Basic Fracture Research Articles

The Level of Knowledge and Attitude Toward Dealing With Fractures at Accident Sites Among Al Baha Population.

A fractured bone is a medical emergency that causes bone continuity to be partially or completely disrupted. Effective fracture management at accident sites is crucial for minimizing complications and improving outcomes. Despite its importance, this study aimed to assess the level of knowledge and attitude toward fracture management among residents of Al Baha province and explore the association of this knowledge with demographic factors. A cross-sectional descriptive study involving 389 participants was carried out employing a structured online self-administered questionnaire that contained sociodemographic information about the participants along with a basic knowledge assessment regarding fractures at accident sites. To investigate relationships between variables, statistical analysis was used, including the Chi-square test. This investigation revealed a majority of participants demonstrated moderate to high levels of knowledge about fracture management, with 166 (42.7%) classified as having high knowledge and 187 (48.1%) as having moderate knowledge. Meanwhile, four (1%) were found to have poor levels. Significant associations were found between knowledge levels and gender (p = 0.048), residency (p = 0.014), and marital status (p = 0.011). Males, residents of Al Baha, and married individuals showed the highest levels of knowledge. However, gaps were identified in responses related to open fractures and spine injuries. In conclusion, a study of 389 participants highlights a generally high level of knowledge about fracture management among Al Baha residents, with notable differences linked to demographic factors. While the findings suggest a solid understanding of basic fracture management principles, there are specific areas where knowledge could be improved. Targeted educational interventions, especially those addressing identified knowledge gaps and tailored to different demographic groups, are recommended to enhance public preparedness and response to fractures.

Epidemiological characteristics of post-traumatic stress symptoms and its influence on length of hospital stay in inpatients with traumatic fractures in Zunyi, China.

To investigate the clinical epidemiological characteristics and occurrence of post-traumatic stress symptoms (PTSS) in patients with traumatic fractures, we sought to analyze the factors that influence the prognosis of a length of hospital stay (LOS) and provide valuable insights to prevent PTSS in fracture patients and improve their prognosis. Inpatients with traumatic fractures were recruited from a third-class comprehensive general hospital in southwest China between November 2019 and October 2020. Case data of traumatic fracture patients were collected, and a questionnaire that included general information and basic fracture details was completed. The post-traumatic stress disorder Self-rating Scale was used to assess PTSS among the fracture inpatients. A total of 204 inpatients who experienced traumatic fractures were included in this study. Falls accounted for the largest proportion of traumatic fractures. A Cox's regression analysis revealed that serious injury [Hazard Ratio (HR) = 2.44, 95% Confidence Interval (CI): 1.33-4.46], critical illness during hospitalization (HR = 1.70, 95% CI: 1.13-2.54), and undergoing two surgeries (HR = 1.87, 95% CI: 1.20-2.93) were risk factors for longer LOS. Among the fracture patients, 30.39% exhibited positive PTSD symptoms, and physical activity during the fracture [Odds Ratio (OR) = 0.63, 95% CI: 0.45-0.88] and increased pain (OR = 3.34, 95% CI: 1.82-6.11) were identified as influencing factors. Given the high detection rate of PTSS following traumatic fractures, it is crucial for relevant departments to implement targeted measures to protect high risk individuals. Furthermore, strengthening the care provided to the patients' physical and mental health is urgently needed to reduce the incidence of PTSS.

Fracture Mechanics Induced by Drilling and Blasting in Underground Openings: Prevailing Practices and Studies

This article presents the prevailing practices and literature review on the study of fracture mechanics of rock mass, during the construction of underground openings, by drill and blast method (DBM). The paper makes an introductory discussion on basic fracture and failure mechanics on the rock, followed by a review due to the blast-induced failure mechanism. The damage zone in drill and blast openings is discussed which is followed by the conclusions of the literature. DBM is a widely acceptable and broadly applicable approach in the underground construction method. The blasting damaged zones are classified as the borehole expansion zone, crushed zone, nonlinear fracture zone, and radial crack propagation zone. Blasting activities create stress waves in construction work, which fundamentally influence the fracture and failure mechanics of rock with pre-existing discontinuities, in-situ stress, and groundwater conditions. On the other hand, the cumulative action of subsequent explosion gas and stress waves defines the final damage limit and crack pattern map. Thus, it is of utmost importance to investigate the blast-induced fracture and failure mechanism to mitigate the instability in the underground openings.

Fatigue crack propagation near a corrosion pit in a HSS specimen

Corrosion and fatigue are very common forms of metal degradation, and thus an aspect of the complex issues involved is analysed within this work. A rectangular specimen with a surface fatigue crack and a surface corrosion pit subjected to remote tensile loading was modelled via the finite element method in order to assess the crack behaviour for various configurations of both the crack and the pit. A perpendicular crack was considered along with an angled crack, and the basic fracture parameters have been determined and discussed regarding the influence of the corrosion pit on further crack propagation. Additionally, selected fracture criteria have been applied in their classical one-parameter as well as generalised multi-parameter form to estimate the angle of further crack propagation. The results obtained are discussed thoroughly, and it is proved that the larger the corrosion pit, and the closer it is to the crack, the higher its effect on the fatigue crack behaviour is.

Study on hydraulic cracking mechanism and propagation characteristics of ice hole based on Peridynamics

Drilling of polar deep ice cores is an important means to study the evolution of the earth's climate. When drilling into complex formations such as brittle ice layer, warm ice layer, basement meltwater layer, or ice-rock interlayer, drilling problems frequently occur, especially the hydraulic cracking of ice holes. This paper studies the dynamic propagation process and the influence mechanism by theory and simulation to solve the problem of cracks initiation and propagation around the ice hole. Based on continuum mechanics, a stress model is established to obtain the stress state around the borehole well. In local continuum mechanics, the stress state is represented by spatial partial differential equations, and its spatial partial derivatives cannot describe the discontinuous situation. Peridynamics (PD) use integral equations to solve this problem effectively. The PD model of the ice hole is established to realize the unified description of the continuous and discontinuous space around the ice hole. The dynamic cracks propagation process, the influence mechanism of hydraulic pressure and fracture toughness are analyzed. The loading rate of ice in the paper and experiment is 0.008 mm/s, the elastic modulus is 9 GPa, and the basic fracture toughness is 175 kPa·m0.5. Case study shows that hydraulic pressure promotes cracks propagation, the hydraulic pressure increases by 1 MPa, the volume ratio of cracks increases from 7.67% to 14.93%. The volume ratio of cracks is defined: the ratio of the cracks volume to the total model volume. Fracture toughness hinders cracks propagation, which increases from 150 kPa·m0.5 to 175 kPa·m0.5, the proportion of cracks volume decreases from 13.85% to 7.67%. When drilling into the formation with prominent ductile-brittle transition, the mud density shall be adjusted in time to control the hydraulic pressure in the hole to reduce cracks propagation and ensure the safety and efficiency of ice drilling.

Uniquely determine fracture dimension and formation permeability from diagnostic fracture injection test

Estimating formation permeability is crucial for production estimation, hydraulic fracturing design optimization and rate transient analysis. Laboratory experiments can be used to measure the permeability of rock samples, but the results may not be representative at a field scale because of reservoir heterogeneity and pre-existing natural fracture systems. Diagnostic Fracture Injection Tests (DFIT) have now become standard practice to estimate formation pore pressure and formation permeability. However, in low permeability reservoirs, after-closure radial flow is often absent, which can cast significant uncertainties in interpreting DFIT data. Without knowing the fracture dimension prior, open fracture stiffness/compliance can't be determined, which is required for formation permeability estimation. Previous work has to assume a fracture radius or fracture height in order to estimate formation permeability, thus dent the confidence in the interpretation results. In the study, we present a new approach to determine fracture dimension, leak-off coefficient and formation permeability uniquely based on material balance and basic fracture mechanics, using data from shut-in to after-closure linear flow. Field examples are also presented to demonstrate the simplicity and effectiveness of this new approach.

Study on the Hydraulic Fracturing of the Inter-Salt Shale Oil Reservoir with Multi-Interfaces

Hydraulic fracture morphology and propagation mode are difficult to predict in layers of the various lithological strata, which seriously affects exploitation efficiency. This paper studies the fundamental mechanical and microscopic properties of the two main interfaces in inter-salt shale reservoirs. On this basis, cement-salt combination samples with composite interfaces are prepared, and hydraulic fracturing tests are carried out under different fluid velocities, viscosity, and stress conditions. The result shows that the shale bedding and salt-shale interface are the main geological interfaces of the inter-salt shale reservoir. The former is filled with salt, and the average tensile strength is 0.42 MPa, c = 1.473 MPa, and φ = 19.00°. The latter is well cemented, and the interface strength is greater than that of shale bedding, with c = 2.373MPa and φ = 26.15°. There are three basic fracture modes for the samples with compound interfaces. Low-viscosity fracturing fluid and high-viscosity fracturing fluid tend to open the internal bedding interface and produce a single longitudinal crack, respectively, so properly selecting the viscosity and displacement is necessary. Excessive geostress differences will aggravate the strain incompatibility of the interface between different rock properties, which makes the interfaces open easily. The pump pressure curves’ morphological characters are different with different failure modes.

Prediction of Reservoir Fracture Parameters Based on the Multi-Layer Perceptron Machine-Learning Method: A Case Study of Ordovician and Cambrian Carbonate Rocks in Nanpu Sag, Bohai Bay Basin, China

Developing a model that can accurately predict internal fractured reservoirs in the context of the ultra-low physical properties of carbonate rocks by only employing conventional mathematical methods can be very challenging. This process is challenging because the relationship between basic fracture parameters and the logging response in carbonate reservoirs has not been studied, and the traditional method lacks adaptability due to the complex relationship between basic fracture parameters and the logging response. However, data-driven approaches supplemented by machine learning algorithms based on multi-layer perceptrons (MLP) provide a more reliable solution to this challenge. In this paper, a classical fracture parameter evaluation data set is established using fracture porosity, fracture density, fracture length, and fracture width data that can be identified by resistivity and acoustic imaging logging. Another data set can be composed of different types of logs, and it can be used to identify reservoirs. Two different data sets were validated by regression task evaluation indicators in machine learning, and the correlation coefficient R2 is greater than 0.82. This means that the model accuracy of the algorithm can reach 82%. Combined with the comparison results of eight conventional machine learning algorithms, the reliability and application validity of the MLP model are verified. This method’s accuracy is also verified by oil test data, which show that the MLP machine-learning algorithm can effectively simulate the relationship between lithology and fracture development. In addition, it can be used to predict key exploration horizons before drilling. The relationship between lithology and fracture development degree is well-simulated by the MLP machine learning algorithm, which shows that the degree of fracture development is mainly affected by fractures, indicating that the method can be used to predict key exploration horizons before drilling.

Fracture resistance of 3D nano-architected lattice materials

Exploiting small scale material effects and structural topology, nano-architected lattices represent a recent novel class of mechanical metamaterials, which exhibit unprecedented combination of mechanical properties. Together with scarce resistance to fracture and catastrophic failure, understanding of the fracture characteristics and properties of 3D nano-architected lattices still represents a limiting factor for the design and realization of future engineering applications. Here, using a combination of in-situ tensile fracture experiments and finite element simulations, we first show the possibility to reach stable crack growth in nano-architected materials harnessing only the intrinsic plastic toughening mechanism. Exploring the effect of lattice topology on the fracture properties, we then demonstrate similar performance between the octet and 3D kagome architecture (along one direction). Based on the experimental and numerical results, a power-scaling law of normalized crack initiation toughness with relative density ρ¯ (i.e., fraction of material per unit volume) KIC/σyL∝ρ¯1.11, ρ¯1.17−1.27 is exhibited by the octet and 3D kagome topology, respectively, given the yield strength σy and the unit cell size L. Owing to the combination of the parent material’s size effect and plasticity (3D-printed photo-resist polymer), the fracture initiation toughness (considering σy=27MPa) of our octet nano-architected lattices is ∼ 8 times that of previously realized macroscopic octet titanium structures. After crack initiation, the two architectures manifest rising (in average ∼ 18%) fracture resistance curves (i.e., R-curves), without catastrophic failure. In addition, we find that the fracture toughness of architected lattices, measured by means of compact tension specimens, seems not to be dependent on the sample’s thickness, forcing to re-think the plain strain toughness definition for this class of materials. Our results uncover the basic fracture characteristics of 3D architected materials exhibiting stable crack growth, providing insights for the design of light-weight, tough materials, with implications for future macro-scaled structural applications.

Experimental Research and Fatigue Life Prediction of Ultra-High-Strength Steel Aermet100

This study concentrates on the fatigue performance of ultra-high-strength steel Aermet100 under different loading rates. The standard specimen measured the static mechanical properties of Aermet100 steel, based on which the basic mechanical properties and fracture characteristics of the sample before and after necking was obtained. To take the strain rate effect into account, this study uses the dynamic constitutive model Johnson-Cook. The equation parameters are fitted through dynamic mechanical tests and quasi-static tests. This model is input into ABAQUS user-defined program afterward. Referring to the work done above, along with the extended finite element method (XFEM), this study establishes the dynamic fracture finite element model of the Aermet100 steel specimen on the basis of the continuous damage mechanics. Five groups of specimen fatigue tests were carried out in the laboratory. Simulation results show the feasibility and accuracy of the integrated XFEM model with the same loading and boundary conditions. The experimental data and simulation results prove that, in the loading time range of 0.0001 ~ 1s, the life cycles increase as the loading rate increases. It is worth mentioning that when the loading time is in the order of 0.0001s, the life changes significantly.

Microstructure Characterization and Small Punch Test Analysis in Nickel-Based Alloy 617 by High Energy Neon Implantation

Nickel-based alloys are good candidate structural materials for ultra-high temperature gas-cooled reactors due to their excellent mechanical properties under high-temperature conditions. The operating environment in the compact high-temperature gas-cooled reactor proposes more stringent requirements with higher displacement and temperatures higher than 700 °C. The irradiation resistance of nickel-based alloy 617 is evaluated by 120 MeV neon ion irradiation. The neon ion fluence is set with reference to the number of helium atoms generated by the reaction of (n, α) in nickel-based alloy under actual service conditions. With the application of an energy gradient degrader, the irradiation damage area is more uniform with increasing depth. The neon ion irradiation causes no significant surface damage to alloy 617 while the evolution of defects such as inherent dislocation lines is affected, thus leading to the deterioration of mechanical properties. By using the small punch test to analyze the irradiation effects, it is found that the neon ion irradiation results in the tendency of irradiation softening and does not lead to changes in the basic fracture characteristics under different annealing conditions. After annealing at 700 and 800 °C for 2 h, the irradiation embrittlement trend is intensified, with the fracture characteristic values of irradiated samples showing a more obvious decreasing trend.

Fatigue properties of Ti-6Al-4V Gyroid graded lattice structures fabricated by laser powder bed fusion with lateral loading

Graded lattice structures (GLSs) have drawn much attention in engineering and biological areas due to the enhanced mechanical properties and energy absorption capacity that benefit from the graded design. This study aims to investigate the effect of gradient on fatigue behaviors of lattice structures under the cyclic loading lateral to the gradient direction. The Gyroid-type triply periodic minimal surface was utilized to design GLS with continuously varied volume fraction (VF) from 10% to 40%. Uniaxial compressive testing and compression-compression fatigue testing were conducted on the Ti-6Al-4V Gyroid lattice structures with both uniform and graded VFs fabricated by laser powder bed fusion. Three typical fracture modes and mixed fracture modes were all observed on the fracture surfaces of struts after fatigue testing. The fatigue life of Gyroid GLSs is 1.21–1.67 times that of uniform counterparts with an identical overall VF. The enhancement mechanism on fatigue properties coming from the gradient design is elaborated through the finite element analysis and experimental characterization. The lower level of tensile stress, bigger macro-area and micro-plastic zone on struts of the main loading-bearing constituent of Gyroid GLS relieve the stress concentration around the crack tip, thus, lower the crack propagation rate and provide stronger fatigue crack resistance. Furthermore, the struts in the main loading-bearing constituent are more prone to stretching, therefore, provide long-term carrying capacity even after the occurrence of penetrating cracks. Experiment results show that the carrying capacity can be still provided by these struts even with penetrating cracks. • Gyroid graded lattice structures were designed and made via laser powder bed fusion. • Three basic fracture modes and mixed modes were observed from the fracture surfaces. • Thick struts in the graded lattice structure has a lower tensile stress. • Few penetrating cracks do not lower the carrying capacity of the graded lattice. • The gradient design dramatically improves the fatigue properties.

Surgical Site Infection Following Intramedullary Nailing of Subtrochanteric Femoral Fractures.

Aim: To investigate the incidence, risk factors and pathogenic micro-organisms causing superficial and deep infection in subtrochanteric femoral fractures managed with an intramedullary nail. Materials and Methods: Following institutional board approval, all consecutive patients presenting with a subtrochanteric fracture were retrospectively identified, over an 8-year period. Basic demographics, fracture characteristics, fracture union, revision operation, mortality and other complications were reported and analysed. Variables deemed statistically significant (p-value < 0.05) were then included into a revised adjusted model of logistic regression analysis, where we reported on the odds ratio (OR). Results: The overall incidence of infection was 6.4% (n = 36/561; superficial: 3.7%; deep: 2.7%). Associations with deep infection included: non-union (OR 9.29 (2.56–3.38)), the presence of an open fracture (OR 4.23 (3.18–5.61)), the need for massive transfusion (OR 1.42 (2.39–8.39)), post-operative transfusion (OR 1.40 (1.10–1.79)) and prolonged length of stay (OR 1.04 (1.02–1.06)). The Commonest causes of superficial infection were Staphylococcus aureus (28.5%), enteric flora (23.8%) and mixed flora (23.8%); whereas coliforms (60%) and Staphylococcus aureus (26.7%) were the commonest micro-organisms isolated in deep infection. Polymicrobial infection was identified in 38.5% and 80% of superficial and deep infections, respectively. Conclusion: Causative micro-organisms identified in both superficial and deep infection were similar to those reported in post-traumatic osteomyelitis. In an attempt to minimise infection, the treating clinician should focus on modifiable risk factors with adequate patient optimisation, prompt surgical treatment, adequate antibiotic coverage and wound care when treating patients with subtrochanteric femur fracture.

Fracture Behavior of Modified Polymer Materials by Digital Image Correlation Method

Polymer materials play an important role in today's social development, and become important materials in industry, agriculture, national defense and other fields. With the further development of modern engineering material technology, polymer materials, together with information technology and biotechnology, promote the progress and development of society. The performance and quality of modified polymer materials have also entered the research field of vision of various industries and become the focus of exploration and analysis. The following is the research on the fracture behavior of modified polymer materials with the help of digital image correlation method. The purpose of this paper is to clarify the basic fracture work, shaping work and other fracture work parameters of various modified polymer materials, and grasp the root cause of fracture work parameters of modified polymer materials, so as to clarify the modification processing parameter means of these polymer materials.

Development of 3‐D Curved Fracture Swarms in Shale Rock Driven by Rapid Fluid Pressure Buildup: Insights From Numerical Modeling

AbstractDespite the variety of studies that have investigated the development of fracture networks during kerogen maturation in organic‐rich shale, the fracture interaction modes and generation mechanisms in three‐dimensions are not yet fully understood. In this study, we introduce a novel numerical approach to model the evolution of fracture swarms with three‐dimensional nonplanar geometries. This model enables precise simulation of the propagation, interplay, and coalescence of the fracture swarms with variable apertures and geometries via solving fluid flow, fracture growth, and stress interference. Our results suggest five basic fracture interaction modes between neighboring fractures. The evolving fracture swarms exhibit simultaneous, alternant, and differential growth characteristics at different development phases. We also elucidate the mechanical mechanisms that determine the evolution of three‐dimensional curved fracture swarms. This work yields an improved understanding of fluid‐driven fracture swarms' development in organic‐rich shale due to rapid fluid generation.

Fewer reoperations after posterolateral plate positioning compared with lateral plate positioning in ankle fractures—a retrospective study on 453 AO/OTA 44-B injuries

IntroductionAnkle fractures are commonly treated by open reduction and internal fixation with plate and screws. Unplanned return to theatre is common, in many cases to extract prominent osteosynthesis material from the lateral malleolus as swelling subsides. We hypothesised that patients operated with a posterolateral plate placement on the lateral malleolus would have fewer reoperations, and fewer complications, compared to patients with a lateral plate placement. Materials and MethodsFrom a prospectively collected database of all orthopaedic surgery performed at our institution, we identified 664 ankle fractures undergoing plate fixation between 2008-01-01 and 2012-04-30. Radiographs were analysed to only include AO/OTA 44-B-fractures (n = 453), and to define study groups based on plate positioning. Hospital files were assessed to identify possible confounding factors, and any unplanned reoperation or complication. Complications were classified according to Dindo-Clavien. ResultsThe risk of reoperation was 13% after posterolateral plating, compared with 24% after lateral plating; absolute risk reduction 10% (95% CI: 2.5–18), p = 0.02. After adjusting for possible confounders, the odds ratio of undergoing reoperation after lateral plating was 2.2 (95% CI: 1.17–4.1), p = 0.01. The two surgical methods did not differ with regard to complication frequency: 31% vs 34%, p = 0.6, but complications following lateral plate fixation were more serious, p = 0.03. Plate positioning depended on surgeon preference. DiscussionThe two studied methods are both considered standard treatment of ankle fractures, and relatively simple surgical procedures. High rates of secondary surgery after plate fixation have been reported, but no study comparing plate positioning has been previously published to our knowledge. AO Sweden has recently switched to teaching posterolateral plating in group exercises during the AO Basic Fracture Surgery course, based on the belief that it may be safer than lateral plating. Our findings support this change in practice. ConclusionsPosterolateral plate positioning on the lateral malleolus in AO/OTA 44-B-fractures may be preferential to lateral plate positioning, due to a large difference in unplanned secondary surgery.

Mechanical Properties of Commercial Purity Aluminum Modified by Zirconium Micro-Additives

The mechanical properties and the fractured surfaces of commercial purity aluminum modified by zirconium micro-additives were investigated by means of experimental examination. A commercial purity Al specimen was used as a reference material and seven Al-Zr alloys in the 0.02–0.14 wt.% Zr composition range (with 0.02 wt.% Zr step) were prepared by microalloying methods. Optical microscopy was used to examine the microstructures and to calculate the grain sizes of the prepared specimens. The phase assemblage diagrams were plotted and the relative amounts of solid phases were calculated at room temperature using FactSage thermochemical software and databases. Proof stress, strength coefficient and strain hardening exponent were measured from the stress-strain curves obtained from tensile experiments and Charpy impact energy was calculated for all specimens. The experiments showed that the grain size of commercial purity Al was reduced by adding any Zr concentration in the investigated composition range, which could be due to the nucleation of new grains at Al3Zr particle sites. Accordingly, the microhardness number, tensile properties and Charpy impact energy were improved, owing to the large grain-boundary areas resulted from the refining effect of Zr, which can limit the movement of dislocations in the refined samples. The basic fracture mode in all specimens was ductile, because Al has an FCC structure and remains ductile even at low temperatures. The ductile fractures took place in a transgranular manner as could be concluded from the fractured surface features, which include voids, ridges and cavitation.

A Virtual Curriculum to Prepare Medical Students to Achieve Accreditation Council for Graduate Medical Education Level-1 Milestones in Orthopaedic Surgery.

As a part of the American healthcare system's response to the Coronavirus Disease 2019 (COVID-19) global pandemic, the Association of American Medical Colleges recommended that medical schools temporarily remove students from clinical settings and transition to an entirely online learning environment. This posed an unprecedented challenge to students in the clinical years of their medical education. To address this unexpected shift, we modified an in-person workshop to teach orthopaedic trauma basics to 5-week virtual course for third year medical students from several schools in New Jersey and Pennsylvania. We focused on moving students toward the Level-1 milestones for basic fracture care with a combination of weekly lectures and virtual interactive small group sessions, all conducted via WebEx and proctored by an orthopaedic attending or resident. The course was well received by students. Participation in the course was completely voluntary and did not count for credit at any institution. The course was valuable to students because the students who registered chose to fully complete the 5-week course and no student missed more than one small group session. On a postcourse survey, 100% of students said they would be highly likely to recommend the course to a future student, and the average rating for educational value of the course was 4.98 of 5. Given the current limitations in clinical education because of the COVID-19 pandemic, our course provides a reasonable alternative to clinical experience and prepares students with the knowledge and many of the skills that are required to succeed as orthopaedic interns. Furthermore, the success of our course this year suggests that similar programing may be a useful adjunct to clinical experiences even when it is safe to return to more traditional medical school scheduling.

Effect of non-associated flow rule on fracture prediction of metal sheets using a novel anisotropic ductile fracture criterion

The ductile fracture behavior of anisotropic materials was investigated and modeled by the uncoupled ductile fracture criterion for aluminum alloys 6016-AC200. The ductile fracture model takes into account micro-mechanisms of void nucleation, void growth, and evolution of void coalescence. The anisotropic yield function and non-associated flow rule were applied to increase the accuracy of the ductile fracture prediction. Series of uniaxial tensile tests, equi-biaxial tension test, and hydraulic bulge test were utilized to identify coefficients of the plasticity model. Various standard fracture tests covering a wide range of stress triaxiality from negative to moderate and high-stress triaxiality were used in order to calibrate the ductile fracture parameters for AA6016-AC200. The strain field on the surface of specimens was captured by the non-contact measurement DIC system for all tests. The fracture surface, fracture locus, and fracture forming limit diagram constructed by the proposed ductile fracture criterion were plotted. These basic fracture tests and a square cup drawing test were simulated by the ABAQUS/Explicit commercial software to verify the efficiency of the proposed fracture criterion and the advanced plastic model in predicting the onset of ductile fracture behavior. The results indicated that the proposed ductile fracture criterion can be utilized for predicting the onset of the anisotropic ductile fracture behavior in sheet metal forming.

Efficiency of Power Versus Hand Screwdriver for Cortical Lag Screw Insertion

Introduction: Limited studies exist on which modality, power or manual instruments, is superior for cortical screw placement. More efficient screw insertion could decrease operative time and reduce overall cost. The purpose of this study is to compare the speed and accuracy of lag screw placement in sawbone models using power and manual screwdrivers. Materials and Methods: A total of 48 orthopedic faculty, orthopedic residents, and medical students participated. Eight stations were tested, each with a different anatomic location (femur/tibia/radius), trajectory (anterior-posterior, lateral-medial, oblique), and screw length (18 to 95 mm). Each station had 1 correct passage and 4 false passages to assess for accuracy. The time required to place the screw in the correct passage using both power and hand screwdrivers was recorded along with the total attempts. Results: There was no significant difference in speed or accuracy of screw placement using power or manual screwdrivers. However, more accurate screw placement was significantly associated with faster insertion time. Level of training and attendance of a basic fracture course were significantly associated with faster insertion times and more accurate insertion when using the power screwdriver on certain stations, but there was no difference using the manual screwdriver. Conclusions: The difference in time between the actual techniques of using power or manual tools is marginal as accuracy is the most important factor for screw insertion efficiency. We propose that surgeons utilize the modality they are more accurate with to prevent misdirected screws and increase efficiency in the operating room.