1. Simulating convective impingement heating in HASPIF
Shubhamkar Kulkarni
Advised by:
Dr. Gregory Mocko

2. Introduction
Single point incremental forming is a process for dieless forming of sheets
Localized heating has shown to improve the formability (HASPIF)
Empirical knowledge but limited theoretical understanding; need for simulation

3. Research Overview
Objective: Simulation of HASPIF for improved understanding and planning
Validation

4. Lit review Two possible approaches to model the moving heated spot:
I. Using Computational Fluid Dynamics:
CFD simulations techniques exists in ANSYS but computationally expensive
Issues with updating the domain of the fluid
II. Using thermal boundary conditions:
1. Modelling the heated spot as a moving heat flux
Has been used for modelling welding and laser assisted SPIF of metals
Not suitable as heat flux depends on the temperature difference
2. Modelling the heated spot as a temperature load
Applying temperatures to different nodes
3. Modelling the heated spot as a convective/impingement jet (HTC distribution)
Empirical correlations exist for Nusselt number distributions based on Reynolds number and some geometrical dimensionless numbers
Valid for steady state conditions and comparatively high Reynolds number (>6000)
Valid for stationary nozzle(s) without structural hindrance introduced due to the tool
Requirement: model for moving heat source, transient heat transfer and low Reynolds number flow

5. Old setup Structural support: Hot air gun Issues with stiffness
Experimental setup
Old setup Structural support: Hot air gun Issues with stiffness
New setup
Structural support: Collet
Additional chute to channel air
Circular blank for symmetrical boundary conditions

6. Data Acquisition FluxTeq PHS 01-e heat flux sensor
MS Excel
Postprocessing
LabView and NI 93210
Record the analog signals
FluxTeq PHS 01-e heat flux sensor
Measure heat flux and temperature

7. Theoretical background
Equations used:
Heat transfer through convection
𝑄=ℎ𝐴∆𝑇
Heat Flux
𝐻𝐹= 𝑄 𝐴 =ℎ∆𝑇
Convective heat transfer coefficient (HTC)
𝐻𝐹 ∆𝑇 =ℎ
Record the heat flux and temperature, post process to calculate HTC

8. Test 1: Stationary nozzle test
For quantifying boundary conditions required for version 1.0 of model
Assumed the value of HTC to be equal in discrete concentric regions
Similar to the data presented in the literature
Procedure:
Position the tool axis at a certain (X,Y) position with the tool barely touching the sensor
Start recording data
Switch on the hot air gun
Stop recording after 60 seconds (approx.)

9. Test 1: Stationary nozzle test
It was observed that the HTC value varied
Literature shows similar results for water impingement cooling
Since the duration of heat transfer is small, the variation of HTC value cannot be ignored
Complexity is increased because the tool is also moving; the path of travel of the nozzle relative to a point’s location will result in different profile of HTC variation

10. Test 2: constant velocity nozzle movement test
For quantifying boundary conditions for version 2.0 of the model
The heated spot is split into two regions representing the leading and trailing regions relative to the tool motion
Procedure:
Position the centroid of the sensor at (0,0)
Position the tool axis at a certain (-1.5,0) position
Start recording data and switch on the hot air gun simultaneously
Move the hot air gun with velocity equal to the feed used for forming
Stop recording the data once the tool reaches (1.5,0)
Direction of tool travel

11. Test 2: constant velocity nozzle movement test
During post processing, the timestep associated with each recorded data point was used to identify the location of the tool axis
The region was discretized into regions depending upon the value of the X coordinate
The HTC values associated with all data points were averaged for each region

12. Test 2: constant velocity nozzle movement test
Upper bound
Lower Bound
ℎ 1
1.5 1
ℎ 2
0.5
ℎ 3
ℎ′ 3
-0.5
ℎ′ 2 -1
ℎ′ 1
-1.5

13. Test 2: constant velocity nozzle movement test
Assumptions:
The sensor is assumed to be a point object, located at its centroid. The values are essentially average values of flux on the sensor
The manual error associated with the starting the data recording and the heat gun simultaneously is neglected
The delay in response of the sensor and the delay to start the motion of the tool is neglected
The value of HTC has been assumed to be constant in different discretized regions. In reality, it varies depending upon the location
The HTC distribution is assumed to be independent of the deformation of the blank

14. Simulation workflow

15. Implementing in ANSYS

16. Simulation results

17. Validation Miniature thermocouples will be used
Record temperature versus time data for validating experimental results
Tests: Linear test, spiral test and if possible actual forming test
Linear
Spiral

18. Conclusion
A model for simulating the transient convective heat transfer encountered in HASPIF is presented
Validation studies are ongoing

19. References

20. Thank you

21. Outline Intro Lit review Theory Primary testing Proposed modelling
Simulation results
Validation