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Hemmerlein E, Vorndran E, Schmitt AM, Feichtner F, Waselau AC, Meyer-Lindenberg A. In Vivo Investigation of 3D-Printed Calcium Magnesium Phosphate Wedges in Partial Load Defects. Materials (Basel) 2024; 17:2136. [PMID: 38730942 PMCID: PMC11085615 DOI: 10.3390/ma17092136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 04/26/2024] [Accepted: 04/30/2024] [Indexed: 05/13/2024]
Abstract
Bone substitutes are ideally biocompatible, osteoconductive, degradable and defect-specific and provide mechanical stability. Magnesium phosphate cements (MPCs) offer high initial stability and faster degradation compared to the well-researched calcium phosphate cements (CPCs). Calcium magnesium phosphate cements (CMPCs) should combine the properties of both and have so far shown promising results. The present study aimed to investigate and compare the degradation and osseointegration behavior of 3D powder-printed wedges of CMPC and MPC in vivo. The wedges were post-treated with phosphoric acid (CMPC) and diammonium hydrogen phosphate (MPC) and implanted in a partially loaded defect model in the proximal rabbit tibia. The evaluation included clinical, in vivo µ-CT and X-ray examinations, histology, energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) for up to 30 weeks. SEM analysis revealed a zone of unreacted material in the MPC, indicating the need to optimize the manufacturing and post-treatment process. However, all materials showed excellent biocompatibility and mechanical stability. After 24 weeks, they were almost completely degraded. The slower degradation rate of the CMPC corresponded more favorably to the bone growth rate compared to the MPC. Due to the promising results of the CMPC in this study, it should be further investigated, for example in defect models with higher load.
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Affiliation(s)
- Elke Hemmerlein
- Clinic for Small Animal Surgery and Reproduction, Ludwig Maximilians University Munich, 80539 Munich, Germany (A.-C.W.); (A.M.-L.)
| | - Elke Vorndran
- Department for Functional Materials in Medicine and Dentistry, University of Würzburg, 97070 Würzburg, Germany (A.-M.S.)
| | - Anna-Maria Schmitt
- Department for Functional Materials in Medicine and Dentistry, University of Würzburg, 97070 Würzburg, Germany (A.-M.S.)
| | - Franziska Feichtner
- Clinic for Small Animal Surgery and Reproduction, Ludwig Maximilians University Munich, 80539 Munich, Germany (A.-C.W.); (A.M.-L.)
| | - Anja-Christina Waselau
- Clinic for Small Animal Surgery and Reproduction, Ludwig Maximilians University Munich, 80539 Munich, Germany (A.-C.W.); (A.M.-L.)
| | - Andrea Meyer-Lindenberg
- Clinic for Small Animal Surgery and Reproduction, Ludwig Maximilians University Munich, 80539 Munich, Germany (A.-C.W.); (A.M.-L.)
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Wang Y, Fan Y, Zhupanska OI. Challenges and Future Recommendations for Lightning Strike Damage Assessments of Composites: Laboratory Testing and Predictive Modeling. Materials (Basel) 2024; 17:744. [PMID: 38591613 PMCID: PMC10856118 DOI: 10.3390/ma17030744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 01/29/2024] [Accepted: 01/31/2024] [Indexed: 04/10/2024]
Abstract
Lightning strike events pose significant challenges to the structural integrity and performance of composite materials, particularly in aerospace, wind turbine blade, and infrastructure applications. Through a meticulous examination of the state-of-the-art methodologies of laboratory testing and damage predictive modeling, this review elucidates the role of simulated lightning strike tests in providing inputs required for damage modeling and experimental data for model validations. In addition, this review provides a holistic understanding of what is there, what are current issues, and what is still missing in both lightning strike testing and modeling to enable a robust and high-fidelity predictive capability, and challenges and future recommendations are also presented. The insights gleaned from this review are poised to catalyze advancements in the safety, reliability, and durability of composite materials under lightning strike conditions, as well as to facilitate the development of innovative lightning damage mitigation strategies.
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Affiliation(s)
- Yeqing Wang
- Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, NY 13244, USA
| | - Yin Fan
- School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Olesya I. Zhupanska
- Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, AZ 85721, USA;
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Patel PR, Welle EJ, Letner JG, Shen H, Bullard AJ, Caldwell CM, Vega-Medina A, Richie JM, Thayer HE, Patil PG, Cai D, Chestek CA. Utah array characterization and histological analysis of a multi-year implant in non-human primate motor and sensory cortices. J Neural Eng 2023; 20:10.1088/1741-2552/acab86. [PMID: 36595323 PMCID: PMC9954796 DOI: 10.1088/1741-2552/acab86] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 12/14/2022] [Indexed: 12/15/2022]
Abstract
Objective.The Utah array is widely used in both clinical studies and neuroscience. It has a strong track record of safety. However, it is also known that implanted electrodes promote the formation of scar tissue in the immediate vicinity of the electrodes, which may negatively impact the ability to record neural waveforms. This scarring response has been primarily studied in rodents, which may have a very different response than primate brain.Approach.Here, we present a rare nonhuman primate histological dataset (n= 1 rhesus macaque) obtained 848 and 590 d after implantation in two brain hemispheres. For 2 of 4 arrays that remained within the cortex, NeuN was used to stain for neuron somata at three different depths along the shanks. Images were filtered and denoised, with neurons then counted in the vicinity of the arrays as well as a nearby section of control tissue. Additionally, 3 of 4 arrays were imaged with a scanning electrode microscope to evaluate any materials damage that might be present.Main results.Overall, we found a 63% percent reduction in the number of neurons surrounding the electrode shanks compared to control areas. In terms of materials, the arrays remained largely intact with metal and Parylene C present, though tip breakage and cracks were observed on many electrodes.Significance.Overall, these results suggest that the tissue response in the nonhuman primate brain shows similar neuron loss to previous studies using rodents. Electrode improvements, for example using smaller or softer probes, may therefore substantially improve the tissue response and potentially improve the neuronal recording yield in primate cortex.
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Affiliation(s)
- Paras R. Patel
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Elissa J. Welle
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Joseph G. Letner
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Hao Shen
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Autumn J. Bullard
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Ciara M. Caldwell
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Alexis Vega-Medina
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48019, United States of America,Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI 48109, United States of America
| | - Julianna M. Richie
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Hope E. Thayer
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, United States of America
| | - Parag G. Patil
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, United States of America,Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI 48109, United States of America,Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, United States of America,Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI 48109, United States of America
| | - Dawen Cai
- Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI 48109, United States of America,Department of Biophysics, University of Michigan, Ann Arbor, MI 48109, United States of America,Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48019, United States of America
| | - Cynthia A. Chestek
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, United States of America,Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI 48109, United States of America,Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, United States of America,Robotics Program, University of Michigan, Ann Arbor, MI 48109, United States of America, Corresponding author:
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Milone A, Landolfo R. A Simplified Approach for the Corrosion Fatigue Assessment of Steel Structures in Aggressive Environments. Materials (Basel) 2022; 15:2210. [PMID: 35329661 DOI: 10.3390/ma15062210] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 03/08/2022] [Accepted: 03/15/2022] [Indexed: 12/10/2022]
Abstract
Fatigue performance is often a key aspect when dealing with existing steel structures such as steel bridges or offshore constructions. This issue proves to be more critical as these structures are usually located in aggressive environments and are thus exposed to progressive degradation. Indeed, disruptive phenomena such as corrosion can severely worsen the fatigue performance of the steel components. Currently, the normative standards do not provide a codified procedure for the fatigue checks of steel structures subjected to ongoing corrosion. Within this framework, in this paper a simplified approach for the life-cycle assessment of corroded steel structures is proposed. For this purpose, the concept of “critical corrosion degree” is introduced, allowing the expression of corrosion fatigue checks in a more direct “demand vs. capacity” form with respect to the currently available methods. A first validation of such methodology is reported for the corrosion fatigue tests drawn from the literature. The predicted levels of critical corrosion are in good agreement with the values of artificially induced corrosion (i.e., 4, 8, and 12% of mass loss, respectively), with a maximum relative error of ≈9.3% for the most corroded specimen. Finally, parametrical analyses are performed, highlighting the influence of the model parameters on the corrosion fatigue performance of the steel elements.
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Saleem MZ, Akbar M. Review of the Performance of High-Voltage Composite Insulators. Polymers (Basel) 2022; 14:polym14030431. [PMID: 35160421 PMCID: PMC8840764 DOI: 10.3390/polym14030431] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Revised: 10/29/2021] [Accepted: 01/18/2022] [Indexed: 02/04/2023] Open
Abstract
In the present literature survey, we focused on the performance of polymeric materials encompassing silicone rubber (SiR), ethylene propylene diene monomer (EPDM) and epoxy resins loaded with micro, nano, and micro/nano hybrid fillers. These insulators are termed as composite insulators. The scope of the added fillers/additives was limited to the synthetic inorganic family. Special attention was directed to understanding the effect of fillers on the improvement of the thermal conductivity, dielectric strength, mechanical strength, corona discharge resistance, and tracking and erosion resistance performance of polymeric materials for use as high-voltage transmission line insulators. The survey showed that synthetic inorganic fillers, which include silica (SiO2) and hexagonal boron nitride (h-BN), are potential fillers to improve insulation performance of high-voltage insulators. Furthermore, nano and micro/nano filled composites performed better due to the better interaction between the filler and polymer matrix as compared to their only micro- or nano filled counterparts. Finally, some aspects requiring future work to further exploit fillers are identified and discussed.
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Abstract
The impact of an aircraft is widely known to be one of the worst events that can occur during the operation of a plant (classified for this reason as beyond design). This can become much more catastrophic and lead to the loss of strength of/collapse of the structures when it occurs in the presence of ageing (degradation and alteration) materials. Therefore, since the performance of all plant components may be affected by ageing, there is a need to evaluate the effect that aged components have on system performance and plant safety. This study addresses the numerical simulation of an aged Nuclear Power Plant (NPP) subjected to a military aircraft impact. The effects of impact velocity, direction, and location were investigated together with the more unfavorable conditions to be expected for the plant. The modelling method was also validated based on the results obtained from the experiments of Sugano et al., 1993. Non-linear analyses by means of finite element (FE) MARC code allowed us to simulate the performance of the reinforced concrete containment building and its impact on plant availability and reliability. The results showed that ageing increases a plant’s propensity to suffer damage. The damage at the impact area was confirmed to be dependent on the type of aircraft involved and the target wall thickness. The greater the degradation of the materials, the lower the residual resistance capacity, and the greater the risk of wall perforation.
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Affiliation(s)
- Rosa Lo Frano
- Department of Industrial and Civil Engineering (DICI), University of Pisa, 56126 Pisa, Italy
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Balakrishnan M, Shrestha P, Lee C, Ge N, Fahy KF, Messerschmidt M, Scholta J, Eifert L, Maibach J, Zeis R, Hatton BD, Bazylak A. Degradation Characteristics of Electrospun Gas Diffusion Layers with Custom Pore Structures for Polymer Electrolyte Membrane Fuel Cells. ACS Appl Mater Interfaces 2021; 13:2414-2427. [PMID: 33405503 DOI: 10.1021/acsami.0c15324] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Electrospinning has been demonstrated to be a versatile technique for producing hydrophobic gas diffusion layers (GDLs) with customized pore structures for the enhanced performance of polymer electrolyte membrane (PEM) fuel cells. However, the degradation characteristics of custom hydrophobic electrospun GDLs (eGDLs) have not yet been explored. Here, for the first time, we investigate the degradation characteristics of custom hydrophobic eGDLs via an ex situ accelerated degradation protocol using H2O2. The surface contact angle of degraded eGDLs (44 ± 12°) was lower than that of pristine eGDLs (137 ± 6°). The loss of hydrophobicity was attributed to the degradation (via hydrolysis) of the fluorinated monolayers (formed via a direct fluorination treatment) on the electrospun carbon fiber surfaces as evidenced by the reduction in surface fluorine content. Degradation of the surface monolayers affected fuel cell performance under multiple operating conditions. At 100% relative humidity (RH), the loss of monolayers led to higher liquid water content and lower cell voltages compared to the pristine eGDL. At 50% RH, the degraded eGDL led to lower cell voltages due to the lower electrical conductivity of the degraded materials. The lower electrical conductivity was attributed to the oxidation of carbon fibers upon loss of the monolayers. Our results indicate the importance of designing robust hydrophobic surface treatments for the advancement of customized GDLs for effective long-term fuel cell operation.
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Affiliation(s)
- Manojkumar Balakrishnan
- Thermofluids for Energy and Advanced Material Laboratory, Department of Mechanical and Industrial Engineering, Faculty of Applied Science and Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, M5S 3G8, Canada
| | - Pranay Shrestha
- Thermofluids for Energy and Advanced Material Laboratory, Department of Mechanical and Industrial Engineering, Faculty of Applied Science and Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, M5S 3G8, Canada
| | - ChungHyuk Lee
- Thermofluids for Energy and Advanced Material Laboratory, Department of Mechanical and Industrial Engineering, Faculty of Applied Science and Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, M5S 3G8, Canada
| | - Nan Ge
- Thermofluids for Energy and Advanced Material Laboratory, Department of Mechanical and Industrial Engineering, Faculty of Applied Science and Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, M5S 3G8, Canada
| | - Kieran F Fahy
- Thermofluids for Energy and Advanced Material Laboratory, Department of Mechanical and Industrial Engineering, Faculty of Applied Science and Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, M5S 3G8, Canada
| | - Matthias Messerschmidt
- Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg, Helmholtzsraße 8, 89081 Ulm, Baden-Württemberg, Germany
| | - Joachim Scholta
- Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg, Helmholtzsraße 8, 89081 Ulm, Baden-Württemberg, Germany
| | - László Eifert
- Karlsruhe Institute of Technology, Helmholtz Institute Ulm, Helmholtzsraße 11, 89081 Ulm, Baden-Württemberg, Germany
| | - Julia Maibach
- Karlsruhe Nano Micro Facility, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Baden-Württemberg, Germany
| | - Roswitha Zeis
- Karlsruhe Institute of Technology, Helmholtz Institute Ulm, Helmholtzsraße 11, 89081 Ulm, Baden-Württemberg, Germany
- Institute of Physical Chemistry, Karlsruhe Institute of Technology, Fritz-Haber-Weg 2, 76131 Karlsruhe, Baden-Württemberg, Germany
| | - Benjamin D Hatton
- Functional and Adaptive Surfaces Group, Department of Materials Science and Engineering, Faculty of Applied Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4, Canada
| | - Aimy Bazylak
- Thermofluids for Energy and Advanced Material Laboratory, Department of Mechanical and Industrial Engineering, Faculty of Applied Science and Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, M5S 3G8, Canada
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De Melo N, Murrell L, Islam MT, Titman JJ, Macri-Pellizzeri L, Ahmed I, Sottile V. Tailoring Pyro-and Orthophosphate Species to Enhance Stem Cell Adhesion to Phosphate Glasses. Int J Mol Sci 2021; 22:ijms22020837. [PMID: 33467686 PMCID: PMC7829838 DOI: 10.3390/ijms22020837] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/11/2021] [Accepted: 01/13/2021] [Indexed: 12/29/2022] Open
Abstract
Phosphate-based glasses (PBGs) offer significant therapeutic potential due to their bioactivity, controllable compositions, and degradation rates. Several PBGs have already demonstrated their ability to support direct cell growth and in vivo cytocompatibility for bone repair applications. This study investigated development of PBG formulations with pyro- and orthophosphate species within the glass system (40 − x)P2O5·(16 + x)CaO·20Na2O·24MgO (x = 0, 5, 10 mol%) and their effect on stem cell adhesion properties. Substitution of phosphate for calcium revealed a gradual transition within the glass structure from Q2 to Q0 phosphate species. Human mesenchymal stem cells were cultured directly onto discs made from three PBG compositions. Analysis of cells seeded onto the discs revealed that PBG with higher concentration of pyro- and orthophosphate content (61% Q1 and 39% Q0) supported a 4.3-fold increase in adhered cells compared to glasses with metaphosphate connectivity (49% Q2 and 51% Q1). This study highlights that tuning the composition of PBGs to possess pyro- and orthophosphate species only, enables the possibility to control cell adhesion performance. PBGs with superior cell adhesion profiles represent ideal candidates for biomedical applications, where cell recruitment and support for tissue ingrowth are of critical importance for orthopaedic interventions.
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Affiliation(s)
- Nigel De Melo
- School of Medicine, University of Nottingham, Nottingham NG7 2RD, UK; (N.D.M.); (L.M.-P.)
| | - Lauren Murrell
- Advanced Materials Research Group, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK; (L.M.); (M.T.I.)
| | - Md Towhidul Islam
- Advanced Materials Research Group, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK; (L.M.); (M.T.I.)
- Department of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Noakhali Science and Technology University, Noakhali 3814, Bangladesh
| | - Jeremy J. Titman
- School of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK;
| | - Laura Macri-Pellizzeri
- School of Medicine, University of Nottingham, Nottingham NG7 2RD, UK; (N.D.M.); (L.M.-P.)
| | - Ifty Ahmed
- Advanced Materials Research Group, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK; (L.M.); (M.T.I.)
- Correspondence: (I.A.); (V.S.)
| | - Virginie Sottile
- School of Medicine, University of Nottingham, Nottingham NG7 2RD, UK; (N.D.M.); (L.M.-P.)
- Department of Molecular Medicine, The University of Pavia, 27100 Pavia, Italy
- Correspondence: (I.A.); (V.S.)
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Liao B, Sun B, Yan M, Ren Y, Zhang W, Zhou K. Time-Variant Reliability Analysis for Rubber O-Ring Seal Considering Both Material Degradation and Random Load. Materials (Basel) 2017; 10:E1211. [PMID: 29053597 DOI: 10.3390/ma10101211] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 10/16/2017] [Accepted: 10/17/2017] [Indexed: 11/16/2022]
Abstract
Due to the increase in working hours, the reliability of rubber O-ring seals used in hydraulic systems of transfer machines will change. While traditional methods can only analyze one of the material properties or seal properties, the failure of the O-ring is caused by these two factors together. In this paper, two factors are mainly analyzed: the degradation of material properties and load randomization by processing technology. Firstly, the two factors are defined in terms of material failure and seal failure, before the experimental methods of rubber materials are studied. Following this, the time-variant material properties through experiments and load distribution by monitoring the processing can be obtained. Thirdly, compressive stress and contact stress have been calculated, which was combined with the reliability model to acquire the time-variant reliability for the O-ring. Finally, the life prediction and effect of oil pressure were discussed, then compared with the actual situation. The results show a lifetime of 12 months for the O-ring calculated in this paper, and compared with the replacement records from the maintenance workshop, the result is credible.
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Li Y, Jing H, Zainal Abidin IM, Yan B. A Gradient-Field Pulsed Eddy Current Probe for Evaluation of Hidden Material Degradation in Conductive Structures Based on Lift-Off Invariance. Sensors (Basel) 2017; 17:E943. [PMID: 28441328 DOI: 10.3390/s17050943] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 04/17/2017] [Accepted: 04/22/2017] [Indexed: 11/16/2022]
Abstract
Coated conductive structures are widely adopted in such engineering fields as aerospace, nuclear energy, etc. The hostile and corrosive environment leaves in-service coated conductive structures vulnerable to Hidden Material Degradation (HMD) occurring under the protection coating. It is highly demanded that HMD can be non-intrusively assessed using non-destructive evaluation techniques. In light of the advantages of Gradient-field Pulsed Eddy Current technique (GPEC) over other non-destructive evaluation methods in corrosion evaluation, in this paper the GPEC probe for quantitative evaluation of HMD is intensively investigated. Closed-form expressions of GPEC responses to HMD are formulated via analytical modeling. The Lift-off Invariance (LOI) in GPEC signals, which makes the HMD evaluation immune to the variation in thickness of the protection coating, is introduced and analyzed through simulations involving HMD with variable depths and conductivities. A fast inverse method employing magnitude and time of the LOI point in GPEC signals for simultaneously evaluating the conductivity and thickness of HMD region is proposed, and subsequently verified by finite element modeling and experiments. It has been found from the results that along with the proposed inverse method the GPEC probe is applicable to evaluation of HMD in coated conductive structures without much loss in accuracy.
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11
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van Houdt CIA, Preethanath RS, van Oirschot BAJA, Zwarts PHW, Ulrich DJO, Anil S, Jansen JA, van den Beucken JJJP. Toward accelerated bone regeneration by altering poly(D,L-lactic-co-glycolic) acid porogen content in calcium phosphate cement. J Biomed Mater Res A 2015; 104:483-92. [PMID: 26454146 DOI: 10.1002/jbm.a.35584] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 09/26/2015] [Accepted: 10/08/2015] [Indexed: 01/18/2023]
Abstract
This work aimed to compare in vitro degradation of dense PLGA microspheres and milled PLGA particles as porogens within CPC, considering that the manufacturing of milled PLGA is more cost-effective when compared with PLGA microspheres. Additionally, we aimed to examine the effect of porogen amount within CPC/PLGA on degradation and bone formation. Our in vitro results showed no differences between both forms of PLGA particles (as porogens in CPC; spherical for microspheres, irregular for milled) regarding morphology, porosity, and degradation. Using milled PLGA as porogens within CPC/PLGA, we evaluated the effect of porogen amount on degradation and bone forming capacity in vivo. Titanium landmarks surrounded by CPC/PLGA with 30 and 50 wt % PLGA, were implanted in forty femoral bone defects of twenty male Wistar rats. Histomorphometrical results showed a significant temporal decrease in the amount of CPC, for both formulas, and confirmed that 50 wt % PLGA degrades faster than 30 wt%, and allows for a 1.5-fold higher amount of newly formed bone. Taken together, this study demonstrated that (i) milled PLGA particles perform equal to PLGA microspheres, and (ii) tuning of the PLGA content in CPC/PLGA is a feasible approach to leverage material degradation and bone formation.
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Affiliation(s)
- C I A van Houdt
- Department of Biomaterials, Radboudumc university medical center, Nijmegen, The Netherlands
| | - R S Preethanath
- Department of Biomaterials, Radboudumc university medical center, Nijmegen, The Netherlands.,Department of Periodontics and Community Dentistry, King Saud University, Riyadh, Saudi Arabia
| | - B A J A van Oirschot
- Department of Biomaterials, Radboudumc university medical center, Nijmegen, The Netherlands
| | - P H W Zwarts
- Department of Biomaterials, Radboudumc university medical center, Nijmegen, The Netherlands
| | - D J O Ulrich
- Department of Plastic and Reconstructive Surgery, Radboudumc, Nijmegen, The Netherlands
| | - S Anil
- Department of Periodontics and Community Dentistry, King Saud University, Riyadh, Saudi Arabia
| | - J A Jansen
- Department of Biomaterials, Radboudumc university medical center, Nijmegen, The Netherlands
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