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The effect of heat input on residual stress distribution of steel welds measured by neutron diffraction

100%

Paradowska A. M. , Price J. W. H. , Ibrahim R. , Finlayson T. R.

Journal of Achievements in Materials and Manufacturing Engineering

2006

tom Vol. 17, nr 1-2

385--388

Purpose: of this paper is to investigate the effect of increase in the value of heat input due to change in the welding speed and its influence on residual stress distribution in steel weldments. Design/methodology/approach: The use of the neutron diffraction (ND) technique for residual stress measurements is described. Fully restrained, single-bead-on-plate specimens have been examined. Detailed measurements within a small gauge volume were taken 1.5 mm below the surface, across the sample. In addition, studies of macrostructure and hardness were conducted. Findings: Residual stresses in restrained welds and weld repairs are very complex. The heat input affects the value and distribution of residual stress in the specimen. This peak stress in all three samples occurred not at the toe, but in the middle of the weld bead, where the yield stress is higher. The transverse residual stresses of around half the maximum value of longitudinal stress have been observed. Research limitations/implications: Measurements of residual stress can be very expensive and time consuming. The ND technique is capable of non-destructive investigation in a relatively small gauge volume in depth of the material. However, a number of important issues still remain puzzling, including the uncertainties in the measurement, reliability and interpretation of the results, particularly in regards to the sampling volume and generally in the lack of an engineering standard procedure. The results may be used to calibrate finite element modelling of the welding process. Practical implications: The findings have important consequences with respect to design of welding procedures and fitness-for-purpose assessments. Originality/value: The authors have used ND assessment of residual stresses to follow in detail the changes due to heat input in a small gauge volume. This paper could be an interesting source of information for engineers and researchers who work with welded structures

A comparative study of 2DOF PID and 2DOF fractional order PID controllers on a class of unstable systems

88%

Bingi K. , Ibrahim R. , Karsiti M. N. , Hassan S. M. , Harindran V. R.

Archives of Control Sciences

2018

tom Vol. 28, No. 4

635--682

The proportional-integral-derivative (PID) controllers have experienced series of structural modifications and improvements. Example of such modifications are set-point weighting and fractional ordering. While the former is to achieve two-degree-of-freedom (2DOF) ability of set-point tracking and disturbance rejection, the latter is to ensure smooth control action. Therefore, this paper reviews various forms of PID controllers and provides a comparative analysis of 2DOF PID and 2DOF fractional order PID (FOPID) controllers. The paper also discusses the conversion of one PID form to another. For the comparative analysis of the various controllers, a class of unstable systems are considered. Simulation result shows that in most cases the conversion from one form to another does not significantly affect the performance of the system. It is also observed that the 2DOF controllers (2DOF PID and 2DOF FOPID) improved significantly the performance of the ordinary PID controllers.

Degradation and physical properties of sugar palm starch/ sugar palm nanofibrillated cellulose bionanocomposite

63%

Atikah M. S. N. , Ilyas R. A. , Sapuan S. M. , Ishak M. R. , Zainudin E. S. , Ibrahim R. , Atiqah A. , Ansari M. N. M. , Jumaidin R.

Polimery

2019

tom T. 64, nr 10

680--689

This paper aims to study the degradation rate of sugar palm nanofibrillated cellulose (SPNFCs) and sugar palm starch (SPS). SPNFCs were isolated from sugar palm fiber, while SPS is extracted from sugar palm trunk. The SPNFCs were reinforced with SPS biopolymer as biodegradable reinforcement materials of different diameter/length based on the number of passes of high pressurize homogenization process (5, 10 and 15 passes represented by SPS/SPNFCs-5, SPS/SPNFCs-10, and SPS/SPNFCs-15). These SPNFCs were incorporated into SPS plasticized with glycerol and sorbitol via solution casting method. Soil burial experiment performed on SPS and SPS/SPNFCs bionanocomposites showed that SPS was degraded more rapidly by losing 85.76% of its mass in 9 days compared to 69.89% by SPS/SPNFCs-15 bionanocomposite. The high compatibility between SPNFCs nanofiber and SPS biopolymer matrices can be observed through field emission scanning electron microscopy (FE-SEM).

Zbadano szybkość degradacji nanowłóknistej celulozy wyizolowanej z palmy cukrowej (Arenga pinnata) (SPNFCs) oraz skrobi wydzielonej przez ekstrakcję z rdzenia pnia tej palmy (SPS). SPNFCs uzyskiwano z włókien palmy cukrowej, poddawanych homogenizacji pod wysokim ciśnieniem w 5, 10 lub 15 cyklach, otrzymując nanowłókna celulozy o różnej długości i średnicy. SPNFCs wprowadzano do SPS uplastycznionego mieszaniną (1 : 1) glicerolu isorbitolu. Metodą odlewania z roztworu wytwarzano błony nanokompozytowe SPS/SPNFCs-5, SPS/SPNFCs-10 i SPS/SPNFCs-15. Test glebowy procesu biodegradacji wykazał, że SPS ulegało szybszej degradacji, tracąc 85,76% swojej masy w ciągu 9 dni, w porównaniu z ubytkiem masy 69,89% w wypadku bionanokompozytu SPS/SPNFCs-15. Na podstawie analizy metodą skaningowej mikroskopii elektronowej z emisją polową (FE-SEM) stwierdzono dużą kompatybilność między nanowłóknami SPNFCs i biopolimerową osnową SPS.