回火过程应力场计算机模拟

回火过程应力场计算机模拟林家骝，杨振枢，于震宗，段贵明（清华大学）郭剑仁，史全兴，谢克仁（内蒙古第一机器厂）ＡＳｔｕｄｙｏｆＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆＳｔｒｅｓｓＦｉｅｌｄｄｕｒｉｎｇＴｅｍｐｅｒｉｎｇ￥ＬｉｎＪｉａｌｉｕ；ＹａｎｇＺ...     

容器焊缝错边残余应力与载荷应力的测定研究

本文对焊接容器错边和不错边的焊接接头进行了电测法的残余应力测试，确定了焊接残余应力的大小及方向，并在加载的条件下，对各焊接接头测点进行了综合应力测试，并给出了受载条件下的应力分布。     

Thermal Shock Failure in Thick Epoxy Coatings

In this paper we describe an apparatus for reproducibly measuring thermal shock resistance of thick polymer layers bonded to metals. The thermal shock behavior is discussed in terms of epoxy samples bonded to an aluminum substrate. It was found that both high resin toughness and low resin thermal expansion coefficient improved thermal shock resistance of thick coatings, but only a sample containing 60wt. % glass beads did not develop a failure crack. Effects of sample thickness, temperature gradient, and resin composition on thermal shock behavior are discussed.     

Single-machine parallel-batching scheduling with family jobs to minimize weighted number of tardy jobs

We consider the problem of scheduling n jobs in batches on a single parallel-batching machine, where the jobs are partitioned into jobs families and the jobs in each family have the same due date. The objective is to minimize the weighted number of tardy jobs. We first devise an efficient pseudo-polynomial time and a fully polynomial time approximation scheme for the weighted problem. Then we present $O(n^2)$-time and $O(n\log n)$-time algorithms for the case where the jobs have the same weight and for the case where the jobs have the same processing time, respectively.     

Evaluation of two cooling systems under a firefighter coverall

Firemen often suffer from heat strain. This study investigated two chest cooling systems for use under a firefighting suit. In nine male subjects, a vest with water soaked cooling pads and a vest with water perfused tubes were compared to a control condition. Subjects performed 30 min walking and 10 min recovery in hot conditions, while physiological and perceptual parameters were measured. No differences were observed in heart rate and rectal temperature, but scapular skin temperature and fluid loss were lower using the perfused vest. Thermal sensation was cooler for the perfused vest than for the other conditions, while the cool pad vest felt initially cooler than control. However, comfort and RPE scores were similar. We conclude that the cooling effect of both tested systems, mainly providing a (temporally) cooler thermal sensation, was limited and did not meet the expectations.     

The effect of pre-warming on performance during simulated firefighting exercise

This study examined the effect of active pre-warming on speed and quality of performance during simulated firefighting exercise. Twelve male firefighters performed two trials in counterbalanced order. They were either pre-warmed by 20-min cycling at 1.5 Watt kg⁻¹ body mass (WARM) or remained thermoneutral (CON) prior to a simulated firefighting activity. After the pre-warming, gastrointestinal temperature (P < 0.001), skin temperature (P = 0.002), and heart rate (P < 0.001) were higher in WARM than in CON. During the firefighting activity, rating of perceived exertion, thermal sensation and discomfort were higher for WARM than for CON. Finish time of the firefighting activity was similar, but the last task of the activity was completed slower in WARM than in CON (P = 0.04). In WARM, self-reported performance quality was lower than in CON (P = 0.04). It is concluded that pre-warming reduces the speed during the last part of simulated firefighting activity and reduces self-reported quality of performance.     

Tensile Stress Relaxation of Alumina at High Temperature

The development of a tensile testing methodology for ceramics which enables a stress vs strain-rate response to be measured at high temperature is described. The test involves a carefully controled stress relaxation test at constant total strain using an experimental procedure and phenomenological analysis previously developed for metallic materials. It is demonstrated here with preliminary tests on alumina at 1050° and 1150°C. This offers, with further development, the possibility of establishing design stresses associated with low strain-rate behavior for structural applications. The results demonstrate that data covering four decades of strain rate may be generated in tests lasting a few hours. The inelastic strain consists of substantial anelastic recoverable strain in addition to a permanent creep strain.     

基于敲击声振法的风机叶片脱层检测系统设计

脱层是风机叶片的主要损伤形式,根据风电叶片的材料特性及外形特点,分析和研究了敲击声振检测原理和现场检测的可行性。叶片出现脱层时,缺陷处刚度下降,敲击应力持续时间增大。依据此检测原理,计算出合理的等效锤头质量,利用压电薄膜作为动态冲击力传感器进行了力锤的结构设计;利用FPGA设计了便携式检测仪,对敲击信号进行信息提取和处理,计算敲击力脉冲信号的宽度,具有结果图形显示和串行通信的功能。经过实验,验证了脉冲宽度与损伤深度的关系。     

应力型微悬臂梁生化传感器响应机理研究进展

针对静态微悬臂梁表面特异性结合产生表面应力信号的响应机制问题,介绍了微悬臂梁生化传感器的工作原理,阐述了应力响应机制的简化模型,从纵向界面上和横向分子间2个方面对特异性吸附引起的悬臂梁表面应力的变化进行了剖析,讨论了界面能变化、位阻作用、静电力、氢键作用等与表面应力大小及方向之间的关系,总结了应力型微悬臂梁生化传感器的响应机理的研究。     

冷却器盘管失效分析及防范措施

本文介绍了冷却器盘管破裂泄漏的情况，分析了失效破坏的原因，并提出防止冷却器盘管破裂泄漏的措施。