共查询到20条相似文献,搜索用时 62 毫秒
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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。 相似文献
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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。 相似文献
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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. 相似文献
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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。 相似文献
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设备因素对POY蛛网丝产生的影响分析 总被引:1,自引:0,他引:1
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... 相似文献
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Partially oriented polyesters yarns (POY) were strained at different strain rates (0.03–12.00 min?1) and temperatures above and below Tg (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 Tg. Above Tg, 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 Tg at 65–69°C, two glass transitions occur: an upper Tg (u) and a lower Tg (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 Tg (u) and Tg (l). 相似文献
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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。 相似文献
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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。 相似文献
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Hongmei Zhu Heng Sun Lie Xu Ping Peng 《International Journal of Adhesion and Adhesives》2007,27(8):621-628
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. 相似文献
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Simulation of the thermal stress in mass concrete using a thermal stress measuring device 总被引:2,自引:0,他引:2
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. 相似文献