94 results about "Fracture Toughness Testing" patented technology

The invention discloses a method for measuring fracture toughness of pipeline steel by using a unilateral notched tensile test. The method is characterized by comprising the steps of preparing a unilateral notched tensile test sample; prefabricating a tensile sample crack by wire-electrode cutting and fatigue crack growth rate test method; calculating crack growth amount according to the tensile sample cracks; and acquiring J integration and stress intensity factor K for characterizing the fracture toughness of the pipeline steel by drawing a J-R curve for characterizing crack resistance of the crack growth. The method measures the fracture toughness of the pipeline steel by using tensile samples (SENT samples), overcomes the defects that the scope of measurement results of tensile samples (SENT samples) by a conventional technology is so small that the fracture toughness of the pipeline steel can not be evaluated; the crack toughness value of the tensile samples (SENT samples) can be more reasonable; waste of test for pipeline steel materials can be prevented; and the method has the advantages of high measurement accuracy.

The invention provides a method for testing the fracture toughness of rattan canes based on a three-point bending mode. The method comprises the following steps: preparing a sample, and regulating a water content rate so as to obtain a sample of which the water content rate is 10-12%; recording a load-crack opening displacement (PV) curve, measuring actual crack depths, and calculating critical loads PQ and critical stress intensity factors KQ. According to the method provided by the invention, the crack opening displacement is measured by a C.O.D Gauge, and the test precision is improved. Aiming at the characteristics of the rattan materials, the sampling method for testing the fracture toughness of rattan canes is ensured, and the measured results having high accuracy and good reproducibility are obtained. The calculation method for testing the fracture toughness of rattan cane, provided by the invention, provides qualitative and quantitative bases for the utilization of the rattan canes.

The invention discloses a self-centering double shear test device which comprises a sample box.A horizontal through hole and a vertical through hole are formed in the sample box and are orthogonal.A first normal pressing block and a second normal pressing block are arranged at the two ends of the horizontal through hole respectively.The first normal pressing block abuts against one end of a position adjusting rod, and the other end of the position adjusting rod is connected with a threaded hole in a first counter-force support through a thread.The second normal pressing block abuts against a normal force loading device which is arranged on a second counter-force support.The first counter-force support and the second counter-force support are connected through a horizontal dowel bar.The invention further discloses a rock sample shear strength parameter test method and a type II fracture toughness test method.The self-centering double shear test device is simple in structure, easy to manufacture and high in applicability, has a self-balancing function, can be easily combined with an existing rock mechanical test system, and can be used for carrying out a rock type II fracture toughness test.

The invention relates to a new rock II-type fracture toughness test method. According to the invention, on the basis of an original shear box test, by means of adjustments of the stress state of a loaded mould and arrangement of a sample to eliminate rotation tendency of the sample, generation of an excessive tensile stress on a crack tip is inhibited, thereby achieving rock II-type fracture toughness test. A test model includes a square rock sample and two steel loading moulds. Straight cracks are pre-formed on the middle parts of the two sides of the square rock sample, wherein the lengths and the widths of the two straight cracks are equal to each other. The two straight cracks are arranged symmetrically. The loading moulds can achieve 45-degree loading of the sample with a loading end surface being flat and smooth. The widths of two contact surfaces between the loading moulds and the square rock sample are both half of the side length of the sample. An upper end and a lower end of the whole system are subjected to a uniform load. The method enables processing of the rock sample and the loading moulds to be more convenient, is simplified in test process, ensures accuracy of test data, is suitable for the II-type fracture toughness test of various rocks, and provides basis for researching the II-type fracture of rocks and a problem of composite fracture mainly comprising II-type fracture.

The invention discloses a test piece assembly for testing rock I-II compound dynamic fracture toughness and a testing method. The test piece assembly comprises a test piece body with a groove and a loading platform, and cylindrical pressing heads supporting and abutting against the test piece body. The test piece body is a semi-disc-shaped plate, the groove stretches into a test piece from the straight side plane of the semi-disc-shaped test piece along the axial symmetry surface of the semi-disc-shaped test piece, the loading platform is located in the center of the arc surface of the semi-disc-shaped test piece, and the table plane is parallel to the straight side plane of the test piece. The pressing heads are straight arc cylindrical surface pressing heads. During testing, the two cylindrical pressing heads are located on the two sides of the groove respectively, the test piece assembly is arranged between an incidence rod and a transmission rod of a Hopkinson pressure bar testing device, the test piece is collided through an impact bar of the testing device, and the I-II compound dynamic fracture toughness of the rock test piece is tested through strain signals. The preparation process of the rock I-II compound dynamic fracture toughness testing test piece and the testing process of the rock I-II compound dynamic fracture toughness are greatly simplified.

The invention provides a device and a method for testing breaking tenacity of a compact tension specimen in a low-temperature environment. The device comprises an insulated container for containing low-temperature liquid medium, upper and lower clamps and a displacement transmitting mechanism, wherein a specimen is soaked in low-temperature liquid medium and comprises a crack mouth in a horizontal orientation; the upper and lower clamps are connected with the specimen, respectively arranged at two sides of the crack mouth, and respectively connected with upper and lower pistons of a tensile testing machine; the displacement transmitting mechanism comprises two vertical guide rails which are parallel and slide oppositely; upper and lower blades are respectively arranged at two ends of the each vertical lead rail; the upper blades of the two vertical guide rails are oppositely arranged to form an upper tool edge connected with an extensometer; the lower blades of the two vertical guide rails are arranged oppositely to form a lower tool edge connected with the crack mouth, so that a loaded line displacement of the specimen is transferred to the extensometer above the liquid level of the low-temperature liquid medium, so as to accurately measure the loaded line displacement. Meanwhile, the extensometer is prevented from directly contacting the low-temperature liquid medium to be easily damaged, and the device and the method are simple and reliable in structure, and convenient to install and operate.

The invention relates to a device and a method for measuring the I-type creep fracture toughness and the fracture toughness of rock. A rock single axle tensile creep fracture test and a conventional fracture test are carried out on the device for measuring the I-type creep fracture toughness and the fracture toughness of rock, thus the I-type creep fracture toughness and the fracture toughness of rock are measured. The measuring method comprises the steps of: transferring a pressure applied by the exterior into a tensile force of the interior of a rock test piece so as to realize the single axle tension of the rock test piece. The invention enables the operation of the indoor measuring method of rock fracture toughness to be simpler, guarantees the accuracy of the measured data of the test and has rather high precision, therefore having excellent using and popularizing values.

A compact pipe specimen applicable to a fracture toughness test used to evaluate physical properties of a pipe material is provided. The compact pipe specimen includes: a pipe having a notch portion formed in a circumferential direction and a crack portion formed at the edge of the notch portion; and first and second jigs having openings to which a pressurizing unit is coupled so as to cause a bending load on the pipe, having the notch portion therebetween, and attached to the exterior surface of the pipe, respectively. It is unnecessary to correct the influence of a constraint effect due to varying sizes and shapes of the specimen. There is no restriction to the curvature and thickness of a pipe. A fracture behavior of a pipe crack portion can be precisely simulated.

The invention provides a method for testing rock composite fracture toughness based on asymmetric three-point bending loading of an NDB sample, and the method comprises the steps: enabling a test piece body to be a rectangular deep beam (NDB) with a cutting groove, enabling the shape of the test piece body to be a cuboid, prefabricating a cutting groove with the height of a in the middle cross section of the body, extending towards the thickness direction of the body, and penetrating through the front and rear end faces in the body thickness direction; wherein the length L of the test piece body is twice the width W of the test piece body, and the thickness B is not less than 0.8 W. Based on the NDB sample, the invention provides a method for carrying out rock purity type I, rock purity type II and rock purity type I-II composite fracture toughness testing by using asymmetric three-point bending loading, and application of tension and shear load is realized through asymmetric loading.The NDB sample used in the invention has a simple structure and is easy to process by using rock blocks. A clamp used for loading is a common three-point bending clamp, only asymmetric arrangement ofthe supports is needed, experiment loading is quite convenient, and the pure I type, the pure II type and the I-II-type composite fracture toughness of the whole composite loading interval can be achieved.

The invention relates to an experimental device for testing fracture toughness of rocks under a pore pressure condition. The experimental device comprises a testing machine, a confining pressure cavity and a clamping clamp. The testing machine comprises a testing machine rigid frame, a rigid frame pressing head, a trolley, a sliding rail, a hydraulic shaft and a hydraulic cylinder; the confining pressure cavity comprises a confining pressure barrel pressing head, a confining pressure barrel, a confining pressure barrel base and a positioning rod; the clamping clamp comprises a clamping base, a stand column, a supporting plate, a supporting roller, a pore pressure end socket, a compaction part, an upper cover plate, a clamp pressing head, an upper ring, a fixed bolt, a probe and a lower plate. The experimental device is simple in structure, convenient to operate and high in practicability, can be used for carrying out a fracture toughness test on rock materials and artificial materials under confining pressure-containing, high-temperature and pore pressure-containing conditions; an obtained result is more accurate, and accurate fracture toughness parameters are provided for calculation of hydraulic fracture models of oilfields and research institutes.

The invention discloses a method for estimating plane-strain fracture toughness of a metal material, and belongs to the technical field of fracture toughness of metal materials. The method comprises three steps: performing a fracture toughness experiment on a small sample to obtain an experimental value Kq, performing linear fitting on Kq2B and specimen thickness B and performing accurate calculation through straight line slope to obtain KIC. According to the method, the plane-strain fracture toughness of the material can be measured simply and effectively, so that the experiment cost is greatly reduced; in addition, as the KIC of materials (such as amorphous alloys or nano-metal materials) cannot be measured due to a preparation process or relatively high toughness of the materials, accurate parameters can be provided through the method, so that a strong basis is provided for material selection, and particularly, a theoretical basis is provided for the damage tolerance design of a component of the aviation manufacturing industry.

The invention discloses a sample component and method for a nuclear power plant reactor pressure container irradiation inspection test. The component comprises a tensile sample, an impact sample and a compact tensile sample, wherein the tensile sample is used for acquiring the tensile strength, the yield strength, the elongation and the cross section reduction ratio of irradiated materials, the impact sample is used for acquiring impact toughness of the irradiated materials, the compact tensile sample is used for acquiring fracture toughness of the irradiated materials and provided with notches, circular portions and side grooves which are sequentially formed in a first side face and a second side face from top to bottom, and the notch with an isosceles trapezoidal section, the circular portions and the notch with a V-shaped bottom jointly form an extensometer placement space. The method includes the steps of sample preparation, sample loading, sample testing and result evaluation. Arrangement of a bent sample is canceled, the quantity proportion of the other samples is optimized, the shape of the compact tensile sample is optimally improved, and test failure risks in fracture toughness testing are decreased.

The invention belongs to the technical field of fracture toughness test and provides a method for calculating fracture toughness through an indentation method. The method comprises the following steps: 1) obtaining relationship between depth and load during material pressing-in and unloading stages; 2) obtaining plastic residual depth and contact depth state parameters according to a load-displacement curve during material unloading; 3) predicting a radial displacement correction factor and a Berkovich pressing head non-axisymmetric correction factor of the material under the function of a pressing head by utilizing finite element software; 4) carrying out material uniaxial tension experiment to obtain material elasticity modulus, and obtaining critical hole rate of the material based on the GTN theory with the help of the finite element software; and 5) associating indentation work with fracture energy and carrying out equivalence with strain energy density to obtain a fracture toughness equation characterized by the critical plastic residual depth. The fracture toughness test method can quickly obtain the elastic modulus and the fracture toughness value of the material at low loss through a small-range indentation experiment of the material.

The invention relates to a prediction method for a mixed type delamination resistance curve of a composite. The prediction method comprises the following steps: (1) designing and manufacturing a carbon fiber reinforced composite laminate sample; (2) respectively carrying out an I type delamination experiment, an II type delamination experiment and an I/II mixed type delamination experiment by adopting a double cantilever beam, an end part notch bending device and a mixed mode bending device; (3) determining an I type delamination resistance curve, an II type delamination resistance curve and an I/II mixed type delamination resistance curve of the sample; (4) fitting data by adopting a delamination resistance curve theoretical formula, and determining fracture toughness initial values and stable values as well as fiber bridging lengths of different delamination experiments; (5) respectively fitting the fracture toughness initial values and stable values at different mixing ratios by adopting a B-K criterion, so that criterion coefficients etainit and etaprop are obtained; and (6) establishing a mixed type delamination resistance curve prediction formula with a loading mixing ratio as an independent variable. The prediction method provided by the invention predicts a delamination resistance curve at any other mixing ratio by virtue of delamination fracture toughness testing on acarbon fiber reinforced composite laminate at a specific mixing ratio, is convenient for engineering application and can reduce experimental cost.

The invention discloses a device and test method for testing circumferential fracture toughness of a thin-wall pipe. The device comprises a disc-shaped clamping device, two connecting devices and fixing pins for fixing the clamping device and the connecting devices; the clamping device is divided into two semicircular slices with different sizes, and fixing holes are formed in both of the semicircular slices; each connecting device comprises a connecting handle and a Pi-shaped connector, the connecting handle is fixed with the center of a cross beam of the connector, and pin holes are formed in both of two side walls of the connector. The method comprises the following steps of: (i) measuring the size of the thin-wall pipe; (ii) mounting the device; (iii) prefabricating cracks;(iv) testing the circumferential fracture toughness; and (v) calculating the circumferential fracture toughness. According to the invention, annular specimen cracks are prefabricated without loss, the fracture toughness is tested through a simple tension test to avoid specimen defects brought about in a specimen bending process, and the circumferential fracture toughness of the thin-wall metal pipe can be accurately and directly tested.

The invention belongs to the fields of preparation and mechanical properties of carbon fiber/resin-based laminated composite materials, and relates to a method for toughening composite interlayers byusing multiwalled carbon nanotubes (MWCNTs). The method comprises the steps that the multiwalled carbon nanotubes low in cost are used as a toughening material for the composite prepreg interlayers, after cutting of prepreg is completed, the multiwalled carbon nanotubes are quantitatively put into acetone or ethyl alcohol liquid in proportion, fully dispersed through ultrasonic waves and uniformlysprayed to the surface of each layer of the prepreg by using an air pressure gun, after the acetone or the ethyl alcohol is completely volatilized, the prepreg is laid and then fed into a hot-press tank for heating and pressurizing solidification, and finally, the prepreg is cut into DCB and ENF standard samples for I and II fracture toughness testing. The testing results show that when the spraying surface density is 1 g/m<2>, GIC and GIIC of the material are remarkably improved, the interlayer toughness of a composite laminated structure is improved, and the deficiency of the interlayer performance of the laminated composite material is made up for.

The invention relates to the field of materials, in particular to the filed of new methods for testing mechanical property slight damages of service materials, weld materials and new materials, in particular to a method for obtaining fracture toughness of a material by repeatedly loading and unloading a spherical indenter and pressing-in. The method comprises the steps of: using a spherical indenter of hard material, conducting press-in test on the surface of a smoothed tested material through a method of N times of repeatedly loading and unloading to obtain a continuous indentation load P-indentation depth h curve of the tested material, and then acquiring the fracture toughness of the material through application of the method. The method overcomes the deficiencies that an existing spherical indenter press-in test technology requires an extra destructive uniaxial tensile test or relies on certain materials, and the test method is simple, convenient, and accurate, has good universality, and is beneficial to the popularity and application of the spherical indenter press-in test technology. The method for obtaining the fracture toughness of the material by repeatedly loading and unloading the spherical indenter and pressing-in is suitable for occasions that sampling is difficult to perform according to requirements of a conventional fracture toughness test, especially for the deterioration of material properties of bridges, ships, and the like, and the need to discuss the difference of fracture toughness of local materials.

The invention discloses a method for determining the facture toughness and the tensile strength of a brittle material through a two-point loading test piece. The method comprises the following steps: preparing a test piece, cutting a crack, performing two-point static force loading, recording peak load, calculating nominal strength sigma n, calculating an equivalent crack length ae, and the like; finally, performing regression analysis and simultaneously obtaining the tensile strength ft and the fracture toughness KIC of the brittle material. The method disclosed by the invention is simple in form; the test is easy to operate; the accuracy is enough; the result reasonability is easy to judge. The facture toughness KIC and the tensile strength ft of the brittle material can be determined at the same time by the peak load of a small-sized two-point loaded test piece which is loaded at two points.

The invention discloses a method for determining fracture toughness and strength by using double-cut small-sized specimens. The method comprises the following steps: pouring the specimens, cutting out cracks, loading a static force, recording the peak loads, calculating the nominal strengths sigman, calculating geometric parameters A of the specimens, and finally performing regression analysis to obtain the fracture toughness K and the tensile strength f of a material without a size effect. Based on an idea of progressive extrapolation as well as theoretical analysis in elastoplastic fracture mechanics, material parameters of infinitely large slab specimens (the material parameters of the infinitely large slabs have no size effect) are extrapolated from experimental data of finite-size specimens, so that the fracture toughness and the strength of the material without the size effect can be determined only according to the key loads F of the small-sized specimens; strict current domestic and foreign specifications on the sizes and the types of the specimens, loading conditions and the like are not required to be met, and the stability of the double-sided tensile specimens is better than that of the single-sided tensile specimens, so that operation is easier.

The invention discloses a DCB (double-cantilever beam) fracture toughness testing device. The device comprises a mechanical transmission system, an electronic collection system and a data terminal processing system, wherein the electronic collection system is connected with the mechanical transmission system and the data terminal processing system; the mechanical transmission system comprises a sample clamping component, a tension transmission mechanism and a pressure transmission mechanism; the electronic collection system comprises a potential data collection card, an LVDT (linear variable differential transformer) displacement sensor, a pressure sensor and a tension sensor; the data terminal processing system is used for processing, filtering and sampling the collected data. The DCB fracture toughness testing device is simple, easy to understand and convenient to operate, a test result is accurate, data such as extension speed, cracking displacement, extension length and the like ofa type I fracture can be recorded and measured effectively, and a method foundation is provided for design research of rock fracture toughness.

The invention provides a slotting cutter, equipment and a slotting method for testing fracture toughness of a graphite material. The slotting cutter for testing the fracture toughness of the graphitematerial is included. The slotting cutter for testing the fracture toughness of the graphite material comprises a cutter handle and a blade. The cutter handle is coaxially connected with a main shaftof a numerical control machine tool, and the blade rotates to perform numerical control slotting on a graphite material sample clamped and fixed by a fixture on a worktable instead of manual slotting,the influence of manual slotting on the accuracy of the test results is avoided, the technical problem of inaccuracy, caused by manual slotting, of graphite material fracture toughness testing is solved, the consistency of graphite sample material slotting is ensured, and the testing accuracy of the graphite material sample during fracture toughness testing is improved; and besides the numericalcontrol machine tool drives the specific slotting cutter to perform full-automatic slotting on the graphite material sample, the slotting speed and efficiency of the slotting cutter are far higher than the speed of manual slotting, and the testing efficiency is improved.

The invention provides a fracture toughness testing device under a low temperature high pressure hydrogen charged environment. The device comprises a sealed box body and a tensile device. The tensiledevice is set on the sealed box body. The device also comprises a refrigeration assembly, a liquid pressurization assembly, an electrochemical assembly, a detection assembly and an industrial personalcomputer. The liquid pressurization assembly is used for supplying a high pressure electrolyte solution to the interior of the sealed box body. The refrigeration assembly is used for cooling the electrolyte solution. The electrochemical assembly is used for generating hydrogen on a surface of a tensile test sample. The detection assembly is used for detecting a pressure and a temperature in the sealed box body and an opening crack state of the tensile test sample. The industrial personal computer is used for controlling the refrigeration assembly, the liquid pressurization assembly, the electrochemical assembly and the tensile device through collection and analysis of information of the detection assembly. The device is used for testing fracture toughness under a low temperature high pressure hydrogen rich environment. A relatively systematical and complete testing scheme is formed. A low temperature high pressure hydrogen rich deep sea environment is effectively simulated. Reliability of final testing data is improved.