The invention relates to a method for observing a magnetic field of a material volume, in particular for determining properties of a workpiece under, in particular, magnetic, mechanical, thermal, and/or electrical excitation of a material volume of the workpiece, wherein the magnetic field of the material volume is sensed as a function of time and of frequency with high frequency resolution.

The present invention provides a surface property inspection method including a step of setting a resistance ratio between resistors R1 and R2 of an AC bridge circuit 20 in a surface properly inspection apparatus 1. The step includes a step for placing a non-surface-treated reference test pieces S on a reference detector 22 and an inspection detector 23 and measuring a first setting output signal while changing the resistance ratio , a step for placing the reference test piece S on the reference detector 22, placing a surface-treated setting test piece on the inspection detector 23, and measuring a second setting output signal while changing the resistance ratio, a step for calculating the differential value between the first and second output signals, and a step for setting the resistance ratio so that the absolute value of the differential value is maximized.

The present invention provides a surface property inspection method including a step of setting a resistance ratio between resistors R1 and R2 of an AC bridge circuit 20 in a surface properly inspection apparatus 1. The step includes a step for placing a non-surface-treated reference test pieces S on a reference detector 22 and an inspection detector 23 and measuring a first setting output signal while changing the resistance ratio , a step for placing the reference test piece S on the reference detector 22, placing a surface-treated setting test piece on the inspection detector 23, and measuring a second setting output signal while changing the resistance ratio, a step for calculating the differential value between the first and second output signals, and a step for setting the resistance ratio so that the absolute value of the differential value is maximized.

Embodiments of the invention relate to polycrystalline diamond (PCD) exhibiting enhanced diamond-to-diamond bonding. In an embodiment, PCD includes a plurality of diamond grains defining a plurality of interstitial regions. A metal-solvent catalyst occupies at least a portion of the plurality of interstitial regions. The plurality of diamond grains and the metal-solvent catalyst collectively exhibit a coercivity of about 115 Oersteds (Oe) or more and a specific magnetic saturation of about 15 Gauss.Math.cm.sup.3/grams (G.Math.cm.sup.3/g) or less. Other embodiments are directed to polycrystalline diamond compacts (PDCs) employing such PCD, methods of forming PCD and PDCs, and various applications for such PCD and PDCs in rotary drill bits, bearing apparatuses, and wire-drawing dies.

Embodiments of the invention relate to polycrystalline diamond (PCD) exhibiting enhanced diamond-to-diamond bonding. In an embodiment, PCD includes a plurality of diamond grains defining a plurality of interstitial regions. A metal-solvent catalyst occupies at least a portion of the plurality of interstitial regions. The plurality of diamond grains and the metal-solvent catalyst collectively exhibit a coercivity of about 115 Oersteds (Oe) or more and a specific magnetic saturation of about 15 Gauss.Math.cm.sup.3/grams (G.Math.cm.sup.3/g) or less. Other embodiments are directed to polycrystalline diamond compacts (PDCs) employing such PCD, methods of forming PCD and PDCs, and various applications for such PCD and PDCs in rotary drill bits, bearing apparatuses, and wire-drawing dies.

A device of detecting magnetic characteristic change for a long material includes: an exciting coil into which the long material is inserted and which magnetizes the long material in a longitudinal direction; a detecting coil into which the long material is inserted and which detects a magnetic flux generated in the long material due to magnetization by the exciting coil; and a yoke member which has a first opening portion which is positioned on one side of the long material in the longitudinal direction and into which the long material is inserted and a second opening portion which is positioned on the other side of the long material in the longitudinal direction and into which the long material is inserted, and has a shape which is substantially axially symmetrical about an axis passing the first opening portion and the second opening portion, and the exciting coil and the detecting coil are surrounded by the yoke member, the first opening portion, and the second opening portion.

A device of detecting magnetic characteristic change for a long material includes: an exciting coil into which the long material is inserted and which magnetizes the long material in a longitudinal direction; a detecting coil into which the long material is inserted and which detects a magnetic flux generated in the long material due to magnetization by the exciting coil; and a yoke member which has a first opening portion which is positioned on one side of the long material in the longitudinal direction and into which the long material is inserted and a second opening portion which is positioned on the other side of the long material in the longitudinal direction and into which the long material is inserted, and has a shape which is substantially axially symmetrical about an axis passing the first opening portion and the second opening portion, and the exciting coil and the detecting coil are surrounded by the yoke member, the first opening portion, and the second opening portion.

To provide a surface characteristics evaluation method that evaluates the residual stress in a subject made of steel material subjected to a surface modification treatment. A surface characteristics evaluation method includes a step of preparing a surface characteristics evaluation apparatus, a step of placing the subject in such a manner that an alternating magnetic field induced by a coil of the surface characteristics evaluation apparatus permeates into the steel material, a step of generating an eddy current in the subject, a step of successively changing the alternating magnetic field applied to the coil, a step of calculating the impedance Z1 for each of different frequencies from the potential difference across the coil and the value of the current flowing through the coil, a step of performing computation based on the impedance Z1, and a step of evaluating the residual stress in the steel material based on the computation result.

To provide a surface characteristics evaluation method that evaluates the residual stress in a subject made of steel material subjected to a surface modification treatment. A surface characteristics evaluation method includes a step of preparing a surface characteristics evaluation apparatus, a step of placing the subject in such a manner that an alternating magnetic field induced by a coil of the surface characteristics evaluation apparatus permeates into the steel material, a step of generating an eddy current in the subject, a step of successively changing the alternating magnetic field applied to the coil, a step of calculating the impedance Z1 for each of different frequencies from the potential difference across the coil and the value of the current flowing through the coil, a step of performing computation based on the impedance Z1, and a step of evaluating the residual stress in the steel material based on the computation result.

Embodiments of the invention relate to polycrystalline diamond (PCD) exhibiting enhanced diamond-to-diamond bonding. In an embodiment, PCD includes a plurality of diamond grains defining a plurality of interstitial regions. A metal-solvent catalyst occupies at least a portion of the plurality of interstitial regions. The plurality of diamond grains and the metal-solvent catalyst collectively exhibit a coercivity of about 115 Oersteds (Oe) or more and a specific magnetic saturation of about 15 Gauss.Math.cm.sup.3/grams (G.Math.cm.sup.3/g) or less. Other embodiments are directed to polycrystalline diamond compacts (PDCs) employing such PCD, methods of forming PCD and PDCs, and various applications for such PCD and PDCs in rotary drill bits, bearing apparatuses, and wire-drawing dies.