► Ferritic/austenitic stainless steels were laser fillet welded. ► Parametric effects on bead geometry and mechanical properties were investigated. ► Focused beam and smallest possible incident angle ...accommodated lower laser power and faster welding speed. ► Shearing force had a linear positive relationship with resistance length. ► Resulted angular distortions were random and much less than the acceptable limit.
This paper investigates laser beam welding of dissimilar AISI 304L and AISI 430 stainless steels. Experimental studies were focused on effects of laser power, welding speed, defocus distance, beam incident angle, and line energy on weld bead geometry and shearing force. Metallurgical analysis was conducted on a selected weld only to show various microstructures typically formed at different zones and consequent change in microhardness. Laser power and welding speed were the most significant factors affecting weld geometry and shearing force. All the bead characteristics but radial penetration depth decreased with increased beam incident angle. The focused beam allowed selecting lower laser power and faster welding speed to obtain the same weld geometry. Weld shape factor increased rapidly due to keyhole formation for line energy input ranging from 15
kJ/m to 17
kJ/m. Fusion zone microstructures contained a variety of complex austenite–ferrite structures. Local microhardness of fusion zone was greater than that of both base metals.
This paper presents experimental design approach to process parameter optimization for CW Nd/YAG laser welding of ferritic/austenitic stainless steels in a constrained fillet configuration. To ...determine the optimal welding parameters, response surface methodology was used to develop a set of mathematical models relating the welding parameters to each of the weld characteristics. The quality criteria considered to determine the optimal settings were the maximization of weld resistance length and shearing force, and the minimization of weld radial penetration. Laser power, welding speed, and incident angle are the factors that affect the weld bead characteristics significantly. A rapid decrease in weld shape factor and increase in shearing force with the line energy input in the range of 15–17 kJ/m depicts the establishment of a keyhole regime. A focused beam with laser power and welding speed respectively in the range of 860–875 W and 3.4–4.0 m/min and an incident angle of around 12° were identified as the optimal set of laser welding parameters to obtain stronger and better welds.
This paper presents an experimental design approach to process parameter optimization for the laser welding of martensitic AISI 416 and AISI 440FSe stainless steels in a constrained overlap ...configuration in which outer shell was 0.55
mm thick. To determine the optimal laser-welding parameters, a set of mathematical models were developed relating welding parameters to each of the weld characteristics. These were validated both statistically and experimentally. The quality criteria set for the weld to determine optimal parameters were the minimization of weld width and the maximization of weld penetration depth, resistance length and shearing force. Laser power and welding speed in the range 855–930
W and 4.50–4.65
m/min, respectively, with a fiber diameter of 300
μm were identified as the optimal set of process parameters. However, the laser power and welding speed can be reduced to 800–840
W and increased to 4.75–5.37
m/min, respectively, to obtain stronger and better welds.
This paper presents experimental investigation of laser beam welding of martensitic stainless steels in a constrained overlap configuration. Experimental studies were focused on the effects of laser ...power, welding speed and fiber diameter on bead geometry and mechanical properties of the weld. Metallurgical study of a selected welded joint was done only to show various microstructures typically formed at different zones. Laser power and welding speed were found the most significant factors affecting the weld geometry and shearing force. The contour plots showing constant response lines indicated the evidence of two-factor interaction effects of laser power-welding speed, welding speed-fiber diameter, and fiber diameter-laser power on all the responses except the weld width. Moreover, energy density plots illustrated its linear relationship with penetration depth and limited nonlinear effects on others. Additionally, metallurgical analysis of fusion zone showed dendritic structures consisted of martensitic with eutectic ferrite along solidification grain and subgrain boundaries.
A PMT-Block test bench Adragna, P.; Antonaki, A.; Boudagov, I. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2006, Letnik:
564, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The front-end electronics of the ATLAS hadronic calorimeter (Tile Cal) is housed in a unit, called
PMT-Block. The PMT-Block is a compact instrument comprising a light mixer, a PMT together with its ...divider and a
3-in-1 card, which provides shaping, amplification and integration for the signals. This instrument needs to be qualified before being assembled on the detector. A PMT-Block test bench has been developed for this purpose. This test bench is a system which allows fast, albeit accurate enough, measurements of the main properties of a complete PMT-Block. The system, both hardware and software, and the protocol used for the PMT-Blocks characterization are described in detail in this report. The results obtained in the test of about 10
000 PMT-Blocks needed for the instrumentation of the ATLAS (LHC-CERN) hadronic Tile Calorimeter are also reported.
We present a setup devoted to the study of adsorption and desorption processes of alkali atoms after deposition on a 300 nm thick porous alumina substrate in an Ultra High Vacuum chamber. Rubidium ...atoms, delivered by a dispenser source, enter the 20-30 nm diameter pores, diffuse in and stick to their walls. A 1 W power laser is used in order to induce detachment and take the atoms back in the vapor phase in a very tight confinement region. The desorbed atoms coming out the sample can be monitored via both a resonant optical detection and an electronic amplifier after ionization. The desorbing laser is also able to promote the formation of Rubidium nanoparticles, as the high Rb vapor density in the pores favors aggregation around nucleation point defects. In this way, the apparatus allows for the study of the fundamental processes related to atom – surface interactions in presence of light as well as of several promising application to nanomaterials.
Testbeam studies of production modules of the ATLAS Tile Calorimeter Alexa, C.; Anderson, K.; Biscarat, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2009, Letnik:
606, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We report test beam studies of 11% of the production ATLAS Tile Calorimeter modules. The modules were equipped with production front-end electronics and all the calibration systems planned for the ...final detector. The studies used muon, electron and hadron beams ranging in energy from 3 to 350GeV.
Two independent studies showed that the light yield of the calorimeter was ∼70pe/GeV, exceeding the design goal by 40%. Electron beams provided a calibration of the modules at the electromagnetic energy scale. Over 200 calorimeter cells the variation of the response was 2.4%. The linearity with energy was also measured. Muon beams provided an intercalibration of the response of all calorimeter cells. The response to muons entering in the ATLAS projective geometry showed an RMS variation of 2.5% for 91 measurements over a range of rapidities and modules. The mean response to hadrons of fixed energy had an RMS variation of 1.4% for the modules and projective angles studied. The response to hadrons normalized to incident beam energy showed an 8% increase between 10 and 350GeV, fully consistent with expectations for a noncompensating calorimeter. The measured energy resolution for hadrons of σ/E=52.9%/E⊕5.7% was also consistent with expectations.
Other auxiliary studies were made of saturation recovery of the readout system, the time resolution of the calorimeter and the performance of the trigger signals from the calorimeter.
The response of pions and protons in the energy range of 20–180
GeV, produced at CERN's SPS H8 test-beam line in the ATLAS iron–scintillator Tile hadron calorimeter, has been measured. The test-beam ...configuration allowed the measurement of the longitudinal shower development for pions and protons up to 20 nuclear interaction lengths. It was found that pions penetrate deeper in the calorimeter than protons. However, protons induce showers that are wider laterally to the direction of the impinging particle. Including the measured total energy response, the pion-to-proton energy ratio and the resolution, all observations are consistent with a higher electromagnetic energy fraction in pion-induced showers. The data are compared with GEANT4 simulations using several hadronic physics lists. The measured longitudinal shower profiles are described by an analytical shower parametrization within an accuracy of 5–10%. The amount of energy leaking out behind the calorimeter is determined and parametrized as a function of the beam energy and the calorimeter depth. This allows for a leakage correction of test-beam results in the standard projective geometry.
A measurement is presented of the Formula: see text production cross section at Formula: see text = 7 TeV using Formula: see text collision data corresponding to an integrated luminosity of ...383 Formula: see text, collected with the ATLAS experiment at the LHC. Selection of Formula: see text(1020) mesons is based on the identification of charged kaons by their energy loss in the pixel detector. The differential cross section is measured as a function of the transverse momentum, Formula: see text, and rapidity, Formula: see text, of the Formula: see text(1020) meson in the fiducial region 500 Formula: see text 1200 MeV, Formula: see text 0.8, kaon Formula: see text 230 MeV and kaon momentum Formula: see text 800 MeV. The integrated Formula: see text-meson production cross section in this fiducial range is measured to be Formula: see text = 570 Formula: see text 8 (stat) Formula: see text 66 (syst) Formula: see text 20 (lumi) Formula: see text.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This paper presents a study of the performance of the muon reconstruction in the analysis of proton-proton collisions at Formula: see text TeV at the LHC, recorded by the ATLAS detector in 2010. This ...performance is described in terms of reconstruction and isolation efficiencies and momentum resolutions for different classes of reconstructed muons. The results are obtained from an analysis of Formula: see text meson and Formula: see text boson decays to dimuons, reconstructed from a data sample corresponding to an integrated luminosity of 40 pbFormula: see text. The measured performance is compared to Monte Carlo predictions and deviations from the predicted performance are discussed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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