Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a...Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a multi-field coupled model was established and the finite element method （FEM） was presented to calculate the entire transduction process. The multi-field coupled model included the static magnetic field, pulsed eddy current field and mechanical field. The FEM equations of the three fields were derived by Garlerkin FEM method. Thus, the entire transduction process of the EMAT was calculated through sequentially coupling the three fields. The transduction process of a Lamb wave EMAT was calculated according to the present model and method. The results show that, by the present method, it is valid to calculate the particle displacement under the given excitation signal and non-uniformly distributed static magnetic field. Calculation error will be brought about if the non-uniform distribution of the static bias magnetic field is neglected.展开更多
Tension-compression fatigue test was performed on 0.45% C steel specimens.Normal and tangential components of magnetic memory testing signals,Hp(y) and Hp(x) signals,with their characteristics,K of Hp(y) and Hp(x)M of...Tension-compression fatigue test was performed on 0.45% C steel specimens.Normal and tangential components of magnetic memory testing signals,Hp(y) and Hp(x) signals,with their characteristics,K of Hp(y) and Hp(x)M of Hp(x),throughout the fatigue process were presented and analyzed.Abnormal peaks of Hp(y) and peak of Hp(x) reversed after loading; Hp(y) curves rotated clockwise and Hp(x) curves elevated significantly with the increase of fatigue cycle number at the first a few fatigue cycles,both Hp(y) and Hp(x) curves were stable after that,the amplitude of abnormal peaks of Hp(y) and peak value of Hp(x) increased more quickly after fatigue crack initiation.Abnormal peaks of Hp(y) and peak of Hp(x) at the notch reversed again after failure.The characteristics were found to exhibit consistent tendency in the whole fatigue life and behave differently in different stages of fatigue.In initial and crack developing stages,the characteristics increased significantly due to dislocations increase and crack propagation,respectively.In stable stage,the characteristics remained constant as a result of dislocation blocking,K value ranged from 20 to 30 A/(m·mm)-1,and Hp(x)M ranged from 270 to 300 A/m under the test parameters in this work.After failure,both abnormal peaks of Hp(y) and peak of Hp(x) reversed,K value was 133 A/(m·mm)-1 and Hp(x)M was-640 A/m.The results indicate that the characteristics of Hp(y) and Hp(x) signals were related to the accumulation of fatigue,so it is feasible and applicable to monitor fatigue damage of ferromagnetic components using metal magnetic memory testing(MMMT).展开更多
To avoid the serious accidents caused by the failure fastening bolts on reciprocating compressor cylinder cover,a new nondestructive testing(NDT) technology,metal magnetic memory(MMM) testing,was applied to safety eva...To avoid the serious accidents caused by the failure fastening bolts on reciprocating compressor cylinder cover,a new nondestructive testing(NDT) technology,metal magnetic memory(MMM) testing,was applied to safety evaluating and failure analyzing for the fastening bolts.Based on the dynamic stress calculation of the failure bolts,MMM testing was carried out at workshop.Given are the MMM stress distribution characteristics of the failure bolts and fracture faces.It has been found that the MMM signal variation amplitude of the crack transition zone in the fracture surface is minimal,that of the crack initiation zone is in the middle,and that of the tear fracture zone is maximal.The failure reasons were analyzed with MMM effect.The results of the metallographic examination showed that the validity and feasibility of MMM testing and failure analysis.This means MMM technology is a new,fast and validity method of failure analysis.展开更多
Improvement of the fatigue life of welded tubular T-joints in offshore platforms due to weld toe grinding and TIG dressing is studied physically and experimentally. It is shown that the two methods of treatment can im...Improvement of the fatigue life of welded tubular T-joints in offshore platforms due to weld toe grinding and TIG dressing is studied physically and experimentally. It is shown that the two methods of treatment can improve the fatigue strength of welded tubular joints not only in the environment of air but even in the envirnment of seawater accordingly.展开更多
The effect of mechanical cyclings on the stress-strain(S-S) curves was studied systematically using tensile tests over a wide temperature range. Two-stage yielding was observed in the temperature range between Ms and ...The effect of mechanical cyclings on the stress-strain(S-S) curves was studied systematically using tensile tests over a wide temperature range. Two-stage yielding was observed in the temperature range between Ms and the ultimate temperature to induce martensite, denoted by Md. The first stage was confirmed to be associated with stress-induced martensite(SIM) and the second stage was associated with the yielding of SIM. When the samples were mechanically cycled between Ms and Md, a stress-softening phenomenon was observed. The cyclings made the martensite amount increase, critical stress σc of SIM decrease according to exponential law, and the entropy(also enthalpy) of the parent to martensite transformation also decrease. The variations of SIM relative amount were determined by recording the changes of electrical resistances in the course of tension.展开更多
In the present paper the effects of additions of Zr and Y on the microstructure and mechanical properties for Ti-(6.0 approximately 6.5)Al-(2.0 approximately 3.0)Sn-(1.5 approximately 6.0)Zr-(0.8 approximately 1.0)Mo-...In the present paper the effects of additions of Zr and Y on the microstructure and mechanical properties for Ti-(6.0 approximately 6.5)Al-(2.0 approximately 3.0)Sn-(1.5 approximately 6.0)Zr-(0.8 approximately 1.0)Mo-1.0Nb-0.25Si alloys are reported. The experimental results shows that: with increasing of Zr content, tensile strength and creep resistance of the alloys increase, and reduction in area and thermal stability of the alloys decrease. Decrease in thermal stability of the alloys mainly caused by surface thermal unstability. After heat treatment Y addition can make grain size of the alloys refine. The reduction in area and thermal stability of the alloys with Y addition are improved, and tensile strength slightly decreases and creep resistance is essentially the same as the alloy without Y addition. These phenomena are explained in brief.展开更多
Plane-strain forming limit strain （also known as FLD0） is an important data point on a forming limit diagram （FLD）. The effects of friction coefficients and material parameters on the specimen width associated wit...Plane-strain forming limit strain （also known as FLD0） is an important data point on a forming limit diagram （FLD）. The effects of friction coefficients and material parameters on the specimen width associated with the FLDo （W FLD0） in Marciniak test were studied by finite element simulation. WFLD0 was expressed as a function of the Lankford coefficients, n-value, k-value and sheet thickness and validated with various sheet materials. The determination of W FLD0 is of significance not only to reduce iterative attempts to accurately obtain FLDo, but also to obtain a full valid FLD with the least number of test specimens, which largely increases the efficiency and reduces cost to experimentally measure valid FLDs.展开更多
In today’s era of rapid technological advancement,the precise measurement of metal strain holds crucial significance across numerous fields.From mechanical manufacturing to civil engineering,aerospace to biomedical s...In today’s era of rapid technological advancement,the precise measurement of metal strain holds crucial significance across numerous fields.From mechanical manufacturing to civil engineering,aerospace to biomedical sciences,understanding the strain behavior of metals under stress is essential for ensuring structural safety and the proper functioning of equipment.This paper focuses on five commonly used sensors for measuring metal strain:resistance sensors,fiber optic sensors,piezoelectric sensors,Hall effect sensors,and capacitive sensors.It delves into their working principles,practical applications,advantages and disadvantages,as well as future development trends,aiming to provide a comprehensive reference for research and practice in related fields.展开更多
基金Project(10974115) supported by the National Natural Science Foundation of China
文摘Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a multi-field coupled model was established and the finite element method （FEM） was presented to calculate the entire transduction process. The multi-field coupled model included the static magnetic field, pulsed eddy current field and mechanical field. The FEM equations of the three fields were derived by Garlerkin FEM method. Thus, the entire transduction process of the EMAT was calculated through sequentially coupling the three fields. The transduction process of a Lamb wave EMAT was calculated according to the present model and method. The results show that, by the present method, it is valid to calculate the particle displacement under the given excitation signal and non-uniformly distributed static magnetic field. Calculation error will be brought about if the non-uniform distribution of the static bias magnetic field is neglected.
基金Projects(50975283,50975287)supported by the National Natural Science Foundation of ChinaProject(2011CB013401)supported by the National Basic Research Program,China
文摘Tension-compression fatigue test was performed on 0.45% C steel specimens.Normal and tangential components of magnetic memory testing signals,Hp(y) and Hp(x) signals,with their characteristics,K of Hp(y) and Hp(x)M of Hp(x),throughout the fatigue process were presented and analyzed.Abnormal peaks of Hp(y) and peak of Hp(x) reversed after loading; Hp(y) curves rotated clockwise and Hp(x) curves elevated significantly with the increase of fatigue cycle number at the first a few fatigue cycles,both Hp(y) and Hp(x) curves were stable after that,the amplitude of abnormal peaks of Hp(y) and peak value of Hp(x) increased more quickly after fatigue crack initiation.Abnormal peaks of Hp(y) and peak of Hp(x) at the notch reversed again after failure.The characteristics were found to exhibit consistent tendency in the whole fatigue life and behave differently in different stages of fatigue.In initial and crack developing stages,the characteristics increased significantly due to dislocations increase and crack propagation,respectively.In stable stage,the characteristics remained constant as a result of dislocation blocking,K value ranged from 20 to 30 A/(m·mm)-1,and Hp(x)M ranged from 270 to 300 A/m under the test parameters in this work.After failure,both abnormal peaks of Hp(y) and peak of Hp(x) reversed,K value was 133 A/(m·mm)-1 and Hp(x)M was-640 A/m.The results indicate that the characteristics of Hp(y) and Hp(x) signals were related to the accumulation of fatigue,so it is feasible and applicable to monitor fatigue damage of ferromagnetic components using metal magnetic memory testing(MMMT).
基金Sponsored by the National Natural Science Foundation of China (Grant No. 11072056)Natural Science Foundation of Heilongjiang Province of China(Grant No.A200907)Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20092322120001)
文摘To avoid the serious accidents caused by the failure fastening bolts on reciprocating compressor cylinder cover,a new nondestructive testing(NDT) technology,metal magnetic memory(MMM) testing,was applied to safety evaluating and failure analyzing for the fastening bolts.Based on the dynamic stress calculation of the failure bolts,MMM testing was carried out at workshop.Given are the MMM stress distribution characteristics of the failure bolts and fracture faces.It has been found that the MMM signal variation amplitude of the crack transition zone in the fracture surface is minimal,that of the crack initiation zone is in the middle,and that of the tear fracture zone is maximal.The failure reasons were analyzed with MMM effect.The results of the metallographic examination showed that the validity and feasibility of MMM testing and failure analysis.This means MMM technology is a new,fast and validity method of failure analysis.
文摘Improvement of the fatigue life of welded tubular T-joints in offshore platforms due to weld toe grinding and TIG dressing is studied physically and experimentally. It is shown that the two methods of treatment can improve the fatigue strength of welded tubular joints not only in the environment of air but even in the envirnment of seawater accordingly.
文摘The effect of mechanical cyclings on the stress-strain(S-S) curves was studied systematically using tensile tests over a wide temperature range. Two-stage yielding was observed in the temperature range between Ms and the ultimate temperature to induce martensite, denoted by Md. The first stage was confirmed to be associated with stress-induced martensite(SIM) and the second stage was associated with the yielding of SIM. When the samples were mechanically cycled between Ms and Md, a stress-softening phenomenon was observed. The cyclings made the martensite amount increase, critical stress σc of SIM decrease according to exponential law, and the entropy(also enthalpy) of the parent to martensite transformation also decrease. The variations of SIM relative amount were determined by recording the changes of electrical resistances in the course of tension.
文摘In the present paper the effects of additions of Zr and Y on the microstructure and mechanical properties for Ti-(6.0 approximately 6.5)Al-(2.0 approximately 3.0)Sn-(1.5 approximately 6.0)Zr-(0.8 approximately 1.0)Mo-1.0Nb-0.25Si alloys are reported. The experimental results shows that: with increasing of Zr content, tensile strength and creep resistance of the alloys increase, and reduction in area and thermal stability of the alloys decrease. Decrease in thermal stability of the alloys mainly caused by surface thermal unstability. After heat treatment Y addition can make grain size of the alloys refine. The reduction in area and thermal stability of the alloys with Y addition are improved, and tensile strength slightly decreases and creep resistance is essentially the same as the alloy without Y addition. These phenomena are explained in brief.
文摘Plane-strain forming limit strain （also known as FLD0） is an important data point on a forming limit diagram （FLD）. The effects of friction coefficients and material parameters on the specimen width associated with the FLDo （W FLD0） in Marciniak test were studied by finite element simulation. WFLD0 was expressed as a function of the Lankford coefficients, n-value, k-value and sheet thickness and validated with various sheet materials. The determination of W FLD0 is of significance not only to reduce iterative attempts to accurately obtain FLDo, but also to obtain a full valid FLD with the least number of test specimens, which largely increases the efficiency and reduces cost to experimentally measure valid FLDs.
文摘In today’s era of rapid technological advancement,the precise measurement of metal strain holds crucial significance across numerous fields.From mechanical manufacturing to civil engineering,aerospace to biomedical sciences,understanding the strain behavior of metals under stress is essential for ensuring structural safety and the proper functioning of equipment.This paper focuses on five commonly used sensors for measuring metal strain:resistance sensors,fiber optic sensors,piezoelectric sensors,Hall effect sensors,and capacitive sensors.It delves into their working principles,practical applications,advantages and disadvantages,as well as future development trends,aiming to provide a comprehensive reference for research and practice in related fields.
