A Comparative Study of Fatigue Behavior and Life Predictions of Forged Steel and PM Connecting Rods

Abstract

This study investigates and compares fatigue behavior of forged steel and powder metal connecting rods. The experiments included strain-controlled specimen testing, with specimens obtained from the connecting rods, as well as load-controlled connecting rod bench testing. Monotonic and cyclic deformation behaviors, as well as strain-controlled fatigue properties of the two materials are evaluated and compared. Experimental S-N curves of the two connecting rods from the bench tests obtained under R =-1.25 constant amplitude loading conditions are also evaluated and compared. Fatigue properties obtained from specimen testing are then used in life predictions of the connecting rods, using the S-N approach. The predicted lives are compared with bench test results and include the effects of stress concentration, surface finish, and mean stress. The stress concentration factors were obtained from FEA, and the modified Goodman equation was used to account for the mean stress effect. Fractography of the connecting fracture surfaces were also conducted to investigate the failure mechanisms. A discussion of manufacturing cost comparison and recent developments in "crackable" forged steel connecting rods are also included.

Vehicular Engine Design

“…The text then listed devotes a chapter to connecting rod fatigue, and rig testing for rod development (See Afzal and Fatemi 2004;Park et al 2003;Wright 1995). The next paper discusses fracture-split connecting rod design.…”

“…Continuously Variable Systems (Flierl and Klüting 2000;Kreuter et al 2003): Camless Systems and Performance Impact (Allen and Law 2002;Turner et al 2004;Pischinger et al 2000): exhaust manifold, 168, 246, 276, 277 piston, 246, 300 Thermal loads, cylinder head, 40, 187 Thermal transients, piston, 303 Thermostat, 108, 127, 135, 157-159 Thrust bearing, crankshaft, 130, 131, 197, 332 Tooling, 31, 53-55, 58, 59, 93, 110, 111, 113, 128, 132, 177, 272 Torque bolt, 278 plate, 317 Torque-plus-turn, 279 Torque-to-yield, 279 Torsional vibration, 54, 332-336, 338, 259 Transfer lines, 111 Tribology, 42, 43, 50 Tri-metal bearings, 208 True fracture strength, 39 Tumble, intake flow, 162 Turbocharging,7,8,67 Turbulence,149 Underwood bearing rig, 209, 210 Uprating, 68 Validation testing, 59 Valve intake and exhaust, 3,4,49,157,161,301,378 burning,372 flow area,158,159 press fit,seat,174,187,246 seat,174,187,246 spring,40,75,156,163,175,361,364,372,374,378 stem,46,156,…”

Design, Buckling and Fatigue Failure Analysis of Connecting Rod: A Review

“…Olaniran et al [4] investigated a new crack able alloy of forged steel (FS) for connecting rod application. The material properties for connecting rod material are given in Table 1 [6]. …”

An approach to integrate manufacturing process information in part design phases

“…A PP is a process characteristic that reflects a process constraint or requirement to achieve the design parameters (DPs) (e.g. the material anisotropy generated during the forging process can affect whether some mechanical properties are obtained (Afzal and Fatemi, 2004)). A PP is a type of process attribute, but it is only related to DPs and not to other design specifications or constraints like product cost (Ferrer, 2007).…”

“…ing processes were obtained. Second, they are currently the most common process technologies for the bulk production of connecting rods (Afzal and Fatemi, 2004).…”