LUBRICATION FILM FORMATION MECHANISM OF SLIPPER PAIRS IN LOW SPEED HIGH TORQUE HYDRAULIC MOTORS

Pressure-flow analytical formulas of lubrication film of slipper pairs on camshaft connect- ing rod type low speed high torque (LSHT) hydraulic motors are put forward. The bottom surface of slipper pairs is rectangle, and the effect of squeeze flow and pressure differential flow is considered. The dynamic process of lubrication film formation through squeezing is numerically studied by com- puter simulation. Effects of supply pressure, initial lubrication film thickness, velocity damping coef- ficient, loading impact and gravity, etc are studied. Advantages of novel slipper pairs with large oil cavity area are pointed out.     

Effect of La2O3 Particles on the Oxidation of Electrodeposited Nickel Films

Electrodeposited Ni-La₂O₃composite films with nanometer-sizeLa₂O₃ oxide inclusions werefabricated by the codeposition of nickel withLa₂O₃ particles. The comparativeoxidation behavior in air at 900 and 1000°C of nickel coated with theNi-La₂O₃ composite and films withand without nickel-plating was studied by TGA, AE,SEM/EDX, EPMA, and TEM/EDX. In general, theNi-La₂O₃ composite-coated nickelhad the slowest rate and the best resistance tothermal cycling. AE tests revealed that cracking eventsin NiO scales on Ni-La₂O₃composite-coated nickel was significantly reduced incomparison to that of the scale on nickel-coated nickel during thermalcycling at 900°C. SEM investigation showed that theLa₂O₃-free NiO scale was composedof outer coarse columnar grains and inner equiaxed ones.By contrast, the scale on the Ni-La₂O₃composite-coated nickel consisted of only fine equiaxedNiO grains. The scale on theLa₂O₃-free samples wascharacterized by cracks that originated at thescale-substrate interface and spanned the scale thickness. By contrast,no scale cracks formed at theLa₂O₃-doped NiO scale-substrateinterface, but small voids were created at the triplepoints of the grain boundaries of NiO. In the La₂O₃-doped NiOscale, segregation of La ions to the NiO grainboundaries near the scale-surface was observed by EDXmicroanalyses in the TEM. It is believed that the Laions segregated at the grain boundaries of NiO led to an increase in thecohesion between nickel oxides and in a reduction of thescaling rate and the formation of scale with fineequiaxed crystal structure by blocking the outward and lateral growth of scale. The latter was dueto the predominant outward diffusion of nickel along NiOgrain boundaries being inhibited effectively by thesegregated La ions. The mechanism of the effect of the added La₂O₃particles on the nickel electrodeposits is discussed indetail.     

Characterisation of mechanical properties of thin polymer films using a bi-axial tension based on blow-up test

Abstract

Blow-up tests were carried out to evaluate mechanical properties of the thin Nylon film used as bagging films. A new method for calculating bi-axial stress and strain of the thin film in blow-up tests was developed based on the theory of membrane with large strain solutions. The bi-axial tensile elastic modulus, Poisson's ratio, yield strength, fracture stress and bi-axial stress–strain relationship of the thin Nylon film were obtained. Meanwhile, uni-axial tensile tests were conducted and the results were compared with those from blow-up tests. For the Richmond HS-8171 thin Nylon film studied, the bi-axial tensile elastic modulus was slightly more than 2 times greater than the uni-axial tensile elastic modulus. The yield strength was the same for both bi-axial and uni-axial tension. The bi-axial fracture stress was about one-third greater than the uni-axial one, while the bi-axial failure strain was about two-thirds greater than the uni-axial counterpart.     

A new understanding on the mechanism of fountain solution in the prevention of ink transfer to the non-image area in conventional offset lithography

In conventional offset lithographic printing, it has been well established that the existence of a continuous layer of fountain solution (FS) on the surface of the non-image area is an essential condition to ensure correct operation of lithography. However, the mechanistic function of FS in preventing the ink from being transferred onto the non-image area has not been fully understood. Several major mechanistic interpretations can be found in the literature, which are based either on comparing of static works of adhesion and cohesion of ink and FS, or on the splitting of the 'weaker' FS layer. Although the latter becomes more accepted, direct experimental evidence is difficult to find in the literature. On the other hand, confusing information found in the literature showed that the ink-transfer (or non-transfer) observations reported in many case studies correlate well with simple comparisons of works of adhesion, cohesion and spreading data of ink/FS, ink/plate and FS/plate obtained under the static condition. These results, therefore, imply that, in explaining the function of FS in preventing ink transfer to the non-image area, the ink/FS interfacial adhesion failure would be the dominant mechanism. The work presented in this study covered two specific areas in order to address and better understand the responses of ink and FS layers and their interface to forces encountered during ink transfer. Firstly, an analysis of lithographic plates contaminated with a cationic polymer revealed that the violation of the ink non-transfer condition of the plate non-image area due to contamination could be predicted by traditional criteria of plate wetting and works of adhesion and cohesion. However, these traditional criteria cannot reliably predict the non-transfer condition of the ink on the clean non-image area that was covered by FS. Secondly, in some novel experiments conducted in this study using ice or Teflon as a substrate, the works of adhesion and cohesion were not able to predict ink transfer in most cases. Direct experimental evidence from this work revealed that splitting of the FS layer was involved in the prevention of ink transfer to the non-image areas, and that the thickness of the FS layer was critical in allowing the splitting to occur.     

Thermal and hygroscopic reliability of flip-chip packages with an anisotropic conductive film

Thermal and hygroscopic reliability of anisotropic conductive film (ACF) joints in relation to flip-chip bonding force was evaluated by thermal shock and constant temperature/humidity testing. The failure mode by thermal shock testing varied with increasing bonding force, i.e., (1) formation of a conduction gap between conductive particles and Au bump or Ni/Au plated Cu pad at low bonding force and (2) delamination of adhesive matrix from the plated Cu pad on the flexible substrate at high bonding force. The delamination initiated as a crack under a conductive particle and propagated sideward resulting in a complete delamination of the ACF from the Cu pad. However, delamination was observed between the ACF and Au bump on the chip side after the constant temperature/humidity testing for 500 h. A theoretical calculation was also conducted to predict the connection resistance of the ACF joint before and after reliability tests. The calculation showed the importance of the bonding gap between the electrodes.     

Formation and stability of pyrochlore in sputtered SBT thin films

Abstract

In magnetron sputtering of SrBi₂Ta₂O₉ (SBT) thin films, bismuth deficiency tends to result in formation of an unwanted pyrochlore phase. In this paper, the dependence of deposition parameters on phase evolution in Sr deficient SBT thin films is studied. Only when bismuth is over stoichiometric (Sr_0.74Bi_2.2Ta₂O_9+x) can one obtain pure SBT structure. Decreasing the Bi content encourages formation of the Bi deficient pyrochlore phase. At 1.04 of Bi, only the pyrochlore phase forms. The pyrochlore phase is very stable even at 900°C.     

Thermoplastic film adhesives based on phenol-functional acrylic copolymers: synthesis,mechanical and adhesion properties

Acrylic polymers possessing varying proportions of pendant phenol groups were synthesized by the free radical copolymerization of N-(4-hydroxyphenyl) maleimide (HPM) with butyl acrylate (BuA) and acrylonitrile (AN) and characterized. These thermoplastics form excellent films and their mechanical and adhesion properties were evaluated as a function of the phenol content. Enhancing the HPM content increased both the tensile strength and the modulus but decreased the elongation. A nominal increase in the phenol content was found to be conducive for improving the adhesion properties of the films. At higher concentrations, the adhesion properties showed a decreasing trend due to the embrittlement caused by the rigid maleimide groups. The adhesion property at 50°C increased linearly with the HPM content due to an increased T _g, whereas a reverse trend was observed for the adhesion property measured at-196°C, due to the dominance of the embrittlement effect. The reduced flow characteristics of the high HPM-loaded systems led to a diminished honeycomb flat-wise tensile strength. Enhancing the HPM concentration in the chain promoted the adhesion properties for the vulcanization bonding of nitrile rubber to aluminium. Addition of silica filler marginally improved the lap shear strength (LSS) for the metal-metal system, but was detrimental for rubber-metal bonding; a reverse trend was observed for the carbon-filled system. The diminished performance for metal-metal bonding by carbon could be attributed to the weakening of the interphase, whereas the enhanced rubber-metal bonding could be due to possible reinforcement of the rubber phase by carbon. The fillers generally improved the high temperature adhesion. However, they impaired the flow properties of the resin and, thereby, adversely affected the flat-wise tensile strength in both cases.     

Characterisation of flame retardant plasma polymer deposited BOPP film

Abstract

Flame retardancy of polypropylene films was studied by plasma polymerisation technique. The surface of BOPP film was modified by boron containing plasma polymers at different plasma conditions. Plasma polymer coated polypropylene films were examined by flame retardancy test (limiting oxygen index, LOI) and TGA. Boron containing plasma polymer deposition on the film surface showed an improvement of flame retardancy. Furthermore, TGA thermograms pointed out that the first degradation temperature of treated polypropylene film was increased from 331 to 396°C, and the second degradation temperature was shifted from 401 to 455°C. Also, the plasma polymers were characterised by FTIR spectroscopy and XPS. According to XPS results, the BOPP surfaces treated with TMB showed significant difference in the composition with respect to the untreated sample. The FTIR spectra of plasma polymers obtained indicated that when the treatment time was increased to 60 min with a constant discharge power at 80 W, the absorption intensities of all the functional groups increased. As a result, boron containing plasma polymer treatment was found to be an effective method in enhancing the flame retardancy of BOPP film.     

New BST–silica suspension coating material for dielectric thin films fabricated at low temperatures

Abstract

A new Ba_0·7Sr_0·3TiO₃ (BST)–silica suspension has been developed as a coating material for dielectric thin films. Using a spin on glass (SOG) wet process, a thin layer consisting of nanoparticles of BST and silica was formed on an Al/SiO₂/Si wafer. The BST–silica suspension was made by mixing a BST nanoparticle dispersion with methyl siloxane oligomer. A silicon wafer was coated with the BST–silica suspension using a spin coater and heat treated. The sample was then coated with methyl siloxane oligomer and heat treated again, and finally, a top electrode was applied. The Al/SiO₂/BST–SiO₂/Al/SiO₂/Si stack thus prepared is a metal insulator metal (MIM) capacitor. The electrical properties of the MIM capacitor were evaluated and its capacitance, dissipation factor and voltage coefficient of capacitance were determined to be 1054 pF mm^?2, <0·1 and <100 ppm V^?1 respectively.     

Application of FFT-Based Signal Analysis to Micro-Scratch Testing for Adhesion Strength Measurement of Thin Films and Measured Results Based on Different Measurement Parameters

An FFT-based signal processing method for the micro-scratch test, proposed by Baba was compared with a conventional micro-scratching method to quantitatively evaluate the suitability of the technique. Original scratch signals from a micro-scratch system were first digitized by a 16-bit analog-to-digital converter with a sampling frequency of 44.1 kHz, which were fed into a personal computer. Then, the FFT-based method and the conventional method were used to process the signals according to their individual algorithms. The output results from the two methods were compared, showing that the FFT-based method effectively reduces unnecessary signals arising from the micro-scratching mechanism, and that the output level of the unnecessary signals for the FFT-based method is about 50% lower than that observed in the conventional method. The FFT-based method was implemented into a micro-scratch tester for actual application and critical loads of various thin films were measured using various measurement parameters. The results showed that the critical load increases with increasing stylus radius, or increasing thickness of the film, whereas it decreases with increasing frequency of forced vibration. It is also shown that the amplitude of the forced vibration has only little effect on the critical load.