Comparison of Constitutive Models for predicting the formability of SS 304 by tubular hydroforming process

Finite Element (FE) simulation of sheet/tube forming precision depends mainly on the accuracy of the constitutive modeling. The present paper aim is to compare the constitutive models to fit the stress-strain curves. The accurate deformation behavior of the SS 304 tubes depends on the constitutive modeling of hardening behavior. Deformation data of the tensile specimens cut from tubular sample were collected by conducting Uniaxial tensile tests (UTT) at three different rolling directions. Five constitutive relationships were then recognized by fitting the true stress and strain data with the constitutive models of Hollomon, Power, Krupowsky, Voce and Ghosh, and the fitting accuracy were analyzed and compared. Effects of hardening models on Forming Limit Curves (FLC), pressure loading and bulge height of the hydroformed tube were then studied. The obtained FLC from the simulations were compared with experimental FLC to predict the accuracy of the hardening models.

The effect of time variation on the steels corrosion rate in 0.5 M H2SO4 solution

Previous researches have carried out studying the corrosion behavior of steels, the most frequently used steels are medium carbon steel, alloy steel, and stainless steel. This is due to their wide range of applications. So, corrosion behavior is necessary to be analyzed for every steel type because of its wide function. This study was aimed to analyze the corrosion rate, macrostructure, and the XRD results of the AISI 1045, AISI 4140, and SS 304 which represent every steel type. Then, the steels were exposed to the 0.5M H2SO4 solution with various corrosion times. The variation of the corrosion time was 48, 96, and 144 hours. The results of this study revealed that AISI 1045 showed the highest corrosion rate with the value of 183.7 mpy at 144 hours of the time variation. All specimens obtained an increase in the corrosion rate with the increase in the corrosion time. Furthermore, for the macrostructure results, AISI 1045 and AISI 4140 gave obvious rust on the surface of the specimens for all time variation. The corrosion spots appear in the time variation of 96 and 144 hours for SS 304 specimens. XRD analysis confirmed the presence of metal oxides as corrosion products.

UNJUK KERJA TURBIN CROSS-FLOW DENGAN SIMULASI CFD PADA NOSEL DAN MANUFAKTUR PADA RUNNER

Covid-19 pandemic has lead disruption in energy sector, new-and-renewable energy demand is increasing, which show that renewable energy is promisable to be developed. As one of the hydraulic turbine, the cross-flow turbine is prospective primve mover in line with the 7th goal of the SDG’s Goals. Cross-flow turbine is radial atmospheric turbine which generates power by converting hydraulic energy from water to mechanical energy on the shaft by using nozzle and runner. The advantages make this device is became famous, including simple construction and geometry, low maintenance & cost and can be used at wide range operation scheme. However, the cross-flow turbine system is also known to have low efficiency. Based on this condition, this research is aims to improve the efficiency with design the nozzle and to manufacture the runner with two material. The operating condition is set to 1 phase water as working fluid with 1,4 L/s of flow. Nozzle design conducted with CFD 3D simulation from 3 different model. Runner manufacturing is conducted numerically with CAM simulation and experimentally by using CNC machining with Stainless Stell 304 and Aluminium 6061. CFD simulation on the nozzle shows that nozzle model 3 with total length of 400 mm, width 124 mm and throat radius 75 mm.resulting the maximum outlet velocity to the runner 0,135 m/s. Manufacturing of the runner and experiment on the system with nozzle model 3 show that the runner with SS 304 is able to generates larger power to 8,38 Watt,100% larger than the Aluminium 6061.Keywords: Renewable Energy, Cross-flow turbine, CFD, CAMAbstrakPandemi Covid-19 mengakibatkan disrupsi pada sektor energi, dimana konsumsi energi baru dan terbarukan mengalami kenaikan. Fenomena ini menunjukkan bahwa energi terbarukan menjanjikan untuk terus dikembangkan. Sesuai dengan goal ke-7 dari SDG’s oleh PBB, turbin cross-flow merupakan turbin radial yang menghasilkan daya melalui konversi energi hidrolik dari air sebagai sumber energi terbarukan, menjadi energi mekanis pada poros melalui penggunaan nosel dan runner, banyak digunakan karena beberapa kelebihannya, antara lain konstruksi yang sederhana dan simetris hanya memerlukan biaya perawatan yang rendah dan sederhana serta dapat digunakan pada rentang beban yang cukup besar. Namun demikian, turbin cross-flow secara umum memiliki nilai efisiensi yang lebih rendah. Efisiensi sistem dapat ditingkatkan dengan penggunaan material runner yang seusai. Penelitian ini bertujuan untuk melakukan perancangan terhadap nosel dan proses manufaktur runner cross-flow sehingga dapat diperoleh geometri nosel serta jenis material dan proses manufaktur runner yang sesuai untuk rentang operasi, yaitu aliran air 1 fasa dengan debit 1,4 L/s. Pengembangan nosel dilakukan dengan menggunakan metode CFD pada 3 model geometri. Pengembangan terhadap runner meliputi simulasi CAM dan manufaktur pada 2 jenis material, yaitu SS 304 dan Aluminium 6061. Hasil simulasi CFD 3D menunjukkan bahwa nosel model 3 dengan dimensi panjang total 400mm, lebar 124 mm, dan radius pada throat 75mm menghasilkan kecepatan pada sisi outlet sebesar 0,135 m/s. Hasil simulasi CAM dan Manufaktur terhadap runner serta eksperimen terhadap sistem dengan nosel model 3 menunjukkan bahwa bahwa runner dengan material SS 304 menghasilkan daya, yaitu 8.38 Watt, 100% lebih besar dibandingkan dengan runner dengan material Aluminium 6061.

Creep Parameters Determination by Omega Model to Norton Bailey Law by Regression Analysis for Austenitic Steel SS-304

In the material’s creep failure analysis, the difficulty of assessing the applied thermo-mechanical boundary conditions makes it critically important. Numerous creep laws have been established over the years to predict the creep deformation, damage evolution and rupture of the materials subjected to creep phenomena. The omega model developed by the American Petroleum Institute and Material Properties Council is one of the most commonly used creep material models for numerical analysis over the years. It is good in defining the fitness of mechanical equipment for service engineering evaluation to ensure the reliable service life of the equipment. The Omega model, however, is not readily accessible and specifically incorporated for creep evaluation in FEA software codes and creep data is always scarce for the complete analysis. Therefore, extrapolation of creep behavior was performed by fitting various types of creep models with a limited amount of creep data and then simulating them, beyond the available data points. In conjunction with the Norton Bailey model, based on API-579/ASME FFS-1 standards, a curve fitting technique was employed called regression analysis. From the MPC project omega model, different creep strain rates were obtained based on material, stress and temperature-dependent data. In addition, as the strain rates increased exponentially with the increase in stresses, regression analysis was used for predicting creep parameters, that can curve fit the data into the embedded Norton Bailey model. The uncertainties in extrapolations and material constants has highlighted to necessitate conservative safety factors for design requirement. In this case study, FEA creep assessment was performed on the material SS-304 dog bone specimen, considered as a material coupon to predict time-dependent plastic deformation along with creep behavior at elevated temperatures and under constant stresses. The results indicated that the specimen underwent secondary creep deformation for most of the period.

Analisis Radiografi Sinar-X Terhadap Sambungan Pelat Baja Tahan Karat Aisi 304 Hasil Pengelasan Tungsten Inert Gas Dengan Arus 40–60 Ampere

X-Ray Radiographic Analysis of Aisi 304 Stainless Steel Plate Joints From Inert Gas Tungsten Welding Results with 40 – 60 Ampere Current. Metal welding process is one of the main processes in machine construction. The quality of welded joints determines the strength and toughness of a machine construction. The quality of welded joints of installed construction can be determined by the non-destructive test method using X-ray radiography equipment. This study aims to obtain a butt joint obtained from TIG welding of AISI 304 stainless steel plate with a current of 40 - 60 A, identification of defects in the 1G butt joint, and analysis of the quality of the weld joint. The research method used is testing of welded joints using X-ray radiography which refers to the ASME V article II standard and the connection quality refers to ASME section IX. The results showed that TIG welding with a current of 60 Ampere produced a butt joint butt joint that was penetrated and there was no gap between the plates, whereas with a current of 40 A and 50 A the weld joint was not see-through but there was still a gap between the plates. Incomplete penetration weld defects were found in the welded SS 304 plate joints with a current of 40 A. Welded porosity defects were found in the welded SS 304 plate joints with a current of 50 A. Weld defects were not found in the SS 304 plate joints with a current of 60 A. Butt joint connections TIG welded SS 304 plate with the best current of 60 A compared to the current of 40 A and 50 A.