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Peralatan tempur di Indonesia harus siap pakai dan memiliki kandungan lokal minimal 85% sesuai amanat UU. Salah satu komponen penting pada kendaraan tank adalah ground pad shoe (GPS) atau tapak pada roda tank yang terbuat dari karet. Kebutuhan GPS untuk tank baru dan suku cadang sangat banyak, akan tetapi saat ini masih impor dari Turki dengan waktu tunggu mencapai satu tahun dan harus membeli dalam jumlah banyak, hal ini menyebabkan ketergantungan dari luar negeri dan biaya tinggi. Material karet yang berpotensi untuk GPS adalah Styrene Butadiene Rubber (SBR) dan Butadiene Rubber (BR) yang mana karet ini banyak digunakan untuk GPS, memiliki sifat yang sesuai, dan jumlahnya banyak di dunia. Saat ini, Proses pembuatan karet secara umum membutuhkan biaya mahal dan waktu lama serta masih mengandalkan pengalaman seseorang. Produk karet dibuat dengan cetakan khusus dan mempertimbangkan banyak faktor. Setelah produk jadi, karet diuji dengan standar tertentu untuk mengetahui karakteristik dasar karet, yaitu: tensile strength, modulus 200%, strain at break, specivic gravity, kekerasan, dan keausan. Apabila ada banyak variasi kompon karet yang dibuat, maka waktu dan biaya yang dibutuhkan akan sangat besar. Untuk mengurangi waktu percobaan dan memangkas biaya, maka dilakukan penelitian model numerik untuk karet. Tujuan dari penelitian ini ada lima, yaitu (1) mendapatkan karakteristik material GPS impor dan tegangan yang terjadi akibat beban tank, (2) menghasilkan kompon karet untuk material GPS, (3) mendapatkan model hyperelastic dan parameter untuk kaji numerik karet Styrene Butadiene Rubber (SBR) - Butadiene Rubber (BR), (4) Mendapatkan persamaan matematika antara komposisi karet SBR-BR dan parameter model hyperelastic, dan (5) implementasi persamaan baru. GPS menjadi studi kasus untuk penelitian karet ini, selanjutnya hasil penelitian ini dapat digunakan untuk produk karet lainnya. Metode penelitian dilakukan melalui kajian pustaka, eksperimen, numerik, curvefitting, dan validasi. Kajian pustaka dilakukan dengan mempelajari karakteristik dan pengujian material karet, pembuatan kompon dan spesimen karet, model hyperelastic dan kaji numerik, pembuatan persamaan baru, dan curve-fitting. Metode eksperimen dilakukan dengan pengujian GPS impor, pembuatan dan pengujian kompon karet SBR-BR. Metode numerik dilakukan dengan metode elemen hingga seperti pada pengujian eksperimen karet. Hasil kaji numerik dibandingkan dengan hasil uji eksperimen dan dilihat deviasi yang terjadi. Metode eksperimen dan numerik menggunakan 4 variasi komposisi karet SBR-BR, yaitu: SBR 100% - BR 0% (SB0), SBR 60% - BR 40% (SB4), SBR 40% - BR 60% (SB6), dan SBR 0% - BR 100% (SB10). Komposisi tambahan dibuat untuk validasi persamaan matematika baru yang dibuat yaitu SBR 20% - BR 80% (SB2) dan SBR 80% - BR 20% (SB8). Salah satu komposisi terbaik dipilih berdasarkan tensile strength, modulus 200%, dan strain at break yang paling mendekati GPS impor. Model hyperelastic yang digunakan pada penelitian ini adalah Mooney-Rivlin, neo- Hookean, Yeoh, Ogden, Arruda-Boyce, Polynomial, dan Reduced-Polynomial. Beberapa kajian dilakukan untuk menguji model numerik yang dikembangkan yaitu: (1) hubungan test data dan parameter model hyperelastic pada input material, (2) uji konvergensi mesh, (3) uji sensitivitas parameter Mullins effect. Dari hasil kaji numerik, persamaan komposisi karet dan parameter model hyperelastic dimodelkan menjadi sebuah persamaan matematika dengan curvefitting. Motode curve-fitting dilakukan dengan membuat grafik antara komposisi SBR-BR dan parameter model hyperelastic. Uji sensitivitas parameter persamaan matematika dilakukan dengan metode one-at-a-time. Metode validasi dilakukan dua tahap, yaitu: (1) validasi nilai parameter hyperelastic dari persamaan matematika dengan hasil uji eksperimen SB2 dan SB8, (2) memvalidasi tensile strength, modulus 200%, strain at break, specivic gravity hasil dari persamaan matematika dengan hasil uji eksperimen SB2 dan SB8. Terakhir adalah aplikasi dari persamaan matematik untuk membuat daftar parameter hyperelastic. Hasil penelitian ini menunjukkan GPS impor memiliki karakteristik material maksimum tensile strength 16,9 MPa, modulus 200% 14,7 MPa, dan strain at break 2,28 mm/mm, yang memiliki safety factor dari tegangan sebesar 3,8. Model hyperelastic yang paling cocok untuk GPS impor adalah model neo-Hookean. Komposisi karet SBR-BR terbaik yang berpotensi untuk menggantikan GPS impor adalah SBR 60% dan BR 40% dengan model neo-Hookean paling tepat untuk model numerik kompon SBR-BR. Persamaan matematika antara komposisi SBRBR dan model hyperelastic berbentuk linier yaitu = ?0,0032 + 1,61 dengan merupakan komposisi SBR-BR dan adalah C10 Neo-Hookean. Nilai parameter 10 neo-Hooekan SBR-BR berkisar dari 1,29 – 1,61. Hasil lain penelitian ini adalah (1) penggunaan test data maupun parameter model hyperelastic untuk pengaturan material model numerik explicit-dynamic hasilnya sama, (2) ukuran mesh 1 mm atau setengah dari ukuran terkecil pada spesimen menghasilkan hasil tegangan yang konvergen, dan (3) uji tarik dan uji tekan pada SBR-BR memiliki nilai yang konsisten. Kata kunci : ground pad shoe, karet, styrene butadiene rubber, butadiene rubber, kaji numerik, model hyperelastic. ABSTRACT DESIGN AND DEVELOPMENT OF A NUMERICAL MODEL FOR STYRENE BUTADIENE RUBBER - BUTADIENE RUBBER GROUND PAD SHOE IN COMBAT VEHICLES By Angki Aprilinadi Rachmat NIM : 33119003 (Doctoral Program in Mechanical Engineering) Defence equipment in Indonesia is required by national legislation to be fully operational and composed of at least 85% locally sourced components. One critical component of tank is the Ground Pad Shoe (GPS), which functions as the tread on the tank's wheels and is fabricated from rubber. The demand for GPS for new tanks and replacement parts is substantial. However, current procurement relies on imports from Turkey, which involve a lead time of up to one year and require bulk purchasing. This reliance results in high costs and a significant dependency on foreign supply chains. Styrene butadiene rubber (SBR) and butadiene rubber (BR) are promising materials for ground pad shoe (GPS) applications due to their favorable mechanical properties, widespread use in existing GPS components, and global availability. Currently, rubber manufacturing remains a costly and time-intensive process, often dependent on individual experience. The production of rubber products involves the use of specialized molds and must account for numerous factors. Upon completion, the materials are evaluated using standardized tests to determine key mechanical properties, including tensile strength, 200% modulus, strain at break, specific gravity, hardness, and wear resistance. When multiple variations of rubber compounds are produced, the associated time and financial costs can be substantial. To minimize experimental time and reduce production costs, this study employs a numerical method for rubber materials. The research objectives are fivefold: (1) to characterize the mechanical properties of imported Ground Pad Shoe (GPS) materials and evaluate stress responses under tank loading conditions; (2) to develop alternative rubber compounds for GPS applications; (3) to identify appropriate hyperelastic models and corresponding parameters for Styrene Butadiene Rubber (SBR)–Butadiene Rubber (BR) blends; (4) to derive mathematical relationships between SBR-BR compositions and hyperelastic model parameters; and (5) to implement these equations for predictive modeling. The GPS component serves as the primary case study for this investigation, and the methodology and findings are broadly applicable to other rubber-based products. The research methodology encompassed a comprehensive literature review, experimental testing, numerical modelling, curve-fitting, and validation. The literature review focused on the mechanical characterization and testing of rubber materials, formulation of SBR-BR compounds and specimens, exploration of hyperelastic models, numerical analyses, and the derivation of new mathematical equations, and curve-fitting. The experimental phase involved testing imported GPS materials as well as preparing and evaluating SBR-BR rubber compounds. Numerical simulations were conducted using the FEM, mirroring the experimental procedures. Results from the simulations were compared against experimental data to assess deviations and ensure model reliability. Four baseline compositions were examined: SBR 100%–BR 0% (SB0), SBR 60%–BR 40% (SB4), SBR 40%–BR 60% (SB6), and SBR 0%–BR 100% (SB10). Two additional formulations—SBR 20%– BR 80% (SB2) and SBR 80%–BR 20% (SB8) were developed to validate the derived mathematical equations. One of the most optimal rubber compositions was selected based on its tensile strength, 200% modulus, and strain at break—parameters that most closely match those of the imported GPS material. Several hyperelastic models were evaluated: Mooney-Rivlin, neo-Hookean, Yeoh, Ogden, Arruda- Boyce, Polynomial, and Reduced Polynomial. Numerical modelling was further supported by studies, including: (1) the relationship between experimental data and hyperelastic input parameters, (2) mesh convergence analysis, and (3) Mullins effect sensitivity testing. Experimental and numerical methods were applied using four primary variations of SBR–BR rubber compositions: SBR 100% – BR 0% (SB0), SBR 60% – BR 40% (SB4), SBR 40% – BR 60% (SB6), and SBR 0% – BR 100% (SB10). To validate the newly developed mathematical equations, two additional compositions SBR 80% – BR 20% (SB2) and SBR 20% – BR 80% (SB8) were formulated, representing intermediate ratios between the primary variations. Based on the results of numerical simulations, a new mathematical model was derived to represent the relationship between rubber composition and hyperelastic parameters, which was subsequently validated against the experimental outcomes of SB2 and SB8. Based on the results of the numerical method, the relationship between rubber composition and hyperelastic model parameters was formulated into a mathematical equation using a curve-fitting approach. This method involved plotting the SBR-BR composition against corresponding hyperelastic model parameters to establish a predictive equation. Sensitivity analysis of the equation parameters was conducted using the one-at-a-time technique to assess their influence. Validation was performed in two stages: (1) by comparing the hyperelastic parameters predicted by the equation with experimental data from SB2 and SB8 specimens, and (2) by comparing tensile strength, 200% modulus, strain at break, and specific gravity predictions with corresponding experimental values for SB2 and SB8. Finally, the validated equation was employed to generate a comprehensive list of hyperelastic parameters for various SBR-BR compositions. The findings of this study reveal that the imported GPS material exhibits a maximum tensile strength of 16.9 MPa, 200% modulus of 14.7 MPa, and strain at break of 2.28 mm/mm, corresponding to a stress safety factor of 3.8. Among the evaluated hyperelastic models, the neo-Hookean model was identified as the most suitable for characterizing the mechanical behaviour of the imported GPS. The optimal formulation of an SBR-BR rubber compound capable of substituting the imported GPS is a composition of 60% SBR and 40% BR. This compound also aligns best with the neo-Hookean model for numerical analysis. The relationship between the SBR-BR composition and the hyperelastic model is linear, described by the equation y = -0.0032x + 1.61, where x represents the SBR-BR composition and y denotes the Neo-Hookean C10 parameter. The estimated values of C10 for the SBR-BR compound range from 1.29 to 1.61. Additional findings from this study include: (1) the integration of experimental data with hyperelastic model parameters for configuring the explicit-dynamic numerical material model yields consistent results; (2) a mesh size of 1 mm or half of the smallest specimen dimension ensures stress convergence; and (3) tensile and compressive testing of the SBR-BR compound produces stable and consistent mechanical values.