Fatigue damage evaluation by metal magnetic memory testing

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).

MMM testing and failure analysis of fastening bolts on reciprocating compressor cylinder cover

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.

A Test Approach for Look-Up Table Based FPGAs

This paper describes a test architecture for minimum number of test configurations in test of FPGA （Field Programmable Gate Array） LUTs （Look Up Tables）. The test architecture includes a TPG （Test Pattern Generator） that is tested while it is generating test data for LEs （Logic Elements） that form the CUT （Circuit Under Test）. This scheme eliminates the need for switching LEs between CUT, TPG and ORA （Output Response Analyzer） and having to perform many more reconfiguratioas of the FPGA. An external ORA locates faults of the FPGA under test. In addition to the LUTs, a scheme is presented for testing other parts of LEs. Compared with other methods, the presented scheme uses the least number of reconfigurations of an FPGA for its LUT testing.

Electroacupuncture inhibits hippocampal oxidative stress and autophagy in sleep-deprived rats through the protein kinase B and mechanistic target of rapamycin signaling pathway

OBJECTIVE:To investigate the effects of acupuncture on learning and memory impairment,oxidative stress and autophagy induced by sleep depriv ation in rats,and to analyze the related mechanism.METHODS:Thirty Wistar rats were randomly divided into a normal group,sleep deprivation group and acupuncture group.The rat model of sleep deprivation was established by a modified multiplatform sleep deprivation method.The Baihui(GV20),Shenmen(HT7)and Sanyinjiao(SP6)acupoints of rats were located to give electroacupuncture(density wave,frequency 20 Hz,intensity 1 mA)to maintain the needle feeling,and to keep the needle for 15min and continuous acupuncture for 7 d.The spatial learning and memory abilities of the rats were detected by the water maze test.The content of malondialdehyde(MDA)and the activities of superoxide dismutase(SOD)and glutathione peroxidase(GPX)in the brain were detected by an assay kit,and the autophagy related proteins light chain 3 alpha(LC3A),light chain 3 beta(LC3B)and Beclin 1 and the activation of the protein kinase B(PKB/AKT)and mechanistic target of rapamycin(mTOR)signaling pathway in the rat's brain were detected by Western blotting.RESULTS:Compared with the normal group,the time spent in the target quadrant(P<0.05)and the number of times entering the target quadrant(P<0.05)in the rats of sleep deprivation group were significantly reduced,and the content of MDA was significantly increased(P<0.01),while the activities of SOD and GPX(P<0.01)in the brain were significantly decreased,and LC3AⅡ/Ⅰ,LC3BⅡ/Ⅰand Beclin 1 increased significantly(P<0.01),while pAKT(ser473)/AKT,p-mTOR(ser2448)/mTOR and pp70s6K(thr389)/p70S6 decreased significantly(P<0.01).Compared with the sleep deprivation group,the time spent in the target quadrant and the times of entering the target quadrant(P<0.05)in the rats of acupuncture group after 7 d of treatment were significantly increased,Additionally,the content of MDA was significantly decreased(P<0.05),while the activities of SOD and GPX(P<0.05)in the brain were significantly increased.Moreover,the levels of LC3AⅡ/Ⅰ,LC3BⅡ/Ⅰand Beclin 1 decreased significantly(P<0.05),and that of pAKT(ser473)/AKT,p-mTOR(ser2448)/mTOR and pp70s6K(thr389)/p70s6k increased significantly(P<0.05).CONCLUSION:Acupuncture can significantly improve the learning and memory damage caused by sleep deprivation and inhibit oxidative stress and autophagy,and its effect is related to the activation of AKT/mTOR signaling.

Electroacupuncture with Bushen Jiannao improves cognitive deficits in senescence-accelerated mouse prone 8 mice by inhibiting neuroinflammation

OBJECTIVE:To investigate effect of electroacupuncture(EA)with Bushen Jiannao on learning and memory ability in senescence-accelerated mouse prone 8(SAMP8)mice and the related mechanisms.METHODS:8-month-old senescence-accelerated-resistant(SAMR1)and SAMP8 mice were treated with EA at Baihui(GV 20),Shenshu(BL 23),and Taixi(KI 3)acupoint once a week for 8 weeks.The Morris water maze,enzyme linked immunosorbent assay,immunohistochemistry,and Western blot were used to assess Alzheimer’s disease(AD)-associated cognitive and neuroinflammatory phenotypes.RESULTS:Our data showed that EA treatment decreased activation of microglia and astrocytes,decreased levels of inflammatory factors including tumor necrosis factor-α(TNF-α),interleukin(IL)-6,and IL-17,and improved spatial memory deficits in SAMP8 mice.EA therapy with Bushen Jiannao exhibited anti-inflammatory properties and improved cognitive function.CONCLUSION:The present study indicates that EA treatment based on the interaction between kidney and brain can improve learning and memory ability by inhibiting activation of astrocytes and microglia and decreasing expression of pro-inflammatory cytokines,TNF-αand IL-17.EA treatment based on the interaction between kidney and brain may be an effective treatment for AD.