Thermal Stresses due to a Laser Pulse: Elastic Solution

1996 ◽  
Vol 63 (1) ◽  
pp. 38-46 ◽  
Author(s):  
L. G. Hector ◽  
R. B. Hetnarski
Keyword(s):  
Thermal Stresses ◽  
Functional Form ◽  
Single Pulse ◽  
Elastic Half Space ◽  
Laser Resonator ◽  
Continuous Beam ◽  
Mode Structure ◽  
Pulse Profile ◽  
Thermal Stress Field ◽  
Temporal Pulse

The thermal stress field in an elastic half-space due to a single pulse from a laser is derived for the general case of a mixed-mode structure beam. The mode structure models the output from a cylindrical laser resonator and thus defines a radially symmetric intensity distribution about the beam axis. The functional form of the temporal pulse profile is quite general in that it models the temporal pulse shapes emitted by a laser that is either internally pulsed through radio frequency modulation of its power supply, Q-switched, or mode locked. It also models a continuous beam that is mechanically chopped through external means.

Analysis of Thermal Stresses and Residual Stress Changes in Railroad Wheels Caused by Severe Drag Braking

1977 ◽  
Vol 99 (1) ◽  
pp. 18-23 ◽  
Author(s):  
M. R. Johnson ◽  
R. E. Welch ◽  
K. S. Yeung
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Yield Point ◽  
Thermal Stresses ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Residual Stress Field ◽  
Thermal Stress Field ◽  
Stress Changes ◽  
Railroad Wheels

A finite-element computer program, which takes into consideration nonlinear material behavior after the yield point has been exceeded, has been used to analyze the thermal stresses in railroad freight car wheels subjected to severe drag brake heating. The analysis has been used with typical wheel material properties and wheel configurations to determine the thermal stress field and the extent of regions in the wheel where the yield point is exceeded. The resulting changes in the residual stress field after the wheel has cooled to ambient temperature have also been calculated. It is shown that severe drag braking can lead to the development of residual circumferential tensile stresses in the rim and radial compressive stresses in the plate near both the hub and rim fillets.

scholarly journals Single Pulses from the Galactic Center Magnetar with the Very Large Array

2017 ◽  
Vol 13 (S337) ◽  
pp. 263-266
Author(s):  
S. Chatterjee ◽  
R. S. Wharton ◽  
J. M. Cordes ◽  
G. C. Bower ◽  
B. J. Butler ◽  
...  
Keyword(s):  
Galactic Center ◽  
Single Pulse ◽  
Line Of Sight ◽  
Time Variability ◽  
Dispersion Measure ◽  
Pulse Profile ◽  
Very Large Array ◽  
Pulse Behavior ◽  
Average Profile ◽  
Scattering Time

AbstractPhased VLA observations of the Galactic center magnetar J1745-2900 over 8-12 GHz reveal rich single pulse behavior. The average profile is comprised of several distinct components and is fairly stable over day timescales and GHz frequencies. The average profile is dominated by the jitter of relatively narrow pulses. The pulses in each of the four profile components are uncorrelated in phase and amplitude, although the occurrence of pulse components 1 and 2 appear to be correlated. Using a collection of the brightest individual pulses, we verify that the index of the dispersion law is consistent with the expected cold plasma value of 2. The scattering time is weakly constrained, but consistent with previous measurements, while the dispersion measure DM = 1763+3−10 pc cm−3 is lower than previous measurements, which could be a result of time variability in the line-of-sight column density or changing pulse profile shape over time or frequency.

Thermal stresses in an elastic half-space

1984 ◽  
Vol 24 (3) ◽  
pp. 437-441 ◽  
Author(s):  
L. N. Germanovich ◽  
I. D. Kill'
Keyword(s):  
Half Space ◽  
Thermal Stresses ◽  
Elastic Half Space

The Transient Temperature and Thermal Stresses on Metal Material Irradiated by Multi-Pulse Short Power

2011 ◽  
Vol 130-134 ◽  
pp. 873-878
Author(s):  
Guang Ying Xu
Keyword(s):  
Thermal Stress ◽  
Laser Pulse ◽  
Pulse Width ◽  
Thermal Stresses ◽  
Transient Temperature ◽  
Fourier Law ◽  
Pulse Laser Irradiation ◽  
Metal Material ◽  
Laser Pulse Width ◽  
Thermal Stress Field

Based on the non-Fourier law and thermo-elastic theory, the non-Fourier expressions of the temperature field and the thermal stress field of metal material under multi-pulse laser irradiation were deduced. Taken stainless metal and two pulse width (ω=4ps,4fs) as an example, The effects that distributions and variations of transient temperature and thermal stress are influenced by laser pulse width are studied. The results show that the magnitude and frequency of transient temperature and thermal stress are seriously affected by the laser pulse width. More narrower the laser pulse width, faster and higher the local temperature rise; as well as the thermal stresses.

Analysis of Maladjustment Sensitivity and Calibration Method for a Positive-Branch Confocal Unstable Resonator

2011 ◽  
Vol 301-303 ◽  
pp. 1351-1355
Author(s):  
Xiang Zhang
Keyword(s):  
Calibration Method ◽  
Vertical Movement ◽  
Optic Axis ◽  
Laser Resonator ◽  
Mode Structure ◽  
Optical Elements ◽  
Main Component ◽  
Coma Aberration ◽  
High Order Aberrations ◽  
Structure Properties

The effect of intracavity aberration perturbation on output mode structure properties of unstable laser resonator is been experimentally researched using Hartmann-Shack wavefront sensor on the basis of numerical analysis. Results show that intracavity tilt aberration notablely affects outcoupled intensity distribution, but only a small intracavity tilt perturbation will not obviously augment the high-order aberrations of beam phase properties. The tilt aberration, coma aberration and astigmatism will all be brought, and also tilt aberration is the main component when intracavity mirrors have a vertical movement along the direction of optic axis. When adaptive optical elements such as deformable mirrors are adopted for intracavity aberration correction, the correction for tilt aberration should be considered firstly.

Boundary Element Formulation for Thermal Stresses During Pulsed Laser Heating

2000 ◽  
Vol 68 (3) ◽  
pp. 480-489 ◽  
Author(s):  
P. H. Tehrani ◽  
L. G. Hector, ◽  
R. B. Hetnarski ◽  
M. R. Eslami
Keyword(s):  
Boundary Element ◽  
Thermal Stresses ◽  
Radiant Energy ◽  
Pulsed Laser ◽  
Heat Propagation ◽  
Thermomechanical Coupling ◽  
Stress Fields ◽  
Laser Resonator ◽  
Element Formulation ◽  
Anodized Aluminum

Pulsed lasers are used in a variety of materials processing applications that range from heating for metallurgical transformation to scribing vehicle identification numbers on anodized aluminum strips. These lasers are commonly configured to deliver a large quantity of heat energy in very short time intervals and over very small areas due to the manner in which radiant energy is stored within, and then released from, the laser resonator. At the present time, little is known about the effect of pulse duration on thermomechanical distortion during heating without phase change. To explore this issue, a boundary element method was developed to calculate temperature, displacement, and thermal stress fields in a layer that is rigidly bonded to an inert semi-space. The layer absorbs thermal energy from a repetitively pulsed laser in the plane of its free surface. The effects of two pulse durations, which differ by four-orders-of-magnitude, were examined in this work. The temporal profiles of ultrafast pulses of the order of ten picoseconds (such as those emitted by a mode-locked laser), and pulses of the order of tens-of-nanoseconds (such as those emitted by a Q-switched Nd:YAG laser) were mathematically modeled using a rectified sine function. The spatial profile of each pulse was shaped to approximate a Gaussian strip source. The equations of coupled thermoelasticity, wherein the speed of mechanical distortion due to material expansion during heat absorption is finite, but the speed of heat propagation within the layer is infinite, were solved for both pulse durations. The resulting temperature and stress fields were compared with those predicted in the limit of no thermomechanical coupling.

scholarly journals Correlated emission and spin-down variability in radio pulsars

2017 ◽  
Vol 13 (S337) ◽  
pp. 58-61
Author(s):  
Benjamin Shaw ◽  
Benjamin W. Stappers ◽  
Paul R. Brook ◽  
Aris Karastergiou ◽  
Andrew G. Lyne ◽  
...  
Keyword(s):  
Radio Emission ◽  
Gaussian Processes ◽  
Pulse Shape ◽  
Functional Form ◽  
Radio Pulsars ◽  
Pulse Profile ◽  
Period Derivative ◽  
Timing Noise ◽  
The Relationship ◽  
Shape Changes

AbstractThe recent revelation that there are correlated period derivative and pulse shape changes in pulsars has dramatically changed our understanding of timing noise as well as the relationship between the radio emission and the properties of the magnetosphere as a whole. Using Gaussian processes we are able to model timing and emission variability using a regression technique that imposes no functional form on the data. We revisit the pulsars first studied by Lyne et al. (2010). We not only confirm the emission and rotational transitions revealed therein, but reveal further transitions and periodicities in 8 years of extended monitoring. We also show that in many of these objects the pulse profile transitions between two well-defined shapes, coincident with changes to the period derivative. With a view to the SKA and other telescopes capable of higher cadence we also study the detection limitations of period derivative changes.

Quasi-static thermal stresses due to a concentrated moving heat source in a thin plate

2016 ◽  
Vol 22 (2) ◽  
pp. 243-256
Author(s):  
Amir Reza Shahani ◽  
Samad Kalani
Keyword(s):  
Thermal Stress ◽  
Stress Field ◽  
Heat Source ◽  
Thin Plate ◽  
Thermal Stresses ◽  
Static Solution ◽  
Stress Distributions ◽  
Moving Heat Source ◽  
Displacement Potential ◽  
Thermal Stress Field

Temperature and thermal stress distributions in a two-dimensional infinite thin plate subjected to a moving heat source with variable power and velocity are obtained by solving quasi-static thermoelasticity equations analytically with the aid of a thermoelastic displacement potential. The results show good agreement with experimental data for a stationary source with constant power and with a steady-state analytical solution in the open literature. It is shown that the quasi-static solution can predict changes of the thermal stress field during the movement of the heat source, and can give the effect of changes of power and velocity of the heat source on the thermal stress field during its movement.

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