Tunnel Defects Research Articles

Cost effective synthesis of 3-dimensional V4O9: A promising high-capacity lithium cathode

The earthly abundant vanadium exhibits multi-oxidation states and different crystalline structures in their oxide compounds offering unique electrical, opto-electronic, and catalytic properties to be applicable for various applications including energy storage materials. The stable vanadium oxides (V2O5, VO2, V2O3) are mostly studied while metastable oxides such as V4O9 is less explored. The latter possesses a tridimensional (3D)-tunnel defect type structure with different polyhedral wherein VO5 pyramids and VO6 octahedra are connected by corner oxygen atoms from the VO4 tetrahedra with V4+ and V5+ oxidation states, respectively, making it an appealing host candidate for lithium-ions insertion. Herein, we present a cost-effective single pot synthesis of 3D V4O9 nanoparticles using versatile low temperature solvothermal method. The obtained material has been fully characterised in terms of phase identity and crystal structure using x-ray diffraction, Raman spectroscopy and high-resolution-transmission-electron-microscopy while surface composition and valence- and/ oxidation states using x-ray photoelectron spectroscopy followed by investigation of its electrochemical performance against lithium. Upon first discharge, V4O9 could intercalate ∼6 Li+ per formula unit corresponding to highest discharge capacity of 464.5 mA h g−1 and a reversible first Coulombic efficiency of 75.3% between 1.5 – 4.0 V against Li in a half-cell configuration. In the long run, the V4O9 exhibited a reversible capacity of 160.8 mA h g−1 at 100 mA g−1 even after 2000 cycles against lithium rendering it as suitable positive electrode with high capacity and cyclability for lithium-ion battery applications.

Mechanical Properties of FSW Joints Magnesium Alloy at Different Rotational Speeds

Magnesium (Mg) has become a focus in the transportation industry due to its potential in reducing fuel consumption and gas emissions while improving recyclability. Mg alloys are also known for their low neutron absorption, good resistant of carbon dioxide as well as thermal conductivity which makes them suitable for use in industrial equipment for nuclear energy. there has been an increasing interest in the research and development of Mg alloys. These are the lightest of all metallic structural materials and are approximately 33% lighter than aluminium (Al) and 75% lighter than ferrous (Fe) alloys and have excellent specific mechanical properties. In this work, FSW of AZ31B Alloy was examined at the various rotational speeds of 900 -1440 rpm, with fixed welding speed of 40mm/min and 2° tool tilt angle using an HSS tool. The mechanical properties were compared for the different rotational speeds. The quality of FSW joints is dependent on input value of heat and material flow rate, which are prejudiced by process parameters., higher rotation speeds may cause abnormal stirring, resulting in a tunnel defect at the weld nugget due to increased strain rate and turbulence.

Role of tool shoulder profile and tool rotational speed on the mechanical performance of friction stir welded Al5083 joints

AbstractIn the current work, Al5083 weld joints have been produced by friction stir welding using three different tool shoulder profiles (flat, concave and convex) at three different tool rotational speeds (900 min−1, 1120 min−1 and 1400 min−1) with an objective to investigate the role of tool shoulder profile and welding parameters on the joint quality. The cross sectional microstructural observations revealed the development of perfect weld joint at 900 min−1 and 1120 min−1 with flat and concave shoulder profiles due to the better material flow in the stir zone. Other weld joints revealed the presence of tunneling defect at the bottom of the nugget zone. Hardness measurements of the weld joints showed increased values at 1120 min−1 with concave shoulder. From the impact test data, all the weld joints exhibited similar impact energy compared with the base material except the weld joint produced with concave shoulder at 1120 min−1. Tensile tests of the weld joints demonstrated better joint strength for the weld joints obtained with both the flat and concave shoulder profiles at 1120 min−1 without losing the ductility similar to that of the base alloy.

Study on the materials flow, microstructure and mechanical properties of ultrasonic vibration-assisted friction stir weld of 1500 MPa martensitic steel

In this study, friction stir welding (FSW) was conducted on 1500 MPa martensitic steel with a thickness of 2.3 mm at 500 rpm and 60 mm/min with and without the application of ultrasonic vibration. The utilization of pure nickel as a marker material could help to visualize the material flow behavior throughout the whole FSW process. In addition, the width change of the marker material was used to distinguish the welding stages. At the same time, the microstructure was also characterized to study the effect of ultrasonic vibration on the welding process. The conventional FSW (C-FSW) joint had tunnel defects due to poor material flow, while the ultrasonic vibration-assisted FSW (U-FSW) joint was defect-free. To study the microstructure and texture evolution during the process, a fully austenitized welding zone was reconstructed from martensite to prior austenite grain (PAG) based on the Kurdjumov-Sachs orientation relationship. The strain rate increased in U-FSW compared to that in C-FSW, resulting in a reduction of the PAG size and an alteration of its shear texture components from type-A to type-B. The uniaxial tensile tests showed that the ultimate tensile strength (UTS) of the stir zone (SZ) of U-FSW was significantly increased compared with that of C-FSW.

Batched-image detection model and deployment method for tunnel lining defects using line-scan cameras based on experiments study

High-performance line-scan cameras are highly accurate and efficient for tunnel detection, however, the exponential growth of image data creates new challenges for real-time image processing. The inference speed of existing tunnel detection algorithms is insufficient for massive amounts of image data, and traditional data structures limit the parallelism of the detection system, thereby reducing the speed of image processing. In this study, a deep learning (DL) network is developed for real-time tunnel defect detection based on the you only look once (YOLO) family. The network includes innovative defect feature-extraction modules, optimization of the network architecture, and improvement of the decoupling heads to increase defect detection accuracy and efficiency. Furthermore, we developed critical technologies for real-time detection. First, our method employs a deployment method for DL networks based on TensorRT, which enables our network to be applied directly to C++ image acquisition programs away from the traditional DL frameworks. The proposed line-scan data structure enables the raw images to be fed into the neural network in batches, which, combined with the simultaneous technique of image acquisition, detection, and storage, significantly increases the efficiency of real-time detection. The paper demonstrates the advantages of the proposed model and hardware system through an experiment study. The test results indicate that the mean average precision and F1-score of our network were 86.07% and 84.53%, respectively, while it had 21.42 M parameters. Combined with the proposed storage strategy, a recall rate of more than 90% was achieved for defect detection. Moreover, batch image processing method has a significant advantage in terms of inference speed, with 243.9 FPS in PyTorch, 381.46 FPS in TensorRT, and 305.3 FPS in real-time detection, which is five times faster than existing defect-detection models. This study significantly increases the efficiency of tunnel lining detection, which has positive implications for the visual detection of other infrastructures.

Effect of friction stir welding on microstructure and foaming mechanism of rolled-state anisotropic powder

Friction stir welding (FSW) has a significant impact on welding aluminum foam sandwich (AFS) precursor. Yet, the understanding of the microstructure and foaming process on rolled-state powder of welded precursor remains limited. This study exploited the single-pass double-sided forming welding approach to weld the AFS precursor, while the impact of different process parameters of FSW on the microstructure of rolled-state powder was evaluated. Meanwhile, the foaming process of anisotropic powder at different directions was observed in-situ using synchrotron radiation. The results display that FSW transforms gap-like voids, which were ∼20 µm in width and 100–400 µm in length, into circular voids with a diameter of ∼6 µm in the powder at the weld zone (WZ). The welding process eliminates powder agglomeration aggregation and increases the relative density (>97%) of rolled-state powder. However, the low thermal conductivity of the rolled-state powder (117 W·m−1·K−1) leads to a tunnel defect at the root of the WZ. In addition, in-situ observation experiments of the foaming process found that the bubble nucleation of rolled-state powder exhibits anisotropic characteristics, and the welding process causes a transition in the types of bubble nucleation in the WZ region. This study demonstrates the feasibility of improving the anisotropy of powders caused by processing methods to obtain an isotropic pore formation and foam expansion by FSW technology.

High-Performance Artificial Ligament Made from Helical Polyester Fibers Wrapped with Aligned Carbon Nanotube Sheets.

Repairing high-load connective tissues, such as ligaments, by surgically implanting artificial grafts after injury is challenging because they lack biointegration with host bones for stable interfaces. Herein, a high-performance helical composite fiber (HCF) ligament by wrapping aligned carbon nanotube (CNT)sheets around polyester fibers is proposed. Anterior cruciate ligament (ACL)reconstruction surgery shows that HCF grafts could induce effective bone regeneration, thus allowing the narrowing of bone tunnel defects. Such repair of the bone tunnel is in strong contrast to the tunnel enlargement of more than 50% for commercial artificial ligaments made from bare polyester fibers. Rats reconstructed with this HCF ligamentshow normal jumping, walking, and running without limping. This work allows bone regeneration in vivo through a one-step surgery without seeding cells or transforming growth factors, thereby opening an avenue for high-performance artificial tissues.

Evaluation of Hydraulic Tunnel Lining Durability Based on Entropy–G2 and Gray Correlation–TOPSIS Methods

Under long-term water flow, the physical and chemical properties of hydraulic tunnel linings are more likely to deteriorate than those of road tunnels, thus affecting the normal operation of tunnels. Evaluating the durability of hydraulic tunnel linings can help to grasp the durability of tunnels in a timely and accurate manner and provide a basis for the routine maintenance of tunnels. This paper proposes new methods for evaluating the durability of hydraulic tunnel linings. Firstly, the types of tunnel defects are divided, the durability indices corresponding to the defects are selected scientifically, and a hydraulic tunnel durability evaluation index system is established. Then, the G2 method is modified by the entropy value method to make it a subjective and objective weighting method, which can make the weights fit the reality while the calculation is easy, and the TOPSIS method is modified by the gray correlation degree to optimize the judgment criteria between the evaluation scheme and the ideal solution. Finally, the practicality and accuracy of this method are verified by the calculation of the five sections of a tunnel with lining durability grades of A, B, C, B, and C, respectively, which matched the calculation results of the RAGA-PP method in the related literature.

Combination Calcium Hydroxide and Epigallocatechin-3-gallate in Dentistry: A Narrative Review

Background: Pulp capping and pulpotomy are treatments for exposed pulp due to injury. Calcium hydroxide is the gold standard material in pulp capping and pulpotomy because it stimulates reparative dentin formation in exposed pulp. Calcium hydroxide has the disadvantage of causing chronic inflammation, cell necrosis, the formation of tunnel defects, and weak antibacterial properties against certain bacteria. Epigallocatechin-3-gallate (EGCG) is the main catechin component of green tea and has potent anti-inflammatory and antibacterial properties against both gram-negative and positive bacteria. The addition of EGCG to calcium hydroxide has the potential to prevent chronic inflammation and improve the antibacterial properties of calcium hydroxide. Purpose: This review aims to explain the potential of the combination of calcium hydroxide and EGCG in dentistry. Review(s): EGCG has potent anti-inflammatory and antibacterial effects against Enterococcus faecalis. The addition of EGCG to calcium hydroxide has the potential to reduce the inflammatory effect and improve the antibacterial properties of calcium hydroxide. Conclusion: This review concludes that the combination of calcium hydroxide and EGCG has the potential to reduce the inflammatory effect and promote the antibacterial effect of calcium hydroxide. Further research is needed to prove the potential of the combination of calcium hydroxide and EGCG in dentistry as a material for pulp capping and pulpotomy.

Lightweight Tunnel Defect Detection Algorithm Based on Knowledge Distillation

One of the greatest engineering feats in history is the construction of tunnels, and the management of tunnel safety depends heavily on the detection of tunnel defects. However, the real-time, portability, and accuracy issues with the present tunnel defect detection technique still exist. The study improves the traditional defect detection technology based on the knowledge distillation algorithm, the depth pooling residual structure is designed in the teacher network to enhance the ability to extract target features. Next, the MobileNetv3 lightweight network is built into the student network to reduce the number and volume of model parameters. The lightweight model is then trained in terms of both features and outputs using a multidimensional knowledge distillation approach. By processing the tunnel radar detection photos, the dataset is created. The experimental findings demonstrate that the multidimensional knowledge distillation approach greatly increases the detection efficiency: the number of parameters is decreased by 81.4%, from 16.03 MB to 2.98 MB, while the accuracy is improved by 2.5%, from 83.4% to 85.9%.

MFF-YOLO: An Accurate Model for Detecting Tunnel Defects Based on Multi-Scale Feature Fusion.

Tunnel linings require routine inspection as they have a big impact on a tunnel's safety and longevity. In this study, the convolutional neural network was utilized to develop the MFF-YOLO model. To improve feature learning efficiency, a multi-scale feature fusion network was constructed within the neck network. Additionally, a reweighted screening method was devised at the prediction stage to address the problem of duplicate detection frames. Moreover, the loss function was adjusted to maximize the effectiveness of model training and improve its overall performance. The results show that the model has a recall and accuracy that are 7.1% and 6.0% greater than those of the YOLOv5 model, reaching 89.5% and 89.4%, respectively, as well as the ability to reliably identify targets that the previous model error detection and miss detection. The MFF-YOLO model improves tunnel lining detection performance generally.

Efficacy of mixture of injectable-platelet rich fibrin and type-1 collagen particles on the closure of through-and-through periapical bone defects - A randomized controlled trial.

To determine the efficacy of a combination of injectable-platelet rich fibrin and type-1 collagen particles on the healing of through-and-through periapical bone defect and subsequent closure of bony window. The clinical trial was registered in ClinicalTrials.gov(NCT04391725). Thirty eight individuals with radiographic evidence of periapical radiolucency in maxillary anterior teeth and confirmed loss of palatal cortical plates in cone beam computed tomographic imaging were randomly assigned to either experimental group(n=19) or the control group(n=19). Mixture of i-PRF and collagen as a graft was applied to the defect in adjunct to periapical surgery in experimental group. No guided bone regeneration procedures were used in the control group. The healing was evaluated using Molven's(2D) and modified PENN 3D(3D) criteria. Percentage reduction of the buccal and palatal bony window area, and complete closure of through-and-through periapical bony window (tunnel defect) were assessed using Radiant Diacom viewer software(Version 4.0.2). The reduction in the periapical lesion area and volume was measured using Corel DRAW and ITK Snap software. Thirty four participants(18 and 16 in the experimental and control group, respectively) reported for follow-up at 12 months. There was 96.9% and 97.96% reduction of buccal bony window area in experimental and control groups respectively. Similarly, palatal window showed 99.03% and 100% reduction in experimental and control groups respectively. No significant difference in both buccal and palatal window reduction was noticed between the groups. A total of 14 cases(7 in experimental and 7 in control group) showed complete closure of through-and-through bony window. No significant difference in clinical, 2D and 3D radiographic healing, percentage reduction in area and volume was observed between experimental and control group(P>0.05). Neither the area nor the volume of lesion, and the size of buccal or palatal window had significant effect on healing of through-and-through defects. Endodontic microsurgery results in high success rate in large peripical lesions with through-and-through communication with more than 80% reduction in volume of lesion and size of both buccal and palatal window after one year. Mixture of type-1 collagen particles and i-PRF, adjunct to periapical micro-surgery did not improve the healing in through-and-through periapical defects.

An in-situ defect detection method for aluminum alloy bobbin tool friction stir welding assisted by lateral force

This paper proposes a force-driven method for in-situ defect detection in aluminum alloy bobbin tool friction stir welding (BTFSW). The variations of the three component forces in BTFSW, including traverse force (Fx), lateral force (Fy) and plunge force (Fz) are studied. The mean value of Fy exhibits the highest correlation with tunnel defects. Numerical simulation results show that higher stress on the retreating side due to insufficient material flow and severe material jam results in an abnormal increase of Fy for defective joints, revealing the response mechanism of Fy to tunnel defects. The proposed method offers a promising approach for real-time detecting tunnel defects in aluminum alloy BTFSW.

Potential Combination of Acemannan Sponge and Calcium Phosphate Cement-Calcium Sulfate Hemihydrate (CPC-CSH) as Direct Pulp Capping Alternative Materials for Reparative Dentin Formation

Abstract Background Health problem that affects hard tissues of the teeth is dental caries, which is experienced by around 2.3 billion people in the world, with prevalence in Indonesia reaching 88.8. Direct pulp capping (DPC) is a vital pulp therapy used to maintain pulp vitality. Calcium hydroxide (Ca(OH)2) is the gold standard pulp capping material, but has poor adhesion to dentin and mechanical properties, bacterial infiltration, formation of tunnel defects in the pulp resorption, and dentin bridge. Therefore, it is necessary to develop alternative therapy, namely, a combination of acemannan sponge and calcium phosphate cement (CPC)-calcium sulfate hemihydrate (CSH) for reparative dentin formation. Purpose This article describes the potential combination of acemannan sponge and CPC-CSH as DPC alternative materials for reparative dentin formation. Reviews Acemannan extracted from aloe vera exhibits anti-inflammatory, antimicrobial, and cytocompatibility properties. As DPC material, acemannan induces pulp proliferation and differentiation to osteoblast-like, growth factor synthesis, and promotes reparative dentin formation. However, acemannan sponge is radiolucent, allowing misinterpretation between pulp and acemannan sponge. CPC can be combined with CSH to shorten the setting time. CPC-CSH is radiopaque, has good compressive strength, and biocompatibility. CPC-CSH is a calcium-based material with neutral pH that can induce the dentin bridge formation. CPC-CSH showed good bioactivity because it induces the formation of apatite which plays a significant part in dentin and pulp regeneration. Conclusion The combination of acemannan sponge and CPC-CSH has the potential as DPC alternative materials for reparative dentin formation.

Tibial Press-Fit Fixation Technique in Anterior Cruciate Ligament Reconstruction

Implant-free press-fit tibial fixation technique has gained popularity recently due to the problems in bone tunnel expansion, defect, and revision surgery due to the tibial fixation material preferred in anterior cruciate ligament surgery. Patellar tendon-tibial bone autograft offers several advantages in anterior cruciate ligament reconstruction. We describe a tibial tunnel preparation method and the use of patellar tendon-bone graft in the implant-free tibial press-fit technique. We call this the Kocabey press-fit technique.

Inspection of defects in friction stir welded Al-7075 T6 alloy

ABSTRACT In this work, the evaluation of tunnel defects in Al-7075 T6 sheets processed by friction stir welding (FSW) is explored using computed tomography (CT) and the finite element method (FEM). The effect of axial force and temperature generated during the FSW was assessed using four rotary speeds (1600, 1700, 1800 and 1900 rpm), each at two different welding speeds (15 and 30 mm/min). These joints were CT-scanned, reconstructing the voxels from the X-Ray images. A voxel size of 46 m, a spot size of 59 m and a magnification of 4.35 using a Cu filter of 0.5 mm were selected. The 3D images of the welds showed the forms, places and levels of the detected defects. The tunnel defects were found at 2 mm from the bottom edge of the weld plates, and the tendency for the defects formation was reduced at 1900 rpm based on CT scans. The numerical results of FSW revealed that with a higher rotational speed, the generated heat and strain were increased, while the stress decreased for higher welding speeds. The coupling of CT and numerical results provide an in-depth understanding of material flow and defect formation during friction process.

Friction stir processing of hybridized AZ31B magnesium alloy-based composites by adding CeO2 and ZrO2powders: mechanical, wear, and corrosion behaviors

To improve the properties of AZ31B Mg alloy and for the first time, the rare earth cerium oxide (CeO2) and zirconium dioxide (ZrO2) were combined for synergistic benefits and introduced into the structural AZ31B magnesium alloy through the solid-state friction stir processing procedure to form the hybridized AZ31B Mg/ZrO2+CeO2 composites under variable levels of the tool's rotational speed up to 1200 rpm. The macro-/microstructure, hardness, shear punching strength, tensile strength, corrosion behaviours, and tribological characteristics such as weight/wear loss, wear rate, coefficient of friction, worn surfaces, and debris of the AZ31B Mg/ZrO2+CeO2 hybrid composites were investigated and compared. The results indicated that void, tunnel defect, and ZrO2+CeO2 agglomeration could not be prevented at low speed (800 rpm) while defect-free composites were obtained at high speed (1200 rpm). Grain refinement from 7.39 μm to 3.38 μm and the ZrO2+CeO2 fragmentation (4.52–2.49 μm) ensued after a rise in the tool's rotational speed owing to higher plastic straining, dynamic recrystallization, and ZrO2+CeO2 particle-aided pinning effects. Improvements in hardness (99–135 HV), shear punching strength (121–237 MPa), tensile strength (172–228 MPa) and wear properties of the composite were attained due to the defect elimination, inherent finer Mg grains, and the uniformly dispersed ZrO2+CeO2 particles. These attributes also enhanced the corrosion resistance of the AZ31B Mg/ZrO2+CeO2 composite at the elevated rotating speed of the tool. The combination of the CeO2 and ZrO2 particles is an effective particle-blend for improving the properties of Mg alloy to expand its application scope.

Prediction of various defects and material flow behavior during dissimilar FSW of DH36 shipbuilding steel and marine grade AA5083 using FE-based CEL approach

Dissimilar friction stir welding (FSW) of steel-Al is a very tedious job. Inappropriate welding process parameters can lead to the initiation of inevitable defects associated with dissimilar FSW processes. These can be presented as tunnel defects, void generation, excessive flash formation, and other surface irregularities. Using conventional experimental trials makes it usually challenging to identify such defects. This research adopted an Abaqus/Explicit® framework utilizing a 3D thermo-mechanical based coupled Eulerian-Lagrangian (CEL) methodology. In order to predict commonly observed defects in the FSW process, the proposed FEM uses the volume of fluid approach. By monitoring the material flow into and out of the computational/void domain, the suggested framework has made it feasible to predict surface, sub-surface, and volumetric defects. Defect formation is studied at a constant tool rotation speed of 875 rpm, welding speed of 90 mm min−1, and tilt angle of 0°. Tilt angles of 0° caused welding joints with a small tunnel defect. Thermal history, axial force variation, and material flow behavior are all strongly aligned with the principle of defect generation. An experimental trial has been conducted to validate the proposed finite element model. The previous analysis found that the average axial force closely matches the welding-related experimental findings with a percentage error of 7.85%. While a proportion error of approximately ∼0.57% was found between the compared numerical and experimental diameters of the pin end-hole defect. Furthermore, the proposed model accurately predicted the process of material flow along the thickness direction of the workpiece. It was seen that the stress generated at the root of the flashes reached a higher value ranging between 485.6 and 582.7 MPa. Finally, a good agreement between the numerical results and the experimental trial was established, showing the robustness of the developed computational FEM technique.

Mechanical properties and defects in friction stir welded acrylonitrile butadiene styrene polymer

In this research work, a butt joint between acrylonitrile butadiene styrene (ABS) sheets was made using Friction stir welding (FSW). Polymers such as ABS have great potential to be used as body parts in automotive industries because of their high strength-to-weight ratio. In the aerospace industry, polymers are preferred over metals as they can retain their properties at low temperatures and their light weight reduces fuel consumption. The objective of this research work was to investigate mechanical properties and defect characterization in weldments. Maximum weld strength achieved was 19.4 MPa which is 61% of the base material at a rotational speed of 224 r/min, travel speed of 50 mm/min, external heating temperature of 45°C, and shoulder diameter of 16 mm. The images of macro and microstructure from an optical microscope and scanning electron microscope, respectively, showed that in FSW of ABS polymer defects were mainly formed on the retreating side of the weld nugget, unlike FSW of metals having it on the advancing side. Only two experiments out of L18 experiments showed tunneling defect, i.e., Experiment no. 8 and Experiment no. 10 and four experiments showed undercutting defect, i.e., Experiment no. 6, 9, 12, and 18. By performing the Vickers microhardness test it was observed that the hardest region formed in and around the weld nugget.

Effect of tool tilt angle on microstructure, mechanical properties and fracture behavior of dissimilar friction stir lap welding joint of SiCp/ZL101 and ZL101

In order to achieve the lightweight goal of urban rail train braking system, friction stir lap welding (FSLW) was used to weld SiCp/ZL101 and ZL101 sheets to prepare a new type of brake disc material. The effects of different tool tilt angles (TTAs) on microstructure and mechanical properties of the welding joints were systematically studied. The TTA had a significant effect on the microstructure and defect formation of the dissimilar FSLW joints. There were tunnel defects under the advancing side at 1° and 2°. Internal defect-free weld structures were formed at 3° and 3.5°. A large number of dislocations caused by plastic deformation remained in the microstructure of the weld region at 1° and 2°, and the transformation of the microstructure of the weld region at 3° and 3.5° was dominated by dynamic recovery and dynamic recrystallization. The distribution of SiC particles in the nugget area was uniform, and the grains were obviously refined. With the increase of the TTA, the average grain size of the nugget area increased, the average size of the SiC particles decreased, and the average hardness of the nugget area increased. The four samples all formed a transition zone with good metallurgical bonding at the welding interface. The shear strength of the welding joints increased first and then decreased with the increase of the TTA. In the absence of welding defects, the shear strength reached the best level of 130.71 MPa at 3°. Both shear and tensile fractures were ductile fractures.