The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Bernd Stühn - One of the best experts on this subject based on the ideXlab platform.
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structure and Thermoelastic Behavior of synthetic rubber organoclay nanocomposites
Macromolecular Chemistry and Physics, 2003Co-Authors: V P Privalko, S. M. Ponomarenko, F. Schön, Wolfram Gronski, Rosina Staneva, E G Privalko, Bernd StühnAbstract:Nanocomposites of synthetic styrene-co-butadiene rubber and three types of organoclay fillers,, ere prepared by melt-compounding and characterized by small-angle X-ray scattering (SAXS), differential calorimetry and stretching calorimetry. The in-rubber structure of the organoclay particles is characterized by different degrees of intercalation with interlayer distances ranging from 3.1-4.9 nm. In contrast to the pristine rubber, all nanocomposiws exhibited irreversibility of both mechanical work land heat effects in stretching/contraction cycles at fairly low elongations. Moreover, at the same filler loading both the mechanical reinforcement effect and the magnitude of specific heat effects proved strongly dependent on the degree of intercalation, In the range of low elongations, significantly earlier onsets of the heat inversion phenomenon (compared to theoretically expected), as well as the overshoots of exothermal heat effects in contraction Above the endothermal heat effects in-stretching for nanocomposites, suggested the contribution of structural re arrangements at the rubber/filler interface by the mechanism of chain slippage operative in both,stretching and contraction regimes., In the range of high elongations, the Thermoelastic Behavior of nanocomposites could be accounted for quantitatively by the model, which assumed explicitly the contributions of local strain Amplification for the rubber matrix and of successive decay of nanoparticle clusters with increasing strain, generating the exothermal effects, of external friction between nanoparticles.
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Structure and Thermoelastic Behavior of Synthetic Rubber/Organoclay Nanocomposites
Macromolecular Chemistry and Physics, 2003Co-Authors: Valery P. Privalko, Eleonora G. Privalko, S. M. Ponomarenko, F. Schön, Wolfram Gronski, Rosina Staneva, Bernd StühnAbstract:Nanocomposites of synthetic styrene-co-butadiene rubber and three types of organoclay fillers,, ere prepared by melt-compounding and characterized by small-angle X-ray scattering (SAXS), differential calorimetry and stretching calorimetry. The in-rubber structure of the organoclay particles is characterized by different degrees of intercalation with interlayer distances ranging from 3.1-4.9 nm. In contrast to the pristine rubber, all nanocomposiws exhibited irreversibility of both mechanical work land heat effects in stretching/contraction cycles at fairly low elongations. Moreover, at the same filler loading both the mechanical reinforcement effect and the magnitude of specific heat effects proved strongly dependent on the degree of intercalation, In the range of low elongations, significantly earlier onsets of the heat inversion phenomenon (compared to theoretically expected), as well as the overshoots of exothermal heat effects in contraction Above the endothermal heat effects in-stretching for nanocomposites, suggested the contribution of structural re arrangements at the rubber/filler interface by the mechanism of chain slippage operative in both,stretching and contraction regimes., In the range of high elongations, the Thermoelastic Behavior of nanocomposites could be accounted for quantitatively by the model, which assumed explicitly the contributions of local strain Amplification for the rubber matrix and of successive decay of nanoparticle clusters with increasing strain, generating the exothermal effects, of external friction between nanoparticles.
Jochen M. Schneider - One of the best experts on this subject based on the ideXlab platform.
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Electronic structure tuning of the anomalous Thermoelastic Behavior in Nb-X (X = Zr, V, Mo) solid solutions
Journal of Applied Physics, 2019Co-Authors: Philipp Keuter, Denis Music, Michael Stuer, Jochen M. SchneiderAbstract:Nb exhibits an anomalous temperature dependency of the elastic constant c44, which increases from around 500 to 2500 K. This anomaly can be affected by alloying. To study the effect of atomic size and electronic structure on the Thermoelastic Behavior in bcc Nb-X (X = Zr, V, Mo) solid solutions, the shear Thermoelastic constants c44(T) and c′(T) are investigated theoretically using a density functional theory based model in which electronic and thermal expansion effects are treated separately. For all binary solid solutions, an anomalous Thermoelastic Behavior is predicted, which can be attributed to the electronic entropy induced by a high population of electronic states at the Fermi level (>0.8 states/eV atom). The onset of the increase in c44 remains unchanged for isoelectronic Nb-V indicating the absence of a size effect on the anomalous Thermoelastic Behavior. In contrast, the anomalous Thermoelastic Behavior can be tuned by alloying with Zr or Mo, due to the valence electron concentration induced change in the density of states in the vicinity of the Fermi level, leading to a shift in the anomalous trend of c44 to lower temperatures. An anomalous temperature Behavior is also predicted for the shear elastic constant c′ for Nb-Mo solid solutions with Mo concentrations between 24 and 33 at. %. With increasing Mo concentrations, the anomaly in both elastic constants is suppressed due to the continuous reduction in electronic states at the Fermi level.Nb exhibits an anomalous temperature dependency of the elastic constant c44, which increases from around 500 to 2500 K. This anomaly can be affected by alloying. To study the effect of atomic size and electronic structure on the Thermoelastic Behavior in bcc Nb-X (X = Zr, V, Mo) solid solutions, the shear Thermoelastic constants c44(T) and c′(T) are investigated theoretically using a density functional theory based model in which electronic and thermal expansion effects are treated separately. For all binary solid solutions, an anomalous Thermoelastic Behavior is predicted, which can be attributed to the electronic entropy induced by a high population of electronic states at the Fermi level (>0.8 states/eV atom). The onset of the increase in c44 remains unchanged for isoelectronic Nb-V indicating the absence of a size effect on the anomalous Thermoelastic Behavior. In contrast, the anomalous Thermoelastic Behavior can be tuned by alloying with Zr or Mo, due to the valence electron concentration induced ch...
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electronic structure tuning of the anomalous Thermoelastic Behavior in nb x x zr v mo solid solutions
Journal of Applied Physics, 2019Co-Authors: Philipp Keuter, Denis Music, Michael Stuer, Jochen M. SchneiderAbstract:Nb exhibits an anomalous temperature dependency of the elastic constant c44, which increases from around 500 to 2500 K. This anomaly can be affected by alloying. To study the effect of atomic size and electronic structure on the Thermoelastic Behavior in bcc Nb-X (X = Zr, V, Mo) solid solutions, the shear Thermoelastic constants c44(T) and c′(T) are investigated theoretically using a density functional theory based model in which electronic and thermal expansion effects are treated separately. For all binary solid solutions, an anomalous Thermoelastic Behavior is predicted, which can be attributed to the electronic entropy induced by a high population of electronic states at the Fermi level (>0.8 states/eV atom). The onset of the increase in c44 remains unchanged for isoelectronic Nb-V indicating the absence of a size effect on the anomalous Thermoelastic Behavior. In contrast, the anomalous Thermoelastic Behavior can be tuned by alloying with Zr or Mo, due to the valence electron concentration induced change in the density of states in the vicinity of the Fermi level, leading to a shift in the anomalous trend of c44 to lower temperatures. An anomalous temperature Behavior is also predicted for the shear elastic constant c′ for Nb-Mo solid solutions with Mo concentrations between 24 and 33 at. %. With increasing Mo concentrations, the anomaly in both elastic constants is suppressed due to the continuous reduction in electronic states at the Fermi level.Nb exhibits an anomalous temperature dependency of the elastic constant c44, which increases from around 500 to 2500 K. This anomaly can be affected by alloying. To study the effect of atomic size and electronic structure on the Thermoelastic Behavior in bcc Nb-X (X = Zr, V, Mo) solid solutions, the shear Thermoelastic constants c44(T) and c′(T) are investigated theoretically using a density functional theory based model in which electronic and thermal expansion effects are treated separately. For all binary solid solutions, an anomalous Thermoelastic Behavior is predicted, which can be attributed to the electronic entropy induced by a high population of electronic states at the Fermi level (>0.8 states/eV atom). The onset of the increase in c44 remains unchanged for isoelectronic Nb-V indicating the absence of a size effect on the anomalous Thermoelastic Behavior. In contrast, the anomalous Thermoelastic Behavior can be tuned by alloying with Zr or Mo, due to the valence electron concentration induced ch...
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From qualitative to quantitative description of the anomalous Thermoelastic Behavior of V, Nb, Ta, Pd and Pt.
Journal of physics. Condensed matter : an Institute of Physics journal, 2019Co-Authors: Philipp Keuter, Denis Music, Michael Stuer, Volker Schnabel, Jochen M. SchneiderAbstract:To study the anomalous Thermoelastic Behavior of bcc V, Nb, Ta as well as fcc Pd and Pt a density functional theory (DFT) based model is used, which allows for the calculation of the elastic constant [Formula: see text] and [Formula: see text] as a function of temperature. Available experimental [Formula: see text] trends are correctly reproduced indicating that the electronic structure mechanisms enabling anomalous Behavior are captured by the model. A DFT based correlative investigation between V, Nb, Ta, Pd and Pt with anomalous Thermoelastic properties and Mo and Cu with ordinary Behavior reveals a high density of states (DOS) at the Fermi level to be a necessary but not sufficient condition for an anomalous Thermoelastic Behavior. In addition, anomalous metals in contrast to ordinary metals reallocate electronic states in the vicinity of the Fermi level upon lattice distortion, causing an increase in bond strength as identified by crystal orbital Hamilton population (COHP) analysis. Hence, we have identified the combination of high DOS and electronic reallocation upon lattice distortion to be the physical origin for anomalous Thermoelastic Behavior in metals. The absence of an anomaly for [Formula: see text]-type distortion in V, Nb, Ta, Pd and Pt is suggested to be due to the less pronounced reallocation of states compared to [Formula: see text]-type distortion.
Valery P. Privalko - One of the best experts on this subject based on the ideXlab platform.
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Structure and Thermoelastic Behavior of Synthetic Rubber/Organoclay Nanocomposites
Macromolecular Chemistry and Physics, 2003Co-Authors: Valery P. Privalko, Eleonora G. Privalko, S. M. Ponomarenko, F. Schön, Wolfram Gronski, Rosina Staneva, Bernd StühnAbstract:Nanocomposites of synthetic styrene-co-butadiene rubber and three types of organoclay fillers,, ere prepared by melt-compounding and characterized by small-angle X-ray scattering (SAXS), differential calorimetry and stretching calorimetry. The in-rubber structure of the organoclay particles is characterized by different degrees of intercalation with interlayer distances ranging from 3.1-4.9 nm. In contrast to the pristine rubber, all nanocomposiws exhibited irreversibility of both mechanical work land heat effects in stretching/contraction cycles at fairly low elongations. Moreover, at the same filler loading both the mechanical reinforcement effect and the magnitude of specific heat effects proved strongly dependent on the degree of intercalation, In the range of low elongations, significantly earlier onsets of the heat inversion phenomenon (compared to theoretically expected), as well as the overshoots of exothermal heat effects in contraction Above the endothermal heat effects in-stretching for nanocomposites, suggested the contribution of structural re arrangements at the rubber/filler interface by the mechanism of chain slippage operative in both,stretching and contraction regimes., In the range of high elongations, the Thermoelastic Behavior of nanocomposites could be accounted for quantitatively by the model, which assumed explicitly the contributions of local strain Amplification for the rubber matrix and of successive decay of nanoparticle clusters with increasing strain, generating the exothermal effects, of external friction between nanoparticles.
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Composition-Dependent Properties of Polyethylene/Kaolin Composites: VI. Thermoelastic Behavior in the melt state
Journal of Thermal Analysis and Calorimetry, 2000Co-Authors: Valery P. Privalko, V. V. Korskanov, Eleonora G. Privalko, Rolf Walter, Klaus FriedrichAbstract:The equilibrium pressure-volume-temperature properties and Thermoelastic Behavior of kaolin-filled composites of the injection molding grade of high density polyethylene (HDPE) were studied in the temperature interval 423–473 K and in thepressure range 30–100 MPa. It was established that the HDPE melts in filled composites existed in a somewhat expanded, more compressible state. This effect was quantitatively accounted for by the increased number of external degrees of freedom derived from the Simha-Somcynsky equation of state. The effect of the coupling agent on thermal diffusivities and specific heat capacities of filled samples turned out negligibly small.
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composition dependent properties of polyethylene kaolin composites vi Thermoelastic Behavior in the melt state
Journal of Thermal Analysis and Calorimetry, 2000Co-Authors: Valery P. Privalko, V. V. Korskanov, Eleonora G. Privalko, Rolf Walter, Klaus FriedrichAbstract:The equilibrium pressure-volume-temperature properties and Thermoelastic Behavior of kaolin-filled composites of the injection molding grade of high density polyethylene (HDPE) were studied in the temperature interval 423–473 K and in thepressure range 30–100 MPa. It was established that the HDPE melts in filled composites existed in a somewhat expanded, more compressible state. This effect was quantitatively accounted for by the increased number of external degrees of freedom derived from the Simha-Somcynsky equation of state. The effect of the coupling agent on thermal diffusivities and specific heat capacities of filled samples turned out negligibly small.
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Thermoelastic Behavior of carbon fiber/polycarbonate model composites
Polymer Engineering & Science, 1999Co-Authors: Valery P. Privalko, Dmitry I. Sukhorukov, József Karger-kocsisAbstract:Model composites of polycarbonate (PC) containing single, multiple and chopped carbon fibers (CF) with and without and epoxy sizing were prepared by hot pressing. The Thermoelastic Behavior of model CF/PC composites was characterized by stretching calorimetry at room temperature. For small strains £ (i.e., e 0.01) the specific mechanical work, specific heat effects and specific internal energy changes AU were completely reversible in stretching/contraction cycles and quantitatively obeyed the standard relationships for elastic solids. Young's moduli E and ΔU were significantly higher, whereas the linear thermal expansivities α L were lower for model CF/PC composites compared to those for the neat PC. Smaller values of the above parameters for composites reinforced with sized CF suggested weaker CF/PC interfacial interactions. Current theoretical models of Thermoelastic properties of composite materials suggest the existence of unusually stiff, highly oriented PC structures in fairly thick boundary layers around CF. The onset of inelastic deformation, as well as mechanical failure in CF/PC model composites at significantly smaller strains compared to the neat PC were tentatively explained by the yield and subsequent plastic flow of the matrix polymer initiated by heat effects of fiber fragmentation processes, and by higher concentration of microvoids generated in fiber fragmentation/debonding events, respectively.
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Thermoelastic Behavior of the Single Carbon Fibre/Polycarbonate Microcomposites
Advanced Composites Letters, 1997Co-Authors: Valery P. Privalko, Dmitry I. Sukhorukov, József Karger-kocsisAbstract:Stretching calorimetry technique was used to evaluate Young's moduli ( E), linear expansivities (α L) and internal energy changes (Δ U) in stretching/contraction cycles for single carbon fiber/ polycarbonate (CF/PC) microcomposites. Within the interval of elastic strains, microcomposites with both sized and unsized CF were characterized by significantly higher values of E and Δ U and by lower values ofα L compared to the plain PC matrix. The results obtained suggest the formation of interfacial boundary PC layers with changed structure around CF which affect the Thermoelastic properties of the CF/PC microcomposites.
Philipp Keuter - One of the best experts on this subject based on the ideXlab platform.
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Electronic structure tuning of the anomalous Thermoelastic Behavior in Nb-X (X = Zr, V, Mo) solid solutions
Journal of Applied Physics, 2019Co-Authors: Philipp Keuter, Denis Music, Michael Stuer, Jochen M. SchneiderAbstract:Nb exhibits an anomalous temperature dependency of the elastic constant c44, which increases from around 500 to 2500 K. This anomaly can be affected by alloying. To study the effect of atomic size and electronic structure on the Thermoelastic Behavior in bcc Nb-X (X = Zr, V, Mo) solid solutions, the shear Thermoelastic constants c44(T) and c′(T) are investigated theoretically using a density functional theory based model in which electronic and thermal expansion effects are treated separately. For all binary solid solutions, an anomalous Thermoelastic Behavior is predicted, which can be attributed to the electronic entropy induced by a high population of electronic states at the Fermi level (>0.8 states/eV atom). The onset of the increase in c44 remains unchanged for isoelectronic Nb-V indicating the absence of a size effect on the anomalous Thermoelastic Behavior. In contrast, the anomalous Thermoelastic Behavior can be tuned by alloying with Zr or Mo, due to the valence electron concentration induced change in the density of states in the vicinity of the Fermi level, leading to a shift in the anomalous trend of c44 to lower temperatures. An anomalous temperature Behavior is also predicted for the shear elastic constant c′ for Nb-Mo solid solutions with Mo concentrations between 24 and 33 at. %. With increasing Mo concentrations, the anomaly in both elastic constants is suppressed due to the continuous reduction in electronic states at the Fermi level.Nb exhibits an anomalous temperature dependency of the elastic constant c44, which increases from around 500 to 2500 K. This anomaly can be affected by alloying. To study the effect of atomic size and electronic structure on the Thermoelastic Behavior in bcc Nb-X (X = Zr, V, Mo) solid solutions, the shear Thermoelastic constants c44(T) and c′(T) are investigated theoretically using a density functional theory based model in which electronic and thermal expansion effects are treated separately. For all binary solid solutions, an anomalous Thermoelastic Behavior is predicted, which can be attributed to the electronic entropy induced by a high population of electronic states at the Fermi level (>0.8 states/eV atom). The onset of the increase in c44 remains unchanged for isoelectronic Nb-V indicating the absence of a size effect on the anomalous Thermoelastic Behavior. In contrast, the anomalous Thermoelastic Behavior can be tuned by alloying with Zr or Mo, due to the valence electron concentration induced ch...
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electronic structure tuning of the anomalous Thermoelastic Behavior in nb x x zr v mo solid solutions
Journal of Applied Physics, 2019Co-Authors: Philipp Keuter, Denis Music, Michael Stuer, Jochen M. SchneiderAbstract:Nb exhibits an anomalous temperature dependency of the elastic constant c44, which increases from around 500 to 2500 K. This anomaly can be affected by alloying. To study the effect of atomic size and electronic structure on the Thermoelastic Behavior in bcc Nb-X (X = Zr, V, Mo) solid solutions, the shear Thermoelastic constants c44(T) and c′(T) are investigated theoretically using a density functional theory based model in which electronic and thermal expansion effects are treated separately. For all binary solid solutions, an anomalous Thermoelastic Behavior is predicted, which can be attributed to the electronic entropy induced by a high population of electronic states at the Fermi level (>0.8 states/eV atom). The onset of the increase in c44 remains unchanged for isoelectronic Nb-V indicating the absence of a size effect on the anomalous Thermoelastic Behavior. In contrast, the anomalous Thermoelastic Behavior can be tuned by alloying with Zr or Mo, due to the valence electron concentration induced change in the density of states in the vicinity of the Fermi level, leading to a shift in the anomalous trend of c44 to lower temperatures. An anomalous temperature Behavior is also predicted for the shear elastic constant c′ for Nb-Mo solid solutions with Mo concentrations between 24 and 33 at. %. With increasing Mo concentrations, the anomaly in both elastic constants is suppressed due to the continuous reduction in electronic states at the Fermi level.Nb exhibits an anomalous temperature dependency of the elastic constant c44, which increases from around 500 to 2500 K. This anomaly can be affected by alloying. To study the effect of atomic size and electronic structure on the Thermoelastic Behavior in bcc Nb-X (X = Zr, V, Mo) solid solutions, the shear Thermoelastic constants c44(T) and c′(T) are investigated theoretically using a density functional theory based model in which electronic and thermal expansion effects are treated separately. For all binary solid solutions, an anomalous Thermoelastic Behavior is predicted, which can be attributed to the electronic entropy induced by a high population of electronic states at the Fermi level (>0.8 states/eV atom). The onset of the increase in c44 remains unchanged for isoelectronic Nb-V indicating the absence of a size effect on the anomalous Thermoelastic Behavior. In contrast, the anomalous Thermoelastic Behavior can be tuned by alloying with Zr or Mo, due to the valence electron concentration induced ch...
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From qualitative to quantitative description of the anomalous Thermoelastic Behavior of V, Nb, Ta, Pd and Pt.
Journal of physics. Condensed matter : an Institute of Physics journal, 2019Co-Authors: Philipp Keuter, Denis Music, Michael Stuer, Volker Schnabel, Jochen M. SchneiderAbstract:To study the anomalous Thermoelastic Behavior of bcc V, Nb, Ta as well as fcc Pd and Pt a density functional theory (DFT) based model is used, which allows for the calculation of the elastic constant [Formula: see text] and [Formula: see text] as a function of temperature. Available experimental [Formula: see text] trends are correctly reproduced indicating that the electronic structure mechanisms enabling anomalous Behavior are captured by the model. A DFT based correlative investigation between V, Nb, Ta, Pd and Pt with anomalous Thermoelastic properties and Mo and Cu with ordinary Behavior reveals a high density of states (DOS) at the Fermi level to be a necessary but not sufficient condition for an anomalous Thermoelastic Behavior. In addition, anomalous metals in contrast to ordinary metals reallocate electronic states in the vicinity of the Fermi level upon lattice distortion, causing an increase in bond strength as identified by crystal orbital Hamilton population (COHP) analysis. Hence, we have identified the combination of high DOS and electronic reallocation upon lattice distortion to be the physical origin for anomalous Thermoelastic Behavior in metals. The absence of an anomaly for [Formula: see text]-type distortion in V, Nb, Ta, Pd and Pt is suggested to be due to the less pronounced reallocation of states compared to [Formula: see text]-type distortion.
Jialing Yang - One of the best experts on this subject based on the ideXlab platform.
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Thermoelastic response of a one-dimensional semi-infinite rod heated by a moving laser pulse
Canadian Journal of Physics, 2016Co-Authors: Yu Xin Sun, Xin Wang, Ai Kah Soh, Jialing YangAbstract:In the present study, Thermoelastic Behavior of a semi-infinite rod, which is subjected to a time exponentially decaying laser pulse, is formulated. The rod is free at the left end and the laser pu...
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Thermoelastic Behavior in metal films induced by ramp-type heating
Proceedings of 2011 International Conference on Electronics and Optoelectronics, 2011Co-Authors: Yu Xin Sun, Yan Jiang, Jialing YangAbstract:In metal thin film, two effects become dominant. One is the non-Fourier effect in heat conduction, and the other is the coupling effect between the temperature and strain rate. In the present paper, an ultrafast Thermoelasticity model utilizing the parabolic two-step heat conduction model and the generalized Thermoelastic theory was formulated to describe the Thermoelastic Behavior of a thin metal film subjected to a ramp-type heating. An analytical-numerical technique based on the Laplace transform was used to solve the governing equations and the time histories of the electron temperature, lattice temperature, displacement and stress in a gold film were analyzed. The influence of the thickness of the film was also analyzed. In addition, the propagation of the stress wave through the film was analyzed.
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Ultrafast laser-induced Thermoelastic Behavior in metal films
International Journal of Mechanical Sciences, 2010Co-Authors: Yu Xin Sun, Masumi Saka, Jialing YangAbstract:Abstract When a thin metal film is irradiated by an ultrafast laser, the energy of the laser is first absorbed by electrons and then transferred to the lattice. In addition, a Thermoelastic wave is generated due to the Thermoelastic coupling effect. An ultrafast Thermoelasticity model utilizing the parabolic two-step heat conduction model and the generalized Thermoelastic theory was formulated to describe the Thermoelastic Behavior of a thin metal film irradiated by a femtosecond laser pulse. The temporal profile of the ultrafast laser was regarded as being non-Gaussian. An analytical–numerical technique based on the Laplace transform was used to solve the governing equations and the time histories of the electron temperature, lattice temperature, displacement and stress in a gold film were analyzed. The influence of the thickness of the film was also analyzed. In addition, the propagation of the stress wave through the film was analyzed.