复合材料胶接方式的设计

研究了复合材料的各种胶接接头的形式 ,分析了胶接应力 ,提出了三维编织预制件的混合连接、双搭斜接、混合斜接的三种方法以及通过模具设计控制表面光洁度、尺寸精度以提高三维编织复合材料胶接质量的观点     

三维编织复合材料缝合连接设计及破坏机制

 针对三维编织复合材料的缝合连接设计问题,在研究制造工艺基础上,建立缝合连接的强度校核和参数设计公式,绘制连接部件的内力响应。对不同搭接长度和缝合密度的三维编织缝合连接复合材料试件进行拉伸试验,发现缝合连接接头主要发生3种形式的破坏:在搭接的一端或两端整体断裂;搭接缝合区分层断裂;缝合区中部分分层、部分整体断裂。机制分析表明,断裂模式主要受缝合参数的影响,也与内力分配和是否存在应力集中有关,实际应用中可以根据情况采用不同的连接形式。     

杉木板条横向线拼工艺初探

探索通过浸胶线绳连接的方式横拼杉木板条取代传统胶拼。采用单线拉伸的方式测定浸胶线绳连接的胶接性能,研究浸胶线绳连接中线绳种类、胶种、开槽宽度等因素对浸胶线绳胶接破坏载荷的影响,分析优化浸胶线绳连接方式。结果表明,市售棉线及尼龙线作为连接线绳的破坏载荷较高,同时开槽宽度为1.5 mm时的破坏载荷优于开槽宽度为1.0 mm的破坏载荷;通过对浸胶线绳连接工艺参数的进一步优化,并结合工业化生产要求,可得最优的条件为:胶种为热熔胶,线绳为棉线,开槽深度为2.0 mm。利用该工艺制备的细木工板的横向静曲强度和表面胶合强度达到了国家标准GB/T 5849—2016《细木工板》的要求。     

接头新技术—无结捻接法

为了减少织物表面结疵,改善产品品质,提高生产效率和经济效益,一种新的丝线断头捻接技术,正在国外崛起。从此跳出了纺织生产中丝(纱)线断头一向靠打结连接的老规矩。目前,对丝线断头或清除类节进行再接的无结捻接法大致有下列两种:即胶接或熔接和捻接或绞接。所谓胶接就是将丝线的两端用化学胶粘合在一起;所谓熔接,就是通过一定温度将丝的两端熔接起来,故这种方法只限用于可熔性合纤。而捻接或绞接     

木塑复合材料表面胶接特性研究进展

简要介绍了木塑复合材料目前常采用的连接方式及胶黏剂,并从木塑复合材料的表面处理方法和胶接机理这两方面对木塑复合材料表面胶接特性的研究进展进行了综述,展望了今后木塑复合材料表面胶接特性的重点和发展方向。     

环锭细纱机开车粘接橡胶节能锭带的方法

为了提高纱线质量、减少能耗,由橡胶节能锭带(加热胶连接)逐渐替代“布锭带”(以缝织方式连接),基本杜绝了因粘接部位造成的纱线捻度不匀,可减少锭间差异,同时可减少能耗,延长锭带的使用寿命,提高生产效率。检修工连接“布锭带”时,按照正确方式连接后即可在细纱机运行状态下进行,危险系数很低;而橡胶节能锭带摩擦因数较高,在串连搭接过程中和主轴、锭盘的摩擦力较大,极易缠绕在主轴或锭盘上,造成人身伤害或机器损坏,危险系数较大。经多次试验,利用正确的方式串连搭接,可降低橡胶节能锭带的连接风险。     

PA9接装机接装纸搭接系统的改进

PA9接装机接装纸搭接系统原采用混态搭接方式,搭接时由于备用接装纸与在用接装纸相对速度较大,容易出现搭接质量差等问题.改进后采用了动态搭接技术,使备用接装纸与在用接装纸在搭接时处于相对静止状态,提高了搭接的稳定性和可靠性,避免了混态搭接时出现接装纸抖动、断纸等现象.     

复合材料加筋壁板压缩试验研究与仿真分析

文章对含预埋筋条胶接缺陷的复合材料加筋板进行了压缩试验,研究了不同长度胶接缺陷对复合材料加筋结构破坏形式和破坏强度的影响。并建立了含筋条胶接缺陷复合材料加筋板的非线性有限元分析模型,研究结构的后屈曲行为、脱粘扩展细节和破坏机理。有限元分析结果与试验结果吻合良好,证明了该模型及分析方法的有效性。     

ZJ17卷接机组接装纸胶位在线微调装置设计

为解决ZJ17卷接机组生产花式涂胶卷烟时无法实时调整胶位等问题,通过对接装纸涂胶过程进行分析,基于杠杆原理及偏心轴结构设计了一种接装纸胶位在线微调装置。该装置主要由连接板、调整摆杆、偏心轴等部分组成,通过分离并移动接装纸导辊支架中的左导辊,改变涂胶辊到吸纸轮之间的路径长度,进而实现不停机调整涂胶相位的功能。以长沙卷烟厂"白沙(精品)"牌卷烟为对象进行测试,结果表明:该装置可对±5 mm范围内的胶位偏移量进行实时调整,改进后停机次数降低4.74次/班次,胶位调整时间减少12.95 min/班次。该技术可为提高卷接设备运行效率和卷烟产品质量提供支持。     

双曲率U型蜂窝夹芯金属胶接件校验膜制造和胶接工艺研究

通过改变影响双曲U型蜂窝夹层结构胶接件胶接界面配合间隙的多个工艺参数进行试验,分析对比校验了膜效果,确定了最佳工艺参数。试验结果表明:固化压力是影响双曲U型蜂窝夹层结构金属胶接件的主要因素。随着固化压力增加,胶接界面配合间隙减小。为提高固化压力,采用自制硫化橡胶均压板,所得金属胶接件校验膜合格且满足无损检测要求。     

Plug shear failure in nailed timber connections

Brittle failures in mechanical timber joints should be avoided, because this often results in low capacity and brittle failure of the structure. Nailed joints experience three ultimate failure modes: embedding, splitting or plug stear failure. To avoid plug shear failure, short and wide joints are preferred, limiting the number of fasteners in line with the load and grain direction. Plug shear failure was examined in short-term experiments on nailed steel-to-timber joints in glulam loaded in tension parallel to the grain with five different joint geometries. The aim of the study was to examine if the fastener group layout can be adjusted to avoid plug shear failure and to gain an insight into the causes of failure initiation. Using spring models, it is shown that the load distribution creates pronounced stresses at the last nail in the joint, which probably initiates the plug shear failure. Test results are compared with prediction models found in the literature. It was found that fasteners placed in groups can be a successful way of reducing the risk of plug shear failure. The failure is probably initiated at the nail farthest from the free end, where tensile stresses perpendicular to grain occur.     

Use of a resilient bond line to increase strength of long adhesive lap joints

The load capacity of long adhesive lap joints is often governed by stress concentrations at the lap ends. This paper investigates a method to minimize these stress concentrations by using a bond line with low shear stiffness and sufficient strength, here denoted as a resilient bond line. The resilient bond line is intended to increase the load carrying capacity of long lap joints by achieving a more uniform shear stress distribution while maintaining an elastic joint behaviour without damage or plastic deformation. The study comprises analytical, numerical and full-sized experimental work on double lap joints with lengths 200–700 mm comparing conventional stiff bond lines to resilient bond lines. Different resilient bonds lines were obtained by using rubber-like adhesives and by having a rubber mat within the bond line. An analytical definition of a ‘long’ lap joint is suggested and a study of adhesive-rubber bonding is also presented. The numerical analysis clearly indicates that an increase in load carrying capacity is made possible using resilient bond lines. A good agreement is also found between the numerical results and the analytical Volkersen theory, indicating that reasonable strength predictions can be obtained by hand calculations if the joint is designed in order to minimize the influence of peel stress. The experimental results of the resilient bond line verify the numerical findings, although production difficulties decrease the statistical significance of the result. On the contrary, the experimental results of the conventional bond lines significantly exceeded the numerical predictions, showing similar load carrying capacities to the resilient bond line. This is probably due to the specific boundary conditions used in the test setup. Despite some contradictory experimental results, the conclusion of this study is that the efficiency of long lap joints can be increased by the use of a bond line with low shear stiffness and sufficient strength.     

Leichtbauplatten aus Holzwerkstoffen—Teil I: Eckverbindungen

This paper describes the main properties of corner joints of lightweight panels made of wood based materials. With this investigations the suitability of the lightweight panels for application in furniture industries should be proofed. The observed properties of the tested specimens are the ultimate load and the deformation at the moment of break. For testing specimens with corner joints through lamello, a standard jointing system in the furniture industry, were produced. Altogether 70 specimens were produced, while following specimen parameters varied: panel thickness, used glue system, ambient climate, form of corner joint and direction in which the force effects the corner joint. The results show a relation between the failure load and the ambient climate, the used glue system and the form of load. A high correlation between ultimate load and the deformation at the moment of failure at tensile load could be observed for the specimens made of 38 mm thick lightweight panels. This correlation is a very important finding to evaluate the deformation properties of the lightweight panel as construction material for furniture.     

Beigefestigkeit von Brettschichtholzträgern in Abhängigkeit von den festigkeitsrelevanten Einflußgrößen

The bending strengths of glulam beams with wood failure and failure due to finger joints depending on beam size and load configuration was investigated. Size effects are more pronounced in case of beams with finger joint failure. This may be explained by the higher variation of strength values in case of “material” finger joint. On the basis of the strength values of the corresponding standard beams, these investigations make it possible to determine the “true” strength distributions of the two influencing “materials” wood and finger joint for any beam size and load configuration.     

Traglastberechnung von Nagelverbindungen

To determine characteristic values of the strength of nonpredrilled nailed connections, ultimate loads were calculated for Monte-Carlo simulated joints with differing numbers of nail rows and nails row. Simulation of the load-slip curves of single nails within a joint was based on the correlation structure of the parameters of the lead-slip behaviour, determined in previous studies. When rows are arranged parallel to load, the characteristic ultimate load per nail is independent of the number of nails per row and increases slightly with the number of rows.     

Festigkeit großflächig geleimter Knotenverbindungen

The load bearing behaviour of joints with large overlapped glued areas was tested experimentally in 203 specimens. The following parameters were varied: The angle of gluing (0°, 30°, 60°, 90°), size of overlapped glued area (50, 100, 200, 400, 600 cm²), clamping pressure (0.2 and 0.6 MPa) and pressure technique (conventional clamping pressure, pressure by nailing), wood quality (knots in the overlapped glued area) and the kind of load transmission in the overlapped glued area (shear by loading in tension-compression, shear by loading in pure tension). Corresponding to the joint design the shear strength values obtained ranged from 1.4 MPa to 3.8 MPa. The angle of gluing, the kind of load transmission and, in small overlapped glued areas, the tension stresses perpendicular to the grain as a result of excentric chord junction were found to be the decisive parameters. Nailed-glued joints proved equivalent to conventional glued joints.     

Influence of the stiffness of corner joint on case furniture deflection

The stiffness of corner joints affects the strength of case furniture. The stiffness of corner joint was varied by changing the dowel quantity of case corner joints in this study. At first, the stiffness of corner joint parts was studied by experiments. then the Finite Element Method (FEM) was used to analyse and calculate the deflections of case furniture based on the jointing coefficienty R and the moduls of elasticityE ^* deduced from measurements on corner joint parts. Finally experiments to determine case furniture strength were carried out and the reliability of the calciulation of FEM was verified. The results of calculations and experiments showed that the deflection of case furniture could be reduced by 5–15 percent by increasing the dowel quanlity of corner joint from two dowels to four dowels or from four dowels to eight dowels. The defelection of case furniture containing shelves could be reduced by increasing the stiffness or corner joints.     

Effect of cooking and cooling method on the processing times, mass losses and bacterial condition of large meat Joints

This study compares the heating and cooling times of and mass losses from meat joints in three systems: convective air, water immersion and pressure/vacuum. Cooling times were compared with the UK Department of Health (DoH, 1989) guidelines which state that joints should be cooled to 10°C or below in less than 150 min.
Five types of joint were used: 50-mm thick (0.94kg) slabs of beef m. semitendinosus, 2.7kg rolled beef forequarter and silverside, 6.4kg rolled turkey and 7.1kg boned-out ham joints. Six replicates of all joints were cooked from 5 to 75°C (beef), 80°C (ham) or 85°C (turkey) and then cooled to a maximum internal temperature of 10°C.
Average cooking times for convection, immersion and pressure were 263, 278 and 135 min, respectively. Average cooling times for convection, immersion and vacuum were 433, 298 and 50 min, respectively. Vacuum cooling times did not depend on joint size but may have been affected by porosity of the meat. The DoH guidelines could be achieved by immersion or vacuum methods when cooling the small beef slabs but only vacuum cooling was sufficiently rapid when cooling the larger joints.
Mass losses due to pressure cooking (mean 37.4%) were greater than those during convection heating (28.9%). Vacuum cooling resulted in an average mass loss of 8.2% but losses were smaller after convection cooling (2.5%). Average total viable counts (log10 no. of bacteria cm⁻²) after processing and 12h storage were 1.0 at both the surface and interior.     

基于平行机构的简便机器人运动学逆解算法

在机器人结构中，通过引入平行四边形机构，充分发挥其连杆的平移特性，可简化合并2平行回转轴关节的运动变换矩阵；当与另一正交回转关节组成基本运动单元时，能综合表示为一个等效变换矩阵．仅须2单元串联就能构造6回转关节机器人，且所推导的关节控制角公式简单，便于并行运算，经模拟试验表明：其逆解时间可缩减50％，运算精度提高80％。     

Axial glued-in steel timber joints—experimental and numerical analysis

This paper reports the results of an investigation on the behaviour of axially loaded joints utilising glued-in steel rods. A finite element model has been set up, in order to study the most influencing parameters for the shear stress distribution. Then, a series of tests have been carried out on joints made with Norway Spruce blocks and threaded steel bars, with different epoxy resin formulations and various ratios of hole/bar diameters. Different bar diameters have been used in experimental survey, ranging from 8 to 12 mm. Clearances of 1 or 2 millimetres have been left between bar and hole wall. The reported results are based on a sample of 240 specimens, which can be considered sufficient for statistical reliability. A statistical analysis has been performed, which confirms that: 1) the system proved to be highly efficient and reliable, with regard both to failure load and to joint stiffness; 2) with the epoxy-based adhesive used, the most important parameters affecting the strength and the stiffness of these joints seem to be the thickness of glue line and the viscosity property of the adhesive during the pouring phase; 3) these kinds of joints can be designed as ductile for specific purposes, choosing a suitable diameter of the bar.