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  • 标题:Application of the C-test methodology for the validitation of boundary condition for oil quenching process.
  • 作者:Adamcikova, Andrea ; Taraba, Bohumil
  • 期刊名称:Annals of DAAAM & Proceedings
  • 印刷版ISSN:1726-9679
  • 出版年度:2008
  • 期号:January
  • 语种:English
  • 出版社:DAAAM International Vienna
  • 摘要:The aim of this paper is the presentation of partial results of the heat transfer phenomena research by cooling of parts in choosen coolants used in industrial production. Knowledge of parameters of cooling medium, physical, mechanical material properties and geometry of a quenched part allows to predict behavior of a part during cooling process. The quantification of the combined heat transfer coefficient (CHTC) by the cooling process in quenching oil and verification of its validity are presented. The obtained boundary condition for convection heat transfer was based on the Wolfson's test. Combining the experimental temperature measurement and numerical analysis, the cooling condition usable for vertical wall was determined. The validity of CHTC obtained was verified at the same experimental conditions as in Wolfson's test. Isomax 166 quenching oil in unagitated state at the temperature of 60[degrees]C was used as a cooling medium for the C-shaped tested part. The Wolfson's probe and the tested part were made of DIN 1.4541 material. ANSYS interpretation computer code was used and solution procedures were transient and nonlinear.

Application of the C-test methodology for the validitation of boundary condition for oil quenching process.


Adamcikova, Andrea ; Taraba, Bohumil


1. INTRODUCTION

The aim of this paper is the presentation of partial results of the heat transfer phenomena research by cooling of parts in choosen coolants used in industrial production. Knowledge of parameters of cooling medium, physical, mechanical material properties and geometry of a quenched part allows to predict behavior of a part during cooling process. The quantification of the combined heat transfer coefficient (CHTC) by the cooling process in quenching oil and verification of its validity are presented. The obtained boundary condition for convection heat transfer was based on the Wolfson's test. Combining the experimental temperature measurement and numerical analysis, the cooling condition usable for vertical wall was determined. The validity of CHTC obtained was verified at the same experimental conditions as in Wolfson's test. Isomax 166 quenching oil in unagitated state at the temperature of 60[degrees]C was used as a cooling medium for the C-shaped tested part. The Wolfson's probe and the tested part were made of DIN 1.4541 material. ANSYS interpretation computer code was used and solution procedures were transient and nonlinear.

2. EXPERIMENTAL

The oil Isomax 166 belongs to intensive quenching oils of low viscosity (v= 12.5 [10-.sup.6] [m.sup.2]. x [s.sup.-1] at 40[degrees]C) and is generally applied for quenching non-alloyed, low-alloyed, alloyed and carbonized steels. It is resistant to evaporation. The recommended working temperatures of Isomax 166 range from 40[degrees]C to 70[degrees]C (www.petrofer.com.ua 2008). The experimental equipment consisted of an electrical resistance furnace of LM 212.10 type, cylinder-shaped experimental Wolfson's probe (www.extra.ivf.se 2008), Isomax 166 oil and NI USB 9211 for digital record of the temperatures measured. Before quenching, the probe was heated up to the initial temperature of 850[degrees]C. The temperatures were measured by the encapsulated 304 SS thermocouple of K type by the diameter of 1.53 mm situated in the center of the probe. The tested "C" part (tube) had a longitudinal slot in the tube body by the initial width of 1.72 mm. In the process of cooling the probe and the tested part, the oil temperature was kept constant at 60[degrees]C, where the cooling ability of Isomax 166 is maximum (Taraba & Lascek 2006).

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

3. THEORETICAL BACKGROUND

Thermal problem. For the presented problem, temperature fields are transient and they can be described by the Fourier-Kirchoff differential equation of heat conduction in cylindrical coordinate system (probe) and the Cartesian coordinate system (tube), respectively. Material is considered to be isotropic. Thermal and mechanical properties were given by functions of temperature for the temperature interval from 20[degrees]C to 900[degrees]C (Tab. 1). Thermal load represented the boundary condition of the 3rd type, i. e. the heat transfer by convection (Incropera). Structural problem. The temperature field, tube shape, thermal expansion and mechanical properties (elastic modulus, Poisson's ratio and yield stress) generate thermal stress-strain states. Stress fields are described by the equation for temperature stress state (Trebuna at al. 2002). An elastic-plastic material model with bilinear isotropic hardening (Fig. 3) was used. Generation of plastic strains was evaluated by the Huber-Mises-Hencky's hypothesis (Trebuna at al. 2002). The reference temperature for structural task was 60[degrees]C. The geometric models and generated meshes were generated for one half of the probe (Fig. 1b) and a quarter of the tube (Fig. 2b).

For probe meshing, 2D elements PLANE77 with the option axisymmetric were used.

[FIGURE 3 OMITTED]

The tube model was meshed by the element of BRICK90 (thermal problem) and BRICK 186 (structural problem) types (ANSYS 10.0 2005). For structural analysis, symmetry conditions according to the Fig. 2b were used. The "C" model was gripped in the point 1 considering the displacement in the direction of x axis.

4. RESULTS

Fig. 4 shows the measured cooling curve from the Wolfson's test. The solution was searched via fitting the curves (measured vs. computed temperatures) and applying the iterative approach to the CHTC, as the function of surface temperature. The correlation coefficient by value of 0.995 was achieved by the fitting of curves. The CHTC curve is shown in the Fig. 5 and it can be considered the boundary condition for the vertical walls cooling.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

The tested part. Fig. 6 illustrates the comparison of the temperature field in the time of 3.2 s after immersing the tube into the oil, as well as the real photo taken at the same time. Each of the three types of cooling process is evident: vapor blanked (A), boiling oil zone (B), convection after ending of boiling (C). There is a reference temperature field from numerical simulation in Fig. 6b. Distribution of residual stresses after cooling the part to the temperature of 60[degrees]C is shown in Fig. 7b. It is evident from the Fig. 7b that in the process of cooling, the stresses reach and exceed the yield stress of material. The existing residual stresses resulted in the contraction of the slot width. Time history of the slot width can be seen in Fig. 7a. The maximum change of the slot width was observed during the cooling in the phase of oil boiling. The final slot width after cooling was 1.43 mm.

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

5. CONCLUSIONS

The relation between the experiment and numerical simulation allows us to obtain the knowledge and better understanding of the relationships of cooling parameters in the process of oil quenching.

Loading boundary condition of cooling, obtained by combination of the Wolfson's test and numerical analysis, was proved acceptable for vertical walls cooling.

The influence of particular parameters on the stress-strain state of a tested part during cooling can be determined by the indirect measurement of the change in the slot width. The slot width after experimental cooling on one hand, and the computed slot width on the other hand, exhibited the difference of 0.08 mm.

The research was supported by the projects No. 1/0721/08, 1/0837/08 and 2/7167/27 within VEGA Ministry of Education and the Slovak Academy of Science, Slovak Republic.

6. REFERENCES

Ansys Theoretical Manual, Release 10.0. (2005). Available from: http://www.tsne.co.kr/intra/data_center/ansy s/theory. pdf Accessed 2008-06-23

Available from: www.extra.ivf.se/smartquench/dokument/down load.asp?id=21 Accessed 2008-06-23

Available from:www.petrofer.com.ua/content/hardening_comp ound/2_1.htm Accessed 2008-06-23 Incropera, F., P. (1996). Fundamentals of Heat and Mass Transfer, John Wiley Sons, ISBN 0-471-30460-3, New York

Taraba, B. & Lascek, M. (2006). The influence of Isomax 166 quenching oil temperature on its cooling properties. Acta Mechanica Slovaca, 10, 01, (01 2006) ISSN 1335-2393, 567-572

Trebuna, F.; Simcak, F. & Jurica, V. (2002). Elasticity and strenght II, Vienala, ISBN 80-7165-364-0, Presov
Tab. 1. Material DIN 1.4541, thermal & mechanical properties.

Temperature Thermal Specific Density
 T conductivity heat [rho]
[[degrees] [lambda] c [kg.[m.sup.-3]
 C] [W. [J.
 [m.sup.-1]. [kg.sup.-1]
 [K.sup.-1] .[K.sup.-1]

 0 14.8 455 7940
 100 15.8 475 7911
 200 17.0 495 7871
 300 18.4 508 7830
 400 20.0 525 7787
 500 22.0 550 7745
 600 24.0 572 7703
 700 25.7 602 7662
 800 27.5 620 7620
 900 29.4 630 7578

Temperature Elasticity Thermal Yield
 modulus expansion stress
 E coefficient R.[MPa]
 [GPa] [[alpha]
 .sub.1].
 [10.sup.6]
 [K.sup.-1]

 0 200 16.8 235
 100 195 17.2 233
 200 188 17.6 230
 300 181 17.8 222
 400 172 1S.0 206
 500 165 1S.3 174
 600 157 1S.5 137
 700 147 1S.8 94
 800 135 19.0 55
 900 100 19.2 36

Temperature Poison's Tangent
 ratio modulus
 v [E.sub.1]
 [-] [MPa]

 0 0.3 1185
 100 0.3 1175
 200 0.3 1160
 300 0.3 1080
 400 0.3 950
 500 0.3 812
 600 0.3 660
 700 0.3 470
 800 0.3 250
 900 0.3 185
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