029 μm from the prime surface to grounded and polished surface. However, the joint shear strength first increased and then decreased with the lowered Sa, the maximum shear strength reached 107.87 MPa at the Sa ∼ 0.131 μm. Compared to other surfaces with low Sa, the relatively high surface roughness enhanced the interfacial thermal deposition both spatially and temporally which in turn promoted the diffusion of interface elements and the formation of jagged mechanical interlocking structures. Therefore, the appropriate rough metal surface was beneficial for the enhancement of sapphire/metal dissimilar joints. This report is of great significance in simplifying the surface preparation process in the USP laser microwelding of transparent hard and brittle materials with metals, therefore promoting this technique from lab to industry.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"35 45","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141800456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xin Du, Qiang Wu, Tong Zhang, Mingfu Wang, Jingmin Chen, J. Zou, Rongshi Xiao
This study focused on the mechanical properties and microstructure of fiber laser-welded joints of Ta-10W alloy manufactured by selective laser melting (SLM) and rolled. In the SLMed base material side of the weld, columnar grains were formed along the weld, extending up to half of the weld width. The base material’s anisotropy influenced the subgrain morphology, and grain orientation changed after welding. When the building direction of the SLMed Ta-10W was perpendicular to the welding direction, slender columnar subgrains were prone to forming in the SLM side weld. In contrast, when the building direction was parallel to the welding direction, equiaxed subgrains tended to form in the weld. In the rolling base material side weld, mainly equiaxed grains were formed, with subgrain morphology and orientation randomly distributed. In the weld center, fine-grain zones of 10–20 μm, comprising fine grains of 2–5 μm diameter, were observed in all welds under study. Room-temperature tensile strengths of both welds were approximately 620 MPa, falling between the strengths of the two base materials. Their fracture surfaces displayed a mixed mode of cleavage and intergranular fracture. High-temperature strengths of rolled-SLMed joints varied with SLM directions X and Z, reaching 124.94 and 107.87 MPa, respectively, and exhibiting similar fracture characteristics dominated by intergranular fracture.
{"title":"Microstructure and properties of SLMed Ta-10W and rolled Ta-10W fiber laser welded joint","authors":"Xin Du, Qiang Wu, Tong Zhang, Mingfu Wang, Jingmin Chen, J. Zou, Rongshi Xiao","doi":"10.2351/7.0001410","DOIUrl":"https://doi.org/10.2351/7.0001410","url":null,"abstract":"This study focused on the mechanical properties and microstructure of fiber laser-welded joints of Ta-10W alloy manufactured by selective laser melting (SLM) and rolled. In the SLMed base material side of the weld, columnar grains were formed along the weld, extending up to half of the weld width. The base material’s anisotropy influenced the subgrain morphology, and grain orientation changed after welding. When the building direction of the SLMed Ta-10W was perpendicular to the welding direction, slender columnar subgrains were prone to forming in the SLM side weld. In contrast, when the building direction was parallel to the welding direction, equiaxed subgrains tended to form in the weld. In the rolling base material side weld, mainly equiaxed grains were formed, with subgrain morphology and orientation randomly distributed. In the weld center, fine-grain zones of 10–20 μm, comprising fine grains of 2–5 μm diameter, were observed in all welds under study. Room-temperature tensile strengths of both welds were approximately 620 MPa, falling between the strengths of the two base materials. Their fracture surfaces displayed a mixed mode of cleavage and intergranular fracture. High-temperature strengths of rolled-SLMed joints varied with SLM directions X and Z, reaching 124.94 and 107.87 MPa, respectively, and exhibiting similar fracture characteristics dominated by intergranular fracture.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"28 17","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141816828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuyuan Tang, Xiangfan Nie, Haonian Wu, Ming Xu, Li Yan
Laser-induced shock wave (LSW) represents a significant phenomenon arising from the interaction between laser radiation and matter. In this study, we establish a finite element and optimization model constrained by a physical framework. Utilizing multichannel photon Doppler velocimeter experimental data as the target for matching, we directly acquire the spatiotemporal pressure characteristics of LSW through the multi-island genetic algorithm. The optimized outcomes show deviations from experimental results within 10%. Research reveals that the spatial uniformity of pressure deteriorates with increasing power density, accompanied by a gradual reduction in the proportion of peak pressure. Temporally, aside from the pressure caused by plasma, there are some small pressure peaks. When the laser's full width half maximum reaching 100 or 200 ns, the pressure decays prematurely. The duration of pressure does not extend to two to three times the duration of the laser pulse.
{"title":"Spatial-temporal characteristics analysis of laser-induced shockwave pressure by reverse optimization with multi-island genetic algorithm","authors":"Yuyuan Tang, Xiangfan Nie, Haonian Wu, Ming Xu, Li Yan","doi":"10.2351/7.0001403","DOIUrl":"https://doi.org/10.2351/7.0001403","url":null,"abstract":"Laser-induced shock wave (LSW) represents a significant phenomenon arising from the interaction between laser radiation and matter. In this study, we establish a finite element and optimization model constrained by a physical framework. Utilizing multichannel photon Doppler velocimeter experimental data as the target for matching, we directly acquire the spatiotemporal pressure characteristics of LSW through the multi-island genetic algorithm. The optimized outcomes show deviations from experimental results within 10%. Research reveals that the spatial uniformity of pressure deteriorates with increasing power density, accompanied by a gradual reduction in the proportion of peak pressure. Temporally, aside from the pressure caused by plasma, there are some small pressure peaks. When the laser's full width half maximum reaching 100 or 200 ns, the pressure decays prematurely. The duration of pressure does not extend to two to three times the duration of the laser pulse.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"104 21","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141820944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wire laser direct energy deposition enables the mass production of large-scale industrial components and parts. However, energy utilization efficiency is limited in conventional wire laser material deposition to avoid keyhole defects, resulting in a low deposition efficiency. This work presents a high-efficiency wire laser material deposition process that increases energy utilization by generating a keyhole in the filler wire, which can also avoid the keyhole defects in the deposited sample. The influence of process parameters on deposition quality and efficiency was thoroughly examined to determine the process window. A high deposition efficiency of 0.87 kg/(h kW) for 316L stainless steel was achieved with a laser power of 3 kW, approximately three times that of the conventional wire laser material deposition process. The defect-free multitrack and multilayer deposition demonstrated the feasibility of our proposed high-efficiency process.
{"title":"New method for high-efficiency keyhole-based wire direct energy deposition: Process innovation and characterization","authors":"Rongshi Xiao, Shihui Guo, Min Zheng, Baoqi Zhu, Qiang Wu, Jiejie Xu, Ting-Yun Huang","doi":"10.2351/7.0001388","DOIUrl":"https://doi.org/10.2351/7.0001388","url":null,"abstract":"Wire laser direct energy deposition enables the mass production of large-scale industrial components and parts. However, energy utilization efficiency is limited in conventional wire laser material deposition to avoid keyhole defects, resulting in a low deposition efficiency. This work presents a high-efficiency wire laser material deposition process that increases energy utilization by generating a keyhole in the filler wire, which can also avoid the keyhole defects in the deposited sample. The influence of process parameters on deposition quality and efficiency was thoroughly examined to determine the process window. A high deposition efficiency of 0.87 kg/(h kW) for 316L stainless steel was achieved with a laser power of 3 kW, approximately three times that of the conventional wire laser material deposition process. The defect-free multitrack and multilayer deposition demonstrated the feasibility of our proposed high-efficiency process.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":" 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141830807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fei Ji, Yuanxing Li, Wenxin Dong, Ping Jiang, Hui Chen
Ti6Al4V alloy and ZrO2 ceramic have similar application fields and complementary properties. Brazing connections can broaden the application range. When using sealing glass with good air tightness, good electrical insulation, and low connection temperature to connect, the solder is difficult to wet on the metal surface. The traditional method is to oxidize the surface of the alloy at a high temperature, but the film is not uniform and the treatment time is long. In this study, nanosecond laser surface treatment was used as a prewelding pretreatment method to form a micro-nano structure on the surface and perform oxidation treatment. It is particularly important to select the brazing process. After the laser parameters and processing times were determined, the effects of different welding temperatures and holding times on the properties of the joints were compared, and it was found that there were regular changes. Finally, it is concluded that the maximum shear strength is 46 MPa when the welding temperature is 650 °C and the holding time is 30 min. Under this process, the performance of the joint significantly improved under the dual effects of mechanical bonding and metallurgical bonding. This study provides a new idea for the connection of metal and ceramic and has reference value for the selection of the brazing process.
{"title":"Effect of brazing process on microstructure evolution and mechanical properties of Ti6Al4V/ZrO2 joints after laser surface treatment","authors":"Fei Ji, Yuanxing Li, Wenxin Dong, Ping Jiang, Hui Chen","doi":"10.2351/7.0001406","DOIUrl":"https://doi.org/10.2351/7.0001406","url":null,"abstract":"Ti6Al4V alloy and ZrO2 ceramic have similar application fields and complementary properties. Brazing connections can broaden the application range. When using sealing glass with good air tightness, good electrical insulation, and low connection temperature to connect, the solder is difficult to wet on the metal surface. The traditional method is to oxidize the surface of the alloy at a high temperature, but the film is not uniform and the treatment time is long. In this study, nanosecond laser surface treatment was used as a prewelding pretreatment method to form a micro-nano structure on the surface and perform oxidation treatment. It is particularly important to select the brazing process. After the laser parameters and processing times were determined, the effects of different welding temperatures and holding times on the properties of the joints were compared, and it was found that there were regular changes. Finally, it is concluded that the maximum shear strength is 46 MPa when the welding temperature is 650 °C and the holding time is 30 min. Under this process, the performance of the joint significantly improved under the dual effects of mechanical bonding and metallurgical bonding. This study provides a new idea for the connection of metal and ceramic and has reference value for the selection of the brazing process.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":" 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141830055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a method that can predict the interface width in an overlapping joint configuration for laser welding of Al alloys using sensors and a convolutional neural network (CNN)-based deep-learning model. The inputs for multi-input CNN-based deep-learning prediction models are spectral signals, represented by the light intensity measured by a spectrometer and dynamic images of the molten pool filmed by a charge-coupled device (CCD) camera. The interface width, used as learning data for modeling, was constructed as a database along with the process signal by cross-sectional analysis. In this study, we present results showing high accuracy in predicting the interface width in the overlap joint configuration for Al alloy laser welding. For predicting the interface width, five models are created and compared: a single CCD and spectrometer sensor algorithm, a multi-sensor algorithm with two input variables (CCD, spectrometer), a multi-sensor algorithm excluding the processing beam in the spectrometer data on the combination of Al 6014-T4 (top)/Al 6014-T4 (bottom), and a multi-sensor algorithm applied to the combination of Al 6014-T4 (top)/Al 5052-H32 (bottom). The multi-sensor algorithm with two input variables (CCD and spectrometer) on the same material combination showed the highest accuracy among the models.
我们介绍了一种利用传感器和基于卷积神经网络（CNN）的深度学习模型预测铝合金激光焊接重叠接头配置中界面宽度的方法。基于 CNN 的多输入深度学习预测模型的输入是光谱信号（由光谱仪测量的光强度和电荷耦合器件 (CCD) 摄像机拍摄的熔池动态图像表示）。作为建模学习数据的界面宽度是通过横截面分析与过程信号一起构建的数据库。在本研究中，我们展示了高精度预测铝合金激光焊接重叠接头配置界面宽度的结果。为了预测界面宽度，我们创建了五个模型并进行了比较：单一 CCD 和光谱仪传感器算法、具有两个输入变量（CCD、光谱仪）的多传感器算法、在 Al 6014-T4（上）/Al 6014-T4（下）组合的光谱仪数据中排除加工光束的多传感器算法，以及应用于 Al 6014-T4（上）/Al 5052-H32（下）组合的多传感器算法。在相同的材料组合中，具有两个输入变量（CCD 和光谱仪）的多传感器算法显示出最高的精确度。
{"title":"Prediction of interface width in overlap joint configuration for laser welding of aluminum alloy using sensors","authors":"Yoo-Eun Lee, Woo-In Choo, Sungbin Im, Seung Hwan Lee, Dong Hyuck Kam","doi":"10.2351/7.0001367","DOIUrl":"https://doi.org/10.2351/7.0001367","url":null,"abstract":"We present a method that can predict the interface width in an overlapping joint configuration for laser welding of Al alloys using sensors and a convolutional neural network (CNN)-based deep-learning model. The inputs for multi-input CNN-based deep-learning prediction models are spectral signals, represented by the light intensity measured by a spectrometer and dynamic images of the molten pool filmed by a charge-coupled device (CCD) camera. The interface width, used as learning data for modeling, was constructed as a database along with the process signal by cross-sectional analysis. In this study, we present results showing high accuracy in predicting the interface width in the overlap joint configuration for Al alloy laser welding. For predicting the interface width, five models are created and compared: a single CCD and spectrometer sensor algorithm, a multi-sensor algorithm with two input variables (CCD, spectrometer), a multi-sensor algorithm excluding the processing beam in the spectrometer data on the combination of Al 6014-T4 (top)/Al 6014-T4 (bottom), and a multi-sensor algorithm applied to the combination of Al 6014-T4 (top)/Al 5052-H32 (bottom). The multi-sensor algorithm with two input variables (CCD and spectrometer) on the same material combination showed the highest accuracy among the models.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"6 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141653817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A computer model predicting thresholds for laser induced corneal injury was used to systematically analyze wavelength, pulse duration, and beam diameter dependencies for wavelengths between 1200 and 1500 nm, for the exposure duration regime of 10 μs to 100 s. The thresholds were compared with the maximum permissible exposure (MPE) values to protect the cornea as specified in ANSI Z136.1-2022, ICNIRP 2013, and IEC 60825-1:2014. In the wavelength range between 1200 and 1400 nm, the dominant hazard transitions from the retina to the cornea. Consequently, limits are needed to protect both the cornea and the retina. In the lower wavelength range, the retinal limits are more conservative, while in the higher wavelength range, the corneal limits are lower. Comparison with injury thresholds shows that ANSI MPEs include a large safety margin for all wavelengths. Due to the 7 mm aperture stop defined in IEC 60825-1, levels permitted by the Class 3B limit exceed the predicted injury thresholds for small beam diameters and wavelengths between approximately 1350 and 1400 nm. The Class 3B limit does not appear to be sufficiently protective for these conditions. For skin MPEs, the margin between corneal injury thresholds and MPEs decreases steadily for wavelengths approaching 1400 nm. However, normal eye movements can be expected to reduce the effective exposure so that skin MPEs may serve as adequate limits to protect the cornea for wavelengths less than 1400 nm until a specific limit to protect the cornea is promulgated by ICNIRP.
{"title":"Comparison of laser induced corneal injury thresholds with safety limits for the wavelength range of 1200–1500 nm","authors":"K. Schulmeister, B. Stuck","doi":"10.2351/7.0001375","DOIUrl":"https://doi.org/10.2351/7.0001375","url":null,"abstract":"A computer model predicting thresholds for laser induced corneal injury was used to systematically analyze wavelength, pulse duration, and beam diameter dependencies for wavelengths between 1200 and 1500 nm, for the exposure duration regime of 10 μs to 100 s. The thresholds were compared with the maximum permissible exposure (MPE) values to protect the cornea as specified in ANSI Z136.1-2022, ICNIRP 2013, and IEC 60825-1:2014. In the wavelength range between 1200 and 1400 nm, the dominant hazard transitions from the retina to the cornea. Consequently, limits are needed to protect both the cornea and the retina. In the lower wavelength range, the retinal limits are more conservative, while in the higher wavelength range, the corneal limits are lower. Comparison with injury thresholds shows that ANSI MPEs include a large safety margin for all wavelengths. Due to the 7 mm aperture stop defined in IEC 60825-1, levels permitted by the Class 3B limit exceed the predicted injury thresholds for small beam diameters and wavelengths between approximately 1350 and 1400 nm. The Class 3B limit does not appear to be sufficiently protective for these conditions. For skin MPEs, the margin between corneal injury thresholds and MPEs decreases steadily for wavelengths approaching 1400 nm. However, normal eye movements can be expected to reduce the effective exposure so that skin MPEs may serve as adequate limits to protect the cornea for wavelengths less than 1400 nm until a specific limit to protect the cornea is promulgated by ICNIRP.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"63 22","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141654387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jilong Guo, Lilong Zhou, Yong Zhao, Feiyun Wang, Juan Fu, Xueyan Yang, Yinjun Liu
Welded T-joints of 945 shipbuilding steel are widely used in plate-beam connections, and their impact toughness directly affects the service life of shipboard structural components. However, current research efforts have primarily focused on the static mechanical properties of welded T-joints, with few scholars investigating the impact properties of welded T-joints under dynamic loading conditions. In this paper, laser-MAG hybrid welding of 945 shipbuilding steel T-joints is utilized to study the effects of heat input on the microstructure evolution and dynamic mechanical properties of welded T-joints. The results show that the increase in heat input results in a decrease in the cooling rate, which promotes the formation of lath martensite in weld metal and the formation of granular and lath bainite in coarse grain heat affected zone (HAZ). Concurrently, the higher heat input increases the width of the HAZ and leads to grain coarsening, resulting in a 298.9% increase in average grain area when the heat input rises from 12.1 to 14.6 kJ/cm. The changes in martensite content and morphology result in a reduction in the microhardness of welded T-joints. The HAZ becomes the most vulnerable region to dynamic impact loading, and the higher heat input leads to ductile fracture. Compared to high heat input, the drop hammer acceleration decreases by 34.0%, the maximum displacement increases by 45.9%, and the fracture energy increases by 43.1%, for low heat input. The changes in the drop hammer impact metrics further illustrate that welded T-joints with lower heat input are favorable for improving impact toughness.
945 号造船钢焊接 T 型接头广泛用于板梁连接，其冲击韧性直接影响船用结构部件的使用寿命。然而，目前的研究工作主要集中在焊接 T 型接头的静态力学性能上，很少有学者研究焊接 T 型接头在动态载荷条件下的冲击性能。本文利用激光-MAG 混合焊接 945 号造船钢 T 型接头，研究了热输入对焊接 T 型接头微观结构演变和动态力学性能的影响。结果表明，热输入的增加会导致冷却速度的降低，从而促进焊缝金属中板条马氏体的形成以及粗晶粒热影响区（HAZ）中粒状贝氏体和板条贝氏体的形成。同时，较高的热输入增加了热影响区的宽度并导致晶粒粗化，当热输入从 12.1 kJ/cm 上升到 14.6 kJ/cm 时，平均晶粒面积增加了 298.9%。马氏体含量和形态的变化导致焊接 T 型接头的显微硬度降低。热影响区成为最易受动态冲击载荷影响的区域，较高的热输入导致韧性断裂。与高热输入相比，低热输入的落锤加速度降低了 34.0%，最大位移增加了 45.9%，断裂能增加了 43.1%。落锤冲击指标的变化进一步说明，热输入较低的焊接 T 型接头有利于提高冲击韧性。
{"title":"Microstructure and dynamic fracture behaviors of laser-MAG hybrid welded T-joints of 945 shipbuilding steel with different heat inputs","authors":"Jilong Guo, Lilong Zhou, Yong Zhao, Feiyun Wang, Juan Fu, Xueyan Yang, Yinjun Liu","doi":"10.2351/7.0001397","DOIUrl":"https://doi.org/10.2351/7.0001397","url":null,"abstract":"Welded T-joints of 945 shipbuilding steel are widely used in plate-beam connections, and their impact toughness directly affects the service life of shipboard structural components. However, current research efforts have primarily focused on the static mechanical properties of welded T-joints, with few scholars investigating the impact properties of welded T-joints under dynamic loading conditions. In this paper, laser-MAG hybrid welding of 945 shipbuilding steel T-joints is utilized to study the effects of heat input on the microstructure evolution and dynamic mechanical properties of welded T-joints. The results show that the increase in heat input results in a decrease in the cooling rate, which promotes the formation of lath martensite in weld metal and the formation of granular and lath bainite in coarse grain heat affected zone (HAZ). Concurrently, the higher heat input increases the width of the HAZ and leads to grain coarsening, resulting in a 298.9% increase in average grain area when the heat input rises from 12.1 to 14.6 kJ/cm. The changes in martensite content and morphology result in a reduction in the microhardness of welded T-joints. The HAZ becomes the most vulnerable region to dynamic impact loading, and the higher heat input leads to ductile fracture. Compared to high heat input, the drop hammer acceleration decreases by 34.0%, the maximum displacement increases by 45.9%, and the fracture energy increases by 43.1%, for low heat input. The changes in the drop hammer impact metrics further illustrate that welded T-joints with lower heat input are favorable for improving impact toughness.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"61 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141654795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The transient temperature field during laser-directed energy deposition has a crucial impact on the quality of manufactured parts. In this study, in order to solve the problems that the transient temperature field is difficult to measure directly and the traditional numerical simulation data are not real time and the model is inaccurate, a transient temperature field twin method based on the optimization of measured parameters is proposed. First, based on heat transfer, a twin model of temperature-dependent thermophysical parameter fluctuations is built, and the model defines the time-dependent power parameters. In order to perform numerical simulations for the acquisition of the temperature field distribution and to verify the accuracy of the model through the comparison of synchronized lateral validation experiments, an integrated measurement-validation experimental system is constructed. A twin model validation method is proposed, in which the frontal measurement experiments are synchronized with the lateral validation experiments. The real-time radius of the molten pool and temperature parameters are extracted from the frontal measurement experiments and inputted into the twin model. In order to confirm the great realism of the built twin model, the simulation of the twin temperature field under various laser strengths is examined in the last step. The experimental findings demonstrate that the temperature field twin physical model developed in this work is capable of faithfully simulating temperature field variations brought about by real-time laser additive process parameter changes. This approach reduces the number and expense of actual tests, helps to adjust process parameters to ensure an improvement in product quality and performance, and makes up for the lack of real-time problems in traditional numerical simulation. It also improves the accuracy and real-time simulation model. Finally, it has the ability to instantly provide input and track the production process in real time. It helps to advance the application of digital-twin technology in the field of additive manufacturing.
{"title":"Research on twin method of transient temperature field in laser additive manufacturing based on optimization of measured parameters","authors":"Zhen-Ying Xu, Yao-Feng Wang, Ying-Jun Lei","doi":"10.2351/7.0001383","DOIUrl":"https://doi.org/10.2351/7.0001383","url":null,"abstract":"The transient temperature field during laser-directed energy deposition has a crucial impact on the quality of manufactured parts. In this study, in order to solve the problems that the transient temperature field is difficult to measure directly and the traditional numerical simulation data are not real time and the model is inaccurate, a transient temperature field twin method based on the optimization of measured parameters is proposed. First, based on heat transfer, a twin model of temperature-dependent thermophysical parameter fluctuations is built, and the model defines the time-dependent power parameters. In order to perform numerical simulations for the acquisition of the temperature field distribution and to verify the accuracy of the model through the comparison of synchronized lateral validation experiments, an integrated measurement-validation experimental system is constructed. A twin model validation method is proposed, in which the frontal measurement experiments are synchronized with the lateral validation experiments. The real-time radius of the molten pool and temperature parameters are extracted from the frontal measurement experiments and inputted into the twin model. In order to confirm the great realism of the built twin model, the simulation of the twin temperature field under various laser strengths is examined in the last step. The experimental findings demonstrate that the temperature field twin physical model developed in this work is capable of faithfully simulating temperature field variations brought about by real-time laser additive process parameter changes. This approach reduces the number and expense of actual tests, helps to adjust process parameters to ensure an improvement in product quality and performance, and makes up for the lack of real-time problems in traditional numerical simulation. It also improves the accuracy and real-time simulation model. Finally, it has the ability to instantly provide input and track the production process in real time. It helps to advance the application of digital-twin technology in the field of additive manufacturing.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"38 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141653867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Laser transmission welding is a highly accurate method for joining plastics, but its diverse process parameters require effective modeling for optimal results. Traditional artificial neural networks (ANNs) typically establish predictive models between laser processing parameters and welding strength, neglecting the crucial role of welding morphology in feature extraction, thus diminishing accuracy. To address this, we developed a serial ANN model based on statistically evident correlations, which predicts joint morphology and strength sequentially, resulting in a 47% improvement in predictive accuracy and a mean error of just 7.13%. This two-layered approach effectively reduces the stepwise propagation of errors in ANNs, allowing the first layer to provide a refined data representation for the second layer to predict welding strength. Furthermore, finding the optimal laser parameter set is time-consuming and computationally demanding with traditional ANN-based optimization methods. To address this, we integrated the Markov decision process with the serial ANN for the first time and proposed a novel varying step strategy for the model, enabling a balance of swift convergence and avoidance of suboptimal solutions. Notably, the Markov-serial ANN model attained enhanced optimization results using only 15.5% of the computational resources required by a standard parameter interval optimization methodology. Welding experiments verified the reliability of the Markov-serial ANN, achieving a mean error of 4.54% for welding strength.
激光透射焊接是一种高精度的塑料连接方法，但其工艺参数多种多样，需要建立有效的模型才能获得最佳效果。传统的人工神经网络（ANN）通常在激光加工参数和焊接强度之间建立预测模型，忽略了焊接形态在特征提取中的关键作用，从而降低了精度。为解决这一问题，我们开发了一种基于统计学上明显相关性的串行人工神经网络模型，该模型可依次预测接头形态和强度，从而将预测精度提高了 47%，平均误差仅为 7.13%。这种双层方法有效地减少了人工神经网络中误差的逐步传播，使第一层能够为第二层预测焊接强度提供精细的数据表示。此外，传统的基于 ANN 的优化方法需要耗费大量时间和计算量才能找到最佳激光参数集。为此，我们首次将马尔可夫决策过程与序列 ANN 相结合，并为模型提出了一种新颖的变化步长策略，从而在快速收敛和避免次优解之间实现了平衡。值得注意的是，马尔可夫序列 ANN 模型仅使用了标准参数区间优化方法所需计算资源的 15.5%，就获得了增强的优化结果。焊接实验验证了马尔可夫序列 ANN 的可靠性，焊接强度的平均误差为 4.54%。
{"title":"Prediction and optimization of joint quality in laser transmission welding using serial artificial neural networks and their integration with Markov decision process","authors":"Yuxuan Liu, Fei Liu, Wuxiang Zhang, Xilun Ding, Fumihito Arai","doi":"10.2351/7.0001384","DOIUrl":"https://doi.org/10.2351/7.0001384","url":null,"abstract":"Laser transmission welding is a highly accurate method for joining plastics, but its diverse process parameters require effective modeling for optimal results. Traditional artificial neural networks (ANNs) typically establish predictive models between laser processing parameters and welding strength, neglecting the crucial role of welding morphology in feature extraction, thus diminishing accuracy. To address this, we developed a serial ANN model based on statistically evident correlations, which predicts joint morphology and strength sequentially, resulting in a 47% improvement in predictive accuracy and a mean error of just 7.13%. This two-layered approach effectively reduces the stepwise propagation of errors in ANNs, allowing the first layer to provide a refined data representation for the second layer to predict welding strength. Furthermore, finding the optimal laser parameter set is time-consuming and computationally demanding with traditional ANN-based optimization methods. To address this, we integrated the Markov decision process with the serial ANN for the first time and proposed a novel varying step strategy for the model, enabling a balance of swift convergence and avoidance of suboptimal solutions. Notably, the Markov-serial ANN model attained enhanced optimization results using only 15.5% of the computational resources required by a standard parameter interval optimization methodology. Welding experiments verified the reliability of the Markov-serial ANN, achieving a mean error of 4.54% for welding strength.","PeriodicalId":508142,"journal":{"name":"Journal of Laser Applications","volume":"114 45","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141666014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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