7003合金双峰时效工艺研究

采用洛氏硬度计、显微硬度计、光学显微镜（OM）、拉伸试验机等技术对7003铝合金时效行为、力学性能及组织进行了研究。结果表明,7003合金的硬度及强度都具有时效双峰特征。两个时效峰的硬度和强度相差不多,在较低温度下,时效第二峰的强度、硬度、塑性、韧性较高。     

超高分子量聚乙烯齿轮在超弹性条件下的有限元分析

超高分子量聚乙烯是一种高弹性体材料，作为齿轮材料在承受载荷时，其变形具有非线性、大应变的特点。采用超弹性的Arruda—Boyce模型来模拟超高分子量聚乙烯齿轮在工作状态下的应力分布，计算结果表明：超高分子量聚乙烯齿轮的最大应力出现在齿根部位。     

超高分子量聚乙烯异型材挤出工艺的有限元分析

设计了超高分子量聚乙烯异型材的导轨挤出流道,应用有限元软件模拟超高分子量聚乙烯熔体和聚丙烯熔体这两种聚合物熔体在同一流道内的流动规律,获得流道内部的压力场、速度场和温度场。研究表明,所设计的异型材导轨挤出流道对两种聚合物熔体压力分布的影响明显,对速度分布和温度分布的影响基本一致。最后通过试验验证了超高分子量聚乙烯异型材导轨挤出流道设计的合理性。     

山东东方管业有限公司

山东东方管业有限公司是从事超高分子量聚乙烯新材料应用研究、开发、生产、销售、服务一体化的专业生产超高管材、板材、异型件的高新技术企业。可根据用户要求生产直径89-800mm、工作压力1-3MPa的各种超高管材。 超高分子量聚乙烯产品具有极高的耐磨。耐腐蚀、耐低温、耐环境应力开裂、抗冲击、良好的自润滑、化学稳定性等优越性能。     

JHMGC100S管材获自主创新产品证书

日前,由吉林石化研发的高密度聚乙烯管材专用料JHMGC100S新产品获得中国石油天然气集团公司颁发的自主创新重要产品证书。     

多层复合管制造技术和工程应用

多层复合管制造技术和工程应用中山市电力实业发展总公司（５２８４００）贺家智多层复合管又称复合管，是采用涂覆－粘合工艺将聚乙烯塑料（ＰＥ）与金属铝管（或钢管）复合而成的一种新型管材。多层复合管由５层材料组成，管子横截面从内到外依次为：高密度聚乙烯—粘合...     

直埋式耐高温复合保温管

Q/PDG02·29—92直埋式耐高温复合保温管的保温层,是以无机名温材料和异氰脲酸酯泡沫塑料复合而成。其输送热介质管道是钢管,外保护层为高密度聚乙烯管材。该产品具有     

聚乙烯管韧性破坏寿命预测方法研究

聚乙烯管在静液压作用下有3种失效模式：蠕变韧性破坏、慢速裂纹脆性破坏和材料劣化破坏。提出基于粘弹性应力分析模型的聚乙烯管材蠕变韧性破坏寿命预测方法。在内压作用下,聚乙烯管材的蠕变导致其壁厚不断减薄,环向应力逐渐增大。同时,基于粘弹性应力分析模型得到管材蠕变的应变率逐渐减小,由于聚乙烯的屈服应力具有明显的率相关性,屈服应力也随之逐渐减小。当增加后的环向应力值与管材瞬时屈服应力相等时,聚乙烯管材发生韧性失效,从而得到韧性失效寿命与内压载荷之间的关系。     

金属表面超高分子量聚乙烯涂层的制备

通过铸造方法在金属表面形成“拉钩”结构,再采用模压成型,在金属表面制备了超高分子量聚乙烯涂层,对涂层性能进行了研究。结果表明：“拉钩”结构提高了基体与涂层的结合力；预压(6MPa)→烧结(200～210℃×3．5h)→加压(8MPa)→保压→冷却→出模的模压成型工艺可在金属表面制备出超高分子量聚乙烯涂层,且涂层具有良好的耐磨性及导热性。     

薄层扫描仪重叠峰处理的改进

本文提出采用无约束最优化中最小二乘法对薄层扫描仪的重叠峰进行拟合处理,以提高分峰的准确性。主要论述拟合函数的选择,初始条件的确定等。     

Determination of molecular weight distribution parameters of polymers and additives by field desorption mass spectrometry

The applicability of the field desorption mass spectrometry (FD‐MS) technique to the determination of the molecular weight distribution parameters of various commercially available petroleum sulphonates is demonstrated. The technique has been substantiated using standards such as polyethylene glycols, polystyrenes, and sodium petroleum sulphonates. This study of molecular weight averages compares the results from gel permeation chromatography and FD‐MS.     

Broadening the polyethylene molecular weight distribution by controlling the hydrogen concentration and catalyst feed rates

This paper discusses the control of an industrial gas-phase polyethylene reactor to produce a desired molecular weight distribution (MWD) of the polymer. The controller objective is to regulate online the entire molecular weight distribution by either manipulating the hydrogen content inside the reactor or coordinating the feed rates of two different types of catalysts. In this work, the molecular weight distribution is modeled as a function of the reaction kinetics and hydrogen to monomer ratio. Nonlinear model predictive controller (NLMPC) algorithm is used to maintain the desired molecular weight distribution online. The closed-loop simulations indicated the effectiveness of NLMPC to achieve its goal even in the presence of modeling errors. Moreover, the results showed that, altering the hydrogen concentration solely can produce the required polymer quality provided that an efficient mechanism is available to readily alter the hydrogen composition. Alternatively, the desired MWD can also be guaranteed with proper manipulation of the catalyst feed rates while the other process inputs are kept constant.     

On the pressure dependence of the wear of ultrahigh molecular weight polyethylene

The wear of polyethylene in bovine serum was evaluated as a function of load and molecular weight. The range and distribution of contact loadings simulated those which exist in currently available total hip and total knee prostheses. The wear increased exponentially with load at constant molecular weight. An increasing molecular weight parametrically displaced the exponential curve to higher loads, lowering the overall rate. It is proposed that the behavior of these materials be described in terms of a critical pressure-velocity product although the specific mechanisms for wear acceleration are not known in this case.     

The effect of polyethylene thickness in fixed- and mobile-bearing total knee replacements

In this paper fixed- and mobile-bearing implants were simulated using a multibody dynamic model and a finite element model to investigate the contact pressure distribution in the ultra high molecular weight polyethylene tibial bearing component. The thickness of polyethylene varied from 6.8 to 12.3 mm and the polyethylene was modelled as a non-linear material. It was found that the contact pressure on the polyethylene decreased in the fixed-bearing implant when the thickness of polyethylene increased from 6.8 to 8 and 9.6 mm, but there was little further decrease in pressure with the increase of polyethylene thickness from 9.6 to 11.0 and 12.3 mm. In the mobile-bearing implant, no increase in contact pressure on the superior surface was found with the increase in the thickness of the polyethylene; however, the contact pressures on the inferior contact surface of the thicker designs were higher than those in the 6.8 mm design. The numerical results obtained in this paper are in good agreement with published experimental test results. Moreover, the paper presents a detailed pressure distribution on the tibial bearing component during a full gait cycle.     

Effect of Carbon Nanotube Addition on Tribological Behavior of UHMWPE

Carbon nanotubes (CNTs) were added to Ultra-high molecular weight polyethylene (UHMWPE) to improve the tribological properties of UHMWPE. CNTs which have a diameter of about 10–50 nm, while their length is about 3–5 nm were produced by the catalytic decomposition of acetylene gas using a tube furnace. Ball-on-disc-type wear tests were performed to evaluate the tribological performance of UHMWPE composites reinforced with CNTs. The results showed that addition of carbon nanotube up to 0.5 wt% lowered wear loss significantly and increased friction coefficient slightly. Also through the scanning electron microscope (SEM), the surfaces of UHMWPE were observed and analyzed to discuss the tribological behavior of CNT added UHMWPE.     

沟槽结构对水润滑超高分子量聚乙烯轴承力学性能的影响

通过pore/mechanic模版,建立不同沟槽形式下高分子量聚乙烯水润滑轴承的模型,应用有限元分析方法,分析沟槽形式对轴承应力应变及位移的影响。结果表明:沟槽形状的变化对轴承位移影响不大,但影响轴承应力及应变的分布;当沟槽的形状为圆弧形时,轴承的应力应变的变化趋势比较平缓,容易保持轴承的稳定性。     

Characterization of the thermal oxidative degradation kinetics of thermoplastics

Thermal oxidative degradation kinetics of polyethylene, poly(ethylene terephthalate), and polystyrene were investigated by thermogravimetric analysis. The samples included low-density polyethylene, medium-density polyethylene, high-density polyethylene, a starch-based biodegradable thermoplastic polyester, polyethylene natural gas pipe, a poly(ethylene terephthalate) water bottle, and a polystyrene drinking cup. The kinetics were conducted under dynamic conditions at heating rates of 10, 20, 30, and 40°C min^?1 between 25 and 650°C in air. The Kissinger, Flynn–Wall–Ozawa, and Coats–Redfern methods were used for investigation of degradation of these polymers. Thermal oxidative degradation of the polymers was compared. Low-density polyethylene, medium-density polyethylene, high-density polyethylene, and polyethylene pipe obeyed a diffusion mechanism for oxidative thermal degradation. The starch-based biodegradable thermoplastic polyester, polystyrene cup, and poly(ethylene terephthalate) bottle followed random nucleation, diffusion, and phase boundary-controlled reaction mechanisms, respectively.     

The application of a zero wear model to metal/ polyethylene sliding pairs

The application of a zero wear model to polyethylene/metal pairs has been examined using a rider-on-a-flat geometry. It was found that the model enabled the number of passes to reach the zero wear limit to be predicted but that deviation between the theory and experiment occurred for large numbers of passes.It was found that both high density polyethylene and ultrahigh molecular weight polyethylene gave the same behavior in the zero wear region. This is in contrast to the non-zero wear region in which high density polyethylene wears much faster than ultrahigh molecular weight polyethylene. The sources of difficulty in predicting the non-zero wear behavior from the behavior in the zero wear region are examined.     

Exploratory investigations on the structure dependence of the wear resistance of polyethylene

A relatively simple hemisphere-on-flat sliding wear tester was devised for screening samples of polyethylene prior to their trial in total joint simulators and ultimately in implanted total joint replacements. Testing was done in bovine serum and wear debris was recovered quantitatively by a method previously devised. The debris, wear surfaces and wear rates were all consistent with previous work, including simulators and clinical materials. It was found that the wear rate increases by a factor of more than 30 when the molecular weight is decreased from 2 × 10⁶ to 5 × 10⁵, that irradiation in doses typical of sterilization procedures improves wear resistance, as does reduction in fusion defect size in ultrahigh molecular weight material, and that chemical cross-linking improves wear resistance in high density polyethylene but still not to the level of the ultrahigh molecular weight material. In material with a molecular weight typical of total joint replacements, an exponential dependence of wear rate on load was found.