Producing Crack-Free, High Density M2 HSS Parts by Selective Laser Melting: Pre-Heating the Baseplate

Cracks and delamination, resulting from residual stresses are a barrier in the world of Additive Manufacturing and Selective Laser Melting (SLM) that prohibits the use of many metals in this field. By preheating the baseplate, thermal gradients are lowered and stresses can be reduced. In this work, some initial tests were performed with M2 Tool Steel. Results show that pre-heating enables the production of dense M2 parts. The influence of pre-heating on density and mechanical and physical properties is investigated. The paper shows many promising results for the production of SLM parts in materials that are very sensitive to crack formation and delamination. When using a pre-heating of 200°C, crack-free parts were produced with a relative density of 99.8%.Mechanical Engineerin

No difference in effects of ‘PACE steps to success’ palliative care program for nursing home residents with and without dementia : a pre-planned subgroup analysis of the seven-country PACE trial

Background: 'PACE Steps to Success' is a multicomponent training program aiming to integrate generalist and non-disease-specific palliative care in nursing homes. This program did not improve residents' comfort in the last week of life, but it appeared to improve quality of care and dying in their last month of life. Because this program included only three dementia-specific elements, its effects might differ depending on the presence or stage of dementia. We aimed to investigate whether the program effects differ between residents with advanced, non-advanced, and no dementia. Methods: Pre-planned subgroup analysis of the PACE cluster-randomized controlled trial in 78 nursing homes in seven European countries. Participants included residents who died in the previous 4 months. The nursing home staff or general practitioner assessed the presence of dementia; severity was determined using two highly-discriminatory staff-reported instruments. Using after-death questionnaires, staff assessed comfort in the last week of life (Comfort Assessment in Dying-End-of-Life in Dementia-scale; primary outcome) and quality of care and dying in the last month of life (Quality of Dying in Long-Term Care scale; secondary outcome). Results: At baseline, we included 177 residents with advanced dementia, 126 with non-advanced dementia and 156 without dementia. Post-intervention, respectively in the control and the intervention group, we included 136 and 104 residents with advanced dementia, 167 and 110 with non-advanced dementia and 157 and 137 without dementia. We found no subgroup differences on comfort in the last week of life, comparing advanced versus without dementia (baseline-adjusted mean sub-group difference 2.1; p-value = 0.177), non-advanced versus without dementia (2.7; p = 0.092), and advanced versus non-advanced dementia (- 0.6; p = 0.698); or on quality of care and dying in the last month of life, comparing advanced and without dementia (- 0.6; p = 0.741), non-advanced and without dementia (- 1.5; p = 0.428), and advanced and non-advanced dementia (0.9; p = 0.632). Conclusions: The lack of subgroup difference suggests that while the program did not improve comfort in dying residents with or without dementia, it appeared to equally improve quality of care and dying in the last month of life for residents with dementia (regardless of the stage) and those without dementia. A generalist and non-disease-specific palliative care program, such as PACE Steps to Success, is a useful starting point for future palliative care improvement in nursing homes, but to effectively improve residents' comfort, this program needs further development

THE INTERNAL FRICTION BEHAVIOUR OF MARTENSITIC Cu-Zn-Al ALLOYS

Dans cet article, nous présentons une description des deux pics de frottement intérieur observés dans la phase martensitique des alliages de Cu-Zn-Al. Le pic à basse température (215 K) a été reconnu comme "pic de relaxation" tandis que celui observé à 315 K serait dû à l'entraînement des défauts par les dislocations.In this paper, internal friction peaks, occurring in martensitic Cu-Zn-Al alloys are described. The peak at 215 K is explained as a relaxation peak while the peak at 315 K is explained as due to the dragging of point defects by dislocations

THE INFLUENCE OF STRAIN-RATE, AMPLITUDE AND TEMPERATURE ON THE HYSTERESIS OF A PSEUDOELASTIC Cu-Zn-Al SINGLE CRYSTAL

The hysteresis loop, described during the formation of stressinduced pseudoelastic martensite in a Cu-Zn-Al betaphase single crystal, was studied as a function of strain-rate, deformation amplitude and temperature. The σp→m, the stress at which the transformation starts at a given constant temperature, is strain-rate independent but the hysteresis described by the stress-strain curve shows a maximum at intermediate strain-rates (3.3 x 10-3 sec-1). For very low strain rates (3.3 x 10-5 sec-1) the relative energy-loss (ƊW/W) was independent of amplitude. The amplitude-dependence was the strongest at intermediate strain-rates. The absolute hysteresis, i.e. energy loss, measured at constant strain-rate seems to be independent of temperature in the region (Ms+60, Ms+110). The change in hysteresis as a function of strain-rate can be attributed to the heating and cooling of the sample due to the exothermic character of the beta-martensite transformation and the reverse endothermic transformation. At very low strain-rates the transformation occurs isothermally so that nearly no hysteresis is found. Only at very high strain-rates the sample is deformed adiabatically

Thermoelectric power measurements on stabilised Cu-Zn-Al martensite

The stabilisation kinetics of polycrystalline Cu-Zn-Al martensite are studied by means of thermoelectric power measurements (TEP). It is shown that the TEP increases until it reaches a saturation value, which is temperature dependent. The martensite can be further stabilised by increasing the ageing temperature, while subsequent destabilisation by lowering the ageing temperature is not observed. On the basis of these results, a discussion is presented on the important aspects of martensite stabilisation in Cu-Zn-Al.status: publishe

Generation of Recovery Stresses : Thermodynamic Modelling and Experimental Verification

Shape memory elements generate significant recovery stresses when the shape recovery associated with the reverse martensitic transformation is impeded during heating. This process of stress generation is influenced by many parameters. A fundamental model has been developed to describe this generation of recovery stresses. The model is based on a generalised thermodynamic analysis of shape memory behaviour. The mathematical approach and the assumptions in this model are selected in such a way that the calculations yield close approximations of the real behaviour and that the final mathematical equations are relatively simple. The paper presents also experimental measurements of recovery stress generation for complex restraining conditions. Comparison of the experimental results with the calculated results confirm that this model can be used to predict quantitatively the generation of recovery stresses