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This paper describes the application of a life prediction method for stainless steel exhaust manifolds. Examination of the exhaust manifold cracks indicated that many of the failures could be attributed to out-of-phase thermal fatigue due to compressive strains that occur at high temperatures. Therefore, the plastic strain range was used as the crack initiation criteria. In addition, the comparison of the calculated thermal fatigue stress-strain hysteresis to the experimental hysteresis made it clear that it was essential to use the stress-strain data that was obtained through tensile and compression testing by keeping the test specimens at the maximum temperature of the thermal fatigue test mode. A finite element crack prediction method was developed using the aforementioned material data and good results were obtained.

ϵ-caprolactam was polymerized in the interlayer space of montmorillonite, the clay mineral yielding a nylon-clay hybrid (NCH). X-ray and TEM measurements revealed that each template of the silicate, which was 1 nm thick, was dispersed in the nylon 6 matrix, and that the interlayer distance of clay increased continuously from 1.2 nm for the unintercalated material to 21.4 nm for the intercalated material. Thus, NCH is a polymer-based molecular composite or a nano-composite. NCH contains 1-15 vol% of monolayer clay. Injection-molded NCH showed excellent mechanical properties compared with nylon 6 in terms of tensile strength, tensile modulus and heat resistance. The tensile modulus of NCH was twice that of Nylon 6, and the heat distortion temperature increased from 65°C for nylon 6 to 145°C for the NCH containing only 1.6 vol% of a clay mineral. It was found that such excellent properties of an NCH system was due to the strong ionic interaction between nylon 6 and the silicate layer.

The effect of GTL diesel fuel on organic materials used in fuel delivery systems of vehicles was investigated. Specimens made from 16 kinds of organic materials were immersed in GTL diesel fuels synthesized at Refinery-A and Refinery-B (referred to as GTL-A and GTL-B, respectively) and then subjected to tensile testing. The tensile test results revealed that elongation of the nylon sample immersed in GTL-A was extremely small, about 4% of that of untreated nylon. In the light of this finding, the GTL diesel fuels and nylons before and after immersion test were analyzed in detail using about 20 analysis methods to determine the cause for poor elongation. The following points were found. (1) GTL-A consisted of low molecular-weight paraffins. (2) GTL-A had low molecular-weight i-paraffins. (3) The nylon immersed in GTL-A contained low molecular-weight paraffins. (4) The paraffins in the nylon immersed in GTL-A were richer in i-paraffins than the original GTL-A.

In a previous paper (Part 1 of this series), nylon-66 specimens were immersed in two GTL diesel fuels (GTL-A and GTL-B) and then subjected to tensile testing. The tensile test results revealed that the elongation of the specimen immersed in GTL-A was dramatically reduced. The GTL diesel fuels and nylon specimens before and after immersion were analyzed to determine the cause of the decline in elongation. It was found that the poor elongation was caused by penetration and oxidation of low molecular-weight paraffins and that the ease of penetration and oxidation of paraffin depended on the structure of paraffin. In this paper, the low molecular-weight paraffins detected in GTL-A were mixed to produce model fuels. Then, pieces of nylon cut from the tensile test specimen, were immersed in the model fuels. In addition, partial oxidation products of the paraffin (alcohol, aldehyde or ketone and acid) were used in immersion tests of the nylon pieces.

A high strength and high toughness new bainitic steel has been developed which shows comparable mechanical properties, fatigue property, and machinability to those of quenched and tempered SAE 5140. The heat treatment of the bainitic steel is aging after hot forging in order to improve ratio of 0.2% proof stress and tensile strength (i.e. yield ratio) and to avoid warpage associated with quenching. The new bainitic steel has been applied to the slender and lightweight lower arms for automotive suspension. As a result, the total production costs in the lower arms have been reduced by nearly 15 percent.

The new intelligent VVT (Variable Valve Timing) -i, is one of the systems developed to improve engine performance. The pulley unit is one of the most important mechanical components of the system. We developed a suitable process for the four main parts of the VVT-i pulley in order to achieve the target performance at a minimal cost. The requirements for the mechanical component, the pulley unit, include light weight and compact design as well as a quick response time. To satisfy these requirements, we developed three helical gears having unique profiles and high accuracy, and a timing pulley which must prevent pressurized oil from leaking. The inner gear is a helical gear with external teeth,and a key way on its inside diameter. The piston gear is a helical gear of which the inside and outside teeth have opposite helix angles. We developed a unique powder compacting technology for these two gears. The timing pulley is also made of sintered metal alloy.

In October 1998, a new mass-produced car with titanium engine-valves was released from TOYOTA Motor Corporation. Both intake and exhaust valves were manufactured via a newly developed cost-effective P/M forging process. Furthermore, the material which was specially designed for the exhaust one is a unique titanium metal matrix composite (MMC). This paper discusses the materials and manufacturing methods used. The tensile, fatigue strength and creep resistance of the MMC are always superior to those for the typical heat-resistant steel of 21-4N. Both valves have achieved sufficient durability and reliability with a manufacturing cost acceptable for mass-produced automobile parts.

The new Toyota FCV “Mirai” has reduced the weight, size, and cost of the high-pressure hydrogen storage system while improving fueling performance. The four 70 MPa tanks used on the 2008 Toyota FCHV-adv were reduced to two new larger diameter tanks. The laminated structure of the tanks was optimized to reduce weight, and a high-strength low-cost carbon fiber material was newly developed and adopted. The size of the high-pressure valve was reduced by improving its structure and a high-pressure sensor from a conventional vehicle was modified for use in a high-pressure hydrogen atmosphere. These innovations helped to improve the weight of the whole storage system by approximately 15% in comparison with Toyota FCHV-adv, while reducing the number of component parts by half and substantially reducing cost. The time required to fuel the FCV was greatly reduced by chilling the filling gas temperature at the hydrogen filling station to −40°C (as per SAE J2601).