Cool covered sky-splitting spectrum-splitting FK

Placing a plane mirror between the primary lens and the receiver in a Fresnel Köhler (FK) concentrator gives birth to a quite different CPV system where all the high-tech components sit on a common plane, that of the primary lens panels. The idea enables not only a thinner device (a half of the original) but also a low cost 1-step manufacturing process for the optics, automatic alignment of primary and secondary lenses, and cell/wiring protection. The concept is also compatible with two different techniques to increase the module efficiency: spectrum splitting between a 3J and a BPC Silicon cell for better usage of Direct Normal Irradiance DNI, and sky splitting to harvest the energy of the diffuse radiation and higher energy production throughout the year. Simple calculations forecast the module would convert 45% of the DNI into electricity

Maximizing The Efficiency Of A 4-cell FK Module

The outdoor measurements of both a single-cell and a 4-cell CPV modules reaching, respectively, maximum peak efficiencies of 36.0% and 34.8% (both corrected @Tcell=25°C) are presented. This is the result of the joint effort by LPI and Solar Junction to demonstrate the potential of combining their respective state-of-the-art concentrator optics and solar cells. The LPI concentrator used is a Fresnel Köhler(FK), which is an advanced nonimaging concentrator using 4-channel Köhler homogenization, based on a primary Fresnel lens and a free-form secondary glass lens. Solar Junction's cell is a triple-junction solar cell with the A-SLAM{trade mark, serif} architecture using dilute-nitrides

Experimental investigation on the accuracy of surface topography measurements of additively manufactured metal parts scanned by X-ray micro computed tomography

Additive manufacturing of metals is increasingly used for producing highly customizable parts, including complex and internal geometries. However, such parts are characterized by surface topographies that are difficult to be measured with contact or optical techniques, due to several complexities, including: presence of undercuts, non-totally melted powder particles and overhangs. Micro X-ray computed tomography has recently started to be considered as an alternative technique for topographical measurements of additive manufacturing surfaces, as it is capable of measuring also non-accessible surfaces and micro-scale surface features including undercuts. This work proposes a new method to determine the accuracy of surface topography measurements obtained by computed tomography as well as by optical areal measuring techniques. Ti6Al4V specimens were produced by selective laser melting. Specifically designed markers were then micro-milled on the surfaces of interest, to allow for accurate alignment and comparison of different areal topography measurements. Reference 2D roughness profiles were obtained after cutting and polishing the specimens at specific locations, by measuring the resulting cut-sections using an imaging probing system

Investigation on the effect of the test object material on the metrological performances of X-ray computed tomography systems

X-ray computed tomography (XCT) plays a significant role in industrial metrology, supporting the evolution of manufacturing technologies and the developments of advanced application. Indeed, it enables the measurement of a wide range of complex parts, characterized by internal and non-accessible features, micrometric details or free-form surfaces. However, the effect of a number of quantities, which affect the measurement results, limit the diffusion of the technology and need to be investigated. In this work, the effect of the material of the inspected object is analysed. A reference standard, consisting of a hole plate with a specific distribution of the holes, was designed in order to evaluate the influence of the material of the test object on the metrological performances of an industrial XCT system. The indications provided by the current draft of the ISO 10360-11 standard were followed to metrologically characterize the system, testing two hole-plates of different material, manufactured and calibrated for the study, separately and in combination with a ball plate

New method to evaluate the accuracy of CT surface topography measurements of additively manufactured metal parts

Surface topographies of metal additive manufactured components are inherently characterized by the presence of complex surface characteristics (e.g. re-entrant features), which are not accessible by contact or optical techniques. Micro X-ray computed tomography has been demonstrated capable of measuring non-accessible surfaces and micro-scale surface features, including undercuts. In this work, an innovative approach for evaluating the accuracy and establishing the traceability of surface topography measurements obtained by X-ray computed tomography is presented. Reference samples produced by selective laser melting of Ti6Al4V were specifically designed in order to acquire reference cross-sectional surface profiles representing the actual morphology (including re-entrant features) using an imaging probing system. Surface topographies were measured on these samples by X-ray computed tomography, confocal microscopy and focus variation. Moreover, the effect of different voxel dimensions on the accuracy of surface topography measurements performed by X-ray computed tomography was investigated

Accuracy of X-ray computed tomography dimensional measurements of additively manufactured metal lattice structures

Metal additive manufacturing (AM) technologies are capable of producing highly complex and customizable lattice structures with advantageous strength-to-weight properties, which are of growing interest in several industrial sectors, including aerospace and biomedical. However, the geometrical and dimensional quality of AM lattice structures – which often needs improvements to meet specific industrial requirements – needs to be assessed by adequate measurement techniques. Differently from conventional contact and optical coordinate metrology, X-ray computed tomography (CT) enables non-destructive measurements of both external and difficult-to-access struts, as well as of internal defects and features. The accuracy of CT measurements – fundamental to effectively improve the AM process – is investigated in this work using a metrological CT system to scan Ti6Al4V lattice structures fabricated by laser powder bed fusion. In particular, methods for the determination of measurement errors and uncertainty are studied, with the aid of a new reference object specifically designed and produced for the purpose

Metrological X-ray computed tomography for fiber geometrical characterization and mechanical properties prediction in fiber-reinforced plastic parts

Injection-molded fiber-reinforced thermoplastic parts are increasingly used in several industrial applications thanks to their low weight, high mechanical properties, vast design possibilities, and reduced costs. However, the geometrical characteristics of fibers (i.e. fiber orientation, length, and concentration) have a considerable impact on the mechanical properties of the fabricated parts. The conventional methods used to study the relationship between the fiber characteristics and the resulting mechanical properties typically rely on destructive and time-consuming techniques. Micro X-ray computed tomography, instead, allows performing non-destructive measurements of the geometrical characteristics of fibers. Nevertheless, tomographic measurements are still affected by a consistent number of influence factors, hindering the results accuracy. This work proposes a methodology to verify and enhance the accuracy of tomographic fiber geometrical measurements as well as to determine their uncertainty. The improved outcomes are then exploited to accurately predict the mechanical properties of injection-molded glass-fiber-reinforced specimens characterized by different fiber volume fractions

Development of a reference object for accuracy evaluation of CT measurements of additively manufactured metal lattice structures

Additive manufacturing (AM) technologies can be successfully used to produce metal parts with controlled and complex lattice structures. However, AM parts are intrinsically characterized by dimensional and geometrical errors, which need to be properly identified and quantified to improve the quality of AM processes and the properties of end products. In this work, X-ray computed tomography (CT) is applied to enable advanced non-destructive dimensional measurements. The CT measurement accuracy is evaluated using a reference object specifically designed and produced to be similar to AM lattice structures. The reference object can be used to implement the substitution approach as well as to validate alternative methods for uncertainty determination

Optimization of fiber measurements performed by X-ray computed tomography to predict the mechanical properties of fiber-reinforced polymeric components

The mechanical properties of fiber-reinforced polymers (FRP) depend significantly on the geometrical characteristics of fibers, including orientation, length and volume fraction. The conventional methods used to analyze such characteristics often involve the use of destructive and time-consuming techniques. In this context, X-ray computed tomography (CT) offers the advantage of performing a complete and non-destructive analysis of fibers. This work focuses on the optimization of CT fiber measurements to predict the mechanical properties of FRP components accurately. In particular, the proposed optimization procedure includes the use of reference samples similar to actual industrial FRP components to assess and correct systematic errors and determine the uncertainty of CT fiber measurements. The ultimate tensile strength (UTS) of injection-molded glass-fiber-reinforced specimens was successfully predicted from the improved CT characterization with a deviation below 7% of the experimental UTS

New Approach for Verifying the Accuracy of X-ray Computed Tomography Measurements of Surface Topographies in Additively Manufactured Metal Parts

Surface topographies of metal additively manufactured components are inherently characterized by the presence of complex surface characteristics that are not accessible by contact or optical measuring techniques. Micro X-ray computed tomography is capable of measuring non-accessible surfaces and micro-scale surface features, including undercuts. In this work, an innovative approach for evaluating the accuracy and establishing the traceability of surface topography measurements obtained by X-ray computed tomography is presented. Reference samples produced by selective laser melting of Ti6Al4V were specifically designed in order to acquire reference cross-sectional surface profiles representing the actual morphology (including re-entrant features) using an imaging probing system. Surface topographies were measured on these samples by using three different techniques: X-ray computed tomography, confocal microscopy and focus variation. Moreover, the effect of different voxel dimensions on the accuracy of surface topography measurements performed by X-ray computed tomography was investigated. Results showed that X-ray computed tomography (at the highest tested resolution) can acquire surfaces and re-entrant features with small deviations with respect to the reference profiles; the deviations were quantified. On the contrary, focus variation and confocal microscopy can measure surfaces obtaining results that are close to the reference profiles only if such surfaces have no undercuts or inaccessible features