抗事故包装箱抗冲击性能的相似准则

目的研究跌落情况下抗事故包装箱模型设计的相似准则,建立可在相似冲击载荷情况下推断抗事故包装箱原型的抗事故能力的设计方法。方法以抗事故包装箱内容器底部圆心和半径处的应力作为表征其抗冲击能力的指标,找出影响应力的主要物理量,通过量纲分析,建立原型与模型应力相关的无量纲关系式,确立相应的相似设计准则。结果对原型和模型进行了跌落冲击的数值模拟计算,分析结果表明,基于所建立的相似设计准则,缩比模型的应力响应与原型的响应具有较高的相似性。结论在材料相同、几何形状相似、有效载荷与包装箱有效载荷的质量比相同的情况下,利用相似准则进行分析,抗事故包装箱原型和模型的受载水平基本相同,基于缩比模型进行的试验设计具有可行性。     

大塑性变形制备纳米结构材料

大塑性变形(Severe Plastic Deformation,SPD)具有将粗晶材料的晶粒细化到纳米量级的巨大潜力,近年来已经引起人们的极大关注.介绍了几种大塑性变形制备纳米晶材料的方法和原理,如往复挤压、等通道角挤压、高压扭转变形、叠轧、往复折皱-压直等,分析了SPD纳米晶材料的强度与韧性、超塑性、热稳定性等性能,以及当前研究中存在的主要问题,并展望了大塑性变形的应用前景.     

食品用塑料包装材料的卫生性能

目前商品生产中,广泛使用各式各样的包装,按其承担的主要功能分有运输包装和销售包装两个大类;按包装的层次分,有外包装、中包装、内包装之分;包装的基本功能主要可归纳为保护商品、方便储存与运输、促进销售等等。随着市场经济的发展商品销售半径的不断增大,商品货架期的不断增加,加之降低生产成本、     

制备块体纳米/超细晶材料的大塑性变形技术

综述了采用SPD技术制备块体超细晶(UFG)和纳米晶(NC)材料的几种新方法，如等通道角挤压、高压扭转、多向锻造、多向压缩、板条马氏体冷轧法、累积轧焊法、冷拔、反复弯曲平直法等，分析了采用这些工艺制备的块体纳米材料所共有的微观组织特点。着重阐述了SPD技术的研究进展。     

强变形制备超细晶金属材料的方法

强变形是细化晶粒的有效方法,甚至可以制备纳米材料,最近十几年来大量的强变形方法涌现出来,研究也越来越多.介绍了等通道角挤压、高压扭转、连续限制带材角轧挤、循环挤压、限制斜槽压缩、反复弯曲校平、累积叠轧焊等方法,回顾了各种方法可以得到的最大应变量、细化晶粒效果及应变量计算公式.阐述了强变形及剪切变形细化晶粒的机制.     

Criteria for Realizing Room-Temperature Electrical Transport Applications of Topological Materials

The unusual electronic states found in topological materials can enable a new generation of devices and technologies, yet a long-standing challenge has been finding materials without deleterious parallel bulk conduction. This can arise either from defects or thermally activated carriers. Here, the criteria that materials need to meet to realize transport properties dominated by the topological states, a necessity for a topological device, are clarified. This is demonstrated for 3D topological insulators, 3D Dirac materials, and 1D quantum anomalous Hall insulators, though this can be applied to similar systems. The key parameters are electronic bandgap, dielectric constant, and carrier effective mass, which dictate under what circumstances (defect density, temperature, etc.) the unwanted bulk state will conduct in parallel to the topological states. As these are fundamentally determined by the basic atomic properties, simple chemical arguments can be used to navigate the phase space to ultimately find improved materials. This will enable rapid identification of new systems with improved properties, which is crucial to designing new material systems and push a new generation of topological technologies.     

海外传真——塑料包装材料新亮点

随着包装安全要求的提高，包装材料的种类也在日益多样化。包装材料必须要有高阻隔性、阻氧性、阻湿性、透气性，还要有高的抗拉伸强度、耐撕裂、耐冲击强度、优良的化学稳定性，耐高温性，满足内容物的高温消毒和低温储藏等要求。为了满足这些要求。塑料包装材料越来越向多元化发展，下面就国外的塑料包装新亮点作一介绍。     

塑性加工法制备各向异性稀土永磁材料的研究进展

塑性加工是一种可制备各向异性材料并可实现近终形成形的方法,已有一系列尝试将其应用于制备高性能各向异性稀土永磁材料的研究报导.介绍了用于制备各向异性磁体或磁粉的塑性加工方法,包括热压、模压、轧制、正挤压、反挤压、等径角挤压等,和用各种塑性加工方法提高永磁材料性能的基本原理、效果,以及工业化应用进展.     

Similarity of Stress-Singularity Problems for Materials with Linear and Bilinear Behaviors

An analogy is established between the solutions of the problems of singularities of stresses in linear and bilinear elastic isotropic media. It is shown that the distributions of stresses and displacements in the vicinity of singular points on the boundary of the body (characterized by the singularities of stresses) are described, in both cases, by the same functional dependences on the space coordinates but with different characteristics of the material. We deduce expressions for the effective moduli of elasticity and Poisson's ratio of the bielastic medium including the parameter of hardening of the material. The solution of the problem of singularities of stresses in bilinear materials is obtained from the solution of the corresponding problem for the linear elastic medium by replacing the elastic constants with the corresponding effective values depending on the parameter of hardening of the material. The cases of wedge-shaped notches (for various boundary conditions imposed on their edges), two-component wedges, plane wedge-shaped cracks, and circular conic notches or rigid inclusions in the bielastic space are studied in detail.     

聚丙烯塑料食品接触材料中再生料的鉴别探析

对常用的食品接触材料聚丙烯（PP）制品中,再生料的鉴别进行了探析。首先,采用傅里叶变换红外光谱（FTIR）、差示扫描量热（DSC）和热失重分析（TGA）法对样品的组成、结构和热性能进行对比分析,筛选异常数据。利用场发射扫描电子显微镜（SEM）和能谱仪（EDS）相结合的技术对样品的形貌和元素组成进行分析,从微观组成形貌对样品进行精确分析。进一步对筛选出的样品进行荧光增白剂、重金属、增塑剂等有害物质的含量和迁移进行测试研究。研究结果表明,待测样品中的1#样品为PP材质,但热性能不佳,其基体中无其他杂质,未检出重金属和荧光增白剂有害物质,备受关注的邻苯二甲酸酯类增塑剂的检测结果也达标。     

Acoustic-Emission Criteria for Rapid Analysis of Internal Defects in Composite Materials

We present the results of acoustic-emission investigation of volume damage of composite materials with various types of stacking of carbon fibers. All 16 layers of fibers placed in the same matrix give different contributions to the strength properties of the material with varying acoustic-emission activity in the process of loading. We established criteria for the quantitative estimation of volume damage of composite materials with regard for the specific character of changes in amplitudes of acoustic-emission signals at various stages of loading. The analysis of spectral characteristics of acoustic-emission pulses passed through original and damaged materials of the specimen confirms the efficiency of the proposed criteria. We give values of criterional parameters for the investigated types of specimens of composite materials.     

Fracture Mechanism in Plastic Sheet Materials

The method of complete stress–strain diagrams has been proved efficient for the assessment of a sheet material's resistance to macrocrack propagation in thin-wall structural elements and for the prediction of stresses that correspond to the growth onset of macrocracks of various lengths in wide plates by the results of testing small specimens.     

塑料食品包装中化学物迁移模型研究进展

食品包装材料中物质迁移的数学模型大都基于菲克扩散定律。在此基础上,对迁移模型的假设,塑料食品包装中单层、双层、3层材料的迁移模型以及影响迁移过程的两个重要参数(扩散系数和分配系数)进行了综述介绍。以进一步完善食品包装材料中化学物迁移模型的理论研究,使之可以更好地预测食品包装中化学物的迁移。     

火焰喷塑材料的研究进展

阐述了火焰喷塑技术的发展历程，介绍了尼龙11、聚醚醚酮、聚烯烃等几种火焰喷塑材料的物理、化学性能及最新研究进展；指出了该领域今后的研究方向。     

塑料包装材料内的小分子物质扩散系数模型

试验表明,基于Fick扩散定律可对塑料包装材料内小分子物质向食品(模拟物)的迁移进行模拟预测。但无论是扩散模型的解析解或数值解,模型动力学控制参量扩散系数DP都必须是已知或可求的。近年来,开发高效实用的扩散系数预测模型成了迁移研究的一个重点方向。文中就四个常用的扩散系数模型作了分析比较。     

基于电子剪切散斑法的塑封材料的无损检测

为检测轻工业产品的密封性能,应用电子错位散斑法对密封盖、药用密封装置以及食品塑封进行了检测。结果表明:电子错位散斑法能够较好地识别不同密封装置,不同部位,大小、形状各不相同的缺陷,迅速准确地对塑料密封结构质量做出判断;该方法操作简便,对缺陷部位敏感,能够较好地应用于实际现场测试。     

Limitations Of Some Strength Criteria For Composite Materials

Strength of Materials - Based on an analysis of four different types of stress state, the incorrectness of application of the maximum stress strength and maximum strain strength criteria, which are...     

金属材料塑性应变比r值的测试

ISO10113：2006及GB／T5027-2007规定,对于不均匀塑性应变材料,采用线性拟合回归方法测试塑性应变比,并设定必须通过原点的边界条件。分别采用单点法、过原点线性回归法（设定截距为0）及常规线性回归法（不设定任何边界条件）3种测试方法计算分析了均匀塑性应变材料和不均匀塑性应变材料的r值,并进行比较,探讨了线性回归法设定边界条件的合理性。结果表明：对于均匀塑性应变材料,单点法、过原点线性回归法和常规线性回归法均可准确地分析其r值;对于不均匀塑性应变材料,只能采用常规线性回归法分析其r值,而不能采用单点法和过原点线性回归法分析其r值。