The interaction of high-power fiber laser irradiation with intrusive rocks

Laser cutting of intrusive rocks, including granite, gabbro, and diorite, is carried out in order to assess the cut characteristics through geometrical measurements, such as kerf width, melting width, and penetration depth. The absorption rate for each specimen at the wavelength of 1064 nm is measured using a spectrophotometer. A multimode fiber laser is used in this study with the power of 9 kW and different cutting speeds. Furthermore, nitrogen gas at 13 bar is applied as the assistant gas in order to remove the melted material effectively. As a result of the experiment, the relationship between the cutting speed and geometrical measurements is investigated. Furthermore, variations of penetration depth are performed in accordance with the number of laser cuts. In addition, through energy dispersive X-ray (EDX) element mapping, minerals that comprise the rocks are classified and characterized. Subsequently, the changes in the microstructure and chemical composition of each specimen, before and after laser cutting, are compared using scanning electron microscope (SEM) and EDX analyses. Experimental results demonstrate that the cutting characteristics vary, depending on the types of minerals that make up the rock. Based on a series of tests, it is identified that volume energy of more than 3.06E + 13 $$\mathrm{J}/{\mathrm{m}}^{3}$$ J / m 3 is required to fully cut intrusive rocks that have a thickness of 25 mm.

Mesoscopic simulation of overlapping behavior in laser powder bed additive manufacturing

The prediction of the flow behavior of Metal micro-molten pool is prerequisite for high-quality Laser Powder Bed Fusion (L-PBF). In this study, mesoscopic scale numerical simulation modelling for L-PBF process was used to help understand the melting process of pure copper micro-melt pool.In this study, the orthogonal test was designed to study the influence of laser power, laser scanning velocity, hatching space on the flow behavior of molten pool and the overlapping rate of adjacent molten tracks. The results shows that laser scanning speed has the greatest influence on both the size and overlapping rate of the molten pool, and the overall trend was that the size of molten pool continues to increase as the volume energy density increases, and the maximum molten pool size was 243.6um × 110um with volume energy density 370.037 J/mm3, overlapping rate of adjacent molten tracks was 48.84% with volume energy density 285.71 J/mm3. The optimized pure copper laser process parameters were obtained: laser power 300 KW, laser scanning speed 500 mm/s, hatching space 0.07mm, overlapping rate 48.84%.

Tensile Properties and Deformation of AISI 316L Additively Manufactured with Various Energy Densities

Additive manufacturing (AM) is an emerging fabrication technology that offers unprecedented potential for manufacturing end-to-end complex shape customized products. However, building products with high performance by AM presents a technological challenge. Inadequate processing parameters, fabrication environment or changes in powder properties may lead to high defect density in the part and poor mechanical properties. Microstructure, defect structure, and mechanical properties of AISI 316L stainless steel pieces, additively manufactured by the laser powder bed fusion method using three different volume energy densities (VEDs), were investigated and compared with those of a commercial wrought AISI 316L sheet. Scanning and transmission electron microscopies were employed for characterization of grain and defect structures, and mechanical properties were determined by tensile testing. It was found that the number of defects such as pores and lack of fusion in AM specimens did not affect the strength, but they impaired the post-uniform elongation, more significantly when processed with the low VED. Twinning was found to be an active deformation mechanism in the medium and high VED specimens and in the commercially wrought material in the later stage of straining, but it was suppressed in the low VED specimens presumably because the presence of large voids limited the strain attained in the matrix.

Thermodynamics of solid and liquid aluminium

Based on thermodynamic calculations, it is shown that in the temperature range of 298–1273 K, heating and cooling of aluminum are thermodynamically equilibrium processes. When aluminum is heated, the molar volume energy of Gibbs decreases and the molar boundary energy of nanocrystals increases. When aluminum is cooled, the molar volume energy of Gibbs increases and the molar boundary energy of nanocrystals decreases. Liquid aluminum is a nanostructured system. Dendritic microcrystals are formed from nanocrystals. They play a large role in the processes of changing the structure of aluminum during its heating and cooling.

Nutrition and oncology: best practice and the development of a traffic light system

Malnutrition is common in oncology patients, with age, disease stage and tumour type all influencing malnutrition risk. There are several detrimental effects of malnutrition in oncology patients, including weight loss, which is associated with negative oncological outcomes, and reduced survival. The causes of malnutrition in this group may be multifactorial and include effects from the tumour itself, altered metabolism, increased nutritional requirements, and cancer treatments and their associated side effects, which can impact on an individual's ability and desire to eat. Nutritional screening to identify early nutritional risk is essential and should involve the use of a validated screening tool, with commonly used tools usually assessing nutritional risk and weight loss over a period of months, for example a 3- to 6-month period. It is also important to consider weight changes over a shorter time period to identify rapid weight changes. Multidisciplinary teamworking is essential in tackling malnutrition, with collaborative working between the dietitians and the nutrition nurses shown to be beneficial in the authors' practice to develop community pathways and improve their service and manage increasing patient numbers. Malnutrition within oncology can often be managed with additional supplementation with oral nutritional supplements or enteral nutrition, where indicated. A low-volume, energy-dense, high-protein supplement can help to meet nutritional needs and to achieve dietetic aims, with compliance improved by the use of a low-volume product.

Influence of Pulsed Exposure Strategies on Overhang Structures in Powder Bed Fusion of Ti6Al4V Using Laser Beam

Manufacturing structures with low overhang angles without support structures is a major challenge in powder bed fusion of metals using laser beam (PBF-LB/M). In the present work, various test specimens and parameter sets with continuous wave (cw) and pulsed exposure are used to investigate whether a reduction of downskin roughness and overhang angle can be achieved in PBF-LB/M of Ti6Al4V. Starting from cw exposure, the limits of overhang angle and surface roughness at the downskin surface are investigated as a reference. Subsequently, the influence of laser power, scanning speed, and hatch distance with fixed pulse duration (τpulse = 25 µs) and repetition rate (υrep = 20 kHz) on surface roughness Ra is investigated. Pulsed exposure strategies enable the manufacturing of flatter overhang angles (≤20° instead of ≥25°). Furthermore, a correlation between the introduced volume energy density and the downskin roughness can be observed for pulsed exposure. As the reduction in volume energy density causes an increase in porosity, the combination of pulsed downskin exposure and commercial cw infill exposure is investigated. The larger the gap in volume energy density between the infill area and downskin area, the more challenging it is combining the two parameter sets. By combining cw infill and pulsed downskin exposure, flatter overhang structures cannot be manufactured, and a reduction in roughness can be achieved.

A Revised Approach for the Life Prediction of Metal Materials Fabricated by Additive Manufacturing

In this work, a new fatigue damage model considering the additive manufacturing (AM) effects is established. We first present the elastoplastic constitutive model with the newly established fatigue damage model considering AM effects. The method to calibrate the material parameters is put forward, and the numerical solution of the theoretical model is implemented. Second, the fatigue lives of two AM metal materials are predicted, and the applicability of the theoretical model is verified by the test results. Finally, the influence of the volume energy density ratio on the fatigue life of AM metal materials is analyzed, and the results show that the volume energy density ratio has a great influence on the fatigue behavior of AM metal materials. When the ratio is less than 1.0, the fatigue life increases rapidly with the increase of the ratio. The fatigue life increases with the stress ratio when the volume density ratio keeps as a constant. The research work in this paper provides a feasible method to predict the fatigue life of AM metal materials by continuum damage mechanics in engineering.

Nutrition and oncology: best practice and the development of a traffic light system

Malnutrition is common in oncology patients, with age, disease stage and tumour type all influencing malnutrition risk. There are several detrimental effects of malnutrition in oncology patients, including weight loss, which is associated with negative oncological outcomes, and reduced survival. The causes of malnutrition in this group may be multifactorial and include effects from the tumour itself, altered metabolism, increased nutritional requirements, and cancer treatments and their associated side effects, which can impact on an individual's ability and desire to eat. Nutritional screening to identify early nutritional risk is essential and should involve the use of a validated screening tool, with commonly used tools usually assessing nutritional risk and weight loss over a period of months, for example a 3- to 6-month period. It is also important to consider weight changes over a shorter time period to identify rapid weight changes. Multidisciplinary teamworking is essential in tackling malnutrition, with collaborative working between the dietitians and the nutrition nurses shown to be beneficial in the authors' practice to develop community pathways and improve their service and manage increasing patient numbers. Malnutrition within oncology can often be managed with additional supplementation with oral nutritional supplements or enteral nutrition, where indicated. A low-volume, energy-dense, high-protein supplement can help to meet nutritional needs and to achieve dietetic aims, with compliance improved by the use of a low-volume product.