On the accuracy of estimation of rigid body inertia properties from modal testing results

Ashory, M.R.,Malekjafarian, A.,Harandi, P. Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.1

The rigid body inertia properties of a structure including the mass, the center of gravity location, the mass moments and principal axes of inertia are required for structural dynamic analysis, modeling of mechanical systems, design of mechanisms and optimization. The analytical approaches such as solid or finite element modeling can not be used efficiently for estimating the rigid body inertia properties of complex structures. Several experimental approaches have been developed to determine the rigid body inertia properties of a structure via Frequency Response Functions (FRFs). In the present work two experimental methods are used to estimate the rigid body inertia properties of a frame. The first approach consists of using the amount of mass as input to estimate the other inertia properties of frame. In the second approach, the property of orthogonality of modes is used to derive the inertia properties of a frame. The accuracy of the estimated parameters is evaluated through the comparison of the experimental results with those of the theoretical Solid Work model of frame. Moreover, a thorough discussion about the effect of accuracy of measured FRFs on the estimation of inertia properties is presented.

On the accuracy of estimation of rigid body inertia properties from modal testing results

M.R. Ashory,A. Malekjafarian,P. Harandi 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.1

The rigid body inertia properties of a structure including the mass, the center of gravity location, the mass moments and principal axes of inertia are required for structural dynamic analysis, modeling of mechanical systems, design of mechanisms and optimization. The analytical approaches such as solid or finite element modeling can not be used efficiently for estimating the rigid body inertia properties of complex structures. Several experimental approaches have been developed to determine the rigid body inertia properties of a structure via Frequency Response Functions (FRFs). In the present work two experimental methods are used to estimate the rigid body inertia properties of a frame. The first approach consists of using the amount of mass as input to estimate the other inertia properties of frame. In the second approach, the property of orthogonality of modes is used to derive the inertia properties of a frame. The accuracy of the estimated parameters is evaluated through the comparison of the experimental results with those of the theoretical Solid Work model of frame. Moreover, a thorough discussion about the effect of accuracy of measured FRFs on the estimation of inertia properties is presented.

Optimum amount of additive mass in scaling of operational mode shapes

Khatibi, M.M.,Ashory, M.R.,Albooyeh, A.R. Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.5

Recently, identification of modal parameters using the response only data has attracted considerable attention particularly where the classic modal testing methods is difficult to conduct. One drawback of the response only data, also known as Operational Modal Analysis (OMA), is that only the unscaled mode shapes can be obtained which restricts the applications of OMA. The Mass change method is a usual way to scale the operational mode shapes. In this article a new method is proposed to optimize the additive mass for scaling of the unscaled mode shapes from OMA for which a priori knowledge of the Finite Element model of structure is required. It is shown that the total error of the scaled mode shapes is minimized using the proposed method. The method is validated using a numerical case study of a beam. Moreover, the experimental results of a clamped-clamped beam demonstrate the applicability of the method.

Optimum amount of additive mass in scaling of operational mode shapes

M.M. Khatibi,M.R. Ashory,A.R. Albooyeh 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.5

Recently, identification of modal parameters using the response only data has attracted considerable attention particularly where the classic modal testing methods is difficult to conduct. One drawback of the response only data, also known as Operational Modal Analysis (OMA), is that only the unscaled mode shapes can be obtained which restricts the applications of OMA. The Mass change method is a usual way to scale the operational mode shapes. In this article a new method is proposed to optimize the additive mass for scaling of the unscaled mode shapes from OMA for which a priori knowledge of the Finite Element model of structure is required. It is shown that the total error of the scaled mode shapes is minimized using the proposed method. The method is validated using a numerical case study of a beam. Moreover, the experimental results of a clamped-clamped beam demonstrate the applicability of the method.

Effect of Chitosan Addition on the Surface Properties of Kenaf (Hibiscus cannabinus) Paper

Ashori Alireza,Raverty Warwick D.,Harun Jalaluddin The Korean Fiber Society 2005 Fibers and polymers Vol.6 No.2

The present paper studies the effect of chitosan, cationic starch and polyvinyl alcohol (PVA) as sizing agents to enhance surface properties of kenaf paper. The polymers were incorporated into the sheets by spray application. The results clearly showed that the addition of chitosan to a sheet formed from beaten fibers had excellent improvement in surface properties, compared to the effect of other additives. Sizing quality of cationic starch fairly matched with the sizing quality of chitosan, however, it was able to reduce the water absorption potential of paper more than chitosan at a same concentration. In most other properties, particularly the most important property for printing papers, surface smoothness, chitosan-sized papers are superior to the paper sized with cationic starch or PVA.

Pulp and Paper from Kenaf Bast Fibers

Ashori Alireza The Korean Fiber Society 2006 Fibers and polymers Vol.7 No.1

Samples of kenaf (Hibiscus cannabinus) grown in Malaysia were examined to determine the kraft pulp and paper-making properties of their bast (or bark) fibers. Using kraft pulping process showed that bast fibers were relatively easy to cook resulting good pulp yields in the range of 45-51 %. The bast pulp produced sheets with great density, tear index and dry zero-span breaking length. Kenaf bast fiber is considered promising for production of high-grade printing, writing and specialty papers.

Mechanical and thermo-mechanical properties of short carbon fiber reinforced polypropylene composites using exfoliated graphene nanoplatelets coating

Alireza Ashori,Saman Menbari,Reza Bahrami 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.38 No.-

This work reports an improvement in the mechanical and thermo-mechanical properties of short carbonfiber (SCF)/polypropylene (PP) composite, resulting from coating of the SCFs with exfoliated graphenenanoplatelets (xGnPs). Firstly, the xGnPs were coated on the SCFs surface by a simple physical absorptionmethod, and then the composites were manufactured by melt blending and hot-press processing. Theamount of SCFs was kept constant at 15 wt% and the amount of xGnP was varied up to 3 wt%. Results oftensile and impact measurements indicated that, for the xGnP–SCF/PP composite, maximum tensilestrength, tensile modulus and impact strength were 43.4 MPa, 1.052 GPa, and 38.1 J/m, respectively,corresponding to 13.6%, 41.7%, and 7.3% enhancement compared to the untreated SCF/PP composite. Inaddition, the results of dynamic mechanical thermal analyses indicated enhancement in storagemodulus and damping capacity for the treated samples; however, no significant difference was observedin the glass transition temperature. The xGnP–SCF/PP interface adhesion enhancement was clearlyshown by scanning electron microscopy (SEM) images of the tensile failure surfaces. Finally, the optimalxGnP content for effectively improving the overall composite mechanical and thermo-mechanicalperformance was found to be 1 wt%.