About Residual Stress State of Castings: The Case of HPDC Parts and Possible Advantages through Semi-Solid Processes

Nowadays, one of the most crucial focus in the aluminium-foundry sector is the production of high-quality castings. Mainly, High-Pressure Die Casting (HPDC) is broadly adopted, since by this process is possible to realize aluminium castings with thin walls and high specific mechanical properties. On the other hand, this casting process may cause tensile states into the castings, namely residual stresses. Residual stresses may strongly affect the life of the product causing premature failure of the casting. Various methods can assess these tensile states, but the non-destructive X-Ray method is the most commonly adopted. Namely, in this work, the residual stress analysis has been performed through Sinto-Pulstec μ-X360s. Detailed measurements have been done on powertrain components realized in aluminium alloy EN AC 46000 through HPDC processes to understand and prevent dangerous residual stress state into the aluminium castings. Furthermore, a comparison with stresses induced by Rheocasting processes is underway. In fact, it is well known that Semi-Solid metal forming combines the advantages of casting and forging, solving safety and environmental problems and possibly even the residual stress state can be positively affected.

Investigation on Mechanical and Wear Behaviors of LM6 Aluminium Alloy-Based Hybrid Metal Matrix Composites Using Stir Casting Process

In this investigation, aluminium-silicon-based alloy (LM6) with the addition of (0, 2.5, 5, and 10%) copper-coated short steel fiber and 5% boron carbide (B4C) element-strengthened composites was fabricated by the stir casting method. Mechanical properties and tribological behaviors of LM6-based hybrid composites were investigated, and microstructures of different castings were examined by an image analyzer. The test was conducted at different loads (10, 20, 30, and 40 N) and different sliding spaces (500, 1000, 1500, and 2000 m), respectively. The results revealed that the sample loaded with 10% of reinforcement recorded the highest tensile strength of 231 MPa. On the other hand, the hardness value increased from 71 to 144 BHN, when 15% of reinforcement was added to the sample. It was also noted that 10% copper-coated steel fiber improved wear resistance up to 50% when compared to LM6. A field emission scanning electron microscope was employed to observe the morphology of the worn surfaces of composites at different sliding distances and load conditions. The hybrid composite revealed that the combination of both short steel fibers and reinforcement of ceramic particles enhanced the mechanical properties, obtaining superior wear resistance.

Structure Optimization of Semi-Solid Die Cast Steering Knuckle and its Experiment Verification

Steering knuckles are vital functional and structural components in automotive suspension systems, requiring high strength, high ductility, and complex shapes. In this study, an aluminum alloy knuckle with the semi-solid die casting process was developed to replace the conventional steel components. This research aims to optimize product design based on both structural simulation and casting process simulation to avoid defects and to meet mechanical requirements. Furthermore, the optimal design solutions need to be verified through the filling experiments and defect analysis. The results show that the removal of support rib located in the thick area of the shock absorber mounting arm is helpful to avoid the rewelding defects in the filling frontier of the SSM melt. Besides, the position of the steering rod is of medium thickness, and two ribs from different directions come together to support that area. Rewelding defects were detected when two ribs come together. To avoid rewelding defects in local areas of steering rod position, the ribs were reduced to uniform wall thickness. Thus, the local flow state was modified and the SSM melt was reinforced shear action. Ultimately, by controlling all the processes of the SSM die casting process, the high performance of aluminum knuckle was successfully developed.

Treatment of infantile idiopathic scoliosis using a novel thoracolumbosacral orthosis: a case report

Background The recommended treatment for mild to moderate infantile idiopathic scoliosis curves involves serial casting. There are concerns, however, regarding the safety of repeated casting in very young children owing to the requirement for anesthetization during the casting process. Very little research has been conducted on the influence of bracing as an initial treatment for scoliosis in this age group. This report details the successful treatment of a large thoracic curve using a thoracolumbosacral orthosis in an infant diagnosed with infantile idiopathic scoliosis. Case presentation The Dutch-Australian patient presented at 11 weeks of age with a 44° thoracic scoliosis and a rib vertebral angle difference of 14°. The history and physical examination failed to reveal a cause of the curvature, and a diagnosis of infantile idiopathic scoliosis was made. The patient was prescribed a thoracolumbosacral orthosis (ScoliBrace) to be worn on a part-time basis for a period of 8 months. At the end of the bracing program, the patient’s curve had been reduced to 7° and a rib–vertebral angle difference of 0°. A final follow-up of the patient at 2 years after the cessation of treatment revealed no evidence of scoliosis. The parents were compliant with the bracing protocol and reported that the treatment was tolerated by the infant. Conclusion The use of an orthosis as a standalone treatment in this patient resulted in significant reduction in a large thoracic scoliosis. Based on the results witnessed in this patient, further investigation into bracing as an alternative to casting is warranted.

Analysis of Mechanical Behavior of Al6061 Composites Reinforced with Titanium Dioxide

Aluminum alloys are used low density good mechanical properties, better wear resistance as compared to predictable metals and their alloys. The industries are continuing in demand to develop light weight material, inexpensive and strong material which has led to the growth of aluminum alloy metal matrix composites. The aluminum based metal matrix composites have been moulded using TiO2 as reinforcement materials using the stir casting process. The hardness and tensile strength have been calculated addition to the TiO2 in Aluminium matrix improves the hardness of the material. The tensile strength and hardness increases above 4% of titanium oxide particles in the matrix.

Production and Assessment of AZ91 Reinforced with Nano SiC through Stir Casting Process

Magnesium, a light weight alloy used in multiple engineering industrial applications because of its good Physical, Chemical and Thermal characteristics. Magnesium composites play an important role in partial or entire replacement of numerous alloys.This current work deals with Nano silicon carbide of about 100nm was incorporated with AZ91magnesium alloy through liquid state composite processing. Two samples are made using 0% Nano SiC and 3% Nano SiC and are characterized through tensile test in Universal Testing Machine, Micro hardness test in Vickers hardness tester and Microstructure in Optical Microscopy. From the study it was clear that there is a peak increase in hardness of about 36% when compared to as casted AZ91.

The Effect of Different Fibre Lengths on the Mechanical Properties of Biocomposites

Kenaf is a nonwoody fibrous plant, and its fibre can be potentially used as a reinforcement in the matrix to produce biocomposite materials. The properties of biocomposite materials are highly dependent on the reinforcing material and the matrix used as a binder. This study used kenaf fibre as a reinforcing material with different compositions (10, 20, and 30 wt.%) and different fibre lengths (1 cm and 3 cm) in the matrix using the casting process. Low viscosity epoxy resin (635 thin epoxy resin) with a viscosity of 6 poise was used as the matrix. The results showed that the highest flexural strength, impact strength and shore hardness were obtained at a 30 wt.% kenaf fibre composition with a 1-cm kenaf fibre length, namely, 85 MPa, 338 KJ/m2 and 98 SHD, respectively. The length of the fibre in the matrix affects the mechanical properties of the resulting biocomposite. This condition is caused by kenaf fibres with a length of 1 cm being more dispersed in the matrix than fibres with a length of 3 cm.

BIODEGRADATION OF MANGO SEED STARCH FILMS IN SOIL

The typical petroleum-based plastics have triggered environmental problems. For this purpose, biodegradable polymers such as starch are often used to manufacture biodegradable plastics. At present, the efforts are underway to extract starch as a promising biopolymer from mango seeds and subsequently to produce a biodegradable starch film to be used as plastic packaging. As such, in this work, glycerol-plasticized mango starch films were prepared using a solution casting process, using different amounts of citric acid as a cross-linking agent. The blend ratio of starch to glycerol was set at 3:5 wt. each, while the amount of citric acid ranged from 0 to 10 wt.%. Then, the casted films underwent 21 days of soil burial testing in the natural environment to determine their biodegradability behavior. The soil burial test is one of the common methods chosen to assess the biodegradability of polymers. The idea is that, by burying samples in the soil for a fixed time, samples are exposed to microorganisms (i.e. bacteria and fungi) present in the soil that serve as their food source. This is somehow likely to facilitate the process of deterioration. For this reason, the soil burial test can be regarded as an authentic approach to the process of deterioration in the natural environment. The films' susceptibility to biodegradation reactions was assessed within intervals of seven days through their physical appearance and weight loss. Interestingly, it was found that the cross-linked starch films have been observed to degrade slower than the non-cross-linked starch films as burial time progressed. The declining percentages of weight loss, as well as the presence of microorganisms and eroded surface on the films observed by SEM, explained the degradation behavior of the cross-linked starch films compared to the non-cross-linked starch films. Hence it is believed that cross-linked starch-glycerol films are biodegradable in soil, henceforth, the potential to be commercialized as a biodegradable packaging material soon. At the same time, this plastic packaging is expected to be recognized as a value-added product since the raw materials ergo mango seeds utilized to develop this product are from waste, therefore, environmentally friendly. ABSTRAK: Plastik yang berasaskan petroleum telah mencetuskan masalah persekitaran. Untuk tujuan ini, polimer biodegradasi seperti kanji sering digunakan untuk membuat plastik yang boleh terurai. Pada masa ini, usaha sedang dilakukan untuk mengekstrak pati sebagai biopolimer yang menjanjikan dari biji mangga dan kemudiannya menghasilkan filem pati yang terbiodegradasi untuk digunakan sebagai kemasan plastik. Oleh yang demikian, dalam karya ini, filem pati mangga plastik-gliserol disusun menggunakan proses pemutus larutan, menggunakan jumlah asid sitrik yang berlainan sebagai agen penghubung silang. Nisbah campuran pati dan gliserol ditetapkan pada 3:5 wt.% masing-masing, sementara jumlah asid sitrik berkisar antara 0 hingga 10 wt.% berat. Kemudian, sampel plastik tersebut ditanam di dalam tanah selama 21 hari di persekitaran semula jadi untuk menentukan tingkah laku biodegradasinya. Ujian penguburan tanah adalah salah satu kaedah biasa yang dipilih untuk menilai biodegradasi polimer. Ideanya adalah bahawa, dengan menguburkan sampel di tanah untuk waktu yang tetap, sampel terdedah kepada mikroorganisma (iaitu bakteria dan jamur) yang terdapat di dalam tanah yang berfungsi sebagai sumber makanan mereka. Ini mungkin memudahkan proses kemerosotan. Atas sebab ini, ujian penguburan tanah dapat dianggap sebagai pendekatan yang sahih terhadap proses kemerosotan di persekitaran semula jadi. Kerentanan filem terhadap reaksi biodegradasi dinilai dalam selang waktu tujuh hari melalui penampilan fizikal dan penurunan berat badan. Menariknya, didapati bahawa filem-filem pati berangkai silang telah dilihat menurun lebih perlahan daripada filem-filem pati yang tidak bersilang ketika masa pengebumian berlangsung. Peratusan penurunan berat badan yang menurun, serta kehadiran mikroorganisma dan permukaan yang terhakis pada filem yang diperhatikan oleh SEM, menjelaskan tingkah laku degradasi filem pati berangkai silang berbanding dengan filem pati yang tidak bersilang. Oleh itu, dipercayai bahawa filem kanji-gliserol berangkai silang dapat terbiodegradasi di dalam tanah, dan seterusnya, potensi untuk dikomersialkan sebagai bahan pembungkusan yang boleh terurai tidak lama lagi. Pada masa yang sama, pembungkusan plastik ini diharapkan dapat diakui sebagai produk bernilai tambah kerana bahan mentah ergo mangga yang digunakan untuk mengembangkan produk ini adalah dari sisa, oleh itu, mesra alam.

Synthesis and Characterization of Mechanical Properties of AA8014 + Si3N4/ ZrO2 Hybrid Composites by Stir Casting Process

Lightweight materials are extremely needed for the manufacturing of industrial parts and are used in aerospace, automobile body shops, biomedical instruments, etc. Aluminium alloy is one of the light-weight materials, and it fulfills the industrial demands based on their natural strength/stiffness, enhanced temperature permanence, superior wear, and corrosion resistance. This experimental work considered aluminium alloy (AA8014) with reinforced particles of silicon nitride (Si3N4) and zirconium dioxide (ZrO2) for preparing aluminium hybrid composites. Hybrid composites are prepared by a stir casting process involving different process parameters. L27 orthogonal array is used for optimizing the stir casting parameters with the assistance of the statistical Taguchi approach. Stir casting parameters are the percentage of reinforcement (4%, 6%, and 8%), stir speed (400 rpm, 500 rpm, and 600 rpm), stir time (20 min, 25 min, and 30 min), and molten temperature (700 oC, 800 oC, and 900 oC). Mechanical performance such as wear and microhardness of the hybrid composites is evaluated. Minimum wear and higher microhardness are encountered at a percentage of reinforcement = 6%, stir speed = 400 rpm, stir time = 30 min, and molten temperature = 900°C. In wear analysis, the percentage of reinforcement highly influences the wear properties (7.06% contribution). In microhardness analysis, molten temperature parameter is the extreme influencer (11.15% contribution).