Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
Tham khảo tài liệu 'mechanics of microelectromechanical systems - n.lobontiu and e.garcia part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 168 Chapter 3 The terms in the right-hand side of Eq. 3.111 are the axial stiffnesses of the two compliant members taken with respect to their local frames their x-axes are parallel to their length dimensions . The spring stiffness about the out-of-the-plane motion the z-direction of the mass can be found by also using Fig. 3.37. A force F Z is applied at point 1 about the z-direction and the corresponding Ulz out-of-the-plane displacement can be determined by considering bending and torsion of the two compliant members. The z-direction stiffness of the half-model is which is valid when the two compliant segments are of constant crosssections. The whole folded-beam microspring is formed of two parallelconnection identical parts as the one sketched in Fig. 3.37 and therefore the stiffness of the full microspring is KZ 2KZ 3.113 Example 3.13 In a folded-beam microsuspension the long legs cannot exceed a maximum length of 11 max 200 gm. What is the length of the short legs which would produce a specified stiffness Kx 60 N m of the microsuspension about the motion direction for a given rectangular crosssection and material properties w t 5 gm E 130 GPa Solution If the short leg length is connected to the length of the long leg as Figure 3.38 Stiffness K.x for a folded-beam suspension 3. Microsuspensions 169 2 cZ1 3.114 and for the given moment of inertia and Young s modulus the stiffness Kx depends on 11 and c as shown in Fig. 3.38. The stiffness Kx decreases with 11 and c increasing. For the values of lirnax and Kx the solution is c 0.94 and therefore the length of the short leg is 12 188 gm. Example 3.14 A sagittal suspension and a folded-beam spring can be inscribed within the same a x b rectangular area a 300 gm b 200 gm . What are their stiffnesses about the motion direction in the case both designs have the same cross-section of their compliant members Consider that Oi 15 and 11 213 for the sagittal spring and that 1 3 1 4 for the folded-beam suspension. Solution
