机械原理作业答案_叶仲和_蓝兆辉(上)

REFERENCE ANSWER for EXERCISE BOOK of 《Mechanisms and Machine Theory》 TRG of Machinery Theory and Design College of Mechanical Engineering Fuzhou University 2003 Name Class Student No. Date 2-1 Draw the kinematic diagrams of the mechanisms shown in Fig2-1. 4 scale 3:1 1 B C 2 3 A 4 2 A 3 C 1B Fig2-1(a) 1 1 2 2 3 3 4 4 A B C A B C Fig2-1(b) Name Class Student No. Date 2-2 Draw the kinematic diagrams of the mechanisms shown in Fig2-2. 1 2 3 3 4 4 5 5 6 6 A B C D E A BC D E F F 2 1 Fig2-2(a) Name Class Student No. Date 2-3 Draw the kinematic diagram of the mechanism shown in Fig2-3. 8 I 7 B 6 5 H A 1 G 2 C 3 E 4 D F 2 7 8 I 1 56 H A G F C B 3 E D 4 Fig2-3 Name Class Student No. Date 2-4 Calculate the degree of freedom of the mechanisms shown in Fig2-4,and point out what should be paid attention to during the calculation . 解： (a) 左右为对称结构，设左侧为虚约 束。 (b) E 为杆 4、5、6 的复合铰链。(c) 滑 块 7 与机架 8 间为移动副。 F=3n-2PL-Ph=3×7-2×10=1 解： (1)红线内的构件为重复结构，构成虚约束。 (2)去掉以上构件后，C 仍为构件 2、3、4 的复合铰链。 (3)滑块 5 与机架 6 之间为移动副。 F= 3n-2PL-Ph =3×5–2×7=1 A B C D E F G H I J Redundnt constraint 2 3 4 5 6 7 8 Fig2-4(a) 1 B C D EF G HI J K Redundant constraint A 23 4 5 6 Fig2-4(b) Name Class Student No. Date 2-5 Calculate the degree of freedom of the mechanisms shown in Fig2-5,and point out what should be paid attention to during the calculation . 解： (a) 两个滚子有局部自由度。 (b) 滚子 D 与凸轮 1 之间只能算一 个高副。 F=3n-2PL-Ph =3×7 –2×9 -2=1 解： (1)杆件 BC 与齿轮 2 焊接在一起。 (2) A 为齿轮 4、杆件 1 和机架 5 的复合 铰链。 F= 3n-2PL-Ph =3×4 –2×5 -1 =1 常见错误：认为 B 是复合铰链，而不认为 A 是复合铰链。 A B C D E F G L M N O 1 2 3 4 5 6 7 8 Fig2-5(a) B D A 5 1 2 3 4 Fig2-5(b) Name Class Student No. Date 2-6 Calculate the degree of freedom of the mechanisms shown in Fig2-6,and point out what should be paid attention to during the calculation . 解： (a) C 为构件 2、3、4 的复合铰链。 (b) C 处有两个转动副和两个移动 副。 E 处有一个转动副和两个移 动副。 F= 3n-2PL-Ph =3×7 –2×10=1 注意：E 不是复合铰链！ 解： 当构件尺寸任意时，构件 2 作平面复杂运动，而杆 4 与机架间组成移动副， 所以杆 4 仅作平动。因此，构件 2 和构件 4 之间有相对转动。因此，应该有构 件 6，并且构件 4 和 6 之间有转动副，如右图所示。 当 AB＝CD 且 BC＝AD 时，杆 2 仅作平动。杆 4 与机架间组成移动副， 所以杆 4 也仅作平动。这样，构件 2 和构件 4 之间就没有相对转动，只有相对 移动。即：构件 4 和构件 6 之间就没有相对转动了，因此，可将构件 6 与构件 4 焊接起来（去掉构件 6），如左图所示。 然而，在计算机构自由度时，应该按一般尺寸情况下进行分析，即：应该 按照右图情况来分析机构的自由度。 F= 3n-2PL-Ph =3×5 –2×7=1 A B C D E 12 3 6 7 8 4 Fig2-6(a) A B C D AB=CD BC=AD A B C D 1 2 3 4 5 1 2 3 4 5 6 Fig2-6(b) Name Class Student No. Date 2-7 The kinematic diagram of an engine mechanism is given in Fig2-7. (1) Calculate the degree of freedom of the mechanism, and point out what should be paid attention to during the calculation. (2) Make the structural analysis for the mechanism. (3) Make the structural analysis for the mechanism when link EFG is regarded as the driver. Note: During structural analysis, list the assembly order of Assur groups, the type of group, the grade of group, the grade of the mechanism, the link serial numbers, the inner pair and the outer pairs of each group in each mechanism. 解： （1） F= 3n-2PL-Ph =3×7 –2×10=1 （2） 当 AB 为原动件时， （3）当 EFG 为原动件时， A B C D E F G H 1 2 34 6 5 7 8 第一杆组 RRP RRR 2,3 4,5 内副 E 外副 B,移C F,D第二杆组 类型杆号 第三杆组 RRP 6,7转H6-7 G,移H 转C2-3 3-8 7-8 A B C D E F G H 1 2 34 6 5 7 8 III级杆组 RRP 1,2,3,4 6,7 内副 外副 A,E,移C 类型 杆号 B,D,转C 3-8 转H G,移H7-8 Name Class Student No. Date 2-8 Make the structural analysis for the mechanism shown in Fig2-8. (a) When link 1 is regarded as the driver. (b) When link 5 is regarded as the driver. Note: During structural analysis, list the assembly order of Assur groups, the type of group, the grade of group, the grade of the mechanism, the link serial numbers, the inner pair and the outer pairs of each group in each mechanism. 解： (a) 当 1 为原动件时 杆件 2, 3, 4 和 5 组成一个三级 Assur group. (b) 当 5 为原动件时 杆件 3 和 4 组成第一个 RPR Assur group. 杆件 1 和 2 组成第二个 RPR Assur group B C3 6 2 1 A D 4 5 E Fig2-8 2 3 6 A 1 C D B 5 4 E 2 3 6 1 A C B D 5 E 4 A B C D E F A B C D E F A B C grade II grade III grade IV 2 3 6 A 1 C D B 5 4 E B D 3 6 A 1 5 2 4 C E C A D B D 5 3 B 4 A 6 C E Name Class Student No. Date 2-9 The schematic diagram of a punch machine designed by someone is shown in Fig2-9. This machine should be able to transform a continuous rotation of gear 1 into a translation of the punch 4. Can the machine work properly? If it can’t ,please rectify it. 解：不能正常工作。 改正如图(或者改成题目 2-3 构件 5、6、7 的连接) 1 2 3 4 5 Fig2-9 Name Class Student No. Date 2-10 The schematic diagram of a mechanism designed by someone is shown in Fig2-10. This mechanism should be able to transform a continuous rotation of link1 into an oscillation of link4. Can the mechanism work properly? If it can’t ,please rectify it. 解：不能正常工作。 改正后 A D B C E 1 2 3 4 5 Fig2-10 A D B C E 1 2 4 A B C E DA B C Name Class Student No. Date 3-1 Locate all instant centres of mechanisms in the position shown in Fig3-1. 2 1 3 4 P14 P12 P23 P34 P13 P24 Fig3-1(a) 1 2 3 4 P12 P24∞) P14 P23 P34P13 ∞ Fig3-1(b) 12 1 2 3 P 23 ∞ P P13 O n n Fig3-1(c) 24 14 P( 2A 1 15(P ) G B 25(P ) n P( )12 E (P45) PJ H F n 423C P( 3 D ) )P34( ) 12 24 41 2 14P P P 14 P P 15 P 45 1 5 4 5 Fig3-1(d) Name Class Student No. Date 1 2 3 A B C E D G F 12P ( ) 13P( ) P( ) P23 P14∞ V1 ( ) Fig3-1(e) 1 2 3 341 1413 P 12 P P 23 P P 43 P 13 2324 P 12 P 2 1 P 14 P 4 2 PP 24 34 3 4 A P14)( B P12 C P( )23 34(PD ) 1 2 3 4 ∞ P13 24P Fig3-1(f) Name Class Student No. Date 3-2 In the position shown in Fig3-2, determine the ratio 3/1 of the angular velocity of gear 3 to that of gear 1, using the method of instant centres. 解： P13 是构件 1 和 3 的瞬心，等速重合点， 所以1LAE =3LDE 3/1=LAE/LDE 3-3 In the position shown in Fig3-3, determine the ratio 2/1 of the angular velocity of follower 2 to that of cam 1, using the method of instant centres. 解： E（P12）是构件 1 和 2 的瞬心，等速重合点， 所以1LOE=2LAE 2/1=LOE/LAE 6 1 2 3 4 5 A B C D E F 1 2 3 361 PP P P PP 161312 23 6313 ( )P36 ( )P 23 ( )P12 ( )P 16 E( 13 P ) Fig3-2 O A ( ) ( ) T 1 2 3 12 13 23P P PE( ) Fig3-3 Name Class Student No. Date 3-4 In the pivot four-bar linkage shown in Fig3-4, 1= 10rad/sec. Using the method of instant centres, (a) Find the velocity of point C in the position shown in the figure. (b) In the position shown in the figure, locate the point E on the line BC (or its extension) which has the minimum velocity among all points of line BC and its extension, and then calculate its velocity. (c) draw two positions of the crank AB when VC=0. 解： （a）VB1= 1LAB=VB2= 2LFB ，所以 VC= VC2= 2LFC= 1LABLFC/LFB (b)VE=2LFE。 (c ) VC=0 所对应的曲柄 AB 的两个位置: Name Class Student No. Date 14A(P ) 12P B ( ) 23 C(P ) ) D P( 341 2 3 4 P24 E ω 1 ω 2 F Fig3-4 14A(P ) 12P B ( ) 23 C(P ) D 1 2 4 ω 1 B B C C 1 1 2 2 34(P ) 3 3-5 In the six-bar mechanism shown in Fig3-5, XA=0, YA=0, XD=450mm, YD=0, LAB=150mm, LBC=400mm, LDC=350mm, CDE=30, LDE=150mm, LEF=400mm. The crank AB rotates at a constant speed 10rad/sec.Write a main program to analyze the output motion of the point F when the driver AB rotates from 0 to 360 with a step size of 5.. 解： FOR I=0 TO 360 STEP 5 CALL LINK(0, 0, 0, 0, 0, 0, I*PI/180, 10, 0, 150, XB, YB, VBX, VBY, ABX, ABY) CALL RRR(450, 0, 0, 0, 0, 0, XB, YB, VBX,VBY, ABX,ABY,350,400,Q3,W3,E3,Q2,W2,E2) CALL LINK(450, 0, 0, 0, 0, 0, Q3-PI/6, W3, E3, 150, XE, YE, VEX, VEY, AEX, AEY) CALL RRP(1, 0, 400, XE, YE, VEX, VEY, AEX, AEY, Q5, W5, E5) CALL LINK(XE,YE,VEX,VEY,AEX,AEY,Q5,W5, E5, 400, XF, YF, VFX, VFY, AFX, AFY) PRINT I, XF, YF, VFX, VFY, AFX, AFY NEXT I A B C E F 2 3 4 5 θω 11 6D Fig3-5 Name Class Student No. Date 3-6 In the mechanism shown in Fig3-6,XA=0, YA=0, XD=200mm, YD=0, LAB=80mm, LCD=60mm and LBE=380mm. The crank AB rotates at a constant speed of 10rad/sec. Write a main program to analyze the output motion of the point E when the driver AB rotates from 0 to 360 with a step size of 5. FOR I=0 TO 360 STEP 5 CALL LINK(0, 0, 0, 0, 0, 0, I*PI/180, 10, 0, 80, XB, YB, VBX, VBY, ABX, ABY) CALL RPR(1, XB, YB, VBX, VBY, ABX, ABY, 200, 0, 0, 0, 0, 0, 60, Q2, W2, E2) CALL LINK(XB, YB, VBX, VBY, ABX, ABY, Q2, W2, E2, 380, XE, YE, VEX, VEY, AEX, AEY) PRINT I, XE, YE, VEX, VEY, AEX, AEY NEXT I A C D E 2 3 4 θ ω 1 1 Fig3-6 A B C D2 34 ω1 2 3 φ2 φ2 (200,0) (80) (60) (3 80 ) =10 (0,0) Name Class Student No. Date 3-7 . In the mechanism shown in Fig3-7, XG=YG=0, XB= - 42, YB=39, XD=70, YD=75, LBA=34mm, LGF=24mm, LFE=95mm, LEC=69mm, LDC=48mm, EFG=90. The crank BA rotates at a constant speed of 10 rad/sec. Write a main program to analyze the output motion of the point C when the driver BA rotates from 0 to 360 with a step size of 5. FOR I=0 TO 360 STEP 5 CALL LINK(-42, 39, 0, 0, 0, 0, I*PI/180, 10, 0, 34, XA, YA, VAX, VAY, AAX, AAY) CALL RPR(-1, 0, 0, 0, 0, 0, 0, XA, YA, VAX, VAY, AAX, AAY, 24, QFE, W3, E3) CALL LINK(0, 0, 0, 0, 0, 0, QFE+PI/2, W3, E3, 24, XF, YF, VFX, VFY, AFX, AFY) CALL LINK(XF, YF, VFX, VFY, AFX, AFY, QFE, W3, E3, 95, XE, YE, VEX, VEY, AEX, AEY) CALL RRR(XE, YE, VEX, VEY, AEX, AEY, 70, 75, 0, 0, 0, 0, 69, 48,QEC, W4, E4, QDC, W5, E5) CALL LINK(70, 75, 0, 0, 0, 0, QDC, W5, E5, 48, XC, YC, VCX, VCY, ACX, ACY) PRINT I, XC, YC, VCX, VCY, ACX, ACY NEXT I B A F G E C D 1 2 3 4 5 6 6 6 Fig3-7 Name Class Student No. Date 3-8 In the six-bar mechanism shown in Fig3-8, XB=0, YB=0, XF=37.2, YF=17.5, YC=28.8, LFE=16.8mm, LEC=39.2mm, LCD=20.633mm, LDE=36.4mm, BGA=90, LBG=9mm, LGA=58mm. The crank FE rotates clockwise at a constant speed of 10 rad/sec. Write a main program to analyze the output motion of the point A.when the driver FE rotates from 360 to 0 with a step size of -5. For I = 360 To 0 Step -5 Call LINK(37.2, 17.5, 0, 0, 0, 0, 16.8, I*PI/180, 10, 0, XE, YE, VEX, VEY, AEX, AEY) Call RRP(-1, 28.8, XE, YE, VEX, VEY, AEX, AEY, 39.2, QEC, W4, E4, XC) Call LINK(XE, YE, VEX, VEY, AEX, AEY, QEC-QCED, W4,E4,XD,YD, VDX, VDY, ADX, ADY) Call RPR(1, 0, 0, 0, 0, 0, 0, XD, YD, VDX, VDY, ADX, ADY, LBG, QGA, W2, E2) Call LINK(0, 0, 0, 0, 0, 0, LBG, 3 * PI / 2 + QGA, W2, E2, XG, YG, VGX, VGY, AGX, AGY) Call LINK(XG, YG, VGX, VGY, AGX, AGY, LGA, QGA, W2, E2, XA, YA, VAX, VAY, AAX, AAY) Print I, XA, YA, VAX, VAY, AAX, AAY Next I A C D E F 2 3 4 5 6 ω1 B Fig3-8 Name Class Student No. Date 4-1 Determine the type of the pivot four-bar linkages whose dimensions are shown in Fig4-1. 双曲柄机构 曲柄摇杆机构 双摇杆机构 双摇杆机构 40 70 90 110 Fig4-1(a) 120 45 100 70 Fig4-1(b) 60 50 70 100 Fig4-1(c) 50 90 70 100 Fig4-1(d) Name Class Student No. Date 4-2 In the revolute four-bar mechanism shown in Fig4-2 (1) Find the pressure angle  and the transmission angle  of the mechanism in the position shown in the figure. (2) Find the angular stroke max of the link DC. (3) Find the crank acute angle  between the two limiting positions. (4) Find the maximum pressure angle max and the minimum transmission angle min. (5) Is there dead-point during the whole cycle of the motion when the link DC is regarded as the driver? If there is, when? And draw the dead-point positions of the mechanism. (5)当 DC 为原动件时，此机构有死点位置。 死点位置为图中 AB1C1D 和 AB2C2D。 1 2 3 4 A B C D α γ C2 C1 B2 B1 ψmax θ C1 B2 C2 B1 γmin αmax Fig4-2 Name Class Student No. Date 4-3 Design an offset slider-crank mechanism ABC in which the crank AB is the driver. The maximum pressure angle max=30. Find the stroke H of the slider and the crank acute angle  between the two limiting positions. 4-4 Determine the angular strokes of the rockers AB and CD shown in Fig4-4, respectively, using graphical method. A B e B B B C C C 1 2 1 2 3 3 30° θ H Fig4-3 A B C D AB CDφ φ Name Class Student No. Date 4-5 In Fig4-5 there are two positions, B1C1 and B2C2, of the coupler BC of a revolute four-bar linkage ABCD. The link AB is a driver. The pressure angle  at the first position is 0 o . The second position of the mechanism is a toggle position. Design the linkage and write out the drawing steps briefly. 解： a) 链点 A 必在 B1B2 的垂直平分线上。 b) 类似的，铰链点 D 必在 C1C2 的垂直平分线上。 c) AB 为原动件时，机构在第一位置的压力角为 0o 得到 B1C1C1D。 d) 机构的第二位置为一死点位置得到 A, B2, C2 三点共线。 B B C C 1 1 2 2 A D Name Class Student No. Date 4-6 In a crank-slider mechanism, two sets of corresponding positions of the slider and a line segment AE on the crank ABE are shown in Fig4-6. The position C1 of the slider is its left limiting position. Find the first position B1 of the revolute B and write out the drawing steps briefly. 解： 作 AC2’E1AC2E2，且字母旋向相同，得 C2 ’。因 C1 为滑块的极限位置之 一，所以 B1 点在 AC1 连线上。 作 C1C2’的中垂线与 AC1 交于待定活动铰链点 B 的第一个位置点 B1。 A E E C C 1 2 2 C2' 1B 1 Fig4-6 Name Class Student No. Date 4-7 In a revolute four-bar linkage ABCD, side link AB is the driver. Two sets of corresponding positions of the side link CD and a line segment CE on the coupler CBE are shown in Fig4-7. The first position of the linkage is also a dead point. Find the second position B2 of the revolute B and write out the drawing steps briefly. 解： 作 A2’C1E1AC2E2，得 A2’点。因 AB 为原动件且机构第一位置为死点， 所以 B1 点在 DC1 的延长线上。 作AA2’的中垂线与DC1的延长线交于待定活动铰链点B的第一个位置点B1。 A C C D E E 1 1 2 2 B 1 A'2 Fig4-7 Name Class Student No. Date 4-8 In a crank-rocker linkage ABCD, side link AB is the driver. Two positions of the rocker CD are shown in Fig4-8. At the first position , the pressure angle of the linkage is zero. Position DC2 is one of the limit positions of the rocker. Find the first position B1 of the revolute B and write out the drawing steps briefly. 解： 因 A 点在 C2B2 延长线上, 故在 C1B1 延长线上截取 C1A2’=C2A，得 A2’点。 作 AA2’的中垂线与 C1B1 交于待定活动铰链点 B 的第一个位置点 B1。 A C D 2 B 2 C 1 B 1 A'2 Fig4-8 Name Class Student No. Date 4-9 In an offset slider-crank mechanism ABC, two sets of corresponding positions of the crank AB and a point F on the slider are shown in Fig4-9. When the crank AB is located at position AB1, the slider reaches its left limit position. Find the first position C1 of the revolute C on the slider and write out the drawing steps briefly. 解： 作 B2B2’ //=F1F2，得 B2’点因为第一位置是滑块的左极限位置,故 C1 在 B1A 的延长线上. 作 B1B2’的中垂线，交 B1A的延长线于待定活动铰链点 C 的第一个位置点 C1。 作 C1C2=F1F2，得 C2 点。 A B B F 1 1 2 C1 2B' 2F E21E Fig4-9 Name Class Student No. Date 4-10 In a crank-rocker mechanism ABCD, the coefficient of travel speed variation(k) is1.25, when crank AB rotate constantly. The angular stroke of rocker DC =60o .The length of the rocker DC is 40mm. The length of the frame AD is 50mm. Design the mechanism and write out the drawing steps briefly. 解：（取比例尺μ l =0.001m/mm） 取 DC1=DC2=40mm，作直角三角形 C1C2H,其中∠C1C2H=90º－θ =70º 作三角形 C1C2H 的外接圆，以 D 点为圆心，以 50mm 为半径作圆，两圆的交 点为铰链点 A。 连接 AC1、AC2,以 A 点为圆心，以（AC2 －AC1）／2 为半径作圆得铰链点 B,AB=17.98mmBC=53.72mm 0 0 01 1.25 1180 180 20 1 1.25 1 k k           D ψ 70° A A 50 B1 B2 C2 C1 90°E F H Name Class Student No. Date 4-11 In an offset slider-crank mechanism, the offset e is 20mm. The coefficient of travel speed variation k is 1.3. The working stroke H of the slider is 50mm. Design the offset slider-crank mechanism 解： （取比例尺μ l =0.001m/mm） 作C1C2=50mm,作等腰三角形OC1C2其中∠OC1C2=∠OC2C1=90º－θ =86.5º, 以 O 为圆心，以 OC1 为半径作圆 作一与 C1C2 平行且距离为 20mm 的直线，此直线与圆 O 的交点为铰链点 A 以 A 为圆心，以（AC2－AC1）／2 为半径作圆 A 得到铰链点 B。 BC=55.06mm,AB=22.83mm. 0 0 01 1.3 1180 180 23.5 1 1.3 1 k k           C1 C2 A B1 B2 86.5° 86.5° O Name Class Student No. Date 5-1 A plate cam with positive-offset translating roller follower has the following motion: a rise through lift h=40mm with a sine acceleration motion curve during 0=150, S=30, a return with a 3-4-5 polynomial motion curve during 0'=120, and S'=60. The cam rotates clockwise. And rP=40mm. rR=12mm, e=12mm and rC=25mm. Construct the pitch curve and the cam contour graphically with a scale of 1:1. Label in red the centerline of the follower, S, the roller and  when  = 60 and  = 0.  0 30 60 90 120 150 180 210 240 270 300 330 360 S(mm) 0 7.86 15.72 23.58 31.44 40 40 35.86 20 4.14 0 0 0 O ω B0 B1 B1' B2 B2 B3 B3 B4 B4 B5 B5 B6 B6 B7 B7 B8 B8 B9 B9 B10 B11 S=0 S α α Name Class Student No. Date 5-2 A plate cam with translating offset roller follower has the same motion curve and dimensions as exercise5-1 has. Write a program to calculate the co-ordinates of the pitch curve, the cam contour and the locus of the center of the milling cutter,  and B. SET WINDOW -100,120,-100,60 LET M=-1 LET N=+1 LET RP=40 LET E=12 LET RR=12 LET RC=25 LET H=40 LET DELTA0=150*PI/180 LET DELTAS=30*PI/180 LET DELTA01=120*PI/180 LET DELTAS1=60*PI/180 LET S0=SQR(RP^2-E^2) BOX CIRCLE -RP,RP,-RP,RP BOX CIRCLE -E,E,-E,E FOR I=0 TO 360 STEP .005 LET DELTA=I*PI/180 IF DELTA<=DELTA0 THEN LET DD=DELTA/DELTA0 LET S=H*(DD-1/2/PI*SIN(2*PI*DD)) LET S1=H/DELTA