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Kaishu Guan - One of the best experts on this subject based on the ideXlab platform.
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A procedure for predicting strength properties using small Punch Test and finite element simulation
International Journal of Mechanical Sciences, 2019Co-Authors: Jiru Zhong, Kaishu Guan, Tong Xu, Jerzy A. SzpunarAbstract:Abstract Developing a universal approach for acquiring yield strength and ultimate tensile strength by small Punch Test (SPT) is a long-standing challenge. In this paper, a methodology is proposed to obtain strength properties of bulk materials from SPT results. It involves extracting true stress–strain curves from SPT data using iterative finite element simulation. Acquired curves show that initial yield stress cannot be reproduced. This is attributed to the inhomogeneous deformation of SPT specimens. Finite element simulations were then conducted on tensile Tests with the extracted true stress–strain curves to obtain strength. Results indicate that predicted strength shows a convergent tendency with the times of iterative finite element simulation. An approach is proposed to process the predicted strength, based on data analysis. The acquired strength properties are in good agreement with those obtained by standard tensile Testing. This is an entirely novel procedure that predicts reliable tensile properties via a single SPT run. It can be employed with confidence to cases for which standard tensile Testing is impractical.
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Study on Temper Embrittlement and Hydrogen Embrittlement of a Hydrogenation Reactor by Small Punch Test
MDPI AG, 2017Co-Authors: Kaishu Guan, Jerzy A. Szpunar, Karel Matocha, Duwei WangAbstract:The study on temper embrittlement and hydrogen embrittlement of a Test block from a 3Cr1Mo1/4V hydrogenation reactor after ten years of service was carried out by small Punch Test (SPT) at different temperatures. The SPT fracture energy Esp (derived from integrating the load-displacement curve) divided by the maximum load (Fm) of SPT was used to fit the Esp/Fm versus-temperature curve to determine the energy transition temperature (Tsp) which corresponded to the ductile-brittle transition temperature of the Charpy impact Test. The results indicated that the ratio of Esp/Fm could better represent the energy of transition in SPT compared with Esp. The ductile-to-brittle transition temperature of the four different types of materials was measured using the hydrogen charging Test by SPT. These four types of materials included the base metal and the weld metal in the as-received state, and the base metal and the weld metal in the de-embrittled state. The results showed that there was a degree of temper embrittlement in the base metal and the weld metal after ten years of service at 390 °C. The specimens became slightly more brittle but this was not obvious after hydrogen charging. Because the toughness of the material of the hydrogenation reactor was very good, the flat samples of SPT could not characterize the energy transition temperature within the liquid nitrogen temperature. Additionally, there was no synergetic effect of temper embrittlement and hydrogen embrittlement found in 3Cr1Mo1/4V steel
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deciphering deviation in mechanical properties of differently processed aisi 316l austenitic stainless steel using the small Punch Test
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Ming Song, W Qin, J A Szpunar, N P Gurao, Kaishu GuanAbstract:Abstract Suitability of small Punch Test (SPT) was studied by determining the mechanical behaviors of AISI 316L austenitic stainless steel samples with different crystallographic textures and similar grain size prepared by different modes of rolling and annealing treatment. It was demonstrated that SPT can capture differences in mechanical properties that arises from different crystallographic textures. Such capacity can be attributed to higher length scales involved in SPT which enables it to capture the effect of texture unlike routine micro-hardness measurements. It is also shown that important additional information like rate of strain hardening and mode of fracture that can be obtained from SPT is consistent with results expected from conventional tensile Test.
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size effect criteria on the small Punch Test for aisi 316l austenitic stainless steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Kaishu Guan, Ming Song, W Qin, J A Szpunar, Ji ChenAbstract:Abstract The miniature specimen Test technique has been extensively studied for quantifying the properties of bulk materials with greatly reduced volume recently. In this paper small Punch Test (SPT) is used to evaluate effects of specimen thickness, grain size and thickness-to-grain size ratio (TGR) on mechanical properties of 25 samples of type 316L austenitic stainless steel with nearly the same crystallographic texture. Effective SPT yield and maximum loads were measured and correlated with yield and ultimate strengths of conventional tensile Test. The results show that SPT is sensitive not only to grain size, but also to thickness and TGR. Size effects exist between SPT and standard-sized samples. The present work gives a size effect criterion of SPT for engineering application. In addition, the underlying mechanisms of these size effects are provided.
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evaluation of stress corrosion cracking susceptibility of nanocrystallized stainless steel 304l welded joint by small Punch Test
Materials & Design, 2013Co-Authors: Tao Bai, Kaishu GuanAbstract:Abstract A small Punch Test (SPT) was carried out to evaluate the stress corrosion cracking (SCC) susceptibility of nanocrystallized stainless steel (SS) 304L welded joint in 1 mol/L NaCl + 0.5 mol/L HCl aq. The surface mechanical attrition treatment (SMAT) was applied to realize the surface naocrystallization (SNC). Mechanical properties and micro-structural evolutions of S nanocrystallized SS 304L welded joint were investigated through optical microscopy (OM), X-ray diffraction (XRD), micro-Vickers hardness Test and transmission electron microscopy (TEM). The SPT was conducted in both ambient air and corrosive solution at the loading rate 3 × 10 −3 mm/min, and SNC phenomena were observed at the welded seam (WS) and heat affected zone (HAZ) after SMAT. The results show that for both HAZ and WS materials, specimens with 30 min SMAT have higher hardness, higher yield strength, and lower ductility than the as-received counterparts in ambient air. After SPT in the corrosive solution, the as-received HAZ specimen showed a mixed type of both the intergranular SCC (IGSCC) and transgranular cleavage fracture; The SMAT sample shows a typical intergranular stress corrosion cracking (IGSCC) mode with a higher SCC susceptibility. Neither the as-received nor the SMAT WS specimen showed significant SCC susceptibility, they had the similar fractures with their counterparts in ambient air.
Allan Avram Edidin - One of the best experts on this subject based on the ideXlab platform.
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miniature specimen shear Punch Test for uhmwpe used in total joint replacements
Biomaterials, 2002Co-Authors: S M Kurtz, C W Jewett, Jude R Foulds, J S Bergstrom, Allan Avram EdidinAbstract:Abstract Despite the critical role that shear is hypothesized to play in the damage modes that limit the performance of total hip and knee replacements, the shear behavior of ultra-high molecular weight polyethylene (UHMWPE) remains poorly understood, especially after oxidative degradation or radiation crosslinking. In the present study, we developed the miniature specimen (0.5 mm thickness×6.4 mm diameter) shear Punch Test to evaluate the shear behavior of UHMWPE used in total joint replacement components. We investigated the shear Punch behavior of virgin and crosslinked stock materials, as well as of UHMWPE from tibial implants that were gamma-irradiated in air and shelf aged for up to 8.5 years. Finite element analysis, scanning electron microscopy, and interrupted Testing were conducted to aid in the interpretation of the shear Punch load–displacement curves. The shear Punch load–displacement curves exhibited similar distinctive features. Following toe-in, the load–displacement curves were typically bilinear, and characterized by an initial stiffness, a transition load, a hardening stiffness, and a peak load. The finite element analysis established that the initial stiffness was proportional to the elastic modulus of the UHMWPE, and the transition load of the bilinear curve reflected the development of a plastically deforming zone traversing through the thickness of the sample. Based on our observations, we propose two interpretations of the peak load during the shear Punch Test: one theory is based on the initiation of crystalline plasticity, the other based on the transition from shear to tension during the Tests. Due to the miniature specimen size, the shear Punch Test offers several potential advantages over bulk Test methods, including the capability to directly measure shear behavior, and quite possibly infer ultimate uniaxial behavior as well, from shelf aged and retrieved UHMWPE components. Thus, the shear Punch Test represents an effective and complementary new tool in the armamentarium of miniature specimen mechanical Testing methods for UHMWPE used in total joint replacement components.
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a small Punch Test technique for characterizing the elastic modulus and fracture behavior of pmma bone cement used in total joint replacement
Biomaterials, 2001Co-Authors: Virginia L Giddings, S M Kurtz, C W Jewett, Jude R Foulds, Allan Avram EdidinAbstract:Polymethylmethacrylate (PMMA) bone cement is used in total joint replacements to anchor implants to the underlying bone. Establishing and maintaining the integrity of bone cement is thus of critical importance to the long-term outcome of joint replacement surgery. The goal of the present study was to evaluate the suitability of a novel Testing technique, the small Punch or miniaturized disk bend Test, to characterize the elastic modulus and fracture behavior of PMMA. We investigated the hypothesis that the crack initiation behavior of PMMA during the small Punch Test was sensitive to the Test temperature. Miniature disk-shaped specimens, 0.5 mm thick and 6.4 mm in diameter, were prepared from PMMA and Simplex-P bone cement according to manufacturers' instructions. Testing was conducted at ambient and body temperatures, and the effect of Test temperature on the elastic modulus and fracture behavior was statistically evaluated using analysis of variance. For both PMMA materials, the Test temperature had a significant effect on elastic modulus and crack initiation behavior. At body temperature, the specimens exhibited "ductile" crack initiation, whereas at room temperature "brittle" crack initiation was observed. The small Punch Test was found to be a sensitive and repeatable Test method for evaluating the mechanical behavior of PMMA. In light of the results of this study, future small Punch Testing should be conducted at body temperature.
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influence of mechanical behavior on the wear of 4 clinically relevant polymeric biomaterials in a hip simulator
Journal of Arthroplasty, 2000Co-Authors: Allan Avram Edidin, S M KurtzAbstract:Abstract The elastic and large-deformation mechanical behavior of 4 materials with known clinical performance was examined and correlated with the wear behavior in a hip simulator. Acetabular liners of a commercially available design were machined from ultra-high molecular weight polyethylene (UHMWPE), high-density polyethylene (HDPE), polytetrafluoroethylene (PTFE), and polyacetal and wear Tested in a multidirectional hip joint simulator. Elastic and large-deformation mechanical behavior was directly measured from the wear-Tested liners using the small Punch Test. The finite element method was used to compute elastic modulus from the measured small Punch Test initial stiffness, and the contact stress for the liners was calculated using the theory of elasticity solution. Positive, statistically significant correlations were observed between the hip simulator wear rate and the initial peak load, ultimate load, and work to failure from the small Punch Test. Negative correlations were observed between the wear rate and the elastic modulus and contact stress. The results of this study support the hypothesis that the large-deformation mechanical behavior of a polymer plays a greater role in the wear mechanisms prevalent in total hip replacements than the elastic behavior.
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radiation and chemical crosslinking promote strain hardening behavior and molecular alignment in ultra high molecular weight polyethylene during multi axial loading conditions
Biomaterials, 1999Co-Authors: Steven M Kurtz, Leslie A Pruitt, C W Jewett, Jude R Foulds, Allan Avram EdidinAbstract:The mechanical behavior and evolution of crystalline morphology during large deformation of eight types of virgin and crosslinked ultra high molecular weight polyethylene (UHMWPE) were studied using the small Punch Test and transmission electron microscopy (TEM). We investigated the hypothesis that both radiation and chemical crosslinking hinder molecular mobility at large deformations, and hence promote strain hardening and molecular alignment during the multiaxial loading of the small Punch Test. Chemical crosslinking of UHMWPE was performed using 0.25% dicumyl peroxide (GHR 8110, GUR 1020 and 1050), and radiation crosslinking was performed using 150 kGy of electron beam radiation (GUR 1150). Crosslinking increased the ultimate load at failure and decreased the ultimate displacement of the polyethylenes during the small Punch Test. Crosslinking also increased the near-ultimate hardening behavior of the polyethylenes. Transmission electron microscopy was used to characterize the crystalline morphology of the bulk material, undeformed regions of the small Punch Test specimens, and deformed regions of the specimens oriented perpendicular and parallel to the Punch direction. In contrast with the virgin polyethylenes, which showed only subtle evidence of lamellar alignment, the crosslinked polyethylenes exhibited enhanced crystalline lamellae orientation after the small Punch Test, predominantly in the direction parallel to the Punch direction or deformation axis. Thus, the results of this study support the hypothesis that crosslinking promotes strain hardening during multiaxial loading because of increased resistance to molecular mobility at large deformations effected by molecular alignment. The data also illustrate the sensitivity of large deformation mechanical behavior and crystalline morphology to the method of crosslinking and resin of polyethylene.
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a miniature specimen mechanical Testing technique scaled to articulating surface of polyethylene components for total joint arthroplasty
Journal of Biomedical Materials Research, 1999Co-Authors: S M Kurtz, C W Jewett, Jude R Foulds, Allan Avram EdidinAbstract:The small Punch Test was developed to investigate the mechanical behavior of polyethylene using miniature specimens (<14 mg) measuring 0.5 mm in thickness and 6.4 mm in diameter. The objective of this study was to demonstrate the feasibility and reproducibility of the small Punch Test when applied to clinically relevant polyethylenes. Mechanical behavior was characterized during 66 Tests performed on GUR4150HP and GUR4120 specimens following alternate sterilization methods and 4 weeks of accelerated aging at 80°C. The small Punch Test was found to be highly reproducible with regard to characterizing the ductility, ultimate strength, and fracture resistance of sterilized and aged polyethylene. In the future, the small Punch Test can be used to directly measure mechanical properties near the articulating surface of retrieved components. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 48: 75–81, 1999
C Rodríguez - One of the best experts on this subject based on the ideXlab platform.
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analysis of key factors of hydrogen environmental assisted cracking evaluation by small Punch Test on medium and high strength steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: B Arroyo, R Lacalle, Trinidad Garcia, J A Alvarez, C Uribe, C RodríguezAbstract:Abstract In this paper, the response of a high-strength and a mid-strength steel in response to hydrogen embrittlement processes are analyzed by means of the quasi-non-destructive Test known as the small Punch Test (SPT). The SPT has been successfully employed in the evaluation of tensile properties, creep behavior, fracture, and some recent research proposes that it might be applied for the determination of mechanical properties in brittle scenarios. In a first stage, standardized hydrogen embrittlement and stress corrosion cracking Testing techniques have been applied, confirming some of their disadvantages, and the SPT has been proposed as a simple and economic alternative when it is not possible to carry them out. It is recommended to use the SPT under static load, with the specimen pre-charged and submerged in the environment during the whole Test. The study is completed with hydrogen content measurements. Based on the experimental results of slow strain rate Tests (SSRT), and the SPT performed under static load in embrittlement environments, it was proved that the SPT Punch displacement versus time to rupture curve has the same typology as the usual creep curves. Inspired on SPT creep methodologies, a simple and effective way to correlate the results of SPT and conventional Tests in embrittlement situations is proposed. It is based on matching the same breaking times in both types of Tests when performed under the same environment to obtain the rupture stress from the static loads applied in SPT Tests. Subsequently, it is proved that for the aforementioned situations, the numerical value of the deformation rate (uniaxial Test) and the Punch rate (SPT) that take place during these two Tests will be alike for similar rupture times. Finally it is pointed that when the uniaxial slow strain rate Test maximum stress and the SPT static load have a similar numerical value, the deformation rate (SSRT) and the Punch rate (SPT) will be related, thus providing a simple way to estimate deformation rates using SPT instead of conventional SSRT Tests.
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application of the miniature small Punch Test for the mechanical characterization of polymer materials
Theoretical and Applied Fracture Mechanics, 2016Co-Authors: C Rodríguez, I I Cuesta, Ll M Maspoch, F.j. BelzunceAbstract:The aim of this paper is to demonstrate the applicability of the Small Punch Test (SPT) in the mechanical characterization of polymers, following previous achievements in metallic materials. For this purpose, different polymers with a wide variation of tensile properties were examined. The applicability of this type of Test to characterize polymeric materials is especially interesting when these products are in the form of films, as their greatly reduced thickness enables an easy preparation of the SPT specimens. All the polymer materials were characterized by means of small Punch and tensile Tests. The tensile stress-strain curves were compared with the load-displacement SPT curves and the representative SPT parameters were defined accordingly. A good correspondence was found between the tensile elastic modulus and the initial slope of the SPT plot (Slopeini/t), with t being the specimen thickness, and a good correlation was also observed between the tensile yield strength and the SPT Pym/t2 parameter. On the contrary, no corresponding relationship was found to predict the ultimate tensile strength or the failure elongation, since these properties depend greatly on the stress state of the Test (uniaxial or biaxial).
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small Punch Test methodologies for the analysis of the hydrogen embrittlement of structural steels
Theoretical and Applied Fracture Mechanics, 2016Co-Authors: C Rodríguez, F.j. Belzunce, Trinidad Garcia, B Arroyo, J A AlvarezAbstract:Abstract In the present study, a new small Punch Test (SPT) methodology has been used to analyse the effect of hydrogen embrittlement on the tensile properties of three different grades of CrMoV steel: the base metal (CrMoV-1), weld metal (CrMoV-2) and this same weld metal subjected to an intermediate heat treatment (CrMoV-3). SPT results were compared with those obtained in standard tensile Tests carried out in a hydrogen environment. Moreover, a new SPT methodology was used to analyse the environmental effects on a CrNiMn steel under cathodic protection and cathodic charge. Results obtained shows the usefulness of the SPT to estimate the grade of deterioration induced by hydrogen embrittlement, especially when a lack of Testing material makes impossible the Test of standard specimens.
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effect of hydrogen embrittlement on the tensile properties of crmov steels by means of the small Punch Test
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: T.e. García, C Rodríguez, F.j. Belzunce, I I CuestaAbstract:Abstract In the present study, a new small Punch Test (SPT) methodology has been used to analyse the effect of hydrogen embrittlement on the tensile properties of three different grades of CrMoV steel: the base metal (CrMoV-1), weld metal (CrMoV-2) and this same weld metal subjected to an intermediate heat treatment (CrMoV-3). SPT results were compared with those obtained in standard tensile Tests carried out in a hydrogen environment. The SPT was fully able to detect the deterioration induced by hydrogen in all steels. However, a higher level of embrittlement was obtained in the tensile Tests. Furthermore, due to the aggressiveness of the environment meant, it was not possible to compare the results for CrMoV-2, which is highly susceptible to embrittlement due to its microstructure composed of low tempered bainite. As regards CrMoV-1 and CrMoV-3, the results obtained by means of the SPT fully agreed with those obtained in the tensile Tests. It was observed that the poor behaviour of CrMoV-2 in a hydrogen environment was improved by applying a heat treatment of 680 °C for 4 h (CrMoV-3), although the excellent performance of CrMoV-1 when in contact with hydrogen was not achieved. The feasibility of the small Punch Test to estimate the deterioration of the tensile mechanical properties of CrMoV steels due to hydrogen embrittlement has been demonstrated.
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fracture toughness characterization through notched small Punch Test specimens
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Emilio Martinezpaneda, T.e. García, C RodríguezAbstract:Abstract In this work a novel methodology for fracture toughness characterization by means of the small Punch Test (SPT) is presented. Notched specimens are employed and fracture resistance is assessed through a critical value of the notch mouth displacement δ SPT . Finite element simulations and interrupted experiments are used to track the evolution of δ SPT as a function of the Punch displacement. The onset of crack propagation is identified by means of a ductile damage model and the outcome is compared to the crack tip opening displacement estimated from conventional Tests at crack initiation. The proposed numerical–experimental scheme is examined with two different grades of CrMoV steel and the differences in material toughness captured. Limitations and uncertainties arising from the different damage phenomena observed in the lowest toughness material examined are thoroughly discussed.
Ming Song - One of the best experts on this subject based on the ideXlab platform.
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deciphering deviation in mechanical properties of differently processed aisi 316l austenitic stainless steel using the small Punch Test
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Ming Song, W Qin, J A Szpunar, N P Gurao, Kaishu GuanAbstract:Abstract Suitability of small Punch Test (SPT) was studied by determining the mechanical behaviors of AISI 316L austenitic stainless steel samples with different crystallographic textures and similar grain size prepared by different modes of rolling and annealing treatment. It was demonstrated that SPT can capture differences in mechanical properties that arises from different crystallographic textures. Such capacity can be attributed to higher length scales involved in SPT which enables it to capture the effect of texture unlike routine micro-hardness measurements. It is also shown that important additional information like rate of strain hardening and mode of fracture that can be obtained from SPT is consistent with results expected from conventional tensile Test.
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size effect criteria on the small Punch Test for aisi 316l austenitic stainless steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Kaishu Guan, Ming Song, W Qin, J A Szpunar, Ji ChenAbstract:Abstract The miniature specimen Test technique has been extensively studied for quantifying the properties of bulk materials with greatly reduced volume recently. In this paper small Punch Test (SPT) is used to evaluate effects of specimen thickness, grain size and thickness-to-grain size ratio (TGR) on mechanical properties of 25 samples of type 316L austenitic stainless steel with nearly the same crystallographic texture. Effective SPT yield and maximum loads were measured and correlated with yield and ultimate strengths of conventional tensile Test. The results show that SPT is sensitive not only to grain size, but also to thickness and TGR. Size effects exist between SPT and standard-sized samples. The present work gives a size effect criterion of SPT for engineering application. In addition, the underlying mechanisms of these size effects are provided.
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assessment of toughness in long term service crmo low alloy steel by fracture toughness and small Punch Test
Nuclear Engineering and Design, 2011Co-Authors: Kaishu Guan, Li Hua, Qiongqi Wang, Xiaohui Zou, Ming SongAbstract:Abstract Small Punch Test (SPT) is a miniature sample Test technique which can evaluate in-service material properties with an almost non-destructive method. In this paper, the 2.25Cr1Mo steel samples serviced for 10 years in hydrogenation reactor (with temper embrittlement), 1.25Cr0.5Mo supper-pressure vapor pipe serviced for 14 years at 520 °C and several other low alloy steels have been studied by JIC fracture toughness and SPT. The linear relationship between the small Punch (SP) equivalent fracture strain and the fracture toughness of JIC was created. The correlations applied to the experimental data indicated advantages of using SPT for the determining fracture toughness of in-serviced low alloy steels. Additionally, size affects the fracture pattern. Small Punch samples of small size show dimple fractures whereas large fracture toughness samples show quasi-cleavage fractures.
S M Kurtz - One of the best experts on this subject based on the ideXlab platform.
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miniature specimen shear Punch Test for uhmwpe used in total joint replacements
Biomaterials, 2002Co-Authors: S M Kurtz, C W Jewett, Jude R Foulds, J S Bergstrom, Allan Avram EdidinAbstract:Abstract Despite the critical role that shear is hypothesized to play in the damage modes that limit the performance of total hip and knee replacements, the shear behavior of ultra-high molecular weight polyethylene (UHMWPE) remains poorly understood, especially after oxidative degradation or radiation crosslinking. In the present study, we developed the miniature specimen (0.5 mm thickness×6.4 mm diameter) shear Punch Test to evaluate the shear behavior of UHMWPE used in total joint replacement components. We investigated the shear Punch behavior of virgin and crosslinked stock materials, as well as of UHMWPE from tibial implants that were gamma-irradiated in air and shelf aged for up to 8.5 years. Finite element analysis, scanning electron microscopy, and interrupted Testing were conducted to aid in the interpretation of the shear Punch load–displacement curves. The shear Punch load–displacement curves exhibited similar distinctive features. Following toe-in, the load–displacement curves were typically bilinear, and characterized by an initial stiffness, a transition load, a hardening stiffness, and a peak load. The finite element analysis established that the initial stiffness was proportional to the elastic modulus of the UHMWPE, and the transition load of the bilinear curve reflected the development of a plastically deforming zone traversing through the thickness of the sample. Based on our observations, we propose two interpretations of the peak load during the shear Punch Test: one theory is based on the initiation of crystalline plasticity, the other based on the transition from shear to tension during the Tests. Due to the miniature specimen size, the shear Punch Test offers several potential advantages over bulk Test methods, including the capability to directly measure shear behavior, and quite possibly infer ultimate uniaxial behavior as well, from shelf aged and retrieved UHMWPE components. Thus, the shear Punch Test represents an effective and complementary new tool in the armamentarium of miniature specimen mechanical Testing methods for UHMWPE used in total joint replacement components.
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a small Punch Test technique for characterizing the elastic modulus and fracture behavior of pmma bone cement used in total joint replacement
Biomaterials, 2001Co-Authors: Virginia L Giddings, S M Kurtz, C W Jewett, Jude R Foulds, Allan Avram EdidinAbstract:Polymethylmethacrylate (PMMA) bone cement is used in total joint replacements to anchor implants to the underlying bone. Establishing and maintaining the integrity of bone cement is thus of critical importance to the long-term outcome of joint replacement surgery. The goal of the present study was to evaluate the suitability of a novel Testing technique, the small Punch or miniaturized disk bend Test, to characterize the elastic modulus and fracture behavior of PMMA. We investigated the hypothesis that the crack initiation behavior of PMMA during the small Punch Test was sensitive to the Test temperature. Miniature disk-shaped specimens, 0.5 mm thick and 6.4 mm in diameter, were prepared from PMMA and Simplex-P bone cement according to manufacturers' instructions. Testing was conducted at ambient and body temperatures, and the effect of Test temperature on the elastic modulus and fracture behavior was statistically evaluated using analysis of variance. For both PMMA materials, the Test temperature had a significant effect on elastic modulus and crack initiation behavior. At body temperature, the specimens exhibited "ductile" crack initiation, whereas at room temperature "brittle" crack initiation was observed. The small Punch Test was found to be a sensitive and repeatable Test method for evaluating the mechanical behavior of PMMA. In light of the results of this study, future small Punch Testing should be conducted at body temperature.
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influence of mechanical behavior on the wear of 4 clinically relevant polymeric biomaterials in a hip simulator
Journal of Arthroplasty, 2000Co-Authors: Allan Avram Edidin, S M KurtzAbstract:Abstract The elastic and large-deformation mechanical behavior of 4 materials with known clinical performance was examined and correlated with the wear behavior in a hip simulator. Acetabular liners of a commercially available design were machined from ultra-high molecular weight polyethylene (UHMWPE), high-density polyethylene (HDPE), polytetrafluoroethylene (PTFE), and polyacetal and wear Tested in a multidirectional hip joint simulator. Elastic and large-deformation mechanical behavior was directly measured from the wear-Tested liners using the small Punch Test. The finite element method was used to compute elastic modulus from the measured small Punch Test initial stiffness, and the contact stress for the liners was calculated using the theory of elasticity solution. Positive, statistically significant correlations were observed between the hip simulator wear rate and the initial peak load, ultimate load, and work to failure from the small Punch Test. Negative correlations were observed between the wear rate and the elastic modulus and contact stress. The results of this study support the hypothesis that the large-deformation mechanical behavior of a polymer plays a greater role in the wear mechanisms prevalent in total hip replacements than the elastic behavior.
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a miniature specimen mechanical Testing technique scaled to articulating surface of polyethylene components for total joint arthroplasty
Journal of Biomedical Materials Research, 1999Co-Authors: S M Kurtz, C W Jewett, Jude R Foulds, Allan Avram EdidinAbstract:The small Punch Test was developed to investigate the mechanical behavior of polyethylene using miniature specimens (<14 mg) measuring 0.5 mm in thickness and 6.4 mm in diameter. The objective of this study was to demonstrate the feasibility and reproducibility of the small Punch Test when applied to clinically relevant polyethylenes. Mechanical behavior was characterized during 66 Tests performed on GUR4150HP and GUR4120 specimens following alternate sterilization methods and 4 weeks of accelerated aging at 80°C. The small Punch Test was found to be highly reproducible with regard to characterizing the ductility, ultimate strength, and fracture resistance of sterilized and aged polyethylene. In the future, the small Punch Test can be used to directly measure mechanical properties near the articulating surface of retrieved components. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 48: 75–81, 1999
