防老剂种类及用量对丁腈橡胶疲劳裂纹扩展的影响

考察了防老剂种类及用量对丁腈橡胶疲劳过程中预制裂纹扩展的影响,并对其断面形貌进行了SEM观察。结果表明,在MB/RD、DTPD、4010和2246 4组防老剂中,防老剂2246耐疲劳性能最好,其用量为4份时效果最佳。     

碳黑种类及用量对丁腈橡胶疲劳裂纹扩展的影响

在受到周期应力的作用下,丁腈橡胶内已存在的裂纹会不断扩展而最终橡胶断裂。本文考察了碳黑种类及用量对丁腈橡胶疲劳过程中预制裂纹扩展情况的影响并对断面形貌进行了观察。结果表明,在N220、N330和N550三种碳黑中,N220碳黑补强的丁腈橡胶抑制裂纹增长的性能最好;采用N330补强填料时,碳黑含量为20和30份时效果均较好。     

铸钢焊接接头裂纹扩展行为研究

简要介绍了某深水气田开发项目中出现的高强度铸钢类型，针对该材料的焊接，选用气体保护药芯焊丝开发焊接工艺。测定了焊接接头区域疲劳裂纹扩展速率及疲劳裂纹扩展门槛值，结果表明：整体焊接接头疲劳裂纹扩展性能较好，耐裂纹性能按高低顺序为焊缝>热影响区>铸钢母材。     

07MnCrMoVR钢焊件疲劳裂纹扩展速率

为鉴定０７ＭｎＣｒＭｏＶＲ钢焊件的疲劳性能，通过试验得到了焊接接头以及焊接热影响区的疲劳裂纹扩展速率，同时给出了它们存活率为９７．７３％时的各自疲劳裂纹扩展速率，并对焊接接头与焊接热影响区疲劳裂纹扩展速率进行比较。最后还把结果与“在役含缺陷压力容器安全评定规程”［１］和ＢＳＩＰＤ６４９３［２］推荐结果进行了对比，认为该钢种疲劳裂纹扩展速率在其容许范围内慢于１６ＭｎＲ钢的疲劳裂纹扩展速率     

双向载荷条件下Ⅰ型裂纹的疲劳扩展

研究了双轴向应力状态下Ⅰ型穿透裂纹的疲劳扩展规律，采用构形合理且经精确标定应力强度因子值的双向十字形试样，在电液伺服双轴向疲劳试验机上对低合金钢（１６ＭｎＲ）进行了多种载荷比的疲劳裂纹扩展速率试验，得到了双轴向应力状态下的Ｐａｒｉｓ方程，为目前按缺陷评定规范依据单轴向疲劳试验所得数据对工程构件进行疲劳评定提供参考数据，并就当前研究者们对于双向应力场中横向载荷对疲劳裂纹扩展行为的影响的不同看法进行分析探讨。     

压力容器不同服役周期下初始裂纹临界尺寸研究

测量了压力容器用钢在3.5%Na Cl溶液中的应力腐蚀门槛值KISCC和腐蚀疲劳裂纹扩展速率da/d N。通过逆推法计算了不同服役周期下初始裂纹或缺陷的临界尺寸,发现在a/c1的情况下裂纹主要沿着深度a方向扩展,而在长度c方向基本没有扩展,裂纹的形状逐渐由椭圆形向圆形转变。     

丙烯腈含量对螺杆泵定子橡胶机械物理性能的影响

本文通过对不同丙烯腈含量的丁腈橡胶的耐油性能、耐磨损试性能和耐疲劳性能进行研究,分析了丙烯腈含量对螺杆泵定子橡胶机械物理性能的影响。结果表明,随丙烯腈含量的增加,丁腈橡胶的力学性能和耐油性增强;在55℃的工作温度下,N220S橡胶的损耗因子最小;丙烯腈含量越高,其耐磨损性能越差;丙烯腈含量最高的橡胶,耐屈挠性能和耐伸张疲劳性能最好。     

橡胶疲劳失效行为的研究进展

介绍橡胶疲劳失效行为的研究进展。橡胶疲劳失效的研究方法有裂纹成核法和裂纹扩展法;分析交联网络、填料、应力-应变条件和环境条件等对橡胶疲劳寿命的影响因素;综述耐疲劳橡胶的研究进展。橡胶疲劳失效的研究应多关注交联网络和填料分散等微观现象,进一步探讨纳米填料对橡胶疲劳性能的影响。     

疲劳试验评价缺陷对PE管热熔焊接接头长期性能的影响

高密度聚乙烯（HDPE）管广泛用于运输油气等,然而HDPE管在焊接过程中可能产生焊接缺陷,影响焊接接头的长期性能,目前主要通过静液压试验研究焊接缺陷对HDPE管长期性能的影响,但该方法所需时间较长。通过人工引入焊接缺陷,采用疲劳试验研究缺陷对HDPE管热熔焊接接头长期性能的影响。结果表明：在较低应力作用下,缺陷越大疲劳寿命越短,在较高应力作用下,缺陷对疲劳寿命的影响较小。疲劳裂纹扩展试验可用于快速评价PE管长期性能中的耐慢速裂纹扩展性能和影响,因此推断出疲劳试验方法可用于评价缺陷对HDPE管焊接接头长期性能中静液压强度的影响。     

21/4Cr1Mo钢的高温疲劳裂纹扩展行为研究

对 2 14 Cr1 Mo钢在常温、 2 0 0℃、 42 0℃和 50 0℃下的疲劳裂纹扩展速率进行测试和分析 ,得到四种温度下的疲劳裂纹扩展规律 ;并从机械力学性能和疲劳断口两个方面分析 2 14 Cr1 Mo钢随温度变化的疲劳裂纹扩展速率的变化机理     

环氧树脂增强聚氯乙烯/丁腈橡胶共混胶的性能

用环氧树脂(EP)增强聚氯乙烯/丁腈橡胶(PVC/NBR)共混胶,研究了EP用量对共混胶力学性能的影响,考察了EP对炭黑增强PVC/NBR共混胶力学性能的影响,并用扫描电子显微镜分析了共混胶的微观形貌。结果表明,用EP增强PVC/NBR共混胶,胶料的力学性能提高,且老化后性能变化不明显。在EP用量为18份左右时共混胶的综合性能最佳。EP对炭黑增强PVC/NBR共混胶力学性能的改善有一定作用。EP在PVC/NBR共混胶中原位聚合生成了直径约为200 nm的纤维。     

溴化丁基橡胶/丁腈橡胶并用胶微观结构及性能研究

用改性沥青作相容剂,研究溴化丁基橡胶(BIIR)/丁腈橡胶(NBR)并用胶的微观结构和性能。结果表明:与未添加改性沥青CJ-100的BIIR/NBR并用胶相比,添加改性沥青CJ-100的BIIR/NBR并用胶的相容性较好,加工性能改善,气密性、耐屈挠和耐臭氧性能提高;添加5份改性沥青CJ-100的BIIR/NBR(并用比为80/20)并用胶物理性能、气密性、耐屈挠和耐臭氧性能较好,气密性接近全BIIR胶料,有望用于全钢载重子午线轮胎气密层。     

Crack initiation and propagation in circular rubber bearings subjected to cyclic compression

The fatigue failure mechanism of rubber bearings under cyclic compression is important in evaluating their fatigue lives and thus is analyzed theoretically and numerically here. At first, the stress distributions in a bonded rubber cylinder derived from three different existing models were utilized to calculate the cracking energy densities within it. Next, the location of fatigue crack initiation and the direction of subsequent crack propagation in circular rubber bearings were consecutively determined. Furthermore, finite element numerical results were compared to those obtained theoretically from the three models to check their validity in predicting the fatigue crack initiation and propagation in circular rubber bearings. Based on the quasi‐statically theoretical and numerical results, it is found that the fatigue cracks initiate first at the outermost boundary between rubber and steel plates and propagate later inwards to the center of circular rubber bearings. The corresponding fatigue failure mechanism obtained theoretically and numerically is consistent with experimental findings reported previously. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Strength and Fatigue Properties of Optical Glass Fibers Containing Microindentation Flaws

The inert strength and dynamic fatigue properties of fused-silica optical fibers are studied using subthreshold indentation flaws, i.e., flaws without radial cracks. These subthreshold properties differ from those obtained in comparative tests on silica rods containing postthreshold indentation flaws in three major respects: (1) the inert strengths are significantly higher than predicted by extrapolation of the postthreshold data; (2) the slopes of the dynamic fatigue plots are likewise greater, indicating a greater susceptibility of the subthreshold flaws to chemical kinetic effects; and (3) the scatter in strengths is wider. These trends reflect the change in mechanical response reported for optical fibers with "natural" flaw populations in going from ordinary to ultra-high-strength regions. Direct observations of the indentation sites up to the point of failure indicate that the property differences can be interpreted in terms of a transition from propagation-controlled to initiation-controlled fracture instabilities at reduced contact loads. The subthreshold instability condition is modeled qualitatively as a two-step, deformation-fracture process, with strong emphasis on the importance of residual stress fields in parametric evaluations. The relevance of the results to the practical issue of fiber reliability, most notably in connection with the potential dangers of using macroscopic crack velocity data to predict long-lifetime characteristics, is addressed.     

Fracture properties of natural rubber filled with hybrid carbon black/nanoclay

Hybrid carbon black (CB) and nanoclay (NC) in a rubber matrix have provided superior mechanical performances over conventional composites. Yet the fracture and fatigue properties have not been fully explored. In this paper, the mechanical properties of the hybrid-filled natural rubber (NR) were investigated with regard to the tensile strength, fatigue crack growth (FCG) and cut resistance. The ruptured crack tip and the torn surface were studied by using optical microscopy and scanning electron microscopy (SEM), respectively. It was found that the fatigue resistance at large tearing energy and cut strength were enhanced with hybrid filler. Subsidiary cracks were observed at the ruptured tip in rubber with NC. Morphology analysis revealed that the hybrid filler led to a rougher torn surface than rubber with non-hybrid filler. It was proposed that the clay layers constructed a dual phase filler network with CB aggregates. The filler network could cause strength anisotropy in the matrix and introduce more energy dissipation mechanisms to the system, resulting in enhanced fatigue resistance.     

碳纳米管增强丁腈橡胶的性能研究

研究了碳纳米管用量对丁腈橡胶硫化特性、力学性能、高温拉伸性能、导热性能、耐磨性能、压缩疲劳性能和动态力学性能的影响,并通过扫描电子显微镜观察碳纳米管在橡胶中的分散情况。结果表明：随着碳纳米管含量的增加,胶料的最小扭矩和最大扭矩逐渐增大,焦烧时间和正硫化时间逐渐减少;拉伸强度和撕裂强度均是先提高后降低,拉断伸长率逐渐降低,100%定伸应力和300%定伸应力显著提高;高温拉伸性能中,性能保持率逐渐提高;导热系数逐渐提高,DIN磨耗体积逐渐降低;静压缩率逐渐降低,永久变形和疲劳温升逐渐增加。在动态力学性能中,加入碳纳米管后,橡胶的损耗因子峰值降低,储能模量在温度较低时较小。由扫描电子显微镜观察拉伸试样断面可知,碳纳米管在橡胶中整体分散均匀,局部存在团聚现象。     

橡胶改性PP共混体系的研究

本文研究了SBR／PP共混比、硫化体系、不同橡胶以及增容剂对橡胶／PP共混物力学性能的影响。试验得出：橡塑比（SBR／PP）在30／70,采用半有效硫化体系（CZ／S）时,所制得共混物力学性能较好,共混体系PP／POE的综合性能比PP／EPDM、PP／SBR、PP／NBR共混体系要好,加入增容剂PP－g－MAH可以显著提高共混物的力学性能。     

不同增塑体系对丁腈橡胶老化前后及胶管扣压过程性能的影响

本文主要研究了不同增塑体系对丁腈橡胶老化前后物理机械性能的影响,以热油老化后的丁腈橡胶的应力-应变曲线作为材料参数,考察不同增塑体系对丁腈胶管扣压过程中性能变化的影响;硫化特性实验结果表明:使用DOP或DOA作为增塑剂时,硫化胶转矩差值较大,使用液体丁腈或聚硫橡胶作为增塑剂时,转矩差值相对较低,其中使用聚硫橡胶作为增塑剂时,焦烧时间较短;物理机械性能实验结果表明:使用液体丁腈或聚硫橡胶作为增塑剂时,丁腈橡胶硫化胶耐热空气老化性能保持率相对较高,耐热油老化后质量体积变化率相对较低;仿真计算结果表明:使用DOP或DOA作为增塑剂时,静刚度、应变能密度及节点处Mises应力较大,使用液体丁腈或聚硫橡胶作为增塑剂时,静刚度、应变能密度及节点处Mises应力相对较小。