SISTEM PENILAIAN KKomponen Penilaian : AAbsensi (10 %) TTugas/Quis (10 %) UUjian I (mid semester) (40 %) UUjian II (akhir semester) (40 %) QQuis dapat dilakukan setiap saat, tanpa pemberitahuan sebelumnya, dapat dilakukan pada awal atau akhir setiap perkuliahan SSehingga p pp persiapkan diri anda setiap saat SSetiap quis digunakan kertas ukuran A4 (setiap mahasiswa harus membawa sendiri)
Dynamics, in physics, dynamics refers to the effects of forces on the motion of objects Kinematics is a branch of physics which describes the motion of objects without consideration of the circumstances leading to the motion. An example is the prediction of centripetal force in uniform circular motion, regardless of whether the circular path is due to gravitational attraction, a banked curve on a highway, or an attached string.centripetal forceuniform circular motiongravitational attractionbanked curve Kinetics a branch of dynamics, concerned with what motions of bodies are produced under the action of particular forces (or affect the motion). Not to be confused with kinematics, the study of what forces are implied by selected motions. dynamics kinematics
Dynamics Study of Forces and machine behaviour under forces and how to use them in the design of mechanisms. You need to know “Statics” and “Dynamics” !
Kinematics Study of Motion and how to achieve a desired motion. kinematics also deals with velocities, size, shape, weight, etc. These parameters might be the inputs to the mechanism design process ( which will affect the final outcome of the mechanism design: type, configuration, etc. ) A B Translation Rotation
In order to design a mechanism and its components we need to understand how the mechanism transfers energy. We need to identify the forces to be able to determine the proper dimensions of the components (i.e., design ). We need to know how the input forces flow through the mechanism (power flow or power transmission) to the output link. The objective of the force analysis of mechanisms is to find the transformation of forces from the input link to the output link This transformation depends on the position of the mechanism (i.e., it is a function of time ) It is important to find out how these forces change “during one cycle” to find their maxima (for example)
Analytical Methods – this approach is suitable for automatic computation. Once a solutions if obtained the solution for the entire motion range is obtained. Graphical Methods – provide the designers with a quick straightforward method but parameters cannot easily be manipulated to create the solution for the entire range of motions. Free Body Diagram(s)
In force analysis two type of forces must be considered: External: Forces applied to the links from external sources w.r.t. the mechanism (e.g., motors, pistons, etc.). Internal: Forces acting between the joints (constraint of reaction forces). Solutions to Force Analysis: Solutions to Force Analysis: Direct Dynamics: The motion is caused by known external forces, and can be found by formulating and solving differential equations describing the dynamic equilibrium of the mechanism at any moment in time. Direct Dynamics: The motion is caused by known external forces, and can be found by formulating and solving differential equations describing the dynamic equilibrium of the mechanism at any moment in time. Inverse Dynamics: When the motion is known (motion of the input link is known), then from the kinematic analysis, the accelerations of all links are known (thus, the inertial forces associated to all links can be obtained). The known inertial forces (considered as external forces) and force analysis is reduced to solving equilibrium equations for the mechanism at any given position. Inverse Dynamics: When the motion is known (motion of the input link is known), then from the kinematic analysis, the accelerations of all links are known (thus, the inertial forces associated to all links can be obtained). The known inertial forces (considered as external forces) and force analysis is reduced to solving equilibrium equations for the mechanism at any given position.
9 First steps in problem solving similar for both Statics/Dynamics and Mechanics of Materials: Draw a FREE BODY DIAGRAM Solve for unknown external forces and moments F x = 0, Fy = 0, M A = 0
Tiga buah gaya dalam keseimbangan Tiga buah gaya yang bekerja (gambar a) akan berada dalam keseimbangan jika gaya – gaya tersebut membentuk sistem poligon tertutup (gambar b)
Kasus pertama Empat buah gaya F1, F2, F3, dan F4 dimana gaya F1 diketahui arah dan besarnya, sedangkan yang lainya hanya diketahui arahnya
Kasus kedua Empat buah gaya F1, F2, F3, dan F4 dimana gaya F1 dan F2 diketahui arah dan besarnya, sedangkan F3 hanya diketahui arahnya dan F4 diketaui titik garis kerja
Gaya P diketahui arah dan besarnya, sedangkan F1 dan F2 hanya diketahui arah gayanya.