scholarly journals An analysis of fracture toughness, at third mode fracture in concretes containing fly-ash additives

2013 ◽  
Vol 12 (3) ◽  
pp. 145-152
Author(s):  
Grzegorz Golewski
Keyword(s):  
Fracture Toughness ◽  
Fly Ash ◽  
Test System ◽  
Mode Fracture ◽  
The Third ◽  
Axial Torsion ◽  
Half Height ◽  
Torsional Test ◽  
Circumferential Notch ◽  
Made In

This paper presents the results of fracture toughness tests of concrete with fly ash (FA), specified at the third model fracture. Concrete composites with the additives of 0%, 20% and 30% siliceous FA were analysed. Fracture toughness tests were performed on axial torsion machine MTS 809 Axial/Torsional Test System, using the cylindrical specimens with dimensions of 150/300 mm, with a circumferential notch made in the half-height of cylinders. The studies examined effect of FA additive on the parameter KIIIc. The Analysis of the results revealed that a 20% FA additive causes increase in KIIIc, while a 30% FA additive causes decrease in fracture toughness.

A Study of Mode III Fracture Toughness in Young and Mature Concrete with Fly Ash Additive

2016 ◽  
Vol 254 ◽  
pp. 120-125 ◽  
Author(s):  
Grzegorz Ludwik Golewski ◽  
Tomasz Sadowski
Keyword(s):  
Fracture Toughness ◽  
Fly Ash ◽  
Fracture Mechanics ◽  
Test System ◽  
Special Device ◽  
Mode Iii ◽  
Concrete Mixtures ◽  
Young Concrete ◽  
Torsional Test ◽  
Class F Fly Ash

A description of processes of formation and propagation of cracks in material requires the knowledge of all fracture mechanics parameters, i.e.: KIc, KIIcand KIIIc. In this study a new testing method and estimation of the fracture toughness in Mode III (antiplane shear) of concretes containing: 0, 20 and 30% volume content of the class F fly ash (FA) was proposed. Fracture toughness tests were performed on axial torsion machine MTS 809 Axial/Torsional Test System. The studies examined effect of FA additive on the parameter KIIIc. In order to determine the fracture toughness KIIIca special device was made. Experimental investigation under third mode fracture was carried out both in young and mature concrete composites (after: 3, 7, 28, 90, 180 and 365 days). 20% addition of FA as well as a 30% addition of FA causes a reduction in fracture toughness of young concrete. After 28 days of couring a significant increase of the KIIIc was noticed in composites with a 20% additive of FA while concrete mixtures with a higher additive of FA still had lower analyzed fracture mechanics parameter.

scholarly journals Slice–push, formation of grooves and the scale effect in cutting

2016 ◽  
Vol 6 (3) ◽  
pp. 20160019 ◽  
Author(s):  
A. G. Atkins
Keyword(s):  
Fracture Toughness ◽  
Abrasive Wear ◽  
Characteristic Length ◽  
Depth Of Cut ◽  
Separation Processes ◽  
The Third ◽  
Hard Particles ◽  
Energy Scaling ◽  
Shear Yield ◽  
Made In

Three separate aspects of cutting are investigated which complement other papers on the mechanics of separation processes presented at this interdisciplinary Theo Murphy meeting. They apply in all types of cutting whether blades are sharp or blunt, and whether the material being cut is ‘hard, stiff and strong’ or ‘soft, compliant and weak’. The first topic discusses why it is easier to cut when there is motion along (parallel to) the blade as well motion across (perpendicular to) the cutting edge, and the analysis is applied to optimization of blade geometries to produce minimum cutting forces and hence minimum damage to cut surfaces. The second topic concerns cutting with more than one edge with particular application to the formation of grooves in surfaces by hard pointed tools. The mechanics are investigated and applied to the topic of abrasive wear by hard particles. Traditional analyses say that abrasive wear resistance increases monotonically with the hardness of the workpiece, but we show that the fracture toughness of the surface material is also important, and that behaviour is determined by the toughness-to-hardness ratio rather than hardness alone. Scaling forms the third subject. As cutting is a branch of elasto-plastic fracture mechanics, cube-square energy scaling applies in which the important length scale is ( ER / k 2 ), where E is Young's modulus, R is the fracture toughness and k is the shear yield strength. Whether, in cutting, material is removed as ductile ribbons, as semi-ductile discontinuous chips, or by brittle ‘knocking lumps out’ is shown to depend on the depth of cut relative to this characteristic length parameter. Scaling in biology is called allometry and its relationship with engineering scaling is discussed. Some speculative predictions are made in relation to the action of teeth on food.

scholarly journals Effect of fly ash addition on the fracture toughness of plain concrete at third model of fracture

2017 ◽  
Vol 23 (5) ◽  
pp. 613-620 ◽  
Author(s):  
Grzegorz Ludwik GOLEWSKI
Keyword(s):  
Fracture Toughness ◽  
Fly Ash ◽  
Plain Concrete ◽  
Test System ◽  
Initial Crack ◽  
Steel Plates ◽  
Special Device ◽  
Fracture Toughness Test ◽  
Mode Iii ◽  
Fracture Surfaces

A new testing method and estimation of the fracture toughness in Mode III (antiplane shear) of concretes contain­ing: 0, 20 and 30% volume content of the class F fly ash (FA) was proposed. Fracture toughness tests were performed on axial torsional machine MTS 809 Axial/Torsional Test System using special device. The Device for the fracture toughness test at the Mode III fracture consisted of the cylindrical specimen with the formed initial crack, steel plates, and screws with washers securing the specimen in the press holders. The specimens applied for experiments were cylinders with dimensions of 150/300 mm, having an initial circumferential notch made in the half-height of cylinders. The specimens were subjected to pure torsion. The studies examined effect of FA additive on the parameter KIIIc. 20% FA additive causes a small increase of the KIIIc in comparison to the concrete without the FA, while 30% FA additive causes a significant decrease in fracture tough­ness. The fracture surfaces of the specimens analysed macroscopically were planar. Scanning microscopic observations (SEM) indicate that in the fracture surfaces multilevel cracks occur in the shape of semicircles.

KERCH STRAIT IN KAMYSH-BURUN SPIT AREA: HIGH-RESOLUTION SEISMOACOUSTIC APPROACH

2018 ◽  
Author(s):  
В. Зинько ◽  
V. Zin'ko ◽  
А. Зверев ◽  
A. Zverev ◽  
М. Федин ◽  
...  
Keyword(s):  
High Resolution ◽  
Fracture Zone ◽  
Sedimentary Cover ◽  
Sedimentary Rocks ◽  
The West ◽  
Early Generation ◽  
The Third ◽  
Azov Sea ◽  
Kerch Strait ◽  
Made In

The seismoacoustical investigations was made in the western part of the Kerch strait (Azov sea) near Kamysh-Burun spit. The fracture zone with dislocated sedimentary rocks layers and buried erosional surface was revealed to the west of spit. Three seismofacial units was revealed to the east of spit. The first unit was modern sedimentary cover. The second ones has cross-bedding features and was, probably, the part of early generation of Kamysh-Burun spit, which lied to the east of its modern position. The lower border of the second unit is the erosional surface supposed of phanagorian age. The third unit is screened by acoustic shedows in large part.

Introduction

2018 ◽  
Author(s):  
Nora Goldschmidt ◽  
Barbara Graziosi
Keyword(s):  
Material Culture ◽  
The Body ◽  
Specific Site ◽  
Entire Volume ◽  
The Third ◽  
Religious Significance ◽  
Classical Poetry ◽  
Life Of The Mind ◽  
The Mind ◽  
Made In

The Introduction sheds light on the reception of classical poetry by focusing on the materiality of the poets’ bodies and their tombs. It outlines four sets of issues, or commonplaces, that govern the organization of the entire volume. The first concerns the opposition between literature and material culture, the life of the mind vs the apprehensions of the body—which fails to acknowledge that poetry emerges from and is attended to by the mortal body. The second concerns the religious significance of the tomb and its location in a mythical landscape which is shaped, in part, by poetry. The third investigates the literary graveyard as a place where poets’ bodies and poetic corpora are collected. Finally, the alleged ‘tomb of Virgil’ provides a specific site where the major claims made in this volume can be most easily be tested.

The Hydraulic Operation of Lathes for the Production of Shells

1944 ◽  
Vol 151 (1) ◽  
pp. 70-86
Author(s):  
W. Littlejohn Philip
Keyword(s):  
Machine Tools ◽  
Hydraulic Power ◽  
The Third ◽  
Hydraulic Machine ◽  
Hydraulic Machinery ◽  
Simple Machines ◽  
High Level ◽  
Shell Production ◽  
Hydraulic Operation ◽  
Made In

The paper is limited to the application of hydraulic power to lathes designed for shell making although, in the author's opinion, there is an immense field for the application of the same principles in other directions. Self-contained hydraulic machine tools have been dealt with by Mr. H. C. Town,† but in the system to be described all the machines are operated from a central hydraulic plant. Three complete installations on this principle have been established by the author, and the present paper contains an account of this work from the first experiments in 1915 until about four years ago. The first plant was constructed in 1915 for the production of 3·29-inch shells, known as “18-pounders”, from the solid bar. The output was 2,000 shells per week of 135 hours, with girl operators working on three shifts. The second plant was put down in 1916–17 for an output of 500 9·2-inch howitzer shells per week of 135 hours, also with girls working on three shifts. The third plant is of recent design. It was started in 1938 for the production of 3·45-inch shells, known as “25-pounders”; and was laid out for an output of 1,000 shells per week of 47 hours. This plant included four types of hydraulic lathes which the author was engaged to design for the War Office. Soon after the commencement of the last war in 1914 it became evident that shell production would have to be greatly increased, and engineering firms were pressed to take up shell manufacture. The author, on behalf of his firm, undertook to help in the movement, and he at once set about the construction of some simple machines for the job. These conformed on general lines to the practice of the period as regards design and operation. He soon realized, however, that drastic changes would have to be made if production was to reach the high level that circumstances demanded. Although quite familiar with hydraulic machinery of various types and of many applications in presses and certain types of heavy tools, he was not aware of any instance in which hydraulic power had been applied to the movements of a lathe. It appeared to him, nevertheless, that it would be possible to construct a very useful machine on these lines, and he accordingly started immediately to carry out experiments and to prepare designs. It was considered essential that machines for the duty which the author had in mind should be much heavier and more rigid than the ordinary machines of the time, so that they should be free from vibration and “chatter” or spring with the heaviest possible cutting. The standard of rigidity aimed at was that which would permit a half-crown coin to remain balanced on edge on the moving saddle or turret while the tools were making the heaviest cuts. This object was achieved, and the demonstration was frequently made in the presence of those who came to see the lathes at work.

(Re)Made in America: Survivorship after the Shoah

2021 ◽  
Vol 24 (1) ◽  
pp. 28-44
Author(s):  
Alyson Cole
Keyword(s):  
Public Discourse ◽  
The United States ◽  
Moral Authority ◽  
Crimes Against Humanity ◽  
Rape Victims ◽  
The Third ◽  
United States Today ◽  
Negative Attributes ◽  
Made In ◽  
The Welfare State

Until the l970s, ‘survivor’ referred predominantly to individuals who outlived others in the aftermath of disaster, or stood to inherit the remains of an estate; it was not imbued with evaluative connotations. In the United States today, however, survivorship abounds with positive meanings. This transvaluation rests on three intersecting trajectories that together transformed survivorship from denoting that one sustained or was spared a hardship to signifying a superior social status. The first trajectory follows the aftermath of the Shoah, when survivors acquired moral authority as victims of and public witnesses to a new violation, ‘crimes against humanity’. The second tracks the stigmatization of the term ‘victim’ in American public discourse. A consequence of struggles over the welfare state and other progressive policies, victimhood is now associated less with specific harms or injuries, and more with the supposed negative attributes of the victim herself. The third traces how survivorship became integral to the recuperative strategies of new therapeutic disciplines addressing the traumatized – from war veterans and rape victims to cancer patients. These three processes coalesced to create and legitimize a hierarchical opposition between ‘victims’ and ‘survivors’, transforming these terms into political categories and emblems of personal and group identity. In this essay, I argue that the victim/survivor binary constitutes one juncture where neoliberalism converges with Trump-era populism.

COMBATING TRANSNATIONAL CRIME IN AFRICA: PROBLEMS AND PERSPECTIVES

2006 ◽  
Vol 50 (2) ◽  
pp. 145-160 ◽  
Author(s):  
JOHN HATCHARD
Keyword(s):  
Transnational Crime ◽  
Environmental Crime ◽  
The Political ◽  
Political Will ◽  
The Third ◽  
Major Threat ◽  
Proceeds Of Crime ◽  
Made In

Transnational crime is a major problem for African states with corruption, trafficking of persons, drugs trafficking, environmental crime and the like posing a major threat to development and stability. This article examines three challenges that states must tackle in order to combat transnational crime effectively. The first is how to deal with criminals who operate outside the jurisdiction. The second concerns the investigation of crimes with a transnational element. The third challenge involves tracing and then recovering the proceeds of crime that have been moved out of the country where the crime occurred. Here the need for Western states to cooperate with those in Africa is highlighted. Drawing on examples from Lesotho and Nigeria in particular, it is argued that some progress is being made in meeting these challenges. However, the article notes that developing the political will to tackle transnational crime is fundamental to any lasting improvement.

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