影响POY长丝动态热应力的因素分析

动态热应力可以反映POY长丝的内在质量,着重讨论了纺丝温度、冷却条件、生产负荷等因素对POY长丝动态热应力的影响,并提出了为改善POY的动态热应力,以及提高POY后加工性能的措施。     

用动态热应力仪评价POY内在质量

介绍了动态热应力仪在 POY物理指标测试中的应用 ,举例说明不同 POY之间的指标差别 ,并且提出了建议指标     

用动态热应力仪评介POY内在质量

介绍了动态热应力仪在ＰＯＹ物理指标测试中的应用,举例说明不同ＰＯＹ之间的指标差别,并且提出了建议指标。     

POY底层丝动态热应力波动原因分析及解决方法

动态热应力是一项能准确反映预取向丝(POY)内在品质的指标。动态热应力的高低与后道加弹在线张力表现为正相关,着重讨论了造成POY底层丝的加弹在线张力相比非底层丝高的原因,并提出了提高POY底层丝与非底层丝动态热应力统一性,解决POY底层丝因加弹在线张力超设定上限引起切丝的方法。     

测试条件对涤纶POY条干不匀率测定值的影响

用 Uster 条干均匀度仪以 Normal 试验方法研究了测试条件对涤纶 POY 条干不匀率测定值的影响。结果发现,1~#—4~#测量槽,测定值极差3.31%,在12.5%—100%刻度范围,测定值极差1.23%,在0—9下张力旋钮位置,测定值极差5.37%,在2—5的捻度旋钮位置.测定值极差1.33%。也就是说,如果上述条件选择不当,可能引起测定值比实际值大1—5倍的严重偏差。此外,测试时间、试样速度、引丝角度、上张力旋钮位置等条件,对测定值无明显影响.     

设备因素对POY毛丝产生的影响分析及对策

本文针对ＰＯＹ丝生产过程中出现的毛丝现象作了探索，通过对卷绕成形全过程的仔细观察研究，认为在原材料质量指标符合要求，工艺稳定成熟的情况下，毛丝产生的主要原因应从设备因素考虑，从而找出解决生产中出现毛丝的办法。     

设备因素对POY蛛网丝产生的影响分析

设备因素对ＰＯＹ蛛网丝产生的影响分析蒋德荣（仪化集团扬州合成化工总厂，江苏，２２５００３）蛛网丝是ＰＯＹ生产中经常出现的问题，一旦有蛛网丝，即使原丝质量极佳，也会在外观检验中，出现轻度情况降等，重度情况作废丝处理的结果。因为它会使ＤＴＹ加工时退卷困难...     

高热通量下热电器件热结构耦合数值模拟

太阳能热电发电系统的热端热通量过高会导致热应力过高,从而引起翘曲,危及系统的使用寿命。基于此,建立了高热通量下热电发电模块的热结构耦合数学模型,分析聚热层厚度、电偶臂间距、铜片厚度等对热电模块最大热应力的影响。数值模拟结果表明：减小聚热层厚度、减小电偶臂间距以及减小铜片厚度都能有效减小热应力。     

Straining phenomena of POY revealed by thermal retraction and other techniques

Partially oriented polyesters yarns (POY) were strained at different strain rates (0.03–12.00 min^?1) and temperatures above and below T_g (3–92°C). Thermal retraction, density, DSC, and WAXS techniques show that strain-induced crystallization takes place by straining at temperatures above as well as below T_g. Above T_g, depending upon the strain rate, two regimes are observed: Below the strain rate of 1.5 min^?1, the flow regime; the degree of crystallinity is reduced as the strain rate increases. Above the strain rate of 1.5 min^?1, the strain-induced crystallization regime; the degree of crystallinity increases as the strain rate increases. Thermal retraction, stress–relaxation, and sonic modulus techniques indicate that, upon cold straining, instead of the original T_g at 65–69°C, two glass transitions occur: an upper T_g (u) and a lower T_g (l). For POY strained at 3°C and at a strain rate of 10 min^?1, the values are 78°C and 37°C, respectively. The higher the strain rate and the lower the straining temperature, the large the difference between T_g (u) and T_g (l).     

低温手术过程组织瞬态热应力有限元分析

通过有限元分析,给出使用同时具有冷冻和加热能力的两种新型冷刀进行低温手术过程中组织瞬态应力场,考察“低温手术-热疗结合型冷刀”与“Endocare型氩氦冷刀”两种新型冷刀的共性和差别,从热应力角度揭示冷刀的杀伤半径。充分考虑组织物性和内热源的非线性,使用基于有限容积法的大型商业有限元软件Ansys双向耦合求解经典生物传热方程与应力方程。结果表明：（1）组织内水的相变导致的体积膨胀是热应力引发的主要因素,而温度梯度则是产生热应力的次要因素;（2）两种冷刀在低温手术过程中均会导致相变区域内出现应力集中;（3）低温手术-热疗结合型冷刀由于可提供更大的冻结区域,使其经历高应力,从而具有更大杀伤半径;（4）低温手术过程中,组织会发生明显的热应变。     

粘涂层中的温度应力测试与分析

对粘涂层中内应力的形成过程作了分析，指出在环境温差作用下，粘附在金属基体上的胶层中会产生内应力。将电阻应变片置于环氧树脂胶层中，通过电阻应变仪测定了粘附于钢板上的胶层在室温下固化后因环境温度波动所引起涂层的纵、横向应变。结果表明，所测得的环氧树脂胶粘涂层中的应变与环境温度关系密切。     

热应力对管道的破坏及预防措施

热力系统管道在交变温度作用下会产生交变热应力 ,在热应力集中区造成金属疲劳 ,当疲劳达到极限时将产生裂纹。本文就热应力对管道的破坏提出处理及预防措施。     

涤纶POY上油不匀的原因分析及对策

采用特性黏数为0.645 dL/g的半消光PET熔体直接纺丝生产135 dtex/72 f涤纶POY,从工艺及设备等分析了涤纶POY上油不匀的原因,并提出了解决措施。结果表明:涤纶POY上油不匀的主要原因是油嘴丝路不正确、出油不连续及油剂性能差等;控制油剂系统调配槽、高位槽、现场槽的工艺温度分别为35,25,20℃,油剂泵转速大于8 r/min,油剂调配时间小于1 h,丝束与油嘴接触夹角为5°,可以有效避免涤纶POY上油不匀,纤维的条干不匀率可降低至1.25%。     

Transient thermal stress analysis of threaded-adhesive joints applied in non-magnetic Dewar

A transient thermal stress analysis of threaded-adhesive joints applied in a non-magnetic Dewar at cryogenic temperature was conducted using the finite element method (FEM). A large temperature gradient was observed in the adhesive fillet region of the lower threaded-adhesive joint at the beginning of the cooling process. This caused a transient thermal stress that was much higher than that at the steady state. The peak von Mises stress of the lower adhesive joint reached the maximum value of 189 MPa at about 10 s after the introduction of liquid nitrogen into the Dewar and was 149% larger than the maximum thermal stress at the steady state. Attention should be paid on this serious transient thermal stress in the design and usage of non-magnetic Dewar.     

火力发电厂水平衡测试及节水分析

为查清全厂用水现状,确定各用水系统之间用水量的定量关系及全厂各用水系统的合理用水量,对某火力发电厂4×600 MW超临界机组的取水、用水、排水、耗水进行了测定,根据测试结果进行水平衡计算和用水状况分析,提出电厂节水和综合利用的建议.结果表明,该厂地下管网泄漏严重,并且废水回收、处理系统管理维护存在不足,理论上在现取水总...     

Simulation of the thermal stress in mass concrete using a thermal stress measuring device

An experimental study is conducted to simulate the thermal stresses generated in mass concrete. Accurate prediction of the thermal stresses by analysis is quite difficult particularly at early ages, due to uncertain age-dependent properties of concrete. A series of tests was conducted in which the amount of restraint in a thermal stress device (TSD) was varied. The effect of aging and the amount of restraint on stress development that can occur in realistic structures was evaluated. The influence of the uncertain early-age properties of concrete (i.e., elastic modulus, thermal dilation, autogenous deformation and transitional thermal creep), on the generation of thermal stresses was incorporated using a TSD due to the simultaneous development of temperature and the corresponding stress in a restrained specimen from the very beginning of the process. The effect of various amounts of restraint on the generation of thermal stress was pronounced. Numerical simulations of the thermal stress setup were also performed using the finite element code DIANA to verify and extend the experimental interpretation and to determine the maximum value of restrained stress which would occur under highest level of restraint. Adopting this methodology may simplify the complexity of thermal stress analyses (i.e., more precise 3-D thermal stress analysis can be performed using material properties achieved from 1-D uniaxial tests) due to the difficulty of accurately determining the early-age properties of concrete.     

用X射线荧光光谱仪测定磷矿多元素分析熔片制样条件的选择

<正>玻璃熔片法能使样品中的化合物与混合熔剂形成真熔液,将熔体冷却形成固态玻璃体,得到均匀的玻璃片,可直接进入光谱仪进行测量。玻璃熔片法的优点:消除了矿物效应、粒度效应等造成的不