Comparative Analysis of Locally Available Materials for Treadle Pump Seals in Senegal, West Africa

For rural farmers in Senegal, West Africa, pulling water for irrigation can be a laborious but necessary task during the dry season to earn income from vegetable gardening. Traditional water pulling methods are inexpensive but require great physical effort, while modern machines decrease the labor burden but at a high financial cost. This study looked at an intermediate water pulling technology, the treadle pump, and how it could be improved to become more desirable for use in agricultural irrigation. A treadle pump was built and tested during field work in a rural Senegalese village. Observations from field testing prompted a single component of the treadle pump, the piston seals, to be further investigated for improvement. Locally available materials were procured to make novel, experimental piston seals that were preliminarily field tested. Problems arising during field testing created the need for more consistent tests in a controlled environment. Laboratory testing was performed to draw conclusion about the new materials regarding operation force and performance of the piston seal. Results showed that three of the six materials tested had the potential to serve as functional replacements for the standard treadle pump piston seals. These materials shared similar properties as they were all foams and performed within a close range of one another. A financial comparison showed these materials to cost 97.3% less than the standard seals leading to a 16.4% reduction in the overall cost of the treadle pump. While the recommended materials could presently work as functional piston seals, future work is recommended to determine the lifetime of the materials

Distributed manufacturing with 3-D printing: a case study of recreational vehicle solar photovoltaic mounting systems

International audienceFor the first time, low-cost open-source 3-D printing provides the potential for distributed manufacturing at the household scale of customized, high-value, and complex products. To explore the potential of this type of ultra-distributed manufacturing, which has been shown to reduce environmental impact compared to conventional manufacturing, this paper presents a case study of a 3-D printable parametric design for recreational vehicle (RV) solar photovoltaic (PV) racking systems. The design is a four-corner mounting device with the ability to customize the tilt angle and height of the standoff. This enables performance optimization of the PV system for a given latitude, which is variable as RVs are geographically mobile. The open-source 3-D printable designs are fabricated and analyzed for print time, print electricity consumption, mechanical properties, and economic costs. The preliminary results show distributed manufacturing of the case study product results in an order of magnitude reduction in economic cost for equivalent products. In addition, these cost savings are maintained while improving the functionality of the racking system. The additional electrical output for a case study RV PV system with improved tilt angle functionality in three representative locations in the U.S. was found to be on average over 20% higher than that for conventional mass-manufactured racking systems. The preliminary results make it clear that distributed manufacturing-even at the household level-with open-source 3-D printers is technically viable and economically beneficial. Further research is needed to expand the results of this preliminary study to other types of products

Anisotropic rate-dependent mechanical behavior of Poly(Lactic Acid) processed by Material Extrusion Additive Manufacturing

The strain-rate dependence of the yield stress for Material Extrusion Additive Manufacturing (ME-AM) polylactide samples was investigated. Apparent densities of the ME-AM processed tensile test specimens were measured and taken into account in order to study the effects of the ME-AM processing step on the material behavior. Three different printing parameters were changed to investigate their influence on mechanical properties, i.e. infill velocity, infill orientation angle, and bed temperature. Additionally, compression molded test samples were manufactured in order to determine bulk properties, which have been compared to the ME-AM sample sets. Anisotropy was detected in the strain-rate dependence of the yield stresses. ME-AM samples with an infill angle of 0° have a higher strain-rate dependence than specimens with αor = 90°. Remarkably, the strain-rate dependence manifested by the ME-AM samples is considerably lower than that displayed by compression molded test specimens. The Ree-Eyring modification of the Eyring flow rule is able to accurately describe the strain-rate dependence of the yield stresses, taking two molecular deformation processes into account to describe the yield kinetics. The results from this paper further show a change from a brittle behavior in case of compression molded samples to a semi-ductile behavior for some of the ME-AM sample sets. This change is attributed to the processing phase and stresses the importance that the temperature profile (initial fast cooling combined with successive heating cycles) and the strain profile during ME-AM processing have on the resulting mechanical properties. Both these profiles are significantly different from the thermo-mechanical history that material elements experience during conventional processing methods, e.g. injection or compression molding. This paper can be seen as initial work that can help to further develop predictive numerical tools for Material Extrusion Additive Manufacturing, as well as for the design of structural components

Notch static strength of additively manufactured acrylonitrile butadiene styrene (ABS)

The present theoretical/experimental investigation deals with the problem of performing the static assessment of notched components made of additively manufactured Acrylonitrile Butadiene Styrene (ABS). The notch strength of this 3D-printed material was investigated by testing a large number of specimens, with the experiments being run not only under tension, but also under three-point bending. The samples contained geometrical features of different sharpness and were manufactured (flat on the build plate) by changing the printing direction. Being supported by the experimental evidence, the hypothesis was formed that the mechanical response of 3D-printed ABS can be modelled effectively by treating it as a material that is linear-elastic, brittle, homogenous and isotropic. This simplifying hypothesis allowed the Theory of Critical Distances to be employed also to assess static strength of 3D-printed ABS containing geometrical features. The validation exercise based on the experimental results being generated demonstrates that this theory is highly accurate, with its use leading to predictions falling mainly within an error interval of about ±20%. This level of accuracy is certainly satisfactory especially because this static assessment methodology can be used in situations of engineering relevance by making use of the results obtained by solving standard linear-elastic Finite Element models

Climate Change Mitigation Through Reduced-Impact Logging and the Hierarchy of Production Forest Management

The proposed hierarchy of production forest management provides modus operandi for forest concessions to move incrementally towards Sustainable Forest Management (SFM) via Reduced-Impact Logging (RIL) and forest certification. Financial benefits are sourced in the “Additionality Zone”, financing the rise in the hierarchy and offsetting prohibitive forest and carbon certification costs. RIL carbon registration components consist of developing credible baseline, additionality and leakage arguments around the business-as-usual scenario through the quantification of historical forest inventory and production records, forest infrastructure records and damage to the residual forest. If conventional harvesting is taken as a baseline, research indicates RIL can potentially reduce emissions by approximately 1–7 tCO2e ha−1yr−1. The current market price of USD $7.30 per tCO2e may result in over USD$50 ha−1yr−1 in additional revenue, well above the estimated USD $3–5 ha−1 in carbon transaction costs. Concessions in Sabah Malaysia demonstrate the financial viability of long-term RIL and certification planning. This may act as a basis for future planned forest management activities involving RIL, carbon and forest certification through the hierarchy of production forest management

Observation of fracture behavior of 3-D printed specimens under rolling contact fatigue in water

Polymer bearing was widely used in the corrosive conditions because of its high corrosion durability. The polymer bearing had been formed using molding and machining until the new 3-D printing method was developed. In this study, we performed the rolling contact fatigue tests of the 3-D printed specimens in water and observed the fracture behaviour of the specimens. We found that the surface cracks are related to both the rolling direction and the lamination directions