聚丙烯面包袋拉伸强度不确定度的评定

分析了聚丙烯面包袋拉伸强度测定的不确定度,通过建立测量不确定度的数学模型,分析了重复性测试、拉力机计量、厚度测量、宽度测量等因素对于测量不确定度的影响,并对其进行评定,研究表明重复性测试对于不确定度结果的影响最大。     

改性聚丙烯弯曲强度不确定度的评定

本文按照GB/T9341-2008建立数学模型,从设备、方法及试验重复性等方面对改性聚丙烯弯曲强度测量结果的不确定度进行评定,分析测量过程中不确定度的来源及改性聚丙烯弯曲强度测量结果的不确定度主要影响因素。     

聚丙烯/有机蒙脱土纳米复合材料的制备及性能

以马来酸酐接枝低分子量的聚丙烯(M APP)为相容剂,采用熔融插层法,制备了聚丙烯(PP)/有机蒙脱土(OMM T)纳米复合材料;采用微机控制电子万能试验机、悬臂梁冲击试验机研究了复合材料的力学性能;采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和偏光显微镜(POM)等对复合材料的微观结构进行了研究。结果表明,熔融插层法能够获得较好的插层效果,适量蒙脱土的加入使聚丙烯的球晶数量增多,球晶尺寸变小;复合材料的拉伸强度和冲击强度都是先增加后降低,总体上来说,拉伸强度高于纯聚丙烯,冲击强度与纯聚丙烯相近。     

FBG应变挠度法标定及过程仿真

介绍了一种基于挠度分析的等强度悬臂梁FBG传感器应变标定测试方法和装置,研究了FBG传感器应变传递过程中的相关参量的仿真分析方法,精确测量了应变传递过程中的相关参量,并且针对不同载荷下的等强度悬臂梁的表面应变和挠度进行了理论分析和仿真。同时解析了挠度与梁表面应变、FBG传感器应变的关系,给出了标定后FBG传感器的应变灵敏度,并对挠度法测量FBG传感器的标定结果进行了不确定度评定。当包含因子k=2时,FBG传感器应变灵敏度的相对扩展不确定度＜0.5％,能够满足高精度的应变测试要求,为高精度FBG传感器的应变标定提供了技术支持。     

塑料薄膜拉伸强度测定的不确定度分析与计算

主要介绍了不确定度的定义和来源,并以塑料薄膜拉伸强度测定的不确定度分析为例,考虑了试验机的重复性,拉力测试不确定度、厚度测试不确定度和宽度测试不确定度的影响,系统介绍了实验室不确定度的分析和计算方法。     

阻燃型PA6／PP／硅灰石复合材料的制备及阻燃机理研究

采用固相力化学方法制备的聚丙烯接枝羟甲基丙烯酰胺作增容剂，以高效低毒的三聚氰胺三聚氰酸盐（MCA）作阻燃剂制备了阻燃型硅灰石填充尼龙6/聚丙烯复合材料，该复合材料具有很好的力学和阻燃性能，当MCA与聚合物质量比为10%时，该复合材料的极限氧指数达到31，拉抻强度为54.1MPa，悬臂梁缺口冲击强度为59.7J/m。通过TG和FT-IR分析对阻燃机理作了初步的探讨。     

药用聚丙烯密度测量的不确定度评定

目的:评估药用聚丙烯瓶密度测定的不确定度,以控制药品包装材料的质量。方法:通过建立数学模型,分析称量、温度、容积密度等因素对密度测量不确定度的贡献,计算各不确定度分量,对药用聚丙烯瓶密度的不确定度进行评估。结果:给出合成不确定度和扩展不确定度,不确定度主要来源于样品质量的称量。结论:建立的方法可用于药用聚丙烯瓶密度测定的不确定度评价。     

双向拉伸聚丙烯薄膜(BOPP)拉伸强度测量不确定度评定

通过对双向拉伸聚丙烯薄膜(BOPP)拉伸强度测量不确定度的评定,对其影响因素进行分析与评定,以确定主要影响因素。     

聚丙烯/蒙脱土纳米复合材料在低频振动场的性能

以聚丙烯/蒙脱土纳米复合材料为研究对象,利用自行研制的低频振动注射实验装置,实现振动注射成型和常规注射成型。研究了振动参数对注塑试样的拉伸强度,冲击强度的影响,并对试样进行SEM,W AXD测试。结果表明,在特定的振动工艺条件下,拉伸强度和冲击强度都得到了提高,拉伸强度的最大增幅为17%,冲击强度的最大增幅达到177%。     

塑料拉伸屈服应力不确定度的评定

摘要：采用ISO527标准对某一牌号的聚丙烯进行了拉伸屈服应力的测试，依据JJF1059-1999《测量不确定度评定与表示》标准，建立了不确定度计算的数学模型，分析了对试验影响的各项因素，并对其不确定度的计算和评定进行了探讨。     

中低频集中质量悬臂式簧片仪基频分析方法研究

簧片仪是一种中低频冲击响应谱测量装置,设计时可将其简化为端部附带集中质量的悬臂梁。簧片仪的振型方程中存在超越函数,对于等截面簧片仪来说,可使用二分法等数值方法求解,计算量较大,该方法不适用于复杂截面簧片仪基频设计。首先利用悬臂梁自由端受集中力的挠度公式,推导出其等效刚度等效单自由度的弹簧振子系统,利用弹簧振子相关频率公式解决求解集中质量等截面悬臂梁的基频问题,该方法与振型方程求解的基频对比,发现在10 Hz以下的中低频区域,可以很好的保证等截面悬臂梁的基频精度,大于10 Hz的中频段,误差随频率的升高而迅速增大。接下来,通过Mohr积分的方法,推导出等强度集中质量悬臂梁自由端的最大挠度,并给出其基频的设计公式,该方法与试验进行对比,发现误差与等截面悬臂梁有相同趋势,因此利用瑞利能量法修正设计公式中的质量参数,修正后与实验误差在5%左右。经理论与试验验证,所提出的簧片仪设计方法简单可行、计算结果可信。     

Comparative strengths of fresh water ice

In order to gain a quantitative comparison among the various mechanical properties of ice, a series of tests was performed on fresh water ice in which several of the mechanical properties were tested under identical experimental conditions. In particular, the tests were standardized with respect to ice growth conditions, ice type, grain size and orientation, sample size, test temperature and strain rate. The average results of the test were: flexural strength ? cantilever beam = 770 ± 150 kPa; flexural strength ? simple beam (top tension) = 2200 ± 320 kPa; flexural strength ? simple beam (bottom tension) = 1770 ± 190 kPa; $\text{fracture toughness}\text{= 83 ± 7}\text{kPa m}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$; shear strength = 500 ± 220 kPa; compressive strength (horizontal loading) = 4400 ± 700 kPa and strain modulus ? cantilever beam = 1.6 ± 0.4 GPa. Since most of the tests were performed using a portable compression test machine, the strength values can serve as baseline values for comparison with field results.     

Effect of linear density and yarn structure on the mechanical properties of ramie fiber yarn reinforced composites

Effects of linear density and yarn structure on both static and dynamic mechanical properties of ramie fiber yarn reinforced composites (RYRCs) were investigated. The failure mechanisms of RYRCs were analyzed with the aid of ultrasonic C-scan and Scanning electronic microscopy (SEM). The results showed that the tensile strength of RYRCs increased gradually with increase of the linear density of the single yarns. The maximum tensile strength was obtained when the linear density reached 67.3 tex. However, a downtrend of the tensile strength was observed with further increase of the linear density of ramie single and plied yarns. The interlaminar fracture toughness was relatively high for RYRCs made from yarns with lower linear density due to the extensive fiber bridging observed during the double cantilever beam test. Meanwhile, the linear density and structure of ramie yarn had remarkable influence on the failure mode of RYRCs during the drop weight impact test.     

低频簧片仪冲击特性与破坏规律分析

低频簧片仪是低频段冲击谱测量的主要装置,其结构为一组具有不同固有频率的集中质量悬臂梁。舰艇受到爆炸冲击时,集中质量悬臂梁易发生塑性变形或断裂,直接影响测量结果。为分析集中质量悬臂梁抗冲击能力,利用模态叠加法建立集中质量悬臂梁在冲击载荷作用下理论模型,分析集中质量悬臂梁在冲击载荷作用下动态响应及破坏规律。研究结果表明:集中质量悬臂梁固有频率越高,应力峰值越大,越容易发生塑性变形或断裂;对于集中质量悬臂梁,冲击载荷破坏能力仅与极限谱位移有关,极限谱位移越大,其破坏能力越大;负波延迟对集中质量悬臂梁的破坏能力具有一定影响,可在常规抗冲击设计中通过增大极限谱位移考虑此影响。     

悬臂梁支座附近表层嵌入FRP筋后性能研究

对悬臂梁支座附近受弯面和侧面表层嵌入FRP筋材后的性能开展了试验研究,探讨了FRP筋类型、试验梁侧面开槽嵌粘方式和初始荷载对悬臂梁性能影响,分析了试验梁的特征荷载、悬臂端挠度、钢筋和FRP筋材的应变。试验结果显示,内嵌FRP筋能够提高悬臂梁的开裂荷载、屈服荷载和极限荷载,试验梁的极限荷载提高范围为48.9%~64.2%;内嵌FRP筋有效地抑制悬臂端挠度,控制了悬臂梁的变形,持续荷载作用下试验梁加固后特征荷载要比其它无初载作用的加固试验梁略低,变形略大,不过,加固效果仍很明显。由此可见,悬臂梁采用FRP筋嵌粘是一种有效的加固方法。     

Fracture mechanics approach to facesheet delamination in honeycomb: measurement of energy release rate of the adhesive bond

Two types of experiments were designed and performed to evaluate the adhesive bond in honeycomb sandwich panels. The tensile bond strength between the facesheet and the core was determined through the flatwise tension test. The fracture toughness of the bond line was measured through the double cantilever beam test. Fracture toughness values varied for different facesheet thicknesses and core materials. Toughness was also different for the bag and tool sides of the panels for all specimen types.     

A small cantilever beam test for determination of creep properties of materials

The application of small specimen creep test techniques in the evaluation of creep properties of materials in‐service has been increasing. To obtain the creep data accurately and conveniently, a new creep test method with small cantilever beam specimens is proposed. Analytical equations are derived that can convert the load to equivalent uniaxial stress and the displacement rate to equivalent uniaxial strain rate. Three types of the cantilever beam specimens are designed. The optimal configuration of the cantilever beam specimens is recommended with the aid of finite element method, which is further validated by the cantilever beam and uniaxial specimen tests. The results show that parameters obtained from the cantilever beam tests correspond reasonably well with those from uniaxial tests at low stress levels. With a relatively large equivalent gauge length, the cantilever beam specimen allows the small creep strain rate data obtained with a high accuracy.     

SPTW 对聚丙烯复合材料力学性能的影响

目的研究六钛酸钾晶须添加量的不同对聚丙烯复合材料力学性能的影响。方法采用硅烷偶联剂KH550改性六钛酸钾晶须(SPTW),利用熔融共混法,将改性过的六钛酸钾晶须与聚丙烯(PP)、马来酸酐接枝聚丙烯(PP-g-MAH)熔融共混制得PP/PP-g-MAH/SPTW复合材料。结果比较不同含量的六钛酸钾晶须对复合材料力学性能的影响,发现添加适量改性过的六钛酸钾晶须可明显改善复合材料的力学性能。随着六钛酸钾含量的不断增加,其弯曲强度也增大,当SPTW的质量分数为12%时,弯曲强度提高了21.5%,随着含量的继续增加,弯曲强度开始下降;其拉伸强度和冲击强度都呈先增加后降低的趋势,在SPTW质量分数为8.3%左右时,其拉伸强度和冲击强度分别提高了19.7%和31.8%。结论在聚丙烯中添加经硅烷偶联剂KH550改性的SPTW,其质量分数为12%时,力学性能最佳。     

Experimental investigation of compression moulding of glass/PA12-PMI foam core sandwich components

The manufacturing of sandwich components from pre-consolidated glass/polyamide 12 faces and polymethacrylimide foam core by compression moulding has been studied. A statistical experiment design was used initially to identify the dominant process parameters in terms of interfacial bond strength, evaluated using the transverse tensile test method. In a subsequent extended study, the influence of face temperature and moulding pressure on the mechanical properties of the face–core interface and the sandwich construction as a whole, were characterised in terms of mode I interfacial fracture toughness, shear strength, shear stiffness, and flexural rigidity. These properties were evaluated using a modified double cantilever beam test, shear test, and four point bend test.