Heat generation and distribution in the ultrasonic hot embossing process

Kosloh, Julia; Sackmann, Johannes; źAkalys, Rokas; Liao, Shaowei; Gerhardy, C.; Schomburg, Werner Karl

doi:10.1007/s00542-016-2836-0

Cited by 18 publications

(8 citation statements)

References 16 publications

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“…Moreover, for elements that were not located at the interface, the friction heat flux was not present. Thus, the heat equation was rewritten as in Equation (9).…”

Section: The Numerical Modelmentioning

confidence: 99%

“…One way to monitor weld spot development during ultrasonic welding is the measurement of the temperature through placement of thermocouples or temperature measurement films in the weld spot [5,7,9,10]. However, introducing thermocouples on one hand might slightly influence the initial phase of the welding process and on the other hand it gives limited information on a single spot in the weld zone.…”

Section: Introductionmentioning

confidence: 99%

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A Numerical Analysis of the Temporal and Spatial Temperature Development during the Ultrasonic Spot Welding of Fibre-Reinforced Thermoplastics

Tutunjian

Dannemann

Modler

et al. 2020

JMMP

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The ultrasonic spot welding of fibre-reinforced thermoplastic laminates has received great interest from researchers, mainly in the fields of aerospace and automotive industries. It offers an efficient solution to join large thermoplastic composite parts through the spot welding approach with a high level of automation. In this paper, the temporal and spatial development of the temperature in an ultrasonic weld spot between two fibre-reinforced thermoplastic laminates was modelled. During the ultrasonic welding of thermoplastic composite laminates without energy directors a sudden temperature jump in the weld spot is usually observed. The temperature increase occurs rapidly up to the decomposition of the thermoplastic matrix and causes the degradation of the weld spot. To understand the temperature distribution within the weld spot and to calculate its temporal development, the thermal problem was analysed using a two-dimensional explicit finite difference method. To evaluate the models, the calculated time traces of the temperature in the weld spot were compared with the experimentally obtained values under comparable conditions.

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“…Moreover, for elements that were not located at the interface, the friction heat flux was not present. Thus, the heat equation was rewritten as in Equation (9).…”

Section: The Numerical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Numerical Analysis of the Temporal and Spatial Temperature Development during the Ultrasonic Spot Welding of Fibre-Reinforced Thermoplastics

Tutunjian

Dannemann

Modler

et al. 2020

JMMP

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“…To visualize the polymer flow during friction embossing, a transparent plate, 4 mm in thickness, and colored foils, all 250 lm in thickness, from PP in the colors blue, red and yellow were employed for friction embossing. A similar tool as for the experiment in Kosloh et al (2017) was applied. As shown in Fig.…”

Section: Polymer Flowmentioning

confidence: 99%

“…10 Micro structures generated by friction embossing without (left) and with (right) heating of the tool Fig. 11 Top view and a stripe cut out of a sample fabricated by hot embossing with (a) and without (b) ultrasound (Kosloh et al 2017) and friction embossing (c) (color figure online) Schweißtechnik GmbH in Berkatal, Germany (cf. Fig.…”

Section: Large Scale Friction Embossingmentioning

confidence: 99%

Friction embossing

Zou

Schomburg

2020

Microsyst Technol

Self Cite

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A new fabrication process for micro structures from thermoplastic polymers is presented. Two layers of thermoplastic polymer are placed onto a tool with micro structures. By a friction welding machine, the polymer surfaces are rubbed against each other generating friction heat and melting the polymer. The polymer adapts to the surface shape of the micro structures on the tool. Then, the movement of the machine stops and the polymer cools down and hardens in the shape of the micro structures. The entire process is finished within a few seconds and the required investment costs are in the range of some 10,000 € to approximately 200,000 €. Compared to ultrasonic hot embossing, samples with larger overall dimensions can be fabricated and the heat distribution has been proven to be more homogeneous.

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“…These difficulties also occur when pressure and temperature distribution shall be measured in the process of ultrasonic welding. In recent papers, there is described how temperature and pressure during ultrasonic welding were measured employing thin film thermocouples, and both piezoelectric and pyroelectric sensor foils from polyvinylidene fluoride (PVDF) [23][24][25][26][27][28]. This paper introduces the simultaneous measurement of shear stress and temperature rise generated in PVDF foils by linear and circular friction welding.…”

Section: Introductionmentioning

confidence: 99%

PVDF Sensor Foils Employed to Measure Shear Stress and Temperature of Friction Welding

Zou

Schomburg

2020

Sensors

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Friction welding is a popular process for joining metal and polymer work pieces by rubbing them against each other. This way, friction heat is generated in a zone of the faying surfaces, thinner than 1 mm. After cooling down, the heated surfaces establish a tight and strong bond. To improve this joining process, a method is desirable allowing measuring generated temperature and shear stress in the zone between the joining work pieces. Unfortunately, this is a very difficult task because the welding zone cannot be accessed with a sensor without significantly altering the process and thereby the desired measurement results. This paper describes how shear stress and temperature change generated by rubbing polymer pieces in a friction welding machine have been measured between the faying surfaces by employing sensor foils from the piezoelectric and pyroelectric polymer polyvinylidene fluoride (PVDF). This way, heating and cooling rates, pressure rise of the pneumatic system, frequency rise of the starting machine, the duration of starting and stopping, the damping of the vibrations after the drive was stopped, and the stress generated by the pullback of the machine head have been measured. A careful characterization of the sensor was necessary to enable distinguishing the measured voltage due to straining, shearing and temperature change.

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Heat generation and distribution in the ultrasonic hot embossing process

Cited by 18 publications

References 16 publications

A Numerical Analysis of the Temporal and Spatial Temperature Development during the Ultrasonic Spot Welding of Fibre-Reinforced Thermoplastics

A Numerical Analysis of the Temporal and Spatial Temperature Development during the Ultrasonic Spot Welding of Fibre-Reinforced Thermoplastics

Friction embossing

PVDF Sensor Foils Employed to Measure Shear Stress and Temperature of Friction Welding

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