Nuclear-grade pipelines are essential for nuclear safety, and their failure can lead to severe accidents. Traditional deterministic methods tend to be overly conservative, overlook uncertainties in key factors, and struggle to accurately assess reliability under complex conditions. This paper aims to present a probabilistic fracture mechanics methodology to evaluate the reliability of circumferential cracks in primary piping welds under transient loads. A dedicated software tool, developed based on this method, calculates rupture and leakage probabilities by incorporating parameter uncertainties alongside deterministic fracture models. Furthermore, the influence of various in-service inspection schedules on weld reliability is examined through case studies. The results indicate that excessively long inspection intervals result in actual failure probabilities at 60 years that exceed the safety goal of 10-6 failures per year. In accordance with current ASME Code, Section XI, the first inspection should occur by the 10th year, while subsequent intervals may be optimized to every 20 years. Sensitivity analyses reveal that the initial crack depth and crack half-angle have the greatest impact on probabilities, followed by the tensile strength, the safety factor, the yield strength, and the probability of detection model.

In this study, the applicability of the notched plate tension (NPT) specimen for establishing the multiaxial stress rupture criterion (MSRC) of the titanium alloy Ti-6Al-2Cr-2Mo is systematically evaluated using direct, indirect, and empirical determination methods. The investigation considers four widely adopted MSRCs: the Sdobyrev-Hayhurst-Leckie (SHL), Cane, and Nix criteria-collectively referred to as Type-1 MSRC with an adjustable factor-and the Huddleston criterion, referred to as Type-2 MSRC without such a factor. Results demonstrate that the suitability of the NPT specimen depends on the specific MSRC considered, the stress-state factor, the notch acuity, and the location from which stresses are extracted. The three Type-1 MSRCs yield essentially equivalent predictions of multiaxial creep life; however, unlike circumferentially notched tension (CNT) specimens, NPT specimens are unsuitable for direct calibration of Type-1 MSRCs, as the determined adjustable factor exhibits high sensitivity to both stress-state factor and notch acuity, and often falls well below zero-outside its physically admissible range. For the Type-2 MSRC, close agreement between predicted and experimental creep lives is obtained only when stress components at the notch center center, rather than at the skeletal point, are used. The intrinsic equivalence of the three Type-1 MSRCs is also examined. To address the limitations of NPT specimens in Type-1 MSRC calibration, two NPT-based approaches are proposed and validated, enabling a more reliable determination of MSRC for creeping material.

Fracture toughness at different temperatures is important in engineering for the integrity assessment of reactor pressure vessels. However, the large dependence on temperature and scatter in the ductile-to-brittle transition temperature region, along with the application of different indexing parameters, results in mass uncertainties in fracture toughness. In this paper, these uncertainties were quantified and characterized based on the Oak Ridge National Laboratory KIc database. The reference nil-ductility transition temperature RTNDT and reference temperature T0 were used as indices for the epistemic uncertainties. The quantity RTNDT - T0 was characterized by a three-parameter Weibull distribution using the commonly used parameter estimation methods. Combining the Master Curve method, a Weibull statistical model of the plain strain fracture toughness KIc was established to account for the aleatory uncertainties. A procedure was proposed for treating the epistemic and aleatory uncertainties for probabilistic fracture mechanics analysis. The effects of fracture toughness uncertainties on the crack initiation probability were evaluated for a cracked pressure vessel. The results show that considering both epistemic and aleatory uncertainties can reduce over-conservatism, and epistemic uncertainties strongly affect the crack initiation probability.

激光-CMT复合焊接是将激光焊接与冷金属过渡焊接(CMT)结合的一种新型激光电弧复合焊,与传统的激光复合焊接相比,其热输入极低,焊接过程更加稳定,基本无飞溅,而且生产效率和焊接质量均得到提高.本文介绍了激光-CMT复合焊接的原理及特点,概括了激光-CMT复合焊接中接头、熔池形貌、熔滴过渡以及焊缝成形等方面的研究现状以及目前存在的一些问题,最后总结了激光-CMT复合焊接的发展方向和研究重点.

激光-CMT复合焊接是将高能束激光与冷金属过渡(CMT)技术相结合的一种新型激光-电弧复合焊接技术,与传统的激光-MIG复合焊接相比,CMT工艺热输入极低,焊接过程更加稳定,能够实现高效无飞溅焊接过程,易获得高质量焊接接头.该项技术越来越受到国内外学者关注,在难熔难焊连接方面被不断探索和认知,具有广泛的工业应用场景.在分析相关文献的基础上,首先,概述了激光-CMT复合焊接系统构成及内涵,介绍了激光-CMT复合焊接中焊缝成形、熔滴过渡、熔池形貌以及焊接接头等方面的发展现状,以及目前还存在的一些问题;其次,提出了关于激光-CMT复合焊接过程的模拟仿真必要性及研究方法;最后,展望了激光-CMT复合焊接技术的未来发展方向和研究重点.

以Arduino为开源的物理计算平台,Marlin为开源固件,将雕刻技术与主从嵌入式系统相结合,对激光雕刻机进行了结构与控制系统的设计.设计出了便携式的激光雕刻机设备,具有稳定性高、简单可替换、便于后期升级的优点.

高强铝合金在激光焊接时,易出现气孔、热裂纹、焊接接头性能差、厚板与不等厚板难以焊接、熔池温度场与流场变化难以测量等问题,严重限制着高强铝合金的发展.目前,双焦点激光焊接技术能够有效地改善高强铝合金激光焊接中出现的问题.本文简要介绍了双焦点激光焊接的原理及实现方式,探究双焦点激光焊接对上述高强铝合金激光焊接中出现的问题的影响.

随着生态文明建设逐渐成为城市绿色、低碳发展的重要措施,人们将全面落实城市生活垃圾分类政策,从而保证社会持续发展.现阶段,生活垃圾的30％左右都可回收利用,提高垃圾的利用率并实现可持续发展,已成为我国亟待解决的问题.本文详细介绍了垃圾分类智能预处理收集箱的工作原理,分析其主要的设计要点和技术性能,实现垃圾预处理,提高资源利用效率.

在高速增长的快递业背后,大量的快递包装产生的能源消耗和环境污染等问题给环境带来沉重的负担,并造成巨大的资源浪费.目前我国居民生活垃圾新增部分90％都来自于电商包裹,快递包装垃圾将造成难以估计的危害.本文简要介绍了循环理念下做好折叠快递箱绿色设计工作的意义,分析其主要的设计要点、技术性能和工作原理,希望能有效减少快递包装的浪费,为居民提供一个更为干净、舒适的居住空间.

据中国城市环境卫生协会统计,在我国每年处理产生垃圾中,生活垃圾所占比例约10％,其中有30％至40％是可以回收利用的资源.因此,生活垃圾分类处理,已成为我国现阶段亟待解决的问题.本文主要介绍了通过“互联网+”运营管理服务模式的垃圾分类代扔服务,来实现对居民所扔垃圾进行完整的数据统计、分析与管理;确保整个垃圾分类代扔服务行业向着健康公益型的方向发展.

针对7系列超硬铝在传统熔焊过程中易出现热裂纹、气孔和焊接接头软化等问题,研究振动焊接工艺过程中,焊接工艺参数变化与焊接接头强度间的非线性关系机理,建立基于焊接过程工艺参数测量数据的7075超硬铝振动焊接接头强度非线性时间序列预测模型.文中在7075超硬铝振动焊接过程参数测量数据的基础上,建立了焊接过程参数时间序列,并在此基础上研究建立了焊接过程系统相空间重构参数及确定性检验方法.根据重构相空间的相点演化轨迹与焊接接头强度参数间的非线性关系,建立相空间相点演化轨迹的人工神经网络拟合模型,对焊接接头的断后伸长率、抗拉强度、硬度、焊缝余高、晶枝最大粗度、晶粒数量等物理参数进行计算.根据建立的模型进行的一系列焊接接头强度试验显示.结果表明,该模型的预测结果可以满足工程需要,具有工程实用价值.

随着物流行业和互联网的快速发展,AGV等智能物流设备被大量应用于各行各业.本文基于AGV智能物流机器人从仓储物流机器人硬件和软件两个主要方面对机器人所需材料和硬件结构进行了选型和设计,并对导航、避障、举升等软件模块进行了设计.设计出一款智能化、便捷化、成本低的举升物流机器人,并对其控制系统进行了调试.

针对7系超硬铝在传统熔焊过程中易出现热裂纹、气孔和焊接接头软化等问题,研究振动焊接工艺过程中,焊接工艺参数与焊接接头强度系数间的非线性关系机理,建立7075超硬铝振动焊接接头强度系数的双重人工神经网络评估模型,包括以焊接参数作为输入接头的焊缝参数、抗拉强度、伸长率和硬度预测模型,以及以4个子模型的预测输出为输入接头的焊接强度系数预测模型.根据建立的预测模型进行焊接接头强度试验,预测结果可以满足工程需要,具有工程实用价值.

The characterization of residual stress in complicated components is a tough issue. The method of Rayleigh surface wave-based V(z) curve is adopted in this work to evaluate the distribution of residual stresses in aeroengine blades. First, the velocity of Rayleigh surface wave in aeroengine blade was measured by the V(z) curve technique, which can be used to calculate the local residual stress because the change of velocity is thought to be correlated with the contribution from residual stress. Two kinds of plastic-deformed Ti-6Al-4V samples were fabricated by ball-gun shooting to artificially induce distribution of residual stress and then measured by the proposed method. The results indicate that the distribution of the residual stress in both of the samples displays a predictable symmetry. The error of the measured stress is much less than 10% of the yielding stress in Ti-6Al-4V (i.e., about 800 MPa). Finally, the measured residual stresses were verified by X-ray diffraction method, whose results correlate reasonably well with each other. The proposed V(z) curve method and its experimental set-up appear to be a potential in characterizing residual stress at a point-like region, such as in complicated components.

AA7075-T651 super-hard aluminum alloy plates with thickness of 6.35 mm were welded by using the double pulsed MIG welding-mechanical vibration combined process, and the process parameters were optimized by means of orthogonal experiment. The tensile properties test, microstructure observation and XRD analysis of the welded joint under optimized parameters were tested by universal tensile testing machine, metallographic microscope and X-ray diffractometer.The results show, that when the vibration frequency is 40 Hz, the vibration amplitude is 0.08 mm, the welding current is 190 A, the welding speed is 0.78 cm/s the joint has the highest tensile strength of 352.6 MPa. The grain size of the welded joint with vibration is smaller than that without vibration under the optimum parameters.

A micro-mechanism based void growth model involving the void shape change during the creep deformation is proposed, referring to the traditional Cocks-Ashby (C-A) model framework, for multiaxial power-law creep rupture prediction. Accordingly, an improved prediction for creep lifetime and multiaxial creep ductility are derived. Results indicate that the creep life and creep ductility are significantly affected by the void shape evolution in the low stress triaxiality range. By contrast, such an effect could be neglected under the situation of high stress triaxiality. In addition, a large fraction of creep ductility is consumed during the tertiary creep stage. A good agreement has been achieved between the proposed model and the collected experimental data.

辽宁省第一批跨校修读学分项目正式启动后,对积极推动教育教学改革探索、课程资源共享和教学管理新模式具有重大的意义.本文以辽宁工程技术大学和沈阳工业大学合作项目“材料科学基础”课程为例,在对项目进行简单介绍的基础上,从项目的实施经验和体会等方面提出了看法,为后续项目的成功实施提供了建议.

The high strength aluminum alloy 7075-T651 with thickness of 6.35 mm was welded by double-pulse MIG welding. The effects of heat input on microstructure and mechanical properties of the welded joint were investigated by means of macromorphology and microstructure observation, scanning electron microscope observation, X-ray diffraction analysis, tensile test and microhardness measurement. The results show that with the increase of welding heat input, the microstructure of the weld zone appears grain coarsening, the main strengthening element Zn evaporates and burns, the precipitation of strengthening phase decreases and the mechanical properties significantly decrease. The fracture mode of welded joint appears mixed fracture of intergranular fracture and transgranular fracture, and there are more second phase particles in fracture of welded joint under smaller heat input. There is a significant relationship between the softening degree of the welded joint and the welding heat input.

弧焊电源是材料成型及控制工程专业基础课,涉及多门学科的交又综合.在教学过程中,不断探索如何提高学生工程实践能力.改变传统课件授课方式,采用仿真软件教学.改变学生学习思想,提高学生解决工程实践问题的能力.

Mechanical property and microstructure of welded joint of AA7075-T651 sheetswere investigated by using ER5556 and ER5356 welding wires with the method of double pulsed MIG (DP-MIG) welding.The results show that the typical cast dendrite is obtained in the weld seam zone of the joints with the two types of welding wires.Compared with ER5556 welding wire,more second phases precipitate at grains boundaries at heat affected zone of the joint with ER5356 welding wire.The lowest hardness of the joint welded with ER5556 welding wire is 90.6 HV,the tensile strength is 342.5 MPa,and the elongation is 8.5％.The lowest hardness of the joint welded with ER5356 welding wire is 80.8HV,the tensile strength is 292.5MPa,and the elongation is 3.5％.There is an obvious tearing ridge in the tensile fracture surface of the joint welded with ER5556 welding wire.