To easily detect a crack having occurred in a steel material. A current measurement device 10 measures a value of a current flowing through a target steel material 100 that is immersed in an electrolyte aqueous solution 30 and applied with tensile stress while subjected to hydrogen charging, and a device 20 for detecting the occurrence of a crack or the like uses the measured current value to determine the occurrence of a crack in the target steel material 100 when the amount of change in the current flowing through the target steel material 100, the change rate of the amount of change in the current, or the change rate of the change rate of the amount of change in the current exceeds a threshold value. The device 20 for detecting the occurrence of a crack or the like determines the occurrence of a crack in the steel material when the change rate of the change rate of the amount of change in the current is less than a negative value of an absolute value of the threshold value, and determines the occurrence of fracture in the steel material when the change rate exceeds the absolute value of the threshold value.

Systems and methods for testing shear bond strength of cement with a composite sample under downhole conditions form a bonding surface of the sample oriented at an angle between 50 and 70 degrees from a plane perpendicular to a longitudinal axis of the sample. The composite sample is formed by bonding the cement to the sample with the cement in contact with the bonding surface of the sample.

A window drop test apparatus includes a support protruding in a first direction from the prop, and a guide portion that defines a drop space together with the support, where a drop test is performed through the drop space.

The device for preparing sheet specimens comprises a base (1) for placing on it a sheet specimen (2) and a cutting punch (3) for cutting sheared cracks or sharp notches in said sheet specimen (2). Preferably, said cutting punch (3) comprises a beveled lower end (31) and/or a central vertical groove (32). Permits the cracks to be formed cutting directly the sheet, and not by cyclic loading, so that the preparation of the sheet specimen takes a reduced time in comparison with the conventional devices.

An indenter is made of polycrystalline diamond and has a tip having a spherical surface with a radius of 10 to 2000 μm.

A device for assessing the solidity of a material comprising an ancillary tool (2) having an end (2B) in the form of a point or blade, an impactor (4) for striking the ancillary tool (2), a sensor (12) and a processing unit (30). The ancillary tool (2) is placed between a material (8) and the impactor (4) and transmits the impact force generated by the impactor (4) to the material (8). The sensor (12) is capable of measuring a quantity from among the impact force and the deformation of the impactor, and of supplying a measurement signal. The processing unit (30) is suitable for calculating, from the measurement signal, an indicator representative of the solidity of the material (8). The indicator corresponds to the duration of a time window between the first peak (P1) of maximum amplitude of the measurement signal and the second peak of maximum amplitude (P2).

A method for defining a threshold stress curve utilized in fatigue and/or damage tolerance analysis, the method including conducting a direct test method on a plurality of specimens with a notch to generate raw data, the notch in each of the specimens having a notch dimension; determining a plurality of analyzed data points based upon the raw data; determining a regression line based upon the plurality of data points, the regression line including an exponential portion and a power law portion; and connecting the exponential portion and the power law portion of the regression line to form a threshold stress curve based on the regression line.

A method for estimating life of a component includes obtaining fracture data corresponding to a component. The fracture data includes a first dataset corresponding to a threshold region where the crack in the component is dormant below a fatigue threshold. The method further includes determining initial estimates of parameters of a crack growth rate model and parameters of temperature models corresponding to the crack growth rate model based on the fracture data. The method also includes computing optimized parameters of temperature models corresponding to the crack growth rate model, and a scatter parameter via simulation of a joint optimization method using the initial estimates. The method includes determining a cumulative distribution function based on the optimized parameters and the scatter parameter and estimating life of the component based on the cumulative distribution function.

A method for preparing a SiC ingot includes: disposing a raw material and a SiC seed crystal facing each other in a reactor having an internal space; subliming the raw material by controlling a temperature, a pressure, and an atmosphere of the internal space; growing the SiC ingot on the seed crystal; and collecting the SiC ingot after cooling the reactor. The wafer prepared from the ingot, which is prepared from the method, generates cracks when an impact is applied to a surface of the wafer, the impact is applied by an external impact source having mechanical energy, and a minimum value of the mechanical energy is 0.194 J to 0.475 J per unit area (cm.sup.2).

An apparatus and a method for measuring a creep crack growth property using a small specimen with a micro groove are provided. The apparatus for measuring a creep crack growth property includes a lower die on which an edge of the specimen is mounted and which includes a lower die hole formed in the center thereof, an upper die coupled to an upper portion of the lower die so as to fix the specimen, and a punching unit inserted into an upper die hole formed in the center of the upper die so as to press an upper surface of the specimen, wherein a semielliptical micro groove is formed in a lower surface of the specimen to measure a creep crack growth property.