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A known factor which limits the life cycle performance of automotive front-end accessory serpentine belt drive is cracking of the elastomer located in the rib tip. In this paper, fracture mechanics was used to study crack growth in belt rib. Tearing energy and J-integral were employed to characterize the fracture behavior of rubber compound. A global-local strategy was adopted to predict the crack initiation in V-ribbed belt rib. The global finite element model of the belt was created with relatively coarse mesh. The local model with fine mesh around the crack tip region was used to evaluate the J-integral. The J-integral computed using finite element analysis was compared with the threshold value found by experiments to predict the onset of crack initiation in belt rib.

A geometrical set of closed form trigonometric equations are developed as a simplified alternative to the complex numerical computations required for determining lateral belt tracking locus due to pulley misalignment tolerances. Solutions are validated by a comprehensive statistically designed database. Further, analytical verification is obtained from ABAQUS/Explicit results based on a nonlinear hyperelastic Ogden finite element model. Three-dimensional geometric equations form the basis of a computer tool developed to predict belt displacement across a flat backside pulley, as well as angles of entering and exiting spans. Predictions are performed for the critical combination of a grooved-flat-grooved pulley arrangement typically found in automatically tensioned front-end automotive serpentine accessory drives. Excellent correlation is found between the three-dimensional finite element analysis, experimental data, and the simplified geometrical model.

This paper investigates the effect of ambient temperature on the performance characteristics of an automotive poly-rib belt operating in an under-the-hood temperature environment. A three-dimensional dynamic finite element model consisting of a driver pulley, a driven pulley, and a complete V-ribbed belt was constructed. Belt tension and rotational speed were controlled by means of loading and boundary inputs. Belt construction accounts for three different elastomeric compounds and a single layer of helical wound reinforcing cord. Rubber was considered as hyperelastic material. Cord is linear elastic. The material model was implemented in ABAQUS/Explicit for the simulation. Analysis was focused on rib flank and tip since stress concentrations in these regions are known to contribute to crack initiation and fatigue failure.

A three-dimensional dynamic finite element model was built to study the stress distribution in V-ribbed belts. Commercial finite element code ABAQUS was used for the simulation. The model consists of a pulley and a segment of V-ribbed belt in contact with the pulley. Different belt pulley tracking configurations can be obtained by varying the pulley diameter and the belt wrap angle. Belt tension and pulley rotating speed can be controlled by the load and boundary conditions. Both driving and driven pulley can be modeled by applying different sets of load and boundary conditions. Rubber is modeled as hyperelastic material. Reinforcing cord and fabric are modeled as rebar defined in ABAQUS. Emphasis was put on the belt rib tip stress because it causes belt wear and belt rib fatigue cracking. The stress at the belt rib tips depends on tension in the belt, pulley contact friction coefficients, rib rubber properties, pulley diameter and belt wrap angle.

A general three-dimensional finite element model was built to simulate the tracking conditions inherent in automotive front-end accessory drives, specifically, serpentine V-ribbed belt drives. Commercial finite element code ABAQUS was used for the simulation. The analysis is based on a hyper-elastic material model for the belt, and includes the effect of the reinforced cords and fibers in the rubber compound. The model can be used to study different parameters of the belt drive system such as rib number, pulley misalignment, drive wrap angle and drive speed. Experiments were used to validate the finite element model. Belt misalignment force of two, four and six ribbed belts under different misalignment conditions was obtained from experiment and compared with the results from the finite element model. Good correlation between these results brings confidence to the finite element model. Finally, typical FEA simulation results for a six-ribbed belt are presented.

Two instrumented pulleys were developed to empirically measure the dynamic lateral forces of V-Ribbed belts used in automotive accessory drives. The first test pulley utilizes two cantilever beams cut into the pulley with strain gauges attached to measure the lateral dynamic forces in each individual belt rib caused by misalignment. A test stand which simulates multiple accessory drive configurations at low-end drive speeds typical in automotive engines was implemented to create the dynamic response necessary. This test stand allows variations in lateral offset, toe, camber, tension, and span length, as well as in the speed of the system through a variable speed AC motor. The second test pulley utilizes a unidirectional load cell oriented to measure the total lateral force on the test pulley. After conducting static calibration tests of the two experimental systems, dynamic results were obtained using real time data acquisition.

A three-dimensional V-Ribbed belt model was developed for use in the prediction of out of plane forces and displacements. A two dimensional model was first created to assist in developing the techniques needed to build the three dimensional model. A non-ribbed three-dimensional model was then developed to minimize the computer time needed to run the simulations. This belt model was used along with both frontside and backside pulleys to stretch the belt into position from its original round configuration. This model was also used for movement of the pulleys into or out of the belt plane, and toe and camber movements were applied to the pulleys. The knowledge gained from the first two models was then used to construct a program to generate the ribbed three-dimensional belt and pulleys. The models generated incorporated up to eight ribs and as many as nine pulleys in any model.

A mathematical model is presented that simulates belt tension forces in an automotive belt drive during rapid engine acceleration. The model is formulated as a base excitation problem in which the known motion of the crankshaft is used to excite the system. The elasticity of the belt is included by using linear elastic springs in the open spans and on the arc of contact of the belt with each pulley. The complete model includes the movement of the automatic tensioner arm, the variation of accessory load torques with speed, the effects of centrifugal tension, and the inertia of each component. A numerical example is presented which shows good agreement with experimental data. Similar results have been obtained for other cases tested.

V-belt replacement costs on alternator, air-conditioning, and power-steering drives can be reduced significantly by installing new belts at a time established by an age or block replacement plan, instead of waiting for belt failure. Methodology and a realistic example are presented for determining such plans and associated cost reductions. The plans are based upon historical belt failure data and upon the increase in after-failure replacement costs over those resulting from scheduled replacement prior to failure.

Equations have been derived for designing automatic tensioning variable speed V-belt drives. Such drives employ a screw principle to increase tension in the belt as loading of the drive increases. Adjustable tensioning makes it possible for variable speed drives to transmit significantly larger loads without overly penalizing belt life. This feature is possible because high tensions required by heavy loads are not retained during lighter loads experienced under normal operations. Drives have been designed by these equations and have been proven successful both in the field and laboratory. Experience in designing the drives is discussed and general recommendations are provided for the design of new torque sensing drives. Other types of applications are described that would also benefit from torque-actuated tensioning.