高いSN比を有する超音波パルスエコー計測のための多角形バッファーロッドの開発

国立大学法人長岡技術科学大

Pencirian dan perbandingan serbuk aloi titanium (Ti6Al4V) yang digunakan dalam Peleburan Laser Selektif (SLM)

Ciri serbuk aloi titanium (Ti6Al4V) yang digunakan dalam pembuatan aditif logam (MAM) amat penting dalam menjamin mutu produk yang dihasilkan. Salah satu teknologi dalam MAM adalah Peleburan Laser Selektif (SLM). Mesin pencetakan SLM telah dibangunkan oleh beberapa syarikat seperti SLM Solutions Group AG dan Renishaw PLC. Bagi menjamin kualiti produk mesin masing-masing, setiap syarikat menghasilkan serbuk logam tersendiri. Hal ini membataskan potensi penggunaan SLM kerana pengguna tidak boleh menggunakan serbuk logam mereka sendiri. Maka, kajian ini bertujuan untuk mengkaji perbezaan antara serbuk Ti6Al4V yang dihasilkan oleh SLM Solutions dan Renishaw, dan juga menentukan ciri serbuk Ti6Al4V yang sesuai untuk kaedah SLM. Pencirian sampel serbuk telah dilakukan bagi mengkaji bentuk dan saiz zarah, rencaman kimia dan struktur kristalografi. Sampel serbuk Ti6Al4V daripada SLM Solutions dan Renishaw masing-masing ditandakan sebagai S1 dan S2. Analisis SEM menunjukkan sampel S2 mempunyai bentuk sfera yang lebih sempurna berbanding sampel S1. Analisis rencaman kimia menunjukkan kedua-dua sampel mempunyai taburan unsur kimia yang serupa dengan nilai kajian lampau. Selain itu, analisis taburan saiz zarah menunjukkan saiz zarah S1 dan S2 adalah kurang daripada 45 μm dengan nilai tersebut masih dalam lingkungan yang boleh diterima dalam MAM iaitu 10 hingga 60 μm. Analisis XRD menunjukkan kedua-dua sampel mempunyai puncak keamatan dan struktur kristal berbentuk heksagon yang serupa. Diharapkan makalah ini dapat dijadikan panduan bagi mereka yang ingin menghasilkan sendiri serbuk Ti6Al4V bagi penggunaan proses fabrikasi SLM

Prestasi bahan polimer komposit dicetak menggunakan pemodelan pemendapan bersatu : suatu ulasan ringkas

Penambahan kandungan pengisi polimer komposit dapat meningkatkan kekonduksian elektrik dan terma yang baik, serta mempunyai kekuatan tegangan dan modulus yang tinggi telah memperluaskan aplikasi dalam industri peranti elektronik. Walau bagaimanapun, penambahan kandungan pengisi yang kurang daripada 20 bt.% akan mengakibatkan ketidaksempurnaan dalam penyebaran serta terdapat gumpalan pengisi ke dalam komposit. Ulasan kajian ini adalah untuk mengenal pasti pengaruh penambahan kandungan pengisi bagi bahan konduktif polimer komposit menggunakan percetakan 3D terhadap sifat elektrik, terma dan mekanikal. Ulasan ini merangkumi penggunaan bahan konduktif polimer komposit yang dibentuk melalui kaedah Pemodelan Pemendapan Bersatu (FDM) yang merupakan salah satu daripada percetakan 3D. Proses percetakan 3D yang dilapisi oleh lapisan demi lapisan akan menghasilkan struktur objek yang kompleks serta proses pembuatan yang cepat telah memberi sumbangan kepada penghasilan konduktif polimer komposit. Kekonduksian elektrik dapat ditingkatkan dengan penambahan kandungan pengisi sehingga 50 bt.%. Selain itu, penambahan kandungan pengisi yang dapat menawarkan permukaan yang lebih berkesan antara permukaan pengisi dan matriks telah meningkatkan suhu penghabluran (Tc) dan suhu puncak penghabluran (Tp) dalam sifat terma serta nilai kekuatan tegangan dan modulus dalam sifat mekanik. Penambahan kandungan pengisi polimer komposit sehingga 50 bt.% dapat meningkatkan kesesuaian bahan untuk digunakan pada peranti elektronik

Rheological test of flowability and diffusion behavior of carbon fibre reinforced polyamide

Various materials have been produced to be used as feeder material in 3D printing application to obtain the level of mechanical properties and physical properties of a product. Before to its usage as a 3D printing feed material, polyamide-reinforced carbon fibre composites were investigated for flowability and diffusion behaviour. Using a heated nozzle to transform polymer filament into a semi-liquid that is extruded to create a structure layer-by-layer, the primary issue to prevent is delamination. For the success of this study, there are 2 main methods, namely to study the physical properties of carbon fibre reinforced polyamide composites against the composition of 20 wt.% carbon fibre and to study the temperature and rheological load on the rheological properties. Rheological test analysis found that the material flowability of 20 wt.% CF/PA at temperature parameters 210 °C, 230 °C and 250 °C against rheological loads (40, 60, 80) N recorded a range of viscosity values between 48.80 Pa.s to 97.88 Pa.s and shear rate value range between 19700 s-1 to 20270 s-1. Parameter optimization analysis using Taguchi method found that the largest factor contributing to the viscosity of CF/PA composite feed material was the addition of load applied. Moreover, the microstructural results of CF/PA composites show that smoother surfaces and good polymer structural bonding occur at an extrusion temperature of 250 °C. As a result, the rheology-derived flow rate may be used to tackle the problem of delamination and layer separation in 3D printin

The effect of kenaf filler reinforcement on the mechanical and physical properties of injection moulded polypropylene composites

Natural fibres potentially offer better reinforcement to improve the mechanical and physical properties of polymer composites. However, these natural materials at this stage are not fully explored yet due to the fibres themselves have limited heat resistance and are quite sensitive to moisture. This limitation will weaken the adhesion when interacting with thermoplastic matrices during the processing of composites. Therefore, the main purpose of this study is to investigate inherent strength characteristics among kenaf (core and bast) fillers as a reinforcement in polypropylene composites at various geometries and loadings via the injection moulding process. The composite materials consisted of kenaf with the geometric core filler of the 20 mesh (992 μm), 40 mesh (460 μm) and bast filler (166.9 μm) were mixed with polypropylene based on the filler loadings of 10 up to 40 wt. %. The results showed that bast filled composites had the highest tensile strength of 19.52 MPa at 30 wt. %, compared to core filled composites. Instead, 20 mesh core filled composites were obtained had the highest flexural strength which values were 25 MPa and 29 MPa at 20 wt. % and 30 wt. %, respectively. While 40 mesh core filled composites had the highest values of 25.35 MPa at 40 wt. % of filler loading compared to bast filled composites. SEM micrograph images showed the good interfacial bonding of core filler which surrounded by PP leading to diffusion and permeation of bonding. In conclusion, the use of kenaf (core and bast) fillers as a reinforcement in composite materials is reasonable to maximise the use of fibre from natural sources

Simulation analysis of graphene addition on polymeric composite

Natural fibres in composite materials, such as kenaf fibres, are used to reinforce polypropylene (PP) due to their light weight and high mechanical performance required in various applications, such as automotive. Although natural fibres seem to be the most promising material, manufacturing parameters and material composition are crucial to determining balanced output performance. Therefore, this study provides essential knowledge on defining the parameters and the effect of addition of graphene content to kenaf fibres composites using computer simulation via Abaqus CAE software. Detailed analyses were compared with the experimental data of Young’s modulus and tensile strength. General static and dynamic explicit analyses were conducted using Abaqus CAE simulations, and set at 40 wt. % kenaf fibres, 0, 1, 3, and 5 wt. % graphene. Short kenaf fibres were utilised together with graphene nanoplatelets and prepared using a hot-pressing technique with the temperature set at 190 °C and pressure of 5 MPa for 5 min. The findings indicated that the simulation and experimental data from previous studies data congruent which is Young’s modulus and tensile strength increased with addition of graphene content. Thus, the simulated data could predict the experimental mechanical performance, in which 24 MPa of tensile strength was recorded for 3 wt. % of graphene additions

Reinforced composite as a feeder for 3D printing application

Kenaf fibre has a low environmental impact because it is recyclable, light density and strong to be used as a product. Natural fibres, especially kenaf fibre, are undertilised and understudied in 3D printing technology. 3D technology is gaining traction to replace traditional methods because it saves cost and production time. This study focuses on producing kenaf composite materials that can be used as a feeder for 3D printing. This study used different fibre compositions (20,25,30) % mixed with polypropylene set at 190 ˚C temperature, 45 rpm speed, and 25 minutes. The material was left to cool to form clot to go through for the rheology process, and injection analysis was performed using Autodesk Moldflow Insight 2014. This study showed that a mixing temperature of 190 ˚C was suitable for forming a high shear mechanism. Kenaf fibre was treated in an alkaline solution of NaOH to 3 hours to prevent damage to the surface of the filler fibre in composites. Kenaf fibre at 6% of NaOH solution reaches a higher value for mechanical strength and roughness, resulting in better mechanical interlocking between the fibres and the matrix. In addition, analysis from Autodesk Moldflow Insight 2014 reveals that at 200 ˚C injection temperature pretend, the shear rate is higher creating smoother melt flow characteristics

Pengoptimuman parameter sonikasi dan pengacauan magnetik bagi mendapatkan penyerakan sebati komposit kuprum-grafin berdasarkan sifat morfologi

Kajian mengenai grafin kini semakin meluas disebabkan sifat kebolehaliran terma yang mampu meningkatkan potensi bahan komposit. Penambahan grafin dalam matriks kuprum dikaji dengan menggunakan gabungan bahan pengikat iaitu polietilena glikol (PEG), polimetil metakrilat (PMMA) dan asid stearik. Penggunaan grafin sebagai bahan pengisi dalam matriks kuprum merupakan pendekatan baru yang bertujuan untuk meningkatkan kebolehaliran terma produk yang dihasilkan. Namun, penambahan grafin dalam matriks kuprum boleh menyebabkan ketidaksamarataan zarah komposit kerana penggumpalan zarah-zarah grafin. Oleh itu, kaedah sonikasi dan pengacauan magnetik semasa proses pra-campuran digunakan bagi menghasilkan bahan suapan yang sebati dan penyerakan grafin yang lebih baik tanpa penggumpalan. Suhu proses sonikasi telah ditetapkan pada 55˚C dengan masa sonikasi yang berbeza iaitu 30 minit, 60 minit dan 90 minit. Bagi proses pengacauan magnetik, parameter yang digunakan adalah 55˚C, selama 21 jam pada kelajuan yang berbeza iaitu 300, 350 dan 400 rpm. Analisis imej Pancaran Medan Mikroskopi Elektron Pengimbasan (FESEM) dan Pemetaan EDX telah dijalankan bagi mengkaji penyerakan grafin dalam komposit kuprum grafin. Keputusan menunjukkan hasil yang lebih baik diperoleh selepas proses sonikasi dan pengacauan magnetik dijalankan. Penyerakan terbaik yang lebih seragam dan sebati diperoleh pada masa sonikasi 60 min dan pengacauan magnetik pada kelajuan sederhana iaitu 350 rpm. Zarah grafin didapati kurang bertumpu pada satu tempat dan penggumpalan semula juga tidak berlaku. Penyerakan sebati ini menjadikan hubungan antara muka zarah-zarah grafin dan kuprum menjadi lebih baik seterusnya mampu mengurangkan keliangan bagi penghasilan jasad akhir

Quantitative roughness characterization of non-gaussian random rough surfaces by ultrasonic method using pitch-catch and pulse-echo configurations

Fundamental study to quantitatively evaluate not only the root-mean-square (rms) roughness Rq but also skewness Rsk of non-Gaussian random rough surfaces by ultrasonic method is presented. In this work, Johnson distribution together with Kirchhoff theory have been employed to derive a newly proposed Johnson characteristic function, which provides a theoretical relationship among ultrasonic reflection coefficient, Rq and Rsk. Based on the characteristics of such relationship, an effective ultrasonic measurement method consisting of a pitch-catch and a pulse-echo configuration to quantitatively characterize Rq and Rsk has been proposed. A general guideline for such characterization method has also been suggested. The validation of the proposed method has then been conducted numerically in the case of an air-coupled ultrasound. Good agreements between the numerically estimated Rq and Rsk and the corresponding reference values thus confirm the validity of the proposed metho

Antibacterial mechanism with consequent cytotoxicity of different reinforcements in biodegradable magnesium and zinc alloys : A review

Benefits achieved by the biodegradable magnesium (Mg) and zinc (Zn) implants could be suppressed due to the invasion of infectious microbial, common bacteria, and fungi. Postoperative medications and the antibacterial properties of pure Mg and Zn are insufficient against biofilm and antibiotic-resistant bacteria, bringing osteomyelitis, necrosis, and even death. This study evaluates the antibacterial performance of biodegradable Mg and Zn alloys of different reinforcements, including silver (Ag), copper (Cu), lithium (Li), and gallium (Ga). Copper ions (Cu2+) can eradicate biofilms and antibiotic-resistant bacteria by extracting electrons from the cellular structure. Silver ion (Ag+) kills bacteria by creating bonds with the thiol group. Gallium ion (Ga3+) inhibits ferric ion (Fe3+) absorption, leading to nutrient deficiency and bacterial death. Nanoparticles and reactive oxygen species (ROS) can penetrate bacteria cell walls directly, develop bonds with receptors, and damage nucleotides. Antibacterial action depends on the alkali nature of metal ions and their degradation rate, which often causes cytotoxicity in living cells. Therefore, this review emphasizes the insight into degradation rate, antibacterial mechanism, and their consequent cytotoxicity and observes the correlation between antibacterial performance and oxidation number of metal ions