Women's motivation for family planning in Kisii District: potentials and barriers

This paper is tentatively arguing that women in Kisii District are confronted with a number of factors which are acting both as potentials as well as barriers to their motivation for family planning. Focus is put on progressive and regressive changes in female status and role at the household level. Factors such as changing sexual division of labour, changing gender relations and gender roles and changing decision-making pattern are discussed as well as the way in which these changes are interacting positively or negatively on women’s motivation for limiting their child births and making use of family planning. As men and their attitude to family planning seem to create a major barrier for many women, research on men was included in the study, and their attitudes are tentatively discussed. Other factors interacting with women's motivation for family planning are considered to be value and costs of children and fears of side-effects. Also availability and quality of family planning services are discussed. It is argued that a number of potential users are lost because of inadequate services

Damage and fracture of biological and biomedical materials

In the last decade, the topic of damage and fracture of biological and biomedical materials not only became one of the central research areas in the healthcare engineering, but also drew attention of specialists in mechanics of materials and fracture. One of the motivations behind these developments is a continuing increase in the use of medical devices made of various materials that are exposed to challenging loading and environmental conditions. Many of them should have significant levels of durability to avoid recurring surgical interventions (typical examples being implants for hip and knee replacements or dental implants). A lack of understanding of their responses to specific conditions and interaction with biological environment can result in malfunctioning and failures or traumas to surrounding tissues. The typical application problems are additionally complicated by insufficient knowledge of mechanical behaviour of biomaterials at various length and time scales and under different loading conditions including their fracture and fatigue. These types of application presuppose the understanding of properties and performance of two classes of materials – natural (biomaterials) and engineering (biomedical materials), as well as their interaction at interfaces between, on the one hand, life tissues (or organs) and, on the other hand, implants and prostheses. Among engineering materials, used in such applications, are familiar metals and alloys, ceramics, polymers and composites. Their properties and performance seem to be well studied; still, biomedical applications are characterised by rather specific usability envelopes as well as, in most cases, additional constraints such as non-toxicity (biocompatibility) and/or resistance to harsh physiological environments. In some cases, a requirement, opposite to structural integrity, is needed, e.g. controlled degradation for scaffolds and stents..

Mechanical Stimuli in Prediction of Trabecular Bone Adaptation: Numerical Comparison

Adaptation is the process, with which bone responds to changes in loading environment and modifies its properties and organisation to meet the mechanical demands. Trabecular bone undergoes significant adaptation when subjected to external forces, accomplished through resorption of old and fractured bone and formation of a new bone material. These processes are assumed to be driven by mechanical stimuli of bone-matrix deformation sensed by bone mechanosensory cells. Although numerous in vivo and in vitro experimental evidence of trabecular bone morphology adaptation was obtained, the exact nature of mechanical stimuli triggering biological responses (i.e., osteoclastic resorption and osteoblastic formation) is still debated. This study aims to compare different mechanical stimuli with regard to their ability to initiate the load-induced adaptation in trabecular bone. For this purpose, a 2D model of two trabeculae, connected at their basement, with bone marrow in the intertrabecular space was developed. The finite-element method was implemented for the model loaded in compression to calculate magnitudes of several candidates of the bone-adaptation stimuli. A user material subroutine was developed to relate a magnitude of each candidate to changes in the shape of trabeculae

Computational assessment of residual formability in sheet metal forming processes for sustainable recycling

This paper introduces a new computational scheme addressing a problem of cold recyclability of sheet–metal products based on the assessment of their post-manufacture residual formability. Formability of sheet metals has been studied for several decades, and various techniques were suggested since a Forming Limit Diagram was first introduced in the 1960s. At the same time, cold recycling, or re-manufacturing, of sheet metals is an emerging area studied mostly empirically; in its current form, it lacks theoretical foundation. In order to address the challenge of residual formability for sheet-metal products, a reformability index is introduced in this study. The proposed method takes advantage of the latest developments in the area of evaluating multiple-path formability and introduces a quantitative re-formability index for the manufactured material. This index represents possible levels of strains for deformation along different paths, based on Polar Effective Plastic Strain (PEPS). PEPS provides robustness against non-linear strain-path effects, thus making a reliable basis for such analysis. Based on residual formability, a predictive model was sought to assess a degrading effect of the flattening process. Taking advantage of extensive numerical simulation, a wide range of geometrical parameters in an unbending process, as a predominant mechanism in flattening, was studied. The re-formability index alongside prediction of degradation in flattening allows evaluation of prospective re-manufacturing. The significance of this research is its advancement towards recycling of sheet-metal products without melting them by facilitating design for sustainability. The proposed scheme also provides a subroutine friendly framework for numerical simulations

Theoretical analysis on needle-punched carbon/carbon composites

© 2019, Springer Nature B.V. Needle-punched carbon/carbon composites (NP-C/Cs) are advanced materials widely used in aerospace applications. The needle-punching technique improves the integrality of carbon-fibre plies, however, it also introduces many defects, affecting the mechanical behavior of NP-C/Cs. A theoretical model of irregular beams is suggested to investigate the mechanical behavior of unidirectional needle-punched carbon/carbon composites. Stress distributions in punched and squeezed fibres and an effect of the needle-punching technology are assessed

Tensile Behavior of Low Density Thermally Bonded Nonwoven Material

A discontinuous and non-uniform microstructure of alow-density thermally bonded nonwoven materialdisplays in a complicated and unstable tensilebehavior. This paper reports uniaxial tensile tests of alow density thermally bonded nonwoven toinvestigate the effect of the specimen size and shapefactor, as well as the cyclic tensile loading conditionsemployed to investigate the deformational behaviorand performance of the nonwoven at differentloading stages. The experimental data are comparedwith results of microscopic image analysis and FEmodels

Finite Element Modelling of Conventional and Hybrid Oblique Turning Processes of Titanium Alloy

AbstractThis study is a part of the on-going research at Loughborough University, UK, on finite element (FE) simulations of ultrasonically assisted turning (UAT) coupled with hot machining processes. In UAT, vibration is superimposed on the cutting tool movement, resulting in several advantages of the process, especially in machining of high-strength engineering materials. Direct experimental studies of machining processes are expensive and time consuming, especially when a wide range of machining parameters affects, complex thermo-mechanical high-deformation processes in machined materials. In recent years, a use of mathematical simulations and, in particular, FE techniques has gained prominence in the research community. These techniques provide an accurate and efficient modelling paradigm for machining processes. In the present work, thermo-mechanically coupled three-dimensional FE models of conventional, ultrasonically assisted turning and a new hybrid turning technique called hot ultrasonically assisted oblique turning for a case of titanium alloy are presented. A nonlinear temperature-sensitive material behaviour is incorporated in our numerical simulations based on the results of the split-Hopkinson pressure bar tests. The simulation results obtained at different cutting conditions are compared to elucidate main deformation mechanisms responsible for the observed changes in the material's responses to various cutting techniques