282 (1) An independent development of a set of triaxial loading test equipment for insert indentation rock-breaking capable of simulating the axial pressure and confining pressure conditions of real formations. (2) A systematic investigation of the performance differences between spherical and conical inserts under single and combined in-situ stress fields, focusing on the interaction effects of indentation speed, penetration depth, and insert shape on rock-breaking efficiency. (3) The introduction of 3D topography scanning technology for high-precision quantitative characterization of the crushing pits, obtaining geometric parameters such as area and morphology, thereby establishing direct correlations between operational parameters, insert shape, and fragmentation outcomes. (4) An extension of the research object from single inserts to dual-insert combinations (spherical-spherical, conical-conical), preliminarily exploring the synergistic or interference effects under multi-insert interaction to provide an experimental basis for the optimization of insert layout on hybrid bits. Through these integrated innovative approaches, this study aims to deeply reveal the mechanisms behind the rock-breaking differences between spherical and conical inserts under various operational parameters in an in-situ stress environment, providing theoretical support and data reference for the customized design of high-performance hybrid bits and the optimization of drilling parameters. 2. EXPERIMENTAL EQUIPMENT AND MATERIALS 2.1 Triaxial Rock Penetration Equipment Based on calculations concerning pressure chamber dimensions and reliability, the designed triaxial rock penetration equipment is illustrated in Figure 2. The insert motion mechanism is primarily powered by a stepper motor, which, via a reducer and lead screw drive, can achieve a maximum thrust of 20 kN. The inserts used for rock penetration are made of tungsten carbide alloy, with both spherical and conical inserts having a diameter of 5 mm. The rock specimens have dimensions of Φ50 mm × h100 mm. The entire testing system (Figure 2) mainly consists of control software, a controller, and the triaxial rock penetration and breaking apparatus. During the testing process, the control software is used to program test instructions, including axial pressure, confining pressure values, loading sequence, and insert penetration speed. These instructions are then sent by the controller to a 64 MPa volumetric pressure controller and the stepper motor to execute the loading and penetration processes. Test data is monitored and recorded by load and displacement sensors.
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