Three-dimensional Laser Scanning Research Articles

Quantitative Assessment of Upper-Limb Volume: Implications for Lymphedema Rehabilitation?

Upper-limb lymphedema is a chronic condition characterized by the accumulation of lymphatic fluid in the arm or hand, resulting in swelling and functional impairment. The accurate and reliable volumetric assessment of limb volume is crucial for the correct management of lymphedema. This narrative review provides an overview of the different methods proposed in the literature for the volumetric assessment of upper-limb lymphedema. In more detail, several methods of volumetric assessment have been proposed in recent years, including water displacement, the centimetric method, perometry, bioimpedance spectroscopy, dual-energy X-ray absorptiometry, magnetic resonance imaging, computed tomography, and three-dimensional laser scanning techniques. On the other hand, each method is characterized by specific strengths and limitations in terms of accuracy, reliability, practicality, and cost-effectiveness. Moreover, factors including operator experience, equipment availability, and patient population characteristics might have several implications in the optimal assessment of upper-limb volume. In this context, a precise volumetric assessment is crucial to improving the rehabilitation framework, patient education, and research outcomes. As a result, the integration of emerging technologies is needed to improve the tailored management of patients with upper-limb lymphedema. In conclusion, volumetric assessment methods provide valuable insights in the management of upper-limb lymphedema, improving patient care, treatment outcomes, and research advancements. Future research should focus on testing these innovative solutions on larger samples of patients to enhance the reproducibility, accuracy, accessibility, and clinical utility of volumetric assessment methods in the complex treatment framework of upper-limb lymphedema.

Towards Automated Measurement of As-Built Components Using Computer Vision.

Regular inspections during construction work ensure that the completed work aligns with the plans and specifications and that it is within the planned time and budget. This requires frequent physical site observations to independently measure and verify the completion percentage of the construction progress performed over periods of time. The current computer vision techniques for measuring as-built elements predominantly employ three-dimensional laser scanning or three-dimensional photogrammetry modeling to ascertain the geometric properties of as-built elements on construction sites. Both techniques require data acquisition from several positions and angles to generate sufficient information about the element's coordinates, making the deployment of these techniques on dynamic construction project sites challenging. This paper proposes a pipeline for automating the measurement of as-built components using artificial intelligence and computer vision techniques. The pipeline requires a single image obtained with a stereo camera system to measure the sizes of selected objects or as-built components. The results in this work were demonstrated by measuring the sizes of concrete walls and columns. The novelty of this work is attributed to the use of a single image and a single target for developing a fully automated computer vision-based method for measuring any given object. The proposed solution is suitable for use in measuring the sizes of as-built components in built assets. It has the potential to be further developed and integrated with building information modelling applications for use on construction projects for progress monitoring.

3D-printed helmet-type neuro-navigation approach (I-Helmet) for transcranial magnetic stimulation.

Neuro-navigation is a key technology to ensure the clinical efficacy of TMS. However, the neuro-navigation system based on positioning sensor is currently unable to be promoted and applied in clinical practice due to its time-consuming and high-cost. In the present study, we designed I-Helmet system to promote an individualized and clinically friendly neuro-navigation approach to TMS clinical application. I-Helmet system is based on C++ with a graphical user interface that allows users to design a 3D-printed helmet model for coil navigation. Besides, a dedicated coil positioning accuracy detection method was promoted based on three-dimensional (3D) printing and 3D laser scanning for evaluation. T1 images were collected from 24 subjects, and based on each image, phantom were created to simulate skin and hair. Six 3D-printed helmets with the head positioning hole enlarged by 0-5% tolerance in 1% increments were designed to evaluate the influences of skin, hair, and helmet-tolerance on the positioning accuracy and contact force of I-Helmet. Finally, I-Helmet system was evaluated by comparing its positioning accuracy with three skin hardnesses, three hair styles, three operators, and with or without landmarks. The accuracy of the proposed coil positioning accuracy detection method was about 0.30 mm in position and 0.22° in orientation. Skin and hair had significant influences on positioning accuracy (p < 0.0001), whereas different skin hardnesses, hair styles, and operators did not (p > 0.05). The tolerance of the helmet presented significant influences on positioning accuracy (p < 0.0001) and contact force (p < 0.0001). The positioning accuracy significantly increased (p < 0.0001) with landmark guided I-Helmet. 3D-printed helmet-type Neuro-navigation approach (I-Helmet) with 3% tolerance and landmarks met the positioning requirements for TMS in clinical practice with less than 5 N mean contact force, 3-5 mm positioning accuracy, 65.7 s mean operation time, and 50-yuan material cost. All the results suggest that the cost of I-Helmet system may be much less than the that of training clinical doctors to position the coil of TMS operation during short period of time.

Three-dimensional laser scanning and numerical investigation on the influence of freeze-thaw and hang-wall mining on the instability of an open-pit slope

The instability of the open-pit slope and associated disasters of complex orebodies such as hanging-wall mining are the key problems to be solved urgently in the development of western resources. In this work, taking the hanging-wall mining in the open-pit mine of Hejing iron mine, for example, the disaster mechanism influenced by the coupling freeze-thaw and hanging-wall mining is systematically studied by 3D laser scanning and numerical simulation. Firstly, the rock mass structure information such as dip, dip angle, spacing, and equivalent trace length characteristics was obtained using 3D intelligent recognition technology. Then, numerical simulation is employed to reveal the influence of freeze-thaw and excavation sequences on the overall stability of the open-pit slope. The stress, displacement, plasticity zone, and maximum shear strain patterns are revealed in detail. The results show that the excavation engineering will lead to frequent increase and unloading of the internal stress of the rock mass, and the gradual increase of the goaf area will cause great damage to the rock mass. The slope failure mode is strongly impacted by freeze-thaw weathering and orebody excavation.

Generating Topologically Consistent BIM Models of Utility Tunnels from Point Clouds.

The development and utilization of urban underground space is an important way to solve the "great urban disease". As one of the most important types of urban underground foundations, utility tunnels have become increasingly popular in municipal construction. The investigation of utility tunnels is a general task and three-dimensional laser scanning technology has played a significant role in surveying and data acquisition. However, three-dimensional laser scanning technology suffers from noise and occlusion in narrow congested utility tunnel spaces, and the acquired point clouds are imperfect; hence, errors and redundancies are introduced in the extracted geometric elements. The topology of reconstructed BIM objects cannot be ensured. Therefore, in this study, a hierarchical segmentation method for point clouds and a topology reconstruction method for building information model (BIM) objects in utility tunnels are proposed. The point cloud is segmented into facades, planes, and pipelines hierarchically. An improved mean-shift algorithm is proposed to extract wall line features and a local symmetry-based medial axis extraction algorithm is proposed to extract pipelines from point clouds. A topology reconstruction method that searches for the neighbor information of wall and pipeline centerlines and establishes collinear, perpendicular, and intersecting situations is used to reconstruct a topologically consistent 3D model of a utility tunnel. An experiment on the Guangzhou's Nansha District dataset successfully reconstructed 24 BIM wall objects and 12 pipelines within the utility tunnel, verifying the efficiency of the method.

Intelligent Construction Monitoring Method for Large and Complex Steel Structures Based on Laser Point Cloud

Large and complex steel structures play a vital role in building construction. However, deviations between the design model and the actual construction state are inevitable, which seriously affects the quality and safety of building construction. In our study, an intelligent construction monitoring method for large and complex steel structures based on laser point cloud is proposed. Firstly, three-dimensional laser scanning technology is introduced to capture accurate and complete spatial information on steel structures. Then, considering the inconsistency of the coordinate system between the design model and the laser point cloud, the building information model (BIM) is converted into the point cloud model, and the datum unification of the two types of the point cloud is achieved by adopting a coarse-to-fine registration strategy. Finally, the spatial information of steel structures is extracted from the laser point cloud based on the as-designed model, and the distance deviation between the two models is analyzed to reflect the actual construction state. To demonstrate the applicability of the proposed method, the steel structures’ point cloud of the stadium and the high-speed railway station is captured by the terrestrial three-dimensional laser scanner. The experimental results demonstrate that the method can extract the deviation between the design model and the actual construction, to provide accurate data sources for the intelligent fine construction of steel structures.

Study on the Tribological Properties of Micro-Al2O3 Modified Carbon Fiber Hybrid-Reinforced Polymer

Micro-sized Al2O3-modified carbon fiber hybrid reinforced polymer composites (CFHRP) were prepared using the vacuum-assisted resin transfer molding (VARTM) process, and friction and wear tests were performed on an MRTR-1 multifunctional friction and wear tester to study the effect of carbon fiber surface doping with trace amounts of Al2O3 and its content on the tribological properties of carbon fiber reinforced polymer composites. The surface morphology of the composite material was characterized using a three-dimensional confocal laser scanning microscope (LSM). The results showed that under dry friction conditions, the wear behavior of the composite material with micro-Al2O3 added was mainly abrasive wear and adhesive wear. Under the condition of water lubrication, the friction coefficient of the composite material with micro-Al2O3 added was higher than that of the carbon fiber/epoxy resin-based composite material without Al2O3, and the abrasive wear and adhesive wear were significantly reduced. In addition, under the condition of water lubrication, the cooling and boundary lubrication of water played a dominant role in the tribological behavior, so the influence of transfer film on the tribological behavior of the composite material was smaller than that under dry friction conditions. When the micro alumina content is 6%, the friction and wear reduction of CFHRP composite material are improved under water containing conditions. Under dry friction conditions, the content of micrometer alumina has a minimal effect on the change in friction coefficient.

Simulation analysis of rockfall movement characteristics with debris slope using Unity3D based on UAV remote sensing DSM: a case study of the G318 Highway on the Tibetan Plateau

Rockfalls on debris slopes pose a significant hazard to canyon roads on the Tibetan Plateau. In order to assess risks and develop effective engineering solutions, it is crucial to fully understand the characteristics and processes of rockfall movement. This research utilizes UAVs and three-dimensional (3D) laser scanners to capture images and data, while Pix4D is employed to create a high-precision 3D model from the collected data. Unity3D is utilized to analyze the movement characteristics and deposition positions of rockfall. Various movement characteristic indexes, such as velocity, acceleration, displacement, energy loss, and deposit position, are computed and examined for blocks with different shapes, sizes, instability types on the debris slope, and blocks composed of various slope materials and inclinations. The aim is to obtain insights into the specific movement mechanisms of debris slopes, which differ from conventional slopes. Field experiments have confirmed the effectiveness of the Unity3D simulation approach. Building upon this foundation, a high-precision 3D simulation model for the debris slope of the G318 Highway on the Tibetan Plateau is developed using Unity3D. This model is used to calculate the movement characteristics, energy variation, and deposition positions of rockfall. The findings are then compared with those of common models. The results demonstrate that the high-precision 3D simulation model computed by Unity3D provides more accurate and reasonable results compared to the common model. Moreover, the movement characteristics, energy variation, and deposition positions of rockfall on debris slopes exhibit specific characteristics. By employing Unity3D simulation analysis, a comprehensive understanding of the phenomena and behavior of rockfall on debris slopes can be achieved, enabling the proposal of more reasonable engineering protection measures.

Poster 130: Accuracy of Distal Femoral Condyle Osteochondral Allograft Transplantation Using Patient Specific Instrumentation

Objectives: As a surgical treatment option for cartilage defects in the knee, osteochondral allograft (OCA) transplantation reconstructs the damaged area with a fully formed articular hyaline cartilage/osseous unit. For patients undergoing this procedure, topography matching between the donor and recipient sites is essential to limit premature wear of the OCA. To help prevent graft failure, the surgeon must precisely reconstruct the original anatomic curvature of the articular surface. For this to be successful, the graft needs to be chosen and harvested from the correct location on the donor femoral condyle, and then placed correctly on the recipient condyle during surgery to minimize step-off relative to the surrounding cartilage. Currently, the process of donor and recipient graft matching as well as intra-operative techniques to match these surfaces are fairly rudimentary and require significant experience from the treating surgeon. The purpose of this study is to evaluate a novel topography matching technique for distal femoral condyle OCA transplantation using three-dimensional (3D) laser scanning to create 3D printed patient-specific instrumentation in a human cadaveric model. Methods: Twelve cadaveric knees were dissected to isolate the distal femoral condyles (DFC) with cartilage intact and then 3D laser scanned. An 18-mm circular osteochondral recipient defect was virtually created on the medial femoral condyle (MFC) and the position and orientation of the best topography matched osteochondral graft from a paired donor lateral femoral condyle (LFC) was determined using an in-silico analysis algorithm minimizing articular step-off (Figure 1). Donor (LFC) and recipient (MFC) 3D-printed patient-specific guides were created based on 3D reconstructions of the scanned condyles. Using the guides, OCAs were harvested from the previously defined best-match position on the LFC and transplanted to the reamed recipient defect site (MFC) (Figure 2). The post-OCA recipient condyles were laser scanned. The 360-degree articular step-off and cartilage mismatch topography were calculated by a point-to-surface distance calculation algorithm and compared to the in-silico result. Results: The in-silico cartilage step-off and graft perimeter mismatch for the virtual OCA transplant was 0.073 ± 0.029 mm (range: 0.005-0.113 mm) and 0.166 ± 0.039 mm (range: 0.120-0.243 mm), respectively. Comparatively, our cadaveric specimens post-implant had significantly larger step-off differences (0.173 ± 0.085 mm, range: 0.082-0.399 mm, P = 0.001) but equivalent surface topography matching (0.181 ± 0.080 mm, range: 0.087-0.396 mm, P = 0.678). Conclusions: This novel technique for OCA articular step-off and topography matching demonstrated the ability to optimize cartilage topography matching for LFC to MFC transplantation. Despite a larger mean step-off in the cadaveric specimens compared to the ideal in-silico model, our study demonstrated substantially lower mismatch values compared to previous orthopedic literature evaluating LFC to MFC transplantation that reported means of 0.48 mm for articular step-off (range: 0.335-0.738 mm) and 0.63 mm for surface area mismatch (range: 0.349-1.461 mm). It should be noted that clinically, surgeons performing OCA for the femoral condyles will preferentially select the ipsilateral condyle from the donor to take a plug for the recipient, as this will generally allow for optimal surface matching. Our results show better mismatch values than prior work using this contralateral technique, and even the maximum step-off distance in our cadaveric model fell well below the 0.5 cm –1.0 cm maximum step-off values assigned to be clinically significant by prior studies evaluating ipsilateral OCA transplantations. Using this novel technique in a model performing MFC to MFC transplantation would likely yield further enhanced results due to improved radii of curvature matching. Improving upon topography matched graft implantation for focal chondral defects of the knee in young patients will improve surface matching and associated long-term outcomes. Additionally, efficient selection of the allograft using patient-specific guides would also improve availability of the limited allograft sources and reduce surgical time.

Treatment Durations and Whitening Outcomes of Different Tooth Whitening Systems.

Background and Objectives: Tooth whitening is a relatively conservative and effective option to treat discolored teeth. However, questions remain whether in-office or at-home tooth whitening products with short treatment durations are as effective and stable as products with longer treatment durations. Materials and Methods: Forty human third molars with intact enamel surfaces were divided into four groups of ten each, subjected to discoloration challenges with coffee for 60 h, and they were treated with four professional tooth whitening systems: two for take-home use-6% hydrogen peroxide for 30 min/d for a total of 7 h in 14 days (HP6), 10% carbamide peroxide for 10 h/d for 140 h in 14 days (CP10), as well as two for in-office use-35% HP for 10 min × 3 (HP35) for a total of 30 min and 40% HP for 20 min × 3 (HP40) for a total of 60 min. Teeth colors were assessed in the CIE L*a*b* color space with a spectrophotometer immediately and six months after whitening treatments. Surface roughness (Sa) for the treated and untreated enamel surfaces of the teeth in all groups were evaluated with a three-dimensional laser scanning microscope after six months. Results: No significant differences were found between HP6 and CP10 groups immediately after whitening (∆E 10.6 ± 1.6 vs. 11.4 ± 1.7, p > 0.05) and at six months after treatments (∆E 9.0 ± 1.9 vs. 9.2 ± 2.5, p > 0.05), or between HP35 and HP40 groups immediately after whitening (∆E 5.9 ± 1.2 vs. 5.3 ± 1.7, p > 0.05) and at six months after treatments (∆E 7.2 ± 1.6 vs. 7.7 ± 1.3, p > 0.05). The two at-home whitening systems achieved significantly better whitening outcomes than the two in-office products immediately after whitening (p < 0.05). However, at six months after treatments, the differences between at-home and in-office treatments had narrowed significantly (p > 0.05). There were no statistically significant differences with respect to the Sa values between the treated and untreated surfaces (p > 0.05). Conclusions: Tooth whitening products in the same product category have similar whitening efficacies, despite significant differences in treatment durations (7 vs. 140 h, and 30 min vs. 60 min, respectively). Take-home products achieved better whitening outcomes than in-office products, but they needed 14 to 280 times longer treatment durations.

Experimental study on the true triaxial fracturing of tight sandstone with supercritical CO2 and slickwater

Under the effect of the goal of carbon peaking and carbon neutrality, the use of supercritical CO2 has gradually become a research hotspot as a new waterless fracturing fluid, supercritical CO2 fracturing is expected to become an effective techniques to solve the problem of fracturing fluid backflow in low pressure sandstone reservoirs. The outcrop of the Shaximiao Formation in the Sichuan Basin was selected as the research object, the true triaxial fracturing experiments with supercritical CO2 and slickwater were carried out by the large true triaxial fracturing experimental equipment, the computed tomography (CT) scanner and three-dimensional laser scanner to investigate the initiation, propagation patterns, fracture tortuosity and fractal dimension of fractures produced in tight sandstone via supercritical CO2 and slickwater fracturing and to clarify the influences of the different fluids, displacement rates, and in-situ stress differences on the propagation of fractures in tight sandstone. The results showed that the supercritical CO2 fracturing had a lower fracturing pressure and a longer rock fracturing time than slickwater fracturing. Furthermore, the supercritical CO2 fracturing produced fractures with greater tortuosity and fractal dimension as well as a more complex spatial morphology. In addition, the increase in the displacement rate and the decrease in the in-situ stress difference for supercritical CO2 fracturing was more conducive to the multi-point initiation and reorientation of the hydraulic fractures, increasing the complexity of the reservoir fractures and improving the flow effect. It can provide the important theoretical foundation for the creating plans for supercritical CO2 fracturing of tight sandstone with the experimental knowledge.

Cataclastic Characteristics and Formation Mechanism of Dolomite Rock Mass in Yunnan, China

The dolomite rock mass on the slope of the Yanhe domestic waste incineration power plant was used as the research object. The macro- and micro-structural characteristics of intact rock blocks and rock discontinuities were analyzed qualitatively and quantitatively using in-hole television, wave velocity testing, three-dimensional laser scanning techniques, photogrammetry, image processing techniques, and scanning electron microscopy (SEM). The study shows that the degree of fracturing generally decreases with depth over the exposed borehole depth range, and the rock masses are generally very fractured. The wave velocity of dolomite generally increases with the depth of the borehole, and the integrity of the dolomite is either broken or extremely broken. The excavation profile reveals six sets of discontinuities and joints that are straight, smooth, interconnected, and largely unfilled. The angles of the structural bodies of different grain sizes are sharp, with roundness being angular and sharp-angled. The smaller the blocks, the more complex the surface morphology. SEM observations show that the ultramicroscopic fractures are not flat and smooth, and the fractures are folded. Fracturing mainly occurs along intercrystalline and crystal interfaces. These fracture features suggest that the fracturing of dolomite is mainly related to the original sedimentary construction and tectonism.

Soft Segmentation of Terrestrial Laser Scanning Point Cloud of Forests

As the three-dimensional (3D) laser scanner is widely used for forest inventory, analyzing and processing point cloud data captured with a 3D laser scanner have become an important research topic in recent years. The extraction of single trees from point cloud data is essential for further investigation at the individual tree level, such as counting trees and trunk analysis, and many developments related to this topic have been published. However, constructing an accurate and automated method to obtain the tree crown silhouette from the point cloud data is challenging because the tree crowns often overlap between adjacent trees. A soft segmentation method that uses K-Nearest Neighbor (KNN) and contour shape constraints at the overlap region is proposed to solve this task. Experimental results show that the visual effect of the tree crown shape and the precision of point cloud segmentation have improved. It is concluded that the proposed method works well for tree crown segmentation and silhouette reconstruction from the terrestrial laser scanning point cloud data of the forest.

The Research on Obtaining the Geometric Dimension of Cable-Stayed Bridges Based on 3D Laser Scanning

The traditional manual measurement methods are time-consuming and error-prone when they are used for cable-stayed bridges’ geometric dimensions acquisition. They are always limited by various adverse conditions such as large bridge spans, the high height of bridge towers, more risk of manual operation, and many other unpredictable factors. In contrast, three-dimensional (3D) laser scanning technology is extremely useful for solving the above problems. After obtaining plenty of point cloud data and point cloud models, precise and accurate geometric dimensions of cable-stayed bridges can be obtained accurately and conveniently. Taking a cable-stayed bridge named XingLinBao as an example, the accuracy and convenience of 3D laser scanning are verified.

Effect of Geometry Precision and Load Distribution on Branch Mechanical Response

Tree risk assessment requires mechanical response studies, but simplification of the shape, material, or boundary conditions is necessary when dealing with such complex structures. To observe overall tree response, sub-structuring to several levels of detail can be used, enabled by recent developments in numerical methods and three-dimensional laser scanning (3D scan). This study aimed to determine an appropriate level of geometry and loading simplification allowed for high-order branches at the crown border, which is useful for the mechanical analysis of structured tree models. Four higher-order branches were pruned and experimentally tested by single-point loading. Beam and solid finite-element models (FEMs) were created based on measured geometric parameters and detailed 3D scans, respectively. The FEMs were used to analyze seven loading scenarios with force applied at (a) the center of gravity, (b) the top of side branches, (c) key discrete points, and (d) uniformly to the whole volume (to each finite element). Force was distributed by ratios weighted according to the mass, area, and diameter of side branches; or according to the mass of each finite element. The results showed no significant difference between the beam model and 3D scan-based model. The scenarios with finite elements’ mass-based force distribution deviated significantly from those of the other scenarios. The most simplified single-point loading caused a deviation in the deflection curve. The deviation of single-point loading in the case of the bending moment was related to force distribution ratios given by the branches architecture. Therefore, such loading simplification is not considered always appropriate. Consistency between the bending moment and branch deflection provided a representative mechanical response, recommended for further modeling of trees by sub-structuring.

Degradation of Steel Rebar Tensile Properties Affected by Longitudinal Non-Uniform Corrosion.

Rebar corrosion is the primary cause of the durability degradation of reinforced concrete (RC) structures, where non-uniform corrosion is the typical pattern in engineering. This study experimentally and numerically investigated the tensile degradation properties of non-uniform corroded rebars. Corrosion morphology was accurately determined by three-dimensional (3D) laser scanning techniques, studying the characteristics of longitudinal non-uniform corrosion. The results showed that the non-uniformity of corrosion increased with an increase in corrosion levels. From tensile tests, the differences in nominal stress-strain curves among rebars with similar average corrosion levels indicated that corrosion non-uniformity has appreciable effects on the tensile behavior of rebars. The residual load-bearing capacity of corroded rebars was dominated by the reduced critical cross-section, while residual ductility was associated with the cross-section loss throughout the entire length of rebars. The degradation relations of nominal yield and ultimate strength, ultimate strain, and elongation after fracture were better correlated to the maximum cross-section loss than to the average volume loss. Additionally, numerical calculation based on the cross-sectional areas of corroded rebars was conducted to evaluate the tensile behavior of non-uniform corroded rebars. Equivalent distribution models simulating the longitudinal non-uniform corrosion were proposed, on the basis of probability characteristics of cross-sectional areas, for practical application of the numerical method.

Construction Quality Inspection Method of Substation Fabricated Structure Based on 3D Laser Scanning

The substation construction project is highly professional and comprehensive, requiring multiple disciplines’ cooperation. It is greatly affected by geographical and environmental factors and has the characteristics of high management requirements and difficult quality control in the construction process. Based on the good initial position of the point cloud to be registered, if this requirement cannot be met, the registered point cloud data is prone to the optimal local solution. Thus, this paper introduces three-dimensional laser scanning to detect the construction quality of the substation assembly structure. On this basis, the data registration method realizes the accurate point cloud registration, and the data’s main feature vector is extracted through a linear transformation. Through the spatial transformation of the principal axis direction, the registration of the point cloud number is completed. The problem of the optimal local solution of registration is effectively solved. The point cloud data model is created by actual data acquisition, and the influencing factors of reverse construction of the geometric model are analyzed. The specific implementation scheme is put forward to ensure the accuracy of the geometric model construction. The test verified the reasonable and effective application of 3D laser scanning in the prefabricated building installation. Besides, the effective method of the high-precision point cloud model data output is determined.

A State-of-the-Practice Review of Three-Dimensional Laser Scanning Technology for Tunnel Distress Monitoring

A State-of-the-Practice Review of Three-Dimensional Laser Scanning Technology for Tunnel Distress Monitoring

Effects of interlayer surface characteristics on the interface bonding between double-layered asphalt systems

ABSTRACT This study aims at comparing the surface characteristics of the interface between double-layered asphalt specimens composed of conventional or rubberised asphalt concrete mixtures. To this end, first, the double-layered asphalt specimens with a novel interlayer isolation film (IIF) in between were manufactured, and then the asphalt specimens were non-destructively separated at the layer interface. Subsequently, an ultra-high-resolution three-dimensional (3D) laser scanner was utilised to acquire the respective 3D point cloud data. Next, the 3D morphology of the interface between asphalt layers was reconstructed using image processing techniques, and the corresponding surface characteristics were determined accordingly. In this respect, three indicators of impact ratio (IR), degree of curvature (DC), and curvature ratio (CR), which are dependent together and developed in a successive approach, were developed respectively to quantitatively describe interlayer surface characteristics of adjacent layers. Subsequently, the relationship between the interface shear strength and interface characteristics of double-layered specimens was compared and analyzed. The results showed that the CR could effectively reflect the surface characteristics of the interface between double-layered asphalt specimens. Finally, the statistical analysis revealed that the interlayer surface characteristics (CR) statistically had a significant effect on the interface shear strength.

Ballistic penetration of high-entropy CrMnFeCoNi alloy: Experiments and modelling

Ballistic impact experiments are conducted on a CrMnFeCoNi high-entropy alloy (HEA) using spherical steel projectiles, to investigate the penetration behavior in a wide range of impact velocities (∼800 to 2300 m s−1). Penetration processes are captured by high-speed camera. Postmortem samples are characterized via three-dimensional laser scanning, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy and microhardness tests. Both depth and diameter of impact crater show a nearly linear increase with increasing impact velocity. Penetration induces increased hardness; hardness is the same near the crater bottom and the sidewall, and the peak hardness (∼400 Hv1.0) is independent of impact velocity. The penetration-induced hardening is caused by multiple deformation defects including dislocations, twins and kink bands (KBs). Quantitative analysis further reveals that KB boundaries have a 5–50° misorientation angle, and their density decreases with increasing misorientation angle. KB boundary density is higher near the crater bottom than near the crater sidewall, while this trend is inverse for twinning boundary density. A finite element method model based on measured static and dynamic mechanical properties reproduces experimental observations and is used for interpreting deformation mechanisms.