Tensile properties and failure behavior of chopped and continuous carbon fiber composites produced by additive manufacturing

The use of additive manufacturing (AM) is rapidly expanding in many industries mostly because of the flexibility to manufacture complex geometries. Recently, a family of technologies that produce fiber reinforced components has been introduced, widening the options available to designers. AM fiber reinforced composites are characterized by the fact that process related parameters such as the amount of reinforcement fiber, or printing architecture, significantly affect the tensile properties of final parts. To find optimal structures using new AM technologies, guidelines for the design of 3D printed composite parts are needed. This paper presents an evaluation of the effects that different geometric parameters have on the tensile properties of 3D printed composites manufactured by fused filament fabrication (FFF) out of continuous and chopped carbon fiber reinforcement. Parameters such as infill density and infill patterns of chopped composite material, as well as fiber volume fraction and printing architecture of continuous fiber reinforcement (CFR) composites are varied. The effect of the location of the initial deposit point of reinforcement fibers on the tensile properties of the test specimens is studied. Also, the effect that the fiber deposition pattern has on tensile performance is quantified. Considering the geometric parameters that were studied, a variation of the Rule of Mixtures (ROM) that provides a way to estimate the elastic modulus of a 3D printed composite is proposed. Findings may be used by designers to define the best construction parameters for 3D printed composite parts

Development of an Android OS Based Controller of a Double Motor Propulsion System for Connected Electric Vehicles and Communication Delays Analysis

Developments of technologies that facilitate vehicle connectivity represent a market demand. In particular, mobile device (MD) technology provides advanced user interface, customization, and upgradability characteristics that can facilitate connectivity and possibly aid in the goal of autonomous driving. This work explores the use of a MD in the control system of a conceptual electric vehicle (EV). While the use of MD for real-time control and monitoring has been reported, proper consideration has not been given to delays in data flow and their effects on system performance. The motor of a novel propulsion system for an EV was conditioned to be controlled in a wireless local area network by an ecosystem that includes a MD and an electronic board. An intended accelerator signal is predefined and sent to the motor and rotational speed values produced in the motor are sent back to the MD. Sample periods in which the communication really occurs are registered. Delays in the sample periods and produced errors in the accelerator and rotational speed signals are presented and analyzed. Maximum delays found in communications were of 0.2 s, while the maximum error produced in the accelerator signal was of 3.54%. Delays are also simulated, with a response that is similar to the behavior observed in the experiments

Review of Capabilities of a Linear Micropositioner Based on a Flexible Mechanism

This article presents the development of an actuator for micro electrical discharge machining (ìEDM). A lineal micropositioner was developed using a solenoidflexural element architecture and an open-loop control configuration. The open-loop control system uses a personal computer (PC) connected to a microcontroller through an interface developed on language C and linked to the RS232 protocol. The system varies the force delivered by the solenoid using the technique of pulse width modulation (PWM). The capabilities of the actuator were evaluated by displacing a 1 kg mass over a 30ìm lenght. The position of the micropositioner was measured using a linear variable differential transformer (LVDT) with a resolution of 0.5ìm. Experimental data was collected by a data acquisition system developed in LabView. The results show that the actuator is capable of archiving accuracies that fall within the limits of uncertainty of the measuring system. A Design of Experiments (DoE) was used to evaluate the micropositioner performance. The displacement behavior of the actuator presents hysteresis due its electromagnetic constitution. The impact of each of the control parameters on the hysteresis behavior of the actuator was evaluated. An optimal control parameter combination that reduces hysteresis and magnifies displacement range is proposed.Este articulo presenta el analisis de capacidades de un actuador lineal de resolucion micrometrica que puede ser empleado para lograr posicionamiento de la pieza de trabajo en el proceso de micro electroerosion. El actuador fue desarrollado utilizando un elemento flexible accionado por un solenoide, un sistema de control de lazo abierto fue empleado para el posicionamiento. El sistema de control utiliza una computadora personal conectada a un microcontrolador a traves del protocolo RS232 y el microcontrolador ejecuta un programa escrito en lenguaje C que interpreta comandos provenientes de la computadora. El sistema varia la fuerza producida por un solenoide utilizando la tecnica de modulacion de ancho de pulso (PWM por sus siglas en ingles). Las capacidades del actuador fueron evaluadas mediante el desplazamiento de una masa de 1 kg en una distancia de 30�Êm. La posicion del resultante de la masa fue medida utilizando un transformador variable diferencial (LVDT) con una resolucion de 0.5�Êm. Datos experimentales fueron recolectados utilizando un sistema de adquisicion de datos desarrollado en el lenguaje de instrumentacion LabView. Los resultados muestran que el actuador es capaz de alcanzar una precision de magnitud similar a la del sistema de medicion empleado. Un diseno de experimentos fue realizado para evaluar las capacidades del actuador. El comportamiento de desplazamiento del actuador presenta histeresis debido a su constitucion basada en elementos electromagneticos. El impacto de los parametros de control sobre la histeresis fue evaluado. Una combinacion optima de parametros de control es propuesta la cual permite rangos de desplazamiento optimos y reduce la histeresis

Sistema de control de espaciamiento para micro electroerosión mecanizada gap

The present article shows the results on the implementation of a gap monitoring and controlling system that allows the fabrication of microchannels on conductive materials by the micro electro discharge machining (μEDM) method. The gap monitoring and controlling system was implemented using analog and digital components of generic use and the capabilities of the system were evaluated in a mechanical system compose of three orthogonal axis driven by stepper motors. The machining of microchannels on Titanium (Hardness 32 Rockwell C HRC) was done for evaluation of the systemEl presente artículo muestra los resultados en la implementación de un monitoreo y sistema de control de espaciamiento que permite la fabricación de microcanales sobre materiales conductores por el método de micro mecanizado por electro (μEDM). El seguimiento y sistema de control de espaciamiento se implementan utilizando componentes analógicos y digitales de uso genérico y las capacidades del sistema se evaluaron en un sistema mecánico de composición de tres ejes ortogonales impulsada por motores paso a paso. El mecanizado de microcanales en titanio (Rockwell C 32 HRC) se llevó a cabo para la evaluación del sistema

Modal Analysis of a New Thermosensitive Actuator Design for Circuit Breakers Based on Mesoscale U-Shaped Compliant Mechanisms

A new mesoscale thermosensitive actuator design for circuit breakers based on a U-shaped compliant mechanism was introduced as a potential replacement for bimetal strips in miniature circuit breakers. In a previous study, the response of this design to the thermal fields produced by a steady current flow was analyzed. This article presents a modal analysis of the compliant mechanism. The goal of the analysis is to compare the natural frequencies of the mechanism with the frequency of the magnetic loads caused by the flow of the alternating currents. Simulations with simple beam elements and 3D elements are presented and results are compared with experimental measurements. The study finds that the natural frequency of the mechanism differs by a factor of about 8 with the AC frequency. The conclusion is that the proposed compliant mechanism design’s performance as a thermal actuator will not be affected by the cyclic loads generated by the forces induced by the AC magnetic fields

Restauración de Torno de Control Numérico Empleando Software Libre

This work presents the result of the restoration of a numeric control lathe. The lathe is thirty years old without a functional controller. The restoration was made using open source tools for numerical control and low cost hardware of in home fabrication. The machine was discontinued by the manufacturer several years ago. The resulting machine is capable of follow industrial G code. Pieces were made in aluminum and plastic to evaluate the resulting characteristics of the lathe.En este trabajo se presentan los resultados obtenidos en la restauración operativa de un torno de control numérico didáctico con 30 años de antigüedad. El estado del torno anterior a la restauración era inoperativo, dada la falta de soporte del control numérico original y la descontinuación del modelo de maquina por parte del fabricante. La restauración se realizo empleando herramientas de software de control numérico libre basadas en Linux y hardware de bajo costo de fabricación propia. El torno restaurado es capaz de interpretar comandos en código industrial. Las capacidades del torno restaurado fueron evaluadas maquinando piezas de geometría no trivial en plástico para ingeniería así como aluminio

Die casting die deflections: Prediction and attenuation. Final report, July 1, 1995--September 30, 1997

The objective of this work was to develop and test die casting design evaluation techniques based on the visualization of geometric data that is related to potential defects or problems. Specifically, thickness information is used to provide insight into potential thermal problems in the part and die. Distance from the gate and a special type of animation of the fill pattern is used to provide an assessment of gate, vent and overflow locations. Techniques have been developed to convert part design information in the form of STL files to a volume-based representation called a voxel model. The use of STL files makes the process CAD system independent. Once in voxel form, methods that were developed in this work are used to identify thick regions in the part, thin regions in the part and/or die, distance from user specified entry locations (gates), and the qualitative depiction of the fill pattern. The methods were tested with a prototype implementation on the UNIX platform. The results of comparisons with numerical simulation and field reported defects were surprisingly good. The fill-related methods were also compared against short-shots and a water analog study using high speed video. The report contains the results of the testing plus detailed background material on the construction of voxel models, the methods used for displaying results, and the computational geometric reasoning methods used to create die casting-related information from the voxel model for display to the user

Development of an android OS based controller of a double motor propulsion system for connected electric vehicles and communication delays analysis

Developments of technologies that facilitate vehicle connectivity represent a market demand. In particular, mobile device (MD) technology provides advanced user interface, customization, and upgradability characteristics that can facilitate connectivity and possibly aid in the goal of autonomous driving. This work explores the use of a MD in the control system of a conceptual electric vehicle (EV). While the use of MD for real-time control and monitoring has been reported, proper consideration has not been given to delays in data flow and their effects on system performance. The motor of a novel propulsion system for an EV was conditioned to be controlled in a wireless local area network by an ecosystem that includes a MD and an electronic board. An intended accelerator signal is predefined and sent to the motor and rotational speed values produced in the motor are sent back to the MD. Sample periods in which the communication really occurs are registered. Delays in the sample periods and produced errors in the accelerator and rotational speed signals are presented and analyzed. Maximum delays found in communications were of 0.2 s, while the maximum error produced in the accelerator signal was of 3.54%. Delays are also simulated, with a response that is similar to the behavior observed in the experiments. © 2015 Pedro Daniel Urbina Coronado et al

Method for modeling electrorheological dampers using its dynamic characteristics

A method for modeling an Electrorheological (ER) damper is proposed. The modeling method comprehends two simple steps: characterization and model customization. These steps are based on the experimental data of the damper behavior. Experiments were designed to explore the nonlinear behavior of the damper at different frequencies and actuation signals (i.e., automotive domain). The resulting model has low computational complexity. The method was experimentally validated with a commercial damper. The error-to-signal Ratio (ESR) performance index was used to evaluate the model accuracy. The results were quantitatively compared with two well-known ER damper models: the Choi parametric model and the Eyring-plastic model. The new proposed model has a 44% better ESR index than the Choi parametric model and 28% for the Eyring-plastic model. A qualitative comparison based on density plots highlights the advantages of this proposal. © 2015 Carlos A. Vivas-Lopez et al