Effects on mechanical properties in electron beam welding of TC4 alloy by laser shock processing

The surface of TC4 titanium alloy welding line by electron beam welding (EBW) was processed by high power Q-switched and repetition-rate Nd: glass laser. Effects of laser power and spot diameter on residual stress and microhardness of the TC4 alloy welding line by laser shock processing (LSP) have been analyzed. Results show that residual stresses almost do not change as laser power is 45.9 J, spot diameter is ϕ9 mm; While laser power is 45.9 J, spot diameter less than ϕ3 mm, the distribution of residual stress in welding line occurs obvious variation, which residual stress increase obviously with spot diameter decrease. When power density is bigger than 1.8 × 10¹⁰ W/cm², residual stresses of electron beam welding line occur change by LSP, which improve obviously residual stress distribution; while laser power is bigger than 1.2 × 10¹⁰ W/cm², the surface micro-hardness of electron beam welding line occurs change by LSP, which improve obviously micro-hardness distribution. Mechanical properties of TC4 titanium alloy welding line will be improved by LSP, which provides experimental foundation for further controlling the distributions of residual stress and micro-hardness during laser shock processing. __________ Translated from Journal of Jiangsu University (Natural Science), 2006, 27(3): 207–210 [译自: 江苏大学学报 (自然科学版)]     

铝合金激光冲击强化技术的研究

对激光冲击诱导的应力波峰值压力进行了理论估算，提出了激光参数的选择原则。对铝合金２０２４Ｔ６２进行的激光冲击试验的结果表明，经冲击试件的疲劳寿命获得了很大程度的提高。最后对激光冲击强化的机理进行了初步分析。     

Effects of laser shock processing on mechanical properties of laser welded ANSI 304 stainless steel joint

With the rapid development of engineering component with integration,high-speed and multi-parameter,traditional techniques haven’t met practical needs in extreme service environment.Laser welding,a new welding technology,has been widely used.However,it would generate the drop of mechanical properties for laser welded joint due to its thermal effect.Laser shock processing(LSP) is one of the most effective methods to improve the mechanical properties of laser welded ANSI 304 stainless steel joint.In this paper,the effects of LSP on the mechanical properties of laser welded ANSI 304 stainless steel joint have been investigated.The welded joint on the front of the tensile samples is treated by LSP impacts,and the overlapping rate of the laser spot is 50%.The tensile test of the laser welded joint with and without LSP impacts is carried out,and the fracture morphology of the tensile samples is analyzed by scanning electron microscope(SEM).Compared with the yield strength of 11.70 kN,the tensile strength of 37.66 kN,the yield-to-tensile strength ratio of 0.310 7,the elongation of 25.20%,the area reduction of 32.68% and the elastic modulus of 13 063.876 MPa,the corresponding values after LSP impacts are 14.25 kN,38.74 kN,0.367 8,26.58%,42.29% and 14 754.394 MPa,respectively.Through LSP impacts,the increasing ratio of the yield strength and tensile strength are 121.79% and 102.87%,respectively;the elongation and area reduction are improved by 5.48% and 29.38%,respectively.By comparing with coarse fracture surface of the welded joint,the delamination splitting with some cracks in the sharp corner of the welded joint and asymmetric dimples,LSP can cause brighter fracture surface,and finer and more uniform dimples.Finally,the schematic illustration of dimple formation with LSP is clearly described.The proposed research ensures that the LSP technology can clearly improve the yield strength,tensile strength,yield-to-tensile strength ratio,elongation,area reduction and elastic modulus of the welded joint.The enhancement mechanism of LSP on laser welded ANSI 304 stainless steel joint is mainly due to the fact that the refined and uniform dimples effectively delay the fracture of laser welded joints.     

激光冲击强化对LZ50车轴钢疲劳性能影响试验研究

为了研究激光冲击强化对LZ50车轴钢疲劳性能的影响,对LZ50车轴钢车轴试样进行激光冲击强化处理并在JD-1轮轨模拟试验机上进行了旋转弯曲疲劳试验。结果显示:采用不同参数激光冲击强化处理的2个试样,硬度分别增大18%和27%;对LZ50车轴钢试样的过盈配合面进行激光冲击处理后产生了塑性变形层,形成了较高的残余压应力;试验后试样过盈配合表面两侧区域都可见明显的环形损伤带,出现了以剥落和犁沟为特征的磨损形貌,损伤机制为磨粒磨损、氧化磨损和剥层。激光冲击前后试样断口形貌特征相似,疲劳源呈多源性;在裂纹扩展区域段观察到大量的准解理小面,属于脆性穿晶断裂;瞬断区内出现大量韧窝和二次裂纹。激光冲击强化处理显著提高了车轴钢的疲劳寿命,不同激光冲击强化参数处理的2个车轴试样疲劳寿命比未处理试样疲劳寿命分别提高31%和21%。     

企业内部用户网络访问监控系统的研究与实现

在企业建立的内部网络中,为了防止员工滥用网络资源、通过网络向外传播机密数据,需要对用户的网络访问进行监视和控制。在研究了Winsock2 SPI技术之后,提出一种基于LSP监控用户访问网络的方法,并利用该方法实现了网络访问监控系统。该系统能监视每个用户访问网络的具体情况,可以针对不同用户使用的应用程序制定不同的网络访问控制规则,并且能按制定的规则控制应用程序的网络访问。     

一种新农村钢结构住宅节能墙体应用技术研究

介绍一种新农村钢结构住宅节能墙体系统的构造及特性,针对保温与防火性能关键指标要求,给出评价其防火性能的试验结论和热工计算方法,确定系统材料主要性能指标,简述其节点构造和施工做法,阐明其在农村钢结构住宅建筑工程中的应用关键技术。     

EFFECTS OF LASER SHOCK PROCESSING ON MATERIAL'S PROPERTIES

ＥＦＦＥＣＴＳＯＦＬＡＳＥＲＳＨＯＣＫＰＲＯＣＥＳＳＩＮＧＯＮＭＡＴＥＲＩＡＬＳＰＲＯＰＥＲＴＩＥＳ①ＤａｉＳｈｕｊｕａｎ，ＬｉｕＦｕｒｏｎｇ，ＹａｎｇＸｉａｏ，ＺｏｕＨｏｎｇｃｈｅｎｇＮａｔｉｏｎａｌＬａｂｏｒａｔｏｒｙｏｆＰｌａｓｔｉｃＦｏｒｍ...     

多段伪线在PTN设备中的实现方案设计

在PTN设备业务模型基础上提出了多段伪线(MS-PW)的一种实现方案,论述了该方案在实现传输路径汇聚与保护叠加的思路,通过实验对该方案的实现效果进行了测试验证.     

Effects of laser shock processing on stress corrosion cracking susceptibility of AZ31B magnesium alloy

Laser shock processing (LSP) is a new technique for strengthening metals. The effects of LSP on the stress corrosion cracking (SCC) susceptibility of AZ31B magnesium (Mg) alloy were investigated. Water-immersed specimens of AZ31B magnesium alloy were shocked by Q-switched Nd: glass laser with a wavelength of 1064 nm. A fine-grained structure with an average sub-grain size of 5.8 μm was obtained after four laser impacts. Residual stress distribution as a function of depth was assessed by using X-ray diffraction technology. It was observed that with increasing the number of laser impacts, the compressive residual stress near the surface increased. The depth of the compressive residual stress induced by LSP exceeded 0.8 mm from the surface. SCC test in 1 wt.% NaOH solution showed that LSP retarded the SCC initiation and growth in AZ31B Mg alloy.     

基于ATM的MPLS数据转发技术分析

多协议标记交换(MPLS)具有技术的高效性与良好的扩展性,异步传输模式技术(ATM)具有强大的转发能力及高可靠性,通过对标记交换的链路层数据转发机制与网络层的选路机制结合进行研究,提出一种基于ATM的MPLS数据转发方法,并对其进行设计和实现。通过模拟实验对功能和性能进行验证表明,此方法能够提高数据业务的效率和可靠性。