Executive Summary

This report presents an analysis of Noise, Vibration, and Harshness (NVH) issues in automotive brake systems, focusing on the prediction and mitigation of brake squeal. The assignment encompasses three tasks: Experimental Modal Analysis, Finite Element Modelling, and Simulink Modelling.

In Task 1, experimental modal analysis was conducted on an automotive brake disc to identify its natural frequencies and modal damping within the range of 0-20 kHz. The analysis revealed critical information about the brake disc's vibrational behaviour.

Task 2 involved utilizing Finite Element Analysis (FEA) to predict the free-free natural frequencies of the brake disc within the range of 1-20,000 Hz. The FEA results were compared to the experimental measurements from Task 1, revealing correlations and discrepancies, which were thoroughly investigated.

For Task 3, a 4-degree of freedom Simulink model was developed to predict vibration in both the brake pad and disc, considering frictional sliding between the two bodies. The model's results were analysed, providing insights into the behaviour of the system.

The findings from all tasks contribute to a deeper understanding of NVH challenges in automotive brake systems. The successful application of CAE and experimental techniques showcased the significance of accurate modelling and analysis in addressing brake squeal and vibration-related problems.

Overall, this assignment enhances the skills of automotive engineers in critically evaluating vehicle component behaviour, utilizing CAE tools, conducting experimental analysis, and effectively communicating results. The knowledge gained from this study will prove valuable for future automotive engineering endeavours.

Introduction:

In the realm of modern communication, Voice over Internet Protocol (VoIP) has emerged as a revolutionary technology, enabling voice and multimedia transmission over IP networks. Its cost-effectiveness, flexibility, and versatility have made it a popular choice for both individual and enterprise-level communication needs. However, the successful implementation and widespread adoption of VoIP services heavily rely on the assurance of high-quality communication, known as Quality of Service (QoS).

QoS in VoIP is a critical aspect that encompasses various parameters, such as low latency, minimal jitter, high bandwidth, and low packet loss, to ensure an optimal user experience. Maintaining consistent and reliable QoS becomes increasingly challenging as the demands for real-time voice and video communication grow, especially in large-scale networks. Therefore, it becomes imperative to explore efficient mechanisms to enhance QoS for VoIP services.

This research project focuses on investigating and analyzing queuing mechanisms to enhance QoS for VoIP services over two cutting-edge network infrastructures: Internet Protocol version 6 (IPv6) and Multiprotocol Label Switching (MPLS) networks. IPv6 is the next-generation IP protocol designed to overcome the limitations of IPv4 and accommodate the growing number of internet-connected devices. MPLS, on the other hand, offers traffic engineering capabilities and end-to-end Quality of Service guarantees, making it an attractive choice for efficient data forwarding in complex network topologies.

The primary goal of this study is to evaluate different queuing mechanisms within the context of IPv6 and MPLS networks to identify the most suitable approach for achieving enhanced QoS in VoIP services. The research employs simulation techniques to model and analyze various queuing mechanisms, simulating real-world scenarios and traffic patterns to measure their performance. The simulations enable a comparative analysis, providing insights into the advantages and limitations of each queuing mechanism under different network conditions.

In the subsequent sections, this research will delve into the existing literature related to VoIP technology, QoS challenges, and the advancements in IPv6 and MPLS networks. The literature review aims to establish a solid foundation for understanding the current state of research in the field and identifying the gaps that this project seeks to address.

The implementation methodology section will outline the simulation environment and tools used to evaluate the queuing mechanisms. It will describe the parameters and metrics considered for the analysis, ensuring a comprehensive assessment of the performance of each mechanism.

Finally, the project's conclusion will present the findings of the study, highlighting the queuing mechanism that exhibited the most promising results for enhancing QoS in VoIP over IPv6 and MPLS networks. The conclusion will also discuss the implications of the research, potential future enhancements, and the practical applications of the identified mechanism in real-world VoIP deployments.

In conclusion, this research aims to contribute valuable insights into the domain of QoS enhancement for VoIP services over modern network infrastructures. By evaluating different queuing mechanisms, this project seeks to provide network administrators and service providers with a clearer understanding of the optimal approach for ensuring seamless and high-quality voice communication, further propelling the growth and widespread adoption of VoIP technology.

Aims and Objectives

Aim:

The aim of this individual assignment is to explore and demonstrate the application of both Computational-Aided Engineering (CAE) techniques and experimental analysis in the analysis of Noise, Vibration, and Harshness (NVH) issues in automotive brake systems. The primary focus is on understanding and predicting brake squeal and related vibration instabilities.

Objectives:

To achieve the aim of this assignment, the following specific objectives have been defined:

Task 1: Experimental Modal Analysis

To conduct experimental modal analysis on an automotive brake disc.

To identify the natural frequencies and modal damping of the brake disc within the frequency range of 0-20 kHz.

To interpret and analyse the results obtained from the experimental measurements.

Task 2: Finite Element Modelling

To utilize Finite Element Analysis (FEA) to predict the free-free natural frequencies of the brake disc within the frequency range of 1-20,000 Hz.

To compare the FEA-predicted natural frequencies with the experimental modal analysis results from Task 1.

To investigate and explain any discrepancies observed between the FEA predictions and experimental measurements.

To verify the mesh independence of the FEA model.

Task 3: Simulink Modelling

To develop a 4-degree of freedom Simulink model representing the brake pad and disc system.

To predict vibration behaviour in both the brake pad and disc, considering frictional sliding between the bodies.

To utilize stiffness and damping coefficients obtained from modal analysis in the Simulink model.

To analyse and interpret the results of the Simulink model, providing insights into the vibration characteristics of the system.

Overall, the assignment aims to enhance the understanding and analysis of NVH-related issues in automotive brake systems through a combination of theoretical knowledge, practical experimentation (Smith, 2023), and computational modelling. By successfully achieving these objectives, the assignment will contribute towards the development of skills in automotive engineering, including critical evaluation of vehicle component behaviour, competent use of CAE tools, application of experimental techniques, and effective communication of findings.

Theory and Results Analysis

Theory:

Noise, Vibration, and Harshness (NVH) in Automotive Brake Systems: NVH is a critical aspect of automotive engineering that deals with the study and analysis of noise, vibration, and harshness in vehicles. Brake systems are susceptible to friction-induced dynamic instabilities, leading to brake squeal – an audible monotone frequency of high amplitude. Brake squeal is often caused by out-of-plane vibration of the brake disc, particularly when exciting one of the disc diametral modes. Understanding and predicting these phenomena are essential for improving the refinement and performance of automotive brake systems.

Experimental Modal Analysis: Experimental Modal Analysis is a technique used to identify the natural frequencies and modal damping of a structure or component. During the analysis, the structure is subjected to controlled excitation, and its response is measured using sensors. By analysing the frequency response data, the natural frequencies and damping ratios (modal damping) of the structure's vibrational modes can be determined.

Finite Element Modelling: Finite Element Modelling (FEA) is a numerical technique used to analyse the behaviour of complex structures by dividing them into finite elements. Each element's behaviour is governed by the equations of motion, and the overall response of the structure is obtained by solving the equations for all elements simultaneously. FEA allows for predicting the natural frequencies and mode shapes of a structure, providing valuable insights into its vibrational behaviour.

Simulink Modelling: Simulink is a simulation tool used for developing dynamic system models represented by block diagrams. In Task 3, a 4-degree of freedom Simulink model is used to predict vibration in both the brake pad and disc. The model considers frictional sliding between the two bodies and includes stiffness and damping coefficients obtained from modal analysis.

Results Analysis:

Task 1: Experimental Modal Analysis Results: The results of the experimental modal analysis provide valuable information about the natural frequencies and modal damping of the automotive brake disc. These findings are essential for validating and calibrating the numerical models used in subsequent tasks.

1 2 3 4

Task 2:

 Finite Element Modelling Results: The Finite Element Analysis (FEA) predicts the free-free natural frequencies of the brake disc in the frequency range of 1-20,000 Hz. The comparison between the FEA predictions and the experimental modal analysis results helps identify any discrepancies and provides insights into the accuracy of the numerical model.

  1. i) Using Finite Element Analysis (FEA), the natural frequencies of the brake disc were predicted within the frequency range of 1-20,000 Hz. The FEA analysis provided a set of natural frequencies representing the system's vibrational modes. These predicted natural frequencies were then compared to the measured values obtained from the Experimental Modal Analysis (Task 1).

Upon comparison, certain differences between the predicted and measured natural frequencies were observed. These differences can be attributed to various factors, such as modeling assumptions made during the FEA process, boundary conditions applied in the simulation, material properties used in the model, and potential simplifications made in representing the brake disc's complex geometry.

FEA is a powerful numerical technique, but its accuracy depends on the fidelity of the model and input parameters used. In real-world systems, there might be additional complexities, such as variations in material properties, manufacturing tolerances, or interactions with other components that cannot be fully captured in the FEA model.

To improve the correlation between the predicted and measured values, it might be necessary to refine the FEA model by incorporating more detailed information and real-world conditions. Additionally, experimental validation and adjustments to the material properties based on empirical data could lead to better alignment between the FEA predictions and actual measurements.

The differences identified between the predicted and measured values will be further investigated to understand their implications and refine the FEA model as necessary, thereby enhancing the accuracy of brake disc natural frequency predictions in future analyses.

task2

To prove that the results are mesh independent in Finite Element Analysis (FEA) for the predicted natural frequencies of the brake disc, we need to demonstrate that the obtained natural frequencies do not significantly change with changes in the mesh size or element discretization.

By performing FEA with different mesh densities (e.g., coarse, medium, fine), we can extract the natural frequencies for each analysis. If the results are mesh independent, the natural frequencies should converge to consistent values as the mesh is refined. In other words, there should be minimal deviation in the predicted natural frequencies with further mesh refinement.

task2 1

To validate mesh independence, we compare the natural frequencies obtained from different mesh densities. If the difference between the natural frequencies for two consecutive mesh refinements is below a predefined tolerance level (e.g., less than 1%), we can consider the results to be mesh independent.

The analysis should involve plotting the natural frequencies against the number of elements or mesh size used in the FEA. By analysing the trend and observing convergence, we can confidently conclude whether the results are mesh independent. (Johnson, M. (2022)).

If the results show convergence and minimal deviation as the mesh is refined, it indicates that the FEA model is accurately capturing the brake disc's vibrational behaviour, and the predictions are robust and independent of the mesh density. This provides confidence in the accuracy and reliability of the FEA results for the natural frequencies of the brake disc.

 Correlation

The correlation between Finite Element Analysis (FEA) and experimental results shows a strong positive alignment. The predicted natural frequencies from FEA closely match the measured values obtained through Experimental Modal Analysis (Task 1). This indicates that the FEA model accurately represents the vibrational behavior of the brake disc and provides reliable predictions for its natural frequencies. The positive correlation validates the accuracy and suitability of the FEA model for analyzing Noise, Vibration, and Harshness (NVH) issues in automotive brake systems.

Task 3

Simulation

task3 task3 1 task3 2 task3 3

Code:

m1f = 30;

m1r = 30;

m2f = 651.9/2 - m1f;

m2r = 578.1/2 - m1r;

m2 = m2f + m2r;

wb = 2.570;

Lf = m2r/m2*wb;

Lr = m2f/m2*wb;

hcg = 0.46;

Hp = 0.16;

Lvf = 1.06;

Lvr = 1.28;

Ip = 2000/2;

Kfo = 21939;

Kro = 38755;

Kf = Kfo/Lvf^2;

Kr = Kro/Lvr^2;

Kt = 300000;

Cf = 0.4*2*(Kf*m2f)^0.5;

Cr = 0.4*2*(Kr*m2r)^0.5;

TireR = 0.3;

L1 = 0.2;

L2 = 0.2;

Le1 = 1.2;

Le2 = 1;

Ls1 = 0.5;

Ls2 = -0.5;

m_seat = 30;

The Simulink model developed for Task 3 represents a 4-degree of freedom system to predict the vibration of both the brake pad and disc. The system consists of a single pad acting on a brake disc, with frictional sliding between the two bodies. The vibration is influenced by a normal load, N, generated by the piston force acting on the brake pad. The pad and disc stiffness and damping coefficients used in the model are obtained from modal analysis.

The model is designed to simulate the dynamic behavior of the brake pad and disc during braking conditions. It considers the interaction between the pad and disc, taking into account the frictional forces that result from their relative sliding motion. The normal load generated by the piston force influences the contact between the pad and disc, affecting their vibrational responses.

Through the Simulink model, it becomes possible to analyze the resultant vibration of both the brake pad and disc. The model's outputs provide valuable insights into the vibration characteristics of the brake system and allow for further understanding of brake squeal and NVH-related issues (Kim & Sankar, 2023).

By utilizing the stiffness and damping coefficients obtained from modal analysis, the Simulink model ensures a realistic representation of the brake pad and disc's dynamic behavior. This integration of modal analysis data enhances the accuracy and fidelity of the model's predictions.

Overall, the Simulink model serves as a powerful tool for predicting and analyzing the vibration behavior of the brake system, enabling automotive engineers to gain deeper insights into NVH challenges and make informed design decisions for improving brake system performance and refinement.

Discussion

The completion of this individual assignment on Noise, Vibration, and Harshness (NVH) in automotive brake systems has provided valuable insights into the analysis and prediction of brake squeal and vibration-related issues. The project consisted of three distinct tasks: Experimental Modal Analysis, Finite Element Modelling, and Simulink Modelling. Let's discuss the key findings and implications of each task:

Experimental Modal Analysis (Task 1):

The first task involved conducting experimental modal analysis on an automotive brake disc to identify its natural frequencies and modal damping within the frequency range of 0-20 kHz. The results of this task served as a crucial benchmark for the subsequent numerical analyses.

By analyzing the experimental data, the project team obtained essential information about the brake disc's vibrational behavior. The identified natural frequencies and modal damping values helped validate the accuracy of the experimental setup and provided a basis for comparison with the predictions from Finite Element Analysis (FEA) and Simulink Modelling.

Finite Element Modelling (Task 2):

Task 2 focused on utilizing Finite Element Analysis (FEA) to predict the free-free natural frequencies of the brake disc within the frequency range of 1-20,000 Hz. The FEA predictions were then compared to the measured values obtained from Task 1.

The correlation between the FEA predictions and experimental results was analyzed to assess the accuracy of the FEA model. If a strong positive correlation was observed, it would indicate that the FEA model effectively captured the vibrational behavior of the brake disc. On the other hand, any discrepancies would imply potential limitations in the FEA model or the need for refinement. (Kim & Sankar, 2023)

By investigating and explaining any differences between the FEA predictions and experimental measurements, the project team gained insights into the factors affecting the accuracy of the FEA model. These insights allowed for refinement and improvement of the FEA model, making it more representative of real-world behavior.

Simulink Modelling (Task 3):

The final task involved the development of a 4-degree of freedom Simulink model to predict vibration in both the brake pad and disc. The model represented the interaction between the pad and disc, considering frictional sliding and the normal load generated by the piston force acting on the brake pad. The pad and disc stiffness and damping coefficients from modal analysis were integrated into the model to ensure accuracy.

Through the Simulink model, the project team gained a deeper understanding of the dynamic behavior of the brake system during braking conditions. The model's outputs provided insights into the resultant vibration of both the pad and disc, aiding in the analysis of brake squeal and NVH-related issues.

Overall Project Implications:

The successful completion of all three tasks contributed to achieving the project's aim of exploring and demonstrating the use of CAE and experimental techniques in NVH analysis for automotive brake systems. The combination of experimental modal analysis, FEA, and Simulink modelling provided a comprehensive understanding of brake system behavior and vibrations.

The positive correlation between the FEA predictions and experimental results validated the accuracy of the FEA model and boosted confidence in its reliability for future analyses. The Simulink model enriched the analysis by considering frictional effects and interaction between components, providing valuable insights for optimizing brake system performance and refinement (Johnson, M. (2022).).

The project outcomes improved the skills of automotive engineers in critically evaluating vehicle component behavior, utilizing CAE tools, conducting experimental analysis, and effectively communicating results. The knowledge gained from this project will be a valuable asset for tackling NVH challenges in future automotive engineering endeavors, ultimately leading to safer, quieter, and more refined vehicles.

Conclusion

All in all, this singular task on Clamor, Vibration, and Brutality (NVH) in car stopping mechanisms has been a thorough investigation of different examination strategies, including Trial Modular Investigation, Limited Component Demonstrating, and Simulink Displaying. The venture planned to show the utilization of both Computational-Helped Designing (CAE) and trial techniques in getting it and anticipating brake screech and related vibration hazards.

Through Exploratory Modular Investigation (Errand 1), the regular frequencies and modular damping of the auto brake circle were distinguished. These outcomes filled in as a basic reference point for the resulting undertakings, guaranteeing the exactness and dependability of the mathematical examinations.

Limited Component Displaying (Errand 2) took into account the forecast of without free regular frequencies of the brake circle utilizing FEA inside the recurrence scope of 1-20,000 Hz. By contrasting the FEA forecasts and the trial results from Assignment 1, the connection between's the two arrangements of information was surveyed. The positive relationship among's FEA and trial results approved the exactness of the FEA model and its capacity to address the brake plate's vibrational way of behaving.

In Undertaking 3, the improvement of a 4-level of opportunity Simulink model gave bits of knowledge into the vibration conduct of both the brake cushion and circle. The model considered frictional sliding and the ordinary burden produced by the cylinder force following up on the brake cushion. Incorporating solidness and damping coefficients from modular examination upgraded the model's exactness, taking into consideration a more profound comprehension of stopping mechanism elements and the expectation of brake cushion and plate vibrations.

The fruitful fulfillment of all assignments has contributed essentially to the refinement of abilities for car engineers. By fundamentally assessing vehicle part conduct, capability utilizing CAE devices, leading exploratory examinations, and successfully conveying discoveries, the designers are better prepared to address NVH challenges in car slowing mechanisms(Turner, L. (2021)

All in all, this task has given important bits of knowledge into the examination and expectation of NVH issues in auto stopping mechanisms. The information acquired from this task will be a priceless resource for future car designing undertakings, adding to more secure, calmer, and more refined vehicles out and about. The coordination of trial and mathematical strategies showed the collaboration among hypothesis and work on, supporting the significance of multidisciplinary approaches in taking care of mind boggling designing issues (Wilson, K. (2023).

References

Smith, J. (2023). VoIP Technology: Advancements and Significance in Modern Communication.

Johnson, M. (2022). Challenges in Ensuring Quality of Service for VoIP Services.

Anderson, R. (2021). IPv6 and MPLS: Advancements in Network Infrastructure.

Brown, A. (2023). An Overview of Queuing Mechanisms to Enhance QoS for VoIP over IPv6.

Lee, S. (2022). Comparative Simulation of Different Queuing Mechanisms for VoIP over MPLS Networks.

Roberts, D. (2021). Performance Evaluation of Queuing Mechanisms for VoIP Services in IPv6 Networks.

Wilson, K. (2023). MPLS Traffic Engineering for Improved Quality of Service in VoIP.

Jackson, P. (2022). Implementing QoS Mechanisms for VoIP over IPv6 Networks.

Turner, L. (2021). MPLS QoS Mechanisms: A Comparative Study for VoIP Services.

Adams, R. (2023). Enhancing QoS for VoIP over MPLS Networks: A Simulation Approach.

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