Conventional method evaluating rubber material property is the least square method. However, there are some problems such as low precision and tedious pre-solving process. In this study, we propose a simple but powerful method to estimate rubber material property using the successive zooming genetic algorithm (SZGA)[2]. This method results in dependable and precise rubber property for various Mooney-Rivlin models by simple change of the objective function only. To demonstrate the effectiveness of this proposed method, we compared it with the Haines & Wilson's method, MARC, and ABAQUS.

View full abstract

In this work, an attempt was made to pre-vulcanization of natural rubber with microwave energy using rectangular wave guide (MODE: TE10). Natural rubber was mixed with curatives, antioxidants, sulfur and carbon black on Two Roll Mill at 50℃. The rubber compounding was subjected to microwave energy. The increase in sulfur content results in increasing of % crosslink, with the maximum of 0.08 mol/cm.The resulting rubber was structural characterized by FTIR spectroscopy.

View full abstract

Dilatometry is the technique most often used for studying the kinetics of polymerization by following the volume change which accompanies polymer formation. In this work, the kinetics of the ring-opening bulk polymerization of ε-caprolactone at 140 ℃ using 0.1 mol% stannous hexoxide as a novel initiator were studied. After a prolonged induction period, the results showed a close adherence to first-order kinetics with respect to monomer with a first-order rate constant, k_1, of 4.00×10^<-2> min^<-1>.

View full abstract

This research aims to investigate the functionality of nano-precipitated calcium carbonate (NPCC) as filler in thermoplastic resins based on property enhancement. Three types of thermoplastics were used: polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC). The resins were evaluated by determining the effect of different NPCC loading on the chemical structure, thermal and mechanical properties of thermoplastics. Results showed that there was an interfacial bonding with the NPCC surface and the thermoplastics. The melting temperature of filled thermoplastics is higher than unfilled while the crystallinity of the polymers decreased with the addition of filler. Tremendous increase on the tensile and impact strength was exhibited by the NPCC filled PVC composites while PE and PP composites maintained a slight increase in their mechanical properties.

View full abstract

μSIL is produced by grinding silica in jet mill and it exhibits excellent physical properties in terms of particle size and shape. The amorphous layer in the near surface of silica produce during jet milling operation has reduced the CTE values when μSIL is incorporated with epoxy. Epoxy filled with μSIL has comparable thermal properties and better mechanical properties compare to epoxy filled with fused silica.

View full abstract

The hybrid mesoporous organosilica incorporating a biphenyl moiety in the framework were synthesized using the surfactant-mediated polymerization of 4,4'-bis(triethoxysilyl) biphenyl precursor with bis(triethoxysilyl)ethane and tetraethoxysilane to control the cross-linking network. Longer reaction time of mesoporous materials resulted to the enhanced formation from granular to rope/rod type morphology. Transmission electron microscopy investigation showed a hexagonal array of mesoporous and straight lattice fringes along and perpendicular to the pore axis.

View full abstract

A new alloy, Fe-C-Cu-MoS_2, was developed for gear applications. Spur gears were compacted from the prealloyed powders and sintered. The contact stress-life curves have been established for both base and MoS_2 contained gears. A thin layer of lubricant film formed on the gear affects the performance.

View full abstract

The wear behaviour of a sintered Fe-based alloy reinforced with mechanically alloyed Fe_3Al intermetallic has been studied using pin-on-disk wear testing machine in dry condition. It is evident from the results that, as-sintered iron matrix shows higher wear compared to that of 10 and 20% Fe_3Al containing MMC. Alumina reinforced Fe-based MMCs impart good wear resistance only during shorter sliding distances and the beneficial effects of Al_2O_3 tend to decrease as the sliding distance increases.

View full abstract

An experimental study of different friction materials namely GCI, Sintered Fe based brake pad employed in MIG-21 fighter aircraft, and newly developed brake pads by a novel P/M technique other than compacting and sintering based on hot powder forging are studied. The friction and wear characteristics of these friction materials were analyzed by using pin-on-disc wear testing machine. The parameters for wear test are two loads (low and high) at constant sliding speed; these are fixed for all friction materials. The experimental results include measurement of COF and wear loss. Average values of COF and specific wear for these friction materials are compared. The temperature rise in the pin near to wearing surface and the noise level are measured. The results of wear test show that the developed brake pad is much better than GCI and sintered pad. The COF of the sintered pad and developed pad are in same range. But the developed pads offer high wear resistance and low temperature rise for long period of time than the sintered pad and GCI. Thus, these properties of the developed friction pads show a bright scope as an initial step to further work on this technique. The characteristics of friction materials are also monitored by hardness, and density measurements.

View full abstract

This paper reports an investigation of two types of aluminium alloys; A2124 and A5056, against an M2 tool steel counterface. With block-on-ring configuration, the wear test was carried out at different loads ranging from 23-140N, in a dry sliding condition. Detailed seconday electron microscopy (SEM) performed on the longitudinal cross sections of the worn alloys indicates that the subsurface deformed layer beneath the worn surfaces is composed of a number of distinct layers like the mechanically mixed layer (MML), the shear deformed and bulk layers with increased hardness as the surface was approached. The relationship between the characteristic of the MMLs especially on the work hardening as a function of alloy type is also discussed.

View full abstract

This study presents a steady state and transient solution for a finite width two-lobe bearing operating with non-Newtonian lubricants, obeying the power law model. The modified Reynolds equation is solved separately for each lobe by finite difference technique with a successive over-relaxation scheme. Performance parameters of two-lobe bearing like load carrying capacity, Sommerfeld number, attitude angle; are determined and compared with the established results for Newtonian lubricants. A non-linear transient analysis is carried out and the orbital stability of journal is ensured by solving equation of motion by the fourth order Runge-Kutta method. Stability parameters are compared with circular bearings.

View full abstract

Nano Barium Titanate [NBT] materials were synthesized by slow-rate sol-gel process for different compositions of Barium and Titanium precursors. The materials were identified by XRD pattern and it has been found that the materials are of polycrystalline phase with tetragonal structure. The crystallite size of 14 nm range was calculated by Scherrer formula for equal ratios of barium and titanium. The TG analyses of BT materials were studied. It was found that at low temperature there was a small amount of CO_2 absorption. When the temperature increases from 100℃ to 700℃ there was a minimum change in weight of the materials. The T_c of 111.8℃ has been obtained in the DTA analysis of the NBT materials for the equal composition of barium and titanium.

View full abstract

The effect of SiO_2 doping on the microstructural change of the WO_3 nanoplate was investigated. The SiO_2 was doped by mixing tetraethylorthosilicate into the W precursor during precipitation of the tungsten oxide. It was found that SiO_2 significantly retarded the particle growth, preserved the nanoplate structure, and resulted to more porous WO_3 powder.

View full abstract

Electrospun nanofbers of a quaternary ammonium salt of chito-oligosaccharide, N-(2-hydroxy)-propyl-3-trimethylammonium chitosan chloride (NHTCC), were prepared by electrospinning the aqueous solution of NHTCC/ poly(vinyl alcohol) (PVA) blend. The average nanofiber diameter was in the range of 40-80 nm. The higher blend concentration (30 wt%) resulted in bead-free nanofibers with larger diameters. In the study of the effect of high voltage supply electrode, the negative electrode produced bead-free fibers with larger diameter while the positive electrode generated bead-free fibers with smaller diameter and few beads were seen at the lower concentration (25 wt%).

View full abstract

X-ray target made of Tungsten-10%Rhenium (W-10%Re) using in CT-scan is subjected to severe thermal load induced by energetic electron beam shot when x-ray is generating. The intense thermal stress concentration is generated and is able to lead to thermal shock failure in this component. Thermal shock failure of Tungsten-10%Rhenium was experimentally and numerically studied in order to understand the thermal shock resistant and mechanism of failure. Laser irradiation method was used for thermal shock heat source. In the experimental study, disk shape specimen was radiated by laser beam at the top center. The energy from laser beam caused rapid heating inside laser irradiation area. Thermal shock failure was found in case of high power intensity. From Finite Element Method (FEM) analysis, the thermal shock failure mechanism was clarified. The shrinkage crack was generated during solidificatio process and behaved as an initial crack, which propagated to outside melted area.

View full abstract

Using notched specimens of austenitic steel SUS310S, creep rupture tests are conducted in tension, torsion and combined tension-torsion stress states at 700℃. The creep fractures especially the initiation and growth behaviors of creep voids in the specimens are investigated and discussed. It is suggested that the von Mises effective stress and the mean stress promote the initiation and growth of creep voids, respectively.

View full abstract

In the study, the monosemousness of cyclic thermal plastic strain is found on the thermal fatigue life in the thermal fatigue test of ferrite ductile cast iron. Therefore, the monosemousness in the thermal fatigue phenomenon is discussed here. First, the meaning of monosemousness in thermal fatigue is described. Next, the monosemousness of thermal fatigue is proofing to formula and, then, it is verified by the thermal fatigue test. By doing so, the feature on the thermal fatigue of ferrite ductile cast iron is clarified.

View full abstract

In the study, with forecast formula of fatigue crack growth rate and the hypothetic expression of crack tip opening configuration, the crack growth rate and crack tip opening configuration of 7/3 brass and 6/4 brass are predicted. Further using CT specimen of the brasses, the fatigue tests under air and corrosive atmosphere were carried out. And the presumed values are compared and discussed with experimental values obtained under various test conditions. Therefore, the equivalent value, representing the crack tip opening configuration and coefficient to crack opening displacement are introduced and the new knowledge on the behavior of fatigue crack propagation has been found.

View full abstract

The influences of plane stress and plane strain on fracture toughness behavior and mechanism of thermoset epoxy resin with polyamine hardener were investigated using 3-point bending fracture toughness tests under various displacement rates (10^<-1>-10^3 mm/min) and thicknesses (4-10 mm). The critical stress intensity factor (K_<IQ>) decreased with increasing displacement rate and thickness, and became stable at high displacement rate (>10 mm/min) and high thickness (>7 mm). The blunting of crack due to a localized plastic deformation process, i. e. the formation of stretched zone and crazes, and the condition of plane stress were dominated mechanisms for thin specimens tested under low displacement rates, while brittle fracture and the condition of plane strain were dominated mechanisms for thick specimens tested under high displacement rates.

View full abstract

Fracture tests have been performed for both macro- and micro-sized specimens prepared from a Fe-3% Si alloy single crystal, and the size effects on fracture behavior have been considered. Notch plane was set to be (100), which is a cleavage plane of this material, and notch direction was set to be [010] for both type of specimens. For macro-sized specimens, cleavage fracture occurred during introducing fatigue pre-crack. In contrast, the micro-sized specimens were fractured by ductile manner. This phenomenon is discussed based on the plastic zone at crack tip and the ligament size. The results obtained in this investigation provide important information for designing actual MEMS devices.

View full abstract

In this work, the effects of surface treatments such as wet blast, anodized coating and bonded solid lubricant on fretting fatigue strength of aluminum alloy (JIS A7N01) were investigated. As the result of fretting fatigue test, the fretting fatigue strength of the specimens treated by wet blast and anodized coating were almost equal to each other, and they were slightly higher than that of the untreated one. The fretting fatigue life of the specimen contacted with the contact pads coated with bonded solid lubricant was extremely improved compared to that of the specimen treated by the wet blast or the untreated one and matched the plain fatigue life.

View full abstract

Thermally tempered glass is made by cooling rapidly after heating float glass to near a softening point. The compressive residual stresses generated at the surface layer by thermal expansion strengthen the material. However, the tensile residual stress layer will be also generated in the interior of the material to balance with the surface compression residual stress. The presence of these residual stress layers in thermally tempered glass will play an important role from the viewpoint of crack growth in fatigue. In this study, to examine the fatigue crack growth behavior of thermally tempered glass in detail, a simple and effective method suggested by Gupta^<(1)> was applied. As a result, it was found that the surface compressive residual stress in thermally tempered glass not only strengthens but also restrains the crack growth.

View full abstract

In order to clear the effects of the residual stress generated in the interior of a thermally tempered glass on the slow crack growth behaviors, both a crack growth and a static fatigue tests were carried out using a hydraulic servo fatigue testing machine at a room temperature. In the crack growth test, the crack length during fatigue process was successively observed using a crack length measurement method developed newly by author^(1). As a result, it was confirmed that the compressive residual stress in the thermally tempered glass restrains the slow crack growth and increases the crack growth resistance, and extends the static fatigue life.

View full abstract

The purpose of the present work is to study the effect of fabricating process on fatigue behavior of structure steel. HSLA steel has been designed to provide specific combinations of formability and weld ability properties for fabricating process. Rectangular bar specimens taken from different stages of fabricating processes were used to perform the four-point bending fatigue test under the stress ratio, R, of 0.1. Effects of forming and cold spinning on fatigue performance were investigated comparing with that of as-rolled plate. The results indicated that the increase in fatigue limit resulted from work hardening due to fabricating process.

View full abstract

Surface modification using oil jet peening is a recently developed process used for the introduction of compressive residual stresses. Aluminum alloy AA6063-T6 specimens were peened for different peening durations. Peening duration was found to affect the magnitude of residual stress and hardness. Fatigue life depends upon the on compressive residual stress as well as surface roughness of the peened parts.

View full abstract

Cyclic deformation and fracture behavior, under total strain controlled low cycle fatigue (LCF) conditions, have been evaluated for 316(N) weld metal and 316L(N)/316(N) weld joint between 300-873 K. A peak in life has been observed at around 573 K. An anomalous stress response and drastic reduction in fatigue life concomitant with dynamic strain aging (DSA) has been observed between 573-823 K, in both weld metal and weld joint. Manifestations like decrease in half-life plastic strain and increase in half-life stress amplitudes and degree of hardening, reflected the occurrence of DSA. Weld metals have shown better fatigue life compared to weld joints.

View full abstract

The creep-fatigue interaction behaviour of a 15Cr-15Ni, Ti modified austenitic stainless steel has been characterized as a function of Ti/C ratio and microstructure. The material was tested at 923 K in Ti/C ratios of 4 and 8 and in the solution annealed, cold worked and aged conditions. It has been ascertained that precipitation controls creep-fatigue interaction properties in this alloy. Carbides which precipitate on the grain boundaries in the solution annealed material are found to be beneficial to creep-fatigue interaction properties, while fine titanium carbides which precipitate in the matrix in cold worked and aged conditions of the alloy, have been found detrimental to creep-fatigue interaction properties.

View full abstract

Stress distributions beneath the contact surface of ceramic plat in contact with round bar were analyzed by 3-D FEM. On the basis of analytical results, the contact strength was evaluated by considering varied sizes and positions of pre-existing defects from a viewpoint of fracture mechanics. The contact rupture occurs from a surface defect that pre-exists in the vicinity of the edge of the plate. If a defect size and a distance from contact boundary to its defect are assumed, the contact rapture load can be estimated by using the proposed equation.

View full abstract

Ceramics strength under a contact stress with horizontal force was analyzed using finite element method. When ceramic plate was compressed with a ball or round bar, it was found that the occurring position of a surface crack under the compressive condition by round bar becomes further from the contact boundary compared with that by a ball. On the other hand, the surface crack taking part in failure becomes larger. The maximum contact stress and maximum stress intensity factor at tip of a surface flaw slightly outside contact boundary become larger with increasing of horizontal force. And the position of their maximum value approaches the contact boundary. As seen in experimental results, the surface crack occurrence position was found to approach the contact boundary with increasing of horizontal force.

View full abstract

Ceramics have the properties of high-stiffness, proof-corrosion, and light-weight superior to metal materials and so have been applied to a ball and a race in high performance ball bearing and etc. As a recent expansion of this application, a ceramics ball has been applied to the backflow valve, which is comprised in automotive fuel supply system. However, it must be considered sufficiently that ceramic balls can maintain a high confidence over long-term without being broken by cyclic contact loadings, which are generated between a ceramic ball and housing on switching a backflow valve. In this investigation, the stress analysis by FEM was conducted for clarifying failure mechanism due to cyclic contact stress. As results of analysis, the place of highest contact stress was seen directly underneath the contact region between a ball and housing. In ceramics of brittle material, the fracture occurs usually from a microscopic latent flaw in materials. Therefore, it was probabilistically clarified from a view-point of fracture mechanics that a latent internal microscopic flaw was a starting point of fracture.

View full abstract

An analysis of anti-plane shear crack in finite thickness plates is shown by the use of continuous dislocations model comparing the case of the crack in infinite thickness plate.

View full abstract

In this research, the creep behavior of shape memory polymer (SMP) was researched. On this material, master curve of creep compliance was obtained, and time-temperature superposition principle was confirmed. The effect of physical aging on creep behavior was researched, too. The effect of physical aging on creep behavior was described on the aging shift factors, and the effect was depended on the change of time and temperature. From this result, time-physical aged time superposition principle was confirmed. Using the master curve and the shift factors of time, temperature and physical aging, it makes to be able to estimate the creep deformation including the effect of physical aging on creep behavior.

View full abstract

Stress fields on elastic-creep bi-material interfaces with different creep material thickness are analyzed by finite element method (FEM). The results reveal that the thicker creep material gives the higher stress intensity near the interface edge at the same transition period and the distribution of the stress intensity does not change further when the thickness-width ratio (h/W) of creep material is larger than 1.0. In addition, the variation of the creep material thickness contributes the effect on the transition period, in which the thicker creep material, the longer time need to reach the steady state.

View full abstract

This paper aims to clarify riveting conditions for achieving both small plate's distortion and high joint strength. First, the distortion and the joint strength for riveted plates are investigated. Next, one process which decreases riveting force to reduce plate's distortion, and the other process which strengthens by pressing an area around rivet hole in advance to improve the joint strength are examined. From the results, it is found that to strengthen the area around rivet hole in plate is an effective process for improvement of the joint strength.

View full abstract

Deformation behavior in three-point bending test of Mo-Si-B alloy was investigated by recourse to finite element analysis (FEA) with microstructure incorporated. This Mo-Si-B alloy consists of hard, brittle T2 (Mo_5SiB_2) phase embedded in soft matrix of Mo solid solution. The sample contains pre-crack configuration at the middle in order to study the effect of the second phase (T2 particles) onto a crack tip during the bending test. Various optical micrographs were scanned, digitized and meshed for FEA. The results were used to rationalize the recrystallization observed in the experiment.

View full abstract

The effects of power-law plasticity (yield strength σ_yand strain hardening exponent n) on the plastic strain distribution underneath a Vickers indenter was explicitly investigated by recourse to macro- and micro-indentation experiments on heat-treated Al-Zn-Mg alloy. With carefully designed aging profile, Al alloy can achieve similar σ_y, with different n, and vice versa. Using the Vickers tip, the samples were macro-indented, sectioned and micro-indented to construct the sub-surface strain distribution. Thus, the effects of σ_y and n on stain distribution underneath Vickers indenter were revealed.

View full abstract

One of fundamental problems concerning casting of standard test specimen of aluminum alloys is difficulty in eliminating operating variations. These variations are due mainly to inconsistency of the operator. This work presents an automated permanent-mold system that we have developed to enable efficient casting of standard tension test specimen of aluminum alloys. Test results in terms of mechanical properties of the test specimens imply that the automated mold system helps minimize the variations during casting. This can be observed statistically in terms of both typical standard deviation and the so-called Weibull distribution of the ultimate tensile strength data.

View full abstract

The paper studies the influence of compatibilizer (polypropylene-graft-maleic anhydride, PP-g-MA) on morphology of polypropylene/zinc oxide composites. Polypropylene (PP) and zinc oxide (ZnO) composites were prepared by melt mixing technique in a twin screw extruder and the effect of PP-g-MA compatibilizer on the morphology of composites was investigated. Dispersion of ZnO in the matrix polymer was investigated using scanning electron microscope (SEM). The results obtained show that the addition of a small of PP-g-MA compatibilizer during melt extrusion improved the dispersion of ZnO particles.

View full abstract

The work focuses on the influence of zinc oxide on the mechanical properties of polypropylene (PP) and compatibilized PP composites. These composites were compared using the melt mixing in a twin screw extruder. The results obtained show that the Young's modulus of PP increased after adding 8 wt% of ZnO. By adding the compatibilizer (polypropylene-graft-maleic anhydride) to PP/ZnO (4 wt% of ZnO) composites the tensile strength did not change but the Young's Modulus significantly increased.

View full abstract

Al_2O_3-based ceramic was the important composite system in cutting tool application. The addition of TiC and SiC particle to Al_2O_3 matrix provide greater microwave absorption of the composite and also improve its mechanical properties. The preliminary study on microwave sintering of Al_2O_3-TiC-SiC was performed in a multimode microwave furnace field of 2.45 GHz. The A1_2O_3-TiC-SiC composite was sintered to high density in a short processing time. The use of a particulate SiC susceptor combined with a suitable insulation configuration enhanced the efficiency of microwave coupling to high temperature.

View full abstract