Study of vibration welding mechanism

Abstract

The study on the vertical and horizontal spot vibration welding of Inconel 690 alloy was carried out to observe the dendrite morphologies and estimate the temperature gradient G and growth rate R under different vibration conditions. The purpose is to further understand the mechanism of microstructure changes under vibration. Based on different temperature distributions along vertical and horizontal directions in the centre of a melting pool, it is found that vertical and horizontal vibrations induce the divergence of the nucleates site and grain growth rate then affect the grain morphologies. Vertical vibration welding creates a coarse dendrite structure with sturdy secondary and tertiary dendrite arms, and the X-ray diffraction (XRD) profile of this structure shows a strong (200) peak. Horizontal vibration welding results in grain refinement and a relatively disordered structure, which is reflected by its low XRD intensity. The study shows that vibration affects the weld structure by improving nucleates and changing growth rate.     

Improving vibration weld joint strength through process and equipment modifications

Abstract

Vibration welding is a process used to join thermoplastic components. Currently, under optimised low pressure welding, the weld strength of butt joints of unreinforced polymer can be equivalent to the strength of unwelded material. However, in short glass fibre reinforced polymer, the optimised weld strength is significantly lower than that of unwelded material and is closer to the strength of the resin matrix. This lower strength is attributable to the unfavourable orientation of the short glass fibres in the weld zone. The fibres tend to align parallel and in the plane of the weld zone and thus provide no reinforcement in the direction perpendicular to the weld zone. In the present work the impact of various modifications to the existing vibration welding technology was examined, with the objective of increasing the current achievable weld strength of glass reinforced nylon. The introduction of a secondary vibratory motion perpendicular to the weld plane during welding resulted in strengths 20% higher than those of samples welded using the standard vibration welding process.     

Effect of vibration on weld metal hardness and toughness

Abstract

Vibration of welded parts is usually applied to achieve effects similar to thermal stress relief. With vibration, it is not only residual stresses that are affected. Using two different welding processes, the influence of vibration on hardness and toughness of the weld was measured. For each welding process, two series of Charpy specimens were made over the temperature range from -60 to +20°C. The only difference between the two series was in performing welding with or without vibration. Slight differences in weld metal hardness were observed. Toughness measurements show an increase in impact toughness and a significant increase in fracture toughness in samples which were vibrated during welding.     

New Equipment Materials And Techniques

Abstract

Holographic interferometry has been applied to in situ measurements of vibration fields of large diameter conduits undergoing unsteady internal excitations. The ambient conditions under which the measurements were carried out were extremely difficult. The measurements, covering an area of several square meters with each holographic recording, were performed using a portable one joule pulsed ruby laser system capable of producing two sequential Q-switched pulses each with duration of ～25 ns with a variable pulse separation between 10 and 800 μs. The entire assembly of laser and holographic camera was constructed as a single unit incorporating an internal reference beam; the reference beam included a mirror with the facility to make an angular tilt between the two laser pulses with the objective of providing a facility to obtain information relating to the phase of antinodes within the recorded area of the hologram.     

High performance automotive and railway components made from novel competitive aluminium composites

Abstract

The traditional materials encounter difficulties to comply with all the properties required by new components under service conditions. The automotive and the railway industries require low cost solutions to improve the final performance of components made from steel, cast iron, or even conventional aluminium alloys (e.g. clutch discs, brake discs, or pistons). Weight reduction, improvement in wear behaviour, high thermal conductivity, low coefficient of thermal expansion, and easy recycling are sought, among other characteristics, in order to obtain more efficient products leading to a reduction of pollutant emissions. The range of materials that can meet these requirements is presently very narrow and their final price is more expensive (e.g. aluminium matrix composites) than currently used materials. In this paper a new low cost metal matrix composite that has been used to produce pistons, clutch discs, and train brake discs is presented.     

Vibration weld strength data for a poly(phenylene oxide)/polyamide blend

The weldability of a commercial, impact-modified blend of poly(phenylene oxide) and polyamide 6,6 is assessed through 120 Hz vibration welds. Relative weld strengths on the order of 100%, with very high strains to failure, have been demonstrated.     

Vision-Based Task-Level Control of a Flexible-Link Manipulator

This paper discusses a vision-based approach to implement task-level control in flexible-link manipulators. The proposed approach emphasizes the advantage of using vision in the control of flexible manipulators. It is pointed out that taking advantage of the inherent robustness, implementation of an image-based visual servo can be regarded as a synthetic solution to precise task-level control of flexible manipulators. This approach is implemented in a three-dimensional flexible-link manipulator. The implementation makes good use of filters in decoupling task-level control and vibration suppression control. Moreover, we point out that although the robustness of the approach can help to overcome the difficulty in control resulting from the complex measurement of the link's elastic deformation, it lacks in capability of tip trajectory specification. This problem is analyzed in this research and it leads to the proposal for the integration of the image interpolation technique. This technique makes the proposed approach adequate for tasks involved with complex tip trajectories. For flexible-link manipulators, the proposed approach with the remedy is the first vision-based synthetic solution that attempts to make a flexible manipulator usable for a practical task.     

A compact planar distributed tactile display and effects of frequency on texture judgment

This paper describes the development of a planar distributed tactile display and the evaluation of the results of its effectiveness for displaying textures. The tactile display is composed of a 6 × 5 pin array actuated by 30 piezoelectric bimorphs. The distance between each pin's centers is 1.8 mm. Vertical excursion of each pin is controlled over a 0–0.7 mm range. Perceptual experiments were conducted to evaluate the performance of the system under three conditions: active touch, passive touch with vibration and passive touch without vibration. The experimental results showed that vibrational stimuli helped subjects discriminate tactile patterns. Measurements of the error rate during discrimination tasks were used to find an optimal vibration frequency for stimuli presented at a constant sensation level (32 SLdB above threshold). The experiment was repeated, this time holding the energy transferred mechanically to the fingertip tissue constant. At low frequencies, we found that the passive stimulation allowed subjects to discriminate just as well as active touch of static stimuli did. The results suggested new possibilities for displaying texture using passive touch, constant energy and spatially varied vibration frequency.     

Accelerated method for testing soldering tendency of core pins

Abstract

An accelerated method for testing die soldering has been proposed and tested. High intensity ultrasonic vibration has been applied through a core pin to molten aluminium in order to simulate service conditions under die casting. Such conditions include high pressure and high impingement speed of molten metal on the pin. Soldering tendency of H-13 steel pins with or without commercial coatings was tested using this accelerated method. The experimental results indicate that soldering occurs within a few minutes of testing using this new method, much faster than that using the conventional methods. The coating failure mechanism identified in this new method is identical to that observed in the conventional methods, suggesting that the new method is suitable for testing soldering tendency of core pins under die casting conditions.     

The vibration welding of poly(methyl methacrylate) to itself and to polycarbonate,poly(butylene terephthalate), and modified poly(phenylene oxide)

The weldability of poly(methyl methacrylate) (PMMA) to itself and to polycarbonate (PC), poly(butylene terephthalate) (PBT), and modified poly(phenylene oxide) (M-PPO) is assessed through 120 and 250 Hz vibration welds. Weld strengths equal to those of the base resin have been demonstrated in welds of PMMA and M-PPO to themselves. In welds of PMMA to PC and to M-PPO, weld strengths equal to those of PC and M-PPO, respectively, have been demonstrated. PMMA does not weld well to PBT; the highest weld strength obtained was 21% of the strength of PBT resin.