During aluminum die-casting, tensile residual stress accumulates on the cavity surface of the die by repeated heating and cooling processes. Recently, to improve productivity, dies with high cycle and longer life have become necessary, and reduction or removal of tensile residual stress can be used to prevent heat cracks that cause mold fracture. Heat treatment is often used for residual stress reduction but a more efficient residual stress reduction method that can be carried out with simpler equipment is required. In this study, the relationship between the residual stress after forced vibration and the amplitude at the time of excitation is investigated by mechanical vibration of the SKD61 die materials and the die-casting mold through the application of forced vibration by an eccentric motor. Residual stress on the surface of each test plate treated by the heat treatment and the surface of mold cavity after excitation is evaluated by the X-ray residual stress measurement. It was found that the residual strain after excitation accumulated in compression as the amplitude of oscillation of the specimen became negative. Residual stress in the excitation direction of the specimens increased in the compression direction due to the excitation, demonstrating the effective stress reduction by the excitation method.

1. [1] M. Hihara, “Thermal Fatigue Characteristics for Die Casting Dies and Evaluations of Their Die Life,” J. Soc. Electr. Mach. Eng. Jpn, Vol.35, No.78, pp. 1-11, 2001.
2. [2] J. H. Ryu and S. W. Nam, “Effect of surface roughness on low-cycle fatigue life of Cr-Mo-V steel at 550^◦,” Int. J. Fatigue, Vol.11, No.6, pp. 433-436, 1989.
3. [3] M. Nikawa, K. Usui, H. Iwahori, A. Sato, and M. Yamashita, “Estimation of Die Release Force of mboxJIS-ADC12 Aluminum Alloy Die Castings Manufactured Through High-Pressure Die Casting via Computer Simulation,” Int. J. Automation Technol., Vol.12, No.6, pp. 955-963, 2018.
4. [4] K. Yano, K. Hiramitsu, Y. Kuriyama, and S. Nishido, “Optimum Velocity Control of Die Casting Plunger Accounting for Air Entrapment and Shutting,” Int. J. Automation Technol., Vol.2, No.4, pp. 259-265, 2008.
5. [5] Y. Frayman, H. Zheng, and S. Nahavandi, “Machine Vision System for Automatic Inspection of Surface Defects in Aluminum Die Casting,” J. Adv. Comput. Intell. Intell. Inform., Vol.10, No.3, pp. 281-286, 2006.
6. [6] K. Teramoto, “On-Machine Estimation of Workpiece Deformation for Thin-Structured Parts Machining,” Int. J. Automation Technol., Vol.11, No.6, pp. 978-983, 2017.
7. [7] C. Cao, J. Zhu, T. Tanaka, and D. Pham, “Investigation of Corrosion Resistance Enhancement for Biodegradable Magnesium Alloy by Ball Burnishing Process,” Int. J. Automation Technol., Vol.14, No.2, pp. 175-183, 2020.
8. [8] C. Cao, J. Zhu, T. Tanaka, F. Shiou, S. Sawada, and H. Yoshioka, “Ball Burnishing of Mg Alloy Using a Newly Developed Burnishing Tool with On-Machine Force Control,” Int. J. Automation Technol., Vol.13, No.5, pp. 619-630, 2019.
9. [9] H. Iwabe, M. Hiwatashi, M. Jin, and H. Kanai, “Side Milling of Helical End Mill Oscillated in Axial Direction with Ultrasonic Vibration,” Int. J. Automation Technol., Vol.13, No.1, pp. 22-31, 2019.
10. [10] H. Kitano and T. Nakamura, “Predicting Residual Weld Stress Distribution with an Adaptive Neuro-Fuzzy Inference System,” Int. J. Automation Technol., Vol.12, No.3, pp. 290-296, 2018.
11. [11] M. Duscha, F. Klocke, and H. Wegner, “Residual Stress Model for Speed-Stroke Grinding of Hardened Steel with CBN Grinding Wheels,” Int. J. Automation Technol., Vol.5, No.3, pp. 439-444, 2011.
12. [12] https://www.formula62.com/stress-relief-vibration-vsr.html  [Accessed April 30, 2020]
13. [13] https://www.technocoat.co.jp/vibrodyn/vd01 [Accessed April 30, 2020]
14. [14] X. C. Zhao, Y. D. Zhang, H. W. Zhang, and Q. Wu, “Simulation of vibration stress relief after welding based on FEM,” Acta Metall. Sin. (Engl. Lett.), Vol.21, No.4, pp. 289-294, 2008.
15. [15] B. Denkena, J. Köhler, R. Meyer, and J. Stiffel, “Modification of the Tool-Workpiece Contact Conditions to Influence the Tool Wear and Workpiece Loading During Hard Turning,” Int. J. Automation Technol., Vol.5, No.3, pp. 353-361, 2011.
16. [16] S. Afazov, S. Ratchev, A. Becker, S. Liu, and J. Segal, “Numerical Analyses of Turning-Induced and Mapped Ti6Al4V Residual Stresses for a Disc Subjected to Centrifugal Loading,” Int. J. Automation Technol., Vol.5, No.3, pp. 326-333, 2011.
17. [17] S. Kikuchi, Y. Nakamura, K. Nambu, and T. Akahori, “Formation of Hydroxyapatite Layer on Ti-6Al-4V ELI Alloy by Fine Particle Peening,” Int. J. Automation Technol., Vol.11, No.6, pp. 915-924, 2017.
18. [18] H. Isobe, N. Sasada, K. Hara, and J. Ishimatsu, “Visualization of Stress Distribution by Photoelastic Method Under Ultrasonic Grinding Condition,” Int. J. Automation Technol., Vol.13, No.6, pp. 736-742, 2019.
19. [19] H. Sakamoto, T. Matsuda, and S. Shimizu, “Effect of Clamped Toolholders on Dynamic Characteristics of Spindle System of Machining Center,” Int. J. Automation Technol., Vol.6, No.2, pp. 168-174, 2012.
20. [20] N. Tomitaka, “On the Tempering Behaviour of 3Cr-W, 3Cr-W-Co and 12Cr-W-Co Type Tool Steels for Hot Work,” Trans. Iron Steel Inst. Jpn., Vol.53, No.2, pp. 116-130, 1967.
21. [21] Y. Manabe, R. Oda, T. Hirogaki, E. Aoyama, and K. Ogawa, “Whole Quenching of Small Thin Plate with Low-Power Semiconductor Laser Based on Feed-Speed Combination Problem,” Int. J. Automation Technol., Vol.10, No.6, pp. 923-933, 2016.
22. [22] T. Azuma, R. Ito, S. Soma, S. Murakami, and T. Kuriyagawa, “Development of Non-Destructive Technology for Detecting Grinding Burns,” Int. J. Automation Technol., Vol.7, No.6, pp. 700-707, 2013.
23. [23] J. Herwan, S. Kano, O. Ryabov, H. Sawada, N. Kasashima, and T. Misaka, “Predicting Surface Roughness of Dry Cut Grey Cast Iron Based on Cutting Parameters and Vibration Signals from Different Sensor Positions in CNC Turning,” Int. J. Automation Technol., Vol.14, No.2, pp. 217-228, 2020.
24. [24] Y. Kameyama, H. Sato, and R. Shimpo, “Ridge-Texturing for Wettability Modification by Using Angled Fine Particle Peening,” Int. J. Automation Technol., Vol.13, No.6, pp. 765-773, 2019.
25. [25] P. Mitsomwang, R. Borrisutthekul, U. Kitkamthorn, and S. Nagasawa, “Investigation of Strain Hardening in Aluminum Alloy Sheared Sheet Based on Microhardness Measurement and FEM Analysis,” Int. J. Automation Technol., Vol.12, No.5, pp. 714-722, 2018.
26. [26] T. Aizawa, Y. Saito, H. Hasegawa, and K. Wasa, “Fabrication of Optimally Micro-Textured Copper Substrates by Plasma Printing for Plastic Mold Packaging,” Int. J. Automation Technol., Vol.14, No.2, pp. 200-207, 2020.
27. [27] M. Kurose, H. Nakamura, M. Nishi, T. Hirashima, N. Abe, and T. Kaburagi, “Development of Warm-Press-Forming Method of CFRTP Motor Vehicle Floors with Complicated Shapes,” Int. J. Automation Technol., Vol.11, No.1, pp. 74-80, 2017.
28. [28] T. Kaburagi, M. Kurose, T. Ogawa, H. Kuroiwa, and T. Iwasawa, “Investigation of Flow and Sink Initiation Process in Mold Shapes in Injection Molding,” Int. J. Automation Technol., Vol.9, No.1, pp. 10-18, 2015.
29. [29] M. Anahara and M. Kurose, “Influence of Vibration Freauency on Residual Stress Reduction of Die Casting Mold,” J. Soc. Mech. Eng. Proc. Conf. Kanto Br., Jpn., Vol.2017.23, 1208, 2017.
30. [30] S. Iwanaga, Y. Sakakibara, T. Konaga, M. Nakamura, and T. Kamiya, “Relationship between Heat Checking and Residual Stress in Aluminum Die Casting Dies,” J. Soc. Mater. Sci., Jpn., Vol.36, No.411, pp. 1355-1360, 1987.
31. [31] S. Iwanaga, Y. Sakakibara, T. Konaga, M. Nakamura, and T. Kamiya, “Initiation and Propagation of Heat Checking in Aluminum Die Casting Dies,” J. Soc. Mater. Sci., Jpn., Vol.36, No.405, pp. 604-609, 1987.