鞋类钢勾心自身结构对纵向刚度的影响因素研究

本文基于钢勾心的结构,从厚度、筋高、宽度、长度等方面进行研究,探讨钢勾心自身结构对纵向刚度值的影响。厚度、筋高、宽度等自身结构对钢勾心纵向刚度值有影响,位于弯曲力臂上的孔洞对刚度值有影响,长度对钢勾心纵向刚度值无影响。     

鞋类勾心纵向刚度的不确定度分析与评定

钢勾心的质量对鞋类的安全性能具有重要的影响,通过介绍国内鞋类钢勾心的标准情况,依据GB/T3903.34-2019《鞋类勾心试验方法纵向刚度》规定的方法,采用钢勾心纵向刚度测试仪,测试并计算勾心纵向刚度。从勾心纵向刚度的计算公式模型出发,对不确定度的来源进行了分析和评定。结果显示,重复性测量引入的不确定度贡献较大,位移大小、质量(力值)、力臂引入的不确定度贡献较小。     

影响钢勾心纵向刚度的因素及其机制

解决钢勾心纵向刚度质量问题的首要工作是找出影响纵向刚度的因素及其机制。通过整理分析检测数据,比较了钢勾心各参数对纵向刚度的影响。结果显示,纵向刚度虽由横截面形状决定,但也受纵向弯曲程度的影响,硬度的影响可以忽略不计;筋高是决定性因素,并以多次方的方式影响纵向刚度,增加厚度、宽度、弯曲程度和降低相对筋宽,都可提高纵向刚度,改变长度和硬度,对纵向刚度的影响不大。     

皮鞋钢勾心纵向刚度不确定度评定

分析了皮鞋钢勾心纵向刚度测定的不确定度。通过建立测量不确定度数学模型,分析了重复性测试、百分表、砝码、游标卡尺等因素对于测量不确定度的影响,并对其进行评定,结果表明,重复性测试对于不确定度结果的影响最大。     

鞋类钢勾心硬度和纵向刚度测试不确定度的评估

对GB28011-2011《鞋类钢勾心》中的硬度和纵向刚度两个强制性检测项目的测试不确定度进行了评估,讨论了硬度和纵向刚度的测量不确定度的产生原因及其评定方法,并对不确定度各个分量进行评定、合成,最后给出了合成不确定度及扩展不确定度。通过不确定度的分析提出了试验中的注意事项。     

钢勾心纵向刚度测量准确性与稳定性研究

分析了影响钢勾心纵向刚度测量准确性与稳定性的主要影响因素,包括后夹具夹持力大小、弯曲力臂测量准确性、百分表读数误差、施力点位置(百分表表头触点位置)偏差等;对比了两台不同型号的勾心纵向刚度测试仪测试勾心标准品的测试结果,发现对上述影响因素进行有效改进后的仪器,其测量准确性与稳定性均有明显提高.     

钢勾心自身因素对刚度的影响

通过观察钢勾心自身存在的因素,主要分析了钢勾心筋高、厚度、跷度以及筋宽对刚度测试结果的影响。结果表明筋高、跷度和筋宽对刚度影响较大,厚度较小,并提出了提高勾心刚度及应在标准中规定力臂长度的建议。     

钢勾心纵向刚度检测方法中影响因素的研究

在皮鞋勾心纵向刚度检测方法标准中,对影响测定结果的因素没有详细规定,通过对测试皮鞋钢勾心纵向刚度时可能的影响因素如夹具的夹持力、勾心的水平程度、表头触点位置、夹具夹持受力位置、施加砝码的方式和测定前的调零准确度等,进行试验研究,得出结论:固定夹持力、夹具表面受力位置、勾心水平程度对勾心刚度测定结果有直接影响;砝码施加方式、测定表头触点位置、调零方式等对勾心纵向刚度测定结果没有影响;用扭矩扳手固定比手工固定夹持的测定结果具有更好的重现性。     

热定形工艺对成形毛针织物尺寸稳定性的影响

成形毛针织物的尺寸稳定性受生产过程中织物成形机理的复杂性以及不同后整理工艺过程的影响.后整理是提高成形毛针织物尺寸稳定性的重要措施之一,而热定形工艺是成形毛针织物后整理中不可缺少的工序,所以它对成形毛针织物的尺寸稳定性有着一定的影响.通过正交试验,分析定形温度、时间和横、纵向扩幅比率对成形毛针织物尺寸稳定性的影响,找出了比较理想的热定形工艺,为成形毛针织物的尺寸稳定性提供保障.     

新型化纤盖板针布的设计与性能研究(下)

(二)材料选择盖板针布,主要由钢丝和底布组合而成,它与规格设计同样重要。先进的引进针布已有较大改进,但我们在研制中,不得不从实际出发,参照国情和条件作出如下选择。 1.钢丝 (1)提高钢丝的抗弯强度,增加图4中b的尺寸,就可提高材料的钢度,并从表4比较了3种形状钢丝惯性矩大小后确定选用扁圆形钢丝(如图4)。从表4计算值可以看出,不论纵向或横向惯性矩,扁圆形截面钢丝都高于椭圆形与圆形截面钢丝,纵向惯性矩,扁圆形比椭圆形要高1.3倍,比圆形高4.4倍。横     

基于神经网络和遗传算法的锭子弹性管性能优化

为得到减振弹性管对下锭胆的支承弹性和锭子高速运动下的稳定性等性能的最优匹配效率,依据减振弹性管的等效抗弯刚度及底部等效刚度系数公式,利用MatLab数值分析软件构建弹性管抗弯刚度和底部挠度数学模型。首先,结合Isight优化软件基于径向基神经网络构建其近似模型,且使精度达到可接受水平,并以模型的关键结构参数弹性模量、螺距、槽宽、壁厚为设计变量,结合遗传算法对弹性管抗弯刚度和底部挠度进行多目标优化设计,得到Pareto最优解集和Pareto前沿图,确定出减振弹性管结构工艺参数的优化方案。通过对优化数据进行分析发现,该方案在保证减振弹性管弹性的同时,其底部振幅明显减弱。     

Prediction of timber bending strength and in-member cross-sectional stiffness variation on the basis of local wood fibre orientation

Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3,600 mm³, a coefficient of determination as high as 0.68–0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.     

Cracking Force Analysis for Apricot Pit Decortication Based on Mathematical Model of Hertz’s Theory

In decortication of wild apricot pit a mathematical model based on Hertz’s theory of contact stress was developed for the prediction of force required to break the pit. Using pits subjected to a uniaxial compression stress, in their lateral axis between rigid parallel plates, and those propelled to impinge a rigid cylindrical seat along its lateral axis, experimental verification of the model was conducted comparing the theoretical predictions with estimates from the representations of conventional methods employed in pit cracking. Properties including size, shape, and mass, required in the derived model were determined for wild apricot pits. Material stiffness was obtained from the force-deformation curve. Material stiffness obtained was 51.1 × 10⁶ to 46.9 × 10⁶ Nm-1 for different sizes of the pits (12, 11, 10, and <10 mm). The respective ranges of geometric mean diameters were between 16.92–15.05 mm. There was no significant variation of pit sphericity with size of pits. Force prediction from the Hertzian model proposed gave good prediction of cracking force that was not significantly different from that obtained from an impact force decorticator (1.2 kg weight reciprocating with 100 rpm and 30 cm stroke length) and compression force required calculated from a texture analyzer.     

惯性往复振动机械水平和铅垂支承刚度设计

建立惯性往复振动机械的力学模型和动力学方程,通过对动力学方程的求解及分析,获得水平支承刚度和铅垂支承刚度与振动体振动轨迹的关系;进一步分析水平支承刚度和铅垂支承刚度对振动轨迹的形状、方向和振幅的影响,提出水平支承刚度与铅垂支承刚度的设计方法,为该类机械的水平支承刚度和铅垂支承刚度的工程设计提供了理论依据.     

凹印机变频收卷张力控制系统建模研究

正确合理的数学模型是控制系统设计的前提和基础。文章在分析凹印机张力控制系统一般特性的基础上,结合凹印机具体的收卷张力系统设计出张力控制结构框图,以此为基础推导收卷张力控制系统各个环节的数学模型,包括料卷卷径和转动惯量的实时模型、收卷的动力学模型、张力模型、检测摆辊模型以及矢量控制的变频调速模型。建立的张力控制系统数学模型为进一步研究凹印机提供了理论基础。图6参11     

Computer simulation of plain woven fabric appearance from yarn photographs

This article proposes a method for simulating plain woven fabric appearance based on photographs taken by still camera of actual yarns along their lengths. The survey mathematically models the transformation of yarns from a straight circular cylinder to a flattened and crimped form in the fabric structure. The simulation is performed by yarn images that are obtained by image processing techniques and resized according to mathematical models developed by means of the software prepared. Transforming circular yarn cross-section to elliptical one for simulating yarn flattening and modelling the crimped shape of yarn by an elastica curve are both convenient and realistic. The simulation of plain woven fabric can be performed by a method based on raster graphics. This article provides a model for yarn shape in fabric structure as well as a method for simulating plain woven fabric appearance. This method may be used in textile industry for design and quality control.     

Combined heat transfer and kinetic models to predict cooking loss during heat treatment of beef meat

A heat transfer model was used to simulate the temperature in 3 dimensions inside the meat. This model was combined with a first-order kinetic models to predict cooking losses. Identification of the parameters of the kinetic models and first validations were performed in a water bath. Afterwards, the performance of the combined model was determined in a fan-assisted oven under different air/steam conditions. Accurate knowledge of the heat transfer coefficient values and consideration of the retraction of the meat pieces are needed for the prediction of meat temperature. This is important since the temperature at the center of the product is often used to determine the cooking time. The combined model was also able to predict cooking losses from meat pieces of different sizes and subjected to different air/steam conditions. It was found that under the studied conditions, most of the water loss comes from the juice expelled by protein denaturation and contraction and not from evaporation.     

On modeling changes in food and biosolids at and around their glass transition temperature range

Temperature‐induced mechanical and other changes in biosolids are regulated by three types of kinetics, depending on whether the material is in the glassy state, undergoing a transition, or fully plasticized. The transition itself can take place over a considerable temperature range, which in many food and biological systems happens to be the most pertinent to their functionality and stability. At the transition onset, the plot of stiffness vs. temperature has a downward concavity. It is reversed only at an advanced stage of plasticization after much of the stiffness has already been lost. Consequently, the WLF, Arrhenius, or any other model that implies a continuous upward concavity cannot account for changes in the transition region, and it is unsafe to use them to predict properties through extrapolation.

The mechanical changes in the transition region can be described by a model with the mathematical structure of Fermi's function. Its applicability has been demonstrated with published data on a variety of foods and biosolids. Because the plot of stiffness vs. moisture, or water activity, has the same general shape as that of the stiffness vs. temperature plot, it too can be described by a model with the same mathematical format.

Because moisture lowers the transition center temperature in a manner that can be described by a simple algebraic expression, the combined effects of temperature and moisture can be incorporated into a single general model. The latter can be used to create three‐dimensional displays of the stiffness‐temperature‐moisture characteristic relationships of biosolids at and around their transition. At temperatures well above that of the transition, though, where a plot of log stiffness vs. temperature has a clear upper concavity, this model is no longer applicable, and the changes are better described by the WLF or an alternative model.     

果冻食品高速双面贴标机伺服系统主振频率研究

建立全自动果冻食品高速双面贴标机伺服系统的动力学模型,得出伺服系统的等效转动惯量和等效综合刚度;借助于伺服系统动力学方程,求得伺服系统的传递函数和主振频率;通过根轨迹图和系统振动稳定L(ω)曲线,指出提高系统传动刚度、削减工作机构惯性和惯性元件的失动量或提高阻尼,可以削弱谐振烈度;采用校正网络和综合贴标贴膜速度反馈亦可减弱谐振。