A novel simultaneous photoelastic and two‐beam interferometric system: I. Dynamic full‐field evaluation of the elasticity modulus profile of polymeric fibres

A novel optical setup for simultaneous capturing of photoelastic and two‐beam interference patterns was designed. The designed optical setup was used to simultaneously record two types of patterns. The first pattern is two‐beam interference pattern, and the second one is photoelastic interference pattern produced by objects under stress. This simultaneous capturing of the two patterns allowed us to calculate the full‐field distribution of the elasticity modulus profile of fibres. A mathematical expression of the profile of the elasticity modulus was derived. This was applied to evaluate the elasticity modulus of anisotropic isotactic polypropylene fibres during stretching processes. The profile of the elasticity modulus was determined for both static and dynamic in situ cases where the propagation of different structural deformations was observed and studied using the designed optical setup. Patterns were given for illustration.     

Experimental investigation of craze morphology of isotactic polypropylene using computed tomography

In this paper we investigated the morphology of crazes formed during the fracture process of polymeric fibres. Computed tomography technique was applied to reconstruct the image of fibrils‐voids structure of crazes. This allowed us to investigate the initial stages of crazes formation during the fracture process of mechanically stretched isotactic polypropylene fibres. The density and morphology of crazes were studied at different regions inside the stretched sample. Accordingly, we are able to visualize the internal structure of the stretched fibres in three dimensions. This revealed in‐depth information on the fracture process of polymeric fibres.     

A novel double‐image Fizeau system for accurate investigation of anisotropic polymer fibres

This paper introduces a double‐image multiple‐beam Fizeau fringes system. The introduced system can dynamically determine the variations of the refractive indices for both parallel and perpendicular polarization simultaneously. This is achieved by the simultaneous capturing of two multiple‐beam interference patterns during the mechanical processing of isotactic polypropylene fibre. This parallel determination of the refractive indices of both polarization directions allowed us to determine the full‐field distribution of the stress vector, S . To accomplish this, a mathematical model was deduced to calculate the components of the stress vector, S , i.e. parallel stress component, S₁, and perpendicular stress component, S₂. Double‐image Fizeau fringes system and the deduced mathematical model were used to investigate the variation of the refractive index and stress components of the fibre during the stretching process and propagation of necked regions.     

Nonray‐tracing determination of the 3D refractive index profile of polymeric fibres using single‐frame computed tomography and digital holographic interferometric technique

In this paper, we present a nonray‐tracing technique for evaluating the three dimensional distribution of the refractive index values inside polymeric fibres. This technique, named ‘single‐frame computed‐tomography (SFCT)’, is applied to digital holography. A comparative study between the calculated optical phase values using ordinary tomography and SFCT is carried out, and a negligible deviation is detected. The proposed technique is used to determine the three‐dimensional refractive index profile of isotactic Polypropylene fibres, IPP. The variation of the optical properties is measured before, during and after the formation of the necking phenomenon. In addition, SFCT technique is applied to the online determination of the change of the optical properties of IPP fibres. Holograms are given for illustration.     

Automated segmentation of wood fibres in micro‐CT images of paper

A novel algorithm has been developed and validated to isolate individual papermaking fibres in micro‐computed tomographic images of paper handsheets as a first step to characterize the structure of the paper. The three‐step fibre segmentation algorithm segments the papermaking fibres by (i) tracking the hollow inside the fibres via a modified connected component methodology, (ii) extracting the fibre walls using a distance transform and (iii) labelling the fibres through collapsed sections by a final refinement step. Furthermore, postprocessing algorithms have been developed to calculate the length and coarseness of the segmented fibres. The fibre segmentation algorithm is the first ever reported method for the automated segmentation of the tortuous three‐dimensional morphology of papermaking fibres within microstructural images of paper handsheets. The method is not limited to papermaking fibres, but can be applied to any material consisting of tortuous and hollow fibres.     

Characterization of the 3Dimension optical,geometrical, and mechanical profiles of iPP fiber with necking deformation

We present a method for evaluating the 3D refractive indices and 3D true stress and/or 3D true strain profiles of “isotactic polypropylene iPP” fibers during necking deformation. Observing the changes in geometrical shape during the deformation process is necessary to understand the mechanical performance of iPP fibers. 3D geometric shape profile and actual stress and strain profiles were measured for iPP fibers during the propagation of neck deformation. These measurements were performed with the aid of an in‐situ opto‐ mechanical device to dynamically characterize different properties of fibers at different strain rates. A software image analysis program was used to calculate the 3D opto‐mechanical properties of iPP fibers. The obtained results show that the used dynamic stretching device can be easily used to monitor the deformation process with high accuracy. The effective stress and strain can be determined from the filaments profile. For illustration microinterferograms are given.     

Online interferometric study of viscoelastic rupture and necking deformation of as‐spun (iPP) fibres due to creep process

Creep deformation under constant load leads to rupture when the polymer chains can no longer separate and accommodate the load. This fracture phenomenon is investigated interferometrically. The creep behaviour of as‐spun isotactic Polypropylene (iPP) fibres is studied at different stresses, different initial lengths and different radii. The creep rate, which defines the velocity of the creep deformation and the dimensional stability of the material, is studied. The failure time and stress of iPP due to creep process is determined. The necking deformation was in situ detected during creep process. The mean refractive indices (n^P and) profiles of iPP fibres were determined at different positions along the fibre axis before and after necking. The relation between the creep behaviour and different optical and structural parameters is investigated. Microinterferograms are given for illustration.     

包含颈缩失稳的中厚钢板应力应变关系

为弥补传统引伸计在颈缩区域测量方面的不足,提出一种基于三维数字图像相关(3D-DIC)技术的截面分析方法。以轧制方向为0°的QStE700中厚钢板为研究对象,采用截面分析方法获得单向拉伸过程中截面几何形貌及面积,确定颈缩失稳发生时刻,并分析包含颈缩失稳的应力-应变演化过程及截面积变化规律。利用改进的Bridgeman方程对颈缩失稳后的真实应力-应变曲线进行校正,获得包含颈缩失稳的中厚钢板等效应力-应变曲线。分别以传统的幂指硬化曲线和改进的等效应力-应变曲线为本构模型,建立中厚钢板单向拉伸有限元仿真模型,获得截面积随时间变化曲线及载荷与位移关系曲线。结果表明,以改进的等效应力-应变曲线为本构模型的仿真结果与试验结果吻合较好,验证了基于3D-DIC技术的截面分析方法的正确性。此方法可用于描述包含颈缩失稳的整个拉伸过程。     

摆线针轮行星传动中摆线轮最佳修形量的分析与计算

通过对目前摆线针轮行星传动中摆线轮的修形方式进行了分析 ,提出了最佳修形齿廓的概念 ,对采用“负移距 +正等距”修形方法获得最佳修形齿廓原理进行了探讨 ,推导出了摆线针轮最佳修形量的计算公式。根据最佳修形量研制的样机通过试验也证明了修形理论的正确性     

摆线针轮行星传动中摆线轮最佳形量的确定方法

在对摆线针轮行星传动中摆线轮的修形方式进行分析的基础上,提出了最佳修形齿廓的概念,对采用"负移距+正等距"修形方法获得最佳修形齿廓原理进行了探讨, 推导出了摆线轮最佳修形量的计算公式.采用新齿形的样机试验结果也证明了修形理论的正确性.     

The chord length transform and the segmentation of crossing fibres

Segmentation of crossing fibres is a complex problem of image processing. In the present paper, various solutions are presented basing on tools of morphological image processing. Two new image transforms are introduced – the lineal distance transform and the chord length transform. Both transforms are applied to two‐dimensional images and their results are three‐dimensional images. Thus, the segmentation problem originally formulated for crossing fibres observed in a two‐dimensional image can be reformulated as a segmentation problem in a three‐dimensional image. This can be solved by a segmentation in the three‐dimensional image. Algorithms for the lineal distance transform and the chord length transform are given and their use in image analysis is demonstrated. Furthermore, the chord length distribution function of the foreground of a binary image can efficiently be estimated via the chord length transform.     

Method for 3D fibre reconstruction on a microrobotic platform

Automated handling of a natural fibrous object requires a method for acquiring the three‐dimensional geometry of the object, because its dimensions cannot be known beforehand. This paper presents a method for calculating the three‐dimensional reconstruction of a paper fibre on a microrobotic platform that contains two microscope cameras. The method is based on detecting curvature changes in the fibre centreline, and using them as the corresponding points between the different views of the images. We test the developed method with four fibre samples and compare the results with the references measured with an X‐ray microtomography device. We rotate the samples through 16 different orientations on the platform and calculate the three‐dimensional reconstruction to test the repeatability of the algorithm and its sensitivity to the orientation of the sample. We also test the noise sensitivity of the algorithm, and record the mismatch rate of the correspondences provided. We use the iterative closest point algorithm to align the measured three‐dimensional reconstructions with the references. The average point‐to‐point distances between the reconstructed fibre centrelines and the references are 20–30 μm, and the mismatch rate is low. Given the manipulation tolerance, this shows that the method is well suited to automated fibre grasping. This has also been demonstrated with actual grasping experiments.     

Computation of a tetrahedral mesh for striated muscle deformation simulation

Competing concepts exist regarding surgery for instance of the cleft lip and palate to date. Morphology‐based simulations at histological scale may one day be used to help the surgeon predict the possible outcome of a variety of approaches. It however can be a challenge to generate volume meshes that are applicable to the mathematical modelling of three‐dimensional spatial modifications. Computation of surface meshes may be considered less delicate. The aim of this study is to design and evaluate a novel algorithm that supports finite element methods. Images of histological serial sections of a striated muscle were segmented. Results of the three‐dimensional reconstruction of multiple layers of the polygonal segmentation data characterized the hull of the muscle. The corresponding surface mesh was then converted into a tetrahedral mesh to generate volume. This was achieved by mapping multiple template types onto neighbouring intersection polygons. Muscle contraction was subsequently simulated by mesh deformation. The technique successfully generated volumes and was able to provide data on contraction directions. The mesh supported a novel approach to simulate representations of contraction. However, several drawbacks were evident. Mathematical modelling of scenarios with more than one striated muscle will require considerable modification of the currently presented approach. Future studies need to then evaluate the applicability of volume meshes to represent arrays of three‐dimensional biological objects. Surface mesh based mathematical modelling of cleft lip and palate surgery and its results are therefore not yet in reach.     

Light microscopy evaluation of polyurethane vascular grafts porosity by Sudan Black B staining

In small‐diameter vascular grafts, the porosity of the internal surface plays an important role because it affects initial thrombus deposition and therefore the graft’s patency. As well as many other studies reported in the literature we have carried out a study of the relationship between porosity and the manufacturing parameters of polyurethane (PU) grafts by standard scanning electron microscopy (SEM) analysis. However, SEM was not completely satisfactory for evaluating the ‘sponge‐like’ uptake of water by the graft due to the unavoidable water loss and metal coating during preparation. In fact this preparation produces artefacts of the three‐dimensional porous structure. To avoid this problem we investigated the possibility of observing the graft’s internal surface through a stereomicroscope after it had absorbed water. We looked into a simple staining procedure which preferentially colours the PU graft fibres with respect to the void areas. After testing different kinds of stains, we eventually found that Sudan Black B, which usually stains for all kinds of lipid, turned out to be an excellent stain for the water‐loaded PU grafts when diluted with ethanol. This staining procedure, coupled with a computerized image analysis system, allowed us to evaluate the degree of void and average void size of the graft internal surface and to correlate these data with graft density and manufacturing parameters.     

离心泵内部三维流场的试验研究

利用五孔球形测针仪对离心泵内部三维流场的速度、压力进行了试验研究，初步得出了内部流场主要特征和分布规律。为进一步探索泵内部三维流场的其它参数及泵的设计提供了理论依据。     

无缝钢管双向等长缩径时壁厚变化的试验研究

利用普通液压机对初始直径为φ102mm、壁厚为4.5mm的20号热轧无缝钢管试件进行四次双向等长缩径,管坯试件上端润滑,下端不润滑.通过测量试件周向四个方向上的初始壁厚以及缩径后端部及均匀区的壁厚及外径,揭示出缩径后管坯壁厚在周向上变化不均匀的现象,给出了管坯初始壁厚偏差、润滑条件对各次缩径后管坯壁厚变化的影响以及管坯法向应变与周向应变比值的变化规律,解释了缩径中出现的管坯内壁周向起皱及管端轴向开裂等特殊现象,以利于实际生产中合理限定无缝管坯的初始壁厚偏差并对其进行正确润滑,从而得到壁厚变化较为均匀的合格制件.     

铲磨基于DXF文件的复杂刀具砂轮修形软件的开发

针对当前砂轮修形设备中采用刀具参数输入效率低,甚至对复杂成型铣刀参数无法输入的问题。本文提出利用DXF图形输入的方法。根据铲磨过程中,刀具主轴、砂轮构架及铲磨运动建立计算砂轮廓形数学模型,以VC++为平台开发基于DXF文件的复杂刀具砂轮修形软件,精准地计算出砂轮廓形并生成NC代码,提高了精度和效率。     

流体机械叶轮中三维粘性流动的势流边界层迭代解

本文用三维热流和三维边界层相互作用法求解叶轮中的粘性流动。在叶睡表面三维边界层计算中采用了半正交曲线坐标系,各向异性三维涡粘性的湍流模型,变换域技术和Keller分块解法。在叶轮流道及上下延伸体所组成的法语解域中的三维势流计算中,采用了直接边界元法。算例表明,本方法正确可行。     

弧齿锥齿轮无根切最小变位系数的确定

通过用空间啮合原理的方法,推导出常用的弧齿锥齿轮无根切δ－θ／ｍａｘ线图,并用曲线拟合得到该种锥齿轮的无根切量小变位系数计算公式,为设计者了提供了较准的设计依据。     

可转位球头立铣刀周刃与端刃的搭接方法

建立了可转位球头立铣刀周刃与端刃搭接的数学模型 ,利用该模型可计算出刀刃搭接处附近加工表面的几何形状误差并确定周刃修形的控制参数。提出了减小加工误差的措施 ,给出了计算实例