Effect of welding processes on tensile properties of AA6061
ORIGINAL ARTICLE
Effect of welding processes on tensile properties of AA6061 aluminium alloy joints
https://www.docsj.com/doc/e810402662.html,kshminarayanan&V.Balasubramanian&
K.Elangovan
Received:1June2007/Accepted:19November2007/Published online:18December2007
#Springer-Verlag London Limited2007
Abstract The present investigation is aimed at to study the effect of welding processes such as GTAW,GMAW and FSW on mechanical properties of AA6061aluminium alloy.The preferred welding processes of these alloys are frequently gas tungsten arc welding(GTAW)and gas metal arc welding(GMAW)due to their comparatively easier applicability and better economy.In this alloy,the weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification.This often causes inferior weld mechanical properties and poor resistance to hot cracking. Friction stir welding(FSW)is a solid phase welding technique developed primarily for welding metals and alloys that heretofore had been difficult to weld using more traditional fusion techniques.Rolled plates of6mm thickness have been used as the base material for preparing single pass butt welded joints.The filler metal used for joining the plates is AA4043(Al-5Si(wt%))grade aluminium alloy.In the present work,tensile properties, micro hardness,microstructure and fracture surface mor-phology of the GMAW,GTAW and FSW joints have been evaluated,and the results are compared.From this investigation,it is found that FSW joints of AA6061 aluminium alloy showed superior mechanical properties compared with GTAW and GMAW joints,and this is mainly due to the formation of very fine,equiaxed microstructure in the weld zone.
Keywords AA6061aluminium alloy.
Gas metal arc welding.Gas tungsten arc welding.
Friction stir welding.Tensile properties
1Introduction
Aluminium alloys find wide applications in aerospace, automobile industries,railway vehicles,bridges,offshore structure topsides and high speed ships due to its light weight and higher strength to weight ratio.In all cases, welding is the primary joining method which has always represented a great challenge for designers and technolo-gists.As a matter of fact,lots of difficulties are associated with this kind of joint process,mainly related to the presence of a tenacious oxide layer,high thermal conduc-tivity,high coefficient of thermal expansion,solidification shrinkage and,above all,high solubility of hydrogen,and other gases,in the molten state[1].Further problems occur when attention is focused on heat-treatable alloys,since heat,provided by the welding process,is responsible for the decay of mechanical properties,due to phase transforma-tions and softening[2].AA6061aluminium alloy(Al-Mg-Si alloys)is the most widely used medium strength aluminium alloy,and has gathered wide acceptance in the fabrication of light weight structures[3].The preferred welding processes for these alloys are frequently gas tungsten arc welding (GTAW)and gas metal arc welding(GMAW)due to their comparatively easier applicability and better economy[4]. Welding of these alloys,however,still remains a challenge. Apart from softening in the weld fusion zone and heat-
Int J Adv Manuf Technol(2009)40:286–296
DOI10.1007/s00170-007-1325-0
https://www.docsj.com/doc/e810402662.html,kshminarayanan
:V.Balasubramanian(*)
Center for Materials Joining Research(CEMAJOR), Department of Manufacturing Engineering,Annamalai University, Annamalainagar608002Tamil Nadu,India
e-mail:visvabalu@https://www.docsj.com/doc/e810402662.html,
K.Elangovan
Department of Mechanical&Production Engineering, Sathyabama University,
Chennai,Tamil Nadu,India
affected zone,hot cracking in the weld can be a serious problem[5].Friction stir welding(FSW)is an innovative solid phase welding process in which the metal to be welded is not melted during welding,thus the cracking and porosity often associated with fusion welding processes are eliminat-ed[6].Therefore,the FSW process can also be used to weld heat-treatable aluminum alloys in order to obtain high-quality joints.However,earlier studies[7–9]on the micro-structural characteristics and mechanical properties of the friction-stir-welded joints have indicated that FSW gives rise to softening in the joints of the heat-treatable aluminum alloys such as7075-T651and7475-T76because of the dissolution or growth of strengthening precipitates during the welding thermal cycle,thus resulting in the degradation of mechanical properties of the joints.Stefano Maggiolino et al.
[10]reported a comparative study on the corrosion resistance of AA6060-T5and AA6082T6jointed surfaces via FSW and GMAW process respectively and found friction stir welded sample has a better behaviour concerning the pitting corrosion than that of the GMAW sample.Moreira et al.
[11]investigated the contrasting difference of fatigue behaviour of joints made from the traditional process of metal inert gas(MIG)welding,and the emerging process of friction stir welding.They reported that MIG and FS welded
samples have a tensile strength of65%and70%of the base material respectively.Squillace et al.[12]proposed a comparison on electrochemical properties of gas tungsten arc welded and friction stir welded butt joints.Cabello Munoz et al.[13]investigated the microstructural and mechanical properties of friction stir welded and gas tungsten arc welded Al-Mg-Sc alloy and reported that the yield strength of friction stir welded and gas tungsten arc welded joints are decreased20%and50%respectively compared to the base metal.However,no systematic study and detailed comparison has been reported on the mechanical properties of GMAW,GTAW and FSW joints of AA6061aluminium alloy.Hence,in this investigation,an attempt has been made to evaluate the mechanical properties of GMAW,GTAW and FSW joints of AA6061alloy.
2Experimental work
The rolled plates of AA6061aluminium alloy were machined to the required dimensions(300mm×150mm). Single‘V’butt joint configuration,as shown in Fig.1a,was prepared to fabricate GTA and GMA welded joints.The initial joint configuration was obtained by securing the plates in position using tack welding for GTA and GMA welds.The direction of welding was normal to the rolling direction.All necessary care was taken to avoid joint distortion,and the joints were made with suitable clamps.Single pass welding was used to fabricate the joints. AA4043(Al-5%Si)grade filler rod and wire were used for GTA and GMA welding processes,respectively.High purity(99.99%)argon gas was the shielding gas.Square butt joint configuration as shown in Fig.1b was prepared to fabricate FSW joints.A non-consumable,rotating tool made of high carbon steel was used to fabricate FSW joints.The friction stir welding process is dominated by the effects associated with material flow and large mechanical deformation,which in turn is affected by process parame-ters such as rotational speed,welding speed and axial force. Compared to fusion welding processes,there is no porosity or other defects related to fusion.However,the hardening precipitates responsible for the good mechanical properties of heat treatable aluminium alloy are shown to be very affected by this process,partly because of their low stability.The process parameters must be optimized to get defect free joints.From the previous work done in our laboratory[14,15],the optimum friction stir welding process parameter for joining AA6061aluminium alloy are1200rpm,1.25mm/s(75mm/min)and7kN.Trial experiments and macrostructural analysis(to identify any visible defects)were carried out for each mentioned process to find out the optimum process parameters.The welding conditions and optimized process parameters presented in Table1were used to fabricate the joints.Subsize cylindrical tensile specimens were prepared from the weld metal region (longitudinal direction)alone as per the ASTM E8M-04 standard to evaluate all weld metal tensile properties.
The
chemical composition and mechanical properties of base metal and weld metals are presented in Tables2and3.
The welded joints were sliced(as shown in Fig.2a) using a power hacksaw and then machined to the required dimensions as shown in Fig.2b,c.American Society for Testing of Materials(ASTM E8M-04)guidelines were followed for preparing the test specimens.Two different tensile specimens were prepared to evaluate the transverse tensile properties.The smooth(unnotched)tensile speci-mens were prepared to evaluate yield strength,tensile strength,elongation and reduction in cross sectional area. Notched specimens were prepared to evaluate notch tensile strength and notch strength ratio of the joints.Tensile testing was carried out using a100kN,electro-mechanical controlled Universal Testing Machine(Make:FIE-Bluestar, India;Model:UNITEK-94100).The0.2%offset yield strength was derived from the load-displacement diagram. Vicker’s microhardness tester(Make:Shimadzu,Japan and Model:HMV-2T)was used for measuring the hardness of the weld metal with a0.05kg load.Microstructural examination was carried out using a light optical microscope (Make:MEJI,Japan;Model:MIL-7100)incorporated with an image analyzing software(Metal Vision).The specimens for metallographic examination were sectioned to the required sizes from the joint comprising weld metal,HAZ and base metal regions and polished using different grades of emery papers.Final polishing was done using the diamond compound(1μm particle size)in the disc polishing machine. Specimens were etched with Keller’s reagent to reveal the micro and macrostructure.
3Results
3.1Tensile properties
The transverse tensile properties such as yield strength, tensile strength,percentage of elongation,notch tensile strength,and notch strength ratio of AA6061aluminium alloy joints were evaluated.In each condition,three specimens were tested,and the average of the three results is presented in Table4.The yield strength and tensile strength of unwelded parent metal are302MPa and 335MPa,respectively.However,the yield strength and ten-sile strength of GMAW joints are141MPa and163MPa, respectively.This indicates that there is a51%reduction in strength values due to GMA welding.Similarly,the yield strength and tensile strength of GTAW joints are188MPa and211MPa,respectively which are37%lower compared to parent metal.However,the yield strength and tensile strength of FSW joints are224MPa and248MPa, respectively.Of the three types of welded joints,the joints fabricated by FSW process exhibited higher strength values, and the enhancement in strength value is approximately34%
Table1Welding conditions and process parameters
Process GMAW GTAW FSW
Welding machine Lincoln,USA Lincoln,USA RV Machine Tools,India Tungsten electrode diameter(mm)–3–
Filler rod/wire diameter(mm) 1.6 3.0–
V oltage(volts)2020–
Current(amps)190175–
Welding speed(mm/min)11013075
Heat input(kJ/mm) 2.021 1.2120.84
Shielding gas Argon Argon–
Gas flow rate(lit/min)1616–
Tool rotational speed(rpm)––1200
Axial force(kN)––7
Tool pin profile––Threaded
Tool shoulder diameter(mm)––18
Pin diameter(mm)––6
Pin length(mm)–– 5.5
Table2Chemical composition(wt%)of base metal and all weld metals
Type of Material Mg Si Fe Cu Cr Mn Zn Ti Al Base Metal(AA6061-T6)0.90.620.330.280.170.060.020.02Bal Weld metal(GTAW)0.05 5.00.050.12–0.22––Bal Weld metal(GMAW)0.04 5.00.060.10–0.20––Bal Weld metal(FSW)0.80.600.350.260.190.080.010.01Bal
compared to GMAW joints and 15%compared to GTAW joints.
Elongation and reduction in the cross-sectional area of the unwelded parent metal are 18%and 12.24%,respec-tively.However,the elongation and reduction in the cross-sectional area of GMAW joints are 8.4%and 5.8%,respectively.This suggests that there is a 53%reduction in ductility due to GMA welding.Similarly,the elongation
Table 3Mechanical properties of base metal and all weld metals Type of Material
Yield Strength (MPa)
Ultimate Tensile Strength (MPa)
Elongation (%)
Reduction in cross sectional area (%)Hardness (VHN)
Base Metal (AA 6061)3023341812.24105Weld Metal (GTAW)1602308 5.4565Weld Metal (GMAW)1502206 4.560Weld metal (FSW)2452951410.2
85
a Scheme of welding with respect to rolling direction and extraction of tensile
specimens
b
Dimensions of flat smooth tensile specimen
c Dimensions of flat notch tensile specimen
ASTM E8M-04 All dimensions are in ‘mm’
Fig.2Dimensions of tensile specimen
and reduction in the cross-sectional area of GTAW joints are11.8%and8.26%,respectively,which are34%lower compared to the parent metal.However,the elongation and reduction in the cross-sectional area of FSW joints are 14.2%and9.56%,respectively.Of the three types of welded joints,the joints fabricated by FSW exhibited higher ductility values,and the improvement in ductility is approximately41%compared to GMAW joints and17% compared to GTAW joints.
Notch tensile strength(NTS)of unwelded parent metal is 386MPa.However,the notch tensile strength of a GMAW joint is175MPa.This reveals that the reduction in NTS is approximately55%due to GMA welding.Similarly,the NTS of GTAW is228MPa and the NTS of FSW is 279MPa.Of the three types of welded joints,the joints fabricated by FSW exhibited higher NTS values,and the enhancement is37%compared to GMAW and18% compared to GTAW.Another notch tensile parameter, NSR,is found to be greater than unity(>1)for all the joints.This suggests that the AA6061alloy is insensitive to notches and it is a“notch ductile materials”.The NSR is 1.15for unwelded parent metal,but it is1.07and1.09for GMAW and GTAW joints respectively.Of the three types of welded joints,the joints fabricated by FSW exhibited a relatively higher NSR(1.13),and the improvement in NSR is5.2%compared to GMAW and3.5%compared to GTAW process.
Joint efficiency is the ratio between tensile strength of welded joint and tensile strength of the unwelded parent metal.The joint efficiency of GMAW joints is approxi-mately49%and the joint efficiency of GTAW joints is 63%.Of the three types of welded joints,the joints fabricated by FSW exhibited a relatively higher joint efficiency(74%),and the joint efficiency is34%higher compared to the GMAW joints and15%higher compared to GTAW joints.
3.2Hardness
The hardness across the weld cross section was measured using a Vickers Micro-hardness testing machine,and the values are presented in Table4.The hardness of base metal (unwelded parent metal)in its initial T6condition is 105VHN.However,the hardness of the GMAW and GTAW joints in the weld metal region is58VHN and 70VHN respectively.This suggests that the hardness is reduced by47VHN and35VHN in the weld metal region of GMAW and GTAW joints,respectively due to welding heat and the usage of lower hardness filler metal(Al-5%Si). However,the FSW process increases the hardness to some extent in the weld metal region,and the hardness of the FSW joints in the weld metal region is85VHN.The hardness of FSW is85VHN,which is relatively higher,compared to GMAW and GTAW joints,and compared with the parent metal,the hardness is reduced by20VHN.This may be due to dissolution or growth of strengthening precipitates during the welding thermal cycle.However FSW exhibited higher hardness compared to GMAW and GTAW joints due to shear stresses induced by tool motion which lead to the generation of a very fine grain structure,which allows a partial recovery of hardness values.
3.3Microstructure
Microstructure of all the joints was examined at different locations,but most of the tensile specimens failed in the weld metal region,and the optical micrographs taken at the weld metal region alone are displayed in Fig.3for comparison purpose.The base metal contains coarse and elongated grains with uniformly distributed very fine precipitates(Fig.3a).The fusion zone of GMAW (Fig.3b)and GTAW(Fig.3c)joints contain dendritic structure and this may be due to the fast heating of base metal and fast cooling of molten metal due to welding heat. The only difference between these two dendritic structures is the dendrite arm spacing.The spacing is marginally wider in GMAW joint and narrower in GTAW joint. However,the weld region of FSW joint(Fig.3d)contains very fine,equiaxed grains and this may be due to the dynamic recrystallisation that occurred during FSW pro-cess.Macrostructure of the joints are displayed in Fig.4.
3.4Fracture surface
The tensile specimen,before and after testing,are displayed in Fig.5.In all the specimens,the location of failure is in
Table4Transverse tensile properties of welded joints
Joint Type Yield
strength
(MPa)
Ultimate tensile
strength(MPa)
Elongation
(%)
Reduction
in c.s.a(%)
Notch tensile
strength(MPa)
Notch strength
ratio(NSR)
Joint
Efficiency
(%)
Weld region
hardness
(VHN)
GMAW1411638.4 5.80175 1.07348.8058 GTAW18821111.88.26228 1.09162.5770 FSW22424814.29.56279 1.12574.2585
the weld metal region only.The fractured surface of tensile
specimens of welded joints was analyzed using SEM to reveal the fracture surface morphology.Figures 6and 7display the fractographs of unnotched and notched tensile specimens,respectively.The displayed fractographs invari-ably consist of dimples,which are an indication that most of the tensile specimens failed in a ductile manner under the action of tensile loading.An appreciable difference exists in the size of the dimples with respect to the welding processes.An intergranular fracture feature has been observed in GMAW joints (Figs.6a and 7a).This may be
due to the combined influence of a coarse grained weld metal region and a higher amount of precipitate formation at the grain boundaries.Coarse dimples are seen in GTAW joints (Figs.6b and 7b)and fine dimples are seen in FSW joints (Figs.6c and 7c).Since fine dimples are a characteristic feature of ductile fracture,the FSW joints have shown higher ductility compared to all other joints (Table 4).The dimple size exhibits a directly proportional relationship with strength and ductility,i.e.,if the dimple size is finer,then the strength and ductility of the respective joint is higher and vice versa [16].
a GMAW
b GTAW
c FSW
d Bas
e metal
50 μm
50 μm
50 μm
50 μm
Fig.3Optical micrographs of weld metal region
a GMAW
b GTAW
c FSW
Fig.4Macrostructure of welded joints
4Discussion
Transverse tensile properties of the welded joints presented in Table 4indicate that the FSW joints are exhibiting superior tensile properties compared to GMAW and GTAW joints.During tensile test,all the specimens invariably failed in the weld region (Fig.4).This indicates that the weld region is comparatively weaker than other regions and hence the joint properties are controlled by weld region chemical composition and microstructure.
The higher strength of the base metal is mainly attributed to the presence of alloying elements such as silicon and magnesium and these two elements combine and undergo precipitation reaction and form a strengthening precipitate of Mg 2Si.Fine and uniform distribution of these precip-itates throughout the aluminium matrix provides higher strength and hardness to these alloys [17].When these alloys are welded using non-heat treatable filler metals (Al-5%Si)to avoid solidification cracking problem,the weld region is composed of fewer Mg 2Si precipitates when compared to base metal [18].In fusion welding,the dilution of base metal in weld metal is a common phenomenon.Even though,a large amount of silicon is available (available in base metal and filler metal)for precipitation reaction,the available magnesium (available in base metal alone)in the molten weld pool for the precipitation reaction is very low.Hence,the weld region of AA6061aluminium alloy,when welded with AA4043filler metal usually contains a lower amount of Mg 2Si precipitates compared to the base metal region.In the weld region of GMAW and GTAW joints,there is a depletion of Mg 2Si precipitates due to above said reasons [19].On the other hand,the weld region of the FSW joint contains the alloying elements similar to that of base metal (Table 1a).In FSW,there is no filler metal addition,and there is no melting of base metal.Hence there is no dilution of alloying elements in the weld region.The base metal is plastically stirred under the action of the rotating tool.Due to this severe plastic deformation,the coarse elongated grains are fragmented into fine,equiaxed grains,and coarse strengthening precipitates are fractured into very fine uniformly distributed particles in the friction stir processed zone [20].Ying chun chen et al.,[19]opined that during higher rotation speeds,particles would suffer more fragmentation.The metastable precip-itates will be dissolved and solutionized in the aluminium matrix during FSW,but the stable precipitates remained and are prone to segregate in the high-strain region [21].Fonda et al.[22]reported that as the rotational speed increased,and the temperature within the nugget becomes higher and more uniform,the volume fraction of coarse second
phase
Fig.5Fracture location of tensile specimens
particles decreased at different positions within the nugget zone region.The fracture location therefore corresponds to the region with the least precipitate strengthening.As the peak temperature during FSW was about400°C for this alloy and was not sufficient to force stable precipitates to dissolve and solutionize into the aluminium matrix.In the weld region of FSW joints,there is no possibility of depletion of Mg2Si precipitates as in the case of GMAW and GTAW joints.
The grain size of the weld region also plays a major role in deciding the joint properties.The grain size of the weld region is influenced by the heat of the welding process.Of the three welding processes used in this investigation to fabricate the joints,the GMAW process has higher heat input compared to the GTAW and FSW processes[23]. Since GMAW is a consumable electrode process,the filler metal is always connected to positive(reverse)polarity of the direct current(DCRP).This leads to a large amount of heat generation(approximately two-thirds of total heat generation)at the filler metal end.Further,a current of190
A is passing through a small diameter of filler metal
(1.6mm),and the current density is very high in the GMAW process.Much heat generation and very high current density combine to enhance the arc temperature and arc forces[24].Very high arc temperature increases the peak temperature of the molten weld pool causing a slow cooling rate.This slow cooling rate,in turn,causes relatively wider dendritic spacing in the fusion zone.These microstructures generally offer lower resistance to indenta-tion and deformation and this may be one of the reasons for lower hardness and inferior tensile properties of GMAW joints.
In GTAW,the alternating current(AC)polarity is used, and the high heat generation end is continuously changing (50times in one second).Whenever,the electrode becomes positive,more heat is generated(two-thirds of total heat)at this end.Similarly,whenever the workpiece becomes positive,more heat is generated at this end.In one half of a cycle,electrode attains maximum heat and in the other half of a cycle,the workpiece attains minimum heat,and this will change in the next cycle[25].So,while using alternating current,the maximum heat generation end is not fixed as in the case of GMAW.However,in both processes, the heat energy from the arc is utilized to melt the
filler
metal as well as to melt the base metal.However in GTAW, the filler rod is melted in the plasma region of the arc(midway between positive and negative polarity)and not in the positive polarity as in the case of GMAW.Due to this reason,heat input of GTAW is lower than for GMAW.Lower heat input and lower current density reduces the arc temperature and arc forces in GTAW[26].Lower arc temperature reduces the peak temperature of the molten weld pool causing fast cooling.This fast cooling rate,in turn,causes relatively narrower dendritic spacing in the fusion zone.These micro-structures generally offer improved resistance to indentation and deformation and this may be one of the reasons for higher hardness and superior tensile properties of GTAW joints compared to GMAW joints.
In FSW,the heat generation beneath the rotating tool is always in the order of400°C and hence there is no possibility of formation of a molten weld pool[27].Tang et al.[28]reported that when the process parameters are changed,the temperature field was then changed simulta-neously.However,the variations of the temperature values are limited by the melting point of the welding material and the maximum temperature ranges from80%to90%of the melting point.It implies that the variation of process parameters does not affect the temperature field significant-ly although a relation between the temperature field and process parameters exists[29].Colegrove et al.[30]opined that the effect of changing the welding or rotation speeds on the peak temperature is small,for conditions that produce sound welds.Zhang et al.[31]investigated the effect of axial pressure in friction stir welding of AA6061alumin-ium alloy and reported that the maximum temperature and plastic contribution to the temperature field can be increased with an increase in the axial pressure.Due to the frictional heat generated between the tool shoulder and the base metal,the material under the action of the rotating tool attains a plastic state.The axial force applied through the rotating tool causes the plasticized metal to extrude around the tool pin in the vertical direction and get consolidated in the back side when the tool moves forward. Both the stirring and extrusion causes the elongated grains to fragment into smaller grains and fractures the strength-ening precipitates into very fine
particles.
Su et al.[32]confirmed that during FSW the original base metal grain structure is completely eliminated and replaced by a very fine equiaxed grain structure in the FSP zone.They opined that it was unlikely that the dynamic recrystallisation occurred via a conventional discontinuous process during FSW.In the more conventional context, recrystallisation proceeds by nucleation and growth of new grains surrounded by high angle boundaries.However,the microstructural evidence in their study did not support conventional grain nucleation with high angle grain boundaries,nor grain boundary migration as required by a discontinuous dynamic recrystallisation mechanism.Rather, it appeared that a continuous dynamic recrystallisation process was the primary mechanism.In friction stir processed(FSP)AA7075alloy,Ma and Mishra[33]made three important observations using TEM micrographs:(i) the fine precipitates were uniformly distributed within the interior of grains and at the grain boundaries(ii)while the grain boundary particles usually exhibited a needle or disc type morphology,the precipitates inside the grains gener-ally had an equiaxed shape;(iii)the precipitates in the FSP zone were fine and generally had a size of<0.5μm.This may be one of the reasons for superior tensile properties of FSW joints compared to GMA and GTA welded joints.
5Conclusions
In this paper,the mechanical properties of GMAW,GTAW and FSW joints of AA6061aluminum alloy were evaluat-ed.From this investigation,the following important con-clusions have been derived:
(i)Of the three welded joints,the joints fabricated by
FSW process exhibited higher strength values and the enhancement in strength value is approximately34% compared to GMAW joints,and15%compared to GTAW joints.
(ii)Hardness is lower in the weld metal(WM)region compared to the HAZ and BM regions irrespective of welding technique.Very low hardness is recorded in the GMAW joints(58VHN)and the maximum hardness is recorded in the FSW joints(85VHN). (iii)The formation of fine,equiaxed grains and uniformly distributed,very fine strengthening precipitates in the weld region are the reasons for superior tensile properties of FSW joints compared to GTAW and GMAW joints. Acknowledgements The authors are grateful to the Department of Manufacturing Engineering,Annamalai University,Annamalainagar, Tamil Nadu,India for extending the facilities of Metal Joining Laboratory and Materials Testing Laboratory to carryout this investigation.The authors also wish to express their sincere thanks to Aeronautical Research&Development Board(ARDB),Ministry of Defence,New Delhi for the financial support to carryout this investigation through sponsored project No.DARO/08/1061356/M/I. Appendix-1
Heat input calculations of processes used
Gas metal arc welding
Heat Input?V?I?η?60
S?1000
?190?20?0:75?60
110?1000
?2:021kJ=mm
Gas tungsten arc welding
Heat Input?V?I?η?60
S?1000
?175?20?0:75?60
130?1000
?1:212kJ=mm
Where V-V oltage in volts,I-Current in Amps,η-Arc efficiency is assumed as0.75for GMAW and GTAW[34] Friction stir welding
The heat input for friction stir welding process can be calculated as[35]
q?2π
3S
?μ?p?ω?R S?η
?2π
3?1:25
?0:3?7?26:6?0:009?0:8
?0:84KJ=mm
Where,
μ-Co-efficient of friction,P-Normal force in kN,ω-Rotational speed in rev/sec
R s-Shoulder radius in m,S-Welding speed in mm/s. References
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505调节系统中文说明书
引言 505/505E是以微处理器为基础的调速器，适用于单执行机构或双执行机构的汽轮机控 制。调速器采用菜单驱动软件以引导现场工程师根据具体的发电机或机械驱动应用要求对调速器进行编程组态。本说明书主要介绍调速器的工作原理、系统构成、面板操作。由于英文版手册存在不断增加和更改内容等方面的因素，使用woodward 505/505E 时，还请 参考随调速器提供的woodward正式英文版手册。 二、505/505E 的工作原理及系统介绍 505/505E电子调节器比一般液压系统控制精度高，自动化水平大大提高，热电负荷 自整性也高，它能实现升速（手动或自动），配合电气并网，负荷控制（阀位控制或功频控制），抽汽热负荷控制及其它辅助控制，并与DCS通讯，控制参数在线调整和超速保护功能等。能使汽轮机适应各种工况并长期安全运行。 2.1基本原理 并网前在升速过程中，转速闭环为无差控制，505/505E控制器将测量的机组实际和给 定转速的偏差信号经软件分析处理及PID运算后输出标准电流信号给电液转换器，电液转 换器接受调节器输出的标准电流信号，输出与输入电流信号相对应的调节信号油压。调节 信号油压经液压伺服机构放大，控制油动机活塞移动，通过调节杠杆，改变调节汽阀的开 度，调节汽轮机高压段、低压段的进汽量。从而减少转速偏差，达到转速无差控制，当转速达到3000r/min，机组可根据需要定速运行，此时505/505E可接受自动准同期装置发出的或运行人员手动操作指令，调整机组实现同步，以便并网。 机组并网后，如果采用功率闭环控制，可根据需要决定505/505E使机组立即带上初
负荷，DEH实测机组功率和机组转速作为反馈信号，转速偏差作为一次调频信号对给定功 率进行修正，功率给定与功率反馈比较后，经PID运算和功率放大后，通过电液转换器和 油动机控制调节阀门开度来消除偏差信号，对机组功率实现无差调节，若功率不反馈，则以阀位控制方式运行，即通过增加转速设定，开大调节汽阀，增加进汽量达到增加负荷的目的。在甩负荷时，505/505E自动将负荷调节切换到转速调节方式。机组容量较小时建议可不采用功率闭环控制。 在机组带上一定电负荷后可根据需要带热负荷，投入抽汽控制。505/505E控制器根据 机组工况图对机组电负荷及抽汽压力进行自整控制。 2.2 505/505E 系统构成 505/505E是基于32位微处理器控制用的数字控制器。它集现场组态控制和操作盘于一体。操作盘包括一个两行（24个字符）显示，一个有30个操作键的面板，操作盘用来组态505/505E，在线调整参数和操作汽轮机起停及运行。通过操作面板上的两行液晶屏可观察控制参数的实际值和设定值。 控制回路/ / 505/505E 控制器内有三个相互独立的控制器通道：转速/负荷控制PID 回路、辅助控制PID回路、抽汽控制PID回路。前两者通过低选输出，另外有一个PID控制回路可串接在转速控制回路上用于串级控制。其通讯接口有三种。控制器有三种操作模式：程序模式、运行模式和服务模式，程序模式用于组态控制器的功能以适合具体的控制要求，程序模式一旦组态后不再改变，直至需要改变控制功能时。运行模式主要用于操作汽轮机启动正常运行至停机整个控制过程。服务模式可以在运行状态修改参数，根据具体汽轮机控制需要通过编程组态于相应的系统。 输入及输出//本系统控制器有两个控制回路输出4-20mA,负载能力为360ohm,同
低频治疗仪工作原理介绍
低频治疗仪工作原理介绍 现代人颈椎病的发病率相当高，颈椎病 的病理特征：颈椎生理曲度改变、错位、骨 骼变形增生，损伤型炎症，颈椎间盘突出， 水肿等。这样就必然压迫颈椎附近丰富的血 管、神经丛及其他组织。引起一系列症状， 发生各种病变。因此，颈椎病也叫颈椎综合 症。 而目前治疗颈椎病的最好选择就是 低频治疗仪了。 低频治疗仪是目前国际上最为先进，应用率最高，人体反映效果最好的一种家庭、个人保健理疗产品。 低频治疗仪可以瞬态将功率谱的能量按照一定的调制特性集中与扩散，非常逼真的模拟出真人捶背、敲打、按摩、推拿、针灸以及火罐的实际感觉。 低频治疗仪如果作用在经络穴位上，能够十分有效地治疗以及缓解各种病痛，经常有计划地使用低频治疗仪可以置于许多慢疾病甚至顽症，工作之余和工作之中也可以使用低频治疗仪进行按摩，舒畅心身。 低频治疗仪是根据针灸捻转留针得气的感觉形成的超低频作用，又结合具有高能量分布的脉冲，按照人体刺激能够形成的种种感觉的谱线，模拟分布进行低频调制，从而刺激经穴地反射效果形成闭环感觉以达到真实的治疗方式与效果。 低频治疗仪工作原理介绍 现代人颈椎病的发病率相当高，颈椎病的病理特征：颈椎生理曲度改变、错位、骨骼变形增生，损伤型炎症，颈椎间盘突出，水肿等。这样就必然压迫颈椎附近丰富的血管、神经丛及其他组织。引起一系列症状，发生各种病变。因此，颈椎病也叫颈椎综合症。 而目前治疗颈椎病的最好选择就是低频治疗仪了。 低频治疗仪是目前国际上最为先进，应用率最高，人体反映效果最好的一种家庭、个人保健理疗产品。 低频治疗仪可以瞬态将功率谱的能量按照一定的调制特性集中与扩散，
非常逼真的模拟出真人捶背、敲打、按摩、推拿、针灸以及火罐的实际感觉。 低频治疗仪如果作用在经络穴位上，能够十分有效地治疗以及缓解各种病痛，经常有计划地使用低频治疗仪可以置于许多慢疾病甚至顽症，工作之余和工作之中也可以使用低频治疗仪进行按摩，舒畅心身。 低频治疗仪是根据针灸捻转留针得气的感觉形成的超低频作用，又结合具有高能量分布的脉冲，按照人体刺激能够形成的种种感觉的谱线，模拟分布进行低频调制，从而刺激经穴地反射效果 各种中低频家用治疗仪工作原理 治疗原理人体被称为支柱的脊髓的中心在统治和操纵的脊髓神经是利用磁力﹑指压﹑温热﹑拔罐﹑针灸﹑低频的科学原理，对脊椎进行矫正，并圆活脏器官的组合型低频脉冲治疗仪。 指压的原理人体部神经和主要血液交会的位置叫经穴。共有365个。经穴是针﹑针灸﹑指压的位置，在这些位置上施加压力，可起到对各种疾病的治疗作用。新进CHAOS的6个温球正是利用这样的指压原理。新进CHAOS的6个温球通过调整高度和宽度，对准经穴，使用适当的压力，压住经穴，可起到缓解紧神经，排除淤血的作用。 灸的原理古代的时候，人们把艾草或石头，放在穴位上加热，来松弛神经，消除淤血，缓解痛症，促进血液循环，从而达到了针灸的作用。新进CHAOS正是利用这种针灸的原理，使温球温度控制在30-70度之间，加适当的热度在经穴上，利用简单又方便的热原理，得到了针灸的效果。 针灸的原理新进CHAOS利用了针灸的原理与最近使用的激光无痛苦作手术的光线针一样，新进CHAOS也利用远红外线的原理在穴位上无痛苦注射远红外线针。 脊椎矫正的原理随着时代的发展，人类的生活环境也随之改变，生活的无秩序和工作围的制约，导致人长期保持一个姿势或动作，可能会维持不了脊椎的正常状态，导致人体的脊椎变形。新进CHAOS对这种不正常的脊椎状态，通过温热﹑指压相加的温球对各部位的脊椎实施按摩并予以矫正。
电力系统低频振荡的产生原因及危害性
电力系统低频振荡的产生原因及危害性(图文) 2010-10-23 10:28:14 互联网浏览： 1111 发布评论( 0) 介绍电力系统低频振荡的产生原因及危害性、PSS的基本原理、参数、作用及现场试验过程，并对实验结果进行探讨。 关键词：低频振荡励磁调节器电力系统稳定器(PSS) 1 前言 天津大唐盘山发电有限责任公司是装机容量为2×600MW的新建大型火力发电厂，它同原有天津国华盘山发电有限责任公司的2×500MW俄罗斯汽轮机组构成一个电源点，经三条500KV线路向系统送电，地处京津唐负荷中心，对电网稳定起着重要的支撑作用。作为京津唐电网最大的发电机组，其发电机励磁系统性能的优劣对华北电网的稳定运行具有举足轻重的影响。 根据国家十五计划实现全国联网的要求，华北电网规定，新建大型发电机组励磁系统应有系统稳定措施并调整好后才能并网运行，为此我厂先后完成了对3#、4#机组的电力系统稳定器(PSS)定值整定和试验工作,实验效果明显。应国家电力调度中心要求，2003年6月18日，在华北电力调度局方式处的组织下PSS正式投入运行。 2 低频振荡产生原因分析及危害性 电力系统低频振荡在国内外均有发生，通常出现在远距离、重负荷输电线路上，或者互联系统的弱联络线上，在采用快速响应高放大倍数励磁系统的条件下更容易出现。随着电力电子技术的快速发展，快速励磁调节器的时间常数大为减少，这有效地改善了电压调节特性，提高了系统的暂态稳定水平。但由于自动励磁调节器产生的附加阻尼为负值，抵消了系统本身所固有的正阻尼，使系统的总阻尼减少或成为负值，以至系统在扰动作用后的功率振荡长久不能平息，甚至导致自发的低频振荡，低频振荡的频率一般在0.2-2Hz之间。(风险管理世界-) 低频振荡会引起联络线过流跳闸或系统与系统或机组与系统之间的失步而解列，严重威胁电力系统的稳定。解决低频振荡问题成为电网安全稳定运行的重要课题之一。 3 PSS原理及其作用 为了既能利用高放大倍数的励磁调节器又能避免其负阻尼效应，人们对传统励磁系统进行了改进。对一个可能引起负阻尼的励磁调节器，向其中注入某些附加控制信号，使之可以提供正的阻尼，平息振荡，这就是PSS最
505操作说明
505操作说明 一、505一般介绍 （一）505转速控制器的键盘和显示器 505转速控制器的操作屏由操作面板上的键盘和显示器组成。显示器具有二行，每行显示14个字符，用于以英文显示运行参数和故障报警查向参数。此外，还有30个键，提供丁505调速面板上的全部操作。汽轮机的控制操作不需要附加的控制屏，每个汽轮机控制功能都能通过505转速控制器的面板执行。 （二）505键盘上：各个键的功能 1）键盘中央的大菱形键，在其四个角上带有箭头。 ←→(左右翻动)使编程或运行方式下的功能块显示左移或右移。 ↑↓ (上下翻动)使编程或运行方式下的功能块显示上下移动。2）SELECT(选择键) 选择键用于505显示器上行或下行变量的选择控制。@符号用于指出哪一行(变量)能通过调整键ADJ来进行调整。只有当上、下行都为可调变量时，SELECT键和@符号才能起作用。当显示器只显示一个变量时，SELECT 键和@符号的位置将不起作用。 3）ADJ(调整键) 在运行方式中，“▲”增大可调参数，“▼”减少可调参数。 4）PRGM(编程键) 当505处于跳车状态或停机状态时，用该键选择编程方式。在运行方式中，该键用于选择程序临视方式。在程序临视方式中，能浏览所编制的程序但不能修改。 5）RUN(运行键) 从505画面显示(CONTROLLING PARAMETR／PUSH RUN OR PRGM)状态触发汽轮机运行即启动指令。 6）STOP(停止键) 一旦予以确认，触发汽轮机控制停机(运行方式)。能过通过服务方式设定值(在“键选择”下来取消“STOP”指令。
7）RESET(复位键) 对运行方式的报警和停机状态作复位／清除。在停机后按该键还可使调速器返回到(CONTROLLING PARAMETR／PUSH RUNORPRGM)状态。 8）O／NO： 输入O／NO或退出。 9）1／YES： 输入1／YES或投入。 10)2／ACTR(执行机构)： 输入2(编程方式)或显示执行机构位置(运行方式)，按“下翻箭头”显示输入执行机构的电流。 11)3／CONT(控制参数)： 输入2(编程方式)或显示控制参数(运行方式)，按“下翻箭头”显示505的最近—次跳车原因、达到的最高转速和就地／远程状态。 12)4／CAS(串级控制)： 输入4或显示串级控制信息(运行方式)，未使用。 13) 5／RMT<远程控制)： 输入5或显示远程转速给定值控制信息(运行方式)。 14) 6／LMTR(阀位限制器)： 输入6或显示阀位限制器信息。 15) 7／SPEED： 输入7或显示就地转速值(二选一，选最高值)和转速设定值。 16) 8／AUX(辅助)： 输入8或显示辅助控制信息(运行方式)。 17) 9／KW(负荷)： 输入9或显示KW／负荷或第一级压力信息(运行方式)。 18)CLEAR：
二类医疗器械明细表
6810矫形外科（骨科）手术器械 6815注射穿刺器械 6821医用电子仪器设备 6821医用电子仪器设备无创医用传感器无创医用传感器II 6821医用电子仪器设备心电诊断仪器单导心电图机、多导心电图 机、胎儿心电图机、心电向量 图机、心电图综合测试仪、晚 电位测试仪、无损伤心功能检 测仪、心率变异性检测仪、心 电分析仪、运动心电功量计、 心电多相分析仪、心电遥测 II 分类名称名称品名举例管理分类6815注射穿刺器械注射穿刺器械玻璃注射器II
仪、心电电话传递系统、实时心律分析记录仪、长程心电记录仪、心电标测图仪、心电工作站 6821医用电子仪器设备脑电诊断仪器脑电图机、脑电阻仪、脑电波 分析仪、脑地形图仪、脑电实 时分析记录仪 II 6821医用电子仪器设备肌电诊断仪器肌电图机II 6821医用电子仪器设备其他生物电诊断仪器眼动图仪、眼震电图仪、视网 膜电图仪、诱发电位检测系统 （含视、听、体） II 6821医用电子仪器设备电声诊断仪器听力计、小儿测听计、心音图 仪、舌音图仪、胃电图仪、胃 肠电流图仪 II 6821医用电子仪器设备无创监护仪器病人监护仪（监护参数含心 电、血氧饱和度、无创血压、 脉搏、体温、呼吸、呼吸末二 氧化碳）、麻醉气体监护仪、 呼吸功能监护仪、睡眠评价系 统、分娩监护仪 II 6821医用电子仪器设备呼吸功能及气体分析测定装 置 综合肺功能测定仪、呼吸功能 测试仪、氧浓度测定仪、肺通 气功能测试仪、CO2浓度测 定仪、肺内气体分布功能测试 仪、弥散功能测试仪、氮气计、 微量气体分析器、压力型容积 描绘仪、肺量仪 II 6821医用电子仪器设备医用刺激器声、光、电、磁刺激器II 6821医用电子仪器设备血流量、容量测定装置脑血流图仪、阻抗血流图仪、 电磁血流量计、无创心输出量 计、心脏血管功能综合测试仪 II 6821医用电子仪器设备电子压力测定装置电子血压脉搏仪、动态血压监 护仪 II
低频电疗法实验报告
低频电疗法实验报告 第十九章低频电疗法 第十九章低频电疗法 一、学习要点 1.掌握感应电疗法、功能电刺激、经皮电刺激疗法的治疗作用、适应证、禁忌证及操作方法。 2.熟悉低频电流的作用、感应电疗法、功能电刺激、经皮电刺激疗法的定义、功能电刺激、经皮电刺激疗法的治疗原理。 3.了解感应电疗法、功能电刺激、经皮电刺激疗法的物理特性。 二、内容要点 【概述】 感应电流又称法拉第电流，应用这种电流治疗疾病的方法，称为感应电疗法。 (一)低频电流的生理作用和治疗作用 1. 兴奋神经肌肉组织 2. 镇痛 3. 促进局部血液循环 (二)参数及其意义 1.频率(f) 每秒钟内脉冲出现的次数，即为频率。 2.周期(T) 一个脉冲波的起点到下一个脉冲波的起点相距的时间，即为周期。 3.波宽每个脉冲出现的时间，即为波宽。 4.波幅由一种状态变到另一种状态的变化量。 5.脉冲间歇时间即脉冲停止的时间，等于脉冲周期减去脉冲宽度的时间。 6.通断比是指脉冲电流的持续时间与脉冲间歇时间的比例。
7.占空因素是指脉冲电流的持续时间与脉冲周期的比值。 8.常见低频电流波形方波、三角波、调制波。 【感应电疗法】 (一)物理特性 感应电是用电磁感应原理产生的一种双相、不对称的低频脉冲电流。感应电流的两相中，主要有作用的时高尖部分，其低平部分由于电压过低而常无生理的治疗作用。 (二)生理作用和治疗作用 1.感应电流的生理作用 (1)电解作用不明显 (2)有兴奋正常神经和肌肉的能力 2.感应电的治疗作用 (1)防治肌萎缩 (2)防治粘连和促进肢体血液和淋巴循环 (3)止痛:感应电刺激穴位或病变部位，可降低神经兴奋性，产生镇痛效果。 (三)治疗技术 1.设备感应电疗法的仪器(感应电流电疗机)、导线、金属电 极板、衬垫以及电极固定用品均与直流电疗法基本相同。 2.治疗方法 (1)固定法:两个等大电极并置于病变两侧或两端或在治疗部位对置或主电极置神经肌肉运动点，副电极置有关肌肉节段区。 (2)移动法:手柄电极或滚动电极在运动点，穴位或病变区移动刺激(也可固定作用断续刺激);另一片状电极置相应部位固定。
505调速器说明书
一、引言 505/505E是以微处理器为基础的调速器，适用于单执行机构或双执行机构的汽轮机控制。调速器采用菜单驱动软件以引导现场工程师根据具体的发电机或机械驱动应用要求对调速器进行编程组态。本说明书主要介绍调速器的工作原理、系统构成、面板操作。由于英文版手册存在不断增加和更改内容等方面的因素，使用woodward505/505E时，还请参考随调速器提供的woodward正式英文版手册。 二、505/505E的工作原理及系统介绍 505/505E电子调节器比一般液压系统控制精度高，自动化水平大大提高，热电负荷 自整性也高，它能实现升速（手动或自动），配合电气并网，负荷控制（阀位控制或功频 控制），抽汽热负荷控制及其它辅助控制，并与DCS通讯，控制参数在线调整和超速保护 功能等。能使汽轮机适应各种工况并长期安全运行。 2.1基本原理 并网前在升速过程中，转速闭环为无差控制，505/505E控制器将测量的机组实际和给定转速的偏差信号经软件分析处理及PID运算后输出标准电流信号给电液转换器，电液转换器接受调节器输出的标准电流信号，输出与输入电流信号相对应的调节信号油压。调节信号油压经液压伺服机构放大，控制油动机活塞移动，通过调节杠杆，改变调节汽阀的开度，调节汽轮机高压段、低压段的进汽量。从而减少转速偏差，达到转速无差控制，当转速达到3000r/min，机组可根据需要定速运行，此时505/505E可接受自动准同期装置发出的或运行人员手动操作指令，调整机组实现同步，以便并网。 机组并网后，如果采用功率闭环控制，可根据需要决定505/505E使机组立即带上初负荷，DEH实测机组功率和机组转速作为反馈信号，转速偏差作为一次调频信号对给定功率进行修正，功率给定与功率反馈比较后，经PID运算和功率放大后，通过电液转换器和油动机控制调节阀门开度来消除偏差信号，对机组功率实现无差调节，若功率不反馈，则以阀位控制方式运行，即通过增加转速设定，开大调节汽阀，增加进汽量达到增加负荷的目的。在甩负荷时，505/505E自动将负荷调节切换到转速调节方式。机组容量较小时建议可不采用功率闭环控制。 在机组带上一定电负荷后可根据需要带热负荷，投入抽汽控制。505/505E控制器根据机组工况图对机组电负荷及抽汽压力进行自整控制。
维廉科技{脑反射治疗仪}功能及效果测评讲解
维廉科技【脑反射治疗仪】功能及效果测评面对失眠，人们对药物的信任度已逐渐降低，特别是对传统的安眠药。虽然安眠药一向以见效快著称，但长期服用后造成的依赖成瘾和对身体上一系列显著或潜在的副作用，仍为广大失眠人群所诟病。在几乎所有安眠药成为固定处方药后，美国联邦药监局FDA甚至向广大失眠患者发出呼吁：安眠药，特别是常见的右佐匹克隆服用量应减少为常规的三分之一，最直接的原因是其服用后会影响到次日开车及其他行为，发出这一公告其实也在意料之中。 小编作为资深失眠人士，现在为大家介绍一款专门治疗失眠的仪器——脑反射治疗仪。这款仪器是目前失眠类专科医院临床上应用量最大的仪器，相信认识这款仪器后，安眠药不再是你唯一的选择。 产品名：维廉科技脑反射治疗仪 型号：WL-HA-3 生产厂家：上海维廉科技 产品尺寸：97×14×12MM 单机重量：200g 产品构成设计 卸掉外包装，仪器主要由一个主机，一副黑色眼罩和一副耳机构成，另配一纸单页和一本说明书，构造相对简单。 目测仪器外观尚属普通，主机呈长方形，一只手可操作，颜色偏暗但，材质为轻质的塑材，指下有温没有金属冰冷感，按键不算突兀。眼罩可调节长度，整体为塑材，戴上轻盈，没有压迫感。耳机分左右耳，较贴合耳廓。
按键设计分明，眼罩插孔在仪器上方，旁边便是亮度调节旋钮。右侧凸出的开关推钮，设计上算是小白版本，这也是考虑到各个年龄层的失眠人群。 右侧的插孔是耳机插孔，耳机设计上分左右耳，下面是调节声音的两个旋钮。主界面上有14个节目，其中针对失眠和强迫症的是两个节目，每个节目的设置均同时控制眼罩和耳机，节目停止后，眼罩的闪烁和耳机的声音均停止。这一点承袭了家用仪器操作的便利性。
电力系统低频振荡
第36卷第22期电力系统保护与控制Vol.36 No.22 2008年11月16日Power System Protection and Control Nov. 16, 2008 电力系统低频振荡 郭权利 （沈阳工程学院电气工程系，辽宁 沈阳 110136） 摘要：由于系统缺乏阻尼或系统负阻尼引起的输电线路上的功率波动频率一般在 0.1～2.0 Hz之间，通常称之为低频振荡。随着电力系统规模的不断扩大和快速励磁系统的大量应用，电网的低频振荡问题越来越引起人们的关注。低频振荡影响电力系统稳定性和继电保护装置的可靠性。介绍了低频振荡的一些概念、各种机理、研究现状、常用的分析方法和控制方法，并对以后的工作重点做了进一步的阐述。 关键词: 低频振荡；频率波动；负阻尼；分析方法 Low Frequency Oscillation in Power System GUO Quan-li （Electrical Engineering Department，Shenyang Institute of Engineering，Shenyang 110136，China） Abstract: Because of the lack of damping system or negative damping system on the transmission line caused power fluctuations generally between 0.1-2.0 Hz, usually called as low-frequency oscillations. With the development of the size of the power system and large applicationl of the rapid excitation system, the low-frequency oscillation (LFO) of the power system are causing for more and more concern. And low-frequency oscillation affect the stability of the power system and the reliability of the relay device. This text introduces the concept of low-frequency oscillations, all kinds of mechanism and research status, analysis and control methods, and elaborate the focus of the work for a further step. Key words: low-frequency oscillation; frequency fluctuating; negative damping; analysis method 中图分类号： TM711 文献标识码： A 文章编号： 1674-3415(2008)22-0114-03 0 引言 低频振荡产生的原因是由于电力系统的负阻尼效应，常出现在弱联系、远距离、重负荷输电线路上，在采用快速、高放大倍数励磁系统的条件下更容易发生。系统缺乏阻尼甚至阻尼为负，对应发电机转子间的相对摇摆，表现在输电线路上就出现功率波动，由系统缺乏阻尼或系统负阻尼引起的输电线路上的功率波动频率一般在 0.1~2.0 Hz之间，通常称之为低频振荡（又称功率振荡，机电振荡）。一般来说，电力系统振荡模式可分为两种类型：地区振荡模式和区域振荡模式，若系统低频振荡频率很低（0.1~0.5 Hz），则一般认为属互联系统区域间振荡模式。而如果振荡较高，在1 Hz以上，则认为是本地或区域间机组间的振荡模式[1]。对于地区振荡模式，振荡频率较高，参与的机组较少，因而只要在少数强相关机组上增加阻尼，就能显著地增加振荡模式的阻尼。对于区域振荡模式，振荡频率较低，参与的机组较多，因而只有在多数参与机组上增加阻尼，才能显著地增加振荡模式的阻尼。显然，抑制区域振荡模式的低频振荡要比抑制地区振荡模式的低频振荡更加复杂和困难，所以，系统运行中更容易发生区域振荡模式的低频振荡。 由于低频振荡影响着系统的安全稳定运行，并对继电保护装置动作行为产生相当大的影响，因而本文从低频振荡的一些概念和当前研究状况分析，总结了当前分析低频振荡问题的方法和进一步的研究方向。 1 低频振荡的负阻尼机理 电力系统受到扰动时，会发生发电机转子间的相对摇摆，表现在输电线上就会出现功率波动。如果扰动是暂时的，在扰动消失后，可能出现两种情况：一是发电机转子间的摇摆很快平息，二是发电机转子间的摇摆平息的很慢甚至持续增长，若振荡幅值持续增长，以致破坏了互联系统之间的静态稳定，最终将使互联系统解列。产生后者情况的原因是系统缺乏阻尼或者系统阻尼为负，现象表现为受
Zoom505-2效果Zoom505-2效果器使用说明书
Zoom505-2效果Zoom505-2效果器使用说明书 Zoom505-2效果Zoom505-2效果器使用说明书 一、原厂的24种音色 尽管鲜有人使用，但还是有必要说明一下，这是你进行各类音色设置的 最直接参照，在此基础上修改会事半功倍。 A组：1-适合于SOLO的失真？ 2-带延迟效果的原音？ 3-适合于节奏的失真？ 4-极度失真的重金属？ B组：1-适合SOLO的浅失真 2-带哇音的过载失真？ 3-带飘忽效果的原音？ 4-带和声效果的原音 C组：1-适合节奏的浅失真 2-带和唱效果的原音 3-重金属效果的失真 4-略带飘忽的电原音 D组：1-另外一种过载失真 2-带飘忽效果的FUNK 3-闪烁回音的浅失真 4-木吉他的仿真效果 E组：F组： （因进行了复杂设置，原厂音色记不清了，懒的再恢复，呵呵，大伙多原谅。） 二、演奏中变换音色的方法： 1、基本的：连接好以后，接通电源（或装电池，接上吉他即开。505没有电源开关。）根据需要踩（踩一下即可）踏板1或踏板2，你将看到组、号的逐次变换，这时，就出现了相应的音色。 非演奏中，比如分段录音时，还可以使用图1中的“组的更换键”，这样， 每次按一下，将变换一个组，而组号不变。 2、锁定音色 A、锁定一组：进入该组，按住“编辑键”，1秒钟后进入锁定组的状态， 再次按住，1秒钟后自动解锁。 B、缩定单一音色：同上，所不同的是按住“存储键”。 三、直通和调弦功能 将踏板1和踏板2同时踩下后，进入直通状态，此状态中可以调弦。 弹响一个音后，505将自动显示该音的首调唱名，同时，有一个闪烁 的小灯，这是该音的标准位置指示灯，其他闪动的灯与此平齐时，显 示的唱名和你的弹奏音音高一致。 我个人通常使用12品泛音+7品音调弦。 结束直通：随意踩下踏板1或踏板2（无须同时踩下）。 四、外接踏板的使用（图2-3的插孔说明） 这是一个很容易被忽视的地方，大伙普遍都认为505不值得外接踏板， 其实，它在这方面的性能还是很不凡的。因我的条件有限，只借了个踏板 简单的玩了一次，可能说的有错漏。
维廉科技 脑反射治疗仪 产品功能说明
维廉科技脑反射治疗仪产品功能说明 产品名：维廉科技脑反射治疗仪 型号：WL-HA-3 生产厂家：上海维廉科技 产品尺寸：97×14×12MM 单机重量：200g 产品构成设计 卸掉外包装，仪器主要由一个主机，一副黑色眼罩和一副耳机构成，另配一纸单页和一本说明书，构造相对简单。 目测仪器外观尚属普通，主机呈长方形，一只手可操作，颜色偏暗但，材质为轻质的塑材，指下有温没有金属冰冷感，按键不算突兀。眼罩可调节长度，整体为塑材，戴上轻盈，没有压迫感。耳机分左右耳，较贴合耳廓。
按键设计分明，眼罩插孔在仪器上方，旁边便是亮度调节旋钮。右侧凸出的开关推钮，设计上算是小白版本，这也是考虑到各个年龄层的失眠人群。
右侧的插孔是耳机插孔，耳机设计上分左右耳，下面是调节声音的两个旋钮。主界面上有14个节目，其中针对失眠和强迫症的是两个节目，每个节目的设置均同时控制眼罩和耳机，节目停止后，眼罩的闪烁和耳机的声音均停止。这一点承袭了家用仪器操作的便利性。
作用原理 从原理上讲，脑反射治疗仪与安眠药是类似的，两者均是作用于大脑较高的脑电波频率。安眠药均是通过口服进入人体肠胃吸收，肝肾解毒排毒，再通过血脑屏障作用于大脑，该过程几乎贯穿了人体所有的器官，会对身体造成伤害的同时，药物的功效也会大打折扣。维廉科技脑反射治疗仪采用的声光原理，红色正弦光和两耳差拍的白噪音共同牵引过高
的脑电波降低，从而达到一种睡眠的状态。从这上面来讲，脑反射治疗仪更无害，到达治疗病灶区也更直接。 体验时，安装四节五号电池，插上眼罩和耳机，打开开关，选择固定的节目，运行即可。初次使用略紧张，使用几分钟后，大脑便适应了，初始的紧张感渐渐消失，意识被声光带动，这种情况以往习惯性的睡前胡思乱想也不存在。特别注意的是耳机有两个声音，一种是类似火车或者风吹的声音，一种是流水鸟鸣的声音，听着比较放松，不是传统意义上的音乐疗法。
ZOOM505Ⅱ效果器中文说明
面板各部位名称（图1） ---------------------- | | A1 | | 存储键●| | 音色| |●+参数值（编辑时）/组的更换↑ | | | | | | | | 编辑键●|------| 灯|------|●-参数值（编辑时）/组的更换↓ | *|* | | 踏板1 | 踏板2 | ---------------------- 后侧各插孔意义（图2） --------------------------- | 1 2 3 4 | | ◎◎ ZOOM ◎◎| --------------------------- 1、→电吉他 2、→9V变压器电源 3、→外接踏板 4、输出插口→音箱或耳机 三、原厂的24种音色 尽管鲜有人使用，但还是有必要说明一下，这是你进行各类音色设置的最直接参照，在此基础上修改会事半功倍。
A组 1-适合于SOLO的失真2-带延迟效果的原音 3-适合于节奏的失真 4-极度失真的重金属 B组 1-适合SOLO的浅失真2-带哇音的过载失真 3-带飘忽效果的原音 4-带和声效果的原音 C组 1-适合节奏的浅失真 2-带和唱效果的原音 3-重金属效果的失真 4-略带飘忽的电原音 D组 1-另外一种过载失真 2-带镶边效果的FUNK 3-闪烁回音的浅失真
4-木吉他的仿真效果 E组、F组 进行了设置,原厂音色记不清了. 四、演奏中变换音色的方法 1、基本的 连接好以后，接通电源（或装电池，接上吉他即开。505没有电源开关。）根据需要踩（踩一下即可）踏板1或踏板2，你将看到组、号的逐次变换，这时，就出现了相应的音色。 非演奏中，比如分段录音时，还可以使用图1中的“组的更换键”，这样，每次按一下，将变换一个组，而组号不变。 2、锁定音色 A、锁定一组：进入该组，按住“编辑键”不放，2秒钟后进入锁定组的状态，再次按住不放，2秒钟后自动解锁。 B、锁定单一音色：同上，所不同的是按住“存储键”。 五、直通和调弦功能 将踏板1和踏板2同时踩下后，进入直通状态，此状态中可以调弦。弹响一个音后，505将自动显示该音的首调唱名，同时，有一个闪烁的小灯，这是该音的标准位置指示灯，其他闪动的灯与此平齐时，显示的唱名和你的弹奏音音高一致。
505控制器使用方法
505 控制器使用方法 一、505 控制器常用键功能： PRGM ——编程RUN ——运行RESET——复位 STOP――停止（需要按YES或NO键确认） F1――报警F2――超速实验［F2+ADJ （上升）］ SELECT——选择SPEED——速度 AUX——功率限制KW——功率（负荷）显示 CLEAR ――清除ENTER――回车（确认） EMERGENCY SHUTDOWN ――紧急停机 二、PRGM ――编程键一般情况下用户不能动，一般由厂家和DCS 设计单位联合来完成编程，编程时设计有密码。 三、通常模式下启动（505 面板操作） 通电一一505控制器自检（约1分钟）——自动跳到CONTROLLING PARAMETER——如果有报警（F1键红灯亮），按F1 键观察报警条目。报警包括（MPU FAILED 转速传感器故障、CASCADE INPUT FAILED 阀前压力传感器故障、KW INPUT FAILED 功率传感器故障、OVER SPEED超速等） 自动启动： 1. 启动前应按RESET 键复位报警，F1 红色灯熄灭，方可 启动。启动前保证主汽阀处于全关状态 2. 按RUN 键运行，505 转速设定值按照编制的程序上升到500rpm ，此时调节阀门逐渐全部打开。
3. 逐渐打开主汽阀冲转，当转速达到500rpm 设定值时，调节阀门回缩到某一稳定位置，505 接替控制，按预先编制的低暖机时间进行暖机。 4. 暖机时间达到时，505 自动控制转速上升到1200rpm，按预先编制的高速暖机时间进行暖机。 5. 暖机时间达到后，505 将自动控制转速越过临界转速而逐渐达到3000rpm 后稳定运行。 手动启动： 1. 启动前应按RESET 键复位报警，F1 红色灯熄灭，方可启动。启动前保证主汽阀处于全关状态。 2. 按RUN 键运行，505 转速设定值按照编制的程序上升 到500rpm ，此时调节阀门逐渐全部打开。 3. 目标转速设定：通过按SPEED 键找到SETPT 后，按ENTER 后，直接输入转速设定值，再按ENTER 确认，此时逐渐打开主汽阀，转速就会按照设定值进行升速。（此后每次转速目标值都如此进行设定） 4. 暖机时间设定：若需要延长暖机时间，可通过按SPEED 键找到STATUS后，按NO键终止自动顺序，从而人为延长暖机时间。当按SPEED 键找到STATUS 后，按YES 键又可以恢复到自动顺序控制状态，505 将按照编制好的程序继续自动控制。如果希望减短暖机时间，可通过SPEED键找到SETPT后，按方向键立刻提升或降
安思定失眠治疗仪采用CES疗法治疗抑郁症研究
经颅微电流刺激疗法辅助治疗抑郁症的疗效研究 魏英，杨忠，潘惠，赵胜军，方建忠 经颅微电流刺激疗法(cranial electrotherapystimulation，CES)是一种非创伤性治疗焦虑、抑郁和失眠等的非药物治疗方法，在美国已有几十年的历史，于2002 年引入我国，目前主要在精神科、心理科等临床推广。Shealy 等报道志愿者在使用CES 疗法后，脑脊液和血浆中神经递质发生变化，从而迅速有效地控制和缓解焦虑、抑郁、失眠等症状。另外杨启辉等在经颅微电流刺激仪的设计及其对α脑电波作用的研究中表明，CES 疗法在使用时能有效增强α脑电波的产生，从而缓解病症。因此，笔者采用CES 辅助治疗抑郁症，并观察其急性期疗效、安全性及对认知功能的影响。 1 资料与方法 1.1 一般资料 选取2011 年11 月至2013 年12 月我院门诊及住院患者80 例，均符合《中国精神障碍分类与诊断标准》第3 版(CCMD-3)抑郁症诊断标准;年龄16～68 岁，性别不限。。排除标准：有严重的躯体及脑器质性疾病者;已知的酗酒或其它活性物质滥用史;哺乳期、妊娠或妊娠可能的妇女;癫痫患者;体内植入电子设备如心脏起搏器或胰岛素泵的患者;对治疗不配合者。脱落标准：在治疗过程中出现难以耐受的不良反应者;原有抑郁症状加重、有自杀倾向及行为、转躁等则终止研究;在治疗中需电休克治疗者。全部患者采用随机排列表法分为2组各40 例： 1.2 方法 1.2.1 治疗方法2 组均给予抗抑郁药治疗，CES 组还给予CES 治疗。CES 组抗抑郁药种类：去甲肾上腺素。CES 治疗：采用南京好乐医疗科技有限公司提供的美国EPI 公司研发生产的CES 治疗仪(Alpha-Stim)。首先清洁患者耳垂皮肤，用导电液湿润耳夹上的小棉贴，将电极夹在两侧耳垂根部，打开电源开关，设置治疗时间和刺激强度(频率0.5 Hz、电流10~500 μA)，逐步增加强度直至出现一阵舒服的、微弱的针刺感。嘱患者放松，感受治疗效果。5 d 为一个疗程，每天1 次，每次20 min，每个疗程间休息2 d，每位患者接受4 个疗程治疗，共20 次。治疗期间禁止合并其他抗精神病药物、抗抑郁药、心境稳定剂及电抽搐治疗;禁用对试验有影响的系统心理治疗等。 2 结果 CES 组的不良反应出现频数为31 例次，不良反应多在2 周内出现，随着治疗延续，各种不良反应逐渐减轻并能耐受。2 组均未发现血象、心电图、肝肾功能明显改变。 3 讨论 抑郁症是一种常见的情感障碍性精神疾病，临床治愈与功能恢复是抑郁症治疗的主要目标，快速起效和早期治愈对预后有较好的预测作用，因此，起效快可以缩短抑郁症状导致的主观痛苦体验和改善认知功能损害，其次可以显著减少抑郁症患者的自杀风险，降低患者病
505操作简单介绍
操作指南 简介 键盘和显示器 505E的服务面板由调速器面板上的键盘和LED（发光二极管）显示器组成。LED显示器可以显示2行（每行24个字符），用来显示运行参数和故障检测参数，使用的语言是简单的英文。通过505E前面板上的30个按键可以实现全部的控制操作，操作控制透平时无需另外的控制面板，所有的透平控制功能都通过505E的前面板执行。 下面针对每个键的功能作以说明。具体有些说明请参见505E说明书操作流程图（第五章），里面详细介绍了每个功能键下的菜单，如何操作，请仔细阅读。 SCROLL（翻页键）：键盘中央的大菱形键，菱形的四个角上各标有一个箭头。 ?，?（左、右翻动）：在编程或运行模式下使功能块显示左、右移动。 ▲，▼（上下翻动）：在编程或运行模式下使功能块显示上、下移动。 SELECT（选择键）：用于505E显示器上行或下行变量的控制选择。符号@用于指示哪一行（变量）能通过调整变量（动态、阀门标定模式）时，才会使用SELECT键和@符号来决定哪一行的变量可北调整。当显示器上只有一个可调整参数时，SELECT键不能改变@符号的位置。 ADJ（调整键）：在运行模式下，▲增大可调参数，▼减小可调参数。 PRGM(编程键)：当调速器处于停机状态时，用该键可进入编程模式。当
调速器处于运行模式时，用该键可进入程序查看模式。在程序查看模式下，程序只能看，不能修改。 RUN（运行键）：当机组准备就绪后，按RUN键发出一个透平运行或启动的指令给505E. STOP（停止键）：一旦给予确认，触发透平控制停机（运行模式下）。通过服务模式设定（在“键选项”下）可以禁用STOP命令。 RESET（复位键）：用于复位、消除运行模式下报警和停机。在停机后按该键，还能使调速器返回到（Controlling Parameter /Push Run or Prgm）状态. 0/NO:输入0/NO:回退出。 1/YES:输入1/YES或投入. 2/ACTR(执行器):输入2或显示执行器位置(运行模式下). 3/CONT(控制参数):输入3或显示当前的控制参数(运行模式下);按“向下翻页”键显示调速器的最后一次跳闸原因、条件存在图的优先权（steam map priority）\达到的最高转速、就地/远程状态(如果使用的话). 4/CAS(串级)：输入4或显示串级控制信息（运行模式下）. 5/RMT(远程):输入5或者显示远传转速给定控制信息(运行模式下). 6/LMTR（阀位限制器）：输入6或者显示阀位限制器信息（运行模式下）。7/SPEED(转速)：输入7或显示转速控制信息（运行模式下）。 8/AUX(辅助)：输入8或显示辅助控制信息（运行模式下）。 9/KW(负荷)：输入9或显示KW/负荷或第一级压力信息（运行模式下）。
脑波仪使用说明
使用说明书 头带 USB连接线 PC 适配器 T2410连接线 驱动光盘 备用电极 使用说明书 安装驱动 连接方式 双击桌面上的NeuroHarmony图标运行 出现开始画面和音乐，随后出现第一个菜单，叫初始菜单。
图【1-1】初始画面 G 是神经反馈训练游戏程序菜单。 黄色M 是脑电波检测和分析程序菜单。 红色M 是冥想程序窗口。 C 是电脑通信端口设置菜单。点击下端的EXIT 可以退出程序。 《端口设置方法》 首先打开C(Config) ，选择连接端口。点击Auto Detect 会自动搜索选择COM1 到COM8。一般设定在COM1。
图【1-3】脑电波检测菜单 单击画面中的波形（）图案。 弹出脑电波检测程序窗口。先点击菜单中的钟表图标（）。钟表图标用于专测基础律动，每隔40秒会有一次响声，共测试2分钟。首先，睁开双眼检测，出现第一次响声闭上双眼，再次出现响声就睁开双眼。 单击菜单中的钟表图标（）。 就会出现脑电波检测画面。 A:原始脑电波B: 分带柱形曲线C: 3维功率谱 ①脑电波强度（mV）, ②频率（Hz）, ③时间（s），④现在时间和经过的时间
打开保存的BWD格式文件。 保存为BWD格式。 打开保存的TXT格式文件。 保存为TXT格式。 读取文件。 停止检测。 开始检测。 开始检测基础律动。 暂停检测。 1）检测 脑电波是非常细微的信号，所以检测仪要能够检测到非常微弱的信号。被检测者的移动或肌肉紧张，甚至电子信号也会测到。因此为了更精确的检测脑电波，环境是非常重要的。尽量在一个没有建筑的振动，没有家电产品引起的电子波干扰，无人员移动，安静的、宽敞的环境中检测是最理想的。另外适当的调节室内温度和湿度防止出汗。检测脑电波之前先检查周围环境。 把头带放在桌面上，电极朝上。 手不要放在桌上，不要冲击桌子，查看显示器上出现的柱形曲线的变化。 一般无任何信号全体显示深蓝色为正常。万一出现任何一个信号表示周围环境不符合脑电波的检测，或是头带的状态不良。 检查头带的方法如下。电极朝上放平，用2个手指同时接触中间的电极和靠近耳夹的电极，这时会显示左脑脑电波有强烈的信号。相反，用手指同时触碰中间和右边的电极，会显示右脑脑电波有强烈的信号。如果没有出现信号就说明了头带不良。 2）保存数据 现在开始保存测得的脑电波数据。在上面菜单中 点击图标（）终止检测。
WOODWARD_505_操作说明
WOODWARD 505 操作说明 一、概述 WOODWARD 505 是美国WOODWARD 公司专门为控制汽轮机研制生产的以微处理器为基础的数字式转速调节器。其特点是控制精度高、稳定性好、操作简便。可根据每一台汽轮机的特性、参数，以及应用场合，对505进行组态。其组态直接在WOODWARD 505面板上进行。 二.控制原理 WOODWARD505接受二个转速探头(SE)监测的汽轮机转速信号(频率信号), 与内部转速设定值比较，经转速PID放大器作用后, 输出4-20mA操纵信号。该信号送经电液转换器I/H (1742)转换成二次油压信号(1.5-4.5bar),二次油通过油动机(1910)控制调阀(0801)开度，调节进汽量,调整汽机出力,使汽轮机转速稳定在设定值。如下图1。 WOODWARD505也接受来自中控室或DCS的转速遥控信号(4-20mA)，以使汽轮机转速满足工艺流程的需要(4mA对应xxxrpm，20mA对应xxxrpm)。 WOODWARD505输出一个实际转速信号(4-20mA)用作中控室指示。 汽轮机的启动、暖机、升/降速可以在WOODWARD505面板上完成。此外汽机旁的电气操作间上，也设置了升速和降速按钮，也可以完成上述功能。 利用WOODWAR505可以进行汽轮机的超速试验。 505面板上会显现报警信号。 WOODWAR505监测到超速时发出一跳闸信号至ESD,ESD控制停机电磁阀, 泄 掉速关油，快速关闭速关阀,切断汽源，以保证汽机安全。
三、操作规程 。 馈板上调节螺钉,使油动机上指针指示hvmax。2)使505输出4mA时。调整电液转换器上电位器×O，使二次油压为1.5bar，再调错油门上调整螺钉,使油动机上指针指示O。