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All Journal Dinamika Teknik Mesin : Jurnal Keilmuan dan Terapan Teknik Mesin
I.M.A. Sayoga
University of Mataram ID Scopus: https://www.scopus.com/authid/detail.uri?authorId=57201669044
Aerospace Engineering Automotive Engineering Mechanical Engineering Physics

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Analysis of the Effects of Shock Absorber Degradation on Vehicle Dynamic Response Using a Half-Car Model and a Fault Severity Index Based on Numerical Simulation I.M.A. Sayoga; S. Salman
Dinamika Teknik Mesin Vol 16, No 2 (2026): Dinamika Teknik Mesin: Jurnal Keilmuan dan Terapan Teknik Mesin
Publisher : Universitas Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/dtm.v16i2.1346

Abstract

The suspension system plays a critical role in maintaining vehicle ride comfort, stability, and safety by attenuating vibrations induced by road surface irregularities. Progressive degradation of shock absorbers reduces damping capability, leading to significant changes in vehicle dynamic behavior. This study investigates the effects of shock absorber degradation on vehicle dynamic responses using a four-degree-of-freedom (4-DOF) half-car model and proposes a Fault Severity Index (FSI) as a quantitative indicator of suspension fault severity. Numerical simulations were conducted in MATLAB considering damping coefficient degradation levels of 0%, 25%, 50%, 75%, and 90%. The results show that increasing degradation raised RMS displacement from 0.00133 m to 0.00430 m (223%), suspension travel from 0.00170 m to 0.00482 m (184%), and dynamic tire load from 229.8 N to 543.8 N. The proposed FSI increased progressively from 0 to 183.47, enabling quantitative discrimination of suspension fault severity. Curve-fitting analysis demonstrated that the relationship between degradation and RMS displacement was better represented by a quadratic model (R² = 0.9672) than by a linear model (R² = 0.8162). The findings indicate that RMS displacement, suspension travel, dynamic tire load, and the proposed FSI are the most sensitive indicators for detecting shock absorber degradation. The proposed FSI represents the main contribution of this study and shows strong potential for vibration-based condition monitoring and predictive maintenance of automotive suspension systems.
Numerical Investigation of Capillary Tube Diameter and Thermostatic Expansion Valve Effects on the Performance of an R-134a Automotive Air Conditioning System I.M.A. Sayoga; M. Mirmanto
Dinamika Teknik Mesin Vol 16, No 2 (2026): Dinamika Teknik Mesin: Jurnal Keilmuan dan Terapan Teknik Mesin
Publisher : Universitas Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/dtm.v16i2.1338

Abstract

Automotive air conditioning (AC) systems require an effective expansion device to regulate refrigerant mass flow and achieve high cooling capacity and energy efficiency. This study aims to investigate the effects of capillary tube diameter and compare its performance with a Thermostatic Expansion Valve (TXV) in an R-134a automotive air conditioning system using MATLAB-based numerical simulation. The mathematical model was developed based on the vapor-compression refrigeration cycle by incorporating mass and energy conservation, the Darcy–Weisbach equation for pressure drop, the Blasius correlation for friction factor, a compression-ratio-based compressor model, and an evaporator effectiveness approach. Capillary tube diameters of 0.8, 1.0, 1.2, and 1.4 mm were evaluated at an evaporator temperature of 5 °C and a condenser temperature of 45 °C. The simulation results show that increasing the capillary tube diameter increases the refrigerant mass flow rate from 0.00268 to 0.01212 kg/s while reducing the pressure drop from 694.22 to 606.63 kPa. Consequently, the cooling capacity increases from 0.330 to 1.604 kW, whereas the compressor power increases from 0.088 to 0.320 kW, resulting in an improvement in the Coefficient of Performance (COP) from 3.751 to 5.013. Under the same operating conditions, the TXV model produced a COP of 2.955. The difference is mainly attributed to the assumptions adopted in the numerical model; therefore, the proposed model is more appropriate for parametric analysis and preliminary design optimization than for direct representation of actual operating conditions.
Co-Authors M. Mirmanto, M. S. Salman