Riveted joints are very crucial in many industrial applications. Several studies have been carried out to understand the response of lap joints and butt joints with single and double row of rivets emphasizing on total fatigue life and residual stress evaluation. Studies that deal with initial crack and stress intensity factors (SIF) during its progress are very less. In addition, there is very less data on joints formed with Lozenge pattern. The present work aims to bridge this gap with studies on the Lozenge pattern of rivets with focus on the SIF in strap plates, given the fact that the initial cracks appear on them when the strap thickness is less than or equal to the plate thickness. The strap plate considered has six joints in Lozenge pattern in 3-2-1 fashion. Cracks were induced at different joint locations and variation of the stress intensity factor with progress in crack size was evaluated using Finite Element Analysis. Studies were conducted for various interference levels of practical interest. The most critical location of the crack and the most beneficial levels of interference were identified. Limits of interference, beyond which SIF increases drastically, were identified. Combined influence of interference and neighboring geometrical aspects such as holes and boundaries was recorded. Studies were also conducted to evaluate if there is a need for uniform interference at all joint locations. Also, to simulate the real world scenario, several combinations of random interference were induced at the joints and the SIF results were compared with that of uniform interference values. Finally, the effect of change in back pitch of the joints was also studied.
{"title":"A Study of Stress Intensity Factors in Lozenge Pattern of Joints","authors":"K. Hithendra, R. Prakash","doi":"10.1115/imece2021-70138","DOIUrl":"https://doi.org/10.1115/imece2021-70138","url":null,"abstract":"\u0000 Riveted joints are very crucial in many industrial applications. Several studies have been carried out to understand the response of lap joints and butt joints with single and double row of rivets emphasizing on total fatigue life and residual stress evaluation. Studies that deal with initial crack and stress intensity factors (SIF) during its progress are very less. In addition, there is very less data on joints formed with Lozenge pattern. The present work aims to bridge this gap with studies on the Lozenge pattern of rivets with focus on the SIF in strap plates, given the fact that the initial cracks appear on them when the strap thickness is less than or equal to the plate thickness. The strap plate considered has six joints in Lozenge pattern in 3-2-1 fashion. Cracks were induced at different joint locations and variation of the stress intensity factor with progress in crack size was evaluated using Finite Element Analysis. Studies were conducted for various interference levels of practical interest. The most critical location of the crack and the most beneficial levels of interference were identified. Limits of interference, beyond which SIF increases drastically, were identified. Combined influence of interference and neighboring geometrical aspects such as holes and boundaries was recorded. Studies were also conducted to evaluate if there is a need for uniform interference at all joint locations. Also, to simulate the real world scenario, several combinations of random interference were induced at the joints and the SIF results were compared with that of uniform interference values. Finally, the effect of change in back pitch of the joints was also studied.","PeriodicalId":23837,"journal":{"name":"Volume 3: Advanced Materials: Design, Processing, Characterization, and Applications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76489196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Chockalingam, J. Ryu, Md. Didarul Islam, Myers Harbinson
Bioinspired Micro/Nano textured rough topography of a surface has many applications in super-hydrophobicity, self-cleaning surface, anti-icing coatings, anti-biofouling, and drag reduction surfaces. The role of hierarchical and complex surface topography in nature is to amplify the hydrophobicity and maximize the fouling resistance. Thus, a similar micro- and nano-scale 3-D topographic surfaces inspired from the nature were fabricated using a simple and scalable two roll coating process. This process was based on the ribbing instabilities associated with the shearing of non-Newtonian fluids between two rollers. The polymer composite retains the deformed shape due to the recovery of high-viscosity after removing the shear stress. The relationship between the process conditions and the textured structure were studied with the shear rate, capillary number and the surface roughness parameters (e.g., Wenzel factor and density of peaks). The results showed that the samples’ Wenzel roughness factor increased with the increase in shear rate up to a particular value and then decreased. Similarly, the density of peaks in the sample increased with an increase in capillary number up to a particular value and then decreased. These bioinspired surfaces with hierarchical textured patterns produced using two roll coating process show a tremendous potentiality to be used in super-hydrophobic, anti-biofouling, and drag reduction applications.
{"title":"Fabrication of Bioinspired Micro/Nano Textured Rough Surfaces Through the Scalable Roll Coating Process","authors":"S. Chockalingam, J. Ryu, Md. Didarul Islam, Myers Harbinson","doi":"10.1115/imece2021-71880","DOIUrl":"https://doi.org/10.1115/imece2021-71880","url":null,"abstract":"\u0000 Bioinspired Micro/Nano textured rough topography of a surface has many applications in super-hydrophobicity, self-cleaning surface, anti-icing coatings, anti-biofouling, and drag reduction surfaces. The role of hierarchical and complex surface topography in nature is to amplify the hydrophobicity and maximize the fouling resistance. Thus, a similar micro- and nano-scale 3-D topographic surfaces inspired from the nature were fabricated using a simple and scalable two roll coating process. This process was based on the ribbing instabilities associated with the shearing of non-Newtonian fluids between two rollers. The polymer composite retains the deformed shape due to the recovery of high-viscosity after removing the shear stress. The relationship between the process conditions and the textured structure were studied with the shear rate, capillary number and the surface roughness parameters (e.g., Wenzel factor and density of peaks). The results showed that the samples’ Wenzel roughness factor increased with the increase in shear rate up to a particular value and then decreased. Similarly, the density of peaks in the sample increased with an increase in capillary number up to a particular value and then decreased. These bioinspired surfaces with hierarchical textured patterns produced using two roll coating process show a tremendous potentiality to be used in super-hydrophobic, anti-biofouling, and drag reduction applications.","PeriodicalId":23837,"journal":{"name":"Volume 3: Advanced Materials: Design, Processing, Characterization, and Applications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88612017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Allameh, D. Alexander, Roger A. Miller, Avery Lenihan, H. Allameh
Fabrication of prototypes and custom-made parts, made of various metals, has become possible by additive manufacturing. Like any new technology, reliability of the products is of utmost importance, especially, when it comes to life-sustaining structures or for applications where human life is at stake. A less common method of making 3D metallic object is by 3D welding. This method is more appropriate for structures where dimensional and esthetic characteristics of the structures are of secondary importance. An example is steel rebar in concrete where it requires rough corrugated surfaces of the rebars. This walled metallic structures, used especially for loadbearing applications, where load is not fixed will require investigation of fatigue properties. Conventional testing methods may not be appropriate for small cross sections. To address this problem, microtensile testing allows characterization of mechanical properties of small structures as thin as a few millimeters. Past work on the monotonic and cyclic properties of microsamples extracted from weldments made on metallic substrates has shown superior tensile strength and enhanced fatigue resistance compared to the base metal. It is interesting to see how the results would be different if ceramic substrates were used. This study utilizes a gantry type 3D printer, equipped with the gun of a MIG welding machine to fabricate steel weldments on ceramics using 3D welding technique. The process involves starting of the arc from a grounded piece of metal, then continue the motion of the gun and guide the motion of the molten metal pool in desired direction, maintaining the continuity through the solidifying bead. Weldment samples fabricated by this technique are then machined by a CNC mill to extract microscale dog-bone-shaped samples with a width of 200 micron and a gage length of 1000 micron. The top and bottom surfaces of the samples are polished to a mirror finish and subsequently the microsamples are mounted in the grippers of an Electropulse 1000 Instron load frame. Monotonic and cyclic loading mechanical tests in tensile mode are conducted and data are collected and plotted in terms of stress-strain as well as stress-life curves. These results are then compared with those of samples made by 3D welding of steel-on-steel substrate. Since the cooling rate of molten metal on steel substrates differs from that of ceramic substrate, fatigue properties may be different too. The implications of the reliability of reinforcement steel bars printed by 3D welding will be discussed.
{"title":"On the Fatigue Properties of 3D Steel Structures Welded Onto Ceramics","authors":"S. Allameh, D. Alexander, Roger A. Miller, Avery Lenihan, H. Allameh","doi":"10.1115/imece2021-72572","DOIUrl":"https://doi.org/10.1115/imece2021-72572","url":null,"abstract":"\u0000 Fabrication of prototypes and custom-made parts, made of various metals, has become possible by additive manufacturing. Like any new technology, reliability of the products is of utmost importance, especially, when it comes to life-sustaining structures or for applications where human life is at stake. A less common method of making 3D metallic object is by 3D welding. This method is more appropriate for structures where dimensional and esthetic characteristics of the structures are of secondary importance. An example is steel rebar in concrete where it requires rough corrugated surfaces of the rebars. This walled metallic structures, used especially for loadbearing applications, where load is not fixed will require investigation of fatigue properties. Conventional testing methods may not be appropriate for small cross sections. To address this problem, microtensile testing allows characterization of mechanical properties of small structures as thin as a few millimeters. Past work on the monotonic and cyclic properties of microsamples extracted from weldments made on metallic substrates has shown superior tensile strength and enhanced fatigue resistance compared to the base metal. It is interesting to see how the results would be different if ceramic substrates were used. This study utilizes a gantry type 3D printer, equipped with the gun of a MIG welding machine to fabricate steel weldments on ceramics using 3D welding technique. The process involves starting of the arc from a grounded piece of metal, then continue the motion of the gun and guide the motion of the molten metal pool in desired direction, maintaining the continuity through the solidifying bead. Weldment samples fabricated by this technique are then machined by a CNC mill to extract microscale dog-bone-shaped samples with a width of 200 micron and a gage length of 1000 micron. The top and bottom surfaces of the samples are polished to a mirror finish and subsequently the microsamples are mounted in the grippers of an Electropulse 1000 Instron load frame. Monotonic and cyclic loading mechanical tests in tensile mode are conducted and data are collected and plotted in terms of stress-strain as well as stress-life curves. These results are then compared with those of samples made by 3D welding of steel-on-steel substrate. Since the cooling rate of molten metal on steel substrates differs from that of ceramic substrate, fatigue properties may be different too. The implications of the reliability of reinforcement steel bars printed by 3D welding will be discussed.","PeriodicalId":23837,"journal":{"name":"Volume 3: Advanced Materials: Design, Processing, Characterization, and Applications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76446623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents Compressive Stress Relaxation (CSR) results for various elastomer samples to ascertain their performance in sealing applications. The paper presents results of percent retained sealing force (%RSF) behavior and its relationship with compression set and hardness. Materials studied are used in critical piping and medical seal applications. CSR methodology is used to benchmark various materials in terms of sealing performance. Potential problems with the current standard of testing have also been identified that can affect the resolution and variability of the test. The paper details all the steps involved to perform accurate CSR testing and discusses advantages and disadvantages CSR testing might have over conventional tests used to verify seal performance such as compression set. This is only an introductory study and requires further tests with the same elastomers subjected to other process conditions, such as heat aging are also studied to understand how they affect %RSF. This can also be expanded to other materials to build a database of standard %RSF behavior under identical conditions.
{"title":"Compressive Stress Relaxation (CSR) Testing of Elastomers","authors":"Dilip Menon, R. Michael, David Gee","doi":"10.1115/imece2021-68181","DOIUrl":"https://doi.org/10.1115/imece2021-68181","url":null,"abstract":"\u0000 This paper presents Compressive Stress Relaxation (CSR) results for various elastomer samples to ascertain their performance in sealing applications. The paper presents results of percent retained sealing force (%RSF) behavior and its relationship with compression set and hardness. Materials studied are used in critical piping and medical seal applications. CSR methodology is used to benchmark various materials in terms of sealing performance. Potential problems with the current standard of testing have also been identified that can affect the resolution and variability of the test. The paper details all the steps involved to perform accurate CSR testing and discusses advantages and disadvantages CSR testing might have over conventional tests used to verify seal performance such as compression set. This is only an introductory study and requires further tests with the same elastomers subjected to other process conditions, such as heat aging are also studied to understand how they affect %RSF. This can also be expanded to other materials to build a database of standard %RSF behavior under identical conditions.","PeriodicalId":23837,"journal":{"name":"Volume 3: Advanced Materials: Design, Processing, Characterization, and Applications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90040972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Isaiah Yasko, A. Lutfullaeva, C. Fais, Muhammad Ali, K. Alam
Tapered-land hydrodynamic thrust bearings require taper depths of approximately 20–100 μm to operate efficiently within the hydrodynamic regime. Machining the tapers in traditionally manufactured bearings increase production time and costs. The thermo-mechanical analysis presented in this work shows that the utilization of composite laminas in place of taper machining may be used to provide taper formation in hydrodynamic bearings by exploiting the thermal expansion produced from frictional heating. Thermal expansion of three different carbon/epoxy composite layups (AS-4/3501-6, IM7/3501-6, T-300/3501-6) was analyzed using ABAQUS/CAE composite module. The analysis shows that the composites provide bidirectional taper depths of 24.25 μm, 23.7 μm, and 22.27 μm while being subjected to in-service film pressures and temperatures.
{"title":"Thermal Expansion Simulation of Bi-Directional Taper Formation in Composite Hydrodynamic Thrust Bearings","authors":"Isaiah Yasko, A. Lutfullaeva, C. Fais, Muhammad Ali, K. Alam","doi":"10.1115/imece2021-70430","DOIUrl":"https://doi.org/10.1115/imece2021-70430","url":null,"abstract":"\u0000 Tapered-land hydrodynamic thrust bearings require taper depths of approximately 20–100 μm to operate efficiently within the hydrodynamic regime. Machining the tapers in traditionally manufactured bearings increase production time and costs. The thermo-mechanical analysis presented in this work shows that the utilization of composite laminas in place of taper machining may be used to provide taper formation in hydrodynamic bearings by exploiting the thermal expansion produced from frictional heating. Thermal expansion of three different carbon/epoxy composite layups (AS-4/3501-6, IM7/3501-6, T-300/3501-6) was analyzed using ABAQUS/CAE composite module. The analysis shows that the composites provide bidirectional taper depths of 24.25 μm, 23.7 μm, and 22.27 μm while being subjected to in-service film pressures and temperatures.","PeriodicalId":23837,"journal":{"name":"Volume 3: Advanced Materials: Design, Processing, Characterization, and Applications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81705268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Min Zhu, Yansong Zhang, Qiao Zheng, Wei Wu, Weifang Qian, Baosen Wang
Residual stress prediction and controlling is important for structural integrity assessment of weldments. In current work, finite element and experimental methods were integrated to study the influence of welding sequence on the SUS304/Q235 bimetallic clad plate joints during multi-layer and multi-pass welding. The results show that the peak residual stress values on flyer plate surface are weakly affected by welding sequences but the width of high surficial longitudinal stress area of joint with base layer welded first is bigger. Meanwhile, welding sequence has a great influence on the longitudinal residual stress evolution law inside joints. When base seam layer is welded first, the highest stress concentration appears in the transition layer. However, it would be transferred into the first base seam layer due to martensite phase transformation when flyer seam layer is welded first. Residual stress controlling in the bimetallic clad plate joint should attract more attention from researchers.
{"title":"Influence of Welding Sequence on Residual Stress Evolution in SUS304/Q235 Bimetallic Clad Plate Butt-Welded Joints","authors":"Min Zhu, Yansong Zhang, Qiao Zheng, Wei Wu, Weifang Qian, Baosen Wang","doi":"10.1115/imece2021-69766","DOIUrl":"https://doi.org/10.1115/imece2021-69766","url":null,"abstract":"\u0000 Residual stress prediction and controlling is important for structural integrity assessment of weldments. In current work, finite element and experimental methods were integrated to study the influence of welding sequence on the SUS304/Q235 bimetallic clad plate joints during multi-layer and multi-pass welding. The results show that the peak residual stress values on flyer plate surface are weakly affected by welding sequences but the width of high surficial longitudinal stress area of joint with base layer welded first is bigger. Meanwhile, welding sequence has a great influence on the longitudinal residual stress evolution law inside joints. When base seam layer is welded first, the highest stress concentration appears in the transition layer. However, it would be transferred into the first base seam layer due to martensite phase transformation when flyer seam layer is welded first. Residual stress controlling in the bimetallic clad plate joint should attract more attention from researchers.","PeriodicalId":23837,"journal":{"name":"Volume 3: Advanced Materials: Design, Processing, Characterization, and Applications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81708160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The fatigue characterization of additively manufactured Ti-6Al-4V plays a vital role in ensuring the structural safety. This study focuses on image based surface characterization and the fatigue mechanical property investigation of as-built additively manufactured Ti-6Al-4V. Three sets of processing parameters (the absorbed laser power, scan velocity, building orientation) are adopted corresponding to the EOS nominal settings, lack-of-fusion and keyhole regimes. Before the fatigue testing, the specimens are scanned using X-ray micro-computed tomography (microCT) and the complete surface morphology is obtained. During fatigue testing, the specimen is scanned using microCT after certain numbers of loading cycles to capture the fatigue crack initiation locations and trace the crack growth trajectories. After the fatigue testing is completed, the fractured specimen is scanned by both microCT and scanning electron microscope (SEM). Based on the experimental investigation, vertically built specimens have lower average surface roughness than angled specimens along the transverse direction. Along longitudinal direction, the average surface roughness does not very significantly among all specimens. The fatigue crack may initiate from near surface pores or external rough surface. Cracks initiating from different locations at the similar height coalesce while propagating. Fracture surfaces present tortuous or tearing features, which corresponds to shorter and longer fatigue lives under the same fatigue loading, respectively.
{"title":"Imaging-Based Fatigue Mechanism Investigation of Additively Manufactured Ti-6Al-4V","authors":"Jie Chen, Changyu Meng, Yongming Liu","doi":"10.1115/imece2021-72865","DOIUrl":"https://doi.org/10.1115/imece2021-72865","url":null,"abstract":"\u0000 The fatigue characterization of additively manufactured Ti-6Al-4V plays a vital role in ensuring the structural safety. This study focuses on image based surface characterization and the fatigue mechanical property investigation of as-built additively manufactured Ti-6Al-4V. Three sets of processing parameters (the absorbed laser power, scan velocity, building orientation) are adopted corresponding to the EOS nominal settings, lack-of-fusion and keyhole regimes. Before the fatigue testing, the specimens are scanned using X-ray micro-computed tomography (microCT) and the complete surface morphology is obtained. During fatigue testing, the specimen is scanned using microCT after certain numbers of loading cycles to capture the fatigue crack initiation locations and trace the crack growth trajectories. After the fatigue testing is completed, the fractured specimen is scanned by both microCT and scanning electron microscope (SEM). Based on the experimental investigation, vertically built specimens have lower average surface roughness than angled specimens along the transverse direction. Along longitudinal direction, the average surface roughness does not very significantly among all specimens. The fatigue crack may initiate from near surface pores or external rough surface. Cracks initiating from different locations at the similar height coalesce while propagating. Fracture surfaces present tortuous or tearing features, which corresponds to shorter and longer fatigue lives under the same fatigue loading, respectively.","PeriodicalId":23837,"journal":{"name":"Volume 3: Advanced Materials: Design, Processing, Characterization, and Applications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82095211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Doctor Enivweru, Qingyu Wang, A. Ayodeji, Ayouba Moussa Hassane
One of the most common threats to the integrity of reactor fuel cladding is the geometric imperfections such as the missing pellet surface (MPS) that produces a remarkable surge in the local fuel-clad gap. The cooling water could occupy this gap leading to secondary hydriding (SH) and hydrogen embrittlement. Most studies on this subject have identified extensive radiolysis in boiling water reactors (BWRs) to be responsible for hydrogen evolution during accident conditions. However, the quantitative determination of hydrogen and how it affects zircaloy-2 during normal reactor operation has not been given adequate attention. To bridge this gap and to better predict the onset of cladding failure, this study investigates secondary hydriding and its characteristic phenomenon in a fuel cladded with zircaloy-2. Multiphysics model is used to model diffusion of heat and hydrogen, then the effect of an intermediary porous/non-protective oxide layer and the impact of dose rate from different types of radiation are studied. The contributions of the source term due to radiolysis of neutrons (n), gamma (γ), alpha (α) and beta (β) radiations are also considered. Results showed that neutrons, having a maximum dose rate of 39.9 kGy/s accounts for over 99% of ZrH precipitation in a UO2 fuel with MPS. The effect of oxide (ZrO2) thickness in SH, and the derivative of oxide thickness are also discussed.
{"title":"A Study on the Onset of Secondary Hydriding in Defective Zr-2 Fuel for Boiling Water Reactors","authors":"Doctor Enivweru, Qingyu Wang, A. Ayodeji, Ayouba Moussa Hassane","doi":"10.1115/imece2021-73284","DOIUrl":"https://doi.org/10.1115/imece2021-73284","url":null,"abstract":"\u0000 One of the most common threats to the integrity of reactor fuel cladding is the geometric imperfections such as the missing pellet surface (MPS) that produces a remarkable surge in the local fuel-clad gap. The cooling water could occupy this gap leading to secondary hydriding (SH) and hydrogen embrittlement. Most studies on this subject have identified extensive radiolysis in boiling water reactors (BWRs) to be responsible for hydrogen evolution during accident conditions. However, the quantitative determination of hydrogen and how it affects zircaloy-2 during normal reactor operation has not been given adequate attention. To bridge this gap and to better predict the onset of cladding failure, this study investigates secondary hydriding and its characteristic phenomenon in a fuel cladded with zircaloy-2. Multiphysics model is used to model diffusion of heat and hydrogen, then the effect of an intermediary porous/non-protective oxide layer and the impact of dose rate from different types of radiation are studied. The contributions of the source term due to radiolysis of neutrons (n), gamma (γ), alpha (α) and beta (β) radiations are also considered. Results showed that neutrons, having a maximum dose rate of 39.9 kGy/s accounts for over 99% of ZrH precipitation in a UO2 fuel with MPS. The effect of oxide (ZrO2) thickness in SH, and the derivative of oxide thickness are also discussed.","PeriodicalId":23837,"journal":{"name":"Volume 3: Advanced Materials: Design, Processing, Characterization, and Applications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88562533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Regalla, P. Shyam, Sampath Mylavarapu, Sai Harshini Irigineni, P. Shrivastava
The authors have developed trans-tibial prosthetic sockets using additive manufacturing. These sockets made with mono-material thermoplastics such as Acrylonitrile Butadiene Styrene (ABS) and Polylactic Acid (PLA) at lower thicknesses were found to fracture within a few days of use by the amputees. The fracture was repeatedly found to occur at specific locations such as the lobe corners and the socket’s lower one-third zone. The most probable causes of crack initiation are lack of fusion (LOF) sites and voids. The causes of crack propagation are the lower interlayer bond strength compared to intra-layer bond strength. However, no scientific work exists that clearly explains these phenomena and methods to prevent such potential crack initiation sites and arrest the propagation of such fracture in additively manufactured polymeric structures. Therefore, in the present work, the investigation was carried out into possible enhancement in the resistance to fracture by different strength-enhancing post-processing techniques. In the first technique, the placement of stiffener features at selected locations on the socket was investigated. Three-point bending tests were carried out on D790 standard ABS specimens with different stiffeners introduced on the bottom face. The study focused on fracture characteristics in the stiffener-based topologically optimized geometric design of plate structures made by Fused Deposition Modeling (FDM) under flexural loading. The D790 three-point bending specimens were provided with differently shaped stiffeners, namely, triangular, prismatic, cuboidal, and pyramidal, extending all along the specimen’s length and spread with differential gaps in the width direction. In the second method, thermosetting epoxy resin coatings were applied on the three-point bending specimens of ABS, and the effect of the coating on the flexural strength was investigated. Bending tests were done on three specimens, the first specimen without any coating, the second specimen with only the epoxy resin coating, and the third specimen with two different coating layers. The first of the two coating layers on the third specimen was with primer and the second layer was with epoxy resin. Scanning electron microscope (SEM) and energy dispersion spectroscopy (EDS) scanning analyses were conducted on the fractured specimens. The scanning images indicated that both the primer and resin materials showed a tendency to diffuse into the substrate of ABS, thereby weakening the extreme fibers of material on the specimen’s tension side, resulting in premature crack initiation and propagation. Significant gain in the flexural strength was observed in both the strength enhancement techniques compared to plain specimens.
{"title":"Study of Flexural Strength and Fracture of Additive Manufactured Parts With Stiffeners","authors":"S. Regalla, P. Shyam, Sampath Mylavarapu, Sai Harshini Irigineni, P. Shrivastava","doi":"10.1115/imece2021-71519","DOIUrl":"https://doi.org/10.1115/imece2021-71519","url":null,"abstract":"\u0000 The authors have developed trans-tibial prosthetic sockets using additive manufacturing. These sockets made with mono-material thermoplastics such as Acrylonitrile Butadiene Styrene (ABS) and Polylactic Acid (PLA) at lower thicknesses were found to fracture within a few days of use by the amputees. The fracture was repeatedly found to occur at specific locations such as the lobe corners and the socket’s lower one-third zone. The most probable causes of crack initiation are lack of fusion (LOF) sites and voids. The causes of crack propagation are the lower interlayer bond strength compared to intra-layer bond strength. However, no scientific work exists that clearly explains these phenomena and methods to prevent such potential crack initiation sites and arrest the propagation of such fracture in additively manufactured polymeric structures. Therefore, in the present work, the investigation was carried out into possible enhancement in the resistance to fracture by different strength-enhancing post-processing techniques. In the first technique, the placement of stiffener features at selected locations on the socket was investigated. Three-point bending tests were carried out on D790 standard ABS specimens with different stiffeners introduced on the bottom face. The study focused on fracture characteristics in the stiffener-based topologically optimized geometric design of plate structures made by Fused Deposition Modeling (FDM) under flexural loading. The D790 three-point bending specimens were provided with differently shaped stiffeners, namely, triangular, prismatic, cuboidal, and pyramidal, extending all along the specimen’s length and spread with differential gaps in the width direction. In the second method, thermosetting epoxy resin coatings were applied on the three-point bending specimens of ABS, and the effect of the coating on the flexural strength was investigated. Bending tests were done on three specimens, the first specimen without any coating, the second specimen with only the epoxy resin coating, and the third specimen with two different coating layers. The first of the two coating layers on the third specimen was with primer and the second layer was with epoxy resin. Scanning electron microscope (SEM) and energy dispersion spectroscopy (EDS) scanning analyses were conducted on the fractured specimens. The scanning images indicated that both the primer and resin materials showed a tendency to diffuse into the substrate of ABS, thereby weakening the extreme fibers of material on the specimen’s tension side, resulting in premature crack initiation and propagation. Significant gain in the flexural strength was observed in both the strength enhancement techniques compared to plain specimens.","PeriodicalId":23837,"journal":{"name":"Volume 3: Advanced Materials: Design, Processing, Characterization, and Applications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83046852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Om Saran, Brandon Stoyanovich, Hong Guo, P. Iglesias
Protic ionic liquids (PILs) are an emerging class of environmentally friendly lubricants and lubricant additives PILs can be easily synthesized through proton transfer from a Brønsted acid to a Brønsted base and exhibit significant potential as lubricant additives on account of their high thermal stability, non-flammability, low melting points, lack of vapor pressure, low cost, and biodegradability. This research covers the tribological performance of three halogen-free protic ionic liquids, 2-hydroxyethylammonium 2-ethylhexanoate (Eet), 2-hydroxyethylammonium p-toluenesulfonate (Ets), and 2-hydroxyethylammonium 4-dodecylbenzenesulfonate (Eds) which are designed and synthesized using the same base (ethanolamine) but different acids of varying acidity and alkyl chain length. The relationship among their ionicity, molecular structures, and tribological properties are investigated when these protic ionic liquids are used as lubricant additives to water. Each PIL was evaluated as a lubricant additive in a 1 wt.% aqueous solution. The solutions were tested using a ball-on-flat reciprocating tribometer under room temperature for steel-ceramic contact using distilled water was used as a base line lubricant. PIL solutions yielded significant reductions in frictional coefficients and wear volumes. The wear mechanisms and surface interactions were also discussed in terms of PIL-steel surface interactions from SEM and EDX data.
{"title":"Protic Ionic Liquids as Lubricant Additives","authors":"Om Saran, Brandon Stoyanovich, Hong Guo, P. Iglesias","doi":"10.1115/imece2021-69792","DOIUrl":"https://doi.org/10.1115/imece2021-69792","url":null,"abstract":"\u0000 Protic ionic liquids (PILs) are an emerging class of environmentally friendly lubricants and lubricant additives PILs can be easily synthesized through proton transfer from a Brønsted acid to a Brønsted base and exhibit significant potential as lubricant additives on account of their high thermal stability, non-flammability, low melting points, lack of vapor pressure, low cost, and biodegradability. This research covers the tribological performance of three halogen-free protic ionic liquids, 2-hydroxyethylammonium 2-ethylhexanoate (Eet), 2-hydroxyethylammonium p-toluenesulfonate (Ets), and 2-hydroxyethylammonium 4-dodecylbenzenesulfonate (Eds) which are designed and synthesized using the same base (ethanolamine) but different acids of varying acidity and alkyl chain length. The relationship among their ionicity, molecular structures, and tribological properties are investigated when these protic ionic liquids are used as lubricant additives to water. Each PIL was evaluated as a lubricant additive in a 1 wt.% aqueous solution. The solutions were tested using a ball-on-flat reciprocating tribometer under room temperature for steel-ceramic contact using distilled water was used as a base line lubricant. PIL solutions yielded significant reductions in frictional coefficients and wear volumes. The wear mechanisms and surface interactions were also discussed in terms of PIL-steel surface interactions from SEM and EDX data.","PeriodicalId":23837,"journal":{"name":"Volume 3: Advanced Materials: Design, Processing, Characterization, and Applications","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87361832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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