Influence of the orientation of steel parts produced by DMLS on the fatigue behaviour

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2020. The goal of this paper is to present studies of the influence of orientation of steel samples during additive manufacturing to their fatigue behaviour. The samples were produced from maraging steel EOS MS1 and stainless steel EOS PH1 using direct laser metal sintering technology. Three sets of samples were manufactured for each of the materials, with slopes of longitudinal axis of the samples being 0° (horizontal), 45° (slanted) and 90° (vertical) with respect to the horizontal building plane. All the samples were post-processed by heat treatment, shot-peening and machining, and tested according to the ISO 1143 standard. The curves for finite life domain were calculated using ISO 12107, and an estimation of the fatigue limit was made by Dixon-Mood method. The obtained results show that the building orientation has no significant influence on fatigue strength of maraging steel samples, while the stainless steel samples with slanted orientation of the axis have fatigue strength of up to 20% higher than the samples with horizontal or vertical orientation of the axis.The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455.The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455

Proširenje frekvencijskog opsega za eksperimentalno određivanje disperzione relacija talasa savijanja u štapovima primenom korelacione metode

The dispersion relation is the key for studies of wave propagation. The experimental determination of a dispersion relation by measurements of wave properties in different points in space meets the challenge of spatial aliasing, which is further augmented by numerical instability of calculations. This paper presents and discusses a concept aimed to overcome the spatial aliasing problem in measurements of dispersion relation of mechanical waves propagating through beams. The concept is based on the properties of the dispersion relationship and it may be extended to the case of all other waves with monotonous dispersion relationship.Publishe

Fatigue response of as built DMLS processed Maraging Steel and effects of machining and heat and surface treatments

The main motivations for this study arise from the need for an assessment of the fatigue performance of DMLS produced Maraging Steel MS1, when it is used in the \u201cas fabricated\u201d state. The literature indicates a lack of knowledge from this point of view, moreover the great potentials of the additive process may be more and more incremented, if an easier and cheaper procedure could be used after the building stage. The topic has been tackled experimentally, investigating the impact of heat treatment, machining and micro-shot-peening on the fatigue strength with respect to the \u201cas built state\u201d. The results indicate that heat treatment significantly enhances the fatigue response, probably due to the relaxation of the post-process tensile residual stresses. Machining can also be effective, but it must be followed (not preceded) by micro-shot-peening, to benefit from the compressive residual stress state generated by the latter

Air flow resistance of polyamide 12 made by selective laser sintering

This paper presents the measurements of the air flow resistance of polyamide 12 samples made by selective laser sintering. The results have shown that, due to the porosity of the microstructure, the samples with thickness smaller than 1.7 mm cannot be considered airtight, while the samples with thickness 2.2 mm are airtight. The airflow resistance of the samples that allow airflow increases with air speed.The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455.Publishe

Primjena optičke DIC mjerne metode na projektu A_MADAM

The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455.Publishe

Assessing the influence of DMLS production process factors on fatigue resistance of Maraging steel MS1 in the finite life domain using ANN prediction abilities

Analysis-of-variance (ANOVA) is a standard statistic method for assessment of the influence of various factors on fatigue resistance in the finite life domain. However, the previous research has shown that this method was not capable to determine with sufficient confidence if the build orientation, the thickness of allowance for machining, and the position in the production chamber affect fatigue resistance of Maraging steel MS1 products made by direct metal laser sintering (DMLS) technology. To contribute to a better understanding of the subject, the results of fatigue test experiments were used for training of four types of artificial neural networks (ANN) for assessment of fatigue resistance in the finite life domain. Each ANN had different structure of inputs, which corresponded to a different combination of the factors of DMLS production process. The differences between the predictive abilities of the ANN were attributed to influences of the respective factors on the fatigue resistance of the material in the finite life domain. The approach was verified by the agreement with the conclusive results of ANOVA analyses. Furthermore, in the cases when ANOVA does not lead to a clear result, the analyses of the predictive ability of the ANN strongly suggest that build orientation and thickness of allowance do not influence, while the position of a part in production chamber influences, the fatigue resistance in the finite life domain of Maraging steel MS1 produced by DMLS technology.The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455.Publishe

Experimental study on the sensitivity of DMLS manufactured Maraging Steel fatigue strength to the build orientation and allowance for machining

This work derives its motivations from the increasing interest towards Additive Manufacturing and the lack of studies, mainly in the field of fatigue. The effect of build orientation and of allowance for machining on DMLS produced Maraging Steel MS1 has been assessed. The experimental results, properly set up by tools of Design of Experiment, have been statistically processed and compared. The outcomes were that, probably due to effect of the thermal treatment, machining and material properties, the aforementioned factors do not have a significant impact on the fatigue response. This made it possible to work out a global curve that accounts for all the results, consisting in a high amount of data points. This can be regarded as one of the most generable and reliable fatigue models being currently available in the literature. Fracture surfaces have been carefully studied as well, individuating the initiation points being usually located at sub-surface porosities. Micrographies along the stacking direction and the build plane have been performed as well.The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455.Publishe

DMLS Built Maraging Steel Fatigue Response Investigated for Different Build Orientations and Allowance for Machining

This work derives its motivations from the increasing interest towards Additive Manufacturing and the lack of studies, mainly in the field of fatigue. The effect of build orientation and of allowance for machining on DMLS produced Maraging Steel MS1 has been assessed. The experimental results, properly set up by tools of Design of Experiment, have been statistically processed and compared. The outcomes were that, probably due to effect of the thermal treatment, machining and material properties, the aforementioned factors do not have a significant impact on the fatigue response. This made it possible to work out a global curve, accounting for all the result. Fracture surfaces have been carefully studied as well.The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455.Publishe

Gear unit housing effect on the noise generation caused by gear teeth impacts

The basic hypothesis of the paper is that machine part surfaces are membranes that divide inner and outer space, receive disturbance power from inner space and emit it to the surroundings. Additionally, machine systems operation causes numerous disturbances such as collisions, sliding, rolling, etc. Gear drives are a very interesting case for analysis of teeth impacts, which cause restorable free vibrations and spreading of disturbance power through elastic structure. The gear unit housing has a dominant role in the transformation of disturbance power and modulation of the sound emitted to the surroundings. This is an important detail for monitoring and diagnostics by emitted noise measurements. By combination of theoretical, numerical and experimental analyses, using a classical gear drive unit (reducer), this article explains the process of spreading disturbance power through the elastic structure, especially the role of the gear unit housing. Its role in the noise frequency spectrum modulation is determined by modal sensitivity to disturbances and noise isolation ability of the housing. The analysis of modal behavior of the housing and its modal shape excitation presents the main content of the paper. © 2012 Journal of Mechanical Engineering

An extension to the methodology for characterization of thermal properties of thin solid samples by photoacoustic techniques

The paper presents a study of possibilities to extend the present methodology for thermal characterization of thin solid samples by photoacoustic techniques. The present methodology consists of linear fitting of the experimental data to approximate the expressions derived from the composite piston model of photoacoustic response and it is mainly used for calculation of thermal diffusivity of thin samples. The study has shown that the methodology may be extended to calculation of thermal diffusivity, thermal conductivity and thermal expansion coefficients of thin samples by linear fitting in multiple frequency ranges and by analysis of the intersection frequency, which is the frequency where the magnitudes of two components of photoacoustic response in the composite piston model are equal. The analysis of numeric errors of the methodology has revealed the dominant sources and magnitude of the errors, leading to the conclusion that photoacoustic techniques should be carefully used as a tool for extensive thermal characterization of thin samples in the cases when other techniques are not applicable or have larger errors. (C) 2016 Elsevier Masson SAS. All rights reserved