CFD Investigation of Quench Media and Orientation Effects ...

CFD Investigation of Quench Media and Orientation Effects on Structural Stress Induced in the Intense Quenching Processes for Aluminum Cylinder Heads

James Jan, Madhusudhan Nannapuraju Ford Motor Company, Livonia, Michigan, USA

Abstract

Heat treatment is a common manufacturing process in automotive industry to produce high performance components such as cylinder heads and cylinder blocks. Although heat treatment incorporating a quenching process, either by high velocity air flow or water, can produce parts with durable mechanical properties, an unwanted effect of intense quenching processes is that they also induce thermal residual stress, which often is a leading cause for quality issues associated with high cycle fatigues. During product development cycle, it is not uncommon to switch between air and water quench media and change quench orientation in order to minimize residual stress. However, the choice of quench media and quench orientation is often determined by intuitive engineering judgement at best and trial-and-error iterative method at worst. With the advancement of CFD technologies, the temperature profile and history of quenching processes now can be accurately calculated. Since thermal residual stress is directly linked to non-uniform temperature distribution in the metal, spatial temperature gradient of each quenching process is evaluated to study and compare the performance of different quench media and configuration. The conclusion of this study can be used to establish engineering guidelines for future product development.

Introduction

As the automotive companies are competing on fuel economy and vehicle performance, more high performance, light weight compact engines are using aluminum instead of steel for major components. It is said that 1 kg aluminum can replace up to 2 kg of steel or cast iron[1] and 10% mass reduction will generate about 6% improvement of fuel economy[2].

Although weight of aluminum is about one third of the weight of steel, aluminum is not as strong as steel. In order to enhance the mechanical properties of aluminum, heat treatment process, shown in Figure 1, is a typical manufacturing process applied to the part after casting in automotive applications. While the process can increase the hardness of the aluminum part, the high temperature gradient, induced in the intense quenching process also results in thermal residual stress. These residual stresses, when combined with high stresses due to engine operating load, often lead to cracks[3] in the critical area, shown in Figure 2, causing companies high warranty costs.

Most design verification processes incorporate some sort of residual stress measurement at selected locations to reduce the

risk of quality issues in the field. However, measuring residual stress is a challenging task. There are several methods to measure residual stress in the test lab[4][5]; one of the popular techniques is the hole drilling method[6][7]. Since residual stress is not a quantity that can be directly measured, experimental measurement usually is lengthy, tedious and expensive. Furthermore, since physical measurement is performed at few pre-selected points, it may not be a comprehensive representation of a complicated residual stress map. It also runs the risk of missing the actual high residual stress at other locations of the part where measurements are not performed.

In recent years, with the advancement of computational simulation tools such as finite element analysis (FEA) method, digital verification using virtual tools are gaining popularity because of its efficiency and accuracy[8]. The maturity of numerical method in material science even extends to modeling the casting processes. A notable one is the Virtual Aluminum

Casting methodology, developed and implemented in Ford Motor Company[9]. The computational method to predict the residual stress involves two calculations. The first one is to calculate the temperature history and profile. Then the temperature data are used as thermal loads to structure analysis for stress and deformation calculation.

Figure 1: Heat Treatment Process for Aluminum Cylinder

Heads.

Figure 2: Cracks in Combustion Chamber due to High Cycle

Fatigue (photo source: http:www.flowspeed.com).

Heat Treat 2017: Proceedings of the 29th ASM Heat Treating Society Conference October 24–26, 2017, Columbus, Ohio, USA

Copyright © 2017 ASM International® All rights reserved.

www.asminternational.org

Literature survey finds that there are extensive research and publication about using finite element analysis (FEA)[10], with high degree of success, to calculate residual stress. The accuracy of the FEA result, however, is limited because it depends upon the quality of temperature data. Before the industry adapts computational fluid dynamics (CFD) method for heat transfer analysis, a widely popular method for temperature calculation is heat transfer coefficient (HTC) method since it is simple and computation efficient[11][12][13]. The biggest drawback of the HTC method is that the method still relies on physical thermocouple measurement data to calibrate the coefficient and the calibrated parameters may not be applicable to different design and quenching processes.

With the advancement of 3-D CFD methodology, it is now possible to model the entire quenching process using computer simulation. Not only is it cost effective and predictive, without the requirement of calibration by thermocouple data, it also provides the full temperature map for comprehensive residual stress prediction. The objective of this paper is to survey the progress of quenching simulation using CFD and using the temperature data obtained by CFD to compare the quenching performance of various quench media and quenching processes.

Thermal Stress and Temperature Gradient

Metal expands and contracts in response to temperature change. In the general case, the volumetric thermal expansion can be described by thermal expansion coefficient, 𝛼𝑉:

𝛼𝑉 =1

𝑉(

𝜕𝑉

𝜕𝑇)

𝑝

(1)

When metal is free to expand and contract and volumetric change is uniform, there will be no strain and stress in the system. When temperature gradient exists in the system and thermal expansion is non-uniform, then strain and stress will be formed. The relationship between temperature gradient and thermal stress can be explained by a 1-D model in Figure 3:

Figure 3: Bar with 1-D Temperature Gradient varying in x-

direction.

In this model, temperature is varying in the x-direction and uniform in all other directions. The thermal expansion in the y-direction for an element of width dx is expressed as:

𝑑𝑙 = 𝛼𝐿𝐿 ∙ (𝑇 − 𝑇0) (2)

𝑇0 is the initial temperature and 𝛼𝐿 is the linear thermalexpansion coefficient. Because thermal expansion is constrained by neighboring elements, the strain caused by temperature difference, 𝜖𝑇, is the average deformation of twoadjacent elements:

𝜖𝑇 =𝑑𝑙(𝑥 + 𝑑𝑥) + 𝑑𝑙(𝑥)

2𝐿=

1

2𝛼𝐿 ∙

𝜕𝑇

𝜕𝑥∙ 𝑑𝑥 (3)

This equation proves that the state of stress in the metal is directly related to the temperature gradient. In this paper, the temperature gradient is used as a criteria to compare quenching performance. It is important to note that state of stress is not equivalent to residual stress. While temperature gradient provides a hint to the location of high stress, it is not an indication that residual stress will actually occur. Residual stress only forms when local stress exceeds yielding stress and plastic deformation begins to take place. When metal cools to room temperature and all thermal loads are removed, the plastic deformation becomes permanent, creating residual stress.

Temperature gradient usually is not directly output from most CFD packages. To calculate the temperature gradient for each cell in an unstructured CFD mesh, we applied the divergence theorem to compute the cell volume, using area and normal of all the faces enclosing the volume:

𝑉𝑐𝑒𝑙𝑙 =1

3(∇ ∙ �⃗�)𝑉𝑐𝑒𝑙𝑙 =

1

3∑ �⃗� ∙ (𝐴𝑓𝑎𝑐𝑒�̂�)

𝑖

𝑁𝑓𝑎𝑐𝑒

𝑖=1(4)

�⃗� = 𝑥𝑖̂ + 𝑦𝑗̂ + 𝑧�̂�

Similarly, the temperature gradient can be computed by:

∇𝑇𝑐𝑒𝑙𝑙 =1

𝑉𝑐𝑒𝑙𝑙

∑ (𝑇𝐴𝑓𝑎𝑐𝑒�̂�)𝑖

𝑁𝑓𝑎𝑐𝑒

𝑖=1(5)

Air Quench Process for Cylinder Heads

Validation of Air Quench CFD Model

To quench aluminum cast parts by air, the parts are first heated to near solutionizing temperature and then placed in the quenching chamber under strong air flows with high velocity. It is very common that fan speed and air flow velocity remain constant throughout the entire quenching process. The main heat transfer mechanism is forced convection heat transfer. In our CFD simulation, it is assumed that the buoyancy effect and radiation heat transfer have negligible impact on the accuracy.

Ford Motor Company has conducted testing, collected thermocouple data and compared experimental temperature data with CFD computation to validate the CFD model[14]. The computational model setup and air flow visualization are shown in Figure 4 and the comparison of temperature data from CFD calculation and thermocouple measurement is shown in Figure 5. The near overlapping temperature curves validate the methodfor further quenching studies.

Figure 4: CFD model and results for Air Quenching a Cylinder

Block with Riser Attached[14].

Figure 5: Temperature Comparison at Pan Rail (left) and Bulk

Head (right) [14].

In-depth discussion on flow and thermal characteristics of air quenching processes can be found in publications by the same author in 2015 Heat Treat Conference[15] and 2016 SAE

International Journal of Passenger Cars[16].

Air Quench Performance Comparison

Four different quenching configurations, listed in Table 1 and shown in Figure 6, are selected for quenching performance comparison. Configuration (a) and (b) have the same nozzle number and size but quench orientations of the cylinder heads are different. Configuration (b) is (a) rotated 90° in the cam shaft direction. Configuration (c) have the same cylinder head orientation as (a) but much larger nozzles. The air flow rate in (c) is equivalent to (a). In other words, (a) and (c) use the sameamount of air, or fan equipment, but incoming air flow velocitywill be different; velocity in (c) is only a quarter of (a). Inconfiguration (a), (b), and (c), cylinder heads are placed in arow, representing a conveyer style, open to atmosphere, andcontinuously quenching environment. Configuration (d)represents a basket style quenching environment, where 28cylinder heads are placed upright in a basket and quenched bybatch in a closed chamber.

Table 1: Air Quenching Configurations.

Figure 6: Air Quench Configurations.

It is not necessary to model the entire quench chamber because of the repetitive pattern in the cylinder heads placement. For each configuration, CFD mesh is created for only one cylinder head plus its surrounding air, represented as a virtual box in the figure. Symmetric boundary conditions are applied to the sides of the computation domain. It assumes fixtures has negligible effect on the cooling characteristics and therefore are not included in the model. Figure 6 also shows relative positions of the nozzles (for (a), (b), and (c)) or inlet boundary condition (for (d)). The flow patterns, visualized by particle trace, are shown in Figure 7, and stagnant air pocket sizes and shapes surrounding the cylinder heads are shown in Figure 8.

We can draw some conclusions already on the quenching performance by studying the air pocket sizes and shapes, spread of temperature, and velocity profile in Figure 8. For the same air jet configuration in (a) and (b), (a) cools slightly faster. This is because (a) has a larger area to receive air. Even though the orientations of cylinder head and air flow volumetric rate are the same for (a) and (c), quenching performance for (c) is not as good as (a). This can be explained by the analytical form of free forced convection on a flat plate[17], expressed as:

𝑁𝑢𝐿 =ℎ𝐿

𝑘= 𝐶Re𝐿

𝑚Pr𝑛 (6)

It explains that heat transfer coefficient (in Nusselt number) is directly related to velocity (in Reynolds number).

Config. Air Flow Direction Nozzle Size (Number) Air Speed Flow Rate

(a) cam cover + joint face 48mm x 360mm (2) 40 m/s 2929 CFM

(b) intake + exhaust 48mm x 360mm (2) 40 m/s 2929 CFM

(c) cam cover + joint face 192mm x 360mm (2) 10 m/s 2929 CFM

(d) rear face 176mm x 416mm (1) 30 m/s 4654 CFM

Figure 7: Air Flow Surrounding Cylinder Head for All Air

Quenching Configurations, 60 seconds into Quenching.

Figure 8: Air Pocket near Cylinder Head for All Air Quenching

Configurations, 60 seconds into Quenching.

The cooling curves for all air quenching configurations are shown in Figure 9. The cooling curve plot shows that cylinder head quenched in a basket (d) cools faster compared to those quenched on a conveyer (a), (b), and (c).

Figure 9: Cooling Curve for All Air Quenching Configurations.

When cylinder heads are quenched in a basket, the air flow are forced to pass through narrow gaps between cylinder heads at much higher velocity, shown in Figure 10, because of conservation of mass. As a matter of fact, the maximum velocity is 79.78 m/s, or 266.6% of incoming flow velocity, for basket quenching (d), comparing to 59.96 m/s, or 149.9% of incoming flow velocity, for conveyer quenching (a). The velocity and temperature information for all air quenching configurations are listed in Table 2.

Table 2: Velocity and Temperature Spread for All Air

Quenching Configurations, 60 seconds into Quenching.

Figure 10: Accelerated Air Flow passing through narrow gaps

between Cylinder Heads in a Basket Quenching Environment.

The quenching performance can be studied using temperature gradients, calculated by Equation 4 and 5 and plotted as a function of time in Figure 11. In general, basket quenching (d) cools faster overall with higher temperature gradient than conveyer quenching (a) and (c). The only exception is (b), which also exhibits a larger temperature spread as illustrated in Table 2. Figure 12 shows locations of high temperature gradient for conveyer quenching (a) and basket quenching (d).

Figure 11: Temperature Gradient for All Air Quenching

Configurations.

Figure 12: High Temperature Gradient Locations for Conveyer

Quenching (a) and Basket Quenching (d), 60 seconds into

Quenching.

Config. V-max V-inlet V-max (%) T-avg (°K) T-max (°K) T-min (°K)

(a) 59.96 40.00 149.90% 618.81 662.90 288.48

(b) 55.29 40.00 138.23% 632.38 745.02 298.94

(c) 14.83 10.00 148.30% 721.07 699.02 298.22

(d) 79.98 30.00 266.60% 560.60 619.67 299.95

High temperature gradient, when appearing in functionally critical areas, could cause serious quality concerns. In the case of designing a cylinder head, water jacket, intake and exhaust port and top of combustion chamber are subject to engine operating load; thus, high temperature gradient should be avoided. It is shown in Figure 12 and Figure 13 that temperature gradients in these critical areas for basket quenching (d) are higher than those of conveyer quenching (a). Quench orientation also changes the location of high temperature gradient. It can be seen in Figure 12 that high temperature gradient distribution in the intake port area is uneven for basket quenching (d) compared to conveyer quenching (a).

Figure 13: High Temperature Gradient at Intake Port and

Water Jacket Wall, 60 seconds into quenching.

Lumped Mass Analysis (LMA) for Air Quenching Models

In the previous technical paper published in 2015 Heat Treat

Conference[15], it is proven that the heat transfer coefficient (HTC) is a strong function of geometry and location but is a weak function of temperature. When cylinder heads are quenched by air flow with constant velocity[15], HTC’s become almost constant. The same paper also provides evidence that traditional HTC method based on pointwise thermocouple calibration is not sufficient to calculate correct temperature profile. Figure 14 provides further evidence that the constant HTC finding is valid for all quenching configurations, including conveyer quenching and basket quenching, except that it decreases a small amount near the end of quenching for a very strong forced convection case, (d).

Figure 14: Average heat transfer coefficient (HTC) of Entire

Surface for All Quenching Configurations.

The constant HTC finding is the key enabler for approximating quenching characteristics by Lumped Mass Analysis (LMA). In the cylinder head air quenching applications, the average HTC for all quenching configuration are computed and listed in Table 3, along with the material properties for AL 356, which is a common material for cylinder heads. Also computed and included in the table are the dimensionless Biot numbers, defined as:

Bi =ℎ𝐿

𝑘(7)

Table 3: Material Properties at T=300°C, Average HTC and

Biot Number for All Quenching Configurations.

When Biot numbers are very small, it is an indication that conduction heat transfer inside the metal is more significant than convection heat transfer on the metal surface. In other words, the temperature inside the metal could be assumed uniform when studying the cooling characteristics of the entire part. The uniform temperature assumption is the foundation of lumped mass analysis (LMA).

In LMA, the 3-D heat transfer equation will be reduced to a single temperature equation that is a function of time only:

𝜌𝐶𝑝𝑉𝑑𝑇

𝑑𝑡= −ℎ𝐴(𝑇 − 𝑇∞) (8)

If the material properties are constant, the analytical solution to Equation 8 could be derived and expressed as:

𝑇 − 𝑇∞

𝑇0 − 𝑇∞

= 𝑒−

ℎ𝐴𝜌𝐶𝑝𝑉

𝑡(9)

Config. HTC (W/m2.°K) Bi Number

Density 2609 kg/m3 (a) 94.5213 0.0025878

Heat Capacity 999.5 J/kg.°K (b) 89.6505 0.0024545

Conductivity 153 W/m.°K (c) 37.2656 0.0010203

Char. Length 4.188909 mm (d) 145.4352 0.0039818

AL 356

The actual cooling curves and LMA predictions are plotted in Figure 15 and LMA predictions error are plotted in Figure 16. In general, LMA predicts a slightly faster cooling because conduction heat transfer in the metal is infinitive (𝑘 = ∞). In addition, the material properties in the CFD calculation are temperature dependent, approximate by a second order polynomial, rather than constant. The coefficients of the polynomial are listed in Table 4. Nonetheless, LMA predictions is still a very good representation of the cooling characteristics.

Figure 15: Actual Cooling Curve and LMA Predictions.

Figure 16: Error by LMA Prediction.

Table 4: Coefficients of Second Order Polynomial for

Temperature Dependent Material Properties.

The objective of cylinder head quenching is to enhance the mechanical properties by rapidly cooling the work piece using air, water or other media. In the quenching process, the cooling rate has a direct impact on eventual mechanical properties[19]. The metal cooling rate has two opposite effects on the final outcome. On one hand, fast cooling usually results in better mechanical properties but on the other hand it causes higher residual stress. The optimization of the quenching process is essentially to balance those two effects of the cooling rate.

If a desired cooling rate could be found by metallurgy or material engineering, LMA could be used to calculate the effective heat transfer coefficient to achieve the quality objective. From Equation 6, the effective HTC is directly related to incoming flow velocity. Once the coefficients in Equation 6 are determined, then incoming flow velocity is also determined. The determination of the coefficients in Equation 6 is an ongoing research in Ford Motor Company and the results will be presented in future publication.

Water Quench Process for Cylinder Heads

Validation of Water Quench CFD Model

The physics of water quenching process is much more complex than air quenching process. First of all, the temperature drop in the cylinder head water quenching is more than 400°C. In this temperature range, water boiling goes through three different regimes: film boiling, transition boiling and nucleate boiling[20]. The water quenching problem cannot be solved by typical VOF one-fluid CFD method because of the phase change between water and vapor (evaporation and condensation) and the large-scale momentum exchange between vapor and water. There are research work and publications on using Eulerian-Eulerian two-fluid method to model the water quenching process with great success. The first such work was presented by Wang et al. in 2002[21]. The methodology was further developed to focus on accurate temperature prediction within the solid, as discussed by Srinivasan et al.[22][23][24][25]. Additional enhancements were made to model variable Leidenfrost temperature effects and to include additional forces acting on the vapor phase, presented by Kopun et al.[26][27].

Ford Motor Company has done comprehensive water quench testing for cylinder heads and blocks in which thermocouple data are obtained to correlate the CFD computation[28][29]. The experimental setup is shown in Figure 17. The vapor pattern from CFD computation is compared to the video taken in the lab, shown in Figure 18. Furthermore, the temperature data and cooling rate are compared and the comparison at selected thermocouples is shown in Figure 19. The agreement of vapor pattern and temperature curves proves that the CFD model is accurate enough for quenching studies.

Figure 17: Experimental Setup to Measure Temperature for

Cylinder Head Water Quenching[29].

Figure 18: Comparison of computed and observed vapor

pattern, 20 seconds into quenching[29].

Figure 19: Comparison of Computed and Measured

Temperature and Cooling Rate at Selected Thermocouples[29].

Water Quench Performance Comparison

Six different quench orientations, listed in Table 5 and shown in Figure 20, are selected for water quenching performance comparison. There are other quenching parameters such as agitation, water pool temperature and Leidenfrost temperature that could influence the outcome. Those parameters require much more complicated models to simulation and additional test data to validate; thus they are not included in the scope of current project.

Figure 20: Water Quench Orientations.

Usually multiple cylinder heads are placed inside one basket for a single quenching batch job. In our computation model, only one cylinder head is considered. There are efforts in Ford Motor

Company to model cluster quenching process in order to study the neighboring effect in a quenching basket[30]. Nonetheless, the results of single object quenching may not be directly applicable to production process but it is sufficient to study orientation effect and compare quenching performance.

Table 5: Water Quench Orientations.

Figure 21: Vapor Pattern and Vapor Pocket Entrapped inside

Cylinder Heads, 20 seconds into quenching.

Config. Quench Orientation

(RE) rear face up

(CC) cam cover face up

(IN) intake port face up

Config. Quench Orientation

(FR) front face up

(JF) joint face up

(EX) exhaust port face up

Figure 21 shows the vapor pattern and vapor pockets entrapped inside the cylinder heads for various quench orientations. It can be seen that vapor entrapment is particularly significant for joint face up (JF) case. Figure 22 shows the cooling curves and Figure 23 shows the maximum temperature gradients. The nearly overlapping curves in Figure 22 and similar maximum temperature gradients (except shift in time) in Figure 23 imply that quench orientation has little effect on overall cooling characteristics and its impact will be localized in specific locations. The orientation effect on local residual stress requires further FEA study and is the subject for future study.

Figure 22: Cooling Curve for All Water Quenching

Configurations.

Figure 23: Maximum Temperature Gradient for All Water

Quenching Configurations.

Figure 24 shows the location of the high temperature gradient for rear face up (RE) and cam cover face up (CC) case. In both cases, high temperature gradient is observed in the intake port area, similar to the air quenching cases. Since high temperature gradient appears near intake port for all quenching cases, it is very likely a design related issue. In fact, close examination of Figure 13 reveals that there is a rapid metal thickness change between intake port and water jacket. The combination of dominant conduction heat transfer and large metal thickness variation results in a local high temperature gradient.

Figure 24: High Temperature Gradient Locations for Rear

Face up (RE) and Cam Cover Face up Quenching (CC), 20

seconds into Quenching.

Comparison of Air and Water Quenching Process

The underlying physics and heat transfer mechanisms of air and water quenching are very different. While air quenching relies on the convection of heated air to cool the metal, the convection of heated water only plays a very small role in water quenching. Instead, water quenching relies on phase change from water to vapor to transport the thermal energy away from metal. Using water latent heat (2,260 kJ/kg), air density (1.125 kg/m3), specific heat (1.003 kJ/kg·°K) data as an example, vaporizing 0.001 m3 (1 liter) of water is equivalent to heating up 18.394 m3 (649.57 cubic feet) of air with 100°C temperature increase. Therefore, it is understandable that metal cools much faster in water quenching than in air quenching, illustrated in Figure 25. By the same token, the maximum temperature gradient for water quenching is also much larger than air quenching, shown in Figure 26. Since water only vaporizes in areas in contact with hot surface, the metal heat loss is a local phenomenon subject to vapor escape routes and supplies of fresh water. In other words, the heat transfer may not be as smooth as air quenching and it is reflected in the fluctuation of high temperature gradient in Figure 26.

An important observation in Figure 26 is that the duration of peak temperature gradient only lasts about 15 seconds. In this duration, the metal may already exceed yielding stress and plastic deformation starts. However, the final deformation also

depends how long the state of stress stays in the plastic deformation zone. On the contrary, the temperature gradient for air quench is smaller but it also lasts longer. The eventual residual stress can only be calculation by the FEA method. The quenching performance study based the FEA residual stress calculation is the subject for future research.

Figure 25: Cooling Curve for Selected Air and Water

Quenching Configurations.

Figure 26: Maximum Temperature Gradient for Selected Air

and Water Quenching Configurations.

Conclusions

The rapid, large temperature drop in the quenching process has two opposite effects on the eventual outcome. Large cooling rate produce metals with better quality but induces residual stress. Thanks to the advancement of 3D CFD methodology, now the metal cooling in the quenching process can be much better understood using computer simulations. This project is a first attempt to evaluate the quenching performance of various quenching media and configuration by using temperature gradient as a measurement criteria.

The first portion of the paper is to establish the relationship between stress state (not residual stress) and temperature gradient. It also includes formulations to calculate temperature

gradient for an unstructured CFD mesh. The second portion is the study of air quenching process. Comparison of thermocouple data and CFD calculation is cited to validate the methodology. The study finds that cylinder heads cool faster in basket quenching than in a conveyer quenching environment. It can be explained that air flow is accelerated when passing through the narrow gaps between cylinder heads in the basket quenching environment. The study also establishes an important finding that heat transfer coefficients are almost constant throughout the entire quenching process for all air quenching configurations. Since Biot number is very small for all cases, the LMA method could be applied to approximate the cooling rate. The third portion of paper focuses on studying the water quenching process. A comparison of thermocouple data and CFD calculation is also cited to validate the methodology. The study finds the orientation has little effect on the overall cooling rate and maximum temperature gradient. The quench orientation effect on the residual stress will be localized to specific locations which requires further FEA study. The results also show that temperature gradient in the water quenching process is much larger than the air quenching process but last a shorter period of time. Studying the temperature gradient for all air and water quenching cases reveals a weak spot between the intake port and the water jacket. Since this issue appears in all quenching cases, it should be remedied by a design change rather than changing the quenching processes.

Acknowledgments

The authors would like to acknowledge the technical assistance of Eben Prabhu, Dr. Ulrich Weiss and Dr. Xuming Su at Ford Motor Company, all specializing in casting, advanced material science and CAE in fluid mechanics and structural analysis. Eben, Ulrich and Xuming were technical leads in the development of CFD air and water quenching numerical modeling methodology, which are used extensively in all the quenching simulations in this project.

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