Abstract
Laser welding is widely used in titanium alloy welding due to its high energy density, small heat affected zone, and rapid processing ability. However, problems with laser welding, such as deformation and cracking caused by residual stress, need to be resolved. In this paper, the residual stress in laser welding of TC4 titanium alloy was studied using an ultrasonic laser. The residual stress in titanium alloy plates is considered a plane stress state. A pre-stress loading method is proposed and acoustoelastic coefficients are obtained. Based on the known acoustoelastic coefficients, the transverse and longitudinal residual stresses in laser welding are measured using an ultrasonic laser. The results show that longitudinal residual stress is greater than the transverse stress. The distribution regularity of the residual stress is similar to normal welding, but the tensile stress zone is much narrower. Then, the influence of heat input and welding speed on residual stress is discussed. With increasing heat input, the welding zone widens, and the peak value of the residual stress increases. A higher welding speed should be chosen when the welding power is constant. This research has important significance for the measurement and control of residual stress in the laser welding process.
Highlights
The high temperature mechanical properties, high strength-to-weight ratio, and good corrosion resistance of titanium and titanium alloys have led its diversified and successful application in a variety of fields with demanding performance and reliability requirements, such as in the aerospace, automotive, medical, nuclear, petrochemical, and power generation industries [1,2]
For welds 1 and Figure 8 presents the longitudinal residual stress measurements for a series of laser welding, with the same heat input of 28 kJ/m, there was little change in the distribution and the maximum grouped by increasing heat input
An ultrasonic laser technique was used to measure the residual stress in laser welding of TC4
Summary
The high temperature mechanical properties, high strength-to-weight ratio, and good corrosion resistance of titanium and titanium alloys have led its diversified and successful application in a variety of fields with demanding performance and reliability requirements, such as in the aerospace, automotive, medical, nuclear, petrochemical, and power generation industries [1,2]. Duquennoy et al [10] measured surface residual stress in steel bars with different heat treatments processes using a laser-induced ultrasonic surface wave. Dong et al [15] used laser-induced surface waves to determine the velocity distribution around the laser welded joint of an aluminum alloy sheet, from which the profile of the principal residual stress was calculated based on acoustoelastic theory. Fernandes et al [18] used the laser Nd:YAG (Neodymium Yttrium Aluminum Garnet) welding machine to determine the optimal welding parameters of dual-phase steel, and heat treatment was used to reduce the hardness of the HAZ. Ultrasonic laser technology, a noncontact method using laser for the generation and detection of ultrasonic waves, is used to measure residual stress in laser welding of TC4 titanium alloy. The contribution of this paper is important for the optimization of laser welding parameters and the evaluation of residual stress
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