漏洩磁場測定による溶接管のオンライン検査(Non-Destructive Testing,9-1,1976)(文献紹介)

Additive manufacturing has been established as a process to produce structural and load-bearing parts, and this process has become attractive to many industries such as medical, aerospace, automotive, and oil and gas. These industrial applications are commonly characterized by high and stringent regulatory requirements. Due to the disparity and lack of consensus in mechanical properties reported in the literature, and the need to test and validate the components manufactured by the additive manufacturing process, this work aimed at performing an experimental simulation study of the effects of the slimness ratio on the mechanical properties of as-built Ti–6Al–4V electron beam additively manufactured parts subjected to tensile tests. From the obtained results, we propose an accurate method for the prediction and correlation of mechanical properties of specimens with different geometries. The main conclusion from this study is that elongation at fracture and tensile toughness follow a logarithmic equation and that symmetric cross-section specimens show superior mechanical strength with similar mechanical behavior to high-stress-triaxiality parts subjected to tensile tests. The fracture mode and associated micromechanisms are strongly influenced by the specimen’s width/thickness ratio, and the use of the Bertella–Oliver equation coupled with finite element method (analysis) tools was effective toward understanding the mechanical behavior of specimens subjected to tensile tests. In summary, the method presented here may be useful for predicting and comparing the data of specimens that do not comply with normative values.

A highly accurate methodology for the prediction and correlation of mechanical properties based on the slimness ratio of additively manufactured tensile test specimens

Neutron and X-Ray tomography as research tools for applied research in South Africa

Investment cast ASTM F75 Cobalt Chromium Molybdenum (CoCrMo) alloy is commonly used for orthopaedic implants due to its biocompatibility and wear characteristics. Apart from the values listed in the standard, the relationship between individual processing parameters and the resulting physio-mechanical properties are not well documented. This study characterises the effect of melt temperature on the physical properties and chemical composition of investment cast CoCrMo alloy. Furnace loads of ∼23−34 kg of alloy were inductively melted using 125 kW of power and cast into tensile test bars and chemistry coupons. The bars were ground to create samples conforming to ASTM E8M and tested per ISO 6892-1. The oxygen and nitrogen content of the chemistry coupons were assessed using Inert Gas Fusion (IGF) per ASTM E1019. It was found that increasing the melt temperature had the effect of removing nitrogen from the melt and adding oxygen. It was also determined that there was a strong positive correlation between nitrogen content and strength values. If desired, there is scope to minimise both oxygen pickup and nitrogen loss, nitrogen is correlated to increased mechanical properties, of this alloy system by targeting lower melt temperatures. However, this would be at the expense of melt viscosity and mould filling.

The effect of melt temperature on the mechanical properties of cast ASTM F75 CoCrMo alloy as explained by nitrogen and oxygen content

In this study, X-ray tomography was applied as a non-destructive test to investigate the internal defects of the green part produced with Powder injection molding (PIM). PIM is a material processing technology that combines injection molding with powder metallurgy. The determination of multiple parameters such as rheology, molding, bonding, and sintering stages in the PIM method requires a long time, energy, and high cost. Metal and ceramic injection molded parts are known to be susceptible to defects like cracks, weld lines, bubbles, or gaps. The examination and elimination of these defects are critical to the safety of the products because even a very short crack can significantly reduce the tensile and fracture strength of the parts. The internal structure analysis of the green parts after molding is very difficult. Defects (internal cracks, micropores, jetting, etc.) occurring in the green part will occur in the sintered. Therefore, it is essential to analyze the possible defects on molded parts before applying the ongoing process to save time and costs. Since the medical implants are in complex shape in general, the more internal defects can be seen at molding stage, it is needed to check the internal structure without any destruction, because there is no chance toleave them for recycle in the case of any defect. In experimental studies, it was observed that there were defects of edge, interior, and gaps in X-ray analysis for four different injection parameters. In X-ray analysis, the defects free parts were obtained for green part 4 parameters (temperature of 237 °C, flow rate of 20.11 cm3/s and pressure of 120 MPa). As a result of X-ray analysis, the difference between green part 1 and green part 4 is clearly visible in terms of defect. Injection temperatures, speeds and pressure play important role on originating of defects.

Analysis of biomedical titanium implant green parts by X-Ray tomography

Determination of tensile properties of materials is required to reliably predict performance of engineering materials in service and for design purposes. Tensile properties are also used as a measure of product quality. Various testing standards recommend specific specimen sizes for reporting of tensile properties. This recommendation is normally a challenge in materials development where the required specimen size is not achievable due to component size limitation. In addition, the materials developer still wants to compare their tensile results with the reference materials produced from standard sizes or produced from different geometries. It is well documented that tensile properties are affected by the specimen geometry (gauge length and cross sectional area). It is therefore the purpose of this study to investigate the effect of specimen geometry on tensile properties. In addition, this study seeks to determine suitable specimen geometry required to yield comparable tensile properties obtained from other specimen geometries. Various dog bone specimen geometries were produced from a titanium alloy metal sheet and tensile properties determined. Yield strength, Ultimate tensile strength and, % elongation were compared. Yield strength and ultimate tensile strength were not affected by different specimen geometries. However, % elongation differed for different geometries.

https://iopscience.iop.org/article/10.1088/1757-899X/430/1/012015/pdf

The effect of specimen geometry on tensile properties of titanium alloy metal sheet.

Journal of the Southern African Institute of Mining and Metallurgy, vol. 116(10): doi.org/10.17159/2411-9717/2016/v116n10a13

http://www.scielo.org.za/pdf/jsaimm/v116n10/15.pdf

X-ray computed microtomography studies of MIM and DPR parts

Metastable ß-Ti alloys intended for orthopaedic implants typically possess undesirable α′, α″, ω precipitates, which increase the elastic modulus. Non-toxic Sn was reported as an effective suppressor of α′, α″ and ω precipitates. Furthermore, increasing Sn content was reported to decrease the elastic modulus. In this study, the cluster plus glue atom (CPGA) model was used to develop structurally stable ß-Ti alloys through the addition of Sn. Arc melting was conducted to fabricate the alloys. The effect of substituting Mo atoms with 0.4 and 0.5 Sn atoms on the microstructure and mechanical properties of [(Mo,Sn)(Ti)14](Nb)1 alloys was investigated. The microstructure of the alloys exhibited large equiaxed beta grains with the [(Mo0.6Sn0.4)(Ti)14](Nb)1 and [(Mo0.5Sn0.5)(Ti)14](Nb)1 alloys showing substructures. The XRD results showed that the alloys consisted of the β phase; however, the presence of α” was observed in the [(Mo0.6Sn0.4)(Ti)14](Nb)1 alloy. The study showed that substitution of 0.5 Mo atoms with 0.5 atoms of Sn to form the [(Mo0.5Sn0.5)(Ti)14](Nb)1 cluster resulted in an elastic modulus of 49 GPa.

/pdf/influence-of-sn-on-the-microstructure-and-mechanical-8aocjrzk.pdf

Noluntu S Muchavi

Papers

The effect of specimen geometry on tensile properties of titanium alloy metal sheet.

X-ray computed microtomography studies of MIM and DPR parts

INFLUENCE OF Sn ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Ti-Mo-Nb ALLOYS FOR ORTHOPAEDIC APPLICATIONS