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Fracture splitting notches from C70S6 steel used in a connecting rod and from gray cast iron used in an engine crankcase main bearing bracket were processed by a YAG pulse laser,and the fracture splitting experiment was conducted in the fracture splitting device.The geometry appearances,microstructures,micro-hardness change as well as the fracture surface of fracture splitting notches were studied by a tool microscope,a scanning electronic microscope and a micro-hardness tester.Characteristics of fracture splitting notches processed by the pulse laser were discussed,and the influence of pulse laser processing fracture splitting notches from ductile/brittle materials on the expansion and breaking performance of the notchs was revealed.The results indicate that the geometry appearances and notch effects of the fracture splitting notches from ductile/brittle materials processed by the pulse laser are obviously superior to those of the broaching and linear cutting processing,and the gap sensitivity of gray cast iron has been strengthened greatly.The brittle martensite has been produced nearby the fracture splitting notches from ductile/brittle materials,and micro crack appears in the root of notch.The organization is obviously refined.The micro-hardnesses of melting zone and the solid phase transition zone of ductile/brittle materials approximately are 820/850 HV and 860/550 HV,respectively,which are higher than that of the substrate,and show a remarkable hardening effect.The ductile tearing phenomenon can not be seen in the C70S6 steel notch root zone.The ductile/brittle material fracture shows the brittle fracture characteristic,which satisfies the fracture splitting technological requirement.

Taper-leaf springs are important elastic parts in the suspension system of many vehicles. Precision roll-forging is an advantaged technology for processing taper-leaves. The present paper is concerned with experimental research on the precision roll-forging of iso-width taper-leaf vehicle springs. Equations to evaluate the width-extension and slip-forward values that affect the workpiece quality and their correcting curves have been determined experimentally, such equations having been proven to be both practical and reliable in use. Satisfactory results were obtained when the equations were applied to the design of the roll-forging process and dies for forming different taper-leaf springs: there was no flash on the parts, the dimensional accuracy was high and the surface quality was excellent. Industrial applications have shown that the precision roll-forging technique for taper-leaf springs can increase the productivity, decrease production costs and investment in equipment, and meet the requirements for product quality and properties being especially economical and suitable for the production of massive taper-leaf springs.

The stress state during “simple” superplastic bulge forming (without a back pressure) is different from that when a back pressure is applied. In the former procedure, specimens or components are deformed under a biaxial tensile stress state, while in the latter, the deformation is achieved under the combination of a biaxial tensile stress and a uniaxial compressive stress state. Both theoretical and experimental studies have shown that when a back pressure is present, the deformation cannot be treated as simply governed by the difference between the forming pressure and the back pressure. The analytical expressions for the forming relationships and the influence of back pressure on experimental m-log $$\dot \varepsilon _e $$ (where m is the strain-rate sensitivity and $$\dot \varepsilon _e $$ is the equivalent tensile strain rate for bulge forming) relationships for Zn-22 wt% Al and Zn-4 wt% Al-1% Cu are given. Results show that with increasing back pressure, the m-log $$\dot \varepsilon _e $$ curve shifted towards higher strain rates, but the maximum m values were not affected.

Laser fracture splitting technology significantly improves the processing quality and efficiency of engine crankcase main bearing block. In order to research the splitting mechanism of ductile iron material fracture notch cauterized by Nd: YAG Laser, the FEAmodel of fracture splitting processing of engine crankcase main bearing block has been developed successfully. The splitting parameters of ductile iron material (QT500-7) main bearing block is analyzed. The numerical simulation results indicate that: among all the key parameters affecting the quality of fracture splitting, the effect of notch depth on fracture splitting load is more obvious than that of the notch opening angle and radius. The value of splitting load decreases rapidly with the increasing notch depth, while the splitting load increases with the increasing notch angle and radius. The optimum value of the notch depth, angle, and radius should be respectively at 0.5 mm, 60 o, and 0.2 mm. The results have been proved by experiments. The optimum parameters obtained from the ABAQUS simulation and experiments provide a numerical reference for significantly reducing the splitting load and optimizing the fracture splitting process, help to achieve the rapid development of engine block process and promote the green manufacture of automobile industry.