Lightweight material for the speed reducer housing of a car chassis

Lightweight materials improve the fuel efficiency and carbon emissions of vehicles. The purpose of this study is to develop a light-weight, injectable, high-stiffness plastic composite material to replace aluminum in the housing of the speed reducer of a car chassis. The material was tested computationally and experimentally by analyzing the physical properties of specimens with different amounts of reinforcement in the base materials. POM, PA, PEI, PES, PPS and PPA were used as the base materials, while Glass fiber (GF) and Carbon fiber (CF) were used as reinforcement material. The computations were carried out using Moldflow insight software to simulate the injection molding process. The volumetric shrinkage and shear rate of the PA66+GF70 % specimen were 5.3 % and 2985.25 1/s, respectively. The mold material must withstand this shear rate. This sample had the most suitable properties, and the tensile strength, elongation, flexural strength, and thermal expansion coefficient were 312.15 MPa, 1.5 %, 329.2 MPa and 0.022 (10^-5/°C), respectively. As a result of this study, a patent was received for this lightweight material technology.     

Effect of nitrogen on the dynamic strain ageing behaviour of type 316L stainless steel

The dynamic strain ageing (DSA) behaviours of type 316L stainless steels containing different nitrogen contents (0.01–0.15 wt% N) were studied in tension under varying strain rates (1 × 10^–2–2 × 10^–4s^–1) and the test temperatures (R.T.–1023 K). The temperature range for DSA was moved to higher temperature for increasing nitrogen contents. The critical strain, _c for the onset of serration increased with nitrogen content at 773 K and then became almost constant at 873 K. Type A and B serrations were observed at 873 K with the value of the strain required to effect the transition from type A to type B serration increasing for nitrogen contents upto 0.1 wt% and then becoming saturated. The activation energy for DSA was 23.4–26.2 kcal mol^–1 (97.8–109.5 kJ mol^–1) at the onset and 65.0–76.6 kcal mol^–1 (271–320.2 kJ mol^–1) at the end of serration. The lower activation energy was related to vacancy diffusion and the higher activation energy was attributed to the diffusion of chromium to dislocations. The activation energy for DSA was slightly increased with nitrogen addition. DSA was retarded by an increase in the nitrogen content since nitrogen reduced the chromium diffusion to dislocations due to a strong interaction between the nitrogen and chromium.     

Surface modification of monodisperse‐crosslinked polymeric microspheres using a redox initiation system

The surface modification of monodisperse‐crosslinked polymeric microspheres was carried out by introducing hydroxyl groups on the surface and utilizing the redox initiation system. The emulsions of the second monomer mixture were swollen into the monodisperse PS seed particles. The hydroxyl groups were introduced by hydrolysis of the acetate groups on the surface of microspheres. Ceric ammonium sulfate in sulfuric acid solution was employed to graft the acrylic monomer onto the polymeric microspheres. The surface characteristics of the surface‐modified particles were confirmed by FTIR, SEM, and TGA measurements. From the FE‐TEM image, a uniform coating layer was confirmed on the surface of microsphere. In DSC analysis, only an exothermal peak appeared when high content of DVB was used in the seeded polymerization, while, T_gs emerged after hydrolysis and graft polymerization using the low content of DVB in the second monomer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1349–1356, 2006     

Study on fiber structure formation in wet spinning of aliphatic polyketone using aqueous solution of complex metal salts—Characteristics of solid structure formation in drying step and its effects on superdrawing step

Solid structure formation in the drying step for wet spinning of poly(1‐oxotrimethylene) using as a solvent an aqueous solution of complex metal salts of calcium chloride/zinc chloride was studied. Because the degree of structural densification and the crystal structure both differ depending on the drying temperature, the drying temperature had a major effect on the drawing behavior and the strength achieved after drawing. With higher drying temperature, the denseness increased due to smaller voids in the dried undrawn fiber, while there was also a tendency toward higher strength with respect to the draw ratio. However, an excessively high drying temperature altered the crystal structure from a rough crystalline form to a dense crystalline form and reduced both the maximum draw ratio and strength. Mechanical cleavage of the molecular chains occurred between the ethylene groups and carbonyl groups of the main chains in the drawing step. This cleavage made it possible to suppress the inhibition of drawing due to entanglement of the molecular chains, thereby enabling superdrawing to afford a high performance fiber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 446–452, 2004     

Modification of rubber powder with peroxide and properties of polypropylene/rubber composites

Waste tire powder was functionalized in the presence of various concentrations of allylamine and benzoyl peroxide. Fourier transform infrared spectroscopy studies confirmed the presence of allylamine on the surface of the rubber powder. The surface energy of the functionalized rubber powder revealed that the introduction of allylamine onto the rubber powder surface increased the surface activity. Improvements in the tensile strength, elongation at break, and storage modulus were observed for polypropylene/modified rubber powder/maleic anhydride grafted polypropylene, and this was attributed to an improvement in the compatibility due to the chemical interaction between the rubber powder and compatibilizer. Evidence for the reaction between the rubber surface and compatibilizer was observed in Fourier transform infrared studies. This peroxide‐initiated monomer‐grafting technique is feasible for large‐scale processes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2237–2243, 2007     

Biomechanical features of level walking by transtibial amputees wearing prosthetic feet with and without adaptive ankles

This study aimed to evaluate the kinematics and kinetics of the lower limb in both the intact and amputated leg in individuals with transtibial amputations wearing Energy storage and return feet (ESRFs) with fixed ankles and Prosthetic feet with adaptive ankles (PFAAs) during level walking. Three individuals with transtibial amputations walked on level ground wearing their own ESRFs and PFAAs. Spatiotemporal parameters, kinematics, and kinetics of the lower-extremity joints were measured in the amputated and intact legs. There were differences in the kinematics of the joints in the amputated leg and of the ankle in the intact leg between ESRFs and PFAAs. Differences in joint moments, power, and stiffness in most joints in both legs and braking impulse were found between ESRFs and PFAAs. Thus, although it was a pilot study with three subjects, ankle angle control mechanisms (ESRFs: Fixed ankle vs. propriofoot: Mechanical motor vs. élan and echelon: Hydraulic actuator) might affect biomechanical features during level walking.

     

Note: Recent achievements at the 60-MeV linac for sub-picosecond terahertz radiation at the Pohang Accelerator Laboratory

A femtosecond (fs) terahertz (THz) linac has been constructed to generate fs-THz radiation by using ultrashort electron beam at the Pohang Accelerator Laboratory. To generate an ultrashort electron beam with 60-MeV energy, a chicane bunch compressor has been adopted. Simulation studies have been conducted to design the linac. In this note, recent achievements at 60-MeV linac are presented.     

High-quality isosurface generation using an oversampling method

Isosurface generation from medical images was done using an oversampling method. The key idea of the proposed method was based on the fact that oversampling and downsampling together can improve the signal-to-noise (SNR) ratio. The procedure consisted of four phases: (1) oversampling of a voxel, (2) topology estimation, (3) low-pass filtering, and (4) downsampling. The effectiveness of the method was verified in terms of SNR, compactness, and surface roughness of the fabricated rapid prototyping parts.     

Dynamic responses and fuzzy control of a simply-supported beam subjected to a moving mass

This paper deals with the active vibration control of a simply-supported beam traversed by a moving mass using fuzzy control. Governing equations for dynamic responses of a beam under a moving mass are derived by Galerkin’s mode summation method, and the effect of forces (gravity force, Coliolis force, inertia force caused by the slope of the beam, transverse inertia force of the beam) due to the moving mass on the dynamic response of a beam is discussed. For the active control of dynamic deflection and vibration of a beam under the moving mass, the controller based on fuzzy logic is used and the experiments are conducted by VCM (voice coil motor) actuator to suppress the vibration of a beam. Through the numerical and experimental studies, the following conclusions were obtained. With increasing mass ratioy at a fixed velocity of the moving mass under the critical velocity, the position of moving mass at the maximum dynamic deflection moves to the right end of the beam. With increasing velocity of the moving mass at a fixed mass ratioy, the position of moving mass at the maximum dynamic deflection moves to the right end of the beam too. The numerical predictions of dynamic deflection of the beam have a good agreement with the experimental results. With the fuzzy control, more than 50% reductions of dynamic deflection and residual vibration of the tested beam under the moving mass are obtained.