Abstract:
The present invention relates to a residual stress estimation method using an instrumented indentation technique. According to an embodiment of the present invention, the residual stress estimation method using the instrumented indentation technique is provided for estimating the residual stress when the residual stress does not exist in a test piece.
Abstract:
PURPOSE: An apparatus for an indentation test with a micom and a method for evaluating residual stress using the same are provided to be used for a large structure by controlling the range of an applied load. CONSTITUTION: An apparatus for an indentation test with a micom comprises an actuator, a slider, a slider guide, an indenter, a load sensor, a displacement sensor, a micom, and a main computer(150). The actuator is installed inside a tester body(110). The slider is connected to a ball screw and a screw nut and comprises a cylinder slid along a rotary shaft. The slider guide is coupled to the tester body and guides the sliding of the slider. The indenter is connected to the slider and applies a load to a test piece. The load sensor measures the load applied to the test piece. The displacement sensor measures the depth that the indenter is inserted into the test piece. The micom is installed inside the tester body and controls the actuator. When the measured values of the load sensor and the displacement sensor exceed a reference value, the main computer stops power supply.
Abstract:
PURPOSE: An evaluation method of the anisotropic residual stress using the instrumented indentation technique is provided to measure isotropic residual stress among the mechanical property valuations of a material by an anisotropic indenter. CONSTITUTION: An instrumented indentation test using an anisotropic indenter proceeds after applying biaxial tension residual stress including one axial tension and isotropic property. It is compared that a slope of the indentation load-depth curve in indentation and the slope of the indentation load-depth curve under non-stress while the biggest residual stress is being applied in a longitudinal axis of the anisotropic indenter. It is compared that the slope of the indentation load-depth curve in indentation and the slope of the indentation load-depth curve under non-stress while the longitudinal axis of the anisotropic indenter is in parallel with the direction where the biggest residual stress is applied.
Abstract:
A measurement method of fictitious strain-hardening exponent, strength coefficient, yield strength, and tensile strength using a continuous indentation test is provided to analyze elastic deflection and plastic pile-up as analyzing factors of a contacting area between an indenter and a sample material when testing indentation tensile and yield properties. A measurement method of fictitious strain-hardening exponent, strength coefficient, yield strength, and tensile strength using a continuous indentation test includes the steps of setting an n value of a virtual strain-hardening exponent of a specific austenite metal, estimating a value of f(n) by substituting the set value of n into f(n), estimating a value of (dm)k at a kth indentation test by substituting the estimated value of f(n) into dm(f(n),hf), where k is an integer from 1 to m, estimating a value of nj to allow m number of (dm)k to approach (Lmax)k=lambda(dm)khj+2, comparing the value of nj with the value of n set in the setting step, repeating the step of setting, the step of estimating the value of f(n), the step of estimating the value of (dm)k, the step of estimating the value of nj, and the step of comparing by setting n to as nj when the value of nj is different from the value of n, and determining a final value of nf as nf=nj when the value of nj is equal to the value of n. The value of n is 0.001 when the setting is performed at first time.
Abstract:
PURPOSE: A jig apparatus for shear test is provided to test adhesion force of different material regardless of the type and shape of the different material, while allowing alignment of specimen and load to be easily carried out. CONSTITUTION: A jig apparatus(20) comprises a load transfer unit(22) and a specimen fixing unit(24). The load transfer unit includes a connector(25) having an upper portion connected to a load generating device and a lower portion fixing a plate(28); and the plate having an upper portion fixed by the connector and a lower portion extended in a vertical direction, such that the lower end of the plate contacts a specimen so as to apply a shear stress to the specimen. The specimen fixing unit includes a specimen support(34) having a front surface for fixing the specimen; and a fixing member for fixing the specimen support at the bottom, and which is screw-coupled with the specimen support. The fixing member includes a base(30) having a guide groove formed in a lengthwise direction, and a tray(32) having a lower portion engaged with the guide groove of the base and an upper portion extended in a vertical direction.