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Papers by Jeremy Seidt

An Experimental Investigation of the Influence of the State of Stress on the Ductile Fracture of 2024-T351 Aluminum

Journal of Engineering Materials and Technology

This paper investigates the influence of stress state on the equivalent plastic fracture strain i... more This paper investigates the influence of stress state on the equivalent plastic fracture strain in 2024-T351 aluminum alloy. Eighteen unique stress states at failure—with triaxialities ranging from 0.388 (compressive) to −0.891 (tensile) and Lode parameters ranging from −0.978 to 1.000—are explored through mechanical experiments on 2024-T351 aluminum specimens with various geometries under multiple loading conditions. These include tension tests of plane stress (thin), plane strain (thick), and axisymmetric specimens, as well as pure shear and combined axial–torsional loading on thin-walled tubes. Using a hybrid numerical–experimental approach, the dependence of fracture strain on stress triaxiality and Lode parameter is quantified for each experiment. Fracture strains are measured using three-dimensional digital image correlation. Equivalent plastic fracture strain for 2024-T351 generally increases with stress triaxiality (moving toward a more compressive state). Fracture strain de...

Dynamic Mechanical Response of T800/F3900 Composite Under Tensile and Compressive Loading

Dynamic Behavior of Materials, Volume 1, 2018

The effect of strain rate on the mechanical response of T800/F3900, a strengthened epoxy carbon-f... more The effect of strain rate on the mechanical response of T800/F3900, a strengthened epoxy carbon-fiber reinforced polymer, is studied by conducting compression and tensile tests at different strain rates. Low strain rate tests (0.001 s−1 and 1 s−1) are done using a hydraulic frame and high strain rate tests (300 s−1–600 s−1) are done with the SHB technique. Digital Image Correlation is used in all tests to obtain full-field strain measurements. Tension tests have been done on unidirectional laminates in the 90 ° direction. Compression tests have been done on unidirectional laminates in the 90 ° and through the thickness directions. No or small strain rate effect is observed between the low strain rate tests. The results from the high strain rate tests show significant strain rate effects.

An Efficient Iterative Approach for Determining the Post-Necking True Stress-Strain Response of Aerospace Metals

To numerically simulate the plastic deformation of aerospace metals during extreme events (e.g., ... more To numerically simulate the plastic deformation of aerospace metals during extreme events (e.g., turbine engine blade-out/rotor-burst events and automotive crashworthiness assessment), accurate experimental knowledge of the metal’s hardening behavior at large strains is requisite. Tensile tests on thin (plane stress) specimens are frequently used for this purpose, with the metal’s large-strain plasticity ultimately captured by an equivalent true stress vs. equivalent true plastic strain curve. It is now well known that if axial strain is measured using an extensometer (either physical or virtual), the equivalent true stress-strain curve is valid only up to the onset of diffuse necking, when the strain field heterogeneously localizes in the specimen gage. A number of approaches have been proposed to correct the post-necking strain hardening response. Perhaps the most widely used technique involves inputting a suite of candidate post-necking true stress-strain curves into finite-element software; a tensile test simulation is run for each candidate curve, and the curve that produces the best agreement between simulation and experiment is ultimately adopted. In this talk, a novel variation of this iterative approach is presented that addresses some of its key deficiencies. Notably, we use local/pointwise in-plane Hencky (true) strain data from digital image correlation to generate an upper bound for the iterative simulation process, resulting in an efficient and computationally inexpensive post-necking correction procedure. Our approach is successfully demonstrated using experimental data for both wrought and additively manufactured Ti-6Al-4V titanium alloy.https://ecommons.udayton.edu/stander_posters/2855/thumbnail.jp

Full-Field Mechanical and Thermal Strain-Rate Dependence of CFRP Laminates

The aim of the project is to characterize the strain rate dependence of a representative carbon f... more The aim of the project is to characterize the strain rate dependence of a representative carbon fiber reinforced polymer unidirectional laminate for thermal and mechanical properties. Digital image correlation is used to obtain full-field deformation and thermal effects of CFRP samples at strain rates of 0.001 s−1, 1 s−1, 100 s−1, and 1000 s−1. A combination of hydraulic load frame and split-hopkinson bar tests are used to load samples while optical and IR imaging is used to obtain deformation and thermal footage. Strain rate dependence is known to occur in the clear-cast polymer material, and is not prevalent in the carbon fiber material. Therefore, the strain rate dependence of the CFRP at varying orientations and loading conditions including tension, compression, and shear are of interest. Initial results show strong strain rate dependence in the polymer-dominated 90° orientation and clear-cast specimens.

Failure Testing Under In-Plane Biaxial Tension and Out-of-Plane Compression

Fracture, Fatigue, Failure and Damage Evolution, Volume 6, 2018

The deformation and failure behavior of 2024 aluminum was investigated under combined in-plane eq... more The deformation and failure behavior of 2024 aluminum was investigated under combined in-plane equi-biaxial tension and out-of-plane compression. This loading configuration yields stress states of Lode parameter = −1 and triaxialities ranging from −0.67 to 0.17. Testing was performed using a variation of the standard ASTM quasi-static hemispherical punch test, with a reduced punch diameter and the addition of an annealed copper backing plate behind the specimen. The reported stress states at the failure point were then determined numerically using LS-DYNA.

The deformation and failure of metals and composites is known to be affected by strain rate and t... more The deformation and failure of metals and composites is known to be affected by strain rate and temperature. Material models in LS-DYNA® account for these effects and material coupon testing is required for determining the input parameters for the models. The present paper presents a new experimental setup that provide means for investigating the coupled effects of temperature and strain rate during plastic deformation, and new strain rate sensitivity data for fibrous composites that was obtained from static and dynamic tests. Although coupled, the effects of strain rate and temperature are usually determined separately in tests at different strain rates and different initial temperatures, neglecting temperature increase that might be taking place during the deformation. In the present paper a new experimental setup is introduced in which full-field deformation and full-field temperature are measured simultaneously during tensile tests in various strain rates (including high strain ...

Journal of Physics: Conference Series, 2018

Extensive material testing is required for setting up, calibration and validation newly-developed... more Extensive material testing is required for setting up, calibration and validation newly-developed material models for dynamic plastic deformation and fracture. One example is the material models MAT224 and MAT264 in the LS-DYNA code which are extension of the Johnson-Cook viscoplastic damage model. The tabulated form of these models extends their validity to a wide range of loading conditions, strain rates, temperatures, and fracture modes, but requires data from many experiments to setup. This paper describes the experiments that were used and new experiments that have been developed during the development of these material models. It includes compression, tension, and shear tests over a wide range of strain rates, including high strain rates using the Split Hopkinson bar (SHB) technique. Quasi-static and dynamic continuous and interrupted punch tests that include 3D DIC strain measurement of the deformation at the back surface of the specimen during the test. Tensile tests over wide range of strain rates (including SHB experiments) in which full-field deformation (using DIC) and full-filed temperature (using very high speed IR camera) are measured simultaneously during the experiment. Data from testing at various strain rates, various temperatures, and different specimen geometries is used for setting up the plasticity material model, and a failure surface that gives the equivalent plastic fracture strain as a function of triaxiality and the Lode parameter. Punch tests with different punch geometries that produce different failure modes are used for validating the plasticity-failure model. The setup of the dynamic punch test is shown in Figure 1. The specimen is mounted on the transmission bar of a compression SHB apparatus with a holder that provide optical path to two high-speed cameras to the back surface of the specimen. The punch is attached to the input bar. A specimen following a test and a sample of data is shown in Figure 2. DIC images that show the history of the maximum strain measured on the back surface of the specimen during the test are shown in Figure 3.

The International Journal of Prosthodontics, 2021

T he goal of an interim implant-supported, fixed, complete-arch prosthesis (ISFCAP) is to fulfill... more T he goal of an interim implant-supported, fixed, complete-arch prosthesis (ISFCAP) is to fulfill the patient's esthetic and functional needs without biologic or technical complications until the definitive prosthesis is placed. 1-4 An interim ISFCAP needs to withstand masticatory forces during the osseointegration period, 1,5 and so an interim ISFCAP should have adequate strength, especially when used in cantilevered situations. 1,6-8 Conventionally, interim ISFCAPs have been fabricated from autopolymerized or heat-polymerized polymethyl methacrylate (PMMA) acrylic resin. 1,9 Despite their common use, fractures have been reported in clinical studies with varying frequency. 1,9 Therefore, reinforcing with fiber meshes, metallic bars, or metal wires has been reported to improve fracture and impact strength of the conventional interim Purpose: To analyze the load to failure of different CAD/CAM high-density polymers (HDPs) and zirconia when titanium (Ti) bases were included in a cantilevered situation. Materials and Methods: Five specimens were fabricated from five different CAD/CAM polymethyl methacrylate (PMMA) HDPs (Copratemp [CT]; Tempo-CAD [TC]; Solid Shade PMMA Disc [TD]; M-PM Disc pink [MPM]; M-PM Disc white [MPMW]), and five specimens were prepared from an yttrium-stabilized tetragonal zirconia (3Y-TZP; FireZr [FZR]; control). Ti bases (D Master Dental Implants) were cemented onto the specimens (8 mm thick × 7 mm wide × 30 mm long). Each specimen was fixated using a clamp for a cantilever loading distance of 10 mm. The load was applied on the cantilever until failure, and the maximum load to failure values (N) were analyzed using analysis of variance (GLIMMIX procedure) with a log-normal error distribution in addition to the restricted maximum likelihood estimation method to eliminate the need for equality of variances and Tukey Honest Significant Difference test (α = .05). Results: Differences among the load-to-failure values of HDPs were not significant (P > .05); however, zirconia had significantly higher load-to-failure values than HDPs (P < .001). The behavior of HDPs and zirconia under loading was different in terms of displacement. HDPs showed weaker but more ductile behavior than zirconia, which is stronger, but more brittle. Conclusion: The tested brands of HDPs performed similarly under loading. Zirconia with a Ti base showed higher strength compared to all tested HDPs with a Ti base. The loads that fractured the specimens with Ti bases were close to the maximum occlusal bite forces recorded in previous clinical studies.

Procedia Engineering, 2017

Tensile tests at low and high strain rates in which full-field strain and full-field temperature ... more Tensile tests at low and high strain rates in which full-field strain and full-field temperature are measured simultaneously on the surface of the specimen during the test are presented. Various testing methods are used (including the tensile Split Hopkinson Bar for testing at high strain rates) for loading the specimens. Strain measurements are done using the Digital Image Correlation technique and temperatures are measured with a high-speed IR camera. The experiments provide details of the strain and temperature during the uniform deformation before the initiation of necking and in the necking region during the necking. Results from testing 316L stainless steel show a uniform temperature rise during the uniform deformation which is higher with increasing strain rate and a significant increase in the strain rate and temperature during the necking in the necking region. The strain rate in the necking area can be three times the nominal strain rate and, at a high strain rate test, the temperature in the necking area can increase by 300°C.

The Journal of Prosthetic Dentistry, 2019

The use of implant-supported prostheses in the replacement of natural missing teeth is a reliable... more The use of implant-supported prostheses in the replacement of natural missing teeth is a reliable and effective treatment option. 1 Obtaining accurate dental impressions is a crucial step in any implant treatment. 2-4 Inaccurate transfer of the implant position can lead to an ill-fitting prosthesis, which may put unnecessary strain on the various prosthetic components in the system and ultimately result in complications. 5,6 Impression procedures

The Journal of prosthetic dentistry, Jan 5, 2018

The load-to-fracture performance of computer-assisted design and computer-assisted manufacturing ... more The load-to-fracture performance of computer-assisted design and computer-assisted manufacturing (CAD-CAM) high-density polymer (HDP) materials in cantilevers is unknown. The purposes of this in vitro study were to evaluate the load-to-fracture performance of CAD-CAM-fabricated HDPs and to compare that with performance of autopolymerized and injection-molded acrylic resins. Specimens from 8 different brands of CAD-CAM HDPs, including Brylic Solid (BS); Brylic Gradient (BG); AnaxCAD Temp EZ (AE); AnaxCAD Temp Plus (AP); Zirkonzahn Temp Basic (Z); GDS Tempo-CAD (GD); Polident (Po); Merz M-PM-Disc (MAT); an autopolymerized acrylic resin, Imident (Conv) and an injection-molded acrylic resin, SR-IvoBase High Impact (Inj) were evaluated for load-to-fracture analysis (n=5). CAD-CAM specimens were milled from poly(methyl methacrylate) (PMMA) blocks measuring 7 mm in buccolingual width, 8 mm in occlusocervical thickness, and 30 mm in length. A wax pattern was prepared in the same dimensions ...

Journal of Prosthodontic Research, 2017

To compare the displacements of CAD-CAM zirconia and titanium abutments into different internal c... more To compare the displacements of CAD-CAM zirconia and titanium abutments into different internal connection systems after torquing. Methods: OsseoSpeed EV and OsseoSpeed TX implants (n = 10) were placed in resin blocks. Zirconia and titanium abutments (n = 5) were first hand tightened and then tightened to the recommended torque (20 N cm for TX and 25 N cm for EV). Displacements of abutments between screw tightening by hand and torque driver was measured using three-dimensional digital image correlation (3D DIC) technique. Displacements were measured in U (front/back), V (into/outward), W (right/left) directions and 3dimensionally (3D). ANOVA with restricted maximum likelihood estimation method was used to analyze the data. Bonferroni-corrected t tests was used to determine the statistical differences (a = 0.05). Results: 3D displacement of zirconia and titanium abutments was significantly greater in OsseoSpeed EV implant (P < 0.001). Displacement of zirconia and titanium abutments was not significantly different within implant systems, 3D (P ! 0.386) and in each direction (P ! 0.382). In U and V directions, zirconia and titanium abutments displaced significantly more towards negative in OsseoSpeed EV implant (P < 0.019). Within the OsseoSpeed TX system, abutments displaced significantly more in V direction compared to the U and W (P 0.005), and within the Osseospeed EV system, abutment displacements were significantly different amongst directions and displacements in V were the greatest (P < 0.001). Conclusion: Abutments displaced more in the implant that required higher torque values to tighten the abutment. The amount of displacement in both systems was clinically small. Abutment material did not affect the magnitude of displacement.

Comparison of 3D displacements of screw-retained zirconia implant crowns into implants with different internal connections with respect to screw tightening

The Journal of prosthetic dentistry, Jan 5, 2017

Internal conical implant-abutment connections without horizontal platforms may lead to crown disp... more Internal conical implant-abutment connections without horizontal platforms may lead to crown displacement during screw tightening and torque application. This displacement may affect the proximal contacts and occlusion of the definitive prosthesis. The purpose of this in vitro study was to evaluate the displacement of custom screw-retained zirconia single crowns into a recently introduced internal conical seal implant-abutment connection in 3D during hand and torque driver screw tightening. Stereolithic acrylic resin models were printed using computed tomography data from a patient missing the maxillary right central incisor. Two different internal connection implant systems (both ∼11.5 mm) were placed in the edentulous site in each model using a surgical guide. Five screw-retained single zirconia computer-aided design and computer-aided manufacturing (CAD-CAM) crowns were fabricated for each system. A pair of high-resolution digital cameras was used to record the relationship of th...

The Journal of prosthetic dentistry, Jan 12, 2017

The dimensions of implant-supported fixed cantilevered prostheses are important to prevent mechan... more The dimensions of implant-supported fixed cantilevered prostheses are important to prevent mechanical and biological complications. Information on the optimum thickness and cantilever length for improving the strength of zirconia cantilevered frameworks is limited in the literature. The purpose of this in vitro study was to investigate the effect of cantilever length and occlusocervical thickness on the load-to-fracture and strain distribution of zirconia frameworks. Twenty-seven rectangular prism-shaped specimens (6 mm thick buccolingually) were fabricated using a computer-aided design and computer-aided manufacturing (CAD-CAM) milling technique. The specimens were prepared in 9 groups (n=3) according to their vertical dimensions (6×6 mm, 8×6 mm, and 10×6 mm) and cantilever loading distance (7 mm, 10 mm, and 17 mm). All specimens were heat treated in a porcelain furnace and thermocycled for 20000 cycles before the tests. Each framework was secured using a clamp attached to the firs...

The Journal of prosthetic dentistry, Jan 23, 2017

Many aftermarket abutments for cement-retained crowns are available for the tapered screw-vent im... more Many aftermarket abutments for cement-retained crowns are available for the tapered screw-vent implant. Aftermarket abutments vary widely, from stock to custom abutments and in materials such as zirconia, titanium, or a combination of the two. How these aftermarket abutments perform under occlusal loads with regard to strain distribution is not clear. The purpose of this in vitro study was to measure and compare the different strains placed upon the bone around implants by 9 different abutments for cement-retained crowns on an implant with an internal hexagonal platform. Nine 4.1×11.5-mm tapered screw-vent implants were placed into a 305×51×8-mm resin block for strain measurements. Five abutment specimens of each of the 9 different abutments (N=45) were evaluated with 1 of the 9 implants. Monolithic zirconia crowns were then fabricated for each of the 9 different abutments, the crowns were cyclically loaded (maximum force 225 N) at 30 degrees, twice at a frequency of 2 Hz, and the s...

Journal of Intelligent Material Systems and Structures, 2017

High-pressure nozzles and ultrasonic atomizers are the two most common devices used to generate s... more High-pressure nozzles and ultrasonic atomizers are the two most common devices used to generate sprays. Each of these has some disadvantages, such as controllability in high-pressure nozzles and fluid management challenges in ultrasonic devices. To overcome these limitations, a new atomization technology using a synthetic jet actuator was developed and is presented here. The work includes design and experimental analysis of both the stand-alone synthetic jet actuator and the synthetic jet-based atomization device. The synthetic jet actuator is designed using a model-based approach and characterized by measuring dynamic orifice pressure, diaphragm peak-to-peak displacement, flow rate, and power consumption. Orifice pressure reaches 296 Pa at a flow rate of 16 mL/s and 186 Pa at a flow rate of 37 mL/s for two possible synthetic jet actuator geometries, respectively. Piezoelectric diaphragm displacement reaches 50 µm with a brass substrate thickness of 0.20 mm. The synthetic jet-based ...

The Journal of Prosthetic Dentistry, 2017

A single anterior implant restoration poses many challenges. Factors that play a role in determin... more A single anterior implant restoration poses many challenges. Factors that play a role in determining the outcome of the restoration include the amount of alveolar bone, the morphologic type of soft tissue, the correct positioning of the implant, the interim restoration phase, and the material and design of the abutment and the implant crown. 1,2 A single-implant restoration can be either screw-retained or cementretained. While screwretained restorations have the significant advantage of being retrievable, in some situations, a screw-retained restoration is not possible because of the implant position. 3,4 Cement-retained restorations can be used more universally. In addition to being more esthetic, achieving passivity is easier with cement-retained restorations, especially for implantsupported fixed dental prostheses. 3,5 With the correct selection and proper handling of the cement, cement-retained restorations can be made retrievable without compromising esthetics or function. 5 The significant grayish discoloration at the gingiva caused by titanium abutments led to the development of ceramic abutments. 6,7 The combination of a ceramic abutment and crown increases translucency compared with a metal abutment and a metal ceramic crown and therefore an improved esthetic outcome. 8,9 However, a 1-piece zirconia abutment has reduced fracture resistance compared with a titanium abutment. 10 Attempting to tighten the abutment prior to seating it correctly generates higher internal stresses which can lead to fracture.

Full-Field Temperature and Strain Measurement in Dynamic Tension Tests on SS 304

Conference Proceedings of the Society for Experimental Mechanics Series, 2016

The thermomechanical response of 304-stainless steel tension specimens to a range of strain rates... more The thermomechanical response of 304-stainless steel tension specimens to a range of strain rates from 7 × 10−3 s−1 to 2600 s − 1 was investigated. Quasi-static tests (7 × 10−3 to 0.8 s−1) were completed on a hydraulic load frame, intermediate tests (200 s−1) were performed with a modified pressure bar, and high strain rate tests (2600 s−1) on a split Hopkinson pressure bar. Full-field infrared thermography and strain measurements were recorded during each test. Infrared measurements were taken using the Telops FAST-IR 1000 infrared camera at rates up to 30,0000 frames per second. 2D-DIC was used to compute strain from simultaneously recorded visible images taken at rates up to 90,000 frames per second. Max temperatures of 290 °C were recorded in the necking region of a uniaxial specimen at a strain rate of 2600 s−1. These measurements can be used to investigate the transition of isothermal deformation to adiabatic deformation and to determine the portion of plastic work converted to heat at each strain rate.

Plastic Deformation of Ti-6Al-4V Plate over a Wide Range of Loading Conditions

Conference Proceedings of the Society for Experimental Mechanics Series, 2012

Plastic deformation of Ti-6Al-4V plate stock is investigated under multiple loading conditions. T... more Plastic deformation of Ti-6Al-4V plate stock is investigated under multiple loading conditions. The objective of the test program is to generate experimental data that can be used for the development and calibration of constitutive and failure models for numerical simulations of dynamic events. Uniaxial tension, compression and pure shear experiments are conducted at strain rates ranging from 1E-4 to 3,000 s−1. Specimens are fabricated from both 6.35 mm (0.25 in.) and 12.7 mm (0.5 in.) thick plate stock. Compression and tension tests are conducted on specimens oriented in several different directions within the plate. The data shows significant strain rate sensitivity in tension, compression and shear. Both plates exhibit anisotropic plastic deformation behavior in tension and compression. The response of 6.35 mm plate is significantly different than the 12.7 mm plate in tension, compression.

Mechanical Response of T800/F3900 Composite at Various Strain Rates

Conference Proceedings of the Society for Experimental Mechanics Series, 2016

Composite materials are becoming more and more popular in the automotive and aerospace industries... more Composite materials are becoming more and more popular in the automotive and aerospace industries. Many models exist that can describe the plastic deformation and failure response of composites, however, a new orthotropic material model (MAT_213 in LS-DYNA) has been developed to improve the predictive accuracy of numerical simulations of dynamic structural events involving composite materials. A test series was devised to calibrate this model for T800/F3900, a strengthened epoxy carbon-fiber reinforced polymer. In this paper, the mechanical response of T800/F3900 is studied experimentally under different loading conditions. Tests include in plane uniaxial compression, in plane transverse tension, compression and out of plane tension, compression at various strain rates. High rate tension and compression tests are conducted using the split Hopkinson bar technique, while static tests are conducted on a hydraulic load frame. In plane and out of plane deformations are studied using Digital Image Correlation (DIC).

An Experimental Investigation of the Influence of the State of Stress on the Ductile Fracture of 2024-T351 Aluminum

Journal of Engineering Materials and Technology

This paper investigates the influence of stress state on the equivalent plastic fracture strain i... more This paper investigates the influence of stress state on the equivalent plastic fracture strain in 2024-T351 aluminum alloy. Eighteen unique stress states at failure—with triaxialities ranging from 0.388 (compressive) to −0.891 (tensile) and Lode parameters ranging from −0.978 to 1.000—are explored through mechanical experiments on 2024-T351 aluminum specimens with various geometries under multiple loading conditions. These include tension tests of plane stress (thin), plane strain (thick), and axisymmetric specimens, as well as pure shear and combined axial–torsional loading on thin-walled tubes. Using a hybrid numerical–experimental approach, the dependence of fracture strain on stress triaxiality and Lode parameter is quantified for each experiment. Fracture strains are measured using three-dimensional digital image correlation. Equivalent plastic fracture strain for 2024-T351 generally increases with stress triaxiality (moving toward a more compressive state). Fracture strain de...

Dynamic Mechanical Response of T800/F3900 Composite Under Tensile and Compressive Loading

Dynamic Behavior of Materials, Volume 1, 2018

The effect of strain rate on the mechanical response of T800/F3900, a strengthened epoxy carbon-f... more The effect of strain rate on the mechanical response of T800/F3900, a strengthened epoxy carbon-fiber reinforced polymer, is studied by conducting compression and tensile tests at different strain rates. Low strain rate tests (0.001 s−1 and 1 s−1) are done using a hydraulic frame and high strain rate tests (300 s−1–600 s−1) are done with the SHB technique. Digital Image Correlation is used in all tests to obtain full-field strain measurements. Tension tests have been done on unidirectional laminates in the 90 ° direction. Compression tests have been done on unidirectional laminates in the 90 ° and through the thickness directions. No or small strain rate effect is observed between the low strain rate tests. The results from the high strain rate tests show significant strain rate effects.

An Efficient Iterative Approach for Determining the Post-Necking True Stress-Strain Response of Aerospace Metals

To numerically simulate the plastic deformation of aerospace metals during extreme events (e.g., ... more To numerically simulate the plastic deformation of aerospace metals during extreme events (e.g., turbine engine blade-out/rotor-burst events and automotive crashworthiness assessment), accurate experimental knowledge of the metal’s hardening behavior at large strains is requisite. Tensile tests on thin (plane stress) specimens are frequently used for this purpose, with the metal’s large-strain plasticity ultimately captured by an equivalent true stress vs. equivalent true plastic strain curve. It is now well known that if axial strain is measured using an extensometer (either physical or virtual), the equivalent true stress-strain curve is valid only up to the onset of diffuse necking, when the strain field heterogeneously localizes in the specimen gage. A number of approaches have been proposed to correct the post-necking strain hardening response. Perhaps the most widely used technique involves inputting a suite of candidate post-necking true stress-strain curves into finite-element software; a tensile test simulation is run for each candidate curve, and the curve that produces the best agreement between simulation and experiment is ultimately adopted. In this talk, a novel variation of this iterative approach is presented that addresses some of its key deficiencies. Notably, we use local/pointwise in-plane Hencky (true) strain data from digital image correlation to generate an upper bound for the iterative simulation process, resulting in an efficient and computationally inexpensive post-necking correction procedure. Our approach is successfully demonstrated using experimental data for both wrought and additively manufactured Ti-6Al-4V titanium alloy.https://ecommons.udayton.edu/stander_posters/2855/thumbnail.jp

Full-Field Mechanical and Thermal Strain-Rate Dependence of CFRP Laminates

The aim of the project is to characterize the strain rate dependence of a representative carbon f... more The aim of the project is to characterize the strain rate dependence of a representative carbon fiber reinforced polymer unidirectional laminate for thermal and mechanical properties. Digital image correlation is used to obtain full-field deformation and thermal effects of CFRP samples at strain rates of 0.001 s−1, 1 s−1, 100 s−1, and 1000 s−1. A combination of hydraulic load frame and split-hopkinson bar tests are used to load samples while optical and IR imaging is used to obtain deformation and thermal footage. Strain rate dependence is known to occur in the clear-cast polymer material, and is not prevalent in the carbon fiber material. Therefore, the strain rate dependence of the CFRP at varying orientations and loading conditions including tension, compression, and shear are of interest. Initial results show strong strain rate dependence in the polymer-dominated 90° orientation and clear-cast specimens.

Failure Testing Under In-Plane Biaxial Tension and Out-of-Plane Compression

Fracture, Fatigue, Failure and Damage Evolution, Volume 6, 2018

The deformation and failure behavior of 2024 aluminum was investigated under combined in-plane eq... more The deformation and failure behavior of 2024 aluminum was investigated under combined in-plane equi-biaxial tension and out-of-plane compression. This loading configuration yields stress states of Lode parameter = −1 and triaxialities ranging from −0.67 to 0.17. Testing was performed using a variation of the standard ASTM quasi-static hemispherical punch test, with a reduced punch diameter and the addition of an annealed copper backing plate behind the specimen. The reported stress states at the failure point were then determined numerically using LS-DYNA.

The deformation and failure of metals and composites is known to be affected by strain rate and t... more The deformation and failure of metals and composites is known to be affected by strain rate and temperature. Material models in LS-DYNA® account for these effects and material coupon testing is required for determining the input parameters for the models. The present paper presents a new experimental setup that provide means for investigating the coupled effects of temperature and strain rate during plastic deformation, and new strain rate sensitivity data for fibrous composites that was obtained from static and dynamic tests. Although coupled, the effects of strain rate and temperature are usually determined separately in tests at different strain rates and different initial temperatures, neglecting temperature increase that might be taking place during the deformation. In the present paper a new experimental setup is introduced in which full-field deformation and full-field temperature are measured simultaneously during tensile tests in various strain rates (including high strain ...

Journal of Physics: Conference Series, 2018

Extensive material testing is required for setting up, calibration and validation newly-developed... more Extensive material testing is required for setting up, calibration and validation newly-developed material models for dynamic plastic deformation and fracture. One example is the material models MAT224 and MAT264 in the LS-DYNA code which are extension of the Johnson-Cook viscoplastic damage model. The tabulated form of these models extends their validity to a wide range of loading conditions, strain rates, temperatures, and fracture modes, but requires data from many experiments to setup. This paper describes the experiments that were used and new experiments that have been developed during the development of these material models. It includes compression, tension, and shear tests over a wide range of strain rates, including high strain rates using the Split Hopkinson bar (SHB) technique. Quasi-static and dynamic continuous and interrupted punch tests that include 3D DIC strain measurement of the deformation at the back surface of the specimen during the test. Tensile tests over wide range of strain rates (including SHB experiments) in which full-field deformation (using DIC) and full-filed temperature (using very high speed IR camera) are measured simultaneously during the experiment. Data from testing at various strain rates, various temperatures, and different specimen geometries is used for setting up the plasticity material model, and a failure surface that gives the equivalent plastic fracture strain as a function of triaxiality and the Lode parameter. Punch tests with different punch geometries that produce different failure modes are used for validating the plasticity-failure model. The setup of the dynamic punch test is shown in Figure 1. The specimen is mounted on the transmission bar of a compression SHB apparatus with a holder that provide optical path to two high-speed cameras to the back surface of the specimen. The punch is attached to the input bar. A specimen following a test and a sample of data is shown in Figure 2. DIC images that show the history of the maximum strain measured on the back surface of the specimen during the test are shown in Figure 3.

The International Journal of Prosthodontics, 2021

T he goal of an interim implant-supported, fixed, complete-arch prosthesis (ISFCAP) is to fulfill... more T he goal of an interim implant-supported, fixed, complete-arch prosthesis (ISFCAP) is to fulfill the patient's esthetic and functional needs without biologic or technical complications until the definitive prosthesis is placed. 1-4 An interim ISFCAP needs to withstand masticatory forces during the osseointegration period, 1,5 and so an interim ISFCAP should have adequate strength, especially when used in cantilevered situations. 1,6-8 Conventionally, interim ISFCAPs have been fabricated from autopolymerized or heat-polymerized polymethyl methacrylate (PMMA) acrylic resin. 1,9 Despite their common use, fractures have been reported in clinical studies with varying frequency. 1,9 Therefore, reinforcing with fiber meshes, metallic bars, or metal wires has been reported to improve fracture and impact strength of the conventional interim Purpose: To analyze the load to failure of different CAD/CAM high-density polymers (HDPs) and zirconia when titanium (Ti) bases were included in a cantilevered situation. Materials and Methods: Five specimens were fabricated from five different CAD/CAM polymethyl methacrylate (PMMA) HDPs (Copratemp [CT]; Tempo-CAD [TC]; Solid Shade PMMA Disc [TD]; M-PM Disc pink [MPM]; M-PM Disc white [MPMW]), and five specimens were prepared from an yttrium-stabilized tetragonal zirconia (3Y-TZP; FireZr [FZR]; control). Ti bases (D Master Dental Implants) were cemented onto the specimens (8 mm thick × 7 mm wide × 30 mm long). Each specimen was fixated using a clamp for a cantilever loading distance of 10 mm. The load was applied on the cantilever until failure, and the maximum load to failure values (N) were analyzed using analysis of variance (GLIMMIX procedure) with a log-normal error distribution in addition to the restricted maximum likelihood estimation method to eliminate the need for equality of variances and Tukey Honest Significant Difference test (α = .05). Results: Differences among the load-to-failure values of HDPs were not significant (P > .05); however, zirconia had significantly higher load-to-failure values than HDPs (P < .001). The behavior of HDPs and zirconia under loading was different in terms of displacement. HDPs showed weaker but more ductile behavior than zirconia, which is stronger, but more brittle. Conclusion: The tested brands of HDPs performed similarly under loading. Zirconia with a Ti base showed higher strength compared to all tested HDPs with a Ti base. The loads that fractured the specimens with Ti bases were close to the maximum occlusal bite forces recorded in previous clinical studies.

Procedia Engineering, 2017

Tensile tests at low and high strain rates in which full-field strain and full-field temperature ... more Tensile tests at low and high strain rates in which full-field strain and full-field temperature are measured simultaneously on the surface of the specimen during the test are presented. Various testing methods are used (including the tensile Split Hopkinson Bar for testing at high strain rates) for loading the specimens. Strain measurements are done using the Digital Image Correlation technique and temperatures are measured with a high-speed IR camera. The experiments provide details of the strain and temperature during the uniform deformation before the initiation of necking and in the necking region during the necking. Results from testing 316L stainless steel show a uniform temperature rise during the uniform deformation which is higher with increasing strain rate and a significant increase in the strain rate and temperature during the necking in the necking region. The strain rate in the necking area can be three times the nominal strain rate and, at a high strain rate test, the temperature in the necking area can increase by 300°C.

The Journal of Prosthetic Dentistry, 2019

The use of implant-supported prostheses in the replacement of natural missing teeth is a reliable... more The use of implant-supported prostheses in the replacement of natural missing teeth is a reliable and effective treatment option. 1 Obtaining accurate dental impressions is a crucial step in any implant treatment. 2-4 Inaccurate transfer of the implant position can lead to an ill-fitting prosthesis, which may put unnecessary strain on the various prosthetic components in the system and ultimately result in complications. 5,6 Impression procedures

The Journal of prosthetic dentistry, Jan 5, 2018

The load-to-fracture performance of computer-assisted design and computer-assisted manufacturing ... more The load-to-fracture performance of computer-assisted design and computer-assisted manufacturing (CAD-CAM) high-density polymer (HDP) materials in cantilevers is unknown. The purposes of this in vitro study were to evaluate the load-to-fracture performance of CAD-CAM-fabricated HDPs and to compare that with performance of autopolymerized and injection-molded acrylic resins. Specimens from 8 different brands of CAD-CAM HDPs, including Brylic Solid (BS); Brylic Gradient (BG); AnaxCAD Temp EZ (AE); AnaxCAD Temp Plus (AP); Zirkonzahn Temp Basic (Z); GDS Tempo-CAD (GD); Polident (Po); Merz M-PM-Disc (MAT); an autopolymerized acrylic resin, Imident (Conv) and an injection-molded acrylic resin, SR-IvoBase High Impact (Inj) were evaluated for load-to-fracture analysis (n=5). CAD-CAM specimens were milled from poly(methyl methacrylate) (PMMA) blocks measuring 7 mm in buccolingual width, 8 mm in occlusocervical thickness, and 30 mm in length. A wax pattern was prepared in the same dimensions ...

Journal of Prosthodontic Research, 2017

To compare the displacements of CAD-CAM zirconia and titanium abutments into different internal c... more To compare the displacements of CAD-CAM zirconia and titanium abutments into different internal connection systems after torquing. Methods: OsseoSpeed EV and OsseoSpeed TX implants (n = 10) were placed in resin blocks. Zirconia and titanium abutments (n = 5) were first hand tightened and then tightened to the recommended torque (20 N cm for TX and 25 N cm for EV). Displacements of abutments between screw tightening by hand and torque driver was measured using three-dimensional digital image correlation (3D DIC) technique. Displacements were measured in U (front/back), V (into/outward), W (right/left) directions and 3dimensionally (3D). ANOVA with restricted maximum likelihood estimation method was used to analyze the data. Bonferroni-corrected t tests was used to determine the statistical differences (a = 0.05). Results: 3D displacement of zirconia and titanium abutments was significantly greater in OsseoSpeed EV implant (P < 0.001). Displacement of zirconia and titanium abutments was not significantly different within implant systems, 3D (P ! 0.386) and in each direction (P ! 0.382). In U and V directions, zirconia and titanium abutments displaced significantly more towards negative in OsseoSpeed EV implant (P < 0.019). Within the OsseoSpeed TX system, abutments displaced significantly more in V direction compared to the U and W (P 0.005), and within the Osseospeed EV system, abutment displacements were significantly different amongst directions and displacements in V were the greatest (P < 0.001). Conclusion: Abutments displaced more in the implant that required higher torque values to tighten the abutment. The amount of displacement in both systems was clinically small. Abutment material did not affect the magnitude of displacement.

Comparison of 3D displacements of screw-retained zirconia implant crowns into implants with different internal connections with respect to screw tightening

The Journal of prosthetic dentistry, Jan 5, 2017

Internal conical implant-abutment connections without horizontal platforms may lead to crown disp... more Internal conical implant-abutment connections without horizontal platforms may lead to crown displacement during screw tightening and torque application. This displacement may affect the proximal contacts and occlusion of the definitive prosthesis. The purpose of this in vitro study was to evaluate the displacement of custom screw-retained zirconia single crowns into a recently introduced internal conical seal implant-abutment connection in 3D during hand and torque driver screw tightening. Stereolithic acrylic resin models were printed using computed tomography data from a patient missing the maxillary right central incisor. Two different internal connection implant systems (both ∼11.5 mm) were placed in the edentulous site in each model using a surgical guide. Five screw-retained single zirconia computer-aided design and computer-aided manufacturing (CAD-CAM) crowns were fabricated for each system. A pair of high-resolution digital cameras was used to record the relationship of th...

The Journal of prosthetic dentistry, Jan 12, 2017

The dimensions of implant-supported fixed cantilevered prostheses are important to prevent mechan... more The dimensions of implant-supported fixed cantilevered prostheses are important to prevent mechanical and biological complications. Information on the optimum thickness and cantilever length for improving the strength of zirconia cantilevered frameworks is limited in the literature. The purpose of this in vitro study was to investigate the effect of cantilever length and occlusocervical thickness on the load-to-fracture and strain distribution of zirconia frameworks. Twenty-seven rectangular prism-shaped specimens (6 mm thick buccolingually) were fabricated using a computer-aided design and computer-aided manufacturing (CAD-CAM) milling technique. The specimens were prepared in 9 groups (n=3) according to their vertical dimensions (6×6 mm, 8×6 mm, and 10×6 mm) and cantilever loading distance (7 mm, 10 mm, and 17 mm). All specimens were heat treated in a porcelain furnace and thermocycled for 20000 cycles before the tests. Each framework was secured using a clamp attached to the firs...

The Journal of prosthetic dentistry, Jan 23, 2017

Many aftermarket abutments for cement-retained crowns are available for the tapered screw-vent im... more Many aftermarket abutments for cement-retained crowns are available for the tapered screw-vent implant. Aftermarket abutments vary widely, from stock to custom abutments and in materials such as zirconia, titanium, or a combination of the two. How these aftermarket abutments perform under occlusal loads with regard to strain distribution is not clear. The purpose of this in vitro study was to measure and compare the different strains placed upon the bone around implants by 9 different abutments for cement-retained crowns on an implant with an internal hexagonal platform. Nine 4.1×11.5-mm tapered screw-vent implants were placed into a 305×51×8-mm resin block for strain measurements. Five abutment specimens of each of the 9 different abutments (N=45) were evaluated with 1 of the 9 implants. Monolithic zirconia crowns were then fabricated for each of the 9 different abutments, the crowns were cyclically loaded (maximum force 225 N) at 30 degrees, twice at a frequency of 2 Hz, and the s...

Journal of Intelligent Material Systems and Structures, 2017

High-pressure nozzles and ultrasonic atomizers are the two most common devices used to generate s... more High-pressure nozzles and ultrasonic atomizers are the two most common devices used to generate sprays. Each of these has some disadvantages, such as controllability in high-pressure nozzles and fluid management challenges in ultrasonic devices. To overcome these limitations, a new atomization technology using a synthetic jet actuator was developed and is presented here. The work includes design and experimental analysis of both the stand-alone synthetic jet actuator and the synthetic jet-based atomization device. The synthetic jet actuator is designed using a model-based approach and characterized by measuring dynamic orifice pressure, diaphragm peak-to-peak displacement, flow rate, and power consumption. Orifice pressure reaches 296 Pa at a flow rate of 16 mL/s and 186 Pa at a flow rate of 37 mL/s for two possible synthetic jet actuator geometries, respectively. Piezoelectric diaphragm displacement reaches 50 µm with a brass substrate thickness of 0.20 mm. The synthetic jet-based ...

The Journal of Prosthetic Dentistry, 2017

A single anterior implant restoration poses many challenges. Factors that play a role in determin... more A single anterior implant restoration poses many challenges. Factors that play a role in determining the outcome of the restoration include the amount of alveolar bone, the morphologic type of soft tissue, the correct positioning of the implant, the interim restoration phase, and the material and design of the abutment and the implant crown. 1,2 A single-implant restoration can be either screw-retained or cementretained. While screwretained restorations have the significant advantage of being retrievable, in some situations, a screw-retained restoration is not possible because of the implant position. 3,4 Cement-retained restorations can be used more universally. In addition to being more esthetic, achieving passivity is easier with cement-retained restorations, especially for implantsupported fixed dental prostheses. 3,5 With the correct selection and proper handling of the cement, cement-retained restorations can be made retrievable without compromising esthetics or function. 5 The significant grayish discoloration at the gingiva caused by titanium abutments led to the development of ceramic abutments. 6,7 The combination of a ceramic abutment and crown increases translucency compared with a metal abutment and a metal ceramic crown and therefore an improved esthetic outcome. 8,9 However, a 1-piece zirconia abutment has reduced fracture resistance compared with a titanium abutment. 10 Attempting to tighten the abutment prior to seating it correctly generates higher internal stresses which can lead to fracture.

Full-Field Temperature and Strain Measurement in Dynamic Tension Tests on SS 304

Conference Proceedings of the Society for Experimental Mechanics Series, 2016

The thermomechanical response of 304-stainless steel tension specimens to a range of strain rates... more The thermomechanical response of 304-stainless steel tension specimens to a range of strain rates from 7 × 10−3 s−1 to 2600 s − 1 was investigated. Quasi-static tests (7 × 10−3 to 0.8 s−1) were completed on a hydraulic load frame, intermediate tests (200 s−1) were performed with a modified pressure bar, and high strain rate tests (2600 s−1) on a split Hopkinson pressure bar. Full-field infrared thermography and strain measurements were recorded during each test. Infrared measurements were taken using the Telops FAST-IR 1000 infrared camera at rates up to 30,0000 frames per second. 2D-DIC was used to compute strain from simultaneously recorded visible images taken at rates up to 90,000 frames per second. Max temperatures of 290 °C were recorded in the necking region of a uniaxial specimen at a strain rate of 2600 s−1. These measurements can be used to investigate the transition of isothermal deformation to adiabatic deformation and to determine the portion of plastic work converted to heat at each strain rate.

Plastic Deformation of Ti-6Al-4V Plate over a Wide Range of Loading Conditions

Conference Proceedings of the Society for Experimental Mechanics Series, 2012

Plastic deformation of Ti-6Al-4V plate stock is investigated under multiple loading conditions. T... more Plastic deformation of Ti-6Al-4V plate stock is investigated under multiple loading conditions. The objective of the test program is to generate experimental data that can be used for the development and calibration of constitutive and failure models for numerical simulations of dynamic events. Uniaxial tension, compression and pure shear experiments are conducted at strain rates ranging from 1E-4 to 3,000 s−1. Specimens are fabricated from both 6.35 mm (0.25 in.) and 12.7 mm (0.5 in.) thick plate stock. Compression and tension tests are conducted on specimens oriented in several different directions within the plate. The data shows significant strain rate sensitivity in tension, compression and shear. Both plates exhibit anisotropic plastic deformation behavior in tension and compression. The response of 6.35 mm plate is significantly different than the 12.7 mm plate in tension, compression.

Mechanical Response of T800/F3900 Composite at Various Strain Rates

Conference Proceedings of the Society for Experimental Mechanics Series, 2016

Composite materials are becoming more and more popular in the automotive and aerospace industries... more Composite materials are becoming more and more popular in the automotive and aerospace industries. Many models exist that can describe the plastic deformation and failure response of composites, however, a new orthotropic material model (MAT_213 in LS-DYNA) has been developed to improve the predictive accuracy of numerical simulations of dynamic structural events involving composite materials. A test series was devised to calibrate this model for T800/F3900, a strengthened epoxy carbon-fiber reinforced polymer. In this paper, the mechanical response of T800/F3900 is studied experimentally under different loading conditions. Tests include in plane uniaxial compression, in plane transverse tension, compression and out of plane tension, compression at various strain rates. High rate tension and compression tests are conducted using the split Hopkinson bar technique, while static tests are conducted on a hydraulic load frame. In plane and out of plane deformations are studied using Digital Image Correlation (DIC).