Mapping internal strain fields of fused filament fabrication metal filled polylactic acid structure using digital volume correlation.

With the advancement in Fused Filament Fabrication (FFF), its application is increasing widely across different industries such as aeronautical, biomedical, robotics, etc. The internal structure is becoming more complex and intricate with varying materials of reinforcement which are used to improve mechanical properties. Current measurement techniques like Digital Image Correlation (DIC) are non-destructive testing methods that do not provide enough information on the behaviour of internal microstructure for anisotropic FFF materials. Digital Volume Correlation (DVC) is non-destructive testing technique which provides full field internal 3D deformation and strain fields. Copper particle filled PLA samples manufactured using FFF method with 20, 40, 60 and 80 infill percentages were loaded in tension inside Micro-CT. X-rays were passed through the sample to get a volumetric dataset for different loadings. Using DVC method on the dataset, internal displacement and strain fields were generated for 20, 40, 60 and 80 infill percentage FFF sample.

Digital volume correlation analysis of polylactic acid based fused filament fabrication printed composites.

Fused filament fabrication (FFF) has rapidly begun to see implementation in industrial fields as a method of rapid manufacturing. Traditional FFF parts are made from a single thermoplastic polymer. The polymer is heated to its melting point and deposited on a work bed where a model is gradually built from the base up. While traditional FFF parts have low mechanical properties, a reinforcing phase allows for improved mechanical properties. The addition of a reinforcing material to the base polymer and complex internal microstructure of the 3 D printed party leads to anisotropic mechanical properties. Thus, these materials' mechanical properties become challenging to characterize using traditional measurement techniques due to the previously mentioned factors. Therefore, it is essential to develop a method in which mechanical properties can be measured and analyzed. This study aims to characterize the mechanical behaviour under a uniaxial tensile load of an FFF produced polylactic acid (PLA)-copper particulate composite. The internal response of the FFF sample was imaged using micro-computed tomography at predetermined loads. The µ-CT images were input into an open-source digital volume correlation (DVC) software to measure the internal displacements and strain tensor fields. The study results show the development of different strain fields and interior features of the FFF parts.

A new method for the rapid characterization of root growth and distribution using digital image correlation.

Rapidly determining root growth patterns is biologically important and technically challenging. Current methods focus on direct observation of roots and require destructive excavations or time-consuming root tracing. We developed a novel methodology based on analyzing soil particle displacement, rather than direct observation of roots. This inferred root growth method uses digital image correlation (DIC) analysis, an established and high-throughput method used in many engineering and science disciplines. By applying DIC analyses to repeated images of plants grown in clear window boxes, we produced visually intuitive and quantifiable strain maps, indicating the magnitude and direction of soil movement. From this, we could infer root growth and rapidly quantify root system metrics. Strain measures were closely associated with the spatial distribution of roots and correlated with root length measured using conventional approaches. The method also allowed for the detection of root proliferation in nutrient-enriched soil patches, indicating its suitability for quantifying biological patterns. This novel application of DIC in root biology is effective, scalable, low cost, flexible and complementary to existing technologies. This method offers a new tool for answering questions in plant biology and will be particularly useful in studies involving temporal dynamics of root processes.

Development of a standardized testing system for orthodontic sliding mechanics.

BACKGROUND: The primary objective of this study was to develop a computer-controlled three-dimensional friction measuring system, the orthodontic friction simulator (OFS). A clinically-based in vitro experiment considering wet and dry friction for conventionally and self-ligated brackets is presented to elucidate debate surrounding sliding mechanics and illustrate capabilities of the OFS. METHODS: The OFS was designed and manufactured using sound engineering principles and with the primary concern of being able to measure all forces and moments generated during sliding mechanics. This required the implementation of a six-axis load cell. A variety of translation and rotation stages were also incorporated to allow for precise positioning of the bracket relative to the archwire. Once designed and built, the OFS was then used to compare conventional and self-ligation methods in both the wet and dry state. Damon Q brackets and 0.018″ × 0.025″ stainless steel wires were used for all tests with a sample size of n = 65 for each ligation method. Archwires were pulled at a speed of 0.1 mm/s in 11 increments of 0.1 mm. At each increment, the bracket would be rotated 0.5° resulting in a total archwire travel of 1.1 mm and a second-order bracket angle range of 0°-5°. A repeated measures ANOVA was conducted to determine if ligation method and/or addition of moisture effected resulting orthodontic loads. RESULTS: The developed equipment for studying orthodontic sliding mechanics was able to measure forces and moments in all three directions; a capability not previously realized in the literature. Additionally, it was found that passive ligation significantly reduced resistance to sliding, P ≤ 0.05, while the dry/wet state did not. CONCLUSIONS: The OFS certainly proved to be an adequate instrument for the scientific evaluation of orthodontic sliding mechanics. It is capable of measuring loads generated in all directions and is a fully automated apparatus allowing for simple and repeatable friction tests to be conducted. Furthermore, the addition of saliva was not found to significantly influence the loads generated during sliding mechanics regardless of ligation method.

Evaluation of fiber reinforced cement using digital image correlation.

The effect of short fiber reinforcements on the mechanical properties of cement has been examined using a splitting tensile - digital image correlation (DIC) measurement method. Three short fiber reinforcement materials have been used in this study: fiberglass, nylon, and polypropylene. The method outlined provides a simple experimental setup that can be used to evaluate the ultimate tensile strength of brittle materials as well as measure the full field strain across the surface of the splitting tensile test cylindrical specimen. Since the DIC measurement technique is a contact free measurement this method can be used to assess sample failure.

Investigation into the effects of stainless steel ligature ties on the mechanical characteristics of conventional and self-ligated brackets subjected to torque.

OBJECTIVE: Torque is applied to orthodontic brackets in order to alter the buccal-lingual angulation of a tooth. One factor that can affect torque is the ligation mode used to retain the archwire in the bracket slot. The objective of this study was to investigate the effects of stainless steel ligation on torque expression and bracket deformation. METHODS: This study utilized 60 upper right central incisor Damon Q brackets and 60 Ormco Orthos Twin brackets. The brackets used in this study were subdivided into four groups: (1) Damon Q ligated with SS ligature; (2) Damon Q with the sliding bracket door; (3) Orthos Twin bracket ligated with SS wire; and (4) Orthos Twin ligated with elastic ties. All brackets were tested using an orthodontic torque simulating device that applied archwire rotation from 0° to 45°. RESULTS: All brackets ligated with stainless steel ties exhibited greater torque expression and less deformation than brackets without stainless steel ties. As well, Damon Q brackets exhibit less bracket deformation than Orthos Twin brackets. CONCLUSIONS: Stainless steel ties can reduce the amount of plastic deformation for both types of brackets used in this study.

Comparison of deformation and torque expression of the orthos and orthos Ti bracket systems.

Orthodontic torque expression is the result of axial rotation of rectangular archwires within a rectangular bracket slot. This study investigates the effect of bracket material on torque expression. Torque exerted by a rotating archwire on each bracket will be measured as well as the relative deformation of each bracket slot. A total of 60 tests were performed where archwires were rotated within a bracket slot to produce torque within a bracket. Thirty Ormco Orthos Ti and 30 Orthos SS were compared to investigate the effect of torque on bracket material. Each bracket was mounted on a six-axis load cell that measured forces and moments in all directions. The archwire was rotated from an initial angle of 0 degree in 3 degrees increments to maximum angle of 51 degrees and then returned to the initial position. An overhead camera took images at each 3 degrees increment. The bracket images were post-processed using a digital image correlation technique to measure the relative deformation of each bracket slot. The maximum torque expressed at 51 degrees was 99.8 Nmm and 93.0 Nmm for Orthos Ti and Orthos SS, respectively. Total plastic deformation measured at 0 degrees post-torquing of the Orthos SS was 0.038 mm compared to 0.013 mm for Orthos Ti. The Orthos Ti brackets plastically deformed less than the Orthos SS brackets after torquing. The Orthos SS bracket plastic deformation was 2.8 times greater than that of Orthos Ti brackets. The Orthos Ti brackets expressed more torque than the stainless steel brackets but exhibited substantial variation.

Modeling stress-relaxation behavior of the periodontal ligament during the initial phase of orthodontic treatment.

The periodontal ligament is the tissue that provides early tooth motion as a result of applied forces during orthodontic treatment: a force-displacement behavior characterized by an instantaneous displacement followed by a creep phase and a stress relaxation phase. Stress relaxation behavior is that which provides the long-term loading to and causes remodelling of the alveolar bone, which is responsible for the long-term permanent displacement of the tooth. In this study, the objective was to assess six viscoelastic models to predict stress relaxation behavior of rabbit periodontal ligament (PDL). Using rabbit stress relaxation data found in the literature, it was found that the modified superposition theory (MST) model best predicts the rabbit PDL behavior as compared to nonstrain-dependent and strain-dependent versions of the Burgers four-parameter and the five-parameter viscoelastic models, as well as predictions by Schapery's viscoelastic model. Furthermore, it is established that using a quadratic form for MST strain dependency provides more stable solutions than the cubic form seen in previous studies.

Three-dimensional deformation of orthodontic brackets.

Braces are used by orthodontists to correct the misalignment of teeth in the mouth. Archwire rotation is a particular procedure used to correct tooth inclination. Wire rotation can result in deformation to the orthodontic brackets, and an orthodontic torque simulator has been designed to examine this wire-bracket interaction. An optical technique has been employed to measure the deformation due to size and geometric constraints of the orthodontic brackets. Images of orthodontic brackets are collected using a stereo microscope and two charge-coupled device cameras, and deformation of orthodontic brackets is measured using a three-dimensional digital image correlation technique. The three-dimensional deformation of orthodontic brackets will be evaluated. The repeatability of the three-dimensional digital image correlation measurement method was evaluated by performing 30 archwire rotation tests using the same bracket and archwire. Finally, five Damon 3MX and five In-Ovation R self-ligating brackets will be compared using this technique to demonstrate the effect of archwire rotation on bracket design.

Three-dimensional deformation comparison of self-ligating brackets.

INTRODUCTION: Archwire rotation is used in orthodontic treatment to alter the labiolingual orientation of a tooth. Measurement of the 3-dimensional (3D) motion of the orthodontic brackets requires a new configuration of the orthodontic torque simulator. METHODS: The orthodontic torque simulator was coupled with a stereo microscope and 2 cameras to allow for the 3D bracket motion to be determined during wire twisting. The stereo camera images were processed with a 3D digital image correlation technique to determine the 3D deformation of the orthodontic brackets. Three self-ligating brackets (Damon Q, Ormco, Orange, Calif; In-Ovation R, GAC, Bohemia, NY; and Speed, Strite Industries, Cambridge, Ontario, Canada) were compared by using the 3D digital image correlation method to demonstrate the difference in 3D motion of self-ligating brackets components. RESULTS: Contour plots of the 3 brackets demonstrate the 3D motion of the bracket tie-wings and the archwire retentive component. The 3D motion of the bracket tie-wings and archwire retentive component were quantified. The displacement values of the archwire retentive component measured with the 3D orthodontic torque simulator were found to be 2.0 and 3.5 times less for the In-Ovation and Damon Q brackets than the values in previous studies that examined the compliance of the archwire retentive component. CONCLUSIONS: The 3D digital image correlation method used to quantify bracket deformation showed the 3D motion of the bracket tie-wings and the motion of the archwire retentive component. The use of a 3D optical measurement system is useful to understand the motion of the archwire retentive component but is not necessary to quantify bracket tie-wing motion. This measurement technique can be used to evaluate brackets of varying designs.

An investigation into the mechanical characteristics of select self-ligated brackets at a series of clinically relevant maximum torquing angles: loading and unloading curves and bracket deformation.

Edgewise orthodontic treatment utilizes a force couple in order to achieve labial-lingual tooth angulation. Two self-ligating brackets (Damon Q and Speed) were examined across a range of clinically relevant torques in order to assess the loading and unloading curves and bracket deformation. A previously developed torquing and load measurement system was utilized to rotate a 0.199 × 0.25 in stainless steel wire in a fixed bracket slot to the following angles: 16, 20, 24, 28, 32, and 40 degrees. The torque on the bracket was measured during both wire loading and unloading cycles. The torque play for the Damon brackets was determined to increase by less than 0.4 degrees when torqued to 70 Nmm, whereas the increase for the Speed brackets was 2.1 degrees at the same torque magnitude. The deformation curves for the Damon and Speed brackets were found to be different for loading and unloading. Speed brackets were found to start to plastically deform when torqued to 24 degrees (26 Nmm of torque), while Damon brackets did not plastically deform until 28 degrees (38 Nmm of torque). Damon brackets were found not to plastically deform as easily and to have a smaller increase in torque play than Speed brackets. Both the Damon and the Speed brackets demonstrated minimal effect of plastic deformation and torque play at maximum angles of twist less than 20 degrees. Torque measured in the brackets was different for loading and unloading.