Degree Of Stress Concentration Research Articles

Grain boundary deformation in uniaxial strained Nb3Sn

We generated a three-dimensional stress map of grains and grain boundaries in uniaxial strained Nb3Sn composite, using a scale-coupled model generated by the polycrystalline finite element method and based on the linear elastic theory of closely packed fiber-reinforced composites. The model takes into account the transfer of stress from a Cu-Sn matrix to a single Nb3Sn filament composed of inner elongated and outer equiaxed grains. Due to differences in grain morphology and orientation, stress inhomogeneity arises first in the filament. The interconnected grain boundary networks in Nb3Sn constrain grain deformation by fostering stress concentration at intersections between multiple grains. The degree of stress concentration can be as high as 2.08. Our model simulations show a random distribution of grain boundary orientations within stress concentration zones and provide detailed information on how and where stress inhomogeneity is likely to produce crack initiation in Nb3Sn.

Coal and Gas Outburst Affected by Law of Small Fault Instability during Working Face Advance

To analyze the effect of small faults in the working face on coal and gas outbursts, the coal and gas outburst accident in the 21431 working face was studied with the 3DEC numerical simulation method, and the main research contents were the change laws of both stresses at the small fault and the overburden strata movement rate in the small fault zone of which the drop height and the strike were designed into different groups. The results show that the risk of small fault slip increases with the advancing working face. In addition, there is a positive correlation between the risk and the small fault throw. The movement rate of overburden strata in the small fault zone increases along with the rising of the small fault throw, which increases the energy transferred to the coal seam from the surrounding rock under the effect of the small fault. Hence, the effect of small faults on the working face on coal and gas outbursts was positively correlated with the small fault throw. Under the influence of a small fault strike, the closer it is to the small fault along the dip distance at the same working face, the greater the risk will be of a coal and gas outburst. And the bigger the small fault strike is, the greater is the stress concentration degree in front of the working face and the more the elastic energy is stored and the greater is the possibility of an outburst. The paper analyzes the influence of small faults on coal and gas outbursts in the working face, which has reference significance for the prediction and prevention of coal and gas outburst disaster in the working face.

Use of the Equivalent Mining Height Method for Understanding Overlying Strata Movement and Stress Distribution in an Isolated Coal Pillar

In order to study the changing rules of displacement filed and stress field of overlying strata on isolated pillar with filling mining method, a self-designed model of isolated pillar with an equivalent mining height and a monitoring system of stress is employed to study the progressive failure of overlying strata and the changing rules of induced displacement and stress, as the equivalent mining height increases. The findings from the trial tests show the following: (1) When the equivalent mining height is small, the overlying strata on the isolated coal pillar only bend and subside, but the overlying strata located on the goafs of two sides remain stable. (2) As the equivalent mining height increases, the degree of stress concentration on section coal pillar will rise and produce plastic failure in the first place near large caving goaf. The strata can subside between isolated working face and adjacent large caving goaf. (3) As the equivalent mining height increases further, new cracks in the roof of isolated working face will unite the cracks of carving goaf on two sides in horizontal direction, leading to a significant rise of the height of cracks. Three goafs will evolve into a large carving goaf, and the vertical cracks on the outer side of the carving goaf intersect with one another to form “fracture band”. The research acquires the key points for prevention in mining the isolated coal pillar with filling method and provides guidelines to implement this technique and to prevent rock burst.

Overall Design and Optimization of Mining Sequence in High-Stress Environment of Thick Orebody

After entering deep mining, the stress concentration level because of engineering excavation is considerably greater than the strength of the engineering rock mass. Here, we consider the engineering impact of a high stress environment in the deep mine plan, integrate the high-stress environment and its evolution with the mining process into the mining plan, and realize the balance of improving the stress state and getting the maximum net present value. Using Map3d boundary element simulation software, we planned two vertical and four horizontal mining sequences for deep and thick orebody backfill mining, respectively, and then analyzed the changes in stress and rock mass energy because of mining disturbance. The results show that the surrounding mining sequence can effectively improve the mining stress environment and increase production capacity. Using large-spaced dispersion and mining sequence from the middle to both ends can gradually redistribute the stress to adjacent areas, thus reducing the degree of stress concentration.

Study on the Crack Growth Law and Mechanism of the Rock Mass with Defect Combination

There are different defect combinations in natural rock mass. In the process of underground engineering excavation, the existence of defect combination poses a serious threat to the construction safety. In this paper, the uniaxial compression test of red sandstone with prefabricated defects combination angles of 15°, 30°, 45°, 60° and 90° was conducted by Shimadzu universal testing machine respectively, and the crack propagation law and mechanism of red sandstone with different defects are studied, The test results showed that the red sandstone with different angle defects only produced tensile cracks, there had not shear cracks, and finally resulted in tensile failure. This was due to the existence of defects combination which weakened the local stress concentration and releases part of energy in advance. With the increasing of the defect combination angle, the weakening degree of stress concentration increased, and the uniaxial compressive strength of the specimen decreased as a whole, and with 45° as the boundary. There was an obvious strength area division, and the failure time of the specimen was obviously prolonged, furthermore, the brittle failure characteristics of specimens are obviously weakened. The test results have important guiding significance and reference value for the construction design in the field of underground engineering.

Tool path selection for high-speed ball-end milling process of hardened AISI D2 steel based on fatigue resistance

This paper aims at revealing how tool paths influence the fatigue resistance of high-speed ball-end hard milled surfaces and proposing corresponding tool path selection methods. Three kinds of tool paths (tool paths A, B, and C with angles relative to the length direction of cuboid workpiece 0°, 90°, and 45°, respectively) were utilized during high-speed milling process of hardened AISI D2 steel. The fatigue resistance of samples for different tool paths was evaluated through three-point bending fatigue tests. Results shows that tool paths have significant effect on fatigue resistance, and the maximum discrepancy in fatigue life can reach about 37.6% for different tool paths. Samples for tool path C shows the longest fatigue life when radial depth of cut ae = 0.1 mm. However, with the further increase of ae, samples for tool path A have the best fatigue resistance, followed by tool path C and B. Microscopic stress concentration and effective residual stress are the main ways by which tool paths influence the fatigue resistance. Changing tool paths leads to the difference in surface topography orientation and then in degree of microscopic stress concentration. Moreover, the effective residual stress (residual stress component in direction parallel to cyclic tensile stress) is also directly determined by tool paths. Tool path selection methods are put forward based on the aforementioned influence mechanisms. This study indicates that improving the fatigue resistance of high-speed ball-end hard milled surfaces suffering given cyclic tensile stress is feasible by choosing appropriate tool paths.

Finite element analysis of different diameter prosthesis ball head in artificial femoral head replacement

In order to select the proper size of prosthesis ball head, the biomechanical changes of hip joint using different diameter prosthesis ball head was studied by three-dimensional finite element analysis. The thin-layer CT data and related parameters of artificial femoral head prosthesis were used to establish the finite element model of hip joint after artificial femoral head replacement with different ball diameter of prosthesis(M0:preoperative model;M1:ball head diameter=original femoral head diameter;M2:ball head diameter=original femoral head diameter+1 mm;M3:Ball head diameter= Original femoral head diameter -1 mm;M4:ball head diameter =original femoral head diameter -2 mm). Loading the joint forces and related muscle loads were loaded, and the stress distribution and change of bone and cartilage around acetabulum were analyzed by simulating the standing state of one foot when walking slowly. (1) In M1 to M4, the stress concentration in pelvis was different. The peak value of Von Mises stress in the pelvis of M3 was 44.8 MPa, which was the closest to that before operation, with an increment of 13.4%. The displacement of the pelvis of M3 was the smallest in the four groups after operation, with an increment of 1.40 mm. The next was M1, with a peak value of 47.3 MPa, with an increment of 19.7%, and a pelvic displacement of 1.59 mm. (2) In acetabulum area, the peak value of Von Mises stress in M3 was 23.3 MPa, which was the closest to that before operation, with an increment of about 6.3%, followed by M1, with a peak value of 24.0 MPa and an increment of about 8.1%. (3) On the acetabulum cartilage, the stress distribution of M1 and M3 was similar to that before operation, and the peak value of Von Mises stress of M3 was 18.5 MPa, which was the closest to that before operation, followed by M1, which was 22.5 MPa. (4) M1 to M4 showed different degree of stress concentration in the outer upper quadrant of the artificial femoral head, but showed stress shielding under it;among them, the von Mises stress distribution of M3 was more uniform than that of other models, and its peak value (70.8 MPa) was the lowest in each group, followed by M1 (80.7 MPa). When femoral head replacement is performed, it is suggested that the prosthesis ball head with the diameter less than 1 mm and the prosthesis ball head with the same diameter as the original femoral head should be used first, so as to obtain the closest natural mechanical characteristics of the hip joint before the replacement and reduce the risk of complications caused by size differences.

Analysis of Failure of a Chassis Long Member Manufactured from E-46 Grade Hot-Rolled Steel Coil

In the present study, failure investigation was performed to find the root cause of the defects that occurred during bending operation for fabrication of a long chassis member. The component was manufactured from E-46 grade hot-rolled coil with ferrite–pearlite microstructure. Several longitudinal cracks were formed on one side of the outer bends of the long member. Detailed microstructural examination revealed occurrence of long unidirectional unbranched cracks with deposits and intermittent stringers of nonmetallic entrapments in the rolling direction. EDS analyses showed majority of these deposits and entrapments were FeO-rich manganese silicate associated with silicomanganese and ferromanganese alloy added to the molten steel for chemistry adjustment. Bending operation of the coil perpendicular to the rolling direction of steel sheet and orientation of the entrapments as well to cold form the chassis long member resulted in high degree of stress concentration around the entrapments. Finally, localized tearing of the outer surface layer of the bend at multiple locations occurred.

Stress concentration analysis of butt welds with variable wall thickness of spanning pipelines caused by additional loads

In the field of oil and natural gas gathering and transportation, the pipeline is likely to be span under the geological load. With the influence of gravity, internal pressure and other additional loads the stress concentration at the variable wall thickness weld on the spanning pipeline would further threaten the safe operation of pipelines. In this paper, finite element method is used to establish the numerical model of variable wall thickness butt weld of free spanning pipelines. The SCF(Stress Concentration Factor) is used to reflect the stress concentration degree of the weld with variable wall thickness under the affect of additional stress, and the stress distribution of variable wall thickness welds is studied. The influence of spanning pipe length, welding positions, internal pressure, thickness ratios and conical surface lengths on the SCF of the spanning pipe are obtained. The results illustrate that under the action of additional stress the existence of variable wall thickness weld has a great influence on the welding root at the bottom of the pipeline, which is not conducive to the stress of the spanning pipeline. The change of pipe spanning length has great influence on the SCF at the weld root at the bottom of the pipe. As the length of the spanning increases, the SCF growth rate at the root of the weld is greater. The position of variable wall thickness weld has a certain impact on the SCF of spanning pipeline. As the variable wall thickness weld is close to the mid-span position of pipeline, the stress concentration part of the weld gradually transfers from the top of the pipe to the bottom of the pipe. The change of pipeline internal pressure has little influence on SCF. The wall thickness ratio and the conical surface length have a great influence on the pipeline, which is the main influencing factor of the stress concentration of the spanning pipeline. Reducing the wall thickness ratio or increasing the conical surface length can effectively reduce the stress concentration of the variable wall thickness weld.

Measurement and application of vibration signals during pressure relief hole construction using microseismic system

Pressure relief drilling (PRD) is a frequently-used measure in underground coal mine to control and prevent rock burst, which achieved the purpose of pressure relief by constructing PRD holes at the side of roadway. But up to now PRD is only used to achieve the pressure relief purpose, the important indicative information occurred in the process of drilling construction are all ignored. This paper innovatively put forward a new measurement method for monitoring-while-drilling (MWD) by arranging microseismic (MS) system beside the PRD hole, the MS system pick up vibration signals during PRD hole construction process and achieved excellent application results. The monitoring data can express the depth of PRD hole, identify and record drilling dynamic phenomena such as sticking drilling and vibration events, reflect the stress concentration degree in different depths, and evaluate pressure relief effect of PRD. The measurement method makes full use of PRD hole construction and achieves the aim of “one hole and multi-purpose”.

Fatigue behavior improvements of laser-induction hybrid welded S690QL steel plates

In this paper, the improvements of fatigue performances of S690QL steel welded by laser-induction hybrid welding (LIHW) method were performed, mainly through the infrared imaging device to obtain the weld thermal cycle, fatigue machine to test the fatigue strength and scanning electron microscope to observe the fracture morphology. In fatigue tests, tension-tension fatigue loading and stress ratio R = 0.1 was selected. The LIHW fitted S-N curves were derived. It was found that the cracks with symmetrical grooves were initiated at the weld center (WC), while the single-laser welding (SLW) fatigue samples were fractured at the WC. However, the LIHW samples were finally fractured near heat-affected zone (HAZ). The fracture morphology of fatigue samples with stress amplitude of 108 MPa and 144 MPa were further selected to analysis. Due to different degree of defects or stress concentration, and different welding heat input absorption ability and cooling rate, in sudden fracture region, SLW fatigue samples mainly contained the brittle transient failure mode, LIHW fatigue samples mainly showed a ductile failure mode. It can thus be concluded that the LIHW method could improve the fatigue performance of S690QL steel joints.

Evaluation of stress concentration degree of ferromagnetic steels based on residual magnetic field measurements

The aim of this research is to correlate the residual magnetic field (RMF) with the stress concentration degree of ferromagnetic steel subjected to tensile stress. Specimens of X80 pipeline steel were machined into smooth plates with circular holes and rectangular holes for various stress concentration factors. Variations of the tangential component and the normal component of the RMF signals with the applied tensile load were studied. Relationships of the maximum gradient Kmax of the RMF components with the applied tensile load and the stress concentration factor were investigated, respectively. Magnetic parameter β based on the maximum gradient Kmax was introduced to characterize the stress concentration degree. The magnetic parameter β shows significant advantages compared with the maximum gradient Kmax when characterizing the stress concentration degree. Correlations of its average value βm with the stress concentration factor and the defect area were both studied. This research will greatly promote the development of quantitative evaluation method of the stress concentration degree using the metal magnetic memory (MMM) testing.

Stress Analysis of Surrounding Rock of Rectangular Pipe Gallery in Mountain City

In this paper, the basic methods and principles of complex variable function to solve the excavation problem of caverns in single connected domain are studied. Based on the basic principle of conformal transformation and the engineering practicability, the problem of excavating rectangular section single warehouse pipe gallery in a single rock stratum is simplified as a semi-infinite plane rectangular hole problem. The rectangular hole problem is transformed into an equivalent circular hole by conformal transformation. A simplified calculation model of the extruding rectangle comprehensive pipe gallery is proposed and its surrounding rock stress calculation formula is deduced. Combined with the example of mountainous city comprehensive pipe gallery project, Theoretical calculation and numerical simulation show that the surrounding rock stress of the comprehensive pipe gallery is close, which verifies the applicability of the simplified formula. The structural design and construction design of rectangular integrated pipe gallery provide theoretical support. Comparing the stress of surrounding rock of different width pipe gallery, it is found that the stress concentration degree at the top corner of the rectangular pipe gallery increases with the increase of the width of the pipe gallery. The width of the excavation of the rectangular pipe gallery must be strictly controlled during construction.

Influence of amygdale on crack evolution and failure behavior of basalt

Amygdaloidal basalt is one of the two major types of surrounding rocks that are widely exposed in the super large-scale underground powerhouse caverns of Baihetan Hydropower Station, China. Excavation of the caverns induced a series of mechanical responses, including cracking and fracture relaxation. This study comprehensively explored the deformation and failure characteristics and the fracture evolution process of the amygdaloidal basalt using conventional MTS triaxial laboratory testing equipment and continuous–discontinuous modeling (FDEM) with the aim of clarifying its failure mechanism. The research results indicate that: (1) amygdales significantly changed the deformation and failure characteristics of basalt. Whereas the post-peak mechanical behavior of cryptocrystalline basalt was brittle, that of amygdaloidal basalt was brittle under low confining stresses and ductile under high confining stresses. Meanwhile, whereas the failure mode of cryptocrystalline basalt was fragmentation failure, that of amygdaloidal basalt was splitting failure at low confining stresses and shear failure at high confining stresses. (2) An FDEM model considering the heterogeneity of the rock mesostructure was established based on the statistical laws of the amygdales in real samples, and this confirmed the stress–strain curve characteristics, failure modes, and characteristic strengths measured in laboratory tests. (3) A complicated inhomogeneous stress field formed readily around amygdales and had a significant effect on the fracture path. (4) With an increase in confining stresses, the degree of tensile stress concentration at the upper and lower tips of amygdales decreased and the lateral displacement became restricted. Consequently, the total number of micro-cracks and the ratio of tensile cracks to shear cracks decreased, the crack initiation mode changed from tensional cracking to shear cracking at the tips of the amygdale, and the distribution of crack orientations transitioned from an approximately vertical direction to preferential concentration along fracture planes. The research results form a solid foundation for the accurate understanding of the mechanical response and fracture mechanism of the rock surrounding underground powerhouse caverns at Baihetan hydropower station, and also provide a reference for the prediction of the mechanical properties of rock with flaws and the stability control of engineering rockmasses.

Study on the Relationship between Stress and Charge of Coal Mass under Uniaxial Compression

This paper presents a new method to identify the stress concentration degree and stress distribution characteristics in front of working face in coal mine, based on the close relationship between charge and stress during fracture of coal mass. This method overcomes many disadvantages of conventional stress-monitored methods. First, the stress and charge relationship of coal mass was established through damage theory and statistical strength theory. Then, the relationship between stress and charge was studied by a laboratory test, and finally, the field charge monitoring test was performed. The results show that there is a nonlinear relationship between loading stress (σ) and cumulative charge (Q), which can be represented by polynomials. The fitting results of the laboratory test between σ and Q conform to a cubic polynomial function, Q=aσ3+bσ2+cσ+d. It verifies the rationality of the theoretical relationship formula. The field monitoring results show that average charge is great and cumulative charge changes from rapid upward to sharp upward before roof falling. The magnitude and position of average charge and the upward trend of cumulative charge can be used to identify the stress concentration and stress distribution in front of working face, and the abnormal stress area can be predicted. The results can provide certain guidance for the forecast of rock burst in coal mine.

Study on Flow Field and Rotor Safety Characteristics of MSPs Based on Flow Thermo-Coupling

In order to obtain the structural intensity under the operation conditions of MSP (molten salt pump), the rotor component of MSP is taken as the research object. In this paper, the influence of material properties change on the structural performance of MSP at different temperatures is analyzed. The stress distribution and strain distribution of MSP rotor components under different loads are investigated, and the intensity calculation of MSP rotor system is carried out to explore whether it meets the intensity requirements under high temperature operation, which lays a foundation for the high temperature test of MSP. The results show that the maximum deformation position of the blade working face appears at the outer edge of the impeller. When the fluid-structure coupling is applied, the blade strain law and the strain law during thermo-coupling are similar. The effect of the temperature field on the degree of blade deformation is not significant, provided that other factors remain the same. The position where the impeller equivalent stress is the largest is mainly concentrated in the area where the blade is in contact with the front and rear cover plates at the outlet of the impeller. Different degrees of stress concentration occur in the area where the blade is in contact with the impeller hub. The distribution law of the equivalent stress on the surface of the impeller cover plate is that the equivalent stress value changes periodically along the circumferential direction of the impeller, and the number of change cycles is equal to the number of impeller blades. This study can provide a reference for the structural design of MSPs.

Inhibition of CACNA1H attenuates doxorubicin-induced acute cardiotoxicity by affecting endoplasmic reticulum stress

BackgroundDoxorubicin (DOX) is an anticancer drug that has been widely used in the clinic. However, recently its application has been limited due to the cardiotoxic effects it has caused. Severe cardiotoxicity of DOX causes cardiac hypertrophy that may lead to heart failure. It has previously been demonstrated that CACNA1H is re-expressed in hypertrophic cardiomyocytes. In this study, we aimed to investigate the role of CACNA1H in DOX-induced acute cardiotoxicity, and to investigate its possible underlying mechanisms of action involved. MethodsFirstly, DOX-induced cardiac injury and changes in the expression of CACNA1H were evaluated. We explored the role of endoplasmic reticulum (ER) stress and apoptosis in mice that underwent DOX-induced cardiac injury. Next, to explore the role of CACNA1H in this process, we evaluated the changes in DOX-induced cardiac injury and ER stress after treatment with the CACNA1H specific inhibitor ABT-639. Next, we used ER stress inhibitor UR906 to verify the role of ER stress in DOX induced cardiotoxicity in H9C2 cells. ResultsDOX-treatment caused acute heart injury, leading to a decrease in cardiac function in mice, an increase in apoptosis of cardiac myocytes, and a significant increase in the expression level of CACNA1H in heart tissue. Next, mice were treated with CACNA1H inhibitor ABT-639 and we demonstrated that it partly protects myocardial function and reduces myocardial cell apoptosis. In addition, our data indicated that CACNA1H may play a role in alleviating DOX-induced cardiotoxicity by reducing the severity of ER stress because the use of ABT-639 significantly changed ER stress-related proteins, including p-PERK, PERK, CHOP, GRP78, ATF6, and ATF4. Furthermore, we found that the use of ER stress inhibitor UR906 in H9C2 cells significantly alleviated the increased expression of ER stress related proteins and apoptosis related proteins caused by DOX, and meanwhile reduced the degree of intracellular oxidative stress and intracellular calcium ion concentration. ConclusionCACNA1H inhibitors significantly alleviated DOX-induced cardiotoxicity and apoptosis induced by ER stress.

Waste rock filling in fully mechanized coal mining for goaf-side entry retaining in thin coal seam

A large amount of waste rock is generated during thin seam coal mining operations underground. The waste rock material stacked on surface also adds to the environmental pollution. So it is important to reduce the amount of waste rock by exploring gainful utilization methods. This paper deals with an investigation undertaken to develop an alternate gob filling material in laboratory and evaluating its efficiency numerically as well as in field. A coal–waste rock separation system and a roadway layout system were designed, and a new technique of fully-mechanized goaf-side entry retaining and goaf filling back hydraulic supports was proposed. These methods helped realize the goal of green mining, which was featured by waste rock consumption in nearby region without any need to be elevated to ground surface. This study demonstrated that the two proposed mining methods, namely, caving mining method and mining with filling method, differed in mechanical environments where roadside filling body was located, deformation, and failure scope. The maximum principal stress concentration degree near the roadside filling body for caving mining method was high with a maximum value of 42.5 MPa because of key rock blocks in overburden. As a result, the surrounding rock of roadside filling body was severely deformed with a maximum displacement of 1117 mm. The entire roadside filling body moved toward the inside roadway and experienced plastic failure. After goaf filling, filling bodies in goaf, roof and floor strata, and roadside were combined to form an entire withstanding deformation. The motion space of overburden rock was limited, the adjustment range of surrounding rock stress near the roadside filling body was narrowed, the maximum principal stress decreased to 29.5 MPa, and the main roof did not rupture. Accordingly, the deformation of surrounding rocks of the roadside filling body was small, the maximum displacement of roof and floor was 457 mm, and the roadside filling body did not experience plastic failure. The study results enrich goaf-side entry retaining theory in thin coal seam and mechanized filling technology and provide a theoretical foundation for thin coal seam mining with difficulty in waste rock treatment.

Evaluation of stress concentration of U‐shaped notch based on residual magnetic field measurements

AbstractIn this research, the correlation between the stress concentration and the residual magnetic field (RMF) of 30Cr steel was investigated. Tensile tests were carried out to measure the RMF signals on the surface of U‐shaped defect specimens. It was found that the tangential RMF signal at the defect area is correlated to the applied load and the stress concentration factor. A new method based on magnetic field to evaluate the stress concentration degree is proposed. This research provides a potential possibility for quantitative inspection of the stress concentration in ferromagnetic steels using the RMF measurements.

Metal Magnetic Memory Inspection of Q345 Steel Specimens with Butt Weld in Tensile and Bending Test

Metal magnetic memory (MMM) method is a non-destructive testing method based on the analysis of self-magnetic-leakage field (SMLF) distribution on components’ surfaces. The MMM method can determine stress concentration zones, imperfections, and heterogeneity in the microstructure of the material and in welded joints. In order to study the magnetization of defective and non-defective butt welded Q345 steel specimens under tensile and bending loads, the normal component of the SMLF (Hp(y)) field values were measured. The results demonstrate that Hp(y) field values and gradients are effective in capturing different stress states under tensile and bending loads. The distribution of Hp(y) field values for flexural tests are quite different from that of tensile tests. The gradient values can be used to determine the degree of stress concentration. In addition, three characteristic parameters were calculated. All three parameters can predict failures with early warnings. Specifically, whether the specimen is in tensile stress state or in compressive stress state can be distinguished by the average value of Hp(y) field area. The quality of the butt weld can be judged by the magnetic index (m). The judging criteria can be a significant complement to the inspection of welded joints using MMM method. Further research could help to validate the judging criteria and analyse the factors affecting the accuracy of the predictions.