International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 03 Issue: 06 | June-2016 www.irjet.net p-ISSN: 2395-0072 © 2016, IRJET | Impact Factor value: 4.45 | ISO 9001:2008 Certified Journal | Page 3017 INERTIA RELIEF ANALYSIS OF AUTOMOTIVE CONTROL ARM Rahul Kumar Rajan 1 , P.Naveenchandran 2 , C.Thamotharan 3 1 Student ,Dept of Automobile Engineering , Bharath University, Selaiyur , Chennai 2 HOD ,Dept of Automobile Engineering , Bharath University, Selaiyur , Chennai 3 Professor, Dept of Automobile Engineering , Bharath University, Selaiyur , Chennai ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - To carry out inertia relief analysis of automotive control arm using Optistruct finite element solver to evaluate displacement and stress characteristic. Inertia relief allows the simulation of unconstrained structures. Typical applications are an airplane in flight, suspension parts of a car, or a satellite in space.With inertia relief, the applied loads are balanced by a set of translational and rotational accelerations. These accelerations provide body forces, distributed over the structure in such a way that the sum total of the applied forces on the structure is zero. This provides the steady-state stress and deformed shape in the structure as if it were freely accelerating due to the applied loads. Boundary conditions are applied only to restrain rigid body motion. Because the external loads are balanced by the accelerations, the reaction forces corresponding to these boundary conditions are zero. Key Words: Inertia relief, Optistruct, Unconstrained structures, Boundary conditions, Reaction forces, Steady-state stress. 1.INTRODUCTION In automotive suspension, a control arm, also known as an A-arm, is a hinged suspension link between the chassis and the suspension upright or hub that carries the wheel. The inboard (chassis) end of a control arm is attached by a single pivot, usually a rubber bushing. It can thus control the position of the outboard end in only a single degree of freedom, maintaining the radial distance from the inboard mount. Although not deliberately free to move, the single bushing does not control the arm from moving back and forth; this motion is constrained by a separate link or radius rod. This is in contrast to the wishbone. Wishbones are triangular and have two widely-spaced inboard bearings. These constrain the outboard end of the wishbone from moving back and forth, controlling two degrees of freedom, and without requiring additional links. Most control arms form the lower link of a suspension. A few designs use them as the upper link, usually with a lower wishbone. The additional radius rod is then attached to the upper arm. So here we carried inertia relief analysis of control arm to evaluate displacement and stress characteristic. 1.1 History of Vehicle Suspension System Pioneering vehicle manufacturers were faced early on with the challenges of enhancing driver control and passenger comfort. The early 1900's, cars still rode on carriage springs. Early drivers had bigger things to worry about than the quality of their ride like keeping their cars rolling over the rocks and ruts that often passed for roads. These early suspension designs found the front wheels attached to the axle using steering spindles and kingpins. This allowed the wheels to pivot while the axle remained stationary. Suspension systems have been widely applied to vehicles from the horse-drawn carriage with flexible leaf springs fixed in the four corners, to the modern automobile with complex control algorithms. The vehicle design typically represents a trade-off between performance and safety since durability especially of safety components is important. This means that the design of the components must be adapted as accurately as possible to the operating conditions (AA, 2004). 2. TYPES OF VEHICLE SUSPENSIONS SYSTEM Suspension systems from one key subsystem of an automobile that are used to isolate the occupants from shocks and vibrations induced due to road surface irregularities. It is also used as a wheel locating and guiding mechanism when the vehicle is in motion. 2.1 Front Suspensions Front suspensions are classified as dependent and independent suspensions. The most common dependent front suspension is the beam axle, which is used less and less in recent vehicles because of numerous disadvantages like large unsprung mass, packaging space, and considerable caster change. However, some off-road application vehicles tend use still to the beam axle dependent front suspension as they offer high articulation and high ground clearance. The most common types of front independent suspensions are the double wishbone suspension and the Macpherson strut. The double wishbone suspension also known as the double A-arm suspension has parallel lower and upper lateral control arms. The main advantage of the double wishbone is that the camber can be adjusted easily by varying the length of the lateral upper control arm such that it has a negative