Determination of the Interface Heat Transfer Coefficient for Non-Isothermal Bulk-Forming Processes

Semiatin, S. L.; Collings, E. W.; Wood, Van E.; Altan, Taylan

doi:10.1115/1.3187094

Cited by 81 publications

(28 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[13,14] However, as shown in Table IV, model predictions of the temperature throughout the mill are consistent (i.e., within ‫5ע‬ pct) with those predicted by an industrial rolling mill model (calibrated with industrial data) which is employed to set up the mill. From Table IV, it is, furthermore, apparent that a heat-transfer coefficient of 25 kW/m 2 ЊC, instead of the 250 to 400 kW/m 2 ЊC coefficient used in the rolling model, leads to unacceptably high differences in temperature when compared to those determined industrially (Table IV).…”

Section: A Strip Temperature/mill Loadsmentioning

confidence: 82%

Modeling the microstructural changes during hot tandem rolling of AA5XXX aluminum alloys: Part III. Overall model development and validation

Wells

Samarasekera

Brimacombe

et al. 1998

Metall Mater Trans B

View full text Add to dashboard Cite

Part III of this article presents the overall mathematical development for the microstructural and textural evolution during industrial hot tandem rolling of AA5182 and AA5052 alloys and validation of the mathematical model, by comparison to both industrial data and information from the literature. The model consists of a plasticity module to simulate the temperature and deformation in the roll bite and an interstand module to characterize the changing microstructure, texture, and temperature in the strip between the rolling stands. The plasticity module was developed using a commercial finite-element package, DEFORM, a two-dimensional transient Lagrangian model which couples the thermal and deformation phenomena and is able to predict the temperature, strain rate, and strain distribution in the strip at any position in the roll bite. The interstand module incorporates semiempirical equations, developed in this study, which quantify the microstructural (percent recrystallization and recrystallized grain size) and textural changes in the strip between the rolling stands. The interstand model also includes a temperature module to predict the through-thickness temperature distribution in the strip based on one-dimensional heat conduction. Validation of the model against industrial data indicated that it gave reasonable predictions for the temperature, grain size, and volume fraction of some of the deformation texture components after recrystallization was completed. However, the model overestimated the mill loads in the last stands for both the AA5182 and AA5052 alloys and underestimated the amount of cube ({100}ϽuvwϾ) and S ({123}Ͻ634Ͼ) texture in the recrystallized strip.

show abstract

Section: A Strip Temperature/mill Loadsmentioning

confidence: 82%

Modeling the microstructural changes during hot tandem rolling of AA5XXX aluminum alloys: Part III. Overall model development and validation

Wells

Samarasekera

Brimacombe

et al. 1998

Metall Mater Trans B

View full text Add to dashboard Cite

show abstract

“…mm were machined, heat treated, and coated with a glass Two-dimensional simulations were used in a parametric lubricant (Deltaglaze 153, manufactured by Acheson Colstudy to explore the effects of preheat temperature (900 ЊC loids Company (Port Huron, Michigan)). Before each extruor 985 ЊC), flow-stress properties of the workpiece, interfasion, the die was lubricated with Anti-Seize (manufactured cial heat transfer between the workpiece and die, [7] and by Permatex Division of Loctite Corporation (Rocky Hill, dwell time of the hot workpiece in the cooler die prior to CT)). deformation, on metal flow ( Table I).…”

Section: Introductionmentioning

confidence: 99%

Finite-element modeling of nonisothermal equal-channel angular extrusion

DeLo

Semiatin

1999

Metall Mater Trans A

Self Cite

117

View full text Add to dashboard Cite

Deformation during conventional (nonisothermal) hot working of metals via equal-channel angular extrusion (ECAE)was investigated using two-dimensional (2-D) and three-dimensional (3-D) finiteelement modeling (FEM) analysis. The effects of material flow properties, die-workpiece heat-transfer and friction conditions, and die design on metal flow were examined. Friction and die design were shown to be the most important parameters governing the formation of dead-metal zones during extrusion. On the other hand, thermal gradients induced by die chill and deformation heating were found to exacerbate the extent of flow localization that arises due to material-flow softening alone. The FEM predictions were validated by ECAE experiments on a Ti-6Al-4V alloy with a colony alpha microstructure. Preforms exhibited minor edge cracking and mild flow localization during extrusion at 985 ЊC, but severe shear localization and fracture during extrusion at 900 ЊC. The 2-D FEM simulations predicted deformation detail, including shear localization, that was in good agreement with the experimental results, but 3-D FEM simulations were required to realistically predict die chill. A combined approach, in which thermal data were extracted from 3-D simulations and inserted into 2-D simulations, produced load-stroke and fracture predictions in general agreement with measured values.

show abstract

“…For the shrink-on casting, the shrink-on h 0 for titanium reached a steady-state maximum value, while for aluminum, h 0 continued to increase (b) with time. One possible explanation for this difference can be deduced based on the results of Semiatin et al [9] and Hu et al [10] which showed that h 0 reaches a steady-state maximum at a critical value of applied pressure. It is possible that the interface pressure did not reach the critical value in the aluminum castings but did in the titanium castings.…”

Section: Shrink-off Castingmentioning

confidence: 98%

“…remains constant. [9,10] (5) Steps 3 and 4 were repeated using different values of To generate an interface-heat-transfer-coefficient curve h 0 (T ) until a suitable agreement between the simulated based on the above description, h 0 was assumed to be a and measured temperature profiles was obtained.…”

Section: H 0 Determinationmentioning

confidence: 99%

Determination of interface heat-transfer coefficients for permanent-mold casting of Ti-6Al-4V

Kobryn

Semiatin

2001

Metall Mater Trans B

Self Cite

View full text Add to dashboard Cite

Interface heat-transfer coefficients (h 0 ) for permanent-mold casting (PMC) of Ti-6Al-4V were established as a function of casting surface temperature using a calibration-curve technique. Because mold geometry has a strong effect on h 0 , values were determined for both of the two limiting interface types, "shrink-off" and "shrink-on." For this purpose, casting experiments with instrumented molds were performed for cylinder-and pipe-shaped castings. The measured temperature transients were used in conjunction with two-dimensional (2-D) axisymmetric finite-element method (FEM) simulations to determine h 0 (T ). For the shrink-off interface type, h 0 was found to decrease linearly from 2000 to 1500 W/m 2 K between the liquidus and the solidus, from 1500 to 325 W/m 2 K between the solidus and the gap-formation temperature, and at a rate of 0.3 W/m 2 K/K thereafter. For the shrink-on interface type, h 0 was found to increase linearly from 2000 to 2500 W/m 2 K between the liquidus and the solidus temperatures, from 2500 to 5000 W/m 2 K between the solidus and the gap-formation temperature, and to remain constant thereafter. The shrink-on values were up to 100 times the shrinkoff values, indicating the importance of accounting for the interface geometry in FEM simulations of this process. The FEM-predicted casting and mold temperatures were found to be insensitive to certain changes in the h 0 values and sensitive to others. A comparison to published h 0 values for PMC of aluminum alloys showed some similarities and some differences.

show abstract

Determination of the Interface Heat Transfer Coefficient for Non-Isothermal Bulk-Forming Processes

Cited by 81 publications

References 0 publications

Modeling the microstructural changes during hot tandem rolling of AA5XXX aluminum alloys: Part III. Overall model development and validation

Modeling the microstructural changes during hot tandem rolling of AA5XXX aluminum alloys: Part III. Overall model development and validation

Finite-element modeling of nonisothermal equal-channel angular extrusion

Determination of interface heat-transfer coefficients for permanent-mold casting of Ti-6Al-4V

Contact Info

Product

Resources

About