Laser-arc hybrid welding at a speed of 6 000 mm/min is carried out on 2 mm thick magnesium alloy AZ61 plateand completely-penetrated butt joints are obtained, lnvestigations of the influence of parameters on weld fo...Laser-arc hybrid welding at a speed of 6 000 mm/min is carried out on 2 mm thick magnesium alloy AZ61 plateand completely-penetrated butt joints are obtained, lnvestigations of the influence of parameters on weld formation show that Ihe addition of pulsed laser can effctively enhance tlle heat penetrability attd directivity nf the hybrid heat source. Measurements on microstructures and mechanical properties the joint indicate that grain in the.fhsion zone is refined and the grain size is sensitive to the arc current ; the fitsioa zone exhibits the highest hardaess; the tensile strength of the joint reaches 93% of base metal; there is the brittle fracture along the grain bozmdaries in the fusion zone. High-speed camera images exhibit that although the two adjacent laser pulses can not overlap, the recorery relaxation of the concentrated electric arc after laser intlse action can still maintain the continuous welding process.展开更多
This paper reports the effect of friction stir welding （FSW） process parameters on tensile strength of cast LM6 aluminium alloy. Joints were made by using different combinations of tool rotation speed, welding speed...This paper reports the effect of friction stir welding （FSW） process parameters on tensile strength of cast LM6 aluminium alloy. Joints were made by using different combinations of tool rotation speed, welding speed and axial force each at four levels. The quality of weld zone was investigated using macrostructure and microstructure analysis. Tensile strength of the joints were evaluated and correlated with the weld zone hardness and microstructure. The joint fabricated using a rotational speed of 900 r/min, a welding speed of 75 mm/min and an axial force of 3 kN showed superior tensile strength compared with other joints. The tensile strength and microhardness of the welded joints for the optimum conditions were 166 MPa and 64.8 Hv respectively.展开更多
The thin wafer(such as BOC) is often cracked easily after Die-Attach process and large numbers of products in some semiconductor company failed as a result of crack.So it is urgent to get the solution to assure the qu...The thin wafer(such as BOC) is often cracked easily after Die-Attach process and large numbers of products in some semiconductor company failed as a result of crack.So it is urgent to get the solution to assure the quality and increase the yield.This article explained the relation of crack,the chip strength,as well as Die-Attach pin-up speed and how to solve that issue.For example,additional polishing process can significantly decrease the grind mark damage;pin-up speed optimization can make pin-up force best.So linear crack of thin chip can be avoided effectively.展开更多
【目的】通过研究不同热循环下高强钢热影响区的微观组织与力学性能转变规律,为以后相同钢种的实际工程应用提供理论依据。【方法】以30MnCrNiMo高强钢为研究对象,由于钢在连续加热和冷却过程中,会经历几个相变过程,在此过程中,钢的晶...【目的】通过研究不同热循环下高强钢热影响区的微观组织与力学性能转变规律,为以后相同钢种的实际工程应用提供理论依据。【方法】以30MnCrNiMo高强钢为研究对象,由于钢在连续加热和冷却过程中,会经历几个相变过程,在此过程中,钢的晶格结构发生改变,从而引起体积的变化,所以会在正常的膨胀曲线上出现转折点,基于此原理,利用Gleeble-3500热模拟试验机分别建立低加热速度为150℃/s和高加热速度为1100℃/s的焊接热影响区连续冷却转变(Simulated heat affected zone continuous cooling transforming,SHCCT)曲线,对其微观组织转变规律进行了对比与分析。【结果】结果表明,在低加热速度和高加热速度下的SHCCT曲线图均包含M,M+B,B,B+P+F 4个区域,且4个区域对应的硬度值由500 HV1向200 HV1递减;低加热速度SHCCT曲线在3.0℃/s的冷却速度下就可以发生F和P转变,而高加热速度SHCCT曲线需要在冷却速度为0.5℃/s时才能产生F和P转变;与低加热速度下的SHCCT曲线相比,高加热速度下的SHCCT曲线具有更高的Ac1,Ac3和Ms点,且Ac1与Ac3的温度差增大,F和P转变需要更长的孕育期。【结论】在相同钢种的实际工程应用中,为了得到板条状马氏体组织以达到良好的使用性能,可以在激光-熔化极活性气体保护(Metal active gas welding,MAG)复合焊接时,将冷却速度控制在7.5℃/s以上,在单MAG焊接时,将冷却速度控制在10.0℃/s以上。展开更多
检索足球运动员力量与其它身体素质结合训练的相关文献,整合并评述结合训练的研究进展。在Web of science、PubMed、中国知网数据库检索2000———2023年发表的相关文献,依照排除和纳入标准最终得到文献36篇,其中力量结合耐力、协调、...检索足球运动员力量与其它身体素质结合训练的相关文献,整合并评述结合训练的研究进展。在Web of science、PubMed、中国知网数据库检索2000———2023年发表的相关文献,依照排除和纳入标准最终得到文献36篇,其中力量结合耐力、协调、速度、灵敏的文献分别为12、5、11、8篇。研究结果显示:①在力量与耐力结合训练方面,任意负荷强度均能提升非高水平运动员的力量和心肺功能,而精英运动员则需要次极限强度的刺激才能提升其专项力量、冲刺速度、灵敏性及有氧耐力,且课内训练内容的顺序效益相近;②在力量与协调结合训练方面,先进行动态或静态协调训练可为随后的高质量力量训练奠定基础,训练安排选用板块分期模式更为有效;③在力量与速度结合训练方面,超等长与速度相结合的日间交替安排有助于提高冲刺及跳跃能力,而课内交替练习对提升跳跃、冲刺和变向能力等专项力量和速度的效果良好;④在力量与灵敏结合训练方面,日常技战术训练中采用力量与灵敏的课内交替,可以提高其跳跃、冲刺、转向及平衡能力。综上所述,可以从阶段、周、课3个层次建构足球运动员多素质相结合的训练组织与安排。展开更多
文摘Laser-arc hybrid welding at a speed of 6 000 mm/min is carried out on 2 mm thick magnesium alloy AZ61 plateand completely-penetrated butt joints are obtained, lnvestigations of the influence of parameters on weld formation show that Ihe addition of pulsed laser can effctively enhance tlle heat penetrability attd directivity nf the hybrid heat source. Measurements on microstructures and mechanical properties the joint indicate that grain in the.fhsion zone is refined and the grain size is sensitive to the arc current ; the fitsioa zone exhibits the highest hardaess; the tensile strength of the joint reaches 93% of base metal; there is the brittle fracture along the grain bozmdaries in the fusion zone. High-speed camera images exhibit that although the two adjacent laser pulses can not overlap, the recorery relaxation of the concentrated electric arc after laser intlse action can still maintain the continuous welding process.
文摘This paper reports the effect of friction stir welding （FSW） process parameters on tensile strength of cast LM6 aluminium alloy. Joints were made by using different combinations of tool rotation speed, welding speed and axial force each at four levels. The quality of weld zone was investigated using macrostructure and microstructure analysis. Tensile strength of the joints were evaluated and correlated with the weld zone hardness and microstructure. The joint fabricated using a rotational speed of 900 r/min, a welding speed of 75 mm/min and an axial force of 3 kN showed superior tensile strength compared with other joints. The tensile strength and microhardness of the welded joints for the optimum conditions were 166 MPa and 64.8 Hv respectively.
文摘The thin wafer(such as BOC) is often cracked easily after Die-Attach process and large numbers of products in some semiconductor company failed as a result of crack.So it is urgent to get the solution to assure the quality and increase the yield.This article explained the relation of crack,the chip strength,as well as Die-Attach pin-up speed and how to solve that issue.For example,additional polishing process can significantly decrease the grind mark damage;pin-up speed optimization can make pin-up force best.So linear crack of thin chip can be avoided effectively.
文摘【目的】通过研究不同热循环下高强钢热影响区的微观组织与力学性能转变规律,为以后相同钢种的实际工程应用提供理论依据。【方法】以30MnCrNiMo高强钢为研究对象,由于钢在连续加热和冷却过程中,会经历几个相变过程,在此过程中,钢的晶格结构发生改变,从而引起体积的变化,所以会在正常的膨胀曲线上出现转折点,基于此原理,利用Gleeble-3500热模拟试验机分别建立低加热速度为150℃/s和高加热速度为1100℃/s的焊接热影响区连续冷却转变(Simulated heat affected zone continuous cooling transforming,SHCCT)曲线,对其微观组织转变规律进行了对比与分析。【结果】结果表明,在低加热速度和高加热速度下的SHCCT曲线图均包含M,M+B,B,B+P+F 4个区域,且4个区域对应的硬度值由500 HV1向200 HV1递减;低加热速度SHCCT曲线在3.0℃/s的冷却速度下就可以发生F和P转变,而高加热速度SHCCT曲线需要在冷却速度为0.5℃/s时才能产生F和P转变;与低加热速度下的SHCCT曲线相比,高加热速度下的SHCCT曲线具有更高的Ac1,Ac3和Ms点,且Ac1与Ac3的温度差增大,F和P转变需要更长的孕育期。【结论】在相同钢种的实际工程应用中,为了得到板条状马氏体组织以达到良好的使用性能,可以在激光-熔化极活性气体保护(Metal active gas welding,MAG)复合焊接时,将冷却速度控制在7.5℃/s以上,在单MAG焊接时,将冷却速度控制在10.0℃/s以上。
文摘检索足球运动员力量与其它身体素质结合训练的相关文献,整合并评述结合训练的研究进展。在Web of science、PubMed、中国知网数据库检索2000———2023年发表的相关文献,依照排除和纳入标准最终得到文献36篇,其中力量结合耐力、协调、速度、灵敏的文献分别为12、5、11、8篇。研究结果显示:①在力量与耐力结合训练方面,任意负荷强度均能提升非高水平运动员的力量和心肺功能,而精英运动员则需要次极限强度的刺激才能提升其专项力量、冲刺速度、灵敏性及有氧耐力,且课内训练内容的顺序效益相近;②在力量与协调结合训练方面,先进行动态或静态协调训练可为随后的高质量力量训练奠定基础,训练安排选用板块分期模式更为有效;③在力量与速度结合训练方面,超等长与速度相结合的日间交替安排有助于提高冲刺及跳跃能力,而课内交替练习对提升跳跃、冲刺和变向能力等专项力量和速度的效果良好;④在力量与灵敏结合训练方面,日常技战术训练中采用力量与灵敏的课内交替,可以提高其跳跃、冲刺、转向及平衡能力。综上所述,可以从阶段、周、课3个层次建构足球运动员多素质相结合的训练组织与安排。
