This article presents the first comprehensive investigation coupling phase transformation, mechanical properties, and tribological behavior across build height in large scale laser wire directed energy deposition (LW‐DED) fabricated NiTi alloy. A 140 × 135 × 10 mm wall is deposited to conduct location specific characterization and tribo‐mechanical testing that can reveal the phase and property heterogeneity along the build height. X‐ray diffraction quantified B2 austenite decreasing from 23 wt% at the upper region to 0 wt% at the lower region while R‐phase peaked at 45 wt% in the middle region of printed NiTi wall. Differential scanning calorimetry showed martensite start temperatures ranging from 30.20 to 34.21 °C along the build height. Tensile testing demonstrated ultimate strength variations from 412 MPa in the lower region to 578 MPa in the upper region, representing ≈40% strength increase. Reciprocating wear tests on sectioned NiTi samples against AISI 52100 counter ball revealed build height dependent wear resistance, with the upper region exhibiting higher wear volume despite similar friction coefficients. The middle region presented a balance between strength and tensile ductility with the highest R‐phase content, suggesting the crucial effects of thermal gyration during LW‐DED on tribo‐mechanical behavior in large scale NiTi components.

The NiTi alloy has attracted significant interest owing to its notable wear and corrosion resistance, suggesting the significant promise of utilizing additively manufactured NiTi alloys in tribological applications. In this study, dry sliding wear tests with sliding velocity of 0.1 m/s for total distance of 250 m at room temperature, 50 degrees C, 100 degrees C, and 200 degrees C were carried out on samples of NiTi alloy samples fabricated using laser powder and laser wire directed energy deposition (LP-DED and LW-DED) processes. Enhanced friction and wear behavior of LP-DED samples were captured at lower temperatures due to higher hardness and the stable dominating NiTi B2 austenite phase in the sample microstructure as confirmed from x-ray diffraction (XRD) analysis. Accumulated transferred material at lower temperatures played a crucial role in modifying the wear mechanisms. However, at higher temperatures both LP-DED and LW-DED samples presented similar wear mechanisms.

In recent years, Carbon Fiber Reinforced Plastics (CFRP) or Glass Fiber Reinforced Plastics (GFRPs) have become a very common material for aircraft and wind turbine structures. These structures are often protected from lightning strikes using conventional metal-based protective films/foils. Non-conventional, non-metallic lightning strike protection (LSP) technologies have not yet been fully realized, but research on non-conventional LSP systems for CFRPs has gained momentum in the last few years. The discovery of new structural conductive materials and improvements in the processing of carbon nano-filler based composites have challenged the conventional metal-based LSP systems by providing the potential for lightweight, non-metallic alternatives. However, a major challenge in using non-conventional LSP is the complex nature of a lightning strike event and its complicated thermal and mechanical impact on CFRP structures. Understanding the direct effect of a lightning strike on a CFRP structure requires understanding multiple transient loads, such as electrical, thermal, magnetic, acoustics, shock, and inertia. This review article focuses on new findings and discusses the complex direct effects of lightning on CFRPs. The focus is to find the important factors that regulate and control the damage to FRPs and they are classified and discussed with the help of available literature based on experimental results. Possibilities and limitations to these new findings are also discussed.

Laser metal deposition with wire (LMD-w) is a developing additive manufacturing (AM) technology that has a high deposition material rate and efficiency and is suitable for fabrication of large aerospace components. However, control of material properties, geometry, and residual stresses is needed before LMD-w technology can be widely adopted for the construction of critical structural components. In this study, we investigated the effect of interlayer cooling time, clamp constraints, and tool path strategy on part distortion and residual stresses in large-scale laser additive manufactured Ti-6Al-4V components using finite element method (FEM). The simulations were validated with the temperature and the distortion measurements obtained from a real LMD-w process. We found that a shorter interlayer cooling time, full clamping constraints on the build plates, and a bidirectional tool path with 180° rotation minimized part distortion and residual stresses and resulted in symmetric stress distribution.

A non-contact speckle correlation sensor for the measurement of robotic tool speed is described that is capable of measuring the in-plane relative velocities between a robot end-effector and the workplace or other surface. The sensor performance has been assessed in the laboratory with sensor accuracies of +/- 0.01 mm/s over a +/- 70 mm/s velocity range. The effect of misalignment of the sensor on the robot was assessed for variation in both working distance and angular alignment with sensor accuracy maintained to within 0.025 mm/s (< 0.04%) over a working distance variation of +/- 5 mm from the sensor design distance and +/- 0.4 mm/s (0.6%) for a misalignment of 5 degrees. The sensor precision was found to be limited by the peak fitting accuracy used in the signal processing with peak errors of +/- 0.34 mm/s. Finally an example of the sensor's application to robotic manufacturing is presented where the sensor was applied to tool speed measurement for path planning in the wire and arc additive manufacturing process using a KUKA KR150 L110/2 industrial robot.

Owing to the high reactivity of titanium with oxygen at high temperatures, oxidation is often observed during wire and arc additive manufacture (WAAM) of Ti-6Al-4V. As a sign of oxidation, discoloration of titanium components built by WAAM is usually observed, due to the formation of a thin oxide scale on the surface. This generally constitutes a major concern from the end user. Together with the oxide scale, oxidation also produces the formation of a brittle oxygen-enriched layer near the surface (Alpha Case) and it can be detrimental in terms of mechanical properties. Hence, it is of major interest to investigate the influence of surface oxidation on the bulk material property of WAAM of Ti-6Al-4V and understand the oxidation process during WAAM deposition. In this work, oxidation of titanium during WAAM was investigated to determine the mechanisms and main process parameters controlling this phenomenon. To address this, plasma-transferred arc and wire deposition samples were manufactured by changing either deposition parameters or oxygen levels in the fusion atmosphere. Subsequently, samples were characterized by means of visual inspection, optical microscope, scanning electron microscope, and tensile mechanical testing. For any containing level of oxygen in the shielding environment, it was found that if temperatures are high enough and exposure times long, oxidation of titanium is observed. In addition, it was possible to determine that oxidation is more significant in the region of the first deposited layers. The maximum depth of Alpha Case was found to be 200 mu m for the samples built with higher current (220 A) and wider oscillation width. Tensile testing revealed that increasing 40 times the oxygen levels in the shielding environment does not affect the tensile strength significantly.

A non-contact speckle correlation sensor for the measurement of robotic tool speed is presented for use in robotic manufacturing and is capable of measuring the in-plane relative velocities between a robot end-effector and the workpiece or other surface. The sensor performance was assessed in the laboratory with the sensor accuracies found to be better than 0.01 mm/s over a 70 mm/s velocity range. Finally an example of the sensors application to robotic manufacturing is presented where the sensor was applied to tool speed measurement for path planning in the wire and arc additive manufacturing process using a KUKA KR150 L110/2 industrial robot.