Specimen Orientation Research Articles

Lumbar Spine Orientation Affects Compressive Fracture Outcome.

Understanding how spinal orientation affects injury outcome is essential to understand lumbar injury biomechanics associated with high-rate vertical loading. Whole-column human lumbar spines (T12-L5) were dynamically loaded using a drop tower to simulate peak axial forces associated with high-speed aircraft ejections and helicopter crashes. Spines were allowed to maintain natural lordotic curvature for loading, resulting in a range of orientations. Pre-test X-rays were used to quantify specimen orientation at the time of loading. Primary fracture types were identified (wedge, n = 6; burst, n = 4; hyperextension, n = 4) and compared for loading parameters and lumbar orientation. Fracture type was dependent on peak acceleration, bending moment, Cobb angle, sagittal spinal tilt, and location of the applied load. Lumbar spine orientation under high-rate axial acceleration affected the resulting fracture type. Analysis of pre-test X-rays revealed that spines that sustained wedge and burst fractures were oriented straighter at the time of loading. The load was applied centrally to T12 in spines with burst fractures, and anteriorly to T12 in spines with wedge fractures. Spines that sustained hyperextension fracture had lower peak accelerations, larger Cobb angles at the time of loading, and sustained larger extension moments. Fracture presentation is an important and understudied factor that influences biomechanical stability, clinical course, and long-term patient outcomes.

Exploring the influence of specimen types on the intralaminar fracture behavior of fiber-reinforced polymer matrix composites

The accurate determination of fracture toughness of fiber-reinforced composites is critical for the assessment of structural integrity. Although there have been many studies on the intralaminar fracture behavior of composites, satisfactory results have not yet been obtained regarding the influence of specimen types. In this paper, commonly used fracture specimens (DCT, CT, ESET, pin-loaded SENT and clamped SENT specimen) are applied to study their applicability in the fracture behaviors of composites with different orientations. And the impact of data processing methods for the area method, GC-compliance and GC-stress intensity factors on fracture performance was analyzed. The results showed that the above three data processing methods have obtained relatively consistent fracture properties. Different specimens obtained significantly various results, showing a gradually decreasing trend from clamped SENT, ESET, pin-loaded SENT, CT to DCT. Furthermore, considering that the clamped SENT specimen is closest to the Mode-I fracture toughness obtained from the DCB specimen, and there is no compression damage in the experiments under different orientations, this specimen type is the most recommended specimen. Finally, the failure mechanisms of carbon fiber-reinforced composite under different specimen types and orientations were revealed. As the orientation angle increases (β from 0° to 90°), the failure mode gradually transitions from matrix cracking and interface debonding to matrix shear and fiber fracture. The above achievements will contribute to a deeper understanding of the intralaminar fracture process and failure mechanism of fiber-reinforced composites.

Electrolyte jet tomography: Three-dimensional microstructure mapping with an electrochemical machine tool and an optical microscope

There is a general separation between the manufacturing processes that add value to materials on the factory floor and the techniques engineers use in the laboratory to evaluate the microstructures and the surface integrity that results. These techniques are often destructive or require a vacuum and are incompatible with production lines. However, this information has intrinsic value and could be exploited to inform production decisions during manufacture. In this study, a novel approach to acquire this information is presented that is underpinned by electrolyte jet machine tool coupled with optical microscopy, which can allow the extraction of both grain-wise partial orientation and morphological information, and crystallographic macro textures in three dimensions. Here, iterative sections are precisely machined into the near surface of a commercially pure titanium alloy using an electrochemical jet and subsequently imaged, allowing the reconstruction of high-fidelity microstructure models rapidly and under ambient conditions. In doing so, new insights into the specific orientation-dependent dissolution mechanisms are offered, and the acquisition of appropriate conditions that result in nanoscale roughness surfaces (avoiding the dominance of pitting and preferential grain removal) is firstly explored. Building on prior work, a piecewise approach is presented to analyse the acquired image stacks to map partial crystal orientations, while different approaches are proposed to account for jet-specific surface artefacts and waviness. This is repeated over 20 layers in an individual specimen and layer-wise orientation maps are used to construct volumetric models of the specimen. These data sets are then explored from the perspective of materials/manufacturing engineers, who may use to this information to effect advancements to materials processing technologies.

A New Approach to Breast Specimen Orientation: Avoiding Pitfalls with the Specimen Plate Concept.

Accurate specimen marking is crucial during breast cancer surgery to avoid misorientation, which can lead to inadequate re-excision and tumor recurrence. We studied the marking methods at various breast cancer centers to create a tool that would prevent specimen misorientation. An online questionnaire was used to survey marking procedures at major breast cancer centers in Hungary, and a tool was developed using a troubleshooting method. Twelve out of twenty units responded (60%). Nine use an institutionally standardized marking system. Less than half of the surgical teams found specimen mammograms to be unambiguous. In more than 70% of departments, pathologists were uncertain about breast specimen orientation. Ambiguous marking methods caused orientation errors in half of the cases, while unclear marking directions caused the rest. Most pathologists (85%) and surgeons (75%) believed that coronal plane specimen mammography would help solve the problem. A plastic specimen plate has been developed to anchor breast tissue to a coronal breast scheme as seen in mammography images, providing clear localization information throughout the surgical process. There is a lack of standardization in breast specimen orientation and marking in Hungary. An optimized orientation toolkit is being developed to ensure consistent interpretation of specimen mammograms by surgeons and pathologists.

Deep learning and defocus imaging for determination of three-dimensional position and orientation of microscopic objects

We present a method to determine the three-dimensional position and orientation of microscopic, non-spherical objects in microfluidic and laboratory-on-a-chip systems observed through conventional optical microscopes. The method is based on the combination of the General Defocusing Particle Tracking technique [Barnkob et al., “General defocusing particle tracking,” Lab Chip 15, 3556–3560 (2015)] and deep learning. It requires minimal input from the user, is suitable for real-time applications, and can be applied to any microscopic object with an approximately ellipsoidal shape, such as unicellular swimming organisms, red blood cells, or spheroidal colloids. The main challenge is linked to the construction of suitable training datasets for the neural network. We provide a procedure generally valid for active microswimmers and discuss possible strategies for other types of objects. An implementation using the Visual Geometry Group convolutional neural network (VGG-16) is presented and tested on synthetic images with different backgrounds and noise levels. The same implementation is used to track the position and orientation of different specimens of the heterotrophic ciliate Euplotes Vannus in free-swimming motion. The measurements were performed with a 10 × objective over a depth of 800 μm with an average estimated uncertainty in the orientation angles of 9.0%.

On the fatigue crack growth behavior of nanocrystalline CrMnFeCoNi

The fatigue crack growth (FCG) behavior of the equimolar CrMnFeCoNi Cantor-alloy in the nanocrystalline grain size regime has been explored with special focus on the influence of specimen orientation and the effect of additional heat-treatments. For the synthesis severe plastic deformation using high-pressure torsion (HPT) was used. The results were critically discussed regarding the impact of grain size on the FCG-behavior and compared to a conventional 316L stainless steel in the nanocrystalline state: The reduction of grain size in the Cantor alloy from the micrometer to the nanometer regime invokes crack growth rates being about one order of magnitude higher paired with significantly lower threshold values. Furthermore, the sensitivity of thresholds and crack growth rates in the Paris regime on the applied load ratio in the NC material state is also profoundly reduced. This can be explained based on a diminishing contribution of crack closure effects, especially roughness induced closure. Even though the chemical composition differs distinctively, the crack growth rates and fatigue threshold values of the nanocrystalline Cantor alloy and the stainless steel are comparable with the latter being slightly lower for the CrMnFeCoNi alloy. Moreover, the extent of anisotropy is more pronounced than for 316L. Heat-treatment leading in the NC-Cantor alloy to an increasing hardness, has also an effect on the FCG-rate and depends on the specimen orientation. In addition, an unusual self-annealing behavior affecting the FCG behavior of the Cantor alloy was found.

On The Preparation Of Training Data For 3D Tracking Of Position And Orientation Of Microswimmers Using Defocusing And Deep Learning

The use of image analysis algorithms based on deep convolutional neural networks (CNNs) is opening new possibilities in experimental techniques for fluid dynamics. In the field of microscopic 3D particle tracking based on defocusing, it has been shown on synthetic images that CNNs can be used to determine not only the depth position but also the orientation of non-spherical microscopic particles or specimens. However, the translation of such approaches to experimental setups is challenging, especially due to the difficulty of obtaining reliable labeled images to train the neural networks. In this work, we propose a method to obtain labeled images of microswimmers from conventional microscopy images, exploiting the properties of the swimming motion at low Reynolds numbers, where inertial effects are negligible. This method allows us to obtain ground truth values of orientation and depth position of a microorganism swimming at a regular pace that can be used as training data for CNNs. The proposed methodology was used to obtain labeled images from experimental videos of the micro-organism Euplotes Vannus. The labeled images were used to train a VGG16 network, providing an estimated uncertainty in the determination of the orientation angles psi, theta, phi, and the depth position Z of 2.4%, 1.4%, 2.3%, and 3.5%, respectively.

Augmented Reality-Guided Frozen Section Analysis: Bringing the Pathologist From the Laboratory to the Operating Room.

Due to the anatomic complexity of the head and neck and variable proximity between laboratory and operating room (OR), effective communication during frozen section analysis (FSA) between surgeons and pathologists is challenging. This proof-of-concept study investigates an augmented reality (AR) protocol that allows pathologists to virtually join the OR from the laboratory. Head and neck cancer specimens were scanned ex vivo using a 3-dimensional scanner and uploaded into an AR platform. Eight head and neck specimens were discussed by surgeons and pathologists in an AR environment. AR-guided intraoperative consultation was used for specimen orientation and discussion of FSA margin sampling sites. One patient had positive initial margins on FSA andwas re-resected to negative final margins. AR-guided FSA is possible and allows pathologists to join the operating from any location for intraoperative discussion.

Anisotropic creep property related to non-spherical shape of mechanically alloyed powder of oxide dispersion strengthened F82H

Nanometric oxide particles dispersed within the matrix play an important role in improving the creep property of Oxide Dispersion Strengthened (ODS) steels. Conventional studies have primarily focused on investigating the distribution of the particles to control the creep property of ODS steels. However, achieving complete control over the creep property still poses challenges, as there are potentially other microstructural features like different matrices, micrometric precipitates, and inclusions derived from powder metallurgical processes that can influence it.In our previous research, we examined one such microstructural feature known as prior particle boundary (PPB). PPB refers to the surface of mechanically alloyed (MA) powder before consolidation. We revealed that the ODS steel with fine PPBs produced from smaller MA powder, exhibited shorter creep rupture times, compared to that with coarse PPBs produced from larger MA powder. This result was attributed to the increased formation of creep cavities on the PPBs in the ODS steel produced from smaller MA powder. Therefore, the size of MA powder affected the formation of creep cavity and had an impact on the creep property.In this study, we shifted our focus to the shape of MA powder with non-spherical shapes containing flake-like shape. Such shapes have the potential to induce anisotropy in the formation of creep cavities and/or the creep crack initiation and growth along anisotropic prior particle boundaries (PPBs), ultimately leading to anisotropic creep behavior.We conducted small punch creep tests on specimens with two different orientations to study the possible anisotropy. The results revealed that the creep rupture times varied depending on the orientation of specimen, thus indicating anisotropic creep property. This anisotropic creep property was related to the non-spherical shape of MA powder. This research highlighted the significance of managing the shape of MA powder in controlling the creep property of ODS steels.

Experimental Investigation of Strain Rate Influence on Anisotropy of Uniaxial Tensile Mechanical Properties of CuFe2P Alloy Sheet.

Wire crimping, a process commonly used in the automotive industry, is a solderless method for establishing electrical and mechanical connections between wire strands and terminals. The complexity of predicting the final shape of a crimped terminal and the imperative to minimize production costs indicate the use of advanced numerical methods. Such an approach requires a reliable phenomenological elasto-plastic constitutive model in which material behavior during the forming process is described. Copper alloy sheets, known for their ductility and strength, are commonly selected as terminal materials. Generally, sheet metals exhibit significant anisotropy in mechanical properties, and this phenomenon has not been sufficiently investigated experimentally for copper alloy sheets. Furthermore, the wire crimping process is conducted at higher velocities; therefore, the influence of the strain rate on the terminal material behavior has to be known. In this paper, the influence of the strain rate on the anisotropic elasto-plastic behavior of the copper alloy sheet CuFe2P is experimentally investigated. Tensile tests with strain rates of 0.0002 s-1, 0.2 s-1, 1 s-1, and 5.65 s-1 were conducted on sheet specimens with orientations of 0°, 45°, and 90° to the rolling direction. The influence of the strain rate on the orientation dependences of the stress-strain curve, elastic modulus, tensile strength, elongation, and Lankford coefficient was determined. Furthermore, the breaking angle at fracture and the inelastic heat fraction were determined for each considered specimen orientation. The considered experimental data were obtained by capturing the loading process using infrared thermography and digital image correlation techniques.

Statistical evaluation of measured biomechanical properties of human brain aneurysm samples.

<p>Human brain aneurysms may often prove fatal if not re&shy;cognized in time and treated accordingly. The understanding of development and rupture of aneurysms can significantly be improved by the application of numerical modelling, which in turn, requires the knowledge of mechanical properties of vessel wall. This study aims to identify assumed differences with respect to age, sex, spatial orientation, and rupture by utilizing detailed statistical analysis of uniaxial tensile measurements of human brain aneurysm samples, performed by the authors in a previous project.</p>. <p>At surgery of 42 patients, aneu&shy;rysm fundi were cut distally to the clip. In each case, depending on size, varying number of stripes (altogether 88) were prepared and uniaxial stress-strain measurements were performed. Quantities related to the capacity, energy absorption or stiffness were determined and statistically analysed.</p>. <p>The number of specimens in the aneurysm sample was sufficient to establish statistical differences with respect to sex and rupture (p&lt;0.05). No significant differences were detected in orientation, though higher values of stresses and deformations were ob&shy;tained in the circumferential direction com&shy;pared to the meridional direction.&nbsp;</p>. <p>Significant differences bet&shy;ween sexes with respect to ultimate deformations were demonstrated according to expectation, and the hypothesis on equality of energy capacity could be supported. Similarity of curves with respect to specimen orientation was also observed and ruptured aneurysm sacs tended to be smaller in size. It seems that differences and trends described in this paper are realistic and need to be applied in numerical modelling.</p>.

Investigation of fibre distribution and orientation in SFRC specimens and their influence on flexural properties

The distribution and orientation of fibres were qualitatively estimated using statistical methods, and finite element analysis was conducted to evaluate the flexural behaviours based on these characteristics. The results demonstrate that the fibres disperse well in the concrete matrix when the water-to-binder ratio is 0.35, and the concrete mixture is prepared by sequentially adding coarse/fine aggregates, powder materials, water and steel fibres. In contrast to the order of fibre addition, the water-to-binder ratio significantly influences the fibre distribution coefficient and orientation factor. A water-to-binder ratio of 0.35 results in a higher orientation factor ( gh) of 0.7. Furthermore, statistical analysis reveals that the orientation of fibres on the cutting section follows a Gaussian distribution, with the peak occurring at approximately 40° to 50°. Finite element analysis revealed that the orientation distribution of fibre affects not only the flexural strength, more significantly, the post-cracking flexural stiffness.

Influence of deformation, microstructure, and temperature on the fracture resistance of technically pure tungsten

The fracture resistance of technically pure W with pre-deformed and recrystallized microstructures was tested in a temperature range of ambient to 700 °C. To account for the impact of microstructure anisotropy, samples with different specimen orientations were investigated. Room temperature tests were carried out in a scanning electron microscope and at elevated temperatures in a vacuum furnace. Both, microstructure and testing temperature significantly influence the fracture resistance of W and a strong dependence of the crack propagation resistance on the crack plane orientation was found. Pre-deformation of the testing material increases the fracture resistance in terms of the crack initiation toughness but shortens the measurable crack resistance curve (R-curve). Testing at elevated temperatures results in higher initiation toughness for both states, pre-deformed and recrystallized; however, only the recrystallized structure shows an R-curve behavior for the used sample geometry.

Experimental determination of the charring rate of cross-laminated timber panels

Recent design guides include charring models for cross-laminated plane timber (CLT) members. When the bond line integrity is not maintained, charring is illustrated as a combination of sequenced phases. Significant research has been conducted on the charring behaviour of CLT panels, and the criterion of 300 °C has been an accepted definition for the char front line. The charring rate of a solid wood-based panel is determined by the char depth divided by the time to reach the char depth. In the CLT structure, this method can be applied to the first lamella layer. However, due to the char fall-off, it cannot be directly applied to the lamella layers behind the first layer. In this research, eight fire tests were conducted to investigate how charring rates of different lamella layers can be determined from measured temperatures. An assessment method based on the mean char depth development determined from experimental temperature distributions of CLT panels is introduced. Also, the effects of thermocouple positioning and specimen orientation on the assessment results were analysed. The charring rates determined for both horizontal and vertical specimens align well with the results calculated using the European Charring Model and a post-protection factor k3 of 2.

Effect of Short-Fiber Orientation on the Tensile Strength of Epoxy Adhesives

Short-glass-fiber-reinforced adhesives are state-of-the-art materials used in the bond lines of wind turbine blades. Various alignments of the short fibers are emerging, which depend on the adhesive flow during the application and joining processes. This induces a spectrum of direction-dependent mechanical properties. The tensile strength, for instance, can vary by about 20% depending on the load direction. Therefore, the adhesive performance, which is normally determined under controlled laboratory conditions and implemented in bond line design routines, can deviate from the in situ application. This work investigates the effect of the short-fiber alignment on the tensile strength distribution of an industry-standard adhesive used in wind turbine rotor blades. The smeared short-fiber orientation of the tensile specimens tested is estimated locally near the damaged surface using a material model that is fed with thermomechanical measurements and calibrated via micro-computed-tomography analysis. A linear correlation between tensile strength and short-fiber alignment has been identified. This augments the identification of the material’s upper and lower strength limits for bond line design purposes.

Experimental investigation and numerical modelling of the cyclic plasticity and fatigue behavior of additively manufactured 316 L stainless steel

This study addresses the critical need for a constitutive model to analyze the cyclic plasticity of additively manufactured 316L stainless steel. The anisotropic behavior at both room temperature and 300 °C is investigated experimentally based on cyclic hysteresis loops performed in different orientations with respect to the build direction. A comprehensive constitutive model is proposed, that integrates the Armstrong-Frederick nonlinear kinematic hardening, Voce nonlinear isotropic hardening and Hill's anisotropic yield criterion within a 3D return mapping algorithm. The model was calibrated to specimens in the 0° and 90° orientations and validated with specimens in the 45° orientation. A single set of hardening parameters successfully represented the elastoplastic response for all orientations at room temperature. The algorithm effectively captured the full cyclic hysteresis loops, including historical effects observed in experimental tests. A consistent trend of reduced hardening was observed at elevated temperature, while the 45° specimen orientation consistently exhibited the highest degree of strain hardening. The applicability of the model was demonstrated by computing energy dissipation for stabilized hysteresis loops, which was combined with fatigue tests to propose an energy-based fatigue life prediction model.

The effect of hydrogen and notch orientation in SENT specimens on the fracture toughness of an API 5L X70 pipeline steel

Transporting hydrogen gas through pipelines is an important topic within the context of energy transition. An essential challenge hereto is the phenomenon of hydrogen embrittlement of pipeline steels which includes a reduction in fracture toughness. As the theories accounting for hydrogen embrittlement are still debated, improving fundamental insights into the underlying mechanisms is crucial. Fracture toughness tests on single edge notched tension (SENT) specimens have been performed to examine the influence of hydrogen on the fracture behavior of a pipeline steel. An API 5L X70 steel was selected for this purpose, characterized by a distinctive banded microstructure commonly seen in pipeline steels. The test specimens were extracted from the steel pipe, and a notch in two different orientations was machined. By using a combination of fractography and X-ray micro-CT (Computed Tomography), the fracture mechanisms are revealed. The tearing resistance characteristics of the steel, with and without the presence of hydrogen, are demonstrated through tearing resistance curves. The experiments show that the banded microstructure plays a key role in the results through the development of splits at the microstructural bands. While these splits are also present in uncharged toughness test specimens, they are increasingly present in hydrogen charged specimens suggesting a hydrogen related weakening of the banded microstructure. In addition, it is demonstrated that hydrogen induces an increasingly zigzagged crack path. This is attributed to a potential combination of accelerated void nucleation at the microstructural bands, and accelerated shear-driven fracture.

Dynamic Shear Mechanical Properties and Microscopic Deformation Characteristics of Laser Cladding IN625 Alloy

To reveal the dynamic shear mechanical properties of laser cladding Inconel 625 (IN625) alloy, dynamic shear mechanical properties experiments are conducted on forged specimens and laser cladding specimens by split Hopkinson press bar experimental device. Optical microscopy, scanning electron microscopy, and electron backscattered diffraction (EBSD) are used to characterize the microscopic morphology, crystal orientation, and grain size of laser cladding specimens before and after dynamic shear deformation. In the results, it is shown that the yield strength and shear strength of both forged and laser clad specimens increase with the increase of shear strain rate, reflecting a remarkable strain‐rate‐strengthening effect, and the shear strength of the laser cladding specimen is higher than that of the forged specimen. After dynamic shear loading, the grains in the shear region of the laser cladding specimen are severely deformed, deformation bands appear, and some dendrites are transformed into equiaxed crystal. After shear deformation, the preferred orientation strength of the crystal increases, the small‐size grain and low‐angle grain boundary increase, and a large number of dislocations are formed in the shear region, which dominates the dynamic shear deformation behavior of the material. Dislocation is an important dominant mechanism of dynamic shear deformation.

Optimization of intraoperative lumpectomy specimen labeling

BackgroundAccurate lumpectomy specimen orientation is critical as incorrect orientation may result in excision of the wrong lumpectomy margin. Our goal was to determine if specimen orientation achieved by labeling three surfaces is superior to two. MethodsThis was a prospective single-institution study including 22 breast surgical oncologists. Intraoperative labeling of either two or three surfaces of the lumpectomy specimen was based on surgeon preference. The specimen was delivered to Pathology where it was oriented by the pathology team and the surgeon then determined if the specimen was correctly oriented or if re-orientation was required. Surgeons subsequently recorded orientation technique and if re-orientation was required. Specimen weight, patient age, and BMI were recorded. Fisher’s exact test and two-sample Wilcoxon rank-sum test were used to determine p-values. ResultsOf 268 specimens, 40 (14.9%) required re-orientation. Labeling specimens on three surfaces was superior to two (22 of 195 (11.2%) versus 18 of 73 (24.6%), p = 0.01). Specimens requiring re-orientation were more likely to be heavier (36 g vs. 24 g, p = 0.02). In multivariable analysis, labeling specimens on three surfaces resulted in a 70% reduction in discordance rates between the surgeon and pathology team (OR 0.3, p = 0.001). Using mean weight of lumpectomy specimens, specimens >33 g were more likely to require reorientation (OR 2.8, p = 0.004). Age and BMI did not impact the need for re-orientation. ConclusionLumpectomy specimen labeling using three surfaces was superior to two. Surgeons should routinely orient their specimens on three or more surfaces to decrease discordance rates.

Analysis of material removal mechanism in nanoscale machining of copper

In the current study, molecular dynamics modeling and simulation are carried out to analyse mechanisms in tool-workpiece interaction in nanoscale cutting. Various combinations of a/ r ratios for constant r ( r = tool edge radius and a = uncut chip thickness) are considered and different crystal orientations of the workpiece specimen are employed in the nanoscale cutting model. From the simulation, material anisotropy behavior is observed during the nanoscale cutting of copper material. Analysis at the molecular scale reveals that the crystal orientations family {1 1 0}&lt;1 0 0&gt; is hard to machine and the family of crystal planes {1 1 1}&lt;1 1 0&gt; is easiest to cut. While comparing in different crystal planes and directions, it was noticed that the material deformation in nanoscale machining takes place only in slip directions, that is, &lt;1 1 0&gt; family of directions. It is also found that as the uncut chip thickness is decreased, the cutting mechanism changes from shear plane cutting to plowing to sliding in Cu.