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Estimation of temperature-dependent yield strength and modulus of elasticity during laser bending
摘要： In this work, an inverse method is developed to estimate the temperature-dependent value of yield strength (Y) and modulus of elasticity (E) of the material during a laser bending process. The method requires measurement of bend angle of the laser scanned workpiece. The inverse model uses the bend angle computed by a direct model. The temperature-dependent Y and E are inversely estimated by minimizing the difference between actual and direct model predicted bend angles. The validation of the proposed method is demonstrated with the help of two examples. For this purpose, inversely estimated values of E and Y are used to predict bend angles for various processing conditions and predicted values are compared with actual values. In examples, actual data has been obtained from a detailed FEM simulation in lieu of shop floor experiments. Later on, the proposed method is also validated by performing shop floor experiments for AH36 steel.
关键词： Inverse technique,Finite element method,Yield strength,Laser bending,Modulus of elasticity
更新于2025-09-19 17:13:59
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[IEEE 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Sao Paulo, Brazil (2019.10.7-2019.10.9)] 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Evaluation of the Adhesive Strength in Dentin after Irradiation with Ti:Sapphire Ultrashort Laser Pulses
摘要： This study was done to evaluate whether the irradiation of dentine with ultrashort laser pulses prior to adhesive procedures contributes to increase the adhesive resistance to microtraction essays. Twenty-four human teeth (third molars) were used, divided into 4 groups (n=6): standard adhesive procedures with etch-rinse adhesive were used in the control group, and in the experimental groups, the dentin was irradiated by 25 fs pulses prior to the adhesive procedures, with varying fluences. One tooth from each group was used to evaluate its surface roughness. After 24h, the teeth were sectioned with perpendicular cuts, producing toothpicks that were submitted to the microtraction test. The results showed that the groups irradiated with fluences under 4 J/cm2 presented similar results among themselves, comparable to the control group, while the group irradiated with 8 J/cm2 showed lower adhesive strength. We propose that the adhesive strength and surface roughness reduction resulting from the fluence increase is probably related to the shielding arising from an electron plasma formation during the ablation, decreasing the material removal efficiency. Nevertheless, the lower energy densities did not affect the adhesiveness, maintaining values similar to the control.
关键词： dentin,femtoseconds laser pulses,microtensile bond strength,adhesion,Ti:Sapphire laser irradiation
更新于2025-09-19 17:13:59
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Effects of initial density during laser machining assisted CVI process and its influence on strength of C/SiC composites
摘要： Novel laser-assisted chemical vapor infiltration (LA-CVI) technique has been used to improve the density and strength of carbon fiber reinforced SiC composites (C/SiC). Initial density of C/SiC before laser machining played an important role in determining the final density and strength of composites. Results show that final density and bending strength of lower initial density composites were better than that of higher initial density samples after LA-CVI process, while the porosity exhibited opposite behavior. Micro-CT and COMSEL simulation results verify that after LA-CVI process, dense band width of C/SiC with initial density of 1.5 g/cm3 was twice as that of C/SiC with initial density of 1.8 g/cm3. This led to crack propagation bypassing the micro-hole. In conclusion, low initial density when laser machining was carried out resulted in better properties of final composites.
关键词： Bending strength,LA-CVI,C/SiC composites,Micro-structure
更新于2025-09-19 17:13:59
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Laser-Milled Microslits Improve the Bonding Strength of Acrylic Resin to Zirconia Ceramics
摘要： Heightened aesthetic considerations in modern dentistry have generated increased interest in metal-free “zirconia-supported dentures.” The lifespan of the denture is largely determined by the strength of adhesion between zirconia and the acrylic resin. Thus, the effect on shear bond strength (SBS) was investigated by using an acrylic resin on two types of zirconia ceramics with differently sized microslits. Micromechanical reticular retention was created on the zirconia surface as the novel treatment (microslits (MS)), and air-abrasion was used as the control (CON). All samples were primed prior to acrylic resin polymerization. After the resin was cured, the SBS was tested. The obtained data were analyzed by using multivariate analysis of variance(α = 0.05). After the SBS test, the interface failure modes were observed by scanning electron microscopy. The MS exhibited significantly higher bond strength after thermal cycles (p < 0.05) than the CON. Nevertheless, statistically comparisons resulted in no significant effect of the differently sized microslits on SBS (p > 0.05). Additionally, MS (before thermal cycles: 34.8 ± 3.6 to 35.7 ± 4.0 MPa; after thermal cycles: 26.9 ± 3.1 to 32.6 ± 3.3 MPa) demonstrated greater SBS and bonding durability than that of CON (before thermal cycles: 17.3 ± 4.7 to 17.9 ± 5.8 MPa; after thermal cycles: 1.0 ± 0.3 to 1.7 ± 1.1 MPa), confirming that the micromechanical retention with laser-milled microslits was effective at enhancing the bonding strength and durability of the acrylic resin and zirconia. Polycrystalline zirconia-based ceramics are a newly accessible material for improving removable prosthodontic treatment, as the bond strength with acrylic resin can be greatly enhanced by laser milling.
关键词： thermocycling,zirconium oxide,acrylic resin,bond strength,laser
更新于2025-09-19 17:13:59
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Prediction of Preheating Temperatures for S690QL High Strength Steel Using FEM-Simulation for High Power Laser Welding
摘要： This study investigates a method for predicting the effect of preheating temperatures on the resulting hardness for high power laser welding of high strength steel. An FEM model is introduced containing a hardness calculation based on an existing model. Moreover, the hardness values of experimental results have been measured in order to show the performance of the model. The hardness calculation requires the chemical composition and the t8/5-time at the point of measurement. It is claimed that a calibration of the melt pool width and depth at room temperature only is enough to get reasonable results from the FEM-model for higher preheating temperatures. From the experimental result of a single experiment the width of a weld seam and the depth was deducted. In this study experiments have been done at various preheating temperatures in order to show the correlation between the model and the experimental results at various temperatures. The hardness equation provides suitable results in the verification with the measurements. The prediction of preheating temperature can be done with the resulting t8/5-time of the FEM-model. This method can decrease the amount of time and costs within a production according to testing and analyzing a matrix of process parameters. Moreover it is concluded that this methodology might be used for single item production.
关键词： Deep penetration laser welding,FEM-welding simulation,High strength steel,Preheating,Predicting hardness
更新于2025-09-19 17:13:59
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Enhanced bonding strength of InP/Si chip-on-wafer by plasma-activated bonding using stress-controlled interlayer
摘要： This study demonstrates high-yield InP/Si CoW plasma-activated bonding using a chip holder with pockets, the depth of which is precisely controlled. Additionally, finite element simulations are used to determine that the stress-controlled interlayer consisting of InP-based epitaxial layers with tensile strain effectively suppresses stress at the InP/Si bonding interface, which affects the bonding strength. Thus, a high bonding strength of 20 MPa in 2 mm × 2 mm InP chips on the Si substrate was achieved by introducing a superlattice structure consisting of GaInAsP and InP (with tensile strain) as the stress-controlled interlayer.
关键词： chip-on-wafer,plasma-activated bonding,bonding strength,InP/Si,stress-controlled interlayer
更新于2025-09-19 17:13:59
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Photodynamic activation of irrigation (using different laser prototypes) on push out bond strength of fiber posts
摘要： Background: To evaluate the influence of photodynamic therapy (PDT) and light activated irrigation (LAI) using different laser prototypes Er,Cr:YSGG (ECYL), Er:Yag (EYL), Nd-Yag (NYL) on pushout bond strength of Pre-fabricated fiber reinforced composite (PFRC) post to radicular dentin. Material and method: Fifty maxillary and mandibular teeth were collected, cleaned and decoronated. Canals were instrumented using crown-down technique. Flaring of canals was performed using protaper S1, SX files. F1, F2 and F3 files were utilized for finishing of canal preparations. Prepared root canals were dried and obturated with gutta percha. Teeth were placed vertically within the section of polyvinyl pipes using acrylic resin. Post space preparation was completed using peso-reamers. Based on the PDT and laser activated irrigation (LAI) with different laser prototypes, samples were divided into five groups of 10 specimens each. Group 1- PDT, group 2–5.25 % NaOCl (sodium hypochlorite) and 17 % EDTA (ethylene diamine tetra acetic acid), group 3–5.25 % NaOCl with 17 % EDTA and NYL, group 4–5.25 % NaOCl with 17 % EDTA and EYL ; and group 5–5.25 % NaOCl +17 % EDTA and ECYL. Fiber post were luted in root canals with self-etch dual cure cement and teeth were sectioned at three levels (apical, middle and coronal). Push-out test was performed by placing the specimens in universal testing machine. Failure analysis of debonded surfaces was evaluated using stereomicroscope at 40× magnification. Means and standard deviations of push out bond strength were assessed by one-way analysis of variance (ANOVA). Comparison between means of push out bond strength was evaluated using Tukey multiple comparison tests (p = 0.05). Result: The highest push out bond strength was observed in group 5 at all three levels, coronal (10.08 ± 0.74 MPa), middle (8.95 ± 0.94 MPa) and apical (6.00 ± 0.88 MPa). The lowest push out bond strength was demonstrated by group 2 at all levels, coronal (6.15 ± 1.22 MPa), middle (5.65 ± 0.95 MPa) and apical (2.25 ± 0.55 MPa). Intra-group comparison showed decrease in push out bond strength in the coronal to apical direction among all investigated groups. Inter-group comparison exhibited comparable push out bond strength at all three levels of root for group 1 and group 2 specimens (p > 0.05). Conclusion: LAI with different laser prototypes improved push out bond values of PFRC post to root dentin as an adjunct to NaOCl and EDTA treatment. PDT improved push out strength compared to conventional canal cleaning regime.
关键词： Light activated irrigation,Bond failure,Photodynamic therapy,Push out bond strength,Laser prototypes
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE International Ultrasonics Symposium (IUS) - Glasgow, United Kingdom (2019.10.6-2019.10.9)] 2019 IEEE International Ultrasonics Symposium (IUS) - Integrated Ultrasound and Photoacoustic Imaging for Effective Endovenous Laser Ablation: A Characterization Study
摘要： A Taguchi particle swarm optimization (TPSO) with a three-layer feedforward artificial neural network (ANN) is used to model and optimize the chemical composition of a steel bar. The novel contribution of a TPSO is the use of a Taguchi method mechanism to exploit better solutions in the search space through iterations, the use of the conventional non-linear PSO to increase convergence speed, and the use of random movement for particle diversity. The exploration and exploitation capability of the TPSO were confirmed by performance comparisons with other PSO-based algorithms in solving high-dimensional global numerical optimization problems. Experiments in this paper showed that the TPSO provides higher computational efficiency and higher robustness when solving problems involving seven non-linear benchmark functions, including three unimodal functions, one multimodal functions, two rotated functions, and one shifted functions. The results for the computational experiments show that the TPSO outperforms other PSO-based algorithms reported in the literature. Finally, the results obtained by a TPSO-based ANN model of the chemical composition of the steel bar were consistent with the actual data. That is, the proposed TPSO with three-layer feedforward ANN can be used in practical applications.
关键词： yield point,feedforward artificial neural network,tensile strength,particle swarm optimization,chemical composition of steel bar,Taguchi method
更新于2025-09-19 17:13:59
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Effect of normal scratch load and HF etching on the mechanical behavior of annealed and chemically strengthened aluminosilicate glass
摘要： Micro-cracks generated by hard body scratch are a major cause of strength decrease for silicate glass. The influence of normal scratch load on the cracking patterns and flexural strength of annealed glass (AG) and chemically strengthened glass (CSG) were studied. With the increase of the normal load, the load capacity of scratched AG specimens decreased to about 40MPa at 20gf immediately. However, the residual strength of CSG decreased to a steady value of 145MPa as the scratch load increased to 500gf. Then the effect of hydrofluoric acid (HF) etching on the surface morphology and mechanical properties of the 500gf scratched glass were investigated. After 8min (for CSG) and 16 min (for AG) acid treatment, the flexural strength of CSG and AG increased to a considerable value of 900MPa, which is 3.6 and 5.5 times higher than the flexural strength of undamaged specimens. Microscopic observations show that the blunting and eliminating of median cracks as well as the formation of new surfaces are the main causes of strength enhancement.
关键词： morphology,aluminosilicate glass,scratch,flexural strength,HF etching
更新于2025-09-19 17:13:59
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Effect of different laser types on bonding strength of CAD/CAM-customized zirconia post to root canal dentin: an experimental study
摘要： In clinical dentistry, the strength of bonding zirconia posts to root canal dentinal walls currently needs enhancement, and laser application can be an important contribution owing to its features that accommodate adjustable modifications on dental materials. Herein, the effect of different laser treatments applied to dentin surfaces on the strength of bonding zirconia posts to root canal dentinal walls is evaluated by using the pull-out bond strength test in a laboratory setting. A total of 40 single-rooted permanent mandibular premolar teeth that were freshly extracted were used here. The root canal preparation steps were performed using the crown-down technique. Custom-made zirconia posts were produced using CAD/CAM technology. Prior to the application of resin cement, the internal surfaces of the root canals were irradiated using Nd:YAG, Er:YAG, and KTP lasers. Pull-out tests were performed on each specimen by using a universal testing machine. One-way analysis of variance and Tukey post hoc tests were used to compare the pull-out bond strength data. The bond strengths of the laser-treated specimens were greater than those of the untreated controls (p < 0.05). While the value of the pull-out bond strength after Nd:YAG laser treatment was significantly higher than the values obtained after the applications of the Er:YAG and KTP lasers (p < 0.05), the pull-out bond strength after Er:YAG laser treatment was considerably greater than that after KTP laser treatment (p < 0.05). The bond strength between the root canal dentin and the CAD/CAM custom-made zirconia post was improved upon using all the laser modalities in current laboratory settings, among which, application of the Nd:YAG laser was the most successful.
关键词： KTP laser,Zirconia post,Nd:YAG laser,Dentin treatment,Er:YAG laser,Pull-out bond strength
更新于2025-09-19 17:13:59