研究目的
Investigating the use of VHF heating to alleviate thermal instability problems in selective laser melting (SLM) of metal powders.
研究成果
A novel VHF heating system for potential use in Selective Laser Melting manufacturing of metal parts has been proposed, analyzed, and demonstrated. The unusual electromagnetic field interactions of metal powders have been leveraged to achieve full heating penetration in a sample of practical volume, using moderate RF power. Temperatures up to 7000C have been observed.
研究不足
The measurement of sample temperature is a major challenge, as current methods measure surface temperature only. The temperature deep within the sample could be much higher. The field uniformity is degraded in the use of R2, and the sample is bathed in both H and E fields.
1：Experimental Design and Method Selection:
A resonant structure at VHF (100-500MHz) and a medium power VHF source (delivering up to 75 W) are used to heat tungsten carbide powdered samples.
2：Sample Selection and Data Sources:
Powdered tungsten carbide (WC) samples of volumes of 40cm3 are used.
3：List of Experimental Equipment and Materials:
A helical structure at VHF frequencies, a vector network analyser (Agilent E5071C), a Micro-epsilon pyrometer, and a wide-field thermal imaging camera.
4：Experimental Procedures and Operational Workflow:
The sample-loaded coil is tuned via a π matching network. The system locks onto the resonance frequency and measures |S11|; Q is extracted by fitting the resonance absorption curve.
5：11|; Q is extracted by fitting the resonance absorption curve. Data Analysis Methods:
5. Data Analysis Methods: Changes in 1/Q are plotted, relating to changes in resonant bandwidth for R2, and are directly proportional to the power loss in the sample.
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