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.

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.

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.

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.

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.

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.

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.

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-

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.

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.

The methodology flaws in Hinman's acupuncture clinical trial, Part Ⅰ: Design and results interpretation

In the October 2014 edition of JAMA, Dr. Hinman and her colleagues published an acupuncture clinical trial entitled Acupuncture for Chronic Knee Pain： A Randomized Clinical Trial＂ and concluded that in patients older than 50 years with moderate or severe chronic knee pain, neither laser nor needle acupuncture conferred benefit over sham for pain or function. Our findings do not support acupuncture for these patients[1].

The methodology flaws in Hinman's acupuncture clinical trial, Part Ⅱ: Zelen design and effectiveness dilutions

In the October 2014 publication of JAMA, Dr. Hinman and colleagues published the study “Acupuncture for Chronic Knee Pain： A Randomized Clinical Trial,” which concluded that in patients older than 50 years with moderate or severe chronic knee pain, neither laser nor needle acupuncture conferred benefit over sham for pain or function. Our findings do not support acupuncture for these patients.

Effect of loading direction on interaction of two pre-existing open and closed flaws in a rock-like brittle material

Investigations of the growth,interaction,and coalescence of cracks are important because they help to provide tools for the more realistic modeling of rock masses containing low persistence discontinuities and better estimations of the strength and stiffness of a rock material.Understanding the coalescence mechanism is useful for justifying the mechanism of continental crustal deformation,evaluating the structural failure of slopes with rock bridges,and analyzing the stability of tunnels when a mode I or mix mode failure mechanism is involved.The evaluation of crack growth can provide valuable information about the mechanism for the formation of new geological structures,and the formation,evolution,and growth of faults.This paper reports the results of diametrical compression tests on rocklike disk-shaped specimens.Each specimen contained two pre-existing open or closed flaws.The growth,interaction,and coalescence of the pre-existing flaws were investigated both physically and numerically.A hybrid bonded particle-finite element system was used in the numerical simulation.The results of the physical and numerical studies were in good agreement.In particular,the induced crack patterns showed close agreement in the physical and numerical tests.Digital microscope image processing was used in the physical tests to study the dislocations along the initial flaws.It was shown that wing crack formation was responsible for the failure of the specimen when flaws were inclined with respect to the loading direction.The crack growth and linkage were shown to be affected by the friction between faces of the flaws.In addition,the slip distributions at the flaws surfaces were illustrated and examined to understand the crack propagation mechanism.The effects of the flaws on the disk failure loads were assessed both numerically and experimentally as well.

The methodology flaws in Hinman's acupuncture clinical trial, Part Ⅲ: Sample size calculation

In the October 2014 publication of JAMA,Dr.Hinman and colleagues published the study＂Acupuncture for Chronic Knee Pain：A Randomized Clinical Trial,＂in which the authors concluded that＂in patients older than50 years with moderate or severe chronic knee pain,neither laser nor needle acupuncture conferred benefi t over sham for pain or function.Our fi ndings do not support acupuncture[1]

Experimental investigations on the cracking and mechanical responses of PMMA samples with two 3D embedded elliptic flaws under uniaxial compression

In this paper,the cracking and mechanical responses are studied for the Polymethylmethacrylate(PMMA)sample with two three-dimensional embedded coplanar elliptic flaws subjected to uniaxial compression.The experimental results indicate that both the peak stress and crack initiation stress first decrease and then increase with increasing flaw angle,and they increase linearly with increasing flaw spacing.Moreover,five crack modes occur in these tested samples,including the coplanar secondary cracks,wing cracks,petal cracks,anti-wing cracks,and vertical giant cracks.The growth length of wing cracks is approximately equal to the length of the long axis of preexisting flaw.However,the maximum width is roughly equal to half the length of the long axis of pre-existing elliptic flaw.The final failure modes include the splitting failure induced by wing cracks and vertical giant cracks,and the mixed tensile-shear failure induced by coplanar secondary cracks and wing cracks.

Fracture behavior of sandstone with partial filling flaw under mixed-mode loading: Three-point bending tests and discrete element method

The fracture behavior of natural fracture in the geological reservoir subjected to filling property,affects the crack initiation and propagation under stress perturbation.Partial filling flaws were intermediate between open fractures and filled fractures,the fracture response may be worth exploring.In this work,the effect of the filling property of sandstone with partial filling flaws on the fracture behavior was systematically investigated based on three-point bending tests and the numerical approach of discrete element method(DEM).In the laboratory,semi-circular three-point bending tests were carried out with partial filling flaws of various filling strengths.Based on this,numerical simulations were used to further investigate the effect of the filling ratio and the inclination of the partial filling flaw on the mechanical and fracture responses,and the effect of the partial filling flaw under mixed-mode loading on the fracture mechanism was elucidated coupled with acoustic emission(AE)characteristics.The obtained results showed that the increase in filling strength and filling ratio of partial filling flaw led to an increase in peak strength,with a decreasing trend in peak strength with the inclination of partial filling flaw.In terms of crack propagation pattern,the increasing filling strength of the partial filling flaw induced the transformation of the fracture mechanism toward deflection,with a tortuosity path,while the filling ratio and inclination of partial filling flaw led to fracture mechanism change from deflection to penetration and attraction,accompanied with a larger AE event source in filler.Accordingly,the b-value based on the Gutenberg-Richter equation fluctuated between 5 and 4 at low filling ratio and inclination and remained around 5 at high filling ratio and inclination of partial filling flaw.Related results may provide an application prospective for reservoir stimulation using the natural fracture system.

Fixing Flaws in the Law

China’s top legislature has adopted a draft amendment to the Law on Lawyers that will make it easier for lawyers to meet criminal suspects and obtain evidenceA change to China’s 11-year-old Law on Lawyers is set to empow- er the country’s legal profession. The amendment to the law,which will come into effect on June 1 next year,will allow individuals to open a law firm,improve access to clients and enable lawyers to build a case more easily. Lawyers in China have traditionally lacked power and this has hampered devel- opment of the industry.The amendment could change this and lead to rapid growth in the profession.

Damage evolution and crack propagation in rocks with dual elliptic flaws in compression

To give an insight into the understanding of damage evolution and crack propagation in rocks,a series of uniaxial and biaxial compression numerical tests are carried out.The investigations show that damage evolution occurs firstly in the weak rock,the area around the flaw and the area between the flaw and the neighboring rock layer.Cracks mostly generate as tensile cracks under uniaxial compression and shear cracks under biaxial compression.Crack patterns are classified and divided.The relationship between the accumulated lateral displacement and the short radius（b）is fitted,and the equation of crack path is also established.