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Abstract:In this paper, a vibration testing and health monitoring system based on an impulse response excited by laser is proposed to detect damage in membrane structures. A high power Nd: YAG pulse laser is used to supply an ideal impulse to a membrane structure by generating shock waves via laser-induced breakdown in air. A health monitoring apparatus is developed with this vibration testing system and a damage detecting algorithm which only requires the vibration mode shape of the damaged membrane. Artificial damage is induced in membrane structure by cutting and tearing the membrane. The vibration mode shapes of the membrane structure extracted from vibration testing by using the laser-induced breakdown and laser Doppler vibrometer are then analyzed by 2-D continuous wavelet transformation. The location of damage is determined by the dominant peak of the wavelet coefficient which can be seen clearly by applying a boundary treatment and the concept of an iso-surface to the 2-D wavelet coefficient. The applicability of the present approach is verified by finite element analysis and experimental results, demonstrating the ability of the method to detect and identify the positions of damage induced on the membrane structure.

It is important to determine and control the clamping force of a bolted joint. Due to its simple setup, the torque control method is typically used to control the clamping force when tightening bolts. After tightening, hammer tests, ultrasonic techniques and methods employing sheet materials as sensors are often used. Many methods have been proposed, but using them to determine and control the clamping force during or after tightening bolts is labor intensive or expensive. Here we conduct impact tests with an impulse hammer combined with experimental modal analysis to determine the clamping force by interpreting the change in the local mode frequency of a bolt head in the high frequency region as a function of the clamping force. To demonstrate the applicability of our method, we also investigate its limits with regard to bolt sizes. Keywords Vibration • Non-destructive testing • Clamping force • Bolted joint • Experimental modal analysis IntroductionMultiple bolts are often used to join or restrain the components of a structure. Because loosening of these bolts may damage the structure, it is important to be able to monitor and control the clamping force of bolted joints [1]. Methods Naoki Hosoya B

PENGARUH RASIO MASSA KITIN/NaOH DAN WAKTU REAKSI TERHADAP KARAKTERISTIK KITOSAN YANG DISINTESIS DARI LIMBAH INDUSTRI UDANG KERING. Kitosan merupakan polimer yang dapat dibuat dari kitin menggunakan proses deasetilasi. Tujuan penelitian ini untuk mempelajari pengaruh rasio massa kitin dengan volume NaOH dan waktu reaksi terhadap karakteristik kitosan yang disintesis dari limbah industri udang kering. Kitin diisolasi dari cangkang udang dengan metode deproteinasi dan demineralisasi. Deasetilasi kitin dilakukan pada suhu 120°C, kecepatan pengadukan 150 rpm, rasio massa kitin dengan volume NaOH 1:15, 1:20, 1:25 (w/v), dan waktu reaksi 0,5-3 jam. Hasil penelitian menunjukkan bahwa peningkatan nilai rasio massa kitin dengan volume NaOH terhadap waktu reaksi mengakibatkan peningkatan derajat deasetilasi dan penyusutan kadar abu dan rendemen kitosan, sedangkan kadar air tidak memiliki efek yang signifikan. Derajat deasetilasi kitosan adalah 85,7% pada rasio massa kitin

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Cutting tool is an important part of machining processes which in the operation frequently runs into wear. The wear cutting tool produces an imprecise product with low quality surface, may endanger machine tools by stimulating chatter. In this study, low cost and fast analysis of the wear of cutting tools in turning and drilling processes are proposed. For that purpose, the experimental set-up which consists of operating turning and drilling machine, simple microphone and Personal Computer (PC) with a sound card are set out. The wear of cutting tools are made by applying artificial wear. The sound data from normal and wear cutting tools of operating turning and drilling machines are recorded by using simple microphone and PC with a sound card. The obtained sound signals are then analyzed in the form of time and frequency domain, spectrogram by Wavelet Transform (WT). It is found that sound signals in time and frequency domain have a significant rise of amplitudes in wear conditions. The spectrograms exhibit the special contours which sign the existence of wear. The results demonstrate that the proposed method can analyze the cutting tool wear very well.

One of the most commonly used geospatial mapping methods is photogrammetry (aerial mapping). Photogrammetry is a method of mapping objects on the surface of the earth by using aerial photography as a medium. The aerial mapping process is carried out through cameras installed on Unmanned Aerial Vehicle (UAV). From the aerial photography, object interpretation and geometry measurements will be carried out to produce line maps, digital maps and photo maps. In general, photogrammetry is a mapping technology by utilizing aerial photography to be processed into a geo-spatial information system. Batu Bersurat Village is one of the villages located in Subdistrict XIII Koto Kampar, Kampar Regency, which did not have a geospatial information map. Community service team from the Mechanical Engineering Department of the University of Riau had a plan to carry out community service activities in Batu Besurat Village in the form of making geospatial information maps through aerial mapping. This aerial mapping activity was carried out by utilizing UAV with the type of fixed wing. In its implementation, the community service activities were planned to involve Mechanical Engineering students, university students of the University of Riau, village officials and the local community. It is expected that with this community service program, the geospatial information system map made by Batu Bersurat Village can be  used in village spatial planning for agricultural land, residential land and validation of village boundaries.

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