Single Lap Joints with Rounded Adherend Corners: Stress and Strain Analysis

One of the major difficulties in designing adhesive lap joints is the stress singularity present at the adherend corners at the ends of the overlap. One way to overcome this problem is to assume that the corners have a certain degree of rounding. The objective of the present study was to better understand the effect of the change in the geometry of the adherend corners on the stress distribution and, therefore, on the joint strength. Various degrees of rounding were studied and two different types of adhesives were used, one very brittle and another which could sustain a large plastic deformation. The study gives a detailed stress and strain distribution around the rounded adherends using the finite element method. The major finding is that the stresses or strains in the adhesive layer of a joint with rounded adherend corners are finite. In real joints, adherends generally have small rounded corners. Consequently, the model with small radius corners may be used to represent real adherends.     

Structural integrity and petrochemical industry

Abstract

The importance of engineering structural integrity in the petrochemical industry, which has broader implications for energy applications, is discussed in the context of the history of many serious accidents that have taken place in refineries, storage facilities and processing plants in recent years. A number of critical incidents from around the world are reviewed, and several cases investigated in North America are cited. These demonstrate the important role of well conducted regular inspections, based on sound advanced planning, in maintaining in service assessment of fitness for purpose of plant. The significant contribution of risk based inspection procedures, together with the need for a sound knowledge of potential degradation mechanisms, is emphasised. Finally, it is noted that there is a need for a safety conscious organisational culture underpinned by robust, relevant and continued training and development, for the entire workforce including management and supervisory staff.     

Dynamic Analysis of a Macro–Micro Redundantly Actuated Parallel Manipulator

In this paper the dynamic analysis of a macro–micro parallel manipulator is studied in detail. The manipulator architecture is a simplified planar version adopted from the structure of the Large Adaptive Reflector (LAR), the Canadian design of next-generation giant radio telescopes. In this structure it is proposed to use two parallel redundant manipulators at the macro and micro level, both actuated by cables. In this paper, the governing dynamic equation of motion of such a structure is derived using the Newton–Euler formulation. Next, the dynamic equations of the system are used in the open-loop inverse dynamics simulations, as well as closed-loop forward dynamics simulations. In the open-loop dynamic simulations it is observed that the inertial forces of the limbs contribute only 10% of the dynamic forces required to generate a typical trajectory and, moreover, the total dynamic forces contribute only 10% of the experimentally measured disturbance forces. Furthermore, in the closed-loop simulations using decentralized PD controllers at the macro and micro levels, it is shown that the macro–micro structure results in a 10 times more accurate positioning than that in the first stage of the macro–micro structure. This convincing result promotes the use of the macro–micro structure for LAR application.     

A Modular Platform for In-plane Ground Reaction Forces Detection in a Mouse Model: Design,Development and Verification

Movement and behavior analysis is a key research area in the domain of biomedical engineering and in many other medical research domains aiming at the understanding of physiological motor and cognitive basic mechanisms. The systematic application of robotic and mechatronic technologies to realize new tools and measurement methods for quantitatively assessing motor and cognitive functions in humans, as well as in animal models is gaining increasing popularity. This work represents a first step towards the development of a sensorized environment for behavioral phenotyping of animal models. In particular, this paper focuses on tremor analysis in Reeler mice, an emerging potential animal model for anatomical and behavioral traits observed in autism. Ground reaction force (GRF) sensing is indeed the most direct means of measuring tremor. Although force platforms have extensively been used for large-size animals, only a few attempts have been made to measure GRFs at a single paw for animals as small as mice or rats. Under the hypothesis that in-plane GRF components are directly connected to tremor, a small-size, modular, mechanically simple, two-axis force sensor for measuring the in-plane components of GRFs was designed and developed. Special care was paid to design a structure that allowed self-aligned assembly, for repeatability and modularity for combining multiple platforms for a sensorized floor. Preliminary testing was performed with both Reeler and wild-type mice. Fourier analysis validated the hypothesis of a direct connection between tremor and in-plane GRFs. Data analyzed and filtered highlight a peculiar spectrum frequency in Reeler mice tremor, centered around 21 Hz. This tremor, which was never quantitatively observed and measured before, is completely absent in wild-type mice.     

Nanotailoring of polyurethane adhesive by polyhedral oligomeric silsesquioxane (POSS)

The development and commercialization of nanoparticles such as nanoclays (NCs), carbon nanotubes (CNTs) and polyhedral oligomeric silsesquioxanes (POSS) offers new possibilities to tailor adhesives at the nanoscale. Four types of POSS, with reactive mono-functional groups of isocyanatopropyl, glycidoxypropyl, aminoethyl and non-reactive octaphenyl, were incorporated in concentrations of 1, 3 and 5 wt% into a polyurethane (PU)-based adhesive. Thermo-mechanical bulk properties were studied using dynamic mechanical analysis (DMA). Adhesive properties were characterized in shear and peel modes. Atomic force microscopy (AFM) was used to study the nanoscale morphology. DMA measurements indicated that the neat PU possessed a glass transition temperature (T _g) of ≈ 30°C. The T _g of PU/POSS-glycidoxypropyl nanocomposite adhesive increased gradually with POSS concentration to 50°C for 5 wt%. PU/POSS-octaphenyl nanocomposite adhesive exhibited an increased T _g by 10°C for 5 wt%. The incorporation of POSS-isocyanatopropyl in the PU had no effect on the T _g. With respect to shear properties of POSS-octaphenyl-, POSS-isocyanatopropyl- and POSS-glycidoxypropyl-based PU nanocomposite adhesives, shear strength improved by 230, 178 and 137%, respectively, compared to neat PU. POSS-aminoethyl exhibited lower shear and peel strengths, while POSS-isocyanatopropyl provided the best balance of both higher shear and peel strengths compared to neat PU. It was concluded that the grafted functional group on the POSS and its reactivity with the PU network components were the decisive factors with respect to the thermo-mechanical, morphological and adhesive properties of the resulting nanocomposite adhesives. Consequently, the POSS/polyurethane based nanocomposite adhesives could be tailored for a large range of applications.     

Thermal analysis applied to estimation of solidification kinetics of Al–Si aluminium alloys

Abstract

Evaluation of solidification kinetics by thermal analysis is a useful tool for quality control of Al–Si melts before pouring provided it is rapid and highly reproducible. Series of thermal analysis records made with standard cups are presented that show good reproducibility. They are evaluated using a Newton's like approach to get the instantaneous heat evolution and from it solidification kinetics. An alternative way of calculating the zero line is proposed which is validated by the fact that the latent heat of solidification thus evaluated is within 5% of the value calculated from thermodynamic data. Solidification kinetics was found highly reproducible provided appropriate experimental conditions were achieved: high enough casting temperature for the cup to heat up to the metal temperature well before solidification starts; and equal and homogeneous temperatures of the metal and of the cup at any time in the temperature range used for integration.     

In situ observation of phase selection in undercooled Ni–Al melts

Abstract

Raney-Ni type Ni–68·5 at-% Al alloys are used for catalytic applications in the chemical industry. In this work, melt undercooling experiments were performed by means of the electromagnetic levitation technique. High-energy X-ray diffraction was used to determine the solidification pathway and the origin of microstructure peculiarities in gas atomised powders. The direct observation of the phase selection in Ni–68·5 at-% Al has unambiguously revealed the primary phase formation of β-AlNi to be independent of the level of undercooling up to a maximum of 320 K. On cooling the β-AlNi phase undergoes a fast peritectic transformation L + AlNi → Al₃Ni₂ and is therefore not found in the as-solidified microstructure.     

Process simulation of powder injection moulding: identification of significant parameters during mould filling phase

Abstract

Simulating and optimising the powder injection process are complex problems since a number of linked material, geometry and process variables have to be considered. In addition, it is very difficult to identify critical parameters for designing binder systems, feedstocks, parts, moulds and processing conditions owing to the fact that multiple objective functions have to be considered. Towards the goal of identifying the level of significance of various material, process and geometry parameters during powder injection moulding, a systematic procedure for sensitivity analysis has been successfully developed for the mould filling phase of the PIM process. In this sensitivity analysis, all input parameters were defined for the mould filling simulation and all output parameters for optimum design of part, mould and processing conditions and dimensionless sensitivity values for all input and output parameters were calculated, which allow parameters with different units to be compared quantitatively. The sensitivity analysis procedure developed will be an invaluable tool for both the design engineer in the PIM industry who has to determine the critical input parameters for given design targets, as well as for the production engineer who has to optimise and monitor the production stage.     

37—THE AIR-FLOW FINENESS OF GREASY WOOL: INTER-LABORATORY TESTS OF A PROPOSED STANDARD PROCEDURE

An account is given of an inter-laboratory trial of a method of measuring the fineness of greasy wool by means of a Wira Air-flow Fineness Meter. Eight laboratories took part in two tasks: firstly, a calibration by each laboratory of its own air-flow meter in terms of internationally standardized wools; and, secondly, the measurement of the fineness of greasy-wool core samples by means of the specified method, which included a normal laboratory washing of the wool followed by opening on a wool-type Shirley Analyser.

As a result of the trial, the method was considered to be suitable for use by testing authorities, and tentative limits of precision of the method of measuring the fineness of greasy wool were established. The mean difference between any two laboratories ranged from 0.2 μm at 20-μm diameter to 0.5 μm at 28-μm diameter. This does not include sampling errors.     

12—A CRITIQUE OF SOME HYPOTHESES RELATING TO THE HETEROGENEITY OF THE HIGH-SULPHUR PROTEINS OF WOOL

Joubert and Burns prepared a large number of fractions from the high-sulphur proteins of wool and estimated their molecular weights and amino-acid compositions. Their data have been re-examined in order to look for statistically significant interrelations between amino acids and between the proportion of various amino acids and molecular weight. Statistical analysis of the data is also used to examine the credibility of some hypotheses concerning the mechanism of keratin biosynthesis and to provide further evidence for the existence of families of proteins within the high-sulphur fractions of wool.