YOGITA ARYA 2021ME10996 The effect of cutting fluid on high strain rate dynamic mechanical property and cutting force of ultra-high-strength steel Introduction – The emphasis of this research paper is on ultra-high-strength steel, which is essential for many heavyduty applications in sectors including ships, aircraft, and automobiles. Cutting fluid is frequently utilized to speed up the difficult process of cutting this steel. Cutting fluids aid in cutting by lowering friction and heat generation, which enhances the cut's quality and surface smoothness. Cutting fluids have historically progressed from simple lubricants to more intricate formulas, with an increasing focus on environmental factors. The precise ways in which cutting fluids affect machining performance are still not entirely established. This study addresses the gap in understanding how different cutting fluids impact the dynamic mechanical properties and cutting performance of ultra-high-strength steel. The authors conducted experiments to assess the effects of various cutting fluids on this type of steel's behavior under different conditions. They also mention the "Rehbinder effect," which involves the adsorption of surfactant molecules on material surfaces, leading to changes in material strength and hardness. The ultimate goal of this research is to enhance the surface integrity of structural components made from ultra-highstrength steel. To achieve this, the study focuses on how cutting fluids affect dynamic mechanical properties and cutting performance. The research intends to provide direction for high-quality machining of ultra-high-strength steel and maybe open the path for the improvement of cutting fluids by better understanding these interactions. Experimental procedures – The main goal of the experimental procedures is the Investigation of the effects of various cutting fluids on the dynamic mechanical characteristics and cutting performance of ultra-high-strength steel (45CrNiMoVA). The properties of the material are detailed, including its chemistry, yield stress, and tensile stress. The tests make use of three different cutting fluids: TRIM E709, Vasco 7000, and HY-103. These cutting fluids are diluted to a 5% concentration in deionized water before application, and their additive compositions are detailed. Notably, Vasco 7000 is an environmentally friendly cutting fluid. Dynamic Mechanical Property Experiments: To understand the material's behavior during cutting, dynamic mechanical properties are assessed using Split Hopkinson Pressure Bar (SHPB) test. In the SHPB test, the shear band width represents the cutting depth, and the shear strain rate represents the strain that would be felt during actual cutting. For the experiments, hat-shaped samples with various shear band widths (400 um, 200 um, 100 um, and 50 um) are created. The samples are submerged in several cutting fluids (HY-103, TRIM E709, and Vasco 7000) for 30 minutes prior to the SHPB test. For accuracy, tests are run three times at each of three distinct impact velocities (15 m/s, 20 m/s, and 25 m/s). YOGITA ARYA 2021ME10996 Hat-shaped samples: (a) before and (b) after split Hopkinson pressure bar tests. Cutting Experiments: Cutting experiments are designed to investigate the impact of three different cutting fluids on cutting forces. The experiments involve turning a cylindrical bar of 45CrNiMoVA steel with specific cutting parameters: turning speed of 140 m/min, feed rate of 0.10 mm/rev, and cutting depth of 0.20 mm. Using traditional flood coolant procedures, the cutting fluids are fed to the cutting zone at a flow rate of 2500 L/h. Cutting is done using a carbide tool with particular tool angles and a support tool holder. A Kistler force measurement device and digital signal processing with Dynoware software are used to measure the cutting forces (radial force Fx, tangential force Fy, and axial force Fz) in real-time. Results and discussion – Shear strain rate: The research revealed distinct patterns: firstly, as the shear band width decreased while keeping the impact velocity constant, shear strain rates gradually increased. Secondly, when the shear band width remained consistent, higher impact velocities resulted in greater shear strain rates. These trends were consistently observed across multiple groups of samples. Notably, even transitional groups with different velocities and shear band widths exhibited increasing shear strain rates. Overall, the study demonstrated a systematic and continuous rise in shear strain rates from left to right across all groups, offering valuable insights into material behavior under diverse testing conditions. Shear strain rate of hat-shaped samples under different test conditions YOGITA ARYA 2021ME10996 Stress-shear strain curve and shear failure stress: The study examined the shear stress-shear strain curves of hat-shaped samples subjected to different cutting fluids, shear band widths, and impact velocities. Three distinct trends emerged: Category I: When the shear band width was large and the impact velocity was small, the shear stress remained relatively stable after strain hardening due to the opposing effects of strain hardening and thermal softening. Subsequently, ductile fracture occurred as strain increased. Category II: When the shear band width decreased and the impact velocity increased, the strain rate increased significantly, resulting in rapid thermal softening. This led to shear stress-strain curves approximating a parabolic shape, except for one case. The study also explored the influence of cutting fluids on material failure stress, with HY-103 consistently yielding the highest failure stress, followed by Vasco 7000 and TRIM E709. The Rehbinder effect of cutting fluids, involving surfactant infiltration into the shear zone and the reduction of surface energy, was proposed as an explanation for these differences. Furthermore, the influence of three factors on shear deformation strength was discussed: work hardening, strain rate strengthening, and thermal softening. The results showed that these factors played varying roles depending on shear band width and impact velocity. In some cases, the size effect became prominent, leading to increased material strength with decreasing shear band width. The shear stress-shear strain curves at 3.42 * 10^4 1/s under three cutting fluids Fracture morphology of shear zone: Using SEM analysis, the study looked at the fractured surface properties of hat-shaped samples under various strain rates and cutting fluids. Major conclusions include: • Ductile fracture was observed in all cases. • With higher shear strain rates, dimples grew longer and were worn. • Common parabolic shear dimples revealed by tiny pores suggested plastic deformation and hole development. • The parabolic opening was opposing the direction of shear deformation. • Dimple properties varied with strain rate; at high rates, dimple area dropped while dimple depth increased. • High magnification SEM revealed wear in TRIM E709, longer dimples in HY-103, and the influence of the Rehbinder effect. YOGITA ARYA 2021ME10996 These findings emphasize the importance of considering strain rate and cutting fluids in high-speed cutting processes for optimal production and surface quality. Cutting force: In-depth investigation of cutting forces in three directions under various cutting fluids was conducted in the study, which turned up some interesting patterns. Notably, a predictable pattern emerged in the cutting forces, with HY-103 producing the highest forces, followed by Vasco 7000 and TRIM E709. The differences were significant, with cutting forces significantly lower for TRIM E709 and Vasco 7000 in comparison to HY-103 for each of the three force components (Fx, Fy, and Fz). In particular, the forces were lowered by TRIM E709 by 23.93% and 33.08% in Fx and Fy, respectively, and by Vasco 7000 by 13.42% and 14.49%.The most notable reduction was in the vertical force component (Fz), with TRIM E709 and Vasco 7000 reducing forces by 50.29% and 22.05%, respectively, compared to HY-103. These cutting force trends were strongly related to the material's failure stress, with the same order of HY-103, Vasco 7000, and TRIM E709 in both categories. The Rehbinder effect of cutting fluid surfactants, which affects material characteristics and therefore cutting forces, was cited as the cause of this correlation. The study essentially emphasizes the significance of the Rehbinder effect in boosting surface quality and optimizing machining operations, particularly in precision machining applications. YOGITA ARYA 2021ME10996 Conclusion – This research explored the influence of various cutting fluids on the dynamic mechanical properties and cutting performance of ultra-high-strength steel. The study utilized a combination of Split Hopkinson Pressure Bar (SHPB) tests and cutting experiments to investigate these effects. Important trends in shear strain rates, stress-strain behavior, and cutting forces under varied circumstances and with different cutting fluids were found. These discoveries have significance for enhancing surface quality and machining procedures in sectors like aerospace and automotive. Overall, this research contributes to our understanding of how cutting fluids impact the behavior of ultra-high-strength steel during machining, paving the way for potential advancements in precision manufacturing. Positive Aspects of the Paper – 1. Relevance to Industry: The research is highly relevant to industries dealing with ultra-highstrength steel, such as automotive, aerospace, and shipbuilding. These industries are continually looking for ways to improve machining processes. 2. Experimental Rigor: The use of Split Hopkinson Pressure Bar (SHPB) tests and cutting experiments adds credibility to the findings. Experimental data provides valuable real-world insights. 3. Rehbinder Effect: The paper sheds light on the Rehbinder effect, an important but often overlooked factor in machining. Understanding how cutting fluids affect material properties can lead to better fluid selection. Suggestions – 1. Surface Finish: The paper focuses on mechanical properties and cutting forces but does not delve much into surface finish. Investigating how different cutting fluids impact surface roughness and quality could be beneficial, especially for applications with stringent surface requirements. 2. Tool Wear: The study discusses material wear but does not extensively address tool wear. It would be valuable to investigate how different cutting fluids affect tool life and tool wear rates during machining. 3. Optimization Techniques: The research focuses on the effects of cutting fluids but does not provide optimization strategies for achieving the best machining outcomes. Providing recommendations or guidelines for selecting the most suitable cutting fluid under different machining conditions could be useful for practitioners. YOGITA ARYA 2021ME10996 4. Cost Analysis: The cost of cutting fluids can significantly impact machining processes. An economic analysis of the different cutting fluids, considering factors like fluid consumption and tool replacement frequency, could help industries make informed decisions. 5. Advanced Testing Techniques: Explore advanced testing techniques beyond the SHPB tests to gain deeper insights into the dynamic mechanical properties of ultra-high-strength steel under various cutting conditions. Incorporating these additional considerations could enhance the comprehensiveness of future research in this area and provide a more holistic understanding of the complex dynamics involved in machining ultra-high-strength steel.
