ISSN:0032-3888    

DOI:10.1002/pen.760292302

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractDie‐drawing techniques recently developed at Leeds University make it possible to produce oriented polymer tubes with both axial draw and hoopwise expansion. These products have increased axial stiffness, improved barrier properties, and excellent resistance to chemical reagents. Normally mechanical methods are used to join such tubes in order to preserve their orientation: however we show that electrofusion techniques produce joints of strengths such that in tensile tests, failure always occurs in the fittings, not at the joint interfaces. Optical and electron microscopy reveal different zones in the welds and indicate that only 20 percent of the wall thickness is affected by the electrofusion process. The pipe studied was biaxially drawn medium density polyethylene of outside diameter 63 mm with draw ratios of 4 in the axial direction and 2, inner hoop. Optimum welding conditions were determined using socket and saddle electrofusion fittings. The joints did not fail in a standard crush test. Careful control of welding parameters is essential in butt fusion welding when the maximum weld strength exceeds that of the undrawn polyme

ISSN:0032-3888    

DOI:10.1002/pen.760292303

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractIn order to achieve high fatigue strengths in heated‐tool butt welds in plastic pipes used in gas and water supply lines, it is essential that optimum welding parameters be selected. In this paper, the different process phases are described by means of dimensionless characteristic parameters that have been obtained by applying similarity principles to heated‐tool butt welding. On the basis of strength studies conducted on welded Joints, it is shown that the best weld quality is attained when the welding parameters are selected such that identical sheaf deformations result in the joint zones of small and large pipes. Laws for scaling data from small‐pipe to large‐pipe welds are then based on the values of these nondimensional

ISSN:0032-3888    

DOI:10.1002/pen.760292304

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractWelding represents one of the key stages in the manufacture of injection molded or blow molded plastics products. One process frequently employed is heated‐tool butt welding. However, the high seam quality associated with this process can only be attained through reliable process control and optimized welding parameters. This paper presents a simple new method for determining these parameters. Mathematical and physical descriptions of the individual process stages and a computer‐controlled heated‐tool butt welding machine serve as the basis for determining the param

ISSN:0032-3888    

DOI:10.1002/pen.760292305

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractShort welding times make spin welding particularly suitable for mass production. This paper presents an analysis of the friction phase, which makes it possible to estimate the influence of the welding parameters and the material being welded on the temperature in the welded zone, the melt rate, and the torque in the spin welding of semicrystalline thermoplastics. A comparison of experimental and calculated results shows an acceptable correlation. In addition, the influence of speed, axial pressure, and braking on the weld seam quality of different amorphous and semicrystalline thermoplastics is discussed.

ISSN:0032-3888    

DOI:10.1002/pen.760292306

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractA measuring method is presented for process monitoring and process analysis of linear vibration welding of thermoplastics. The method works by recording and evaluating time‐dependent signals that describe the process—such as the frequency‐dependent signals of the displacement of the two parts being joined, the tangential force in the welding plane—and the nonperiodic signals of the welding process, i.e. the normal force in the welding plane and the melting or joining displacement of the parts being joined. It is possible to determine the energy input into the welding zone as a function of the selected machine parameters and the process sequence ov

ISSN:0032-3888    

DOI:10.1002/pen.760292307

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractUnder the right conditions, high strengths are shown to be achievable in vibration welded polycarbonate to polyetherimide Joints. While welding of thermoplastic interfaces of the same material can be understood in terms of interchain diffusion at elevated temperatures, this mechanism is severely limited in the case of dissimilar materials. Scanning electron microscopy is used to show that part of the bond strength in such dissimilar materials results from mechanical interlocking of the two polymers, which is caused by viscous mixing. The effects of the weld parameters on the weld morphology are considered in detail.

ISSN:0032-3888    

DOI:10.1002/pen.760292308

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractA study has been made of vibration butt welds between plaques of polypropylene. The quality of the welds, as determined by impact tests, has been examined as a function of the welding variables: pressure and vibration amplitude. In addition, the microstructure of the welds has also been examined, classified, and correlated with the welding variables and weld quality. Penetration as a function of time shows three distinct regimes and It is shown that the impact strength of the welds is independent of time once the third regime is reached. The time required to reach the third regime decreases as pressure or amplitude increases and is more sensitive to amplitude of vibration than to pressure. The highest quality welds were produced at low pressure and low amplitude with corresponding long times to reach regime three and exhibited a unique, readily identifiable microstructure.

ISSN:0032-3888    

DOI:10.1002/pen.760292309

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractIn vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. Past work on welding characterized the effects of weld parameters such as the weld frequency, the weld pressure, and the weld time, on the welding process and weld strength, and showed that the most important parameter affecting weld strength Is the weld penetration—the decrease in the distance between the parts being welded that is caused by lateral outflow of material in the molten film. However, those weld studies were based on specimens of constant nominal thickness (6.35 mm, 0.25 in). This paper is concerned with the effects of specimen thickness on the weld process and weld strengt

ISSN:0032-3888    

DOI:10.1002/pen.760292310

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractUltrasonic welding is one of the most popular techniques for joining thermoplastics because it is fast, economical, and easily automated. In near‐field ultrasonic welding, the distance between the horn and the joint interface is 6 mm or less. This study investigated the near‐field ultrasonic welding of amorphous (acrylonitrile‐butadiene‐styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. High frequency ultrasonic wave propagation and attenuation measurements were made in order to estimate the dynamic mechanical moduli of the polymers. The estimated moduli were entered into a lumped parameter model in order to predict heating rates and energy dissipation. Experimental results showed that variations in the welding pressure had little effect on energy dissipation or joint strength; Increasing the amplitude of vibration increased the energy dissipation and the weld strength. For the semicrystalline polymers, increasing the weld time improved strength up to weld times greater than 1.5 s, where strength leveled off. For the amorphous polymers, the weld strength increased with Increasing weld time up to times of 0.8 s; for longer weld times, the power required was too high, causing overloading of the welder. Monitoring of the energy dissipation and static displacement or collapse provided valuable information on weld

ISSN:0032-3888    

DOI:10.1002/pen.760292311

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY