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In response to the issue of weak laser connection strength between 304 stainless steel and the carbon fiber-reinforced polymer PCCF30, this study proposes the addition of a polyethylene terephthalate (PET) intermediate layer between 304 stainless steel and PCCF30, along with surface texture pretreatment of the stainless steel surface, to enhance the joint connection strength. First, three types of surface textures (vertical, wavy, and vertical plus wave) were investigated for their effect on joint quality. Once the optimal texture type was determined, the effect of texture scanning repetition on the surface morphology and groove cross-sectional geometry of 304 stainless steel was examined. The joint strengths achieved by adding intermediate layers and employing different surface texture treatment methods were compared, followed by a comparison of the joint strengths obtained from different pretreatment methods. Finally, the connection mechanism of the joint was analyzed. The results indicated that the maximum joint strength achieved through the vertical and wavy texture design was 4.39 MPa, which is 3.3 times greater than that achieved without reinforcement. Moreover, the maximum joint strength achieved with the addition of a PET intermediate layer and surface texture composite treatment was 11.85 MPa, which is approximately nine times greater than that achieved via direct connection. The inclusion of a PET intermediate layer enhances the fluidity of the molten polymer at the joint, facilitating better filling of the grooves with surface texture. This strengthens the mechanical anchoring effect of the joint and contributes to the improvement in the joint’s connection strength. An XPS analysis revealed that after multiple etchings of the joint interface with an added intermediate layer, the Cr in the stainless steel chemically bonded with the PET, resulting in the formation of Cr–O–C chemical bonds, which is advantageous for enhancing joint quality.

Microscale laser dynamic forming, as a novel high-speed microforming technique, can overcome the shortcomings of traditional microforming methods. However, in practical applications, laser dynamic microforming technology is often affected by the rebound behavior of the workpiece, limiting the further improvement of processing quality and efficiency. This paper aims to reduce the rebound effect in laser dynamic forming by using multi-pulse laser shock loading. The forming results of workpieces under different laser energies and laser impact numbers were studied using experimental and numerical simulation methods. After multiple laser shocks, numerical simulations of the forming results were conducted using ANSYS/LS-DYNA software. These numerical simulation results were then experimentally validated and compared. The surface morphology of the workpieces was characterized using a confocal microscope and a scanning electron microscope (SEM). Energy-dispersive spectroscopy (EDS) was used to analyze the chemical element content changes in the collision regions at the bottoms of the workpieces after multi-pulse loading. The SEM and EDS results revealed the collision behavior patterns during the forming process. Finally, the forming laws of workpieces under multiple laser shocks were summarized.

The production of pipe assembly for a rocket engine has experienced challenges owing to the higher requirements of the joining and sealing performance. An adjustable laser bending pipe is a flexible and economical means of compensating for production errors after welding, located in the “closing” segment. To improve the productivity and accuracy of the adjustable laser bending pipe, inline measurement systems are integrated into production to develop an adaptive control system. The models of adjustable laser bending pipe to compensate for pipe assembly production errors are established using kinematics and the displacement screw system, and the proposed adaptive control system is validated by the experiment based on the springback-free laser pipe bending process. Using the proposed adaptive control system, the angle deviation decreases from 7.086° to 0.154°, and the distance deviation decreases from 5.076 mm to 0.104 mm. The validation results satisfactorily meet the requirement of the welding axis alignment of the pipe ends. These models demonstrate significant potential to be applied for calculating the feedback parameters required in the adjustments to compensate for pipe assembly production errors.

The size effect seriously affects the forming quality of micro-formed parts in the field of micro-forming. This paper focuses on the influence of the mold size effect in microscale laser dynamic flexible bulging (μLDFB). The experimental results indicate that, for the copper foil with a given thickness, there are suitable mold characteristic sizes to obtain better forming quality. The surface quality of bulging parts is poor when the mold characteristic size is small. However, the forming symmetry and forming uniformity of bulging samples are reduced when the mold characteristic size is large. As the laser pulse energy increases, the plastic strain increases, and the bulging samples experience five stages: uniform plastic deformation, local necking, cracks in the bulging zone, complete fracture in the bulging zone and complete rupture at the mold entrance zone. The increase of the surface roughening rate caused by the increase of grain size and mold characteristic size makes local necking easier, which further leads to fracture. On this basis, in this paper laser pre-shocking (LPS) is introduced to improve the forming quality. Comparative experiments show that LPS has a positive effect on improving the surface quality and the forming performance of bulging samples. The forming limit of bulging samples is increased and the occurrence of local necking is delayed.

The fragmentation mechanism of copper sheet in laser dynamic forming (LDF) process is investigated. The investigation of the fragmentation mechanism in the moving sample is quite difficult, so finite element method is adopted to provide detailed information on the stress state during micro-forming. The shock loading was generated using laser-shock-rubber loading technique in which a layer of rubber is inserted to improve laser shock efficiency. When laser power density is 0.491 GW cm ^−2 , the obvious circular fragmentation is located at the center region of rear surface. When laser power density is 0.658 GW cm ^−2 , the diameter of the fragmentation region increased, and what’s more, circumferential and radial cracks were formed in the fragmentation region. The void linkages and terrace-like pattern were also observed. Finite element model reveals that the fragmentation in the moving sheet is not caused by the initial rubber direct loading, but the deceleration at the last stage of forming. Because the curvature in the tip has the highest value at the stopping point, deceleration passes through its maximum value and then causes fragmentation at the last stage of forming. When laser power density is 0.658 GW cm ^−2 , the single layer fragmentation, multiple layer fragmentation, circumferential crack, and radial cracks occur in that sequence.

The aim of this paper is to fabricate micro-gears via laser shock punching with Spitlight 2000 Nd-YAG Laser, and to discuss effects of process parameters namely laser energy, soft punch properties and blank-holder on the quality of micro-gears deeply. Results show that dimensional accuracy is the best shocked at 1690 mJ. Tensile fracture instead of shear fracture is the main fracture mode under low laser energy. The soft punch might cause damage to punching quality when too high energy is employed. Appropriate thickness and hardness of soft punch is necessary. Silica gel with 200 µm in thickness is beneficial to not only homogenize energy but also propagate the shock wave. Polyurethane films need more energy than silica gel with the same thickness. In addition, blank-holders with different weight levels are used. A heavier blank-holder is more beneficial to improve the cutting quality. Furthermore, the simulation is conducted to reveal typical stages and the different deformation behavior under high and low pulse energy. The simulation results show that the fracture mode changes under lower energy.

Microscale laser dynamic flexible forming (µLDFF) is a novel ultrahigh strain rate manufacturing technology with high efficiency and low cost. However, the µLDFF is just confined to single-layer foil at present. In this work, sheet metal laminates (Cu/Ni) were selected as the experimental material for its excellent mechanical and functional properties, and a new micro-bending method of sheet metal laminates by laser-driven soft punch was proposed in warm conditions. The micro-mold and warm platform were designed to investigate the effects of temperature and energy on formability, which were characterized by forming accuracy, surface quality, element diffusion, and so on. The experimental results show that the forming accuracy and quality increased first and then decreased with laser energy, but the hardness increased consistently. In warm conditions, the fluidity of material was improved. The forming depth and accuracy increased for the relieved springback, and the surface quality increased first and then decreased. The tensile fracture disappeared with temperature for the decreased hardness and thinning ratio, and the element diffusion occurred. Overall, this study indicates that the formability can be improved in warm conditions and provides a basis for the investigation of micro-bending of sheet metal laminates by µLDFF in warm conditions.

Multilayer metal composite sheets possess superior properties to monolithic metal sheets, and formability is different from monolithic metal sheets. In this research, the feature size effect on formability of multilayer metal composite sheets under microscale laser flexible forming was studied by experiment. Two-layer copper/nickel composite sheets were selected as experimental materials. Five types of micro molds with different diameters were utilized. The formability of materials was evaluated by forming depth, thickness thinning, surface quality, and micro-hardness distribution. The research results showed that the formability of two-layer copper/nickel composite sheets was strongly influenced by feature size. With feature size increasing, the effect of layer stacking sequence on forming depth, thickness thinning ratio, and surface roughness became increasingly larger. However, the normalized forming depth, thickness thinning ratio, surface roughness, and micro-hardness of the formed components under the same layer stacking sequence first increased and then decreased with increasing feature size. The deformation behavior of copper/nickel composite sheets was determined by the external layer. The deformation extent was larger when the copper layer was set as the external layer.

Laser flexible shock micro-bulging (LFSB) is a novel micro fabrication technology, which combines laser dynamic forming and flexible die forming, which is a type of high strain rate micro-forming. The LFSB of 304 stainless steel foils was investigated in this paper. Experimental and simulated results indicated that the bulging depth and thickness thinning rate of bulging parts increased with an increase of laser energy and a decrease of workpiece thickness. Experimental results also showed the surface morphology of bulging parts. The hardness distribution in the cross section of bulging parts was revealed by nanoindentation experiments. The internal microstructure of micro bulging parts was observed by TEM. In addition, the equivalent stress and plastic strain distribution of bulging parts were shown in the numerical simulation under different workpiece thicknesses and laser energies.

Compound process technology has been investigated for many years on a macro scale, but only a few studies can be found on a micro scale due to the difficulties in tool manufacturing, parts transporting and punch-die alignment. In this paper, a novel technology of combining the laser shock wave and soft punch was introduced to fabricate the dish-shaped micro-parts on copper to solve these difficulties. This compound process includes deep drawing, punching and blanking and these processes can be completed almost at the same time because the duration time of laser is quite short, so the precision of the micro-parts can be ensured. A reasonable laser energy of 1550 mJ made the morphology, depth of deformation, dimensional accuracy and surface roughness achieve their best results when the thickness of the soft punches was 200 μm. In addition, thicker soft punches may hinder the compound process due to the action of unloading waves based on the elastic wave theory. So, the greatest thickness of the soft punches was 200 μm.

A novel laser indirect shock forming, which has used laser-driven flyer to load the workpiece, is described. The effect of laser energies on the deformation mechanism is examined and the results have shown that the finite element analysis has predicted the final shape of workpiece properly.

In this paper a novel laser impact spot welding (LISW) method is described, in which a hump was formed on the flyer plate on the intended welding spot location by local pre-forming. When the flyer and base plates were placed together to perform welding, the two plates kept in contact over their entire surfaces except at the hump, where a local air gap was enough to guarantee the impact velocity and collision angle to achieve spot welding using laser pulse energy. The presented approach was implemented to join thin titanium foils to copper foils under low laser energy system. Joints with regular shapes were obtained. The microstructure in the weld interface was studied with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It was found that the jetting occurred at the central region of the weld spots due to oblique impact. Wave features were observed in the weld interfaces. The impact energy was found to have significant influence on the wave's characteristics. Moreover, SEM images and EDS analysis did not show apparent element diffusion across the weld interface. Besides, the lap shearing test was used to characterize the mechanical properties of the spot welded joints. [ABSTRACT FROM AUTHOR]

This paper describes a novel technique for joining similar and dissimilar metal foils, namely micro clinching with cutting by laser shock forming. A series of experiments were conducted to study the deformation behavior of single layer material, during which many important process parameters were determined. The process window of the 1060 pure aluminum foils and annealed copper foils produced by micro clinching with cutting was analyzed. Moreover, similar material combination (annealed copper foils) and dissimilar material combination (1060 pure aluminum foils and 304 stainless steel foils) were successfully achieved. The effect of laser energy on the interlock and minimum thickness of upper foils was investigated. In addition, the mechanical strength of different material combinations joined by micro clinching with cutting was measured in single lap shearing tests. According to the achieved results, this novel technique is more suitable for material combinations where the upper foil is thicker than lower foil. With the increase of laser energy, the interlock increased while the minimum thickness of upper foil decreased gradually. The shear strength of 1060 pure aluminum foils and 304 stainless steel foils combination was three times as large as that of 1060 pure aluminum foils and annealed copper foils combination. [ABSTRACT FROM AUTHOR]

Plasticine is widely used in the analysis of metal forming processes, due to its excellent material flow ability. In this study, plasticine is used as the soft punch to fabricate array micro-channels on metal sheet in the micro sheet stamping process. This is because plasticine can produce a large material flow after being subjected to force and through the material flow, the plasticine can cause the sheet to fill into the micro-channels of the rigid die, leading to the generation of micro-channels in the sheet. The distribution of array micro-channels was investigated as well as the influence of load forces on the sheet deformations. It was found that the depth of micro-channels increases as the load force increases. When the load force reaches a certain level, a crack can be observed. The micro sheet stamping process was also investigated by the method of numerical simulation. The obtained experimental and numerical results for the stamping process showed that they were in good agreement. Additionally, from the simulation results, it can be seen that the corner region of the micro-channel-shape work piece has a risk to crack due to the existence of maximum von Mises stress and significant thinning. [ABSTRACT FROM AUTHOR]

Laser indirect shock forming is a novel microfabrication technique to introduce 3D profiles in metallic thin films. Experiments were performed by allowing the laser-driven flyer to impact the thin film, which is placed above a micromould. The effects of laser energy and sample thickness on deformation mechanism were investigated experimentally. The experimental results show that increasing the laser energy could increase the deformation depth, but may induce fracture along the edges of the micromould when the laser energy is too high. Moreover, the target plate was completely sheared off for 10 µm copper when the pulse energy is 1200 mJ. So it can be found that the technique can also realize micro punching of metallic thin films. The transient deformation of copper foil impacted by laser-driven flyer is simulated in this paper. Experimental data obtained were then used to validate the corresponding simulation model. Good agreement has been obtained between the numerical simulation and the experiments under different laser energy. The rising temperature due to the adiabatic conditions is taken into account. And the strain distribution has been also calculated numerically. [ABSTRACT FROM AUTHOR]