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Tăng trưởng nứt mỏi theo chế độ cắt 3D trong thép maraging và Ti-6Al-4V
Tóm tắt
Các thí nghiệm về sự phát triển nứt mỏi trong chế độ kết hợp II + III đã được thực hiện trên thép maraging và Ti-6Al-4V. Sự phát triển 3D của các bề mặt nứt - được đo bằng SEM sau các thí nghiệm gián đoạn - đã được phân tích, cân nhắc đến sự giảm lực điều khiển nứt hiệu quả do sự khóa chéo và ma sát của các điểm gồ ghề trên bề mặt của vết nứt. Trong điều kiện biến dạng quy mô nhỏ, tỷ lệ phát triển nứt theo chế độ kết hợp được cho là tương quan tốt nhất với ${\sqrt{{\Delta {\rm K}}_{\rm II}^{{\rm eff}^{2}}+1.2\Delta {\rm K}_{\rm III}^{{\rm eff}^{2}}}}$ trong thép maraging, trong khi đối với Ti-6Al-4V, ${\sqrt{\Delta {\rm K}_{\rm II}^{{\rm eff}^{2}}+0.9\Delta {\rm K}_{\rm III}^{{\rm eff}^{2}}}}$ được cho là phù hợp. Đối với sự dẻo kéo mở rộng, một phương pháp dự đoán phát triển nứt đã được đề xuất và xác nhận cho Ti-6Al-4V. Phương pháp này dựa trên các tính toán F.E. đàn hồi-dẻo và ứng dụng, phía trước mỗi nút trên bề mặt nứt, của một tiêu chí mỏi chiếm ưu thế bởi cắt.
Từ khóa
#nứt mỏi #thép maraging #Ti-6Al-4V #chế độ kết hợp II + III #phát triển nứt #phương pháp dự đoánTài liệu tham khảo
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