Residual Stresses in Bulk Metallic Glasses due to Differential Cooling or Thermal Tempering

1998 ◽  
Vol 554 ◽  
Author(s):  
E. Ustundag ◽  
B. Clausen ◽  
J. C. Hanan ◽  
M. A. M. Bourke ◽  
A. Winholtz ◽  
...  
Keyword(s):  
Residual Stress ◽  
Thermal Expansion ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Thermal Gradients ◽  
Processing Conditions ◽  
Strain Gages ◽  
Compressive Stresses ◽  
Thermal Tempering ◽  
Stress Buildup

AbstractDue to their very low thermal conductivities and large thermal expansion values, bulk metallic glasses (BMGs) undergo differential cooling during processing. Large thermal gradients are generated across a specimen leading to residual stress buildup. A thin surface layer contains compressive stresses balanced by tension in the middle. Such stresses can not only influence the mechanical behavior of BMGs, but they can also lead to problems during manufacturing of large or intricate components. Analytical and finite element modeling was used to predict the values and distribution of such stresses as a function of processing conditions. Neutron diffraction measurements were then performed on model specimens which included crystalline phases as “strain gages”. It was shown that significant stresses, on the order of several hundred MPa, can be generated in BMGs. Modeling and diffraction results are presented and their implications discussed.

Microscale Thermoplastic Forming of Bulk Metallic Glasses: Numerical Simulations and Experiments

2008 ◽  
Author(s):  
David L. Henann ◽  
Lallit Anand
Keyword(s):  
Numerical Simulation ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Processing Parameters ◽  
Hot Embossing ◽  
Simulation Tool ◽  
Processing Conditions ◽  
Trial And Error ◽  
Physical Experiments ◽  
Thermoplastic Forming

An extremely promising microscale processing method for bulk metallic glasses called thermoplastic forming has emerged in recent years. However, most of the recent experimental thermoplastic forming studies have been conducted by trial-and-error. In this paper, the large-deformation constitutive theory of Henann and Anand [1] is used as a numerical simulation tool for the design of micro-hot-embossing processes. This numerical simulation capability is used to determine appropriate processing parameters in order to carry out several successful micron-scale hot-embossing operation on the metallic glass Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vitreloy-1). By carrying out the corresponding physical experiments, it is demonstrated that microscale features in Vitreloy-1 may be accurately replicated under the processing conditions determined by use of the numerical simulation capability.

Microscale Thermoplastic Forming of Bulk Metallic Glasses: Numerical Simulation and Experiments

2007 ◽  
Vol 1048 ◽  
Author(s):  
David Henann ◽  
Lallit Anand
Keyword(s):  
Numerical Simulation ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Processing Parameters ◽  
Hot Embossing ◽  
Processing Method ◽  
Simulation Tool ◽  
Processing Conditions ◽  
Trial And Error ◽  
Thermoplastic Forming

AbstractAn extremely promising microscale processing method for bulk metallic glasses called thermoplastic forming has emerged in recent years. However, most of the recent experimental thermoplastic forming studies have been conducted by trial-and-error. In this paper, we use the large-deformation constitutive theory of Henann and Anand [1] as a numerical simulation tool for the design of a micro-hot-embossing process. This numerical simulation capability is used to determine appropriate processing parameters in order to carry out a successful micron-scale hot-embossing operation on the metallic glass Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vitreloy-1). By carrying out a corresponding physical experiment, we demonstrate that micron-scale features in Vitreloy-1 may be accurately replicated under the processing conditions determined by use of the numerical simulation capability.

Formation and interesting thermal expansion behavior of novel Sm-based bulk metallic glasses

2007 ◽  
Vol 15 (7) ◽  
pp. 929-933 ◽  
Author(s):  
Guo Jing ◽  
Bian Xiufang ◽  
Lin Tao ◽  
Zhao Yan ◽  
Taibao Li ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Thermal Expansion Behavior ◽  
Expansion Behavior

Thermal Tempering of Bulk Metallic Glasses

2002 ◽  
Vol 754 ◽  
Author(s):  
Cahit C. Aydiner ◽  
Ersan Üstündag
Keyword(s):  
Metallic Glasses ◽  
Casting Process ◽  
Glass Forming Ability ◽  
Stress Generation ◽  
Copper Mold ◽  
Glass Forming ◽  
Viscoelastic Models ◽  
Compressive Stresses ◽  
Thermal Tempering ◽  
Stress Profiles

ABSTRACTThe recent development of multi-component alloys with exceptional glass forming ability has allowed the processing of large amorphous metal samples. The possibility of formation of thermal tempering stresses during the processing of these bulk metallic glass (BMG) specimens was investigated using the (1) instant freezing, and (2) viscoelastic models. Both models yielded similar results although from vastly different approaches. It was shown that fast convective cooling of Zr41.2Ti13.8Cu12.5Ni10Be22.5 plates could generate significant compressive stresses on the surfaces balanced with mid-plane tension. The crack compliance method was then employed to measure the stress profiles in a BMG plate that was cast in a copper mold. These profiles were roughly parabolic suggesting that thermal tempering was indeed the dominant residual stress generation mechanism. However, the magnitude of the measured stresses (with peak values of only about 1.5% of the yield strength) was significantly lower than the modeling predictions. Possible reasons for this discrepancy are described in relation to the actual casting process and material properties.

Characterisation and modelling of thermal expansion coefficient of woven carbon/epoxy composite and its application to the determination of spring-in

2016 ◽  
Vol 51 (11) ◽  
pp. 1527-1538 ◽  
Author(s):  
Yasir Nawab ◽  
Camille Sonnenfeld ◽  
Abdelghani Saouab ◽  
Romain Agogué ◽  
Pierre Beauchêne
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Thermal Expansion ◽  
Volume Fraction ◽  
Epoxy Composite ◽  
Fibre Volume Fraction ◽  
Fibre Volume ◽  
Woven Composites ◽  
Thermal Gradients ◽  
Experimental Values

Properties of resin and composite, especially anisotropic coefficients of thermal expansion, are very crucial to precisely determine residual stress generated in a composite part. No comprehensive study is available in the literature to determine these properties for woven composites and then its application to model residual stress in woven carbon epoxy composite parts. In the present article, experimental results on thermal coefficients of RTM6 epoxy resin as well carbon/epoxy woven composites obtained using different experimental techniques are compared with homogenised coefficients of thermal expansion results. Evolution of spring-in angle of L-shaped carbon/epoxy woven composite (during and after cure) with three different thicknesses is modelled by simultaneously solving the thermal-kinetics and thermal-chemical-mechanics coupling by using finite element code COMSOL Multiphysics. Objective was to quantify the contribution of curing and cooling to the formation of residual stress. Anisotropic properties of composite, during and after cure, required for numerical simulation are obtained using an analytical method. Variation in properties with degree of cure and thermal gradients induced in the part during fabrication are considered while modelling. Modelled properties of cured composites were compared with experimental values and were found in agreement. The spring-in angle values obtained by numerical simulation are compared with the results of the analytical model as well as experiments. Effect of variation of fibre volume fraction and presence of thermal gradients on spring-in was studied as well.

Residual Stresses in Bulk Metallic Glasses due to Thermal Tempering

2005 ◽  
Vol 490-491 ◽  
pp. 515-520 ◽  
Author(s):  
Cahit Can Aydiner ◽  
Ersan Üstündag
Keyword(s):  
Experimental Data ◽  
Residual Stresses ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Viscoelastic Model ◽  
Structural Materials ◽  
Thin Layers ◽  
Stress Generation ◽  
Experimental Stress ◽  
Thermal Tempering

Bulk metallic glasses (BMGs) are attractive structural materials that develop residual stresses during processing due to thermal tempering. In this process, compressive surface stresses are generated within thin layers balanced with tension in the interior. In the present study, stress generation was analyzed experimentally and theoretically in a BMG plate and a cylinder. The residual stresses were measured using the crack compliance method. It was shown that high stresses can be attained in metallic glasses due to thermal tempering: over −300 MPa compression on the surface balanced by +150 MPa tension in the middle. The experimental data were then compared to the predictions of a viscoelastic model that took into account the equilibrium viscosity of BMG as a function of temperature. The model was shown to be accurate within 5 to 25% of the experimental stress data. It is therefore a powerful tool for estimating processing-induced residual stresses in bulk metallic glasses.

FREE VOLUME CHANGE OF METALLIC GLASSES STUDIED BY THERMAL EXPANSION MEASUREMENTS

1980 ◽  
Vol 41 (C8) ◽  
pp. C8-875-C8-877
Author(s):  
E. Girt ◽  
P. Tomić ◽  
A. Kuršumović ◽  
T. Mihać-Kosanović
Keyword(s):  
Thermal Expansion ◽  
Free Volume ◽  
Volume Change ◽  
Metallic Glasses
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