瓦楞纸箱结构强度设计中相关因素的研究

结构强度是纸容器的重要指标，文章对瓦楞纸箱设计中涉及的某些因素，如包装要素的确定，箱体外形尺寸对结构强度用料率及堆码的影响，人体因素的考虑，隔衬和内装物支撑性的考虑，作了分析研究。得出有益的结论，产品包装实例说明研究结果合理可靠，有推广意义，文章对建立我国瓦楞纸箱抗压强度计算方法提出了具体建议。     

纸箱包装材料箱体接合方式的探讨及检测技术的研究

瓦楞纸箱箱体的接合强度及接合质量直接影响瓦楞纸箱的抗压强度和产品质量,箱体接合强度的检测也应该重视起来。本来分析了粘合剂、胶带和箱订三种接合方式的特点,检测方法标准发展情况,目前采用国标遇到的问题,并重点介绍了采用TAPPI T813国标的拉力试验机测试法。     

瓦楞纸箱结构参数对其承压能力的影响

利用有限元程序对不同结构参数条件下瓦楞纸箱的承压能力进行了分析,得到瓦楞纸箱在不同参数条件下的变形分布特点,分析了箱体高度以及层数对纸箱承压能力的影响,结果表明:瓦楞纸箱的最大变形发生在顶部,箱体承压性能随高度增加减小,随纸板层数增加而增大.分析结果为瓦楞纸箱的结构设计提供了理论依据.     

瓦楞纸箱局部增强技术的研究

以 02 型瓦楞纸箱为研究对象,根据纸箱承载重量设计原理及预定强度要求,对瓦楞纸箱箱体进行局部复合,增强纸箱在流通、堆码、储藏等环节的物理性能,以实现减量化生产。 实验和生产案例表明,在选择合适复合材料和工艺的前提下,采用瓦楞纸箱局部增强技术生产相同抗压强度的纸箱,生产成本比常规工艺低13% 。 对瓦楞纸箱减量化设计具有一定的指导意义。     

与瓦楞纸箱强度有关的若干因素

瓦楞纸箱强度是包装容器质量检验的重要技术指标，这些指标的高低，一方面反映了原材料质量的优劣程度，另一方面也反映了加工工艺的质量状况。生产工艺情况表明，要提高瓦楞纸箱的强度，仅仅只靠采购好的原材料是不够的，做好生产过程的质量控制，也是提高瓦楞纸箱强度的重要一环。所以，正确了解和认识影响瓦楞纸箱强度的有关因素，     

压水堆核电站核级过滤器箱体抗震性能分析

核级过滤器箱体是压水堆核电站通风空调系统中的重要设施,用于净化受到污染的空气。为了对核级过滤器箱体进行抗震分析和评定,以验证其结构的完整性,采用Ansys软件进行数值建模,分别对核级过滤器箱体的最大应力及强度、壳体的最大变形、螺栓应力、预埋板焊缝强度、支架稳定性进行校核。研究结果表明,在考虑自重、压力、风管载荷和地震载荷作用下,根据RCC-M进行评定,该核级过滤器箱体的结构满足抗震要求。     

瓦楞纸箱运输包装系统设计

瓦楞纸箱是一种薄壁结构的绿色包装容器，广泛应用于商品包装。瓦楞纸箱运输包装系统的优化设计是一个多目标函数、多变量的优化问题，以仓储空间利用率最大为优化目标函数，瓦楞纸箱强度为约束条件，优化瓦楞纸箱结构、配料方案及装载模式，能够较全面进行纸箱优化设计，较好实现瓦楞纸箱对产品的安全保护、方便储运功能。     

瓦楞纸箱底部结构与强度设计

通过对底部结构不同瓦楞纸箱进行试验分析 ,从中总结出数学模型 ,找出影响瓦楞纸箱底部强度的几种因素 ,以改善瓦楞纸箱的抗压强度     

提高广东地区出口瓦楞纸箱粘合强度合格率的探讨

结合近年来广东地区出口瓦楞纸箱粘合强度检测情况,对影响广东地区瓦楞纸箱粘合强度合格率的几个因素进行了探讨,并提出了相应的改进措施,对提高瓦楞纸箱粘合强度的合格率具有一定的积极意义.     

瓦楞纸箱纸板抗压及堆码强度计算研究

瓦楞纸箱应该具有较大的刚性和承载能力,同时需要具有较好的缓冲防震性能。在瓦楞纸箱结构设计过程中,必须进行瓦楞纸板的强度计算。本文对瓦楞纸箱设计过程中的强度计算方法进行探讨,在归纳影响瓦楞纸箱强度的因素基础上,分析总结了瓦楞纸箱纸板抗压及堆码强度计算公式及方法。应用于生产实际可极大提高设计效率和准确性。     

Compaction-interaction packing model: regarding the effect of fillers in concrete mixture design

For the design of defined-performance concrete, predicting the material properties of concrete becomes more and more important. To be able to select the right type of fillers and control the water demand in such mixtures, an extension to the compressible packing model was developed to optimize the particle packing of aggregates as well as powders in concrete. Modelling mixtures with particles smaller than 125 μm requires advanced interaction equations, taking due account of surface forces like van der Waals forces, electrical double layer forces and steric forces. In this paper the equations for the newly developed compaction-interaction packing model are presented, including the additional effects of agglomerating particles on the wall and loosening effect. Calculated packing densities are related to the results of compressive strength experiments on 50 mortar mixtures. Higher packing densities leave less space for voids to be filled with water, which reduces the water demand and increases the strength of concrete mixtures. This is shown by the cement spacing concept. The relation between the cement spacing factor and strength can be used as a tool to predict concrete strength in defined-performance concrete mixtures.     

Superfine cement for improving packing density, rheology and strength of cement paste

Superfine cement is a cement ground to a much higher fineness than ordinary cement. The addition of a small quantity of superfine cement to fill into the voids of ordinary cement can improve the packing density of the cement and thereby reduce the amount of mixing water needed to fill the voids. In this study, the effects of superfine cement on the packing density of cement (directly measured by a wet packing test), the water film thickness of cement paste (taken as the excess water to solid surface area ratio), and the flowability, rheology and strength of cement paste were investigated. The results showed that the addition of 10% to 20% superfine cement can significantly increase the packing density of the cement and the water film thickness of the cement paste. Such increases in packing density and water film thickness would then improve the flowability, rheology and strength of the cement paste. Hence, superfine cement is an effective cementitious filler for improving cement performance.     

Defined-performance design of ecological concrete

Energy consumption and CO₂-emission of concrete can be reduced when cement is replaced by secondary materials such as residual products from other industries. However, for the design of such environmentally friendly concretes, predicting its performance is very important. In this article a cyclic design method is presented, which can predict the strength of a concrete mixture based on particle packing technology. In the procedure, the amount of water is estimated from the required workability and calculated packing density. After that, the strength of that mixture is predicted from packing density calculations and the amount of water in the mixture via the cement spacing factor. This cycle is repeated until the mixture composition does not have to be adjusted anymore to comply with the desired performance or strength class. With the presented cyclic design procedure cement contents can be decreased without changing concrete properties in a negative way, thereby saving up to 57 % of Portland cement and reducing CO₂-emission with 25 %. This is shown by experimental results of ecological concrete mixtures tested on compressive strength, tensile strength, modulus of elasticity, shrinkage, creep and electrical resistance. The results confirmed that relationships between cube compressive strength, tensile splitting strength and modulus of elasticity correspond to those for normal concrete. The experimental program showed the possibility to use cube compressive strength as the governing design parameter in the cyclic design procedure for ecological concrete. Furthermore, it is shown how the cyclic design method can be used for defined-performance concrete design.     

A New Method for Prediction of Bulk Particle Packing Behavior for Arbitrary-Shaped Particles inContainers of Any Shape

This article describes the recent developments in the computer modeling of packing of complex-shaped particles and prediction of physical properties of the structures represented by the packing. The computer model DigiPac is capable of packing particles of any shapes and sizes in a container of arbitrary geometry. The ability to predict the packing structure of real particle shapes and to compute directly some structure-dependent physical properties such as liquid permeability, mechanical strength/stability, compaction and sintering, and dissolution and leaching is obviously highly desirable and has significant potential in industrial applications. Examples are presented relating to the packing of bulk and granular materials.     

A New Method for Prediction of Bulk Particle Packing Behavior for Arbitrary-Shaped Particles inContainers of Any Shape

This article describes the recent developments in the computer modeling of packing of complex-shaped particles and prediction of physical properties of the structures represented by the packing. The computer model DigiPac is capable of packing particles of any shapes and sizes in a container of arbitrary geometry. The ability to predict the packing structure of real particle shapes and to compute directly some structure-dependent physical properties such as liquid permeability, mechanical strength/stability, compaction and sintering, and dissolution and leaching is obviously highly desirable and has significant potential in industrial applications. Examples are presented relating to the packing of bulk and granular materials.     

Packing of fine particles in an electrical field

A numerical model based on the Discrete Element Method (DEM) is developed to study the packing of fine particles in an electrical field related to the dust collection in an electrostatic precipitator (ESP). The particles are deposited to form a dust cake mainly under the electrical and van der Waals forces. It is shown that for the packing formed by mono-sized charged particles, increasing either particle size or applied electrical field strength increases packing density until reaching a limit corresponding to the density of random loose packing obtained under gravity. The corresponding structural changes are analyzed in terms of coordination number, radial distribution function and other topological and metric properties generated from the Voronoi tessellation. It is shown that these properties are similar to those for the packing under gravity. Such structural similarities result from the similar changes in the competition of the cohesive forces and the driving force in the packing. In particular, it is shown that by replacing the gravity with the electrical field force, the previous correlation between packing density and the ratio of the cohesive force to the packing-driven force can be applied to the packing of fine particles in ESP.     

An empirical approach for the optimisation of aggregate combinations for self-compacting concrete

The fresh and hardened properties of self-compacting concrete (SCC) depend on number of factors such as paste composition, paste content, aggregate content, aggregate gradation etc. In the present investigation, the influence of the packing density of aggregates on the properties of SCC was evaluated. Experiments were conducted to measure the packing density for different combinations of aggregates precisely. A ternary packing diagram (TPD) was developed based on the packing density of measured and interpolated data. Considering the limitations in generalising the TPD and the difficulty involved in adopting mathematical models for aggregates, an attempt was made to establish a simple method for the selection of the combination of aggregates resulting in maximum packing density from the particle size distribution of aggregates (represented by the Coefficient of uniformity??C _u). Further, studies were extended to investigate the effect of aggregate packing density on fresh and hardened SCC properties. The results indicate that for a constant paste volume and paste composition, with increase in packing density of aggregates, the fresh properties and the compressive strength of SCC were improved positively. An attempt was also made to identify the influence of 10 different proportions of aggregates having the same packing density on the properties of SCC. The results indicate that at the same aggregate packing density, the fresh concrete properties were influenced significantly by the choice of the aggregate combination, while there was little or no influence on the hardened properties. Furthermore, the experimental data obtained was used for supplementary validation of the existing model (compressible packing model) for predicting the packing density and the fresh behaviour of SCC.     

Effect of particle-size distribution and specific surface area of different binder systems on packing density and flow characteristics of cement paste

The particle-size distribution (PSD) and specific surface area (SSA) of binders significantly affect the fresh and hardened characteristics of cement-based materials. An experimental investigation was undertaken to evaluate the influence of PSD and calculated SSA of various binary and ternary binder systems on flow characteristics, packing density, and compressive strength development of cement paste. The influence of dispersion state of the binder on packing density was evaluated using the wet packing density approach to determine the optimum water demand (OWD) needed to achieve maximum wet density. The modified Andreasen and Andersen (A&A), Rosin–Rammler (RR), and power law grading models were employed to optimize the PSD of binder system to achieve maximum packing density, while maintaining relatively low water demand. The incorporation of high-range water reducing admixture (HRWRA) is shown to decrease the OWD and increase the packing density resulting from greater degree of dispersion of the binder. The combined effect of lower OWD, greater packing density, and higher SCM reactivity results in higher compressive strength. The increase in SSA from 425 to 1600 m²/kg results in an enhancement in packing density from 0.58 to 0.72, while further increase in SSA from 1600 to 2200 m²/kg reduces the packing density from 0.72 to 0.62. Binder systems using a distribution modulus between 0.21 and 0.235 determined from the A&A model exhibited 18%–40% lower minimum water demand (MWD) to initiate flow, 8%–35% higher OWD to reach maximum wet density, and 15%–25% higher packing density compared to the binder with 100% cement. Binder systems with lower A&A distribution modulus resulted in higher relative water demand (RWD) required to increase fluidity, thus reflecting greater level of robustness. Good correlations were established between the A&A distribution modulus, SSA, RR spread factor, and power law distribution exponent.     

Compaction and arching in tapped pentagon deposits

We simulate the process of compaction under vertical tapping for a two-dimensional system of particles deposited in a rectangular box. The particles consist in regular pentagons and our main objective is to analyze the novel behavior recently found for the packing fraction as a function of the tapping strength applied to the system (Vidales et al. in Phys Rev E 77:051305, 2008). We will relate the behavior of the number and type of arches, mean coordination number and number and type of contacts to the peculiar packing density increase found for increasing tapping strength. Finally, we present results of an annealed tapping on our packings to compare the results to the constant tapping protocol. All our results are compared with the analogous simulations carried out on disks.     

Effects of superfine zeolite on strength,flowability and cohesiveness of cementitious paste

Superfine zeolite (SFZ) is a natural zeolite ground to higher fineness than cement. Being a pozzolanic material, it can be used to replace part of the cement to reduce the cement consumption and carbon footprint of concrete production. In this study, in order to evaluate the effects of SFZ on strength and fresh properties, a total of 30 cementitious paste mixes with different SFZ contents and different W/CM ratios were produced for 7-day, 28-day, 70-day strength tests, and flowability and cohesiveness tests. And, to evaluate the effectiveness of SFZ as a superfine filler, the changes in packing density and water film thickness (WFT) due to the addition of SFZ were measured and determined. It was found that the addition of SFZ as cement replacement up to 20% slightly decreased the early strength, but slightly increased the long-term strength. Moreover, it increased the packing density and exerted its influence on the fresh properties of cementitious paste through the corresponding change in WFT. It also significantly increased the cohesiveness at the same flowability.