Material Engineering

This contribution describes experimental results under combined loading of specimens manufactured from common construction steel 11523. Specimens were gradually loaded by amplitude of the torque, then by combination of torque and tension prestress. The last set of specimens was loaded in combination of torque and inner overpressure. To obtain the required input values the stress-strain analysis of specimens by finite element method in software Ansys was performed within the last experiment. For evaluation of the results the Fuxa's criterion was applied. The performed experiments and their results embody a good agreement with bellow mentioned conjugated strength criterion. The experiments were performed on reconstructed testing machine equipped by pressure chamber.

This project involved the design and assembly of a functional light dimmer circuit using a Silicon Controlled Rectifier (SCR) and a potentiometer on a printed circuit board. The system utilizes the principle of phase control, where the potentiometer adjusts the SCR’s triggering point to vary the average power delivered from a 220V AC supply to an incandescent lamp. Experimental results confirmed that the circuit operates reliably, providing smooth transitions in brightness and validating the practical application of SCRs in power regulation.

In CO2 mould hardening, once mould cavity is produced, CO2 gas is passed through it which reacts with sodium silicate to make the mould harder. CO2 moulding process due to its ability to produce harder moulds is widely used for casting variety of metals and especially high density alloys like steels. The study is focused on development of a system for optimization of CO2 consumption & process time. In previous practice, the CO2 from CO2 cylinder was directly passed into mould at lower temperature than desired & higher pressure due to uncontrolled throttling through air gun which resulted in loss of CO2, non-uniform mould strength & more process time. To overcome these problems, a gassing system has been developed which reduces CO2 consumption as well as process time. Also, an automation of the system is proposed to time the gas flow in more efficient manner.

The power losses of the worm gearbox, which are expressed through the efficiency, depend on various influencing factors, of which the operating conditions play a very important role. In order to analyze the influence of operating conditions on power losses, experimental tests of the efficiency of the single-stage worm gearbox on the AT200 device were performed. The experimental worm pair consists of a worm made of improved steel 42CrMo4 and a worm gear made of tin bronze CuSn12. The tests were carried out by varying two values of the rotational speed of 1500 min-1 and 2500 min-1 and five load levels (output torques), where mineral oil with a viscosity of 1000 mm2/s was used as a lubricant. After the experimental tests, the power losses in the meshing of the gear teeth, as well as the power losses in the bearings and shaft seals, were calculated. Based on the obtained results, it is concluded that with the increase in the circumferential speed, the values of the efficiency increase between 3% and 5%. On the other hand, at a higher circumferential speed there is an increase in power losses in the gear meshing between 53% and 55% and an increase in power losses in the bearings between 47% and 58%, taking into account all test conditions.

Rising adoption of low-voltage DC electronics demands robust overvoltage protection for wide input ranges (3-30V). We address this with an integrated module combining: (1) Astable boost converter (<5V activation), (2) LM317 regulator (5V±1.5% stability), and (3) LM339 comparator-driven cutoff (>5.1V, <1.2 ms response). NI MULTISIM simulation and hardware validation confirm ≤ ±1.5% output deviation across solar/battery/DC sources (0-800 mA). The design outperforms discrete solutions with 57% cost reduction vs. buck-boost ICs, seamless transitions, and 30V surge resilience-establishing a scalable framework for resilient power management in deployable systems.

An experimental program was conducted to investigate the shear strength of elastic end-web panels of steel plate girders strengthened with intermediate-modulus carbon fiber-reinforced polymers, CFRP, strips. Test parameters included; number of strips, aspect ratio of end-web panel and width-to-thickness ratio of web plate. Twelve plate girder specimens composed of mild-steel were loaded in a four-point bending test till failure. The girders were proportioned so that the load capacity was governed by elastic web buckling. Four specimens were not strengthened to serve as reference girders whereas the remaining specimens were strengthened by applying CFRP strips in the diagonal tension direction on one or both sides of the web. Test results indicated that the buckling strength of strengthened specimens was not improved, however, the ultimate shear strength increased by 6% to up to 120% due to significant increase in post-buckling strength. The increment in post-buckling strength due to pasting CFRP strips on web plate was several multiples of that of reference girders and was reduced when slender web plates or long end-web panels were utilized. In addition to higher ultimate shear capacity, it was observed that vertical deflections, out-of-plane displacements of the web and bending curvature of transverse stiffeners of strengthened girders were reduced at ultimate load. It was concluded that the ultimate shear strength of elastic end-web panels was successfully improved using intermediate-modulus CFRP strips. On the other hand, current design rules adopted by current AISC specifications need to be revised to account for post-buckling strength of elastic end-web panels.

Artisanal green sand casting of aluminium pots is a highly profitable avenue for small to medium scale self-employment as well as technological and economic development in Kaduna metropolis. The casting process had nevertheless been observed to be characterized with reruns before attaining defect-free castings. This was seen to be capable of increasing the unit casting cost and lowering productivity and profitability and morale of the involved shop floor personnel. The aim herein is to statistically provide basic insight into the total defects level of artisanal cast aluminium pots at Panteka Tudunwada, the main area of aluminium pot casting activities in Kaduna metropolis. The statistical analysis was conducted with Microsoft Excel tools using 10-week collated number of defect-free and defective pot castings produced from the 10 most productive foundry shops in the area. Collated information indicates that within the 10-week period, 25611 defect-free and 9639 defective pot castings were produced in the area. Analyses of the information indicated that the number of defective pot castings varied from shop to shop to overall level of 27.3%. This defect level was seen to be rather high compared to what is obtainable from foundries with Research and Development (R&D) units where better control of casting variables are achieved through research efforts, and defects levels are usually kept in 3 to 15% range. The analyses also showed that the skills used in controlling foundry variables were not the same among the artisans; and there is high correlation between the number of defective and defect-free pot castings within the foundry shops. The identified common types of defects that resulted in the defective castings included open blow holes, burnt skin, cracks, and hard spots. The information is hereby posited for any improvement strategy in the pot-casting business and for relevant research interests.

The reliability of the structural performance of any given structure is affected by both in-service loading and material deterioration due to environmental attack. In this paper, probabilistic assessment of reinforced concrete members exposed to chlorine ingress was undertaken. A simply supported reinforced concrete slab was specifically used for the investigation. The mathematical models of capacity loss of reinforcing steel under corrosion, developed elsewhere, were incorporated in the analysis. The uncertainties in structural resistance and the applied loading were fully accommodated using probabilistic method. Limit state function for the flexural capacity of the slab was developed and evaluated using first order reliability method (FORM). The entire process was implemented through a developed program using MATLAB.

Artisanal green sand casting of aluminium pots is a highly profitable avenue for small to medium scale self-employment as well as technological and economic development in Kaduna metropolis. The casting process had nevertheless been observed to be characterized with reruns before attaining defect-free castings. This was seen to be capable of increasing the unit casting cost and lowering productivity and profitability and morale of the involved shop floor personnel. The aim herein is to statistically provide basic insight into the total defects level of artisanal cast aluminium pots at Panteka Tudunwada, the main area of aluminium pot casting activities in Kaduna metropolis. The statistical analysis was conducted with Microsoft Excel tools using 10-week collated number of defect-free and defective pot castings produced from the 10 most productive foundry shops in the area. Collated information indicates that within the 10-week period, 25611 defect-free and 9639 defective pot castings were produced in the area. Analyses of the information indicated that the number of defective pot castings varied from shop to shop to overall level of 27.3%. This defect level was seen to be rather high compared to what is obtainable from foundries with Research and Development (R&D) units where better control of casting variables are achieved through research efforts, and defects levels are usually kept in 3 to 15% range. The analyses also showed that the skills used in controlling foundry variables were not the same among the artisans; and there is high correlation between the number of defective and defect-free pot castings within the foundry shops. The identified common types of defects that resulted in the defective castings included open blow holes, burnt skin, cracks, and hard spots. The information is hereby posited for any improvement strategy in the pot-casting business and for relevant research interests.

In recent years, invisibility has become a research area of increasing interest due to the advances in material engineering. It may be possible to achieve invisibility through cloaking devices by coating the body using one or more layers of materials with the proper electromagnetic properties. By using techniques associated to plasmonic cloaking it is maybe possible to obtain also invisibility for small objects with several layers of homogeneous materials working from inside the object. We demonstrate numerically that it is, therefore, possible to achieve invisibility through an inner system based on scattering cancellation techniques.

ABSTRAK Perkembangan industri kelapa sawit dewasa ini semakin pesat. Salah satu hasil industri kelapa sawit yang kerap menjadi limbah adalah Tandan Kosong Kelapa Sawit (TKKS). TKKS ini dapat diolah menjadi serat yang akhirnya dapat dimanfaatkan sebagai material engineering. Tujuan penelitian ini adalah untuk menganalisa mutu fisik dan respon mekanik yang diterima genteng komposit dan genteng komersil akibat beban impak jatuh bebas. Spesmen yang akan di uji berukuran 380 × 235 × 20 mm. kekuatan mekanik material diperoleh dengan cara melakukan pengujian yaitu menggunakan alat uji impak jatuh bebas. Dari hasil analisa mutu fisik, berat genteng dapat direduksi hingga 44,89% dan memiliki berat rata-rata 1,518 kg, rata-rata area porositas pada genteng komposit adalah 55,85%, dan hasil uji rembesan air tidak ditemukan adanya kerusakan struktur dan rembesan air, namun penyerapan air hingga 62%. Pada pengujian impak jatuh bebas diperoleh gaya impak yang diterima genteng komposit pada ketingg...

Tandan Kosong Kelapa Sawit (TKKS) memiliki nilai untuk direkayasa menjadi material alternatif yang dapat dimanfaatkan dengan alasan masih berlimpahnya bahan baku, mudah diolah menjadi bentuk serat halus, dapat didaur ulang, bebas korosi, tahan dan mampu menyerap suhu panas, serta ekonomis, seperti untuk pembuatan papan partikel. Tujuan penelitian ini untuk menganalisa respon mekanik produk batako ringan dari bahan concrete foam diperkuat serat tandan kosong kelapa sawit (TKKS) akibat beban impak jatuh bebas. Pembuatan batako ringan menggunakan mortar; semen = 30%, pasir = 45%, air = 15%. Lalu ditambahkan bahan pengembang = 7%. Bahan concrete foam ini diberi penguat matriks berupa serat TKKS = 3%. Dimensi batako ringan 600×200×100 mm. Metode penelitian yang dilakukan adalah metode penelitian eksperimen. Data diperoleh melalui pengujian makrostruktur dan impak jatuh bebas. Hasil pengujian impak jatuh bebas ketinggian 0,5 m tegangan rata-rata 0,0035 MPa , tegangan lentur 8,1 MPa dan en...

Ab stract The ki netic study of hydration pro cess of sintered CaO pellets by X-Ray dif frac tion method was stud ied in this work. Sintered CaO pel lets were in tro duced in opened sys tem, which was continuosly sup plied with wa ter steam. The actual tem per a ture as well as rel a tive hu mid ity were changed by tem per a ture change in wa ter ther mo stat. Hydration exper i ments were real ised at the se lected rel a tive humidities of 98, 57, 37 and 21 %. At cho sen in ter vals the pel lets were sub mit ted to X-Ray dif frac tion phase anal y sis. The observed char ac ter is tics was the rel a tive in ten si ties I (101) Ca(OH)2 / I (200) CaO ra tio. This re veals the for ma tion of the new phase Ca(OH) 2 and the miss ing phase CaO at the pel let sur face. It fol lows from ex per i men tal re sults that tem per ature plays more im por tant role in the hydration pro cess as rel a tive hu mid ity. The ap par ent ac ti va tion en ergy E A of 3.6 kJmol-1 was de ter mined. Based on achieved ex per i men tal re sults the nu cle ation (diffusional) con cept of hydration pro cess was spec i fied.

A 0.2%C steel was subjected to quenching and tempering heat treatment in this work. During both oil and water quenching hardness of the as received material reasonably increased, reaching a maximum from 53.75-68.65 HRA during water quenching. Ultimate tensile strength also increased to a maximum of 1096.38MPa from 853.89MPa corresponding to the as received material. Tempering of the quenched specimen resulted in a decrease in both the hardness and tensile strength over the entire temperature range studies. Also the effect of tempering on ductility of the quenched steel was not very clear.

A methodology for assessing the commercial potential and thus, the business case, for a materials innovation was presented in Ž. a companion paper Maine and Ashby, 'An investment methodology for materials' Mater Design, 2002. The investment Ž. methodology for materials IMM is here applied to a recent innovation ᎏ that of metal foams. Several processes for making foamed aluminium are now in the process of scale-up for large scale production, although none, at this point in time, have found a viable commercial application. Here one class of application ᎏ that of energy absorption in automotive design ᎏ is explored in depth, examining technical viability, market structure and the probability of value capture, illustrating IMM in operation. The method helps direct R& D programs, informs business decision-making and guides investment policy-making.

Lightweight materials are the great demand in the aerospace sector to enhance system performance. The automotive, aerospace sector has utilized the composite materials to strengthen the physical and mechanical qualities of less weight materials and to improve their functionality. In this study, three different base matrix alloy combinations comprise the specimens being examined. Selective laser melting was used to combine boron carbide, graphite, and iron oxide powder (2.5, 5 and 7.5 wt.%) with an aluminium alloy matrix. Use the ASTM B-557M standards, specimens are prepared for testing the hybrid composite including such wear, and scanning electron microscopy. The purpose of the current study is to use Taguchi-based gray relational analysis (TGRA) to improve the wear parameters of aluminium matrix composite. Grey relationship study has shown that the optimal combinations for determining the hybrid composite's wear rate and coefficient of friction are 40 N load (level 3), 6 m/s sliding speed (level 3), and 1000 m sliding distance (level 1). Hybrid composites are said to have better wear properties and to offer enhanced components for the automotive, marine, and aerospace industries as compared to earlier metal matrix composites.

In this paper, the structural, elastic, and electronic properties of RIn3 and RSn3 (R = Sm, Eu, Gd) compounds have been investigated using the full potential linearized augmented plane wave plus local orbital method within the density functional theory. The structural properties are investigated using the LDA, GGA, and the band correlated LDA+U and GGA+U schemes. The lattice parameters are in good agreement with the available experimental results and the divalent state of Eu is also verified. The spin-orbit coupling is included in order to predict the correct electronic properties and splitting of 4f states of the rare earth elements is also incorporated. We calculated Bulk modulus, shear modulus, Young&#39;s modulus, anisotropic ratio, Kleinman parameters, Poisson&#39;s ratio, Lame&#39;s co-efficient, sound velocities for shear and longitudinal waves, and Debye temperature. We also predict the Cauchy pressure and B/G ratio in order to explore the ductile and brittle behaviors of th...

Ajaokuta Steel Plant is the largest integrated steel complex in black Africa, located along the west bank of river Niger in Nigeria. Though full take off was delayed, it is expected that when it becomes operational it will attract lots of ancillary and small to heavy industries to the area. These would require large foundry plants for the spare and completely knocked down parts. This study investigated foundry properties of river Niger sand behind the steel plant for its possible uses in sand casting in the foundries. Bentonite and kaolin were used as binders. Experimental techniques which included the mechanical sieve analysis, determination of clay content and refractoriness of river Niger sand and mechanical analyses consisting of green/dry compressive, green hardness, permeability and shatter index tests of moulded specimens were conducted to measure foundry properties of the sand. Its physiochemical properties showed it is alumino-silicate with low fusion temperature of 1380°C,...

The most effective economical baking conditions were determined for foundry cores bonded with the grade 3 Nigerian acacia species exudates. Silica sand base cores bonded with the material were oven baked at temperatures ranging from 160 to 250ºC for varying periods oven cooled and then subjected to tensile strength tests to ascertain the best baking conditions for different alloy castings. The experimental core specimens were in accordance with foundry test standard, shaped like figure number eight. They were tested with standard universal strength machine equipped with attachment for gripping the cores and an instantaneous meter from which the test values were read. The result were compared with established standard foundry core property table which showed that the class V iron/steel cores are best made with 3% acacia bonded silica sand baked at 160ºC for 1 h. For magnesium cores, sand bonded with 4.5% acacia baked at 160ºC for 1-2 h was optimum. For class IV iron/steel cores 4.5% acacia bonded sand baked at 180ºC for 1 hour was optimal. Sand bonded with 4.5% grade 3 acacia baked at 200ºC for 1.0-2.0 h was optimum for copper, aluminium, classes II and III iron/steel cores. Sand bonded with 8.0-13.0% grade 3 Nigerian acacia species baked at 200ºC for 1.5-2 h was found most effective for class I iron and steel cores.

Defined quantities of grades 1 and 4 Nigerian gum Arabic were mixed with refined kaolin clay as composite binders for sand cores. Foundry mechanical properties like green compressive strength, permeability, shatter index and baked tensile strength tests were carried out on core specimens to ascertain degree of suitability of the composites for sand casting. The green compressive strength, permeability and shatter tests were carried out on cylindrically shaped specimens using standard universal strength machine, permeability meter and shatter machine. Tensile strength specimens shaped like the figure eight were oven baked at 200°C for 1-3 hours and cooled before tests. Core samples bonded with these composite binders were used for trial castings to ascertain its practical performance. The research showed that kaolin clay addition to gum Arabic improved permeability by about 18%, shatter index by 5%, green compressive strength by 8% and baked tensile strength by 11-15% over cores bonded with plain grades 1 and 4 Nigerian gum Arabic. On the other hand addition of gum Arabic to kaolin clay bonded cores improved green compressive strength by 15% and baked tensile strength by 17%, while it decreased shatter index and permeability by 6% and 5% respectively. Gum Arabic and kaolin clay composite binders gave cores that produced clean cast cavities which also collapsed easily after casting solidification.

The effect of addition of linseed oil to Nigerian gum Arabic grades 2 and 4 on baked tensile strength of sand cores used as implants in foundry moulds was studied. Defined quantities of gum Arabic and linseed oil were mixed together and used to bind sand cores that were later baked at 180°C and 200°C and then analysed for tensile strength to establish any property improvements over cores bonded with plain gum Arabic. Core specimens shaped like figure eight in accordance with foundry practice were baked in an electrically powered oven and then tested with a universal strength machine after oven cooling them to room temperature. The research showed that addition of linseed oil to plain grades 2 and 4 Nigerian gum Arabic caused property enhancements. The effects were in the form of increased tensile strength of baked cores of about 12% and reduced baking period of about 1 hour. Permeability and shatter index were marginally reduced by about 3% over cores bonded with plain gum Arabic. v...

The potential of composite combination of each of grades 1 and 2 Nigerian acacia species exudates and bentonite clay as sand mould binder was investigated. The study involved foundry property analyses of sand mould specimens bonded with composites mixes of grades 1 and 2 acacia species exudates and bentonite clay. Standard foundry equipment that included universal strength machine, permeability meter, hardness tester, shatter index machine and quick moisture teller in the foundry workshop and laboratory of Ajaokuta Steel Company Limited, Nigeria were used as the research equipment. The foundry properties measured were the moisture content, green and dry compressive strength, permeability and shatter index of sand moulds bonded with varied combinations of the composite materials. The result was compared to existing foundry standard and past related work. It showed that composite combination of 8% grade 1 acacia species with 1% bentonite clay was a suitable binder for green and dry sand mould for casting light steel, grey iron and non-ferrous alloys. A composite of 8% grade 2 acacia species and 1% bentonite clay was a suitable binder for green and dry sand mould for casting grey iron and non-ferrous alloy. Presence of bentonite clay generally improved mould sand binding ability of grades 1 and 2 Nigerian acacia species exudates.

ABSTRAK Perkembangan industri kelapa sawit dewasa ini semakin pesat. Salah satu hasil industri kelapa sawit yang kerap menjadi limbah adalah Tandan Kosong Kelapa Sawit (TKKS). TKKS ini dapat diolah menjadi serat yang akhirnya dapat dimanfaatkan sebagai material engineering. Tujuan penelitian ini adalah untuk menganalisa mutu fisik dan respon mekanik yang diterima genteng komposit dan genteng komersil akibat beban impak jatuh bebas. Spesmen yang akan di uji berukuran 380 × 235 × 20 mm. kekuatan mekanik material diperoleh dengan cara melakukan pengujian yaitu menggunakan alat uji impak jatuh bebas. Dari hasil analisa mutu fisik, berat genteng dapat direduksi hingga 44,89% dan memiliki berat rata-rata 1,518 kg, rata-rata area porositas pada genteng komposit adalah 55,85%, dan hasil uji rembesan air tidak ditemukan adanya kerusakan struktur dan rembesan air, namun penyerapan air hingga 62%. Pada pengujian impak jatuh bebas diperoleh gaya impak yang diterima genteng komposit pada ketingg...

Tandan Kosong Kelapa Sawit (TKKS) memiliki nilai untuk direkayasa menjadi material alternatif yang dapat dimanfaatkan dengan alasan masih berlimpahnya bahan baku, mudah diolah menjadi bentuk serat halus, dapat didaur ulang, bebas korosi, tahan dan mampu menyerap suhu panas, serta ekonomis, seperti untuk pembuatan papan partikel. Tujuan penelitian ini untuk menganalisa respon mekanik produk batako ringan dari bahan concrete foam diperkuat serat tandan kosong kelapa sawit (TKKS) akibat beban impak jatuh bebas. Pembuatan batako ringan menggunakan mortar; semen = 30%, pasir = 45%, air = 15%. Lalu ditambahkan bahan pengembang = 7%. Bahan concrete foam ini diberi penguat matriks berupa serat TKKS = 3%. Dimensi batako ringan 600×200×100 mm. Metode penelitian yang dilakukan adalah metode penelitian eksperimen. Data diperoleh melalui pengujian makrostruktur dan impak jatuh bebas. Hasil pengujian impak jatuh bebas ketinggian 0,5 m tegangan rata-rata 0,0035 MPa , tegangan lentur 8,1 MPa dan en...

The goal of this study was to investigate the changing characteristics of Heat-Treated Aluminum Alloy 6101 quenched in various media. The research methodology of this research includes performing heat treatment on the Aluminum Alloy 6101 samples at various temperatures, specifically 250℃, 350℃ and 450℃ as well as carrying out quenching processes of the samples using Brine and Water as the main quenchants, and then allowing some samples to cool in the furnace and the rest to be normalized in air, after which mechanical tests (hardness and impact test) will then be carried out on the samples, followed by the microstructural analysis of the alloy. The study concluded that Aluminum Alloy 6101 should be heated to 250°C to achieve the greatest positive effect on its hardness properties, and the air was found to be the best cooling medium. It was also established that Brine Solution used as a quenching media has no significant effect on the hardness property of Aluminum Alloy 6101. Further...

We preformed first-principle calculations for the structural, electronic, elastic and magnetic properties of Cu 2 GdIn, Ag 2 GdIn and Au 2 GdIn using the full-potential linearized augmented plane wave (FP-LAPW) scheme within the generalized gradient approximation by Wu and Cohen (GGA-WC), GGA þ U, the local spin density approximation (LSDA) and LSDAþ U. The lattice parameters, the bulk modulus and its pressure derivative and the elastic constants were determined. Also, we present the band structures and the densities of states. The electronic structures of the ferromagnetic configuration for Heusler compounds (X 2 GdIn) have a metallic character. The magnetic moments were mostly contributed by the rare-earth Gd 4f ion.

Using the experimental determinations obtained on the basis of compressive stress, some mechanical properties were studied for composite materials with the matrix of three types of resin, epoxy, unsaturated polyester and hybrid based on Dammar natural resin, which was reinforced with isophthalic resin granules NPG (Neopentyl Glycol) Chromat Kayan / Javari / Payette type. The stress-strain diagrams, compressive yield strength, compressive strength and modulus of elasticity in uniaxial compression were obtained. With the EDS analysis, the graphical distribution of the atomic spectra of the elements identified in the hybrid resin was determined and the image of the fracture surface of a hybrid resin specimen was presented based on the stereomicroscopic analysis (SEM).

The paper deals with the issue of separation in particular:-restaurant, hotel and kitchen waste,-biodegradable waste in the food industry (packaged and unpackaged, fresh, canned, bottled, chilled and frozen...etc.),-biodegradable waste from shops and wholesalers, including vegetables, fruit, bakery, dairy, smokehouse and other products (packaged and unpackaged in all forms),-biodegradable municipal waste from public spaces and households-mixed municipal waste, etc. A new line for wet (dust-free) mechanical separation of these wastes is also described.

Research on the thermal and thermo-oxidative degradation of polyacetals allows for the development of effective methods of utilization of the waste of these polymers towards the recovery of monomers. For this purpose, in addition to qualitative analysis, it is necessary to understand the mechanisms of chemical reactions accompanying the decomposition process under the influence of temperature. Therefore, in this article, with the experimental results from the thermal analysis of the POM homopolymer of three various stages of life—POM-P—unprocessed sample; POM-R—recycled sample, and POM-O—sample waste—we took steps to determine the basic kinetic parameters using two well-known and commonly used kinetic models: Friedman and Ozawa-Flynn-Wall (OFW). Knowing the values of the course of changes in apparent activation energy as a function of partial mass loss, theoretical curves were fitted to the experimental data. The applied calculation models turned out to be consistent in terms of the...

In this paper effects of welding on mechanical and microstructural characteristics of high-strength low-alloy steel joints is presented. Testing was done at models prepared with Vgroove butt joints that are done by two different welding processes. Considered welding processes were done by MMA or MIG for root pass and MAG for other passes with related consumables. Experimentally determined basic mechanical characteristics were put in correlation to relate ones that were numerically calculated. The experimentally obtained yield strength and tensile strength showed that welding process MMA/MAG provide better mechanical properties then MIG/MAG. It is implicated that selection of welding process at high-strength low-alloy steels is multi criterion analysis. If only proper welding is obtained, applications of high-strength low-alloy steel are adequate. Those applications caused specific problems related to its specific characteristics and properties especially weldability. As welding processes can be analysed from different aspects, selection of specific welding process at high-strength low-alloy steel are more complex.

Dodos merupakan salah satu jenis alat panen tandan buah segar (TBS) kelapa sawit. Salah satu permasalahan yang dihadapi industri kecil menengah (IKM) sekarang adalah ketersediaan bahan baku. IKM membuat dodos dari skrap baja per (baja karbon medium) yang ketersediaannya terbatas dan kurang berkelanjutan. Saat ini baja karbon medium belum bisa diproduksi di dalam negeri sehingga ketergantungan akan skrap baja karbon medium tinggi. sehingga bahan baku alternatif untuk membuat dodos diperlukan untuk mendukung kebutuhan dalam negeri. Baja karbon rendah merupakan bahan baku alternatif untuk membuat dodos dan mudah didapatkan di pasaran. Untuk memenuhi persyaratan teknis dodos, proses tambahan diperlukan. Metode Pack Karburisasi merupakan metode pengerasan di permukaan yang dapat diaplikasikan pada dodos. Dalam penelitian ini, parameter metoda karburisasi padat yang divariasikan adalah temperatur, waktu penahanan, dan komposisi bahan karburisasi. Kekerasan maksimal didapat pada kondisi temperatur 950 0 C, waktu penahanan 30 menit, komposisi arang 50%+barium karbonat 50 % yang menghasilkan kekerasan 55,49±3,74 HRC. Kondisi kekerasan minimal pada kondisi temperatur 900 0 C, waktu penahanan 15 menit, komposisi arang batok 70%+barium karbonat 50 % didapatkan kekerasan 42,63 ±5,29 HRC.

A sequential digital display is an electronic system that is used to display information to the public. It is a device that contains light emitting diodes that conveys messages by a programmable controller or mechanical processes, regardless of size. Sequential digital display is fast gaining acceptance and application in different spheres of life. In this work, a sequential digital display system was designed and implemented. The components used include transformer, diodes, voltage regulator, resistors (fixed and variable types), capacitors, NE 555 timer, IC4017, IC7432, light emitting diodes and transistors. The aim of the project was to carry out a cost effective design, therefore, the components of the design were readily available and relatively cheap. The light emitting diodes displayed a message written as: Welcome to NOUN Ado-Ekiti study center. The project was tested and commissioned and found to meet specified design requirements.Keywords—Integrated Circuit, Light Emitting...

In recent years, invisibility has become a research area of increasing interest due to the advances in material engineering. It may be possible to achieve invisibility through cloaking devices by coating the body using one or more layers of materials with the proper electromagnetic properties. By using techniques associated to plasmonic cloaking it is maybe possible to obtain also invisibility for small objects with several layers of homogeneous materials working from inside the object. We demonstrate numerically that it is, therefore, possible to achieve invisibility through an inner system based on scattering cancellation techniques.

This paper presents the experimental and numerical investigations of lean duplex stainless steel hollow sections subjected to web crippling. The test specimens were strengthened with different fibrereinforced polymer (FRP). The web crippling tests were conducted under end-two-flange, interiortwo-flange, end-one-flange and interior-one-flange loading conditions. A series of web crippling tests was conducted. The investigation was focused on the effects of surface treatment, web slenderness, different adhesives and FRPs for the strengthening of lean duplex stainless steel hollow sections against web crippling. The lean duplex stainless steel type EN 1.4162 was used in the investigation. Two different surface treatments, three different adhesives and six different FRPs were investigated in this study. The tests were performed on five different sizes of square and rectangular hollow sections that covered a wide range of web slenderness ratio from 8.1 to 57.3. Three different failure modes were observed in the tests of the strengthened specimens, namely the adhesion, interlaminar failure of FRP plate and combination of adhesion and interlaminar failure of FRP plate. Finite element models have been developed and verified against the test results of the specimens subjected to two-flange loading conditions.

Cold-formed stainless steel tubular structural members which may experience web crippling failure due to localise concentrated loads or reactions are investigated. A series of tests on fibre-reinforced polymer (FRP) strengthening of cold-formed stainless steel tubular structural members subjected to End-Two-Flange and Interior-Two-Flange loading conditions is presented. The strengthening only applied to a localise area of the members under concentrated load. A total of 58 web crippling tests were conducted. The investigation mainly focused on the effects of different surface treatment, different adhesive, and FRP for strengthening of stainless steel tubular sections against web crippling. The behaviour of stainless steel members strengthened by different widths of FRP plate against web crippling has been also investigated in this study. The test specimens consisted of ferritic stainless steel EN 1.4003 square and rectangular hollow sections. Two different surface treatments were considered. Furthermore, six different adhesives and six different FRPs were also considered in this study. The properties of adhesive and FRP as well as the bonding between the FRP and stainless steel tube have significant influence on the effectiveness of the strengthening. Most of the strengthened specimens were failed by debonding of FRP plates form the stainless steel tubes. Six different failure modes were observed in the tests, namely the adhesion, cohesion, combination of adhesion and cohesion, interlaminar failure of FRP plate, FRP delaminating failure and web crippling failure. The failure loads, failure modes, and the load-web deformation behaviour of the ferritic stainless steel sections are presented in this study. It was found that the web crippling capacity of ferritic stainless steel tubular sections may increase up to 51% using FRP strengthening.

Hybrid nanocomposites have wide application in many industries. Nanocomposites with base alloy ZA27 reinforced with Al 2 O 3 and Gr are commonly used for bearing applications. Taguchi based Grey relational analysis (GRA) was applied for the multi response optimization of parameters of nanocomposite for improving the tribological characteristics. In this investigation considered parameters are load (10, 15, 20, 25 N), reinforcement content of Gr and Al 2 O 3 (1, 2, 3, 4 vol.%), while time and speed are constant as 30 min and 100 rpm, respectively. ANOVA analysis was used to determine influence parameters on wear loss and coefficient of friction (CoF) of nanocomposite. It was observed that the most influential parameter on tribological characteristics of nanocomposites was reinforcement content of Al 2 O 3. Combination of parameters for optimal tribological characteristics is A1B1C4 i.e. load of 10 N, reinforcement content of 1 vol.% Gr and reinforcement content of 4 vol.% Al 2 O 3. Obtained nanocomposite has shown good tribological properties which lead to less wear loss and therefore expectedly longer life of the bearing in various segments of the automotive industry.

This paper analyses wear behaviour of Al-Si alloy A356 (AlSi7Mg) based composite reinforced with 10 wt. % SiC, and compare it with the base A356 alloy. Composite are obtained using the compocasting procedure. Tribological testing have been conducted on a block-on-disc tribometer with three varying loads (10, 20 and 30 N) and three sliding speeds (0.25, 0.5 and 1 m/s), under dry sliding conditions. Sliding distance of 300 m was constant. The goal of the paper was to optimize the influencing parameters in order to minimize specific wear rate using the Taguchi method. The analysis showed that the sliding speed has the greatest influence on specific wear rate (39.5 %), followed by the load (23.6 %), and the interaction between sliding speed and load (19.4 %). A regression analysis and experiment corroboration was conducted in order to verify the results of the optimization. Specific wear rate prediction was done using artificial neural network (ANN).

Plasma Transferred Arc (PTA) is a process used to repair H13 steel, in which the weld deposits are characterized by low levels of inclusion and an improvement in wear resistance. In this investigation, tungsten carbide                  nanoparticles (WC NPs), with a size of 80 nm in average, were utilized with a nanostructure cobalt based filler metal with 0.5 and 2 wt% using sonication with ultrasonic equipment at room temperature for 30 minutes and drying at 80 °C.

Soft robots have received an increasing attention due to their advantages of high flexibility and safety for human operators but the fabrication is a challenge. Recently, 3D printing has been used as a key technology to fabricate soft robots because of high quality and printing multiple materials at the same time. Functional soft materials are particularly well suited for soft robotics due to a wide range of stimulants and sensitive demonstration of large deformations, high motion complexities and varied multi-functionalities. This review comprises a detailed survey of 3D printing in soft robotics. The development of key 3D printing technologies and new materials along with composites for soft robotic applications is investigated. A brief summary of 3D-printed soft devices suitable for medical to industrial applications is also included. The growing research on both 3D printing and soft robotics needs a summary of the major reported studies and the authors believe that this review a...

In this work, the effect of functionalized hydroxyapatite (HAp-g-PEG) on the thermal degradation behaviour and flammability of polyoxymethylene copolymer (POM_C) was investigated. Organic–inorganic hybrid additive, obtained by grafting of poly(ethylene glycol) on HAp surface using 1,6-hexamethylene diisocyanate as a linker, has been incorporated into POM matrix through an extrusion process. TG analyses show that the incorporation of HAp-g-PEG into POM_C leads to the significant improvement in the thermal stability of the polymer matrix. This is an important finding as POM, being an engineering polymer, suffers from a relatively low thermal stability that limits processing options to develop advanced composite materials. Based on TG results kinetic parameters of the thermal degradation process using Friedman isoconversional method and nonlinear regression method have been calculated; an increase in activation energy of POM degradation process after incorporation of HAp-g-PEG has been...

In this paper, the influence of mass-average molar mass (M w) of polyoxymethylene (POM) copolymer on the thermooxidative degradation behavior of its nanocomposites with hydroxyapatite (HAp) is reported. POM copolymers' thermal stability slightly decreases with a decrease in mass-average molar mass. Thermal stability of POM/HAp nanocomposites is lower in comparison with pure POM, and it gets lower with a decrease in massaverage molar mass of POM copolymer. For POM copolymer with the highest molar mass, thermal stability of POM/HAp nanocomposite was ca. 30°C lower than for pure POM. To get a more in-depth insight into the decomposition process, kinetic analysis of POM/HAp nanocomposite thermal degradation process was performed using Friedman, Ozawa-Flynn-Wall and multiple nonlinear regression methods. The best fit for pristine T2, T3 and T4 copolymers with different molar mass of 100768, 74727 and 68377 g mol-1 , respectively, was obtained for onestage degradation mechanism with autocatalysis, while for T2/10 % HAp and T3/10 % it was parallel reaction model with autocatalysis (Bna) and phase-boundary reaction models (R3). For T4/10 % HAp, the best approximation was found for R2-Bna-D3 reaction model. From hyphenated TG-MS and TG-FTIR thermoanalytical studies, it was found that the main degradation product for POM/HAp nanocomposites is formaldehyde and the amount of other degradation products is lower in comparison with nonmodified POM copolymers.

In this work the influence of molecular weight of three polyoxymethylene (POM) copolymers on the properties of (POM)/hydroxyapatite (HAp) nanocomposites for long-term bone implants have been investigated by various physicochemical methods. Electron microscopy observations confirmed uniform dispersion of HAp in the polymer matrix, whereby DSC results show that HAp influences the degree of crystallinity of POM matrix. Temperature modulated differential scanning calorimetry (TMDSC) was applied to study the melting and recrystallization processes of POM matrix-it was found that with decreasing of POM molecular weight the amout of reversible melting increases. WAXD results show no shift in 2θ for pure POM copolymers and all POM/hydroxyapatite nanocomposites, indicating that the addition of HAp does not change the hexagonal system of POM. For all three copolymers, Young's modulus increases with increasing hydroxyapatite concentration, whereby elongation at break decreases. On the contrast, HAp concentration does not have a significant influence on the tensile strength.

This paper deals with the analysis of impact of various factors on power loss and efficiency of worm gearing. Factors that significantly affect the power losses are, principally, types of materials of meshed gears and geometry of worm pair, type and viscosity of lubricating oils, input rotational speed, worm shape, loading, temperature, etc. Results of experimental tests of worm gearing efficiency are also presented in the paper. Tests were conducted according to planned experiment schedule on specialized device AT200, where single-stage worm gearboxes with transmission ratio i=18 has been used. During the test stage, oils of different viscosities (ISOVG 220, ISOVG 460 and ISOVG 680) have been used and their impact on efficiency was monitored. The values of efficiency level are determined at different input rotational speeds (circumferential velocity) and output torques (loads).

The bending analysis of thick and moderately thick functionally graded square and rectangular plates as well as plates on Winkler–Pasternak elastic foundation subjected to sinusoidal transverse load is presented in this paper. The plates are assumed to have isotropic, two-constituent material distribution through the thickness, and the modulus of elasticity of the plate is assumed to vary according to a power-law distribution in terms of the volume fractions of the constituents. This paper presents the methodology of the application of the high order shear deformation theory based on the shape functions. A new shape function has been developed and the obtained results are compared to the results obtained with 13 different shape functions presented in the literature. Also, the validity and accuracy of the developed theory was verified by comparing those results with the results obtained using the third order shear deformation theory and 3D theories. In order to determine the procedur...

The light and sound detector I am presenting to you is based on a relatively simple yet effective electronic circuit, utilizing basic electronic components to detect light and sound, and subsequently trigger an electrical load, namely a 220V lamp and a buzzer. The uniqueness of this device lies in the fact that during the daytime, the 220V lamp remains idle, but concurrently, the sound detector remains functional both at night and during the day. Here is a description of how this circuit operates.

The effect of quenching on the mechanical properties of medium carbon steels using coconut (CW) water, pap water (PW) and spent engine oil (SPE) which have been largely considered as wastes was investigated. All specimens were normalized at a temperature of 840 in order to remove residual stresses induced during machining operations. Various specimens were heated to ranges of 730-790 and soaked for the range of 30-60 minutes respectively. Brinnel hardness tester was used to obtain the hardness values while Testometric M500-50AT model machine was used for the tensile test of the specimens. The highest hardness value (609.97 BHN) was obtained from the specimen heated to 790 quenched in pap water as compared with 166.4 BHN for the normalized as-received sample. The yield (YS) and ultimate tensile (UTS) strengths of the quenched specimens were better than the normalized as-received sample. SPE-quenched samples yielded the highest YS and UTS combined. The hardness value increased while Y...

This paper presents a simple low-cost design and implementation of a rechargeable mosquito repellent. The circuit is based on 555 Timer IC and a Transformer-less power supply using X-rated capacitors. It is simple and easy to build with few components. The system has been broken down into two major parts namely; DC power supply and repellent circuit. Details of each sub-circuit are described in the paper.

The research investigated the mechanical behavior of samples of steel rods obtained from three selected Steel Rolling Companies in South Western part of Nigeria. This was done by carrying out some mechanical tests such as tensile, impact and hardness as well as microstructural examination.Four sets of 16 mm steel rod samples were collected from Tiger steel industries, Phoenix steel and Oxil steel Industies, all located in South West Nigeria, The chemical composition was carried out using a Spectrometer (EDX3600B). Afterwards, different samples were prepared, cut and machined according to ASTM standards dimensions of tensile and impact tests as well as hardness test from which their Ultimate tensile Strength, Yield strength, Percentage elongation, Impact strength and Brinell hardness number were obtained and compared to three standards (ASTM A706, BS 4449 and Nst 65-Mn). Their microstructures were also examined and analyzed.The results showed that the Ultimate tensile strength for th...