Effects of the Vibration Amplitude in Vibratory Stress Relief on the Fatigue Life of Structures

This research aims to investigate the effects of vibration amplitude in vibratory stress relief (VSR) on the fatigue strength of structures with residual stress. Experiments are carried out on specimens with residual stress generated by local heating. Flat specimens made of A36 steel are prepared to be suitable for setting up fatigue bending tests on a vibrating table. Several groups of samples are subjected to VSR at resonant frequencies with different acceleration amplitudes. The results show that VSR has an important influence on the residual stress and fatigue limit of steel specimens. The maximum residual stress in the samples is reduced about 73% when the amplitude of vibration acceleration is 57 m/s2. The VSR method can also improve the fatigue limit by up to 14% for steel samples with residual stress.

Materials Selection and Design Options Analysis for a Centrifugal Fan Impeller in a Horizontal Conveyor Dryer

Comparative strength analysis of two popular options of the radial centrifugal fan impeller design used in horizontal conveyor dryer for fine-grained raw materials is presented. Three types of materials for impeller manufacturing—ASTM A36 steel, Hardox 450 steel and aluminium alloy 6061-T6 are considered. The finite element method (FEM) has been used to investigate stresses and deformations of the impeller within the operational speed range. Analysis shows that the better design is the impeller made of Hardox 450 steel with a central disk. Although the maximum stress is slightly higher in the blades slot for central disk fitting for this design option, it has greatly reduced stresses in contact edges with two other disks (by 22–38%) and blades bending deformation (by 51%). For this design, the maximum operational rotation speed is 1135 min−1 according to the yield strength with a 15% safety factor, while for basic design, it is 1225 min−1. The rational choice of material depends on maximum value of the yield stress to density ratio as well as taking into account the operating conditions and required fan performance. Recommendations for manufacturing the centrifugal fan impeller related to chosen material are given.

Analysis of Welding Position and Current on Mechanical Properties of A36 Steel using Shield Metal Arc Welding

Welding is an assembly process that is most often used in the world of construction today. Welding is often used for repairing and maintenance of all tools made of metal, both as a process for filling cracks, temporary joining, or cutting metal parts. This study aims to determine the effect of welding current and position on the tensile strength and Vickers hardness (HV). This study uses ASTM A36 steel plate as base material. The variation of welding currents used are 90A, 110A, and 130A combine with variations in positions 1G, 2G, and 3G. The electrode used in this study is E6013 electrode with a diameter of 3.2 with a butt joint connection. All of processes are performed in room temperature with a strict condition. The results are as follow, the highest Ultimate Tensile Strength is obtained at 90A current and 3G position with a value of 471.93 MPa. For the highest hardness in the Vickers test, it is also obtained at 90A current and 3G position with a value of 242.20 Kgf/mm2.

Rancang Bangun Rangka Kendaraan Penyemprot Hama Otomatis

Abstrak Dari berbagai cara pengaplikasian pestisida, penyemprotan merupakan aplikasi pestisida yang paling umum. Di Indonesia sendiri penyemprotan dilakukan secara manual. Penyemprotan manual memiliki kendala yaitu membutuhkan tenaga manusia. Penyemprotan secara manual mengakibatkan petani akan mudah terpapar oleh pestisida sehingga diperlukan adanya penyemprot hama otomatis. Tujuan penelitian ini adalah merancang bangun rangka kendaraan penyemprot hama otomatis untuk tanaman hortikultura. Rangka didesain menggunakan software Solidworks 2016 untuk mensimulasikan kekuatan rangka. Dari simulasi rangka dengan bahan yang digunakan baja ASTM A36 diketahui nilai yield strength bahan ASTM A36 2,5 X 108 N/m2 didapat nilai tegangan tertinggi 3,461 x 107 N/m2. Rangka ini menggunakan baja siku berukuran 50 mm x 50 mm x 5 mm. Jenis rangka yang jadi acuan yaitu jenis rangka ladder frame, yaitu jenis rangka menyerupai tangga, dengan jenis rangka ini memiliki kelebihan kekuatan yang tinggi. Roda yang digunakan adalah roda sepeda dengan diameter 19 cm dan tebal 4 cm. Motor penggerak yang digunakan yaitu tipe gearbox. Dimensi kendaraan, panjang = 320 cm, lebar = 80 mm, dan tinggi 150 mm. jenis transmisi yang digunakan yaitu transmisi roda gigi lurus dengan perbandingan gigi 16 : 32. Hasil pengujian pembebanan pada kondisi kendaraan diam dan bergerak, bahwa rangka mampu menahan semua beban komponen – komponen yang ada seperti box elektrikal, tangki pestisida, dan pompa. Kata kunci: pestisida, ASTM A36, Kendaraan Penyemprot Hama, Ladder Frame. Abstract Of the various ways of application of pesticides, spraying is the most common application of pesticides. In Indonesia, the spraying is done manually. Manual spraying has a problem. Namely, it requires human labour. Spraying manually causes farmers to be easily exposed to pesticides, so an automatic pest sprayer is needed. The purpose of this study was to design an automatic pest spraying vehicle frame for horticultural crops. The frame is designed using Solidworks 2016 software to simulate the strength of the frame. From the simulation of the frame with the material used by ASTM A36 steel, it is known that the yield strength value of ASTM A36 material is 2.5 X 108 N / m2, the highest stress value is 3.461 x 107 N / m2. This frame uses steel angles measuring 50 mm x 50 mm x 5 mm. The type of frame that is the reference is the type of ladder frame, a type of frame that resembles a ladder, with this type of frame having a high strength advantage. The wheels used are bicycle wheels with a diameter of 19 cm and a thickness of 4 cm. The driving motor used is the gearbox type. Vehicle dimensions, length = 320 cm, width = 80 mm, and height 150 mm. The type of transmission used is a straight gear transmission with a gear ratio of 16: 32. The results of loading tests on stationary and moving vehicle conditions show that the frame can withstand all the load of existing components such as electrical boxes, pesticide tanks, and pumps. Keyword : pesticide, ASTM A36, Pest Spraying Vehicles, Ladder Frame

Analysis of the coefficient of linear relationship, generated by the exponential heating during the welding process for an A36 steel plate

The present study presents the relationship of temperature and deformation as well as the analysis of heat transfer and deformation produced during welding of a steel plate. The method consists of strategically welding a base metal plate (A-36) with a high-hardness filler material to obtain an overall increment in wear resistance. However, the thermal cycles generated during welding produced deformation, thus changing the flatness of the plate. Different sequences of welding were applied to obtain a relationship between the heat transfer and deformation. A filler material was applied to 100 holes (1/2” diameter and 8 mm depth) in a ½” steel plate. The temperature and deformation were measured for 3 different welding sequences. Plate 1 reached a final mean temperature of 467 °C and deformation of 0.016”, plate 2 reached 472.9 °C and -0.008”, and plate 3 reached 354.2 °C and 0.020”. The results indicate that the deformation is not function of the final temperature, instead the deformation is function of the slope of the curve temperature vs deformation. The behavior of the curve temperature vs deformation is linear for all cases studied, confirming the findings of the lowest deformation for plate 2 which exhibited the lowest slope.

Mechanical and Microstructural Properties of A36 Marine Steel Subjected to Underwater Wet Welding

Underwater wet welding (UWW) is applied to repair basic offshore structures, underwater pipelines, water transportation, docks, and port equipment. The underwater wet welding method used in the current research was shield metal arc welding (SMAW), and this was conducted on an A36 steel plate. We investigated the effect of a water temperature of 10 ± 5 °C and different types of water flow (without flow, non-uniform flow with baffle bulkhead, and non-uniform flow without baffle bulkhead). The defects found on the specimen included spattering, irregular surfaces, porosity, and undercutting. A high cooling rate led to the formation of more acicular ferrite (AF) phases in the weld metal area than a slow cooling rate. The microstructure of the heat affected zone (HAZ) area led to the formation of finer and small grains. Values of tensile, impact, and hardness strength were greater with higher cooling rates. The highest tensile strength value was 585.09 MPa, and this occurred with non-uniform flow without a baffle bulkhead. The highest values of absorbed energy and impact strength were 41.9 J and 2.05 J/mm2, respectively, and these occurred with a non-uniform flow without a baffle bulkhead. The greatest hardness values were found with a non-uniform flow without a baffle bulkhead in the weld metal area.

Caracterización dimensional con ultrasonido por arreglo de fases de discontinuidades inducidas en acero ASTM A36 mediante procesos de electroerosión y soldadura SMAW

This research evaluates the effect of the variables of Phased Array Ultrasonic Testing(PAUT) on the sectoral angular beam scans “S-Scan” and the geometric morphology of planar discontinuities such as the inclination forthe ultrasonic beam and the shape of the extremity on accuracy in measurements. The study was carried out in two stages. Duringthe first stage, eight ASTM A36 steel samples with machined notches by penetration from EDM and a welded sample with lack of penetration in a butt weld were designed and produced. In the second stage, it wasmeasured the size of the discontinuities using ultrasound inspection and different configurations of the phase arrangement. The effect of each variable and inspection setting with errors between 0.2 % and 120 % were determined by statistical analysis.

Simulation of boronizing kinetics of ASTM A36 steel with the alternative kinetic model and the integral method

In this study, two different mathematical models have been proposed for estimating the diffusivities of boron in the Fe2B layer on ASTM A36 steel in the range of 1173 to 1273 K with exposure times of 2 to 8 h. The boride incubation period required for the formation of such a layer was constant regardless of the boriding conditions. In both approaches, the boron diffusivity in the iron phase was considered in an unsaturated matrix. The first approach was derived from the mass balance equation at the (Fe2B/substrate) interface while the second approach employed the integral diffusion model. The calculated values of boron activation energies for ASTM A36 steel were found to be very comparable for the two approaches (161.65 and 160.96 and kJ mol-1). Afterwards, these values of activation energy were confronted with the results from the literature. Experimental validation of these two approaches has been done by comparing the experimental value of Fe2B layer thickness measured at 1123 K for 2.5 h with the simulated values. Finally, the predicted values of Fe2B layer thickness were in line with the experimental measurement.