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Roughening of the free surface in micro-forming results in the local necking and subsequent fracture, which seriously affects the formability of sheet metals. In this work, laser pre-shocking (LPS) was introduced into microscale laser dynamic flexible bulging (μLDFB) to reduce surface roughening in terms of reducing the surface roughness and refining the internal grains. In LPS experiments, when the laser energy is 447 mJ, the rebound of the copper foils can be negligible. LPS can be expected to suppress the surface roughening by reducing the initial roughness R0, increasing the N value and decreasing the rate of surface roughening. The copper foils subjected by 447 mJ LPS were used for the μLDFB experiments. The 50 μm T2 copper foils with four different grain sizes were used in μLDFB under different laser pulse energies. When laser pulse energy ranges from 325 mJ to 575 mJ, compared with μLDFB without LPS, the surface roughness on the bottom surface of the bulging sample is decreased. And the nano-hardness, elastic modulus and forming uniformity are significantly improved. In μLDFB experiments without LPS, for fine-grained samples, the cracks initiate in the bulging transition zone under 725 mJ laser energy due to surface roughening. As laser energy increases to 1050 mJ, the cracks initiate in the mold entrance zone due to the strong stress concentration. For coarse-grained samples, cracks initiate under 575 mJ laser energy, and the propagations of the cracks are difficult to predict due to non-uniform distribution of grain size and the difference of grain orientation. The experimental results suggest that LPS can reduce the possibility of the premature fracture caused by the local necking, and alleviate the uncertainty in the fracture mode.

Laser dynamic flexible forming (LDFF) is a novel high velocity forming (HVF) technology, in which the foil metal is loaded by laser shock wave. Strain localization is readily to occur around the bulge edge, which will result in the ultimate dynamic failure. In this work, the microstructures before and after dynamic fracture are characterized by transmission electron microscopy (TEM) to investigate the dynamic failure mechanism. The plastic deformation regions of copper foil are composed of shock compression, strain localization and bulge. Microstructure refinement was observed in three different plastic deformation regions, particularly, dynamic recrystallization (DRX) occurs in the strain localization and bulge regions. In bulge region, extremely thin secondary twins in the twin/matrix (T/M) lamellae are formed. The microstructure features in the strain localization region show that superplastic flow of material exists until fracture, which may be due to DRX and subsequent grain boundary sliding (GBS) of the recrystallized grains. The grain coarsening in strain localization region may degrade the material flowing ability which results in the dynamic fracture.

Micro-scale laser dynamic forming (μLDF) is a kind of high velocity forming processes, which uses laser shock wave to load the sheet metal. The surface degradation of micro-mold in μLDF and its effects on workpiece are first investigated in this work. The surface degradation is the gradual failure of micro-mold due to the regular repeated laser shock loadings, and some micro-channel defects with the dimensions of several micrometers are observed on the mold surface. During μLDF process, the material of workpiece flows into the cavities of micro-defects on mold surface when the laser power density increases to 6.46 GW/cm2, and the more obvious defect-like features are formed on the rear surface of workpiece as laser power density increases. This type of single-side forming is very interesting, and similar to coining. In order to investigate the surface degradation evolution process, laser shock target experiments are performed. The surfaces of the nodular cast iron targets were irradiated by different numbers of laser pulses, and the corresponding surface morphologies were observed to investigate the surface degradation evolution process. The experimental results show that, surface degradation of micro-mold is formed by void nucleation, growth, and coalescence under the repeated shock loadings. Numerical simulations considering micro-defect on mold surface are performed to investigate the effect of micro-defect on workpiece. Numerical results also show that laser shock wave can be used to replicate micro-coining feature on metal surface.

A novel laser shock forming process called micro-laser shock hydraulic forming (MLSHF) was proposed to fabricate a micro-bowl with miniature concave at the apex of the bottom. Liquid water, used as a soft punch, can generate pressure waves under the action of laser shock to deform a 30-μm-thick copper foil. The influence of laser energy on morphology, forming accuracy, thickness distribution, and surface quality under MLSHF process was discussed through experimental means. Experimental results showed that the miniature concave was fabricated at 1050 mJ, and the whole micro-bowl was formed at 1550 mJ. With the increase of laser energy, the fittability improved and rebound became increasingly severe. Serious thinning occurred at the fillet of the miniature concave. Moreover, the die with great surface quality reduced the surface roughness of the workpiece surface that contacted with the die. A numerical finite element analysis (FEA) model was established by Hypermesh/LS-DANA. The FEA model was firstly verified through an experiment, and then it was used to investigate the deformation behavior including dynamic forming process and strain distribution.

In this study, a novel micro-forming process called laser shock micro hydraulic bulging was proposed to fabricate micro feature on copper foil. In this process, liquid medium water was used as a soft punch, rubber layer with thickness of 200 μm was used to squeeze liquid medium, and laser shock wave was used as driving force. Forming depth, surface quality, thickness thinning ratio, and cross section micro hardness were investigated under different laser energies. Experimental results showed that the forming depth and surface roughness increased with the laser energy. However, the surface roughness increased slightly with the increase of laser energy, and no thermal response area was found at forming area. Maximum thickness thinning occurred at the fillet when laser energies were 565, 835 and 1200 mJ, while fracture occurred at the bottom area (not the apex) when the laser energy increased to 1380 mJ. Hardness test indicated that, when the material was in cold-rolled, the hardness along the cross-section of the formed area showed an irregular trend. When the material was changed with copper foil annealed at 450 °C, the hardness improved remarkably.

Micro-scale laser dynamic flexible forming (μLDFF) is a new kind of high velocity forming (HVF) process, which uses laser shock wave pressure to realize thin metal sheets micro-forming. Rebound effect usually occurs when forming deep complex micro-features, which has a significant effect on the forming precision. This work firstly investigates the impact and rebound behaviors of workpiece in μLDFF with rubber medium to probe the main affecting factors of rebound effect, then proposes a new μLDFF with plasticine medium to reduce the rebound effect. With the increase of laser energy, the average surface roughness of impact-affected zone (IAZ) reduces firstly by flattening behavior, and then increases afterward due to coining-like operation. The 3D deviation analyses between workpieces and micro-die are performed to characterize the fitability. When laser energy is 675 mJ, bottom region of workpiece fits well with the micro-die. When laser energy is increased to 1020 mJ, bottom region of workpiece separates from the micro-die due to rebound effect. A finite element model considering the machining marks on micro-die surface is built, and the predicted results are validated by experimental results. Coefficient of restitution (COR) and the rebound ratio (α) are used to investigate the impact and rebound process. The results show that rebound effect is dominated by laser energy, surface morphology of micro-die, and loading duration. To effectively reduce the rebound effect, the plasticine layer is first introduced as pressure-carrying medium in this work. The deformation behavior of plasticine medium is like a Reiner-Rivlin fluid. So the plasticine medium closely contacts with the sample during forming, this is equivalent to indirectly increasing the stiffness of sample and prolonging the loading duration. In addition, the plasticine layer can absorb impact-induced reflection wave. So plasticine medium can effectively improve the forming precision.

Laser dynamic flexible forming (LDFF) is a novel high velocity forming (HVF) technology, in which the high-energy laser shock waves act on the workpiece via a flexible medium. Dynamic bulge tests of copper sheet are performed to investigate the deformation and fracture behaviors in LDFF in this paper. The laser ablation states on K9 glass surfaces under different laser energies were characterized. The samples after LDFF were characterized by optical microscopy and scanning electron microscopy. For laser energy ranging from 1020 mJ to1380 mJ, as laser energy increases, the average surface roughness (Ra) in bulge region rapidly increases due to surface free forming. However, the Ra in laser shock compression region slowly decreases due to shock flattening. Strain localization occurs around the bulge edge, and the composition of oxygen element in this region is increased with laser energy. When laser energy is equal to or greater than 1690 mJ, localized deformation evolved into the dynamic failure. Apart from the elongated micro-voids, three interesting phenomena were observed: the melting marks, the serrated fracture boundaries and filaments. As the laser energy increases, the fracture mode varies from a tensile fracture mode to a shear fracture mode, then to a filament fracture mode. The filament fracture mode indicates that superplastic flow of material may exist until fracture, and oxidation behaviors make a great contribution to the superplastic flow.

The influences of ablative layer, soft punch, die depth, and laser energy on novel micro clinching of Al/Cu were investigated. Ablative layer thickness notably influenced metal flow including neck and interlock; the relationship between reasonable ablative layer thickness and certain laser energy range was summarized. Soft punch with 100 μm was more suitable than with other thickness for the process. In the joinable laser energy range, with increase of laser energy, interlock thickness gradually increased, whereas the neck and bottom thicknesses gradually decreased. The process window of Al/Cu combination was acquired, and a certain thickness difference which was at least 40 μm inevitably existed between the upper and lower metal foils. For every joinable combination, matching function of optimum die depth are derived based on Al and Cu foil thickness when the thickness of each metal foil was less than 200 μm. The single lap shearing test showed that the tensile strength and failure model of the joint both depended on neck and interlock thicknesses; only the joint that simultaneously formed a large interlock and large neck can attain a high joining strength.

The case of fabricating micro-channel on copper foil using micro-scale laser dynamic flexible forming (μLDFF) is investigated in this work. To study the deformation and fracture behaviors, the copper foils are subjected to increasing laser power density until the occurrence of fracture. When laser power density ranges from 0.110 GW/cm2 to 0.441 GW/cm2, smooth micro-channel features are formed on copper foils, and the depth of the micro-channel gradually increases. Melting marks are observed at the micro-die entrance of the sample with 0.441 GW/cm2 laser power density. When laser power density is 0.544 GW/cm2, partial fractures are observed. The surface of fracture region is rougher than that of micro-cracks and no micro-cracks regions, which is caused by the higher strain in fracture region. And the fracture edge is irregular, which is caused by the soft effect of material. Complete fracture occurs when laser power density is 0.691 GW/cm2.

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.

Laser high speed flexible micro-forming (LHSFF) process has been applied to the formation of metal sheets due to its unique advantages compared to conventional micro forming processes. The materials investigated in LHSFF were all single-layer metal sheets so far. However, new materials have been developed to replace single-layer metal sheets in some industry occasions because of their superior properties. This paper investigated a new process that employed LHSFF on the formation of multilayer metal sheets. The feasibility of this new process for three-layer Ni/Cu/Ni metal sheets was verified firstly. Some results could be obtained from the experiments. Surface roughening happened in formed components, and surface quality became worse with laser energy increasing. As thickness of soft punch increased, the forming depth of Ni/Cu/Ni metal sheets decreased under LHSFF. The thickness reduction and the amplification of micro-hardness of the external layer were larger than those of the middle layer, and those of the middle layer were larger than in the internal layer. Unlike conventional forming processes, the formation of Ni/Cu/Ni metal sheets did not suffer from delamination failure any more under LHSFF.

A forming process called the mask and flexible pad laser shock forming was proposed to fabricate the micro-features on the copper foil. In this process, the mask and laser beam were used as rigid punches. Shock waves induced by plasma were used as the source of loading and plasticine was used as a flexible pad. This was a micro scale and high strain rate forming process and the traditional forming method with micro-mold was changed. In the experiment, surface morphology of formed parts was represented and it was found that the mask played a significant role in the forming process. In order to understand the forming process in the experiment, process parameters, including laser pulse energy, numbers of laser pulse and grain size, were analyzed. The experimental results showed that different parameters had different effects on formed parts. The surface quality and the thickness distribution of formed parts were investigated. It was found that formed parts could keep good surface quality after laser shocking and the reasons were explored. The thickness distribution was measured and the thickness thinning rate was calculated. There was no local tightening or rupture in the forming area. In this paper, the micro-features could be obtained on metallic foils and the method of mold-free was proved to be feasible.

Overlapping laser shock imprinting (LSI) is proposed to alter the surface wettability of copper sheet. By using a micro-die with rough concave texture, under the action of laser shock waves, multiscale surface microstructures can be accurately fabricated. The homogeneity of the micro-pattern array under different overlap rates were investigated. The radial expansion effect can reduce the inhomogeneity, but the shock pressure induced by the radial expansion effect in the non-irradiated area is weaker than that in laser irradiated area. Observed contact angle result is in accord with theoretical Cassie-Baxter mode, and it increases first and then tends to be stable when the number of laser pulse ranges from 2 to 6. Multiscale surface microstructures can be observed in 4 and 6 laser pulses cases. LSI can reduce the surface free energy by decreasing its polar component, and it sharply decreases first and then tends to be stable when the number of laser pulse ranges from 2 to 6. The grain size of protruding feature decreases with laser pulse numbers. And nano-scale grains are observed on the surface layer, which is caused by the material flowing on the rough surface of micro-die. The nano-indentation tests indicated that mechanical properties are enhanced.

A novel laser dynamic flexible punching process is employed to fabricate micro-gears to address the difficulties in punch-to-die alignment in the conventional micro-punching process. In this process, induced shockwaves act as micro-punches and soft punch acts as the media to transmit pressure. The influences of laser intensity, foil thickness and grain size on dimensional accuracy and rollover diameter have been investigated experimentally. In addition, the changes in the hardness and elastic modulus of the workpiece after the laser shock effect are characterized by nano-indentation experiments. It is revealed that the dimensional accuracy is optimal when the laser intensity is 5.6 GW/cm2, but the laser intensity has little effect on the rollover diameter. Punched gears of thicker foils result in worse dimensional accuracy and larger rollover diameter. Foils annealed at 350 °C achieve the best punching accuracy but compromise with regard to the maximum rollover diameter. Furthermore, both the nano-hardness (9.92%) and elastic modulus (14.37%) are improved after the laser shock effect, as the evidence of an increase of surface strength and material stiffness. The proposed method, laser dynamic flexible punching, will potentially lead to new methods for micro-gears fabrication in the future.

Laser pre-shocking (LPS) was introduced into the laser dynamic flexible micropunching process to refine the grain size of a workpiece to improve the forming quality of punched parts. T2 copper foils with five different grain sizes and seven different laser power densities with and without LPS were used for the experiment. The results showed that the grains are refined and the average surface roughness decreases after LPS. For copper foils annealed at 650 &deg, C, the value of decreases from 0.430 to 0.363 &micro, m. The increase in laser energy density and grain size leads to the deterioration of the fracture surface. LPS can improve the quality of the fracture surface. Compared with punched holes without LPS, the dimensional accuracy and shape accuracy of punched holes can be improved by LPS. When grain size is close to the thickness of the copper foil, the forming quality of the punched parts becomes uncertain, owing to the difference in the orientation of the initial grains. The instability of laser dynamic flexible micropunching can be reduced by LPS. Especially, the improvement of forming quality of the punched part brought by LPS is significant for the copper foils with coarse grains.

In this paper, a laser-generated shock wave was used to induce plastic deformation of metallic foils using Plasticine as a flexible support. In this new micro-drawing process, the laser-generated shock wave and the Plasticine are used to replace the conventional metal punch and mold. By undergoing large plastic deformation under the laser-generated shock wave, Plasticine accurately keeps the shape of the deformed workpiece, thereby improving the forming quality. Moreover, this is a damage-free forming process because the Plasticine is softer than metal foils. The feasibility of this new drawing process was conducted experimentally on aluminum, cooper, and titanium foils. The thickness distribution at the cross-section of the work piece was studied to evaluate the risk of crack. Meanwhile, the arrays of craters were fabricated on titanium foils. The results show that mold-free laser shock micro-drawing forming is an effective method to fabricate controlled micro-craters on metallic foils.

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.

Microscale laser dynamic flexible forming (µLDFF) is a novel micro-forming process. Laser-induced shockwaves act on the soft punch to deform the metal foils. In this article, the forming properties of the µLDFF process are studied from four angles, namely, the maximum deformation depth, accuracy, thickness thinning ratio, and surface quality. The maximum deformation depth of the samples formed under different laser energies was measured. The 2D profiles of the workpieces were measured to study the accuracy. The results show that the deformed samples replicated the mold features well. The cold-mounted technique was used to measure the thickness of the deformed metal foils along the cross section and to discuss the thickness thinning ratio. The results show that µLDFF can reduce localized necking and stress concentrations effectively. The surface roughness was characterized to study the surface quality of the workpieces, and the results indicated that the deterioration of the formed surface was weakened dur...

Metal foil forming by laser-driven flyer (LDF) is a new micro-forming technology. The performance of the flyer is one of the main factors affecting the forming quality of workpiece. Considering the features of this technology, this paper presents a novel multi-layered flyer. Via magnetron sputtering, the absorption layer (titanium) and the ablation layer (aluminum) are produced on the confining medium. The impactor layer is manufactured by special cutting (a micro-punching method) and adhered to the center of the ablation layer by a gluing method. A pressure measurement system is conducted to measure the shockwave forming pressure of the laser-driven flyer, and a series of forming experiments are carried out to investigate the forming ability of the multi-layered flyer. Experimental results show that the multi-layered flyer can enhance the laser coupling efficiency to the flyer and achieve higher forming pressure than the single-layered flyer. Especially, the multi-layered flyer with the nonmetallic impactor layer of 100 µm polyurethane rubber has good forming quality in the laser-driven flyer micro-forming (LDFµF).

Laser indirect shock micro-embossing is a novel micro-high velocity forming technique, which uses laser-driven flyer to load the workpiece. In this paper, laser indirect shock micro-embossing of commercially pure copper and titanium sheet are investigated using both experimental and numerical methods. A fully 3-D finite element mode is proposed to simulate the transient deformation behaviors. The effects of material and laser energy on the deformations are investigated experimentally. Thickness distribution at the cross-section of the micro-channel is analyzed experimentally. Strain states during micro-embossing are used to interpret the variation in thickness distribution. Fracture along the inner edges of the micro-mould occurs for 8 μm copper when the pulse energy is 1200 mJ, 1380 mJ and 1550 mJ. Moreover, the 13 μm titanium is completely sheared off along the inner edge of the micromould when the pulse energy is 1550 mJ. With further development, the laser-driven flyer technique can realize the blanking forming. And experimental data obtained are then used to validate the corresponding simulation model. The results show that the finite element analysis can predict the final shape of the work piece properly.

Laser shock forming is a three-dimensional forming technique. It is promising for achieving precise, well-controlled, low-cost, high efficiency 3D metallic microstructures. In this research, a combined process of embossing and blanking is studied by experimental and simulation methods, in which the embossing and blanking of copper sheets are performed at the same time in only one operation. In order to obtain multi-workpieces in one process, overlapping laser spots were applied in the experiment. Moreover, the influence of laser energies on the work pieces were considered, and the results show that the micro features on the boss surface of the mold were successfully replicated on the blanking copper foil surface with the suitable energy. By evaluating the surface roughness data, it can imply that the work piece surface can fit the mold surface. Meanwhile, the process of the combined embossing and blanking was also studied by numerical simulation, the simulation results show that the finite element analysis can predict the final shape of work piece properly, verifying the feasibility of this process.

A novel microscale laser dynamic flexible punching technology combining flexible punching and laser shock forming is presented. The ultrahigh strain rates of workpiece’s material and soft punch driven by dynamic shock load are the significant feature of this process. In the present study, arrays of 300 μm × 300 μm square holes with good sheared edges quality are obtained on 20 μm Al foils. The shearing behavior is also investigated through investigating cross section of punched hole. As a piece of polyurethane rubber loaded by the ultra-high transient pressure of laser supported detonation wave (LSD) is employed as soft punch, the new process has such advantages as homogenizing pressure, easy demould and reducing springback. To study more details in an extremely short interval, simulations are conducted by ANSYS/LS-DYNA and LS-PrePost. The methods of Finite Element Mesh (FEM) and Smoothed Particle Hydrodynamics (SPH) are used. The relationship between soft punch thickness and corresponding minimum punching energy for various workpiece thicknesses is revealed. In addition, the material flowing behavior around the sheared edges has also been discussed. The results in this paper indicate that the present process is promising to fabricate high quality micro holes in the micro scale application.

The influence of nanosecond laser pulses applied by the overlapping laser shock micro-adjustment with Nd:YAG laser operating at a wavelength of λ =1064 nm on aluminum has been investigated. Systematic study was carried out in the term of effects of various factors on the surface quality and the adjusting results, including the laser energies, the overlap rates and the number of impacts. According to the results, a fine surface quality can be obtained by adjusting the process parameters. Depending on the local plastic deformation of material area beneath each laser shock, both convex and concave curvatures can be generated. Furthermore, the investigation of the overlapping laser shock micro-adjustment effect on mechanical properties was evaluated based on the residual stress distribution. From an industrial point of view, the overlapping laser shock micro-adjustment experiments without absorbent coating were also carried out.

Laser shock embossing is a new three-dimensional (3D) forming technique, which utilizes laser-generated shock wave to shape the workpiece with micro-mold. Micro rectangular array feature with dimensions of 500 μm×450 μm×14 μm were successfully fabricated on metallic foil surface using overlapping laser shock embossing. The investigation reveals that 3D rectangular array features have a high spatial resolution at the micron level. However the micro rectangular features located on the overlap region is not so perfect. With further development, micro-mold based overlapping laser shock embossing holds promise for achieving large-area three-dimensional array features on metallic foil surface. And the forming experiment of the flower shape feature proves that the fabrication cost is independent of the microstructures complexity.

Laser shock micro-adjustment is a new adjustment technique using laser-shock-waves to adjust the curvature of micro-components (micro-mechanical cantilevers). A full empirical study has been conducted, with the effects of laser energy, laser shock region and sample thickness investigated. And, the influences of laser processing parameters on the surface qualities are also taken into consideration and investigated. According to the result, compared with the surface roughness in the shock and un-shock regions, it can be found that the average surface roughness (Ra) of adjustment surface is lower than that of other un-shock surface, implying the surface quality would be upgraded via the shock micro-adjustment processing. A fine surface quality can be obtained by means of adjusting the laser parameters and the thickness of coating, as well as other process details. Such a technique is simple to implement, yet very useful for applications involving adjustment of micro-components in the field of MEMS.

This paper describes a precise and non-contact adjustment technique using the water-confined laser-generated plasma to adjust the curvature of micro-components (micro-mechanical cantilevers). A series of laser shock micro-adjustment experiments were conducted on 0.4 mm-thick Al samples using pulsed Nd:YAG lasers operating at 1064 nm wavelengths to verify the technical feasibility. Systematic study was carried out in the term of effects of various factors on the adjusting results, including laser energies, laser focus positions, laser shock times and confined regime configuration. The research results have shown that the different bending angles and bending directions can be obtained by changing the laser processing parameters. And, for the adjustment process, the absence of confined regime configuration could also generate suitable bending deformation. But, in the case of larger energy, the final surfaces would have the sign of ablation, hence resulting in poor surface quality. An analysis procedure including dynamic analysis performed by ANSYS/LS-DYNA and static analysis performed by ANSYS is presented in detail to attain the simulation of laser shock micro-adjustment to predict the final bending deformation. The predicted bending profiles is well correlated with the available experimental data, showing the finite element analysis can predict the final curvatures of the micro-cantilevers properly.

This paper presents a novel microscale laser dynamic flexible forming (μLDFF) technique on plastic forming of thin metal sheets. This process utilizes flexible rubber material as a soft punch, under the pressure generated by laser-induced shock wave, to act on the thin metal sheet. This novel technique has many new features and the forming mechanism is complex, as well as it takes place in the scale of nanoseconds, which is too short to monitor the deformation behaviors during the process. In order to reduce the experiment times and cost, this paper firstly investigates the feasibility of the process numerically using finite element software ANSYS/LSDYNA, and some key process parameters, such as hardness and thickness of soft punch, thickness of thin metal sheet, aspect ratio of rigid die, as well as laser pulse energy are detailed studied to obtain reasonable parameters. Then a series of experiments based on these reasonable parameters are conducted, and good experimental results are obtained, which verifies the feasibility of the use of simulation to guide the experiment. The results of both numerical simulations and experiments show that the use of combination of soft punch and thin metal sheet can increase the deformation depth in comparison to focusing the beam directly onto thin metal sheet, which is due to the impedance mismatch at the soft punch–thin metal sheet interface.

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.

A novel technology called mask and plasticine laser shock forming (MAPLSF) was introduced to manufacture micro-features on the surface of pure copper foil with the thickness of 40μm. In this process, the laser-generated shock wave and plasticine are used to replace the conventional rigid punch and die. The result showed that the shape of laser beam can be roughly manufactured on the surface of the workpiece and this mold-free laser shock forming process is a fast method to fabricate controlled micro-feature on the metallic foils. In this damage-free forming process, the workpicec can keep good surface, because the plasticine is softer than metal foils.

A novel micro-plastic microfabrication technique for embossing is presented, which uses laser-driven flyer as the loading method in forming. Experiments were performed by allowing the laser-driven flyer to impact the thin film, which is placed above a micromold. Micro-channel with dimension of 160 μm×45 μm was successfully fabricated on copper foil surface using laser-driven flyer. The effects of laser energy on deformation mechanism were investigated experimentally. Surface roughness changes on formed sample were discussed. The novel technique holds promise for achieving precise, well-controlled, low-cost, high efficiency of three-dimensional metallic microstructures. In addition, this technique can cold form high strength or difficult materials.

Micromold-based laser shock embossing is a new three-dimensional (3D) forming technique, which utilizes laser-generated shock wave to shape the workpiece. In this article, the microchannel networks mold was produced by micro-wire electrical discharge machining (Micro-WEDM). Large-area three-dimensional microchannel networks were successfully fabricated on metallic foil surface using laser-generated shock wave. The investigation reveals that 3D microchannel networks have a high spatial resolution at the micron level. The fracture in the forming experiment was also detected. The fabrication cost is independent of the microstructures complexity. Therefore, micromold-based laser shock embossing holds promise for achieving precise, well-controlled, low-cost, high efficiency of 3D metallic microstructures.

A novel process technology for micro punching of thin sheet metals is presented in this paper. The laser induced shock waves act as the micro punch. The forming speed can be controlled by adjusting the laser energy. Micro holes of 250 μm in diameter were successfully punched on sheet metal of 10 μm in thickness by single pulse, and good edge quality was obtained. The micro die-opening is produced by electrical discharge machining (EDM) using the copper electrode of φ=220 μm. In the experiment, a sacrificial coating is used to generate high-pressure plasma under a laser pulse, so no signs of melting, burning, or ablation were observed on the workpiece. The novel process of micro scale laser high speed punching is also numerically studied. In addition, this method can be used to fabricate noncircular micro holes on thin sheet metals with noncircular micro die-openings. With further development, laser high speed punching may become an important micro punching technology, which is characterized by non-contact, low cost, and high efficiency.

Laser shock forming is a new material processing technology. Micro-channel with dimension of 260 μm × 59 μm was successfully fabricated on metallic foil surface using laser-generated shock wave. The work piece has a high spatial resolution at the micron-level. A series of experiments was conducted to validate the finite element model. An analysis procedure including dynamic analysis performed by ANSYS/LS-DYNA and static analysis performed by ANSYS is presented in detail to attain the simulation of laser shock embossing to predict the surface deformation. Micromould based laser shock embossing holds promise for achieving precise, well-controlled, low-cost, high efficiency of three-dimensional metallic microstructures. In addition, this technique can fabricate complex 3D microstructures directly by single pulse.

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.

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.

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.

A novel laser high speed punching is presented. The laser induced shock wave acts as a punch. The forming speed can be controlled by adjustment of the laser energy. The previously-reported experimental results show that laser high speed punching is possible. This paper reports an investigation into the laser high speed punching process through finite element simulation. The Johnson-Cook model shear damage model is used as the fracture criterion for laser high speed punching. The finite element method was applied through the use of ANSYS/LS-DYNA code.

In order to overcome the deficiencies of the traditional laser surface texturing, a useful surface texturing method by generating micro dents based on the laser shock processing technology was investigated in this paper. A series of experiments focusing on the effects of pulse energies and shock numbers for laser shock micro dents were carried out. An analysis procedure including dynamic analysis performed by ANSYS/LS-DYNA and static analysis performed by ANSYS is presented in detail to establish a 3D finite element model. By establishing more reasonable and accurate model, the simulation results would have better correlation with the experimental results. The bulges around the dents are observed in the experiment and simulation results. Besides, the calculation formula of laser shock wave pressure can be revised by comparing simulation results with experimental results.

A novel laser indirect shock forming is presented, which uses laser-driven flyer to load the workpiece. Experiments were performed by allowing the laser-driven flyer to impact a stationary workpiece. The flyer can protect the workpiece from thermal effects so that pure mechanical effects are induced. The experimental results show that laser indirect shock forming is possible and the workpiece have a high spatial resolution at the micron level. In addition, the forming technology can effectively prevent wrinkling. The effect of laser energies on the deformation mechanism was investigated experimentally, and experimental data obtained were then used to validate the corresponding simulation model. The results show that the finite element analysis can predict the final shape of workpiece properly.