Chamfer Angle Research Articles

Determination of the total resistance of the ploughshare when the blade is blunted

The article notes that when plowing, the traction resistance of a ploughshare with an occipital chamfer increases in proportion to the volume of compacted soil. When working, the traction resistance of the ploughshare with the occipital chamfer increases in proportion to the volume of the compacted soil. It was revealed that with an increase in the angle of the occipital chamfer of 5 to 40 degrees, the traction resistance increases 11.3 times, Whereas with an increase in the width of the occipital chamfer from 0.5 mm to 4 mm, the traction resistance increases 60...64 times. For the longest operation of the ploughshare, it is necessary to develop such a technical solution for the ploughshare, during the operation of which an occipital chamfer with the largest dimensions, that is, with a minimum area, was formed from the back side. Then the pushing force of the ploughshare from the soil will have a minimum value, which will ensure the operation of the plough for the most maximum time without violating agrotechnical requirements for the depth of processing.

Chip formation, cutting temperature and forces measurements in hard turning of Gcr15 under the influence of PcBN chamfering parameters

Hard turning is a key technology for difficult-to-cut materials with high precision and efficiency. However, the turning of GCr15 hardened steel leads to elevated cutting temperature and forces even at very low cutting parameters. Therefore, cutting parameters, tool geometric parameters, and cooling mediums are generally used to improve the machinability of such hard materials. This research aims to investigate the hard turning of GCr15 by varying the chamfering angle and chamfering width of polycrystalline cubic boron nitride (PCBN) at constant cutting conditions. The workpiece material and PCBN tool parameters were designed and modeled using 2D simulations using DEFORM®. Through simulation analysis and experimental research, the cutting force, cutting temperature, and the development of saw-tooth chips were studied and compared. The results achieved from experiments and simulations are very close with a maximum error of less than 5% for cutting forces and 6.3% for cutting temperatures. It is important to mention that 2D Finite Element Modeling (FEM) of hard turning is effective and efficient to forecast and measure the cutting temperature.

Numerical Prediction of the Performance of Chamfered and Sharp Cutting Tools during Orthogonal Cutting of AISI 1045 Steel

This paper presents a numerical investigation of the effects of chamfered and sharp cemented carbide tools using finite element method-based DEFORM-2D software and cutting parameters on different machining characteristics during the orthogonal cutting of AISI 1045 steel. The objective is to study the interactions between chamfer width, chamfer angle, sharp angle and the cutting speed and feed rate on the cutting temperature, effective stress and wear depth. These effects were investigated statistically using the analysis of variance (ANOVA) test. The obtained numerical results showed that for the chamfer tool, high values of temperature, stress and wear depth were obtained for chamfer widths of 0.35 mm and 0.45 mm. In terms of combined influences, for the cutting temperature and stress, a strong interaction between the cutting speed and chamfer width was obtained. For the sharp tool design, and in terms of temperature, strong interactions are mostly observed between cutting speeds and feed rates. The ANOVA showed that for both chamfer and sharp tools, the feed rate, the cutting speed and their interactions are the most significant parameters that influence temperature and stress.

Evaluation of the performance of very narrow tines with different geometrical structures for tilling natural grassland

Natural grassland is an important ecological barrier in northern China and using mechanised improvement methods to restore degraded natural grassland is significant. This paper aimed to evaluate the working performance of different very narrow tines through full-factorial experiments, and provide basic references for design novel and specialised tillage tools applicable to natural grasslands. The thickness, cutting edge angle, and rake angle were chosen as the independent variables, and related working resistance and soil disturbance indicators were selected as the dependent variables. Different shank-type tines and a test bench were designed and manufactured. Field experiments under different working depths were conducted. The results showed that the thickness, rake angle, and cutting edge angle all had statistically significant influences on the working resistance (P < 0.05), and interaction functions were found between these three factors. The soil overturning rate, soil bulkiness value, and soil disturbance coefficient created by the tines were in the ranges of 0.5–14.5%, 12–40%, and 50–68%, respectively. The tine with the thickness of 14 mm, the rake angle of 45°, and the cutting edge angle of 60° provided the best working performance. The grassland surface disturbance situation, soil overturning rate, disturbed cross-section area, soil bulkiness value, and soil disturbance coefficient well described the disturbance situation. The working depth and geometrical parameters of the tines all had influence on the working resistance and soil disturbance which should be considered together as the evaluation factors of the working performance of special tines for tilling natural grasslands. • Thickness, rake angle, and chamfer angle all significantly affect working resistance. • Soil disturbance coefficient of the grassland produced by shank-type tines is 50–68%. • Shank-type tine with chamfers cause low soil disturbance and small roots' damage. • Having cutting edge or not causes big differences in the soil overturning rate. • Rake angle of 45°, chamfer angle of 60°, thickness of 14 mm are optimum combination.

Study on the Formation Mechanism of Cutting Dead Metal Zone for Turning AISI4340 with Different Chamfering Tools.

Tools with chamfered edges are often used in high speed machining of hard materials because they provide compelling cutting toughness and reduced tool wear. Chamfered tools are also responsible for the dead metal zone (DMZ). Through numerical simulation of orthogonal cutting with AISI 4340 steel, this paper examines the mechanism of the DMZ, the cutting speed, the impacts of the chamfer angle, and the coefficient of friction on the generation of the DMZ. The analysis is based upon the Arbitrary Lagrangian-Eulerian (ALE) finite element method (FEM) for the continuous process of chip formation. The different chamfered angles, cutting speeds, and friction coefficient conditions are utilized in the simulation. The research demonstrates that a zone of trapped material called DMZ has been formed beneath the chamfer and serves as an effective cutting edge of the tool. Additionally, the dead metal zone DMZ becomes smaller while the cutting speed increases or the friction coefficient decreases. The machining forces rise with increasing chamfer angles, rise with increasing friction coefficients, and fall with increasing cutting speed in both the cutting and thrust directions. In this paper, the effect of different chamfering tools on AISI 4340 steel using carbide tools in the simulation environment is studied. It has certain reference significance for studying the formation mechanism of the dead zone of difficult-to-machine materials such as AISI4340 and improving the processing efficiency and workpiece surface quality.

Theoretical and Experimental Study on the Effect of Selected Parameters in a New Method of Extrusion with a Movable Sleeve.

This paper presents a new method for forming hollow flanged products. The method involves extrusion with the use of a sleeve moving in the opposite direction to that of the punch. A tube with a constant hole diameter and two different outside diameters, made of aluminum alloy EN AW 6060 was used as a material. Numerical calculations were performed using Deform 2D/3D. Experiments were conducted on the PYE 160SS hydraulic press equipped with a specially designed device in which the punch is driven by the press slide while the moveable sleeve is driven by two hydraulic servomotors. Both numerical simulations and experiments were conducted under cold forming conditions. The aim of this study was to determine the effect of selected parameters (flange diameter, height of the cavity in the moveable sleeve, and the chamfer angle between the regions with different outside diameters on the workpiece and in the moveable sleeve cavity) on the stability of the extrusion process. Results were then used to undertake detailed comparative analyses of underfill, flange heights, and flange flank inclination angles. Findings of the analyses served as a basis for drawing conclusions regarding the effect of the analyzed parameters on the investigated extrusion process.

Numerical investigation of pentagonal V-shape ribs to enhance heat transfer in hydrogen rocket engine cooling channels

Keeping the combustion chamber walls at a sufficiently low temperature ensures liquid rocket engines' safe and reliable operation. The most promising method to achieve that is the heat transfer enhancement techniques which optimize the heat transfer coefficient and increase the thermo-hydraulic performance. The present work is concerned with numerical studies on the effect of the pentagonal V-shape ribs to enhance the heat transfer coefficient of the rocket engine's cooling channels. Numerical simulations for various chamfering angels of the pentagonal V-shape rib are performed by the (SST,k−ω) turbulent model. The simulation findings show that the overall performance of the ribbed channel improved inversely with the pentagonal chamfering angle. Compared with a conventional channel, the average Nusselt Number and thermal-hydraulic performance of the ribbed channel enhanced up to 66.6% and 52% respectively, and the 5° pentagonal V-shape rib has higher thermal-hydraulic performance with a slight high the pressure loss penalty.

Experimental investigation of cavitating flow around chamfered cylinders vertically inserted in a circular pipe

An experimental investigation was conducted to study the cavitating flow around cylinders with different chamfer angles vertically inserted in a circular pipe. The experiments were performed in a variable-pressure closed-loop cavitation rig at a constant Reynolds number of Re=1.2×105 with cavitation numbers corresponding from inception to supercavitation. In practical hydraulic systems, numerous structures can be modeled as vertically inserted chamfered cylinders and the cavitation phenomenon can occur around such structures with serious side effects. This work is an attempt to understand the cavity dynamics and the influence of the chamfer angle θ on the characteristics of cavitating flows, with the aim of providing guidelines for designing relevant structures. The low- and high-speed images of the cavitating flow in different cavitation regimes were analyzed to investigate the dynamics of the cavitating flow around the cylinder with chamfer angle θ=60°. From the space–time diagram obtained from the high-speed series, it is found that for cavitation number σ>0.80, the shedding of the small vapor filaments is induced by interfacial instabilities; for cavitation number σ<0.75, the re-entrant jet accounts for the periodic shedding of the vapor clouds. In the transition region (0.75<σ<0.80), the shedding is caused by a complex combination of both mechanisms. The dominant shedding frequency, expressed as Strouhal number St, drops with the decrease of the cavitation number σ in the regime dominated by interfacial instabilities; while in re-entrant jet regime, it is almost insensitive to the change of the cavitation number σ. In addition, the influences of the chamfer angle θ on the inception condition, cavity length, pressure drop, and pressure fluctuation are also discussed in the present work. With the increase of θ, the cavitation resistance becomes better and the pressure drop through the test section decreases.

Multi-objective optimization of a bow thruster based on URANS numerical simulations

In this study, a multi-objective design optimization of a bow thruster, which involved both experimental and numerical analyses, was performed. By changing the chamfer form at the tunnel opening of the bow thruster and the position of the anti-suction tunnel, the optimization procedure aimed to improve the propulsion efficiency, reduce the amplitude of the fluctuating pressure on the tunnel wall, and balance the pressure difference on the hull caused by the speed. First, model tests were conducted to measure the thrust and torque of the bow thruster as well as the fluctuating pressure acting on the tunnel. Numerical simulations were also performed under the same conditions based on the unsteady Reynolds-averaged Navier-Stokes (URANS) method. The accuracy of the numerical results was verified by comparison with the experimental data. Second, the chamfer depth and angle of the tunnel opening and the distance between the anti-suction tunnel and the propeller axis in the length and height directions were taken as the design variables. A sample set that contained 30 sampling points was selected using the optimal Latin hypercube sampling (opt-LHS) method. A surrogate model was built based on the Support Vector Regression (SVR) algorithm, and the multi-island genetic algorithm was utilized during the tuning process of the surrogate model parameters. On this basis, the non-dominated sorting genetic algorithm II (NSGAII) was used for the three-objective optimization and the Pareto solution set was obtained. Due to the inverse relationship between the propulsion efficiency and the fluctuating pressure amplitude, four optimal solutions were selected from the Pareto optimal solution set, and direct numerical computations were conducted to verify the optimization results. The results showed that, compared with the original shape, the fluctuating pressure amplitudes for the four optimal solutions were reduced significantly after the optimization, with a maximum reduction of 18.56%, but their propeller propulsion efficiencies were slightly lower than the original hull. Increasing the chamfer angle and depth significantly reduced the flow-separation area around the tunnel entrance, but it correspondingly increased the flow velocity in the tunnel, which caused the propeller to not work at its highest efficiency point; thus, the propulsion efficiency was reduced to a certain extent. Moreover, the position of the anti-suction tunnel could be determined using the SBD method, but with an increase in the chamfer angle, the location where the jet of the bow thruster re-attached to the hull after mixing with the external flow moved towards the stern. This led to an expansion of the low-pressure area near the rear of the tunnel that correspondingly increased the pressure difference on the hull. If the chamfer angle was large enough, although the pressure difference could be reduced to a fairly low value through the anti-suction tunnel, it could not be balanced completely.

Characterization of material flow mechanism for chamfered tools utilizing coupled slip-line-slab method

Sintered carbide tools with their edge chamfered have superior resistance against brittle fracture of the main edge. Such advantage is mainly attributed to the formed built-up edge (BUE) anterior to the chamfer face. However, as the cutting process, certain materials including cracked BUE in that vicinity will inevitably flow aside along the chamfer face, which eventually causes severe notch wear and lateral burr formation. Given this deficiency, both theoretical and experimental works were carried out for the cutting process with chamfered tools in the current study. In the theoretical part, the material flow mechanism was analyzed and modeled by classifying the process into three typical modes concerning specific chip-tool contact patterns, for which three sets of modified slip-line solutions were developed accordingly. Furthermore, a unique solution to the three-dimensional (3-D) material flow status was achieved by combining slip-line theory with the slab method. On this basis, the effects of tool preparation factors, i.e. chamfer width, chamfer angle, tool-workpiece friction coefficient and rake angle, on the BUE extrusion were discussed in detail. The results indicate that with proper chamfered edge design, accumulative BUE will be flowing in an optimal condition. In this case, the lateral burrs were found effectively restrained as had been evidenced by conducting extensive orthogonal cutting experiments with chamfered tools. By comparing with released models and experimental measurements, the present model yields more accurate predictions of material flow states. These findings of present study can contribute to the optimal design of cutting tools with chamfered edge.

Effect of chamfer width and chamfer angle on tool wear in slot milling

The tool geometry is generally of great significance in metal cutting performance. The response surface method was used to optimize chamfer geometry to achieve reliable and minimum tool wear in slot milling. Models were developed for edge chipping, rake wear, and flank wear. The adequacy of the models was verified using analysis of variance at a 95% confidence level. Each response was optimized individually, and the multiple responses were optimized simultaneously using the desirability function approach. The Monte Carlo simulation method was applied to tolerance analysis. All milling tests were conducted at dry conditions; the chamfer width and the chamfer angle varied between 0.1 and 0.3 mm, and 10 and 30°, respectively. Optimal chamfer geometry for minimizing chipping and rake wear was small chamfer width and chamfer angle. The flank wear reached the minimum value for the tool with 0.18 mm chamfer width and 10° chamfer angle. The obtained composite model predicted good edge strength and minimum overall wear when the chamfer was 0.1 mm wide at a 10° angle. Thermal cracks were observed on the tools. They were small on the edges with the finest and least negative chamfer but were more significant on the more negative and greater chamfer. A great chamfer width and chamfer angle also resulted in insufficient chip evacuation. The results show how the edge geometry affects the tool’s reliability and wear and may help manufacturers minimize tool cost and downtime.

Machining-Induced Work Hardening Behavior of Inconel 718 Considering Edge Geometries

As a representative type of superalloy, Inconel 718 is widely employed in aerospace, marine and nuclear industries. The significant work hardening behavior of Inconel 718 can improve the service performance of components; nevertheless, it cause extreme difficulty in machining. This paper aims to investigate the influence of chamfered edge parameters on work hardening in orthogonal cutting of Inconel 718 based on a novel hybrid method, which integrates Coupled Eulerian-Lagrangian (CEL) method and grain-size-based functions considering the influence of grain size on microhardness. Orthogonal cutting experiments and nanoindentation tests are conducted to validate the effectiveness of the proposed method. The predicted results are highly consistent with the experimental results. The depth of work hardening layer increases with increasing chamfer angle and chamfer width, also with increasing feed rate (the uncut chip thickness). However, the maximum microhardness on the machined surface does not exhibit a significant difference. The proposed method can provide theoretical guidance for the optimization of cutting parameters and improvement of the work hardening.

Effect of cutting parameters on the generated surface integrity of hard-turned martensitic AISI 52100 bearing steel

Hard turning offers improved manufacturing efficiency but requires great control of the cutting process to achieve the required machining-induced surface integrity with respect to residual stresses, surface topography, and near-surface microstructure. This research work is focused on studying the effect of the cutting speed, feed rate, depth of cut, chamfer angle, and coolant pressure on the surface integrity after hard turning of martensitic AISI 52100 steel. The results showed that the feed rate had a significant influence on the residual stresses and the surface topography. The discontinuous mechanically induced white layer was observed at high cutting speed and high chamfer angle with increased thickness.

Optimization and Experimental Study of the Subsea Retractable Connector Rubber Packer Based on Mooney-Rivlin Constitutive Model

The sealing performance of the rubber packer is of vital importance for the subsea retractable connector, and the cross-sectional shape of the rubber packer is one of the most important factors affecting it. The compression distance of the rubber packer is increased by 19.54% utilizing the established two-dimensional numerical model. In addition, a new parameter called the anti-shoulder extrusion variable was defined in this paper. Shoulder extrusion will not occur when using this variable as a constraint during simulation. In general, the upper end and the lower end of a rubber packer are subject to different constraints, and the structural parameters of the rubber packer affect each other in terms of sealing performance. Therefore, the importance and originality of this study are exploring the optimization of the thickness and chamfer angles of the upper and lower ends of the rubber packer by use of a combination of the response surface optimization method and the multi-objective genetic algorithm, taking the thickness and chamfer angles of the upper and lower ends as design variables, and the stress on the inner side of the casing wall and the axial force of the compressed rubber packer as optimization objectives. Besides that, the anti-shoulder extrusion variables are also introduced as constraints to prevent shoulder extrusion. Ultimately, the cross-sectional shape of the rubber packer with a smaller-thickness and larger-angle upper end, and a larger-thickness and smaller-angle lower end can be obtained. The result to emerge from the test in this paper is that the pipe pressure that can be sealed by the optimized rubber packer structure is 25.61% higher than that before optimization. The anti-shoulder extrusion variable and the asymmetric cross-sectional shape of the rubber packer proposed in this paper shed new light on the finite element simulation of rubber and the research on similar seals.

Research on micro-texture placement position and cutting performance of negative chamfering ball-end milling cutter

In order to optimize the position of the micro-texture on the negative chamfering edge ball-end milling cutter, the experiment of milling titanium alloy with the negative chamfering micro-texture ball-end milling cutter was carried out. The effects of micro-texture at different placement positions (rake and flank faces of cutting tools) on cutting performance were compared when the cutting depth was 0.3 mm, and the effects of negative chamfering and micro-texture parameters on cutting performance of the cutter were studied. Finally, the negative chamfering and micro-texture parameters were optimized based on genetic algorithm. The results show that the micro-texture of the flank face can improve the cutting performance, and the negative chamfering angle and width have the greatest influence on the cutting performance. The parameter optimization results are: the negative chamfering angle is 10.016°, the negative chamfering width is 199.995 μm, the micro-pit diameter is 49.996 μm, the micro-pit spacing is 174.004 μm, and the micro-pit distance from the edge is 109.993 μm. The above research realizes high efficiency and high-quality machining of titanium alloy.

The Effect of the Structure and Parameters of Diesel Injector on Atomization Characteristics

The quality of the fuel injection system mainly depends on the fuel injection characteristics and atomization characteristics of the system. The structural parameters of the fuel injector play an important role in the flow condition of fuel injection, thus affecting the atomization characteristics of fuel injection. The atomization characteristics of the fuel injection system are seriously affected by the nozzle structure. In this paper, the influence of the nozzle diameter and the chamfering at the nozzle entrance on the atomization characteristics of the system is analyzed. The results show that the diameter of the jet hole increases, the area of the negative pressure increases, the cavitation intensity decreases, the flow coefficient of the nozzle relatively decreases, and the fuel injection speed decreases, but the range of the oil beam and the spray cone angle increase. With the increase of the chamfer angle at the entrance of the nozzle, the area of the negative pressure decreases, the cavitation intensity relatively decreases, but the uniformity of fuel injection speed increases, the flow coefficient of the nozzle increases, the average fuel injection speed increases, and the fuel oil range and the spray cone angle increase. The back pressure has no obvious effect on the internal flow and overall atomization of the nozzle. The response surface method (RSM) is used to obtain the response surface function of the mass flow and the chamber pressure. The analysis shows that in order to increase the mass flow rate, it is necessary to increase the spray hole diameter as much as possible. In order to increase the chamber pressure and reduce the cavitation, it is necessary to reduce the diameter of the spray hole, the top radius of the valve core and the diameter of the pressure chamber ball as much as possible. It provides theoretical and practical guidance for the structural optimization design of fuel injection system.

Pengaruh Double Chamfer terhadap Distribusi Suhu dan Daerah Zpl pada Sambungan Las Gesek AL6061 dengan Simulasi Komputer

Welding is one of the metal joining processes in manufacturing. CDFW (continuous drive friction welding) is a welding process to join two workpieces by applying pressure at one end of the object and rotating another one where the friction action applies at interface. The purpose of this study is to study temperature distribution on the surface of the welding area and the heat-affected zone represented by a fully plasticized zone (Zpl) and to get an insight of a friction welding process. The variables of CDFW used were double chamfer angle, upset pressure, and burn off length. The initial area of friction was equal that is at a diameter of 14 mm. The method of modeling the CDFW friction welding is via computer simulations using ANSYS 18.1 software. This research uses aluminum material type Al6061. The Taguchi method was applied in designing the simulations. In this modeling, the model with the double chamfer of 15 °, the upset pressure of 120 MPa, and the burn-off length of 9 mm has a small ZPl area of 10.256 mm2. Whilst the specimen model, with a double chamfer angle of 45 °, the upset pressure of 240 MPa, and the burn-off length of 7 mm has a large Zpl area of 56.55mm2. The area of a narrow fully plasticized area caused by small chamfer angle and an upset pressure of 240 MPa. The area of fully plasticized zone shows how much material can be integrated during the friction welding process and how much strength of the weld metal. The model with the chamfer angle of 15 º, the upset pressure of 240 MPa, and the burn-off length of 9 mm has the widest temperature distribution and the highest maximum temperature. Meanwhile, the model with the chamfer angle of 30º, the upset pressure of 120 MPa, and the burn-off length of 9 mm has the narrowest temperature distribution and the lowest maximum temperature. The smaller chamfer angle increased upset pressure and burn-off length result in the wider temperature distribution, higher maximum temperature, and smaller Zpl.

The Study of Male-Female Chamfer Angle Effect on Aluminum 6061 Forging at Rotary Friction Welding Process

This research aims to investigate male-female chamfer angle effect on forging pressure, specimen length and the maximum tensile strength in splicing 6061 aluminum material, which used the rotary friction welding process. This research employed the analytical method to determine the timing of forging pressure as an initial reference to conduct the experimental study for the specimens test. The specimens were tested by varying the male-female chamfer angle, namely 0°, 15°, 30°, 45°, 60°. The results test were obtained the longest application of forging pressure at the male-female chamfer angle of 60° and the fastest application of forging pressure at the male-female chamfer angle of 15°. The change in length of the specimen during the welding process for each variation of the male-female chamfer angle varies due to the friction time different. The largest change in length was at the male-female chamfer angle of 15° and the smallest change in length at the male-female chamfer angle of 60°. The maximum tensile strength was obtained at the variation of male-female chamfer angle of 60° with a value of 226.47 MPa.

Analysis of effect of bentleg opener geometry on performance in cohesive soil using the discrete element method

Bentleg furrow openers can significantly reduce soil disturbance and reaction forces relative to conventional narrow point openers used in no-tillage farming. The effect of bentleg opener geometry on soil disturbance and reaction forces in a cohesive soil was assessed in a virtual soil bin using the discrete element method. Soil disturbance and reaction forces at an operating depth and a speed of 100 mm and 8 km h −1 , were shown to be minimised by using (1) a shank lateral offset of 70 mm, (2) a side leg bend angle that ensures the elbow, which is the transition between the side leg and vertical shank, is not located below the soil surface, (3) an arched instead of angled elbow, (4) a cutting edge chamfer angle as low as practical, and (5) tine thickness as small as practical. Furrow size was found to be more dependent on shank lateral offset and side leg bend angle than side leg forward angle. Though side leg forward angles >90° reduce particle displacement and will work better in fields with stones and roots, they also considerably increase draught and penetration resistance. A low rake angled foot minimises soil reaction forces and drives soil loosening. Reducing foot height and interaction of the vertical shank with soil particles minimises surface soil displacement. These results have expanded the understanding of bentleg opener mechanics and are in close agreement with those reported for sandy soils. Therefore, similar criteria can be followed to optimise bentleg opener design for different soil types. • Discrete element method predicted bentleg opener geometry effects in Black Vertosol. • Geometries that cause minimum soil disturbance and reaction forces were identified. • Shank lateral offset should be large and arched elbow protrude above soil surface. • Cutting edge chamfer angle and thickness as small as practical are recommended. • Low foot rake angle and foot height reduce soil forces and soil throw, respectively.

Failure analysis on girth weld cracking of underground tee pipe

Three girth weld cracking events were found by X-ray inspection in one natural gas station. To determine the failure cause, one of the three failure events was studied by visual inspection, nondestructive testing, microstructure examination, scanning electronic microscopy (SEM) coupled with energy dispersive spectrometry (EDS), blasting tests, finite element simulations and a series physical and chemical tests. The results revealed that the welding defects were original failure factor, and these welding defects led to crack initiation and propagation through the wall thickness under three aspects of stress concentration effects with internal pressure. The stress concentration effects were originated from the unqualified inner chamfering angle, unequal wall thickness, and inherent shape of tee pipe. The reason causing welding defects of girth weld is that the slag inclusions were not cleaned up timely, and then the slag inclusions led to the existence of welding defects.