Shear Failure of Inconel 718 under Dynamic Loads

Kinetics of deformation and fracture of nickel–iron alloy Inconel 718 under dynamic shear loading was measured using a split torsional Hopkinson bar facility and high-speed photography. Tubular specimens with a reduced gage length and a starter notch were sheared at strain rates up to 6 × 10³ s⁻¹. High-speed photographs of fiducial lines scribed on the specimen surface showed the development of local strains and cracking. This paper describes the experimental and analytical procedures, illustrates average and local plastic strain evolution, and presents shear crack initiation times and propagation speeds.     

Towards a Fundamental Understanding of the Mechanics of Crystal Agglomeration: A Microscopic and Molecular Approach

A novel experimental apparatus has been developed which enables the measurement of adhesion forces between two crystals suspended in a supersaturated solution and allowed to agglomerate over a fixed time period. The geometry of the crystal surfaces at the contact points and the dynamic development of the bond are captured on video and characterised using an image analysis technique. The experimental apparatus has been designed to allow control of supersaturation, orientation of crystal faces, distance between crystals, relative movement of crystals and contact time. The experimental results show that the agglomerate bond strength, expressed as the agglomerate adhesion force per unit contact area, increases with increasing supersaturation and is higher for faster growing faces than for slower growing faces. In addition, a qualitative comparison has been made between the measured force and a theoretical estimation of the interaction force between crystal faces, determined through molecular modelling. It is shown that the speed of approach of two opposing crystal faces is a key parameter in the nature of the subsequent bond, as is their atomic structure.     

Untersuchung von Milch und Molkereiprodukten

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Literatur

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Effect of Traditional Cooking and Sous Vide Heat Treatment,Cold Storage Time and Muscle on Physicochemical and Sensory Properties of Beef Meat

Consumers are avoiding the consumption of highly processed foods, aware of the negative effects of the additives or high temperatures used on the biological value of the food. This causes an interest in ways of minimal processing or low-temperature cooking procedures. However, to achieve the desired organoleptic quality, it is necessary to know the relationship between the parameters of the treatments and the type of raw material. The purpose of this study was to investigate the complex effects of traditional cooking and sous vide heat treatment, cold storage time and muscle on the physicochemical and sensory properties of beef. The study material consisted of samples of musculus longissimus thoracis and musculus semitendinosus obtained from beef half-carcasses. The muscles were subjected to traditional cooking in water at 95 °C until the temperature inside the piece reached 65 °C and sous vide treatment at 65 °C for 2 h. The study was performed after 2 and 21 days of cold storage. Instrumental evaluation of texture parameters, color and sensory evaluation of meat was carried out. Meat stored for 21 days was characterized by more favorable TPA test (Texture Profile Analysis) results compared to meat evaluated 48 h post mortem. The study also showed positive effects of sous vide heat treatment on texture parameters and sensory properties (especially on tenderness and palatability), as well as differences in the formation of quality traits between muscles. Given the trends associated with energy-saving technologies, it is desirable to seek the optimal combination of temperature and time of fixation treatments at an acceptable level of quality. The use of low-temperature cooking for as little as 2 h, yields positive results in sensory evaluation of juiciness, tenderness, or palatability.