共查询到20条相似文献,搜索用时 15 毫秒
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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。 相似文献
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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、 相似文献
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强变形制备超细晶金属材料的方法 总被引:1,自引:0,他引:1
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. 相似文献
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Matthew Brahlek 《Advanced materials (Deerfield Beach, Fla.)》2020,32(50):2005698
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. 相似文献
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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. 相似文献
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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。 相似文献
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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. 相似文献
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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. 相似文献
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塑料包装材料内的小分子物质扩散系数模型 总被引:2,自引:0,他引:2
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。 相似文献
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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。 相似文献
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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... 相似文献
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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。 相似文献