scholarly journals Opto-Thermal Investigation of Additively Manufactured Steel Samples as a Function of the Hatch Distance

Sensors ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 46
Author(s):  
Dennis Höfflin ◽  
Maximilian Rosilius ◽  
Philipp Seitz ◽  
Andreas Schiffler ◽  
Jürgen Hartmann
Keyword(s):  
Quality Assurance ◽  
Thermal Diffusivity ◽  
Relative Density ◽  
Process Parameters ◽  
Material Properties ◽  
Sharp Decrease ◽  
Melting Process ◽  
Design Guidelines ◽  
Flash Method ◽  
Topology Optimisation

Nowadays, additive manufacturing processes are becoming more and more appealing due to their production-oriented design guidelines, especially with regard to topology optimisation and minimal downstream production depth in contrast to conventional technologies. However, a scientific path in the areas of quality assurance, material and microstructural properties, intrinsic thermal permeability and dependent stress parameters inhibits enthusiasm for the potential degrees of freedom of the direct metal laser melting process (DMLS). Especially in quality assurance, post-processing destructive measuring methods are still predominantly necessary in order to evaluate the components adequately. The overall objective of these investigations is to gain process knowledge make reliable in situ statements about component quality and material properties based on the process parameters used and emission values measured. The knowledge will then be used to develop non-destructive tools for the quality management of additively manufactured components. To assess the effectiveness of the research design in relation to the objectives for further investigations, this pre-study evaluates the dependencies between the process parameters, process emission during manufacturing and resulting thermal diffusivity and the relative density of samples fabricated by DMLS. Therefore, the approach deals with additively built metal samples made on an EOS M290 apparatus with varying hatch distances while simultaneously detecting the process emission. Afterwards, the relative density of the samples is determined optically, and thermal diffusivity is measured using the laser flash method. As a result of this pre-study, all interactions of the within factors are presented. The process variable hatch distance indicates a strong influence on the resulting material properties, as an increase in the hatch distance from 0.11 mm to 1 mm leads to a drop in relative density of 57.4 %. The associated thermal diffusivity also reveals a sharp decrease from 5.3 mm2/s to 1.3 mm2/s with growing hatch distances. The variability of the material properties can also be observed in the measured process emissions. However, as various factors overlap in the thermal radiation signal, no clear assignment is possible within the scope of this work.

Thermal Characterization of Carbon-Carbon Composites

2011 ◽  
Author(s):  
Messiha Saad ◽  
Darryl Baker ◽  
Rhys Reaves
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Critical Role ◽  
Carbon Composite ◽  
Flash Method ◽  
Carbon Composites ◽  
Energy Storage Devices ◽  
Graphitized Carbon

Thermal properties of materials such as specific heat, thermal diffusivity, and thermal conductivity are very important in the engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells and solar cells. Thermal conductivity plays a critical role in the performance of materials in high temperature applications. Thermal conductivity is the property that determines the working temperature levels of the material, and it is an important parameter in problems involving heat transfer and thermal structures. The objective of this research is to develop thermal properties data base for carbon-carbon and graphitized carbon-carbon composite materials. The carbon-carbon composites tested were produced by the Resin Transfer Molding (RTM) process using T300 2-D carbon fabric and Primaset PT-30 cyanate ester. The graphitized carbon-carbon composite was heat treated to 2500°C. The flash method was used to measure the thermal diffusivity of the materials; this method is based on America Society for Testing and Materials, ASTM E1461 standard. In addition, the differential scanning calorimeter was used in accordance with the ASTM E1269 standard to determine the specific heat. The thermal conductivity was determined using the measured values of their thermal diffusivity, specific heat, and the density of the materials.

scholarly journals A FEM-Based 2D Model for Simulation and Qualitative Assessment of Shot-Peening Processes

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2784
Author(s):  
Georgios Maliaris ◽  
Christos Gakias ◽  
Michail Malikoutsakis ◽  
Georgios Savaidis
Keyword(s):  
Process Parameters ◽  
Material Properties ◽  
Shot Peening ◽  
Qualitative Assessment ◽  
Experimental Investigations ◽  
Elastoplastic Material ◽  
Size Distributions ◽  
User Friendly ◽  
The Impact ◽  
2D Model

Shot peening is one of the most favored surface treatment processes mostly applied on large-scale engineering components to enhance their fatigue performance. Due to the stochastic nature and the mutual interactions of process parameters and the partially contradictory effects caused on the component’s surface (increase in residual stress, work-hardening, and increase in roughness), there is demand for capable and user-friendly simulation models to support the responsible engineers in developing optimal shot-peening processes. The present paper contains a user-friendly Finite Element Method-based 2D model covering all major process parameters. Its novelty and scientific breakthrough lie in its capability to consider various size distributions and elastoplastic material properties of the shots. Therewith, the model is capable to provide insight into the influence of every individual process parameter and their interactions. Despite certain restrictions arising from its 2D nature, the model can be accurately applied for qualitative or comparative studies and processes’ assessments to select the most promising one(s) for the further experimental investigations. The model is applied to a high-strength steel grade used for automotive leaf springs considering real shot size distributions. The results reveal that the increase in shot velocity and the impact angle increase the extent of the residual stresses but also the surface roughness. The usage of elastoplastic material properties for the shots has been proved crucial to obtain physically reasonable results regarding the component’s behavior.

Resistance spot welding of additively manufactured maraging steels Part II: Failure behavior

2021 ◽  
pp. 1-31
Author(s):  
Cheng Luo ◽  
Yansong Zhang ◽  
Michael Oelscher ◽  
Yandong Shi ◽  
Niels Pasligh ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Fracture Mode ◽  
Automotive Industry ◽  
Material Properties ◽  
Resistance Spot Welding ◽  
Spot Welding ◽  
Melting Process ◽  
Spot Welds ◽  
Laser Melting ◽  
Maraging Steels

Abstract Application of maraging steels via selective laser melting process in the automotive industry was unavoidably involved in the resistance spot welding with conventional steels. Due to the rapid cooling rate of welding process, selective laser melted maraging steels with unique chemical components and stack microstructure could induced the different microstructural evolution, resulting in the complicated fracture behavior in the spot welds. This paper developed a FEA model to predict the fracture mode of spot welds of DP600 to maraging steel and the effect of test conditions and printing orientations were studied. A method was proposed to calculate the material properties of fusion zone by introducing the combined effect of melting DP600 and maraging steels via selective laser melting, resulting in the accurate prediction of fracture mode and strength of spot welds. An interlayer with lower strength was found around the fusion zone and the fracture path propagated in the region, resulting in the partial interfacial failure of spot welds. Meanwhile, the printing orientation had no significant effect on the fracture mode and strength of spot welds, but the different material properties of maraging steels could affect the fracture displacement of spot welds. These findings could pave a way to guide the application of maraging steels via selective laser melting process in multiple industries, especially in the automotive industry.

Benchmark test artifacts for selective laser melting – a critical review

2021 ◽  
Vol 15 ◽  
Author(s):  
Weishi Li ◽  
Kuanting Wang ◽  
Shiaofen Fang
Keyword(s):  
Selective Laser Melting ◽  
High Surface ◽  
Dimensional Accuracy ◽  
Melting Process ◽  
Design Guidelines ◽  
Laser Melting ◽  
Specific Test ◽  
Benchmark Test ◽  
High Surface Quality ◽  
Machine Performance

Background: Selective laser melting is the best-established additive manufacturing technology for high-quality metal part manufacturing. However, the widespread acceptance of the technology is still underachieved, especially in critical applications, due to the absence of a thorough understanding of the technology, although several benchmark test artifacts have been developed to characterize the performance of selective laser melting machines. Objective: The objective of this paper is to inspire new designs of benchmark test artifacts to understand the selective laser melting process better and promote the acceptance of the selective laser melting technology. Method: The existing benchmark test artifacts for selective laser melting are analyzed comparatively, and the design guidelines are discussed. Results: The modular approach should still be adopted in designing new benchmark test artifacts in the future, and task-specific test artifacts may also need to be considered further to validate the machine performance for critical applications. The inclusion of the design model in the manufactured artifact, instead of the conformance to the design specifications, should be evaluated after the artifact is measured for the applications requiring high-dimensional accuracy and high surface quality. Conclusion: The benchmark test artifact for selective laser melting is still under development, and a breakthrough of the measuring technology for internal and/or inaccessible features will be beneficial for understanding the technology.

Schadenserfassung auf Radsatzlaufflächen/Defect detection on wheelset treads – Measurement of Magnetic Barkhausen Noise to detect varying workpiece conditions

2019 ◽  
Vol 109 (11-12) ◽  
pp. 811-815
Author(s):  
B. Denkena ◽  
B. Bergmann ◽  
H. Blech
Keyword(s):  
Acoustic Emission ◽  
Process Parameters ◽  
Defect Detection ◽  
Material Properties ◽  
Barkhausen Noise ◽  
Magnetic Barkhausen Noise ◽  
Optimal Process ◽  
Process Reliability

Unterschiedliche Belastungshistorien von Eisenbahnrädern führen zu Werkstoffveränderungen in der Lauffläche. Diese verursachen sporadisches Werkzeugversagen und verringern so die Prozesssicherheit. Die Messung der Material- und Prozesseigenschaften mit Barkhausenrauschen und Körperschall erlauben, individuelle Bearbeitungsparameter für jedes Exemplar festzulegen. Gezeigt werden die Herausforderungen in der Radsatzbearbeitung, und welche Informationen sich durch die Messtechniken gewinnen lassen.   Different load histories of train wheels lead to high variance of material properties on the running tread. Those cause unpredictable tool break and reduce process reliability. The measurement of magnetic Barkhausen noise and acoustic emission allow to gain information of the workpiece and the running process, to find optimal process parameters for the reconditioning of every individual wheel. Typical issues in train wheel machining and results of measurements are presented.

Effect of material properties and process parameters on quality of friction stir forming

2021 ◽  
Vol 70 ◽  
pp. 553-559
Author(s):  
Francesco Gagliardi ◽  
Mahsa Navidirad ◽  
Giuseppina Ambrogio ◽  
Wojciech Z. Misiolek
Keyword(s):  
Process Parameters ◽  
Material Properties ◽  
Friction Stir

Study of the Thermal Diffusivity Variation in Thin Duplex Steel Plates Welded by GTAW Process

2018 ◽  
Vol 930 ◽  
pp. 460-465
Author(s):  
Evandro Giuseppe Betini ◽  
Maurilio Pereira Gomes ◽  
Cristiano Stefano Mucsi ◽  
Temístocles de Souza Luz ◽  
Marcos Tadeu D'azeredo Orlando ◽  
...  
Keyword(s):  
Thermal Diffusivity ◽  
Welding Process ◽  
Laser Flash ◽  
Nitrogen Atmosphere ◽  
Steel Plates ◽  
Digital Data ◽  
Flash Method ◽  
Temperature Profiles ◽  
Butt Weld ◽  
Duplex Steel

This study describes the thermal diffusivity of thin duplex steel plates in the thickness direction measured using the laser-flash method after welding. The work reports the experimental efforts in recording temperature profiles of the grade UNS S32304 duplex steel during autogenous welding. The butt weld autogenous joints were carried out by the GTAW (gas tungsten arc welding) process with either argon or argon - 2% nitrogen atmospheres. The amount of nitrogen in the heat affected regions, after welding, was measured and correlated with the variation of the thermal diffusivity of the studied material. The temperature profiles were obtained using k-type thermocouples connected to a digital data acquisition system. Different thermal cycles and thermal diffusivity values were observed in the heat-affected zone (HAZ) for both samples. In the solidified zone (SZ) was observed similar increase of the thermal diffusivity values for the plates welded with pure argon and argon plus nitrogen atmosphere.

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