Academic literature on the topic 'L. Wolff Manufacturing Co'

Biocompatible and biodegradable polymers represent the future in the manufacturing of medical implantable solutions. As of today, these are generally manufactured with metallic components which cannot be naturally absorbed within the human body. This requires performing an additional surgical procedure to remove the remnants after complete rehabilitation or to leave the devices in situ indefinitely. Nevertheless, the biomaterials used for this purpose must satisfy well-defined mechanical requirements. These are difficult to ascertain at the design phase since they depend not only on their physicochemical properties but also on the specific manufacturing methods used for the target application. Therefore, this research was focused on establishing the effects of the manufacturing methods on both the mechanical properties and the thermal behavior of a medical-grade copolymer blend. Specifically, Injection and Compression Molding were considered. A Poly(L-lactide-co-D,L-lactide)/Poly(L-lactide-co-ε-caprolactone) blend was considered for this investigation, with a ratio of 50/50 (w/w), aimed at the manufacturing of implantable devices for tendon repair. Interesting results were obtained.

The article analyzes the book by the famous German literary historian O. L. B. Wolff (1799–1851), The Fine Literature of Modern Europe (1832), in which an attempt was made for the first time to create a canon of European literature, which at that moment was a substitute for the non-existent canon of world literature. This article provides a comparative study of Dutch, Danish, and Swedish literatures in this work, which introduced Dutch, Swedish, and Danish authors Little-known at the time to the general reading public outside their own countries. The introduction of this forgotten source allows us to reconstruct the criteria for evaluating “Northern” literatures within the circle of “major” European literatures and to identify a “set” of those writers who, from the author’s perspective, deserved some attention and could therefore form a canon for the literatures described, which only partially coincides with the modern canon. Of particular interest is the comparison of the German text of the book with its Russian translation, published in 1835, which contains elements of a veiled polemic with the German scholar, manifested not only in cuts made and the stylistic treatment of Wolff ’s value judgements, but also in replacing certain sections by texts of Russian origin whose authorship was established for the first time in the article. The juxtaposition of the original text and its Russian translation demonstrates a discrepancy of perceptions about the hierarchy of specific literatures within the constitutive canon of the period and the translator’s desire to place Russian literature at the forefront, which he saw eclipsing the literatures of the Netherlands, Sweden, and Denmark.

A fragrance manufacturing wastewater is to be treated using a flowsheet which includes combined equalization and organics stripping, biological treatment followed by catalyzed chemical oxidation and waste sludge handling. Two biological processes were investigated for comparison. The first was a conventional extended aeration process, using a bench-scale reactor; the second was a cyclically operated activated sludge system batch reactor using a demonstration unit on-site. Operating parameters for generating an effluent quality of around 600 mg/L COD, through biological treatment, were established. It was found necessary to adjust the feed substrate concentration with a concentrated wastewater component to support microbial growth. The combined fragrance manufacturing waste stream was characterized by an initial COD of around 23000 mg/L. The treatment facility is required to meet a 300 mg/L COD, 175 mg/L BOD and 250 mg/L TSS effluent quality by the regulatory authorities. Satisfactory removal of residual COD to meet the discharge specification was obtained in bench tests using catalyzed chemical oxidants following biological treatment. The design intent of the full-scale facility is 38000 litres/day.

Abstract The aim of this study was to investigate the influence of residual glycerine (5 and 10% w/w) from the biodiesel industry, used as a co-substrate, on biogas production from maize silage. The experiments were conducted in a laboratory-scale, single-stage anaerobic digester at 39ºC and hydraulic retention time (HRT) of 60 d. Addition of 5% residual glycerine caused organic load rate (OLR) to increase to 1.82 compared with 1.31 g organic dry matter (ODM) L-1d-1 for maize silage alone. The specific biogas production rate and biogas yield were 1.34 L L-1d-1 and 0.71 L g ODM-1 respectively, i.e. 86% and 30% higher than for maize alone. Increasing the residual glycerine content to 10% increased OLR (2.01 g ODM L-1d-1), but clearly decreased the specific biogas production rate and biogas yield to 0.50 L L-1d-1 and 0.13 L g ODM-1 respectively. This suggested that 10% glycerine content inhibited methanogenic bacteria and organics conversion into biogas. As a result, there was accumulation of propionic and valeric acids throughout the experiment.

The Ni-Co/SiC composite coatings were prepared via jet electrodeposition in the presence of magnetic field. The microstructure and texture orientation of the composite coatings were analyzed via field emission scanning electron microscopy, three-dimensional profiling, and X-ray diffraction. The microhardness and wear resistance were characterized by a microhardness tester and a friction–abrasion testing machine. The results indicated that nano-SiC particles improved the surface morphology of the Ni-Co/SiC composite coating. In jet electrodeposition, globular structure aggregation began to form protrusions in the Ni-Co/SiC composite coating due to nanoparticle agglomeration when 6 g/L of nano-SiC was added. The Ni-Co/SiC (6 g/L) composite coating became uniform and densification by jet electrodeposition in magnetic field, with higher microhardness and better wear resistance. The microhardness of the Ni-Co/SiC composite coating increased to 626 ± 14 HV, and the corresponding friction coefficient was as low as 0.317.

The enormous potential of additive manufacturing (AM), particularly laser powder bed fusion (L-PBF), to produce radiofrequency cavities (cavities) has already been demonstrated. However, the required geometrical accuracy for GHz TM010 cavities is currently only achieved by (a) avoiding downskin angles <40∘, which in turn leads to a cavity geometry with reduced performance, or (b) co-printed support structures, which are difficult to remove for small GHz cavities. We have developed an L-PBF-based manufacturing routine to overcome this limitation. To enable arbitrary geometries, co-printed support structures are used that are designed in such a way that they can be removed after printing by electrochemical post-processing, which simultaneously reduces the surface roughness and thus maximizes the quality factor Q0. The manufacturing approach is evaluated on two TM010 single cavities printed entirely from high-purity copper. Both cavities achieve the desired resonance frequency and a Q0 of approximately 8300.

Purpose The purpose of this paper is to report on the developments in manufacturing soft magnetic materials using laser powder bed fusion (L-PBF). Design/methodology/approach Ternary soft magnetic Fe-49Co-2V powder was produced by gas atomization and used in an L-PBF machine to produce samples for material characterization. The L-PBF process parameters were optimized for the material, using a design of experiments approach. The printed samples were exposed to different heat treatment cycles to improve the magnetic properties. The magnetic properties were measured with quasi-static direct current and alternating current measurements at different frequencies and magnetic flux densities. The mechanical properties were characterized with tensile tests. Electrical resistivity of the material was measured. Findings The optimized L-PBF process parameters resulted in very low porosity. The magnetic properties improved greatly after the heat treatments because of changes in microstructure. Based on the quasi-static DC measurement results, one of the heat treatment cycles led to magnetic saturation, permeability and coercivity values comparable to a commercial Fe-Co-V alloy. The other heat treatments resulted in abnormal grain growth and poor magnetic performance. The AC measurement results showed that the magnetic losses were relatively high in the samples owing to formation of eddy currents. Research limitations/implications The influence of L-PBF process parameters on the microstructure was not investigated; hence, understanding the relationship between process parameters, heat treatments and magnetic properties would require more research. Originality/value The relationship between microstructure, chemical composition, heat treatments, resistivity and magnetic/mechanical properties of L-PBF processed Fe-Co-V alloy has not been reported previously.

In aerospace, aircraft weight is one of the important factors essential for long range and high fuel efficiency. Instead of fastening, bonding methods like co-curing, co-bonding and secondary bonding are used on the aircraft parts. Secondary bonding was developed for integrated parts because of easy handling, less defect ratio and low cost. During manufacturing, the integrated parts using secondary bonding, bonding strength can show a wide range of failure strengths. Due to inconstant failure strength, the design value can be dropped and reinforcement methods should be applied. To avoid over-designing and to get a constant value for failure, the adhesive failure cases are studied in this project. In this study, L joining composite parts are investigated under tensile loading. Different conditions are tested to select a suitable manufacturing method for secondary bonding methods. From the experimental results, the secondary bonding was sensitive at exposed temperature/time and shape conditions of the fillet. The results show that the failure strength depends on the shape of fillet and exposed time for curing.

Polyhydroxyalkanoates are biopolyesters whose biocompatibility, biodegradability, environmental sustainability, processing versatility, and mechanical properties make them unique scaffolding polymer candidates for tissue engineering. The development of innovative biomaterials suitable for advanced Additive Manufacturing (AM) offers new opportunities for the fabrication of customizable tissue engineering scaffolds. In particular, the blending of polymers represents a useful strategy to develop AM scaffolding materials tailored to bone tissue engineering. In this study, scaffolds from polymeric blends consisting of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(D,L-lactide-co-glycolide) (PLGA) were fabricated employing a solution-extrusion AM technique, referred to as Computer-Aided Wet-Spinning (CAWS). The scaffold fibers were constituted by a biphasic system composed of a continuous PHBV matrix and a dispersed PLGA phase which established a microfibrillar morphology. The influence of the blend composition on the scaffold morphological, physicochemical, and biological properties was demonstrated by means of different characterization techniques. In particular, increasing the content of PLGA in the starting solution resulted in an increase in the pore size, the wettability, and the thermal stability of the scaffolds. Overall, in vitro biological experiments indicated the suitability of the scaffolds to support murine preosteoblast cell colonization and differentiation towards an osteoblastic phenotype, highlighting higher proliferation for scaffolds richer in PLGA.

Abstract This chapter presents a broad overview of Section XII Transport Tank Code, which provides rules for construction and continued service of pressure vessels used in the transportation of dangerous goods via highway, rail, or water. It begins with an overview of the scope and general requirements of the Code including rules on pressure relief devices, stamping, marking certification, reports, and records. The scope of the Code applies to pressure vessels 450 L and above, including additional components and criteria addressed in Modal Appendices that are to be used along with applicable regulations and laws. The Modal Appendix covers Categories 406, 407, 412, 331, and 338 cargo tanks permanently mounted on trucks or wheels used for transporting hazardous materials over public roads. The sections on materials and design rules cover design conditions and allowable stresses, design temperatures, design and allowable working pressures, the design of formed heads, and external pressure design. The coverage also includes information on flat heads and covers, openings and reinforcements, the design of welded joints, and articles covering portable cryogenic tanks including materials and design. The rules for fatigue design are also given in the article covering portable cryogenic tanks. The sections on fabrication, inspection, and testing provide information on general requirements for tanks fabricated by welding; the responsibilities and duties for inspection of transport tanks while being manufactured and for continued service; requirements for nondestructive examination; and rules for transport tanks after they leave the manufacturing facility and are in use by the carriers of hazardous materials. History Stephen V. Voorhees was the co-author of this chapter for the first edition. The second-fourth editions were updated by Mahendra D. Rana and Stanley Staniszewski. Mahendra D. Rana, Stanley Staniszewski and Kang Xu updated the fifth edition and the current online edition.

Abstract Co based superalloy Mar M 509 having excellent high temperature oxidation and hot corrosion resistance is studied via the laser powder bed fusion (LPBF) process. The microstructure and mechanical properties of Mar M 509 in the as-printed (AsP) and heat-treated (HT) condition are compared, as a function of two build orientations (longitudinal (L) and transverse (T)), to establish a working range for application of the alloy. The AsP condition has a distinct cellular microstructure (500–600 nm) with 50–60 nm carbide particles decorating the cell boundaries. The L build orientation displays a strong &lt;001&gt; texture, has columnar grains with a grain size of 8–35 μm (along major axis) and a grain aspect ratio of 4, while the T orientation displays a more equiaxed, but bi-modal microstructure with a grain size of 5–28 μm. The room temperature mechanical properties show variability between L and T with T having 15% higher hardness and 34% higher 0.2% yield strength (YS), 30% lower elongation than L. After a short cycle heat treatment at 1250°C, the weld bead structure and cellular boundaries are broken down and there is substantial grain growth in both L (25–33 μm along major axis) and T orientations (5–42 μm), along with coarsening of carbides (250–350 nm). The dislocation density reduces substantially, indicating recrystallisation, and the lattice parameter of the matrix drops significantly, suggesting solute depletion that contributes to precipitate growth and enrichment of the carbides. There is a drop in the yield strength from 860 MPa to 740 MPa in L and from 1150 MPa to 840MPa in T and an increase in ductility from 14% to 23% in L.

Abstract. Cermets are composite materials made of a ceramic reinforcement and a metal matrix, generally cobalt as binder, with mass content from 6 to 20 wt.%. Cermets are produced by conventional sintering process and are known for their high hardness, low friction coefficient, high wear resistance, and high melting temperature. Laser Powder Bed Fusion (L-PBF) is an additive manufacturing technology widely applied for direct fabrication of functional metallic parts with complex geometry such as internal channels or lattices structures. Considering several studies, production of cermets by L-PBF process is challenging. Recent publications have demonstrated the feasibility to produce WC-Co parts by L-PBF combined with Hot Isostatic Pressure (HIP) heat-treatment. HIP process is sometimes additionally performed as post-treatment to remove defects. HIP is performed at high temperatures and isostatic pressures in a furnace [1]. In this study, following an experimental design a parametric optimization was conducted in order to maximize the mass density of WC-17Ni. Process parameters were compared to those used for WC-17Co parts from recent study [2]. To improve the printed specimen integrity, the as-built samples were heat-treated. As-built and HIP samples were analyzed and compared in terms of mass density, microstructure, crystallographic phases, and macro hardness.

Abstract Nanocomposite coating has a substantial impact on thermomechanical characteristics. There are several methods for developing nanocomposite coatings; however, electrodeposition is one of the additive manufacturing approaches that has been shown to be suitable due to its adjustable parameters, cost-effective and ease of process. Copper composite coatings have been extensively utilized in the aerospace and automotive industries due to their superior mechanical, electrical, and thermal properties. In the proposed study, a “In-house pulse electrodeposition setup” was developed and used to effectively deposit Cu/SiC nanocomposite coatings from an aqueous sulphate solution. Scanning electron microscopy (SEM) and x-ray diffractometer (XRD) are used to examine the surface morphology, which confirmed the successful co-deposition. The microhardness of the Cu/SiC composite coatings and effect of process parameters is predicted using response surface methodology (RSM). Artificial neural network-particle swarm optimization (ANN-PSO) is used to train, test, and validate experimental data and to investigate the correlation between electrodeposition process parameters and their effects on microhardness. The process was operated at: pulse frequency (10 Hz-100 Hz), duty cycle (20–80%), bath agitation (200–500 rpm), and SiC concentration (1–5 g/L). The determination coefficient (R2), root mean square error (RMSE), mean bias error (MBE), and mean absolute percentage error (MAPE) is used to validate several ANN-PSO models. The optimal morphology with the highest microhardness is produced under the following conditions: 10 Hz pulse frequency, 50% duty cycle, 350 rpm bath agitation, and 5 g/L SiC concentration. The findings showed that the suggested model is an appropriate, flexible, and reliable way for estimating the microhardness of Cu/SiC nanocomposite coatings.

The adiabatic, steady-state liquid crystal technique was used to measure surface adiabatic film cooling effectiveness values in the near-hole region (X / D < 10). A parametric study was conducted for a single row of short holes (L / D ≤ 3) fed by a narrow plenum (H / D = 1). Film cooling effectiveness values are presented and compared for various L / D ratios (0.66 to 3.0), three different blowing ratios (0.5, 1.0, and 1.5), two different plenum feed configurations (co-flow and counter flow), and two different injection angles (35° and 90°). Injection hole geometery and plenum feed direction were found to significantly affect short hole film cooling performance. Under certain conditions, comparable or improved coverage was achieved with 90° holes as with 35° holes. This result has important implications for manufacturing of thin-walled film-cooled blades or vanes.

Anterior cruciate ligament (ACL) reconstructive surgery is a major health concern world-wide because of a large aging population and increased occurrence of sport-related damage. Tissue engineering is a rapidly growing interdisciplinary field that offers a promising new approach for ACL repair. In order to overcome the shortages of current existing surgical fixation devices, we are combining gradient cellular structure (GCS) injection molding technique and biomedical engineering to develop novel surgical fixation devices (screw, anchor, plate, pin, staple, etc.) that not only incorporate bioactive materials such as growth factors, healing drugs and cells, but have natural bone GCS structure, intended to mimic the natural bone and promote bone tissue growth and eventually eliminate the defects associated with existing surgical fixation devices. In this work, a series of novel poly-L-lactic acid (PLLA) scaffolds with micro-porous structure were prepared by injection molding an immiscible polymer blend, with spatially controlled thermal conditioning to adjust the phase size from core to surface. The produced scaffolds were observed under SEM, which shows a co-continuous structure was created successfully through our method. The biocompatibility and the feasibility of produced micro-porous structural PLLA and PLLA/HA scaffolds as a matrix supporting cell growth tested by culturing murine osteoblasts cell line (7F2) for up to 9 days were assessed by Alamar Blue™ assay, which showed that the manufacturing process had no negative effects on cell proliferation. The cell attachment, spreading, migration and proliferation to confluence were assessed by fluorescent nuclear staining with Hoechst 33258. In order to evaluate the functional and cell biological applicability of the micro-porous structural PLLA scaffolds, a subcutaneous biodegradation test was performed through rat model for 1 week and 1 month time period, respectively. Our results showed that the micro-porous structural PLLA scaffolds are non-toxic, and they showed a mild foreign body reaction and complete fibrous encapsulation after implantation. Well created interconnected porous structure and biocompatibility suggest great potential of the micro-porous PLLA scaffolds in application for ACL reconstruction.

The widespread approach for Multi-Disciplinary Optimization (MDO) problems adopted in the Space industry generally follows a sequential logic by neglecting the interconnection among different disciplines. However, since the optimization objectives in the different fields are often conflicting, this methodology can fail to find global optimal solutions. By restricting the analysis to just structure and control fields, the common hierarchy is to preliminary define the structure by optimizing the physical design parameters and then leave the floor to the control optimization. This process can be iterated several times before a converging solution is found and control performance is met. Especially for large flexible structures, the minimization of the structural mass corresponds in fact to an increase in spacecraft flexibility, by bringing natural modes to lower frequencies where the interaction with the Attitude Control System (ACS) can be critical, especially in the presence of system uncertainties. Modern MDO techniques nowadays represents a tool to enhance the optimization task by integrating in a unique process all the objectives and constraints coming from each field. Two kinds of architectures can be distinguished in the MDO framework: monolithic and distributed. In a monolithic approach, a single optimization problem is solved, while in a distributed architecture the same problem is partitioned into multiple sub-problems containing smaller subsets of the variables and constraints. The development in the last decade of structured H∞ control synthesis opened the possibility of robust optimal co-design of structured controllers and tunable physical parameters. In fact, Linear Fractional Transform (LFT) formalism allows one to embed in the dynamic model tunable physical parameters treated as parametric uncertainties. In addition, thanks to these techniques, particular properties can be imposed on the controller, such as internal stability or performance respecting a frequency template, in the face of all the parametric uncertainties of the plant. This point is particularly important for aerospace applications where requirements are generally challenging and structural uncertainty, coming for example from an imperfect manufacturing or assembly, cannot be neglected. It has to be said that these techniques do not guarantee a global optimal solution of problem, so a good first guess can enhance the quality of the result. Alazard et al. [1] demonstrated how this multi-model methodology implemented in H∞ framework can be enlarged to include integrated design between certain tunable parameters of the controlled system and the stabilizing structured controller. There exist as well in literature a large class of problems where coupling between structure and control is considered unidirectional. This means that the objective function of the structural sub-problem depends only on the structural design parameters while the control criterion depends on both structural and control design parameters. A partition of the structure and controller design variables is desirable for practical implementation when the impact of the controller variables on the structural objective is relatively small. A strategy in this case is to solve the system-level problem as a nested optimization one, as in the BIOMASS test case [2]. For the present study both monolithic and distributed architectures are investigated on a real benchmark, the ENVISION spacecraft preliminary design. In particular, the problem formulation in the multi-body Two-Input Two-Output Ports (TITOP) [3] modelling approach allows the author to easily define an MDO problem by including all possible system uncertainties from the very beginning of the spacecraft design. In this way not only a structure/control co-design is possible, but system performance is robustly guaranteed. Where an analytical model of the structure is sufficient to describe the various spacecraft sub-components, a dependency from the design parameters can be captured in a minimal LFT model (built in SDTlib). In this approach the control/structure co-design problem is solved in a unique iteration by using the non-smooth techniques available in the Robust Control community. When the complexity of a structure cannot be handled with a simple analytical model (i.e. finer Finite Element Model (FEM) are necessary to ensure representativeness), a distributed architecture will be preferred. A nested optimization process is in fact necessary when a FEM software such as NASTRAN has to be interfaced with the control synthesis/analysis tools available within MATLAB/SIMULINK. In this case, the strategy is to iteratively optimize an inner H∞ control problem, which depends on both control and structural design variables, and the structural design themselves tare optimized by an outer global optimization routine. The aim of this paper is finally to contribute to the evolution of industrial practice in control/structure co-design, by proposing a unified and generic approach based on a well-posed modelling problem that integrates both design parameters and parametric uncertainties in a unique representation. The advantage offered by this framework is dual: to shortcut the unnecessary iterations among different fields of expertise and to speed up the validation and verification process by directly producing a robust preliminary design. References [1] Alazard, D. et al. Avionics/Control co-design for large flexible space structures. (2013) In: AIAA Guidance, Navigation, and Control (GNC) Conference, 12 August 2013 – 22 August 2013 (Boston, United States). [2] Falcoz, A., Watt, M., Yu, M., Kron, A., Menon, P. P., Bates, D., ... & Massotti, L. (2013). Integrated Control and Structure design framework for spacecraft applied to Biomass satellite. IFAC Proceedings Volumes, 46(19), 13-18. [3] Alazard, D., Perez, J. A., Cumer, C., & Loquen, T. (2015). Two-input two-output port model for mechanical systems. In AIAA Guidance, Navigation, and Control Conference (p. 1778).