Validation of a numerical-experimental methodology for structural health monitoring on automotive components

In the recent years, the materials composing the traditional of aircrafts are being progressively replaced with lower density materials, as the Reinforced Plastics. The same trend has been highlighted in the Automotive field to assess the reduction of fuel consumption and CO2 emission. In order to achieve an optimization of maintenance a variety of on-board systems has been applied for on-line SHM based on piezoelectric transducers earned a particularly high interest for continuous monitoring on metallic and composite structures. The application of this system in automotive could enhance passenger safety, through the monitoring of the vehicle composite material structure health status. In this paper, six mathematical models for evaluating the electrical response of piezoelectric sensors have been implemented, with the aim of selecting the most effective model for damage identification. Experimental tests were carried out on three types of simpler specimens of different geometries made of different materials (steel, aluminum and carbon fiber). A correlation study has been carried on in order to support the positioning of sensors. The proposed numerical-experimental methodology is an essential foundation for the introduction of monitoring systems based on piezoelectric transducers in the Automotive sector

Feasibility study on piezoelectric actuated automotive morphing wing

Active aerodynamics is a promising technology to improve vehicle performance and efficiency, but so far in the automotive field the actuation methods suffer with several drawbacks that jeopardize its functioning and broad implementation. Morphing wings represent a technology already studied for aerospace applications that could help overcoming some of those issues. This paper proposes a piezoelectric transducer actuation for a composite material automotive wing and seeks to validate it through virtual models and physical tests. Experimental validation with a 3D-printed simplified wing profile confirms the feasibility of the technology and helps determining the best position for the piezo actuator. Furthermore, a FEM model is presented, where the piezo effect is simulated through a thermal analogy. An optimization of the composite stacking sequence is performed to maximize the trailing edge displacements, and its results are compared with the deflection caused by aerodynamic loads observed in the wing. The displacement of the trailing edge is in the order of tenths of a millimeter, even though further investigations are necessary to improve overall impact of the solution the preliminary results are promising

Specific Energy Absorption Evaluation on GFRP Laminate Plate by Optical, Thermographic and Tomographic Analysis

Over the years, a large number of studies have been carried out on glass fiber composite materials in order to analyze their impact behavior. This is very important for the automotive applications, for example for bumper or crash-box. This paper presents the analysis performed on GFRP (Glass Fiber Reinforced Polymer) laminated plate specimens (epoxy matrix reinforced with E-glass, twill woven, 200 g/m2) subjected to drop impact tests. The tests have been conducted at two different impact speeds in Low Impact Velocity LVI maintaining the same impact energy to estimate the strain-rate effect. All the tests were performed referring to ASTM 7136 at standard ambient temperature. Then the SEA (Specific Energy Absorption) of the specimens was calculated, using three different non-destructive measurement techniques (Optical Analysis, IRThermography and X-ray Computed) to analyze the surfaces of rupture and the specimen interlaminar damages. The chosen geometry of the specimens allowed to reduce the costs and to use a simplest test bench giving additional information to the material behavior

Electrochemical Impedance Spectroscopy of Li-Ion battery on-board the Electric Vehicles based on Fast nonparametric identification method

Electrochemical Impedance Spectroscopy (EIS) is commonly used for the diagnosis of electrochemical energy accumulators, for example Li-Ion batteries in Electric and Hybrid Vehicles. Measuring the impedance in a wide frequency range, it is possible to investigate on the modifications of the internal electrochemical cell process, evaluating its current state of life. EIS test consists of the excitation of the battery, or cell, with a defined current signal, and then measuring the cell voltage, the frequency response of the system is computed. The classical EIS test, based on the excitation with a frequency controlled sine wave in input, requires expensive instruments and long time test procedures; therefore it has many problems on the integration on the embedded systems. In this paper, a pseudo random square signal, which shows a simply hardware implementation, is used as excitation signal input on the cell for the impedance evaluation. The effectiveness of the method has been validated based on simulation test, in order to obtain good results in terms of impedance estimation accuracy, minimizing time duration and energy consumption

Methodology and Application on Load Monitoring Using Strain-Gauged Bolts in Brake Calipers

As technology evolves, the number of sensors and available data on vehicles grow exponentially. In this context, it is essential to use sensors for monitoring key components, increasing safety and reliability, and gathering data useful for mechanical dimensioning and control systems. This paper presents an application of strain-gauged bolts on brake calipers fixation of two electric vehicles. With this approach it was possible to evaluate the loads applied to the brake pads fixation zone and correlate them with braking behavior, therefore gaining insights on braking conditions and system state for an improved braking function control. The goal of the study is analyzing the strengths and limitations of the method and proposing developments to deploy it in real applications. This is particularly important and novel for electric vehicles, where powertrains can create positive/negative torques and generate complex interactions with braking system. Strain-gauges are a long-known technology applied in many fields, and its usage in bolts and screws is well established. However, within automotive field, it could represent cutting edge technology for load sensing and monitoring. The application shows promising results and proves a valid option for monitoring safety components due to its low cost, small dimensions, and reliability. The presented case study takes place in a straight-line test track, where three braking maneuvers were performed: low-pressure braking, mid-pressure braking, and emergence braking. The effects of ABS intervention and wet disk conditions were investigated from an experimental point of view. The paper describes the method used for the strain-gauge application in the bolts, calibration in a dynamometer traction and compression test, installation in the vehicle, and data analysis and post-processing. Results present consistent readings in the higher-pressure conditions, while for the low-pressure cases, the challenges related to load sensing sensitivity are more evident, with a clear tradeoff between system stiffness and measure sensitivity. Finally, evolutions of the system and further investigations on this promising technology applied to the automotive field are presented

Simplified modeling and characterization of the internal impedance of lithium-ion batteries for automotive applications

This paper presents a fast and simple approach to model and characterize internal impedance of Li-ion battery. This is an important aspect because, measuring the impedance in a wide frequency range, it is possible to investigate on the modifications of the internal electrochemical cell process and evaluating its State of Health (SOH), that it is an important parameter for the automotive applications. The first part of the paper explains the concept of Electrochemical Impedance Spectroscopy (EIS) and how Li-ion batteries can be represented through electrochemical or empirical models. EIS test consists of the excitation of the battery, or cell, with a sinusoidal current signal, and then measuring the cell voltage, while the frequency response of the system is computed. Then the paper describes a procedure to test the cell and extract the parameters necessary for the model, in particular, the dependence between the parameters of the model and the State of Charge (SOC). Finally the paper shows how the internal impedance of a Li-ion battery is a dynamic parameter that depends on different factors and illustrate how the EIS can be used to obtain an impedance model

Experimental Characterization of Piezoelectric Transducers for Automotive Composite Structural Health Monitoring

Composite materials are a natural choice for automotive applications where mechanical performance and lightweight are required. Nevertheless, attention should be directed to the defects into the material. This paper presents the building up of a Structural Health Monitoring system based on a piezoelectric transducers network: A continuous data system acquisition has been carried out in order to detect the presence of faults inside the analyzed structure. A piezoceramic patch has been coupled to a host structure in composite, to characterize the acquisition and the transmission of a wave signal on the material. The importance of this advanced technology research and the positive results obtained in the case study constitute the starting point for future application of piezoelectric-based Structural Health Monitoring systems over real industrial components