ENGINEERING NEWS IN BRIEF

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                  ENGINEERING NEWS IN BRIEF
                        E-Mail Newsletter

                               No.63
             Issued by the Asian TOP Panel, March 2007

           The Chinese Mechanical Engineering Society (CMES)
           The Institution of Engineers, Indonesia (PII)
           The Japan Society of Mechanical Engineers (JSME)
           The Korean Society of Mechanical Engineers (KSME)

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    According to the agreement made in the 2nd Asian TOP Panel Meeting,
the ENGINEERING NEWS IN BRIEF (E-mail newsletter) has now been edited
by the CMES for the year 2007.

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[Contents]

(1) Magnetic Memory Testing for Medium Carbon Steel Under the Condition of Fatigue      Experiment (Source: CMES)
(2) Propagation Characteristics Of High Frequency Longitudinal Ultrasonic Guided Waves      In Steel Rod Embedded In Infinite Medium(Source: CMES)
(3) New Elastic-Plastic Model for the Contact of Rough Surfaces (Source: CMES)
(4) Demonstration of High Efficient Power Generation System Using A New
     Latent Heatrecovering Boiler From Sewage Sludge Gasification Gas
     (Source: JSME)
(5) Challenge to Le-Mans 24- Hour Endurance Race Aiming to Educate Creative
     Young Engineers (Source: JSME)
(6) Nondestructive Evaluation of the Subsurface Damage Layers in Silicon Wafers Using      (Source: JSME)
(7) Degradation Characteristics of Filament-Winding-Laminated Composites Under      Accelerated Environmental Test (Source: KSME)
(8) Experimental Test and Numerical Simulation on the SMA Characteristics and      Behaviors for Repeated Actuations (Source: KSME)
(9) Experiments on the Flow Characteristics of Circular Multiple Jets Arrayed      Circumferentially (Source: KSME)

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(1) Magnetic Memory Testing for Medium Carbon Steel Under the Condition of Fatigue Experiment

     YIN Dawei Airplane Staff Room, Aviation University of Air Force
     XU Binshi DONG Shiyun DONG Liho. National Key Laboratory for Remanufacturing,      Armored Forces Engineering Institute

Metal magnetic memory testing technology is a new kind of testing method in the field of nondestructive testing. With special testing concept, it is expected to accomplish veracious nondestructive testing job for ferromagnetic metal work pieces in the early damage phase. Owing to the immature development of metal magnetic memory testing technology, a lot of basic researches about theory and application range of this new technology need to be carried out. The change of magnetic memory signals for medium carbon 45 steel is studied by a variety of fatigue experiments. The research shows that magnetic memory signals varies regularly in the special fatigue mode. The magnetic memory testing technology can test the high-load fatigue damage better than it can do for the low-load one. It has better ability of testing defect specimens than that of testing the smooth ones. Furthermore, the cause of formation of magnetic memory phenomenon is analyzed. It is deduced that it is the fatigue action that results in the formation and development of dislocation stress fields in the weak region of loaded specimens and arises obviously different distribution of magnetic domains between these weak regions and normal regions, and these special regions can be found by special magnetic signals. Experiments reveal that, magnetic memory testing technology is useful to judge damage state of metal materials, but the judge veracity may be influenced by a variety of factors, such as the condition of loading and specimen shape.

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(2)Propagation Characteristics of High Frequency Longitudinal Ultrasonic Guided Waves     in Steel Rod Embedded in Infinite Medium

    HE Cunfu SUN Yaxin College of Mechanical Engineering and Applied Electronics     Technology, Beijing University of Technology

Propagation characteristics of longitudinal ultrasonic guided waves of steel rod embedded in infinite medium are studied in theory. Due to the characteristic of dispersion and multi-mode of rod , a longitudinal mode whose attenuation is smallest in all modes and its energy velocity which is the fastest at special frequency can be excited. This high frequency loss attenuation mode can propagate longer distance and be received firstly, which indicates that this mode can be used to the inspection of rod embedded in infinite medium. At the same time, the experiments about diameter 22 mm, 1 m length rod embedded in grout detected using ultrasonic guided wave are carried out, and time-frequency analysis is also performed for the results of experiments. Experiment results are consistent with those of theory.

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(3)New Elastic-Plastic Model for the Contact of Rough Surfaces

    ZHAO Yongwu LU Yanming JIANG Jianzhong School of Mechanical Engineering,     Southern Yangtze University

A new elastic-plastic model for the contact of rough surfaces is presented. The model is developed based on contact mechanics and the assumption that the transitions from elastic, through elastic-plastic, to fully plastic deformation of a contacting asperity is continuous and smooth. The deformation behavior of a single contacting asperity is firstly modeled in detail, particularly, for the elastic-plastic deformation. The contact between the two rough flat surfaces is then modeled by using probability theory. The model developed is compared with the GW elastic model and CEB elastic-plastic model on their predicted real contact area and mean separation for a wide range of contact load and plasticity index. It is shown that the present model predicts larger real contact area and smaller mean separation than GW model under the same contact load and plasticity index. Besides, the difference of the predicted results based on the present model and GW model increases with the contact load and plasticity index. The comparison results strongly indicate that the present model is consistent with experimental observation and physical intuition, and is more reasonable in describing the contact behavior between rough surfaces.

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(4) Demonstration of High Efficiency Power Generation System Using A New
     Latent Heat Recovering Boiler From Sewage Sludge Gasification Gas

      Younosuke HOSHI, Mitsubishi Heavy lndustries, LTD,
      Technical Headquarters,Yokohama Research＆Development Center

Recently, effective biomass energy utilization has been necessary to prevent
global warming.
Sewage sludge is a sort of wet biomass generated from a sewage treatment process
and not highly utilized for its energy nowadays.
In this report，a high-efficiency sewage sludge pyrolysis and gasification power
generation system and a new type latent heat recovering boiler applied to the system
are proposed and the results of the demonstration plant are described.
This proposed system has two main characteristics as follows:
1）A high efficiency heat recovering system equipped with a new type latent heat
recovering boiler is applied.
2）A gas engine that has high power generation efficiency even in a low power range
is applied.
Therefore，self energy supply ratio of sewage treatment plant applying this power
generation system that includes the process of"sludge thickening～dewatering～
gasification", achieved almost 100％.Namely, the surplus electricity of this power
generation system can be supplied to "sludge thickness～dewatering" process.
Demonstration plant (nominal treatment capacity of dewatered sludge cake:5t/d）equipped
with a gas engine and a new type latent heat recovering boiler from gasification gas
was operated stably and the obtained results proved its good performance.

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(5) Challenge to Le-Mans 24-Hour Endurance Race Aiming to Educate Creative
     Young Engineers

     Kouzaburo MUKAI, Tokai University

Unique and challenging education has been carried out at Tokai University under a theme of the graduation study "Research and Development of a Le-Mans Car", for the purpose of brushing up young engineers who are expected to create new technologies. The students can expand their capabilities how to discover and solve the break-through problems aiming Le-Mans endurance car race, which requires ultimate technologies for successful results in the leading race of the world. Le-Mans 24-Hour race is called as one of the world biggest three endurance car races, and it will be the first attempt in its history if the students are engaged in design development and participate as mechanics. A precedent study car was produced to collect the running data at Fuji Speed Way already, and it recorded the maximum vehicle speed of 311km/h there. Based on the results of these analyses, the designing of the first car to attend is ongoing now. Production order was made to an Italian maker and a British one with our design drawings and structure calculations. As well as the fulfillment of technical refinement, achievement of the teamwork training including mechanics and drivers are now proceeding.

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(6) Nondestructive Evaluation of the Subsurface Damage Layers in Silicon Wafers
     Using Micro Laser Raman Spectroscopy

     Jiwang YAN, Department of Nanomechanics, Tohoku University

Laser micro-Raman spectroscopy was used to examine the ultraprecision machined silicon substrates using diamond tools in the micro-nano scales. The results showed that the subsurface layer was partially transformed from the crystalline phase to the amorphous phase, and the extent of amorphization can be detected by the intensity of laser micro-Raman spectroscopy. It was also indicated that there was a correlation between the Raman intensity ratio of the amorphous phase to the crystalline phase and the depth of the amorphous layer. This finding provides a powerful approach for quantitatively evaluating the subsurface damage layers of silicon substrates caused by machining processes. Compared to the conventional evaluation methods, the present method is fast, nondestructive and able to be used for mapping measurement.

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(7) Degradation Characteristics of Filament-Winding-Laminated Composites Under      Accelerated Environmental Test

Duck-Jae Kim, Nak-Sam Choi, and Young-Ju Yun,
Hanyang University

Degradation behaviors of filament-winded composites have been evaluated under the accelerated environmental test of high temperature, water immersion and thermal impact conditions. Two kinds of laminated composites coated by an urethane resin have been used: carbon-fiber reinforced epoxy(T700/Epon-826, CFRP) and glass-fiber reinforced phenolic (E-glass/phenolic, GFRP). For tensile strength of 0° composites, CFRP showed little degradation while GFRP did high reduction by 25% under the influence of high temperature and water. However for water-immersed 90° composites tensile strength of both CFRP and GFRP showed high reduction. Bending strength and modulus of 90° composites were largely reduced in water-immersion as well as high temperature environment. Urethane coating on the composite surface improved the bending properties by 20%, however hardly showed such improvement for water-immersed 90° composites. In case of shear strength and modulus, both CFRP and GFRP showed high reduction by water-immersion test but did a slight increase by high temperature and thermal impact conditions.

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(8) Experimental Test and Numerical Simulation on the SMA Characteristics and      Behaviors for Repeated Actuations

     Sanghaun Kim and Maenghyo Cho,
     Seoul National University

In this study, we observe the application of shape memory alloy(SMA) into smart structures for repeatable actuation, because SMA changes its material properties and characteristics progressively under cyclic loading conditions and finally reaches stable path(state) after a certain number of stress/temperature loadingunloading cycles, so called 'training'. In this paper, SMA wires that have been in a stable state through the training are used. Stress-strain curve of the SMA wire at different temperature levels are measured. In addition, we observe other important effects such as the rate effect according to strain rates for rapid actuation response. The current work presents the experimental test using SMA wire after training completion by mechanical cycling. Through these tests, we measure the characteristics of SMA. With the estimated SMA properties and effects, we compare the experimental results with the simulation results based on the SMA constitutive equations.

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(9) Experiments on the Flow Characteristics of Circular Multiple Jets Arrayed      Circumferentially

     Haksu Jin, Sungcho Kim, Jeong Soo Kim, and Jongwook Choi,
     Sunchon University

This paper describes the flow characteristics of circular multiple jet investigated by hot-wire anemometry. The nozzle arrays were classified into two cases; 6- or 7-nozzle located circumferentially in equal interval without or with a central jet. The flow field was measured according to the number of nozzles when the Reynolds number based on the nozzle exit is about 10,000. Mean velocity, Reynolds shear stress and turbulent kinetic energy were investigated in the downstream of jets. The Tollmien's theory holds far downstream only when a nozzle locates at the center. Jet interaction is influenced due to with or without a center nozzle. In addition, the two-dimensional numerical computation was conducted for 3-nozzle case to obtain the general flow structure near the nozzle exit, which verifies the formation of the recirculation region with captive vortices, that is, the evidence of the interaction between jets.

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Editor : Tian Ruizhu
           The Dept. of Internationa Affairs
           Chinese Mechanical Engineering Society