scholarly journals Repeatability of multipass laser forming of sheet materials

2021 ◽  
Vol 5 (1) ◽  
pp. 122-129
Author(s):  
Alexey Kaglyak ◽  
Odarka Prokhorenko ◽  
Bogdan Romanov ◽  
Alexey Honcharuk ◽  
Alexander Siora ◽  
...  
Keyword(s):  
Software Package ◽  
Treatment Process ◽  
Spatial Configuration ◽  
Sheet Material ◽  
Physical Experiment ◽  
Laser Forming ◽  
Sheet Materials ◽  
Methodical Approach ◽  
The Difference ◽  
Number Of Passes

Laser forming (LF) of sheet material is a progressive treatment process and have some benefits. Laser forming is a flexible process and need no heavy metal-intensive equipment and tools. Materials with high rigidity, brittle, elastic materials can be treated by laser forming.  Therefore, the investigation of LF is important task. An important point to study is repeatability of multipass laser forming of sheet materials and explore of the possibilities of stabilizing process parameters. Actually, this research is aimed at these issues.   Methods and results of experimental investigation of repeatability of multipass laser forming of sheet materials on parallel and multidirectional passes are described. A methodical approach of using the VisualWeld software package for modeling the process of multi-pass laser forming has been developed. The mentioned software package was used for modeling as an alternative to a physical experiment to predict sample deformations and determine treating parameters.  It has been experimentally established that the repeatability in laser forming is quite high, the difference in the amount of deformation preferably did not exceed 5%. In addition, it is shown that by varying the direction of irradiation trajectories, their step and the number of passes on each trajectory, it is possible to obtain a complex spatial configuration of the product.

Quanitative aspects of electron diffraction using electron holography

1995 ◽  
Vol 53 ◽  
pp. 616-617
Author(s):  
E. Völkl ◽  
L.F. Allard ◽  
B. Frost ◽  
T.A. Nolan
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Software Package ◽  
Spatial Coherence ◽  
Electron Holography ◽  
Image Intensity ◽  
Interference Fringes ◽  
Complex Image ◽  
The Difference ◽  
Recorded Image

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.

scholarly journals Switch Strategy from Direct Aspiration First Pass Technique to Solumbra Improves Technical Outcome in Endovascularly Treated Stroke

2021 ◽  
Vol 18 (5) ◽  
pp. 2670
Author(s):  
Enrico Pampana ◽  
Sebastiano Fabiano ◽  
Gianluca De Rubeis ◽  
Luca Bertaccini ◽  
Alessandro Stasolla ◽  
...  
Keyword(s):  
Added Value ◽  
Stroke Patients ◽  
First Line ◽  
Anterior Circulation ◽  
First Pass ◽  
Procedural Time ◽  
The Mean ◽  
The Difference ◽  
Number Of Passes ◽  
Switch Strategy

Background: The major endovascular mechanic thrombectomy (MT) techniques are: Stent-Retriever (SR), aspiration first pass technique (ADAPT) and Solumbra (Aspiration + SR), which are interchangeable (defined as switching strategy (SS)). The purpose of this study is to report the added value of switching from ADAPT to Solumbra in unsuccessful revascularization stroke patients. Methods: This is a retrospective, single center, pragmatic, cohort study. From December 2017 to November 2019, 935 consecutive patients were admitted to the Stroke Unit and 176/935 (18.8%) were eligible for MT. In 135/176 (76.7%) patients, ADAPT was used as the first-line strategy. SS was defined as the difference between first technique adopted and the final technique. Revascularization was evaluated with modified Thrombolysis In Cerebral Infarction (TICI) with success defined as mTICI ≥ 2b. Procedural time (PT) and time to reperfusion (TTR) were recorded. Results: Stroke involved: Anterior circulation in 121/135 (89.6%) patients and posterior circulation in 14/135 (10.4%) patients. ADAPT was the most common first-line technique vs. both SR and Solumbra (135/176 (76.7%) vs. 10/176 (5.7%) vs. 31/176 (17.6%), respectively). In 28/135 (20.7%) patients, the mTICI was ≤ 2a requiring switch to Solumbra. The vessel’s diameter positively predicted SS result (odd ratio (OR) 1.12, confidence of interval (CI) 95% 1.03–1.22; p = 0.006). The mean number of passes before SS was 2.0 ± 1.2. ADAPT to Solumbra improved successful revascularization by 13.3% (107/135 (79.3%) vs. 125/135 (92.6%)). PT was superior for SS comparing with ADAPT (71.1 min (CI 95% 53.2–109.0) vs. 40.0 min (CI 95% 35.0–45.2); p = 0.0004), although, TTR was similar (324.1 min (CI 95% 311.4–387.0) vs. 311.4 min (CI 95% 285.5–338.7); p = 0.23). Conclusion: Successful revascularization was improved by 13.3% after switching form ADAPT to Solumbra (final mTICI ≥ 2b was 92.6%). Vessel’s diameter positively predicted recourse to SS.

Sheet Material Property Effects upon Dynamic Behavior in Self-Pierce Riveted Joints

2011 ◽  
Vol 675-677 ◽  
pp. 999-1002 ◽  
Author(s):  
Xiao Cong He
Keyword(s):  
Natural Frequency ◽  
Transverse Vibration ◽  
Spot Welding ◽  
Sheet Material ◽  
Vibration Characteristics ◽  
Efficient Design ◽  
Material Density ◽  
Sheet Materials ◽  
Riveted Joints ◽  
Free Transverse Vibration

Self-pierce riveting (SPR) technology offers an alternative to resistance spot welding (RSW) for joining sheet materials. It has been found that the SPR technology produced a much stronger joint than the RSW in fatigue test. For efficient design of SPR structures, the knowledge of dynamic characteristics of the SPR beams is essential. In this paper, the free transverse vibration characteristics of single lap-jointed cantilevered SPR beams are investigated in detail. The focus of the analysis is to reveal the influence on the natural frequency and natural frequency ratio of these beams caused by variations in the material properties of sheet materials to be jointed. It is shown that the transverse natural frequencies of single lap jointed cantilevered SPR beams increase significantly as the Young’s modulus of the sheet materials increases, but change slightly corresponding to the change in Poisson’s ratio. It is also found that the material density of the sheets have significant effects on the free transverse vibration characteristics of the beams.

2. Adhesion of the plasma-polymerized fluorocarbon films to silicon substrates The adhesion properties of the plasma-polymerized FC coatings were determined by using a test, already employed by Yasuda and Sharma [13] (see Fig. 1 and Table 1) in which the silicon substrates coated with plasma FC-films were boiled in a0.9% sodium chloride solution. The FC thin films produced in the processes 1 and 2 were lifted after a very short time (15 minutes). Coatings generated in process 3 were lifted after the second cycle of boiling. The films produced in processes 4 and 5 withstood the complete test procedure. The results are shown in Fig. 3. The poor adhesion of the polymerized films in the first two processes is due to the fact that these processes do not involve a plasma pre-treatment process. The difference between processes 1 and 3 is only in the plasma pre-treatment (process 1 does not contain the pre-treatment step of the silicon surface). The fluorocarbon films deposited by processes 4 and 5 have shown the best adhesion. These test results indicate that the plasma pre-treatment is very important and necessary for a good adhesion of the FC coatings to the silicon surfaces. 2.3. Patterning of FC films 2.3.1. Patterning through resist mask. The patterning of the FC films through a photoresist mask (conventional All resist AR-P351) was examined after deposition for process No. 5. Different coating parameters were investigated to improve the adhesion of the resist to the FC surface. The best adhesion results were obtained using the process parameters, shown in Table 3. Differences in the thickness uniformity of so-deposited resists were in a range below 5%. The samples were etched in a pure oxygen plasma in an RIE-system after the lithography steps (pre-bake, exposure, development, post-bake). A resolution of 2 /xm was obtained. A significant increase in the surface energy was not observed after resist stripping. The sessile contact angle of water was 103°. 2.3.2. Lift-off process for patterning thin plasma polymerized FC films. A lift-off process was also examined to pattern the thin FC films. The lithography steps were used before the plasma polymerization process was carried out (Fig. 2). A standard resist AR-P351 was coated directly onto the Si substrates. After all lithography

2014 ◽  
pp. 275-278
Keyword(s):  
Treatment Process ◽  
Test Procedure ◽  
Silicon Surfaces ◽  
Silicon Substrates ◽  
Fluorocarbon Films ◽  
Si Substrates ◽  
Complete Test ◽  
The Difference ◽  
Pre Treatment ◽  
Lift Off

scholarly journals Experimental Consideration of Conditions for Measuring Residual Stresses of Rails Using Magnetic Barkhausen Noise Method

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5374
Author(s):  
Young-In Hwang ◽  
Yong-Il Kim ◽  
Dae-Cheol Seo ◽  
Mu-Kyung Seo ◽  
Woo-Sang Lee ◽  
...  
Keyword(s):  
Residual Stresses ◽  
High Speed ◽  
Barkhausen Noise ◽  
Noise Band ◽  
Magnetic Barkhausen Noise ◽  
Continuous Increase ◽  
Fracture Characteristics ◽  
Fatigue And Fracture ◽  
The Difference ◽  
Number Of Passes

Residual stress, a factor affecting the fatigue and fracture characteristics of rails, is formed during the processes of fabrication and heat treatment, and is also generated by vertical loads on wheels due to the weight of vehicles. Moreover, damage to rails tends to accelerate due to the continuous increase in the number of passes and to the high speed of passing vehicles. Because this can have a direct effect on safety accidents, having a technique to evaluate and analyze the residual stresses in rails accurately is very important. In this study, stresses due to tensile loads applied to new rails and residual stresses remaining in used rails were measured by using magnetic Barkhausen noise method. First, a magnetization frequency and noise band suitable for the rails were selected. Moreover, by applying tensile loads to specimens and comparing the difference in magnetization amplitudes for each load, the stresses applied to the rails by using the magnetic Barkhausen noise method were measured, and the analysis of the results was verified. Based on these results, the difference in the results for the loads asymmetrically applied according to the wheel shape was analyzed by measuring for the head parts of used rails.

scholarly journals III. On the uneliminated instrumental error in the observations of magnetic dip

1869 ◽  
Vol 17 ◽  
pp. 427-429
Keyword(s):  
Mean Value ◽  
Usual Method ◽  
Centre Of Gravity ◽  
Single Reading ◽  
The Mean ◽  
The Difference ◽  
The One ◽  
Number Of Passes ◽  
Source Of Error ◽  
Complete Observation

A single reading of one end of a dipping-needle placed in a dip-circle provided with microscopes for observing is liable to a variety of instrumental errors, which are eliminated by taking the mean of the sixteen readings of the two ends in the eight different positions included in a complete observation. Nevertheless it is found that with the best modern instruments a mean value results from these sixteen observations different for each different needle, and that the difference between the results obtained with two different needles is not the same at all times. The irregularities in the values of the dip observed at Bombay with two needles of excellent character made by Barrow of London, led the author to investigate the effect of a hypothetical irregularity in the shape of the axle of the needle, such that a section of the axle by a plane perpendicular to its axis would be elliptical instead of circular in form. Another source of error, which was brought to the notice of the Royal Society many years ago in a paper published in the Proceedings, is the displacement of the centre of gravity of the needle from the centre of the axle, combined with inequality in the magnetization of the needle when the poles are direct and reversed. Experience has led the author to the conclusion that the usual method of magnetization, by a definite number of passes of the same pair of bar-magnets, communicates magnetism to the needle very unequally when the one end of the needle is made north and when the other end is made north. Consequently it is advisable to investigate the effects of ellipticity of the axle and of displacement of the centre of gravity at the same time, which the author proceeds to do.

Discussion and Improvement of Carburizing Defects

2013 ◽  
Vol 385-386 ◽  
pp. 27-29
Author(s):  
Yue Ying Liu ◽  
Xiu Hua Gao ◽  
Huan Na Li
Keyword(s):  
Heat Treatment ◽  
Production Efficiency ◽  
Treatment Process ◽  
Surface Hardness ◽  
Heat Treatment Process ◽  
Layer Depth ◽  
Part Surface ◽  
Carburized Layer ◽  
The Difference

mproving of the heat treatment process for carburizing bushing,Using the new charging rack for the bushing to solve the problems about the difference of the carburized layer depth on part surface, hardness uneven after heat treatment. At the same time, the production efficiency is also improved.

Study on Treatment of Sewage from Channel Discharge with Biological Accelerator-Biofilm Process

2011 ◽  
Vol 183-185 ◽  
pp. 644-648
Author(s):  
Gai Mei Guo ◽  
Hui Fen Qin
Keyword(s):  
Treatment Effect ◽  
Treatment Process ◽  
Removal Rate ◽  
Sewage Treatment ◽  
Ammonia Nitrogen ◽  
Promoting Effect ◽  
Research Results ◽  
The Difference ◽  
Biofilm Process

This paper studied treatment of sewage from channel discharge with biological accelerator-biofilm process, and investigated the promoting effect of biological accelerator on biofilm process during the sewage treatment process. Meanwhile, compared the difference between the laboratory developed compounded enzyme and the foreign composite enzyme. The research results indicated that using biofilm process, the composite enzyme-biofilm process and the compounded enzyme-biofilm process for treating sewage, the removal rate of CODcr was separately 70.5%, 78.4% and 74.0% and that of ammonia nitrogen was separately 38.2%, 48.6% and 45.9%, which accounted for that under the strengthening action of biological accelerator, the treatment effect was remarkable for using biofilm process disposing channel disordered discharge sewage. Furthermore, the promoting effect of the compounded enzyme was equivalent to that of the composite enzyme for biofilm process, and the compounded enzyme could come into use instead of the composite enzyme.

Experimental Study on Galling Behavior of Advanced High Strength Steel in Sheet Metal Forming

2012 ◽  
Vol 502 ◽  
pp. 36-40
Author(s):  
Ying Ke Hou ◽  
Shu Hui Li ◽  
Yi Xi Zhao ◽  
Zhong Qi Yu
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Sheet Material ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Process ◽  
Advanced High Strength Steels ◽  
Sheet Materials ◽  
Materials Used

Galling is a known failure mechanism in many sheet metal forming processes. It limits the lifetime of tools and the quality of the products is affected. In this study, U-channel stamping experiments are performed to investigate the galling behavior of the advanced high strength steels in sheet metal forming . The sheet materials used in the tests are DP590 and DP780. In addition to the DP steels, the mild steel B170P1 is tested as a reference material in this study. Experimental results indicate that galling problem becomes severe in the forming process and the galling tendency can be divided into three different stages. The results also show that sheet material and tool hardness have crucial effects on galling performance in the forming of advanced high strength steels. In this study, DP780 results in the most heaviest galling among the three types of sheet materials. Galling performance are improved with increased hardness of the forming tool.

Study on overlapping of two sequential scans in laser forming

2007 ◽  
Vol 221 (9) ◽  
pp. 993-997 ◽  
Author(s):  
H Shen ◽  
J Zhou ◽  
Z Q Yao
Keyword(s):  
Plastic Strain ◽  
Material Properties ◽  
Structural Model ◽  
Three Dimensional ◽  
High Strength ◽  
Laser Beams ◽  
Laser Forming ◽  
Numerical Investigations ◽  
Localized Heating ◽  
The Difference

Laser forming can utilize localized heating for the forming of high strength alloys and use combinations of straightandcurved lines to produce three-dimensional formedcomponents, which are of significant value to industries of aerospace, shipbuilding, and microelectronics. A three-dimensional non-linear, indirectly coupled thermal—structural model for the overlapping ratio of two sequential laser beams scanning is established, accounting for temperature dependency of material properties. Numerical results are verified by experimental data. Numerical investigations are carried out to examine the difference in plastic strain distributions under different overlapping ratios. The results show that the bending angle is larger when the size of plastic zone on the top surface is wider, although the plastic strain is smaller.

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