Search Results (34)

Climate concerns are driving the automotive industry to adopt advanced manufacturing technologies that aim to improve energy efficiency and reduce vehicle weight. In this context, lightweight structural materials such as aluminium alloys have gained significant attention due to their favorable strength-to-weight ratio. Laser welding plays a crucial role in assembling such materials, offering high flexibility and fast joining capabilities for thin aluminium sheets. However, welding these materials presents specific challenges, particularly in controlling heat input to minimize distortions and ensure consistent weld quality. As a result, numerical simulations based on the Finite Element Method (FEM) are essential for predicting weld-induced phenomena and optimizing process performance. This study investigates welding-induced distortions in laser butt welding of 1.5 mm-thick Al 6061 samples through FEM simulations performed in the SYSWELD 2024.0 environment. The methodology provided by the software is based on the Moving Heat Source (MHS) model, which simulates the physical movement of the heat source and typically requires extensive calibration through destructive metallographic testing. This transient approach enables the detailed prediction of thermal, metallurgical, and mechanical behavior, but it is computationally demanding. To improve efficiency, the Imposed Thermal Cycle (ITC) model is often used. In this technique, a thermal cycle, extracted from an MHS simulation or experimental data, is imposed on predefined subregions of the model, allowing only mechanical behavior to be simulated while reducing computation time. To avoid MHS-based calibration, this work proposes using thermal cycles acquired in-line during welding via infrared thermography as direct input for the ITC model. The method was validated experimentally and numerically, showing good agreement in the prediction of distortions and a significant reduction in workflow time. The distortion values from simulations differ from the real experiment by less than 0.3%. Our method exhibits a slight decrease in performance, resulting in an increase in estimation error of 0.03% compared to classic approaches, but more than 85% saving in computation time. The integration of real process data into the simulation enables a virtual representation of the process, supporting future developments toward Digital Twin applications. Full article

This study develops an optimized femtosecond laser welding process for joining quartz glass and TC4 titanium alloy (Ti-6Al-4V) under non-optical contact conditions, specifically addressing the manufacturing needs of specialized photoelectric effect research containers. The joint primarily consists of parallel laser-welded zones (WZ) interspersed with base material. The defocus distance of the femtosecond laser predominantly influences the depth and phase composition of the WZ, while the weld spacing influences the crack distribution in the joint region. The maximum shear strength of 14.4 MPa was achieved at a defocusing distance of +0.1 mm (below the interface) and a weld spacing of 40 μm. The XRD stress measurements indicate that the defocusing distance mainly affects the stress along the direction of laser impact (DLI), whereas the weld spacing primarily influences the stress along the direction of spacing (DS). GPA results demonstrate that when the spacing is less than 30 μm, the non-uniform shrinkage inside the WZ induces tensile stress in the joint, leading to significant fluctuations in DS residual stress and consequently affecting the joint’s shear strength. This study investigates the effects of process parameters on the mechanical properties of dissimilar joints and, for the first time, analyzes the relationship between joint residual strain and femtosecond laser weld spacing, providing valuable insights for optimizing femtosecond laser welding processes. Full article

In recent years, thermoplastic polymers and composites have seen increasing application across various industrial sectors to develop lightweight structures. These materials have gained popularity in the market due to advancements in additive manufacturing. Thermal direct joining serves as an effective solution for integrating such thermoplastic materials into existing or de-novo metal structures. This method enables the creation of lightweight and virtually reversible joints, which foster end-of-life recyclability, thus aligning with the principles of a circular economy. However, these joints are still affected by a low strength, which is mostly related to the poor polymer–metal interaction. The use of surface treatments that promote mechanical interlocking of the polymer within surface asperities in the mating metallic adherend can be an effective strategy to enhance the strength, as well as to improve the toughness and damage tolerance of the joints. In this work, a laser treatment was used to modify the surface texture of an aluminum sheet prior to thermal bonding with 3D-printed polylactic acid (PLA). Different surface textures were analyzed by modifying the main process parameters. Roughness and wettability measurements were performed to identify the most effective processing condition. Finally, mechanical tests were performed to verify the improvement in joint resistance obtained by interface modification. Full article

We describe a method to calibrate angular positioning errors of a rotation stage using a laser tracker (LT), a plane mirror mounted on the stage, and stationary registration nests placed around the stage. Our technique involves determining the direction of the normal vector to the plane of the mirror at each angular step by performing two LT measurements—one directly to a stationary spherically mounted retroreflector (SMR), and another to the same SMR by bouncing the laser off a mirror mounted on the rotation stage. Because the angular range that can be measured from a single LT station is limited by the angle of incidence on the mirror, multiple LT stations are necessary to cover the full 360°, hence the need for stationary registration nests to tie the LT data into a common coordinate frame. We compare this technique against a direct approach involving a rigid bar with two SMRs mounted on the rotation stage so that we can measure the direction of the line joining the SMRs at each angular position using the LT and, therefore, the angle between positions. Through experiments, we demonstrate that our mirror-based approach provides errors on the order of ±0.5″, smaller than the ±1.5″ for the direct approach, when compared against a reference instrument with accuracy better than 0.3″. Through simulations, we estimate the uncertainty in our mirror-based angle measurements to be 0.4″ (k = 2). Placing the LT close to and the SMR away from the rotation stage results in lower uncertainty for our mirror-based angle measurements. Full article

Currently, the quartz glass–TC4 dissimilar joint has been applied in fields such as radiation environment testing, reactor engineering, and other areas. However, the high brittleness of the quartz glass and thermal mismatch during the welding process limit require further development. Thus, a femtosecond laser was employed to perform the direct joining of these materials under non-optical contact conditions, with the aid of a well-designed clamp and optimized process, and the effect of pulse energy on the microstructure and mechanical properties was analyzed. It was revealed that a lot of welding zones form at the interface through the diffusion of Si, O, and Ti and, thus, consist of a stable joint. Element distribution is related to pulse energy, which can affect the composition of secondary phases in the weld zones. The maximum shear strength of joints was 10.4 MPa with laser pulses of 0.3 mJ, while a further increase in the pulse energy led to more defects and stress unevenness. These findings provide valuable insights into enhancing the reliability of metal–glass welding joints and the promotion of femtosecond laser technology. Full article

The conventional near-infrared laser transmission welding (LTW) process for joining dissimilar transparent polymers is limited by the need to incorporate optical absorbents, which compromises joint performance and raises biocompatibility concerns. To address these issues, this study proposed a surface modification technique using femtosecond laser ablation prior to the welding process. Experiments involved 520 nm femtosecond laser ablation of transparent polymers, followed by LTW of dissimilar transparent polymers using an 808 nm laser, with subsequent characterization and mechanical property evaluations. A maximum joint strength of 13.65 MPa was achieved. A comprehensive investigation was conducted into the physical and chemical mechanisms through which laser ablation improved the welding performance of dissimilar transparent polymers. The results demonstrated that laser ablation generated microstructures that serve as substitutes for optical absorbents while also facilitating the formation of numerous oxygen-containing functional groups. These enhancements improve miscibility and bonding performance between dissimilar polymers, enabling absorbent-free welding between ablated polycarbonate (PC) and polystyrene (PS). This work confirms both the feasibility and potential application of this process for direct LTW of dissimilar transparent polymers. Full article

The relevance of the study is related to the need to join dissimilar copper and nickel alloys by laser direct energy and material deposition (LDED). The purpose of research is studying the distribution of elements, structure, and properties of contact zone of nickel-based super alloy and CuCr1 bronze obtained by direct energy and material deposition with preliminary formation of relief of contact surface. For the purposes of research, samples were made from UNS C18200 copper alloy CuCr1 without relief, with a relief of 0.5 mm depth, and with a relief of 1 mm depth. The Ni₅₀Cr₃₃W_4.5Mo_2.8TiAlNb (EP648) alloy powder was deposited onto the bronze samples with a micro-relief. The deposition was produced by direct injection of energy and material. The influence of interphase interaction of CuCr-chromium carbide system on the possibility of initiation of a crack in the area of carbide secretions is not significant and does not exceed 3.1% according to CIC criterion from the background level for CuCr1 (CIC = 1.54% for CuCr1-Al₄C₃ interface and CIC = 3.1% for CuCr1-Cr₂₃C₆ interface). An X-ray analysis revealed the presence of tensile residual macro-stresses, arising from differences in thermal expansion coefficients in the CuCr1-EP648 interface area, which may be the main cause of crack formation. Cracks are generated and run along the grain boundaries, on which traces of excretion are visible. The contact surface in the CuCr1-EP648 interface area has no visible defects, which indicates the good adhesion of materials when applying an initial layer of EP648 by LDED. The presence of a 0.5-mm micro-relief on CuCr1 has a positive effect on the strength of the connection, as it increases the surface area of the contact CuCr1-EP648 and therefore reduces the contact stress of the breakout. Full article

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. Full article

Material shaping and joining are the two fundamental processes that lie at the core of many forms of metal manufacturing techniques, including additive manufacturing. Current metal additive manufacturing processes such as laser/e-beam powder bed fusion and Directed Energy Deposition predominantly use heat and subsequent melt–fusion and solidification to achieve shaping and joining. The energy efficiency of these processes is severely limited due to energy conversion losses before energy is delivered at the point of melt–fusion for shaping and joining, and due to losses through heat transfer to the surrounding environment. This manuscript demonstrates that by using the physical phenomenon of lowered yield stress of metals and enhanced diffusion in the presence of low amplitude high frequency oscillatory strain, metal shaping and joining can be performed in an energy-efficient way. The two performed simultaneously enable a metal additive manufacturing process, namely Resonance-Assisted Deposition (RAD), that has several unique capabilities, like the ability to print net-shape components from hard-to-weld alloys like Al6061 and the ability to print components with a very high aspect ratio. In this study, we show this process’s capabilities by printing solid components using aluminum-based metal alloys. Full article

This study focuses on developing an experimental setup to investigate the Selective Melt Dispersion (SMD), a Directed Energy Deposition (DED) process. SMD as a means of in-process joining (IPJ) aims to integrate components and assemblies during additive manufacturing, combining the advantages of various processes for eco-friendly and economical resource utilization. The research initially analyzed DED systems and defined requirements for subsystems and the overall system. Critical subsystems, including the energy source, material feed, and others, were sequentially developed, and a proof of concept involved building 20 stacked welded tracks, validated through micrograph analysis. The study concludes by evaluating and discussing the fulfillment of the defined requirements. The system comprises a centrally arranged vibration-assisted powder feed; a laterally arranged laser incidence at a 45° angle; a kinematic structure where all axes are arranged on the workpiece, so the powder supply does not require movement; and a shield gas supply. Full article

Basal cell carcinoma (BCC) is a slow-growing, locally aggressive, rarely metastasizing, low-grade cutaneous neoplasm that arises from the epidermal basal layer and invades the adjoining tissues. It is the most common skin cancer. It is fairly common in fair Caucasians and quite uncommon in dark-skinned populations. It contributes to 65–75% of cutaneous malignancies in whites and 20–30% in Asian Indians. The most important causal factors appear to be radiation exposure and genetic predisposition. It may present as a nonhealing lesion that occasionally bleeds or as a pruritic lesion with no symptoms. Tumours rarely spread to regional lymph nodes. The clinical appearances and morphology of BCC are diverse. Clinical types include nodular, cystic, superficial, pigmented, morphoeaform, (sclerosing), keratotic and fibroepithelioma of Pinkus. Most of the lesions appear on the head and neck, usually above the line joining the tragus and the angle of the mouth. A biopsy should be performed on all lesions suspected of BCC. The primary aim of treatment is the complete excision of the tumour tissue. Other treatment modalities include cryotherapy, immunomodulatory drugs, laser treatment or locally applicable chemotherapeutic agents. Prevention consists of lifestyle changes such as avoiding sunburn, tanning beds and prolonged direct sun exposure, shade seeking, sunscreen application on the skin, and physical barrier methods such as protective clothing, hats and sunglasses. Regular sunscreen use in childhood and adolescence seems more beneficial than in adulthood. Full article

Laser direct joining enables non-destructive and lightweight joining of carbon fiber reinforced thermoplastic (CFRTP) composites and aluminum alloys. The interfacial bonding process determines the joint performance and is influenced by the time-varying temperature distribution. However, the interfacial bonding process occurs inside the joint, making it difficult to study the effect of temperature distribution. To resolve this issue, a novel online observation device for the interfacial bonding process between CFRTP composites and aluminum alloys is design, and the polymer melting, flowing, and bonding with metal during laser direct joining are observed. Further, temperature field simulation models for laser direct joining are established, and temperature distribution and gradient are calculated. The results show that the temperature distribution determines the melting of CFRTP composites, and bubbles generated by the thermal decomposition of the polymer hinder the melting. The temperature gradient is related to the movement of the molten matrix and fibers, and the movement towards the aluminum alloy induces cracking and delamination. Once the interface is filled with polymer, the motion changes to along the laser scanning direction and the joining defects are reduced. The study can provide a foundation for promoting interfacial bonding and reducing the defects of laser direct joining. Full article

Additive-manufacturing-based joining methods enable tailored or even functionalized joints and allow for hybridization at small scales. The current study explored an innovative joining method for aluminum cast alloys (AlSi12) with thermoset carbon-fiber-reinforced polymers (CFRPs) via laser powder bed fusion (LPBF). The direct build-up of AlSi12 on a CFRP substrate proved to be challenging due to the dissimilar thermal properties of the considered materials, which led to substrate damage and low joint adhesion. These effects could be overcome by introducing an AlSi12 foil as an interlayer between the two joining partners, acting as a thermal barrier and further improving the AlSi12 melt wettability of the substrate. Within LPBF, the energy input in the form of volumetric laser energy density influenced both the porosity of the fused layers and the formation of thermally induced stresses due to the high cooling rates and different thermal expansion properties of the materials. While the AlSi12 volume density increased with a higher laser energy input, simultaneously increasing thermal stresses caused the debonding and deformation of the AlSi12 foil. However, within a narrow processing window of laser parameters, the samples achieved remarkably high shear strengths of τ > 20 MPa, comparable to those of conventional joining methods. Full article

Transparent hard and brittle (THB) materials have generated significant interest due to their excellent properties, such as wide spectral transmittance, heat resistance, chemical inactivity and high mechanical strength. To further explore the application of THB materials, it is inevitable to be confronted with a range of joining THB materials and THB material–metals. Ultrafast (UF) laser microwelding enables a new means of joining THB materials and THB material–metals, due to a localized energy deposition method, which is dominated by nonlinear absorption. This process can realize high-quality micro-zone direct joining of THB materials or THB material–metals without the assistance of a light-absorbing intermediate layer. In this paper, we review the advances in UF laser microwelding of THB materials and THB material–metals considering the last two decades, from the analysis of the interaction mechanism between UF laser and matter to the key influencing factors and practical applications of this technology. Finally, the existing problems and the future research focus of UF laser microwelding technology of THB materials and THB material–metals are discussed. Full article

The suitability of the direct energy deposition process of exothermic powders Fe-Ti in joining dissimilar metals to produce small parts of a complete shape for various applications is considered. The procedure of the direct energy deposition of commercial pure iron and titanium in various proportions and the modes of the process are described. Optical microscopy and SEM with EDX analysis, X-ray analysis, and microhardness measurements of laser-fabricated intermetallics are applied. Intermetallic compounds of FeTi, Fe₂Ti, eutectoids, complex titanium oxides and nitrides, and iron carbides are found. Interlayer and trans-layer cracks and pores are observed. A microhardness growth from 150 HV to 900 HV was obtained for all samples due to the precipitation of brittle intermetallic phases in the gradient Fe-Ti system during the DED. The dispersion of microhardness values becomes significant in Ti-rich areas; there, pores and cracks are found. The revealed structure features are considered in relation to published results and explained. Increased concentrations of Ti to Ti + Fe = 3:1 on the Fe- and Fe + Ti -substrate with concentrations of Ti + Fe = 1:1 and Ti + Fe = 1:3 lead to increasing hardness and its distribution, but also increases in residual microstress. Recommendations are given to reduce the power during the direct energy deposition of titanium layers and to apply Fe-substrate, which can reduce residual stress, pores, and cracks. Full article