A note on shakedown

The residual stresses developed beneath a rigid ball pressed into an ideally elastoplastic half-space are found on the centre-line of contact. Using the theoretical results of Johnson a shakedown limit based on the criterion that residual stresses are maintained at less than the yield criterion is found, and experimental results confirm that this limit obtains.     

A note on the existence of Bennett mechanism

The existence of Bennett mechanism has long been recognized. Since the discovery of this mechanism, kinematicians have further extended to the vast spatial domain. The present paper developes the existence criteria for this pioneer mechanism through the use of tensor analysis.     

A note on dwell-cam follower-motion synthesis

As an alternative to the usual procedure, it is suggested that theoretically exact dwells are not demanded from cams so that a single motion law to cover the entire cycle and its repetitions can be prescribed, thus avoiding sudden changes in the motion derivatives of all orders. A way is shown to arrive at such a motion law for dwell-rise-dwell cams with freedom to optimize for kinematic or dynamic characteristics. Unequal top and bottom dwells as well as unequal rise and fall times can be obtained. The use of a finite trigonometric series to cover the entire motion cycle enables direct control over high frequency components of the motion. Calculations for the case of unequal rise and fall times can be reduced, if the finite trigonometric series is sacrificed. Numerical evidence is included.     

A note on Nayak's third paper

The importance of Nayak's work on contact patches is emphasised, and a new estimate of the density of holes, and hence of contact patches, is offered. This strongly suggests that in asperity models of the contact of rough surfaces, the coalescing of asperities must be considered.     

A note on optimal design of columns

To illustrate characteristic aspects of optimal design of columns, a discrete model of an elastically clamped column is used, which consists of rigid segments that are joined by elastic hinges to each other and to the supports. It is shown that the optimum is analytical when the elastic clamping is weak, but nonanalytical when it is strong.     

A note on the three-point method for roundness measurement

This technical note presents two enhancements to three-point method for roundness measurement. They enable measuring a larger bandwidth and also present a logical progression from two-point profile to three-point roundness measurement using the combined method. Simulated profiles with and without step variations are used to demonstrate these improvements.     

A note on productivity gains in flexible robotic cells

Flexible robotic cells combine the capabilities of robotic flow shops with those of flexible manufacturing systems. In an m-machine flexible cell, each part visits each machine in the same order. However, the m operations can be performed in any order, and each machine can be configured to perform any operation. We derive the maximum percentage increase in throughput that can be achieved by changing the assignment of operations to machines and then keeping that assignment constant throughout a lot's processing. We find that no increase can be gained in two-machine cells, and that the gain in three- and four-machine cells each is at most 14 %.     

A note on the homogeneity of the roughness on oblique finish turned surfaces

The homogeneity of the roughness on oblique finish turned surfaces is investigated statistically by an analysis of variance technique applied to experimental data obtained during the useful life of a carbide turning tool. In general, a highly significant row effect (due to tool wear) has been established. A significant column effect has also been found to be present in some of the selected specimens, particularly in those of smaller length. The results of this analysis provide a guide for surface roughness measurements in practice.     

A note on the stereological implications of irregular spacing of sections

Stereological methods for serial sections traditionally assume that the sections are exactly equally spaced. In reality, the spacing and thickness of sections can be quite irregular. This may affect the validity and accuracy of stereological techniques, especially the Cavalieri estimator of volume. We present a new formula for the accuracy of the Cavalieri estimator that includes the effect of random variability in section spacing. A modest amount of variability in section spacing can cause a substantial increase in estimator variance.     

A note on tensile deformation of flat sheets

It is shown that the results of previous calculations [7] are insensitive to the precise value of the constant of proportionality between radii ratio and neck strain, for a wide range of choices for this constant.     

A note on the radial vibrations of an isotropic spherical shell

Results and a graphical appeciation for the study of the frequencies of radial vibration in a hollow spherical shell are given.     

A brief note on the concept of planarity for kinematic chains

In this note the concept of planarity is briefly reviewed with the aim of suggesting a unified interpretation of this word as an attribute of the concept of kinematic chain. The lack of a correct and unambiguous meaning of the concept of planar kinematic chain may cause serious misunderstandings nowadays, as in the reported example.     

A note on spherical structures in chars from vitrinites of coking rank

Spherulitic aromatic structures with relatively simple optical characters that form as a transitional phase in the development of mosaic textures are well known in pitch fractions and certain polymers when carbonized. Their occurrence in coal macerals that soften prior to the formation of a mosaic is less certain. Other spherulitic structures, much larger in size than mesophase spherules, can, however, develop from vitrinites with a high potential fluidity under certain carbonization conditions, when fast heating rates are employed. These bodies, besides displaying optical characters that indicate structural symmetry, also show mosaic textures.     

Short note on parallel illumination in the TEM

Parallel illumination conditions are required for several experiments in the transmission electron microscope (TEM). The image rotation induced by the helical trajectory of electrons passing through the magnetic field of the TEM lenses inevitably induces an inclination of the beam relative to the optical axis in the object plane--even for an electron which travels parallel to the optical axis in the far field. This angle (shear angle) is vectorially added to the convergence angle; it depends both on the distance to the optical axis and the magnetic field. By using a beam tilt compensation method, the minimum shear angle is found to be of the order of 1 mrad for a field of view of 2 microm in a 200 kV TEM. In practice, "parallel illumination" can only be obtained for fields of view 1 microm.     

A note on single-machine scheduling problems with the effects of deterioration and learning

This paper studies two single-machine scheduling problems with the effect of deterioration and learning. In this model, the processing times of jobs are defined as functions of their starting times and positions in a sequence. For the following two objective functions: the weighted sum of completion times and the maximum lateness, this paper proposes two heuristics according to the corresponding single machine problems without learning effect. This paper also gives the worst-case error bound for the heuristics and provides computational results to evaluate the performance of the heuristics.