Elimination of loading reverberation in the split hopkinson torsional bar

The loading reverberation is a multiple wave effect on the specimen in the split Hopkinson torsional bar (SHTB). Its existence intensively destroys the microstructure pattern in the tested material and therefore, interferes with the study correlating the deformed microstructure to the macroscopic stress-strain response. This paper discusses the problem of the loading reverberation and its effects on the post-mortem observations in the SHTB experiment. The cause of the loading reverberation is illustrated by a stress wave analysis. The modification of the standard SHTB is introduced, which involves attaching two unloading bars at the two ends of the original main bar system and adopting a new loading head and a couple of specially designed clutches. The clutches are placed between the main bar system and the unloading bars in order to lead the secondary loading wave out of the main bar system and to cut off the connection in a timely manner. The loading head of the standard torsional bar was redesigned by using a tube-type loading device associated with a ratchet system to ensure the exclusion of the reflected wave. Thus, the secondary loading waves were wholly trapped in the two unloading bars. The wave recording results and the contrasting experiments for examining the post-mortem microstructure during shear banding both before and after the modification highly support the effectiveness of the modified version. The modified SHTB realizes a single wave pulse loading process and will become a useful tool for investigating the relation between the deformed microstructure and the macroscopic stress-strain response. It will play an important role especially in the study of the evolution of the microstructure during the shear banding process. (C) 1995 American Institute of Physics.

Experimental-study on the criteria and mechanism of spallation in an aluminum-alloy

In this paper, a damage function defined by the residual strength of spalled specimens of an aluminium alloy is given to characterize the spallation of the material. Based on this function a simple method for continuously describing the spallation may be developed. Stress wave profiles showing the signal of spallation were successfully obtained with carbon gauges. Microscopic observations of the spalled aluminium alloy specimens reveal that the nucleation of spallation initiates from cracking of the second phase particles. Spallation is a process of crack nucleation, growth and coalescence to final, complete disintegration.

Microstructure of shear localization in low-carbon ferrite pearlite steel

A study has been made of the microstructure of the thermally assisted band in a low carbon ferrite-pearlite steel, resulting from high speed torsional testing with an average strain rate of about 1500 s���1. Metallographic examination showed that there are several fine shear bands distributed over a deformed region (the gauge length of the specimen). The width of these bands is estimated to be of the order of magnitude of 50 ��m, and the spacing between them is roughly about 100 ��m. Detailed scanning electron microscopy studies indicate that damage of the microstructure within the band is very apparent, as evidenced by microcrack initiation and coalescence along the shear deformation band. However, there is no evidence that the material in the band had become microcrystalline or non-crystalline.

Statistical modeling of damage evolution in spallation

<span style="font-family: Verdana, sans-serif; line-height: 15px; text-align: justify">In order to understand the mechanism of the incipient spallation in rolled metals, a one dimensional statistical mode1 on evolution of microcracks in spallation was proposed. The crack length appears to be the fundamental variable in the statistical description. Two dynamic processes, crack nucleation and growth, were involved in the model of damage evolution. A simplified case was examined and preliminary correlation to experimental observations of spallation was made.</span>

Practicumaren eragina gizarte langintzako heziketan: Gasteizko Eskolaren kasua 1964-2009

353 p. : tab.

Soundings: the Newsletter of the Monterey Bay Chapter of the American Cetacean Society. 1993

(PDF contains 127 pages.)

La civilizaci��n vasca medieval: vida(s), cotidiana(s), mentalidad(es) y cultura(s)

[ES]A lo largo de las p��ginas de este trabajo se pasa revista a diversas cuestiones que permiten realizar una aproximaci��n a las diversas formas de vida cotidiana y mentalidad del Pa��s Vasco y Navarra durante los siglos bajomedievales. Esas cuestiones aluden al primum vivere, al ciclo vital, al control de la vida privada de los individuos y p��blica de las comunidades por parte de las autoridades, las fiestas, las supersticiones y distintos aspectos relativos a la cultura, como literatura, historiograf��a y arte.

Influence of the northeastern Atlantic oceano-meteorological variability on the northern hake ("merluccius merluccius"). Analysis of the 1978-2006 period

316 p. : il., graf., map.

La actividad siderometal��rgica guipuzcoana durante el siglo XVII: transformaciones y productividad

[ES]Este art��culo pretende analizar la situaci��n de la actividad siderometal��rgica guipuzcoana durante el siglo XVII y testar la verdadera repercusi��n de la crisis del siglo XVII en dicho sector. Para ello se ha utilizado un amplio elenco documental procedente tanto de archivos locales como regionales y nacionales, que responde a una amplia variedad tipol��gica.

Labores forestales en Gipuzkoa durante los siglos XVI-XVIII

N��mero monogr��fico publicado bajo el t��tulo:" Mendia, gizartea eta kultura. Monta��a, sociedad y cultura. Montagne, societ�� et culture".

Planifificaci��n de un proyecto de obra civil

Duraci��n (en horas): M��s de 50 horas. Destinatario: Estudiante

Administrazio zuzenbidea eta ekonomian esku hartzeko teknikak

Formazio ekonomikoa edo enpresa kudeaketan formazioa dutenei zuzendutako materiala da; edozelan ere, Administrazioaren jarduteko moduak ezagutu nahi duen orori baliagarri gerta dakioke. Liburu honetan atal hauek agertzen dira : Administrazio zuzenbidea eta Administrazio Zuzenbide iturrien teoria. Administrazio antolakuntzaren oinarriak. Administrazio-egintzari buruzko teoria, administrazio-prozedura, administrazio-egintzen berrikuspena eta errekurtsoak. Administrazioak ekonomian esku hartzeko baliatzen dituen teknikak

Primera y segunda parte de Guzman de Alfarache por Mateo Aleman, criado del Rey Nuestro Senor, natural, y vezino de Sevilha : dedicada ao muy noble cavallero, Don Florencio Alonso Carrafa, Calderon, Trexo, Paniagua : con licencia

Gvzman de Alfarache �� um dos mais extensos e Importantes romances picarescos de que se tem noticia. Foi publicado, inicialmente, em duas partes: a primeira, em Madri, em 1599, intitulada ���Primera parte de la vida dei P. ��caro Gvzman de Alfarache���, a segunda, em Barcelona, em 1605, com o titulo ���Segvnda parte de la vida de Gvzman de Alfarache, atalaya de la vida humana, por Mateo Aleman, su verdadero autor���. Consta que, em 1602, por ter sido publicada uma segunda parte ap��crifa escrita pelo advogado valenciano Juan Jos�� Marti, Alem��n acrescentou ao t��tulo a informa����o ���su verdadeiro autor���. O romance �� a autobiografia de um velhaco que depois de aventuras de todo g��nero, conta com detalhes, a sua vida em tom c��tico e pessimista, com o estoicismo espanhol e caracter��sticas t��picas do Barroco. Em seis anos o romance teve vinte e tr��s edi����es e foi traduzido para o franc��s, o ingl��s e o italiano. Alem��n utilizou pela primeira vez o termo p��caro para simbolizar a humanidade propens��o crime