Failure Characteristics of Rock-like Mortar Specimens with Arc-shaped Flaws under Freezing-thaw Cycles and Uniaxial Compression

To investigate the freeze-thaw(F-T)damages and failure characteristics of rock mass with arc-shaped joints in cold regions,three types of cement mortar specimens with different central angles and prefabricated arc-shaped flaws are subjected to uniaxial compressive tests under different F-T cycles.Experimental observations show that the uniaxial compressive strength of specimens are significantly influenced by F-T cycles and their failure modes are mainly affected by the central angleαof the prefabricated flaws.Unlike the specimens with a central angle of 60°,the specimens with a central angle of 120°and 180°have greater curvature of flaws,so tensile cracks occur in the arc-top area of their prefabricated flaws.According to experimental images observed by environmental scanning electron microscope(ESEM),as the number of F-T cycles increases,the deterioration effect of the specimen becomes more obvious,which is specifically reflected in the increase of the mass loss,peak stress loss,and damage variables as a power function,and the peak strain decreases as a quadratic polynomial.According to numerical results using two-dimensional particle flow code(PFC2D),it is found that F-T cycles cause more damage to the specimen in the early stages than in the later ones.The area of the concentrated compressive stress zone in the middle is decreased due to the increased number of F-T cycles,while the area of the surrounding tensile-shear stress zone is increased.The models appear different failure modes due to the release of concentrated stress in different tensile-shear zones.

I-DCGAN and TOPSIS-IFP:A simulation generation model for radiographic flaw detection images in light alloy castings and an algorithm for quality evaluation of generated images

The intelligent detection technology driven by X-ray images and deep learning represents the forefront of advanced techniques and development trends in flaw detection and automated evaluation of light alloy castings.However,the efficacy of deep learning models hinges upon a substantial abundance of flaw samples.The existing research on X-ray image augmentation for flaw detection suffers from shortcomings such as poor diversity of flaw samples and low reliability of quality evaluation.To this end,a novel approach was put forward,which involves the creation of the Interpolation-Deep Convolutional Generative Adversarial Network(I-DCGAN)for flaw detection image generation and a comprehensive evaluation algorithm named TOPSIS-IFP.I-DCGAN enables the generation of high-resolution,diverse simulated images with multiple appearances,achieving an improvement in sample diversity and quality while maintaining a relatively lower computational complexity.TOPSIS-IFP facilitates multi-dimensional quality evaluation,including aspects such as diversity,authenticity,image distribution difference,and image distortion degree.The results indicate that the X-ray radiographic images of magnesium and aluminum alloy castings achieve optimal performance when trained up to the 800th and 600th epochs,respectively.The TOPSIS-IFP value reaches 78.7%and 73.8%similarity to the ideal solution,respectively.Compared to single index evaluation,the TOPSIS-IFP algorithm achieves higher-quality simulated images at the optimal training epoch.This approach successfully mitigates the issue of unreliable quality associated with single index evaluation.The image generation and comprehensive quality evaluation method developed in this paper provides a novel approach for image augmentation in flaw recognition,holding significant importance for enhancing the robustness of subsequent flaw recognition networks.

AN IMPROVED FOSM METHOD FOR CALCULATING FAILURE PROBABILITY OF WELDED PIPES WITH FLAWS

The R F first order second moment method will produce more error for calculating the reliability of welded engineering pipe structures when the failure function is seriously nonlinear and the random variables don′t serve as normal distribution. In order to increase the computing accuracy of reliability, an improved FOSM method is used for calculating the failure probability of welded pipes with flaws in this paper. Because of solving the problems of the linear expansion of failure function at the failure point and constructing equivalent normal variables, the new algorithm can greatly improve the calculating accuracy of probability of the welded pipes with cracks. The examples show that this method is simple, efficient and accurate for reliability safety assessment of the welded pipes with cracks. It can save more time than the Monte Carlo method does, so that the improved FOSM method is recommended for engineering reliability safety assessment of the welded pipes with flaws.

Experimental study on cracking behaviour of moulded gypsum containing two non-parallel overlapping flaws under uniaxial compression

Failure of rock mass that is subjected to compressive loads occurs from initiation, propagation, and linkage of new cracks from preexisting fissures. Our research investigates the cracking behaviour and coalescence process in a brittle material with two non-parallel overlapping flaws using a high-speed camera. The coalescence tensile crack and tensile wing cracks were the first cracks to occur from the preexisting flaws. The initiation stresses of the primary cracks at the two tips of each flaw were simultaneous and decreased with reduced flaw inclination angle. The following types of coalescence cracks were identified between the flaws: primary tensile coalescence crack, tensile crack linkage, shear crack linkage, mixed tensile-shear crack, and indirect crack coalescence. Coalescence through tensile linkage occurred mostly at pre-peak stress. In contrast, coalescence through shear or mixed tensile-shear cracks occurred at higher stress. Overall, this study indicates that the geometry of preexisting flaws affect crack initiation and coalescence behaviour.

Mechanical behavior and failure analysis of brittle sandstone specimens containing combined flaws under uniaxial compression

Based on the axial stress-axial strain curves,the effect of fissure angle on the strength and deformation behavior of sandstone specimens containing combined flaws is analyzed.The mechanical parameters of sandstone specimens containing combined flaws are all lower than that of intact specimen,but the reduction extent is distinctly related to the fissure angle.The results of sandstone specimens containing combined flaws are obtained by the acoustic emission,which can be used to monitor the crack initiation and propagation.The ultimate failure mode and crack coalescence behavior are evaluated for brittle sandstone specimens containing combined flaws.Nine different crack types are identified on the basis of their geometry and crack coalescence mechanism(tensile crack,hole collapse,far-field crack and surface spalling)for combined flaws.The photographic monitoring was also adopted for uniaxial compression test in order to confirm the sequence of crack coalescence in brittle sandstone specimens containing combined flaws,which recorded the real-time crack coalescence process during entire deformation.According to the monitored results,the effect of crack coalescence process on the strength and deformation behavior is investigated based on a detailed analysis for brittle sandstone specimens containing combined flaws by using digital photogrammetry.

Imperfect Emma:An Analysis of Emma's Character Flaws

Emma is the heroine of one of the novels written by Jane Austen(1775-1817) who is among the most widely read writers in English literature.In the novel,also named Emma,Austen portrayed Emma as a young,pretty and smart gentlewoman,yet she was not a perfect or flawless character.She dose not seem to have any sense of her own limitations.Her self-conceit and meddling nature are two of her most fatal character flaws.In this article,we will give a detailed analysis of Emma's flaws supported by various incidents as the novel progresses.We will also find out the two major factors that contribute to develop these character flaws,which are the negative effects caused on her by people very close to her and also the society of her time.

Image Processing Technology of Flaws within Infrared Transmitting Glasses

We investigated image processing algorithms of the original infrared glass flaw image. Using the Laplacian edge enhancement following LSD （Line Segment Detector） algorithm, we can get a good flaw image very consistent with the original one. This study is very helpful to further enhance the infrared glass flaw inspection technique.

Structure and flaws of CuCr alloys by explosive compaction

CuCr alloys are prepared by mechanical alloying and explosive compaction. After we have studied their structure and flaws, the results show that the CuCr alloys have definite strength and toughness, while their fractured surface displays ductile characteristics. In the metallurgical structure, CuCr alloys are composed of two phases of uniform distribution; the SEM morphology is like thin strips with an end arrangement that is bonded to each other and the two-phase distribution of CuCr alloys is more homogenous. It is in only in a very small zone that formation of Cu-rich and Cr-rich phases take place. The flaws of the compaction samples are mainly central-holes and cracks.

Tragic Flaws of the Protagonists——Hamlet and Gatsby

Hamlet is the most discussed of Shakespeare's tragedies, while The Great Gatsby is the masterpiece of Fitzgerald. It is true that the tragic flaws of the protagonists would be a key factor driving the development of the plots. In these two dramas, the flaws of the protagonists leaded to their tragic endings which are related to their own characteristics of the protagonists. And the ends of the stories are with the tragedies.

Mechanical response and microscopic damage mechanism of pre-flawed sandstone subjected to monotonic and multilevel cyclic loading:A laboratory-scale investigation

This study aims to investigate the mechanical response and acoustic emission(AE)characteristic of pre-flawed sandstone under both monotonic and multilevel constant-amplitude cyclic loads.Specifically,we explored how coplanar flaw angle and load type impact the strength and deformation behavior and microscopic damage mechanism.Results indicated that being fluctuated before rising with increasing fissure angle under monotonic loading,the peak strength of the specimen first increased slowly and then steeply under cyclic loading.The effect of multilevel cyclic loading on the mechanical parameters was more significant.For a single fatigue stage,the specimen underwent greater deformation in early cycles,which subsequently stabilized.Similar variation pattern was also reflected by AE count/energy/b-value.Crack behaviors were dominated by the fissure angle and load type and medium-scale crack accounted for 74.83%–86.44%of total crack.Compared with monotonic loading,crack distribution of specimen under cyclic loading was more complicated.Meanwhile,a simple model was proposed to describe the damage evolution of sandstone under cyclic loading.Finally,SEM images revealed that the microstructures at the fracture were mainly composed of intergranular fracture,and percentage of transgranular fracture jumped under cyclic loading due to the rapid release of elastic energy caused by high loading rate.

Automatic Detection of Steel Ball's Surface Flaws Based on Image Processing

A new method to detect steel ball's surface flaws is presented based on computer techniques of image processing and pattern recognition. The steel ball's surface flaws is the primary factor causing bearing failure. The high efficient and precision detections for the surface flaws of steel ball can be conducted by the presented method, including spot, abrasion, burn, scratch and crack, etc. The design of main components of the detecting system is described in detail including automatic feeding mechanism, automatic spreading mechanism of steel ball's surface, optical system of microscope, image acquisition system, image processing system. The whole automatic system is controlled by an industrial control computer, which can carry out the recognition of flaws of steel ball's surface effectively.

Euler Characteristic Scheme of Globally Searching for Flaws in Surface Modeling

This paper presents a new scheme of flaw searching in surface modeling based on Euler Characteristic. This scheme can be applied to surface construction or reconstruction in computer. It is referred to as Euler Accompanying Test (EAT) algorithm in this paper. Two propositions in algebraic topology are presented, which are the foundation of the EAT algorithm. As the modeling is the first step for rendering in the animation and visualization, or computer-aided design (CAD) in related applications, the flaws can bring some serious problems in the final image or product, such as an artificial sense in animation rendering or a mistaken product in industry. To verify the EAT progressive procedure, a three-dimensional (3D) stamp model is constructed. The modeling process is accompanied by the EAT procedure. The EAT scheme is verified as the flaws in the stamp model are found and modified.

Flaws in the Field of Digital Security in the Workplace: Case of Companies in Burkina Faso

Digital in the daily life of companies undeniably leads them to use services and applications of all kinds. Companies in their permanent quest for the exchange of information devote themselves to the use of the Internet which nowadays constitutes an open door for the birth of several types of faults, some of which are unknown to certain digital professionals in the field. Corporate. The purpose of this research is to show the probable existence of digital security flaws in the daily activities carried out by companies in Burkina Faso. In companies in Burkina Faso, we seem to see a way of working that does not respect the standards and safety standards prescribed by ISO 27001. We seem to see a way of working based on the result of the gain and not on the securities measures and integrity of critical data, data confidentiality, management and prevention of possible security risks related to their activities. We seem to be witnessing in companies the immanent presence of faults which could be the work of the users of the system, of the infrastructure used which is outdated or badly configured, of software anomalies linked to programming errors, and to poor implementation of the security policy within the companies. This research is important because it exposes the handicaps that companies have in terms of digital security. The expected result is to bring out existing flaws that are not taken seriously by IT staff and propose possible solutions to overcome these security risks.

An Analysis of the Flaws in the Spanish Tragedy

The Spanish Tragedy, written by Thomas Kyd in the late 1580 s, was the grandfather of all revenge tragedies. It established a new genre named revenge tragedy in English theater. Its well-developed characters, timeless themes, dramatic intrigue and pioneering adoption of blank verse enabled it to be viewed as a classic of London theater. Yet it also has received criticisms over the past centuries. Based on Aristotle's opinion of a perfect tragedy in"Poetics", this paper aims to point out the flaws of the play from five perspectives: the fate of Hieronimo, the cause of it, Bel-imperia's sudden love for Horatio, subplot concerning Villuppo and Alexandro, the discovery and the diction.

Admitting Flaws

In the mid-1980’s researchers at Cleveland State University made a startling discovery. They conducted an experiment by creating two fictitious job candidates—David and John.Thecandidates had identical resumes and letters of reference.The only difference was that John’s letterincluded the sentence“Sometimes,John can be difficult to get along with.”They showed the re-

我国数字乡村建设水平评价指标体系研究进展与前瞻

该研究主要介绍了我国数字乡村建设水平评价研究与实践的基本情况,分析了不同研究主体构建该类评价指标体系的目标与特点,提出现有指标体系存在指标设置不齐全、指标内涵交叉重复、指标体系不合适用于中长期评价三大问题,建议加强相关的理论、方法和调查研究,借鉴并结合乡村振兴和农业农村现代化评价经验,构建逻辑更严密,条理更清晰,内容更丰富、完整,普适性更强,适用于数字乡村建设水平中长期评价的指标体系。

基于改进YOLOv5s 的白酒瓶盖瑕疵检测

目的瓶装白酒生产过程中,瓶盖表面瑕疵会影响产品外观质量。针对白酒瓶盖表面瑕疵检测效率低和目标检测效果差的问题,提出一种基于YOLOv5s的改进算法DTS-YOLO。方法首先,在主干网络中引入可变形卷积,以提高模型对极端长宽比瑕疵的检测精度。其次,引入Transformer编码块,使网络聚焦于提取图像的全局信息。最后,在颈部网络构建C3SE-Lite模块,将C3模块嵌入SE注意力模块的同时引入Ghost卷积,减少参数量的同时,增强对瓶盖瑕疵的检测能力。结果实验结果表明,本文所提方法相较于基础网络,参数量减少了10%,平均精度均值达95%,平均检测速度达30帧/s。结论本文方法有效实现了白酒瓶盖表面瑕疵快速、准确地检测,可广泛应用于瓶装白酒生产过程中瓶盖表面检测。

超大规格风电用连铸圆坯的氢含量控制

针对直径大于等于800 mm的超大规格风电用连铸圆坯因氢含量高出现探伤不合缺陷的问题,通过检测原辅料水分、利用Hydris定氢仪探究全工序钢水氢含量的变化规律。结果表明,铸坯氢含量的主要来源是原辅料水分、炉气气氛潮湿、耐火材料不完全分解。为降低铸坯氢含量,提出了工艺改进措施:转炉吹炼8 min后应不加或加入水分含量较低的原辅料;LF精炼工序投入较少的原辅料;入VD工序前小渣量控制,破空后低速喂线,控制喂线数量及种类在较小范围;小火烘烤连铸中间包60 min,定期清理中间包透气孔。工艺优化后,VD到站钢水w(H)≤3.6×10^(-6),VD离站钢水w(H)≤0.77×10^(-6),连铸中间包首炉钢水w(H)≤2.0×10^(-6),第2炉w(H)≤1.6×10^(-6),连浇炉次w(H)≤1.1×10^(-6),成功降低了超大规格风电用连铸圆坯的氢含量,保证了成品锻件的质量。

船舶维修机械臂水下探伤系统稳定性分析

为了满足船舶远海航行时对于水下船体探伤的作业需求,基于自主设计的水下机械臂系统,在其末端执行机构安装水下摄像头,以代替潜水员下水进行探伤作业,并对搭建的水下维修机械臂探伤系统的操控稳定性进行了分析验证。首先,基于拉格朗日函数建立了水下机械臂探伤系统的动力学方程,并利用Fluent软件仿真计算出在不同流速下机械臂探伤系统各关节处所受的水阻力大小;然后,将计算所得各关节水阻力作为载荷添加至动力学仿真分析中,利用Matlab软件对水下维修机械臂探伤系统进行了动力学仿真,得到各关节在空气中和水下不同环境中的力矩,求得水阻力对各关节力矩的影响因子;最后,在空气中和水下两种环境中对机械臂探伤系统进行运动控制试验,实际的力矩反馈和流体模型的建立验证了水下维修机械臂探伤系统良好的操控稳定性,为运用于船舶远航实际水下探伤作业提供了数据和实验支持。