Welding defects are common during the production of large welded structures. However, few studies... more Welding defects are common during the production of large welded structures. However, few studies have explored methods of compensating for clear welding defects without resorting to re-welding. Here, an ultrasonic peening method to compensate for the deteriorated mechanical properties of overlap weld defects without repair welding was studied. We experimentally investigated changes in the mechanical properties of defective welds before and after ultrasonic peening. The weld specimen with an overlap defect contained a large cavity-type defect inside the weld bead, which significantly reduced the fatigue life. When the surface of the defective test piece was peened, the fatigue life of the weld plate was restored, resulting in an equivalent or higher number of cycles to failure, compared to a specimen with a normal weld. The recovery of mechanical properties was attributed to the effect of surface work hardening by ultrasonic peening and the change in stress distribution. Thus, ultra...
International Journal of Mechanical Engineering and Robotics Research, 2022
An experimental study was carried out to substantiate the simultaneous removal of excess moisture... more An experimental study was carried out to substantiate the simultaneous removal of excess moisture from two layers of wet leather semi-finished products. For the experiment, a multilayer package was compiled, consisting of two layers of wet leather semi-finished products and two layers of permeable cloth, laid between them. The selection of samples of semi-finished leather products for the experiment were selected from chromeplated bovine hide of medium weight, double. The excess moisture content from the wet leather semi-finished products was squeezed out by means of a vertical chain transmission on the base plate under pressure between the rotating shafts. The working shafts are covered with a permeable cloth. The experiment used the second-order Doptimal planning method. On the basis of the obtained experimental results, mathematical equations were obtained expressing the amount of moisture removed from the first and second layers of leather semi-finished products, depending on different feed rates and clamping forces of the working shafts. The main parameters of the technological process of two-layer processing of wet leather semi-finished products with their vertical feeding on the base plate between the shafts are experimentally substantiated. The parameters of the feed rate, the pressing force of the working shafts and the values of the residual moisture of the processed wet leather semi-finished products have been determined. In the future, the results obtained will serve to determine the maximum (permissible) number of layers of wet capillary-porous materials during their simultaneous processing, taking into account the provision of the necessary residual moisture in each of them.
Additive Manufacturing (AM) which is also known as metal 3D printing technique is one of the prom... more Additive Manufacturing (AM) which is also known as metal 3D printing technique is one of the promising manufacturing processes due to the capability to process a complex geometry component. This is implemented in wide range of applications in various industries such as automotive, aerospace, power plants, etc. The aging nuclear power plant components and the obsolescence of those components has become a concern in this industry, and AM has come as an alternative solution for this matter. The Board on Pressure and Technology Codes and Standards (BPTCS) and Board on Nuclear Codes and Standards (BNCS) Special Committees started to study the application of Powder Bed Fusion (PBF) technique for pressure retaining equipment made from UNS S31603. Also, later Korean International Working Group (KIWG) was also started a Task Group on Additive Manufacturing for Valves which focusing on Powder Bed Fusion (PBF) and Direct Energy Disposition (DED) process for pressure-retaining valve manufacturi...
Materials manufactured by powder metallurgy (PM) are widely used in various applications such as ... more Materials manufactured by powder metallurgy (PM) are widely used in various applications such as water pump, shock absorber, and airplane components due to the reduction in the cost and weight. In this study, tribological properties of carbon steel subjected by surface treatment were investigated. The main purpose is to increase the strength and improve the tribological properties by reducing pores that formed by PM. Moreover, the surface treatment was carried out at room and high temperatures (RT and HT). The surface roughness of the untreated (NON) and treated (AFTER) samples was measured. It was found that the surface roughness was reduced after both the RT AFTER and HT AFTER compared to RT NON sample. The tribological properties of the samples were performed against bearing steel ball under dry conditions. The friction coefficient of the RT NON samples was reduced by 22% and 56% RT AFTER and HT AFTER, respectively. The wear volume of the RT NON sample was also reduced by 43% and 87% RT AFTER and HT AFTER, respectively. Tribocorrosion tests were also performed and it was found that the surface of the RT AFTER, HT AFTER samples was less corroded compared to RT NON sample. The HT AFTER sample demonstrated a relatively higher corrosion potential in comparison with the RT AFTER samples. Hence, it was confirmed that after surface modification the surface roughness and hardness of the samples were significantly improved resulting in improvement in tribological and tribocorrosion behaviors of PM carbon steel.
Additive Manufacturing (AM) which is also known as metal 3D printing technique is a promising pro... more Additive Manufacturing (AM) which is also known as metal 3D printing technique is a promising process with a massive potential for developing a component for wide range applications for various industries. Recently, AM process was introduced to the nuclear power plant industry as AM is capable of manufacturing the substitution of aging and obsolete component. However, the AM component has inferior mechanical properties and performance in terms of fatigue strength and wear resistance compared to its conventionally manufactured counterpart. Ultrasonic Nanocrystal Surface Modification (UNSM) is one of mechanical surface modification treatment known for improving fatigue strength and wear resistance of wrought material. Hence, in this study effect of UNSM treatment on fatigue strength and wear resistance of additive manufactured material was investigated. The investigation was done to Ni-based alloy 718 (UNS N07718) as this material is used for nuclear power plant components and was man...
A challenge for owners operating nuclear power plants and spent fuel canisters is to provide soun... more A challenge for owners operating nuclear power plants and spent fuel canisters is to provide sound technical basis for the safety and security of long-term operation and storage, respectively. Two code cases N-729-6 and N-770-5 provide performance requirements for mitigation of Primary Water Stress Corrosion Cracking (PWSCC) in ASME Section XI and Code Case N-860 “Examination Requirements and Acceptance Standards for Spent Nuclear Fuel Storage and Transportation Containment Systems” is under development in ASME Section XI. The primary degradation concern being addressed in N-860 is Chloride Induced Stress Corrosion Cracking (CISCC). ASME Section III has formed two Task Groups with the intent to reduce PWSCC and CISCC in operation by mitigating residual stresses during new construction of components. ASME Section III formed Task Group Weld Residual Stress (TG-WRS) to incorporate lessons learned into the Code from operating plants regarding their experience with stress corrosion crack...
Abstract The importance of a newly developed dual UNSM (ultrasonic nanocrystal surface modificati... more Abstract The importance of a newly developed dual UNSM (ultrasonic nanocrystal surface modification) technology on rolling friction (RF) and rotary bending fatigue (RBF) of a ball screw made of AISI 4150H steel was investigated. RF tests against AISI 52100 steel were performed under grease-lubricated conditions. The results revealed that the RF and RBF were improved after dual UNSM technology, where an improvement in surface integrity and an introduction of compressive residual stress played an influential role, respectively. Based on these results, it can be assured to achieve a smooth motion, a low noise, small torque fluctuations and an extended service life of ball screws.
Abstract In this study, the beneficial effect of ultrasonic nanocrystal surface modification (UNS... more Abstract In this study, the beneficial effect of ultrasonic nanocrystal surface modification (UNSM) treatment at room and high temperatures (RT and HT) on the mechanical properties and fatigue performance of Nickel-base 718 alloy that is fabricated by laser directed energy deposition (LDED) process was investigated. UNSM treatment at RT and HT demonstrated a significant enhancement in fatigue performance by approximately of 43% and 57%, respectively. This can be attributed to the introduction of a high compressive residual stress (CRS) and the generation of nanostructured surface layer. Moreover, it was found that the surface roughness reduced, while the hardness increased after UNSM treatment at RT and HT. Furthermore, it was found by analysing the fatigued surfaces that the main crack initiation site was located at the subsurface for the UNSM-treated samples, while it was located at the top surface for the untreated ones. Introduction of a high CRS by UNSM treatment at RT and HT shifted a crack initiation site into subsurface.
A study on deformation and filtration properties of a leather semi-finished product after chrome ... more A study on deformation and filtration properties of a leather semi-finished product after chrome tanning are presented. The analytical dependences of compressive load on compressive (recovery) strain and moisture content of a leather semi-finished product are obtained. The empirical dependences of hydraulic gradient on filtration rates are determined for various compression ratios of the leather semi-finished product. It was revealed that with an increase in compressive load and moisture content of the leather semi-finished product, the compressive deformation increases. The shoulder section is subject to the greatest deformation, then the belly section and the least deformation is observed in the butt section. A linear relationship has been established between the hydraulic gradient and the rate of moisture filtration through the leather semi-finished product in the directions perpendicular and parallel to its surface. Graphical abstract
Glass with strong durability and transparency has been in the spotlight in various fields, includ... more Glass with strong durability and transparency has been in the spotlight in various fields, including displays. Elastic and shear moduli and Poisson’s ratio are important properties of glasses. The purpose of this study is to evaluate the change in mechanical properties, such as the dynamic elastic modulus and Poisson’s ratio, with respect to the chemical strengthening time of glass for display applications, as measured by static and dynamic methods. The basic measurement principle of the dynamic method is to measure acoustic speed or resonant frequency using an ultrasonic generator. The mechanical properties of both non-strengthened and chemically strengthened glasses were investigated. It was found that the strength of the chemically strengthened glass decreased when chemical strengthening time increased. Chemical strengthening increased the bending strength and decreased the elastic modulus due to the introduction of compressive residual stress at the surface.
Individual and synergy effects of shot peening (SP) and ultrasonic nanocrystal surface modificati... more Individual and synergy effects of shot peening (SP) and ultrasonic nanocrystal surface modification (UNSM) on rotary bending fatigue (RBF) behavior of AISI 4340 steel were systematically investigated at various bending stress levels in the range of 275-600 MPa. The results revealed that the fatigue behavior of the as-received sample was enhanced by SP and it was further enhanced by SP and UNSM combination, while the UNSMtreated one exhibited the highest enhancement in fatigue behavior. The fatigue behavior of the SP þ UNSM sample was enhanced after SP, but it was found to be detrimental after UNSM. Apart from RBF experiments, individual and synergy effects of SP and UNSM on surface roughness, hardness, residual stresses and grain size were analyzed as well. Fractography of the samples was characterized by scanning electron microscope (SEM) and fatigue mechanisms of each sample were discussed based on the obtained observations. The finest grain size and highest compressive residual stress (CRS) obtained by UNSM in comparison with those of the SP and SP þ UNSM was responsible for the best fatigue performance.
The role of ultrasonic nanocrystalline surface modification at elevated temperature on the hydrog... more The role of ultrasonic nanocrystalline surface modification at elevated temperature on the hydrogen charging behavior of high-Mn steels, Materialia (2020), doi:
This work comparatively investigated the strength (hardness, yield strength, dynamic elastic modu... more This work comparatively investigated the strength (hardness, yield strength, dynamic elastic modulus, and surface residual stress), fretting failure, and corrosion resistance of the as-received and treated Ni-based superalloy Alloy 718. The goal of the current research is to improve the hardness, fretting wear, and corrosion resistances of Alloy 718 through the ultrasonic nanocrystal surface modification (UNSM) process with the aim of extending the lifespan of aircraft and nuclear components made of Alloy 718. The experimental results revealed that the surface hardness increased by about 32%, the fretting wear resistance increased by about 14%, and the corrosion resistance increased by about 18% after UNSM process. In addition, the UNSM process induced a tremendous high compressive surface residual stress of about −1324 MPa that led to an increase in yield strength and dynamic Young’s modulus by about 14 and 9%, respectively. Grain size refinement up to ~50 nm after the UNSM process...
The following results were obtained from a series of studies to accumulate data to reduce the coe... more The following results were obtained from a series of studies to accumulate data to reduce the coefficient of friction for press dies by performing tribological tests before and after the UNSM treatment of SM45C. The UNSM-treated material had a nano-size surface texture, high surface hardness, and large and deep compressive residual stress formation. Even when the load was doubled, the small amount of abrasion, small weight of the abrasion, and width and depth of the abrasion did not increase as much as those for untreated materials. When loads of 5 N, 7.5 N, and 10 N were applied to the untreated material of SM45C, the coefficient of friction was approximately 0.76-0.78. With the large specimen, a value of 0.72-0.78 was maintained at a load of 50 N despite the differences in the size of the wear specimen and working load. Tribological tests of large specimens of SM45C treated with UNSM under tribological conditions of 100 N and 50 N showed that the frictional coefficient and time constant stably converged between 0.7 and 0.8. The friction coefficients of the small specimens treated with UNSM showed values between 0.78 and 0.75 under 5 N, 7.5 N, and 10 N. The friction coefficients of the SM45C treated with UNSM were comparable to each other.
A novel b-type Tie29Nbe13Tae4.6Zr (TNTZ) alloy with a low Young's modulus, high bio-corrosion res... more A novel b-type Tie29Nbe13Tae4.6Zr (TNTZ) alloy with a low Young's modulus, high bio-corrosion resistance, and excellent biocompatibility has been recently introduced for implant applications. Here, ultrasonic nanocrystal surface modification (UNSM) treatment was applied to TNTZ alloy to improve its wear resistance and biofunctionality. Application of UNSM to a TNTZ alloy resulted in the generation of a nanostructured surface layer. The wear resistance of the UNSM-treated specimen was observed to be more than 7 times higher than that of the untreated one. Cell culture tests indicated that MC3T3 cells adhered and spread more readily on the UNSM-treated specimen than on the untreated one. MTT assays after 1 and 4 days in culture also indicated enhancement of cell proliferation on the UNSM-treated specimen than that of the untreated one. Live/dead assay revealed no significant cytotoxicity in either substrate. The significant improvement of cell adhesion, spreading, and proliferation on the UNSMtreated TNTZ alloy specimen were attributed to both grain refinement and micro-patterned surface effects. These results demonstrate that UNSM-treatment not only improves the wear resistance of TNTZ alloy, but also enhances its biocompatibility, which makes it a strong candidate for applications in medical implants.
In this study, microstructural evolution and mechanical properties of the ultrasonic nanocrystall... more In this study, microstructural evolution and mechanical properties of the ultrasonic nanocrystalline surface modification (UNSM) processed twinning-induced plasticity (TWIP) steels were investigated. As a result, UNSM TWIP steel achieves high strength and large elongation. Moreover, the strength-ductility combination of the UNSM TWIP improves as the applied impact force increases.
In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was applied to... more In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was applied to normal and heat-treated rails made of 60 kgK steel to enhance the wear resistance of the wheel-rail interaction. The hardness and compressive residual stress values of the untreated and UNSM-treated rails were measured by the Brinell hardness tester and X-ray diffraction technique, respectively. It was found, according to the measurement results, that the hardness was increased by about 20% and 8%, whereas the compressive residual stress was induced by about 52% and 62% for the UNSM-treated normal and heat-treated rails, respectively. The UNSM-treated normal rail showed a slightly higher hardness than the heat-treated rail. The wear resistance of rails with respect to rotating speed and rolling time was assessed using a rolling contact wear (RCW) tester under dry conditions. The RCW test results revealed that the wear of the UNSM-treated rails was enhanced in comparison with those of the untreated rails. Also, the wear amount of the rails was increased with increasing the rotation speed. The UNSM-treated normal rail exhibited the highest wear resistance with respect to the rotation speed. The wear mechanisms of the rails are also discussed based on microscopic images of the worn out surfaces.
This paper deals with the improvement in surface properties and microscratch resistance of graphi... more This paper deals with the improvement in surface properties and microscratch resistance of graphites by means of an ultrasonic nanocrystalline surface modification (UNSM) technique. The surface roughness and surface hardness of the untreated and UNSM-treated graphites were investigated using an atomic force microscopy (AFM) and a microhardness tester, respectively. The scratch resistance was assessed using a microscratch tester at a progressive load. Moreover, a Raman spectroscopy was employed to characterize the microstructure of graphites before and after UNSM treatment. The scratch test results revealed that the resistance to scratch of both UNSM-treated graphites was found to be better in comparison with the untreated graphites. The increase in scratch resistance of both UNSM-treated graphites may be mainly attributed to the reduced surface roughness and increased surface hardness by UNSM treatment. The graphite produced by Poco exhibited a higher resistance to scratch compared ...
In this study, an alumina (Al2O3) ceramic powder was sprayed onto an AISI H13 hot-work tool steel... more In this study, an alumina (Al2O3) ceramic powder was sprayed onto an AISI H13 hot-work tool steel substrate that was subjected to sanding and ultrasonic nanocrystalline surface modification (UNSM) treatment processes. The significance of the UNSM technique on the adhesive failure of the Al2O3 coating and on the hardness of the substrate was investigated. The adhesive failure of the coating sprayed onto sanded and UNSM-treated substrates was investigated by a micro-scratch tester at an incremental load. It was found, based on the obtained results, that the coating sprayed onto the UNSM-treated substrate exhibited a better resistance to adhesive failure in comparison with that of the coating sprayed onto the sanded substrate. Dry friction and wear property of the coatings sprayed onto the sanded and UNSM-treated substrates were assessed by means of a ball-on-disk tribometer against an AISI 52100 steel ball. It was demonstrated that the UNSM technique controllably improved the adhesive failure of the Al2O3 coating, where the critical load was improved by about 31%. Thus, it is expected that the application of the UNSM technique to an AISI H13 tool steel substrate prior to coating may delay the adhesive failure and improve the sticking between the coating and the substrate thanks to the modified and hardened surface.
Welding defects are common during the production of large welded structures. However, few studies... more Welding defects are common during the production of large welded structures. However, few studies have explored methods of compensating for clear welding defects without resorting to re-welding. Here, an ultrasonic peening method to compensate for the deteriorated mechanical properties of overlap weld defects without repair welding was studied. We experimentally investigated changes in the mechanical properties of defective welds before and after ultrasonic peening. The weld specimen with an overlap defect contained a large cavity-type defect inside the weld bead, which significantly reduced the fatigue life. When the surface of the defective test piece was peened, the fatigue life of the weld plate was restored, resulting in an equivalent or higher number of cycles to failure, compared to a specimen with a normal weld. The recovery of mechanical properties was attributed to the effect of surface work hardening by ultrasonic peening and the change in stress distribution. Thus, ultra...
International Journal of Mechanical Engineering and Robotics Research, 2022
An experimental study was carried out to substantiate the simultaneous removal of excess moisture... more An experimental study was carried out to substantiate the simultaneous removal of excess moisture from two layers of wet leather semi-finished products. For the experiment, a multilayer package was compiled, consisting of two layers of wet leather semi-finished products and two layers of permeable cloth, laid between them. The selection of samples of semi-finished leather products for the experiment were selected from chromeplated bovine hide of medium weight, double. The excess moisture content from the wet leather semi-finished products was squeezed out by means of a vertical chain transmission on the base plate under pressure between the rotating shafts. The working shafts are covered with a permeable cloth. The experiment used the second-order Doptimal planning method. On the basis of the obtained experimental results, mathematical equations were obtained expressing the amount of moisture removed from the first and second layers of leather semi-finished products, depending on different feed rates and clamping forces of the working shafts. The main parameters of the technological process of two-layer processing of wet leather semi-finished products with their vertical feeding on the base plate between the shafts are experimentally substantiated. The parameters of the feed rate, the pressing force of the working shafts and the values of the residual moisture of the processed wet leather semi-finished products have been determined. In the future, the results obtained will serve to determine the maximum (permissible) number of layers of wet capillary-porous materials during their simultaneous processing, taking into account the provision of the necessary residual moisture in each of them.
Additive Manufacturing (AM) which is also known as metal 3D printing technique is one of the prom... more Additive Manufacturing (AM) which is also known as metal 3D printing technique is one of the promising manufacturing processes due to the capability to process a complex geometry component. This is implemented in wide range of applications in various industries such as automotive, aerospace, power plants, etc. The aging nuclear power plant components and the obsolescence of those components has become a concern in this industry, and AM has come as an alternative solution for this matter. The Board on Pressure and Technology Codes and Standards (BPTCS) and Board on Nuclear Codes and Standards (BNCS) Special Committees started to study the application of Powder Bed Fusion (PBF) technique for pressure retaining equipment made from UNS S31603. Also, later Korean International Working Group (KIWG) was also started a Task Group on Additive Manufacturing for Valves which focusing on Powder Bed Fusion (PBF) and Direct Energy Disposition (DED) process for pressure-retaining valve manufacturi...
Materials manufactured by powder metallurgy (PM) are widely used in various applications such as ... more Materials manufactured by powder metallurgy (PM) are widely used in various applications such as water pump, shock absorber, and airplane components due to the reduction in the cost and weight. In this study, tribological properties of carbon steel subjected by surface treatment were investigated. The main purpose is to increase the strength and improve the tribological properties by reducing pores that formed by PM. Moreover, the surface treatment was carried out at room and high temperatures (RT and HT). The surface roughness of the untreated (NON) and treated (AFTER) samples was measured. It was found that the surface roughness was reduced after both the RT AFTER and HT AFTER compared to RT NON sample. The tribological properties of the samples were performed against bearing steel ball under dry conditions. The friction coefficient of the RT NON samples was reduced by 22% and 56% RT AFTER and HT AFTER, respectively. The wear volume of the RT NON sample was also reduced by 43% and 87% RT AFTER and HT AFTER, respectively. Tribocorrosion tests were also performed and it was found that the surface of the RT AFTER, HT AFTER samples was less corroded compared to RT NON sample. The HT AFTER sample demonstrated a relatively higher corrosion potential in comparison with the RT AFTER samples. Hence, it was confirmed that after surface modification the surface roughness and hardness of the samples were significantly improved resulting in improvement in tribological and tribocorrosion behaviors of PM carbon steel.
Additive Manufacturing (AM) which is also known as metal 3D printing technique is a promising pro... more Additive Manufacturing (AM) which is also known as metal 3D printing technique is a promising process with a massive potential for developing a component for wide range applications for various industries. Recently, AM process was introduced to the nuclear power plant industry as AM is capable of manufacturing the substitution of aging and obsolete component. However, the AM component has inferior mechanical properties and performance in terms of fatigue strength and wear resistance compared to its conventionally manufactured counterpart. Ultrasonic Nanocrystal Surface Modification (UNSM) is one of mechanical surface modification treatment known for improving fatigue strength and wear resistance of wrought material. Hence, in this study effect of UNSM treatment on fatigue strength and wear resistance of additive manufactured material was investigated. The investigation was done to Ni-based alloy 718 (UNS N07718) as this material is used for nuclear power plant components and was man...
A challenge for owners operating nuclear power plants and spent fuel canisters is to provide soun... more A challenge for owners operating nuclear power plants and spent fuel canisters is to provide sound technical basis for the safety and security of long-term operation and storage, respectively. Two code cases N-729-6 and N-770-5 provide performance requirements for mitigation of Primary Water Stress Corrosion Cracking (PWSCC) in ASME Section XI and Code Case N-860 “Examination Requirements and Acceptance Standards for Spent Nuclear Fuel Storage and Transportation Containment Systems” is under development in ASME Section XI. The primary degradation concern being addressed in N-860 is Chloride Induced Stress Corrosion Cracking (CISCC). ASME Section III has formed two Task Groups with the intent to reduce PWSCC and CISCC in operation by mitigating residual stresses during new construction of components. ASME Section III formed Task Group Weld Residual Stress (TG-WRS) to incorporate lessons learned into the Code from operating plants regarding their experience with stress corrosion crack...
Abstract The importance of a newly developed dual UNSM (ultrasonic nanocrystal surface modificati... more Abstract The importance of a newly developed dual UNSM (ultrasonic nanocrystal surface modification) technology on rolling friction (RF) and rotary bending fatigue (RBF) of a ball screw made of AISI 4150H steel was investigated. RF tests against AISI 52100 steel were performed under grease-lubricated conditions. The results revealed that the RF and RBF were improved after dual UNSM technology, where an improvement in surface integrity and an introduction of compressive residual stress played an influential role, respectively. Based on these results, it can be assured to achieve a smooth motion, a low noise, small torque fluctuations and an extended service life of ball screws.
Abstract In this study, the beneficial effect of ultrasonic nanocrystal surface modification (UNS... more Abstract In this study, the beneficial effect of ultrasonic nanocrystal surface modification (UNSM) treatment at room and high temperatures (RT and HT) on the mechanical properties and fatigue performance of Nickel-base 718 alloy that is fabricated by laser directed energy deposition (LDED) process was investigated. UNSM treatment at RT and HT demonstrated a significant enhancement in fatigue performance by approximately of 43% and 57%, respectively. This can be attributed to the introduction of a high compressive residual stress (CRS) and the generation of nanostructured surface layer. Moreover, it was found that the surface roughness reduced, while the hardness increased after UNSM treatment at RT and HT. Furthermore, it was found by analysing the fatigued surfaces that the main crack initiation site was located at the subsurface for the UNSM-treated samples, while it was located at the top surface for the untreated ones. Introduction of a high CRS by UNSM treatment at RT and HT shifted a crack initiation site into subsurface.
A study on deformation and filtration properties of a leather semi-finished product after chrome ... more A study on deformation and filtration properties of a leather semi-finished product after chrome tanning are presented. The analytical dependences of compressive load on compressive (recovery) strain and moisture content of a leather semi-finished product are obtained. The empirical dependences of hydraulic gradient on filtration rates are determined for various compression ratios of the leather semi-finished product. It was revealed that with an increase in compressive load and moisture content of the leather semi-finished product, the compressive deformation increases. The shoulder section is subject to the greatest deformation, then the belly section and the least deformation is observed in the butt section. A linear relationship has been established between the hydraulic gradient and the rate of moisture filtration through the leather semi-finished product in the directions perpendicular and parallel to its surface. Graphical abstract
Glass with strong durability and transparency has been in the spotlight in various fields, includ... more Glass with strong durability and transparency has been in the spotlight in various fields, including displays. Elastic and shear moduli and Poisson’s ratio are important properties of glasses. The purpose of this study is to evaluate the change in mechanical properties, such as the dynamic elastic modulus and Poisson’s ratio, with respect to the chemical strengthening time of glass for display applications, as measured by static and dynamic methods. The basic measurement principle of the dynamic method is to measure acoustic speed or resonant frequency using an ultrasonic generator. The mechanical properties of both non-strengthened and chemically strengthened glasses were investigated. It was found that the strength of the chemically strengthened glass decreased when chemical strengthening time increased. Chemical strengthening increased the bending strength and decreased the elastic modulus due to the introduction of compressive residual stress at the surface.
Individual and synergy effects of shot peening (SP) and ultrasonic nanocrystal surface modificati... more Individual and synergy effects of shot peening (SP) and ultrasonic nanocrystal surface modification (UNSM) on rotary bending fatigue (RBF) behavior of AISI 4340 steel were systematically investigated at various bending stress levels in the range of 275-600 MPa. The results revealed that the fatigue behavior of the as-received sample was enhanced by SP and it was further enhanced by SP and UNSM combination, while the UNSMtreated one exhibited the highest enhancement in fatigue behavior. The fatigue behavior of the SP þ UNSM sample was enhanced after SP, but it was found to be detrimental after UNSM. Apart from RBF experiments, individual and synergy effects of SP and UNSM on surface roughness, hardness, residual stresses and grain size were analyzed as well. Fractography of the samples was characterized by scanning electron microscope (SEM) and fatigue mechanisms of each sample were discussed based on the obtained observations. The finest grain size and highest compressive residual stress (CRS) obtained by UNSM in comparison with those of the SP and SP þ UNSM was responsible for the best fatigue performance.
The role of ultrasonic nanocrystalline surface modification at elevated temperature on the hydrog... more The role of ultrasonic nanocrystalline surface modification at elevated temperature on the hydrogen charging behavior of high-Mn steels, Materialia (2020), doi:
This work comparatively investigated the strength (hardness, yield strength, dynamic elastic modu... more This work comparatively investigated the strength (hardness, yield strength, dynamic elastic modulus, and surface residual stress), fretting failure, and corrosion resistance of the as-received and treated Ni-based superalloy Alloy 718. The goal of the current research is to improve the hardness, fretting wear, and corrosion resistances of Alloy 718 through the ultrasonic nanocrystal surface modification (UNSM) process with the aim of extending the lifespan of aircraft and nuclear components made of Alloy 718. The experimental results revealed that the surface hardness increased by about 32%, the fretting wear resistance increased by about 14%, and the corrosion resistance increased by about 18% after UNSM process. In addition, the UNSM process induced a tremendous high compressive surface residual stress of about −1324 MPa that led to an increase in yield strength and dynamic Young’s modulus by about 14 and 9%, respectively. Grain size refinement up to ~50 nm after the UNSM process...
The following results were obtained from a series of studies to accumulate data to reduce the coe... more The following results were obtained from a series of studies to accumulate data to reduce the coefficient of friction for press dies by performing tribological tests before and after the UNSM treatment of SM45C. The UNSM-treated material had a nano-size surface texture, high surface hardness, and large and deep compressive residual stress formation. Even when the load was doubled, the small amount of abrasion, small weight of the abrasion, and width and depth of the abrasion did not increase as much as those for untreated materials. When loads of 5 N, 7.5 N, and 10 N were applied to the untreated material of SM45C, the coefficient of friction was approximately 0.76-0.78. With the large specimen, a value of 0.72-0.78 was maintained at a load of 50 N despite the differences in the size of the wear specimen and working load. Tribological tests of large specimens of SM45C treated with UNSM under tribological conditions of 100 N and 50 N showed that the frictional coefficient and time constant stably converged between 0.7 and 0.8. The friction coefficients of the small specimens treated with UNSM showed values between 0.78 and 0.75 under 5 N, 7.5 N, and 10 N. The friction coefficients of the SM45C treated with UNSM were comparable to each other.
A novel b-type Tie29Nbe13Tae4.6Zr (TNTZ) alloy with a low Young's modulus, high bio-corrosion res... more A novel b-type Tie29Nbe13Tae4.6Zr (TNTZ) alloy with a low Young's modulus, high bio-corrosion resistance, and excellent biocompatibility has been recently introduced for implant applications. Here, ultrasonic nanocrystal surface modification (UNSM) treatment was applied to TNTZ alloy to improve its wear resistance and biofunctionality. Application of UNSM to a TNTZ alloy resulted in the generation of a nanostructured surface layer. The wear resistance of the UNSM-treated specimen was observed to be more than 7 times higher than that of the untreated one. Cell culture tests indicated that MC3T3 cells adhered and spread more readily on the UNSM-treated specimen than on the untreated one. MTT assays after 1 and 4 days in culture also indicated enhancement of cell proliferation on the UNSM-treated specimen than that of the untreated one. Live/dead assay revealed no significant cytotoxicity in either substrate. The significant improvement of cell adhesion, spreading, and proliferation on the UNSMtreated TNTZ alloy specimen were attributed to both grain refinement and micro-patterned surface effects. These results demonstrate that UNSM-treatment not only improves the wear resistance of TNTZ alloy, but also enhances its biocompatibility, which makes it a strong candidate for applications in medical implants.
In this study, microstructural evolution and mechanical properties of the ultrasonic nanocrystall... more In this study, microstructural evolution and mechanical properties of the ultrasonic nanocrystalline surface modification (UNSM) processed twinning-induced plasticity (TWIP) steels were investigated. As a result, UNSM TWIP steel achieves high strength and large elongation. Moreover, the strength-ductility combination of the UNSM TWIP improves as the applied impact force increases.
In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was applied to... more In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was applied to normal and heat-treated rails made of 60 kgK steel to enhance the wear resistance of the wheel-rail interaction. The hardness and compressive residual stress values of the untreated and UNSM-treated rails were measured by the Brinell hardness tester and X-ray diffraction technique, respectively. It was found, according to the measurement results, that the hardness was increased by about 20% and 8%, whereas the compressive residual stress was induced by about 52% and 62% for the UNSM-treated normal and heat-treated rails, respectively. The UNSM-treated normal rail showed a slightly higher hardness than the heat-treated rail. The wear resistance of rails with respect to rotating speed and rolling time was assessed using a rolling contact wear (RCW) tester under dry conditions. The RCW test results revealed that the wear of the UNSM-treated rails was enhanced in comparison with those of the untreated rails. Also, the wear amount of the rails was increased with increasing the rotation speed. The UNSM-treated normal rail exhibited the highest wear resistance with respect to the rotation speed. The wear mechanisms of the rails are also discussed based on microscopic images of the worn out surfaces.
This paper deals with the improvement in surface properties and microscratch resistance of graphi... more This paper deals with the improvement in surface properties and microscratch resistance of graphites by means of an ultrasonic nanocrystalline surface modification (UNSM) technique. The surface roughness and surface hardness of the untreated and UNSM-treated graphites were investigated using an atomic force microscopy (AFM) and a microhardness tester, respectively. The scratch resistance was assessed using a microscratch tester at a progressive load. Moreover, a Raman spectroscopy was employed to characterize the microstructure of graphites before and after UNSM treatment. The scratch test results revealed that the resistance to scratch of both UNSM-treated graphites was found to be better in comparison with the untreated graphites. The increase in scratch resistance of both UNSM-treated graphites may be mainly attributed to the reduced surface roughness and increased surface hardness by UNSM treatment. The graphite produced by Poco exhibited a higher resistance to scratch compared ...
In this study, an alumina (Al2O3) ceramic powder was sprayed onto an AISI H13 hot-work tool steel... more In this study, an alumina (Al2O3) ceramic powder was sprayed onto an AISI H13 hot-work tool steel substrate that was subjected to sanding and ultrasonic nanocrystalline surface modification (UNSM) treatment processes. The significance of the UNSM technique on the adhesive failure of the Al2O3 coating and on the hardness of the substrate was investigated. The adhesive failure of the coating sprayed onto sanded and UNSM-treated substrates was investigated by a micro-scratch tester at an incremental load. It was found, based on the obtained results, that the coating sprayed onto the UNSM-treated substrate exhibited a better resistance to adhesive failure in comparison with that of the coating sprayed onto the sanded substrate. Dry friction and wear property of the coatings sprayed onto the sanded and UNSM-treated substrates were assessed by means of a ball-on-disk tribometer against an AISI 52100 steel ball. It was demonstrated that the UNSM technique controllably improved the adhesive failure of the Al2O3 coating, where the critical load was improved by about 31%. Thus, it is expected that the application of the UNSM technique to an AISI H13 tool steel substrate prior to coating may delay the adhesive failure and improve the sticking between the coating and the substrate thanks to the modified and hardened surface.
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Papers by Auezhan Amanov