Flow and fracture of austenitic stainless steels at cryogenic temperatures

In this paper, we have characterized the microstructural evolution and the plastic flow and fracture behaviours of AISI 304L and AISI 316LN stainless steel grades at liquid nitrogen temperature (4 K) and at liquid helium temperature (77 K). Uninterrupted tensile experiments, where the sample is continuously deformed under quasi-static loading conditions until fracture, have been carried out with a Single-Section Sample to obtain the stress–strain characteristics of the two grades. Interrupted tensile experiments, in which the sample is unloaded before fracture, have been performed with a novel Double-Section Sample to later characterize the strain-induced martensitic transformation at different levels of deformation. The content of martensite has been determined post-mortem, using magnetic induction, electron backscatter diffraction and quantitative light optical micrography. The results obtained with the three methods show quantitative agreement, and reveal that the martensitic transformation in AISI 304L occurs faster and to a greater extent than in AISI 316LN both at 77 K and at 4 K. To the authors’ knowledge, in this paper we provide the first experimental results for the evolution of the content of strain-induced martensite in AISI 304L and AISI 316LN samples tested at liquid helium temperature. In addition, the experimental data for the evolution of the martensite volume fraction with the strain have been used to identify the temperature-dependent parameters of the martensitic transformation kinetic model proposed by Olson and Cohen (1975). Moreover, Mode I fracture tests with fatigue-precracked Compact Samples have been carried out to determine the fracture properties of the two investigated materials using the “resistance curve procedure” (ASTM-E1820-20a). The crack-growth resistance curves have been obtained with four different methods here referred to as ASTM Compliance Method, W–N Compliance Method, Modified W–N Compliance Method and ASTM Normalization Method, which is an original methodological contribution of this paper. While the four approaches yield similar results for the fracture toughness, only the W–N Compliance Method and the Modified W–N Compliance Method, the latter being proposed in this paper, fulfil all the requirements of the standard ASTM-E1820-20a so that the calculated fracture toughness can be accepted as a material property. The comparison of results for both materials and testing temperatures shows that AISI 316LN displays higher fracture toughness than AISI 304L. Moreover, post-mortem microstructural analysis of the Compact Samples near the fracture surface has revealed that the content of martensite is greater in AISI 304L than in AISI 316LN. Furthermore, for AISI 304L more martensite is formed in the sample tested at 77K because the plastic deformation near the crack is more than at 4K

Motivación y satisfacción de los trabajadores y su influencia en la creación de valor económico en la empresa Motivation and satisfaction of the workers and their influence in creating economic value in business

La gestión del valor económico implica que la dirección de la empresa debe preocuparse de forma eficaz en como alcanzar esta eficiencia en la generación del valor y en como lograr su equitativa distribución, ya que la sociedad actual no puede ser concebida solamente como un mercado sino que está constituida por un conjunto de personas que participan de forma cooperativa y competitiva en la comunidad, que tienen determinadas motivaciones y que actúan colectivamente, coordinando sus acciones según los objetivos de sus empresas, en la búsqueda de alcanzar sus propias expectativas, por lo que al centrar nuestro interés en los trabajadores de la empresa surgen dos variables de análisis y que están directamente relacionadas con la motivación, independientes en su génesis, pero que interactúan entre sí, por un lado la falta de insatisfacción laboral, y por otro la satisfacción laboral, aspectos que son analizados en este artículo y su influencia en la creación de valor económico en la empresa. Es fundamental que la empresa identifique y conozca las expectativas de cada uno de sus trabajadores, con lo cual se podrá establecer estrategias que le permitan poder alinear éstas a los objetivos organizacionales y a la creación o incremento de su valor económico, y así tender a reducir la falta de insatisfacción y apuntar a la motivación y satisfacción del personal.<br>Economic value management implies that management should be interested in reaching an efficient generation of value and its fair distribution. Our society cannot be conceived only as a market because it is constituted by a community of people who participate competitively and cooperatively. They have their own motivations and act collectively by coordinating their actions according to the objectives of their businesses so as to fulfill their expectations. While centering our interest in the workers, two variables of analysis emerge. These variables are directly related to motivation and independent in their genesis, although there is interaction between them: the lack of satisfaction at work and job satisfaction. Both aspects are analyzed in this paper and their influence in the creation of economic value in business. In this scenario, it is fundamental that the firm identify and know the expectations of each one of its workers. This will allow to establish strategies to harmonize these expectations with the organizational objectives and the creation of economic value. This type of initiative tends to reduce the lack of satisfaction and to improve personal motivation