Technical study of the effect of laser engraving using uArm swift pro robot

<p>Laser engraving is the most non - traditional and efficient working method in the machining of materials of different geometry as compared to conventional methods. The main objective of this study is to determine the impact of uArm swift pro robot operated laser engraving process on a wooden pitch board piece. However, the robot was connected with uArm Studio 1.1.22 software to perform laser engraving operation. For this purpose the effect of process parameters like spot diameter and depth of penetration were investigated with different working length of the robot end effector, measured from wooden pitch board base. Experimental observation method was used to investigate the formation of deep and light engraving pattern on the pitch board surface by measuring penetration depth and spot diameter in suitable condition. The result obtained from the experiment and statistical parameters showed a new dimension to find a suitable working length of the robot assisted laser nozzle where the laser penetration effect was clearly perceptible for the wooden material.</p>

Laser therapy in the complex treatment of patients with compression-ischemic neuropathy

Material and methods. Twenty-two patients with compression-ischemic neuropathy were included into the study. Low-level laser device “ALOK-1” was used for laser therapy. Its beam impacts tissues directly; its power is 1 mW, wavelength – 0.63 μm, spot diameter – 0.8 mkm.Results. Subjective, objective and instrumental findings became significantly better, if to compare with the pre-operative period.Conclusion. The developed technique has shown its good efficiency. The intraoperative laser therapy CIN patients decreased the severity of symptoms up to their complete regression; patients were highly satisfied with their postoperative outcomes.

Composite Materials with the Coating to Detect Barely Visible Impact Based on the Retroreflective Film

A new method of indicating contact damage of composite materials, using a polymer retroreflective film (PRF) with micro-prisms, is proposed. Impact contact action leads to deformation of microprisms and with directed lighting allows seeing the place of impact in the form of a dark spot. In experimental studies, using STEF fibreglass as an example, the dependences of the spot diameter on the contact pressure up to 530 MPa were studied. An assessment of the residual strength and stiffness of a composite specimen-beam with a contact defect was obtained with three-point bending. It is shown that, during bending, the strength of STEF with contact defects decreases from 615 to 386 MPa. The data obtained allow to assess the danger of contact pressure by the known diameter of the dark spot on the PRF.

The Thermo-Mechanical Coupling Effect in Selective Laser Melting of Aluminum Alloy Powder

In the selective laser melting process, metal powder melted by the laser heat source generates large instantaneous energy, resulting in transient high temperature and complex stress distribution. Different temperature gradients and anisotropy finally determine the microstructure after melting and affect the build quality and mechanical properties as a result. It is important to monitor and investigate the temperature and stress distribution evolution. Due to the difficulties in online monitoring, finite element methods (FEM) are used to simulate and predict the building process in real time. In this paper, a thermo-mechanical coupled FEM model is developed to predict the thermal behaviors of the melt pool by using Gaussian moving heat source. The model could simulate the shapes of the melt pool, distributions of temperature and stress under different process parameters through FEM. The influences of scanning speed, laser power, and spot diameter on the distribution of the melt pool temperature and stress are investigated in the SLM process of Al6063, which is widely applied in aerospace, transportation, construction and other fields due to its good corrosion resistance, sufficient strength and excellent process performance. Based on transient analysis, the relationships are identified among these process parameters and the melt pool morphology, distribution of temperature and thermal stress. It is shown that the maximum temperature at the center point of the scanning tracks will gradually increase with the increment of laser power under the effect of thermal accumulation and heat conduction, as the preceded scanning will preheat the subsequent scanning tracks. It is recommended that the parameters with optimized laser power (P = 175–200 W), scanning speed (v = 200–300 mm/s) and spot diameter (D = 0.1–0.15 mm) of aluminum alloy powder can produce a high building quality of the SLM parts under the pre-set conditions.

Correlation study of fuel injection strategies on engine emission and lubricating oil performance

Based on different fuel injection strategies, this paper analyzes the factors such as engine original emission smoke, exhaust temperature, soot content, wear spot diameter and kinematic viscosity. The study found that delaying injection timing, increased afterburn, engine original soot emissions, exhaust gas temperature increase, but will increase the thermal load of the parts. At the same time, the growth rate of lubricant soot and kinematic viscosity increased; The wear spot diameter at the same soot content is reduced, and the wear is reduced. In the end, the paper finally selects 1°CA BTDC as the optimal fuel injection strategy to achieve rapid aging of engine lubricating oil in order to complete the assessment of the anti-wear performance of lubricating oil.

Optimization of laser repair parameters for precracked 304 stainless steel components with nanocomposites addition

The optimization of process parameters is usually essential for achieving improved properties at efficient and cost-effective process conditions. The influence of laser parameters, i.e. laser power, spot diameter, and laser heating time, on the fracture property of repaired specimens was investigated by Taguchi experiment. Cracks were first fabricated on 304 stainless steel compact tension specimens by wire cutting and then repaired by adding nanocomposites at crack tips under different combinations of laser parameters. The repairing effects were evaluated by crack opening displacement measured by digital image correlation and microstructure characterized by scanning electron microscope. The analysis of variance was used to investigate the contribution of factor variables to the fracture parameter of crack opening displacements. The fracture property was improved most at the optimal repair process parameters of laser power of 1800 W, spot diameter of 3 mm, and heating time of 0.5 s within the selected range of experiments. The influence of laser parameters on the fracture properties of repaired specimens is found in the sequence of spot diameter, laser power, and heating time. This paper reveals the relationship of process–microstructure–fracture property in laser repair and provides a guideline for the selection of laser parameters to improve the quality of crack repair.