Homogeneous Charge Compression Ignition (HCCI) combustion has attracted considerable interest in recent years as a new combustion concept for internal combustion engines. The HCCI combustion process has four issues to be resolved: ignition timing control, slower combustion reaction rate (maximum heat release rate), difficulty expanding stable operation to the high load region and avoidance of knocking. In this study, the influence of using double componential fuels (n-heptane and iso-octane) on combustion characteristics of HCCI engine was investigated. As the result, the ignition timing can be controled and the amount of fuel was able to be increased while avoiding the knocking by using a fuel having two components with different ignition characteristics.

View full abstract

The In-Direct Injection (IDI) two-stroke cycle compression ignition engine with DME low pressure electronically controlled direct injection system is proposed to increase engine output power. It was experimentally investigated that the influence of sub-chamber volume and a cross-sectional area of connecting passage of divided-chamber on engine performance. Tests were performed under constant engine speed 1500 rpm, and DME consumption was varied. On the high load condition, the brake thermal efficiency was increased and the ignition delay was decreased as the cross-sectional area of connecting passage reduced, because the swirl in sub-chamber was enhanced. When a small sub-chamber volume was used, the ignition timing was not so delayed even though the connecting passage area was large. However, as the sub-chamber volume increased, the engine could be operated for further high load condition and the thermal efficiency was also improved because a lot of DME could be burned in sub-chamber.

View full abstract

We researched the dependences of film thickness distribution on CO_2 flow rate and temperature, using a one-dimensional flow-type reaction system, for supercritical fluid chemical deposition (SCFD) of Cu. It was found that the film thickness became thinner with the distance from the fluid inlet. This is because the Cu precursor is consumed and its density is decreased. When the flow rate was high, the deposition rate decreased near the inlet of the reactor because of the limitation of heat transfer from the reactor to the deposition ambient. Based on these results, we discussed the necessity of a pre-heating system and studied a possible reactor structure large-area deposition.

View full abstract

A copper electroplating process of via filling for three-dimensional packaging was investigated using electrochemical analysis and computational fluid dynamics (CFD) simulation. A new plating solution was selected and applied to a dip-type plating system with paddle agitation. The plating solution has suppression function of Cu deposition that depends upon flow rate of the solution. The paddle agitation in the vertical dip-type plating cell was used for making a conformed agitation flow over wafer. The flow in via and over wafer surface caused by the reciprocating paddles was simulated using CFD. The results suggest that it is important to adjust the right paddle speed for each via size. This optimal combination of the plating solution and the plating system with paddle agitation achieves the bottom-up filling for Through Silicon Via (TSV) without void formation.

View full abstract

We used a 10 MHz quartz crystal microbalance (QCM) to detect small mass changes during the copper corrosion phenomena. Copper corrosion in de-ionized water (DIW) was evaluated in terms of dissolved oxygen (DO) and conductivity (S) of DIW. It was not sufficient to suppress the DO concentration in DIW alone to decrease the copper corrosion rate. Suppression of DIW conductivity also becomes necessary when a potential difference exists on Cu films locally. The time constant for the diffusion of oxygen into a DIW layer was 0.6 sec in a 10 um layer and 0.06 sec in a 1 um layer. This shows that the oxygen diffusion into DIW is significantly fast. We were able to estimate that in an actual spin-rinse-dry (SRD) process, the DIW layer was immediately saturated in oxygen in atmospheric conditions.

View full abstract

This paper studies fine particles in slurry on chemical mechanical polishing (CMP) process for SiO_2 layer. The material removal phenomena in CMP process is not revealed perfectly yet. Therefore, the function of fine particles in slurry acting on the wafer surface have not explained. It is said that material removal phenomena in oxide wafer CMP process was considered conventionally that fine particles in slurry are thrusted into wafer surface with polishing pad, and then scratch and remove wafer material as small fragments. However, this assumption has a lot of contradictions. In addition it is not clear that the function of fine particles in slurry acting on the wafer surface. In this study, we focused on basic function of particles in slurry. First, we attempted to observe material removal phenomena with AFM in the way that AFM stylus tip was presumed as SiO_2 particle. Next, fine particles in slurry before and after CMP were obserbed by super- dynamic light scattering spectrophotometer and transmission electron microscope (TEM).

View full abstract

As the first stage of predicting the step height reduction of Cu wiring pattern in dissolution-type electro-chemical mechanical polishing (ECMP), the removal rate dependency on the polishing pressure was simulated. Simulation results showed lower removal rate than experimental value, but the difference was almost within the range of the experimental error. Therefore, the simulation method is thought applicable to simulate the step height reduction of wiring pattern.

View full abstract

A microchannel is very essential in studying chemical reactions and downsizing in a system. To fabricate the microchannel from devices, thorough understanding of the diffusion reactions inside the microchannel from the viewpoint of multiphase flow dynamics is needed. It is necessary to consider the electric field caused by the electrodes and the force distribution inside the microchannel. Because of a non-uniform electric field distribution inside the system, the forces inside the particles are not equal.

View full abstract

The IPMC (the abbreviation of ionic polymer-metal composite) is one of the "artificial muscles" (also called electro active polymer: EAP). The IPMC can be driven in water by applying low voltage at most 3V and have 10msec respondence were reported. Because of those features, the IPMC is hopeful for under water bio-mimetic robots. In this paper, we proposed the underwater peristaltic micropump using IPMC. A micro gate by IPMC-polyethylene was manufactured and applied square wave voltage at 2V to 3V. The gate can be almost opened and closed by about 1.2mm at 0.2Hz and moreover gushed water from the gate.

View full abstract

In this study, the tensile test have been carried out to commercially available amorphous silicon (a-Si) flexible solar cell and its failure processes have been characterized by acoustic emission (AE) technique. Open circuit voltage (V_<oc>) has been measured simultaneously during the test. V_<oc> starts to decrease at strain of 〜0.9%, and cumulative AE energy of the AE signals with frequency range of 600-800 kHz, which are classified based on wavelet transform analysis, starts to increase at the same time. By observation with scanning electron microscope after the test, it is revealed that mechanical damages due to tensile strain in a-Si solar cell are classified into 4 modes. From V_<oc> measurement during the test, it is considered that different failure modes take place intermittently and have the combined effect on degradation of V_<oc>. In addition, structural factor, such as the location of grid electrode, can affect the failure mode of a-Si solar cell.

View full abstract

The formation process of the bristles brush structure consisted of nano scale diamond particles under ac electric field is investigated with a micro scope observation and a micro particle image measurement and the generating conditions of it are classified according to the electric filed intensity and the frequency. This structure is generated self-assembly near sharped electrode with dielectric characteristics of the nano scale diamond particles suspended in liquid medium and the size of this self-assembled micro structure is controlled with the electric field conditions. This bristles brush structure of nano scale diamond particles have significant potential for manufacturing tools of a nano precision processing and a platform of a bioengineering.

View full abstract

Drying-up suspension that contains fine particles, regular nanostructures of the particles are self-assembled. This is one of the effective processes to produce large-scale nano-structures This paper proposes a patterned self-assembly with the combimation of dispensor and stage control. The spreading of suspension is affected by various factors and width of pattern will change. Thus, the relationship between control variables and pattern width toestablish the control to keep the pattern accuracy. It was found from the basic experiment using only water that gap between the nozzle and substrate should be controlled precisely as well as the control of other parameters as dispense rate. Finally, line patterns assembly of silica particles of 1μm in diameter were fabricated using suspension.

View full abstract

There are not so many papers concerning a prediction of fatigue strength for finite life of shot-peened materials. Since it is difficult too complex to know the effects of a magnitude of dent and compressive residual stress distribution on the fatigue strength of shot-peened materials. In this study the effects of the hardness of material and SP conditions on fatigue strength for finite life are evaluated by rotary bending fatigue tests. Therewith the prediction of fatigue strength for finite life is analyzed by the fracture mechanics.

View full abstract

Vacuum carburizing material of SCM420H was treated by shot peening process using shot particles of Haig speed steel, amorphous and cast steel. 4 point fatigue test of these specimen were performed until 10^6 cycles. After shot peening treatment, residual stress, surface roughness and surface hardness of specimen were measured and cross section of them were observed respectively. From these experimental results, the fatigue strength in the case of using amorphous was the highest value.

View full abstract

Laser peening is an emerging surface technology to enhance fatigue properties of metallic materials through imparting compressive residual stress on the surface. Samples of AC4CH cast aluminum alloy were peened with a Q-switched and frequency-doubled Nd:YAG laser. Compressive residual stress was introduced from the surface to the depth of 1mm or deeper. High-cycle fatigue testing by rotating-bending was performed for samples with and without laser peening. In order to visualize fatigue cracks in the samples, computed tomography (CT) was attempted with high-energy synchrotron radiation of SPring-8. Three-dimensional (3D) images of the fatigue cracks were clearly reconstructed by CT with phase contrast effect. The image of a crack in an unpeened sample was obviously larger than that in a laser-peened sample, which strongly suggested that laser peening had retarded the fatigue crack propagation.

View full abstract

We investigated the dependence of a pulse width on peening effects, such as residual stress distribution, hardness distribution, and surface roughness. Aluminum alloy (A2017-T4) was irradiated by three types of the lasers (ns, ps, and fs pulsed-lasers). As a result, the residual stress distributions in the cases of ns- and ps-laser irradiations had similar tendencies in the depth and maximum value of the compressive residual stress. On the other hand, we confirmed lower magnitude compressive residual stress by the fs-laser irradiation in comparison with the ns- and ps-laser irradiations, since the fs-laser irradiation would not cause plastic deformation required for the peening. Additionally, the ns- and ps-laser irradiations could produce higher magnitude compressive residual stress than that by shot peening.

View full abstract

Friction-velocity characteristics of ZDDP containing oils were determined with a pin-on-disk type tribometer. The gradient of friction μ-velocity V curve significantly depended upon the kinds of ZDDP. That is, secondary alkyl ZDDP showed the large negative gradient, while primary ZDDP with linear long alkyl chain group showed the positive gradient. After the macro scale tribotests, the local topography and the electrical current images on the wear track of the disks were determined with a scanning probe microscope. The topographical images exhibited that the surfaces for both ZDDPs were highly heterogeneous and they were composed of the pads and the cavities between the pads. By comparing the local topographical images with electric current images, it was suggested that the pads were covered with tribofilm having high electrical resistance.

View full abstract

A small-sized CVD (chemical vapor deposition) equipment with simple structure was developed aiming at coating of DLC film on rubber. Tribological properties of some DLC film-coated-rubber were determined with a ball-on-disk type tribometer under unlubricated conditions, room temperature and a load of 1N. As a result, NBR coated by CVD method with DLC film showed a remarkable effect of friction reduction compared to NBR base material. On the other hand, NBR coated by PVD (physical vapor deposition) method was inferior in stability of friction coefficient to NBR coated by CVD. Both DLC film-coated urethane and PTFE were inferior in antiwear performance to NBR coated by CVD.

View full abstract

The present study presents an inverse analysis technique to determine the yield stress on the modified surface of metals. The method utilizes a depth-sensing instrumented indentation technique using a spherical indenter. Especially, a strategy of inverse analysis using finite element analyses has been established to determine the yield stress from the results of indentation tests. First, using a damage mechanics model, we revealed that the indentation load-depth curve is influenced by the degradation of Young's modulus, due to the damage effect at a highly-deformed plastic region under the tip of the indenter. Therefore, we present the method to evaluate the yield stress on the modified surface, excluding the damage effect. We applied the method to evaluate the yield stress of SUS 316L modified by cavitation peening.

View full abstract

A study on life distribution and reliability for a roller guide with cage type is carried out with the total number of 51 test samples and fatigue life distribution functions, such as the log-normal distribution, the two-parameter and the three-parameter Weibull distribution function are used for discussion The basic dynamic load rating obtained ISO formula is compared with the life test data in relation to the effect of crownings of carriage raceway both end portions. As a result, the best fit for the life test series is obtained by the three-parameter Weibull distribution function introduced a minimum life with Weibull slope m = 27/20 and load life exponent p = 10/3, followed by the log-normal distribution as second, and the two-parameter Weibull distribution as the third

View full abstract

This paper deals with the life distribution of ball spline under simultaneously applied radial load and torque. Life test data are plotted by the log-normal, the two-parameter and the three-parameter Weibull distribution function respectively. The rating load is derived from theoretical load distribution in ball spline as well as life test results. The obtained results are as follows: (1) The life distributions of ball spline are conformed well to the three-parameter Weibull distribution function with a Weibull slope m=10/9 introduced minimum life γ. (2) The rating life and rating load for ball spline under the application of combined torque and radial load may be evaluated by the applied torque.

View full abstract

Preloaded ball screws with a double nut have the characteristic that the loaded balls wedge into a right angle direction to a ball rolling direction because the directions of screw shaft and nut raceways differ from the ball rolling direction. Loaded balls of preloaded ball screws with a double nut have two contact points geometrically. When the ball screw is operated under the condition of screw shaft turning and nut stationary, the wedging forces of balls are produced by differences between the screw shaft and nut raceways, and then loaded balls wedge into nut grooves. When the ball wedging motion is significantly increased, loaded balls make contact with another flank of the nut groove, that is, three points contact occur. In the present study, the authors describe a theoretical analysis of the frictional torque in three point contact ball screw. In addition, the frictional torqueses of the preloaded ball screw with double nut are measured under the condition of varied preload, and the results were compared with analytical data

View full abstract

How misalignment of nut effect to drive performance of ball screw hasn't been known. So the authors establish manner to set angular misalignment on the nut and experimentally make clear it. In addition, calculating load distribution of ball screw which have angular misalignment, authors estimate effect of angular misalignment, obtained results are as follows. 1) Angular misalignment on nut increase frictional torque of ball screw. 2) It is estimated that load distribution of ball screw effect to increase of frictional torque.

View full abstract

In rolling contact fatigue (RCF) of rails, surface cracks form at a shallow angle inclined to the traveling and horizontal directions, and grow primarily in the traveling direction underneath the rail surface, which are generally called 'squats'. This paper attempted to analyze the cracks through finite element method (FEM) and linear elastic fracture mechanics (LEFM). The analysis incorporated three-dimensional FEM model of rail and the squat-type crack, which was common in tracks with high-speed traffic. The history of mixed Mode I, II and III stress intensity factors (SIFs) during rolling of a wheel was calculated from the model. Fully reversed Mode II and III SIFs were obtained, while Mode I range was small when the fluid pressurized action was not taken into account.

View full abstract

In the previous research, an electrical current density for occurring electrical pitting and a voltage for starting conduction were clarified. In this paper, duration test for electrical pitting were worked out using electrically conductive grease. The grease is to reduce the internal resistance of bearing as a method for restrain the electrical pitting. In the result, although the time period to occur electrical pitting could be extended, the electrical pitting occurred eventually.

View full abstract

SCM420H has been used for rolling bearings, linear bearings and ball screws, etc. It is thought that for this material when the fatigue test is carried out, in the domain of high cycle fatigue of the S-N curve so-called the Wohler curve, a fatigue limit appears. This type of fatigue limit has been used in the ISO-2007 with a life modification factor a_<ISO> for rolling bearings. However, at present even in the life test of bearing or S-N fatigue test of material, the experimental data does not show any apparent sign of the fatigue limit. In this paper, alternating torsion fatigue test for probabilistic stress-life (P-S-N) evaluation is carried out under standard stress values, from τ = 0.93 GPa to τ = 0.53 GPa for five lots made up of a total of 108 samples, and P-S-N curves were determined based on the three-parameter Weibull and the log-normal distribution function.

View full abstract

In the case of the engine mounting layout, it's very important to prevent the coupled vibration of lateral and rolling mode for the isolation of engine vibration and shock torque. On the other hand, the lower natural frequency, which means the lower rolling stiflhess, is also necessary for the isolation of engine vibration, but it is limited in terms of spring rate in maintaining the fatigue life of solid rubber. Therefore, in this study, an air spring is newly applied to the actual engine mount system of a medium duty truck and many vehicle tests are conducted for checking its vibration isolation effect and its big displacement caused by engine shock torque. As a result, the engine vertical vibration level at 19.1Hz dropped below 1/5 in of the current vehicle installed with cushion rubber and the engine displacement by its big torque was within the limit

View full abstract

Azimuth thruster, a kind of marine vessels' thruster, is divided into two versions generally. Motors for thrust are installed on ship's hull, and propellers are driven by mechanical transmission gears in case of one version of azimuth thruster. This type of thruster has a perpendicular middle driving shat, the reaction torque acts on the pod because of the driving torque of the perpendicular middle driving shat. When the single perpendicular middle shat is modified to contra-rotating system and the driving torque of outer perpendicular middle shat is equal to that of inner perpendicular middle shat, it is possible to cancel the reaction torque acting on the pod and to prevent the interference between rotation of motor and gyration of pod in principle.

View full abstract

The purpose of this study is to examine the effectiveness of active seat suspension when it is applied to small cars and the problems associated with its practical use. A small active seat suspension is installed for one-seater electric automobiles. In an actual driving test, a test road, in which the concavity and convexity of an actual road surface were simulated using hard rubber, has been prepared and the control performance of vertical vibrations of the seat surface during driving has been examined. In this paper, we examined the effectiveness of the active seat suspension in outdoor. As a result, the ride comfort improvement of the small vehicle was able to confirm that active seat suspension was effective on off road.

View full abstract

In this study, the moods of drivers were estimated using physiological information; fluctuations in heart rate were measured by an electrocardiogram to measure autonomic nervous activity. We estimated the level of relaxation of drivers during driving by comparing the sympathetic nervous and parasympathetic nervous activities of drivers when they are driving cars with and without an active seat suspension. A frequency analysis of the nervous activities was carried out using a real-time system that analyzes the fluctuations of heart rate. The moods of the drivers were also examined using a questionnaire to evaluate the correlation between the moods of drivers during driving estimated on the basis of electrocardiographic measurements and those estimated on the basis of responses to the questionnaire. Furthermore, their correlation was also examined by conducting a questionnaire survey with a five-point scale with three as a reference value to examine the subjective ride comfort of drivers in cars with and without an active seat suspension.

View full abstract

The vibration and noise of automobiles by lightening might cause decreasing the product value. In this study, an improvement of the door closing sound of lightened door and a structural modification of the door outer panel were investigated in consideration of human sensibility. To forecast by CAE easily, a series of verifications was done with a simplified door experiment model. Acoustic sensitivity analysis was used to detect an effective position for structural changing. Finally, an actual door closing sound was designed to a pleasant sound.

View full abstract

Reduction of seismic response of house is an important problem for a seismic design. In this paper, two story house are focused on and an oil damper of spherical shapes are proposed. The spherical damper is expected to suppress three dimensional vibration. The damper is improved to increase the effect on reduction of seismic response. The effectiveness of the damper is examined experimentally. It is concluded that the peaks of the frequency response function of the first and the second vibration mode decrease and depend on amplitude of excitation when dampers are used.

View full abstract

Many houses were destroyed in destructive earthquakes in the world. Then, control of seismic response of house is important for protection from destruction. In this paper, two story houses are focused on and a new type of oil damper is proposed. Oil damper is connected to the ceiling of the first story and the foundation. The spherical damper with silicon oil is proposed. The effectiveness of the damper is examined experimentally. It is concluded that the peaks of the frequency response in reduced function when dampers are used.

View full abstract

This study deals with the effectiveness of connected control method(CCM) by connecting conventional structure with base isolated structure. By connecting them, the vibration reduction effect for the conventional structure subjected to ordinary earthquake and the effect for base isolated structure subjected to long-period earthquake are expected to be modified simultaneously. Two buildings structure arranged in parallel is introduced as a control object. To confirm the reduction effect of vibration, passive control experiments using earthquake excitations are carried out.

View full abstract

When a structure has multiple part connection uncertainty such as bolt fasting torque, the FE model of the structure becomes very complicated to apply Monte Carlo simulation for vibration robust design. In this paper, instead of investigating every uncertainty by changing fasting torque, only the relative mode amplitude at the part connection is deal with. A simple joint plate model is used to confirm the proposed method.

View full abstract

An electrical generating device using piezoelectric element (PZT) has been developed to convert structural vibration energy into electrical energy. This paper describes the electrical generation characteristics of PZT including Nb and laminated PZT under vibration load. Vibration tests are performed by using an experimental equipment composed of PZT, weights and a frame. Sinusoidal wave excitation tests are carried out under the condition of the constant initial compressive load acting on PZT. Effects of the number of PZT layers, vibration frequency and vibration load on generated voltage and electric power are evaluated.

View full abstract

In this study, several different lengths of delamination and transverse crack densities were introduced into carbon fiber reinforced plastic (CFRP) simply-supported beams and then their vibration and damping properties were evaluated. The experimental measurements shows that the bending mode frequencies decrease when delamination is introduced in the specimens. On the other hand, their modal damping ratio increased. Also, the effect of transverse crack densities showed the increase of modal damping ratio. However, the bending mode frequencies are found to be insensible to the cracks. These results snowed that there was able to estimate measurement of damage from the bending mode frequencies and modal damping ratio.

View full abstract

We have proposed a magnetic levitation control system for flexible steel plates and confirmed its feasibility through a digital control experiment. However, there is a risk that side slipping or the dropping of the plate may occur owing to inertial force because the levitation control system does not provide a restraining for the direction of travel. Therefore we have proposed the addition of electromagnetic actuators to control the horizontal motion of levitated steel plate. In addition, we have reported that it is possible to suppress the elastic vibration of steel plate in the vertical direction using the electromagnetic actuators for horizontal positioning. In this paper effect of magnetic field from horizontal direction on the transportation performance of a magnetically levitated flexible steel plate is reported.

View full abstract

In the transport system of a thin-steel-plate production line, there is a problem that the quality of the plate surface deteriorates over time because the plate is usually in contact with rollers. To solve this problem, studies of electromagnetic levitation technology have been carried out. However, when a flexible thin steel plate with a thickness of less than 0.3 mm is targeted for levitation, levitation control becomes difficult because the thin plate undergoes increased flexure. We propose the levitation of a flexible thin steel plate that is bent to an extent that does not induce plastic deformation. In this study, we examine the levitation performance of flexible thin steel plate when electromagnet position changed.

View full abstract

It is important for disaster prevention of structures to understand the dynamic behavior of structure components. In this paper, the dynamic behavior of structure components with stiffness change was investigated by vibration test. Compared to natural frequency between a component without stiffness change and with stiffness change, a component with stiffness change is higher than without one. From the damping ratio point of view, at the upper and lower location with stiffness change, they indicate almost same values.

View full abstract

It is important for structure and machine maintenance to detect the damage location and to evaluate the level of damage at that point. To understand the relation between damping ratio and cut depth of structure component which was made by steel, dynamic behavior of structure component was investigated by vibration test. Damping ratio of slight damage case is bigger than that of no damage case. But the relation of this does not indicate linear relation. So it may be possible to detect damage but is difficult to evaluate the level of damage.

View full abstract

A vibration system which a linear spring is jointed at right angles to the oscillating direction shows a nonlinear vibration. In addition, the spring force shows asymmetric restoring force in the case that the oscillator on the settled guide way has any angle against the vibration direction,. In this study, the chaos vibration machine with a tapered guide way has been produced, and behaviors of chaos vibration, periodic vibration and bifurcation-chaos have been experimentally and analytically investigated by using the produced chaos vibration machine.

View full abstract

We have presented a vibration system subjected to a horizontally asymmetric two-well potential type restoring force. The linear spring is installed perpendicularly to the direction of excitation. In addition, the guide way of the oscillator has an angle to the vibration direction. The chaos vibration characteristics in this system under sinusoidal excitation have clarified. In this study, we examine the chaotic vibration characteristics of the system under non-sinusoidal excitation. The periodic waveform created by using the originally presented map function applies to the excitation waveform. From the numerical analysis results, it is found that the period doubling bifurcation-chaos occurs by the varying of the excitation waveform shape.

View full abstract

This study presents experimental results on chaotic vibrations of a curved panel with a concentrated mass. The panel is excited with lateral periodic acceleration. In typical two ranges of the exciting frequency, chaotic responses are generated. These chaotic responses are examined with the Fourier spectra, the principal component analysis and the maximum Lyapunov exponents. The results of the panel are compared with the results of the panel without a concentrated mass. Furthermore, by changing the location of the concentrated mass, influences of the concentrated mass of the panel are examined on the chaotic responses. In the lower region of the exciting frequency, the chaotic responses are not so influenced by the concentrated mass. On the contrary, in the higher region of the exciting frequency, the maximum Lyapunov exponent of the chaotic responses are decreased as the concentrated mass of the panel is increased.

View full abstract

Experimental results are presented on nonlinear vibrations of a bowed-type beam deformed by stretched strings under periodic lateral excitations. A beam is clamped at the center and deformed to a curved configuration by stretched strings which connect both ends of the beam. Nonlinear responses of the beam are measured under periodic lateral excitation. Chaotic response of the bowed-type beam is examined by the power spectrum and the maximum Lyapunov exponent. Vibration modes which contribute to the chaos are inspected by the principal component analysis. Dominant chaotic response of the bowed-type beam is generated from the sub-harmonic resonances of 2/3 order with the lowest mode of vibration accompanied by the dynamic snap-through. From the results of the principal component analysis, it is found that the chaotic response is dominated by the lowest mode of vibration and by a symmetric mode due to the dynamic snap-through.

View full abstract

Experimental results are presented on a plate with mixed boundary of circular and rectangular shape. The plate is excited by lateral periodic acceleration. In a typical frequency range, a non-periodic response is observed. The non-periodic response is examined by the Fourier spectrum and the maximum Lyapunov exponent. The response is found to be the chaotic response which is generated from the internal resonance with the lowest mode and three higher modes. The time response also shows the irregular movement with amplitude modulation. Applying the principal component analysis on the long time interval responses, it is found that five modes of vibration are generated in the chaos. The lowest mode of vibration and the sixth mode of vibration contribute to the chaos dominantly. Furthermore, the principal component is calculated on the chaotic response with short time intervals. In the larger amplitude response, the response is dominated by the lowest mode of vibration. On the contrary, in the smaller amplitude of the response, the responses of higher modes of vibration are increased.

View full abstract

An analytical method is proposed for the response of the primary mass with an impact absorber having hysteresis damping. The impact absorbers in which motion of auxiliary mass is limited by motion limiting stop or placed inside a container. We tried to obtain the response curve of impact absorber subjected to periodic displacement excitation by the Fourier series method. Then, we analyze the response for the nonstationary random acceleration excitation by the simulation and equivalent linearization method. Some numerical results are shown.

View full abstract

We proposed application of van der Pol-type self-excited oscillation as the method to excite the probe-cantilever in AFM. The van der Pol-type self-excited oscillation presents the advantage that the oscillation frequency always coincides with the natural frequency of the probe-cantilever. Furthermore, it has another advantage: we can suppress the steady state amplitude of the cantilever to an extremely low level thanks to the nonlinear feedback effect, while maintaining stable self-excited oscillation. The quality of images obtained using vdP-AFM is comparable to that of pictures obtained using contact-mode AFM. Moreover, the non-contact state is maintained during themeasurement experiments. In each case, the distance between the sample and the probe-cantilever is greater than the vibration amplitude of the cantilever. This fact confirms results of the non-contact observation.

View full abstract