Modelling of multiple impacts for the prediction of distortions and residual stresses induced by ultrasonic shot peening (USP)

During a manufacturing process, the ultrasonic shot peening (USP) technique can be used as the final surface treatment. The aim of this operation is to introduce surface compressive residual stresses in order to prevent crack propagation advancement. Although the numerical simulation method is able to predict the level of residual stresses in a peened part, the 3D modelling of the real USP process, in which many successive and shifted impacts take place, is very delicate to perform and costly in terms of computing time and memory space required. In this paper, a two step method based at first on the calculation of the averaged plastic strain tensor in a half-space by using a semi-analytical method and in a second time on the transfer of this plastic strain field to a finite element model is proposed in order to simulate the effects of the USP process in thin structures. The accuracy and advantages of the semi-analytical method are validated by a benchmark with several finite element codes. Experiments, similar to the Almen test, are performed on thin plates of Inconel 600. Numerical results in terms of distortions and residual stresses are compared with the experimental data

Recent Studies in Andean Prehistory and Protohistory: Papers from the Second Annual Northeast Conference on Andean Archaeology and Ethnohistory

The contributions in this volume represent nine of the twenty-three papers presented at the Second Annual Northeast Conference on Andean Archaeology and Ethnohistory (NCAAE) held at the American Museum of Natural History on November 19-20, 1983. Papers include The Preceramic and Formative Period Occupations in the Cordillera Negra: Preliminary Report by Michael A. Malpass, The Early Horizon--Early Intermediate Period Transition: A View from the Nepena and Viru Valleys by Richard E. Daggett, Paracas in Chincha and Pisco: A Reappraisal of the Ocucaje Sequence by Dwight T. Wallace, Impressions in Metal: Reconstructing Burial Context at Loma Negra, Peru by Anne-Louise Schaeffer, The Moche Moon by Elizabeth P. Benson, Archaeological Investigation in the Andean Piedmont and High Llanos of Western Venezuela: A Preliminary Report by Charles S. Spencer and Elsa M. Redmond, Pachacamac--An Andean Oracle Under Inca Rule by Thomas C. Patterson, The Spanish League and Inca Sites: A Reassessment of the Itinerary of Juan de Matienzo through N.W. Argentina by Gordon C. Pollard, and Written Sources on Andean Cosmogony by George Kubler.https://digitalcommons.library.umaine.edu/andean_past_special/1001/thumbnail.jp

Conceptual Art

Providing a re-examination of what Osborne identifies as a major turning point in contemporary art, this monograph takes a chronological and stylistic look at conceptual art from its “pre-history” (1950-1960) to contemporary practices that use conceptual strategies. Osborne surveys the development of the movement in relation to the social, cultural and political contexts within which it evolved. With extended captions, key works are compiled according to ten themes that also serve to present a collection of critical texts, artists’ statements, interviews and commentaries. Includes biographical notes on artists (6 p.) and authors (2 p.), a bibliography (2 p.) and an onomastic index (4 p.) Circa 150 bibl. ref

Neural Correlates of Visual Motion Prediction

Predicting the trajectories of moving objects in our surroundings is important for many life scenarios, such as driving, walking, reaching, hunting and combat. We determined human subjects’ performance and task-related brain activity in a motion trajectory prediction task. The task required spatial and motion working memory as well as the ability to extrapolate motion information in time to predict future object locations. We showed that the neural circuits associated with motion prediction included frontal, parietal and insular cortex, as well as the thalamus and the visual cortex. Interestingly, deactivation of many of these regions seemed to be more closely related to task performance. The differential activity during motion prediction vs. direct observation was also correlated with task performance. The neural networks involved in our visual motion prediction task are significantly different from those that underlie visual motion memory and imagery. Our results set the stage for the examination of the effects of deficiencies in these networks, such as those caused by aging and mental disorders, on visual motion prediction and its consequences on mobility related daily activities

ARQUITECTURA BIOCLIMÁTICA

La arquitectura bioclimática no debería considerarse como una moda o una tendencia en la arquitectura, sino una parte constitutiva de la misma arquitectura que, por motivos académicos, es enseñada como un curso particular. En el contexto actual, donde ha surgido una conciencia sobre el medio ambiente, la conservación de los recursos y la utilización de energías renovables que revitaliza las ideas de la Carta de Atenas y de Michael Reynolds, así como las técnicas del acondicionamiento ambiental enseñados durante las últimas décadas del siglo XX dentro del currículo de las carreras de arquitectura, adquieren, en este nuevo contexto, un nuevo significado. De ese modo, se ha conseguido una arquitectura sustentable que garantice un desarrollo sostenible. No obstante, conscientes de que la arquitectura bioclimática todavía está en ciernes, pues no existe una unidad para medir la sustentabilidad de los materiales o de las edificaciones, por el momento debemos conformarnos con conocer todas las variables y esperar que adquiramos prudencia para ponderarlas adecuadamente como profesionales sin caer en el discurso ideológico del ecologismo y las políticas absurdas como los bonos de carbono. El libro Arquitectura bioclimática es el producto de un gran esfuerzo y varios años de enseñanza de los cursos de Acondicionamiento Ambiental. Está pensado, al igual que su antecesor Acústica para arquitectos, con la intención de ser guía y apoyo en clase para los estudiantes de pregrado de arquitectura. Así, no copiarán tablas ni largos textos de la pizarra. Eso permitirá que se concentren en la exposición del docente. Asimismo, ayudará a ordenar los temas para que se evidencie una continuidad desde lo básico hacia un desarrollo más elaborado. El libro recopila una serie de saberes actualizados sobre la arquitectura bioclimática que resulta relevante para la enseñanza de la arquitectura como sostenibilidad, geometría solar, ventilación natural, termicidad, cuadro bioclimática e iluminación natural. Además, se expone el resultado del artículo del autor “Daylighting, Optimizing the illumination level in light wells by making use of the correct relation of their sides” con temas que se exponen de manera gráfica mediante gráficos, tablas e infografías y hojas Excel que ayuden a revisar las gráficas solares y e

Modelling of multiple impacts for the prediction of distortions and residual stresses induced by ultrasonic shot peening (USP)

International audienceDuring a manufacturing process, the ultrasonic shot peening (USP) technique can be used as the final surface treatment. The aim of this operation is to introduce surface compressive residual stresses in order to prevent crack propagation advancement. Although the numerical simulation method is able to predict the level of residual stresses in a peened part, the 3D modelling of the real USP process, in which many successive and shifted impacts take place, is very delicate to perform and costly in terms of computing time and memory space required. In this paper, a two step method based at first on the calculation of the averaged plastic strain tensor in a half-space by using a semi-analytical method and in a second time on the transfer of this plastic strain field to a finite element model is proposed in order to simulate the effects of the USP process in thin structures. The accuracy and advantages of the semi-analytical method are validated by a benchmark with several finite element codes. Experiments, similar to the Almen test, are performed on thin plates of Inconel 600. Numerical results in terms of distortions and residual stresses are compared with the experimental data