Energy-Derived, Damage-Based Failure Criterion for Fatigue Testing

Author(s):  
Khalid A. Ghuzlan ◽  
Samuel H. Carpenter

Determination of the failure limit in a repeated-load fatigue test in the laboratory has relied entirely on the arbitrary selection of a fixed criterion. The constant strain and constant stress modes of fatigue loading have been described by a consistent definition of failure in flexural fatigue testing because of the distinctly different application of energy during the loading history. The most widely accepted definition is a decrease in initial stiffness by 50 percent. Procedures examining energy input and dissipated energy have required different schemes for each mode in an attempt to describe similar states of damage in the mixture. A proposed method is presented for examining dissipated energy to select a consistent level of material behavior that is indicative of the damage accumulation in the mixture. This procedure shows the similarity between the constant stress and constant strain modes of testing and is shown to provide the potential for unifying the now phenomenological description of fatigue with a more rational energy-based description.

2021 ◽  
Vol 10 (2) ◽  
pp. 55-66
Author(s):  
Amélie Vallet-Courbin ◽  
Soizic Lacampagne ◽  
Rose Marie Canal-Llauberes ◽  
Sigolène Mattalana Malzieu ◽  
Tihomir Kanev ◽  
...  

A new Test of Filterability has been developed. Measurements carried out with different types of wines indicate that the new filterability index is a useful tool for understanding and predicting the propensity to fouling of treated or untreated wines, e.g. with or without enzyme addition. The measurement method used in the Test of Filterability, requires only one type of membrane for all types of wine, and uses the same equipment as the traditional Fouling Index. Numerous trials have demonstrated that the filtration of wines is governed by standard blocking law. The definition of the new Test of Filterability, based on this filtration law, is proposed. The choice of membrane and the selection of the optimal pore size were based on the results of the experiments. Current methods used for the determination of fouling properties in wine filtration have been developed for the membrane filtration of small quantities of suspended matter. Enzyme treatment is a process often used in wine clarification. The new Test of Filterability indicates the best conditions for the filtration of all types of wines. The test is easy to implement and has been validated with various wines. This new Test of Filterability is an important tool for winemakers as it constitutes a simplified test of a wine's filterability. The new test may also be used to determine the filtration process that is best adapted to each wine while reducing the number of operations. The same approach may be adopted for the filtration of other liquids. 


1982 ◽  
Vol 104 (1) ◽  
pp. 148-158 ◽  
Author(s):  
R. G. Mitchiner ◽  
H. H. Mabie

This paper presents a simple and direct approach to the problem of the definition of the root profile for standard and nonstandard external spur gear teeth. Equations are developed for the location of the tooth center-line intercept at the constant-stress parabola. Also, the expression for the location of the point of tangency of the parabola with the root trochoid is given as well as the derivative of this expression. The AGMA Standards present charts of geometry factors, but the method by which these factors were determined is graphical and in some instances is not sufficiently accurate nor convenient to use. Although other investigators have considered this problem, their methods are either graphical or very complicated analytically. This treatment of the problem has been developed because it is not available in the open literature. Tables and charts are given for both Y and J factors for many profile variations.


2020 ◽  
Author(s):  
Seda Çellek

Abstract. The phase after the determination of the landslide area in landslide susceptibility studies is the selection of methods and parameters to be used. Approximately 1500 randomly selected publications show that it is necessary to select a parameter based on the area. Research has shown that the parameter of slope is greatly preferred. There is nearly consensus of opinion among researchers regarding the use of the parameter. The research included the definition of slope made by different researchers, the advantages and disadvantages of the use of the parameter, different classifications that are used, the formation intervals of landslides, their use together with other parameters, and its effect on the formation of landslides. Classifications were studied based on the slope values at which landslides. Generally, automatic slope classifications are used in the preparation of landslide maps. There isn’t standard in parameter maps. Therefore, there isn’t class range that is referenced when preparing slope maps. In this study, preferred class ranges and slope values where landslides occur were determined in the literature. 40 landslides area has been selected in Turkey. These were evaluated in the slope classes determined according to the literature. The results compared with the literature were found to be compatible.


Tribologia ◽  
2018 ◽  
Vol 280 (4) ◽  
pp. 81-88
Author(s):  
Andrzej RYNIEWICZ ◽  
Anna M. RYNIEWICZ ◽  
Tomasz MACHNIEWICZ ◽  
Łukasz BOJKO ◽  
Wojciech RYNIEWICZ

The aim of the study was to conduct strength analysis of a knee joint in order to experimentally determine the destructive fatigue loading under the conditions of cyclic compression. Animal joints were used as the study material. They were periodically subjected to variable axial loading. The degree of joint deformity and damage to articular surfaces and menisci were globally determined after isolation of the joint structures. The application of the variant of axial loading without slip and rolling results in the rupture of the medial meniscus, which is an important biotribological structure. Fatigue testing of the joints allowed for the determination of the parameters of biomechanical extortions, which lead to the loss of normal lubrication conditions and the degradation of the meniscus and cartilage structures on the femoral condyles.


2003 ◽  
Vol 1832 (1) ◽  
pp. 131-138 ◽  
Author(s):  
Samuel H. Carpenter ◽  
Khalid A. Ghuzlan ◽  
Shihui Shen

The existence of a fatigue endurance limit has been postulated for a considerable time. With the increasing emphasis on extended-life hot-mix asphalt pavement, or perpetual pavement, verification of the existence of this endurance limit, a strain below which none or very little fatigue damage develops, has become a substantial consideration in the design of these new multilayered full-depth pavements. Fatigue data are presented that were collected on a surface mix and a binder mixture tested for an extended period from 5 million to 48 million load repetitions at strain levels down to 70 microstrain. The fatigue results are analyzed in the traditional manner and using the dissipated energy ratio. This analysis shows that there is a difference in the data at normal strain levels recommended for fatigue testing and at the low strain levels. This difference cannot substantiate an endurance limit using traditional analysis procedures, but the dissipated energy approach clearly shows a distinct change in material behavior at low flexural strain levels, which supports the fact that at low strain levels the damage accumulated from each load cycle is disproportionately less than what is predicted from extrapolations of fatigue testing at normal strain levels. This reduced damage may be attributed to the healing process. The conclusion of this study is that laboratory testing can verify the existence of a fatigue endurance limit in the range of 90 to 70 microstrain below which the fatigue life of the mixture is significantly extended relative to normal design considerations.


2019 ◽  
pp. 58-68
Author(s):  
I. Pyrih

The article deals with problematic issues related to the norms of criminal procedure legislation, considering the involvement of an expert as an investigative action. Among criminal scientists and proceduralists there is no consensus on the procedural definition of forensic examination. Most of them include forensics to investigative actions. By the definition of a forensic examination, it is clear that an integral feature of a procedural action is to conduct it exclusively by officials of state bodies authorized by law to conduct criminal proceedings. These include: employees of the operational units, an investigator, a prosecutor, a judge. The subject of the examination is an expert – a person not authorized by law to conduct investigative actions. That is why, in our opinion, it is impossible to refer an examination to investigative actions. Proponents of referring a forensic examination to investigative actions most often mean it as «the appointment and conduct of a forensic examination». It is argued that actions regarding the appointment and conduct of the examination are different in nature and subjects of conduct. If we consider the stage of appointment of the examination, and for the current Criminal Procedure Code of Ukraine – the involvement of an expert, then its subject is the investigator. The subject of the examination is an expert. Considering the characteristic features of the investigative action, it can be concluded that the stage of appointment of the examination or the involvement of an expert, which scientists consider as preparatory to the examination, has all the signs inherent in an independent investigative action. It is governed by the rules of procedural law, carried out in the framework of criminal proceedings, authorized by the person. When an expert is involved, the investigator conducts certain actions, the result of which is reflected in the ruling of the investigating judge. The purpose of the examination is to obtain, research and verify evidence. Considering the involvement of an expert as a separate investigative action, we define its content, divided into generally accepted stages: preparatory, working and final. To the preparatory stage, we include such actions: the decision to conduct an examination; selection of an expert institution or a private expert; determination of the type of examination and subject of study; determining the order of appointment of examinations in relation to the same objects; timing of appointment examination. The following should be attributed to the working stage: selection of objects for examination; receipt of the decision of the investigating judge for the examination. The final stage consists of the following stages: determining the circle of persons who may be present during the examination; referrals and necessary materials to the expert institution. Key words: investigative (search) action, forensic examination, appointment of expertise, involvement of an expert.


Author(s):  
Sung R. Choi ◽  
John P. Gyekenyesi

The determination of ‘ultra’-fast fracture strengths of five silicon nitride ceramics at elevated temperatures has been made by using constant stress-rate (“dynamic fatigue”) testing with a series of ‘ultra’-fast test rates. The test materials included four monolithic and one SiC whisker-reinforced composite silicon nitrides. Of the five test materials, four silicon nitrides exhibited the elevated-temperature strengths that approached their respective room-temperature strengths at an ‘ultra’-fast test rate of 33 × 104 MPa/s. This implies that slow crack growth responsible for elevated-temperature failure can be eliminated or minimized by using the ‘ultra’-fast test rate. These ongoing experimental results have shed light on laying a theoretical and practical foundation on the concept and definition of elevated-temperature “inert” strength behavior of advanced ceramics.


1999 ◽  
Vol 121 (1) ◽  
pp. 18-24 ◽  
Author(s):  
S. R. Choi ◽  
J. P. Gyekenyesi

The determination of “ultra” fast fracture strengths of five silicon nitride ceramics at elevated temperatures has been made by using constant stress-rate (“dynamic fatigue”) testing with a series of “ultra” fast test rates. The test materials included four monolithic and one SiC whisker-reinforced composite silicon nitrides. Of the five test materials, four silicon nitrides exhibited the elevated-temperature strengths that approached their respective room-temperature strengths at an “ultra” fast test rate of 3.3 × 104 MPa/s. This implies that slow crack growth responsible for elevated-temperature failure can be eliminated or minimized by using the “ultra” fast test rate. These ongoing experimental results have shed light on laying a theoretical and practical foundation on the concept and definition of elevated-temperature “inert” strength behavior of advanced ceramics.


Author(s):  
Mirosław J. Lipiński ◽  
Małgorzata K. Wdowska

Abstract The paper concerns laboratory methods for determination of soil stiffness. Major criterion for selection of analysed equipment is range of strain in which stiffness can be reliably determined. Substantially, various configurations of triaxial apparatus are referred to i.e. with standard cell and with the modified one. Additional system for internal measurement of strain is described and rational (based on test results) for use of it is presented. As to shear wave velocity measurement as a mean to obtain initial stiffness, requirements for proper measurement and interpretation was given. Finally, an approach to determine Poisson’s ratio on the basis of combined results of cyclic triaxial and resonant column tests was presented.


2020 ◽  
pp. 096100062098083
Author(s):  
Małgorzata Fedorowicz-Kruszewska

Since the beginning of the 1990s, libraries have been undertaking a number of activities aimed at minimizing their negative impact on the environment. Those that show such activity are called ‘green libraries’. This term appears in scientific, professional and popular science literature, but its definitions are vague and ambiguous. A preliminary analysis of the content of publications dealing with the issue of green libraries shows a modest representation of theoretical and synthetic texts. This article aims to fill this gap. It has three goals: (1) clarification of the term ‘green library’, (2) conceptualization of the term ‘green librarianship’ and (3) determination of ‘green librarianship’ areas. To achieve them, first, an analysis of the environmental discourse on green libraries and green librarianship in library science literature was performed to abstract green library indicators. Then, these indicators were verified. The selection of the sample for research was deliberate. The materials were collected using the Library, Information Science & Technology Abstract (LISTA) bibliographic and abstract database. As a result, the number of green library indicators has been extended, which has made it possible to clarify the definition of this term. The definition of ‘green librarianship’ was then formulated, and the areas of green librarianship were indicated. Conceptualization of the terms ‘green library’ and ‘green librarianship’ constitutes the value of this article. The practical implication of the study is the expansion of the number of green library indicators. These indicators can be used to develop a codebook for the content analysis of documents in the discussed area. This article may also contribute to the development of methods for the evaluation of activities and development of green libraries.


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