研究目的
The aim of the present work is experimental and numerical study the stress distribution during laser metal deposition of a 4-pass 50-layer Ti-6Al-4V wall. Long dwell time between passes and a rigid substrate was used in order to simulate conditions of large scale parts fabrication.
研究成果
An analysis of the calculated and experimentally measured residual stress field showed that near the edges of the buildup there is a region where all three components of stress field are tensile, and normal stress exceeds the yield stress by more than 25%. Moreover, normal plastic strain in this area are also tensile and reaches 2.5-3%. The longitudinal tensile stress closes to yield stress on almost the entire length of the several last layers near the top of the buildup. The average level of transverse stress is small, but near the substrate close to the buildup edges tensile stress exceeds half of the yield stress. Residual stress field calculated using neutron diffraction data according to interplanar lattice distance obtained assuming plane stress approach has a satisfactory agreement with FE simulated results.
研究不足
The study is limited by the use of a specific material (Ti-6Al-4V) and a specific deposition process (laser metal deposition with long dwell time between passes and a rigid substrate). The findings may not be directly applicable to other materials or deposition processes.
1：Experimental Design and Method Selection:
The study involved laser metal deposition of a 50-layer wall of Ti-6Al-4V on a Ti-6Al-4V plate, using a Fanuc robot equipped with a 5 kW fiber laser and a coaxial powder nozzle. The process parameters included a beam power of
2：6 kW, a beam oscillation amplitude of 1 mm, a beam radius of 0 mm, and a forward speed of 30 mm s-After each pass, the buildup was cooled down to 60-80 °C. Sample Selection and Data Sources:
A four pass 50 layers wall of Ti-6Al-4V was deposited on the edge of a 12 mm thick plate of conventionally processed Ti-6Al-4V.
3：4V. List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: The laser metal deposition system consisted of a Fanuc robot equipped with a 5 kW fiber laser and a coaxial powder nozzle. The measurement of residual stress field was carried out on a STRESS diffractometer.
4：Experimental Procedures and Operational Workflow:
The measurement of residual stress field in the buildup was carried out using neutron diffraction. The reference values of the lattice spacing d0 corresponding to the stress-free state were determined using a method based on the assumption that in a thin plate the through thickness stress perpendicular to the plate is zero.
5：Data Analysis Methods:
The strain components along the principal directions were measured and, using the generalized Hooke's law, the stress components along these directions were calculated.
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