Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.

Experimental Research on Effects of Process Parameters on Servo Scanning 3D Micro Electrical Discharge Machining

Servo scanning 3D micro electrical discharge machining (3D SSMEDM) is a novel and effective method in fabricating complex 3D micro structures with high aspect ratio on conducting materials. In 3D SSMEDM process, the axial wear of tool electrode can be compensated automatically by servo-keeping discharge gap, instead of the traditional methods that depend on experiential models or intermittent compensation. However, the effects of process parameters on 3D SSMEDM have not been reported up until now. In this study, the emphasis is laid on the effects of pulse duration, peak current, machining polarity, track style, track overlap, and scanning velocity on the 3D SSMEDM performances of machining efficiency, processing status, and surface accuracy. A series of experiments were carried out by machining a micro-rectangle cavity (900 μm×600 μm) on doped silicon. The experimental results were obtained as follows. Peak current plays a main role in machining efficiency and surface accuracy. Pulse duration affects obviously the stability of discharge state. The material removal rate of cathode processing is about 3/5 of that of anode processing. Compared with direction-parallel path, contour-parallel path is better in counteracting the lateral wear of tool electrode end. Scanning velocity should be selected moderately to avoid electric arc and short. Track overlap should be slightly less than the radius of tool electrode. In addition, a typical 3D micro structure of eye shape was machined based on the optimized process parameters. These results are beneficial to improve machining stability, accuracy, and efficiency in 3D SSMEDM.

Research on 3D Laser Scanning Reconstruction of Ancient Buildings Combined with BIM Technology

After more than 30 years of scientific and social development, surveying and mapping technology by leaps and bounds, engineering surveying technology has undergone tremendous changes. In the process of protecting ancient buildings, it is necessary to obtain the precise dimensions of architectural details. In this study, the path of 3D laser scanning combined with BIM technology is explored. Taking the observation and protection of the ancestral hall of the Liu family as an example, this study aims to draw drawings that reflect the relevant information about the ancient buildings, the accurate three-dimensional model of ancient buildings is established with BIM technology, which provides new methods and ideas for the research and protection of ancient buildings. .

Development of 3D Scanning System for Robotic Plasma Processing of Medical Products with Complex Geometries

This paper describes the development of an intelligent automated control system of a robot manipulator for plasma treatment of medical implants with complex shapes.The two-layer coatings from the Ti wire and hydroxyapatite powders are applied on the surface of Ti medical implants by microplasma spraying to increase the biocompatibility of implants.The coating process requires precise control of a number of parameters,particularly the plasma spray distance and plasma jet traverse velocity.Thus,the development of the robotic plasma surface treatment involves automated path planning.The key idea of the proposed intelligent automatic control system is the use of data of preliminary three-dimensional (3D) scanning of the processed implant by the robot manipulator.The segmentation algorithm of the point cloud from laser scanning of the surface is developed.This methodology is suitable for robotic 3D scanning systems with both non-contact laser distance sensors and video cameras,used in additive manufacturing and medicine.

Experimental Investigation of Laser Surface Hardening of AISI 4340 Steel Using Different Laser Scanning Patterns

Laser surface transformation hardening becomes one of the most modern processes used to improve fatigue and wear properties of steel surfaces. In this process, the material properties and the heating parameters are the factors that present the most significant effects on the hardened surface attributes. The control of these factors using predictive modeling approaches to achieve desired surface properties leads to conclusive results. However, when the dimensions of the surface to be treated are larger than the cross-section of the laser beam, various laser-scanning patterns are involved. This paper presents an experimental investigation of laser surface hardening of AISI 4340 steel using different laser scanning patterns. This investigation is based on a structured experimental design using the Taguchi method and improved statistical analysis tools. Experiments are carried out using a 3 kW Nd: YAG laser source in order to evaluate the effects of the heating parameters and patterns design parameters on the physical and geometrical characteristics of the hardened surface. Laser power, scanning speed and scanning patterns (linear, sinusoidal, triangular and trochoid) are the factors used to evaluate the hardened depth and the hardened width variations and to identify the possible relationship between these factors and the hardened zone attributes. Various statistical tools such as ANOVA, correlations analysis and response surfaces are applied in order to examine the effects of the experimental factors on the hardened surface characteristics. The results reveal that the scanning patterns do not modify the nature of the laser parameters’ effects on the hardened depth and the hardened width. But they can accentuate or reduce these effects depending on the type of the considered pattern. The results show also that the sinusoidal and the triangular patterns are relevant when a maximum hardened width with an acceptable hardened depth is desired.

Assessment of handheld mobile terrestrial laser scanning for estimating tree parameters

Sustainable forest management heavily relies on the accurate estimation of tree parameters.Among others,the diameter at breast height(DBH) is important for extracting the volume and mass of an individual tree.For systematically estimating the volume of entire plots,airborne laser scanning(ALS) data are used.The estimation model is frequently calibrated using manual DBH measurements or static terrestrial laser scans(STLS) of sample plots.Although reliable,this method is time-consuming,which greatly hampers its use.Here,a handheld mobile terrestrial laser scanning(HMTLS) was demonstrated to be a useful alternative technique to precisely and efficiently calculate DBH.Different data acquisition techniques were applied at a sample plot,then the resulting parameters were comparatively analysed.The calculated DBH values were comparable to the manual measurements for HMTLS,STLS,and ALS data sets.Given the comparability of the extracted parameters,with a reduced point density of HTMLS compared to STLS data,and the reasonable increase of performance,with a reduction of acquisition time with a factor of5 compared to conventional STLS techniques and a factor of3 compared to manual measurements,HMTLS is considered a useful alternative technique.

Automated cone photoreceptor cell identication in confocal adaptive optics scanning laser ophthalmoscope images based on object detection

Cone photoreceptor cell identication is important for the early diagnosis of retinopathy.In this study,an object detection algorithm is used for cone cell identication in confocal adaptive optics scanning laser ophthalmoscope(AOSLO)images.An effectiveness evaluation of identication using the proposed method reveals precision,recall,and F_(1)-score of 95.8%,96.5%,and 96.1%,respectively,considering manual identication as the ground truth.Various object detection and identication results from images with different cone photoreceptor cell distributions further demonstrate the performance of the proposed method.Overall,the proposed method can accurately identify cone photoreceptor cells on confocal adaptive optics scanning laser ophthalmoscope images,being comparable to manual identication.

Sedimentary processes in Zenisu deep-sea channel revealed by side-scan imagery

Side-scan sonar data collected by Cruises 99-09 Leg 2 and 00-06 Leg 1 of R/V Yokosuka were used to reveal the sedimentary processes in Zenisu deep-sea channel. The middle and lower segments of the channel are rich in turbidite and other debrite deposits. By high-resolution imaging, three sedimentary processes were distinguished with distinct acoustic features. 1. Slumps and slides occur with contrasting backscatter, rough surface textures, blockings, and acoustic shadows at headwalls. They are very extensive and often in lobate form downslope. 2. Debris flow has uniform, general medium backscatter, sometimes showing marbling/lineation in lobate form. 3. Turbidity current is characterized by low backscatter confined to the channel as acoustic signal is attenuated. Regional tectonics must be the dominating factor that controls deposition pattern in this area.

特征自适应的复杂曲面扫描路径生成方法

为了解决现有自动化扫描方法在面对复杂曲面时扫描完整性不足、普适性不佳等问题,提出了一种特征自适应的自动化扫描路径规划方法。首先,构建了激光扫描仪的扫描约束条件,分析其对扫描精度的影响,为特征自适应的复杂扫描路径规划提供理论支撑。其次,针对扫描仪姿态规划问题,提出了一种新的测量倾角约束聚类算法,对离散复杂曲面后获得的采样点进行聚类处理,实现扫描仪姿态的规划,并在此基础上获得扫描路径点。再次,针对扫描路径规划问题,引入法向矢量夹角矩阵作为惩罚矩阵,优化改进最近邻算法,实现符合需求的扫描路径规划。最后,为验证该方法可行有效,以汽车车门作为扫描对象,搭建了一个组合式自动化柔性测量系统,与传统行切扫描方法、手动扫描方法进行对比试验。试验结果表明,该方法相较于行切扫描方法在扫描仪姿态变换次数上减少了54%,测量精度提高了64.5%,降低了人工干预因素的影响,扫描完整性与手动扫描方法接近,可以实现针对复杂曲面的自动化扫描测量。

硼砂煅制工艺优化及质量评价

目的 优化硼砂煅制工艺,并对其进行质量评价。方法 以铺设厚度、煅制温度、煅制时间为影响因素,失水率、蓬松度、粉碎率、四硼酸钠含量为评价指标,星点设计-效应面法优化硼砂煅制工艺。采用扫描电镜(SEM)、热重分析(TG)、拉曼光谱、X射线衍射(XRD),比较硼砂煅制前后质量差异。结果 最佳条件为铺设厚度2 cm,煅制温度365℃,煅制时间100 min。煅制后,硼砂微观形态、成分组成、晶型结构发生变化,失去全部结晶水而转变为非晶体状态。结论 该方法稳定可行,可用于工业大批量生产煅硼砂。

增材制造316L熔覆层表面成形质量实验研究

增材制造是近些年来新兴的一种制造方法,具有绿色环保、节约材料、生产周期短等优点,激光熔覆技术是金属材料增材制造的主要方法。通过激光熔覆实验制备316L熔覆层,分析了熔覆层表面成形质量,探究了激光功率、送粉速率、扫描速度、搭接率、每层提升量、扫描路径对316L熔覆层表面形貌的影响,对实验结果进行分析得到:随着激光功率的增大,熔覆线宽度和熔深增大,熔覆线高度先增大后减小,稀释率先减小后增大;随着扫描速率的增大,熔覆线高度、宽度、熔深均减小,稀释率总体的变化趋势是增大;随着送粉速率的增大,熔深先增大后减小,熔覆线高度增大,宽度和稀释率减小;当横向搭接率为45%时,熔覆层表面较为平整;当z轴抬升量等于单层熔覆高度时,成形件高度最高且成形形貌好,无塌陷现象;采用往返扫描方式成形的试件两边高度形貌均匀且高度一致,没有明显坍塌现象。实验结果为激光熔覆316L的技术提供了数据支持和实验依据。

基于点云的多源数据融合技术

三维激光扫描技术是一门逆向工程应用技术,凭借其高速、全面且高自动化的特点,显示出了强大的不可替代性。三维点云数据有着其多样化、精度高、数据完整的优点。多源数据融合技术使不同设备获取的点云数据、影像数据、空载数据能够相互弥补,提高不同场景环境下的作业效率,完善数据的结构和精度质量,使空、地、水下三维数据的一体化成为可能。通过对不同射程多台三维激光扫描仪的数据进行相对精度分析、调整和融合,并对不同融合方法获取的多源融合数据进行精度验证,探索一种多源数据融合的方法,形成多源数据融合的通用技术流程。为多种载体三维激光扫描技术的数据和影像数据的融合方法研究奠定基础。

激光后处理实现图案化结构色调控研究

为使人工制备的结构色实现色调的精确调控,本研究以硅片为衬底,采用自组装法制备聚苯乙烯微球(PS微球)的平面六角密堆积结构,通过磁控溅射方法在其上沉积不同厚度的金薄层;再利用532nm脉冲激光后处理,研究不同扫描速度的激光后处理对结构色薄膜呈色性能的影响。结果表明:镀膜时间相同,随激光扫描速度逐渐减小,样品扫描区域颜色的变化为玫红—橙红—橙黄—黄绿—蓝绿—蓝紫,反射光谱中心波长发生蓝移;在此基础上制备了图案化的样品,发现随着观察角度增加,扫描后区域的颜色发生蓝移。

球孢白僵菌侵染长林小蠹的致病性及侵染显微观察

【目的】筛选球孢白僵菌并探究其对长林小蠹幼虫和成虫的致病性,以及分析球孢白僵菌对长林小蠹幼虫和成虫的侵染过程。【方法】1)通过形态学鉴定和分子生物学鉴定确定所筛选菌株的品系;2)利用Excel2016软件计算累计校正死亡率,SPSS 26.0软件进行方差分析,并计算毒力回归方程式和LC50;3)利用扫描电镜观察球孢白僵菌侵染长林小蠹幼虫和成虫的过程。【结果】1)经鉴定,从长林小蠹僵虫虫体上分离纯化得到的是4株不同的球孢白僵菌(编号分别为Bbz1、Bbz2、Bbz3和Bbz4);2)对长林小蠹幼虫和成虫进行毒力测定,4株球孢白僵菌对长林小蠹幼虫和成虫毒力并不相同,其中,菌株Bbz4对幼虫的毒杀效果最好,接种7 d后,1×10^(8)孢子/m L浓度的孢子悬浮液对长林小蠹幼虫致死率达到100%,LC50为3.68×10^(5)孢子/m L,对成虫毒杀效果最好的是菌株Bbz1,接种7 d后,1×10^(8)孢子/m L浓度的孢子悬浮液对长林小蠹成虫致死率达到100%,LC_(50)为3.27×10^(6)孢子/m L;3)使用菌株Bbz4和菌株Bbz1对长林小蠹幼虫和成虫的侵染进行超微结构观察发现,在接种0~12 h时,菌株分生孢子接触并附着在长林小蠹体表;接种18 h时,发现孢子萌发并产生芽管;接种36 h时,发现有菌丝向内穿透体壁的现象出现;接种72 h时,菌丝伸出体外;接种96~120 h时,整个虫体被菌丝覆盖。【结论】确定了从长林小蠹僵虫虫体上分离到的是4株不同球孢白僵菌,其中菌株Bbz4和Bbz1分别对长林小蠹幼虫和成虫致病性最强,并确定接种后不同时间节点上白僵菌的侵染进程。

基于误差修正的激光扫描复杂零件加工系统

针对降低复杂零件加工过程中的零件误差问题,设计基于误差修正的激光扫描复杂零件加工系统。以激光扫描为基础设计复杂零件加工系统的整体架构。基于系统整体架构利用激光扫描模块获取材料信息,并采用网格修正法修正扫描单元中的振镜误差;将激光扫描结果传输至DSP控制模块内,通过直线、圆弧插补运算确定加工模块内不同加工单元的刀具加工路径,同时利用不同伺服单元的位置等反馈信号对比,实现机械手模块运动控制。实验结果显示该系统激光扫描误差控制在0.5 mm以下,符合风机应用标准,加工时间最高为37 min,有效提升了零件可应用率。

核桃壳/酚醛树脂生物质复合材料选择性激光烧结工艺参数研究

黑龙江省作为农林业大省,盛产核桃,这种果壳来源丰富且产量高,同时也伴随着大量农业废弃物的产生。为改善这一现状,需要对废弃核桃壳进行合理资源利用。选取废弃核桃壳作为粉末基体材料,将碳含量丰富的酚醛树脂粉作为黏结剂,制备用于选择性激光烧结的核桃壳/酚醛树脂生物质复合材料,不仅可以扩大生物质复合材料粉体的种类,还可以通过该技术的三维性,定制复杂结构的多孔碳前驱体,在海水淡化、新能源方面作出贡献。建立四因素三水平的正交试验方案,通过方差分析法和综合加权评价法,探讨激光功率、扫描速度、扫描间距和分层厚度4因素对烧结件密度、弯曲强度和Z轴精度的影响规律,确定最优激光烧结工艺参数组合,使用扫描电镜(scanning electron microscope,SEM)对成型件烧结断面进行表征。试验结果表明,激光功率对烧结件密度、弯曲强度和Z轴精度的影响最大,扫描速度对烧结件密度和弯曲强度的影响最小,扫描间距对Z轴精度影响最小;最优工艺参数组合为激光功率10 W、扫描速度2 m/s、扫描间距0.1 mm、分层厚度0.12 mm。

SLAM激光扫描技术在地铁隧道竣工测量中的应用

轴线偏差和断面测量一直是隧道竣工测量的两个重要指标。传统使用全站仪或断面仪进行测量的方式不仅作业效率低,采集的数据量也较少,难以反映隧道内的真实情况,无法满足隧道竣工测量的要求。本文提出了一种基于SLAM手持激光扫描仪进行地铁隧道竣工测量的方法,并在上海市某在建地铁隧道内进行了现场试验。比较激光点云后处理得到的断面中心与设计数据,二者平均点位精度小于3 cm。这表明使用SLAM手持激光扫描仪进行地铁隧道竣工测量的方法有效可行,精度能够满足竣工测量的要求,具有广阔的应用前景。

汽车流水槽成形性分析及回弹研究

根据客户要求并结合流水槽形状特点,确定冲压工艺方案,利用Autoform R8软件进行CAE成形分析,获得零件回弹方向及回弹量,确定最佳拉深造型。通过现场零件质量验证工艺方案的可行性,最后对零件进行白光扫描,运用GOM软件对比扫描数据与零件数据,验证前期CAE分析的可靠性,该方案对类似零件的开发提供了参考依据。

基于纹理特征的钢渣沥青路面抗滑性能测试与评价

沥青路面的抗滑性能快速下降一直是各国学者高度关注的问题。随着表面纹理逐渐磨损,沥青路面的抗滑性能也持续减弱。为了能更科学地评估和预测路面抗滑性能的衰减,有必要定量地建立起路面纹理和抗滑性能之间的关系。本研究采用了小型加速加载设备、高精度三维扫描设备以及数字图像处理来模拟路面纹理的磨损过程。本研究基于三维纹理特征系统评价了沥青路面的抗滑性能衰减。研究结果显示,英国摆值(BPN)与本研究采用的评价指标三维纹理参数(Sq、Ssk、Vmp、Vmc和Vvc)之间存在着紧密的联系。随着加载次数的增加,BPN和三维纹理参数都呈现出相同的衰减趋势。这些三维纹理参数不仅可以作为评估沥青路面抗滑性能的指标,还能精确地描绘钢渣沥青路面的微观磨损机制。本研究建立的关系将有助于预测路面的抗滑衰减情况,为钢渣沥青路面的路用性能研究提供了有力的技术支持。

整木生产进度跟踪二维码扫描系统的设计与应用

生产进度跟踪是整木定制家具企业生产管理的重要内容。实现对生产环节各个节点进度的精确把控,通过对M家具公司的生产车间流程的调查研究,总结出整木生产进度管理具有信息化程度低、同项目齐套管理难度大、采购进度难跟踪的难点。以M家具公司作为案例进行研究,以二维码扫描技术为基础,按照“批次-订单-部件”的结构,制定了整木生产进度跟踪二维码扫描系统的技术方案,并以此为基础,设计出管理系统的功能框架。将二维码扫描系统投入使用后,通过经验总结的方法,制定各个生产环节的标准操作流程。新系统的使用,降低车间工作的透明度,能够获得生产信息的及时反馈,大大降低了生产进度管理的难度,是企业在信息化道路上迈出的重要一步。